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Biomedical subjects

E V Vovk

Publications and source records attributed to E V Vovk.

14 recordsLinked to original sources
PubMed2000

Spectroscopic study of low temperature interactions in Sm-mesogenic cyanophenyl co-condensates.

The IR- and UV-Vis spectroscopic study of samarium-mesogenic 4-pentyl-4'-cyanobiphenyl low temperatures co-condensates was made in temperature range 90-300 K. Two labile complexes with different metal/ligand ratio of 1:2 and 1:1 were found. They were characterized by methods of IR- and UV-spectroscopy. The solid state transformation of complex Sm(5CB)2 to Sm(5CB) was shown to take place at 170-210 K. The kinetics of the process revealed a wide distribution of complex reactivity and of reaction activation energy.

Biphenyl Compounds↗
PubMed1989

Studies of the inhibitory non-adrenergic neuromuscular transmission in the smooth muscle of the normal human intestine and from a case of Hirschsprung's disease.

A modified sucrose-gap method was used to study both non-adrenergic inhibitory neuromuscular transmission and effects of adenosine 5'-triphosphate (ATP) on isolated smooth muscle preparations from the human intestine. It was found that non-adrenergic inhibition in the circular smooth muscle layer was of larger amplitude than in the longitudinal layer. Study of the ionic mechanisms underlying non-adrenergic inhibition indicated that an increase in K+ conductance was responsible for the generation of non-adrenergic inhibitory junction potentials (IJPs). The results suggest that the inhibitory actions of the endogenous neurotransmitter and exogenous ATP are due to increases in Ca2+-dependent K+ conductance. The K+-channel blockers tetraethylammonium and 4-aminopyridine had no effect on IJPs or ATP, while apamin slightly decreased both the amplitude of the IJP and the hyperpolarization of the circular smooth muscle caused by ATP. These results are consistent with the purinergic hypothesis of non-adrenergic inhibition. In addition to inhibitory purinoceptors, the existence of excitatory purinoceptors was identified in the longitudinal muscle, activation of which probably caused an increase in Na+-conductance. The excitatory purinoceptor-mediated contraction in the longitudinal muscle from the constricted region of large intestine from patients with Hirschsprung's disease was greater than that found in control specimens. It is possible that excitatory purinoceptors play a role in the pathophysiology of Hirschsprung's disease.

Action Potentials↗
PubMed1983

[Mechanism of the formation of complexes between monomer fibrin and the inhibitor of its polymerization - fragment D].

It was found that fragment D derived from fibrinogen may be coupled with the fibrin monomer to produce complexes of unstable and stable types. The native fibrin monomer forms unstable complexes; the stable ones arise when the labile peripheral domains of the fibrin molecules are reversibly modified and their specific intermolecular affinity for the thrombin-activated central domains is lowered or eliminated. Fragment D, the free peripheral domain possessing polymerization centers, is strongly bound to the modified monomer occupying the polymerization sites of its central domain. The modification was induced by using acid pH (around 3.7) or by urea or NaBr taken at concentrations which caused no denaturation. In neutral media the acid-modified monomer passes to its normal state which is accompanied by simultaneous decrease of fragment D binding and restoration of codgulability. Fragment D presumably competes with the peripheral domain for the central one. Peripheral domains of the intact monomer are predominant competitors; fragment D only reduces the rate of polymerization due to temporary complex formation. However, modification results in a formation of stable complexes and thus decreases the accumulation of polymeric fibrin.

Animals↗
PubMedDate not supplied

[Effect of a passive orthostatic test on lymph circulation].

Anesthesized dogs were exposed to a 30 minute tilt test at 30 degrees. Most significant changes were seen in venous and lymphatic vessels. During the first minutes of the tilt test lymph flow from the thoracic compartment diminished rapidly and later it partially recovered. Pressure in the thoracic lymphatic duct diminished in parallel with that in the jugular vein. Lymph flow from the neck vessel at first increased and then decreased. After the animals were returned to the recumbent position, their venous and lymphatic pressure reached the pretest level. Lymph flow from the thoracic duct increased drastically and then returned to the baseline level. During moderate orthostatic effects lymph circulation undergoes significant changes produced by gravitational shifts and morphofunctional specificities of lymphatic vessels.

Acceleration↗
PubMedDate not supplied

[Soluble complexes of the NH2-terminal disulfide knot of fibrin with molecules containing D domains].

Soluble complexes of an NH2-terminal disulphide knot of fibrin (N-DSK alpha) with fragment D, its dimer (DD) and fibrinogen were detected by sepharose gel filtration. The main component of fragment D and N-DSK alpha mixture is represented by a specific complex eluted as a separate peak. Inactive fibrinogen N-DSK produce no complexes with fragment D. The DD-N-DSK complex is eluted together with free DD. Soluble oligomers which are partially eluted in the free column volume as well as insoluble aggregates of N-DSK alpha and fibrinogen are formed in mixture of these components. The molar D/N-DSK alpha ratio was determined in complexes isolated from mixtures with different D/N-DSK alpha ratio. A conclusion is drawn that a N-DSK alpha molecule may bind at most two fragment D molecules.

Animals↗