Juvenile Hormone Secretion Research Articles

The embryonic role of juvenile hormone in the firebrat, Thermobia domestica, reveals its function before its involvement in metamorphosis.

To gain insights into how juvenile hormone (JH) came to regulate insect metamorphosis, we studied its function in the ametabolous firebrat, Thermobia domestica. Highest levels of JH occur during late embryogenesis, with only low levels thereafter. Loss-of-function and gain-of-function experiments show that JH acts on embryonic tissues to suppress morphogenesis and cell determination and to promote their terminal differentiation. Similar embryonic actions of JH on hemimetabolous insects with short germ band embryos indicate that JH's embryonic role preceded its derived function as the postembryonic regulator of metamorphosis. The postembryonic expansion of JH function likely followed the evolution of flight. Archaic flying insects were considered to lack metamorphosis because tiny, movable wings were evident on the thoraces of young juveniles and their positive allometric growth eventually allowed them to support flight in late juveniles. Like in Thermobia, we assume that these juveniles lacked JH. However, a postembryonic reappearance of JH during wing morphogenesis in the young juvenile likely redirected wing development to make a wing pad rather than a wing. Maintenance of JH then allowed wing pad growth and its disappearance in the mature juvenile then allowed wing differentiation. Subsequent modification of JH action for hemi- and holometabolous lifestyles are discussed.

The females' response to male attractiveness: Mate choice, larvae production and differential brain protein expression

AbstractSexual Selection has been studied predominantly from a functional perspective with relatively limited investigation of the mechanistic basis of female choice. In this study, we evaluated female choice and larvae production in response to attractive or less attractive males and concurrently examined the protein profile in the brains of females, using the mealworm beetle Tenebrio molitor as a model system. Females were found to prefer males with high levels of pheromones, which requires the secretion of juvenile hormone (JH). Male attractiveness was enhanced using the JH analog methoprene, resulting in less female rejection and higher mating frequency and offspring production. Importantly, reproductive success was not due to differences in testis size or sperm production, or viability. Out of the 1833 proteins detected in the brain, only 32 were differentially expressed in females mating with attractive versus less attractive males. These proteins involved memory, metabolism, olfactory detection, reproduction, and movement. Although some brain proteins have been linked to mate choice in vertebrates, most of the differentially expressed molecules found in this study have not been previously reported concerning mate choice.

Juvenile hormone suppresses the FoxO-takeout axis to shorten longevity in male silkworm

Juvenile hormone (JH) plays a crucial endocrine regulatory role in insect metamorphosis, reproduction, and longevity in multiple organisms, such as flies, honeybees, and migratory monarch butterflies. However, the molecular mechanism of JH affecting longevity remains largely unknown. In this study, we showed that JH III and its analog methoprene shortened the survival days significantly in the adulthood of male silkworm. At the same time, the allatostatin, a neuropeptide that inhibits the secretion of JH by the corpora allata, could extend the survival days dramatically after adult eclosion in male silkmoth. Interestingly, a central pro-longevity FoxO transcription factor was reduced upon JH stimulation in silkworm individuals and BmN-SWU1 cells. Furthermore, the analysis of the upstream sequence of the FoxO gene identified a JH response element which suggested that FoxO might be regulated as a target of JH. Surprisingly, we identified a Bmtakeout (BmTO) gene that encodes a JH-binding protein and contains a FoxO response element. As expected, FoxO overexpression and knockdown up- and down-regulated the expression of BmTO respectively, indicating that BmTO functions as a FoxO target. BmTO overexpression could release the inhibitory effect of JH on the BmFoxO gene by reducing JH bioavailability to block its signal transduction. Collectively, these results may provide insights into the mechanism of the JH-FoxO-TO axis in aging research and pest control.

