False-positive Histoplasma antigenemia caused by antithymocyte globulin antibodies

False-positive Histoplasma antigen results were identified in two patients who received rabbit antithymocyte globulin (ATG, Thymoglobulin(R)) to prevent allograft rejection. To determine the prevalence of false-positive results following the administration of Thymoglobulin, sequential specimens were tested from a cohort of transplant recipients. Of 107 such patients, 17 (15.9%) demonstrated false-positive tests for Histoplasma antigenemia. False antigenemia peaked at 2-4 weeks after ATG administration and cleared over the next few months. Physicians should be aware of the potential for false-positive results in specimens from patients who have received ATG.     

Biotransformation of aesculin by human gut bacteria and identification of its metabolites in rat urine

AIM： To observe the biotransformation process of a Chinese compound, aesculin, by human gut bacteria, and to identify its metabolites in rat urine.
METHODS： Representative human gut bacteria were collected from 20 healthy volunteers, and then utilized in vitro to biotransform aesculin under anaerobic conditions. At 0, 2, 4, 8, 12, 16, 24, 48 and 72 h postincubation, 10 mL of culture medium was collected. Metabolites of aesculin were extracted 3 × from rat urine with methanol and analyzed by HPLC. For in vivo metabolite analysis, aesculetin （100 mg/kg） was administered to rats via stomach gavage, rat urine was collected from 6 to 48 h post-administration, and metabolite analysis was performed by LC/ESI-MS and MS/MS in the positive and negative modes.
RESULTS： Human gut bacteria could completely convert aesculin into aesculetin in vitro. The biotransformation process occurred from 8 to 24 h post-incubation, with its highest activity was seen from 8 to 12 h. The in vitro process was much slower than the in vivo process. In contrast to the in vitro model, six aesculetin metabolites were identified in rat urine, including 6-hydroxy-7-glucocoumarin（M1）, 6-hydroxy-7-sulf-coumarin （M2）, 6, 7-digluco-coumarin （M3）, 6-glc-7-gluco-coumarin （M4）, 6-O-methyl-7-gluco-coumarin （MS） and 6-O-methyl-7- sulf-coumarin （M6）. Of which, M2 and M6 were novel metabolites.
CONCLUSION： Aesculin can be transferred into aesculetin by human gut bacteria and is further modified by the host in vivo. The diverse metabolites of aesculin may explain its pleiotropic pharmaceutical effects.     

Measurement of urine human growth hormone levels by ultra-highly sensitive enzyme immunoassay

A highly sensitive enzyme immunoassay (EIA) for measurement of urine hGH was set up by a modification of the method of Hashida and Ishikawa, which was a sandwich enzyme immunoassay using anti-hGH antibody coated polystyrene balls and anti-hGH antibody-peroxidase conjugate. Anti-hGH serum was obtained in rabbits by subcutaneous injections of hGH emulsified in complete Freund's adjuvant. In order to reduce non-specific binding to the solid phase, anti-hGH IgG was precipitated from rabbit serum followed by digestion to F(ab')2 and affinity purification. Fab'-peroxidase conjugate was produced by maleimide method. The assay procedure was as follows. 1. 100 microliters of urine samples or hGH standard were incubated with anti-hGH IgG coated polystyrene balls. 2. Polystyrene balls were then incubated with Fab'-peroxidase conjugate. Polystyrene balls were carefully washed three times in saline after incubation with Fab'-peroxidase conjugate, which reduced contamination and non-specific binding. 3. Peroxidase activity bound to the balls was assayed by enzyme reaction using 3(p-hydroxyphenyl) propionic acid as a substrate, and fluorescence intensity was measured by a spectrofluorophotometer (Shimadzu RF-540). Reducing the energy of excitation by setting the slit width of the spectrofluorophotometer at 2nm made it possible to gain stable fluorescence. The minimum detectable quantity of hGH was 30fg/tube in the assay, so that the detection limit was 0.3 pg/ml when 100 microliters of urine samples were used. Coefficient of intra- and inter-assay variation was 6.0% and 8.6%, respectively. The recovery was 98.8 +/- 2.8 (+/- SE) on average. Multiple dilution of acromegalic urine and urine after insulin injection produced dose-response curves parallel to those of the standards. Urine hGH levels in acromegalic patients were significantly greater than those in normal subjects. These findings indicate that sensitive EIA of urine hGH is potentially useful for evaluating the pituitary function.     

磁微粒酶联免疫吸附法检测人体尿液中日本血吸虫抗体

目的应用磁微粒酶联免疫吸附法（MPAIA）检测日本血吸虫病患者尿液中日本血吸虫特异性抗体,探索血吸虫病新的无创性免疫诊断方法。方法采用MPAIA对158例日本血吸虫病患者和100例健康人的尿液进行检测,并同步进行血清检测,评价其检测效果。结果 MPAIA尿液检测加样量确定为10μl未特殊处理原尿,尿液与血清阳性检出率分别为48.10%（76/158）和88.61%（140/158）,两者差异有统计学意义（χ2=60.24,P〈0.05）,尿液及血清检测特异度均为100%。结论 MPAIA可用于检测日本血吸虫病患者尿液中抗日本血吸虫抗体,但还须对影响其阳性检出率的多种因素进行系统研究,以提高其敏感性。     

电化学发光免疫分析方法及其应用

电化学发光免疫分析方法是近年来在生物分析领域兴起的一种非放射性微量检测技术,该方法具有灵敏度高、线性范围宽和适用面广等特点,被广泛应用于激素、肿瘤标志物和细胞因子等物质的检测,在医学、食品和环境分析等方面具有广阔的应用前景.该文就该方法的基本原理、类型、应用和发展作简要综述.     

