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At least 721 records · Page 40Linked to original sources
PubMed1985

The measurement of plasma vitamin B6 compounds: comparison of a cation-exchange HPLC method with the open-column chromatographic method and the L-tyrosine apodecarboxylase assay.

A cation-exchange high-performance liquid chromatographic (HPLC) method was found to be comparable to the open-column (OCC) method for measuring six different B6 compounds in human plasma and the L-tyrosine apodecarboxylase (LTD) assay for pyridoxal-P (PLP). Plasma samples were obtained from 9 subjects before and after 7 days of pyridoxine (PN) supplementation. PLP, pyridoxal (PL) and 4-pyridoxic acid (4-PA) were the major B6 compounds in plasma and the only compounds which increased after supplementation. The coefficients of correlation between any 2 of the 3 methods in measuring plasma PLP were greater than 0.93, and between HPLC and OCC in quantifying PL and 4-PA were 0.82 and 0.63, respectively. With the low plasma levels of pyridoxamine-P, PN and pyridoxamine, the results from OCC were consistently higher than those from HPLC. However, recoveries of spiked B6 compounds in plasma by these methods were between 84 to 105 percent for all the 5 vitamers and 4-PA.

Adult↗
PubMed1979

Comparison of an automated radioimmunoassay method and a competitive protein-binding method for evaluation of serum cortisol.

A competitive protein-binding method (CPB) for serum cortisol determination has been compared with a newly developed automated radioimmunoassay (RIA) technic with respect to reproducibility and correlation of patient results. The RIA method uses an immobilized anti-cortisol antibody covalently coupled to the inner surface of a plastic cartridge. A mixture of 3H-labeled and unlabeled cortisol is passed through the cartridge to achieve separation of free and bound cortisol. The bound cortisol is later eluted to regenerate the antibody for the next sample. The RIA procedure had a day-to-day coefficient of variation (CV) of 7% at three cortisol levels. The CPB method had a day-to-day CV of 10% at a concentration of 8 microgram/dl. A comparison of 67 patient samples showed no statistically significant difference between the methods. The regression equation was RIA = 0.96 CPB + 0.14 microgram/dl, with a correlation of 0.92.

Binding, Competitive↗
PubMed1981

Detection of ABH tissue isoantigens by immunoperoxidase methods in normal and neoplastic urothelium. Comparison with the erythrocyte adherence method.

The expression of the ABH blood group antigens (BGAg) by carcinomas of the urinary bladder at the time of initial biopsy heralds a relatively benign clinical course, whereas antigen deletion in histologically similar tumors is often predictive of tumor recurrences and invasion. The use of BGAg as a tumor marker in the clinical setting has been limited by difficulties in demonstrating BGAg in tissue sections with the erythrocyte adherence test, especially for antigen H. In this study, immunoperoxidase methods were used to detect BGAg in deparaffinized tissue sections of normal and malignant human urothelium, and the results were compared with those of the erythrocyte adherence test performed on adjacent sections. Results with the two methods were similar for antigens A and B; however, a novel lectin-antilectin immunoperoxidase method was clearly superior for detecting antigen H. The immunoperoxidase method significantly reduced false-positive test results for antigen deletion in normal urothelium and more accurately predicted the subsequent clinical course in patients having urinary bladder cancer.

ABO Blood-Group System↗
PubMed1987

Comparison of four leukocyte differential methods with the National Committee for Clinical Laboratory Standards (NCCLS) reference method.

The authors compared four leukocyte differential counting methods with the National Committee for Clinical Laboratory Standards Reference Leukocyte Differential Method H20-T to determine the clinical sensitivity of the methods. The three-part differential performed by the Coulter Counter Model S-Plus IV and the Toa E-5000, when combined with instrument flags and defined laboratory checking limits for red blood cell and platelet values, are safe and efficacious screening methods for the presence of morphologic abnormalities. The Geometric Data Hematrak 590 proved comparable in clinical sensitivity to a random 100-cell eye-count differential.

Adolescent↗
PubMed1983

Two methods for determining erucic acid in edible fats and oils: results from a collaborative study on a rapid, open-tubular (capillary) GLC method and comparison with an isolation TLC procedure.

The results of an international collaborative study for the determination of 5% erucic acid in four samples of edible fats and oils with differing levels of 22:1 isomers other than erucic acid, based on the use of wall-coated (SILAR-5CP) open-tubular gas-liquid chromatography, are examined. The same samples had been analyzed in a separate collaborative study by an alternative and more complex method based on argentation thin-layer chromatography. Both methods rejected about the same proportion of participating laboratories and a few individual results from otherwise acceptable laboratories. The means and repeatabilities of the two methods were similar, but the gas-liquid chromatographic method showed better reproducibility.

