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Biomedical subjects

M A Ostrovskiĭ

Publications and source records attributed to M A Ostrovskiĭ.

At least 73 records · Page 4Linked to original sources
PubMedDate not supplied

[Effect of melanin on the free-radical states of gamma-irradiated proteins and lipids].

It was shown that the concentration of paramagnetic centres of dihydroxyphenylalanine-melanin increased after gamma-irradiation (60Co) both at room temperature (an irreversible increase) and at 77 K (a reversible increase). The accumulation of paramagnetic centres in gamma-irradiated albumin at room temperature was found to slow down appreciably in the presence of melanin. This effect is thought to be associated with the antiradical activity of the pigment.

Albumins↗
PubMedDate not supplied

[Rhodopsin photo-oxidation: oxygen consumption and spectrum of activity].

The coincidence of action spectrum of SH-groups and lipid oxidation is shown in the photoreceptor photodamaging process. Dose dependence of the process is measured in the maximum of photooxidation (380 nm). Dose of 0.1 J/cm2 is the threshold of photodamaging of photoreceptor membrane. Oxygen consumption in photooxidation of rhodopsin SH-groups and lipids are determined.

Animals↗
PubMedDate not supplied

[The system of protection of the eye structures from photo damage. Screening pigments in vertebrates--melanosomes as inhibitors of photo-oxidation processes].

Melanosomes from retinal pigmented epithelium readily inhibit photooxidation of lipids. This effect is due to both passive screening of light and chemical interaction of melanosomes with products of oxidation. The role of melanosomes is discussed in the system of optic and chemical protection of eye structures from photo injury. It is suggested that in other tissues (skin) melanosomes account for the similar function of optic and chemical (antioxidative) protection from the injurious effect of UV and visible light.

Animals↗
PubMedDate not supplied

[Quenching of singlet molecular oxygen by screening pigments-- melanins and ommochromes].

Synthetic DOPA-melanin and natural screening pigments--sepiomelanin and ommochromes are shown to quench the luminescence of singlet molecular oxygen (1O2) in aqueous (D2O, pD = 7.5-8.1) solutions. The rate constants of 1O2 quenching are found to be equal to (1.2 +/- 0.6) 10(8) M-1 s-1 for monomeric units in DOPA-melanin and to (3 +/- 1) 10(6) M-1 s-1 for ommochromes. The data suggest that screening is not the only function of melanins, which may play a role of inhibitors of photodynamic damage in living tissues.

Animals↗
PubMedDate not supplied

[Study of the binding of iron ions by melanoprotein granules of the eye pigment epithelium using gamma-resonance spectroscopy].

Interaction between Fe2+ ions and melanoproteid granules (MPG) of bovine eye pigment epithelium was studied by gammaresonance spectroscopy. MPG was found to form complexes with bi- and three-valent ferrum ions. MPG can both directly bind Fe2+ ions and oxidize them Fe3+ inactive in prooxidant state and bind the latter. The activity of ferrum ion binding increases when suspension is illuminated with visible light and pH of the incubation solution increases. The protein part of MPG does not participate in the complex formation with ferrum ions. The complex formation proceeds mainly by carboxyl, amino- and imino-groups of melanin polymer.

Animals↗
PubMedDate not supplied

[Binding of iron ions by shielding eye pigments of vertebrates and invertebrates--melanosomes and ommochromes].

Melanosomas of eye pigment epithelium tissue of vertebrates, synthetic DOPA-melanin and ommochromas from eye of invertebrates bind effectively bivalent iron ions. Constants of the binding process are calculated. Endogenic iron concentration in melanosomas of the frog eye pigment epithelium is determined. A conclusion is drawn that mechanism of antioxidation action of shielding eye pigments may include Fe2+ ion binding into inactive components.

Animals↗
PubMedDate not supplied

[Comparative study of crystallins from the nucleus and cortex of the bovine ocular lens by the gel filtration and x-ray diffraction methods].

Water--soluble proteins (alpha-, beta H-, beta L- and gamma-crystallins) from the bovine lens nucleus and cortex were fractionated and compared by gel filtration on Sephadex G-200. X-ray diffraction patterns from concentrated gels of these proteins were obtained. It allowed to compare qualitatively the structures of different crystallins and also to identify the maxima on X-ray diffraction patterns of the lens intact tissue.

Animals↗
PubMedDate not supplied

[Retinal-sensitized photo-oxidation of rhodopsin].

Kinetics of retinal photosensitized initiation of radicals of sulfhydryl groups of cysteine and rhodopsin is investigated by spin trapping. Photooxidation of both systems is the result of free radical mechanism. Photooxidation of SH-groups proceeds both with singlet oxygen participation and by direct interaction of photosensitizer with the substrate. The rate constants of these reactions are measured. The rate constant with oxygen participation (K0 = 1.1 X 10(9) M-1 S-1) is higher than the one without oxygen (K = 2.5 X 10(8) M-1 S-1) correspondingly. The lifetime of retinal triplet state in photoreceptor membrane is tau = 4 X 10(-6) s.

Animals↗