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PubMedDate not supplied

Long-term effects of Bacillus thuringiensis subsp. israelensis on Aedes aegypti.

Immediate (24 hours exposure) and long-term (until the emergence of the adults) effects of different doses of a primary powder of Bacillus thuringiensis subsp. israelensis (B.t.i.) against first and second instar Aedes aegypti larvae were monitored. The long-term effect was dose-dependent and was materialized by a prolongation of the preimaginal development and continuous cumulative mortality until the emergence of the adults. Mortality values were higher during the fourth larval instar and the pupal stage. Some of the larvae reaching the fourth instar were smaller in size and remained in this state a 2-4 times longer period than in the control and finally died as larvae or very small pupae. The long-term effect was more intense as the treatment was applied earlier during the larval development. The correlation of the immediate lethal effect with the late effect allows the evaluation of the total impact of a larvicidal treatment.

Aedes↗
PubMed1993

Salmonid pituitary gonadotrophs. III. Chronological appearance of GTH I and other adenohypophysial hormones in the pituitary of the developing rainbow trout (Oncorhynchus mykiss irideus).

The first appearance of adenohypophysial cells in the developing rainbow trout embryo was studied by immunocytochemistry. Antibodies generated against the beta subunits of coho salmon gonadotropins (GTH I and GTH II), the beta subunit of human thyroid stimulating hormone (TSH), chum salmon prolactin (PRL), chum salmon growth hormone (GH), and synthetic alpha-MSH were used as immunocytochemical probes. The pituitary anlage was first recognized at developmental stage 21 (18 days postfertilization). At this stage, immunoreactive (ir) PRL and alpha-MSH cells were identified in the rostral and caudal regions of the pituitary, respectively. Cells containing ir-GH and ir-adrenocorticotropin (ACTH) appeared at stage 28 (35 days postfertilization). At the last stage before hatching (stage 29, 42 days postfertilization) ir-TSH cells were identified. Ir-GTH I cells were first observed in the pituitary at stage 32 (15 days after hatching), when mitosis of gonadal germ cells also was observed. At stage 35 (35 days after hatching), meiotic figures were first observed in a few germ cells of some fish indicating that gonadal sex differentiation probably begins at about this time. Cells containing ir-GTH II were not apparent in the pituitary at any stage of embryonic or larval development (up to stage 35) and were not present in pituitaries of trout at 6 months of age when the ovaries were in the perinucleolus stage and when only spermatogonia, but no spermatocytes were present in the testis. These observations suggest that GTH I, but not GTH II, may regulate initial gonadal growth and development in the embryonic and larval rainbow trout.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenocorticotropic Hormone↗
PubMed1993

Morphogenetic differentiation of the brain of the cichlid fish, Oreochromis mossambicus.

In the present study, the morphogenetic brain differentiation of the cichlid fish, Oreochromis mossambicus, is described using conventional histological methods. Cross sections through the developing brain of fish larvae aged 2, 8, 10, 12 and 20 days post hatch, and of adults, were investigated in order to characterize individual brain regions and nuclei, especially parts of the diencephalon, brainstem and cerebellum during critical phases of early larval development. The above age stages conform to the following developmental (larval) stages: 2 days = stage 7, 8 days = stage 10, 10 days = stage 11, 12 days = stage 12 and 20 days = stage 15. An increasing number of nuclei and a volumetric increase in size of individual brain parts in older fish larvae and in adult fish were registered. In the optic tectum, an extreme lateral extension was found in contrast to an insignificant increase in stratification at this developmental time. In one part of the brainstem, the Area octavolateralis (AOL) of 2-day-old larvae, only a few undifferentiated perikarya were found and in the AOL of 20-day-old animals up to 5 nuclei, versus 7 AOL-nuclei in adult fish brain, could be discriminated. Variations in the position of the Mauthner cell versus the surrounding and corresponding brain nuclei were shown during the ontogenetic development. The results were presented by cartoon portrayals of the relationships between characteristic nuclei and by drawings of specific brain cross sections in different aged larval stages.

Aging↗
PubMed1986

The action of acetylcholine upon heart rate changes markedly with development in bullfrogs.

