Effect of Free-Air CO2 Enrichment (FACE) on the Community Structure of Aquatic Organisms in Floodwater of a Japanese Paddy Field during the Flooding Period of Rice Cultivation

In the present study, the effect of free-air CO₂ enrichment (FACE) on the diversity and the community structure of aquatic organisms in the floodwater of a paddy field in northern Japan was evaluated. The varieties and the number of aquatic organisms ranging from 30 μm to 2 cm were compared four times at intervals of 20 d between the FACE (599 ppm CO₂) and ambient air (384 ppm CO₂) plots during the flooding period of rice cultivation. Aquatic organisms were classified mainly at the order level. Twenty-eight taxonomical groups were detected, and the number of groups in the FACE plots was significantly lower than that in the ambient plots. Zygnematales and Chaetonotida were less frequently detected in the FACE plots. The population densities of Zygnematales, and Chaetonotida also tended to be lower in the FACE plots than in the ambient plots in the late flooding period (after 50 d of flooding). No groups showed a significantly higher population density and frequency of presence in the FACE plots than in the ambient plots. The seasonal variations in the number of taxonomical groups and the community structure of aquatic organisms were less conspicuous in the FACE plots than in the ambient plots. We concluded that the FACE conditions adversely affected the communities of aquatic organisms in paddy fields.     

Effects of elevated carbon dioxide concentration on biological nitrogen fixation, nitrogen mineralization and carbon decomposition in submerged rice soil

Controlled-environment chambers were used to study the effects of elevated CO₂ concentrations on biological N fixation, N mineralization and C decomposition in rice soil. In three chambers, CO₂ concentration was maintained at 353ᆣ/396ᆫ µmol mol^-1 (day/night; ambient CO₂), while in another three, CO₂ was maintained at 667ᆸ/700ᆽ µmol mol^-1 (day/night; elevated CO₂) throughout the growing season. Rice (var. Nipponbare) seedlings were grown under either ambient or elevated CO₂ concentrations, and then transplanted into the soils in the corresponding chambers. At different growth stages, soil samples were taken from surface (0-1cm) and sub-surface (1-10cm) layers at the centre of four hills, then sieved (<1 mm) to remove root residues. Fresh soil was used to measure N fixation activity (using the acetylene reduction assay), NH₄⁺ content and organic C. Separate sets of soil samples were transferred to serum bottles and anaerobically incubated at 30°C for 30 days to measure potential rates of N mineralization and C decomposition. Under an elevated atmospheric CO₂ concentration, acetylene reduction activity significantly increased in the surface soil layer during the early cultivation stages and in the sub-surface soil layer during the latter part of cultivation. There was no difference in the amount of NH₄⁺ in fresh soils between elevated and ambient CO₂ chambers, while the rate of N mineralization was increased by elevated CO₂ during the latter part of cultivation. Soils from the elevated CO₂ chambers had obviously higher rate of C decomposition than that from the ambient CO₂ chambers. CH₄ production gradually increased with the growth of rice plants. These results suggest that elevated CO₂ affected biological N fixation, N mineralization and C decomposition in submerged rice soil during the different growth stages of rice.     

Receptor assay-guided isolation of anti-GABAergic insecticidal alkaloids from a fungal culture

The gamma-aminobutyric acid (GABA) receptor bears sites of action for insecticides. To discover GABA receptor-directed insecticides in natural products, fungal culture extracts were screened for their ability to inhibit specific binding of the radiolabeled noncompetitive antagonist [3H]1-(4-ethynylphenyl)-4-n-propyl-2,6,7-trioxabicyclo[2.2.2]octane to housefly head membranes. The screening efforts led to the isolation of two alkaloids from Aspergillus terreus: PF1198A (alantrypinone) and PF1198B (serantrypinone), which had IC50 values of 0.34 and 2.1 microM, respectively, in this assay. These compounds were ca. 47-61-fold selective for housefly vs rat GABA receptors. Both compounds showed insecticidal activity against Myzus persicae in the range of 100-500 ppm. Binding assay-guided screening should provide significant opportunities for the identification of novel and selective insecticides.     

Kinetics of diarrhetic shellfish poisoning toxins,okadaic acid,dinophysistoxin-1, pectenotoxin-6 and yessotoxin in scallops <Emphasis Type="Italic">Patinopecten yessoensis</Emphasis>

ABSTRACT:   Four toxins, okadaic acid (OA), dinophysistoxin-1 (DTX1), pectenotoxin-6 (PTX6), and yessotoxin (YTX), all associated with diarrhetic shellfish poisoning (DSP), were administered via syringe to Scallops Patinopecten yessoensis and their distribution in the hepatopancreas, adductor muscle, and combined other tissues (mantle, gill, gonad) was analyzed by liquid chromatography-mass spectrometry. Toxins exclusively remained in the hepatopancreas irrespective of the injection site, adductor muscle or hepatopancreas. When injected into hepatopancreas, OA, DTX1, and YTX were metabolized to 7- O -palmitoylOA, 7- O -palmitoylDTX1 and 45-hydroxyyessotoxin (45OH-YTX), respectively. Such metabolic changes were insignificant when toxins were injected into the adductor muscle. The residual ratio for each toxin in the hepatopancreas was less than 20%. Mortalities of scallops treated with PTX6 were lower than those treated with other toxins.     