Regulation of Krüppel homolog 1 expression by photoperiod in the bean bug, Riptortus pedestris

AbstractIn Riptortus pedestris (Hemiptera, Alydidae), adult females develop their ovaries under long‐day conditions (LD), but enter reproductive diapause with suppression of ovarian development under short‐day conditions (SD). This photoperiodic response is regulated by juvenile hormone (JH). Krüppel homolog 1 (Kr‐h1) encodes a JH‐inducible transcriptional factor and plays a pivotal role for reproduction in some insects. In the present study, we molecularly characterized Kr‐h1 and investigated Kr‐h1 expression patterns under SD and LD in R. pedestris. The open reading frame of Kr‐h1 was 1320 bp encoding a protein of 440 amino acids. The deduced protein contained eight conserved C2H2‐type zinc finger domains. The expression levels of Kr‐h1 increased from 5 days and peaked at 7 days after transfer from SD to LD. By contrast, Kr‐h1 was constantly expressed at a low level under SD. Topical application of a JH analogue induced ovarian development and Kr‐h1 expression even under SD, suggesting that Kr‐h1 is a JH‐inducible gene in R. pedestris. Then, we examined the effect of knockdown of circadian clock genes Clock (Clk) and mammalian‐type cryptochrome (cry‐m) by RNA interference (RNAi) on the ovarian development and Kr‐h1 expression. Clk RNAi prevented ovarian development and decreased the Kr‐h1 expression under LD, whereas cry‐m RNAi induced ovarian development and Kr‐h1 expression under SD. These results imply that JH secretion is prevented by Clk RNAi under LD and induced by cry‐m RNAi under SD. From these results, we suggest that Kr‐h1 expression is JH dependent and closely correlates with photoperiodic regulation of ovarian development.

Endocrine Proxies Can Simplify Endocrine Complexity to Enable Evolutionary Prediction.

It is well understood that much of evolutionary change is mediated through the endocrine system with growing interest to identify how this occurs. This however, causes a conflict of sorts. To understand endocrine mechanism, a focus on detail is required. In contrast, to understand evolutionary change, reduction to a few key traits is essential. Endocrine proxies, measurable traits that accurately reflect specific hormonal titers or the timing of specific hormonal events, can reduce endocrine complexity to a few traits that enable predictions of how the endocrine system regulates evolutionary change. In the tobacco hornworm (Manduca sexta, Sphingidae), three endocrine proxies, measured on 5470 individuals, were used to test explicit predictions of how the endocrine system regulates the response to 10 generations of simultaneous selection on body size and development time. The critical weight (CW) reflects the variation in the cessation of juvenile hormone (JH) secretion in the last larval instar, the interval to cessation of growth (ICG) reflects the variation in prothoracicotropic hormone and 20-hydroxyecdysone (20E). Growth rate (GR) reflects the nutrient signaling pathways, primarily the insulin and TOR This is a standard identity similar to DNA signaling pathways. These three endocrine proxies explained 99% and 93% of the variation in body size and development time, respectively, following the 10 generations of simultaneous selection. When the two focal traits, body size and development time, were selected in the same direction, both to either increase or both to decrease, the response to selection was determined primarily by the CW and the ICG, proxies for the developmental hormones JH and 20E, and constrained by GR. In contrast, when the two focal traits were selected in opposite directions, one to increase and the other to decrease, the response to selection was determined primarily by the insulin and TOR signaling pathways as measured by their proxy, GR, and constrained by the CW and the ICG. Thus, the use of endocrine proxies may be a powerful tool to reduce endocrine complexity to enable explicit and testable predictions how the endocrine system can enable or constrain evolutionary change.

Importance of juvenile hormone signaling arises with competence of insect larvae to metamorphose

