Storage of specimens at 4 degrees C or addition of sodium fluoride (1%) prevents formation of ethanol in urine inoculated with Candida albicans.
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The microbial synthesis of ethanol was investigated in urine specimens containing 0.5% or 1.0% (w/v) glucose and inoculated with the yeast Candida albicans (100 cfu/mL). Aliquots (10 mL) of urine were dispensed into plastic tubes containing enough sodium fluoride to give final concentrations of 0.1%, 0.25%, 0.5%, 0.75%, 1%, and 2% (w/v), and C. albicans was added. The tubes were tightly stoppered and allowed to stand either at room temperature (22 degrees C) or in a refrigerator (4 degrees C) for up to 34 days before concentrations of ethanol were determined by headspace gas chromatography. Urine samples stored at 22 degrees C without sodium fluoride produced 0.25 g/L ethanol after two days, and the concentration increased to 2.10 g/L and 4.50 g/L after eight days for specimens containing 0.5% (w/v) and 1% (w/v) glucose, respectively. The ratio of the serotonin metabolites 5-hydroxytryptophol/5-hydroxyindoleacetic acid (5HTOL/5HIAA) in urine remained within the reference range (< 15 pmol/nmol) despite high concentrations of ethanol being produced. Urine samples kept at 4 degrees C did not produce any ethanol (< 0.01 g/L) even without sodium fluoride present as a preservative. The production of ethanol by C. albicans was stopped completely by adding 1% or 2% (w/v) sodium fluoride but not by concentrations of 0.75% (w/v) or less. The microbial synthesis of ethanol in urine samples initially stored at room temperature without sodium fluoride was slowed down considerably by moving them into a refrigerator at 4 degrees C. In conclusion, the production of ethanol in urine by C. albicans can be prevented by storage of samples in a refrigerator at 4 degrees C or by adding sodium fluoride > or = 1% (w/v). Measuring the ratio of 5HTOL/5HIAA can help to distinguish postsampling production of ethanol from metabolism and excretion processes. (+info)
Determination of opiates and cocaine in hair as trimethylsilyl derivatives using gas chromatography-tandem mass spectrometry.
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An analytical method for the determination of heroin, 6-monoacetylmorphine, morphine, codeine, cocaine, benzoylecgonine, and cocaethylene in human hair using gas chromatography-tandem mass spectrometry is presented. The analytes were extracted from finely cut hair with methanol at 56 degrees C for 18 h in the presence of nalorphine as the internal standard. After the incubation, methanol was evaporated to dryness, and all the analytes, except heroin, cocaine, and cocaethylene, were converted to their trimethylsilyl derivatives. The reaction products were identified and quantitated using product ions formed from the parent ions by collision-induced dissociation in the ion-trap mass spectrometer. This method provided excellent sensitivity and specificity for analytes at the concentrations usually found in the keratin matrix. (+info)
Over-the-counter anabolic steroids 4-androsten-3,17-dione; 4-androsten-3beta,17beta-diol; and 19-nor-4-androsten-3,17-dione: excretion studies in men.
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Since the appearance of 4-androsten-3,17-dione (I) as a nutritional supplement in early 1997, we have frequently observed a characteristic deterioration of endogenous steroid profiles in athletes' urine in routine anabolic steroid testing in which concentrations of major endogenous urinary steroids and testosterone exceed normal. Human excretion studies are performed with I and newer, over-the-counter "supplements" 4-androsten-3beta,17beta-diol (II) and 19-nor-4-androsten-3,17-dione (III). Endogenous urinary steroids affected by I and II are androsterone, etiocholanolone, their hydroxylated derivatives 5alpha- and 5beta-androstan-3alpha,17beta-diols, testosterone, and epitestosterone. Their concentrations briefly increase by one to two orders of magnitude and return to normal 24 h after oral administration of I and II. The average male may test positive for testosterone because testosterone concentration rises faster than that of epitestosterone, causing the testosterone/epitestosterone (T/E) ratio to rise above the positive cutoff of 6:1. A remarkable distinction in excretion patterns was observed in eastern Asian men, for whom I and II did not affect urinary concentrations of testosterone and did not increase the T/E ratio. First-pass metabolism deactivates most of the orally administered drugs I and II, rapidly converting them into inactive androsterone and etiocholanolone. Drug II is a more effective testosterone booster because of its different metabolic pathway. After the use of III, a precursor of the potent anabolic nandrolone, high concentrations of norandrosterone and noretiocholanolone appear in urine, similar to nandrolone. These are detectable in urine for 7-10 days after a single oral dose of III (50 mg). (+info)
Selection, validation, standardization, and performance of a designated comparison method for HDL-cholesterol for use in the cholesterol reference method laboratory network.
