The isolated canine brain preparation will be utilized in studies to: a) correlate the magnitude of hypoxic brain damage with changes in mitochondrial function and energy metabolism and b) identify the pathways involved in brain glucose utilization during hypoxia and post-hypoxic reoxygenation. a) Brains will be perfused at PaO2's ranging from 10 to 50 mmHg for periods of 16 to 125 min to vary O2 deficit ((Normal CMRO2 - Experimental CMRO2) x Time) and time to achieve a specific O2 deficit. Fresh cerebral cortex with O2 deficits totaling 10 to 80 Mumol/g and 0, 30, or 60 min of reoxygenation will be exercised and the mitochondria isolated for measurement of respiration. Similar samples of cortex will be frozen in situ and examined for ATP, ADP, AMP, PCr, FFA, glucose, G-6-P, G-1-P, glycogen and lactate. Extracellular Ca++ will be measured continuously and CMRO2 at 3 min intervals throughout the study. A two level factorial analysis will be made to determine whether: i) CMRO2 reflects the status of variables aassociated with energy metabolism, ii) O2 deficit is a factor in producing mitochondrial damage and iii) the decrease in extracellular Ca++ correlates with the onset of irreversible changes in cerebral energy metabolism. b) The metabolic fate of U14C-glucose will be studied by pulse labeling brain and measuring 14CO2 efflux before, during or after 30 min of either PaO2 30 or 40 mmHg hypoxia. In addition, cerebral cortex will be frozen in situ, fractionated into constituent FFA, lipids, amino acids, proteins and polysaccharides, quantified and analyzed for radioactivity. To quantify the amount of glucose entering the various pathways, the U14C-glucose experiments will be repeated with variously labeled (1-14C, 6-14C, and 3,4-14C)-glucose. If CMRglu is known one can calculate the contribution of each pathway based on the percent of total glucose radioactivity entering brain which appears as 14CO2 with each of the specific labels. Pathways of glucose utilization together with labeling and tissue levels of the constituents at PaO2 30 mmHg will be compared with corresponding PaO2 40 mmHg values to determine how glucose metabolism is altered by a further decrease in O2 availability and whether the changes can explain the inability of the PaO2 30 mmHg group to recover from hypoxia.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS005961-23
Application #
3393436
Study Section
Neurology B Subcommittee 1 (NEUB)
Project Start
1976-12-01
Project End
1989-11-30
Budget Start
1988-12-01
Budget End
1989-11-30
Support Year
23
Fiscal Year
1989
Total Cost
Indirect Cost
Name
University of Wisconsin Madison
Department
Type
Schools of Medicine
DUNS #
161202122
City
Madison
State
WI
Country
United States
Zip Code
53715
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Gilboe, D D; Kintner, D; Anderson, M E et al. (1993) Inorganic phosphate compartmentation in the normal isolated canine brain. J Neurochem 60:2192-203
Gilboe, D D; Kintner, D; Fitzpatrick, J H et al. (1991) Recovery of postischemic brain metabolism and function following treatment with a free radical scavenger and platelet-activating factor antagonists. J Neurochem 56:311-9
Allen, A; Yanushka, J; Fitzpatrick, J H et al. (1989) Acute ultrastructural response of hypoxic hypoxia with relative ischemia in the isolated brain. Acta Neuropathol 78:637-48
Emoto, S E; Kintner, D; Feyzi, J M et al. (1988) Relating cerebral ischemia and hypoxia to insult intensity. J Neurochem 50:1952-8
Hogan, K; Fitzpatrick, J (1988) The cerebral origin of the alpha rhythm. Electroencephalogr Clin Neurophysiol 69:79-81
Kintner, D B; Kao, J L; Woodson, R D et al. (1986) Evaluation of artificial plasma for maintaining the isolated canine brain. J Cereb Blood Flow Metab 6:455-62
Kintner, D B; Kranner, P W; Gilboe, D D (1986) Cerebral vascular resistance following platelet and leukocyte removal from perfusate. J Cereb Blood Flow Metab 6:52-8
Louie, J A; Javid, M J; Gilboe, D D (1985) Vasomotor response to hormonal norepinephrine in canine cerebral and hindlimb vessels. Am J Physiol 248:H232-9