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Toad
About: Toad is a research topic. Over the lifetime, 1624 publications have been published within this topic receiving 28732 citations.
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74 citations
TL;DR: In view of the growing body of information pointing at a close relationship between protein synthesis and hormonal steroid action, it was thought that aldosterone might exert its action on this metabolic pathway with antibiotics characterized by their inhibiting properties on definite steps of protein synthesis.
Abstract: ALDOSTERONE stimulates the active transport of sodium across the isolated urinary bladder and ventral skin of the toad (Bufo marinus), after treatment of the animal with the hormone and incubation of these membranes in its presence1–3. With the toad bladder an interval of 1 h approximately elapses at room temperature between addition of aldosterone to the incubation fluid and the first noticeable increase in sodium transport, regardless of the concentration of the steroid. Yet, the amounts of aldosterone fixed on the bladder tissue exceeded medium concentrations after 15 min incubation2. It was, therefore, proposed that aldosterone exerts its influence on the process under study via the stimulation of synthesis of a substance involved in the active transport of sodium1. In view of the growing body of information pointing at a close relationship between protein synthesis and hormonal steroid action4,5 it was thought that aldosterone might exert its action on this metabolic pathway. Investigations were, therefore, made with antibiotics characterized by their inhibiting properties on definite steps of protein synthesis. ‘Puromycin’ is at present considered as blocking ribosomal elaboration of proteins6, while actinomycin D presumably acts in the cell nucleus on the DNA-dependent synthesis of RNA7,8.
73 citations
TL;DR: It was considered that useful information might be obtained by the use of these manometers for measuring vascular pressures in the frog and toad and thereby throwing some light on this problem.
Abstract: The account of the distribution of the blood in the Amphibia given in the text-books of zoology, and now generally called the 'classical theory', postulates that the pressures obtaining in the pulmo-cutaneous arches are lower than those in the systemic arches, while the pressures in the carotid arches are higher. Because of these pressure differences it is further postulated that the blood issuing from the ventricle flows first into the pulmo-cutaneous arches and then successively into the systemic and carotid arches. Attempts have been made to check these postulates by measuring the blood pressures and registering the pulse waves in the arterial arches, but the results obtained have in general been unconvincing. This has undoubtedly been due to technical difficulties and the comparative crudeness of the instruments used which, with one exception, have been small manometers of low natural frequency. The development recently of electronic condenser manometers, however, has provided an extremely sensitive, efficient and easily used instrument. It was considered, therefore, that useful information might be obtained by the use of these manometers for measuring vascular pressures in the frog and toad and thereby throwing some light on this problem.
73 citations
TL;DR: The results suggest that toad stomach muscle contains a ryanodine-sensitive Ca2+ release channel with properties similar but not identical to those of the mammalian skeletal and cardiac Ca(2+)-release channels.
Abstract: Although a role for the ryanodine receptor (RyR) in Ca2+ signaling in smooth muscle has been inferred, direct information on the biochemical and functional properties of the receptor has been largely lacking. Studies were thus carried out to purify and characterize the RyR in stomach smooth muscle cells from the toad Bufo marinus. Intracellular Ca2+ measurements with the Ca(2+)-sensitive fluorescent indicator fura-2 under voltage clamp indicated the presence of a caffeine- and ryanodine-sensitive internal store for Ca2+ in these cells. The (CHAPS)-solubilized, [3H]ryanodine-labeled RyR of toad smooth muscle was partially purified from microsomal membranes by rate density centrifugation as a 30-S protein complex. SDS/PAGE indicated the comigration of a high molecular weight polypeptide with the peak attributed to 30-S RyR, which had a mobility similar to the cardiac RyR and on immunoblots cross-reacted with a monoclonal antibody to the canine cardiac RyR. Following planar lipid bilayer reconstitution of 30-S stomach muscle RyR fractions, single-channel currents (830 pS with 250 mM K+ as the permeant ion) were observed that were activated by Ca2+ and modified by ryanodine. In vesicle-45Ca2+ efflux measurements, the toad channel was activated to a greater extent at 100-1000 microM than 1-10 microM Ca2+. These results suggest that toad stomach muscle contains a ryanodine-sensitive Ca2+ release channel with properties similar but not identical to those of the mammalian skeletal and cardiac Ca(2+)-release channels.
73 citations
TL;DR: There is a high density of cAMP-gated channels in the cilia where olfactory transduction is thought to take place in amphibian Olfactory receptor cells.
Abstract: Spatial distribution of the cAMP-gated channel was investigated in amphibian olfactory receptor cells. Low doses of cAMP applied to the cytoplasmic side of a membrane patch excised from cilia produced single channel activity of unitary conductance 28pS. Variance analysis showed that the ciliary membrane contained 920 cAMP gated-channels/microns2 in the newt and 2400 channels/microns2 in the toad. In contrast, the membrane of the dendrite and cell body contained only 2 cAMP-gated channels/microns2 (newt) and 6 channels/microns2 (toad). Thus, there is a high density of cAMP-gated channels in the cilia where olfactory transduction is thought to take place.
73 citations