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At least 253 records · Page 14Linked to original sources
PubMed2003

Ovarian growth during larval development of queen and worker of Apis mellifera (Hymenoptera: Apidae): a morphometric and histological study.

The present work reports the differences between the ovarian grow in queen and worker larvae of A. mellifera, from the start of differential feeding. The observations made of the growth rates in larvae of both castes showed that the queen and worker larvae have the same rates of cephalic capsule growth from one instar to another but the weight gain is greater in queens. In the same way, the draw areas of ovaries of queens increase more and continuously, while from the 5th instar on the ovaries of workers decrease in size. The decrease is due to a loss of ovariole numbers that starts early in the worker larvae and increases in the 4th-5th instar. The ovarian shape in queens and workers became different in the last larval instars.

Animals↗
PubMed2005

Inner ear formation during the early larval development of Xenopus laevis.

The formation of the eight independent endorgan compartments (sacculus, utricle, horizontal canal, anterior canal, posterior canal, lagena, amphibian papilla, and basilar papilla) of the Xenopus laevis inner ear is illustrated as the otic vesicle develops into a complex labyrinthine structure. The morphology of transverse sections and whole-mounts of the inner ear was assessed in seven developmental stages (28, 31, 37, 42, 45, 47, 50) using brightfield and laser scanning confocal microscopy. The presence of mechanosensory hair cells in the sensory epithelia was determined by identification of stereociliary bundles in cryosectioned tissue and whole-mounts of the inner ear labeled with the fluorescent F-actin probe Alexa-488 phalloidin. Between stages 28 and 45, the otic vesicle grows in size, stereociliary bundles appear and increase in number, and the pars inferior and pars superior become visible. The initial formation of vestibular compartments with their nascent stereociliary bundles is seen by larval stage 47, and all eight vestibular and auditory compartments with their characteristic sensory fields are present by larval stage 50. Thus, in Xenopus, inner ear compartments are established between stages 45 and 50, a 2-week period during which the ear quadruples in length in the anteroposterior dimension. The anatomical images presented here demonstrate the morphological changes that occur as the otic vesicle forms the auditory and vestibular endorgans of the inner ear. These images provide a resource for investigations of gene expression patterns in Xenopus during inner ear compartmentalization and morphogenesis.

Actins↗
PubMed2006

Essential roles of 3'-phosphoadenosine 5'-phosphosulfate synthase in embryonic and larval development of the nematode Caenorhabditis elegans.

Sulfation of biomolecules, which is widely observed from bacteria to humans, plays critical roles in many biological processes. All sulfation reactions in all organisms require activated sulfate, 3'-phosphoadenosine 5'-phosphosulfate (PAPS), as a universal donor. In animals, PAPS is synthesized from ATP and inorganic sulfate by the bifunctional enzyme, PAPS synthase. In mammals, genetic defects in PAPS synthase 2, one of two PAPS synthase isozymes, cause dwarfism disorder, but little is known about the consequences of the complete loss of PAPS synthesis. To define the developmental role of sulfation, we cloned a Caenorhabditis elegans PAPS synthase-homologous gene, pps-1, and depleted expression of its product by isolating the deletion mutant and by RNA-mediated interference. PPS-1 protein exhibits specific activity to form PAPS in vitro, and disruption of the pps-1 gene by RNAi causes pleiotropic developmental defects in muscle patterning and epithelial cell shape changes with a decrease in glycosaminoglycan sulfation. Additionally, the pps-1 null mutant exhibits larval lethality. These data suggest that sulfation is essential for normal growth and integrity of epidermis in C. elegans. Furthermore, reporter analysis showed that pps-1 is expressed in the epidermis and several gland cells but not in neurons and muscles, indicating that PAPS in the neurons and muscles is provided by other cells.

Adenosine Triphosphate↗
PubMed1991

Intra-uterine larval development of the polystomatid monogeneans, Pseudodiplorchis americanus and Neodiplorchis scaphiopodis.

