The effects of acute alveolar hypoxia on pulmonary blood flow were studied in upright standing human subjects by means of a constant expiration technique combined with continuous analysis of the C₂H₂ fraction in the expired gas. The subject rapidly and deeply inhaled a gas mixture containing 4.87% C₂H₂, 0.99% O₂, N₂ for balance and exhaled the alveolar gas via a constant flow valve. The P_O2 of the alveolar gas fell to 37.6±5.6 mmHg. The C₂H₂ curve showed a clear downward inflection 7 to 10 sec after the completion of washout of the dead space gas. This inflection indicates an increase of the C₂H₂ uptake rate produced by an increase in pulmonary blood flow. The pulmonary blood flow calculated for the time range of 10.0 to 12.5 sec after the establishment of acute alveolar hypoxia (6.5±1.1 1/min) was significantly larger than the blood flow under normoxia (5.5±0.91/min). This increase associated with a quick rise in systemic arterial blood pressure which was probably induced by a chemical reflex.

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Variations in the counts of circulating basophile leucocytes in 225 subjects were studied. The results obtained are as follows: 1) The counts (per mm³) show a gradual rise with growth, from infancy to adolescence, and maintain a fair constancy in adults. 2) No significant sex difference was found in the peripheral basophile counts. 3) A definite diurnal variation in the counts exists, which is lowest in the morning and highest in the evening. 4) The counts are altered in different phases of the menstrual cycle. 5) Pregnant women show lower counts than nonpregnant women. 6) Surgical trauma and a single electroconvulsive shock lowers the counts significantly but variations are not significant after meals and physical exercise. 7) Smokers have slightly higher counts than non-smokers. 8) A course of irradiation therapy lowers the counts significantly in patients with inoperable neoplastic diseases. 9) Counts show insignificant variation with alteration of blood glucose level. The results mentioned above are discussed.

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The effects of various ions on water response was studied by recording unitary discharges in single superior laryngeal nerve fibers of the rabbit. The water response was strongly influenced by anions. The inorganic anions used were divided into two groups. One group consisted of anions which depress the water response (depressing anions), the depressing action sequence being SCN^->Br^->Cl^->I^->NO^-₃. Another one consisted of anions which facilitate the water response (facilitating anions), the facilitating action sequence being citrate>SO^2-₄>IO^-₃>F^->BrO^-₃>acetate. Physicochemically, facilitating anions belong to “the water structure-making ions” group;on the other hand, depressing anions belong to “the water structure-breaking ions” group. SO^2-₄weakened the depressing effect of Cl^-when the concentration of Cl^-was below 60mM, and enhanced it when the concentration was above 60mM.Na⁺and Li⁺had no appreciable effect on the water unit activity, but K⁺had a weakly stimulating effect. It is concluded that an outflux of anions through the membrane stimulates the water receptor while an influx of anions depresses it, and SO^2-₄facilitates Cl^-permeability. The mechanism of the facilitating effect of SO^2-₄on Cl^-permeation is discussed in terms of the interaction between the water structure surrounding the ions and the receptor membrane.

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The mechanisms of the action of hemolysin extracted from Vibrio parahaemolyticus in the S-A node and right atrium cells of rabbit were studied by means of the single sucrose gap and isometric tension recording methods. Hemolysin caused the membrane to depolarize reversibly without affecting the action potential generating mechanism. Lowering of [Na⁺]_o inhibited membrane depolarization in the presence of hemolysin while the readmission of normal Tyrode solution induced depolarization. Tetrodotoxin (TTX) barely antagonized the depolarizing action of hemolysin but slowed the rate of development of depolarization. Therefore, this depolarization is considered to be primarily due to the increase in conductance to Na which TTX may not block. The dose-response relationship was obtained by measuring a change in membrane resistance. The concentration necessary to yield one-half of the maximum reduction of the membrane resistance was determined to be 7.5μg/ml.
Accumulation of Na within the cell may be responsible for an increase of twitch tension observed during the action of a low concentration of hemolysin. On the other hand, a higher concentration of hemolysin seemed to promote exchange of intracellular Na with extracellular Ca, especially when the Na concentration of the perfusing solution was reduced, and led to stronger contracture.

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The mechanism of post-tetanic hyperpolarization (PTH) occurrence was investigated using the intracellular recording technique. The median giant axon of a crayfish abdominal nerve cord was repetitively stimulated to elicit PTH.
When the membrane potential was hyperpolarized by intracellularly applied currents, PTH reversed its sign. K⁺ removal from the external medium increased the size of PTH and shifted its reversal potential in the hyperpolarizing direction. This result shows that an increase in K⁺ conductance contributes to the formation of PTH. In a K⁺-free medium, the size of PTH was reduced by replacement of Na⁺ with Li⁺ in the external medium, by application of ouabain or DNP, or by cooling. These procedures shifted the reversal potential in the depolarizing direction. These findings are interpreted as showing that, with K⁺ absent, PTH is partly due to the activity of an electrogenic Na pump. With lowering of external Na⁺ concentration, PTH became larger and the reversal potential moved in the hyperpolarizing direction. The experiment suggests that Na⁺ conductance is also increased when PTH is elicited because one expects the amount of Na⁺ entering per impulse and the activation of the Na pump to be reduced by reducing Na⁺ concentration in the external medium.
It is concluded that PTH in the median giant axons of crayfish is produced by at least two mechanisms. One is an increase in activity of the electrogenic Na pump, and the other is an increase of membrane conductance to K⁺ and Na⁺.

