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Results for “Repeatability and Reproducibility”

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PubMed2005

Discrimination of isolates of Mycobacterium bovis in Northern Ireland on the basis of variable numbers of tandem repeats (VNTRs).

The ability to reproducibly discriminate Mycobacterium bovis isolates and trace their transmission has the potential to clarify sources of infection and major routes of transmission for bovine tuberculosis (TB). A PCR-based genotyping assay has been developed to discriminate between strains of M bovis by examining multiple sites in its genome that consist of variable numbers of tandem repeats (VNTRS). The discriminatory power and reproducibility of this VNTR typing has been compared with that of the established PCR-based spoligotyping technique by using a panel of 461 isolates of M bovis prevalent in Northern Ireland. The VNTR assay discriminated 40 different profiles, the most prevalent of which constituted 21 per cent of the total, compared with 14 profiles discriminated by spoligotyping, the most prevalent of which constituted 65 per cent. No significant differences were observed between the prevalences of the VNTR profiles in the years from 1999 to 2003. A preliminary evaluation indicated that most genotypes predominated in particular areas of the country. This VTNR typing assay was found to be highly discriminating, with the performance characteristics to support its systematic application to the molecular epidemiology of bovine TB.

Animals↗

PubMed2004

[Gene differential expression of liver tissues in crossbred versus purebred chicken and their relationship with heterosis of meat trait].

The concept of heterosis has already been put forward for a century. The hypothesis of Dominance, Superdominace and Epistasis has also been brought forward to explain the phenomenon of heterosis. As we know, there is spatio-temporal speciality about the expression of gene and only expressed genes contribute to the formation of heterosis. So the study on heterosis in expression level becomes more meaningful. A lot of studies on heterosis in this level have been done in plants, but there is no such study carried on animals in this area. In this study, the technique of mRNA Reverse Transcription Differential Display was used to research the heterosis molecular mechanism of animal. In order to expound the molecular genetic mechanism of animals heterosis, the 4 x 4 completely diallele cross experiment of 4 purebreds chicken was conducted among White Polymouth Rock (EE), Chinese Silk Chicken (CC), CAU Brown (DD) and White Leghorn (AA). The chicken of 16 cross combinations were reared to 8 weeks old, then 30 chicken in each combination were selected randomly and slaughtered. The traits of body weight of 8 weeks, wing weight, eviscerated weight, eviscerated weight with giblet, breast muscle yield, leg muscle yield, body length, abdomen fat weight, intramuscular fat width, tibia length were measured, and in which 8 individuals in each combination were selected randomly to collect the liver tissue samples, which were stored in liquid nitrogen or at -80 degrees C to be used for total RNA (TRNA) extracting. After the total RNA (TRNA) was extracted, 16 TRNA pools were formed in the same quantitative according to the concentration of 8 individual TRNA. They were reversely transcribed with three anchor primers H-T11 A, H-T11 G and H-T11 C. Then the reverse transcription PCR for each transcript product was done in two repeats at the same time with the same anchor primers and 8 random primers. The polyacrylamide gel electrophoresis of each PCR product was run in Bio-Rad Power 3,000 temperature control system. After electrophoresis, the gel was stained by AgNO3 according to the stain method described by Echt et al. The differential display bands in the polyacrylamide gel were counted. The band displayed is counted as 1 whereas no band is counted as 0 and only expression bands reproducible in two repeats were statistically analyzed. The correlation analysis between heterosis percentage and gene expression patterns was done with statistic analysis software (SAS) package. The statistic results indicated that among 690 total numbers of bands, the percentage of differential expression bands reproducible (457) is 66.23%. Eight kinds of gene differential expression patterns were found and listed as follow: 1): Band presents only in one purebred (P1);2): Band in one crossbred and its corresponding paternal purebred; or Band in one crossbred and its corresponding maternal purebred (P2);3): Band in purebreds and one crossbred (P3); 4): Band only in one crossbred (P4);5): Bands in both crossbreds and one purebred (P5);6): Bands only in both crossbreds (P6);7): Bands only in purebreds (P7);8): Bands both in purebreds and crossbreds P8. The differential expression of gene between purebred and crossbred chicken was detected for the first time. The proportion of each pattern in each kind of purebred combination is different. The percentage of P8 (75.34%) is the highest. The total percentage of differential expression patterns (24.66%) showed that the gene differential expression exists as a matter of fact. Among all the gene differential expression patterns, the percentage of P3 is the highest whereas the percentage of P7, P6 and P4 is very low, it indicated that different genes may have different expression patterns in purebreds and crossbreds. The results are similar to the study results on plants, which indicates that the gene differential expression between purebred and crossbred exists universally in biology. The correlation between gene expression patterns and heterosis percentage was studied, but correlation between P8 and the heterosis percentage is not significant (P > 0.05), it indicates that some patterns of gene differential expression may be the molecular genetic basic of heterosis. Among all the gene differential expression patterns, each pattern affects the expression of meat trait in different manner. There is significantly negative correlation between P4 and heterosis percentage of body weight of 8 weeks, breast muscle yield, leg muscle yield, eviscerated weight with giblet and eviscerated weight (P < 0.05); P1 is of significantly negative correlation with heterosis percentage of abdomen fat weight (P < 0.05) and of very significantly negative correlation with heterosis percentage of body length (P < 0.01); The negative correlation between P2 and heterosis percentage of intramuscular fat width is significant (P < 0.05); The positive correlation between P7 and heterosis percentage of leg muscle yield, wing weight, eviscerated weight with giblet and intramuscular fat width is significant (P < 0.05); The positive correlation between P5 and heterosis percentage of tibia length (P < 0.05) is significant. These results show that these 5 kinds of patterns play important role in heterosis forming of meat trait. P1 and P7 show that expressed gene in purebreds is depressed; P4 indicates that new gene expression occurs in crossbreds; P5 reveals that expressed gene only in one purebred express in all crossbreds. All genes of crossbreds come from purebred, which are not only the simple adding of these purebred genes, giving birth to unknown interaction between these genes coming from different purebreds, then leading to differential expression of genes. These gene differential expressions maybe form the heterosis of meat trait.

