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A V Dmitriev

Publications and source records attributed to A V Dmitriev.

At least 19 recordsLinked to original sources
PubMed2002

Data failures in the "Riabina-2" experiment on MIR orbital station.

Experimental data about high-energy particle fluxes obtained in 1990-2000 in the Riabina-2 experiment on board MIR orbital station are analyzed in the sense of data failures. There are two types of failure. The first type is represented as sharp positive or negative spikes on the relatively smooth time profiles of the particle fluxes. The second type is randomly distributed data gaps with durations of up to tens minutes. These two kinds of the data failures are formalized in the form of "failure occurrence probability" (FOP). The comparison analysis of the FOP with solar activity, solar wind conditions and geomagnetic activity shows that one half of the observed data failures are owing to noise originating mostly from electronic equipment on board MIR station. The other half of the data failures are closely connected to geomagnetic storms and interplanetary disturbances. The space station surface charge and radio signal distortion in disturbed ionosphere are considered as possible phenomena responsible for the data failures.

Electronic Data Processing↗
PubMed2002

[Study of IS-elements aimed at establishing a degree of the relationship of multiple-serotype Streptococcal strains of group B].

The presence and restriction fragment length polymorphism of IS 861 and IS 1548 were analyzed among 113 streptococcal strains of group B. 13 strains were found to possess both IS 861 and IS 1548, 54 strains were found to possess only IS 861, and 46 strains had neither IS 861 nor IS 1548. 9 HindIII and 6 EcoRI restriction patterns, hybridizing correspondingly with IS 861 and IS 1548, were discovered. A certain correlation between IS 1548 and IS 861 hybridizing patterns, on the one hand, and restriction patterns, found by pulse-electrophoresis, on the other hand, was established. It was demonstrated that restriction fragment length polymorphism of IS 1548 and 861 can be used to evaluate the degree of relationship between the strains.

Animals↗
PubMed2001

Circadian clock regulation of pH in the rabbit retina.

Although it is generally accepted that the acid-base ratio of tissue, as represented by the pH, is strictly regulated to maintain normal function, recent studies in the mammalian nervous system have shown that neuronal activity can result in significant shifts in pH. In the mammalian retina, many cellular phenomena, including neuronal activity, are regulated by a circadian clock. We thus investigated whether a clock regulates retinal pH, using pH-sensitive microelectrodes to measure the extracellular pH (pH(o)) of the in vitro rabbit retina in the subjective day and night, that is, under conditions of constant darkness. These measurements demonstrated that a circadian clock regulates the pH(o) of the rabbit retina so that the pH(o) is lower at night than in the day. This day/night difference in retinal pH(o) was observed when the rabbits were maintained on a normal light/dark cycle and after they were maintained on a light/dark cycle that was phase-delayed by 9 hr. Continuous recordings of retinal pH(o) around subjective dusk indicated that the change from daytime to nighttime pH(o) is relatively fast and suggested that the clock that regulates pH(o) is located in the retina. The lowest pH(o) recorded in the retina in both the day and night was in the vicinity of the inner segments of photoreceptor cells, supporting the idea that photoreceptors serve as the primary source of protons. The circadian-induced shift in pH(o) was several times greater than light-induced pH(o) changes. These findings suggest that a circadian clock in the mammalian retina regulates retinal pH.

Animals↗
PubMed2000

A circadian clock regulates the pH of the fish retina.

Although it is generally accepted that the acid/base ratio of tissue, as represented by the pH, is strictly regulated to maintain normal function, recent studies in the nervous system have shown that neuronal activity can result in significant shifts in pH. In the vertebrate retina, many cellular phenomena, including neuronal activity, are regulated by a circadian clock. We thus investigated whether a circadian clock regulates the pH of the retina. pH-sensitive microelectrodes were used to measure the extracellular pH of the in vitro goldfish retina superfused with a bicarbonate-based Ringer solution in the subjective day and night; that is, under conditions of constant darkness. These measurements demonstrated that a circadian clock regulates the pH of the vertebrate retina so that the pH is lower at night compared to the day. This day-night difference in retinal pH was observed at two different values of Ringer solution pH, indicating that the circadian phenomenon is independent of the superfusion conditions. The circadian-induced shift in pH was several times greater than light-induced pH changes and large enough to influence synaptic transmission between retinal neurons. These findings indicate that a circadian clock regulates the pH of the vertebrate retina. Thus, an intrinsic oscillator in neural tissue may modulate metabolic activity and pH as part of normal daily function.

