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At least 19 recordsLinked to original sources
PubMed1962

The electrical potential profile of the isolated toad bladder.

The electrical potential profile of the isolated toad bladder was examined in the spontaneously active, chronically short-circuited, and intermittently short-circuited states by means of glass micropipettes. The position of the micropipette tip within the bladder was evaluated by measuring the D.C. resistance between the micropipette tip and the reference electrode on the serosal side of the bladder. In the spontaneously active state, with concentrations of sodium in the mucosal solution ranging from less than 1 to 114 meq per liter, the potential profile consisted in the majority of impalements of two steps, each positive to the mucosal solution. A minority of impalements showed more than two potential steps, each positive to the mucosal solution. In the short-circuited state, the interior of the bladder was found to be negative to the bathing solution by approximately 5 mv. The results are interpreted as showing a potential step at the two surfaces of the epithelial cell layer of the toad bladder. In the spontaneously active state the potential change at the mucosal boundary is of the wrong polarity to bring about net sodium entry; the small electrical driving force across the mucosal surface which is present in the short-circuited state may contribute to the net entry of sodium from mucosal solutions with low sodium concentration.

Anura↗
PubMed1962

Movement of sodium across the mucosal surface of the isolated toad bladder and its modification by vasopressin.

Studies have been made on the isolated urinary bladder of the toad, Bufo marinus, in an attempt to evaluate gradients of chemical activity across the mucosal surfaces of the epithelial cells which would serve to maintain a net movement of sodium from the mucosal medium into the cells. The likelihood of such chemical gradients has been established by the demonstration of lower contents of sodium within the tissue, expressed as microequivalents per gram of tissue water, than of concentrations of sodium in the mucosal medium at all levels of the latter examined. The transepithelial transport of sodium and the sodium content of the tissue were found to increase rapidly with rise in concentration of sodium in the mucosal medium up to values of 30 to 60 meq per liter. Further increase in concentration of the medium above this value failed to induce further stimulation of sodium transport or increase in the sodium content of the tissue. Vasopressin increased the rate of transport of sodium at every concentration of sodium in the mucosal medium without altering this relationship. Although entry of sodium across the mucosal surface of the epithelial cells may be passive it is not by free diffusion but involves some considerable interaction with the mucosal surface of the bladder and constitutes the major determinant of the rate of transepithelial transport of sodium. Vasopressin acts to enhance this initial step in the transport of sodium.

Animals↗
PubMed1962

Action of antidiuretic hormone on the equivalent pore radius at both surfaces of the epithelium of the isolated toad skin.

A previously described method (1) allows the observation of swelling and shrinking of the epithelial cells of the isolated toad skin, when the solution bathing either the outer or inner side of the skin is modified. Thus, the concentration of probing molecules of graded size, isotonic to the epithelial cells, across each face of the isolated toad skin can be determined. These concentrations have been used for the estimation of the equivalent pore radius at the outer and inner face of the skin epithelium, following the approach of Goldstein and Solomon for red cells (3). An equivalent pore radius of 4.5 A for the outer surface, and one of 7 A for the inner surface have been obtained. Antidiuretic hormone had an effect only when added to the inner side. This effect was only at the outer surface and is interpreted as widening of the 4.5 A pores to about 6.5 A. A model membrane, formed by narrow and wide pores in series, may explain some of the apparent inconsistencies previously observed.

Animals↗
PubMed1960

Perception of apparent motion in the common toad.

A simple and inexpensive apparatus makes possible the feeding of nonliving objects to the toad. The device is used to demonstrate the perception of apparent or "induced" motion. Two methods are successful: (i) toad and food moving together at a constatnt velocity in a stationary environment; (ii) toad and food stationary with the environment moving. The phenomena are similar to those found in human beings.

Animals↗
PubMed1962

Parotoid secretions of Indonesian toads.

A preliminary study of the parotoid secretions of Bufo melanostictus and B. asper shows that a methanol extract is rich in digitalis-like bodies (bufo-dienolides) and that an acid extract contains indolethylamine derivatives.

Animals↗