Tissue concentrations of mercury after chronic dosing of squirrel monkeys with thiomersal

Squirrel monkeys were dosed intranasally with saline or thiomersal (sodium ethylmercurithiosalicylate, 0.002 percent w/v) daily for six months. The total amounts of thiomersal given during the six months period were 418 mug (low dose group) and 2280 mug (high dose group). This was equivalent to 207 and 1125 mug mercury. The dose differential was achieved by more frequent administration to the high dose group. Mercury concentrations were significantly raised over control values in brain (high dose group only), liver, muscle and kidney, but not in blood. Concentrations were highest in the kidney, moderate in liver and lowest in brain and muscle. Much of the mercury was present in the inorganic form (37-91 percent). No evidence of toxicity due to thiomersal was seen in any animal. Nevertheless accumulation of mercury from chronic use of thiomersal-preserved medicines is viewed as a potential health hazard for man.

Effects of angular acceleration on man: choice reaction time using visual and rotary motion information

This experiment was concerned with the effects of rotary acceleration on choice reaction time (RTc) to the motion of a luminous line on a cathode-ray tube. Specifically, it compared the RTc to rotary acceleration alone, visual acceleration alone, and simultaneous, double stimulation by both rotary and visual acceleration. 13 airline pilots were rotated about an earth-vertical axis in a precision rotation device while they observed a vertical line. The stimuli were 7 rotary and visual accelerations which were matched for rise time. The pilot responded as quickly as possible by displacing a vertical controller to the right or left. The results showed a decreasing RTc with increasing acceleration for all conditions, while the RTc to rotary motion alone was substantially longer than for all other conditions. The RTc to the double stimulation was significantly longer than that for visual acceleration alone.

Analysis of the inhibition of pethidine N-demethylation by monoamine oxidase inhibitors and some other drugs with special reference to drug interactions in man

1. N-Demethylation of pethidine was studied in microsomal suspensions from unstarved male rat liver and the N-demethylase identified as belonging to the class of hepatic microsomal mixed function oxidases.2. A study of the structure/action relationships of compounds inhibiting pethidine N-demethylase revealed that hydrazine derivatives including phenylhydrazine, methylphenylhydrazine and mebanazine were all potent competitive inhibitors.3. Pethidine N-demethylase was only slightly inhibited by histamine and amphetamine but not by adrenaline and ephedrine nor by several miscellaneous compounds including piperidine, N-ethylpiperidine, N-methylpiperidine, N-methylammonium, hydrallazine or pethidinic acid.4. Several psychotropic drugs were all found to be potent competitive inhibitors of pethidine N-demethylase. These included monoaminoxidase inhibitors (the most active being nialamide and phenoxypropazine [K(i)=0.01 mM]; the least active iproniazid [K(i)=1.05 mM]); the tranquillizers promazine, propiomazine and chlorpromazine and tricyclic antidepressants (opipramol [K(i)=0.01 mM], imipramine [K(i)=0.03 mM], desipramine [K(i)=0.03 mM] and amitryptyline [K(i)=0.03 mM]). Hydrocortisone [K(i)=0.3 mM], prednisolone [2.8 mM] and nalorphine [0.07 mM] were also inhibitors, whilst SKF 525A was the most active of all [K(i)=0.002 mM].5. These results are discussed in relation to the clinically observed drug interactions which may occur between monoamineoxidase inhibitors and pethidine. It is concluded that since many different groups of drugs, including monoamineoxidase inhibitors, tranquillizers, tricyclic antidepressants, steroids, nalorphine, SKF 525A and barbiturates compete for cytochrome P(450) reductase, it is possible that this mechanism may account, at least in part, for the observed interactions of these various drugs in man.