Ovarian Proteolytic Enzymes and Ovulation PDF

Gonadotropin releasing hormone. (GnRH) agonists can also be used to trigger ovulation by stimulating a sudden release of endogenous FSH and LH (32). PCOS

Understanding-ovulation-and-the-fertile-window.pdf

When you want to have a baby you can improve your chance of getting pregnant if you know about ovulation and the. 'fertile window' in the menstrual cycle.

Follicular Development and Ovulation in Sows: Effect of hCG and

in sows ovulating spontaneously and sows in which the ovulation was attempted in- duced by hCG or GnRH. Indwelling catheters were placed on day 1 (weaning=

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Ovulation induction with fertility drugs is also used in patients without ovulatory dysfunction. The goal is to stimulate the ovaries to produce more than one

Ovulation Induction With Bromocriptine (CB154) in Patients With

04-Nov-1977 Two of these subjects conceived and the third had cycles of ovarian response of follicular maturation only or ovulation with deficient corpus ...

Induction of ovulation after GnRH antagonists

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Medications for Inducing Ovulation

These medications can help a woman to ovulate more regularly increasing her chance of getting pregnant. These medicines

Novel Signaling Pathways That Control Ovarian Follicular

It is localized to granulosa cells of ovulating follicles between 4–12 hours after exposure to the. LH surge just prior to ovulation. Thus

Ovarian Proteolytic Enzymes and Ovulation

of ovulation and in many in- stances a thin translucent stigma

Natural and controlled ovulation in South American camelids

17-Feb-2018 Based on daily ultrasonography of the ovaries in llamas spontaneous ovulation occurred in 2 of 25 (8%) unmated llamas and failure to ovulate ...

BIOLOGYOFREPRODUCTION10,216-235(1974)

LAWRENCEL.ESPEY

TrinityUniversity,SanAntonio,Texas78284

Mammalianovulationisadynamicphe-

nomenonwhichrequiresdisruptionofthe vascularsystemanddisplacementofthe connectivetissueinthewalloftheGraafian follicleastheovumisreleased.Inmost mammals,thewholefollicleprotrudes moremarkedlyfromtheovariansurface atthetimeofovulation,andinmanyin- stancesathintranslucentstigma,the maculapellucida,formsattheapexofthe follicleasthefinalsignofimpendingrup- ture.Thisunusualmorphologicalchange hasleftastrikingimpressiononthosewho haveactuallyobservedit.

Kelly(1931)was

sofascinatedwhileobservingarabbitfol- liclenearrupturehestated"astension portionaroundthepolebeginsto bulge....Itnowstandsoutlikethenip- pleonabreast."Themomentofrupture sometimesappearsasanexplosiveevent, leadingobserverstocompareittoa"vol- canoerupting"(Hilletal.,

1935)ora

"blisterthatbursts"(Blandau,1966).

Thereareseveralreportswhichprovide

detailedaccountsofthemacroscopicand microscopicchangesthatoccurduringthis process(WaltonandHammond,1928;

Blandau,1966).

Untilthepastdecadelittleprogresshas

beenmadeintheelucidationoftheactual mechanismoffollicularrupture.Lackof knowledgeOnthisimportanteventinthe ofmoststudiesconductedpriorto1960 waslimitedtovisualandhistologicalobser- vationsofthefollicle.Buteventhereports oftheseexperimentswereeithernegative orsoinconsistentthat[theinvestigators] wereunabletoproduceanyconclusiveevi- dence"(GuttmacherandGuttmacher,

1921),and"theproblemstillremainsin

thisconditionofuncertainty"(Kraus,

1947).AsHisaw(1961)counseledadozen

yearsago,"thesolutionoftheproblemof ovulationmaybefoundbyinvestigating thebasicphysiologicalprocessesthatgoon inthefollicle."Theinformationpresented inthissymposium,whichDr.Nalbandov hassotimelyorganized,revealsthatsteps havebeentakenintherightdirection.

NONENZYMATICTHEORIES

Manyhypothesestoexplainovulation

wereformulatedpriorto1960,eventhough sounilexperimentaldatawerelacking.

Hisaw(1947)hasthoroughlyreviewedthe

theoriesuptothemiddleofthetwentieth century.BlandauandRumery(1963)have extendedthereviewthroughthenext15 yr,andRondell(1970a)hascoveredthe importantliteratureduringthepast decade.Therearenumerousotherreports whichincludeextensivereferencematerial onthemechanismofovulation(Asdell,

1962;Blandau,1966,1967,1968;Espey,

1964;EspeyandBetteridge,1970;Espey

andLipner,1965).Ishallnotendeavor toitemizeallthetheorieswhichhavebeen publishedinthismaterial;however,several pointsarenoteworthy.

