Nonequilibrium mechanics of active cytoskeletal networks

Cells both actively generate and sensitively react to forces through their mechanical framework, the cytoskeleton, which is a nonequilibrium composite material including polymers and motor proteins. We measured the dynamics and mechanical properties of a simple three-component model system consisting of myosin II, actin filaments, and cross-linkers. In this system, stresses arising from motor activity controlled the cytoskeletal network mechanics, increasing stiffness by a factor of nearly 100 and qualitatively changing the viscoelastic response of the network in an adenosine triphosphate-dependent manner. We present a quantitative theoretical model connecting the large-scale properties of this active gel to molecular force generation.     

Characterization of a vitamin B12 compound from unicellular coccolithophorid alga (Pleurochrysis carterae).

A unicellular coccolithophorid alga, Pleurochrysis carterae, contained 125.4 +/- 1.2 microg of vitamin B12 per 100 g dry cell weight of the lyophilized algal cells. A vitamin B12 compound was purified from the lyophilized algal cells and partially characterized. The silica gel 60 TLC and reversed-phase HPLC patterns of the purified pink-colored compound were identical to those of authentic vitamin B12, but not those of vitamin B12 analogues inactive for humans. When 22-week-old B12-deficient rats which excreted substantial amounts of methylmalonic acid (75.5 +/- 12.3 mg/day) in urine were fed the P. carterae (10 g per kg diet)-supplemented diet for 12 d, urinary methylmalonic acid excretion (as an index of vitamin B12 deficiency) of the rats became undetectable and hepatic vitamin B12 level of the rats was significantly increased.     

Sr Isotopic Signature in Plant-Derived Ca in Rain

The ⁸⁷Sr/⁸⁶Sr ratios in rain at three sites in Japan were about 0.706 to 0.712, whereas those at one site in central Korea were higher (0.711 to 0.716), reflecting the difference in geology between the two countries. Because the ⁸⁷Sr/⁸⁶Sr ratios of exchangeable sites in soil minerals are indistinguishable from those of associated plants, aerosol Sr originating from both can be grouped together as plant-derived Sr. Spatial and temporal variations in ⁸⁷Sr/⁸⁶Sr and Sr/Ca ratios in the rain suggest the presence of plant-derived Sr and Ca in addition to Sr and Ca derived from sea-salt, acid-soluble aeolian carbonate from China, and cement-derived carbonate. However, systematic data on the ⁸⁷Sr/⁸⁶Sr ratios and elemental concentrations of soils, plants, fly-ash, and road dust are required to put reliable constraints on the provenance of atmospheric Ca.     

Impact of nutrient enrichment in a waterchestnut ecosystem at Takahama-iri Bay of Lake Kasumigaura,Japan

The waterchestnut ecosystem of Lake Kasumigaura is at the climax stage of eutrophication. Organic debris in the ecosystem showed highly dynamic fluctuations throughout the year. This was chiefly attributed to high viable fractions of organic matter in the hypereutrophic water. The stability of steady-state equilibrium of organic debris was found to be maintained even in such a dynamic ecosystem, likely due to the precedence of heterotrophic processes over autotrophic processes. Using a mathematical model approximated by in situ data, the turnover time of organic solutes was analyzed to be between four and six months through these active heterotrophic processes.     

Alanine racemase activity in the microalga <Emphasis Type="Italic">thalassiosira</Emphasis> sp.

ABSTRACT:   In this paper, the authors report the detection of alanine racemase activity in the marine diatom Thalassiosira sp. Since the Thalassiosira sp. was cultured under germ-free conditions, it appeared that D-alanine was not derived from bacteria but was produced through catalysis by algal alanine racemase. The rate of conversion of L-alanine to D-alanine was approximately the same as that for the reverse reaction, and the enzyme catalyzed the equilibration of the D- and L-forms. The crude enzyme preparation obtained from the cells at the stationary phase of the growth cycle had an optimal pH of approximately 9.5. The Lineweaver–Burk analysis showed that the K _m for D- and L-alanine was 16.5 mM and 29.4 mM, respectively. It appears that the enzyme is highly specific for D- or L-alanine because it does not catalyze the racemization of other amino acids. In addition, after gel filtration, the enzyme did not require exogenous pyridoxal 5'-phosphate (PLP) for its activity, however, the effects of several chemicals suggest that the enzyme may be PLP-dependent. The enzyme is more similar to that found in invertebrates when compared with that found in bacteria. This is the first report on the occurrence of alanine racemase activity in the microalga Thalassiosira sp.     

Toxicity of wild juvenile “komonfugu” Takifugu flavipterus in the Bay of Sanriku Coast,Tohoku Area,Northern Japan

To clarify the mechanism of tetrodotoxin (TTX) accumulation in pufferfish, we compared the toxicity of two sets of wild juvenile “komonfugu” Takifugu flavipterus. The first set was sampled from Onisawa Fishing Port (FP) located in Okirai Bay, the Pacific Coast of Sanriku, Tohoku Area, Northern Japan. The second set was collected from the Onisawa FP and reared in an outdoor laboratory tank supplied with different seawater (Yoshihama Bay). The fish were sampled regularly and on the same days. The amount of TTX (mouse unit (MU)/fish) in the fish at Onisawa FP increased until 20 days and thereafter it did not change, while the amount of TTX in the fish in the laboratory tank remained low, and the TTX concentration (MU/g fish) decreased. Next, we compared the toxicity of wild juvenile T. flavipterus collected from Okirai Bay (Onisawa FP and Okirai FP) and Yoshihama Bay (Yoshihama FP). Large differences in TTX levels were observed among the fish from the three FPs. The amounts and concentrations of TTX in the fish at Onisawa FP were higher than those in the fish from the other two FPs. These results indicate that a large variation in toxic activity exists in the juvenile T. flavipterus in the bay of the Sanriku Coast.

     

An H5N1 highly pathogenic avian influenza virus that invaded Japan through waterfowl migration

In 2010, an H5N1 highly pathogenic avian influenza virus (HPAIV) was isolated from feces of apparently healthy ducks migrating southward in Hokkaido, the northernmost prefecture of Japan. The H5N1 HPAIVs were subsequently detected in domestic and wild birds at multiple sites corresponding to the flyway of the waterfowl having stopovers in the Japanese archipelago. The Hokkaido isolate was genetically nearly identical to H5N1 HPAIVs isolated from swans in the spring of 2009 and 2010 in Mongolia, but less pathogenic in experimentally infected ducks than the 2009 Mongolian isolate. These findings suggest that H5N1 HPAIVs with relatively mild pathogenicity might be selected and harbored in the waterfowl population during the 2009-2010 migration seasons. Our data provide "early warning" signals for preparedness against the unprecedented situation in which the waterfowl reservoirs serve as perpetual sources and disseminators of HPAIVs.     

农产品品质无损检测技术应用研究

研究目标是开发一种用可见光和近红外光谱(Vis/NIR)检测农产品的非破坏性测定方法。用波长范围为310～1 100nm的可见/近红外分光仪得到枣的光谱测量数据,用于测定交互作用下的枣的内部可溶性固体含量和基于反射系数的枣的表面缺陷;用多元线性回归校准模型来预测可溶性固体含量,校正判别分析判断大枣有或没有表面缺陷。