Autoanalysis↗
PubMed2003

Improvements to EPA method 531.1 for the analysis of carbamates that resulted in the development of U.S. EPA Method 531.2.

This project is undertaken to fully optimize the U.S. Environmental Protection Agency Method 531.1 post-column chemistries and to incorporate recent advances in liquid chromatographic separation, post-column derivatization, and detection techniques. Sample preservation and storage stability studies establish citric acid as a suitable replacement for the caustic monochloroacetic acid in the current method and confirm its antimicrobial effectiveness. Performance of an alternate set of commercially available post-column reagents is also investigated. This research has resulted in the publication of Method 531.2, a high-performance liquid chromatographic direct injection method for the analysis of N-methylcarbamoyloximes and N-methylcarbamates using post-column derivatization and fluorescence detection.

Carbamates↗
PubMed2006

Ovulation detection methods for urinary hormones: precision, daily and intermittent sampling and a combined hierarchical method.

BACKGROUND: We evaluate the performance of ovulation detection methods and present new approaches, including evaluation of methods for precision, combining multiple markers into a hierarchical system and using ovulation markers in intermittent sampling designs. METHODS: With serum LH peak day as the 'gold standard' of ovulation, we estimated accuracy and precision of ovulation day algorithms using 30 ovulatory menstrual cycles with daily urinary and serum hormones and transvaginal ultrasound. Sensitivity and specificity for estimating the presence of ovulation were tested using visually assessed ovulatory (30) and anovulatory (22) cycles. RESULTS: Sensitivity and specificity ranged from 70 to 100% for estimating presence of ovulation with twice-per-cycle, weekly, twice weekly, every-other-day and daily specimens. A combined hierarchical method estimated ovulation day using daily specimens within +/-2 days of the gold standard in 93% of cases. Accuracy of estimating ovulation day within +/-2 days using intermittent sampling ranged from 40% (weekly sampling) to 97% (every-other-day). CONCLUSIONS: A combined hierarchical algorithm using precise and accurate markers allows maximal use of available data for efficient and objective identification of ovulation using daily specimens. In intermittent sampling designs, the presence and the timing of ovulation can be estimated with good sensitivity, specificity and accuracy.

Adult↗
PubMed1999

Evaluation of a new 3-h hybridization method for detecting the mecA gene in Staphylococcus aureus and comparison with existing genotypic and phenotypic susceptibility testing methods.

A new 3-h hybridization assay for detection of the staphylococcal mecA gene and the Staphylococcus aureus nuclease gene was evaluated by comparing the assay with existing genotypic and phenotypic methods. A total of 275 S. aureus strains were tested, including 257 epidemiologically unrelated strains (135 mecA-positive and 122 mecA-negative; collection I), and 18 strains with known borderline resistance to methicillin (collection II). Complete agreement was obtained for both collections when comparing the new assay with genotypic methods. We further evaluated a range of phenotypic susceptibility methods recommended in Europe and/or USA using the presence of the mecA gene as the defining standard. For collection I a high degree of agreement was found for both Etests (256 strains) and the oxacillin screen plate test (255 strains); the degree of agreement was lower for agar dilution methicillin (250 strains) and oxacillin 1 microg discs (239 strains). For the borderline strains a high degree of agreement was only obtained by the oxacillin screen plate test (17 of 18 strains). The other tests were less accurate, in the following order: agar dilution methicillin, Etest methicillin, Etest oxacillin and oxacillin discs with disagreement for four, five, nine and 13 strains, respectively. In conclusion, the new hybridization assay is a rapid and exact method for detecting the mecA gene and the S. aureus nuclease gene. This study confirms that phenotypic tests for methicillin resistance in S. aureus strains creates both false-susceptible and false-resistant results, especially for borderline resistant strains.

Bacterial Proteins↗
PubMed1983

Left ventricular systolic time intervals. A comparison between the conventional carotid pulse curve method and the doppler ultrasound method.

From amplitude registration of the doppler ultrasound signal, timing of cardiac valve opening and closure may be achieved and used for the registration of the time intervals of the cardiac cycle. In 42 normal subjects and unselected patients with heart disease a comparison was made of the simultaneously derived left ventricular systolic time intervals (LVSTI) from the conventional noninvasive method of electrocardiogram, phonocardiogram and carotid pulse curve tracing and from an alternative more direct noninvasive method by use of the amplitude tracing of the doppler ultrasound signal. There was a strong correlation between the two methods for each of the different periods of the LVSTI. Differences between the pulse transmission times of curve upstroke and incisura, and possible limitations of both methods are discussed.

