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The synthetic activity and glandular volume of the corpus allatum during ovarian maturation in the desert locust Schistocerca gregaria
Pergamon Press
Lite Sciences Vol . 17, pp . 417-422 Printed in the U.S .A .
THE SYNTHETIC ACTIVITY AND GLANDULAR VOLUME OF THE CORPUS ALLATUM DURING OVARIAN MATURATION IN THE DESERT LOCUST SCHISTOCERCA GREGARIA Stephen S . Tobe* and Grahams E . Pratt Agricultural Research Council, Untt of Invertebrate Cheml~try and Physiology, University of 9ussex, Falmer, Brightm BN1 9QJ, U .K . aad *Dept . of Zoology, University of Tormto, Tormto, Ontario M5S lAl, Canada . (Received in final form June 25, 1975) âllmmar9 We have compared, m an Individual baris, the volume art the corpora spats with their sbülty to synthesize and release juvenile hormme (JH) using glands taken at daily intervals throughout the period of sexual ++t~~"Ystim and the first two ovarisa cycles in Schlstocerca aria. A staadard_tn vitro radiochemical assay wa~ used to measure the rates of both epmtaneous JH biosynthesis from 14 lmlne, and of JH biosynthesis stimulated by optimal cancen[methyl- C m tratians of rC-2 -farnesenic acid . Computatlm of results showed that there are, during this period, changes of up to 250-fold In the rate a~f spmtaneous JH biosynthesis per unit volume corpora spats . It Ls cmcluded that the volume of the corpora allata is of no value as as indicator of the spmtsaeoue synthetic activity ad the glands to this specter, and that the overall rate of JH synthesis is regulated by mechaalems that do not involve large changes in the vdume of the gland cells . However, in the presmoe of farnesenic acid, there is a correlatim between stimulated JH synthesis and glandular volume, suggesting that the volume of the gland reflects the meaimum activity of the final two stages In JH biosynthesis . The oorpora spats (CA) are now the defined source of juvenile hormone (JH) in several Insect ßpecies . We have recently descrü~ed a direct radiochemical method for mmitoring the rate of synthesis and release of locust JH (C 18 JH) by isolated CA of _S . gra~aria In vitro (1,2,8,4) . This method assays the capacity of the CA to synthesize JH both epmtaaeously (tn the presence of mly simple precursors) and when stimulated by the addltim of the exogenous precursor, farnesenic acid (see 1) . However, previous workers have found It necessary to use indirect methods for the estimatim of CA activity . Perhaps the simplest method has been the use of the volume of üie CA as the criterim for activity (see 5,8 for reviews) . Cyclic changes In CA volume have been observed to the locusts S . re a is (7, B) and S . paraaenste (9) but not In the migratory locust, *Present address 417
418
Activity and Volume of Corpus Allatum
Vol . 17, No . 3
us mtaraLoria (10) . However, recent work has suggested that there may be llt#le correlation between CA volume and "CA activity", at leiast to females of Tenebrio (11), Calll ore (12), MelaaoDlus (13) and Locuste (10) and melee of Locusts (14) (see also lb) . However, ccnolueive evidence either for or agelast this conelatian hoe not base forthcoming because a direct method for assaying activity of CA has not beam available . Using our short term to vitro assay, we have monitored the synthetic capacity oP female 8, gyre ri CA daring the first two ganotrop~hio cycles and we report here an the relation between Ibis synthetic capacity and the volume of the CA . These results conclusively demonstrate that there to no relation between CA volume and epantaneoue JH synthetio capao(iy, but that there is a conelatiaa with stimulated JH syathesla . Materials aa~i Methods Locuata were reared on a diet of fresh wheat eeedllags, rolled oats and agar-base medlnm containing the anttblotto Thipyrameth u previously described (18) . In two dlûereat series of eaperlmente, aaimale were aaorificed at daily intervals cn days 3-17 as adult life . The syatheste and release of C l JH by CA is v~ was assayed uelag the tncorporaticn of the methyl moiety at Meg4C]-methicniae (Radiochemical Centre, Amersham, U, K. ; final apeolflo activity 38 . T mCt/mmd) tnXo C ie .TH is the case ad spontaneous synthesis, and Me- 