Metallothionein (MT) is thought to play a central role in the detoxification of heavy metals, and thus studies on its regulation are toxicologically important. Heavy metal-dependent induction of MT genes is mediated by metal responsive elements (MREs) located upstream of the genes. Zinc regulatory factor (ZRF) is a zinc-dependent MRE-bind-ing protein that was originally detected in HeLa cell nuclear extracts using the most proximal MRE of the human MT-IIA gene (hMREa) as a probe. We show that ZRF in HeLa cell nuclear extracts can also bind to the most potent MRE of the mouse MT-I gene (mMREd). This finding was further confirmed by using partially purified ZRF. Moreover, cadmium could not promote complex formation between ZRF and mMREd at any concentra-tion tested, as is also the case with ZRF and hMREa. These observations suggest that the transcriptional regulatory system of MT genes by zinc is conserved beyond species.
Intratracheal instillation of GaAs suspension has been histopathologically shown to induce a diffuse pulmonary response. In the present study, magnetometry was used to evaluate the effects of intratracheally instilled GaAs on the behavior of externally magne-tized iron particles instilled in rabbit lung. Magnetometric evaluation of the effects of GaAs in rabbits dosed with 30 mg or 300 mg/animal showed significant decreased relaxation of iron particles at 1, 3, 7, 14, 21 and 28 days following instillation compared with the controls. Relaxation indicates a rapid decrease of remanent magnetic field following magnetization of the lungs due to random rotation of phagocytized iron particles in macrophages. Clearance of the iron particles was measured by serial determinations of the remanent magnetic field at the end of magnetization estimated from relaxation curves. Clearance was significantly impaired in rabbits exposed to both doses of GaAs at 14, 21 and 28 days after instillation. Dose-effect relationships were observed in both cases. Histological examination of lungs instilled with these doses indicated active phagocytosis of GaAs and iron particles by alveolar macrophages.
The results of several field visits to orthopaedic clinics and the data obtained from a postal questionnaire were used to evaluate the segmental vibration and noise exposure levels in orthopaedists. The analysis of 54 (85.7%) complete questionnaires showed that hand-held plaster saws were used (Mean±SE, 12.3±1.7 min/week) more often than other tools. The mean frequency-weighted acceleration levels while using these tools were in the range of 2.3-2.4 m/s2. The A-weighted sound pressure levels in orthopaedic clinics while using the same instruments were in the range of 88.7-93.4 dB(A). Regarding the vibration magnitude and exposure time, segmental vibration seems not to be a serious problem in orthopaedists. However, the noise level produced from operating orthopaedic tools may have deleterious effects such as masking of speech communication among staff members. Patients' sleep or rest was thought to be disturbed by such noise levels.
Urinary Cadmium (Cd) levels were measured twice a year from 1986 to 1992 in five workers exposed to cadmium pigment dust. At the end of 1987, the work environment was improved, and urinary Cd was monitored in association with atmospheric Cd. The five subjects were exposed to cadmium dust at maximum concentrations of 0.857 mg/m3 and 0.045 mg/m3, before and after the improvement, respectively. By arbitrarily setting the urinary Cd level of each worker before improvement at 100, the values after improvement ranged from 41.7 to 94.6, yielding no significant difference. Although the environmental level of Cd was decreased by ten-fold or more, no significant decrease in urinary Cd could be detected.
Forty-one stone quarriers were studied with regard to various factors affecting vibration-induced white finger (VWF), i. e., age, total operating time (TOT), body mass index (BMI), smoking, drinking, past history of diseases and sensitivity to cold in childhood. Subjects were asked about these factors by interview according to a questionnaire. TOT and BMI were significantly different between subjects with VWF (VWF group) and those without VWF (NON-VWF group). TOT was considered to be a great factor in stone quarriers. BMI was 21.6 (kg/m2) in VWF group against 24.0 (kg/m2) in NON-VWF group, which suggests that lean subjects may be susceptible to VWF. As for other factors such as age, smoking, drinking, past history of diseases and sensitivity to cold in childhood, our findings showed no significant difference between VWF group and NON-VWF group.