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C Ripoll

Publications and source records attributed to C Ripoll.

48 records · Page 3Linked to original sources
PubMed1992

Anthroylcholine bromide: a fluorescent ligand for the muscarinic receptor.

The action of anthroylcholine bromide, a new fluorescent probe, has been studied at the cellular (contraction of intestinal muscle) and subcellular levels (binding of 3H-quinuclidinyl benzilate to brain cortex membranes, fluorescence and enzyme activity) with the following results: 1. Anthroylcholine bromide competitively antagonized the contractile effect of acetylcholine in isolated rat duodenum (pA2 = 6.12), but had no effect either on the concentration response curves to histamine or to noradrenaline in isolated guinea pig ileum and rat vas deferens. 2. Anthroylcholine bromide displaced competitively 3H-quinuclidinyl benzilate from brain cortex membranes (Ki = 0.77 mumol/l). 3. Direct binding to the muscarinic site could be measured by exploiting the fluorescence properties of the probe. Binding displaceable by atropine (approximately 20% change in fluorescence) had an apparent affinity constant similar to that found with indirect methods. In contrast, d-tubocurarine did not displace the probe from its site, and atropine- or d-tubocurarine-sensitive binding of anthroylcholine bromide to Torpedo marmorata electric organ membranes, rich in nicotinic receptors, was not observed. These properties suggest the applicability of the probe to study the distribution, structure and/or kinetic properties of the muscarinic receptor.

Acetylcholine↗
PubMed1991

Lithium transport in the mouse brain.

Using the stable isotopes of lithium 6Li and 7Li, and the nuclear reaction 6Li(n,alpha)3H for detection, we have studied the isotopic exchange of lithium in various areas of the mouse brain and in the mouse plasma, under conditions of constant concentration of total lithium. The neutron irradiations were performed using 'cold' neutrons, at the European Institute Von Laue-Langevin. The nuclear reaction track densities were determined using an automatic image analyser. In the plasma, the isotopic ratios, 6Li/7Li, were measured using 'Secondary Ion Mass Spectrometry'. The concentration of total lithium in the plasma was kept close to 0.28 mM. The brain concentration of total lithium (referred to the tissue water content) ranged from more than 2 mM in the thalamus to less than 0.65 mM in the white matter of the cerebellum. The Nernst potential of lithium thus ranged from approx. -50 to approx. -20 mV, which means that lithium is probably not far from electrochemical equilibrium between brain cells and plasma. At any moment, the isotopic abundance of 6Li (ratio of 6Li to total lithium) in the different brain areas, were not significantly different from one another. The time-course of the isotopic abundance of 6Li in the brain was fitted by the composition of two exponential terms. The time-course of the isotopic abundance of 6Li in the plasma was also fitted by the composition of two exponential terms. These analytic curves (for the brain and for the plasma) were not significantly different from each other, at the precision of the measurements. This means that the isotopic equilibration of lithium between brain and plasma is almost instantaneous (i.e. accomplished in a few min at the most).

Animals↗
PubMed1991

ATP-sensitive potassium channel modulation of the guinea pig ventricular action potential and contraction.

The role of ATP-sensitive potassium (KATP) channels in modulating the action potential and contraction of guinea pig ventricular myocytes was investigated. Under voltage clamp, the maximum whole-cell KATP channel conductance was estimated (195 +/- 10 nS, n = 6) by exposing the cells to complete metabolic blockade (2 mM cyanide in the presence of 10 mM 2-deoxy-glucose). In isolated inside-out membrane patches, the ATP dependence of KATP channel activity under relevant conditions was measured (half-maximal inhibition at 114 microM). Under current clamp (with intracellular ATP concentration = 5 mM), the effect of graded KATP channel activation on the action potential and the twitch was estimated by injection of a current (proportional to voltage) that simulated the KATP conductance. As this "conductance" was increased, the action potential was shortened, and contractile amplitude declined, as expected. From the results of these experiments, the quantitative dependence of the action potential duration on intracellular ATP concentration was estimated, without relying on a mathematical model of the cell membrane. The results imply that KATP-dependent action potential shortening is likely to occur if ATP concentration falls below normal levels (approximately 5 mM), as may happen regionally, or globally, during myocardial ischemia.

