Jan Jakubowski

Middle cerebral artery occlusion without craniectomy in rats. Which method works best

Background and Purpose Our purpose was to assess the effectiveness of middle cerebral artery occlusion in producing acute focal ischemia in the rat by the use of Koizumis and Longas methods, in which occlusion is achieved by passing a nylon thread into the internal carotid artery. Methods Cerebral blood flow was measured by using the hydrogen clearance method, and the brains were examined histologically to assess ischemic damage. Results By Koizumis method profound reduction in cerebral blood flow was achieved in 28 of 30 rats (93%). The mean cerebral blood flow in the middle cerebral artery territory was 10.7 (95% confidence interval, 9.9–11.5) ml/100 g per minute. By Longas method reduction in cerebral blood flow was achieved in only 29 of 52 rats (56%), and in these animals mean cerebral blood flow was 33 (95% confidence interval, 28.3–33.7) ml/100 g per minute (p < 0.001 compared with Koizumis method). Cerebral blood flow was reduced to <16 ml/100 g per minute in only seven animals (24%). Conclusions By Koizumis method the depth of ischemia is more profound, occlusion is achieved in a much higher proportion of cases, and the incidence of perforation of the intracranial internal carotid is much less frequent than by Longas method.

The Sheffield Model of Subarachnoid Hemorrhage in Rats

BACKGROUND AND PURPOSE There is no comprehensive and reliable model available in small animals that is suitable for the study of subarachnoid hemorrhage (SAH). Most of the existing models either require extensive surgery to achieve SAH or neglect the importance of an injury to the vessel and the impact of suddenly raised intracranial pressure (ICP). The presented model is designed to overcome these shortcomings. METHODS Forty-three male Wistar rats were anesthetized. Regional cerebral blood flow was measured using the H2 clearance method bilaterally in the middle cerebral artery territory. ICP and blood pressure were continuously monitored. Blood gases were kept within physiological limits. SAH was produced by passing a nylon thread up through the right internal carotid artery and piercing a hole in the right anterior cerebral artery. The animals were divided into three experimental groups treated with varied operative techniques. After 3 hours the surviving animals were killed, and SAH was confirmed by postmortem examination. RESULTS The described method proved to be a reliable way of producing SAH in rats. The onset of SAH was characterized by a sudden increase in ICP. There were some differences in the reduction of regional cerebral blood flow and the survival rate in the experimental groups. This may represent differing degrees of severity of the produced SAH. CONCLUSIONS We present an inexpensive and reliable model of SAH in the rat that allows the early course of biochemical, physiological, and pathological changes to be studied.

Clinical evaluation of magnetic stimulation in cervical spondylosis.

Conduction in central motor pathways and motor roots was assessed, using the new technique of magnetic stimulation, in 39 patients with cervical spondylosis. Recordings were taken from abductor digiti minimi in all patients and from biceps brachii and abductor hallucis in some. Findings were abnormal ipsilaterally in 27 out of 63 muscles examined in patients with myelopathy, and in 2 out of 38 muscles in patients with radiculopathy. No abnormality was found in 11 muscles examined in patients with negative radiology. There was some correlation between the degree of electrophysiological change and clinical disability. Abnormal conduction was found in some patients with cord compression at the C3/4 or C4/5 interspace but not in a small group with compression at the C5/6 interspace. It seems that magnetic stimulation will provide objective confirmation of upper motor neurone involvement and may provide some measure of its degree, but at present it does not appear to be superior to clinical methods in diagnosing its presence. It may also aid the selection of the correct level for surgical decompression.

Synovial cysts of the lumbar spine: a review.

Four cases of synovial cyst (ganglion) arising from the facet joints of the lumbar spine are reported. A typical presenting feature was exacerbation of pain on standing or walking, mimicking vascular claudication. MRI proved in all four cases to be the definitive investigation and surgery the treatment of choice, producing excellent results.

Coil embolization of giant serpentine aneurysms: report of two cases arising from the posterior cerebral artery

The authors describe the presentation, investigation and successful treatment of two giant serpentine aneurysms with Guglielmi detachable coils. Both aneurysms selectively involved the P2 segment of the posterior cerebral artery. The authors describe an endovascular approach to these challenging lesions as an alternative/adjunct to conventional surgery.

