摘要:

WE HAVE EXAMINED the effects of experimental subarachnoid hemorrhage (SAH), induced by delivering autologous blood into the subarachnoid space, on the adrenergic mechanisms of the goat cerebrovascular bed. To achieve this, the response to noradrenaline was recorded both in vivo, by measuring cerebral blood flow in unanesthetized animals, and in vitro, by recording isometric tension in isolated cerebral arteries. In addition, we checked the function of adrenergic innervation by measuring the tritium efflux evoked by electrical stimulation in cerebral arteries preloaded with [3H]-noradrenaline, and we examined this innervation by using both fluorescent and electron transmission microscopy. All studies were performed before and 3, 7, and 14 days after SAH. Injections of noradrenaline (0.1–10 μg) directly into the cerebroarterial supply produced reductions in cerebral blood flow, with no concomitant changes in mean arterial blood pressure and heart rate, which were significantly enhanced (P< 0.01) 3 and 7 days after SAH and returned to control values 14 days after hemorrhage induction. In isolated cerebral arteries, noradrenaline (10-8-10-4mol/L) produced concentration-dependent contractions, which were also significantly enhanced (P< 0.05) 3 and 7 days after SAH and returned to control values in cerebral arteries obtained 14 days after SAH. On the other hand, increases in the release of tritium induced by electrical stimulation in cerebral arteries preloaded with [3H]-noradrenaline were significantly lower (P< 0.01) after SAH. Moreover, microscopical studies showed a reduction in catecholamine fluorescence and signs of sympathetic degeneration in some perivascular axons after SAH. These results show that SAH produces sympathetic denervation of the cerebral arteries in the goat, which causes supersensitivity of the cerebrovascular bed to noradrenaline during the first week after SAH, and could contribute to develop cerebral vasospasm. Down-regulation of cerebrovascular adrenergic receptors could explain the recovery of the normal sensitivity to noradrenaline during the second week after hemorrhage induction.

ISSN:0148-396X    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

THE PRESENT WORK aimed at examining the effect of tirilazad mesylate (U74006F), a newly developed lipid peroxidation inhibitor, on the intraluminal narrowing of basilar artery subjected to subarachnoid hemorrhage (SAH) in beagle dogs. In Experiment 1, an intravenous bolus injection of either vehicle or U74006F (0.5, 1.5 and 3.0 mg/kg) was repeated every 8 hours after an induction of the first SAH until the animals were killed. A dose of 0.5 mg/kg of U74006F provided the greatest beneficial effect. In Experiment 2, an intravenous infusion of 100 ml of saline containing either vehicle or U74006F (0.3 and 1.0 mg/kg) was given in the same time schedule as in Experiment 1. Post-SAH treatment of U74006F, at a dosage of approximately 0.5 mg/kg, showed a beneficial effect by infusion as well as by bolus administration. The present study demonstrates that U74006F has an ability to prevent chronic vasospasm in the canine SAH model.

ISSN:0148-396X    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

ALTHOUGH NOT THE sole factor, glutamate-mediated excitotoxicity is accepted as a major mechanism of ischemic neuronal damage. MK-801 and mild hypothermia, two cerebroprotective modalities, which have been documented to alter glutamatergic action, were tested in the rat middle cerebral artery occlusion (MCAO) model simulating permanent focal ischemia. We administered normothermic (37°C) animals with either MK-801 (1.0 mg/kg 30 min before MCAO or 2.5 mg/kg 30 min before, immediately after, 4 hours, and 8 hours after MCAO) or saline vehicle (30 min before MCAO). Mildly hypothermic (33°C) animals were administered either MK-801 (1.0 mg/kg) or saline vehicle 30 minutes before MCAO. Mild hypothermia was induced over a 20-minute period before MCAO in hypothermic animals. All animals were killed 24 hours after MCAO; their brains were sectioned and stained with 2,3,5-triphenyltetrazolium chloride and their infarct volumes were calculated. In normothermica animals given 1.0 mg/kg and multidose 2.5-mg/kg intraperitoneal injections of MK-801, the infarct volumes (as a percentage of right hemispheric volume) were 16.8 ± 3.5% and 16.3 ± 3.0%, respectively. These infarct volumes were significantly different (P< 0.05; single-variable analysis of variance) from the normothermic, drug-free control (26.8 ± 1.9%), but not significantly different from each other. Analysis of the data using a nonparametric test (Kruskal-Wallis;P= 0.02) confirmed the same significant differences in infarct size. The infarct volumes from the mildly hypothermic groups were not different (1 mg/kg of MK-801, 15.5 ± 2.3% and saline control, 15.4 ± 1.1%). However, the percentage of infarct size in the mildly hypothermic drug-free group was significantly reduced compared with the normothermic drug-free control (P< 0.0005; two-tailed Student'st-test). There was no significant difference between normothermic and mildly hypothermic animals given 1 mg/kg of MK-801. Therefore, in a rat permanent focal cerebral ischemia model, it appears that mild hypothermia and MK-801 offer similar cerebroprotective effects when administered separately, but do not yield additive effects when used in combination.

