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Query: UNIPROT:P00750 (PLA)
 16,800 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The principal goals of thrombolytic therapy for stroke are early restitution of cerebral blood flow, reduction of ischaemia, and attenuation of neurological disability through lysis of an occluding thrombus and consequent rapid restoration of circulation in the affected territory. Therapy should be initiated as soon as possible, at least within 4-6 h of stroke onset, to prevent major infarction and to salvage the hypoperfused but potentially viable zone adjacent to the central ischaemic area known as the ischaemic penumbra. This survey focuses on the safety and efficacy of thrombolytic therapy in acute ischaemic stroke in clinical trials. The results of two successful major randomized studies using tissue plasminogen activator (t-PA) were recently published. Intravenous thrombolysis seemed to be effective in improving functional and neurological outcome in a clearly defined subgroup of patients meeting the inclusion criteria of the studies. However, the identification of those patients proved to be difficult and depended on expertise in recognizing the early infarction signs on initial computed tomography. Since treating ineligible patients is associated with an unacceptable risk of intracranial bleeding complications and death, intravenous thrombolysis should only be performed at selected centres in selected patients.
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PMID:Acute ischaemic stroke: revascularizing therapy. Stroke Council of the American Heart Association. 975 93

Echoplanar magnetic resonance imaging (EPI) enables rapid, non-invasive imaging and analysis of cerebral pathophysiology in acute stroke. It represents an important clinical advance over computed tomography (CT) and conventional magnetic resonance (MR) scanning. It can rapidly delineate infarcted cerebral tissue and distinguish acute from chronic stroke. In addition, EPI has the potential to quickly determine the presence and degree of potentially viable brain tissue in the ischaemic penumbra. Thrombolysis is thought to reperfuse the penumbra and hence reduce infarct size. The thrombolytic agent tissue plasminogen activator (t-PA) improves outcome in ischaemic stroke when administered within the first 3 hours of onset. However, there is a significant risk of haemorrhage, and the time window for benefit may well exceed 3 hours in some patients. Hence, by facilitating diagnosis of 'at-risk' tissue in the ischaemic penumbra, a major clinical role of EPI may well become the rational selection of patients for acute interventional stroke therapy.
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PMID:Echoplanar magnetic resonance imaging in acute stroke. 1084 41

Neuroserpin, a recently identified inhibitor of tissue-type plasminogen activator (tPA), is primarily localized to neurons within the central nervous system, where it is thought to regulate tPA activity. In the present study neuroserpin expression and its potential therapeutic benefits were examined in a rat model of stroke. Neuroserpin expression increased in neurons surrounding the ischemic core (ischemic penumbra) within 6 hours of occlusion of the middle cerebral artery and remained elevated during the first week after the ischemic insult. Injection of neuroserpin directly into the brain immediately after infarct reduced stroke volume by 64% at 72 hours compared with control animals. In untreated animals both tPA and urokinase-type plasminogen activator (uPA) activity was significantly increased within the region of infarct by 6 hours after reperfusion. Activity of tPA then decreased to control levels by 72 hours, whereas uPA activity continued to rise and was dramatically increased by 72 hours. Both tPA and uPA activity were significantly reduced in neuroserpin-treated animals. Immunohistochemical staining of basement membrane laminin with a monoclonal antibody directed toward a cryptic epitope suggested that proteolysis of the basement membrane occurred as early as 10 minutes after reperfusion and that intracerebral administration of neuroserpin significantly reduced this proteolysis. Neuroserpin also decreased apoptotic cell counts in the ischemic penumbra by more than 50%. Thus, neuroserpin may be a naturally occurring neuroprotective proteinase inhibitor, whose therapeutic administration decreases stroke volume most likely by inhibiting proteinase activity and subsequent apoptosis associated with focal cerebral ischemia/reperfusion. (Blood. 2000;96:569-576)
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PMID:Neuroserpin reduces cerebral infarct volume and protects neurons from ischemia-induced apoptosis. 1088 20

