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Query: UMLS:C0019829 (Hodgkin's disease)
 30,247 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The anatomy and physiology of the Drosophila larval neuromuscular junction were studied. 2. The dependence of muscle resting potentials on [K+]o and [Na+]o follows the Goldman-Hodgkin-Katz equation (PNa/PK=0-23). Chloride ions distribute passively across the membrane. 3. The mean specific membrane resistance of muscle fibres is 4-3 X 10(3) omega cm2, and the mean specific membrane capacitance is 7-1 muF/cm2. The muscle fibre is virtually isopotential. 4. Transmitter release is quantal. Both the miniature excitatory junctional potential and the evoked release follow the Poisson distribution. 5. Transmitter release depends on approximately the fourth power of [Ca2+]o. If Sr2+ replaces Ca2+, it depends on approximately the fourth power of [Sr2+]o. Mg2+ reduces transmitter release without altering the fourth power dependence on [Ca2+]o.
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PMID:Properties of the larval neuromuscular junction in Drosophila melanogaster. 1 39

The endogenous Cl- conductance of Spodoptera frugiperda (Sf9) cells was studied 20-35 h after plating out of either uninfected cells or cells infected by a baculovirus vector carrying the cloned beta-galactosidase gene (beta-Gal cells). With the cation Tris+ in the pipette and Na+ in the bath, the reversal potential of whole-cell currents was governed by the prevailing Cl- equilibrium potential and could be fitted by the Goldman-Hodgkin-Katz equation with similar permeabilities for uninfected and beta-Gal cells. In the frequency range 0.12 < f < 300 Hz, the power density spectrum of whole-cell Cl- currents could be fitted by three Lorentzians. Independent of membrane potential, >50% of the total variance of whole-cell current fluctuations was accounted for by the low frequency Lorentzian (fc = 0.40 +/- 0.03 Hz, n = 6). Single-Cl- channels showed complex gating kinetics with long lasting (seconds) openings interrupted by similar long closures. In the open state, channels exhibited fast burst-like closures. Since the patches normally contained more than a single channel, it was not possible to measure open and closed dwell-time distributions for comparing single-Cl- channel activity with the kinetic features of whole-cell currents. However, the power density spectrum of Cl- currents of cell-attached and excised outside-out patches contained both high and low frequency Lorentzian components, with the corner frequency of the slow component (fc = 0.40 +/- 0.02 Hz, n = 4) similar to that of whole-cell current fluctuations. Chloride channels exhibited multiple conductance states with similar Goldman-Hodgkin-Katz-type rectification. Single-channel permeabilities covered the range from approximately 0.6.10(-14) cm5/s to approximately 6.10(-14) cm3/s, corresponding to a limiting conductance (gamma 150/150) of approximately 3.5 pS and approximately 35 pS, respectively. All states reversed near the same membrane potential, and they exhibited similar halide ion selectivity, P1 > PCl approximately PBr. Accordingly, Cl- current amplitudes larger than current flow through the smallest channel unit resolved seem to result from simultaneous open/shut events of two or more channel units.
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PMID:Endogenous chloride channels of insect sf9 cells. Evidence for coordinated activity of small elementary channel units. 878 71

