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41.
Ken’ichi Osaka Yasuhiro Nakajima Katsuhiro Suzuki Sadao Eguchi Hidetaka Katou 《Soil Science and Plant Nutrition》2013,59(5):558-565
ABSTRACTQuantitative evaluation of denitrification by the dual isotope approach, which measures the stable isotope ratios of nitrogen (δ15N) and oxygen (δ18O) in nitrate, has been hampered by the wide range of values reported for the ratio of enrichment factors for 15N and 18O (15ε and 18ε, respectively) during denitrification. The objectives of this study were to determine 15ε and 18ε values at different denitrification rates under controlled conditions, and to infer possible mechanisms by which the 18ε/15ε ratio is influenced under different conditions. Column experiments were conducted at 25, 15, and 10°C, which enabled determination of 15ε and 18ε at different denitrification rates, in the absence of nitrate replenishment from ammonium oxidation and other sources. The values of 15ε and 18ε ranged from ?11.8 to ?14.9‰ and from ?8.4 to ?15.9‰, respectively, with 15ε less sensitive to changes in the denitrification rates. The resultant 18ε/15ε ratio, ranging from 0.70 to 1.17, was close to the values reported for sediment incubations, and larger than those for groundwater systems. These results are consistent with the explanations that 18ε/15ε value itself is close to unity during denitrification, and that at smaller denitrification rates, concurrent reactions including re-oxidation of nitrite to nitrate lead to smaller apparent fractionation of 18O and smaller 18ε/15ε ratios. This suggests that while linear relationships between δ18O and δ15N give a strong evidence of denitrification, apparent 18ε/15ε values are site specific and depend on the ambient conditions. In evaluating denitrification in such systems, we suggest the use of 15ε in preference to 18ε because 15ε is less sensitive to denitrification rates. 相似文献
42.
Katsuhiro Shiono Masato Ejiri Kana Shimizu Sumiyo Yamada 《Plant Production Science》2013,16(2):285-295
ABSTRACT Root growth into hypoxic or anoxic waterlogged soil relies on internal aeration in plants. The plant hormone ethylene helps adapt to waterlogging by inducing the formation of aerenchyma, which provides a low-resistance pathway for the transport of oxygen from the shoot to the root apex. Waterlogging-susceptible crops including barley start to form aerenchyma after suffering waterlogging stress. But waterlogging can be fatal if aerenchyma formation is not fast enough. Here, we investigated whether pre-treating barley with ethephon, an ethylene-releasing agrochemical, could improve its tolerance to mimicked waterlogging conditions (using stagnant deoxygenated agar nutrient solution). In barley growing in aerated nutrient solution, ethephon treatment enhanced aerenchyma formation at the root tips and induced the development of shorter and shallower roots. Pre-treating barley leaves also delayed waterlogging-caused whiting and increased the percentages of viable root-tips under waterlogging conditions. However, the pretreatment did not noticeably increase fresh weight or shoot length. Further studies are needed to optimize ethephon treatment conditions to improve barley production under waterlogged conditions. 相似文献
43.
Hiroaki Somura Hajime Tanji Koshi Yoshida Osamu Toda Katsuhiro Higuchi 《Paddy and Water Environment》2005,3(3):177-186
Efficient management of water resources in paddy fields requires an understanding of the volume of supplementary water used.
However, quantifying the volume is laborious due to the large amount of data that must be collected and analyzed. The purpose
of our study was to estimate the volume of supplementary water used in paddy fields, based on several years of available statistical
data, and to provide information on how much water can be supplied to paddy fields in each target area. In this study, the
lower Mekong River basin of northeast Thailand, Laos, and Cambodia was selected as the study area. In the first step, we used
agricultural statistics for each country, rainfall data acquired from the Mekong River Commission Secretariat (MRCS), and
the value of virtual water required per unit of rice production. Because several years of data were used for dry season harvested
areas and rice production in each country, the supplementary water to paddy fields in each province was calculated using virtual
water and rainfall. This method made it possible to estimate changes in supplementary water in each province. Through this
study, the supplementary water to paddy fields during the dry season in three countries was approximated from the minimum
number of data sets. Moreover, for cases in which it is not possible to procure agricultural water use data for a hydrological
model simulation, an alternative solution is proposed. 相似文献
44.
