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Volume 25, Issue 1
Displaying 1-8 of 8 articles from this issue
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Enrique LÓPEZ1975 Volume 25 Issue 1 Pages 1-15
Published: 1975
Released on J-STAGE: June 07, 2011
JOURNAL FREE ACCESSThe perfused heart in situ and strip preparations were used. In the in situ preparation, low-Na hypoosmotic saline had a positive inotropic effect, shortened the A-V interval and abolished arrhythmia or A-V blocking. The return to normal saline caused a transient offresponse: further acceletation of the heartbeat and further shortening of the A-V interval. Low-Na isoosmotic saline (sodium replaced by sucrose) increased pacemaker activity but the effect on the length of the A-V interval was variable. In the strip preparation, Low-Na hypoosmotic saline increased the rate of rise of the action potentials of atrioventricular ring (R-potentials) and shortened its latency of activation. The effects of the isoosmotic saline varied with the substitute used, either sucrose or lithium. Sucrose saline gave unpredictable results, though the rate of rise of R-potentials increased in 14 out of 24 experiments. Lithium saline decreased the rate of rise of R-potentials and blocked atrioventricular propagation in all experiments. Tetrodotoxin (10-5g/ml) did not abolish R-potentials. An increase of calcium concentration to 3 and 5 times the normal decreased the rate of rise of R-potentials and blocked atrio-ventricular propagation. While the Low-Na saline blocked pacemaker activity at the sinus venosus, it stimulated the generation of R-potentials, so that throughout low-Na treatment, the site of pacemaker activity shifted to the A-V ring. The situation was reversed when normal saline was restored. The data are discussed according to the current ideas of action potential generation.View full abstractDownload PDF (12044K) -
Julio MIYAMOTO, Takeshi KOBAYASHI, Alfonso M. MIYAMOTO1975 Volume 25 Issue 1 Pages 17-28
Published: 1975
Released on J-STAGE: June 07, 2011
JOURNAL FREE ACCESSThe role played by the cardiac sympathetic fibers in the pulmonary depressor reflex was analyzed in twenty dogs.
The selective perfusion with homologous blood of the inferior lobar vessels of the left lung with pressures of 40 to 60 mmHg decreased the spontaneous background discharges recorded from the left superior or inferior cardiac sympathetic nerves. This decrease was maximal at perfusion pressure of 80-100 mmHg. Following the decrease in the sympathetic discharges, the systolic and diastolic systemic arterial blood pressure decrease about 10 percent. These changes were reversible when the perfusion pressure was returned to the control. The intravenous injection of atropine sulphate did not change either the systemic hypotension or the responses of the sympathetic efferent discharges induced by elevation of the pressure in the vascular bed of the lung lobe. Thus, it is believed that the systemic arterial blood pressure during, this reflex may have fallen due to a diminution of the vascular tone caused by a decrease in the sympathetic efferent discharges.
After transection of the vagus nerve ipsilateral to the tested lobe, the reduction of the sympathetic discharges as well as the decrease of the systemic arterial blood pressure were no longer observed. Our results further substantiate the concept that the vagus nerve is the afferent pathway for the pulmonary depressor reflex, and it may be con-cluded that during this reflex the sympathetic efferent activities are inhibited.View full abstractDownload PDF (1347K) -
Naotoshi MURAKAMI, Yoshiyuki SAKATA1975 Volume 25 Issue 1 Pages 29-40
Published: 1975
Released on J-STAGE: June 07, 2011
JOURNAL FREE ACCESSThe effects of antipyretics on the ear skin and rectal temperature (Te and Tre) were investigated in non-febrile rabbits placed in a cold environment or when they were cooled locally in the hypothalamus. Intravenous injections of sulpyrin (25-500 mg/kg) or sodium salicylate (25-100 mg/kg) produced the dose-related increase in Te and slight fall in Tre. Decrease in Te induced by hypothalamic cooling was also reversed by the intravenous injection of antipyretics. Intraventricular injections of sulpyrin and salicylate (0.5-5.0 mg/kg) also caused the vasodilatation of the pinna skin and the fall in Tre. Bilateral microinjections of sulpyrin were made into various areas of the brain stem in order to locate the site of action. The injection sites where the vasodilatatory effect was elicited were the anterior hypothalamus, ventromedial nucleus of hypothalamus and the midbrain reticular formation. The responses elicited from the ventromedial nucleus were usually accompanied by restless and violent struggling. Injection of antipyretics into the mammillary body had no effect on Te. Intrahypothalamic injection of procaine depressed the sulpyrin-induced vasodilatation. These findings suggest that action of antipyretics on the normal body temperature is mediated through anterior hypothalamus and midbrain reticular formation.View full abstractDownload PDF (1114K) -
Takeyuki YAMAMOTO1975 Volume 25 Issue 1 Pages 41-50
Published: 1975
Released on J-STAGE: June 07, 2011
JOURNAL FREE ACCESSThe mechanical response of the red and white muscles of the silver carp was investigated using linearly stimulating currents. In the presence of tetrodotoxin, the peak tension increased when the rate of rise was reduced to about 0.3mA/sec in the red muscle, and to about 3mA/sec in the white muscle, provided that the maximum current applied always reached 3mA. Further reduction of the rate of rise decreased the tension, particularly in the white muscle. Low concentrations of caffeine (0.5 mM) potentiated mainly the early phase of contraction. However, the tension produced by a stimulating current with a rate lower than this value was suppressed by caffeine. When the external K ion was cumulatively increased to more than 13.5mM in the red muscle and to more than 10.8mM in the white muscle, the tension elicited by a linearly rising current was reduced. La and Mn ions suppressed mainly the late phase of contraction.
