In order to study vibration transmission to the human body and to design seats or suspensions for vibration isolation in the vehicles, a driving point mechanical impedance was measured on various kinds of body postures. A force pickup which was newly developed using a sheet of thin polymer film and an accelerometer were used as a detector for the impedance measurement. An instrument with analogue computing circuits was also employed, which could automatically calculate the im-pendance and draw an impedance chart expressed by magnitude and phase within 90 sec after the start of measurement The mechanical impedance were measured in the frequency range from 3 to 200 Hz on kneeling, sitting, and standing postures and in addition, at local parts of the body such as the head, hands, and legs. Because of contraction of measur-ing time, the impedances even in unstable postures were able to be measured. As a result, the difference of mechanical impedance was clarified among various sorts of the postures, and transmission mechanism of the vibration in the body could be estimated through the change of the mechanical impedance.
The enzymic activity of lysozyme has been colorimetrically determined by 3, 4- dinitrophenyl-tetra-N-acetyl-β-chitotetraoside. The hydrolytic reaction of the sub-strate by human milk lysozyme is most effective in the buffer, pH 6, with Na+ concentration of 0.1 M. The hydrolytic activities of three human lysozymes and hen egg white lysozyme have been measured by the colorimetric assay.
The relationship between pH and δ-aminolevulinic acid (ALA) dehydratase activity in both erythrocyte and liver tissue was studied in men and mice exposed to lead and compared with that in the normal subjects. When exposed to lead, the pH optimum of ALA dehydratase activity in the liver and blood shifts to a more acid pH than occurs in normal subjects. The exposure to lead also causes depression of this enzyme activity. Especially, in the workers who were exposed to lead during a long term, the change in the pH activity curve of erythrocyte ALA dehydratase caused by lead was reversed to approximately normal by heating the hemolysate or by incubating in the presence of dithiothreitol.
Alveolar macrophage was lavaged from lungs of rats exposed to inhalation of the particles of Sb, Pb, Cd, CaCO3 or poly vinyl chloride (PVC) and its number and 14C-leucine incorporating activity were studied. The number of free cell lavaged from the lung decreased remarkably by the exposure to Sb or Cd fume, while by the exposure to Pb fume, CaCO3 or PVC particles the number of lavaged cells did not change from that of control group breathing air in the exposure chamber. There was found a linear correlation 1 hr after inhalation between 14C-leucine in-corporation value for total cell and the number of lavaged cell in all the experi-mental groups except unrestrained (bred freely under normal condition) group and Sb group. That is, the incorporation value per cell in all the experimental groups except Sb group and unrestrained group was almost equal. In the case of Sb group and unrestained group the incorporation value per cell was lower than those of the other groups. Although the incorporation of 14C-leucine into cell in control group decreased by level of unrestrained group 21 hr after inhalation, in the Pb, CaCO3 or PVC group 14C-leucine incorporation into cell 21th hour did not change from that 1 hr after inhalation. 14C-leucine incorporation per cell in Sb group 21 hr after inhalation remarkably increased. This tendency was also seen in Cd group. The effects of the particles used in the inhalation experiment on the macrophage in vitro were also studied. The Sb fume was the most effective of all the samples and followed by Cd fume and then by Pb fume. The particles of CaCO3 or PVC were practically inert to the macrophage.
The effect of zinc on manganese induced testicular injury was investigated. It was observed that daily intraperitoneal administration of MnSO4•4H2O (6 mg Mn/kg) to the rats for 30 days produced degeneration of some of the seminiferous tubules whereas simultaneous administration of ZnSO4•H2O (2 mg/kg) to these rats pro-tected them from the toxic effects of manganese on testis. The concentration of manganese in testis of rats treated with manganese and zinc salts was lower as compared to that observed in testis of rats treated with manganese alone, while zinc content in this group was significantly higher than in the testis of animals treated with zinc alone. The exact mechanism of interaction of these two metals in pro-tecting testis from injurious effects of manganese is not known.
In the largest iron and steel works in Japan, six cases of lung cancer had been found among coke oven workers from 1947 to 1971. Labour Standard Bureau of the Ministry of Labour organized a task group of specialists to conduct an investiga-tion whether these cases should be considered as occupational. This paper is an English version of the report submitted to Labour Standard Bureau from the task group.An epidemiological survey conducted by the Ministry of Labour indicated that lung cancer incidence among retired blast furnace coke oven workers in the iron and steel works exceeded that of the expected number calculated from the general Japanese male polulation and the relative frequency of lung cancer cases to malign-ant neoplasia of all sites also exceeded that of the expected number. The task group was not able to conduct research on coke manufacturing chemical companies and manufacturing (specialized) companies because the number of lung cancer cases was too small.