Objective To determine the function of conserved amino acids in the fusion-promoting domain of Newcastle disease virus (NDV) hemagglutinin-neuraminidase (HN) protein,clearly understanding mechanism of cell fusion.MethodsUsing a PCR-based site-directed mutagenesis method and the method of homology recombination occurred in vivo to change six conservative amino acids into alanine respectively.Wild type (WT) and all mutant HN proteins were exepressed in BHK-21 cells by the vacciniaT7 RNA polymerase expression system.The amount of each HN protein at the cell surface was determined by fluorescence-activated cell sorter (FACS).Cell fusion efficiency,hemadsorption activity (or receptor binding activity) and neuraminidase activity were determined.Results There was no statistic difference of cell surface expression among WT and each mutant HN protein ( P＜0.05 ).Cell fusion efficiency of each mutant protein decreased to some extent,especially 1103A decreased to 14.2％ in head.Hemadsorption activity of mutant proteins were reduced in different extent,the maximum reduction of which was also 1103A,28.2％ of wt NDV HN.There was different neuraminidase activity among each mutant HN protein.L74A increased slightly to 118.6％.L110A decreased most to 5.2％.I103A decreased second most to 5.7％.Conclusion Conserved amino acids in fusion-promoting domain of NDV HN played an important role in cell fusion.I103 was identified as a key amino acid in this domain.

Objective:The treatment of Tossy type Ⅲ acromioclavicular joint dislocation with clavicular hook plate combined with coracoclavicular ligament repair, and to explore its clinical effect.Methods:80 patients with Tossy type Ⅲ acromioclavicular joint dislocation who were admitted to our hospital from January 2014 to January 2019 were selected. They were randomly divided into control group ( n=39, treated with clavicular hook plate) and study group ( n=41, treated with clavicular hook plate combined with coracoclavicular ligament repair) by number table method. The clinical efficacy at 12 months after operation, related clinical indicators, recovery at 12 months after operation and complications after operation were compared between the two groups. Results:The excellent and good rate was 92.68% in the study group at 12 months after operation, which was higher than 76.92% in the control group ( P<0.05). There were no significant differences in operation time, intraoperative bleeding volume and hospital stay between the study group and the control group ( P>0.05). At 12 months after operation, the abduction activity and flexion activity of the study group were higher than those of the control group, and the visual analogue score (VAS) score was lower than that of the control group ( P<0.05). The incidence of complications in the study group was slightly lower than that in the control group, but there was no significant difference between the two groups ( P>0.05). Conclusions:For Tossy type Ⅲ acromioclavicular joint dislocation, clavicular hook plate combined with coracoclavicular ligament repair has a good clinical effect. It can improve shoulder joint function, alleviate shoulder pain, and have fewer complications. It can provide a reference for clinical treatment of this type of acromioclavicular joint dislocation.