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At least 523 records · Page 29Linked to original sources
PubMed2006

Connectivity-based parcellation of human cortex using diffusion MRI: Establishing reproducibility, validity and observer independence in BA 44/45 and SMA/pre-SMA.

The identification of specialized, functional regions of the human cortex is a vital precondition for neuroscience and clinical neurosurgery. Functional imaging modalities are used for their delineation in living subjects, but these methods rely on subject cooperation, and many regions of the human brain cannot be activated specifically. Diffusion tractography is a novel tool to identify such areas in the human brain, utilizing underlying white matter pathways to separate regions of differing specialization. We explore the reproducibility, generalizability and validity of diffusion tractography-based localization in four functional areas across subjects, timepoints and scanners, and validate findings against fMRI and post-mortem cytoarchitectonic data. With reproducibility across modalities, clustering methods, scanners, timepoints, and subjects in the order of 80-90%, we conclude that diffusion tractography represents a useful and objective tool for parcellation of the human cortex into functional regions, enabling studies into individual functional anatomy even when there are no specific activation paradigms available.

Adult↗
PubMed1980

Quantitative aspects of myocardial perfusion imaging.

Myocardial perfusion measurements have traditionally been performed in a quantitative fashion using application of the Sapirstein, Fick, Kety-Schmidt, or compartmental analysis principles. Although global myocardial blood flow measurements have not proven clinically useful, regional determinations have substantially advanced our understanding of and ability to detect myocardial ischemia. With the introduction of thallium-201, such studies have become widely available, although these have generally undergone qualitative evaluation. Using computer-digitized data, several methods for the quantification of myocardial perfusion images have been introduced. These include orthogonal and polar coordinate systems and anatomically oriented region of interest segmentation. Statistical ranges of normal and time-activity analyses have been applied to these data, resulting in objective and reproducible means of data evaluation.

Coronary Disease↗
PubMed2001

Advanced database methodology for the Collation of Connectivity data on the Macaque brain (CoCoMac).

The need to integrate massively increasing amounts of data on the mammalian brain has driven several ambitious neuroscientific database projects that were started during the last decade. Databasing the brain's anatomical connectivity as delivered by tracing studies is of particular importance as these data characterize fundamental structural constraints of the complex and poorly understood functional interactions between the components of real neural systems. Previous connectivity databases have been crucial for analysing anatomical brain circuitry in various species and have opened exciting new ways to interpret functional data, both from electrophysiological and from functional imaging studies. The eventual impact and success of connectivity databases, however, will require the resolution of several methodological problems that currently limit their use. These problems comprise four main points: (i) objective representation of coordinate-free, parcellation-based data, (ii) assessment of the reliability and precision of individual data, especially in the presence of contradictory reports, (iii) data mining and integration of large sets of partially redundant and contradictory data, and (iv) automatic and reproducible transformation of data between incongruent brain maps. Here, we present the specific implementation of the 'collation of connectivity data on the macaque brain' (CoCoMac) database (http://www.cocomac.org). The design of this database addresses the methodological challenges listed above, and focuses on experimental and computational neuroscientists' needs to flexibly analyse and process the large amount of published experimental data from tracing studies. In this article, we explain step-by-step the conceptual rationale and methodology of CoCoMac and demonstrate its practical use by an analysis of connectivity in the prefrontal cortex.

Animals↗
PubMed1997

Genome mapping by fluorescent fingerprinting.

The construction of sequence-ready maps of overlapping genomic clones is central to large-scale genome sequencing. We have implemented a method for fluorescent fingerprinting of bacterial clones to assemble contig maps. The method utilizes three spectrally distinct fluorescently tagged dideoxy ATPs to specifically label the HindIII termini in HindIII and Sau3AI restriction digests of clones that are multiplexed prior to electrophoresis and data collection. There is excellent reproducibility of raw data, improved resolution of large fragments, and concordance between the results obtained using this and the equivalent radioactive protocol. This method also allows detection of smaller overlaps between clones when compared to the analysis of restriction digests on nondenaturing agarose gels.

