Juvenile Hormone Binding Protein Titers During Adult Metamorphosis in Manduca sexta

ABSTRACT ABSTRACT During the pupal and adult stages, the JHBP levels displayed a sex-related difference, with females showing higher levels than males. A sharp increase in JHBP levels was observed at day 2 of the pupal stage. After day 2 the JHBP titer declined precipitously, and then remained unchanged until day 12 in males. JHBP titers in females decreased slightly after day 2 and then remained relatively constant until day 12. In both sexes, the JHBP levels showed a steep increase and peaked around day 15. During the previtellogenic period, the JHBP titers declined dramatically until adult ecdysis. During early adult stage, JHBP titiers in the female remained constant at preecdysis level. This information could broaden our understanding of pest physiology during adult metamorphosis, and could have extensive implications for developing insect growth regulators to control agricultural pests.     

Ecdysteroids influence the circadian system timing ecdysis in the insectRhodnius prolixus (Hemiptera)

Summary 20-hydroxyecdysone (20HE) injections induced transient delays in the time of ecdysis inRhodnius prolixus reared in L/D cycles. Sustained phase delays in the ecdysis rhythm were revealed by transfer to constant dark during the scotophase following 20HE injection. The magnitude of the phase delays depended on the time in the L/D cycle at which 20HE was injected with major delays occurring at times when the endogenous titre is declining. Therefore the increases and decreases in the endogenous titre which are themselves timed in a circadian fashion may be involved in phase setting the ecdysis rhythm to the environmental cycle. Populations maintained in LL which are arrhythmic with respect to both ecdysteroid titres and ecdysis, can be induced to display gated ecdysis by injection of either 20HE or antiserum to ecdysteroids. Multiple injections of 20HE or antiserum are capable of inducing an ecdysis rhythm whose period (22.3 h) and gate location are very similar to that produced by altering the environmental cycle. Therefore manipulations of the endogenous titre of ecdysteroids can mimic the effects of L/D cycles on the timing of ecdysis. Ecdysis inRhodnius may therefore be timed at least partially as a result of circadian timing of the ecdysteroid titre.Abbreviations AZT Arbitrary Zeitgeber Time - DD constant darkness - LL constant light - L/D 24 h light dark cycle - 12L/12D 12 h of light 12 h of dark - 20HE 20-hydroxyecdysone     

The ecdysteroid titres during the last-larval instar of Ephestia kuehniella Z. (Lepidoptera: Pyralidae)

The ecdysteroid titre and the body weight during the last-larval instar of Ephestia kuehniella were determined. Slightly elevated ecdysteroid titres occur during the first 12 h following the last larval-larval ecdysis (38 ng/g) and again some 120 h later, lasting about 48 h (33 ng/g). A high ecdysteroid peak (750 ng/g) with a maximum in prepupae of the eye-class A4 precedes the larval-pupal ecdysis. The basal levels between these increased ecdysteroid titres are between 13 ng/g and 15 ng/g. Compared with the body weight, the first sligtly increased ecdysteroid titre 12 h after ecdysis is associated with the beginning of food intake, the second increase at 144 h after ecdysis with reduced gain in body weight. The prepupal ecdysteroid peak occurs whilst the body weight remains constant. Correlations between the varying ecdysteroid titre and morphological and physiological events accompanying the progress in larval-pupal development are discussed.     

土耳其斯坦叶螨的发育起点温度与有效积温

本文研究了土耳其斯坦叶螨 Tetranychus turkestani(Ugrou & Nikolski)在实验条件下的发育起点温度和有效积温。结果表明土耳其斯坦叶螨全世代发育起点温度和有效积温分别为雌螨10 .74 73℃和 16 4 .0 1日度 ,雄螨为 11.56 0 3℃和 113.2 9日度。在 15,2 0 ,2 5,30℃的恒温条件下 ,雌螨 1代平均历期分别为 35.15,19.0 5,11.0 4和 8.6 8天。     

Embryonic development of adriatic sturgeon,Acipenser naccarii (Bonaparte 1836), in farming conditions: a guide

