BACKGROUND: Under specially physical environment, for example weightlessness, metabolism of bone tissue may have remarkable changes; however, osteoblast is a core of bone metabolism and bone formation, so it is very sensitive to changes of gravity environment.OBJECTIVE: To observe the effects of simulated weightlessness on bone marrow stromal cell count and osteogentic capacity of weight bearing bone in rats so as to reveal the mechanism of bone loss.DESIGN : Randomized pairing and controlled study.SETTING: College of Aerospace Medicine and Department of Pathology of Stomatology College, the Fourth Military Medical University of Chinese PLA.MATERIALS: A total of 20 adult healthy male SD rats were selected in this study. At the beginning of experiment, rats based on their body mass were randomly divided into control group and suspension group with 10 in each group. Alkaline phosphatase kit was provided by Beijing Zhongsheng Bioengineering High-technological Company.METHODS: The experiment was carried out in the Department of Pathology, Collage of Stomatology, the Fourth Military Medical University of Chinese PLA from November 1999 to July 2000. Rats were randomly divided into tail suspension group and control group with 10 in each group. Rats in the tail suspension group were given tail suspension for 28 days. Their heads maintained 30° low position, and their hindlimbs freely suspended and were not given weight loading. While, rats in the control group were fed normally. At the end of experiment, bone marrow stromal cells were obtained from femur for primary and transferring cultures.MAIN OUTCOME MEASURES: Cell counting and methylthianolyldiphenyl-tetrazolium bromide (MTT) assay were used to draw growth curve of cells in primary and transferring cultures and to measure activity of alkaline phosphatase and forming quantity of mineralized nodules in vitro.RESULTS : ① Activity of alkaline phosphatase: Activity of alkaline phosphatase of cells in the primary and transferring cultures in the suspension group was lower than that in the control group, and there was significant difference between them (P＜0.05). ② Forming quantity of mineralized nodules: Forming quantity of mineralized nodules in the suspension group was less than that in the control group, and there was significant difference between them (P＜0.05). ③ Cell growth: Growth curve of femoral stromal cells in primary and transferring culture manifested as S. Doubling time of cells in the suspension group was similar to that in the control group. ④ Amount of bone marrow stromal cells in femur: Amount of bone marrow stromal cells in primary culture in the suspension group was decreased as 50% as that in the control group (P＜0.05).CONCLUSION: Under simulated weightlessness, amount of bone marrow stromal cells decreases obviously; in addition, amount of osteoblast also decreases in weight bearing bone of hindlimbs and osteogentic capacity in vitro decreases simultaneously.

The peacekeeping area in Sudan belongs to the tropical rain forest climate with heavy rain water and large air humidity. The power supply by diesel engine is unsteady. The peacekeeping persons will be replaced every 8 months because of the demand of peacekeeping mission. Because of the above reasons, the dental instruments are easily damaged. According to the above three characteristics, the dental chair and accessories, dental X-ray system and steam sterilizer are effectively maintained to guarantee dental medical treatments in peacekeeping operation in Sudan.

Objective:To investigate the effects of 125I radioactive particle implantation in the treatment of maxillofacial malignancy. Methods:43 patients with maxillofacial malignancy were treated with 125I radioactive particle implantation.The procedure was carried out according to the treatment planning system(TPS),with the particles spaced uniformly at 1 cm intervals and with the activity of 0.7 m Ciby 41 particles per case on a verage.All patients were followed up for 6-60 months.Results:The whole treatment procedurewas successful,and no particle displaced.The follow-up rate was 93.02% and treatment effective rate(CR+PR) was 90.70%.Norecur-rence was foundinall target areas.The mortality due to tumor was 9.30%and total survival rate was 74.43%.The cumulative survival rate of the patients in 0.5,1,2,3 and 5 years was 93.0%,85.7%,79.3,69.8% and 56.9% respectively.Survival periodon aver-age was 36.06-50.04 months,with the median of 43.05 months.The longest tumor-free survival period was 60 months.Radiation in-jury rate was 20.93% and only level 1 radiation injury was observedinall the cases.Facial nerve dys function was found in 2 cases and recovered after treatment.Conclusion:Treatment of maxillofacial malignancy by implantation of 125I particles is convenient and mini-mally invasive.The treatment canincrease survival rate of the patients and guaran tee the oropharynxes' function.