It is postulated that two different mechanisms are involved in increasing the intracellular-free Ca concentration. The early phase of contraction may be a result of Ca release from the surface of terminal cisternae of the sarcoplasmic reticulum triggered by depolarization. The late phase produced by a prolonged depolarization may be a consequence of Ca movement across the plasma membrane or the membrane of sarcoplasmic reticulum. There seems to be an inactivation process for both the early phase and late phase. The difference in mechanical properties between the red and white muscles may be due to the presence of strong inactivation in the excitation-contraction coupling in the white muscle.View full abstractDownload PDF (872K) -
Reiji NATORI1975 Volume 25 Issue 1 Pages 51-63
Published: 1975
Released on J-STAGE: June 07, 2011
JOURNAL FREE ACCESSWith skinned fibres prepared by removing sarcolemma in liquid paraffin from single fibres isolated from m. adductor magnus, m. sartorius or m. rectus internus major of toad (Bufo bufo japonicus), it was determined whether or not an action potential (“internal action potential”, or IAP) could be detected during a propagated contraction evoked by electrical square pulses of 1 msec duration.
The IAP less than 10mV was recorded with a glass capillary microelectrode inserted into the skinned fibre during a contraction propagating along the skinned fibre. The shape of the IAP was similar to the action potential of a surface membrane of the skeletal muscle fibre, although its time course was far slower. The rate of rise of IAP was more rapid than that of the mechanical movement which was measured by the change in scattered light quantity of a gas-laser beam.
When a contraction wave was propagated as far as the unskinned portion, it reflected there and began to propagate backwards along the skinned portion. Whenever a contraction wave passed through the microelectrode-inserted portion, the IAP was recorded.
When the propagation of a contraction wave was blocked somewhere in the skinned fibre, a potential change in reverse direction was recorded there. The phase of this potential change corresponded with the after potential of the IAP.View full abstractDownload PDF (11795K) -
Hiroshi KAWATA, Kimie KAWAGOE1975 Volume 25 Issue 1 Pages 65-78
Published: 1975
Released on J-STAGE: June 07, 2011
JOURNAL FREE ACCESSIntroduction: A study of the effects of hyper -and hypotonic media on resting tension were examined in ventricular muscle of the bullfrog was undertaken because only few studies on resting tension from the viewpoint of E-C coupling in the heart muscle are available. Materials and Methods: Thin strips obtained from the bullfrog ventricle were perfused in the sucrose-gapped chamber, which allowed the effective stimulation and the simultaneous measurement of the contractile tension and the intracellular membrane potential. Results and Conclusions: Hypertonic solutions up to 3.0 T, prepared by adding NaCl or sucrose, induced a triphasic response, namely an initial rapid decline, a secondary slow development of contracture and a final transient offcontraction. Both the second and the final responses were strongly sensitive to the calcium concentration of the bathing medium and were completely abolished by depleting external calcium ions. The initial decreasing phase was not sensitive to external calcium but was progressively augmented by increasing the initial muscle length, whereas the dehydration process, estimated by measuring the muscle weight, was unaffected by muscle stretch. The changes in the membrane potential were not essential for these responses. It was concluded that the initial tension decline results from the passive process due to volume change while the sustained contracture as well as the transient off-contraction are produced by some active process involved in E-C coupling. Hypotonic solutions induced a monophasic contracture which is insensitive both to the external calcium concentration and muscle stretch. The possible mechanism for the genesis of the response was discussed.View full abstractDownload PDF (1529K) -
1975 Volume 25 Issue 1 Pages 78
Published: 1975
Released on J-STAGE: June 07, 2011
JOURNAL FREE ACCESSDownload PDF (61K) -
Tetsuji HIRONAKA1975 Volume 25 Issue 1 Pages 79-91
Published: 1975
Released on J-STAGE: June 07, 2011
JOURNAL FREE ACCESSSynaptic events in a chloride-deficient condition were studied to elucidate functional aspects of presynaptic inhibitory synapses. The extracellular junctional potentials and nerve terminal potentials were concurrently recorded from a synaptic region. Inhibitory stimulation produced repetitive spikes on the inhibitory nerve terminal and then the excitatory nerve terminal, which resulted in the extracellular excitatory junctional potentials. Excitatory stimulation did not produce repetitive spikes on the inhibitory nerve terminal, indicating one-way signal transmission in this axo-axonal synapse from inhibitory to excitatory axon. The interval required for an inhibitory stimulation to produce the first response in the postsynaptic muscle membrane ranged widely from 10 to 800msec. When γ-aminobutyric acid (GABA, 1×10-4M) was added in these experimental conditions, the muscle membrane was transiently depolarized by about 10 mV. The action of GABA mimics that of the neurotransmitter at presynaptic inhibitory synapses. The experimental observations may be well explained by the concept of synapses on synapses, i. e., presynaptic inhibition, where the neurotransmitter may be GABA and chloride ions may be playing essential roles as in the case of postsynaptic inhibition.View full abstractDownload PDF (10542K)
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