Toad

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

Anion permeability of toad skeletal muscle incubated in plasma and ringer solution

Abstract: Isolated semitendinosus muscles of the toad were incubated in both Ringer solution and toad plasma for periods ranging from 45 to 170 minutes. The extracellular volume (ECV), as measured from the equilibrium distribution of 35SO4(2-), was found to increase (in gram extracellular (EC) water/gram wet weight) from 0.15 +/- 0.01 to 0.20 +/- 0.02 in muscles incubated in Ringer solution, whereas the ECV was found to remain constant in tissues incubated in plasma (0.16 +/- 0.01 to 0.17 +/- 0.01), for periods up to 170 minutes. Since the true ECV, as measured morphometrically, was found to remain unchanged for muscles incubated in Ringer solution for up to 3 hours, the data for these muscles were interpreted to represent a change in anion permeability of the cellular membranes in response to the absence of some plasma fraction from the Ringer solution (with an electrolyte composition and pH similar to that of plasma). When toad plasma albumin was added to the Ringer solution, in physiological concentrations, the ECV of the muscles was observed to remain relatively constant during the 3-hour incubation period. This albumin effect on anion permeability was found to be albumin concentration-dependent. Further, other sources of albumin were found to have varying degrees of effect on the anion permeability of toad muscle, with bovine albumin serving as the most acceptable substitute for toad albumin, when incubating semitendinosus muscles.

Respiratory and Phosphorylative Activity of Amphibian Spermatozoa

Abstract: Bufo arenarum or Leptodact vi us chaquensis spermatozoa have an endogenous respiration (Z,, 1.4 4.2) that s as not significantly enhanced k glucose or fructose. Succinate s as oxidized b these spermatozoa at higher rates (Z0, = 5 14) while endogenous respiration was only slightly stimulated by glutamate or citrate. Both the endogenous and exogenous respiration were sensitive to respiratory chain inhibitors (rotenone. antimycin or cyanide). The respiration of frog and toad sperm was coupled to the synthesis of ATP. P/O ratios of 0.54 were determined in the presence of potassium fluoride and exogenous hexokinase. Oligomvcin inhibited phosphorylation completely and respiration partialls. The latter inhibition s as released h uncouplers like dinitrophenol. It is concluded that frog and toad sperm have an active oxidative metabolism coupled to the synthesis of ATP.

Ba2+-inhibitable 86Rb+ fluxes across membranes of vesicles from toad urinary bladder.

Abstract: 86Rb+ fluxes have been measured in suspensions of vesicles prepared from the epithelium of toad urinary bladder. A readily measurable barium-sensitive, ouabain-insensitive component has been identified; the concentration of external Ba2+ required for half-maximal inhibition was 0.6 mM. The effects of externally added cations on 86Rb+ influx and efflux have established that this pathway is conductive, with a selectivity for K+, Rb+ and Cs+ over Na+ and Li+. The Rb+ uptake is inversely dependent on external pH, but not significantly affected by internal Ca2+ or external amiloride, quinine, quinidine or lidocaine. It is likely, albeit not yet certain, that the conductive Rb+ pathway is incorporated in basolateral vesicles oriented right-side-out. It is also not yet clear whether this pathway comprises the principle basolateral K+ channel in vivo, and that its properties have been unchanged during the preparative procedures. Subject to these caveats, the data suggest that the inhibition by quinidine of Na+ transport across toad bladder does not arise primarily from membrane depolarization produced by a direct blockage of the basolateral channels. It now seems more likely that the quinidine-induced elevation of intracellular Ca2+ activity directly blocks apical Na+ entry.