this invention is based on the discovery that certain yeast strains can be activated by electromagnetic fields (“ emf ”) having specific frequencies and field strengths to produce agents useful in treating liver diseases , e . g ., hepatitis b . yeast compositions containing activated yeast cells can be used as medication , or as a dietary supplement in the form of health drinks or dietary pills . since the activated yeast cells contained in these yeast compositions have been cultured to endure acidic conditions ( ph 2 . 5 - 4 . 2 ), the compositions are stable in the stomach and can pass on to the intestines . once in the intestines , the yeast cells are ruptured by various digestive enzymes , and the bioactive agents are released and readily absorbed . the types of yeasts useful in this invention include , but are not limited to , yeasts of the genera of saccharomyces , rhodotorula , and schizosaccharomyces . exemplary species within the above - listed genera include , but are not limited to , the species illustrated in table 1 . yeast strains useful in this invention can be obtained from laboratory cultures , or from publically accessible culture depositories , such as cgmcc and the american type culture collection , 10801 university boulevard , manassas , va . 20110 - 2209 . non - limiting examples of useful strains ( with the accession numbers of cgmcc ) are saccharomyces cerevisiae hansen as2 . 561 and as2 . 69 , saccharomyces sp . as2 . 311 , schizosaccharomyces pombe lindner as2 . 994 , saccharomyces sake yabe accc2045 , saccharomyces uvarum beijer iffi1044 , saccharomyces rouxii boutroux as2 . 180 , saccharomyces cerevisiae hansen var . ellipsoideus as2 . 612 , saccharomyces carlsbergensis hansen as2 . 377 , and rhodotorula rubar ( demme ) lodder as2 . 282 . other non - limiting examples of useful strains are listed in table 1 . in general , preferred yeast strains in this invention are those used for fermentation in the food and wine industries . as a result , compositions containing these yeast cells are safe for human consumption . the preparation of the yeast compositions of this invention is not limited to starting with a pure strain of yeast . a yeast composition of the invention may be produced by culturing a mixture of yeast cells of different species or strains . an electromagnetic field useful in this invention can be generated and applied by various means well known in the art . for instance , the emf can be generated by applying an alternating electric field or an oscillating magnetic field . alternating electric fields can be applied to cell cultures through electrodes in direct contact with the culture medium , or through electromagnetic induction . see , e . g ., fig1 . relatively high electric fields in the medium can be generated using a method in which the electrodes are in contact with the medium . care must be taken to prevent electrolysis at the electrodes from introducing undesired ions into the culture and to prevent contact resistance , bubbles , or other features of electrolysis from dropping the field level below that intended . electrodes should be matched to their environment , for example , using ag — agcl electrodes in solutions rich in chloride ions , and run at as low a voltage as possible . for general review , see goodman et al ., effects of emf on molecules and cells , international review of cytology , a survey of cell biology , vol . 158 , academic press , 1995 . the emfs useful in this invention can also be generated by applying an oscillating magnetic field . an oscillating magnetic field can be generated by oscillating electric currents going through helmholtz coils . such a magnetic field in turn induces an electric field . the frequencies of emfs useful in this invention range from about 7900 mhz to 12400 mhz ( e . g ., 7900 - 8100 , 9850 - 10050 , or 12200 - 12400 mhz ). exemplary frequencies include 7986 , 8009 , 9949 , 12293 , and 12312 mhz . the field strength of the electric field useful in this invention ranges from about 240 - 500 mv / cm ( e . g ., 260 - 280 , 270 - 290 , 290 - 320 , 300 - 330 , 310 - 340 , 320 - 350 , 330 - 360 , 360 - 390 , 400 - 440 , or 430 - 470 mv / cm ). exemplary field strengths include 267 , 272 , 285 , 298 , 315 , 317 , 327 , 337 , 347 , 375 , 416 , and 446 mv / cm . when a series of emfs are applied to a yeast culture , the yeast culture can remain in the same container while the same set of emf generator and emitters is used to change the frequency and / or field strength . the emfs in the series can each have a different frequency or a different field strength ; or a different frequency and a