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Results for “Repeatability and Reproducibility”

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PubMed2003

Reproducibility of callosal effects of transcranial magnetic stimulation (TMS) with interhemispheric paired pulses.

Transcranial magnetic stimulation (TMS) of the motor cortex of one hemisphere (conditioning stimulus (CS)) inhibits EMG responses evoked in distal hand muscles by a later magnetic stimulus given at an appropriate interval, over the opposite hemisphere (test stimulus (TS)). This effect is commonly attributed to an inhibition produced at cortical level via a transcallosal route. The present study assessed the reproducibility of the transcallosal inhibition effects in different sessions in healthy subjects. Within- and between-subject variability, relating to interhemispheric differences was also evaluated. A magnetic CS on one hemisphere effectively inhibited EMG responses of the abductor digiti minimi stimulated by a TS delivered over the opposite hemisphere in a range of intervals centered at 12 ms. Even though group effects were reproduced in separate sessions, the high between- and within-subject variability yielded low test-retest correlations. This differentiation forces the definition of reproducibility (or repeatability), as the replication of the same mean curves of EMG reduction, and of reliability, as the between- or within-subject correlations between values of specific EMG measures.

Adult↗

PubMed2001

Analysis of post-harvest fungicides by micellar electrokinetic chromatography.

A method based on solid-phase extraction (SPE) and micellar electrokinetic chromatography (MEKC) was developed for the simultaneous determination of carbendazim, imazalil, methylthiophanate, O-phenylphenol, prochloraz, procimidone, thiabendazole and triadimefon residues in grape, lettuce, orange and tomato. Selectivity and resolution were studied changing the pH and the concentration of the buffer, the type and concentration of surfactant and the methanol content in the mobile phase. A buffer consisting of 4 mM borate with 75 mM sodium cholate (pH 9.2) gave the best results. The recoveries of the fungicides in spiked fruit and vegetable samples ranged from 30 to 105%, and the limits of detection were between 0.1 and 1 mg kg(-1). The reproducibility and repeatability of the combination of SPE pretreatment and MEKC were good for all the compounds, except for imazalil and O-phenylphenol in oranges, due to some matrix compounds interfering with the separation. The method was applied to post harvest treated samples, and the fungicides were sometimes detected at concentration levels lower than maximum residue limits (MRLs).

Buffers↗

PubMed1994

Strain gauge plethysmography and Doppler ultrasound in the measurement of limb blood flow.

The maintenance of adequate oxygen delivery (DO2) and tissue uptake (VO2) has become central dogma in the management of the critically ill. However, these parameters are derived using gas tensions measured in mixed venous blood and may not reflect changes in regional blood flow. Therefore, it has become necessary to provide estimates of blood flow to specific organs and to evaluate the most adequate techniques available. In order to define the best means of assessing blood flow to the lower limb noninvasively in normal subjects, measurements of superficial femoral arterial blood flow using Doppler ultrasound (DU) and strain gauge plethysmography (SGP) were compared in 10 normal volunteers at rest and during exercise. To evaluate the effect of strain gauge positioning, results of measurements made under four different combinations of cuff/strain gauge placement were compared in 15 other volunteers. The correlation of the limb blood flow obtained using the two methods at rest and exercise was 0.57 and 0.62 and the limits of agreement (d +/- 2SD) were 0.40 +/- 2.49 and -0.86 +/- 5.22 ml 100 ml-1 tissue min-1 at rest and on exercise, respectively. Results obtained using SGP were more reproducible (Coef. repeat. 0.45 vs. 0.94 ml 100 ml-1 tissue min-1, for SGP and DU, respectively). The various combinations of cuff/strain gauge positioning showed a tendency to over-read when the latter was placed on the thigh, but were not significantly different (P > 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1994

Determination of theophylline metabolites in human liver microsomes by high-performance liquid chromatography.

