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Although glucosamine has been suggested to be effective in the treatment of osteoarthritis, its effect on disc degeneration remains unclear. We sought to explore whether glucosamine can activate autophagy in rat nucleus pulposus (NP) cells and protect cells treated with IL-1b or hydrogen peroxide (H 2 O 2 ). Autophagy in cells was examined by detecting for LC3, Beclin-1, m-TOR, and p70S6K, as well as by analyzing autophagosomes. To inhibit autophagy, 3-methyladenine (3-MA) was used. In the cells treated with IL-1b, the levels of Adamts-4, Mmp-13, aggrecan, and Col2a1 were analyzed by real-time PCR and immunofluorescence. Apoptosis was analyzed by TUNEL. Cell senescence under H 2 O 2 was revealed by SA-b-Gal staining. Glucosamine could activate autophagy in a dose-dependent manner within 24 h and inhibit the phosphorylation of m-TOR and p70S6K. Autophagy in IL-1b or H 2 O 2 -treated cells was increased by glucosamine. Glucosamine attenuated the decrease of aggrecan and prevented the apoptosis of the NP cells induced by IL-1b, whereas 3-MA partly reversed these effects. The percentage of SA-b-Gal-positive cells induced by H 2 O 2 treatment was decreased by glucosamine, accompanied by the decline of p70S6K phosphorylation. Glucosamine protects NP cells and up-regulates autophagy by inhibiting the m-TOR pathway, which might point a potential therapeutic agent for disc degeneration. ß

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The first dog-associated outbreak of rabies in swine in China (Hunan province) has been diagnosed and the related virus isolated. Sequence analysis showed that the pig isolate was a genotype 1 rabies virus with a very high nucleotide identity to local dog isolates.

a b s t r a c tFractures in natural rocks have an important effect on the strength and failure behavior of rock mass, which are often evaluated in rock engineering practice. The theoretical evaluation of mechanical behavior of fractured rock mass has no satisfactory answer due to the role of confining pressure and crack geometry. Therefore, in this paper, conventional triaxial compression experiments were carried out to study the strength and failure behavior of marble samples with two pre-existing closed cracks in non-overlapping geometry. Based on the experimental results of a number of triaxial compression tests, the effect of crack coalescence on the axial supporting capacity and deformation property were investigated with different confining pressures. The results show that intact samples and flawed samples (marble with pre-existing cracks) have different deformation properties after peak stress, which change from brittleness to plasticity and ductility with the increase of confining pressure. The peak strength and failure mode are found depending not only on the geometry of flaw, but also on the confining pressure. The strength of flawed samples shows distinct non-linear behavior, which is in a better agreement with non-linear Hoek-Brown criterion than linear Mohr-Coulomb criterion. For a kind of rock that has been evaluated as a Hoek-Brown material, a new evaluation criterion is put forward by adopting optimal approximation polynomial theory, which can be used to confirm more precisely the strength parameters (cohesion and internal friction angle) of flawed samples. For intact samples, the marble leads to typical shear failure mode with a single fracture surface under different confining pressures, while for flawed samples, under uniaxial compression and a lower confining pressure (r 3 = 10 MPa), tests for coarse and medium marble (the coarse and medium refer to the grain size) exhibit three basic failure modes, i.e., tensile mode, shear mode, and mixed mode (tensile and shear). Shear mode is associated with lower strength behavior. However, under higher confining pressures (r 3 = 30 MPa), for coarse marble, the axial supporting capacity is not related to the geometry of flaw. The friction among crystal grains determines the strength behavior of coarse marble. For medium marble, the failure mode and deformation behavior are dependent on the crack coalescence in the sample. The present research provides increased understanding of the fundamental nature of rock failure under conventional triaxial compression.

Ovarian cancer G protein-coupled receptor 1 (OGR1) has been shown to be a receptor for protons. We investigated the role of protonsensing G protein-coupled receptors in the apoptosis of endplate chondrocytes induced by extracellular acid. The expression of proton-sensing G protein-coupled receptors was examined in rat lumbar endplate chondrocytes. Knockdown of OGR1 was achieved by transfecting chondrocytes with specific short hairpin RNA (shRNA) for OGR1. Apoptotic changes were evaluated by DNA fragmentation ELISA, electron microscopy, and flow cytometry. Intracellular calcium ([Ca 2þ ]i) was analyzed with laser scanning confocal microscopy. The mechanism of OGR1 in acid-induced apoptosis of endplate chondrocytes was also investigated. We found that OGR1 was predominantly expressed in rat endplate chondrocytes, and its expression was highly upregulated in response to acidosis. Knocking down OGR1 with shRNAs effectively attenuated acid-induced apoptosis of endplate chondrocytes and increased [Ca 2þ ]i. Blocking OGR1-mediated [Ca 2þ ]i elevation inhibited acid-induced calcium-sensitive proteases such as calpain and calcineurin, and also inhibited the activation of Bid, Bad, and Caspase 3 and cleavage of poly (ADP-ribose) polymerase (PARP). OGR1-mediated [Ca 2þ ]i elevation has a crucial role in apoptosis of endplate chondrocytes by regulating activation of calcium-sensitive proteases and their downstream signaling.