K+ channels in cardiomyocytes of the pulmonate snail helix.

We used the patch-clamp technique to identify and characterize the electrophysiological, biophysical, and pharmacological properties of K(+) channels in enzymatically dissociated ventricular cells of the land pulmonate snail Helix. The family of outward K(+) currents started to activate at -30 mV and the activation was faster at more depolarized potentials (time constants: at 0 mV 17.4 +/- 1.2 ms vs. 2.5 +/- 0.1 ms at + 60 mV). The current waveforms were similar to those of the A-type family of voltage-dependent K(+) currents encoded by Kv4.2 in mammals. Inactivation of the current was relatively fast, i.e., 50.2 +/- 1.8% of current was inactivated within 250 ms at + 40 mV. The recovery of K(+) channels from inactivation was relatively slow with a mean time constant of 1.7 +/- 0.2 s. Closer examination of steady-state inactivation kinetics revealed that the voltage dependency of inactivation was U-shaped, exhibiting less inactivation at more depolarized membrane potentials. On the basis of this phenomenon, we suggest that a channel encoded by Kv2.1 similar to that in mammals does exist in land pulmonates of the Helix genus. Outward currents were sensitive to 4-aminopyridine and tetraethylammonium chloride. The last compound was most effective, with an IC(50) of 336 +/- 142 micro mol l(-1). Thus, using distinct pharmacological and biophysical tools we identified different types of voltage-gated K(+) channels.

[Spatial organization of colonies of dimorphic micromycetes]. / Prostranstvennaia organizatsiia kolonii dimorfnykh mikromitsetov.

The peculiarities of the formation of colonies of dimorphous epilithic fungus Phaeococcomyces de Hoog isolated from marble were studied. The data obtained can be used for modeling the formation of colonies of dimorphous microscopic fungi.

[Response of membranes of mechanosensitive neurons in Astacus astacus to the intracellular injections of solutions under pressure]. / Reaktsii membrany mekhanochuvstvitel'nogo neirona rechnogo raka (Astacus astacus) na vnutrikletochnuiu in''ektsiiu rastvorov pod davleniem.

Injections of iso- and hypertonic solutions of some potassium salts caused an obvious depolarisation and reduction of electrical resistance in the crayfish slowly adapting stretch receptor neurones' membrane. This response could be eliminated with gadolinium. The stretch-activated channels in the crayfish stretch receptor neurone seem to be affected by an intracellular hydrostatic pressure.

A new point of view on the problem of G-protein aggregation. Assembly-disassembly of tubulin as an oscillation process.

Basic principles of nonlinear thermodynamics are used to develop a theory of tubulin assembly. The presence of GTP/GDP switch provides different ways for tubulin aggregation. The GTP-tubulin assembly results in determining the regime of limit cycle favoring growth of tubulin spiral with the formation of microtubules. The GDP-tubulin assembly, on the contrary, results in forming double rings. The difference between the GTP- and GDP-tubulin assemblies is that the former is a dynamical oscillation process while the latter is no more than a transition from a weakly nonequilibrium point to the equilibrium state along a thermodynamical path. Corresponding equations for the GTP- and GDP-tubulin assemblies are proposed.

[The action of tetraethylammonium on the electrical responses of the neurons of the stretch receptors in the crayfish]. / Deistvie tetraétilammoniia na élektricheskie otvety neironov retseptorov rastiazheniia raka.

The effects of intracellular pressure injection of tetraethylammonium and potassium salt solution has been studied for its effect on the receptor potential of the slowly adapting stretch receptor of crayfish. It was found that the pressure injection caused an increase in the static phase of the receptor potential. Intracellular microiontophoretic injection and extracellular application of tetraethylammonium have not exert an effect on the adaptation of receptor potential. The results suggest that tetraethylammonium-sensitive potassium channels are not involved in adaptation of the receptor potential of mechanoreceptors.

The spatial organization of the cytoskeleton in crayfish stretch receptor.