Juvenile hormone (JH) postpones metamorphosis of insect larvae until they have attained an appropriate stage and size. Then, during the final larval instar, a drop in JH secretion permits a metamorphic molt that transforms larvae to adults either directly (hemimetaboly) or via a pupal stage (holometaboly). In both scenarios, JH precludes metamorphosis by activating the Kr-h1 gene through a JH receptor, Methoprene-tolerant (Met). Removal of Met, Kr-h1, or JH itself triggers deleterious precocious metamorphosis. Although JH is thought to maintain the juvenile status throughout larval life, various methods of depleting JH failed to induce metamorphosis in early-instar larvae. To determine when does JH signaling become important for the prevention of precocious metamorphosis, we chose the hemimetabolous bug, Pyrrhocoris apterus, and the holometabolous silkworm, Bombyx mori. Both species undergo a fixed number of five larval instars. Pyrrhocoris larvae subjected to RNAi-mediated knockdown of Met or Kr-h1 underwent precocious adult development when treated during the fourth (penultimate) instar, but younger larvae proved increasingly resistant to loss of either gene. The earliest instar developing minor signs of precocious metamorphosis was the third. Therefore, the JH-response genes may not be required to maintain the larval program during the first two larval instars. Next, we examined Bombyx mod mutants that cannot synthesize authentic, epoxidized forms of JH. Although mod larvae expressed Kr-h1 mRNA at severely reduced levels since hatching, they only entered metamorphosis by pupating after four, rarely three instars. Based on findings in Pyrrhocoris and Bombyx, we propose that insect postembryonic development is initially independent of JH. Only later, when larvae gain competence to enter metamorphosis, JH signaling becomes necessary to prevent precocious metamorphosis and to optimize growth.

Microarrays reveal discrete phases in juvenile hormone regulation of mosquito reproduction

Mosquitoes are vectors of some of the world’s most devastating human diseases: malaria, dengue fever, and yellow fever in the tropics, and encephalitis and West Nile virus in the United States. The female mosquito usually requires a blood meal before she makes a batch of eggs, and one for each subsequent batch thereafter. This repeated blood feeding makes her an exceptional disease vector, picking up a pathogen with one blood meal and then transmitting it on successive meals. After emergence (eclosion) as an adult, the female must mature before she can produce eggs in response to the blood meal. This maturation is initiated by an insect-specific juvenile hormone (JH), a sesquiterpenoid that acts on the fat body (the liver and the adipose tissue of the insect) to increase both its metabolic machinery and its protein-synthesizing capacity so that it can synthesize the yolk protein vitellogenin in response to the blood meal (Fig. 1) (1). JH also directs previtellogenic development of the ovary. In PNAS, Zou et al. (2) show, using microarray analysis, that JH controls the maturation of the fat body of the yellow fever, dengue mosquito Aedes aegypti in a time-dependent manner by regulating three major gene clusters. Early-posteclosion (EPE) gene expression peaks at 6 h, mid-posteclosion (MPE) genes at 24 h, and late-posteclosion (LPE) genes at 66 h after eclosion (Fig. 1). These times correspond to low, intermediate, and high JH titers because JH secretion begins at eclosion and peaks at 36 h (3). The EPE and MPE genes are primarily involved in carbohydrate and lipid metabolism, whereas the late genes are primarily for the buildup of the protein-synthesizing machinery based on gene ontology, as discussed below.

Photoperiodic diapause under the control of circadian clock genes in an insect

BackgroundMost organisms have evolved a circadian clock in order to anticipate daily environmental changes and many of these organisms are also capable of sophisticated measurement of daylength (photoperiodism) that is used to regulate seasonal events such as diapause, migration and polymorphism. It has been generally accepted that the same elements are involved in both circadian (daily) and seasonal (annual) rhythms because both rely upon daily light-dark cycles. However, as reasonable as this sounds, there remains no conclusive evidence of such a molecular machinery in insects. We have approached this issue by using RNA interference (RNAi) in Riptortus pedestris.ResultsThe cuticle deposition rhythm exhibited the major properties of circadian rhythms, indicating that the rhythm is regulated by a circadian clock. RNAi directed against the circadian clock genes of period and cycle, which are negative and positive regulators in the circadian clock, respectively, disrupted the cuticle deposition rhythm and distinct cuticle layers were produced by these RNAi. Simultaneously, period RNAi caused the insect to avert diapause under a diapause-inducing photoperiod whereas cycle RNAi induced diapause under a diapause-averting photoperiod. The expression patterns of juvenile hormone-regulated genes and the application of juvenile hormone analogue suggested that neither ovarian development itself nor a downstream cascade of juvenile hormone secretion, were disturbed by period and cycle RNAi.ConclusionsThis study revealed that the circadian clock genes are crucial not only for daily rhythms but also for photoperiodic diapause. RNAi directed against period and cycle had opposite effects not only in the circadian cuticle deposition rhythm but also in the photoperiodic diapause. These RNAi also had opposite effects on juvenile hormone-regulated gene expression. It is still possible that the circadian clock genes pleiotropically affect ovarian development but, based on these results, we suggest that the circadian clock operated by the circadian clock genes, period and cycle, governs seasonal timing as well as the daily rhythms.See Commentary: http://www.biomedcentral.com/1741-7007/8/115

