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Biomedical subjects

M Reivich

Publications and source records attributed to M Reivich.

At least 73 records · Page 4Linked to original sources
PubMed1989

Parallel changes in brain tissue blood flow and mitochondrial function during and after 30 minutes of bilateral forebrain ischemia in the gerbil.

Forebrain ischemia was induced in Mongolian gerbils by bilateral occlusion of the common carotid arteries for 30 minutes. These animals do not have a complete circulus arteriosus Willisii. Mitochondria were prepared from the forebrain tissue at the end of the 30 minutes occlusion period as well as at different time points after the release of the occlusion. Tissue blood flow in the forebrain was also determined by measuring the brain tissue accumulation of 14C-iodoantipyrine. Tissue blood flow in the forebrain decreased from a control level of 1.43 +/- 0.03 ml/min/gr to 0.13 +/- 0.03 ml/min/gr by the 30th minute of ischemia, increased to 1.12 +/- 0.25 ml/min/gr after 5 minutes of reflow, but decreased again to 0.41 +/- 0.07 ml/min/gr after 1 1/2 hours of reflow. Oxygen consumption rate of mitochondria prepared from the forebrain (glutamate + malate as substrates in the presence of ADP) was 98 +/- 13 nmoles O2/min/mg protein in control animals, decreased to 61 +/- 9 nmoles O2/min/mg protein after 30 minutes of occlusion, recovered to 106 +/- 9 nmoles O2/min/mg protein during the first 30 minutes of reperfusion. During extended reperfusion, mitochondrial respiratory activity declined reaching 20 +/- 5 nmoles O2/min/mg protein after 5 1/2 hours of reperfusion. Respiratory control ratio of the mitochondria (relative increase of respiration upon addition of ADP) was 9.2 +/- 1.3 in control animals, 7.0 +/- 1.5 after 30 minutes of carotid occlusion, 9.0 +/- 1.2 after 30 minutes of reperfusion, and 5.8 +/- 0.8 after 5 1/2 hours of reperfusion. Superoxide dismutase activity of the forebrain mitochondria was 5.10 +/- 0.7 I.U./mg protein in control animals, decreased to 3.3 +/- 1.6 I.U./mg protein after 30 minutes of occlusion and remained at this level throughout the reperfusion period. These data confirm earlier reports that deterioration of mitochondrial function may contribute to the development of ischemic and post-ischemic brain tissue damage. It also appears possible that postischemic damage of mitochondrial function develops secondary to postischemic deterioration of tissue blood flow.

Animals↗
PubMed1988

Positron emission tomography in patients with glioma. A predictor of prognosis.

Positron emission tomography (PET) studies have been performed using 18-F-fluorodeoxyglucose in 29 adult subjects with primary brain tumors. Seventy-two percent of the patients were treated previously. The glucose metabolic state in the lesions was increased in 16 patients, and was normal or decreased in 13 patients. The hypermetabolic tumors tended to behave in a more malignant fashion. Patients with hypermetabolic tumors had a median survival of 7 months after PET scan, compared to 33 months for those with hypometabolic lesions. Among the high-grade glioma patients, the PET results separated them into a good prognosis group (hypometabolic, with 78% 1-year survival) and a poor prognosis group (hypermetabolic, with a 29% 1-year survival after PET). These results suggest that glucose metabolic studies may provide an independent measure of the aggressiveness of a brain tumor, and may supplement pathologic grading.

Adult↗
PubMed1988

In vivo measurement of cytosolic free calcium during cerebral ischemia and reperfusion.