Murata S Sasaki K Kishimoto T Niwa S Hayashi H Takahama Y Tanaka K 《Science (New York, N.Y.)》2007,316(5829):1349-1353
Proteasomes are responsible for generating peptides presented by the class I major histocompatibility complex (MHC) molecules of the immune system. Here, we report the identification of a previously unrecognized catalytic subunit called beta5t. beta5t is expressed exclusively in cortical thymic epithelial cells, which are responsible for the positive selection of developing thymocytes. Although the chymotrypsin-like activity of proteasomes is considered to be important for the production of peptides with high affinities for MHC class I clefts, incorporation of beta5t into proteasomes in place of beta5 or beta5i selectively reduces this activity. We also found that beta5t-deficient mice displayed defective development of CD8(+) T cells in the thymus. Our results suggest a key role for beta5t in generating the MHC class I-restricted CD8(+) T cell repertoire during thymic selection. 相似文献
45.
46.
Hiroyuki Mizuta Tomoki Kai Katsuhiro Tabuchi & Hajime Yasui 《Aquaculture Research》2007,38(12):1323-1329
Responses of the sporophytes of Laminaria japonica to blue, red and white lights were investigated using segments, discs and whole plants. The relative growth rate with regard to the blade's length and width showed no difference among the light conditions during 2 weeks of culturing. On the contrary, the elongation rates of the stipe and the holdfast were 1.7–2.5 times higher under red light than that under white light as a control. Callus formation in the segments was also promoted more under red light conditions than under white or blue light. Blue light irradiation resulted in a 48% and 12% decrease in the relative growth rate of the stipe and the holdfast, respectively, in comparison with the control. When sporophyte discs were cultured for 10 weeks, all discs formed zoosporangial sori 2–3 weeks earlier under blue light than under white light. However, red light inhibited the formation of zoosporangia. Indoleacetic acid (IAA) oxidase activity was about two‐fold higher under blue light than under red light, suggesting that the difference in response between the blue and red light conditions is related to the internal IAA level of the tissues. The developmental, reproductive and morphological effects of blue and red lights will be useful for the artificial control of the life cycle of Laminaria plants and for the development of more efficient cultivation techniques. 相似文献
47.
Kasumi Ito Yumi Oura Hiroyuki Takeya Shigeaki Hattori Katsuhiro Kitagawa Dinesh Paudel Govindra Paudel 《Journal of Forest Research》2005,10(6):453-463
Despite high expectations of nongovernmental organizations (NGOs) as project partners in bilateral-aid community forestry
(CF) projects in Nepal, it remains unclear whether the NGO involvement favored by donors is efficient. This study examined
the influence of NGOs on local people's perceptions of CF management by using a quantitative analysis based on a questionnaire
survey. Three different forest user groups (FUGs) supported by the Nepal Swiss Community Forestry Project were selected from
the Dolakha and Ramecchap districts: an FUG supported by another FUG acting as an NGO, an FUG supported by an NGO specializing
in CF, and an FUG without NGO support. A structured survey examined the perception of CF management based on satisfaction,
involvement, and self-reliance in 244 selected households belonging to the three FUGs. Knowledge of CF and personal information
was also surveyed and analyzed. The results showed that NGO involvement influences factors such as self-reliance and knowledge
of CF. FUG members who were supported by an NGO or an FUG had a significantly higher perception with respect to self-reliance
and knowledge than did members without such support. This indicates that experienced FUGs can serve as adequate service providers
for the CF formation procedure, in a manner similar to that of NGOs. On the other hand, the limited support from NGOs or FUGs
during the formation process seemed insufficient to fulfill the expectations of aid agencies with respect to the enhancement
of satisfaction and active participation on the part of FUG members. If aid agencies expect NGOs and FUGs to enhance the satisfaction
and participation of members, these intermediary organizations should be assigned to support more CF activities than just
the formation procedure. Aid agencies should take responsibility for strengthening the capabilities of NGOs and FUGs, as needed. 相似文献
48.
