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At least 883 records · Page 49Linked to original sources
PubMed1997

Evaluating current methods for determination of the susceptibility of mycobacteria to pyrazinamide, conventional, radiometric Bactec and two methods of pyrazinamidase testing.

The authors compared conventional and Bactec determinations of pyrazinamide susceptibility with pyrazinamidase activity determined using either standard Dubos Oleic agar or Middlebrooks 7H9 agar. Of the 26 Mycobacterium tuberculosis tested, Bactec found 16 strains susceptible and 10 resistant, conventional methods found six susceptible and 20 resistant. Dubos identified 13 and Middlebrooks 10 strains as producing pyrazinamidase (susceptible). Of the 11 strains susceptible in Bactec and resistant by conventional methods, eight produced pyrazinamidase. All mycobacteria other than tuberculosis (6) and Mycobacterium bovis (2) were resistant by all methods. Bactec results gave a better correlation with pyrazinamidase results than conventional tests.

Amidohydrolases↗
PubMed2005

Density-functional theory-based chemical reactivity indices in the Hartree-Fock method. I. Unrestricted Hartree-Fock method for a noninteger number of electrons.

Correct evaluation of the reactivity indices, such as chemical potential, hardness, and Fukui function demands for the extension of the formalism beyond the integer particle picture. An ensemble approach is used as an extension of the unrestricted Hartree-Fock (UHF) method for noninteger electron number systems. A prescription is given for the construction of an ensemble Fock operator for a system with partially filled spin-orbitals. The comparison between the ensemble HF method and the hyper-HF method in terms of density matrices and spin-orbitals is presented. The equivalence of the equiensemble case and the ensemble UHF case with unequal weight factors is shown.

Journal Article↗
PubMed2007

Simulated scaling method for localized enhanced sampling and simultaneous "alchemical" free energy simulations: a general method for molecular mechanical, quantum mechanical, and quantum mechanical/molecular mechanical simulations.

A potential scaling version of simulated tempering is presented to efficiently sample configuration space in a localized region. The present "simulated scaling" method is developed with a Wang-Landau type of updating scheme in order to quickly flatten the distributions in the scaling parameter lambdam space. This proposal is meaningful for a broad range of biophysical problems, in which localized sampling is required. Besides its superior capability and robustness in localized conformational sampling, this simulated scaling method can also naturally lead to efficient "alchemical" free energy predictions when dual-topology alchemical hybrid potential is applied; thereby simultaneously, both of the chemically and conformationally distinct portions of two end point chemical states can be efficiently sampled. As demonstrated in this work, the present method is also feasible for the quantum mechanical and quantum mechanical/molecular mechanical simulations.

Algorithms↗
PubMed2002

Advanced diagnostic methods in oral and maxillofacial pathology. Part II: immunohistochemical and immunofluorescent methods.

The practice of pathology is currently undergoing significant change, in large part due to advances in the analysis of DNA, RNA, and proteins in tissues. These advances have permitted improved biologic insights into many developmental, inflammatory, metabolic, infectious, and neoplastic diseases. Moreover, molecular analysis has also led to improvements in the accuracy of disease diagnosis and classification. It is likely that, in the future, these methods will increasingly enter into the day-to-day diagnosis and management of patients. The pathologist will continue to play a fundamental role in diagnosis and will likely be in a pivotal position to guide the implementation and interpretation of these tests as they move from the research laboratory into diagnostic pathology. The purpose of this 2-part series is to provide an overview of the principles and applications of current molecular biologic and immunologic tests. In Part I, the biologic fundamentals of DNA, RNA, and proteins and methods that are currently available or likely to become available to the pathologist in the next several years for their isolation and analysis in tissue biopsies were discussed. In Part II, advances in immunohistochemistry and immunofluorescence methods and their application to modern diagnostic pathology are reviewed.

Antigens, Neoplasm↗
PubMed1981

An electron microscopic method for localization of ribosomal proteins during transcription of ribosomal DNA: a method for studying protein assembly.

