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At least 883 records · Page 49Linked to original sources
PubMed2004

Development and validation of a method for the purity determination of (3beta,20R)-4,4-dimethylcholesta-8,14,24-trien-3-ol(FF-MAS) in pharmaceutical products containing recombinant human albumin.

A simple and sensitive method has been developed and validated for purity determination of FF-MAS (also known as (3beta,20R)-4,4-dimethylcholesta-8,14,24-trien-3-ol an endogenous substance usually present in the pre-ovulatory follicular fluid) at very low concentrations (200 ng per unit) in pharmaceutical formulations containing RECOMBUMIN (recombinant human albumin) as the matrix. The paper focuses on development of the sample preparation for the product containing recombinant human albumin. After removal of recombinant human albumin by precipitation using a mixture of water and ethanol, the FF-MAS was concentrated by evaporation using a vacuum centrifuge and the prepared sample was analyzed. The purity method was based on a reversed-phase high performance liquid chromatography (RP-HPLC) with ultraviolet absorption detection at 250 nm. The method was validated according to ICH guidelines. The method indicated a significant degree of specificity with good selectivity and no significant effect from the matrix. The limit of detection was found to be 0.3-0.8% (depending on the impurity) corresponding to 1.9-5.1 ng. The limit of quantification was found to be 0.8-2.5% (depending on the impurity) corresponding to 5.2-16 ng. The recovery was found to be between 90 and 101% for the FF-MAS, and 100-129% for the six known impurities. The tested range for FF-MAS was from 320 to 960 ng corresponding to 50-150% of the nominal concentration (640 ng, injection volume is 100 microl). The linearity of each compound (FF-MAS and the six impurities) was investigated. The squared correlation coefficient (r(2)) was 0.999 for FF-MAS (50-150% level) and 0.977-0.998 for the six known impurities (at four levels: 0.20, 0.50, 1.00, 2.00%). The R.S.D. in the repeatability study was found to be 9.2% for the total amount of impurities, and 10.4% for single impurities. The R.S.D. in the intermediate precision study was found to be 10.9% for total impurities, and 12.0% for single impurities. The validation results showed that the method was suitable for the purity analysis. The validated method was then ready for use for samples analysis of phase II clinical studies and the stability investigations of the pharmaceutical product.

Albumins↗
PubMed2006

Effects of Fe-doping on the photocatalytic activity of mesoporous TiO2 powders prepared by an ultrasonic method.

Highly photoactive nanocrystalline mesoporous Fe-doped TiO(2) powders were prepared by the ultrasonic-induced hydrolysis reaction of tetrabutyl titanate (Ti(OC(4)H(9))(4)) in a ferric nitrate aqueous solution (pH 5) without using any templates or surfactants. The as-prepared samples were characterized by thermogravimetry and differential thermal analysis (TG-DTA), X-ray diffraction (XRD), N(2) adsorption-desorption measurements, UV-visible adsorbance spectra (UV-vis) and X-ray photoelectron spectroscopy (XPS). The photocatalytic activities were evaluated by the photocatalytic oxidation of acetone in air. The results showed that all the Fe-doped TiO(2) samples prepared by ultrasonic methods were mesoporous nanocrystalline. A small amount of Fe(3+) ions in TiO(2) powders could obviously enhance their photocatalytic activity. The photocatalytic activity of Fe-doped TiO(2) powders prepared by this method and calcined at 400 degrees C exceeded that of Degussa P25 (P25) by a factor of more than two times at an optimal atomic ratio of Fe to Ti of 0.25. The high activities of the Fe-doped TiO(2) powders could be attributed to the results of the synergetic effects of Fe-doping, large BET specific surface area and small crystallite size.

Catalysis↗
PubMed1982

Liquid chromatography-mass spectrometry in the pharmaceutical industry: objectives and needs.

The role of liquid chromatography-mass spectrometry (LC-MS) in the analysis of drugs is discussed. The main fields of application are thermally labile compounds, compounds with low volatility and compounds with rather high molecular weights, all of which are not generally suitable for analysis by combined gas chromatography-mass spectrometry. The objectives, needs, limitations and abilities of LC-MS for the analysis of by-products, degradation products, traces of drug substances for pharmacokinetic studies and metabolites in complex matrices are presented. The LC-MS coupling is discussed as a sophisticated LC detector for sensitive and selective quantitative determinations or as an on-line sample-introduction system for the mass spectrometer to obtain structural information for identification or structural elucidation. LC-MS combined with a flow-switching technique can be used for the analysis of mixtures containing large amounts of components which otherwise would be detrimental to the LC-MS technique. With flow-injection techniques the LC-MS interface is used as a sample-introduction system with possibilities for sample preparation, sample clean-up and chemical derivatization.

