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Results for “sensitivity analysis”

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At least 307 records · Page 17Linked to original sources
PubMed2003

High-sensitivity analysis of serum C-reactive protein in young patients with lumbar disc herniation.

We measured the serum concentration of C-reactive protein (CRP) by a high-sensitive method in patients with lumbar disc herniation. There were 48 patients in the study group and 53 normal controls. The level and type of herniation were evaluated. The clinical data including the neurological findings, the angle of straight leg raising and post-operative recovery as measured by the Japanese Orthopaedic Association (JOA) score, were recorded. The high-sensitive CRP (hs-CRP) was measured by an ultrasensitive latex-enhanced immunoassay. The mean hs-CRP concentration was 0.056 +/- 0.076 mg/dl in the patient group and 0.017 +/- 0.021 mg/dl in the control group. The difference was statistically significant (p = 0.006). There was no other correlation between the hs-CRP concentration and the level and type of herniation, or the pre-operative clinical data. A positive correlation was found between the concentration of hs-CRP before operation and the JOA score after. Those with a higher concentration of hs-CRP before operation showed a poorer recovery after. The significantly high concentration of serum hs-CRP might indicate a systemic inflammatory response to impingement of the nerve root caused by disc herniation and might be a predictor of recovery after operation.

Adolescent↗
PubMedDate not supplied

High-sensitivity analysis of human plasma proteome by immobilized isoelectric focusing fractionation coupled to mass spectrometry identification.

Immobilized pH gradients isoelectric focusing (IPG-IEF) is the first dimension typically used in two-dimensional gel electrophoresis (2-DE). It can also be used on its own in conjunction with tandem mass spectrometry (MS/MS) for the analysis of proteins. Here, we described a strategy combining isoelectric focusing in immobilized pH gradient strips, and mass spectrometry to create a new high-throughput and sensitive detection method. Protein mixture is separated by in-gel IEF, then the entire strip is cut into a set of gel sections. Proteins in each gel section are digested with trypsin, and the resulted peptides are subjected to reversed-phase high performance liquid chromatography followed by electrospray-linear ion-trap tandem mass analysis. Using this optimized strategy, we have identified 744 distinct human proteins from an IPG strip loaded only 300 microg of plasma proteins. When compared with other works in published literatures, this study offered a more convenient and sensitive method from gel to mass spectrometry for the separation and identification proteins of complex biological samples.

Adult↗
PubMed2005

Highly sensitive analysis of the anti-tumor agent 1-[4-(furo[2,3-b]-quinolin-4-ylamino)phenyl]ethanone in rat plasma by high-performance liquid chromatography using electrochemical detection.

A sensitive high-performance liquid chromatography method with electrochemical detection was developed for the purpose of determining the concentration of the new anti-tumor agent 1-[4-(furo[2,3-b]-quinolin-4-ylamino)phenyl]ethanone (FQPE) in rats. The plasma samples were spiked with the internal standard diclofenac and extracted using dichloromethane. A C(18) 250 mm x 4mm column was used for the separation of analyte with a mobile phase consisting of 50% acetonitrile and 50% pH 3.0 of sodium 1-pentansulfonate solution at a flow rate of 1.0 mL/min. FQPE was detected by electrochemical detector at 1.0 V and 20 nA. Intra-day and inter-day precision and accuracy were acceptable down to the limit of quantization of 1 ng/mL. The lower limit of detection (LOD) was 0.5 ng/mL. The pharmacokinetic parameters of FQPE in rats after intravenous administration of 2.1 and 4.2 mg/kg were determined. The apparent volume of distribution, half-life of elimination, and clearance showed no significant difference between the two dosages. The area under the plasma concentration time curve increased proportionally with dose. The half-life of FQPE was prolonged about 2.4-fold, compared with amsacrine.

Amsacrine↗
PubMed2003

Sensitivity analysis of radionuclide migration in compacted bentonite: a mechanistic model approach.

