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Biomedical subjects

B H Yuen

Publications and source records attributed to B H Yuen.

At least 19 recordsLinked to original sources
PubMed2001

Intracytoplasmic sperm injection could minimize the incidence of prematurely condensed human sperm chromosomes.

OBJECTIVE: To compare the fertilization and prematurely condensed human sperm chromosomes (PCCs) rates between two intracytoplasmic sperm injection (ICSI) techniques. DESIGN: A retrospective study. SETTING: The data were obtained from the University of British Columbia in vitro fertilization (IVF) laboratory. PATIENT(S): ICSI cycles (n = 105) were performed for couples suffering from severe male-factor infertility and dysfunction of fertilization. INTERVENTION(S): Two types of ICSI techniques were used for ICSI procedures. MAIN OUTCOME MEASURE(S): Fertilization and pregnancy rates in group B using the improved ICSI technique were compared with those of group A using the standard ICSI technique. Unfertilized oocytes from the two groups were studied with cytogenetic methods. RESULT(S): Oocyte damage dropped from 14.8% in group A to 5.3% in group B. Normal fertilization for each group was 57.3% and 88.4%, respectively (P<.05). Pregnancy rate per egg retrieval was 15.6% in group A and 27.4% in group B (P<.05). PCCs occurred in 19.4% of unfertilized oocytes in group A and did not occur in group B. CONCLUSION(S): This study indicates that ICSI not only yields high fertilization rates, but also minimizes the incidence of PCCs. It may be directly related to two crucial steps (immobilization of sperm and aspiration of oocyte cytoplasm) used in ICSI procedures. This study also suggests that it is possible to overcome one cause of IVF failure resulting from the formation of PCCs by using the improved ICSI technique.

Chromosomes↗
PubMed2001

Cytogenetic investigation of fetuses and infants conceived through intracytoplasmic sperm injection.

OBJECTIVE: To determine the incidence of aneuploidy among fetuses and infants conceived through intracytoplasmic sperm injection (ICSI) in our clinic using umbilical cord blood samples. DESIGN: Follow-up study of the cytogenetic outcome of ICSI pregnancies. SETTING: University-based IVF clinic. PATIENT(S): Forty-six couples who underwent ICSI and conceived. INTERVENTION(S): Umbilical cord blood was taken after delivery of the infant for analysis. Samples of chorionic villi and chorion were taken for studies on the spontaneous abortuses. Amniocentesis was performed for couples that chose prenatal diagnosis. MAIN OUTCOME MEASURE(S): The cytogenetic chromosomal status of the pregnancy outcome. RESULT(S): Fifty pregnancies and 55 live births were recorded, with nine spontaneous abortions. Of 43 separate umbilical cord blood samples analyzed, 1 abnormality (2%) was found, 45, XX,+21. Nine births went through prenatal diagnosis alone, with four accepting both forms of analysis-no abnormalities were found. Origin of abnormality was established in two spontaneous abortion cases (45, XO and 45, XY,-21), and the maternal chromosome was lost in both cases. CONCLUSION(S): Using umbilical cord blood obtained after birth, we obtained karyotype results from 78% of the ICSI population in our clinic. Combined with results from five additional cases that underwent prenatal diagnosis but not umbilical cord blood sampling, a chromosomal result was obtained in 87% of our ICSI population. The use of umbilical cord blood for cytogenetic analysis substantially improves the ability to determine rates of chromosomal abnormalities in newborns produced via ICSI clinics.

Adult↗
PubMed2001

Maternal origin of monosomy 21 derived from ICSI.

With the worldwide diffusion of the intracytoplasmic sperm injection (ICSI) procedure in recent years, the issue of possible genetic risks of this new and powerful technique has attracted considerable attention. An important concern is whether ICSI facilitated the passage of genetic defects from spermatozoa to offspring. ICSI was performed with spermatozoa from a frozen-thawed sperm sample from a testicular sperm extraction (TESE) of a 38 year old man who suffered from azoospermia. His wife was 36 years old. The resulting pregnancy spontaneously aborted at 8 weeks gestation after embryo replacement. Cytogenetic investigation displayed monosomy 21. The paternal origin of the single chromosome 21 was determined by molecular analysis. The segregation error leading to loss of one chromosome 21 is likely to have occurred during oogenesis rather than as a direct consequence of ICSI. Nonetheless, monosomy 21 is extremely rare and it cannot be excluded that ICSI assisted the fertilization of an abnormal oocyte.

