摘要:

To study the effect of non-hypotensive hemorrhage on cerebral blood flow in normo- and hypertensive states, chloralose anesthetized cats were subjected to graded blood loss (5 ml/kg) every 30 min. Cerebral blood flow was measured using radiolabelled microspheres or H2 clearance. Hypertension was produced by infusion of phenylephrine to a diastolic blood pressure of 100 mm Hg. Control animals suffered no net blood loss. PCO2 was between 28 and 32 mm Hg for all groups over the entire experiment. In normotensive cats, cerebral blood flow increased following withdrawal of 10 ml/kg of blood. In hypertensive cats, cerebral blood flow increased after withdrawal of 20 ml/kg of blood. These findings were consistent for all brain regions examined. Animals without blood loss, whether normo- or hypertensive showed no consistent change in cerebral blood flows. Possible explanations for these findings, particularly neurally mediated responses, are discussed.

ISSN:0039-2499    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

Regional cerebral blood flows and shunting of microspheres with four different sizes (9,12, 16 and 25 microns) into the superior sagittal sinus were determined in twelve dogs. Venous blood was collected from the superior sagittal sinus for 120 min after the injection of microspheres, and the dogs were then sacrificed immediately. Results on blood flow measurements and venous shunting determinations were similar between left ventricular and left atrial injections. Blood flows measured by 12, 16 and 25 microns spheres were comparable in various brain tissues, except the choroid plexus. 9 microns spheres underestimated blood flows in all regions studied: by 13–19 percent in the cerebral cortex, midbrain, brain stem and cerebellum, by 34–42 percent in the cortical white matter, corpus callosum and cervical cord, and by 64–81 percent in pituitary gland and choroid plexus. These results probably reflect regional difference in microvascular architecture. Venous shunting of 9, 12, 16 and 25 microns spheres during a 24 hr period were 23.6 +/− 2.5, 12.6 +/− 1.2, 4.8 +/− 1.4, and 4.0 +/− 1.2 percent (mean +/− SEM), respectively, with respect to the arterial delivery. Although most of the venous shunting occurred during the first 3 min after the injection of microspheres, it continued 3–60 min after the injection. Beyond 60 min, the venous shunting became minimal for 16 and 25 microns spheres, while significant amount of 9 microns spheres continued to appear in sagittal sinus. This time dependent shunting indicates that some microspheres may be transiently trapped in the microcirculation and become gradually dislodged with time. Failure to consider this time dependence may underestimate the shunting of microspheres through the microcirculation.(ABSTRACT TRUNCATED AT 250 WORDS)

ISSN:0039-2499    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

A method is described for measurement of cerebral blood flow utilizing the washout of microwave delivered heating. Using a microwave source attenuated to achieve a brain temperature elevation of 0.5-0.75 degrees C after a 2 second exposure in the rat, cerebral blood flow was calculated from the temperature washout curve monitored by a small thermistor implanted in the brain. The results obtained with this method were comparable to those obtained using the [14C] butanol method. To our knowledge this represents the first description of a method to deliver a blood flow “indicator” atraumatically directly into brain tissue.

ISSN:0039-2499    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

Human major cerebral arteries were fixed under pressure in the brain or after excision and ligation. They were sectioned and stained for light microscopy. Sterological point counting was used on mid-plane longitudinal sections of ten segments to determine that the media occupied 52.0% +/− 6.39 (SD) of the arterial wall and that the smooth muscle comprised 72.0% +/− 4.76 (SD) of the media. In arterial segments containing nine planar bifurcations, areas of varying muscle orientation and composition were identified and mapped out. A circumferential alignment of smooth muscle was consistently found in the cerebral branching systems except for the bifurcation region proximal to the apex at major bifurcations where the regular pattern was replaced by multilayered multidirectional smooth muscle. Theoretical models relating smooth muscle contraction to arterial caliber in cylindrical segments are outlined. In the extreme case of complete closure of an artery, our prediction is that for a typical cerebral arterial media the outermost muscle cells should have to contract to 42% of their relaxed length. The possible importance of medial smooth muscle patterns in the pathogenesis of cerebrovascular lesions is discussed.

ISSN:0039-2499    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

This study evaluates the hypothesis that ethanol alone, or in diluents for drugs used to protect hypoxic mice, is responsible in part for an increased tolerance to hypoxia (4–5% oxygen). The change in hypoxic tolerance following i.v. or i.p. administration of ethanol, diazepam, nimodipine and various diluent components was measured. Diazepam (50 mg/kg i.v.) increased hypoxic tolerance to 700 +/− 47% (n = 11) of saline control, its diluent increased hypoxic tolerance to 468 +/− 60% (n = 10) of saline control but the ethanol component of the diluent accounted for almost half of this diluent effect. Nimodipine (2 mg/kg i.p.), a calcium antagonist, increased tolerance to 180 +/− 18% of control (n = 19) and nimodipine diluent showed an even greater increase to 226 +/− 25% of control (n = 15). In this case essentially all of the protective effect of nimodipine diluent (81.3%) is accounted for by ethanol. Dose response curves indicate the maximum ethanol induced increase in hypoxic tolerance was approximately 335% of control at a dose of 2.4 g/kg. Buffers, etc. in the diluents evidently add to the protective effect of ethanol. Our data clearly indicate ethanol is the important component of some treatments which protect mice from hypoxia. The pharmacological activity of ethanol, even when used in a diluent, should not be ignored in evaluating therapeutic intervention for protection from hypoxia.

