Homology modeling of human sialidase enzymes NEU1, NEU3 and NEU4 based on the crystal structure of NEU2: hints for the design of selective NEU3 inhibitors

Four types of human sialidases have been cloned and characterized at the molecular level. They are classified according to their major intracellular location as intralysomal (NEU1), cytosolic (NEU2), plasma membrane (NEU3) and lysosomal or mitochondrial membrane (NEU4) associated sialidases. These human isoforms are distinct from each other in their enzymatic properties as well as their substrate specificity. Altered expression of sialidases has been correlated with malignant transformation of cells and different sialidases have been known to behave differently during carcinogenesis. Particularly, increased expression of NEU3 has been implicated in the survival of various cancer cells and also in the development of insulin resistance. In the present study, we have modeled three-dimensional structures of NEU1, NEU3 and NEU4 based on the crystal structure of NEU2 using the homology modeling program MODELER. The best model in each enzyme case was chosen on the basis of various standard protein analysis programs. Predicted structures and the experimental protein-ligand complex of NEU2 were compared to identify similarities and differences among the active sites. The molecular electrostatic potential (MEP) was calculated for the predicted models to identify the differences in charge distribution around the active site and its vicinity. The primary objective of the present work is to identify the structural differences between the different isoforms of human sialidases, namely NEU1, NEU2, NEU3 and NEU4, thus providing a better insight into the differences in the active sites of these enzymes. This can in turn guide us in the better understanding and rationale of the differential substrate recognition and activity, thereby aiding in the structure-based design of selective NEU3 inhibitors.     

Synthesis and structure of vinyl polymer-poly(α-amino acid) graft copolymers

N-(2-Carbobenzyloxyaminoethyl)acrylamide (CAEA) which is a vinyl compound carrying a protected aliphatic primary amino group in the side chain has been synthesized and its homopolymerization and copolymerization induced by radical initiators have been investigated. CAEA was found to possess good copolymerizability with vinyl monomers having large Q values such as styrene, 2-vinyl pyridine, acrylonitrile and methyl methacrylate. Vinyl polymers containing a small amount of aliphatic primary amino group in the side chain were produced by the treatment of vinyl polymers containing a small amount of CAEA unit with HBr/AcOH or $\text{H}{}_2\text{Pd}$. Using the former polymers as initiators for the polymerization of N-carboxyanhydrides of (RS)-Phe and (S)-Glu(OBz), vinly polymer (trunk)-poly-(α-amino acid) (branch) graft copolymers were synthesized. These copolymers were investigated by transmission electron microscopy, and the development of domain structure due to microphase separation was observed.     

Greedy information acquisition algorithm: A new information theoretic approach to dynamic information acquisition in neural networks

In this paper, we proopose a new information theoretic approach to competitive learning. The new approach is called greedy information acquisition , because networks try to absorb as much information as possible in every stage of learning. In the first phase, with minimum network architecture for realizing competition, information is maximized. In the second phase, a new unit is added, and thereby information is again increased as much as possible. This proceess continues until no more increase in information is possible. Through greedy information maximization, different sets of important features in input patterns can be cumulatively discovered in successive stages. We applied our approach to three problems: a dipole problem; a language classification problem; and a phonological feature detection problem. Experimental results confirmed that information maximization can be repeatedly applied and that different features in input patterns are gradually discovered. We also compared our method with conventional competitive learning and multivariate analysis. The experimental results confirmed that our new method can detect salient features in input patterns more clearly than the other methods.     