The development of additional acute stroke therapies to complement and supplement intravenous recombinant tissue-type plasminogen activator within the first 3 hours after stroke onset remains an important and pressing need. Much has been learned about the presumed target of acute stroke therapy, the ischemic penumbra, and clinically available imaging modalities such as magnetic resonance imaging and computed tomography hold great promise for at least partially identifying this region of potentially salvageable ischemic tissue. Understanding the biology of ischemia-related cell injury has also evolved rapidly. New treatment approaches to improve outcome after focal brain ischemia will likely be derived by looking at naturally occurring adaptive mechanisms such as those related to ischemic preconditioning and hibernation. Many clinical trials previously performed with a variety of neuroprotective and thrombolytic drugs provide many lessons that will help to guide future acute stroke therapy trials and enhance the likelihood of success in future trials. Combining knowledge from these three areas provides optimism that additional acute stroke therapies can be developed to maximize beneficial functional outcome in the greatest proportion of acute stroke patients possible.
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PMID:New perspectives on developing acute stroke therapy. 1250 43

Neuroserpin is a member of the serine proteinase inhibitor (serpin) gene family that reacts preferentially with tissue-type plasminogen activator (tPA) and is primarily localized to neurons in regions of the brain where tPA is also found. Outside of the central nervous system (CNS) tPA is predominantly found in the blood where its primary function is as a thrombolytic enzyme. However, tPA is also expressed within the CNS where it has a very different function, promoting events associated not only with synaptic plasticity but also with cell death in a number of settings, such as cerebral ischemia and seizures. Neuroserpin is released from neurons in response to neuronal depolarization and plays an important role in the development of synaptic plasticity. Following the onset of cerebral ischemia there is an increase in both tPA activity and neuroserpin expression in the area surrounding the necrotic core (ischemic penumbra), and treatment with neuroserpin following ischemic stroke or overexpression of the neuroserpin gene results in a significant decrease in the volume of the ischemic area as well as in the number of apoptotic cells. TPA activity and neuroserpin expression are also increased in specific areas of the brain by seizures, and treatment with neuroserpin slows the progression of seizure activity throughout the CNS and results in significant neuronal survival in the hippocampus. Mutations in human neuroserpin result in a form of autosomal dominant inherited dementia which is characterized by the presence of intraneuronal inclusion bodies and is known as Familial Encephalopathy with Neuroserpin Inclusion Bodies.
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PMID:Neuroserpin: a selective inhibitor of tissue-type plasminogen activator in the central nervous system. 1498 20

The current status of thrombolytic therapy approved by the US Food and Drug Administration is intravenous recombinant plasminogen activator given within 3 h of the onset of ischemic stroke. Intra-arterial therapy is possible for up to 6 h but is not Food and Drug Administration-approved for this purpose. Based on current radiologic methods (i.e., magnetic resonance imaging and perfusion computed tomography scans), it is being increasingly realized that the time window for effective thrombolytic therapy is variable, and salvageable tissue in the form of the ischemic penumbra may exist for longer periods of time and could therefore offer a greater time window based on these imaging studies. Development of an effective neuroprotective drug would greatly enhance the stability of the penumbra and offer further opportunities for extending the time window for reperfusion.
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PMID:Thrombolytic therapy for acute ischemic stroke: 3 h and beyond. 1585 92

Neuroprotection of patients with acute ischemic stroke should start at the scene and continue in the ambulance with the assessment and treatment of the airway, breathing, circulation, body temperature, and blood glucose. The key goal in eligible patients should be fast vessel recanalization with intravenous recombinant tissue-type plasminogen activator Results from a meta-analysis suggest that systemic thrombolysis is effective when given within 4.5 hours after stroke onset. The time window extends to 6 hours for patients undergoing intravascular thrombolysis. Acute stroke patients should be admitted to stroke care units. A crucial component of neuroprotection is the prevention of secondary brain damage, which can be caused by hypoxemia, hypotension, hyperthermia and hyperglycemia. This can be achieved by avoiding complications, e.g. aspiration, and intensive control of oxygenation, hydration and blood pressure, body temperature, blood glucose, and cardiac monitoring. Neuroprotective agents are designed to try to salvage brain tissue within the penumbra. Thus far, despite promising preclinical studies, clinical trials with neuroprotective drugs in acute ischemic stroke have been disappointing. However, we have been able to identify many of the factors that were responsible for these failures, and better-designed clinical trials with neuroprotective drugs should look more promising. Mild induced hypothermia is another form of neuroprotective treatment that is currently being investigated in acute stroke.
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PMID:Neuroprotection in acute ischemic stroke. 1625 52

