Articles de revues : « Microgram samples »

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L'Hermite-Balériaux, M., G. Copinschi et E. Van Cauter. « Growth hormone assays : early to latest test generations compared ». Clinical Chemistry 42, n^o 11 (1 novembre 1996) : 1789–95. http://dx.doi.org/10.1093/clinchem/42.11.1789.

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Abstract We compared the data from four growth hormone (GH) immunoassays for analyzing 24-h GH profiles in four apparently normal subjects and four obese subjects (508 serum samples). The detection limit was 0.02 microgram/L for one immunochemiluminometric assay (ICMA), 0.1 microgram/L for two IRMAs, and 0.4 microgram/L for one RIA. All GH pulses with a peak ICMA value > 1 microgram/L were detected by each of the other methods. Overall, the correlation coefficient between the values obtained with all four assays exceeded 0.90. However, for GH concentrations < or = 0.25 microgram/L, acceptable concordance (r2 > or = 0.80) was reached only between the ICMA and one IRMA; between the ICMA and the RIA, concordance was acceptable only for GH concentrations > or = 10 micrograms/L. In the normal subjects, the percentage of undetectable values was 0% with the ICMA but 29% with one of the IRMAs; in obese subjects, the corresponding values were 12% and 38%.

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Vessella, R. L., J. Noteboom et P. H. Lange. « Evaluation of the Abbott IMx® Automated Immunoassay of Prostate-Specific Antigen ». Clinical Chemistry 38, n^o 10 (1 octobre 1992) : 2044–54. http://dx.doi.org/10.1093/clinchem/38.10.2044.

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Abstract We detail the performance characteristics of the new IMx PSA immunoassay developed by Abbott Laboratories, addressing PSA recovery, assay reproducibility, standard curve storage, lower limit of detection, dilution linearity, and correlation with the Hybritech Tandem-R PSA immunoassay. We analyzed 686 sera for PSA retrospectively, testing 555 of these concurrently with the IMx and the Tandem-R immunoassays. The IMx PSA standard curve was linear from 0 to 100 micrograms/L, and curve storage was maintained for 4 weeks. The lower limit of detection of the IMx PSA assay was < or = 0.03 microgram/L; allowing for the assay precision yielded a biological detection limit of 0.06 microgram/L. We conservatively set the clinical threshold at 0.1 microgram/L. Regression analysis of dilution linearity involving 10 samples (0.44-200 micrograms/L) resulted in coefficients of correlation ranging from 0.9972 to 1.000. Reproducibility studies with 18 specimens within the range of 0.39-413.67 micrograms/L gave intra- and interassay CVs < 6.5%. The interassay 95% confidence interval for a specimen containing 0.06 microgram of PSA per liter was 0.03-0.09 microgram/L. Correlation between IMx and Tandem-R PSA assay results was excellent: r = 0.9909 and slope = 0.95. Overall, the IMx PSA immunoassay, with the conveniencies of automation, curve storage, and nonisotopic handling, provided an improved lower limit of PSA detection, which allows for earlier indication of residual or recurrent disease after radical prostatectomy.

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Karlsson, M., S. Hammers, I. Nilsson-Ehle, A. S. Malmborg et B. Wretlind. « Concentrations of doxycycline and penicillin G in sera and cerebrospinal fluid of patients treated for neuroborreliosis. » Antimicrobial Agents and Chemotherapy 40, n^o 5 (mai 1996) : 1104–7. http://dx.doi.org/10.1128/aac.40.5.1104.

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Concentrations of doxycycline and penicillin G in serum and cerebrospinal fluid (CSF) were analyzed in 46 patients during treatment for neuroborreliosis. Twenty patients were treated intravenously with penicillin G at 3 g every 6 h (q6h), and 26 patients were treated orally with doxycycline at 200 mg q24h. All samples were collected on day 13 of treatment. The median concentrations of penicillin G in serum were 0.5, 37, and 5.6 micrograms/ml before and 1 and 3 h after drug administration, and that in CSF was 0.5 (range, 0.3 to 1.6) microgram/ml after 2 to 3 h. The median concentrations of doxycycline in serum were 2.1, 6.1, and 4.7 micrograms/ml before and 2 and 6 h after drug administration, and that in CSF was 0.6 (range, 0.4 to 2.5) microgram/ml after 4 h. All patients had concentrations of penicillin G or doxycycline in CSF above the lowest reported MICs of penicillin G (0.003 microgram/ml) and doxycycline (0.12 microgram/ml) for Borrelia burgdorferi. However, no patients had a drug concentration in CSF above the highest reported MIC of penicillin G (8 micrograms/ml), and only one had a drug concentration in CSF above the highest reported MIC of doxycycline (2 micrograms/ml), despite good clinical response to treatment. No treatment failure or relapse was observed during a 1-year follow-up, although one patient treated with penicillin G and one treated with doxycycline were retreated because of residual pain. The chosen dosages of penicillin G and doxycycline seem to give sufficient concentrations in serum and CSF for the treatment of neuroborreliosis.

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Murthy, V. V., et A. Karmen. « A study of the CEDIA digoxin immunoassay ». Clinical Chemistry 36, n^o 3 (1 mars 1990) : 559–61. http://dx.doi.org/10.1093/clinchem/36.3.559.

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Abstract We evaluated the CEDIA digoxin immunoassay (Microgenics, Inc., Concord, CA), as performed with the Cobas-Bio centrifugal analyzer. In assays of sera with known concentrations of digoxin, the enzyme activity, measured when two beta-galactosidase (EC 3.2.1.23) fragments were combined according to the assay format, was proportional to the digoxin concentration. Results of assays of sera containing 0 to 3 micrograms of digoxin per liter correlated well when compared with an RIA method: CEDIA, microgram/L = 1.00 x RIA - 0.06 microgram/L (n = 90, r = 0.95, Sxy = 0.05). Duplicate assays of three control sera containing 0.8, 2.2, or 3.3 micrograms/L, each analyzed 20 times a day with each group of patients' samples, gave within-run CVs of 1-3% and day-to-day CVs of 3-12%. The reconstituted CEDIA reagents were stable for at least a month at 5 degrees C. As many as 25 samples and controls can be assayed in half the time needed to complete a similar number of RIA measurements with comparable results.

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Vogel, J. S., D. E. Nelson et J. R. Southon. « Accuracy and Precision in Dating Microgram Carbon Samples ». Radiocarbon 31, n^o 2 (1989) : 145–49. http://dx.doi.org/10.1017/s0033822200044799.

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The accuracy of AMS radiocarbon determinations on very small samples has been tested by measuring a suite of microgram-sized samples of a known-age material. The total measurement precision for the smallest sample (50μg) was found to be ± 3% and the precision improved with larger sample size. The accuracies of the measurements were found to be within the measurement precisions.

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Feist, Peter, et Amanda Hummon. « Proteomic Challenges : Sample Preparation Techniques for Microgram-Quantity Protein Analysis from Biological Samples ». International Journal of Molecular Sciences 16, n^o 2 (5 février 2015) : 3537–63. http://dx.doi.org/10.3390/ijms16023537.

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Tagliati, S., A. Rydh, R. Xie, U. Welp et W. K. Kwok. « Membrane-based calorimetry for studies of sub-microgram samples ». Journal of Physics : Conference Series 150, n^o 5 (1 mars 2009) : 052256. http://dx.doi.org/10.1088/1742-6596/150/5/052256.

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Doettinger-Zech, S. G., M. Uhl, D. L. Sisson et A. Kapitulnik. « Simple microcalorimeter for measuring microgram samples at low temperatures ». Review of Scientific Instruments 72, n^o 5 (mai 2001) : 2398–406. http://dx.doi.org/10.1063/1.1355263.