Chromosome Mapping↗
PubMed2004

The Use of DNA Microarrays to Investigate the Pharmacogenomics of Drug Response in Living Systems

With the advent of DNA microarray analysis, it is now possible to examine the response of virtually the entire human genome to cellular drug exposure and to uncover a wide variety of genes correlating with the establishment of drug resistance. This relatively new field of "pharmacogenomics" is likely to vastly increase our understanding of the mechanisms of drug action and how cells respond and adapt to drug exposure. However, DNA microarray studies typically result in the identification of hundreds of genes that may or may not be of relevance in vivo-particularly when large, genetically diverse study populations are used. The challenge to the researcher is to design experimental systems and approaches which minimize variability in the data, increase the reproducibility amongst experiments, allow array data from multiple experiments to be assessed by a variety of statistical, supervised learning, and data clustering approaches, and provide a clear link between drug response and the expression of specific genes. This review provides a description and critical analysis of recent studies on the pharmacogenomics of drug response and discusses current guidelines and approaches for the performance and analysis of DNA microarray experiments in this area.

Animals↗
PubMedDate not supplied

Quality management tool for mass casualty emergency responses and disasters.

INTRODUCTION AND BACKGROUND: Quality management (QM) principles generally have not been applied to multi-casualty and disaster situations. Quality management incorporates quality assurance (QA) and quality improvement (QI) supported by a management information system (MIS). Since responders to disasters and multi-casualty incidents generally operate on standing orders and/or protocols, the character of the responses lends itself to quality management methods. Standards and indicators of performance readily can be developed for these situations. OBJECTIVES: 1) to format disaster medical records as data collection instruments; 2) to develop appropriate tools that are easy to use for rapid assessments; 3) to develop a mechanism for determination of causes of injuries; and 4) to develop methods to: a) track patients; b) document response and recovery; and c) document the circumstances associated with the event. METHODS: Model tools using checklists and short, fill-in answers are provided. These tools are designed to be incorporated into the trauma or EMS registries. Emergency medical technicians, nurses, physicians, and medical students scored the same disaster scenario for the functional areas of calling the state of the disaster, triage, and field stabilization. RESULTS: Testing indicated that the checklists are completed in less than one minute, and produce objective data per patient in each functional area evaluated. In one instance, data were compiled for 38 patients from one bus accident in less than 10 minutes. The same data were reproduced, without variation, in the same amount of time, by three different providers of varied professional backgrounds.

Data Collection↗
PubMed2006

[Dissolution study of the gentin tablets].

To establish individual dissolution test for the tablets gentin, which have a marked influence on the secretory function of the stomach (increase the free acidity of the gastric juice and stimulate enzymoproduction function of the stomach), and gastroprotective functioning, the conditions for the test realization were studied and specified, using apparatus "Rotating Basket" (Dissolution test, apparatus 1, p.1791, USP XXIII, 1995). For the quantification of the active ingredients in buffer solutions chromatospectrophotometric method was used. The same conditions were used for the accomplishment of the dissolution test using apparatus "Rotating Paddle" (Dissolution test, apparatus 2, p.1791, USP XXIII, 1995). Metrologic characteristics were compared for the evaluation of the reproducibility of the results. Obtained data showed better reproducibility of the results for the apparatus "Rotating Paddle" compare to the apparatus "Rotating Basket". Estimated conditions are useful for the routine control of the tablets "Gentin" in the case of manufacturing.

Buffers↗
PubMed1991

The dose-response slope: a useful method for expressing the results of methacholine provocation tests in healthy subjects?

In order to study the reproducibility of different indices of airway responsiveness, two bronchial provocations with increasing methacholine concentrations up to 256 mg ml-1 were performed within 2 weeks on 30 healthy volunteers. The dose-response slope [DRS = maximal fall (%) in pulmonary function/maximal non-cumulative methacholine dose (mumol)] was calculated from forced expiratory volume in 1 s (FEV1) and from area under the expiratory flow-volume curve (AEFV). DRS reproducibility within 2 weeks in responsive (decline in FEV1 greater than 20%) and non-responsive subjects (decline in FEV1 less than 20%) was assessed. After log-transformation of the data the reproducibility was assessed with intraclass correlations (ICC) [with 95% confidence intervals (CIicc)], mean difference with limits of agreement (delta +/- SD), 95% confidence intervals for a single measurement (CIsm), and the absolute difference of the observations of the two days from each other (zero = ideal reproducibility). Provocative doses (PD20FEV1) could be calculated for 14 subjects on both occasions. In this responsive group the reproducibility of all the parameters used (PD20FEV1, DRSFEV1 and DRSAEFV) was high. In the non-responsive group, DRSFEV1 demonstrated a slightly, but not clearly, lower ICC than DRSAEFV. However, DRSFEV1 had clearly wider limits of agreement and CIsm than DRSAEFV. Also, with DRSFEV1 the observations of the two days differed significantly more from each other than with DRSAEFV (P less than 0.05).