The sequence and timing of the embryonic development of Adriatic sturgeon (Acipenser naccarii) are described at a constant temperature (17 ± 1 °C), from fertilisation to hatch in a hatchery. Fertilised eggs, obtained from one female and two males, were held in a flow‐through system. On the first day, embryos were sampled every 20 min during the first 12 h, and every 40 min in the following 12 h. Embryos were sampled hourly on the second day. On the third and fourth days, embryos were sampled every 2 h, and every 3 h on the fifth and sixth days. The first cleavage furrow appeared at 1 h 40 min postfertilisation. Blastulation concluded at 12 HPF (hours postfertilisation), when the dorsal blastopore lip formed. The completion of gastrulation was at 18 HPF, closing of the neural tube at 23 HPF and formation of the s‐shape heart at 31 HPF. The mass hatch occurred at 120 HPF. A. naccarii is a relatively common sturgeon species in aquaculture and possesses similar developmental patterns to those of other sturgeons; hence, we can use this species as a model for further studies about sturgeon species which are more difficult to breed artificially. Information about the embryonic development of the Adriatic sturgeon could assist restocking programmes.     

Climate Change and Spatiotemporal Distributions of Vector-Borne Diseases in Nepal – A Systematic Synthesis of Literature

Background

Despite its largely mountainous terrain for which this Himalayan country is a popular tourist destination, Nepal is now endemic for five major vector-borne diseases (VBDs), namely malaria, lymphatic filariasis, Japanese encephalitis, visceral leishmaniasis and dengue fever. There is increasing evidence about the impacts of climate change on VBDs especially in tropical highlands and temperate regions. Our aim is to explore whether the observed spatiotemporal distributions of VBDs in Nepal can be related to climate change.

Methodology

A systematic literature search was performed and summarized information on climate change and the spatiotemporal distribution of VBDs in Nepal from the published literature until December2014 following providing items for systematic review and meta-analysis (PRISMA) guidelines.

Principal Findings

We found 12 studies that analysed the trend of climatic data and are relevant for the study of VBDs, 38 studies that dealt with the spatial and temporal distribution of disease vectors and disease transmission. Among 38 studies, only eight studies assessed the association of VBDs with climatic variables. Our review highlights a pronounced warming in the mountains and an expansion of autochthonous cases of VBDs to non-endemic areas including mountain regions (i.e., at least 2,000 m above sea level). Furthermore, significant relationships between climatic variables and VBDs and their vectors are found in short-term studies.

Conclusion

Taking into account the weak health care systems and difficult geographic terrain of Nepal, increasing trade and movements of people, a lack of vector control interventions, observed relationships between climatic variables and VBDs and their vectors and the establishment of relevant disease vectors already at least 2,000 m above sea level, we conclude that climate change can intensify the risk of VBD epidemics in the mountain regions of Nepal if other non-climatic drivers of VBDs remain constant.     

Sequential sampling protocols for Spodoptera frugiperda (Lepidoptera: Noctuidae), on Zea mays fields: influence of sampling unit size

Spodoptera frugiperda (J.E. Smith) is a major pest in maize fields in Argentina. However, a sampling method that accounts for spatial pattern and allows reliable pest density estimations is still lacking. This paper addresses the issue of how sampling unit size can influence the characterization of S. frugiperda spatial pattern and the performance of sampling plans. An intensive sampling programme for S. frugiperda larvae was carried out in maize fields from October until March in four growing seasons. On each sampling date, 12 to 20 sampling units were taken at random. Each unit consisted of 1, 2, 4, 6, 8, 10 or 12 consecutive plants along a row. The linearized version of the Taylor's power law (TPL) was fitted to mean and variance estimated for each sampling date and data set through least squares regression. In general, b values from TPL were significantly >1 (P<0.05), indicating an aggregated sampling distribution. Regression slopes (b) ranged from 1.28 to 1.48 in small larvae and from 1.06 to 1.24 in large larvae, indicating stronger clumping in the former. TPL parameters were used to develop constant precision sampling plans. The efficiency of these plans in terms of expected total cost (searching and handling sampling units) was very sensitive to the size of the sampling units with small larvae but not with large larvae. The influence of sampling unit size and spatial pattern on TPL parameters and sampling costs is discussed.     

