Study of Histopathological and Molecular Changes of Rat Kidney under Simulated Weightlessness and Resistance Training Protective Effect

To explore the effects of long-term weightlessness on the renal tissue, we used the two months tail suspension model to simulate microgravity and investigated the simulated microgravity on the renal morphological damages and related molecular mechanisms. The microscopic examination of tissue structure and ultrastructure was carried out for histopathological changes of renal tissue morphology. The immunohistochemistry, real-time PCR and Western blot were performed to explore the molecular mechanisms associated the observations. Hematoxylin and eosin (HE) staining showed severe pathological kidney lesions including glomerular atrophy, degeneration and necrosis of renal tubular epithelial cells in two months tail-suspended rats. Ultrastructural studies of the renal tubular epithelial cells demonstrated that basal laminas of renal tubules were rough and incrassate with mitochondria swelling and vacuolation. Cell apoptosis in kidney monitored by the expression of Bax/Bcl-2 and caspase-3 accompanied these pathological damages caused by long-term microgravity. Analysis of the HSP70 protein expression illustrated that overexpression of HSP70 might play a crucial role in inducing those pathological damages. Glucose regulated protein 78 (GRP78), one of the endoplasmic reticulum (ER) chaperones, was up-regulated significantly in the kidney of tail suspension rat, which implied that ER-stress was associated with apoptosis. Furthermore, CHOP and caspase-12 pathways were activated in ER-stress induced apoptosis. Resistance training not only reduced kidney cell apoptosis and expression of HSP70 protein, it also can attenuate the kidney impairment imposed by weightlessness. The appropriate optimization might be needed for the long term application for space exploration

Study on Preparation and Physical Mechanical Properties of Si3N4 Composite Ceramics

In this paper, by using the hot-pressed sintered technology, pure Si3N4 ceramics and Si3N4 composite ceramics containing different volume fraction(hBN) are prepared with the sintered catalyst of Al2O3 and Y2O3(total 10vol%) by HIGH MULTI 5000 multi-functional high temperature sintering furnace. And the phase compositions, microstructure and mechanical properties of specimen were studied. The results show that, based on the hot pressing sintering process, the α-Si3N4 is all changed into β-Si3N4. Addition of hBN into Si3N4 inhibits the growth of the crystal grain and makes the ceramic materials generate hBN segregation zone in internal materials, which causes the addition of hBN that cannot improve the physical mechanical properties effectively just because the serious stress concentrates and fatigue break down. In addition, compared with other sintering process, the physical and mechanical properties of Si3N4 prepared by hot-pressing sintering are better than other methods. Improvement of sintering temperature and time can refine the crystal grain and be a helpful densification. The changed β-Si3N4 grain completely forms an intertwined structure and increases the physical and mechanical properties of Si3N4. Meanwhile, Y2O3 and Al2O3 additives are melted and filled into Si3N4 particles at the high temperature, leading to a significant drop of the porosity and the increase of density

Study on Preparation and Physical Mechanical Properties of Si

In this paper, by using the hot-pressed sintered technology, pure Si3N4 ceramics and Si3N4 composite ceramics containing different volume fraction(hBN) are prepared with the sintered catalyst of Al2O3 and Y2O3(total 10vol%) by HIGH MULTI 5000 multi-functional high temperature sintering furnace. And the phase compositions, microstructure and mechanical properties of specimen were studied. The results show that, based on the hot pressing sintering process, the α-Si3N4 is all changed into β-Si3N4. Addition of hBN into Si3N4 inhibits the growth of the crystal grain and makes the ceramic materials generate hBN segregation zone in internal materials, which causes the addition of hBN that cannot improve the physical mechanical properties effectively just because the serious stress concentrates and fatigue break down. In addition, compared with other sintering process, the physical and mechanical properties of Si3N4 prepared by hot-pressing sintering are better than other methods. Improvement of sintering temperature and time can refine the crystal grain and be a helpful densification. The changed β-Si3N4 grain completely forms an intertwined structure and increases the physical and mechanical properties of Si3N4. Meanwhile, Y2O3 and Al2O3 additives are melted and filled into Si3N4 particles at the high temperature, leading to a significant drop of the porosity and the increase of density

Morphology and Molecular Mechanisms of Hepatic Injury in Rats under Simulated Weightlessness and the Protective Effects of Resistance Training.