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Bannon, D. I., C. Murashchik, C. R. Zapf, M. R. Farfel et J. J. Chisolm. « Graphite furnace atomic absorption spectroscopic measurement of blood lead in matrix-matched standards ». Clinical Chemistry 40, n^o 9 (1 septembre 1994) : 1730–34. http://dx.doi.org/10.1093/clinchem/40.9.1730.

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Abstract Now that the level of concern for a toxic blood lead concentration is 0.482 mumol/L (10 micrograms/dL), laboratories must meet new requirements to shorten analysis times and increase accuracy and precision of blood lead determinations. We used a matrix-matching method to estimate the lead concentration in blood by graphite furnace atomic absorption spectroscopy (GFAAS). For CDC proficiency samples and the NIST-Certified Blood Reference standard, the performance of this method compared favorably with that of previously published GFAAS methods and of the anodic stripping voltammetric method routinely used in our laboratory. At lead concentrations of 0.242 mumol/L (5.01 micrograms/dL) and 1.478 mumol/L (30.63 micrograms/dL), within-run CVs were 2.78% and 0.68%, respectively; between-run CVs were 4.9% and 1.35%. In 52 study samples with lead content ranging from 0.097 to 3.812 mumol/L (2 to 79 micrograms/dL), 87% of results by the matrix-modified method were within 0.048 mumol/L (1 microgram/dL) of consensus values.

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Knight, G. J., G. E. Palomaki, D. H. Lea et J. E. Haddow. « Exposure to environmental tobacco smoke measured by cotinine 125I-radioimmunoassay. » Clinical Chemistry 35, n^o 6 (1 juin 1989) : 1036–39. http://dx.doi.org/10.1093/clinchem/35.6.1036.

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Abstract We describe a polyclonal-antiserum-based 125I-radioimmunoassay for cotinine that is suitable for measuring nonsmokers' passive exposure to tobacco smoke in the environment. The standard curve ranged from 0.25 to 12.0 micrograms/L, with an estimated lower limit of sensitivity of 0.2 microgram/L (95% B/Bo = 0.2 microgram/L; 50% B/Bo = 4.0 micrograms/L). The median within-assay CVs for patients' samples with cotinine values from 0.4 to 1.3, 1.4 to 2.4, 2.5 to 4.6, and 4.7 to 15.6 micrograms/L were 13.9%, 7.2%, 5.1%, and 5.7%, respectively. Between-assay CVs for two quality-control sera with average values of 1.53 and 3.68 micrograms/L were 14.3% and 7.8%, respectively. Analytical recoveries of cotinine from smokers' sera diluted in zero calibrant ranged from 91% to 116%. Cotinine values determined on 79 paired sera and urines from nonsmokers showed significant correlation with self-reported exposure to environmental tobacco smoke (r = 0.49, P less than 0.001 for sera; r = 0.57, P less than 0.001 for urine). The log of the values for serum and urine cotinine were also significantly correlated (r = 0.85, P less than 0.001). Evidently, polyclonal antiserum can be used to develop a cotinine assay for measuring exposure to environmental tobacco smoke that compares well with that described for monoclonal-based assays.

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Patterson, T. F., J. Peters, S. M. Levine, A. Anzueto, C. L. Bryan, E. Y. Sako, O. L. Miller, J. H. Calhoon et M. G. Rinaldi. « Systemic availability of itraconazole in lung transplantation. » Antimicrobial Agents and Chemotherapy 40, n^o 9 (septembre 1996) : 2217–20. http://dx.doi.org/10.1128/aac.40.9.2217.

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Systemic availability of itraconazole in lung transplantation was evaluated by serially measuring the bioactivity of itraconazole in lung transplant patients who received itraconazole for prophylaxis (n = 12) or therapy (n = 5). These patients also received concomitant antacid and H2 blocker therapy. In patients receiving itraconazole at 200 and 400 mg/day, the median concentrations in serum were 0.5 microgram/ml (range, < 0.05 to 2.7) and 3.5 micrograms/ml (< 0.5 to 14), respectively. The concentration following administration of 400 mg/day was > 2.5 micrograms/ml in 56% of samples, while only 4% of samples from patients who were administered 200 mg/day had levels over 2.5 micrograms/ml. This study documents that itraconazole can be absorbed in patients receiving concomitant antacid and H2 blocker therapy. However, the reduced and variable absorption suggests the importance of confirming drug delivery by measurement of concentrations in serum.

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Ioannou, P. C., et D. G. Konstantianos. « Fluorometric determination of magnesium in serum with 2-hydroxy-1-naphthaldehyde salicyloylhydrazone. » Clinical Chemistry 35, n^o 7 (1 juillet 1989) : 1492–96. http://dx.doi.org/10.1093/clinchem/35.7.1492.

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Abstract This simple, rapid, sensitive fluorometric method for determining magnesium is based on formation of a fluorescent complex of magnesium with 2-hydroxy-1-naphthaldehyde salicyloyl-hydrazone in alkaline ethanolic medium (lambda ex = 420 nm, lambda em = 460 nm). The detection limit of the method is 0.05 microgram/L (2 nmol/L) and the relative standard deviations (CVs) are 0.8%, 1.1%, and 2.5% at magnesium concentrations of 50, 5.0, and 0.50 microgram/L, respectively. The standard curve is linear from 0 to 250 micrograms/L (0-10 mumol/L). We investigated the chemistry of the reaction, and have applied the method to determine magnesium in 100-fold-diluted, otherwise untreated serum samples. Within-run CVs for the method were 1.7%, 1.1%, and 1.3% at mean magnesium concentrations of 15.7, 26.4, and 36.2 mg/L, respectively. Day-to-day CVs were 2.7%, and 3.6% at mean magnesium concentrations of 10.1 and 25.5 mg/L, respectively. Samples from 96 hospitalized patients in intensive-care units were analyzed by the proposed method (y) and by an automated colorimetric method involving Magon sulfonate reagent (x). Linear regression analysis of the results yielded: y = 1.01x - 0.04 (r = 0.982, Sxy = 0.90).

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T. Jafer, Zainab M., et Esmail K. Shubber. « Cytogenetic studies of methotrexate drug on the peripheral blood samples from patients suffered of ulcerative colitis & ; ulcerative colitis developed to pseudopolyps &colon cancer ». Journal of Biotechnology Research Center 4, n^o 1 (1 janvier 2010) : 44–53. http://dx.doi.org/10.24126/jobrc.2010.4.1.92.

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The investigation was done on 43 samples of peripheral blood which drawn from patients suffered of chronic ulcerative colitis, 20 samples from patients of colon cancer, 10 samples from ulcerative colitis developed to pseudopolyps & 20 samples of healthy individuals. The samples were taken from female and male of different ages. The cytogenetic studies was done in order to define the damaging effects of the disease and the drug on the peripheral blood lymphocytes, these damages were manifested through the significant reduction in the blastogenic index, mitotic index, replication index, sister chromatid exchange, and mutation fraction after cells were grown in RPMI media supplemented with 10% of bovine serum, 10 microgram/ml of Budr, 0.3ml of PHA & different concentrations of drug (0.2,0.5,1,2,4,8) microgram/ml. The results indicated reduction in the blastomeric, mitotic, replication indices & mutation fraction to zero with high concentrations of the drug (1, 2, 4, 8) microgram / ml. Furthermore, the results showed presence of resistant cells with low concentration of drug (0.2, 0.5 microgram /ml) through measuring mutation fraction. Moreover, means of SCEs were increased in treated groups (patients & normal individuals) in comparison with untreated groups. Finally presence of mutated cells within low conc. of drug showed resistant to the drug in comparison with high conc. of drug which showed cytotoxic effect on the cells of the patients under investigations.

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Okayama, A., Y. Ichikawa, M. Yoshida, I. Hara et K. Morimoto. « Determination of 4,4'-methylenebis(2-chloroaniline) in urine by liquid chromatography with ion-paired solid-phase extraction and electrochemical detection. » Clinical Chemistry 34, n^o 10 (1 octobre 1988) : 2122–25. http://dx.doi.org/10.1093/clinchem/34.10.2122.

