Effects of a multi-hour immersion with intermittent exercise on urinary excretion and tilt table tolerance in athletes and nonathletes. The circulatory and diuretic responses of athletes and non-athletes to 6-h water i-mersion with intermittent swimming exercise (series I) as well as to 8-h inactive immersions (series II) were studied. With simultaneous intermittent exercise, the normally arising diuresis during a water bath was strongly suppressed in athletes and even abolished in nonathletes. In subsequent tilt table tests, 3 of 11 (27.3%) athletes of series I and 3 of 4 (75%) of series II collapsed, whereas all nonathletes tolerated the vertical position without any subjective complaints. By use of the so-called "orthostatic index" (4) the later group, however, was also shown to yield a substantially better orthostatic stability in series I than in series II. The protective effect of intermittent physical activity for simulation of the weightless state can possibly be explained by assuming a less-reduced plasma volume via a diminished urinary excretion.


Physiological reactions to wet-cold.

Physiological reactions to wet-cold. Changes in extremity temperatures during general cold stress were investigated. The changes in local temperatures were found equal to those seen under circulatory arrest. In order to investigate the influence of these changes on motor function, the relation between local temperature and nervous conduction velocity in a peripheral motor nerve (n. ulnaris) was carried out in subjects exposed to a minor cold stress (to aboid the influence of Lewis hunting reaction). The decrease in conduction velocity was found to be 15 m/s per 10 degrees C fall in temperature. At a local temperature of 8-10 degrees C a complete nervous block was established. This leads to an explanation of the clinical findings in wet-cold situations, where the very rapid onset of physical impairment corresponds to the effect of a local cooling in the extremities and not, as commonly accepted, to a developing general hypothermia.


Optimal use of nitrogen to suppress the high pressure nervous syndrome. Five subjects were compressed to 1000 ft (31 ATA) for 2 h breathing 3.2 ATA nitrogen, 0.5 ATA oxygen, and the remainder helium. The compression took 33 min with a 10-s stage at 50 ft (2.5 ATA), 1 MIN AT 320 FT (10.7 ATA), and 2 min at 700 ft (22 ATA). Hypothetically, this 1:10 ratio for nitrogen-helium partial pressures should induce neither nitrogen narcosis nor the High Pressure Nervous Syndrome (HPNS). Tests, therefore, were made during the experiment of postural tremor, spontaneous electroencephalogram, psychomotor and intellectual activities, and subjective sensations. One diver worked underwater for 40 min on a simulated engineering assembly while breathing with a closed-circuit breathing apparatus and wearing a battery-heated suit in water at 56 degrees F. Decompression was in 4 d using 0.8 ATA oxygen and helium. The performance tests indicated no narcosis and little or no signs of HPNS. No tremor or EEG changes were seen. The "wet" diver reported sensations of mild euphoria but the other four reported no difficulties. No nausea or dizziness of HPNS was reported. It is concluded that use of a ratio of 1:10::N2:He is effective in the control of narcosis and HPNS during rapid compression to 1000 ft (31 ATA).


Respiration during heat stress.

Respiration during heat stress. In human subjects at rest changes in heart rate pulmonary ventilation, tidal volume, respiratory rate, and end-tidal carbon dioxide tension were examined at increases in deep body temperature of 1 degrees C and 2 degrees C. Each of these latter target temperatures was achieved at two different rates of temperature increase. The increase in deep body temperature  was associated with a rise in heart rate and tidal volume and a reduction in respiratory rate. An increase in pulmonary ventilation associated with a reduction in end-tidal carbon dioxide tension occurred only when deep body temperature increase reached 1.5 degrees C. The apparently greater change in both pulmonary ventilation and end-tidal carbon dioxide tension during the more rapid increase in deep body temperature by 2 degrees C was not significant.


Plasma thyroxine changes of the Apollo Crewman. Blood drawn from Apollo crew member; to the mission, at recovery, and postmission was used to examine the effect Apollo mission activities have on tyroid hormone levels. At recovery, statistically significant increases in thyroxine and the free thyroxine index were found. Serum cholesterol and triglycerides were decreased. No change of statistical significance was found in the T3 binding percentage, total serum proteins, and albumin. We conclude that apollo activities and environment caused the postmission increase in serum cholesterol may be one result of the increased thyroxine activity.


Re-evaluation of a tilt-back seat as a means of increasing acceleration tolerance. Relaxed tolerance was determined on seven subjects exposed to rapid onset (RO; 1 G/s) and gradual onset (GO; 1 G/10 s) acceleration at seat back angles of 13 degrees, 30 degrees, 45 degrees, 55 degrees, 65 degrees, and 75 degrees from the vertical. There was no significant difference between relaxed tolerance at the control angle of 13 degrees and tolerance at 30 degrees. However, at 45 degrees there was a significant 0.5 G increase in tolerance compared to control. Thereafter, tolerance continued to increase in an exponential manner to 8 G at 75 degrees, an increase over control of 100%. As relaxed tolerance increased with increasing back angle, peak heart rate during acceleration significantly decreased. In addition, four subjects were instrumented with an esophageal balloon for the measurement of intrathoracic pressure, which was equated as work during the M-1 straining maneuver. The amount of thoracic pressure necessary to maintain a preselected visual field declined as the back angle was increased from 13 degrees to 45 degrees to 65 degrees at the same acceleration level. The increase in relaxed tolerance along with the decrease in heart rate and the decrease in esophageal pressure at the greater back angles all demonstrate the acceleration protection provided by the tilt-back seat.


Distribution characteristics of methyl-hydrazine in the plasma and cerebrospinal fluid of monkeys. A Lumped parameter mathmatical model including extracellular fluid, intracellular fluid, and cerebrospinal fluid compartments has been applied to describe methylhydrazine (MMH) distribution kinetics in the blood and cerebrospinal fluid of Rhesus monkeys. Ten monkeys average weight 5.5 kg, were given intravenous infusions of MMH while blood and cerebrospinal fluid samples were periodically collected and analyzed for MMH. The mathematical model was used to simulate the infusions and the simulations were compared with experimental data to validate the model and to evaluate the mass transfer parameters required by the model.


Normal coronary angiography in an aircrewman with serial exercise test changes. A 45-year-old asymptomatic aircrewman is presented who developed an abnormal ST segment response to maximal treadmill testing after normal responses for 3 previous years. Coronary angiography performed after his abnormal stress test reveled no change from a previously normal study. It has been demostrated that serially performing exercise tests can increase the sensitivity of detecting latent coronary artery disease. The importance of the case report is to demonstrate that the change from a normal exercise test to an abnormal one does not absolutely indicate that an individual has a coronary artery disease and that it is mandatory to search for other possible causes. Further studies will be required to determine the significance of such serial changes.


Accident statistics and the human-factor element. The number of fatal accidents involving public transport aircraft has increased significantly in recent years and, because more and more "wide-bodied" aircraft have been coming into service, this has resulted in a rapid increase in the number of fatalities. A combined attack on the problem by all concerned with flight safety is required to improve the situation. The collection and analysis of aircraft accident data can contribute to safety in two ways; by giving an indication of where to concentrate future effort and by showing how successful past efforts have been. An analysis of worldwide accident statistics by phase of flight and causal factor show that the largest percentage of accidents occurs in the approach and landing phase and are caused by "pilot error". Further research is needed to find out why pilots make errors and how such errors can be eliminated.


Sudden incapacitation encountered in flight by professional pilots in French civil aviation, 1948-1972. This report concerns 17 incidents of sudden incapacitation of professional airline pilots in flight in the period 1948-1972. The high incidence of cardio-vascular accidents is noteworthy: 13 cases of which 11 were due to coronary infarction. There were two cases of unperdictable epileptic fits. None of the above gave rise to an accident. For an accident to occur, several conditions must be fulfilled at the same time: 1) The incapacity must affect the pilot at the controls; (2) The incapacity must be sudden; (3) The incapacity must  take place during a critical phase of take-off or final apprach.


Review of aviation safety measures which have application to aviation accident prevention. Introduction of certain human-factors techniques has been followed by market reduction in military and airline accident rates. In this study, these safety measures are analyzed to determine the value of their application to general aviation activity. Some techniques are already in use. They are: 1. medical evaluation of iarcrews; 2. aeronautical innovations which tailor the machine to the man; 3. imporvement of precision navigational air traffic control and flight procedures; 4. standardization of flight training and flight procedures. A remaining field of interest, and one which appears to be underused, is that of supervision. After ending his association with the flight instructor, the general aviation pilot is essentially unsupervised. Accident data gathered over several years show that with increases in the proportion of pilots who have not maintained an association with a flight instructor, the general aviation fatal accident rate is increased. Current regulations, which require revalidation of airman's certificates, provide a method by which this association can be maintained. The flight instructor, or some similar aviation professional, can maintain an element of supervision with otherwise independent general aviation pilots. Data from previous years supports the hypothesis that such a program would make a substantial improvement in general aviation safety.


Air crash survival: injuries and evacuation toxic hazards. Carbon monoxide and cyanide gas have resulted from inflight or post-crash fires which have pyrolyzed certain cabin interior materials. Three air carrier accidents have been studied in depth from the standpoint of carbon monoxide effects on passengers. Post-crash hydrogen cyanide in victim blood levels has similarly been investigated and certain laboratory synergistic studies of carbon monoxide and hydrogen cyanide have been conducted. The latter investigations indicate that a combination of carbon monoxide and hydrogen cyanide has a pharmacologic effect which exceeds that of either alone. The effect is that of incapacitation, and certain remedial steps are possible which diminish the production of these substances during post-crash fires.


Some highlights of aircraft passenger behavior research. A brief review is offered of the field of aircraft passenger safety research. Probelms associated with passenger behavior, e.g. panic, and passenger safety education studies and requirements are discussed. In addition, a comparison is drawn between commerical and corporate aircraft passenger safty requirements and current research and development programs. It is concluded there is a need for increased funding and more emphasis to be placed on education in the areas of aircraft passenger safty research.


Reaction time performance with and without backscatter from intense pulse light. Twenty male graduate students, 22-30 years of age, were asigned by a table of randome numbers to two groups, and visual reaction time performance with and without backscatter was measured. The subjects' task was to observe a 5 cm dial face whose needle deflected 2 mm either left or right of center. Meter deflections were either preceded by 10 light pulse from a Grimes "360 strobe or they were not preceded by light pulses. Two measures of performance were recorded: 1) voice reaction time in milliseconds, and 2) errors. Error rate (3.5%) did not discriminate between groups or conditions. Reaction time was almost twice as long with backscatter than without backscatter (1,556 ms and 854 ms, respectively). This RT increase was highly reliable statistically. Variability of RT performance increased markedly with backscatter. In practical terms, the results suggest that the effects of backscatter could induce a cumulative performace decrement in instrument scanning which might endanger air safety.


