RESUMO
The effect of middle cerebral artery (MCA) thrombosis on the integrity of the blood-brain barrier (BBB) was studied in rats using horseradish peroxidase (HRP). Endothelial injury with subsequent platelet thrombosis was produced by means of a rose bengal-sensitized photochemical reaction, facilitated by irradiating the right proximal MCA segment with the focused beam of an argon laser. At 15 minutes following thrombosis formation, diffuse leakage of HRP was observed bilaterally within cortical and subcortical brain areas. Peroxidase extravasation was most dense within the territory of the occluded artery including neocortical areas and dorso-lateral striatum. Contralaterally, a similar distribution was observed but with less intense HRP leakage. Ultrastructural studies demonstrated an increase in permeability to HRP within arterioles, venules and capillaries. At these sites, the vascular endothelium contained HRP-filled pinocytotic vesicles and tubular profiles. Although less intense, bilateral HRP leakage was also observed following MCA stenosis or femoral artery occlusion. Endothelial-platelet interactions at the site of vascular injury may be responsible for releasing substances or neurohumoral factors which contribute to the acute opening of the BBB.
Assuntos
Embolia e Trombose Intracraniana/metabolismo , Animais , Barreira Hematoencefálica , Artérias Cerebrais/efeitos da radiação , Artérias Cerebrais/ultraestrutura , Constrição Patológica , Embolia e Trombose Intracraniana/etiologia , Embolia e Trombose Intracraniana/patologia , Microscopia Eletrônica , Microscopia Eletrônica de Varredura , Lesões Experimentais por Radiação , Fatores de TempoRESUMO
The microvascular and neuronal consequences of nonocclusive common carotid artery (CCA) thrombosis were documented in rats. Thrombosis of the CCA was produced by a rose bengal-mediated photochemical insult and regional patterns of blood-brain barrier (BBB) disruption were documented by horseradish peroxidase (HRP) histochemistry at 15 min (n = 12), 4 h (n = 3), 1 day (n = 5) or 7 days (n = 5) after vascular injury. At 15 min and 4 h after thrombosis, multiple foci of BBB disruption were present throughout the thrombosed hemisphere; protein leakage was occasionally detected contralaterally. Extravasated HRP was associated with well-perfused arterioles and arterioles containing luminal platelet aggregates at different stages of degranulation. Evidence for local platelet adhesion and aggregation or endothelial disruption at these sites was not detected. However, HRP-containing endothelial plasmalemmal vesicles were present at leaky sites. Variable degrees of parenchymal injury were documented including dendritic and astrocytic swelling with neuronal necrosis. By 1 day after CCA thrombosis, the overall frequency of permeable sites, more commonly associated with luminal leukocytes and parenchymal necrosis, was reduced. At 7 days, vessels permeable to HRP were associated with tissue necrosis, reactive astrocytes and microglial infiltration. Arteriole wall thickening and leukocyte accumulation within arterioles and venules were also detected. Widespread platelet embolization leading to variable degrees of BBB disruption and tissue injury occurs after CCA thrombosis. Acute abnormalities in vascular permeability are thus hypothesized to play an important role in the acute pathogenesis of cerebrovascular thrombosis. Delayed leukocyte accumulation in this model of embolic infarction may represent a secondary insult to the injured brain.
Assuntos
Plaquetas/patologia , Doenças das Artérias Carótidas/patologia , Circulação Cerebrovascular , Embolia e Trombose Intracraniana/patologia , Neurônios/patologia , Animais , Vasos Sanguíneos/patologia , Barreira Hematoencefálica , Artéria Carótida Primitiva , Peroxidase do Rábano Silvestre , Masculino , Microcirculação , Microscopia Eletrônica , Ratos , Ratos WistarRESUMO
The effects of bilateral carotid artery occlusion/recirculation on cortical CBF (cCBF) were studied in rats following the intravenous administration of either the nitric oxide synthase inhibitor NG-nitro-L-arginine methyl ester hydrochloride (L-NAME; 30 mg/kg) or an equivalent volume of saline (500 microliters). Induction of bilateral carotid occlusion (BCO) in L-NAME-treated animals resulted in a reduction of cCBF to 30% of baseline. During recirculation subsequent to 20 min of BCO, cCBF in L-NAME-infused animals remained at 30% of baseline. In contrast, cCBF in saline-treated control animals returned to the original baseline level following a similar reduction to 30-40% of baseline during BCO. These results indicate that inhibition of nitric oxide generation limits normalization of regional cortical perfusion following occlusion of proximal large cerebral vessels.
