Dose-dependent potentiation and inhibition of single Ca2+-activated K+ channels by flufenamic acid

Using the patch-clamp technique in an inside-out configuration, we studied the action of an antiinflammatory drug, flufenamic acid (FFA), on single large-conductance Ca2+-activated K+ channels in cultured Vero kidney cells. Depending on its concentration, FFA caused either potentiation or inhibition of K(Ca) channel activity of the same channel. Within the concentration ranges of about 5 to 10 microM and of 50 to 500 microM, FFA increased the channel activity; and within the intermediate range of about 10 to 50 microM, FFA inhibited the channels. The effects were only partially reversible. The activating phases were accompanied by an increase in the channel open time and decreases in the channel closed time and slope factor of the Ca2+ concentration-response curve. An apparent dissociation constant of Ca2+ interaction with the channel changed slightly. Possible mechanisms of the FFA effects are discussed.     

The independence of the family Channaculinidae (Crustacea: Copepoda: Cyclopoida)

New family name Pillainidae Kazatchenko fam. nov. is suggested instead of family name Channaculinidae. The keys of the families and genera of fish parasitic copepods of suborder Cyclopoida are given.     

Single potential-dependent K+ channels and their oligomers in molluscan glial cells

Single K+ channels were studied using the patch-clamp method. A potential-dependent K+ channel of large conductance (about 100 pS at 100 mM of KCl on both membrane sides) was detected. Some properties of the channel (current-voltage relations, kinetic parameters, etc.) are presented. The channel was found to have about 16 resolvable quantized conductance substates. The data are confirmed by spontaneous channel degradation, i.e., spontaneous splitting of the channel conductance into independent conductance oligomers. Some properties of the conductance oligomers of different order are described. The degree of potential dependency of the conductance oligomer parameters is a function of potential dependency. The data obtained are in agreement with a hypothesis that the channels studied are clusters (aggregates) of elementary channel subunits.     

Cooperative phenomena in the activity of single ion channels

Using the patch-voltage-clamp method kinetics of the fast potential-dependent K+-channels in molluscan neurones was investigated. It was found that under given experimental conditions the amplitudes of single current impulses have a wide spectrum. The amplitudes are proportional to a number of the current substates involved. Averaged fronts of the current impulses are S-shaped, and have duration greater than 1 ms. Averaged duration of the current impulses increases (from 0.25 to 30-40 ms) with the impulse amplitude (or with the number of the substates involved). There is a sharp bend of the dependence at the impulse amplitude 0.6-0.7 of maximal value. The phenomena investigated reflect, probably, cooperativity of the channel transitions between the substates. The degree of the cooperativity depends on the membrane potential value.     

Interaction of melittin with ion channels of excitable membranes

The effect of the neurotoxin melittin on the activation of ion channels of excitable membrane, the plasmalemma of Characeae algae cells, isolated membrane patches of neurons of mollusc L. stagnalis and Vero cells was studied by the method of intracellular perfusion and the patch-clamp technique in inside-out configuration. It was shown that melittin disturbs the conductivity of plasmalemma and modifieds Ca(2+)-channels of plant membrane. The leakage current that appears by the action of melittin can be restored by substituting calmodulin for melittin. Melittin modifies K(+)-channels of animal cell membrane by disrupting the phospholipid matrix and forms conductive structures in the membrane by interacting with channel proteins, which is evidenced by the appearance of additional ion channels.     

Effect of self-association on the structural organization of partially folded proteins: inactivated actin

The propensity to associate or aggregate is one of the characteristic properties of many nonnative proteins. The aggregation of proteins is responsible for a number of human diseases and is a significant problem in biotechnology. Despite this, little is currently known about the effect of self-association on the structural properties and conformational stability of partially folded protein molecules. G-actin is shown to form equilibrium unfolding intermediate in the vicinity of 1.5 M guanidinium chloride (GdmCl). Refolding from the GdmCl unfolded state is terminated at the stage of formation of the same intermediate state. An analogous form, known as inactivated actin, can be obtained by heat treatment, or at moderate urea concentration, or by the release of Ca(2+). In all cases actin forms specific associates comprising partially folded protein molecules. The structural properties and conformational stability of inactivated actin were studied over a wide range of protein concentrations, and it was established that the process of self-association is rather specific. We have also shown that inactivated actin, being denatured, is characterized by a relatively rigid microenvironment of aromatic residues and exhibits a considerable limitation in the internal mobility of tryptophans. This means that specific self-association can play an important structure-forming role for the partially folded protein molecules.     

The genetic-demographic approach in anthropological research. IX. The spatial structure of Khakass populations]

The rural population of Khakassia is characterized by genetic isolation due to marital traditions and ethnic-territorial subdivisions. The type of Khakass settling limits the choice of a marital partner within the territory occupied by one ethnographic group, preventing an active migration of alleles from one population to another. Formation of local zonal anthropologic type (84% of marital couples) occurs on the territory approximately equal to the area of one administrative district.     

A discrete type of potassium channel conductance in snail neurons

The results of further investigations on a single potential dependent K+ channel are described. It was shown that ionic selectivity of the channel for monovalent ions is too high: Li+, Na+, and Cs+ are practically impermeant ions. Permeability of the channel for Rb+ is approximately 10 times less, and for Tl+ it is 2 times more than permeability for K+. Besides, it was found that open K+ channel has 16 multiple conductance levels.