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M Dhont

Publications and source records attributed to M Dhont.

At least 91 records · Page 5Linked to original sources
PubMed1996

Transport intracytoplasmic sperm injection (ICSI): a cost-effective alternative.

PURPOSE: Transport in vitro fertilization (IVF) programs are operational in a lot of countries and especially popular in The Netherlands, where IVF activities are strictly regulated. Since the introduction of intracytoplasmic sperm injection (ICSI) in the IVF laboratory, many laboratories are now setting up this new technique, which necessitates major investments in terms of infrastructure and specialized personnel. METHODS: We present a cost effective alternative, consisting of patient selection, preparation, and oocyte retrieval at one center and transport of oocytes to a second center, where the ICSI procedure and embryo transfer are performed. Since early 1994 several Dutch centers have a transport ICSI program running with the Gent University Infertility Center, and we wish to present the results of our cooperation with two major centers, comparing them to our local results, for the first 10 months of 1994. Patient selection was similar at all three centers: only couples with previously failed in vitro fertilization or having been refused for routine IVF were enrolled in the program. Stimulation schemes and follow-up of the stimulation were different at all three centers. Transport of oocytes was carried out in a transport box or by attaching the closed tubes containing the follicular aspirates to the chest of the husband. Transport times varied between 1.5 and 3 hr, depending on traffic conditions. RESULTS: Up to November 1, 1994, a total of 77 transport ICSI cycles and 294 own ICSI cycles were carried out. Although locally significantly more oocytes were retrieved and thus available for ICSI than in transport cycles, fertilization and pregnancy rates were not different between the two groups. CONCLUSIONS: These results suggest that long-distance transport of human oocytes seems not to be harmful to their capacity to be successfully injected and to further embryonic development and their implantation potential. Transport ICSI seems to be a valuable and cost-effective approach to treat high numbers of patients at a restricted number of highly specialized IVF laboratories, especially in countries where ICSI is not commonly available.

Academic Medical Centers↗
PubMed1996

Does assisted hatching improve implantation rates after in vitro fertilization or intracytoplasmic sperm injection in all patients? A prospective randomized study.

PURPOSE: Preliminary data from some research centers indicate that assisted hatching might be of value to increase embryo implantation rate in the human, at least in selected cases. It is not clear, however, whether this technique would be of benefit for all patients undergoing an embryo transfer. We therefore performed a prospective randomized study to evaluate the effect of assisted hatching on the implantation rate in our in vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI) program. METHODS: In total, 120 couples undergoing an embryo transfer were randomized between two groups: in one group no assisted hatching was performed (AH-), whereas in the other group the embryos selected for transfer were subjected to partial zona dissection (PZD) immediately prior to the transfer (AH+). Using a computer-generated minimization procedure, patients were allocated to one of the two groups according to four pre-selected criteria: the number of embryos transferred, the cumulative score of transferred embryos, the age of the patient, and the use of ICSI. RESULTS: Pregnancy and implantation rates in the AH+ and AH- groups were, respectively, 42.1 versus 38.1% and 17.9 versus 17.1%. CONCLUSIONS: From our data we conclude that assisted hatching through partial zona dissection prior to embryo transfer does not improve pregnancy and embryo implantation rates in unselected patients undergoing IVF or ICSI.

Adult↗
PubMed1996

Unprotected freezing of human spermatozoa exerts a detrimental effect on their oocyte activating capacity and chromosome integrity.

The influence of unprotected freezing of mammalian spermatozoa on their oocyte activating capacity and chromosome integrity is unknown. However, this type of sperm treatment has been used in assisted reproduction by intracytoplasmic sperm injection in cattle and humans. The mouse oocyte injection test was used to analyse the influence of unprotected freezing of human spermatozoa on their reproductive characteristics. Mouse oocytes were microinjected with intact human spermatozoa or spermatozoa treated with two cycles of unprotected freeze-thawing. Oocytes surviving the injection were either cultured without further treatment or exposed to ethanol solution to induce parthenogenetic activation. Both injected and activated oocytes were used for sperm chromosome analysis. The results revealed a significant reduction in oocyte activating capacity and a tenfold increase in the incidence of structural chromosomal abnormalities in human spermatozoa treated by unprotected freezing. We conclude that unprotected freezing of human spermatozoa has a detrimental effect on their reproductive characteristics. Our data also provide a new perspective on the stability of mammalian spermatozoa to physical factors and demonstrate the importance of detailed analysis of the stability of sperm structures for successful development of new approaches in assisted reproduction.

Animals↗
PubMed1996

Complete and partial luteinized unruptured follicle syndrome after ovarian stimulation with clomiphene citrate/human menopausal gonadotrophin/human chorionic gonadotrophin.

