Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Sampling”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 235 records · Page 13Linked to original sources
PubMed1995

Human symbolic matching-to-sample performance: Effects of reinforcer and sample-stimulus probabilities.

Four experiments, each with 6 human subjects, varied the distribution of reinforcers for correct responses and the probability of sample-stimulus presentation in symbolic matching-to-sample procedures. Experiment 1 held the sample-stimulus probability constant and varied the ratio of reinforcers obtained for correct responses on the two alternatives across conditions. There was a positive relation between measures of response bias and the ratio of reinforcers. Experiment 2 held the ratio of reinforcers constant and varied the sample-stimulus probability across conditions. Unlike previous studies that used pigeons as subjects, there was a negative relation between bias and the ratio of sample-stimulus presentations. In Experiment 3, the sample-stimulus probability and the reinforcer ratio covaried across conditions. Response bias did not vary systematically across conditions. In Experiments 1 to 3, correct responses were reinforced intermittently. Experiment 4 used the same procedure as Experiment 3, but all correct responses now produced some scheduled consequence. There was a positive relation between response bias and the ratio of reinforcers. The results suggest that human performance in these tasks was controlled by both the relative frequency of reinforced responses and the relative frequency of nonreinforced responses.

Journal Article↗
PubMed2003

Capillary electrophoresis of small anions in complex samples with a hollow fiber sampling inlet end.

A hollow fiber sampling inlet end of capillary electrophoresis (CE) for small ions in complex samples is described. A short piece of hollow fiber, which only permits small ions to pass through its wall, was directly connected to one end of a capillary. Small ions in complex samples were injected into the capillary through the hollow fiber by an electrokinetic method. The experimental results of CE for standard anion mixture solutions, river water, and milk samples show that the hollow fiber sampling inlet end is a simple and useful method for the CE of complex samples. Furthermore, it has been shown that the method can be used to study small anion changes during the milk storing process.

Animals↗
PubMed2003

Good preclinical bioanalytical chemistry requires proper sampling from laboratory animals: automation of blood and microdialysis sampling improves the productivity of LC/MSMS.

The preclinical bioanalytical process with animal models begins with sampling biological fluids and tissue. The goal is to understand oral absorption kinetics, distribution, metabolism, excretion, blood brain barrier penetration, drug-drug interactions, and the influences on biomarkers, hematology, electrophysiology, cardiology, blood pressure and behavior. An overview is obtained by periodic blood sampling of 8-12 samples over a total time span of 10-24 h. Urine, feces, bile and microdialysates can augment the information available from whole blood. In today's preclinical environment, the majority of samples are processed by LC/MSMS augmented by robotic sample preparation tools. These tools save labor and improve precision for smaller volume/lower concentration samples. Our laboratories have been engaged in a project that is focused on improving both the quality and throughput for laboratory animal studies, while providing for reduced numbers of animals and enhanced animal comfort. We have implemented a robotic system that can accomplish most of the above goals for laboratory rats, dogs and primates. Studies with mice are at an earlier stage, but feasibility has been demonstrated. This presentation is a progress report on this evolving research program in cooperation with multiple pharmaceutical and drug development companies. We will illustrate results and discuss future directions.

Animals↗
PubMed1996

Biosafety implications in sample introduction: module design characteristics for discrete-sample systems used in critical whole blood analyte testing environments.

Systems designed for the measurement of pH/blood gases and expanded versions of these systems that include the ability to measure electrolytes or other related quantities, all incorporate one or more sampling modules that are limited in their ability to allow for the safe handling of potentially biohazardous blood samples. Systems that provide for injection of sample from a syringe use more than the required volume for sample testing and have the potential for causing splash-back of the sample if the introduction port is blocked. The probes of aspiration-based systems require manual dexterity by the operator and present the possibility of operator injury with a contaminated probe tip or the possibility of system damage as the probe extends and the operator moves the collection device into place. Some systems have the potential for both types of biohazards. This report describes the implications for system design of the sample collection devices commonly in use, and it offers a design solution that combines the ergonomics of an injection system and the operational advantages of an aspiration system, in combination, addressing the biosafety aspects in a unique fashion.

Blood Gas Analysis↗
PubMed1998

Characteristics of the LacTek test as applied to tissue samples: assessment of performance using incurred field samples.

