Mental fatigue due to a measuring task in conveyor and non-conveyor systems, exposure to continuous, regular and intermittent white noises, muscular load by a bicycle ergometer, and a continuous maintenance of concentration by the TAF-test was analysed from the viewpoint of higher nervous activity in the human brain. The function of maintaining concentration (TAF), electroencephalogram (EEG), and averaged auditory evoked response (AER) were administered for evaluating the fatigue. The results showed that the reduction of TAF, changes in brain wave appear-ance ratio, reduction or prolongation of peak latency, and decrease and increace in peak-to-peak amplitudes in AER were available for the evaluation of mental fatigue.
Pulse amplitude of blood flow in the middle finger phalanx of the right hand was investigated by photo-plethysmograph on five male subjects, who were given transient vibration of three types on a vertical whole body vibration table. The vibration types were: single shock motion (SSM), one period sinusoidal vibration at an ultra-low frequency (OPV), and single burst random vibration (SBR). Blood flow decreased abruptly, due to vasoconstriction, shortly after the onset of vibration and recovered gradually to approximately the pre-test level observed under the usual rest conditions. Similar plethysmogram patterns were obtained regardless of the type of transient vibration. Blood flow was inversely related to the amplitude of the transient vibration, and in addition, was influenced by the characteristics of the vibration such as duration of the SSM, fundamental frequency of the OPV, or build-up time of the SBR. Relations between blood flow and these factors were quantified by variance analysis in the experimental design. From the results, blood flow response could be used to evaluate the nature of the whole body vertical transient vibration.
Male Wistar rats were injected intraperitoneally with cadmium acetate (20μmoles/kg body weight) at two day intervals for six times. The increase of body weight was inhibited by the first injection of cadmium, but subsequent injections did not affect the further increase of body weight. The weights of liver, kidney and spleen of the cadmium treated rats were not differed from control rats after six intraperitoneal injections. The contents of DNA and protein of livers were also not affected by the administration of cadmium. The nuclear 3H-dTTP incorporating activity and the activity of glucose-6-phos-phatase of livers were inhibited by the treatment of cadmium, while 14C-leucine incorporating activity of nuclei, acid phosphatase and monoamine oxidase were hardly affected. It is suggested that cadmium inhibits the DNA polymerase activity directly or by affecting synthesis of the enzyme, or affects the initiation sites on DNA chains. It is also suggested that the enzymes participated in the nuclear incorporation of amino acids are fairly resistant to cadmium. These results might be of value to help explain the carcinogenic or teratogenic action of cadmium.
The effects of cadmium oxide dusts on the rat lung were studied after exposure of 90min with its concentration of 19.5mg/m3, and for the comparison the similar experiments were carried out on calcium carbonate and polyvinyl chloride dusts with different concentrations. Alveolar macrophages, protein and phospholipid in the lung washing fluids of rats as well as the lung weights were determined 1 hr and 21 hr after exposure to each dust. Remarkable points in the results were the decrease in number of macrophages and increase of protein 21 hr after exposure to cadmium oxide dusts. The decrease of macrophages was observed also 1 hr after exposure to cadmium oxide dusts. Cadmium oxide dusts were dissolved easily in water or Tyrode's solution added with protein or amino acid as in the case of cadmium fume reported previously. Cadmium oxide dusts added in the washing fluid from the lung of rats 21 hr after exposure showed a higher solubility compared with that added in the washing fluid from non-exposed (control) rat lung. Cadmium which was dissolved from cadmium oxide dusts in albumin or glycine solution showed a strong toxic action on the intraperitoneal macrophages and 3T6 cells. From these results, decrease of macrophages and increase of protein in the lung washing fluid by exposure to cadmium oxide dusts was assumed to be evoked by the toxic action of cadmium of which solubility was enhanced by the biological medium in the lung containing protein and others.