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At least 469 records · Page 26Linked to original sources
PubMed1993

Sample cleanup by solid-phase extraction for the ultratrace determination of polychlorinated dibenzo-p-dioxins and dibenzofurans in biological samples.

A sample cleanup method for the isolation of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) by solid-phase extraction is described. A C18 bonded silica cartridge is used for the initial extraction and enrichment of the analytes. Subsequent cleanup is achieved with a dual-cartridge arrangement consisting of a bonded benzenesulfonic acid cartridge in series with a silica cartridge. A Florisil cartridge is employed for the final cleanup step. Sample preparation procedures used for blood plasma and animal tissues are described. The precision and accuracy of the method is validated by determining recoveries of 2,3,7,8-substituted PCDD and PCDF congeners spiked at various levels in blood plasma and in animal tissues. The effectiveness of the cleanup method is shown by the analysis of wild bird eggs which are highly contaminated with a variety of pesticides and polychlorinated biphenyls. The application of this cleanup method to human plasma containing PCDDs/PCDFs at parts-per-quadrillion levels and results of analyses by high-resolution mass spectrometry and low-resolution mass spectrometry are presented. The validity of this method is demonstrated by the comparable results obtained from this method and from other established methods.

Animals↗
PubMed2005

Integrated sample processing system involving on-column protein adsorption, sample washing, and enzyme digestion for protein identification by LC-ESI MS/MS.

An automated system has been developed for protein identification using mass spectrometry that incorporates sample cleanup, preconcentration, and protein digestion in a single stage. The procedure involves the adsorption of a protein or a protein mixture from solution onto a hydrophobic medium that is contained within a microcolumn. The protein is digested while still bound to the hydrophobic support. The peptides are then eluted from surface digestion to an electrospray ionization mass spectrometer for detection and sequencing. The entire system is fully automated wherein the mass spectrometer is collecting data continuously. We demonstrate that this system is capable of identifying standard protein samples at concentrations down to 100 nM. Further development of this technique may offer a potential solution for proteomics applications that require unattended operation, such as on-line monitoring and identification of microorganisms on the basis of the detection of their protein biomarkers.

Adsorption↗
PubMed2004

An investigation of liquid carryover and sample residual for a high-throughput flow cytometer sample delivery system.

The phenomenon of intersample contamination in air-segmented continuous-flow assays has been studied for many years, and new uses are being found for these sampling techniques every day. One application that has been developed recently employs a flow cytometer to conduct high-throughput screening assays of biological compounds. We have explored the sources of intersample contamination in the system and shown how methods developed previously can be applied to describe these phenomena. Using a simple model, we were able to accurately measure liquid film thickness in the sample tubing and demonstrate the effects of intersample contamination in a flow cytometer assay. Also, measures have been taken to reduce the level of intersample contamination in cytometric screening assays, helping to make the system a more viable tool for drug screening applications.

Capillaries↗
PubMedDate not supplied

Monitoring a complex medium fermentation with sample-sample two-dimensional FT-NIR correlation spectroscopy.

The possibility of monitoring state transitions during the time course of a fermentation through the analysis of the on-line collected near-infrared (NIR) spectra with sample-sample two-dimensional correlation spectroscopy (SS-2DCoS) was investigated. SS-2DCoS has proved to be useful for extracting process information directly from the spectra collected on-line. The complexity of the system studied prevented the extraction of concentration profiles, but nevertheless, the application of SS-2DCoS enables the identification of fermentation state transitions due to metabolic and morphological changes of the microorganism.

Cells, Cultured↗
PubMed2004

Classification of wine and alcohol vinegar samples based on near-infrared spectroscopy. Feasibility study on the detection of adulterated vinegar samples.

Near-infrared (NIR) spectroscopy was used to discriminate between wine vinegar (red or white) and alcohol vinegar. One orthogonal signal correction method (OSC) was applied on a set of 73 vinegar NIR spectra from both origins and artificial blends made in the laboratory in order to remove information unrelated to a specific chemical response (tartaric acid), which was selected due to its high discriminant ability to differentiate between wine vinegar and alcohol vinegar samples. These corrected NIR spectra, as well as raw NIR spectra and 14 physicochemical variables, were used to develop separate classification models using the potential functions method as a class-modeling technique. The aforementioned models were compared to evaluate the suitability of NIR spectroscopy as a rapid method for discriminating between vinegar origins. The transformation of vinegar NIR spectra by means of an orthogonal signal correction method prompted a notable improvement in the specificity of the constructed classification models. The classification model developed was then applied to artificial vinegar blends made in the laboratory to test its capacity to recognize adulterated vinegar samples.

Acetic Acid↗
PubMed1992

Monkeys (Macaca fascicularis) with rhinal cortex ablations succeed in object discrimination learning despite 24-hr intertrial intervals and fail at matching to sample despite double sample presentations.

