Toad

About: Toad is a research topic. Over the lifetime, 1624 publications have been published within this topic receiving 28732 citations.

Diversity of opsin immunoreactivities in the extraretinal tissues of four anuran amphibians.

Abstract: The pineal complex, deep brain, and skin have been known to function as extraretinal photoreceptors in non-mammalian vertebrates. To see the diversity of localization of extraretinal photoreceptors in lower vertebrates having different habitats, we analyzed the opsin-like immunoreactivities in anuran amphibians, Xenopus laevis, Rana catesbeiana, Rana nigromaculata, and Bufo japonicus. An antiserum (toad Rh-AS) was raised against rhodopsin purified from the retinas of Japanese toad, B. japonicus. In the retina of all the anurans examined, the outer segments of rods were immunopositive to toad Rh-AS. The outer segments of most pinealocytes were immunopositive in R. catesbeiana, R. nigromaculata, and B. japonicus. The outer segments of photoreceptor-like cells within the frontal organ of R. nigromaculata were immunostained. Interestingly, toad Rh-AS immunostained many secretory cells of mucous glands in the head skin of B. japonicus, implying the presence of a novel photoreceptive molecule. Within the hypothalamus, toad Rh-AS immunostained many cells in the magnocellular preoptic nucleus of R. catesbeiana and B. japonicus. Toad Rh-AS also labeled cerebrospinal fluid (CSF)-contacting cells in the anterior preoptic nucleus of R. nigromaculata and those adjacent to the lateral ventricle within the septum of R. catesbeiana. Thus the distribution patterns of the rhodopsin-like immunoreactivities among the anurans were highly diverged, and there was no relationship between the distribution patterns and their habitats. J. Exp. Zool. 286:136-142, 2000.

Characterization and localization of epithelial Na+ channels in toad urinary bladder

Abstract: The toad urinary bladder and epithelial cell lines derived from the urinary bladder, including TBM, serve as model systems for the study of transepithelial Na+ transport. We examined biochemical characteristics of epithelial Na+ channels in toad urinary bladder and TBM cells and their cellular localization in the urinary bladder. The radiolabeled amiloride analogue [3H]benzamil bound to a single class of high-affinity binding sites in membrane vesicles from toad urinary bladder with a dissociation constant (Kd) of 10 nM. Photoactive benzamil analogues specifically labeled a 135,000-Da polypeptide in toad urinary bladder and TBM cells. A monoclonal anti-Na+ channel antibody directed against the amiloride-binding component of the channel specifically recognized a 135,000-Da polypeptide in TBM cells. Polyclonal anti-Na+ channel antibodies generated against purified bovine epithelial Na+ channel specifically recognized a 235,000-Da polypeptide in toad urinary bladder and localized Na+ channels to the apical plasma membrane of urinary bladder epithelial cells. The biochemical characteristics and the cellular localization of epithelial Na+ channels in toad urinary bladder are similar to those previously described in mammalian kidney and in the A6 cell line.

Comparison of toad bladder aldosterone-induced proteins and proteins synthesized in vitro using aldosterone-induced messenger RNA as template.

Abstract: Using double-labeled isotope techniques, it can be shown that aldosterone induces the synthesis of several proteins in the mitochondria-rich (MR) cells of the toad's urinary bladder. Induced proteins have been identified both in the plasma membrane (mol wt=170,000, 85,000 and 12,000) and the cytosol (mol wt=36,000, 12,000 and 6,000) fractions of these mucosal cells. We have also shown that aldosterone (Aldo) induces the synthesis of a class of RNA having the properties of messenger RNA (mRNA). mRNA isolated from Aldo-treated mucosal cells was used as template in a cell-free protein-synthesis system prepared from rabbit reticulocytes. Preparations charged with mRNA from Aldotreated cells synthesized two proteins that were not labeled when mRNA from control tissues was used as template. The electrophoretic mobility of one of these proteins was similar to an Aldo-induced membrane protein (mol wt=70,000) found in the intact tissue.