We describe a method for the localization of ribosomal proteins on electron microscopic spreads of active rRNA genes. The method consists of raising antibodies against Drosophila melanogaster proteins and allowing these antibodies to react with lysates of D. melanogaster egg chambers. The locations of the bound IgGs in the active transcripts are detected with goat anti-rabbit IgGs that have been labeled with electron-dense polymethacrylate spheres. By statistical analysis we can generate a confidence interval for the initial point of protein assembly for a particular protein. The first point of protein assembly for S14 is located near the 5' end of the pre-18S rRNA. In contrast, the first point of protein assembly for L4 is at 0.38 unit from the initiation point (a unit being the length of a ribosomal transcription unit). The binding patterns of S14 and L4 are consistent with the 5' proximal and the 5' distal orientations of the pre-18S and the pre-28S rRNAs. The method described here provides an approach to the elucidation of the assembly of eukaryotic ribosomal proteins in vivo.

Animals↗
PubMed2000

A simple method to establish short-term cultures of normal human colonic epithelial cells from endoscopic biopsy specimens. Comparison of isolation methods, assessment of viability and metabolic activity.

BACKGROUND: Abnormalities in colonic epithelial cell function have been implicated in the pathogenesis of various intestinal disorders, especially inflammatory bowel disease (IBD). The mechanisms, however, remain obscure owing to the lack of representative human colonic epithelial cell models. The aim of this study was to develop and validate a method for establishment of short-term culture of normal human colonic epithelial cells from endoscopic biopsies. METHODS: Epithelial cells were isolated from colonoscopic biopsies by means of ethylenediaminetetraacetic acid/ethylene glycol tetraacetic acid (EDTA/EGTA) (10 or 60 min) or by enzyme treatment and cultured in collagen-coated wells. Viability was measured with a methyltetrazoleum conversion assay, confocal laser, and electron microscopy. Metabolic function was measured by means of butyrate oxidation, 14C-leucine and 3H-glucosamine incorporation; DNA synthesis by means of 3H-thymidine incorporation, and apoptosis with an enzyme-linked immunosorbent assay (ELISA) for histone-associated DNA fragments. Cell types were identified by immunocytochemistry. RESULTS: Ten minutes of EDTA/EGTA treatment released intact crypts and was superior to both the 60-min treatment and enzymatic treatment in terms of viability and nonepithelial cell contamination, respectively. Despite activation of detachment-induced apoptosis, a median 51% of the isolated cells was viable after 24 h of culture and metabolically active as judged by 3H-thymidine, 14C-leucine, and 3H-glucosamine incorporation. Butyrate oxidation followed more complex kinetics (substrate activation) than observed previously in other models. The apparent Km values (medians) were 0.7 mM and 4.5 mM in low and high concentration ranges, respectively. CONCLUSION: We report a simple method to establish culture of human colonic epithelial cells from endoscopically obtained biopsy specimens, producing sufficient viable cells to perform metabolic studies pertinent to the pathogenesis of IBD and related human disorders.

Biopsy↗
PubMed2004

Analytical methods for the determination of alkylphenolic surfactants and polybrominated diphenyl ethers in wastewaters and sewage sludges. II method development.

Analytical methods for the determination of two groups of compounds, the non-polar alkyl phenols along with their more polar ethoxylates, and the hydrophobic polybrominated flame retardants in wastewater samples have been developed. The methods allow for determination of the analytes in both the aqueous and solid phases, which were separated by centrifugation and filtration. Extraction from the aqueous phase involved the use of SPE for the surfactants, however, liquid-liquid extraction was found to be more efficient for the PBDE. Alkyl phenols and their ethoxylates were extracted from the solid phase by shaking with solvent and Soxhlet was used for extraction of PBDE. Sample cleanup was based on alumina columns for the PBDE and surfactants when extracted form solids. Quantification of surfactants utilised LC-MS with ESI in both positive and negative ionisation mode, and GC-MS (NCI) was used to determine the PBDE, with the exception of the deca congener, where a 10 m column installed on GC-ECD resulted in short run times and reduced thermal decomposition. Method recoveries for the surfactants were above 80%, and for PBDE 92.5% from the solid phase and 95+/-5% from the liquid phase.

Chromatography, Liquid↗
PubMed1988

Chemical protective clothing standard test method development. Part 1. Penetration test method.

