A comparison of children's electric wheelchairs

During the past few years, the Occupational Therapists at the Kitchener-Waterloo Rotary Children's Centre have explored and prescribed electric wheelchairs for handicapped children from 2-19 years of age. This paper presents a comparison of three children's electric wheelchairs, the Bec, Solo, and Everest and Jennings.

Effects of beta-adrenoreceptor blocking drugs on adrenergic transmission

The peripheral actions of beta-adrenoreceptor antagonists on adrenergic transmitter mechanisms have been reviewed. In addition to receptor blockade, beta-adrenoreceptor antagonists may in high concentrations inhibit neuronal uptake of noradrenaline; inhibit monoamine oxidase; inhibit the uptake of noradrenaline into transmitter storage vesicles and inhibit the extraneuronal uptake of noradrenaline. High concentrations of beta-adrenoreceptor antagonists (threshold about 30 muM) also release noradrenaline from intraneuronal stores; however, their intrinsic sympathomimetic activity is generally attributed to their partial agonist property. Beta-adrenoreceptor antagonists possess adrenergic neurone blocking activity and quinidine-like or local anaesthetic activity. The existance of a positive feedback mechanism involving prejunctional beta-adrenoreceptors is discussed. It is suggested that bradycardia produced by beta-adrenoreceptor antagonists is due to blockade of the action of circulating catecholamines or of transmitter noradrenaline at cardiac extrajunctional beta-adrenoreceptor sites.

Effects of some catecholamines on noradrenergic transmission in the rabbit ear artery

1. The effects of noradrenaline, adrenaline, isoprenaline, dopamine and the N-methyl and alpha-methyl homologoues of dopamine were studied on tritium release and on vasoconstrictor responses to sympathetic nerve stimulation in isolated arteries of the rabbit ear after labelling noradrenergic transmitter stores with 3H-noradrenaline. These observations were made in the presence of cocaine (100 muM). 2. Noradrenaline (0-5 and 5 muM) inhibited transmitter release and abolished vasoconstrictor responses. A concentration of 0-05 muM had no effect on transmitter release, although the vasoconstrictor response was reduced and there was sometimes a vasodilator response. 3. Adrenaline in concentrations of 0-05, 0-5 and 5 muM decreased transmitter release and vasoconstrictor responses; sometimes there was a vasodilator response. 4. Isoprenaline in concentrations of 0-05, 0-5 and 5 muM did not affect transmitter release. Vasoconstrictor responses were either unaffected or enhanced by all concentrations of isoprenaline when infusions had been in progress for 15 min; but immediately after beginning the infusion of 5 muM isoprenaline, the response was reduced. 5. Dopamine (0-05, 0-5 and 5 muM) produced a concentration-dependent decrease in transmitter release, but vasoconstrictor responses were not reduced with infusions of 0-05 or 0-5 muM; during infusions of 5 muM, stimulation produced a vasodilator response.