Ten male volunteers were subjected to heat stress in winter and in summer and changes in volume and composition of the body fluids were followed for about 24 hr afterwards.
In summer, sodium and chloride concentration in serum and serum osmolality increased most just after sweating and returned to the control value within a day of heat exposure, while in winter they were highest three hours after sweating, and the effect of heat stress lasted until the following morning. Both in winter and in summer, the circulating blood volume tended to increase even when hemoconcentration was obvious. Plasma protein which was determined in summer experiments showed an increase after heat stress and the importance of plasma protein in maintaining the circulating blood volume during or after sweating and its contribution to so called voluntary dehydration are discussed.

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1) Two kinds of indices are proposed for the assessment of heat tolerance. Indices I and S are calculated utilizing the following equations:
I=√A²+B²+C², S=/√A²+C²
where: A=relative water loss
B=relative rise in body temperature
C=relative salt loss
during the sweating test.
2) Ohara's sweating type method, representing a relation between local sweat rate and sodium concentration in sweat, was modified by using salt loss in place of sodium concentration. Sweating patterns were classified into U, N, and T Types in the Q'(salt loss)-V (peak sweat rate) plane. Type U corresponds to Ohara's Type 1, the least heat tolerant, and Type T corresponds to Ohara's Type 4, the most heat tolerant.
3) Results obtained with the authors' method and Index I coordinated well. Type U showed the highest value of Index I, Type T the lowest which suggest that the lower value of Index I indicates a greater heat tolerance.
4) The three type method and Index S revealed no significant correlation, which suggests that Index S is not a measure to be applied to heat tolerance. It was discussed that Index S may be utilized as an index to represent effectiveness of homeostatic mechanism to thermal regulation.
5) Ohara's four sweating types and Index I showed no significant correlation. Thus, the three-type method appears to be a more satisfactory tool for examining heat tolerance.

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Effects of cold adaptation and high-fat diet on the metabolic responses as well as cold resistance to acute cold exposure were investigated in rats with emphasis on elucidating the mechanism underlying the favorable effect of high-fat diet in a cold environment previously reported.
An increment in body weight was greater in rats on a high-fat diet and smaller in cold-adapted rats than in control rats. However, food intake was significantly greater in cold-adapted rats. Daily urine volume and urinary nitrogen excretion increased in cold-adapted rats, but did not change in rats on a high-fat diet. The high-fat diet caused higher bloodfree fatty acid (FFA) and ketone body concentrations, and lower urinary excretion of ketone bodies. Urinary vanilmandelic acid excretion was significantly elevated in cold-adapted rats, while it was lower in rats fed a high-fat diet as compared with that in control rats. This result suggests an increased sympathetic activity in cold-adapted rats and a rather suppressed activity in rats on a high-fat diet.
The fall in the colonic temperature due to cold exposure for the period of time up to four hours was significantly less in cold-adapted rats, but did not differ in animals fed a high-fat diet from that in control rats. This result signifies that there is no significant difference in cold resistance between control rats and rats on a high-fat diet. Blood FFA level as well as blood ketone body level was significantly raised in all experimental groups in response to cold exposure. It was observed, however, that an increment in blood FFA concentration was less in cold-adapted rats. The degree of increase in blood FFA became greater with length of exposure to the cold. Blood glucose concentration was significantly elevated in cold-adapted rats after an eighty minutes exposure to the cold, but did not vary in control rats and rats on a high-fat diet. Four hours after the cold exposure the blood glucose level was significantly decreased in all groups as compared with that at 25°C.
There was a significant correlation between the blood FFA and ketone body concentrations on the whole data before and after cold exposure in all groups. Regression coefficient between blood compositions was significantly greater in rats fed a high-fat diet than in control and coldadapted rats. It was also shown that there was an inverse correlation between the blood glucose and FFA levels after cold exposure. Furthermore, lessened falling of colonic temperature due to cold exposure was significantly associated with less variations in the blood FFA and glucose levels concomitantly determined in control and cold-adapted rats and this tendency was strongly documented in cold-adapted rats.
The present results indicate that the prolonged cold exposure increases the cold resistance to acute cold exposure, while the high-fat diet feeding may not be necessarily favorable to the cold resistance, although a high-fat diet causes certain metabolic changes, suggesting a favorable effect to some extent.

