Thrombolysis with rhPro-UK 3 to 6 hours after embolic stroke in rat

ABSTRACT

Objectives: To investigate the thrombolysis with recombinant human prourokinase (rhPro-UK) on thromboembolic stroke in rats at different therapeutic time windows (TTW).

Methods: Rats were subjected to embolic middle cerebral artery occlusion. RhPro-UK and positive control drugs rt-PA,UK were administered 3 h, 4.5 h, 6 h after inducing thromboem-bolic stroke. Neurological deficit scoring (NDS) was evaluated at 6 h and 24 h after the treatment. The lesion volume in cerebral hemispheres was measured by MRI scanning machine after 6 h of thrombolysis, and the infarct volume was measured by TTC stain, together with hemorrhagic volume quantified by a spectrophotometric assay after 24 h of thrombolysis.

Results: RhPro-UK 10, 20 × 10⁴ U/kg significantly improved the NDS after cerebral thromboembolism in rats at 3 h, 4.5 h TTW, and at the 6 h TTW, the NDS was improved by 28.0% (P = 0.0690) and 29.2% (P = 0.0927) at 6 h and 24 h after rhPro-UK 20 ×10⁴ U/kg administration, respectively. RhPro-UK 10, 20 × 10⁴ U/kg significantly reduced the brain lesions measured by MRI at 3 h and 4.5 h TTW. RhPro-UK 10, 20 × 10⁴ U/kg significantly reduced the cerebral infarction measured by TTC at 3 h, 4.5 h TTW. There was no increase in cerebral hemorrhage compared with untreated group after rhPro-UK administration.

Conclusions: RhPro-UK had an obvious therapeutic effect on ischemic stroke caused by thrombosis, and could be started within 4.5 h TTW with less side effects of cerebral hemorrhage than that of UK.     

Clot injection technique affects thrombolytic efficacy in a rat embolic stroke model: implications for translaboratory collaborations

Current recommendations encourage the use of embolic stroke (ES) models and replication of results across laboratories in preclinical research. Since such endeavors employ different surgeons, we sought to ascertain the impact of injection technique on outcome and response to thrombolysis in an ES model. Embolic stroke was induced in Male Wistar Kyoto rats (n=166) by a fast or a slow clot injection (CI) technique. Saline or recombinant tissue plasminogen activator (rtPA) was given at 1 hour after stroke. Flow rate curves were assessed in 24 animals. Cerebral perfusion was assessed using laser Doppler flowmetry. Edema corrected infarct volume, hemispheric swelling, hemorrhagic transformation, and neurologic outcome were assessed at 24 hours after stroke. Clot burden was estimated in a subset of animals (n=40). Slow CI resulted in significantly smaller infarct volumes (P=0.024) and better neurologic outcomes (P=0.01) compared with fast CI at 24 hours. Unexpectedly, rtPA treatment attenuated infarct size in fast (P<0.001) but not in slow CI experiments (P=0.382), possibly related to reperfusion injury as indicated by greater hemorrhagic transformation (P<0.001) and hemispheric swelling (P<0.05). Outcome and response to thrombolysis after ES are operator dependent, which needs to be considered when comparing results obtained from different laboratories.     

Cerebral tissue repair and atrophy after embolic stroke in rat: A magnetic resonance imaging study of erythropoietin therapy