A "round-robin" interlaboratory study was conducted to validate the relative precision of the American Society for Testing and Materials (ASTM) F-903 test method for measuring the resistance of protective materials to penetration by liquids. The study utilized seven independent laboratories performing three trials of five protective clothing materials challenged by five widely used commercial liquids. The level of overall agreement for interlaboratory results suggests a relatively high confidence in the precision of the method. Systematic errors, however, may reduce the confidence of this method for certain materials and solvents. Recommendations to eliminate or reduce variability due to systematic errors include reduction of test pressure, use of a support screen, reporting of permeation evidence as a failure, and the use of a fluorescent dye to enhance visibility.

Butanones↗
PubMed1997

Methods of dietary and nutritional assessment and intervention and other methods in the Multiple Risk Factor Intervention Trial.

Various dietary assessment instruments were used in the Multiple Risk Factor Intervention Trial (MRFIT), either to assist with the special intervention program or to assess trial outcomes. For the latter purpose, the 24-h recall was the main method and was selected with the understanding that the single recall collected at baseline and at most annual visits--considered by itself--would be useful mainly for assessing groups rather than individuals. Major components of the data collection and analysis system developed for the 24-h recall included central training and certification of nutritionists, a central nutrient coding system, and a food grouping system to assist interventionists in using recall data for counseling. Several additional nutritional assessment methods were used for men in the special intervention group only to assist them in attaining the dietary goals. These goals consisted chiefly of reduced intake of saturated fat and cholesterol and a modest increase in intake of polyunsaturated fat; total fat intake was also decreased, primarily for control of energy intake. Short-term success at attainment of these nutritional goals was evaluated by means of 3-d food records collected before the intervention and after the initial 10-wk intensive intervention period. The MRFIT nutrient goals, which became more vigorous at certain points in the trial, were translated into food patterns. Adherence to these food patterns was also assessed by scoring of 3-d records and by subjective evaluation by nutritionists throughout the trial. Methods of collecting other trial data are also described in this chapter.

Blood Pressure↗
PubMed2001

Development and testing of a hierarchical method to code the reason for admission to intensive care units: the ICNARC Coding Method. Intensive Care National Audit & Research Centre.

A computer-based hierarchical method was developed to code conditions leading to admission to intensive care in the UK. The hierarchy had five tiers: surgical status, body system, anatomical site, physiological or pathological process and medical condition. The hierarchy was populated initially using the free-text descriptions of the reason for admission from 10,806 admissions recorded as part of the Intensive Care Society's UK APACHE II study. After refinement and error-checking, a prospective evaluation was undertaken on 22,059 admissions to 62 UK intensive care units. Individual units coded between 60 and 1610 (mean 356) admissions. All but 50 (0.2%) of the admissions could be coded and 38 units coded every admission. Fifty admissions (0.2%) could not be coded within 24 h of admission but were coded subsequently when more information became available. Of the admissions, 96.1% were coded at all levels of the hierarchy in the coding method. Six hundred and thirty-seven of the 741 unique conditions (85.9%) were used in one of the five reasons for admission and 564 (76.1%) in the primary reason for admission. Five conditions account for 19.4% of all primary reasons for admission. This is the first method to be developed empirically for coding the reason for intensive care admission.

Diagnosis-Related Groups↗
PubMed2004

Establishing a selectivity survey as part of the method development activity for an isocratic reversed-phase liquid chromatographic method.

Often high-performance liquid chromatography method development is done by choosing a single C18 column and optimizing only the mobile phase composition. In this paper, it is demonstrated how to evaluate and optimize the best combination of the different stationary phase chemistries and mobile phases for a limited method development activity. By using column and mobile phase switching, it is possible to automate most of the activity in a nine-step process. Columns are chosen to represent the range of selectivity currently available. Interestingly, although the most popular column is the C18 phase, it is not the best column for the optimized methods in the cases studied.

Journal Article↗
PubMed2001

Comparison of ELISA method versus MEIA method for daily practice in the therapeutic monitoring of tacrolimus.