Animals↗

PubMed2000

Transgenic mice carrying large human genomic sequences with expanded CTG repeat mimic closely the DM CTG repeat intergenerational and somatic instability.

Myotonic dystrophy (DM) is caused by a CTG repeat expansion in the 3'UTR of the DM protein kinase (DMPK) gene. A very high level of instability is observed through successive generations and the size of the repeat is generally correlated with the severity of the disease and with age at onset. Furthermore, tissues from DM patients exhibit somatic mosaicism that increases with age. We generated transgenic mice carrying large human genomic sequences with 20, 55 or >300 CTG, cloned from patients from the same affected DM family. Using large human flanking sequences and a large amplification, we demonstrate that the intergenerational CTG repeat instability is reproduced in mice, with a strong bias towards expansions and with the same sex- and size-dependent characteristics as in humans. Moreover, a high level of instability, increasing with age, can be observed in tissues and in sperm. Although we did not observe dramatic expansions (or 'big jumps' over several hundred CTG repeats) as in congenital forms of DM, our model carrying >300 CTG is the first to show instability so close to the human DM situation. Our three models carrying different sizes of CTG repeat provide insight on the different factors modulating the CTG repeat instability.

3' Untranslated Regions↗

PubMed1994

Assessment of functional capacity in chronic heart failure: time-limited exercise on a self-powered treadmill.

OBJECTIVES: To assess the efficacy of a 9-minute walking test on a self-powered treadmill in a group of patients with various degrees of heart failure, to investigate the reproducibility of the technique, and to establish the safety of the technique. PATIENTS AND METHODS: 24 controls and 37 patients with various grades of heart failure were studied. Peak oxygen consumption was measured in patients and controls. The distance walked in 9 minutes on a self-powered treadmill was measured in all groups and the test was repeated to assess reproducibility. RESULTS: The distance walked in 9 minutes correlated with peak oxygen consumption in patients, controls, and both groups combined. There was a significant difference in the distance walked by controls and patients and in the distance walked by patients with severe rather than with mild or moderate heart failure. There was no significant difference between the results of successive 9-minute walking tests in any group. No serious adverse reaction was seen in any patient during or after the test. CONCLUSION: The 9-minute walking test on a self-powered treadmill is a sensitive, reproducible, safe, and inexpensive method of assessing functional capacity in patients with all grades of heart failure.

