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PubMed1999

Repeatability and reproducibility of retention data and band profiles on reversed-phase liquid chromatography columns. III. Results obtained with Kromasil C18 columns.

The reproducibility of the retention data and the band profiles was investigated with Kromasil C18 columns (silica-based monomeric type reversed-phase packing material). High precision data were obtained and statistically compared among five columns from the same batch (column-to-column reproducibility) and six columns, one from each of six different batches (batch-to-batch reproducibility). These data were acquired under five different sets of chromatographic conditions, for a group of 30 neutral, acidic and basic compounds selected as probes following an experimental protocol previously described. Data characterizing the retention time, the retention factor, the separation factor, the column efficiency and the peak asymmetry for the different probe compounds are reported. Factors describing the silica surface interaction with the selected probe compounds, such as the hydrophobic interaction selectivity, the steric selectivity, and the separation factors of basic compounds at different pH values were also determined. The influence of the underlying silica on these data and correlations between the chromatographic and physico-chemical properties of the different batches are discussed.

Chromatography, Liquid↗
PubMed2006

Peripheral nerve morphometry: Comparison between manual and semi-automated methods in the analysis of a small nerve.

Manual nerve morphometry has been usually described as tedious, time consuming, difficult to perform correctly and subject to many sources of errors. The above considerations might suggest that fully automated image analysis systems could be ideally programmed to analyze myelinated fibers. However, operator intervention is necessary to manually eliminate dark tissue elements such as pericytes and Schwann cell nuclei. The aims of the present study were to compare the manual and semi-automated techniques in the evaluation of a small nerve, comparing the most commonly used morphometric parameters for nerve descriptions. The aortic depressor nerves (ADN) of male Wistar rats (N = 12) were prepared with conventional techniques for epoxy resin embedding. Manual morphometry was performed on photomicrographs using a digitizing tablet. Semi-automated morphometry was performed with the aid of computer software, on the same negative images used on the photographic procedure, which were scanned and digitized to a microcomputer. Our results show no differences between data obtained with both methods, for any of the evaluated parameters (area, perimeter, diameters, myelin sheath thickness, g ratio, distribution histograms). In conclusion, manual morphometry reproduced data obtained with semi-automated technique in a small nerve, with the advantages of being less-expensive and an affordable method.

Anatomy↗
PubMed2005

Application of multilocus sequence analysis (MLSA) for rapid identification of Enterococcus species based on rpoA and pheS genes.

The aim of this study was to evaluate the use of RNA polymerase alpha subunit (rpoA) and phenylalanyl-tRNA synthase (pheS) gene sequences as species identification tools for enterococci. Ninety-six representative strains comprising all currently recognized Enterococcus species were examined. rpoA gene sequences generated a robust classification into species groups similar to the one based on 16S rRNA gene sequence analysis. On the other hand, the pheS gene is a fast-evolving clock even better suited for species delineation than the rpoA gene, but not for recognition of species groups within Enterococcus as determined by both rpoA and 16S rRNA genes. All enterococcal species were clearly differentiated on the basis of their rpoA and pheS sequences. Evaluation of intraspecies variation showed that both rpoA and pheS genes have a high degree of homogeneity among strains of the same species. Strains of the same enterococcal species have at least 99% rpoA and 97% pheS gene sequence similarity, whereas, different enterococcal species have at maximum 97% rpoA and 86% pheS gene sequence similarity. It was concluded that both genes can be used as reliable tools for identification of clinical and environmental species of Enterococcus and are efficient screening methods for the detection of novel species. The sequence data obtained in this study were compared to the available atpA and 16S rRNA gene sequences. The MLSA approach to Enterococcus taxonomy provides portable, highly reproducible data with lower costs for rapid identification of all enterococcal species.

Bacterial Typing Techniques↗
PubMed1979

[Evaluation of accuracy comparing three types of urological manometers (author's transl)].

Manometrical examinations of the female urinary bladder are important in the field of urodynamic diagnosis. Accuracy in these measurements is a prerequisite for the reproducibility of the results. In this study, three types of urological manometers, differing in their principles of measurement, were tested for their physical and technical properties. Pressure was measured with a membrane manometer (instrument A) with Statham elements (instrument B), and with a micro-transducer (instrument C). The results using Statham elements and micro-transducers were exactly reproducible and varied only in their interference with external factors, which affect the quality of the results in clinical routine. Concerning the physical technique of measurement, instrument C with micro-transducers gives the most accurate results and is the easiest one to manage. For research and clinical routine it is superior to instrument B. It supplies reproducible data which are independent of external parameters such as the patient's position, attention and the way the instrument is set up. Our results only urodynamical measurements using micro-transducers can be taken as absolute measurements of excellent accuracy and are comparable among themselves as well as with other absolute measurements for long-term series of measurement. Using a membrane manometer (instrument A), measurements were hardly reproducible so that these results can be accepted as orienting data only.

