Publications by authors named "Yiu-Man Chan"

This study provides an accurate and efficient method to reconstruct detailed and high-resolution digital 3D models of carpological materials by photogrammetric method, in which only about 100 to 150 images are required for each model reconstruction. The 3D models reflect the realistic morphology and genuine color of the carpological materials. The 3D models are scaled to represent the true size of the materials even as small as 3 mm in diameter.

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Introduction: Chromosomal microarray analysis is recommended as the first-tier test for the evaluation of fetuses with structural anomalies. This study aims to investigate the incremental diagnostic yield of chromosomal microarray over conventional karyotyping analysis in fetuses with anomalies restricted to one anatomic system and those with nonspecific anomalies detected by sonography.

Material And Methods: This is a retrospective cohort analysis of 749 fetuses undergoing prenatal diagnosis for abnormal ultrasound findings isolated to one anatomic system and normal karyotype, utilizing chromosomal microarray.

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Background: Microdeletions and microduplications can occur in any pregnancy independent of maternal age. The spectrum and features of pathogenic copy number variants including the size, genomic distribution, and mode of inheritance are not well studied. These characteristics have important clinical implications regarding expanding noninvasive prenatal screening for microdeletions and microduplications.

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Purpose Of Review: To provide updated information on preimplantation genetic testing for aneuploidy (PGT-A), focusing on its implications on prenatal diagnostic approaches after transferal of mosaic aneuploid embryos.

Recent Findings: PGT-A is a technology to screen for chromosome aneuploidy or major chromosome structural rearrangement in embryos before implantation using different cytogenetic analyses. PGT-A has been shown to reduce the negative effect of increasing maternal age on in-vitro fertilization (IVF) outcomes.

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Objective: To explore the acceptance of pregnant Chinese women on giving birth to a child with beta-thalassemia major.

Materials And Methods: Women's acceptance on having a child with beta thalassemia major was assessed using standard gamble metrics during an interviewer-administered survey on 309 women recruited in the antenatal clinic. Utility scores were determined and the association with sociodemographic factors was assessed.

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A retroesophageal left brachiocephalic vein is an extremely rare anomaly and has only been reported in 6 postnatal cases. Two prenatally diagnosed cases are reported. On the 3-vessel view, the vein appears as an aberrant vessel transversely coursing behind the aorta and trachea, which subsequently drains into the superior vena cava, giving rise to a U-shaped configuration.

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Objectives: The phenotype for 10q22q23 duplication is diverse, ranging from intellectual disability and dysmorphism to normal development. Interpreting the clinical significance of the duplication identified in this region is difficult, especially in the prenatal setting. This study aimed to characterize the prenatal findings associated with this submicroscopic imbalance and discuss the dilemmas in predicting the phenotype of 10q22q23 duplications.

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Haploinsufficiency of SATB2 causes cleft palate, intellectual disability with deficient speech, facial and dental abnormalities, and other variable features known collectively as SATB2-associated syndrome. This phenotype was accompanied by osteoporosis, fractures, and tibial bowing in two previously reported adult patients; each possessed SATB2 mutations either predicted or demonstrated to escape nonsense-mediated decay, suggesting that the additional bone defects result from a dominant negative effect and/or age-dependent penetrance. These hypotheses remain to be confirmed, as do the specific downstream defects causing bone abnormalities.

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Objective: The objective of the study was to evaluate the uptake of non-invasive cell-free fetal DNA screening test (NIDT) after a high-risk screening result for trisomy 21 METHODS: Association between maternal and pregnancy characteristics on women's test choice was assessed after adjusting for confounding factors in Hong Kong Chinese women who had a high-risk (term risk ≥1:250) first-trimester or second-trimester screening test at three public hospitals. Main outcome measures were rate of declining further testing and obstetric and maternal factors impacting on patient's selection of testing options.

Results: Compared with the pre-NIDT period, the availability of NIDT resulted in a 45% (P < 0.

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Background: Prenatal sonographic diagnosis of Optiz G/BBB syndrome is difficult because the common clinical features, such as hypertelorism, hypospadias and abnormalities of midline structures, including laryngotracheoesophageal defects, are subtle.

Method: Chromosomal microarray (CMA) analysis using a target enriched Fetal DNA Chip design was performed on the DNA of a fetus with congenital cardiac abnormalities.

Results: Fetal DNA chip revealed a 48Kb single copy number loss within chromosome region Xp22.

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Objective: To assess how pregnant women choose between a non-invasive DNA test (NIDT) and an invasive prenatal test (IPD) based on the accuracy of the test.

Materials And Methods: Pregnant women who attended for first-trimester combined screening assessment of risk of Down syndrome were invited to participate in an interviewer-administered survey. Women were asked to choose between NIDT (variable detection rate but no miscarriage risk) and IPD (∼100% detection rate but 0.

