Demonstration of cytoplasmic receptors for the molting hormones in crayfish

Summary From in vitro experiments using different binding assays it is in crayfish demonstrated that the cytosol of target tissues is able to bind both ecdysone and ecdysterone. The ability to bind ecdysteroids is destroyed by heating and by treatment with -chymotrypsin and N-ethyl-maleinimide (NEM) (Figs. 4, 5). In target tissues there is a strong positive correlation between protein content and binding (Fig. 6). The association of the hormone-protein-complex is rapid, taking only a few min even at 5° C (Fig. 3). The binding of the two hormones to the cytosol is both specific and saturable. The association constants for the cytoplasmic receptors from hypodermis, hindgut and midgut gland are in the range of 3–6×10⁷ M^–1 for ecdysone and 5–7×10⁸ M^–1 for ecdysterone (Fig. 8). The data suggest the existence of cytoplasmic ecdysteroid receptors.     

Phytochrome destruction: an apparent requirement for protein synthesis in the induction of the destruction mechanism

Examination of the phytochrome destruction reaction as a function of age in etiolated oat (Avena sativa L. cv. Garry) seedlings demonstrates that following illumination of 3-day-old shoots there is a lag, not observed in 4- or 5-day-old oats, prior to the onset of destruction. This light-mediated induction of the phytochrome destruction mechanism in 3-day-old shoots is inhibited by chloramphenicol, actinomycin D, and puromycin suggesting that protein synthesis is required. In 4-day-old shoots, actinomycin D and puromycin do not alter the kinetics of destruction while chloramphenicol partially inhibits the process. Thus, the inhibitors have a specific effect on the induction of the destruction mechanism but not its subsequent operation.     

Acetylcholinesterase induction by beta-ecdysone in Drosophila cell lines and their hybrids

Drosophila S3 line cells maintain a high basal level of acetylcholinesterase (AChE) activity, which is lost and then reinduced following exposure to the steroid, beta-ecdysone. Electrophoretic studies indicate that the basal and reinduced AChE activities may be different isozymes. In contrast, MDR line cells have a low basal AChE activity which is induced to a modest level by hormone. In S3/MDR hybrids the high basal level phenotype is extinguished, and the hormone-induced AChE level is modest. MDER line cells, which continue to grow in the presence of beta-ecdysone and are therefore termed resistant, show a low basal AChE level that is not further elevated by hormone. This phenotype and response also occurred in beta-ecdysone-resistant S3/MDER hybrids.     

昆虫滞育诱导的分子调控机制

滞育是昆虫长期适应不利环境的重要对策之一,对昆虫的生存、繁衍和进化都具有重要意义.滞育一般分为滞育前期、滞育期和滞育后期3个阶段,其中,滞育前期包括滞育诱导期和滞育准备期,是确保昆虫顺利进入滞育的重要时期.本文首先简要概括了光周期、温度、湿度、食料等外界环境因素在不同昆虫滞育诱导中的作用;然后系统综述了滞育激素、保幼激...     

Lymphokine-induced cytotoxicity: requirement of two lymphokines for the induction of optimal cytotoxic response

Lymphokines induce the generation of cytotoxic cells (LICC) in the absence of antigenic or mitogenic stimulation. In the present study, we have demonstrated that at least two lymphokines are involved. They are interleukin 2-conditioned medium (CM-IL 2), which was produced by W/Fu rat spleen cells cultured with concanavalin A-conjugated Sepharose beads, and cytotoxic cell differentiation factor-conditioned medium (CM-CCDF), which was produced primarily by the unstimulated mouse peritoneal macrophages. It was first established that CCDF synergized with IL 2 to induce the generation of LICC in normal spleen cells, and that this process was specifically blocked by the rat anti-IL 2 receptor monoclonal antibody. The maximal synergistic effect was obtained by using 10% CM-CCDF (v/v) and 0.1 to 0.3 U/ml of CM-IL 2. Higher doses of IL 2 (3 to 10 U/ml) reduced the cytotoxic response. The effectors of LICC were Thy-1+, Lyt-2- and AGM1-; therefore, they were neither classic CTL nor NK cells. The precursors were AGM1+, Lyt-2- cells that were consistent of being NK-like cells. When examining the temporal relationship between CCDF and IL 2, we found that 4 hr preincubation of the responders with IL 2 was sufficient to activate the cytotoxic precursor cells. CCDF was needed later for the differentiation of the activated precursors into cytotoxic effectors. In contrast, preincubation of the responders with CCDF, followed by additional incubation with IL 2, failed to induce any cytotoxic response. These results established that lymphokine-induced cytotoxicity can be separated into two phases. In the activation phase, IL 2 provides the first signal to activate the cytotoxic precursors, with the process being completed in 4 hr. In the differentiation phase, CCDF provides the second signal to induce the differentiation of the IL 2-activated precursors into cytotoxic effectors, with this process requiring 48 hr to complete. The sequential presence of these lymphokines at an appropriate time during the activation and differentiation phases is critical for the generation of LICC response.     

