Résumé
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.
Résumé
OBJECTIVE:To explore the reasons for leg length discrepancy following total hip arthroplasty,and to summarize the prevention and treatment of leg length discrepancy after total hip arthroplasty.DATA SOURCES:A computer-based online search was conducted in PubMed (www.ncbi.nlm.nih.gov/pubmed) for the English articles published between 2001 and 2008 with keywords "Leg length discrepancy,hip arthroplasty" and Wanfang database (http://www.wanfangdata.com.cn) for the Chinese articles published between 2004 and 2009.DATA SELECTION:Totally 154 literatures were retrieved by computer,including 116 English articles and 38 Chinese articles,through reading title and abstract,112 independent and 51 repeated papers were excluded.The remained 29 literatures were performed further analysis.MAIN OUTCOME MEASURES:Reasons for leg length discrepancy and the prevention and treatment of leg length discrepancy following total hip arthroplasty.RESULTS:The main cause of leg length discrepancy after total hip arthroplasty included redundant neck of femur stump,used longer prothesis neck,diminished femur eccentricity,selected longer neck of femur prothesis,as well as larger movement of cotyloid cavity rotation center.The effective approaches of leg length discrepancy after total hip arthroplasty included careful preoperative planning,intraoperative measurement digital templating and image-guided surgery.It could be the adjusted with heel and shaped bottom for the limbs length which was more than 15 mm after operation,and revision operation maybe applied to patients who had more than 20 mm limbs length or combined with complications.CONCLUSIONS:Leg length discrepancy is one of the common complications following total hip arthroplasty.Along with the development of science and technology,to design individual prothesis and computer-assisted navigation joint can be recover farthest joint function.