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Koop BE Lewis JL Fedewa MM Oegema TR 《Journal of materials science. Materials in medicine》2002,13(9):823-828
Fracture toughness of cartilage and cartilage replacement tissues is important in injury and disease. For example, cartilage is thought to weaken before it fibrillates in the disease osteoarthritis. Since both loading rate and proteoglycan content affect viscoelastic properties, they may both affect fracture toughness of cartilage and cartilage analogs. In this study, fracture toughness of tissue grown in chondrocyte culture was measured as a function of loading rate and proteoglycan digestion. Control tissue and tissue digested with chondroitinase ABC (cABC) to remove proteoglycans were tested at displacement rates of 0.1 and 0.5 mm/sec. Displacement rate had no effect on fracture toughness for either control or digested tissue. Proteoglycan digestion reduced tissue thickness by 30% and when evaluated on a material basis increased fracture toughness. There was no interaction between digestion and loading rate. When the fracture toughness was normalized to collagen content, which removed the effect of tissue shrinkage, there was no effect of proteoglycan digestion on fracture toughness. These data suggest that proteoglycans do not contribute to tissue toughness, other than by reducing thickness and increasing collagen density. 相似文献
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Genetic interactions link ARF1, YPT31/32 and TRS130 总被引:1,自引:0,他引:1
Zhang CJ Bowzard JB Greene M Anido A Stearns K Kahn RA 《Yeast (Chichester, England)》2002,19(12):1075-1086
A genetic screen for synthetic lethal interactions with arf1(-) identified a recessive mutation in TRS130, one of 10 components in the trafficking protein particle (TRAPP) complex (Sacher et al., 2000). As TRS130 is an essential gene, the synthetic lethal allele (trs130-101) is a novel one that requires ARF1 for viability. This allele was found to exhibit no defects in secretory function, i.e. processing of carboxypeptidase Y or invertase. YPT31 and YPT32 were identified in a subsequent screen as high-copy suppressors of arf1(-)trs130-101. Increasing the gene dosage of YPT31/32 also suppressed lethality resulting from deletion of TRS130 or TRS120 but not three other essential TRAPP subunit-encoding genes. Although unable to suppress defects in several alleles of ARF1, increasing the gene dosage of YPT31/32 suppressed the cold sensitivity of gcs1(-), an Arf GTPase-activating protein (GAP). Thus, these genetic interactions provide initial evidence for linkage of Arf and TRAPP signalling and for Ypt31/32 proteins functioning downstream of both components in the TRAPP complex and of Arf signalling via the Gcs1 Arf GAP. 相似文献
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Surface crystalline phases and nanoindentation hardness of explanted zirconia femoral heads 总被引:1,自引:0,他引:1
Catledge SA Cook M Vohra YK Santos EM McClenny MD David Moore K 《Journal of materials science. Materials in medicine》2003,14(10):863-867
One new and nine explanted zirconia femoral heads were studied using glancing angle X-ray diffraction, scanning electron microscopy, and nanoindentation hardness techniques. All starting zirconia implants consisted only of tetragonal zirconia polycrystals (TZP). For comparison, one explanted alumina femoral head was also studied. Evidence for a surface tetragonal-to-monoclinic zirconia phase transformation was observed in some implants, the extent of which was varied for different in-service conditions. A strong correlation was found between increasing transformation to the monoclinic phase and decreasing surface hardness. Microscopic investigations of some of the explanted femoral heads revealed ultra high molecular weight polyethylene and metallic transfer wear debris. 相似文献