Yukio Seki

Age-dependent changes in metallothionein levels in liver and kidney of the Japanese.

Samples of liver, renal cortex, and medulla were obtained from 55 forensic autopsies (0- to 95-yr-old Japanese). Metallothionein (MT) was determined by the Ag-hem or Cd-hem method. Zinc (Zn), copper (Cu), and cadmium (Cd) were determined by atomic absorption spectrophotometry. The mean levels of MT were 250 μg/g in the liver, and 394 μg/g (cortex) and 191 μg/g (medulla) in the kidney. Age-dependent changes were observed in both the liver and kidney. In the liver, MT level decreased during infancy and increased thereafter with age. Similar age-dependent changes in the levels of Zn and Cu were observed. In the kidney cortex, MT level increased with age, although no correlation was found after middle age. The levels of Cd and Zn also increased with age until middle age; however, they decreased thereafter. These results suggest that age-dependent changes in renal MT levels are associated with accumulation of Cd.

Trichloro-compounds in the urine of humans exposed to methyl chloroform at sub-threshold levels

SummarySurvey was carried out in 4 intaglio printing factories where methyl chloroform, the sole organic solvent in the entire process, was employed to remove excess ink. The medical interview and clinico-laboratory examinations revealed no dose-consistent adverse effects among the four groups of workers who had been exposed at the average concentrations of 4, 25, 28 and 53 ppm, respectively. Linear relationship was observed between environmental vapour concentrations and total trichloro-compounds levels in the urine of workers exposed. Increased levels of urinary metabolites towards the week-end, together with the biological half-life of 8.7 hrs as measured from the decrease in the urinary metabolites, suggested the storage of methyl chloroform in the body after repeated exposures. Perusal of previous reports as well as present results regarding toxic potency of methyl chloroform supports, with emphasis of possible accumulation, the German threshold of 200 ppm as a tentative value of choice for the time being.

A Study on the Relative Breakthrough Time (RBT) of a Respirator Cartridge for Forty-Six Kinds of Organic Solvent Vapors

The breakthrough time of a commercially available respirator cartridge was measured for 46 kinds of organic solvents. The condition of the test air flow was set according to the Japanese government standard for the National Approval Test: at 300 ppm of an organic solvent vapor concentration, a temperature of 20 degrees C, a relative humidity of 50 percent, and a flow rate of 30 L/min. The interval between the start of passing the test flow through a cartridge and the time when the concentration of organic solvent vapors at the downstream of the cartridge reached 5 ppm was measured. The ratios of breakthrough times of organic solvents to that of cyclohexane which is designated as the standard test vapor in Japan, were calculated to obtain the relative breakthrough times (RBTs). Nine of the 46 organic solvents had breakthrough times shorter than that of cyclohexane, and these organic solvents with shorter RBTs were characterized by low boiling points and small molecular weights. The RBTs of 34 organic solvents were compared with the breakthrough times reported by Nelson et al. The relationship between the RBTs of this experiment and those reported by Nelson correlated well (correlation coefficient: 0.861).

A Linear Pharmacokinetic Model Predicts Usefulness of N-Methyl-2-Pyrrolidone (NMP) in Plasma or Urine as a Biomarker for Biological Monitoring for NMP Exposure

A Linear Pharmacokinetic Model Predicts Usefulness of N‐Methyl‐2‐Pyrrolidone (NMP) in Plasma or Urine as a Biomarker for Biological Monitoring for NMP Exposure: Xiaofei E, et al. Department of Hygiene, Akita University School of Medicine—N‐methyl‐2‐pyrrolidone (NMP: C5H9NO:CAS number 872‐50‐4) is an increasingly used solvent due to the lack of ozone depleting activity. The aim of this study is to construct a simple pharmacokinetic model for NMP. In factory A, four workers who were exposed to NMP at 0.09‐0.69 ppm for 12 h by time weighted average (TWA) were followed up for an entire workweek. Their NMP concentrations in plasma and urine were monitored during the observation period. Five volunteers were exposed to NMP during the observation of workers in the factory A for eight hours. NMP kinetics in plasma and urine were monitored for 2 d after exposure. Concentrations of NMP in plasma and urine as standardized by creatinine concentrations were used to construct a one compartment pharmacokinetic model. The model successfully simulated the kinetics in four workers and five volunteers. In the next step, the model was applied to eight workers in another factory: they were exposed to NMP for 12 h at 0.04 to 0.59 ppm by TWA. The model could successfully predict kinetics of NMP levels in plasma and urine at the end of work. The model was then applied to experimental exposure cases in the literature. The model successfully predicted the concentrations of NMP in plasma and urine at the exposure intensity level of 12 ppm x 8 h. These results imply that metabolic saturation does not occur up to the exposure intensity of 12 ppm x 8 h and demonstrate the usefulness of determinations of NMP in plasma and urine for biological monitoring.

