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Biomedical subjects

R Braun

Publications and source records attributed to R Braun.

At least 217 records · Page 12Linked to original sources
PubMed1977

Timing of mitosis in Physarum polycephalum: effects of agents affecting cyclic AMP concentrations.

Cultures of Physarum polycephalum incubated with caffeine or theophylline for over 100 min prior to mitosis exhibited mitotic delay proportional to the time of treatment before 100 min. Starved cultures exhibited mitotic delay at times of starvation longer than 180 min and slight stimulation from 100-180 min. Dibutyryl cAMP appeared to accelerate reconstruction of the nucleus following mitosis.

Bucladesine↗
PubMed1977

The influence of N-methyl-N-beta-chloroethyl hydrazines on the mitotic index of Ehrlich ascites tumor cells and the leukopoiesis of the mouse.

The cytostatic activity of N'-methyl-N'-beta-chloroethylbenzaldehyd hydrazone (B1) is at least equal to that of procarbazine when its effect is tested with the Ehrlich ascites tumor cells of the mouse and the Yoshida sarcoma of the rat. B1 causes a slighter decrease of mitotic cells and no shift from prophase to metaphase. These results suggest that the cytostatic effect of B1 is due to interference with cell metabolism or an effect at the cell membrane and not to an effect on cell proliferation. This assumption is supported by a considerable depression of lymphocytes and a minor effect on granulopoiesis, which is especially sensitive towards proliferation toxins. All these findings suggest a different mechanism of action of B1 and procarbazine.

Animals↗
PubMed1977

Activation of an endogenous C-type RNA virus in rat embryo cells after transformation by herpes simplex virus types 1 and 2.

Reverse transcriptase activity was detected in the supernatants of rat embryo fibroblast cell cultures transformed by HSV types 1 and 2 at either the sub-optimal temperature of 20 degrees C or the supra-optimal temperature of 42 degrees C. Rat cells clones which had been transformed at 20 degrees C contained higher levels of C-type virus DNA polymerase than did cell clones which had been transformed at 42 degrees C. Syncytia formation typical for C-type RNA viruses occurred at passages higher than 24. The activation of endogenous C-type RNA viruses was independent of the virus and transformation method used.

Animals↗
PubMed1977

[On structure-activity relationships of N'methyl-N'-beta-chloroethyl-benzaldehyde hydrazones (author's transl)].

The inhibition of uridine and thymidine in Ehrlich ascites cells is a basic property of the methylhydrazone structure and is reinforced by introducing a beta-chloroethyl group. This was shown by variation of the substituents at the N'-nitrogen atom of N'-methyl-N'-beta-chloroethyl-benzaldehyde hydrazone. Probably this action is due to an ethylenimmonium intermediate. This is derived from the observation that substituents which increase the nucleophilic property of the N'-nitrogen atom show a greater inhibitory effect in vitro. The therapeutic effect, however, is not enhanced when tested on the solid Ehrlich ascites tumor of mice. A better therapeutic effect resulted from introduction of chlorine atoms in positions 3 and 4 of the ring which inhbiits as well a probable metabolic hydroxylation of the ring.

Animals↗
PubMed1976

[On the cytostatic mechanism of action of N-methyl-N-beta-chloroethylhydrazine and its benzaldehydhydrazone (author's transl)].

N-Methyl-N-beta-chloroethyl-hydrazine and its bezaldehydhydrazone inhibit the synthesis of DNA and RNA in ascites cells in vitro faster and stronger than N,N-Dimethylhydrazine and procarbazina does. The benzaldehydhydrzone essentially inhibits influx and phosphorylation of nucleosides whereas N-Methyl-N-beta-chloroethylhydrazine acts directly on DNA synthesis.

Animals↗
PubMed1976

[On the cytosic action of N-methyl-N-beta-chloraethyl-hydrazine and its benzaldehydhydrazone (author's transl)].

N-Methyl-N-beta-chloroethyl-hydrazine and its benzaldehydhydrazone are two new cytostatic methylhydrazines. Administered intraperitoneally, they are more effective in inhibiting the ascites tumor growth (Ehrlich's carcinoma in mice and Yoshida sarcoma in rats) than procarbazine in vitro as well as in vivo. The intraperitoneal administration of hydrazone shows a minor effect on the solid tumor. This may be explained by a different pharmacocinetical behaviour. Hydrazone is less toxic than procarbazine.

Animals↗
PubMed1976

Experimental coronary artery bypass operation. Myocardial blood flow, ventricular performance and regional myocardial function.

Myocardial blood flow and ventricular function was studied in seven dogs with chronic myocardial ischemia before and after coronary bypass grafting. Restoring blood flow in an area of 25% of the anterior wall of the left ventricle did not significantly improve overall ventricular function. Assessment of intramyocardial pressure as an index of regional myocardial function revealed a consistent enhancement of myocardial contraction at rest, and under pharmacological stress of the heart.

Animals↗