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Biomedical subjects

M Dhont

Publications and source records attributed to M Dhont.

At least 19 recordsLinked to original sources
PubMed1999

Fertilization abnormalities and pronucleus size asynchrony after intracytoplasmic sperm injection are related to oocyte postmaturity.

OBJECTIVE: To study the effect of delayed intracytoplasmic sperm injection (ICSI) on the fertilization and cleavage of human in vitro matured (IVM) oocytes. DESIGN: Prospective experimental study. SETTING: Academic hospital-based fertility center. PATIENT(S): The experimental group consisted of 73 spare germinal vesicle-stage oocytes from 25 patients. The control group consisted of sibling in vivo matured oocytes from the same patients that were subjected to ICSI in the clinical program. INTERVENTION(S): Equal numbers of sibling IVM oocytes were subjected to ICSI either soon after maturation (30 hours, group 1) or after a 6-hour delay (36 hours, group 2). In a subsequent set of experiments, spermatozoa were labeled with a fluorescent mitochondria-specific vital dye and injected into 17 IVM oocytes that were intentionally aged by 6-8 hours. The resultant zygotes were fixed. MAIN OUTCOME MEASURE(S): Incidence of fertilization and cleavage, numbers and mean diameters of pronuclei, and incidence of zygotes with significant pronucleus size asynchrony. Identification of the male pronucleus by its proximity to the fluorescent sperm midpiece remnant. RESULT(S): Group 2 had significantly lower rates of normal fertilization (60%) than the control group (82.9%) and significantly lower cleavage rates (46.7%) than both group 1 (85%) and the control group (98.1%). The incidence of oocytes that developed one pronucleus and pronucleus size asynchrony was significantly higher in group 2 (32% and 40%, respectively) than in group 1 (4% and 5%, respectively) and in the control group (4.1% and 4.4%, respectively). All the zygotes with significant pronucleus size asynchrony that developed after delayed ICSI with labeled spermatozoa showed proximity of the fluorescent sperm midpiece remnant to the smaller pronucleus. CONCLUSION(S): For IVM oocytes, the incidence of one pronucleus, pronucleus size asynchrony (possibly related to a smaller male pronucleus), and cleavage failure increase when ICSI is delayed after maturation. Thus, the timing of ICSI is critical for optimum fertilization of IVM oocytes.

Cell Nucleus↗
PubMed1999

Effect of post-ovulatory age and calcium in the injection medium on the male pronucleus formation and metaphase entry following injection of human spermatozoa into golden hamster oocytes.

The occurrence of parthenogenetic activation is a major hurdle in obtaining sperm chromosome metaphases after heterospecific intracytoplasmic sperm injection (ICSI) of golden hamster oocytes with human spermatozoa. We addressed two potential contributors to parthenogenetic activation namely, post-ovulatory age of the oocyte and Ca2+ content of the injection medium. In serial experiments, hamster oocytes were retrieved at 11.5, 13, 16 and 21 h after the ovulatory dose of human chorionic gonadotrophin (HCG) and microinjected with human spermatozoa suspended alternately in a regular (1.9 mM Ca2+) or a Ca2+-free medium. A progressive decrease in the rates of male pronucleus (MPN) formation and metaphase entry and increase in the rates of parthenogenetic activation without male pronucleus occurred with increasing post-ovulatory age. The favourable influence of Ca2+-free injection medium on the mean rates of MPN and metaphase entry was restricted to the relatively older oocytes (MPN 16 h: 49.5 versus 32.3%, P< 0.008; 21 h: 22.2 versus 11.1%, P< 0.001; metaphase entry 16 h: 36.8 versus 25.1%, P< 0.02; 21 h: 13.3 versus 5.2%, P< 0.01 in the Ca2+-free and regular groups respectively). Our data confirm the increased activation sensitivity with post-ovulatory ageing and its adverse influence on the MPN formation and metaphase entry after heterospecific ICSI of hamster oocytes.

Animals↗
PubMed1999

Presence and dynamic redistribution of type I inositol 1,4,5-trisphosphate receptors in human oocytes and embryos during in-vitro maturation, fertilization and early cleavage divisions.

