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Volume 29, Issue 1
Displaying 1-9 of 9 articles from this issue
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Tomiyasu KOYAMA, Yuji KIKUCHI, Yoshihiro KAKIUCHI, Chosetsu NAGASHIMA1979 Volume 29 Issue 1 Pages 1-13
Published: 1979
Released on J-STAGE: June 07, 2011
JOURNAL FREE ACCESSThe colloid osmotic pressure (COP) of blood from the great cardiac vein was continuously measured by means of a membrane colloid osmometer during the reactive hyperemia following temporary occlusion of the anterior descending branch of the left coronary artery in anesthetized open-chest dogs. The COP increased sharply after releasing the occlusion, then decreased below the preocclusion level before gradually returning to it. These findings indicate that a measurable amount of water moved from the capillary blood into the myocardial tissues and then flowed back slowly into the capillary blood. To analyse the factors affecting this water movement, a method is proposed in which the Starling mechanism is combined with the interstitial volume elasticity and a steadystate solution of a Navier-Stokes equation. The pressure observed with a catheter wedged into a branch of the great cardiac vein was used as a measure of capillary perfusion pressure. During the coronary arterial occlusion, the filtration constant increased while the volume elasticity of the myocardial interstitial spaces decreased rapidly. The filtration constant and volume elasticity of the interstitial space under normal conditions were approximately estimated to be 2.4 × 10-11 cm/(sec · dyn · cm-2) and 1.1 × 107 dyn · cm-2, respectively.View full abstractDownload PDF (5533K) -
Masashi KURAHASHI, Akihiro KUROSHIMA1979 Volume 29 Issue 1 Pages 15-23
Published: 1979
Released on J-STAGE: June 07, 2011
JOURNAL FREE ACCESSThe changes in the number and affinity of binding sites in the β-adrenergic receptors of rat white adipocytes after cold exposure were studied with the aid of (-)-[3H] dihydroalprenolol. One day cold exposure did not change the number and affinity of binding sites in β-adrenergic receptors. Chronic exposure of rats to cold (5°C) for 1 and 4 weeks significantly decreased the affinity of β-adrenergic receptors without any alteration in the number of binding sites. Such changes in the binding affinity observed in cold-acclimated rats (4 weeks, 5°C) remained for 18 hr after these animals were transferred to a warm environ-ment of 25°C. The decreased affinity of binding sites in β-adrenergicreceptor induced by cold acclimation could not explain the enhanced metabolic response of cold-acclimated animals to noradrenaline.View full abstractDownload PDF (946K) -
Junna HATAE1979 Volume 29 Issue 1 Pages 25-36
Published: 1979
Released on J-STAGE: June 07, 2011
JOURNAL FREE ACCESSThe effects of procaine on the contractility of the bullfrog's ventricular muscle were investigated. The addition of 10-5 g/ml of pro-caine potentiated the twitch tension which was accompanied by an eleva-tion as well as a prolongation of the action potential plateau. This positive inotropism of procaine was not induced by endogenous catecho-lamine because a β-blocking agent did not influence this twitch potentia-tion. The twitch potentiation was increased in proportion to the external Ca concentration, suggesting the possibility of augmentation of Ca influx during the action potential. In normal Ringer solution, procaine sup-pressed potassium contracture which was composed of two components: an initial phasic component and a late tonic one. Potassium contracture after perfusion with Ca-free solution was also suppressed by procaine. However, potassium contracture which had been treated previously with La was composed of only a tonic component and was potentiated by procaine in spite of perfusion with Ca-free solution. The tonic com-ponent of potassium contracture may be considered to occur with in-tracellular Ca. Procaine may increase the Ca inward current, acting on the intracellular Ca storage site and consequently accelerate the excita-tion-contraction coupling in frog ventricular muscle.View full abstractDownload PDF (1232K) -
