Neuropeptides and related nucleic acid sequences detected in peneid shrimps by immunohistochemistry and molecular hybridizations.

The neurosecretory cells in the eyestalks of Penaeus indicus and P. vannamei were studied by immunocytochemistry using polyclonal antisera raised against purified Homarus americanus neuropeptides. Cross-reactions between two H. americanus anti-crustacean hyperglycemic hormone antisera and Penaeus neurosecretory material were observed. The specific anti-vitellogenesis inhibiting hormone antiserum only showed an immunological reaction in the nervous tract and the sinus gland of Penaeus, suggesting a progressive exposure of a characteristic epitope which was amenable to immunological detection. Molecular hybridizations were performed in P. indicus and P. vannamei with a digoxigenin tailed 23mer oligonucleotide probe deduced from two partial sequences of uncharacterized, purified P. duorarum neuropeptides. Two distinct clusters of positive cells were observed by in situ hybridization experiments in the medulla terminalis ganglionic X-organ. Classical control tests gave negative results. Northern and Southern blot analyses were performed with the same tailed probed and allowed the determination of molecular weights for the mRNA and for a DNA restriction fragment (Pst 1), 1.7 kb and 200 bp, respectively. These observations show the existence of a strong homology between the P. duorarum sequence (selected for synthesizing the probe), and some P. indicus and P. vannamei neuropeptide sequence(s). Heterologous antisera were tested in other Arthropods to complete our analyses. In the centipede Lithobius forficatus and the scorpion Euscorpius carpathicus, the anti-crustacean hyperglycemic hormone antiserum induced a strong cross-reaction. A monoclonal anti-bombyxin-1 antiserum showed an immunoreaction in the neurosecretory system of the insects Tenebrio molitor and Labidura riparia. In contrast, the anti-bombyxin-1 antiserum did not react either in Penaeus or in Lithobius, and the Homarus hyperglycemic hormone antiserum did not react in the insects that were tested. A comprehensive view of these observations is discussed in relation to a divergence in Arthropod evolution.

Hormones regulating structural changes in the adipocytes of the female earwig Labidura riparia.

Changes in periovarian fat body fine structure occur during the reproductive cycle of the female earwig Labidura riparia. During the process of vitellogenesis, high levels of protein synthesis are seen in the adipocytes. Simultaneously, the formerly osmiophilic lipid droplets become non-osmiophilic, while an osmiophilic material diffuses from lipid droplets to the cisternae of the rough endoplasmic reticulum (RER). These structural features alter during non-vitellogenic periods: RER and Golgi apparatus regress and seem to be inactive. Lipid droplets are once again osmiophilic and no material enters into RER cisternae. Using microsurgical manipulations, hormonal treatments and light and electron microscopy, we have investigated the regulation of these changes. The neuroendocrine cerebral centre pars intercerebralis, by the action of the juvenile hormone of the corpus allatum. triggers protein metabolism. Another neuroendocrine center, the pars lateralis. and the hormone 20-hydroxyecdysone, regulate structural lipid droplet changes in the adipocytes.

In vivo inhibition of vitellogenesis in the Dermapteran Labidura riparia by 20-hydroxyecdysone.

In previous studies we have described the existence of cyclical changes in ecdysteroid levels during the female reproductive life of the earwig Labidura riparia. High levels of ecdysteroids are observed at the end of each vitellogenic period just before follicle degeneration, in coincidence with the beginning of each non-vitellogenic period. In the present work, using in vivo [(35)S]methionine incorporation, electrophoresis and electron microscopy, we study the effects on fat body and ovaries of 20-hydroxyecdysone (20E) injections into young vitellogenic females. This resulted in a reduction of proteosynthetic organelles (scarce Golgi complexes and fragmented RER cisternae), inhibition of vitellogenin synthesis in adipocytes, vitellogenesis arrest and premature follicular atresy. All these effects are suppressed when juvenile hormone treatment is associated with 20E injections. 20E does not inhibit vitellogenesis when applied to pars lateralis deprived females, which display continuous vitellogenesis. Thus, 20E does not act directly on ovaries nor on corpus allatum: the presence of the pars lateralis cells is required for 20E to inhibit vitellogenesis. These findings are explained in terms of the existence of a 20E feed back loop. This hormone acts via lateral neurosecretory cells of the brain which probably have an allatostatic effect.