Acute ischemic stroke (AIS) is a common disorder that has only one associated approved therapy: intravenous tissue plasminogen activator (iv t-PA). A limiting factor to the use of iv t-PA is that it must be initiated within 3 h of stroke onset. Efforts to expand the therapeutic time window are underway and include image evaluation of the ischemic penumbra to target those patients who are most appropriate for treatment. Intra-arterial t-PA is also used only in some treatment centers despite convincing proof of efficacy of this therapy. Devices to restore perfusion that have been approved in the US for recanalization exist, but these are not approved for use in stroke therapy. Many neuroprotective drugs have been evaluated as potential acute stroke therapies, but none have shown efficacy, hence the future of neuroprotection as a strategy for acute ischemic stroke therapy remains uncertain.
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PMID:Treating acute ischemic stroke. 1872 14

After large CT-based clinical trials have failed to prove the benefits of intravenous tissue plasminogen activator (tPA) administration for ischemic stroke patients beyond 3 hours of the onset of the concept of PWI/DWI mismatch which is the volume difference between a PWI lesion and DWI lesion on MRI scans, has been proposed to facilitate the selection of patients with a salvageable area. PWI/DWI mismatch is considered to represent the tissue that is not irreversibly injured and can respond to early reperfusion therapy. When an ischemic lesion is divided into 4 regions, namely, ischemic core, reversible DWI lesion, penumbra and benign oligemia, both the reversible DWI lesion and penumbra are considered to be an optimal targets for thrombolysis. In order to clarify the clinical significance of PWI/DWI mismatch in the selection of candidates for tPA therapy, some multicenter trials were performed. The results of DIAS (desmoteplase in acute ischemic stroke)/DEDAS (dose escalation of desmoteplase for acute ischemic stroke)/DIAS-2 did not difinitly demonstrate the clinical benefits of desmoteplase administration in patients with PWI/DWI mismatch between 3 to 9 hours of onset; in fact, DIAS-2 could not prove any effect of the drug. DEFUSE (diffusion and perfusion imaging evaluation for understanding stroke evolution), in which tPA was administered to all participants between 3 to 6 hours of stroke onset, showed that the occurrence of early reperfusion led to a favorable clinical response in patients with PWI/DWI mismatch. In contrast, early reperfusion was not beneficial in patients without PWI/DWI mismatch. In EPITHET (echoplanar imaging thrombolysis evaluation trial), stroke patients who showed PWI/DWI mismatch after 3 to 6 hours of the onset were assigned to receive either alteplase or placebo administration: lesion growth was lesser in patients with alteplase than in those who received placebo, although the difference was not statistically significant because of a small number of participants. Although these results supported the importance of the PWI/DWI concept, there still remain some issues to be resolved. Regarding the definition of PWI/ DWI mismatch, a larger mismatch ratio than the one that has been typically used seems to be recommended. Most useful parameters of PWI should be determined to standardize volume evaluation using MRI scans. For the institutes where MRI scans are not available 24 hours a day, clinical DWI mismatch has been proposed as an alternative to of PWI/DWI mismatch. The application of MRI-based decision making strategy for stroke patients may facilitate the assessment and treatment of stroke patients beyond 3 hours of stroke onset, and is expected to allow the use of tPA for a substantially greater number of patients.
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PMID:[Intravenous administration of a tissue plasminogen activator beyond 3 hours of the onset of acute ischemic stroke--MRI-based decision making]. 1897 5

After ischaemic stroke onset, potentially viable (ie, penumbral) tissue might be salvageble for as long as 48 h. By increasing the therapeutic time window for treatment of stroke with intravenous alteplase from 3-4.5 h to 9 h, many more patients could be treated. Use of a combination of diffusion-weighted and perfusion-weighted MRI or perfusion CT might improve selection of patients with penumbral tissue. Several phase II trials of alteplase lend strong biological support to the use of this strategy for up to 6 h after stroke. However, the negative results of the phase III Desmoteplase In Acute ischaemic Stroke trial (DIAS-2) with desmoteplase given up to 9 h after stroke suggest that some refinements are needed. For trials of neuroprotection, the concept of freezing the penumbra (ie, preventing further deterioration of the vulnerable tissue) might be a more realistic expectation. Recent advances in penumbral imaging technology should enable a phase III alteplase trial to be done beyond 4.5 h by use of techniques to select patients with penumbral tissue.
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PMID:Penumbral selection of patients for trials of acute stroke therapy. 1923 36


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