Barrier disruption in the major cerebral arteries following experimental subarachnoid hemorrhage

The effects of experimental subarachnoid hemorrhage (SAH) on the blood-arterial wall barrier in the major cerebral arteries were studied in 20 normotensive dogs. Horseradish peroxidase (HRP) was given intravenously before the animals were sacrificed to assess the integrity of the barrier. Transient elevation of intracranial pressure (ICP) produced by cisternal injection of saline solution resulted in HRP leakage at the branching points of the major cerebral arteries. Extensive disturbance of the blood-arterial wall barrier was consistently observed in the major cerebral arteries after SAH, with or without elevation of ICP. These results suggest that both subarachnoid clot and a sudden rise in the ICP are important factors causing the breakdown of the blood-arterial wall barrier, but that the effect of the clot is the most profound. Electron microscopy revealed that opening of the interendothelial junctions is one of the important mechanisms responsible for the HRP leakage in the major cerebral arteries following SAH. Disturbance of arterial permeability in the major cerebral arteries following SAH probably accounts for the abnormal post-contrast enhancement that occurs in patients who are prone to develop vasospasm following aneurysm rupture, and is probably involved in the pathogenesis of vasospasm.     

Barrier disruption in the major cerebral arteries after experimental subarachnoid hemorrhage in spontaneously hypertensive and normotensive rats

The effects of experimental subarachnoid hemorrhage (SAH) on the blood-arterial wall barrier in the major cerebral arteries were studied in 24 spontaneously hypertensive rats (SHR) and 13 Sprague-Dawley rats (SDR). Horseradish peroxidase (HRP) was given intravenously before killing the animals to assess the integrity of the barrier. In the acute experimental group, transient elevation of intracranial pressure (ICP) and systemic arterial pressure produced by cisternal injection of whole blood, saline solution, or Elliott's B solution resulted in extensive disturbance of the blood-arterial wall barrier. In the chronic group, only the cisternal injection of whole blood in SHR brought about an extensive and marked disturbance of the arterial permeability. These results suggest that: (a) early breakdown of the blood-arterial wall barrier seems to be due to a sudden rise in the ICP or arterial pressure; (b) in the chronic experiments, the subarachnoid clot is the most important factor responsible for the permeability changes; and (c) in the chronic SAH experiments, the blood-arterial wall barrier seems to be more vulnerable in SHR than in Sprague-Dawley rats. Due to the well-known similarities between SHRs and hypertensive human beings, patients with chronic hypertension should be considered at high risk after SAH for extensive blood-arterial wall barrier disturbances.     

Morphologic changes in cerebral arteries after subarachnoid hemorrhage

The premise of this article is that morphologic changes observed in cerebral arteries after subarachnoid hemorrhage play an important role in the pathogenesis of associated ischemic deficits observed in this disorder. Secondly, the arteriopathic response of cerebral arteries to subarachnoid blood is similar in many respects to that observed in systemic vessels under various pathologic conditions, and common pathogenic mechanisms may exist. The data supporting these premises may be summarized as follows: 1. Morphologic changes in human and animal cerebral arteries after subarachnoid hemorrhage are temporally associated with angiographic and clinically significant vasospasm. 2. Profound morphologic changes in cerebral arteries after subarachnoid hemorrhage do not contribute to structural narrowing of the lumen through increases in vessel wall mass. Nevertheless, structural changes may act in concert with contractile mechanisms to alter normal physiologic responses and maintain a narrowed lumen. 3. The agent responsible for arterial narrowing and morphologic changes in cerebral arteries after subarachnoid hemorrhage is contained in the erythrocyte component of whole blood and is most likely hemoglobin. 4. The volume and duration of exposure of subarachnoid blood to the artery appears to be significant in the development of the angiopathic response. 5. Ultrastructural abnormalities in systemic vessels associated with hypertension, atherogenesis, and endothelial damage are similar in many respects to those seen after subarachnoid hemorrhage.     

