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Biomedical subjects

M Papasova

Publications and source records attributed to M Papasova.

At least 55 records · Page 3Linked to original sources
PubMed1982

On the character of the electrical activity of the stomach, pyloric sphincter and duodenum of cats.

In cats with chronically implanted electrodes in the muscle wall of the gastro-intestinal tract, the electrical activity of the stomach (S) pyloric sphincter (PS) and duodenum (D) is characterized by cycles consisting of two phases: active--whereby 2 to 3 slow potential changes (SPC) are accompanied by spike potentials (SP) and a pause during which for 60-90 s only SPC are recorded. After bilateral transthoracic vagotomy there is a disruption of the cyclic character of the electrical activity in the investigated regions of the gastro-intestinal tract--SP from S and PS are recorded with each SPC. The active phase of the cycle from D is strongly prolonged at the expense of the shorter pause. This lasts for 1-2 days, after which there is a tendency towards shaping the cycles characteristic of the electrical activity of S, PS and D of cats. The pauses, however remain relatively short and the number of SP in the group is much greater. Gradually during the second month the character of the electrical activity of S, PS, and D approaches that prior to the vagotomy, but even until the 6th month after vagotomy the number of SP in the group is greater and the active phase of the cycle is longer. On the background of antagonists of the adrenoreceptors (propranolol--2 mg/kg and dihydroergotamine--300 micrograms/kg), the cyclic character of the electrical activity of S, PS and D is disturbed. The relatively rapid restoration of the cyclic character of cat S, PS and D after vagotomy is assumed to be the result of the organizing role of the intrinsic nervous system. The disturbance of the cyclic character after adrenoblockers demonstrates the significance of the balance between the cholinergic and adrenergic parts of the intrinsic nervous system for the realization of the cyclic character of the electrical activity of S, PS and D of cats.

Animals↗
PubMed1981

Effects of PGE1 and PGF2 alpha on the responses of gastrointestinal sphincters to field stimulation.

The study concerned the effects of PGE1 and PGF2 alpha on the spontaneous tone and the responses to field stimulation of isolated strips from: lower esophageal sphincter (LES), pyloric sphincter (PS) and ileocaecal sphincter (ICS) of cats. PGE1 and PGF2 alpha (0.3 microM) increased the LES tone and abolished the PS contractions. PGF2 alpha increased the tone of ICS while PGE1 had no effect at all. The effects of the prostaglandins (PG) were reduced when the preparations were pretreated with atropine, propranolol and phenoxybenzamine (1 microM). PGE1 and PGF2 alpha decreased the LES relaxation in response to field stimulation (0.5 msec, 2 Hz for 10 sec at supramaximal current). No responses of PS to field stimulation were observed after PG treatment. PGF2 alpha increased the amplitude of the relaxation response in the ICS to field stimulation. PGE1 did not change the effect of field stimulation in ICS. The effects of PGE1 and PGF2 alpha on the LES and ICS responses to field stimulation were not influenced by adrenergic and cholinergic blocking agents. The data suggest a PG effect on non-adrenergic, non-cholinergic (purinergic) transmission in the gastrointestinal sphincter smooth muscle on field stimulation. Due to the high concentration of PG used this effect was probably a pharmacological one.

Alprostadil↗
PubMed1981

Comparative quantitative estimation of the granular vesicles in the intramural ganglia of Auerbach's plexus in the nonsphincter and sphincter parts of cat alimentary tract.

The spatial size and density of the granular vesicles (GV) in the axonal varicosities of the intramural ganglia in parts of the alimentary tract adjacent to the lower esophageal, pyloric and ileo-caecal sphincters are determined. The results obtained are compared with the data about the density and size of GV in these sphincters, described earlier (Lolova et al., 1980). The results concerning GV size show: (1) absence of very small differences in GV diameters from the 1st and 2nd populations (average diameter around 40, respectively 55 nm) between the sphincter and nonsphincter parts; (2) absence of 3rd population GV (average diameter 77 and 90 nm) in the nonsphincter parts of the fundus close to the terminal ileum; (3) GV from 4th and 5th populations (average diameter around 125 nm, 150 nm respectively) are larger in the nonsphincter parts than in the sphincters. The following observations are made with respect to GV density: (1) the smallest GV have the greatest density in all parts studied; (2) the GV density from the different populations differs in the nonsphincter and sphincter parts; (3) certain characteristic features become prominent upon comparing GV density in the parts of the gastro-intestinal tract from cranial to distal direction. The results obtained are discussed with a view to the functional characteristics of the nonsphincter and sphincter parts and with the participation of various transmitters in them.