Mechanistic model calculations for the migration of Cs, Ra, Am and Pb in compacted bentonite have been carried out to evaluate sensitivities with respect to different parameter variations. A surface chemical speciation/electric double layer model is used to calculate: (i) porewater composition and radionuclide speciation in solution and at the bentonite surface, yielding the distribution of mobile and sorbed species and (ii) interaction of diffusing species with negatively charged pore walls to obtain diffusion parameters. The basic scenario considers the interaction of compacted bentonite with a fresh-type groundwater; variations include the presence of bentonite impurities and saline groundwater. It is shown that these scenarios result in significant variations of porewater composition that affect migration via three mechanisms that can partly compensate each other: (1) effects on sorption through radionuclide complexation in solution, and competition of major cations for surface sites; (2) changes in radionuclide solution speciation leading to different diffusing species under different conditions; (3) effects on diffusion through changes in the electric double layer properties of the clay pores as a function of ionic strength.

Aluminum Silicates↗
PubMed2006

High sensitivity analysis of amyloid-beta peptide composition in amyloid deposits from human and PS2APP mouse brain.

Cortical amyloid-beta (Abeta) deposition is considered essential in Alzheimer's disease (AD) and is also detectable in nondemented individuals with pathologic aging (PA). The present work presents a detailed analysis of the Abeta composition in various plaque types from human AD and PA cases, compared with plaque Abeta isolated from PS2APP mice. To determine minute amounts of Abeta from 30 to 50 laser-dissected amyloid deposits, we used a highly sensitive mass spectrometry procedure after restriction protease lysyl endopeptidase (Lys-C) digestion. This approach allowed the analysis of the amino-terminus and, including a novel ionization modifier, for the first time the carboxy-terminus of Abeta at a detection limit of approximately 200 fmol. In addition, full length Abeta 40/42 and pyroglutamate 3-42 were analyzed using a highly sensitive urea-based Western blot procedure. Generally, Abeta fragments were less accessible in human deposits, indicative of more posttranslational modifications. Thioflavine S positive cored plaques in AD were found to contain predominantly Abeta 42, whereas thioflavine S positive compact plaques and vascular amyloid consist mostly of Abeta 40. Diffuse plaques from AD and PA, as well as from PS2APP mice are composed predominantly of Abeta 1-42. Despite biochemical similarities in human and PS2APP mice, immuno-electron microscopy revealed an extensive extracellular matrix associated with Abeta fibrils in AD, specifically in diffuse plaques. Amino-terminal truncations of Abeta, especially pyroglutamate 3-40/42, are more frequently found in human plaques. In cored plaques we measured an increase of N-terminal truncations of approximately 20% between Braak stages IV to VI. In contrast, diffuse plaques of AD and PA cases, show consistently only low levels of amino-terminal truncations. Our data support the concept that diffuse plaques represent initial Abeta deposits but indicate a structural difference for Abeta depositions in human AD compared with PS2APP mice already at the stage of diffuse plaque formation.

Aged, 80 and over↗
PubMed2001

Use of rosaniline hydrochloride dye for atmospheric SO2 determination and method sensitivity analysis.

The para-rosaniline hydrochloride (PRA) dye-based manual method (P. W. West and G. C. Gaeke, Anal. Chem., 1956, 28, 1816) is widely used for sulfur dioxide measurements in the atmosphere, particularly in developing countries. In this investigation, the properties of a less costly, rosaniline hydrochloride (RA) dye were found to be similar to those of the PRA dye, and showed no significant variation in atmospheric SO2 determination. Furthermore, the sensitivity of various operational parameters to slight changes similar to those encountered during normal use in the different stages of monitoring, namely sample collection and chemical analysis, was evaluated using both dyes, and the deviations in the method response from the reference parameter value were quantified. The method was found to be highly sensitive to the amount of reagent (HCHO and dye) addition in SO2 exposed samples for colorimetric determination. Therefore, utmost care is required in the preparation of reagents and in the addition of the appropriate amount of reagents during chemical analysis in order to obtain the actual concentrations of SO2 in the atmosphere.

Air Pollutants↗
PubMed1986

Sensitive analysis of blood for amodiaquine and three metabolites by high-performance liquid chromatography with electrochemical detection.

