Phospholipid synthesis in the fat body endoplasmic reticulum during primary and secondary juvenile hormone stimulation of vitellogenesis inLeucophaea maderae

Summary Juvenile hormone (JH) treatment coordinately stimulated the dose-dependent synthesis of vitellogenin and endoplasmic reticulum (ER) membrane phospholipids in fat body cells from allatectomized adult females ofLeucophaea maderae. Animals were pulse-labeled in vivo with [³²P] to simultaneously measure the rates of synthesis of the phosphorylated subunits of vitellogenin and the structural phospholipids of the ER membranes. Phospholipid synthesis in ER membranes from nontarget tissues for JH such as thoracic muscle, midgut, and larval fat body was unresponsive to hormone treatment. The proliferation of ER in response to JH treatment was thus restricted to tissue that was competent to synthesize vitellogenin.Primary and secondary vitellogenin induction was measured in allatectomized adult females treated 12 days apart with JH-III. The time-course of the primary response for vitellogenin and ER phospholipid synthesis was characterized by a 24 h latent period, a rapid increase to a maximum at 72 h, and then a gradual decline. During secondary induction, vitellogenin accumulated in the hemolymph nearly twice as fast as before and peaked at a concentration of 38 g/l. This vitellogenin titer was approximately two-fold higher than that found at the height of the primary response. During both primary and secondary stimulation with JH, ER phospholipid synthesis, as measured by [¹⁴C]choline incorporation into microsomal phosphatidylcholine, was stimulated five-fold over the untreated control animals. The amplified production of vitellogenin during the secondary response was associated with a 24 h-earlier peak of ER phospholipid synthesis in the fat body.     

Antenna contact and agonism in the male lobster cockroach, Nauphoeta cinerea

On any given day, about 35% of 80- to 85-day-old socially na?ve male (SNM) lobster cockroaches (Nauphoeta cinerea) spontaneously adopted an aggressive posture (AP) without encountering another male [spontaneous AP (SAP)]. Although SAP SNMs showed significantly higher release of the pheromone 3-hydroxy-2-butanone (3H-2B) than non-SAP SNMs, there was no significant difference in hemolymph juvenile hormone (JH) III titer. When different body parts were tested for induction of the attack behavior, the antenna was found to be the most effective. After 1 min of contact with an antenna from another SAP SNM, attack behavior was induced in 100% of SAP and 76.2% of non-SAP SNMs, and the JH III titer was significantly increased in all responders. Among the non-SAP SNMs, the JH III titer before antenna contact was significantly lower in the non-responders than in the responders, and, although the JH III increase induced by 1 min antenna contact was similar between responders and non-responders, the final JH III titer of the non-responders was significantly lower. A similar attack response, JH III titer change, and 3H-2B release were seen when the individual's own antenna was used. After 5 min of contact with an antenna from another SAP SNM, attack behavior was induced in 100% of SAP and 82% of non-SAP SNMs; in the former, 3H-2B release was similar before and after antenna contact, but the JH III titer was significantly increased after antenna contact, while, in the latter, both 3H-2B release and JH III titer were significantly increased after antenna contact. Among the non-SAP SNMs, JH III titer in the non-responders was not elevated after 5 min antenna contact, and was significantly lower than that in the responders. A pentane-washed antenna did not induce attack behavior or increase the hemolymph JH III titer, and a pentane-washed antenna coated with 3H-2B also failed to induce attack behavior. These results indicate that N. cinerea male-male agonistic interactions, to which the vertebrate challenge hypothesis can be applied, are due to contact pheromone on the antenna, resulting in the concomitant expression of attack behavior and an increase in 3H-2B release and JH III titer.     

Juvenile Hormone titre and vitellogenin gene expression related to ovarian development in primary reproductives compared with nymphs and nymphoid reproductives of the termite Reticulitermes speratus

To elucidate the reproductive cycle of termite queens, incipient colonies of Reticulitemes speratus (Isoptera: Rhinotermitidae) are established under laboratory conditions, and the transition of colony development is observed at 0.5, 1.5, 2.5, 3.5, and 7.5 months (stages I–V, respectively) after colony foundation. Ovarian development, vitellogenin gene expression and Juvenile Hormone (JH) titres are examined in the queens and in nonphysogastric nymphoids collected from natural colonies. A reproductive cycle in queens is observed, in which the oviposition rate is relatively higher during stages I and II, and then decreases during stages III and IV. Vitellogenic oocytes are not observed in the ovaries during stages III and IV, and the expression level of the vitellogenin gene is low, suggesting that egg production in queens is repressed during these stages. However, vitellogenin gene expression and egg deposition in queens resumes during stage V. Juvenile Hormone levels rise during the transition from nymphs to stage I queens, and elevated JH titres are observed also during stages III and IV. The decrease in JH titre in queens at stage II precedes the decline in vitellogenesis at stages III and IV. Thus, JH titre and vitellogenesis are correlated in an offset pattern. However, nonphysogastric nymphoid reproductives do not have vitellogenic oocytes in their ovaries, and their JH titre is two‐fold higher than that of queens, suggesting that elevated JH titre precedes vitellogenesis, as in queens.     

