Metabolitkonzentrationen in Herz, Gehirn, Niere und Leber des Hundes bei kontrollierter Hypotension

The young-adult and normally aged brain. Its blood flow and oxidative metabolism. A review--part I

Blood flow and oxidative metabolism of the mature and healthy young-adult human brain account for about 20% of the cardiac output and about 20 and 25% of the requirements of oxygen and glucose, respectively, for the whole body. Normal cerebral aging is associated with only smaller reductions in the cerebral metabolic rates of oxygen and glucose while cerebral blood flow would seem to be unchanged. The age-dependent reduction in oxidative brain metabolism may be related to a decline in glycolytic flux due to a diminution of enzyme activities also involving acetylcholine synthesis. This metabolic reduction with age may be tentatively accounted for by a physiologically occurring loss of neurons, dendrites and dendritic spines in distinct brain areas. The mechanisms of autoregulation of cerebral blood flow, of CO2 reactivity of the brain vessels, of arterial hypoxemia on cerebral blood flow and their effects on oxidative and energy metabolism are well documented in young-adult brain. There is, however, no or only minimal information on the responsiveness of the normally aged brain to changes of these important biological parameters controlling and influencing brain blood flow and metabolism.

Energy state and glycolysis in human cerebral edema

✓ A new freeze-stop device using a liquid nitrogen reservoir and an automatic biopsy mechanism has been developed, suitable for rapid, sterile, and standardized sampling of cerebral tissue in man. In animal experiments a 200 mg piece of cerebral cortex was cooled from a room temperature of 18°C to −40°C within 7 sec which is twice as fast as when it was immersed in liquid N2. The method was then applied to metabolic tissue studies of perifocal edematous cortex from patients undergoing neurosurgery for intracranial tumors. Energy-rich phosphate compounds or parameters of the energy state were found to be less affected in this type of brain edema than the glycolytic activity which was markedly enhanced, indicated by lactic and pyruvic acid determinations. The tissue water content correlated closely with the lactic acid concentration, and very little with measurements of the energy state such as the energy charge potential or the adenosinetriphosphate-adenosinediphosphate (ATP/ADP) ratio. It is suggested that in perifocal brain edema increased levels of lactic acid are associated with mechanisms leading to an increased water uptake.