14 01-methtoaine and ~C-2 ~-farneseaic acid (specific activity 25 mCt/mmol ; Real concentration 20 pài) into C1 8JS In the case of stimulated ayathesie . The freshly isolated glaada were iaoubated to the radlolabelled medium for 2 or S hours, as described elsewhere (18) and the amount of C18JH bloey~esised was determined by a standard aaalysia ualng thin-layer chromatography and liquid eotnttllattcn canting (1) . Foüowiag diseeotian of the CA from the animal, each gland was placed to a drop of Insect Ringer (1) an a cavity slide and the diameter of its three priaelpal axes measured at X 82 . b m a Wüd dissecting mloroaaope equipped wig as eyepiece micrometer . For the purpose d this iavestlgatlan,~it h`a_s been assumed that the CA are ablate spi~eroids and aooordùngly the formnla V ~ ~ has beam used, where V a volume of CA and a, b and e represent the radii of the three principal axes . Volumes of CA have been expressed a. neaol[tres (ni) and for the graphical pres~icn of JH eyathesis per unit volume, the overall rate of C i BJH synthesis by the four CA per tube has been divided by the sum a[ the vdume of the four glands In the cane of the first aeries a1 experimeata, while in the second series, the rate of synthesis of each pair of CA per tube has bees divided by the total volume of the two glands and the mesa of the synthesis per unit volume for four separate pairs of CA per experimental day plotted. Reeulta Volume of the CA increased from ib-20 nl, S days alter adult emergence, to a maximum of SO-Sb al during the fleet ganotxnphio cycle (days 8-12) and then decreased to about 2b al . During the second gcnotrophio cycle (days 12-1T in the first series and days 12-18 In the second series), the changes were not clear-oat, although there was ageia sa overall increase during the ayole . These findings are to eeaential agreement with those of previous workers (T, ~ . The C18JH synthesis rate per unit volume for glands sy~heslziag JH either spoataneouely or when annotated by the addttten ad faraesenic acid is shown to Ftg . i
Vol . 17, No . 3
Activity and Volume of Corpus Allatum
419
(first aeries a~f experiments) and Flg . 2 (seccad aeries) . It to already lmowa that the rate of release of JIi by S. re rte CA is directly proporticoal to the rate o~f JH eyntheete (2, 3, 4) . These figures show the changes to JH synthesis per salt volume during the ftret two goaotrophic cycles and are presented as a log linear plot ao that the large ohaages which occur in volume-related spcataneous synthesis can be easily visualized. It is clear that this volume-related epoataneous synthesis changed by a factor ad 250 in the first aeries (compare for example days il or 15 with days 3 or 14 in Flg . 1) . Large changes were also observed to the spoataaeous syatheata rate per unit volume to the seccad series (Fig. 2) but these changes were not as great ae those observed to the first series and in general did not exceed 40-fold . We must therefore conclude that the synthesis of C1gJI3 is not normally related to any functional way to the volume of the CA .
FIt~. 1 X10 °f rate of ~ eyatheate per unit volume of CA as a fimatica ad adult age for satmale of the first experimental series (solid llaee) . Circles represent glands synthesiztag JIi epoataaeousiy (average a~f four pairs of glands), triangles represent glands stimulated wtth farneseatc acid (average of two pairs of glands) . Vertical arrows lad[cate times of asset of vltellogeneete In suoceBSive waves of oocytes . For purposes of comparlsca, the release of C1gJIi from the same glands aver the same eucperlmeatal period is also shown (dotted lines) and is based m data presented by Tobe sad Pratt (lg) . In the case of JH ayathesis stlm~ilated by the addition of farnea~ic acid, however, there appears to be a relation between CA volume and synthesis, In,general the rate of synthesis of C1gJH per unit volume being about 1 pmol per hour per al of gland in both series of experiments (Figs . 1 and 2) . The observed relatively small amplitude fluctuations around this value (t 50~) do not cotaclde In the two settee of experiments, ualtke the ahaages to epoataaeous ay~hesle per un[t volume, sad may have little physiological aignlflcaaoe.