Dose-response curves for the action of acetylcholine (ACh) and its antagonist, atropine, upon heart rate in situ were made for three larval stages and adults of the bullfrog, Rana catesbeiana. The absolute magnitude of heart rate inhibition at any ACh concentration progressively increased throughout larval development. Unexpectedly, metamorphosis to the adult resulted in a sharp decrease in cholinergic cardiac sensitivity down to levels similar to the earliest larvae. Thus, cholinergic sensitivity of heart rate, reflecting properties of the cardiac pacemaker, is greatest immediately before metamorphosis and lowest in early larvae and adults.

Acetylcholine↗
PubMed1993

Insect-resistant chrysanthemum calluses by introduction of a Bacillus thuringiensis crystal protein gene.

A 3'-end truncated crystal protein gene, derived from Bacillus thuringiensis (Bt) subsp. aizawai 7.21, encoding the toxic fragment of the insecticidal protein cryIA(b), was constructed. The gene was inserted into a transformation vector, also carrying the neomycin phosphotransferase II (nptII) gene and the beta-glucuronidase (gus) gene, and introduced in the oncogenic Agrobacterium tumefaciens strain A281, harbouring the Ti-plasmid pTiBO542. The recombinant Agrobacterium strain was used to transform leaf explants of chrysanthemum (Dendranthema grandiflora) cultivar Parliament. The resulting tumours were kanamycin-resistant, exhibited beta-glucuronidase activity and produced agropine and mannopine. In most tumours, all simultaneously transferred genes were expressed, owing to selection for the presence of both T-DNAs, but no correlation was found between the level of expression of the various genes. A bioassay was developed, in which larvae were fed with tumorous chrysanthemum tissue, in order to detect the effect of the transferred toxin gene on larval development. Using this bioassay with second instar larvae of Heliothis virescens (tobacco budworm), 17 tumour lines were tested. Several of these lines proved to be strongly inhibitory to larval growth. These results indicate that Bt-based insect resistance might be used as a tool in reducing the amount of pesticides used in chrysanthemum culture.

Agrobacterium tumefaciens↗
PubMed1992

The influence of weather and egg contamination on the development of third-stage larvae of Cooperia oncophora on pasture.

The influence of weather and egg contamination on the dynamics of herbage contamination with infective larave of Cooperia oncophora was investigated on artificially contaminated grass plots and in a grazing experiment with 24 first-year grazing calves from May to October 1987 in Lower Saxony, Germany. On the experimental plots the larval translation was highest at the beginning of July and in the second part of September, following high mean weekly temperatures. Between July and September peak recovery of larvae from herbage occurred 4 weeks after contamination. A seasonal pattern of larval translation similar to that on the experimental plots could be demonstrated on the grazed pastures when the number of larvae per m2 of pasture had been adjusted to the previous egg output by means of a contamination index. The resulting 'relative larval density' is regarded as a good indicator for larval development on pasture. From July to September the larval population on pasture resulted mainly from the egg contamination 2-3 weeks earlier. The short persistence of the infective larvae on herbage was probably due to the frequent and heavy rainfall throughout the season, causing a passive washout of larvae into the soil. On single pastures the larval density started to increase within 1 week after the calves had first contact with these fields. The impact of the calves on the distribution of larvae is discussed.

Animals↗
PubMed1999

Development of patent Ascaris suum infections in pigs following intravenous administration of larvae hatched in vitro.

The normal tissue migration of Ascaris suum in the pig host involves larval development in the liver accompanied by considerable pathological changes. The vast majority of larvae that reach the small intestine are later expelled by unknown mechanisms. We show that when migration through the liver is bypassed by inoculation of pigs with an intravenous dose of larvae hatched in vitro, the larvae not only complete migration and return to the small intestine, but they also seem to have a greater chance of survival to adulthood. This technique offers new possibilities for studies on specific lung involvement in protective immunity, provides valuable information for the understanding of self cure by larval expulsion, and adds to our understanding of the evolution of migration of Ascaris larvae in tissues.

Animals↗
PubMed2000

Regulation of cellular growth by the Drosophila target of rapamycin dTOR.

