PubMed Health⌕ Search

Biomedical subjects

T Yorio

Publications and source records attributed to T Yorio.

88 records · Page 5Linked to original sources
PubMed1977

The permeability of the skin of a neotenous urodele amphibian, the mudpuppy Necturus maculosus.

1. The permeability of the isolated skin of a neotenous urodele amphibian, the mudpuppy Necturus maculosus, to Na, Cl, urea and water was measured. 2. Unidirectional transcutaneous flux measurements and the action of ouabain and amiloride, showed that there was normally no active Cl or Na transport, nor a Cl/Cl exchange diffusion process. 3. Amphotericin B initiated a transcutaneous potential difference and short-circuit current, which could be inhibited by ouabain. 4. The short-circuit current was nearly equivalent to the net Na Transport and this was also inhibited by ouabain. 5. A transcutaneous active Na transport mechanism thus appears to be incipient in the mudpuppy but is limited by a low permeability of the outer barrier of the cells. 6. Vasotocin increased the skin's diffusion permeability for water but had no effect on the influx of Na or urea. 7. The function of Necturus skin is in several respects unique compared to that of other amphibians.

Amiloride↗
PubMed1977

Permeability of the rabbit colon in vitro.

The rabbit colon, in vitro as everted-sac or diaphragm preparations, exhibits a transmural PD, as high as 70 mV, a short-circuit current (SCC) of 100 to 150 muA cm-3 and a resistance of 300-500 omega-cm2. It maintains these functions for at least 3 h. The SCC can be abolished by amiloride or increased by amphotericin B. Na, Cl, and K flux measurements showed a net influx (mucosa to serosa) of Na and a net efflux of K. The SCC can be accounted for by the movements of these ions. The SCC in the presence of amphotericin B was nearly equivalent to the net Na flux. Amiloride abolished the net Na transfer but did not ht (Ktrnas X 10(7)) for water was 5,000 cm s-1 while that for urea was 26 cm s-1. The rabbit provides a viable pn and the present observations appear to be consistent with its physiological role.

Amiloride↗
PubMed1977

Asymmetrical permeability of the integument of tree frogs (Hylidae).

The skin from four species of North American tree frogs (Hylidae) was found in vitro, to be remarkably permeable to water in the presence or absence of the neurohypophysial hormone vasotocin. This property was, however, only seen in preparations from the ventral integument; osmotic water movement across the dorsal skin was negligible. The ionic permeability, reflected by the electrical resistance, was also much greater in the ventral skin. Unidirectional fluxes of 22Na, 36Cl, 14C-urea and tritiated water were measured in vitro in a single species, Agalychnis dacnicolor Cope. The ventral skin was 10-20 times more permeable to these molecules than the dorsal skin. The short-circuit current (usually reflecting active transmural Na transport) across the ventral skin was increased by aldosterone and vasotocin but these responses were absent on the dorsal side. The lipid content of the dorsal skin was four times greater than that on the ventral surface.

Aldosterone↗
PubMed1977

The mode of action of bumetanide: inhibition of chloride transport across the amphibian cornea.

The diuretic drug bumetanide (10(-7 M) reduced the transmural potential difference and short-circuit current across the amphibian cornea in vitro. This effect reflected a decline in the outflux (endothelial to epithelial, or tear, side) of CI, which is the direction of its active transport. There was no change in the influx. The effect was slowly reversible at 10(-4) M and was about two times as great when the drug was on the endothelial as compared to the epithelial side. Furosemide had a similar effect on CI transport, but the dose-response curves of the two drugs were not parallel. Furosemide was about 60 to 200 times less potent than bumetanide. The effect of furosemide was about five times as great when the drug was on the endothelial rather than when it was placed on the epithelial side. Thiocyanate (2 x 10(-2) M) also inhibited the active CI transport across the cornea, but it was equally effective on either side of the membrane. Bumetanide had no effect on the passive CI movements across the toad lens or frog skin in vitro. The response of the skin differs from that of furosemide and thiocyanate. These observations of the effects of bumetanide on CI transport may be relevant to the mechanism of its diuretic actions in the kidney tubule.

Animals↗
PubMed1976

Effect of furosemide on unidirectional fluxes of sodium and chloride across the skin of the frog, Rana pipiens.

1. The diuretic furosemide, when added to the outside solution at a concentration of 5-10-4 M, increases the electrical potential difference (PD) across the isolated frog skin, but the short-circuit current (Isc) is unchanged. Lower concentrations had no significant effect on these electrical parameters. 2. When SO42- or NO3- are substituted for Cl- in the Ringer's solution furosemide has no effect on the PD or Isc. 3. Simultaneous unidirectional fluxes of Na+ and Cl- show that furosemide (5-10-4 M outside) reduces both the influx and outflux of Cl-, while the Na+ fluxes are not altered. 4. Furosemide (5-10-4 M) on the corium side of the frog skin had no significant effect on either PD, Isc or undirectional fluxes of Cl-. 5. It is suggested that furosemide reduces passive Cl- transfer, possibly by interacting with the Cl-/Cl- exchange diffusion mechanism which has been observed in this tissue. These observations further suggest that perhaps the diuretic action of furosemide may be mediated by such an effect on passive Cl- permeability which is linked to the active Cl- transport mechanism in the renal tubule.

Animals↗
PubMed1976

The passive permeability of the skin of anuran amphibia: a comparison of frogs (Rana pipiens) and toads (Bufo marinus).

