Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0022116 (ischemia)
 91,303 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Sudden extreme physical stress is associated with an increased risk of myocardial infarction mainly in people with preexisting atherosclerosis. In this study we compared the effect of submaximal exercise on coagulation and fibrinolysis in patients with peripheral arterial occlusive disease (PAOD) with that in healthy control subjects. Fifteen PAOD) patients with intermittent claudication and 15 healthy control subjects, matched for age, sex, medication use, smoking habit, and conditioning, were studied. Thrombin-antithrombin III complex (TAT), D-dimer, tissue plasminogen activator (t-PA) and plasminogen activator inhibitor (PAI)-1 antigens (Ag), t-PA activity, and plasmin-alpha2-antiplasmin complex (PAP), as well as plasma catecholamines, were measured before and after a treadmill exercise test. At rest, fibrinogen (3.3+/-0.5 versus 2.9+/-0.5 g/L [mean+/-SD]; P<.05), D-dimer (392+/-128 versus 271+/-113 ng/mL; P<.05), t-PA Ag (9.1+/-5.1 versus 5.5+/-1.2 ng/mL; P<.02), and PAI-1 Ag (14.9+/-7.1 versus 7.6+/-3.8 ng/mL; P<.002) levels in plasma were markedly higher in the patient group than in the control group. In patients but not in control subjects, exercise of similar intensity elevated circulating concentrations of TAT (from 3.43+/-1.45 to 4.83+/-2.27 ng/mL; P<.05). Exercise caused a parallel increase in D-dimer, t-PA Ag, t-PA activity, PAP, and catecholamines in both groups, whereas PAI-1 Ag remained stable. Plasma lactic acid was significantly higher in patients after exercise and was associated with lower-limb ischemia. Compared with healthy control subjects, patients with PAOD showed higher t-PA Ag, PAI-1 Ag, and D-dimer levels both at rest and after exercise. Notably, submaximal exercise on a treadmill enhanced thrombin formation in patients with PAOD but not in the control subjects. Sudden catecholamine release and local ischemia during exercise may accelerate the preexisting prothrombotic potential of the atherosclerotic vessel wall.
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PMID:Physical exertion induces thrombin formation and fibrin degradation in patients with peripheral atherosclerosis. 948 89

Prompt restoration of coronary flow is the principal mechanism by which reperfusion therapy improves survival and other clinical outcomes in patients with acute myocardial infarction. Thrombolytic therapy has been the standard for care over the past decade. The use of accelerated administration of tissue plasminogen activator (t-PA) and modified or mutant t-PA which can be administered with a single bolus intravenous injection might bring further benefits. Primary balloon angioplasty (percutaneous transluminal coronary angioplasty: PTCA) is safe and effective when it can be performed quickly by experienced operators, resulting in better coronary flow and short-term survival rates than are obtained with thrombolytic therapy. However, several studies reporting data from more than 5,000 patients, of whom many were treated in low-volume local hospitals showed mortality with primary angioplasty was substantially higher than that reported from high-volume medical centers, and similar to that observed with thrombolysis with accelerated t-PA. The strategy of rapid administration of thrombolytic therapy and subsequent angioplasty only for recurrent ischemia seems to be as effective as primary angioplasty. Recently several reports have indicated that coronary stenting, when performed for suitable lesions and with good technique by experienced operators, is superior to the results obtained with balloon angioplasty and thrombolysis. However, further studies are required to establish the efficacy of primary stenting compared to PTCA.
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PMID:[Reperfusion therapy in acute myocardial infarction today: thrombolysis, balloon angioplasty and stenting]. 948 50