电化学发光免疫分析方法及其应用

电化学发光免疫分析方法是近年来在生物分析领域兴起的一种非放射性微量检测技术,该方法具有灵敏度高、线性范围宽和适用面广等特点,被广泛应用于激素、肿瘤标志物和细胞因子等物质的检测,在医学、食品和环境分析等方面具有广阔的应用前景.该文就该方法的基本原理、类型、应用和发展作简要综述.     

Agranulocytosis caused by ticlopidine and its mechanism

A 75-year-old female patient with agranulocytosis caused by ticlopidine is reported. She took the drug at 200 mg/day for 30 days to prevent recurrence of cerebral infarction. The leukocyte count at the nadir was 500/microliters on the 34th day since she started to take the drug. Complete recovery of her peripheral leukocytes came 12 days after its withdrawal. In this patient, mechanisms of ticlopidine-caused agranulocytosis were studied. The lymphocyte stimulation test using ticlopidine was negative. In the culture of marrow cells depleted of lymphocytes, ticlopidine directly inhibited the CFU-C in a dose-dependent manner. Neither the serum on the day of admission nor the T-lymphocytes pre-cultured with ticlopidine had any effect on the CFU-C. The lymphocyte stimulation test is useless in an attempt to find the causal drug in agranulocytosis if it is caused in a directly toxic manner. Agranulocytosis caused by ticlopidine is rare, but careful follow-up is necessary in the case of patients on the drug because there are some whose marrow cells are very sensitive to it.     

Falsely normal anion gap in severe salicylate poisoning caused by laboratory interference

Severe salicylate poisoning is classically associated with an anion gap metabolic acidosis. However, high serum salicylate levels can cause false increase of laboratory chloride results on some analyzers. We present 2 cases of life-threatening salicylate poisoning with an apparently normal anion gap caused by an important laboratory interference. These cases highlight that the diagnosis of severe salicylism must be considered in all patients presenting with metabolic acidosis, even in the absence of an increased anion gap.     

Falsely low serum thyroxine levels caused by interference with the thyroxine assay

A case of euthyroid hypothyroxinaemia caused by the interference of the patient's serum with the Abbott thyroxine TDx assay is reported. This cause of falsely low serum thyroxine levels is probably rare but possibly underrecognized. Clinical implications are discussed.     

Pseudo-Cushing syndrome caused by fenofibrate interference with urinary cortisol assayed by high-performance liquid chromatography

Urinary free cortisol (UFC) excretion over 24 h reflects the production rate of cortisol and is used commonly in the diagnosis of Cushing syndrome. We report on two patients evaluated for Cushing syndrome who had elevated UFC when analyzed by HPLC but normal values for the analysis performed by RIA and HPLC-mass spectrometry/mass spectrometry (HPLC-MS/MS). Other laboratory testing was inconsistent with the diagnosis of Cushing syndrome and raised doubts about the diagnosis. We identified a probable cause of analytical interference as coming from fenofibrate (Tricor), medication taken by the patients. Fenofibrate peak overlapped with the HPLC peak of cortisol and produced an MS/MS transition overlapping the major transition of cortisol. A second MS/MS transition was free from interference. In summary, fenofibrate administration may cause false elevation of UFC values determined by HPLC or HPLC-MS/MS in patients evaluated for Cushing syndrome. An HPLC-MS/MS method using multiple mass transitions, rather than a single transition, allows accurate quantitation of urinary cortisol in patients taking fenofibrate.     

Characterization of nitric oxide release by nebivolol and its metabolites

BACKGROUND: Nebivolol is a selective beta(1)-adrenergic receptor antagonist that causes a direct vasodilator effect attributed to the action on vascular nitric oxide (NO). This study aimed to investigate whether nebivolol or its metabolites induces NO production and to explore the mechanisms underlying this pharmacologic effect. METHODS: Conductance and resistance arteries from Wistar-Kyoto rats (WKY) (n = 33) incubated with the fluorescent probe diaminofluorescein-2 (DAF-2) were stimulated with increasing concentrations of nebivolol or its enantiomers and metabolites, and NO release was histologically evaluated. RESULTS: Nebivolol induced a dose-dependent increase in NO levels in the endothelium of both arteries. Levels of NO were significantly increased at 10(-6)mol/L and reached a plateau state at 10(-5)mol/L. Induction of NO is not a general action of beta-adrenoceptor antagonists, as atenolol had no effects. Nebivolol action on NO release was mainly caused by the D-isomer. Moreover NO production is also maintained after hepatic metabolism, as the three main metabolites of nebivolol were able to induce a significant increase in endothelial NO release. Finally, nebivolol-activated calcium mobilization is crucial to NO production. CONCLUSION: Our study shows the effects of D-nebivolol and its metabolites on endothelial NO production in both conductance and resistance arteries, and clarifies that this effect is realized through a calcium-dependent mechanism.