Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Larval development”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 217 records · Page 12Linked to original sources
PubMed1995

Characterization and genetic analysis of Drosophila melanogaster photobehavior during larval development.

In Drosophila melanogaster, during the mid third instar of development larvae cease foraging and commence a period of increased locomotor activity referred to as wandering behavior. In this study, we quantified the wild type larval response to light during the foraging (first, second, and early third instars) and wandering (late third instar) stages of development. Foraging larvae in the first, second and early third instars exhibited a robust and marked aversion to light (negative phototaxis). From the mid larval third instar larvae showed a decrease in photonegative behavior, until just before pupation when the response of wandering larvae to light became random. The photobehavior of several strains known to affect the adult visual system were also studied. All but four exhibited normal phototaxis in the foraging and wandering stages. gl mutant larvae failed to respond to light during the foraging stage likely due to lack of larval photoreceptors. Larvae carrying three different mutations in the rhodopsin RH1 gene continued to express negative phototaxis throughout both the foraging and wandering stages. These results suggest that the transition from negative phototaxis toward photoneutral behavior characteristic of the wandering third instar larva requires vision.

Animals↗
PubMed1994

The Caenorhabditis elegans small GTP-binding protein RhoA is enriched in the nerve ring and sensory neurons during larval development.

p21 Ras has been implicated in vulval differentiation in Caenorhabditis elegans. We now describe the characteristics during nematode development of the related p21 RhoA which has been ascribed a morphological role in mammals. The CeRhoA cDNA isolated in this study encodes a sequence of 192 amino acids residues with 87.6% identity to human RhoA. Genomic Southern analysis indicates the presence of a single Rho gene in C. elegans. Its 2-kilobase mRNA is expressed at the highest levels during embryogenesis and decreases gradually thereafter. However, the level of the 24-kDa protein detected by the anti-CeRhoA antibody is high at the larval stages but low in embryos. The glutathione S-transferase/CeRhoA fusion protein expressed in Escherichia coli displays conserved biochemical activities. Unlike its counterpart in mammalian cells which is predominantly cytosolic, most of CeRhoA is associated with the membrane and the cytoskeleton throughout development. Indirect immunofluorescence analysis indicates an ubiquitous expression of CeRhoA throughout development with a particular enrichment at larval stages in the pharyngeal nerve ring and at the tip of the head containing chemosensory and mechanosensory neurons. This suggests a stage-specific role for p21 RhoA in mediating the signaling pathway underlying the sensory circuitry in C. elegans post-embryonic development.

Amino Acid Sequence↗
PubMed1990

Synthetic and naturally occurring retinoids inhibit third- to fourth-stage larval development by Onchocerca lienalis in vitro.

A series of synthetic retinoids was screened for the ability to inhibit the third-to fourth-stage larval molt by Onchocerca lienalis in vitro. Of the 14 retinoids tested, eight gave significant inhibition of the molt at a concentration of 30.6 microM or less. Probit analysis of dose-response data collected for these active compounds indicated values for ED50 in the range of 3.7-17.1 microM. In general, the most active of these N-substituted retinamides were those with small alkyl or monohydroxy alkyl substituents. The most active of these was all-trans-N-(2-hydroxyethyl)retinamide with an ED50 of 3.7 microM. Both the all-trans and 13-cis isomers of the alkyl substituted derivatives were active, the all-trans-N-hydroxyethyl derivative being approximately 5 times as active as the corresponding 13-cis isomer. The N-2,3 dihydroxypropyl derivative, two derivatives with aromatic side chains and three N-(retinoyl)amino acids were inactive by the criteria set in the initial screening. There was no strict correlation between growth regulating activity against O. lienalis and binding affinity for a retinol binding protein from Onchocerca gibsoni.

Animals↗
PubMed2002

Programmed cell death in the ascidian embryo: modulation by FoxA5 and Manx and roles in the evolution of larval development.

