for the purposes of promoting an understanding of the principles of the invention , reference will now be made to the preferred embodiments thereof , and specific language will be used to describe the same . it will nevertheless be understood that no limitation of the scope of the invention is thereby intended , such alterations , modifications , and further applications of the principles of the invention being contemplated as would normally occur to one skilled in the art to which the invention relates . the present invention provides microparticle formulations which comprise polyesters as the supporting matrix and peptides as the contained , biologically active agents . the microparticles are prepared by a solvent evaporation technique which incorporates the peptides in a stable and active form . the microparticles are biodegradable , and afford a controlled , sustained release of the peptides . the rate of drug release is controlled by adjusting factors such as the degree of peptide loading , molecular weight of the biodegradable polymer , and in certain instances the ratio of copolymer components . the microparticles , and preparatory methods , of the present invention are distinctive from the prior art in providing formulations in which the peptides remain chemically stable , physically stable ( conformation ), and biologically active . the methods of the present invention also achieve a greater proportion of peptide to polymer than prior art solvent evaporation techniques for microparticles incorporating water - soluble polypeptides . the microparticles of the present invention provide sustained release of the contained peptides . as a result of the method of preparing the microparticles , the biologically active compounds , e . g ., peptides and the like , are entrapped in the polymer network during fabrication . the peptides are then released over time during the degradation of the matrix , and to a limited extent , by diffusion through the polymer network . the release profile may be adjusted by appropriate choice or control of various parameters . for example , release characteristics will charge with the polymer composition , particularly the type and proportion of polymers ; the molecular weight of the polymers ; the weight - average molecular weight ( m w ); the molecular weight range ( or polydispersity ) measured by the ratio of the weight - average molecular weight ( m w ) to the number - average molecular weight ( m n ) i . e . m w / m n ; the size and shape of the microparticles ; and the proportion of peptide to polymer , i . e ., the loading . the microparticles of the present invention may be prepared from polyesters , e . g ., poly ( d , l - lactide ), poly ( d , l - lactide - co - glycolide ), poly ( epsilon - caprolactone ), polyaminoacids , poly ( orthoesters ), polyanhydrides , polyalkyl cyanoacrylates . any polyesters which are biodegradable and / or bioerodible , and yield biocompatible materials upon degradation are contemplated . the polylactides are especially preferred for use in accordance with the present invention . polymeric materials for preparation of the microparticles are available commercially . the term polylactide is used in a generic sense to include polymers and mixtures of polymers of lactic acid alone , copolymers of lactic acid and glycolic acid and mixtures of such copolymers , and mixtures of such polymers and copolymers , the lactic acid being either in racemic or in optically active form . the term pla / pga is used herein to refer to the various copolymers of lactic and glycolic acids . the molecular weigh of the polymers ranges from about 29 , 000 daltons to about 90 , 900 daltons . the ratio of lactide units to glycolide units ranges from 100 : 0 to 50 : 50 . for example , one pla / pga polymer used had a ratio of pla to pga of 85 : 15 , an inherent viscosity of 0 . 