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Biomedical subjects

M E Raichle

Publications and source records attributed to M E Raichle.

At least 163 records · Page 9Linked to original sources
PubMed1982

Effects of hemorrhagic and pharmacologic hypotension on cerebral oxygen utilization and blood flow.

Cerebral oxygen utilization and blood flow were measured by the washout of oxygen-15 isotopes injected into the internal carotid artery in baboons during hypotension produced by acute hemorrhage, trimethaphan, and sodium nitroprusside. Acute hemorrhage, trimethaphan, and sodium nitroprusside lowered the mean arterial blood pressure to 52 per cent, 55 per cent, and 47 per cent, respectively, of control values. There were corresponding decreases in cerebral blood flow to 76 per cent (P less than 0.01), 81 per cent (P less than 0.05), and 79 per cent (P less than 0.01) of control values. When the mean arterial blood pressure was decreased 11 per cent with hemorrhage, auto-regulation of the cerebral vasculature was preserved and cerebral oxygen utilization increased 10 per cent (P less than 0.01). When cerebral autoregulation was lost with acute hemorrhage, cerebral oxygen utilization declined 17 per cent (P less than 0.05). When cerebral autoregulation was lost with pharmacologic hypotension, cerebral oxygen utilization was preserved with trimethaphan and increased 17 per cent (P less than 0.05) with sodium nitroprusside. The increase in cerebral oxygen utilization seen with sodium nitroprusside and hemorrhagic (autoregulation preserved) hypotension may be due to stimulation of the sympathetic nervous system with release of circulating catecholamines. However, the mechanism by which circulating catecholamines mediate an increase in cerebral oxygen metabolism during hypotension is not clear.

Animals↗
PubMed1981

Measurement of cerebral vascular extraction fractions in the rat using intracarotid injection techniques.

A small volume (5 microliters) common carotid arterial injection method is described for the quantitation of cerebral vascular extraction fractions (Et) of diffusion limited tracer molecules in the rat. The method is a modification of a technique introduced by Oldendorf and widely used for the study of blood-brain barrier phenomena. While the Oldendorf technique has proven valuable for estimating the relative permeabilities of substances, it is limited in measuring Et under conditions of physiologically or pharmacologically altered permeability or blood flow. The method described in this paper--using a small volume (5 microliters) common carotid injection, a freely diffusible reference tracer, [14C]butanol, and a 5 sec circulation time--allows for measurements of Et that reflect changes in blood flow and small differences in permeability. The modified method is important for the study of the regulation of cerebral vascular permeability and flow in an inexpensive animal model.

Animals↗
PubMed1981

Cerebral hemodynamics and metabolism in postoperative cerebral vasospasm and treatment with hypertensive therapy.

A 24-year-old woman developed subarachnoid hemorrhage from an aneurysm at the bifurcation of the right internal carotid artery. Following successful clipping of the aneurysm she developed a left hemiplegia associated with focal cerebral vasospasm, which markedly improved when systemic blood pressure was raised with intravenous dopamine infusion. Regional cerebral blood flow and oxygen utilization were significantly depressed in both cerebral hemispheres, while blood volume was significantly elevated only on the side with vasospasm. Oxygen extraction was significantly elevated in both hemispheres, indicating a generalized impairment in oxygen delivery to the brain.

Adult↗
PubMed1981

An introduction to the measurement of the cerebral oxygen uptake rate by inhalation of 15O2; analysis of the contribution of 15O2 and H2 15O in brain radioactivity.

This paper introduces a model for the computation of the regional cerebral metabolic rate of oxygen from the data of cerebral regional radioactivity collected after inhalation of 15O2. A method was devised for the differential determination of the respective contribution of radiooxygen and of radiowater in the inflow and the outflow of radioactivity in the brain after or during such on inhalation. The results demonstrate the feasability of such a model and outline some of the methodological to be taken into account in the numerical analysis of the data.

Animals↗
PubMed1981

Measurement of local cerebral blood flow and metabolism in man with positron emission tomography.

Positron emission tomography (PET) is a computer based, nuclear medicine imaging technique that permits the quantitative, in vivo measurement of local tissue concentration or radiopharmaceuticals labeled with positron-emitting radionuclides (i.e., 15O, 13N, 11C, and 18F). These measurements can be made through any desired section of the human brain thus creating, in effect, a quantitative in vivo autoradiogram. Combining this imaging technique with appropriate radiopharmaceuticals and mathematical models for the interpretation of tracer behavior permits the safe measurement of local blood flow and metabolism in humans.

Brain↗
PubMed1980

The effect of dibenzazepines (tricyclic antidepressants) on cerebral capillary permeability in the rat in vivo.

The degree of equilibration of [3H]water across the cerebral capillary was evaluated by measuring its cerebral extraction fraction (Ew) by using a dual label radioactive tracer technique. All tricyclic antidepressants (125 mumol/kg i.p. at 5 min) increased Ew as compared to base line. The rank order of the drugs in producing this response was doxepin greater than amitriptyline greater than imipramine greater than nortriptyline greater than desmethylimipramine greater than protriptyline. The effect of amitriptyline, the prototype tricyclic for this study, was rapid in onset (maximal effect within 5 min), reversible (duration 15 min), dose-dependent and generalized throughout the brain. Amitriptyline also induced a marked increase in the cerebral extraction fraction of [3H]ethanol. A difference in the time course of the drug effect on these two tracers indicated that the elevation in E was due to the increase in cerebral capillary permeability to both polar and lipid soluble substances. This work demonstrates that tricyclic antidepressants have important central effects on non-neuronal tissue.

Amitriptyline↗
PubMed1979

beta-Adrenergic regulation of adenosine 3',5'-monophosphate concentration in brain microvessels.

Norepinephrine increases the concentration of adenosine 3',5'-monophosphate (cyclic AMP) in an incubated suspension of brain microvessels. This response can be matched by other drugs that stimulate the beta receptors, but the alpha-adrenergic agonist phenylephrine is without effect; beta-adrenergic blockade abolishes the response while alpha-adrenergic blockade produces no change. The data support the contention that cerebral capillary function is subject to adrenergic neural control.

Adrenergic beta-Agonists↗