different field strength . such frequencies and field strengths are preferably within the above - described ranges . although any practical number of emfs can be used in a series , it may be preferred that the yeast culture be exposed to a total of 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , or more emfs in a series . in one embodiment , the yeast culture is exposed to a series of emfs , wherein the frequency of the electric field is alternated in the range of about 7900 - 8100 , 9850 - 10050 , and 12200 - 12400 mhz . although the yeast cells can be activated after even a few hours of culturing in the presence of an emf , it may be preferred that the activated yeast cells be allowed to multiply and grow in the presence of the emf ( s ) for a total of 40 - 160 hours . fig1 illustrates an exemplary apparatus for generating alternating electric fields . an electric field of a desired frequency and intensity can be generated by an ac source ( 3 ) capable of generating an alternating electric field , preferably in a sinusoidal wave form , in the frequency range of 5 to 20 , 000 mhz . signal generators capable of generating signals with a narrower frequency range can also be used . if desired , a signal amplifier can also be used to increase the output . the culture container ( 2 ) can be made from a non - conductive material , e . g ., glass , plastic or ceramic . the cable connecting the culture container ( 2 ) and the signal generator ( 3 ) is preferably a high frequency coaxial cable with a transmission frequency of at least 30 ghz . the alternating electric field can be applied to the culture by a variety of means , including placing the yeast culture ( 1 ) in close proximity to the signal emitters such as a metal wire or tube capable of transmitting emfs . the metal wire or tube can be made of red copper , and be placed inside the container ( 2 ), reaching as deep as 3 - 30 cm . for example , if the fluid in the container ( 2 ) has a depth of 15 - 20 cm , 20 - 30 cm , 30 - 50 cm , 50 - 70 cm , 70 - 100 cm , 100 - 150 cm or 150 - 200 cm , the metal wire can be 3 - 5 cm , 5 - 7 cm , 7 - 10 cm , 10 - 15 cm , 15 - 20 cm , 20 - 30 cm , and 25 - 30 cm from the bottom of the container ( 2 ), respectively . the number of metal wires / tubes used can be from 1 to 10 ( e . g ., 2 to 3 ). it is recommended , though not mandated , that for a culture having a volume up to 10 l , metal wires / tubes having a diameter of 0 . 5 to 2 mm be used . for a culture having a volume of 10 - 100 l , metal wires / tubes having a diameter of 3 to 5 mm can be used . for a culture having a volume of 100 - 1000 l , metal wires / tubes having a diameter of 6 to 15 nun can be used . for a culture having a volume greater than 1000 l , metal wires / tubes having a diameter of 20 - 25 mm can be used . in one embodiment , the electric field is applied by electrodes submerged in the culture ( 1 ). in this embodiment , one of the electrodes can be a metal plate placed on the bottom of the container ( 2 ), and the other electrode can comprise a plurality of electrode wires evenly distributed in the culture ( 1 ) so as to achieve even distribution of the electric field energy . culture media useful in this invention contain sources of nutrients that can be assimilated by yeast cells . complex carbon - containing substances in a suitable form ( e . g ., carbohydrates such as sucrose , glucose , dextrose , maltose , xylose , cellulose , starch , etc .) can be the carbon sources for yeast cells . the exact quantity of the carbon sources can be adjusted in accordance with the other ingredients of the medium . in general , the amount of carbohydrates varies between about 1 % and 10 % by weight of the medium and preferably between about 1 % and 5 %, and most preferably about 2 %. these carbon sources can be used individually or in combination . amino acid - containing substances such as beef extract and peptone can also be added . in general , the amount of amino acid containing substances varies between about 0 . 1 % and 1 % by weight of the medium and preferably between about 0 . 1 % and 0 . 5 %. among the inorganic salts which can be added to a culture medium are the customary salts capable of yielding sodium , potassium , calcium , phosphate , sulfate , carbonate , and like ions . non - limiting examples of nutrient inorganic salts are ( nh 4 ) 2 hpo 4 , caco 3 , kh 2 po 4 , k 2 hpo 4 , mgso 4 , nacl , and caso 4 . to activate or enhance the ability of yeast cells to produce agents useful for treating live diseases ( e . g ., hepatitis b ), these cells can be cultured in an appropriate medium under sterile conditions at 20 - 35 ° c . ( e . g ., 28 - 32 ° c .) for a sufficient amount of time ( e . g ., 60 - 145 hours ) in an alternating electric field or a series of alternating electric fields as described above . an exemplary set - up of the culture process is depicted in fig1 ( see above ). an exemplary culture medium contains the following per 1000 ml of sterile water : 18 g of mannitol , 50 μg of vitamin b 6 , 50 μg of vitamin b 12 , 50 μg of vitamin b 3 , 100 □ g of vitamin h , 35 ml of fetal bovine serum , 0 . 