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OBJECTIVE To investigate the activation of xanthine oxidase(XO)from the human liver by vitamin K3 and the mechanism.METHODS Using human liver S9(0.1 g·L-1)as the source,XO was incubated with substrate xanthine of 0,2,4,8,and 16 μmol·L-1 at 37℃ for 90 min.The Michaelis constant(Km)of the reaction of xanthine oxidation was determined using the liquid chromatography diode array method.At the concentration of Km,the three-point method(1,10 and 100 μmol·L-1)was used to detect the activity of vitamin K3 activators.The multi-point method(vitamin K3 1,2,5,10,20,50,100,200 and 400 μmol·L-1)was adopted to determine the half effective concentration(EC50)of activated XO.Kinetic parameters(Km and Vmax)and the fit of double reciprocal curves were determined via vitamin K3 of 1/2EC50,EC50 and 2EC50.The changes in kinetic behavior at different concentrations of vitamin K3 were observed and their types of activation were analyzed.The interactions between XO and activator vitamin K3 were explored via molecular docking.RESULTS The Km of XO-mediated xanthine oxidation reac-tion was 4.71 μmol·L-1.As an activator of this reaction,vitamin K3 activated XO in a concentration-dependent manner(according to the logistic fitting formula y=A2+(A1-A2)/(1+(x/x0)
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Objective To investigate the inhibitory effects of pyruvate-ferredoxin oxidoreductase(PFOR)by luteolin and its anti-Clostridium difficile effect.Methods The PFOR encoding sequence of Clostridium difficile was cloned into the expression vector pET-2a and transformed into competent Escherichia coli.The crude enzyme was prepared after induction with IPTG(Isopropyl β-D-Thiogalactoside).The inhibitory rate of the test compounds on PFOR was determined after an 8-hour anaerobic reaction between PFOR and 40 μmol·L-1 of test compounds at 25℃.The minimum inhibitory concentration(MIC)of PFOR inhibitors against C.difficile strains(ATCC BAA 1382 and ATCC BAA 1870)was determined by monitoring the OD600 of the bacterial culture.Molecular docking was performed to investigate the possible interaction mechanisms between PFOR and inhibitors.Results Among the tested compounds,the luteolin showed the strongest inhibitory activity against PFOR,with a single-point inhibition rate of approximately 33%,which is comparable to that observed with the positive inhibitor nitazoxanide(40%).Molecular docking revealed that luteolin could form hydrogen bonds with Asp428,Val431,Gly429,Asp456,Lys458,Lys459,and other residues in the PFOR domain.The MIC of luteolin against C.difficile was approximately 32 μg·mL-1.Conclusion Luteolin exhibits good activity against C.difficile,and PFOR may be a target for its antibacterial action.
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Objective:To analyze the registration status of acute pancreatitis-related clinical studies registered on the Chinese Clinical Trial Registry (ChiCTR) and USA ClinicalTrials.gov database.Methods:The ChiCTR and ClinicalTrials.gov database were searched to collect, sort and analyze the clinical studies related to acute pancreatitis registered from the establishment of the database to December 31, 2020. The clinical trials were manually grouped, and the features of clinical researches were compared based on different registered data (2007-2014 vs 2015-2020) and different financial sources (self-support, enterprise support or public support). Results:A total of 157 registered clinical studies related to acute pancreatitis have been included (ChiCTR n=99; ClinicalTrial.gov n=58). The top three areas with the greatest number of registered clinical studies were Sichuan (28.0%), Shanghai (14.6%) and Jiangsu (12.1%), totally accounting for 54.7%. There were 91 interventional studies, 41 observational studies and 25 other type studies. Masking was performed in 34 studies (21.6%). Randomized parallel controlling was performed in 84 studies (53.5%). 30 trials (19.1%) were at Ⅳ phase, and 7 trials (4.4%) were at Ⅱ or Ⅲ phase. 2007-2014 group tended to use randomized parallel controlled design (68.3% vs 45.4%, P=0.005) and randomization grouping (76.7% vs 47.4%, P=0.001). 2015-2020 group tended to use relatively large sample (72.6% vs 47.4%, P=0.002)and data management committee (53.6% vs 25.0%, P=0.001). The differences between the two groups were statistically significant. Of 92 trials from ChiCTR database, 48 were self-supported, 5 was supported by enterprise, and 38 was supported by the public. The percentage of self-support and public support was 86.9%. Conclusions:The number of acute pancreatitis-related clinical studies registered on ChiCTR was generally on the increase. Most registered studies were funded by public finances or by the researchers' institutions self. There was a lack of phaseⅡ or phase Ⅲ.
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Objective To assess whether FICE or IC is more effective at detecting colonic diseases.Method We searched PubMed, CINAHL, CQVIP and the Cochrane Library databases for relevant papers published between January 2008 and August 2013 using the following keywords: lfexible spectral imaging color enhancement, indigo carmine, colonoscope, colonic lesions, colon tumor and chromoendoscopy. We included eight articles, and all data were subdivided for analysis.Results We used odds ratios (OR