The shattering habit in buckwheat occurs because of brittle or weak pedicels. Brittle pedicels are observed in wild buckwheat
but not in cultivated buckwheat. Using 2 self-compatible lines, 01AMU2 with brittle pedicels and Kyukei SC2 (KSC2) with non-brittle
pedicels, produced by an interspecific cross between Fagopyrum esculentum cv Botansoba (non-brittle) andF. homotropicum (brittle), we investigated the inheritance of brittle pedicels. F1 plants derived from crosses between Botansoba × 01AMU2 and Botansoba × KSC2 had brittle pedicels. The F2 population derived from the cross between Botansoba × 01AMU2 showed segregation of brittle and non-brittle pedicels that
fit the expected 3:1 ratio, suggesting that non-brittle pedicel in Botansoba is controlled by a single recessive gene (sht1). Another F2 population, derived from the cross between Botansoba × KSC2, showed segregation of brittle and non-brittle pedicels that
fit an expected ratio of 9:7,suggesting that non-brittle pedicel in KSC2is controlled by a different single recessive gene
(sht2). Thus, brittle pedicel is achieved by 2 complementary genes Sht1 and Sht2. The sht1 locus is linked to the S locus with a recombination frequency of5.46±1.18 (%). We investigated whether common buckwheat has the allele sht2by crossing 6 common buckwheat lines withKSC2. An analysis of the preliminary data showed that some of the F1 had brittle pedicels and others had non-brittle pedicels, suggesting that some common buckwheat lines possess both the allelesSht2 and sht2.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
49.
Yukie Tada Norio Yano Hiroshi Takahashi Katsuhiro Yuzawa Hiroshi Ando Yoshikazu Kubo Akemichi Nagasawa Akiko Inomata Akio Ogata Dai Nakae 《Journal of toxicologic pathology》2013,26(4):393-403
Information about potential risks of iron nanomaterials is still limited, while a wide variety of applications are expected. We recently reported acute phase responses of male and female Fischer 344 rats after a single intratracheal spray instillation of Fe3O4 nanoparticles (magnetite), clearly showing dose-dependent pulmonary inflammatory changes (Tada et al., J Toxicol Pathol 25, 233–239, 2012). The present study assessed long-term responses of male and female Fischer 344 rats to multiple administrations of magnetite. Ten-week-old male and female Fischer 344 rats (n=20/group) were exposed to a total of 13 quadweekly intermittent intratracheal spray instillations of magnetite during the experimental period of 52 weeks, at doses of 0, 0.2 (low), 1.0 (medium) and 5.0 (high-dose) mg/kg body weight per administration. Absolute and relative lung weights of the high-dose group were significantly higher than those of the control group. Macroscopically, slight enlargement and scattered black patches were recognized in the lungs and the lung-associated lymph nodes of the high-dose group. Histopathologically, infiltration of macrophages phagocytosing magnetite (all dose groups) and of chronic inflammatory cells (medium- and high-dose males and high-dose females), alveolar bronchiolization and granuloma (high-dose group) were observed. In addition, alveolar hyperplasias were observed in some rats of the high-dose group, and cytoplasmic overexpression of β-catenin protein was immunohistochemically found in such lesions. The present results clearly show that instilled magnetite causes chronic inflammatory responses in the lung. These responses occur in a dose-dependent manner without apparent differences among sexes 相似文献
50.
Yukie Tada Norio Yano Hiroshi Takahashi Katsuhiro Yuzawa Hiroshi Ando Yoshikazu Kubo Akemichi Nagasawa Akio Ogata Dai Nakae 《Journal of toxicologic pathology》2012,25(4):233-239
Iron nanomaterials are of considerable interest for application to
nanotechnology-related fields including environmental catalysis, biomedical imaging, drug
delivery and hyperthermia, because of their superparamagnetic characteristics and high
catalytic abilities. However, information about potential risks of iron nanomaterials is
limited. The present study assessed pulmonary responses to a single intratracheal spray
instillation of triiron tetraoxide nanoparticles (magnetite) in rats. Ten-week-old male
and female Fischer 344 rats (n=5/group) were exposed to a single intratracheal spray
instillation of 0 (vehicle), 5.0, 15.0 or 45.0 mg/kg body weight (BW) of magnetite. After
14 days, the rats were sacrificed, and biological consequences were investigated. The lung
weights of the 15.0 and 45.0 mg/kg BW male and female groups were significantly higher
than those of the control groups. The lungs of treated rats showed enlargement and black
patches originating from the color of magnetite. The typical histopathological changes in
the lungs of the treated rats included infiltration of macrophages phagocytosing
magnetite, inflammatory cell infiltration, granuloma formation and an increase of goblet
cells in the bronchial epithelium. The results clearly show that instilled magnetite
causes foreign body inflammatory and granulating lesions in the lung. These pulmonary
responses occur in a dose-dependent manner in association with the increase in lung
weight. 相似文献