2 g of kh 2 po 4 , 0 . 25 g of mgso 4 . 7h 2 o , 0 . 3 g of nacl , 0 . 2 g of caso 4 . 2h 2 o , 4 g of caco 3 . 5h 2 o , and 2 . 5 g of peptone . yeast cells of the desired strain ( s ) are then added to the culture medium to form a mixture containing 1 × 10 8 cells per 1000 ml of culture medium . the yeast cells can be of any of the strains listed in table 1 . the mixture is then added to the apparatus shown in fig1 . the activation process of the yeast cells involves the following steps : ( 1 ) maintaining the temperature of the activation apparatus at 24 - 33 ° c . ( e . g ., 28 - 32 ° c . ), and culturing the yeast cells for 24 - 30 hours ( e . g ., 28 hours ); ( 2 ) applying an alternating electric field having a frequency of 7986 mhz and a field strength of 260 - 280 mv / cm ( e . g ., 267 mv / cm ) for 11 - 17 hours ( e . g ., 15 hours ); ( 3 ) then applying an alternating electric field having a frequency of 8009 mhz and a field strength of 310 - 340 mv / cm ( e . g ., 315 mv / cm ) for 32 - 38 hours ( e . g ., 36 hours ); ( 4 ) then applying an alternating electric field having a frequency of 9949 mhz and a field strength of 320 - 350 mv / cm ( e . g ., 337 mv / cm ) for 38 - 44 hours ( e . g ., 42 hours ); ( 5 ) then applying an alternating electric field having a frequency of 12293 mhz and a field strength of 330 - 360 mv / cm ( e . g ., 347 mv / cm ) for 35 - 41 hours ( e . g ., 39 hours ); and ( 6 ) then applying an alternating electric field having a frequency of 12312 mhz and a field strength of 260 - 280 mv / cm ( e . g ., 272 mv / cm ) for 6 - 12 hours ( e . g ., 10 hours ). the activated yeast cells are then recovered from the culture medium by various methods known in the art , dried ( e . g ., by lyophilization ) and stored at 4 ° c . preferably , the concentration of the dried yeast cells is no less than 10 10 cells / g . because the yeast compositions of this invention must pass through the stomach before reaching the small intestine , where the effective components are released from these yeast cells , it is preferred that these yeast cells be cultured under acidic conditions to acclimatize the cells to the gastric juice . this acclimatization process results in better viability of the yeast cells in the acidic gastric environment . to achieve this , the yeast powder containing activated yeast cells can be mixed with a highly acidic acclimatizing culture medium at 10 g ( containing more than 10 10 activated cells per gram ) per 1000 ml . the yeast mixture is then cultured first in the presence of an alternating electric field having a frequency of 12293 mhz and a field strength of 360 - 390 mv / cm ( e . g ., 375 mv / cm ) at about 28 to 32 ° c . for 42 to 50 hours ( e . g ., 46 hours ). the resultant yeast cells can then be further incubated in the presence of an alternating electric field having a frequency of 12312 mhz and a field strength of 300 - 330 mv / cm ( e . g ., 317 mv / cm ) at about 28 to 32 ° c . for 16 to 28 hours ( e . g ., 20 hours ). the resulting acclimatized yeast cells are then dried and stored either in powder form (≧ 10 10 cells / g ) at room temperature or in vacuum at 0 - 4 ° c . an exemplary acclimatizing culture medium is made by mixing 700 ml fresh pig gastric juice and 300 ml wild chinese hawthorn extract . the ph of the acclimatizing culture medium is adjusted to 2 . 5 with 0 . 1 m hydrochloric acid ( hcl ) and 0 . 2 m potassium hydrogen phthalate ( c 6 h 4 ( cook ) cooh ). the fresh pig gastric juice is prepared as follows . at about 4 months of age , newborn holland white pigs are sacrificed , and the entire contents of their stomachs are retrieved and mixed with 2000 ml of water under sterile conditions . the mixture is then allowed to stand for 6 hours at 4 ° c . under sterile conditions to precipitate food debris . the supernatant is collected for use in the acclimatizing culture medium . to prepare the wild chinese hawthorn extract , 500 g of fresh wild chinese hawthorn is dried under sterile conditions to reduce water content (≦ 8 %). the dried fruit is then ground (≧ 20 mesh ) and added to 1500 ml of sterilized water . the