Home About us Contact
|
Home About us Contact | ||
|
|
||
Kinetic Profile (kinetic + profile)
Selected AbstractsKINETIC BEHAVIOR OF SOYBEAN LIPOXYGENASE: A COMPARATIVE STUDY OF THE FREE ENZYME AND THE ENZYME IMMOBILIZED IN AN ALGINATE SILICA SOL-GEL MATRIX,JOURNAL OF FOOD BIOCHEMISTRY, Issue 1 2000AN-FEI HSU Lipoxygenase (LOX) is an enzyme that regioselectively introduces a hydroperoxide into polyunsaturated fatty acids (PUFA). We recently reported a procedure that immobilizes soybean LOX within an alginate sol-gel matrix. In this study, the kinetic profile of free LOX was compared with that of the sol-gel immobilized LOX. The temperature dependent activity profile of free LOX was optimal at 25C whereas immobilized LOX had optimal activity over the temperature range of 25,35C. Enzyme activity, measured in aqueous buffer, for both the free and immobilized LOX preparations had Km values of 2.5 and 1.40 mmoles/L, respectively, and Vmax values of 0.056 and 0.02 ,mol/min, respectively. The relative rates of oxidation of linoleic acid and acylgfycerols containing linoleoyl residues catalyzed by free and immobilized LOX also were determined The results showed that both free and immobilized LOX favor linoleic acid as a substrate. Relative substrate preference for free LOX was linoleic acid >1-monolinolein > 1,3-dilinolein >trilinolein, and for immobilized LOX was linoleic acid >l, 3-dilinolein >1-monolinolein >trilinolein. In general, LOX immobilized in alginate silica sol-gel matrix retained the physical and chemical characteristics of free LOX. [source] Pharmacokinetic parameters estimation using adaptive Bayesian P-splines modelsPHARMACEUTICAL STATISTICS: THE JOURNAL OF APPLIED STATISTICS IN THE PHARMACEUTICAL INDUSTRY, Issue 2 2009Astrid Jullion Abstract In preclinical and clinical experiments, pharmacokinetic (PK) studies are designed to analyse the evolution of drug concentration in plasma over time i.e. the PK profile. Some PK parameters are estimated in order to summarize the complete drug's kinetic profile: area under the curve (AUC), maximal concentration (Cmax), time at which the maximal concentration occurs (tmax) and half-life time (t1/2). Several methods have been proposed to estimate these PK parameters. A first method relies on interpolating between observed concentrations. The interpolation method is often chosen linear. This method is simple and fast. Another method relies on compartmental modelling. In this case, nonlinear methods are used to estimate parameters of a chosen compartmental model. This method provides generally good results. However, if the data are sparse and noisy, two difficulties can arise with this method. The first one is related to the choice of the suitable compartmental model given the small number of data available in preclinical experiment for instance. Second, nonlinear methods can fail to converge. Much work has been done recently to circumvent these problems (J. Pharmacokinet. Pharmacodyn. 2007; 34:229,249, Stat. Comput., to appear, Biometrical J., to appear, ESAIM P&S 2004; 8:115,131). In this paper, we propose a Bayesian nonparametric model based on P-splines. This method provides good PK parameters estimation, whatever be the number of available observations and the level of noise in the data. Simulations show that the proposed method provides better PK parameters estimations than the interpolation method, both in terms of bias and precision. The Bayesian nonparametric method provides also better AUC and t1/2 estimations than a correctly specified compartmental model, whereas this last method performs better in tmax and Cmax estimations. We extend the basic model to a hierarchical one that treats the case where we have concentrations from different subjects. We are then able to get individual PK parameter estimations. Finally, with Bayesian methods, we can get easily some uncertainty measures by obtaining credibility sets for each PK parameter. Copyright © 2008 John Wiley & Sons, Ltd. [source] Integrated analytical approach in veal calves administered the anabolic androgenic steroids boldenone and boldione: urine