Environmental and Biological Monitoring of 2, 2-Dichloro-1, 1, 1-trifluoroethane (HCFC-123)

Received Sept 16, 1998; Accepted Sept 28, 1998 Correspondence to: S. Tanaka, Faculty of Hygienic Technology, School of Allied Health Sciences, Kitasato University, 1-15-1 Kitasato, Sagamihara, Kanagawa 228-8555, Japan Table 1. Analytical condition of gas chromatograph

A Simple Method for Detecting Breakthroughs in Used Chemical Cartridges

This study was intended to develop a simple method using a gas detector tube to detect the end of the service lives of chemical cartridges for organic solvent vapors. The practical usefulness of this method was confirmed by two series of experimental observations of cartridge service lives: (1) The breakthrough times for six organic solvents were determined by passing a test airflow through a cartridge, and the concentration at each breakthrough was measured with a gas chromatograph (GC). These GC-obtained concentrations were compared with the migrated vapor concentrations through each broken cartridge measured with a gas detector tube. (2) CS2 breakthrough of the cartridges used on 32 viscose rayon workers were measured with detector tubes, after which the residual service life of each cartridge was determined. In laboratory experiments the released concentrations detected by the gas detector tube were approximately equal to the final leak concentrations measured by GC. In a field survey the used cartridges exhibiting a stain of CS2 from detector tubes for concentrations greater than 4 ppm were found not to have enough residual adsorption capacity for CS2. Migrated concentrations of CS2 measured with detector tubes were found to be a reasonable predictor of remaining service life.

Metallothionein-like cadmium binding protein in rat testes administered with cadmium and selenium.

It is well known that the testicular damage caused by acute cadmium toxicity are protected by simultaneous selenium administration with cadmium, and that the cadmium concentration in the testis increases remarkably as compared with that of only cadmium administration. The increased cadmium in the testis was found in the high molecular weight fraction containing selenium, and it has been thought that the shift of cadmium from the low molecular weight fraction to the high molecular weight fraction containing selenium is an important protection mechanism. However, the cadmium concentration in this high molecular weight fraction decreased with time, then re-shifted to the fraction of metallothionein, a low molecular weight protein having a protective effect against cadmium toxicity. While recently studying the cadmium binding protein, like metallothionein, in testes, it has been reported that the amino acid composition of cadmium binding protein in testis is not similar to that of the hepatic metallothionein. The present study was undertaken to clarify the properties of the increased cadmium binding protein in the testis protected by simultaneous selenium administration with cadmium.

Metallothionein in the cerebral cortex of rats showing hereditary high ability in sidman avoidance test

The changes in metallothionein (MT) and trace elements (Zn, Cu, Fe, Mn) in the cerebral cortex with aging were investigated for THA (Tokai High Avoider) rats and Wistar rats as control. The level of MT in the cerebral cortex of THA rats increased until 8 weeks old, and the high MT level was maintained thereafter (about 2.5 fold) compared to the levels in Wistar rats. MT in Wistar rats maintained a lower level from age 3 days to 15 weeks, and thereafter increased gradually up to age 40 weeks. In line with the change in MT level in the cerebral cortex, Zn concentration of THA rats also increased with age of rats. It was found that MT concentration in the cerebral cortex of THA rats increased significantly in response to the increasing Zn concentration from early age, compared to Wistar rats. However, the increased Zn concentration in Wistar rats did not correspond to the increase in MT level. The relationship between MT levels and trace elements, particularly Zn, in the cerebral cortex of THA rats, is described with respect to the age of rats.

Induction of metallothionein-like cadmium binding protein in testis and its protective role against cadmium toxicity

Despite the numerous studies conducted on the testicular Cadmium (Cd) binding protein (Cd-BP) or metallothionein (MT), there is still no consensus on whether the testicular Cd-BP is the same as MT. Moreover, it is unclear whether the testicular Cd-BP is inducible. Therefore, the possible induction of MT-like Cd-BP was investigated in rat testis after oral Cd administration and Cd injection.