A post-ecdysial plasticization of the abdominal cuticle in Rhodnius

The ecdysis and emergence of fifth instar larvae of Rhodnius prolixus have been closely observed. At the time of ecdysis the cuticle of the head, legs, and wingpads is soft and readily deformed. it does not become sufficiently rigid for normal use until about 90 min later. The cuticle of the abdomen is however hard and inextensible at the time of ecdysis. From about 60 min onward this cuticle undergoes a plasticization; it is maximally extensible at about 180 min, thereafter becoming inextensible again. Unlike the plasticization of the abdominal cuticle which occurs after feeding, this post-ecdysial plasticization is not under direct nervous control. Although it seems that there is some temporal link with the darkening of the cuticle, it is considered unlikely that plasticization is a direct consequence of the tanning process. The significance of this post-ecdysial plasticization is not obvious.     

Spatial distribution of growth rates and of epidermal cell lengths in the elongation zone during leaf development in Lolium perenne L.

Relative elemental growth rates (REGR) and lengths of epidermal cells along the elongation zone of Lolium perenne L. leaves were determined at four developmental stages ranging from shortly after emergence of the leaf tip to shortly before cessation of leaf growth. Plants were grown at constant light and temperature. At all developmental stages the length of epidermal cells in the elongation zone of both the blade and sheath increased from 12 m at the leaf base to about 550 m at the distal end of the elongation zone, whereas the length of epidermal cells within the joint region only increased from 12 to 40 m. Throughout the developmental stages elongation was confined to the basal 20 to 30 mm of the leaf with maximum REGR occurring near the center of the elongation zone. Leaf elongation rate (LER) and the spatial distributions of REGR and epidermal cell lengths were steady to a first approximation between emergence of the leaf tip and transition from blade to sheath growth. Elongation of epidermal cells in the sheath started immediately after the onset of elongation of the most proximal blade epidermal cells. During transition from blade to sheath growth the length of the blade and sheath portion of the elongation zone decreased and increased, respectively, with the total length of the elongation zone and the spatial distribution of REGR staying near constant, with exception of the joint region which elongated little during displacement through the elongation zone. Leaf elongation rate decreased rapidly during the phase when only the sheath was growing. This was associated with decreasing REGR and only a small decrease in the length of the elongation zone. Data on the spatial distributions of growth rates and of epidermal cell lengths during blade elongation were used to derive the temporal pattern of epidermal cell elongation. These data demonstrate that the elongation rate of an epidermal cell increased for days and that cessation of epidermal cell elongation was an abrupt event with cell elongation rate declining from maximum to zero within less than 10 h.Abbreviations LER leaf elongation rate - REGR relative elemental growth rates     

Assessment of appropriate species-specific time intervals to integrate GPS telemetry data in ecological niche models

Ecological niche models use presence-only data, which is often affected by lack of true absences leading to sampling bias. Over the last decade, there has been an uptick in the integration of occurrence data from global positioning systems telemetry data in ecological niche models and/or species distribution models. These data types can be affected by serial autocorrelation at high relocation frequencies yet have been used in ecological niche models using geographic filters and subsampling techniques. Yet, no study to date has attempted to discern a method to identify the appropriate time interval for a particular species if integrating GPS telemetry occurrence data in a MaxEnt framework. We demonstrate a rigorous spatial technique using a robust contemporary dataset from ocelots (Leopardus pardalis) to assess the appropriate time intervals to use in a species-specific ecological niche model. We assessed a range of daily time intervals (every 0.5, 1–4, 6, 8, and 12 h) commonly used in teresstrial mammalian carnivore studies. We observed the predictive performance of shorter time intervals every 2 h was comparable to much longer intervals every 12 h. These shorter intervals under/overestimated the least amount of data compared to 12 h. This study demonstrates that by accounting for serial autocorrelation and conducting rigorous spatial analyses, scientists can identify the appropriate time interval to integrate GPS telemetry data use in ecological niche models in MaxEnt. These results can also be transferable across highly mobile terrestrial taxa at different spatial scales, which can help inform species management or conservation strategies.     

