Diving seals, ischemia-reperfusion and oxygen radicals.

The cardiovascular adaptations of seals that contribute to their ability to tolerate long periods of diving asphyxial hypoxia result in episodic regional ischemia during diving and abrupt reperfusion upon termination of the dive. These conditions might be expected to result in production of oxygen-derived free radicals and other forms of highly reactive oxygen species. Seal organs vary during dives with respect to the degree and persistence of ischemia.

Effects of hypoxemia and reoxygenation with 21% or 100% oxygen in newborn piglets: extracellular hypoxanthine in cerebral cortex and femoral muscle.

Objective: To determine whether reoxygenation with an FIO2 of 0.21 (21% oxygen) is preferable to an FIO2 of 1.0 (100% oxygen) in normalizing brain and muscle hypoxia in the newborn.

Ascorbic acid enhances hydroxyl radical formation in iron-fortified infant cereals and infant formulas.

Unlabelled: Infant cereals and formulas are usually fortified with iron to prevent iron deficiency. To enhance iron bioavailability, supplemental ascorbic acid is recommended. Ascorbic acid is considered to be an antioxidant in vivo, but has pro-oxidant effects when exposed to non-protein-bound iron.

Plasma hypoxanthine reacts more abruptly to changes in oxygenation than base deficit and uric acid in newborn piglets.

Previously, high postmortem concentrations of hypoxanthine have been found in vitreous humor of children dying from sudden infant death syndrome (SIDS). We wanted to investigate further the accumulation of hypoxanthine in vitreous humor during hypoxia. Twenty-four piglets aged 9-15 days were exposed to continuous hypoxemia (180 min 11% O2, n = 6), long interval intermittent hypoxemia (60 min 11% O2, 20 min room air, n = 7) or short interval intermittent hypoxemia (10 min 9% O2, 10 min room air with (n = 6) or without (n = 5) superimposed ligation of both carotid arteries).

Beta-endorphin may be a mediator of apnea induced by the laryngeal chemoreflex in piglets.

To determine whether beta-endorphin is involved in the laryngeal chemoreflex, we initially injected 0.01-1 mg of beta-endorphin into the cisterna magna (i.c.