Intrafollicularpressure.Upto1963,the

mostpopularspeculationsincorporatedthe ideathatruptureresultedfromanincrease inintrafollicularpressure.Thisdeduction

216Downloaded from https://academic.oup.com/biolreprod/article/10/2/216/2841277 by guest on 23 October 2023

PROTEOLYTICENZYMESANDOVULATION217

wasbasedprimarilyonthedynamic changesonthesurfaceofthefollicleat thetimeofovulation.Itissurprisingthis "pressuretheory"wasnotchallengedmore seriouslybeforethepastdecade.Asearly as1919,Corner(1919)pointedoutthat thethecaexternaofthefollicle"iscom- posedchieflyofcollagenousfibrilsand theirassociatedfibroblasts."Becauseofthe hightensilestrengthofthiscollagenous layerofthefolliclewall,Guttmacherand

Guttmacher(1921)couldnotinducerup-

tureinsowfolliclesbymaintainingacon- stantheadofpressureofwellover300 mmllgintheovarianarteriesforhours atatime.Theynotedthat"thefollicular vesselscouldbeseentowashoutclearly butrupturedidnotoccurinasinglein- stance,eventhoughonebracedhimself againstawallandpushedthepistonof theinjectionsyringewithallofthephysical strengthavailable."Yet,seriousquestion ofthepressuretheoriesdidnotcomeuntil the1960swhenthreeseparatestudies (BlandauandRumery,1963;Espeyand

Lipner,1963;Rondell,1964)demonstrated

thatfollicularpressuredoesnotincrease priortoovulation.(Thisisnottoirnpl\ thatthelowintrafollicularpressurewhich existsisnotanessentialhydrostaticforce inthedissociationofa"weakened"follicle wall.)

Smoothmuscle.In1849,Kolliker(1849)

firstmentionedsmoothmuscleasastruc- turalconstituentoftheovary.Severalyears laterthehypothesiswasformulated (Rouget,1858;Grohe,1863)that,incon- tracting,themusclefibersoftheovary compressedthebloodvessels,andthe congestionfromimpairedvenousreturnled totheruptureofthematurefollicles.This ideahasbeensupportedforthepast100 yrbynumeroushistologicalreports(see

Espey,1964)ofsmoothmusclecellsinthe

thecaltissue.However,observationswitha polarizingmicroscope(Claesson,1947)do notrevealsmoothmusculatureinthefol- liclewallincow,swine,rabbit,orguinea andYatvin,1970)revealedsmoothmuscle cellsintheovarianfollicle.Furtherchal- lengetothesmoothmuscletheorycame fromevidencethatawidevarietyof smoothmusclestimulantsfailedtoinduce contractileactivityinsowfollicles(Espey,

1964).Inaddition,recordingofintrafol-

licularpressuresduringovulationdonot indicatethatsmoothmusclecontractions areimportantinthisprocess(Espeyand

Lipner,1963).

Inspiteofalltheevidencetothecon-

trary,duringthepastseveralyearsthere hasbeenaresurginginterestinthepossible roleofsmoothmusclecellsinthemecha- nismofovulation.Newreportssupportthe presenceofthistypeofcellandthetheory thatthey"mayplayaroleintheprocess ofovulation"(O'Shea,1970)bycausing "folliculardehiscenceandatusia"(Fum- agallietal.,1971)through"acontractile forcewhichseemstobeeffectivein dissociatingtheconnectivetissue"(Okam- uraetat.,1972)leadingto"anopeningof thestigmaandtheextrusionofthefolli- cularcontents'(PaltiandFreund,1972).

However,itismyopinionthatnoneofthe

recentultrastructuralstudiesclearlydem- onstratesmoothmusclecellsinthethecal layerofthefolliclewall.Inonecase (Okamuraetat.,1972),theelectronmicro- graphwhichreportedlydemonstratesa "smoothmusclecell"appearsactually tobetakenfromaregionoftheovarian stroma,ratherthanthethecafolliculi.