A high-performance liquid chromatographic method using oxidative electrochemical detection has been developed for selective and sensitive quantification of the antimalarial drug amodiaquine and three of its metabolites in the blood of dosed individuals. The method requires only one extraction step and has detection limits of 1 ng/ml for amodiaquine and its metabolites desethylamodiaquine and bisdesethylamodiaquine and 3 ng/ml for 2-hydroxydesethylamodiaquine. Minor modification of the mobile phase preserves the chromatographic separation and allows ultraviolet spectroscopic detection, which, although appreciably less sensitive, permits monitoring of levels of amodiaquine and the three metabolites in blood and urine samples if an electrochemical detector is unavailable. Levels of amodiaquine and the three metabolites were determined for two volunteers undergoing a nine-week chemoprophylactic regimen in connection with travel to a malarious area. Data are included to compare the in vitro antimalarial activities against three strains of Plasmodium falciparum of amodiaquine and the three metabolites considered.

Amodiaquine↗
PubMed2000

Sensitivity analysis of a physiological model for 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD): assessing the impact of specific model parameters on sequestration in liver and fat in the rat.

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has dose-dependent tissue distribution because of induction of CYP1A2, a TCDD-binding protein, in the liver. Induction requires transcriptional activation of the CYP1A2 gene product by TCDD and the Ah receptor. An empirical model for dose-dependent distribution (Carrier et al., 1995, Toxicol. Appl. Pharmacol. 131, 253-266) included two simple descriptors: one for the maximum liver sequestration (Fmax) and the other for body burden leading to half maximum sequestration (Kd). Physiologically based pharmacokinetic (PBPK) models include specific parameters for protein receptors, protein binding, tissue solubility, and protein induction. We have applied a PBPK model to define two macroscopic constants related to these dose-response curves, i.e., the inflection point, and the maximum values of these curves. The dose-response curves generated from the PBPK model were for the proportion sequestered in liver and the liver to fat concentration ratio. Our analysis assessed the specific biological factors in the PBPK model that governed the values of these two macroscopic constants. For the fraction in liver, the Hill coefficient (a shape exponent describing the relationship between the Ah receptor-TCDD complex with the DNA receptor) resulted in the largest shift in inflection when using PBPK model parameters specific for TCDD. For the liver to fat ratio, the inflection point was most affected by the number of available Ah receptors. Conventional normalized sensitivity coefficients for the liver-to-fat ratio at the maximum were highest for the fat-to-blood partition coefficient, CYP1A2 binding affinity, and maximum extent of induction of CYP1A2. A similar pattern was observed for the liver fraction, except that the sensitivity coefficients were much smaller. The behavior of different TCDD congeners was evaluated by altering the value of key parameters. Our results demonstrate that the inflection point is more related to characteristics of DNA binding/induction steps of the Ah receptor-DNA complex than by the CYP1A2 affinity of TCDD or concentrations of CYP1A2. Surprisingly, the maximum is more sensitive to changes in CYP1A2 concentrations and affinity for TCDD. In addition, the analysis showed that the liver-to-fat ratio is a more useful experimental measure than is proportion in liver because the ratio responds with similar sensitivity over a much wider range of input parameters.

Adipose Tissue↗
PubMed2002

The decoupled direct method for sensitivity analysis in a three-dimensional air quality model--implementation, accuracy, and efficiency.

The decoupled direct method (DDM) has been implemented in a three-dimensional (3D) air quality model in order to calculate first-order sensitivities with respect to emissions and initial and boundary concentrations. This required deriving new equations for the sensitivities from the equations of the hybrid chemistry solver and the nonlinear advection algorithm in the model. The sensitivities for the chemistry and advection steps were tested in box-model and rotating-hill simulations, respectively. The complete model was then applied to an ozone episode of the Lake Michigan region during July 7-13, 1995. The DDM was found to be highly accurate for calculating the sensitivity of the 3D model. The sensitivities obtained by perturbing the inputs (brute-force method) converged toward the DDM sensitivities, as the brute-force perturbations became small. Ozone changes predicted with the DDM sensitivities were also compared to actual changes obtained from simulations with reduced inputs. For 40% reductions in volatile organic compound and/or NOx emissions,the predicted changes correlate highly with the actual changes and are directionally correct for nearly all grid cells in the modeling domain. However, the magnitude of the predicted changes is 10-20% smaller than the actual changes on average. Agreement between predicted and actual ozone changes is better for 40% reductions in initial or boundary concentrations. Calculating one sensitivity by the DDM is up to 2.5 times faster than calculating the concentrations alone.

