Selected Contribution: Carotid body as a model for aging studies: is there a link between oxygen and aging?

The carotid body (CB) is the site in the body that triggers awareness of changes in blood oxygen pressure. Aging is characterized by a decrease in oxygen supply to tissues, in reduction of tissue Po2, and in the activity of several enzymes and metabolic factors. The ventilatory response to hypoxia is attenuated with aging related to the age-dependent structure modifications including the basal reduction of oxygen requirements. The aged CB shows an increase in extracellular matrix, a reduction in number and volume of type I cells, and a reduction in volume of mitochondria that was consistent with and similar to that during chronic hypoxia; this phenomenon seems to operate also during aging as shown by the reduced volume of mitochondria in the aged CB. During chronic hypoxia, CB hypertrophy is less evident in aged CB than in young CB. Therefore, hypoxia and aging seem to share some type of link at different cell sites. CB represents an experimental model adequate for studying aging processes because of its high blood flow and metabolism, and thus it serves as a means to understanding the oxygen modulation of the aging process.

Hyperbaric oxygen and persistence of vision in retinal ischemia

When retinal ischemia is produced by elevating the intraocular tension, normal vision persists for about 4 sec in healthy subjects breathing air at atmospheric pressure. Persistence times were determined at alveolar oxygen pressures up to 4 atm abs (3,000 mm Hg), obtained by oxygen breathing in a high-pressure chamber. Below an alveolar Po2 of 2 atm the rise in persistence time is relatively small. Above that level the time increases in direct proportion to the increase in alveolar Po2 and may exceed 50 sec at 4 atm. The rise of persistence time follows a pattern similar to that of computed blood oxygen pressure assuming an oxygen extraction of about 3 vol%. high pressure; blood oxygen tension; tissue oxygenation; intraocular tension; retinal circulation; visual blackout Submitted on February 7, 1964