Pulse electrical arc stimulator based on single-electrode for active exercise in tail-suspension rat

To make rat do active exercise to counteract bone loss in the rat tail-suspension model, a pulse electrical stimulator based on single-electrode with a low-current and a high-voltage was designed. The stimulator was controlled by SCM (single chip micyoco) that could accurately control the stimulation duration and the interval between stimulations, and cease the operation after the recorded number of stimulation had reached the value set by the program. With the help of posture estimation part, the device would operate intelligently by determining whether to stimulate or not, depending on the posture of rat's limb. Software was developed to make operator control the stimulator using computer, save the experiment data and print the report. In practical experiment, the voltaic arc is generated by the stimulator, and impacted on the rat's thenar. This induced pain to the rat and the rat would actively contract its hindlimb to evade the pain, so active exercise was carried out. The tail-suspension rats were trained twice every day for 14 d. At the 0 and 14th day, bone mineral density of rat femurs was determined by dual energy X-ray absorptiometry (DXA). The results show that the active exercise stimulated by the pulse electrical arc stimulator can attenuate weightlessness-induced bone loss, and this device is a convenient steady performance electrical stimulator that can surely induce rat's hindlimb to do active exercise.

Effects of Simulated Weightlessness on Tight Junction Protein Occludin and Zonula Occluden-1 Expression Levels in the Intestinal Mucosa of Rats

This study investigated the tight junction（TJ） protein expression of the intestinal mucosa in a rat tail-suspension model under simulated weightlessness.Twenty-four Wistar rats were randomly divided into three groups：CON group（n=8）,control; SUS-14 d group（n=8）,tail-suspension for 14 days; SUS-21 d group（n=8）,tail-suspension for 21 days.Occludin and Zonula Occluden-1（ZO-1） expression levels were determined by immunohistochemical analysis and mRNA fluorescent quantitative PCR.Plasma levels of diamine oxidase（DAO） and d-lactate were determined using enzymatic spectrophotometry.Immunohistochemical results for occludin and ZO-1 showed disruption of the TJs in the intestinal mucosa in SUS-14 d and SUS-21 d groups.The expression levels of occludin and ZO-1 in SUS-21 d group were lower than those in SUS-14 d group,and significantly lower than those in CON group（Occldin：0.86±0.02 vs 1.01±0.03 vs 1.63±0.03 and ZO-1：0.82±0.01 vs 1.00±0.02 vs 1.55±0.01,P〈0.01）.Moreover,the levels of plasma DAO and d-lactate in SUS-21 d group were higher than those in SUS-14 d group,and significantly higher than those in CON group（DAO：27.58±0.49 vs 20.74±0.49 vs 12.94±0.21 and d-lactate：37.86±0.74 vs 28.26±1.01 vs 17.76±0.91,P〈0.01）.There were significant negative correlations between occludin or ZO-1 expression levels and DAO（r2=0.9014,r2=0.9355,P〈0.01） or d-lactate levels（r2=0.8989,r2=0.9331,P〈0.01）.Occludin and Zo-1 were reduced in intestinal mucosa both in mRNA and protein levels in the rat tail-suspension model.The significant negative correlations between expression levels of TJs and plasma levels of DAO or d-lactate support the hypothesis that intestinal permeability is increased due to a decrease in TJ protein expression during tail-suspension from 14 days to 21 days.

Effects of simulated microgravity on antioxidant system in testis of adult rats

Objective： To study the effects of simulated microgravity induced by tail-suspension on histological structures and antioxidant system in testis of adult rats. Methods： Forty Spraque-Dawley adult male rats were randomly divided into four groups, two experimental groups and two synchronic control groups. Rats in the two experimental groups were tail-suspended for 14 d and 28 d respectively, then serum hormone, testicular morphology and biochemical changes were evaluated. Results： Compared with the synchronic controls, serum testosterone （T） levels and testicular superoxide dismutase （SOD） significantly decreased（P 〈 0.05）, while testicular malondialdehyde（MDA） significantly increased （P 〈 0.05） in tail-suspended rats. The changes were more prominent in the 28 d tail-suspended rats. In addition, hematoxylin and eosin （HE） staining showed that seminiferous tubules atrophied, spermatogenic cells decreased, and seminiferous epithelial cells disintegrated and shed, abnormal multinucleated giant cells appeared and the lumina were azoospermic in tail-suspended rats. ConcIusion： Simulated microgravity induced by tailsuspension has a harmful effect on male reproduction of adult rats by decreasing the ability of testicular antioxidant defense.