Sex differences in phenotypic plasticity of a mechanism that controls body size: implications for sexual size dimorphism

The degree and/or direction of sexual size dimorphism (SSD) varies considerably among species and among populations within species. Although this variation is in part genetically based, much of it is probably due to the sexes exhibiting differences in body size plasticity. Here, we use the hawkmoth, Manduca sexta, to test the hypothesis that moths reared on different diet qualities and at different temperatures will exhibit sex-specific body size plasticity. In addition, we explore the proximate mechanisms that potentially create sex-specific plasticity by examining three physiological variables known to regulate body size in this insect: the growth rate, the critical weight (which measures the cessation of juvenile hormone secretion from the corpora allata) and the interval to cessation of growth (ICG; which measures the time interval between the critical weight and the secretion of the ecdysteroids that regulate pupation and metamorphosis). We found that peak larval mass of males and females did not exhibit sex-specific plasticity in response to diet or temperature. However, the sexes did exhibit sex-specific plasticity in the mechanism that controls size; males and females exhibited sex-specific plasticity in the growth rate and the critical weight in response to both diet and temperature, whereas the ICG only exhibited sex-specific plasticity in response to diet. Our results suggest it is important for the sexes to maintain the same degree of SSD across environments and that this is accomplished by the sexes exhibiting differential sensitivity of the physiological factors that determine body size to environmental variation.

Age‐ and division‐of‐labour‐dependent differential expression of a novel non‐coding RNA, Nb‐1, in the brain of worker honeybees, Apis mellifera L.

To elucidate the molecular mechanisms underlying honeybee social behaviours, we identified a novel gene, Nb-1, whose expression in the worker brain changes according to the age-dependent division of labour in normal colonies. The open reading frames contained in the Nb-1 cDNA were not conserved in the homologue of a related species, suggesting that the Nb-1 gene product is a non-coding RNA. The distribution of Nb-1-expressing cells partially overlapped that of octopamine-immunoreactive cells and neurosecretory cells, the latter of which are involved in the synthesis and secretion of juvenile hormone (JH). Octopamine and JH control worker task transition, and thus Nb-1 might be involved in task transition through the modulation of octopamine/JH synthesis and secretion.

A Physiological Perspective on the Response of Body Size and Development Time to Simultaneous Directional Selection

Natural selection typically acts on multiple traits simultaneously. Quantitative genetics provides the theory for predicting the response to selection of multiple traits and predicts symmetrical responses to selection (the response to upward selection on both traits is equal to their response to downward selection). In reality, however, the response to simultaneous selection on two traits is often asymmetrical. We provide a physiology-based framework to explain the asymmetrical response to simultaneous selection on two important life history traits: body size and development time. The tobacco hornworm, Manduca sexta, is particularly well suited for such a study, as the physiological control of body size and development time is well known in this species. Three physiological factors control both life history traits in M. sexta: growth rate, the critical weight that measures the timing of the onset of the cessation of juvenile hormone secretion (which initiates the processes leading to pupation) and the time interval between the critical weight and secretion of the molting hormone 20-hydroxyecdysteroid (the interval to cessation of growth, ICG). Asymmetry in the response to simultaneous selection on the two life history traits is due to the different types of selection acting on the three physiological factors. The critical weight and ICG are always under synergistic selection when both focal traits are selected in the same direction and under antagonistic selection when the focal traits are selected in opposite directions. Growth rate follows the opposite pattern. We propose a general model to explain the asymmetric response to simultaneous selection. This model emphasizes the importance of physiological processes in understanding evolutionary responses to selection and the control of complex traits.

