Biomedical subjects

W S B Yeung

Publications and source records attributed to W S B Yeung.

18 recordsLinked to original sources

PubMed2006

Mitochondrial DNA content and 4977 bp deletion in unfertilized oocytes.

Previous studies analysing the incidences of mitochondrial DNA (mtDNA) deletions and mtDNA content in unfertilized oocytes in relation to donors' age have been controversial. The objective of the study was to compare these two parameters in unfertilized oocytes and relate them to the donors' age. Fifty-two women donated 155 unfertilized metaphase II (MII) oocytes. The incidence of 4977 bp deletion was 34.6%, and the mtDNA copy number was 598 350 +/- 265 862. Women >or=35 years of age had a significantly higher incidence of 4977 bp deletion, lower mtDNA copy number, higher FSH level and poorer ovarian response when compared with younger women. The mtDNA copy number was negatively correlated with the donor's age. The higher incidence of mtDNA deletion and lower mtDNA copy number in older women suggested that these two parameters may reflect ovarian ageing.

Adult↗

PubMed2006

Nuchal translucency in dichorionic twins conceived after assisted reproduction.

OBJECTIVES: As opposed to biochemical markers of Down syndrome, nuchal translucency (NT) was once thought to be a more reliable screening marker for high order multiple pregnancies and pregnancies conceived after assisted conception. Recent data suggested that NT in singleton fetuses from assisted reproduction technology (ART) was thicker than those from singleton pregnancies. The present study compared the thickness of NT in dichorionic twins from natural conception and assisted reproduction. METHODS: A retrospective analysis for comparison of NT thickness on 3319 spontaneous singletons, 19 pairs of spontaneous twins and 27 pairs of assisted reproduction twins was performed. RESULTS: The median NT multiple of median (MoM) of spontaneous singletons was 1.00. For twins, the median NT MoM for pregnancies after assisted reproduction and natural conception were 1.02 and 1.07 respectively. There was no statistical difference in the NT thickness among the three pregnancy groups. CONCLUSION: Contrary to the observed increase in NT in singleton pregnancies from assisted reproduction, the NT in dichorionic twins was comparable to the spontaneous ones. The mode of conception appears to impose differential influence on singletons and twins.

Female↗

PubMed2005

Nuchal translucency in pregnancies conceived after assisted reproduction technology.

OBJECTIVES: Levels of maternal serum markers of fetal Down syndrome in pregnancies conceived after assisted reproduction are different from those of normal spontaneous pregnancies. The present study examined the effects of conventional in-vitro fertilization (IVF), intracytoplasmic sperm injection (ICSI) and embryo cryopreservation on nuchal translucency (NT) thickness. METHODS: A retrospective analysis on 16 673 spontaneous pregnancies, 119 pregnancies with fresh embryos from IVF, 62 pregnancies with frozen-thawed embryos from IVF, 81 pregnancies with fresh embryos from ICSI and 39 frozen-thawed embryos from ICSI was performed. All were singletons with known normal outcomes. Multiples of the median (MoM) of NT were compared. RESULTS: The median NT MoM of spontaneous pregnancies was 1.01. In the assisted reproduction pregnancies, the median NT MoM were significantly increased to 1.07 (P = 0.003), 1.09 (P = 0.009) and 1.09 (P = 0.001) in pregnancies conceived with fresh embryos from IVF, frozen-thawed embryos from IVF and fresh embryos from ICSI, respectively. A non-significant increase in median NT MoM (1.04; P = 0.489) was also observed in pregnancies with frozen-thawed embryos from ICSI. CONCLUSIONS: Increased NT in assisted reproduction pregnancies is postulated to be due to some delay in fetal development. Another possible reason might be related to adverse antenatal course in these pregnancies.

Case-Control Studies↗

PubMed2004

Embryotrophic factor-3 from human oviductal cells enhances proliferation, suppresses apoptosis and stimulates the expression of the beta1 subunit of sodium-potassium ATPase in mouse embryos.