Circadian regulation of the lark RNA-binding protein within identifiable neurosecretory cells

Molecular genetic analysis indicates that rhythmic changes in the abundance of the Drosophila lark RNA-binding protein are important for circadian regulation of adult eclosion (the emergence or ecdysis of the adult from the pupal case). To define the tissues and cell types that might be important for lark function, we have characterized the spatial and developmental patterns of lark protein expression. Using immunocytochemical or protein blotting methods, lark can be detected in late embryos and throughout postembryonic development, from the third instar larval stage to adulthood. At the late pupal (pharate adult) stage, lark protein has a broad pattern of tissue expression, which includes two groups of crustacean cardioactive peptide (CCAP)-containing neurons within the ventral nervous system. In other insects, the homologous neurons have been implicated in the physiological regulation of ecdysis. Whereas lark has a nuclear distribution in most cell types, it is present in the cytoplasm of the CCAP neurons and certain other cells, which suggests that the protein might execute two different RNA-binding functions. Lark protein exhibits significant circadian changes in abundance in at least one group of CCAP neurons, with abundance being lowest during the night, several hours prior to the time of adult ecdysis. Such a temporal profile is consistent with genetic evidence indicating that the protein serves a repressor function in mediating the clock regulation of adult ecdysis. In contrast, we did not observe circadian changes in CCAP neuropeptide abundance in late pupae, although CCAP amounts were decreased in newly-emerged adults, presumably because the peptide is released at the time of ecdysis. Given the cytoplasmic localization of the lark RNA-binding protein within CCAP neurons, and the known role of CCAP in the control of ecdysis, we suggest that changes in lark abundance may regulate the translation of a factor important for CCAP release or CCAP cell excitability.     

桑尺蠖的发育起点温度和有效积温

在室内恒温条件下测定了桑尺蠖的发育历期。对试验结果采用 2种方法计算 ,并用变异系数来检验。结果表明 ,对于早春出蛰后的越冬幼虫和非越冬代 ,用直接最优化法计算所得的结果更接近实际 ;越冬幼虫的发育起点温度 (C)为 (3.4± 0 .7)℃ ,有效积温 (K )为 4 97.5日度 ;非越冬代幼虫和全世代发育起点温度 (C)分别为 (4 .2± 1.4 )℃和 (6 .0± 1.3)℃ ,相应的有效积温 (K)分别为 50 5.8日度和 781.7日度。     

Characterization of thymosin alpha 1 and beta 4 during the bovine estrual period: effects of elevated estradiol and progestin

At present, there is a renewed interest in thymic function and its secretions in relation to endocrine control and reproductive function. In an initial experiment, 60 crossbred heifers (18-20 mo) were detected in estrus and assigned to control or FSH superovulatory groups. On Days 7-14 of the subsequent estrous cycle, FSH was administered for 5 days and prostaglandin F2 alpha (PGF2 alpha) was administered at 48 and 60 h after the initial FSH injection. Control animals received only PGF2 alpha injections between Days 9 and 15 of the cycle. Blood samples were collected from all animals at the time of PGF2 alpha injection and every 12 h thereafter to 72 h post PGF2 alpha injection. In a subsequent experiment, 103 crossbred heifers (16-18 mo) were superovulated with FSH and synchronized to estrus with PGF2 alpha administered 60 h after the initial FSH injection. Twenty-eight of the heifers received Norgestomet implants 12 h prior to the initial PGF2 alpha injection to inhibit the LH surge. Blood samples were collected from animals at 12-h intervals until the PGF2 alpha injection and every 6 h thereafter until 108 h post PGF2 alpha treatment. Although thymosin beta 4 concentrations did change over the estrual period, no differences were noted between control and superovulatory animals in the initial experiment even though estradiol concentrations were increased tenfold from the FSH stimulated ovary. In the second experiment, thymosin beta 4 and alpha 1 increased as the estrual period progressed and decreased (p less than 0.05) subsequent to the LH surge. (ABSTRACT TRUNCATED AT 250 WORDS)     

Mechanisms of midgut remodeling: juvenile hormone analog methoprene blocks midgut metamorphosis by modulating ecdysone action