Juvenile hormone biosynthesis,oocyte growth and vitellogenin accumulation in Choristoneura fumiferana and C. rosaceana: a comparative study

We assessed the effects of age and mating status on in vitro juvenile hormone (JH) biosynthesis, oocyte growth, egg production and vitellogenin (Vg) accumulation in the tortricid moths, Choristoneura fumiferana and C. rosaceana. To determine whether vitellogenesis is dependent on the presence of JH, we also examined the effects of decapitation and JH analog treatments on egg production. In both species, the corpora allata (CA) of adult females released fmol quantities of JH, with JH II being the major homolog produced. The CA began producing detectable quantities of JH around the time of emergence. Full activation of the CA was observed a few hours sooner in C. fumiferana than in C. rosaceana. In pharate adults and young virgin females of both species, growth of the basal oocyte reflected changes in CA activity. Decapitation of newly emerged females significantly reduced egg production, but treatment of decapitated females with the JH analog methoprene resulted in egg production that was similar to (C. fumiferana) or greater than (C. rosaceana) that of controls, indicating that JH is required for oocyte maturation. Vg was first observed in the hemolymph before the presumptive time of CA activation, suggesting that the synthesis of this protein is not dependent on JH. The presence of normal quantities of Vg in the hemolymph of pupae decapitated before CA activation confirmed this hypothesis. The Vg titer underwent a transient decline following CA activation and was significantly lower in mated than in virgin females of both species 3 and 5 days after copulation. Since CA activation at emergence and mating are both expected to cause a rise in the JH titer, we suggest that the declines in the levels of Vg result from JH-enhanced Vg uptake by the developing oocytes. Mating induced a significant increase in egg production but had no measurable impact on rates of JH biosynthesis in vitro.     

早熟素II对家蝇卵黄发生的影响

本实验通过卵巢发育分级的解剖观察、可溶性蛋白质和核酸的定量测定、火箭免疫电泳定量测定卵黄原蛋白及激素处理等方法,研究了早熟素对家蝇(Muscadomestica vicina)卵黄发生的影响。试验结果表明用20ug早熟素处理每头刚羽化家蝇时,家蝇卵黄发生处于不完全抑制状态,其卵黄发生过程比对照组“延迟”约12小时。处理后48小时,血淋巴中卵黄原蛋白的滴度为lo.5ug/ul,接近对照组,而其卵巢鲜重和发育等级明显低于对照组,这种不完全抑制状态表明卵母细胞对卵黄原蛋白的吸收作用受到抑制。当用高剂量100ug早熟素11处理每头刚羽化家蝇时,血淋巴中卵黄原蛋白滴度、卵巢鲜重及其发育均受到明显的抑制,这种抑制效应能自然恢复。 当早熟素11和保幼激素(JH-III)、20-羟基蜕皮酮共同处理时,保幼激素具有明显的去抑制作用,可使血淋巴中卵黄蛋白浓度成倍增加,20-羟基蜕皮酮的去抑制效应不明显。本文还对早熟素作用于双翅目昆虫的方式作了讨论。     

The hemolymph JH titer exhibits a large-amplitude, morph-dependent, diurnal cycle in the wing-polymorphic cricket, Gryllus firmus

The hemolymph juvenile hormone (JH) titer was measured in over 500 flight-capable and flightless, adult female Gryllus firmus at 3-6 h intervals during each of days 2-8 of adulthood. The flight-capable morph exhibited a large-amplitude daily cycle in the hemolymph JH titer, while the flightless morph exhibited a barely perceptible cycle. The JH titer cycle was observed on all days in the flight-capable morph, but the large amplitude cycle (>15-20 fold increase in mean titer; >100-fold increase in some individuals), began on day 5. For both the large and small amplitude cycles, the JH titer peaked near the end of the photophase-beginning of the scotophase. The hemolymph ecdysteroid titer did not exhibit a corresponding large amplitude daily cycle, although a low amplitude cycle (1-3-fold change) was seen in both morphs. The large magnitude rise in the JH titer in the flight-capable morph during the photophase was not due to decreased hemolymph volume or JH degradation. Daily cycles in the JH titer may be common, but may have gone unnoticed in other insect species due to restricted temporal sampling. Failure to identify these cycles can result in substantial errors in inferring biological roles for JH. Because JH regulates flight behaviors, morph-specific daily cycles in the JH titer may be especially common in dispersal-polymorphic insects, in which flight is restricted to one morph during a limited period of the day or night. However, because JH regulates numerous biological traits, analogous cycles may be common in insects exhibiting other types of complex (e.g. caste or phase) polymorphism, in which morphs differ in a biological characteristic that is restricted to a specific period of the photophase or scotophase.     