Telemetric control of heart adaptation during automatic and free-fall parachute jumps. Telmetered heart rate recordings have been ovtaine from 17 parachutists (6 during automatic jumps) 9 Catecholamine (adrenaline and noradrenaline) concentrations have been measured in urine and plasma of six of these subjects. No difference appears between heart rates recorded in the two jumps at egress and at parachute deployment. On the other hand, higher heart rate values are recorded during automatic jumps during descent and at ground impace. The urine catecholamine analysis after jump shows a statistically significant increase in adrenaline and noradrenaline concentration. It is suggested that simulation of the orthosympathetic system is due to two facts; muscular work performed during jumping and the emotional stress which it involves. The importance of these two causes varies with the jump circumstances.


Changes in serum proteins, viscosity, and protein-bound carbohydrates during prolonged bedrest. Studies were carried out on eight young males before, during and after 24 or more weeks bedrest. Measurements of serum viscosity, total serum protein, serum electrophoretic components, total serum solids, serum protein-bound carbohydrate, and plasma volume were carried out. A loss of plasma volume occurred early in bedrest which produced an increase in total serum protein level. Despite continuing reduced plasma volume during bedrest, the elevated serum protein level returned toward its pre-bedrest concentration with stabilization of the levels of all electrophoretic components at values very near those present before bedrest. Serum viscosity changes paralleled total serum protein values. Increase in total serum solids was measured and found to be greater than the rise in total serum protein. The excess total serum solid was nondialyzable and had little effect on viscosity. Increase in protein-bound hexose and fucose level were observed during bedrest which persisted during early reambulation. The proportionate fucose increase was greater than hexose despite stability of the gamma globulin fraction with which the majority of serum protein-bound fucose is normally associated, but no change in fucose content of haptoglobin, alpha2-macroglobulin, or alpha1-acid glycoprotein was detected in two subjects on whom sufficient material was present to allow study.


Changes in haptoglobin and other plasma proteins of rats during exposure to pure oxygen at 760 torr. Changes in plasma haptoglobin, total protein, hematocrit, and hemoglobin content of blood were studied in rats at various times during a 7-d exposure to oxygen at 760 torr. Plasma haptoglobin and other plasma proteins were fractionated and quantitatively evaluated for a 3-d exposure period. Total protein and haptoglobin were depressed after 7 d of exposure. Significant changes were not noted before this time. With a 3-d exposure, for which plasma proteins were fractionated, fibrinogen showed a considerable increase whereas albumin, gamma globulins, and the beta 1 globulin fraction decreased significantly. Individual variations in albumin and haptoglobin were correlated inversely to the hematocrit. These variations indicate that the altered composition of the plasma protein is due, in part, to a variable loss of the various plasma protein fractions as a result of increased vascular permeability.


Characteristics of the electrocardio-gram under physical and emotional stress in man. The changes in the length of interval R-R and in heart rate are widely used for estimation of man's physical state. How-ever, this ECG index has several drawbacks including a relatively low sensitivity and non-specificity, unindirection of changes under different states: attention  and fatigue, physical and emotional stress, etc. Moreover, one and the same factor, e.g. emotional stress, can lead both to a decrease and an increase in the heart rate. Hence, it is necessary to find other more adquate ECG parameters, which would enhance the reliability and accuracy of assessment of man's state. The analysis of data found in literature and the results of our preliminary experiments have shown that the amplitude of the t-peak and duration of the R-T interval of ECG can be used as such parameters.


Glucose tolerance of lowlanders during prolonged stay at high altitude and among high altitude natives. The fasting blood sugar level and glucose tolerance were investigated in seven amle lowlanders at sea level, during their stay at an altitude of 4,000 m at intervals of 2 weeks, 10, 15, 20, and 24 months and again on return to sea level during the first week and after 1 month. For  comparison, the glucose tolerance of six male Ladakhis (natives of high altitude area) was also determined at altitude. The fasting blood sugar among lowlanders increased to 136.0 plus or minus 4.39 mg per 100 ml during 10 months of stay at altitude followed with a gradual decrease to a value of 76.4 plus or minus 3.8 at the end of 24 months. On return to sea level, the blood glucose showed a tendency to increase. Ladakhis had a lower blood sugar level at altitude (86.4 plus or minus 7.28) as compared with lowlanders at sea level (92.6 plus or minus 2.29). The glucose tolerance curves of lowlanders ran paralell to each other at altitude and at sea level. However, the peak of the glucose tolerance curve shifted towards the left during the 20th and 24th months of stay at altitude and at sea level. However, the peak of the glucose tolerance curve shifted towards the left during the 20th and 24th months of stay at altitude and on return to sea level. The tolerance curve of Ladakhis was similar to that of lowlanders at altitude, but showed a sharper blood sugar decline rate.


Somatic-evoked brain responses as indicators of adaptation to nitrogen narcosis. Two 2-week experimental pressure chamber exposures to nitrogen-oxygen breathing mixtures afforded an opportunity to study adaptation to nitrogen narcosis. Somatic-evoked brain responses induced by electrical stimulation of the median nerve in the wrist were processed on-line with a signal averager. The N1P2 interval was seen generally to be reduced in amplitude as a result of exposure to increased nitrogen partial pressure. Compressions with air were made from sea level and saturation to 200, 250 and 300 ft of sea water (fsw) equivalent (61, 76, and 91m). The decrement was found to be less, for equivalent exposures, in subjects who had been saturated at the pressure of 90 and 120 fsw (27 and 36 m); we interpret this as evidence of a nonspecific "adaptation." Less adaptation was seen from 30 and 60 fsw (9 and 18 m). These results are consistent with performance tests on the same exposures, and with subjective impressions. Saturation with 3 0r 4 atm of nitrogen may permit somewhat deeper diving without serious narcosis, than is possible from sea level.


Determination of body fluid compartments by electrical impedance measurements. ?The ratio of the LF and HF impedances appears to be an excellent and simple tool for investigation of liquid specimens, either of the total human body, taking into consideration global impedances, or of a particular organ, taking into consideration local impedances. We have sketched out in this communication a study of the global impedance ratio variations with age, but a large number of studies still remain to be undertaken in those cases of severe denutrition, as in all cases of metabolic illnesses. We can state that, in most cases, not only does the ratio decrease but that there is extreme difficulty in reestablishing normal values. Whatever action is undertaken, it seems that the intracellular liquid compartment remains insufficient with respect to that of the extracellular liquid compartment. It is as if the water will not enter in the cells or as if it were no longer retained within the cells. Finally, with this concept of impedance ratios of Zlf/Zhf a promising experimental method has been found which will, perhaps, enable better infestigations in a field which has often been left to one side.


Investigation of electrical impedance variations of dog brain tissue during experimental metabolic disturbances. Experiments were carried out on dogs using bielectrode probes having as adequate impedancemeter. The probe is introduced via a cranial opening into the grey matter. This gives the following: a low frequency reading which is related to the extra cellular fluid component; a high frequency reading which is related to the total overall liquids; and a proportionality ratio of these liquids in the explored volume. The impedance variations are functions of the nature and intessity of vascular disturbance. Variation of the low frequency impedance (5 kHz) is the most significant. The experimental prodedure consists of: 1) Abrupt and permanent circulatory arrest; 2) Circulatory reduction by haemorrhage followed by recovery (if necessary by means of blood transfusion); 3) Anoxia by CO inhalation, recovery affected by means of O2 inhalation; and 4) Hypoglycemic coma induced by intravenous injection of insulin. The changes in the biochemical state of the cerebral tissue give very large variations of the low frequency impedance. It is these variations which are to constitute the object of this communication.


Emesis in monkeys following exposure to ionizing radiation. There were 129 male rhesus monkeys (Macaca mulatta) exposed to prompt radiations (neutron/gamma = 0.4 and pulse width = 50 ms) ranging from 700 to 5600 rad (midhead dose). The animals were fasted 18 h preexposure and observed for incidence of vomiting for 2 h postexposure. For doses less than 1000 rads the number of animals that vomited increased directly with dose. Above 1000 rads, the number of animals that vomited decreased with increasing dose. The total number of vomits per dose group followed a nearly identical pattern to the incidence of emesis. In all dose groups, most of the emetic episodes occurred between 20 and 50 min postirradiation.


Human amino acid excretion patterns during and following prolonged multistressor tests. As a feasibility study, two men were tested in a series of simulated flights which comprised a factorial experiment. Plysiologic data were collected during a 2-d baseline period, four 36-h experimental periods, and four recovery periods. The experimental conditions were as follows: a) uncomplicated simulated flight, b) flight complicated by extreme environmental dryness, c) flight complicated by mild hypoxia, and d) flight complicated by both dryness and -ypoxia. Throughout each flight the subjects alternately worked 2 h and rested 2 h, performing on psychomotor measuring devices during each work period. Five other men were studied under baseline conditions and during a 48-h simulated flight complicated by hypoxia. Urinary nitrogenous metabolites, including individual amino acids, were examined for sensitivity to the stressor complexes. Certain of the amino acids had high stressor sensitivity, tending to differentiate the effects of the single, double, and triple stressor complexes. They also differentiated the physiologic states in the experimental and recovery periods.


Climatologic aspects of obesity and therapeutic semistarvation. Multifactor stress was studied, using obese men subjected to long-term (49 d) semistarvation in either a temperate or a not climate. The study was wide in scope, fiving information on endocrine-metabolic effects of a) uncomplicated obesity, b) ovesity in combination with climatic heat, c) obesity plus semistarvation, and d) ovesity combined with semistarvation plus climatic heat. The test subjects--groups of 12 to 13 obese men--remained on a diet which provided 335-400 kcal/d and contained at least 45 g protein, 14 g carbohydrate, and 11 g fat. Overnight urine specimens collected at 7-d intervals were analyzed for epinephrine, norepinephrine, 17-OHCS, ketones, urea, uric acid, creatinine, inorganic phosphate, sodium, and potassium. There was transitory hyperketonuria which related inversely to environmental thermal levels. Most of the physiologic response patterns in the triple-stressor circumstance (obesity plus climatic heat plus semistarvation) were unlike those in the double-stressor situation (obesity plus semistarvation). Thus, there was evidence of compounding of stressor effects. Evidence of diminished sensitivity to heat appeared when obesity was lessened.