Animals↗
PubMed1981

Analysis of the innervation of the gastroduodenal region.

Under isometric conditions simultaneous recordings are made of the contractile activity of smooth-muscle strips isolated along the circular axis from the pyloric sphincter (PS) and at 1 cm proximally an distally from it -- from the antrum (A) and duodenum (D). The effect of transmural electrical stimulation is studied after the method of Burn and Rand (1960) (duration of the impulses 0.5 ms, frequency from 2 to 20 Hz and supramaximal current values for 20 s). The responses of the smooth-muscle strips isolated from A and D to transmural electrical stimulation are similar. Switching on of the stimulation causes contraction (on-response) throughout the entire stimulation period, while its switching off leads to additional last contraction (off-response). A dependence is observed between the amplitudes of the on- and off-responses and the frequency of the impulses, the maximum being reached in the high-frequency range (16-20 Hz). After Atropinum sulfuricum (5 x 10(-6)M) the on-response is considerably reached, no off-response being observed. In PS triggering of the stimulation results in inhibition of the phasic activity, accompanied by marked relaxation (on-response). The amplitude and the duration of the relaxation depend on the frequency of the impulses applied, the amplitude being maximal at 4-6 Hz, while its duration reaches the maximum between 16 and 18 Hz. Atropinum sulfuricum (5 x 10(-6)M) does not change essentially the amplitude of the relaxation. After Atropinum sulfuricum, Phentolamine and Propranolol (10(-5)M) the amplitude of the relaxation increases significantly in the low-frequency region (4-8 Hz), while its duration decreases considerably.

Animals↗
PubMed1980

Specific features in the electrical and contractile activities of the gastro-intestinal sphincters.

Muscle strips (2/20 mm) are isolated from cat gastro-intestinal sphincters (GIS): lower esophageal sphincter (LES), pyloric sphincter (PS), ileo-caecal sphincter (ICS) and from the fundus. The activity of the four fibres is recorded simultaneously under isometric conditions in a bath. In another series of experiments the electrical and contractile activity of GIS was traced by the sucrose gap method. LES manifests only tonic changes which are associated only with changes in the membrane potential (MP); PS - rhythmic spike-dependent phasic contractions, ICS - in one part of the preparations both tonic and phasic contractions. The tonic changes in LES and ICS are sensitive both to nitroprusside-Na (10-6M) and to Verapamil (10-6 to 5X10-6 M). GIS sensitivity to external Ca2+ is different: maximum contractions in LES and ICS occur at Ca=2.5 mM, in PS at Ca=1.5mM. Ba2+ and Sr2+ (at CA=0) increase the sensitivity of LES and ICS to polarizing currents. After several stimulations there appear spontaneous spike-dependent phasic contractions in LES. TEA (5 mM) induces spike-dependent phasic contractions in LES and ICS. In PS the stimulating effect of TEA is manifested at very low concentrations (0.05-0.4 mM), while higher concentrations inhibit the electrical and contractile activity.

Action Potentials↗
PubMed1980

Structure of the myenteric plexus in the sphincters of cat gastro-intestinal tract. V. Ultrastructure of the nerve cell bodies and dendrites.

A description is given of the nerve cell bodies and dendrites in the myenteric ganglia in the lower esophageal, pyloric and ileo-caecal sphincters of cats. The perikarya within one ganglion are differentiated depending on the position and predominance of one type of intracellular organelles or another. The question is raised whether these differences are a manifestation of the functional state, age characteristics or functional differentiation. The neurones in the myenteric plexus of the sphincters are characterized by the variety of dendrite branches, differing in shape and size.

Animals↗
PubMed1980

Responses for smooth-muscle strips from the ileo-caecal region to transmural electrical stimulation.

