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At least 685 records · Page 38Linked to original sources
PubMed1985

Simultaneous computer mapping to facilitate intraoperative localization of accessory pathways in patients with Wolff-Parkinson-White syndrome.

Sixteen patients with the Wolff-Parkinson-White syndrome underwent simultaneous intraoperative computer mapping from multiple sites before surgical division of the accessory pathways. A 16-bipolar electrode band was positioned around the atrioventricular groove. Ventricular epicardial electrograms from single beats were recorded simultaneously during atrial pacing, resulting in maximal preexcitation, and atrial electrograms were recorded during orthodromic supraventricular tachycardia. Four-level transmural plunge needle electrodes were used concomitantly in 3 patients. Electrograms were processed separately using a guarded signal conditioner that isolates, amplifies, filters and analog-to-digitally converts synchronously at 2 kHz with 12-bit accuracy. Digital data were transmitted by fiber optics to a high-density digital recorder and processed with a computer having rapid interactive graphics. Results in the 16 patients revealed 20 distinct Kent bundles. Two patients had only nonsustained supraventricular tachycardia induced intraoperatively and 1 patient manifested intermittent anterograde ventricular preexcitation. Multiple pathways were identified in 4 patients. This simultaneous multiple electrode mapping procedure facilitates intraoperative mapping by requiring only a single beat for analysis of anterograde and retrograde activation times, decreases cardiac manipulation during mapping and obviates the need for cardiopulmonary bypass, and permits analysis of transmural activation patterns. This approach decreases markedly the time required for mapping and permits accurate study of nonsustained arrhythmias as well as rapid identification of multiple accessory pathways.

Adolescent↗
PubMed1976

Renal cyclic adenosine monophosphate: an accurate index of parathyroid function.

Measurement of total urine cyclic 3':5'-adenosine monophosphate (cyclic AMP) only incompletely discriminates between normal, hyperparathyroid, and nonparathyroid hypercalcemic patients. Only a fraction of total urine cyclic AMP is contributed by parathyroid hormone (PTH) action on the proximal nephron (renal cyclic AMP); the remainder is derived from plasma by glomerular filtration. We dtermined total urine and plasma cyclic AMP and PTH (by carboxy-terminal specific radioimmunoassay) in control, hyperparathyroid, nonparathyroid hypercalcemic, and surgically hypoparathyroid patients. Renal cyclic AMP was calculated as total urine cyclic AMP minus the filtered component. Of these determinations, only renal cyclic AMP segregated normal from hyperparathyroid, and hyperparathyroid from nonparathyroid hypercalcemic patients with complete accuracy. These data suggest that measurement of renal cyclic AMP provides an accurate index of parathyroid activity and allows clinical discrimination and appropriate treatment of the sub-groups of patients with malignancy and nonparathyroid hypercalcemia from those with hyperparathyroidism.

Adult↗
PubMed1988

Lexical decision and visual hemifield: an examination of the RT-accuracy relationship.

Visual hemifield, stimulus duration and angle of eccentricity were manipulated using a lexical decision paradigm (discrimination of words from non-words). Lexical decision was measured by several dependent variables: reaction time, (RT); accuracy, d'; and beta. The results support the generalization of RVF superiority in a lexical decision task for parafoveal stimulation for three dependent variables, RT, accuracy and d'. No significant effect of any stimulus manipulation was found for beta. When RT is plotted as a function of accuracy, the data separate into two groups (one for words, one for non-words) each best described by a linear equation with negative slope. The implication of this analysis is discussed, and the hypothesis offered that the same basic process discriminates words from non-words in a lexical decision task, regardless of visual field, parafoveal angle of eccentricity or stimulus duration. Visual field is processed no differently from the other stimulus manipulations.

Adult↗
PubMed1986

Characterization of biological media by means of their non-linearity.

This review presents the state-of-the-art in applications of the second order acoustic non-linearity parameter, B/A, for the characterization of biological media. The close relationship between B/A and the molecular structure of certain liquids, as well as the influence of the inhomogeneous nature of biological materials on B/A, are discussed. The finite amplitude and the thermodynamic methods are presented, and their advantages, disadvantages and accuracy of data produced are discussed. A new and promising procedure, real time non-linear parameter tomography, is critically evaluated and its prospective application for in vivo studies is treated in some depth. B/A values covering a broad variety of biological materials are presented and a world-wide collaborative research scheme is suggested for systematic and in-depth studies of non-linearity of biological media and for clinical exploitations of the results of these studies.

