Toad

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

Isolation and partial characterization of immunoglobulin from a urodele amphibian (Necturus masculosus)

Abstract: The primitive amphibian species, Necturus maculosus, a urodele, possessed serum immunoglobulin characterized by a mol. wt of approximately 900,000. Upon reduction of disulphide bonds and analysis under dissociating conditions, this molecule was resolved into polypeptide chains resembling light chains and μ-type heavy chains and having mol. wt of 22,000 and 70,000 respectively. The Necturus immunoglobulin was antigenically related to the IgM-like immunoglobulins of the toad (Bufo marinus) and the Xenopus. Unlike these anuran amphibians, however, the Necturus did not possess detectable amounts of low molecular weight immunoglobulins. The finding raises the evolutionary possibility that the γ-like heavy chains of advanced amphibians may represent the results of a gene duplication independent of that which was responsible for the emergence of the γ heavy chain of mammals.

Distribution of mRNA encoding the FA-CHIP water channel in amphibian tissues: effects of salt adaptation.

Abstract: A water channel, the frog aquaporin-CHIP (FA-CHIP) was recently cloned from Rana esculenta urinary bladder. The 28.9 kDa encoded protein shows 78.8%, 77.4%, 42.4% and 35.6% identity with rat CHIP28, human CHIP28, rat WCH-CD and γ-TIP, other members of the new transmembrane water channel family (Aquaporin-CHIP). We have now studied membranes from different frog (R. esculenta) organs employing semiquantitative PCR using FA-CHIP specific primers and an internal standard to quantify the PCR products. The FA-CHIP mRNA was abundantly expressed in the frog urinary bladder, skin, lung and gall bladder, while a lower expression was detected in the colon, liver and oviduct. FA-CHIP mRNA was not detected in the frog kidney, erythrocytes and brain but its expression was observed in the toad (Bufo arenarum) urinary bladder and skin, showing that FA-CHIP is probably a general amphibian water channel. Salt acclimation is known to increase the water permeability of frog and toad epithelia. We have now observed that salt acclimation for 1, 3, 4 or 5 days markedly increased skin and urinary bladder FA-CHIP mRNA expression. It is generally accepted that water permeability is controlled in these tissues by the rate of water channel transfer from subapical vesicles (aggrephores) to the apical membrane. Our results indicate that water permeability is also regulated at the level of the FA-CHIP transcription.