SEARCH · PubMed Health

Results for “Repeatability and Reproducibility”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

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

At least 703 records · Page 39Linked to original sources

PubMed1999

DNA pooling identifies QTLs on chromosome 4 for general cognitive ability in children.

General cognitive ability (g), which is related to many aspects of brain functioning, is one of the most heritable traits in neuroscience. Similarly to other heritable quantitatively distributed traits, genetic influence on g is likely to be due to the combined action of many genes of small effect [quantitative trait loci (QTLs)], perhaps several on each chromosome. We used DNA pooling for the first time to search a chromosome systematically with a dense map of DNA markers for allelic associations with g. We screened 147 markers on chromosome 4 such that 85% of the chromosome were estimated to be within 1 cM of a marker. Comparing pooled DNA from 51 children of high g and from 51 controls of average g, 11 significant QTL associations emerged. The association with three of these 11 markers ( D4S2943, MSX1 and D4S1607 ) replicated using DNA pooling in independent samples of 50 children of extremely high g and 50 controls. Furthermore, all three associations were confirmed when each individual was genotyped separately ( D4S2943, P = 0. 00045; MSX1, P = 0.011; D4S1607, P = 0.019). Identifying specific genes responsible for such QTL associations will open new windows in cognitive neuroscience through which to observe pathways between genes and learning and memory.

Adolescent↗

PubMedDate not supplied

Anticoagulant poisoning in animals: a simple new high-performance thin-layer chromatographic (HPTLC) method for the simultaneous determination of eight anticoagulant rodenticides in liver samples.

The purpose of this study was to develop and evaluate a technique for the analysis of anticoagulant rodenticides in serum and liver samples using a new high-performance thin-layer chromatographic apparatus. Detection limits were estimated at 0.2 micrograms/g in liver extracts for eight different substances. Overall, this technique was repeatable and reproducible. The percent recovery was greater than 87% for each substance. Liver and serum samples of animals known to be exposed to one anticoagulant and showing clinical signs of poisoning were analyzed. Concentrations measured varied between 0.2 and 3 micrograms/g (liver extracts). Only blood samples from one dog could be analyzed. The concentration was 150 ng/mL the first day after admission and 140 ng/mL the following day. Analyses are technically easily and rapidly performed, and they are inexpensive. Therefore, this technique could be a valuable alternative to current high-performance liquid chromatographic methods.

4-Hydroxycoumarins↗

PubMed1987

Diet and health: scientific concepts and principles conference commentary.

The conference concluded that dietary guidelines are needed, but that they cannot apply to everyone in the population nor to the same extent. Furthermore, a mechanism or structure is needed in which the guidelines can be periodically reviewed and updated. In making dietary recommendations, genetic variability, age, sex and body size need to be considered. Survival, extension of life span, relief of selected symptoms and biochemical improvements of risk factors are some of the criteria to be used in assessing the role of diet in health and disease. The most important questions that remain unresolved in the nutritional sciences concern the relation of diet to the development of chronic disease. The science of nutritional epidemiology needs to be strengthened and etiologic research in epidemiology ought to be performed and evaluated with the same standards used in other branches of science. Therefore, there is a need to establish guidelines for the validity of methods in assessing dietary intake and for a minimum acceptable correlation for the reproducibility and repeatability of dietary intake data. Research on the role of genetic variation and nutrition, the metabolic effects of omega-3 fatty acids and their relationship to omega-6 fatty acids, the energy expenditure after weight reduction and improving the scientific base of nutritional epidemiology will enhance the scientific basis of nutrition and our understanding of the role of diet in health and disease.

Diet↗

PubMed1996

Variability of motor-evoked potentials recorded during nitrous oxide anesthesia from the tibialis anterior muscle after transcranial electrical stimulation.

When recorded as a compound muscle action potential (CMAP), the motor-evoked potential (MEP) is affected by volatile anesthetics and nitrous oxide. However, MEPs recorded using epidural electrodes in the presence of nitrous oxide are highly reproducible from trial to trial. We wished to establish the reproducibility over time of the CMAP produced by supramaximal transcranial electrical stimulation of the human motor cortex. Cascades of 100 successive CMAPs were recorded from the tibialis anterior muscles of six anesthetized patients undergoing scoliosis surgery, in response to transcranial electrical stimuli of > 500 V. Satisfactory CMAPs could be recorded in the presence of nitrous oxide, but not isoflurane. Latencies and amplitudes were reproducible in repeated sequences of 100 responses. However, amplitude and, to a lesser extent, latency, were highly variable within a sequence. In addition, occasional individual stimuli, although rarely successive ones, failed to evoke a CMAP. CMAPs have a much higher trial-to-trial variability than corticospinal volleys recorded from the epidural space. Using the present methodology it would be difficult to rely on CMAP recordings as an indicator of corticospinal function in the clinical monitoring situation.