Six cynomolgus monkeys (Macaca fascicularis) learned preoperatively a set of 10 concurrent object discriminations with 24-hr intertrial intervals. Three then had the rhinal cortex removed bilaterally, whereas the other 3 remained as unoperated controls. The animals with ablations were impaired in reacquiring the preoperatively acquired set but subsequently learned without any impairment a new set of 10 discriminations that was presented in the same way. The monkeys with rhinal cortex ablations then failed to learn delayed matching to sample, with double sample presentations, in 510 trials, whereas the control animals learned this task in 270 trials on average. The results add to existing evidence that rhinal cortex ablation produces a severe impairment in visual short-term recognition memory and show for the first time that this impairment is accompanied by normal long-term discrimination learning ability.

Animals↗
PubMed2002

Dental arch space and permanent tooth size in the mixed dentition of a skeletal sample from the 14th to the 19th centuries and 3 contemporary samples.

Dental arch space and permanent tooth size in the mixed dentition were studied in 4 cohorts: (1) 48 skulls from the 14th to the 19th centuries from The Schreiner Collection in the Department of Anatomy, University of Oslo; (2) 39 boys and 34 girls of Sami origin born in the 1980s living in northern Norway; (3) 31 boys and 30 girls born in the 1960s living in southern Norway; and (4) 32 boys and 26 girls born in the 1980s living in the same part of southern Norway as the previous group. The sexes were unknown in the skeletal sample, and the groups were analyzed with the sexes pooled. The crown sizes of the permanent teeth in the mixed dentition of the Norwegian children who had lived between the 14th and the 19th centuries were smaller than those of contemporary children living in the same country. Probable reasons for this increase in tooth size include improved nutrition and reduced morbidity, because this study ruled out attrition as a major cause of the discrepancy in tooth size. The relative space (arch perimeter minus tooth size) in the group born in the 1960s deviated from that in the other 3 groups, indicating a greater degree of crowding in this group. The relative space in the skulls did not differ significantly from that in the groups born in the 1980s. This means that the improved caries situation during the last decades has changed the dental arch space in these populations. The irregularity index of the 4 mandibular permanent incisors was larger in the skulls than in the modern samples.

Analysis of Variance↗
PubMed1977

Improvements in the validity of charcoal tube sampling by the use of a unique low flow true total volume sampling pump.

Standard methods of determining toxic vapor exposures rely heavily on charcoal tube sampling. The validity of results depends critically on accurate determination of the total air volume and avoidance of saturation breakthrough. The difficulty of substantiating sampling validity has stimulated a search for more absolute methods. A novel pump will be described which fulfills the requirement of true total volume measurement and has a flowrate capability down to 1 cc/min. This low flow feature lends itself to a variety of new detection techniques which will be outlined together with a detailed description of the unit's function.

Air Pollutants↗
PubMed1999

Corticosterone plasma concentration in male mule ducks: effects of sampling sites, repeated samplings and ACTH injections.

1. Changes in plasma corticosterone concentrations according to puncture sites and various challenges including injections of an ACTH agonist (Immediate Synacthen) were investigated in male mule ducks. 2. Lower concentrations were measured in samples drawn by puncture from the occipital sinus than at a wing vein site. 3. Immobilisation and a single intramuscular injection of saline solution (1 ml, 0.9%) had no effect on plasma corticosterone after 15 min. 4. A single intramuscular injection of ACTH (5 microg/kg body weight) produced a rise (P<0.05) in corticosterone. Maximum concentrations were measured after 10 min and, in the absence of further sampling, a return to initial levels was observed by 1 h. 5. On the other hand, repeated bleedings following ACTH challenge maintained higher corticosterone concentrations. 6. A single intramuscular injection of ACTH at doses ranging between 0.625 to 20 microg/kg body weight increased corticosterone concentrations (P<0.05) in a dose-dependent manner, with the responses plateauing at doses of 1.25 microg/kg and higher.

Adrenocorticotropic Hormone↗
PubMed2000

Comparison of pesticide residues in composite samples and in individual units: the Swedish approach to sampling.

The method used to take samples for residues testing in Sweden involves taking three subsamples of 1-2 kg. These are split in two for laboratory analyses. Where required one of these laboratory samples can be used to determine the variability between individual units. Details of the variation in residues in individual units of a number of commodities are presented. The highest variability factors, around 600, expressed as the quotient of the maximum and the minimum residue, were found for methamidophos in peppers and monocrotophos in grapes.

Food Analysis↗
PubMed1998

Kinetic sequential sampling (KSS) system: an automated sampling system for measuring vertical concentration profiles of airborne particles.

