Effects of Changes in Mechanical Loading on Endochondral Bone Formation in Hindlimb-suspended Rats / 항공우주의학회지

BACKGROUND: To examine the effects of changes in mechanical loading on endochondral bone formation, a simulated rat model of weightlessness was introduced and the changes in the growth plate were evaluated. METHODS: Unloading condition on the hindlimb of Sprague-Dawley rats was created by fixing a tail and lifting the hindlimb. Six rats aged 6 weeks old were assigned to each group of unloading and reloading with their control group. Unloading was maintained for three weeks, and then reloading was applied for another one week afterwards. Histomorphometry for the assessment of vertical length of the growth plate, 5-bromo-2'-deoxyuridin (BrdU) immunohistochemistry for cellular kinetics, and biotin nick end labeling TUNEL assay for chondrocytes in the growth plate were performed. RESULTS: The vertical length of the growth plate and the proliferative potential of chondrocytes were decreased in the unloading group than those of the control group. Inter-group differences were more significant in the proliferative and hypertrophic zones. Reloading increased the length of growth plate and proliferative potential of chondrocytes as evidenced by the increase of the ratio of positive BrdU stained cells. However, the apoptotic changes in the growth plate were not affected by the alterations of the weight bearing. CONCLUSION: Alterations in the weight bearing induced changes in the chondrocytic proliferative potential of the growth plates and had no effect on the apoptosis occurrence. This may suggest that deprived weight bearing due to various clinical situations hamper normal longitudinal bone growth. Further studies regarding the factors for reversibility of chondrocytic proliferation upon variable mechanical stresses are needed.

Effects of tu-chung extract administrating on serum testosterone in hindlimb-suspended rats / 体力科学

The purpose of this research was to study the effects of Tu-Chung extract (Eucommia ulmoides OLIV.) administration on serum testosterone and the possible mechanisms in hindlimb- suspended rats. 25 five-week old male Wistar rats were used. All rats were randomly divided into two groups : those treated with Tu-Chung extract (Tu-Chung G, n=suspended for 37 days in hindlimb. 1 mg/ml Tu-Chung extract was administered orally once daily at a dose of 1 ml/100 g body weight. Distilled water was administered in a similar way to the control group. The following results were observed :<BR>1. Serum testosterone concentration in Tu-Chung G was significantly higher than in Cont. G (P<0.001) .<BR>2. There was no significant difference between Tu-Chung G and Cont. G in serum LB concentrations.<BR>3. The Testicular cAMP level in Tu-Chung G was significantly higher than that in Cont. G (P<0.01) .<BR>4. 24-h urinary excretion of 17-ketosteroid in Tu-Chung G was significantly higher than that in Cont. G (P<0.001) .<BR>5. There were no significant differences between the two groups in the weights per body weight of the kidneys, adrenal grand and testes. These results suggest that the adininstration of Tu-Chung extract inducing high serum testosterone concentrations in hindlimb-suspended rats might be due to enhanced testicular and adrenal functions, not pituitary.