Adolescent↗

PubMed1991

Determining the 222Rn exhalation rate of building materials using liquid scintillation counting.

A new method for determining the free 222Rn exhalation rate from building materials is described. The sample is enclosed in a container from which the exhaled Rn is continuously purged by nitrogen gas. After 2-3 h, when the Rn level in the container has reached a steady-state concentration, the outflowing Rn is trapped on silica gel at about -190 degrees C. About 16 h after sampling, the silica gel is analyzed by liquid scintillation counting to determine the area exhalation rate. The method described has a good repeatability and reproducibility with coefficients of variation of 7.8% and 8.3%, respectively, at 5 Bq m-2 h-1. The low limit of detection of 11 mBq 222Rn offers the opportunity to quantify the exhalation rate of almost all kinds of building materials. It was found that the air humidity strongly influences the exhalation rates of building material and, therefore, should be controlled. Two typical building materials were investigated. For gypsum, an increase in the exhalation rate with increasing water vapor pressure was found, whereas for concrete, a linear decrease with increasing water vapor pressure was observed. The 222Rn area exhalation rates of 20 Dutch building materials, including some experimental ones, were determined at 50% RH, 20 degrees C, showing a range of less than 0.02-15.8 Bq m-2 h-1. The lowest values were found for natural gypsum board, the highest for phosphogypsum blocks. Building materials containing fly ash gave area exhalation rates comparable to those of similar materials without fly ash.

Air Pollutants, Radioactive↗

PubMed1985

Dual-energy projection radiography in the evaluation of femoral neck strength, density, and mineralization.

Two different dual-energy projection radiography techniques were utilized in an attempt to predict femoral neck strength, bone density, and bone mineral content in 19 pairs of cadaver specimens. Positive simple linear correlation was observed between dual-energy scanned projection measurements and dry density, ash fraction, cross-sectional cortical bone area and, to a lesser degree, force required for fracture, but not trabecular bone volume, failure time, or Singh trabecular grade. Dual-energy film radiography was found to be a less reliable indicator of femoral neck strength, density, and mineral content. Dual-energy scanned projection results related linearly to mineral-equivalent solution (K2HPO4) concentration, and demonstrated long-term reproducibility in repeated specimen studies. Correction factors derived to account for differences in femoral size and rotation were shown to be reliable over a moderate range of neck projections. Although bone mineral measurement at other sites may provide comparable or greater information concerning hip fracture risk, dual-energy scanned projection radiography appears to be a useful technique for assessment of bone density, mineral content, and strength in the femoral neck.

Absorptiometry, Photon↗

PubMedDate not supplied

BRL 34915, a novel antihypertensive agent: comparison of effects on blood pressure and other haemodynamic parameters with those of nifedipine in animal models.

The effects of BRL 34915, (+/-) 6-cyano-3,4-dihydro-2,2-dimethyl-trans-4-(2-oxo-1-pyrrolidyl)-2H-b enzo [b]-pyran-3-ol, on blood pressure and other haemodynamic parameters in animals have been investigated in comparison with those of nifedipine. In conscious spontaneously hypertensive rats and renal hypertensive cats and dogs the oral doses of BRL 34915 lowering blood pressure are 10 to 30 times lower than those of nifedipine. Tachycardia evoked by BRL 34915 tends to be less than that produced by nifedipine in the cat and of similar magnitude in the dog. The antihypertensive response to BRL 34915 in these models is reproducible on repeat once daily dosing without rebound hypertension on cessation of dosing. In studies using electromagnetic flow probes to measure regional blood flow in anaesthetised cats the intravenous administration of BRL 34915, unlike that of nifedipine, markedly increases renal blood flow yet BRL 34915 lacks the marked effect of nifedipine on femoral blood flow. BRL 34915, a compound structurally unrelated to existing cardiovascular drugs, is a potent new antihypertensive agent having an interesting profile of activity that renders this compound of clinical interest.

Animals↗

PubMed1998

Posterior tibial nerve somatosensory cortical evoked potentials in adolescent idiopathic scoliosis.

