An experimental study was carried out to clarify the relationships between lead exposure and the changes in nerve conduction velocities or in por-phyrin metabolism in rats. The rats in Groups A, B and C received intraperitoneal lead injections in respective doses of 0, 0.2 and 2.0 mg/kg of lead, once a week for 22 weeks. During the experiment, all rats grew normally, and there was no signi-ficant difference in the group mean body weights. Lead concentrations in the blood and organs increased in these groups as the lead dose increased. Significant changes in nerve function and in biochemical indices relating to porphyrin metabolism were observed only in Group C treated with 2.0 mg/kg of lead, and not in the other groups. In Group C, urinary coproporphyrin and free erythrocyte protoporphyrin increased from an early stage, 4-6th week, of the lead administration, and urinary δ-aminolevulinic acid increased from the 8th week. Slight but significant slowing of conduction velocity in motor nerves appeared from the 10th week, when the rats had received lead injection 9 times in total. The change in distal motor latency occurred from the 16th week. No functional change in sensory nerves was ob-served in this study.
Fluctuations in accommodation, accommodative function, visual acuity and subjective symptom were investigated on the basis of two hours of character search work by VDT operators. As a means to determine the visual load en-countered in VDT work, the fluctuations in accommodation were analyzed using the computer method developed by the authors in eight young women. Visual acuity and amplitude of accommodation in the dominant eye diminished with VDT work time. In terms of the fluctuations in accommodation, it was found that, as VDT work time progressed, the frequency of the peak frequency band range lowered and the low-frequency ratio increased. Compared to the pre-test level, there was a significant increase in the low-frequency ratio after 2 hours of VDT work. With time, the mean number of complaints of eye strain and fatigue increased significantly in VDT work. The low-frequency ratio of fluctuation in accommodation was showed to increase before the number of complaints were found to increase. Results suggested that computer analysis using the scale method offers a faster, more objective approach to measure visual load from VDT work.
Changes in the concentrations of adrenaline and noradrenaline in various organs of the rat were examined during and following four hours' swimming in 25°C water. During the period of swimming, the adrenaline concentration increased time-dependently in the heart, spleen, kidney, liver, lung, abdominal wall muscle and thigh muscle, whereas the noradrenaline concentration tended to decrease. Three hours after the end of swimming, adrenaline concentrations in the peripheral organs were reduced, but were still higher than those of the control group. The adrenaline value returned to normal within 24 hours. From these results, adrenaline concentrations in the heart and various other peripheral organs are considered to increase gradually with the duration of swimming and to be considerably high for at least several hours after the cessation of swimming.
Nonselect Wistar rats and high-and stable-avoidance and low-variability (HA) rats were exposed to 100 ppm toluene vapor or air seven hours a day from the 13th day of gestation to 48 days of age. After termination of toluene exposure, the rats were examined by the Sidman avoidance test for 10 days. There was no difference between the toluene-exposed group and the control in the appearance of developmental signs in either the nonselect Wistar rats of HA rats. In the exposed HA males, learning acquisition was slow, and the individual variation in avoidance rates was as large as that of the nonselect rats. In the control HA males, avoidance learning was acquired rapidly and stabilized. A significant difference in avoidance was indicated between the exposed and the control HA rats. In HA females, learning acquisition and speed and magnitude of individual variation in avoidance rates in the exposed rats did not differ greatly from those of the controls. Slow learning acquisition and a large magnitude of individual variation in avoidance rates were displayed in the male and female nonselect Wistar rats. But in both the male and female controls of the nonselect rats, learning acquisition and individual variation did not differ from those of the exposed nonselect rats. No difference in avoidance was indicated between the exposed rats and the controls in either males or females.
It has been confirmed by several animal experiments that the exposure of the part of visible light called blue light (wavelength region : approximately 400-500 nm) produces photochemical lesions on the retina. The American Conference of Governmental Industrial Hygienist (ACGIH) recommended an evaluation method of blue-light radiation hazards and threshold limit values (TLVs) based on it : blue-light effective radiance (integrated spectral radiance weighted against bluelight hazard function) of a light source should be measured to evaluate its blue-light radiation hazards and should be compared with the TLV. But very few studies have been made on blue-light radiation hazards in the workplace because suitable methods of measuring blue-light effective radiance have not been developed yet. In this study, an instrument to measure blue light was developed, and the bluelight effective radiance of welding arcs was determined with it under 14 different welding conditions. The maximum of the obtained ACGIH blue-light effective radiance is 2.4 W/cm2-sr of metal active gas (MAG) welding of soft steel, of which the permissible exposure duration per day would be approximately 42 seconds, according to the recommendation of the ACGIH. This is the level at which welders do not suffer retinal injury from blue-light radiation, if they wear an eye protector with a filter suitable for their vision during welding operations, as they actually do in the workplace.
We developed a method for the determination of erythrocyte pyrimidine 5'-nucleotidase (P5N) activity in human blood using a high-performance liquid chromatograph (HPLC). In this method, UMP (uridine 5'-monophosphate disodium salt) was used as a substrate and assay solutions were directly prepared from whole blood. Uridine formed by the enzyme reaction of P5N was determined spectrophotometrically at 260 nm after separation from the substrate and blood components by HPLC. The optimum pH of this reaction was 7.5. This HPLC method was very rapid and simple compared to the conventional method, because of eliminating the need for dialysis of erythrocyte lysate prior to the assay. The present method was applied to the examination of P51N activity in the blood of lead workers, indicating that the P5N activity is significantly inhibited in these workers.