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PubMed1975

The effect of ablation of the olfactory pits on the development of the habenular nuclei in Rana pipiens.

The habenular nuclei in the diencephalon of the frog, Rana pipiens, are asymmetrical structures: two discrete cell groups develop on the left side (as medial and lateral nuclei), while a single nucleus is formed on the right side. Experimental animals were subjected to bilateral removal of the olfactory pits at an early embryonic stage, and were maintained with normal control animals until metamorphosis was complete. The length, relative volume and cell number for each of the three nuclei were determined in the control and experimental animals at regular intervals during larval development. In the control animals, the left medial nucleus developed similarly to the right nucleus spatially and temporally; however, the left lateral nucleus was significantly different in its development in the three parameters measured. In the experimental animals the left medial and the right habenular nuclei were alone affected by the removal of the olfactory pits. The results provide experimental evidence that the right and left medial, but not the left lateral, habenular nuclei are centers receiving afferent olfactory fibers.

Animals↗
PubMed1992

Identification of surrogate rodent hosts for larval Onchocerca lienalis and induction of protective immunity in a model system.

The objectives of this project were to screen a variety of inbred rodent species and strains to determine their usefulness as surrogate hosts for the study of the early larval development of Onchocerca lienalis and then to use a selected model to study the induction of protective immunity. In the primary screen, 6 strains of mice, 5 strains of rats, jirds, and multimammate rats were tested. Animals were infected with fresh O. lienalis by subcutaneous implantation of third-stage larvae (L3) contained in diffusion chambers covered with 5.0-microns pore-size membranes. After 7 days the chambers were recovered, and larval viability and growth were assessed. Approximately one-half of inoculated larvae were recovered alive regardless of the host tested. Larvae were implanted in CBA/J and DBA/2J mice in chambers covered with membranes that prevented host cells from entering; survival and growth rates of the larvae were not altered by the absence of cells from the chambers. Cryopreserved larvae were implanted in chambers with 5.0-microns pore-size membranes in CBA/J and DBA/2J mice and Wistar Furth rats for 3-28 days. No statistically significant difference was seen in the larval recoveries on days 3-28 in all 3 hosts. Statistically significant increases in length were seen in the 3 strains from day 3 to day 14, after which growth appeared to cease. Molting from L3 to fourth-stage larvae was observed in all 3 hosts beginning on day 3, with most larvae completing the molt by day 7.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2002

Comparative studies of the development and differentiation of chloride cells in tilapine fish with different reproductive styles.

Using light and electron microscopy and fluorescent probes, we followed the ontogenesis of selected organs in embryos of several species of tilapia (Cichlidae, Pisces) with emphasis on chloride cell differentiation in species with two different reproductive styles: we compared the substrate-brooder Tilapia zillii and the mouth-brooders Oreochromis niloticus, O. aureus, Sarotherodon galilaeus, and Tristramella sacra. In all species a transitory blood network system nurtured by the vena caudalis inferiores supplied the yolk sac and preanal finfold during the advanced stages of embryonic and initial stages of larval development. During these stages chloride cells occurred on the yolk sac, as a part of the abdominal epithelium. The cells and their associated blood plexus remained active here until the gill-lamellae, operculum, and mouth became functional. The chloride cells of their epithelium and blood system then took over, concomitant with a gradual degradation of the transitory blood system on the yolk sac. Ontogenesis of these systems (transitory and permanent) progressed at a higher rate in substrate-brooders than in mouth-brooders and was correlated with the earlier functioning of the gill-operculum system. Thus, at a constant temperature of 26 degrees C, the more exposed T. zillii progeny completed metamorphosis at 7-8 days after fertilization, calculated around 5,000 +/- 80 h/temp, whereas juveniles of more protected mouth-brooders attained a similar stage only 15 +/- 1 days after fertilization and around 9,000 +/- 200 h/temp. This earlier development of chloride cells and other pivotal organs in environmentally exposed progeny of substrate-brooders, as compared to the protected progeny of mouth-brooders, shows that their ontogeny was selected for the optimal survival style under specific etho-ecological conditions.

