Mechanism of action of acetyl kidamycin. I. Interaction with DNA

Acetyl kidamycin, an antitumor antibiotic, was strongly bound to DNA in vitro, consequently, the melting temperature of DNA was significantly increased, and its buoyant density was decreased. From these results, it was suggested that acetyl kidamycin stabilized residual links between complementary strands by binding to DNA. An additional action was observed in that acetyl kidamycin caused single-strand scission of DNA in an alkaline sucrose density gradient solution.

Glucocorticoids and mammalian motor nerve excitability

Short-term treatment of cats with high doses of triamcinolone and related steroids strikingly increased the capacity of soleus motoneurons to generate posttetanic stimulus-bound repetition (SBR) and the obligatory postetanic potentiation (PTP) of muscle. The edrophonium chloride (Tensillon)-induced SBR and twitch potentiation were likewise augmented. These effects reflect an increase in the excitability of the motoneuron. This glucocorticoid effect suggests that the motoneuron is the site of the antimyasthenic action of the hormone. Certainly, the enhanced SBR is a neuronal representation of the adverse epileptogenic action of the glucocorticoids. The glucocorticoid effect on motoneuron outlasts the dosing period, suggesting an underlying alteration in the neuron. Other glucocorticoids caused the same effects, but varied in their potencies. Mineralocorticoids were less effective. The single androgen that was tested proved to be minimally effective.

Effect of chronic pentobarbital treatment on blood-cerebrospinal fluid kinetics

Cats were made tolerant and physically dependent by twice daily equieffective anesthetic dosing with sodium pentobarbital intragastrically for 5 weeks. Serial blood and CSF samples were simultaneously collected on day 1 and day 35 and analyzed for pentobarbital by a gas chromatographic method. Pentobarbital penetration into CSF was rapid and unchanged by chronic treatment. The concentration in blood and CSF increased significantly with chronic treatment; however, the relative CSF/blood concentration ratios were unchanged.

Tolerance characteristics produced during the maximally tolerable chronic pentobarbital dosing in the cat

The method of "maximally tolerable" dosing technique for establishing a reproducible state of barbiturate dependence in cats was used for the study. The development of tolerance in animals treated by this method has been quantitatively assessed. Sodium pentobarbital was administered morning and evening for 35 days via a plastic tube implanted into the stomach through the abdominal wall. A range of neurological signs of intoxication was scored before and after each dose and during the day at certain preset intervals. Based on the scoring of neurological impairment, each cat was given the maximally tolerable anesthetic dose of sodium pentobarbital. All of the animals treated by this method exhibited severe withdrawal signs upon abrupt withdrawal of the drug. For each cat, blood pentobarbital concentrations were determined every day before and 1 to 11/4 hours after the morning dose. Also, a complete blood pentobarbital elimination study was made on days 1, 7, 14, 21, 28 and 35 of the regimen. These results distinguished between dispositional and functional tolerance. The dispositional tolerance developed maximally within a week and was maintained at that level as long as the treatment was continued. The functional tolerance, on the other hand, developed more gradually and progressed with continued treatment.