Structure,haemolymph titre,and regulatory effects of juvenile homone during ovarian maturation in Leucophaea maderae

Juvenile hormone (JH) synthesized and secreted in vitro by the corpora allata of mated adult Leucophaea maderae females was determined to be JH III (methyl-10,11-epoxy-3,7,11-trimethyl-2,6-dodecadienoate).The haemolymph titre of JH was determined during maturation of the terminal oöcytes in the first reproductive cycle of L. maderae. In virgin females, JH is not detectable in the haemolymph during the first eight days following adult emergence; however, by 10 days after emergence, trace quantities of JH are apparent. Mating stimuli induce a dramatic increase in the concentration of haemolymph JH, with a peak occurring approximately 12 days after mating; thereafter, the JH concentration declines until it has reached an undetectable level 19 days after mating, at the time of chorion deposition.During ovarian maturation, changes in the rates of synthesis of vitellogenin by the fat body and DNA by the ovary correlate closely with the haemolymph titre of JH. However, no such correlation exists between the JH titre and the extensive ovarian protein synthesis that occurs in L. maderae coincident with chorion formation.The effects of JH I and JH III on both vitellogenin synthesis and ovarain DNA synthesis are statistically similar.     

Juvenile hormones and their titer regulation in Galleria mellonella

Juvenile hormones I, II and III occur in Galleria but JH II is dominant. Its concentration reaches a peak of 3 pmol/g body wt in the penultimate instar, drops to zero in the last larval instar and, except for a small peak in prepupae (0.2 pmol/g), remains undetectable until pharate adults. After emergence the titer reaches over 5 pmol/g in both sexes. Presence of JH II is associated with JH II acid; JH III acid occurs even more often, including stages lacking JH III. Brain implantation into freshly ecdysed last instar larvae effects a similar JH peak as in the penultimate instar and causes an extra larval molt. The opposite treatment, i.e. decerebration of fresh last instar larvae, elicits a continuous rise of JH II to 10 pmol/g and an increase of otherwise rare JH I to 3 pmol/g. Sham operations of these larvae or decerebration of old larvae elevate practically only JH II titer to 1–1.5 pmol/g. Implanted brain-corpora cardiaca-corpora allata complexes maintain in various hosts 0.14–1.6 pmol/g of JH II. The significance and regulation of these fluctuations in JH titer are discussed.     

Juvenile hormone III titers and regulation of soldier caste in coptotermes formosanus (Isoptera: Rhinotermitidae)

Juvenile hormone (JH) is an important growth hormone in insects that has also been implicated in caste determination in termites. Gas chromatography-mass spectrometry was used to establish that the JH in the Formosan subterranean termite, Coptotermes formosanus Shiraki, is JH III. JH III titers were measured in workers, pre-soldiers, and soldiers from samples collected from the field. The average titers of JH III in workers and soldiers were about 13 and 25 pg mg(-1), respectively. However, pre-soldiers contained a significantly higher amount, 596 pg mg(-1). As expected, treatment of workers with a JH-analogue, methoprene, triggered rapid formation of pre-soldiers. However, these pre-soldiers had a very low JH III titer (62 pg mg(-1)). It appears that the application of JHA, while inducing pre-soldier formation, does not increase the endogenous JH III titer. The titer, however, increased as the pre-soldiers aged and before transforming into soldiers.     

The function of juvenile hormone in adult worker honeybees, Apis mellifera

The injection of high doses of JH-III into adult worker honeybees causes the hypopharyngeal glands to degenerate and lowers the vitellogenin synthesis rate as well as the total haemolymph protein concentration. The injection of low doses increases the protein titre and stimulates vitellogenin synthesis while the hypopharyngeal glands develop.The effects of high doses of JH corresponds to the normal physiological changes in the ageing bee, especially at the time of the transformation into field bees. Hormone titre measurements show a drastic increase during adult life, which together with the injection experiments seems to indicate stimulating effects of low JH titre on protein synthesis and hypopharyngeal gland development during the first phase of adult life, and inhibiting and degeneration inducing effects of the high JH titre during the second phase of life.Thus it is possible that the physiological changes correlated with changes in behaviour of the adult worker bee are controlled by the JH titre.     

