Effects of phosphorus addition with and without ammonium, nitrate, or glucose on N2O and NO emissions from soil sampled under Acacia mangium plantation and incubated at 100 % of the water-filled pore space

An incubation experiment was conducted to examine the effects of phosphorus (P) addition with and without ammonium, nitrate, or glucose on N₂O and NO emissions from soil taken under Acacia mangium plantation and incubated at 100 % water-filled pore space (WFPS). Additions of NO ₃ ^? stimulated the N₂O and NO emissions while NH ₄ ⁺ did not, showing that denitrification was the main process of N₂O and NO production in the study condition. When NO ₃ ^? was added with P significantly (P?<?0.05) increased N₂O emissions regardless of the ratio of the added nitrogen and carbon, suggesting that P addition stimulated denitrification activity. The activation of denitrification by P addition is possibly attributed to two mechanisms: (1) the added-P stimulated denitrification by relieving P shortage for denitrifying bacteria and (2) the added-P stimulated activity of heterotrophic soil microflora with increased O₂ consumption promoting the development of anaerobic conditions with stimulation of denitrification.     

Involvement of endogenous vasopressin in high plasma osmolality-induced anorexia via V1 receptor-mediated mechanism

It is known that water deprivation or injection of hypertonic saline induces anorexia. The present study examined the possible involvement of vasopressin in the suppression of food intake during high plasma osmolality. Intraperitoneal injection of vasopressin (20 microg/kg) into male rats significantly suppressed food intake for 1 hr. This anorectic effect of vasopressin was reversed by simultaneous injection of a peptide antagonist for V(1) receptor (40 microg/kg), but not for V(2) receptor (40 microg/kg). Intraperitoneal injection of hypertonic saline (20% NaCl, 2 ml/kg) similarly suppressed food intake for 2 hr, which was associated with a transient increase in plasma vasopressin concentrations. This hypertonic saline-induced suppression of food intake was blocked by a V(1) receptor antagonist. Vasopressin (40 ng/2 microl) directly administered into the third ventricle of the brain also suppressed food intake for 1 hr. These results suggest that vasopressin participates in the suppression of food intake during high plasma osmolality, the action of which is mediated by V(1) receptors in the brain.     

Effects of the number of pollen grains on cold tolerance at the booting stage in rice lines with QTLs for cold tolerance

This study was conducted to clarify the relationship between the number of pollen grains per anther and spikelet fertility under low temperature conditions in the rice cultivars and lines including lines with quantitative trait loci (QTL) for cold tolerance, adapted to the Tohoku region of northern Japan. Cold-water treatment decreased anther length, the number of pollen grains per anther, and spikelet fertility in all cultivars and lines. The number of pollen grains was proportional to anther length in all cultivars and lines and under all temperatures. Spikelet fertility decreased with decreasing the number of pollen grains in cold-water treatments at 18.5 and 19.3?°C. ‘Ouu 415’, with the qLTB3 QTL for cold tolerance, had 28% more pollen grains and 9% higher spikelet fertility than the recurrent parent, ‘Hitomebore’, in the 18.5?°C cold-water treatment, suggesting that qLTB3 increased both parameters. Lines with the qCTB8 QTL for cold tolerance had significantly more pollen grains in two of the three years and significantly higher spikelet fertility in all three years in the 19.3?°C cold-water treatment, suggesting that qCTB8 reinforced cold tolerance. Ctb1, a proposed cold-tolerance QTL, had no effect on the number of pollen grains or spikelet fertility. In conclusion, the cultivars and lines with more pollen grains had a higher cold tolerance. Some of QTLs were inferred to increase the number of pollen grains and reinforce cold tolerance.     

