ABSTRACT
Anti Orthostatic Hypokinetic posture in rats by tail suspension for 15 days (d) simulates the deconditioning effects of weightlessness on the weight bearing bones. The present study evaluates the effects of daily 4 hour (h) weight support (WS) during simulated weightlessness (S-W) in preventing these changes. Adult male albino rats were divided into three groups as (i) Control (CON, n = 12), (ii) Hind limb unweighing by tail suspension for 15 d (HU, n = 18), (iii) HU with daily 4 h WS (4 HRWS, n = 11). After 15 d tibia from all the animals were removed and subsequently dried, ashed and then calcium content of the bones were determined. HU showed reductions in the water content by 35.8%, organic matrix by 12.2% and calcium content by 33.4% of tibia. 4 h WS during S-W resulted in complete prevention of water loss and organic matrix loss and partial prevention of the loss of calcium content. Calcium content of tibia in 4 HRWS remained 15.2% less as compared to CON. These findings indicate that 4 h WS is partially successful in preventing the demineralisation effects of S-W on weight bearing bone tibia.
Subject(s)
Animals , Bone Demineralization, Pathologic/physiopathology , Male , Physical Conditioning, Animal/methods , Rats , Rats, Wistar , Tibia/physiology , Time Factors , Weight-Bearing/physiology , Weightlessness Countermeasures , Weightlessness Simulation/methodsABSTRACT
Weightless environment due to prolonged Space mission results in decreased mineralisation of the weight bearing bones. Hind limb unweighting (HU) in rats by tail suspension was used to simulate the effect of weightlessness on tibia. Adult male albino rats were divided into two groups as (i) Control (CON, n = 12) and (ii) HU for 15 days (HU, n = 18). After 15 days of HU tibia from all the animals were removed and subsequently dried and ashed. The calcium content of these bones were then determined. HU resulted in atrophic changes in the weight bearing bone, tibia, due to the reductions of water content (-35.8%), organic matrix (-12.2%) and calcium content (-33.4%). The reduction in the dry wt of tibia (-13.5%) was due to proportionate reductions in the organic matrix and total mineral content of the bone. The reduction in the mineral content was solely due to the reduction in calcium content of the bone.
Subject(s)
Animals , Bone Density , Bone and Bones/chemistry , Calcium/analysis , Male , Organ Size , Rats , Rats, Wistar , Water/analysis , Weightlessness SimulationABSTRACT
Weightlessness during space mission results in atrophic changes in those muscles which have maximum weight bearing function and consist primarily of slow twitch fibres. In the present study an animal model was designed to evaluate the effects of 15 days of hindlimb unloading (HU) in rats by tail suspension on the (i) weight of gastrocnemius (G), plantaris (P), both predominantly having fast twitch fibres and soleus (S) muscle, predominantly having fast twitch fibres and (ii) contractile properties viz peak twitch contraction (Pt) and peak tetanic contraction (Po) of GPS muscle. HU rats showed significant weight reductions of G (-17.9%), P (-13.3%) and S (-41.2%) muscles. Pt and Po were also reduced in HU group but when these were expressed per gm of GPS muscle, no significant changes in Pt and Po were observed. These findings confirm that HU in rats result in maximum atrophic change in those muscles which have predominantly slow twitch fibres and reductions in contractile properties of muscles are in proportion to reduction in muscle weight. Also, HU by tail suspension provides a good ground based model for developing the deconditioning of muscles as applicable to weightlessness of space and offers a scope for the development of various countermeasures.