and plasma kinetic profile and changes in plasma protein expressionPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 17 2007Rosa Draisci Abstract Surveillance of illegal use of steroids hormones in cattle breeding is a key issue to preserve human health. To this purpose, an integrated approach has been developed for the analysis of plasma and urine from calves treated orally with a single dose of a combination of the androgenic steroids boldenone and boldione. A quantitative estimation of steroid hormones was obtained by LC-APCI-Q-MS/MS analysis of plasma and urine samples obtained at various times up to 36 and 24,h after treatment, respectively. These experiments demonstrated that boldione was never found, while boldenone ,- and ,-epimers were detected in plasma and urine only within 2 and 24,h after drug administration, respectively. Parallel proteomic analysis of plasma samples was obtained by combined 2-DE, MALDI-TOF-MS and ,LC-ESI-IT-MS/MS procedures. A specific protein, poorly represented in normal plasma samples collected before treatment, was found upregulated even 36,h after hormone treatment. Extensive mass mapping experiments proved this component as an N-terminal truncated form of apolipoprotein A1 (ApoA1), a protein involved in cholesterol transport. The expression profile of ApoA1 analysed by Western blot analysis confirmed a significant and time dependent increase of this ApoA1 fragment. Then, provided that further experiments performed with a growth-promoting schedule will confirm these preliminary findings, truncated ApoA1 may be proposed as a candidate biomarker for steroid boldenone and possibly other anabolic androgens misuse in cattle veal calves, when no traces of hormones are detectable in plasma or urine. [source] Dose-dependent pharmacokinetics of 1-(2-Deoxy- , - D - ribofuranosyl)-2,4-difluoro-5-iodobenzene: A potential mimic of 5-iodo-2,-deoxyuridineBIOPHARMACEUTICS AND DRUG DISPOSITION, Issue 9 2003Panteha Khalili Abstract The dose-range pharmacokinetics of l-(2-deoxy- , - D -ribofuranosyl)-2,4-difluoro-5-iodobenzene (5-IDFPdR), a C -aryl nucleoside mimic of IUdR, were studied in male Sprague-Dawley rats following single intravenous (i.v.) and oral doses. After i.v. administration, the blood clearance decreased from ,32 ml/min/kg at a dose of 15 mg/kg, to ,19 ml/min/kg when dosed at 54 mg/kg, and the elimination half-life increased from 8.4 min to 21.5 min, for the respective doses. While the dose-normalized area under the concentration-time curve (AUCnorm) remained practically unchanged (0.132 kg min ml,1) upon increasing the i.v. dose from 5 to 15 mg/kg, it increased by about 44% (,0.19 kg min ml,1) when the i.v. dose was increased from 15 to 54 mg/kg. Similarly, there was a dose-dependent increase in AUCnorm with increasing oral doses: AUCnorm increased by 49% as the oral dose increased from 20 to 40 mg/kg, and further by 55% as the oral dose was increased from 40 mg/kg to 54 mg/kg. For the respective oral doses, the elimination half-life increased from 24.5 min to 176 min, while blood clearance was reduced from ,37 ml/min/kg to ,17 ml/min/kg. The urinary recoveries of unchanged 5-IDFPdR and its glucuronides (as percent of the dose) were somewhat increased at higher doses. This increase was more pronounced following the highest oral dose. The total biliary recovery of 5-IDFPdR (as percent of the dose) was, however, decreased with increasing doses. The overall kinetic profile of 5-IDFPdR based on these data is suggestive of dose-dependent pharmacokinetics. Decreased elimination of 5-IDFPdR with increasing dose, as supported by longer elimination half-lives at higher doses, is one likely mechanism contributing to the dose-dependent behaviour of this compound. Saturable non-renal metabolism might explain the reduced total body clearance of 5-IDFPdR at higher doses, despite the unchanged or increased urinary clearance. For drugs exhibiting nonlinear kinetics, the dosage regimens may need to be carefully designed to avoid potential unpredictable toxicity and/or lack of pharmacological response associated with the disproportional