We studied the presence and distribution of the intracellular calcium channel regulating type I inositol 1,4,5-trisphosphate receptors (IP3R) in human immature and mature oocytes, pronuclear zygotes and cleaved embryos using a specific antibody. Two approaches were used: (i) fluorescence immunocytochemistry using a confocal laser scanning microscope (CLSM) and (ii) Western blotting. With confocal microscopy, the receptors were found in the oocytes, fertilized zygotes as well as cleaved embryos at all stages studied. The pattern and distribution of the receptor staining in the oocytes changed gradually from a diffuse granular patchy one at the germinal vesicle (GV) stage to a reticular and predominantly peripheral one through the metaphase I and metaphase II (MII) stages. After fertilization, the distribution changed gradually to both, peripheral and central in the zygotes and early 2-4-cell embryos and predominantly perinuclear in the 6-8-cell embryos. Furthermore, an overall increase in the staining intensity was observed from GV to MII stage oocytes and from zygotes to 6-8-cell embryos. We also studied the spatial distribution of the receptor in detail by constructing three-dimensional images from the serial optical sections obtained on the CLSM. Peculiar peripheral aggregates of receptor clusters were noted in the MII stage oocytes, zygotes and some blastomeres from early cleaved embryos. Finally, Western blots performed on the extracts of 72 in-vitro matured oocytes and 50 spare cleavage stage embryos showed positive bands at approximately 260 kDa. These findings coincide with and thus possibly represent the dynamic changes occurring in the cellular Ca2+ release systems through oocyte maturation, fertilization and early embryogenesis. Thus, type I IP3R are likely to play a role during these stages of early development in the human.

Animals↗
PubMed1999

GyneFix-LNG: preliminary clinical experience with a copper and levonorgestrel-releasing intrauterine system.

A novel intrauterine contraceptive drug delivery system derived from the conventional GyneFix intrauterine implant system is described and the preliminary results in 22 women are discussed. The first objective of the development of the GyneFix-levonorgestrel system was to reduce menstrual bleeding, whether or not related to the effect of copper, by combining a shortened version of the standard GyneFix implant, having a copper surface area of 200 mm2, with a system for the sustained intrauterine delivery of levonorgestrel. The results of this initial observational study indicate that the GyneFix-levonorgestrel system, apart from being well tolerated, is safe and effective. The levonorgestrel component appears to have a beneficial effect on the amount of bleeding. A study on menstrual blood loss will be carried out to substantiate this assumption.

Adolescent↗
PubMed1999

GyneFIX. The frameless intrauterine contraceptive implant--an update for interval, emergency and postabortal contraception.

This article reviews the clinical experience with the GyneFix intrauterine implant system for interval, emergency and post-abortal contraception. The relatively high rate of unintended pregnancies and abortions in the world signifies that greater access to contraception is necessary. Unwanted pregnancies and abortions could be avoided by widening the range of effective and acceptable contraceptive methods for use in situations where current methods are far from optimal. High effectiveness, protection against sexual transmitted infections, long duration of action, reversibility and safety are some of the most important attributes of contraceptives valued by women. The development of the frameless intrauterine device is a response to the need to develop contraceptives with high user continuation rate. GyneFix has the lowest failure rate of all copper IUDs currently available. Its performance is further optimised by the atraumatic frameless design which minimises the side effects and discomfort experienced with conventional IUDs. GyneFix could, therefore, be a useful new contraceptive option in looking at ways to reduce the number of unwanted pregnacies and induced abortions.

Abortion, Induced↗
PubMed1998

Management of transient ovarian failure: pregnancy after in vitro fertilization and intracytoplasmic sperm injection--a case report.

PURPOSE: The case history of a 36-year-old patient with transient ovarian failure, presumably induced by previous ovarian surgery and a recent pelvic inflammatory disease, is described. METHODS: During several months, the patient underwent transvaginal ultrasound and hormonal follow-up. Ovulation was triggered by hCG in a cycle in which spontaneous follicular ripening had occurred. Transvaginal puncture of the single follicle was performed for in vitro fertilization. RESULTS: One oocyte was retrieved and fertilized by intracytoplasmic sperm injection, giving rise to a single good-quality embryo. A singleton pregnancy, which ended in the birth of a healthy daughter, was established. CONCLUSIONS: This case demonstrates that it is worthwhile to monitor patients with transient ovarian failure closely, and if other infertility factors are present, IVF of one oocyte may be considered.

Adult↗
PubMed1998

Prevention of severe ovarian hyperstimulation by coasting.