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BACKGROUND: Accurate and precise HDL-cholesterol (HDL-C) measurements are essential for effective application of National Cholesterol Education Program treatment guidelines. The Cholesterol Reference Method Laboratory Network (CRMLN) assists manufacturers of in vitro diagnostic products to establish traceability to the accuracy base. CRMLN sought to implement a designated comparison method (DCM) that overcomes the impracticalities of the expensive and labor-intensive reference method for HDL-C. METHODS: CRMLN evaluated candidate DCMs and selected one that uses 50-kDa dextran sulfate with magnesium ions as the precipitation reagent followed by measurement of cholesterol by the CDC reference method. After validating the method, we transferred it to all CRMLN laboratories and successfully standardized it using CDC frozen serum reference materials. CRMLN laboratories participate in monthly performance evaluations. RESULTS: CRMLN laboratories were able to meet a precision goal, as indicated by SD, of /=1.09 mmol/L (42 mg/dL) 95.6% of the time. CRMLN is working to further improve its performance by implementing a bias criterion of 0.03 mmol/L (1 mg/dL) for all HDL-C concentrations. CONCLUSIONS: CRMLN selected, validated, standardized, and implemented a DCM for HDL-C that is accurate, robust, transferable, and practical. The DCM is being used to assist manufacturers in calibrating their products so that ultimately, clinical laboratories using the products will more accurately measure HDL-C. (+info)
A critical evaluation of the Mefar dosimeter.
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Multicentre studies of airway responsiveness (AR) are increasingly important tools in asthma epidemiology. Because comparisons of AR are made between centres it is essential that measurement techniques are accurate and standard. This study investigated the Mefar dosimeter which is currently used in the 35 centre European Community Respiratory Health Survey (ECRHS) with the next phase currently being planned. Significant differences were found in driving pressures and aerosol outputs between the three Mefar dosimeters in the laboratory. A linear relationship was also found between driving pressure and aerosol output (R2=0.96). These differences are important as they may lead to variations between centres of < or =35% in the drug dose delivered in AR measurement, which could potentially diminish the power of individual study centres to accurately detect national differences in AR. Dosimeter driving pressure and nebulizer output should be standardized in future studies of airway responsiveness. With relatively simple quality control measures in place it is believed that the Mefar dosimeter can produce reliable between-centre longitudinal data with an increase in the accuracy of these important studies. (+info)
Prediction of clean mohair, fiber diameter, vegetable matter, and medullated fiber with near-infrared spectroscopy.
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Four experiments were conducted in three separate years to test the utility of near-infrared spectroscopy (NIRS) to predict the clean mohair content of Angora goat fleece. Mohair fleece samples were obtained each year from yearling billies at the conclusion of the Angora Goat Performance Test conducted at the Texas A&M University Research Station, Sonora. In Exp. 1 (n = 293) and Exp. 2 (n = 256), fleeces were scanned with a Pacific Scientific (Silver Spring, MD) near-infrared spectrometer fitted with a fiber-optic probe, and calibrations were developed for clean mohair content. In Exp. 3, 59 mohair fleeces collected at the Texas A&M Research Station in San Angelo were sampled four times each. Each sample was scanned with the same spectrometer in reflectance mode fitted with a transport mechanism. This mechanism allowed the instrument to scan a 15-cm2 segment of the fleece sample. Conventional procedures to determine reference values for mohair yield, vegetable matter content, fiber diameter, and percentage of medullated and kemp fibers were conducted. Prediction equations were developed that related NIR spectra to reference values for yield and diameter parameters and were used to predict mohair characteristics for each fleece sample. The predicted and reference values were subjected to a simple analysis of variance to determine variation within and across samples. In Exp. 1, mohair base was related to NIR spectra with R2 = .46 and standard error of calibration (SEC) = 2.84%. In Exp. 2, similar repeatability errors for mohair base could be obtained for both reference- and NIRS-derived values. Fiber diameter and medullated fibers were poorly related to NIR spectra. When samples were scanned using the transport mechanism (Exp. 3), R2 and SEC were .82 and 1.19% for mohair base and .93 and .98 microm for fiber diameter, respectively. The CV for mohair base and diameter were 1.0 and 1.4%, whereas those for predicted mohair base and diameter were 1.4 and 3.4%, respectively. The increased variation within samples for predicted values represents sampling error and lack of fit between NIRS and the laboratory determined values. When the samples from Exp. 1 and 2 were rescanned with the NIRS transport (Exp. 4), R2 and SEC were .79 and 2.03% for mohair base and .52 and 3.49 microm for fiber diameter. The fiber optic probe would facilitate real-time analysis on the shearing floor, but our data indicate that the spectral limitations so far are too severe. A large sample device such as the transport gave excellent results for predicting mohair base and fiber diameter. (+info)
Entamoeba histolytica and Entamoeba dispar: epidemiology and comparison of diagnostic methods in a setting of nonendemicity.