Establishment of a model for chemoattraction of <Emphasis Type="Italic">Symbiodinium</Emphasis> and characterization of chemotactic compounds in <Emphasis Type="Italic">Acropora tenuis</Emphasis>

Corals harbor symbiotic dinoflagellates, Symbiodinium spp., acquired from surrounding environments. Because Symbiodinium are present at low densities in the water column, corals may attract these symbionts using chemotactic compounds. To examine whether corals contain chemotactic compounds, we established an assay to measure the chemotactic activity for Symbiodinium using an extract of the coral Acropora tenuis, a major reef-building coral in Japan. Our assay revealed that Symbiodinium strain NBRC102920 (clade A), which is taken up by juvenile A. tenuis polyps, is attracted to crude A. tenuis extracts. We found that the chemotactic compounds are water-soluble, heat-labile macromolecules and that the chemotactic activity was inhibited by N-acetyl-d-glucosamine (GlcNAc). We separated the GlcNAc-binding fraction (Fr-ActL) and identified it as the most plausible candidate for the chemoattractant, since the chemotactic activity of the crude A. tenuis extract appeared to be mainly attributable to the activity of Fr-ActL and was also inhibited by the addition of GlcNAc. These results indicate that chemoattraction is mediated via the binding of Symbiodinium to Fr-ActL.     

Effects of acidified seawater on early life stages of scleractinian corals (Genus Acropora)

Ocean acidification, caused by increased atmospheric carbon dioxide (CO₂) concentrations, is currently an important environmental problem. It is therefore necessary to investigate the effects of ocean acidification on all life stages of a wide range of marine organisms. However, few studies have examined the effects of increased CO₂ on early life stages of organisms, including corals. Using a range of pH values (pH 7.3, 7.6, and 8.0) in manipulative duplicate aquarium experiments, we have evaluated the effects of increased CO₂ on early life stages (larval and polyp stages) of Acropora spp. with the aim of estimating CO₂ tolerance thresholds at these stages. Larval survival rates did not differ significantly between the reduced pH and control conditions. In contrast, polyp growth and algal infection rates were significantly decreased at reduced pH levels compared to control conditions. These results suggest that future ocean acidification may lead to reduced primary polyp growth and delayed establishment of symbiosis. Stress exposure experiments using longer experimental time scales and lower levels of CO₂ concentrations than those used in this study are needed to establish the threshold of CO₂ emissions required to sustain coral reef ecosystems.     

Effect of halomethyl-1,3,5-triazines on nitrification of ammonia

Nitrification inhibitory activity of halomethyl-1,3,5-triazines was determined by measuring the inhibitory activities on ammonia-oxidation to nitrate (NO₃⁻-N) in an upland soil and on ammonia-oxidation to nitrite (NO₂⁻-N) by Nitrosomonas europaea ATCC 25978 (ATCC) and Nitrosomonas sp TK 794 (TK). Within the chlorinated trimethyl-1,3,5-triazines, those bearing at least one trichloromethyl group inhibited nitrification more strongly, both in soil and in cell suspension of ATCC, than other mono- or dichlorinated methyl-1,3,5-triazines. Introduction of an amino group to 2,4,6-tris(trichloromethyl)-1,3,5-triazine gave 10- and 100-fold increases of nitrification inhibitory activity in soil and ATCC cell culture, respectively. Within the trihalomethyl-1,3,5-triazines, those having tribromomethyl group(s) exhibited rather weaker nitrification inhibition in soil than the corresponding trichloromethyl-1,3,5-triazines, although they showed a strong inhibition in cell suspension. Ammonium oxidation in ATCC was inhibited more strongly than that in TK. In QSAR studies, the optimum log P values were calculated as c 4.30. By using this value it will become possible to design highly active trichloromethyl-1,3,5-triazine nitrification inhibitors.     

alpha-Klotho as a regulator of calcium homeostasis

alpha-klotho was identified as a gene associated with premature aging-like phenotypes characterized by short lifespan. In mice, we found the molecular association of alpha-Klotho (alpha-Kl) and Na+,K+-adenosine triphosphatase (Na+,K+-ATPase) and provide evidence for an increase of abundance of Na+,K+-ATPase at the plasma membrane. Low concentrations of extracellular free calcium ([Ca2+]e) rapidly induce regulated parathyroid hormone (PTH) secretion in an alpha-Kl- and Na+,K+-ATPase-dependent manner. The increased Na+ gradient created by Na+,K+-ATPase activity might drive the transepithelial transport of Ca2+ in cooperation with ion channels and transporters in the choroid plexus and the kidney. Our findings reveal fundamental roles of alpha-Kl in the regulation of calcium metabolism.