Age Factors↗
PubMed2026

Mitochondrial genetic effects mediate the response to stress through development, but not adult metabolic rate in Drosophila.

Energy expenditure is fundamental to physiology, behaviour, ecology, and life history, yet the mechanisms that regulate metabolic rate remain poorly understood. At the cellular level, incompatibilities between the maternally inherited mitochondrial genome and the nuclear genome can impair energy production, signalling and gene expression, with potential to disrupt a wide range of physiological processes. However, how these often-subtle genomic mismatches influence whole-organism traits such as metabolic rate, activity, and fitness remains unclear. Here, we generated mitonuclear-mismatched fly lines to test how early-life dietary and metabolic stress affect larval and adult physiology. Our results revealed sex and line-specific physiological effects, with larval development, survival and female fertility strongly contingent on the haplotypes and treatment, while adult resting metabolic rate and activity were not influenced by mitochondrial haplotype, nor by developmental stress.

Drosophila melanogaster↗
PubMed2001

The role of the Drosophila TAK homologue dTAK during development.

The TAK kinases belong to the MAPKKK group and have been implicated in a variety of signaling events. Originally described as a TGF-beta activated kinase (TAK) it has, however, subsequently been demonstrated to signal through p38, Jun N-terminal kinase (JNK) and Nemo types of MAP kinases, and the NFkappaB inducing kinase. Despite these multiple proposed functions, the in vivo role of TAK family kinases remains unclear. Here we report the isolation and genetic characterization of the Drosophila TAK homologue (dTAK). By employing overexpression and double-stranded RNA interference (RNAi) techniques we have analyzed its function during embryogenesis and larval development. Overexpression of dTAK in the embryonic epidermis is sufficient to induce the transcription of the JNK target genes decapentaplegic and puckered. Furthermore, overexpression of dominant negative (DN) or wild-type forms of dTAK in wing and eye imaginal discs, respectively, results in defects in thorax closure and ommatidial planar polarity, two well described phenotypes associated with JNK signaling activity. Surprisingly, RNAi and DN-dTAK expression studies in the embryo argue for a differential requirement of dTAK during developmental processes controlled by JNK signaling, and a redundant or minor role of dTAK in dorsal closure. In addition, dTAK-mediated activation of JNK in the Drosophila eye imaginal disc leads to an eye ablation phenotype due to ectopically induced apoptotic cell death. Genetic analyses in the eye indicate that dTAK can also act through the p38 and Nemo kinases in imaginal discs. Our results suggest that dTAK can act as a JNKKK upstream of JNK in multiple contexts and also other MAPKs in the eye. However, the loss-of-function RNAi studies indicate that it is not strictly required and thus either redundant or playing only a minor role in the context of embryonic dorsal closure.

Amino Acid Sequence↗
PubMed1997

Growth and death of rohon-Beard cells in Rana pipiens and Ceratophrys ornata.

Rohon-Beard (R-B) neurons of the medulla oblongata and spinal cord of anurans originate during gastrulation, become distinguishable just after closure of the neural tube, and are present in maximum numbers at the end of the embryonic period, just before feeding begins. Cell deaths are first seen in the earliest larval stages; in Rana pipiens and Ceratophrys ornata, they may not be complete until the very end of larval development or a day or two later, in the juvenile froglet. This is in sharp contrast with Xenopus laevis, in which the last R-B cells die well before the onset of metamorphic climax. Cell losses tend to reach completion in the trunk in a craniocaudal progression, that is, first in the medulla oblongata, then sequentially at brachial, postbrachial, and lumbar levels. Nuclei and cells increase in size through embryonic and early larval stages, reaching maxima at stages X-XIV (of 25 larval stages), then shrinking before cell death occurs. While Ceratophrys produces only two-thirds as many R-B cells as does R. pipiens, its rate of cell death is slower, gauged by attained stage, and at every stage, X-XXIV, Ceratophrys displays a greater number of surviving cells. In hypophysectomized Rana pipiens larvae some 7-15% of the peak numbers of R-B cells are still present after 400 days, more than 4 times the length of the usual larval period. Most or all of these surviving cells are in the tail. The extreme persistence of R-B cells in hypophysectomized larvae is consistent with the view that the R-B cell population can be characterized as being divided into those cells whose death occurs relatively early and those in which cell destruction occurs late, presumably dependent upon different factors. The critical factor for onset of cell death in late larvae may well be the surge in thyroid hormone concentration, which characterizes metamorphic climax.