Bromocriptine↗
PubMed2001

New ultrasonically prepared Co-based catalysts for Fischer-Tropsch synthesis.

An extensive study of different preparation methods for Co/SiO2 catalysts is reported in this paper. In addition to the conventional impregnation, other more innovative methods are used including ultrasound. The prepared samples are fully characterized and tested in the CO hydrogenation (Fischer-Tropsch synthesis). The best catalytic performance, both as CO conversion and hydrocarbons selectivity, is shown by one of the sample prepared using ultrasound.

Journal Article↗
PubMed1999

Body composition, water turnover and energy turnover assessment with labelled water.

Our understanding of human energy metabolism has benefited greatly from the application of water labelled with 2H and 18O for the measurement of total body water, water turnover and total daily energy expenditure. Applications include validation of techniques for the assessment of dietary intake and physical activity, assessment of water and energy requirement and the assessment of the effect of dietary and physical activity interventions, including its use with endurance athletes competing at the highest level. Critical aspects of the application are isotope dose preparation, sample collection, sample analysis and the calculation procedure. The labelled-water method can easily be applied in normal living conditions, including exercise, and in the clinical setting. However, sample analysis requires a sophisticated laboratory with an isotope-ratio mass spectrometer and a sample preparation system. Examples of insights based on labelled-water studies are: (1) self-reported dietary intakes often underestimate energy requirements; (2) subjects have problems maintaining energy balance when daily energy expenditure exceeds 2.5 times resting energy expenditure. Devices for the assessment of physical activity validated using labelled water allow the study of activity patterns and strategies to influence the activity level of a sedentary society.

Body Composition↗
PubMed2000

Prestructured MALDI-MS sample supports.

Prestructured MALDI-MS sample supports have been developed that simplify high-throughput analysis of biomolecules and improve the detection sensitivity. The mass spectrometric sample support is coated with a thin layer of hydrophobic Teflon that carries an array of 200-microm gold spots, which provide hydrophilic sample anchors. Each transferred sample droplet contacts one anchor, on top of which, after solvent evaporation, the sample is exclusively deposited due to the strongly water repellent nature of the Teflon surface. The initial matrix concentration is kept low, enabling sample up-concentration by more than 2 orders of magnitudes before crystallization commences. As a result, the detection sensitivity is improved as documented by mass spectra recorded from 100 amol of various peptides, 1 fmol of a DNA 20 mer, and 5 fmol of a 130 bp PCR product. Size and spacing of the hydrophilic anchors are optimized for MALDI-MS performance (sample spot size approximately = laser irradiation spot size), for short analysis times (predetermined sample coordinates), and for high throughput sample preparation (sample anchor array according to the 1536 microtiter plate format).

DNA↗
PubMed2004

Electrowetting-based microfluidics for analysis of peptides and proteins by matrix-assisted laser desorption/ionization mass spectrometry.

A new technique for preparing samples for matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is reported. The technique relies on electrowetting-on-dielectric (EWOD) to move droplets containing proteins or peptides and matrix to specific locations on an array of electrodes for analysis. Standard MALDI-MS reagents, analytes, concentrations, and recipes are demonstrated to be compatible with the technique. Mass spectra are comparable to those collected by conventional methods. Nonspecific adsorption of analytes to device surfaces is demonstrated to be negligible. The results suggest that EWOD may be a useful tool for automating sample preparation for high-throughput proteomics and other applications of MALDI-MS.

Equipment Design↗
PubMed2006

Pressure cell assisted solution characterization of galactomannans. 3. Application of analytical ultracentrifugation techniques.

The pressure heating cell approach previously applied to galactomannans in two earlier studies is now used to prepare samples for characterization using the analytical ultracentrifuge. Sedimentation velocity data were obtained for both guar gum and locust bean gum samples. These were compared to our earlier light scattering and intrinsic viscosity measurements on samples prepared using identical temperature and pressure profiles. A number of methods were then employed to obtain chain persistence lengths, including the Hearst-Stockmayer and Bohdanecky wormlike chain approaches. These results were compared to earlier results obtained using methods appropriate for excluded volume coil and rodlike chains, respectively.

Carbohydrate Sequence↗
PubMed2004

CO oxidation on Aun/TiO2 catalysts produced by size-selected cluster deposition.