The Physiological Basis of Reaction Norms: The Interaction Among Growth Rate, the Duration of Growth and Body Size

The general effects of temperature and nutritional quality on growth rate and body size are well known. We know little, however, about the physiological mechanisms by which an organism translates variation in diet and temperature into reaction norms of body size or development time. We outline an endocrine-based physiological mechanism that helps explain how this translation occurs in the holometabolous insect Manduca sexta (Sphingidae). Body size and development time are controlled by three factors: (i) growth rate, (ii) the timing of the cessation of juvenile hormone secretion (measured by the critical weight) and (iii) the timing of ecdysteroid secretion leading to pupation (the interval to cessation of growth [ICG] after reaching the critical weight). Thermal reaction norms of body size and development time are a function of how these three factors interact with temperature. Body size is smaller at higher temperatures, because the higher growth rate decreases the ICG, thereby reducing the amount of mass that can accumulate. Development time is shorter at higher temperatures because the higher growth rate decreases the time required to attain the critical weight and, independently, controls the duration of the ICG. Life history evolution along altitudinal, latitudinal and seasonal gradients may occur through differential selection on growth rate and the duration of the two independently controlled determinants of the growth period.

Mas-allatotropin/Lom-AG-myotropin I immunostaining in the brain of the locust, Schistocerca gregaria.

Mas-allatotropin (Mas-AT) and Lom-accessory gland-myotropin I (Lom-AG-MTI) are two members of a conserved family of insect neuropeptides, collectively termed allatotropins, which have diverse functions, ranging from stimulation of juvenile hormone secretion to myotropic effects on heart and hindgut. In addition, allatotropins appear to be abundant within the nervous system, suggesting neuroactive roles. To identify neurons in the insect brain suitable for a neurophysiological analysis of the roles of allatotropins, we used antisera against Mas-AT and Lom-AG-MTI to map allatotropin-immunoreactive neurons in the brain of a suitable insect, the locust Schistocerca gregaria. Both antisera revealed basically identical staining patterns throughout the locust brain with more than 12,500 immunostained interneurons per brain hemisphere. Neurosecretory cells were not labeled, and the retrocerebral complex was devoid of immunostaining. Prominent immunoreactive cell types include about 9,600 lamina monopolar neurons, medulla to lobula interneurons, local neurons of the antennal lobe, a giant interneuron of the mushroom body, projection neurons of the glomerular lobe to the mushroom body, and three systems of tangential neurons of the central complex. Several groups of neurons showed colocalization of Mas-AT- and gamma-aminobutyric acid immunostaining. Mass spectrometric analysis identified a peptide with a molecular mass identical to Lom-AG-MTI in all major parts of the locust brain but not in the retrocerebral complex. This study strongly suggests that Lom-AG-MTI is highly abundant in the locust brain, and is likely to play a neuroactive role in many brain circuits including all stages of sensory processing, learning and memory, and higher levels of motor control.

Hormonal regulation and functional role of Drosophila E75A orphan nuclear receptor in the juvenile hormone signaling pathway

Ecdysone and juvenile hormone (JH) are important regulators of insect growth and development. While ecdysone initiates a transition from one developmental stage to another, JH determines the nature of the transition. How these two hormones interact at the molecular level is not known. Here we report the JH inducibility of the E75A nuclear receptor encoded by the E75 early ecdysone-inducible gene. In Drosophila S2 cells, E75A transcription is specifically activated by JH at concentrations well within the physiological range found in larvae and adults. The induction is rapid and does not require a concurrent protein synthesis, and thus represents a primary hormone response. Consistent with JH regulation, E75A mRNA levels are reduced in ovaries of apterous 4 mutant adults defective in JH secretion. Expression is rescued by topical methoprene application. We further provide evidence that ectopic E75A is sufficient to perform several functions in the JH signaling pathway. First, it can down-regulate its own transcription. Second, E75A can potentiate the JH inducibility of a secondary response gene, JhI-21. Finally, in the presence of JH, E75A can repress ecdysone activation of early genes including Broad-Complex. Based on these data, we propose a model for the role of E75A in the ecdysone-JH regulatory interplay.

