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At least 595 records · Page 33Linked to original sources
PubMed1998

The nuoM arg368his mutation in NADH:ubiquinone oxidoreductase from Rhodobacter capsulatus: a model for the human nd4-11778 mtDNA mutation associated with Leber's hereditary optic neuropathy.

Mutation at position 11778 in the nd4 gene of the human mitochondrial complex I is associated with Leber's hereditary optic neuropathy. Type I NADH:ubiquinone oxidoreductase of Rhodobacter capsulatus displays similar properties to complex I of the mitochondrial respiratory chain. The NUOM subunit of the bacterial enzyme is homologous to the ND4 subunit. Disruption of the nuoM gene led to a bacterial mutant exhibiting a defect in complex I activity and assembly. A nuoM-1103 point mutant reproducing the nd4-11778 mutation has been introduced in the R. capsulatus genome. This mutant showed a reduced ability to grow in a medium containing malate instead of lactate which indicated a clear impairment in oxidative phosphorylation capacity. NADH supported respiration of porous bacterial cells was significantly decreased in the nuoM-1103 mutant while no significant reduction could be observed in isolated bacterial membranes. As it has been observed in the case of the nd4-11778 mitochondrial mutation, proton-pump activity of the bacterial enzyme was not affected by the nuoM-1103 mutation. All these data which reproduce most of the biochemical features observed in patient mitochondria harboring the nd4-11778 mutation show that the R. capsulatus complex I might be used as a useful model to investigate mutations of the mitochondrial DNA which are associated with complex I deficiencies in human pathologies.

Amino Acid Sequence↗
PubMed2006

Study of gel materials as radioactive 222Rn gas detectors.

Commercial hair gel material (polyvinyl pyrolydone triethanolamine carbopol in water) and bacteriological agar (phycocolloid extracted from a group of red-purple algae, usually Gelidium sp.) have been studied as radioactive radon gas detectors. The detection method is based on the diffusion of the radioactive gas in the gel material, and the subsequent measurement of trapped products of the natural decay of radon by gamma spectrometry. From the several radon daughters with gamma radiation emission (214Pb, 214Bi, 214Po, 210Pb, 210Po), two elements, 214Pb (0.352 MeV) and 214Bi (0.609 MeV), were chosen for the analysis in this work; in order to determine the best sensitivity, corrections were made for the short half-life of the analysed isotopes. For the gamma spectrometry analysis, a hyperpure germanium solid state detector was used, associated with a PC multichannel analyser card with Maestro and Microsoft Excel software. The results show the viability of the method: a linear response in a wide radon concentration range (450-10,000 Bq m(-3)), reproducibility of data, easy handling and low cost of the gel material. This detection methodology opens new possibilities for measurements of radon and other radioactive gases.

Dose-Response Relationship, Radiation↗
PubMed1987

Quantitative assessment of atherosclerotic lesions in mice.

The well-defined genetic systems of the mouse are proving useful in experimental studies of atherosclerosis. Inbred mouse strains differ in atherosclerosis susceptibility, and several variants of apolipoproteins have been identified and mapped. This report explores the location and timing of lesion formation in the mouse in an effort to provide a basis for quantitatively comparing groups of mice. After 14 weeks on an atherogenic diet containing 1.25% cholesterol, 15% fat, and 0.5% cholic acid, C57BL/6J female mice had aortic lesions at each of the intercostal arteries, at the junction of the aorta to the heart, and in scattered areas covering 1.1% +/- 0.5 (SD) of the aortic surface. After 9 months on the atherogenic diet, those lesions near the heart and intercostal arteries were extensive, 8% +/- 3 (SD) of the remainder of the aorta was involved in lesions, and lesions were found in the coronary arteries. Results indicated that one suitable location for scoring lesions was in a 300 micron area of the aorta just beyond the aortic sinus. The mean number of lesions/mouse in the selected area after 14 weeks on the atherogenic diet was 1.1 +/- 0.3 (SD). The results were reproducible over 10 separate experiments. The number of lesions per mouse fit a Poisson distribution indicating that the presence of one lesion did not predispose the mouse to acquiring a second lesion. Lesion formation and cholesterol levels did not vary with the season of the year as demonstrated by 9 separate experiments over more than 12 months. Methods of evaluating the number and size of lesions were compared including sizing with a microscope eyepiece grid and computer-assisted planimetry. The resulting data provide reproducible methods of quantitatively comparing lesion formation in various strains or groups of mice, thereby increasing the usefulness of the mouse as an experimental system for atherosclerosis research.