Adult↗

PubMed1998

Comparative reproducibility of QT, QT peak, and T peak-T end intervals and dispersion in normal subjects, patients with myocardial infarction, and patients with hypertrophic cardiomyopathy.

Abnormal repolarization is associated with arrhythmogenesis. Because of controversies in existing methodology, new computerized methods may provide more reliable tools for the noninvasive assessment of myocardial repolarization from the surface electrocardiogram (ECG). Measurement of the interval between the peak and the end of the T wave (TpTe interval) has been suggested for the detection of repolarization abnormalities, but its clinical value has not been fully studied. The intrasubject reproducibility and reliability of automatic measurements of QT, QT peak, and TpTe interval and dispersion were assessed in 70 normal subjects, 49 patients with acute myocardial infarction (5th day; MI), and 37 patients with hypertrophic cardiomyopathy (HC). Measurements were performed automatically in a set of 10 ECGs obtained from each subject using a commercial software package (Marquette Medical Systems, Milwaukee, WI, U.S.A.). Compared to normal subjects, all intervals were significantly longer in HC patients (P < 0.001 for QT and QTp; p < 0.05 for TpTe); in MI patients, this difference was only significant for the maximum QT and QTp intervals (P < 0.05). In both patient groups, the QT and QTp dispersion was significantly greater compared to normal subjects (P < 0.05) but no consistent difference was observed in the TpTe dispersion among all three groups. In all subjects, the reproducibility of automatic measurement of QT and QTp intervals was high (coefficient of variation, CV, 1%-2%) and slightly lower for that of TpTe interval (2%-5%; p < 0.05). The reproducibility of QT, QTp, and TpTe dispersion was lower (12%-24%, 18%-28%, 16%-23% in normal subjects, MI and HC patients, respectively). The reliability of automatic measurement of QT, QTp, and TpTe intervals is high but the reproducibility of the repeated measurements of QT, QTp and TpTe dispersion is comparatively low.

Adult↗

PubMed2001

Interlaboratory study on thermal cycler performance in controlled PCR and random amplified polymorphic DNA analyses.

BACKGROUND: Intercomparisons of PCR-based data between laboratories require an assurance of assay reproducibility. We performed an interlaboratory study to investigate the contribution made by a variety of thermal cyclers to PCR performance as measured by interblock reproducibility and intrablock repeatability. METHODS: Two standardized assays designed to minimize the introduction of non-thermal-cycler-dependent variations were evaluated by 18 laboratories in the United Kingdom, using 33 thermal cyclers of various makes and models. We used a single-product (590 bp) PCR, established in our laboratory as a robust and specific reaction. The second reaction, a multiproduct random amplified polymorphic DNA (RAPD) PCR, was known to be more susceptible to small changes in block temperature and was therefore considered a way of assessing block uniformity with respect to temperature. Assay repeatability data were analyzed with respect to temperature calibration status, the type of temperature control mechanism, thermal cycler age, and the presence of oil overlay or heated lid systems. RESULTS: All (100%) of the laboratories produced the correct target for the single-product PCR assay, although substantial variation in yield in replicate reactions was observed in 9.4% of these. The RAPD reaction generated results that varied extensively both within the same block and between different thermal cyclers. For eight replicates of a positive sample, 88% intrablock repeatability was demonstrated in calibrated thermal cyclers, which decreased to 63% in noncalibrated instruments. CONCLUSIONS: Irrespective of the make and model of thermal cycler, temperature-calibrated instruments consistently generated more repeatable RAPD data than noncalibrated instruments. Guidelines are offered on optimizing and monitoring thermal cycler performance.

Calibration↗

PubMed2004

Evaluation of a covalent mix-enzyme linked immunosorbent assay for screening of Salmonella antibodies in pig serum.