hawthorn slurry is allowed to stand for 6 hours at 4 ° c . under sterile conditions . the hawthorn supernatant is collected to be used in the acclimatizing culture medium . to manufacture the yeast compositions of the invention , an apparatus depicted in fig2 or an equivalent thereof can be used . this apparatus includes three containers , a first container ( a ), a second container ( b ), and a third container ( c ), each equipped with a pair of electrodes ( 4 ). one of the electrodes is a metal plate placed on the bottom of the containers , and the other electrode comprises a plurality of electrode wires evenly distributed in the space within the container to achieve even distribution of the electric field energy . all three pairs of electrodes are connected to a common signal generator . the culture medium used for this purpose is a mixed fruit extract solution containing the following ingredients per 1000 l : 300 l of wild chinese hawthorn extract , 300 l of jujube extract , 300 l of schisandra chinensis ( turez ) baill seed extract , and 100 l of soy bean extract . to prepare hawthorn , jujube and schisandra chinensis ( turez ) baill seed extracts , the fresh fruits are washed and dried under sterile conditions to reduce the water content to no higher than 8 %. one hundred kilograms of the dried fruits are then ground (≧ 20 mesh ) and added to 400 l of sterilized water . the mixtures are stirred under sterile conditions at room temperature for twelve hours , and then centrifuged at 1000 rpm to remove insoluble residues . to make the soy bean extract , fresh soy beans are washed and dried under sterile conditions to reduce the water content to no higher than 8 %. thirty kilograms of dried soy beans are then ground into particles of no smaller than 20 mesh , and added to 130 l of sterilized water . the mixture is stirred under sterile conditions at room temperature for twelve hours and centrifuged at 1000 rpm to remove insoluble residues . to make the culture medium , these ingredients are mixed according to the above recipe , and the mixture is autoclaved at 121 ° c . for 30 minutes and cooled to below 40 ° c . before use . one thousand grams of the activated yeast powder prepared as described above ( section v , supra ) is added to 1000 l of the mixed fruit extract solution , and the yeast solution is transferred to the first container ( a ) shown in fig2 . the yeast cells are then cultured in the presence of an alternating electric field having a frequency of 12293 mhz and a field strength of about 400 - 440 mv / cm ( e . g ., 416 mv / cm ) at 28 - 32 ° c . under sterile conditions for 32 hours . the yeast cells are further incubated in an alternating electric field having a frequency of 12312 mhz and a field strength of 290 - 320 mv / cm ( e . g ., 298 mv / cm ). the culturing continues for another 12 hours . the yeast culture is then transferred from the first container ( a ) to the second container ( b ) which contains 1000 l of culture medium ( if need be , a new batch of yeast culture can be started in the now available first container ( a )), and subjected to an alternating electric field having a frequency of 12293 mhz and a field strength of 430 - 470 mv / cm ( e . g ., 446 mv / cm ) for 24 hours . subsequently the frequency and field strength of the electric field are changed to 12312 mhz and 260 - 280 mv / cm ( e . g ., 272 mv / cm ), respectively . the culturing continues for another 12 hours . the yeast culture is then transferred from the second container ( b ) to the third container ( c ) which contains 1000 l of culture medium , and subjected to an alternating electric field having a frequency of 12293 mhz and a field strength of 310 - 340 mv / cm ( e . g ., 327 mv / cm ) for 24 hours . subsequently the frequency and field strength of the electric field are changed to 12312 mhz and 270 - 290 mv / cm ( e . g ., 285 mv / cm ), respectively . the culturing continues for another 12 hours . the yeast culture from the third container ( c ) can then be packaged into vacuum sealed bottles for use as a dietary supplement , e . g ., health drinks , or medication in the form of pills , powder , etc . if desired , the final yeast culture can also be dried within 24 hours and stored in powder form . the dietary supplement can be taken three to four times daily at 30 - 60 ml per dose for a three - month period , preferably 10 - 30 minutes before meals and at bedtime . in some embodiments , the compositions of the invention can also be administered intravenously or peritoneally in the form of a sterile injectable preparation . such a sterile preparation can be prepared as follows . a sterilized health drink composition is first treated under ultrasound ( 20 , 000 hz ) for 10 minutes and then centrifuged for another 10 minutes . the resulting supernatant is adjusted to ph 7 . 