Personality aspects of involvement in pilot-error accidents. The consistently high frequency of pilot-error accidents in both military and civilian aviation programs does much to support exploratory research which might help alleviate the problem. Cattell's Sixteen Personality Factor Questionnaire (16 PF), Mehrabian Achievement Scale, and a dynamic decision making task (under risk) were given to 51 Army aviators. Accident files were then examined in order to classify the aviators as to their prior pilot-error accident involvement. Stepwise discriminant analyses revealed that the decision-making task scores and the achievement scores were unrelated to the pilot error accident groupings while the 16 PF scores were able to correctly classify 86% of the aviators as to whether or not they had been previously listed as a cause factor in a military aviation accident.


Catecholamine and phagocytic responses in infected mice exposed to hyperbaric helium-oxygen atmospheres. Exposure of mice to exotic gaseous environments (97% helium and 3% oxygen) maintained at 20% cand 8 ATA (100 psig) increased host susceptibility to aerosol infection with klebsiella pneumoniae. The animals became ill earlier than the controls and the respiratory LD50 for the hyperbaric mice was about 50% smaller than for controls under ambient conditions. Furthermore, hyperbaricity induced an acute depression in phagocytic activity and a marked elevation in the circulating levels of epinephrine, norepinephrine and dopamine.


EEG criteria for flying fitness applied by the German air force institute of aviation medicine. A re-evaluation of EEGs of more than 1,000 applicants for flying training is presented. All EEG abnormalities were reevaluated by three EEG specialists. Out of 1,630 EEG records, 5.4% were classified as abnormal and, of these, 24 were found to have a bearing on flying qualification. SW-variants and paroxysms were cause for elimination in any case. This study led to the adoption of the following policy: Any subject showing EEG abnormalities, possibly requiring a permanent elimination, will undergo a second EEG by another examiner. In cases with EEG anomalies, a followup EEG is done with a concurrent sensory-motor performance test. This is supplemented by an evaluation of collateral cerebral circulation, using uni-and bilateral compression of the vertebral and carotid arteries. In cases without noticeable performance deficiencies another EEG is done a year later in order to exclude a progression of the EEG anomalies.


Drug interactions: How to identify them. Interactions between theraputic agents have been recognized as increasingly important causes of drug at their usual recommended dose may, under certain conditions, produce toxicity of life-endangering proportions. While the recognition of drug toxicity resulting from interactions is of importance to all physciains, it is especially so for the clinician responsible for the welfare of those in the aerospace environment. This paper attempts to provide a basis for the understanding and identifications of important drug interactions. Guidelines are provided to assist the clinician in his logical approach to the identification of drug interactions when serious drug toxicity is encountered in a pateint. Only with knowledge of the interaction can the therapeutic regimen be altered so as to provide therapeutic levels of necessary drugs while avoiding toxicity.


Pseudo-internuclear oculomotor ophthalmoplegia secondary to Guillain-Barré polyneuronitis simulating myasthenia gravis in a air transport pilot. A 32-year old experienced co-pilot was grounded because of handicapping and disabling doulbe vision and was off-flight from October, 1969, until January, 1972. He presented with a bilateral external ophthalmoplegia with alternate extreme divergent strabismus, and polyneuronitis. The clinical picture was confused by features resembling either a polyneuronitis of the Guillain-Barrè type, (confused by a false positive Tensilon test), myasthenia gravis, or a demyelinizing process. Because the prognosis for return to flight was so contradictory in these respective conditions, a long observative followup time was essential. The pilot recovered completely after 4 months. The long 2 year followup effectively ruled out the entity of myasthenia gravis as well as a progressive demyelinizing disease. The pilot was returned to full flight duties with no handicapping residuals. He has shown no evidence of recurrence to the date of this report (April, 1974). This case was reviewed and presented for its obvious aerospace implications.


Prejudice and dietary counseling.

Prejudice and dietary counseling. Current medical practice requires us to be able to educate and alter an individual's approach to health maintenance. The objective is to prevent illness--not only to treat illness. This approach should result in keeping people out of hospitals and clinics. Diet should be thought of as a noun, not a verb. It is not synonymous with the corrective measures it supposedly sill insure, i.e., correct obesity, reduce hypertension, control blood lipid abnormalities. In keeping with this approach, USAF medical team members should be able to do dietary counseling. This paper will examine each of these topics, emphasizing dietary prejudice at the level of the counselor, the subject and his family, and the USAF medical team.


Efficiency of constant-flow oxygen masks for general aviation: a new method of mask evaluation. Three commercially popular oxygen masks for general aviation were tested by measuring arterial blood gases at altitude and alveolar gases at ground level with a respiratory mass spectrometer. At 4,575 m (15,000 ft) and 3.65 1/min oxygen flow, calculated fractional inspired oxygen (F102) averaged 38.1% for the Hudson-type mask; 49.6% for the Scott Sky Mask; and 52.4% for the Scott Duo Seal Mask. At ground level, 1280 m (4,200 ft) 2.6 1/min oxygen flow, F102 calculated from alveolar gases averaged 41.5% plus or minus S.D. 5.3 for the Hudson Mask; 48.0% plus or minus 5.2 for the Scott Sky Mask; and 54.9% plus or minus S.D. 6.2 for the Scott Duo Seal Mask. The asymptomatic hyperventilation observed in all subjects at altitude degraded the performance of all three masks to a sufficient degree to offset the benefits of increased oxygen flow achieved through the regulator at higher altitudes. The respiratory mass spectrometer provides a new technique for analyzing efficiency of oxygen masks and the effect of changes in mask design.


Excitability of the cortex in normal and adrenalectomized rats during repeated exposures to high oxygen pressure. The excitability of the cortex in adrenalectomized and normal adult male rats to High Oxygen Pressure (HOP) was studied 2, 3, 4, 6, 8, 12 and 22 d after bilateral adrenalectomy and implantation of cerebral electrodes. Continuous electroencephalographic (EEG) recordings were obtained until the appearance of the first paroxysmal electrical discharges, which was considered to be the first indicator of the toxic effects of hyperbaric oxygen. A statistically significant change in excitability of the cortex to oxygen toxicity from 2 to 22 d following adrenalectomy was shown. Comparison of the sensitivity of the normal and adrenalectomized rats to HOP 2 d after the operation showed significant resistance of adrenalectomized rats at this time. This resistance disappeared gradually, when compared with normal rats, and cortical susceptibility increased significantly 22 d after adrenalectomy. The possible disturbances responsible for the changes in excitability of the cortex to HOP in adrenalectomized rats are discussed.


Relationship between saturation exposure pressure and subsequent decompression sickness in mice. Despite the fact that the pressure reduction is acknowledged to be the single most cogent factor in producing decompression sickness, little has been done to define accurately the allowable limits beyond 2 ATA. This study provides some theoretical guidelines for future manned dives related to this problem. There were 324 albino mice used to define the relationship between saturation exposure pressure and the safe abrupt pressure reduction. The results from both the helium-oxygen and nitrogen-oxygen exposures support the idea of a linear, depth-dependent relationship between the saturation depth and the allowable pressure reduction. Support is presented for the use of a modified decompression ratio P1/P2 (P1 equals saturation pressure and P2 equals pressure following decompression) to account for the observed incidence of decompression sickness. An attempt is made, using the existing human data to relate this empirical relationship to the operational dive setting.


Effects of long-term rotation and hypergravity on developing rat femurs. Male and female Sprague-Dawley rats derived from a single mating were raised for three generations under constant centrifugation at 1.03 G (Rotation Controls) and at 2 G. When the third generation rats were 3 months old, they were sacrificed, and their femurs removed. After fixation and cleaning, the femurs were then measured for length and diameter. Then right femurs were sectioned longitudinally, left femurs transversely. After staining with Hematoxylin and Eosin, right femurs were examined for ossification patterns and left femurs were measured for cortical thickness. All rotation control rats showed marked stimulation of ossification in the femoral head, and males showed significant cortical thinning when compared to non-rotated earth gravity controls. All 2 G femurs showed decreased length and aspect (L/D) ratios, and increased cortical thickness/diameter ratios when compared to earth controls or rotation controls. Ossification of the femoral head was slightly advanced, while the distal epiphyseal plate was thinned.


Effect of nitrogen narcosis on cortical and subcortical evoked responses in the cat. Four cats were chronically implanted with gross, monopolar electrodes in the lateral geniculate nucleus (LGN), pretectum-superior colliculus (P-SC), primary visual cortex (VI), and secondary visual cortex (VII). Following recovery and preliminary testing, the animals were dived in a dry hyperbaric chamber to the sea water equivalent of 103 m (i.e. 340 ft.) where visual evoked responses were recorded. No decrements in the amplitude of the visual evoked response were found at the LGN, but significant decreases did occur at the other three sites. These data suggested: 1) that the effects of nitrogen narcosis on the visual system are primarily central, and not simply peripheral in nature; 2) that these effects are not limited to the visual cortical mantle; and 3) that the narcosis apparently influences structures involving different anatomical levels of the brain which presumably mediate various types of visual processes. The findings were discussed as they relate to current ideas concerning the underlying neurological causes and behavioral effects of nitrogen narcosis.


Vertical vibration of seated subjects: effects of posture, vibration level, and frequency. The transmissibility of 12 seated subjects to sinusoidal vertical vibration was measured at 12 frequencies in the range of 7 to 75 Hz. Transmissibility, the ratio of seat vibration to vertical head vibration measured on a bite-bar, was determined at each of six levels of vibration (0.2 to 4.0 m/s2 r.m.s.) in two body postures. The postures were defined by the body positions that maximised and minimised the sensation of vibration at the subjects' heads. Measurements of the fore-and-aft (ax), lateral (ay), and pitch motions of the head were measured on three subgroups. Posture was found to have a very large effect on the vibration of the head with an approximate 6:1 difference in the mean vertical head vibration of the subjects between the two postures in the range 35 to 50 Hz. In both postures the mean transmissibility of the subjects decreased as frequency increased from 7 to 75 Hz and there were statistically significant reductions in transmissibility with increasing levels of vibration. Some results from individuals are presented to illustrate the large differences between subjects. The reactions of the subjects to the vibration are outlined and some implications of the results are discussed.