The isolated epithelium of toad skin was disintegrated into single cells by treatment with collagenase and trypsine. Chloride channels of cell-attached and excised inside-out apical membrane-patches of mitochondria-rich cells were studied by the patch-clamp technique. The major population of Cl- channels constituted small 7-pS linear channels in symmetrical solutions (125 mM Cl-). In cell-attached and inside-out patches the single channel i/V-relationship could be described by electrodiffusion of Cl- with a Goldmann-Hodgkin-Katz permeability of, PCl = 1.2 x 10(-14) - 2.6 x 10(-14) cm3. s-1. The channel exhibited voltage-independent activity and could be activated by cAMP. This channel is a likely candidate for mediating the well known cAMP-induced transepithelial Cl- conductance of the amphibian skin epithelium. Another population of Cl- channels exhibited large, highly variable conductances (upper limit conductances, 150-550 pS) and could be activated by membrane depolarization. A group of intermediate-sized Cl(-)-channels included: (a) channels (mean conductance, 30 pS) with linear or slightly outwardly rectifying i/V-relationships and activity occurring in distinct "bursts," (b) channels (conductance-range, 10-27 pS) with marked depolarization-induced activity, and (c) channels with unresolvable kinetics. The variance of current fluctuations of such "noisy" patches exhibited a minimum close to the equilibrium-potential for Cl-. With channels occurring in only 38% of sealed patches and an even lower frequency of voltage-activated channels, the chloride conductance of the apical membrane of mitochondria-rich cells did not match quantitatively that previously estimated from macroscopic Ussing-chamber experiments. From a qualitative point of view, however, we have succeeded in demonstrating the existence of Cl-channels in the apical membrane with features comparable to macroscopic predictions, i.e., activation of channel gating by cAMP and, in a few patches, also by membrane depolarization.
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PMID:Heterogeneity of chloride channels in the apical membrane of isolated mitochondria-rich cells from toad skin. 892 67

The unitary conductances and permeability sequences of the rat connexin40 (rCx40) gap junction channels to seven monovalent cations and anions were studied in rCx40-transfected neuroblastoma 2A (N2A) cell pairs using the dual whole cell recording technique. Chloride salt cation substitutions (115 mM principal salt) resulted in the following junctional maximal single channel current-voltage relationship slope conductances (gamma 1 in pS): CsC1 (153), RbC1 (148), KC1 (142), NaC1 (115), LiC1 (86), TMAC1 (71), TEAC1 (63). Reversible block of the rCx40 channel was observed with TBA. Potassium anion salt gamma j are: Kglutamate (160), Kacetate (160), Kaspartate (158), KNO3 (157), KF (148), KC1 (142), and KBr (132). Ion selectivity was verified by measuring reversal potentials for current in rCx40 gap junction channels with asymmetric salt solutions in the two electrodes and using the Goldman-Hodgkin-Katz equation to calculate relative permeabilities. The permeabilities relative to Li+ are: Cs+ (1.38), Rb+ (1.32), K+ (1.31), Na+ (1.16), TMA+ (0.53), TEA+ (0.45), TBA+ (0.03), Cl- (0.19), glutamate+ (0.04), and NO(3)- (0.14), assuming that the monovalent anions permeate the channel by forming ion pairs with permeant monovalent cations within the pore thereby causing proportionate decreases in the channel conductance. This hypothesis can account for why the predicted increasing conductances with increasing ion mobilities in an essentially aqueous channel were not observed for anions in the rCx40 channel. The rCx40 effective channel radius is estimated to be 6.6 A from a theoretical fit of the relationship of relative permeability and cation radius.
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PMID:Monovalent cation permeation through the connexin40 gap junction channel. Cs, Rb, K, Na, Li, TEA, TMA, TBA, and effects of anions Br, Cl, F, acetate, aspartate, glutamate, and NO3. 910 8