In holometabolous insects such as mosquito, Aedes aegypti, midgut undergoes remodeling during metamorphosis. Insect metamorphosis is regulated by several hormones including juvenile hormone (JH) and 20-hydroxyecdysone (20E). The cellular and molecular events that occur during midgut remodeling were investigated by studying nuclear stained whole mounts and cross-sections of midguts and by monitoring the mRNA levels of genes involved in 20E action in methoprene-treated and untreated Ae. aegypti. We used JH analog, methoprene, to mimic JH action. In Ae. aegypti larvae, the programmed cell death (PCD) of larval midgut cells and the proliferation and differentiation of imaginal cells were initiated at about 36h after ecdysis to the 4th instar larval stage (AEFL) and were completed by 12h after ecdysis to the pupal stage (AEPS). In methoprene-treated larvae, the proliferation and differentiation of imaginal cells was initiated at 36h AEFL, but the PCD was initiated only after ecdysis to the pupal stage. However, the terminal events that occur for completion of PCD during pupal stage were blocked. As a result, the pupae developed from methoprene-treated larvae contained two midgut epithelial layers until they died during the pupal stage. Quantitative PCR analyses showed that methoprene affected midgut remodeling by modulating the expression of ecdysone receptor B, ultraspiracle A, broad complex, E93, ftz-f1, dronc and drice, the genes that are shown to play key roles in 20E action and PCD. Thus, JH analog, methoprene acts on Ae. aegypti by interfering with the expression of genes involved in 20E action resulting in a block in midgut remodeling and death during pupal stage.     

Organochlorine residue concentrations and burdens in grey seal (Halichoerus grypus) blubber during the first year of life

Between 1988 and 1991 grey seal ( Halichoerus grypus ) pups at various developmental stages were sampled at Sable Is., NS, and blubber samples were analysed for lipid content and organochlorine (OC) residue concentrations. Blubber lipid content increased significantly between birth and 12 d, and then stayed relatively constant. Blubber OC residue concentrations were fairly constant during the first 12–16 d of life. From weaning (approx. 16 d) until four months, the pups are learning to feed but are relying on blubber fat reserves; thus, during this period blubber weight declined to minimum levels, and OC residue concentrations in blubber lipid increased significantly. Blubber lipid OC concentrations then declined slightly as the pups gained weight, until at the end of one year they were about twice those immediately post-weaning. Blubber lipid residue burdens calculated from these data showed that at weaning, about 98% of the seal's residues were accumulated from maternal milk. After weaning, there were no significant changes in the burdens of any residue until the end of the first year of the pup's life, and the organochlorine concentration changes reflected a fairly constant organochlorine burden around which lipid contents varied. These data suggest that the capacity of the seal to degrade the residue inherited from its mother is very limited. Furthermore, the absence of any significant accumulation of organochlorines during the second six months of the seal's life suggests that the juvenile seal must feed at a low trophic level which is not highly contaminated with organochlorines.     

The role of eclosion hormone in the larval ecdyses of Manduca sexta

Each larval moult in Manduca sexta consists of an identical series of developmental and behavioural events leading up to ecdysis. Injections of eclosion hormone into staged larvae in any instar resulted in the premature elicitation of the larval pre-ecdysis behaviour, comprising a rhythmic sequence of muscle contractions, followed by the larval ecdysis behaviour.A marked depletion of eclosion hormone stores form the ventral chain of ganglia coincided with each larval ecdysis and in the moult to the fifth instar, eclosion hormone activity appeared in the blood at the onset of the pre-ecdysis behaviour.Responsiveness to eclosion hormone for pre-ecdysis and ecdysis behaviour developed about 12 and 6 hr before normal ecdysis, respectively. Elicitation of ecdysis behaviour by exogenous hormone inhibited both subsequent behavioural responses to eclosion hormone and endogenous hormonal release.In conclusion, the behavioural programme involved in each larval ecdysis appears to be controlled by the eclosion hormone.     