Evaluation Studies as Topic↗
PubMedDate not supplied

Measuring physiological variables in nursing research.

Physiological indicators of health status are recommended for observational and intervention research with children, adolescents, and families. Sources of measurement error including those relevant to participants, the research protocol, and the specific physiological indicator must be identified and minimized. To this end, information presented is this column is designed to enhance the collection of accurate, reliable, and reproducible data with the ultimate goal of informing and enhancing evidence-based practice.

Bias↗
PubMed1990

On the generality of the "sit and reach" test: an analysis of flexibility data for an aging population.

Head rotation, shoulder extension and rotation, ankle plantar and dorsiflexion, hip flexion, and sit and reach (SR) scores were examined in 41 women and 39 men, aged 45-75 years. The SR gave more reproducible data than the other measurements (intraclass test/retest correlation over 8 months, r = .83). SR scores were independent of standing height (r2 = .068) but were greater in women (p less than .002). The flexibility at all joints was less than reported for young adults. There were age-related decreases of flexibility scores for the head and shoulder joints (p less than .01), with a parallel trend (p less than .05) for ankle plantar flexion and SR scores (the last only after inclusion of an age-gender interaction term). A principal components analysis identified three factors (tentatively identified as general trunk, ankle, and shoulder flexibility) accounting for 55.9% of total variance. SR scores had a moderate correlation with the first factor (r = .61) but only weak correlations with the second and third. Although the SR test is the most reliable simple instrument, it provides only limited information about the flexibility at other joints in an older population.

Adult↗
PubMed1998

The continuing problem of incorrect heart rate estimation in psychophysiological studies: an off-line solution for cardiotachometer users.

A wide variety of procedures are commonly used to record and estimate heart rate in psychophysiological studies. We analyze biases inherent in some estimates of mean heart rate based on cardiotachometers. Two types of errors are described, the time lag error and the incorrect weighted averaging error. These lead to an overestimation of the true heart rate, even when the analysis is based on digitized samples. Digitized samples provide a series of heart rate values per beat which correspond to the prior interbeat interval but during a time which does not correspond to the prior interval, but to the current one. A simple and practical solution, which eliminates both types of errors, is presented: an algorithm that corrects off-line the cardiotachometer data, reproducing the heart rate value with a length of time equal to the length of its own R R interval. Several comparisons between the corrected and uncorrected data are made to illustrate the magnitude of the error.

Heart Rate↗
PubMed2000

An insole pressure measurement system: repeatability of postural data.

This study analyzed the ability of an in-shoe plantar pressure measurement system to provide repeatable measurements of postural sway data for both healthy and clinical patients. Each participant's in-shoe pressure data were recorded for three trials during each test session during quiet stance. Healthy individuals (n = 9) participated on three consecutive days while clinical participants (n = 5) were tested on one day. Nine response variables were measured to assess their postural stability. Intrasubject measures were evaluated using the Kerlinger reliability procedure. Values provided directly by the Parotec System for a single day of testing yielded the following average coefficients: r = 0.95 (left), r = 0.97 (right) with mean coefficient values from the three day tests of: r = 0.98 (left), r = 0.98 (right). Variables calculated from raw data on a single day produced mean coefficients of: r = 0.77 (left), r = 0.76 (right) and over three days of: r = 0.65 (left), r = 0.66 (right). The ability to record highly reproducible data of postural sway parameters should assist clinicians to treat patients more confidently for balance deficiencies.

Biomechanical Phenomena↗
PubMed1982

Reliability of the thermodilution method in the determination of cardiac output in clinical practice.

The thermodilution (TD) method of determining cardiac output (CO) is widely used in clinical practice, but its reliability in this setting is not well understood and may be poor. This is especially true when dealing with unstable patients and using commercial TD devices. Numerous published reports have shown markedly variable results when comparing simultaneously the TD method and the Fick or dye-dilution methods in catheterization laboratories, intensive care units, or operating rooms. In order to assist clinicians in interpreting the reliability of the TD method in measuring CO, we analyzed all available published data (14 reports). The differing results in these reports were evaluated by standard statistical methods and by an extension of the influence function method of structural analysis developed to differentiate reproducibility and accuracy errors of each technique. Comparing the accuracy of the TD method with that of the Fick or the dye-dilution methods reveals that the 3 methods are of equal merit and can be used as independent references. Our reproducibility data show that when using commercial TD devices there must be a minimal difference of 12 to 15% (average, 13%) between determinations of cardiac output (3 measurements per determination) to suggest clinical significance. Minimal differences of 20 to 26% (average, 22%) are required between determinations when using 1 measurement per determination. There was no difference in the quality of the TD method when comparing rapid injection of iced or room temperature thermal indicator.