Animals↗
PubMed1999

Inhibition of membrane-bound carbonic anhydrase decreases subretinal pH and volume.

PURPOSE: The lipophilic carbonic anhydrase (CA) inhibitor acetazolamide has been shown to enhance subretinal fluid resorption, reduce subretinal pH, and can improve cystoid macular edema, but its clinical use is limited by systemic side effects. While these are most likely a result of inhibiting intracellular CA isoenzymes, retinal pigment epithelial (RPE) transport is thought to be modulated via membrane-bound CA. This study investigates whether benzolamide, a hydrophilic CA inhibitor that does not readily penetrate cell membranes, is sufficient to modulate subretinal volume and pH. METHODS: Volume and pH were assessed in the subretinal space (SRS) of the perfused chick retina-RPE-choroid preparation by calculating these variables from data obtained with two different double-barreled, ion-selective electrodes (H+ for pH and the extracellular space marker tetramethylammonium (TMA+) for SRS volume). Light induced variations and changes in baseline measurements were recorded before and after addition of 10(-4) M acetazolamide or benzolamide to the basal perfusion. RESULTS: Basal perfusion with either drug induced both an acidification of the SRS by 0.02-0.04 pH units, which occurred within 60 s, as well as an increase in the amplitude of the light-induced alkalinisation of the SRS. TMA+ concentration in the SRS increased steadily over a period of several minutes after basal perfusion with either of the CA inhibitors, and the calculated SRS volume was reduced by 40% within 8-10 min. CONCLUSION: The observation that benzolamide had effects equal to acetazolamide suggests that inhibition of membrane-bound CA at the basolateral membrane of the RPE is sufficient to decrease subretinal pH and volume. This may represent a clinically important mechanism for the resorption of sub- and intraretinal fluid.

Acetazolamide↗
PubMed1998

Energetic neutron and gamma-ray spectra under the earth radiation belts according to "SALYUT-7" [correction of "SALUTE-7"]-"KOSMOS-1686" orbital complex and "CORONAS-I" satellite data.

The spectra of neutrons >10 MeV and gamma-rays 1.5-100 MeV under the Earth Radiation Belts, restored from the data, obtained onboard orbital complex "SALYUT-7" [correction of "SALUTE-7"]-"KOSMOS-1686", are presented. The spectra shapes are similar to those for albedo neutrons and gamma-rays, but absolute values of their fluxes (0.2 cm-2 s-1 for neutrons, 0.8 cm-2 s-1 for gamma-rays at the equator and 1.2 cm-2 s-1, 1.9 cm-2 s-1, accordingly, at L=1.9) are several times as large. It is possibly explained by the fact that most of the detected particles were produced by the cosmic ray interactions with the orbital complex matter. Neutron and gamma-ray fluxes obtained from "CORONAS-1" data are near those for albedo particles.

Cosmic Radiation↗
PubMed1998

[Genetic analysis of pathogenic streptococci groups A and B].

The study deals with the genetic mapping of chromosomal DNA of groups A (AS) and B (BS) pathogenetic Streptococci. Its stages are presented and considered. The maps of these microorganisms are compared. A collection of epidemic AS and BS was analyzed by employing pulsed field gel electrophoresis. AS and BS were found to show heterogeneity of DNA sequences and the common pattern of gene location on the chromosomes.

Child↗
PubMed1996

[Obtaining and properties of recombinant protein G].

A gene for G protein from Streptococcus strain G148 was cloned in Escherichia coli, which gave rise to several plasmids. One plasmid containing a 1.5 kb insert coding for entire G protein with 63 kD. This protein had both an IgG binding capacity and albumin-binding activity. The second plasmid containing a 0.7 kD insert coded for protein with MM of 38 kD and had only an IgG-binding activity. The third coding for protein with 25 kD has only albumin-binding activity. After subcloning the 1.5-kb insert into the other vector pSP65 and analysing the nucleotide sequence of this insert both in pSP65 vector, the authors came to the conclusion that the proteins obtained are fusion protein of G protein and beta-galactosidase. All the proteins were prepared by affinity chromatography on IgG sepharose or on HSA sepharose. The interaction between G protein and polyclonal and monoclonal IgG of the reactions between G protein and human IgG have determined.

