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Biomedical subjects

J Concha

Publications and source records attributed to J Concha.

At least 19 recordsLinked to original sources
PubMed1998

Effect of dietary oils, cholesterol and antioxidant vitamin supplementation on liver microsomal fluidity and xenobiotic-metabolizing enzymes in rats.

This study was undertaken to compare the effects of four oils: corn (C), olive (O), hazelnut (H) or fish (F), and the intake of two supplements: cholesterol, 1% (Ch) or dl-alpha-tocopherol acetate, 500 mg/kg, and beta-carotene, 30 mg/kg (V), on liver microsomal fluidity, cyt P450 content and aniline hydroxylase (AH), aminopyrine-N-dimethylase (AND) and UDP-glucuronyltransferase (UDP-GT) activities. Male Sprague-Dawley rats (n = 6/group) were fed semipurified diets containing 15% oil, without or with Ch or V, for 20 days. Dietary intake and feed efficiency were lower in rats fed F. Relative liver weight was higher in animals fed F, similar in O and H, and lower in the group fed C. The intake of V increased feed intake in C+V group and decreased the relative liver weight of F+V group, which also decreased with the intake of F+Ch. Ch intake increased the relative liver weight in all groups consuming vegetable oils. Cyt P450 content was higher in rats fed F. Decreased cyt P450 content was observed in C+Ch and F+Ch groups, while it augmented in H+Ch group. Mixture V increased cyt P450 in rats fed C+V, F+V and O+V. The highest membrane fluidity was observed in rats fed F. Fluidity was also higher in group H versus O or C. The intake of Ch decreased microsomal fluidity in all groups, while V induced an increase in microsomal fluidity in group O+V. Rats fed F exhibited higher enzyme activities. AND activity increased with V only in rats fed H+V, while AH activity increased with V intake in groups F+V and O+V. In the C+V group, fluidity was not affected by V, while the cyt P450 content and UDP-GT activity increased. The O+V group exhibited lower UDP-GT activity and higher fluidity and cyt P450 content. The activity of AH decreased in groups F+Ch and C+Ch. UDP-GT activity was higher in rats fed F. It diminished after the intake of Ch in H+Ch and F+Ch. These results indicate that although AH and AND act in the same microsomal metabolic pathway, their localization into the membrane may be determinant of their activity and the response to dietary lipids. It is shown that F intake exerts the most significant effects upon liver microsomal properties, e.g. higher fluidity, cyt P450 content and enzymatic activities, an effect that prevails over the intake of the supplements tested.

Animals↗
PubMed1996

Influence of nitric oxide on transepithelial transport in toad skin: effects of cholinergic agents and morphine.

The effects induced by L-arginine (L-Arg) on the short-circuit current and potential difference of Pleurodema thaul skin were investigated. L-Arg, but not D-Arg significantly increased the short-circuit current and potential difference when applied to the serosal surface. The effects of L-Arg were antagonized by amiloride, NG-nitro-methyl-L-arginine (L-NAME) and by methylene blue. Carbachol and acetylcholine induced significant increases of both electrical parameters of the toad skin. These effects of the muscarinic cholinergic drugs were potentiated by a low concentration of L-Arg and antagonized by L-NAME or methylene blue. Carbachol and acetylcholine induced significant increases of both electrical parameters of the toad skin. These effects of the muscarinic cholinergic drugs were potentiated by a low concentration of L-Arg and antagonized by L-NAME or methylene blue. Addition of dibutyryl cyclic guanosyl monophosphate (db cGMP) or dibutyryl cyclic adenosine monophosphate (db cAMP) increased short-circuit current and potential difference. The effects of db cGMP, but not those of db cAMP were antagonized by L-NAME. The consecutive application of db cGMP and db cAMP induced additive effects. These results suggest that L-Arg increases transport in toad skin presumably acting through the formation of nitric oxide, which then stimulates cytoplasmic guanylate cyclase and leads to increased Na+ and K+ transport. The effects of L-Arg and carbachol were antagonized by acute application of morphine; however, a rebound response was observed when carbachol or noradrenaline were given after prolonged exposure of the skin to morphine, which suggests an adaptive response of the skin involving both cGMP and cAMP. Responses to both nucleotides were unchanged by morphine.

