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Biomedical subjects

A Marty

Publications and source records attributed to A Marty.

At least 73 records · Page 4Linked to original sources
PubMed1991

Arterial stent placement with use of the Wallstent: midterm results of clinical experience.

Self-expandable stents of the Wallstent type were used in 26 iliac and 15 femoropopliteal artery lesions of 31 patients to treat stenoses or occlusions. The indications were confined to complex lesions, including residual stenoses and dissections after percutaneous procedures or previous surgery in the iliac artery lesions, and long-segment (mean, 13.5 cm) occlusions with inadequate response to percutaneous recanalization in the femoropopliteal artery lesions. In the iliac artery group, after stent placement, 96% of the lesions were patent at a mean follow-up of 16 months (range, 6-30 months). In the femoropopliteal artery group, of 11 patients available for follow-up, only six had patent stents at 7-26 months (mean, 20 months). Four of these six patients required one to three secondary interventions. Self-expanding endoprostheses are of great value in complex iliac artery lesions where simple balloon dilation is insufficient. Stent placement for long femoral artery lesions should be performed with utmost reserve, and the extent of stent placement should be as short as possible.

Aged↗
PubMed1989

The physiological role of calcium-dependent channels.

Calcium (Ca2+)-dependent channels may be classified in three broad categories, which are, respectively, selective for potassium ions, for chloride ions, and for monovalent cations. The usual action of Ca2+ is to increase the probability of opening of the channels, but examples of the reverse, Ca2+-induced inhibition of ion channels, have recently been found. Ca2+-dependent channels help to shape the action potentials of excitable cells as well as the synaptic currents of muscular and neuronal preparations. They are involved in several aspects of electrolyte transport including regulation of osmolarity in animal cells and of turgor in plant cells, electrolyte secretion in exocrine glands, fluid absorption and secretion in epithelial tissues.

Action Potentials↗
PubMed1989

Diffusion into the patch-clamp recording pipette of a factor necessary for muscarinic current response.

Ca-dependent K and Cl currents were measured in isolated cells from rat lacrimal glands using the tight-seal whole-cell recording method. Upon application of acetylcholine (ACh), both K and Cl-selective currents were activated. The size of the ACh-activated currents declined after a few minutes of whole-cell recording. The rundown curve was composed of an initial stable period followed by a rather rapid decline. Both the length of the initial plateau and the speed of the falling phase were dependent on cell size and recording pipette resistance. The results suggest that the rundown was due to washout of an unknown cytosolic substance. Another manifestation of washout was an increase in the delay of the response. Plots of the inverse of the delay as a function of time in whole-cell recording showed again an initial plateau and a falling phase, but the stable period lasted less than in amplitude plots. Analysis of the washout time course suggested that the cytosolic substance has a diffusion coefficient of 5.4 x 10(-6) cm2/s, corresponding to a molecular weight of 350. Washed-out cells were insensitive to GTP-gamma-S, but responded normally to an internal application of inositol-trisphosphate (InsP3), introduced through the pipette. Thus, the step of the response which is sensitive to washout is closely related to the production of InsP3. Addition of various exogenous water soluble substances failed to halt washout. Among the inactive substances were GTP (or a combination of Mg and GTP) and small water soluble precursors of InsP3. The results imply that the production of InsP3 by muscarinic agonists in exocrine glands requires the presence of a small molecular weight, water soluble substance. It is suggested that this substance is an unknown co-factor of phospholipase C or of Gp, the GTP binding protein governing the production of InsP3.

Acetylcholine↗
PubMed1989

Measurement of Na-K pump current in acinar cells of rat lacrimal glands.

Isolated cells from rat lacrimal glands were voltage clamped using the tight-seal whole-cell recording technique. The intracellular solution contained ATP and an elevated Na concentration (70 mM). Removing external K ions elicited an inward current shift. Ouabain (0.5 mM) induced an inward current shift of identical amplitude, but with slower kinetics. In the presence of ouabain, removal of K ions did not alter the cell current. The potassium- and ouabain-sensitive current was outward between -120 and +20 mV, and its amplitude decreased below -60 mV. This current was highly sensitive to temperature, and was not affected by blockers of the K channels which are present in these cells. It was attributed to an inhibition of the Na-K pump. The Na-K pump current was estimated to be 15 pA for an average acinar cell at physiological temperature, with 70 mM internal Na ions and 20 mM external K ions. Implications of this value in terms of electrolyte secretion are discussed.

Animals↗
PubMed1989

The initiation of calcium release following muscarinic stimulation in rat lacrimal glands.