Electrical response of the eye at varying intervals following an adapting flash exposure. Electroretinograms (ERG) were recorded at varying intervals following an adapting flash exposure. Both amplitude and latency variations are exhibited for short interflash intervals. The ERG following the longer interflash intervals are not significantly different from the dark-adapted ERG. The relationship between the electrophysiological and psychophysical data is discussed.


Thermal fields and heat generation effects in tissue, awake and under halothane anesthesia. In order to further document the heat generation terms used in models predicting heat transmission in tissue, a series of temperature fields were generated and measured in cat brain with an implantable cylindrical source and thermocouple apparatus. The experimental technique allowed measurements to be made under fully awake in vivo conditions as well as for 3 to 45% levels of halothane anesthesia. Fields resulting from probe forcing function temperatures of 4 degrees C, 18 degrees C, and 28 degrees C were warmer in the anesthetized tissue indicating an increase in heat generation resulting from blood flow and metabolic heat. Values of the heat generation were obtained by applying the Bio-Heat Equation directly to the experimental data. A simple blood flow heat generation model gave a reasonable prediction of the heat generation in a temperature range lower than 3 to 4 degrees C below the inlet blood temperature, and with a Q10 equals 3 variation of blood flow rate with temperature. Results also indicate that the heat generation effect under halothane anesthesia conditions are such that the use of the apparent property concept in thermal modeling may not be valid.


Oxygen cost during exercise in simulated subgravity environments. Oxygen cost (VO2) and heart rate (HR) were determined during treadmill walking in simulated subgravity environments. The long axis of the subject's body was suspended parallel to the floor in a slow rotation room with feet aligned on the surface of a treadmill mounted 90 degrees on the wall. Without rotation, the subjects were virtually weightless against the treadmill; with centrifugation, environments of 0.25, 0.5 and 1 G were simulated. VO2 (open circuit) and HR (ECG) were measured during the 5th minute of walking at 3.2, 4.7 and 6.1 km/h. Similar measurements were also determined during walking at 1/2-G using the inclined plane technique. VO2 per unit mass and HR were significantly reduced in all subgravity environments. However, net VO2 per unit weight carried and, therefore, mechanical efficiency was found to be independent of gravity. This supports the idea that the most probable cause for the decreased O2 cost with reduced gravity is less body weight carried.


Comparisons of pilot performance in simulated and actual flight. Five highly experienced professional pilots performed instrument landing system approaches under simulated instrument flight conditions in a Cessna 172 airplane and in a Link-Singer GAT-1 simulator while under the influence of orally administered secobarbital (0, 100, and 200 mg). Tracking performance in two axes and airspeed control were evaluated continuously during each approach. The data from the airplane and simulator were compared. Error and RMS variability were about half as large in the simulator as in the airplane. The observed data were more strongly associated with the drug level in the simulator than in the airplane. Further, the drug-related effects were more consistent in the simulator. Improvement in performance suggestive of learning effects were seen in the simulator, but not in actual flight. It is concluded that the GAT-1 simulator is a useful and sensitive device for studies of the effects of mild stress on pilot performance, but extrapolation of simulator data to the flight environment must be approached with considerable caution.


Personality factors in selection and flight proficiency. Personality development is a dynamic process involving life forces, instinct drives, growth processes, life stresses, reactions to significant persons, both in and out of the family, and reactions to the environment in general, along with the mastery of methods and techniques for coping in solving problems and in providing for the satisfaction of one's needs. The love and fear of flying and the motivation and conflicts in flying involve many personality factors which deserve careful evaluation in selection of pilot and other flight personnel. These personality factors, variations, and traits also require close surveillance of pilot personnel by flight surgeons, aviation medical and operational personnel in predicting and preventing potential breakdown or difficulties and, more importantly, in the interest of maintaining optimum personnel effectiveness, proficiency, and safety in aviation.


Incident of pain with undetermined etiology in hypobaric chamber operations. On a routine, low-pressure chamber training flight to 25,000 ft (7,620.0 m/282.4 mm Hg), a subject experienced moderate to severe pain in the right hip while descending through an altitude of 9,500 ft (2,895.6 m/532.9 mm Hg). Standard operating procedures for dealing with such reactions were initiated resulting in the diminishing of symptoms as the chamber was reascended to an altitude of 12,000 ft (3,657.6 m/483.4 mm Hg). The symptoms reappeared upon descent through 7,500 ft (2286.0 m/575.6 mm Hg). After three relief attempts, descent was commenced at a rate of 1,000 ft/min (304.8 m/min), and the subject was asymptomatic at sea level. A subsequent reevaluation flight was scheduled for the following day and produced similar results. Medical evaluation produced no data that could be used to determine the etiology of this reaction that took place under hypobaric conditions.


Human factors in air force aircraft accidents. Advances have been made in the design and reliability of Air Force aircraft; however, there continues to be materiel failure accidents. The design of man has not changed, although training programs have been improved to reduce accidents caused by human error. This study was conducted to determine the human factors causation of aircraft accidents. A review of 545 aircraft accidents revealed that over 50% were caused by human error. These errors involved supervision, limited experience, and errors in judgment. Since materiel factors in accidents have remained relatively constant, more emphasis must be placed on training and selection of our aircrews and supervisors.


Preliminary results of examinations of rats after a 22-day flight aboard the Cosmos-605 biosatellite. The results of biomedical investigations carried out in flights of the Salyut and Skylab orbital stations give evidence that during prolonged weightlessness cosmonauts and astronauts remain in a good physical and mental condition. They fill specialists with optimism in regards to a further increase of the duration of manned space flights. In order to make reliable plans for such missions, it is necessary to accumulate detailed knowledge about the mechanism of the effect of weightlessness on different functions of the human body. In addition to manned experiments, of great interest are animal experiments. They may yield data that cannot be obtained in human studies, which is obviously very important from the point of view of space medicine. This was the purpose of the experiment carried out in November 1973 on the biosatellite Cosmos-605; 45 rats aboard the biosatellite flew for 22 d. Preliminary results of examinations of rats after a 22-d space flight in the Cosmos-605 satellite demonstrated not only physiological and biochemical but also morphological changes in the animal body due to prolonged weightlessness. These changes were reversible.


Independence of inherited susceptibility to spontaneous and printed audiogenic seizures in mice. The familial distribution of spontaneous and primed audiogenic seizures is independent in Binghamton HET mice. Spontaneous susceptibility may be attributable to homozygosity for asp (Collins and Fuller). A strong genetic influence on sensitivity to priming is also indicated.


Long-term maintenance therapy with azathioprine in systemic lupus erythematosus. One hundred ten patients with systemic lupus erythematosus (SLE) were classified into two groups, patients with central nervous system (CNS) or severe renal disease (usually associated with a poor prognosis) and patients without these manifestations, to define criteria for azathioprine therapy. Fifty-four of 68 patients with a poor prognosis received azathioprine. Azathioprine-treated patients showed improved long-term survival (72% vs 29%, P less than .005) and fewer hospitalizations (0.24/patient-years vs 0.89/patient-years, P less than .001). Azathioprine therapy in 19 of 42 patients with a good prognosis was associated with fewer hospitalizations (.02/patient-years vs .17/patient-years, P less than .05), but no decrease in maintenace prednisone requirement. Progression from a good to a poor prognosis was less frequent (1 of 20 vs 11 of 34, P = less than .05) among azathioprine-treated patients. Toxicity of azathioprine was minimal. Azathioprine therapy is indicated in patients with CNS or severe renal disease, and in patients whose prognosis was good with frequent hospitalizations or a maintenance prednisone requirement greater than 15 mg/day.


Dipeptidase activity in the small intestinal mucosa during pregnancy and lactation in the rat. 1. Rats were mated and at weekly intervals during pregnancy and lactation, and after weaning, the dipeptidase activity in the supernatant fraction from small intestinal mucosa extracts was determined for two dipeptides: glycyl-L-leucine dipeptidase (EC 3.4.3.2) AND L-alanyl-L-glutamic acid dipeptidase. 2. Dipeptidase activity is found mainly in the soluble (spernantant) fraction of the mucosa homogenate. 3. Compared with those values obtained for unmated controls, the food consumption of the animals and the nitrogen content, total and specific activities of the dipeptidases (per unit quantity of N) in the soluble fraction of the small intestinal mucosa extracts increased slightly during pregnancy and markedly during lactation. After the pups were weaned, values for all these measurements fell rapidly. 4. Whether the increases found in enzyme activity were simply a response to increased food intake or were the result of hormonal stimulus is discussed.


The arthritis of Sweet's syndrome.

The arthritis of Sweet's syndrome. A detailed evaluation of the articular manifestations of Sweet's syndrome is described in a 24-year-old man. Fever, mild leukocytosis, tender cutaneous erythematous plaques or nodules with neutrophilic infiltration were accompanied by multiple painful, swollen joints. A knee effusion contained 1,575 leukocytes with many large phagocytic cells. Since it may include significant articular disease, rheumatologists should be aware that this syndrome does exist.


Chondrocalcinosis in elderly persons.

Chondrocalcinosis in elderly persons. Fifty-eight elderly people were surveyed for chondrocalcinosis with knee, hip and pelvic roentgenograms using Type M industrial x-ray film. Chondrocalcinosis was found in 16 subjects (27.6%), an incidence greater than reported in previous studies. Roentgenograms of the knees alone showed the presence of chondrocalcinosis in 15 subjects. Varus deformity of the knees, increased wrist complaints and wrist involvement with clinical arthritis were significantly more common in subjects with chondrocalcinosis. Symptoms associated with acute inflammatory arthritis were not more common in people with chondrocalcinosis.


The effect of pregnancy and lactation on food intake, gastrointestinal anatomy and the absorptive capacity of the small intestine in the albino rat. 1. Food consumption, live weight, anatomical measurements on the gut organs and the absorptive capacity of the small intestine for L-leucine and D(plus)-glucose were made on virgin (control), pregnant and lactating albino rats. 2. Food intake increased by approximately 60% during pregnancy and a further 250% during lactation. 3. Pregnancy did not markedly influence the gross anatomy of the gastrointestinal tract. There was evidence for increased villus height and percentage water in the small intestine and for increased length of the colon during pregnancy. 4. During lactation, the alimentary canal progressively increased in weight and size. It partially regressed following weaning. 5. All anatomical measurements, except the length of the small intestine, completely regressed to control values within 20 d of weaning. The increased intestinal length had not completely regressed by day 30 post-weaning. 6. No significant change was observed in absolute absorption of glucose or leucine during pregnancy. 7. Absolute absorption of leucine and of glucose was increased during lactation. Greatest absorption occurred on the 10th day of lactation. 8. Results for absorption of leucine and glucose per unit length indicated that the ability of the mucosal cells to absorb or the number of absorptive cells/mm had changed during lactation and the post-lactation periods.


