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Volume 26 (1976)
- Issue 6 Pages 577-
- Issue 5 Pages 441-
- Issue 4 Pages 345-
- Issue 3 Pages 235-
- Issue 2 Pages 101-
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Volume 26, Issue 2
Displaying 1-10 of 10 articles from this issue
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Tomio KANNO, Toshihiro SUGA, Masao YAMAMOTO1976 Volume 26 Issue 2 Pages 101-115
Published: 1976
Released on J-STAGE: June 07, 2011
JOURNAL FREE ACCESSA technique is described for perfusing isolated rat pancreas with a modified Krebs-Henseleit solution. This preparation made feasible the simultaneous measurement of transmembrane potential, effective membrane resistance, rate of flow of pancreatic juice and amylase output. The hyperpolarizing effect of cholecystokinin-pancreozymin (CCKPZ) was confirmed by perfusion with a solution containing 5 mU CCKPZ/ ml. The hyperpolarizing effect of CCK-PZ was enhanced when the pancreas was perfused with an oxygenated solution containing dog erythrocytes. This effect was inhibited by ouabain and anaerobic conditions. It is suggested that the oxidative metabolism supplies energy for a mechanism which is responsible for the hyperpolarizing effect of CCKPZ. The amylase output and the rate of flow of pancreatic juice were enhanced concurrently under conditions that augumented the hyperpo larizing effect, and they were inhibited under conditions that suppressed the effect.Cellular events in stimulus-secretion coupling in the pancreatic acinar cell are discussed by correlating the electrophysiological responses and the secretory responses under various conditions.View full abstractDownload PDF (1772K) -
Isao OOTA, Isao KOSAKA, Torao NAGAI1976 Volume 26 Issue 2 Pages 117-126
Published: 1976
Released on J-STAGE: June 07, 2011
JOURNAL FREE ACCESSSingle fibers isolated from frog semitendinosus muscle continued to twitch for 5-8 min in calcium-free Ringer solution containing 1mM ethylene glycol bis (β-aminoethyl ether)-N, N'-tetraacetic acid (EGTA). Even after twitching was completely abolished, the tension of potassium contracture was not depressed, although the time course was markedly shortened.The resting potential recorded from single fibers 10 min after immersion in EGTA-Ringer solution decreased slightly. These fibers failed to generate action potential, however, in a whole sartorius muscle the self-exchangeable calcium was not significantly reduced by 1mM EGTA, while it was reduced by about 27% during the potassium contracture induced in the EGTA solution.From these results, it is suggested that the calcium bound on the surface sites of the transverse tubular membrane and the sarcolemma can serve as a trigger for the release of calcium from the sarcoplasmic reticulum and can produce a resting potential and maintain relatively long duration excitability under the condition of extracellular calcium deficiency.View full abstractDownload PDF (1220K) -
Hiromi TOKURA, Fumie HARA, Morihiko OKADA, Fumio MEKATA, Wataru OHSAWA1976 Volume 26 Issue 2 Pages 127-132
Published: 1976
Released on J-STAGE: June 07, 2011
JOURNAL FREE ACCESSEffect of clipping the coat of the Japanese macaque on thermoregulatory responses was studied. Heat production was significantly increased in clipped animals in comparison without clipped coats at ambient temperatures ranging from 5 to 25°C. At ambient temperatures of 5, 15, and 25°C tissue thermal conductance and cooling constant were significantly higher in clipped animals. Clipped animals could maintain thermal equilibrium at an ambient temperature of 5°C, compensating for the increase of heat loss by elevating heat production markedly.View full abstractDownload PDF (524K) -
Hiroshi IRISAWA, Akinori NOMA1976 Volume 26 Issue 2 Pages 133-144
Published: 1976
Released on J-STAGE: June 07, 2011
JOURNAL FREE ACCESSA study was made on both hyperpolarization and contracture which developed in the rabbit sinoatrial node cell during perfusion with Na-depleted solution. The membrane was hyperpolarized in 19 out of 27 specimens (-69.5±6.0mV), while in the remaining 8 specimens the value of the membrane potential remained low (-39.4±2.7mV). Slope conductance increased as the membrane was hyperpolarized in Na-depleted solution, but not when the value of the membrane potential remained at low. The amplitude of hyperpolarization increased with decrease in Na concentration, increase in Ca concentration and increase in perfusate temperature.
A marked increase in diastolic tension was observed in 23 out of 29 specimens but in the 6 remaining specimens the increase in tension was small. Tension increased with decrease in Na concentration, increase in Ca concentration, and increase in perfusate temperature.