OBJECTIVE: To evaluate the efficiency of withholding gonadotropins and deferring the administration of hCG until E2 levels start dropping (coasting) in the prevention of ovarian hyperstimulation syndrome (OHSS) in a high-risk population. DESIGN: Retrospective case-control study. SETTING: In vitro fertilization program at a university center. PATIENT(S): The case group consisted of 120 women undergoing ovarian stimulation for IVF who were considered to be at risk for ovarian hyperstimulation (serum E2 levels >2,500 pg/mL or >20 follicles at the time of hCG administration). INTERVENTION(S): Gonadotropin administration was withheld when serum E2 levels exceeded 2,500 pg/mL, and hCG administration was delayed until E2 levels dropped below 2,500 pg/mL. Outcomes were compared with those from 120 matched patients in whom serum E2 levels and the number of follicles at the time of hCG administration were comparable to those at the beginning of coasting (control group). MAIN OUTCOME MEASURE(S): Incidence of moderate and severe OHSS. The number of oocytes retrieved and pregnancy rate (PR) were compared in both groups. RESULT(S): Coasting decreased the incidence of moderate and severe OHSS. The odds ratio of severe OHSS in the coasting group was 0.11 (95% confidence interval 0.01-0.86). Although the number of oocytes was significantly lower in the coasting group (19.7 +/- 0.6 versus 22.1 +/- 0.6), coasting did not affect the PR (37.5% versus 36.7%). CONCLUSION(S): Our study indicates that coasting is an efficient method for reducing the incidence and severity of OHSS without compromising the PR.

Adult↗
PubMed1998

Fluorescent in-situ hybridization on human embryos showing cleavage arrest after freezing and thawing.

Our current freezing-thawing policy is to transfer only embryos that cleave further in the 24 h following thawing. The purpose of our study was to investigate the incidence of numerical abnormalities for chromosomes X, Y and 1 in blastomeres of human preimplantation embryos that survived cryopreservation but did not cleave further after thawing. A total of 63 embryos surviving a freezing-thawing cycle but not cleaving further within 24 h after thawing were screened. Of the 63 screened embryos that showed cleavage arrest 24 h after thawing, 56 embryos (88.9%) remained arrested 48 h after thawing and slightly more than half of these (29/56; 51.8%) showed further deterioration in morphological quality. Seven embryos (11.1%) showed signs of further cleavage; five embryos showed additional cleavage of one blastomere and two developed a blastocoelic cavity. Fluorescent in-situ hybridization (FISH) with three specific probes for simultaneous detection of chromosomes X, Y and 1 was performed and was successful in 60 out of 63 embryos. Of these successfully labelled embryos, 26 (43.3%) were in the diploid range: 12 (20%) were uniformly diploid for the chromosomes X, Y and 1; three embryos showed aneuploidy in all their blastomeres (two were XXY-karyotype and one was monosomy 1) and in 11 embryos nondisjunction was detected. Thirteen embryos were categorized as being either haploid, triploid, tetraploid or hexaploid. Nine embryos were classified as mosaic and 12 as being highly abnormal or chaotic. These preliminary results suggest that a large proportion of embryos that do not cleave further after freezing and thawing carry chromosomal aberrations. This finding supports our policy of not transferring cryopreserved embryos which do not cleave further 24 h following thawing.

Aneuploidy↗
PubMed1998

Embryos cultured in vitro with multinucleated blastomeres have poor implantation potential in human in-vitro fertilization and intracytoplasmic sperm injection.

The aim of the present study was to investigate pregnancy rates ensuing from transfer of embryos with multinucleated blastomeres. In our in-vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI) programme, 1735 embryo transfers were performed from January 1, 1995 to August 31, 1996. In 136 of these transfers at least one embryo with one or more multinucleated blastomeres was present per transfer (study group). For each of these 136 transfers, two matched controls with transfer of exclusively mononucleated embryos were selected (control group). Matching was carried out according to age, method of fertilization (IVF or ICSI), number of transferred embryos and quality score of transferred embryos. In the study group, there were eight transfers of exclusively multinucleated embryos from which one pregnancy ensued and 128 transfers in which multinucleated and mononucleated embryos were transferred together leading to 23 pregnancies. The overall clinical pregnancy rate per transfer was 16.9% in the study group versus 28.7% in the control group (P = 0.01). The ongoing pregnancy rate per transfer was 13.2% in the study group versus 23.2% in the control group (P = 0.03). The implantation rate per transferred embryo was 6.0% in the study group versus 11.3% in the control group (P = 0.003). This study shows that embryos with one or more multinucleated blastomeres have a poorer implantation potential than embryos with mononucleated blastomeres. Transfer of embryos with multinucleated blastomeres should hence only be considered when insufficient numbers of embryos with only mononucleated blastomeres are present.