A method for the quantitation of three metabolites of theophylline, 1-methylxanthine (1 MX), 3-methylxanthine (3MX), and 1,3-dimethyluric acid (13DMU) in human liver microsomes has been developed. The method is based on a simple one-step extraction followed by isocratic, reversed-phase high-performance liquid chromatography with uv detection (detection wavelength: 273 nm). The detection limit was 0.03 nmol.mg-1.h-1, which corresponds to 10 pmol per sample for all three metabolites. Linear standard curves were obtained for all three compounds within a concentration range of 0.6-6.0 nmol.mg-1.h-1 for 3MX and 1MX and 2.4-24.0 nmol.mg-1.h-1 for 13DMU. The absolute recoveries ranged from 61 to 80%, 68 to 74%, and 74 to 85% for 1MX, 3MX, and 13DMU, respectively, within the concentration range of the standard curve. The reproducibility and repeatability showed a coefficient of variation < 12% at five concentrations within the standard curve range. The accuracy for all three metabolites was within +/- 5% at three concentrations, except for 1MX in the lowest concentration (12%). The simple but sensitive method developed is highly suitable as a probe for cytochrome P4501A2 (CYP1A2) and probably also CYP2E1 function in human liver microsomes.

Chromatography, High Pressure Liquid↗

PubMed2007

Reliability and usefulness of a new in vivo measurement system of the pivot shift.

Residual pivot shift after ACL reconstruction is a crucial factor related to poor clinical outcome. However, no method exists that is able to evaluate pivot shift quantitatively and noninvasively. We propose a new measurement system for the pivot shift test using an electromagnetic device and have evaluated its reliability and clinical usefulness. Posterior translation, lateral translation and maximum velocity during the reduction phase of pivot shift were calculated and used as parameters for evaluation. In measurement system analysis, discrepancies of motion between the bones and the sensors were minimal, while reproducibility in repeated measurement was acceptable. Next, clinical usefulness was evaluated by correlating the values obtained by kinematic measurement with the clinical grade. We found differences in each of the measured parameters among clinical grades. These data suggest the system is a valuable measurement tool for clinical evaluation of the pivot shift test.

Anterior Cruciate Ligament↗

PubMed1982

Computer analysis of slow vital capacity spirograms.

We have developed a digital computer program which evaluates the vital capacity and its subdivisions, expiratory reserve volume and inspiratory capacity. The algorithm examines the multibreath spirogram, a continuous record of quiet breathing interspersed among repeated slow, large volume maneuvers. Quiet breaths are recognized by comparing features of each breath to the respective average and variation of these features for all breaths. A self-scaling, iterative procedure is used to identify those end-tidal points that most likely represent the subject's functional residual capacity. A least-squared error baseline is then fit through these points to partition the vital capacity. Twenty-three spirograms from patients with documented pulmonary disease were independently analyzed by the computer, a pulmonary function technician, and the laboratory supervisor. No practical differences were found among the results. However, the computer's values, in contrast to those of the technician, were reproducible on repeated trials and free of computational and transcriptional errors.

Computers↗

PubMed2000

Description and validation of a novel liquid metal-free device for venous congestion plethysmography.

We present a newly developed electromechanical sensor with automated calibration for strain-gauge plethysmography (filtrass) and compare it to a conventional mercury-in-Silastic strain-gauge plethysmograph (MSG). Fluid filtration capacity (K(f)) and isovolumetric venous pressure (Piv) of the limb were assessed noninvasively with both devices in 29 healthy volunteers. We found significantly higher K(f) and Piv values with MSG [4.6 +/- 2.0 x 10(-3) ml. min(-1). mmHg(-1). 100 ml tissue(-1) (K(f) units; K(f)U) and 21.2 +/- 8.1 mmHg for Pvi], than with filtrass, giving values of 3.1 +/- 0.8 K(f)U and 15.1 +/- 7.1 mmHg. Because K(f) and Piv are profoundly influenced by the calibration, we investigated the quality of the calibration signal and its impact on the obtained values. We could show that the reproducibility of repeated calibrations was higher with filtrass (58% lower mean +/- SD). The data were grouped according to the quality of calibration, and we found no significant difference in K(f) and Piv between filtrass (3.0 +/- 0.7 K(f)U and 15.9 +/- 6.9 mmHg, respectively) and MSG with good calibration signal (3.3 +/- 0. 8 K(f)U and 18.6 +/- 7.1 mmHg, respectively; no significant difference). However, we obtained significantly higher MSG values (5. 6 +/- 2.0 K(f)U and 23.1 +/- 8.4 mmHg, respectively; P < 0.001) in the group with a bad calibration signal. We suggest that the filtrass sensor, which performs an automatic, standardized calibration procedure and shows a linear signal response to stretch, gives highly reproducible and reliable results and thus is more suitable for routine application.

Adult↗

PubMed2003

Multiplex single nucleotide extension: a robust and high throughput method for HLA-A locus typing.