[Hormonal control of the ovarian cycle in Labidura riparia (author's transl)]. / Les contrôles hormonaux des cycles ovariens chez la femelle d'un insecte dermaptère: Labidura riparia pallas.

The ovaries in female Labidura riparia undergo cyclical development. They require approximately 10 days to complete one vitellogenesis. During this period the Insect eats and and also mates. About 7 to 9 follicles in each ovariole are loaded progressively with vitellus and secrete a chorion. Before each oviposition degenerative phenomena appears in immature follicles. The ovaries remain at a less developed stage during the 10 days of maternal eggs cares. The follicles at the base of each ovariole degenerate. The cerebral neurosecretory centers and the corpus allatum are active during each vitellogenesis and inactive during each period when follicles degenerate and when the female cares her eggs. An experimental study shows that neurosecretory centers control the activity of the corpus allatum which itself influences the evolution of the vitellogenesis.

[Influence of a juvenile hormone analog on ovarian function in parasectomized Labidura riparia (Insecta, Dermaptera) females]. / Influence d'un mimétique de l'hormone juvénile sur le fonctionnement ovarien des femelles de Labidura riparia (Insecte, Dermaptère) privées de pars-intercerebralis

The juvenile hormone analogue (methyl 3.7.11-trimethyl 11-chloro 2-dodecanoate), after administration at various doses on parsectomised female earwigs prevented the degeneration of follicular cells of ovaries and also induced a rapid vitellogenesis followed usually by an oviposition. However, the normal reproductive cycle and the parental care could not be restored in such treated female Insects.

[The effect of a juvenile hormone mimetic on the ovarian function of allatectomized females of Labidura riparia (Insecta, Dermaptera]. / Influence d'un mimétique de l'hormone juvénile sur le fonctionnement ovarien des femelles allatectomisées de Labidura riparia (Insecte Dermaptère)

The methyl-3, 7, 11-trimethyl-11-chlorine-2-dodecanoate, a Juvenile Hormone analogue, used at different doses on allatectomised females of Labidura riparia, starts a vitellogenesis, a rapid disappearance of follicular degenerations and in some cases an intensive eggs laying. However, neither the normal reproductive cycle nor the parental comportment have been reconstituted.

Detection of the mRNA encoding vitellogenesis inhibiting hormone in neurosecretory cells of the X-organ in Homarus americanus by in situ hybridization.

Vitellogenesis inhibiting hormone (VIH)-mRNA in secretory cells of the eyestalk of Homarus americanus was detected by nonradioactive in situ hybridization (ISH) using two digoxigenin-tailed oligonucleotide probes deduced from the peptide sequence. Two distinct clusters of positive cells were observed in the medulla terminalis ganglionic X-organ (MGTX). Only one of them gave a strong immunoreaction after incubation with a specific polyclonal anti-VIH serum and corresponded to the conventionally described VIH producing cells. The significance of the cells reacting positively in ISH but not in immunocytochemistry (ICC) is discussed. Northern blot analysis using 32P-labeling confirms the specificity of the probes and indicates an approximate size of 2.5 kb for VIH mRNA.

Localization of a crustacean hyperglycemic hormone-like immunoreactivity in the neuroendocrine system of Euscorpius carpathicus (L.) (Scorpionida, Chactidae).

The neuroendocrine system of Euscorpius carpathicus was immunohistochemically localized using a polyclonal antiserum raised against a purified Homarus americanus crustacean hyperglycemic hormone (Hoa-cHHA). There were cross-reactions in E. carpathicus procerebral and subesophageal neurosecretory cells, neurohemal organs, and intra- and extraganglionic neurosecretory tracts. Among the neurohemal structures, the Kwartirnikov's organ, the Tropfenkomplex, and the coxal disc reacted strongly. In Euscorpius, the differing results between adults and juveniles suggest neurosecretory variations related to developmental stage. These immunohistochemical observations suggest the presence of substances related to the cHH in scorpions; however, in this heterologous system, it is not at present possible to assess physiological significance.