Oostatic Hormone Research Articles

Aedes aegypti TMOF modulates ecdysteroid production by prothoracic glands of the gypsy moth, Lymantria dispar.

Trypsin modulating oostatic factor (TMOF) is a decapeptide that inhibits the biosynthesis of trypsin-like enzymes in the midgut of several insect species and, as such, serves as a dipteran oostatic hormone. In vitro incubation of lepidopteran prothoracic glands with Aedes aegypti TMOF revealed that this decapeptide, in the presence of brain extract, modulates ecdysteroid production. The modulatory effect was highly dependent on both the concentration of TMOF and brain extract. Typically, TMOF was stimulatory in the presence of lower concentrations of Lymantria dispar brain extract (0.01 and 0. 025 brain equivalent), and either neutral or inhibitory at higher concentrations (0.25, 0.5, and 1.0 brain equivalent) of extract. In the presence of European corn borer (Ostrinia nubilalis) brain extract, TMOF also exhibited modulatory effects, effects that again were dependent on the concentrations of both brain extract and TMOF present in the incubation medium. At 1.5 brain equivalents, TMOF was inhibitory at all but the highest concentration tested (5x10(-6) M), at 1.0 brain equivalent, TMOF was stimulatory at 10(-6) M and at 0. 5 brain equivalents, TMOF did not significantly affect PTG synthesis of ecdysteroids. Results suggest the presence of a modulatory peptide(s), which fine tunes the synthesis and release of ecdysteroids by PTGs in accordance with the insect's developmental/physiological requirements.

The C-Terminus Shortened Analogs of the Insect Peptide Oostatic Hormone with Accelerated Activity

Shortened analogs1a–1fof the oostatic hormone1gwith a decreased number or an omission of the C-terminal Pro residues were synthesized for investigation of their effect on oogenesis in the flesh flySarcophaga bullata Parker(Diptera). Peptides1b–1gwere prepared by solid-phase synthesis on polystyrene/divinylbenzene polymer with a 2-chlorotrityl linker using Fmoc/tBu strategy in dimethylformamide (DMF). Tetrapeptide1a, devoid of all the carboxy-terminal Pro residues, was prepared by stepwise procedure in DMF solution from HCl-H-Ala-OMe using Boc-Pro-OH, Z-Asp(OtBu)-OSu, and Boc-Tyr-OSu. In general, the peptides assayed affected processes of egg development in 20–80% of ovarioles causing changes in the follicular epithelium, proliferation of its nuclei, and cell division toward the inner part of the egg chamber. This process leads to the occurrence of a multilayered follicular epithelium which later fills up almost the whole egg chamber and then degenerates. Such ovarioles are never able to produce eggs. The shortening of the peptide sequence accelerated the observed effects on egg development. The application of the125I-labeled peptides made possible to express quantitatively the time dependence of the radioactivity distribution in the insect body, including ovaries through which it is transferred to the next F1 generation. The radioactivity was measured in larvaes and, consequently, in newborn flies. For different peptide sequences applied, different radioactivity distributions in the insect body were found using the same radiolabeling.

Synthesis, radiolabeling and biological activity of peptide oostatic hormone and its analogues.

A series of Pro peptides containing the sequence of the oostatic hormone 3d and its shorter analogues 3a-3c differing in a number of the C-terminal Pro residues was prepared for a study of its effect on oogenesis in Sarcophaga bullata Parker (Diptera). Peptides 3a-3d were synthesized in solution by the fragment condensation of Boc-Tyr-Asp(OtBu)-Pro-Ala-Pro-OH (2f) with Pro oligopeptides H-(Pro)2-5-OtBu. The amino-terminal protected pentapeptide acid 2f was prepared by a stepwise procedure from TFA.H-Ala-Pro-OMe using Boc-Pro-OH, Z-Asp(OtBu)-OSu and Boc-Tyr-OSu. The H(Z)-(Pro)2-5-OtBu oligopeptides 1a-1h were synthesized from Z-Pro-OH and H-Pro-OtBu by a combination of stepwise procedure and fragment condensation. The 125I-labeled molecules of the octapeptide 3b and decapeptide 3d were used for radiotracer distribution studies. Evidence of content of the labeled peptide material in various parts of the insect body (ovaries, head, intestine) is presented. The time distribution of the labeled material in the insect organs was correlated with results of histological analysis of ovaries treated by nonlabeled peptides. The peptides assayed affected processes of egg development in 20-60% of ovarioles. The decapeptide 3d caused changes consisting in some resorbed egg chambers and normal appearance of vitellogenic eggs, whereas the octapeptide 3b caused abnormal yolk deposition and formation of big eggs with irregular yolk granules, proliferation of follicular epithelium in some egg chambers and about the same amount of resorbed egg chambers as decapeptide. These structural differences are complementary to the different values of organ radioactivities.

