Abstract
The radioactive noble gas radon-222 ($\mathrm{^{222}Rn}$) produced in the uranium series is a crucial background source in many underground experiments. We have estimated the adsorption ...property of Rn with activated carbon fibers (ACFs) in air, argon, and xenon gas. We evaluated six ACFs, named A-7, A-10, A-15, A-20, A-25, and S-25, provided by Unitika Ltd. We measured the intrinsic radioactivity of these ACF samples, and found A-20’s radioactivity of the uranium series to be $<5.5$ $\mathrm{mBq/kg}$ with $90\%$ confidence level. In air and Ar gas, we found that ACF A-15 has an adsorption efficiency of $1/10000$ reduction at maximum before saturation of Rn adsorption, and more than $97\%$ adsorption efficiency after the saturation. In Xe gas, we found that ACF A-20 has the best Rn adsorption ability among the tested ACFs. We also found that S-25, A-25, and A-15 have similar Rn adsorption performance.
Programmed cell death (PCD) was studied in the petals of Antirrhinum majus, Argyranthemum frutescens, and Petunia hybrida, using DNA degradation and changes in nuclear morphology as parameters. The ...petals exhibit loss of turgor (wilting) as a visible symptom of PCD. DNA degradation, as shown on agarose gels, occurred in all species studied, prior to visible wilting. The number of DNA masses in all the petals of a flower, determined by flow cytometry, markedly increased in Argyranthemum and Petunia, but decreased in Antirrhinum. Many small DNA masses were observed in Argyranthemum and Petunia. The surface of each small DNA mass stained with the lipophilic fluorochrome 3,3′-dihexyloxacarbocyanine iodide (DiOC6), indicating that these masses were surrounded by a membrane. In Antirrhinum, in contrast, the chromatin fragmented into several small spherical clumps that remained inside a large membranous structure. Nuclear fragmentation, therefore, did not occur in Antirrhinum, whereas nuclear fragmentation possibly was a cause of the small DNA masses in Argyranthemum and Petunia. It is concluded that at least two contrasting nuclear morphologies exist during PCD. In the first, the chromatin fragments inside the nucleus, not accompanied—or followed—by nuclear fragmentation. In the second, a large number of DNA masses were observed each enveloped by a membrane. The second type was probably due, at least partially, to nuclear fragmentation.
The tangerine pathotype of Alternaria alternata produces host-selective ACT-toxin and causes Alternaria brown spot disease of tangerine and tangerine hybrids. Sequence analysis of a genomic BAC clone ...identified part of the ACT-toxin TOX (ACTT) gene cluster, and knockout experiments have implicated several open reading frames (ORF) contained within the cluster in the biosynthesis of ACT-toxin. One of the ORF, designated ACTTS3, encoding a putative polyketide synthase, was isolated by rapid amplification of cDNA ends and genomic/reverse transcription-polymerase chain reactions using the specific primers designed from the BAC sequences. The 7,374-bp ORF encodes a polyketide synthase with putative β-ketoacyl synthase, acyltransferase, methyltransferase, β-ketoacyl reductase, and phosphopantetheine attachment site domains. Genomic Southern blots demonstrated that ACTTS3 is present on the smallest chromosome in the tangerine pathotype of A. alternata, and the presence of ACTTS3 is highly correlated with ACT-toxin production and pathogenicity. Targeted gene disruption of two copies of ACTTS3 led to a complete loss of ACT-toxin production and pathogenicity. These results indicate that ACTTS3 is an essential gene for ACT-toxin biosynthesis in the tangerine pathotype of A. alternata and is required for pathogenicity of this fungus.