Musical murmurs in human cerebral arteries after subarachnoid hemorrhage

A transcranial ultrasonic method for the recording of murmurs from cerebral vessels is described. Using the new approach the authors have observed musical murmurs of pure tone quality in 15 patients with increased flow velocities in the cerebral arteries after spontaneous subarachnoid hemorrhage (SAH). The frequency range of the pure tones was from 140 to 820 Hz, corresponding to flow velocities between 73 and 215 cm/sec. The musical murmurs occurred as a transitional state between silent flow and the well known phenomenon of bruit. They were observed between the 4th and the 20th day after SAH. The most likely cause of the musical murmur is a periodic shedding of vortices in the cerebral arteries, commonly referred to as "a von Kármán vortex street." Clinically the presence of musical murmurs indicated that pathologically increased blood velocities were present in the artery under investigation. This probably reflected the degree of spasm.     

An experimental study of the acute stage of subarachnoid hemorrhage

A baboon model of subarachnoid hemorrhage (SAH) has been developed to study the changes in cerebral blood flow (CBF), intracranial pressure (ICP), and cerebral edema associated with the acute stage of SAH. In this model, hemorrhage was caused by avulsion of the posterior communicating artery via a periorbital approach, with the orbit sealed and ICP restored to normal before SAH was produced. Local CBF was measured in six sites in the two hemispheres, and ICP monitored by an implanted extradural transducer. Following sacrifice of the animal, the effect of the induced SAH on ICP, CBF, autoregulation, and CO2 reactivity in the two hemispheres was assessed. Brain water measurements were also made in areas of gray and white matter corresponding to areas of blood flow measurements, and also in the deep nuclei. Two principal patterns of ICP change were found following SAH; one group of animals showed a return to baseline ICP quite quickly and the other maintained high ICP for over an hour. The CBF was reduced after SAH to nearly 20% of control values in all areas, and all areas showed impaired autoregulation. Variable changes in CO2 reactivity were evident, but on the side of the hemorrhage CO2 reactivity was predominantly reduced. Differential increase in pressure lasting for over 7 minutes was evident soon after SAH on the side of the ruptured vessel. There was a significant increase of water in all areas, and in cortex and deep nuclei as compared to control animals.     

The significance of morphological changes in cerebral arteries after subarachnoid hemorrhage

A porcine model was developed to allow quantitative assessment of morphological changes in cerebral arteries after subarachnoid hemorrhage and to determine the significance of structural changes in producing arterial narrowing. Whole blood was selectively applied to the middle cerebral artery (MCA) of seven pigs. After 10 days, vessels were perfusion-fixed and examined by light and transmission electron microscopy and immunohistochemistry. The MCA's exposed to whole blood for 10 days showed prominent luminal narrowing associated with profound ultrastructural changes affecting all layers of the vessel wall. Morphometric analysis, however, demonstrated that significant reductions in the luminal cross-sectional area (-55.8% +/- 12.5%, p less than 0.005) and increases in radial wall thickness (75.1% +/- 10.5%, p less than 0.005) were associated with only minimal increase in the cross-sectional area of the vessel wall (12.5% +/- 15%, p less than 0.025). By stereological analysis, the volume density of individual components of the arterial wall was unchanged in MCA's exposed to blood. Vessels exposed to blood showed a 44% reduction in smooth-muscle cell immunoreactive actin and increased collagen in the extracellular matrix of the vessel wall. These data suggest that structural changes in cerebral arteries after subarachnoid hemorrhage do not directly contribute to vessel narrowing through increases in wall mass. Nevertheless, such changes may reflect pathological mechanisms which act to augment prolonged vasoconstriction or inhibit the maintenance of normal vascular tone.     

Up-regulation of parathyroid hormone receptor in cerebral arteries after subarachnoid hemorrhage in monkeys