Using magnetic resonance imaging (MRI) protocols of T₂‐, T₂*‐, diffusion‐ and susceptibility‐weighted imaging (T2WI, T2*WI, DWI, and SWI, respectively) with a 7T system, we tested the hypothesis that treatment of embolic stroke with erythropoietin (EPO) initiated at 24 hr and administered daily for 7 days after stroke onset has benefit in repairing ischemic cerebral tissue. Adult Wistar rats were subjected to embolic stroke by means of middle cerebral artery occlusion (MCAO) and were randomly assigned to a treatment (n = 11) or a control (n = 11) group. The treated group was given EPO intraperitoneally at a dose of 5,000 IU/kg daily for 7 days starting 24 hr after MCAO. Controls were given an equal volume of saline. MRI was performed at 24 hr and then weekly for 6 weeks. MRI and histological measurements were compared between groups. Serial T2WI demonstrated that expansion of the ipsilateral ventricle was significantly reduced in the EPO‐treated rats. The volume ratio of ipsilateral parenchymal tissue relative to the contralateral hemisphere was significantly increased after EPO treatment compared with control animals, indicating that EPO significantly reduces atrophy of the ipsilateral hemisphere, although no significant differences in ischemic lesion volume were observed between the two groups. Angiogenesis and white matter remodeling were significantly increased and occurred earlier in EPO‐treated animals than in the controls, as evident from T2*WI and diffusion anisotropy maps, respectively. These data indicate that EPO treatment initiated 24 hr poststroke promotes angiogenesis and axonal remodeling in the ischemic boundary, which may potentially reduce atrophy of the ipsilateral hemisphere. © 2010 Wiley‐Liss, Inc.     

Early administration of pyrrolidine dithiocarbamate extends the therapeutic time window of tissue plasminogen activator in a male rat model of embolic stroke

Tissue plasminogen activator (tPA) is used in fewer than 4% of patients after ischemic stroke because of its narrow therapeutic time window. We tested whether pyrrolidine dithiocarbamate (PDTC), a drug with multiple mechanisms to provide neuroprotection, can be used to extend the therapeutic time window of tPA. Three‐month‐old male Sprague‐Dawley rats were subjected to embolic stroke in the area supplied by the right middle cerebral artery. tPA at 10 mg/kg was given intravenously 4 h after the onset of stroke. PDTC at 50 mg/kg was given via gastric gavage at 30 min or 4 h after the onset of stroke. Two days after the stroke, neurological outcome was evaluated and the right frontal cortex area 1 (Fr1), an ischemic penumbral region, was harvested for analysis. PDTC given at 30 min after the stroke reduced infarct volumes and improved neurological functions no matter whether the rats received tPA. PDTC also reduced tPA‐increased hemorrhagic volumes. Consistent with these results, PDTC in the presence or absence of tPA treatment attenuated the increase of proinflammatory cytokines, oxidative stress and matrix metalloprotease 2 activity in the right Fr1. However, PDTC given at 4 h after the onset of stroke did not improve the neurological outcome of rats treated with or without tPA. Our results suggest that PDTC given at an early time point but not in a delayed phase provides neuroprotection against embolic stroke and may be used to extend the therapeutic time window of tPA.     

非粘附性液体栓塞剂Onyx栓塞脑动静脉畸形

目的 探讨非粘附性液体栓塞剂Onyx栓塞治疗脑动静脉畸形的可行性和安全性。方法 采用Onyx液体栓塞剂栓塞24例脑动静脉畸形，并对血管内治疗效果和手术的注意事项进行分析。结果 24例患者经过26次Onyx栓塞操作。畸形血管团完全栓塞5例，70％以上栓塞11例，70％以下栓塞8例。并发症情况：术后出血1例，未能撤出微导管而留置体内2例。其余病例无严重并发症。结论 Onyx栓塞脑动静脉畸形允许术者长时间缓慢注射，在掌握一定的推注技巧和控制返流技术后，可以显著提高脑动静脉畸形血管内治疗的效果。     