Animals↗
PubMed2000

Distribution of growth-blocking peptide in the insect central nervous tissue.

Parasitization of the armyworm Pseudaletia separata by the endoparasitic wasp Cotesia kariyai inhibits larval growth and delays pupation, conditions necessary for proper maturation of the parasite larvae. Parasitization is correlated with an elevated level of a 25-amino-acid hormone-like peptide, growth-blocking peptide (GBP, ENFSGGCVAGYMRTPDGRCKPTFYQ). Injection of synthetic GBP into nonparasitized larvae dose dependently mimics the effects of parasitization by delaying the larval development. Here we studied the relationship between parasitization and both the production and distribution of GBP in central nervous tissues. We found that parasitization is correlated with an elevated expression of GBP mRNA, and increased concentrations of both proGBP and GBP in the host insect brain and subesophageal ganglion. The increase in proGBP precedes that of the mature GBP by about 12 h. In situ hybridization analysis using sections of parasitized and nonparasitized larval brains showed strong expression of GBP mRNA in perineural cells and/or class I neuroglia in the rind of both larval brains. The expression in parasitized larval brain-subesophageal ganglion is approximately two- to threefold higher than that in nonparasitized larvae. The presence of GBP in insect neural tissue, and its role in inhibiting growth, suggest an involvement in the regulation of neurosecretory cells.

Animals↗
PubMed2006

Predator defense along a permanence gradient: roles of case structure, behavior, and developmental phenology in caddisflies.

Species replacements along freshwater permanence gradients are well documented, but underlying mechanisms are poorly understood for most taxa. In subalpine wetlands in Colorado, the relative abundance of caddisfly larvae shifts from temporary to permanent basins. Predators on caddisflies also shift along this gradient; salamanders (Ambystoma tigrinum nebulosum) in permanent ponds are replaced by predaceous diving beetles (Dytiscus dauricus) in temporary habitats. We conducted laboratory and field experiments to determine the effectiveness of caddisfly cases in reducing vulnerability to these predators. We found that larvae of a temporary-habitat caddisfly (Asynarchus nigriculus) were the most vulnerable to salamanders. Two relatively invulnerable species (Limnephilus externus, L. picturatus) exhibited behaviors that reduced the likelihood of detection and attack, whereas the least vulnerable species (Agrypnia deflata) was frequently detected and attacked, but rarely captured because cases provided an effective refuge. Vulnerability to beetle predation was also affected by cases. The stout cases of L. externus larvae frequently deterred beetle larvae, whereas the tubular cases of the other species were relatively ineffective. Two of these vulnerable species (A. nigriculus and L. picturatus) often co-occur with beetles; thus, case construction alone is insufficient to explain patterns of caddisfly coexistence along the permanence gradient. One explanation for the coexistence of these two species with beetles is that they develop rapidly during early summer and pupate before beetle larvae become abundant. One species (L. picturatus) pupates by burying into soft substrates that serve as a refuge. The other (A. nigriculus) builds stone pupal cases, which in field experiments, more than doubles survival compared to organic pupal cases. The combined results of these experiments suggest that caddisfly distributions along permanence gradients depend on a suite of primary and secondary predator defenses that include larval and pupal case structure, predator-specific escape behaviors, and the phenology of larval development.

Ambystoma↗
PubMed1990

Neuropeptide Y- and substance P-like immunoreactive amacrine cells in the retina of the developing Xenopus laevis.