The Lactek test, marketed for antimicrobial residue detection in milk, was validated for the detection of antimicrobial residues in tissues. A previous study found that the LacTek test could confidently identify tissue samples spiked with antimicrobial residues. However, the test could not reliably distinguish violative from nonviolative spiked samples relative to Canadian maximum residue limits (MRLs). The objectives of this study were to assess and compare the performance of the LacTek tests for beta-lactams, tetracyclines, gentamicin, and sulfamethazine on samples containing naturally incurred residues by running the test in parallel with the standard microbial inhibition test (MIT) presently used for the routine testing of tissues at our facility and to assess the agreement with high pressure liquid chromatographic (HPLC) determinative methods. Parallel testing with the official MIT found that the Lactek tests could be confidently used for testing tissue samples containing incurred residues. Among 1,008 MIT-positive samples, the LacTek test found that 90% contained beta-lactams and/or tetracyclines. A further 7.3% of violative residues could not be identified to an antimicrobial class. In addition, 9% of samples testing negative on the MIT were found to contain an antimicrobial residue by the LacTek tests. Comparative testing with HPLC methods found that there was very good agreement between the two tests and that most violations were due to penicillin G and oxytetracycline. Although the LacTek test cannot be used to distinguish violative from nonviolative residue levels, it does offer several advantages over the present MIT. These include speed, ease of use, the ability to identify residues to a specific class, and an improved sensitivity at the MRL level for the most commonly found antimicrobials in tissue.

Anti-Bacterial Agents↗
PubMed2005

Accuracy of screening for fecal occult blood on a single stool sample obtained by digital rectal examination: a comparison with recommended sampling practice.

BACKGROUND: Many expert panels recommend colorectal cancer screening for average-risk asymptomatic individuals older than 50 years of age. Recent studies have found that 24% to 64% of primary care providers use only the digital fecal occult blood test (FOBT) as their primary screening test. The effectiveness of a single digital FOBT is unknown. OBJECTIVE: To compare the sensitivity and specificity of digital FOBT and the recommended 6-sample at-home FOBT for advanced neoplasia in asymptomatic persons. DESIGN: Prospective cohort study. SETTING: 13 Veterans Affairs medical centers. PATIENTS: 3121 asymptomatic patients 50 to 75 years of age. INTERVENTION: 2665 patients had 6-sample at-home FOBT and digital FOBT, followed by complete colonoscopy. MEASUREMENTS: We measured the sensitivity of digital and 6-sample FOBT for advanced neoplasia and the specificity for no neoplasia. We calculated predictive values and likelihood ratios for advanced neoplasia, defined as tubular adenomas 10 mm or greater, adenomas with villous histology or high-grade dysplasia, or invasive cancer. RESULTS: Of all participants, 96.8% were men; their average age was 63.1 years. The 6-sample FOBT and the single digital FOBT had specificities of 93.9% and 97.5%, respectively, as defined by studying 1656 patients with no neoplasia. Sensitivities for detection of advanced neoplasia in 284 patients were 23.9% for the 6-sample FOBT and 4.9% for the digital FOBT. The likelihood ratio for advanced neoplasia was 1.68 (95% CI, 0.96 to 2.94) for positive results on digital FOBT and 0.98 (CI, 0.95 to 1.01) for negative results. LIMITATIONS: Most patients were men. CONCLUSIONS: Single digital FOBT is a poor screening method for colorectal neoplasia and cannot be recommended as the only test. When digital FOBT is performed as part of a primary care physical examination, negative results do not decrease the odds of advanced neoplasia. Persons with these results should be offered at-home 6-sample FOBT or another type of screening test.

Aged↗
PubMed1999

[Measurement of cerebral blood flow the blood sampling method using 99mTc-ECD: simultaneous scintigram scanning of arterial blood samples and the brain with a gamma camera].

To measure regional cerebral blood flow (rCBF) by blood sampling using 99mTc-ECD we devised a method of measuring the radioactive concentration in arterial blood sample with a gamma camera. In this method the head and a blood sample are placed within the same visual field to record the SPECT data of both specimens simultaneously. The results of an evaluation of the counting rate performance, applying the 30 hours decaying method using 99mTc solution showed that this method is not comparable to the well-type scintillation counter and in clinical cases the active concentration in arterial blood sample remained well within the dynamic range. In addition, examination of the influence of scattered radiation from the brain by the dilution method showed that it was negligible at a distance of more than 7.5 cm between the brain and the arterial blood sample. In the present study we placed a head-shaped phantom next to the sample. The results of the examinations suggested that this method is suitable for clinical application, and because it does not require a well-type scintillation counter, it is expected to find wide application.

