Comparison of the effects of 9-tetrahydrocannabinol, 11-hydroxy- 9-tetrahydrocannabinol, and ethanol on the electrophysiological activity of the giant axon of the squid

External and intra-axonal application of Δ⁹-tetrahydrocannabinol was without effect on impulse conduction in the giant axon of the squid whereas 10^?8m 11-hydroxy-Δ⁹-tetrahydrocannabinol reversibly blocked conduction in this preparation. This pharmacological effect of 11-hydroxy-Δ⁹-tetrahydrocannabinol compares in some respects with that produced by the intra-axonal injection of ethanol into these fibres.     

Effect of diallyl sulfide on rat liver microsomal nitrosamine metabolism and other monooxygenase activities

It has been reported that p.o. administration of diallyl sulfide (DAS), a naturally occurring component of garlic (Allium sativum), inhibits 1,2-dimethylhydrazine-induced colon and liver cancer in rodents. A possible mechanism for this protective effect is inhibition of hepatic activation of the procarcinogen. The effect of DAS on P450IIE1, an isozyme of cytochrome P-450 which is active in the oxidative metabolism of dimethylhydrazine, was conveniently assayed in the present study by determination of N-dimethylnitrosamine demethylase (NDMAd) activity at 1 mM N-dimethylnitrosamine in Sprague-Dawley rat liver microsomal incubations. DAS was found to be a competitive inhibitor of NDMAd, in contrast to the irreversible inactivation of NDMAd produced by carbon tetrachloride incubated under similar conditions. The inhibition by DAS of the demethylation of several substrates was selective. The thioether was most potent against N-dimethylnitrosamine, less effective against N-nitrosomethylbenzylamine, and essentially ineffective against benzphetamine and ethylmorphine. Microsomes prepared at 3 h after DAS administration (200 mg/kg in corn oil intragastrically) showed moderate inhibition (less than 30% inhibition compared to control microsomes) of several demethylase activities; however, microsomes prepared 18 h posttreatment showed a marked decrease (about 80% inhibition compared to controls) in NDMAd activity, minor effects on other demethylase activities, and a 6-fold increase in pentoxyresorufin dealkylation. These trends at 18 h agreed with immunoblot analyses which showed suppression in the level of P450IIE1 and an elevation in P450IIB1. The selective inhibition of P450IIE1 activity and suppression of its level in microsomes may contribute to the reported chemoprotective effects of DAS.     

Evaluation of endodontic instruments as received from the manufacturer: the demand for quality control.

Two hundred seventy new files, reamers, and Hedstr?m files from three different manufacturers were evaluated for debris and defects. Statistical analysis of the new instruments showed that one company's instruments were cleaner than the other two but still contained defects. A standard for quality is proposed.     

The effects of phencyclidine and ketamine on sensory thresholds and reaction times in the baboon

Adult male baboons were trained on a reaction time procedure, and absolute thresholds and reaction times to both a 16.0 kHz pure tone and a white light were obtained. Acute IM injections of phencyclidine (0.0032 to 0.1 mg/kg) or ketamine (0.032 to 3.2 mg/kg) were given at the beginning of 2-hr test sessions. Phencyclidine had no effect on auditory thresholds, visual thresholds, or visual reaction times, but selectively elevated auditory reaction times. Ketamine, on the other hand, elevated auditory thresholds and both auditory and visual reaction times, while having no effect on visual thresholds. Ketamine was also less potent than phencyclidine in elevating auditory reaction times, and recovery from these impairments was evident during the two-hour test sessions for ketamine, but not for phencyclidine.     

The electron microscopy of bacteriophage-like particles in dental plaque.

The morphology of bacteriophage-like particles contained in samples of dental plaque is described. The phage-like particles were observed within fusiform-shaped bacteria and in clumps between bacteria. The particles were hexagonal in cross section, approximately 1,100 nm in diameter and contained an electron-dense core. In areas of cell lysis tail forms were observed both free and in association with the particles. Occasional particles were attached to bacterial cell walls by means of shortened tailpieces.     

Periodontosis: a case report with scanning electron microscopic observations.

A tooth and associated periodontal tissues from a patient with the diagnosis of periodontosis was subjected to scanning electron microscopic evaluation after reflection of the soft tissue portion of the lingual defect. The cemental surface of the apical portion of the lesion was found to be populated by markedly similar rod-shaped organisms. The microorganisms were observed to be continuously present in a coronal-apical direction as the transition from cementum to the attached soft tissues at the base of the defect were examined. These findings provide additional evidence that the lesion of periodontosis is characterized by a rather distinct microbial population of rod-shaped organisms located predominately at the base of the defect.