Cardiac Output↗
PubMed1994

Rapid determination of the antimycotic drug flucytosine in human serum by micellar electrokinetic capillary chromatography with direct sample injection.

The rapid determination of flucytosine (5-FC) in human serum by micellar electrokinetic capillary chromatography (MECC) with direct sample injection is discussed. Minute (nanoliter) quantities of patient sera are applied to the beginning of a fused silica capillary filled with a phosphate/borate buffer (pH 9.2) containing 75 mM sodium dodecyl sulfate. Upon application of an electric field along the capillary, endogenous and drug substances are transported toward the cathode and separated into distinct zones that are detected by on-column ultraviolet absorption. Depending on the capillary and instrument used, 5-FC is shown to elute within 2-3.5 min of current application and free of endogenous interferences. 5-FC becomes also well separated from another often coadministered antimycotic drug, amphotericin B. Thus, quantitation of 5-FC is accomplished without any sample pretreatment. MECC data of 60 patient sera produced on two different automated instruments and 5-FC serum levels obtained by an agar-based bioassay are shown to agree well. For MECC, intraday and interday reproducibility data (80 micrograms/ml level) are shown to be < or = 4.5 and < 7%, respectively. Due to short run times and short capillary equilibration time intervals between runs, a sample throughput of 15/h is feasible. Thus, this technology is suitable for rapid determination of 5-FC serum levels, the time requirement for running a complete calibration, two control sera, and several patient samples being approximately 1 h only.

Calibration↗
PubMed2002

Studying genotype-phenotype relationships: cardiovascular disease as an example.

Cardiovascular disease is a multifactorial disorder resulting from the complex interaction of a plethora of both environmental and genetic factors. The "candidate gene" approach aims at identifying the genes contributing to cardiovascular disease assessing their entire polymorphic spectrum and the consequences of their combination in appropriate large association studies. In view of the sequence data available for the entire human genome, candidate sequences will more easily be traced and located in their chromosomal context. More powerful sequencing devices are available and will hopefully give reliable and reproducible data not only on the nucleotide sequence diversity in different populations throughout candidate regions of the human genome. The choice and the assessment of disease-related or intermediate phenotypes, especially in clinical settings, will be again more crucial in the future when the knowledge of gene sequence variation significantly increases. Identification of relevant genes and genetic variants involved in the different pathophysiological steps leading to cardiovascular disease may considerably improve our understanding of the mechanisms of the disease course. This may help to identify high-risk individuals and groups or subgroups in whom specific therapeutic interventions are indicated or necessary, leading to an individually adapted clinical management.

Cardiovascular Diseases↗
PubMed2006

Gene expression analysis of the hepatotoxicant methapyrilene in primary rat hepatocytes: an interlaboratory study.

Genomics technologies are used in several disciplines, including toxicology. However, these technologies are relatively new, and their applications require further investigations. When investigators apply these technologies to in vitro experiments, two major issues need to be clarified: a) can in vitro toxicity studies, in combination with genomics analyses, be used to predict the toxicity of a compound; and b) are the generated toxicogenomics data reproducible between laboratories? These questions were addressed by an interlaboratory study with laboratories of four pharmaceutical companies. We evaluated gene expression patterns from cultured rat primary hepatocytes after a 24-hr incubation with methapyrilene (MP). Extensive data analysis showed that comparison of genomics data from different sources is complex because both experimental and statistical variability are important confounding factors. However, appropriate statistical tools allowed us to use gene expression profiles to distinguish high-dose-treated cells from vehicle-treated cells. Moreover, we correctly identified MP in an independently generated in vitro database, underlining that in vitro toxicogenomics could be a predictive tool for toxicity. From a mechanistic point of view, despite the observed site-to-site variability, there was good concordance regarding the affected biologic processes. Several subsets of regulated genes were obtained by analyzing the data sets with one method or using different statistical analysis methods. The identified genes are involved in cellular processes that are associated to the exposure of primary hepatocytes to MP. Whether they are specific for MP and are cause or consequence of the toxicity requires further investigations.

Animals↗
PubMed2006

Cross-species hybridizations on a multi-species cDNA microarray to identify evolutionarily conserved genes expressed in oocytes.

