ISSN:0739-4462    

DOI:10.1002/(SICI)1520-6327(1996)32:3/4<269::AID-ARCH1>3.0.CO;2-O

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractJuvenile hormone (JH) allows larval molting in response to ecdysteroids but prevents the switching of gene expression necessary for metamorphosis. I first review our efforts to isolate the nuclear receptor for JH in the larval epidermis ofManduca sextausing photoaffinity analogs and our recent findings that the molecule isolated does not bind JH I with high affinity. The reported apparent high affinity binding of JH I by the recombinant 29 kDa protein (rJP29) was artifactual due to the presence of contaminating esterases. Purified rJP29 bound little detectable JH I, but its binding of the photoaffinity analog was prevented by JH I as well as other isoprenoids, indicating a low affinity for these compounds. Our recent studies focus on the effects of JH on the early molecular events induced by 20‐hydroxyecdysone (20E). Culture of day 2 5th larval epidermis with 10−6M 20E for 24 h caused first pupal commitment, then the onset of the predifferentiative events necessary for pupation. Biphasic increases in the mRNAs of the two isoforms of the ecdysone receptor (EcR‐A and EcR‐B1) and of E75A, an ecdysteroid‐induced transcription factor, coincided with these two phases. The mRNAs for Ultraspiracle (USP) and the metamorphosis‐specific Broad‐Complex (BR‐C) increased only during the second phase. The presence of JH had no effect on the initial increases in EcR mRNAs but caused an increased accumulation of E75A mRNA. This JH also prevented the later changes in EcR, USP, and BR‐C mRNAs. Thus, JH influences only certain of the early actions of 20E which then result in its preservation of the “status quo.”

ISSN:0739-4462    

DOI:10.1002/(SICI)1520-6327(1996)32:3/4<271::AID-ARCH2>3.0.CO;2-W

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractThe identification of neuropeptides that inhibit juvenile hormone (JH) synthesis by the corpora allata (CA) has verified the existence of these allatostatins, which, from much experimental evidence, have long been postulated to occur. It also makes possible new approaches for studying the role of allatostatins in the regulation of JH synthesis. Allatostatins, localized immunocytochemically, occur in lateral neurosecretory cells of the brain that innervate the CA. Presumably their effect on the CA results from the release of allatostatins at these nerve endings. Allatostatins also occur in the hemolymph in cockroaches and have been shown to act on the CA through this pathway. The ability of allatostatins to inhibit CA depends not only on the concentration of the peptides but also on the sensitivity of the CA to them. MaleDiploptera punctatawere treated with JH analog following denervation of CA and implanted with a previtellogenic or vitellogenic ovary or injected with saline. Animals implanted with a vitellogenic ovary, compared to the previtellogenic ovary or saline, showed significantly increased JH synthesis by their CA and a reduced amount of allatostatin in the hemolymph. The denervated CA from these JH analog treated animals, following implantation with a previtellogenic and vitellogenic ovary, showed a tendency toward increased and decreased sensitivity, respectively, to a given dose of allatostatin in vitro compared to those from saline injected controls. Experiments such as these suggest that changes in release of allatostatins and in sensitivity of CA to them could be postulated to be major factors regulating JH synthesis in the cockroach. © 1996 Wiley‐Liss, I

ISSN:0739-4462    

DOI:10.1002/(SICI)1520-6327(1996)32:3/4<287::AID-ARCH3>3.0.CO;2-Q

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractUnlike inBlettella germanicaandSupella longipalpa,the corpora allata (CA) ofDiploptera punctataexhibited cyclic changes in cell number during the reproductive cycle. In mated females, a wave of DNA synthesis followed by mitosis resulted in a significant increase in CA cell number from about 9,000 cells on day 0 to 12,000 cells at ovulation on day 8. Subsequently, the number of cells per CA underwent a gradual decline to about 10,000 cells by day 64. During this long period of gestation, mitotic activity was undetectable (by colchicine arrest) and pycnotic nuclei were frequently observed by transmission electron microscopy. Just before parturition on day 72 another mitotic wave was detected and CA cell number increased again. The early wave of CA cell proliferation could be postponed by delaying mating or abolished by maintaining females as virgins. Neural disconnection of the CA from the brain mimicked the effect of mating, suggesting that enhanced cell proliferation is permitted by the removal of inhibitory signals from cerebral neurosecretory cells. The proliferative activities after mating were neither abolished by ovariectomy, which suppressed the normal increase in JH synthesis, nor elevated by unilateral allalectomy, which doubled the rates of JH synthesis in the remaining CA. These data corroborate previous results (Szibbo and Tobe, 1981a; Tobe et al., 1984; Johnson et al., 1993) and suggest that waves of cell proliferation and JH synthesis, though simultaneous, are regulated independently by inhibitory signals from cerebral neurosecretory cells. © 1996 Wiley‐Liss, I

