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H Obazawa

Publications and source records attributed to H Obazawa.

At least 19 recordsLinked to original sources
PubMed1992

Reduced glutathione levels in senile cataractous lens epithelial cells.

A sensitive assay, utilizing high performance liquid chromatography and sulfhydryl (SH) fluorescence labeling, was used for the quantitative determination of reduced glutathione (GSH) and cysteine (CySH) in senile cataractous lens epithelial cells. The capsule-epithelia (CE), obtained following cataract surgery, were soaked in 0.3 ml saline at room temperature for 1 hour. Detached epithelial cells and the capsule with attached residual cells were assayed for GSH and CySH. Regression analysis of the relation between epithelial protein content and capsule wet weight was performed to evaluate the amount of contamination of the CE samples with lens cortex. GSH levels in the cataractous lens epithelial cells were 23.0 +/- 11.2 (Mean +/- S.D.) nmol/mg protein (n = 15); CySH levels were 0.51 +/- 0.50 nmol/mg protein (n = 12). No differences in GSH levels were observed between immature and mature cataracts. Thus, GSH levels in the lens epithelial cells did not appear to decrease with the progression of the senile cataracts.

Aged↗
PubMed1991

Regional and subcellular distribution of ascorbate free radical reductase activity in the human lens.

This paper reports that the human lens is endowed with a characteristic regional and subcellular distribution of ascorbate free radical (AFR) reductase (EC 1.6.5.4) activity, and it is associated with the soluble fraction of the lens protein. AFR reductase activity in either immature senile cataractous or transparent lens was higher in the cortex, where the level of insoluble protein is lower, than in the nucleus. The high reductase activity and low insoluble protein content of the cortex were comparable between the assayed cataractous and transparent lenses. In the nucleus, in contrast, the reductase activity tended to decrease with an increase in the level of insoluble protein and with the development of nuclear coloration (sclerosis). As for the subcellular distribution of AFR reductase activity, 70-90% of the enzyme activity in the lens was located in the cytosol fraction. Based on the above results, it was proposed that cytosolic free radicals may be involved in oxidation, coloration and aggregation of lens protein in senile cataractogenesis and in lens aging.

Aged↗
PubMed1990

Activities of ascorbate free radical reductase and H2O2-dependent NADH oxidation in senile cataractous human lenses.

Changes in activities of ascorbate free radical (AFR) reductase (NADH:AFR oxidoreductase) and H2O2-dependent NADH oxidation were correlated with levels of insoluble protein in senile cataractous human lenses. The H2O2-dependent NADH oxidation activity was measured to reflect the content of free glutathione. AFR reductase activities in all the cataractous lenses assayed here tended to decrease with increase of insoluble protein contents. A similar tendency in the relationship between lens protein aggregation and H2O2-dependent NADH oxidation activities, i.e. free glutathione contents was recognized in the lenses with pale yellow, yellow or dark yellow nucleus. However, for the highest levels of insoluble protein, some of the brunescent cataractous lenses exhibited very high activities of H2O2-dependent NADH oxidation, and some brunescent lenses had very low activities. From the above results, it is suggested that lens protein aggregates in the brunescent and non-brunescent cataractous lenses may be formed through significantly different oxidation processes, respectively. The possible mechanisms such as free radical reaction and disulfide bond formation are discussed.

Aged↗
PubMed1990

Classification system for cataracts. Application by the Japanese Cooperative Cataract Epidemiology Study Group.

A cataract classification and grading system for the main purpose of cataract epidemiological studies is proposed by the Japanese Cooperative Cataract Epidemiology Study Group. Cataractous types are classified principally into cortical, nuclear and subcapsular opacities. Stages of cataract advancement are classified into grade I (early stage), grade II (moderate stage) and grade III (advanced stage). Regarding cortical opacities an opacified area obtained from red-reflex images is utilized for grading judgment. Nuclear opacity grading is based on the intensity of scattering at the nucleus. Grading of subcapsular opacities is judged from their extension in the three different pupillary areas. To help grading judgments, standard pictures of cortical and nuclear cataracts are provided. Gradings of lens coloration are divided into pale yellow (grade I), yellow (II), brownish yellow (III) and brown including reddish and black brown (IV). A recording chart is also provided.

Adult↗
PubMed1990

H2O2-dependent NADH oxidation activity in senile cataractous human lens: its relation to glutathione redox cycle.

The present study has demonstrated that H2O2-dependent NADH oxidation activity in aged transparent and senile cataractous human lenses is due to a glutathione redox cycle which consists of reduced glutathione, oxidized glutathione, glutathione peroxidase and glutathione reductase. Especially, the NADH oxidation activity was proportional to the content of free glutathione (reduced plus oxidized forms) under our assay conditions. Employing this simple assay method, the present report has also shown that in the aged and cataractous lenses with pale yellow, yellow or dark yellow nucleus, the free glutathione contents tend to decrease with the increase of insoluble protein contents. However, lens protein was remarkably insolubilized in the lenses with cataracta brunescens, regardless of their exhibiting low or high glutathione contents. The relationship among protein aggregation, coloration and glutathione concentration in the cataractous lenses has been discussed from these findings.

Aged↗
PubMed1989

[A cataract classification and grading system].

