The influence of lipofuscin granules and melanosomes from human retinal pigment epithelium on the light-induced photooxidation of cardiolipin liposomes and the generation of superoxide radicals was studied. Lipofuscin granules were able to stimulate, while melanosomes inhibited, the cardiolipin photooxidation. The visible light irradiation of both melanosomes and lipofuscin granules generated superoxide radicals with mean rates of 1.5 nmole/min/10(7) and 38 nmole/min/10(7) granules, accordingly. However, melanosomes but not lipofuscin granules reacted readily with superoxide radicals. Moreover, the rate constant of degradation of superoxide radicals in the presence of melanosomes was about five orders of magnitude higher than the rate constant of its photogeneration. Therefore, we propose that melanosomes in retinal pigment epithelium cells have a photoprotective role whereas lipofuscin granules may stimulate photodestructive reactions.

Adult↗

PubMedDate not supplied

[Photochromism of visual pigments. I. Formation of isochrome products during reversible transformations of frog rhodopsin].

Reversible phototransformations of rhodopsin of the frog in vitro (in digitonine extracts) at -22 degrees C under the effect of light with gamma 579 and 435 nm are reversible processes. However, while heating photogeneration product, besides true rhodopsin, thermo-unstable form is (pseudorhodopsin) is revealed. It owes its name due to the similarity of its spectral properties and photosensitivity with rhodopsin. At temperatures higher than -22 degrees C the reversibility of the system is disturbed. The nature of pseudorhodopsin is discussed.

Animals↗

PubMedDate not supplied

[Photochromism of visual pigments. II. Kinetics of photoconversion of frog rhodopsin].

A kinetic scheme is suggested of reversible processes of rhodopsin phototransformation at --22 degrees C under light effect with lambda 579 and 435 mm. On the basis of this scheme quantum yields of certain stages are calculated from initial rates of transformations. Dependence of the quantum yield of photolysis of rhodopsin transformation on the wavelength of light and temperature is studied. The scheme of frog rhodopsin transformation is compared with the similar scheme of bovine rhodopsin phototransformation.

Animals↗

PubMedDate not supplied

[Photochromism of visual pigments. III. Comparative study of photoconversions in bovine and frog rhodopsin].

Phototransformations of digitonin extracts of rhodopsin and suspensions of outer segments of frog rods at minus 22 degrees C under the effect of light with lambda 579 and 435 nm are studied. It is shown that the results are not dependent on the presence of digitonin and glycerine, but are characteristic of frog rhodopsin. Phototransformations of bovine rhodopsin under the same conditions differ from those of frog rhodopsin.

Animals↗

PubMedDate not supplied

[Studies of alpha- and betaL-crystallin complex formation in solution at 60 degrees C].

Studies of molecular mechanisms of chaperone-like activity of alpha-crystallin became an active field of research over last years. However, fine interactions between alpha-crystallin and the damaged protein and their complex organization remain largely uncovered. Complexation between alpha- and betaL-crystallins was studied with thermal denaturation of betaL-crystallin at 60 degrees C using small-angle X-ray scattering (SAXS), light scattering, gel-permeation chromatography and electrophoresis. A mixed solution of alpha- and betaL-crystallins in concentrations about 10 mg/ml incubated at 60 degrees C was found to contain their soluble complexes with mean radius of gyration approximately 14 nm, mean molecular weight approximately 4000 kDA and maximal size approximately 40 nm. In pure betaL-crystallin solution, complexes were not observed at 60 degrees C. In SAXS studies, transitions in the alpha-crystallin quaternary structure at 60 degrees C were shown to occur and result in a double increase of the molecular weight. It suggests that during the temperature-induced denaturation of betaL-crystallin it binds with modified alpha-crystallin or, alternatively, alpha-betaL-crystallin complexation and alpha-crystallin modifications are concurrent. Estimates of the alpha-betaL-crystallin dimensions and relative contents of alpha- and betaL-crystallins in the complex suggest that several alpha-crystallin molecules are involved in complex formation.

Crystallins↗

PubMedDate not supplied

[Antibodies to retinal S antigen in the tear and serum as an indicator of the nature of a course of endogenous uveitis in children].

Antibodies (IgM and IgG) to retinal S antigen were studied by enzyme immunoassay in the tear (n = 135) and blood serum (n = 221) samples taken from 45 children with chronic endogenous uveitis during a follow-up (for 6 months to 5 years). The studies have confirmed the early evidence that detection of serum autoantibodies may be used for the diagnosis of autoimmune and infectious-and-autoimmune uveitis, the verification and prediction of renal alterations, risks for lesions in the second eye in unilateral uveitis and prerecurrence in bilateral uveitis. Criteria for detecting antibodies to lacrimal S antigen were developed. Its has been ascertained that it is expedient to use this procedure as a method for controlling the efficiency of treatment in uveitis involving the posterior parts of the eye, confirming, and predicting the risk for involvement of the retina into an inflammatory process, detecting trends for development of chronic forms of both bilateral and unilateral uveitis. Simultaneous accumulation of IgM and/or IgG antibodies in the lacrimal fluid and serum, as well as imbalance, i.e. a prolonged enhancement of only local or only systemic response to S antigen (of both classes), are prognostically unfavorable.

Adolescent↗

PubMedDate not supplied

[Interaction of rhodopsin with quinone].

The reaction of rodopsin extracted with cetyltrimethylammonium bromide with p-benzoquinone was studied with spectrophotometric and ESR methods. In the dark quinone reacted with three SH-groups of rodopsin, in the light with three more SH- and two unknown groups of decolourized rodopsin. The interaction of quinone with SH-groups liberated under light effect on rodopsin proceeds with the formation of intermediate free-radical products.

Animals↗

PubMedDate not supplied

[The "sensory" safety of drugs: photosensitizing damage to the structures of the eye].

Phototoxic side effects of a number of different drugs and natural photosensitizers [correction of photosensors] (psoralenes, psychotropic phenotiazines, anti-malaria drugs, porphirines, adriamycine, etc.) have been analyzed. The ways of study of sensory harmlessness of drugs have been discussed.

Eye↗

PubMedDate not supplied

[Presence of 2 closely situated SH-groups in the rhodopsin molecule].

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Chemical Phenomena↗

PubMedDate not supplied

[Effect of inhibitors of free radical processes on the "dark" paramagnetic centers of the melanoprotein granules of the pigment epithelium of the eye].

Effect of three inhibitors of free radical processes (IFRP) differing in antiradical activity (2-tret. butyl-6-methyl-3-oxipyridin, 2-ethyl-6-methyl-3-oxipyridin and 3-oxipyridin) on paramagnetic centres of melanoprotein granules of pigment epithelium was studied by ESR method at room temperature. It was shown that IFRP decreased the dark signal and that the reaction of paramagnetic particles dissociation proceeded according to the equation of the first order reaction. The rate constants of these reactions were calculated. It was found that the relative amount of reacting and non-reacting paramagnetic particles with the inhibitor depended on the nature and concentration of IFRP.

Animals↗

PubMedDate not supplied

[The absence of channel structures in the photoreceptor membrane of the rod disc].

Comparison of electric characteristics of photoreceptor disc and plasma membranes of photoreceptor was made by means of photopotential registration from the adhized to the impregnated by lipids filters photoreceptor discs or isolated rod outer segments. The resistance of the photoreceptor disc membrane is shown to be by three orders of magnitude higher than the resistance of photoreceptor plasma membrane; namely 1-2 MOhm X cm2 versus 1-2 KOhm X cm2. This is the evidence for the absence of channel structures in the disc membrane.

Animals↗