Ayako ISHIDA, Hidenobu MASHIMA, Shigeko TANAKA1979 Volume 29 Issue 1 Pages 37-48
Published: 1979
Released on J-STAGE: June 07, 2011
JOURNAL FREE ACCESSThe intracellular distribution of calcium was investigated by 45Ca electron microscope autoradiography in the frog or rat ventricular muscle and guinea pig papillary muscle. The muscle was incubated for 30 min in 45Ca-Ringer's solution or high Ca solution in which 1/10-1/20 of Ca was replaced with 45Ca. The distribution of developed silver grains sensitized by the 45Ca (45Ca grains) was found to be 38 % in the mito-chondria, 43 % in the myofibrils and 19 % in the other regions (8 % in the cytoplasma and 11 % in the various membranous structures) in the frog muscle cell incubated in the 45Ca-Ringer's solution. After electrical stimulation (10 Hz, 5 min), the distribution was 22 % in the mitochondria, 53 % in the myofibrils and 25 % in other regions. Similar results were ob-tained after high K stimulation in the frog ventricular muscles and after electrical stimulation in high Ca solution in guinea pig papillary muscles. Following the addition of 1×10-6 g/ml adrenaline into the incubating solution, the grain distribution in guinea pig papillary muscles did not show significant change but the distribution in myofibril decreased after-electrical stimulation, while it increased in the mitochondria. Longitudi-nal localization of 45Ca grains along the myofibril was also examined and it was a general tendency throughout all animals examined that the grain density at the A band and near the Z band decreased after electrical stimulation, while it increased at the I band and, especially, at the A-I junction.View full abstractDownload PDF (12534K) -
Mitsuru TAKATA, Satoshi FUJITA, Etsuo SHOHARA1979 Volume 29 Issue 1 Pages 49-60
Published: 1979
Released on J-STAGE: June 07, 2011
JOURNAL FREE ACCESSIn nembutalized cats intracellular potentials were recorded from hypoglossal motoneurons innervating either protruder or retractor muscles of the tongue (protruder and retractor motoneurons: P-Mns and R-Mns). Responses to stimulation of the hypoglossal nerve were explored and found to consist of an antidromic spike followed by an afterhyperpolarization (AHP) and a postsynaptic potential (PSP). When hypoglossal nerve stimulation was made with an intensity three times as large as the threshold for the hypoglossal motor fibers, the PSPs became evident under blockage of soma-dendritic invasion of the anti-dromic spike. In most of P-Mns or R-Mns, the PSPs were IPSPs, independent of the side of peripheral stimulation. The latencies were about 12 msec. Even when the cell membrane was hyperpolarized by injecting a hyperpolarizing current of up to 16 nA, the reversal point of the IPSP was difficult to find. In a small fraction of hypoglossal moto-neurons the PSPs to hypoglossal nerve stimulation were EPSPs with latencies of 10 to 12 msec.View full abstractDownload PDF (1295K) -
Itaru NAGAI, Isao OOTA, Torao NAGAI1979 Volume 29 Issue 1 Pages 61-73
Published: 1979
Released on J-STAGE: June 07, 2011
JOURNAL FREE ACCESSThe effect of SCN on potassium contracture, especially the time course and the mechanical inactivation of the contracture, was investigated using frog twitch muscle fibers. SCN increased the magnitude and the rate of rise of the potassium contracture tension and prolonged its time course. These effects of SCN depended on the concentration of K+ in the external medium and on the duration of pretreatment of the fibers with SCN-Ringer solution. The potentiating effect of SCN on the potassium contracture tension was pronounced at lower and moderate concentrations of K+ and this effect attained a maximum within 1 min after the pretreatment. In the contracture induced by exposure of the fibers to K-SCN-solution without the pretreatment, the time course of the contracture, especially the retardation of the spontaneous relaxation, was marked at higher concentrations of K+. This retarding effect of SCN attained a maximum at more than 10 min after the pretreatment with SCN-Ringer solution. SCN shifted the mechanical inactivation curve of potassium contracture toward lower concentrations of K+, as in the case of the activation curve, and markedly increased the rate of the inactivation induced by conditioning with 15 mm K+. In addition, SCN delayed the recovery of potassium contracture from the mechanical inactivation induced by preceding K-SCN-contracture. On the basis of these results, the sites and the mechanism of action of SCN on potassium contracture are discussed.View full abstractDownload PDF (1877K) -