Abortion, Spontaneous↗
PubMed1998

A delayed-implantation-associated protein prevents resumption of DNA synthesis by the trophectoderm of delayed-implanting mouse blastocysts in vitro.

Objective of this study was to determine the ability of a delayed-implantation-associated protein (MW 170,000, DIAP170K) to inhibit DNA synthesis by mouse blastocysts. Mice were ovariectomized on day 3 of pregnancy and treated with daily injections with 1 mg progesterone till day 7 to induce delayed implantation. Blastocysts were collected on day 8 with or without a single injection of 25 ng estradiol-17 beta on day 7 that activates blastocyst metabolisms (activated blastocysts and delayed-implanting blastocysts respectively). DNA synthesis was determined by measuring [3H]thymidine incorporation by blastocysts. DIAP170K at 10 micrograms/m/ suppressed resumption of DNA synthesis by delayed-implanting blastocysts and suppression was maximal at 50 micrograms/m/. However, DIAP170K did not affect DNA synthesis by blastocysts obtained on day 5 of pregnancy (normal blastocysts) and activated blastocysts. Resumption of DNA synthesis in the inner cell mass (ICM) and trophectoderm from delayed-implanting blastocysts was then separately assessed. DNA synthesis resumed in the trophectoderm of intact blastocysts during 24-hr culture but not in the trophectoderm cultured apart from the ICM. DIAP170K inhibited the resumption of DNA synthesis by the trophectoderm of intact delayed-implanting blastocysts but did not affect DNA synthesis by the ICM. In conclusion, DIAP170K inhibits resumption of DNA synthesis by trophectoderm of delayed-implanting blastocysts. This action of DIAP170K may play a central role in maintaining, but not achieving, dormancy of DNA synthesis by delayed-implanting blastocysts in mice.

Animals↗
PubMed1998

Regulation of prostaglandin F2alpha-receptor mRNA in human granulosa-luteal cells by human chorionic gonadotrophin and prostaglandin F2alpha.

This study examined the effects of prostaglandin F2alpha (PGF2alpha) and human chorionic gonadotropin (hCG) on the levels of PGF2alpha-receptor (PGF2alpha-R) mRNA and steroidogenesis, in the human granulosa luteal cell (hGLC). Human GLCs collected from patients undergoing in vitro fertilization, were cultured for 24 h, after which cells were exposed to culture media containing either vehicle, hCG (1IU/mL), or hCG plus PGF2alpha (10(-11)-10(-6) M), for a further 24 h. Following the treatment period, media were collected and stored (-20 degrees C) until assayed for progesterone and 17beta-estradiol (estradiol). Immediately following the treatment period, cells were extracted for total RNA. Transcripts for PGF2alpha-R were detected by PCR with two different sets of oligonucleotide primers based on the published human and rat PGF2alpha-R sequences. PCR products were confirmed to be those of PGF2alpha-R by size and by Southern blot hybridization with an internal oligo nucleotide probe. All experiments were performed a minimum of three times, on cells from a minimum of three separate patients. Prostaglandin F2alpha-R mRNA was significantly downregulated, whereas progesterone and estradiol production were significantly stimulated by hCG. Conversely, both low (10(-11)M) and high concentrations (10(-6) M) of PGF2alpha restored PGF2alpha-R mRNA levels to those of the controls, whereas steroidogenesis was significantly inhibited by these conditions. At a concentration of 10(-9)M PGF2alpha-R mRNA was barely detectable. Progesterone and estradiol production were inversely related to PGF2alpha-R levels, since hCG-stimulated progesterone and estradiol production were completely restored in the presence of 10(-9) M PGF2alpha. Messenger RNA levels for the housekeeping gene beta-actin were unaltered by the above treatments. In conclusion, in the human granulosa luteal cell, PGF2alpha-R mRNA levels are inversely related to hCG-stimulated steroidogenesis (which was biphasic in nature). Moreover, in the presence of hCG, PGF2alpha downregulates its receptor mRNA, thus providing a potential form of negative feedback on its own actions, which may be important in rescuing the corpus luteum from PGF2alpha-mediated luteolysis should pregnancy occur.

