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1.
Oikawa S Watabe T Inatomi N Isoyama N Misonoo J Suzuki C Nakahara M Nakamura R Morizono S Fujii S Hara T Kido K 《Journal of environmental radioactivity》2011,102(3):302-310
A radioactivity survey was launched in 1991 to determine the background levels of 239+240Pu in the marine environment off a commercial spent nuclear fuel reprocessing plant before full operation of the facility. Particular attention was focused on the 240Pu/239Pu atom ratio in seawater and bottom sediment to identify the origins of Pu isotopes. The concentration of 239+240Pu was almost uniform in surface water, decreasing slowly over time. Conversely, the 239+240Pu concentration varied markedly in the bottom water and was dependent upon the sampling point, with higher concentrations of 239+240Pu observed in the bottom water sample at sampling points having greater depth. The 240Pu/239Pu atom ratio in the seawater and sediment samples was higher than that of global fallout Pu, and comparable with the data in the other sea area around Japan which has likely been affected by close-in fallout Pu originating from the Pacific Proving Grounds. The 240Pu/239Pu atom ratio in bottom sediment samples decreased with sea depth. The land-originated Pu is not considered as the reason of the increasing 239+240Pu concentration and also decreasing the 240Pu/239Pu atom ratio with sea depth, and further study is required to clarify it. 相似文献
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Ruchi Jain Seshagiri Raghukumar Kari Sambaiah Yasuyuki Kumon Toro Nakahara 《Marine Biology》2007,151(5):1657-1664
Thraustochytrid protists characteristically accumulate high amounts of lipids, much of which is comprised of the polyunsaturated
fatty acid, docosahexaenoic acid (DHA). Since DHA is important in human health, thraustochytrids have attracted much attention
from the point of view of biotechnology. However, the biological rationale of DHA production in the storage lipids of these
organisms is not clear. We carried out three experiments to study this. (1) The fate of lipids in thraustochytrids during
development was studied by staining lipids of vegetative cells with the fluorescent vital stain for lipids, namely Nile blue,
following the growth of the cells. The fluorescent lipid bodies decreased in abundance in freshly formed motile limaciform
amoeboid cells and subsequently disappeared when they moved away. When vegetative cells produced vast extensions of plasma
membrane, the ectoplasmic net elements (EN), the fluorescent lipids appeared to be transported to them. (2) Changes in lipids
and DHA during starvation were examined in cells with enhanced lipid and DHA contents and those in which they were not enhanced.
Cells in which lipids and DHA were enhanced by refrigerating them for 48 h survived starvation for a longer period. Compared
to cells that had not been refrigerated, total fatty acids, as well as DHA were marginally higher in pre-refrigerated cells,
while palmitic acid levels were lower. Starvation of cells resulted in a gradual decrease of absolute concentrations and percentage
levels of DHA after 8 days, while percentage of palmitic acid levels increased. (3) The relationship between DHA and specific
gravity of cells was studied by comparing cells pre-refrigerated as above with those which were not pre-refrigerated. Refrigerated
cells with increased lipids and DHA showed higher specific gravities than non-refrigerated cells. We suggest the following
roles for storage lipids and DHA in thraustochytrids: (1) lipids serve as energy sources during movement of cells and for
production of EN; (2) DHA in storage lipids become distributed in the plasma membrane when EN are formed; (3) DHA is preferably
utilized as a fatty acid energy reserve during starvation and (4) an unknown mechanism results in negative buoyancy of cells
when total lipids and DHA are marginally enhanced. DHA in storage lipids might be crucial to the survival of thraustochytrid
cells. 相似文献
4.
Content ratios of strontium (Sr) to calcium (Ca) in the otolith of Conger myriaster metamorphosing leptocephali and elvers increased with increasing increment number from the core to the 110th increment and
subsequently decreased. The otolith region from the 110th increment to the edge corresponded to the metamorphic stage. The
Sr:Ca ratios in otolith edges of metamorphosing leptocephali were inversely related to metamorphic stage, suggesting that
the changes in otolith Sr:Ca ratios were influenced by some physiological factor(s) rather than by environmental factors.