Programmed cell death (PCD) has been discounted in the ascidian embryo because the descendants of every embryonic cell appear to be present in the tadpole larva. Here we show that apoptotic PCD is initiated in the epidermis and central nervous system (CNS) but not in the endoderm, mesenchyme, muscle, and notochord cells during embryogenesis in molgulid ascidians. However, the affected cells do not actually die until the beginning of metamorphosis. Although specific patterns of PCD were different in distantly related ascidian species, the results suggest that removal of CNS cells by apoptosis is a urchordate feature predating the origin of the vertebrates. Certain molgulid ascidian species have evolved an anural (tailless) larva in which notochord cells fail to undergo the morphogenetic movements culminating in tail development. These anural species include Molgula occulta, the sister species of the urodele (tailed) species Molgula oculata. We show that PCD in the notochord cell lineage precedes the arrest of tail development in M. occulta and other independently evolved anural species. The notochord cells are rescued from PCD and a tail develops in hybrid embryos produced by fertilizing M. occulta eggs with M. oculata sperm, implying that apoptosis is controlled zygotically. Antisense inhibition experiments show that zygotic expression of the FoxA5 and Manx genes is required to prevent notochord PCD in urodele species and hybrids with restored tails. The results provide the first indication of PCD in the ascidian embryo and suggest that apoptosis modulated by FoxA5 and Manx is involved in notochord and tail regression during anural development. Differences in PCD that occur between ascidian species suggest that diversity in programming apoptosis may explain differences in larval form.

Animals↗
PubMed1988

Synthesis of two storage proteins during larval development of the tobacco hornworm, Manduca sexta.

Studies of synthesis and accumulation of the two storage proteins arylphorin and female-specific protein (FSP) during the final two larval instars of the tobacco hornworm showed both stage and temporal specificity. Arylphorin was present in both stages, but its synthesis ceased during the molt, during starvation, and at the wandering stage, and then resumed about 24 hr after the onset of feeding. During the larval molt about 25% of injected iodinated arylphorin was incorporated into the newly forming fifth instar cuticle. The cessation of arylphorin synthesis was mimicked by exposure of the fat body to 1 microgram/ml 20-hydroxyecdysone (20HE) in complete Grace's medium or to dilutions of Grace's medium greater than 50%. Lower concentrations of 20HE were ineffective, indicating that the cessation of synthesis in vivo was likely due to a combination of lack of excess nutrients and the hormonal milieu. The female-specific protein was not synthesized until the final larval instar, appearing first in females on Day 2 and later in males at the time of wandering, with synthesis continuing throughout the prepupal period. In vitro studies showed that this protein was synthesized as a 620-kDa protein, and then during secretion a 730-kDa immunoreactive form also appeared. Synthesis of FSP was inhibited by exposure of Day 2 fat body to 1 microgram/ml 20HE for 24 hr. Ligation followed by 20HE infusion showed that the disappearance of FSP from the hemolymph during the prepupal period was controlled by the rising ecdysteroid titer.

Adipose Tissue↗
PubMed1989

Precursor immigration and thymocyte succession during larval development and metamorphosis in Xenopus.

The developing thymus in Xenopus was examined at four different levels: 1) precursor immigration of cytogenetically distinct embryonic stem cells; 2) waves of colonization during tadpole life and metamorphosis; 3) inter-thymic exchange of cells between separate lobes; and 4) development of cortical and medullary thymocytes. Based on the flow cytometric analysis of cytogenetically distinct thymocytes, there were at least two periods of stem cell immigration into the thymus, one during early larval life and the second before or during metamorphosis. Within the thymus, cohorts of cells derived from the first wave of immigration expanded at different times. The initial expansion occurred before 35 days of development. Cells involved in the second period of expansion were also derived from the initial immigrants, expanded after 35 days, and resulted in a turnover of thymocytes during the larval period. Precursor cells entering the thymus during metamorphosis expanded and resulted in an additional replacement of thymocytes. Cortical and medullary thymocytes were isolated from animals that received embryonic stem cell grafts. No differences in the presence or absence, or in the percentages, of donor thymocytes in these different fractions were observed. When limiting numbers of stem cells were transplanted, several cases of asymmetrical thymic lobe colonization were observed. These data suggested that an inter-thymic exchange of cells did not occur during larval life.

Animals↗
PubMed1996

Control of C. elegans larval development by neuronal expression of a TGF-beta homolog.

The Caenorhabditis elegans dauer larva is specialized for dispersal without growth and is formed under conditions of overcrowding and limited food. The daf-7 gene, required for transducing environmental cues that support continuous development with plentiful food, encodes a transforming growth factor-beta (TGF-beta) superfamily member. A daf-7 reporter construct is expressed in the ASI chemosensory neurons. Dauer-inducing pheromone inhibits daf-7 expression and promotes dauer formation, whereas food reactivates daf-7 expression and promotes recovery from the dauer state. When the food/pheromone ratio is high, the level of daf-7 mRNA peaks during the L1 larval stage, when commitment to non-dauer development is made.

