Biomedical subjects

A V Maximov

Publications and source records attributed to A V Maximov.

4 recordsLinked to original sources

PubMed2003

Multibeam effects on fast-electron generation from two-plasmon-decay instability.

Experiments with multiple laser beams have been carried out in both spherical and planar geometry to study two-plasmon-decay instability, the predominant source of suprathermal electrons in direct-drive inertial confinement fusion experiments. These electrons are observed using the hard x rays generated through electron-target interactions. The experiments show for the first time that the total overlapped intensity governs the scaling of the suprathermal-electron generation regardless of the number of overlapped beams, in contrast to conventional theories that are based on the single-beam approximation.

Journal Article↗

PubMed1997

Ca-dependent regulation of Na+-selective channels via actin cytoskeleton modification in leukemia cells.

With the use of the patch-clamp technique, physiological mechanisms of Na+ channel regulation involving submembranous actin rearrangements were examined in human myeloid leukemia K562 cells. We found that the actin-severing protein gelsolin applied to cytoplasmic surface of membrane fragments at a high level of [Ca2+]i (1 microM) increased drastically the activity of Na-selective channels of 12 pS unitary conductance. In the experiments on intact cells, the elevation of [Ca2+]i using the ionophore 4Br-A23187 also resulted in Na+ channel activation. Addition of actin to the cytoplasmic surface of membrane patches reduced this activity to background level, likely due to actin polymerization. Our data imply that Ca-dependent modulations of the actin cytoskeleton may represent one of the general mechanisms of channel regulation and cell signalling.

Actins↗

PubMed1997

Voltage-insensitive Na channels of different selectivity in human leukemic cells.

Patch clamp method was used to search for, and characterize ion channel activity which may participate in cation influx in human myeloid K562 cells. In cell-attached, outside-out and whole-cell experiments two types of voltage-insensitive Na-permeable channels were identified with different selectivities for monovalent cations, referred to as channels of high (HS) and low (LS) selectivity. The unitary conductance was similar for both channel types being 12 pS (145 mmol/l Na, 23 degrees C). The relative permeability PNa/PK estimated from the extrapolated reversal potential values were 10 and 3 for HS and LS channels, respectively. Both HS and LS channels were found to be impermeable to bivalent cations (Ca2+ or Ba2+). The activity of HS and LS channels displayed a tendency to increase with depolarization. Both channel types were not blocked by tetrodotoxin and were insensitive to amiloride in the concentration range of up to 100 mumol/l. At higher concentrations (0.1-2 mmol/l), amiloride reversibly inhibited HS channels only. The results obtained lead us to conclude that, under physiological conditions, both types of Na-permeable channels may provide sodium influx in leukemic cells. Our data imply the existence of a novel family of Na channels in blood cells.

Amiloride↗

PubMed1996

Disruption of actin filaments increases the activity of sodium-conducting channels in human myeloid leukemia cells.

With the use of the patch clamp technique, the role of cytoskeleton in the regulation of ion channels in plasma membrane of leukemic K562 cells was examined. Single-channel measurements have indicated that disruption of actin filaments with cytochalasin D (CD) resulted in a considerable increase of the activity of non-voltage-gated sodium-permeable channels of 12 pS unitary conductance. Background activity of these channels was low; open probability (po) did not exceed 0.01-0.02. After CD, po grew at least 10-20 times. Cell-attached and whole-cell recordings showed that activation of sodium channels was elicited within 1-3 min after the addition of 10-20 micrograms/ml CD to the bath extracellular solution or in the presence of 5 micrograms/ml CD in the intracellular pipette solution. Preincubation of K562 cells with CD during 1 h also increased drastically the activity of 12 pS sodium channels. Whole-cell measurements confirmed that CD-activated channels were permeable to monovalent cations (preferentially to Na+ and Li+), but not to bivalent cations (Ca2+, Ba2+). Colchicine (1 microM), which affect microtubules, did not alter background channel activity. Our data indicate that actin filaments organization plays an important role in the regulation of sodium-permeable channels which may participate in providing passive Na+ influx in red blood cells.

Actin Cytoskeleton↗