Air Movements↗
PubMed2003

Sensitive analysis of alkyl alcohols as decomposition products of alkyl nitrites in human whole blood and urine by headspace capillary GC with cryogenic oven trapping.

The abuse of alkyl nitrites is becoming a serious social problem worldwide. In this report, a simple and sensitive method is presented for the determination of n-butyl alcohol, isobutyl alcohol, and isoamyl alcohol as decomposition products of alkyl nitrites in human whole blood and urine samples using capillary gas chromatography (GC) with cryogenic oven trapping. After heating a whole blood or urine sample containing each alkyl alcohol and t-butyl alcohol [the internal standard (IS)] in a 7-mL vial at 55 degrees C for 15 min, 5 mL of the headspace vapor is drawn into a gas-tight syringe and injected into a GC inlet port. The vapor is introduced into an Rtx-BAC2 medium-bore capillary column in the splitless mode at 0 degrees C oven temperature in order to trap the entire analytes, and then the oven temperature is programmed up to 240 degrees C for the GC measurements by flame ionization detection. These conditions give sharp peaks for each compound and the IS and low background noise for whole blood or urine samples. The detection limits of the analytes are 10 ng/mL for whole blood and 5 ng/mL for urine. Linearity and precision are also tested to confirm the reliability of this method. Isobutyl alcohol and methemoglobin could be determined from the whole blood samples of three male volunteers who had sniffed isobutyl nitrite.

Alcohols↗
PubMed2006

Sensitive analysis of aconitine, hypaconitine, mesaconitine and jesaconitine in human body fluids and Aconitum tubers by LC/ESI-TOF-MS.

The Aconitum species (Ranunculaceae) are widely distributed in northern Asia and North America. Their roots are popularly used in herbal medicines in China and Japan. Many cases of accidental, suicidal and homicidal intoxication with this plant have been reported; some of these were fatal because the toxicity of Aconitum is very high. It is thus important to detect and quantify Aconitum alkaloids in body fluids, with high sensitivity. We have developed a simple and sensitive method for measuring four kinds of Aconitum alkaloids (aconitine, hypaconitine, jesaconitine and mesaconitine) by LC/electrospray (ESI)-time-of-flight (TOF)-MS. For all of them, only molecular ions were observed at an orifice voltage of 75 V; at 135 V, base peaks corresponding to [M - 60 + H]+ ions were observed. These four compounds and methyllycaconitine (internal standard) in human plasma samples were purified by solid-phase extraction. The four extracted compounds were completely separated in mass chromatograms; the calibration curves showed good linearity in the range 10-300 ng/ml, and the detection limits were estimated to be 0.2-0.5 ng/ml. Using our method, we also determined the amounts of these compounds in tuber samples. The present method is applicable in clinical and forensic toxicology.

Aconitine↗
PubMed1999

Sensitive analysis of recombination activity using integrated cell surface reporter substrates.

BACKGROUND: Recombination processes play a crucial role in the functioning of the immune system and are also involved in mutation events that result in various malignancies. So far the study of recombination activity has frequently relied on the use of reporter substrates that are limited by low sensitivity as well as tedious and distorting readout procedures. METHODS: Immunoglobulin class switch recombination substrates were generated which, upon recombination, resulted in the surface expression of human CD4 or murine MHC class I H-2K(k) and thus allowed for cytometric evaluation. RESULTS: Recombining cells harboring integrated reporter substrates were analyzed by immunofluorescence and flow cytometry and could easily be isolated by high-gradient magnetic cell sorting (MACS). The analysis was not influenced by cloning efficiencies, as would be the case after drug selection, or prokaryotic recombination that might occur after analysis of recovered substrates in bacteria. In addition, cytometric readout is much faster, as it can be performed immediately after recombination. The substrate exhibited properties compatible with the detection of immunoglobulin class switch recombination and permitted the detection of recombination events down to 10(-5) per cell and generation. CONCLUSIONS: The high sensitivity of this system allows precise detection of very rare recombination events and thus permits the study of cell types with extremely low recombination activities.