This report describes a typing method that can identify all known human leukocyte antigen A (HLA-A) alleles by determining nucleotides present at polymorphic sites using single nucleotide extension. Allele specific primers are bound to capture oligonucleotides which allows for a multiplex approach during single nucleotide extension (SNE) reactions. Eleven group-specific polymerase chain reaction amplifications were performed to obtain the templates to be analyzed with sets of primers designed to investigate the polymorphisms. Extension of biotin-labeled ddNTPs onto allele-specific primers was catalyzed by a DNA polymerase and each primer was hybridized to a specific capture oligonucleotide covalently bound to a bead. After staining with streptavidin-PE, incorporated fluorescence was determined with a flow cytometer. Fluorescence intensities were interpreted by computer and the nucleotide sequence was translated into HLA-A genotypes. Group-specific amplification reactions and primer sets for SNE were validated with 42 reference samples of known HLA-A alleles. In addition, 296 samples from three populations (N. A. Caucasian, African-American, Terena S. A. Indian) were analyzed and results compared to previous typing by SSOP. Reproducibility between repeated typings was 100% and ambiguities were quite rare. The method has been found to be accurate, relatively simple to perform and fast. It is our method of choice for high resolution clinical HLA-A typing.

Alleles↗

PubMed2003

SBSE-GC-ECD/FPD in the analysis of pesticide residues in Passiflora alata Dryander herbal teas.

Stir bar sorptive extraction (SBSE) in combination with GC-ECD/FPD analysis is here applied to the determination of the residues of 11 pesticides (hexachlorobenzene, lindane, chlorothalonil, parathion methyl, parathion ethyl, fenitrothion, malathion, dieldrin, alpha- and beta-endosulfan, and tetradifon) in herbal teas prepared with Passiflora alata Dryander spiked leaves. The method was optimized using spiked herbal teas in a range from 0.05 to 1 pg/microL for organochlorine pesticides and from 0.15 to 3 pg/microL for organophosphorus pesticides. The method is reproducible and repeatable with recoveries calculated from herbal teas prepared with spiked plant material versus spiked herbal teas, varying from about 30% for tetradifon to about 90% for parathion methyl and malathion. The limits of quantitation (LOQs) ranged from 0.017 pg/microL for lindane to 0.117 pg/microL for malathion.

Beverages↗

PubMed2001

Characterization of secondary hyperalgesia produced by topical capsaicin jelly--a new experimental tool for pain research.

Peripheral administration of the nociceptive agent capsaicin is used as an experimental tool to study neurophysiological and pharmacological aspects of the generation and control of pain. When investigating secondary hyperalgesia phenomena, current topical and intradermal capsaicin delivery methods have two key limitations. Intradermal injection can evoke severe chemogenic pain and both delivery methods produce an unstable area of dynamic mechanical allodynia. We present validity studies of a new preparation for capsaicin delivery that overcomes these limitations. The novel capsaicin formulation consists of a water-based semisolid jelly preparation containing 1% capsaicin which is applied topically under adhesive-free occlusion to a small area of the skin. We demonstrate that in healthy human subjects this model evokes areas of flare, punctate hyperalgesia and mechanical allodynia which are equivalent to established models and that these areas are stable over time and reproducible on repeat experiments. The jelly formulation evokes only minimal chemogenic pain and, as the preparation remains in situ throughout the study providing constant capsaicin exposure, a stable area of dynamic mechanical allodynia is produced. These validation studies show that this novel capsaicin administration method is a practical, reliable and viable tool for investigating experimental secondary hyperalgesia.

Administration, Topical↗

PubMed1994

Evaluation of standardized methods for registration of time-dependent orthodontic tooth movements.

An in vitro study was conducted to compare reproducibility of repeated recordings obtained from devices constructed for standardized registrations. An existing radiographic method and a new photographic technique were employed. On five in vitro models, half of the maxilla from dry skulls, special designed splints with a Troll-biten film holder were constructed. A stiff metal bar attached to the splints and to either an X-ray apparatus or a standard photographic camera made it possible to obtain standardized registrations. For each model 10 radiographs and photographs were taken before and after the canine was moved. Subtracting the values from well defined points for these pictures, 10 pairs of coordinates were available for each of the models with both methods. The findings showed very similar reproducibility for the two methods with 95 per cent of the discrepancies within a magnitude of 0.12 mm for the radiographic method and 0.14 mm for the photographic method. When evaluating the canine movements, similar results were observed. No significant difference could be detected in the five in vitro models. In addition, the results showed that a splint can be used as a stable reference for registration of tooth movements. Because of ethical objections to unnecessary radiation, the photographic registration technique might substitute the radiographs in future investigations where standardized periodic records are necessary for the description of tooth movement.

