Overlapped Partitioning for Ensemble Classifiers of P300-Based Brain-Computer Interfaces

A P300-based brain-computer interface (BCI) enables a wide range of people to control devices that improve their quality of life. Ensemble classifiers with naive partitioning were recently applied to the P300-based BCI and these classification performances were assessed. However, they were usually trained on a large amount of training data (e.g., 15300). In this study, we evaluated ensemble linear discriminant analysis (LDA) classifiers with a newly proposed overlapped partitioning method using 900 training data. In addition, the classification performances of the ensemble classifier with naive partitioning and a single LDA classifier were compared. One of three conditions for dimension reduction was applied: the stepwise method, principal component analysis (PCA), or none. The results show that an ensemble stepwise LDA (SWLDA) classifier with overlapped partitioning achieved a better performance than the commonly used single SWLDA classifier and an ensemble SWLDA classifier with naive partitioning. This result implies that the performance of the SWLDA is improved by overlapped partitioning and the ensemble classifier with overlapped partitioning requires less training data than that with naive partitioning. This study contributes towards reducing the required amount of training data and achieving better classification performance.     

Isolation and characterization of a protein from hagfish serum that is homologous to the third component of the mammalian complement system.

The 192-kDa protein HX, a major component of serum that specifically binds to zymosan particles, was prepared from the plasma of the hagfish (Eptatretus burgeri) by ion-exchange chromatography and gel filtration. HX, present at a concentration of 0.8 mg/ml in the original plasma, was composed of two distinct subunits of 115 kDa and 77 kDa, respectively, which were linked by disulfide bonds. The protein had the same electrophoretic mobility as beta-globulin. Digestion by trypsin resulted in a specific cleavage of the 115-kDa subunit and a change in its immunoelectrophoretic mobility in the anodal direction, leaving the 77-kDa subunit intact. Treatment with SDS and urea resulted in the splitting of the 115-kDa subunits into 68-kDa and 45-kDa components, but this splitting was inhibited by pretreatment with methylamine, suggesting the presence of a thiol ester bond in the 115-kDa subunit. The amino acid composition of HX revealed a striking resemblance to that of human C3. We conclude, therefore, that the 192-kDa protein isolated in this study is analogous to C3, which plays a key role in the mammalian C system.     

Endogenous d-Serine in Rat Brain: N-Methyl-d-Aspartate Receptor-Related Distribution and Aging

Abstract: Recently, a substantial amount of free d -serine has been demonstrated in rat brain, although it has long been presumed that d -amino acids are uncommon in mammals. The anatomical distribution and age-related changes in endogenous d -serine have been examined here to obtain insight into its physiological functions. Free d -serine exclusively occurs in brains, with a persistent high content from birth to at least 86 postnatal weeks. The patterns of the regional variations and the postnatal changes in brain d -serine are closely correlated with those of the N -methyl- d -aspartate (NMDA)-type excitatory amino acid receptor. Because d -serine potentiates NMDA receptor-mediated transmission by selective stimulation of the strychnine-insensitive glycine site of the NMDA receptor, it is proposed that d -serine is a novel candidate as an intrinsic ligand for the glycine site in mammalian brain.     

Conformational analysis of chitobiose and chitosan

The relaxed potential energy surfaces of chitobiose were calculated based on the MM3-force field by optimizing dimer structures on a 10° grid spacing of the torsional angles about the glycosidic bonds (Φ,Ψ). The 36 conformations; the four combinations of the hydroxymethyl group orientations coupled with the nine of the secondary group ones— were assumed for each Φ,Ψ conformation. The four conformations, each differing in the hydroxymethyl group orientations, were considered for the whole Φ,Ψ space, and all the 36 conformations, for the restricted space of low energy. While the resulting energy map and the structures of the energy minima were similar to those proposed for cellobiose in many respects, more restricted energy profile was suggested for the relaxed map of chitobiose where differences in the energy level between the global minimum and the local minima were within 5.4 kcal/mol, compared with the equivalent value of 3.6 kcal/mol for cellobiose. Further depression of the global minimum occurred when the acidic residue was used. The Monte Carlo samples of the chitosan chain were generated based on the relaxed map to predict the unperturbed coil dimension in solution. The chitosan chains showed Gaussian behavior at x = 500 (x, degree of polymerization) and gave the characteristic ratio C_x, of about 70, which was much larger than the experimental values observed for the chitosan and cellulosic chains. © 1994 John Wiley & Sons, Inc.     

Role of isozyme group-specific sequence 4 in the isozyme-specific properties of human aldolase C

To assess which regions of the aldolase C molecule are required for exhibiting isozyme-specific kinetic properties, we have constructed nine chimeric enzymes of human aldolases A and C. Kinetic studies of these chimeric enzymes revealed that aldolase C absolutely required its own isozyme group-specific sequences (IGS), particularly IGS-4, for exhibiting the characteristics of aldolase C which differ significantly from those of isozymes A and B (Kusakabe T, Motoki K, Hori K. Human aldolase C: characterization of the recombinant enzyme expressed in Escherichia coli. J Biochem (Tokyo) 1994;115:1172–7). Whereas human aldolases A and B required their own isozyme group-specific sequences-1 and -4 (IGS-1 and -4) as the main determinants of isozyme-specific kinetic properties (Motoki K, Kitajima Y, Hori K. Isozyme-specific modules on human aldolase A molecule. J Biol Chem 1993;268:1677–83; Kusakabe T, Motoki K, Sugimoto Y, Takasaki Y, Hori K. Human aldolase B: liver-specific properties of the isoenzyme depend on type B isozyme group-specific sequence. Prot. Eng. 1994;7:1387–93), the present studies indicate that the IGS-1 is principally substitutable between aldolases A and C. The kinetic data also suggests that the connector-2 (amino acid residues 243–306) may modulate the interaction of IGS units with the α/β barrel of the aldolase molecule.     