Seasonal and nutritional effects on serum proteins and urea concentration in the reindeer (Rangifer tarandus tarandus L.). 1. The effects of seasonal conditions and nutrition on serum proteins and serum urea concentrations were studied in female reindeer and reindeer calves in Finland. With the exception of one group in winter, the reindeer were roaming wild in the forests. This one group was kept in captivity, out of doors, on a comparatively high nutritional plane. One group lived wild during the winter in very poor nutritional conditions. 2. A very clear seasonal variation in the serum protein and urea concentration was found. The serum protein concentration was low in late winter and increased rapidly during the summer, being high in the autumn. The serum urea concentration was also low in the winter and high in the summer. In the autumn, however, the serum urea concentration was again low. 3. Changes in the serum protein concentration were normally associated with the serum globulins. Only in the very poor-nutrition group did the albumin content decrease significantly. As a result of the large changes in the concentration of serum globulins, there were also considerable changes in the albumin: globulin ratio. 4. The serum protein concentration was much lower in the reindeer calves than in the adult reindeer. The concentration of globulins in particular was much lower than in the adults.


Treatment of septic arthritis: comparison of needle aspiration and surgery as initial modes of joint drainage. Surgery and needle aspiraton have been evaluated as initial modes of drainage in 59 patients with acute septic arthritis. Full recovery was noted in 42% treated surgically at the outset. On the other hand, 67% of those treated by needle aspiration recovered without sequelae, despite the greater prevalence in this group of adverse host factor-eg, serious underlying illness, concommitant extraarticular infection, prior arthritis in the infected joint, and recent antibiotic or immunosuppressive therapy.


Therapeutic studies in NZB/W mice. III. Relationship between renal status and efficacy of immunosuppressive drug therapy. Female NZB/W mice develop a disease closely resembling human systemic lupus and serve as an animal model for therapeutic studies. Several previous studies have demonstrated the efficacy of different immunosuppressive drug regimens in the therapy of glomerulonephritis in NZB/W mice. After the onset of immune complex deposition, treatment with intermittent high doses of cyclophosphamide or daily low doses of the combination of cyclophosphamide, azathioprine, and methylprednisolone has been effective. The present study was designed to compare such effective regimens in mice early in the course of their renal disease versus mice late in the course of glomerulonephritis. One to three injections of high-dose cyclophosphamide during active immune complex deposition and early histologic changes were significantly effective in prolonging survival, whereas treatment late in the course of glomerulonephritis was less effective. Even more striking was the result of low-dose combination therapy. Daily treatment with cyclophosphamide, azathiprine, and methylprednisolone (C + A + M) effectively prolonged survival when started in mice 5 months old, but was of no benefit when started in those 8 months of age. In a concluding experiment, older mice were selected on the basis of degree of renal disease and studied with regard to proteinuria and survival. Those with mild renal disease responded to daily treatment for 6 months with C + A + M at 1 mg/kg of each drug, whereas those with advanced renal disease at the onset of therapy did not benefit.


The effect of retinol and retinoic acid on physiological and biochemical changes in retinol-deficient rats. 1. The effects of retinol and retinoic acid supplementation of retinol-deficient rats were studied for a variety of metabolic processes shown to be affected by retinol-deficiency. 2. Retinol-deficient rats were found to have decreased body-weight, liver and testes weights, a degeneration of testicular germinal cells, an increased incorporation of labelled choline into liver and testes phospholipids, an increased protein synthetic activity (in vitro) of liver ribosomes, an increased transfer-RNA methyltransferase activity in liver and a decreased activity in testes, an increased DNA content of testicular nuclei, and a decreased uptake of [3-H]thymidine by testicular nuclear DNA. 3. In retinol-deficient rats supplemented for 8 weeks with retinol these changes were reversed, measurements returning to control levels. 4. In retinol-deficient rats supplemented for 8 weeks with retinoic acid all changes were reversed except those in the testes. 5. Testicular signs of retinol deficiency appeared to be delayed when retinoic acid was added to the retinol-deficient diet of weanling rats. This suggests a sparing action of retinoic acid on the rat's utilization of retinol. 6. Suggestions are offered as to why retinoic acid will support growth and development but not spermatogenesis in the rat.


Jejunal absorption of an amino acid mixture simulating casein and an enzymic hydrolysate of casein prepared for oral administration to normal adults. 1. An intestinal perfusion technique was used in six normal human subjects to study absorption of sixteen individual amino acids from an amino acid mixture simulating casein and from an enzymic hydrolysate of casein, prepared for oral administration to these subjects, which consisted of a mixture of oligopeptides and free amino acids. 2. Total absorption of alpha-amino nitrogen was greater from the casein hydrolysate than from the amino acid mixture, and the considerable variation in percentage absorption of individual amino acids from the amino acid mixture was much reduced when the enzymic hydrolysate solution was perfused, as a number of amino acids which were poorly absorbed from the amino acid mixture were absorbed to a greater extent from the casein hydrolysate. 3. These findings indicate that after extensive intestinal resections or in malabsorption there might be significant nutritional advantages in the administration of protein hydrolysates rather than amino acid mixtures.


Maintenance requirements for energy in cross-bred cattle. 1. Twenty-seven energy and protein balances were done using nine cross-bred (Brown Swiss times Sahiwal) mature bullocks in a series of three balance trials. The bullocks were fed 75, 100 and 125 percent of the metabolizable energy (ME) and digestible crude protein standard values recommended by the (US) National Research Council (1966). Heat production was estimated by indirect calorimetry, by collection and analysis of respiratory gases. 2. Utilization of energy for maintenance and fat production was estimated by computing regression of energy balance v. digestible energy (DE) and ME separately on a metabolic body size (kg body-weight (W)0-75) basis. Maintenance energy requirements and efficiency of utilization of ME for lipogenesis were estimated using multiple regression of ME intake, also. Heat production (and thus energy balance) was corrected for excess nitrogen intake. 3. An attempt was made to measure basal heat production of bullocks so that the net energy requirements for maintenance could be estimated. Extrapolation of the regression line of energy balance v. ME intake below maintenance on a W0-75 basis gave a basal metabolism of 348-09 kJ/W0-75 per d. 4. Energy requirements for maintenance were (kJ/kg W0-75 per d): 539-43 DE, 448-81 ME and 348-09 net energy. The results of multiple regression gave a requirement of 432-15 kJ ME/kg W0-75 per d for maintenance. 5. The efficiency of utilization of ME for maintenance was 81-34 percent while for lipogenesis it was 54-5 percent.


Anthropometric measurements and amounts of body fat and serum cholesterol in samples of three Nigerian populations. 1. Skinfold thicknesses, arm circumferences, heights, weights and serum cholesterol levels were determined in ninety-one university students, 207 soldiers and 102 out-patients, all male subjects. Some of these measurements were used to determine the amount of body fat, Quetelet's index and mid-arm muscle circumference. 2. Quetelet's indices and body-fat values obtained were similar to previously reported values for lean or moderately built males. 3. Serum cholesterol levels were generally low, with means ranging from 3-98 mmol/l for 18-to 29-year-old students to 5-19 mmol/l for 40- to 69-year-old out-patients. 4. The mean values for triceps skinfold thickness, the amount of body fat and serum cholesterol levels for healthy adults obtained in this study are probably normal for northern Nigerian populations. 5. There was a significant correlation between the amount of body fat and values for triceps and subscapular skinfold thicknesses, Quetelet's index and body-weight for all adults. The correlation between muscle circumference and the amount of body fat was significant for all subjects except adult soldiers.


Concentrations of amino acids and urea in the plasma of the preruminant calf and estimation of the amino acid requirements. 1. A study was made of factors affecting the plasma concentrations of free amino acids (PAA) and urea (PU) in calves receiving liquid diets. 2. When calves were given whole milk (approximately 0-05 kg/kg live weight) at 10.00 and 17.00 hours there were marked decreases in PAA and slight decreases in PU for about 3-4 h after the morning feed. Both PAA and PU thereafter increased slightly and then remained constant for the next 10 h. In subsequent comparative experiments samples were taken 3 h after the morning feed. The variation in plasma methionine, isoleucine, leucine, phenylalanine, tyrosine and total PAA was apparently greater between than within animals. 3. In calves transferred from a diet of whole milk to one consisting of diluted whole milk supplemented with appropriate nutrients, including amino acids, but deficient in methionine, PU increased markedly and plasma methionine decreased. 4. Two calves (50-60 kg live weight) given the latter diet supplemented to give an intake of more than 4-5 g L-methionine/d together with 0-3 g cystine/d showed marked increases in plasma methionine. This was considered to correspond with the point at which methionine requirements were met and that under these conditions the methionine requirement for these calves (mean value plus or minus SE) was 4-5 plus or minus 0-2 g/d. In the same two calves PU decreased markedly with increasing levels of methionine supplementation up to 3-9 g/d and the estimated methionine requirement (mean value plus or minus SE) was 3-9 plus or minus 0-4 g/d.


The effect of pelleting on the voluntary intake and digestibility of leaf and stem fractions of three grasses. 1. Leaf is eaten in greater quantities than stem of similar digestibility. To determine whether this difference is caused by physical or chemical factors, leaf and stem fractions from Digitaria decumbens, Chloris gayana and Setaria splendida were fed ad lib, to sheep in the chopped and pelleted forms. Pellets were made from leaf and stem which had been ground through a screen with 3 mm holes. All sheep received a protein and mineral supplement. 2. Voluntary intake of chopped leaf was 34 percent higher than that of the chopped stem fraction (40-3 and 30-0 g/kg body-weight 0-75 respectively, P smaller than 0.01) although dry matter digestibility ratios were similar (0-478 and 0-450 respectively, P greater than 0-05). The higher intake of leaf was associated with a larger surface area (13 400 and 5200 mm2/g for chopped leaf and stem respectively), lower bulk density (60 and 180 kg/m3 respectively) and lower neutral-detergent fibre (706 and 724 g/kg respectively), acid-detergent fibre (383 and 413 g/kg respectively) and lignin (42 and 59 g/kg respectively) contents. Chopped leaf was retained in the reticulo-rumen for a shorter time than the stem fraction (19.9 and 26.4 h respectively). 3. Grinding and pelleting increased the voluntary intake of the leaf fraction by 88 percent and the stem fraction by 60 percent. This increased voluntary intake caused by grinding and pelleting was not accompanied by any significant changes in the chemical composition of the diet. Grinding and pelleting reduced the time that the food was retained in the reticulo-rumen and this change appeared sufficient to account for the observed increases in voluntary intake. 4. It was concluded that the higher intake of the leaf fraction of grasses is caused by differences in retention time of food in the reticulo-rumen. These differences in retention time are caused by differences in physical properties and not chemical composition.


