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Parotid secretion of alpha-amylase and potassium (K+) was determined in young adults following intense exercise. Exercise stress led to a significant elevation in alpha-amylase and K+ secretion, indicating an activation of adrenergic receptors supplying the parotid gland. Evidence of circadian variation or adaptation over days was not found.

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Accumulation of gentamicin by gentamicin-susceptible Staphylococcus aureus was examined by using the ionophorous antibiotic, valinomycin and the protontranslocating ATPase inhibitor N,N'-dicyclohexylcarbodiimide. The effects of these inhibitors on the transmembrane electrical potential (delta psi) were determined by measuring the equilibrium distribution of the tetraphenylphosphonium ion. The results indicate a direct correlation between delta psi and the extent of gentamicin uptake. However, under conditions where a significant delta psi existed across the plasma membrane, uptake of gentamicin was negligible. A threshold delta psi may thus be required to initiate gentamicin uptake. The proposed threshold delta psi appears to vary depending upon the external concentration of gentamicin.