Mitsuo ISHIZAWA, Eisaku MIYAZAKI1979 Volume 29 Issue 1 Pages 75-83
Published: 1979
Released on J-STAGE: June 07, 2011
JOURNAL FREE ACCESSCa-induced contracture and the effect of Na on it were investigated in the K-depolarized longitudinal and circular muscles of guinea pig stomach. In the absence of Na, Ca produced rapid contracture in longitudinal muscle, but slow and S-shaped contracture in circular muscle. The sensitivity to Ca for the contracture was about tenfold higher in longitudinal muscle than in circular muscle. The presence of external Na (7.5-60 mM) inhibited the contracture induced by Ca (0.1 mM) in longitudinal muscle in a dose-dependent manner. In circular muscle, however, Na potentiated the initial speed of contracture induced by Ca (1 mM), and inhibited the height of contracture at 30 min showing maximum inhibition at 15 mM Na. Li instead of Na produced inhibition of Ca contractures in both muscle layers. Na-induced potentiation in circular muscle was markedly depressed by lowering the temperature, and was reduced by a high concentration (1 mM) of ouabain.
These observations indicate that the Ca contracture in longitudinal and circular muscles differs and the effect of Na on this contracture may modulate Ca ion movements through the muscle membrane by inhibiting Ca influx in both muscle layers, and initially potentiating it in circular muscle in an ouabain-sensitive process.View full abstractDownload PDF (889K) -
Hidenobu MASHIMA, Takao OKADA, Hiroshi OKUYAMA1979 Volume 29 Issue 1 Pages 85-98
Published: 1979
Released on J-STAGE: June 07, 2011
JOURNAL FREE ACCESSTension-length, load-velocity and tension-extension relations were studied in the taenia coli muscle of the guinea pig weighing 0.25-0.5 kg at 36-37°C. The muscle was relaxed by 10-6 g/ml adrenaline and stimulated by a strong AC field. The tension-length diagram was far wider than that of the skeletal muscle and sufficient tension was generated at longer lengths than 1.8 Lm, where Lm is the optimal length at which the maximum tension, Fm, is generated. The developed force per unit cross-sectional area was almost unchanged between 1.2-2.0 Lm. Average of the maximum forces was 2.2 kg/cm2. Load-velocity curves obtained at various isometric forces at Lm, coincided with each other, if the velocity was plotted against the relative force. All curves can be expressed by a single force-load-velocity equation.
(P+A)(v+b)=b(F+A), A=(F/Fm) a.
where P is the load, F the isometric force, v the velocity, a and b are constants. The maximum velocity per unit muscle length was constant, irrespective of the muscle length. The compliance of the series elastic component, that is, the slope of the tension-extension curve, did not depend on the isometric force but decreased with decreasing muscle length. The internal lengthening of the series elastic component by the full isometric tension was about 3 % of the muscle length at Lm.View full abstractDownload PDF (1502K) -
Naoki HINO1979 Volume 29 Issue 1 Pages 99-102
Published: 1979
Released on J-STAGE: June 07, 2011
JOURNAL FREE ACCESSIn the crayfish stretch receptor neuron, extracellularly applied NH4+ acted on the nonsynaptic membrane and produced not only a depolarizing shift of EIPSP but also depolarization and conductance increase. Under certain conditions these actions may become the main cause of the disinhibitory effect of NH4+ on the inhibitory synapse.View full abstractDownload PDF (402K)
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