The response of hind-limb muscles of the weanling rat to undernutrition and subsequent rehabilitation. 1. Weanling male rats were maintained at constant body-weight for 28 d by feeding them reduced amounts of their normal diet. They were rehabilitated for 0, 3, 7, 10 or 16 d, and compared with two sets of control groups, one set of the same body-weight and the other of the same age. 2. The quadriceps, gastrocnemius and anterior tibialis muscles from the left hind-limb were weighed, and DNA, RNA, extracellular protein and intracellular protein estimated in the quadriceps and gastrocnemius muscles. 3. Each muscle responded differently during undernutrition and rehabilitation if compared with "age controls", but if compared with "body-weight controls" there was a tendency for muscle weight to remain appropriate for body-weight. 4. The amount of DNA did not change in the gastrocnemius or quadriceps muscles during undernutrition, and on rehabilitation did not begin to increase until after 7 d. RNA decreased during undernutrition, but increased rapidly on rehabilitation. The rate of increase in RNA was greatest in the quadriceps during the first 3 d, but in the gastrocnemius was greatest between 3 and 7 d. The peak values for the rate of RNA increase corresponded with the initiation of intracellular protein accretion in each muscle. Extra cellular protein increased during undernutrition, and on rehabilitation, responded in the same way as DNA, that is, it increased only after 7 d. 5. It is concluded that the differences found between muscles of the hind-limb during rehabilitation are due mainly to differences in the rates of DNA and intracellular protein accretion. It is suggested that these differences are the result of a differential response of RNA to rehabilitation.


Acute cold exposure and the metabolism of blood glucose, lactate and pyruvate, and plasma amino acids in the hind leg of the fed and fasted young ox. 1. Young steers were fed either 3-4 or 20 h before exposure to a thermoneutral or a moderately cold environment. Measurements were made of total oxygen consumption (total V 0-2), respiratory quotient (rq), blood packed cell volume (PCV), and hind-leg blood flow (leg Q) and oxygen uptake (leg VO-2). The arteriovenous differences in whole blood glucose, lactate and pyruvate, and individual amino acid and urea concentrations across the leg were also measured. Net exchange and fractional uptake of these metabolites by the leg were calculated from these results. 2. Cold exposure doubled total VO-2, significantly decreased RQ and significantly increased PCV. Leg Q and leg VO-2 increased 3- to 5-fold and 4- to 13-fold respectively in both feeding groups. Arterial blood glucose increased slightly but significantly in both 20 h- and 3 h-fed steers. There was a substantial increase in mean net leg uptake of glucose in both feeding groups. This was much greater in the 20 h-fed group because of the significant increase in fractional uptake occurring only in this group. Cold did not significantly affect arterial blood lactate or pyruvate levels, but the net leg output of lactate found in both feeding groups in thermoneutrality was increased in the 20 h-fed steers, and reversed to a net uptake in the 3 h-fed animals. Cold caused a small but significant decrease in the total plasma amino acid level in the 20 h-fed but not in the 3 h-fed group; individual amino acid levels or leg uptakes were not affected. 3. Feeding before the experiment caused a significant increase in RQ. Leg Q, leg uptake of glucose and leg output of lactate increased after feeding in the thermoneutral environment only. Arterial pyruvate increased significantly, but net leg output was not significantly affected by feeding. Arterial plasma concentration of several individual, but not of total amino acids, increased significantly in both environments, and the net output of many individual amino acids in the 20 h-fed steers was decreased or reversed to a net uptake in the 3 h-fed group in thermoneutrality only. 4. The results suggest that blood glucose could be a significant fuel for oxidation in shivering skeletal muscle in young steers, and that output of amino acids from skeletal muscle could not contribute significantly to this increased glucose supply by hepatic gluconeogenesis.


Studies on the nutrition of marine flatfish. The metabolism of glucose by plaice (Pleuronectes platessa) and the effect of dietary energy source on protein utilization in plaice. 1. The effects of dietary energy level and dietary energy source on protein utilization by plaice (Pleuronectes platessa) were examined by giving diets containing 400 g crude protein/kg to nine groups of fish. Five of these diets contained only lipid as a source of energy (in addition to protein) and their energy contents were varied by increasing the lipid level in a step-wise manner from 56 to 176 g/kg. The remaining four diets contained both lipid and carbohydrate (glucose plus dextrin) together as energy sources: two levels of carbohydrate (100 and 200 g/kg) being used at each of two (56 and 86 g/kg) lipid levels. 2. Weight gains of plaice given the diets containing only lipid as an energy source did not differ significantly from each other. Weight gains of plaice given diets containing carbohydrate as well as protein and lipid were superior to those given diets lacking carbohydrate. 3. Values obtained for protein efficiency ratio (PER) and net protein utilization (NPU) increased with increasing dietary energy level in both those fish given the diets containing carbohydrate and those given diets lacking it. Both PER and NPU values were greater for plaice given diets containing carbohydrate than for fish diets without carbohydrate even when the total energy content of the diets was approximately the same. 4. Liver glycogen levels were significantly higher in plaice given diets containing 200 g carbohydrate/kg than in plaice given diets without carbohydrate. Blood glucose levels and hepatic hexokinase (EC 2-7-1-1) levels were not significantly different in plaice given these diets. No glucokinase (EC 2-7-2-2) was detected in plaice given either diet. 5. The metabolic fate of glucose carbon in plaice was investigated by injecting the fish intraperitoneally with [U-14C] glucose and examining, 18 h afterwards the distribution of radioactivity in different biochemical fractions from the fish. 6. Glucose was respired much less rapidly in the carnivorous plaice, irrespective of dietary treatment, than in omnivorous mammals (mouse and rat). The rate of production of 14CO2 from (U-14C) glucose by plaice given diets containing carbohydrate was not significantly greater than that by plaice given diets lacking carbohydrate. 7. More glucose was incorporated into liver glycogen when plaice were given carbohydrate in their food than when it was absent. Otherwise no differences were apparent in the fate of glucose C by plaice which could be related to the diets used. 8. No mortalities occurred nor was any histopathology observed in the plaice as a consequence of the inclusion of carbohydrate in the food.


Twelve generations of marginal protein deficiency. 1. Colonies of rats have been maintained for twleve generations on diets adequate (dietary protein energy: total metabolizable energy (NDp: E) 0-1) or marginally deficient in protein (NDp: E 0-068). 2. In the malnourished colony, the proportion of "small-for-gestational-age" offspring was ten times as high as amongst the well-nourished colony, growth was slow, sexual maturation delayed, especially in the females, and, when adult, both sexes were significantly lighter and shorter than adults of the well-nourished colony. Organs, other than the eye, weighed less than those of well-nourished "age" controls, but when expressed relative to body-weight, the brain, pituitary, thyroid, adrenals, testes, thymus and eyes were larger, the pancreas unchanged and the kidneys smaller than those of the well-nourished "age" controls. The relative weight of the liver showed little change, being slightly increased in the males and, like the ovaries, slightly reduced in the females. On a body-weight basis, the brains were about 50 percent heavier than normal, but in absolute terms were 5-5-5 percent lighter than those of the well-nourished animals, the cerebellum (10-5 percent lighter in males and 12-9 percent lighter in females) being more severely affected than the cerebrum (4 percent lighter). 3. The young malnourished rats showed increased exploratory activity, transient head tremors and an increased sensitivity to noises, the latter being long-lasting if not permanent. When adult, they showed marked differences in behaviour and learning patterns and it was difficult to attract and hold their attention. In situations demanding a choice the animals were very excited, emitted loud squeals and tried to escape from what was clearly a stressful situation. However, a casual examination of the malnourished adults revealed a rather small, badly groomed, excitable rat without gross abnormalities. 4. The findings are discussed in relation to changes found in malnourished human communities.


Nutritional studies on East African herbivores. 2. Losses of nitrogen in the faeces. 1. A series of nitrogen-balance trials was done using groups of four animals of various species of wild and domesticated ruminants using pelleted diets (Arman & Hopcraft, 1975). 2. Various herbivores were given grass or grass hays, legumes, herbs and shrubs. Food and faecal samples were analysed for N. 3. With the pelleted diets, the N content of the faecal dry matter (DM) was low for eland (Taurotragus oryx Pallas), high for sheep and cattle (Bos taurus and Bos indicus) and intermediate for the three small antelope species (hartebeest (Alcelaphus buselaphus cokei Günther), Thomson's gazelle (Gazella thomsonii Günther) and duiker (Sylvicapra grimmia L.)). With the natural doffers, similar relationships were found, together with variations associated with the type of diet. 4. Three forms of equation were used to express the relationship between faecal N and food N. One of the forms, the linear regression of g faecal N/kg DM intake v. g food N/kg DM  intake, fitted the results less well than did the other two and was not used to estimate metabolic faecal N(MFN) losses9 5. MFN was calculated by extrapolation of linear regressions of g faecal N/kg faecal DM v. g N intake/kg faecal DM for the pelleted diets. The range of values was (g N/kg faecal DM): Friesians 7-6, eland 8-1, zebu cattle 11-0 and small antelope and sheep 11-5-12-69 There were significant differences (P smaller than 0-001) between species in slopes and intercepts. 6. MFN was calculated from linear regressions of g faecal N/kg faecal DM v. g food N/kg food DM for all diets. This method gave the best fit for the pelleted diets. Values for these diets were (g N/kg faecal DM): eland 8-3, cattle and sheep 9-3-11-0 and small antelope 11-6-12-3. Species differences were significant (P smaller than 0-001). With grasses, values ranged from 5-9 for non-ruminants (rabbit (domesticated), warthog (Phacohoerus aethiopicus Pallas) and hippopotamus (Hippopotamus amphibius L.)) plus eland and wildebeest (Connochaetes taurinus Burchell), to 8-4 for for the other ruminants (sheep, goat, hartebeest, gazelle, duiker, buffalo (Syncerus caffer Sparrman)), kob (Adenota kob thomasi Sclater), reedbuck (Redunca redunca Pallas) and topi (Damalisucs korrigum Ogilby). For ruminants (sheep, hartebeest, duiker and kob), excluding eland, given legumes the value was 8-6, and for sheep and duiker given herbs the value was 14-7. With shrubs, faecal-N losses were variable and sometimes high. 7. With the pelleted diets, true digestibilities of crude protein (N times 6-25) varied from 0-84 to 0-91. 8. The results are discussed in relation to the digestive physiology and feeding habits of the various species, and there is an examination of the feasibility of using linear regressions of crude protein in the diet v. N in the faecal DM for evaluating the quality of the diets selected by free-ranging East African herbivores.


