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Biomedical subjects

J L WEBB

Publications and source records attributed to J L WEBB.

At least 19 recordsLinked to original sources
PubMed1963

Sex hormone studies. The effects on the cellular membrane potentials and contractility of isolated rat atrium.

The effects of estradiol, testosterone and progesterone on the electrical and mechanical characteristics of rat atria were determined. Cellular membrane potentials were obtained with microelectrodes and the contractility recorded from a sensitive strain gauge. All three steroids at concentrations near 10(-5) M produced characteristic changes in the membrane potentials, the most striking effect being a pronounced slowing of the depolarization of the action potential, without simultaneously reducing the magnitudes of the resting or action potentials. As a result, there was slower impulse conduction in the atria, a lengthening of the action potential and a consequent increase in the refractory period. The repolarization rate was slowed. These changes are due to effects on the transmembrane fluxes of Na(+) and K(+), a decrease in permeability being assumed. These effects are similar to those produced by the standard antiarrhythmic drugs, such as quinidine; and these steroids, particularly testosterone, have been found to be potent in the prevention and abolishment of atrial arrhythmias, both in vitro and in vivo. The steroids also block the effects of acetylcholine on the atria and this may play a role in the reduction in excitability and automaticity.Testosterone, but not estradiol nor progesterone, exerts a temporary stimulation of the atrial contractility, which is not due to any effect on the membrane, but is related in some manner more directly to the contractile systems.

Action Potentials↗
PubMed1956

The incorporation of acetate-1-C14 into cholesterol and fatty acids by surviving tissues of normal and scorbutic guinea pigs.

The synthesis of cholesterol and fatty acids from acetate-l-C(14) by the isolated liver, adrenal, and aorta of scorbutic and pair-fed control guinea pigs has been studied. It was found that ascorbic acid deficiency does not affect the rate of incorporation of C(14)-acetate into cholesterol and fatty acids by the tissues investigated, under our experimental conditions. The relatively high metabolic activity of the artery with regard to cholesterogenesis and lipogenesis was noted. The elevation of serum cholesterol and hexosamine in scurvy has been confirmed.

Acetates↗