Yamamura K

Physical training and fasting erythrocyte activities of free radical scavenging enzyme systems in sedentary men

SummaryEffects of 10 weeks of physical training on free radical scavenging enzyme systems in erythrocytes were investigated in 7 sedentary healthy male students. The training consisted of running over 5 km, 6 times/week. Their maximum oxygen uptake and 12 min walk-run performance increased significantly after training. Of the antioxidant enzyme systems examined in the erythrocytes, both catalase activity and concentration and total glutathione reductase (GR) activity also showed significant increases following the training. The erythrocyte GR activity coefficient also increased significantly. These results suggest that chronic aerobic exercise increases riboflavin requirements and has some positive effects on antioxidative processes.

Effect of intermittent (traffic) noise on man — Temporary threshold shift, and change in urinary 17-OHCS and saliva cortisol levels

SummaryEight healthy male college students were selected and eight noise exposure conditions were planned. The noise exposure time of all the experiments was 14 h. Measurement of the TTS growth at 4 kHz was investigated during these 14 h. Saliva collected every 3 h was also examined for cortisol throughout the 24-h period. The exposure noises used in this experiment were pink noise and pure tone of 3 kHz. The time patterns of trapezoidal noise were as follows. The rise and decay times were 1 s respectively and the peak level was 1 s for the (A I type), being 500 ms and 1.5 s respectively for the (A II type).Three measurement were made:TTSUnder intermittent noise exposure at 80 dB(A), exposure of 20% of the on fraction induced significant TTS growth, but exposure of 13% of the on fraction did not induce TTS growth. Under exposure at 75 dB(A), exposure of 66% of the on fraction did not induce TTS growth. Under pure tone exposure of 3 kHz at 75 dB(A), exposures of 20% and 30% of the on fraction did not induce TTS growth. There was a significant difference between the TTS induced by a steady state of 73 dB (A) (Leq of Exp. 2) and that of Exp. 2.Urinary 17-OHCS LevelDuring the noise exposure period (14 h), there was a statistically significant difference between the urinary 17-OHCS level of the control condition and that of Exp. 3. In addition, there was no statistically significant difference among the urinary 17-OHCS levels of post-noise exposure.Saliva CortisolWith intermittent “pink noise” of 75 or 80 dB(A) (Exp. 2, 3, and 4), however, temporary elevation of the saliva cortisol level occurred only at the initial stage of exposure, and lasted for only one hour. Moreover, with steady state noise exposure, evanescent elevation occurred at the lower level of 71 dB(A).

An investigation of biological response induced by intermittent noise (trapezoidal noise)

SummaryAudiometrically normal, male students (aged 18–22, 6–12 persons) were exposed to intermittent and steady-state noise (480 min, pink noise), after which Temporary Threshold Shift (TTS) and urinary 17 OHCS levels were measured. The rise-decay time of an exposed noise (trapezoidal noise, cf. Fig. 1) was ca. 500 ms and its duration was 6.5 s. Peak levels of intermittent noises were 80 dB (A) and 90 dB (A). Exposure conditions examined were (1) control; (2) peak level of 90 dB (A) with an exposure time of 2 min; (3) peak 90 dB (A), exposure 1 min; (4) peak 90 dB (A), exposure 24 s; (5) peak 90 dB (A), exposure 12 s; (6) Peak 80 dB (A), exposure 2 min; (7) peak 80 dB (A), exposure 1 min; (8) peak 80 dB (A), exposure 24 s; (9) peak 80 dB (A), exposure 12 s; (10) steady-state noise of 90 dB (A); (11) steady-state noise of 80 dB (A). The coefficient of regression of TTS growth induced by exposures 1, 2, 3, 6, 7, or 8 did not have significance, but that by exposure 4, 5, 9, 10, or 11 was significant. When the TTS2 of the noise exposure for 480 min was studied by the on-fraction rule based on these regression equations, the TTS of exposures 4 and 5 (on-fraction 25%, 50%) was found to be same as 29% and 40% of the TTS of exposure 10. There was a significant difference between the 8-h urinary 17 OHCS levels induced by exposures 6 and 7 and those induced by control conditions. However, there was no significant difference between urinary 17 OHCS levels induced by other noise exposures (8, 9, and 11) and that induced by control conditions. The coefficient of regression between the 8-h urinary 17 OHCS levels and the logarithm of the on-fraction was significant.