420
Activity and volume of Corpus Allatum
vol . 17, No . 3
FI(}. 2 Legend as for Fig . 1, but second experimental series . Discusstcn It 18 class that the large and rapid changes In the spontaaeous activity of the CA per unit volume of gland during early adult life of the female locust are a reAecttaa of the dynamic endocriae role these glands play is sezual maturattan and the regulatlm of cyclto ovarian development . A detailed oomparisan bebveen the total synthetic activity of the CA and several parameters of ovaries development (1~ tadicated that the activity of the CA aaanot be reliably predicted sdely an the basis of the state of maturity of the follicles a[ the ovary ; this suggests that there must be several importaat aspects of the mode of action aI JH as ovarian development which require further clarification . Here we have been concerned with chaagea taking place within the glands, namely the relaticnehip between JH synthetic activity and changing glandular size durtng the gonotrophic cycles, but the emergent pattern of spontsaeous synthetic activity per unit volume of gland diäers only quantitatively from the pattern c2 total activity per gland described by Tab~ and Prat! (16) (see also Flgs. 1 sad 2--CigJH release per gland) . Ia pastlcular, the first burst of CA activity oa day 4 [s relatively small and precedes the onset of vltellogenesis by several days (Figs . 1 and 2) and subsequent peaks of glandular activity do not oobtoide precisely with the onset of vitellogeaesis is the ensuing ganotraphlc cycles . The method employed here for the determining of the volume of CA differs from the method used by Joly (10) sad Htghnam et al. (8) because of our requirement (a) not to damage the glands by excessive manlpalatim prior to the tnoubatian, and (b) to analyze the glands for the radtoaotlve components lmmedlatoly after the hacubstian . Our estimates of glandular volume, .based upon measuremeata of the three principal radii of fresh matsrlal, are consistently higher than those obtained by Hlghnam et al. (8) fra~m
Vol . 17, No . 3
Activity and Volnme of Corpus Allatsan
421
measurements of Bectiane of füced material, f~r which we envisage two possible eaplsaattoae : firstly, our use of the simple formula -wabc which is only accurate for perfect oblate spheroids may introduce a eystemat[c d~erestimate of the volume ; secondly, their method may underestimate the volume owing to the ehrtaisge of the tissue during ftxatlar and embedding . Perhaps the true volume of a CA lies to between the estimates obtained by these two methods . However, apart from this discrepancy, there is good agreement between our present ffmdtnga sad those of Htghnam et al . (8) . Our results caaftrm that cyclic changes to the volume of the CA do occur during the first two ganotroph[c cycles . Such changes have been observed previously to female 3 . re arte (7, 8) ae well as in other taeecta (see 8) and apparently correlate well with the gcnotrophtc cycles . However, tt Is clear from the present study that at least in adult female _S . aZe¢aris , the volume of the CA to no tadlcator of the cnrreat rate a~f JH synthesis and release in ~e glande . Joly (10) has suggested that the activity of CA, as determined by a chromatatsopic transplantatiar bioassay, is mugüly praporticnal to their volumr, during the fourth and fifth tnstar of L, mt¢ratorla and at least at day 5 a~f adult life . Unfortunately, we do not know whether or not the transplanted glands to Joly~e chromatotropic bioassay retain the same level of JH secretory activity during üie three day period of the bioassay ae they ~d[d In situ before transplaatattan . Ia contrast, Strong (9) concluded that transplantation of CA from adult female 3, araneneis lato