title: Acceleration-induced effects on baboon blood chemistry.
abstract: Gravity-induced loss of consciousness (G-LOC) is known to have occurred in pilots since the early 1920's. Most of the research in this area has shown that G-LOC occurs due to a decrease in cerebral blood pressure and a concomitant reduction in brain perfusion. Since a reduction in cerebral blood flow can cause transient hypoxia, it is important to study the cerebral metabolism during high +Gz exposure. One component of these studies should include measurements of substrate availability and degradative products. In the present study, adult baboons were given multiple high +Gz exposures (2 to 6) using the Armstrong Laboratory human centrifuge. Venous blood was collected by an automatic syringe withdrawal pump before, during and after centrifuge exposures. The concentration of blood gases, glucose and lactate tended to decrease during the centrifuge exposure followed by an increase after the run. Total creatine kinase activity in serum was not significantly altered. These results suggest that during +Gz exposure, anaerobic glycolysis is stimulated resulting in elevated lactate production due to a reduction in cerebral blood flow (CBF). The elevated tissue lactate is released into the central circulation upon resumption of normal CBF (after the termination of centrifuge run). Therefore, the observed decrease in lactate concentration during the run may result from a lag in the release of tissue lactate into the blood due to a reduction in CBF. It is speculated that at high +6 Gz, G-LOC may occur as a protective response to reduce the brain metabolic rate, to maintain energy levels and to prevent severe cellular acidosis.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Operational Technologies Corporation, San Antonio, TX.
authors.forename: A R
authors.initials: AR
authors.lastname: Shahed
authors.forename: J
authors.initials: J
authors.lastname: Barber
authors.forename: P M
authors.initials: PM
authors.lastname: Werchan
mesh_terms: D000054:Acceleration / Q000009:adverse effects; D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D001921:Brain / Q000378:metabolism*; D002245:Carbon Dioxide / Q000097:blood; D003402:Creatine Kinase / Q000097:blood; D004195:Disease Models, Animal; D004569:Electroencephalography; D006112:Gravitation; D006863:Hydrogen-Ion Concentration; D007773:Lactates / Q000097:blood; D019344:Lactic Acid; D010100:Oxygen / Q000097:blood; D010215:Papio; D014474:Unconsciousness / Q000097:blood* / Q000209:etiology
chemical_list: D001786:Blood Glucose; D007773:Lactates; D002245:Carbon Dioxide; D019344:Lactic Acid; D003402:Creatine Kinase; D010100:Oxygen