Acetylcholine↗
PubMed1993

Calcium channel blockers apparently decrease noradrenaline release from nerve-skin terminals in Caudiverbera caudiverbera.

1. The effects of three calcium channel blockers, verapamil, diltiazem and nifedipine were examined on the response of the skin neuroepithelial synapse of the toad Caudiverbera caudiverbera to electrical stimulation. 2. The stimulus induced a significant rise in potential difference (PD) and short-circuit current (SCC). The three calcium antagonists reduced the responses in a dose-dependent manner. The greatest reduction was induced by verapamil followed by diltiazem and nifedipine. 3. Amiloride treatment did not affect the responses to electrical stimulation, indicating that the response to nerve stimulation is not due to current flowing through sodium channels. 4. When the preparation was blocked by either of the three antagonists, the skin response to noradrenaline was not affected. 5. It may be concluded that verapamil, diltiazem or nifedipine reduce the release of noradrenaline at the neuroepithelial synapse of C. caudiverbera.

Amiloride↗
PubMed1991

Stimulatory effect of angiotensin II on electrolyte transport in canine tracheal epithelium.

1. The present study examines the effect of angiotensin11 (A11) on Cl- and Na+ transport in canine tracheal epithelium. 2. A concentration-dependent increase in the potential difference and in short-circuit current of the trachea was found. 3. Frusemide reduced values of Cl- dependent electrical parameters; net Cl- flux from serosa to mucosa accounted for 72% of total short-circuit current. 4. Frusemide, indomethacin and chlorpromazine blocked the stimulatory effect of A11. 5. These reactions show that A11 stimulates ion transport across the canine tracheal epithelium and suggest that two mechanisms may be proposed to explain the action of A11 on Cl- flux: (1) Ca(2+)-dependent increase in intracellular cAMP and (2) increase in Na(+)-2Cl2-K+ Cotransport activity.

Angiotensin II↗
PubMed1991

[Vibration and acoustic stimulation during labor with external monitoring. Pathology of fetal heart rate].

Vibratory acoustic stimulation was done in patients with an abnormal fetal heart rate tracing in external continuous electronic monitoring during labor, correlating with Apgar score, meconium staining and umbilical cord pH, describing a 83.3% sensitivity, 81.3% specificity and 62.5% positive predictive value. The authors recommend the use of vibratory acoustic stimulation in those cases with an abnormal fetal heart rate tracing in external continuous electronic monitoring, when we can not install internal electronic monitoring or obtain a fetal blood pH on assessment of fetal well-being.

Acoustic Stimulation↗
PubMed1990

The action of progesterone on sodium transport of isolated toad skin. Further evidences of a metabolic action.

To understand the mechanism of progesterone inhibition of the sodium influx in the toad skin, the effects of the hormone on the active sodium transport and oxidative metabolism of the transporting cells were examined. A direct relationship was observed between the initial value of the short circuit current and the sensitivity of a given skin toad preparation to progesterone. Progesterone had a higher effect on the sodium potential than on any other parameter of an equivalent electrical circuit of toad skin. Direct measurement of oxygen consumption indicated that progesterone can act as a blocking agent of the respiratory chain of the sodium transporting cells of toad skin.

Animals↗
PubMed1988

Stimulatory effect of angiotensin II on the electric properties of the isolated toad skin.