58 dl / g , and a molecular weight of approximately 90 , 900 daltons . this particular polymer was obtained from birmingham polymers , incorporate ( bpi ), and is prepared by ionic , ring - opening , addition polymerization of the respective cyclic dimers of lactic and glycolic acids . upon exposure to water , the polyesters degrade through hydrolysis of ester linkages to yield biocompatible products . for example , the preferred pla / pga polymers degrade to lactic acid and glycolic acid . the 85 : 15 pla / pga copolymer has been reported to have a biodegradation time of approximately 5 months , depending on surface area , porosity and molecular weight . other blends of pla / pga have degradation times ranging from 2 months to 24 months . a 50 : 50 pla / pga polymer , which has alternately been used , has a reported degradation time of 2 months . similarly , the other polyesters used in the present invention have suitable biocompatibility and degradation times . the microparticles prepared in accordance with the disclosed methods are suitable for use in the administration of various peptide agents . an advantage of this invention is that it provides microparticles containing small , biologically - active polypeptides . generally , peptides of molecular weights up to 10 , 000 daltons are called polypeptides , while peptides of molecular weights above 10 , 000 daltons are called proteins . in the past , the solvent evaporation technique for preparing microparticles has typically resulted in low loading of small water - soluble peptides due to the incompatibility of such peptides with this process . typically , loadings of below 10 % have been reported . low loading of microparticles may not provide a proper dose . however , in spite of its limitations , the solvent evaporation procedure is preferred because of its ease and reliability . the methods of the present invention employ an aqueous medium in which the biological agent is insoluble , and the process results in microparticles having loading up to 25 %. the present invention addresses the need for convenient methods to incorporate polypeptides into microparticles with loading of 5 - 25 %. the present invention provides microparticles containing water - soluble polypeptides such as somatogenin . somatogenin ( ly293404 ) is the name proposed to the united states adopted names council ( usan ) for a 4 - methylhippuroyl ( 1 ) porcine ghrh ( 2 - 76 )-- oh , which is an analog of a natural porcine ghrh prohormone . this compound has a molecular weight of 8846 . 89 daltons and its molecular formula is c 379 h 624 n 127 o 118 . methods for the preparation of somatogenin are described in u . s . patent application , ser . no . 07 / 692 , 090 , filed on apr . 26 , 1991 , now abandoned and entitled &# 34 ; superactive grf analogs &# 34 ;. the structure of somatogenin is represented by the following , seq id no : 1 ## str1 ## composition table______________________________________ala 7 gly 5 pro 0arg 11 his 1 ser 5asp 4 ile 3 thr 3asn 4 leu 12 tyr 1cys 0 lys 0 trp 1glu 4 met 0 val 3gln 11 phe 1______________________________________ the preparatory method of the present invention is demonstrated in the following examples . in general , the polymeric material is dissolved in a suitable organic solvent , e . g . methylene chloride or chloroform , and the bioactive , water - soluble peptide , e . g . somatogenin , is added thereto . preferably , the somatogenin has been reduced in particle size by air milling . see u . s . pat . no . 5 , 021 , 554 , the pertinent portions of which are hereby incorporated by reference . the polymer solution / peptide suspension is preferably sonicated to primary particles size . the suspension is then emulsified into a suitable aqueous media in which the bioactive peptide is insoluble , preferably , phosphate buffered saline . the medium may contain a stabilizer such as poly ( vinyl alcohol ), sodium dodecyl sulfate , cetyltrimethyl ammonium bromide , methylcellulose or gelatin . various excipients may be added to the above at concentrations up to about 10 %. excipients may include , for example , fatty acids , such as stearic acid , myristic acid , lauric acid , and preferably , palmitic acid . the solvent is allowed to evaporate with the consequent formation of the microparticles . the evaporation is preferably aided with stirring . the particles are collected , preferably by vacuum filtration . the particles may then be dried in a desiccator under vacuum , and sieved to size appropriate for use . this invention is applicable to polypeptides , and the following list , which is not intended to be exhaustive , is indicative of polypeptides which may be employed in the formulations of this invention : growth horone releasing factor , somatogenin , oxytocin , vasopressin , adrenocorticotrophic hormone ( acth ), epidermal growth factor ( egf ), prolactin , luliberin or luteininzing hormone releasing hormone ( lh - rh ), transforming growth factor , insulin , somatostatin , glucagon , interferon , gastrin , tetragastrin , pentagastrin , urogastrone , secretin , calcitonin , enkephalins , endorphins , angiotensins , renin , bradykinin , bacitracins , polymyxins , colistins , tyrocidin , gramicidines , and synthetic analogs and modifications and pharmacologically - active fragments thereof . upon collection of the microparticles , a desired range of particle sizes may be directly obtained by sieving . in addition , the particles may be milled , such as by an ultracentrifuge mill . the microparticles are perferably sized less than about 250 microns , more preferably between about 120 and about 250 microns . the resulting particles are combined with a suitable liquid for administration . the microparticles may be dispersed , e . g . suspended , in other known , suitable liquid vehicles for administration , such as water , dextrose solution , glycerol , or water containing 2 % w / v sodium carboxyl - methyl - cellulose 330 ( nacmc ) or hydroxypropylmethyl cellulose ( hpmc ), to increase viscosity to prevent microparticles from settling out of suspension . the particles may be administered to living organisms ; including pigs or other mammals and birds , such as chickens or turkeys . for example , somatogenin microparticle formulations may be placed in suspension and injected subcutaneously in the flank of swine . the microparticle formulations may also be injected directly into a bird or administered indirectly into a bird embryo by injection into the air sac of an egg as described in u . s . patent application , ser . no . 08 / 068 , 413 , now abandoned ( lly 40 ), entitled method for administering biological agents , incorporated herein by reference . it will further be appreciated by those skilled in the art that the microparticles containing incorporated drugs for release to target cells or tissues may be administered alone or in a mixture with appropriate pharmaceutical diluents , carriers , excipients or adjuvants suitably selected with respect to the intended route of administration and conventional pharmaceutical practices . these inert pharmaceutically acceptable adjuvants are well known in the art . for example , for parenteral injections , dosage unit forms may be utilized to accomplish intravenous , intramuscular or subcutaneous administration , and for such parenteral administration , suitable sterile aqueous or non - aqueous solutions or suspensions , optionally containing appropriate solutes to effect isotonicity , will be employed . the following specific examples are provided for purposes of illustrating the invention , and no limitations on the invention are intended thereby . microparticles were prepared using pla / pga , 85 / 15 , bpi , and the microparticle preparation technique of solvent evaporation from dulbecco &# 39 ; s phosphate buffered saline ( pbs ) containing polyvinyl alcohol ( pva ). to 250 ml of freshly prepared dulbecco &# 39 ; s pbs ( without cacl 2 ) was added 1 . 0 g of air products airvol 205 polyvinyl alcohol to prepare a 0 . 4 % w / v solution of pva in pbs . the pva was dispersed in pbs at room temperature using magnetic stirring , and the temperature was raised to 45 ° c . to complete pva dissolution . the dulbecco &# 39 ; s pbs solution containing pva was allowed to return to room temperature before use . 1 . 80 g of pla / pga , 85 / 15 , bpi , inherent viscosity of 0 . 58 dl g in chcl 3 @ 30 ° c . ( m w = 90 , 900 daltons , m n = 50 , 100 daltons ), was dissolved in approximately 50 ml of methylene chloride . to this polymer solution was added 0 . 20 g of air milled somatogenin . the active somatogenin was dispersed to primary particle size using gentle swirling and sonication for approximately one minute . the polymer solution -- somatogenin suspension was added to the vortex of the stirred dulbecco &# 39 ; s pbs containing pva . the rate of stirring was 270 - 280 rpm . a 400 ml pyrex beaker and plastic stirring rod with 3 - bladed propeller were used to contain and stir the resulting oil - in - water emulsion . this was allowed to continue stirring overnight , resulting in complete evaporation of methylene chloride and the subsequent formation of microspheres , which were recovered using vacuum filtration . the microspheres were placed in a drying dish in a desicator under vacuum to dry . 1 . 80 g + 1 . 85 g ( 3 . 65 g , representing two batches ) of dried microparticles were recovered , and sieved to the following mesh cuts : assay of combined product showed a 9 . 8 % w / w ( 10 . 2 , 9 . 4 , 9 . 