BACKGROUND: As the end product of lipid peroxidation, malondialdehyde (MDA) content can be used for assessment lipid peroxidation injury.Glutathione peroxidase (GSH-Px) acts as a free radical scavenger. Currently the effect of static magnetic field on the organism, whether positive or negative, has not been elucidated.OBJECTIVE: To study the effect of static magnetic field on anti-oxidation capacity of mouse hepatic tissues and its intensity dependence for producing such effects.DESIGN: A controlled comparative experiment.SETTING: Laboratories of Medical Physics and Biochemistry of Jiangsu University.MATERIALS: The experiment was conducted in the Laboratories of Medical Physics and Biochemistry of Jiangsu University from January to December 2003. Totally 30 mice of either sex weighing 18-20 g were selected and subjected to magnetic filed exposure using a self-designed ferrite magnet apparatus.METHODS: The mice were equally randomized into normal control group and 4 exposure groups exposed to magnetic field of (24.6±4.2) mT,(42.0±2.1) mT, (63.5±3.0) mT, and (85.1±2.9) mT, respectively. The mice in the 4 exposure groups were exposed to static magnetic field of the specified intensity for 2 hours twice a day, while those in the normal control group were subjected to the sham exposure apparatus without magnetic field at scheduled time points every day. After 15 days of exposure, the mice were sacrificed and the GSH-Px activity and the MDA content in the hepatic tissue were assayed.MAIN OUTCOME MEASURES: GSH-Px activity and MDA content in hepatic tissue of the mice.RESULTS: Thirty mice entered the final analysis without losses. MDA content in (24.6±4.2) mT and (42.0±2.1) mT groups were obviously lower than that in the normal control group [(12.70±0.53), (12.96±0.72), and (17.62±0.91) μmol/g, respectively, F=10.4, 9.89, P ＜ 0.01]. The GSH-Px activity in the hepatic tissue in (24.6±4.2) mT and (42.0±2.1) mT groups were obviously higher than that in the normal control group [(143.36±8.34),(150.69±12.00), (87.51±11.34) μkat/g, respectively, F=10.0, 11.3, P ＜ 0.01].CONCLUSION: Static magnetic field of appropriate intensity can lower MDA content and enhance the GSH-Px activity in the hepatic tissue of mice, and may also improve the activity of antioxidase and reduce the production of lipid peroxidation to diminish the consequent injuries and delay the aging process.

Tissue-engineering bone with porous ,betatricalcium phosphate (3-TCP) ceramic and autologous bone marrow mesenchymal stem cells (MSC) was constructed and the effect of this composite on healing of segmental bone defects was investigated. 10-15 ml bone marrow aspirates were harvested from the iliac crest of sheep, and enriched for MSC by density gradient centrifugation over a Percoll cushion (1. 073 g/ml). After cultured and proliferated, tissue-engineering bones were constructed with these,cellS seeded onto porous f-TCP, and then the constructs were implanted in 8 sheep left metatarsus defect (25 mm in length) as experimental group. Porous ,-TCP only were implanted to bridge same size and position defects in 8 sheep as control group, and 25 mm segmental bone defects of left metatarsus were left empty in 4 sheep as blank group. Sheep were sacrificed on the 6th, 12th, and 24th week postoperatively and the implants samples were examined by radiograph, histology, and biomechanical test. The 4 sheep in blank group were sacrificed on the 24th week postoperatively. The results showed that new bone tissues were observed either radiographic or histologically at the defects of experimental group as early as 6th week postoperatively, but not in control group, and osteoid tissue, woven bone and lamellar bone occurred earlier than in control group in which the bone defects were repaired in "creep substitution" way, because of the new bone formed in direct manner without progression through a cartilaginous intermediate. At the 24th week, radiographs and biomechanical test revealed an almost complete repair of the defect of experimental group, only partly in control group. The bone defects in blank group were non-healing at the 24th week. It was concluded that engineering bones constructed with porous -TCP and autologous MSC were capable of repairing segmental bone defects in sheep metatarsus beyond "creep substitution" way and making it healed earlier. Porous ,-TCP being constituted with autologous MSC may be a good option in healing critical segmental bone defects in clinical practice and provide insight for future clinical repair of segmental defect.
Bone Marrow Cells/cytology ; Calcium Phosphates/*pharmacology ; Cells, Cultured ; Fractures, Bone/*therapy ; Implants, Experimental ; Mesenchymal Stem Cells/*cytology ; Metatarsus/*injuries ; Porosity ; Sheep ; Tissue Engineering

Tissue-engineering bone with porous β-tricalcium phosphate (β-TCP) ceramic and autologous bone marrow mesenchymal stem cells (MSC) was constructed and the effect of this composite on healing of segmental bone defects was investigated. 10-15 ml bone marrow aspirates were harvested from the iliac crestof sheep, and enriched for MSC by density gradient centrifugation over a Percoll cushion (1. 073 g/ml). After cultured and proliferated, tissue-engineering bones were constructed with these cells seeded onto porous β-TCP, and then the constructs were implanted in 8 sheep left metatarsus defect (25 mm in length) as experimental group. Porous β-TCP only were implanted to bridge same size and position defects in 8 sheep as control group, and 25 mm segmental bone defects of left metatarsus were left empty in 4 sheep as blank group. Sheep were sacrificed on the 6th, 12th, and 24th week postoperatively and the implants samples were examined by radiograph, histology, and biomechanical test. The 4 sheep in blank group were sacrificed on the 24th week postoperatively. The results showed that new bone tissues were observed either radiographic or histologically at the defects of experimental group as early as 6th week postoperatively, but not in control group, and osteoid tissue, woven bone and lamellar bone occurred earlier than in control group in which the bone defects were repaired in "creep substitution" way, because of the new bone formed in direct manner without progression through a cartilaginous intermediate. At the 24th week, radiographs and biomechanical test revealed an almost complete repair of the defect of experimental group, only partly in control group. The bone defects in blank group were non-healing at the 24th week. It was concluded that engineering bones constructed with porous β-TCP and autologous MSC were capable of repairing segmental bone defects in sheep metatarsus beyond "creep substitution" way and making it healed earlier. Porous β-TCP being constituted with autologous MSC may be a good option in healing critical segmental bonedefects in clinical practice and provide insight for future clinical repair of segmental defect.