Amino Acid Sequence↗
PubMed1975

[Endocrine glands of Chironomus thummi Kief. during larval development and metamorphosis].

The general morphology of the complex of endocrine glands in Chironomus thummi is described (corpora allata, peritracheal glands, cardial bodies). Each of these glands is characterized during the 3rd, 4th larval instars and metamorphosis by specific developmental features. Enlargement of corpora allata is due, mainly, to more than 10-fold increase in cell number. The process of growth in the peritracheal gland is realized mainly at the expense of increase in cell size and formation of polytene nuclei; the latter is witnessed both by nuclear morphology and increase of DNA content per nucleus. It was shown by cytophotometric measurements that DNA content per nucleus in the peritracheal gland of a just moulted larva of the 4th instar amounts to 0.202 +/- 0.02 relative units, in prepupa to 2.98+/-0.01, whereas the corresponding values for nuclei of corpora allata equal 0.107+/-0.01 and 0.212+/-0.1. The number of cells and the morphology of nuclei suffer no significant changes in cardial bodies but 2 giant cells intimately connected with cardial bodies increase in volume from 18 to 200,000 mu3 and typical polytene chromosomes form in them.

Animals↗
PubMed2005

The membranous labyrinth during larval development in lamprey (Lampetra planeri, Bloch, 1784).

SEM and CLSM studies were performed on the membranous labyrinth of Lampetra planeri, a threatened species of brook lamprey, spanning from the 1st to the 4th year of ammocoetes larval stages and on the adults. In all the examined stages, the entire membranous labyrinth does not show any morphologic differences, but only a progressive increase in size. SEM and CLSM observations show that the ciliated chamber is lined with numerous unsensorial multiciliated cells. In the early stages, the ciliary bundles were approximately 15 microm long, while in the late stages they reached 30 microm. In the crista sensory area, we observed two populations of hair cells. "Type II" cells are peculiar for this species and show both long stereocilia decreasing in length and a long kinocilium (10-12 microm). Two other types of ciliary bundles have been found on the sensory hair cells of the Macula communis: the first one has both kinocilium and stereocilia about 4-5 microm long; the second shows a long kinocilium (7-10 microm in length) and short stereocilia bundles with a gradual increase in length. In the early stages of development, the three macular areas show few and sparsely distributed hair cells. In the late developmental stages, hair cells become more numerous and densely populated.

Analysis of Variance↗
PubMed1997

Specific cellular localization of tyrosinase mRNA during Ciona intestinalis larval development.

A Ciona intestinalis cDNA clone that encodes a protein highly homologous to other tyrosinases was isolated. Northern blot analysis showed that expression of Ciona tyrosinase starts at the early neurula stage and continues throughout the tail-bud and tadpole larval stages. The earliest tyrosinase expression was detected, by in situ hybridization, at the neural plate stage, in pigment precursor cells located along the two neural folds, in the animal region of the embryo. In the course of embryonic development the strong hybridization signal was always localized, within the rostral part of the developing brain, in the pigment precursor cells and was later detected in the otolith and ocellus. These results are discussed in relation to tyrosinase as an early marker of neural induction.

Amino Acid Sequence↗
PubMedDate not supplied

Ancient ontogenies: larval development of the Lower Cretaceous anuran Shomronella jordanica (Amphibia: Pipoidea).

The Lower Cretaceous anuran Shomronella jordanica (Pipoidea) is represented by an assemblage of nearly 300 tadpoles of different ages. The size of the assemblage allows a reconstruction of the larval ontogeny of this species. We describe the ossification sequence and growth rates of S. jordanica and present reconstructions of tadpoles at different stages. The ontogeny of the species seems to be similar to that of extant pipids in many aspects. Larvae are similar in shape and size to those of Xenopus laevis but lack the anterior barbels that are typical for all extant pipids. The ossification sequence is closer to that of pipids than to that of other anurans. We present evidence that suggests that this species was terrestrial as an adult, and we discuss the implications of these data for the evolution of anuran development.