Larvae of the monogeneans Pseudodiplorchis americanus and Neodiplorchis scaphiopodis develop within egg capsules retained in the uterus of the parent parasite. This study reveals adaptations for the storage and nutrition of infective stages which have no known precedent amongst other platyhelminths. The vitelline system is greatly reduced and appears to contribute little to embryo nutrition. An electron-dense 'shell' which encloses the newly formed embryos is subsequently replaced by a thin flexible sac composed of concentric layers of membranes which are derived from the uterus wall. Further membranes are added to this multi-laminate structure as the encapsulated embryos pass along the uterus, and this enables the sac to expand continuously as the larva inside it grows. The capsule lining extends into fine cytoplasmic processes which 'plumb in' to the larval tegument between ciliated cells. These connexions are packed with glycogen and appear to perform a placenta-like function. The unique adaptations correlate with the demands of the life-cycle. Large numbers of oncomiracidia (up to 300) can be packed, in membranous sacs, within the storage capacity of the uterus; direct transfer of nutrients from parent to offspring enables resources to be supplied over an extended period; and infective larvae can be maintained in readiness for an unpredictable opportunity for transmission.

Animals↗
PubMed2002

Larval development of Fasciola hepatica in experimental infections: variations with populations of Lymnaea truncatula.

A retrospective study was undertaken on 70 French populations of Lymnaea truncatula experimentally infected with Fasciola hepatica to determine whether or not susceptibility of snails to infection influenced redial and cercarial production. Results were compared with those obtained from two control populations, known for prevalences higher than 60% when experimentally infected with F. hepatica. In the 70 other populations examined, the prevalences ranged from 2 to 75%. In 55 of these populations, where the prevalence was more than 20%, a high proportion (50.1-56.8%) of snails died after cercarial shedding, whereas in the other groups (non-shedding snails with the most differentiated larvae being free cercariae, rediae containing cercariae, immature rediae, or sporocysts, respectively), snail death was significantly less. In 11 populations, where the prevalence values were 5-19%, only 14% of snails died after cercarial shedding, whereas snails with free cercariae, rediae with cercariae, or immature rediae showed significant increases in snail mortality. In the remaining four snail populations, with prevalences of less than 5%, the most differentiated larval forms were only immature rediae and/or sporocysts. Overall, the number of rediae containing cercariae significantly decreased with decreasing prevalence values. The low prevalence of experimental infection in several populations of snails might be explained by the occurrence of natural infections with miracidia originating from a mammalian host other than cattle, and/or by genetic variability in the susceptibility of snails to infection.

Animals↗
PubMed2006

Altered glucosinolate hydrolysis in genetically engineered Arabidopsis thaliana and its influence on the larval development of Spodoptera littoralis.

The antiherbivore potential of the glucosinolate-myrosinase defense system found in plants of the order Capparales is heavily influenced by the types of hydrolysis products (e.g. isothiocyanates, nitriles) formed from the parent glucosinolates upon plant damage. However, comparison of the effects of glucosinolate hydrolysis products on insect herbivores has been hampered by the lack of suitable experimental tools for rigorous bioassays, such as intact plants differing only in the types of hydrolysis products they produce, or artificial diets that can accurately simulate glucosinolate hydrolysis. The wide array of molecular resources for Arabidopsis thaliana has facilitated the identification of several genes that play a role in glucosinolate hydrolysis. One of these encodes the epithio-specifier protein (ESP) that promotes the formation of nitriles at the expense of isothiocyanates in certain ecotypes of A. thaliana. We overexpressed the ESP cDNA from the nitrile-producing ecotype Landsberg erecta in the isothiocyanate-producing ecotype Columbia-0 to generate transgenic lines of A. thaliana that differed from wild-type plants in the type of glucosinolate hydrolysis products formed upon tissue damage, whereas parent glucosinolate profile and myrosinase activity levels, as well as plant morphology and growth habit, remained unchanged. Bioassays with the model generalist herbivore Spodoptera littoralis (Lepidoptera: Noctuidae) demonstrated that larvae reared on the nitrile-producing lines on average gained weight faster in the first larval stages than larvae that fed on isothiocyanate-producing control plants. Furthermore, larvae with medial growth rates showed a tendency to pupate earlier on the ESP-overexpressing plant lines. Together with the results of previous studies, these findings suggest that isothiocyanates are more effective defenses against insect herbivores than nitriles, and raise questions about what conditions select for nitrile formation in plants.