In this study, a commercial Salmonella covalent mix-enzyme linked immunosorbent assay (ELISA) for serological detection of Salmonella infection in swine was evaluated by comparing it with the conventional fecal culture method and inter-laboratory proficiency testing, using a panel of sera tested in 5 laboratories from Europe and North America. Comparison with culture results showed that 88.5% of 26 culture-positive animals were ELISA positive, as were 55% of 60 animals from 2 culture-positive pig herds. Of 90 animals from 2 high health farms with no clinical symptoms of salmonellosis, 98.9% tested negative. The interlaboratory comparison study found a kappa value of 0.9 between our laboratory (using an automated system) and the manufacturer laboratory (using the manual method). Comparison of ELISA results from all 5 participating laboratories showed very good to excellent agreement, between 85% and 97.5%. We found this assay to be useful for the screening of antibodies against Salmonella present in swine serum. It agrees well with bacterial cultures, is reproducible, sensitive, specific, repeatable, and suitable for automation.

Animals↗

PubMed1987

Routine high-performance liquid chromatographic determination of carboxylic acids in wines and champagne.

Carboxylic acids have an important influence on the biological stability and the organoleptic properties of wines. A simple, rapid and reproducible high-performance liquid chromatographic method for the determination of the main carboxylic acids (tartaric, malic, shikimic, lactic, acetic, citric, succinic, fumaric and propionic acids) in wines is described. There is no interference from either sugars or amino acids. The method does not need any preparation or extraction of the sample. The linearity, the level of detection, the repeatability and the reproducibility were studied for each acid. The results are compared with those obtained by chemical and enzymatic assays.

Carboxylic Acids↗

PubMed1997

Comparative evaluation of etest for susceptibility testing Neisseria meningitidis with eight antimicrobial agents. An investigation using U.S. Food and Drug Administration regulatory criteria.

Invasive infections caused by Neisseria meningitidis continue to be a serious clinical problem for therapy, epidemiology, and potential prophylaxis. Multiple antimicrobial resistances have emerged among meningococcal strains including elevated MICs to penicillin, sulfonamides, tetracyclines, and rifampin. Thus, the need to perform accurate susceptibility testing of meningococci in clinical practice and for surveillance programs has renewed priority. In this study, for the first time Etest (AB Biodisk, Solna, Sweden) was compared to a reference agar dilution method using a large number (100) of clinical strains selected for a range of drug resistances. Etest quantitative accuracy (+/-one log2 dilution agreement) ranged from 94% (penicillin) to 100% (three drugs) for the eight clinically useful antimicrobial agents tested. Intermethod categorical accuracy for all drug ranged from 92% (penicillin, erythromycin) to 100% (five drugs), without false-susceptible or -resistant errors using Etest. Etest and reference methods were highly reproducible (99.6 to 100.0%, respectively). Quantitative discords between methods (> or = two log2 dilutions) were not reproducible and resolved following repeated testing. Etest method proved to be an accurate and reproducible quantitative method for testing N. meningitidis strains for the compared antimicrobial agents (eight) often utilized for therapy and prophylaxis of serious meningococcal disease.

Anti-Bacterial Agents↗

PubMed2006

Simultaneous determination of 7 N-acetyltransferase-2 single-nucleotide variations by allele-specific primer extension assay.

BACKGROUND: Genotyping of N-acetyltransferase-2 (NAT2) is useful in predicting the risk for toxicity of NAT2 substrates. Current methods cannot detect the 7 most important single-nucleotide variations in NAT2 simultaneously in 1 tube. METHODS: We developed an assay that uses allele-specific primer extension (ASPE) and microsphere hybridization for the simultaneous detection of 7 single-nucleotide variations in NAT2. Using 12 samples previously genotyped by a TaqMan-based assay for method development and as positive controls, we amplified the genetic locus of NAT2 comprising the single-nucleotide variations of interest by PCR and then performed ASPE with allele-specific primers and biotinylated dCTP followed by bead hybridization and streptavidin-R-phycoerythrin binding. Genotypes were determined according to the allele-specific fluorescent signal ratios. RESULTS: The mean (SD) allelic ratios for homozygous common, heterozygous variant, and homozygous variant NAT2 genotypes were 0.0394 (0.0113) (n = 80), 0.4372 (0.0270) (n = 148), and 0.9331 (0.0127) (n = 325). The assay had 100% (95% confidence interval, 99%-100%) within-run reproducibility for 12 samples repeated 6 times and 100% (98%-100%) between-run reproducibility for a 5-sample subset run on 6 different days. NAT2 genotypes of 30 blinded samples determined by this assay were 100% (98%-100%) concordant with results obtained using the TaqMan method. CONCLUSIONS: The developed assay can simultaneously determine single-nucleotide variations in NAT2. The assay demonstrates no overlap in allele-specific signal ratios between homozygous common, heterozygous, and homozygous variant and shows agreement with a reference method and reproducibility of genotype identification.

