Essential role of PI3-kinase pathway in p53-mediated transcription: Implications in cancer chemotherapy

The PI3-kinase pathway is the target of inactivation in achieving better cancer chemotherapy. Here, we report that p53-mediated transcription is inhibited by pharmacological inhibitors and a dominant-negative mutant of PI3-kinase, and this inhibition was relieved by a constitutively active mutant of PI3-kinase. Akt/PKB and mTOR, the downstream effectors of PI3-kinase, were also found to be essential. LY294002 (PI3-kinase inhibitor) pre-treatment altered the post-translational modifications and the sub-cellular localization of p53. Although LY294002 increased the chemosensitivity of cells to low concentrations of adriamycin (adriamycin-low), it protected the cells from cytotoxicity induced by high concentrations of adriamycin (adriamycin-high) in a p53-dependent manner. Further, we found that LY294002 completely abolished the activation of p53 target genes (particularly pro-apoptotic) under adriamycin-high conditions, whereas it only marginally repressed the p53 target genes under adriamycin-low conditions; in fact, it further activated the transcription of NOXA, HRK, APAF1 and CASP5 genes. Thus, the differential effect of PI3-kinase on p53 functions seems to be responsible for the differential regulation of DNA damage-induced cytotoxicity and cell death by PI3-kinase. Our finding becomes relevant in the light of ongoing combination chemotherapy trials with the PI3-kinase pathway inhibitors and underscores the importance of p53 status in the careful formulation of combination chemotherapies. Oncogene (2010) 29, 3605-3618; doi: 10.1038/onc.2010.123; published online 26 April 2010

Nitric oxide is the key mediator of death induced by fisetin in human acute monocytic leukemia cells

Nitric oxide ( NO) has been shown to be effective in cancer chemoprevention and therefore drugs that help generate NO would be preferable for combination chemotherapy or solo use. This study shows a new evidence of NO as a mediator of acute leukemia cell death induced by fisetin, a promising chemotherapeutic agent. Fisetin was able to kill THP-1 cells in vivo resulting in tumor shrinkage in the mouse xenograft model. Death induction in vitro was mediated by an increase in NO resulting in double strand DNA breaks and the activation of both the extrinsic and the intrinsic apoptotic pathways. Double strand DNA breaks could be reduced if NO inhibitor was present during fisetin treatment. Fisetin also inhibited the downstream components of the mTORC1 pathway through downregulation of levels of p70 S6 kinase and inducing hypo-phosphorylation of S6 Ri P kinase, eIF4B and eEF2K. NO inhibition restored phosphorylation of downstream effectors of mTORC1 and rescued cells from death. Fisetin induced Ca2+ entry through L-type Ca2+ channels and abrogation of Ca2+ influx reduced caspase activation and cell death. NO increase and increased Ca2+ were independent phenomenon. It was inferred that apoptotic death of acute monocytic leukemia cells was induced by fisetin through increased generation of NO and elevated Ca2+ entry activating the caspase dependent apoptotic pathways. Therefore, manipulation of NO production could be viewed as a potential strategy to increase efficacy of chemotherapy in acute monocytic leukemia.

Use of S1 nuclease and formamide in combination for the reassociation studies on GC-rich DNA

The optimal parameters in the use of nuclease S1 in DNA reassociation kinetics in the presence of formamide have been determined. The conditions are especially suitable for the study of DNA rich in mole percent GC. A 10-fold dilution of the reassociation samples leading to a decrease in both NaCl and formamide concentrations, consequently resulting in a lowering of Tm by only 1.5°C, and the S1 digestion at temperatures identical to the reassociation assay in order to retain the stability of the duplex, are two important aspects of this system. Under these conditions, the kinetics of reassociation followed the theoretically predicted pattern, while the earlier reported methods have shown lower values.

