In February, 2019, a patient with a defect of open dorsal cartilage and bone in the first metatarsal head, including the defects of soft tissue, tendon and joint capsule, was treated in our department. After multiple debridement, the vascularised medial femoral condyle osteochondral chimeric tissue flap was transferred to repair the composite tissue defect in the metatarsal head at the second stage. After 18 months of follow-up, the patient felt no pain in the foot and walking, and there was no sign of lameness and discomfort at donor sites. The postoperative functional recovery was satisfactory.

Objective To investigate the optimal centrifugation conditions for preparation of rat and mouse platelet rich plasma (PRP) by single centrifugation.Methods Arterial blood of rats and mice by femoral artery cannulation and cardiac puncture were obtained respectively, anticoagulation with 14％CPDA-1, while white blood cells in the blood were filtered out.Then the blood was divided into sterile EP tubes, while PRP was prepared by centrifugation in different conditions (the centrifugal force was 300×g-600×g, and the centrifugal time was 4-12min).The number of blood cells of the anticoagulant whole blood, the leukocyte-depleted blood sample and PRP were counted by hematology analyzer, and platelet recovery rates were compared between different methods.Results The platelet recovery rate was highest when the blood samples of rats and mice were centrifuged at 400×g and 300×g for 8min respectively.Conclusion It is a key to prepare PRP by single centrifugation that selecting the appropriate centrifugal force and time and reaching a critical state before the formation of the buffy coat.

Objective To evaluate the repeatability and stability of double antibody sandwich ELISA kit for micro-quantitative soluble complement receptor 1(sCR1) in human serum and to understand its practical application effect .Methods 50 patients with middle and advanced liver cirrhosis and 50 individuals undergoing physical examination served as the liver disease group and normal control group respectively .The mouse anti-human CD35 monoclone antibody ,rabbit anti-human sCR1 polyclonal antibody and goat anti-rabbit IgG labeled by horseradish peroxidase served as the envelope antibody ,sandwich antibody and detection antiboby .The purified recombinant human sCR1 protein served as the standard substance .The human serum micro-quantitative double antibody sandwich CR1 ELISA kit was established .Then the repeatability and stability tests were performed .Then the sCR1 protein level of two group of serum was detected by this kit .Results The linear range of double antibody sandwich ELISA for detecting human se-rum micro-quantitative sCR1 protein was 15 .60 -250 .00 ng/mL ;the regression equation of sCR1 protein concentration to absor-bance value was Y=112 .10X2 +18 .21X+1 .694(r2 =0 .998);in the repeatability test ,the intra-batch relative standard deviation (RSD) in high and low concentrations of standard substance detection value was 6 .20% and 7 .40% respectively ,the inter-batch RSD was 6 .70% and 7 .90% respectively ;in the stability test ,RSD was not more than 0 .01;the serum sCR1 expression level in the liver disease group was significantly higher than that in the normal control group (P<0 .01) .Conclusion The human serum double antibody sandwich ELISA kit for detecting human sCR1 has wide linear range ,good repeatability ,is easy to be stored and suitable for clini-cal and scientific research detection work .

Objective To establish a sensitive real-time quantitative PCR assay with TaqMan probe for rapid detection of mcr-1 gene in clinical isolated strains. Methods According to the mcr-1 gene sequence, a pair of specific primers and a TaqMan probe were designed. Moreover, a recombinant plasmid with mcr-1 gene was constructed as the positive standard. TaqMan probe-based fluorescence quantitative PCR assay was used to detect the colistin resistance gene mcr-1. The sensitivity, repeatability and specificity of the assay were evaluated. Results There was a good linear relationship between the initial template amount and Ct value (R2>0. 999). The lower limit of detection was 10 copies/μL, which was 100 times more sensitive than the conventional PCR. Results of test for specificity showed that only the strains carrying the mcr-1 gene were positive, while the remaining strains were negative. Coefficients of variation of intra-and inter-group repeatability tests were less than 1％. Two out of 150 clinical isolated strains carried mcr-1 re-sistance gene and both of them were identified as Escherichia coli. Conclusion TaqMan probe-based fluo-rescence quantitative PCR for the detection of colistin resistance gene mcr-1 was established with strong spe-cificity, high sensitivity and good repeatability. It could be used for the specific detection of clinical drug-re-sistant strains positive for mcr-1 gene and provide reference for pharmacotherapy.