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Biomedical subjects

O Quesada

Publications and source records attributed to O Quesada.

25 records · Page 2Linked to original sources
PubMed1984

Effect of guanidinoethane sulfonate on taurine uptake by rat retina.

Guanidinoethane sulfonate (GES) markedly decreased 3H-taurine accumulated in the retina by the high-affinity uptake process. The effect of GES was dose-dependent. Analysis of the kinetics of GES effect revealed that it is a competitive inhibitor. The uptake of taurine by GES was less affected in rat cerebral cortex slices, where the inhibition by 1 mM GES was only 28%. Taurine accumulation by tissues of rats treated with GES (0.1% and 1% in the drinking water) was found to be particularly decreased in the retina, although accumulation by heart and liver was also affected by the higher dose. Taurine uptake by cerebellum and cerebral cortex slices was unaffected by GES. Treatment of rats with GES is known to produce an alteration in the structure and function of the retina, but apparently not in other organs. We discuss whether the marked effect of GES on taurine transport by the retina is related to the deleterious effect of the inhibitor in this organ.

Animals↗
PubMed1983

Effects of the taurine transport antagonist, guanidinoethane sulfonate, and beta-alanine on the morphology of rat retina.

Newborn rats treated for the first weeks of life with guanidinoethane sulfonate (GES), a blocker of taurine transport producing taurine depletion, showed a severe disruption of photoreceptor structure. Photoreceptor damage consisted of a marked reduction of the size of the photoreceptor layer, deformation of the outer segments, and a profound disorganization of the disc membranes. The GES-induced degeneration pattern was very similar to that observed in cats fed a taurine-deficient diet. Injection of beta-alanine, another antagonist of taurine transport, also produced a disruption of photoreceptor structure. These results confirm the requirement of taurine for maintaining photoreceptor structure in different species.

Alanine↗
PubMed1982

Minimal nephrotoxicity with cephalosporin-aminoglycoside combinations in patients with neoplastic disease.

Patients with cancer and suspected sepsis were treated in a prospective, randomized trial with one of four cephalosporin-aminoglycoside combinations: cephalothin and tobramycin; cephalothin and gentamicin; cefamandole and tobramycin; or cefamandole and gentamicin. Carbenicillin was added if the absolute granulocyte count was less than 1,000/mm3. Of 199 patients receiving 20 to more doses of an aminoglycoside and having serial determination of serum creatinines, nephrotoxicity developed in seven (3.5%) given any of the four combinations. There were no significant differences between patients receiving either cephalosporin or either aminoglycoside. Nephrotoxicity developed less frequently among children (2 or 125; 1.6%) than adults (5 of 74; 6.8%).

Adolescent↗
PubMed1981

Protective effect of taurine on the light-induced disruption of isolated frog rod outer segments.

Isolated frog rod outer segments (ROS) incubated in a Krebs-bicarbonate medium, and illuminated for 2 h, show a profound alteration in their structure. This is characterized by distention of discs, vesiculation, and a marked swelling. The light-induced ROS disruption requires the presence of bicarbonate and sodium chloride. Replacement of bicarbonate by TRIS or HEPES protects ROS structure. Also, substitution of sodium chloride by sucrose or choline chloride maintains unaltered the ROS structure. Deletion of calcium, magnesium, or phosphate does not modify the effect produced by illumination. An increased accumulation of labeled bicarbonate and tritiated water is observed in illuminated ROS, as compared with controls in the dark. The presence of taurine, GABA, or glycine, at concentrations of 5-25 mM, effectively counteracts the light-induced ROS disruption. Taurine (25 mM) reduces labeled bicarbonate and tritiated water levels to those observed in the dark incubated ROS.

Animals↗
PubMed1981

Light-stimulated release of taurine from retinas of kainic acid-treated chicks.

The light-stimulated release of [3H]taurine from chick retina was studied in chicks intraocularly injected with kainic acid (60 nmol). This treatment produced a loss of more than 80% of the inner nuclear and the inner synaptic layers, sparing the outer retinal layers. Concomitantly, the treatment produced a marked decrease of endogenous GABA and glycine but not of taurine. The activity of glutamate decarboxylase was also markedly decreased in the kainic acid-treated retinas. The release of [3H]taurine, either spontaneous or stimulated by light, was unaffected by the treatment. These results suggest that the light-stimulated efflux of taurine occurs from the retinal layers which are not affected by the kainic acid treatment.

Amino Acids↗
PubMed1980

Effects of the ionophores X537A and A23187 on GABA, glycine, and taurine release from chick retinal subcellular fractions.

The ionophore X537A at concentrations of 5--20 microM stimulated the release of [3H]GABA and [35S]taurine from retinal subcellular crude nuclear (P1) and crude synaptosomal (P2) fractions. The release of [3H]GABA increased 114% and 136% over control values in P1 and P2 fractions, respectively. The efflux of [35S]taurine from P1 was increased by 45% and that from P2 by 21%. X537A increased 45Ca2+ uptake in the P2 fraction but not in the P1 fraction. The effect of X537A on the amino acid release was not dependent on the presence of exogenous calcium. X537A did not affect [3H]GABA or [35S]taurine uptake by the retinal fractions. A23187 enhanced [3H]GABA release from P1 and P2 by 52% and 105%, respectively. The ionophore also increased [14C]glycine liberation in both P1 (35%) and P2 (50%) but failed to stimulate [35S]taurine release. A23187 produced a transient increase of 45Ca2+ uptake of 38% in P1 and 30% in P2. The effects of A23187 on the release of amino acids were calcium dependent. The amino acid uptake was not affected by the ionophore. These results are consistent with the suggested neurotransmitter role for GABA at the outer synaptic layer and for GABA and glycine at the inner synaptic layer of the retina. A neurotransmitter role for taurine is not supported by the present results.

Animals↗