An investigation of the effects of impulse noise exposure on man

SummaryThe effects of impulse noise of a relatively low peak level were examined to develop damage risk criteria for impulse noise. Eight to 13 normal male students (age: 20–24 years) were exposed to impulse noise. Peak levels of impulse noise were 100 dB (S. P. L.) and 105 dB (S. P. L.), B-duration of impulse noise being 10 ms, 50 ms, and 100 ms, and the repetition rates of impulse noise were 3 per 1 s and 1 per 3 s. Exposure time was 8 h in all exposure conditions. Exposure conditions of long B-duration induced greater TTS2 than those of short B-duration (P<0.05). Impulse noise exposure at a high peak level induced slightly larger TTS2 than that at a low peak level. TTS2 increased proportionally to the logarithm of the amount of impulse noise. Exposure to impulse noise induced smaller TTS2 than that of steady-state noise of an equal energy level. In addition, exposure to large amounts of impulse noise induced slightly greater urinary 17 OHCS levels than small amounts of impulse noise, and exposure to impulse noise induced smaller urinary 17 OHCS levels than steady-state noise of an equal energy level (P<0.05). The decreasing effect of the acoustic reflex on the acoustic energy of impulse noise was considered to be the reason for the results obtained. This experiment supported the modified CHABA Limit of Damage Risk Criteria of impulse noise proposed by the US Environmental Protection Agency.

Effects of infrasound on the Rota-Rod Treadmill performance of rats

SummaryThe present study was designed to evaluate the effects of infrasound on behavioral performance in rats. The rats were divided into two groups, one selected for good performance (six rats: superior group) and the other for poor performance (six rats: inferior group) on the Rota-Rod Treadmill.Exposure conditions were as follows:Exp. 1 Control (150 min), Exp. 2 Exposure to infrasound with a main frequency of 16 Hz and a sound pressure level of 105 dB (S.P.L.) (70 min), Exp. 3 Exposure to infrasound with a main frequency of 16 Hz and a sound pressure level of 95 dB (S.P.L.) (70 min), Exp. 4 Exposure to infrasound with a main frequency of 16 Hz and a sound pressure level of 85 dB (S.P.L.) (150 min), Exp. 5 Exposure to infrasound with a main frequency of 16 Hz and a sound pressure level of 75 dB (S.P.L.) (150 min), Exp. 6 Exposure to Pink Noise of 72 dB (A) (70 min).Comparison of the pre-exposure endurance time (Maximum: 2 min) on the Rota-Rod Treadmill with endurance after exposure to infrasound showed that the endurance time of the superior group after exposure to 16 Hz, 105 dB was not reduced. The endurance of the inferior group was reduced by exposure to 16 Hz, 105 dB after 10 min, to 16 Hz, 95 dB after 70 min, and to 16 Hz, 85 dB after 150 min.

The effects of variable noise levels on man with peak levels below 75 dB(A)

SummaryTo estimate the effect of variable traffic noise levels by field study, six healthy students were exposed to such noise for 8 h in a building beside a highway. TTS increases and blood pressure changes were observed. A summary of the results is as follows:1.Noise level slightly exceeded 70 dB(A) (Equivalent Sound Level, Leq). The ninety percent range of the changing noise level was within L50+10 dB(A).2.The Temporary Threshold Shift (TTS) induced by variable noise increased slightly in this field experiment.In particular, regression of the logarithm of exposure time (min) to TTS at the “S” ward office, was statistically significant.3.Some subjects showed a rise of blood pressure due to noise exposure.4.Even though noise level is below 75 dB(A), 8 h noise exposure induces TTS increase and elevation of blood pressure.

