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Biomedical subjects

S L Tan

Publications and source records attributed to S L Tan.

At least 37 records · Page 2Linked to original sources

Pregnancy and delivery after cryopreservation of zygotes produced by in-vitro matured oocytes retrieved from a woman with polycystic ovarian syndrome.

This case report describes the birth of a healthy infant after cryopreservation of zygotes produced by in-vitro matured oocytes retrieved from an anovulatory woman with polycystic ovarian syndrome (PCOS). To initiate the treatment cycle, the patient received intravaginal progesterone at night for 10 days to induce a withdrawal bleed. Oocyte retrieval was performed on day 11 following a withdrawal bleed. The patient was administered 10,000 IU of HCG subcutaneously 36 h prior to oocyte collection. A total of 63 immature oocytes were obtained; 10 were morphologically abnormal. Following incubation for 24--48 h in the maturation medium, TC-199 supplemented with 20% patient's own serum, 75 mIU/ml FSH and LH, 77.4% (41/53) of the oocytes were at the metaphase-II stage. Thirty-one (31/41, 75.6%) were fertilized using ICSI with her husband's spermatozoa, 15 fertilized oocytes were cultured for embryo transfer and 16 were frozen at the pronuclear stage. Pregnancy ensued following fresh embryo transfer. Unfortunately, the pregnancy was miscarried eight weeks later. However, the second frozen-thawed embryo transfer attempt resulted in a full-term pregnancy with delivery of a healthy male infant.

Administration, Intravaginal↗

The development of preimplantation genetic diagnosis for myotonic dystrophy using multiplex fluorescent polymerase chain reaction and its clinical application.

Preimplantation genetic diagnoses (PGD) for single gene defects require considerable time and resources for the standardization of polymerase chain reactions that are rapid, sensitive and reliable. Developing tests for the trinucleotide repeat diseases, where the expansion of unstable repeats produces the phenotypes, are particularly complex. One of these disorders is myotonic dystrophy where, at present, diagnosis at the single cell level relies on the detection of the normal alleles from both the affected and unaffected parent. The incorporation of short tandem repeat polymorphisms in the assay can give additional information to improve the accuracy of diagnosis. We have developed a multiplex fluorescent reaction for myotonic dystrophy and one of two closely mapped, highly heterozygous, short tandem repeats (D19S219 and D19S559) on chromosome 19 to reduce the possibility of misdiagnosis due to contamination, act as a control for allelic drop-out and maximize the number of embryos genotyped. This protocol was designed as a general diagnosis for myotonic dystrophy, using the most informative of the two polymorphisms for each couple. Subsequently this approach was used in a PGD treatment cycle.

Adult↗

Regulation of mRNA translation and cellular signaling by hepatitis C virus nonstructural protein NS5A.

The NS5A nonstructural protein of hepatitis C virus (HCV) has been shown to inhibit the cellular interferon (IFN)-induced protein kinase R (PKR). PKR mediates the host IFN-induced antiviral response at least in part by inhibiting mRNA translation initiation through phosphorylation of the alpha subunit of eukaryotic initiation factor 2 (eIF2alpha). We thus examined the effect of NS5A inhibition of PKR on mRNA translation within the context of virus infection by using a recombinant vaccinia virus (VV)-based assay. The VV E3L protein is a potent inhibitor of PKR. Accordingly, infection of IFN-pretreated HeLa S3 cells with an E3L-deficient VV (VVDeltaE3L) resulted in increased phosphorylation levels of both PKR and eIF2alpha. IFN-pretreated cells infected with VV in which the E3L locus was replaced with the NS5A gene (VVNS5A) displayed diminished phosphorylation of PKR and eIF2alpha in a transient manner. We also observed an increase in activation of p38 mitogen-activated protein kinase in IFN-pretreated cells infected with VVDeltaE3L, consistent with reports that p38 lies downstream of the PKR pathway. Furthermore, these cells exhibited increased phosphorylation of the cap-binding initiation factor 4E (eIF4E), which is downstream of the p38 pathway. Importantly, these effects were reduced in cells infected with VVNS5A. NS5A was also found to inhibit activation of the p38-eIF4E pathway in epidermal growth factor-treated cells stably expressing NS5A. NS5A-induced inhibition of eIF2alpha and eIF4E phosphorylation may exert counteracting effects on mRNA translation. Indeed, IFN-pretreated cells infected with VVNS5A exhibited a partial and transient restoration of cellular and viral mRNA translation compared with IFN-pretreated cells infected with VVDeltaE3L. Taken together, these results support the role of NS5A as a PKR inhibitor and suggest a potential mechanism by which HCV might maintain global mRNA translation rate during early virus infection while favoring cap-independent translation of HCV mRNA during late infection.

