To estimate the effects of night work on the human cognitive function, P300 event related potentials (ERPs) evoked with an auditory "oddball" paradigm were recorded for 17 nurses (mean age 27.4±6.1 years; range 21－41 years) for 3 epochs; after a night of work, after a day of work and on a holiday, and for 12 elderly security guards (mean age 62.8±2.2 years; range 60－67 years) for 2 epochs; after a night of work and on a holiday. The Stress Arousal Check List (SACL) was used for all the subjects just prior to the P300 ERP recording to determine the extent of stress and the arousal grades. Fourteen of the nurses were in their twenties (mean age 24.9±2.6 years; range 21－29 years), and 3 (39.0±2.6) were older (36, 40 and 41 years). The 14 nurses were classed as the young group. All the security guards were classed as the elderly group. In the young group, the stress grade scores increased significantly (P＜0.05) and the arousal grades decreased significantly (P＜0.01) after night work as compared to the holiday values. Although statistically not significant, the amplitude of the P300 component tended to decrease after night work, whereas the latency was very stable for these 2 epochs. The P300 latencies of the 3 older nurses were as stable as those of the young group, but their amplitudes were significantly reduced after night work as compared with the holiday amplitudes (P＜0.05). In contrast, the 12 elderly security guards showed no statistically significant changes in the scores for the stress and arousal grades between the 2 epochs, after night work and holiday. Latency prolongation however, was statistically significant (P＜0.01) after night work. The P300 amplitudes for many of the elderly security guards also tended to decrease after night work, but were not statistically significant. The P300 amplitude is considered to reflect the amount of attentional resources and the latency to reflect the time needed for the cognitive process, indicating that the elderly security guards experienced slowing of the cognitive process in night work. Our results suggest that the effect of night work on the cognitive function is greater for elderly than for young workers. We conclude that P300 can be used to evaluate changes in the human cognitive function produced by night or rotating shift work and that the results provide useful information with which to plan shift schedules on the basis of worker age.

View full abstract

Concentrations and size distributions of airborne welding fumes in work environments were measured. Samples were collected from 20 workplaces in 13 companies. In all workplaces, the stationary samplings including A-sampling and B-sampling and the personal sampling were carried out simultaneously. The fume concentration in the stationary sampling was measured with a digital dust monitor. A low volume air sampler and an Andersen cascade impactor was also used to determine the conversion factor of the values obtained by the digital dust monitor and the size distributions of the fumes. The personal exposure levels were measured with a TR sampler and a personal cascade impactor. The concentrations by the personal sampling (average: 11.3 mg/m³) were much higher than those by the A-sampling (average: 0.4 mg/m³ and range: 0.15－0.64 mg/m³) but lower than those by the B-sampling (average: 46.8 mg/m³, range: 0.66－152.8 mg/m³). The mass median aerodynamic diameter (MMAD) of the stationary and the personal samplings were 2.41μm and 0.80μm, respectively. Fumes were observed under a scanning electron microscope. Most of the fume particles were sphere in shape but smaller fumes were aggregated and formed larger secondary particles.