Multiparametric ISODATA analysis of embolic stroke and rt-PA intervention in rat

To increase the sensitivity of MRI parameters to detect tissue damage of ischemic stroke, an unsupervised analysis method, Iterative Self-Organizing Data Analysis Technique Algorithm (ISODATA), was applied to analyze the temporal evolution of ischemic damage in a focal embolic cerebral ischemia model in rat with and without recombinant tissue plasminogen activator (rt-PA) treatment. Male Wistar rats subjected to embolic stroke were investigated using a 7-T MRI system. Rats were randomized into control (n=9) and treated (n=9) groups. The treated rats received rt-PA via a femoral vein at 4 h after onset of embolic ischemia. ISODATA analysis employed parametric maps or weighted images (T1, T2, and diffusion). ISODATA results with parametric maps are superior to ISODATA with weighted images, and both of them were highly correlated with the infarction size measured from the corresponding histological section. At 24 h after embolic stroke, the average map ISODATA lesion sizes were 37.7+/-7.0 and 39.2+/-5.6 mm2 for the treated and the control group, respectively. Average histological infarction areas were 37.9+/-7.4 mm2 for treated rats and 39.4+/-6.1 mm2 for controls. The R2 values of the linear correlation between map ISODATA and histological data were 0.98 and 0.96 for treated and control rats, respectively. Both histological and map ISODATA data suggest that there is no significant difference in infarction area between non-treated and rt-PA-treated rats when treatment was administered 4 h after the onset of embolic stroke. The ISODATA lesion size analysis was also sensitive to changes of lesion size during acute and subacute stages of stroke. Our data demonstrate that the multiparameter map ISODATA approach provides a more sensitive quantitation of the ischemic lesion at all time points than image ISODATA and single MRI parametric analysis using T1, T2 or ADCw.     

纳米自组装肽作为液体栓塞剂在大鼠动脉瘤模型中的应用

背景：使用液体栓塞剂栓塞动脉瘤是治疗动脉瘤的一种有效的方法。理想的栓塞剂应具有无毒,组织相容性好,并能有效诱导相应的细胞向材料内生长而达到永久性栓塞动脉瘤的特性。 目的：探讨纳米自组装材料RADA16-Ⅰ在大鼠颈总动脉瘤中作为液体栓塞剂的可行性。 设计、时间及地点：随机对照动物实验,于2008-03/09在四川大学华西医院科技园完成。 材料：RADA16-Ⅰ粉末由上海波泰生物公司合成,醋酸纤维素聚合物购自国药集团化学试剂有限公司。 方法：①体外实验：流变仪频率扫描测量短肽10 g/LRADA 16-Ⅰ水溶液与PBS等体积混合前后的流变学特性。 ②动物手术：15只Wistar大鼠随机分为3组,10 g/L RADA16-Ⅰ组,醋酸纤维素聚合物组,假手术组各5只。麻醉后,小心剥离右侧颈总动脉,并向颈总动脉结扎处2 mm近心端注入RADA16-Ⅰ或醋酸纤维素聚合物溶液。假手术组只结扎动脉,不进行栓塞治疗。 主要观察指标：①应用TA Instruments Advantage软件分析10 g/L RADA 16-Ⅰ流变学特性。②术后14 d取右侧颈总动脉,制备切片进行苏木精-伊红染色和Masson染色;同时10 g/L RADA 16-Ⅰ组进行抗平滑肌α-actin抗体免疫组织化学检测。 结果：①加入PBS的10 g/L RADA16-Ⅰ水凝胶更接近标准的弹性体行为。②假手术组大鼠颈总动脉血管壁明显增厚;醋酸纤维素聚合物组血管壁变薄,管腔内为呈粉色(苏木精-伊红染色)或蓝色(Masson染色);RADA 16-Ⅰ组血管壁增厚,血管壁新生内膜细胞向管腔内生长,栓塞材料降解,长入动脉瘤管腔的细胞主要为α-actin阳性的血管平滑肌细胞。 结论：RADA16-Ⅰ作为一种液体栓塞剂是可行的。     

In‐hospital stroke: a multi‐centre prospective registry

Background: In‐hospital strokes (IHS) are relatively frequent. Avoidable delays in neurological assessment have been demonstrated. We study the clinical characteristics, neurological care and mortality of IHS. Methods: Multi‐centre 1‐year prospective study of IHS in 13 hospitals. Demographic and clinical characteristics, admission diagnosis, quality of care, thrombolytic therapy and mortality were recorded. Results: We included 273 IHS patients [156 men; 210 ischaemic strokes (IS), 37 transient ischaemic attacks (TIA) and 26 cerebral haemorrhages]. Mean age was 72 ± 12 years. Cardiac sources of embolism were present in 138 (50.5%), withdrawal of antithrombotic drugs in 77 (28%) and active cancers in 35 (12.8%). Cardioembolic stroke was the most common subtype of IS (50%). Reasons for admission were programmed or urgent surgery in 70 (25%), cardiac diseases in 50 (18%), TIA or stroke in 30 (11%) and other medical illnesses in 71 (26%). Fifty‐two per cent of patients were evaluated by a neurologist within 3 h of stroke onset. Thirty‐three patients received treatment with tPA (15.7%). Thirty‐one patients (14.7%) could not be treated because of a delay in contacting the neurologist. During hospitalization, 50 patients (18.4%) died, 41 of them because of the stroke or its complications. Conclusions: Cardioembolic IS was the most frequent subtype of stroke. Cardiac sources of embolism, active cancers and withdrawal of antithrombotic drugs constituted special risk factors for IHS. A significant proportion of patients were treated with thrombolysis. However, delays in contacting the neurologist excluded a similar proportion of patients from treatment. IHS mortality was high, mostly because of stroke.     