OBJECTIVE: Complementary deoxyribonucleic acid array analysis was used to determine whether vasospasm after subarachnoid hemorrhage (SAH) is associated with changes in gene expression. METHODS: Right SAHs were created in three monkeys, and the right and left middle cerebral arteries were collected 3, 7, or 14 days after SAH. Vasospasm was assessed by angiography performed on Day 0 and at tissue harvest. A complementary deoxyribonucleic acid array containing 5184 genes was used to screen for changes in gene expression by comparing the right and left middle cerebral arteries. RESULTS: There was significant expression (greater than fivefold expression of messenger ribonucleic acid compared with internal standard control) of 537 genes (10%) in the middle cerebral arteries. One hundred sixty-four genes (31%) did not change significantly, and 373 (69%) were differentially expressed at 3, 7, or 14 days after SAH. These 373 genes changed from 1.2- to 7-fold as compared with control arteries. The most common pattern was a progressive increase with increased time after SAH. The functions of differentially expressed genes included the regulation of gene expression, cell proliferation, inflammation, membrane proteins and receptors, kinases, and phosphatases. There was a marked increase in parathyroid hormone and parathyroid hormone receptor with time after SAH. Immunoblotting demonstrated a significant increase in parathyroid hormone receptor protein. CONCLUSION: The up-regulation of these proteins involved in vascular relaxation suggests that they may play a role in vasospasm. The progressive increase in messenger ribonucleic acids involved in the functions noted suggests that the pathogenesis of cerebral vasospasm involves cell proliferation, inflammation, and possibly smooth muscle phenotype change.     

Disturbance in the intramural circulation of the major cerebro-pial arteries after experimental subarachnoid haemorrhage

The intramural fluid circulation of the cerebral arterial wall was investigated using horseradish peroxidase (HRP) as a tracer which was injected intravenously or intracisternally in dogs with or without subarachnoid haemorrhage (SAH). In the control dogs, the endothelial barrier function was confirmed for intravenous HRP, whereas the intracisternal HRP passed freely through the interstitial spaces of the adventitia and media to reach the intima within a few minutes. However, on the 5th day after SAH the barrier function of the intima for intravenous HRP was lost. In addition, there was a marked decrease in the amount of HRP reaching the intima when injected intracisternally. The intercellular space appears to be the main route for leakage of HRP into the subendothelial layer from the arterial lumen. Obstruction of the interstitial space in the adventitia by blood elements may be the cause of the disturbed intramural circulation of cerebrospinal fluid. These results suggest that this disturbance in the intramural circulation of the cerebral arterial wall plays a role in the development and/or progression of delayed cerebro-arterial narrowing after SAH.     

Disturbances of cerebrospinal fluid circulation during the acute stage of subarachnoid hemorrhage

Radioisotope cisternography was performed and the erythrocyte and hemoglobin contents of the cerebrospinal fluid (CSF) were determined within the first 4 days after subarachnoid hemorrhage in 42 patients. The clinical condition of the patients was related to the severity of the CSF circulation disturbances. Thirty-five patients had some degree of disturbance of CSF flow, and only 2 of the 42 patients had normal flow. In 5 cases the cisternograms were inconclusive. The severity of CSF circulation disturbances correlated well with clinical condition. No relationship was found between the number of erythrocytes in the CSF and the development of CSF circulation disturbances. The CSF erythrocyte content did not correlate with the clinical condition. It is suggested that flow disturbances of the CSF during the acute stage of subarachnoid hemorrhage might play an important role in the pathomechanism of the disease.     

Comparison of intimal platelet accumulation in cerebral arteries in two experimental models of subarachnoid hemorrhage

Intimal accumulation of indium-111-labeled platelets in the middle cerebral arteries was examined in two different models of experimental subarachnoid hemorrhage (SAH) in the cat. SAH was produced in 7 subjects by a transorbital rupture of the right middle cerebral artery (RMCA) and in 10 subjects by the transorbital cisternal injection of 2 ml of autologous arterial blood around the RMCA. Animals in both experimental groups were sacrificed at 2, 4, 24, and 48 hours after SAH. The radioactivity (in counts per minute) of the RMCA segment was divided by that of the left middle cerebral artery (LMCA) to produce a radioactivity ratio (RMCA/LMCA). This radioactivity ratio was determined for each animal and was scored as positive if it was 1.25 or greater, and as negative if it was less than 1.25. The scores derived from the radioactivity ratios in both experimental SAH groups were mostly positive (86 and 70%, respectively) and were significantly different (P less than 0.05) from those of intact controls (n = 7) or sham-operated controls (n = 5; n = 4). There was, however, no significant difference (P = 0.35) between the scores of the two experimental groups in the first 48 hours after SAH. The results indicate that subarachnoid blood placed upon the adventitial surface of intact cerebral arteries activates platelet aggregation to a degree comparable to that which occurs after mechanical vessel rupture in the acute stages of SAH. We suggest that the noxious agents responsible for arterial injury and subsequent intimal platelet aggregation after SAH exert their influence primarily from the abluminal surface of the cerebral artery.     

