Biomedical subjects

Kerong Dai

Publications and source records attributed to Kerong Dai.

26 records · Page 2Linked to original sources

PubMed2003

[Preparation of a biphasic calcined bone of beta-TCP/HAP and its application in BMP-2 gene medicine].

In this study, we produced a biphasic absorbable calcined bone (CB) of beta-TCP/HAP, and evaluated its function as a carrier of bone marrow derived mesenchymal stem cells(BMSCs) in BMP-2 gene medicine. Biphasic CB was manufactured and its surface was coated by collagen. X-ray diffraction analysis, scanning electron microscopy and biomechanical measurement were performed on the product. Heterotopic bone induction of product as carrier of BMP-2 gene transferred BMSCs and its biodegradability were tested in nude mice and goats. X-ray diffraction analysis showed biphasic patterns of HAP and beta-TCP. Scanning electron microscopy showed the porosity were similar to those of the cancellous bone, and the adhesion of cells on the CB surface were better after surface-coating with collagen. It had certain biomechanical strength and appropriate biodegradability. Biphasic CB loaded with Adv-hBMP-2 transduced BMSCs could induce much bony callus at the subcutaneous site of nude mice and the tibial bone defects of goats. The results showed biphasic CB is a superior carrier of cells in BMP-2 gene medicine.

Animals↗

PubMed2002

Substitution of porcine small intestinal submucosa for rabbit Achilles tendon, an experimental study.

OBJECTIVE: To study the effect of substitution of porcine small intestinal submucosa (SIS) for rabbit Achilles tendon. METHODS: Porcine SIS was taken out and processed. Part of Achilles tendons of 20 rabbits' right legs were removed and substituted by porcine SIS and the Achilles tendon of the left legs were used as controls. One, four, eight, twelve, and sixteen weeks after the operation 4 rabbits were killed and their right Achilles tendons were taken out to be examined histologically and their maximum load was tested. RESULTS: One week after the operation, the porcine SIS was already fused with the remaining part of rabbit Achilles tendon. Sixteen weeks after all the Achilles tendons looked like normal one. The maximum load of experimental Achilles tendon was 48 N +/- 9 N one week after the operation, and increased gradually. In the 16th week after the operation, the maximum load was 178 N +/- 6 N for the experimental Achilles tendon and 174 N +/- 10 N for the control tendon. The differences of maximum load between different weeks after operation, except that between one week and 4 weeks after, were statistically significant (P < 0.01). CONCLUSION: Substitution of porcine SIS for injured Achilles tendon is effective, thus proving the feasibility of in vivo tissue engineering technology.

Achilles Tendon↗

PubMed2002

[Measurement and classification of geometric parameters in Chinese proximal femur].

This study sought to establish a set of hip prostheses for the Chinese population and improve the design guidelines for hip prostheses. 480 cadaveric adult femora were obtained for X-ray imaging. 21 geometric parameters of femora were sampled on the anteroposterior(AP) and mediolateral(ML) views of radiograph in conjunction with computer-aided image processing technology. The curves of canal of proximal femur were fitted and made statistics. Pattern recognition was used to classify these geometric parameters. The results of classification corresponded with the 10 groups of data for design. On the basis of the numerous set of data, the results and classification would serve as means and guidelines for optimizing the design of prosthetic components and so far as custom-built hip prosthetics.

Femur↗

PubMed2000

Experimental study of effect of stress-relaxation bone plate on fracture healing.

OBJECTIVE: To study the change of the stress shi elding rate of stress-relaxation plate in vivo and its influence on fracture he aling. METHODS: The diaphyses of bilateral tibias in 70 New Zealand ra bbits were osteotomized and fixed with stress-relaxation plates (SRP, the SRP g roup) and rigid plates (RP, the RP group), respectively. The fracture healing pr ocess in these 2 groups was investigated by radiography, light and polarized l ight microscopy and biomechanical test at 2 to 48 weeks postoperatively. RESULTS: Early after fixation the stress shielding rate was abo ut 70% in both groups. While in the SRP group the stress shielding rate decrease d gradually as time passed, which was significantly lower than that of the RP gr oup (P<0.05) by the end of the 8th postoperative week, and stabilized at the level of about 27% at 36-48 weeks after fixation. Abund ant external callus associated with the formation of cartilaginous callus could be observed in the SRP group at 2-4 weeks postoperatively. The transformation o f the callus into the lamellar bone began at 8-12 weeks, the collagen gradually arranged in order, and the mechanical nature of the united bone was gradually s trengthened, too. In the RP group, the external callus was scarce at the early s tage of fracture healing, and the callus remodeling at the late stage of fractur e healing was dominated by bone absorption. The ultimate bending strength (UBS) was only 57.95% of that of the normal by 48 weeks. CONCLUSIONS: The decrease of the stress shielding rate of SRP i n vivo was well interrelated with the time of fixation. The application of SRP c ould promote the callus formation and bone reconstruction thus to favor the reco very of the mechanical strength of the united bone.

Journal Article↗

PubMed2000

A biomechanical investigation on the incorporation of cortical allograft in rabbit ulna defects.

