Biomedical subjects

S M Sanioto

Publications and source records attributed to S M Sanioto.

7 recordsLinked to original sources

PubMed1996

Effect of oxytocin on transepithelial transport of water and Na+ in distinct ventral regions of frog skin (Rana catesbeiana).

Thoracic, abdominal, and pelvic fragments of ventral skin of Rana catesbeiana were analysed regarding the effect of oxytocin on: (1) transepithelial water transport; (2) short-circuit current; (3) skin conductance and electrical potential difference; (4) Na+ conductance, the electromotive force of the Na+ transport mechanism, and shunt conductance; (5) short-circuit current responses to fast Na+ by K+ replacement in the outer compartment, and (6) epithelial microstructure. Unstimulated water and Na+ permeabilities were low along the ventral skin. Hydrosmotic and natriferic responses to oxytocin increased from thorax to pelvis. Unstimulated Na+ conductance was greater in pelvis than in abdomen, the other electrical parameters being essentially similar in both skin fragments. Contribution of shunt conductance to total skin conductance was higher in abdominal than in pelvic skin. Oxytocininduced increases of total skin conductance, Na+ conductance, and shunt conductance in pelvis were significantly larger than in abdomen. An oscillatory behaviour of the short-circuit current was observed only in oxytocin-treated pelvic skins. Decrease of epithelial thickness and increase of mitochondria-rich cell number were observed from thorax to pelvis. Oxytocin-induced increases of interspaces were more conspicuous in pelvis and abdomen than in thorax.

Animals↗

PubMed1994

Effect of crude extract of roots of Bredemeyera floribunda Willd. I. Effect on arterial blood pressure and renal excretion in the rat.

The infusion of the dried roots of Bredemeyera floribunda Willd. is used in Brazilian popular medicine as a potent diuretic, especially in the treatment of hypertension and nephrolithiasis (renal calculi). Intravenous administration of crude root-extract (20-80 mg/kg) to anesthetized rats induces clear dose-dependent and reversible hypotensive responses. At higher doses the extract leads to bradycardia and death. In doses that do not alter the arterial blood pressure, the extract elicited immediate and dose-dependent reversible increase of water, sodium, and potassium renal excretion. The results, apart from indicating that the renal effect of the extract is not due to its systemic hypotensive action, support the folk therapeutic use of the infusion of the root-extract as a diuretic.

Animals↗

PubMed1994

Effect of crude extract of roots of Bredemeyera floribunda Willd. III. Effect on hormone-stimulated water transport in isolated frog skin.

The diuretic activity of the crude extract of roots of Bredemeyera floribunda Willd. (Polygalaceae) was investigated on basal and hormone-stimulated absorptive water transport in the isolated frog skin. The extract, added to the mucosal skin surface, at the peak of oxytocin (Oxy) action induces steady and dose-dependent reduction of water transport. Pre-treatment of the skins during 2 h with the extract, added to mucosal skin surface, renders the epithelium non-responsive to oxytocin. These effects are not observed when the extract is added to the serosal skin surface. Basal water transport is not altered by the extract. The results, apart from indicating inhibition of the oxytocin-stimulated water transport in frog skin epithelium, support the folk therapeutic use of infusion of the root extract as a diuretic.

Animals↗

PubMed1987

Structural and functional response of the isolated toad skin to mucosal lithium.

Structural and functional changes induced by long-term Li-exposure of the outer surface of toad skin was studied. Electron microscopy revealed that total Na by Li replacement in the outer compartment of short-circuited toad skin promotes a conspicuous cellular damage expressed as focal swollen cells with altered intercellular spaces and nuclear morphology. Short-circuit current (SCC) decreases by about 70% over the first 60 min after 115 mmol/l Li-exposure. An amiloride sensitive transepithelial Li transport remains intact over a further 150 min despite the epithelial damage, indicating that the pathways across the apical barrier are functioning. Increase of the paracellular permeability is detected by elevation of Na-efflux. Partial 50% or 10% Na by Li replacements induce minor structural alterations and are not sufficient to trigger appreciable Na-efflux and SCC alterations. Therefore, low Li concentrations are less effective than 115 mmol/l in promoting morphofunctional responses. Although ouabain and Li reduce the SCC, ouabain does not promote structural lesions, showing that Li-inhibition of Na transport by itself is not responsible for the observed morphological alterations. In the light of this study, Li utilization as a tool to investigate transepithelial Na transport requires careful judgement.

Animals↗

PubMed1985

Lack of PCMB action upon the outer barrier sodium permeability in the absence of Na in toad skin.

The stimulation of apical Na permeability by p-chloromercuribenzoate (PCMB) was evaluated by studying its effect on unidirectional 24Na flux (JNaeff) from inner to outer compartment in the isolated short-circuited toad skin. With Na present in the inner compartment, addition of PCMB to the outer skin surface led to an increase of JNaeff. However, after replacing all Na of the inner compartment by K or choline, the amiloride inhibitable Na permeability of the outer cell membrane increased, and PCMB was no longer effective. It is concluded that PCMB releases the blocking effect of intracellular Na on apical Na channels. If intracellular Na is drastically reduced virtually all Na channels are opened so that PCMB does no longer act.

Amiloride↗

PubMed1983

Cellular Li+ opens paracellular path in toad skin: amiloride blockable effect.

The presence of Li in the solution bathing the outer surface of toad skin under short-circuit condition promotes an unspecific permeability increase characterized by a delayed and progressive increase in the effluxes of 24Na, 42K and 14C sucrose. The effect of Li upon sucrose permeability might indicate an increased permeability of the paracellular pathway. The Li effect is mediated by an intracellular action since blockade of Li entrance into the cell compartment by amiloride prevents the increase in Na, K and sucrose permeability. A possible mechanism of this effect is discussed in terms of a disturbance in the cellular Ca++ balance leading to an increase in cytosolic Ca++ concentration which perturbs the organization of the cytoskeleton and the interplay between cytoskeleton and tight junctions.

Amiloride↗

PubMed1977

Thiamine pyrophosphokinase activity in liver, heart and brain crude extracts of control and thiamine deficient rats.

The activity of thiamine pyrophosphokinase has been measured in liver, heart muscle and brain of normal and thiamine deficient rats. The activity measurement has been performed by use of thiamine-35S as substrate and separation of the reaction products by high voltage electrophoresis. KM has been determined as 7.1.10(-6) mol/l. The activity of thiamine pyrophosphokinase is reduced in liver and heart muscle of thiamine deficient rats significantly, whereas no decrease of the enzyme activity has been found in the brain. The content of thiamine pyrophosphate has been measured in the liver of normal and thiamine deficient rats. Injection of thiamine to deficient rats normalized the content of thiamine pyrophosphate in the liver within 6 hours. Our data suggest that thiamine pyrophosphokinase is an adaptive enzyme, the activity of which depends on the thiamine content of the cells.

Animals↗