Sr concentration in leptocephalus somatic tissues was high and decreased as metamorphosis progressed until the late metamorphic
stage when the preanal myomere to total myomere ratio was 0.4. Ca concentration was constant throughout ontogenesis. Body
Sr:Ca ratios markedly decreased as metamorphosis progressed. Decrease in somatic Sr concentration and the consequent decrease
in body Sr:Ca ratios seemed to be associated with the breakdown of glycosaminoglycan (GAG) in gelatinous matrix, which is
the major constituent of soft tissue in leptocephali. Catabolism of GAG may also cause a decrease in otolith Sr:Ca ratios
during metamorphosis. In leptocephalus otoliths, Sr:Ca ratios may change in association with the synthesis and breakdown of
GAGs during ontogeny.
Received: 29 November 1996 / Accepted: 6 January 1997 相似文献
5.
The octanol/water partition coefficients (P ow) of six monoisocyanate and five diisocyanate compounds were determined by high performance liquid chromatograph (HPLC) methods. Two HPLC peaks, a broad tailed peak followed by a sharp one, were observed with all compounds. The later peak was identified as the isocyanate compound. The P ow value for each isocyanate compound was determined by fitting the capacity factor of the peak to the regression equation drawn from those of reference compounds. The hydrophobic substituent constants for the isocyanate group were calculated with each of the compounds. The value of this constant was strongly dependent on the type of carbon bound to the isocyanate group and the average values for the aromatic and aliphatic isocyanate groups were 0.35 and — 0.52, respectively. Because of the reactivity of those compounds in the aquatic environment, the P ow has little relevance to calculation of their environmental fate and ecotoxicity. 相似文献
6.
Rumana Tasmin Yohei Shimasaki Michito Tsuyama Xuchun Qiu Fatma Khalil Nozomu Okino Naotaka Yamada Shinji Fukuda Ik-Joon Kang Yuji Oshima 《Environmental science and pollution research international》2014,21(2):1064-1070
In the actual environment, temperatures fluctuate drastically through season or global warming and are thought to affects risk of pollutants for aquatic biota; however, there is no report about the effect of water temperature on toxicity of widely used herbicide diuron to fresh water microalgae. The present research investigated inhibitory effect of diuron on growth and photosynthetic activity of a green alga Pseudokirchneriella subcapitata at five different temperatures (10, 15, 20, 25, and 30 °C) for 144 h of exposure. As a result, effective diuron concentrations at which a 50 % decrease in algal growth occurred was increased with increasing water temperature ranging from 9.2 to 20.1 μg L–1 for 72 h and 9.4–28.5 μg L–1 for 144 h. The photochemical efficiency of photosystem II (F v/F m ratio) was significantly reduced at all temperatures by diuron exposure at 32 μg L–1 after 72 h. Inhibition rates was significantly increased with decreased water temperature (P?<?0.01). Intracellular H2O2 levels as an indicator of oxidative stress were also decreased with increasing temperature in both control and diuron treatment groups and were about 2.5 times higher in diuron treatment groups than that of controls (P?<?0.01). Our results suggest water temperatures may affect the toxicokinetics of diuron in freshwater and should therefore be considered in environmental risk assessment. 相似文献
7.
The work describes the uptake, retention/biological elimination and organ/tissue distribution of 137Cs by freshwater Japanese catfish (Silurus asotus Linnaeus) under laboratory conditions. The fish were divided into three groups based on their size and age and reared in 137Cs-spiked water. The concentration of 137Cs in the whole body of the live fish was measured at regular intervals up to 60 days. A significant accumulation of 137Cs was found, but a steady state condition was not achieved by the end of the experiment. The bioaccumulation factors at steady state and the required time to reach steady state were estimated to be 1.55 and 255 days, 1.76 and 180 days and 1.99 and 160 days for large, medium and small size fish, respectively. To determine the effective half-life of 137Cs, the fish were transferred and reared in the non-contaminated host water. The concentration of the remaining 137Cs in the whole body of the live fish was measured up to 66 days. The average effective half-life of 137Cs in the fish species was found to be approximately 142 days for fish of all sizes. The distribution of 137Cs in different organs/tissues of the fish was determined. Accumulation of 137Cs in muscle/flesh of the fish was found to be approximately 75% of whole body accumulation. The uptake rate and the retention capability of juvenile fish were found to be higher and therefore, these were more susceptible to 137Cs than adult and old fish, and could be an important source of 137Cs in the human food chain. 相似文献
8.
