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G P Diadiusha

Publications and source records attributed to G P Diadiusha.

At least 19 recordsLinked to original sources
PubMed1990

[Change in the passive influx of Ca2+ into sarcoplasmic reticulum vesicles as a result of chemical modification of surface amino groups].

Treatment of sarcoplasmic reticulum (SR) vesicles with trinitrobenzene (TNBS) and 1-ethyl-3(3-dimethylaminopropyl)carbodiimide (EDC) stimulates the initial rate of passive influx of Ca2+ into SR vesicles, but does not affect either the binding or the maximal passive loading of SR vesicles with Ca2+. The changes in the kinetics of KCl-stimulated passive influx of Ca2+ depend on the reagent used. It is supposed that stimulation of passive influx of Ca2+ into SR vesicles and the changes in the reaction kinetics may be caused by modification of the Ca2+ channel gating behaviour as a result of binding of surface amino groups.

Amines↗
PubMed1988

[Passive Ca2+ fluxes across the membrane of sarcoplasmatic reticulum of skeletal muscles. The effect of calcium channel blockers].

It was found that the initial rate of passive KC1-stimulated Ca2+ influx into sarcoplasmic reticulum (SR) vesicles follows the saturation kinetics at Ca2+ concentrations of 8-10 mM. The inhibitory effect of Ca2+ channel blockers (La3+, Mn2+, Co2+, Cd2+, Mg2+) on passive Ca2+ influx into SR vesicles is competitive with respect to Ca2+. These blockers also inhibit the initial fast phase of Ca2+ efflux from Ca2+-loaded SR vesicles. Verapamil (0.1-0.5 mM) added to the incubation mixture has no effect on passive Ca2+ fluxes across the SR vesicle membrane or on Ca2+ binding and ATP-dependent Ca2+ accumulation. However, preincubation of SR vesicles with verapamil (18 hours, 4 degrees C) or its introduction into the medium for SR vesicle isolation leads to the inhibition of passive Ca2+ fluxes.

Animals↗
PubMed1981

[Inhibiting effect of adrenaline on the acetylcholinesterase activity of skeletal muscle sarcolemma].

It has been found that epinephrine reversibly inhibits in vitro the acetylcholinesterase activity of intact sarcolemma and partially purified preparation of sarcolemmal acetylcholinesterase. The kinetics analysis has demonstrated a non-competitive type of inhibition with the apparent Ki values of about 4 . 10(-4) M. An increase in the ionic strength intensities the epinephrine-induced inhibition, the effect of CaCl2 being essentially more noticeable than that of NaCl. The number of SH-groups of the sarcolemma available for DTNB decreases in the presence of epinephrine and increases in the presence of CaCl2 or NaCl. The sulfhydryl reagents (e. g. DTNB, NEM) have no effect n the acetylcholinesterase activity of sarcolemma. It is assumed that the inhibiting effect of epinephrine may be due to the conformational changes in the acetylcholinesterase molecules.

Animals↗
PubMed1978

[Isolation of sarcolemma acetylcholinesterase fractions by gel-filtration through Sepharose 2B].

Gel-filtration of 0,6 M NaCl and 0,6 M NaCl--0,1% Triton X-100 extracts of freshly isolated sarcolemma through Sepharose 2B (1,5 X 72 cm) has revealed one symmetric peak of acetylcholinesterase activity containing phospholipid and cholesterol, moving faster than fibrinogen and tyreoglobulin. The acetylcholinesterase fraction is substantially separated from other extract proteins. Gel-filtration of extracts from long-store, treated by ultrasound or high concentration of detergent sarcolemma has revealed some peaks of acetylcholinesterase activity, which may be suggested to be degraded forms of the complex high molecular weight structure. All species of acetylcholinesterase are converted by treatment with trypsin to a form moving upon gel-filtration with enzyme-marker catalase. The microsome extracts contain only the form moving with catalase.

Acetylcholinesterase↗
PubMedDate not supplied

[Passive Ca2+ influx into vesicles of the sarcoplasmic reticulum, modified by succinic anhydride].

Treatment of the sarcoplasmic reticulum (SR) vesicles with succinic anhydride in concentration of 1-2 mM modifies about 20% of amino groups. It increases initial rate and changes the pH-dependence of the passive influx of Ca2+ into vesicles and does not affect either Ca(2+)-binding or maximal passive Ca(2+)-loading of the SR vesicles. It is supposed that this effect may be caused by modification of the Ca-channel gating behaviour as a result of replacement of positive surface amino groups by carboxyl groups.

Animals↗
PubMedDate not supplied

[The effect of pH on the passive transport of Ca2+ by membranes of fragmented sarcoplasmic reticulum of skeletal muscles].

The initial rate of Ca2+ translocation in vesicular preparations of the sarcoplasmic reticulum membranes is shown to fall with a pH decrease to 6.0 or 5.0 and to rise with a pH change to 7.0 to 7.8 in respect to the initial 6.5. It is established that the Ca2+ sorption by the membranes or their fluidity make no essential contribution to the recorded changes of 45Ca2+ level in the membrane preparations. It is shown that the passive Ca2+ transport depends to a considerable extent on the concentration of a proton at the outer surface of the sarcoplasmic reticulum membrane: an excess of H+ inhibits the Ca2+ input and output, while a decrease of the proton concentration promotes an increase in the rate of these processes in the sarcoplasmic reticulum.