A total of 31 clomiphene citrate/human menopausal gonadotrophin (HMG)/human chorionic gonadotrophin (HCG)-stimulated cycles in 28 patients were investigated to determine the fate of each of the matured follicles. A standard stimulation regimen was adhered to, and ultrasound as well as hormonal monitoring was performed. All follicles were measured by vaginal ultrasound at -12, +35 and +45 h relative to HCG administration and at 7 days after HCG administration. Of the 220 follicles, 107 (48.6%) ruptured. The number of ruptured follicles per cycle was correlated with the mid-luteal progesterone concentration (r = 0.63, P = 0.0005). The probability of follicular rupture was related to follicular diameter at 12 h before HCG administration; 6% of follicles < 12 mm in diameter ruptured compared with 87% of follicles 18-19 mm. A complete luteinized unruptured follicle (LUF) syndrome was observed in six cycles (20%). In these cycles, follicular growth and oestradiol, progesterone, luteinizing hormone (LH) and follicle stimulating hormone (FSH) concentrations at 12 h before HCG administration were similar to those in cycles with follicular rupture. However, mid-luteal progesterone concentrations were lower in complete LUF cycles (46.97 +/- 8.95 nmol/l versus 108.74 +/- 12.27 nmol/l; P = 0.02). These data demonstrate that in stimulated cycles many follicles, usually the smaller ones, fail to rupture, even after HCG administration. Complete LUF syndrome, despite a strong exogenous ovulatory signal, and the absence of any difference in peri-ovulatory hormonal parameters, indicates that the defect causing LUF resides in the follicle itself and/or hormonal changes during the follicular phase.

Chorionic Gonadotropin↗
PubMed1996

Oocyte morphology does not correlate with fertilization rate and embryo quality after intracytoplasmic sperm injection.

The fertilization rates and further development of 528 human metaphase II oocytes directly injected by a single spermatozoon were analysed with respect to their morphological features at the light microscopy level at the time of retrieval. The deviations of oocyte morphology which were most frequently observed, after removal of cumulus cells, were dark incorporations, dark zona pellucida, large perivitelline space, spots, vacuoles, refractile bodies and irregular shape. These deviations correlated neither with the fertilization rate nor with the embryo quality score, as compared to 'ideal' oocytes. Since the majority of oocytes displayed deviations from the 'ideal' morphotype but were still fertilized and developed in culture at a normal rate, they were probably as normal as 'ideal' oocytes. Since some of these morphotypes, such as refractile bodies, have been shown to be associated with failure of fertilization, it seems that intracytoplasmic sperm injection may be an appropriate method of treatment for couples in whom repeated failure of in-vitro fertilization is associated with the retrieval of dysmorphic oocytes in the presence of normal semen characteristics.

Cytoplasm↗
PubMed1996

Analysis of the oocyte activating capacity and chromosomal complement of round-headed human spermatozoa by their injection into mouse oocytes.

Intracytoplasmic sperm injection (ICSI) in the human is a very effective procedure which allows the fertilization of the majority of oocytes even in cases of extreme oligoasthenoteratozoospermia. Round-headed acrosomeless human spermatozoa, however, form an exception to this rule, because in about half of the couples with globozoospermia all oocytes remain unfertilized after injection. The incapacity of the spermatozoon to activate the oocyte following injection of round-headed spermatozoa could be the underlying mechanism. To investigate this hypothesis, activation rates of mouse oocytes injected with spermatozoa from a patient with globozoospermia were compared with those obtained after injection with normal spermatozoa. Of mouse oocytes surviving the injection with donor spermatozoa, 95% underwent activation, compared to none of the 88 mouse oocytes surviving the injection with round-headed spermatozoa. After fixation, prematurely condensed sperm chromosomes were found in these oocytes. Parthenogenetic activation of mouse oocytes (8% ethanol at 40 min after injection) injected with round-headed spermatozoa led to the activation of 96% of oocytes. These oocytes developed normally to the first mitosis and were fixed for analysis of the sperm karyotypes. The incidence of chromosomal abnormalities of round-headed spermatozoa (6%) was similar to that in spermatozoa from a fertile donor (9%). These data provide further information on the basic defect in cases of globozoospermia and demonstrate that globozoospermia is not associated with sperm karyotype abnormalities.

Adult↗
PubMed1995

Pre-eclampsia and trisomy 13.

A 41 year old multiparous woman with an uncomplicated obstetric history was referred because of pre-eclampsia. As ultrasonic examination revealed severe IUGR and multiple congenital anomalies, trisomy 13 was suspected and confirmed by amniocentesis. This chromosomal anomaly should be suspected in cases where pre-eclampsia is associated with abnormal fetal morphology.

Adult↗
PubMed1995

Does treatment with testosterone undecanoate improve the in-vitro fertilizing capacity of spermatozoa in patients with idiopathic testicular failure? (results of a double blind study).