Planar model catalysts were prepared by deposition of size-selected gold clusters containing up to seven atoms on rutile TiO2 (110). Molecular oxygen is observed to bind inefficiently to the surface, probably at oxygen vacancies, and some oxygen also appears to bind to the gold clusters. Stable CO binding is observed atop gold for catalysts prepared by Au and Au2 deposition, but not for larger Aun. CO oxidation activity is strongly dependent on cluster size, with Au7-prepared samples >50 times more reactive than samples prepared by Au or Au2 deposition

Journal Article↗
PubMed2005

Rapid screening of wood chemical component variations using transmittance near-infrared spectroscopy.

A rapid transmittance near-infrared (NIR) spectroscopy method was developed to predict the variation in chemical composition of solid wood. The effect of sample preparation, sample quantity (single versus stacked multiple wood wafers), and NIR acquisition time on the quantification of alpha-cellulose and lignin content was investigated. Strong correlations were obtained between laboratory wet chemistry values and the NIR-predicted values. In addition to the experimental protocol and method development, improvements in calibration error associated with utilizing stacked multiple wood wafers as opposed to single wood wafers are also discussed.

Cellulose↗
PubMed1998

Determination of the NMR structure of the complex between U1A protein and its RNA polyadenylation inhibition element.

RNA-protein recognition is critical to post-transcriptional regulation of gene expression, yet poorly understood at the molecular level. The relatively slow progress in understanding this important area of molecular biology is due to difficulties in obtaining good-quality crystals and derivatives, and in preparing samples suitable for NMR investigation. The determination of the structure of the complex between the human U1A protein and its polyadenylation inhibition element is described here. In this paper, we describe the sample preparation, spectral assignments, construction of the NOE-based distance constraints and methodology for calculating the structure of the complex. The structure was determined to an overall precision of 2.03 A (for all ordered regions), and 1.08 A for the protein-RNA interface. The patterns of hydrogen bonding and hydrophobic interactions at the interface were analysed statistically using the final ensemble of 31 structures.

Amino Acid Sequence↗
PubMed2006

Fluorescence in-situ hybridisation on biopsies from clam ileocystoplasties and on a clam cancer.

The incidence of carcinoma following an enterocystoplasty increases with time and is a major concern after such procedures. The aim of this study was to investigate genetic instability (in the form of numerical chromosomal aberrations) at the enterovesical anastomosis in patients who had undergone a clam ileocystoplasty using fluorescent in-situ hybridisation (FISH). Fluorescent in-situ hybridisation was performed on touch preparation samples prepared from fresh endoscopic biopsies obtained from the enterovesical anastomosis and native bladder remnant (control specimens) of 15 patients who had undergone a clam ileocystoplasty. Fluorescent in-situ hybridisation was also performed on one squamous cell cancer specimen. Significant aneusomic changes were found at the enterovesical anastomosis in all 15 patients. Alterations in chromosome 18 copy number were the most frequent abnormal finding (trisomy 18, n=8; monosomy 18, n=7). Nine patients were monosomic for chromosome 9. Isolated monosomy 8 and trisomy 8 were each found in one patient. The control specimens were all normal. An unusually high incidence of polysomic cells was found in the clam tumour specimen, reflecting the aggressive nature of this cancer. Chromosomal numerical abnormalities occur at the enterovesical anastomosis following a clam ileocystoplasty and chromosome 18 appears to be a particularly good marker of genetic instability. The results of this study indicate that morphologically normal tissue obtained from the enterovesical anastomosis displays evidence of chromosomal instability that may predispose to tumour formation. However, further prospective, blinded, longitudinal studies are required to establish whether predetermined FISH signal patterns in enterocystoplasty cells in urine or obtained by biopsy predict the presence or absence of tumour.

Adult↗
PubMed1980

Determination of selenium in tissues, serum, and blood of wild rodents by graphite furnace atomic absorption spectrophotometry.

Selenium (Se) levels were determined in liver, kidney, blood, and serum of wild rodents using graphite furnace atomic absorption spectrophotometry. A simple wet digestion technique was used to prepare samples for analysis. Nickel nitrate was used to suppress volatilization of Se during the char stage. Compared to existing techniques this greatly reduces the effort and time required for sample preparation and allows use of the graphite furnace atomic absorption technique for Se determination.

Animals↗
PubMed1977

Double-antibody solid-phase enzyme immunoassay for the detection of staphylococcal enterotoxin A.

