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Biomedical subjects

M Reivich

Publications and source records attributed to M Reivich.

At least 109 records · Page 6Linked to original sources
PubMed1985

Regional flow-metabolism couple following middle cerebral artery occlusion in cats.

The regional flow-metabolism couple was studied during the recovery period after 1 h of left middle cerebral artery (MCA) occlusion in cats. Local CBF (LCBF) was assessed at the end of ischemia as well as at the end of 4 h of recirculation by the microsphere technique. Local CMRgl (LCMRgl) was measured at the end of the recirculation period with [14C]2-deoxyglucose. Histology was evaluated by light microscopy from coronal brain blocks adjacent to those used for the determination of LCBF and LCMRgl. When LCBF in the central and peripheral MCA territories during the recovery period was between 40 and 115% of the value in sham occlusion studies, LCMRgl was greater than the control level found in the sham studies, and was accompanied by slight histological damage. This finding suggests that anaerobic glycolysis may persist after transient ischemia in spite of the recovery of LCBF to a level that is normally greater than the threshold for the activation of anaerobic glycolysis (less than 40% of the control). Persistent anaerobic glycolysis in the reperfusion period following an ischemic insult may be a sign of early tissue damage. Some of the regions in the peripheral MCA territory with LCBF between 40 and 110% of the levels during the recovery period in the sham studies showed a mild to moderate depression in LCMRgl so that the flow-metabolism ratio remained normal. These regions did not exhibit histological damage. This possible protective mechanism of the tissue in response to ischemia is discussed from the standpoint of the relationship between flow and metabolism.

Animals↗
PubMed1985

Effect of iodoacetate on local cerebral blood flow and glucose metabolism in cats: a double-radionuclide autoradiographic study.

The effect of iodoacetate (IAA), an inhibitor of glycolysis, on local CBF (LCBF) and local CMRglu (LCMRglu) was studied in cats by means of a double-radionuclide autoradiographic method. Artificial CSF containing 5 mM IAA was superfused on the left parietal cortex under a cranial window for 30 min. [14C]2-Deoxyglucose and [123I]iodoantipyrine were injected for the determination of LCMRglu and LCBF, respectively. A marked increase in LCBF, accompanied by a moderate to severe depression of LCMRglu, was observed in the IAA-superfused cortex. This result suggests that LCBF may be closely regulated by the cellular energy state associated with glycolytic activity in brain tissue.

Animals↗
PubMed1985

Regional alterations in glucose consumption and metabolite levels during postischemic recovery in cat brain.

Local CMRgl (LCMRgl) and metabolite levels were measured in the same tissue samples following 4 h of recirculation after 1 h of occlusion of the middle cerebral artery in the cat. The rate of glucose utilization was calculated using direct measurement of tissue deoxyglucose-6-phosphate and using a "lumped" constant corrected in each sample for alterations in tissue glucose. Increased LCMRgl (compared with that in sham-operated animals) occurred in regions with only minor alterations in levels of lactate and phosphocreatine. By contrast, LCMRgl was markedly depressed in regions with major changes in lactate and high-energy phosphates. Interestingly, tissue levels of glucose and unphosphorylated deoxyglucose were abnormally elevated in regions with profound energy failure. These results indicate an inhibition of glucose utilization in regions damaged by ischemia, despite the persistent elevation of tissue lactate. Increased glucose metabolism at 4 h post ischemia was detected only in areas with minor anaerobic alteration of metabolite levels.

Adenosine Triphosphate↗
PubMed1985

Cerebral blood flow with the continuous infusion of oxygen-15-labeled water.

This work describes the determination of CBF in eight normal human subjects with positron emission tomographic (PET) imaging using the continuous intravenous infusion of H2(15)O. A whole-brain CBF model is described that permits the comparison of the CBF values determined using PET with those obtained using other methods. This model includes a correction for whole-brain recovery coefficient, a correction for the underestimation of flow due to the nonlinearity of the CBF model when considering tissue that includes both gray and white matter, the use of in vitro-determined brain-blood partition coefficients for gray and white matter, and a variation of the equilibrium model that permits the arterial concentration to vary. CBF values using this method compare well with values determined previously. Regional determinations using a brain overlay atlas are presented. Radiation dosimetry for the continuous infusion of H2(15)O is also included.