An electronically controlled lift system carrying a real-time particle monitor has been developed for sampling air sequentially, at different heights within the breathing zone. Data are automatically logged at the different receptor levels, for the determination of average vertical concentration profiles of airborne particulate matter. The system is easy to operate, portable, and easily extended to different heights or modified for use with other types of monitors (e.g., a portable CO analyzer). For measuring airborne particle concentrations, a Grimm Dust Monitor 1.104/5 was used. The results of trial runs, which were carried out indoors and in a relatively open semi-rural area, are presented, and applications of the kinetic sequential sampling (KSS) system are discussed.

Air Pollutants, Occupational↗
PubMed2003

Solventless sample preparation for pesticides analysis in environmental water samples using solid-phase microextraction-high resolution gas chromatography/mass spectrometry (SPME-HRGC/MS).

Solid-phase micro-extraction (SPME) coupled on line with high resolution gas chromatography and mass spectrometric detection is described for the analysis of pesticides in environmental water samples. Experiments were performed in order to optimize the SPME extraction conditions for selected pesticides including tiomethon, trichorfon, dimethoate, diazinon, malathion, dicofol, methidathion, ethion, bromopropylate and pyrazophos from spiked water solutions. To enhance the SPME efficiency, experimental conditions including the fiber composition, stirring rate, temperature, adsorption time, desorption time and salt concentration were optimized. After validation, the SPME-GC/MS methodology was applied to real-world environmental water samples.

Acrylic Resins↗
PubMed1988

A rapid method for the quantification of C, N and O in biomedical samples by proton-induced gamma-ray emission analysis applied to human placental samples.

A new fast, accurate and simple quantification method for C, N and O in biomedical samples by external-beam proton-induced gamma-ray emission analysis is presented. Concentration values for C, N and O in commercial standards of NBS bovine liver 1577a, IAEA animal muscle H-4 and IAEA horse kidney H-8 were determined using the new method. The concentrations of C, N, O, Na, Mg and P were determined from placental samples of 13 alcoholic mothers and from 16 abstinent controls. The values obtained for C, N, O, Mg and P were the first values ever obtained for human placentas.

Alcoholism↗
PubMed1998

Rapid automated determination of lipid hydroperoxide concentrations and total antioxidant status of serum samples from patients infected with HIV: elevated lipid hydroperoxide concentrations and depleted total antioxidant capacity of serum samples.

Excessive production of oxygen free radicals causes the oxidation of circulating or membrane lipids, proteins, and DNA. Patients infected with HIV usually have severe malnutrition in the AIDS stage of disease. Therefore, they may be at higher risk of oxidative stress. We measured lipid hydroperoxide concentration, antioxidant status, cholesterol, triglyceride, iron, ceruloplasmin, and transferrin concentrations in the serum samples of 14 patients infected with HIV and compared our results with the results from 14 volunteers who served as controls. Lipid hydroperoxide concentrations in serum samples were measured by a colorimetric assay in which hemoglobin catalyzes the reaction of lipid hydroperoxide with a methylene blue derivative, yielding methylene blue. The total antioxidant capacity of serum was measured by the ability of serum to inhibit the formation of ferrylmyoglobin by metmyoglobin and hydrogen peroxide. Both assays were automated on the Syva-30R analyzer (Behring, San Francisco, Calif). We measured serum cholesterol and triglyceride concentrations by using the Vitro 950 analyzer (Johnson & Johnson, Rochester, NY). The lipid hydroperoxide concentrations were significantly elevated (mean, 1.44; SD, 0.95 micromol/L) in patients with HIV compared with control subjects (mean, 0.25; SD, 0.24 micromol/L). In contrast, the total antioxidant capacity was significantly lower in patients with HIV (mean, 1.04; SD, 0.13 mmol/L of trolox equivalent) compared with control subjects (mean, 1.66; SD, 0.09 mmol/L). We observed a fair correlation between serum lipid hydroperoxide concentrations and serum triglyceride concentrations in patients with AIDS. The correlation between serum hydroperoxide concentration and antioxidant status of serum was relatively poor. The lipid hydroperoxide assay was linear, from 0.1 micromol/L to 50 micromol/L. The within-run and between-run coefficients of variation were 3.5% and 4.5%, respectively, at a lipid hydroperoxide concentration of 2.5 micromol/L. The total antioxidant capacity assay was linear, from 0.1 to 2.5 mmol/L of trolox equivalent. The within-run and between-run coefficients of variation were 1.4% and 4.2% for the standard, with a target total antioxidant capacity of 1.5 mmol/L of trolox equivalent. We conclude that our automated assays for determination of total antioxidant status of serum and lipid hydroperoxide products may be helpful screening tests followed by measuring individual antioxidants, such as tocopherol, ascorbic acid, and other antioxidants for patients with severe deficiency of antioxidant status.

