Objective To investigate the efficacy and safety of low-dose and standard-dose intravenous alteplase for acute ischemic stroke. Methods The patients with acute ischemic stroke treated with intravenous alteplase from August 2012 to January 2016 were analyzed retrospectively. According to the dosage of the drug, the patients were divided into either a low-dose group (0. 6-0. 8 mg/kg) or a standard-dose group (0. 9 mg/kg). The efficacy was evaluated with the modified Rankin Scale (mRS) at 90 days, and a favorable functional outcome was defined as mRS 0-1. The safety was evaluated by the mortality at 90 days and the incidence of symptomatic intracerebral hemorrhage (SICH) within 7 d after onset. Results A total of 790 patients were enrolled, including 612 in the low-dose group and 178 in the standard-dose group. There was no significant difference in each baseline clinical data between the 2 groups. Compared with the standard-dose group, there was no significant difference in the good outcome rate of the small-dose group at day 90 (35. 6% vs. 37. 6% ; χ2 = 0. 872, P = 0. 35) and mortality (5. 1% vs. 6. 2% ;χ2 = 2. 173, P = 0. 14), but the incidence of SICH was significantly lower (1. 8% vs. 5. 1% ; χ2 = 5. 875, P =0. 015). Conclusion The efficacy of low-dose intravenous alteplase for acute ischemic stroke is equivalent to the standard-dose and the safety is better.

Objective:To investigate the antioxidant activity of Maca polysaccharides in vitro.Methods:A chemical reaction system was established to explore the scavenging activity of Maca polysaccharides within the concentration range of 0.18-5.00 mg ·ml-1on hydroxyl radicals (·OH),superoxide anion free radicals (O2-·) and DPPH·,and then the total antioxidant capacity was calculated. The protective effects of Maca polysaccharides on H2O2-induced damage in SH-SY5Y cells were determined. SH-SY5Y cells were divided into the control group,H2O2model group and Maca polysaccharide groups(25,50,100 μg·ml-1). In the Maca polysaccharide groups,SH-SY5Y cells were pre-protected by Maca polysaccharides for 24 h, and then incubated in the presence of 300 μmol·L-1H2O2for 6 h. The detection index was SH-SY5Y cell viability detected by MTT assay. Results:Maca polysaccharide within the concentration range of 0.18-5.0 mg·ml-1all exhibited strong scavenging activity on·OH,O2-· and DPPH·in a dose-dependent manner. When the concentration of Maca polysaccharides reached 2.5 mg·ml-1,the scavenging rate was 60.36% for DPPH·,34.66% for O2-·and 36.01% for·OH,the total antioxidant activity was equivalent to 0.179 μmol FeSO4. Maca polysaccharides at the concentration of 25, 50 and 100 μg·ml-1all showed significant protective effects on H2O2-induced injury in SH-SY5Y cells, and the cell survival rate was 61.71 ± 2.45%,61.73 ± 4.51% and 60.98 ± 3.12%, respectively,which were all significantly higher than those in the model group (P < 0.05). Conclusion:Maca polysaccharides has good antioxidant activity,which is worthy of further research and development as a natural antioxidant.