Action Potentials↗
PubMed1990

[Immunolocalization of parvalbumin in two glutamatergic cell types of the guinea pig cochlea: inner hair cells and spinal ganglion neurons].

Immunoreactions to a monoclonal antibody raised against parvalbumin, a calcium-binding protein, have been detected in the inner hair cells of the organ of Corti and in the spiral ganglion neurons connected to them (type I neurons). Both cell types probably use an excitatory amino acid as a neurotransmitter (glutamate and/or aspartate). No immunoreactivity was found within the second sensory cell type (outer hair cells) nor in the olivocochlear (efferent) fibers or endings in the cochlea. In the central nervous system, parvalbumin may be involved in calcium-dependent mechanisms leading to neurotransmitter release. It could thus be hypothesized that parvalbumin also have similar implications at the level of the inner hair cell and type I neuron synapses. Additional functions could also be hypothesized for this protein in the cochlea. Within the inner hair cells, parvalbumin may be involved in the ionic regulation following potassium entry during the transduction process. Within type I neurons, by buffering sudden increases in the intracellular calcium concentration, it may allow an adaptation of the firing rate to variations in the intensity of sound stimuli.

Animals↗
PubMed1990

Modulation of ATP-sensitive K+ channel activity and contractile behavior in mammalian ventricle by the potassium channel openers cromakalim and RP49356.

We have investigated the effects of potassium channel opening drugs on the ATP-dependence of ATP-sensitive K+ channel activity and on contractile activity in rat and guinea pig ventricular myocytes. The results show that cromakalim (BRL34915), and RP49356, agents reported to open ATP-sensitive K+ channels, do so by shifting the intracellular [ATP] required to cause half-maximal inhibition of channel activity (ki) to higher [ATP]. In guinea pig ventricular myocytes at 37 degrees C, the ki was shifted from 79 to 152 microM by 40 microM cromakalim and, in rat myocytes at room temperature, the ki was also shifted to higher [ATP] by 50 microM RP49356. The effect of externally applied RP49356 on the contractile activity of intact rat ventricular myocytes was investigated. At 100 microM the drug was without effect in the presence of normal bathing solution containing 10 mM glucose. When glucose in the bathing medium had been replaced by 2-deoxyglucose for 84 +/- 2 min, 100 microM RP49356 decreased the twitch amplitude to 23 +/- 4% of control. The negative inotropic effect of 100 microM RP49356 increased with time after perfusion with 2-deoxyglucose, and the negative inotropic effect diminished on reperfusing with glucose; 83 +/- 3 min after reperfusing with glucose, twitch amplitude was decreased by only 52 +/- 6% on exposure to 100 microM RP49356. These results suggest that the effect of the potassium channel opening drugs on contractility and electrical behavior will depend critically on the intracellular [ATP]. The results provide an explanation of how potassium channel openers may become clinically useful as cardioprotective agents without interfering with normal function.

Adenosine Triphosphate↗
PubMed1988

Evidence that muscarinic potentiation of insulin release is initiated by an early transient calcium entry.

The increased insulin release induced by carbamoylcholine (CbCh) in pancreatic islets requires the presence of extracellular Ca2+. Intracellular recordings demonstrate that CbCh produces a transient increase in Ca2+ channel activity lasting from 30 to 60 s. Thereafter activity decreased to levels lower than in controls. When extracellular Ca2+ was present during this initial period, the stimulatory effects of CbCh were not different from those in which Ca2+ was present throughout. These experiments suggest that during muscarinic potentiation of insulin release extracellular calcium is only needed in the first minute.

Animals↗
PubMed1985

[Compartmental analysis of 6Li/7Li isotope exchange in equilibrium conditions in mouse plasma].