allatectomited adult females of the same species results either in failure to Induce overt "activity" In the case of CA taken from Immature females, or results to the rapid loss of "activity" to the case of CA taken from mature females . These apparently conflicting results are dtff[cult to compare because (a) very different btologlcal teats were used to estimate the activity of the transplanted glands, and (b) different spe~otes ôf locust were employed. For these reasons, It may sow be timely to rei~estlgate the relation, if any, between CA volume and JH synthesis during earlier motors of S . to ~ad perhaps other species of locusts, using the meti~ods described la the present paper . It is noteworthy that our observed rates of spontaneous JH synthesie never equal the correapoadtng farnesenic acid attmulatsd rates, altàough they do approach to within 80~ of üie stimulated rate at certain precise times during ovarian maturation . A s[müar phenomenar has been reported to the case of CA from adult female Periplaneta americaaa cultured under similar oardtt[ans (17) . We have laterpretsd these findings ae Indicating that there is normally an excess competence of the glands to effect äie last two stages In JH bloeyutbesls (see also 18) . Nucleo-cytoplasmic ratio of CA cells has also been employed as a method for estimating the JH synthetic capacity of the CA (6,18) . The fact that we have found a relation between CA volume and stimulated JH synthesis might indicate that the enzymes lnvolve~d in the fiasl two stages of JH synthesis and the cytoplasmic cwnnpartment in which they are located, are related to some as yet unexplained way . What is clear is that the physiological changes to the spantaaewus eynthet[c activity a~f the CA daring the course of ovarian maturattar to the locust, are almost entirely ladependent of chsag~es to the volume of the gland . Acknowledgemente We ar~ grateful to our colleagues Dr . A. F . White sad Mlas M . M . Blight for kindly providing H-farneaeaic acid and synthetic referaroe compounds ; to Dr . J . E . Henry for advice and tnformatlar ar the use of Th[pyrameth se a prophylactic agent against
Activity aad Volua of Corpus 7111atum
422
vol . 17, No . 3
M a lnfeotlm, and to the late Joe Ds Costs for rearing the boosts . 9, 9 . T, aclmavledges reosipt d a Natl0nal Research Couaoü d Canada post-doctoral feIIowshtp during the coarse d this work . Re erenoes 1. 2. 3. 4. b. 8. 7. 8. 9. 10 . 11 . 12 . 19 . 14 . 15 . 18 . 17 . 18 .
a. E .
PRATT aad 3 . 9 . TOBE, Lif ( . , 14, b75-688 (1974) . f~.E . PRATT, 8 .9, TOBE, R,J, WEAVER, andJ,R, FIIdNEY, (ien . Como . Endoorinol . , in press . 9, 8, TOBE and (3, E, PRATT, Bioohem . J . , 144, 10?-113 (1874) . 9,9 . TOBE and (~.E, PRATT, Nsture (Londcn) , 282, 474-478 (1974) . 247-998 (1984) . V,B, WI(3(3LESWORTB, Ad~. Inseot Phvsiol . , F, ENßELbIANN, The P'hvsiolo~ d Imeot Reprodaottan , Pergaman Presa, O~dord (19?0) . K, C . $IßFirTAM, Mem . Soo . Eadoor(aol . , 12, 979-390 (1982) . K, C . SIiRiriAM, L, HII.L, AND W. MORDUE, J . Iaseot Phsstol . , 12, 977-994 (1988) . L . 3TRON(i, J. InseOt Ph~s(ol , , 11, 135-148 (1986) . P, JOLY, Ma. 900 . Entamdol . Fr . , 3, 801-808 (1987) . W, MORDUE, (~m . Comn. Ehdoorlnol ., 8, 408-416 (1987) . A,O . LEA sad E, THOM9ÉN, J . ùuect Ph9s(o1 ., 16, 477-482 (1989) . C, CfII.LOTT aud ß.9, DOQRA, (3en . Como . Eadoortnol ., 18, 128-132 (1972) . R,A, J01~T80N and L, HII.L, J . Insect Phvsid . .~, 2468-2487 (1973) . W. MORDUE, K . C, HI(3BZiAM, L, HILL, aad A. d, LUNTZ, Mem . 800 . E.hdoorinol . , 18, 111-198 (1870), 8 .8. TOBE and ß, E . PRATT, d. Exu . Blol . , (a press . a . E, PRATT and R . J, WEAVEB, J . EndoOrinQ1 . , 84, 87 (1975) . F . EN(~ELMANN, J. Inseot Phvs(ol . , 3., 257-278 (1887) .
