Investigations of the mechanism of particle-enhanced uptake of benzo [a] pyrene into model membranes and microsomes have been extended by studying the effects of particulates on the rates of uptake of four additional polynuclear aromatic hydrocarbons (PAH) into model membranes. Adsorption of dibenzo [a, h] anthracene, benzo [g,h,i] perylene, and 3-methylcholanthrene to the surface of particles resulted in enhanced rates of membrane uptake of these PAH. Adsorption to the fibrous asbestos minerals (chrysotile and anthophyllite) produced the greatest enhancement in membrane uptake rates compared to uptake from microcrystalline dispersions of the PAH. Adsorption of these PAH to nonfibrous minerals resulted in uptake rates intermediate between those of the asbestos-adsorbed and microcrystalline states. In contrast, adsorption of dibenzo-[c,g] carbazole to particles did not result in enhanced uptake. In this case, the rates of uptake in the absence and presence of particles were all extremely high, presumably as a result of the high water solubility of this PAH. The methods described in this paper permit characterization of particles-PAH mixtures in terms of the rate of PAH uptake into membranes.

Benz(a)Anthracenes↗

PubMedDate not supplied

Mixed neuromuscular block. A re-assessment using train-of-four stimulation.

Suxamethonium was administered to patients during recovery from non-depolarising muscle relaxation. The effect of suxamethonium varied depending upon the degree of recovery from the non-depolarising block when it was administered. Early in recovery suxamethonium produced reversal of the non-depolarising block without paralysis whereas when administered later, initial recovery of the non-depolarising block was followed by paralysis. If administered after 50% recovery the predominant effect was paralysis without initial recovery. Assessment of neuromuscular blockade with train-of-four stimulation showed that the paralysis produced by suxamethonium under these circumstances, had depolarising and non-depolarising features.

Atropine↗

PubMedDate not supplied

Reversal of pancuronium with edrophonium.

Edrophonium was administered as a bolus of 2, 10 or 50 mg (0.03, 0.14 and 0.71 mg/kg) to antagonize neuromuscular block after pancuronium in man. Neuromuscular transmission was measured using "train-of-four" stimulation. Recovery started within 1 min, was maximum at 2 min and was then followed by a plateau of slow continued improvement. The degree of recovery increased with larger doses of edrophonium and also was related to the total amount of pancuronium administered although reversal was attempted at the same degree of spontaneous recovery. There was no evidence of recurarisation or depolarising block.

Adult↗

PubMedDate not supplied

Species differences in disposition of benzo[a]pyrene.

Comparison of disposition of benzo[a]pyrene (B[a]P) among Sprague-Dawley rats, Gunn rats, hamsters, and guinea pigs was performed. [3H]B[a]P was administered intratracheally to animals, and the rate of excretion of radioactivity into bile, types of metabolites of B[a]P in bile, and distribution of radioactivity among tissues were determined. In Sprague-Dawley rats, Gunn rats, and guinea pigs, the rate of excretion of radioactivity was dependent upon the administered dose. Excretion and tissue distribution of radioactivity were qualitatively similar among these species although quantitative differences were observed. In hamsters, the rate of excretion was essentially independent of dose at the concentrations examined (0.16 and 350 micrograms). The major difference between hamsters and the other species was that increased amounts of radioactivity were retained in lungs of hamsters at the lower dose with a proportional decrease in the amount of radioactivity excreted into bile. The types and relative amounts of conjugated and nonconjugated metabolites of B[a]P were similar in bile of Sprague-Dawley rats and hamsters. Smaller amounts of glucuronides and larger amounts of sulfate conjugates were detected in bile of Gunn rats than in bile of Sprague-Dawley rats or hamsters. Metabolites in bile of guinea pigs were markedly different from those in the other species in that approximately 90% of the metabolites were thioether conjugates. Buthionine sulfoxime was used to reduce tissue levels of glutathione in Sprague-Dawley rats. When liver and lung glutathione levels were reduced to 30% and 82% of control levels, respectively, the amount of radioactivity excreted into bile was not significantly different from controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