Search Results for: xenopus

Author: Marin, M.; Slaby, S.; Marchand, G.; Demuynck, S.; Friscourt, N.; Gelaude, A.; Lemiere, S.; Bodart, J.-F. Description: Few studies have been conducted using Xenopus laevis germ cells as oocytes, though these cells offer many advantages allowing both electrophysiological studies and morphological examination. Our aim was to investigate the effects of metal (cadmium, lead, cobalt and zinc) exposures using cell biology approaches. First, cell survival was evaluated with both phenotypical and electrophysiological approaches. Secondly, the effect of metals on oocyte maturation was assessed with morphological observations and electrophysiological recordings. From…

Author: Scharf, S. R.; Gerhart, J. C. Description: Exposure of eggs of Xenopus laevis to a temperature of 1.0 degree C for 4 min or a pressure of 8000 psi for 5 min in a critical period before first cleavage results in embryos exhibiting a reduction and loss of structures of the body axis. The deficiencies occur in a craniocaudal progression which is dose dependent. In the extreme, totally axis-deficient embryos with radial symmetry are formed. Maximum sensitivity to cold and pressure occurs at 0.6 of the time from fertilization…

Author: Dawson, D. A.; McCormick, C. A.; Bantle, J. A. Description: The FETAX (Frog Embryo Teratogenesis Assay–Xenopus) whole embryo bioassay has been developed to screen for environmental substances that cause birth defects. We have used this assay to test its effectiveness in working with actual water samples from the field. Tar Creek is contaminated by discharges from abandoned lead and zinc mines. In addition to high concentrations of zinc, iron and other metals, water samples are routinely low in pH and oxygen content. The pH values of three Tar Creek…

Author: Houston, Douglas W. Description: In Xenopus eggs, fertilization initiates a rotational movement of the cortex relative to the cytoplasm, resulting in the transport of critical determinants to the future dorsal side of the embryo. Cortical rotation is mediated by microtubules, resulting in activation of the Wnt/B-catenin signaling pathway and expression of organizer genes on the dorsal side of the blastula. Similar cytoplasmic localizations resulting in B-catenin activation occur in many chordate embryos, suggesting a deeply conserved mechanism for patterning early embryos. This review summarizes the experimental evidence for the…

**top choice** Author: Dawson, D.A.; Fort, D.J.; Smith, G.J.; Newell, D.L.; Bantle, J.A. Description: The teratogenic potential of nicotine and a primary metabolite, cotinine, was examined with FETAX (Frog Embryo Teratogenesis Assay: Xenopus). Early embryos of Xenopus laevis were exposed for 96 hr to nicotine or cotinine in two separate static renewal tests of each compound without addition of the metabolic activation system (MAS). Two static renewal tests of nicotine with the MAS were also conducted. Addition of the MAS to nicotine reduced the LC50 from an average of 136…

Author: Yu, S.; Wages, M.R.; Cai, Q.; Maul, J.D.; Cobb, G.P. Description: It has been suggested that Xenopus laevis is less sensitive than other amphibians to some chemicals, and therefore, that the Frog Embryo Teratogenesis Assay-Xenopus (FETAX) may have limited use in risk assessments for other amphibians. However, comparisons are based mostly on results of FETAX, which emphasizes embryos. Larval X. laevis may be more sensitive to chemicals than embryos and may serve as a better life stage in risk assessments. The present study was conducted to determine the lethal…

Author: Walsh, P.T.; Downie, J.R.; Monaghan, P. Description: Investigations of the effect of temperature on body size are largely limited to the larval phase, with our understanding of the effect of temperature during metamorphic climax entirely restricted to the insects. Environmental temperature was manipulated only during metamorphosis in the aquatic amphibian Xenopus laevis. Lower temperatures during metamorphosis resulted in individuals with greater mass, head width and snout-vent length on the completion of metamorphosis. This suggests that temperatures experienced during the relatively short metamorphic phase will play an important part in…

Author: Smith, W.C.; Harland, R.M. Description: Expression cloning from a pool of gastrula cDNAs identified the Wnt family member Xwnt-8 as having dorsal axis-inducing activity in Xenopus embryos. Microinjected Xwnt-8 mRNA was able to rescue the development of a dorsally complete anterior-posterior axis in embryos ventralized by exposure to UV light. Axis induction was observed in embryos injected in either marginal or vegetal blastomeres at the 32-cell stage. Vegetal blastomeres receiving Xwnt-8 mRNA contributed progeny not to the induced dorsal axis, but to the endoderm, a result consistent with Xwnt-8…

Author: Peng, Y.; Yang, P.-H.; Ng, S.S.M.; Lum, C.T.; Kung, H.-F.; Lin, M.C. Description: Accumulated evidence indicates that maternal alcohol consumption causes fetal enteric damage and growth retardation. In this study, we investigated the underlying molecular mechanisms in a Xenopus model of fetal alcohol exposure. We established a condition of transient alcohol exposure that produces tadpoles with delayed gut maturation and decreased body length. We then investigated the roles of reactive oxygen species (ROS) and reactive nitrogen species (RNS) by microinjecting plasmids expressing catalase and peroxiredoxin 5 (PRDX5) into two-cell…

Author: Peng, Y.; Yang, P.-H.; Guo, Y.; Ng, S.S.M.; Liu, J.; Fung, P.C.W.; Tay, D.; Ge, J.; He, M.-L.; Kung, H.-F.; Lin, M.C. Description: PURPOSE: To study the molecular mechanisms underlying alcohol-induced ocular anomalies in Xenopus embryos. METHODS: Xenopus embryos were exposed to various concentrations (0.1%-0.5%) of alcohol, and the subsequent effects in eye development and in eye marker gene expression were determined. To investigate the role of reactive oxygen species (ROS) and reactive nitrogen species (RNS) in fetal alcohol syndrome (FAS)-associated ocular injury, two antioxidant enzymes, catalase and peroxiredoxin…