2,
Lite Sciences Vol . 17, pp . 417-422 Printed in the U.S .A .
THE SYNTHETIC ACTIVITY AND GLANDULAR VOLUME OF THE CORPUS ALLATUM DURING OVARIAN MATURATION IN THE DESERT LOCUST SCHISTOCERCA GREGARIA Stephen S . Tobe* and Grahams E . Pratt Agricultural Research Council, Untt of Invertebrate Cheml~try and Physiology, University of 9ussex, Falmer, Brightm BN1 9QJ, U .K . aad *Dept . of Zoology, University of Tormto, Tormto, Ontario M5S lAl, Canada . (Received in final form June 25, 1975) âllmmar9 We have compared, m an Individual baris, the volume art the corpora spats with their sbülty to synthesize and release juvenile hormme (JH) using glands taken at daily intervals throughout the period of sexual ++t~~"Ystim and the first two ovarisa cycles in Schlstocerca aria. A staadard_tn vitro radiochemical assay wa~ used to measure the rates of both epmtaneous JH biosynthesis from 14 lmlne, and of JH biosynthesis stimulated by optimal cancen[methyl- C m tratians of rC-2 -farnesenic acid . Computatlm of results showed that there are, during this period, changes of up to 250-fold In the rate a~f spmtaneous JH biosynthesis per unit volume corpora spats . It Ls cmcluded that the volume of the corpora allata is of no value as as indicator of the spmtsaeoue synthetic activity ad the glands to this specter, and that the overall rate of JH synthesis is regulated by mechaalems that do not involve large changes in the vdume of the gland cells . However, in the presmoe of farnesenic acid, there is a correlatim between stimulated JH synthesis and glandular volume, suggesting that the volume of the gland reflects the meaimum activity of the final two stages In JH biosynthesis . The oorpora spats (CA) are now the defined source of juvenile hormone (JH) in several Insect ßpecies . We have recently descrü~ed a direct radiochemical method for mmitoring the rate of synthesis and release of locust JH (C 18 JH) by isolated CA of _S . gra~aria In vitro (1,2,8,4) . This method assays the capacity of the CA to synthesize JH both epmtaaeously (tn the presence of mly simple precursors) and when stimulated by the addltim of the exogenous precursor, farnesenic acid (see 1) . However, previous workers have found It necessary to use indirect methods for the estimatim of CA activity . Perhaps the simplest method has been the use of the volume of üie CA as the criterim for activity (see 5,8 for reviews) . Cyclic changes In CA volume have been observed to the locusts S . re a is (7, B) and S . paraaenste (9) but not In the migratory locust, *Present address 417
418
Activity and Volume of Corpus Allatum
Vol . 17, No . 3
us mtaraLoria (10) . However, recent work has suggested that there may be llt#le correlation between CA volume and "CA activity", at leiast to females of Tenebrio (11), Calll ore (12), MelaaoDlus (13) and Locuste (10) and melee of Locusts (14) (see also lb) . However, ccnolueive evidence either for or agelast this conelatian hoe not base forthcoming because a direct method for assaying activity of CA has not beam available . Using our short term to vitro assay, we have monitored the synthetic capacity oP female 8, gyre ri CA daring the first two ganotrop~hio cycles and we report here an the relation between Ibis synthetic capacity and the volume of the CA . These results conclusively demonstrate that there to no relation between CA volume and epantaneoue JH synthetio capao(iy, but that there is a conelatiaa with stimulated JH syathesla . Materials aa~i Methods Locuata were reared on a diet of fresh wheat eeedllags, rolled oats and agar-base medlnm containing the anttblotto Thipyrameth u previously described (18) . In two dlûereat series of eaperlmente, aaimale were aaorificed at daily intervals cn days 3-17 as adult life . The syatheste and release of C l JH by CA is v~ was assayed uelag the tncorporaticn of the methyl moiety at Meg4C]-methicniae (Radiochemical Centre, Amersham, U, K. ; final apeolflo activity 38 . T mCt/mmd) tnXo C ie .TH is the case ad spontaneous synthesis, and Me- 14 01-methtoaine and ~C-2 ~-farneseaic acid (specific activity 25 mCt/mmol ; Real concentration 20 