Under isometric conditions simultaneous recordings are made of the contractile activity of smooth-muscle strips (2/20 mm) isolated from the terminal ileum (T1), the ileo-caecal sphincter (ICS) and the caecum (C) of cats. Transmural electrical stimulation is applied (0.1-0.5 ms. 2-15 Hz at supramaximal current) for 20-60 s. ICS manifests tonic changes (1st type of activity) and sometimes phasic contractions (second type of activity); phasic contractions are recorded in T1 and C. Switching on of the stimulation causes relaxation (on-response) of ICS, with maximum values in the 5-9 Hz interval. Two types of off-response are observed when the stimulation is switched off: in the strips of the first type of off-response is characterized by tonic contraction only, while in the strips of the second type there is high-amplitude contraction followed by a rise in the tone on which phasic contractions are superimposed. Inhibition of the phasic contraction and a slight decrease of the tone characterize the on-response resembles that of the ICS strips of the second type. In the C strips there is an evoked high-amplitude phasic contraction when the stimulation is switched on. The responses of ICS, T1 and C to transmural electrical stimulation are nerve-transmitted, because they are blocked by TTX (10-6 g/l). On the basis of the analysis with atropine (10-6 M), phentolamine (10-5M) and propranolol (10-5M) it is assumed that nonadrenergic inhibitory mechanisms are involved in the on-response of ICS to transmural electrical stimulation, while predominantly cholinergic and adrenergic mechanisms of regulation are manifested in the off-response of ICS and in the responses of T1 and C.

Animals↗
PubMed1980

Structure of the myenteric plexus in the sphincters of cat gastro-intestinal tract. VI. Axonal profiles, axonal varicosities, synapses and other membrane differentiations.

Axonal varicosities of adrenergic, cholinergic and p-ergic types are observed in the myenteric plexus of cat lower esophageal, pyloric and ileo-caecal sphincters. In addition to them, there are varicosities, which cannot be attributed to the above types. The synaptic contacts in the myenteric ganglia manifest a great variety. The three main types of axonal varicosities appear as presynaptic part. Axodendritic synapses predominate. Very frequent findings are the symmetric membrane differentiations between the perikarya, dendrites and axonal profiles, as well as membrane junctions between the nerve and glial cells.

Animals↗
PubMed1980

Structure of the myenteric plexus in the sphincters of cat gastro-intestinal tract. I. Quantitative assessment of the types of dense-core vesicles.

Ultrastructural studies show that dense-core vesicles are among the most frequently occurring types of vesicles in the axonal varicosities of the myenteric plexus of the gastro-intestinal tract, and interest in them is due to their significance for the formation, storage and release of the transmitters. However, measurements so far have been made on the basis of the images of the dense-core vesicles on the electronograms, whereby the size and the type of the vesicles greatly depend on their position with respect to the surface of the sections observed. The methods applied by us made it possible to determine the spatial dimensions and the density of the dense-core vesicles in the myenteric plexus of the sphincters of cat gastrointestinal tract. Using the method of reconstruction in arranging the diameters in geometrical order, five populations of dense-core vesicles with corresponding mean diameter and small mean square deviation are differentiated.

Animals↗
PubMed1980

Structure of the myenteric plexus in the sphincters of cat gastro-intestinal tract.. II. Changes in the quantitative characteristics of the types of dense-core vesicles after reserpine treatment.

In order to elucidate the functional significance of the populations of dense-core vesicles in the myenteric plexus of the sphincters of cat gastro-intestinal tract, studies are made of the changes in their spatial density after reserpine treatment, since the action of reserpine on a definte transmitter-noradrenaline-is known. The different character and intensity of the changes in the density of the different populations of dense-core vesicles probably indicates participation in the metabolism of different transmitter systems. The lack of statistically significant changes in the number of large dense-core vesicles correlates well with the character of the relaxation upon electrical stimulation of the sphincters and suggests participation of these vesicles in the nonadrenergic noncholinergic innervation.

Animals↗
PubMed1980

Structure of the myenteric plexus in the sphincters of cat gastro-intestinal tract. III. Character and distribution of the dense-core vesicles in the axonal varicosities.

Attempts at differentiating the axonal varicosities and the vesicular population in them in the myenteric plexus of the gastro-intestinal tract, result from the participation of these structures in the metabolism of various transmitters. The present work studies the spatial distribution of the populations of dense-core vesicles in the different axonal varicosities in the myenteric plexus of the sphincters of cat gastro-intestinal tract. It is found that the axonal varicosities are characterized by a definite number of populations of dense-core vesicles and by their respective densities. Moreover, each group of varicosities has features common for the sphincters studied and at the same time characteristics observed in only one sphincter. The changes in the densities of the different populations of dense-core vesicles in the groups of axonal varicostities after reserpine treatment suggest their connection with different transmitter systems.

Animals↗
PubMed1980

On the changes in the membrane potential and the contractile activity of the smooth muscle of the lower esophageal and ileo-caecal sphincters upon increased K in the nutrient solution.