Animals↗
PubMedDate not supplied

[Ca 2+ outflow from sarcoplasmic reticulum vesicles during changes in membrane potential, Ca2+ concentration and pH].

The concentration gradient Ca2+ outflux from the vesicles of the fragmented sarcoplasmic reticulum of rabbit skeletal muscles has been studied under conditions of the induced membrane potential, the concentrations of Ca2+ and H+ in the medium washing over the vesicles being different. The Ca2+ outflux from vesicles is shown to be the same with a decrease of the membrane potential from--80 down to -10 mV and gets higher with the zero and subsequent positive values of the latter. A significant intensification of the Ca2+ outflux from vesicles under the effect of external-vesicular Ca2+ has been observed at its concentration of 10(-5) M. Against this background of external-vesicular Ca2+ and zero value of the membrane potential either exogenous AMP or the pH increase from 6.5 up to 7.8 favour a release of more than 70% of passively accumulated Ca2+. The pH effect grows with a decrease in the external-vesicular concentration of Ca2+. A conclusion is drawn on the significance of protons in the regulation of the Ca2+ release from the sarcoplasmic reticulum.

Adenosine Monophosphate↗
PubMedDate not supplied

[A study of passive Ca2+ flow through the sarcoplasmic reticulum of skeletal muscles. I. Passive Ca2+ efflux from vesicle membranes].

The same level of passively loaded Ca2+ was observed both in the heavy (enriched in terminal cisternae) and light (enriched in longitudinal reticulum) sarcoplasmic reticulum (SR) fractions. The level of passively loaded Ca2+ of the both SR fractions decreased in the presence of 150 mM K+. However the rate and extent of Ca2+ release was greater from heavy SR fraction. The rate of Ca2+ release under conditions of antiport of K+, Na+, choline+ and gluconate-, Cl-, SCH- increased proportion with their permeability through the SR membrane. The initial rate of Ca2+ release also became higher under equal concentration of monovalent cation chloride both inside and outside the SR vesicles. Apparently, in this case Ca2+ release occurs through Ca-channels which are open at a membrane potential.

Animals↗
PubMedDate not supplied

[Effect of tetracaine and sovcaine on the ATP-dependent calcium accumulation in sarcoplasmic reticulum vesicles of skeletal muscles].

The tetracaine and cinchocaine in concentration less than 2 mM and 0.5 mM, respectively, stimulate ATP-dependent Ca-loading by enhancing the initial rate of Ca2+-accumulation, do not affect the Ca2+-binding and Ca-ATPase activity of sarcoplasmic reticulum vesicles. These data suggest blocking of Ca2+-efflux from vesicles which occurs during Ca-accumulation. Higher concentrations of the same compounds (above 2 mM and 0.5 mM for tetracaine and cinchocaine, respectively) caused inhibition of the Ca-ATPase activity and decreased the ability of SR vesicles to retain Ca2+, probably, due to their nonspecific lipophilic action.

Adenosine Triphosphate↗
PubMedDate not supplied

[Effect of gradients of monovalent cations on active transport of Ca2+ in the sarcoplasmic reticulum and proteoliposomes].

Artificially generated K+ gradient from the sarcoplasmic reticulum vesicles enhances the ATP-dependent Ca2+ transport. The effect is not specific for K+, and is observed when K+ is replaced by Na+ or choline. Dissipation of the K+, Na+, choline gradient does not influence the ATP-dependent Ca2+ transport in proteoliposomes from asolectin and purified Ca2+-ATPase. The K gradient in the presence of valinomycin stimulates the ATP-dependent Ca2+ transport in proteoliposomes.

Adenosine Triphosphate↗
PubMedDate not supplied

[Inhibition with tetracaine of passive Ca2+ flux through the membrane of the sarcoplasmic reticulum of skeletal muscles].

The initial fast phase of Ca2+ efflux from vesicles of sarcoplasmic reticulum (SR) loaded with Ca2+ passively or in ATP-dependent process and the initial fast phase of Ca2+ influx into the SR vesicles are inhibited by 0.5 mM tetracaine. The inhibitory action of tetracaine observed both with the heavy and light SR fractions is competitive with Ca2+, decreased with varying pH from 5.8 to 7.8 and temperature from 20 degrees C to 37 degrees C. Choline chloride in the concentration of 150 mM at 37 degrees C prevents the inhibitory action of tetracaine. It is supposed that electrostatic interaction plays an essential role in tetracaine-inhibition of passive Ca2+ fluxes through the membrane.

Animals↗
PubMedDate not supplied

[Effect of caffeine on kinetics of accumulation and release of Ca2+ by vesicles of the sarcoplasmic reticulum of skeletal muscle].

The action of caffeine was studied on the heavy sarcoplasmic reticulum fraction enriched by vesicles derived from terminal cisterns. Caffeine lowers the ATP-dependent accumulation of Ca2+ by vesicles and enhances the first rapid phase of the Ci2+ release from vesicles. The action of caffeine was transient, reversed, Ca2+-dependent. The data obtained suggest that the reduction of ATP-dependent calcium accumulation and enhancement of calcium release by caffeine are mediated by the mechanism of Ca2+-induced Ca2+ release and support the view that caffeine may regulate the equilibrium between open and closed states of Ca2+-channel by increasing the affinity of Ca2+-receptor site of the channel.

Adenosine Triphosphate↗