Animals↗
PubMed2005

Temporal changes in DNA synthesis of prothoracic gland cells during larval development and their correlation with ecdysteroidogenic activity in the silkworm, Bombyx mori.

DNA synthesis in prothoracic gland cells of the silkworm, Bombyx mori, was studied immunocytochemically after in vivo labeling with 5-bromo-2'-deoxyuridine (BrdU), and its developmental changes during the 3rd, 4th, and last larval instars were examined. During the early stages of both the 3rd and 4th larval instars, a dramatic increase in the number of DNA-synthesizing cells of the prothoracic glands was detected. However, during the latter stages of each instar, the number of DNA-synthesizing cells greatly decreased. The determination of glandular protein content showed that dramatic increases occurred during the latter stages of each larval instar. Comparison of changes in prothoracic gland cell DNA synthesis with ecdysteroidogenic activity showed that the increase in DNA synthesis precedes ecdysteroidogenesis. The cellular mechanism underlying changes in prothoracic gland cell DNA synthesis during the last two larval instars was further analyzed by determining the in vitro DNA synthesis of the glands, their responsiveness to hemolymph growth factors, and changes in the growth-promoting activity of hemolymph during development. It was found that both growth factors and the responsiveness of the prothoracic gland cells to growth factors from hemolymph may play roles in regulating DNA synthesis of gland cells.

Animals↗
PubMed1990

Genes from two intermoult puffs in Drosophila virilis polytene chromosomes are differentially transcribed during larval development.

Genes from two Drosophila virilis intermoult puffs were isolated by microcloning. From puff 16A on the X-chromosome a 2.9 kb DNA fragment was obtained, which hybridizes with three transcripts. Two of them represent the mRNAs for larval glue proteins. They are found in different abundancies in third larval instar salivary glands, but also in minor amounts in midgut and in fat body. In puff 55E on chromosome III two genes were identified. They are transcribed exclusively in salivary glands during all three larval instars. Therefore, their products must be related to another gland-specific function, which is sustained throughout larval life.

Animals↗
PubMed1991

Mutations in the bli-4 (I) locus of Caenorhabditis elegans disrupt both adult cuticle and early larval development.

The bli-4 (I) gene of Caenorhabditis elegans had been previously defined by a single recessive mutation, e937, which disrupts the structure of adult-stage cuticle causing the formation of fluid-filled separations of the cuticle layers, or blisters. We report the identification of 11 new alleles of bli-4, all early larval lethals, including an allele induced by transposon mutagenesis. Nine of the lethal alleles failed to complement the blistered phenotype of e937; two alleles, s90 and h754, complement e937. The complementing alleles arrested development somewhat later than the noncomplementing alleles, which blocked just prior to hatching. We conclude that bli-4 is a complex locus with an essential function late in embryogenesis. We investigated the blistered phenotype of e937 through interactions with other mutations that alter worm morphology or cuticle structure. Recessive and dominant epistasis of several dumpy mutations over the blistered phenotype was observed. Using two heterochronic mutations that alter the developmental stage at which adult cuticle is expressed, we observed that adult worms that lack an adult-stage cuticle could not express blisters. However, late larval worms that expressed the adult cuticle did not express blisters either. It seems likely that the presence of the adult cuticle is necessary, but not sufficient, for blister expression. Blistering resulting from e937 is more severe in trans to null alleles, indicating that e937 is hypomorphic. We postulate that the adult-specific blistering is due to an altered or reduced function of bli-4 gene product in the adult cuticle.(ABSTRACT TRUNCATED AT 250 WORDS)

Alleles↗
PubMed1995

Blood pressures and heart rate during larval development in the anuran amphibian Xenopus laevis.

Heart rate and blood pressure were measured in lightly anesthetized developing Xenopus laevis from hatching (body mass approximately 3 mg) to the end of metamorphosis (< or = 1 g). Blood pressures in the conus arteriosus, truncus arteriosus, and ventricle were measured by a servo-null micropressure system. Heart rate was determined from blood pressure recordings, and cardiac cycles were videotaped through a dissecting microscope. Heart rate varied from 50 to 150 beats/min and showed a negative correlation with body mass, with a slope less than predicted from allometric equations based on adult vertebrates. Mean truncus pressures showed a positive correlation with body mass, increasing from 4 mmHg in a 25-mg larva to 9 mmHg in a 1-g larva. The pressure waveform during ventricular systole was similar in all developmental stages examined, whereas those in conus and truncus varied with development. Conus pressures differed distinctly from truncus pressure during diastole in all larvae examined, suggesting the existence of functional valves between conus and truncus as early as stage 46 of the Nieuwkoop-Faber larval staging system. Although the developmental patterns of heart rate and blood pressure in X. laevis showed significant correlation with body mass, body mass explained less than one-half of the variation in these variables. Therefore developmental factors other than body mass, such as changes in heart mass and the addition of new resistance vessels, may influence heart rate and blood pressure during development in X. laevis.