BACKGROUND: For the adequate management of transplant patients on tacrolimus therapy, it is important to obtain optimal blood concentrations. The purpose of this study was to determine the most appropriate method for daily practice of tacrolimus determination in whole blood. We compared enzyme-linked immunosorbent assay (ELISA) with microparticle enzyme immunoassay (MEIA), using European controls and blood samples from organ graft recipients treated with tacrolimus. Time, practicability and cost were considered also. METHODS: The assays were performed according to the procedures detailed in the product inserts. In five European controls and 40 blood samples from kidney and liver transplant patients, we determined the blood levels of tacrolimus by both MEIA and ELISA tests. RESULTS: MEIA gave more reliable results with the European controls (y=1.078x+0.092; r=0.996) than ELISA (y=0.956x+1.307; r=0.946). For the patient samples, the correlation between the two tests was 0.85 and the extreme range of values was +65% and -56% for ELISA vs MEIA. Although the manufacturer of the ELISA test used claims the best sensitivity and precision, in our experience the MEIA test was quicker and cheaper. CONCLUSIONS: MEIA provides a quick, reliable and easy-to-handle method for routine monitoring of tacrolimus blood levels.

Enzyme-Linked Immunosorbent Assay↗
PubMed1996

Influence of the mechanism of regurgitation on the quantification of mitral regurgitation by the proximal flow convergence method and the jet area method.

In 84 patients mitral regurgitation was quantified by angiography. The mechanism of regurgitation was determined by echocardiography (organic, n = 54, functional, n = 30). The radii of the proximal isovelocity surface areas in the flow convergence region for 28 and 41 cm.s-1 blood flow velocity and the area and length of the regurgitant jet were measured using colour flow Doppler imaging. The radii of the proximal isovelocity surface areas correlated more closely with the angiographic grade than the jet parameters irrespective of the mechanism of regurgitation. In more than 90% of the patients, grades I-II mitral regurgitation were correctly differentiated from grades III-IV by means of the radii of the proximal isovelocity surface areas. Using the jet parameters, the differentiation was correct in 50-90% of the patients depending on the mechanism of regurgitation. The jet area method particularly failed to identify grades III-IV organic mitral regurgitation due to a high prevalence of eccentric jets in these patients. It is concluded that the proximal flow convergence method was suitable for the quantification of mitral regurgitation irrespective of the mechanism of mitral regurgitation. On the other hand, the value of the jet area method depended largely on the regurgitation mechanism.

Adult↗
PubMed2001

Analytical methods for thorium determination: a journey from conventional methods to novel applications.

Thorium may be determined using a variety of analytical methods. These may be based on chemical or physical principles or may make use of the radioactive decay of the individual thorium isotopes. The method to be used for a certain analytical purpose is selected as a function of the matrix of the sample and of the concentration of thorium. The present paper describes different methodologies, their range of application and discusses selected results. The methods described cover a concentration range of more than twelve orders of magnitude, i.e. from concentrated solutions to micrometre-sized particles. Emphasis is given to active radiometric techniques, chemical and instrumental analysis.

Mass Spectrometry↗
PubMed1998

A method to compare costs of drugs and supplies among anesthesia providers: a simple statistical method to reduce variations in cost due to variations in casemix.

BACKGROUND: Comparison of costs among anesthesia providers using "cost per case" does not adjust for variations in casemix (such as the type of procedure and patient condition). The authors propose an alternative method for comparing costs using the American Society of Anesthesiologists' Relative Value Scale (ASARVS) system, which incorporates basic units (for the procedure), modifier units (for the patient's physical condition), "other" units (such as for the placement of invasive monitors), and time units (proportional to the case duration). METHODS: Data were obtained from a series of 3,340 anesthetics performed at a tertiary hospital. Administered and discarded drug, supply, and fluid costs were used. RESULTS: Costs expressed as dollars per ASARVS unit had 54% less variability than costs expressed as dollars per case (P < 0.0001). Pearson correlations between demographic variables and cost per ASARVS unit ranged from -0.10 to 0.13. Total (e.g., quarterly) costs for simulated sets of cases were predicted within 0.0 +/- 2.3% by multiplying (1) their sum of units and (2) a like set of case's sum of costs divided by sum of units. CONCLUSIONS: Costs of anesthetic supplies and drugs of a case were more accurately reported as "cost per unit" than as "cost per case." This method of calculating the cost of anesthetic drugs and supplies has several applications, including (1) comparison of costs among anesthesia providers and (2) benchmarking costs among hospitals and anesthesia groups. By design, anesthesia providers' time is quantified by their ASARVS units. Together anesthesia costs (personnel, supplies, and drugs) are better reported as "cost per unit" than as "cost per case."