Relationship between an increase of juvenile hormone titer in early instars and the induction of diapause in fully grown larvae of Sesamia nonagrioides

The larvae of Sesamia nonagrioides (Lepidoptera: Noctuidae) grown at 25 degrees C and long photoperiod (16:8h light:dark) pupate in the 5th or 6th (mostly) larval instar, while the larvae reared under a short photoperiod (12:12h) enter diapause during which they consume some food and undergo up to 12 (usually 3-4) stationary larval molts. Diapause programming includes an increase of juvenile hormone (JH) titer in the hemolymph from about 20 to 50 nM in the 4th and 5th instar larvae (titer in earlier instars was not measured). JH I, II, and III are present in approximate ratio 1-2:10:1. The JH titer drops to zero before pupation but remains around 20 nM during diapause. Perfect extra larval molts associated with a body weight increase can be induced in the non-diapausing larvae with a JH analogue (JHA). The weight rise is due to accumulation of reserves and not to a general body growth. The timing of extra molts is similar to the molting pattern of the diapausing larvae only when JHA is present since early larval instars. In the diapausing larvae, JHA application affects neither molting periodicity nor the body weight. It is concluded that (1) Increased JH titer in early larval instars is a part of diapause programming; (2) The extension of larval stage in the diapausing larvae, but not the timing pattern of extra molts, is due to continuously high JH titer; (3) The diapause program includes low food intake, maintenance of a certain body weight, and periodic larval molts.     

Precocious induction of vitellogenin with JH III in the twospotted stink bug, Perillus bioculatus (Heteroptera: Pentatomidae)

The effect of juvenile hormone (JH) III on the hemolymph composition of vitellogenin was examined in Perillus bioculatus. Adult females were treated topically with JH III, and the premature presence of vitellogenin in the hemolymph was then detected using electrophoresis and Western blot analyses. JH III treatment resulted in a dose-dependent early production of vitellogenin that was detectable 48 h before vitellogenin was present in non-treated insects. Vitellogenin was not observed in the hemolymph of JH III-treated adult males. The techniques reported here may be useful for the detection, isolation and characterization of compounds with JH-like activity in P. bioculatus and other species of Heteroptera (which are thought to have JH-like substances other than the JHs with known chemical identity). These same techniques may also provide a method for researchers to investigate the interactions of JH-like compounds and other substances, such as ecdysteroid, in the regulation of vitellogenesis in Heteroptera.     

Morph-associated JH titer diel rhythm in Gryllus firmus: Experimental verification of its circadian basis and cycle characterization in artificially selected lines raised in the field

Previous studies demonstrated a high-amplitude, diel cycle for the hemolymph JH titer in the wing-polymorphic cricket, Gryllus firmus. The JH titer rose and fell in the flight-capable morph (long-winged, LW(f)) above and below the relatively temporally invariant JH titer in the flightless (short-winged, SW) morph. The morph-specific JH titer cycle appeared to be primarily driven by a morph-specific diel cycle in the rate of JH biosynthesis. In the present study, cycles of the JH titer and rate of JH biosynthesis in the LW(f) morph persisted in the laboratory under constant darkness with an approximate 24 h periodicity. The JH titer cycle also shifted in concert with a shift in the onset of the scotophase, was temperature compensated in constant darkness, and became arrhythmic under constant light. These results provide strong support for the circadian basis of the morph-specific diel rhythm of the JH titer and JH biosynthetic rate. Persistence of the JH titer cycle under constant darkness in multiple LW-selected and SW-selected stocks also provides support for the genetic basis of the morph-associated circadian rhythm. The morph-specific JH titer cycle was observed in these stocks raised in the field, in both males and females, in each of 3 years studied. The onset of the cycle in the LW(f) morph, a few hours before sunset, correlated well with the onset of the cycle, a few hours before lights-off, in the laboratory. The morph-specific JH titer cycle is a general feature of G. firmus, under a variety of environmental conditions, and is not an artifact of specific laboratory conditions or specific genetic stocks. It is a powerful experimental model to investigate the mechanisms underlying endocrine circadian rhythms, their evolution, and their impact on life history evolution.     

Coordinated changes in JH biosynthesis and JH hemolymph titers in Aedes aegypti mosquitoes

Juvenile hormone III (JH) is synthesized by the corpora allata (CA) and plays a key role in mosquito development and reproduction. A decrease in JH titer during the last instar larvae allows pupation and metamorphosis to proceed. As the anti-metamorphic role of JH comes to an end, the CA of the late pupa once again synthesizes JH, which plays an essential role in orchestrating reproductive maturation. In spite of the importance of Aedes aegypti as a vector, a detailed study of the changes of JH hemolymph titers during the gonotrophic cycle has never been performed. In the present studies, using a high performance liquid chromatography coupled to a fluorescent detector (HPLC–FD) method, we measured changes in JH levels in the hemolymph of female mosquitoes during the pupal and adult stages. Our results revealed tightly concomitant changes in JH biosynthesis and JH hemolymph titers during the gonotrophic cycle of female mosquito. Feeding high sugar diets resulted in an increase of JH titers, and mating also modified JH titers in hemolymph. In addition these studies confirmed that JH titer in mosquitoes is fundamentally determined by the rate of biosynthesis in the CA.