Autoradiography↗

Endometriosis: aetiology, pathogenesis and treatment.

Endometriosis, which may be defined as the presence and proliferation of endometrial tissue outside the uterine cavity, causes pain and infertility for millions of women worldwide. Studies suggest a prevalence of 0.5 to 5% in fertile and 25 to 40% in infertile women. The most widely accepted aetiological theory is that retrograde flow of menstrual fluid through the Fallopian tubes deposits viable endometrial tissue, which implants on the peritoneal surface. Increasingly, the aetiology of endometriosis is being studied at the immunological and genetic levels. The aim of treatment of endometriosis is to remove or diminish disease deposits. This may be attempted through medical or surgical means. It has long been recognised that endometriotic glands are hormonally sensitive. Medical therapies work by inducing a hypoestrogenic, anovulatory state to induce atrophy within the glandular tissue. Conception is generally not possible during medical therapy and has not been demonstrated to increase afterwards. Medical treatment of endometriosis should be discouraged when infertility is the primary problem. In this situation surgery or an assisted reproduction treatment such as in vitro fertilisation may be more appropriate. Medical treatment of pain caused by endometriosis is generally effective. There is little difference in efficacy between the different medications but their adverse effect profiles differ greatly. It appears that gonadotropin-releasing hormone agonists, particularly when used with add-back estrogen, may be more acceptable to women than other treatments. Laparoscopic surgical treatment of minimal and mild endometriosis has been demonstrated to increase fecundity. Surgical treatment has also been shown to decrease pain scores compared with expectant management. Ongoing and future research examining the aetiology of endometriosis at the immunological and genetic levels should usher in new treatments directed at the actual cause of the disease. More randomised trials examining the role of surgery, and comparing surgical and medical treatments, are also required and are necessary if we are to continue in our attempts to adopt an evidence-based approach to treatment.

Endometriosis↗

Ser(2194) is a highly conserved major phosphorylation site of the hepatitis C virus nonstructural protein NS5A.

Phosphorylation of the nonstructural NS5A protein is highly conserved among hepatitis C virus (HCV) genotypes. However, the precise site or sites of phosphorylation of NS5A have not been determined, and the functional significance of phosphorylation remains unknown. Here, we showed by two-dimensional phosphopeptide mapping that a protein kinase or kinases present in yeast, insect, and mammalian cells phosphorylated a highly purified HCV genotype 1b NS5A from insect cells on identical serine residues. We identified a major phosphopeptide (corresponding to amino acids 2193-2212 of the HCV 1b polyprotein) by using negative-ion electrospray ionization-microcapillary high performance liquid chromatography-mass spectrometry. The elution time of the phosphopeptide determined by negative-ion electrospray ionization-mass spectrometry corresponded with the elution time of the majority of (32)P-label that was incorporated into the phosphopeptide by an in vitro kinase reaction. Subsequent analysis of the peak fraction by automated positive-ion electrospray ionization-tandem mass spectrometry revealed that Ser(2194) was the major phosphorylated residue on the phosphopeptide GpSPPSLASSSASQLSAPSLK. Substitution for Ser(2194) with Ala resulted in the concomitant disappearance of major in vivo phosphorylated peptides. Ser(2194) and surrounding amino acids are highly conserved in all HCV genotypes, suggesting NS5A phosphorylation at Ser(2194) may be an important mechanism for modulating NS5A biological functions.

Amino Acid Sequence↗

P58IPK, a novel cochaperone containing tetratricopeptide repeats and a J-domain with oncogenic potential.

Tetratricopeptide repeats (TPRs) are loosely conserved 34-amino acid sequence motifs that have been shown to function as scaffolding structures to mediate protein-protein interactions. TPRs have been identified in a number of proteins with diverse functions and cellular locations. Recent studies suggest that individual TPR motifs can confer specificity in promoting homotypic and/or heterotypic interactions, often in a mutually exclusive manner. These features are best exemplified by the P58IPK protein, an influenza virus-activated cellular inhibitor of the PKR protein kinase, whose different TPR motifs mediate interactions with distinct proteins. P58IPK, which possesses cochaperone and oncogenic properties, represents a unique class of TPR proteins containing a J-domain. Here we review recent progress on the structural and functional characterization of P58IPK, and discuss the possible mechanisms by which P58IPK modulates PKR and induces tumorigenesis in view of present knowledge of TPR proteins and molecular chaperones.