An increase in cytosolic free calcium concentration ([Ca2+]i) may trigger irreversible cell injury following cerebral ischemia. We have measured changes in [Ca2+]i in cat cortex in vivo during ischemia produced by 1 hour of middle cerebral artery occlusion and during 30 minutes of reperfusion. Indo-1, a fluorescent Ca2+ indicator, was loaded into the exposed cortex by superfusion, and changes in the [Ca2+]i signal (400/506 nm ratio) were measured microfluorometrically during ultraviolet excitation (340 nm). The nicotinamide adenine dinucleotide/reduced nicotinamide adenine dinucleotide (NAD/NADH) redox state and hemodynamic changes were measured simultaneously. The animals showing severe deterioration in their electroencephalograms (EEG) showed a progressive increase in the [Ca2+]i signal during ischemia (baseline: 1.46 +/- 0.05; 60 minutes after occlusion: 2.99 +/- 0.37; n = 7). At 30 minutes following reperfusion, the animals showing little recovery in their EEG exhibited a further increase in [Ca2+]i (4.71 +/- 0.87, n = 3), whereas animals showing significant recovery in their EEG also showed recovery of [Ca2+]i (1.55 +/- 0.09, n = 4). By contrast, the moderate or mild stroke animals with less deterioration in their EEGs showed no increase in [Ca2+]i during either ischemia or reperfusion. These data suggest that the increase in [Ca2+]i might be closely related not only to deterioration of brain function during ischemia but also to poor recovery during the reperfusion period.

Animals↗
PubMed1988

Positron emission tomography and subcortical glucose metabolism in schizophrenia.

Our previous observation of a disturbed subcortical-to-cortical gradient of activity in schizophrenia was further elucidated by examining glucose metabolism in three subcortical structures: lenticular nucleus, caudate nucleus, and thalamus. Local cerebral glucose metabolism was determined with 18F-fluorodeoxyglucose using positron emission tomography (PET) in a sample of 20 unmedicated schizophrenics and 18 normal volunteers. Repeated evaluations were performed for 12 schizophrenics following treatment with psychotropic medications and for 11 controls. Unmedicated schizophrenics had lower cortical and caudate absolute metabolic rates. Subcortical-to-cortical ratios for the lenticular nucleus and thalamus were increased in schizophrenics compared with controls, reflecting a preservation of activity in these structures relative to decreased cortical metabolism. When patients were grouped by length of medication-free period before the initial study, there was a trend for patients who had been medication free less than 6 months to have higher subcortical ratios. However, there were no consistent effects of medication in the subsample of patients whose PET studies were repeated following treatment. The results demonstrate relative hypermetabolism in structures implicated in dopamine pathways. An understanding of the physiological significance of this finding awaits the combined measurement of metabolic activity and neuroreceptors in schizophrenics.

Adult↗
PubMed1988

Regional variations in human newborn cerebral blood flow.

Regional differences in the local cerebral metabolic rate of glucose have been reported in newborn infants. This study was performed to determine if comparable differences exist in neonatal regional cerebral blood flow (rCBF). In 21 infants, rCBF was measured with a modified xenon 133 (133Xe) clearance technique by means of eight extracranial detectors positioned over four homologous regions (frontal, parietal, temporal, and occipital). The rCBF was lowest in the frontal region, higher in the parietal region, and highest in the temporal and occipital regions. Regional differences in rCBF may be caused by regional differences in brain development and function.

Brain↗
PubMed1988

In vivo fluorometric measurement of changes in cytosolic free calcium from the cat cortex during anoxia.

A new approach to assess the mean changes in intracellular free calcium [Ca2+]i directly from the cortex in situ is described along with the [Ca2+]i changes during nitrogen anoxia. Following incision of the dura and part of the pia-arachnoid membrane, quin2 acetoxymethyl ester, 100 microM in artificial CSF, was superfused for 60 min onto the cat cortex. A small cortical area was irradiated with ultraviolet rays (350/30 nm) and the changes in the fluorescence and reflectance were recorded microfluorometrically at 506 and 366 nm, respectively. The net change in the quin2-Ca2+ fluorescence was calculated after correction for the hemodynamic artifact and subtraction of the basal NADH change. The quin2-Ca2+ fluorescence began to increase significantly (48.0 +/- 13.4 units; p less than 0.05) 20 s prior to the isoelectric electrocorticogram (ECoG) and remained elevated during nitrogen anoxia. It decreased steeply 7.3 +/- 1.7 s prior to the recovery of the ECoG activity after the animal was reoxygenated. Thus, the changes in the intracellular free calcium preceded those of the ECoG during a reversible anoxic insult, suggesting that the increase in the [Ca2+]i might be related to the electrical failure during anoxia.

