細胞種選択的広域カルシウムイメージング法による多感覚刺激応答の研究

早大学位記番号:新7900早稲田大

Task-Related Synaptic Changes Localized to Small Neuronal Population in Recurrent Neural Network Cortical Models

Humans have flexible control over cognitive functions depending on the context. Several studies suggest that the prefrontal cortex (PFC) controls this cognitive flexibility, but the detailed underlying mechanisms remain unclear. Recent developments in machine learning techniques allow simple PFC models written as a recurrent neural network to perform various behavioral tasks like humans and animals. Computational modeling allows the estimation of neuronal parameters that are crucial for performing the tasks, which cannot be observed by biologic experiments. To identify salient neural-network features for flexible cognition tasks, we compared four PFC models using a context-dependent integration task. After training the neural networks with the task, we observed highly plastic synapses localized to a small neuronal population in all models. In three of the models, the neuronal units containing these highly plastic synapses contributed most to the performance. No common tendencies were observed in the distribution of synaptic strengths among the four models. These results suggest that task-dependent plastic synaptic changes are more important for accomplishing flexible cognitive tasks than the structures of the constructed synaptic networks

Histological study of the elongated esophagus in a rat model

Background Esophageal elongation by traction suture is used in pediatric patients to manage long-gap esophageal atresia (EA). There was no histological evidence of the esophageal elongation. Here, we sought to clarify the histologic effects of traction on the esophagus by using a rat EA model simulating Foker\u27s method. Materials and methods Rats were randomly assigned into three groups (n = 5 each). The traction group underwent daily stretching of the distal segment of the esophagus. The nontraction group underwent a sham operation, and the normal group served as controls. Seven days after the operation, the distal segments of the esophagus were removed. The length and thickness were measured, and samples were stained with Ki-67, nNOS, and S-100. Results The whole length of the esophagus in the traction group was significantly longer than that in the nontraction group (P < 0.01). The thickness of esophageal mucosa and muscle tended to become thin by traction, but not significantly. The Ki-67-positive ratio of mucosa and muscle was significantly higher in the traction group (P < 0.05). There were no significant differences in Ki-67 between two segments (cardia-middle and middle-stump) in any group. Auerbach\u27s plexus was identified at all sites of elongated esophagus by nNOS and S-100 staining. Conclusions By traction, the esophagus was elongated uniformly and cell proliferation activity was promoted in all parts of the elongated esophagus in the rat EA model

Ferromagnetism in a Hubbard model for an atomic quantum wire: a realization of flat-band magnetism from even-membered rings

We have examined a Hubbard model on a chain of squares, which was proposed by Yajima et al as a model of an atomic quantum wire As/Si(100), to show that the flat-band ferromagnetism according to a kind of Mielke-Tasaki mechanism should be realized for an appropriate band filling in such a non-frustrated lattice. Reflecting the fact that the flat band is not a bottom one, the ferromagnetism vanishes, rather than intensified, as the Hubbard U is increased. The exact diagonalization method is used to show that the critical value of U is in a realistic range. We also discussed the robustness of the magnetism against the degradation of the flatness of the band.Comment: misleading terms and expressions are corrected, 4 pages, RevTex, 5 figures in Postscript, to be published in Phys. Rev. B (rapid communication

Novel BiS2-based layered superconductor Bi4O4S3

Exotic superconductivity has often been discovered in materials with a layered (two-dimensional) crystal structure. The low dimensionality can affect the electronic structure and can realize high transition temperatures (Tc) and/or unconventional superconductivity mechanisms. As standard examples, we now have two types of high-Tc superconductors. The first group is the Cu-oxide superconductors whose crystal structure is basically composed of a stacking of spacer (blocking) layers and superconducting CuO2 layers.1-4 The second group is the Fe-based superconductors which also possess a stacking structure of spacer layers and superconducting Fe2An2 (An = P, As, Se, Te) layers.5-13 In both systems, dramatic enhancements of Tc are achieved by optimizing the spacer layer structure, for instance, a variety of composing elements, spacer thickness, and carrier doping levels with respect to the superconducting layers. In this respect, to realize higher-Tc superconductivity, other than Cu-oxide and Fe-based superconductors, the discovery of a new prototype of layered superconductors needs to be achieved. Here we show superconductivity in a new bismuth-oxysulfide layered compound Bi4O4S3. Crystal structure analysis indicates that this superconductor has a layered structure composed of stacking of Bi4O4(SO4)1-x and Bi2S4 layers; the parent compound (x = 0) is Bi6O8S5. Band calculation suggests that Bi4O4S3 (x = 0.5) is metallic while Bi6O8S5 (x = 0) is a band insulator with Bi3+. Furthermore, the Fermi level for Bi4O4S3 is just on the peak position of the partial density of states of the Bi 6p orbital within the BiS2 layer. The BiS2 layer is a basic structure which provides another universality class for layered superconducting family, and this opens up a new field in the physics and chemistry of low-dimensional superconductors.Comment: 13 pages, 3 figures, 1 tabl