Actins↗
PubMed1998

Stepwise activation of the gonadotropic signal transduction pathway, and the ability of prostaglandin F2alpha to inhibit this activated pathway.

Through selective activation of the gonadotropic signal transduction pathway, we have determined the probable site of the antigonadotropic effects of prostaglandin F2alpha (PGF2alpha) in the human granulosa-luteal cell (hGLC). The gonadotropic signal transduction pathway was activated at the level of the receptor (luteinizing hormone and beta-adrenergic), stimulatory G protein (Gs), adenylate cyclase (AC), and protein kinase A (PKA) by human chorionic gonadotropin (hCG) and isoproterenol (Iso), cholera toxin (CTX), forskolin, and dibutryl cAMP (Db cAMP), respectively. Concomitantly, the ability of PGF2alpha to inhibit progesterone production in response to the activation of this cascade at these different levels was examined. hGLCs were obtained from in vitro fertilization patients and were precultured for 8 d in Medium 199 supplemented with fetal bovine serum (M199; 10% FBS). Following the preculture period, cells were treated with either vehicle or one of the above activators of the gonadotropic pathway, either in the absence or presence of PGF2alpha (in M199; No FBS). Following the treatment period, media were collected and assayed for progesterone by RIA. Prostaglandin F2alpha (10(-6) M) significantly inhibited hCG (1 IU/mL), Iso (10(-5) M), CTX (1 microg/mL), and forskolin- (10(-5) M) stimulated progesterone production. Conversely, PGF2alpha did not inhibit progesterone production stimulated by a saturating concentration of Db cAMP (10(-6) M). The ability of PGF2alpha to inhibit hCG- or CTX-stimulated progesterone production was attenuated by pertussis toxin (PTX; 50 ng/mL). In conclusion, through a pertussis toxin-sensitive G protein, PGF2alpha inhibits progesterone production at a level below AC, and above the activation of PKA by cAMP.

Adenylyl Cyclases↗
PubMed1997

Investigation of effects of pregnant mare serum gonadotropin (PMSG) on the chromosomal complement of CD-1 mouse embryos.

PURPOSE: The objective of this study was to examine the effect of superovulatory doses of gonadotropins on the frequency of chromosomal abnormalities of mouse embryos. METHODS: Chromosome analysis of 8- to 16-cell stage mouse embryos and zygotes was performed by a cytogenetic method. RESULTS: There was no significant effect of the pregnant mare serum gonadotropin (PMSG) dose on the level of aneuploidy and structural abnormalities from 8- to 16-cell-stage embryos among superovulated groups. However, a simple dose-response relationship between the PMSG dose and the incidence of polyploidy was observed, with the level of polyploidy rising from 2.9% with 10 i.u. PMSG to 10.5% with 15 i.u. PMSG. In zygote stage, the proportion of polyploid embryos also increased as the dose increased, from 1.9% in 5 i.u. to 6.7% in 15 i.u. PMSG. It was observed that the extra chromosomal set in polyploidy embryos originated by both fertilization of a diploid oocyte and dispermy. CONCLUSIONS: These results indicate a dose-response relationship between the PMSG dose and the incidence of polyploidy in the CD-1 mouse. Both a disturbance at maturation division and an error at fertilization were the cause of polyploidy.

Aneuploidy↗
PubMed1997

Mechanisms involved in ATP-evoked Ca2+ oscillations in isolated human granulosa-luteal cells.