Alleles↗

PubMed1999

Three-dimensional motion analysis of upper limb movement in the bowing arm of string-playing musicians.

OBJECTIVES: To explore the role of three-dimensional movement analysis in defining patterns of joint movement while bowing on different stringed instruments, and its potential for future use by the clinician in the study of musculoskeletal problems in musicians. DESIGN AND METHODS: A protocol was developed for analysis of bowing arm movements using the MacReflex 3-D analysis system- including definition of marker sites, positioning of the musician within the calibrated area and standardised bowing sequences. This protocol was then used to determine whether the system was sensitive to differences between instrument types and to variation in bowing style and technique between individual players. The ranges of movement in the shoulder, elbow and wrist were compared between instrument groups in a cohort of 39 asymptomatic string players. RESULTS: The system gave reproducible results on repeated testing, and demonstrated clear differences between instruments, as well as stylistic differences between players. Range of shoulder movement increased progressively towards the upper register of the cello, while decreasing on the violin. Maximum elevation of the shoulder was significantly greater on the cello (P<0.001), while elbow flexion, and therefore range, was consistently greater on the violin. CONCLUSIONS: Clear and reproducible differences in style and technique were demonstrated between individuals. The increased range of shoulder movement in the upper register of the 'cello may contribute to the greater prevalence of neck and shoulder symptoms among 'cellists. Further study is required to establish whether different musculoskeletal symptoms produce characteristic patterns which could help in diagnosis and development is required to make the system feasible for routine use. RELEVANCE: Musculoskeletal problems are common among musicians. Different instruments and playing positions make different demands on joints and may contribute to the variance in reported incidence of musculoskeletal symptoms among violinists and cellists. Three-dimensional analysis may prove helpful in the future for the diagnosis of different musculoskeletal syndromes in string players, or for identifying movement patterns which could exacerbate repetitive strain injuries. However, as this is the first application of the technique in this complex area, preliminary work was required to establish feasibility and to obtain data on normal players.

Arm↗

PubMed2000

Reproducibility of heart rate measured in the clinic and with 24-hour intermittent recorders.

This study was undertaken to assess the reproducibility of office versus ambulatory heart rates in 839 hypertensive subjects participating in the Hypertension and Ambulatory Recording Venetia Study (HARVEST). A 24-hour heart rate was recorded twice; this procedure was repeated three months later. Reproducibility was better for ambulatory than for office measurement, and was greater for 24-hour than for daytime heart rate, and lowest for night-time heart rate. Reproducibility of office heart rate was impaired above 85 bpm, and was poorer in subjects with more severe office hypertension. A small but significant decrease in average daytime (-1 bpm, P < 0.0001) and virtually no change in night-time heart rate (-0.3 bpm, NS) were observed at repeat recording. Heart rate reproducibility indices were related to the extent of the heart rate and blood pressure white-coat effect, but did not vary according to age, gender, body mass index, day-night blood pressure difference, or alcohol or tobacco use. Results indicate that heart rate recorded over the 24 hours has a better reproducibility than office heart rate, and could thus be a better prognostic indicator than traditional measurement of resting heart rate in the hospital setting.

Adult↗

PubMed2004

Putting our heads together: a consensus approach to brain/non-brain segmentation in T1-weighted MR volumes.