This study investigated the effects of long-term simulated weightlessness on liver morphology, enzymes, glycogen, and apoptosis related proteins by using two-month rat-tail suspension model (TS), and liver injury improvement by rat-tail suspension with resistance training model (TS&RT). Microscopically the livers of TS rats showed massive granular degeneration, chronic inflammation, and portal fibrosis. Mitochondrial and endoplasmic reticulum swelling and loss of membrane integrity were observed by transmission electron microscopy (TEM). The similar, but milder, morphological changes were observed in the livers of TS&RT rats. Serum biochemistry analysis revealed that the levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were significantly higher (p<0.05) in TS rats than in controls. The levels of ALT and AST in TS&RT rats were slightly lower than in RT rats, but they were insignificantly higher than in controls. However, both TS and TS&RT rats had significantly lower levels (p<0.05) of serum glucose and hepatic glycogen than in controls. Immunohistochemistry demonstrated that the expressions of Bax, Bcl-2, and active caspase-3 were higher in TS rats than in TS&RT and control rats. Real-time polymerase chain reaction (real-time PCR) showed that TS rats had higher mRNA levels (P < 0.05) of glucose-regulated protein 78 (GRP78) and caspase-12 transcription than in control rats; whereas mRNA expressions of C/EBP homologous protein (CHOP) and c-Jun N-terminal kinase (JNK) were slightly higher in TS rats. TS&RT rats showed no significant differences of above 4 mRNAs compared with the control group. Our results demonstrated that long-term weightlessness caused hepatic injury, and may trigger hepatic apoptosis. Resistance training slightly improved hepatic damage

Body and liver weights.

<p>Data are shown as the means ± SD, n = 10.</p><p>* P <0.05</p><p>** P <0.01, significantly different from control group.</p><p>Body and liver weights.</p

Histopathological analysis of rat liver paraffin sections stained with hematoxylin and eosin (H&E), Mallory’s trichrome stain, and Sirius Red stain.

<p>A: Morphological changes in the liver: the normal structure of the rat liver in the control group (A1). In the TS group, we observed mass granular degeneration and the swelling of hepatic cells around the central vein, vague cell boundaries, liver cell cord derangement, edema and the proliferation of bile ducts, and inflammation in liver portal areas (arrow) (A2). In the TS&RT group, pathological changes included the slight vacuolar degeneration of hepatic cells with a completed structure and clear boundaries and fibrosis in the portal areas of the liver in some of the rats (A3). B&C: Sections stained with Mallory’s trichrome (B) and Sirius Red (C) displayed various levels of the proliferation of fibrous liver tissue in the control (B1, C1), TS (B2, C2), and TS&RT groups (B3, C3). Collagen fibers stained blue with Mallory’s trichrome and red with Sirius Red stain (arrow). 400×</p

The analysis of liver glycogen by PAS staining.

<p>A-C: Liver glycogen as demonstrated by PAS staining (purple-red, 100×). A: Liver glycogen in the control group: large areas of hepatic cells around the central vein with positive PAS staining. B: Liver glycogen in the TS group: PAS-positive cells were significantly reduced, mainly at the edge of the portal area, with only scattered, sporadic purple liver cells surrounding the central vein. C: Liver glycogen in the TS&RT group: PAS-positive cells remained mainly in the area around the portal vein, and the number of PAS-positive cells increased around the central vein. D: A semi-quantitative analysis of liver glucose in the PAS-stained slides confirmed the results obtained for the serum glucose levels. Each value represents the percentage of the mean area of glycogen density in each group. n = 150 fields (10 rats) for each value. (Data are expressed as the mean ± SD. ** P <0.01, significantly different from control group.).</p

Immunohistochemical and real-time PCR analysis of Bax and Bcl-2.

<p>A1-C1: Histological sections of livers in control, TS and TS&RT group were stained with Bax antibody, and the positive signals were mainly located around the central veins in the livers. A2-C2: Histological sections of livers in control, TS and TS&RT group were stained with PBS to replace the Bax antibody as blank control; no positive signals were observed. D1-FI: Histological sections of livers in control, TS and TS&RT groups were stained with Bcl-2 antibody, and the location of the Bcl-2 positive signals was similar to the Bax positive signals. D2-F2: Histological sections of livers in control, TS and TS&RT groups were stained with PBS to replace the Bcl-2 antibody as a blank control; no positive signals were observed. G: A semi-quantitative analysis of the ratio of Bax positive staining to the total field. H: A semi-quantitative analysis of the ratio of Bcl-2 positive staining to the total field. I: Relative mRNA levels of Bax and Bcl-2. (Data are expressed as the mean ± SD. * P <0.05, ** P <0.01, significantly different from control group. 400×).</p

Levels of ALT, AST and glucose in serum.

<p>A: Serum ALT and AST levels: ALT and AST levels in the TS group were significantly increased compared with the control group, and ALT and AST levels in the TS&RT group were increased compared with the control group but reduced compared with the TS group; however, these differences were not significant. B: Serum glucose levels: serum glucose levels in the TS and TS&RT groups were significantly decreased compared with the control group (Data are expressed as the mean ± SD. * P <0.05, significantly different from control group).</p