7 ) loading , as compared to 10 % theoretical . somatogenin containing microparticles were prepared using pla / pga , 85 / 15 , bpi , and the microparticle preparation technique of solvent evaporation from dulbecco &# 39 ; s phosphate buffered saline ( pbs ) containing polyvinyl alcohol . to 250 ml of dulbecco &# 39 ; s pbs ( without cacl 2 ) was added 1 . 02 g of air products airvol 205 , polyvinyl alcohol to prepare a 0 . 4 % w / v solution of pva in pbs . the pva was dispersed in pbs at room temperature , and the temperature raised to 45 ° c . to facilitate dissolution . the pbs containing pva solution was allowed to return to room temperature before use . 1 . 75 g of pla / pga , 85 / 15 , bpi , inherent viscosity of 0 . 58 dl / g in chcl 3 @ 30 ° c . ( m w = 90 , 900 daltons , m n = 50 , 100 daltons ), was dissolved in approximately 50 ml of methylene chloride . to this polymer solution was added 0 . 25 g of air milled somatogenin . the somatogenin was dispersed to primary particle size using gentle agitation and sonication for approximately one minute . the polymer solution somatogenin suspension was added to the vortex of the stirred dulbecco &# 39 ; s pbs containing pva , and stirring was continued overnight , resulting in complete evaporation of methylene chloride . the resulting microparticles were recovered using vacuum , n filtration and placed in a drying dish in a desicator under vacuum to dry , yielding 1 . 81 g of dried microparticles , sieved to the following mesh cuts ( u . s . standard ): assay of the 60 - 120 mesh cut showed 12 . 9 % w / w somatogenin ( 12 . 5 % theoretical ). microparticles containing somatogenin were prepared using pla / pga ( 85 / 15 ) bpi and the microparticle preparation technique of solvent evaporation from dulbecco &# 39 ; s pbs containing polyvinyl alcohol ( pva ). to 250 ml of freshly prepared dulbecco &# 39 ; s phosphate buffered saline ( pbs ) ( without cacl 2 ), was added 1 . 0 g of air products v - 205 pva to prepare a 0 . 4 % w / v solution of pva in pbs . the pva was dispersed in the pbs at room temperature , and the temperature was raised to 45 ° c . to aid dissolution . this solution was allowed to cool to room temperature before use . this solution contained 0 . 4 % w / v pva in pbs . 1 . 5 g of pla / pga , 85 / 15 , inherent viscosity of 0 . 58 dl / g in chcl 3 @ 30 ° c . ( m w = 90 , 900 daltons , m n = 50 , 100 daltons ), was dissolved in approximately 50 ml of methylene chloride . to this polymer solution was added 0 . 5 g of micronized somatogenin . the somatogenin was dispersed to primary particle size using gentle agitation and sonication for approximately one minute ( at room temperature ). the polymer solution / somatogenin suspension was added to the vortex of the stirred dulbecco &# 39 ; s pbs solution containing pva . the stirring was allowed to continue overnight , allowing the methylene chloride solvent to completely evaporate . the microparticles were recovered using vacuum filtration and were placed in a drying dish in a desiccator under vacuum to dry . 1 . 84 g of dried microparticles were recovered and were sieved to the following mesh cuts ( u . s . standard ): repetition of the foregoing process yielded 1 . 87 g of dried microparticles , which were sieved to the following mesh cuts ( u . s . standard ): somatogenin containing microparticles were prepared using pla / pga , 85 / 15 , bpi , and the microparticle preparation technique of solvent evaporation from dulbecco &# 39 ; s phosphate buffered saline ( pbs ) containing polyvinyl alcohol ( pva ). to 250 ml of dulbecco &# 39 ; s pbs ( without cacl 2 ) was added 1 . 0 g of air products airvol 205 polyvinyl alcohol to prepare a 0 . 4 % w / v solution of pva in pbs . the pva was dispersed in pbs at room temperature and the temperature raised to 45 ° c . to aid dissolution . this pva containing solution was returned to room temperature before use . 1 . 52 g of pla / pga , 85 / 15 , bpi , inherent viscosity of 0 . 58 dl / g in chcl 3 @ 30 ° c . ( m w = 90 , 900 daltons , m n = 50 , 100 daltons ), was dissolved in approximately 50 ml of methylene chloride . to this polymer solution was added 0 . 50 g of air milled somatogenin , and the active somatogenin was dispersed to primary particle size using gentle agitation and sonication for approximately one minute . the polymer solution - somatogenin suspension was added to the vortex of the stirred dulbecco &# 39 ; s pbs containing pva . a 400 ml . pyrex beaker and a plastic 3 - bladed stirrer and shaft were used to contain and agitate the oil - in - water emulsion . stirring continued overnight , resulting in complete evaporation of methylene chloride . the resulting microparticles were recovered using vacuum filtration and placed in a drying dish in a desicator under vacuum to dry . 