A Combination of Hexagonal and 12-Sided Polygonal Voltage Space Vector PWM Control for IM Drives Using Cascaded Two-Level Inverters

This paper proposes a multilevel inverter configuration which produces a hexagonal voltage space vector structure in the lower modulation region and a 12-sided polygonal space vector structure in the overmodulation region. A conventional multilevel inverter produces 6n plusmn 1 (n = odd) harmonics in the phase voltage during overmodulation and in the extreme square-wave mode of operation. However, this inverter produces a 12-sided polygonal space vector location, leading to the elimination of 6n plusmn 1 (n = odd) harmonics in the overmodulation region extending to a final 12-step mode of operation with a smooth transition. The benefits of this arrangement are lower losses and reduced torque pulsation in an induction motor drive fed from this converter at higher modulation indexes. The inverter is fabricated by using three conventional cascaded two-level inverters with asymmetric dc-bus voltages. A comparative simulation study of the harmonic distortion in the phase voltage and associated losses in conventional multilevel inverters and that of the proposed inverter is presented in this paper. Experimental validation on a prototype shows that the proposed converter is suitable for high-power applications because of low harmonic distortion and low losses.

CSSI-PRO: a method for secondary structure type editing, assignment and estimation in proteins using linear combination of backbone chemical shifts

Estimation of secondary structure in polypeptides is important for studying their structure, folding and dynamics. In NMR spectroscopy, such information is generally obtained after sequence specific resonance assignments are completed. We present here a new methodology for assignment of secondary structure type to spin systems in proteins directly from NMR spectra, without prior knowledge of resonance assignments. The methodology, named Combination of Shifts for Secondary Structure Identification in Proteins (CSSI-PRO), involves detection of specific linear combination of backbone H-1(alpha) and C-13' chemical shifts in a two-dimensional (2D) NMR experiment based on G-matrix Fourier transform (GFT) NMR spectroscopy. Such linear combinations of shifts facilitate editing of residues belonging to alpha-helical/beta-strand regions into distinct spectral regions nearly independent of the amino acid type, thereby allowing the estimation of overall secondary structure content of the protein. Comparison of the predicted secondary structure content with those estimated based on their respective 3D structures and/or the method of Chemical Shift Index for 237 proteins gives a correlation of more than 90% and an overall rmsd of 7.0%, which is comparable to other biophysical techniques used for structural characterization of proteins. Taken together, this methodology has a wide range of applications in NMR spectroscopy such as rapid protein structure determination, monitoring conformational changes in protein-folding/ligand-binding studies and automated resonance assignment.

Experimental investigation of interaction of strong shock heated oxygen gas on the surface of ZrO2 - a novel method to understand re-combination heating

Interaction of shock heated test gas in the free piston driven shock tube with bulk and thin film of cubic zirconium dioxide (ZrO2) prepared by combustion method is investigated. The test samples before and after exposure to the shock wave are analyzed by X-ray diffraction (XRD), X-Ray Photoelectron Spectroscopy (XPS) and Scanning Electron Microscope (SEM). The study shows transformation of metastable cubic ZrO2 to stable monoclinic ZrO2 phase after interacting with shock heated oxygen gas due to the heterogeneous catalytic recombination surface reaction.

Diffusion of Pure CH4 and Its Binary Mixture with CO2 in Faujasite NaY: A Combination of Neutron Scattering Experiments and Molecular Dynamics Simulations

The self-diffusion properties of pure CH4 and its binary mixture with CO2 within MY zeolite have been investigated by combining an experimental quasi-elastic neutron scattering (QENS) technique and classical Molecular dynamics simulations. The QENS measurements carried out at 200 K led to an unexpected self-diffusivity profile for Pure CH4 with the presence of a maximum for a loading of 32 CH4/unit cell, which was never observed before for the diffusion of apolar species in azeolite system With large windows. Molecular dynamics simulations were performed using two distinct microscopic models for representing the CH4/NaY interactions. Depending on the model, we are able to fairly reproduce either the magnitude or the profile of the self-diffusivity.Further analysis allowed LIS to provide some molecular insight into the diffusion mechanism in play. The QENS measurements report only a slight decrease of the self-diffusivity of CH4 in the presence of CO2 when the CO2 loading increases. Molecular dynamics simulations successfully capture this experimental trend and suggest a plausible microscopic diffusion mechanism in the case of this binary mixture.

On the momentum balance in linear-combination models for the transition zone

The momentum balance of the linear-combination integral model for the transition zone is investigated for constant pressure flows. The imbalance is found to be small enough to be negligible for all practical purposes. [S0889-504X(00)00703-0].