changes in steady state drug concentrations on changing dose. Manifestation in the rat of nonlinear kinetics at doses of 5-IDFPdR, which may be of therapeutic relevance, warrants extended dose-range evaluations of this compound in future preclinical and clinical studies, to establish safe and efficacious dosage regimens. Copyright © 2003 John Wiley & Sons, Ltd. [source] Extracellular matrix alters the relationship between tritiated thymidine incorporation and proliferation of MC3T3-E1 cells during osteogenesis in vitroCELL PROLIFERATION, Issue 1 2002W. J. Peterson Bone cells in vivo exist in direct contact with extracellular matrix, which regulates their basic biological processes including metabolism, development, growth and differentiation. Thus, the in vitro activity of cells cultured on tissue culture treated plastic could be different from the activity of cells cultured on their natural substrate. We selected MC3T3-E1 pre-osteoblastic cells to study the effect of extracellular matrix on cell proliferation because these cells undergo a progressive developmental sequence of proliferation and differentiation. MC3T3-E1 cells were cultured on plastic or plastic coated with ECM, fibronectin, collagen type I, BSA or poly l -lysine and their ability to proliferate was assessed by incorporation of [3H]dT or by enumeration of cells. Our results show that (1) ECM inhibits incorporation of [3H]dT by MC3T3-E1 cells; (2) collagen type I, but not BSA, poly l -lysine or fibronectin also inhibits incorporation of [3H]dT; (3) the level of ECM inhibition of [3H]dT incorporation is directly related to the number of cells cultured, but unrelated to the cell cycle distribution or endogenous thymidine content; (4) the kinetic profile of [3H]dT uptake suggest that ECM inhibits transport of [3H]dT from the extracellular medium, and (5) cell counts are similar in cultures whether cells are grown on plastic or ECM. These results suggest that decreased incorporation of [3H]dT by cells cultured on ECM is not reflective of bone cell proliferation. [source] Detection of human neutrophil elastase with peptide-bound cross-linked ethoxylate acrylate resin analogsCHEMICAL BIOLOGY & DRUG DESIGN, Issue 4 2005J.V. Edwards Abstract:, An assessment of elastase-substrate kinetics and adsorption at the solid,liquid interface of peptide-bound resin was made in an approach to the solid-phase detection of human neutrophil elastase (HNE), which is found in high concentration in chronic wound fluid. N-succinyl-alanine-alanine-proline-valine- p -nitroanilide (suc-Ala-Ala-Pro-Val- pNA), a chromogenic HNE substrate, was attached to glycine-cross-linked ethoxylate acrylate resins (Gly-CLEAR) by a carbodiimide reaction. To assess the enzyme-substrate reaction in a two-phase system, the kinetic profile of resin-bound peptide substrate hydrolysis by HNE was obtained. A glycine and di-glycine spacer was placed between the resin polymer and substrate to assess the steric and spatial requirements of resin to substrate with enzyme hydrolysis. The enzymatic activities of suc-Ala-Ala-Pro-Val- pNA and suc-Ala-Ala-Pro-Ala- pNA on the solid-phase resin were compared with similar analogs in solution. An increase in visible wavelength absorbance was observed with increasing amounts of substrate-resin and enzyme concentration. Enzyme hydrolysis of the resin-bound substrate was also demonstrated on a polypropylene surface, which was employed for visible absorbance of released chromophore. A soluble active substrate analog was released from the resin through saponification of the ethoxylate ester linkages in the resin polymer. The resin-released conjugate of the HNE substrate demonstrated an increased dose response with increasing enzyme concentration. The synthesis and assay of elastase substrates bound to CLEAR resin gives an understanding of substrate-elastase adsorption and activity at the resin's solid,liquid interface for HNE detection with a solid-phase peptide. [source] Synthesis, DNA-Binding, Cleavage, and Cytotoxic Activity of New 1,7-Dioxa-4,10-diazacyclododecane Artificial Receptors Containing Bisguanidinoethyl