Adult↗
PubMed1998

Chromatin decondensation, pronucleus formation, metaphase entry and chromosome complements of human spermatozoa after intracytoplasmic sperm injection into hamster oocytes.

Obtaining karyotypes from human spermatozoa after microinjection into Syrian golden hamster oocytes is difficult and the hitherto reported results are unsatisfactory. This may be related to the injection and culture technique or to the high susceptibility of the hamster oocytes to undergo parthenogenetic activation or both. Therefore, we investigated the hamster oocyte-human sperm microinjection model using the following two approaches: (i) application of contemporary techniques for injection (touching the sperm tail) and culture (hamster embryo culture medium, HECM-3, 10% CO2) and (ii) omission of Ca2+ from the injection medium. Thus, in the first series of experiments, 252 hamster oocytes were injected with human spermatozoa. Among the 219 (87%) oocytes that survived the injection procedure, the mean percentages of male pronucleus formation [two pronuclei (2PN), two polar bodies (PB)], mitotic metaphase entry and sperm chromosome spreads were 41.4, 27.8 and 18.2% respectively. Analysis of the oocytes which failed to develop the male pronucleus following injection revealed that most of them had developed only the hamster female PN while the sperm nuclei were either intact or swollen (partially decondensed), indicating that failure of oocyte activation was not the likely reason for the failure of male PN formation in these oocytes. In the next series of experiments, sibling oocytes were alternately injected with spermatozoa suspended either in the regular (1.9 mM Ca2+) or Ca2+-free injection medium (experiment set 2, n=278). A significant improvement was noted in the mean percentages of oocytes with 2PN, 2PB, metaphase entry and sperm chromosome spreads in the Ca2+-free group versus the regular group (2PN, 2PB: 51 versus 36.6%, metaphase entry: 36.3 versus 26.9% and sperm chromosome spreads: 28 versus 20.4%; all P < 0.04). Thus, parthenogenetic activation appears to be one of the contributing factors for the failure of male PN formation after heterospecific hamster ICSI. From these experiments it can be concluded that application of the advanced injection and culture techniques and omission of Ca2+ from the injection medium are promising for the routine application of the hamster oocyte microinjection for karyotyping of human spermatozoa with poor fertilizing capacity.

Animals↗
PubMed1998

In-vitro maturation of human germinal vesicle stage oocytes: role of cumulus cells and epidermal growth factor in the culture medium.

In-vitro maturation (IVM) of oocytes is a promising technique to reduce the costs and avert the side-effects of gonadotrophin stimulation for in-vitro fertilization (IVF). The pregnancy rates from oocytes matured in vitro are much lower than those of in-vivo stimulation cycles indicating that optimization of IVM remains a challenge. Therefore, we investigated the effect of supplementation of the medium with gonadotrophins, oestradiol and epidermal growth factor (EGF) and the effect of retaining or removing the cumulus cells on nuclear and cytoplasmic maturation of immature oocytes. Human germinal vesicle (GV) oocytes obtained after gonadotrophin stimulation for intracytoplasmic sperm injection (ICSI) were cultured in a complex defined medium either supplemented with gonadotrophins, oestradiol and physiological concentrations of EGF (2 ng/ml) or gonadotrophins and oestradiol alone. The cumulus cells were either removed or kept intact. In GV stage oocytes cultured without cumulus (group I) significantly more oocytes reached the metaphase II (MII) stage at 30 h in media supplemented with EGF (64.3 versus 33.9%, P < 0.003). For oocytes cultured with intact cumulus (group II), more oocytes reached MII at 30 h than in group I, but there was no difference in medium with or without EGF supplementation (81.8 and 79.8% respectively). Cytoplasmic maturation of MII oocytes was judged from their capability to activate and fertilize after ICSI. In group I, the rates of activation and normal fertilization were similar. However, in group II, significantly more oocytes underwent normal fertilization in the EGF-supplemented than the unsupplemented group (71.7 versus 45.6%, P < 0.05). The cleavage rates of the fertilized oocytes were similar in the sibling oocyte subgroups cultured with or without EGF supplementation, but the overall cleavage rates were higher in cumulus-intact compared to cumulus-denuded oocytes (88.9 versus 47.8%, P < 0.001). Thus, supplementation of the maturation medium with EGF and maintenance of the cumulus during culture improve the nuclear and cytoplasmic maturation of human oocytes in vitro.