Assuntos
Aminoácido Oxirredutases/antagonistas & inibidores , Isquemia Encefálica/fisiopatologia , Circulação Cerebrovascular , Reperfusão , Animais , Arginina/análogos & derivados , Arginina/farmacologia , Artérias Carótidas , Circulação Cerebrovascular/efeitos dos fármacos , Constrição , Masculino , NG-Nitroarginina Metil Éster , Óxido Nítrico/metabolismo , Óxido Nítrico Sintase , Ratos , Ratos WistarRESUMO
Alterations in local CBF (LCBF) were assessed autoradiographically in the rat at several time points following photochemically induced cortical infarction. Cortical infarction of consistent size and location was produced by irradiating the brain with green light through the intact skull for 20 min following the systemic injection of rose bengal. A consistent pattern of altered LCBF was recorded in both ipsilateral and contralateral brain regions over the course of the study. At 30 min, a severely ischemic zone surrounded by regions of cortical hyperemia was apparent. LCBF was also depressed relative to control values in ipsilateral cortical regions remote from the irradiated area, while contralateral cortical structures were mildly hyperemic. By 4 h, the zone of severe ischemia had enlarged and its margins were no longer hyperemic. Ipsilateral cortical and some subcortical structures demonstrated significantly depressed levels of LCBF. At 5 days, LCBF throughout both ipsilateral and contralateral cortices was depressed compared with control values. By 15 days, LCBF had returned to control levels in most brain structures shown histopathologically not to be irreversibly damaged. The temporal sequence and magnitude of these hemodynamic alterations are consistent with findings in clinical studies in which repeated measurements of CBF have been carried out in patients with acute stroke. The ability to produce a cortical infarct that results in a consistent pattern of altered CBF should facilitate the investigation of stroke mechanisms responsible for these hemodynamic abnormalities.
Assuntos
Córtex Cerebral/patologia , Infarto Cerebral/fisiopatologia , Circulação Cerebrovascular , Hemodinâmica , Animais , Autorradiografia , Infarto Cerebral/etiologia , Infarto Cerebral/patologia , Embolia e Trombose Intracraniana/etiologia , Embolia e Trombose Intracraniana/fisiopatologia , Luz/efeitos adversos , Masculino , Fotoquímica , Ratos , Ratos Endogâmicos , Fatores de TempoRESUMO
Local CMRglu (LCMRglu) values were measured by [14C]2-deoxyglucose autoradiography in the rat at 4 h and 5 days following photochemically induced cortical infarction, and these data were compared with neuropathological findings in adjacent serial sections. At both time periods, LCMRglu was markedly reduced within the lesion center, and irregular regions of moderate-to-marked glucose hypermetabolism were noted within the marginal zone of the developing infarct. At 4 h, the hypermetabolic zones were shown by pathological examination to be characterized by normal-sized, moderately hyperchromatic neurons scattered among occasional dark, shrunken neurons within preserved neuropil. In contrast, the hypermetabolic zones at 5 days coincided with foci of intense macrophage infiltration, with dissolution of the neuropil. Significant decreases in glucose utilization were also demonstrated at 4 h within brain structures remote from the site of focal injury. These structures included the lateral and auditory cortices ipsilaterally, the striatum and thalamus ipsilaterally, and the hippocampus bilaterally. In addition to these remote metabolic effects, depressed metabolism occurred within the homologous cortical region contralateral to the site of infarction. By 5 days, glucose utilization was severely depressed in all ipsilateral cortical regions but not within any contralateral cortical region. Analysis of these data suggests that more than one mechanism is responsible for the metabolic alterations occurring within brain regions remote from the site of irreversible damage. Results are discussed in light of the hemodynamic alterations occurring in this stroke model, which are presented in the accompanying report.
Assuntos
Córtex Cerebral/metabolismo , Infarto Cerebral/metabolismo , Glucose/metabolismo , Animais , Autorradiografia , Córtex Cerebral/patologia , Infarto Cerebral/etiologia , Infarto Cerebral/patologia , Desoxiglucose , Luz/efeitos adversos , Masculino , Fotoquímica , Ratos , Ratos EndogâmicosRESUMO
This study was undertaken to test whether transient depolarizations occurring in periinfarct regions are important in contributing to infarct spread and maturation. Following middle cerebral artery (MCA) occlusion we stimulated the ischemic penumbra with recurrent waves of spreading depression (SD) and correlated the histopathological changes with the electrophysiological recordings. Halothane-anesthetized, artificially ventilated Sprague-Dawley rats underwent repetitive stimulation of SD in intact brain (Group 1; n = 8) or photothrombotic MCA occlusion coupled with ipsilateral common carotid artery occlusion (Groups 2 and 3, n = 9 each). The electroencephalogram and direct current (DC) potential were recorded for 3 h in the parietal cortex, which represented the periinffarct border zone in ischemic rats. In Group 2, only spontaneously occurring negative DC shifts occurred; in Group 3, the (nonischemic) frontal pole of the ischemic hemisphere was electrically stimulated to increase the frequency of periinfarct DC shifts. Animals underwent perfusion-fixation 24 h later, and volumes of complete infarction and scattered neuronal injury ("incomplete infarction") were assessed on stained coronal sections by quantitative planimetry. Electrical induction of SD in Group 1 did not cause morphological injury. During the initial 3 h following MCA occlusion, the number of spontaneous periinfarct depolarization in Group 2 (7.0 +/- 1.5 DC shifts) was doubled in Group 3 by frontal current application (13.4 +/- 2.7 DC shifts; p < 0.001). The duration as well as the integrated negative amplitude of DC shifts over time were significantly greater in Group 3 than in Group 2 rats (duration, 5.7 +/- 3.8 vs. 4.1 +/- 2.5 min; p < 0.05). Histopathological examination disclosed well-defined areas of pannecrosis surrounded by a cortical rim exhibiting selectively damaged acidophilic neurons and astrocytic swelling in otherwise normal-appearing brain. Induction of SD in the ischemic hemisphere led to a significant increase in the volume of incomplete infarction (19.0 +/- 6.1 mm3 in Group 3 vs. 10.3 +/- 5.1 mm3 in Group 2; p < 0.01) and of total ischemic injury (100.7 +/- 41.0 mm3 in Group 3 vs. 66.5 +/- 24.7 mm3 in Group 2; p < 0.05). The integrated magnitude of DC negativity per experiment correlated significantly with the volume of total ischemic injury (r = 0.780, p < 0.0001). Thus, induction of SD in the ischemic hemisphere accentuated the development of scattered neuronal injury and increased the volume of total ischemic injury. This observation may be explained by the fact that with limited perfusion reserve, periinfarct depolarization are associated with episodic energy failure in the acute ischemic penumbra.