Two-dimensional NMR spectroscopy of connected transitions by linear combination of flip angle dependent cosy: An alternative scheme for E.COSY

An alternative pulse scheme which simplifies and improves the recently proposed P.E.COSY experiment is suggested for the retention of connected or unconnected transitions in a coupled spin system. An important feature of the proposed pulse scheme is the improved phase characteristics of the diagonal peaks. A comparison of various experiments designed for this purpose, namely COSY-45, E.COSY, P.E.COSY and the present scheme (A.E.COSY), is also presented. The suppression of unconnected transitions and the measurement of scalar coupling constants and their relative signs are illustrated from A.E.COSY spectra of 2,3-dibromopropionic acid and 2-(2-thienyl)pyridine.

On uniqueness, transfer and combination of acoustic sources in one-dimensional systems

The use of electroacoustic analogies suggests that a source of acoustical energy (such as an engine, compressor, blower, turbine, loudspeaker, etc.) can be characterized by an acoustic source pressure ps and internal source impedance Zs, analogous to the open-circuit voltage and internal impedance of an electrical source. The present paper shows analytically that the source characteristics evaluated by means of the indirect methods are independent of the loads selected; that is, the evaluated values of ps and Zs are unique, and that the results of the different methods (including the direct method) are identical. In addition, general relations have been derived here for the transfer of source characteristics from one station to another station across one or more acoustical elements, and also for combining several sources into a single equivalent source. Finally, all the conclusions are extended to the case of a uniformly moving medium, incorporating the convective as well as dissipative effects of the mean flow.

Ribavirin-Induced Anemia in Hepatitis C Virus Patients Undergoing Combination Therapy

The current standard of care for hepatitis C virus (HCV) infection - combination therapy with pegylated interferon and ribavirin - elicits sustained responses in only similar to 50% of the patients treated. No alternatives exist for patients who do not respond to combination therapy. Addition of ribavirin substantially improves response rates to interferon and lowers relapse rates following the cessation of therapy, suggesting that increasing ribavirin exposure may further improve treatment response. A key limitation, however, is the toxic side-effect of ribavirin, hemolytic anemia, which often necessitates a reduction of ribavirin dosage and compromises treatment response. Maximizing treatment response thus requires striking a balance between the antiviral and hemolytic activities of ribavirin. Current models of viral kinetics describe the enhancement of treatment response due to ribavirin. Ribavirin-induced anemia, however, remains poorly understood and precludes rational optimization of combination therapy. Here, we develop a new mathematical model of the population dynamics of erythrocytes that quantitatively describes ribavirin-induced anemia in HCV patients. Based on the assumption that ribavirin accumulation decreases erythrocyte lifespan in a dose-dependent manner, model predictions capture several independent experimental observations of the accumulation of ribavirin in erythrocytes and the resulting decline of hemoglobin in HCV patients undergoing combination therapy, estimate the reduced erythrocyte lifespan during therapy, and describe inter-patient variations in the severity of ribavirin-induced anemia. Further, model predictions estimate the threshold ribavirin exposure beyond which anemia becomes intolerable and suggest guidelines for the usage of growth hormones, such as erythropoietin, that stimulate erythrocyte production and avert the reduction of ribavirin dosage, thereby improving treatment response. Our model thus facilitates, in conjunction with models of viral kinetics, the rational identification of treatment protocols that maximize treatment response while curtailing side effects.

Reduction of quinolines to 1,2,3,4-tetrahydro derivatives employing a combination of NaCNBH3 and BF3.OEt(2)

A regiospecific reduction of quinolines (and 1,10-phenanthroline) into the corresponding 1,2,3,4-tetrahydro derivatives using a combination of sodium cyanoborohydride and boron trifluoride etherate in refluxing methanol is described. Under the same conditions indole and acridine reduced to the corresponding dihydroderivatives, whereas acyl group transfer from oxygen to nitrogen atom is also noticed in the case of 8-acyloxyquinolines.

The Boltzmann collision integrals for a combination of Maxwellians

The gain and loss integrals in the Boltzmann equation for a rigid sphere gas are evaluated in closed form for a distribution which can be expressed as a linear combination of Maxwellians. Application to the Mott-Smith bimodal distribution shows that the gain is also bimodal, but the two modes in the gain are less pronounced than in the distribution. Implications of these results for simple collision models in non-equilibrium flow are discussed.