Biomedical subjects

S Todorov

Publications and source records attributed to S Todorov.

At least 73 records · Page 4Linked to original sources

PubMed1978

Induction capacity and influence of dThdMP on thymidine kinase activity of type 1 and 2 strains of herpes simplex virus.

The thymidine kinase inducing ability of 104 strains of herpes simplex virus was studied comparatively. A pronounced relationship was established between induction of the enzyme and the serotype of the strains. As a rule, the strains of serotype 2 are weaker inducer of dThd- and dCyd-kinase activity than serotype 1 strains. A certain parallelism exists between induction of both enzymes, however the activity of the thymidine kinase increases after infection with herpes simplex virus 4--5 times more than that of the dCyd-kinase. Adaptation of the strains to cell cultures only slightly modifies the inducing ability of the herpes simplex virus strains. The thymidine kinase activity induced by HSV-1 and HSV-2 differ from each other and are different from the cell enzyme with respect to their thermal stability at 40 degrees C. These differences are expressed more clearly in the presence of 480 muM dThdMP during inactivation. dThdMP stabilizes the type 1 but not the type 2 enzyme.

Culture Techniques↗

PubMed1978

The character of the antagonism by polyphloretin phosphate of contractions to prostaglandins E1 and F 2alpha in guinea-pig ileum.

Polyphloretin phosphate (PPP) produced a dose-dependent decrease in the tone and reduction of the spontaneous phasic contactions of the longitudinal muscle of guinea-pig isolated ileum. PPP (100 microgram ml-1) after a 2 min contact with the ileum decreased the contractile effects of PGE1 0.1 micron by 40.6 +/- 7.4%, of PGE1 0.01 micron by 86.7 +/- 3.3% and of PGE2alpha 0.1 micron by 62.2 +/- 8.6%. After 10 min contact of PPP the contractile effect of PGE1 0.1 micron was decreased by 47.7 +/- 4.7% and that of PGE2alpha 0.1 micron by 89.6 +/- 1.7%. When the contact was longer, PPP showed a pronounced after-effect in respect to the effects of PGE1 and particularly of PGF2alpha. PPP signicantly reduced contractions to 5-HT and BaCL2, but not to acetylcholine, histamine or substance P. The type of antagonism of PGE1 by PPP was examined using cumulative concentration-effect curves for PGE1 in the presence of increasing concentrations of PPP. We conclude that on guinea-pig ileum PPP acts as a non-competitive antagonist of PGE1 and PGF2alpha.

Acetylcholine↗

PubMed1978

On the interactions of Yersinia strains and cell cultures.

Comparative investigations were carried out on the dynamics of invasion of cell cultures by strains Yersinia pestis EV and Yersinia pseudotuberculosis treated vitally with petroleum ether. It was established that the invasiveness of the strains studied was related to the presence of chemical structures of the bacterial surface sensitive to the action of either and whose synthesis was temperature dependent. The penetration and initial stages of intracellular multiplication of the Yersinia were accompanied with a certain activation of the RNA- and protein-syntheses in the host cells. That was clearly expressed in cell populations inoculated with Yersinia variants of high invasiveness. After the 24th hour of inoculation of the cell cultures a decrease of the rate of metabolic processes in invaded cells was observed due to the destructive changes in their cytoplasm. At the end of the investigation it reached values considerably lower than those of the controls.

Animals↗

PubMed1978

Comparative studies of colon reactivity of healthy and ionization-radiated guinea-pigs to some spasmogens and their antagonists.

Comparative studies were carried out of the contractile effects of acetylcholine (1 X 10(-6) M), histamine (1 X 10(-6) M), serotonin (1 X 10(-5) M), nicotine (1 X 10(-5) M), BaCl2 (1 X 10(-3) M) and of the influence on the induced contractions caused by the antagonists of these spasmogens, namely: atropin (1 X 10(-6) M), dipenhydramine (1 X 10(-6) M), benzyloxygramine (1 X 10(-5) M), hexamethonium (1 X 10(-5) M) and papaverine (1 x 10(-5) M) on isolated segment of guinea-pig colon. Experimental acute radiation sickness is found to induce considerable changes in the reactivity of the intestinal smooth-muscle preparation used to the spasmogens applied and to their antagonists. Depending on the nature of the pharmacological agents, the degree of development of the experimental acute radiation sickness, and on other factors, the changes in the reactivity to the drugs tested revealed very great qualitative and quantitative differences. The following more definite changes could be pointed out. The spastic effects of serotonin and BaCl2 were potentiated, while the spastic effects of histamine and nicotine showed a tendency toward decrease. Under conditions of acute radiation sickness tha antagonistic effect of atropine to acetylcholine was intensified, while the antagonistic effects of benzyloxygramine to serotonin, of hexamethonium to nicotine and of papaverine to BaCl2, grew weaker. Diphenhydramine showed potentiated antagonistic effect to histamine on the 72nd h after radiation. Certain possibilities are discussed concerning the mechanisms underlying the changes in the reactivity of the intestinal smooth muscle to pharmacological agents, induced by acute radiation sickness.

Acetylcholine↗

PubMed1978