Evaluation of the microvasculature and cerebral ischemia after experimental subarachnoid hemorrhage in dogs

OBJECT: Whether cerebral vasospasm occurs only in surface vessels or also in parenchymal arterioles is debatable. The present study was undertaken to evaluate comprehensively the microvasculature of the brainstem after experimental subarachnoid hemorrhage (SAH). METHODS: Nine mongrel dogs of either sex, each weighing between 18 and 24 kg, underwent double blood injections spaced 48 hours apart; the injections were infused into the cisterna magna immediately after angiography of the basilar arteries (BAs). Three additional dogs assigned to a control group received no blood injections. The dogs were killed on Day 7. Axial sections obtained from the midpontine region of both control dogs and animals subjected to SAH were evaluated with respect to the morphological characteristics of vessels and neurons, and for ultrastructural changes. Severe vasospasm occurred in the BAs of all dogs subjected to SAH. Nevertheless, in these animals, the luminal areas and vessel perimeter in parenchymal arterioles, but not in parenchymal venules, were observed to have increased when compared with those of control dogs (p < 0.01, t-test). No corrugation of the internal elastic lamina was observed and smooth-muscle and endothelial cells remained normal at the ultrastructural level in the dogs with SAH. CONCLUSIONS: In this model, vasospasm of the BAs did not extend into the region of the pons to affect the intraparenchymal arterioles. Dilation of the parenchymal arterioles might serve as compensation for reduced blood flow. Thus, no neuronal ischemia or infarction resulted in the pontine region of the brain.     

Effects of raloxifene on cerebral vasospasm after experimental subarachnoid hemorrhage in rabbits

Background

The aim of this study was to investigate the ability of a SERM, RLX, to prevent vasospasm in a rabbit model of SAH.

Methods

Thirty-four New Zealand white rabbits were allocated into 3 groups randomly. Subarachnoid hemorrhage was induced by injecting autologous blood into the cisterna magna. The treatment groups were as follows: (1) sham operated (no SAH [n = 12]), (2) SAH only (n = 12), and (3) SAH plus RLX (n = 10). Basilar artery lumen areas and arterial wall thickness were measured to assess vasospams in all groups.

Results

There was a statistically significant difference between the mean basilar artery cross-sectional areas and the mean arterial wall thickness measurements of the control and SAH-only groups (P < .05). The difference between the mean basilar artery cross-sectional areas and the mean arterial wall thickness measurements in the RLX-treated group was statistically significant (P < .05). The difference between the SAH group and the SAH + RLX group was also statistically significant (P < .05).

Conclusions

These findings demonstrate that RLX has marked vasodilatatory effect in an experimental model of SAH in rabbits. This observation may have clinical implications suggesting that this SERM drug could be used as possible anti-vasospastic agent in patients without major adverse effects.     

Electron microscopy of simian cerebral arteries after subarachnoid hemorrhage and after the injection of horseradish peroxidase

A large unilateral subarachnoid hemorrhage (SAH) was created in 21 monkeys, and horseradish peroxidase (HRP) was injected into the cisterna magna or left internal carotid artery in 3 others (normals). Cerebral fixation was performed on Day 14 after SAH or 15 minutes after HRP injection. The major cerebral arteries from both the nonclot (control) and clot sides and the normal animals were examined with scanning and transmission electron microscopy (SEM and TEM). SEM of the adventitial surfaces of control and normal arteries revealed tunnel-like structures along the longitudinal axis. No vasa vasorum were seen, but adventitial rounded openings were observed, 10 to 35 micron in diameter in vessels of the anterior circulation and up to 80 micron in diameter in the basilar arteries. The stomas, numbering 5 to 10/mm of specimen, appeared to connect the subarachnoid and intraadventitial spaces or pathways. In SAH arteries, the tunica adventitia was coated with cellular remnants of hematoma or dense, well-organized blood clots, the removal of which revealed blocked stomas. TEM showed HRP in the vessel walls after injection into the cisterna magna, but not after injection into the carotid artery. TEM of control arteries revealed Virchow-Robin (intraadventitial) spaces lined by simple planar epithelium-like cells; Virchow-Robin spaces contained sparse nerve fiber bundles and connective tissue fibers. In SAH arteries, these spaces were almost filled with strands of connective tissue and fibroblasts; no nerve fibers were detected. Vasogenic substances probably reach smooth muscle cells via the adventitial stomas. SAH occluding the stomas may block the cerebrospinal fluid circulation, disturbing nutrition of the arterial wall or removal of wastes from it, thereby aggravating vasospasm.     