STUDY DESIGN: Somatosensory-evoked potentials were used to evaluate neurologic function in patients with adolescent idiopathic scoliosis. OBJECTIVES: To compare the somatosensory-evoked potentials between patients with adolescent idiopathic scoliosis and healthy control individuals, and to determine the incidence of abnormal somatosensory function in patients with adolescent idiopathic scoliosis. SUMMARY OF BACKGROUND DATA: Somatosensory-evoked potentials are sensitive in detecting structural lesions in the somatosensory pathway. Previous studies on somatosensory function in patients with idiopathic scoliosis have demonstrated statistical differences in somatosensory-evoked potential latency between scoliotic and normal groups. However, no documentation of the actual incidence of abnormal somatosensory-evoked potentials is available. SUBJECTS AND METHODS: Posterior tibial nerve somatosensory cortical evoked potentials were evaluated on 147 young patients with adolescent idiopathic scoliosis and 31 healthy control individuals. RESULTS: Seventeen patients with idiopathic scoliosis showed pathologic evoked potentials. Among them were seven with absent somatosensory-evoked potential waveform and 10 with delayed latency. The results were reproducible on repeated measurement. CONCLUSIONS: Adolescent idiopathic scoliosis could be subdivided according to the somatosensory-evoked potential findings into two subgroups, those with and those without a somatosensory pathologic process. Potential clinical significance in predicting curve progression in idiopathic scoliosis could be pursued further.

Adolescent↗

PubMed1992

Rapid and sensitive liquid chromatographic assay of mefenamic acid in plasma.

Mefenamic acid (MA) is a nonsteroidal antiinflammatory analgesic agent widely used clinically. A simple and sensitive liquid-chromatographic assay has been developed for the quantitative determination of MA in human plasma. A reverse phase, 10-microns cyano column (25 x 0.4 cm), a mobile phase of water-acetonitrile-methanol-17 M acetic acid (69:15:15:1 by volume), and an ultraviolet detection (290 nm) are used for the separation of MA and internal standard (methyl-clonazepam). MA and internal standard are extracted from acidified plasma into diethyl ether and after evaporation of the organic phase, the residue is redissolved in methanol. Calibration curves are linear in the range 0.05-3.20 micrograms/ml, and at the plasma level corresponding to the quantification limit (0.05 microgram/ml) coefficients of variation are 7.5% and 10.2% for repeatability and reproducibility studies, respectively. This assay was successfully used in the study of pharmacokinetics of MA in human plasma after a single oral administration of a low MA dose.

Carbamazepine↗

PubMed1996

A simple competitive enzyme immunoassay for the detection of the trypanocidal drug isometamidium.

A new competitive enzyme immunoassay technique has been developed for the determination of concentrations of the trypanocidal drug isometamidium chloride (Samorin) in bovine serum. The method has been shown to be highly repeatable and reproducible, and it has several advantages over previous immunoassay techniques for the drug. There are fewer incubation steps overall; microtitre plates may be of coated in batches and stored frozen for future use; and the competition incubation is overnight and is followed only by a brief colour development stage of 10 min. Coefficients of variation (CVs) of duplicate samples were approximately 5%, and mean response variances of untreated cattle (n = 57) were small (CV, 10%). Partitioning of variance showed 77% of this variability to be intrinsic to the samples, and the remaining 23% was due to the procedure. The limit of detection was approximately 0.5 ng ml-1, which was considered to be satisfactory for the intended use of the method. The drug could be detected in serum of treated cattle for up to 10 weeks following treatment, and determinations showed a high level of reproducibility.

Animals↗

PubMed2002

Is LC-MS suitable for a comprehensive screening of drugs and poisons in clinical toxicology?

This paper reviews the different attempts made to develop efficient LC-MS techniques for systematic toxicologic analysis, or general unknown screening (GUS) of drugs and toxic compounds. Only particle beam interfaces are compatible with electron ionization, but they mainly cover the same range of compounds as GC-MS, i.e. nonpolar, thermally stable molecules. Using the more used electrospray sources, several approaches were used: tandem-mass spectrometry (MS/MS); MS/MS with data-dependent or information-dependent acquisition (DDA or IDA); and single mass spectrometry with in-source collision induced dissociation (CID). The MS/MS strategy is not really compatible with a GUS procedure, as it requires selecting a limited number of ions in the first step, before fragmenting them. DDA or IDA are auto-adaptive MS/MS product-ion scan modes where the m/z ratios the intensity of which is above a given threshold are selected at each unit time. Preliminary studies showed their potential for GUS, but it will probably be necessary to improve the detection of signals of toxicologic interest among background noise. This is also the case for single-MS techniques with in-source CID. Such methods have been proposed by several teams, who demonstrated their repeatability and reproducibility, at least on a same type of instrument and on an intralaboratory basis. Optimized extraction procedures are necessary to recover polar and even hydrophilic drugs, which are those supposed to be detectable by LC-ES-MS and not GC-MS, and such nonselective extraction may be responsible for high chemical noise. Chromatographic conditions and the resulting separation, resolution and signal-to-noise ratio are also probably important determinants of the efficiency of such procedures. Preliminary results using an optimized LC-ES-MS GUS technique showed that it is probably as efficient as GC-MS or HPLC-DAD for the detection of drugs and toxicants in clinical serum samples and that it is complementary to both these techniques.