Blood supply, blood flow and autoregulation in the adenohypophysis, and altered patterns in oestrogen-induced adenomatous hyperplasia

The article addresses the fascinating topic of blood flow in the normal and the adenomatous anterior pituitary gland. This is considered in conjunction with the anatomy and physiology of the area and the neuro secretion. The mechanisms of the control of the development and growth of the prolactinoma and the changes in the microcirculation of the tumour are discussed. It is felt that its altered microvascular pattern and in particular the influx of the systemic low dopamine blood through the supplementary and newly developed blood supply plays an important role in the natural history of these tumours.

An in vitro Study of the Pharmacological Responses of Rat Middle Cerebral Artery: Effects of Overnight Storage

This study was designed to establish the in vitro pharmacological responses of rat middle cerebral arteries (MCA), and also their susceptibility to overnight cold storage at 4 degrees C. MCAs were harvested from rats and pharmacological responses were studied using a Mulvany myograph. Responses to prostaglandin F2 alpha (PGF2 alpha), uridine triphosphate (UTP), noradrenaline (NA) and histamine were determined to investigate receptor-dependent responses, sodium nitroprusside and papaverine to investigate receptor-independent relaxation and L-arginine and N omega-Nitro-L-arginine methyl ester (L-NAME) to examine nitric oxide synthase-dependent responses. Responses in fresh arteries were established and compared with responses in arteries which had been mounted on a myograph and stored overnight at 4 degrees C before study the next day. The MCAs had an effective lumen diameter of 263 microns (SD 25) and sustained concentration-dependent contractions were produced by 124 mM K+, PGF2 alpha, UTP and L-NAME. Sodium nitroprusside, NA, histamine, papaverine and L-arginine produced concentration-dependent relaxations in precontracted arteries. Overnight cold storage did not alter the pharmacological responses to any of the agonists tested.

In vitro Contractility Studies of the Rat Middle Cerebral Artery after Stereotactic Gamma Knife Radiosurgery

The middle cerebral artery (MCA) was irradiated in 94 rats using the Gamma Knife. The vessels receiving 20, 50, 80 and 200 Gy were removed 24 h later and mounted on a myograph. Contractility responses to potassium and prostaglandin (PG) F2 alpha were tested. After precontraction with PGF2 alpha, the relaxant effects of histamine, papaverine, L-arginine and sodium nitroprusside were examined. Other vessels were preincubated with ouabain or N omega-nitro-L-arginine methyl ester before testing with the relaxant agents. After irradiation, the contractile response to maximal potassium and PGF concentrations was diminished, suggesting dose-dependent radiation damage to the contractile mechanism. The normal MCA shows an initial relaxation in the presence of a low K+ concentration, which is Na+, K(+)-ATPase dependent. According to this study, the endothelium-derived relaxation function was suppressed by radiation, suggesting that there is an early change in irradiated vessels, demonstrable by functional studies, which affects both the smooth muscle and endothelial layers.

Failure testing cerebral arteries: are branch points weaker than unbranched vessels?

The bursting pressure of samples of cerebral arteries was measured. Eighty-five samples of cerebral arteries were taken from 11 fresh cadavers. These samples were filled with saline under pressure to the point of bursting. The bursting pressures were recorded. The mean bursting pressure of all samples was 1.8 bar (1370 mmHg). The range was 0.7–4.6 (530–3190 mmHg). The mean bursting pressures of samples containing branch points was 1.6 and that of those without branch points was 2.2. This difference was significant with p < 0.001. Samples taken from persons dying from subarachnoid haemorrhage were weaker (mean 1.45 bar) than those taken from persons dying from other causes (mean 1.971 bar). This difference was significant with p < 0.001. Bursting pressure was found to decline at 2% per year of age. This figure was different from 0 with p - 0.003.

Changes of Blood Flow in Oestrogen-induced Hyperplastic Anterior Pituitary Lobe following Bromocriptine Administration

Anterior pituitary hyperplasia and histologically verified adenomas were induced by diethylstilboestrol (DES) containing implants in a total of 104 female F344 rats. Thirty rats were used as controls. Blood flow in the anterior pituitary (PBF) was measured using the hydrogen clearance method. PBF was progressively reduced to 25% by DES in 13 weeks but the total adenohypophysial blood flow (flow as measured per unit weight multiplied by weight of the gland) was raised by 75%. Bromocriptine (BC, 1 mg/kg intravenously) reduced PBF by a maximum of 27% in tumour-bearing rats. When bromocriptine (1 mg/kg/day subcutaneously) was given for 7 days before the measurements the hyperplastic effect of DES on the pituitary gland and the total blood flow through the pituitary were both reduced by 23%. Reduction of blood supply may be one of the reasons that bromocriptine is clinically useful.