Blood Specimen Collection↗
PubMed2001

[Analyses of preanalytical issues on samplings and samples].

To obtain "exact" laboratory data which show or reflect the pathophysiological conditions of patients, preanalytical, analytical and postanalytical processes should be checked. However, it is difficult to know the preanalytical situation or out of laboratories. We realize preanalytical issue is one of the weak points in current laboratory medicine. I reported the results of analyses on the issues concerning abnormal laboratory data produced by inadequate handling of samples and sample collection. Five issues are described as follows: 1) The effect of detergents on fecal occult blood test. Immunological methods were affected markedly to moderately by various sanitizers and detergents tested. In collecting feces for immunological fecal occult blood test, contact of feces with toilet flush water dissolving sanitizers should be inhibited. 2) Blood storage and potassium(K) release. Causes of slight elevation of K in serum are sometimes unknown. Addition of injection drugs in vitro showed that various drugs induced K release from erythrocytes. Cold storage of blood is well-known to bring elevation of K level, however, the detailed mechanism is still unknown. We developed a simple method to measure K flux activity of erythrocytes and the decreased activity was shown in patients with chronic renal insufficiency and the aged as well as the aged erythrocytes. 3) Thawed serum and concentration difference. Frozen serum samples were thawed without mixing and various layers contained different concentrations in 60 items tested. Comparing the concentration before freezing, the upper layer contained 1/2 and the bottom 2 times more. T3 and FT4 showed exceptionally smaller difference, significance of which is unknown. 4) Two syringe method in blood collection. Blood samples drawn in the first half and the latter half were comparatively measured for APTT, PT and TT. Blood amount of 1 ml or more showed no differences. TT showed elevation in the first half in 0.5 ml-sample. The effects of local treatment by warming, tapping and congestion were examined. In some cases, tissue factor level elevated by such physical pretreatment. However, in usual blood collection in human, two syringe method is not necessarily employed. 5) Heat-inactivation and cold storage of serum. Preheating sera at 56 degrees C for 30 min reduced markedly the levels of ALT, ALP, CK, ChE, ATIII and alpha 2-PI. In seroimmunology, some complement components are markedly affected and rheumatoid factor of IgM classes was also affected. In about a half of HCV-Ab positive sera, CH50 levels were decreased by the cold storage(cold activation). We reported previously the non-participation of C1q in this phenomenon. In such sera, temperature management is important. Scientific data on the storage and collection of samples should be informed not only to laboratory staffs but to nurses and doctors in order to provide "exact" data.

Blood Preservation↗
PubMed2002

[Vapour pressure effect of sample evaporation in blowing powder sample into arc discharge].

Vapour pressure effect of sample evaporation in blowing powder sample into arc discharge is described in this paper. Since vapour pressure of basic composition of sample in arc is very high, evaporation of this basic composition will be reduced greatly, and the evaporation of impurity elements in the sample are stronger than basic composition, because vapour pressure of impurity elements in arc are lower than the basic composition. This effect is characteristic in sample evaporation during blowing powder sample into arc source. Determination limit of this method is therefore lowered due to the existence of this effect.

English Abstract↗
PubMed2000

[Determination of chromium in geological samples with slurry sampling and probe atomization in GFAAS].

A method of loading a slurry prepared from a solid sample for analysis of chromium in geological samples using graphite furnace atomic absorption spectrometry had been approached by combining slurry sampling with probe atomization. The factors that influence the performances of chromium including ashing and atomization temperature, atomization surfaces were investigated. The results showed that the determination of chromium in geological samples could be performed by direct slurry sampling with the use of a calibration established with aqueous standards. The relative standard deviations(RSD) of the method were 3.0%-6.5%. The detection limit was 5.1 x 10(-12) g Cr. The Analytical results of the geological reference samples were consistent with the certified values.

English Abstract↗
PubMedDate not supplied

Application of strategically designed sample composition to the rapid analytical screening of milk samples for polychlorinated biphenyls.