1. Acinar cells were isolated from rat lacrimal glands, and the Ca2+ release response of these cells was studied using two experimental approaches. In one approach, changes in Ca2+ concentration, Cai2+, were monitored by measuring Ca2(+)-dependent Cl- currents using tight-seal whole-cell recording. Alternatively, such changes were measured as a fluorescence signal in cells loaded with Fura-2. 2. Following bath application of ACh (0.5 microM), the cell current recorded at -60 mV was unchanged for ca 0.8 s, then rose in a biphasic manner. The initial phase of the current rise ('hump') took different appearances depending on the cell studied, and it sometimes stood out from the main part of the response as a partially isolated transient. 3. In cells which had been loaded with Fura-2, Cai2+ was found to rise abruptly following a silent period. The delay was larger if ACh (0.2-0.5 microM) was applied in a depolarizing isotonic K+ saline than if it was applied in the normal saline. In addition, the maximum of the Cai2+ response was reduced with depolarizing stimulating solutions. This indicates that membrane potential modulates the Cai2+ response. 4. Responses to 5 microM-ACh, a saturating agonist concentration, were almost identical in K+ saline and in normal saline. 5. If the cell potential was hyperpolarized, the delay of the ACh-induced current became shorter. 6. Breaking into an acinar cell with a pipette containing an elevated Ca2+ concentration (0.1-1 mM) led to a transient activation of Ca2(+)-induced currents during the first seconds of whole-cell recording. These transients were obtained more reliably if the transition to the whole-cell mode was achieved by applying a sharp pulse of potential ('zapping') rather than by applying suction to the pipette compartment. At -60 mV, the transients elicited with the former method by 0.5 mM-Ca2+ had a time-to-peak near 0.6s and an amplitude varying between 10 and 600 pA. With 0.1 mM-Ca2+, similar transients were also observed, but a number of cells failed to respond. Calcium-induced transients were blocked if cells were previously loaded with 50 microM-Ruthenium Red. 7. Performing the same experiments with inositol trisphosphate (InsP3, 20 microM) in the pipette solutions also led to early transient Ca2(+)-induced currents. Amplitudes, times-to-peak and 20-80% transition times were similar for 0.5 mM-Ca2+ and 20 microM-InsP3 stimulations.(ABSTRACT TRUNCATED AT 400 WORDS)

Acetylcholine↗
PubMed1989

Selective effector coupling of muscarinic acetylcholine receptor subtypes.

Attempts have been made by means of recombinant DNA technology to understand the molecular basis of the functional heterogeneity of the muscarinic acetylcholine receptor (mAChR). Molecularly defined mAChR subtypes have been produced from the cloned DNAs in Xenopus oocytes and NG108-15 neuroblastoma-glioma hybrid cells as transient and stable expression systems, respectively, and agonist-induced cellular responses have been examined. The results obtained provide evidence that mAChR subtypes are selectively coupled with different effector systems, albeit not exclusively.

Animals↗
PubMed1988

Intracellular calcium release mediated by two muscarinic receptor subtypes.

Four subtypes of muscarinic acetylcholine receptor (mAChR) were stably expressed in neuroblastoma-glioma hybrid cells (NG108-15). By combining fluorescent indicator dye (fura-2) studies with electrophysiological measurements it is shown that stimulation of mAChR I and mAChR III readily leads to release of calcium from intracellular stores and to associated conductance changes, whereas stimulation of mAChR II and mAChR IV exerts no such effect. Dose-response curves describing the amplitude or the delay of the calcium rise induced by acetylcholine suggest that the apparent affinity of mAChR III for its agonist is higher by about one order of magnitude than that of mAChR I. Ionic substitution experiments and current fluctuation analysis indicate that calcium activates a K+-specific conductance of 'small' single-channel amplitude similar to the SK type. Furthermore, an outward current (M current) suppressed by activation of mAChR I and mAChR III has a single-channel amplitude corresponding to a conductance of approximately 3 pS.

Acetylcholine↗
PubMed1988

Patch-clamp recording of amino acid-activated responses in "organotypic" slice cultures.

