Masaaki Kurasaki

Combined effects of working environmental conditions in VDT work

The combined effects of city noise and luminance of the computer display were evaluated from the changes in lymphocytes and mental activities of participants. Healthy male students were tested under the following four experimental conditions: (1) a calculating task on a video display terminal (VDT) with luminance of 90 cd m-2 without city noise; (2) a calculating task on a VDT with luminance of 20 cd m-2 without city noise; (3) a calculating task on a VDT with luminance of 90 cd m-2 with city noise of 70 dB(A); and (4) a calculating task on a VDT with luminance of 20 cd m-2 with city noise of 70 dB(A). A visual reaction test (VRT) was performed, and critical flicker fusion frequency (CFF), heart rate (HR), numbers of circulating white blood cells (WBCs), lymphocyte subsets and subjective symptoms of fatigue were measured (1) before; (2) just after; and (3) 30 min after each 60 min test. Subjective symptoms of fatigue significantly increased just after experiments conducted under the two noisy conditions. VRT and CFF showed significant changes in the case of the highluminance display with noise. WBCs and neutrophils showed significant increases in the two quiet conditions. These results suggested that high luminance with noise had the most effect on subjective fatigue and mental activities.

Protective effect of taurine against renal interstitial fibrosis of rats induced by cisplatin

Abstract. This study was undertaken to investigate the effect of taurine on the infiltration of macrophages and the progression of renal interstitial fibrosis in the kidneys of rats treated with cisplatin (CDDP). Male rats in different groups were treated as follows: (1) saline as control, (2) CDDP and (3) CDDP plus taurine in drinking water. At weeks 2, 4 and 6 after the fifth CDDP injection, we examined platinum content, the kinetics of macrophages and the areas of fibrosis. In the histologic analyses, fibrotic areas were found to have developed around dilated or atrophic tubules in the corticomedullary junction in the kidneys of CDDP-treated rats, while CDDP-plus-taurine-treated rats showed a reduction of the extent and magnitude of damage. These findings reflect the fact that the percentage of fibrotic areas in the kidney of CDDP-plus-taurine-treated rats was significantly lower than in that of CDDP-injected rats throughout the recovery period (P<0.05). Compared with normal rats, the macrophages in CDDP-injected rats showed significant increases in number at weeks 2, 4 and 6 (P<0.05). In contrast, the number of macrophages in CDDP-plus-taurine-treated rats was significantly smaller than that of CDDP-injected rats. These results suggested that taurine suppressed the increase of infiltrating macrophages, and led to the attenuation of renal interstitial fibrosis (P<0.05).

Bcl-2-linked apoptosis due to increase in NO synthase in brain of SAMP10.

We examined the linkage of nitric oxide (NO)-induced apoptosis to acceleration of brain aging of senescence-accelerated mouse prone 10 (SAMP10). The expression of neuronal nitric oxide synthase (nNOS) increased in the cerebral cortex of the brain of SAMP10 in an age-dependent manner and significantly higher levels of neuronal nitric oxide synthase (nNOS) were observed in both young and old SAMP10 as compared to age-matched controls. Moreover, a lower level of anti-apoptotic protein Bcl-2 and a higher level of pro-apoptotic protein cytochrome c in cytosol were observed in SAMP10 compared to the control. However, there was no significant difference in the expression of pro-apoptotic protein p53 between SAMP10 and the control. Furthermore, terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL)-positive apoptotic cells were more abundant in the cerebral cortex of aged SAMP10 than in the control. The present results suggest that an age-dependent increase of NO by up-regulation of nNOS promotes the Bcl-2-linked apoptosis in the cerebral cortex of SAMP10 and this may cause the acceleration of brain aging of SAMP10.

2,4,5-Trichlorophenoxyacetic acid inhibits apoptosis in PC12 cells.

2,4,5-Trichlorophenoxyacetic acid (2,4,5-T) is an endocrine disrupter that exerts cytotoxic effects on organisms. In this study, the influence of 2,4,5-T at low concentrations on apoptosis in PC 12 cells was investigated. Although no apoptotic features were observed in PC12 cells treated with 2,4,5-T, it inhibited the DNA fragmentation induced by serum deprivation. In addition, the cell viability of PC12 cells increased after treatment with 2,4,5-T. In conclusion, 2,4,5-T suppressed the apoptosis of the cultured cells. Since apoptosis is a morphological and biochemical description of a physiological mechanism of cell death that is commonly associated with programmed events necessary for development of individuals and organs, the inhibitory effect of 2,4,5-T on apoptosis might cause serious damage to cell homeostasis and differentiation.

Localization of the induced metallothionein and DNA damage in rat kidney after gold injection.

To clarify the relationships between DNA damage and Cu-MT and between DNA damage and Cu in kidneys of rats injected with Au, we examined the histochemical localization of DNA damage, metallothionein (MT), and the accumulated Cu in the kidneys of rats injected with Au, Cu, or Cu-MT. The immunoreactivity of MT was observed predominantly in the outer stripe of the outer medulla and the inner cortex of the Au-injected rat, and the signals of terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-biotin nick end labeling (TUNEL) were observed in the cortex. Cu detected by Timms method was mainly distributed in the cortex of the Au-injected rat. These results indicated that DNA damage could be caused by free Cu in the cortex but not by the Cu bound to MT in the outer stripe of the outer medulla. This consideration was supported by the data from rats injected with Cu and Cu-MT. Furthermore, we determined the Cu contents in three fractions (cytosol, organelle, and precipitate-containing nuclei) of the kidneys. Interestingly, most of the Cu content in the kidney of the rat injected with Au or Cu-MT was detected in the cytosol, whereas most of the Cu content in the kidney of the rat injected with Cu was detected in the nuclei-containing precipitate. These findings suggest that the DNA damage in the kidneys of rats injected with Au may be associated with Cu-binding proteins but not with Cu-MT.