Histochemical observation of the halo on the epidermal cell wall of barley leaves attacked by Erysiphe graminis hordei

Summary Histochemical characters of the halo on the epidermal cell wall of barley leaves attacked byErysiphe graminis hordei were investigated with light microscope. The area corresponding to the halo showed reduced intensity of stain reactions for cuticle, pectin and cellulose, especially at the penetration point. From the several histochemical reactions, it was concluded that reducing substances with aldehyde groups (such as hexose), pentoses and possibly uronic acids occur in the halo. According to these results, it can be concluded that the halo is caused by the degeneration of the epidermal cell wall by the fungal enzymes.Contributions from Laboratory of Plant Pathology, Kyoto Univ., No. 230.     

Formation of Gold Particles via Thiol Groups on Glycoconjugates Comprising the Sheath Skeleton of Leptothrix

Leptothrix, iron-oxidizing bacterium, produces microtubular sheaths that surround the catenulate cells. Organic nanofibrils excreted from the cell surfaces interweave and coalesce to form immature sheaths, which attract aqueous-phase inorganics to eventually form mature organic–inorganic sheaths. Such inorganic encrustation of the sheaths results from interactions between functional groups in the sheath skeleton and inorganics. Based on our previous findings that Leptothrix sheath skeleton sorbed 47 inorganics (Au was one of the most abundant adsorbates), we examined the sorption status of Au cations on cell-enclosing sheaths and their protein-free remnants and found that nano to sub-micron Au particles (AuNPs and AuSMPs, respectively) formed on the sheath-forming polymer consisting of a glycoconjugate (an amphoteric glycan modified with cysteine, glycine, and 3-hydroxypropionic acid). When the purified polymer was incubated in HAuCl₄ solution, AuNPs and AuSMPs formed on the polymer surfaces. Both particles formed also on cell-enclosing sheaths and protein-free sheath remnants incubated in HAuCl₄ solution. When SH groups in the cell-enclosing sheaths were masked with a fluorescent protein, Au particles did not form after incubation in HAuCl₄ solution. Results implicate that SH groups are at least partially involved in the reduction of Au cations to metallic Au and eventual formation of Au particles.     

Blockade of the Ras/MEK/ERK and Ras/PI3K/Akt pathways by statins reduces the expression of bFGF, HGF, and TGF-β as angiogenic factors in mouse osteosarcoma

The tumor microenvironment plays a critical role in modulating malignant behavior and can dramatically influence cancer treatment strategies. We investigated whether statins inhibit the expression of vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), hepatocyte growth factor (HGF), and transforming growth factor-β (TGF-β) mRNA in the mouse osteosarcoma cell line LM8. We found that statins significantly inhibited mRNA expressions of bFGF, HGF, and TGF-β, and bFGF, HGF, and TGF-β secretions at concentrations that did not have antiproliferative effects on LM8 cells, but had no effect on the mRNA expression and secretion of VEGF. The inhibition of bFGF, HGF, and TGF-β mRNA expression, and bFGF, HGF, TGF-β secretions was reversed when geranylgeranyl pyrophosphate (GGPP), an intermediate in the mevalonate pathway, was used in combination with statins. Furthermore, statins reduced the membrane localization of K-Ras, phosphorylated extracellular signal-regulated kinase 1/2 (ERK1/2), and phosphorylated Akt. Our research indicates that statins inhibit GGPP biosynthesis in the mevalonate pathway, and then inhibit signal transduction in the Ras/ERK and Ras/Akt pathways, thereby inhibiting bFGF, HGF, TGF-β expression in LM8 cells. These results suggest that statins are potentially useful as anti-angiogenic agents for the treatment of osteosarcoma.     

Eugregarine infection within the digestive tract of larval Antarctic krill, Euphausia superba

The infection rate of eugregarine parasites, Cephaloidophora pacifica, within the digestive tract of larval Antarctic krill, Euphausia superba, was examined using samples collected from the Indian sector of the Southern Ocean. Immature and mature eugregarine gamont stages were found at all larval stages older than Calyptopis I stage. Eugregarine infection in 14.0% (N = 108) of the first feeding stage (Calyptopis I) suggested that krill larvae are at risk from being infected during physiological transition from non-feeding to feeding stages. Eugregarine prevalence and intensity of infection at the three calyptopis stages increased with stage/krill length. Statistical analysis showed that the intensity of C. pacifica infection also increased with host density. Thus, krill density is probably a key determinant of the intensity of infection. We found gamont stage eugregarines in the host hind-gut, blocking the passage of food. Eugregarine infections in larval krill may have a negative impact on digestion and absorption in the host digestive tract.     

Nanometer-scale visualization and structural analysis of the inorganic/organic hybrid structure of Gallionella ferruginea twisted stalks

The so-called Fe/Mn-oxidizing bacteria have long been recognized for their potential to form extracellular iron hydroxide or manganese oxide structures in aquatic environments. Bacterial species belonging to the genus Gallionella, one type of such bacteria, oxidize iron and produce uniquely twisted extracellular stalks consisting of iron oxide-encrusted inorganic/organic fibers. This paper describes the ultrastructure of Gallionella cells and stalks and the visualized structural and spatial localization of constitutive elements within the stalks. Electron microscopy with energy-dispersive X-ray microanalysis showed the export site of the stalk fibers from the cell and the uniform distribution of iron, silicon, and phosphorous in the stalks. Electron energy-loss spectroscopy revealed that the stalk fibers had a central carbon core of bacterial exopolymers and that aquatic iron interacted with oxygen at the surface of the carbon core, resulting in deposition of iron oxides at the surface. This new knowledge of the structural and spatial associations of iron with oxygen and carbon provides deeper insights into the unique inorganic/organic hybrid structure of the stalks.     

Structural and spatial associations between Fe, O, and C in the network structure of the Leptothrix ochracea sheath surface

The structural and spatial associations of Fe with O and C in the outer coat fibers of the Leptothrix ochracea sheath were shown to be substantially similar to the stalk fibers of Gallionella ferruginea, i.e., a central C core, probably of bacterial origin, and aquatic Fe interacting with O at the surface of the core.