共查询到20条相似文献,搜索用时 15 毫秒
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This article is a study of the fast Na current during action potentials. We have investigated the outward Na current (Mazzanti, M., and L.J. DeFelice. 1987. Biophys. J. 52:95-100) in more detail, and we have asked whether it goes through the same channels associated with the rapid depolarization phase of action potentials. We address the question by patch clamping single, spontaneously beating, embryonic chick ventricle cells, using two electrodes to record the action potential and the patch current simultaneously. The chief limitation is the capacitive current, and in this article we describe a new method to subtract it. Varying the potential and the Na concentration in the patch pipette, and fitting the corrected currents to a standard model (Ebihara, L., and E.A. Johnson. 1980. Biophys. J. 32:779-790), provides evidence that the outward current is carried by the same channels that conduct the inward current. We compare the currents in beating cells to currents in nonbeating cells using whole-cell and cell-attached patch clamp recordings. The latter tend to show more positive Na reversal potentials, with the implication that internal Na is higher in beating cells. We propose that the plateau of the action potential, which is partly due to an inward Ca current, exceeds Na action current reversal potentials, and that this driving force gives rise to an outward movement of Na ions. The existence of such a current would imply that the fast repolarization phase after the upstroke of cardiac action potentials is partly due to the Na action current. 相似文献
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This paper characterizes a photoelectric recording system which monitors individual beating heart cells in vitro. A culture procedure which supports continued beating for up to three months without confluent overgrowth or aggregation is described. 相似文献
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Erucic acid oxidation by beating heart cells in culture 总被引:2,自引:0,他引:2
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Fetal human heart cells have been dissociated by trypsinization and successfully grown in tissue culture on two occassions. The characteristics of the growth and mitotic activity were quite similar to those previously found for rodent heart cells. The maximum beating rates seen in the cultures from each specimen were 33 and 75 per minute. 相似文献
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The subcellular distribution of ATP, ADP, creatine phosphate and creatine has been analyzed by fast detergent fractionation of isolated frog heart cells. Digitonin fractionation (0.5 mg/ml, 10 s at 2 degrees C in 20 mM 4-morpholinepropanesulfonic acid/3 mM EDTA/230 mM mannitol medium) was used to separate mitochondria and myofilaments from cytosol. To separate myofilaments from the other cellular compartments. Triton X-100 was used (2%, 15 s in the same medium as digitonin). For either resting or beating cells the total cellular contents of ATP, ADP, creatine phosphate and creatine was similar, nevertheless the O2 consumption was 6-times higher. The compartmentation of these metabolites was also identical. Myofilaments contain 1.1 nmol ADP per mg total cellular proteins. In the cytosolic compartment the metabolite concentrations, all measured in nmol per mg total cellular proteins, were: ATP, 13; ADP, 0.25-0.05; creatine phosphate, 18.5 and creatine, 14. This indicated that the reaction catalyzed by creatine kinase was in a state of (or near) equilibrium. 相似文献
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Dispersion and isolation of beating cells from adult rat heart 总被引:7,自引:0,他引:7
The cells of adult rat heart ventricles were dispersed using crude bacterial collagenase. An investigation into the effect of shaking speed, stroke length, concentration of enzyme, ionic composition, and pH of the dispersing medium permitted the development of optimal conditions for obtaining beating myocytes. Approximately one-quarter of the initial protein content of ventricular chunks could be routinely recovered as single cells after such dispersion. Centrifugation through solutions of Ficoll in phosphate buffer selectively concentrated the beating myocytes and removed contaminating cells and tissue debris. 相似文献
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In search of a fluorescent dye suitable for monitoring membrane potentials of beating heart cells, we noticed that the carbocyanine dyes, CC5 and CC6, show a unique pattern of intracellular distribution in vital and glutaraldehyde-fixed cardiomyoblasts. This distribution is clearly different from that observed in fibroblasts. In heart cells, it parallels the localization of actin-myosin containing myofilaments as visualized by fluorescent antibody staining but it does not correspond to the localization of actin filaments or the microtubules. In fibroblasts these dyes stain only fine filaments and granules in the perinuclear space which correspond to the endoplasmic reticulum. This observation is evidence in support of the hypothesis that carbocyanine dyes accumulate selectively in the sarcoplasmic reticulum. It indicates that certain carbocyanine dyes may be useful tools to differentiate between muscle cells and connective tissue cells in cell cultures. 相似文献
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Sherman Bloom 《生物化学与生物物理学报:生物膜》1978,514(2)
Beating hyperpermeable myocardial fragments, suspended in fresh medium, show a Ca uptake rate which greatly exceeds the release rate. Under these conditions, Ca influx and contraction frequeny co-vary with temperature. Ca efflux, however, is not temperature responsive. In addition, influx, but not efflux, is ATP-dependent. This implies that influx, but not efflux, is a controlled process, the activity of which has the same determinants as does contraction. However, under conditions approximating the steady state, the Ca influx rate was found to decrease, while the efflux rate increased. This suggests the possibility, at least, that the source of contraction-activating Ca can vary with the prevailing conditions. 相似文献
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Hypertonic stress caused by sucrose and sorbitol followed by reincubation in isotonic medium causes irreversible damage to synchronously beating heart cells. These results can be explained by a “Minimum Cell Volume” theory as proposed by Meryman. During exposure to hypertonic NaCl solutions damage to the contractility depends on the incubation time. Damage to the individual cell survival seems to be less dependent on the incubation period. 相似文献
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