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Biomedical subjects

K Yamamura

Publications and source records attributed to K Yamamura.

At least 307 records · Page 17Linked to original sources
PubMed1981

The effects of intermittent (trapezoidal) noise on man.

Eight healthy students were exposed to intermittent noise to evaluate the effects of traffic noise on man. The experimental noise exposure conditions were as follows: Exp. 1: Control. Exp. 2: Peak level, 80 dB(A); rise-decay time, 1 sec; duration, 3 sec; and duty cycle 8 sec (on fraction 25%). Exp. 3: Peak level, 75 dB (A); rise-decay time, 500 msec; duration, 4.5 sec; and duty cycle, 8 sec (on fraction 50%). In all experiments, the exposure time was 14 hr. Temporary threshold shift (TTS) growth was followed for 14 hr while saliva cortisol levels were measured for a 24-hr period. Although the coefficient of the regression line of TTS growth recorded in Exp. 1 or Exp. 3 was not statistically significant, the value in Exp. 2 was statistically significant. The circadian rhythm pattern of the saliva cortisol level (during a 24-hr period, mean of 8 examinees) was observed in the three experiments. Essentially, the early morning level of saliva cortisol was high, while the daytime level was relatively low.

Adult↗
PubMed1980

Effects of infrasound on the rota-rod treadmill performance of rats.

The 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 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.

Animals↗
PubMed1980

An investigation of the effects of impulse noise exposure on man: impulse noise with a relatively low peak level.

The 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 less than 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 less than 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.

17-Hydroxycorticosteroids↗
PubMed1980

Behavioural effects in rats following repeated exposure to methyl bromide.

Rats were exposed to methyl bromide (MB) at concentrations of 200 ppm and 300 ppm, 4 h per day, 5 times weekly, for 3 weeks. After the final exposure, behavioural tests for emotional response equilibrium function, the function of the peripheral nerve and the circadian rhythm of spontaneous activity were performed. Relatively prolonged dysfunction of the peripheral nerve as well as disturbance of the circadian rhythm of spontaneous activity were observed.

Animals↗
PubMed1978

Febrile convulsions followed by nonfebrile convulsions: analysis based on a maximum likelihood method and discriminant function.

Two hundred sixty-two nontreated patients with febrile convulsions only and 107 with later nonfebrile convulsions were analyzed based on a maximum likelihood method and discriminant function. The formula for discrimination is as follows: y = 2.9193 x (basic EEG abnormality at the first examination) + 2.2134 x (more than 20 minutes in duration of convulsion) + 1.7358 (fever under 38.4 degrees C before convulsion) + 1.7005 x (specific EEG abnormality at the first examination) + 1.6703 x (more than 5 recurrences) + 1.5610 x (over 4 years of age at the last convulsion) + 1.4921 x (exogenous causes) + 0.3741 x (family histroy of febrile convulsions among second or third relatives)--3.0397. If an item is positive, coefficient x 1 is to be used, and if it is negative, coefficient x 0 is to be applied. When one classifies patients with y greater than 0 as the FCC group, and those with y less than 0 as the FC group, misclassification may be theoretically expected in 18.9% of cases (accuracy in 81.1%).

Age Factors↗