Hiroshi Koyama

Increased urinary cadmium excretion and its relationship to urinary N-acetyl-β-d-glucosaminidase activity in smokers

To assess the renal effects of low-level exposure to cadmium due to smoking we examined blood and urinary levels of cadmium and urinary excretions of N-acetyl-β-d-glucosaminidase (NAG), β2-microglobulin (BMG) and metallothionein in 94 male workers aged 18–55 years. Both blood and urinary cadmium levels indicated excess exposure to cadmium caused by smoking. The urinary cadmium concentration ranged between 0.1 and 5.0 μg/g creatinine and increased significantly with age in the smokers. Neither urinary NAG nor BMG was increased in the smokers compared from non-smokers. A positive relationship between urinary cadmium and metallothionein was obtained not only in the smokers but also in the non-smokers. Furthermore, in the smokers urinary cadmium and metallothionein was positively related with urinary NAG. Since NAG in urine mostly originates from tubular cells by lysosomal exocytosis, the results may reflect an early cadmium effect on the lysosomal functions. Inhibitory effect of cadmium on the lysosomal degradation activities was discussed as a possible explanation of the positive relationship of urinary cadmium and metallothionein to urinary NAG.

DETERMINATION OF SELENIUM IN THE HUMAN BRAIN BY GRAPHITE FURNACE ATOMIC ABSORPTION SPECTROMETRY

For the investigation of neurological disorders, a development of simple and accessible methods for determining selenium in human brain samples is required. We devised a method of determining selenium using graphite furnace atomic absorption spectrometry (GFAAS). An electrodeless discharge lamp provided the sufficient sensitivity to determine brain selenium. The matrix interferences were avoided by using high temperature, a prolonged pyrolysis step, and a palladium matrix modifier. The technique of standard addition was used to evaluate the sample concentrations. The accuracy of the method was confirmed by a bovine liver reference material. The detection limit of selenium was 0.04 ng. The determined selenium concentrations of human brain cortex and white matter were higher than those of putamen (115–155 and 206–222 ng/g wet wt, respectively). These GFAAS values agreed with those obtained by fluorometric analysis (r=0.91,n=10). Moreover, the GFAAS values were compatible to those reported by other researchers (99–274 ng/g wet wt), in which selenium concentrations in putamen also tended to be higher than the other two regions. We conclude that GFAAS is useful for selenium analysis in brain samples.

Consistent relationship between selenium and apolipoprotein A-II concentrations in the sera of fasting middle-aged male abstainers and regular consumers of alcohol

Several studies have suggested that selenium serum levels may be associated with serum lipids and apolipoproteins. In the present study, 99 clerical workers aged 40–49 yr were selected based on their drinking and smoking habits. The serum concentration of selenium was not affected by these lifestyle factors. The regular drinkers had raised serum high-density lipoprotein cholesterol, apo A-I, and apo A-II concentrations. Correlation analysis showed that serum selenium was positively and consistently associated with apo A-II regardless of alcohol consumption. Factor analysis revealed that serum selenium had no association with factors that represented each lipoprotein fraction (LDL, HDL, and VLDL). The present study indicates that serum selenium is positively correlated only with apo A-II levels.

Daily Response of Blood Pressure to Day-to-Day Variation of Urinary Sodium to Potassium Ratio

The relationship between blood pressure and urinary sodium-to-potassium (Na/K) ratio was assessed in eight healthy men, none of whom used antihypertensive medications. Blood pressure and urinary sodium and potassium concentrations were measured for 11 to 33 days without any dietary restriction. For two of the eight subjects, the urinary Na/K ratio significantly correlated with systolic blood pressure (r=0.70 and 0.45, respectively), and in one of the two subjects, the urinary ratio also positively correlated with diastolic blood pressure (r=0.72). In the others, no relationship between the ratio and blood pressure was observed (r=-0.24 to 0.26). The results indicate that, in some individuals, the daily variation of urinary Na/K ratio is closely correlated with day-to-day changes in blood pressure level, and suggest that the urinary Na/K ratio is useful in the management of the daily sodium and potassium intake balance of hypertensive patients who need to restrict salt intake.

Matrix interferences in the analysis of digested biological tissues with inductively coupled plasma-mass spectrometry

To investigate the physiological roles or toxicity of trace or toxic elements, multielement analysis of limited quantities of samples in the biological tissues is required. Inductively coupled plasma mass spectrometry (ICP-MS) suits this requirement, but spectral and nonspectral interferences are inevitable. We examined correction methods for the nonspectral interferences by analyzing signals of 21 elements in various concentrations of HNO3 as well as five major elements (Na, K, P, Ca, and Cl). Using internal standards, the interferences caused by the major elements were corrected, but the interferences caused by HNO3 were impossible to correct for elements with high ionization potentials. The analytical results using the standard addition method on 14 elements in standard reference materials and fresh brain tissues confirmed the accuracy of this method. Thus, we concluded that the standard addition method is useful to correct for the nonspectral interferences.

High zinc content of scalp hair in rural West Java: A rice‐eating community

Zinc concentrations in scalp hair were determined in 50 Sundanese villagers in West Java, Indonesia. Hair zinc levels increased with age until about 20 years of age and then became constant. The mean level and S.D. of the zinc concentration in adults aged 20 years or more was 199.8 ± 26.7 μg/g (n = 36), which was higher than the reported values in several countries. Our previous study revealed that the dietary zinc intake amounted to 24.9 mg/day for adults and the high consumption of rice, their staple food, contributed 60% of the total daily zinc intake. Although there are some problems in the Sundanese diet such as a shortage of animal products, a diet depending much on rice seems to have an advantage as concerns the nutritional status of zinc.