Amino Acid Sequence↗
PubMed1996

Larval development of tectal efferents and afferents in Xenopus laevis (Amphibia Anura).

The development of tectal connections in Xenopus laevis had been investigated using the degeneration technique to demonstrate the efferent pathways and the retrograde HRP transport to label the afferent pathways. Bilateral tectal efferents were present as soon as the beginning of metamorphosis. Ascending efferents originated from the anterior tectal part terminate in the secondary visual thalamic centres whereas the descending efferents coming from the posterior tectal part reached the tegmentum and the medulla oblongata. At this same time, the optic tectum already received secondary visual afferents originating in the ipsilateral pretectum and non-visual afferents from the ipsilateral semicircular torus and tegmentum. Some sparse bilateral isthmotectal connections were also present. Later, efferent pathways showed an increasing number of fibres whereas the sites of origin of afferents became more diversified: the dorsal thalamus, the suprachiasmatic area, the tegmental nuclei and in the medulla oblongata, the reticular and octavolateral areas sent bilateral projections to the optic tectum. At the end of metamorphosis, we noted ipsilateral olivotectal fibres and reciprocal connections between the tectum and the area of the Vth nerve. These last findings and the presence of the following direct projections, not previously reported in Anurans: the reciprocal connections between the tectum and the semicircular torus or the octavolateral area, underline the implication of the optic tectum in the multisensory (visual, acoustic, vibratory) integration elicited during the larval behavior. Also, the relations between the optic tectum and the lateral line system are particularly examined in the discussion.

Afferent Pathways↗
PubMed2001

Larval development in Cnidaria: a connection to Bilateria?

Among the basal animal phyla, the Cnidaria display many characteristics similar to the Bilateria (the higher Metazoa). However, the relation of that outgroup phyla to the Bilateria is still equivocal. Additionally to morphological and genetic data, studies on cnidarian embryogenesis are essential to clarify the Cnidaria-Bilateria relationship. We analyzed cellular differentiation during planula larvae development of the jellyfish Podocoryne carnea. Within 24 to 30 h postfertilization, the diploblastic body structure and all cell types found in polyps have already differentiated in the larva. Whereas the differentiating smooth muscles, RFamide-positive nerve cells, or nematocytes (stinging cells) express no axial polarity, a newly discovered tyrosine-tubulin-positive nervous system develops gradually in repetitive patterns from anterior to posterior. These data demonstrate that part of the cnidarian nervous system develops from anterior to posterior in serially repeated patterns. This developmental mechanism seems to follow the bilaterian pattern and would have antedated the Cambrian explosion.

Animals↗
PubMed1995

Effects of space flight on Xenopus laevis larval development.

Fifty-three fertilized Xenopus laevis embryos at early tail bud stage were launched into orbit aboard a Biocosmos satellite and remained in microgravity for 11.5 days. During this period, the embryos hatched and continued to develop as free-living larvae. Forty-eight individuals survived the mission. Upon recovery these tadpoles had smaller heads/bodies and proportionately longer tails than ground controls. Almost all the flight animals had caudal lordosis and consequently swam in backward somersaults. Compared to ground-based controls, their notochords were significantly larger in cross-sectional area and were deformed. Caudal muscle fibers were less dense and involuted in a fashion indicative of degeneration. In contrast, cranial muscles associated with buccal pumping did not differ between the flight and control animals. Upon landing, the flight larvae were found to be negatively buoyant and lay on the bottom when they were not swimming. They had significantly smaller lungs than controls, suggesting that they had failed to inflate their lungs in microgravity. Additionally, the branchial baskets, gill filters and thymuses all showed signs of retarded development or degeneration. The caudal deformity that we observed in the flight X. laevis has been independently observed in three other space flight experiments where embryos were launched then hatched in space. In contrast, Xenopus larvae from another orbital experiment that were raised from fertilization through hatching in space did not exhibit any caudal abnormalities. These divergent results suggest that either features of the launch itself (i.e., high acceleration and vibration) or an abrupt decrease in gravity during the tail bud stage detrimentally affects musculoskeletal development in anurans.