We describe an approach to brain extraction from T1-weighted MR volumes that uses a hierarchy of masks created by different models to form a consensus mask. The algorithm (McStrip) incorporates atlas-based extraction via nonlinear warping, intensity-threshold masking with connectivity constraints, and edge-based masking with morphological operations. Volume and boundary metrics were computed to evaluate the reproducibility and accuracy of McStrip against manual brain extraction on 38 scans from normal and ataxic subjects. McStrip masks were reproducible across six repeat scans of a normal subject and were significantly more accurate than the masks produced by any of the individual algorithmic components.

Algorithms↗

PubMed2003

Intrasubject reproducibility of presurgical language lateralization and mapping using fMRI.

BACKGROUND: fMRI is becoming a standard tool for the presurgical lateralization and mapping of brain areas involved in language processing. However, its within-subject reproducibility has yet to be fully explored. OBJECTIVE: To evaluate within-test and test-retest reliability of language fMRI in consecutive patients undergoing evaluation for epilepsy surgery. METHODS: Thirty-four unselected patients were investigated once (within-test reliability) and 12 patients twice (test-retest reliability). The imaging series consisted of an alternating 25-second synonym judgment condition with a 25-second letter-matching condition repeated 15 times. Reproducibility of activation maps of the first and second half of session 1 or activation maps of sessions 1 and 2 was evaluated by comparing one global and three regional lateralization indexes (Broca's area, remaining prefrontal cortex, temporoparietal area) and on a voxel-by-voxel basis (intraclass correlation coefficient, percentage overlap, correlation of t-values). RESULTS: Global and regional language lateralization was achieved with high reliability within and across sessions. Reproducibility was evenly distributed across both hemispheres but not within each hemisphere. Frontal activations were more reliable than temporoparietal ones. Depending on the statistical threshold chosen, the voxel-by-voxel analysis revealed a mean overlap of activations derived from the first and second investigation of up to 48.9%. CONCLUSION: Language fMRI proved sufficiently reliable for the determination of global and regional lateralization of language representation in individual unselected patients with epilepsy.

Adolescent↗

PubMed1996

Reproducibility of thermodilution cardiac output determination in critically ill patients: comparison between bolus and continuous method.

OBJECTIVE: A semi-continuous thermodilution method (CCO) was recently developed to measure cardiac output with less risk of bacterial contamination, fluid overload, and user-induced errors than the classical bolus technique (BCO). Previous comparison between these two methods showed negligible bias. However, large limits of agreement suggest that the two methods are not interchangeable. We hypothesized that this poor agreement may be due to differences in reproducibility. METHODS: In 23 critically ill patients, 369 paired measurements of CCO and BCO were compared (range of cardiac outputs: 2.8 to 16 L/min). The reproducibility of BCO and CCO methods was evaluated on a sample of 205 and 209 determinations, respectively. RESULTS: The comparison between the CCO and the BCO methods confirmed previous results: i.e., small bias (-0.39 L/min) and large limits of agreement (-2.06 to +1.28 L/min). Reproducibility showed no bias for either the CCO or the BCO method. Limits of reproducibility agreement between repeated determinations were approximately 50% less for CCO than for BCO method: respectively -0.87 to +0.82 L/min for the CCO method and -1.56 to +1.37 L/min for the BCO method. Consequently, the threshold necessary to ascertain that the difference between two measurements was not due to the internal variability of the method (3 x SEM) was 0.39 for the CCO method and 0.75 L/min for the BCO method. CONCLUSION: Differences in reproducibility may explain the poor agreement between the CCO and BCO methods. The better reproducibility of the CCO method allows the detection of smaller variations in cardiac output and suggests the superiority of this new method.

Cardiac Output↗

PubMed2006

The intersubject and intrasubject reproducibility of FMRI activation during three encoding tasks: implications for clinical applications.