A simple double-antibody enzyme immunoassay that uses a microtechnique was developed for detecting staphylococcal enterotoxin A in food products. Sample preparation can be completed in less than 15 min. Assay sensitivity ranges from 0.4 ng (20-h test time) to 3.2 ng (1- to 3-h test time) of toxin per ml of prepared sample. Separation and detection of enterotoxin from spiked food products ranged between 72 and 98% of the amount added.

Enterotoxins↗
PubMed2006

Microarray analysis in drug discovery and clinical applications.

DNA microarray analyzes genome-wide gene expression patterns and is used in many areas including drug discovery and clinical applications. This chapter summarizes some of these applications such as identification and validation of anti-infective drug target, study mechanisms of drug action and drug metabolism, classification of different types of tumors, and use of molecular signatures for prediction of disease outcome. A step-by-step protocol is provided for sample preparation, sample labeling and purification, hybridization and washing, feature extraction, and data analysis. Important considerations for a successful experiment are also discussed with emphasis on drug discovery and clinical applications. Finally, a clinical study is presented as an example to illustrate how DNA microarray technology can be used to identify gene signatures, and to demonstrate the promise of DNA microarray as a clinical tool.

Computational Biology↗
PubMed2000

Nuclear volume estimation using different sampling, measurement and calculation methods.

OBJECTIVE: To study the reliability of volume parameter measured on tissue sections through different sampling, measurement and calculation methods. STUDY DESIGN: The largest nuclear profile image under a 100x, NA 1.30 oil immersion objective of primary spermatocytes and spherical spermatoblasts on 11-micron-thick seminiferous tubule sections and tissue images, under a 20x objective, on 4-micron sections were captured. Their volumes were measured and calculated by the five methods provided by the Technology for Image and Graphics Engineering Research cell image analysis system. RESULTS: The nuclear volumes obtained by nucleator and area equivalent diameter on the largest nuclear profile image were almost the same, including binary images by automated and manual interactive nucleator and grey scale images only by the latter. Nuclear volumes, calculated by random Feret diameter and equivalent diameter of the perimeter, the minimal circumference of the largest nuclear profile binary image, were obviously larger than those of the nucleator and area equivalent diameter. Due to different-sized nuclear slices entrapped in the same section, those nuclear volumes from the seminiferous tubule tissue images were strikingly lower than that of the largest nuclei profile image. The shape factors of primary spermatocytes and spherical spermatoblast nuclei under 100x and 20x objectives were approximately the same. CONCLUSION: The sample preparation, sampling methods and calculation formulas suitable to nuclear form are necessary to obtain reproducible volume parameters.

Animals↗
PubMed1988

[Methods of quick-freezing and cryosubstitution of biological tissues in analytical ion microscopy].

The localization and relative concentration of diffusible ions (Li+, K+) or bound but easily displaceable ions (Ca2+) have been studied in myocardium prepared by rapid-freeze fixation and compared with results from chemically prepared samples. Contrary to chemical fixation which gives diffused potassium imaging, cryofixation enables elemental precise mapping in cellular compartment. Bound displazable external calcium, extracted by chemical fixation, is visualized after rapid-freeze fixation. Its localization is distinguished by a bright cellular outline, which corresponds to the glycocalix. Intracellular calcium is less emissive and has the same distribution and concentration whatever the sample preparation. Very movable and present at low concentration in tissues, lithium is localized after rapid-freeze fixation. Those qualitative and quantitative results show the adequation of rapid freeze fixation and freeze substitution to the study of diffusible ions by means of analytical ion microscopy.

Animals↗
PubMed1996

Analysis of low-dose benzodiazepines by HPLC with automated solid-phase extraction.

We describe a simple, specific, and sensitive reversed-phase HPLC method with automated solid-phase extraction (SPE) for analyzing alprazolam, clonazepam, and nitrazepam concentrations in human serum or plasma. We prepare samples and calibrators with an automated sample preparer, using 100-mg Bond-Elut C18 SPE columns. The HPLC method uses isocratic elution with acetonitrile:methanol:dipotassium hydrogen phosphate, 10 nmol/L, pH 3.7 (30:2:100 by vol), at a flow rate of 1.5 mL/min to separate the drugs. We detect the benzodiazepines with diode-array detector at 240 nm; analyses of peak purity are performed at 210-365 nm. The recoveries were between 94% and 100%. The intraassay and interassay CVs were between 1.0% and 4.1%. The detection limit is 5 nmol/L. The antiepileptic and antidepressant drugs tested did not interfere with the assay. We developed the method for use in a clinical laboratory for therapeutic drug monitoring.

Alprazolam↗