Discovery and active exploration of the furosemid-sensitive derived-active co-transport of sodium-potassium-chlorine ions took place in the end of 1970-es-1980-es. This transportation mechanism was discovered in various types of cells, both of plant and of animal origin. This review describes properties of the transportation process, which was most comprehensive explored in experiments with erythrocytes, epithelium cells and muscles. The review covers the following properties: anion and cation selectivity of the chlorine transportation, its sensitivity to the specific blocking agents (furocemid, bumetanid, etc.), stoichiometry of the transportation process, etc. For energy source, the chlorine transportation is based on transmembrane electrochemical gradient for sodium ions. The article provides the most recent results of investigation of the chemical nature of the molecule of the chlorine membrane transport. Based on various studies, the molecule of this protein weighs from 120 to 200 kD, includes about 1200 amino acid residua, and forms long cytoplasmatic NH2 and COOH-termini. The gene encoding the amino acid sequence has been cloned. The article discusses the issues of regulation of the chlorine transportation. Humoral control of intensity of the chlorine transportation has been mostly studied in experiments with plain muscles, the issues related to nervous regulation--with only skeleton muscle fibers. The article provides specific data on the mechanisms of the above types of the physiological regulation of active chlorine transportation. In general, the humoral factors, which increase the intracellular concentration of cAMF stimulate chlorine transportation. On the contrary, the hormones, which increase concentration of cGMF in cytoplasm reduce its activity in plain muscles. The discussion of the mechanisms of the nervous controls of the chlorine transportation in the skeleton muscles includes the original results of the author. These results indicate that the suppressive influence of the motor innervation on intensity of the chlorine transportation involves the non-quantum acetilcholine and glutamate secreted from the motor nerves. These agents produce Ca(2+)-dependent molecules of nitrogen oxide in sarcoplasm, which act in the retrograde mode on the nervous terminal and activate there the synthesis of cGMF. Disruption of this bilateral transsynaptic signalization resulting from cutting a nerve of blocking of its axoflow creates more active chlorine transportation and subsequent de-innervation changes in properties of the muscle fibers. The functions of chlorine transportation, which are best studies as of today and therefore, discussed in more detail in the review, include participation of this process in the regulatory rehabilitation of the volume of various cells in non-isotonic medium, and the role of chlorine transportation in development of a negative charge at the interior side of membrane of the skeleton muscle fibers. The former function essentially means that dehydration of a cell in the hypertonic medium increases activity of the sodium, potassium and chlorine co-transport directed to the cell, resulting in increase of the amount of the osmosis-active cytoplasm material, and inflow of water, which fully restores the cell volume in these conditions. Starting from the pioneer studies by Hodgkin and Horowicz [correction of Hojkin and Gorovits], the role of chlorine ions in forming a charge on the membrane of excited cells has been generally interpreted as exclusively passive. I.e., distribution of these ions over both sides of membrane was assumed as equilibrium with the existing values of the membrane potential in the non-excited state. The review provides data obtained in the recent decade, which have proved that the non-excited membrane potential in muscle fibers is co-created by the diffusional potassium and chlorine potential. (ABSTRACT TRUNCATED)
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PMID:[The sodium-potassium-chloride cotransport of the cell membrane]. 965 82

Tetrodotoxin and acidic pH do not change the resting membrane potential (RMP), whereas Na+ or Cl- free solutions or ouabain and furosemide equally depolarize the membrane of the earthworm somatic muscle cells. The findings of the RMP depending on extracellular K+ concentration corroborate theoretical model by Goldman-Hodgkin-Katz only in Na(+)-free medium or in presence of ouabain. The data suggest that the RMP is the sum of potassium and chlorine diffusion potentials as well as of the potential produced by electrogenic component of Na+ pump and, probably, by furosemide-sensitive Na+,K+Cl- co-transport.
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PMID:[Influence of sodium pump and Na(+), K(+), CL(-)-cotransport on the resting membrane potential of somatic muscle cells of the earthworm Lumbricus terrestris]. 1176 27

Hodgkin-Huxley model has been reframed to incorporate the physical parameters of fluid inside the axon. The reframed model comprises of set of partial differential equations containing the physical parameters: density, mass fraction of sodium, potassium and chlorine ions, longitudinal diffusivity of ions and rate of additions of ions along with the temperature. Obtained conduction velocity of 19.5m/sec at a temperature of 18.5 degree celcius and conduction velocity dependency on temperature within the range 5 to 25 degree celcius are two important results that strongly validate the proposed model. The behavior of all the physical parameters has been characterized with respect to the action potential. Action potential conduction velocity along with axoplasmic fluid viscosity has been characterized with respect to different temperatures. Longitudinal diffusivity of ions is also quantified.
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PMID:Hodgkin-Huxley model based on ionic transport in axoplasmic fluid. 2889 25