The goal of the present study was to evaluate the inter- and intrasubject reproducibility of FMRI activation for three memory encoding tasks previously used in the context of presurgical functional mapping. The primary region of interest (ROI) was the medial temporal lobe (MTL). Comparative ROIs included the inferior frontal and fusiform gyri which are less affected by susceptibility-induced signal losses than the MTL regions. Eighteen subjects were scanned using three memory encoding paradigms: word-pair, pattern, and scene encoding. Nine subjects underwent repeat scanning. Intersubject reproducibility of FMRI activation was evaluated by examining the percent of subjects who showed activation within a given ROI and the range to which individual laterality indices (LIs) varied from the mean. Intrasubject test-retest reproducibility was evaluated by examining the LI test-retest correlation, the average difference between LIs from two separate imaging sessions, and concordance ratios of activation volumes (R(volume) and R(overlap)). For scene encoding the reproducibility of activation volume and LIs within the MTL were as good as or better than the reproducibility within the fusiform and inferior frontal ROIs. For pattern encoding and word-pair encoding, the reproducibility of activation volume and LIs within the MTL tended to be worse compared to the fusiform and inferior frontal ROIs. The differences in FMRI reproducibility appeared more dependent on the task than the susceptibility effects. The results of this study suggest that FMRI-based assessment of the neural substrates of memory using a scene encoding task may be a useful clinical tool.

Acoustic Stimulation↗

PubMed1995

Impedance planimetry: an integrated approach for assessing sensory, active, and passive biomechanical properties of the human esophagus.

OBJECTIVES: Our objective was to study the biomechanical properties and their relationships to the sensory and motor function of the esophagus, which has seldom been examined in humans. METHODS: We used impedance planimetry, to study these properties. This system measures cross-sectional area (CSA) and intraluminal pressure simultaneously and facilitates calculation of some of the biomechanical properties of the esophageal wall. We performed 15 studies in 12 healthy volunteers. In three subjects, the studies were repeated to test reproducibility. RESULTS: Stepwise increments in balloon pressure from 5 to 40 cm H2O induced an increase in CSA (mean +/- SD), 91 +/- 27 to 469 +/- 63 mm2, the wall tension 27 +/- 4 to 484 +/- 32 mm x cm H2O, and the strain 0.2 +/- 0.1 to 1.3 +/- 0.3. The tension/strain relationship increased exponentially. The compliance did not change. The threshold for first sensation was 30 +/- 11 cm H2O (mean +/- SD). In three subjects, when the balloon was distended > 40 cm H2O, chest pain was induced at a threshold of 62 +/- 3 cm H2O, and the compliance decreased. Balloon distension induced tertiary contractions and secondary peristalsis at thresholds of 15 +/- 4 cm H2O, and 19 +/- 5 cm H2O. Repeat studies showed good correlation (r = 0.9). CONCLUSION: Graded balloon distension increases esophageal CSA, wall tension, and strain. When a threshold is reached, tertiary contractions and secondary peristalsis develop at pressures less than 50% of sensory threshold. At higher pressures, chest pain is induced. Impedance planimetry promises to be a simple, objective, reproducible, and comprehensive technique for evaluating the sensory, motor, and viscoelastic properties of the esophagus.

Adult↗

PubMed2000

Caveats: numerical requirements in graph theory based quantitation of tissue architecture.

Graph theory based methods represent one approach to an objective and reproducible structural analysis of tissue architecture. By these methods, neighborhood relations between a number of objects (e.g., cells) are explored and inherent to these methods are therefore certain requirements as to the number of objects to be included in the analysis. However, the question of how many objects are required to achieve reproducible values in repeated computations of proposed structural features, has previously not been adressed specifically. After digitising HE stained slides and storing them as grey level images, cell nuclei were segmented and their geometrical centre of gravity were computed, serving as the basis for construction of the Voronoi diagram (VD) and its subgraphs. Variations in repeated computations of structural features derived from these graphs were related to the number of cell nuclei included in the analysis. We demonstrate a large variation in the values of the structural features from one computation to another in one and the same section when only a limited number of cells (100-500) are included in the analysis. This variation decreased with increasing number of cells analyzed. The exact number of cells required to achieve reproducible values differ significantly between tissues, but not between separate cases of similar lesions. There are no significant differences between normal and malignantly changed tissues in oral mucosa with respect to how many cells must be included. For graph theory based analysis of tissue architecture, care must be taken to include an adequate number of objects; for some of the structural features we have tested, more than 3000 cells.

Biometry↗