Animals↗
PubMed2001

Isolation of Dlx and Emx gene cognates in an agnathan species, Lampetra japonica, and their expression patterns during embryonic and larval development: conserved and diversified regulatory patterns of homeobox genes in vertebrate head evolution.

Agnathan cognates of vertebrate homeobox genes, Emx and Dlx, were isolated from embryonic cDNA of a Japanese marine lamprey, Lampetra japonica. Analyses of amino acid sequences indicated that the Dlx cognate was closely related to the common ancestor of gnathostome Dlx1 and Dlx6 groups and termed LjDlx1/6. Southern blot analyses could not rule out the possibility that L. japonica possesses more than one paralog for both LjDlx1/6 and LjEmx, the lamprey cognate of Emx. Expression of LjDlx1/6 was regulated spatially as well as developmentally, and its transcripts were mainly found in the craniofacial and pharyngeal mesenchyme and in the forebrain. The expression pattern of LjEmx changed dramatically during embryogenesis; expression was seen initially in the entire neural tube and mesoderm, which were secondarily downregulated, and secondarily in cranial nerve ganglia and in the craniofacial mesenchyme. No specific expression of LjEmx was seen in the telencephalon. Comparisons of Dlx and Otx gene expression patterns suggested a shared neuromeric pattern of the vertebrate brain. Absence of Emx expression implied that the patterning of the lamprey telencephalon is not based on the tripartite plan that has been presumed in gnathostomes. Expression domains of LjDlx1/6 in the upper lip and of LjEmx in the craniofacial mesenchyme were peculiar features that have not been known in gnathostomes. Such differences in expression pattern may underlie distinct morphogenetic pathway of the mandibular arch between the agnathans and gnathostomes.

Amino Acid Sequence↗
PubMed2003

Role of substrate on larval development of the freshwater teleost Pelvicachromis pulcher.

It is known that, in an aquatic environment, the mineralogical composition of the substrate can affect the structure of settled communities. In marine environments, the presence of quartz negatively influences the formation of biofilm, as well as the selection and the colonization of the substrate by benthic organisms. Direct laboratory observation revealed that the freshwater teleost Pelivicachromis pulcher selects, when available, nonquartzitic brooding substrate. To monitor the effects of substrate on larvae development, ten lots of embryos were distributed in grid nurseries; carbonatic gravel was laid in five of the nurseries, while freshly fractured quartz gravel was used in the remaining ones. All the embryos laid in the two nurseries hatched, and 90% of the carbonate developing larvae reached adulthood, while 100% of those reared on quartz grain died 120 hr post hatching. Examination was made, both in larvae developed on carbonatic substrates and in those developed on quartz substrates, of the expression of the fetal growth factor, the insulin growth factor-II (IGF-II), of the molecular chaperone, the heat shock protein 70 (HSP70), which is involved in the folding of the nascent polypeptide chain, of the key enzyme of the glycolytic pathway, the glyceraldehyde-3-phosphate dehydrogenase (GADPH), and of the housekeeping gene, the beta-actin. All the data were normalized against 18S RNA expression. In larvae reared on quartz substrate, the genes IGF-II and the beta-actin showed a lower expression, while the GADPH was totally suppressed and the expression of HSP70 increased. In conclusion, the data presented in this article demonstrated, for the first time, that the presence of quarzitic substrates is sufficient to stop larvae development through the inhibition of gene transcription in this African cichlid, leading to its death.

Actins↗
PubMed1993

Immunocytochemical and ultrastructural study of Rana dalmatina PRL and GH pituitary cells during larval development.