1 . 80 g of dried microparticles were recovered and sieved to the following mesh cuts ( u . s . standard ): assay of the 60 - 120 mesh cut showed 24 . 9 % w / w somatogenin loading ( 25 % theoretical ). microparticles were prepared using pla / pga , 50 / 50 , bpi , and the microparticle preparation technique of solvent evaporation from dulbecco &# 39 ; s phosphate buffered saline ( pbs ) containing polyvinyl alcohol ( pva ). to 250 ml of freshly prepared dulbecco &# 39 ; s pbs ( without cacl 2 ) was added 1 . 0 g of air products airvol 205 polyvinyl alcohol to prepare a 0 . 4 % w / v solution of pva in pbs . the pva was dispersed in pbs at room temperature using magnetic stirring , and the temperature was raised to 45 ° c . to complete pva dissolution . the dulbecco &# 39 ; s pbs solution containing pva was allowed to return to room temperature before use . 1 . 50 g of pla / pga , 50 / 50 , bpi , inherent viscosity of 0 . 42 dl g in chcl 3 @ 30 ° c . ( m w = 29 , 000 daltons , m n = 20 , 000 daltons ), was dissolved in approximately 50 ml of methylene chloride . to this polymer solution was added 0 . 50 g of air milled somatogenin . the active somatogenin was dispersed to primary particle size using gentle swirling and sonication for approximately one minute . the polymer solution -- somatogenin suspension was added to the vortex of the stirred dulbecco &# 39 ; s pbs containing pva . the rate of stirring was 270 - 280 rpm . a 400 ml pyrex beaker and plastic shirring rod with 3 - bladed propeller were used to contain and stir the resulting oil - in - water emulsion . this was allowed to continue stirring overnight , resulting in complete evaporation of methylene chloride and the subsequent formation of microspheres , which were recovered using vacuum filtration . the microspheres were placed in a drying dish in a desicator under vacuum to dry . 1 . 92 g of dried microparticles were recovered , and sieved to the following mesh cuts : somatogenin containing microparticles were prepared using poly ( dl - lactide ) pla / pga , 85 / 15 , bpi , and the microparticle preparation technique of solvent evaporation from dulbecco &# 39 ; s phosphate buffered saline ( fbs ) containing polyvinyl alcohol ( pva ). to 250 ml of dulbecco &# 39 ; s pds ( without cacl 2 ) was added 1 . 0 g of air products airvol 205 polyvinyl alcohol to prepare a 0 . 4 % w / v solution of pva in pbs . the pva was dispersed in pbs at room temperature and the temperature raised to 45 ° c . to aid dissolution . this pva containing solution was returned to room temperature before use . 1 . 80 g of poly ( dl - lactide ), bpi , inherent viscosity of 0 . 34 dl / g in chcl 3 @ 30 ° c . ( m w = 38 , 300 daltons , m n = 24 , 300 daltons ), was dissolved in approximately 50 ml of methylene chloride . to this polymer solution was added 0 . 20 g of air milled somatogenin , and the active somatogenin was dispersed to primary particle size using gentle agitation and sonication for approximately one minute . the polymer solution - somatogenin suspension was added to the vortex of the stirred dulbecco &# 39 ; s pbs containing pva . a 400 ml beaker and a plastic 3 - bladed stirrer and shaft were used to contain and agitate the oil - in - water emulsion . stirring continued overnight , resulting in complete evaporation of methylene chloride . the resulting microparticles were recovered using vacuum filtration and placed in a drying dish in a desicator under vacuum to dry . 1 . 68 g of dried microparticles were recovered and sieved to the following mesh cuts ( u . s . standard ): somatogenin containing microparticles were prepared using poly ( caprolactone ), bpi , and the microparticle preparation technique of solvent evaporation from dulbecco &# 39 ; s phosphate buffered saline ( pbs ) containing polyvinyl alcohol ( pva ). to 250 ml of dulbecco &# 39 ; s pbs ( without cacl 2 ) was added 1 . 0 g of air products airvol 205 polyvinyl alcohol to prepare a 0 . 4 % w / v solution of pva in pbs . the pva was dispersed in pbs at room temperature and the temperature raised to 45 ° c . to aid dissolution . this pva containing solution was returned to room temperature before use . 1 . 80 g of poly ( caprolactone ) bpi , inherent viscosity of 1 . 