Seventy-seven couples in whom conventional in-vitro fertilization (IVF) had remained unsuccessful because of low fertilization rate and abnormal sperm characteristics were given either testosterone undecanoate 120 mg/day, or placebo during 3 months, after which a new IVF treatment was applied under identical technical conditions. There were no significant changes in sperm characteristics among the treated and placebo couples and the fertilization rate showed a similar increase after treatment in both groups. No significant difference in pregnancies occurred, with 32% pregnancies in the placebo controls and 17% among couples treated with testosterone undecanoate. It is concluded that testosterone undecanoate intake does not improve sperm characteristics, or the in-vitro fertilizing potential, or pregnancy rate over those observed in the placebo controls in cases with primary idiopathic testicular failure.

Adult↗
PubMed1995

Sperm plasma membrane damage prior to intracytoplasmic sperm injection: a necessary condition for sperm nucleus decondensation.

In the present study we investigated the relevance of sperm immobilization prior to intracytoplasmic sperm injection (ICSI) in the fertilization process. Using supravital staining of the spermatozoa with eosin and studying sperm decondensation with 2 mM dithiothreitol (DTT) in conditions imitating sperm handling during ICSI, we demonstrated that immobilization of the spermatozoon by squeezing its tail between the glass pipette and the bottom of the dish damages the sperm plasma membrane. Polyvinylpyrrolidone (PVP), which is usually present in the drop with the spermatozoon to facilitate its handling, was found to impede the access of both eosin and DTT to the sperm nucleus. We conclude that (i) sperm immobilization prior to ICSI damages the sperm plasma membrane, that (ii) this damage is sufficient for thiol-reducing agents to gain access to the sperm nucleus, and finally that (iii) PVP possibly interferes with sperm nucleus decondensation.

Cell Membrane↗
PubMed1995

Timing of sperm and oocyte nuclear progression after intracytoplasmic sperm injection.

We investigated the time course of human oocyte activation after intracytoplasmic sperm injection (ICSI) by observing the oocyte chromosome configuration at different times after injection. One day old human oocytes were injected with spermatozoa and subjected to cytogenetic analysis at 2, 3, 4 and 5 h after injection. We found that anaphase is initiated in the vast majority of the oocytes between 2 and 3 h after injection, and that by 4-5 h after injection most of the oocytes have reached the chromatin mass stage. Two distinguishable stages of sperm nucleus transformation were observed. The first phase-swelling-was reached within 2 h after the injection and was independent of oocyte activation. The second phase-the "brush'-like stage or decondensed chromatin stage-was found only in activated oocytes. Moreover, this stage was not reached before the chromatin mass stage (late telophase) of the oocyte. The same proportion of metaphase II oocyte chromosome configurations and unchanged sperm nuclei was found at any given time after injection. We conclude that: (i) ICSI allows users to obtain an almost synchronized population of activated oocytes; (ii) anaphase II is initiated in the majority of oocytes not later than 2-3 h after injection and telophase II is reached approximately 5 h after injection; and (iii) there are two distinguishable phases of sperm nucleus transformation after ICSI: oocyte activation-independent swelling of the sperm head and oocyte activation-dependent chromatin decondensation which is coupled to the beginning of oocyte chromosome decondensation.

Cell Nucleus↗
PubMed1995

Human oocyte activation following intracytoplasmic injection: the role of the sperm cell.

The aim of this study was to investigate whether the human spermatozoon participates in the activation of human oocytes following intracytoplasmic sperm injection (ICSI) and if so, by what mechanism. In the first series of experiments, we randomized human oocytes which had remained unfertilized after in-vitro fertilization (IVF) or ICSI, for intracytoplasmic injection with live spermatozoa, spermatozoa presumed to be dead and no spermatozoa. Secondly, unfertilized human oocytes and freshly ovulated mouse oocytes were randomized for intracytoplasmic and sub-zonal injection with human sperm cytosolic fraction (CF) before and after heat treatment. We found that oocyte injection with initially motile spermatozoa induces human oocyte activation at a significantly higher rate than injection with dead spermatozoa (61 versus 0%; P < 0.001) or injection without a spermatozoon (61 versus 14%; P < 0.001). Intracytoplasmic injection of CF activated both human and mouse oocytes at the same rate as sperm injection of human oocytes (activation rates of 70 and 65% respectively). This effect was greatly reduced by heat treatment of the CF. From these experiments we conclude firstly that the human spermatozoon injected intracytoplasmically contributes to human oocyte activation and secondly that the spermatozoon releases into the oocyte a heat-sensitive, intracellularly active factor, which is not species-specific.

Cell Death↗
PubMed1995

Prospective randomized study of clomiphene citrate and gonadotrophins versus goserelin and gonadotrophins for follicular stimulation in assisted reproduction.

