Teruo Nagaya

Urinary total protein and β-2-microglobulin in workers exposed to trichloroethylene

Chlorinated solvents are thought to be more nephrotoxic than nonchlorinated solvents in humans. Many workers have been exposed to trichloroethylene (TCE) because TCE is one of the most useful chlorinated solvents in some industries. Thus, to detect adverse effects of human exposure to TCE on kidneys, urinary total protein (U-TP) and beta-2-microglobulin (U-B2M) were determined in 104 male workers occupationally exposed to TCE and 102 male nonexposed controls. The workers have been probably exposed to 15 ppm TCE in air. The U-TP level of the workers, rather than the U-B2M level, was slightly higher than those of the controls. The differences of the U-TP level or the U-B2M level between the two groups, however, were not significant excluding an exception. (The mean U-TP level for 35- to 44-year-old workers was significantly higher than that for corresponding controls.) These results suggest that adverse effects of occupational exposure to TCE on kidney is very mild and glomerular rather than tubular.

Sister-chromatid exchanges in lymphocytes of workers exposed to trichloroethylene

To detect mutagenic effects of trichloroethylene (TCE) on humans, sister-chromatid exchanges (SCEs) were analyzed in lymphocytes of 22 workers occupationally exposed to TCE and 22 matched controls. Although urinalysis in the workers revealed their obvious exposure to TCE, no increase in SCE frequencies was found in lymphocytes of the workers. SCE analysis in lymphocytes could not detect mutagenic effects by occupational exposure to TCE on humans.

Relationships between serum saturated fatty acids and serum total cholesterol and HDL-cholesterol in humans

To investigate the effects of serum saturated fatty acids (FAs) on human cholesterol metabolism, total-cholesterol (T-C), HDL-cholesterol (HDL-C), T-C/HDL-C ratio, and FA composition [myristic acid (MA, 14:0), palmitic acid (PA, 16:0) and stearic acid (SA, 18:0)] were determined in serum from 115 men and 120 women (20–70 years old). MA, PA and SA were expressed as percentages of serum total FAs. Using multivariate analysis to account for the confounding effects of age, body mass index, drinking, and smoking it was found that SA was negatively correlated with T-C and T-C/HDL-C ratio in both men and women. In men MA was negatively correlated with HDL-C, and in women SA was positively correlated with HDL-C. Although PA was the major component of serum saturated FAs, PA had no significant relation to any cholesterol indices in either sex. These results suggest that serum MA may aggravate and serum SA may improve cholesterol metabolism, thereby influencing the risk for ischaemic heart disease.

Subclinical and reversible hepatic effects of occupational exposure to trichloroethylene

SummaryTo detect early hepatic effects of chronic exposure to low-level trichloroethylene (TCE), serum total cholesterol (T-C), high-density-lipoprotein cholesterol (HDL-C) and activities of three serum enzymes [aspartate aminotransferase (AST), alanine aminotransferase (ALT), and γ-glutamyl transpeptidase (GGT)] were determined in 148 workers (a cross-sectional study) and in 13 workers (a 2-year follow-up study) occupationally exposed to TCE in air. In the cross-sectional study, three exposure groups were defined by urinary total trichlorocompounds (U-TTC) levels of the workers [low-exposure group (n = 49) : U-TTC < 10 mg/g creatinine; moderate-exposure group (n = 56): U-TTC 10-<100; highexposure group (n = 43): U-TTC ≽ 100]. With increasing exposure levels, T-C (P = 0.143 by ANOVA) and HDL-C (P = 0.080 by ANOVA) slightly increased. The exposure, however, had no effect on the activities of the three serum enyzmes. In the follow-up study, the fluctuations in U-TTC were well reflected in subclinical changes in HDL-C, AST, and GGT, but not in T-C or ALT. These results suggest that exposure to low-level TCE influences hepatic functions, affecting cholesterol metabolism rather than causing hepatic cell damage, and that these influences are subclinical and reversible. The increases in HDL-C caused by exposure to low-level TCE may be an example of “chemical hormesis” in humans.

