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Biomedical subjects

O B Paulson

Publications and source records attributed to O B Paulson.

At least 19 recordsLinked to original sources
PubMed1992

The effect of ketanserin on cerebral blood flow and cerebrovascular CO2 reactivity in healthy volunteers.

The effect of the anti-hypertensive agent ketanserin on the cerebral blood flow (CBF) and the cerebrovascular CO2 reactivity was examined in 10 healthy volunteers. Ketanserin was administered as an intravenous bolus of 10 mg followed by an infusion of 6 mg/h. Before administration CBF was measured by single photon emission computerized tomography (SPECT) of inhaled 133Xenon. Then arterial CO2 tension was subsequently decreased by voluntary hyperventilation and increased by breathing an air/CO2 mixture. The relative changes in CBF induced by the changes in arterial CO2 tension were estimated by the cerebral arterio-venous oxygen content difference method. One hour following the start of ketanserin infusion the SPECT measurement and CO2 manipulations were repeated. The CO2 reactivity (expressed as the slope of the regression line of the linear relation between CBF and PaCO2), was unchanged, i.e. 3.2%/0.1 kPa before ketanserin and 4.1%/0.1 kPa during ketanserin, respectively. Using regression lines from a semi-logarithmic plot the CO2 reactivity was also unchanged 3.4%/0.1 kPa and 3.5%/0.1 kPa, respectively. Ketanserin did not change CBF. The cerebral oxygen metabolism (CMRO2) was decreased 19% one hour after the start of infusion of ketanserin. In conclusion administration of ketanserin in a clinically relevant dose to healthy volunteers does not change the regional CBF not the cerebrovascular CO2 reactivity, but a decrease in CMRO2 was observed. However further studies are needed to clarify whether ketanserin in fact has a depressing effect on CMRO2 or whether the different results are caused by methodological errors or stochastic variation.

Adult↗
PubMed1992

Increased cerebral blood flow in anemic patients on long-term hemodialytic treatment.

CBF was measured in 15 patients on chronic hemodialytic treatment. CBF was measured with xenon-133 inhalation using single photon emission tomography. In addition, computerized tomography (CT) and a neurological examination were done prior to hemodialysis. Mean CBF was 66.2 +/- 17.3 (SD) ml 100 g-1 min-1, which was significantly higher (t-test, p less than 0.05) than for an age-matched control group (54.7 +/- 10.2 ml 100 g-1 min-1). However, the hematocrit for the patients was considerably lower, 0.30 +/- 0.07, as compared to 0.43 +/- 0.03 in the controls. A significant negative correlation was observed between CBF and the hematocrit (y = -1.79x + 120.7, r = -0.71, p less than 0.01). Calculating CBF from this equation in the dialyzed patients using a hematocrit of 0.43 yielded a mean CBF value of 43.7 ml 100 g-1 min-1, i.e., 20% below the expected. Two patients showed a focal CBF decrease. CT showed central or cortical atrophy in five patients, and two had small hypodense lesions. The neurological examination revealed slight to moderate dementia in seven cases. Although mean CBF was found to be increased by 21% as compared to the control group, an even higher CBF level would have been expected to outweigh the decreased oxygen carrying capacity of the blood. The findings suggest a lowered metabolic demand of the brain tissue, probably due to subtle brain damage.

Adult↗
PubMed1992

Effect of nitric oxide blockade by NG-nitro-L-arginine on cerebral blood flow response to changes in carbon dioxide tension.

The importance of nitric oxide (NO) for CBF variations associated with arterial carbon dioxide changes was investigated in halothane-anesthetized rats by using an inhibitor of nitric oxide synthase, NG-nitro-L-arginine (NOLAG). CBF was measured by intracarotid injection of 133Xe. In normocapnia, intracarotid infusion of 1.5, or 7.5, or 30 mg/kg NOLAG induced a dose-dependent increase of arterial blood pressure and a decrease of normocapnic CBF from 85 +/- 10 to 78 +/- 6, 64 +/- 5, and 52 +/- 5 ml 100 g-1 min-1, respectively. This effect lasted for at least 2 h. Raising PaCO2 from a control level of 40 to 68 mm Hg increased CBF to 230 +/- 27 ml 100 g-1 min-1, corresponding to a percentage CBF response (CO2 reactivity) of 3.7 +/- 0.6%/mm Hg PaCO2 in saline-treated rats. NOLAG attenuated this reactivity by 32, 49, and 51% at the three-dose levels. Hypercapnia combined with angiotensin to raise blood pressure to the same level as the highest dose of NOLAG did not affect the CBF response to hypercapnia. L-Arginine significantly prevented the effect of NOLAG on normocapnic CBF as well as blood pressure and also abolished its inhibitory effect on hypercapnic CBF. D-Arginine had no such effect. Decreasing PaCO2 to 20 mm Hg reduced control CBF to 46 +/- 3 ml 100 g-1 min-1 with no further reduction after NOLAG. Furthermore, NOLAG did not change the percentage CBF response to an extracellular acidosis induced by acetazolamide (50 mg/kg).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Regulation of cerebral blood flow in health and disease.

A review is given of the normal regulation of cerebral blood flow (CBF) and its pathophysiology in hypertension and stroke. In otherwise healthy hypertensive patients, the absolute level of CBF is the same as in normal subjects. CBF autoregulation, however, is shifted towards higher pressure, thus impairing the tolerance to hypotension. In most patients, this does not interfere with the beneficial effect of treatment, i.e., stroke prevention. Cerebral ischemia, however, may be provoked by overzealous pressure lowering in selected clinical settings: initial or intensified treatment of very severe hypertension, treatment of hypertension in the elderly, and treatment of hypertension in acute stroke. In the latter, a complicated sequence of brain ischemia and hyperemia makes antihypertensive intervention difficult in the early phase, when blood pressure is probably best allowed to decrease spontaneously.

