Supported Liquid Membrane Extraction of Anabolic Androgenic Compounds in Biological Matrices and Detection by LC-ESI-MS

A sample work-up and enrichment technique involving the use of supported liquid membrane (SLM) and detection by high performance liquid chromatography coupled to a mass spectrometer operating under positive ion electrospray mode (LC-PI-ESI-MS) has been developed for the determination of six anabolic androgenic compounds in different biomatrices; mainly urine, kidney, liver and milk. Anabolic androgenic compounds analysed included 17α-trenbolone, 17β-trenbolone, 19-nortestosterone, testosterone, 4-androstene-3,17-dione and testosterone benzoate. Several factors affecting the extraction efficiency during SLM enrichment, such as donor pH were studied. The detection limits (DL) were 0.08 μg L–1 for 4-androstene-3,17-dione, 0.7 ng L–1 19-testosterone, 1.1 ng L–1 for testosterone, 0.1 ng L–1 for 17β-trenbolone, 1.6 ng L–1 for 17α-trenbolone and 0.03 μg L–1 for testosterone benzoate. Modification at C17 in the structures of 4-androstene-3,17-dione and testosterone benzoate affected their recoveries with SLM and explained their observed high detection limits.Keywords: Anabolic androgenic compounds, supported liquid membrane, liquid chromatography, electrospray ionization, massspectrometr

An approach to calculating the bit-error rate of a coherent chaos-shift-keying digital communication system under a noisy multiuser environment

Author name used in this publication: W. M. TamAuthor name used in this publication: F. C. M. LauAuthor name used in this publication: C. K. Tse2001-2002 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Diagnosis of dihydropyrimidinase deficiency in a Chinese boy with dihydropyrimidinuria

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Managing malignant pleural effusion with an indwelling pleural catheter: factors associated with spontaneous pleurodesis

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Transcriptional regulation of RET by Nkx2-1, Phox2b, Sox10, and Pax3

Background: The rearranged during transfection (RET) gene encodes a single-pass receptor whose proper expression and function are essential for the development of enteric nervous system. Mutations in RET regulatory regions are also associated with Hirschsprung disease (HSCR) (aganglionosis of the colon). We previously showed that 2 polymorphisms in RET promoter are associated with the increased risk of HSCR. These single nucleotide polymorphisms overlap with the NK2 homeobox 1 (Nkx2-1) binding motif interrupting the physical interaction of NKX2-1 with the RET promoter and result in reduced RET transcription. In this study, we further delineated Nkx2-1-mediated RET Transcription. Methods and results: First, we demonstrated that PHOX2B, like SOX10 and NKX2-1, is expressed in the mature enteric ganglions of human gut by immunohistochemistry. Second, subsequent dual-luciferase-reporter studies indicated that Nkx2-1 indeed works coordinately with Phox2b and Sox10, but not Pax3, to mediate RET transcription. In addition, identification of Phox2b responsive region in RET promoter further provides solid evidence of the potential functional interaction between Phox2b and RET. Conclusion: In sum, Phox2b and Sox10 act together with Nkx2.1 to modify RET signaling and this interaction may also contribute to HSCR susceptibility. © 2009 Elsevier Inc. All rights reserved.postprin

Prophylactic thyroidectomy in ethnic Chinese patients with multiple endocrine neoplasia type 2A syndrome after the introduction of genetic testing

Objective: To evaluate the impact of genetic testing in the management of familial multiple endocrine neoplasia 2A patients. Design: Retrospective study. Setting: University teaching hospital, Hong Kong. Patients: Twenty-two patients from eight multiple endocrine neoplasia 2A families underwent prophylactic total thyroidectomy based on a positive RET mutation genetic testing. All mutations were located at codon 634 of exon 11. Nineteen patients had preoperative basal serum calcitonin measured, and the 12 with normal levels had pentagastrin stimulation tests. Preoperative thyroid ultrasound examination was performed for 17 patients. Results: There were 13 females and 9 males with a median age of 25.1 (range, 6.1-71.9) years. Histopathology revealed medullary thyroid carcinoma in 17 (77%), C-cell hyperplasia in four (18%), and normal pathology in one (5%) of the patients. Five patients with either C-cell hyperplasia or normal pathology were among the youngest (age range, 6-9 years). The youngest patient with medullary thyroid carcinoma was nearly 9 years old. The median size of medullary thyroid carcinomas was 8.3 (range, 0.1-18) mm, but there were no lymph node metastases. Of 15 patients with normal basal calcitonin levels, 10 had medullary thyroid carcinoma, though two tested negative with the pentagastrinstimulated calcitonin assay. Five of six patients with normal preoperative ultrasonographic examinations had medullary thyroid carcinoma. Three (14%) of the patients were prescribed long-term calcium and vitamin D supplementation. After a median follow-up of 49 (range, 13-128) months, no patient had recurrence of medullary thyroid carcinoma. Conclusions: Genetic testing has replaced conventional biochemical and radiological modalities to identifying multiple endocrine neoplasia 2A carriers, in order to offer them prophylactic thyroidectomy. Chinese multiple endocrine neoplasia 2A patients with codon 634 mutation seem to have less aggressive forms of medullary thyroid carcinoma, for whom prophylactic thyroidectomy can be considered at the age of 8 years.published_or_final_versio

Comprehensive comparison of copy number variations detection using Illumina Omni 2.5M and Affymetrix CytoScan® arrays

Posters: Genome Structure, Variation and Function: abstract no. 552TStructural variation has been recognized as a genetic risk factor contributing to human diseases, and in particular, congenital disorders. Smaller scale copy number variations (CNVs) have also been linked to a number of neurodevelopmental phenotypes, including intellectual disability as well as autism spectrum disorders. The precise detection of CNVs is therefore necessary for ...postprin

Patient complexity and genotype-phenotype correlations in biliary atresia: a cross-sectional analysis

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Chinese patients with sporadic Hirschsprung's disease are predominantly represented by a single RET haplotype.

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Bilateral pheochromocytomas in MEN2A syndrome: a two-institution experience

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