Adult↗
PubMed1985

Effects of fentanyl on local cerebral blood flow in the rat.

Fentanyl reduces the cortical cerebral blood flow and metabolic rate for oxygen in rats, though seizure activity occurs in some animals at high doses. However, the effects of fentanyl on blood flow and metabolism in subcortical structures have not been clearly delineated. The present study examines the effects of intravenous fentanyl (100 or 400 micrograms . kg-1) on local cerebral blood flow (1-CBF) in paralyzed, mechanically ventilated rats. Rats ventilated with 70% N2O in 30% O2 served as controls. Local CBF was measured using 14C-iodoantipyrine and autoradiography. Blood pressure, PaO2, PaCO2, pH, and temperature were comparable in all groups. The EEG showed slow wave activity in most animals given 100 micrograms . kg-1 fentanyl while seizure activity occurred in all animals given 400 micrograms . kg-1 fentanyl. With 100 micrograms . kg-1 fentanyl, CBF tended to be depressed in all cortical and subcortical areas, except the peri-aqueductal gray; and with 400 micrograms . kg-1 fentanyl, 1-CBF tended to be elevated (compared to 100 micrograms . kg-1 fentanyl) in most areas of the brain. The limbic system structures, however, were most affected by 400 micrograms . kg-1 fentanyl with statistically significant increases (compared to the 100 micrograms . kg-1 group) in 1-CBF of 86% and 67% respectively in the amygdala and septal nucleus. These results confirm that moderately high doses of fentanyl which cause slow wave activity on the EEG also depress 1-CBF in rats; moreover, doses of fentanyl that produce seizure activity produce increases in 1-CBF in most cerebral structures with greatest effects on limbic system 1-CBF.

Animals↗
PubMed1985

Metabolic, ionic, and electrical responses of gerbil brain to ischemia.

The effects of short- or long-term complete cerebral ischemia were studied in the gerbil brain using a multi-parameter monitoring system. Metabolic (NADH redox state) and hemodynamic responses were monitored by surface fluorometry-reflectometry. Ionic activities (K+ and pH) were measured by surface macroelectrodes. Electrical activity was evaluated by monitoring the general electrocorticogram (ECoG) as well as local DC steady potential (two sites). Two groups of gerbils were studied to compare the effects of 4-5 min occlusions with those of 30 min complete ischemia. During bilateral carotid artery occlusion the cortex is exposed to complete ischemia resulting in the complete depletion of O2 with attendant maximal reduction of NADH. Extracellular K+ began to increase as soon as energy reserves were decreased with a time course suggesting two different kinetic areas. Surface pH decreased very shortly after the occlusion. During the recovery phase, NADH was reoxidized soon after recirculation, whereas the pH and K+ recovery showed a short delay. ECoG did not recover even when all other parameters reached base-line levels. The recovery of all the measured parameters was correlated to the duration of the ischemic insult; i.e., the recovery from 30 min of ischemia took significantly longer than after 5 min of ischemia. We conclude that pH recovery depends on recirculation and adequate O2 supply to the tissue, whereas K+ recovery required not only an adequate O2 supply but also the integrity of the adenosine triphosphatase system.

Animals↗
PubMed1984

Brain function in psychiatric disorders. II. Regional cerebral blood flow in medicated unipolar depressives.

Regional cerebral blood flow was measured during resting baseline and the performance of a verbal and a spatial task in 14 medicated depressives and 25 matched controls. Overall resting flows did not differ, nor were there hemispheric or anteroposterior differences between patients and controls for resting flows. Differences between patients and controls were evident during cognitive activity, and the effects were different for male and female patients. Depressed female patients had higher than normal flows in all conditions, whereas depressed male patients had lower than normal resting flows, which increased to normal during cognitive activity. Their anterior flows increased for the verbal task but not for the spatial task.

Adult↗
PubMed1984

Contralateral cerebellar hypometabolism following cerebral insult: a positron emission tomographic study.