Amino Acid Motifs↗

Effects of laparoscopic ovarian drilling on serum vascular endothelial growth factor and on insulin responses to the oral glucose tolerance test in women with polycystic ovary syndrome.

OBJECTIVE: To evaluate the serum vascular endothelial growth factor concentrations and insulin responses to the oral glucose tolerance test before and after laparoscopic ovarian drilling in women with PCOS. DESIGN: Prospective study. SETTING: University teaching center. PATIENT(S): Twenty-seven women with clomiphene citrate-resistant polycystic ovary syndrome. INTERVENTION(S): Laparoscopic ovarian drilling. MAIN OUTCOME MEASURE(S): VEGF levels and insulin responses to OGTT before and after ovarian drilling. RESULT(S): No difference was found in VEGF levels in women with PCOS before (6.0 +/- 1.2 ng/mL) and after ovarian drilling (5.5 +/- 1.2 ng/mL). VEGF levels before and after ovarian drilling in women who conceived were, respectively, 5.9 +/- 1.0 and 5.1 +/- 0.9 ng/mL and in those who did not conceive were 6.0 +/- 1.3 and 5.7 +/- 1.2 ng/mL. No correlation was found between baseline serum insulin and VEGF levels. VEGF concentrations in women with normal ovaries (4.5 +/- 1.7 ng/mL) were significantly lower than in women with PCOS. There was no difference in glucose and insulin responses to OGTT before and after ovarian drilling. CONCLUSION(S): VEGF levels in women with PCOS are higher than in normal women, and ovarian drilling does not affect these levels. The procedure does not change insulin responses to OGTT.

Analysis of Variance↗

A randomized study of the effect of 10 minutes of bed rest after intrauterine insemination.

OBJECTIVE: To evaluate the effects of 10 minutes of bed rest after intrauterine insemination (IUI) on the pregnancy rate. DESIGN: Prospective randomized study. SETTING: University teaching hospital. PATIENT(S): One hundred sixteen couples with unexplained infertility. INTERVENTION(S): Patients were prospectively randomized either to immediate mobilization after IUI (group I) or to remain in a supine position for 10 minutes after the procedure (group II). MAIN OUTCOME MEASURE(S): Cumulative pregnancy rate. RESULT(S): Ninety-five couples were included in the analysis. Group I consisted of 40 couples (90 cycles), and group II consisted of 55 couples (120 cycles). The pregnancy rate per couple in group I (4 of 40 [10%]) was significantly lower than in group II (16 of 55 [29%]). The pregnancy rate per cycle in group I (4.4%) was also lower than in group II (13. 3%). With use of life-table analysis, the cumulative probability of pregnancy in group II was significantly higher than in group I. CONCLUSION(S): A 10-minute interval of bed rest after IUI has a positive effect on the pregnancy rate. We recommend that mandatory bed rest for 10 minutes after IUI should be adopted into a standard practice.

Adult↗

Impact of reducing the number of embryos transferred from three to two in women under the age of 35 who produced three or more high-quality embryos.

OBJECTIVE: To investigate the effect of a reduction in the number of good-quality embryos transferred in patients <35 years of age on pregnancy and multiple pregnancy rate. DESIGN: Prospective observational study with historical controls. SETTING: Academic tertiary referral unit. PATIENT(S): Three hundred eight patients <35 years of age undergoing IVF-ET. INTERVENTION(S): For patients who had three or more good quality embryos available for transfer, those in group 1 were given the option to have either two or three embryos replaced, whereas those in group 2 were allowed a maximum of two embryos transferred. In both groups, patients who had less than three good-quality embryos had the option to have three embryos transferred. MAIN OUTCOME MEASURE(S): Pregnancy and multiple pregnancy rates. RESULT(S): Patients in group 1, compared with those in group 2, had significantly more embryos (3 vs. 2) of significantly higher cumulative embryo score (31 vs. 24) transferred. This resulted in significantly higher multiple (57.8% vs. 30.8%) and triplet (15.6% vs. 1.4%) pregnancy rates in group 1. However, no difference in overall clinical pregnancy rate (37.2% vs. 41.2%) or live birth rate (28.1% vs. 29.4%) was observed between group 1 and 2. CONCLUSION(S): In women <35 years of age, who have three or more good-quality embryos available for transfer, a maximum of two embryos should generally be transferred.

Adult↗

Effects of functional ovarian cysts detected on the 7th day of gonadotropin-releasing hormone analog administration on the outcome of IVF treatment.