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Abstract This highly specific and sensitive method for measuring urinary 4,4'-methylenebis(2-chloroaniline) (MBOCA) involves liquid chromatography with electrochemical detection. Before chromatography, urine samples are prepared by ion-paired solid-phase extraction on a disposable octadecylsilica column with acidic methanol solution containing 1-heptanesulfonic acid. This enhances the specificity of the method. Mean overall recovery ranged from 97.1% to 99.5% at added MBOCA concentrations of 20 and 100 micrograms/L in urine. Sensitivity for urine was 1 microgram/L. The intra-assay CV was 2.2% at a MBOCA concentration of 100 micrograms/L. We believe that this method is acceptable for routine measurement of MBOCA in urine from individuals exposed to this industrial chemical.

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Napoli, K. L., et B. D. Kahan. « Routine clinical monitoring of sirolimus (rapamycin) whole-blood concentrations by HPLC with ultraviolet detection ». Clinical Chemistry 42, n^o 12 (1 décembre 1996) : 1943–48. http://dx.doi.org/10.1093/clinchem/42.12.1943.

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Abstract During phase I/II clinical trials of sirolimus (rapamycin; SRL), therapeutic drug monitoring was performed with a multistep liquid-liquid extraction of 1-mL aliquots of whole blood followed by reversed-phase HPLC with ultraviolet detection. Blood was sampled according to a standardized protocol and clinical status. SRL concentrations were interpolated from calibration curves with a linear range of 0-50 micrograms/L and 1 microgram/L lower limit of quantification. Quality control was monitored over 68 consecutive analytical runs by using frozen aliquots of SRL-supplemented pooled whole blood at 4, 12, and 32 micrograms/L. These samples showed mean concentrations of 3.7 +/- 0.6, 10.9 +/- 1.1, and 29.6 +/- 2.6 micrograms/L, respectively. This method for therapeutic drug monitoring of SRL permits one full-time technician to analyze 100 clinical specimens per week with a 24-h turnaround time. With this method, a strong linear relation (r2 = 0.946, Sy/x = 0.41, n = 115) between the average SRL concentration over a 24-h period and the SRL concentration at the 24th h was revealed.

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Lambert, W. E., P. M. Cammaert et A. P. De Leenheer. « Liquid-chromatographic measurement of riboflavin in serum and urine with isoriboflavin as internal standard. » Clinical Chemistry 31, n^o 8 (1 août 1985) : 1371–73. http://dx.doi.org/10.1093/clinchem/31.8.1371.

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Abstract We describe how riboflavin can be precisely and accurately measured in serum and urine. A structural analog, isoriboflavin, is used as an internal standard. Urine samples are prepared by adding the internal standard and trichloroacetic acid. For serum, proteins are denatured with trichloroacetic acid. A simple Sep-pak treatment of the supernate removes contaminating interferents. Within- and between-run precision is reflected by respective CVs of 2.2 and 4.9% for urine at 180 micrograms/L and 4.4 and 7.3% for serum at 10 micrograms/L. The standard curve is linear far beyond the concentrations encountered in serum and urine. The detection limit is estimated to be 10 micrograms/L and 1 microgram/L for urine and serum, respectively. The normal reference interval, as determined from 50 results for each matrix, is 36 to 349 micrograms/g of creatinine (mean 112 micrograms/g) for urine and 5.5 to 14.4 micrograms/L (mean 8.8 micrograms/L) for serum. Both distributions are skewed. The method is suited for routine use.

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Yang, Lijun, Jie Liu, Hua Li, Yilian Liu, An He, Peiwu Huang, Weina Gao, Hua Cao, Ruilian Xu et Ruijun Tian. « A fully integrated sample preparation strategy for highly sensitive intact glycoproteomics ». Analyst 147, n^o 5 (2022) : 794–98. http://dx.doi.org/10.1039/d1an02166d.

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A fully integrated spintip-based glycoproteomic technology, termed Intact GlycoSISPROT, was developed for highly sensitive intact glycoproteome analysis with low microgram to nanogram level protein samples.

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Hervey, Michael Brad Strader et Gregory B. Hurst. « Comparison of Digestion Protocols for Microgram Quantities of Enriched Protein Samples ». Journal of Proteome Research 6, n^o 8 (août 2007) : 3054–61. http://dx.doi.org/10.1021/pr070159b.

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Liu, Yong, Mitchell D. Green, Rosemary Marques, Tony Pereira, Roy Helmy, R. Thomas Williamson, Wolfgang Bermel et Gary E. Martin. « Using pure shift HSQC to characterize microgram samples of drug metabolites ». Tetrahedron Letters 55, n^o 40 (octobre 2014) : 5450–53. http://dx.doi.org/10.1016/j.tetlet.2014.06.067.

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Yang, Bin, et A. M. Smith. « Conventionally Heated Microfurnace for the Graphitization of Microgram-Sized Carbon Samples ». Radiocarbon 59, n^o 3 (8 novembre 2016) : 859–73. http://dx.doi.org/10.1017/rdc.2016.89.

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AbstractA new type of miniaturized, externally heated graphitization reaction furnace, the microconventional furnace (MCF), was constructed following our development of the laser heated furnace (LHF). The MCF is comprised of a gas reactor, a cold finger cooling system, and a compact resistive heater, which can raise the temperature of the hot finger to 850°C. The gas reactor is provided with three integrated valves to connect with the hydrogen/vacuum manifold, to isolate the reactor, and to connect with sample vessels. We made two types of MCF: the type 1 furnace (volume of 0.9 mL), with an integral stainless steel cold finger, and the type 2 furnace (volume from 1.3 to 10 mL), with a changeable glass cold finger. The MCF is designed for above atmospheric pressure (up to 2500 mbar) operation to decrease the overall graphitization time and improve the carbon yield. The MCF provides an effective solution for producing graphite from carbon dioxide (CO2) sample gas from 5 to 2000 µg of carbon with only 0.083 μg of 100 pMC extraneous carbon added. Cross-contamination tests show that the MCFs have no memory effect from previous samples.

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Werner, M., M. Hertzman et C. J. Pauley. « Gas-liquid chromatography of phencyclidine in serum, with nitrogen-phosphorus detection. » Clinical Chemistry 32, n^o 10 (1 octobre 1986) : 1921–24. http://dx.doi.org/10.1093/clinchem/32.10.1921.

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Abstract We developed a two-step assay of phencyclidine (PCP), in which 2.5 mL of serum is adsorbed onto a disposable solid-phase extraction column and the eluted drug is determined by gas chromatography with nitrogen-phosphorus detection. Methapyriline is the internal standard. The detection limit of this technique is 0.5 microgram/L and the linear range exceeds 200 micrograms/L. Precision (CV) ranges from 30 to 10% with increasing concentration. No interferences were encountered in more than 400 clinical samples. The assay permits serial observation of low concentrations of the drug in serum for pharmacokinetic study and for quantitative clinical correlation with the Brief Psychiatric Rating Scale.

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Weissenbök, Roland, Steven R. Biegalski, Lloyd A. Currie, Donna B. Klinedinst, Robin Golser, George A. Klouda, Walter Kutschera et al. « 14C Measurements of Sub-Milligram Carbon Samples from Aerosols ». Radiocarbon 40, n^o 1 (1997) : 265–72. http://dx.doi.org/10.1017/s0033822200018130.

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Accelerator mass spectrometry (AMS) at the milligram level is routinely performed, but it is difficult to go substantially below 100 μg of carbon. We discuss various approaches for sample preparation, machine operation and data evaluation, to meet the special requirements of 14C AMS measurements at the microgram-carbon level. Furthermore, we present first results obtained at the Vienna Environmental Research Accelerator (VERA) from 14C measurements of a snow sample from Gaithersburg, Maryland, USA, prepared at the National Institute of Standards and Technology (NIST).