Antihypertensive Agents↗
PubMed1992

Reduced regional cerebral blood flow in Huntington's disease studied by SPECT.

Regional cerebral blood flow (rCBF) was studied in 18 patients with Huntington's disease (HD) and 19 age- and sex-matched controls with high resolution single photon emission computerised tomography (SPECT), using Tc-99m-HMPAO. Significant reductions in tracer uptake were found in the caudate and lentiform nuclei (20 and 8%) and in the cerebral cortex, especially in the frontal and parietal areas (11-13%). No significant reductions were found in the thalamus, mesial temporal cortex, and occipital cortex. Fourteen patients had neuropsychological testing. Relationship between rCBF and cognitive function was tested by regression analysis. A linear relationship was found between test scores of Wisconsin Card Sorting Test, Picture Arrangement Test and blood flow in the caudate nucleus. Other tests of cognitive function (Block Design Test, Face and Word Recognition Test, Street Fragmented Pictures Test, and Similarities Test) correlated better with flow in the cortical regions believed to be involved in solving those particular tests. These findings indicate, that blood flow is reduced in both cortical and subcortical structures in symptomatic HD, and that both reductions in cortical and subcortical blood flow may be related to cognitive function in HD.

Adult↗
PubMed1992

Capillary circulation in the brain.

A close relationship exists between the local capillary density in different brain structures and their local blood flow and metabolism. Capillary density appears to have developed depending on local functional demands. Investigation of single capillary perfusion has shown that all capillaries are perfused with plasma in the brain at any time point. Theories of capillary cycling and capillary recruitment have been based on experimental artifacts. Indirect evidence exists for a heterogeneity of perfusion under normal conditions, especially with respect to erythrocyte flow. The capillary diffusion capacity depends on, among other things, the available capillary surface area, which would increase with recruitment of capillaries. In the case of capillary perfusion heterogeneity, the capillary diffusion capacity may also be increased by homogenization of the perfusion rate (slowly perfused capillaries becoming faster perfused). This could give a physiological impression of an "apparent" increase in the capillary surface area. It is recommended that the terms "capillary cycling" and "recruitment" should be used in conjunction with more specific explanations, like "recruitment of erythrocytes" and "recruitment of previously nonperfused capillaries".

Animals↗
PubMed1979

Transfer of bromocriptine across the blood-brain barrier in man.

The transfer of 14C-bromocriptine across the blood-brain barrier was studied in 10 patients using the double indicator single injection method. The extraction (E) of bromocriptine was 8 % (quartiles: 6 and 14 %). Based on the results the cerebral uptake velocity of bromocriptine was calculated assuming constant arterial drug concentration. Its T 1/2 was found to be 12--24 minutes, depending on the tissue-blood partition coefficient.

Adult↗
PubMed1978

Blood-brain barrier permeability during shortlasting intravascular hyperosmolality.

Blood-brain barrier permeability for 24Na+ and 36Cl- ions and for 3HOH was studied during isoosmolality and during shortlasting intravascular hyperosmolality in twenty-five patients using the double indicatir single injection method. Hyperosmolality was induced by a rapid injection into the internal carotid artery of 8 ml of one of the following hypertonic solutions: 5% saline, 25% mannitol or a contrast medium of the metrizoat group (Isopaque-amine 280). The extractions of the small sodium and chloride ions remained unchanged and essentially zero indicating that 'opening' of the blood-brain barrier did not occur. The blood-brain barrier permeability to water remained unchanged during hyperosmolality, but the extraction of 3HOH increased when mannitol and especially when Isopaque-amine 280 was used as hypertonic agent corresponding to the lower water concentration in these solutions.

Blood-Brain Barrier↗
PubMed1977

The permeability of the blood-brain barrier during electrically induced seizures in man.

The blood-brain barrier (BBB) in man was studied during various conditions using the indicator dilution method of Crone [8]. Using 113m In-DTPA as reference substance the extraction, E, of the small test substances 24Na+, 36Cl-, 14C-urea and 14C-thiourea was estimated from the areas under the venous outflow curves following intracarotid slug injection of tracers. Interlaminar diffusion and red cell carriage were taken into consideration when calculating E. Cerebral blood flow (CBF) was measured using the intra-arterial 133Xe-injection method. Twenty-two patients receiving electroconvulsive therapy (ECT) were studied before and during seizures and during hypercapnia. Before seizures the extraction values in % were as follows: ENa+ 1.6, ECl- 1.9, Eurea 3.9 and Ethiourea 7.8; the corresponding values for the permeability-surface area products (PS) in ml/100 g x min were 0.5, 0.3, 0.7, 4.1, respectively. During seizure a decrease of Ethiourea and an increase of PSurea were significant. During hypercapnia PSNa and PSthiourea rose significantly. Due to the similarity of the findings in those two high flow situations it is suggested that the changes of CBF and not the epileptic activity are responsible for the changes in permeability. The mechanism of action may be a stretching of endothelial cells in the cerebral vessels or an opening up of new capillaries, or a combination of both.

Adult↗
PubMed1977

Does alexia without agraphia always include hemianopsia?

A patient with alexia without agraphia (pure alexia) is reported. Bedside examination of the visual fields disclosed no abnormalities; but perimetric examination demonstrated an incomplete right homonymous hemianopsia with some sparing of the peripheral part of the visual field. The literature on pure alexia without hemianopsia is reviewed and it is concluded that this syndrome has hardly been described with certainity.

Dyslexia, Acquired↗