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PubMed1976

The stimulation of daughter redia production during the larval development of Fasciola hepatica.

In snails maintained at 20 degrees C rediae of Fasciola hepatica merge from sporocysts from 11 days after infection onwards. The number of mother rediae rises steadily thereafter until at least 40 days after infection. Daughter rediae are seldom observed in mother rediae dissected from snails maintained at 20 degrees C. Their production can, however, be stimulated by subjecting the snail host to starvation, to low, and to high temperature shocks. The parasite is susceptible to stress from immediately after infection for about 16 days, when maintained at 20 degrees C. In general, the more extreme the shock, the greater is daughter redial production. Increasing the length of the period of stress from 12 h up to 9 days does not increase the production of daughter rediae, nor does repeated on/off cold shocks or continuous maintenance at 10 degrees C. Daughter rediae develop more rapidly than cercariae and leave the mother rediae several days earlier. There is no evidence that presence of daughter rediae coincides with the suppression of cercarial production. The findings are discussed with reference to possible mechanisms by which parasite development might be controlled.

Animals↗
PubMed1997

Induction of glyoxylate cycle expression in Caenorhabditis elegans: a fasting response throughout larval development.

The mRNA and the bifunctional protein for the two glyoxylate cycle (GC) enzymes, isocitrate lyase and malate synthase, are expressed in a tissue- and stage-specific pattern in Caenorhabditis elegans. Since expression of the two enzymes for the carbon-conserving glyoxylate cycle is regulated by the availability of carbon sources in microorganisms, we have studied the bifunctional GCP gene expression under fasting conditions and in certain mutants of C. elegans in order to understand possible mechanisms regulating its expression during nematode development. The GCP mRNA and protein levels were elevated in early larvae which were never fed, a result consistent with previous enzyme activity measurements (Khan, F.R., & McFadden, B.A. (1982) Exp. Parasitol. 54, 48-54]. However, larvae of later stages also expressed higher levels of GCP mRNA and protein when they were shifted from normal to fasting growing conditions. The GCP expression appeared to be regulated primarily at the transcriptional level throughout development. Although the expression of both the GCP gene and lin-14 peaks at about the same time during development and are induced by fasting, the regulation of the GCP gene is independent of the heterochronic lin-14 control mechanism of postembryonic lineages, as demonstrated by the fact that there was no significant change of the GCP at both mRNA and protein levels in the heterochronic lin-4 (lf) and lin-14 (gf) mutants compared to the wild type.

Animals↗
PubMed1998

Expression of hindlimb abnormalities under rearing temperature effects during the larval development of the salamander Pleurodeles waltl (urodele amphibian).

Anomalie m.p. is a spontaneous and heritable hindlimb abnormality described earlier. Twenty years later, Pleurodeles waltl larvae from the strain bearing anomalie m.p. and reared at room temperature or at 30 degrees C, expressed abnormalities (ectrodactylia, hemimelia, ectromelia). A morphological study of all the hindlimbs and an analysis of the hindlimb skeleton of samples from the experimental animals confirmed that most of the skeletal malformations were identical to those previously reported and affected the disto-proximal and prepostaxial pattern of the hindlimb. Analysis of the effects of rearing temperature on the expression of anomalie m.p. showed that the effects varied according to the developmental period at which the heat treatment was applied; the sooner the heat treatment began, the more numerous and more various were the degrees of severity of the malformations. Moreover, heat treatment induced the expression of two additional malformations not yet described: the first one, named 'reversed knee joint', was characterized by a reversal of the knee joint, and the second one, named 'twisted foot', by a downward twisting of the foot. The epigenetic effects of rearing at 30 degrees C on hindlimb development are discussed with regard to the differentiation or patterning.

Animals↗
PubMed2001

Effects of microgravity on the larval development, metamorphosis and reproduction of the urodele amphibian Pleurodeles waltl.

The FERTILE experiment was twice performed onboard the Mir space station during the Cassiopée and Pégase French space missions. The goal was to analyze the effects of microgravity on fertilization and embryonic development, and then on further development on the ground in the amphibian Pleurodeles waltl. The present paper reports development that occurred in the laboratory after landing. Recovered on the ground at the hatching stage, young larvae reared at room temperature underwent metamorphosis and became adults without obvious abnormalities. Of particular interest was the rearing temperature that induced a delayed metamorphosis for animals from the Cassiopée space mission, but not for animals from the Pégase mission. The rate of development and the morphology were analogous in these animals and in ground controls reared in a similar annual period. Analysis of offspring was performed using these animals. Males born in space were first mated with control ground-born females and then with females born in space. The mating gave progeny that developed normally. Depending on the methods used and on the limits of the analyses, the results clearly demonstrated that animals born in space were able to live and reproduce after return to the ground.

Animals↗
PubMed2002

Eosinophil and mast cell expression in host skin during larval development of the human bot fly Dermatobia hominis.

Eosinophils and mast cells in the skin of Wistar rats (Rattus norvegicus) infested with Dermatobia hominis larvae were quantified and analysed. Eosinophils in parasitised skin increased markedly until 10 days post-infestation (dpi) and then decreased up to 28 dpi, close to the point at which third stage larvae (L3) emerged from the host. In ascending order, the highest numbers of eosinophils were seen in rats at 1, 4, 28, 20, 15 and 10 dpi, corresponding to the first, (1 and 4) third (20 and 28) and second (10 and 15) instars. Except for 1 dpi, eosinophil numbers were significantly higher than those seen in control animals. Mast cell numbers were highest in early infestation (4 dpi), followed by those at 20 dpi. In increasing order, numbers of mast cells were greatest at 10, 28, 15, 1, 20 and 4 dpi, although significant differences with control animals were only seen at 10 and 28 dpi. Eosinophils and mast cells showed negative correlation only in animals with second instar larvae (10 and 15 dpi). Comparative analyses were also carried out after considering the skin into four distinct regions. The results suggest that the expression of both cell types, particularly eosinophils, is an important host response to infestation by D. hominis.

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