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Biomedical subjects

I Aizawa

Publications and source records attributed to I Aizawa.

At least 37 records · Page 2Linked to original sources
PubMed1977

Diurnal changes in gastric motor activity in conscious dogs.

Twenty-four-hour changes in gastric motor activity were recorded in 4 healthy adult dogs in the conscious state by means of extraluminal force transducers. Three major different gastric motor activity patterns were recognized during 24 hr: digestive, intermediate, and interdigestive. The digestive pattern was characterized by steady low-amplitude contractions in the gastric antrum, with no significant motor activity in the gastric body. The interdigestive pattern consisted of series of high-amplitude contractions of 14-23 min duration in both the gastric body and antrum with intervening and long-lasting (68-109 min) motor quiescence. The intermediate pattern is considered to be the pattern midway when the digestive pattern is changing to the interdigestive pattern. These changes in gastric motor activity are precisely controlled day after day if the animals are fed at regular time intervals and are healthy. The digestive pattern may represent principally a mixing function of ingested food and the interdigestive pattern a cleaning function in preparation for the next meal

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PubMed1977

Effect of synthetic motilin on gastric motor activity in conscious dogs.

The effect of intravenous infusion of synthetic motilin on gastric motor activity was investigated by means of chronically implanted force transducers in 4 conscious dogs. Since the gastric motor pattern consisted of two major subpatterns, digestive and interdigestive motor activity, motilin was tested for its motor stimulating activity in both states. It was found that motilin had no influence upon gastric motor activity in the digestive state. However, during the interdigestive state, intravenous infusion of motilin in doses of 0.3-2.7 microgram/kg/hr induced motor activity similar to the naturally occurring interdigestive contractions in a dose-related fashion. Since motilin is released by duodenal alkalinization in the dog, it may be postulated that motilin is a substance to control the interdigestive contractions in the dog, although other reports describe motilin release by duodenal acidification and inhibition of gastric emptying in man. Endogenous stimuli leading to motilin release may be different among species. The present study clearly indicates that motilin induces a contractile pattern similar to that seen during the interdigestive state in conscious dogs.

Animals↗
PubMed1977

An extraluminal force transducer for recording contractile activity of the gastrointestinal smooth muscle in the conscious dogs: its construction and implantation.

An extraluminal strain-gauge force transducer has been developed for recording contractile activity of the gastrointestinal smooth muscle. The details of its construction and implantation were described. The transducer unit allows for continuous long-term recordings (more the 5 months) from conscious experimental animals. It could be constructed in any laboratory and easily implanted in animals if it is done in aseptic technique. Since it is sutured onto the outside of the gut, it does not interfere passage of the contents. The only disadvantages are that it only measures muscle contractions and it is hard to determine movements of intraluminal contents especially in the digestive state.

Animals↗
PubMed1977

Inhibitory effect of pentagastrin and feeding natural and motilin-induced interdigestive contractions in the stomach of conscious dogs.

The interaction between motilin, pentagastrin and feeding was investigated during the interdigestive gastric motor state in 4 healthy conscious dogs. We confirmed previous reports that an i.v. infusion of synthetic motilin always induced a pattern precisely like that of the naturally-occurring interdigestive contractions of the stomach. Pentagastrin inhibited the occurrence of the interdigestive contractions at dose between 0.2-1.6 microgram/kg-hr; this inhibition had a dose-related relationship to the occurrence of the motilin-induced contractions. The ingestion of food strongly inhibited the occurrence of not only the natually-occurring contractions but also the motilin-induced contractions in the stomach and changed the motor pattern to the digestive one. These findings strongly support our hypothesis that the interdigestive contractions in the dog are, at least in part, under the control of motilin. Furthermore, it should be emphasized that pentagastrin not always stimulates gastric motor activity but conversely, in the interdigestive state it inhibits movements characteristic of that condition and replaces them with the digestive pattern.

Animals↗
PubMed1977

[The motility of the lower esophageal sphincter (author's transl)].