The TOR protein kinases (TOR1 and TOR2 in yeast; mTOR/FRAP/RAFT1 in mammals) promote cellular proliferation in response to nutrients and growth factors, but their role in development is poorly understood. Here, we show that the Drosophila TOR homolog dTOR is required cell autonomously for normal growth and proliferation during larval development, and for increases in cellular growth caused by activation of the phosphoinositide 3-kinase (PI3K) signaling pathway. As in mammalian cells, the kinase activity of dTOR is required for growth factor-dependent phosphorylation of p70 S6 kinase (p70(S6K)) in vitro, and we demonstrate that overexpression of p70(S6K) in vivo can rescue dTOR mutant animals to viability. Loss of dTOR also results in cellular phenotypes characteristic of amino acid deprivation, including reduced nucleolar size, lipid vesicle aggregation in the larval fat body, and a cell type-specific pattern of cell cycle arrest that can be bypassed by overexpression of the S-phase regulator cyclin E. Our results suggest that dTOR regulates growth during animal development by coupling growth factor signaling to nutrient availability.

Amino Acid Sequence↗
PubMed1999

Germ line development in fishes.

Classical work on germ cells in fishes has dealt with three main issues; their embryonic origin, the proliferation, and migration pathway during embryonic and larval development. Until recently, primordial germ cells (PGCs) have been studied in a number of fishes using morphological criteria only. The identification of the Drosophila vasa homolog gene of zebrafish now allows comparison of these morphological data with vasa RNA expression patterns in zebrafish. Teleost PGCs can be distinguished from somatic cells by their distinct morphology, at the earliest during gastrulation, and in most fishes their number varies between 10 and 30 during pregonial development. Mitosis is generally not observed in PGCs at extragonadal locations, whereas they are mitotically active once at the gonadal ridges. During gastrulation, PGCs appear to translocate from the epiblast to the hypoblast and during somitogenesis they are found associated with the most peripheral yolk syncitial layer (YSL). From the peripheral YSL they migrate through the median mesoderm into the dorsal mesoderm and then to the dorsal mesentery, where they establish the gonad primordia with mesenchymal cells. Vasa RNA positive cells, the PGCs of the zebrafish conform to these general observations. Interestingly, classical descriptive and experimental data can now be reevaluated using vasa as a molecular marker of the fish germ line. The power of zebrafish genetics together with possibilities of experimental embryology should accelerate research on aspects of vertebrate germ line development such as PGC migration, division and apoptosis, as well as (in) fertility. The present review summarizes some of the classical data on germ line development in fishes in relation to recent data on vasa expression in zebrafish and compares these findings, where appropriate, with those in other model organisms. Special emphasis is placed on vasa gene expression as a potential universal germ line marker and suggestions are made for novel, zebrafish specific approaches to investigate the vertebrate germ line.

Animals↗
PubMed1988

Functional redundancy in the tissue-specific enhancer of the Drosophila Sgs-4 gene.

During the last day of larval development, the Sgs-4 glue gene of Drosophila melanogaster is expressed at high levels in a single tissue, the larval salivary glands. As shown by transformation experiments and by DNA sequence analysis of Sgs-4 underproducing strains, an essential regulatory region for Sgs-4 expression lies between 149 and 568 bp upstream from the transcribed part of the gene. This region shows the positional independence of a transcriptional enhancer and directs at least three regulatory activities: tissue specificity, developmental timing and high-level expression. Here we use a transient transformation assay to identify three elements within this enhancer that are involved in tissue specificity. For at least this regulatory activity the enhancer is internally redundant. Any pairwise combination of the three elements is sufficient to direct salivary gland expression, although none of the three can act alone.

Animals↗
PubMed1998

Multiple roles of the eyes absent gene in Drosophila.

The eyes absent (eya) gene plays an essential role in the events that lead to formation of the Drosophila eye; without expression of eya in retinal progenitor cells, they undergo programmed cell death just prior to the morphogenetic furrow, leading to an eyeless or reduced eye phenotype. The eya gene has recently been found to be highly conserved to humans, defining a new gene family. Insights into the gene's function in the fly, therefore, are likely to be relevant to the role of its homologs in vertebrates. Detailed studies at the subcellular level indicate that the Eya protein is localized to the nucleoplasm, suggesting a role in control of nuclear events. The eya gene shows expression and roles in tissues other than the eye, including subsets of cells of the adult visual system, brain, and ovary, as well as an elaborate expression pattern in the embryo. Various mutations in the eya gene cause loss of ocelli, female sterility, or lethality. Analysis of the embryonic lethal phenotype indicates that mutant alleles show defects in head morphogenesis. These data indicate that eya has critical roles in morphogenesis of a number of tissues in the animal, in addition to its role in early eye formation. Despite multiple roles at multiple stages of development of the fly, both the type I and type II forms of the protein, when expressed ectopically during larval development, can direct eye formation.