Using single-cell microfluorimetry, we have shown that ATP evoked repetitive Ca2+ oscillations in intact Fura-2 loaded human granulosa-luteal cells (hG/LCs) in the absence of extracellular Ca2+. Sustained increases in [Ca2+]i required extracellular Ca2+ and ATP depleted stores were refreshed by brief (2 min) incubation with external Ca2+. Basal [Ca2+]i was unaffected by caffeine (1 mM), but 20 mM caffeine inhibited ATP-evoked Ca2+ release in the absence of external Ca2+. Thimerosal (10 microM) evoked repetitive Ca2+ spikes, under Ca(2+)-free conditions, which fused to form an elevated plateau when external Ca2+ was replaced. Thimerosal-induced changes in [Ca2+]i were reversibly inhibited by the thiol reducing agent dithiothreitol (1 mM). The periodicity and amplitude of the [Ca2+]i oscillations produced by thimerosal and ATP differ. ATP- or thimerosal-evoked changes in [Ca2+]i were unaffected by dantrolene sodium (10 microM). The Ca(2+)-ATPase inhibitor thapsigargin (1 microM) increased [Ca2+]i and attenuated subsequent ATP-evoked changes in [Ca2+]i. We conclude that ATP stimulates an oscillatory release of Ca2+ from InsP3-sensitive stores in hG/LCs.

Adenosine Triphosphate↗
PubMed1997

A somatostatin analogue decreases embryonic loss following superovulation in rats by normalizing insulin-like growth factor-I action in the uterus.

This study was designed to determine whether the somatostatin analogue, octreotide, could prevent embryonic loss by normalizing increased uterine insulin-like growth factor-I (IGF-I) action related to hyperoestrogenaemia following superovulation. Superovulated immature and oestradiol-17beta-treated adult rats were infused with 100 or 300 microg/ml of octreotide respectively, or injected daily with 1 or 10 microg of octreotide from day 1 to day 3 of pregnancy. On day 3, embryos were collected from the oviducts and uteri. Uterine luminal fluid was subjected to embryo culture. The amounts of uterine IGF-I and IGF binding proteins (IGFBP) were determined by radioimmunoassay and ligand binding assay respectively. Octreotide infusion normalized uterine IGF-I action following superovulatory and oestradiol-17beta treatment, by reducing IGF-I concentrations and increasing IGFBP concentrations. Octreotide infusion increased the number of normal embryos by 2.7-fold and 1.7-fold in superovulated and oestradiol-17beta-treated rats respectively, and reversed the detrimental effects of uterine luminal fluid on embryonic development caused by superovulatory and oestradiol-17beta treatment. Daily injections with octreotide had similar but reduced effects in all parameters examined in both treatment groups. In conclusion, octreotide may reduce embryonic loss, at least in part, by normalizing IGF-I action following superovulation.

Animals↗
PubMed1997

Interaction of prostaglandin F2alpha and gonadotropin-releasing hormone on progesterone and estradiol production in human granulosa-luteal cells.

This study examined the effects of prostaglandin-F2alpha (PGF2alpha), GnRH, and their interactions on steroidogenesis in human granulosa-luteal cells (GLCs). Human GLCs collected from in vitro fertilization patients were cultured for one or eight days, followed by a 24-h treatment period, after which media were collected and radioimmunoassayed for progesterone and estradiol. In the first experiment, GLCs were treated with vehicle, PGF2alpha (10(-9) M), GnRH (10(-6) M), or PGF2alpha plus GnRH, with or without hCG (1 IU/ml). Neither PGF2alpha nor GnRH alone had a significant effect; however, the combination of PGF2alpha plus GnRH significantly stimulated steroidogenesis. Similarly, co-application enhanced the luteolytic effects of PGF2alpha. In a second experiment, PGF2alpha and GnRH concentration-response curves were crossed into a matrix of 49 separate treatments. Responses were plotted in three-dimensions and as two-dimensional "slices" that were analyzed statistically. In the presence of high concentrations of GnRH (10(-6) M), PGF2alpha stimulated progesterone production in a biphasic manner, as middle concentrations significantly stimulated (10(-9) M) whereas low and high concentrations did not. In the presence of middle concentrations of PGF2alpha (10(-9) M), GnRH significantly stimulated progesterone production in a linear concentration-dependent manner. Similar complexities were seen with respect to estradiol response. Thus, in the human GLC, GnRH potentiates the luteolytic effects of PGF2alpha, while it acts as a permissive factor for the luteotropic effects. Furthermore, we have revealed the complex interaction of these hormones using a three-dimensional experimental design.

