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Biomedical subjects

C Bravo

Publications and source records attributed to C Bravo.

At least 73 records · Page 4Linked to original sources
PubMed1988

Silymarin-induced mitochondrial Ca2+ release.

The effect of silymarin on different functions of mitochondria isolated from rat kidneys was studied. Addition of silymarin to mitochondria oxidizing succinate, induced stimulation of the respiratory State 4; while in mitochondria oxidizing NAD-dependent substrates, the drug produced inhibition of the oxygen consumption. It is also shown that silymarin induces mitochondrial swelling, a drop in the transmembrane potential, as well as Ca2+ release. It is proposed that due to its hydrophobic character, silymarin produces an alteration in the lipidic milieu of the inner membrane which is conductive to an inhibition of the electron transport in the NAD-CoQ span of the respiratory chain, as well as to the loss of the energy dependent accumulated Ca2+.

Animals↗
PubMed1987

Metabolite transport in mitochondria as a function of osmolarity.

The effect of increasing sucrose concentrations on some mitochondrial functions was studied. The results showed that high osmolarity inhibits oxidative phosphorylation as well as ATPase activity and ATP-dependent delta phi formation as a consequence of adenine nucleotide translocase inhibition. It is also shown that high osmolarity does not affect delta phi formation and energy-dependent Ca2+ uptake as driven by succinate oxidation. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis of membrane proteins showed a different reactivity to o-phenantroline/Cu2+ as function of osmolarity. It is proposed that high sucrose concentrations induce a collapse of the matrix compartment that results in a restricted diffusion of some metabolites.

Adenine Nucleotides↗
PubMed1987

The mechanism of lead-induced mitochondrial Ca2+ efflux.

Addition of Pb2+ to rat kidney mitochondria is followed by induction of several reactions: inhibition of Ca2+ uptake, collapse of the transmembrane potential, oxidation of pyridine nucleotides, and a fast release of accumulated Ca2+. When the incubation media are supplemented with ruthenium red, the effect of Pb2+ on NAD(P)H oxidation, membrane delta psi, and Ca2+ release are not prevented if malate-glutamate are the oxidizing substrates; however, the latter two lead-induced reactions are prevented by ruthenium red if succinate is the electron donor. It is proposed that in mitochondria oxidizing NAD-dependent substrates, Pb2+ induces Ca2+ release by promoting NAD(P)H oxidation and a parallel drop in delta psi due to its binding to thiol groups, located in the cytosol side of the inner membrane. In addition, it is proposed that with succinate as substrate, the Ca2+ -releasing effect of lead is due to the collapse of the transmembrane potential as a consequence of the uptake of Pb2+ through the calcium uniporter, since such effect is ruthenium red sensitive.

Animals↗
PubMed1987

Effects of discrete medial preoptic hypothalamic lesions on the androgen gonadotropin feedback system in the male rat.

The effect of discrete lesions of the Anterior Medial Preoptic Area of the Hypothalamus (MPOA) in the control of pituitary gonadotropins in the adult male Wistar rat has been studied. Electrolytic lesions were made by passing an anodal current through tungsten electrodes. Electrodes were oriented stereotaxically into the MPOA and lesion placement was histologically checked. In sham controls, electrodes were lowered into the MPOA but no current was applied. Serum LH and FSH were measured by RIA. MPOA lesioned animals showed significantly lower plasma LH (p less than 0.01) in comparison to sham lesioned group. Plasma FSH remained unaltered. To test whether these results were related to an alteration in the negative feedback system, the response to administration of Testosterone Propionate (TP) and the secretion patterns of LH and FSH after castration were analyzed. Administration of TP revealed similar LH and FSH 24 and 48 h decrements and the pattern of LH and FSH secretion after gonadectomy was not significantly different in lesioned and sham lesioned animals. Responsiveness to exogenous LHRH was not impaired by MPOA lesions. The results suggest that neural elements within the MPOA are functionally related to pituitary LH secretion in the male rat. The LH control alteration in lesioned animals is not associated with modifications in negative feedback of androgens and pituitary sensitivity to LHRH remains unaltered.

Animals↗
PubMed1986

On the role of K+ on succinic dehydrogenase activity.

The effect of potassium ions on succinic dehydrogenase activity of mitochondria was studied. The results showed that in these organelles K+ induces inhibition of the respiratory control; moreover, in submitochondrial particles potassium inhibits the rate of oxidation of succinate. The results showed also that K+ does not changes the Km for succinate but diminishes the Vmax. In addition, the data provide evidence that mitochondria oxidizing glutamate-malate in a sucrose medium show a higher activity of succinate dehydrogenase than mitochondria incubated in KCl.

Adenosine Triphosphate↗
PubMed1985

Evidence for the involvement of dithiol groups in mitochondrial calcium transport: studies with cadmium.