BACKGROUND: Embrytrophic factor-3 (ETF-3) from human oviductal cells enhanced the development of mouse preimplantation embryos. This report studied the embryotrophic mechanisms of the molecule. METHODS AND RESULTS: Mouse embryos were incubated with ETF-3 for 24 h at different stages of development. ETF-3 treatment between 96 and 120 h post-HCG increased the cell count of blastocysts, whilst treatment between 72 and 96 h post-HCG enhanced the expansion and hatching of the blastocysts. ETF-3 increased the cell number of the embryos by suppressing apoptosis and increasing proliferation as determined by TUNEL and bromodeoxyuridine uptake assays, respectively. Real-time quantitative PCR showed that the in vivo developed and ETF-3-treated blastocysts had a significantly higher mRNA copy number of Na/K-ATPase-beta1, but not of hepsin, than that of blastocysts cultured in medium alone. The former gene was associated with cavitation of blastocysts while the latter was related to hatching of blastocyst. The beneficial effect of ETF-3 on blastocyst hatching was also seen when ETF-3-supplemented commercially available sequential culture medium for human embryo culture was used to culture mouse embryos. CONCLUSIONS: ETF-3 improves embryo development by enhancing proliferation, suppressing apoptosis and stimulating expression of genes related to blastocyst cavitation. Supplementating human embryo culture medium with ETF-3 may improve the success rate in clinical assisted reproduction.

Animals↗

PubMed2004

Establishment of a capillary-cumulus model to study the selection of sperm for fertilization by the cumulus oophorus.

BACKGROUND: Spermatozoa have to traverse the cumulus oophorus before fertilization in vivo. Evidence suggests that the cumulus oophorus plays an important role in the fertilization process. We describe the establishment of a capillary-cumulus oophorus model with which to study the action of cumulus mass on the function of human spermatozoa. METHODS: Human cumulus oophorus was aspirated into a glass capillary. Spermatozoa were allowed to pass through the cumulus mass in the capillary from one end of the capillary. The spermatozoa that had traversed the mass were collected at the other end of the capillary and underwent sperm function analyses. RESULTS: Compared with those spermatozoa cultured in medium alone, spermatozoa exposed to the cumulus mass were more likely to have normal morphology, be capacitated and acrosome reacted, with a distinct motility pattern and better zona-binding capacity. CONCLUSION: A novel in vitro model for spermatozoa penetration through the cumulus oophorus was established. The model can be applied to investigate the effect of the cumulus oophorus on sperm functions.

Acrosome Reaction↗

PubMed2004

The contribution of D-mannose, L-fucose, N-acetylglucosamine, and selectin residues on the binding of glycodelin isoforms to human spermatozoa.

Previous data showed that glycodelin-A from amniotic fluid and glycodelin-F from follicular fluid inhibited sperm-zona pellucida binding. Solubilized zona pellucida reduced the binding of glycodelin-F to sperm extract dose dependently. This study demonstrated that the zona pellucida proteins also reduced the binding of glycodelin-A to sperm extract. Ionophore-induced acrosome reaction reduced the binding of iodinated glycodelin-A and -F to sperm, indicating that the glycodelin-binding sites are on the outer acrosomal membrane or on the sperm plasma membrane overlying the acrosome. While the binding of glycodelin-A to sperm was suppressed by mannose and fucose neoglycoproteins, that of glycodelin-F was also reduced by acetylglucosamine neoglycoprotein. Pretreatment of sperm with inhibitors of mannosidase and acetylglucosaminidase reduced the binding of glycodelin-F to sperm. On the other hand, inhibitor of mannosidase but not of acetylglucosaminidase inhibited the binding of glycodelin-A. In a competition binding assay, mannosidase reduced both glycodelin-A and -F binding whereas acetylglucosaminidase reduced only glycodelin-F binding. While fucosidase reduced the binding of both glycodelins, fucosidase inhibitor was marginally active in suppressing the binding of glycodelins to human sperm. Among the selectins tested, only E-selectin had a slight inhibitory effect on the binding of glycodelin-A to sperm. The binding of glycodelin-F was unaffected by selectins and their antibodies. In conclusion, the binding of glycodelin-A to sperm involves mannose, fucose, and possibly E- selectin residues, while that of glycodelin-F involves mannose, fucose, and N-acetylglucosamine but not the selectin residue.