Thrombolytic therapy of acute ischemic stroke can be successful only as long as there is penumbral tissue perfused at rates between the thresholds of normal function and irreversible structural damage, respectively. To determine the proportion of tissue at risk of infarction, cerebral perfusion was studied in 12 patients with acute ischemic stroke who underwent treatment with systemic recombinant tissue plasminogen activator (0.9 mg/kg body weight according to National Institute of Neurological Disorders and Stroke protocol) within 3 hours of onset of symptoms, using [15O]-H2O positron emission tomography (PET) before or during, and repeatedly after thrombolysis. The size of the regions of critically hypoperfused gray matter were identified on the initial PET scans, and changes of perfusion in those areas were related to the clinical course (followed by the National Institutes of Health stroke scale) and to the volume of infarcted gray matter demarcated on magnetic resonance imaging 3 weeks after the stroke. Whereas the initial clinical score was unrelated to the size of the ischemic area, after 3 weeks there was a strong correlation between clinical deficit and volume size of infarcted gray matter (Spearman's rho, 0.96; P < 0.001). All patients with a severely hypoperfused (< 12 mL/100 g/min) gray matter region measuring less than 15 mL on first PET showed full morphologic and clinical recovery (n = 5), whereas those with ischemic areas larger than 20 mL developed infarction and experienced persistent neurologic deficits of varying degree. Infarct sizes, however, were smaller than expected from previous correlative PET and morphologic studies of patients with acute stroke: only 22.7% of the gray matter initially perfused at rates below the conventional threshold of critical ischemia became necrotic. Actually, the percentage of initially ischemic voxels that became reperfused at almost normal levels clearly predicted the degree of clinical improvement achieved within 3 weeks. These sequential blood flow PET studies demonstrate that critically hypoperfused tissue can be preserved by early reperfusion, perhaps related to thrombolytic therapy. The results correspond with experimental findings demonstrating the prevention of large infarcts by early reperfusion to misery perfused but viable tissue.
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PMID:Tissue at risk of infarction rescued by early reperfusion: a positron emission tomography study in systemic recombinant tissue plasminogen activator thrombolysis of acute stroke. 985 Jan 42

We used an adaptation of a well-established rat model of middle cerebral artery occlusion (MCAO) that is both minimally invasive and reproducible to determine the effects of time to reperfusion and administration of tissue plasminogen activator (t-PA) on the development of hemorrhagic transformation (HT) in a rat model of acute stroke. Animals were randomized to receive either t-PA 10 mg/kg (29 rats) or an equal volume of saline (29 rats) over 20 minutes, beginning 5 minutes before reperfusion. Time to artery reopening varied between 1 and 24 hours after MCAO in both groups. At 18-24 hours after ischemia, the animals were sacrificed and their brains were preserved for analysis of HT. Logistic regression was used to determine the influence of time on HT risk and calculate the time at which 50% of animals developed HT (HT50%). At 24 hours, HT was present in 17 of 29 animals in each group and was significantly influenced by the time of artery reopening: 3 (15%) of 20 animals reperfused less than 3 hours after onset of ischemia and 32 (84%) of 38 reperfused 3 or more hours after the onset of ischemia (p<0.001). There was no difference in HT50% between groups. Time to artery reopening is an important determinant of HT risk in this model of cerebral ischemia. This model may have utility in developing strategies to reduce HT formation after thrombolytic therapy in patients with acute stroke.
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PMID:Hemorrhagic transformation in focal cerebral ischemia: influence of time to artery reopening and tissue plasminogen activator. 1003 Jul 60

The contribution of the complement system to cerebral ischemic and ischemia/reperfusion injury was examined in a rabbit model of thromboembolic stroke by delivery of an autologous clot embolus to the intracranial circulation via the internal carotid artery. A two-by-two factorial design was employed to study the impact of complement depletion via pretreatment with cobra venom factor (CVF, 100 U/kg i.v.) in the setting of permanent (without tissue plasminogen activator; t-PA) and transient (with t-PA) cerebral ischemia. Thirty-two New Zealand white rabbits were assigned to one of four groups (n=8, each group): control without t-PA, control with t-PA, CVF without t-PA and CVF with t-PA. In the complement intact animals, t-PA administration resulted in an approximate 30% reduction in infarct size when compared to the group not receiving t-PA (20.4+/-6.6% of hemisphere area vs. 30.1+/-7.2%; mean+/-SEM). However, infarct sizes in the complement depleted rabbits, with (30.7+/-8.2%) or without (30.2+/-7.9%) t-PA, were no different from the control group receiving no therapy. Similarly, no difference in regional cerebral blood flow or final intracranial pressure values was noted between any of the four groups. Complement activation does not appear to be a primary contributor to brain injury in acute thromboembolic stroke.
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PMID:Complement depletion does not reduce brain injury in a rabbit model of thromboembolic stroke. 1022 42

