Integration of purinergic and angiotensin II receptor function in renal vascular responses and renal injury in angiotensin II-dependent hypertension

Purinergic Signalling - Glomerular arteriolar vasoconstriction and tubulointerstitial injury are observed before glomerular damage occurs in models of hypertension. High interstitial ATP...     

The Glycine-Glomus-Bradyhizobium symbiosis. VIII. Phosphorususe efficiency of CO2 and N2 fixation in mycorrhizal soybean

Soybean [ Glycine max (L.) Merr. cv. Hobbit] plants nodulated by Bradyhizobium japonicum strain USDA 110 were grown in pot cultures in severely P- and N-deficient soil and either colonized by the vesicular-arbuscular mycorrhizal (VAM) fungus Glomus mosseae (Nicol. & Gerd.) Gerd. and Trappe or fertilized with a high (HP) or low (LP) level of KH₂PO₄ (0.6 or 0.3 m M , respectively), After 7 weeks of growth, nodule and chloroplast activities (C₂H₂ reduction and CO₂ exchange rate) were determined. Photosynthetic P-use efficiency of CO₂ fixation was significantly higher in VAM than in HP plants, while that of nitrogenase activity was lower. The LP plants were intermediate in both respects. The ratio of nodule to chloroplast activity [mol C₂H₂ reduced (mol CO₂ fixed)⁻¹] was highest in HP and lowest in VAM plants. Root colonization by the VAM fungus significantly increased nodule number and dry weight and reduced nodule specific mass and activity in comparison to HP plants. In spite of lower nodule activity, VAM plants were significantly larger and had higher N concentrations than the HP plants. The results suggest nonnutritional. VAM-elicited and host-mediated effects on the symbiotic functions of the legume association.     

Burkholderia pseudomallei-induced cell fusion in U937 macrophages can be inhibited by monoclonal antibodies against host cell surface molecules

Burkholderia pseudomallei induces the formation of multinucleated giant cells in cell monolayers. After infection of human macrophage-like U937 cells with B. pseudomallei, addition of monoclonal antibodies against integrin-associated protein (CD47), E-selectin (CD62E), a fusion regulatory protein (CD98), and E-cadherin (CD324) suppressed multinucleated giant cells in a concentration-dependent manner while monoclonal antibodies against other surface molecules did not inhibit fusion despite binding to the cell surface. Flow cytometric analysis showed increased expression of CD47 and CD98, but not CD62E and CD324, upon B. pseudomallei infection. Our data suggest the involvement of specific cellular factors in the process of B. pseudomallei-induced fusion.     

Regulation of matrix Gla protein by parathyroid hormone in MC3T3-E1 osteoblast-like cells involves protein kinase A and extracellular signal-regulated kinase pathways

Inhibition of osteoblast-mediated mineralization is one of the major catabolic effects of parathyroid hormone (PTH) on bone. Previously, we showed that PTH induces matrix gamma-carboxyglutamic acid (Gla) protein (MGP) expression and established that this induction is critical for PTH-mediated inhibition of osteoblast mineralization. In the present study, we focus on the mechanism through which PTH regulates MGP expression in osteoblastic MC3T3-E1 cells. Following transient transfection of these cells with a -748 bp murine MGP promoter-luciferase construct (pMGP-luc), PTH (10 (-7) M) induced promoter activity in a time-dependent manner with a maximal four- to six fold induction seen 6 h after PTH treatment. Both H-89 (PKA inhibitor) and U0126 (MEK inhibitor), suppressed PTH induction of MGP promoter activity as well as the MGP mRNA level. In addition, forskolin (PKA activator) stimulated MGP promoter activity and mRNA levels confirming that PKA is one of the signaling molecules required for regulation of MGP by PTH. Co-transfection of MC3T3-E1 cells with pMGP-luc and MEK(SP), a plasmid encoding the constitutively active form of MEK, led to a dose-dependent increase in MGP promoter activity. Both MGP promoter activity and MGP mRNA level were not affected by the protein kinase C (PKC) inhibitor, GF109203X. However, phorbol 12-myristate 13-acetate (PMA), a selective PKC activator induced MGP mRNA expression through activation of extracellular signal-regulated kinase (ERK). Taken together, these results indicate that PTH regulates MGP via both PKA- and ERK-dependent pathways.     