Acetylglucosamine↗

PubMed2003

Capillary electrophoresis-based immunoassay.

Capillary electrophoresis-based immunoassay (CEIA) is a developing analytical technique with a number of advantages over conventional immunoassay, such as reduced sample consumption, simpler procedure, easy simultaneous determination of multiple analytes, and short analysis time. However, there are still a number of technical issues that researchers on CEIA have to solve before the assay can be more widely used. These issues include method to improve the concentration sensitivity of the assay, requirement for robust separation strategy for different analytes, and method to increase the throughput of the assay. The approaches to solve these issues are reviewed. Several studies have been devoted to develop general separation strategies for CEIA, and to enhance the sensitivity of detection. The recent development of microchip-based CEIA is encouraging and is likely to address more drawbacks of CEIA, particularly on the throughput issue.

Antigen-Antibody Reactions↗

PubMed2003

Specific expression of VCY2 in human male germ cells and its involvement in the pathogenesis of male infertility.

Abnormal spermatogenesis in men with Y-chromosome microdeletions suggests that genes important for spermatogenesis have been removed from these individuals. VCY2 is a testis-specific gene that locates in the most frequently deleted azoospermia factor c region in the Y chromosome. We have raised an antiserum to VCY2 and used it to characterize the localization of VCY2 in human testis. Using Western blot analysis, the affinity-purified polyclonal VCY2 antibody gave a single specific band of approximately 14 kDa in size, corresponding to the expected size of VCY2 in all the collected human testicular biopsy specimens with normal spermatogenesis. Immunohistochemical analyses showed that VCY2 localized to the nuclei of spermatogonia, spermatocytes, and round spermatids, except elongated spermatids. At the ultrastructural level, VCY2 expression was found in the nucleus of human ejaculated spermatozoa. To determine the possible relationship of VCY2 with the pathogenesis of male infertility, we examined a group of infertile men with and without Y-chromosome microdeletions and with known testicular pathology using VCY2 antibody. VCY2 was weakly expressed at the spermatogonia and immunonegative in spermatocytes and round spermatids in testicular biopsy specimens with maturation arrest or hypospermatogenesis. The specific localization of the protein in germ cell nuclei indicates that VCY2 is likely to function in male germ cell development. The impaired expression of VCY2 in infertile men suggests its involvement in the pathogenesis of male infertility.

Adult↗

PubMed2003

Zona-binding inhibitory factor-1 from human follicular fluid is an isoform of glycodelin.

Zona-binding inhibitory factor-1 (ZIF-1), a glycoprotein in human follicular fluid, reduces the binding of spermatozoa to the zona pellucida. ZIF-1 has a number of properties similar to those of glycodelin-A from human follicular fluid. The objective of this study was to compare the biochemical characteristics of these two glycoproteins. N-terminal sequencing and protease-digested peptide mapping showed that ZIF-1 and glycodelin-A have the same protein core. However, these glycoproteins differ in their oligosaccharide chains, as demonstrated by fluorophore-assisted carbohydrate electrophoresis, lectin-binding ability, and isoelectric focusing. ZIF-1 inhibited spermatozoa-zona pellucida binding slightly more than did glycodelin-A and significantly suppressed progesterone-induced acrosome reaction of human spermatozoa. Indirect immunofluorescence staining revealed specific binding of glycodelin-A and ZIF-1 to the acrosome region of human spermatozoa, where ZIF-1 produced a stronger signal than did glycodelin-A at the same protein concentration. These data suggest that ZIF-1 is a differentially glycosylated isoform of glycodelin that potently inhibits human sperm-egg interaction. Future study on the function role of ZIF-1 would provide a better understanding of the regulation of fertilization in humans.

Amino Acid Sequence↗

PubMed2003

Amniotic fluid human chorionic gonadotrophin and alpha-fetoprotein levels in pregnancies conceived after assisted reproduction.