Assuntos
Depressão Alastrante da Atividade Elétrica Cortical , Ataque Isquêmico Transitório/patologia , Animais , Artérias Cerebrais , Constrição , Estimulação Elétrica , Eletroencefalografia , Ataque Isquêmico Transitório/fisiopatologia , Masculino , Necrose , Neurônios/patologia , Lobo Parietal/patologia , Lobo Parietal/fisiopatologia , Ratos , Ratos Sprague-DawleyRESUMO
Hyperglycemia exacerbates neuronal injury in the setting of reversible brain ischemia, but its effect on focal thrombotic infarction has been less extensively characterized. We investigated this problem in two rat models of focal vascular occlusion. In Model I, the right middle cerebral artery (MCA) was exposed via a subtemporal craniotomy in halothane- and nitrous oxide-anesthetized Wistar rats and was occluded photochemically by irradiation with an argon ion laser following the intravenous administration of the photosensitizing dye rose bengal. Permanent MCA occlusion was combined with temporary bilateral common carotid artery ligation. In Model II, similarly anesthetized Sprague-Dawley rats were subjected to permanent photochemical occlusion of the right MCA without common carotid occlusion. In both models, rats were food deprived for 24 h and were administered varying amounts of 50% dextrose (or saline) 15 min prior to vascular occlusion to produce a spectrum of plasma glucose values, ranging from 5 to 44 mumol/ml. Brains were examined histologically 7 days following vascular occlusion, and computer-assisted planimetry was used to compute infarct volumes. In Model I, the volume of neocortical infarction ranged from 30.3 to 108.4 mm3 and exhibited a strong linear correlation with increasing preischemic plasma glucose values (r = 0.70). In contrast, the size of the smaller striatal infarct in this model was not correlated with plasma glucose level. In Model II, there was a prominent striatal infarct, ranging in volume from 14.4 to 96.4 mm3, while neocortical infarction occurred inconstantly. As in Model I, striatal infarct volume in Model II showed no correlation with plasma glucose level.(ABSTRACT TRUNCATED AT 250 WORDS)
Assuntos
Infarto Cerebral/complicações , Circulação Cerebrovascular , Circulação Colateral , Hiperglicemia/complicações , Animais , Glicemia/análise , Infarto Cerebral/sangue , Infarto Cerebral/fisiopatologia , Hiperglicemia/sangue , Hiperglicemia/fisiopatologia , Masculino , Ratos , Ratos EndogâmicosRESUMO
The histopathological and hemodynamic consequences of photochemically induced middle cerebral artery (MCA) thrombosis and recanalization were studied in the rat. Recanalization of the thrombosed MCA segment was achieved by the topical application of nimodipine at 1 h following photochemically induced occlusion. Pathological consequences of permanent and temporary occlusion were compared by morphometric procedures 7 days following thrombus formation. Rats with permanent thrombosis exhibited consistent infarction of both striatum and cortex. MCA recanalization at 1 h was associated with a significant reduction in total infarct volume. In recanalized rats, small cortical infarcts, confined to the peripheral MCA territory, were observed in only three of six rats. In contrast, a mixed pattern of infarction and ischemic cell damage was documented throughout the striatum in all rats. Local CBF (1CBF), measured autoradiographically, was significantly reduced in the MCA territory following 1 h of MCA occlusion, especially within the striatum. At 1 h after recanalization, 1CBF recovered within the previously ischemic brain regions to greater than 50% of control. Perfusion deficits were detected by carbon black infusion within focal areas of the striatum following reperfusion. Thus, cortical neurons appear to tolerate 1 h of MCA occlusion in this model. In contrast, reperfusion following 1 h of photochemically induced MCA occlusion gives rise to selective injury to the striatum.
