摘要:

Micropuncture data suggest that pial arterioles contribute only slightly less than parenchymal cerebral arterioles to total resting cerebrovascular resistance. Care must be taken in interpreting the micropuncture data, or the contribution of pial arterioles to cerebrovascular resistance may be erroneously underestimated. These considerations and the fact that pial arterioles have been shown to be highly reactive to a variety of physiological and abnormal stimuli suggest strongly that changes in pial arteriolar diameter should contribute importantly to control of flow to the underlying brain. In fact, parallels between changes in pial vascular diameter and regional blood flow have been observed. Moreover, since the responses of pial vessels to important vasoactive stimuli are qualitatively similar to those of the cerebral circulation as a whole when the latter are inferred from measurements of flow, the directly observable pial vessels may provide a model for the responses of the unseen parenchymal segments of the cerebrovascular bed. Such a model would be essential to our understanding of the control of cerebral blood flow, even if pial vessels themselves did not participate in the control of flow. Thus there are multiple reasons for continued study of the pial vessels, particularly with modern techniques developed for microcirculatory investigations.

ISSN:0039-2499    

出版商:OVID    

年代:1974

数据来源: OVID

ISSN:0039-2499    

出版商:OVID    

年代:1974

数据来源: OVID

摘要:

Glycerol was administered to control rats and to animals with experimental cerebral microembolism as a single intravenous injection (1 gm per kilogram), a single one-hour intravenous infusion (1.5 gm per kilogram), daily one-hour intravenous infusions (1 gm per kilogram), or in multiple oral doses (1 gm per kilogram per four hours). There were no effects of glycerol on the mortality, brain edema or increased brain sodium concentration and75Seselenate space due to cerebral microembolism. Brain water was not reduced in the hemispheres contralateral to embolization or in glycerol-treated controls. The results suggest that glycerol, at the dose levels reported to be beneficial in human cerebral infarction, is ineffective for cerebral dehydration.

ISSN:0039-2499    

出版商:OVID    

年代:1974

数据来源: OVID

摘要:

In a double-blind study, the effect of high doses of methylprednisolone on the cerebral edema induced by cerebral infarction was evaluated in 76 Mongolian gerbils. The incidence of experimentally induced cerebral infarction following carotid artery ligation is high in these animals because they lack a posterior communicating artery. One hour after the left common carotid artery had been ligated, 34 animals were given 30 mg per kilogram of the adrenocorticosteroid and the dose was repeated 24 and 48 hours later. Thirty-four animals were given normal saline on the same treatment schedule. Eight animals with sham operations were not treated. The animals were observed for ten days for signs of stroke. Surviving animals were killed on the tenth day and all brains were examined macroscopically and microscopically. Stroke developed in 41% of all animals; 31% died within ten days. Of the steroid-treated animals, stroke developed in 38% and 26% died. Of the saline-treated animals, stroke developed in 44% and 35.5% died. The differences were not significant by chi square analysis and the authors concluded that large doses of methylprednisolone given one hour after carotid ligation failed to prevent or influence the course of experimental stroke.

ISSN:0039-2499    

出版商:OVID    

年代:1974

数据来源: OVID

摘要:

Tyramine induces dose-dependent changes in tension of the isolated middle cerebral artery of the goat. Cocaine, phentolamine and reserpine reduce the sensitivity of the tissue to tyramine by factors of 2.8, 3.7 and 3.7, respectively. The norepinephrine (NE) concentration of the arteries of the circle of Willis is 2.10 μg per gram and the corresponding value for the right atria is 1.25 μ per gram. Reserpine pretreatment (0.02 mg/kg/day for three days) reduces the NE concentration of the cerebral arteries to undetectable levels and that of the right atria to 2.4% of the control value. The relatively high concentration of NE of the cerebral arteries of the goat suggests that this tissue receives considerable sympathetic innervation. It is likely that part of the contractile response to tyramine is due to release of endogenous NE from sympathetic stores in the artery. However, some contractile response to tyramine remains after α-adrenergic blockade, reserpine pretreatment and in the presence of cocaine, suggesting that in addition to an indirect action (release of NE) tyramine also possesses a direct stimulatory effect in cerebral arteries.