The effect of cadmium on some functions of mitochondria isolated from kidneys of rat was studied. Addition of cadmium chloride to mitochondria induced stimulation of both State 4 respiratory rate and ATPase activity, which are prevented by the addition of ruthenium red. We also show that cadmium inhibits competitively calcium translocation; this inhibitory effect of cadmium is reverted by the addition of dithiothreitol. From these results, it is proposed that, similarly to Ca2+, cadmium penetrates mitochondria and binds to a membrane dithiol group, which is essential for the translocation of the cation.

Animals↗
PubMed1985

Ionophoretic-like action of diflunisal.

It is shown that diflunisal, a derivative salicylic acid, causes uncoupling of oxidative phosphorylation owing to its property of carrying hydrogen ions through the inner mitochondrial membrane in such way that a short-circuit of protons is promoted. As a consequence of the above, the drug induces a decrease of the internal negative membrane potential and therefore the release of intramitochondrial calcium. In addition this report presents evidences that diflunisal behaves as a ionophore molecule since it induces cation extraction into an organic phase.

1-Butanol↗
PubMed1985

Activation of mammalian endplate receptors by iontophoretic application of reducing and oxidizing sulphydryl reagents.

The effects of microelectrophoretic application of sulphydryl reagents at both the endplate region and extrasynaptic sites have been studied in the mouse diaphragm neuromuscular preparation. Two groups of sulphydryl reagents have been tested: oxidizing agents and reducing agents. Reagents were applied iontophoretically by means of a microelectrophoretic programmer with constant current source. Both groups of sulphydryl reagents elicit depolarizations only when applied at the endplate region. Presynaptic components were ruled out by addition of magnesium chloride to the bathing medium. After blockade of neuromuscular transmission, the depolarizing effect of both groups of sulphydryl reagents persisted. The present results suggest the presence of reactive disulphide bonds and SH groups in the receptor complex of the mammalian neuromuscular junction. These groups could be located at the alpha subunit of the acetylcholine receptor.

Animals↗
PubMed1985

[Sensitivity of the motor endplate to carbachol in the presence of sulfhydryl reagents].

The effect that bath application of sulphydryl reagents (SR) exerts on frog sartorius motor endplate sensitivity to iontophoretically applied carbachol (CCh) has been studied. Sensitivity to CCh is expressed as the ratio of the CCh potential (mV) to the nanocoulombs delivered by the iontophoretic pulse and has been determined before and after addition of SR to the bath. Two groups of SR have been tested: oxidizing reagents, o-iodosobenzoate and reducing agents, dithiothreitol (DTT). CCh was applied iontophoretically by means of a microelectrophoretic programmer with constant current source. Exposure of the muscle to 1 mM DTT in a bath pH range of 7-8 for 2 to 85 min showed no significant differences in endplate sensitivity to CCh before and after addition of the reducing agent. o-Iodosobenzoate at a 1 mM bath concentration (pH 7) for 2 to 19 min strongly decreases endplate sensitivity to CCh. The statistical methods used were Wilcoxon rank tests and linear regression. Since previous studies have shown that oxidizing and reducing SR evoke depolarizations when applied iontophoretically at the endplate region, these results suggest that activation of the receptor is achieved only when SR are delivered iontophoretically, and that discrepancies observed can be attributed mainly to the different techniques of drug application.

Animals↗
PubMed1983

Preliminary report on a postpartum CuT 200 study, Santiago, Chile.

An analysis is presented of a study of the Copper-T 200 (CuT 200) intrauterine device at the Barros Luco Hospital in Santiago, Chile. The devices were inserted in 1142 postpartum patients. The expulsion rate was high, 32.1% at 3 months. Of the 372 women who expelled devices, 349 received a replacement CuT 200. The expulsion rate for these reinsertions was 7.7% at 12 months with a continuation rate of 86.4%.

Adult↗
PubMed1983

Comparison of T Cu 200 and Progestasert IUDs.

Insertions of the T Cu 200 and the Progestasert IUDs in a total of 400 postpartum women were compared. Insertions were carried out within 10 minutes of delivery, either manually or with an inserter. There was a significant difference in the 6 and 12 month expulsion rates (P0.05) between the 2 groups, but no differences were found related to type of insertion. 12 month expulsion rates for the T Cu hand and inserter groups were 9.0 and 8.1, respectively, and 35.8 and 35.2 for the Progestasert hand and inserted groups, respectively. Overall, significantly fewer Progestasert users reported dysmenorrhea at follow-up and the specific 12 month dysmenorrhea rate was significantly lower for the Progestasert users than for the T Cu users. More women in the Progestasert groups reported intermenstrual spotting and bleeding, but specific 12 month rates of intermenstrual pain, spotting, and bleeding showed no differences between the groups.

Contraception↗
PubMed1974

[Not Available].

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Bolivia↗