Implementation of supervised physical training to reduce vasovagal syncope recurrence: A randomized controlled trial.

INTRODUCTION: Physical techniques used for the prevention of vasovagal syncope have limited evidence for efficacy. We aimed to evaluate multimodal supervised physical training as a treatment approach. METHODS: In this 1:1 randomized trial, patients with ≥2 episodes of clinically diagnosed vasovagal syncope were included. On top of standard care, the intervention arm performed supervised tilt training and aerobic exercise in six sessions at a cardiac rehabilitation center (three sessions during the first month, and then at 3-month intervals), plus home tilt training. The control arm received standard care with a similar protocol of home tilt training. The primary outcome was time to first syncopal recurrence during 1 year of follow-up. RESULTS: Fifty participants were randomized (mean age: 34.5 ± 14.8 years; 64% female). The rate of syncopal recurrence was 28% and 64% within the intervention and control arms, respectively, with significantly higher syncope-free survival at 1 year in the intervention arm (Log-rank p = .003). The frequency of recurrent syncopal events was significantly lower with physical training (p = .017). Participants in the intervention arm reported significantly higher adherence to the home tilt training program (80% vs. 52%; p = .037). CONCLUSION: Among patients with recurrent vasovagal syncope, a supervised program of tilt training and aerobic exercise reduced syncopal recurrence. Future trials are warranted to further investigate multimodal supervised physical techniques as a therapeutic approach in treating vasovagal syncope.

Efficient refolding of recombinant reteplase expressed in Escherichia coli strains using response surface methodology.

Reteplase is a deleted variant of human tissue plasminogen activator with a complex structure containing nine disulfide bonds. Reteplase is expressed as inclusion bodies in Escherichia coli and needs the additional step of refolding for activation. In this study an experimental design was performed to find the optimal refolding condition for reteplase. The influence of 14 chemical additives was assessed by one factor at a time method and then Taguchi design followed by response surface methodology was employed to find compounds with most significant effects on reteplase refolding and their optimum concentration. We found that 0.13 M histidine, 1.64 M methionine, 0.33 M cysteine, and 0.34 M arginine in addition to the GSH/GSSG is the optimal condition for refolding of reteplase. We also investigated the refolding yield for inclusion bodies obtained from different E. coli strains and found that BL21 (DE3) has the best recovery yield in comparison to Rosetta-gami and Shuffle T7.

Auto-induction for high level production of biologically active reteplase in Escherichia coli.

Reteplase is a third generation tissue plasminogen activator (tPA) with a modified structure and prolonged half-life in comparison to native tPA. As a non-glycosylated protein, reteplase is expressed in Escherichia coli. Due to presence of several disulfide bonds, high level production of reteplase is complicated and needs extra steps for conversion to biologically active form. Auto-induction represents a method for high-yield growth of bacterial cells and higher expression of recombinant proteins. Here we have tried to optimize the auto-induction procedure for soluble and active expression of reteplase in E. coli. Results showed that using auto-induction strategy at 37 °C, Rosetta-gami (DE3) had the highest level of active and soluble reteplase production in comparison to E. coli strains BL21 (DE3), and Shuffel T7. Temperature dominantly affected the level of active reteplase production. Decreasing the temperature to 25 and 18 °C increased the level of active reteplase by 20 and 60%, respectively. The composition of auto-induction medium also dramatically changed the active production of reteplase in cytoplasm. Using higher enriched auto-induction medium, super broth base including trace elements, significantly increased biologically active reteplase by 30%. It is demonstrated here that auto-induction is a powerful method for expression of biologically active reteplase in oxidative cytoplasm of Rosetta-gami. Optimizing expression condition by decreasing temperature and using an enriched auto-induction medium resulted in at least three times higher level of active reteplase production. Production of correctly folded and active reteplase in spite of its complex structure helps for removal of inefficient and cumbersome step of refolding.