Assuntos
Arteriopatias Oclusivas/tratamento farmacológico , Artérias Cerebrais , Hemodinâmica , Animais , Arteriopatias Oclusivas/etiologia , Arteriopatias Oclusivas/patologia , Arteriopatias Oclusivas/fisiopatologia , Autorradiografia , Carbono , Artérias Cerebrais/ultraestrutura , Circulação Cerebrovascular , Microscopia Eletrônica de Varredura , Fotoquímica/métodosRESUMO
To study the effects of focal infarction on the capacity for functional activation of an ipsilateral somatosensory system remote from the lesion, we produced a small thrombotic infarct in the left frontal pole of male Wistar rats by a photochemical method. Five days later, the awake, restrained rats received tactile stimulation of the large whiskers (vibrissae) of the right side of the face, while a double-label 14C-autoradiographic study of local CMRglc (lCMRglc) and local CBF (lCBF) was performed. Unlesioned and unstimulated animals served as controls. In rats without frontal infarct, vibrissae stimulation led to activation of lCMRglc in the three synaptic relay stations of the barrel-field pathway (ipsilateral trigeminal medullary nucleus, contralateral ventrobasal thalamus, and contralateral barrel-field cortex). The mean increment in lCMRglc was 42% in lamina IV of barrel-field cortex and 49% in ventrobasal thalamus. Normalized lCBF tended to increase in superficial cortical laminae. In unstimulated animals with frontal infarct, lCMRglc was reduced by 20-30% throughout the ipsilateral barrel-field cortex as well as other ipsilateral cortical regions, but not in ventrobasal thalamus or other subcortical areas. In animals with frontal infarct subjected to contralateral vibrissae stimulation, a remarkable suppression of activation was observed throughout the barrel-field cortex so that left-less-than-right hemispheral lCMRglc asymmetry persisted despite stimulation. The ventrobasal thalamus, similarly, failed to increment its lCMRglc with vibrissae stimulation, whereas activation of the trigeminal nucleus was not suppressed. Similar trends were observed in the normalized lCBF data. These observations, which establish that a small frontal infarct is capable of suppressing normal physiological activation in remote ipsilateral brain structures, may have important implications with respect to suppression and recovery of function in human ischemic stroke.
Assuntos
Infarto Cerebral/fisiopatologia , Córtex Somatossensorial/fisiopatologia , Animais , Córtex Auditivo/fisiopatologia , Autorradiografia , Encéfalo/fisiopatologia , Circulação Cerebrovascular , Lobo Frontal/fisiopatologia , Glucose/metabolismo , Masculino , Córtex Motor/fisiopatologia , Lobo Parietal/fisiopatologia , Ratos , Ratos Endogâmicos , Tálamo/fisiopatologia , Córtex Visual/fisiopatologiaRESUMO
We documented the hemodynamic consequences of nonocclusive common carotid artery thrombosis (CCAT) and tested the hypothesis that vasoactive substances capable of altering local CBF (LCBF) are released into the systemic circulation following cerebrovascular injury. Ten minutes after photochemically induced CCAT, an autoradiographic determination of LCBF was conducted with [14C]iodoantipyrine. In blood transfusion studies using donor and recipient rats, a 1-ml sample of thrombogenically activated blood (TAB) collected downstream from the forming thrombus was reinjected into a recipient rat 15 or 60 min before CBF study. A heterogeneous pattern of abnormal LCBF was documented in the ipsilateral hemisphere of CCAT rats and recipient rats receiving TAB 15 min before CBF study. Acute hemodynamic abnormalities included ischemic (less than 35% of control) and hyperemic (greater than 125% of control) foci and more global reductions (50-80% of control) in cortical and subcortical LCBF. Border zone hyperemia exceeding 2.0 ml/g/min was associated with focal sites of severe LCBF reductions. Although recipient rats that received TAB 15 min before CBF study displayed similar hemodynamic abnormalities, LCBF values in 60-min recipient rats were not significantly different from control despite ischemic foci. Humoral factors generated during CCAT appear to be responsible for the acute LCBF consequences of cerebrovascular thrombosis. Vasoactive substances released from a thrombotic site, capable of regionally affecting vascular reactivity in a time-dependent fashion, might be expected to participate in the pathogenesis of transient ischemic attacks and acute stroke.