The development of neuropeptide Y-like (NPY-LI) and substance P-like (SP-LI) immunoreactive neurons was studied in retinas of Xenopus laevis from young tadpole through to adult animals. In adult retina these neuropeptides are present in wide-field amacrine cells located in the inner nuclear layer and the ganglion cell layer of the retina. Retinal wholemount preparations and sectioned material showed that immunoreactive cells appeared during early larval life and NPY-LI occurred earlier than SP-LI cells. The primary dendritic branching of NPY-LI neurons appeared from early larval life whilst SP-LI was evident in dendrites from mid-larval stages. In postmetamorphic animals the numbers of immunoreactive cells increased in proportion to retinal area growth with a relatively constant cell density of about 35 cells/mm2 for SP-LI and 45 cells/mm2 for NPY-LI. The maturation of dendritic morphology of both NPY- and SP-LI amacrine cells appeared later in larval development than the appearance of immunoreactivity in cell somas. However, the sequence of expression of NPY- or SP-LI and their dendritic maturation was different for the two classes of amacrine cells. It is suggested that the maturation of dendritic fields of amacrine cells is complete just prior to metamorphosis, consistent with the postmetamorphic onset of electrophysiological features of ganglion cells attributed to amacrine cells.

Animals↗
PubMed1994

Fertilization of sea urchin eggs in space and subsequent development under normal conditions.

Sea urchin eggs are generally considered as most suitable animal models for studying fertilization processes and embryonic development. In the present study, they are used for determining a possible role of gravity in fertilization and the establishment of egg polarity and the embryonic axis. For this purpose, eggs of the particularly well known and suitable species Paracentrotus lividus have been automatically fertilized under microgravity conditions during the Swedish sounding rocket flights MASER IV and MASER V. It turns out, that fertilization "in Space" occurs normally and that subsequent embryonic and larval development of such eggs, continued on the ground, is normal, leading to advanced pluteus stages.

Animals↗
PubMed2001

Developmental effects of pcbs on the hard clam (Mercenaria mercenaria).

Development of hard clam (Mercenaria mercenaria) larvae was examined as a potential biomarker of exposure to polychlorinated biphenyls (PCBs). Clams from clean sites in Massachusetts Bay were thermally induced to spawn in the laboratory using seawater, and the gametes were collected and pooled by sex prior to fertilization. The larvae were cultured in seawater amended with Aroclor 1254, at concentration ranges bracketing environmentally relevant levels. A dose-response relationship was observed for larval development in the presence of Aroclor 1254; at higher doses, fewer larvae developed to the normal straight-hinge, or D-shaped stage, relative to the controls, while the number of abnormally shaped larvae increased.

Animals↗
PubMed2004

Host location in flow by larvae of the symbiotic barnacle Trevathana dentata using odour-gated rheotaxis.

The detection and location of specific organisms in the aquatic environment, whether they are mates, prey or settlement sites, are two of the most important challenges facing aquatic animals. Large marine invertebrates such as lobsters have been found to locate specific organisms by navigating in the plume of chemicals emitted by the target. However, active plume tracking in flow by small organisms such as marine larvae has received little scientific attention. Here, we present results from a study examining host location in flow by nauplius larvae of the barnacle Trevathana dentata, which inhabits the stony reef coral Cyphastrea chalcidicum. The experiments included analysis of larval motion in an annular flume under four conditions: (i) still water, (ii) in flow, (iii) in still water with waterborne host metabolites and (iv) in flow with host metabolites. Our results show that T. dentata nauplii are unable to locate their target organism in still water using chemotaxis, but are capable of efficient host location in flow using odour-gated rheotaxis. This technique may enable host location by earlier, less-developed larval stages.

Analysis of Variance↗
PubMed1995

Cryopreservation of the first-stage larvae of trichostrongylid nematode parasites.

