Cardiovascular activity of 9-hydroxy-ellipticine

The cardiovascular activity of 9-hydroxy-ellipticine (9-OH-E) has been studied on anaesthetized dogs. The drug has been administered intravenously in one dose ranging from 1 to 10 mg/kg. The variations in the myocardial contractility, the systemic haemodynamics, the respiration and the general metabolism of the anaesthetized dogs were studied to make evident the mechanism of 9-OH-E cardiostimulating action. 9-OH-E from 5 mg/kg i.v. stimulates the contractility of myocardium and improves the cardiac performances of the anaesthetized dogs. This heart-stimulating action is long-lasting and is not accompanied by any modification in the arterial blood pressure. It is inhibited or at least strongly attenuated by beta-adrenergic blocking agents and by the depletion of catecholamines.

[2 new antineoplastic derivatives: 9-hydroxy-2-methyl-ellipticinium (acetate) and 9-hydroxy-2,6-dimethyl-ellipticinium (chloride). Effect on mouse L 1210 leukemia]

The antitumoral activity of two new derivatives of ellipticine, 9-hydroxy-2-methyl ellipticinium and 9-hydroxy-2,6-dimethyl-ellipticinium, has been determined using L 1210 mouse leukemia. The first compound elicits a therapeutic index similar to that of 9-hydroxy-ellipticine but is active at doses ten times smaller. The second compound elicits an exceptionally high therapeutic index. It is still active when used at one hundredth of the sublethal dose.

Rearrangement of mitochondrial DNA molecules during the differentiation of mitochondria in yeast. II. - Labelling studies of the precursor product relationship

The length distribution in sucrose sedimentation gradient of the newly-synthesized pulse-labelled mitochondrial DNA has been established at an early stage of depression in wild type yeast (Saccharomyces cerevisiae). This stage corresponded to the beginning of mitochondrial differentiation. The radioactive DNA was longer (mean lengths 5, 10 and 22-25 mu) than the preexisting cold DNA (mean length 6.5 mu with two shoulders at 4 mum and 10 mum and one minor peak at 2-2.5 mum). These date confirm that the mean size of the different length populations of linear yeast mitochondrial DNA are under physiological control. Chase experiments were undertaken as follows. The yeast cells were uniformly prelabelled under anaerobiosis. Therefore the mitochondrial DNA molecules were short. Respiratory adaptation was performed in a cold medium and the lengthening process was induced. The specific activities of the long molecules made up during the respiratory adaptation did mot markedly differ from that of prelabelled DNA (decrease of specific activity less than 18 per cent). Molecules as long as 40 mum were also recorded. This lengthening seems to proceed through a non reciprocal exchange of polynucleotide stretches between preexisting molecules. We call it rearrangement. It occurs during the differentiation of mitochondria. Much of the mitochondrial DNA is maintained whereas a small amount of DNA is synthesized. This hypothesis is favoured by recent genetical and physical studies on mitochondrial recombination in yeast.

Ethidium bromide mutagenesis in yeast: protection by anaerobiosis

The mutagenesis by ethidium bromide, an intercalating dye, which induces the mutation from wild type (rho+) to the cytoplasmic respiratory deficient petite (rho-) in Saccharomyces cerevisiae, was studied under aerobic and anaerobic conditions. During growth of anaerobic cells at pH 6.5, ethidium bromide at a concentration of 2 mug/ml is unable to induce rho- mutants whereas under aerobic conditions the entire population is converted into rho- cells within 1 generation at the same drug concentration. With ethidium bromide 10 mug/ml 98% of the anaerobic cells are transformed into rho- in 5.5 h (more than 2 generations). In non-growing conditions, ethidium bromide 10 mug/ml has no effect in anaerobic cells. 3 h adapted cells used as control, are converted into rho- in 8 h. Increasing the ethidium bromide concentration to 20 mug/ml resulted in the appearance of some rho- mutants in the anaerobic population but marked at the same time the onset of a detectable toxic effect of the drug.

A new antitumoral agent: 9-hydroxyellipticine. Possibility of a rational design of anticancerous drugs in the series of DNA intercalating drugs

The designing of DNA intercalating drugs with high DNA affinity in the series of ellipticine has led to a new antitumoral agent, 9-hydroxyellipticine, which has a high DNA affinity, a high activity on L 1210 mice leukemia, and a lack of toxicity at therapeutic dose. The possible correlations among chemical structure, DNA reactivity, and pharmacological activity of DNA intercalating drugs are discussed.

Circular oligomers in mitochondrial DNA of human and beef nonmalignant thyroid glands

Circular dimers and higher oligomers of mitochondrial DNA have previously only been described in tumor cells. This work demonstrates that such oligomers are also consistently found in a relatively high content (10-37% in weight) in nonmalignant human and beef thyroid glands. Therefore, these forms cannot be assumed to be specific for malignancy, even if they could be related to it in some instances.

A protein inhibitor of acid deoxyribonucleases

A protein extracted and partially purified (about 100-fold) from mouse liver is able to inhibit the acid DNases from different tissues and species, whereas pancreatic DNase and E. coli endonuclease I are not inhibited. The acid DNase displays typical Michaelis-Menten kinetics in the absence of this inhibitor, but the kinetics become sigmoidal in its presence. The existence of a DNase-inhibitor complex is demonstrated by physicochemical experiments. Moreover, the inhibitor is able to reactivate the DNase treated by urea, probably through a reassociation of the inactive monomers to a dimeric state. An allosteric model in which the DNase-inhibitor complex is composed of catalytic (DNase) and regulatory (inhibitor) subunits could explain these data.