BACKGROUND: Comparative genomic analysis using cDNA microarray is a new approach and a useful tool to identify important genetic sequences or genes that are conserved throughout evolution. Identification of these conserved sequences will help elucidate important molecular mechanisms or pathways common to many species. For example, the stockpiled transcripts in the oocyte necessary for successful fertilization and early embryonic development still remain relatively unknown. The objective of this study was to identify genes expressed in oocytes and conserved in three evolutionarily distant species. RESULTS: In this study we report the construction of a multi-species cDNA microarray containing 3,456 transcripts from three distinct oocyte-libraries from bovine, mouse and Xenopus laevis. Following the cross-species hybridizations, data analysis revealed that 1,541 positive hybridization signals were generated by oocytes of all three species, and 268 of these are preferentially expressed in the oocyte. Data reproducibility analyses comparing same-species to cross-species hybridization indicates that cross-species hybridizations are highly reproducible, thus increasing the confidence level in their specificity. A validation by RT-PCR using gene- and species-specific primers confirmed that cross-species hybridization allows the production of specific and reliable data. Finally, a second validation step through gene-specific microarray hybridizations further supported the validity of our cross-species microarray results. Results from these cross-species hybridizations on our multi-species cDNA microarray revealed that SMFN (Small fragment nuclease), Spin (Spindlin), and PRMT1 (Protein arginine methyltransferase 1) are transcripts present in oocytes and conserved in three evolutionarily distant species. CONCLUSION: Cross-species hybridization using a multi-species cDNA microarray is a powerful tool for the discovery of genes involved in evolutionarily conserved molecular mechanisms. The present study identified conserved genes in the oocytes of three distant species that will help understand the unique role of maternal transcripts in early embryonic development.

Animals↗
PubMed1996

Evaluation of the home pad test in the investigation of female urinary incontinence.

OBJECTIVE: To evaluate the use of the home pad test in the management of patients with urinary dysfunction with reference to feasibility, normal data, reproducibility, compliance and accuracy when compared to video urodynamics. DESIGN: A prospective study to determine 1. the accuracy of weighing pads by healthcare workers compared to weighing by patients with a spring balance; 2. the effects of evaporation; 3. the pad weight increase in continent women; 4. the compliance over 194 tests in terms of acceptability and feasibility; 5. the reproducibility in 112 women for the 24 h and 48 h tests, 6. the comparison with video urodynamic studies in 149 patients. SETTING: A London teaching hospital. MAIN OUTCOME MEASURES: Coefficient of variation and mean deviation analysis were employed to determine the accuracy of measurement. Percentage changes in standardised wet pad weights over a period of 8 weeks were used to determine the rate of weight loss due to evaporation. The percentage of patients completing the test satisfactorily was documented. The increase in the weights of all pads worn during the test period was measured in continent volunteers and incontinent patients. Video urodynamic diagnoses were used as the Gold Standard for comparison. RESULTS: Twelve perineal pads were weighed by 15 healthcare workers with a resulting coefficient of variation equal to 1.55% (standard error = 0.09%). The mean deviation between patient-measured pad weights and staff-measured weights was 49% (SD = 132%). Pads wetted with saline showed no difference in weight after 1 week and less than 5% change in weight after 8 weeks, with the upper 95% confidence limit of less than 10% loss. The mean pad weight increase over 48 h in continent women was 7.13 g (SD = 4.32 g) giving a 95% upper confidence level of less than 15 g. Compliance was reasonably high with 161 (83%) carrying out the test perfectly. Test-retest analysis of the 24 h and 48 h tests showed a strong relationship with correlation coefficients of 0.90 and 0.94 respectively. The reproducibility was also good, with differences as a percentage of the mean between the first and second test being 6.9% and 1.6% for the 24 h and 48 h tests respectively. There was good concordance when the urodynamic study data was compared with pad weight data in terms of incontinence compared with no incontinence (kappa = 0.65), but a high false positive rate was detected for the pads. When eight of these patients with a false positive pad test had repeat video urodynamic studies, six were found to have detrusor instability on the second study. CONCLUSIONS: The home pad test combined with frequency volume chart documentation is an easy test to perform. It is quite robust and reasonably reproducible. This test should be added to complement the routine urodynamic tests and may have a role in detecting occult detrusor instability.

Female↗
PubMed1992

High-performance liquid chromatographic determination of 2-furaldehyde in spirits.