First stage (L1) larvae of Haemonchus contortus, Trichostrongylus colubriformis and Ostertagia circumcincta can be cryopreserved in the presence of DMSO using a two-step freezing protocol involving an initial period at -80 degrees C prior to transfer to liquid nitrogen. Thawed L1 larvae continue development in vitro producing third stage (L3) larvae that are infective to sheep when dosed per os. Establishment rates for L3 larvae grown from thawed L1 larvae were 40 and 80% for H. contortus and T. colubriformis, respectively. There was no difference in survival or infectivity between benzimidazole (BZ)-susceptible and BZ-resistant H. contortus isolates and cryopreservation caused no shift in their BZ-resistance status as indicated in an in vitro larval development assay. Cryopreservation also had no effect on the sensitivity of these isolates to the avermectins or levamisole in vitro. High survival rates (60-70%), good levels of establishment and the stability of anthelmintic resistance status of isolates indicate that little if any selection occurs during the cryopreservation process. L1 larvae of all 3 species have been successfully recovered after 16 months storage in liquid nitrogen, cultured to the L3 stage and established in sheep.

Animals↗
PubMed2006

Soma-germline interactions coordinate homeostasis and growth in the Drosophila gonad.

The ability of organs such as the liver or the lymphoid system to maintain their original size or regain it after injury is well documented. However, little is known about how these organs sense that equilibrium is breached, and how they cease changing when homeostasis is reached. Similarly, it remains unclear how, during normal development, different cell types within an organ coordinate their growth. Here we show that during gonad development in the fruitfly Drosophila melanogaster the proliferation of primordial germ cells (PGCs) and survival of the somatic intermingled cells (ICs) that contact them are coordinated by means of a feedback mechanism composed of a positive signal and a negative signal. PGCs express the EGF receptor (EGFR) ligand Spitz, which is required for IC survival. In turn, ICs inhibit PGC proliferation. Thus, homeostasis and coordination of growth between soma and germ line in the larval ovary is achieved by using a sensor of PGC numbers (EGFR-mediated survival of ICs) coupled to a correction mechanism inhibiting PGC proliferation. This feedback loop ensures that sufficient numbers of PGCs exist to fill all the stem-cell niches that form at the end of larval development. We propose that similar feedback mechanisms might be generally used for coordinated growth, regeneration and homeostasis.

Animals↗
PubMed2001

Direct and indirect sublethal effects of Galanthus nivalis agglutinin (GNA) on the development of a potato-aphid parasitoid, Aphelinus abdominalis (Hymenoptera: Aphelinidae).

Snowdrop lectin (Galanthus nivalis agglutinin, GNA), has been shown to confer partial resistance to two potato aphids Myzus persicae and Aulacorthum solani, when incorporated in artificial diet and/or expressed in transgenic potato. First-tier laboratory-scale experiments were conducted to assess the potential effect of GNA on the aphid parasitoid Aphelinus abdominalis. GNA (0.1% w/v) was successfully delivered to Macrosiphum euphorbiae via artificial diet and induced a reduced growth rate and increased mortality compared to aphids fed a control diet. As aphid parasitoid larvae are endophagous, they may be exposed to GNA during their larval development and potential "chronic toxicity" on A. abdominalis was investigated. The amounts of GNA present in aphid and parasitoid tissues were estimated by western blotting. Results suggest that parasitoids excrete most of the GNA ingested. Sublethal effects of GNA on several parasitoid fitness parameters (parasitism success, parasitoid development and size, emergence success, progeny survival and sex ratio) were studied. No direct detrimental effect of GNA on A. abdominalis was observed. However, GNA had an indirect host-size-mediated effect on the sex ratio and the size of parasitoids developing in GNA-fed aphids. This work highlights the need to determine the exact "causes and effects" when assessing the ecological impact of transgenic plants on non-target beneficial insects. Such bioassays form the basis of a tiered risk assessment moving from laboratory studies assessing individuals towards field-scale experiments assessing populations.

Journal Article↗
PubMed1986

Taenia taeniaeformis: inhibition of metacestode development in the rat by gossypol.