Animals↗
PubMedDate not supplied

Rhinomanometry. III. Procedures and criteria for distinction between skeletal stenosis and mucosal swelling.

Recently developed methods for recording of the pressure-flow relationship of the nose and derivation of data for describing the resistance to the flow through the nose were used in an effort to distinguish between skeletal stenosis and mucosal swelling. It was not possible to define an upper normal limit of the resistance of nasal cavities at rest because of the heart rate above 150/min was found to decongest the mucosa better than nose drops. An upper normal limit of resistance varying with body height was defined for nasal cavities and for the total nose after exercise. The reproducibility of data obtained after decongestion was good in patients with and without skeletal stenosis.

Adolescent↗
PubMed1993

Galactosyl hydroxylysine and deoxypyridinoline: a methodological comparison.

Galactosyl hydroxylysine and deoxypyridinoline are at present the most promising markers of bone resorption. Various studies have indeed shown that these two markers discriminate with high accuracy subjects with different rates of bone turnover and that their accuracies and discriminate power are very similar. The aim of this paper is to compare the practicality and the reproducibility of the HPLC galactosyl hydroxylysine and deoxypyridinoline assays. In summary, this review shows that the galactosyl hydroxylysine and deoxypyridinoline HPLC assays differ mainly in the need, in using deoxypyridinoline, for an acid hydrolysis and a preextraction of the urine samples. This implies two major problems for deoxypyridinoline: 1) more time is required due to the cumbersome preanalytical procedures; and 2) a lower reproducibility. Our data, in fact, show that both the intra-assay and inter-assay coefficient of variation of the deoxypyridinoline assay are almost 100% higher than those of the galactosyl hydroxylysine assay.

Adult↗
PubMed2006

Impact of RNA degradation on gene expression profiles: assessment of different methods to reliably determine RNA quality.

DNA microarray technology enables investigators to measure the expression of several 1000 mRNA species simultaneously in a biological specimen. However, the reliability of the microarray technology to detect transcriptional differences representative of the original samples is affected by the quality of the extracted RNA. Thus, it is of critical importance to standardize sample-handling protocols and to perform a quality assessment of RNA preparations. In this report, 59 human tissue samples were used to evaluate the relationships between RNA quality and gene expression. From Affymetrix GeneChip array data analysis of these samples, we compared the performance of the 28S/18S ratio, two computer methods (RIN and degradometer) and our in-house RNA quality scale (RQS) in assessing RNA quality. The optimal RNA reliability threshold was determined for each method using statistical discrimination measures. We showed that RQS, RIN and degradometer have a similar capacity to detect reliable RNA samples whereas the 28S/18S ratio leads to a misleading categorization. Furthermore, we developed a new approach, based on clustering analyses of full chip expression, to control RNA quality after hybridization experiments. The combination of these methods, allowing monitoring of RNA quality prior to and after the hybridization experiments, ensured reliable and reproducible microarray data.

Cluster Analysis↗
PubMed1990

Reproducibility of a diet history in older men in Hawaii.

A diet history method was tested for reproducibility among 106 older men from the five major ethnic groups (Japanese, Caucasian, Hawaiian, Filipino, and Chinese) of Hawaii. The questionnaire, administered by trained interviewers, was designed to estimate the dietary intakes of total and saturated fat, cholesterol, vitamin A, beta-carotene, vitamin C, and zinc. Subjects were asked to recall their usual frequencies and amounts of consumption during a usual month of more than 100 food items, along with the intake of seasonal foods with a high vitamin A content. A second interview was conducted 1-14 months later to obtain a diet history covering the same time period as the first interview. The same questionnaire was utilized in both interviews. The effects of ethnicity, age, and recall interval (period between the diet reference date and initial interview) on the reproducibility of nutrient intakes were examined. The intraclass correlation coefficient (rI) and the weighted kappa statistic (Kw) were used to assess agreement. The overall levels of reproducibility were relatively good. Neither ethnicity, age, nor length of recall period had a major effect on reproducibility. The data suggested that this diet history method is an appropriate instrument for estimating the usual dietary intakes of a healthy heterogeneous group of older men in Hawaii.