OBJECTIVES: To study the alteration in the second-trimester maternal serum levels of human chorionic gonadotrophin (hCG) and alpha-fetoprotein (AFP) in pregnancies conceived after assisted reproduction. METHODS: We compared the amniotic fluid hCG and AFP concentrations of 45 pregnancies with fresh embryo transfer and 25 pregnancies with frozen-thawed embryo transfer with 269 spontaneous pregnancies. Wilcoxon rank-sum test was used for analysis. RESULTS: The median amniotic fluid hCG MoM in pregnancies conceived after frozen-thawed embryo transfer was significantly increased to 1.41 compared to 1.00 (p = 0.01) in naturally occurring pregnancies and 0.96 (p = 0.049) in pregnancies after fresh embryo transfer. Further analysis showed that this was only observed in frozen embryos fertilized by conventional insemination with MoM of 1.59. The AFP MoMs were similar among the groups. CONCLUSIONS: The observed raised amniotic fluid hCG level in IVF-FET pregnancies may reflect the elevated maternal serum level in these pregnancies. Further studies should be directed towards exploring the underlying pathophysiology.

Adult↗

PubMed2003

Molecular analysis of the androgen receptor gene in Hong Kong Chinese infertile men.

PURPOSE: To investigate the relationship between CAG repeat length in the androgen receptor gene and impaired spermatogenesis in Hong Kong Chinese population. METHODS: The CAG repeat region was amplified by polymerase chain reaction (PCR) in 85 nonobstructive azoospermic or severe oligozoospermic men, and 45 fertile males. The number of CAG repeat was analyzed by DNA sequencing. Serum FSH, LH, and testosterone levels were also determined in these men. RESULTS: Among nonobstructive azoospermic males, three men (5.7%) possessed short CAG repeats (< 16), and three (5.7%) other men possessed long CAG repeats (> 30). Short CAG repeats (< 16) were also found in two severe oligozoospermic males (6.3%). The incidence of infertile men with short or long CAG repeats is significantly higher in the azoospermic group (p = 0.03) but not in the severe oligozoospermic group (p = 0.17) when compared with the fertile controls CONCLUSION: Our data suggest an association between CAG repeat lengths and impaired spermatogenesis in azoospermic males in our population.

Adolescent↗

PubMed2003

Maternal serum hCG and alpha-fetoprotein levels in pregnancies conceived after IVF or ICSI with fresh and frozen-thawed embryos.

BACKGROUND: Studies have shown that levels of serum markers of Down's syndrome were altered in pregnancies conceived after IVF, though the reason for this remains unknown. METHODS: Second-trimester maternal serum levels of hCG and alpha-fetoprotein (AFP) in pregnancies conceived with fresh and frozen-thawed embryos after assisted reproduction were compared with those conceived spontaneously. RESULTS: There were 203 pregnancies with fresh embryo transfers (130 IVF cases, 73 ICSI cases) and 98 pregnancies with frozen-thawed embryo transfers (61 IVF cases, 37 ICSI cases). The controls consisted of 17 145 spontaneous pregnancies. The median hCG multiples of the median (MoM) was significantly increased to 1.24 in 98 pregnancies conceived after frozen embryo transfer. This elevation was observed only in the IVF-frozen embryo transfer subgroup (P < 0.001), but not in the ICSI-frozen embryo transfer subgroup. The median AFP MoM for 203 pregnancies after fresh embryo transfer was 0.90. Among the subgroups, the median AFP MoM was significantly reduced to 0.90 and 0.86 in IVF-embryo transfer (P = 0.04) and ICSI-embryo transfer (P = 0.001) pregnancies respectively, and significantly raised to 1.20 in the IVF-frozen embryo transfer subgroup. CONCLUSIONS: The degree of alterations in maternal serum hCG and AFP levels varied between fresh and frozen-thawed embryos, and also between the mode of fertilization. Pregnancies resulting from ICSI or frozen embryo transfer should be regarded as distinct entities from those of IVF-embryo transfer.