Assuntos
Trombose das Artérias Carótidas/fisiopatologia , Circulação Cerebrovascular , Animais , Autorradiografia , Transfusão de Sangue , Encéfalo/patologia , Trombose das Artérias Carótidas/sangue , Trombose das Artérias Carótidas/patologia , Hemodinâmica , Masculino , Ratos , Ratos EndogâmicosRESUMO
Abnormalities in cerebrovascular reactivity or hemodynamic reserve are risk factors for stroke. The authors determined whether hemodynamic reserve is reduced in an experimental model of thromboembolic stroke. Nonocclusive common carotid artery thrombosis (CCAT) was produced in rats by a rose bengal-mediated photochemical insult, and moderate hypotension (60 mm Hg/30 min) was induced 1 hour later by hemorrhage. Alterations in local cerebral blood flow (ICBF) were assessed immediately after the hypotensive period by 14C-iodoantipyrine autoradiography, and histopathologic outcome was determined 3 days after CCAT. Compared to normotensive CCAT rats (n = 5), induced hypotension after CCAT (n = 7) led to enlarged regions of severe ischemia (i.e., mean ICBF < 0.24 mL/g/min) in the ipsilateral hemisphere. For example, induced hypotension increased the volume of severely ischemic sites from 16 +/- 4 mm3 (mean +/- SD) to 126 +/- 99 mm3 (P < 0.05). Histopathologic data also showed a larger volume of ischemic damage with secondary hypotension (n = 7) compared to normotension (22 +/- 15 mm3 versus 5 +/- 5 mm3, P < .05). Both hypotension-induced decreases in ICBF and ischemic pathology were commonly detected within cortical anterior and posterior borderzone areas and within the ipsilateral striatum and hippocampus. In contrast to CCAT, mechanical ligation of the common carotid artery plus hypotension (n = 8) did not produce significant histopathologic damage. Nonocclusive CCAT with secondary hypotension therefore predisposes the post-thrombotic brain to hemodynamic stress and structural damage.
Assuntos
Encéfalo/fisiopatologia , Trombose das Artérias Carótidas/complicações , Trombose das Artérias Carótidas/fisiopatologia , Circulação Cerebrovascular/fisiologia , Hemodinâmica/fisiologia , Choque/complicações , Choque/fisiopatologia , Animais , Pressão Sanguínea , Encéfalo/irrigação sanguínea , Encéfalo/patologia , Dióxido de Carbono/sangue , Trombose das Artérias Carótidas/patologia , Lateralidade Funcional , Hipotensão/complicações , Hipotensão/patologia , Hipotensão/fisiopatologia , Masculino , Oxigênio/sangue , Pressão Parcial , Ratos , Ratos Wistar , Valores de Referência , Fluxo Sanguíneo Regional , Fatores de Risco , Choque/patologiaRESUMO
The purposes of this study were to determine whether cortical spreading depression occurs outside of the infarct produced by photothrombotic vascular occlusion, and also the direction of spreading. Focal cerebral thrombotic infarction was produced by irradiating the exposed skull of anesthetized rats with green light (560 nm) following systemic injection of rose bengal dye. At proximal sites (approximately 2 mm anterior to the infarct border), transient, severe hyperemic episodes (THEs) lasting 1-2 min were intermittently recorded. THE frequency was greatest in the first hour and declined over a 3-h period. THEs were accompanied (and usually preceded) by a precipitous rise in [K+]0 (from approximately 3 to > 40 mM) and were associated with increases in local tissue oxygen tension (tPO2). Following the rise in [K+]0, clearance of [K+]0 to its pre-THE baseline preceded baseline recovery of CBF. These data indicate that THEs were reactive to physiologic events resembling cortical spreading depression (CSD), which provoked increased demand for oxygen and blood flow, and which spread from proximal sites to areas more distal (approximately 4 mm) from the rim of the evolving infarct. MK-801 (1 mg/kg, i.v.) inhibited subsequent CSD-like episodes. We conclude that photothrombosis-induced ischemia provoked CSD which was triggered either within the infarct core or in the infarct rim and spread to more distal sites. Whether multiple episodes of CSD during infarct generation are responsible for the remote consequences of focal brain injury remains to be determined.
Assuntos
Encéfalo/fisiopatologia , Infarto Cerebral/fisiopatologia , Depressão Alastrante da Atividade Elétrica Cortical/fisiologia , Embolia e Trombose Intracraniana/fisiopatologia , Animais , Encéfalo/patologia , Infarto Cerebral/complicações , Infarto Cerebral/patologia , Maleato de Dizocilpina/farmacologia , Hiperemia/etiologia , Embolia e Trombose Intracraniana/complicações , Embolia e Trombose Intracraniana/etiologia , Luz , Masculino , Lesões Experimentais por Radiação , Ratos , Ratos WistarRESUMO
The hypotheses that cerebral embolic events lead to repetitive episodes of cortical spreading depression (CSD) and that these propagating waves trigger the expression of c-fos, brain-derived neurotrophic factor (BDNF), glial fibrillary acidic protein (GFAP), and heat shock protein 70 (HSP70) mRNA were tested. Wistar rats underwent photochemically induced right common carotid artery thrombosis (CCAT) (n = 18) or sham (n = 8) procedures. In a subgroup of rats (n = 5), laser-Doppler flowmetry probes were placed overlying the right parietal cortex to record CSD-like changes in cortical blood flow during the initial 2-hour postinjury period. Rats were killed by decapitation at 2 or 24 hours after CCAT, and brains were processed for in situ localization of the gene expression. Two to five intermittent transient hyperemic episodes lasting 1 to 2 minutes were recorded ipsilaterally after CCAT. At 2 hours after CCAT, the widespread expression of c-fos and BDNF mRNAs was observed throughout the ipsilateral cerebral cortex. Pretreatment with the N-methyl-D-aspartate receptor blocker MK-801 (2 mg/kg) 1 hour before CCAT reduced the expression of BDNF mRNA expression at 2 hours. At 24 hours after CCAT, increased expression of GFAP mRNA was present in cortical and subcortical regions. In contrast, multifocal regions of HSP70 expression scattered throughout the thrombosed hemisphere were apparent at both 2 and 24 hours after injury. These data indicate that thromboembolic events lead to episodes of CSD and time-dependent alterations in gene expression. The ability of embolic processes to induce widespread molecular responses in neurons and glia may be important in the pathogenesis of transient ischemic attacks and may influence the susceptibility of the postembolic brain to subsequent insults including stroke.