2 - 7 . 4 using 1 m naoh and subsequently filtered through a membrane ( 0 . 22 μm for intravenous injection and 0 . 45 μm for peritoneal injection ) under sterile conditions . the resulting sterile preparation is submerged in a 35 - 38 ° c . water bath for 30 minutes before use . in other embodiments , the compositions of the invention may also be formulated with pharmaceutically acceptable carriers to be orally administered in any orally acceptable dosage form including , but not limited to , capsules , tablets , suspensions or solutions . the yeast compositions of the present invention are derived from yeasts used in food and pharmaceutical industries . the yeast compositions are thus devoid of side effects associated with many pharmaceutical compounds . the following examples are meant to illustrate the methods and materials of the present invention . suitable modifications and adaptations of the described conditions and parameters which are obvious to those skilled in the art are within the spirit and scope of the present invention . the activated yeast compositions used in the following experiments were prepared as described above , using saccharomyces cerevisiae hansen as2 . 561 cells cultured in the presence of an alternating electric field having the electric field frequency and field strength exemplified in the parentheses following the recommended ranges listed in section iv , supra . control yeast compositions were those prepared in the same manner except that the yeast cells were cultured in the absence of emfs . unless otherwise indicated , the yeast compositions and the corresponding controls were administered to the animals by intragastric feeding . the hbv surface coat is composed of hepatitis b surface antigens (“ hbsag ”). hbsag is produced in larger quantities than required for the virus to reproduce . the excess surface antigens clump into spherical particles or form rods of variable length . these spherical particles can also encapsulate a core particle and produce a complete and infectious viral particle that enters the blood stream and infects other liver cells . the excess spheres , rods and complete viral particles enter the blood stream in large numbers and are easily detectable . hbsag - positivity is the current standard used to indicate hbv infection . the presence of hbsag for more than six months is generally taken to indicate chronic infection . in this experiment , the effectiveness of the activated yeast composition in reducing hbsag level was assessed using an elisa assay . under sterile conditions , a bottle ( 100 ml / bottle , about 10 8 cells / ml ) of the activated yeast composition ( ay ) was mixed with 100 ml of de - ionized h 2 o in a 200 ml beaker and the mixture incubated at 28 - 30 ° c . for two hours . the mixture was then sonicated at 3000 hz for 15 minutes and centrifuged at 1000 rpm for 10 minutes . the supernatant was then filtered through a 0 . 45 μm membrane . de - ionized water was added to bring the volume to 100 ml . the ph of the solution was adjusted to 7 . 0 with 0 . 1 m naoh and hcl , and then stored at 4 ° c . before use , three different concentrations of the solution were prepared : 1 × 50 μl ( stock solution without further concentration ), 2 × 50 μl ( 100 μl of stock solution concentrated to 50 μl ), and 3 × 50 μl ( 150 μl of stock solution concentrated to 50 μl ). control yeast composition solutions ( ny ) were prepared in the same way . hbsag was purified from hbsag positive serum ( with a titer of 1 : 8 ) using cellulose ion - exchange affinity chromatography . the preparation was stored in aliquots at 4 ° c . two hbsag concentrations were used for this experiment : p / n ( positive / negative )= 10 . 92 , and p / n = 14 . 26 . p / n is the ratio between the hbsag concentration of an hbsag - positive serum and that of an hbsag - negative serum . six solutions were prepared by mixing 50 μl of the yeast composition solutions at three different concentrations with 50 μl of the hbsag preparations at two different concentrations . hbsag positive ( where no yeast composition solution was added ) and hbsag negative ( no hbsag ) controls , as well as a blank control ( where h 2 o was used in lieu of yeast composition and hbsag ) were also included . these mixtures were incubated at 37 ° c . for four hours . the elisa plate were coated with 100 μl of purified hepatitis b surface antibody (“ hbsab ”) per well at 4 ° c . for 48 hours . the plates were then washed several times with wash buffer and spun dry . the yeast composition solution - hbsag mixtures and the various controls were each added to a hbsab - coated well and incubated at 43 ° c . for two hours . the plates were washed several times and spun dry , and 100 μl of hrp - hbsab ( 1 : 100 ) in 10 % fetal bovine serum was added per well and incubated at 43 ° c . for one hour . the plates were then washed several times and spun dry . 