Case-Control Studies↗

PubMed2003

Embryotrophic factor-3 from human oviductal cells affects the messenger RNA expression of mouse blastocyst.

Our previous results showed that embryotrophic factor-3 (ETF-3) from human oviductal cells increased the size and hatching rate of mouse blastocysts in vitro. The present study investigated the production of ETF-3 by an immortalized human oviductal cell line (OE-E6/E7) and the effects of ETF-3 on the mRNA expression of mouse embryos. The ETF-3 was purified from primary oviductal cell conditioned media using sequential liquid chromatographic systems, and antiserum against ETF-3 was raised. The ETF-3-supplemented Chatot-Ziomek-Bavister medium was used to culture Day 1 MF1 x BALB/c mouse embryos for 4 days. The ETF-3 treatment significantly enhanced the mouse embryo blastulation and hatching rate. The antiserum, at concentrations of 0.03-3%, abolished the embryotrophic effect of ETF-3. Positive ETF-3 immunoreactivity was detected in the primary oviductal cells, OE-E6/E7, and blastocysts derived from ETF-3 treatment. Vero cells (African Green Monkey kidney cell line), fibroblasts, and embryos cultured in control medium did not possess ETF-3 immunoreactivity. The mRNA expression patterns of the treated embryos were studied at the blastocyst stage by mRNA differential display reverse transcription-polymerase chain reaction (DDRT-PCR). The DDRT-PCR showed that some of the mRNAs were differentially expressed after ETF-3 treatment. Twelve of the differentially expressed mRNAs that had high homology with cDNA sequences in the GenBank were selected for further characterization. The differential expression of seven of these mRNAs (ezrin, heat shock 70-kDa protein, cytochrome c oxidase subunit VIIa-L precursor, proteinase-activated receptor 2, eukaryotic translation initiation factor 2beta, cullin 1, and proliferating cell nuclear antigen) was confirmed by semiquantitative RT-PCR. In conclusion, immortalized oviductal cells produce ETF-3, which influences mRNA expression of mouse blastocyst.

Animals↗

PubMed2003

Pre-implantation genetic diagnosis in Hong Kong.

This paper presents the first two successful cases of pre-implantation genetic diagnosis in Hong Kong and discusses the indications and the advantages over prenatal diagnosis. Patients should be informed about the procedure and extensively counselled about the possibility of misdiagnosis and the need for conventional prenatal diagnosis during pregnancy.

Adult↗

PubMed2003

Prognostic factors for successful outcome in patients undergoing controlled ovarian stimulation and intrauterine insemination.

OBJECTIVE: To determine the prognostic factors associated with successful outcome following controlled ovarian stimulation and intrauterine insemination. DESIGN: Retrospective analysis. SETTING: University-based assisted reproductive technology centre, Hong Kong. PATIENTS AND METHODS: Patients included 292 couples undergoing 600 treatment cycles, following a standard protocol of human menopausal gonadotrophin injections. Multiple logistic regression analysis was performed to determine which demographic and sperm parameters gave the maximum discrimination to predict pregnancy. RESULTS: One hundred and eleven pregnancies resulted from treatment. The pregnancy rates were 18.5% per cycle and 37.9% per couple. The age of the women was significantly lower for pregnant cycles, and the serum oestradiol levels and number of follicles greater than 16 mm in diameter were significantly higher, compared with non-pregnant cycles. The sperm concentration and number of motile spermatozoa were also significantly increased in pregnant cycles. Pregnancy rate was significantly increased when the raw semen sample contained 20 million/mL or more spermatozoa, normal forms comprised 7% or more, and when the number of motile spermatozoa in inseminated samples was 1 million or greater. CONCLUSION: Using multiple logistic regression analysis, age of the women and serum oestradiol level had the maximum power to predict pregnancy following ovarian stimulation and intrauterine insemination.

Adult↗

PubMed2002

Comparative study of the biological activity of spermatozoa-zona pellucida binding inhibitory factors from human follicular fluid on various sperm function parameters.