Aminoquinolines↗
PubMed1988

Effect of the ganglioside GM1 on neurologic function, electroencephalogram amplitude, and histology in chronic middle cerebral artery occlusion in cats.

The effect of the ganglioside GM1 on amplitude of the electroencephalogram, neurologic function, and histology has been studied in chronic middle cerebral artery occlusion in cats. Ischemia was produced by a 2-hour occlusion of the left middle cerebral artery and was followed by a 7-day observation period. GM1 was intravenously administered 30 minutes after occlusion and daily during the observation period. Using the reduction in the electroencephalogram amplitude to measure stroke severity, three cats with mild, three cats with moderate, and three cats with severe stroke were treated with 5 mg/kg GM1. Nine cats, three in each group, were treated with 30 mg/kg GM1, while nine cats, three in each group, received middle cerebral artery occlusion but no treatment. In all cats there was a precipitous fall in mean electroencephalogram amplitude during occlusion, followed by a secondary fall during the observation period. Treated cats showed better recovery of electroencephalogram amplitude during the first 4 hours of reperfusion and a smaller secondary fall than untreated cats. Treated cats, especially those treated with 5 mg/kg GM1, showed significant recovery of neurologic deficits compared with untreated cats. Histologic damage was less in treated cats than in untreated cats. Some cats treated with 30 mg/kg GM1 exhibited convulsions, whereas no untreated cat showed any seizure activity. Our findings suggest that gangliosides may improve the recovery of both neurologic deficits and morphologic damage in the central nervous system. These positive effects might be tentatively explained by stimulation of enzymatic activities such as Na+, K+-ATPase and adenyl cyclase.

Animals↗
PubMed1988

Cerebral metabolism and patterned visual stimulation: a positron emission tomographic study of the human visual cortex.

We studied the impact of visual stimulation upon cerebral metabolism in normal young men using FDG-PET. Results obtained from subjects receiving patterned visual stimulation while performing an ocular fixation task were compared with results from ocular fixation alone. Visual stimulation in the macular region of either hemifield produced significant increases in metabolism of the contralateral posterior striate cortex. Visual stimulation induced highly significant asymmetries in metabolism of the prefrontal and inferior parietal cortices. Metabolic activation in extrastriate areas tended to be right-sided. These findings support the classic notion of retinotopic organization within the primary visual sensory cortex. They also indicate that the patterns of cerebral metabolism are not equivalent between the two cerebral hemispheres. This latter finding suggests that in humans the right cerebral hemisphere may be specialized for visual processing.

Adolescent↗
PubMed1988

Resolving metabolic abnormalities in a case of pure alexia.

We report resolving metabolic abnormalities corresponding to clinical improvement in a patient with pure alexia secondary to acute cerebral infarction. Local cerebral glucose metabolism (lCMRgl) was measured with positron emission tomography (PET) using 18F-fluorodeoxyglucose (18F-FDG) close to ictus and 4 1/2 months later. Serial CTs and a subsequent MRI demonstrated small, unchanging left-hemispheric lesions involving the area of the lateral geniculate body and the splenium of the corpus callosum. PET demonstrated the evolution of the metabolic abnormality resulting from intrahemispheric (lateral geniculate) and interhemispheric (splenium) disconnection in the absence of occipital lobe infarction. This case illustrates that cerebral disconnection can result in the syndrome of pure alexia. The factors accounting for focal hypometabolism in the absence of cerebral infarction are discussed.

Brain↗
PubMed1988

Positron emission tomography in the investigation of central nervous system disorders.