Copulation corrupts immunity: a mechanism for a cost of mating in insects.

There are well documented costs of mating in insects but little evidence for underlying mechanisms. Here, we provide experimental evidence for a hormone-based mechanism that reduces immunity as a result of mating. We examined the mealworm beetle Tenebrio molitor and show that (i) mating reduces a major humoral immune effector-system (phenoloxidase) in both sexes, and (ii) that this down-regulation is mediated by juvenile hormone. Because both juvenile hormone and phenoloxidase have highly conserved functions across all insects, the identified mechanism is similarly likely to be highly conserved. The positive physiological function of mating-induced juvenile hormone secretion is gamete and accessory gland production: we propose that its negative effects on immune function are the consequence of physiological antagonism. Therefore, we have identified a physiological tradeoff between mating and immunity. Our results suggest that increasing mating success can result in increasing periods of immune suppression, which in turn implies that reproductively successful individuals may be more vulnerable to infection by, and the negative fitness effects of, pathogens.

Juvenile hormone signaling during oogenesis in Drosophila melanogaster

Juvenile hormone (JH) participates both in the control of insect development and the establishment of reproductive maturity. In cultured Drosophila cells and in ovarian nurse cells, JH and its synthetic analog, methoprene, induce the expression of two related genes. These genes encode highly similar amino acid transport proteins that are homologous to transporters found in a variety of eukaryotes. JhI-21 is a novel Drosophila gene, and minidiscs ( mnd) is a gene that was identified earlier. Two JH-inducible genes are regulated by different molecular mechanisms; JhI-21 behaves as a secondary JH-responsive gene, while mnd behaves as a primary responsive gene. Both JhI-21 and mnd transcripts show developmental profiles, which are consistent with JH regulation. Following eclosion, transcripts from JhI-21 and mnd are synthesized in ovarian nurse cells and subsequently sequestered in the mature egg. Their ectopic accumulation in ovaries can be induced by topical methoprene application. In apterous (ap 4 ) mutant adults defective in JH secretion, mnd and JhI-21 RNA levels are severely reduced, but normal abundance is rescued to a high degree by topical methoprene treatment. Based on the evidence, we propose that during sexual maturation of Drosophila, JH provides a signal to the ovary that leads to the production of several maternally inherited mRNAs.

Factors influencing sperm transfer and insemination in cat fleas (Siphonaptera: Pulicidae) fed on an artificial membrane system.

Sperm transfer through the epididymis, a prerequisite for insemination of cat fleas, Ctenocephalides felis (Bouché) was stimulated by exposure of unfed male fleas to juvenile hormone III residues for 3 d at 25 degrees C or exposure of unfed fleas to 37 degrees C for 6 d. Sperm transfer was completed at least three times faster in unfed males held at 37 degrees C than in those held at 25 degrees C. Although percentage sperm transfer in fleas fed water or 0.15 M saline at 37 degrees C was not significantly increased over that of unfed fleas, a significantly greater percentage of blood-fed males completed sperm transfer at 2, 3, and 6 d. At least two factors influenced insemination: exposure of fleas to host body temperature and amount of food consumption. When blood-fed males and females were paired and fed 0.15 M saline, 0% were inseminated at 25 degrees C versus 35% at 37 degrees C. Because percentage insemination did not increase in blood-fed males and females that were paired and fed 0.15 M saline at 37 degrees C for an additional 48 h, continuous bloodfeeding appeared to be required for maximal rates of mating and insemination. Furthermore, no females were inseminated when blood-fed males and females were paired at 37 degrees C and starved. Treatment of unfed fleas with juvenile hormone III did not substitute for bloodfeeding in stimulating mating and insemination; when blood-fed males were paired with JH III-treated females and vice versa and fed 0.15 M saline at 37 degrees C, 0% were inseminated. However, when fleas were fed 0.15 M saline and exposed to 1,250 ppm juvenile hormone III or fed whole blood and exposed to 12.5, 125, or 1,250 ppm juvenile hormone III, percent insemination was significantly increased in comparison to the controls. Therefore, juvenile hormone secretion in blood-fed fleas may regulate mating success indirectly by stimulating sperm transfer.

