Over a million people of Japanese origin reside in South America. However, only a limited number of studies on their health status and lifestyle factors affecting it have been carried out. The author and his co-workers have been conducting a series of field surveys on the health situation and lifestyle factors in Japanese immigrants and their descendants in various areas of South America.
The subjects of the first-phase study were residents in four agricultural settlements (colonies) in the suburbs of Brazil, Paraguay and Bolivia. The levels of minerals and heavy metals in the hair were measured, and significant variations were found in several elements. These different levels were found to be regulated by the environmental level of their living place and by the dietary pattern.
In the second-phase study, several health-related indicators such as blood pressure, anthropometric features, viral infection markers in sera, and dietary pattern were investigated in two group of immigrants, one from Okinawa and the other from the mainland of Japan, both living in Bolivia. Differences in health situation and lifestyle were identified between them. Traditional habits seen in their original places of residence in Japan still existed in their life in Bolivia, while the introduction of Bolivian lifestyle was prevalent among them.
Although the number of Japanese residents in Brazil is largest in the world outside of Japan, little has been known about their health situation. The subjects of the third-phase study were Japanese Brazilians. A descriptive epidemiologic study was carried out, and the mortality and incidence of cancer were determined. Some changes in disease pattern were noted when compared with Japanese in Japan, but these changes were not as marked as in the case of Japanese in the U. S.. A cross-sectional study on the lifestyle factors of Japanese residents in São Paulo showed some differences in health-related indicators and dietary habits in comparison with Japanese living in five areas of Japan. Such differences were also found among Japanese in São Paulo according to the place of origin in Japan.
These series of studies in Japanese immigrants in South America showed the importance of lifestyle factors, especially dietary habits, for the health situation.

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Although effects of physical environmental stress, including noise and whole-body vibration, on human psychological activities and emotion are not negligible for environmental and occupational hygiene, attempts to elucidate their physiological and biomedical mechanisms have been not made until recently. Neurobiological researches on the effects of the physical environment, e. g., noise and whole-body vibration on organisms were reviewed. It has been well accepted that such effects can be classified into specific and nonspecific reactions to the stressor. Activations of the mesofrontal and the meso-accumbens dopaminergic (DA) systems and changes of frontal substance P (SP) have been reported to play a part in emotional changes and to be induced by acute physical environmental stressors as a nonspecific reaction. On the basis of data demonstrating that these three systems do not show the same changes with the chronic exposure, it is assumed that emotional changes may account for the differences among the systems. Specific responses of amygdaline DA and SP to noise suggest that the psychopharmacological mechanisms by which actions of DA and SP in the cortical association areas for the sensory systems of hearing, as well as in the amygdala and the mesencephalon together, cause the specific sensation of noise, and furthermore lead to psychological and physical nonspecific reactions. In these mechanisms, descending amygdalofugal neural systems of SP, neurotensin (NT) and somatostatin are activated as a common pathway, and subsequently relayed to the hypothalamus-pituitary system responsible for several endocrinological hormones. The involvements of the hippocampal VIP in whole-body vibration and of the DA and NT in cold exposure have been pointed out. Further researches to elucidate the roles of central neurotransmitters in physical environmental stress will be important in the study of human high-level mental activity.

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The application of the spiral plating method, a rapid and labor-saving technique for enumerating bacteria in food, to evaluate bacteria in river water, was examined. Standard plate counts and the numbers of heterotrophic bacteria, coliforms and Flavobacterium spp. in the water were tested by the spiral plating method, the results were compared with those of the conventional method and the optimal conditions for using the spiral plating method were considered and selected to fit the conventional methods.
The optimal conditions selected were as follows: by laser colony counter after incubation at 35°C for 38h. for standard plate counts; by laser colony counter after incubation at 25°C for 48h. for the numbers of heterotrophic bacteria and Flavobacterium spp.; by colony viewer counting reddish colonies≥0.25mm in diameter after incubation at 35°C for 22h. for the number of coliforms.
The numbers of bacteria, except for coliforms, determined by this spiral plating method were found to be closely related to those from conventional methods (r≥0.91), and the replicating variances of both methods were not significant.
The counts of bacteria by laser colony counter gave results similar to those by colony viewer counting by visual inspection.
This spiral plating method saved time, money and labor in the evaluation of bacteria in river water as comparable to that in food.
These results indicate that the spiral plating method can be used in place of conventional methods in evaluating the number of bacteria in river water.

