SummaryIn an attempt to clarify the nutritional enigma of the healthy strong physique of Papua New Guinea (PNG) highlanders who have a protein-deficient diet mainly composed of sweet potato, a pilot study was performed as follows with 10 volunteers of PNG highlanders, and with 8 Japanese controls, one group of whom took an experimental protein-deficient diet in Japan. 1. In 4 groups of subjects, i.e. adults of PNG highlanders, their children, Japanese controls who were having standard Japanese food (SPD), and those who were having a low protein diet (0.5g/kg) for 2 weeks (LPD), urea metabolism was investigated after oral administration of 15N urea. By tracing the cumulative excretion of 15N in urine successively for about 10 days after 15N urea administration, it was found that children of PNG highlanders can retain a large amount of 15N in the body, Japanese controls of LPD fairly well, PNG adult slightly and the Japanese controls of SPD the least of the four groups. It was demonstrated that the 15N atom% excess in the plasma protein of PNG adults, children, and Japanese control of LPD is maintained in the range of 0.02-0.05% fluctuating for 10 days after 15N urea administration. On the other hand, 15N atom% excess in plasma protein of Japanese control of SPD was within the scope of error (0.01%). 15N atom% excess in the lysine fraction of the hydrolysate of plasma protein was found in the range of 0.01-0.05% in a large number of cases of PNG subjects, and Japanese control of LPD, while it was not significantly detectable in Japanese

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The aim of this research is to compare the physical status, basal metabolism and some other physiological characteristics between native Thai in Bangkok, Thailand, and native Japanese in Japan, and discuss the results regarding acclimatization to tropical climate. Measurements of the Thai were made in September in Bangkok, while those of native Japanese were done in August at Nishinomiya(Japan). The subjects were adult males(20-22 years old)in both cases. Physically the Thai are generally a little shorter and more slender than Japanese in the mean value. The mean skinfold thickness for Thai was 8. 4mm, which is significantly less than that of Japanese(11. 0mm). The mean oral temperature measured under basal conditions was the same between both subject groups. The Thai showed a slightly lower basal metabolism per unit body surface, and mean skin temperature measured in a similar environmental condition was lower for Thai than for Japanese. The results of anthropometric measurements and physiological characteristics measured were discussed in view of physiology of acclimatization to tropical climate.It is well known that body shape, body size, deposition of fat and body fluids and basal metabolism of man change according to climate (LEwis et al. , 1960;YOSHIMURA, 1958;OGATA and SASAKI, 1975). The ratio of body surface area to body mass is related to body shape. Heat dissipation increases as the body surface area becomes larger and the heat produced metabolically in the body may be more Received for publication May 13, 1977 S.HORI et al.

It is well-known that the blood properties change with seasons, and especially many reports in respect to change in water content have been made. For example, Kuroda (1) reported that the water content in blood increases in summer, while it decreases in winter. The fact can be explained by the view of Bazett (2), Sjostrand (3), Yoshimura and others (4) that the circulating blood volume, especially its plasma volume, increases in summer, while it decreases in winter. The first demonstration of the relationship between climate and blood volume was provided by Barcroft et al. (5) who were sailing from England to Peru across the equator. This increase of blood volume was attributed by previous authors to the increase of vascular bed which expands in hot climate by dilatation of cutaneous vessels (6). On the other hand, Forbes, Dill and Hall (7) and recently Doupe (8) failed to confirm the findings of Barcroft. Bass and Henschel (8) expressed their opinion in their excellent review on climatic changes of body fluids that the lack of general agreement regarding seasonal variations in body fluids is not surprising in view of the confounding variables in these investigations. Recently, the author (4) pointed out influencial effects of seasonal alteration of water metabolism upon body fluids which may reflect on blood volume. Little work has ever been done on the interrelation of seasonal changes in body fluid compartments with water metabolism. Moreover, the previous reports on climatic changes of body fluids are quite conflicting as was pointed out by Bass and Henshel (8), and further investigations under well controlled experimental conditions are required. The present study was planned firstly to verify seasonal variations in amount and distribution of water and salts of body fluids in human subjects by repeating monthly measurements of body fluids a basal condition. The second aim was to observe seasonal changes of water metabolism under well controlled experimental conditions and to elucidate its possible effects upon body fluid compartments and blood properties. METHODS The experiments were carried out in two series according to the purposes

Electrophysiological studies by LUNDBURG6-10) have thrown light on the study of the salivary gland of which the secretory mechanism is not known. He found that the membrane potentials of acinal cells of cat's submaxillary gland and sublingual gland are hyperpolarized by stimulation of the chorda tympani, and called this hyperpolarized potential the secretory potential. The origin of these potential changes is not clarified in detail. LUNDBURG has discussed the various possibilities and concluded that the hyperpolarization of the intracellular potential is due to an active transport of chloride ion from the extracellular fluid into the cell. It has been previously reported by the present authors4,5) that the intracellular resting potential of the acinal cell of dog's submaxillary gland was-42mV on an average of 150 measurements, and the potential is hyperpolarized by stimulation of the chorda nerve to-57 mV on an average. The site of this potential generation was confirmed to be located in an acinal cell of the gland with the Turnble blue method. In an attempt to examine the hypothesis of LUNDBURG, a perfusion experiment on dog's submaxillary gland was performed, and the intracellular potential was measured with the microelectrode method. The ionic balance study of the nonperfused gland and the analysis of ionic concentrations of the gland tissue were also carried out. METHOD The dogs were anesthetized with sodium thiopental (30-50mg/Kg intravenously). The submaxillary gland was dissected, leaving the nerves, duct, and blood vessels connected to the head of the animal. A cannule was inserted into the duct to collect the saliva flowing out of it. Perfusion. All branches from the carotid artery and juglar vein were ligated except those leading to the submaxillary gland. One of the carotid branches, usually the lingular artery, was connected to a cannule of the perf usion apparatus, which had been