In senescent petals of Ipomoea nil, we investigated the expression of genes showing homology to genes involved in animal programmed cell death (PCD). Three encoded proteins were homologous to ...apoptotic proteins in animals: Bax inhibitor-1 (BI-1), a vacuolar processing enzyme (VPE; homologous to caspases) and a monodehydroascorbate reductase MDAR; homologous to apoptosis-inducing factor (AIF). AIFs harbor an oxidoreductase domain and an apoptotic domain. MDARs exhibit homology to the AIF oxidoreductase domain, not to the apoptotic domain. The three other genes studied relate to autophagy. They encode homologs to vacuolar protein sorting 34 (VPS34) and to the Arabidopsis autophagy-related proteins 4b and 8a (ATG4b and ATG8a). The transcript abundance of MDAR decreased continuously, whereas that of the other genes studies exhibited a transient increase, except ATG4b whose abundance stayed high after an increase. Treatment with ethylene advanced the time to visible petal senescence, and hastened the changes in expression of each of the genes studied. In order to assess the role of VPS34 in petal senescence, we studied the effect of its inhibitor 3-methyladenine (3-MA). 3-MA reduced the time to visible petal senescence, and also accelerated the time to DNA degradation. Remarkably, 3-MA increased the time to nuclear fragmentation, indicating that the time to visible petal senescence was independent of nuclear fragmentation. The data on 3-MA might suggest the idea that autophagy is not a cause of PCD, but part of the remobilization process.
Mitogen-activated protein kinases (MAPKs) are key enzymes that mediate adaptive responses to various abiotic and biotic stresses, including pathogen challenge. The proteinaceous bacterial elicitor ...harpin (secreted by Pseudomonas syringae pv syringae) activates two MAPKs in suspension cultures of Arabidopsis var. Landsberg erecta. In this study, we show that harpin and exogenous hydrogen peroxide (H2O2) activate myelin basic protein kinases in Arabidopsis leaves. Using anti-AtMPK4 and anti-AtMPK6 antibodies, we identify the harpin-activated MAPKs in both leaves and suspension cultures as AtMPK4 and AtMPK6, and show that H2O2, generated by Arabidopsis cells in response to challenge with harpin, activates only AtMPK6. However, treatments with catalase, which removes H2O2, or diphenylene iodonium, which inhibits superoxide and H2O2 production, do not inhibit harpin-induced activation of AtMPK4 or AtMPK6. In addition, activation of AtMPK4 but not AtMPK6 is inhibited by the MAPK kinase inhibitor PD98059. Neither harpin nor H2O2 has any effect on AtMPK4 or AtMPK6 gene expression. In addition, the expression of AtMEKK1, AtMEK1, or AtMKK2, previously shown to be potential functional partners of AtMPK4, were not affected by either harpin or H2O2 treatments. These data suggest that harpin activates several signaling pathways, one leading to stimulation of the oxidative burst and others leading to the activation of AtMPK4 or AtMPK6.
Abstract
Chemical extraction using a molecular recognition resin named “Empore Radium Rad Disk” was developed to improve sensitivity for the low concentration of radium (Ra). Compared with the ...previous method, the extraction process speed was improved by a factor of three and the recovery rate for $^{226}$Ra was also improved from $81\pm4\%$ to $>99.9\%$. The sensitivity on the $10^{-1}$ mBq level was achieved using a high-purity germanium detector. This improved method was applied to determine $^{226}$Ra in Gd$_2$(SO$_4$)$_3{\cdot}$8H$_2$O which will be used in the Super-Kamiokande Gadolinium project. The improvement and measurement results are reported in this paper.
We report an in-situ measurement of the nuclear recoil (NR) scintillation decay time constant in liquid xenon (LXe) using the XMASS-I detector at the Kamioka underground laboratory in Japan. XMASS-I ...is a large single-phase LXe scintillation detector whose purpose is the direct detection of dark matter via NR which can be induced by collisions between Weakly Interacting Massive Particles (WIMPs) and a xenon nucleus. The inner detector volume contains 832 kg of LXe. 252Cf was used as an external neutron source for irradiating the detector. The scintillation decay time constant of the resulting neutron induced NR was evaluated by comparing the observed photon detection times with Monte Carlo simulations. Fits to the decay time prefer two decay time components, one for each of the Xe2* singlet and triplet states, with τS=4.3±0.6 ns taken from prior research, τT was measured to be 26.9+0.7−1.1 ns with a singlet state fraction FS of 0.252+0.027−0.019. We also evaluated the performance of pulse shape discrimination between NR and electron recoil (ER) with the aim of reducing the electromagnetic background in WIMP searches. For a 50% NR acceptance, the ER acceptance was 13.7±1.0% and 4.1±0.7% in the energy ranges of 5–10 keVee and 10–15 keVee, respectively.
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