Patch-clamp recording techniques were used to study the properties of amino acid-activated channels in cultured "organotypic" slices from rat cerebellum and hippocampus. Hippocampal pyramidal cells responded to the three main glutamatergic agonists, N-methyl-D-aspartate (N-Me-D-Asp), quisqualate, and kainate, whereas Purkinje cells responded only to quisqualate and kainate. Analysis of single-channel events recorded in outside-out patches from hippocampal neurons showed large conductance events (50 pS), which occurred more frequently in the presence of glycine. These events could be produced by N-Me-D-Asp and also, at low frequency, by quisqualate. On the other hand, 50-pS events were never observed in Purkinje neurons. This supports the hypothesis that N-Me-D-Asp and "non-N-Me-D-Asp" receptors are distinct molecular entities. Comparison of whole-cell and outside-out patch recordings from Purkinje cells revealed a clear spatial segregation of gamma-aminobutyric acid (GABA) and glutamate receptors: although GABA receptors are found at high density in somatic membrane, quisqualate and kainate receptors are mostly extrasomatic. The results show that organotypic slice cultures are amenable to patch-clamp methods. They also show that, in these cultures, amino acids receptors have specific distribution patterns according to cell type and to region within a cell.

Action Potentials↗
PubMed1988

Muscarinic activation of ionic currents measured by a new whole-cell recording method.

A new method is described as an alternative to whole-cell recording in order to prevent "wash-out" of the muscarinic response to acetylcholine (ACh) in rat lacrimal gland cells. The membrane of a cell-attached patch is permeabilized by nystatin in the patch pipette, thus providing electrical continuity between the pipette and the cytoplasm of the cell without the loss or alteration of cytoplasmic compounds necessary for the maintenance of the response to ACh. With normal whole-cell recording in these cells, the response to ACh, seen as the activation of Ca-activated K and Cl currents, lasts for approximately 5 min. With the nystatin method, the response is not diminished after 1 h. Nystatin, applied extracellularly, is shown to cause a rapid and reversible increase of membrane conductance to cations. In the absence of wash-out, we were able to obtain dose-response curves for the effect of ACh on Ca-activated K currents. An increase of [ACh] caused an increase in the K current, with apparent saturation at concentrations above approximately 1 microM ACh. The delay between ACh application and the activation of K current was inversely related to [ACh] and reached a minimum value of 0.7-1.0 s at high [ACh].

Acetylcholine↗
PubMed1987

TC-83 Venezuelan equine encephalitis vaccine exposure during pregnancy.

A human pregnancy exposed to TC-83 live attenuated Venezuelan equine encephalitis (VEE) virus vaccine resulted in hydrops fetalis and fetal demise. Maternal seroconversion and the finding of a diffuse mononuclear cell infiltrate on postmortem examination are suggestive of a causative role for TC-83 vaccine.

Adult↗
PubMed1987

Dependence of intracellular effects of GTP gamma S and inositoltrisphosphate on cell membrane potential and on external Ca ions.

Single cells from rat lacrimal glands were studied with the tight-seal whole-cell recording method. Ca-dependent K and Cl currents were measured in response to dialysis with inositoltrisphosphate or GTP gamma S, two compounds known for elevating internal Ca2+ concentration. The activation of the Ca-dependent currents elicited by either compound was partially inhibited by sustained depolarization or by removal of external Ca2+. Conversely, hyperpolarization or removal of external Mg2+ led to augmentations of the Ca-dependent currents. These effects became apparent about 1 min after initiation of cell dialysis with inositoltrisphosphate- or GTP gamma S-containing solutions, and they further developed during the ensuing 10 min. Holding potential and external divalent cations did not affect the Ca-dependent currents elicited by dialysing the cells with strongly buffered solutions containing 0.5 microM free Ca2+. In Ca2+-free external saline, cell currents were independent of the holding potential. It is suggested that InsP3 augments intracellular Ca2+ levels not only by releasing Ca2+ from internal stores but also by slowly increasing the Ca permeability of the plasma membrane. The results indicate that Ca2+ entry through the plasma membrane increases with hyperpolarization. The similarity of the effects seen in InsP3- and GTP gamma S-dialysed cells gives support to the hypothesis that production of the former depends on a GTP-binding protein.

Animals↗
PubMed1987

Protein kinase C activators inhibit the inositol trisphosphate-mediated muscarinic current responses in rat lacrimal cells.

1. Pre-incubation (1-5 min) with 12-O-tetradecanoylphorbol-13-acetate (TPA, 8-16 nM), a tumour-promoting phorbol ester known to activate protein kinase C, was found to inhibit acetylcholine-induced Ca2+-dependent K+ and Cl- currents in cells isolated from rat lacrimal glands. 2. Previous work showed that the same currents may be elicited by dialysing cells with a high-Ca2+ (1.0 microM) solution, with inositol trisphosphate (InsP3), or with guanosine 5'-[gamma-thio]triphosphate (GTP-gamma-S). 3. After TPA incubation both types of currents could be elicited by dialysis with elevated Ca2+ solutions, although the magnitude of the K+ current was slightly reduced in comparison with control cells. 4. Responses to intracellular dialysis with InsP3 (20 microM) were similar to those in untreated cells, indicating that the Ca2+ release process was unaffected. 5. However, the response to GTP-gamma-S (0.2-0.5 mM) dialysis was strongly inhibited in TPA-treated cells. 6. These results suggest that protein kinase C exerts an inhibitory action on the pathway leading from receptor activation to inositol trisphosphate production.

