Abrupt increase in phosphorus and potassium fluxes during a masting event in a Bornean tropical forest

Mechanisms by which the productivity of tropical ecosystems is limited by nutrients is a long-standing question, but little information is available on the nutrient dynamics supporting the masting phenomenon in Southeast Asian evergreen rainforests. In this study we examined the nutrient sink and potential nutrient sources of masting in a Bornean tropical forest. We investigated if nutrient flux in fine litter, tree stems, and soils changed temporally in response to intense flower and fruit production. Fifty-five litter traps were installed in a 2-ha plot at the onset of flowering (April 2010), and litter and nutrient fluxes were monitored for more than 4 years (May 2010–December 2014). Wood cores of trunks and coarse roots of abundant species (Shorea spp.) and soil samples were collected in May 2010, September 2010, and September 2011 (coinciding with peak flowering, peak fruiting, and 1 year after fruiting, respectively). The P and K fluxes in the total litter were significantly greater in the mast year (2010) than non-mast years, whereas the Mg, N, and Ca fluxes did not vary in relation to masting. In line with the nutrient fluxes, P and K concentrations in coarse roots of flowering individuals of S. multiflora decreased in September 2011. The present results suggest that tropical trees require extraordinary amounts of P and K for masting, and may retranslocate stored nutrients to meet the elevated nutrient demands for masting.     

Spectral and carbon monoxide binding properties of Fe(II) picket-fence porphyrin and protoheme bound to liposomes

Spectral and CO binding properties of liposome bound heme compounds, Fe(II) picket-fence porphyrin and protoheme, were examined. Phosphatidylethanolamine and phosphatidylcholine were used to make liposomes. Liposome-bound protoheme showed a very low CO affinity, whereas liposome-bound Fe(II) picket-fence porphyrin showed a high affinity. Addition of the ligand, 1-methylimidazole, modulated the CO affinities of both types of complexes to a level comparable to that of hemoglobin. However, autoxidation rates of the liposome bound heme compounds were still considerably high, and no stable oxygenated form could be observed.     

Direct Detection by PCR of Escherichia coli O157 and Enteropathogens in Patients with Bloody Diarrhea

Direct detection of Escherichia coli O157 and foodborne pathogens associated with bloody diarrhea were achieved using polymerase chain reaction (PCR) after the preparation of DNA from stool specimens using the microspin technique. PCR was compared with cultivation and toxin production tests with respect to the efficiency of detection of each pathogen; E. coli O157, Vibrio parahaemolyticus, Salmonella serovar Enteritidis and Campylobacter jejuni. Detection of some or all of the above pathogens in clinical stool specimens was achieved using PCR. The minimum number of cells required for the detection of the above pathogens by PCR was 10¹ CFUs/0.5 g of stool sample. PCR was completed within 6 hr. The above pathogens were also detected in cultivation and toxin production tests. Partial purification of the template DNA using the microspin technique was essential for the elimination of PCR inhibitors from the DNA samples. This PCR method is an accurate, easy-to-read screening method for the detection of Shiga-like toxin producing E. coli O157 and enteropathogens associated with bloody diarrhea in stool specimens.     

The subcellular distribution of alanine-glyoxylate aminotransferase and serine-pyruvate aminotransferase in dog liver.

The subcellular distributions of alanine-glyoxylate aminotransferase and serine-pyruvate aminotransferase in the particulate fraction of dog liver were examined by centrifugation in a sucrose density gradient. Most of both enzyme activities in the particulate fraction were localized in the mitochondria, but not in the peroxisomes.     

Signaling transduction pathway of angiotensin II in human mesangial cells: mediation of focal adhesion and GTPase activating proteins

Human mesangial cells (HMCs) respond to angiotensin II stimulation, which modulates their physiological activities, i.e., contraction and proliferation. It has been revealed that focal adhesion kinase (FAK) and paxillin participate in the angiotensin II-mediated signaling and cytoskeletal rearrangements at focal adhesion. We investigated the influences of cell adhesion upon angiotensin II effects in HMCs. In adherent cells, both FAK and paxillin were tyrosine phosphorylated by angiotensin II, while the cell detachment completely inhibited the tyrosine phosphorylation of paxillin. Activation of p44/42 mitogen-activated protein (MAP) kinase by angiotensin II was accentuated in suspended cells. Moreover, p190, a member of Rho GTPase activating protein (GAP), and RasGAP were coprecipitated with paxillin in adherent cells and angiotensin II stimulation reduced the formation of paxillin-p190 and paxillin-RasGAP complexes. These results suggest that the formation of focal adhesion complexes accelerated by accumulation of mesangial matrices may inhibit the proliferation of HMCs by modulating MAP kinase activity and be related to mesangial cell depletion.     

pH-dependent formation of membranous cytoplasmic body-like structure of ganglioside G(M1)/bis(monoacylglycero)phosphate mixed membranes

Membrane structures of the mixtures of ganglioside G(M1) and endosome specific lipid, bis (monoacylglycero) phosphate (BMP, also known as lysobisphosphatidic acid) were examined at various pH conditions by freeze-fracture electron microscopy and small-angle x-ray scattering. At pH 8.5-6.5, a G(M1)/BMP (1:1 mol/mol) mixture formed small vesicular aggregates, whereas the mixture formed closely packed lamellar structures under acidic conditions (pH 5.5, 4.6) with the lamellar repeat distance of 8.06 nm. Since BMP alone exhibits a diffuse lamellar structure at a broad range of pH values and G(M1) forms a micelle, the results indicate that both G(M1) and BMP are required to produce closely stacked multilamellar vesicles. These vesicles resemble membranous cytoplasmic bodies in cells derived from patients suffering from G(M1) gangliosidosis. Similar to G(M1) gangliosidosis, cholesterol was trapped in BMP vesicles in G(M1)- and in a low pH-dependent manner. Studies employing different gangliosides and a G(M1) analog suggest the importance of sugar chains and a sialic acid of G(M1) in the pH-dependent structural change of G(M1)/BMP membranes.     

Reactive oxygen species generation through NADH oxidation by 6-formylpterin derivatives in the dark

6-formylpterin (6FP) has been reported to produce reactive oxygen species (ROS) such as *O2- and H2O2 from O2 in the presence of NADH under light condition. In the present study, we prepared a variety of 6FP derivatives and found that 2-(N,N-dimethylaminomethyleneamino)-6-formyl-3-pivaloylpteridin-4-one and 2-(N,N-dimethylaminomethyleneamino)-6-formyl-3-methylpteridin-4-one, in which the 2-amino groups are modified by a dimethylaminomethylene group and the 3-positions by pivaloyl and methyl groups and 2-amino-6-formyl-3-methylpteridin-4-one in which the amino group at the 2-position is free and the 3-position is modified by a methyl group generated H2O2 from O2 on oxidation of NADH to NAD+ in the dark. However, 6FP and 2-(N,N-dimethylaminomethyleneamino)-6-formylpteridin-4-one, in which the 3-position is free did not yield H2O2. These results indicate that modification of the 3-position is essential to make the activities of 6FP available in the dark and would be suggestive for designing pharmaceutical compounds that generate appropriate and controllable amounts of ROS in vivo.