Objective To explore the influences of proliferation and differentiation of preadipocytes on high fat diet-induced obesity and obesity prevention through exercises in rats.Methods Forty male Sprague-Dawley rats were divided into a normal diet control group (C,n=8),a normal diet with exercises group (E,n=8),a high fat diet control group (H,n=14) and a high fat diet with exercises group (HE,n=10).Group C and group H kept sedentary,while group E and group HE underwent treadmill exercises at about 75％VO2max level.After 12 weeks of intervention,the body weight,epididymal,perirenal and retroperitoneal fat mass were recorded,and the total fat mass was determinated.Stereology method was used to calculate the number and average diameter of fat cells.Western Blotting was conducted to measure the expression of PPARγ and C/EBPα protein in adipose tissues.Results (1) The body weight and total fat mass of group H were significantly higher than those of group C (P＜0.01).Perirenal,retroperitoneal fat and total fat mass of group E and HE were significantly lower than those of group C and H respectively (P＜0.01).(2) The total fat cell number of group H was significantly higher than that of group C.The average diameter of fat cells in perirenal and retroperitoneal fat pads of group E were significantly lower than that of group C (P＜0.05,P＜0.01),while that of group HE in epididymal,perirenal and retroperitoneal fat pads was significantly lower than that of group H (P＜0.01).(3) Compared with group C,the expression of PPARγ protein of group E and H increased significantly in epididymal,perirenal and retroperitoneal fat pads (P＜0.01).The expression of C/EBPα protein of group H was significantly higher than that of group C in epididymal and perirenal fat pads (P＜0.01),the expression of C/EBPα protein of group E was significantly higher than that of group C in perirenal and retroperitoneal fat pads (P＜0.01),while the expression of C/EBPα protein of group HE was significantly lower than that of group H in perirenal fat pads(P＜0.01).Conclusion The proliferation and differentiation of preadipocyte was enhanced in the development of high fat diet induced obesity and exercises to prevent obesity,but its role and mechanisms were different.The high fat diet increases the number of fat cells which is a compensatory mechanism for the body to adapt to fat accumulation,while exercises might promote cell renewal and decrease the average size of fat cells which is an adaptive mechanism to improve fat storage.

Objective To study the effects of prosthetic alignment on internal contact mechanical characteristics of intact knee joint for transfemoral amputees. Methods The gait experiment of transfemoral amputees was performed under different alignment conditions, and the differences of lower limb motion and ground reaction force (GRF) were analyzed and compared with those of the non-amputees. The three-dimensional （30） finite element model of knee joint was build and used to analyze the effect of alignments of socket adduction and abduction on internal contact mechanical characteristics between femur cartilage, tibia cartilage and meniscus. Results For knee joint of the non-amputees, contact force was mainly concentrated on the medial sides at the moment of the first GRF peak, while contact force was mainly concentrated on the lateral sides at the moment of the second GRF peak. However, for intact knee joint of the transfemoral amputees, contact force was mainly concentrated on the medial side at the moment of two GRF peaks. The stress of the medial meniscus, contact force and contact area between the medial meniscus and cartilage all obviously increased under the alignment of 6° socket adduction. Conclusions Compared with non-amputees, the incidence of knee osteoarthritis (OA) in amputees was higher, which was related to the long-term overload of the medial knee joint. The alignment of socket adduction may increase the risk of knee OA in the intact side of transfemoral amputees. In clinic, excessive adduction of the socket should be avoided during prosthetic alignment.