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Chesley, A., J. D. MacDougall, M. A. Tarnopolsky, S. A. Atkinson et K. Smith. « Changes in human muscle protein synthesis after resistance exercise ». Journal of Applied Physiology 73, n^o 4 (1 octobre 1992) : 1383–88. http://dx.doi.org/10.1152/jappl.1992.73.4.1383.

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The purpose of this study was to investigate the magnitude and time course for changes in muscle protein synthesis (MPS) after a single bout of resistance exercise. Two groups of six male subjects performed heavy resistance exercise with the elbow flexors of one arm while the opposite arm served as a control. MPS from exercised (ex) and control (con) biceps brachii was assessed 4 (group A) and 24 h (group B) postexercise by the increment in L-[1–13C]leucine incorporation into muscle biopsy samples. In addition, RNA capacity and RNA activity were determined to assess whether transcriptional and/or translational processes affected MPS. MPS was significantly elevated in biceps of the ex compared with the con arms of both groups (group A, ex 0.1007 +/- 0.0330 vs. con 0.067 +/- 0.0204%/h; group B ex 0.0944 +/- 0.0363 vs. con 0.0452 +/- 0.0126%/h). RNA capacity was unchanged in the ex biceps of both groups relative to the con biceps, whereas RNA activity was significantly elevated in the ex biceps of both groups (group A, ex 0.19 +/- 0.10 vs. con 0.12 +/- 0.05 micrograms protein.h-1.microgram-1 total RNA; group B, ex 0.18 +/- 0.06 vs. con 0.08 +/- 0.02 micrograms protein.h-1.microgram-1 total RNA). The results indicate that a single bout of heavy resistance exercise can increase biceps MPS for up to 24 h postexercise. In addition, these increases appear to be due to changes in posttranscriptional events.

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Streit, F., U. Christians, H. M. Schiebel, K. L. Napoli, L. Ernst, A. Linck, B. D. Kahan et K. F. Sewing. « Sensitive and specific quantification of sirolimus (rapamycin) and its metabolites in blood of kidney graft recipients by HPLC/electrospray-mass spectrometry ». Clinical Chemistry 42, n^o 9 (1 septembre 1996) : 1417–25. http://dx.doi.org/10.1093/clinchem/42.9.1417.

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Abstract Sirolimus (rapamycin) has a macrolide structure and is under clinical investigation as an immunosuppressant after organ transplantation. An HPLC/mass spectrometry assay to quantify sirolimus in blood was developed. 28-O-Acetyl sirolimus was used as internal standard. Blood samples were extracted with C18 columns. The extracts were injected into an HPLC system and isocratically eluted with methanol/1% formic acid (90/10 by vol) from a 150 X 4 mm C18 analytical column. The HPLC system was connected to a triple-stage quadrupole mass spectrometer with an electrospray interface and positive ions were detected. The limit of quantification in 1 mL of blood was 0.25 microgram/L and the calibration curve in blood was linear up to 250 microgram/L. The recovery from blood was 88 +/- 26% and interassay variation at 1 microgram/L was 19% and at 15 microgram/L 9.3%. Hydroxy, dihydroxy, demethyl, and didemethyl sirolimus as well as sirolimus were detected in blood of kidney graft patients.

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Currie, L. A., G. A. Klouda, D. Elmore et H. E. Gove. « Radiocarbon dating of microgram samples : Accelerator mass spectrometry and electromagnetic isotope separation ». Nuclear Instruments and Methods in Physics Research Section B : Beam Interactions with Materials and Atoms 12, n^o 3 (octobre 1985) : 396–401. http://dx.doi.org/10.1016/0168-583x(85)90039-4.

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Fonseca, R. W., et N. J. Miller-Ihli. « Analyte Transport Studies of Aqueous Solutions and Slurry Samples Using Electrothermal Vaporization ICP-MS ». Applied Spectroscopy 49, n^o 10 (octobre 1995) : 1403–10. http://dx.doi.org/10.1366/0003702953965425.

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Analyte transport of both aqueous solutions and slurry samples was studied with the use of ultrasonic slurry sampling electrothermal vaporization inductively coupled plasma mass spectrometry (USS-ETV-ICP-MS). The elements studied included V, Mn, Ni, Cu, and Pb, and the materials analyzed included NIST SRM 1548 Total Diet, SRM 1632a Coal, SRM 1566a Oyster Tissue, and NRCC LUTS-1 Lobster Hepatopancreas. The effect of microgram amounts of Pd as well as the effect of oxygen ashing on analyte transport were studied. Slurry samples were found to have better analyte transport in comparison to aqueous solutions when no physical carriers were added. Under these experimental conditions, the determined slurry concentrations were apparently high when quantified with the use of external calibration. Microgram amounts of Pd were used to investigate whether it was possible to reduce the difference in analyte transport between slurry samples and aqueous standards. The use of microgram amounts of Pd resulted in signal intensity suppression. Such a signal reduction could be related to the presence of space charge effects or losses of analyte due to condensation of the physical carrier together with the analyte on different parts of the ETV cell or the transfer line. On the other hand, quantitation for slurry samples was improved by the use of Pd as a physical carrier. Pd by itself was not completely effective for samples with high carbon content; therefore the effect of oxygen ashing combined with Pd was studied. An enhancement of signal intensities was observed when oxygen ashing was used, as well as a shift in the carbon signal to earlier times. In this case, signal enhancement was associated with an improvement in analyte transport caused by an increased number of carbon particles leaving the furnace at the same time as the analytes studied. With oxygen ashing, slurry samples behaved more similarly to aqueous solutions, facilitating quantitation with aqueous standards.

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Barber, B. J., R. A. Babbitt, S. Dutta et S. Parameswaran. « Changes in rat mesentery interstitial matrix due to superfusate ». American Journal of Physiology-Heart and Circulatory Physiology 265, n^o 3 (1 septembre 1993) : H852—H856. http://dx.doi.org/10.1152/ajpheart.1993.265.3.h852.

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Animal preparations for microscopy often require a superfusate solution to cover surgically exposed tissue. There are few, if any, data concerning the effects of this solution on extravascular protein concentration and hydration. The effect of superfusion on mesenteric tissue in anesthetized male Sprague-Dawley rats was studied. Tissue samples were taken from nonsuperfused and superfused tissue and analyzed for hydration, albumin, and transferrin content. The mesenteric tissue interstitial matrix was rapidly altered by normal saline superfusate. After superfusion, there was a decrease (P < 0.01) in tissue albumin concentration from 1.17 +/- 0.27 to 0.10 +/- 0.08 g/dl (n = 9). Tissue hydration increased from 4.98 +/- 0.8 micrograms water/microgram dry wt in controls to 7.38 +/- 1.2 micrograms water/micrograms dry wt after superfusion. When a range of superfusate albumin concentrations was used (0, 1, 2, and 3 g/dl), tissue albumin concentration changed 0.59 +/- 0.09 g/dl for each gram per deciliter change in superfusate concentration (P < 0.0001). The large changes in interstitial matrix protein content and hydration suggest that superfusate solution effects need to be considered in microvascular protein transport experiments.

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Koistinen, R., U. H. Stenman, H. Alfthan et M. Seppälä. « Time-resolved immunofluorometric assay of 34-kDa somatomedin-binding protein. » Clinical Chemistry 33, n^o 7 (1 juillet 1987) : 1126–28. http://dx.doi.org/10.1093/clinchem/33.7.1126.

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Abstract In this time-resolved immunofluorometric assay for the 34-kDa somatomedin-binding protein (SmBP), affinity-purified polyclonal antibodies are used, along with solid-phase separation of bound and free analyte. The first antibody is bound to polystyrene microtiter wells; the second is labeled with europium(III) chelate. The detection limit of the method is 0.25 microgram/L, much lower than that (about 8 micrograms/L) for radioimmunoassay. By immunofluorometric assay, SmBP is detectable, and could be accurately quantified, in the serum of all 88 individuals we tested, whereas by radioimmunoassay a third of the samples had concentrations below the detection limit. When SmBP was detectable by both methods, the concentrations measured by the two techniques correlated well (r = 0.98).