27 dl / g in chcl 3 @ 30 ° c . [( m w = 143 , 000 dalons , m n = 83 , 000 daltons ),] was dissolved in approximately 50 ml of methylene chloride . to this polymer solution was added 0 . 50 g of air milled somatogenin , and the active somatogenin was dispersed to primary particle size using gentle agitation and sonication for approximately one minute . the polymer solution - somatogenin suspension was added to the vortex of the stirred dulbecco &# 39 ; s pbs containing fva . a 400 ml . pyrex beaker and a plastic 3 - bladed stirrer and shaft were used to contain and agitate the oil - in - water emulsion . stirring continued overnight , resulting in complete evaporation of methylene chloride . the resulting microparticles were recovered using vacuum filtration and placed in a drying dish in a desicator under vacuum to dry . 1 . 85 g of dried microparticles were recovered and sieved to the following mesh cuts ( u . s . standard ): somatogenin containing microparticles were prepared using poly ( caprolactone ) and the microparticle preparation technique of solvent evaporation from dulbecco &# 39 ; s phosphate buffered saline ( pbs ) containing polyvinyl alcohol ( pva ). to 250 ml of dulbecco &# 39 ; s pbs ( without cacl 2 ) was added 1 . 0 g of air products airvol 205 polyvinyl alcohol to prepare a 0 . 4 % w / v solution of pva in pbs . the pva was dispersed in pbs at room temperature and the temperature raised to 45 ° c . to aid dissolution . this pva containing solution was returned to room temperature before use . 1 . 78 g of polycaprolactone , low molecular weight , polysciences , was dissolved in approximately 50 ml of methylene chloride . to this polymer solution was added 0 . 02 g of palmitic acid . to this solution of polymer - fatty acid was added 0 . 20 g of air milled somatogenin , and the active somatogenin was dispersed to primary particle size using gentle agitation and sonication for approximately one minute . the polymer solution - somatogenin suspension was added to the vortex of the stirred dulbecco &# 39 ; s pbs containing pva . a 400 ml . pyrex beaker and a plastic 3 - bladed stirrer and shaft were used to contain and agitate the oil - in - water emulsion . stirring continued overnight , resulting in complete evaporation of methylene chloride . the resulting microparticles were recovered using vacuum filtration and placed in a drying dish in a desicator under vacuum to dry . 1 . 89 g of dried microparticles were recovered and sieved to the following mesh cuts ( u . s . standard ): somatogenin containing microparticles were prepared using poly ( caprolactone ), and the microparticle preparation technique of solvent evaporation from dulbecco &# 39 ; s phosphate buffered saline ( pbs ) containing polyvinyl alcohol ( pva ). to 250 ml of dulbecco &# 39 ; s pbs ( without cacl 2 ) was added 1 . 0 g of air products airvol 205 polyvinyl alcohol to prepare a 0 . 4 % w / v solution of pva in pbs . the pva was dispersed in pbs at room temperature and the temperature raised to 45 ° c . to aid dissolution . this pva containing solution was returned to room temperature before use . 1 . 70 g of poly ( caprolactone ), low molecular weight , polysciences , was dissolved in approximately 50 ml of methylene chloride . to this polymer solution was added 0 . 10 g of palmitic acid . to this polymer - fatty acid solution was added 0 . 20 g of air milled somatogenin , and the active somatogenin was dispersed to primary particle size using gentle agitation and sonication for approximately one minute . the polymer solution - somatogenin suspension was added to the vortex of the stirred dulbecco &# 39 ; s pbs containing pva . a 400 ml . pyrex beaker and a plastic 3 - bladed stirrer and shaft were used to contain and agitate the oil - in - water emulsion . stirring continued overnight , resulting in complete evaporation of methylene chloride . the resulting microparticles were recovered using vacuum filtration and placed in a drying dish in a desicator under vacuum to dry . 1 . 93 g of dried microparticles were recovered and sieved to the following mesh cuts ( u . s . standard ): somatogenin containing microparticles were prepared using poly ( caprolactone ), and the microparticle preparation technique of solvent evaporation from dulbecco &# 39 ; s phosphate buffered saline ( pbs ) containing polyvinyl alcohol ( pva ). to 250 ml of dulbecco &# 39 ; s pbs ( without cacl 2 ) was added 1 . 0 g of air products airvol 205 polyvinyl alcohol to prepare a 0 . 