Changes in lower esophageal sphincter (LES) motility have been mainly studied by intraluminal manometry. However, it is not suitable for continuous measurement of LES pressure. With extraluminal force transducers developed and constracted in our laboratory, we measured changes in contractile activity of the LES. Three anesthetized mongrel dogs were used for preliminary experiment. A transducer was sutured on the serosal surface of the LES immediately inferior to the phrenoesophageal membrane. A catheter with a side hole was simultaneously passed into the stomach through a mouth so that the side hole was anchored at the highest pressure zone of the gastroesophageal junction. It was found that dose-related changes in motor activity of the LES to pentagastrin were obtained by both methods. This result indicate changes obtained by transducers represent those in intraluminal pressure measured manometory. Transducers were chronically implanted on the LES and the gastric body and antrum to record changes in contractile activity in conscious state. It was found that a group of contractions lasting for 25 +/- 2.5 min occurred at regular intervals of quiescence until next meal. Furthermore, these motor increase precisely coincided with the interdigestive contractions of the stomach.

Animals↗
PubMed1977

[24 hour recording of gastric movements in the conscious dog (author's transl)].

Gastric movements were monitored in five conscious dogs weighing 9 to 13 kg by extraluminal force transducers (EFTs) which were independently developed and constructed in our own laboratory. After chronically implanting EFTs both in the canine gastric body and antrum we succeeded in making continuous recordings of their movements over several days. Dogs fed once a day with regular meals showed a circadian rhythm which was divided into three phases; digestive, intermediate, and an interdigestive phase. The digestive phase, which continued for about 8 to 10 hours after feeding, was characterized by a lack of movement in the body and repetitive rhythmical contractions having a rather small amplitude in the antrum. The interdigestive phase was distinguished from other phases by a peculiar sequence of gastric movements (interdigestive contractions) which did not make their appearance until 16 hours after feeding. These interdigestive contractions were the highest amplitude contractions to occur in both the body and antrum during the day. They continued for 70 minutes and repetitively recurred after intervening quiet periods of about 22 minutes. The intermediate phase was the period interposed between the digestive and interdigestive phase.

Animals↗
PubMed1976

Motilin-induced mechanical activity in the canine alimentary tract.

Gastrointestinal contractile activity from the lower esophageal sphincter to the terminal ileum in the conscious dogs was continuously recorded on a multi-channel polygraph for several weeks by means of chronically implanted strain gage force transducers. It was found that the 24-hour gastrointestinal motor activity consisted of the two different major patterns; the digestive and interdigestive patterns. The interdigestive motor activity was characterized by a cyclic recurring, caudad-moving band of strong contractions interrupted by long lasting motor quiescence. When one band of strong contractions reached the distal ileum, another developed in the LES, stomach and duodenum again and propagated in a caudad-direction. Such recycling episodes repeatedly occurred until the next meal. After ingestion of food, gastrointestinal motor activity was continous and such characteristic interdigestive patterns were not observed. Synthetic motilin, 0.1-2.7 mug/kg/hr, was assayed for its motor stimulating activity in the both states. In the digestive state, an i.v. infusion of motlin had no influence upon the motor activity even if the dose was increased up to 6.0 mug/kg/hr. On the other hand, when motilin was infused during the interdigestive state, it induced a pattern precisely like the naturally-occurring interdigestive contractions. Not only the naturally-occurring contractions but also motilin-induced contractions were strongly inhibited by the ingestion of food or an i.v. infusion of pentagastrin (0.2-1.8 mug/kg/hr). Duodenal acidification (0.1 N HC1, 3-16 ml/kg/hr) in the interdigestive state disturbed or inhibited the regular cycle of the natural contractions but was counteracted by exogenous i.v. infusion of motilin. These findings strongly suggest the view that the interdigestive gastrointestinal motor activity is at least in part regulated by circulating motilin concentration in the blood, however, its cyclic recurring, caudad propagating mechanism may be controlled in part by the nervous system. Motilin is the only substance known to be active during the interdigestive state and therefore may be called the interdigestive hormone.

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