pài) into C1 8JS In the case of stimulated ayathesie . The freshly isolated glaada were iaoubated to the radlolabelled medium for 2 or S hours, as described elsewhere (18) and the amount of C18JH bloey~esised was determined by a standard aaalysia ualng thin-layer chromatography and liquid eotnttllattcn canting (1) . Foüowiag diseeotian of the CA from the animal, each gland was placed to a drop of Insect Ringer (1) an a cavity slide and the diameter of its three priaelpal axes measured at X 82 . b m a Wüd dissecting mloroaaope equipped wig as eyepiece micrometer . For the purpose d this iavestlgatlan,~it h`a_s been assumed that the CA are ablate spi~eroids and aooordùngly the formnla V ~ ~ has beam used, where V a volume of CA and a, b and e represent the radii of the three principal axes . Volumes of CA have been expressed a. neaol[tres (ni) and for the graphical pres~icn of JH eyathesis per unit volume, the overall rate of C i BJH synthesis by the four CA per tube has been divided by the sum a[ the vdume of the four glands In the cane of the first aeries a1 experimeata, while in the second series, the rate of synthesis of each pair of CA per tube has bees divided by the total volume of the two glands and the mesa of the synthesis per unit volume for four separate pairs of CA per experimental day plotted. Reeulta Volume of the CA increased from ib-20 nl, S days alter adult emergence, to a maximum of SO-Sb al during the fleet ganotxnphio cycle (days 8-12) and then decreased to about 2b al . During the second gcnotrophio cycle (days 12-1T in the first series and days 12-18 In the second series), the changes were not clear-oat, although there was ageia sa overall increase during the ayole . These findings are to eeaential agreement with those of previous workers (T, ~ . The C18JH synthesis rate per unit volume for glands sy~heslziag JH either spoataneouely or when annotated by the addttten ad faraesenic acid is shown to Ftg . i
Vol . 17, No . 3
Activity and Volume of Corpus Allatum
419
(first aeries a~f experiments) and Flg . 2 (seccad aeries) . It to already lmowa that the rate of release of JIi by S. re rte CA is directly proporticoal to the rate o~f JH eyntheete (2, 3, 4) . These figures show the changes to JH synthesis per salt volume during the ftret two goaotrophic cycles and are presented as a log linear plot ao that the large ohaages which occur in volume-related spcataneous synthesis can be easily visualized. It is clear that this volume-related epoataneous synthesis changed by a factor ad 250 in the first aeries (compare for example days il or 15 with days 3 or 14 in Flg . 1) . Large changes were also observed to the spoataaeous syatheata rate per unit volume to the seccad series (Fig. 2) but these changes were not as great ae those observed to the first series and in general did not exceed 40-fold . We must therefore conclude that the synthesis of C1gJI3 is not normally related to any functional way to the volume of the CA .
FIt~. 1 X10 °f rate of ~ eyatheate per unit volume of CA as a fimatica ad adult age for satmale of the first experimental series (solid llaee) . Circles represent glands synthesiztag JIi epoataaeousiy (average a~f four pairs of glands), triangles represent glands stimulated wtth farneseatc acid (average of two pairs of glands) . Vertical arrows lad[cate times of asset of vltellogeneete In suoceBSive waves of oocytes . For purposes of comparlsca, the release of C1gJIi from the same glands aver the same eucperlmeatal period is also shown (dotted lines) and is based m data presented by Tobe sad Pratt (lg) . In the case of JH ayathesis stlm~ilated by the addition of farnea~ic acid, however, there appears to be a relation between CA volume and synthesis, In,general the rate of synthesis of C1gJH per unit volume being about 1 pmol per hour per al of gland in both series of experiments (Figs . 1 and 2) . The observed relatively small amplitude fluctuations around this value (t 50~) do not cotaclde In the two settee of experiments, ualtke the ahaages to epoataaeous ay~hesle per un[t volume, sad may have little physiological aignlflcaaoe.