Homologous Desensitization of Serotonin 5-HT2 Receptor-Stimulated Intracellular Calcium Mobilization in C6BU-1 Glioma Cells via a Mechanism Involving a Calmodulin Pathway

Abstract: Serotonin 5-HT₂ receptor-mediated intracellular Ca²⁺ mobilization was investigated in rat glioma C6BU-1 cells. The receptors became desensitized after previous exposure to 5-HT in a time-and concentration-dependent manner. The desensitization of 5-HT₂ receptor-mediated intracellular signaling appeared to be homologous because previous exposure to 5-HT did not alter the response to other transmitters such as thrombin or isoproterenol and because previous exposure to thrombin or isoproterenol did not diminish the response to 5-HT. The desensitization induced by pretreatment with 5-HT was potently prevented by the naphthalenesulfonamide derivative W-7, a calmodulin antagonist, when it was cosupplied with 5-HT. Furthermore, the preventive effect of W-7 was greater than that of W-5, a weak analogue of W-7, and than that of H-7, a nonselective inhibitor of protein kinases. These results suggest that 5-HT₂ receptor-mediated Ca²⁺ mobilization can be desensitized homologously after prolonged exposure to 5-HT in a calmodulin-dependent manner in rat glioma C6BU-1 cells.     

Vagal esophageal receptors in anesthetized dogs: mechanical and chemical responsiveness.

This study was performed to evaluate the characteristics of esophageal receptors in anesthetized and artificially ventilated dogs. The electrical activity of the esophageal afferents was recorded from the peripheral cut end of the cervical vagus nerve. A cuffed catheter was inserted into the esophagus at the level of the third tracheal ring and was used to establish the esophageal location of the endings. Most of the receptors were localized in the intrathoracic portion of the esophagus. The majority of the receptors studied (36 of 43) showed a slow adaptation to a maintained stretch of the esophageal wall. Vagal cooling blocked receptor activity at temperatures ranging from 3.5 to 25 degrees C. Twenty-eight of 43 receptors, including 4 rapidly adapting endings (RAR), were challenged with saline, HCl + pepsin (HCl-P; pH 1) and distilled water (8 ml, 37 degrees C). HCl-P solutions specifically stimulated only three receptors; saline or water did not. Five slowly adapting receptors and two RARs were also challenged with topically applied capsaicin; only one RAR was stimulated. To ascertain a possible effect of smooth muscle contraction, 17 receptors were tested with intravenous injections of ACh and/or asphyxia; only 4 were stimulated. These characteristics do not support an important reflexogenic role of the esophagus in response to chemical stimuli.     

Effects of pulmonary congestion on airway reactivity to histamine aerosol in dogs

We examined the effect of acute pulmonary vascular congestion on bronchial reactivity in dogs in a standard challenge protocol. Airway responsiveness to histamine whose concentration was varied in a stepwise incremental fashion was assessed from changes in pulmonary resistance (RL) and dynamic compliance (Cdyn) in 10 anesthetized dogs. Brief acute pulmonary congestion was created by inflating a balloon placed in the left atrium to raise left atrial pressure to 20-30 cmH2O for 1 min. Pulmonary congestion did not change RL in the control condition. However, after histamine inhalation, RL was further increased by pulmonary congestion, making the two effects synergistic. This phenomenon could not be observed with vagi cut. Pulmonary congestion decreased Cdyn in all dogs regardless of histamine concentration, with or without vagotomy. We conclude that pulmonary vascular congestion makes the bronchi hyperreactive through vagal reflexes. The reduction in Cdyn caused by pulmonary congestion appears to stem mainly from the narrowing of peripheral airways by adjacent vascular engorgement.     

p53-independent apoptosis is induced by the p19ARF tumor suppressor

p19(ARF) is a potent tumor suppressor. By inactivating Mdm2, p19(ARF) upregulates p53 activities to induce cell cycle arrest and sensitize cells to apoptosis in the presence of collateral signals. It has also been demonstrated that cell cycle arrest is induced by overexpressed p19(ARF) in p53-deficient mouse embryonic fibroblasts, only in the absence of the Mdm2 gene. Here, we show that apoptosis can be induced without additional apoptosis signals by expression of p19(ARF) using an adenovirus-mediated expression system in p53-intact cell lines as well as p53-deficient cell lines. Also, in primary mouse embryonic fibroblasts (MEFs) lacking p53/ARF, p53-independent apoptosis is induced irrespective of Mdm2 status by expression of p19(ARF). In agreement, p19(ARF)-mediated apoptosis in U2OS cells, but not in Saos2 cells, was attenuated by coexpression of Mdm2. We thus conclude that there is a p53-independent pathway for p19(ARF)-induced apoptosis that is insensitive to inhibition by Mdm2.