Animals↗
PubMed2006

Parametric sensitivity analysis applied to a specific one-dimensional internal bone remodelling problem.

The relative importance of the various parameters in inducing bone mass loss and osteoclastic perforations is still controversial. Therefore, there is a significant motivation to better understand the parameters behind such dynamic response, and great interest to carry out a parametric sensitivity study as it can provide useful information. As an application, the widely-accepted bone remodelling equation [M.G. Mullender, R. Huiskes, H. Weinans, A physiological approach to the simulation of bone remodeling as self organizational control process, J. Biomech. 27 (1994) 1389.] is investigated using the "n units" model [M. Zidi, S. Ramtani, Bone remodeling theory applied to the study of n unit-elements model, J Biomech. 32 (1999) 743.]. This analysis pointed out that the power in the modulus density relationship p and the power to which density is raised in normalizing the energy stimulus q, known as strongly implicated in the stability condition of the remodelling process, were also stated as insensitive parameters in the bone loss area.

Biomechanical Phenomena↗
PubMed2002

Automated design and sensitivity analysis of wavelengh-division multiplexing filters.

An automated approach to the design of wavelength-division multiplexing (WDM) filters is based on the combination of ideas from classical design approaches with an integer optimization technique. This approach turns out to be extremely efficient from a computational point of view and makes it possible to construct a set of significantly different filter designs with nearly equivalent spectral properties. The sensitivity of WDM filters is analyzed by a computer simulation of the deposition process with turning-point optical monitoring. This analysis enables the designer to compare feasibility properties of various filter designs.

Journal Article↗
PubMed2001

[Classification of urogenital tract infection in 518 cases and drug sensitivity analysis].

In 518 cases with urogenital tract infection detected with mycoplasma identification susceptibility testing reagent box, 308 cases (59.4%) were infected by ureaplasma urealyticum (Uu), 21 cases (4.1%) were infected by mycoplasma hominis (Mh), and 189 cases (36.5%) were infected by both Uu and Mh. Drug sensitivity to the macrolides (erythromycin, roxithromycin, josamycin, azithromycin), the tetracyclines (doxycycline, minocin), and the quinolines (ofloxacin, ciprofloxacin) were detected at the same time. The results showed that the sensitivity to various antibiotics in Uu infection was different from that in Mh infection. Macrolides were more sensitive for Uu infection, and quinolines were more sensitive for Mh infection, while the mixed infection of Mh and Uu had resistance to most antibiotics.

Adolescent↗
PubMed2000

Rapid and sensitive analysis of azadirachtin and related triterpenoids from Neem (Azadirachta indica) by high-performance liquid chromatography-atmospheric pressure chemical ionization mass spectrometry.

Based on reversed-phase high-performance liquid chromatography (RP-HPLC) and atmospheric pressure chemical ionization (APCI) mass spectrometry, a HPLC-MS method was developed to permit the rapid qualitative and quantitative analysis of azadirachtin and related tetranortriterpenoids from seeds and tissue cultures of Neem (Azadirachta indica). APCI+ standard scanning mass spectra of the major Neem triterpenoids were recorded and utilized to select suitable ions for selected ion monitoring (SIM). Transitions for selective reaction monitoring (SRM) were based on MS-MS experiments. Using SIM, major Neem triterpenoids were detected in callus culture material and seed kernels of A. indica. The limit of detection for azadirachtin in extract samples (approximately 1 ng ml(-1) or 10 pg in SIM mode) was determined to be (with respect to injected absolute amounts) approximately 1000-times lower than values quoted in the literature for existing HPLC methods (approximately 200 ng ml(-1) or 10 ng). In addition to high sensitivity, the HPLC-MS method is able to tolerate minimal sample preparation and purification, dramatically reducing total analysis time.

Atmospheric Pressure↗