View full abstract

We have developed a magnetic resonance (MR) spin echo method to obtain diffusion weighted imaging using motion probing gradient (MPG) pulses in orthogonal direction before and after a 180 degree pulse. Phantom models containing water, acetone, cupric sulfate and agar, and normal brains of Wistar rats and puppies were examined. MRI was performed using a SISCO SIS 200/400 MRI/MRS experimental system for small animals (4.7 tesla, 400 mm bore). The apparent diffusion coefficient (ADC) values, given in mm²/sec, were 2.19±0.02×10^-3 in water, 4.51±0.18×10^-3 in acetone, and the ADC of water was independent on longitudinal (T1) or transverse (T2) relaxation time. Time-dependent ADC changes were not demonstrated, however position-dependent ADC changes were significant. It is therefore important to set the sample at the same position for repeated MRI studies and for the evaluation of the time course of experimental studies. Mean ADC values of rat brains were 0.65×10^-3 for cortex, 0.69×10^-3 for caudate-putamen, 0.69×10^-3 (perpendicular to axon) for corpus callosum, 1.11×10^-3 (parallel to axon) for optic nerve, and 1.38×10^-3 (parallel to axon) for trigeminal nerve. Those of puppies were 1.14－1.42×10^-3 for gray matter, 1.17 (parallel to axon) and 0.89 (perpendicular to axon)×10^-3 for white matter, 1.66 (parallel to axon) and 0.57 (perpendicular to axon)×10^-3 for internal capsule, and 0.91－0.95×10^-3 for thalamus. On the in vivo ADC maps, white matter tracts successfully showed anisotropic diffusion. This technique has promising implications for the evaluation of the time course of cerebral damage and degenerative changes.

View full abstract

A polymorphism in exon 7 of the cytochrome P450 1A1 (CYP1A1) and A homozygous gene deletion at the glutathione S-transferase M1 (GSTM1) locus of genomic DNA isolated from peripheral blood were investigated for its relationship with lung, oral and urothelial cancer using the polymerase chain reaction (PCR) technique. As for the CYP 1A1 Val/Val genotype, 5 of 88 healthy controls (5.6%), 1 of 33 lung cancer patients (3.0%, P＞0.05, odds ratio 0.52, 95% confidence interval 0.21－17.3 with Ile/Ile Ile/Val type as base line), 4 of 32 oral cancer patients (12.4% P＞0.05, odds ratio, 2.37, 95% confidence interval 0.60－9.30) and 4 of 85 urothelial cancer patients (4.8% P＞0.05], odds ratio, 0.82, 95% confidence interval 0.21－3.16) were CYP 1A1 Val/Val types. The frequency of GSTM1 deletion genotype was 39.8% in the healthy controls and 45.5%, 50.0% and 61.2% in lung cancer, oral cancer and urothelial cancer patients, respectively. The frequency of GSTM deletion genotype was statistically increased in urothelial cancer patients (P＜0.05, odds ratio 2.38, 95% confidence interval 1.28－4.34). The odds ratio of combined genotypes of CYP1A1 Val/Val and GSTM1 deletion was 1.42 (95% confidence interval 0.12－16.8), 3.64 (95% confidence interval 0.47－27.9), 1.02 (95% confidence interval 0.14－7.53) in lung cancer, oral cancer and urothelial cancer patients, respectively. Thus, the GSTM1 deletion genotype as a host factor predisposing to urothelial cancer was proved in this study.

View full abstract

In order to clarify factors associated with the career choice of medical students of UOEH, an AHP (Analytic Hierarchy Process) analysis was employed for 4th year medical students in 1994 (86 students). As factors associated with career choice, the following three factors were evaluated as important in the following order; 'work worth engaging in', 'income', and 'identity as a medical doctor'. For these three major factors, the surgeon was evaluated as the most favorable, followed by the physician, the clinician of other sectors (ORL, ophthalmology, etc), the occupational physician, researcher, and medical doctors in the administration. When comparing students who wanted to be clinicians and those who wanted to be occupational physicians, the latter group attached more importance to 'stability' and 'scholarship'. Finally, the present AHP analyses clarified that students prefer to become clinicians regardless of their expressed preference for a future career. This fact has created for us an educational problem to be discussed in future curriculum meetings of UOEH.

View full abstract

There is a certain semantic constraint on the anaphoric relation between an indefinite noun phrase with nonspecific reading and a definite noun phrase or a pronoun which has the indefinite NP as its intended antecedent. I assume this constraint to be, above all, cognitively governed and argue how the basic facts discussed in the previous research and the possible counterexamples can be treated in the framework of The Theory of Mental Spaces, which was proposed and has been developed by G. Fauconnier.

View full abstract