The relationship among contractile tension, ATP content and concentration was examined in isolated, superfused ventricular papillary muscle under normoxic (P_O2=300 mmHg) and hypoxic (P_O2=100 mmHg) conditions, using capillary isotachophoresis. The muscle preparations were exposed to each condition for 30 min, and the contractile tension was recorded with a strain gauge. Immediately after the recordings, the preparations were homogenized and the metabolites (ATP, ADP, AMP, creatine phosphate, inosine monophosphate, NAD, NADH, glucose-6-phosphate, pyruvate, and inorganic phosphate) were extracted in 50% methanol-1.25 mm EDTA solution at -20°C for 4 days. The supernatant of the extract was used for the isotachophoretic analysis. Hypoxia markedly depressed ATP content and concentration in the tissue. Under conditions of normoxia, but not hypoxia, the developed tension positively correlated with the ATP content and concentration. Under normoxic conditions, the tension tended to be proportional to the estimated surface area of the preparation, while in hypoxia it tended to be inversely proportional thereto. The ATP concentration appeared to be inversely proportional to the muscle weight, thereby suggesting that the outer layer of the preparation contains more ATP than the inner. In fact, an isotachophoretic analysis of the tissue revealed significantly higher ATP concentrations in the outer layer. Our findings indicate that there is a central anoxic core in the isolated canine papillary muscle superfused with oxygenated Tyrode solution and that surface layer ATP probably plays a pivotal role in the initiation of contraction.

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In the isolated, perfused retina of the carp, properties of the feedback pathway from horizontal cells to cones were investigated by means of electrophysiological and neuropharmacological methods. When horizontal cells were hyperpolarized by illumination with an annulus, a depolarizing synaptic potential was produced in cones at the center of the annulus, suggesting that horizontal cells receive inputs from cones and exert a negative feedback to cones. On the other hand, a hyperpolarizing response (IPSP) was detected in cones, when a transient depolarization (EPSP) was induced in horizontal cells by application of a transretinal current pulse, which activated the release of transmitter from the photoreceptor terminals. The IPSP was abolished when the retina was perfused with a GABA-containing Ringer solution, because of desensitization of the feedback synapse. GABA also hyperpolarized the cone membrane, indicating the presence of a GABA-sensitive site in the cone. These results suggest that the GABA-mediated negative feedback operates from horizontal cells to cones in the dark, and ceases its function in the light.

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In the isolated, perfused retina of the carp, the effects of GABA and its antagonists, picrotoxin and bicuculline, were investigated on spectral responses of horizontal cells. When the GABA-mediated feedback from horizontal cells to cones was desensitized or blocked by these chemicals, remarkable changes were observed in spectral responses, due to selective suppression of responses to long wavelengths. In particular, the depolarizing responses in the biphasic C-type (H2) cell were abolished, while the hyperpolarizing responses to short wavelengths were retained, resulting in a monophasic spectral response curve.
From these results, it was concluded that the GABA-mediated negative feedback plays an essential role in neural mechanisms which convert the trichromatic process at the level of cones into the opponent color process in horizontal cells.

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The effects of an elevation of arterial blood pressure (BP) on heat production (M) and interscapular brown adipose tissue temperature (Tbat) were studied at 15°C in unanesthetized 5°C-acclimated rats. The elevation in blood pressure (BP), caused by phenylephrine (PHE: 5-30μg/(kg·Emin)) infusion for 10 min, decreased M and Tbat accompanied by a marked bradycardia. The decrease in M was not due to the suppression of shivering, because shivering did not appear under the present experimental conditions. After sinoaortic baroreceptor denervation, PHE infusion failed to produce these changes. After premedication with atropine, PHE infusion suppressed M and Tbat without the bradycardia. These results indicate that nonshivering thermogenesis (NST) in the brown adipose tissue (BAT) is suppressed by a sinoaortic baroreceptor reflex in response to an elevation of BP. Since metabolism of BAT is controlled by the sympathetic nervous system, the baroreflex inhibition of NST in the BAT may be largely attributed to the decrease of sympathetic nervous outflow to the BAT.

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A standard indentation (500 μm, 3 sec) was applied 50 times on the receptive field, and responses were successfully recorded from 38 of the 105 slowly adapting cutaneous afferent (SA) units innervating the wart-bearing plantar surface of the frog hind foot. The SA units discharged a small number of spikes with a time course of at least two time constants (0.16-0.39 and 0.72-3.26), and did not produce a maintained discharge in almost all cases. An ensemble of interspike intervals, {X_t (1), X_t (2), …, X_t (50)}, adjacent to some time points after the onset of stimulation (t=500 and 1, 000 msec) over 50 trials of stimulations, was chosen for statistical analysis, instead of a series of the successive interspike intervals in a steady state; the interspike interval histograms were skewed with a large coefficient of variation and gave a good fit to a F distribution, and joint interval diagrams around these time points showed an independence of successive interspike intervals. A similar finding was obtained from statistical analysis of a steady phase of discharges in an exceptional case. In conclusion, the SA units innervating the warty skin of the frog hind foot were similar in discharge pattern to the cutaneous SA type I units of mammals.