ISSN:0739-4462    

DOI:10.1002/(SICI)1520-6327(1996)32:3/4<299::AID-ARCH4>3.0.CO;2-O

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractAn in vitro assay has been developed for determining prenyltransferase activity in larval corpora allata homogenates of the lepidopteranManduca sexta.Optimal activity was obtained by the addition of glycerol and bovine serum albumin. The prenyltransferase required either Mg2+or Mn2+for activity and was inhibited byN‐ethylmaleimide, geranylgeranyl pyrophosphate, and higher concentrations of isopentenyl pyrophosphate (IPP). Because of the prenyltransferase's low sensitivity to phosphate, the addition of 100 mM phosphate could be used to selectively inhibit IPP isomerase, which otherwise remained active under our standard assay conditions. Efficient coupling of geranyl pyrophosphate with IPP to yield farnesyl pyrophosphate required the presence of a nonionic detergent, such as Triton X‐100. Although the addition of up to 3% detergent resulted in significant activity enhancement, the protein is not membrane‐bound, as determined by enzyme localization studies. Preliminary studies using homologous substrates suggest that the lepidopteran enzyme has different substrate specificity than other known prenyltransferases. Competition studies using homodimethylallyl pyrophosphate (HDMAPP) and dimethylallyl pyrophosphate (DMAPP) indicated a 1.8:1 preference for the ethyl‐substituted substrate. Further examination of DMAPP and HDMAPP coupling patterns showed that this specificity is the result of higher discrimination in the first condensation step. These results suggest that lepidopteran prenyltransferase may regulate the proportions of the various juvenile hormone homologues that are biosynthesized within the corpora allata. © 1996 Wiley

ISSN:0739-4462    

DOI:10.1002/(SICI)1520-6327(1996)32:3/4<315::AID-ARCH5>3.0.CO;2-R

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractHistological and immunohistochemical observations showed that four pairs of neurosecretory A cells coincide with the bombyxin neuron which produces the 4K‐prothoracicotropic hormone (4K‐PTTH). The A cells are characterized by a large cytoplasmic vacuole containing homogeneous granular materials, but the vacuole does not contain the bombyxin. Bombyxin axons from the A cells are distributed on the surface of the corpus allatum (CA), and neurosecretory granules (NSGs) are released by exocytosis at earlier stages than those in other neurosecretory axons (NSAs). Embryonic bombyxin neurons show characteristics of secretory function after the bristle formation stage (156 h after egg laying) and become the neurosecretory A cells in the larval stage. © 1996 Wiley‐Lis

ISSN:0739-4462    

DOI:10.1002/(SICI)1520-6327(1996)32:3/4<333::AID-ARCH6>3.0.CO;2-T

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractJuvenile hormone (JH) biosynthesis by corpora allata (CA) from embryos of the cockroachDiploptera punctatawas measured at four stages during the latter half of embryogenesis. Individual glands from 32‐day‐old embryos that had completed 49% of embryonic development synthesized 0.3 pmol JH III h−1. By day 46 (70% development) gland activity rose to 1.1 pmol JH h−1, but on subsequent days JH synthetic rates declined, measuring only 0.8 pmol h−1on day 56 (86% development) and 0.5 pmol h−1on day 60 (92% development). Differences in JH biosynthesis by CA from different‐aged embryos were more evident when gland activity was corrected for either corpus allatum cell number, which increased progressively from fewer than 200 cells per gland on day 32 to almost 700 cells per gland on day 60, or embryo mass, which increased from 1.6 mg per embryo on day 32 to 10.8 mg per embryo on day 60. JH biosynthetic rates were significantly inhibited in a medium containing 10−8M Dip‐allatostatin 7 which suppressed CA activity by 68, 83, 76, and 51% on days 32, 46, 56, and 60, respectively. In all embryonic stages JH production was significantly stimulated by incubation of glands with 200 μM farnesol, a late precursor in the JH biosynthetic pathway. © 1

