Search PubMed⌕ Search

Biomedical subjects

A Clark

Publications and source records attributed to A Clark.

At least 325 records · Page 18Linked to original sources
PubMed1973

Effects of caffeine and isoprenaline on mammalian ventricular muscle.

1. Caffeine, 0.6-20.0 mM, altered the duration of the action potential recorded from kitten papillary muscles; low concentrations shortened and high concentrations prolonged the action potential.2. Caffeine, 20 mM, prolonged the action potential by delaying the final phase of repolarization.3. Caffeine, 2.0-20.0 mM increased the tension developed and the duration of the isometric contraction.4. When large stimulating electrodes were used, all concentrations of caffeine increased the duration of the action potential; this effect was probably due to the interactions of caffeine and released endogenous catecholamines.5. Concentrations of caffeine and isoprenaline, which separately caused little change in the duration of the action potential, greatly prolonged the action potential when used together.6. The effects of caffeine may be due to an increase in membrane calcium current in addition to an action on intracellular calcium stores.

Action Potentials↗
PubMed1969

Morphological and biochemical differentiation of three types of small oral spirochetes.

THIRTY STRAINS OF HUMAN ORAL ANAEROBIC SPIROCHETES WERE ISOLATED IN THREE DIFFERENT MEDIA: veal heart infusion-ascitic fluid, Spirolate-Brain Heart Infusion-rabbit serum, and supplemented PPLO broth. The morphological and biochemical characteristics of the isolates permitted their differentiation into three distinct species: Treponema denticola, T. macrodentium, and T. oralis (proposed new species). These species could be differentiated as follows. Organisms of the T. denticola type had a "2-4-2" axial fibril relationship as determined by electron microscopy, required serum for growth, did not utilize glucose or lactate, and produced indole, ammonia, acetate, and lactate as end products. T. macrodentium had a "1-2-1" axial fibril relationship, did not require serum, utilized glucose but not lactate, did not produce indole or ammonia, and produced formate, acetate, lactate, and succinate as acid end products. T. oralis had a "1-2-1" axial fibril relationship, required serum for growth, utilized lactate but not glucose, produced indole but not ammonia, and produced propionate and acetate as acid end products.

Culture Media↗