The compartmental analysis of lithium in the mouse plasma has been performed using the stable isotopes, 6Li and 7Li, as tracers. The animals were kept under stationary conditions (concentration of total lithium in plasma maintained equal to 0.28 mM) during the experiment. The isotopic exchange, 6Li/7Li, was described to a good approximation by combining two first-order processes (characteristic parameters: 89 microM and 2.071 X 10(-3) X min-1 for the first one, and 193 microM and 2.215 X 10(-4) X min-1 for the second one). From these kinetic data, it was estimated that the lithium capacities of the plasma and of the cells were 282 and 454 nmol X ml-1, and that the unidirectional fluxes of lithium between plasma and cells and through the kidneys were 0.259 and 0.227 nmol X ml-1 X mn-1. Since the method makes use only of stable, hence harmless, isotopes, one might think of extending it to direct experimentation in man.

Animals↗
PubMedDate not supplied

Hypothesis: hyperstructures regulate bacterial structure and the cell cycle.

A myriad different constituents or elements (genes, proteins, lipids, ions, small molecules etc.) participate in numerous physico-chemical processes to create bacteria that can adapt to their environments to survive, grow and, via the cell cycle, reproduce. We explore the possibility that it is too difficult to explain cell cycle progression in terms of these elements and that an intermediate level of explanation is needed. This level is that of hyperstructures. A hyperstructure is large, has usually one particular function, and contains many elements. Non-equilibrium, or even dissipative, hyperstructures that, for example, assemble to transport and metabolize nutrients may comprise membrane domains of transporters plus cytoplasmic metabolons plus the genes that encode the hyperstructure's enzymes. The processes involved in the putative formation of hyperstructures include: metabolite-induced changes to protein affinities that result in metabolon formation, lipid-organizing forces that result in lateral and transverse asymmetries, post-translational modifications, equilibration of water structures that may alter distributions of other molecules, transertion, ion currents, emission of electromagnetic radiation and long range mechanical vibrations. Equilibrium hyperstructures may also exist such as topological arrays of DNA in the form of cholesteric liquid crystals. We present here the beginning of a picture of the bacterial cell in which hyperstructures form to maximize efficiency and in which the properties of hyperstructures drive the cell cycle.

Bacteria↗
PubMedDate not supplied

Hantavirus reservoir hosts associated with peridomestic habitats in Argentina.

Five species of sigmodontine rodents have been identified in Argentina as the putative reservoirs of six circulating hantavirus genotypes. Two species of Oligoryzomys are associated with the genotypes causing hantavirus pulmonary syndrome, Oligoryzomys flavescens for Lechiguanas and O. longicaudatus for Andes and Oran genotypes. Reports of human cases of hantavirus pulmonary syndrome prompted rodent trapping (2,299 rodents of 32 species during 27,780 trap nights) at potential exposure sites in three disease-endemic areas. Antibody reactive to Sin Nombre virus was found in six species, including the known hantavirus reservoir species. Risk for peridomestic exposure to host species that carry recognized human pathogens was high in all three major disease-endemic areas.

Animals↗
PubMedDate not supplied

[Osteoporosis and inflammatory bowel disease].

Inflammatory bowel disease is a chronic disease with an unknown ethiology although multiple factors intervene such as individual, genetic and immunologic susceptibility, as well as different environmental factors. Like other multisystemic diseases, its clinical manifestations are diverse and it may affect other organs besides the gastrointestinal tract. In the last few years there is a growing interest for one of these extraintestinal manifestations, osteoporosis and osteopenia that may affect up to 42% of patients and can condition an important increase in morbility. Inactivity, prolonged corticosteroid treatment, nutritional deficiencies and the disease per se have an important role in the development of this complication. This article reviews clinical and ethiological aspects of inflammatory bowel disease associated osteoporosis and offers a strategy for diagnosis and treatment.

Absorptiometry, Photon↗