Age Factors↗
PubMed2003

Use of arterial transfer functions for the derivation of aortic waveform characteristics.

OBJECTIVE: To investigate the utility and accuracy of radial-aortic arterial transfer functions for the derivation of central blood pressure waveforms. DESIGN Prospective measurement of central and peripheral waveforms in patients undergoing coronary angiography or percutaneous coronary intervention. METHODS: Simultaneous invasive central aortic and non-invasive radial pressure waveforms were recorded in 78 subjects (61 male : 17 female). Data were applied to a single-input/single-output model for the calculation of a transfer function (TF). Individual TFs were derived by two methods and ensemble averaged TFs obtained for the group. Reverse transformation was performed using each averaged TF applied to the radial data of each subject. RESULTS: There was close linear correlation between measured aortic parameters and both radial and TF-derived aortic systolic and diastolic pressures (P < 0.001) and most other waveform parameters. However, despite small mean differences between measured and most TF-derived aortic parameters (systolic pressure 0.8-2.9 mmHg, augmentation index 4.3-5.6%), individual scatter was marked, with 95% limits of agreement of +/- 14.6 mmHg (systolic pressure) and +/- 24.4% [augmentation index (AI)]. Indeed, scatter for AI was so marked that measured and derived values were not statistically significantly correlated. CONCLUSIONS: Transfer functions may be valid for the derivation of some central aortic waveform characteristics. However, in providing neither improved reproducibility nor data on parameters not obtainable from the radial waveform, transfer function techniques may offer no additional clinical benefit. The absence of correlation between measured and TF-derived aortic AI and wide limits of agreement of other parameters should be considered if this technique is utilized in clinical practice.

Aged↗
PubMed2002

Reproducibility of glucose measurements using the glucose sensor.

OBJECTIVE: Recent studies have confirmed that improved glycemic control decreases the risk of diabetic complications in type 1 and type 2 diabetic patients. The Minimed glucose sensor allows continuous 72-h glucose monitoring and represents a potentially important tool to improve diabetes management. Its use is currently limited to the health care team. Our aim was to evaluate the reproducibility of data provided by the device by comparing data provided by two sensors worn simultaneously by the same subject. RESEARCH DESIGN AND METHODS: A total of 11 subjects (6 type 1 and 3 type 2 diabetic patients and 2 healthy subjects) agreed to wear two sensors and perform at least four daily finger-stick glucose determinations during 72 h. The simultaneous glucose values provided by the sensors were compared. To determine the clinical implications of the glucose data, each day was divided into eight periods, and for each period the glucose range was rated as satisfactory, too high, or too low by a blinded clinician experienced in interpreting glucose sensor data in the clinical setting. The evaluation of glycemic levels based on the recordings of the two sensors were compared for each paired time interval. RESULTS: We discarded 18% of the sensor data for technical reasons. Examined as a group, the remaining 3,370 paired data points in all 11 patients were highly correlated (r = 0.84). However, when individual pairs were evaluated, large differences in the glucose values were apparent, with differences of >10% in 70% of the measurements and >50% in 7% of the measurements. Moreover, clinical evaluation of the glucose range provided simultaneously by two sensors was concordant for only 65% of the evaluation periods. CONCLUSION: In a real-life setting, the accuracy of data provided by the Minimed glucose sensor may be less than expected. To avoid therapeutic errors, sensor findings should be confirmed by independent means before clinical decisions are made.

Blood Glucose↗
PubMed1991

Determination of proteolytic enzymes by flow-injection analysis.