Antioxidants↗
PubMed2000

The prevalence of potentially pathogenic bacteria in nasopharyngeal samples from individuals with a long-standing cough-clinical value of a nasopharyngeal sample.

BACKGROUND: A long-standing cough is a common cause for visits to a GP. If the patient also has a respiratory tract infection, one of the concerns of the doctor is to decide if the cough is caused by an underlying bacterial infection. OBJECTIVES: Our aim was to investigate whether a nasopharyngeal sample, obtained in routine medical practice, could yield information about the aetiology of a long-standing cough in patients with a respiratory tract infection. METHODS: The prevalence of potentially pathogenic bacteria (Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis) in nasopharyngeal swab samples from 618 healthy individuals was compared with that from 236 patients with a respiratory tract infection and long-standing cough (>9 days) of the same age in a defined geographical area. RESULTS: The proportion of cultures with potentially pathogenic bacteria decreased with age and was 44% among healthy individuals of pre-school age, 13% in schoolchildren and 6% in adults. The corresponding figures for patients with a long-standing cough were 83, 35 and 36%, respectively. All types of potentially pathogenic bacteria were found more frequently in pre-school children and in adults with a long-standing cough compared with healthy individuals of the same age. CONCLUSIONS: In patients with a respiratory tract infection and a long-standing cough, where a bacterial infection is suspected on clinical grounds, a nasopharyngeal culture could yield information about the aetiology. If M.catarrhalis is found in pre-school children, or if H.influenzae is found in adults, they are likely to be the aetiological agent.

Adolescent↗
PubMed1999

Analysis of chemical modification of RNA from formalin-fixed samples and optimization of molecular biology applications for such samples.

Formalin-fixed archival samples are known to be poor materials for molecular biological applications. We conducted a series of experiments to understand the alterations in RNA in fixed tissue. We found that formalin-fixed tissue was resistant to solubilization by chaotropic agents. However, proteinase K completely solubilized the fixed tissue and enabled the extraction of almost the same amount of RNA as from a fresh sample. The extracted RNA did not show apparent degradation. However, as reported, successful PCR amplification was limited to short targets. The nature of such 'fixed' RNA was analyzed using synthetic homo-oligo RNAs. The heterogeneous increase in molecular weight of the RNAs, measured by MALDI-TOF mass spectrometry, showed that all four bases showed addition of mono-methylol (-CH(2)OH) groups at various rates. The modification rate varied from 40% for adenine to 4% for uracil. In addition, some adenines underwent dimerization through methylene bridging. The majority of the methylol groups, however, could be removed from bases by simply elevating the temperature in formalin-free buffer. This demodification proved effective in restoring the template activity of RNA from fixed tissue. The improvement in PCR results suggested that more than half of the modification was removed by this demodification.

Animals↗
PubMed1989

Religious affiliations in mental health research samples as compared with national samples.

Religious affiliations of patients in research samples in four major psychiatric journals for the years 1978-1982 were compared with those reported in national samples. Protestants and the unaffiliated were underrepresented, whereas Jewish persons were overrepresented. Catholics used mental health services in proportions similar to their presence in the population at large. These findings suggest that religious affiliation may influence the use of mental health services.

Catholicism↗
PubMed2005

Clotting time analysis of citrated blood samples is strongly affected by the tube used for blood sampling.

Our aim was to establish whether differences in clotting times for recalcified blood and plasma samples might be explained by the use of different blood collection tubes. Samples obtained from different plastic vacuum tubes were recalcified and clotting times determined by free oscillation rheometry. The clotting times for blood collected in Vacutainer (Becton Dickinson, Rutherford, New Jersey, USA) or Vacuette (Greiner Bio-One, Kremsmünster, Austria) tubes decreased with time, with maximal effect after 30 min. Blood from Monovette (Sarstedt, Nümbrecht, Germany) tubes displayed longer clotting times, which did not decrease with time. Clotting times for plasma prepared after 1 h storage in Vacutainer or Vacuette tubes were unaffected by subsequent addition of corn trypsin inhibitor to inhibit factor XIIa, although an antibody against factor XI prolonged the clotting time markedly. In Monovette plasma, both corn trypsin inhibitor and anti-factor XI effectively prolonged the clotting time. When corn trypsin inhibitor or anti-factor XI was added to the tubes before blood collection, but both additions clearly prolonged the clotting times in all types of tubes, even though corn trypsin inhibitor was less effective in whole blood. Antibodies against human tissue factor did not affect the clotting times. The amounts of platelet or leukocyte microparticles in plasma were low and similar in all tubes. This indicates that blood collection in Vacutainer or Vacuette tubes induces a rapid activation of factor XII and factor XI.

Antibodies↗