Synthesis and conformational studies in solution of sequential copolypeptides: poly(L-prolyl-L-alpha-phenylglycyl-L-proline). High molecular weight poly(L-porlyl-L-alpha-phenylglycyl-L-proline) was synthesized by condensation of L-prolyl-L-alpha-phenylglycyl-L-proline pentachlorophenyl ester in N,N-dimethylformamide. The solution properties of this material have been investigated by circular dichroism and 220-MHz nuclear magnetic resonance spectroscopy in solvents such as trifluoroethanol (F3EtOH), chloroform, trifluoroacetic acid (F3CCOOH), chloroform-F3CCOOH and F3EtOH-F3CCOOH mixtures. Ordered structures can be formed in F3EtOH and chloroform, which we believe to be similar to the poly-L-proline II form. The ordered form easily undergoes a conformational transition to an unordered form upon addition of small amounts of F3CCOOH to the chloroform solution. The ordered structure is not disrupted upon addition of 12 per cent F3CCOOH to a F3EtOH solution of the polypeptide.


Hydrogen bonding abilities of 2,4-dithiouridine derivatives. The base pairing ability of a di-2,4-thiouridine derivative was studied in carbon tetrachloride solutions by the methods of infrared spectroscopy. The strength of the association by hydrogen bonding was found to decrease in the following order: adenine-uracil, adenine-di-2,4-thiouracil, uracil-uracil, and di-2,4-thiouracil-di-2,4-thiouracil. These findings contrast with the previously demonstrated fact that poly(s2s4U) is strongly self-associated and does not form a complex with poly(A). To correlate these results, it is proposed that long range stabilizing forces are acting between the di-2,4-thiouracil residues in polynucleotide chains. This assumption also explains the existence of an ordered structure in the alternating copolymer poly(s2s4U-A).


Conversion of an androgen epoxide into 17beta-estradiol by human placental microsomes. Three androgen epoxides, 17beta-hydroxy-4beta,5-oxido-5beta-androstan-3-one (II), 3beta,19-dihydroxy-5,6beta-oxido-5beta-androstan-17-one 3-acetate (VIII), and 19-hydroxy-4beta,5-oxido-5beta-androstane-3,17-dione (V), were synthesized and subsequently evaluated as potential precursors in the biosynthesis of estrogens by incubation with human placental microsomes. One of these epoxides (V) was converted into 17beta-estradiol, whereas the other two were metabolized to unidentified products. The possible intermediacy of an androgen epoxide in the biosynthesis of estrone and of 17beta-estradiol is discussed and a mechanism is proposed for the aromatization process.


Modification of the cysteine residue of streptococcal dihydrofolate reducatse. Modification of the single cysteine residue of streptococcal dihydrofolate reducatase with 5,5'-dithiobis (2-nitrobenzoic acid) results in virtually complete inactivation of the enzyme. Reduction of the enzyme-S-nitrobenzoate mixed disulfide with dithiothreitol indicates that 1.0 cysteine has been modified and approximately 70 percent of the original enzyme activity restored. Circular dichroic and fluorescence studies suggest that a localized conformational change involving aromatic residues, possibly tryptophan, has occurred following modification. In addition, nearly stoichiometric amounts of p-hydroxymercuribenzoate lead to complete inactivation of the reducatas. It is suggested that the S-nitrobenzoate moiety bound to the cysteine residue of the enzyme may perturb one or more aromatic side chains and lead to a distortion of the hydrophobic substrate binding site.


Studies on the kinetic mechanism of S-adenosylmethionine: protein O-methyltransferase of calf thymus. Initial velocity studies have been carried out on protein methylase II (S-adenosyl-L-methionine:protein O-methyltransferase, EC 2.1.1.24) purified from calf thymus, using bovine pancreatic ribonuclease as the protein substrate. Initial velocity patterns converging at a point on or near the extended abcissa were obtained with either ribonuclease or S-adenosyl-L-methionine as the variable substrate. Inhibition by the product S-adenosyl-L-homocysteine was linear competitive against both S-adenysyl-L-methionine and ribonuclease, the apparent inhibition constants being dependent on the concentration of the nonvaried substrate. Adenosine was an inhibitor of the reaction, the inhibition being linear competitive against both S-adenosyl-L-methionine (Ki/1.2 times 10-3 mol/1.) and ribonuclease (Ki/4.6 times 10-3 mol/1.). These results are consistent with a random mechanism for the protein methylase II reaction in which the rate-limiting step may be the interconversion of the ternary complexes and all other steps may be in equilibrium. The limiting Michaelis constants for S-adenosyl-L-methionine and ribonuclease are 0.87 times 10-6 and 2.86 times 10-4 mol/1., respectively. The dissociation constants of S-adenosyl-L-homocysteine for its reaction with the free enzyme was 1.03 times 10-6 mol/1. Thus it has about equal affinity for calf thymus protein methylase II as S-adenosyl-L-methionine.


Functional properties of chemically modified hemocyanin. Fixation of hemocyanin in the low and the high oxygen affinity state by reaction with a bifunctional imido ester. Hemocyanin of Helix pomatia is a respiratory protein with a molecular weight of 9 times 10-6; it contains 180 oxygen binding sites. The reaction of hemocyanin with the bifunctional reagent dimethyl suberimido ester, which reacts with amino groups, has been studied. Up to 75 per cent of the amino groups can be modified without inactivation of oxygen binding sites or dissociation of the protein, It appears that hemocyanin can be fixed in a state with low oxygen affinity by modification of the deoxy protein, and in a state with high oxygen affinity by modification of the oxy protein. Using conditions under which native hemocyanin binds oxygen cooperatively (Hill coefficient 2.9), modification of deoxy- and oxyhemocyanin yields derivatives with different oxygen affinities (P50 equals 10  and 2.2 mm, respectively). Both the deoxy and oxy derivatives show strongly reduced cooperativity (Hill coefficients 1.4 and 1.1, respectively). Modification of oxy- and deoxyhemocyanin subunits (molecular weight one-tenth of the native protein), which bind oxygen noncooperatively, results in derivatives with oxygen binding properties identical with those of unmodified subunits. Parallel experiments have been carried out with a unifunctional reagent, methyl acetoimido ester. Modification of partially oxygenated hemocyanin under conditions at which the protein binds oxygen cooperatively yeilds derivatives with redued cooperativity (Hill coefficents 1.1-1.2) and an oxygen affinity depending on the oxygen saturation whivh modification had been carried out. The results are consistent with a simple two-state model for the cooperativity of oxygen binding by these giant hemocyanin molecules.


Neutral and Cationic Sulfonamido Derivatives of the Fluorescent Probe 2-p-Toluidinylnaphthalene-6-sulfonate. Properties and Mechanistic implications. The sensitivity of the fluorescence energy of 2-p-toluidinylnaphthalene-6-sulfonate (TNS) to apparent solvent polarity is considerably greater in methanol-water mixtures and lower primary alcohols than in higher primary alcohols or solvents containing no hydroxyl groups. It is suggested that the behavior of TNS in lower alcohols and their mixtures with water is an anomalous result of the combination of general polarity influences and chanes in the nature of specific interactions of the probe with hydroxyl groups of such solvents. Upon conversion of the sulfonate group of TNS to sulfonamido, the biphasic behavior observed in alcohols is eliminated, and fluorescent probes are obtained which have more nearly equal sensitivites to polarity in the alcohols and nonhydroxyl solvents. The sulfonamido fluorescent probes are more sensitive to general environmental polarity than TNS, and are superior as probes of environmental polarity.


Hybridization of ribosomal RNA labeled to high specific radioactivity with dimethyl sulfate. RNA radioactively methylated with dimethyl sulfate has the advantage of relatively low background noise level when utilized in DNA saturation hybridization employing the membrane filter technique. In addition, the RNA can be methylated with either 3H- or 14C-labeled methyl groups. However, the low specific radioactivity usually obtained with dimethyl sulfate has limited the use of this labeling technique. We describe a detailed characterization of the methylation of rRNA with dimethyl sulfate giving specific radioactivities on the order 10-5 cpm/mug. Kinetics and optimum conditions for the methylation reaction of rRNA were studied. The methylation did not cause excessive degradation of RNA in neutral aqueous solution, and the methyl derivative of RNA was stable under normal hybridization conditions. Specific radioactivitiy of the methylated RNA was found to be a linear function of the product of RNA concentration and specific radioactivity of the dimethyl sulfate in the reaction mixture at a constant incubation time. The methylated bases of the RNA lowered the thermal stability of the DNA-RNA hybrids by 1 degree in Tm per 1.6 per cent methylated RNA bases. rRNA gene dosage values using high specific radioactive methylated RNA were found to be 81 and 180 genes/haploid genome, respectively. Dissociation constants of the hybridization reaction ranged from 0.90 times 10-10 to 2.37 times 10-10 M.


Mechanism of hemin inhibition of erythroid cytoplasmic DNA polymerase. Hemin, which has an important role in the regulation of hemoglobin synthesis, also regulates the activity of cytoplasmic DNA polymerase from erythroid hyperplastic bone marrow cells and reticulocytes. Hemin inhibits DNA synthesis by binding reversibly to the enzyme. Binding assays demonstrated that hemin prevents association and causes dissociation of the DNA-enzyme complex. This is in contrast to inhibitory compounds that specifically interact with DNA such as ethidium bromide and daunomycin which have little or no effect on the DNA polymerase-template complex. Kinetic analysis reveals that hemin inhibition of DNA synthesis is competitive with respect to template and noncompetitive with respect to substrate. The inhibitory effect of hemin can be reversed by subsequent addition of globin, indicating that the inhibition of DNA synthesis by hemin is not due to irreversible inactivation of the enzyme.