Cells, Cultured↗
PubMed1997

Role for insulin-like growth factor I in the regulation of electrolyte composition of uterine luminal fluid.

A potential role for insulin-like growth factor I (IGF-I) in the regulation of the uterine electrolyte environment was studied in conjunction with hyperoestrogenaemia caused by superovulation. Uterine luminal fluid from immature rats treated with 4 (control), 10, 20 and 40 i.u. (superovulation) pregnant mares' serum gonadotrophin (PMSG, day -2) and the electrolyte composition was determined on day 3 of pregnancy. Superovulation increased total cation content in uterine flushes by more than twofold, suggesting a comparable increase in the uterine luminal fluid volume. Percentages of K+ and HCO-3 content to total cations or anions increased by 27% and 16%, respectively, and those of Na+ and Cl- decreased by 26% and 15%, respectively, after superovulation. Daily injections with 1.0 micrograms or more oestradiol, from day 0 to day 2, in the 4 i.u. PMSG-primed immature rats caused similar changes in total cation content and electrolyte composition of uterine luminal fluid. Anti-IGF-I antibody infusion in the superovulated or oestradiol-treated immature rats restored the alterations in cation composition but had no effect on anion composition and total cation content. IGF-I was infused into adult rats to achieve increased IGF-I action observed after superovulation. IGF-I infusion altered electrolyte composition, as is observed after superovulation or oestradiol treatment, but had no effect on total cation content. In conclusion, hyperoestrogenaemia caused by superovulation may alter the uterine electrolyte environment for preimplantation embryonic development. IGF-I appears to play a central role in mediating this action of oestrogen.

Animals↗
PubMed1996

The role for the uterine insulin-like growth factor I in early embryonic loss after superovulation in the rat.

OBJECTIVES: To examine possible roles of the insulin-like growth factor (IGF) system in increased early embryonic loss after superovulation. DESIGN: Changes in the uterine IGF system were examined in superovulated rats. Insulin-like growth factor I (IGF-I) was infused to the right uterine horns to mimic enhanced IGF-I actions after superovulation. Uterine luminal fluids were collected after IGF-I infusions and embryos were cultured with uterine luminal fluids. MAIN OUTCOME MEASURES: Steroid hormones, IGF-I, IGF binding protein (IGFBP), and IGF-I receptor levels, developmental rate, and cell numbers of embryos. RESULTS: Elevated IGF-I levels and suppressed IGFBP levels were found from days 1 to 3 of pregnancy after superovulation. Uterine luminal fluids of the IGF-I infusion and superovulation groups impaired embryo development in vitro. Anti-IGF-I antibody infusions after superovulation reversed detrimental effects of superovulation. Dialysis of uterine luminal fluids of the IGF-I infusion and superovulation groups before culture improved embryo development. CONCLUSIONS: Enhanced IGF-I actions in the uterus after superovulation may be responsible for the increase of early embryonic loss. The detrimental factor for embryo development seems a small molecule and is likely a local product of the uterus in which IGF-I actions are enhanced.

Animals↗
PubMed1996

P2-purinoreceptor evoked changes in intracellular calcium oscillations in single isolated human granulosa-lutein cells.

In this study, we have demonstrated that P2-purinoreceptor agonists evoke oscillatory intracellular calcium ([Ca2+]i) responses in human granulosa-lutein cells (GLCs). Intracellular calcium was measured using microspectrofluorimetric techniques. ATP at concentrations of 1-100 microM increased [Ca2+]i, whereas neither adenosine nor AMP evoked changes in [Ca2+]i. The nonhydrolysable ATP analogue, ATP gamma S, also elevated [Ca2+]i with an efficacy similar to that of ATP, indicating that the changes in Ca2+ were not due to ATP hydrolysis, but that human GLCs possess functional P2-purinoreceptors. Uridine triphosphate (UTP) was equipotent to ATP at stimulating [Ca2+]i, and both ATP and UTP were consistently more effective at eliciting a response than ADP, suggesting that human GLCs possess the P2U class of purinergic receptors (ATP = UTP > > ADP > > AMP = adenosine). We have demonstrated that the purinergic agonist-induced changes in [Ca2+]i involve both Ca2+ influx and Ca2+ mobilization from cytosolic stores. Prolonged ATP treatment in Ca(2+)-free buffer (1 mM EGTA) still evokes transient oscillatory changes in [Ca2+]i in a pertussis toxin-insensitive manner. In Ca(2+)-containing conditions, the sustained phase of the response was generally unaffected by verapamil (10 microM), suggesting that influx is not occurring through voltage-dependent Ca(2+)-channels. These findings are consistent with the hypothesis that ATP and other P2-purinergic receptor agonists elicit changes in [Ca2+]i in human ovarian cells and that these events are initiated by the release of Ca2+ from cytosolic stores, and sustained by extracellular calcium ([Ca2+]e) influx. This is the first time that oscillatory patterns of [Ca2+]i have been reported in human GLCs.

