• MeSH
• Aorta MeSH
• Biomechanical Phenomena MeSH
• Blood Vessels physiology   MeSH
• Research Support as Topic MeSH
• Humans MeSH
• Linear Models MeSH
• Nonlinear Dynamics MeSH
• Elasticity MeSH
• Viscosity MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Animals MeSH
• Publication type
• Review MeSH
• Comparative Study MeSH

In the Czech Hydrometeorological Institute (CHMI) there exists a unique set of meteorological measurements consisting of the values of vertical atmospheric levels of beta and gamma radiation. In this paper a stochastic data-driven model based on nonlinear regression and on nonhomogeneous Poisson process is suggested. In the first part of the paper, growth curves were used to establish an appropriate nonlinear regression model. For comparison we considered a nonhomogeneous Poisson process with its intensity based on growth curves. In the second part both approaches were applied to the real data and compared. Computational aspects are briefly discussed as well. The primary goal of this paper is to present an improved understanding of the distribution of environmental radiation as obtained from the measurements of the vertical radioactivity profiles by the radioactivity sonde system.

• MeSH
• Atmosphere chemistry   MeSH
• Beta Particles MeSH
• Models, Chemical MeSH
• Radiation Monitoring MeSH
• Nonlinear Dynamics MeSH
• Poisson Distribution MeSH
• Regression Analysis MeSH
• Gamma Rays MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH

Recent evidence suggests that energy metabolism contributes to molecular mechanisms controlling stem cell identity. For example, human embryonic stem cells (hESCs) receive their metabolic energy mostly via glycolysis rather than mitochondrial oxidative phosphorylation. This suggests a connection of metabolic homeostasis to stemness. Nicotinamide adenine dinucleotide (NAD) is an important cellular redox carrier and a cofactor for various metabolic pathways, including glycolysis. Therefore, accurate determination of NAD cellular levels and dynamics is of growing importance for understanding the physiology of stem cells. Conventional analytic methods for the determination of metabolite levels rely on linear calibration curves. However, in actual practice many two-enzyme cycling assays, such as the assay systems used in this work, display prominently nonlinear behavior. Here we present a diaphorase/lactate dehydrogenase NAD cycling assay optimized for hESCs, together with a mechanism-based, nonlinear regression models for the determination of NAD(+), NADH, and total NAD. We also present experimental data on metabolic homeostasis of hESC under various physiological conditions. We show that NAD(+)/NADH ratio varies considerably with time in culture after routine change of medium, while the total NAD content undergoes relatively minor changes. In addition, we show that the NAD(+)/NADH ratio, as well as the total NAD levels, vary between stem cells and their differentiated counterparts. Importantly, the NAD(+)/NADH ratio was found to be substantially higher in hESC-derived fibroblasts versus hESCs. Overall, our nonlinear mathematical model is applicable to other enzymatic amplification systems.

• MeSH
• Cell Extracts MeSH
• Electrophoresis, Capillary MeSH
• Embryonic Stem Cells metabolism   MeSH
• Calibration MeSH
• Humans MeSH
• NAD metabolism   MeSH
• Nonlinear Dynamics * MeSH
• Oxazines metabolism   MeSH
• Regression Analysis MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH

• MeSH
• Chemistry Techniques, Analytical MeSH
• Confidence Intervals MeSH
• Nonlinear Dynamics MeSH
• Regression Analysis MeSH
• Models, Statistical MeSH
• Investigative Techniques MeSH

In this study, affinity capillary electrophoresis (ACE) and quantum mechanical density functional theory (DFT) calculations were combined to investigate non-covalent binding interactions between the hexaarylbenzene-based receptor (R) and alkali metal ions, Rb(+) and Cs(+) , in methanol. The apparent binding (stability) constants (K(b) ) of the complexes of receptor R with alkali metal ions in the methanolic medium were determined by ACE from the dependence of effective electrophoretic mobility of the receptor R on the concentration of Rb(+) and Cs(+) ions in the BGE using a non-linear regression analysis. The receptor R formed relatively strong complexes both with rubidium (log K(b) =4.04±0.21) and cesium ions (log K(b) =3.72±0.22). The structural characteristics of the above alkali metal ion complexes with the receptor R were described by ab initio density functional theory calculations. These calculations have shown that the studied cations bind to the receptor R because they synergistically interact with the polar ethereal fence and with the central benzene ring via cation-π interaction.