Previous studies showed that human follicular fluid (hFF) from gonadotrophin stimulated cycles contained two glycoproteins, named as ZIF-1 and ZIF-2, that reduced the zona binding capacity of spermatozoa. The present study showed that the spermatozoa-zona pellucida binding inhibitory activity was also present in hFF from natural cycle. Using the hemizona binding assay, the inhibitory effect of ZIF-1 on the zona binding capacity of spermatozoa was dose-dependent. The effect of ZIF-2 was also dose-dependent, in the range of 10-100 ng/ml. The inhibitory effects of both ZIF-1 and -2 increased with the duration of the spermatozoa-ZIF interaction. The effect of the former was present up to 120 min incubation, whilst that of latter occurred for the first 90 min. The zona binding inhibitory effect of ZIF-1 and -2 was additive when they were used together to treat the spermatozoa. The biological activity of ZIFs on other sperm parameters that might affect spermatozoa-zona pellucida binding was also investigated. ZIF-1 did not affect the acrosomal status of human spermatozoa while ZIF-2 significantly increased the number of acrosome reacted spermatozoa in the range of 0.1-10 microg. However, the increase in the incidence of acrosome-reacted spermatozoa after ZIF-2 treatment could not totally account the inhibitory effect of ZIF-2 on zona binding. Both glycoproteins did not affect the motility of human spermatozoa. Radioactively-labelled ZIFs bound to human spermatozoa. Unlabelled ZIF displaced the bound radioactivity of spermatozoa treated with the corresponding labelled ZIF. These suggested the presence of specific binding sites of ZIFs on human spermatozoa.

Acrosome Reaction↗

PubMed2002

A comparative study of Y chromosome microdeletions in infertile males from two Chinese populations.

PURPOSE: To compare the prevalence and type of Y-microdeletions in Hong Kong and Shanghai men with severe male-factor infertility. METHODS: Seven Y-linked sequence tagged site (STS) primers and seven gene-specific primers were screened in 293 infertile males (139 from Hong Kong and 154 from Shanghai) and 161 fertile men (61 from Hong Kong and 100 from Shanghai). Serum FSH, LH, and testosterone levels were also measured in these men. RESULTS: The incidence of Yq microdeletions in nonobstructive azoospermic men from Hong Kong (8.5%) and Shanghai (6%) was similar. Yq microdeletions were observed in severe oligospermic patients (8.5%) from Hong Kong but not from Shanghai. Among the 9 Hong Kong men with Y-microdeletions, 8 had AZFc deletion and one had AZFb deletion. In contrast, 6 of 9 men from Shanghai with Y-microdeletions had AZFb deletion. The incidence of AZFb deletion among Y-microdeleted men was statistically different between the two populations. Two of the men with AZFb deletion also had AZFa and AZFc deletions. CONCLUSIONS: Regional variations in the type of Y-microdeletion existed between Hong Kong and Shanghai infertile males.

Adult↗

PubMed2002

The synthesis and fate of glycodelin in human ovary during folliculogenesis.

The ontogeny of glycodelin in human ovarian follicles during folliculogenesis was studied. Glycodelin immunoreactivity began to be detected in the granulosa cells and thecal cells of late secondary follicles. Immunoreactivity was also found in both the luteinized granulosa cells and cumulus cells obtained from women undergoing the assisted reproduction treatment. However, only the luteinized granulosa cells, and not the cumulus cells, expressed glycodelin mRNA. Results also showed that the cumulus cells took up radiolabelled glycodelin and partially deglycosylated some of it. Glycodelin (and a partially deglycolsylated form of glycoldelin) appeared to complex with two cytoplasmic or membrane components of the cumulus cells. The data also demonstrated that ZIF-1, a glycoprotein isolated from human follicular fluid, was immunologically similar to glycodelin. In conclusion, we suggest that glycodelin is synthesized in the granulosa cells of ovarian follicles at late secondary follicle stage. It then may be released into the follicular fluid from where it is taken up and partially modified by the cumulus cells.

Binding, Competitive↗