Phosphatidylglycerol in rat lung. I. Identification as a metabolically active phospholipid in isolated perfused rat lung. Isolated rat lungs when perfused for 2 hr with [U-14]glucose, [2-14C]lactate, or [u-14]acetate, were found to contain a phos pholipid which represented a small percentage of the total phospholipid (3.9 per cent), and possessed the highest specific activity of any phospholipid. Using chromatographic, chemical, and mass spectral analysis, the phospholipid has been identified as phosphatidylglyercol. When [2-14C]lactate was present in the perfusion medium, 15.3 per cent of the lactate incorporated into phospholipids was incorporated into phosphatidylglyerol with a relative specific activity of 5.1 compared to phosphatidylcholine, 1.0, and phosphatidylethanolamine, 0.5. Phosphatidylglycerol also had the highest specific activity when lungs were perfused with [1-14C]acetate and [U-14]glucose. While the significance of the content and apparent metabolic activity of phosphatidylglycerol are unknown, its possible role in stabilizing the surfactant complex of lung is discussed.


Evidence that the major cell suface glycoprotein of the TA3-Ha carcinoma contains the Vicia graminea receptor sites. The Vicia graminea lectin receptor of the nonstrain-specific TA3-Ha mammary carcinoma ascites cell of the strain A mouse was shown to be predominantly or exclusively on a large mucin-type surface glycoprotein. TA3-Ha cells adsorbed the lectin in amounts equivalent to 5-9 mg of this glycoprotein/10-9 cells, which was 100-400 times greater than by the strain-specific TA3-St cell, employed as a control. Release of sialic acid by incubation with neuraminidase increased the adsorptivity of the TA3-Ha cell three to fourfold and of the TA3-St cell six- to ten fold. Proteolysis of TA3-Ha cells released into the supernatant solutions approximately the same amount of inhibitory activity, equivalent to approximately 5 mg of the glycoprotein and only 10 per cent of the original adsorptivity remained on the cells. By contrast, TA3-St cells released no detectable inhibitory activity into the medium when subjected to similar proteolysis, even after neuraminidase treatment. Upon fractionation of released material on gel columns, high-molecular weight material and activity were found in the same fractions, but purified samples differed significantly in specific activity and carbohydrate composition. Heterogeneity in the carbohydrate moieties of the macromolecules was further demonstrated by incubation of these samples with neuraminidase, which enhanced their inhibitory activities from two- to tenfold.


Oxygen consumption of human blood platelets. I. Effect of thrombin. The effect of thrombin on the oxygen consumption of washed human platelets was measured polarographically with the Clark oxygen electrode. The average basal respiratory rate was 18 plus or minus 1.6 (mean plus or minus S.E.) natoms oxygen per min per 10-9 platelets. Thrombin (1.9 units/ml) caused a 4-13-fold increase in the rate of oxygen consumption (138 plus or minus 14 (mean plus or minus S.E.) natoms oxygen per min per 10-9 platelets). The thrombin-stimulated increase of oxygen consumption was transient, lasting from 1 to 1.5 min before returning to the respiratory rate observed before the thrombin addition. Release of platelet constituents appeared to precede the stimulation of oxygen consumption. These results may provide a basis for explaining the discrepancy in the literature concerning the effects of thrombin on platelet respiration.


Oxygen consumption of human blood platelets. II. Effect of inhibitors on thrombin-induced oxygen burst. The effect of selected inhibitors on the thrombin-stimulated burst and the basal oxygen consumption of washed human platelets were investigated and compared with inhibition of the release reaction. Cyanide (0.2 mM) caused complete inhibition of the basal respiration, but only 15% inhibition of the thrombin-stimulated burst of oxygen consumption. Similar differential inhibitory effects were observed with oligomycin, antimycin, rotenone and N-ethylmaleimide. Prostaglandin E1 (0.03 mM) and acetylsalicylic acid (0.8 mM) had little effect on basal respiration, but inhibited the thrombin-stimulated burst of oxygen consumption. N-Ethylmaleimide (0.4 mM) inhibited the release of calcium from platelets by 90%, while prostaglandin E1, acetylsalicylic acid and the above mitochondrial inhibitors caused no more than 30% inhibition of the release reaction. Our results provide evidence that basal respiration and a portion of the thrombin-stimulated burst of oxygen consumption are involved in respiratory chain phosphorylation, and that this component of the thrombin-stimulated burst may be coupled to the maintenance of the release reaction.


Study of the chlorophyll fluorescence in chloroplasts and algae with the plastoquinone antagonist dibromothymoquinone. The effect of the plastoquinone antagonist dibromothymoquinone on chlorophyll fluorescence in vitro and in vivo was investigated. 1. With chlorophyll a in solution quenching is observed, more efficient than that of p-benzoquinone (the Stern-Volmer constant K equals to 200 M-1); ascorbate removes this effect. 2. With isolated chloroplasts, a dramatic enhancement of quenching occurs (also abolished by ascorbate) in the following order of importance: thermal step, photochemical step (of variable fluorescence), and constant fluorescence; K for the total variable fluorescence approximately equal to 480 000 M-1, for constant approximately equal to 190 000 M-1. Parallel to the quenching effect, an enlargement of the complementary area of the variable fluorescence is observed. Addition of ascorbate suppresses the quenching and this enlargement. If this area in the presence of reduced dibromothymoquinone is similar to that of the control, this means that A, the pool of oxidant next to Q, remains connected to it, a result contradicted by the O2-burst measurement. However, when the excess of unbound dibromothymoquinone is washed out, which removes the quenching effect, a significant decrease of the area is seen, in agreement then with the burst results. Therefore, the meaning of the complementary area and the nature of the controlling factors may be questioned. 3. With whole cells (Chlorella), no quenching is observed; instead, an enhancement of the thermal step is noticed, together with an even larger increase of the complementary area. Dibromothymoquinone being in an oxidized form at the thylakoid level, it is proposed that in intact membranes, the chlorophyll molecules are not readily accessible to it: thus, no quenching is observable, and the predominant effect is on the redox chain. The specific effect of dibromothymoquinone on the thermal step supports the hypothesis that is normally controlled by a secondary quencher, related to plastoquinone.


Energy transfer by chlorophyll a in detergent micelles. The process of energy transfer was studied in the chlorophyll a-containing detergent micelle, serving as a possible model of the photosynthetic unit. Chlorophyll a was added to aqueous solutions of the detergent Triton X-100 and incorporated into the micelles. The energy transfer process was studied by investigating the concentration depolarization of fluorescence of chlorophyll a. On the basis of the experimental depolarization curves as well as the value of the Förster parameter Ro equals to 56 A calculated from the overlap of absorption and fluorescence spectra it was concluded that energy transfer between chlorophyll a molecules in this model follows the Förster-type mechanism of inductive resonance. Furthermore it was found that the local concentration of chlorophyll a in the micelles is higher by 1-3 orders of magnitude than its overall concentration in the solution and by choosing the appropriate ratio between the consentration of chlorophyll a and the detergent it is possible to reach the in vivo chlorophyll concentration of 0.1 M withing the micelles. Thus the chlorophyll-detergent micelle model may be applied as a model of the separate package-type photosynthetic unit.


Further results on the photoactive chlorophyll aII in photosynthesis. 1. The flash-induced difference spectra of chlorophyll aII in untreated and in heat-treated spinach chloroplasts are presented. 2. Heat-treatment leads to an increase of the half-life of the chlorophyll aII absorbance changes. After the addition of hydroquinone plus sodium ascorbate the half-life of the chlorophyll aII reaction returns nearly to the value in untreated chloroplasts. 3. In digitonin-treated chloroplasts, or in the presence of histone, the chlorophyll aII activity is low when the electron acceptor is benzylviologen and high when ferricyanide is used. 4. The half-life of the chlorophyll aII reaction depends on the temperature of the reaction mixture. The activation energy of the chlorophyll aII reaction is about 7.5 kcal/mol. 5. From the experimental results we conclude that in heat-treated (and in Tris-washed and aged) chloroplasts the linear electron flow in Photosystem II is replaced by a cyclic one, which is sensitive to 3-(3,4-dichlorophenyl)-1,1-dimethylurea.


Light-induced absorbance changes due to photosystems 1 and 2 in spinach chloroplasts at minus 50 degrees C. Absorbance changes in the region 500-565 nm and at 702 nm, brought about by excitation of Photosystems 1 and 2, respectively, were measured in spinach chloroplasts at minus 50 degrees C. Either dark-adapted chloroplasts were used or chloroplasts preilluminated with a number of short saturating flashes just before cooling. Both photosystems were found to cause a light-induced increase of absorbance at 518 nm (due to "P518"). The System 1-induced change was not affected by pre-illumination. It decayed within 1 s in the dark and showed similar kinetics as P700. Experiments in the presence of external electron acceptors (methylviologen or Fe(CN)6-3-) suggested that P518 was not affected by the redox state of the primary electron acceptor of System 1. The absorbance increase at 518 nm due to System 2 decayed in the dark with a half-time of several min. The kinetics were similar to those of C-550, the presumed indicator of the primary electron acceptor of System 2. After two flashes preillumination the changes due to P518 and C-550 were reduced by about 40%, and a relatively slow, System 2-induced oxidation of cytochrome b559 occurred which proceeded at a similar rate as the increase in yield of chlorophyll a fluorescence. The results indicate that at minus 50 degrees C two different photoreactions of System 2 occur. One consists of a photoreduction of the primary electron acceptor associated with C-550, accompanied by the oxidation of an unknown electron donor; the other is less efficient and results in the photooxidation of cytochrome b559.


Induction kinetics of delayed light emission in spinach chloroplasts. Induction curves of the delayed light emission in spinach chloroplasts were studied by measuring the decay kinetics after each flash of light. This study differs from previous measurements of the induction curves where only the intensities at one set time after each flash of light were recorded. From the decay kinetics after each flash of light, the induction curves of the delayed light emission measured 2 ms after a flash of light were separated into two components: one component due to the last flash only and one component due to all previous flashes before the last one. On comparing the delayed light induction curves of the two components with the fluorescence induction curves in chloroplasts treated with 3-(3,4-dichlorophenyl)-1,1-dimethylurea and in chloroplasts treated with hydroxylamine and 3-(3,4-dichlorophenyl)-1,1-dimethylurea, the component due to the last flash only is found to be dependent on the concentration of open reaction centers and the component due to all previous flashes except the last is dependent on the concentration of closed reaction centers. This implies that the yield of the fast decaying component of the delayed light emission is dependent on the concentration of open reaction centers and the yield of the slow decaying component is dependent on the concentration of closed reaction centers.