Blotting, Western↗
PubMed1994

Mathematical model of TMA+ diffusion and prediction of light-dependent subretinal hydration in chick retina.

PURPOSE: To derive a mathematical model of TMA+ diffusion across the retina that can be used to estimate the amplitude and kinetics of the light-evoked increase in subretinal hydration and its effect on the concentration of other ions. METHODS: All experimental data were obtained in chick retina-pigment epithelium-choroid preparations as described in the accompanying paper. RESULTS: Diffusional properties of the retina were derived from the time course of [TMA+]o in the subretinal space (SRS) after changes in the retinal perfusate. Then, the SRS volume changes underlying the light-induced [TMA+]o response can be derived using a mathematical model of TMA+ diffusion. Complete retinal depth series of light-evoked [TMA+]o responses could be simulated by producing a corresponding expansion of the SRS. Volume changes inferred from the diffusion model were 2.2 to 3.8 times larger and more prolonged than could be derived directly from delta [TMA+]o. The model predicted up to a 20% peak increase in subretinal-space hydration during illumination. The effects of this volume increase on subretinal K+ and Ca2+ were estimated. These predictions were supported by inhibiting the volume increase with DIDS, which blocks retinal pigment epithelium basal membrane Cl- conductance. CONCLUSIONS: The primary source of light-evoked changes in extracellular TMA+ concentration recorded throughout the retina is an increase in hydration (volume) of the subretinal space. The response spreads to the inner retina by diffusion. Effects of TMA+ diffusion lead to large underestimates of the underlying volume changes. The light-evoked volume change alters the composition of the subretinal space and light-induced responses of other ions.

Animals↗
PubMed1990

[Work conditions and health status of specialist meteorologists working with weather charts].

The contributors present a generalized description of the labour conditions' hygienic assessment and state of health of the communication service technicians and weather forecasters engaged in the State meteorology service centres in the northern and southern regions of the country. The unfavourable labour conditions' impact on the health state is revealed depending on the specificity of the weather-chart makers' working conditions, which lead to morbidity with temporary disability and occupational skin and upper respiratory tract diseases. A complex of tested measures is proposed for the improvement of the working conditions in question.

Absenteeism↗
PubMed1989

[The role of lysosomal enzymes in the pathogenesis of ciliochoroidal detachment].

The paper discusses the role of lysosomal enzymes, in particular beta-galactosidase, as a starting mechanism in the development of ciliochoroidal detachment. The activity of beta-galactosidase was determined in the suprachoroidal fluid, the aqueous humor, in the blood serum before intraocular operation and in posterior sclerotomy. Ciliochoroidal detachment is shown to be accompanied by accumulation of beta-galactosidase in the suprachoroidal space, not correlating with the enzyme content in the blood serum. This allows to speak about a possible participation of this enzyme in the formation of ciliochoroidal detachment.

Cataract↗
PubMed1988

[Mechanism of the action of baclofen on the contractile activity of the myocardium and blood vessels].

The cardiovascular effects of GABA-analogous-baclofen (10(-5) M) have been investigated in the experiments on isolated myocardium and vessels of the rats. The spontaneous contraction of vena porta segments and contraction of papillary muscle and arterial rings segments induced by electrostimulation were registered. Baclofen induced the growth of arterial tonus, decreased the amplitude of phase contraction as well as resulted in positive inotropic effects in myocardium and vena porta. The obsidan did not influence the baclofen effects, but alpha-adrenolytic dihydroergotoxine inhibited the inotropic effects of the drug. It is supposed that hypertensive baclofen effect which is observed during system injection may be caused not only by central, but also by peripheral regulation of calcium change in the myocytes. The latter (possible) kind of regulation may consist in the drug binding with adrenoreceptor and/or direct influence on the calcium transport across sarcolemma.

Animals↗
PubMed1985

[Contribution of cones to activation of the slow PIII-potential of the frog retina].

A cone-specific subcomponent was separated from the slow PIII response of the frog retina. The time-course of cone sPIII was similar to [K+]0 decrease induced by the cone excitation. In comparison with rod sPIII, the cone sPIII had faster time-course, considerably smaller size and often fell below zero line. The data confirm principle similarity of rods and cones mechanism of excitation but suggest that their off-reactions are different.

Animals↗