The dark-colour-inducing neurohormone of locusts in relation to an albino mutant of Schistocerca gregaria

In the albino mutant of an Okinawa strain of Locusta migratoria (L.) (Orthoptera: Acrididae), albinism is caused by the absence of the dark‐colour‐inducing neurohormone (DCIN), which is present in the corpora cardiaca (CC) of normally coloured phenotypes. This study tests whether the absence of DCIN is responsible for albinism in an albino mutant of another locust, Schistocerca gregaria (Forsk.) (Orthoptera: Acrididae). This seemed feasible because a single Mendelian unit controls albinism in both species. However, implantation of CC, or injection of an extract of CC, from albino donors of S. gregaria, induce dark coloration in crowded nymph recipients of the Okinawa albino mutant of L. migratoria, as effectively as do implanted CC, or injections of extract of CC, from normal phenotype donors of S. gregaria. Therefore, DCIN is present in the albino mutant of S. gregaria, and consequently, the albinism in this mutant is not caused by its absence. Implantation of CC, or injection of extracts of CC, from albino donors of S. gregaria to conspecific albino nymphs does not induce darkening. Only extremely high doses of synthetic DCIN injected into albino nymphs of S. gregaria are effective, inducing some darkening. The dose to induce such darkening in albino nymphs of S. gregaria is 50 nmol, ≈ 5 × 10⁶ times higher than that (10 femtomol) needed to induce equivalent darkening in nymphs of the Okinawa albinos of L. migratoria. The results are discussed and some possible explanations of the observed effects outlined.     

The inhibition of lipid synthesis in vitro in the locust, Schistocerca gregaria, by factors from the corpora cardiaca

ABSTRACT. The rate of lipid synthesis from [¹⁴C]acetate in fat body from Schistocerca americana gregaria has been studied in vitro. Maximum incorporation is found on days 6–10 in adults and day 4 of the fifth stadium. The label appeared in the fatty acid components of triacyl-glycerol, diacylglycerol and phospholipid.
Lipid synthesis in vitro was inhibited by extracts of corpora cardiaca, and such inhibition was most marked (up to 85%) in fat bodies from insects at stages where fatty acid synthesis was greatest. HPLC separation of corpora cardiaca extracts gave several active fractions of which the most active was adipokinetic hormone 1 (AKH-1).     

Partial purification and characterization of locust allatotropin I

Methanol extracts of locust brains, corpora cardiaca (CC), and suboesophageal ganglia (SOG) were separated by gradient and/or isocratic reverse-phase high-performance liquid chromatography (HPLC) and allatotropic activity monitored in the eluted fractions. A major peak of activity, separated by isocratic separation with 12% 2-propanol, designated allatotropin I, exhibited identical retention times in the three tissue extracts. Doseresponse curves of allatotropin I indicate similar content in brain and CC-equivalents, whereas optic lobes, similarly separated by isocratic HPLC, contain only one-tenth of this amount of allatotropin. Allatotropin I is resistant to boiling and is susceptible to tryptic and chymotryptic digestion. Methanol extracts of thoracic muscle, Malpighian tubules, fat body or ovaries, similarly prepared and boiled, did not exhibit allatotropic activity at high doses of tissue equivalents.     

Cloprostenol induced luteal regression in the beef cow. II. Histological evaluation of corpora lutea and correlation with luteal progesterone

Forty-two cycling, multiparous beef cows (percentage-Brahman) were injected twice at 11-d intervals with 500mug Cloprostenol (a prostaglandin F(2alpha) analog) to induce luteolysis. Cows were randomly assigned for ovariectomy at 12 hr intervals from 0 to 72 hr post-injection. Corpora lutea were excised and one-half of the corpus luteum was stored in phosphate-buffered formalin until mounting and staining with hematoxylin and eosin. The other half of the CL was snap-frozen for determination of progesterone content and concentration. Luteal cell density increased following Cloprostenol injection and was significantly correlated with a shift from predominantly healthy Type I cells to predominantly degenerating Types III and V cells. Cell mitosis tended to decrease by 12 hr and was lower by 24 hr post-injection. Cell pyknosis increased by 24 hr post-injection and was correlated with the decrease in percentage of healthy luteal cells. No pattern was detectable in cell karyorrhexis. Histological regression of the CL was inversely correlated with CL progesterone content. Therefore, we conclude that a reduction in cell mitosis is the earliest morphological sign of degeneration of the CL and that the CL follows a well-defined sequence of regression which is accompanied by a decrease in progesterone content.     

Variation in the oxytocin content of caprine corpora lutea across the breeding season

Ovarian tissues were obtained from cyclic goats during the early, mid and late breeding season. Immunoreactive oxytocin was measured by RIA in tissue extracts after chromatography on octadecylsilica cartridges. Luteal oxytocin concentrations were significantly greater during the early breeding season than during the mid or late breeding season. Oxytocin is luteolytic in goats. High concentrations of luteal oxytocin may be related to the high incidence of short estrus at the onset of the breeding season.     