Adult↗
PubMed2000

Comparison of methods of measurements of oxygen consumption in mechanically ventilated patients with multiple trauma: the Fick method versus indirect calorimetry.

OBJECTIVE: The purpose of this study was to compare the measurements of whole body oxygen consumption determined by the Fick method and by indirect calorimetry in mechanically ventilated patients with multiple trauma. DESIGN: A prospective, correlational, within-subjects design. SETTING: Surgical intensive care unit of a Level I trauma center. PATIENTS: Thirty-eight mechanically ventilated adults with multiple injuries who received a pulmonary artery catheter within 24 hrs of admission to the surgical intensive care unit. MEASUREMENTS AND MAIN RESULTS: After the initial resuscitation, simultaneous measurements of oxygen consumption (V(O2) by the reverse Fick equation and by indirect calorimetry were performed every 6 hrs for 24 hrs in normothermic patients who were at rest for at least 30 mins. At each measurement period, the mean V(O2) values determined by indirect calorimetry were significantly greater than the mean V(O2) values determined by the Fick method (time 1: 172+/-38 vs. 125+/-47 mL/min/m2, p < .0001; time 2: 170+/-31 vs. 130+/-48 mL/min/m2, p < .0001; time 3: 170+/-32 vs. 132+/-53 mL/min/m2, p < .0001; time 4: 169+/-29 vs. 130+/-60 mL/min/m2, p < .0002). By using the Bland and Altman technique, the mean bias was 41+/-3.95 mL/min/m2. Correlation coefficients of VO2 values between methods of measurements were statistically significant (r2 = .32, p = .0001; r2 = .32, p = .0001; r2 = .33, p = .0001; r2 = .18, p = .0001). CONCLUSIONS: Indirect calorimetry should be the preferred standard for measurement of oxygen consumption in severely injured patients.

Adult↗
PubMed1985

Simultaneous measurements of cerebral blood flow by the xenon/CT method and the microsphere method. A comparison.

Simultaneous measurements of cerebral blood flow have been performed in baboons to assess the correlation between the acute and invasive nondiffusible microsphere technique and the noninvasive xenon-enhanced CT method. Blood flows in small tissue volumes (approximately 1 cm3) were directly compared. The results of these studies demonstrate a statistically significant association between the two methods (P less than .001). Similar correlations were obtained by both the Kendall tau (tau) and the Spearman (r) methods. The problems and limitations of such correlations are discussed.

Animals↗
PubMed1987

Routine methods in toxicology and therapeutic drug monitoring by high-performance liquid chromatography. I. Rapid method for determination of acetaminophen in plasma, including a STAT procedure.

A method has been developed for rapid determination of acetaminophen levels in plasma using high-performance liquid chromatography (HPLC) including a STAT procedure. Most often, determination of acetaminophen levels is requested in emergency situations. In such situations, hepatic toxicity can occur, in severe cases leading to hepatic failure. Hepatic toxicity is correlated with serum drug concentrations and, in particular, with biological half-life (t1/2). Because hepatic injury only becomes biochemically apparent 24-48 h after overdose ingestion, the potential for developing severe hepatic damage can be much more quickly assessed by determining the serum levels of acetaminophen. Certain concentrations in serum at 4 and 12 h after overdose are associated with probable hepatic damage. Therefore, one must know the levels as soon as possible; thus, STAT is most often ordered. The method described in this article was developed for running acetaminophen stats and is a microscale method, requiring only 10 microliter of the specimen; thus, it is also suitable for pediatric patients. The procedure involves precipitation of proteins and injection of the top clear liquid into the chromatogram.

Acetaminophen↗