RESUMEN
OBJECTIVE: To observe the effect of weightlessness simulation on rats mandible, lumbar vertebra and femur. METHOD: Twenty five Wistar rats were randomly arranged into control group (n=10) and tail-suspension group (n=15 rats). The experiment lasted for 28 d. Then the mandible, lumbar vertebra and femur were excised and the histological structure of condylar process of mandible, molar and premolar area of mandible body, first lumbar, head, middle segment and condyle of femur were examined. RESULT: After tail-suspension there was no distinct change in bone density and bone mass of condylar process. But the degree of interlacement of trabecular bone increased. The bone substance of mandible was very dense in both control and experimental groups. There was no stimulated difference of bone structure and bone mass between the two groups. There was no marked change in the thickness of periodontal membrane. The bone lamella in premolar area of experimental group arranged regularly. And its maturity was higher than that in molar area. The line of bone hyperplasia in molar area of experimental group arranged disorderly and irregularly, which means that much bone remodeling occurred. The component of trabecular bone decreased in femur and lumbar vertebra and the thickness was uneven. The interlacement and connection among trabecular bones was poor. CONCLUSION: Four weeks of stimulated weightlessness can lead to osteoporosis in acantha and femur [correction of feurar] but has no distinct effect on mandible.