Pretreatment with ouabain caused a consistent increase in contracture tension, while its effect on the membrane hyperpolarization was variable among different specimens. These results may be explained by assuming that intracellular Ca concentration increased with Na-Ca exchange in Na-depleted solution. In addition to contracture, increase in intracellular Ca concentration might have caused an increase of membrane K conductance and produced marked hyperpolarization.View full abstractDownload PDF (1150K) -
Moto MATSUMURA, Hidenobu MASHIMA1976 Volume 26 Issue 2 Pages 145-157
Published: 1976
Released on J-STAGE: June 07, 2011
JOURNAL FREE ACCESSCa ions were ionophoretically injected through an intracellular microelectrode into the single muscle fiber of a crayfish, and the resulting contraction sphere was observed under a microscope and photographed with a movie camera. The minimum contraction produced by the threshold current involved usually three or four, sometimes two, sarcomeres on both sides of the injecting pipette but contraction involving only one sarcomere was not observed. The rheobase of the Ca-injectingcurrent was 3.2×10-9 A. The strength-duration curves were determined for Ca-, Sr-, and Ba-injecting currents; all fitted a similar hyperbolic equation. The threshold amount of Ca above rheobasic injection was 2.1×10-15 mol, and the ratios between threshold amounts were Ca:Sr:Ba=1:1.9:3.0. The effects of Ca and Sr were additive for the contraction. More current was required for the Ca-injection to produce the contraction in the K-depolarized- or 15mm-procaine-treated muscle, although less current was sufficient for the muscle treated with 0.5-1.0mM of caffeine.The participation of the Ca-induced Ca release mechanism in the contraction produced by Ca injection and the role of Sr or Ba as a substitute for Ca were discussed.View full abstractDownload PDF (6479K) -
Kenji KUBA, Kenichi CHIKAZAWA, Kyozo KOKETSU1976 Volume 26 Issue 2 Pages 159-175
Published: 1976
Released on J-STAGE: June 07, 2011
JOURNAL FREE ACCESSThe effects of a piperazine derivative, trimetazidine (1-(2, 3, 4-trimethoxybenzyl) piperazine dihydrochloride) on the frog end-plate membrane were studied. Action and resting membrane potentials and the input resistance of muscle fibers were not affected by trimetazidine (82-165μM). Under these conditions, the frequency of the miniature endplate potentials was unchanged while its amplitude was slightly decreased. The amplitude of acetylcholine (ACh) potentials were markedly and reversibly decreased after application of trimetazidine (82-165μm). The dose response curve of the end-plate membrane to ACh showed a non-competitive type of blockade.Trimetazidine (165μM) not only decreased the amplitude of the end-plate currents (EPC) recorded from the glycerinated muscles using a voltage clamp technique, but also drastically shortened its time course. Under these conditions, the falling phase of the EPC became completely voltage insensitive. The equilibrium potential for the EPC slightly shifted to a more negative value in the presence of trimetazidine (165μM). Coefficient of variation of EPC was increased by trimetazidine (165μM), indicating a decrease in the quantal content of the EPC. The rate of desensitization of the end-plate to ACh was facilitated and the rate of decrease in EPC amplitude during tetanic stimulation became voltage sensitive by the action of trimetazidine (133μM). It is concluded that trimetazidine mainly acts on the postsynaptic membrane with a weak presynaptic action. The agent seems to block a step subsequent to the interaction of ACh with its receptor, which presumably involves changes in the ion conductance of the membrane and is responsible for the voltage sensitivity of the response.View full abstractDownload PDF (1864K) -
Akihiro KUROSHIMA, Katsuhiko DOI, Masashi KURAHASHI, Tomie OHNO1976 Volume 26 Issue 2 Pages 177-187
Published: 1976
Released on J-STAGE: June 07, 2011
JOURNAL FREE ACCESSEffects of high-fat and high-protein diets on cold tolerance in fasted rats were investigated. High-fat diets caused significant increases in body weight, blood-free fatty acids (FFA), ketone bodies and glucose, while high-protein diet did not modify any of these parameters. Rats on high-fat diets that were exposed to cold after clipping exhibited an intermediate cold tolerance as assessed by the rate of fall in colonic temperature between control rats on a standard diet and cold-acclimated rats. The extent of increase of blood FFA and decrease of blood glucose due to cold exposure was less in the high-fat diet group than in control group, but greater than in cold-acclimated group. The lower fall in colonic temperature due to cold exposure was significantly associated with less increase in blood FFA and less decrease in blood glucose. In this relation the high-fat diet group was also intermediate between the control and cold-acclimated groups. The high-protein diet did not make any difference in cold tolerance and cold-induced changes in blood metabolites as compared with those in control standard diet, although it resulted in a marked increase in urinary nitrogen excretion.