Strategically designed sample composition (SSC) is a new technique that decreases the number of analytical determinations needed in routine screening to as few as the number of original sample specimens while providing information that is specific to them. Although this new technique has been applied to environmental studies, this paper describes its first application to food safety studies. Contamination of milk samples with polychlorinated biphenyls (PCBs) was chosen as a case study to show the usefulness and potential of the SSC technique with a fast analytical procedure that involves saponification of the samples and solid-phase microextraction of the PCBs. A total of 20 sample specimens can be analyzed in 11 determinations with excellent predictions of the positive samples and the concentration levels of the contaminants. The robustness of the strategy was investigated and demonstrated.

Animals↗
PubMed1998

[Determination of beryllium in geological samples with slurry sampling and probe atomization in graphite furnace atomic absorption spectrometry].

A method of loading a slurry prepared from a solid sample for analysis of beryllium in geological samples using graphite furnace atomic absorption spectrometry was approached by combining slurry sampling with probe atomization. The factors that influence the performances of beryllium including ashing and atomization temperature, atomization surfaces (probe and tube), the materials of the tube and probe, and the use of matrix modifiers were investigated. The results show that the determination of beryllium in geological samples could be performed by direct slurry sampling with the use of calcium as the matrix modifier for a calibration established with aqueous standards. The relative standard deviations (RSD) of the method were 3.1-5.2%. The analytical results of the geological reference samples were consistent with the certified values. The activation energy during beryllium atomization was calculated using the Arrhenius graph method which was in good with the bonding energy of Be-O.

English Abstract↗
PubMedDate not supplied

Optimal sampling and limited sampling strategies for estimation of unbound platinum AUC after nedaplatin infusion.

The aim of this study was to determine the optimal sampling design for empirical Bayesian forecasting for nedaplatin, and also to develop a simple formula for estimating the area under the plasma concentration-time curve (AUC) of platinum which relates to hematological toxicity after nedaplatin dosing using limited sampling points. Plasma unbound platinum concentration data were retrospectively collected from 27 courses administered to 20 Japanese adult patients. To determine the optimal sampling points, 1 - 5 data point(s) were selected with all combinations and clearance in each patient was estimated by the empirical Bayesian method. As measures for the Bayesian predictive performance, mean prediction error and root mean squared error were estimated. These indices suggested that the sampling time(s) of 4 hours in case of the one-point sampling gives better estimates for individual clearance. As for the limited sampling strategy, a simple formula to calculate AUC, AUC = 0.039x dose + 11.6 x Cp4h - 0.88, was obtained, where Cp4h is the concentration at 4 hours after the end of infusin. These results should be helpful for adjusting dosage to achieve the target AUC.

Adult↗
PubMedDate not supplied

[Homogenization of samples for the culture of mycobacteria. A comparative study of samples with and without centrifugation].

A homogenization method for sputum samples for the culture of acid-fast bacilli that omits the use of centrifugation, passage test tubes and balances is described. 10% sodium phosphate was used as decontaminating substance. This method facilitates the laboratory work since the samples so treated are incubated at 37 degrees C up to the next day when they are then cultured. 676 samples prepared according to this method were compared with samples prepared according to the standard method; a 6,21% positivity in the former compared to a 5,47% in the latter as well as a lower percentage of contamination were obtained. Contamination occurred in 9,91% of samples without centrifugation and in 14,35% of centrifuged samples.

Bacteriological Techniques↗
PubMed1982

Composite sampling in the determination of pyrethrins in fruit samples.

A residue method is described for measuring up to 6 naturally occurring pyrethrins in several varieties of fruits. Fresh samples are extracted into acetone, partitioned between water and hexane-dichloro-methane, and cleaned up by adsorption on a Florisil column followed by elution with acetone-hexane (15 + 85). Residues are detected and quantitated by gas chromatography with electron capture detection. Detection limits for single 10 g samples are about 10-30 ng/g. The method was applied to a survey of pyrethrins in fruit samples. Because of the high tolerance (1 ppm) allowed for pyrethrins, the expected low incidence, and the low detection limits of the method, composite samples (up to 5-6) of fruit were used to quickly determine residue levels. This procedure allowed 130 samples to be processed in the time normally needed for 30-40. Provided the above conditions can be met, composite sampling is proposed as an attractive approach to data gathering in pesticide residue analysis.

Chromatography, Gas↗
PubMed1996

[Can examination of spontaneous urine samples adequately replace 24-hour-urine samples for determining excretory rate of various lithogenic and inhibitory substances in metabolic evaluation of kidney calculi patients?].