ISSN:0039-2499    

出版商:OVID    

年代:1974

数据来源: OVID

摘要:

The personality, life stress and affect at onset of illness of white men hospitalized for transient cerebral ischemia and cerebral infarction were compared with those of control subjects admitted to the hospital for acute nonvascular illnesses. A “pressure pattern” of behavior characterized by aggressiveness, ambition and striving for achievement appeared to be the predominant personality feature among patients with cerebrovascular disease who had a history of myocardial infarction or angina pectoris. There was also some evidence that an unpleasant affective state prior to the onset of stroke occurred more frequently in men with combined coronary and cerebrovascular disease than in those without such a history or in control subjects. No relationship was found between personality features and attributes such as hypertension, age, cigarette smoking or education. These findings suggest that certain behavioral features in patients with coronary heart disease should be considered as risk factors in the development of cerebral ischemia or infarction.

ISSN:0039-2499    

出版商:OVID    

年代:1974

数据来源: OVID

摘要:

Experiments with rabbits, cats, and monkeys during recording of complex physiological processes (LEPG, ThG, Po2, Pco2, and ECoG) in functionally discrete brain regions of awake animals have shown that functional changes, expressed as desynchronization effects on ECoG, are followed by an increase of local blood flow (LCBF) in regional brain cortex up to 0.3 to 0.4 ml per minute per 1 gm brain tissue or an increase of 35% to 45% of resting levels of LCBF. Under normal physiological conditions LCBF and Po2change periodically without any external interference at frequency ranges 0.005 to 0.2 cps. This is characteristic of all brain regions and all species of animals investigated. These variations range in amplitude as much as 28% of the mean level of LCBF.Changes of LCBF have no correlation with changes of systemic blood pressure (SAP). Local control mechanisms appear to be responsible for them. The interrelationships of changes of functional activity and CBF in local regions of awake brain are characterized by a very short time delay (less than one second), but under narcosis it increased up to ten seconds. All these facts taken together suggest that control mechanisms responsible for local brain vascular reactions have two components; the first is metabolic and the second is neurogenic in nature.

ISSN:0039-2499    

出版商:OVID    

年代:1974

数据来源: OVID

摘要:

The sequential synaptic alterations which occur during the early phase of developing cortical infarction in the squirrel monkey were studied with the electron microscope. Mild swelling of a few dendritic terminals and clumping of synaptic vesicles were the earliest detectable changes, being present at 45 minutes. The two basic patterns of degeneration of the terminal boutons were shrinkage and swelling, with shrinkage being the predominant response. Many of the shrunken boutons became electron-dense, resembling the changes present in anterograde axonal degeneration. The alterations which developed in the dendritic terminals were relatively unimpressive. Disruption of axosomatic synapses occurred at an earlier stage and was more severe than that of axodendritic synapses. Reduction in the number of synaptic vesicles was first observed at six hours and appeared to be progressive. The edema which developed was morphologically distinct from both “vasogenic” and “cytotoxic” edema in that there was early and progressive enlargement of the extracellular space.

ISSN:0039-2499    

出版商:OVID    

年代:1974

数据来源: OVID

摘要:

Although the dog remains the standard surgical laboratory animal, its extensive collateral circulation makes complete interruption of cerebral blood flow quite difficult. A simple yet reliable canine model for the study of cerebrovascular insufficiency would seem desirable. We have found that complete division of the left subclavian and right brachiocephalic arteries and their major branches can be rapidly performed through a small left thoracotomy. This interruption of blood supply is incompatible with resumption of normal respiratory function, consciousness, or survival, and can be used to evaluate extra-anatomic grafts or anastomoses.

ISSN:0039-2499    

出版商:OVID    

年代:1974

数据来源: OVID

摘要:

Utilizing a defined general population, two investigations were conducted in Washington County, Maryland. In the eight-year mortality study, the relative risk of stroke among cigarette smokers was only 0.85 as compared to nonsmokers. In the two-year morbidity investigation, limited to stroke cases occurring after the age of 50, it appears that the association of cigarette smoking to strokes in the older age groups is at most very small.In atherosclerotic strokes, there may be an association with cigarette smoking, but only in the younger age groups, as suggested by two other studies. In order to investigate this possibility a retrospective case/control study of young cases is recommended. If there is no age dependency of atherosclerotic strokes, this implies that cigarette smoking may not be associated with the atherosclerotic process in cerebral and coronary arteries.

ISSN:0039-2499    

出版商:OVID    

年代:1974

数据来源: OVID