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R N Glebov

Publications and source records attributed to R N Glebov.

At least 37 records · Page 2Linked to original sources
PubMed1988

[Effects of somatotropic hormone on Na, K-ATPase of the synaptosomal membrane of the young rat brain].

Human somatotropic hormone (STH), starting from a concentration of 5.10(38) M, was found to inactivate in vitro (by 37%) the Na, K-ATPase activity of osmotically disrupted synaptosomes from 3-week-old rat brain. The inhibitory effect of STH was stronger with higher concentrations. The synaptosomal Mg- and Ca-ATPase activities were stimulated by STH (5.10(-9)-5.10(-6) M). Only at a concentration of 5.10(-6) M STH did inactivate the synaptosomal Na, K-ATPase from the adult rat brain.

Age Factors↗
PubMed1988

[Changes in serum hormone and peptide levels in rats in experimental epilepsy].

Serum levels of 7 hormones and neuropeptides were studied in the course of development of a generalized epileptic activity (EA) induced in rats by intraperitoneal administration of corasole (75 mg/kg), i.e. 30 s (latent period), 50-150 s, 5-10 min after epileptogenic administration. A significant increase in the levels of ACTH (5.2-fold), glucagon (1.8.-fold), angiotensin I and renin activity were shown to occur 90-180 s later. Further on in the course of EA the level of ACTH remained enhanced but the level of glucagon and renin-angiotensin activity returned to normal. The levels of cortisol, vasopressin and aldosterone were enhanced 2-3-fold 30 min later. The level of insulin 30 min later remained unchanged. The role of neuropeptides and hormones in the onset and suppression of EA is discussed.

Adrenal Cortex Hormones↗
PubMed1988

[Electrogenic character of the functioning of H+-ATPase of synaptic vesicles in the rat brain].

Transmembrane potential (TMP) of synaptic vesicles (SV) from the rat brain was registered by means of potential-sensitive fluorescent probe 3,3' dipropylthiocarbocyanine iodide (dis-C3-(5)). It was found that Mg-ATP generates TMP on the SV membrane suspended in sucrose-buffer medium. TMP did not appear if 0.25 M sucrose medium was replaced by 0.125 M KCl medium or 0.125 NaCl medium, or if the SV membrane was disrupted by triton X-100 or alamethicin, or if there was protonophore m-chlorophenylhydrazone or N-ethylmaleimide influence on SV. The data obtained indicate that functioning of SV proton pump is electrogenic and the level of TMP depends on the presence of anion Cl- in the incubation medium.

Adenosine Triphosphate↗
PubMed1987

[Anion regulation of active transport of protons across the membrane of the synaptic vesicles of the brain].

The dependence of active transport of H+ on the presence of anions in synaptic vesicle membranes from rat brain was studied. The H+ transport was measured by monitoring the acidification of the vesicles with a permeant weak base-acridine orange. The fluorescence changes in the latter were proportional to the magnitude of artificially imposed pH gradients (delta pH). The ATP-dependent generation of delta pH was completely dependent on the presence of a permeant anion, was maximal at 150 mM Cl- and was inhibited, when the medium osmolarity was further increased by sucrose or KCl. At 150 mM only Br-, similar to Cl-, behaved as permeant anions, whereas I- was effective only at low (5-20 mM) concentrations. The anions--SCN-, ClO4-, HSO3- and I-(10-20 mM) as well as 4-acetamido-4'-isothiocyanatostilbene-2.2'-disulfonate (K0.5 = 14 microM) blocked the ATP-dependent generation of delta pH observed in the presence of Cl-, while other anions tested (F-, phosphate, bicarbonate, some organic anions) were virtually without effect and did not support the H+ transport. The dependence of the rate and extent of H+ accumulation on Cl- concentration was sigmoidal with a Hill coefficient of 2.8 and a Km value of 85-90 mM. The effects of anions point to the presence in the membrane of synaptic vesicles of an anion (chloride) channel whose conductance can regulate the H+ transport by switching it from an electrogenic to an electroneutral (coupled entry of H+ and Cl-) mode of operation.

Animals↗
PubMed1987

[Ca2+ ion enhancement of the inhibitory influence of neuroleptics on the Na, K-ATPase of brain synaptosomes].

In the experiments on synaptosomes from the caudate nucleus of the rat brain, neuroleptic drugs (6 types) were found to inhibit the Na, K-ATPase activity considerably stronger (13-51 times, as compared to IC16 values) in the presence of Ca2+ ions (0.25 mM) than in their absence. The enhancement of the inhibitory activity was due to a decrease in the negative cooperation of neuroleptic interaction with the enzyme seen in the absence of Ca2+.

Animals↗
PubMed1987

[Ratio of brain synaptosome Na, K-ATPase to dopamine receptors].

