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Query: UMLS:C0917798 (cerebral ischemia)
 17,036 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We undertook a detailed characterization of the cellular responses to acute global cerebral ischemia complicated by hyperglycemia. Anesthetized, physiologically monitored male Wistar rats received 12.5 min of global forebrain ischemia by bilateral common carotid artery occlusions plus hemorrhagic hypotension to 45 mmHg. Cranial temperature was maintained at normothermic levels. Hyperglycemic animals received dextrose (2.5 ml of a 25% solution, intraperitoneally) prior to ischemia; this doubled the mean plasma glucose concentration to 296 mg/100 ml. At 3 days (n = 10) or 24 h (n = 4) after ischemia, brains were perfusion-fixed and paraffin-embedded for light microscopic histopathology and for the histochemical visualization of activated microglia and the immunocytochemical visualization of glial fibrillary acid protein. Normal-neuron counts in the vulnerable hippocampal CA1 sector of hyperglycemic-ischemic (HI) rats were reduced to one-third the number observed in normoglycemic-ischemic (NI) animals. Ischemic cell counts in the striatum were increased fivefold or more in HI compared to NI rats, and normal small-neuron counts were reduced by two-thirds. The neocortex and striatum of NI rats showed only mild damage, while the majority of HI rats had extensive lesions, and several showed large cortical, striatal or thalamic infarcts. In addition, widespread cortical ischemic neuronal changes were evident in HI animals. No endothelial alterations were present in NI rats. By contrast, HI rats showed prominent peri- and intravascular polymorphonuclear and monocytic accumulation evident at 24 h; frequent white cell thrombi in pial arterioles on day 3; and thickening of vascular endothelium, with foci of parenchymal rarefaction or microinfarction adjacent to occluded vessels. Prominent microglial activation, often along the course of penetrating blood vessels, was common in the striatum and neocortex of HI animals but was much less extensive in the NI group. Activated microglia in HI rats were typically hypertrophic and amoeboid. These results suggest that the detrimental influence of hyperglycemia in ischemia is initially mediated by an action on vascular endothelium, which in turn leads to widespread foci of infarction and neuronal loss.
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PMID:Hyperglycemic exacerbation of neuronal damage following forebrain ischemia: microglial, astrocytic and endothelial alterations. 984 91

Estrogen protects the brain from experimental cerebral ischemia, likely through both vascular and neuronal cellular mechanisms. The purpose of this study was to determine whether chronic estrogen treatment in males and repletion in ovariectomized (Ovx) females reverses abnormalities in pial arteriolar reactivity during reperfusion from global forebrain ischemia (4-vessel occlusion, 15 min) and whether the site of protection is vascular endothelium. Male and Ovx female rats were implanted with either placebo or a 25-microg 17 beta-estradiol pellet 10 days before ischemia. With the use of intravital microscopy, pial vessel dilation to ACh (10 microM) and S-nitroso-N-acetyl-penicillamine (SNAP; 1 microM) and vasoconstriction to serotonin (10 microM) was examined in situ at 30--60 min of reperfusion. Postischemic changes in vessel diameter were compared with preischemic values for each agent. Postischemic response to both ACh and SNAP was lost in males and Ovx females, but not in estrogen pellet-implanted males and estrogen-implanted Ovx females, suggesting that estrogen protects both endothelial and smooth muscle-mediated vasodilation. Ischemia blunted vessel constriction to serotonin regardless of treatment. These data demonstrate that estrogen acts as a vasoprotective agent within the cerebral circulation and can improve microvascular function under conditions of an acutely evolving ischemic pathology.
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PMID:Estrogen restores postischemic pial microvascular dilation. 1140 80

Abnormal platelet reactivity has been linked to unstable angina, myocardial infarction, post angioplasty stenosis, cerebral ischemia, thrombotic stroke and a variety of inflammatory vascular disorders associated with transplantation. Drugs that inhibit blood coagulation, promote fibrinolysis or block platelet activation are important therapeutic agents in cardiovascular medicine. However, many of the current antiplatelet modalities are nonspecific, ineffective or associated with severe side effects that limit their usefulness. In this article, we discuss some basic aspects of platelet pathophysiology to illustrate the importance of ADP stimulation and signaling in platelet activation. CD39, the ATP diphosphohydrolase (ATPDase) expressed on quiescent vascular endothelium, modulates platelet purinoreceptor activity by the sequential hydrolysis of extracellular ATP or ADP directly to AMP. This thromboregulatory potential of CD39 has been recently demonstrated by the generation of mutant mice with disruption of the gene, and by a series of experiments where high level ATPDase expression has been attained by adenoviral vectors in the injured vasculature. Systemic administration of soluble derivatives of CD39 or targeted expression of the native protein to sites of vascular injury may have future therapeutic application.
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PMID:New developments in anti-platelet therapies: potential use of CD39/vascular ATP diphosphohydrolase in thrombotic disorders. 1146 20