Adenosine Triphosphate↗
PubMed1996

An improved technique for molecular cytogenetic analysis of human preimplantation embryos with fluorescence in situ hybridization.

OBJECTIVE: To develop a method for the cytogenetic evaluation of preimplantation embryos using nonradioactive centromeric probes for chromosomes 1, 16 and X. STUDY DESIGN: The embryos used for this study were either fragmented or polyploid embryos rejected from an in vitro fertilization program. Prior to in situ hybridization, the embryos were treated with 0.5% protease. After application of gradual fixation, conventional hybridization protocol was followed. RESULTS: Ten of 11 embryos showed hybridization signals suggesting that the success rate of in situ hybridization of human embryos is improved when a modified method of digesting the zona pellucida and gradual fixation with removal of the cytoplasm are used. CONCLUSION: The method described in this study demonstrates that the zona pellucida is the key to successful in situ hybridization of whole human embryos. When the zona pellucida is removed, penetration by a probe becomes possible.

Chromosome Aberrations↗
PubMed1995

The chromosome pattern of embryos derived from tripronuclear zygotes studied by cytogenetic analysis and fluorescence in situ hybridization.

OBJECTIVE: To detect the chromosomal complement of embryos, which developed from tripronuclear zygote, using nonradioactive centromeric probes. DESIGN: The chromosome pattern of embryos developing from tripronuclear zygote, studied by fluorescence in situ hybridization, was compared with that of embryos studied by standard cytogenetic methods. SETTING: These embryos were obtained from superovulated patients undergoing IVF treatment. RESULTS: We have attempted to examine the chromosomal complement of 72 embryos derived from tripronuclear zygotes using both traditional cytogenetic analysis and fluorescence in situ hybridization. Of these 72 embryos, 22 were analyzed with fluorescence in situ hybridization and 50 were analyzed with traditional cytogenetic analysis. For fluorescence in situ hybridization analysis, probes specific for the centromeric regions of chromosomes 1, 16, and X were used, with results being obtained from 18 embryos. One embryo was haploid (5.6%), five were triploid (27.8%), and one was hexaploid (5.6%). Eleven (61%) embryos were mosaic. Traditional cytogenetic analysis could be performed on 25 of 50 embryos. Five (20%) were haploid, one (4%) was diploid, seven (28%) were triploid, one (4%) were tetraploid, and two were hexaploid. Nine (36%) were mosaic. CONCLUSION: These findings indicate that not all tripronuclear human zygotes develop into triploid embryos. This study also demonstrates the usefulness of fluorescence in situ hybridization for preimplantation diagnosis and screening for chromosome abnormalities.

Cell Nucleus↗
PubMed1994

ProMACE day 1/MOPP day 8 chemotherapy for prolymphocytic leukemia: a case report of prolonged survival.

The treatment result of a case of de novo B-cell prolymphocytic leukemia (B-PLL) is described. The diagnosis was established with histologic, ultrastructural and immunologic studies. The patient was treated with chemotherapy using a total of seven cycles of ProMACE Day 1/MOPP Day 8 lymphoma regimen. Complete remission was achieved after 5 cycles of chemotherapy. The patient remains disease free after a 7-year follow up. This is the first case of PLL being treated with such a regimen and the only case reported achieved such prolonged survival. Results of other treatment modalities are reviewed.

Aged↗