4 % w / v solution of pva in pbs . the pva was dispersed in pbs at room temperature and the temperature raised to 45 ° c . to aid dissolution . this pva containing solution was returned to room temperature before use . 1 . 60 g of poly ( caprolactone ), low molecular weight , polysciences was dissolved in approximately 50 ml of methylene chloride . to this polymer solution was added 0 . 20 g of palmitic acid . to this solution of polymer - fatty acid was added 0 . 20 g of air milled somatogenin , and the active somatogenin was dispersed to primary particle size using gentle agitation and sonication for approximately one minute . the polymer solution - somatogenin suspension was added to the vortex of the stirred dulbecco &# 39 ; s pbs containing pva . a 400 ml . pyrex beaker and a plastic 3 - bladed stirrer and shaft were used to contain and agitate the oil - in - water emulsion . stirring continued overnight , resulting in complete evaporation of methylene chloride . the resulting microparticles were recovered using vacuum filtration and placed in a drying dish in a desicator under vacuum to dry . 1 . 91 g of dried microparticles were recovered and sieved to the following mesh cuts ( u . s . standard ): the microparticles prepared in accordance with the previous examples were used to determine the effect of somatogenin ( ly293404 ) concentration in different pla / pga microparticle concentrations . payout characteristics were measured by urinary urea nitrogen excretion and serum growth hormone levels in finishing swine . the microparticle formulations were placed in suspension , using 2 % w / v sodium carboxyl - methyl - cellulose 330 ( nacmc ) in nano - pure ii purified water . the suspension was injected subcutaneously in the flank . the following treatment ( trt ) materials were prepared : trt b : 5 % somatogenin pla / pga ( 85 : 15 ) microparticles ( 60 - 120 mesh , mw = 90 , 900 , viscosity = 0 . 58 dl / g in chcl3 @ 30 ° c .) suspended in water containing 2 % w / v nacmc 330 to give a dose of 42 mg somatogenin / animal . trt c : 10 % somatogenin pla / plg ( 85 : 15 ) microparticles ( 60 - 120 mesh , mw = 90 , 900 , viscosity = 0 . 58 dl / g in chcl3 @ 30 ° c .) suspended in water containing 2 % w / v nacmc 330 to give a dose of 42 mg somatogenin / animal . trt d : 25 % somatogenin pla / plg ( 85 : 15 ) microparticles ( 60 - 120 mesh , mw = 90 , 900 , viscosity = 0 . 58 dl / g in chcl3 @ 30 ° c .) suspended in water containing 2 % w / v nacmc 330 to give a dose of 42 mg somatogenin / animal . the results of this study demonstrate the efficacy of the microparticles for prolonged release of a contained peptide . urinary nitrogen reduction is a measurement of growth hormone which is stimulated by somatogenin release from microparticles . as shown in fig1 there was a reduction in urinary urea nitrogen excreted in all microparticle treated pigs during the first six days of treatment . the reduction was the greatest for the highest loaded ( 25 %) microparticles , and lowest for the lowest ( 5 %) loaded microparticles . fig2 shows the direct measurement of serum growth hormone for microparticle treated pigs , further evidencing the sustained release from the microparticles of the somatogenin over time . the vertical bars in the figures represent the relative standard deviations . the microparticles prepared in accordance with the previous examples were used to determine the payout characteristics of somatogenin ( ly293404 ) when administered in different pla / plg microparticle formulations as measured by urinary urea nitrogen excretion and serum growth hormone levels in finishing swine . the microparticle formulations were placed in suspension , using 2 % w / v sodium carboxyl - methyl - cellulose 330 ( nacmc ) in nano - pure ii purified water . the suspension was injected subcutaneously in the flank . the following treatment ( trt ) materials were prepared : trt b : somatogenin ( 3 micrograms / kg / day injected twice per day ) as positive control trt c : 11 . 7 % somatogenin pla / plg ( 50 : 50 ) microparticles ( 60 - 120 mesh , mw = 60 , 700 ) suspended in water containing 2 % w / v nacmc 330 to give a dose of 22 . 68 mg somatogenin / animal . trt d : 11 . 4 % somatogenin pla / plg ( 50 : 50 ) microparticles ( 60 - 120 mesh , mw = 29 , 000 ) suspended in water containing 2 % w / v nacmc 330 to give a dose of 7 . 56 mg somatogenin / animal . 11 . 