Physiological responses induced by 555-min exposure to intermittent noise.

SummaryNormal medical college students were exposed to noise for 555 min, while the Temporary Threshold Shift (TTS) and changes in the circulatory system were measured.The exposure noise employed was the so-called pink noise of a trapezoidal form. There were two time patterns, A(I) with 1 s of rise-decay time and 1 s of peak level, and A(II) with 500 ms of rise-decay time and 3.5 s of peak level.Thirteen exposure conditions were examined. The noise exposure time of all experiments was 555 min.The following results were obtained.TTS GrowthSignificant TTS increases were obtained following exposure to intermittent noise of 85 dB(A), intermittent noise of 80 dB(A), and steady state noise of various intensities.The TTS growth observed with steady state noise at 80 dB(A) was significantly greater than that of intermittent noise exposure at 85 dB(A). Moreover, TTS growth observed with steady noise at 82 dB(A) was significantly greater than that with intermittent noise exposure of 85 dB(A).However, the levels of TTS growth observed with steady state noise of 75 dB(A) and steady state noise at 77 dB(A) were almost equal to those of 6 s trapezoidal noise at 80 dB(A) (the “on fraction” being 33%), and 8 s trapezoidal noise at 80 dB(d) (the “on fraction” being 50%).In the above-mentioned experiments, significant increases of TTS growth were observed with various cycle times of trapezoidal noise with peak levels of 85 dB(A) and 80 dB(A), and with four exposure noise conditions of steady state.Under exposure conditions of 75 dB(A), trapezoidal noise with a 6 s cycle time (the “on fraction” being 33%) did not show a significant increase in TTS growth.Changes in the Circulatory SystemThere were no significant differences in systolic and diastolic pressure or pulse rate among the three exposure conditions.The findings on ECG were as follows. Under intermittent noise exposure, decrease in the height of the T wave was observed in all examinees with a depression of the ST segments also being observed in two cases. On exposure to steady state noise, however, slight decrease in the height of the T wave was induced in only two cases, and under control conditions in only one case.

Effects of 8 hour exposure to 40 Hz and 80 Hz low frequency sound at intensities below 100 dB (SPL) on the Rota-Rod Treadmill performance of guinea pigs

Taking fieldwork reports into consideration, an experiment was designed to evaluate the effects of low frequency sound exposure on the vestibular and/or motor coordination of guinea pigs. For 8 hour exposure, 40 Hz at 80 dB(SPL) and 80 Hz at 80 dB(SPL) stimuli, caused significant reductions of the endurance time of the poor performing group on the Rota-Rod Treadmill from 240th to 360th minute and to the 240th minute, respectively. When the intensities were stronger, the changes in the endurance times showed similar patterns to that in the control. In addition, the endurance times at the 480th minute recovered almost to the pre-exposure levels in all conditions of exposure tested.

Growth and recovery of temporary threshold shift at 4 kHz due to a steady state noise and impulse noises

Summary7 audiometrically normal, male students were exposed to a steady state noise S of 98 dBA and 2 steady state-impulse combined noises A and B (steady state component of 97 dBA, hammer noise 102 dBA and air exhaustion noise of 118 or 110 dBA) for 40–60 min. The regression line of temporary threshold shift (TTS) growth due to noise A on exposure duration was significantly steeper than that due to noise B. Both the lines were steeper than that due to noise S. The reason of the relatively larger effects of the noises A and B as compared with noise S could be explained by the fact that the noise S did not contain impulse components, because the octave band level at center frequency of 3 kHz of the noise S was roughly equal to that of the steady state noise component of noise A or B. The relatively larger effect of the noise A than B might be attributed mainly to the air exhaustion noise. It was suggested that the effect of a steady state noise on hearing might be additive to that of an impulse noise. The trend relationship between TTS during recovery and recovery time was nearly the same with the 3 noises.