or Diaminoethyl Double Side ArmsCHEMISTRY - A EUROPEAN JOURNAL, Issue 34 2007Xin Sheng Abstract Novel 1,7-dioxa-4,10-diazacyclododecane artificial receptors with two pendant aminoethyl (3) or guanidinoethyl (4) side arms have been synthesized. Spectroscopy, including fluorescence and CD spectroscopy, of the interactions of 3, 4, and their copper(II) complexes with calf thymus DNA indicated that the DNA binding affinity of these compounds follows the order Cu2+,4>Cu2+,3>4>3, and the binding constants of Cu2+,3 are Cu2+,4 are 7.2×104 and 8.7×104,M,1, respectively. Assessment by agarose gel electrophoresis of the plasmid pUC,19 DNA cleavage activity in the presence of the receptors showed that the complexes Cu2+,3 and Cu2+,4 exhibit powerful supercoiled DNA cleavage efficiency. Kinetic data of DNA cleavage promoted by Cu2+,3 and Cu2+,4 under physiological conditions fit to a saturation kinetic profile with kmax values of 0.865 and 0.596,h,1, respectively, which give about 108 -fold rate acceleration over uncatalyzed supercoiled DNA. This acceleration is due to efficient cooperative catalysis of the copper(II) center and the functional (diamino or bisguanidinium) groups. In-vitro cytotoxic activities toward murine melanoma B16 cells and human leukemia HL-60 cells were also examined: Cu2+,4 shows the highest activity with IC50 values of 1.62×10,4 and 1.19×10,5,M, respectively. [source] Relationship between delta-like and proneural bHLH genes during chick retinal developmentDEVELOPMENTAL DYNAMICS, Issue 6 2008Branden R. Nelson Abstract Notch signaling in the retina maintains a pool of progenitor cells throughout retinogenesis. However, two Notch-ligands from the Delta-like gene family, Dll1 and Dll4, are present in the developing retina. To understand their relationship, we characterized Dll1 and Dll4 expression with respect to proliferating progenitor cells and newborn neurons in the chick retina. Dll4 matched the pattern of neural differentiation. By contrast, Dll1 was primarily expressed in progenitor cells. We compared Dll1 and Dll4 kinetic profiles with that of the transiently up-regulated cascade of proneural basic helix,loop,helix (bHLH) genes after synchronized progenitor cell differentiation, which suggested a potential role for Ascl1 in the regulation of Delta-like genes. Gain-of-function assays demonstrate that Ascl1 does influence Delta-like gene expression and Notch signaling activity. These data suggest that multiple sources of Notch signaling from newborn neurons and progenitors themselves coordinate retinal histogenesis. Developmental Dynamics 237:1565,1580, 2008. © 2008 Wiley-Liss, Inc. [source] A novel in vitro flat-bed perfusion biofilm model for determining the potential antimicrobial efficacy of topical wound treatmentsJOURNAL OF APPLIED MICROBIOLOGY, Issue 6 2009R.M.S. Thorn Abstract Aims:, To develop an in vitro flat-bed perfusion biofilm model that could be used to determine the antimicrobial efficacy of topically applied treatments. Methods and Results:,Pseudomonas aeruginosa and Staphylococcus aureus biofilms were grown within continuously perfused cellulose matrices. Enumeration of the biofilm density and eluate was performed at various sampling times, enabling determination of the biofilm growth rate. Two antimicrobial wound dressings were applied to the surface of mature biofilms and periodically sampled. To enable real-time imaging of biofilm growth and potential antimicrobial kinetics, a bioluminescent Ps. aeruginosa biofilm was monitored using low-light photometry. Target species produced reproducible steady-state biofilms at a density of c. 107 per biofilm support matrix, after 24-h perfusion. Test dressings elicited significant antimicrobial effects, producing differing kill kinetic profiles. There was a good correlation between photon and viable count data. Conclusions:, The model enables determination of the antimicrobial profile of topically applied treatments against target species biofilms, accurately differentiating bactericidal from bacteriostatic effects. Moreover, these effects could be monitored in real time using