Activating (0.3-3 microM) or inhibitory (0.03-0.3 mM) effects of dopamine (DA) in the absence of Ca2+, and its inhibitory effect in the presence of Ca2+ on Na,K-ATPase activity of synaptosomes from the caudate nucleus of the rat brain were confirmed. Na,K-ATPase was shown to be inhibited by 6 neuroleptics, with the degree of inhibition stronger in the presence of Ca2+. It was found that: 1) the biphasic or monophasic nature of DA action on Na,K-ATPase activity was preserved in the presence of neuroleptics, 2) DA enhances the inhibitory effects of neuroleptics on the enzyme, 3) the inhibitory effects of DA on Na,K-ATPase are enhanced by Ca2+ ions. The mechanisms of the modifying action of DA on synaptosomal Na,K-ATPase are discussed.

Animals↗
PubMed1987

[Transport Ca-ATPase activity of brain synaptic membranes in rats with korazol-induced epileptic activity].

Changes in the activity of transport Ca-ATPase in osmotically disrupted synaptosomes were studied in corazol-induced generalized epileptic activity (EA) monitored by electrocorticogram. The enzyme activity was found to be unchanged at the beginning of the latent period, but significantly diminished towards the end of the latent period and further reduced at the peak of EA. After ET was no longer observed the enzyme activity returned to normal. The activity of transport Ca-ATPase in synaptic junction fraction was found to be 3 times higher than in osmotically disrupted synaptosomes. A possible role of the inactivation of membrane Ca pump in synaptic brain structures is discussed in relation to pathological hyperactivity of neurons.

Animals↗
PubMed1987

[Effect of verapamil on focal epileptic activity in the rat cerebral cortex].

Experiments were carried out on 64 nonanesthetized male Wistar rats (200-220 g). Epileptic foci were induced by the application of a filter paper saturated with a solution of benzylpenicillin sodium salt (12,000 and 20,000 U/ml) to the sensorimotor cortex. It was shown that subsequent intraperitoneal administration of verapamil (5 mg/kg and 10 mg/kg) during steady focal epileptic activity (EpA) resulted in the suppression of EpA in most animals. The antiepileptic effect of verapamil was manifested in a reduced frequency and amplitude of spike discharges, decreased power of epileptic foci and less frequent appearance of seizure (ictal) discharges. The role of Ca canals of neuronal membranes in the pathogenesis of epilepsy is discussed.

Animals↗
PubMed1987

[Interaction of isolated brain synaptic vesicles with flat bilayer membranes in the rat].

The conductivity of planar bilayer membrane comprising asolectin and phosphatidylserine (concentration ratio 9:1) in a buffer solution increased sharply in the presence of synaptic vesicles (SV) isolated from the rat brain and added to one side of the membrane only. The bilayer remained stable upon modification, and the conductivity increment was dependent on SV concentration in the range from 4 to 16 mu of the total protein per ml. If I mM CaCl2 was present in the buffer solution, the conductivity increased by 2 to 3 orders of magnitude upon the addition of SV at a final concentration of 3-4 mu protein per ml. The membrane was unstable and its rupture occurred often at an early stage of conductivity changes. In the absence of SV addition the membrane was stable, with its conductivity remaining unchanged for 2 h and more. With I mM CaCl2 addition to the solution already containing SV, no conductivity changes were observed, the cause perhaps, being Ca2+-induced SV aggregation.

Animals↗
PubMed1986

[Action of triftazin on the physicochemical properties and the membrane proton pump of the synaptic vesicles in the rat brain].

The effects of trifluoperazine (TFP) on some membrane processes were studied in the isolated rat brain synaptic vesicles (SV). TFP (10(-5)-10(-4) M) was found to cause a sharp rise in the intensity of light scattering by SV suspension which was due both to an increased vesicle aggregation and to changes in the refraction index of the membrane. In addition, TFP blocked the ATP-dependent proton transport into the vesicles (K0.5 = 10(-6) M) with the concomitant stimulation of the ATPase activity which suggests an uncoupling effect caused by the permeation of this weak base through the membrane and subsequent protonation in an acid interior medium resulting in the elimination of a proton gradient. Thus, the neuroleptic drug--TFP has various effects on membrane processes which are apparently unrelated to its recognized role as a calmodulin antagonist.

Animals↗
PubMed1986

[Interaction of isolated synaptic vesicles with synaptic contacts in the rat brain].

The effects of Mg-ATP, EGTA, EDTA and dicyclohexylcarbodiimide on the changes in the intensity of light scattering were studied in rat brain synaptic vesicles (SV) suspended in saccharose-buffer medium. Specific interactions between SV and isolated synaptic junctional complex were observed in the presence of Mg-ATP and calmodulin. An in vitro model of exocytosis is discussed.

Animals↗
PubMed1985

[Aggregation and swelling of brain synaptic vesicles in rats].