Animals↗
PubMed1992

Simultaneous determination of common benzodiazepines in blood using capillary gas chromatography.

Blood samples were extracted with n-butyl acetate, and the extracts analysed by capillary gas chromatography using DB-1 and DB-1701 capillary columns with electron-capture detection. The DB-1701 column was found to give better separation of different benzodiazepines (BZDs). Recoveries ranged from 79 to 98%. Detection limits ranged from 0.005 to 0.015 microM for triazolam and flunitrazepam, and from 0.02 to 0.1 microM for other BZDs. Data on accuracy and precision are given for diazepam, desmethyldiazepam, flunitrazepam and nitrazepam.

Anti-Anxiety Agents↗
PubMed1991

Estimation of the absorbed dose in radiation-processed food--2. Test of the EPR response function by an exponential fitting analysis.

The use of electron paramagnetic resonance spectroscopy to accurately evaluate the absorbed dose to radiation-processed bones (and thus meats) is examined. Additive re-irradiation of the bone produces a reproducible dose response function which can be used to evaluate the initial dose by back-extrapolation. It was found that an exponential fit (vs linear or polynomial) to the data provides improved accuracy of the estimated dose. These data as well as the protocol for the additive dose method are presented.

Animals↗
PubMed1995

The use of prescription claims databases in pharmacoepidemiological research: the accuracy and comprehensiveness of the prescription claims database in Québec.

Despite the potential benefits of using prescription claims databases for pharmacoepidemiological research, little work has been reported on the nature of available information or its accuracy. The purpose of this study was to describe information contained within the prescription claims database in Québec, and to assess the accuracy of drug information that might be used to monitor drug exposure and physician prescribing. The comprehensiveness of the prescriptions claims database was assessed by examining 1,917,214 records of dispensed prescriptions for a regionally stratified random sample of 65,349 Québec elderly in 1990. We found that values in key fields (individual identifiers, drug, quantity, date dispensed and duration) were missing or out of range in 0-0.4% of records. The accuracy of data were examined in 723 prescriptions filled by 306 elderly patients attending one internal medicine clinic. Of these prescriptions, 83% were filled by the patient and correctly identified the patient and drug and in 89% of these 599 records, the prescribing physician was correctly identified. The quantity and duration of the prescriptions were accurate in 69.1% and 72.1% of records, respectively. We conclude that the prescription claims database in Québec may represent one of the most accurate means of determining drugs dispensed to individuals. There may be limitations in using this database for dosing information.

Drug Prescriptions↗
PubMed1996

Left ventricular mass and function in primary hypertension.

The Hypertension Optimal Treatment study is a prospective, randomized, clinical trial designed to challenge the J curve phenomenon in hypertension. A subpopulation of 665 patients from seven participating centers in the United States were enrolled to evaluate the prevalence of left ventricular mass and its relationship to systolic and diastolic function, as assessed by Doppler echocardiography, and to clinical events during the length of the study. Echocardiographic measurements followed stringent criteria and were rechecked in a core laboratory for accuracy. Baseline data revealed left ventricular hypertrophy in 62% of the patients. Left ventricular hypertrophy was more prevalent in women than in men (72% v 57%, P < .0001). The hypertrophy was further characterized according to left ventricular geometry and found the concentric pattern as the predominant form of hypertrophy (46%). Indices of left ventricular systolic function, including fractional shortening, cardiac index, and ejection fraction, were normal or above-normal. Doppler interrogation of the mitral inflow demonstrated left ventricular diastolic dysfunction in 81% of patients. The constrictive physiology (inversion of the E/A ratio) was the most prevalent mitral flow pattern (79%). Regression of left ventricular hypertrophy, modification of mass index geometry, and alterations in mitral flow characteristics under optimal blood pressure control will be specifically compared with subsequent examinations.

Aged↗
PubMed2004

Wide-angle X-ray solution scattering as a probe of ligand-induced conformational changes in proteins.

A chemical genetics approach to functional analysis of gene products utilizes high-throughput target-based screens of compound libraries to identify ligands that modulate the activity of proteins of interest. Candidates are further screened using functional assays designed specifically for the protein--and function--of interest, suffering from the need to customize the assay to each protein. An alternative strategy is to utilize a probe to detect the structural changes that usually accompany binding of a functional ligand. Wide-angle X-ray scattering from proteins provides a means to identify a broad range of ligand-induced changes in secondary, tertiary, and quaternary structure. The speed and accuracy of data acquisition, combined with the label-free targets and binding conditions achievable, indicate that WAXS is well suited as a moderate-throughput assay in the detection and analysis of protein-ligand interactions.