Oostatic activity in extracts prepared from thoracic ganglia and ovaries of the housefly,Musca domestica vicina(Arthropod a: Insecta: Diptera)

Summary Aqueous extracts prepared from thoracic ganglia and ovaries had oostatic activity when injected into the housefly, Musca domestica vicina. The amount of extractable oostatic hormone in the ovary increased linearly during vitellogenesis with the highest levels occurring in the post-vitellogenic ovary. The oostatic hormone content in the thoracic ganglia fiom flies of different ages fit a parabolic curve with higher levels at emergence and 72 h and lower levels at 36 and 48 h. Aedes aegypti trypsin modulating oostatic factor (TMOF) had oostatic activity when injected into Musca domestica vicina. TMOF antibody reacted with ovarian and thoracic ganglion extracts in dot-ELISA assays. Neurosecretory cells in the periphery of the thoracic ganglion reacted with TMOF antibody.

An improved preparation of a tertiary alcohol proline linker and its use in a synthesis of mosquito oostatic hormone

An improved synthesis of 4-(3′-hydroxy-3′-methylbutyl)phenoxyacetic acid was developed using THF to overcome solubility problems initially encountered in trying to reproduce the published preparation. This hydroxyacid linker was coupled to aminomethyl polystyrene resin and used for a synthesis of the mosquito oostatic hormone by the Fmoc protocol. Attempts to prepare this insect peptide by other techniques had failed because of loss of cyclo-Pro 2 from the resin.

Oostatic hormone inhibits biosynthesis of midgut proteolytic enzymes and egg development in mosquitoes

AbstractInjection of partially purified oostatic hormone (0.7 μg) into female Aedes aegypti inhibited egg development, proteolytic enzyme activity, and blood digestion in the midgut, whereas control injections of saline or insulin chain A (0.7 μg) did not affect these processes. Oostatic hormone given by enema, on the other hand, did not inhibit proteolytic enzyme activity, indicating that the hormone acts outside the midgut. A single injection of oostatic hormone (0.7 μg) caused a 1.7–1.5‐fold reduction in activity of trypsinlike enzymes during blood digestion, with a 10‐h delay in peak activity.Using [1,3‐3H]diisopropylfluorophosphate (DFP) in the presence of 8 mM tosylamide‐2‐phenylethyl chloromethyl ketone, the synthesis of trypsinlike derivatives was followed in the midgut of female A. aegypti. A 4‐fold reduction in [1,3‐3H]diisopropylphosphoryl‐trypsinlike derivatives was noted after oostatic hormone treatment. Several isozymes that are normally synthesized were absent in the presence of DFP, as assessed by polyacrylamide gel electrophoresis. Injection of oostatic hormone into decapitated and ovariectomized females that did not synthesize ecdysteroids inhibited trypsinlike enzyme synthesis and blood digestion in the midgut, indicating that oostatic hormone inhibits the midgut cells and not the ovary or the brain's endocrine system.Comparison between oostatic hormone and soybean trypsin inhibitor indicated that the former inhibited trypsin synthesis whereas the latter inhibited trypsin activity. A. aegypti oostatic hormone is not species specific and injections of the hormone into Culex quinquefasciatus, Culex nigripalpus, and Anopheles albimanus caused inhibition of egg development, blood digestion, and synthesis of trypsinlike enzymes. A direct relation between oostatic hormone synthesis and the regulation of trypsinlike activity in the midgut is proposed.