These results indicate that a high-fat diet could exert a significant favorable effect on cold tolerance in fasted rats, but the effect would not be as much as in cold acclimated rats.View full abstractDownload PDF (1060K) -
Toshiko KURODA1976 Volume 26 Issue 2 Pages 189-202
Published: 1976
Released on J-STAGE: June 07, 2011
JOURNAL FREE ACCESSThe effects of D600 and verapamil on the membrane activity of the X-organ neuron of the crayfish were investigated.In TTX solution, D600 and verapamil reversibly reduced the amplitude and the maximum rate of rise of the Ca-dependent action potential as well as delayed rectification.The decrease and the recovery in amplitude of the Ca spike were usually accompanied by parallel changes in delayed rectification.The threshold concentration for observable effects on the Ca spike was from 5×10-6g/ml to 1×10-5g/ml for both drugs.At 1×10-4g/ml, the Ca spike was almost blocked.The dose-response relation with regard to the maximum rate of rise of the Ca spike showed no noticeable difference in effect between D600 and verapamil.By increasing the extracellular Ca concentration, the Ca spike, which had been reduced bythese drugs, was restored but the delayed rectification remained to be reduced.In Mn solution, both D600 and verapamil reduced the amplitude and the maximum rate of rise of the Na-dependent action potential as well as the delayed rectification.At 1×10-4g/ml, the maximum rate of rise of the Na spike was reduced by 30 to 50% with each drug. From the experiments in the Ca and the Mn solutions, it was inferred that the decrease in K activation by these drugs was not brought about secondarily by the decrease in Ca activation but both activation were inhibited independently. It was concluded that both D600 and verapamil are the inhibitors for Ca activation in the X-organ neuron of the crayfish, although they are not Ca specific.View full abstractDownload PDF (1508K) -
GENERAL OBSERVATIONS OF FIELD POTENTIAL ASSOCIATED WITH SDShigeo MORI, William H. MILLER, Tsuneo TOMITA1976 Volume 26 Issue 2 Pages 203-217
Published: 1976
Released on J-STAGE: June 07, 2011
JOURNAL FREE ACCESSUsing microelectrodes, the field potential change associated with SD (SDP) was recorded from frog retinas conditioned with Cl--free Ringer's. In such retinas, SDP was induced by light or chemical agents such as glutamate, aspartate and K+. These chemicals, when applied iontophoretically, produced a local graded response which eventually triggered SDP.A potential similar to the local response to chemicals was ften discerned on the rising phase of SDPs produced by light or occurring spontaneously. The SDP was maximal across an innermost retinal layer 50um;m or less in thickness with the intraretinal polarity predominantly negative, indicating that the major sink of SDP is in the inner plexiformlayer. The influence of SDP on the receptor potential was relatively small, but the other components completely disappeared at the beginning of SDP, recovering gradually thereafter. Concomitantly, a strongdepolarization occurred in the ganglion cells. Stimulation of the optic nerve could induce SDP, but nerve impulse activity is not important for SDP because tetrodotoxin was unable to prevent SDP due to light or chemical agents.View full abstractDownload PDF (1831K) -
MÜLLER CELL ACTIVITY AND [K+] DURING SDShigeo MORI, Tsuneo TOMITA, William H. MILLER1976 Volume 26 Issue 2 Pages 219-233
Published: 1976
Released on J-STAGE: June 07, 2011
JOURNAL FREE ACCESSBy means of K+ microelectrodes, K+ potentials and [K+] were studied in frog retinas conditioned for SD by Cr-free Ringer's, A marked increase in [K+]0 was observed during SD, the increase being maximal in the inner plexiform layer (up to 50mM or more) and subsiding towards the distal retina, The extracellular K+potential change during SD and also the graded K+potential change produced locally by iontophoretic injection of SD-stimulant chemicals resembled the membrane potential changes in Muller cells under the same conditions, suggesting that the Muller cells act as K+ electrodes, In retinas conditioned by C--free Ringer's Müller cells were swollen, This allowed intracellular recording with K+electrodes in Müuller cells to reveal that upon SD the Müller cells immediately start to cleanse the extracellular space of excess K+ which is probably a product of pathologically enhanced synaptic activity in the inner plexiform layer, The mechanism of SDP, the neld potential change associated with SD, is discussed from a proposed model.View full abstractDownload PDF (4491K)
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