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Biomedical subjects

M A Ostrovskiĭ

Publications and source records attributed to M A Ostrovskiĭ.

At least 19 recordsLinked to original sources
PubMed2005

[Molecular dynamics simulation of dark-adapted rhodopsin and free opsin].

Molecular dynamics simulation was carried out for the rhodopsin protein to investigate its conformational changes in respect to inclusion of 11-cis retinal chromophore. Molecular dynamics calculations were performed within the time frame 3000 ps. Totally, 3 X 10(6) configurations ofrhodopsin and free opsin were analyzed and compared. It has been shown that the 11-cis retinal rearrangement (adaptation) in opsin strongly affects the surrounding amino acid residues of protein binding pocket and the protein cytoplasmic region. The extracellular part, however, shows comparatively little changes. On basis of the simulation results obtained we propose a molecular mechanism for the rhodopsin protein function as a G-protein-coupled receptor in the state of darkness. We discuss the role of the retinal chromophore as a ligand-antagonist stabilizing the inactive conformation of rhodopsin.

Animals↗
PubMed2004

[The protein arrestin as a regulator of the phototransduction process and as a factor of pathogenesis of the eye diseases].

In the first part of the paper, the results of the investigation of the rhodopsin arrestin interaction are presented. The results were mainly obtained with the technique of the selective labelling of the rhodopsin and arrestin SH-groups and the rhodopsin limited proteolysis. These results are discussed in the frame of the latest data on the three-dimensional structure of arrestin. In the second part of the paper, results of the antigenic properties of arrestin (S-antigen) and its role in the pathogenesis of the retina diseases are summarized. The data on the role of the autoimmune processes in the pathogenesis of diabetic retinopathy are presented. We have also described the results of the use of the elaborated technique of the immune diagnostics in the prognosis of the diabetic retinopathy and retinopathy of the premature babies.

Animals↗
PubMed2003

[Peculiarities of rhodopsin photoconversion at the early stages of photolysis].

The primary stages of rhodopsin photolysis were studied with the low temperature absorption spectroscopy technique. Digitonin extract of bovine rhodopsin was irradiated at -155 degrees C with blue light (436 nm). The following changes of the dark spectrum were recorded in the course of slow rise of the temperature in 1-3 degrees C steps. Simultaneous appearance of more than one spectral product was revealed throughout the batho- to lumirhodopsin transition. An intermediate product transformed along with bathorhodopsin to a next product known as a "blue-shifted intermediate", was observed. The data suggest that appearance of more than one intermediate at each stage of the rhodopsin photolysis reflects existence of multiple conformation states of the rhodopsin molecule in the course of its photoconversion.

Animals↗
PubMed2001

[High resistance of the rat retina rods to hypoxia].

The amplitude of photoreceptor potential was shown to be constant in hypoxia. Under this condition, the energy support of the photoreceptor potential seems to be realized through an anaerobic process rather than the oxidative phosphorylation. The effect of hypoxia was shown to manifest itself in a decrease of the sagged peak part of the photoreceptor potential occurring in response to bright flashes. Such changes of wave form are typical for the case when the rod intracellular potential decreases. The decrease of response amplitude to bright flashes shortens the light scale of the amplitude/light intensity curve.

Animals↗
PubMed1989

[The effect of anions on spectral properties of iodopsin and native cones in the frog retina (microspectrophotometric study)].

Absorption spectra of single outer segments of the frog Rana temporaria photoreceptors were registered. Effects of nitrate and chloride ions on spectral properties of cone and rod pigments were compared. These pigments proved to differ in structure of the native photoreceptor membrane and, therefore, in effect of hydrophile environment on the chromophore centrum. Substitution of chloride by nitrate ions led to the hypochromic shift of the cone absorption spectrum (20-25 nm) but does not affect the spectrum on case of rod pigment. The ionochromic behaviour of cone pigments resembles that of the light-sensitive halobacterium protein halorhodopsin, in native membrane. We suppose that the effect of anions on the chromophore centrum may be the cause of bathochromic shifts of absorption spectra of longwave-length retinal-containing pigments.

Animals↗
PubMed1987

[Aggravating action of oxygen in light injury to the retina in the white rat].

Rhodopsin concentration and "a"-wave ERG decrease, depending on illumination in the range of 360-380 nm have been investigated in albino rats. The dose of 1.8 J/cm2 proved sufficient for a decrease of "a"-wave ERG by 70% and for the reduction in rhodopsin concentration by 80%. The substitution of the air for O2 (1 or 2.5 ata) resulted in a considerable increase of photodamage of the retina.

Air Pressure↗
PubMed1986

[Inhibition by melanin of lipid photo-oxidation].

Removal of melanosomes from retinal pigment epithelium cells is accompanied by a sharp rise in the rate of VIS light-induced lipid peroxidation. The synthetic DOPA-melanin effectively suppresses the UV light-induced lipid peroxidation of cardiolipin not only through a passive decrease of irradiation (optical screening), but also by active chemical inhibition of the reaction. It is assumed that the observed active inhibition is due to the interaction between DOPA-melanin and the free radical products generated in cardiolipin upon UV illumination. It is concluded that the high photoresistance of melanin-containing cells of retinal pigment epithelium is due to the ability of melanosomes to exert strong inhibition of photo-induced lipid peroxidation.

Animals↗
PubMed1985

[Comparison of the antioxidative defense system of pigment epithelium of the eye in pigmented animals and in albinos].

The efficiency of lipid peroxidation inhibition by retinal pigment epithelium of pigmented rabbits is higher than that of albino rabbits. The superoxide dismutase and glutathione peroxidase activities are nearly the same in both tissues; the alpha-tocopherol content is higher in retinal pigment epithelium of albino animals; the oxidation of the pigment epithelium lipid fraction si higher in pigmented animals. It is concluded that the high resistance of pigmented tissue to the effects of prooxidant systems is due to the presence of melanoprotein granules in the pigment epithelium.

Albinism↗
PubMed1984

[Generation of superoxides during the interaction of melanins with oxygen].

The rate of nitroblue tetrazolium (NBT) reduction by dihydroxyphenylalanine-melanin, pheomelanin and retinal pigment epithelium melanosomes under aerobic conditions (pH 7.4) is low both in the dark and upon illumination, but increases drastically in the presence of cetyltrimethylammonium bromide (CTAB). Under these conditions, the light insignificantly stimulates NBT reduction (1.3-fold). The reaction is effectively inhibited by superoxide dismutase. This suggests that superoxide anions (O2-. are formed as intermediate reaction products in the course of NBT reduction by melanins. At alkaline values of pH (greater than or equal to 9.0), the O2-.-dependent reduction of NBT can also take place in the absence of CTAB. In contrast with oxidation of photoreduced riboflavin, the melanin oxidation by O2 cannot induce lipid peroxidation. It is concluded that O2-. generation via melanin oxidation of melanosomes occurs only under non-physiological conditions and can hardly take place in vivo.

Animals↗