Positron emission tomography is a noninvasive tomographic technique for measuring regional tissue concentrations of labeled radionuclides in man. Detection of two photons emitted from the annihilation of a positron and an electron is used to reconstruct the distribution of a positron-emitting isotope within an organ. PET provides the capacity to measure quantitatively the local tissue distribution of a variety of radionuclides that are attached to compounds that distribute according to function. Commonly measured functions include local cerebral metabolism using 18F-fluorodeoxyglucose or 11C-deoxyglucose, cerebral blood flow, cerebral oxygen utilization, and cerebral blood volume. Clinical applications of PET are multiple, involving normal and disease states. By demonstrating the metabolic alterations, PET adds another dimension to our understanding of the brain, which up until recently has been based on the structural changes seen on CT and MRI.

Aging↗
PubMed1987

Cerebral glucose consumption following verbal auditory stimulation.

We studied the effect of auditory stimulation upon cerebral glucose metabolism in young normals. The stimulus consisted of a non-English discourse which was presented monaurally to 10 normal blindfolded subjects (5 left ear, 5 right); the opposite ear was plugged. Six subjects studied blindfolded and with ears plugged served as controls. Sixteen discrete homologous cortical and subcortical regions of interest were examined. Regional glucose consumption and side-to-side differences in glucose metabolism were analyzed. Monaural stimulation produced significant increases in temporal metabolism contralateral to the side of stimulation. Significant asymmetries in metabolism were found at the temporoparietal junction, inferior parietal region, insula and corpus collosum. The left frontal speech areas remained unaffected. These findings demonstrate that in man the primary auditory pathways retain a contralateral organization. Further, cerebral activation induced by non-meaningful verbal stimulation is widespread within the left temporal and parietal regions but does not impact upon the frontal speech cortices.

Adult↗
PubMed1987

Regional brain function in schizophrenia. II. Repeated evaluation with positron emission tomography.

Cerebral glucose metabolism was measured twice in a sample of 15 schizophrenics and eight controls, using positron emission tomography (PET) with 18-F-fluorodeoxyglucose. Studies were separated by three to 33 weeks. Patients were unmedicated during the first study, and the majority were receiving neuroleptics during the second study. There were no changes from study 1 to study 2 in average whole-brain metabolic rates, regional cortical activity, or the gradient of subcortical to cortical activity. The steeper subcortical to cortical gradient in schizophrenics, present in the first study, persisted in the second. Changes in this gradient were uncorrelated with changes in clinical status. Laterality (right-left) was stable across studies, and changes toward higher right relative to left hemispheric metabolism were correlated with clinical improvement. The results support the hypothesis of abnormal hemispheric activity in schizophrenia and implicate the subcortical-cortical gradient as another dimension that merits further exploration.

Adult↗
PubMed1987

Age and regional cerebral blood flow at rest and during cognitive activity.

The relationship between age and regional cerebral blood flow (rCBF) activation for cognitive tasks was investigated with the xenon Xe 133 inhalation technique. The sample consisted of 55 healthy subjects, ranging in age from 18 to 72 years, who were studied during rest and during the performance of verbal analogy and spatial orientation tasks. The dependent measures were indexes of gray-matter rCBF and average rCBF (gray and white matter) as well as the percentage of gray-matter tissue. Advanced age was associated with reduced flow, particularly pronounced in anterior regions. However, the extent and pattern of rCBF changes during cognition was unaffected by age. For the percentage of gray matter, there was a specific reduction in anterior regions of the left hemisphere. The findings suggest the utility of this research paradigm for investigating neural underpinnings of the effects of dementia on cognitive functioning, relative to the effects of normal aging.

Adolescent↗
PubMed1987

Recovery of vision after ischemic lesions: positron emission tomography.

We used [18F]fluoro-2-deoxyglucose positron emission tomography (PET) to study serial changes in the local cerebral metabolic rate of glucose in 5 patients with ischemic lesions of the posterior afferent visual system causing homonymous visual field defects. All 5 patients had striking impairment of glucose metabolism in the striate cortex shortly after ictus. In 2 patients, visual field defects abated, and repeat PET scans showed reduced size of the metabolic lesion and improvement of striate metabolism. Three patients did not recover vision, and repeat PET scans did not show improvement. Patients who recovered vision had ischemic lesions outside the occipital lobe, while those who did not experience improvement had primary damage to the occipital lobe itself.