Analysis of Variance↗

PubMed1995

Simultaneous amplification of four DNA repair genes and beta-actin in human lymphocytes by multiplex reverse transcriptase-PCR.

We describe here the development, optimization, and use of a non-radioactive, quantitative, multiplex reverse transcriptase-PCR technique to measure, in a single reaction, the relative levels of the transcripts of four DNA repair genes (XPCC, hMSH2, XRCC1, and ERCC1) and the beta-actin gene in lymphoblastoid cell lines and frozen peripheral blood lymphocytes. Expression of defective DNA repair genes was not detected in DNA repair-deficient human cell lines, whereas the intact genes were detected in repair-proficient cell lines and in lymphocytes from a normal donor. The assay was reproducible, and repeated determinations of the same samples generated highly consistent results for each target gene. This approach should facilitate molecular epidemiological studies that incorporate screening for germline alterations that may affect gene expression and for changes in the levels of gene expression.

Actins↗

PubMed1989

Efficiency of the respiratory muscles in healthy individuals.

We evaluated respiratory muscle performance by determining the energy cost of breathing against incremental threshold loads and calculating the efficiency of the respiratory apparatus for handling the added work. In five subjects, the energy cost of breathing against the loads, and thus the calculated efficiency of the respiratory muscles, was reproducible on repeated measurements. In all subjects, the calculated efficiency varied while breathing with low loads but was relatively constant at loads that resulted in a mouth pressure of 20 to 60% of the subjects' maximal static inspiratory pressure (PImax). The mean efficiency calculated between 20 to 60% of PImax in 30 normal subjects (15 males and 15 females) ranged between 1.54 and 7.98%. It was significantly greater in males (5.41 +/- 0.43%) (mean +/- SEM) than in females (2.41 +/- 0.17%). There was no relationship between efficiency and body size, but the efficiency correlated with inspiratory muscle strength (PImax). We suggest that measurement of the efficiency of the respiratory muscles over a spectrum of incremental threshold loads is a simple, noninvasive, and reproducible method of assessing respiratory muscle performance and may have clinical application.

Adolescent↗

PubMed2002

Impact of anesthesia on cardiac function during echocardiography in mice.

Anesthetics provide sedation and immobility facilitating echocardiography in mice, but influence cardiac function. We studied the effects of intraperitoneal and inhaled anesthetic agents on echocardiographic measurements. Mice were anesthetized with intraperitoneal tribromoethanol (TBE), ketamine-midazolam (K/M), ketamine-xylazine (K/X), or inhaled isoflurane (Isf), and echocardiographic parameters were assessed at 5, 10, 15, and 20 min. In C57BL/6N mice, Isf produced high initial heart rates (HR) that decreased to levels comparable to TBE at 15-20 min (approximately 450 beats/min) and the most stable percent fractional shortening (%FS) and end-diastolic dimension (EDD). With TBE, %FS initially was low, but increased comparable to Isf (approximately 45%) at 15 min. K/M produced similar time trends but lower absolute values compared with TBE for all parameters. K/X produced cardiac depression evidenced by low HR and %FS, and increased EDD. Isf was the most reproducible in repeat studies at 12 days. In C57BL/6J compared with C57BL/6N mice, K/M produced higher HR, and %FS and TBE produced smaller EDD. In conclusion, anesthetic agent, timing of echocardiographic measurements, and genetic background are all critical variables during echocardiography in mice.

Administration, Inhalation↗

PubMed2002

Early clinical experience with the novel proteasome inhibitor PS-519.