Mg-ATPase (1 mM) induces a decrease in the intensity of light scattering (I1) at 620 nm of rat brain synaptic vesicles (SV) suspended in sucrose, with this decrease being indicative of the swelling of the vesicles. The Mg-ATPase-induced swelling appears to be associated with the function of H+-ATPase of SV membranes, since it is completely abolished by the proton pump blocker dicyclohexylcarbodiimide and the protonophore carbonylcyanide m-chlorophenylhydrazone. The Mg-ATPase-induced swelling was enhanced in the presence of the permeable anion Cl- (in the range of 25-50 mM KCl). Ca2+ (and Mg2+) at high concentrations (0.1-1.0 mM) cause aggregation of the SV as measured by changes in the I1. Colchicine and cytochalasin do not affect SV swelling and aggregation whereas Mg-ATP (1 mM) lowers aggregation caused by Ca2+ (1 mM).

Adenosine Triphosphatases↗
PubMed1985

[ATP-dependent proton translocation across the synaptic vesicle membrane in the brain of rats].

Changes in pH in rat brain synaptic vesicles (SV) were studied with the use of the fluorescent slightly basic dye acridine orange. The pH value in isolated SV was found to be acidic, which was confirmed by the ionophore sensitive accumulation of the dye. Addition of ATP provoked further acidification of the intravesicular medium. The acidification rate reached a maximum after dissipation of the existing H+ gradient seen during preincubation in the absence of ATP. The ATP-dependent acidification was eliminated by the protonophore carbonylcyanide m-chlorophenylhydrazone, H4Cl or the detergent triton X-199 (0.025%). Valinomycin inhibited the ATP-dependent translocation of H+ whatever the incubation medium (with KCl or NaCl). Dicyclohexylcarbodiimide, a known inhibitor of proton ATPases (100 microM) as well as ethylmaleimide (100 microM) completely blocked H+ translocation whereas oligomycin, a specific blocker of mitochondrial H+-ATPase, and ouabain did not influence that process. ATP induced H+ translocation only in the presence of Mn2+ or Mg2+ but not in the presence of Ca2+. The translocation of H+ was not affected by the replacement of univalent cations (KCl, NaCl or Cl), however, it was prevented completely upon replacement of the penetrating anion Cl- by the non-penetrating anion O2-4 or upon replacement of the salts by sucrose. It is concluded that the ATP-dependent translocation of H+ in SV is mediated via H+-ATPase which maintains the low pH value in SV.

Acridine Orange↗
PubMed1985

[Effect of dopamine and dopamine mimetics on Na, K-ATPase of corpus striatum synaptosomes].

Dopamine (DA) and DA-mimetics (apomorphine, midantan, piribedil) have a dual effect on Na, K-ATPase of the rat brain striate synaptosomes: activating at micromolar concentrations and inhibitory at higher concentrations (less than or equal to 30 microM). In the presence of Ca2+ (1 mM EGTA + 2.5 mM Ca2+) DA activating effect completely disappears and the inhibitory effect becomes even more pronounced. In the presence of cAMP (50 microM) which has no effect of its own on Na, K-ATPase, DA activation maximum is shifted towards lower concentrations, and the inhibitory effect remains unchanged. The above mentioned effects of DA persist in the presence of ouabain (1 mM), i.e. during measuring of Na, K-ATPase activity by an "ouabain" method, with DA activation maximum shifted towards higher concentrations.

Amantadine↗
PubMed1984

[Dynamics of the change in Na, K-ATPase activity during the development of isoproterenol-induced myocardial necrosis in rats].

Na, K-ATPase activity of heart tissue homogenates was found to be depressed 6 and 24 h after the last injection of isoproterenol to rats (100 mg/kg s. c. daily for 2 consecutive days) whereas after 1 h it was essentially unchanged. The extent of the reduction in the enzyme activity was virtually the same both 6 and 24 h after myocardial necrosis induction (18 and 19%, respectively). The time-course of changes in the activity of the sarcolemmal marker enzyme was compared to the reported data on the increased sarcolemmal permeability in isoproterenol-induced myocardial necrosis.

Adenosine Triphosphatases↗
PubMed1984

[Evidence for the presence of H+-ATPase in the membrane of brain synaptic vesicles in the rat].

Mg-ATPase of rat brain synaptic vesicles (SV) is considerably (by 85%) inhibited by dicyclohexyl carbodiimide (200 microM), a blocker of proton pumps, whereas orthovanadate (100 microM) does not produce any influence on the enzyme. Oligomycin (5 micrograms/ml) does not alter Mg-ATPase activity of the SV, whereas N-ethylmaleimide (300 microM) reduces it to a moderate degree, namely by 35%. This indicates that Mg-ATPase of the SV differs from mitochondrial ATPase. The protonophore p-trichloromethoxycarbonyl cyanide phenylhydrazone (20 microM) and bicarbonate anions (20 mM) stimulate slightly (by 12 to 25%) Mg-ATPase of the SV. Bicarbonate (20 mM) raises 1.8-2.1-fold Mg-ATPase activity of the mitochondria isolated from rat brain. It is assumed that the membrane of brain SV contains proton ATPase (H+-ATPase) differing from mitochondrial H+-ATPase in some of the properties.

Adenosine Triphosphatases↗