Biological activity of structural analogs and effect of oil as a carrier of trypsin modulating oostatic factor of the gray fleshfly Neobellieria bullata.
ABSTRACT The trypsin modulating oostatic factor from the gray fleshfly Neobellieria bullata (Neb-TMOF) is released from the ovary at the end of vitellogenesis and inhibits trypsin biosynthesis in the midgut. This inhibition indirectly results in an arrest of oocyte growth. Additional experiments with N. bullata were performed to characterize its trypsin modulating and oostatic properties in more detail. After suspending the peptide in wheat germ oil, the threshold dose for oostatic activity was lowered one thousand times (2.10(-5) in oil versus 2.10(-2) pmoles per fly in Ringer). By use of the Neobellieria trypsin biosynthesis assay, 17 analogs of the hexapeptide were tested for inhibitory activity. The following structural elements were demonstrated to be critical for biological activity: the alcohol function at position 3 (Thr residue); a positively charged basic group at the C terminus (His residue); and the Asn side chain at positions 1 and 4.
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ABSTRACT: The primary target of the gonadotropic neurohormone of Locusta migratoria (Lom OMP) was investigated in locust fifth instar larvae (last larval instar) and adult females by analysing the effect of Lom OMP and 20-hydroxyecdysone (20-HE) on the appearance of vitellogenin (Vg) in the haemolymph and on ovarian growth. Detection of Vg was carried out using 7.5% polyacrylamide gel electrophoresis of haemolymph while ovarian growth was estimated by measuring the mean length of basal oöcytes. Injections of 20-HE had no effect in larvae but induced, in adults, a precocious occurrence of Vg and precocious ovarian maturation similar to injections of Lom OMP. Moreover, injections of 20-HE counterbalanced the endogenous Lom OMP inactivated by its immune serum. Finally, Lom OMP did not induce the appearance of Vg when it was injected in ovariectomized fifth instar larvae. These results demonstrate, in contrast to the prevailing concept, that ecdysone is a gonadotropic hormone in Locusta and strongly suggest that Lom OMP induces ovarian ecdysone production. The possibility that not only the ovary but also the fat body could be a target organ of Lom OMP is discussed.Journal of Insect Physiology. 01/1996;
- Archives of Insect Biochemistry and Physiology - ARCH INSECT BIOCHEM PHYSIOL. 01/1994; 27(1):27-38.
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ABSTRACT: The hexapeptide Neb-TMOF (H-NPTNLH-OH, trypsin modulating oostatic factor of the gray fleshfly, Neobellieria bullata)2 occurs in vitellogenic ovaries and is involved in negative feedback regulation of trypsin biosynthesis in the gut of late vitellogenic females. Polyclonal antisera were raised against the synthetic peptide and were used to identify and immunolocalize Neb-TMOF epitopes in different fleshfly tissues. Neb-TMOF-immunoreactive material first appears in the cortical layer of young vitellogenic oocytes and later spreads over the yolk granules. This suggests a pinocytosis with the three yolk polypeptides (vitellogenins). Controls treated with the preimmune sera or with anti-Neb-TMOF antiserum preadsorbed to Neb-TMOF peptide coupled to a solid phase support did not stain. There was no immunostaining in the central nervous system (brain and ventral nerve cord), the retrocerebral complex, the fat body, or the testes. Western blot analysis showed that the anti-Neb-TMOF antisera specifically recognize a putative hormone precursor polypeptide (Mr 75 kDa) from vitellogenic ovaries. This protein is virtually absent from the hemolymph. It is not immunologically related to the three yolk polypeptides, since it is not recognized by yolk polypeptides antisera. In adult females the ovary appears to be the only site of synthesis of Neb-TMOF and of its precursor. Immunopositive staining is found in the apical areas of ovarian follicle cells, suggesting these cells as a site of hormone precursor biosynthesis. This is the first demonstration that a protein colocalized with yolk proteins might act as a precursor for a folliculostatic hormone.General and Comparative Endocrinology 10/1996; 103(3):273-80. · 2.82 Impact Factor