Stimulating macrophage activity in mice and humans by oral administration of quillaja saponin

Quillaja saponin (QS) was examined for its immunostimulating effect on mice and humans after oral administration. Mice fed QS for 24 h significantly increased in chemotactic and phagocytosis activities of peritoneal macrophages. This enhancing effect in both activities continued for 4-d after QS administration. Mice fed QS for 24 h prior to an interperitoneal challenge with Escherichia coli showed a higher survival rate than the control group. Peripheral blood analysis of volunteers showed significant increases in chemotactic and phagocytosis activities after oral administration of QS for 7 d. Furthermore, the volunteers did not show significant changes in immunoglobulin, transaminase, IL-1α, or TNF-α levels, or in serum albumin concentrations. Thus orally administered QS can effectively enhance the immune response through stimulation of macrophages without adverse effects.     

Enhanced propionic acid fermentation by Propionibacterium acidipropionici mutant obtained by adaptation in a fibrous-bed bioreactor

Fed-batch fermentations of glucose by P. acidipropionici ATCC 4875 in free-cell suspension culture and immobilized in a fibrous-bed bioreactor (FBB) were studied. The latter produced a much higher propionic acid concentration (71.8 +/- 0.8 g/L vs. 52.2 +/- 1.1 g/L), indicating enhanced tolerance to propionic acid inhibition by cells adapted in the FBB. Compared to the free-cell fermentation, the FBB culture produced 20-59% more propionate (0.40-0.65 +/- 0.02 g/g vs. 0.41 +/- 0.02 g/g), 17% less acetate (0.10 +/- 0.01 g/g vs. 0.12 +/- 0.02 g/g), and 50% less succinate (0.09 +/- 0.02 g/g vs. 0.18 +/- 0.03 g/g) from glucose. The higher propionate production in the FBB was attributed to mutations in two key enzymes, oxaloacetate transcarboxylase and propionyl CoA: succinyl CoA transferase, leading to the production of propionic acid from pyruvate. Both showed higher specific activity and lower sensitivity to propionic acid inhibition in the mutant than in the wild type. In contrast, the activity of PEP carboxylase, which converts PEP directly to oxaloacetate and leads to the production of succinate from glucose, was generally lower in the mutant than in the wild type. For phosphotransacetylase and acetate kinase in the acetate formation pathway, however, there was no significant difference between the mutant and the wild type. In addition, the mutant had a striking change in its morphology. With a threefold increase in its length and approximately 24% decrease in its diameter, the mutant cell had an approximately 10% higher specific surface area that should have made the mutant more efficient in transporting substrates and metabolites across the cell membrane. A slightly lower membrane-bound ATPase activity found in the mutant also indicated that the mutant might have a more efficient proton pump to allow it to better tolerate propionic acid. In addition, the mutant had more longer-chain saturated fatty acids (C17:0) and less unsaturated fatty acids (C18:1), both of which could decrease membrane fluidity and might have contributed to the increased propionate tolerance. The enhanced propionic acid production from glucose by P. acidipropionici was thus attributed to both a high viable cell density maintained in the reactor and favorable mutations resulted from adaptation by cell immobilization in the FBB.     

Loop residues of the receptor binding domain of Bacillus thuringiensis Cry11Ba toxin are important for mosquitocidal activity

Using a Cry11Ba toxin model, predicted loops in domain II were analyzed for their role in receptor binding and toxicity. Peptides corresponding to loops α8, 1 and 3, but not loop 2, competed with toxin binding to Aedes midgut membranes. Mutagenesis data reveal loops α8, 1 and 3 are involved in toxicity. Loops 1 and 3 are of greater significance in toxicity to Aedes and Culex larvae than to Anopheles. Cry11Ba binds the apical membrane of larval caecae and posterior midgut, and binding can be competed by loop 1 but not by loop 2 peptides. Cry11Ba binds the same regions to which anti-cadherin antibody binds, and this antibody competes with Cry11Ba binding suggesting a possible role of cadherin in toxication.     

Seasonal cambial activity of five tropical tree species in central Thailand

The seasonal cambial activity of five tropical tree species was investigated at Khao Yai National Park. The species studied were Tetrameles nudiflora, Magnolia baillonii, Canarium euphyllum Kur, Toona ciliata, and Spondias axillaris. Cambial activity was quantified by counting layers of undifferentiated cells in the cambium zone from wood anatomical micro sections prepared from wood samples collected in monthly intervals from July 2010 to June 2011. The relationship between cambial activity and climatic factors was investigated by using Pearson’s correlation. The growth dynamics of five studied species differed considerably. The cambium of Tetrameles nudiflora and Magnolia baillonii was most active when rainfall reached its maximum amount in June (mid rainy season), whereas the cambium of Canarium euphyllum, Toona ciliata, and Spondias axillaris was most active in March during the transition from the dry to the wet season.