An electron microscopic study of the cytoskeleton of the crayfish stretch receptor was carried out. Longitudinal sections of the sensory neuron axons and dendrites showed wave-like arrays of microtubules with a period of about 5 microns. Transverse sections showed that the microtubules displayed no regularity in the arrays. In oblique sections, transverse and longitudinal views of microtubules (or shorter and longer segments of microtubules) alternated yielding a festoon-like pattern. The data obtained indicate that the cytoskeleton of the stretch receptor has a helical structure in which all the microtubules, the major cytoskeletal components, are arranged in parallel helices that are in register along the length of axons and dendrites. The helical organization of the cytoskeleton is probably responsible for the banded appearance of sensory axons and primary dendrites as seen in the polarized light. Decrease of contrast and disappearance of the banding during stretch of the receptor muscle are supposedly due to the desynchronization of the helical trajectories of the microtubules and to the decrease of the helical amplitude.

[The transformation of the receptor potential of mechanosensitive neurons in the crayfish with the intracellular injection of solutions under pressure]. / Preobrazovanie retseptornogo potentsiala mekhanochuvstvitel'nykh neironov raka v usloviiakh vnutrikletochnoi in''ektsii rastvorov pod davleniem.

Intracellular pressure injection of potassium salt solution has been studied for its effect on the receptor potential of the slowly adapting stretch receptor of crayfish. It was found that the injection caused an increase in the static phase of the receptor potential. The results suggest that the intracellular hydrostatic pressure may be involved in generation of primary receptor responses of mechanoreceptors.

[Features of the ultrastructural organization of neurons with a septal reticulum]. / Osobennosti ul'trasturkturnoi organizatsii neironov s septal'nym retikulomom.

The electron microscopical study of the crayfish stretch receptor neuron, with a distinctive system of the smooth endoplasmic reticulum (SER) cisternae lying at intervals (2 mcn apart) normal to the long axis of axons and dendrites, has revealed a direct continuity of the SER with the outer membrane of mitochondria. Subsurface cisterns were discovered in the neuron. It is concluded that these may be part of cell SER network. A new type of the synapse interaction between excitatory and inhibitory fibres and the stretch receptor neuron dendrite has been described.

[Device for simultaneous bilateral stretching of biological objects without displacing the site under study]. / Prisposoblenie dlia odnovremennogo dvukhstoronnego rastiazheniia biologicheskikh ob"ektov bez smeshcheniia issleduemoi tochki.

A mechanical device is offered for stretching biological objects by 2--6 mm. This is set on the microscope stage and allows simultaneous and independent stretching to the opposite sides, keeping the fixed position of any definite object point. The device and principles of operation are described taking for ellustration experiments with the crayfish receptor that involved an intercellular registration of electrical parametres of the mechanoreceptor neuron under adequate stimulation.

[2 pools of mitochondria in a single mechanoreceptor neuron]. / O dvukh pulakh mitokhondrii v odinochnom mekhanoretseptornom neirone

The microspectrofluorimetric technique was applied to measure the intracellular ratio of oxidized flavoproteins and NADH in isolated neuron preparation from the stretch receptor organ of the crayfish Astacus leptodactilus. Two pools of mitochondria were detected differing from each other in their functional activity in the single cell at the same time. The mitochondria of the pool are localized near the nucleus, those of the other one being placed along the cell membrane. Physiological treatments (stretch, calcium deficient media) produce different changes in the activity of mitochondria belonging to the different pools. It is suggested that these pools of mitochondria furnish with energy different functional mechanisms within the same cell.

[Thermoreceptor function of the stretch receptors of the river crayfish]. / Termoretseptornaia funktsiia retseptora rastiazheniia rechnogo raka

Cooling of the crayfish stretch receptor leads to increase and then decrease the spike frequency of slowly adapting (SA) neuron (maximum frequency at 15 degrees). Impulse activity of quickly adapting (QA) neuron arises about 12 degrees and is recoding for a long time (sometimes during 30 min.). Raising the temperature from 20 degrees to 30 degrees results in a gradual increase of the SA neuron spike frequency. Characteristic for cold thermoreceptors dynamic discharge is observed. Infra-red (IR) radiation (lambda=1--3 mum) causes a decrease of SA neuron spike frequency. QA neuron generates a brief discharge after cuting IR radiation. IR radiation acts on somato-dendro-muscle (sensory) region only. Analysis with polarizing microscope shows that the IR radiation effect on the structural organization of neurons is contrary the effect of warming and colding. It is proposed that the IR radiation effect is defined by the rise of temperature gradient in solution (dT/dx). Obtained results indicate that the crayfish stretch receptor belongs to the type of mechanocoldreceptors.