Josephson current in s-wave superconductor / Sr_2RuO_4 junctions

The Josephson current between an s-wave and a spin-triplet superconductor Sr$_2$RuO$_4$ (SRO) is studied theoretically. In spin-singlet / spin-triplet superconductor junctions, there is no Josephson current proportional to $\sin \phi$ in the absence of the spin-flip scattering near junction interfaces, where $\phi$ is a phase-difference across junctions. Thus a dominant term of the Josephson current is proportional to $\sin 2\phi$ . The spin-orbit scattering at the interfaces gives rise to the Josephson current proportional to $\cos\phi$, which is a direct consequence of the chiral paring symmetry in SRO

Deformation of half-BPS solution in ABJM model and instability of supermembrane

It is well-known that a supermembrane in the light-cone gauge has a continuous spectrum and is unstable. Physical interpretation of this instability is that a supermembrane can have a long thin tube without cost of energy and consequently it becomes a spiky configuration in which multiple membranes are connected by thin tubes. On the other hand, the ABJM model was proposed as a low-energy description of multiple M2-branes in the static gauge. It is natural that an M2-brane is also unstable in this gauge if we believe the physical picture in the light-cone gauge. In order to examine this, we construct a BPS solution explicitly both in the Nambu-Goto action of a supermembrane in the static gauge and in the U(1){\times}U(1) ABJM model, which represents intersecting M2-branes. Since this configuration is regarded as a single M2-brane emitting another one, we study the instability of an M2-brane by analyzing fluctuations around it. We show that a zero mode exists which can deform the configuration. For comparison, we also examine a similar configuration on the D2-brane and check that it does not have such zero modes under a fixed string charge. Furthermore we confirm that the novel Higgs mechanism translates our BPS solution in the ABJM model into that in the D2-brane world volume theory, where the winding number of the former around the fixed point of the orbifold becomes the number of strings ending on the D2-brane in the latter.Comment: 27 page

Phase II study of trifluridine/tipiracil (TAS‑102) therapy in elderly patients with colorectal cancer (T‑CORE1401): geriatric assessment tools and plasma drug concentrations as possible predictive biomarkers

Purpose The current study aimed to determine the efficacy of trifluridine/tipiracil for elderly patients with advanced colorectal cancer. Methods This single-arm, open-label, multicenter, phase II study included elderly patients aged 65 years or more who had fluoropyrimidine-refractory advanced colorectal cancer and received trifluridine/tipiracil (70 mg/m2, days 1–5 and 8–12, every 4 weeks). The primary endpoint was progression-free survival (PFS), while secondary endpoints included overall survival (OS), overall response rate (ORR), toxicities, association between efficacy and geriatric assessment scores, and association between toxicity and plasma drug concentrations. Results A total of 30 patients with a mean age of 73 years were enrolled. Median PFS was 2.3 months (95% confidence interval, 1.9–4.3 months), while median OS was 5.7 months (95% confidence interval, 3.7–8.9 months). Patients had an ORR of 0%, with 57% having stable disease. Grade 4 neutropenia was observed in 13% of the patients. Patients with a higher G8 score (15 or more) showed longer PFS than those with a lower G8 score (median 4.6 vs. 2.0 months; p = 0.047). Moreover, patients with grade 3 or 4 neutropenia showed higher maximum trifluridine concentrations than those with grade 1 or 2 neutropenia (mean 2945 vs. 2107 ng/mL; p = 0.036). Discussion The current phase II trial demonstrated that trifluridine/tipiracil was an effective and well-tolerated option for elderly patients with advanced colorectal cancer. Moreover, geriatric assessment tools and/or plasma drug concentration monitoring might be helpful in predicting the efficacy and toxicities in elderly patients receiving this drug. Trial registration number UMIN000017589, 15/May/2015 (The University Hospital Medical Information Network