Positron emission tomographic studies of 16 patients with cerebral ischemia and brain tumor showed asymmetries in cerebellar metabolism not encountered in 14 normal control subjects. An asymmetry was present in 62.5% of cases. The lower metabolic rate occurred in the cerebellar hemisphere contralateral to the cerebral lesion (p less than 0.001; sign test). In all cases computed tomography showed the supratentorial lesion to be unilateral and the posterior fossa contents to be unaffected. The presence of depressed cerebellar metabolism was highly associated with involvement of the contralateral parietal lobe (p less than 0.02; phi coefficient). The presence of a cerebellar abnormality was not related to the presence of any particular sign. Serial studies showed normalization of cerebellar metabolism over time. It is likely that this effect is a result of interruption of the functional interconnections between the cerebrum and the cerebellum.

Adult↗
PubMed1984

Positron emission tomographic studies of perceptual tasks.

Metabolic mapping in conjunction with positron emission tomography was used to examine the response of the human brain to physiological stimuli. Local cerebral glucose consumption was measured by means of the fluorine-18-labeled fluorodeoxyglucose technique. The coefficient of variation of this measurement for various gray matter structures varies from 19.5 to 26.4%. If repeat measurements are made in the same subject using carbon-11-labeled deoxyglucose as the tracer, the coefficient of variation of repeat measurements for these same structures is reduced to between 5.2 and 8.7%. Stimulation of one visual field in normal subjects produced a significant (p less than 0.01) increase in metabolism in the contralateral visual cortex. An auditory stimulus consisting of a tape-recorded factual story presented through earphones to only one ear produced a significant (p less than 0.001) increase in glucose consumption in the contralateral temporal cortex. The effects of vigilance or attention on cerebral metabolism were also examined. There was significantly greater metabolism in the right versus the left inferior parietal region in subjects attending to a visual or auditory task compared with those who were not. Anxiety appeared to produce significantly greater glucose utilization in the right hemisphere compared with the left in those subjects who had a higher level of anxiety during the measurement. Metabolic mapping promises to be a powerful new tool in furthering our understanding of the organization and functioning of the human brain.

Anxiety↗
PubMed1984

Effects of sufentanil on regional cerebral glucose utilization in rats.

Sufentanil, a narcotic five to ten times more potent than fentanyl, reduces cortical cerebral blood flow and oxygen consumption in rats, with seizure activity occurring in some animals. However, the effects of sufentanil on blood flow and metabolism in subcortical structures have not been defined clearly. The present study examines the effects of intravenous sufentanil (40 or 160 micrograms/kg) on regional cerebral glucose utilization (r-CMRgl) in paralyzed, mechanically ventilated rats using 2-deoxy-D-[14C]glucose and autoradiography. Regional cerebral glucose utilization was decreased in all cortical areas examined in rats receiving either dose of sufentanil; the larger dose of sufentanil (160 micrograms/kg) decreased r-CMRgl in cortical structures 20-45% below control values. Two subcortical structures, the caudate nucleus and the ventral thalamic nucleus, manifested a 39-54% decrease in r-CMRgl at each dose of sufentanil. Limbic system structures responded differently. Sufentanil 40 micrograms/kg produced focal areas of markedly increased r-CMRgl in the amygdala of two of six rats; sufentanil 160 micrograms/kg produced marked increases in r-CMRgl in focal areas of hippocampus (four of eight rats) and amygdala (seven of eight rats). EEG activation suggestive of seizure activity was evident in the two low-dose sufentanil and six of the seven high-dose sufentanil rats that had focally increased r-CMRgl in the amygdala. Sufentanil causes a selective increase in r-CMRgl in subcortical limbic nuclei, particularly the amygdala, in the rat. EEG patterns of seizure activity may reflect subcortical, rather than cortical activation.

Anesthetics↗
PubMed1984

Cerebral hemodynamics in the diagnosis of normal pressure hydrocephalus.

We studied the effect of CSF drainage on cerebral blood flow (CBF) in normal pressure hydrocephalus (NPH) and non-NPH dementia using the 133Xenon inhalation technique. Dementia patients had lower CBF than matched elderly normals. Flow values for NPH and non-NPH patients did not differ before or after CSF drainage. CBF did not increase after lumbar puncture, and these measurements were not useful in predicting the outcome of ventricular shunt surgery. Postoperative CBF did not increase after successful shunting.

Cerebrospinal Fluid Shunts↗
PubMed1984

Effect of transfusion therapy on arteriographic abnormalities and on recurrence of stroke in sickle cell disease.