Single and double simultaneous indirect immunogold methods and ultrathin sagittal sections of Rana dalmatina tadpole heads were used to follow cytodifferentiation of PRL and GH cells in the adenohypophysial primordium from developmental stage 26 to the end of metamorphosis. Rabbit anti-frog (Rana catesbeiana) PRL and rabbit anti-frog GH were employed in the single method, and rabbit anti-frog PRL and monkey anti-rat GH were used in the double simultaneous technique as primary antisera. At stage 27, a couple of cells with few small secretory granules immunoreactive with anti-frog GH are first identifiable. At stage 28, some cells with few membrane-bound secretory granules, 70-90 nm in diameter, and immunoreactive with anti-frog PRL and other cells with few secretory granules, 80-110 nm in diameter, and immunoreactive with anti-frog GH are present. As development progresses, differentiation in both cell types is shown by an increase in the cytoplasmic volume and in the number, size, and immunoreactivity of secretory granules. Neither comparison of adjacent ultrathin sections stained with the single labeling technique nor results of double simultaneous labeling showed the coexistence of PRL and GH within the same cell.

Animals↗
PubMed2001

Characterization of a sea bream (Sparus aurata) thyroid hormone receptor-beta clone expressed during embryonic and larval development.

A clone encoding thyroid hormone receptor-beta (TR-beta) was isolated from a sea bream (Sparus aurata) ovary cDNA library. Sea bream (sb)TR-beta is closely related to its counterparts from other vertebrates and, like them, preferentially binds T3 rather than T4. However, the putative sbTR-beta protein contains a nine-amino-acid insert that is also present in the corresponding proteins from flounder and salmon but absent in TR-betas from zebrafish and terrestrial vertebrates. Semiquantitative RT-PCR analysis showed that sbTR-beta transcripts begin to accumulate during gastrulation and increase markedly in quantity up to the period around hatch (ca. 40 h postfertilization) before declining slightly. In adult tissues, TR-beta mRNA was present in approximately equal quantities in heart, intestine, brain, kidney, skeletal muscle, liver, and gill. The significance of the relatively strong expression of TR-beta during sea bream embryogenesis is discussed.

Amino Acid Sequence↗
PubMed1993

A histochemical and immunohistochemical study of digestive enzymes and hormones during the larval development of the sea bream, Sparus aurata L.

The distribution of different hydrolytic enzymes and the localization of the hormones which regulate glucose metabolism during development of the digestive tract of the sea bream, Sparus aurata L., were studied. The yolk sac contains trypsin, glucose-6-phosphatase, ATPases and acid and alkaline phosphatase activities. Positive insulin, glucagon and somatostatin cells were observed in the pancreas and in the lumen of the intestinal tract during endogenous feeding. From hatching until 3 days later, the digestive tract of sea bream larvae shows no enzymatic activities. During exogenous feeding, the activities of the phosphatases and trypsin generally increase, as do the amounts of the hydrolytic enzymes and trypsin, as well as the pancreatic and intestinal hormones. The enzymatic activities gradually decrease from the anterior part towards the posterior part of the digestive tract.

Acid Phosphatase↗
PubMed1995

Skeletal malformations induced by the insecticides ZZ-Aphox and Folidol during larval development of Rana perezi.

Tadpoles of Rana perezi were kept for 14 weeks in water containing two sublethal levels of the carbamate insecticide ZZ-Aphox or the organophosphate Folidol. Approximate concentrations of their active ingredients were 0.25 and 1 mg/L. Resulting malformations were studied by skeletal analysis and histological and histochemical investigation of te rear limbs of the tadpoles. The pesticides caused the animals to have malformations of the spinal column (scoliosis) and/or limbs (short and thick long bones with the epiphyses grossly twisted). Histochemical study showed differences in the composition of the connective matrix, and microscopic examination of the long bones indicated alterations in the thickness of the uncalcified bone matrix (osteoid) and the presence of abundant vascularised connective tissue in the region of the periosteum. The results confirmed changes in the composition of the connective tissue matrix as the cause of the defects observed in bone formation which are also discussed in relation to vitamin D absorption and calcium homeostasis.

Abnormalities, Drug-Induced↗