Aged↗
PubMed1987

Regional cerebral glucose metabolism in aphemia: a case report.

Local cerebral metabolism was determined in a patient suffering aphemia following cerebral infarction using the 18FDG-PET technique. The syndrome was characterized by profound ictal nonfluency with sparing of other language functions. Speech subsequently improved so that content and grammar were appropriate but mild dysprosody persisted. Conventional CT showed no lesion of the left hemisphere while PET revealed a discrete focus of hypometabolism on the left which partially resolved on serial studies. The metabolic lesion could be localized to the region of the inferior precentral gyrus and the adjacent subcortical space.

Aged↗
PubMed1987

Cerebral energy metabolism measured in vivo by 31P-NMR in middle cerebral artery occlusion in the cat--relation to severity of stroke.

The energy metabolism of the brain has been measured in a middle cerebral artery (MCA) occlusion model in the cat utilizing 31P-nuclear magnetic resonance (NMR). 31P-NMR spectra were serially obtained during 2 h of ischemia and a subsequent 4-h recovery period. The ratio of creatine phosphate (PCr) to inorganic phosphate (Pi) (PCr/Pi) showed a precipitous decrease in parallel with changes in electroencephalographic (EEG) amplitude in severe strokes during ischemia as well as during recirculation. Animals with mild strokes, as determined by EEG criteria, exhibited a much smaller decrease in PCr/Pi during ischemia. In the severe strokes, there was a splitting and significant shift of the Pi peak immediately after occlusion. In addition, the shifted Pi peak rapidly increased and remained elevated throughout the study. In the mild strokes, Pi also increased, but not as markedly. Intracellular pH determination by chemical shift of the Pi peak revealed a decrease from 7.1 to 6.2-6.3 during ischemia and the subsequent recovery period in the animals with severe strokes, whereas the pH in the animals with mild strokes did not show a significant change. A gradual decrease in adenosine triphosphate (ATP) to 57-79% of the control was exhibited in severely stroked animals during both the ischemia and the recovery period, whereas there was no change in ATP in the mild stroked animals. These results suggest that the dynamic process of pathophysiological changes in an MCA occlusion model in the cat leads to significant differences in cerebral metabolism between animals with mild and severe strokes.

Adenosine Triphosphate↗
PubMed1987

The reproducibility of the 133Xe inhalation technique in resting studies: task order and sex related effects in healthy young adults.

Repeated applications of the 133Xe inhalation technique for measuring regional CBF (rCBF) were made during consecutive resting conditions in a sample of young healthy subjects. Subjects were grouped by order and by sex [nine had resting studies as the initial two measurements in a series of four measurement (six men, three women) and six had these measurements later (two men, four women)]. Three flow parameters were examined: f1 (fast flow) and IS (initial slope) for gray matter CBF, and CBF-15 for mean CBF (gray and white matter over 15-min integration), as well as w1, the percentage of tissue with fast clearing characteristics. With all groups combined, there were no significant differences between the two resting measurements, and high test-retest correlations were obtained for the flow parameters and w1. Analyses by order and sex grouping revealed, for the flow parameters, significant interactions of test-retest difference with order. Repeated initial studies showed reduced CBF from the first to second measurement, whereas resting studies performed later in the series showed no reduction. Interactions for test-retest difference with sex indicated that reduced CBF in serial measures was more pronounced for women. No hemispheric or regional specificity to account for these effects was found. Correction for PaCO2 differences did not alter these results. The results resemble data regarding habituation effects measured for other psychophysiologic measures, and suggest that reduction in CBF for consecutive measurements made on the same day may reflect habituation. This underscores the importance of controlling for effects of habituation on serial measurements of CBF and metabolism.

Administration, Intranasal↗