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Aims Of The Study: Stemona alkaloids with distinctly different chemical skeletons are recently reported as the active components in the antitussive herb Baibu derived from the root-tubers of Stemona tuberosa. This study aims to determine if alkaloids of this herb contribute equally to the antitussive functions, act on the same sites of cough reflex, and play any role in inducing central respiratory depressant effects.

Materials And Methods: Antitussive potency of four major alkaloids was evaluated on guinea pigs with citric acid aerosol to induce cough.

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Objective: To assess Chinese women's preference for the choice of a prenatal diagnosis test, karyotyping or rapid aneuploidy, and its relationship to maternal psychological state.

Study Design: Three hundred consenting women completed a self administered structured questionnaire which documented their psychological state and their preferred choice of diagnostic test for chromosomal abnormality using a discrete choice experiment design. Diagnostic tests were categorised according to three attributes: completeness of chromosomal information, procedure-to-result time interval and cost.

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Objectives: To elicit the level of risk of prenatal diagnostic procedure-related miscarriage that Chinese pregnant women were willing to accept.

Methods: An interviewer-administered survey was conducted on 276 women who presented to the University Obstetric Unit. Using the standard gamble approach, subjects were asked to choose between a screening test with a 90% detection rate and a diagnostic test which is definitive but carries a finite risk of abortion.

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Phytochemical investigation of the dried aerial parts of Mikania micrantha led to the isolation of a new sesquiterpene, 3beta-acetoxy-1,10-epoxy-4-germacrene-12,8;15,6-diolide (1), along with six known constituents: 1,10-epoxy-4-germacrene-12,8;15,6-diolide (2), dihydromikanolide (3), potassium mikanin 3-sulfate (4), mikanin (5), alpinetin (6), and ergosta-7,22-dien-3beta-ol (7). Their structures were elucidated by spectroscopic methods, and the molecular structures and stereochemistry of sesquiterpene lactones 1-3 were revealed by single-crystal X-ray analysis. Compound 2 showed moderate activity against respiratory syncytial virus (IC(50) = 37.

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Purpose: We tested the hypothesis that genetic variants in vasoactive and angiogenic factors regulating the retina vasculature contribute to the development of diabetic retinopathy (DR).

Methods: A case-control study was performed to study the genetic association between DR and polymorphic variants of EDN1 (Lys198Asn), LTA (IVS1-80C>A, IVS1-206G>C, IVS1-252A>G), eNOS (Glu298Asp), and ITGA2 (BgI II) in a Chinese population with type 2 diabetes mellitus. A well defined population with type 2 diabetes, consisting of 127 controls and 216 DR patients, was recruited.

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Objective: This study was performed to investigate the preferences of Chinese pregnant women for Down syndrome-affected birth compared to invasive test-related miscarriage, using the standard gamble approach, and to investigate whether there is a difference in Utility Score between general obstetric patients and those who request prenatal screening.

Methods: An interviewer-administered survey was conducted on 67 women who presented to the General Obstetric Clinic for booking visits and 69 women who presented to the first-trimester Combined Screening Clinic for fetal Down syndrome in a University Obstetric Unit. Preferences for Down syndrome-affected birth compared to invasive test-related miscarriage were assessed using the standard gamble approach.

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Phytochemical investigation of the chemical components of Stemona tuberosa led to the isolation of two new alkaloids named tuberostemonine K (1) and tuberospironine (2), together with the known tuberostemonine (3). The new structures of 1 and 2 were elucidated through extensive spectroscopic analyses, while the molecular structure of 3 was confirmed by X-ray analysis. A gradient reversed-phase HPLC-ELSD method was established for the investigation of the chemical diversity of S.

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Alkaloid profiles in Stemona tuberosa were found to be highly variable. Six Stemona alkaloids isolated from the plant were subjected to on-line high-performance liquid chromatography/electrospray ionization mass spectrometry (HPLC/ESI-MS) and tandem mass spectrometry (MS/MS) analyses. Their fragmentation patterns and products were useful for their characterization.

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An alkaloid named 6alpha-hydroxycroomine (1) as well as the known croomine (2), both belonging to the tuberostemospironine-alkaloid type, were isolated from Stemona tuberosa as the major components. The structure of 1 was elucidated through extensive spectroscopic analyses. Comparison of the HPLC profiles of the total alkaloids and the crude methanol extract showed that both compounds are naturally occurring.

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HPLC profile guided study led to the isolation of an acylated secoiridoid glycoside, named gentiotrifloroside (1), together with six known compounds, i.e., loganic acid (2), 6-O-beta-d-glucopyranosylgentiopicroside (3), swertiamarin (4), gentiopicroside (5), sweroside (6) and 2 -(o,m-dihydroxybenzyl)-sweroside (7) from Gentiana triflora and Gentiana rigescens.

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