Intheotherreports,forthemostpart

theinvestigatorshavefailedtorecognize thatitisnotuncommontoobservecyto- plasmicfilamentsinfibroblasts(seeHaust andMore,1967).Iwouldnotdenythat thefolliclewallmayoccasionallycontain whatappeartobemyofibroblasts,butthese cellsarerare,andprobablyrepresentan anomalywhichhasnosignificantfunc- tionalroleinthemechanismofovulation.

Mechanical(mathematical)models.The

matureovarianfollicleisarigidsphere

surroundedbyadenselayerofcollagenousDownloaded from https://academic.oup.com/biolreprod/article/10/2/216/2841277 by guest on 23 October 2023

218ESPEY

connectivetissue.Anidealizedmathemati- calandphysicalmodelofthisspherehas beenusedbyRodbard(1968)toanalyze theprocessofovulation.Heconcluded(1) thatbyusingthephysicalcharacteristics ofthemodelthepreciseconditionsforovu- lationcouldbestatedmathematically,(2) thatasfolliclesreachacriticalsizethe stigmaformationmaybeexplainedby mechanicalfactors,and,finally,(3)that byprovidingamechanicalfinalcommon pathway,thisapproachhasbeenableto reconcilepreviousconflictingdataandthe- oriesconcerningtheeventsofovulaton.

However,hismodelisnotonlyoversimpli-

fied,butbasedonmanygrossassumptions regardingthephysiologicalprocesses withintheovarianfollicle.Anymechanical modelwhichistobecomparedwiththe follicleduringovulationmustincorporate theknownchangesindistensibilityand breakingstrengthofthefolliclewall (Rondell,1970a).Lardner(personalcom- municationfromDr.ThomasLardner,

Dept.Mech.Eng.,M.I.T.)supportsthis

positionofRondellregardingmathematical models.Ibelievethat,becauseofthemany assumptionswhicharenecessaryinthe conversionofalivingsystemintoamathe- maticalmodel,itisdoubtfulthisanalytical approachwillprovideanyusefulinforma- tiononthemechanismofrupture.

DEGRADATIONOFTHEFOLLICLE

Macroscopicchanges.Itisnotdifficultto

recognizefrommacroscopicobservations thatthereisagrosschangeintheintegrity oftheconnectivetissueofafolliclenear rupture(unpublished).Afterhandling hundredsofthousandsofsowovaries,it becomesobviousthatnearovulationfolli- clesaredistinctlymoreflaccid:Exertion ofonlyslightmanualpressurecausessuch folliclestoburst.Asanotherexample,if thewallofarabbitfollicleispenetrated withamicropipette(fordeterminationof gibleforceisrequiredtopenetratethesur- faceofthefollicleifitisclosetorupture.

Thirdly,whenattemptsaremadetodissect

wholefolliclesfromthesurfaceoftherab- bitovary,thefolliclesinprecoitalrabbits aredifficulttoextirpatebecauseofconnec- tivetissueadhesionswhichinterlacethe follicularthecawiththeovarianstroma.

However,nearrupturethisc:innectivetis-

sueappearsdecomposedandthefollicles "peelout"withminimalsurgery.Collec- tively,thesequalitativeobservationssug- gestthereisactivedecompositionofthe connectivetissueintheovarynearrupture.

Microscopicchanges.Microscopictech-

niqueshaveelucidatedsomeofthetransi- tionsinthefinestructureofthefollicle wallasitapproachesrupture.Duringovu- lationintherabbit,thethecaltissueap- pearstoundergosignificantdeterioration (Espey,1967a).Thisinvolvesdissolution oftheextracellulargroundsubstanceand dissociationofthefollicularcollagen.Not onlyisthereaseparationofthecollagen fibers,butthecellsalsoappeartobesparse incomparisontothoseinmaturefolicles distantfromovulation.Intheminutespre- cedingrupture,thefibrousouterlayersof thefolliclewallthintolessthanone-fifth theiroriginalwidth.Thispreovulatory thinningofthefolliclewallhasalsobeen observedintherat(Blandau,1967).

Theseobservationssuggestedthatlyso-

somalhydrolasesmightbeactiveinthe ovulatoryprocess.However,examination oftheultrastructureofmaturerabbitfol- liclesinthislaboratoryhasrevealednegli- giblelysosomalbodies(Stutts,1968).With theexceptionofthegerminalepithelium, lysosomesweresparseinthecellsofthe folliclevall,nordidthosepresentundergo anyconspicuouschangesduringovulation.quotesdbs_dbs48.pdfusesText_48

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