Blocking of tumor necrosis factor activity promotes natural repair of osteochondral defects in rabbit knee

Background and purpose Osteochondral defects have a limited capacity for repair. We therefore investigated the effects of tumor necrosis factor (TNF) signal blockade by etanercept (human recombinant soluble TNF receptor) on the repair of osteochondral defects in rabbit knees

Effects of Surface Texture for Improving Friction Properties of Hydrogenated Amorphous Carbon Films

Hydrogenated amorphous carbon (a-C:H) films exhibit excellent friction properties such as high mechanical hardness, high wear resistance, and low friction. a-C:H films have amorphous structures generally composed of sp2- and sp3-hybridized carbon, which bring about extraordinary friction properties. Some reports have focused on the low-friction mechanism of a-C:H films, concluding that it is induced by the existence of graphitized wear particles at the sliding interface. It is possible to consider the existence of graphitized wear particles as the most important factor in achieving the lower friction of a-C:H films. We focus on the effects of surface texture in trapping the graphitized particles at the sliding interface and discuss the role of surface texture with regard to the friction properties of a-C:H films. Micro slurry-jet erosion (MSE) surface machining was employed to manipulate the surface texture on a high-carbon chromium-bearing steel substrate, upon which a-C:H films were deposited. The friction properties of a-C:H films deposited on a mirror-like polished substrate (a-C:H/mirror-like) and on an MSE-produced substrate (a-C:H/MSE-produced) were compared using a reciprocating-type ball-on-disk sliding tester. From the results of friction testing, it is confirmed that a-C:H/MSE-produced films indicated lower friction coefficients compared with the a-C:H/mirror-like case. Scanning electron microscopy (SEM) and Raman spectroscopy were performed to study the friction improvement mechanism of the a-C:H/MSE-produced films. SEM revealed the existence of wear particles in the wear track of a-C:H/MSE-produced films. It is confirmed by Raman spectroscopic analysis that these wear particles’ structure was changed, adopting a graphite-like structure. From these results, it is possible to consider that the existence of graphitized wear particles induced lower shearing resistance at the sliding interface, enabling friction improvement

The genome of Rhizophagus clarus HR1 reveals a common genetic basis for auxotrophy among arbuscular mycorrhizal fungi

Abstract Background Mycorrhizal symbiosis is one of the most fundamental types of mutualistic plant-microbe interaction. Among the many classes of mycorrhizae, the arbuscular mycorrhizae have the most general symbiotic style and the longest history. However, the genomes of arbuscular mycorrhizal (AM) fungi are not well characterized due to difficulties in cultivation and genetic analysis. In this study, we sequenced the genome of the AM fungus Rhizophagus clarus HR1, compared the sequence with the genome sequence of the model species R. irregularis, and checked for missing genes that encode enzymes in metabolic pathways related to their obligate biotrophy. Results In the genome of R. clarus, we confirmed the absence of cytosolic fatty acid synthase (FAS), whereas all mitochondrial FAS components were present. A KEGG pathway map identified the absence of genes encoding enzymes for several other metabolic pathways in the two AM fungi, including thiamine biosynthesis and the conversion of vitamin B6 derivatives. We also found that a large proportion of the genes encoding glucose-producing polysaccharide hydrolases, that are present even in ectomycorrhizal fungi, also appear to be absent in AM fungi. Conclusions In this study, we found several new genes that are absent from the genomes of AM fungi in addition to the genes previously identified as missing. Missing genes for enzymes in primary metabolic pathways imply that AM fungi may have a higher dependency on host plants than other biotrophic fungi. These missing metabolic pathways provide a genetic basis to explore the physiological characteristics and auxotrophy of AM fungi

Asymbiotic mass production of the arbuscular mycorrhizal fungus Rhizophagus clarus

Arbuscular mycorrhizal (AM) symbiosis is a mutually beneficial interaction between fungi and land plants and promotes global phosphate cycling in terrestrial ecosystems. AM fungi are recognised as obligate symbionts that require root colonisation to complete a life cycle involving the production of propagules, asexual spores. Recently, it has been shown that Rhizophagus irregularis can produce infection-competent secondary spores asymbiotically by adding a fatty acid, palmitoleic acid. Furthermore, asymbiotic growth can be supported using myristate as a carbon and energy source for their asymbiotic growth to increase fungal biomass. However, the spore production and the ability of these spores to colonise host roots were still limited compared to the co-culture of the fungus with plant roots. Here we show that a combination of two plant hormones, strigolactone and jasmonate, induces the production of a large number of infection-competent spores in asymbiotic cultures of Rhizophagus clarus HR1 in the presence of myristate and organic nitrogen. Inoculation of asymbiotically-generated spores promoted the growth of host plants, as observed for spores produced by symbiotic culture system. Our findings provide a foundation for the elucidation of hormonal control of the fungal life cycle and the development of inoculum production schemes

Additional file 1 of The genome of Rhizophagus clarus HR1 reveals a common genetic basis for auxotrophy among arbuscular mycorrhizal fungi

: Figure S1. The k-mer (k = 31) content of R. clarus (left panel) and R. irregularis (right panel) obtained from HiSeq short-reads analyzed with Jellyfish [65]. Figure S2. Common missing pathways in two Rhizophagus species. Figure S3. Pathways in vitamin B6 metabolism. Figure S4. Fermentation pathways converting pyrvate into lactate, formate and acetate, which causes cytosolic acidification. (DOCX 1385 kb