Adolescent↗
PubMed1988

Difference in the nocturnal behaviour of blood pressure between monitorings with the arm-cuff method and with the finger-volume oscillometric method.

The nocturnal behaviour of blood pressure obtained by a new portable device for monitoring ambulatory blood pressure (ABPM 630) was compared with that obtained by a finger-volume oscillometric device (BP-100); the former uses a conventional arm-cuff inflated by CO2 gas to eliminate the noise of the motorized pump, and is based on a cuff-oscillometric as well as the Korotkoff sound technique (microphone method). With the microphone method in ABPM 630, the mean differences from the conventional auscultatory method were -0.28 +/- 6.15 mmHg (mean +/- s.d.) for systolic and 0.96 +/- 6.28 mmHg for diastolic blood pressure, and there was a highly significant correlation between blood pressure values measured by the ABPM 630 and by the auscultatory method. In 40 patients with mild to moderate hypertension 24-h blood pressure was monitored simultaneously with the ABPM 630 and BP-100. The daytime average of systolic blood pressure measured with the ABPM 630 was similar to that measured with the BP-100, whereas the night-time average assessed by the former was significantly higher than that assessed by the latter. Arm-cuff inflation by ABPM 630 caused some degree of sleep disturbance in 35 of 40 subjects, whereas finger-cuff inflation scarcely disturbed the sleep. The performance of the ABPM 630 was excellent.

Arm↗
PubMed1987

Routine methods in toxicology and therapeutic drug monitoring by high performance liquid chromatography. II. A rapid microscale method for determination of chloramphenicol in blood and cerebrospinal fluid.

A highly sensitive, specific method for determining chloramphenicol levels in human blood plasma and cerebrospinal fluid is described. The method uses high performance liquid chromatography for the analysis, requires minimal quantities of patient specimen, and thus is suitable for use in newborn and pediatric patients. The method described in this article is specifically developed for routine use in laboratories engaged in therapeutic drug monitoring. It has advantages over other methods because it is less time consuming and can be used with commercially available controls.

Chloramphenicol↗
PubMed1987

Routine methods in toxicology and therapeutic drug monitoring by high performance liquid chromatography: III. A rapid microscale method for determination of furosemide in plasma and urine.

A highly specific, sensitive, and rapid microscale method is described for determining furosemide levels in plasma and urine. Monitoring furosemide levels has been recommended in patients with impaired renal function and in premature infants since furosemide has been known to cause ototoxicity. The method described here is simple, easy to run, takes only 7 min per sample, and can be set up for routine monitoring of furosemide by clinical laboratories. The method uses ion-pairing high performance liquid chromatography and detection of furosemide by fluorescence, which gives excellent separation and high sensitivity with minimal sample preparation. The method requires only 25 microliters of plasma or urine and, thus, is suitable for use in newborn intensive care units.

Chromatography, High Pressure Liquid↗
PubMed1988

Routine methods in toxicology and therapeutic drug monitoring by high-performance liquid chromatography. IV. A rapid microscale method for determination of propranolol and 4-hydroxypropranolol in plasma.

A fast, simple, and sensitive method for the simultaneous determination of total and free propranolol and its active metabolite 4-hydroxypropranolol in plasma by high performance liquid chromatography is described. Both propranolol and 4-hydroxypropranolol are detected by fluorescence at one wavelength detector setting. The limit of sensitivity of the method is 2 ng/ml for 4-hydroxypropranolol and 1 ng/ml for propranolol. The method is fast since it involves a single extraction step followed by evaporation of organic solvent and chromatography of the residue. The method takes only 10 min per sample and thus can be set up in a therapeutic drug-monitoring laboratory for monitoring propranolol levels routinely.

Chromatography, High Pressure Liquid↗
PubMed1989

Routine methods in toxicology and therapeutic drug monitoring by high-performance liquid chromatography. VI: A rapid microscale method for determination of caffeine in plasma and saliva.

A highly selective and specific method for determining caffeine levels in plasma and saliva is described. The method is a microscale procedure that requires only 25 microliters of specimen, although the assay can be performed with as little as 10 microliters of the specimen and is therefore, particularly suitable for monitoring caffeine levels in the neonates. The method is sensitive to 0.5 microgram/ml and is specific for caffeine as none of the other xanthines shows any interference. The method is also fast as treatment of specimen requires only precipitation of proteins and thus is ideal for use in hospital and clinical laboratories.

Caffeine↗
PubMed2001

Ab initio structure determination of monoclinic 2,2-dihydroxymethylbutanoic acid from synchrotron radiation powder diffraction data: combined use of direct methods and the Monte Carlo method.