100 μl of o - phenylenediamine - hydrogen peroxide was added per well . after incubation at 37 ° c . in the dark for 30 minutes , the reactions were stopped by adding 50 μl of 2 m h 2 so 4 per well . the optical density of the samples was measured at 492 nm , using the blank sample for calibration . the p / n values of the reactions were calculated based on the average od values ( i . e ., od value for the samples divided by the od value of the negative control ). the data are shown in table 2 below . the data demonstrate that the activated yeast composition significantly reduced the level of hbsag ( p / n & lt ; 0 . 95 ) compared to the control yeast composition ( p / n & gt ; 10 . 34 ). by general medical standards , a p / n value of & lt ; 1 . 2 indicates significant effect of treatment ; a p / n value of & lt ; 2 . 1 , average effect ; a p / n value of 3 . 8 - 4 . 25 , low effect ; and a p / n value of & gt ; 4 . 25 , no effect . glutamate - pyruvate transaminase ( gpt ) normally is expressed in hepatocytes . when the liver tissue undergoes necrosis or is otherwise damaged , gpt is released into the blood stream , elevating the level of serum gpt . thus , the serum gpt level is one of the important indicators of liver functions . to evaluate the effects of the activated yeast composition of this invention on serum gpt activity , the yeast compositions were tested in patients with chronic hepatitis b ( either chronic persistent hepatitis b or chronic active hepatitis b ). the study was conducted under the direction of physicians . in this study , the patients with chronic persistent hepatitis b or chronic active hepatitis b ( these two groups of patients were studied separately ) were randomly divided into three groups , namely ay ( for treatment with the activated yeast composition ), ny ( for treatment with the control yeast composition ), ck ( positive control group , for treatment with stronger neominophagen c , or snmc , a known drug for treating hepatitis b ). the ay group patients were each given 30 ml of the activated yeast composition ( about 10 8 cells / ml ), three times daily for six months . the ny patients were treated in the same manner except that they were given the control yeast composition , in lieu of the activated yeast composition . the ck patients were each given 40 ml of snmc ( 1 . 0 mg / ml ) via intraveinous injection daily for six months . at the end of the sixth month , blood samples were taken from each patient to determine the serum gpt level . to do so , 0 . 1 ml of serum from each paitent was mixed with 0 . 5 ml of the glutamate - pyruvate substrate solution ( 1 m ) and incubated in a 37 ° c . water bath for 30 minutes . then 0 . 5 ml of 2 , 4 - dinitrophenylhydrazine was added and the incubation continued for another 20 minutes . finally , 5 ml of 0 . 4 m naoh was added . the control reaction was prepared in the same manner except that the serum was added immediately after , not before , the 30 minute incubation step . the optical density of the sample was measured at 520 nm , using the control reaction for calibration . the gpt concentration was determined using a standard curve . data in table 3 below show that the number of patients in each group whose serum gpt level returned to normal after treatment . the data demonstrate that the activated yeast composition significantly restored serum gpt to normal levels in patients with chronic hepatitis b , and was superior to snmc in doing so . while a number of embodiments of this invention have been set forth , it is apparent that the basic constructions may be altered to provide other embodiments which utilize the compositions and methods of this invention .
the invention provides compositions comprising a plurality of yeast cells , wherein said plurality of yeast cells are characterized by their ability to normalize the level of serum glutamate - pyruvate transaminase , or reduce serum hbsag levels in a subject , said ability resulting from their having been cultured in the presence of an alternating electric field having a specific frequency and a specific field strength . also provided are methods of making and using these compositions .