Quantitation of proteolytic enzymes using N-succinyl-L-Ala-L-Ala-L-Pro-L-Phe-p-nitroanilide has been adapted to flow-injection analysis. This procedure has been developed using two different proteases: subtilisin and chymotrypsin. For both enzymes the influence of substrate concentration on spectrophotometric response has been studied. The assay is based on the merging zones technique combined with a washing step. Results are obtained in less than 15 s and samples may be run at a rate of 90/h with good reproducibility. A linear relation between peak heights and enzyme concentrations was observed for 0-0.15 Anson unit/liter of subtilisin and for 0-30 mg/liter of a commercial preparation of chymotrypsin. The method requires only small sample volumes, and the consumption of the chromogenic substrate is reduced to a minimum by using intermittent pumping.

Amino Acid Sequence↗
PubMed2002

Reconstructed skin kits: reproducibility of cutaneous irritancy testing.

The aim of this study was to determine the reproducibility of data obtained from in vitro irritation testing using three industrial reconstructed human epidermis models, EpiDerm, Episkin and SkinEthic, and one in-house model developed at Wella/Cosmital. A common protocol was established based on the measurement of cytotoxicity in the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay and of extracellular release of proinflammatory mediators and cytosolic enzymes after a range of exposure times to sodium lauryl sulfate (SLS). This time course protocol was applied to 6 different batches of each skin model using triplicate tissue cultures per test condition. The parameters analyzed for intra- and inter-batch reproducibility were the cell viability determined as MTT reduction capacity and the ET-50 values in the 6 batches, as well as the release of the cytokine IL-1alpha and of the cellular enzymes LDH and GOT in 3 batches only. The MTT viability results showed that EpiDerm was the most resistant to the SLS treatment and at the same time the most reproducible model, SkinEthic was the most sensitive to SLS and the least reproducible, and Episkin and the Cosmital model were intermediate. Measurements of IL-1alpha release showed a relatively high intra- and inter-batch variability in all the skin models. It was not possible to detect the extracellular release of the enzymes LDH and GOT in the Episkin assay medium. With the 3 other models, the release of LDH and GOT varied in about the same range as that of IL-1alpha. For all the parameters in this study, the inter-batch variability was generally greater than the intra-batch variability. A possible reduction in the number of batches and replicates for future applications in routine irritancy testing is discussed on the basis of the results obtained using 6 batches in triplicate.

Humans↗
PubMed1995

Depth dose under narrow shielding blocks: a comparison of measured and calculated dose.

This paper describes measurements done to investigate the accuracy of dose calculation algorithms when used to calculate the dose under shielding blocks. Because the prescribed dose is sometimes limited by the dose to organs at risk within the irradiated volume, it is important to know the dose under a block accurately. Five different algorithms from four treatment planning systems were used to calculate the dose under two narrow lead alloy blocks each placed centrally in a 15 x 15-cm beam of 6- and 18-MV X-rays, respectively. Measurements were done in a water phantom with the same geometrical set-up. All measured data have a common feature; a high surface dose (up to about 20%) decreasing linearly within the first 1-2 cm to a minimum ranging from 13 to 6.5%, and then increasing to a maximum depending on the X-ray energy and block width. Beyond the maximum, the dose decreases approximately linearly due to absorption of the primary beam. The first part of the curve is due essentially to secondary electrons. Beyond the minimum, the X-ray scatter dose component increases, due to increasing phantom scatter, to a maximum which is greater for 6 MV than for 18 MV X-rays. Most algorithms could not reproduce measured data accurately.(ABSTRACT TRUNCATED AT 250 WORDS)

Algorithms↗
PubMed1997

Reproducibility of self-administered questionnaire in epidemiological surveys.

We evaluated the reproducibility of data on intake frequency of 33 food items, beverage intake frequency of 3 items, drinking and smoking habits, and past history of 10 diseases obtained from a self-administered questionnaire. The survey subjects consisted of 263 aged 39 to 79 years individuals in the general population. After about one year interval these subjects consecutively participated in two surveys and were unintentionally requested to answer to the same questionnaire. The means of percent exact agreements for 33 food items were 48.4% in all, 42.7% in males and 49.4% in females. The means of their percent agreements within one category difference were 85.4% in all, 83.3% in males and 85.8% in females. The reproducibility of beverage intake frequency was the highest in green tea, followed in order by black tea and coffee. The percent exact agreements were 85.4% in males and 81.8% in females for drinking habit, 87.5% in males and 99.0% in females for smoking habit, and 93.7% in males and 97.2% in females for past history. The reproducibility of the self-administered questionnaire was the highest in past history, followed in order by smoking habit, drinking habit and dietary habit. The values of reproducibility were higher in females than in males except for drinking habit. Although reduction of categories was needed to improve the reproducibility, the obtained values from the self-administered questionnaire were sufficiently high for epidemiological studies.

