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Biomedical subjects

M Reivich

Publications and source records attributed to M Reivich.

At least 145 records · Page 8Linked to original sources
PubMed1980

Heterogeneity of local cerebral blood flow-PaCO2 sensitivity in neonatal dogs.

Local cerebral blood flow (1-CBF) sensitivity to changes in arterial carbon dioxide tension (PaCO2) was measured in nitrous oxide-anesthetized newborn puppies using a quantitative autoradiographic technique and [14C]antipyrine as a tracer. 1-CBF was determined in four experimental groups at PaCO2 levels of 22, 34, 48, and 65 Torr, respectively. All seven brain areas studied demonstrated 1-CBF sensitivity to altered PaCO2. There were no significant differences (P greater than 0.05) in three subcortical white matter regions (frontal, parietal, occipital) in either 1-CBF or 1-CBF-CO2 sensitivity. With the exception of the thalamus, a reciprocal relationship existed between changes in local cerebral vascular resistance and blood flow. In the thalamus, 1-CBF increased at a greater rate than the 1-CVR reduction. The results show that CBF is heterogeneous in different brain areas of the neonatal dog at normocapnia and that differences in 1-CBF-CO2 sensitivity exist.

Animals↗
PubMed1979

Effect of intracerebral vasculitis on regional cerebral blood flow.

Regional cerebral blood flow was measured by the xenon 133-inhalation method in a 40-year-old man during an acute exacerbation of intracranial vasculitis. Neurologic function was quantitated by the Halstead-Reitan Neuropsychological test battery. The patient was also studied during remission that was induced by steroid therapy. Vasculitis produced a diffuse encephalopathy with generalized reduction in cerebral blood flow. During remission, only local symptoms secondary to a small cerebral infarction remained and regional cerebral blood flow returned to the normal range. There seems to be a close correlation between the severity of symptoms in cerebral vasculitis and reduction of flow through diseased vessels.

Adult↗
PubMed1979

The [18F]fluorodeoxyglucose method for the measurement of local cerebral glucose utilization in man.

A method has been developed to measure local glucose consumption in the various structures of the brain in man with three-dimensional resolution. [18F]-2-deoxy-2-fluoro-D-glucose is used as a tracer for the exchange of glucose between plasma and brain and its phosphorylation by hexokinase in the tissue. A mathematical model and derived operational equation are used which enable local cerebral glucose consumption to be calculated in terms of the following measurable variables. An intravenous bolus of [18F]-2-deoxy-2-fluoro-D-glucose is given and the arterial specific activity monitored for a predetermined period of from 30 to 120 minutes. Starting at 30 minutes, the activity in a series of sections through the brain is determined with three-dimensional resolution by an emission tomographic scanner. The method was used to measure local cerebral glucose consumption in two normal volunteers. The values in gray matter structures range from 5.79 mg/100 g per minute in the cerebellar cortex to 10.27 in the visual cortex, whereas, in white matter structures, the values range from 3.64 mg/100 g per minute in the corpus callosum to 4.22 in the occipital lobe. Average values for gray matter, white matter, and whole brain metabolic rates, calculated as a weighted average based on the approximate volume of each structure, are 8.05, 3.80, and 5.90 mg/100 g per minute, respectively. The value of 5.9 mg/100 g per minute compares favorably with values previously reported.

Adult↗
PubMed1978

Local cerebral glucose uptake in awake and halothane-anesthetized primates.

Local glucose consumption within specific brain structures in awake and halothane-anesthetized primates was studied using a quantitative autoradiographic technique for glucose (14C-deoxyglucose). In both awake and anesthetized animals, significant heterogeneity (one-way analysis of variance) in uptake of glucose was found in the cortex, subcortical grey matter, and brainstem nuclei. No significant variability was found for any of the white matter areas sampled under either experimental condition. Halothane produced significant decreases in glucose metabolic rates in the occipital cortex, brainstem nuclei, cerebellar cortex, cerebellar white matter, and anterior commissure, compared with the awake state. The greatest decrease in cerebral metabolic rate was found in the occipital lobes of halothaneanesthetized animals. Results of this study suggest that neurophysiologic and behavioral changes that occur with anesthetic agents can, for the first time, be correlated with alterations in local cerebral glucose metabolism.

Anesthesia, Inhalation↗
PubMed1978

Alterations in regional cerebral hemodynamics and metabolism produced by focal cerebral ischemia.

Since diffuse changes in blood flow and metabolism occur in the brain following a focal ischemic insult, changes of cerebral blood flow on the side opposite a cerebral infarction were observed. We have examined the course of the cerebral hemodynamic changes occurring in 15 patients with unilateral acute strokes. In 12 of these patients, significant blood flow changes (over 15%) occurred in the nonischemic hemisphere during the period of observation. A similar time course of change was found in the ischemic hemisphere and the flow changes in the two hemispheres appeared parallel to one another (diaschisis). Thus we have demonstrated a significant reduction in flow in the contralateral cortex following a unilateral ischemic insult. This reduction in flow was of the order of 38% from the control value which agrees quite well with the reduction in cortical glucose consumption of the order of 31%. We postulate that these changes are the hemodynamic and metabolic concomitants of diaschisis and may in part be due to a transneuronal depression of function.

Animals↗
PubMed1978

Local cerebral blood volume response to carbon dioxide in man.

We used an emission tomographic brain scanner to investigate the relationship between local cerebral blood volume (LCBV) and arterial blood carbon dioxide tension (PaCO2) in normal awake man. Measurements were made separately in three dimensions in various regions of grey and white matter, and the resting LCBV as well as the difference in sensitivity among these regions were compared. Over the range of PaCO2 studied (20-42 torr), the response of both the grey matter and the white matter to carbon dioxide was linear. The LCBV sensitivity of the grey matter to changes in PaCO2 was 0.053 ml/100 g per torr PaCO2 and in the white matter this sensitivity was 0.046 ml/100 g per torr PaCO2. These sensitivities were found not to be significantly different, yielding a slope of 0.049 ml/100 g per torr PaCO2 for the LCBV-PaCO2 curve for the entire brain. This is in excellent agreement with the other data for the whole brain. The resting cerebral blood volume of the grey matter at a PaCO2 of 34.4 torr, which was the average resting arterial carbon dioxide tension of the subjects, was 5.0 ml/100 g and was significantly higher than for white matter, which was 3.6 ml/100 g. At the local level, the cerebral blood volume of the frontal cortex is significantly less than that of the thalamus, whereas the frontoparietal cortex in the region of the sylvian fissure has a local cerebral blood volume significantly greater than that of the thalamus.

Adolescent↗
PubMed1977

Local glucose utilization in acute focal cerebral ischemia: local dysmetabolism and diaschisis.

By means of an autoradiographic technique employing 14C-2-deoxyglucose, abnormalities of local brain glucose utilization were studied 90 minutes following occlusion of the left middle cerebral and common carotid arteries in a series of pentobarbital-anesthetized cats. Sham-insulted control animals exhibited a normal pattern of regional glucose utilization. In animals with vascular occlusion, a zone of greatly suppressed glucose utilization occupied the caudate nucleus of the ischemic hemisphere, with variable extension, and was surrounded by a narrow rim of increased local brain glucose utilization, suggesting the occurrence of enhanced anaerobic glycolysis in the latter zones. The cerebral cortex, which was less constantly affected, showed alternating regions of increased and decreased glucose utilization. Quantitation of local brain glucose utilization values from the contralateral nonischemic hemisphere revealed a mild suppression of cortical glucose utilization relative to the control animals. This may be the metabolic equivalent of diaschisis.

Animals↗