• MeSH
• Benzene Derivatives chemistry   MeSH
• Cesium chemistry   MeSH
• Electrophoresis, Capillary methods   MeSH
• Methanol chemistry   MeSH
• Models, Molecular MeSH
• Nonlinear Dynamics MeSH
• Regression Analysis MeSH
• Rubidium chemistry   MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH

The mixed dissociation constants of four non-steroidal anti-inflammatory drugs (NSAIDs) ibuprofen, diclofenac sodium, flurbiprofen and ketoprofen at various ionic strengths I of range 0.003-0.155, and at temperatures of 25 degrees C and 37 degrees C, were determined with the use of two different multiwavelength and multivariate treatments of spectral data, SPECFIT/32 and SQUAD(84) nonlinear regression analyses and INDICES factor analysis. The factor analysis in the INDICES program predicts the correct number of components, and even the presence of minor ones, when the data quality is high and the instrumental error is known. The thermodynamic dissociation constant pK(a)(T) was estimated by nonlinear regression of (pK(a), I) data at 25 degrees C and 37 degrees C. Goodness-of-fit tests for various regression diagnostics enabled the reliability of the parameter estimates found to be proven. PALLAS, MARVIN, SPARC, ACD/pK(a) and Pharma Algorithms predict pK(a) being based on the structural formulae of drug compounds in agreement with the experimental value. The best agreement seems to be between the ACD/pK(a) program and experimentally found values and with SPARC. PALLAS and MARVIN predicted pK(a,pred) values with larger bias errors in comparison with the experimental value for all four drugs.

• MeSH
• Anti-Inflammatory Agents, Non-Steroidal chemistry   MeSH
• Models, Chemical MeSH
• Financing, Organized MeSH
• Hydrogen-Ion Concentration MeSH
• Least-Squares Analysis MeSH
• Molecular Structure MeSH
• Nonlinear Dynamics MeSH
• Solubility MeSH
• Spectrophotometry methods   MeSH
• Thermodynamics MeSH
• Titrimetry methods   MeSH

The mixed dissociation constants of five drug acids-ambroxol, antazoline, naphazoline, oxymetazoline and ranitidine-at various ionic strengths I of range 0.01 and 1.0 and at temperatures of 25 and 37 degrees C were determined using SQUAD(84) regression analysis of the pH-spectrophotometric titration data. A proposed strategy of efficient experimentation in a protonation constants determination, followed by a computational strategy for the chemical model with a protonation constants determination, is presented on the protonation equilibria of ambroxol. The thermodynamic dissociation constant pK(a)(T) was estimated by non-linear regression of {pK(a), I} data at 25 and 37 degrees C: for ambroxol p K (a ,1)(T )=8.05 (6) and 8.25 (4), logbeta (21)(T )=11.67 (6) and 11.83 (8), for antazoline p K (a ,1)(T )=7.79 (2) and 7.83 (6), p K (a ,2)(T )=9.74 (3) and 9.55 (2), for naphazoline pK (a ,1)(T )=10.81 (1) and 10.63 (1), for oxymethazoline pK (a ,1)(T )=10.62 (2) and 10.77 (7), pK(a,2)(T)=12.03(3) and 11.82 (4) and for ranitidine p K (a ,1)(T )=1.89 (1) and 1.77 (1). Goodness-of-fit tests for various regression diagnostics enabled the reliability of the parameter estimates to be found.