1. Efflux of Na across dorsal skin, in vitro (bathed on both sides with Ringer solution), of frogs and toads were similar, but it was greater in ventral skin from the latter. 2. The efflux of Na declined, in both species, when the external surface of ventral, but not dorsal, skin was exposed to hyposmotic solutions with a low Na concentration. This change in Na permeability was influenced by the low osmotic concentration as well as the low Na concentration. 3. Efflux of Cl was similar in both the dorsal and ventral skin preparations (Ringer on both sides) from frogs and toads. 4. Chloride efflux declined in all skin preparations exposed on the external surface to dilute Ringer solution. Solute replacement with sucrose or choline or Na2SO4 showed that the decreased Cl efflux was principally due to the low Cl concentration, though Na may also contribute. This observation suggests the presence of Cl-/Cl- exchange diffusion mechanism. 5. Cutaneous urea permeability was less in toads than frogs and the dorsal and ventral skin was similar with respect to this solute in each species. 6. The presence of external hyposmotic solutions reduced the efflux, but not the influx, of urea across frog, but not toad, skin and it appeared that solvent 'drag' may contribute to this change. 7. Diffusion permeability to water was greater in frogs than toads and in the latter the ventral skin was more permeable than the dorsal. 8. The passive permeability of amphibian skin shows considerable interspecific and regional differences to various molecules which do not necessarily parallel each other. The control of passive cutaneous permeability appears to involve a variety of specific mechanisms, the distribution of which may have evolved during their adaptation to different environments.

Animals↗
PubMed1976

Effects of ethanol on the permeability of frog skin.

Ethanol (3%) decreases the potential difference and short-circuit current across the isolated frog skin in chloride Ringer's solution. Unidirectional fluxes of Na and Cl indicate that the drop in short-circuit current is due to an inhibition of the sodium influx. However, ethanol had no effect on the electrical parameters or sodium fluxes, when the frog skin was bathed in chloride-free solutions on both sides or the outside alone. The ethanol response is anion-dependent. In addition, chloride-free media in the inside bathing solution reduced the short-circuit current, indicating a sodium transport pathway which is dependent on chloride and confirming previous data in the literature. Other anions such as sulfate and nitrate could not substitute for chloride. The vasopressin-induced natriferic response and the ethanol effect were found to work independently of each other and different pathways of action are suggested for these agents. The intracellular sodium content of the isolated frog skin epithelium increased and potassium decreased in the presence of the Na-K adenosine triphosphatase inhibitor, ouabain, whereas ethanol or amiloride had no effect. The oxygen consumption of the isolated frog skin was unaffected by up to 10% ethanol. A general metabolic action is probably thus not mediating the response. Urea, in iso-osmotic concentrations to the ethanol, did not mimic its effect. Tritiated water fluxes (in the absence of an osmotic gradient) were reduced by 30% in the presence of 3% ethanol. It is suggested that ethanol may impede the flow of water across frog skin by a physicochemical interaction with membrane pores and the water molecules. The permeability coefficient (Ktrans) for ethanol was found to be 10 times smaller than the Ktrans for water.

Animals↗
PubMed1976

Effects of ethanol on the permeability of toad urinary bladder epithelium.

Ethanol (9%) decreases the potential difference across the toad bladder when present at the mucosal surface, the short-circuit current was unchanged. The electrical resistance decreased indicating a change in ion movements across the bladder. Unidirectional 22Na and 36Cl flux measurements showed an increase in the movement of Cl, but no change in Na. The vasopressin-induced increase in Na transport (natriferic response) was also unaffected by the presence of ethanol. It is suggested that ethanol may be altering the apical tight junctions and affecting an anion selective pathway. The hydro-osmotic response of the toad bladder to vasopressin was decreased by 70% in the presence of 3% ethanol. The hydro-osmotic action of cyclic adenosine monophosphate was also inhibited by ethanol, indicating an action subsequent to the endogenous formation of this nucleotide. Tritiated water fluxes (in the absence of an osmotic gradient) were reduced by 30% in the presence of 3% ethanol. The vasopressin-induced increase in diffusional water flow was similarly reduced. Osmotic water movements across glutaraldehyde and N-ethylmaleimide-"fixed" vasopressin-stimulated bladders were also decreased in the presence of ethanol. However, 3% ethanol had no effect on osmotic water transfer across artificial collodion membranes. Ethanol, therefore, probably interacts with the bladder membrane. The Ktrans (permeability coefficient) of ethanol and water is increased by vasopressin. suggesting that their movement is through similar pathways. It is suggested that ethanol empedes the flow of water across the toad bladder by facilitating a physicochemical interaction between the membrane "pore" and the water molecules.

Animals↗
PubMed1975

Effects of cadmium of the hydro-osmotic and natriferic responses to the toad bladder to vasopressin.

Cadmium, 10(-3) mol/l on the mucosal or 10(-5) mol/l on the serosal side of the toad urinary bladder, inhibits the hydro-osmotic effect of vasopressin. This inhibition is irreversible. The osmotic transfer of water in the absence of vasopressin was unaffected by the presence of the Cd2+. The hydro-osmotic response to cyclic AMP was also reduced by the Cd2+, but the response due to hypertonicity of the serosal bathing solution was unaffected. The short-circuit current (reflecting active transmural Na+ transport) was inhibited by 10(-3) mol Cd2+/l on the serosa, but was increased by 10(-3) mol/l at the mucosa or 10(-4) mol/l at the serosa. The natriferic response of the bladder to vasopressin was unaffected when Cd2+ was present under conditions that inhibited the hydro-osmotic response, further emphasizing that separate effector mechamisms may be involved for each effect.

Animals↗