Clonal variation in heartwood norlignans of <Emphasis Type="Italic">Cryptomeria japonica</Emphasis>: evidence for independent control of agatharesinol and sequirin C biosynthesis

• Introduction   

In Cryptomeria japonica, heartwood properties are considered to be affected by specific extractives. It remains unclear whether traits of specific heartwood compounds are under genetic control.     

Prenylated flavanones isolated from flowers of Azadirachta indica (the neem tree) as antimutagenic constituents against heterocyclic amines

Four prenylated flavanones were isolated from the methanol extract of the flowers of Azadirachta indica (the neem tree) as potent antimutagens against Trp-P-1 (3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole) in the Salmonella typhimurium TA98 assay by activity-guided fractionation. Spectroscopic properties revealed that those compounds were 5,7,4'-trihydroxy-8-prenylflavanone (1), 5,4'-dihydroxy-7-methoxy-8-prenylflavanone (2), 5,7,4'-trihydroxy-3',8-diprenylflavanone (3), and 5,7,4'-trihydroxy-3',5'-diprenylflavanone (4). All isolated compounds were found for the first time in this plant. The antimutagenic IC(50) values of compounds 1-4 were 2.7 +/- 0.1, 3.7 +/- 0.1, 11.1 +/- 0.1, and 18.6 +/- 0.1 microM in the preincubation mixture, respectively. These compounds also similarly inhibited the mutagenicity of Trp-P-2 (3-amino-1-methyl-5H-pyrido[4,3-b]indole) and PhIP (2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine). All of the compounds 1-4 strongly inhibited ethoxyresorufin O-dealkylation activity of cytochrome P450 1A isoforms, which catalyze N-hydroxylation of heterocyclic amines. However, compounds 1-4 did not show significant inhibition against the direct-acting mutagen NaN(3). Thus, the antimutagenic effect of compounds 1-4 would be mainly based on the inhibition of the enzymatic activation of heterocyclic amines.     

Study of the Relationship between Elevated Concentrations of Photochemical Oxidants and Prevailing Meteorological Conditions in the North Kanto Area, Japan

Ambient concentrations of photochemical oxidants (Ox) averaged throughout all ambient monitoring stations in Japan have increased slightly during the past two decades despite decreasing emissions of oxidant precursors such as NOx and hydrocarbons. In the Kanto area of Japan, which is heavily populated and industrialized, Ox concentrations are often high, especially in late spring and summer, and a photochemical smog warning is frequently issued. Although the north Kanto area is about 150 km from the southern metropolitan area, and, moreover, local emissions of precursors are limited because of its agricultural and forested character, high Ox concentration levels (>120 ppbv (1-h average)) are often observed there. We analyzed the relationship between the occurrence of high Ox concentrations in the north Kanto and meteorological conditions. By combining the regional wind pattern and the presence of the inversion layer in the atmospheric boundary layer, we identified five distinct meteorological patterns. High Ox concentrations in the north Kanto area were associated with a southerly extended sea breeze accompanied by a subsidence inversion layer. We inferred that the transport of Ox from the southern urban area by southerly winds and restricted dispersion below the inversion layer can lead to high Ox concentrations in the north Kanto area. This meteorological condition is associated with the presence of a high pressure system centered in the southeastern or eastern sector offshore of the Kanto area. Thus, Ox concentrations in the north Kanto area, where emissions of precursors are relatively low, can easily increase to very high levels under favorable meteorological conditions.     

Increase of cells expressing PD-L1 in bovine leukemia virus infection and enhancement of anti-viral immune responses in vitro via PD-L1 blockade

ABSTRACT: The inhibitory receptor programmed death-1 (PD-1) and its ligand, programmed death-ligand 1 (PD-L1) are involved in immune evasion mechanisms for several pathogens causing chronic infections. Blockade of the PD-1/PD-L1 pathway restores anti-virus immune responses, with concomitant reduction in viral load. In a previous report, we showed that, in bovine leukemia virus (BLV) infection, the expression of bovine PD-1 is closely associated with disease progression. However, the functions of bovine PD-L1 are still unknown. To investigate the role of PD-L1 in BLV infection, we identified the bovine PD-L1 gene, and examined PD-L1 expression in BLV-infected cattle in comparison with uninfected cattle. The deduced amino acid sequence of bovine PD-L1 shows high homology to the human and mouse PD-L1. The proportion of PD-L1 positive cells, especially among B cells, was upregulated in cattle with the late stage of the disease compared to cattle at the aleukemic infection stage or uninfected cattle. The proportion of PD-L1 positive cells correlated positively with prediction markers for the progression of the disease such as leukocyte number, virus load and virus titer whilst on the contrary, it inversely correlated with the degree of interferon-gamma expression. Blockade of the PD-1/PD-L1 pathway in vitro by PD-L1-specific antibody upregulated the production of interleukin-2 and interferon-gamma, and correspondingly, downregulated the BLV provirus load and the proportion of BLV-gp51 expressing cells. These data suggest that PD-L1 induces immunoinhibition in disease progressed cattle during chronic BLV infection. Therefore, PD-L1 would be a potential target for developing immunotherapies against BLV infection.