AIMS: The main objective of this study was to investigate the safety, tolerability and pharmacodynamics of the novel proteasome inhibitor PS-519 in young male volunteers. Many pro-inflammatory mediators such as cytokines and cell adhesion molecules that are responsible for the development of the cerebral infarct are under the control of the transcription factor Nuclear Factor kappa-B (NF-kappaB). The activity of NF-kappaB is itself tightly regulated through the multicatalytic enzyme known as the proteasome. PS-519 is a novel and highly selective small molecule that inhibits the proteasome. An ex vivo assay of 20S proteasome activity allows monitoring of the drug effect in blood. PS-519 is protective in multiple animal models of cerebral ischaemia over a range of doses that achieve 20S inhibition of 40%-80%. METHODS: PS-519 has been administered to healthy male volunteers as single and repeated doses up to 1.6 mg m(-2). It was given as an intravenous bolus over 20-30 s in a double blind, randomized, placebo-controlled phase I study, examining vital signs, safety, tolerability and blood 20S proteasome inhibition. RESULTS: Thirty-nine subjects received single doses of 0.012 mg m-2-1.6 mg m(-2) and 28 subjects received doses of 0.5 mg m(-2)-1.6 mg m(-2) on three consecutive days. The drug was well tolerated. There was no clear treatment-emergent symptom or abnormality of laboratory tests. Proteasome inhibition in blood samples as measured by 20S assay achieved the intended maximum target level of 70-80% with 1.6 mg m(-2), and was reproducible with repeated dosing. CONCLUSIONS: This study has demonstrated that proteasome inhibition is well tolerated by healthy subjects at levels that are maximally neuroprotective in experimental conditions. Further clinical evaluation appears justified.

Acetylcysteine↗

PubMed1991

Laboratory evaluation of the vital signs (ICOR) piezoelectric anesthetic agent analyzer.

The Vital Signs (ICOR) anesthetic agent analyzer, which measures anesthetic vapor concentration by a piezoelectric crystal technique, was evaluated by using standard-calibration gases to measure the accuracy, response time, gas interference, and water vapor dependence of the analyzer. The accuracy for the measurement of vapor concentration was better than 0.08 vol%. The reproducibility of repeated measures averaged 0.003 vol%. The offsets caused by other gases were 0.02 vol% for water vapor, 0.08 vol% for 70% nitrous oxide, and less than 0.01 vol% for oxygen and carbon dioxide. Response time (10 to 90%) was 475 ms. The agent analyzer may be well suited for monitoring volatile agent concentrations during anesthesia.

Anesthesia, Inhalation↗

PubMed2006

Monolithic silica columns of various format in automated sample clean-up/multidimensional liquid chromatography/mass spectrometry for peptidomics.

The following particulate and monolithic silica columns were implemented in a fully automated and flexible multidimensional LC/MS system with integrated sample clean-up, to perform the analysis of endogeneous peptides from filtered urine and plasma samples: restricted access sulphonic acid strong cation-exchanger (RAM-SCX) for sample clean-up, RP 18 Chromolith guard columns as trap columns and 100 microm I.D. monolithic RP 18 fused silica capillary columns as last LC dimension. The results show sufficient overall system reproducibility and repeatability. Implementation of monolithic silica columns added an additional flexibility with respect to flow rate variation and adjustment due to the low column back pressures. Also, monolithic columns showed a lower clogging rate in long-term usage for biological samples as compared to particulate columns. The applied system set-up was tested to be useful for the routine peptide screening in search of disease biomarkers.

Chromatography, Liquid↗

PubMed1997

Echocardiographic changes after myocardial infarction in a model of left ventricular diastolic dysfunction.

To determine the early and late effects of myocardial infarction on left ventricular (LV) diastolic function in the rabbit postinfarction model, male New Zealand White rabbits were randomly assigned to ligation of the circumflex artery or sham operation. Serial echocardiographic and Doppler studies were performed on both groups of animals at baseline and 1 h and 3 wk after surgery (n = 10 for each group) after verification of the reproducibility and repeatability of the measurements. At 1 h postinfarction, decreases in early mitral inflow velocity (E wave) and mitral inflow velocity with atrial contraction (A wave) and increases in the mean pulmonary venous systolic-to-diastolic ratio and A wave reversal velocities were observed, without changes in LV geometry. By 3 wk postinfarction, increases in the mitral E-to-A ratio (1.1 +/- 0.3 vs. 2.9 +/- 0.9, P < 0.001) and left atrial area (131 +/- 23 vs. 510 +/- 72 mm2, P < 0.001) and decreases in the pulmonary venous systolic-to-diastolic ratio (0.56 +/- 0.20 vs. 0.79 +/- 0.14, P = 0.008) were consistent with severe diastolic abnormalities (restricted physiology). The findings of this study demonstrate that coronary artery ligation in the rabbit provides a reproducible echocardiographic and Doppler model of LV diastolic dysfunction that is consistent with abnormalities found in humans with previous myocardial infarction, symptoms of heart failure, and preserved LV systolic function.

Animals↗