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29

Schifman, R. B., F. R. Ahmann, A. Elvick, M. Ahmann, K. Coulis et M. K. Brawer. « Analytical and physiological characteristics of prostate-specific antigen and prostatic acid phosphatase in serum compared. » Clinical Chemistry 33, n^o 11 (1 novembre 1987) : 2086–88. http://dx.doi.org/10.1093/clinchem/33.11.2086.

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Abstract We did a comparative analysis of the physiological and analytical properties of prostate-specific antigen (PSA), acid phosphatase (ACP; EC 3.1.32) activity, and acid phosphatase antigen (PAP) in serum. The PSA assay is sensitive to 0.2 microgram/L and demonstrates good linearity (y = 1.01x + 0.74). The CV was 3.9% at 40 micrograms/L, 8.0% at 3.1 micrograms/L. PSA and PAP are less stable at 4 degrees C than at -20 degrees C. Serum PAP and ACP concentrations showed large intra-individual fluctuations (average CVs of 22% and 24%, respectively), which were not observed with PSA measurements (average CV 6.2%). We saw significant correlation with the magnitude of physiological change when analytes were compared for serially collected split samples [y(PSA) = 0.14x(PAP) + 0.00, r = 0.767], which indicates that a common factor is influencing this variation. The excellent analytical performance, tissue specificity, and small degree of intra-individual variance are characteristics that favor the measurement of PSA in serum for monitoring patients with prostatic cancer.

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Goldberger, B. A., W. D. Darwin, T. M. Grant, A. C. Allen, Y. H. Caplan et E. J. Cone. « Measurement of heroin and its metabolites by isotope-dilution electron-impact mass spectrometry ». Clinical Chemistry 39, n^o 4 (1 avril 1993) : 670–75. http://dx.doi.org/10.1093/clinchem/39.4.670.

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Abstract A solid-phase extraction procedure was developed for the isolation of heroin, 6-acetylmorphine, and morphine from blood, plasma, saliva, and urine with subsequent assay by gas chromatography/mass spectrometry. Aprotic solvents, mild elution conditions, and an enzyme inhibitor were used to ensure maximum analyte stability. Samples were extracted and the extract was divided into two equal portions. One portion was assayed directly for heroin; detector response was linear over a concentration range of 1.0 to 250 micrograms/L. The second part of the extract was reacted with N-methyl-bis-trifluoroacetamide and assayed for the trifluoroacetyl derivatives of 6-acetylmorphine and morphine; detector response was linear over a concentration range of 1.0 to 500 micrograms/L. The limit of sensitivity was 1.0 microgram/L for each analyte. Hydrolysis of heroin to 6-acetylmorphine during extraction and analysis was < 5%. The method can be used to corroborate heroin use and to study the pharmacological effects of heroin and its metabolites.

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O'Brien, Rachel E., Kelsey J. Ridley, Manjula R. Canagaratna, John T. Jayne, Philip L. Croteau, Douglas R. Worsnop, Sri Hapsari Budisulistiorini et al. « Ultrasonic nebulization for the elemental analysis of microgram-level samples with offline aerosol mass spectrometry ». Atmospheric Measurement Techniques 12, n^o 3 (14 mars 2019) : 1659–71. http://dx.doi.org/10.5194/amt-12-1659-2019.

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Abstract. The elemental composition of organic material in environmental samples – including atmospheric organic aerosol, dissolved organic matter, and other complex mixtures – provides insights into their sources and environmental processing. However, standard analytical techniques for measuring elemental ratios typically require large sample sizes (milligrams of material or more). Here we characterize a method for measuring elemental ratios in environmental samples, requiring only micrograms of material, using a small-volume nebulizer (SVN). The technique uses ultrasonic nebulization of samples to generate aerosol particles (100–300 nm diameter), which are then analyzed using an aerosol mass spectrometer (AMS). We demonstrate that the technique generates aerosol from complex organic mixtures with minimal changes to the elemental composition of the organic material and that quantification is possible using internal standards (e.g., NH415NO3). Sample volumes of 2–4 µL with total solution concentrations of at least 0.2 g L−1 form sufficient particle mass for elemental ratio measurement by the AMS, despite only a small fraction (∼ 0.1 %) of the sample forming fine particles after nebulization (with the remainder ending up as larger droplets). The method was applied to aerosol filter extracts from the field and laboratory, as well as to the polysaccharide fraction of dissolved organic matter (DOM) from the North Pacific Ocean. In the case of aerosol particles, the mass spectra and elemental ratios from the SVN–AMS agree with those from online AMS sampling. Similarly, for DOM, the elemental ratios determined from the SVN–AMS agree with those determined using combustion analysis. The SVN–AMS provides a platform for the rapid quantitative analysis of the elemental composition of complex organic mixtures and non-refractory inorganic salts from microgram samples with applications that include analysis of aerosol extracts and terrestrial, aquatic, and atmospheric dissolved organic matter.

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Oka, K., T. Hirano, H. Shimodaira, M. Homma, E. Sakurai, T. Tamaki et M. Kozaki. « Suppression of endogenous cortisol for evaluating pharmacodynamics of prednisolone in early allograft rejection in renal transplantation ». Clinical Chemistry 36, n^o 3 (1 mars 1990) : 481–86. http://dx.doi.org/10.1093/clinchem/36.3.481.

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Abstract Concentrations of endogenous cortisol were examined in 34 kidney-transplant recipients by improved "high-performance" liquid chromatography. Ten recipients were treated with prednisolone and azathioprine, the others with prednisolone and cyclosporine. Peripheral serum samples were collected just before transplantation, daily for two weeks after the transplant, weekly until discharge for about two months, and then monthly or occasionally. Mean (+/- SD) cortisol concentrations, initially 145 +/- 87 micrograms/L, decreased immediately to 5.93 +/- 5.11 micrograms/L after transplant, remained at almost these same values for two months, and then swiftly increased to 51 +/- 59 micrograms/L by 1000 days. Cortisol concentrations within the period characterized by a cumulative dose of prednisolone at 300-700 mg were correlated significantly with the presence or absence of acute allograft rejection; patients with cortisol greater than 4 micrograms/L had a higher risk of rejection. The majority of stable patients showed cortisol concentrations between 1 and 4 micrograms/L throughout the cumulative prednisolone period characterized above. Concentrations less than 1 microgram/L after high-dose administration of methylprednisolone were accompanied by severe lung infection. We conclude that suppressed concentrations of endogenous cortisol, as assessed by highly specific HPLC, might provide a basis for predicting the therapeutic efficacy and adverse effects of prednisolone.

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Lubasch, Annette, Ivonne Keller, Klaus Borner, Peter Koeppe et Hartmut Lode. « Comparative Pharmacokinetics of Ciprofloxacin, Gatifloxacin, Grepafloxacin, Levofloxacin, Trovafloxacin, and Moxifloxacin after Single Oral Administration in Healthy Volunteers ». Antimicrobial Agents and Chemotherapy 44, n^o 10 (1 octobre 2000) : 2600–2603. http://dx.doi.org/10.1128/aac.44.10.2600-2603.2000.

