Biomedical subjects

K Boev

Publications and source records attributed to K Boev.

35 records · Page 2Linked to original sources

PubMed1978

Role of intracellular calcium in the phasic and tonic contractions of stomach smooth muscles.

The double sucrose gap is used to study the role of Ca-ions in the electromechanical coupling in the phasic and tonic contractions in the different parts of cat stomach. Extracellular Ca2+ is of primary importance in the activation of the tonic contractions. The regulation of the muscle tone under the action of external stimuli is achieved through gradual changes in the Ca-permeability of the cell membrane. Of primary significance for the activation of the phasic contractions is Ca which is released from the intracellular stores. The Ca2+-influx during the action potential results in additional modelation of the intensity of phasic contractions as well as to a re-charging of the intracellular Ca-depots. It is assumed that the differences in the mechanisms of activation of phasic and tonic contractions result not only from the specificities of membrane control but also from definite differences in the organization of the intracellular systems responsible for these contractions.

Acetylcholine↗

PubMed1976

Disturbances in the electrical and contractile gastric activities after bilateral transthoracic vagotomy.

Experiments were made on four dogs with chronically implanted electrodes. Fistula according to Bassov was made in one of the animals, and in each of the remaining three - two semiconductor silicon tensotransducers were sewn to the gastric wall. Bilateral transthoracic vagotomy results in inco-ordination between the rhythm of slow potentials generation from the body and from the antrum of the stomach. Slow potentials and contractions with frequencies usual for the stomach are recorded from the body of the stomach, while in the antrum there appear from time to time bursts of slow potential groups with relatively high frequency. These groups are not followed by contractions of the stomach wall or by changes in the intragastric pressure. Bilateral transthoracic vagotomy leads to disturbances in the conduction of the slow potential generated in the proximal segments of the stomach, as well as to distrubances in the propagation of the peristaltic wave.

Action Potentials↗

PubMed1976

Coordination between the longitudinal and circular layers of the stomach during the excitator-contractile process.

The coordination between the longitudinal and circular layers of the stomach muscle is studied using strips of cat stomach cut along the longitudinal and circular axis of the stomach, preserving the connection between them. The longitudinal muscle layer plays a leading role both with respect to the bioelectrical and to the contractile activity of the stomach. Under the effect of acetylcholine (10-7) the delay time of the circular muscle layer is shortened compared with the longitudinal layer (from 2.44+/-0.17 to 0.8+/-0.7 s). Under the effect of Ba ions not only shortening of this time is observed, but also inversion of the process-the circular layer becomes leading with respect to the contractile process in some moments.

Animals↗

PubMed1976

Participation of bivalent ions in the acetylcholine-provoked gastric smooth-muscle phasis contractions.

Experiments were carried out on muscle strips from cat antrum. Acetylcholine added to Ca++ -free medium containing EDTA (10-5M) exerted no effect on the phasic contractions of the gastric smooth muscle. Ba++at low concentrations (0,1 to 0,5mM) replaced Ca++with respect to the acetylcholine effect. On the background of blocked cholinergic (atropine 10-5M) and adrenergic (phentolamine 10-5 M and propranolol 10-5M) structures Ba++ provoked slow potentials and cotractions with a frequency of 9 to 10 cpm. delta600 (10-5M) blocked the Ba++-induced myogenic electrical and contractile activities of the smooth muscle. The role of the cholinergic structures for synchronizing the electrical and contractile activities of the smooth muscle is considered.

Acetylcholine↗

PubMed1975