ISSN:0148-396X    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

THE EFFECTS OF phenytoin, carbamazepine and valproic acid on alterations in sodium-potassium-adenosine triphosphatase activity during ischemia were studied in the rat brain. Pretreatment with phenytoin and carbamazepine prevented a reduction of this activity, which, without either treatment, was observed in the cerebral hemisphere exposed to 30-minute ischemia resulting from unilateral middle cerebral artery occlusion. Valproic acid, on the other hand, did not principally affect the ischemic impairment of this membrane-bound enzyme activity. These results lend support to the previously proposed use of phenytoin in cerebral ischemia, but also suggest the therapeutic availability of another common anticonvulsant, carbamazepine, for treatment of the insult.

ISSN:0148-396X    

出版商:OVID    

年代:1994

数据来源: OVID

ISSN:0148-396X    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

CONTROLLED DRUG RELEASE in the central nervous system through an implantable polymeric vector has been developed in recent years. For this purpose, different polymeric devices composed primarily of synthetic biocompatible and biodegradable polymers have been investigated. The first polymeric devices developed were macroscopic implants (monolithic devices), which required open surgery for implantation. Microencapsulation methods, however, allow the production of microparticles or nanoparticles loaded with neuroactive drugs. Because of their size, these micro- or nanoparticles may be easily implanted by stereotaxy in discrete, precise, and functional areas of the brain without causing damage to the surrounding tissue. Presently, this method is most frequently applied in the fields of neuro-oncology and neurodegenerative diseases, but neurologically, the potential applications of drug targeting by stereotactic implantation of drug-loaded particles are legion.

ISSN:0148-396X    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

WE PRESENT THE first use of intraoperative thermographical imaging for the surgical resection of a cerebral arteriovenous malformation. For obtaining intraoperative regional and functional thermographical images, a real-time mode infrared camera was installed to an operating microscope with an exclusively developed attachment device. Changes of the surface temperature of the cortical draining vein and the surrounding cortical surface were observed intraoperatively before and after the occlusion of the main feeder. Intraoperative functional thermography with cold physiological saline solution demonstrated a change in the heat clearance of the draining vein after complete obliteration of the feeder.

ISSN:0148-396X    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

ALTHOUGH THE SHAPES of velocity waveforms obtained with transcranial Doppler examination can indicate such abnormalities as increased intracranial pressure and proximal arterial compromise, the significance of unusual waveform morphologies is often obscure. In this report, we describe four cases in which an unusual waveform morphology was obtained from vessels distorted and narrowed by intracranial masses. The appearance of this unusual morphology as an isolated signal within a transcranial Doppler examination should, therefore, suggest a structural deformation of the insonated vessel to those who interpret transcranial Doppler studies.

ISSN:0148-396X    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

GIANT SERPENTINE ANEURYSMS (GSAs) are infrequent. We present a 37-year-old patient with a giant serpentine aneurysm of the left middle cerebral artery that was treated with a superficial temporal artery to middle cerebral artery bypass and ligature of the left internal carotid artery. After 2 years, the patient presented new symptoms of neurological deterioration and the computed tomographic scan and arteriography showed regrowth of the aneurysm, which was excised. Enlargement of a giant serpentine aneurysm once it has been treated with ipsilateral carotid ligation and/or bypass anastomosis is rare, and only two cases have been described previously.

ISSN:0148-396X    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

THE AUTHORS DESCRIBE a rare case in which an infundibular dilation at the origin of a circumflex branch of the P1 segment of the posterior cerebral artery caused subarachnoid hemorrhage. Wrapping was performed by a subtemporal approach in the delayed stage. At the time of surgery, the rupture point was found in the infundibular dilation.

ISSN:0148-396X    

出版商:OVID    

年代:1994

数据来源: OVID