Assuntos
Depressão Alastrante da Atividade Elétrica Cortical , Expressão Gênica , Embolia Intracraniana/genética , Embolia Intracraniana/fisiopatologia , Animais , Autorradiografia , Fator Neurotrófico Derivado do Encéfalo/genética , Circulação Cerebrovascular , Proteína Glial Fibrilar Ácida/genética , Proteínas de Choque Térmico HSP70/genética , Hemodinâmica , Hibridização In Situ , Embolia Intracraniana/metabolismo , Masculino , Proteínas Proto-Oncogênicas c-fos/genética , RNA Mensageiro/metabolismo , Ratos , Ratos WistarRESUMO
The potential of nitric oxide (NO) to influence positively or negatively the outcome of mechanically induced focal cerebral ischemia is still controversial. Recent evidence suggests that NO of vascular origin, whether synthesized from exogenously administered L-arginine (L-Arg) or from NO donor compounds, is beneficial but that of neuronal origin is not. However, the therapeutic potential of NO to ameliorate stroke induced by arterial thrombosis has not been reported. We assessed the therapeutic effect of L-Arg administration in spontaneously hypertensive rats (SHR) subjected to permanent photothrombotic occlusion of the distal middle cerebral artery (dMCA). The ipsilateral carotid artery was left unligated to enhance L-Arg delivery into the putative penumbral region. Local CBF (LCBF) was assessed at 30 min by the [14C]iodoantipyrine technique (n = 9), while histological infarct volumes and index of peripheral ischemic cell change were determined at 3 days (n = 7). Rats (n = 9) given 300 mg/kg L-Arg at 18 and 3 h before photothrombotic dMCA occlusion and at 5 min afterward displayed no significant differences in LCBF compared with animals (n = 8) injected with water (the carrier vehicle) and similarly irradiated. Infarct volumes were also similar, being 37.0 +/- 9.7 mm3 (SD) in the vehicle-treated and 49.1 +/- 17.2 mm3 (SD) in the L-Arg-treated groups (both n = 7), as were assessments of ischemic neuronal density in the penumbra. In contrast, L-Arg administered intravenously in a dose of 300 mg/kg to nonischemic SHR (n = 5) increased cortical CBF by approximately 75% during a 70-min observation period. We conclude that thrombotic processes superimposed upon cerebral ischemia may facilitate tissue reactions that offset the potentially beneficial effect of L-Arg, and this caveat must be considered when proposing L-Arg for clinical treatment of focal thrombotic stroke.
Assuntos
Arginina/farmacologia , Córtex Cerebral/patologia , Circulação Cerebrovascular/efeitos dos fármacos , Hipertensão/fisiopatologia , Embolia e Trombose Intracraniana/fisiopatologia , Fármacos Neuroprotetores/farmacologia , Animais , Córtex Cerebral/irrigação sanguínea , Limiar Diferencial , Masculino , Ratos , Ratos Endogâmicos SHR/fisiologiaRESUMO
To ascertain the tempo of progression to irreversible injury in focal ischemia, we subjected halothane-anesthetized Sprague-Dawley rats to photochemically induced distal middle cerebral artery occlusion (dMCAO) combined with permanent ipsilateral and 1 h contralateral common carotid artery occlusions. Head temperature was maintained at 36 degrees C. At times centered at either 1.5 or 3 h post-dMCAO, the rate of local glucose metabolism (lCMRgl) was measured by 2-deoxyglucose autoradiography, and cytoskeletal proteolysis was assessed regionally by an immunoblotting procedure to detect spectrin breakdown products. At 1.5 h (n = 5), the cortical ischemic core was already severely hypometabolic (lCMRgl 15.5 +/- 10.8 mumol 100 g-1 min-1, mean +/- SD), whereas the cortical penumbral zone was hypermetabolic (69.0 +/- 9.7). (The lumped constant was verified to be unchanged by methylglucose studies). Neutral red pH studies at this time point showed that both the core and penumbral zones were equally acidotic. By 3 h post-dMCAO (n = 6), lCMRgl in the penumbral zone had fallen to low levels (15.4 +/- 2.2 mumol 100 g-1 min-1) equal to those of the ischemic core (16.7 +/- 4.5). Correspondingly, spectrin breakdown in the ischemic core was advanced at both 2 and 3.5 h post-dMCAO (36 +/- 18% and 33 +/- 18% of total spectrin, respectively), whereas in the penumbral zone spectrin breakdown was less extensive and more highly variable at both times (22 +/- 23% and 29 +/- 16%). We conclude that irreversible deterioration of the ischemic core, as evidenced by the onset of local cytoskeletal proteolysis, begins within 2 h of middle cerebral artery occlusion. In the ischemic penumbra, the transition from glucose hyper- to hypometabolism occurs by 3.5 h and is associated with a milder and more variable degree of spectrin breakdown.