The gold standard for metabolic evaluation of stone-forming patients is the 24-h urine specimen. Recently, some authors have suggested that for routine metabolic evaluation spot urine samples are as valuable as the 24-h urine specimen. The purpose of our study, was to determine the value of the spot urine sample in comparison with the 24-h urine specimens. Eighty-eight healthy volunteers on different diets were investigated (32 vegetarians, 12 body-builders without protein concentrates, 28 body-builders on protein concentrates, and 16 subjects on a regular European diet). Using 24-h specimens, excretion rates of oxalate, calcium, sodium and potassium were determined. The concentration ratio of these electrolytes to creatinine was calculated for spot urine samples. A highly significant correlation between the excretion rates and the results of the spot urine samples was found for all parameters. However, the correlations showed considerable variations. On the other hand, we were able to show that creatinine excretion is highly dependent on daily protein intake, body weight and glomerular filtration rate. This leads to a considerable inter- and intraindividual variation in creatinine excretion. This variation of the creatinine excretion is the major cause for the variation in the results of spot urine samples. It is concluded that spot urine samples are an inadequate substitute for the 24-h urine specimen and that the 24-h urine specimen is still the basis for metabolic evaluation in stone patients.

Adolescent↗
PubMed1989

Characteristics of a multiplex IDDM sample: unexplained differences with other samples.

Characteristics of a multiplex sample of families with insulin-dependent diabetes mellitus (IDDM) are studied and contrasted with similar characteristics in other, more conventionally sampled data sets. Some characteristics remain consistent with earlier observations including the high frequency of human leukocyte antigen (HLA) DR3,4 in affected individuals and the greater than expected percentage of HLA haplotype sharing among affected sib pairs. In other respects, however, differences are seen between this sample and others. "Control" haplotypes, i.e., those not transmitted to the first affected offspring, had a higher frequency of DR3 and DR4 than expected, and a rather high frequency of affected parents was observed. Differences between the first affected and later affected offspring reported in other samples were absent from these families. No effect of the sampling scheme and the resulting distribution of parental phenotypes could be shown to explain this difference.

Child↗
PubMed2006

Site-specific sampling of taurine from rat brain followed by on-line sample pre-concentration, throughout in-capillary derivatization and capillary electrophoresis.

A method of pinpoint-sampling followed by on-line pre-concentration of the sample, throughout in-capillary derivatization and capillary electrophoretic separation was evaluated by demonstrating the detection of taurine, 2-aminoethanesulfonic acid at a specific location of a rat brain. The direct sampling of taurine from the rat brain was accomplished by using voltage injection associated with two kinds of driving forces, electrophoretic flow and electroosmotic flow (EOF). The capillary tube (75 microm of inner diameter x 375 microm of outer diameter) of the capillary electrophoresis (CE) apparatus was already filled with a CE run buffer, viz., 40 mM phosphate-borate buffer (pH 10) containing 2mM o-phthalaldehyde (OPA)/N-acetylcysteine (NAC) as the derivatization reagent. One end of a platinum wire (0.5mm o.d.), used as the anode, and the inlet end of capillary tube (from which a 1.0 cm long polyimide coating was removed), were pricked down onto the surface of either the cerebrum or cerebellum of a rat brain at a location of very small dimension. When a low voltage (5 kV, 30s) was applied, taurine began to move from the rat brain into the capillary tube, and, simultaneously, electric focusing of taurine occurred by the action of "the pH-junction effect" at the inlet end of the capillary tube. After completing the injection, both the platinum wire and capillary tube were detached from the brain and dipped into the run buffer in an anode reservoir filed with the same solution as that in the capillary tube for the CE apparatus. Then, by applying a high voltage (20 kV) between the ends of the capillary tube, taurine was automatically derivatized to yield the fluorescent derivative, separated and detected with fluorescence (E(x)=340 nm, E(m)=455 nm) during migration throughout the capillary tube. The migration profiles obtained from cerebrum and cerebellum appeared to be different, but the peak corresponding to taurine was identified on both electropherograms. The efficacy of the present method including sample on-line pre-concentration prior to throughout in-capillary derivatization CE was first verified with several preliminary experiments by using samples of taurine in water, saline and a piece of 1.5% agar-gel block, as an alternate standard for the rat brain used in this study.

Analytic Sample Preparation Methods↗