Official methods for the determination of 2-furaldehyde in spirits involve for a spectrophotometric evaluation, which is characterized by poor specificity. Gas chromatographic evaluations have also been proposed, which offer a much higher sensitivity, particularly when capillary columns are used. In this paper a high-performance liquid chromatographic (HPLC) method based on the formation of the 2,4-dinitrophenylhydrazones of carbonyl compounds and subsequent reversed-phase separation of these derivatives is described. Derivatization is carried out by utilizing an acidic solution of 2,4-dinitrophenylhydrazine in acetonitrile. Precipitation of the derivatives is avoided and direct injection of the sample into the HPLC system is allowed. The determination offers a high specificity and a detection limit of the order of 10(-8) mol/l. Accuracy and reproducibility data are presented.

Alcoholic Beverages↗
PubMed1987

Experimental parameters and a biological standard for acridine orange detection of drug-induced alterations in chromatin condensation.

We investigated a number of sample-preparative parameters for use of flow cytometry to detect chromatin condensation in cells stained with acridine orange after DNA in situ is partially denatured by acid treatment. Stability and data reproducibility for both control and drug-treated ME-180 and HT-29 cells were assessed over: a range of cell concentrations in 2.56 X 10(-5) M acridine orange; 15 days of storage in fixative; various times between RNase digestion and staining; and increasing times between staining and analysis. Listmode data for red and green fluorescence were collected and mean fluorescence intensities of G1, S, and G2 subpopulations of HT-29 and ME-180 cells were computed. These were normalized to data from HeLa-S3 cells and fluorescent microspheres to control for inter-experiment variations in staining and instrumental parameters, respectively. The normalized red and green fluorescence data were used to calculate alpha 1 for G1 cells [alpha t = red fluorescence/(total fluorescence)]. Exponentially growing HeLa-S3 cells were a very consistent and reproducible biological standard to control for fixation and staining variability. Mean fluorescence intensities of control and difluoromethylornithine-treated (i.e., polyamine depleted) cells remained stable and reproducible across all tested ranges for cell concentration, storage in fixative, and time after RNase digestion. This technique can thus be used to evaluate difluoromethylornithine-induced changes in chromatin condensation of samples stored for as long as 2 weeks and analyzed all on 1 day.

Acridine Orange↗
PubMed2006

The economics of PillCam.

Evaluation of the economics of PillCam technology is in its infancy. Most studies of the use of the PillCam, both small bowel and esophageal, have focused only on the capsules' diagnostic characteristics. Although the results have compared favorably with other more invasive and sometimes less accurate modalities, the true cost effectiveness of PillCam is not yet fully known. The few cost-effectiveness assessments performed suggest that PillCam compares favorably with traditional diagnostic methods in Crohn's disease and in screening for complications of GERD and for esophageal varices. The data included in these models are quite limited, however. Sensitivity analyses can permit assessment of a wide range of possibilities regarding cost and diagnostic efficacy. Still, these models need to be anchored by robust and reproducible data input. Large-scale studies with long-term follow-up are needed. Capture of both direct and indirect medical costs accrued by using PillCam or other diagnostic tests in these studies will permit more robust economic analyses. As data accrue,they may give clinicians more confidence that PillCam use will realize economic savings and improve patient outcomes.

Chronic Disease↗
PubMed1994

Determination of tilmicosin in ovine milk using high-performance liquid chromatography.

Tilmicosin is a novel macrolide antibiotic with a wide range of therapeutic uses against gram positive (+ve) and gram negative (-ve) bacteria and mycoplasmae causing pneumonia and mastitis and can be used to treat these diseases in sheep. After its use there may be residues present in ovine milk that interfere with cheese making and processing of other milk products. It is important to monitor for the presence of tilmicosin in ovine milk and a method has been optimized and validated for its determination. Tilmicosin is extracted from milk into methanol. The methanol extract is acidified and non-polar co-extractives removed using hexane followed by carbon tetrachloride. The pH is adjusted to 9.0 and the tilmicosin partitioned into chloroform. The chloroform extract is evaporated to dryness and the residue resuspended in high-performance liquid chromatography (HPLC) mobile phase. Tilmicosin is determined using reversed-phase HPLC and ultraviolet (UV) detection at 280 nm. Recovery of tilmicosin from ovine milk fortified over the range 50 to 250 micrograms l-1 is in the range 84.3-104.8%, with a relative standard deviation ranging from 6.6 to 12.9%. The proposed procedure allows the determination of residues of tilmicosin in ovine milk at levels less that 50 micrograms l-1 and satisfies the quality criteria specified in European Commission Decision 93/526/EEC with the exception of reproducibility data from interlaboratory trials.

Animals↗