Adult↗
PubMedDate not supplied

Methodological factors in the variability of lung volume and specific airway resistance measured by body plethysmography.

Thoracic gas volume (TGV) and specific airway resistance (sRaw) are commonly measured using pressure type and flow type body plethysmographs. Within-subject variability of the data, defined as the coefficient of variation of eight to ten measurements during the same session, was assessed with the two kinds of instruments and compared in fifteen normal subjects. The reproducibility of data obtained several days apart was also compared. All measurements were made in a 480-l body chamber, which could be used in both the pressure and the flow mode. The signals were processed digitally using three different algorithms: 1) simple linear regression (LR); 2) linear regression with drift correction achieved by adding to, or subtracting from the plethysmographic signal a term proportional to time (LRC); 3) Fourier analysis (FFT). Within-subject variability of TGV was much larger with flow than with pressure plethysmography when the signals were processed by LR (14.5 +/- 7.5 vs 6.3 +/- 3.0%; p less than 0.001), but almost the same using LRC (6.7 +/- 3.2 vs 5.4 +/- 2.7%) and FFT (6.1 +/- 2.4 vs 5.0 +/- 2.4%). For sRaw, variabilities were larger and less influenced by methodological factors. Adequate digital processing may therefore largely remedy the inherently greater variability of TGV measurements with flow plethysmographs.

Adult↗
PubMed2000

[Effect of sample solvents on retention in packed column supercritical fluid chromatography].

Factors affecting the retention in supercritical fluid chromatography(SFC) on C18 and NH2 packed columns have been studied. These factors include the sampling solvent, continuous injection, stationary phase type and concentration of modifier. When supercritical carbon dioxide or low concentration(less than 0.5%) of methanol is employed as the mobile phase, retention time increases with the polarity of the solvent on NH2 column, while it keeps almost constant on C18 column. Methanol will cover the active sites on the surface of the bonded phase, forming the "pseudo" stationary phase, which will lower the interaction between the analytes and the stationary phase, hence the shorter will be the retention time. The hydrogen bond between stationary phase (including the amino group and the remaining hydroxyl group) and methanol is the most obvious. So it's quite more evident on NH2 column than on C18 column that the delaying effect of the solvent, with methanol, acetone and chloroform in decreasing sequence, encourages the elution of the analytes during continuous injections. The elution will recover to the first injection after adequate interval has passed, i.e., more than 10 column volumes. When the methanol concentration is greater than 1.0% in carbon dioxide, the effect decreases and becomes negligible. The solvent effect is significant to the reasonable injection and reproducible chromatographic data in packed column SFC.

Carbon Dioxide↗
PubMed1997

Reliability and validity of stationary cystometry, stationary cysto-urethrometry and ambulatory cysto-urethro-vaginometry.

OBJECTIVE: The purpose of this article is to evaluate the reliability and validity of stationary cystometry, stationary cysto-urethrometry and ambulatory cysto-urethro-vaginometry for the diagnosis of urinary incontinence. MATERIAL AND METHODS: Literature search on reproducibility of cystometry is based on articles written in the English language found in Medline from 1987 to 1993. Five articles were found. These articles had references for another 6 older articles about the same topic. One recently published article is evaluated as well. Data about reproducibility of cystometry performed in these studies are given. Knowledge of reproducibility of cystometry combined with urethrometry, urethro-vagino or rectometry with leak detection during stationary or ambulatory recording is given. An evaluation of validity of the different methods is presented. RESULTS AND CONCLUSION: Conflicting data has been found for sensory parameters of stationary cystometry such as volume or pressure at first desire to void, strong desire to void and maximum cystometric capacity. No data were found concerning the reliability of cystometry for the recording of urinary incontinence. The main problem of urge-incontinent patients is leakage with a strong feeling of urgency. The recording of sensory parameters by cystometry is not valid when the main problem is urge incontinence. Cystometry will be valid for the diagnosis of urge incontinence when a leak detector is used or a mark is made at the tracings when leakage is observed. The reliability of cystometry concerning urge incontinence should be documented. The reliability of a urethral pressure recording when the urethral catheter is extracorporally fixed is low. The reliability and validity of ambulatory cysto-urethro-vaginometry in diagnosing urge incontinence, unstable urethra and genuine stress incontinence seems to be good, but needs better documentation.