A cataract classification and grading system developed for cataract epidemiological survey was introduced. Cataractous opacities were classified into cortical, nuclear and subcapsular types. Gradings of cataract progression were divided into early (Grade I), moderate (II) and advanced (III) stages. The grading of cortical opacity was judged by the opaque area in a maximally dilated pupillary zone of which findings were obtained from a red-reflex image. The grading of nuclear opacity was judged from the intensity of scattering light at the nucleus. Three grading steps were based on the densitometrical analysis of photographed images. Subcapsular opacities were classified into three gradings by extensions up to the normal, moderately dilated and maximally dilated pupil size. Regarding cortical and unclear cataracts, standard images indicating border findings between Grades I and II and Grades II and III were provided to help with classification. Nuclear coloration was classified into pale yellow, yellow, brownish yellow and brown including reddish brown and black brown. To document cataractous findings, a recording chart was made.

Cataract↗
PubMed1989

Calcium-induced opacification of rat lens beta-crystallin solution: its susceptibility to H2O2 oxidation.

Isolation of alpha, beta and gamma-crystallin solutions from rat lens soluble fraction was carried out by DEAE-cellulose ion-exchange column chromatography, and the effects of H2O2 on calcium-induced opacification of these solutions was examined. The alpha-crystallin solution became turbid in the presence of 1-10 mM calcium ions, and the turbidity increased with increasing calcium concentrations. The opacification level of the alpha-crystallin solution was not affected by 200 microM H2O2 treatment for 24 hours. On the other hand, the calcium-induced turbidity of a solution of beta-crystallin not treated with H2O2 was about one-third that of the alpha-crystallin, but by the H2O2 oxidation, its calcium-induced opacification was remarkably accelerated beyond the opacification level of the alpha-crystallin. The gamma-crystallin solution was made turbid by the H2O2 oxidation, but its turbidity was changed little by the addition of calcium ions. From the above results, it is suggested that the H2O2 acceleration of calcium-induced opacification of whole soluble lens protein solution previously reported might be mainly due to the aggregation properties of beta-crystallin. Furthermore, it is proposed that in the whole soluble lens protein, the calcium-induced aggregation of alpha-crystallin might be kept at almost the same low level whether the H2O2 treatment is done or not, and that the beta-crystallin might be more susceptible to H2O2 than the alpha- and gamma-crystallins.

Animals↗
PubMed1988

Ascorbate free radical reductase and ascorbate redox cycle in the human lens.

The presence of ascorbate free radical (AFR) reductase (NADH:AFR oxidoreductase, EC 1.6.5.4) in senile cataractous human lenses was demonstrated by measuring spectrophotometrically NADH oxidation in the presence of ascorbate plus ascorbate oxidase. About 80-85% of the lens AFR reductase was probably recovered in the supernatant of the lens homogenate. Michaelis constants of the reductase were about 10 microM and less than 1 microM for AFR and NADH, respectively. We also showed that AFR reductase activities in the cataractous lenses tended to decrease with increase of insoluble lens protein contents, or showed rather the possibility that the reductase activity may have decreased before the lens protein aggregation. In the highest activity group (about 120-160 nmol NADH oxidized/min/lens), it was roughly calculated that the reductase in the lens could re-reduce immediately the total (or almost total) amount of AFR produced there by ascorbate oxidation even at a high rate of 600-800 microM/min, if NADH concentration in the lens were sufficiently maintained. The above results suggested that AFR reductase in the human lens plays important roles in ascorbate regeneration of its redox cycle, and that activity loss of AFR reductase, as well as of superoxide dismutase, glutathione peroxidase and glutathione reductase, may be responsible for the oxidative changes in lens proteins with the development of senile cataracts.

Aged↗
PubMed1986

Scavenging of chlorpromazine cation radical by ascorbic acid or glutathione.

The report presented here demonstrates that scavenging of chlorpromazine cation radical (an absorption maximum = 530 nm) by ascorbic acid or glutathione can be kinetically and stoichiometrically analyzed at pH 1.5 but not at pH 3.0 and 6.0 using a conventional absorption spectrophotometer. The cation radical decays spontaneously about 10 and 200 times faster at pH 3.0 and 6.0, respectively, than at pH 1.5. At pH 1.5, ascorbic acid scavenges the cation radical faster than glutathione does, and the following different scavenging mechanisms are postulated from the above kinetic and stoichiometric analysis. The reaction of the cation radical with ascorbic acid is second order. The ascorbic acid free radical, which decays mainly by dismutation, is generated by the bimolecular reaction. In the case of glutathione, on the other hand, about 70% of the scavenged cation radical disappears through free radical chain reactions that glutathione thiol anion and glutathione free radical probably initiate. The remaining (about 30%) disappears by conjugation with glutathione. It may be due to relative nonreactivity of ascorbic acid free radical that free radical chain reactions, found commonly in radical chemistry, do not occur in the scavenging reaction by ascorbic acid. Based on the above results, the physiological scavenging mechanisms of the cation radical by the two reducing substances are discussed briefly.

Ascorbic Acid↗
PubMed1985

Calcium-induced lens protein aggregation accelerated by reactive oxygen species photosensitized in the presence of hydroxykynurenines.

Photo-oxidation with 3-OH L-kynurenine O-beta-glucoside or 3-OH L-kynurenine accelerates the aggregation of water-soluble protein in the rat lens due to the presence of calcium ion. The present report demonstrates that hydrogen peroxide and superoxide anion mediate a large part of the photodynamic acceleration with hydroxykynurenine compounds. In addition, 3-OH L-kynurenine O-beta-glucoside seems to photosensitize more of the two reactive oxygen species than 3-OH L-kynurenine. The findings are discussed together with other photodynamic effects of hydroxykynurenine compounds.

Animals↗