Abnormalities, Multiple↗
PubMed2006

Postsynaptic mad signaling at the Drosophila neuromuscular junction.

BACKGROUND: Cell-to-cell communication at the synapse involves synaptic transmission as well as signaling mediated by growth factors, which provide developmental and plasticity cues. There is evidence that a retrograde, presynaptic transforming growth factor-beta (TGF-beta) signaling event regulates synapse development and function in Drosophila. RESULTS: Here we show that a postsynaptic TGF-beta signaling event occurs during larval development. The type I receptor Thick veins (Tkv) and the R-Smad transcription factor Mothers-against-dpp (Mad) are localized postsynaptically in the muscle. Furthermore, Mad phosphorylation occurs in regions facing the presynaptic active zones of neurotransmitter release within the postsynaptic subsynaptic reticulum (SSR). In order to monitor in real time the levels of TGF-beta signaling in the synapse during synaptic transmission, we have established a FRAP assay to measure Mad nuclear import/export in the muscle. We show that Mad nuclear trafficking depends on stimulation of the muscle. CONCLUSIONS: Our data suggest a mechanism linking synaptic transmission and postsynaptic TGF-beta signaling that may coordinate nerve-muscle development and function.

Active Transport, Cell Nucleus↗
PubMed2004

Developmentally regulated and non-sex-specific expression of autosomal dmrt genes in embryos of the Medaka fish (Oryzias latipes).

The dmrtgene family of vertebrates comprises several transcription factors that share a highly conserved DNA-binding domain, the DM domain. Like some of their invertebrate counterparts, e.g. Drosophila doublesex (dsx) and the Caenorhabditis elegans Mab3, several are implicated in sex determination and differentiation. Thus far, dmrt genes represent the only factors involved in sexual development that are conserved across phyla. In the teleost Medaka (Oryzias latipes), a duplicated copy of dmrt1, designated dmrt1bY or dmy, has recently been postulated to be the master regulator of male development in this species. Here, we have analyzed the expression of four additional Medaka dmrt genes during embryonic and larval development. In contrast to other vertebrates, the autosomally located dmrt1a gene of Medaka is not expressed at detectable levels during embryogenesis. On the other hand, dmrt2, dmrt3 and dmrt4 show highly restricted and non-overlapping expression patterns during embryogenesis. While dmrt2 is expressed in early somites, dmrt3 transcripts are found in dorsal interneurons and dmrt4 is expressed in the developing olfactory system. Other than in mouse, they do not show any sex specific expression and no transcription could be detected in the early developing gonads. However, all four analyzed dmrt genes share expression in the differentiating gonad of larvae and in adult testis.

Animals↗
PubMed1996

Fishing for genes controlling development.

In recent years, the zebrafish has become a popular system for studying vertebrate development. Large scale mutant searches have led to the identification of >400 genes with unique functions during embryonic and larval development. A number of these genes play important roles in well studied processes, such as dorsoventral patterning of the early embryo, notochord formation and signaling, somitogenesis and neural specification. Other newly identified genes offer opportunities to investigate less well understood processes, including locomotion behavior, organogenesis, neural crest development and axonal pathfinding.

Animals↗
PubMed1994

The role of the Distal-less gene in the development and evolution of insect limbs.

BACKGROUND: Arthropod diversity is apparent in the variations in limb number, type, and position along the body axis. Among the insects, for example, butterflies and moths (Lepidoptera) develop larval abdominal and caudal appendages ('prolegs'), whereas flies (Diptera) do not. Comparative studies of the expression and regulation during development of limb-patterning genes, such as Distal-less (Dll), may provide insights into arthropod evolution. RESULTS: We report the cloning of a Dll homolog from the butterfly Precis coenia, and present data showing that it is expressed in all developing limbs (except the mandible), including the prolegs; the relationship between Dll and wingless expression observed in Drosophila is conserved in Precis among all limbs. However, Dll is deployed in distinct spatial and temporal patterns within each limb type. CONCLUSIONS: These data suggest that Dll function, suppressed in the abdomen early in insect evolution, has been derepressed in Lepidoptera, and also suggest that there is a common mechanism underlying the formation of all insect appendages. The limb-type-specific patterns of Dll expression (and its exclusion from the mandible) indicate that regulation of Dll expression may be critical to limb morphology, and are inconsistent with Dll functioning in a simple distal-to-proximal concentration gradient.

