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Amphibia & reptiles / Xenopus laevis / Clawed toad, African Clawed Frog
MALTAIS, D., R.L. ROY, 2009. Purification and partial characterization of vitellogenin from shorthead redhorse (Moxostoma macrolepidotum)and copper redhorse (Moxostoma hubbsi) and detection in plasma and mucus with a heterologous antibody. Fish. Physiol. Biochem., 35: 241-254.
Vitellogenin (VTG), the egg yolk precursor protein, was purified from plasma of estradiol-3- benzoate (E2B)-treated male shorthead redhorse (Moxostoma macrolepidotum) and immature copper redhorse (Moxostoma hubbsi) by a two-step chromatographic procedure without precipitation. Intact VTGs appeared as dimers with apparent molecular masses, determined by gel filtration, of ˜425 kDa (copper redhorse) and ˜450 kDa (shorthead redhorse). In native polyacrylamide gel electrophoresis (PAGE), dimeric redhorse VTGs appeared as a 520 kDa band. Both VTGs were reduced to a single monomer of ˜150 kDa in sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) under reducing and nonreducing conditions, indicating that monomers are not linked by disulfide bonds in the dimer form. The purified proteins were characterized as phospholipoglycoproteins. Isoelectric focusing of both VTGs revealed components with isoelectric points ranging from 5.3 to 6.0, suggesting charge heterogeneity. The amino acid composition of both VTGs contains a high proportion of nonpolar amino acids and was similar to those of other teleosts. An antibody developed against carp (Cyprinus carpio) VTG showed cross-reactivity with VTG from both redhorse species. Using this antibody, VTG was detected in plasma and surface mucus of E2B-treated redhorse. This is the most extensive report on purification and characterization of vitellogenin from catostomidid species.©2009 Springer
EDGINTON, A.N., C. ROULEAU, G.R. STEPHENSON, H.J. BOERMANS, 2007. 2,4-D butoxyethyl ester kinetics in embryos of Xenopus laevis: the role of the embryonic jelly coat in reducing chemical absorption. Arch. Environ. Contam. Toxicol., 52: 113-120 .
The role of the jelly coat in providing a protective barrier to chemical absorption was studied using the embryos of the amphibian, <iXenopus laevis. Embryos with or without a jelly coat were water exposed to the butoxyethyl ester of 2,4-dichlorophenoxyacetic acid (2,4-D BEE) and the rates of uptake, metabolism, distribution, and excretion were determined. The water uptake clearance rates were slower for embryos with a jelly coat (1.5-4.5 mlwater·g embryo -1 ·h-1 or 0.040-0.022 mlwater·h-1 per embryo) in comparison to dejellied embryos (14-21 mlwater·g embryo -1 ·h-1 0.0066-0.021 mlwater·hwater·h-1 per embryo). This accounted for the much lower residues in embryos with a jelly coat than in dejellied embryos during 8 h of exposure. Despite quantitative differences in uptake, once 2,4-D BEE had entered the embryos, metabolism and distribution were similar between the two test groups. 2,4-D BEE was metabolized to 2,4-dichlorophenoxyacetic acid (2,4-D) with half-lives ranging from 35 to 42 minutes. The radioactive residues, as determined by whole body autoradiography, appeared throughout the embryo with a slight accumulation in the blastocoel. Furthermore, 35 % of the radioactive residues were located in the jelly coat and 65 % in the developing embryo. Based on a slower 2,4-D elimination in embryos with a jelly coat, the diffusive properties that decreased 2,4-D BEE uptake appeared to similarly decrease elimination of its metabolite. The common practice of removing jelly coats prior to embryonic amphibian toxicity studies, as in the widely used Frog Embryo Teratogenesis Assay-Xenopus</> (FETAX), is discouraged based on the kinetic differences observed in this study.© 2007 Springer Science+Business Media, Inc.
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