Inhibitory effects of oostatic hormone on ovarian maturation and ecdysteroid production in diptera

Extracts from post-vitellogenic ovaries of Musca domestica, Aedes atropalpus and Drosphila melanogaster were examined for the ability to inhibit the vitellogenic phase of growth in newly emerged A. atropalpus and D. melanogaster adult females. All extracts were inhibitory in A. atropalpus. D. melanogaster females were less sensitive than A. atropalpus females, only showing inhibition at a two-fold greater concentration of M. domestica extract. The titre of oostatic hormone in A. atropalpus ovaries correlated with the decline in ecdysteroid synthesis by these ovaries. A. atropalpus ovaries containing post-vitellogenic follicles were shown to inhibit ovarian ecdysteroid synthesis in vitro by vitellogenic ovaries of both A. atropalpus and D. melanogaster. D. melanogaster ovaries were not capable of eliciting such an inhibition in vitro, at least with the numbers of ovaries utilized in our experiments.

Isolation and characterization of highly purified mosquito oostatic hormone

AbstractOostatic hormone, the hormone that inhibits vitellogenesis in mosquitoes, was purified 7,000‐fold with a recovery of 70% from the ovaries of the mosquito Aedes aegypti. The purification procedure included heat treatment and chromatography on ion exchange and gel filtration columns. The hormone is a small peptidelike molecule of molecular weight 2,200 at pH 4.5, which aggregates into larger molecular species of trimer and octamer at pH 7.0 as determined by gel filtration. The hormone is positively charged at pH 7.8 and has a low Rf at pH 9.4 on disc gel electrophoresis.Injection of purified oostatic hormone (9 ng) into female mosquitoes inhibited yolk deposition and vitellogenin synthesis. Activity of the oostatic hormone in the mosquito ovary increased rapidly following blood feeding and reached a maximum after 48 h. Oostatic hormone of A. aegypti injected into autogenous Aedes taeniorhynchus inhibited egg development. Repeated injections of dilute oostatic hormone at 24 h intervals partially arrested egg development, resulting in 60% reduction in the number of eggs laid. This hormone does not block release of egg development neurosecretory hormone (EDNH) from the mosquito brain but rather appears to act on the ovary.

Effects of house fly oostatic hormone on egg development neurosecretory hormone action in Aedes atropalpus

AbstractOostatic hormone, prepared from mature female house flies, Musca domestica, was examined for its effect on processes mediated by egg development neurosecretory hormone (EDNH). When injected into newly emerged adult female mosquitoes, Aedes atropalpus, oostatic extracts inhibited vitellogenic growth of the ovaries. Comparison of oostatic activities in heads, thoraces, and abdomens of house flies showed that the major portion was present in the abdomens, apparently associated with the ovaries. In contrast to untreated vitellogenic females, no ecdysone or 20‐hydroxyecdysone could be detected in female mosquitoes injected with the oostatic extract. Vitellogenic growth and ecdysteroid levels were suppressed in decapitated females injected with a mixture of extracts containing EDNH and oostatic activities. Since the normal vitellogenic and steroidogenic responses to EDNH can be suppressed by simultaneous injection of EDNH and oostatic material, it is suggested that oostatic hormone acts at a level subsequent to EDNH release. However, we cannot rule out at this time that EDNH release, itself, is also affected.

Preparation of a Semipurified Extract of the Oöstatic Hormone and its Effect on Egg Maturation in the House Fly1,3

A semipurified extract with oostatic hormone activity was prepared by grinding mature female house flies, Musca domestica L., in 95% ethanol, filtering and dialyzing the solution, and then precipitating the dialysate with acetone. Oostatic hormone activity of the precipitate was not deactivated by boiling water, air oxidation, or storage as a dry powder at − 10;°C, but it was deactivated when stored as a frozen solution. The injection of 24 micrograms of this precipitate gave 50% inhibition of oocyte development. The injected oostatic hormone retarded egg development by prolonging stage 4 of oogenesis.