Suppression of MyoD induces spontaneous adipogenesis in skeletal muscle progenitor cell culture

The degree of intramuscular adipose tissue accumulation is one of the factors affecting meat quality. Accumulation of adipocytes is also observed under the pathological condition of skeletal muscle such as muscular dystrophy and sarcopenia. The origin of adipocytes seen in skeletal muscle is mesenchymal progenitor cells that can give rise to both adipocytes and fibroblasts. In the present study, we demonstrated that siRNA-mediated suppression of MyoD expression in rat skeletal muscle progenitor cell culture, which comprises both myogenic satellite cells and mesenchymal progenitor cells, resulted in diminished myotube formation and an unexpected spontaneous appearance of white adipocytes. Suppressing myomaker expression also resulted in complete absence of myotube formation without reducing MyoD expression, but no adipogenesis was seen in this scenario, indicating that decline in MyoD expression rather than decreased myotube formation is necessary to induce adipogenesis. In addition, spontaneous adipogenesis induced by suppressing MyoD expression in culture was inhibited by the conditioned medium from control culture, indicating that anti-adipogenic factor(s) are secreted from MyoD-positive myogenic cells. These results indicate the presence of regulatory mechanism on adipogenesis by myogenic cells.     

Blackening of sugi (Cryptomeria japonica D. Don) heartwood in relation to metal content and moisture content

Blackening in heartwood was investigated in relation to the metal contents and the moisture content in xylem of about 50-year-old seedling sugi (Cryptomeria japonica D. Don) planted in a steeply sloped stand in Okutama district (Itsukaichi Tokyo), where blackened heartwood is frequently found. The potassium, calcium, iron, and manganese contents were examined in the variously blackened heartwood and normal heartwood by an atomic absorption method. It was recognized that potassium increased relative to the degree of the blackening of heartwood, resulting in a significant correlation between them. This finding implies that an increase in potassium has an important role in the blackening of heartwood. Moisture content has a tendency to increase in the blackened heartwood, so it seems that the large accumulation of potassium is associated with the high moisture content in heartwood.This work was presented at the 43rd Annual Meeting of the Japan Wood Research Society at Morioka, August 1993     

Genetic and antigenic characterization of bovine viral diarrhea viruses isolated from cattle in Hokkaido,Japan

In our previous study, we genetically analyzed bovine viral diarrhea viruses (BVDVs) isolated from 2000 to 2006 in Japan and reported that subgenotype 1b viruses were predominant. In the present study, 766 BVDVs isolated from 2006 to 2014 in Hokkaido, Japan, were genetically analyzed to understand recent epidemics. Phylogenetic analysis based on nucleotide sequences of the 5′-untranslated region of viral genome revealed that 766 isolates were classified as genotype 1 (BVDV-1; 544 isolates) and genotype 2 (BVDV-2; 222). BVDV-1 isolates were further divided into BVDV-1a (93), 1b (371) and 1c (80) subgenotypes, and all BVDV-2 isolates were grouped into BVDV-2a subgenotype (222). Further comparative analysis was performed with BVDV-1a, 1b and 2a viruses isolated from 2001 to 2014. Phylogenetic analysis based on nucleotide sequences of the viral glycoprotein E2 gene, a major target of neutralizing antibodies, revealed that BVDV-1a, 1b and 2a isolates were further classified into several clusters. Cross-neutralization tests showed that BVDV-1b isolates were antigenically different from BVDV-1a isolates, and almost BVDV-1a, 1b and 2a isolates were antigenically similar among each subgenotype and each E2 cluster. Taken together, BVDV-1b viruses are still predominant, and BVDV-2a viruses have increased recently in Hokkaido, Japan. Field isolates of BVDV-1a, 1b and 2a show genetic diversity on the E2 gene with antigenic conservation among each subgenotype during the last 14 years.     

The use of micro-beam X-ray diffraction for the characterization of starch crystal structure in rice mutant kernels of waxy, amylose extender, and sugary1

Micro-beam X-ray diffraction analyses were carried out on slices from wild-type rice and mutants. The method permitted the crystalline structure to be analyzed with less destruction of cells and fewer artificial effects that occur during the purification of starch from tissue and provided information concerning the localization and crystalline structure of starches distributed in the endosperm. The starch on kernel slices from the wild-type and waxy mutant, carrying a defect for the Granule-bound starch synthase I (GBSSI) gene, displayed an A-type of diffraction pattern; no difference in the crystalline patterns between starches located in the inner and outer region in a kernel were observed. A double mutant of the waxy and amylose extender (ae) mutant carrying a defect for the Starch branching enzyme IIb gene accumulated amylose-free B-type starches. The kernel slice from the double mutant of waxy and sugary1, mutated on the Isoamylase I locus, displayed an A-type diffraction pattern in the outer region and was amorphous in the inner region. A chain-length distribution analysis of polyglucans in kernels from wild-type and mutants showed that ae amylopectin had more long chains and less short chains than the wild-type and waxy amylopectin. On the other hand, the water-soluble polysaccharide in the inner region of the sugary1 endosperm had more short chains than the amylopectin in the outer region counterparts. These results indicate that branch chain length in amylopectin is crucial in determining the formation of A- and B-type starches.     

In planta dynamic analysis of onion yellows phytoplasma using localized inoculation by insect transmission

ABSTRACT Due to the lack of a means to inoculate plants mechanically, the histological dynamics and in planta spread of phytoplasmas have been studied very little. We analyzed the dynamics of plant infection by phytoplasmas, using a technique to infect a limited area of a leaf, nested polymerase chain reaction (PCR), real-time PCR, and immunohistochemical visualization. Following localized inoculation of a leaf of garland chrysanthemum (Chrysanthemum coronarium) by the vector leafhopper Macrosteles striifrons, the onion yellows (OY) phytoplasma spread within the plant from the inoculated leaf to the main stem (1 day postinoculation [dpi]), to the roots and the top leaf (2 dpi), and to other leaves from top to bottom (from 7 to 21 dpi). The populations of the OY phytoplasmas in inoculated leaves and roots increased approximately sixfold each week from 14 to 28 dpi. At 14 dpi, the OY phytoplasmas colonized limited regions of the phloem tissue in both the root and stem and then spread throughout the phloem by 21 dpi. This information should form the basis for elucidating the mechanisms of phytoplasma multiplication and migration within a plant host.     

Atomic-level models of the bacterial carboxysome shell

The carboxysome is a bacterial microcompartment that functions as a simple organelle by sequestering enzymes involved in carbon fixation. The carboxysome shell is roughly 800 to 1400 angstroms in diameter and is assembled from several thousand protein subunits. Previous studies have revealed the three-dimensional structures of hexameric carboxysome shell proteins, which self-assemble into molecular layers that most likely constitute the facets of the polyhedral shell. Here, we report the three-dimensional structures of two proteins of previously unknown function, CcmL and OrfA (or CsoS4A), from the two known classes of carboxysomes, at resolutions of 2.4 and 2.15 angstroms. Both proteins assemble to form pentameric structures whose size and shape are compatible with formation of vertices in an icosahedral shell. Combining these pentamers with the hexamers previously elucidated gives two plausible, preliminary atomic models for the carboxysome shell.