Female↗
PubMed2004

Glyceryl trinitrate triggers premonitory symptoms in migraineurs.

Studying attacks of migraine is considerably hampered by its fundamentally episodic nature. Developing approaches to triggering migraine reliably is important for advancing understanding of the disorder by facilitating its study. Based on the work of the Copenhagen Group we administered an intravenous infusion of 0.5 microg/kg/min glyceryl trinitrate (GTN) to 44 migraineurs, 23 migraine without aura, 21 migraine with aura, and to 12 healthy controls. We sought to characterise the GTN-induced migraine in terms of the clinical features of the attacks and reproducibility of triggering, and included a non-migraine control group for the purpose of comparing any effects to exclude an ordering effect. Of the 44 patients administered GTN, 33 had a migraine attack fulfilling International Headache Society criteria. Thirty-two attacks were of migraine without aura and one of migraine with aura. Twelve patients described typical premonitory symptoms, which have not been previously documented with GTN-induced migraine. A repeat attack was triggered in all subjects but one. In one case a visual aura was also triggered both times. Our study shows that GTN-induced triggering is common in our patients, and remarkably reproducible. The data will facilitate the use of the GTN model in studies requiring extensive planning, such as brain imaging, or where preventive questions are at issue. We also report the first patient with a reproducible GTN-triggered migraine with aura.

Adult↗
PubMed1976

Total and regional cerebral blood flow measurement with 7-10-, 15-, 25-, and 50-mum microspheres.

Cerebral arteriovenous shunting of 7-10-, 15-, 25-, and 50-mum labeled microspheres was studied in 12 anesthetized dogs. Approximately 8% of the 7-10-mum spheres were shunted to cerebral venous blood, whereas less than 2% of the 15-, 25-, and 50-mum spheres were shunted. Cerebral vascular dilatation induced by hypoxia or hypercapnia did not alter the shunting. The calculated total cerebral flow was 10-15% lower with 7-10-mum microspheres as compared with simultaneous flows measured with the larger microspheres which also suggests that 7-10-mu spheres were shunted through the brain. The calculated distribution of cerebral flow was similar with 7-10- and 15-mum spheres but markedly altered when 50-mum spheres were used. Repeated injections of 15-mum spheres were used. Repeated injections of 15-mum microspheres given under stable conditions yielded total cerebral blood flows which averaged +/- 6% of their respective mean and the regional distribution of flow was highly reproducible. These data suggest that, in dogs, 15-mum spheres are an appropriate size to use to measure cerebral blood flows, since shunting is minimal, the distribution is not artifactually distorted, and the measurements are reproducible.

Animals↗
PubMed2001

Monte Carlo track structure for radiation biology and space applications.

Over the past two decades event by event Monte Carlo track structure codes have increasingly been used for biophysical modelling and radiotherapy. Advent of these codes has helped to shed light on many aspects of microdosimetry and mechanism of damage by ionising radiation in the cell. These codes have continuously been modified to include new improved cross sections and computational techniques. This paper provides a summary of input data for ionizations, excitations and elastic scattering cross sections for event by event Monte Carlo track structure simulations for electrons and ions in the form of parametric equations, which makes it easy to reproduce the data. Stopping power and radial distribution of dose are presented for ions and compared with experimental data. A model is described for simulation of full slowing down of proton tracks in water in the range 1 keV to 1 MeV. Modelling and calculations are presented for the response of a TEPC proportional counter irradiated with 5 MeV alpha-particles. Distributions are presented for the wall and wall-less counters. Data shows contribution of indirect effects to the lineal energy distribution for the wall counters responses even at such a low ion energy.

Algorithms↗
PubMed1998

Signal-averaged P wave: predictor of atrial fibrillation.

