47,361 research outputs found
Do intracellular, extracellular or urinary magnesium concentrations predict renal retention of magnesium in critically ill patients?
No full textBackground and objective: Magnesium disorders are common in hospitalized patients. In patients with low or normal magnesium, the intravenous magnesium loading test has been demonstrated to be a sensitive test to assess magnesium deficiency in critically ill patients. However, it is more time consuming and more difficult than the measurement of intracellular or extracellular magnesium concentrations. This study evaluated whether erythrocyte, plasma and urinary magnesium concentrations predict renal magnesium retention measured by the magnesium loading test. Methods: One-hundred-and-three intensive care patients (36 females, 67 males) in a tertiary care centre and 41 healthy subjects (13 females, 28 males) took part in this prospective study. Intracellular, total plasma, ionized extracellular and urinary magnesium concentrations were measured and also magnesium retention by intravenous magnesium loading test. Results: Total plasma magnesium concentration was poorly correlated with magnesium retention (r = 0.36, r(2) = 0.13) and was the only parameter that significantly predicted magnesium retention in intensive care patients (P < 0.01). However, only 10% of the magnesium retention data were linked to the total plasma magnesium concentration. Conclusions: Total plasma magnesium concentration predicts magnesium retention in critically ill intensive care patients but not intracellular and urinary magnesium concentrations. Only a small proportion of the magnesium retention was due to the total plasma magnesium concentration
Determination of thiopurine methyltransferase phenotype in isolated human erythrocytes using a new simple nonradioactive HPLC method
No full textGenetic polymorphism of the S-methylation pathway catalyzed by thiopurine methyltransferase (TPMT) is responsible for variation in the metabolism, toxicity, and therapeutic efficacy of thiopurine drugs. This paper describe a new simple, nonradioactive HPLC method for determination of TPMT activity in isolated erythrocytes (Ery), based on the conversion of 6-mercaptopurine (pH 7.5, 37degreesC) to 6-methylmercaptopurine (6-MMP) using S-adenosyl-L-methionine as methyl donor. The incubation step was stopped by a mixture of trichloroacetic acid/acetonitrile containing the internal standard 4-aminoacetophenone. 6-MMP was quantified by absorbance at 290 nm after chromatographic separation on a Zorbax SB-Phenyl column (5 mum, 4.6 x 250 mm) using mobile phases (flow rate 1.1 mL/min) consisting of acetonitrile, phosphate buffer pH 3.0, triethylamine, and dithiothreitol. The assay was linear up to 50 nmol/(mL Ery (.) h), and the detection limit was 0.3 nmol/(mL Ery (.) h). The extraction efficiency of 6-MMP was 95-103% (n = 3), and its analytic recovery ranged between 98.3% and 101.8% (n = 12). The within-day imprecision using pooled human erythrocytes (n = 12) was 4.4% at a TPMT activity of 14.3 nmol/(mL Ery (.) h) and 4.9% at 6.5 nmol/(mL Ery (.) h). The between-day imprecision (n = 12) was 6.8% and 7.5% nmol/(mL Ery (.) h), respectively. A very good agreement was found between TPMT activity determined with this method (y) and a widely used radiochemical procedure (x) (r = 0.94; n = 130; y = 0.502 + 0.946x; P < 0.05). Genotype analysis of all individuals with TPMT activity under 12.5 nmol/(mL Ery (.) h) revealed a genotype/phenotype concordance of 86%. The new HPLC method for determination of TPMT activity in Ery is a simple, rapid, and reliable nonradioactive procedure that can be successfully used for both research and routine clinical analysis
Evaluation of the magnesium status in athletics
No full textThe purpose of this study was to examine the magnesium balance in endurance athletes. Clarification was to be obtained whether the athletes are more frequently magnesium-deficient than non-athletic persons. In addition, a check was made whether dietary factors are responsible for the onset of magnesium deficiency. 50 volunteers with a mean age of 25 years were enrolled in this randomized, prospective study. Based on a cycle ergometry test women with an aerobic-anaerobic threshold above 2.4 W/kg (n=7) and men above 2.6 W/kg (n=18) were assigned to the group of endurance athletes, the remaining 25 subjects formed the control group (8 women and 17 men), The athletes reported training at least 9 hours per week, the subjects in the control group less than 9 hours per week. Since earlier studies had shown that a serum magnesium concentration within the normal range does not necessarily exclude a magnesium deficiency, and magnesium retention can provide more precise information on the magnesium status using a magnesium loading test, the magnesium retention, plasma magnesium concentration, ionized fraction of plasma magnesium, erythrocytic magnesium concentration, renal magnesium excretion and oral magnesium intake were measured. The mean magnesium retention values in the control group measured using the intravenous magnesium loading test were lower than those in the endurance athletes. No differenees were found in the mean values of plasma magnesium concentration ionized fractions of plasma magnesium and erythrocytic magnesium concentration in the two groups, while the endurance trained subjects excreted significantly more magnesium via the kidneys and had a higher oral magnesium intake than the controt group. The study thus confirms that endurance athletes are more frequently magnesium-deficient than persons who do not engage in endurance sports. This deficiency was caused by elevated renal magnesium excretion. Although the athletes' magnesium intake with food was higher, the magnesium quantity consumed did not suffice to maintain a balanced magnesium status