Etiology of the disruption in blood-arterial wall barrier following experimental subarachnoid hemorrhage

Aneurysmal subarachnoid hemorrhage is associated with a sudden rise in intracranial pressure, acute arterial hypertension, and subarachnoid blood. The role that each of these factors may play in the development of the acute barrier disruption of the major cerebral arteries following subarachnoid hemorrhage was investigated in 42 rabbits. Horseradish peroxidase was given intravenously to assess the integrity of the barrier by transmission electron microscopy. Permeation of the tracer into the vessel was noted only in animals with increased intracranial pressure. A sudden rise in intracranial pressure is suggested to trigger acute barrier disruption following subarachnoid hemorrhage.     

Efficacy of intrathecal liposomal fasudil for experimental cerebral vasospasm after subarachnoid hemorrhage

OBJECTIVE: To investigate the safety and efficacy of liposomal fasudil in a sustained-release form for the prevention of cerebral vasospasm after subarachnoid hemorrhage (SAH). METHODS: Eighteen rats were divided into three groups, each of which received 2.5 mg/kg of liposomal fasudil, 5 mg/kg of liposomal fasudil, or drug-free liposomes after SAH. Next, experimental SAH was induced in 15 dogs by injection of autologous arterial blood into the cisterna magna twice after baseline vertebral angiography. In six dogs, 0.94 mg/kg of liposomal fasudil was injected into the cisterna magna (treatment group). In four dogs, drug-free liposomes were similarly injected (placebo group), and the remaining five dogs were not treated with liposomal injection after SAH (control group). Angiography was repeated on Day 7, and cerebrospinal fluid was collected before the dogs were killed. RESULTS: A high dose of liposomal fasudil caused no significant changes in mean arterial blood pressure and did not induce seizures during the observation period. Gross and microscopic examination of the brains revealed no abnormalities, but severe vasospasm was noted in the rat basilar artery, mainly in the group treated with drug-free liposomes. Likewise, in the canine placebo and control groups, significant vasospasm occurred in the basilar artery on Day 7. In the treatment group, vasospasm in the basilar artery was significantly ameliorated (P < 0.01). In vivo, 90% of fasudil was released from liposomes in the cerebrospinal fluid. CONCLUSION: A single injection of intrathecal liposomal fasudil is safe and effective for the prevention of vasospasm in experimental SAH.     

The inflammation in the gut after experimental subarachnoid hemorrhage

BACKGROUND: Gastrointestinal dysfunction could be frequently observed in the patients suffering from SAH. This study test the hypothesis that experimental SAH could induce histopathological changes and inflammatory response associating with NF-kappaB activation pathway in the gut. MATERIALS AND METHODS: A total of 17 rabbits were randomly divided into two groups: control group (n = 8) and SAH group (n = 9). In the SAH group, the animals were subjected to experimental SAH according to the "two-hemorrhage" method. The histopathological study was performed to detect the intestinal mucosal morphological changes and immunohistochemical study was used to detect the TNF-alpha and ICAM-1 expressions. NF-kappaB binding activity was measured using the electrophoretic mobility shift assay. RESULTS: It was demonstrated that some damage changes and leukocytes infiltration occurred in the intestinal mucosa after SAH. More positive cells for TNF-alpha and ICAM-1 were observed in the SAH group. The NF-kappaB binding activity in the intestines was significantly increased in the SAH group (P < 0.01). CONCLUSIONS: The results of the present study suggest that SAH in the rabbits could induce NF-kappaB and proinflammatory cytokines activation in the intestine, which is associated with morphological changes.