EFFECT OF SIMULATED WEIGHTLESSNESS ON REPRODUCTION OF ADULT MALE RATS

Objective To study the effects of simulated weightlessness induced by tail-suspension on reproduction in adult male rats and its mechanisms. Methods Twenty Spraque-Dawley adult male rats were randomly divided into two groups: the experimental group and control group. Rats in the experimental group were tail-suspended for 14 days. After the treatment, the weight and morphology of testis, the quantity and quality of sperm, the level of serum testosterone and the apoptosis rate of testicular cells were observed. Results Compared with the control, the testicular weight, the quantity and quality of sperm, the level of serum testosterone significantly decreased (P<0.05) while the apoptosis rate of testicular cells significantly increased (P<0.05) in tail-suspended rats. In addition, hematoxylin and eosin (HE) staining showed that seminiferous tubules atrophied, spermatogenic cells decreased, seminiferous epithelial cells disintegrated and shed, and the lumina were azoospermic. Conclusion Simulated weightlessness induced by tail-suspension has a harmful effect on male reproduction of adult rats by increasing the apoptosis of testicular cells.

Effect of Vibration on Cortical Bone in Tail-suspended Rats

Humans in Space suffer from microgravity-induced muscle atrophy and attenuated bone strength. High-frequency, low-amplitude vibration has been proposed as a treatment to prevent bone loss and the decrease in strength of bone. In this study,the effect of vibration on countering microgravity-induced bone loss was investigated.15 SD rats were divided into three groups(n=5, each): tail-suspension(TS), TS plus45 Hz(0.3 g) vibration exercise(TSV), and control(CON). Tail-suspension was to unload rat hindlimbs and a device was developed by our group, with which the rats were trained by vibration twice per day on hindlimbs during tail-suspension. After 21 d, bone mineral density(BMD) was measured by micro-CT and porosity by combining EXAKT and Olympus BX51 in tibia. The results showed that trabecular BMD was significantly decreased and cortical porosity increased in TS compared with CON, while there was no significantly difference between TSV and CON. These suggest that vibration exercise could prevent bone attenuation induced by simulated weightlessness and it is possible to be as a countermeasure of microgravity-induced osteoporosis.

Bone Protection Effects of A Novel Chinese Herbal Formula,Taikong Yangxin Prescription(太空养心方),in Hindlimb Unloaded Rats against Bone Deterioration

ABSTRACT Objective： To investigate the protective effects of a Chinese herbal formula, Taikong Yangxin Prescription （太空养心方,TKYXP） against bone deterioration in a hindlimb unloaded （tail-suspension） rat model. Methods： Thirty-two male Sprague-Dawley rats were divided into 4 groups： tail-suspension group fed with 2.5 g·kg^-1·day^-1 of TKYXP extract （high dose）, tail-suspension group fed with 1.25 g·kg^-1·day^-1 （low dose）, tail-suspended group treated with water placebo （placebo control group） and non tail-suspended group. The effects of TKYXP on bone were assessed using peripheral quantitative computed tomography （pQCT）, micro- computerized tomography （micro-CT） and three-point bending biomechanical test on the femur in vivo. Results： TKYXP had a significant protective effect against bone loss induced by tail-suspension on day 28, as shown in the reduction in bone mineral density （BMD） loss, preservation of bone micro-architecture and biomechanical strength. The administration ofhigh dose TKYXP could significantly reduce the total BMD loss by 4.8% and 8.0% at the femur and tibia regions, respectively, compared with the placebo control group （P〈0.01） on day 28. Its bone protective effect on the femur was further substantiated by the increases of the trabecular BMD （by 6.6%）, bone volume fraction （by 20.9%）, trabecular number （by 9.5%） and thickness （by 11.9%） as compared with the placebo control group. Conclusion： TKYXP may protect the bone under weightless influence from gradual structural deterioration in the tail-suspension model.