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Recent studies suggest that stool antigen assays are more sensitive and specific than microscopy for the diagnosis of Entamoeba histolytica infection. One hundred twelve patients presenting at 3 centers with symptoms or risk factors of E. histolytica infection were prospectively enrolled in this study to evaluate new diagnostic tests for infections with E. histolytica and Entamoeba dispar. Four ELISA-based stool antigen kits for detecting E. histolytica or E. dispar were blindly compared with stool microscopy. Amebic serology was assessed by indirect hemagglutination. When antigen assays were used as the reference standard, microscopy performed at referral centers was more specific (68.4% vs. 9.5%) but less sensitive (70.4% vs. 92.1%) than microscopy performed in community laboratories. Diagnosis with the E. histolytica test and Merlin Optimun S ELISA indicated that only 3 (4.2%) of 72 coproantigen-positive stools were positive for E. histolytica. Indirect hemagglutination was a good predictor of E. histolytica infection when titers of antibody to ameba were >/=1:512. (+info)
Standardized grey scale ultrasonography in Graves' disease: correlation to autoimmune activity.
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OBJECTIVE: Graves' disease leads to thyroid enlargement and to reduction of tissue echogenicity. Our purpose was to correlate grey scale ultrasonography of the thyroid gland with clinical and laboratory findings in patients with Graves' disease. DESIGN: Fifty-three patients with Graves'disease were included in our study, 100 euthyroid volunteers served as control group. Free thyroxine (FT(4)), TSH and TRAb (TSH receptor antibodies) values were measured and correlated with sonographic echogenicity of the thyroid gland. METHODS: All patients and control persons underwent ultrasonographical histogram analyses under standardized conditions. Mean densities of the thyroid tissues were determined in grey scales (GWE). RESULTS: Compared with controls with homogeneous thyroid lobes of normal size (25.6 +/- 2.0GWE, mean +/- S.D.) echogenicity in patients with Graves' disease was significantly lower (21.3 +/- 3. 3GWE, mean +/- S.D., P < 0.0001). Among the patients with Graves' disease significant differences of thyroid echo levels were revealed for patients with suppressed (20.4 +/- 3.1 GWE, mean +/- S.D., n=34) and normalized TSH values (22.5 +/- 3.6GWE, mean +/- S.D., n=19, P < 0.02). Significantly lower echogenicities were also measured in cases of persistent elevated TRAb levels (19.9 +/- 2.9GWE, mean +/- S.D., n=31) in comparison with normal TRAb levels (22.9 +/- 3.5 GWE, mean +/- S.D., n=22, P < 0.0015). No correlation could be verified between echogenicity and either still elevated or already normalized FT(4) values or the thyroid volume. In coincidence of hyperthyroidism and Graves' ophthalmopathy (19.7 +/- 3.5GWE, mean +/- S.D., n=23) significantly lower echogenicity was measured than in the absence of ophthalmological symptoms (22.3 +/- 3.3GWE, mean +/- S.D., n=30, P < 0.016). Patients needing active antithyroid drug treatment revealed significantly lower thyroid echogenicity (20.3 +/- 3.1 GWE, mean +/- S.D., n=40) than patients in remission (23.7 +/- 3.4 GWE, mean +/- S.D., n=13, P < 0.001). Statistical evaluation was carried out using Student's t-test. CONCLUSIONS: Standardized grey scale histogram analysis allows for supplementary judgements of thyroid function and degree of autoimmune activity in Graves' disease. Whether these values help to estimate the risk of recurrence of hyperthyroidism after withdrawal of antithyroid medication should be evaluated in a prospective study. (+info)