Based on the engineering practice, the sealed design of key nodes for high-level biosafety laboratories(BSL-3 and BSL-4 Laboratory) are introduced including the selection and assemblage of panel materials of building enclosure, a variety of channels through walls, and inflatable airtight doors and efficient exhaust filtration unit, which can solve the gastightness questions of building enclosure. The test results of model laboratory show that natural attenuation of the pres- sure is less than 250 Pa in 20 min when he indoor air pressure up to 500 Pa.

AIM:To investigate the effect of different oxygen concentrations on the differentiation of marrow stroma cells into osteoblasts and to evaluate the expression of Cbf?1 /Runx2,bone-morphogenesis protein 2 (BMP2) and peroxisome proliferator-activated receptor ?2 (PPAR-?2) in bone marrow stromal cells. METHODS:The bone marrow stomal cells obtained from 4-month-old female SD rats were cultured in growth medium and were used between passages 3 to 5. The cells were divided randomly into 4 groups,each group has 8 samples. The cells in all 4 groups were used for the following experiments after cultured with different oxygen concentrations for 3 d in osteoblastic differentiation medium:total cellular RNA was isolated using total RNA kit; RT -PCR was performed to detect the mRNA expression of Cbf?1 /Runx2,BMP2 and PPAR?2. The protein expression of Cbf?1 /Runx2 and BMP2 was assayed by Western blotting. RESULTS:Compared to the cells in normoxia condition (20% ),the mRNA and protein expressions of Runx2 were enhanced significantly,the mRNA expression of BMP2 was also enhanced significantly,the protein expression of BMP2 increased and the mRNA expression of PPAR?2 decreased significantly in the cells cultured with lower oxygen concentrations. The lower oxygen con-centration was in the culture,the more Runx2 mRNA,BMP2 mRNA,BMP2 and Runx2 protein were expressed. On the contrary,hypoxia significantly decreased the expression of PPAR?2 mRNA in bone marrow stronmal cells and the lower the oxy-gen concentration was used,the less expression of PPAR?2 mRNA was achieved. CONCLUSION:Hypoxia promotes the mRNA and protein expressions of Runx2 and BMP2,also significantly decreases the expression of PPAR?2 mRNA in bone marrow stronmal cells in an oxygen concentration dependent manner,indicating that hypoxia significantly stimulates the differentiation of bone marrow stromal cells into osteoblasts instead of lipocytes.