Circadian regulation of the lark RNA‐binding protein within identifiable neurosecretory cells

Molecular genetic analysis indicates that rhythmic changes in the abundance of the Drosophila lark RNA‐binding protein are important for circadian regulation of adult eclosion (the emergence or ecdysis of the adult from the pupal case). To define the tissues and cell types that might be important for lark function, we have characterized the spatial and developmental patterns of lark protein expression. Using immunocytochemical or protein blotting methods, lark can be detected in late embryos and throughout postembryonic development, from the third instar larval stage to adulthood. At the late pupal (pharate adult) stage, lark protein has a broad pattern of tissue expression, which includes two groups of crustacean cardioactive peptide (CCAP)‐containing neurons within the ventral nervous system. In other insects, the homologous neurons have been implicated in the physiological regulation of ecdysis. Whereas lark has a nuclear distribution in most cell types, it is present in the cytoplasm of the CCAP neurons and certain other cells, which suggests that the protein might execute two different RNA‐binding functions. Lark protein exhibits significant circadian changes in abundance in at least one group of CCAP neurons, with abundance being lowest during the night, several hours prior to the time of adult ecdysis. Such a temporal profile is consistent with genetic evidence indicating that the protein serves a repressor function in mediating the clock regulation of adult ecdysis. In contrast, we did not observe circadian changes in CCAP neuropeptide abundance in late pupae, although CCAP amounts were decreased in newly‐emerged adults, presumably because the peptide is released at the time of ecdysis. Given the cytoplasmic localization of the lark RNA‐binding protein within CCAP neurons, and the known role of CCAP in the control of ecdysis, we suggest that changes in lark abundance may regulate the translation of a factor important for CCAP release or CCAP cell excitability. © 2000 John Wiley & Sons, Inc. J Neurobiol 45: 14–29, 2000     

Acute reduction in serum progesterone concentrations after feed intake in dairy cows

This study tested the hypothesis that high feed consumption will acutely decrease circulating progesterone concentrations. In the first experiment, a Latin Square design was used to test whether feeding pattern would alter circulating progesterone in pregnant lactating Holstein cows (n = 12). Feed was removed for 12h before the experiment and cows were then either fed 100% of the total mixed ration (TMR), 50% of TMR every 12h, 25% of TMR every 6h, or left unfed for an additional 12h. Blood samples were taken every hour for 24h. Provision of 100 or 50% of TMR decreased circulating progesterone by 1h after feeding and progesterone remained depressed until 8-9h after feeding. Feeding 25% of TMR did not reduce circulating progesterone concentrations. Experiment 2 used a crossover design to measure the effect of acute feeding on circulating progesterone and LH concentrations during delivery of a constant amount of exogenous progesterone (Eazi-Breed CIDRs) in lactating Holstein cows (n = 8) and nonpregnant dry Holstein cows (n = 6). Blood samples were taken every 15min for 8h. There was no change in serum progesterone during the 8h treatment period in unfed cows; however, feeding decreased (P<0.05) circulating progesterone between 2 and 6h after feeding. In lactating cows, feeding increased mean LH (P<0.05). There were more LH pulses (P = 0.01) in lactating than nonlactating cows. Thus, acute feeding reduced circulating progesterone in pregnant lactating cows apparently due to an increase in progesterone metabolism. Interestingly, feeding multiple smaller meals eliminated the acute effect of feeding on circulating progesterone.     

The studies of temporal and spatial characteristics of somitogenesis in fish embryos

New data were obtained corroborating that somitogenesis is a rhythmic process, in which the time of somite formation is strictly constant. This constant (tau s) can be considered as a natural unit of developmental "biological clock" characterizing rhythmic processes. The constant tau s can be determined with an exceptional accuracy that has no analogs among the known biological processes. This fact alone suggests that the accuracy of developmental clock is very high. In addition to the constancy of tau s, all forming somites have equal linear size along the notochord axis. In the process with strictly constant temporal and spatial factors, time plays the leading role in triggering the formation of new somite. This became clear in studies of twin embryos. Both embryos had the same number of somites but they were shorter than in the normal embryos. Also, we measured the length of head and both segmented and unsegmented caudal parts of the trunk. Combined with the published data on somitogenesis, our results suggest that the previously proposed scheme for the role of developmental clock in embryogenesis predicts: (1) a possible loss of some embryonic stages without serious consequences for subsequent development and (2) periodic switching on/off any embryonic processes (at the molecular, cellular, or supercellular level) with intervals multiple to tau s.