Sunano, S., Kato, S., Moriyama, K. and Shimamura, K. Effects of sodium vanadate on smooth muscles of guinea-pig ureter and their relation to extracellular Ca. Japanese Journal of Smooth Muscle Research, 23 (2), 55-66, 1987-The effects of sodium vanadate on electrical and mechanical activities of the guinea-pig ureter were studied. Sodium vanadate at concentrations higher than 10^-5 M induced elevations of basal tension and repetitive twitch-like contractions. The drug depolarized membrane only slightly but induced repetitive action potentials. Sodium vanadate potentiated phasic and tonic contractions of K-contracture. It also increased tension development of high amplitude in Kdepolarized preparations. Thus, the change in the resting membrane potential does not seem to play the only role in the initiation of contractions, though sodium vanadateinduced twitch-like contractions were associated by repetitive action potentials. Sodium vanadateinduced twitch-like contractions were blocked by Ca removal or by verapamil, but elevated basal tension was depressed only slightly under these treatments. Sodium vanadate induced tension development in the absence of Ca both in polarized and K-depolarized preparations. These results suggest that sodium vanadate increased mechanical activities by enhancing Ca influx as well as releasing intracellular bound Ca and/or inhibiting Ca extrusion through cell membrane.

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Sakamoto, Y. and Nasu, Y. Electrical and mechanical interaction between circular and longitudinal muscle layers of the guinea-pig stomach. Japanese Journal of Smooth Muscle Research, 23 (2), 67-73, 1978-The effects of prostaglandin E₁ and F_2α on the mechanical and electrical responses of circular strips dissected from various parts of the guinea-pig stomach were examined. Prostaglandin Ei induced the tonic contraction without an inhibition of the phasic contraction in lower parts of stomach. The amplitude of tonic contraction decayed along with greater curvature of the stomach, that is, it was largest in pylorus region and smallest in upper corpus. Furthermore, the tonic contraction increased depending on concentrations of prostaglandin E₁. When a longitudinal muscle layer was removed from the circular strips, the tonic contraction disappeared. On the other hand, prostaglandin E, or F_2α consistently induced an increase in the resting tone and the phasic contraction in longitudinal strips of all parts of stomach. Simultaneous recordings of the electrical and mechanical activities showed a correlation between membrane depolarization and tonic contraction induced by prostaglandin E₁. Above results were not affected by nerve-blocking agent, atropine or tetrodotoxin. Thus it is suggested that the tonic contraction in circular strips induced by prostaglandin E, is closely related to the longitudinal tonic contractions.

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Using adult mongrel dogs, pyloric mortor activity and gastric emtying observed by phototransducer (P. T.) under anesthesia and by strain gage transducer (S. G. T.) under conciousness. Pyloric motor activity and function were investigated in the dogs with distorted pylorus after instorations of Daclon tube, pyloric resection and pyloric stenosis.
The pyloric sphincter responses to gastrin, pancreozymin, secretin, gulcagon, atropine, morphine, naloxone and enkephalin administrated intravenously were obserbed.
Gastroduodenal motor activity in relation to the changes of gastrointestinal hormon levels were measured before and after truncal vagotomy (TV) and selective proximal vagotomy (SPV) with or without pyloroplasty. Results are summarized as follows;
1. The pyloric motility recorded by P. T. was well correlated with the contractile activity recorded by S. G. T. under the anesthesia, although the pylorus was never completely closed and showed tonic movements.
2. The pyloric motor activity under the consciousness was different from gastric and duodenal motor activity.
3. After SPV, the gastrin responses to the test meals were significantly increased so that the pyloric motility was disturbed. The fact mentioned above, the pyloric functional disorder after the SPV was partly due to the hypergastrinemia. Pyloroplasty for the SPV inhibited the serum gastrin level. It was suggested that the pyloroplasty for the SPV was necessary to prevent possible hypergastrinemia after SPV.

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Uruno, T., Watanabe, A., Takahashi, K., Sunagane, N., Matsuoka, Y. and Kubota, K. Determination of Ca²⁺ -release from the isolated smooth muscle cells in suspension from the guinea-pig ileum. Japanese Journal Smooth Muscle Research, 23 (2), 103-114, 1987-Collagenase-dispersed cells from the guinea-pig ileum were prepared and Ca²⁺ release into Ca²⁺-depleted solution from the isolated single cells obtained by the centrifugation of the dispersed cells on isotonic sucrose solution was determined with a Ca²⁺-selective electrode. A technique employing an isotonic sucrose solution for washing isolated cells permitted removal of contaminating extracellular fluids and obtaining the isolated cells with minimum loss of cellular Ca²⁺. The release of Ca²⁺ from the dispersed cells consisted of at least two phases. The Ca²⁺ release into an isotonic sucrose-Tris solution (ISTS) was significantly reduced and the early phase of the Ca²⁺ release disappeared. At 16°C, Ca²⁺ release depended on the composition of the bathing solution in a Ca²⁺-free salt solution, the later phase of Ca²⁺-release was abolished whereas in ISTS both phases disappeared. Furthermore, Ca²⁺ release was significantly reduced after the treatment of the dispersed cells with dispase (1, 500 units/ml) for 10 min. These results show that Ca²⁺ release into Ca²⁺-depleted solution from the isolated ileal cells with minimum loss of cellular Ca²⁺ show a biphasic curve and suggest that Ca²⁺ sources responsible for these phases may be of distinct origin.

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The origin of anti-peristaltic discharge occured in the distal stomach of canine after transection followed by end-to-end anastomosis is uncertain. The purpose of this paper is investigate electromyographycally whether the mucosa of the distal stomach effects on occurence of anti-peristaltic discharge.
By appling lidocaine to the lumen of the distal stomach after transection followed by end-to-end anastomosis, the retardation of propagation velocity of normo-peristaltic discharge and the decrease of frequency of anti-peristaltic discharge were noted on the antrum.
On respect of frequency of anti-peristaltic discharge, the findings above were remarkable in the high appearant group (5 dogs; ≥80%) compared with low appearant group (2 dogs; ≤60%).
Conclusively, it was suggested that the occurrence of anti-peristaltic discharge was related to the enteric nervous system in the mucosa and/or submucosa.

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