Acetylcholine↗
PubMed1986

3-Hydroxybenzo[a]pyrene glucuronidation by cells: a direct fluorometric assay in culture medium.

A direct fluorometric assay for measuring the glucuronidation by cultured cells using 3-hydroxybenzo[a]pyrene (less than 1 microM) as substrate is described. The method is based on the different characteristics in the fluorescence spectra of 3-hydroxybenzo[a]pyrene and benzo[a]pyrene-3-glucuronide. The analytical procedure operates directly on the culture medium without extraction steps. The sensitivity of detection is 1 nmol glucuronide/1 mumol substrate.

Animals↗
PubMed1986

Blockage of Ca-activated Cl conductance by furosemide in rat lacrimal glands.

Single cells isolated from rat lacrimal glands were studied with the tight-seal whole-cell recording technique. It was found that furosemide (1 mM, applied externally) selectively blocked one part of the electrical response elicited by muscarinic agonists. This component of the response had been shown in a previous work (Marty et al. 1984) to be due to Ca-dependent Cl channels. The action of furosemide was further studied on cells which were dialysed with a high-Ca, high-Na solution, and which mainly displayed the Ca-dependent Cl conductance. In these experiments, furosemide (1 mM) was again found to depress the Ca-dependent Cl current. The present findings offer an explanation for previous reports that furosemide blocks ion fluxes and electrolyte secretion in exocrine glands without necessarily involving the neutral Na-K-Cl carrier usually assumed to be affected by the drug.

Animals↗
PubMed1986

Voltage-dependent channels of human muscle cultures.

Cultures were grown from satellite cells obtained from biopsies of normal children and of boys having Duchenne muscular dystrophy (DMD). Patch-clamp recordings were obtained from mononucleated cells and from young myotubes containing up to five nuclei. Four current types were distinguished. Na currents had a maximum amplitude near -10 mV and a half inactivation point near -60 mV. Single channel currents observed in isolated patches had a main unit size of 1.8 pA at -30 mV. Voltage dependent outward K currents were blocked by applying tetraethylammonium to the bath solution. In some cells, outward currents had a rather slow activation and did not inactivate. In other cells, activation was faster, and the currents inactivated. At large positive potentials, another K current was activated. The corresponding channels displayed large unit steps in isolated patches. Hyperpolarizing voltage pulses elicited in about one third of the cells inward rectifier currents. All currents types were found with similar characteristics in normal and DMD cultures. Whole cell results were very variable. Cells displayed various combinations of the four kinds of currents. To understand the origin of this diversity, clonal cultures were investigated. Clones displayed more homogeneous electrical properties than standard cultures, suggesting the presence of various types of stem cells in the non-clonal cultures.

Adolescent↗
PubMed1986

Potentiation of muscarinic and alpha-adrenergic responses by an analogue of guanosine 5'-triphosphate.

Ca2+-dependent K+ and Cl- currents were recorded in isolated and dialyzed rat lacrimal gland cells by use of the tight-seal whole-cell recording technique. Under control conditions, application of acetylcholine (0.5-1.0 microM) resulted in the full activation of both types of current. When 50-200 microM guanosine 5'-[gamma-thio]triphosphate (GTP[S], a nonhydrolyzable GTP analogue) was added to the intracellular solution, activation of both currents was seen with 1 nM acetylcholine, a dose 1/100th that needed under control conditions. Dialysis with solutions containing 200 microM GTP or cAMP had no, or only slight, potentiation effects. The effects of GTP[S] were obtained only when ATP was included in the intracellular solution. The potentiated responses to acetylcholine were blocked by increasing 10-fold the intracellular Ca2+-buffering capacity and were not dependent on external Ca2+. Thus, the potentiated responses appeared to result from a release of Ca2+ from internal stores. GTP[S] also greatly potentiated the Ca2+-dependent adrenergic (norepinephrine) response of this preparation. In addition, GTP[S] elicited in some cells transient responses without application of acetylcholine or norepinephrine. Finally, rapid and sustained responses were seen as soon as the cells were dialyzed with inositol trisphosphate (20 microM). These findings are discussed in terms of a possible role of a GTP-binding protein as a link between activation of muscarinic or adrenergic receptors and initiation of Ca2+ release by inositol trisphosphate.

Acetylcholine↗