Adult↗
PubMed1998

Fertilization, pregnancy and embryo implantation rates after ICSI with fresh or frozen-thawed testicular spermatozoa.

This study aimed to determine whether fertilization and implantation rates after intracytoplasmic sperm injection (ICSI) with fresh or frozen-thawed testicular spermatozoa were comparable. Between 1 January 1996 and 31 December 1996, 65 ICSI cycles with testicular spermatozoa and 35 cycles with frozen-thawed testicular spermatozoa were carried out. In 50 out of 65 ICSI cycles, testicular spermatozoa could be retrieved and in 34 out of 35 cycles carried out with frozen-thawed testicular spermatozoa, motile spermatozoa could be recovered. The fertilization rate after ICSI with frozen-thawed testicular spermatozoa was significantly lower (71.1%; P < or = 0.008) than with fresh testicular spermatozoa (79.3%). The pregnancy rate was similar for both groups (38.2 and 26.5 %). The implantation rate per transferred embryo, however, was significantly lower in the frozen-thawed rather than in the fresh testicular sperm group (9.1 versus 24.6%; P = 0.001). The live birth rate per transferred embryo was also higher in the group in which fresh testicular spermatozoa were used (18.8 versus 7.9% P = 0.043). This retrospective study shows that is possible to achieve a high fertilization rate after ICSI with both fresh and frozen-thawed testicular spermatozoa but implantation and live birth rates per transferred embryo, however, are significantly lower after ICSI with frozen-thawed than with fresh testicular spermatozoa.

Cryopreservation↗
PubMed1997

Fertilization and pregnancy after assisted oocyte activation and intracytoplasmic sperm injection in a case of round-headed sperm associated with deficient oocyte activation capacity.

OBJECTIVE: To investigate a method of assisted activation of human oocytes for the treatment of infertility resulting from globozoospermia associated with deficient oocyte activation capacity. DESIGN: The mouse oocyte activation test was used to analyze the oocyte activation capacity of the sperm cells of a patient with globozoospermia. Fresh donor human oocytes were used for determining the most appropriate procedure for oocyte activation. SETTING: Infertility Center, University Hospital of Ghent. PATIENT(S): A couple with infertility resulting from globozoospermia. INTERVENTION(S): Intracytoplasmic sperm injection, assisted oocyte activation, and embryo transfer. MAIN OUTCOME MEASURE(S): Oocyte activation and fertilization rates, implantation, and pregnancy. RESULT(S): Deficiency in oocyte activation capacity was found in the sperm of a patient with globozoospermia. This deficiency was proven by the mouse oocyte activation test and was confirmed further by lack of activation of human oocytes after simple sperm injection. Only human oocytes that were injected with sperm and subjected to calcium chloride and ionophore treatment underwent activation. Transfer of embryos obtained by this procedure of assisted oocyte activation resulted in an ongoing pregnancy. CONCLUSION(S): Assisted oocyte activation of human oocytes is useful when globozoospermia is associated with absence of oocyte activation capacity in the sperm. These cases can be identified by the mouse oocyte activation test.

Adult↗
PubMed1997

Perinatal outcome of pregnancies after assisted reproduction: a case-control study.

PURPOSE: A matched case-control study of all pregnancies obtained after either IVF or ICSI was conducted to investigate the perinatal outcome. METHODS: Three hundred eleven singleton and 115 twin pregnancies obtained after assisted reproduction were studied. Controls were selected from a regional register and were matched for maternal age, parity, singleton or twin pregnancy, and date of delivery. RESULTS: No significant difference was observed for gestational age at delivery, birth weight, incidence of congenital anomalies, and incidence of perinatal mortality between ART (singleton and twin) pregnancies and spontaneous controls. ART twin pregnancies showed a higher incidence of preterm deliveries than control pregnancies (52 vs 42%; P < 0.05) and needed more neonatal intensive care (47 vs 26%; P < 0.05). CONCLUSIONS: From this case-control study it is concluded that the perinatal outcome of ART singleton pregnancies is not different from that in matched controls. ART twin pregnancies showed a higher incidence of preterm deliveries than control pregnancies and needed more neonatal intensive care.

Adult↗