Alcohol Dehydrogenase↗
PubMed2004

Chromatographic behaviour of naproxen-cyclodextrin complexes stationary phase C8 alkyl chain as competitor for the drug release from cyclodextrin cavity.

Cyclodextrins are known to alter the absorptivity of the guest molecules, therefore, analytical methods that are based on the spectrophotometric data present accuracy problems. In this work, using RP-HPLC methods for naproxen-cyclodextrins quantitation, extensive analytical inaccuracies are detected. Competitive complexation technique is utilised in an attempt to develop an analytical method enabling the determination of naproxen as a free drug. For this reason, stationary phases with silica ligands that can function as competing agents were used, thus contributing to the drug release. The release of the drug from cyclodextrins complexes is achieved by modification of the thermodynamic parameters that determine the stability constant, by changing: the interactions with the mobile phase components (e.g. pH, organic modifier, competitive agents) and the interactions with the stationary phase ligands (C8). After studying the parameters affecting the interaction between the alkyl-chain C8 and naproxen:cyclodextrin complexes, we developed and validated a new specific method for the accurate determination of the drug. Consecutive accumulation of the cyclodextrins molecules on the stationary phase was studied.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2005

Pleural adenosine deaminase in the separation of transudative and exudative pleural effusions.

OBJECTIVE: The purpose of this study was to evaluate the usefulness of a new parameter, pleural adenosine deaminase (PADA), for separating transudative pleural effusion from exudative pleural effusion, and to compare the results with other tests (albumin gradient and protein gradient). METHODS: From November 2001 to January 2003, 359 consecutive patients with pleural effusion who underwent a diagnostic thoracentesis were included in the study. Effusions were individually classified as transudates or exudates after the careful evaluation of all clinical data and biochemical parameters of pleural fluid and serum of patients on the basis of Light's criteria. The means and standard deviations of PADA, pleural/serum ADA (P/S ADA) ratio, albumin gradient and protein gradient were evaluated for transudative and exudative effusions. The best cut-off values for each test were identified by using the receiver operating characteristic (ROC) curve. The optimum cut-off level was determined by selecting points of test values that provided the greatest sum of sensitivity and specificity. RESULTS: There were 113 transudates and 246 exudates. For each test, differences in mean value between the transudate group and the exudate group were statistically significant (t test, P<0.001). The optimum cut-off levels for PADA and P/S ADA were 15.3 U/L and 0.66 U/L, respectively. ROC analysis confirmed previous recommendations for albumin gradient (12 g/L) and protein gradient (31 g/L). For detecting exudates, the PADA test yielded a sensitivity and specificity of 85.8% and 82.3%, respectively. Sensitivity and specificity of the albumin gradient were found to be 88.5% and 79.3%, and of the protein gradient 85% and 83.2%, respectively. The areas under the curve (AUC) data and accuracy demonstrated similar discriminative properties in the examined tests. CONCLUSIONS: The measurement of PADA is suggested as a reliable test in the separation of pleural exudates from transudates with accuracy similar to that of the albumin gradient and protein gradient.

Adenosine Deaminase↗
PubMed2005

Mathematical modeling of arterial pressure response to hemodialysis-induced hypovolemia.

A computer model of pressure response to hemodialysis-induced hypovolemia is reported. Heart rate and hematocrit, measured in the course of hemodialysis, are imposed as computer model inputs and the model computes the arterial pressure response after tuning model parameters representative of patient's cardiovascular reactivity. Computer model reproduced with good accuracy experimental data (arterial pressure, cardiac output and total peripherical resistance). Parameter identification over successive sessions of the same patients revealed satisfactory reliability, providing a physiological interpretative key to patient's hemodynamic behavior during hemodialysis.

Blood Pressure↗
PubMed2004

Conventional digital subtraction x-ray angiography versus magnetic resonance angiography in the evaluation of carotid disease: patient satisfaction and preferences.