Factors responsible for the initiation of a second oöcyte maturation cycle in the ovoviviparous cockroach Nauphoeta cinerea

The factors responsible for the initiation of a second oöcyte maturation cycle were investigated by measuring oöcyte growth, vitellogenin titre, and corpus allatum activity after injection of juvenile hormone and/or removal of the egg-case from pregnant females and by performing ovary and corpus allatum transplant experiments.Egg-case removal in late pregnancy results in immediate oöcyte growth, whereas in early pregnancy oöcyte growth is resumed only after a lapse of time, even after injection of juvenile hormone. This, however, induces an immediate increase in the haemolymph vitellogenin titre. A single injection of 2 or 10 μg of juvenile hormone II first stimulates some oöcyte growth after this lapse of time and later activates the corpora allata, which in turn leads to completion of oöcyte maturation. A repeat injection of 10 μg stimulates continuous oöcyte growth without activating the corpora allata. In the presence of an egg case, activation of the corpora allata is suppressed, even after injection of 2 μg of juvenile hormone III, and the oöcytes do not grow. Injection of higher doses stimulates oöcyte growth and leads to expulsion of the egg case in up to 95% of the females. This, however, is not a direct consequence of the increase in size of the ovaries. Ovary transplant experiment show that in young pregnant females the second generation of oöcyte is not yet competent for growth and that ovaries which are competent can mature in young pregnant females, treated with juvenile hormone, whose egg case has been removed.The results are summarized in a model demonstrating the various factors involved in regulating corpus allatum activity in oöcyte maturation and pregnancy and after application of juvenile hormone. We prepose that the corpus allatum activating effect of exogenous juvenile hormone is mediated by the growing oöcyte and that this activation can be suppressed by the continuous presence of exogenous juvenile hormone.     

Effects of social conditions on Juvenile Hormone mediated reproductive development in Bombus terrestris workers

Abstract. During the annual life cycle of the bumble bee Bombus terrestris (L.) colony, there is a stage characterized by worker reproduction in the presence of the queen. It has been proposed that this is a result of a decrease in queen inhibition. This hypothesis was examined by studying the effects of queens taken from colonies at different stages of development on several aspects of worker physiology and behaviour: rates of Juvenile Hormone (JH) release in vitro , ovary development, and behaviour associated with reproduction. After optimizing and validating the radiochemical assay for JH release for bumble bee workers, we found that queenless workers had significantly more developed ovaries and higher rates of release of JH than did queenright workers, confirming and extending previous findings that suggest that bumblebee ovarian development is under JH control. Mated queens, separated from their colony and brood, can have the same inhibitory effect on the reproductive development of callow workers. In contrast, workers confined with virgin queens or in queenless groups demonstrated a significantly higher rate of release of JH, overt aggression and threatening behaviours. However, there were no differences in rates of release of JH between workers confined in groups in the laboratory with queens taken from colonies either before or after the onset of worker reproduction. Furthermore, overt aggression and threatening behaviours were similar and low in both types of groups. These results gave no support to the hypothesis that a decrease in queen inhibition is associated with the onset of worker reproduction. We also show that young workers reared in colonies either before or after worker reproduction occurs, or in queenless colonies, all demonstrated similar, low rates of release of JH. These results suggest that older workers may inhibit the corpora allata of younger workers in queenless colonies.     

PRIMARY STRUCTURE OF ALLATOSTATIN 4, A NEVROPEPTIDE INHIBITOR OF JUVENILE HORMONE SYNTHESIS

Abstract Isolation and identification of allatostatin 4 (AST 4) from crude brain extracts of female Diploptera punctata are described. Synthetic analogues of allatostatin 4 truncated from the N-terminal were evaluated to gain some knowledge of structure-activity correlation. AST 4 reversibly inhibits the biosynthesis of JH in vitro . AST 4 has the following sequence: Asp-Arg-Leu-Tyr-Ser-Phe-Gly-Leu-NH₂. This neurohormone (AST 4) has no sequence similarity with any known neuropeptide from other organisms. Synthetic AST 4 as well as truncation fragments, including two with the five and six amino acids terminal residues deleted showed in vitro activity distinguishable from that of the native allatostatin.     

一些因子对七星瓢虫咽侧体活性的影响(英文)

七星瓢虫(Coccmella septimpunctata)为了适应环境的变化,通过咽侧体产生保幼激素的活动调节其生殖作用。为了探索内外因素对咽侧体活动的影响,应用放射化学法及免疫电泳测定了食物、卵巢发育、脑神经肽、保幼激素类似物对卵黄发生期成虫保幼激素生物合成及血淋巴中卵黄原蛋白含量的影响。结果表明咽侧体活性受上述各种因子的影响。咽侧体活性与卵黄原蛋白含量及卵母细胞生长密切相关,说明有反馈作用。食物的质与量影响着咽侧体活性的变化。低剂量外源保幼激素类似物处理成虫则可促使咽侧体活性的变化。脑分泌的神经肽(allatotropin)可活化咽侧体。这些结果表明雌瓢虫保幼激素的生产主要是受起源于脑的促咽侧体信号的调节作用。     

Mating and diapause in hibernating adults ofMenida scotti puton (Heteroptera: Pentatomidae)

InMenida scotti aduts which mate during hibernation, we examined the effect of photoperiod on diapause induction in terms of the developmental degree of reproductive organs and corpora allata. In a hibernating population, mating season and physiological changes related to dipause were investigated. When newly emerged adults were reared under long- or short-day conditions, reservoir of the ectodermal accessory gland and corpora allata in males developed, while the developments of ovary and corpora allata in females were suppressed under both conditions. This suggests that diapause of this species is induced only in females independently photoperiodic conditions during adult stage. In a hibernating population, mating was observed from early to late November and from late March to early May. Observations of the development of reproductive organs and corpora allata suggest that diapause is induced only in females in the former period, while both sexes are not in diapause in the latter period.