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ABSTRACT In an open, randomized, six-period crossover study, the pharmacokinetics of ciprofloxacin, gatifloxacin, grepafloxacin, levofloxacin, moxifloxacin, and trovafloxacin were compared after a single oral dose in 12 healthy volunteers (6 men and 6 women). The volunteers received 250 mg of ciprofloxacin, 400 mg of gatifloxacin, 600 mg of grepafloxacin, 500 mg of levofloxacin, 400 mg of moxifloxacin, and 200 mg of trovafloxacin. The concentrations of the six fluoroquinolones in serum and urine were measured by a validated high-performance liquid chromatography method. Blood and urine samples were collected before and at different time points up to 48 h after medication. Levofloxacin had the highest peak concentration (C max, in micrograms per milliliter) (6.21 ± 1.34), followed by moxifloxacin (4.34 ± 1.61) and gatifloxacin (3.42 ± 0.74). Elimination half-lives ranged from 12.12 ± 3.93 h (grepafloxacin) to 5.37 ± 0.82 h (ciprofloxacin). The total areas under the curve (AUCtot, in microgram-hours per milliliter) for levofloxacin (44.8 ± 4.4), moxifloxacin (39.3 ± 5.35), and gatifloxacin (30 ± 3.8) were significantly higher than that for ciprofloxacin (5.75 ± 1.25). Calculated from a normalized dose of 200 mg, the highestC maxs (in micrograms per milliliter) were observed for levofloxacin (2.48 ± 0.53), followed by moxifloxacin (2.17 ± 0.81) and trovafloxacin (2.09 ± 0.58). The highest AUCtot (in microgram-hours per milliliter) for a 200-mg dose were observed for moxifloxacin (19.7 ± 2.67) and trovafloxacin (19.5 ± 3.1); the lowest was observed for ciprofloxacin (4.6 ± 1.0). No serious adverse event was observed during the study period. The five recently developed fluoroquinolones (gatifloxacin, grepafloxacin, levofloxacin, moxifloxacin, and trovafloxacin) showed greater bioavailability, longer half-lives, and higher C maxs than ciprofloxacin.

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Parrott, R. F., et M. L. Forsling. « CCK-A receptors mediate the effect of cholecystokinin on vasopressin but not on cortisol in pigs ». American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 262, n^o 6 (1 juin 1992) : R1154—R1157. http://dx.doi.org/10.1152/ajpregu.1992.262.6.r1154.

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Bolus intravenous injections of cholecystokinin (CCK) octapeptide induce a rapid rise in plasma vasopressin and a later increase in cortisol in the prepubertal pig. To determine whether these endocrine responses involve CCK-A or CCK-B receptors, this experiment investigated the effect of CCK (1 microgram/kg) in pigs (n = 7) pretreated with the CCK-A antagonist L 364718 (70 microgram/kg) or the CCK-B antagonist L 365260 (10 ng/kg and 10 micrograms/kg). The animals were prepared with jugular vein catheters and given the antagonist vehicle, L 364718, or L 365260 10 min before administration of CCK or saline. Analysis of hormone concentrations in blood samples taken 2, 5, 10, and 20 min after the second injection indicated that an abrupt rise in vasopressin, detectable within 2 min of CCK administration, occurred after vehicle or L 365260 pretreatment but not when CCK was preceded by L 364718. In contrast, the rise in plasma cortisol that was observed approximately 15 min after CCK injection was not prevented by either antagonist. Thus peripherally administered CCK induces vasopressin release by CCK-A receptor activation, in agreement with its inhibitory effect on food intake in this species. However, the effect of CCK on cortisol secretion does not appear to involve either CCK-A or CCK-B receptors.

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Erali, M., R. B. Bigelow et A. W. Meikle. « ELISA for thyroglobulin in serum : recovery studies to evaluate autoantibody interference and reliability of thyroglobulin values ». Clinical Chemistry 42, n^o 5 (1 mai 1996) : 766–70. http://dx.doi.org/10.1093/clinchem/42.5.766.

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Abstract An ELISA for measuring thyroglobulin (Tg) in serum was developed with polyclonal antibodies to Tg on the solid phase and two monoclonal antibodies to Tg as the second antibodies. The assay has a detection limit of 1 microgram/L, a within-run imprecision (CV) of <7%, and a between-run CV of < 10%. Parallelism of the assay was shown in dilution studies, in which the percent observed/expected values for n = 5 autoantibody-containing samples gave a mean of 99% (SD 13.1 %); for n = 5 samples with undetectable autoantibody concentrations, the mean was 103% (SD 11.8%). The correlation of the ELISA with an RIA for Tg in 46 normal samples was ELISA = 1.11(RIA) + 0.52, S y/x = 2.23, SD intercept = 0.54, SD slope = 0.03, range = 0 to 53 micrograms/L, r = 0.980. Comparison of the ELISA with a reference laboratory RIA for 29 clinical samples gave a correlation of: ELISA = 1.53(RIA) - 0.48, S y/x = 9.00, SD intercept = 2.19, SD slope = 0.10, range = 0 to 98 micrograms/L, r = 0.950. To provide additional information concerning the reliability of the Tg measurement in samples containing autoantibodies to Tg, we developed a procedure for determining the percent recovery. A percent recovery greater than or equal to 80% indicates minimal interference by autoantibodies in this assay. The assay is straightforward to perform, results can be posted within 8 h, and the routinely good recovery of Tg in the presence of Tg autoantibodies indicates minimal autoantibody interference in this assay.

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Price, Fionnuala M., J. Rodney Levick et Roger M. Mason. « Analysis of microgram quantities of glycosaminoglycan in milligram samples of microdissected synovial intima ». Biochemical Society Transactions 22, n^o 1 (1 février 1994) : 42S. http://dx.doi.org/10.1042/bst022042s.

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Yang, Bin, A. M. Smith et S. Long. « Second generation laser-heated microfurnace for the preparation of microgram-sized graphite samples ». Nuclear Instruments and Methods in Physics Research Section B : Beam Interactions with Materials and Atoms 361 (octobre 2015) : 363–71. http://dx.doi.org/10.1016/j.nimb.2015.02.009.

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Heda, Ghanshyam D., Upasana Kunwar et Rajiv P. Heda. « A modified protein assay from microgram to low nanogram levels in dilute samples ». Analytical Biochemistry 445 (janvier 2014) : 67–72. http://dx.doi.org/10.1016/j.ab.2013.10.011.

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Bhuvanesh, N., et J. Reibenspies. « D010 Micro X-ray powder diffraction. Ab-initio structure determination from microgram samples ». Powder Diffraction 21, n^o 2 (juin 2006) : 172. http://dx.doi.org/10.1154/1.2219801.

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Bazile-Pham-Khac, S., Q. C. Truong, J. P. Lafont, L. Gutmann, X. Y. Zhou, M. Osman et N. J. Moreau. « Resistance to fluoroquinolones in Escherichia coli isolated from poultry. » Antimicrobial Agents and Chemotherapy 40, n^o 6 (juin 1996) : 1504–7. http://dx.doi.org/10.1128/aac.40.6.1504.

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Quinolone-resistant Escherichia coli strains were isolated from poultry clinical samples in Saudi Arabia. The poultry flocks had been treated with oxolinic acid or flumequine prophylaxis. The measure of the uptake of fluoroquinolones showed that none of the strains had a reduced accumulation of quinolones. The result of complementation with the wild-type E. coli gyrA gene, which restored fluoroquinolone susceptibility, and the isolation of DNA gyrase from six isolates indicated that the resistant strains had an altered DNA gyrase. The minimum effective dose of ciprofloxacin for inhibition of supercoiling catalyzed by the isolated gyrases varied from 0.085 microgram/ml for a susceptible isolate (MIC < 4 micrograms/ml) up to 96 micrograms/ml for the more resistant one (strain 215, MIC > 64 micrograms/ml). For the same two isolates, the minimum effective doses of sparfloxacin varied from 0.17 up to 380 micrograms/ml. The in vitro selection of spontaneous single-step fluoroquinolone-resistant mutants using ciprofloxacin suggested that the more resistant mutants are likely the result of several mutations. These results also show that, as in human medicine, cross-resistance between older quinolones and fluoroquinolones can exist in veterinary isolates and reiterate the need for the prudent use of these drugs.

