Occurrence of Cello-Oligosaccharides in the Apoplast of Auxin-Treated Pea Stems

Treatment of pea (Pisum sativum L.) hypocotyl segments with indole-3-butyric acid, which promotes segment elongation, increased the solubilization of both xyloglucan and cello-oligosaccharides in the apoplast of auxin-treated pea stems. The cello-oligosaccharides were isolated from the apoplastic solution with a charcoal/Celite column and were identified as cellobiose, cellotriose, and cellotetraose after subsequent thin-layer chromatography and paper electrophoresis. Cello-oligosaccharides in the apoplastic fraction were monitored using cellobiose dehydrogenase. Both xyloglucan and cello-oligosaccharides appeared to be formed concurrently within 30 min after treatment with the auxin, and the cello-oligosaccharides increased with stem elongation even after 2 h. The total activity of cellulase did not increase for up to 4 h.     

Synaptic Potentiation Induced by a Protein Factor in Cultured Cerebral Neurons

1.We reported in a previous paper that long-lasting enhancement of spontaneous excitatory post synaptic currents (SEPSCs) in cultured chick cerebral neurons was induced by exposure to a conditioned medium (CM) prepared by Mg²⁺-free treatment of neurons. This suggested that the CM contained a diffusible factor(s) for the potentiation.2.In this paper, the factor(s) was shown to be a protein(s) by heat and trypsin treatment of the CM.3.The factor induced the potentiation within 5 min, but it was not required for maintenance of increased SEPSCs.4.The factors in CM induced the potentiation without protein synthesis.5.Protein synthesis at least in postsynaptic neurons, was indispensable to induce the potentiation by the Mg²⁺-free condition.     

Glutamine supplementation increases Th1-cytokine responses in murine intestinal intraepithelial lymphocytes

Intestinal intraepithelial lymphocytes (IELs) are major effector cells in the gut mucosal immune system, and are phenotypically distinct from thymic and peripheral T cells. Although nutritional supplementation with glutamine affects the intestinal immune response, it remains unclear whether this is a direct effect via the IEL-derived cytokines. This study examined changes in IEL-derived cytokine production following treatment with glutamine in vitro. Murine IELs were purified and activated with PMA plus ionomycin, and then cultured in the presence of various glutamine concentrations. IEL-derived cytokines were measured using a cytometric bead array (CBA) system, and IEL subsets were analyzed by flow cytometry. Treatment with glutamine increased the production of IL-2 and IFN-gamma from IELs in the presence of PMA plus ionomycin, but had no effect on TNFalpha, IL-4, or IL-5 production. Treatment with alanine or glucose had no regulatory effect on IEL-derived cytokines. Glutamine therefore had a direct effect on the production of selected IEL-derived Th1-cytokines, and enteral supplementation with glutamine may influence the intestinal immune responses mediated by IELs.     

Presence of xyloglucan-like polysaccharide in Spirogyra and possible involvement in cell–cell attachment

By methylation analysis, it was found that the cell walls of Spirogyra contained 4,6-linked glucose, 4-linked glucose and terminal xylose, which could be components of xyloglucan. Immunocytochemical analysis was carried out using an anti-serum against xyloglucan. After removal of pectic substances, the cell walls of both rhizoid cells and inner cells were stained. Crude protein extract from Spirogyra had a hydrolase activity for xyloglucans. In addition, the exogenously applied xyloglucan prevented the detachment of the cell wall of the severed cell. Involvement of xyloglucan-like polysaccharide in cell–cell attachment was discussed.     

Regulation of VEGF-mediated angiogenesis by the Akt/PKB substrate Girdin

The serine/threonine protein kinase Akt is involved in a variety of cellular processes including cell proliferation, survival, metabolism and gene expression. It is essential in vascular endothelial growth factor (VEGF)-mediated angiogenesis; however, it is not known how Akt regulates the migration of endothelial cells, a crucial process for vessel sprouting, branching and the formation of networks during angiogenesis. Here we report that Akt-mediated phosphorylation of Girdin, an actin-binding protein, promotes VEGF-dependent migration of endothelial cells and tube formation by these cells. We found that exogenously delivered adenovirus harbouring Girdin short interfering RNA in Matrigel embedded in mice, markedly inhibited VEGF-mediated angiogenesis. Targeted disruption of the Girdin gene in mice impaired vessel remodelling in the retina and angiogenesis from aortic rings, whereas Girdin was dispensable for embryonic vasculogenesis. These findings demonstrate that the Akt/Girdin signalling pathway is essential in VEGF-mediated postneonatal angiogenesis.     