OBJECTIVE: To explore the changes of biomechanic al properties of cortical allograft in different mechanical environments. METHODS: Cortical allograft was transplanted to each side of th e midshaft diaphyseal ulna of each one of 40 rabbits. The left transplanted allo graft underwent normal physiological load, while the right one underwent lower l oad. After animals were killed,specimens were taken for examination of bone mine ral density, bone porosity and maximal three-point-bend breaking load. RESULTS: The union strength of allograft-host bone junction wa s increased constantly; meanwhile, the internal creeping substitution led to an initial greater weakening of the cortical allograft itself and a later recovery of its strength. In comparison, the union strength of the normally loaded graft -host bone construct was significantly higher than that of the lower loaded sid e at the 8th and 16th week after transplantation. At the 16th week, there was gr eater bone strength in normally loaded graft than that in lower loaded graft. CONCLUSIONS: The internal repair can lead to initial greater we akening of cortical allograft and later gradual recovery of its strength. The ef fect of physiological load can accelerate the improvement of the biomechanical p rope rties of allograft.

Journal Article↗

PubMed2000

The effects of stress-relaxation plate on disorganization and repair of regional bone structure: an experimental study.

OBJECTIVE: To study the influence of stress-relaxation plate on disorganization and repair of the cortex beneath the plate. METHODS: A washer made of viscoelastic polyethylene was placed between the screw and the screw hole of conventional stainless rigid plate (RP) to produce a stress-relaxation plate (SRP). Both SRP and RP were applied to osteotomized tibia in 48 New Zealand rabbits. Healing process of the fracture with either SRP or RP fixation (control) was comparatively studied with polarized light microscopy, in situ hybridization of collagen mRNA and immunohistochemical technique from 2 to 36 weeks postoperatively. RESULTS: The study of plated bone remodeling showed that the degree of cortex osteoporosis beneath the plate was similar between the SRP and RP group within 12 weeks postoperatively. In comparison, the disorganization of bone structure in SRP group happened later and milder than that of RP group, and the repair process began at 12 weeks after implantation. As a consequence, the absorption cavities became smaller and the structure of collagen fibers became well oriented along with these changes by polarized light microscopy. In addition to these, the in situ hybridization analysis of collagen genes and the immunohistochemical study of type I, III collagen showed that the osteoblasts lying on the surface of absorption cavities expressed and synthesized type I collagen at 8 to 12 weeks after implantation. From this time on, the changes above became more evident significantly before most of cavities were repaired by 36 weeks. In contrast to the changes in the SRP group, no expression and synthesis of any kind of collagen could be observed during 12 to 36 weeks after implantation in RP group. CONCLUSIONS: Without removal of the bone plate, the SRP fixation not only reduces the degree of plated bone osteoporosis, but also makes the disorganized bone structure restored to normal in terms of the expression and synthesis of type I collagen mRNA of osteoblasts lying on the surface of absorption cavities.

Journal Article↗

PubMed2000

In vitro study of immune tolerance induced by CTLA4-Ig in bone transplantation: The effect on cell proliferation stimulated by lymphocytes and bone supernatant.

To clarify the effect of CTLA4-lg on immune rejection of bone grafts, we observed the effect of CTLA4-lg on lymphocyte proliferation of BALB/C mice stimulated by lymphocytes and bone supernatant of C57BL/6 mice. The splenic lymphocytes and bone supernatant of C57BL/6 mice, as the stimulator cells and stimulator antigens, were cultured in vitro with the splenic lymphocyte of BALB/C mice. At the same time, CTLA4-lg at a dose of 5,10 or 20 &mgr;g/ml and L6 (as control) at 20 &mgr;g/ml were added. Six days later, the incorporation of 3 H-TdR was determined. Results indicated that CTLA4-Ig at a dose of 5, 10 or 20 &mgr;g/ml significantly inhibited the cell proliferation stimulated by lymphocytes and bone supernatant of C57BL/6 mice. The effect was non-cytotoxic. L6 showed no significant inhibition of cell proliferation. CTLA4-Ig can efficiently block the proliferation of alloresponsive T cell stimulated by lymphocytes and bone supernatant of C57BL/6 mice. This study provides a basis for further study of CTLA4-induced immune tolerance of bone grafts.

Journal Article↗

PubMed1999

The relationship between porosity, collagen fiber orientation and strength of plated bone after rigid plate fixation and removal.

OBJECTIVE: To understand the relationship between porosity, collagen fiber orientation and strength of the plated bone after rigid plate fixation and removal. METHODS: Seventy-two New Zealand white rabbits were used in this experiment. Eight animals served as control and the other sixty-four were plated on their intact left tibiae with stainless steel (316L) 4-hole plates to induce early osteoporosis. The plates were removed 2 months after internal fixation in 40 plated animals, 8 of which were sacrificed immediately following plate removal and the other 32 were killed in successive groups with 8 in each group 1, 2, 3 and 4 months after plate removal. The remaining 24 plated animals were killed at 3, 4 and 6 months after plate fixation. After sacrifice, the samples of plated bone were prepared for light microscope, quantitative histological analysis, polarized light microscope and biomechanical test. RESULTS: The internal fixation with a rigid plate could induce the regional osteoporosis which manifested both bone loss and disorganized bone structure (loss of the orientation of the collagen fibers) leading to decreased strength of the plated bone. Although the regional osteoporosis could recover gradually after plate removal, the bone structure remained disorderly even when the bone mass returned to normal. Delayed restoration of bone structure was related to delayed restoration of bone strength. CONCLUSIONS: Besides the bone loss, the disorganized bone structure is the main cause of decrease of bone strength after rigid plate fixation and removal.

Journal Article↗