Assuntos
Isquemia Encefálica/metabolismo , Proteínas do Citoesqueleto/metabolismo , Glucose/metabolismo , Animais , Calpaína/metabolismo , Masculino , Ratos , Ratos Sprague-Dawley , Espectrina/metabolismoRESUMO
We developed a new animal model of stroke which resembles human stroke more closely than existing models. We described the pathology produced in the brain following platelet embolism, previously described only in the retina. The common carotid artery of the rat was irradiated for 6.5 minutes with an argon laser at 514.5 nm after intravenous injection of a photosensitizing agent, rose bengal. A retinal embolus was seen in 1 rat 5 minutes after irradiation. A nonocclusive platelet thrombus was present in the carotid artery 50 minutes after irradiation, with almost all the platelet thrombus being cleared 24 hours later. Acute (1 to 10 days) changes in the brain included 44 small infarcts in 12/13 rats, cortical arterioles occluded with platelets and thickening of small vessels in normotensive rats. Chronic (4 to 12 weeks) changes included lacunes in the brains of normotensive rats and intimal proliferation of smooth muscle in the carotid artery. This is the 1st animal model of (1) stroke with emboli produced in vivo rather than injected into the carotid, (2) intimal proliferation of smooth muscle without invasion of the vessel, and (3) lacunes. This model provides results important to the laboratory study of stroke.
Assuntos
Doenças das Artérias Carótidas/complicações , Transtornos Cerebrovasculares/etiologia , Embolia e Trombose Intracraniana/etiologia , Trombose/complicações , Doença Aguda , Animais , Cegueira/etiologia , Plaquetas , Encéfalo/patologia , Artérias Carótidas/patologia , Doenças das Artérias Carótidas/patologia , Infarto Cerebral/patologia , Embolia/patologia , Embolia e Trombose Intracraniana/patologia , Masculino , Microscopia Eletrônica de Varredura , Ratos , Ratos Endogâmicos , Vasos Retinianos/patologia , Trombose/patologia , Fatores de TempoRESUMO
We studied the degree of edema resulting from focal brain compression in rats raised on vitamin E-deficient, -normal, or -supplemented diets. After release of 24 hours of epidural compression, edema developed ipsilaterally and was characterized by extravasation of serum protein, increased water and sodium content, and little change in potassium. The degree of swelling and increase of sodium in the previously compressed area were most pronounced in the vitamin E-deficient group and mildest in the vitamin E-supplemented group. Degradative processes of biomembranes seem to participate in the pathogenesis of brain edema; vitamin E may stabilize membranes by physicochemical interactions between the phytyl side chain and polyunsaturated phospholipids, or vitamin E may disrupt chains of free radical reactions.
Assuntos
Edema Encefálico/metabolismo , Vitamina E/uso terapêutico , Animais , Edema Encefálico/dietoterapia , Permeabilidade da Membrana Celular , Metabolismo dos Lipídeos , Masculino , Ratos , Ratos Endogâmicos , Vitamina E/metabolismoRESUMO
Oxidative stress has been associated with the development of blood-brain barrier disruption and cellular injury after ischemia. The cytosolic antioxidant, copper/zinc superoxide dismutase, has been shown to protect against blood-brain barrier disruption and infarction after cerebral ischemia-reperfusion. However, it is not clear whether copper/zinc superoxide dismutase can protect against evolving ischemic lesions after thromboembolic cortical ischemia. In this study, the photothrombotic ischemia model, which is physiologically similar to thromboembolic stroke, was used to develop cortical ischemia. Blood-brain barrier disruption and oxidative cellular damage were investigated in transgenic mice that overexpress copper/zinc superoxide dismutase and in littermate wild-type mice after photothrombotic ischemia, which was induced by both injection of erythrosin B (30 mg/kg) and irradiation using a helium neon laser for 3 min. Free radical production, particularly superoxide, was increased in the lesioned cortex as early as 4 h after ischemia using hydroethidine in situ detection. The transgenic mice showed a prominent decrease in oxidative stress compared with the wild-type mice. Blood-brain barrier disruption, evidenced by quantitation of Evans Blue leakage, occurred 1 h after ischemia and gradually increased up to 24 h. Compared with the wild-type mice, the transgenic mice showed less blood-brain barrier disruption, a decrease in oxidative DNA damage using 8-hydroxyguanosine immunohistochemistry, a subsequent decrease in DNA fragmentation using the in situ nick-end labeling technique, and decreased infarct volume after ischemia. From these results we suggest that superoxide anion radical is an important factor in blood-brain barrier disruption and oxidative cellular injury, and that copper/zinc superoxide dismutase could protect against the evolving infarction after thromboembolic cortical ischemia.