Amino Acid Sequence↗
PubMed2004

Rapid herbivore-induced changes in mountain birch phenolics and nutritive compounds and their effects on performance of the major defoliator, Epirrita autumnata.

Insect damage changes plant physiology and chemistry, and such changes may influence the performance of herbivores. We introduced larvae of the autumnal moth (Epirrita autumnata Borkh.) on individual branches of its main host plant. mountain birch (Betula pubescens ssp. czerepanovii (Orlova) Hämet-Ahti) to examine rapid-induced plant responses, which may affect subsequent larval development. We measured systemic responses to herbivory by analyzing chemistry, photosynthesis, and leaf growth, as well as effects on larval growth and feeding, in undamaged branches of damaged and control trees. Larvae reared on leaves from intact branches of the herbivore-damaged trees grew faster than those reared on leaves of control trees, indicating systemic-induced susceptibility. Herbivore damage did not lead to systemic changes in levels of primary nutrients or phenolic compounds. The analyses of photosynthetic activity and individual hydrolyzable tannins revealed a reversal of leaf physiology-herbivore defense patterns. On control trees, consumption by E. autumnata larvae was positively correlated with photosynthetic activity: on damaged trees, this correlation was reversed, with consumption being negatively correlated with photosynthetic activity. A similar pattern was found in the relationship between monogalloylglucose, the most abundant hydrolyzable tannin of mountain birch, and leaf consumption. Among the control trees, consumption was positively correlated with concentrations of monogalloylglucose, whereas among herbivore-damaged trees, this correlation was reversed and became negative. Our results suggest that herbivore performance is related to both concentrations of phenolic compounds and photosynthetic activity in leaves. This linkage between herbivore performance, leaf chemistry, and physiology was sensitive to induced plant responses caused by slight herbivore damage.

Animals↗
PubMed2003

Covariation of larval gene expression and adult body size in natural populations of Drosophila melanogaster.

Understanding adaptive phenotypic variation is one of the most fundamental problems in evolutionary biology. Genes involved in adaptation are most likely those that affect traits most intimately connected to fitness: life-history traits. The genetics of quantitative trait variation (including life histories) is still poorly understood, but several studies suggest that (1) quantitative variation might be the result of variation in gene expression, rather than protein evolution, and (2) natural variation in gene expression underlies adaptation. The next step in studying the genetics of adaptive phenotypic variation is therefore an analysis of naturally occuring covariation of global gene expression and a life-history trait. Here, we report a microarray study addressing the covariation in larval gene expression and adult body weight, a life-history trait involved in adaptation. Natural populations of Drosophila melanogaster show adaptive geographic variation in adult body size, with larger animals at higher latitudes. Conditions during larval development also affect adult size with larger flies emerging at lower temperatures. We found statistically significant differences in normalized larval gene expression between geographic populations at one temperature (genetic variation) and within geographic populations between temperatures (developmental plasticity). Moreover, larval gene expression correlated highly with adult weight, explaining 81% of its natural variation. Of the genes that show a correlation of gene expression with adult weight, most are involved in cell growth or cell maintenance or are associated with growth pathways.

Animals↗
PubMed1979

Development of Onchocerca volvulus in Simulium ochraceum and Simulium metallicum.

The development of Onchocerca volvulus was compared in Simulium ochraceum and S. metallicum by maintaining infected flies under uniform conditions. Larval development in S. ochraceum was synchronous and orderly so that nearly all larvae reaching the thoracic muscles from a single blood meal matured to third-stage infective larvae within 192 hours. In contrast, development in S. metallicum was asynchronous, slower, and retarded. In this species many first-larvae were malformed and stunted after the 5th day of development; and microfilariae and first- and second-stage larvae were still present 8--10 days after a single infecting blood meal when third-stage larvae had developed. The development of O. volvulus in S. ochraceum is more compatible with the intense transmission associated with human disease.

Animals↗