BACKGROUND:Placental mesenchymal stem cels are becoming a new source of seed cels because of wide range of sources, low immunogenicity and not involving ethical issues.
OBJECTIVE:To elaborate the sources, biological characteristics and latest application of placental mesenchymal stem cels.
METHODS:Literature search was performed in PubMed, ScienceDirect, OvidSP, CNKI databases for relevant literatures published from 2003 to 2015. The key words were “placenta, mesenchymal stem cels, placenta mesenchymal stem cels, cel transplantation, application mechanism” in Chinese and English, respectively. Then, 57 papers were further analyzed and reviewed in line with the theme.
RESULTS AND CONCLUSION:Placental mesenchymal stem cels have been isolated and cultured successfuly, and confirmed to have multi-differentiation potential. A large number of placental mesenchymal stem cels have been used in the experimental animal and clinical researches, and they have a great potential in bone tissue engineering, revascularizaion and nerve repair. However, the specific mechanism underlying the application of placental mesenchymal stem cels is not clear. In order to ensure the safety and effectiveness, there are stil many problems to be further studied before placental mesenchymal stem cels are widely used in clinic.

Objective To make analysis and diagnosis on backhand twist technique used by player A, who is the leading men’s player of national table tennis team, so as to provide references for improving his backhand twist technique. Methods The three-dimensional kinematics test and analysis were used. The backhand twist techniques of player A and those of player B who has good backhand twist techniques were compared by quantitative data and picture analysis. Results At the stage of swinging racket backward, the racket swing amplitude, shoulder angle and wrist angle of player A were significantly smaller than those of player B. The roll angle of trunk of player A was significantly larger than that of player B. At the stage of swinging and hitting the ball, the shoulder angle, elbow angle of player A were significantly bigger than those of player B, while the increasing amplitude of shoulder angle and elbow angle, as well as the changing amplitude in roll angle of trunk of Lin Guoyuan were significantly smaller than those of player B. At the stage of swinging racket forward, the shoulder angle and elbow angle of player A were significantly bigger than those of player B. The increasing amplitude of shoulder angle and elbow angle, as well as the roll angle of trunk and its changing amplitude of player A were significantly smaller than those of player B. Conclusions The racket swing amplitude of player A was smaller, and the distance between the racket and the ball of player A was close at the end of swinging racket backward stage. During swinging and hitting the ball stage, the hitting point was far from the body, the shoulder joint was not stable enough to support, so that the wrist was used more. The center of gravity was not enough to force forward, and the outburst power was not concentrated. At swinging racket forward stage, player A’s braking was not active enough, which affected the stability of hitting the ball. At hitting the ball stage, the torsion of the trunk was smaller, and the waist power was not concentrated. On the basis of unaffecting the forehand outburst power, player A should slightly adjust his backhand twisting technique, or appropriately increase the the racket swing amplitude and torsion of the body. In the process of hitting the ball, the sequence of outburst power was the waist, the forearm and the wrist.