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Ha, H. R., B. Funk, P. O. Maitre, A. M. Zbinden, F. Follath et D. A. Thomson. « Midazolam in plasma from hospitalized patients as measured by gas-liquid chromatography with electron-capture detection. » Clinical Chemistry 34, n^o 4 (1 avril 1988) : 676–79. http://dx.doi.org/10.1093/clinchem/34.4.676.

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Abstract The present assay was developed for quantifying midazolam in plasma of patients hospitalized in intensive-care units or undergoing anesthesia and receiving many other drugs as well. Plasma samples are alkalinized with NaOH and midazolam is extracted into n-hexane. The organic phase is evaporated and reconstituted in n-butyl acetate, and the midazolam is quantified by gas-liquid chromatography with electron-capture detection. The calibration graph for midazolam was linear in the ranges 5-200 and 200-800 micrograms/L. The CVs for precision and reproducibility of the assay were less than 8%. The method was very specific for midazolam; most of the drugs commonly used in anesthesia and in the intensive-care unit did not interfere with the assay. The lowest detectable concentration was 1 microgram/L. The method is adaptable for use with an automated chromatographic system.

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Saleh, AMERA, Husam Nafee et Hassan Al-Nori. « Some heavy metals residues in beef and sheep Liver in Anbar province ». Al-Anbar Journal of Veterinary Sciences 12, n^o 1 (20 juin 2019) : 37–49. http://dx.doi.org/10.37940/ajvs.2019.12.1.5.

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The aim of the study To see the effect of location, season and display time on the accumulation of some heavy metals (Lead, copper, zinc, cadmium and cobalt) in sheep and cattle liver. Liver samples were obtained from three districts in Anbar province (Ramadi, Hit and Baghdadi). This study began from January 2017 to November 2017 for all seasons (winter, spring, summer and autumn) Samples were taken from the liver immediately after slaughter for cattle and sheep at 8 am and taken at 4 pm for all areas of study. The results of the study were summarized in the quadratic overlap of the animal type, season, location and time as follows: The highest concentration of lead in liver (38.86 μg / g liver) was recorded in sheep for spring and evening in Ramadi. The lowest concentration was in sheep in Baghdadi for morning and winter (20.06 micro g / g liver). The highest concentration of copper in the liver (34.65 microgram / g liver) was recorded in cows in Ramadi for the winter season and evening time. The lowest concentration was in the sheep liver during the summer season for morning time in the city of al-Baghdadi (20.43 microgram / g liver). The highest concentration was in the liver (603.99 microgram / g liver) in the sheep for the autumn season and the evening time in the city of Ramadi. The lowest concentration was in the sheep in the city of Baghdadi for morning and summer (560.32 microgram / g liver). The highest concentration of cadmium in the liver (30.88 micro g / g liver) was in sheep in Ramadi for the autumn and evening season, and the lowest concentration was in beef in the summer season for morning time in al-Baghdadi city (9.66 μg / g liver). Cobalt was the highest concentration (1.34, 1.34 and 1.35 micro g / g liver) in cow and sheep liver, autumn, summer and evening time for Ramadi. While the lowest concentration of sheep and cattle liver for the city of Baghdadi for the winter season and morning time (0.64 and 0.63 microgram / g liver).

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Ahlers, WW, MR Reid, JP Kim et KA Hunter. « Contamination-free sample collection and handling protocols for trace elements in natural fresh waters ». Marine and Freshwater Research 41, n^o 6 (1990) : 713. http://dx.doi.org/10.1071/mf9900713.

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Techniques that minimize contamination artefacts in the collection, handling and analysis of natural freshwater samples for dissolved trace metals are described. Methods were evolved during a 5-year study of a pristine high-altitude catchment in New Zealand, during which the dominating influence of contamination artefacts arising during the sampling operation was realized. Even with clean-room analysis facilities, order-of-magnitude contamination at the microgram per litre level was easily introduced at this earlier stage. The study calls into question much of the published literature that reports freshwater concentrations of trace elements in the microgram per litre range and below, particularly for Zn, Cd, Hg and Pb in systems whose pollutant sources are not definitively identified. We suggest that a base criterion for the reliability of trace-element measurements in natural fresh waters should be a similarity of spatial and temporal trends with those of conventionally measured properties such as major ions, alkalinity and electrical conductivity.

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McMahon, CD, DF Buxton, TH Elsasser, DR Gunter, LG Sanders, BP Steele et JL Sartin. « Neuropeptide Y restores appetite and alters concentrations of GH after central administration to endotoxic sheep ». Journal of Endocrinology 161, n^o 2 (1 mai 1999) : 333–39. http://dx.doi.org/10.1677/joe.0.1610333.

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The objective of this study was to determine whether neuropeptide Y (NPY) and recombinant human interleukin-1 receptor antagonist (IL-1ra) would: first, increase food intake; secondly, decrease concentrations of GH; thirdly, reduce GHRH-induced release of GH; and fourthly, reduce changes to concentrations of IGF-I in plasma during experimental endotoxemia in sheep. Six treatments were given to six castrated male sheep in a 6x6 Latin square treatment order. Osmotic mini-pumps were implanted at 0 h and a jugular vein was cannulated. Each sheep was continuously infused with saline (0.9%) or lipopolysaccharide (LPS) (20 micrograms/kg per 24 h, s.c.) at 10 microliters/h for 72 h via the osmotic mini-pumps. Blood samples (3 ml) were collected at 15-min intervals from 24 to 33 h. At 26 h, one of three treatments (artificial cerebrospinal fluid, NPY or IL-1ra) was injected i.c.v. within 30 s (0.3 microgram/kg), then infused i.c.v. from 26 to 33 h (600 microliters/h) at 0.3 microgram/kg per h. GHRH was injected i.v. (0.075 microgram/kg) at 32 h after which blood samples were collected at 5, 10, 15, 30, 45 and 60 min. Feed intake was reduced up to 50% for 48 h in LPS-treated compared with non-LPS-treated sheep. NPY restored feed intake in LPS-treated sheep and induced hyperphagia in non-LPS-treated sheep from 24 to 48 h. In contrast, IL-1ra did not affect appetite. Injection of NPY increased concentrations of GH from 26 to 27 h, while IL-1ra had no effect. Infusion of NPY suppressed GHRH-induced release of GH. However, no treatment altered pulse secretion parameters of GH. Concentrations of IGF-I were 20% higher at 72 h in LPS-treated sheep given NPY than in sheep treated with LPS alone, and this may reflect increased appetite from 24 to 48 h. We concluded that reduced appetite during endotoxemia is due to down-regulation of an NPY-mediated mechanism. Furthermore, NPY stimulates release of GH in healthy sheep, does not reduce pulse secretion parameters of GH, but does suppress GHRH-induced release of GH in endotoxic sheep. Therefore, NPY may be an important neurotransmitter linking appetite with regulation of GH during endotoxemic and healthy states in sheep.

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Yang, Bin, A. M. Smith et Quan Hua. « A cold finger cooling system for the efficient graphitisation of microgram-sized carbon samples ». Nuclear Instruments and Methods in Physics Research Section B : Beam Interactions with Materials and Atoms 294 (janvier 2013) : 262–65. http://dx.doi.org/10.1016/j.nimb.2012.08.031.

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Hynning, P. A., P. Anderson, U. Bondesson et L. O. Boréus. « Liquid-chromatographic quantification compared with gas-chromatographic-mass-spectrometric determination of verapamil and norverapamil in plasma. » Clinical Chemistry 34, n^o 12 (1 décembre 1988) : 2502–3. http://dx.doi.org/10.1093/clinchem/34.12.2502.

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Abstract A high-performance liquid chromatographic (HPLC) method for determining verapamil and norverapamil in plasma is presented and compared with gas chromatography/mass spectrometry (GC-MS). The plasma samples were extracted at alkaline pH with hexane containing 2-butanol (20 mL/L) and then back-extracted into phosphate buffer (0.1 mol/L, pH 3.0). For chromatography we used a reversed-phase column (Supelcosil LC-18 DB) with a mobile phase of the phosphate buffer and acetonitrile (70/30 by vol). Fluorescence detection was used (excitation at 203 nm, emission at 320 nm). Overall analytical recovery was 85%. Standard curves were linear from 1 to 1000 micrograms/L. The detection limit was 1 microgram/L. The assays are accurate and precise. We found no interferences by those substances tested. Results by HPLC and GC-MS agreed well (r = 0.99) for both verapamil and norverapamil determinations.