420
Activity and volume of Corpus Allatum
vol . 17, No . 3
FI(}. 2 Legend as for Fig . 1, but second experimental series . Discusstcn It 18 class that the large and rapid changes In the spontaaeous activity of the CA per unit volume of gland during early adult life of the female locust are a reAecttaa of the dynamic endocriae role these glands play is sezual maturattan and the regulatlm of cyclto ovarian development . A detailed oomparisan bebveen the total synthetic activity of the CA and several parameters of ovaries development (1~ tadicated that the activity of the CA aaanot be reliably predicted sdely an the basis of the state of maturity of the follicles a[ the ovary ; this suggests that there must be several importaat aspects of the mode of action aI JH as ovarian development which require further clarification . Here we have been concerned with chaagea taking place within the glands, namely the relaticnehip between JH synthetic activity and changing glandular size durtng the gonotrophic cycles, but the emergent pattern of spontsaeous synthetic activity per unit volume of gland diäers only quantitatively from the pattern c2 total activity per gland described by Tab~ and Prat! (16) (see also Flgs. 1 sad 2--CigJH release per gland) . Ia pastlcular, the first burst of CA activity oa day 4 [s relatively small and precedes the onset of vltellogenesis by several days (Figs . 1 and 2) and subsequent peaks of glandular activity do not oobtoide precisely with the onset of vitellogeaesis is the ensuing ganotraphlc cycles . The method employed here for the determining of the volume of CA differs from the method used by Joly (10) sad Htghnam et al. (8) because of our requirement (a) not to damage the glands by excessive manlpalatim prior to the tnoubatian, and (b) to analyze the glands for the radtoaotlve components lmmedlatoly after the hacubstian . Our estimates of glandular volume, .based upon measuremeata of the three principal radii of fresh matsrlal, are consistently higher than those obtained by Hlghnam et al. (8) fra~m
Vol . 17, No . 3
Activity and Volnme of Corpus Allatsan
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measurements of Bectiane of füced material, f~r which we envisage two possible eaplsaattoae : firstly, our use of the simple formula -wabc which is only accurate for perfect oblate spheroids may introduce a eystemat[c d~erestimate of the volume ; secondly, their method may underestimate the volume owing to the ehrtaisge of the tissue during ftxatlar and embedding . Perhaps the true volume of a CA lies to between the estimates obtained by these two methods . However, apart from this discrepancy, there is good agreement between our present ffmdtnga sad those of Htghnam et al . (8) . Our results caaftrm that cyclic changes to the volume of the CA do occur during the first two ganotroph[c cycles . Such changes have been observed previously to female 3 . re arte (7, 8) ae well as in other taeecta (see 8) and apparently correlate well with the gcnotrophtc cycles . However, tt Is clear from the present study that at least in adult female _S . aZe¢aris , the volume of the CA to no tadlcator of the cnrreat rate a~f JH synthesis and release in ~e glande . Joly (10) has suggested that the activity of CA, as determined by a chromatatsopic transplantatiar bioassay, is mugüly praporticnal to their volumr, during the fourth and fifth tnstar of L, mt¢ratorla and at least at day 5 a~f adult life . Unfortunately, we do not know whether or not the transplanted glands to Joly~e chromatotropic bioassay retain the same level of JH secretory activity during üie three day period of the bioassay ae they ~d[d In situ before transplaatattan . Ia contrast, Strong (9) concluded that transplantation of CA from adult