Analysis of magnetic probe signals including effect of cylindrical conducting wall for field-reversed configuration experiment

A confinement field is disturbed by magnetohydrodynamic (MHD) motions of a field-reversed configuration (FRC) plasma in a cylindrical conductor. The effect of the conductor should be included to obtain a spatial structure of the disturbed field with a good precision. For this purpose, a toroidal current in the plasma and an eddy current on a conducting wall are replaced by magnetic dipole and image magnetic dipole moments, respectively. Typical spatial structures of the disturbed field are calculated by using the dipole moments for such MHD motions as radial shift, internal tilt, external tilt, and n=2 mode deformation. Then, analytic formulas for estimating the shift distance, tilt angle, and deformation rate of the MHD motions from magnetic probe signals are derived. It is estimated from the calculations by using the dipole moments that the analytic formulas include an approximately 40% error. Two kinds of experiment are carried out to investigate the reliability of the calculations. First, a magnetic field produced by a circular current is measured in an aluminum pipe to confirm the replacement of the eddy current with the image magnetic dipole moments. The measured fields coincide well with the calculated values including the image magnetic dipole moments. Second, magnetic probe signals measured from the FRC plasma are substituted into the analytic formulas to obtain shift distance and deformation rate. The experimental results are compared to the MHD motions measured by using a radiation from the plasma. If the error included in the analytic formulas and the difference between the magnetic and optical structures in the plasma are considered, the results of the radiation measurement support well those of the magnetic analysis.     

Predictors of cardiovascular events in hemodialysis patients after stress myocardial perfusion imaging

Cardiovascular prognosis in patients under normal stress myocardial perfusion images (MPI) is generally excellent. However, this is not true for patients with chronic kidney disease (CKD) treated by hemodialysis. This study evaluated prognostic factors of adverse cardiovascular events in hemodialysis patients in whom stress MPI was performed. Pharmacological stress MPI was performed in 88 hemodialysis patients, and we retrospectively followed‐up for 26 months. Cardiovascular events included cardiac death, nonfatal myocardial infarction, and unstable angina. Cardiovascular events occurred in 16 patients (18%). Univariate Cox regression analysis revealed that peripheral artery disease (PAD) and parameters of stress MPI were significant predictors of cardiovascular events. Multivariate Cox regression analysis revealed that only PAD (hazard ratio = 6.54; P = 0.002), and abnormal stress MPI (hazard ratio = 8.26; P = 0.008) were independent and significant predictors of cardiovascular events. Kaplan–Meier analysis showed better prognosis in patients with normal stress MPI than in patients with abnormal stress MPI (P < 0.001, log–rank test). However, in patients with normal stress MPI, cardiovascular events occurred in 10 of the 76 patients (13%). Among patients with normal stress MPI, Kaplan–Meier analysis showed that patients with no PAD had better prognosis than patients with PAD (P = 0.001, log–rank test). In hemodialysis patients, both PAD and stress MPI were powerful cardiovascular predictors. Normal stress MPI alone cannot guarantee good prognosis in terms of cardiovascular events. Consideration of PAD may improve the predictive value of stress MPI in some patients.     

Amorphous phase formation by spray forming of alloys [(Fe0.6Co0.4)0.75B0.2Si0.05]96Nb4 and Fe66B30Nb4 modified with Ti

This paper describes results obtained by spray forming three iron-based alloys, namely [(Fe_0.6Co_0.4)_0.75B_0.2Si_0.05]₉₆Nb₄, Fe₆₅B₃₀Nb₄Ti₁ and Fe₆₃B₂₉Nb₄Ti₄, whose compositions derive from rapid solidification studies, in an attempt to obtain metallic glasses. The [(Fe_0.6Co_0.4)_0.75B_0.2Si_0.05]₉₆Nb₄ alloy presented higher glass-forming ability and showed a high fraction of amorphous phase formation up to a depth of 4 mm in the deposit. On the other hand, the spray formed deposits of the Fe₆₅B₃₀Nb₄Ti₁ and Fe₆₃B₂₉Nb₄Ti₄ alloys showed fully crystalline microstructure, despite the fact that the melt spun ribbons were fully amorphous.     