Past and present studies with ponasterones, the first insect molting hormones from plants.

The search for antitumor compounds from Southeast Asian plants led to ponasterones, the first phytoecdysteroids, just a year after structure determination of ecdysone and 20-hydroxyecdysone. An independent study of Chinese herb constituents by Takemoto et al. at Tohoku University led to the simultaneous and totally independent discovery of phytoecdysteroids. These findings greatly facilitated research in insect and crustacean physiology. The original structural studies on various phytoecdysteroids have led to interdisciplinary bioorganic studies in the area related to ecdysone receptor, ecdysone biosynthetic precursor (or its storage form), crustacean molt inhibitory factors, and so on.     

Differential estradiol requirement for the induction of estrus behavior and the luteinizing hormone surge in two breeds of sheep

For a better understanding of the mechanisms that lead to the preovulatory GnRH/LH surge and estrus behavior, the minimum estradiol (E) requirements (dose and duration) to induce each of these events were determined and compared between two breeds of ewes having either single (Ile de France) or multiple (Romanov) ovulations. The ewes were initially studied during a natural estrus cycle, and were then ovariectomized and run through successive artificial estrus cycles. For these artificial cycles the duration and amplitude of the follucular phase E increase were manipulated by E implants. Under all conditions, the onset of estrus behavior was similar in the two breeds, although its duration was longer in Romanov ewes. While a moderate E signal (6 cm for 12 h) induced an LH surge in 10/10 Ile de France ewes, a larger E signal (12 cm for 12 h) was minimally effective in Romanov ewes (4/10). Additional studies revealed that a small E signal (3 cm for 6 h) induced full estrus behavior in all Romanov ewes but was completely ineffective in Ile de France animals (0/10). Higher doses and mostly longer durations of the E signal (12 cm for 24 h) were required to induce a surge in all the Romanov ewes. These results demonstrate a clear difference in the E requirement for the induction of estrus behavior and the LH surge between breeds of ewes that have different ovulation rates. These data provide compelling evidence that, in one breed, the neuronal systems that regulate both events require different estrogen signals.     

The molting hormones from the embryonated egg of the tobacco hornworm, Manduca sexta (L.)

26-Hydroxyecdysone is the predominant molting hormone in 24- to 44-hour-old embryonated tobacco hornworm eggs, accounting for approximately 80% of the ecdysones present at this stage of development. This molting hormone was previously shown to be the major ecdysone present in 48- to 64-hour-old embryonated eggs of this insect. During both of these periods of embryonic development in the hornworm 20-hydroxyecdysone is a minor component, in contrast to its presence as the major ecdysone in the hornworm during certain stages of post-embryonic development.     

The structure and behaviour of Notiphila riparia and Erioptera squalida, two root-piercing insects

Two species of root-piercing insect, Notiphila riparia (Ephydridae) and Erioptera squalida (Tipulidae) are described. The insertion of the spiracles into the plants is dependent on a firm environment which provides the main bracing element for the movements of the spiracles. The structural features of root-piercing spiracles are described. The spiracles are long enough to reach the gas spaces of the roots of the plants on which the insects are commonly found. The plant epidermis may act as a limiting factor in the respiration of the insects. The emergence of the adults of Erioptera squalida involves a change in buoyancy in the pharate adult as the adult emerges at the surface.     

Molecular-genetic mechanisms of the effect of developmental hormones in insects

A review of the available data on molecular mechanisms underlying the regulation of gene expression by the developmental hormone ecdysone and juvenile hormone. Heterodimer ESP/USP is the main ecdysone receptor in D. melanogaster. Structures similar to ESP/USP were found in other insects. The information about molecular-genetic mechanisms of the effect of juvenoids is less definite. It has been proposed that the juvenile hormone in insects is a modulator of the ecdysone effect.     

