Biomedical subjects

A N Zakharchenko

Publications and source records attributed to A N Zakharchenko.

8 recordsLinked to original sources

PubMed2002

[Spiral computed contrast tomography in diagnosis of juvenile angiofibroma of the base of the skull].

The authors present their experience in surgical and combined treatment of juvenile angiofibroma of the base of the skull (JABS). A total of 180 children were treated, 93.8% of them had advanced tumor and were operated through external approach by Moore. Computed and MR tomographies were made preoperatively and postoperatively in all the patients. Benefits and drawbacks of the above tomographies are analysed. A technique of spiral computed contrast tomography in JABS is described. This tomography has the following advantages: volume visualization of the studied area without artefacts induced by movements; sharper visualization of the vessels; possibility of retrospective reconstruction of the sections with varying interval after the end of the procedure; improved quality of multi-plane reconstructions; reduced radiation dose and time of exposure.

Adolescent↗

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↗

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

[Isolation of Ca 2+-activated photoprotein obelin from Obelia longissima and its use for the recording the outflow of Ca 2+ from fragmented sarcoplasmic reticulum of skeletal muscles].

A high-active stable preparation of obelin has been obtained from the luminescent hydroid Obelia longissima. The preparation is appropriate for determining free Ca2+ in the physiological range of its concentrations Obelin is shown possible to be used to record the processes of Ca2+ release from vesicles of the sarcoplasmic reticulum. In this case a rapid initial phase of Ca2+ outflux replaced by a slower one has been registered. A sharp increase of luminescence caused by the appearance of free Ca2+ in the medium has been registered under the effect of agents either increasing permeability of sarcoplasmic reticulum membranes for Ca2+ (A23187) or destroying the membrane (ethanol, triton X-100). The observed effects are confirmed, a radioactive label being used.

Animals↗

PubMedDate not supplied

[A study of passive Ca2+ flow through the sarcoplasmic reticulum of skeletal muscles. II. Stimulation of passive Ca2+ influx with monovalent cations and anions].

The initial rate of passive Ca2+ influx into "heavy" and "light" fractions of sarcoplasmic reticulum (SR) vesicles increases in the presence of univalent cation chlorides. Stimulation of passive Ca2+ influx decreases in the following order: KCl + valinomycin-KSCN- + valinomycin greater than KSI = NaCl greater than choline chloride. K-gluconate + valinomycin and K-gluconate have no effect on the passive Ca2+ influx into SR vesicles. It is supposed that KCl-stimulation of passive Ca2+ influx into SR vesicles under conditions used may be caused by depolarization of the SR membrane.

Animals↗

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↗