Hypoxia-inducible factor 1α regulates branching morphogenesis during kidney development

The kidneys are exposed to hypoxic conditions during development. Hypoxia-inducible factor (HIF), an important mediator of the response to hypoxia, is believed to have an important role in development. However, the relationship between HIF and branching morphogenesis has not been elucidated clearly.     

A Theoretical Model of Jigsaw-Puzzle Pattern Formation by Plant Leaf Epidermal Cells

Plant leaf epidermal cells exhibit a jigsaw puzzle–like pattern that is generated by interdigitation of the cell wall during leaf development. The contribution of two ROP GTPases, ROP2 and ROP6, to the cytoskeletal dynamics that regulate epidermal cell wall interdigitation has already been examined; however, how interactions between these molecules result in pattern formation remains to be elucidated. Here, we propose a simple interface equation model that incorporates both the cell wall remodeling activity of ROP GTPases and the diffusible signaling molecules by which they are regulated. This model successfully reproduces pattern formation observed in vivo, and explains the counterintuitive experimental results of decreased cellulose production and increased thickness. Our model also reproduces the dynamics of three-way cell wall junctions. Therefore, this model provides a possible mechanism for cell wall interdigitation formation in vivo.     

Immunosuppression induced by Salmonella involves inhibition of tyrosine phosphorylation in murine T lymphocytes

Abstract It is well known that facultative intracellular pathogens such as Salmonella suppress the host immune system. In the present study we attempted to clarify the mechanism responsible for the suppression of T-cell proliferation in mice infected with Salmonella typhimurium . The proliferation of murine spleen cells stimulated with a T-cell mitogen such as phytohemagglutinin (PHA) or concanavalin A (ConA) was significantly suppressed when the mice were infected with S. typhimurium , but not with Eschirichia coli . The suppression of T-cell proliferation did not necessarily parallel the level of interleukin-2 (IL-2) secretion, and was not restored by treatment with a calcium ionophore, indomethacin or IL-2. Only phorbol 12-myristate-13 acetate (PMA), an activator of protein kinase C (PKC), caused a slight recovery of cell proliferation with an augmentation of IL-2 secretion. Furthermore, Western blotting using anti-phosphotyrosine antibodies showed that the mitogen-induced tyrosine phosphorylation of 120-, 106-, 94-, 68- and 57-kDa proteins in murine splenic T-cells was inhibited by S. typhimurium infection. Also, the inhibition of tyrosine phosphorylation was not restored by treatment with PMA. These results suggest that the suppression of T-cell proliferation induced by Salmonella infection may be regulated by inhibition of tyrosine phosphorylation in T-cells, although the inhibition is not associated with PKC activation and subsequent IL-2 secretion of T cells.     

Embigin/basigin subgroup of the immunoglobulin superfamily: Different modes of expression during mouse embryogenesis and correlated expression with carbohydrate antigenic markers

Embigin and basigin are highly glycosylated transmembrane glycoproteins with two immunoglobulin domains and form a subgroup in the immunoglobulin superfamily. Previous studies have demonstrated the functional significance of these molecules. In the present study, in situ hybridization analysis of their expression was performed during mouse embryogenesis. Embigin was strongly expressed in the endoderm during early postimplantation embryogenesis, and in the somite stage in the gut and visceral endoderm. Embryonic ectoderm and its derivative tissues weakly to moderately expressed this molecule. From day 10 to 15 of gestation, no embigin signal was detected. Basigin was more broadly expressed. During the organogenesis period, basigin was expressed in various epithelial tissues, brain ventricles, the spinal cord and dorsal root ganglion. The modes of expression of these two proteins throughout the egg cylinder stage correlated with the expression of the carbohydrate markers that they carry; embigin with Dolichos biflorus agglutinin binding sites and basigin with Le^x antigen and more closely with fucosyltransferase IV, which forms the antigenic epitope. These findings imply that proteins with specific carbohydrate epitopes play roles in early postimplantation embryogenesis.     

Chemical Composition of the Cell Walls of Clostridium botulinum Type A

Cell walls were isolated by sonic disruption of log-phase cells of Clostridium botulinum type A strain 190L and purified by treatment with sodium dodecyl sulfate (SDS) followed by digestion with proteases. Electron microscopy revealed that the cell walls thus obtained were free of both cytoplasmic membrane and cytoplasmic fragments. The purified cell wall contained 8.7% total nitrogen, 15.0% total hexosamines, 22.4% reducing groups, 8.3% carbohydrate, and 3.1% glucose. The content of total phosphorus was very low (0.02%), and therefore it was expected that teichoic acid might be absent in the cell wall. The wall peptidoglycan contained glutamic acid, alanine, diaminopimelic acid, glucosamine and muramic acid in the molar ratios of 1.00:1.85:0:85:1.06:0.67. A low amount of galactosamine was also present, but no other amino acids were found in significant quantities. The SDS-treated cell walls were not attacked by lysozyme, but after extraction with hot formamide they were completely dissolved by the enzyme and released reducing groups. The lysozyme digest was separated into two constituents, the saccharide moiety and the peptide moiety on Sephadex G-50.