The role of low levels of juvenile hormone esterase in the metamorphosis of Manduca sexta

The activity of juvenile hormone esterase (JHE) in feeding fifth instar larvae of Manduca sexta increases gradually with larval weight and rises to a peak after larvae pass the critical weight when juvenile hormone secretion ceases. Starvation of larvae of Manduca sexta (L.) that had exceeded the critical weight inhibited peak levels of JHE, but did not delay entry into the wandering stage when larvae leave the plant in search of a pupation site. This suggests that peak levels of JHE may not be essential for the normal timing of metamorphosis. Starved larvae pupated normally, indicating the peak of JHE was not necessary for a morphologically normal pupation. Treatments of larvae with the selective JHE inhibitor O-ethyl-S-phenyl phosphoramidothiolate (EPPAT) that began immediately after larvae achieved the critical weight (6.0 to 6.5 grams for our strain of Manduca) delayed entry into the wandering stage. By contrast, EPPAT treatment of larvae at weights above 8.0 g had no effect on the subsequent timing of the onset of wandering. Therefore, although the normal timing of the onset of wandering does not require peak levels of JHE, it requires low to moderate levels of JHE to be present until larvae reach a weight of about 8.0 g.

Effects of jinlu, an anti-juvenile hormone on the growth, ultra-structure of the corpora allata and prothoracic gland of silkworm,Bombyx mori L

The 4th instar larvae of the silkworm,Bombyx mori L, when treated with anti-juvenile hormone (Jinlu) had its larval period extended by 2 days and the total larval period shortened by about 4 days. The conversion ratio of tetramolters into trimolters was 100%. But anti-juvenile hormone administration to the 5th instar larvae lengthened the silkworm age by one day. When anti-juvenile hormone was administered, we could find many neurosecretory granules of the brain transferred to the cells of the corpora allata, but there was little endoplasmic reticulum. In the prothoracic gland, the micropile edge was clear and there were large nucleoli, mitochondria and endoplasmic reticulum. This study was carried out to show that anti-JH compound inhibits the secretion of Juvenile hormone in silkwormBombyx mori L. The investigation revealed that the antijuvenile hormone inhibited the secretion of corpora allata and initiated the activity of the prothoracic gland.

Single K+ channels in endocrine cells dispersed from the cricket (Gryllus bimaculatus) corpora allata.

Single channel currents were recorded from cell-attached patches of endocrine cells of the adult male cricket corpora allata. Three distinct types of K+ channels were identified; a weak inward rectifier (Type 1), a strong inward rectifier (Type 2) and a weak outward rectifier (Type 3). The type 1 channel had a slope conductance of 191 +/- 9 pS (n = 4) at negative membrane potentials (Vm) and 101 +/- 6 pS (n = 6) at positive Vm. In addition, the channel showed fast open-closed kinetics at negative Vm and slow open-closed kinetics at positive Vm. The open probability (Po) of this channel was strongly voltage-dependent at positive Vm, but less voltage-dependent at negative Vm. The reversal potential was not modified significantly by the substitution of gluconate for external Cl- but was modified after N-methyl-D-glucamine (NMDG+) was substituted for external K+, according to the Nernst equation for a K+-selective channel. The type 2 channel had a slope conductance of 44 +/- 2 pS (n = 5) at negative Vm, but no detectable outward current was observed at positive Vm. This channel showed very slow open-closed kinetics at negative Vm and its Po was not voltage-dependent. The type 3 channel had a limit conductance of 55 +/- 12 pS (n = 3) at negative Vm and 88 +/- 10 pS (n = 3) at positive Vm. This channel showed slow open-closed kinetics at negative Vm and fast open-closed kinetics at positive Vm. The Po for the channel was voltage-dependent at positive Vm but was voltage-independent at negative Vm. These three types of K+ channels may be important for the control of the resting membrane potential, and may thus participate in the regulation of Ca2+ influx and juvenile hormone secretion in corpora allata cells.