Animals↗

PubMed2003

A rapid and simultaneous determination of several analgesic antiinflammatory agents by capillary zone electrophoresis.

A rapid and simultaneous determination of several analgesic antiinflammatory agents--ibuprofen, acetaminophen, indomethacin, and salicylic acid--in human serum was developed by using capillary zone electrophoresis (CZE) coupled with diode-array ultraviolet detection. After precipitation of serum protein with acetonitrile containing 3-isobutyl-1-methylxanthine as the internal standard, an aliquot of deproteinized samples was applied directly to the CZE system. It enabled us to measure all of these four agents within 6 min, and there were no peaks interfering with the assay of these agents or 3-isobutyl-1-methylxanthine. Both the separation and quantification of these agents in human serum were reproducible after repeated analysis within a day or day-to-day analysis. In addition, there was a good correlation for each drug (r = 0.997-0.999) between the values in serum determined by CZE analysis and those measured either by high-performance liquid chromatography with ultraviolet detection (ibuprofen and indomethacin) or by fluorescence polarization immunoassay (acetaminophen and salicylic acid). Therefore, the present CZE analysis could provide a simple, rapid, and efficient method for the identification as well as monitoring of analgesic antiinflammatory agents, particularly in serum of patients suffering from intoxication by overdosage of these agents.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed1990

Induction of MHC class II expression in recipient tissues caused by allograft rejection.

MHC class II antigens (DR) are not commonly expressed on parenchymal cells of kidney and liver except when they are allografts undergoing rejection. The objective of this study was to determine whether allograft rejection can also induce DR upregulation in parenchymal cells of autologous recipient organs. Dogs had unilateral renal autografts to facilitate kidney sampling. All kidneys were tubular cell DR-negative. After 8-14 days each dog received a tubular cell DR-negative allograft. Tubular cell DR became positive in both allograft and autograft simultaneously, its onset and intensity correlating with blast cell infiltration and rejection in the allograft. Blast cells were first detected in the autograft after allograft nephrectomy, and then disappeared as autograft tubular cell DR diminished over the next 6-8 days. This was reproduced on repeat allografting. In 2 untreated dogs hepatocytes became positive on day 4, with no hepatic blast infiltrate. Four other dogs received cyclosporine immunosuppression. Allograft and autograft tubular cell DR, and hepatocyte DR, increased in all dogs, but were delayed while on CsA until onset of rejection despite transient earlier allograft blast infiltration. Downregulation in autograft and liver occurred together after allograft nephrectomy. An interferon-like substance appeared in plasma after allografting in association with the DR changes in native kidney and liver. Renal allorejection therefore induces upregulation of parenchymal DR expression in autologous liver and kidney of the recipient. It is probably mediated by an interferon-like substance derived from cells infiltrating the allograft. The effect is modified by CsA.

Animals↗

PubMed1997

Comparison of genetic changes in frozen biopsies and microdissected archival material from the same colorectal liver metastases.

Microdissection of tissue sections from formalin-fixed, paraffin-embedded tumor material allows separation of microscopic sites within a sample. DNA can easily be extracted, and polymerase chain reaction (PCR) technology makes it possible to perform different molecular biologic analyses on small cell populations. The presence of normal cells or tumor heterogeneity may cause false negatives in allelic imbalance (AI) studies. Microdissected well-defined cell populations from a tumor section are assumed to increase the sensitivity of AI analyses. The present study has evaluated this in colorectal liver metastases by comparing genotypes in frozen biopsies with genotypes in microdissected archival samples from the same patients. Constitutional genotypes were obtained from corresponding peripheral blood leukocytes as well as normal liver tissue. Archival samples (n = 43) from 16 patients were analyzed after microdissection with 2-5 of 10 selected microsatellite markers. Frozen biopsies from one metastasis of each patient had previously been investigated at numerous microsatellite loci. From those results we selected, for the comparable analysis of archival samples, 41 tumor genotypes at 10 loci representing 11 heterozygotes, 13 AI, 7 losses of heterozygosity (LOHs), 8 homozygotes, and 2 microsatellite unstable cases. The microdissected samples revealed AI or a complete loss of one allele (LOH) in 5 of 11 (45%) genotypes that were previously evaluated as unchanged (retained heterozygosity) in the frozen biopsies, and LOH in 8 of 13 (62%) genotypes at loci known to exhibit AI in the frozen biopsies. Microsatellite instability, LOH, and homozygosity found in the frozen samples were all confirmed by analyses of the archival material. Intertumoral genetic heterogeneity was found in samples from two patients. The same allelic intensities were seen in DNA from tumor-close liver tissue as in blood DNA from the same patient except in one sample. The present study shows a 54% increase in sensitivity of genetic alterations if pure tumor cell components are used (five "new" AIs and LOHs and eight "new" LOHs among previously scored heterozygotes [n = 11] and AI [n = 13], respectively). In total, a 93% success rate (108/115 analyses) was obtained using standard PCR conditions for the 10 selected markers. The fact that standard PCR conditions and 5-micron tumor sections are used shows how easy these analyses are to perform, and that only minor amounts of valuable archival material is used.