During the past decade, there has been a surge of interest in growth factors (GFs) that act selectively on vascular endothelium and perivascular cells. Studies employing mutant mice or the administration of recombinant proteins have suggested that these factors not only mediate the proliferation of endothelial cells, but also regulate vascular differentiation, regression, and permeability. During and after cerebral ischemia, brain vasculature becomes leaky and unstable, and the normally impermeable blood-brain barrier breaks down. Several days after the ischemic insult, endothelial cells begin to proliferate, and angiogenesis occurs. Expression studies have shown that key vascular GFs are regulated, during these processes, in a complex and coordinated manner. The distinct pattern of regulation exhibited by each vascular GF suggests a unique role for each factor during the initial vascular destabilization and subsequent angiogenesis that occurs after cerebral ischemia. Data from studies in other biological systems support these suggested roles. Thus, manipulation of vascular GFs may prove to be an effective means of stabilizing or enriching brain vasculature after ischemia, and ameliorating the detrimental effects of blood-brain barrier breakdown and vessel regression after stroke.
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PMID:Vascular growth factors in cerebral ischemia. 1181 15

Blood-brain barrier (BBB) breakdown is a feature of cerebral ischaemia, multiple sclerosis, and other neurodegenerative diseases, yet the relationship between astrocytes and the BBB integrity remains unclear. We present a simple in vivo model in which primary astrocyte loss is followed by microvascular damage, using the metabolic toxin 3-chloropropanediol (S-alpha-chlorohydrin). This model is uncomplicated by trauma, ischaemia, or primary immune involvement, permitting the study of the role of astrocytes in vascular endothelium integrity, maintenance of the BBB, and neuronal function. Male Fisher F344 rats given 3-chloropropanediol show astrocytic damage and death at 4-24 h in symmetrical brainstem and midbrain nuclear lesions, while neurons show morphological changes at 24-48 h. Fluorescent 10 kDa dextran tracers show the BBB leaking from 24 h, progressing to petechial haemorrhage after 48-72 h, with apparent repair after 6 days. BBB breakdown, but not the earlier astrocytic death, is accompanied by a delayed increase in blood flow in the inferior colliculus. An ED1 inflammatory response develops well after astrocyte loss, suggesting that inflammation may not be a factor in starting BBB breakdown. This model demonstrates that the BBB can self-repair despite the apparent absence of direct astrocytic-endothelial contact. The temporal separation of pathological events allows pharmacological intervention, and the mild reversible ataxia permits long-term survival studies of repair mechanisms.
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PMID:Focal astrocyte loss is followed by microvascular damage, with subsequent repair of the blood-brain barrier in the apparent absence of direct astrocytic contact. 1496 64

Vascular endothelial growth factor (VEGF) is a vascular growth factor which induces angiogenesis (the development of new blood vessels), vascular permeability, and inflammation. In brain, receptors for VEGF have been localized to vascular endothelium, neurons, and glia. VEGF is upregulated after hypoxic injury to the brain, which can occur during cerebral ischemia or high-altitude edema, and has been implicated in the blood-brain barrier breakdown associated with these conditions. Given its recently-described role as an inflammatory mediator, VEGF could also contribute to the inflammatory responses observed in cerebral ischemia. After seizures, blood-brain barrier breakdown and inflammation is also observed in brain, albeit on a lower scale than that observed after stroke. Recent evidence has suggested a role for inflammation in seizure disorders. We have described striking increases in VEGF protein in both neurons and glia after pilocarpine-induced status epilepticus in the brain. Increases in VEGF could contribute to the blood-brain barrier breakdown and inflammation observed after seizures. However, VEGF has also been shown to be neuroprotective across several experimental paradigms, and hence could potentially protect vulnerable cells from damage associated with seizures. Therefore, the role of VEGF after seizures could be either protective or destructive. Although only further research will determine the exact nature of VEGF's role after seizures, preliminary data indicate that VEGF plays a protective role after seizures.
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PMID:Vascular endothelial growth factor (VEGF) in seizures: a double-edged sword. 1525 May 85

Fabry Disease (FD) is an X-linked lysosomal storage disorder (prevalence about 1 : 100 000) caused by a genetic defect associated with a lack of alpha-galactosidase A (alpha-GAL) enzyme activity. As a consequence, neutral glycosphingolipides can not be cleaved and metabolized, and accumulate in lysosomes of several tissues, particularly in vascular endothelium and smooth muscle cells. The most prominent symptoms comprise pain attacks and acroparesthesia, angiokeratoma, corneal opacity, renal and cardiac dysfunction, hypo- and anhidrosis, gastrointestinal symptoms, and cerebrovascular dysfunction with vertigo, headache, and cerebral ischemia. Characteristic symptoms of FD can occur in male and female patients with the same prevalence, while females with FD seem to be less severely affected. The course of untreated illness is progressive with considerable interindividual variability. Since 2001 two enzyme replacement therapies are approved which can possibly stop the disease progress and alleviate symptoms. The very few reports and clinical observations have shown that a very high proportion of FD patients develop neuropsychiatric symptoms. However, accurate data are lacking. Although the pathophysiologic mechanisms are quite unknown, it is surmised that sphingolipid deposits in the endothelium of small cerebral vessels lead to regional cerebral ischemia accompanied by neuropsychiatric symptoms and deficits. Furthermore, patients with FD are chronically distressed by pain attacks and additional somatic and psychological impairment. Frequently, pain attacks are triggered by psychosocial stress. The high interindividual variability can, thus, also be interpreted on the basis of existing stress and coping models. The present paper will review the presently available psychiatric and neuropsychological findings in FD and will discuss difficulties associated with classification and differential diagnosis of psychiatric disorders occurring in patients with FD.
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PMID:[Psychiatric and neuropsychological signs and symptoms in patients with fabry disease: literature review]. 1628 13

