Differential stabilization of topoisomerase-II-DNA cleavable complexes by doxorubicin and etoposide in doxorubicin-resistant rat glioblastoma cells.

Using the technique of alkaline filter elution, we have evaluated the DNA damage induced by doxorubicin and etoposide in a rat glioblastoma cell line, C6, and its doxorubicin-selected resistant variant, C6 0.5. DNA damage paralleled drug-induced cytotoxicity, but it appeared that the same DNA damage generated much less cytotoxicity in resistant cells than in sensitive ones, resistant cells being able to tolerate more DNA damage than sensitive cells.

Relationships between DNA damage and growth inhibition induced by topoisomerase II-interfering drugs in doxorubicin-sensitive and -resistant rat glioblastoma cells.

We have evaluated the DNA breaks occurring after action of three topoisomerase II-interfering drugs (doxorubicin, etoposide and amsacrine) on a line of rat glioblastoma cells in culture and its doxorubicin-resistant variant. DNA breaks were quantified by alkaline unwinding in the presence of a dye exhibiting a quenching of fluorescence with single stranded DNA. The antiproliferative activity of the three drugs was compared to their ability to damage DNA.

Nodular regenerative hyperplasia in the rat induced by a selenium-enriched diet: study of a model.

Weaned male rats were fed a 4 ppm selenium diet. Compared after 2 mo with a control group fed a 0.4 ppm diet, the rats' body weights had not significantly decreased and liver function was normal, but portal pressure was 1.

Reactivity of consecutive basic amino acid residues in peptides.

Different tetrapeptides of general formula L-Ala-X-X-Gly, possessing a basic doublet in the second and third position (X = Arg or Lys), have been synthesized as free or N-acetylated molecules. The chemical reactivity of the arginine guanidino group and of the lysine epsilon-amino group were studied using respectively the Sakaguchi and the ortho-diacetylbenzene reactions, in the tetrapeptides as well as in related molecules. In both cases, the colour yield is markedly influenced by the length of the polypeptide chain and by the relative positions of the arginine and lysine residues, suggesting the occurrence of intramolecular bonds within the tetrapeptide molecule.