ISSN:0039-2499    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

A technique for continuous measurement of cerebral venous outflow in the rat is described. The method involves cannulation of one retroglenoid vein close to its exit from the skull, and diversion of cerebral venous blood through a closed extracorporal circuit with a drop recording device, the blood being returned to the central venous circulation via a catheter in the external jugular vein. Occlusion of the contralateral retroglenoid vein increases measured flow and minimizes extracerebral contamination of the diverted cerebral venous blood. The venous outflow system is not further isolated from cerebral or potential extracerebral collaterals. Thus, the mass of tissue drained cannot be exactly defined anatomically. However, the experiments involving changes of PP, arterial CO2 tension, and induction of epileptic seizure activity, and simultaneous indirect measurements with radioactive tracer technique, indicate that significant extracerebral contamination does not occur and that in short term measurements the venous outflow represents cerebral blood flow (CBF) in a constant mass of (dorsal and central, mainly forebrain) cerebral tissue. Measurement of arterial blood pressure and pressure in the cisterna magna allows calculation of cerebral perfusion pressure (PP). By simultaneous measurement of arterial and cerebral venous oxygen content changes in cerebral oxygen consumption (CMRO2) can be calculated. The method has been applied to document several situations of transient CBF and CMRO2 changes.

ISSN:0039-2499    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

These experiments were designed to test the hypothesis that increases in blood flow to the lower brainstem would be greater than forebrain regions during arterial hypercapnia. Total and regional cerebral blood flow (CBF) was measured via the tracer microsphere technique in seven anesthetized New Zealand white rabbits during normocapnia (arterial PCO2 congruent to 40 torr) and hypercapnia (arterial PCO2 congruent to 80 torr). During normocapnia average CBF was 0.77 ml/min/g, and regional measurements of blood flow indicated significantly greater flow to the cerebrum (0.86 ml/min/g) than either the medulla (0.52 ml/min/g) or the pons (0.49 ml/min/g). When arterial PCO2 was increased average CBF increased 113%, and a significant linear regression was calculated for arterial PCO2 vs CBF [CBF (ml/min/g) = 0.028 PCO2 (torr) - 0.502]. The distribution of blood flow within the brain was similar to normocapnia except that blood flow to the cerebellum was now greater than any other brain region (1.97 ml/min/g for the cerebellum compared to 1.66 ml/min/g for the cerebrum). Absolute increases in blood flow to the lower brainstem were equal to or less than other areas of the brain. We conclude that ponto-medullary blood flow does not increase disproportionate to other areas of the brain during hypercapnia, but some redistribution of CBF does occur in that cerebellar blood flow increased significantly more than the cerebrum, medulla, or pons.

ISSN:0039-2499    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

A 64 y/o man experienced during 2 weeks TIA's or TIA's like episodes, once or twice a day, with or without contralateral pain in the head. CT Scans showed peculiar enhanced areas appended to the superior sagittal sinus. Angiography was refused. Twenty-seven months later during mild exertion a left frontal hematoma developed. Among frontal symptoms and signs laconism, abulia and a striking whispering were prominent. Angiography showed a dural arteriovenous fistula draining into cortical veins on the inner aspect of the left hemisphere. The fistula was successfully operated.

ISSN:0039-2499    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

A 55-year-old woman with an aortic arch syndrome of acute onset and dysphasia, resulting from the excessive administration of ergotamine tartrate suppositories, is described. Complete resolution of symptoms and return of upper limb and carotid artery pulses to normal occurred within four days of cessation of the ergot derivative. Lower limb involvement was conspicuously absent in this case.

ISSN:0039-2499    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

A young man with cerebral infarction, skeletal, cardiac and renal malformations was found to have on angiography a rare lesion involving the cervical left internal carotid artery, formed by the superposition of two arterial lumina. Anti-platelet therapy did not prevent thrombosis of the lesion and reinfarction. Extracranial-intracranial bypass graft was performed, followed by excision of the arterial lesion. Pathological examination revealed fibromuscular dysplasia and dissecting aneurysm. The few reported cases associating fibromuscular dysplasia of the internal carotid artery with dissecting aneurysm are reviewed. Surgical therapy is recommended in such cases when symptomatology progresses. Fibromuscular dysplasia occasionally coexists with somatic malformations, suggesting a congenital origin of this condition.

ISSN:0039-2499    

出版商:OVID    

年代:1983

数据来源: OVID