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The relationship between vibration and human motor unit spikes elicited by reflex and voluntary actions was studied by means of cross-correlograms. Using this method motor unit spikes could be classified into two categories, locked spikes with good correlation to vibratory frequency and unlocked ones with poor correlation to vibratory frequency.
1. Inter-spike intervals of the locked spikes were integer multiples of the cyclic time of the vibration used. This suggests that the locked spikes are elicited by the firing of α-motoneurons that are activated by monosynaptic transmission of Ia vibratory afferents.
2. Locked spikes are only elicited immediately after vibratory application. Spike frequency soon attains its maximum and frequency plateau level is then maintained.
3. Unlocked spikes are slow in appearance and a gradual increase of their spike frequency is a characteristic feature. Increase of the total motor unit spike frequency is therefore attained by the recruitment of unlocked spikes even without apparent increase in the frequency of the locked spikes. This mechanism is held to explain the gradual increment of the tonic vibration reflex activity.
4. It is suggested on the basis of previous work (HOMMA and KANDA, 1973) that polysynaptic transmission caused by sustained Ia vibratory afferent activity elicits a slowly increasing EPSP which is directly responsible for the unlocked spikes.
5. Vibration superposed upon a voluntary effort elicits a considerable increase of locked spikes. These may be the sum of motor unit spikes activated by vibratory Ia impulses and other Ia impulses whose firing had become locked to the vibratory stimuli though originally driven by the gamma loop mobilized by voluntary command.
6. It is thus maintained that the unlocked spikes are elicited either by direct voluntary a-activation or by the polysynaptic slowly rising EPSP.
7. Data collected in the present study revealed that the ratio between unlocked and r-loop driven spikes was 1: 2.4. Since alpha-gamma linkage characterises voluntary command, an α-γ co-activation ratio of 1/2.4 in a light voluntary contraction suggests that under the circumstances indirect loop-activation would be dominant.

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Microelectrodes were inserted into the third cranial nucleus of anesthetized rabbits. The third nucleus was identified by observing the field potentials evoked antidromically upon stimulation of the third cranial nerve trunk or its branch to the inferior oblique muscle. The antidromic field potentials consisted of two large negativities, i. e., an early and a late negative field potential. Extracellular recording from the third nucleus motoneurons revealed two distinct types of unit firing patterns; type I and type II. Type I units were characterized by relatively regular discharges whereas type II units showed burst discharges. When stimulated antidromically, type I units initiated an action potential with a short latency. Type II units responded with a long latency to an antidromic stimulation. Calorically induced nystagmus caused corresponding responses from type I units and their firing patterns could be classified into two groups, phasic and tonic. Type II units showed no relationship to the caloric nystagmus. Histologically it was found that the type I units were localized chiefly in the central portion of the nucleus, whereas most of the type II units were found in the periphery of the nucleus. None of these units responded to photic stimulation. It was considered that the type I and type II units would subserve fast and slow fibers, respectively, in the extraocular muscles of the rabbit.

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1) The effects of adrenaline, ouabain, low-K Ringer, and low-Na Ringer on the time course of twitch contraction were studied in the ventricular preparations of bullfrog, with special reference to their effects on relaxation.
2) Adrenaline (10^-7-10^-6 g/ml) had the effect of enhancing the relaxation of twitch, in addition to its potentiating effect.
3) Ouabain (10^-7-10^-6 M) only potentiated the twitch without an appreciable effect on the relaxation phase.
4) Low-K Ringer (0.16 mm-K), as well as low-Na Ringer (50 %-Na), reduced the rate of relaxation of twitch.
5) Low-Na Ringer had an additional effect to shorten the time to maximum rate of rise of tension.
6) These effects were evaluated quantitatively by an analysis in which the increase in the rate of fall of tension was compared with the increase in peak tension or with the increase in the rate of rise of tension.
7) Possible subcellular mechanisms to explain the results were discussed.

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1) The electrical and mechanical activity of bullfrog ventricle was investigated during and after a prolonged exposure to a K-depleted fluid, which was applied for the purpose of increasing the intracellular Na ions in exchange for K ions.
2) There was a gradual increase in twitch tension during immersion in the K-depleted fluid in addition to the immediate potentiation by this solution. The action potential was slightly depressed in height during the immersion.
3) There was also a relative reduction in the rate of relaxation of twitch with the gradual increase in tension, and the twitch pattern became a type of rapid onset and slow relaxation.
4) The muscles treated with cold K-depleted fluid for an extremely long period of time (24 hr) showed a similar augmentation in contractility and a particularly high sensitivity to extracellular Na-depletion for generating a Na-lack contracture.
5) Possible mechanisms relating the intracellular ionic environment to the myocardial contractility were discussed, and attempts were made to interprete the results in terms of Na-Ca exchange mechanism across the cell membrane or Na-Ca competition at the subcellular membrane sites.

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The effect of thymol on the electrical and mechanical activities of various regions of the guinea pig alimentary canal were investigated.
1) In the stomach, thymol (<0.5mM) suppressed the generation of action potential and slow potential changes without any marked change in membrane potential and membrane resistance. Increased concentrations of thymol (>0.5 mM) reduced membrane potential and membrane resistance.
2) In the ileum and rectum, thymol (<1mM) suppressed spike activity only without any marked change in the membrane potential. However, 1 mm thymol suppressed spike generation, hyperpolarized the membrane and decreased membrane resistance.
3) Thymol (0.5 mM) suppressed spontaneous mechanical responses which appeared in the various regions of the alimentary canal. There was no contracture except in stomach muscle.
4) Although the membrane was completely depolarized, thymol (>1 mM) suppressed the generation of phasic and tonic responses of the K-induced contracture evoked in the various regions of the alimentary canal.
5) Topical differences of the effects of thymol on the various regions of alimentary canal were discussed in relation to the roles of Ca in the cells and the obtained results were compared to those observed in treatment with caffeine.

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