Molecular-genetic mechanisms of the effect of developmental hormones in insects

A review of the available data on molecular mechanisms underlying the regulation of gene expression by the developmental hormone ecdysone and juvenile hormone. Heterodimer ESP/USP is the main ecdysone receptor in D. melanogaster. Structures similar to ESP/USP were found in other insects. The information about molecular-genetic mechanisms of the effect of juvenoids is less definite. It has been proposed that the juvenile hormone in insects is a modulator of the ecdysone effect.     

昆虫对植物蛋白酶抑制素的诱导及适应机制

植物蛋白酶抑制素是植物重要的防御物质之一,一般是分子量较小的多肽或蛋白质,能够与昆虫消化道内的蛋白酶形成复合物,阻断或削弱蛋白酶对食物中蛋白的水解,使昆虫厌食或消化不良而致死。植物蛋白酶抑制素在植物体内一般是诱导表达的,昆虫取食危害后,导致某些植物在伤口产生一种寡聚糖信息素-蛋白酶抑制素诱导因子,蛋白酶抑制素诱导因子诱导叶片局部产生植物蛋白酶抑制素,并刺激产生信号物质系统肽,通过十八烷酸途径在一系列酶的作用下产生茉莉酸,茉莉酸与受体结合,活化植物蛋白酶抑制素基因。昆虫在长期取食植物蛋白酶抑制素后会在生理及行为上产生适应性而导致不敏感,适应方式主要包括：(1)改变肠道蛋白酶对蛋白酶抑制素的敏感性;(2) 水解蛋白酶抑制素;(3)过量取食及干扰产生蛋白酶抑制素的信号通道。由于昆虫能够对植物蛋白酶抑制素产生适应,因此合理利用植物蛋白酶抑制素的抗虫作用显得十分重要。     

Role of gonadal and adrenal steroids and thyroid hormones in the regulation of molting in domestic goose

Plasma levels of testosterone (T), 17-β-estradiol (E2), progesterone (P4), dehydroepiandrosterone (DHEA), corticosterone (B), thyroxine (T4) and triiodothyronine (T3) were monitored during postnuptial and the prenuptial molt in domestic goose (Anser anser domesticus) in both sexes. 1. At the beginning of postnuptial molt (when the old, worn dawny-, and cover feathers' loss starts) in ganders, the levels of T, E2, P4 decrease while DHEA and B significantly increase. The elevated levels of T4 and low T3 concentrations characteristic of the last phase of the reproduction, remain unchanged. In layers, similar changes were observed, however, B decreases. 2. In the early phase of outgrowth of wing and cover feathers, plasma levels of T, E2 and P4 are low. Elevated B, DHEA and T4 concentrations decrease in ganders, while in layers DHEA increases and B and T4 levels remain unchanged. T3 increases in both sexes. 3. The subsequent intensive outgrowth period of wing- and cover feathers both in ganders and in layers is characterized by very low levels of T, E2, DHEA and T4, but P4 increased, and T3 concentration remain high. 4. At the end of postnuptial molt - when the outgrowth of dawny, cover-, and wing feathers stops - very low T, E2, P4, DHEA and T4 levels and and high T3 plasma levels were found in both sexes. Fast increase of plasma B was detected in ganders, while in geese, B concentration remain high. 5. During prenuptial molting (outgrowth of contour and tail feathers) low E2, P4 and T4, increasing T and DHEA, but very high T3 and B plasma concentration were measured in ganders. In layers, very low T, E2, P4, DHEA and T4 levels, and very high B and T3 levels were found. 6. At the beginning of the fall-winter sexual repose (postmolting stage) T, E2, P4, DHEA and T4 levels increase, T3 and B declines in both sexes. 7. In the subsequent phase of fall-winter period (preparatory stage) there is a further increase in T, P4 and T4, a fast increase of B and a decrease of E2, DHEA and T3 in ganders. In layers, T, P4 and DHEA decrease, B increases and the T4 and T3 do not change. 8. At the beginning of reproduction high T level, unchanged DHEA, slightly declined P4, and decreased E2, T4, T3 and a strong decline of B concentrations occur in ganders. In layers, T is further increased, E2 and P4 shows high levels, and, at the same time DHEA and T3 remain unchanged, while B and T4 decrease.