We performed a prospective randomized study of goserelin, a long-acting gonadotrophin-releasing hormone agonist (GnRHa) and human menopausal gonadotrophin (HMG) versus clomiphene citrate and HMG for follicular stimulation in assisted reproduction to investigate whether the use of this GnRHa provides a clear advantage in terms of pregnancy per treatment cycle in unselected patients, who entered a first trial of assisted reproduction. From a retrospective analysis comparing the two stimulation protocols, a relative increase of the pregnancy rate per cycle of 50% was anticipated. To detect this difference with a power of 90%, 300 patients had to be included. The main prognostic factors affecting the outcome of assisted reproduction were equally divided among the two groups by a minimization procedure. The pregnancy rates per cycle were significantly better in the goserelin/HMG group than in the clomiphene citrate/HMG group, both for all procedures of assisted reproduction combined (36.8 versus 24.5%; P < 0.02) and for the main procedure of in-vitro fertilization (IVF) (37.0 versus 23.5%; P < 0.02). Differences in pregnancy rates per oocyte retrieval and per embryo transfer were less pronounced (37.8 versus 30.8%; P = 0.40 and 44.4 versus 36.8%; not significant). On the other hand, stimulation with goserelin/HMG was associated with a higher number of ampoules of HMG (44.9 versus 9.9; P < 0.0001), a longer duration of stimulation (11.2 versus 8.7 days; P < 0.0001) and an incidence of ovarian stimulation of 4.5% (7/154) versus 0% in the clomiphene citrate/HMG group. Goserelin was well tolerated and proved to be very reliable as an adjunct of follicular stimulation in assisted reproduction.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Intracytoplasmic injection of human spermatozoa into mouse oocytes: a useful model to investigate the oocyte-activating capacity and the karyotype of human spermatozoa.

When intracytoplasmic sperm injection (ICSI) is performed, it is important to know the capacity of sperm cells to activate the oocytes, although knowledge of their ability to fuse with the oocytes is not vital. Hamster oocytes are not suitable for this purpose because they are easily activated by the injection procedure Itself. We therefore investigated whether mouse oocytes could be used to assess the activation properties of human spermatozoa. Mouse oocytes were randomized for injection with initially motile spermatozoa, medium, heat-treated or salt-extracted spermatozoa, and the survival and activation rates were examined. About half of the mouse oocytes survived the intracytoplasmic injection of a human sperm cell. Unlike hamster oocytes, the rate of activation provoked by the injection procedure itself was acceptably low (20%), resembling in this respect the behaviour of human oocytes. Following the injection of initially motile human spermatozoa, all mouse oocytes were activated. The injection of heat-treated or salt-extracted human spermatozoa resulted in activation rates of 14 and 15% respectively, comparable with the results following sham ICSI. These data support the hypothesis of a sperm-associated oocyte activation factor. In most activated oocytes, the human sperm nucleus decondensed to form a male pronucleus. Cytogenetic analysis at the first metaphase revealed that human sperm chromosomes were able to undergo replication in a heterologous environment.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Protein binding of propranolol and verapamil enantiomers in maternal and foetal serum.

The protein binding of the enantiomers of propranolol and verapamil was measured in 19 pairs of maternal and foetal serum obtained at delivery. The binding of the enantiomers of both drugs was lower in foetal than in maternal serum. In maternal serum the mean (+/- s.d.) unbound percentages were 22.4 +/- 6.2 and 20.7 +/- 6.6 for R- and S-propranolol, and 16.8 +/- 5.5 and 22.5 +/- 6.2 for R- and S-verapamil; in foetal serum the values were 38.8 +/- 8.6 and 40.4 +/- 10.6 for R- and S-propranolol, and 34.7 +/- 10.5 and 44.8 +/- 10.7 for R- and S-verapamil. For propranolol, in maternal, but not in foetal serum, the difference between the binding of the R- and S-enantiomers was significant; the R/S ratio was significantly (P < 0.01) larger in the mother (1.099 +/- 0.072) than in the foetus (0.973 +/- 0.068). For verapamil, the difference in binding between the R- and S-enantiomers was significant in both maternal and foetal serum, but the R/S ratio was similar in mother (0.735 +/- 0.098) and foetus (0.763 +/- 0.070). Serum alpha 1-acid glycoprotein (AAG) concentrations were markedly higher and albumin concentrations slightly lower in maternal than in foetal samples. The binding of the four enantiomers in maternal and foetal serum was correlated (P < 0.001) with the AAG concentration (r propranolol: R 0.749, S 0.746; r verapamil: R 0.753, S 0.782). Our findings show that measurement of concentrations of total, unresolved drug allow a reasonably accurate assessment of transplacental gradients of individual isomers.

Adult↗