Evaluation of the magnesium status in athletics
No full textThe purpose of this study was to examine the magnesium balance in endurance athletes. Clarification was to be obtained whether the athletes are more frequently magnesium-deficient than non-athletic persons. In addition, a check was made whether dietary factors are responsible for the onset of magnesium deficiency. 50 volunteers with a mean age of 25 years were enrolled in this randomized, prospective study. Based on a cycle ergometry test women with an aerobic-anaerobic threshold above 2.4 W/kg (n=7) and men above 2.6 W/kg (n=18) were assigned to the group of endurance athletes, the remaining 25 subjects formed the control group (8 women and 17 men), The athletes reported training at least 9 hours per week, the subjects in the control group less than 9 hours per week. Since earlier studies had shown that a serum magnesium concentration within the normal range does not necessarily exclude a magnesium deficiency, and magnesium retention can provide more precise information on the magnesium status using a magnesium loading test, the magnesium retention, plasma magnesium concentration, ionized fraction of plasma magnesium, erythrocytic magnesium concentration, renal magnesium excretion and oral magnesium intake were measured. The mean magnesium retention values in the control group measured using the intravenous magnesium loading test were lower than those in the endurance athletes. No differenees were found in the mean values of plasma magnesium concentration ionized fractions of plasma magnesium and erythrocytic magnesium concentration in the two groups, while the endurance trained subjects excreted significantly more magnesium via the kidneys and had a higher oral magnesium intake than the controt group. The study thus confirms that endurance athletes are more frequently magnesium-deficient than persons who do not engage in endurance sports. This deficiency was caused by elevated renal magnesium excretion. Although the athletes' magnesium intake with food was higher, the magnesium quantity consumed did not suffice to maintain a balanced magnesium status
Rapid and sensitive liquid chromatography-tandem mass spectrometry method for determination of monoethylglycinexylidide
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Rapid and sensitive liquid chromatography-tandem mass spectrometry method for determination of monoethylglycinexylidide
No full textDetermination of thiopurine methyltransferase activity in isolated human erythrocytes does not reflect putative in vivo enzyme inhibition by sulfasalazine
No full textDetermination of the acyl glucuronide metabolite of mycophenolic acid in human plasma by HPLC and Emit
No full textBackground: The acyl glucuronide (AcMPAG) of mycophenolic acid (MPA) has been found to possess pharmacologic and potentially proinflammatory activity in vitro. To establish its pharmacologic and toxicologic relevance in vivo, a reversed-phase HPLC method was modified to simultaneously determine MPA, the phenolic MPA-glucuronide (7-O-MPAG), and AcMPAG. In addition, cross-reactivity of AcMPAG in the Emit assay for MPA was investigated. Methods: The procedure used simple sample preparation, separation with a Zorbax Eclipse-XDB-C8 column, and gradient elution. AcMPAG was quantified as 7-O-MPAG-equivalents. Results: The assay was linear up to 50 mg/L for MPA, 250 mg/L for 7-O-MPAG, and 10 mg/L for AcMPAG (r >0.999). Detection limits were 0.01, 0.03, and 0.04 mg/L for MPA, 7-O-MPAG, and AcMPAG, respectively. The recoveries were 99-103% for MPA, 95-103% for 7-O-MPAG, and 104-107% for AcMPAG. The within-day imprecision was <5.0% for MPA (0.2-25 mg/L), <4.4% for 7-O-MPAG (10-250 mg/L), and less than or equal to 14% for AcMPAG (0.1-5 mg/L). The between-day imprecision was <6.2%, <4.5%, and less than or equal to 14% for MPA, 7-O-MPAG, and AcMPAG, respectively. When isolated from microsomes, purified AcMPAG (1-10 mg/L) revealed a concentration-dependent cross-reactivity in an Emit assay for the determination of MPA ranging from 135% to 185%. This is in accordance with the bias between HPLC and Emit calculated in 270 samples from kidney transplant recipients receiving mycophenolate mofetil therapy, which was greater (median, 151.2%) than the respective AcMPAG concentrations determined by HPLC. AcMPAG was found to undergo hydrolysis when samples were stored up to 24 h at room temperature or up to 30 days at 4 degrees C or -20 degrees C. Acidified samples (pH 2.5) were stable up to 30 days at -20 OC. Conclusions: The HPLC and Emit methods for AcMPAG described here may allow investigation of its relevance for the immunosuppression and side effects associated with mycophenolate mofetil therapy. (C) 2000 American Association for Clinical Chemistry
A simple and rapid HPLC method for the determination of meropenem - Preanalytical and analytical aspects
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