• MeSH
• Ambroxol chemistry   MeSH
• Antazoline chemistry   MeSH
• Naphazoline chemistry   MeSH
• Oxymetazoline chemistry   MeSH
• Ranitidine chemistry   MeSH
• Regression Analysis MeSH
• Spectrophotometry MeSH
• Publication type
• Research Support, Non-U.S. Gov't MeSH

Potentiometric and spectrophotometric pH-titration of the multiprotic cytostatics bosutinib for dissociation constants determination were compared. Bosutinib treats patients with positive chronic myeloid leukemia. Bosutinib exhibits four protonatable sites in a pH range from 2 to 11, where two pK are well separated (ΔpK>3), while the other two are near dissociation constants. In the neutral medium, bosutinib occurs in the slightly water soluble form LH that can be protonated to the soluble cation LH4(3+). The molecule LH can be dissociated to still difficultly soluble anion L(-). The set of spectra upon pH from 2 to 11 in the 239.3-375.0nm was divided into two absorption bands: the first one from 239.3 to 290.5nm and the second from 312.3 to 375.0nm, which differ in sensitivity of chromophores to a pH change. Estimates of pK of the entire set of spectra were compared with those of both absorption bands. Due to limited solubility of bosutinib the protonation in a mixed aqueous-methanolic medium was studied. In low methanol content of 3-6% three dissociation constants can be reliably determined with SPECFIT/32 and SQUAD(84) and after extrapolation to zero content of methanol they lead to pKc1=3.43(12), pKc2=4.54(10), pKc3=7.56(07) and pKc4=11.04(05) at 25°C and pKc1=3.44(06), pKc2=5.03(08) pKc3=7.33(05) and pKc4=10.92(06) at 37°C. With an increasing content of methanol in solvent the dissociation of bosutinib is suppressed and the percentage of LH3(2+) decreases and LH prevails. From the potentiometric pH-titration at 25°C the concentration dissociation constants were estimated with ESAB pKc1=3.51(02), pKc2=4.37(02), pKc3=7.97(02) and pKc4=11.05(03) and with HYPERQUAD: pKc1=3.29(12), pKc2=4.24(10), pKc3=7.95(07) and pKc4=11.29(05).

• MeSH
• Aniline Compounds analysis   chemistry   MeSH
• Quinolines analysis   chemistry   MeSH
• Cytostatic Agents analysis   chemistry   MeSH
• Hydrogen-Ion Concentration MeSH
• Least-Squares Analysis MeSH
• Nonlinear Dynamics * MeSH
• Nitriles analysis   chemistry   MeSH
• Potentiometry MeSH
• Spectrophotometry methods   MeSH
• Publication type
• Journal Article MeSH

A comparison of capillary and rotational viscometry of gentle pseudoplastic solutions of hypromellose (HPMC 4000) by using only single-point value of viscosity is difficult. Single-point comparison becomes topical in consequence to the pharmacopoeial requirement that the apparent viscosity of 2% hypromellose solution should be read at the shear rate of approximately 10 s(-1). This communication is focused on the estimation of the suitable shear rate, D eta, at which the apparent viscosity read using the rotational viscometer is numerically equal to the dynamic viscosity read using a capillary viscometer. For the solutions of HPMC in concentrations up to 2% w/v, the non-linear regression equations generated showed the influencing of the D eta value by the dynamic viscosity and/or by the originally derived linear velocity of the solution flowing through the capillary viscometer tube. To compare the apparent viscosity read using the rotational viscometer with the dynamic viscosity read using capillary viscometer, the exact estimation of the shear rate D eta at which both viscosities are numerically equal is essential since it is markedly affected by the concentration of HPMC solution.

• MeSH
• Chemical Phenomena MeSH
• Financing, Organized MeSH
• Chemistry, Physical MeSH
• Pharmaceutical Solutions MeSH
• Methylcellulose analogs & derivatives   chemistry   MeSH
• Nonlinear Dynamics MeSH
• Drug Compounding MeSH
• Regression Analysis MeSH
• Rheology methods   instrumentation   MeSH
• Viscosity MeSH
• Publication type
• Comparative Study MeSH

• MeSH
• Homeopathy methods   MeSH
• Linear Models MeSH
• Nonlinear Dynamics MeSH
• Models, Theoretical MeSH
• Publication type
• Comparative Study MeSH