The effect of gossypol, a polyphenolic compound, on developing Taenia taeniaeformis larvae in the rat liver was examined. Five groups of rats were used. In group 1, subcutaneous injection of gossypol at 10 mg/kg was started 5 days prior to administration of tapeworm eggs. In group 2, gossypol injections were started 5 days after administration of eggs. Groups 3 and 4 were infected and noninfected rats, respectively, which received the vehicle (10% ethyl alcohol in 0.85% NaCl) only. Group 5 rats were noninfected but received gossypol. From each group, 5 rats were killed on days 7, 12, and 22 of infection, respectively. The number and size of larvae and the size of the livers were much less in rats gossypol injected 5 days before infection than those in the vehicle-treated group. Administration of gossypol 5 days after infection resulted in less inhibition. The size and the thickness of the fibrous capsule around larvae of the gossypol-treated rats were much smaller than those of the control-infected group. The actively developing larvae excrete or secrete a sulfated glycosaminoglycan which is specifically stained with alcian blue. There was much more alcian blue-positive substance around the larvae and the capsule of the control-infected liver compared to the gossypol-treated infected animal. The percentage body weight of the spleen was significantly greater in the gossypol-treated rats in both infected and noninfected groups. These results suggest that gossypol may directly inhibit tapeworm larval development or that elimination of the tapeworm may be resulted from gossypol-induced stimulation of host cell-mediated immunity.

Animals↗
PubMed2004

TRA-1/GLI controls development of somatic gonadal precursors in C. elegans.

TRA-1/GLI is best known as a master regulator of sex determination in the nematode C. elegans, but its fly and vertebrate homologs (e.g. Ci, GLI) regulate embryonic patterning and cell proliferation. In this paper, we show that TRA-1/GLI controls development of the two somatic gonadal precursors (SGPs) in both XX and XO animals, in addition to its role in sex determination. Normally, SGPs reside at the poles of the gonadal primordium and divide according to intrinsic gonadal axes. In tra-1-null mutants, however, SGPs assume non-polar positions and the polarity of one SGP is reversed. Consistent with its SGP function, TRA-1 protein is present in SGPs during embryogenesis and early larval development. Previous studies have shown that the ehn-3 gene also affects SGP positions, and we report here that tra-1 and ehn-3 interact genetically. Whereas SGPs in tra-1 and ehn-3 single mutants are largely normal and generate many descendants, those in tra-1; ehn-3 double mutants do not mature or divide. Furthermore, tra-1 is a dominant enhancer of the ehn-3 gonadal defect, which includes the enhancement of a weak sexual transformation in the gonad. We cloned ehn-3, and found that it encodes a C2H2 zinc-finger protein. A rescuing EHN-3::GFP reporter is predominantly nuclear and expressed specifically in SGPs. The EHN-3 protein is therefore likely to regulate gene expression. We propose that TRA-1/GLI and EHN-3 have overlapping roles in regulation of multiple steps of SGP development. We speculate that regulation of SGP development may be an evolutionarily ancient role of TRA-1/GLI in nematode development.

Amino Acid Sequence↗
PubMed2000

The L63 gene is necessary for the ecdysone-induced 63E late puff and encodes CDK proteins required for Drosophila development.

The pulse of ecdysone that triggers Drosophila metamorphosis activates six early genes in a primary response made visible by polytene chromosome puffs. The secondary response is detected by the induction of over 100 late puffs, only a few of which have been subject to molecular genetic analysis. We present a molecular and mutational analysis of the L63 gene responsible for the late puff at 63E. This gene contains overlapping L63A, B, and C transcription units of which the A unit encodes two isoforms and the B unit three. The C unit, which exhibits little activity, encodes one of the B isoforms. Evidence that L63B, but not L63A, transcription is ecdysone responsive derives from their developmental transcription profiles and from P-element mutagenesis showing that ecdysone induction of the 63E puff requires sequences adjacent to the 5' end of L63B but not those adjacent to the 5' end of L63A. L63-specific lethal mutations showed that L63 is required not only for metamorphosis, but also maternally and for embryonic and larval development. The L63 proteins contain a common C-terminal 294-aa sequence that is 71% identical to the CDK sequence of the murine PFTAIRE protein. In vivo tests of L63 proteins altered by site-directed mutagenesis showed that they exhibit CDK functions. L63 proteins are widely distributed among late larval and prepupal tissues and are unlikely to be involved in cell cycle functions.

Amino Acid Sequence↗