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The hair from 9 children living in a Keshan disease prevalent district and from 10 children living in a Keshan disease non-prevalent district in China was analyzed. At the same time, the hair from 35 children of the same age residing in Tsukuba district in Japan was analyzed for comparison of the concentration of essential trace elements with that of children living in the Keshan disease prevalent district. Se concentration was determined by a fluorophotometric method and 16 other elements were analyzed by ICP emission spectrometry. Hg was analyzed by the heating evaporation method and by neutron activation analysis. The Se concentration in the hair of children living in the prevalent district was very low, being one-tenth that of the Japanese. The Ni concentration was particularly low in the prevalent district, and it determined to study more about the effects of Ni deficiency on health. In the prevalent district, Mg and Ca levels were low and those of Pb, Fe, Al, Ti were relatively high. Mn concentrations of both districts in China were very high when compared to the Japanese. The results of this study showed that the low Se concentration in Keshan disease is in agreement with previously reported data. Ecological factors, including nutrition were considered to be important in the etiology of this disease.

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A single dose of a cis-chlordane and trans-chlordane mixture (1:1) was orally administered to mice (total dose: 40mg/kg), and the metabolic fate of the two congeners administered and their major metabolite, oxychlordane, in various tissues, was studied from day 1 after dosing to week 52. Cis-chlordane and trans-chlordane showed the highest concentrations on day 1 after dosing, and disappeared on day 14 except in the liver. The half life in the tissues was approximately one day for both congeners. On the other hand, oxychlordane was observed in various tissues from day 1 after dosing, reaching the maximum concentration on day 1 or 2 showing considerably higher concentrations than those of the congeners. The rate of decrease of oxychlordane in the tissues was extremely slow compared to the congeners. It was found that oxychlordane remained in the tissues even in week 52 (year 1) after dosing. The regression curve for the tissue oxychlordane concentration was diphasic after or at around week 8 after dosing; the half life was approximately 20 days in the first phase and was prolonged to over 100 days in the second phase. These results suggest that the cis-chlordane and trans-chlordane taken into the human body via foods disappear rapidly from the tissues but that oxychlordane, their metabolite, remains in the body over a prolonged period of time.

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The percentage of each sleep stage determined by visual judgment was compared with computerized judgment using continuous and three intermittent sampling data. Comparison of stage agreements of four types of computerized judgments with visual judgment were also conducted. Hypnograms of six healthy young male students were recorded on each of five nights. Data of each subject were compiled individually, and the six data were analyzed.
Agreement rate of the sleep stage by computerized judgment using continuous (method A), one-third (method B), one-ninth (method C), and one-fifteenth (method D) data with that of visual judgment were compared. The agreement rate of visual and computerized judgment using method A showed no difference from that between visual and computerized judgment using method B. There was a significant loss of agreement between visual and computerized judgment using method C or D compared with that between visual and computerized judgment using method A.
Paired t-tests were conducted for each stage percentage against total sleep time of visual judgment and those of computerized judgments using method A, B, C, or D. There were no significant changes in any sleep stage percentages between visual judgment and computerized judgments using method A, B, C, or D.
From sleep stage agreement and the degree of difference from visual judgment, the acceptable limitation of the sampling period was concluded to be one-third of continuous data.

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In order to determine the characteristics of medical institutions which patients with 30 intractable diseases visited, we analyzed data of a nationwide survey conducted by the Epidimiology of Intractable Diseases Research Committee in 1989. Each of 47 prefectural governments in Japan reported information of all patients with 30 intractable diseases who received financial aid for the diseases between April 1988 and March 1989. Information collected about each patient consisted of identification numbers, which included the disease code, sex, age, the code of the municipality where the patient lived, the medical institution which treated the patient, etc. Out of 173, 637 patients whose information was reported by prefectural governments, we used data of 159, 910 patients whose medical institutions were reported completely.
The results can be summarized as follow:
1) Of the 159, 910 patients, 8.6 percent visited medical institutions outside of the prefectures where the patients lived. Many patients living in prefectures located close to large cities, such as Tokyo, visited medical institutions in large cities.
2) The proportion of patients who visited hospitals of medical schools was 27.9 percent.
3) Patients who were affected by diseases causing physical disabilities such as SMON and malignant rheumatoid arthritis tended to visit medical institutions located in their neighborhoods and were treated in small hospitals or clinics. Old patients had the same tendency as patients with such diseases.
4) Although the number of patients receiving aid in 1988, whose data we analyzed in the current study, was larger than that in 1984, the proportion of patients visiting medical institutions outside of the prefecture where the patients lived, and the proportion of patients visiting hospitals of medical schools were nearly equal to those in 1984.