In cultures of Alaria crassifolia Kjellman, unfertilized eggs developed normally into haploid sporophytes which differentiated into a holdfast, stipe and blade with a midrib. The terminal cells of a male gametophyte grew apogamously into haploid sporophytes with narrow blades which lack the midrib. Further, diploid gametophytes were formed by apospory from vegetative cells of a diploid sporophyte. They were monoecious and their fertilized eggs developed into tetraploid sporophytes. Nuclear phases of the sporophytes and gametophytes concerned were confirmed by cytological observations.This work was supported by Grant No. 38803 from the Ministry of Education of Japan. 相似文献
9.
T. Yamada T. Inoue H. Fukuhara O. Nakahara T. Izuta R. Suda M. Takahashi H. Sase A. Takahashi H. Kobayashi T. Ohizumi T. Hakamata 《Water, Air, & Soil Pollution: Focus》2007,7(1-3):259-266
Since 1983, the Ministry of the Environment of Japan has conducted nation-wide acid deposition surveys. To investigate the
effects of acid deposition on surface water, we used the nonparametric Mann–Kendall test to find temporal trends in pH, alkalinity,
and electrical conductivity (EC) in more than 10 years of data collected from five lakes and their catchments (Lake Kuttara:
northernmost; Lake Kamakita: near Tokyo; Lake Ijira: central; Lake Banryu: western; and Lake Unagiike: southernmost). The
pH of Lake Ijira water has declined slightly since the mid-1990s, corresponding with the downward trends seen in the pH and
alkalinity of the river water flowing into the lake. There were significant upward trends in the EC of both the lake and stream
water; the same trends were also found for concentrations. These trends show evidence of acidification due to atmospheric deposition, and this is the first such finding
in Japan based on significant long-term trends. Lake Ijira is located about 40 km north of the Chukyo industrial area near
Nagoya. The annual depositions of H+, nss-, and in Lake Ijira were among the highest of all deposition monitoring sites, suggesting that this is the main cause of the significant
acidification observed in Lake Ijira. No significant trends suggesting acidification were observed in any of the other lake
catchments in spite of the significant upward trends in EC. Upward trends in pH and alkalinity at Lake Banryu and upward trends
in alkalinity at Lake Kamakita were detected, but no change in pH or alkalinity at Lake Kuttara and Lake Unagiike was observed. 相似文献
10.
Masahiro Miura Atsushi Shimahata Toshio Nishikawa Masakazu Aoyama Kiyoshi Tada Junichi Horiuchi Masahiro Nakahara Chikara Sakai 《Journal of Material Cycles and Waste Management》2011,13(1):80-83
To prepare a substrate for microbial conversion of xylose into xylitol, the culm of Sasa senanensis was hydrolyzed with dilute sulfuric acid. When the reaction temperature was fixed at 121°C, an optimum yield of xylose was
obtained by treatment with 2% sulfuric acid for 1 h. An increase in the sulfuric acid concentration or a prolonged reaction
time resulted in a decrease in the xylose yield. A fermentable substrate with a relatively high xylose concentration (36.7
g l−1) was obtained by hydrolysis with 2% sulfuric acid with a liquid-to-solid ratio of 5 g g−1. During hydrolysis at elevated temperatures, certain undesired byproducts were also generated, such as degradation products
of solubilized sugars and lignin, which are potential inhibitors of microbial metabolism. These compounds were, however, successfully
removed from the hydrolysate by treatment with activated char. 相似文献