Roscovitine,a Cyclin-Dependent Kinase-5 Inhibitor,Decreases Phosphorylated Tau Formation and Death of Retinal Ganglion Cells of Rats after Optic Nerve Crush

Tauopathies are neurodegenerative diseases characterized by abnormal metabolism of misfolded tau proteins and are progressive. Pathological phosphorylation of tau occurs in the retinal ganglion cells (RGCs) after optic nerve injuries. Cyclin-dependent kinase-5 (Cdk5) causes hyperphosphorylation of tau. To determine the roles played by Cdk5 in retinal degeneration, roscovitine, a Cdk5 inhibitor, was injected intravitreally after optic nerve crush (ONC). The neuroprotective effect of roscovitine was determined by the number of Tuj-1-stained RGCs on day 7. The change in the levels of phosphorylated tau, calpain-1, and cleaved α-fodrin was determined by immunoblots on day 3. The expression of P35/P25, a Cdk5 activator, in the RGCs was determined by immunohistochemistry. The results showed that roscovitine reduced the level of phosphorylated tau by 3.5- to 1.6-fold. Calpain-1 (2.1-fold) and cleaved α-fodrin (1.5-fold) were increased on day 3, suggesting that the calpain signaling pathway was activated. P35/P25 was accumulated in the RGCs that were poorly stained by Tuj-1. Calpain inhibition also reduced the increase in phosphorylated tau. The number of RGCs decreased from 2191 ± 178 (sham) to 1216 ± 122 cells/mm² on day 7, and roscovitine preserved the level at 1622 ± 130 cells/mm². We conclude that the calpain-mediated activation of Cdk5 is associated with the pathologic phosphorylation of tau.     

Study on Transonic Tone in an Axisymmetric Supersonic Nozzle

This paper describes experimental and numerical works to investigate noise phenomenon in supersonic flow dis- charged from a convergent-divergent nozzle. The noise phenomenon of flow is generated by an emission of ＇transonic tones＇. The results obtained show that the frequency of a transonic tone, that differs from the frequency of a screech tone due to the shock-cell structures in a jet and originates in the shock wave in the nozzle, increases in proportion to the nozzle pressure ratio. The high-order transonic tone has the directivity in the direction of the flow. As for the transonic tone＇s frequency, the separated zone was calculated by using a simple flow model con- sidering the propagating perturbation. The results of the model corresponded to the results of this experiment well.     

Analysis of thyroid hormones in health foods by LC/MS

A method was developed for analysis of thyroid hormones, 3,5,3'-triiodo-L-thyronine (T3) and L-thyroxine (T4), in health foods by liquid chromatography-electrospray ionization-mass spectrometry (LC/ESI-MS). In order to release T3 and T4 from thyroglobulin, samples were first hydrolyzed enzymatically using protease at a temperature of 37 +/- 1 degrees C for 28 h. The T3 and T4 were extracted with ethyl acetate and then the ethyl acetate layer was evaporated. The residue was dissolved in the mobile phase and analyzed by LC/MS. The LC separation was carried out on a ODS-3 column (2.1 x 150 mm) using H2O/CH3CN/CH3COOH (650/350/5) as the mobile phase. LC/ESI-MS was performed in the selected ion monitoring (SIM) mode using [M + H]+ ions at m/z 652 for T3 and m/z 778 for T4. The detection limit of both T3 and T4 released from thyroglobulin was 0.1 microgram/g in health foods. The present method was applied to analysis of three health foods which were labeled as foods for dieting. T3 and T4 were detected in two of the samples, and their contents were 16 and 29 micrograms/g and 31 and 90 micrograms/g, respectively.     

A new route to 4-, 5-, and 6-indolecarboxylic acids

There are many indole derivatives bearing carboxyl or methoxycarbonyl groups on the benzene ring and these often have patent physiological activities. Synthesis of these compounds usually starts from indoles having a halogen group at the desired position on an indole ring. We now report a facile synthesis of 4-, 5-, and 6-indolecarboxylic acids from 2-bromoaniline derivatives ( 1 ). The synthetic route is shown in Figure 1.