Alcohol Drinking↗
PubMed2004

Prediction of left ventricular ejection fraction in patients with coronary artery disease based on an analysis of perfusion patterns at rest. Assessment by an artificial neural network.

BACKGROUND: In CAD, left ventricular function depends on the condition of myocardial perfusion, hence it may be presumed that blood flow abnormalities may enable the LVEF to be predicted. The aim of the study was to apply an Artificial Neural Network (ANN) to investigate the relationships between myocardial perfusion and LVEF, measured simultaneously. MATERIAL AND METHODS: gSPECT examinations were performed in 95 patients with CAD, divided into training (n = 50) and testing (n = 45) groups. using the acquired data, in each subject the LVEF was calculated and a perfusion polar map was constructed and divided into 25 segments. Based on results obtained in the training group, a characteristic configuration of segments was defined, with features enabling differentiation between the individual subjects of that group. The set of those segments, as well as the corresponding LVEF values enabled the optimum network architecture to be constructed and trained. The trained ANN was verified by application to the testing group. RESULTS: Using the above-described procedure, 15 polar map segments were defined which enabled the patients of the training group to be differentiated sufficiently enough to make their further recognition possible. The optimal network structure consisting 25 neurons was obtained by comparing the activity in those segments in individual subjects with corresponding LVEF values. Based on the above model, the obtained network was able to reproduce learning data (r = 0.832; learning error = 4.84%) and to apply the gained knowledge to the testing cases (r = 0.786; testing error = 4.99%). CONCLUSIONS: The obtained network can generalise learned information. To predict LVEF, some polar map segments should be excluded from the analysis. Erroneous LVEF prediction may occur resulting mainly from conditions independent from perfusion abnormalities.

Artificial Intelligence↗
PubMed2006

Reliability of a measure of prediagnosis physical activity for cancer survivors.

PURPOSE: This study was conducted to examine the test-retest reliability of a measure of prediagnosis physical activity participation administered to colorectal cancer survivors recruited from a population-based state cancer registry. METHODS: A total of 112 participants completed two telephone interviews, 1 month apart, reporting usual weekly physical activity in the year before their cancer diagnosis. Intraclass correlation coefficients (ICC) and standard error of measurement (SEM) were used to describe the test-retest reliability of the measure across the sample; the Bland-Altman approach was used to describe reliability at the individual level. The test-retest reliability for categorized total physical activity (active, insufficiently active, sedentary) was assessed using the kappa statistic. RESULTS: When the complete sample was considered, the ICC ranged from 0.40 (95% CI: 0.24, 0.55) for vigorous gardening to 0.77 (95% CI: 0.68, 0.84) for moderate physical activity. The SEM, however, were large, indicating high measurement error. The Bland-Altman plots indicated that the reproducibility of data decreases as the amount of physical activity reported each week increases. The kappa coefficient for the categorized data was 0.62 (95% CI: 0.48, 0.76). CONCLUSION: Overall, the results indicated low levels of repeatability for this measure of historical physical activity. Categorizing participants as active, insufficiently active, or sedentary provides a higher level of test-retest reliability.

Adult↗
PubMed2005

Measurement of fracture kyphosis with the Oxford Cobbometer: intra- and interobserver reliabilities and comparison with other techniques.