bioluminescence. Significance and Impact of the Study:, This is the first in vitro biofilm model which can assess the antimicrobial potential of topical therapies in a dynamic growth environment. [source] Development of a mathematical model for Bacillus circulans growth and alkaline protease production kineticsJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 2 2009Chaganti Subba Rao Abstract BACKGROUND: An unstructured mathematical model was developed to understand information on the relationship between Bacillus circulans growth and metabolism-related protease production (using logistic and Luedeking,Piret equations respectively) in a batch reactor with respect to glucose consumption and fermentation time. The objective was to develop an indispensable tool for the optimisation, control, design and analysis of alkaline protease production. RESULTS: Biomass growth and enzyme production titres changed with a change in substrate concentration. Modelling analysis of biomass and enzyme production titres at different substrate concentrations revealed significant accuracy in terms of statistical consistency and robustness with respect to fermentation kinetic profiles. CONCLUSION: With the B. circulans strain used, an economic protease yield (2837 × 103 U g,1) with respect to biomass and glucose ratio was achieved at low substrate concentration (10 g L,1). The developed model could be effectively utilised for designing, controlling and up-scaling the protease production process in high-density fermentation in selected bioreactors with statistical consistency. Copyright © 2008 Society of Chemical Industry [source] Stereoselective disposition of talinolol in manJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 2 2002Michael Zschiesche Abstract The disposition of the ,-blocking drug talinolol is controlled by P-glycoprotein in man. Because talinolol is marketed as a racemate, we reevaluated the serum-concentration time profiles of talinolol of a previously published study with single intravenous (30 mg) and repeated oral talinolol (100 mg for 14 days) before and after comedication of rifampicin (600 mg per day for 9 days) in eight male healthy volunteers (age 22,26 years, body weight 67,84 kg) with respect to differences in the kinetic profiles of the two enantiomers S(,) talinolol and R(+) talinolol. Additionally, the metabolism of talinolol in human liver microsomes was examined. After oral administration, S(,) talinolol was slightly less absorbed and faster eliminated than R(+) talinolol. The absolute bioavailabilty of the R(+) enantiomer of talinolol was slightly but significantly higher than of its S(,) enantiomer. Coadministration of rifampicin further intensified this difference in the disposition of R(+) and S(,) talinolol (p,<,0.05). Formation of 4-trans hydroxytalinolol was the major metabolic pathway in human liver microsomes. All Clint values of S(,) were higher than of R(+) talinolol; 0.1 ,M ketoconazole inhibited the formation of all metabolites. In conclusion, the stereoselectivity of talinolol disposition is of minor importance, and most likely caused by presystemic biotransformation via CYP3A4. The less active R(+) talinolol might be suitable for phenotyping P-glycoprotein expression in man. © 2002 Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 91:303,311, 2002 [source] Non-aqueous reverse micelles media for the SNAr reaction between 1-fluoro-2,4-dinitrobenzene and piperidine,JOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 12 2006N. Mariano Correa Abstract The kinetics of the nucleophilic aromatic substitution (SNAr) reaction between 1-fluoro-2,4- dinitrobenzene (FDNB) and piperidine (PIP) in ethylene glycol (EG)/ sodium bis (2-ethyl-1-hexyl) sulfosuccinate (AOT)/n -heptane and dimethylformamide (DMF)/AOT/n -heptane non-aqueous reverse micelle systems is reported. EG and DMF were used as models for hydrogen bond donor (HBD) and non-hydrogen bond donor (non-HBD) polar solvents, respectively. The reaction was found not to be base catalyzed in these media. A mechanism to rationalize the kinetic results is proposed in which both