The crystal structure of 2,2-dihydroxymethylbutanoic acid (C(6)H(12)O(4)) in monoclinic form has been determined ab initio from synchrotron radiation powder diffraction data. Two O and five C atoms were first derived by direct methods. Two missing O atoms and one C atom were found by the Monte Carlo method without applying constraint to their relative positions. Positional and isotropic displacement parameters of these non-H atoms were refined by the Rietveld method. Molecules are linked by hydrogen bonds and they make sheet-like networks running parallel to the (010) plane. The Monte Carlo method is demonstrated to be a powerful tool for finding missing atoms in partially solved structure.

Journal Article↗
PubMed1993

3-D computation of E fields by the volume-surface integral equation (VSIE) method in comparison with the finite-integration theory (FIT) method.

An algorithm has been developed for calculation of 3-dimensional E fields by the volume-surface integral equation (VSIE) method. Integration over surface elements is performed by elementary analytical formulas, assuming a linear interpolation of surface charges. Grid points at electrical interfaces are split off, well considering the E field behavior at these contours, specifically at sharp bends and multimedia junctions. Averaging procedures are utilized in order to avoid undefined or infinite values at critical points. The VSIE is solved by iteration using GMRES ("general minimum residuum") solver on a SUN workstation SPARC-IPX or Cray XMP, whereby convergence speed decreases considerably as the heterogeneity of the problem increases. Computation time (e.g., 20 min on a supercomputer for approximately 30,000 cells) needs to be reduced by further code development. Results for 3-D test cases (plane wave illuminating a layered cylinder) generally agree well with the finite-integration-theory (FIT) method if high E field gradients occur perpendicular to electrical boundaries. The VSIE method predicts slightly higher E fields only in critical regions. On the other hand, the FIT method at present is more efficient with respect to computation time for large domains with high cell numbers (> 100,000 cells).

Algorithms↗
PubMed1993

Studies of new short-period method for delayed contact hypersensitivity assay in the guinea pig. (I). Development and comparison with other methods.

A new method for delayed contact hypersensitivity assay of chemical compounds in guinea pigs, a short-period method (14 days) with a high detection sensitivity, has been developed. The new method was as follows; a combination of a Freund's complete adjuvant (FCA, undiluted) intradermal injection and a 24-h occlusive patch on a guinea pig was performed 2x at an interval of 4 days and challenged by non-occlusive topical application 11 days after the first sensitization (with benzyl alcohol during test development). Acanthosis and spongiosis in the epidermis and mononuclear cell infiltration into the dermis were observed histopathologically at the skin reaction site. This newly developed method (adjuvant and 24-h occlusive patch 2x test: AP2 test) could equally and/or better detect the allergenicities of 6 other chemical compounds (bromostyrol, citronellal, benzyl salicylate, p-aminobenzoic acid ethyl ester, p-phenylenediamine and formaldehyde) as compared with the cumulative contact enhancement test (CCET) and the guinea pig maximization test (GPMT).

Animals↗
PubMed1988

National field evaluation of a defined substrate method for the simultaneous enumeration of total coliforms and Escherichia coli from drinking water: comparison with the standard multiple tube fermentation method.

A defined substrate method was developed to simultaneously enumerate total coliforms and Escherichia coli from drinking waters without the need for confirmatory or completed tests. It is a new method based on technology that uses a hydrolyzable substrate as a specific indicator-nutrient for the target microbes. No equipment other than a 35 degrees C incubator and long-wavelength (366-nm) light is necessary. To perform the test, one only has to add water to the powdered ingredients in a tube or flask. If total coliforms are present in the water sample, the solution will change from its normal colorless state (no target microbes present) to yellow. The specific presence of E. coli will cause the same tube to fluoresce under a longwave (366-nm) UV lamp. The test, called Autoanalysis Colilert (AC), was compared with Standard Methods for the Examination of Water and Wastewater 10-tube multiple tube fermentation (MTF) in a national evaluation. Five utilities, representing six U.S. Environmental Protection Agency regions, participated. All water samples came from distribution systems. Split samples from a wide variety of water sources were analyzed for the MPN-versus-MPN comparison. A total of 1,086 tubes were positive by MTF, and 1,279 were positive by AC. There was no statistical difference between MTF and AC. Species identifications from positive tubes confirmed the sensitivity of the AC. A national evaluation of the AC test showed that it: (i) was as sensitive as Standard Methods MTF, (ii) specifically enumerated 1 total coliform per 100 ml, in a maximum of 24 h, (iii) simultaneously enumerated 1 E. coli per 100 ml in the same analysis, (iv) was not subject to false-positive or false-negative results by heterotrophic bacteria, (v) did not require confirmatory tests, (vi) grew injured coliforms, (vii) was easy to inoculate, and (viii) was very easy to interpret.

Bacteriological Techniques↗