OBJECTIVE: To investigate the impact of functional ovarian cysts on the time required to achieve pituitary suppression, follicular development, embryo quality, and pregnancy rates during IVF treatment. DESIGN: Prospective observational study. INTERVENTION(S): Daily treatment with buserelin (sc 500 microg) was initiated on day 2 of menstruation. Ultrasound and hormonal tests were performed on days 1, 7, 11, 14, and weekly thereafter until pituitary suppression was achieved. RESULT(S): 48 patients underwent 51 cycles of IVF treatment. A functional cyst was detected in three cycles (5.8%) with baseline ultrasound scan and in 27 cycles (52.9%) on day 7 of buserelin administration. Patients who developed a cyst required a significantly longer time to achieve pituitary suppression (21 vs. 7 days), had a significantly lower FSH level at the time of initiation of gonadotropins, required more ampules of gonadotropin (45 vs. 41 ampules), developed less follicles (13 vs. 17.5), and had lower embryo quality. However, there were no differences in the implantation (23.5% vs. 17.2%) and pregnancy rates (37.2% vs. 29.2%) between two groups. CONCLUSION(S): Functional cysts prolong the period to achieving pituitary suppression, increase gonadotropin requirements, and decrease follicular recruitment and embryo quality. They have, however, no negative effect on pregnancy rates.

Adult↗

Laparoscopic treatment of polycystic ovaries with insulated needle cautery: a reappraisal.

OBJECTIVE: To evaluate the reproductive outcome and adhesion formation after a standardized laparoscopic treatment of polycystic ovary syndrome (PCOS) in clomiphene-resistant infertile women. DESIGN: Retrospective study. SETTING: University teaching hospital. PATIENT(S): One hundred twelve clomiphene-resistant anovulatory women with PCOS. INTERVENTION(S): Laparoscopic ovarian drilling using an insulated needle cautery. MAIN OUTCOME MEASURE(S): Ovulatory rate, pregnancy rate, and adhesion formation. RESULT(S): After surgery, ovulation occurred spontaneously in 73.2% of patients. The cumulative probability of conception at 12, 18, and 24 months after surgery was 54%, 68%, and 72%, respectively. With use of Cox's proportional hazards model, the effects of age, body mass index, and duration of infertility were evaluated. These factors were not associated with the pregnancy rate. Of 15 women who underwent a second-look laparoscopy, 11 women were found to be free of adhesions. Four women had periadnexal adhesions that were filmy, minimal, and found on the ovarian surface only. CONCLUSION(S): Laparoscopic ovarian drilling is an effective alternative treatment in clomiphene-resistant anovulatory women with PCOS. The use of an insulated needle cautery is associated with a minimal amount of adhesion formation.

Adult↗

Prospective randomized study of human chorionic gonadotrophin priming before immature oocyte retrieval from unstimulated women with polycystic ovarian syndrome.

The present study examined whether the rates of oocyte maturation, fertilization and development, as well as pregnancy rate could be improved by human chorionic gonadotrophin (HCG) priming 36 h before immature oocyte retrieval in patients with polycystic ovarian syndrome (PCOS). Immature oocyte retrieval was performed on day 10-14 of the cycles and patients were randomly allocated either to be primed with 10 000 IU of HCG before the retrieval, or not primed. Immature oocytes were cultured for 24-48 h in TC-199 medium with 20% (v/v) inactivated fetal bovine serum (FBS) supplemented with 75 mIU/ml follicle stimulating hormone (FSH) and luteinizing hormone (LH). Intracytoplasmic sperm injection (ICSI) was performed in all mature oocytes and the resulting embryos were transferred on day 2 or 3 after ICSI. A total of 17 patients underwent 24 completed treatment cycles. Thirteen cycles were primed with HCG and 11 other cycles were not primed. The mean number of oocytes retrieved was comparable in the two groups (7.8 +/- 3.9 versus 7.4 +/- 5.2). The percentage of oocytes achieving maturation at 48 h was significantly higher (P < 0.05) in the HCG-primed group (84.3%, 86/102) than in the non-HCG-primed group (69.1%, 56/81). Oocyte maturation was hastened in the HCG-primed group. Following 24 h of culture, 78.2 +/- 7.1% of oocytes were matured in the HCG-primed group compared with 4.9 +/- 2.5% of oocytes in the non-HCG-primed group (P < 0.001). There were no significant differences in the rates of oocyte fertilization and cleavage in these two groups. There were five clinical pregnancies (38.5%) in the HCG-primed group, and three pregnancies (27.3%) in the non-HCG-primed group.