Animals↗
PubMed2004

lin-35/Rb cooperates with the SWI/SNF complex to control Caenorhabditis elegans larval development.

Null mutations in lin-35, the Caenorhabditis elegans ortholog of the mammalian Rb protein, cause no obvious morphological defects. Using a genetic approach to identify genes that may function redundantly with lin-35, we have isolated a mutation in the C. elegans psa-1 gene. lin-35; psa-1 double mutants display severe developmental defects leading to early larval arrest and adult sterility. The psa-1 gene has previously been shown to encode a C. elegans homolog of yeast SWI3, a critical component of the SWI/SNF complex, and has been shown to regulate asymmetric cell divisions during C. elegans development. We observed strong genetic interactions between psa-1 and lin-35 as well as a subset of the class B synMuv genes that include lin-37 and lin-9. Loss-of-function mutations in lin-35, lin-37, and lin-9 strongly enhanced the defects of asymmetric T cell division associated with a psa-1 mutation. Our results suggest that LIN-35/Rb and a certain class B synMuv proteins collaborate with the SWI/SNF protein complex to regulate the T cell division as well as other events essential for larval growth.

Animals↗
PubMed1981

A scanning electron microscopic study of larval development in the marine polychaete, Galeolaria caespitosa Lamarck (Serpulidae).

Gametes and developing larvae of the polychaete Galeolaria caespitosa were examined by scanning electron microscopy. The sperm display a primitive morphology. When treated with 0.33 M CaCl2, they release a branched acrosomal process. At spawning, the polygonal oocytes have a granular surface made up of spherules and the tips of microvilli. The oocyte coat develops a ridged appearance as the oocyte rounds up. At fertilization, the microvilli are withdrawn from the coat surface. Microvilli again appear on the coat surface during the trochophore stage, but the egg coat appears to be retained as the larval cuticle until the demersal stage. The surface of the larva now shows many microvilli. Details of the organization of several ciliary structures are clarified. Moreover, the present study shows rapid, sequential development of paired setal sacs, with the most anterior pair appearing first.

Animals↗
PubMed1998

Ultrastructure of the olfactory organ in the clawed frog, Xenopus laevis, during larval development and metamorphosis.

Development of the olfactory epithelia of the African clawed frog, Xenopus laevis, was studied by scanning and transmission electron microscopy. Stages examined ranged from hatching through the end of metamorphosis. The larval olfactory organ consists of two chambers, the principal cavity and the vomeronasal organ (VNO). A third sensory chamber, the middle cavity, arises during metamorphosis. In larvae, the principal cavity is exposed to water-borne odorants, but after metamorphosis it is exposed to airborne odorants. The middle cavity and the VNO are always exposed to waterborne odorants. Electron microscopy reveals that in larvae, principal cavity receptor cells are of two types, ciliated and microvillar. Principal cavity supporting cells are also of two types, ciliated and secretory (with small, electron-lucent granules). After metamorphosis, the principal cavity contains only ciliated receptor cells and secretory supporting cells, and the cilia on the receptor cells are longer than in larvae. Supporting cell secretory granules are now large and electron-dense. In contrast, the middle cavity epithelium contains the same cell types seen in the larval principal cavity. The VNO has microvillar receptor cells and ciliated supporting cells throughout life. The cellular process by which the principal cavity epithelium changes during metamorphosis is not entirely clear. Morphological evidence from this study suggests that both microvillar and ciliated receptor cells die, to be replaced by newly generated cells. In addition, ciliated supporting cells also appear to die, whereas there is evidence that secretory supporting cells transdifferentiate into the adult type. In summary, significant developmental additions and neural plasticity are involved in remodeling the olfactory epithelium in Xenopus at metamorphosis.

Animals↗