No increase in sister-chromatid exchange frequency in lymphocytes of chromium platers

To detect mutagenic effects of hexavalent chromium (Cr) in vivo, sister-chromatid exchange (SCE) frequency was analyzed in lymphocytes of 24 Cr platers occupationally exposed to hexavalent Cr and 24 matched controls. There were no significant differences in SCE frequency between the two groups. Smokers, both Cr platers and controls, had a significantly higher SCE frequency than non-smokers.

Spontaneous and induced sister chromatid exchanges in lymphocytes of healthy persons

Spontaneous and mitomycin C-induced sister chromatid exchanges (SCEs) in lymphocytes were analyzed in 46 healthy persons. Our results suggest that the frequency of spontaneous SCE in lymphocytes is useful for evaluation of the biological effects of environmental mutagens, and that the induced-SCE test with a mutagen and lymphocytes may be used to detect persons with a high sensitivity to the mutagen.

Effects of smoking on spontaneous and induced sister chromatid exchanges in lymphocytes

Spontaneous and mitomycin C-induced sister chromatid exchanges (SCEs) in lymphocytes were analyzed in 24 non-smokers and 24 sex- and age-matched smokers. Mean spontaneous SCE frequency for non-smokers was 9.8 SCEs/cell, and that for smokers was 11.5 SCEs/cell. The difference was statistically significant (P less than 0.001 by t-test). These results suggest that spontaneous SCE frequency in lymphocytes is useful for evaluation of biological effects of environmental mutagens. However, we could not find any effects of smoking on the sensitivities of lymphocytes to mitomycin C in vitro. The effects of mutagens on humans may be independent of one another.

Milk consumption decreases activity of human serum alkaline phosphatase: A cross-sectional study

Since the Japanese have not reached the recommended daily allowance (RDA) for calcium (600 mg), milk is recommended as a Ca-rich food to increase Ca intake and prevent osteoporosis in Japan. To determine whether milk consumption influences Ca/bone metabolism in the Ca-deficient population, relationships between milk consumption and serum alkaline phosphatase (Al-P) activity were analyzed in 3,098 premenopausal and 1,182 postmenopausal women and 13,141 men aged 30 to 69 years. Milk consumption was classified into no/yes groups by a self-administered questionnaire that asked Do you drink a glass of milk (180 to 200 mL) or more everyday?. Regardless of age or sex, the yes group had a lower activity of serum Al-P than the no group. Milk consumption decreased the activity to a greater degree in women, especially perimenopausal/postmenopausal women, than in men. These results were confirmed in a multivariate analysis considering age, body mass index (BMI), and smoking and drinking habits as confounding factors. Although menopause obviously increased serum Al-P activity in perimenopausal women, it could not influence the effects of milk consumption on the activity. These results suggest that milk has osteostatic effects on humans via a mechanism different from that of estrogens. Milk consumption, even one glass per day, may be an easy and effective strategy for prevention of osteoporosis in the Ca-deficient population, especially perimenopausal/postmenopausal women.

Early renal effects of occupational exposure to low-level hexavalent chromium

To detect early renal effects of occupational exposure to hexavalent chromium (Cr), urinary total proteins (U-TP), urinary albumin (U-Alb) and urinary retinol-binding protein (U-RBP) were determined in 166 male Cr platers and 106 male controls. The mean employment time in Cr plating for the platers was 12.6 years. Urinary Cr (U-Cr), which was determined as an index of Cr exposure, ranged from “not detected” to 19.91 μg/g creatinine in the platers. The U-Cr level was lower than those in other previous studies. Age-adjusted U-TP, U-Alb or U-RBP levels were not different between the platers and the controls. In the platers, a significant positive correlation was found between age-adjusted U-TP and U-Cr, but U-Cr had no significant relation to age-adjusted U-Alb or U-RBP level. Employment time had no effect on any age-adjusted urinary proteins. The Cr exposure may have been too low to induce definite renal dysfunction. Early renal effects of low-level Cr exposure may be mild, and may not be specific to renal function.