female 3, araneneis lato allatectomited adult females of the same species results either in failure to Induce overt "activity" In the case of CA taken from Immature females, or results to the rapid loss of "activity" to the case of CA taken from mature females . These apparently conflicting results are dtff[cult to compare because (a) very different btologlcal teats were used to estimate the activity of the transplanted glands, and (b) different spe~otes ôf locust were employed. For these reasons, It may sow be timely to rei~estlgate the relation, if any, between CA volume and JH synthesis during earlier motors of S . to ~ad perhaps other species of locusts, using the meti~ods described la the present paper . It is noteworthy that our observed rates of spontaneous JH synthesie never equal the correapoadtng farnesenic acid attmulatsd rates, altàough they do approach to within 80~ of üie stimulated rate at certain precise times during ovarian maturation . A s[müar phenomenar has been reported to the case of CA from adult female Periplaneta americaaa cultured under similar oardtt[ans (17) . We have laterpretsd these findings ae Indicating that there is normally an excess competence of the glands to effect äie last two stages In JH bloeyutbesls (see also 18) . Nucleo-cytoplasmic ratio of CA cells has also been employed as a method for estimating the JH synthetic capacity of the CA (6,18) . The fact that we have found a relation between CA volume and stimulated JH synthesis might indicate that the enzymes lnvolve~d in the fiasl two stages of JH synthesis and the cytoplasmic cwnnpartment in which they are located, are related to some as yet unexplained way . What is clear is that the physiological changes to the spantaaewus eynthet[c activity a~f the CA daring the course of ovarian maturattar to the locust, are almost entirely ladependent of chsag~es to the volume of the gland . Acknowledgemente We ar~ grateful to our colleagues Dr . A. F . White sad Mlas M . M . Blight for kindly providing H-farneaeaic acid and synthetic referaroe compounds ; to Dr . J . E . Henry for advice and tnformatlar ar the use of Th[pyrameth se a prophylactic agent against
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M a lnfeotlm, and to the late Joe Ds Costs for rearing the boosts . 9, 9 . T, aclmavledges reosipt d a Natl0nal Research Couaoü d Canada post-doctoral feIIowshtp during the coarse d this work . Re erenoes 1. 2. 3. 4. b. 8. 7. 8. 9. 10 . 11 . 12 . 19 . 14 . 15 . 18 . 17 . 18 .
a. E .
PRATT aad 3 . 9 . TOBE, Lif ( . , 14, b75-688 (1974) . f~.E . PRATT, 8 .9, TOBE, R,J, WEAVER, andJ,R, FIIdNEY, (ien . Como . Endoorinol . , in press . 9, 8, TOBE and (3, E, PRATT, Bioohem . J . , 144, 10?-113 (1874) . 9,9 . TOBE and (~.E, PRATT, Nsture (Londcn) , 282, 474-478 (1974) . 247-998 (1984) . V,B, WI(3(3LESWORTB, Ad~. Inseot Phvsiol . , F, ENßELbIANN, The P'hvsiolo~ d Imeot Reprodaottan , Pergaman Presa, O~dord (19?0) . K, C . $IßFirTAM, Mem . Soo . Eadoor(aol . , 12, 979-390 (1982) . K, C . SIiRiriAM, L, HII.L, AND W. MORDUE, J . Iaseot Phsstol . , 12, 977-994 (1988) . L . 3TRON(i, J. InseOt Ph~s(ol , , 11, 135-148 (1986) . P, JOLY, Ma. 900 . Entamdol . Fr . , 3, 801-808 (1987) . W, MORDUE, (~m . Comn. Ehdoorlnol ., 8, 408-416 (1987) . A,O . LEA sad E, THOM9ÉN, J . ùuect Ph9s(o1 ., 16, 477-482 (1989) . C, CfII.LOTT aud ß.9, DOQRA, (3en . Como . Eadoortnol ., 18, 128-132 (1972) . R,A, J01~T80N and L, HII.L, J . Insect Phvsid . .~, 2468-2487 (1973) . W. MORDUE, K . C, HI(3BZiAM, L, HILL, aad A. d, LUNTZ, Mem . 800 . E.hdoorinol . , 18, 111-198 (1870), 8 .8. TOBE and ß, E . PRATT, d. Exu . Blol . , (a press . a . E, PRATT and R . J, WEAVEB, J . EndoOrinQ1 . , 84, 87 (1975) . F . EN(~ELMANN, J. Inseot Phvs(ol . , 3., 257-278 (1887) .
2,