Adult↗

The outcome of IVF-embryo transfer treatment in patients who develop three follicles or less.

Among 828 patients undergoing IVF-embryo transfer treatment, the implantation and pregnancy rates of patients who developed < or = 3 follicles were compared prospectively with those patients who had a normal response. Patients who developed 1 to 3 follicles during ovarian stimulation elected to proceed with oocyte collection, have intrauterine insemination if appropriate, or to have their cycle cancelled. In the group of patients who developed < or = 3 follicles and who were aged <40 years, despite a significantly lower number of oocytes collected [2 versus 7; median difference (MD) = 9; confidence interval (CI) = 7-11, and lower number of embryos developed and transferred (1 versus 3; MD = 2; CI = 1-2), no difference in either implantation rate [27.8 versus 20.4%; odds ratio (OR) = 1.58; CI = 0.46-4.54] or pregnancy rate (27.8 versus 36.7%; OR = 0.7; CI = 0.2-2.0) was noted when compared with similarly aged patients who developed >3 follicles. However, in patients aged >40 years who developed < or = 3 follicles, a moderate, albeit non-significant decrease in implantation rate (3.8 versus 7.8%; OR = 1.91; CI = 0.4-57.0) and pregnancy rate (4.2 versus 18.3%; OR = 1.92; CI = 0.38-57.0) was observed when compared with patients of a similar age who developed >3 follicles. Patients aged <40 years, unlike older patients, maintain good implantation and pregnancy rates despite a poor response to ovarian stimulation. This study indicates that for this group of women, continuation of IVF treatment is a better option than cancellation.

Adult↗

Fluorescence in-situ hybridization of sex chromosomes in spermatozoa and spare preimplantation embryos of a Klinefelter 46,XY/47,XXY male.

It has been suggested recently that 47,XXY germ cells are able to progress through meiosis to produce hyperhaploid spermatozoa. We report on a 46,XY/47,XXY Klinefelter patient whose spermatozoa were recovered from the ejaculate and used for intracytoplasmic sperm injection (ICSI). Fluorescence in-situ hybridization (FISH) analysis of the patient's spermatozoa and of spare preimplantation embryos with DNA probes specific for chromosomes X, Y and 18 revealed sex chromosome hyperploidy in 3.9% of the sperm nuclei analysed (2.23% XY18, 1.12% XX18, 0.56% YY18), while only three out of 10 spare embryos analysed were normal for chromosomes tested. The abnormalities included two diploid mosaic embryos with the majority of the blastomeres normal for the chromosomes tested, and five embryos with mostly abnormal blastomeres and chaotic chromosome X, Y and 18 patterns. None of the embryos analysed showed a XXY1818 or XXX1818 chromosome complement. The frequency of sex chromosome hyperploidy in the spermatozoa of the mosaic Klinefelter patient was higher than the mean reported for karyotypically normal males, supporting the hypothesis that 47,XXY germ cells are able to complete meiosis and produce aneuploid spermatozoa. However, most of the spermatozoa analysed were normal for sex chromosomes, and ICSI of the patient's spermatozoa did not result in a spare embryo with a uniform 47,XXY or 47,XXX chromosome complement. Instead, fertilization produced a high percentage of mosaic embryos with chaotic chromosome arrangements.

Adult↗

Translational control of viral gene expression in eukaryotes.

As obligate intracellular parasites, viruses rely exclusively on the translational machinery of the host cell for the synthesis of viral proteins. This relationship has imposed numerous challenges on both the infecting virus and the host cell. Importantly, viruses must compete with the endogenous transcripts of the host cell for the translation of viral mRNA. Eukaryotic viruses have thus evolved diverse mechanisms to ensure translational efficiency of viral mRNA above and beyond that of cellular mRNA. Mechanisms that facilitate the efficient and selective translation of viral mRNA may be inherent in the structure of the viral nucleic acid itself and can involve the recruitment and/or modification of specific host factors. These processes serve to redirect the translation apparatus to favor viral transcripts, and they often come at the expense of the host cell. Accordingly, eukaryotic cells have developed antiviral countermeasures to target the translational machinery and disrupt protein synthesis during the course of virus infection. Not to be outdone, many viruses have answered these countermeasures with their own mechanisms to disrupt cellular antiviral pathways, thereby ensuring the uncompromised translation of virion proteins. Here we review the varied and complex translational programs employed by eukaryotic viruses. We discuss how these translational strategies have been incorporated into the virus life cycle and examine how such programming contributes to the pathogenesis of the host cell.

3' Untranslated Regions↗