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Murthy, V. V., et A. Karmen. « Activity concentration and mass concentration (monoclonal antibody immunoenzymometric method) compared for creatine kinase MB isoenzyme in serum. » Clinical Chemistry 32, n^o 10 (1 octobre 1986) : 1956–59. http://dx.doi.org/10.1093/clinchem/32.10.1956.

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Abstract Results of the "Tandem-E CKMB" immunoenzymometric procedure (y) for creatine kinase (CK; EC 2.9.3.2) were compared with electrophoresis (x) for 160 serum samples from patients suspected of having sustained myocardial infarctions. The results correlated well: y, microgram/L (Tandem assay) = 1.3x-6.3 U/L(electrophoresis) (r = 0.95). CK-MB mass measurement was more stable than enzyme activity after storage and appeared to be more sensitive. Sera from 86 other people, which had no detectable CK-MB upon electrophoresis, gave a mean CK-MB value of 1.1 microgram/L (SD 1.3, range 0-8) with the Tandem assay. To determine whether these low values represented actual isoenzyme, we tested for possible interference by heterophile antibodies in the patients' sera by preincubating the samples with mouse serum before the Tandem assay. The mouse serum did not interfere with the assay of sera that had substantial quantities of CK-MB by electrophoresis. However, in five of six samples that were negative by electrophoresis, the CK-MB values were substantially smaller, indicating that the values measured were false-positives caused by the presence of heterophile antibodies directed against mouse proteins, an interference that could be eliminated by pretreatment with mouse serum.

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Mair, J., C. Larue, P. Mair, D. Balogh, C. Calzolari et B. Puschendorf. « Use of cardiac troponin I to diagnose perioperative myocardial infarction in coronary artery bypass grafting ». Clinical Chemistry 40, n^o 11 (1 novembre 1994) : 2066–70. http://dx.doi.org/10.1093/clinchem/40.11.2066.

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Abstract Cardiac troponin I (cTnI) is a regulatory protein unique to myocardium. We used a cardiospecific 30-min ELISA to measure cTnI in EDTA-plasma samples serially drawn from 28 patients before and after coronary artery bypass grafting (CABG)--26 elective and 2 salvage cases. The cTnI increase in 22 of the elective CABG patients, who did not have perioperative myocardial infarction (not-PMI), reflected the inevitable myocardial damage caused by cannulation and cardioplegic arrest, with peak values of 1.7 +/- 1.0 microgram/L (mean + 2 SD = 3.7 micrograms/L), the peaks occurring on average 8 h (range 4-24) after aortic unclamping. Two of the 22 not-PMI, elective CABG patients showed cTnI peaks > 3.0 micrograms/L (3.9 and 3.4 micrograms/L), indicating more extensive perioperative myocardial damage than the other 20, as confirmed by clinical and electrocardiographic or echocardiographic signs, although creatine kinase isoenzyme MB (CKMB) activity was below our PMI decision limit of 20 U/L (25 degrees C). As classified by electrocardiography, echocardiography, and increased CKMB activity, four of the 26 elective CABG patients did have a PMI. One patient with Q-wave PMI had peak cTnI approximately 30 micrograms/L, and three with non-Q-wave PMI had lower peak values (approximately 5 micrograms/L). The two salvage CABG cases had increased cTnI before surgery. One developed a Q-wave acute myocardial infarction with a 3-h cTnI peak of approximately 35 micrograms/L. We conclude that, after elective CABG, cTnI peaks > 3.7 micrograms/L and concentrations > 3.1 micrograms/L at 12 h or 2.5 micrograms/L at 24 h indicate PMI with high probability.

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Hanna, C. P., J. F. Tyson et S. McIntosh. « Determination of inorganic arsenic and its organic metabolites in urine by flow-injection hydride generation atomic absorption spectrometry ». Clinical Chemistry 39, n^o 8 (1 août 1993) : 1662–67. http://dx.doi.org/10.1093/clinchem/39.8.1662.

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Abstract A method has been developed for the determination of inorganic arsenic [As(III) and As(V)] and its organic metabolites (monomethylarsenic and dimethylarsenic) in urine by flow-injection hydride generation atomic absorption spectrometry. The nontoxic seafood-derived arsenobetaine and arsenocholine species were first separated by a solid-phase extraction procedure. The remaining sample was digested with a mixture of nitric and sulfuric acids and potassium dichromate, followed by attack with hydrogen peroxide. The resulting As(V) was reduced to As(III) with potassium iodide in hydrochloric acid before injection into the flow-injection manifold. The percentage analytical recoveries (mean +/- 95% confidence interval) of various arsenic species added to a urine specimen at 250 micrograms/L were 108 +/- 2, 112 +/- 11, 104 +/- 7, and 95 +/- 5 for As(III), As(V), monomethylarsenic, and dimethylarsenic, respectively. For the determination of arsenic in Standard Reference Material 2670 (toxic metals in human urine), results agreed with the certified value (480 +/- 100 micrograms/L). Analyses of samples for the Centre de Toxicologie du Quebec, containing seafood-derived species, demonstrated the viability of the separation procedure. Detection limits were between 0.1 and 0.2 microgram/L in the solution injected into the manifold, and precision at 10 micrograms/L was between 2% and 3% (CV). These preliminary results show that the method might be applicable to determinations of arsenic in a range of clinical urine specimens.

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Barry, B., M. Muffat-Joly, J. Bauchet, F. Faurisson, P. Gehanno, J. J. Pocidalo et C. Carbon. « Efficacy of single-dose ceftriaxone in experimental otitis media induced by penicillin- and cephalosporin-resistant Streptococcus pneumoniae. » Antimicrobial Agents and Chemotherapy 40, n^o 9 (septembre 1996) : 1977–82. http://dx.doi.org/10.1128/aac.40.9.1977.

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We used a gerbil model of otitis media to assess the efficacy of single-dose ceftriaxone against three Streptococcus pneumoniae strains highly resistant to penicillin (MICs, 4 to 8 micrograms/ml) and with various susceptibilities to ceftriaxone (MICs, 0.5, 4, and 8 micrograms/ml). Middle ear infection was induced by bilateral transbullar challenge with 10(7) bacteria per ear. Antibiotic treatment was administered subcutaneously at 2 h postinfection. Infection status was checked 2 days later by counting the bacteria in middle ear and cerebrospinal fluid samples. With the cefriaxone-susceptible strain (MIC, 0.5 microgram/ml), we tested doses of 5 to 100 mg/kg of body weight. With a dose of 50 mg/kg, treatment outcome was equivalent to that with amoxicillin, which was used as a reference (25 mg/kg, two injections); no bacteria were recovered from 82% of the middle ear samples, and the rate of cerebrospinal fluid culture positivity was significantly reduced to 6%, relative to 59% for the untreated controls. Similar efficacy was obtained with a dose of 100 mg/kg against the two ceftriaxone-resistant strains. Pharmacokinetic study indicates that the values of the parameters in plasma after the administration of a dose of 100 mg/kg (peak level of total drug, 268 +/- 33 micrograms/ml; elimination half-life, 0.8 h; area under concentration-time curve, 488 micrograms.h.ml-1) were still suboptimal compared with the values of the parameters measured in pediatric patients after intravenous or intramuscular administration of a dose of 50 mg/kg. Our results indicate the efficacy of ceftriaxone against experimental cephalosporin-resistant pneumococcal otitis and provide a basis for the clinical use of single-dose ceftriaxone against pneumococcal otitis media.

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