Optimal treatment of the patient who has sustained an acute ischemic stroke requires rapid assessment and early intervention. The leisurely approach to acute stroke management sometimes taken in the past should be replaced by an approach that treats stroke as a true medical emergency. Thrombolysis with tissue plasminogen activator has been labeled for the treatment of acute ischemic stroke, but it must be given within three hours of stroke onset. However, fibrinolytic therapy can be given safely to only a fraction of patients with acute stroke, and more broadly applicable therapies are needed. Recent evidence does not support the routine use of heparin in patients with acute stroke, and early use of aspirin offers only modest benefit. Neuroprotective therapies designed to interfere with cytotoxic events initiated by ischemia are undergoing clinical trials that should be completed within the next year. At present, only tissue plasminogen activator has been labeled for acute stroke treatment; however, other agents are on the horizon, and much can be done supportively to improve neurologic outcome. Because of the unique susceptibility of neurons to ischemia, minutes count. Thus, hospitals providing care for patients with acute stroke should organize clinical protocols and pathways for effective implementation of therapies.
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PMID:Stroke: part II. Management of acute ischemic stroke. 1034 75

Dysfunction in the vascular endothelium disturbs blood flow and predisposes individuals to atherosclerosis. Deteriorated fibrinolysis may further enhance the risk for atherothrombosis. We investigated 14 healthy volunteers and 24 patients with coronary heart disease. Endothelium-dependent (acetylcholine- and ischemia-induced) and endothelium-independent (nitroprusside-induced) vasodilatation in the forearm vasculature were studied using strain-gauge plethysmography, and the fibrinolytic system measured as the response of tissue plasminogen activator (t-PA) to provocation testing (20 min venous occlusion; VOT). When acetylcholine-induced vasodilatation was measured, endothelium-dependent vasodilatation differed between groups: those with coronary heart disease had a median value of 8.5 ml/min per 100 g tissue (25th to 75th percentile 4.8-10.3), compared with 11.6 ml/min per 100 g tissue (7.3-15.5) among healthy volunteers (P = 0.03). However, ischemia-induced vasodilatation showed no difference between the groups [26.8 (22.7-35.0) versus 29.1 (25.6-30.7) ml/min per 100 g tissue, respectively, NS]. Levels of t-PA after VOT also showed no difference between the groups [21.5 (16.5-31.9) versus 20.4 (11.8-31.5) ng/ml, respectively, NS]. Results of ischemia tests and levels of t-PA after VOT correlated only in patients with coronary heart disease (r = 0.5, P = 0.015), and not in healthy volunteers. We observed a positive correlation between endothelium-dependent vasodilatation function and endothelial release of t-PA. This indicates that the same mechanism that results in defective ischemia-induced endothelial relaxation in patients with coronary heart disease may also result in suppressed fibrinolytic capacity, thus making such patients more prone to atherothrombosis.
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PMID:Endothelial release of tissue-type plasminogen activator and ischemia-induced vasodilatation are linked in patients with coronary heart disease. 1039 Jan 17

The hypothesis was tested in rats that brain ischemia by an intracerebral hematoma can be ameliorated by fibrinolysis and aspiration of the hematoma. Intraparenchymal blood clots were generated by the injection of 50 microliters of autologous blood into the right caudate nucleus in two portions seven minutes apart. Thirty or 120 min later 12 microliters recombinant tissue plasminogen activator (rtPA) or 0.9% NaCl were injected and after 30 min the resolved hematoma was aspirated. Six hours later cerebral blood flow (CBF) was determined by 14C-iodoantipyrine autoradiography. Tissue volumes of CBF < 10 ml 100 g-1 min-1 and CBF < 30 ml g-1 min-1 were determined. Clot and lesion volume were quantified histologically from serial sections stained for succinate-dehydrogenase (SDH) activity. In rtPA-treated rats the major part of the hematoma could be evacuated 30 min as well as 120 min after production of the clot. The volume of ischemic brain (CBF < 10) was significantly reduced (p < 0.05) in the rtPA group compared to saline-treated and control groups irrespective of the time of treatment. In contrast, no difference was found between the control group and the experimental groups when the volumes of brain tissue surrounding the lesion were compared which had values of CBF < 30 ml 100 g-1 min-1. In a rat model of intracerebral hemorrhage, treatment by local fibrinolysis followed by aspiration of the hematoma is effective in reducing the volume of ischemic brain tissue and of the remaining clot volume.
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PMID:Fibrinolysis and aspiration of experimental intracerebral hematoma reduces the volume of ischemic brain in rats. 1043 35