Autophagy is important in islet homeostasis and compensatory increase of beta cell mass in response to high-fat diet

Autophagy is an evolutionarily conserved machinery for bulk degradation of cytoplasmic components. Here, we report upregulation of autophagosome formation in pancreatic beta cells in diabetic db/db and in nondiabetic high-fat-fed C57BL/6 mice. Free fatty acids (FFAs), which can cause peripheral insulin resistance associated with diabetes, induced autophagy in beta cells. Genetic ablation of atg7 in beta cells resulted in degeneration of islets and impaired glucose tolerance with reduced insulin secretion. While high-fat diet stimulated beta cell autophagy in control mice, it induced profound deterioration of glucose tolerance in autophagy-deficient mutants, partly because of the lack of compensatory increase in beta cell mass. These findings suggest that basal autophagy is important for maintenance of normal islet architecture and function. The results also identified a unique role for inductive autophagy as an adaptive response of beta cells in the presence of insulin resistance induced by high-fat diet.     

Purple acid phosphatase in the walls of tobacco cells

Purple acid phosphatase isolated from the walls of tobacco cells appears to be a 220 kDa homotetramer composed of 60 kDa subunits, which is purple in color and which contains iron as its only metal ion. Although the phosphatase did not require dithiothreitol for activity and was not inhibited by phenylarsine oxide, the enzyme showed a higher catalytic efficiency (k_cat/K_m) for phosphotyrosine-containing peptides than for other substrates including p-nitrophenyl-phosphate and ATP. The phosphatase formed as a 120 kDa dimer in the cytoplasm and as a 220 kDa tetramer in the walls, where Brefeldin A blocked its secretion during wall regeneration. According to our double-immunofluorescence labeling results, the enzyme might be translocated through the Golgi apparatus to the walls at the interphase and to the cell plate during cytokinesis.     

Molecular characterization of organelle-type Nudix hydrolases in Arabidopsis

Nudix (for nucleoside diphosphates linked to some moiety X) hydrolases act to hydrolyze ribonucleoside and deoxyribonucleoside triphosphates, nucleotide sugars, coenzymes, or dinucleoside polyphosphates. Arabidopsis (Arabidopsis thaliana) contains 27 genes encoding Nudix hydrolase homologues (AtNUDX1 to -27) with a predicted distribution in the cytosol, mitochondria, and chloroplasts. Previously, cytosolic Nudix hydrolases (AtNUDX1 to -11 and -25) were characterized. Here, we conducted a characterization of organelle-type AtNUDX proteins (AtNUDX12 to -24, -26, and -27). AtNUDX14 showed pyrophosphohydrolase activity toward both ADP-ribose and ADP-glucose, although its K(m) value was approximately 100-fold lower for ADP-ribose (13.0+/-0.7 microm) than for ADP-glucose (1,235+/-65 microm). AtNUDX15 hydrolyzed not only reduced coenzyme A (118.7+/-3.4 microm) but also a wide range of its derivatives. AtNUDX19 showed pyrophosphohydrolase activity toward both NADH (335.3+/-5.4 microm) and NADPH (36.9+/-3.5 microm). AtNUDX23 had flavin adenine dinucleotide pyrophosphohydrolase activity (9.1+/-0.9 microm). Both AtNUDX26 and AtNUDX27 hydrolyzed diadenosine polyphosphates (n=4-5). A confocal microscopic analysis using a green fluorescent protein fusion protein showed that AtNUDX15 is distributed in mitochondria and AtNUDX14 -19, -23, -26, and -27 are distributed in chloroplasts. These AtNUDX mRNAs were detected ubiquitously in various Arabidopsis tissues. The T-DNA insertion mutants of AtNUDX13, -14, -15, -19, -20, -21, -25, -26, and -27 did not exhibit any phenotypical differences under normal growth conditions. These results suggest that Nudix hydrolases in Arabidopsis control a variety of metabolites and are pertinent to a wide range of physiological processes.