Cerebral embolism and epileptic seizures — the role of the embolic source

Objectives – To study the clinical outcome of patients with epileptic seizures due to ischemic stroke (IS) of cardiac or artery-to-artery embolism. Methods – Seizures due to IS of cardiac or artery-to-artery embolism are differentiated by clinical, neuroimaging and cardiovascular test data. Results – From 174 cases with supratentorial IS, 13 patients suffered from epileptic seizures due to cardiac embolism, 11 patients due to artery-to-artery embolism. The patients with cardiac IS showed an equal sex distribution and EEG abnormalities in 6 patients, the initial seizure occurred on average after 222 days (SD, ±69 days). Among the 11 patients with artery-to-artery embolic IS, there were 9 males and 2 females and EEG abnormalities in 10 patients. The initial seizure occurred on average after 447 days (SD, ±177 days). Conclusion – In seizures due to artery-to-artery embolism, there is a male preponderance and a higher incidence of EEG abnormalities, symptomatic seizures appear later compared to IS due to cardiac embolism.     

Prevention of embolic stroke by catheter ablation of atrial fibrillation

Background and purpose: Radiofrequency‐catheter‐ablation of atrial fibrillation is now commonly performed. Aim of this short review is to summarize questions and uncertainties concerning radiofrequency ablation of atrial fibrillation with respect to therapeutic mechanisms, long‐term efficacy and stroke‐prevention. Results: The majority of atrial fibrillation patients is too old for radiofrequency ablation. Candidates for radiofrequency ablation belong to a subgroup with a low embolic risk. The radiofrequency ablation procedure itself may increase the embolic risk, and at present it is uncertain how long this embolic risk persists after the procedure. Conclusion: We doubt if radiofrequency ablation prevents embolism in atrial fibrillation.     

Continuous monitoring versus HOLTER ECG for detection of atrial fibrillation in patients with stroke

Background and purpose: Detection of atrial fibrillation is of vital importance because oral anticoagulation decreases the risk of a stroke by 64%. Current standards for stroke unit treatment require continuous electrocardiogram (ECG) monitoring for at least 24 h. Additionally, a 24‐h HOLTER ECG (HOLTER) should be performed in selected patients. It remains unclear whether continuous monitoring at the bedside is equivalent to HOLTER for the detection of atrial fibrillation. Furthermore, we investigate how many additional patients with paroxysmal atrial fibrillation can be identified as a result of a longer duration of continuous monitoring. Methods: In this study, we prospectively compared the detection rates of HOLTER and 24‐h monitoring at the Stroke Unit at the University of Heidelberg over a period of 9 months. Continuous monitoring was analyzed by trained nurses, HOLTER by cardiologists. Results: We included 370 patients with ischemic stroke or transient ischemic attack (TIA) in our study. Of these, 192 patients underwent HOLTER. Previously unknown atrial fibrillation was detected in 44 patients, 13 patients had no atrial fibrillation in baseline ECG, but atrial fibrillation was detected by continuous monitoring. In two patients, the HOLTER showed atrial fibrillation; both patients had also been detected by continuous monitoring. Median time to detection of the atrial fibrillation during continuous monitoring was 43 h after hospitalization. Conclusion: In this study, use of HOLTER does not give any additional benefit in comparison with continuous monitoring with intermittent analysis by trained staff alone. The median detection time of 43 h emphasizes the importance of longer continuous monitoring.