Stroke is a relatively frequent and severe complication of sickle cell disease. We performed cerebral arteriograms in 30 patients with sickle cell disease to evaluate the cause of acute neurologic deficits and to assess the effects of transfusion therapy given for a year or more after the acute episode. Twenty-three patients with motor and speech deficits had multiple abnormalities of major cerebral arteries. The internal carotid and anterior and middle cerebral arteries showed stenosis and/or occlusion at their common junction. Irregular luminal surfaces suggested that endothelial damage and intimal hyperplasia were the basis of stroke. Prolonged transfusion therapy nearly stopped progression of stenosis and markedly decreased the irregularity of the luminal surfaces; in 4 untransfused patients, the degree of stenosis doubled and the luminal abnormalities persisted. Prior to transfusion, 90% of patients had recurrence of stroke. With transfusion therapy, only 10% of patients had recurrence despite persistent arterial abnormalities. Clinical recurrences per patient-month decreased 75-fold. The patients tolerated prolonged transfusion therapy well, despite progressive iron accumulation. Seven patients with smooth abnormalities of a single artery, nonocclusive changes, or with normal arteriograms did not receive transfusions. Only one of this group had recurrence of symptoms.

Acute Disease↗
PubMed1983

The effect of antidepressant drugs on regional cerebral glucose utilization in the rat.

The 2-deoxyglucose (2-DG) technique is a potentially powerful method for assessing the effect of centrally acting drugs on local neuronal function in the brain. Since little is established on the effect of antidepressant drugs on local functional activity throughout the brain, we have employed this technique to study the effects of desmethylimipramine (DMI), a tricyclic antidepressant, and assessing the effect of centrally acting drugs on local neuronal function in the brain. Since little is established on the effect of antidepressant drugs on local functional activity throughout the brain, we have employed this technique to study the effects of desmethylimipramine (DMI), a tricyclic antidepressant, and assessing the effect of centrally acting drugs on local neuronal function in the brain. Since little is established on the effect of antidepressant drugs on local functional activity throughout the brain, we have employed this technique to study the effects of desmethylimipramine (DMI), a tricyclic antidepressant, and phenelzine, a monoamine oxidase inhibitor used clinically as an antidepressant, on local glucose utilization. The drugs were administered either as an acute dose, or repeatedly for 7 days, or chronically for 28 days. The local metabolic rate of glucose was determined in 30 regions of rat brain. Acute DMI increased glucose utilization in 11 regions whereas, in contrast, chronic DMI decreased glucose utilization in 7 regions of rat brain. Many of the areas affected are those of the telencephalon and diencephalon that receive prominent noradrenergic innervation. This is consistent with the notion that acute DMI treatment leads to enhanced and chronic DMI treatment leads to reduced noradrenergic functioning in the CNS. In contrast to these effects with DMI, phenelzine had little effects on glucose utilization either after acute or chronic dosing.

Animals↗
PubMed1983

Brain function in psychiatric disorders. I. Regional cerebral blood flow in medicated schizophrenics.

We measured regional cerebral blood flow during resting baseline and the performance of verbal and spatial tasks in 15 medicated schizophrenics and 25 matched controls. Patients did not differ from controls in resting flows but showed different blood-flow changes during task performance. Controls replicated earlier findings in normal subjects: flow increased during task performance, and the hemispheric increase was greater in the left for the verbal and in the right for the spatial task. In contrast, patients showed no flow asymmetry for the verbal task and greater left hemispheric increase for the spatial task. The latter finding is consistent with the hypothesis that schizophrenia is associated with left hemispheric overactivation for spatial tasks. In addition, schizophrenic women had unusual flow changes in that their highest flow increase was for the verbal task.

Adult↗
PubMed1983

A cognitive-motor network demonstrated by positron emission tomography.

The rate of local cerebral glucose metabolism was measured in subjects receiving a verbal (n = 4) and a spatial (n = 4) task. The verbal task produced greater metabolism in Wernicke's area relative to the right hemispheric homotopic region, whereas the spatial task produced greater metabolic activity in the right hemispheric homotopic region. Broca's area and its right hemisphere counterpart showed symmetrical activity during the verbal task, but there was a significant asymmetry to the right during the spatial task. Lateralized task effects were also obtained in the frontal eye fields, supporting a hypothesized neural network linking cognitive activity with motor orientation.

Adult↗