Colorectal Neoplasms↗

PubMed2005

Morphometry of cells and guttae in subjects with normal or guttate endothelium with a contour detection algorithm.

PURPOSE: To develop a semiautomatic method to analyze morphology of cells and guttae in corneal endothelium. METHODS: Specular endothelial pictures from 42 and 21 subjects with healthy and guttate corneas, respectively, were analyzed independently by two observers with cell contour-extracting routines. One observer also analyzed healthy endothelia with the Corner method (Bambi). Differences between observers and between methods in mean cell area (MCA), coefficient of variation (CV), and percentage of cells with five, six, or seven sides were tested for significance with paired t tests. The Contour analysis of pictures with guttae included their mean area. RESULTS: There were no significant differences in MCA, CV, or the percentage of cells with five, six, or seven sides between the measurements obtained on repeated analysis by the same observer or on a second analysis performed by a different observer with the Contour method. However, the differences between the Contour and Bambi methods were statistically significant for MCA (337.5 +/- 37.7 vs. 327.7 +/- 36.5), CV (0.32 +/- 0.05 vs. 0.30 +/- 0.05), and percentage of cells with six and seven sides, but not for the percentage of five-sided cells. In subjects with guttata, the MCA was 561 +/- 170 microm, and the mean area of guttae was 1,538 +/- 849 microm. CONCLUSIONS: This detection algorithm is repeatable and reproducible, and it generates a cell border overlay useful in analyzing the morphology of cells and guttae. The analysis of corneal guttae could become a useful follow-up procedure to discriminate between patients with corneal guttata and Fuchs dystrophy.

Adult↗

PubMed1987

Evaluation of a bacteriophage-typing scheme for Enterobacter cloacae.

A set of 25 Enterobacter cloacae typing phages was evaluated. Of 384 test strains, 93.8% were lysed by at least one phage; the mean number of reactions/strain was 7.3. Discrimination between strains was satisfactory within the most frequent O serotypes; 0.9 patterns/strain were found for strains of serotypes O3 and O8. Overall, 325 patterns were found. Phage patterns were completely reproducible when duplicates of strains were typed on the same day, but only 40% reproducible when repeated after 18 months. The combination of O serology and phage typing discriminated well between hospital isolates.

Bacteriophage Typing↗

PubMed2000

Coercivity enhancement in exchange biased systems driven by interfacial magnetic frustration

We report the temperature and cooling field dependence of the coercivity of exchange biased MnF(2)/Fe bilayers. When the antiferromagnetic surface is in a state of maximum magnetic frustration and the net exchange bias is zero, we observe a strong enhancement of the coercivity, which is proportional to the exchange coupling between the layers. Hence, the coercivity can be tuned in a reproducible and repeatable fashion in the same sample. We propose that a frustrated interface provides local energy minima which effectively pin the propagating domain walls in the ferromagnet, leading to an enhanced coercivity.

Journal Article↗

PubMedDate not supplied

Flushing due to solitary cutaneous mastocytoma can be prevented by hydrocolloid dressings.

Solitary mastocytomas occur commonly and can occasionally be associated with troublesome flushing related to rubbing. We report a child with a solitary mastocytoma who repeatedly and reproducibly caused flushing only with rubbing and scratching. Conventional treatment with antihistamines was not completely effective and caused sedation. A trial application of double-layer hydrocolloid dressing led to complete abolition of flushing episodes until the child reached an age where he could peel off the dressings. This treatment is particularly suited to very young children with solitary mastocytomas whose parents do not feel comfortable with antihistamine treatment, topical or intralesional corticosteroids, or surgical interventions. This treatment may be used alone or in conjunction with conventional therapy where there has been a failure to achieve complete control of flushing and/or blistering.

Colloids↗