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Fifty-nine elderly patients who had been hospitalized more than six months in five hospitals in the city of Mino in Osaka Prefecture, were studied to clarify the factors influencing prolonged hospital stays by the elderly. Their mean age was 82.2 years, and women accounted for 86% of the patients. One-third had suffered a stroke. As for ADL, 44% were completely dependent when walking, eating, bathing and dressing. Moreover, 36% had severe dementia, 19% suffered from decubitus ulcers, 66% were undergoing rehabilitation, 58% were receiving venous infusion therapy, 36% used a urethral catheter, and 10% were receiving tube feeding.
The subjects were divided into two groups according to the likelihood of discharge assessed by the doctors in charge: one group consisted of 27 patients who might be discharged and the other of 32 patients with an ongoing need for inpatient care. Multivariate analyses using Hayashi's quantification method II indicated that use of a urethral catheter and not undergoing rehabilitation were the main factors associated with the need for inpatient care, while being a woman, being of advanced age and not having one's own room at home were the non-medical factors which made it difficult for the patients to be discharged from the hospital.
As use of a urethral catheter was the factor most strongly related to prolonged hospital stay, multivariate analyses were applied to the 45 patients with urinary incontinence, who were divided into one group of 21 patients with, and one of 24 without a urethral catheter. The factors associated with use of a urethral catheter were then investigated. Use of a urethral catheter was strongly related to venous infusion therapy, not undergoing rehabilitation, the presence of decubitus ulcers and a low ADL level. Our results suggest that, in order to reduce the increase of elderly patients with prolonged hospital stays, more appropriate approaches to urinary incontinence should be developed and more systematic efforts at rehabilitation should be made.

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The identification and concentration of asbestos fibers in tap drinking water supplied in a central area of Akita Prefecture, Japan, were determined by phase-contrast microscopy and a scanning electron microscope equipped with an energy-dispersive X-ray microanalyzer. The following results were obtained.
1. Asbestos fibers were found in the tap water from two areas in which an asbestos-cement pipe was used for public water supply. The concentrations of asbestos fibers in the tap water were 2.7×10⁴ to 27.0×10⁴ fibers per liter of water in area A and 10.0×10⁴ to 21.0×10⁴ in area B. On the other hand, no asbestos fiber contamination was observed in tap water of area C, which shared a common water source with area A. A vinyl chloride pipe was used over the entire length of the water supply in route C.
2. Crocidolite was the predominant type of asbestos fiber detected in the tap water. Chrysotile and a mixture of chrysotile and amosite were also observed.
3. Almost all asbestos fibers detected in the tap water possessed the form of thick or sheaved fibers with lengths ranging from ca. 5 to 10μm. Their shapes were very different from those of asbestos fibers found in the atmosphere. The typical form of the latter is short (ca. 1μm in length) and needle-like.
4. It was suggested that the contamination of asbestos fibers in the tap water was caused by erosion and peeling off of the inner wall of the asbestos-cement pipe used as a conduit. In order to evaluate the safety of drinking water in Japan, an extensive survey on asbestos-fiber contamination in tap water is necessary.

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Triphenyl phosphite (TPP)-induced delayed neurotoxicity, which is thought to resemble but somewhat differ from classical organophosphate-induced delayed neurotoxicity (OPIDN), is known to be age-dependent. The relationship between clinical appearance and histopathological lesions, and the inhibition of neurotoxicity target esterase (NTE) in nervous tissues were compared in young and adult chickens after i. v. administration of TPP. NTE inhibition by TPP in vitro was also compared between the two age groups. Fourteen days after i. v. administration of TPP (50mg/kg), adult chickens (24 months old) showed obvious histopathological lesions as well as obvious clinical neurological signs. On the other hand, young chickens (65 days old) showed few histopathological lesions and only marginal neurological signs. NTE activity in brain, spinal cord, and sciatic nerves was inhibited in a dose-dependent manner in both age groups. While inhibition tended to be mild in the younger chickens, the level of activity was less than 30% of the normal value in all three tissues at 24 hours after administration of 50mg/kg of TPP (14% vs. 8% in brain, 15% vs. 9% in spinal cord and 13% vs. 14% in sciatic nerves). Recovery of NTE activity in the sciatic nerves was faster in the younger chickens. The IC₅₀ of TPP on brain (6.67 vs. 6.76×10^-8M) and spinal cord NTE (1.05 vs. 1.53×10^-7M) was almost the same in the two age groups. These results confirmed age-specific susceptibility to TPP, not only clinically but also histopathologically, and, suggested that the differences in both TPP metabolism and NTE recovery are related to and/or contribute to this age specificity. Judging from the age specificity and the figure of NTE inhibition, the delayed neurotoxicity produced by an i. v. administration of TPP is virtually identical to classical organophosphate-induced delayed neurotoxicity. Hydrolytic products may produce additional effects characteristic of TPP-induced neurotoxicity observed after an s. c. dose.

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