Abnormalities of the P wave seen during sinus rhythm are associated with atrial fibrillation and other supraventricular arrhythmias. Intra-atrial conduction delays can be seen on the surface ECG as P wave prolongation, which is more visible with averaging techniques used in advanced recording devices. Averaging followed by amplification after proper filtering of the electrical signal should allow more precise measurements of duration and amplitude of the P wave. Data on reproducibility, filter settings, required number of beats, and precise definitions of onset and offset are dependent largely on the system used, which can be QRS or, preferably, P wave triggered. This explains conflicting data in the literature. It is clear that P wave duration is one of the best predictors of perioperative atrial fibrillation. For paroxysmal forms, the data are less convincing. Root mean square voltages of the P wave can be useful. Combining the P wave duration with other data often improves the diagnostic value of signal averaging. Standardization of the techniques appears to be necessary.

Atrial Fibrillation↗
PubMed1995

A discontinuous buffer system increasing resolution and reproducibility in DNA sequencing on high voltage horizontal ultrathin-layer electrophoresis.

A novel discontinuous buffer system for DNA sequencing based on horizontal ultrathin-layer gel electrophoresis is described. The optimized system, named unbuffered stacking gel/discontinuous borate EDTA-buffer system, is composed of a 0.5 mm thick stacking gel, where standard sequencing reactions (1 microL volume) are easily loaded, and a 50 microns ultrathin running gel, where DNA fragments are separated. The novel discontinuous buffer system allows for sample concentration and efficient injection from the stacking gel into the capillary slab gel. Increased resolution, assessed by autoradiography, can be achieved within 25 min running time already over a 10.1 cm distance from the gel slot compared to the conventional gel system. An advantage of the new system is the capacity to resolve compressions in GC-rich regions, usually causing migrating artifacts in standard gels. The described system affords a major improvement in speed, resolution and reproducibility in DNA sequencing.

Autoradiography↗
PubMed2001

Sink feedback regulation of photosynthesis in vines: measurements and a model.

An experimental and modelling study of source-sink interactions in Vitis vinifera L., cv. Cabernet Sauvignon, rooted cuttings under non-limiting environmental conditions with a 12 h photoperiod is presented here. After 4 h, measured photosynthesis, stomatal conductance and leaf carbohydrate content reached maximum values. Over the remainder of the photoperiod, photosynthesis and stomatal conductance decreased continuously, whereas leaf carbohydrate content remained relatively constant. Because the experiment took place in a non-limiting environment, the results suggest that stomatal regulation of photosynthesis was mediated by an internal factor, possibly related to sink activity. A simple 1-source, 2-sink model was developed to examine the extent to which the data could be explained by a hypothetical sink-to-source feedback mechanism mediated by carbohydrate levels in either the mesophyll, the source phloem or the phloem of one of the two sinks. Model simulations reproduced the data well under the hypothesis of a phloem-based feedback signal, although the data were insufficient to elucidate the detailed nature of such a signal. In a sensitivity analysis, the steady-state response of photosynthesis to sink activity was explored and predictions made for the partitioning of photosynthate between the two sinks. The analysis highlights the effectiveness of a phloem-based feedback signal in regulating the balance between source and sink activities. However, other mechanisms for the observed decline in photosynthesis, such as photoinhibition, endogenous circadian rhythms or hydraulic signals in the leaf cannot be excluded. Nevertheless, it is concluded that the phloem-based feedback model developed here may provide a useful working hypothesis for incorporation into plant growth models and for further development and testing.

Biological Transport, Active↗
PubMed2003

Computerized quantification of tissue vascularization using high-resolution slide scanning of whole tumor sections.

Assessment of tissue vascularization using immunohistochemical techniques for microvessel detection has been limited by difficulties in generating reproducible quantitative data. The distinction of individual blood vessels and the selection of microscopic fields to be analyzed remain two factors of subjectivity. In this study, we used imaging analysis software and a high-resolution slide scanner for measurement of CD31-immunostained endothelial area (EA) in whole sections of human neuroblastoma xenograft and murine mammary adenocarcinoma tumors. Imaging analysis software provided objective criteria for analysis of sections of different tumors. The use of the criteria on images of entire tumor section acquired with the slide scanner constituted a rapid method to quantify tumor vascularization. Compared with previously described methods, the "hot spot" and the "random fields" methods, EA measurements obtained with our "whole section scanning" method were more reproducible with 8.6% interobserver disagreement for the "whole section scanning" method vs 42.2% and 39.0% interobserver disagreement for the "hot spot" method and the "random fields," respectively. Microvessel density was also measured with the whole section scanning method and provided additional data on the distribution and the size of the blood vessels. Therefore, this method constitutes a time efficient and reproducible method for quantification of tumor vascularization.

Adenocarcinoma↗