STUDY DESIGN: Statistical analysis of 3 techniques for measuring thoracolumbar kyphosis secondary to fracture. OBJECTIVES: To determine the reliability of using an Oxford Cobbometer and assess the most reliable measurement technique. SUMMARY OF BACKGROUND DATA: The reproducibility of Cobb angles for the assessment of saggital plane deformity on spine radiographs has been shown to have significant variability in both intra- and interobserver error. METHODS: Twenty-four lateral spine radiographs of patients with thoracic and lumbar vertebral fractures were measured on 2 separate occasions, in random order, by 4 blinded observers using the same Oxford Cobbometer and ruler. RESULTS: Method 2, the angle from the inferior endplate of the vertebra above the fractured vertebra to the superior endplate of the vertebra below the fractured vertebra, had the greatest intraobserver and interobserver reliabilities (rho = 0.856-0.976 and rho = 0.95, respectively). The other 2 methods had lower reliabilities; however, all 3 methods were well above the statistically acceptable threshold of >0.8, and the intraobserver reliabilities with each observer was 99% overall. These reliabilities supersede results reported previously using the conventional Cobb technique. The absolute mean difference between readings and 95% limit of agreement also improves on previous data, 2 degrees and +/- 5.8 degrees , respectively. CONCLUSIONS: Highest intraclass correlation coefficients were obtained using method 2. Using the Oxford Cobbometer to measure fracture kyphosis has higher reliability than the standard Cobb angle technique. It is easy and quick to use in a clinical setting.

Diagnostic Techniques and Procedures↗
PubMed2006

Interlaboratory reproducibility of atypical glandular cells of undetermined significance: a national survey.

OBJECTIVE: The aim of this study was to evaluate the inter-laboratory reproducibility for atypical glandular cells (AGC) (The Bethesda System (TBS) 2001) of the laboratories involved in the screening programmes in Italy. METHODS: A set of 35 selected slides were circulated among 167 laboratories involved in local population-based cervical screening programmes. Each laboratory provided one single diagnosis per smear. The smears were read blind to the original diagnosis and to the diagnoses provided by other laboratories. A 'majority' diagnosis was defined for each case and assumed as the reference standard. The diagnosis provided from each laboratory was compared with the majority diagnosis. RESULTS: According to the majority report the 35 slides in the set were classified as negative in nine cases, AGC in eight, adenocarcinoma in eight, and squamous lesion or squamous + glandular lesion in 10. The crude agreement between all pairs of laboratories was 49.43%. K-values were 0.46, 0.21, 0.34, 0.36 and 0.32 for negative, AGC/AIS (adenocarcinoma in situ of endocervix), AdenoCa, Sq/Sq + Gl and all reporting categories respectively. Concordance according to overall K was moderate to substantial in 77% of the participating laboratories. CONCLUSIONS: The present study shows that the AGC category is not easily reproducible. The data confirmed the importance, in a screening scenario, of AGC/AIS diagnoses, but also presented difficulties in differentiating between the two diagnoses. In addition to the results obtained from the circulation of the slides, laboratories which had annually a low number of cervical smears were able to gain experience focused on particular morphological pictures.

Adenocarcinoma↗
PubMed1998

Development of a sensitive and accurate enzyme-linked immunosorbent assay (ELISA) system that can replace HPLC analysis for the determination of N1,N12-diacetylspermine in human urine.

N1,N12-Diacetylspermine (DiAcSpm)-specific antibodies were raised in rabbits, using N-acetylspermine coupled to mercaptosuccinylated BSA via N-(4-maleimidobutyryloxy)-succinimide as an antigen. Highly DiAcSpm-specific antibodies were enriched from crude sera through a series of affinity-based fractionations. A competitive ELISA system, intended for measuring DiAcSpm in solution, was constructed using this antibody preparation, with N-acetylspermine coupled to a synthetic peptide via N-(8-maleimidocapryloxy)-succinimide as a solid phase antigen. The Ki value for DiAcSpm with this competitive ELISA system was 33 nM, and the cross-reactivity with DiAcSpm, AcSpm, DiAcSpd, N1-AcSpd, and N8-AcSpd was 100, 0.29, 0.20, 0.033, and 0.055%, respectively. This procedure can be applied to the determination of DiAcSpm in human urine samples, giving highly reproducible results. The coefficients of variation obtained were 6.7 and 4.2% for within-run and between-run precision, respectively. The correlation coefficient between DiAcSpm concentrations in urine estimated by ELISA and those by HPLC analysis was calculated to be 0. 99, and the regression equation was expressed as y = 1.04x + 0.026 microM.

Amino Acid Sequence↗