Tight junctions, the most apical component of intercellular junctions, play pivotal roles in epithelial barrier by sealing the intercellular space. Very recently claudins were identified as the major molecular components of tight junction. Claudins not only work as adhesion molecules but also form tight junction strands probably by their polymerizing activity in the plasma membranes. Identification of claudins has enabled us to examine the molecular mechanism of epithelial barrier and permeability.
A fish school is considered as an autonomous decentralized system. Each individual behaves autonomously, and a specific order of school is established based on the environmental effect and the cooperation among other individuals. For describing such a phenomenon, a mathematical model is presented, and the model parameters are estimated by using water tank experiment data. Simulations are carried out by setting a box-shaped trap in a behavior space as an obstacle. Generation of the cooperative behavior and the adaptability to environmental variations are discussed for two kinds of fish school models with different characteristics.
Behavioral acts are hierarchically organized so that a higher-order act either suppresses or facilitates lower-order ones to be released by specific sensory stimuli. By applying intracellular techniques to an unanesthetized whole-animal preparation, we analyzed neurophysiological mechanisms underlying the facilitatory control of uropod steering reflex during walking in crayfish. The descending sensory-motor pathway was found to be controlled by a multiple gate mechanism in which the sensory signals are amplified by a cascade of interneurons and transmitted to the uropod motor system only when the animal is engaged in walking. The gating signal is, at least partly, mediated by premotor nonspiking interneurons.
We have designed comb-type copolymer with polycation backbone (polylysine) grafted with hydrophilic side chains as a stabilizer for triple helical DNA. The copolymer considerably increased the thermal stability of triplex structure but did not affect the reversible transition between triplex and single-stranded DNA. An in vitro electrophoretic mobility shift assay revealed that the copolymer remarkably diminishes potassium inhibition of the purine motif triplex formation up to 200mM as well as the pH-dependence of the pyrimidine motif. Moreover the triplex-stabilizing efficiency of the copolymer was significantly higher than that of other oligocations like spermine and spermidine. Not only being good DNA triplex stabilizer, it has also been shown to accelerate DNA strand exchange reactions. From these, we conclude that this copolymer is capable of either “stabilizing” or “activating” DNA hybrids.
The active site of the [NiFe] hydrogenase from Desulfovibrio vulgaris Miyazaki F in the oxidized form has been reported as a hetero binuclear Ni-Fe complex with four non-protein ligands (SO, CO, CN, S). In contrast, the non-protein ligands in the hydrogenase from Desulfovibrio gigas were reported as CO, CN, CN and O. The S bridging ligand atom was confirmed by two experiments that the hydrogenase liberates H2S upon reduction with H2 and that the crystal structure of the H2-reduced form lost the bridging ligand between the Ni and Fe atoms. The possible mechanism of the hydrogen activation is discussed.