The beating of cilia and flagella is based on the localized sliding between adjacent outer doublet microtubules; however, the mechanism that produces oscillatory bending is unclear. To elucidate this mechanism, we examined the behavior of frayed axonemes of Chlamydomonas by using high-speed video recording. A pair of doublet microtubules frequently displayed association and dissociation cycles in the presence of ATP. In many instances, the dissociation of two microtubules was not accompanied by noticeable bending, suggesting that the dynein-microtubule interaction is not necessarily regulated by the microtubule curvature. On rare occasions, association and dissociation occurred simultaneously in the same interacting pair, resulting in a tip-directed movement of a stretch of gap between the pair. Based on these observations, we propose a model for cyclical bend propagation in the axoneme.

Natural occurrence of fumonisins B1 (FB1) and B2 (FB2), a promoter for hepato-carcinogenesis, was investigated in corn and corn - based products sampled in Japan, Nepal, and China by high - performance liquid chromatographic method. From the 9 imported corn kernel and 6 gluten feed samples, FB1 was detected in 8 corn (0.6 ∼ 4.1μg/g) and all gluten feed (0.3 ∼ 2.4μg/g) samples, while FB2 was found in the same corn (0.3 ∼ 10μg/g) and 3 gluten feed (0.8 ∼ 8.5μg/g) samples. ELISA analysis also revealed the contamination of aflatoxin B1 in 2 corn and all gluten feed samples along with fumonisins. Of 17 corn grit samples, 14 and 5 samples were contaminated with fumonisin B1 and B2, with maximum levels of 2.6 and 2.8μg/g, respectively. As for corn-based foodstuffs marketed in Japan, no significant contamination of fumonisins was observed. Among 24 corn kernel samples in Nepal, 12 and 7 samples were positive for FB1 and FB2, and averaged to 0.6 and 1.6μg/g, respectively. One sample showed the highest fumonisin contents as 4.6 and 5.5μg/g, respectively. In corn samples harvested at Shanghai and Beijing, China, FB1 and FB2 were detected in various concentrations. Mycological survey has also revealed the presence of a fumonisin - producing fungus in a crop field of Japan. These findings have for the first time demonstrated high levels of contamination of fumonisins in corn and corn - based products in Asian countries. Natural co - occurrence of fumonisins and aflatoxin B1 was also detected in raw materials for mixed feed.

Protein molecules produce diverse functions according to their combination and arrangement as is evident in a living cell. Therefore, they have a great potential for application in future devices. However, it is currently very difficult to construct systems in which a large number of different protein molecules work cooperatively. As an approach to this challenge, we arranged protein molecules in artificial microstructures and assembled an optical device inspired by a molecular system of a fish melanophore. We prepared arrays of cell-like microchambers, each of which contained a scaffold of microtubule seeds at the center. By polymerizing tubulin from the fixed microtubule seeds, we obtained radially arranged microtubules in the chambers. We subsequently prepared pigment granules associated with dynein motors and attached them to the radial microtubule arrays, which made a melanophore-like system. When ATP was added to the system, the color patterns of the chamber successfully changed, due to active transportation of pigments. Furthermore, as an application of the system, image formation on the array of the optical units was performed. This study demonstrates that a properly designed microstructure facilitates arrangement and selforganization of molecules and enables assembly of functional molecular systems.bioengineering | microdevice | molecular robotics W ithin a cell, motor proteins work as mechanical components that efficiently convert chemical energy to mechanical energy. Major motor proteins, such as myosin, kinesin, and dynein, travel unidirectionally along specific filamentous protein polymers, actin filaments, or microtubules, using the chemical energy derived from ATP. Although the action of motor proteins itself is rather simple, they are involved in numerous functions in living cells such as cell division, muscle contractions, ciliary beating, and melanophore color changes (1). These diverse and elaborate functions are realized through highly ordered molecular systems that consist of not only the motor proteins but also various types of protein molecules. For example, myosin and actin form alternatively arranged bundles with tens of other proteins to construct aligned sarcomeres, the basic units of the muscle, which produce efficient contractions under strict Ca 2+ regulation (1). Likewise, in the cilium or flagellum, dynein molecules are integrated into the "9 + 2" arrangement of microtubules and generate oscillatory bending (1). Thus, diversity of in vivo functions of motor proteins is achieved by the variety of manners in which motor proteins are organized into specific higher order systems.In the last decade, remarkable progress has been made in the applications of motor proteins in microscale and nanoscale engineering, which has enabled the control of motor protein movements and the transport of artificial objects by motor protein (2-14). These microtransportation systems are expected to be a shuttle for micrototal analysis systems and other simple tools (15)(16)(17). To fully use the potential...

Since animal intoxication related to corn-based feed is frequently observed in the State of Paraná, Brazil, natural contamination by fumonisins in 48 corn samples (39 from the State of Paraná, and 9 from the Brazilian tropical states, Mato Grosso do Sul and Goias) harvested in 1990-1991 was investigated, along with fungal flora. The total mould count ranged from 6.3 x 10(2) to 5.5 x 10(7) cfu/g, and Fusarium moniliforme and Aspergillus species belonging to section Flavi were detected in 41 and 33 samples, respectively. Regarding the samples from the State of Paraná, F. moniliforme was present in 33 samples at a count of 1.0 x 10(2) to 1.6 x 10(7) cfu/g and Aspergillus spp. in section Flavi in 27 samples at 1.0 x 10(2) to 1.0 x 10(6) cfu/g. HPLC analysis of fumonisins in the corn showed that fumonisins B1 (FB1) and B2 (FB2) were positive for 97.4% and 94.8% of samples respectively. All the corn from North Paraná was positive for fumonisins, with average FB1 levels of 4.79 micrograms/g and average FB2 levels of 3.95 micrograms/g: the Central-West region had average levels of 3.30 and 2.52 micrograms/g, and the Central-East had average of 3.25 and 2.34 micrograms/g, respectively. Except for one negative sample all the corn samples from the Central Region were positive for fumonisins, averaging FB1 levels being 5.45 micrograms/g and FB2 levels being 5.09 micrograms/g. Out of eight samples from the tropical state of Mato Grosso do Sul, F. moniliforme was detected in seven and Aspergillus spp. in section Flavi in five samples with average FB1 levels of 10.59 micrograms/g and average for FB2 levels of 10.31 micrograms/g. The samples from Goias were also contaminated with these two fungi, with the FB1 contamination being 5.83 and the FB2 contamination 3.62 micrograms/g.

Chlamydomonas axonemal extracts containing outer-arm dynein bundle microtubules when added in the absence of ATP. The bundles dissociate after addition of ATP (Haimo et al., Proc Natl Acad Sci USA 76:5759-5768, 1979). In the present study, we investigated the ATP-induced bundle dissociation process using caged ATP. Application of approximately 0.5 mM ATP induced microtubule sliding at approximately 30 microm.s(-1), which was 1.5 times faster than the microtubule sliding observed in protease-treated axonemes and five times faster than microtubule gliding on glass surfaces coated with outer-arm dynein. Bundles formed by mutant dynein molecules that lack one of the three heavy chains (HCs) displayed similar high-speed intermicrotubule sliding. These results suggest that Chlamydomonas outer-arm dynein molecules, when aligned, can translocate microtubules at high speed and that the high-speed sliding under load-free conditions does not require the complete set of the three HCs. It is likely that each of the three HCs has the ability to produce high-speed sliding, which should be an important property for their cooperation.