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Effects of gastrointestinal hormones on the electrical and mechanical activities of the smooth muscle of the cat small intestine were examined. Both spontaneous electrical and mechanical activities of the intestinal smooth muscle were inhibited by tetragastrin, pentagastrin and pancreozymin. The spike activity and the phasic contraction of the smooth muscle were depressed by these hormones while the slow waves were maintained. On the other hand, secretin showed an excitatory action on the mechanical activity of the isolated preparation of smooth muscle. Spike activity disappeared and the level of tone was increased gradually. The inhibitory and excitatory actions of each hormone on the mechanical activity were not abolished by the application of atropine and tetrodotoxin. Furthermore, the inhibitory effects of pentagastrin and pancreozymin on the smooth muscle were not antagonized with phenoxybenzamine or propranolol. These results suggest that the inhibitory actions of pentagastrin and pancreozymin on the smooth muscle were not mediated by alpha or beta receptors and not due to the stimulation of an inhibitory nervous system in the gut. Antagonistic relations between secretin and pentagastrin and also between secretin and pancreozymin were observed. The mechanisms of the actions of gastrointestinal hormones are discussed.

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The effect of adenosine compounds (ATP, ADP, AMP, and adenosine) on membrane potential, current and contractile tension on the bullfrog atrium were studied under voltage clamped and unclamped conditions. The compounds produced immediate positive and late negative inotropic effects in unclamped conditions. The positive isotropic effect and the potency of drugs appeared less marked in the order of ATP, ADP, AMP, and adenosine. Under voltage clamped conditions, only the energy rich compounds, ATP and ADP, produced an enhancement of calcium inward current (I_Ca) and I_Ca-dependent phasic tension, while AMP and adenosine elicited a negative inotropic effect. The delayed outward current was initially depressed but later augmented especially in case of ATP and ADP where I_Ca was enhanced. All adenosine compounds, however, inhibited the I_Ca-independent tonic tension. This effect, appearing nonspecific, was ascribable to the action of common structure of these compounds, purine-riboside moiety.

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The effect of D₂0 and dantrolene-Na (DAN) on the electrical and mechanical responses of single muscle fiber (mouse EDL and frog semitendinosus), Ca²⁺uptake and release of sarcoplasmic reticulum (SR) and contractile proteins was investigated to elucidate the coupling mechanism between depolarization and contraction.
Both agents inhibited tension development induced by depolarization and caffeine, especially the initial phase of contraction (more pronounced in fast muscle) without affecting excitation of membrane and contractile machinery. The effect of DAN can be antagonized by increasing Ca²⁺ concentration and lowering the temperature of the medium. Ca²⁺ uptake and release abilities of isolated SR were not altered significantly in DAN, but were reduced considerably in D₂0.
These results suggest that there is a Ca²⁺-mediated trigger mechanism for the rapid release of activator Ca²⁺from internal storage (SR). DAN and D₂0 interfere predominantly the action of the site (s) of this mechanism, probably on the T-tubules. In addition, D₂O decelerates Ca²⁺ release from SR per se.

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Effects of Na, Ca, anions and isoprenaline on the plateau potential in circular muscle of 11-to 13-day pregnant rat myometrium were investigated using the double sucrose gap method. During the plateau potential, which amounted about 15-20mV and lasted for 10-20 sec, the membrane conductance increased initially, then decreased. The amplitude and duration of the plateau potential increased by raising the external Ca concentration to between 0.3 and 3mM, and decreased when the concentration was increased more. The plateau was prolonged in low Na solution (54mM). When 154mM Cl was replaced with Br the plateau was prolonged, however, the plateau was nearly suppressed when Cl was replaced with benzene sulphonate or isethionate. Isoprenaline increased membrane conductance and depressed the plateau. It was concluded that a decrease in K conductance was largely responsible for the plateau potential, and an inward Ca current may have contributed to its formation.

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Effects of Na, Ca, anions and drugs (isoprenaline, TEA, procaine) on the negative afterpotential in the longitudinal muscle of pregnant rat myometrium were investigated using the double sucrose gap method. The negative afterpotential having a peak amplitude of about 15mV decayed initially rapidly then slowly, the total duration being about 1 sec. Raising the external Ca concentration up to 10mM or reducing Na to 54mM increased the amplitude of the negative afterpotential. Replacement of Cl with Br enhanced the negative afterpotential and replacement with benzene sulphonate or isethionate depressed it.The application of 10mM TEA increased, while 10mM procaine reduced the amplitude of both spike and negative afterpotential. 10^-10-10^-8g/ml isoprenaline depressed the negative afterpotential dosedependently, while leaving the spike potential nearly unaffected. It was concluded that the negative afterpotential was composed of at least two ionic mechanisms, one of Cl origin, the other of Ca origin.

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