The influence of increased K+ in the nutrient solution on the excitatory-contractile process in smooth-muscle strips from the lower esophageal sphincter (LES) and the ileo-caecal sphincter (ICS) of cats is studied. The changes in the membrane potential (MP) and the tension (T) are recorded by the sucrose gap method. The rise of the K+ concentration in the nutrient solution to 30 mM causes hyperpolarization and relaxation of LES, while in ICS depolarization is observed irrespective of the relaxation. In LES the higher K+ concentrations, as well as the isotonic K+ lead to initial brief hyperpolarization, followed by depolarization. A biphasic response in the contraction-relaxation and subsequent contraction corresponds to them. Irrespective of the fact that the response in ICS is also biphasic with respect to the contraction, the changes in MP are manifested only as depolarization. These responses of LES and ICS are not influenced by cholinergic and adrenergic blockers (atropinum sulfuricum, Propranolol, Phenoxybenzamine--(10(-6) to 10(-5) g/ml). In ouabaine-pretreated (10(-6) to 5 x 10(-6) M) smooth muscle from LES and ICS, in all K+ concentrations the response is depolarization and contraction. The effects of increased K+ in the nutrient solution on LES and ICS are connected with the ratio [K]i : [K]o ([K]i--intracellular, [K]o--extracellular). It is assumed that the Na-K pump in LES and ICS functions at a different level compared with the other smooth muscles of the gastro-intestinal tract.

Animals↗
PubMed1980

Structure of the myenteric plexus in the sphincters of cat gastro-intestinal tract. IV. Light-microscopic characteristics.

The structure of the myenteric plexus in the lower esophageal, pyloric and ileo-caecal sphincters of cats is studied in semi-thin sections through impregnation and demonstration of cholinesterase. The plexus ganglia are shown to be well formed structures, with varied sizes and shapes, in the collagen between the muscle layers of the sphincters. Impregnation reveals clearly in them Dogiel's neurones of 1st and 2nd type. The neurones and the nerve bundles of the plexus manifest intensive cholinesterase activity. The morphological data obtained are discussed in view of some functional specificities of the sphincter regions.

Animals↗
PubMed1979

Character of the gastric and duodenal electrical activity after blocking of the adrenoreactive structures.

Experiments are carried out on six dogs with chronically implanted electrodes in the gastric wall and in the duodenum. The electrical activity of the stomach (EGMG) and of the duodenum (EEG) is recorded. The myoelectrical complex of the stomach consists of four phases. The first phase records only slow potentials and lasts 40--60 min. The appearance of spike activity in the duodenum is always preceded by EGMG activation. Intravenous injection of the specific blocker of the alpha-adrenergic structures (phentolamine -- 1 mg/kg) leads to the appearance of spike activity in EGMG and EEG. 50--60 per cent of the slow waves being accompanied by spike potentials. At the same time the frequency of the slow potentials from EGMG is also decreased. Application of beta-adrenoblocker (propranolol -- 2 mg/kg) does not change subatantially EGMG and EEG. Simultaneous administration of alpha- and beta-adrenoblockers prolongs spiking time in the stomach and duodenum (spike potentials are recorded for 120--180 min, duration in the background 40--50 min). The influence of the interactions of cholinergic and adrenergic structures on the character of EGMG and EEG is discussed.

Animals↗
PubMed1979

Inhibitory action of acetylcholine on the smooth muscle from the lower esophageal sphincter.

The effect of acetylcholine (Ach) on smooth-muscle strips isolated along the transversal axis of cat lower esophageal sphincter (LES) is studied. Ach in low concentrations (10(-11)--10(-9) g/ml) causes contraction of the muscle strips. Increase of the concentration to 10(-8) g/ml leads to biphasic effect: contraction with relaxation. Inhibitory response predominates at Ach 10(-6) and 10(-5) g/ml. Atropine (10(-6) M) eliminates the excitatory phase but it has no effect on the second relaxation phase. Propranolol (10(-6), 2 X 10(-6) M) as well as phentolamine turn the inhibitory response to Ach into contraction. Noradrenaline leads to LES contraction while isoprenaline induces relaxation. In smooth-muscle LES strips from cats pretreated with reserpine (1 mg/kg for 3 days), Ach in the concentrations used (10(-5), 10(-6) g/ml) leads to contraction. The changes observed are membrane-dependent -- the contraction is accompanied by depolarization, relaxation by hyperpolarization. The inhibitory effect of Ach on LES smooth muscle is discussed in the light of the hypothesis of Burn and Rand (1960) about the release of noradrenaline under the effect of Ach.

Acetylcholine↗