To establish a xenografted tumor strain of human osteosarcoma in nude mice and a homologous cell line, the osteosarcoma speciments from patients were inoculated into the subcutaneous tissue of nude mice. After the transplanted tumor had grown to about 2cm in diameter, the tumor tissue was cultured in vitro and the continuously growing cells were analyzed by morphology, histochemistry, immunohistochemical straining, cell cycling analysis ,chromosome analysis and heterotransplantation. A newly established cell line designated PL 1 was thus obtained in this laboratory in continuous culture for over 100 passages. Under light and electron microscopes, the cells assumed the main characters of malignancy.Morphological observation, histochemistry analysis and BMP immunohisto chemical straining showed that they had the features of osteosarcoma.The cell cycle analysis showed 53 2% of the cells were in G 1. This cell line could produce ALP and BMP.Chromosome analysis confirmed that they had retained a karyotype of human cancer cells and a hypotriploid feature with a mode number of around 64～66.The tumor formation rate after heterotransplantation was 100%. It had lung metastasis characters. Therefore, PL 1 cell line derived from the xenograft in nude mice has been established and maintained for over 9 months trough 100 passages, and this cell line can provide material and model for further investigation of human osteosarcoma.

To explore the mode of matrix and cell injury of articular cartilage subjected to high stress mechanical loads with a low rate of loading. Loads characterized by a constant stress rate of 0.26MPa/s to a peak stress between 2MPa and 11MPa being applied to the adult bovine articular cartilage explants was designated as the test groups. No mechanical loads were applied to the control group. All the explants were maintained in culture for the next few days after loads. The spatial patterns and severity of chondrocyte injury were determined using fluorescein diacetate and propidium iodide. Matrix damages were assessed by inspection of the microstructure of the collagen fiber network under SEM. When the peak stress was 5MPa and higher, the rate of cell death in the explants of test groups was significantly greater compared with controls, and the greater peak stress applied, the higher percentage of dead versus total cells was documented, and a more diffuse distribution of dead cells was observed. When the peak stress reached 9MPa, cell death involving full depth of the cartilage was observed in test groups . Damages to the collagen fiber network were not observed both in test and control groups. The results indicated that high stress mechanical loads with a low rate of loading resulted in more severe chonrocytes damage rather than collapse of collagen fiber network.