Assuntos
Barreira Hematoencefálica , Isquemia Encefálica/fisiopatologia , Citosol/enzimologia , Trombose Intracraniana/fisiopatologia , Superóxido Dismutase/fisiologia , Absorção , Animais , Isquemia Encefálica/genética , Isquemia Encefálica/metabolismo , Córtex Cerebral/irrigação sanguínea , Infarto Cerebral/patologia , Dano ao DNA , Fragmentação do DNA , Eritrosina/análise , Corantes Fluorescentes/análise , Trombose Intracraniana/etiologia , Trombose Intracraniana/genética , Lasers , Masculino , Camundongos , Camundongos Transgênicos/genética , Sistema Nervoso/fisiopatologia , Estresse Oxidativo/fisiologia , Superóxido Dismutase/genética , Superóxido Dismutase-1 , Fatores de TempoRESUMO
PURPOSE: The authors have previously reported successful photodynamic occlusion of corneal blood vessels using intravenous rose bengal and argon green laser irradiation. To explore the action mechanism of this novel technique of photothrombosis, they examined the photodynamic effect of rose bengal on cultured fibroblasts, smooth muscle cells, and vascular endothelium--the cellular components of blood vessels. METHODS: Five types of cells were exposed to different concentrations of rose bengal and argon green laser irradiation. The irradiated cell areas were analyzed by fluorescence microscopy and fluorometry. Various potential quenchers and proteins were tested for their modulation of the photodynamic action. RESULTS: Upon irradiation with 16 W/cm2 of argon green laser light in conjunction with rose bengal concentrations extending above 1 x 10(-4) M, all cultured cell types showed a dose-dependent photobiologic effect characterized by constriction and detachment of the laser-irradiated cell region from the rest of the cell monolayer. In addition, there was dye photobleaching and development of a blue shift of the fluorescence excitation and emission maxima in the irradiated cell areas. Binding of rose bengal to intracellular components was demonstrated by fluorescence microscopy and by fluorometry showing a red shift of the excitation maximum compared to the maximum in solution. This binding was a prerequisite for expression of the described photobiologic effect, because polymer-conjugated rose bengal (Sensitox II) failed to reproduce it. The addition of native or heat-inactivated bovine serum albumin or catalase decreased this photobiologic effect also owing to dye binding, as indicated by G-75 Sephadex gel filtration chromatography. CONCLUSION: These results indicate that the specific photobiologic effect of monolayer contraction, which simulates the vasoconstriction seen during photothrombosis under argon green irradiation, appears to be caused by the photochemical interaction of rose bengal bound with intracellular components.
Assuntos
Vasos Sanguíneos/efeitos dos fármacos , Vasos Sanguíneos/efeitos da radiação , Lasers , Fármacos Fotossensibilizantes/farmacologia , Rosa Bengala/farmacologia , Animais , Coagulação Sanguínea/efeitos dos fármacos , Coagulação Sanguínea/efeitos da radiação , Catalase/metabolismo , Movimento Celular/efeitos da radiação , Células Cultivadas , Relação Dose-Resposta a Droga , Endotélio Vascular/metabolismo , Endotélio Vascular/efeitos da radiação , Fibroblastos/metabolismo , Fibroblastos/efeitos da radiação , Humanos , Músculo Liso Vascular/metabolismo , Músculo Liso Vascular/efeitos da radiação , Coelhos , Ratos , Rosa Bengala/metabolismo , Soroalbumina Bovina/metabolismo , Superóxido Dismutase/metabolismoRESUMO
Corneal neovascularization may reduce the success of penetrating keratoplasty. Photothrombosis using intravenous rose bengal and argon laser irradiation has shown promise for occluding corneal vessels. It is therefore conceivable that photothrombosis can improve the graft survival in vascularized corneas. Using intracorneal 7-0 silk sutures as the stimuli, corneal neovascularization was induced in 1 eye each of 19 New Zealand white rabbits. Eleven eyes received photothrombosis. Successful occlusion with subsequent regression was verified by corneal fluorescein angiography. Three were assigned for observation. Six of 8 eyes receiving grafts from an outbred rabbit donor after photothrombosis remained clear during 6.5 to 18.5 weeks of follow-up, while vascularization and opacity occurred in 7 of 8 control eyes without photothrombosis. These results indicate that prior photothrombotic occlusion of corneal vessels can significantly improve graft survival in this experimental model and may have clinical applications.