Strong epidemiological evidence indicates that migraine, especially migraine with aura, is associated with increased risk of ischemic stroke. However, the precise mechanisms of such a relation are currently not fully elucidated and are still a matter of speculation. Migraine may directly cause an ischemic event (i.e, migrainous infarct), by inducing cerebral microcirculatory vasoconstriction (cortical spreading depression-related oligemia), intracerebral large vessels spasm, and vascular endothelium-related hypercoagulability. On the other hand, migraine may predispose to cerebral ischemia outside of a migraine attack by affecting endothelial function, alone or in combination with traditional vascular risk factors, or by interacting with pre-existent stroke susceptibility conditions (i.e, patent foramen ovale). At least theoretically, the migraine-stroke link may be the consequence of the unfavourable effect of migraine-specific drugs (i.e, triptans or ergot alkaloids). Finally, migraine and ischemic vascular events may be linked via genetic pathways, certain genes playing a role on both diseases and influencing their relation. The coexistence of ischemic stroke and migraine in the context of specific syndromes (i.e, CADASIL) characterized by peculiar phenotype, proven inherited background and chronic alterations of the wall of cerebral small vessel arteries suggests that migraine and ischemic stroke may be the end phenotype of common pathogenic mechanisms. How to identify those migraineurs at highest risk of ischemic stroke and whether stroke can be prevented by specific therapeutic strategies are the goals of future research.
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PMID:The migraine-ischemic stroke connection: potential pathogenic mechanisms. 1927 30

The inhalation of toxic particles and gases reduces the innate defences of the lung by increasing epithelial permeability, decreasing mucociliary clearance and depressing macrophage function. There is also substantial experimental evidence that lung epithelial cells and alveolar macrophages generate a rich milieu of inflammatory mediators when exposed to atmospheric particles that can be measured in induced sputum, BAL fluid and blood. Here we review evidence that these mediators produce an integrated local lung and systemic inflammatory immune response. That results in an increase in the release of leucocytes and platelets from the bone marrow, an increased production of acute phase proteins from the liver and activation of the vascular endothelium to favour the formation of new and destabilization and rupture of existing atherosclerotic plaques. We postulate that when this response is generated in elderly persons whose lungs are compromised by COPD, it may account for the acute exacerbations of COPD that destroy the quality of life and increase the need for medical attention and hospital admissions. Moreover, the accelerated spread of the atherosclerotic process, and destabilization of existing atherosclerotic plaques in experimental animals that develop atherosclerosis naturally when exposed to atmospheric particles, may account for the acute coronary syndromes, myocardial infarction, transient cerebral ischaemia and stroke that have been documented in humans exposed to episodes of air pollution.
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PMID:Pulmonary and systemic response to atmospheric pollution. 1935 72

Epoxyeicosatrienoic acids (EETs) are arachidonic acid metabolites of cytochrome P450 epoxygenase enzymes recognized as key players in vascular function and disease, primarily attributed to their potent vasodilator, anti-inflammatory and pro-angiogenic effects. Although EETs' actions in the central nervous system (CNS) appear to parallel those in peripheral tissue, accumulating evidence suggests that epoxyeicosanoid signaling plays different roles in neural tissue compared to peripheral tissue; roles that reflect distinct CNS functions, cellular makeup and intercellular relationships. This is exhibited at many levels including the expression of EETs-synthetic and -metabolic enzymes in central neurons and glial cells, EETs' role in neuro-glio-vascular coupling during cortical functional activation, the capacity for interaction between epoxyeicosanoid and neuroactive endocannabinoid signaling pathways, and the regulation of neurohormone and neuropeptide release by endogenous EETs. The ability of several CNS cell types to produce and respond to EETs suggests that epoxyeicosanoid signaling is a key integrator of cell-cell communication in the CNS, coordinating cellular responses across different cell types. Under pathophysiological conditions, such as cerebral ischemia, EETs protect neurons, astroglia and vascular endothelium, thus preserving the integrity of cellular networks unique to and essential for proper CNS function. Recognition of EETs' intimate involvement in CNS function in addition to their multi-cellular protective profile has inspired the development of therapeutic strategies against CNS diseases such as cerebral ischemia, tumors, and neural pain and inflammation that are based on targeting the cellular actions of EETs or their biosynthetic and metabolizing enzymes. Based upon the emerging importance of epoxyeicosanoids in cellular function and disease unique to neural systems, we propose that the actions of "neuroactive EETs" are best considered separately, and not in aggregate with all other peripheral EETs functions.
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PMID:Epoxyeicosanoid signaling in CNS function and disease. 1954 42


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