AIM: To compare conventional digital subtraction x-ray angiography (DSA) and contrast-enhanced magnetic resonance angiography (MRA) of the carotid arteries in terms of patient satisfaction and preferences. METHODS: One hundred and sixty-seven patients with symptomatic carotid artery disease, who underwent both DSA and MRA, were prospectively recruited in this study. Patients' perceptions of each method were assessed by the use of a questionnaire after each procedure. Main outcome measures were anxiety, pain, satisfaction rate and patient preferences. RESULTS: DSA generated more anxiety and pain during the procedure, but the severity of these ill-effects was mild. Satisfaction rates for each method were similar. More patients were, however, willing to have a repeat MRA compared with DSA (67 versus 41%). The majority of patients (62%) preferred MRA over DSA (31%). The shorter MRA imaging time was found to be a significant factor in patients' acceptance of the technique. The main reasons cited by patients for their dislike of a particular procedure was noise and claustrophobia for MRA and invasiveness, pain and post-procedural bed rest for DSA. CONCLUSIONS: MRA is the method that is preferred by the majority of patients, although the actual disutility of DSA may be small. Assuming equal diagnostic accuracy, our data supports replacement of DSA by MRA for routine carotid imaging.

Adult↗
PubMed2004

Determination of levofloxacin in plasma, bronchoalveolar lavage and bone tissues by high-performance liquid chromatography with ultraviolet detection using a fully automated extraction method.

The aim of this study was to develop a specific and sensitive high-performance liquid chromatographic (HPLC) assay for the determination of levofloxacin in human plasma, bronchoalveolar lavage and bone tissues. The sample extraction was based on a fully automated liquid-solid extraction with an OASIS cartridge. The method used ultraviolet detection set at a wavelength of 299 nm and a separation with a Supelcosil ABZ+ column. The assay has been found linear over the concentration range 0.25-25 microg/ml for levofloxacin in plasma, 1-6 microg/ml in bronchoalveolar lavage and 0.5-10 microg/g for bone tissues and it provided good validation data for accuracy and precision. The assay will be applied to determine the penetration of levofloxacin in human bronchoalveolar lavage (BAL) and bone tissues during pharmacokinetic steady state.

Anti-Infective Agents↗
PubMed2004

Determination of linezolid in plasma and bronchoalveolar lavage by high-performance liquid chromatography with ultraviolet detection using a fully automated extraction method.

The aim of this study was to develop a specific and sensitive high-performance liquid chromatographic assay for the determination of linezolid in human plasma, and bronchoalveolar lavage. The sample extraction was based on a fully automated solid-phase extraction with an OASIS HLB cartridge. The method used ultraviolet detection set at a wavelength of 254 nm and a separation with a Zorbax Eclipse XDB C8 column. The assay has been found linear over the concentration range 0.02-30 microg/ml and 0.04-30 microg/ml for linezolid, respectively, in plasma and bronchoalveolar lavage. It provided good validation data for accuracy and precision (CV <4.64% and 5.08%, accuracy in the range 96.93-102.67% and 97.33-105.67%, respectively, for intra- and inter-day). The assay will be applied to determine the penetration of linezolid in human bronchoalveolar lavage during pharmacokinetic steady-state.

Acetamides↗
PubMed2005

Determination of free ertapenem in plasma and bronchoalveolar lavage by high-performance liquid chromatography with ultraviolet detection.

A sensitive assay for the determination of unbound ertapenem in human plasma and bronchoalveolar lavage (BAL) was developed using ultrafiltration of plasma and BAL samples. A rapid HPLC method was used with ultraviolet detection set at a wavelength of 305 nm and a separation on a Prontosil AQ C18 column, with imipenem used as internal standard. This assay was linear over the concentration range of 0.5-100 microg/mL and 0.25-50 microg/mL in plasma and BAL, respectively. Limits of detection and quantitation were respectively 0.05 and 0.25 microg/mL. Validation data for accuracy and precision were CV<2.48 and 8.25%, accuracy in the range 98.1-104.2% and 102.2-108.4%, respectively, for intra and inter-day.

Bronchoalveolar Lavage Fluid↗
PubMed2006

Differential pulse, square wave and adsorptive stripping voltammetric quantification of tianeptine in tablets.

Differential pulse polarographic (DPP) and square wave polarographic (SWP) techniques were applied at hanging mercury drop electrode (HMDE) for quantitative determination of tianeptine (TIA) in tablets. The adsorptive stripping voltammetric (ASV) behavior of TIA was also studied. TIA gave a sensitive reduction peaks at -1256, -1244 and -1072 mV for DPP, SWP and ASV, respectively (versus Ag/AgCl) in Britton-Robinson buffer (B-R buffer) at pH 11. The solution conditions and instrumental parameters were optimized for the determination of TIA in tablets. Calibration plots and regression data validation, accuracy, precision, limit of detection, limit of quantitation and other aspects of analytical merit are presented.

Antidepressive Agents, Tricyclic↗