4 % somatogenin pla / plg ( 50 : 50 ) microparticles ( 60 - 120 , mesh , mw = 29 , 000 ) suspended in water containing 2 % w / v nacmc 330 to give a dose of 22 . 68 mg somatogenin / animal . trt f : 13 . 6 % somatogenin pla / plg ( 85 : 15 ) microparticles ( 60 - 120 mesh , mw = 90 , 900 ) suspended in water containing 2 % w / v nacmc 330 to give a dose of 7 . 56 mg somatogenin / animal . trt g : 13 . 6 % somatogenin pla / plg ( 85 : 15 ) microparticles ( 60 - 120 mesh , mw = 90 , 900 ) suspended in water containing 2 % w / v nacmc 330 to give a dose of 22 . 68 mg somatogenin / animal . as shown in fig3 and 4 , there was a reduction in urinary urea excretion and an elevation in serum gh levels in the somatogenin injected ( bid ) barrows at all time periods for 15 days . urinary urea nitrogen excretion was less and serum gh levels were elevated in all microparticle treated pigs during the first 6 days of treatment . urinary urea nitrogen excretion and serum gh levels returned to baseline levels at approximately 9 days after treatment . test materials for in ovo injection studies , using the products of the previous examples were prepared as follows : trt b : micronized somatogenin dispersed in 50 ml purified water to yield a concentration of 60 μg somatogenin per 100 μl water ; trt c : micronized somatogenin dispersed in 50 ml purified water to yield a concentration of 600 μg somatogenin per 100 μl water ; trt d : microparticles ( somatogenin pla / pga , 60 - 120 mesh ) dispersed in 50 ml of 2 % w / v sodium carboxy methyl cellulose ( nacmc 330 ) to yield a suspension containing microparticles equivalent to 60 μg somatogenin / 100 μl ( amount dispersed on loading ); trt e : microparticles ( somatogenin pla / pga , 60 - 120 mesh ) dispersed in 50 ml of 2 % w / v nacmc 330 to yield a suspension containing microparticles equivalent to 600 μg somatogenin / 100 μl ( amount dispersed based on loading ); and trt f : blank microparticles ( pla / pga , 60 - 120 mesh ) dispersed in 50 ml of 2 % w / v nacmc 330 , approximately equivalent to high dose somatogenin pla / pga ( trt e ). upon injection of the foregoing materials into the air cells of eggs , the particles migrated to the bottoms of the eggs , typically within a few hours . no decrease in hatchability was noted for any treatment . while the invention has been described in detail in the foregoing description , the same is to be considered as illustrative and not restrictive in character , it being understood that only the preferred embodiments have been shown and described , and that all changes and modifications that come within the spirit of the invention are desired to be protected . __________________________________________________________________________sequence listing ( 1 ) general information :( iii ) number of sequences : 1 ( 2 ) information for seq id no : 1 :( i ) sequence characteristics :( a ) length : 76 amino acids ( b ) type : amino acid ( d ) topology : linear ( ii ) molecule type : protein ( ix ) feature :( a ) name / key : paramethylbenzoyl ( b ) location : 1 ( d ) other information : acyl group ( xi ) sequence description : seq id no : 1 : glyalaaspalailephethrasnasntyrargargvalleuthrgln151015leuseralaargargleuleuglnaspileleuserargglnglngly202530gluargasnglngluglnglyalaargvalargleuglyargglnval354045aspserleutrpalaaspglnargglnleualaleugluserileleu505560alathrleuleuglngluhisargasnserglngly657075__________________________________________________________________________
a composition of polyester microparticles containing bioactive polypeptide agents and methods for preparing the composition and administering bioactive agents . the composition comprises biocompatible , biodegradable microparticles having a polyester matrix and from about 5 % to about 25 % by weight of a biologically active , water - soluble polypeptide dispersed throughout the matrix , the polypeptide selected from the group consisting of growth hormone releasing factor , synthetic analogs of growth hormone releasing factor , pharmacologically active fragment thereof and somatogenin . the method for preparing the composition includes dissolving polyester in an organic solvent ; suspending a biologically active agent in the polyester solution ; emulsifying the suspension into an aqueous medium in which the agent is insoluble and evaporating the solvent from the emulsion to produce microparticles . the method for administering a bioactive agent to an organism involves suspending the microparticles in a suitable liquid and injecting the organism .