The expression of tissue factor (TF), tissue factor pathway inhibitor (TFPI), von Willebrand factor (vWF), endothelial nitric oxide (NO) synthase (eNOS), tissue plasminogen activator (tPA), its inhibitor (PAI-1), and myosin, an indicator of local shear stress, was examined in the endothelium of cerebral vessels according to vessel size and location in human autopsy brains, using immunohistochemistry. Expression of TF, vWF, eNOS, tPA/PAI-1, and myosin was much greater in intracerebral perforating arteries and the microvasculature than the pial and carotid arteries. Expression of all antigens studied was normally faint or negative in the pial and carotid arteries. However, TF, vWF, myosin, tPA, and PAI-1 were strongly expressed in the endothelium of the inner wall of the carotid bifurcation where flowing blood collides, but not in the outer wall. In the endothelium of arteries with fibrillary hyperplasia, vWF, myosin, eNOS, tPA, and PAI-1 were strongly expressed. Within the brain, microvascular expression of TFPI was very faint or negative, whereas that of vWF was intense throughout all brain regions. However, expression of TF and myosin was more intense in the basal gray matter and white matter than in the cortex. eNOS was expressed more strongly in the basal gray matter and cortex than the white matter, whereas tPA and PAI-1 expression was more intense in the white matter than the gray matter. In addition to intrinsic properties of individual vessels, these local variations in expression of pro- and antithrombotic factors in cerebral vessels may in part be due to differences in hemorheological and humoral environments to which they are exposed, and may result in local difference in vulnerability to ischemia. The present findings may in part account for the propensity of thrombus generation in the carotid inner wall, an usual source of artery-to-artery microemboli, frequent development of lacunar (small) infarcts in deep brain regions, and diffuse white matter lesions as seen in Binswanger's leukoencephalopathy.
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PMID:Local variation in expression of pro- and antithrombotic factors in vascular endothelium of human autopsy brain. 1044 49

Although the serine protease, tissue plasminogen activator (tPA), is approved by the US Food and Drug Administration for therapy to combat focal cerebral infarction, the basic concept of thrombolytic tPA therapy for stroke was challenged by recent studies that used genetically manipulated tPA-deficient (tPA-/-) mice, which suggested that tPA mediates ischemic neuronal damage. However, those studies were potentially flawed because the genotypes of tPA-/- and wild-type control mice were not entirely clear, and ischemic neuronal injury was evaluated in isolation of tPA effects on brain thrombosis. Using mice with appropriate genetic backgrounds and a middle cerebral artery occlusion stroke model with nonsiliconized thread, which does lead to microvascular thrombus formation, in the present study we determined the risk for cerebrovascular thrombosis and neuronal injury in tPA-/- and genetically matched tPA+/+ mice subjected to transient focal ischemia. Cerebrovascular fibrin deposition and the infarction volume were increased by 8.2- and 6. 7-fold in tPA-/- versus tPA+/+ mice, respectively, and these variables were correlated with reduced cerebral blood flow up to 58% (P<0.05) and impaired motor neurological score by 70% (P<0.05). Our findings indicate that tPA deficiency exacerbates ischemia-induced cerebrovascular thrombosis and that endogenous tPA protects the brain from an ischemic insult, presumably through its thrombolytic action. In addition, our study emphasizes the importance of appropriate genetic controls in murine stroke research.
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PMID:Tissue plasminogen activator (tPA) deficiency exacerbates cerebrovascular fibrin deposition and brain injury in a murine stroke model: studies in tPA-deficient mice and wild-type mice on a matched genetic background. 1089 28


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