reactants may be distributed between the two environments. The distribution constants of FDNB between the organic and each micellar pseudophases were determined by an independent fluorescence method. These results were used to evaluate the amine distribution constant and the intrinsic second-order rate coefficient of the SNAr reaction in the interface. The reaction was also studied in the pure solvents EG and DMF for comparison. The results in EG/AOT/n -heptane at Ws,=,2 give similar kinetic profiles than in water/AOT/n -hexane at W,=,10. With these HBD solvents, the interface saturation by the substrate is reached at around the same value of [AOT] and the intrinsic second-order rate coefficient in the interface, k,b, has comparable values. On the other hand, when DMF is used as a polar non-HBD solvent, the intrinsic second-order rate constant increases by a factor of about 200 as compared to the values obtained using HBD solvents as a polar core. It is concluded that higher catalytic power is obtained when non-HBD solvents are used as polar solvent in the micelle interior. Copyright © 2006 John Wiley & Sons, Ltd. [source] Supported (nBuCp)2ZrCl2 Catalysts: Effects of Selected Lewis Acid Organotin Silica Surface Modifiers on Ethylene PolymerizationMACROMOLECULAR REACTION ENGINEERING, Issue 4 2008Muhammad N. Akhtar Abstract This study investigated the effects of several organotin silica surface modifiers on the ethylene polymerization performance of (nBuCp)2ZrCl2 -based supported catalysts in which MAO and metallocene were sequentially loaded. Each organotin compound acted as a spacer, increasing the catalyst activity. However, the catalyst activity and of the resulting polyethylenes varied as follows: Activity and fractional Sn+ charge: nBuSn(OH)2Cl,>,MeSnCl3,>,nBuSnCl3,>,Reference catalyst; and, : Reference catalyst,>,nBuSnCl3,>,MeSnCl3,>,nBuSn(OH)2Cl. The above catalyst activity rating was explained considering the influence of the Lewis acidity, that is, the fractional Sn+ charge of the organotin modifiers on the generation, concentration, and electron density at the active [(nBuCp)2ZrMe]+ cation. All the catalysts showed fairly stable kinetic profiles and produced narrow molecular weight distribution resins; 2.8,,,PDI,,,3. [source] Field-Flow Fractionation as Analytical Technique for the Characterization of Dry Yeast: Correlation with Wine Fermentation ActivityBIOTECHNOLOGY PROGRESS, Issue 6 2003Ramsés Sanz Important oenological properties of wine depend on the winemaking yeast used in the fermentation process. There is considerable controversy about the quality of yeast, and a simple and cheap analytical methodology for quality control of yeast is needed. Gravitational field flow fractionation (GFFF) was used to characterize several commercial active dry wine yeasts from Saccharomycescerevisiae and Saccharomyces bayanus and to assess the quality of the raw material before use. Laboratory-scale fermentations were performed using two different S. cerevisiae strains as inocula, and GFFF was used to follow the behavior of yeast cells during alcoholic fermentation. The viable/nonviable cell ratio was obtained by flow cytometry (FC) using propidium iodide as fluorescent dye. In each experiment, the amount of dry wine yeast to be used was calculated in order to provide the same quantity of viable cells. Kinetic studies of the fermentation process were performed controlling the density of the must, from 1.071 to 0.989 (20/20 density), and the total residual sugars, from 170 to 3 g/L. During the wine fermentation process, differences in the peak profiles obtained by GFFF between the two types of commercial yeasts that can be related with the unlike cell growth were observed. Moreover, the strains showed different fermentation kinetic profiles that could be correlated with the corresponding fractograms monitored by GFFF. These results allow optimism that sedimentation FFF techniques could be successfully used for quality assessment of the raw material and to predict yeast behavior during yeast-based bioprocesses such as wine production. [source] | |||||||||||||