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Voluntary intake of proteins of various qualities in relation to dietary protein utilization was investigated in growing and adult rats. The rats were given two diets, one containing high protein and the other no protein, and were allowed to self-select protein and energy intakes freely from both diets. The results showed that total food intake (protein diet plus protein-free diet) and body weight gain were similar among five proteins tested. However, the amount of protein consumed by the growing rats per 100 g of total food intake (i.e., dietary protein level) was different depending upon the protein qualities, that is, wheat gluten (WG) 44 g, casein (CA) 30 g, soy protein (SP) 21 g, lactalbumin (LA) 19 g, and amino acid mixture simulating egg protein (AA) 11 g. Net protein utilization (NPU), estimated as the proportion of protein intake that is retained in the body, was as follows: WG, 20%; CA, 33%; SP, 44%; LA, 50%; and AA, 74%. From the above figures, net dietary protein value, which is a measure of utilizable protein in the diet, was calculated by multiplying the dietary protein level by NPU. In contrast to the difference in protein intake, net dietary protein value was quite constant in spite of large differences in the dietary protein quality, being 8 to 10%. A similar relationship between protein intake and protein utilization was obtained also with adult rats, except that the net dietary protein value was smaller in adult rats than in growing rats. These results may suggest that the animals can regulate the intake of dietary protein to keep the amount of protein available for the body constant.

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Effects of sweat gland training by daily local heating were examined and its significance in heat acclimatization was evaluated. Training by 2-hr immersion of an arm in hot water of 43°C caused distinct augmentation of sweat gland activity in the trained area, with reduction in the degree of hidromeiosis, when tested by an arm bag collection of sweat. Concentrations of sweat electrolytes also showed definite decreases. The general tendency that Na and Cl concentrations in sweat rise in the course of hidromeiosis was attenuated or even reversed after the training. The sweat test using resistance hygrometry failed to show a marked or consistent increase in sweat rate of the trained area, although an increase was the common case on the dorsum of the hand and the extensor aspect of the forearm. The effect of training appeared in a few days of training, developed progressively with training days and showed a tendency to develop even after 3 weeks of training. The same training in midsummer failed to exert significant effects on sweat gland activity, suggesting that the sweat gland had been naturally trained to a considerable degree by then. On the other hand, training by repeated radiant heating of a local area caused only obscure changes in the activity of sweat glands. The present results reveal that sweat glands can be trained to be resistant to hidromeiosis in a hot-humid environment and that such peripheral changes appear to play a predominant role in augmentation of sweating capacity in the early stage of heat acclimatization.

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1. Scorpions were starved for 1, 4, 8, and 12 days and then subsequently refed until the sixteenth day. The concentrations of glycogen, amino acid, and protein in the liver were determined to evaluate the effect of starvation and refeeding on these biochemical constituents.
2. The concentration of glycogen decreased gradually but significantly with the progressive days of starvation. After refeeding, the concentration increased sharply and attained the normal condition after 4 days of refeeding.
3. The concentrations of amino acids and proteins increased during first few days of starvation and declined thereafter. After refeeding the concentrations of amino acids and proteins increased gradually and attained the normal conditions after 3 and 4 days respectively.
4. The water content of the liver did not show any significant variation with the progressive days of starvation or after refeeding.

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Restraint for 2 min increased heat production and brown adipose tissue (BAT)-thermogenesis in rats at 27°C. These increases continued for 15-20 min after the release from restraint. After sectioning sympathetic nerves to the BAT, restraint did not produce BAT-thermogenesis. These results indicate that BAT is responsible for the stress-induced hyperthermia in rats.

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To measure intracellular Na⁺ activities, a double-barreled Na ion-selective microelectrode was constructed with a neutral carrier Na⁺ ligand (ETH 227). The slope constant and detection limit were 56 mV and 3-5 mM, respectively, the selectivity of Na⁺/K⁺ being 40-50. In the bullfrog, the cell Na⁺ was 14.4 mEq/liter for the proximal tubule and 12.6 mEq/liter for the sartorius muscle.

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Fluorescent probing with chlorotetracycline (CTC) was employed to test for effects of caffeine on membrane-bound Ca in isolated smooth muscle cells. The decrease in fluorescence by caffeine was associated with the contractile response of muscle cells to caffeine. Caffeine should release the activator Ca²⁺ from membrane or intracellular stores.

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Convergence of visceral afferents was studied in 245 pontine reticular units that responded to afferent stimulation of rectal branches of the pelvic nerve of dogs. Afferents from the urinary bladder and the anal mucosa converged in about 90 % of the units. Thoracic vagal afferents were projected in 20 % of the units.

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In urethane-anesthetized rats, effects of locus coeruleus stimulation on spontaneous and photically evoked discharges of superior collicular neurons were studied. In any layer of the superior colliculus the inhibited neurons were more numerous than the facilitated ones, and the latter increased relative to the former from the superficial to the deep layer.

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Using cultures of dissociated neurons from the lower brain stem of rat embryos, the receptor properties of cholinoceptive neurons were examined pharmacologically. Out of 89 neurons, 41 showed facilitation of unit discharges by the application of acetylcholine. These cholinoceptive neurons were proven to have both nicotinic and muscarinic properties.

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