Shear Stress Transmission Model for the Flagellar Rotary Motor

Most bacteria that swim are propelled by flagellar filaments, which are driven by a rotary motor powered by proton flux. The mechanism of the flagellar motor is discussed by reforming the model proposed by the present authors in 2005. It is shown that the mean strength of Coulomb field produced by a proton passing the channel is very strong in the Mot assembly so that the Mot assembly can be a shear force generator and induce the flagellar rotation. The model gives clear calculation results in agreement with experimental observations, e g., for the charasteristic torque-velocity relationship of the flagellar rotation

Robust state stansfer and rotation through a spin chain via dark passage

Quantum state transfer through a spin chain via adiabatic dark passage is proposed. This technique is robust against control field fluctuations and unwanted environmental coupling of intermediate spins. Our method can be applied to spin chains with more than three spins. We also propose single qubit rotation using this technique

Surface Acoustic Wave Single-Electron Interferometry

We propose an experiment to observe interference of a single electron as it is transported along two parallel quasi-one-dimensional channels trapped in a single minimum of a travelling periodic electric field. The experimental device is a modification of the surface acoustic wave (SAW) based quantum processor. Interference is achieved by creating a superposition of spatial wavefunctions between the two channels and inducing a relative phase shift via either a transverse electric field or a magnetic field. The interference can be used to estimate the decoherence time of an electron in this type of solid-state device

Crystal structure of a novel type of ornithine δ-aminotransferase from the hyperthermophilic archaeon Pyrococcus horikoshii

Ornithine δ-aminotransferase (Orn-AT) activity was detected for the enzyme annotated as a γ-aminobutyrate aminotransferase encoded by PH1423 gene from Pyrococcus horikoshii OT-3. Crystal structures of this novel archaeal ω-aminotransferase were determined for the enzyme in complex with pyridoxal 5′-phosphate (PLP), in complex with PLP and l-ornithine (l-Orn), and in complex with N-(5′-phosphopyridoxyl)-l-glutamate (PLP-l-Glu). Although the sequence identity was relatively low (28%), the main-chain coordinates of P. horikoshii Orn-AT monomer showed notable similarity to those of human Orn-AT. However, the residues recognizing the α-amino group of l-Orn differ between the two enzymes. In human Orn-AT, Tyr55 and Tyr85 recognize the α-amino group, whereas the side chains of Thr92* and Asp93*, which arise from a loop in the neighboring subunit, form hydrogen bonds with the α-amino group of the substrate in P. horikoshii enzyme. Site-directed mutagenesis suggested that Asp93* plays critical roles in maintaining high affinity for the substrate. This study provides new insight into the substrate binding of a novel type of Orn-AT. Moreover, the structure of the enzyme with the reaction-intermediate analogue PLP-l-Glu bound provides the first structural evidence for the “Glu switch” mechanism in the dual substrate specificity of Orn-AT

A Phase II Study of S-1 Monotherapy as a First-line Combination Therapy of S-1 Plus Cisplatin as a Second-line Therapy, and Weekly Paclitaxel Monotherapy as a Third-line Therapy in Patients with Advanced Gastric Carcinoma: A Second Report

Background We have previousy reported on a Phase II study of S-1 monotherapy as a first line, combination therapy of S-1 plus cisplatin as a second line, and weekly paclitaxel monotherapy as a third line therapy in patients with advanced gastric carcinomas. The median survival time (MST) of patients over the whole course of treatment was not previously calculated because 12 out of 19 patients had not yet succumbed. Since then, we have calculated the MST for this study and herein report our findings. Patients and Methods Between 2002 and 2005, 19 patients were enrolled in this study. Chemotherapy consisted of either 60 mg/m 2 of S-1 for 4 weeks at 6-week intervals, a combination of 60 mg/m 2 S-1 for 3 weeks and 60 mg/m 2 cisplatin on day 8 at 5-week intervals, or 60 mg/m 2 paclitaxel at days 1, 8, and 15, at 4-week intervals. The regimens were repeated until the occurrence of unacceptable toxicities, disease progression, or patient noncompliance. The primary end point was the overall survival. Results The median survival time was 774 days. The response rates were 33.3% (3/9), 12.5% (1/8), and 0% (0/4) after the first, second, and third line chemotherapies, respectively. The major adverse hematological toxicity was leukopenia, which reached grades 3–4 in all lines of chemotherapy investigated. In addition, the major adverse non-hematological toxicity was anorexia, which reached grade 3–4 in second line chemotherapy, and no deaths were attributable to the adverse effects of the drugs. Conclusion This sequential therapy was an effective treatment for advanced gastric cancer with acceptable toxic side-effects. We considered this therapy to be effective because of the smooth transition to the next regimen

Modality-Specific Impairment of Hippocampal CA1 Neurons of Alzheimer’s Disease Model Mice

Impairment of episodic memory, a class of memory for spatiotemporal context of an event, is an early symptom of Alzheimer's disease. Both spatial and temporal information are encoded and represented in the hippocampal neurons, but how these representations are impaired under amyloid β (Aβ) pathology remains elusive. We performed chronic imaging of the hippocampus in awake male amyloid precursor protein (App) knock-in mice behaving in a virtual reality environment to simultaneously monitor spatiotemporal representations and the progression of Aβ depositions. We found that temporal representation is preserved, while spatial representation is significantly impaired in the App knock-in mice. This is due to the overall reduction of active place cells but not time cells, and compensatory hyperactivation of remaining place cells near Aβ aggregates. These results indicate the differential impact of Aβ aggregates on two major modalities of episodic memory, suggesting different mechanisms for forming and maintaining these two representations in hippocampus.SIGNIFICANCE STATEMENT:Spatiotemporal memory impairments are common at the early stage of Alzheimer's disease patients. We demonstrate the different impairment patterns of place and time cells in the dorsal hippocampus of head-fixed App knock-in mouse by in vivo two-photon calcium imaging over months under the virtual reality spatiotemporal tasks. These results highlight that place cells were preferentially and gradually damaged nearby Aβ aggregates, while time cells were less vulnerable. We further show these impairments were due to neuronal hyperactivity that occurs near the Aβ deposition. We suggest the differential and gradual impairment in two major modalities of episodic memory under Aβ pathology

Remarks on Muscle Contraction Mechanism II. Isometric Tension Transient and Isotonic Velocity Transient

Mitsui and Ohshima (2008) criticized the power-stroke model for muscle contraction and proposed a new model. In the new model, about 41% of the myosin heads are bound to actin filaments, and each bound head forms a complex MA3 with three actin molecules A1, A2 and A3 forming the crossbridge. The complex translates along the actin filament cooperating with each other. The new model well explained the experimental data on the steady filament sliding. As an extension of the study, the isometric tension transient and isotonic velocity transient are investigated. Statistical ensemble of crossbridges is introduced, and variation of the binding probability of myosin head to A1 is considered. When the binding probability to A1 is zero, the Hill-type force-velocity relation is resulted in. When the binding probability to A1 becomes finite, the deviation from the Hill-type force-velocity relation takes place, as observed by Edman (1988). The characteristics of the isometric tension transient observed by Ford, Huxley and Simmons (1977) and of the isotonic velocity transient observed by Civan and Podolsky (1966) are theoretically reproduced. Ratios of the extensibility are estimated as 0.22 for the crossbridge, 0.26 for the myosin filament and 0.52 for the actin filament, in consistency with the values determined by X-ray diffraction by Wakabayashi et al. (1994)