In 1982 we showed that angiotensin II (Agt II) stimulates the bioelectric properties of the isolated toad skin and that this effect is blocked by pretreatment of the skin with indomethacine [J. B. Concha et al., IRCS Med. Sci. 10, 584 (1982)]. Ussing's technique and several inhibitors were used to continue this study on the isolated Pleurodema thaul skin. Serosal Agt II produced a dose-dependent increase in electrical parameters: a maximal concentration of 6 X 10(-6) M Agt II increased potential difference by 43 +/- 7.8% and short-circuit current by 51.5 +/- 7.7%. The responses were not affected by either alpha or beta blockers or by atropine. Indomethacine blocked responses to the calcium ionophore A23187 and to Agt II which were similar to each other. Additive effects of Agt II and of the calcium ionophore A23187 were found. No response to Agt II was obtained when Ca2+-free Ringer was used on the serosal side. Calcium channel blockers (nifedipine, verapamil, manganese), pentobarbitone and saralasin blocked the response to Agt II. This pharmacological evidence is in favour of the hypothesis that Agt II activates specific membrane receptors, leading to Ca2+ release and formation of prostaglandins which stimulate adenyl cyclase. This increases cAMP secretion, which in turn increases apical membrane permeability to sodium and enhances the active transport system.

Adrenergic alpha-Antagonists↗
PubMed1983

Effects of sodium pentobarbitone on the bioelectric properties of isolated toad skin.

The effects of sodium pentobarbitone on the transepithelial potential difference and on the short-circuit current in the isolated toad skin were studied under different experimental conditions. Pentobarbitone was consistently effective when placed in the solution bathing the inside surface of the skin. The response to small concentrations (1.2, 3.6 and 6.0 x 10(-5) M) was a transient dose-related increase in the transepithelial potential difference and short-circuit current, and a decrease in both parameters at larger concentrations (3.6 x 10(-4) M). Total skin resistance decreased at small and increased at large concentrations. Analysis of the response in terms of the equivalent electrical circuit indicated that in small concentrations the effect was due to an increase in the driving force of the sodium (Na+) pump although the rate of entry of Na+ through the outer barrier was reduced. The activity of (Na+-K+)ATPase was increased within the first 7 min of the effect of pentobarbitone, thus confirming a direct action of the drug on Na+ transport. In large concentrations the electromotive force of the Na+ pump was decreased and inactivation of (Na+-K+)ATPase became evident. The effect of pentobarbitone was unchanged in six reserpinized toads, which would seem to rule out a catecholamine-mediated effect of the drug. The reduction of Na+-influx could indirectly increase transport efficiency since the rate of transport work should be reduced.

Amiloride↗
PubMed1982

Effect of colchicine on the electrophysiological properties of the toad sciatic-gastrocnemius preparations in vivo.

The effects of a single subepineural injection of colchicine on the toad sciatic-gastrocnemius preparation were studied in vivo. The resting membrane potential of the gastrocnemius muscle fibres declined by 15% at day 5. This was followed 2 days later by dispersion and reduction in the amplitude of the compound muscle action potential, decrease in the slope of the accommodation index curve (AI), and a decreased electromyographic interference pattern. These changes were progressive and led to blockage of electrical activity and appearance of pseudodenervation after 2 weeks. Pseudodenervation was confirmed on finding similar alterations in the AI profile in neurotomized toads. In contrast, the hind limbs of toads paralysed by d-tubocurarine had normal muscle AI. The decrease in the AI on the colchicine-treated side was dependent on the length of the severed nerve left attached to the muscle, indicating a centrifugal effect of the drug.

Action Potentials↗
PubMed1981

Electrophysiological effects of methyl 3-O-methyl gallate on single muscle fibres.

The electrophysiological changes induced by methyl 3-O-methyl gallate, a substance extracted from Crinodendron hookerianum, have been studied on 32 muscle fibres of Pleurodema thaul. Four concentrations were used: 1 x 10(-5), 2 x 10(-5), 1 x 10(-4), and 2 x 10(-4) mol/l, the results being a reversible dose-dependent reduction of the overshoot and the amplitude of the action potential, a prolongation of the rise and decay times of the spike, as well as a depolarization of the resting membrane potential. An explanation of these results by a blockade of the potassium and possibly the sodium channels in the cellular membrane is discussed.

Action Potentials↗