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A N Kachman

Publications and source records attributed to A N Kachman.

6 recordsLinked to original sources
PubMed1991

[Kinetics of work of ion channels operated by nicotinic cholinoreceptors in the membrane of mollusk neurons].

The patch-clamp technique in cell-attached configuration was applied to investigate suberyldicholine-induced currents in Planorbarius corneus neurons. The single channels currents registered as inward ones at hyperpolarization of the patches were due to chloride ions efflux from the cell. Suberyldicholine (5 mumol/l) was added into the patch electrode. Usually there were more than one channel in the membrane fragment under the clamp control. The open and closed times, bursts and clusters' lengths were measured and histograms of single-channel parameters were obtained. Histograms were approximated by a sum of exponentials. Single exponentials were fitted to open times; to = 27 +/- 3 ms (n = 21). Histograms of closed times were fitted by three exponentials: tc1 = 9.5 +/- 1.0 ms (n = 21)--short gaps; tc2 = 171 +/- 33 ms (n = 19)--intermediate gaps: tc3 = 5.2 +/- 1.0 s (n = 21)--long gaps. The openings were grouped in bursts: tb2 = 203 +/- 23 ms (n = 10) and in clusters of bursts: tk3 = 1.5 +/- 0.5 s (n = 9). There were some evidences that the single burst was the result of opening, closing and reopening of just the same channel. A kinetic model with one open and three nonconducting states is plausible for single-channel data. Two long-lasting closed times may be associated with desensitization states of the receptor-channel complex. Estimates of the kinetic model parameters were obtained, that may be useful in the further study of a mode of action for cholinergic drugs in Planorbarius corneus neurons.

Animals↗
PubMed1990

[Chlorine channels activated by suberyldicholine in mollusk neurons].

Patch-clamp technique in cell-attached configuration was applied to investigate ion permeability induced by suberyldicholine in the neurons of freshwater mollusc Planorbarius corneus. The inward currents through single channels were registered at patch potentials 50-100 mV more negative than resting potential of the cell. When the patch pipette contained suberyldicholine (5 mol/l), single channel currents were recorded which grouped in bursts and bursts of openings could themselves be grouped together in clusters of bursts. The desensitisation was not too pronounced: usually we were able to observe single-channel currents for 20-30 minutes. The unit conductance gamma was found to be about 10 pS.

Animals↗
PubMedDate not supplied

[A direct microfluorimetric study of organic acid passage through the proximal tubule cells of the surviving Rana temporaria frog kidney].

Accumulation of acid fluorochrome in proximal tubuli in the frog surviving kidney has been investigated. Mean concentration of fluorochrome in the tubuli is linearly related to the duration of incubation. Changes in the mean rate of transport of fluorochrome into the tubuli induced by changes in its external concentration are satisfactorily described by Michaelis-Menten equation, Michaelis constant being equal to 2.1-10(-4). Some equations are suggested which describe the kinetics of organic acid transport across basal and apical membranes of cells.

Aminohippuric Acids↗
PubMedDate not supplied

[Demonstration of different type cholinoreceptors on the membrane of an isolated Planorbarius corneus mollusk membrane].

In experiments on isolated and identified neurones of the pedal ganglion of the gastropod mollusc P. corneus, it was demonstrated that biphasic response to ACh may be obtained both to superfusion and electrophoretic application. Fast (depolarizing) phase may be imitated by a nicotinomimetic drug, suberyldicholine, and blocked by d-tubocurarine. These data indicate that this phase results from activation of nicotinic cholinoreceptors. Slow (hyperpolarizing) phase may be evoked by a muscarinomimetic, dioxolane F-2268, which is taken as an indication of the muscarinic nature of cholinoreceptors responsible for this phase. Experiments on completely isolated neurones directly show that both kinds of cholinoreceptors belong to the same neurone. Biphasic pattern of the response depends on the level of the membrane potential and on the conditions of ACh application. The fast phase is more evident at membrane hyperpolarization, the slow one--at depolarization. The fast phase is more readily obtained by superfusion by high concentrations of ACh or at close position of electrophoretic micropipette to neuronal surface, whereas the slow phase may be easily obtained by superfusion with low concentrations of ACh or when the micropipette is not attached so closely to the cell.

Acetylcholine↗
PubMedDate not supplied

[Study of the chemoreceptor membrane of identified neurons of the gastropod mollusk Planorbarius corneus with different technics of applying chemicals].

Changes in the membrane potential caused by acetylcholine or gamma-aminobutyric acid when added to the perfusion fluid were compared with those induced by their local application to the neuron soma membrane from the micropipette (diameter 100-300 mu). With equal drug concentrations, the responses were found to be of similar amplitude with either method of application. The rate of changes in the membrane potential proved to be however several times higher in the case of local application. Using voltage--clamp technique and local drug application, the dose-response relationships were studied during selective activation either of two kinds of cholinoreceptors available on the identified neuron membrane. The saturation of the muscarinic receptors was shown to be attained at smaller agonist concentrations, the absolute value of maximal response being at least one order of magnitude lower than in case of nicotinic cholinoreceptors of the same cell.

Acetylcholine↗