ISSN:0739-4462    

DOI:10.1002/(SICI)1520-6327(1996)32:3/4<341::AID-ARCH7>3.0.CO;2-V

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractThe transcripts of sericin‐type genesMG1andMG2accumulate inGalleria mellonellasilk glands during feeding and decline during molting. ThreeMG1(1.9, 3.2, and 4.2 kb) and twoMG2(dominant 3.4 kb and minor 5.2 kb) transcripts are detectable from the penultimate instar until the end of cocoon spinning. Experiments with isolated larval abdomens showed that the dramatic change in the ratio of 1.9 and 4.2 kbMG1transcripts in the last larval instar is due to lack of JH. Transient rise of ecdysteroid titre in the wandering larvae (day 5 of the last instar) is associated with appearance of additionalMG1transcripts (10.0, 7.2, and 5.0 kb), while the molt‐inducing ecdysteroid surge on day 7 causes a drop of all transcripts. The drop is prevented and the profile of transcripts is reverted to a larval‐like pattern when the last instar larvae are treated with a juvenoid. The profile ofMG1transcripts is affected only when the treatment is applied prior to the start of cocoon spinning (day 6), whereas the decline of the 3.4 kbMG2transcript is averted with applications up to day 7. Presented results are interpreted as showing that JH causes a “status quo” effect by preventing the disappearance of certain transcripts during molting, exerts a “juvenilizing” effect by restoring the larval pattern of splicing, and affects developmental “programming,” presumably by affecting the future pattern of gene expression. © 19

ISSN:0739-4462    

DOI:10.1002/(SICI)1520-6327(1996)32:3/4<353::AID-ARCH8>3.0.CO;2-T

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractMating elicits two well‐defined reactions in sexually matured females of many insects: reduction of receptivity and increased oviposition. These post‐mating responses have been shown to be induced by factors synthesized in the reproductive tract of the adult male and transferred in the seminal fluid to the female during copulation. One of these factors, named sex‐peptide (SP), has been identified inDrosophila melanogaster.Using an in vitro radiochemical assay, we show that synthetic sex‐peptide considerably activates juvenile hormone III‐bisepoxide (JHB3) synthesis in corpus allatum (CA) excised from Days 3 and 4 post‐eclosion virgin females. Base levels are significantly lower at emergence (Day 0) than on subsequent days, and only weak stimulation is obtained on Day 1, while none is obtained on Day 2, where maximal basal synthesis occurs. The CA of mated females cannot be stimulated further for at least 7 days, but regain responsiveness by Day 10 after mating. Synthesis of JHB3stimulated by SP in vitro persists for at least 4 h after removal of the peptide. Development of responsiveness of the CA to SP in vitro is compared with development of the post‐mating reactions of sex‐peptide injected virgin females. Our results suggest that the CA is a direct target for SP in vivo and that sexual maturity is established separately for the two post‐mating reactions. © 19

ISSN:0739-4462    

DOI:10.1002/(SICI)1520-6327(1996)32:3/4<363::AID-ARCH9>3.0.CO;2-T

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractUsing two‐step reverse phase HPLC, we isolated and purified three peptides with mandibular organ inhibiting hormone (MO‐IH) activity from the spider crabLibinia emarginata.One of the peptides, P22, gave a yield of 355 ng/SG. The others gave lower yields: P21, 9 ng/SG; P25, 67.5 ng/SG. The molecular weight was determined to be 8,439 for P25, 8,474 for P22, and 8,398 for P21 by mass spectrometry. All three peptides have similar amino acid compositions and contain 72–76 residues. We believe these peptides to be different isoforms of one family. The MO is more sensitive to the two minor isoforms, P21 and P25. All three isoforms can inhibit MO activity to a maximum inhibition of 70%. All three isoforms gave a significant hyperglycemic effect when injected into de‐eyestalked fiddler crabsUca pugilator.We believe the MO‐IHs to be members of the crustacean hyperglycemic hormone (CHH) family, having similar amino acid compositions and both biological activities. © 1996 Wiley

ISSN:0739-4462    

DOI:10.1002/(SICI)1520-6327(1996)32:3/4<375::AID-ARCH10>3.0.CO;2-9

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY