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Johan Smitz

Publications and source records attributed to Johan Smitz.

32 records · Page 2Linked to original sources
PubMed2003

Effects of chilling on structural aspects of early preantral mouse follicles.

Chilling injury is one of the major limiting factors for achieving optimal cryopreservation of gametes. This study aimed to determine potential chilling-induced damage on several structural aspects of early preantral mouse follicles. Mechanically isolated intact early preantral follicles (type 3b-4) were exposed to 0 degrees C for 1, 5, 10, or 30 min. Control and chilled follicles were analyzed by confocal microscopy after staining for tubulin, F-actin, and chromatin, and by electron microscopy. Chilling for only 1 min was sufficient to cause depolymerization of microtubules in the oocyte and the surrounding granulosa cell layer as evidenced by a substantial decrease in fluorescence intensity after antitubulin labeling. Cooling for longer periods caused alterations in microtubule organization in the follicle-enclosed oocyte. These alterations included the loss of interphase microtubules, concomitant with the formation of perinuclear or cortical microtubule asters and sometimes a complete disappearance of microtubules. The extent of microtubule modification was related to the time of chilling, but was fully reversible after rewarming follicles at 37 degrees C for 1 h. Chilling had only minor effects on the actin-containing elements located predominantly in the oocyte cortex and the transzonal projections. Ultrastructural analysis confirmed that oocyte-somatic cell interactions were present. There was no influence on the chromatin configuration within the follicle-enclosed oocyte. These results indicate that mouse follicles are relatively tolerant to direct chilling injury and, as a consequence, are able to withstand the cooling-warming steps during conventional cryopreservation procedures.

Actin Cytoskeleton↗
PubMed2003

Human oocytes reversibly arrested in prophase I by phosphodiesterase type 3 inhibitor in vitro.

This study addresses the role of cAMP hydrolytic isoenzyme phosphodiesterase type 3 (PDE 3) modulation on human oocyte maturation in vitro. Presence of phosphodiesterase type 3 A (PDE 3A) mRNA was confirmed in human germinal vesicle-stage (GV) oocytes. Making use of a selective PDE 3 inhibitor, Org 9935 (10 microM), oocytes retrieved from immature follicles were arrested in prophase I with a high efficiency for up to 72 h. Cumulus oocyte complexes (COCs) were retrieved in the follicular phase of the cycle before or after exposure to endogenous LH or hCG administration in vivo and randomly distributed into maturation medium with or without the PDE 3 inhibitor. Previous exposure of small follicles to LH activity in vivo had no influence on the arresting capacity of the PDE 3 inhibitor. Reversal from pharmacological arrest leads to a progression through meiosis in a normal time frame with formation of a well-aligned metaphase plate. Ultrastructure analysis of COC derived from follicles between 8 and 12 mm showed that the induced extension of prophase I arrest in vitro resulted in cytoplasm changes but not in apparent nuclear changes during culture.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed2003

Endometrial integrin expression in the early luteal phase in natural and stimulated cycles for in vitro fertilization.

OBJECTIVE: To investigate the effect of ovarian stimulation on integrin expression in the early luteal phase. STUDY DESIGN: Seven endometrial biopsies were taken 2 days after the oocyte retrieval from stimulated cycles for IVF and 23 from natural cycles, 2 days after ovulation. RESULT: Endometrium was in-phase in 22/23 and 7/7 biopsies from the natural and stimulated cycles, respectively. Integrins alpha(1) and alpha(4) were simultaneously positive in 43.4% from the natural and in all (100%) the stimulated cycles (P<0.03). On the day of the endometrial biopsy, progesterone serum values were higher in the stimulated cycles (55.2+/-9.5 microg/l versus 8.5+/-3.8 microg/l) (P<0.001). HSCORE value was significantly higher in stimulated cycles for both integrins. CONCLUSION: Endometrial integrin expression is more consistently present in the early luteal phase in stimulated cycles than in natural cycles and this may be related to the higher serum progesterone concentration and/or the more advanced endometrial histological features.

Adult↗
PubMed2003

Clinical and biological characterization of macroprolactinemia with and without prolactin-IgG complexes.

OBJECTIVE: Macroprolactinemia, which can be detected by a polyethylene glycol (PEG) precipitation test, is a clinically and biologically heterogeneous condition. In this study, we analyzed whether the clinical presentation, the hormonal findings and the in vitro lactogenic activity differed between macroprolactinemic patients with and without circulating prolactin (PRL)-IgG complexes. DESIGN: Clinical data were reviewed and additional hormonal studies were performed in 50 hyperprolactinemic patients with macroprolactinemia. METHODS: Macroprolactinemia was identified by a PRL recovery after PEG precipitation of <50%, as measured by an automated commercial immunoassay system and circulating PRL-IgG complexes by an abnormal PRL binding to anti-IgG agarose. RESULTS: PRL-IgG complexes were found in 46 patients. The origin of hyperprolactinemia in these 46 patients was idiopathic in 33 patients, while a pituitary lesion or stalk magnetic resonance imaging or computed tomography scan was detected in 13 patients found compression. Galactorrhea was found in 11 of these 46 patients, while this condition was present in three of the four patients without circulating PRL-IgG complexes. The median free PRL concentration was significantly lower in patients with PRL-IgG complexes than in the group without complexes (243 vs 969 mIU/l; P<0.005), whereas median total PRL immunoreactivity and median PRL bioactivity in the Nb2 assay were not significantly different. In patients with circulating PRL-IgG complexes, Nb2 bioassay results correlated significantly with total PRL immunoreactivity (r=0.64; P<0.0001), but not with free PRL results (r=0.24; P<0.17). CONCLUSIONS: These results indicate that PRL-IgG complexes (i) account for most cases of macroprolactinemia--as identified by PEG precipitation--in hyperprolactinemic patients presenting with a variety of diagnoses, (ii) are not associated with a specific clinical presentation, (iii) can be found in patients with diverse pituitary pathologies, and (iv) possess an in vitro lactogenic activity in the Nb2 bioassay in relation to their immunoreactivity.

Adolescent↗
PubMed2002

Alpha-fetoprotein, the major fetal serum protein, is not essential for embryonic development but is required for female fertility.

The alpha-fetoprotein gene (Afp) is a member of a multigenic family that comprises the related genes encoding albumin, alpha-albumin, and vitamin D binding protein. The biological role of this major embryonic serum protein is unknown although numerous speculations have been made. We have used gene targeting to show that AFP is not required for embryonic development. AFP null embryos develop normally, and individually transplanted homozygous embryos can develop in an AFP-deficient microenvironment. Whereas mutant homozygous adult males are viable and fertile, AFP null females are infertile. Our analyses of these mice indicate that the defect is caused by a dysfunction of the hypothalamic/pituitary system, leading to anovulation.

Alleles↗
PubMed2002

Circulating anti-prolactin auto-antibodies must be considered in the differential diagnosis of hyperprolactinaemia in adolescents.

UNLABELLED: In four adolescents (two girls and two boys), who were investigated for galactorrhoea or short stature, we found moderately elevated serum prolactin (PRL) levels, but without a decreased gonadotropin and sex hormone production. Serum PRL levels were not responding to the intravenous injection of thyrotropin releasing hormone. Magnetic resonance imaging of the hypothalamic-pituitary region revealed no abnormality. Initial diagnoses were idiopathic and drug-induced hyperprolactinaemia. The presence of anti-prolactin auto-antibodies was suspected because of low recovery of PRL after precipitation with polyethylene glycol and confirmed by immunoprecipitation with anti-human IgG-agarose. CONCLUSION: anti-prolactin auto-antibodies causing high prolactin values in some immunoassays can cause hyperprolactinaemia in adolescents without other signs of hormonal disturbances or auto-immune disease.

Adolescent↗
PubMed2002

Effect of clomiphene citrate on follicular and luteal phase luteinizing hormone concentrations in in vitro fertilization cycles stimulated with gonadotropins and gonadotropin-releasing hormone antagonist.

OBJECTIVE: To investigate the effect that clomiphene citrate exerts on luteinizing hormone (LH) concentrations in gonadotropin/gonadotropin-releasing hormone (GnRH) antagonist cycles. DESIGN: Retrospective analysis. SETTING: Tertiary referral center. PATIENT(S): Two groups of patients undergoing in vitro fertilization (IVF) were compared. In group I, 20 patients were stimulated with clomiphene citrate (CC) in combination with gonadotropins and 0.25 mg of Cetrorelix (ASTA Medica AG; Frankfurt am Main, Germany) and in group II, 20 patients were stimulated with gonadotropins and 0.25 mg of Cetrorelix. INTERVENTION(S): Blood sampling was performed in the late follicular, periovulatory, early, mid, and late luteal phases. MAIN OUTCOME MEASURE(S): Luteinizing hormone (LH), estradiol, and progesterone. RESULT(S): LH levels were significantly higher in group I than in group II on all the days studied. Progesterone serum concentrations were significantly higher in group II in the early luteal phase, but not in the follicular or the middle and late luteal phases. CONCLUSION(S): LH concentrations are significantly higher in the follicular and luteal phases in cycles stimulated with CC, despite GnRH antagonist administration. This observation might have implications for the dose of GnRH antagonist needed to suppress LH in the follicular phase and questions the need for luteal-phase supplementation in cycles in which CC was used.

Adult↗
PubMed2002

Endometrial hormone receptors and proliferation index in the periovulatory phase of stimulated embryo transfer cycles in comparison with natural cycles and relation to clinical pregnancy outcome.

OBJECTIVE: To investigate the endometrial steroid receptors and proliferation index in GnRH analogue/hMG-stimulated cycles in comparison with natural cycles and their relation to clinical pregnancy outcome. DESIGN: Prospective observational study. SETTING: Tertiary referral center. PATIENT(S): Twenty-seven stimulated patients with GnRH agonist and hMG. Twenty normo-ovulatory patients were the natural cycle controls. INTERVENTION(S): Endometrial aspiration biopsies: in stimulated cycles on the day of oocyte retrieval within the ET cycle (Day OPU) (n = 20) or 2 days later (Day OPU + 2) (n = 7); in natural cycles on the natural day of ovulation (Day NO) (n = 10) or on the day of ovulation + 2 (Day NO + 2) (n = 10). MAIN OUTCOME MEASURE(S): Comparison of endometrial maturation, estrogen (ER) and P receptor (PR), and proliferation index by immunohistochemistry in natural and stimulated cycles, correlation with pregnancy outcome in stimulated cycles. RESULT(S): Stimulated cycles Day OPU showed significantly advanced endometrial maturation compared to natural cycles Day NO; stromal ER and glandular and stromal PR staining was lower in stimulated than in natural cycles, but higher on Day OPU than on Day NO + 2; proliferation index was lower in all stimulated cycles. Steroid receptors and proliferation index in stimulated cycles were unrelated to clinical pregnancy occurrence. CONCLUSION(S): Compared to natural cycles, ovarian stimulation induced an imbalance in endometrial ER and PR and led to a profound antimitotic effect in the peri-ovulatory phase. These parameters were, however, not predictive of clinical pregnancy in cycles with ET.

Adult↗
PubMed2002

Effect of ovarian stimulation with recombinant follicle-stimulating hormone, gonadotropin releasing hormone antagonists, and human chorionic gonadotropin on endometrial maturation on the day of oocyte pick-up.

OBJECTIVE: To assess the effect of ovarian stimulation with recombinant FSH, GnRH antagonists, and hCG on endometrial maturation on the day of oocyte pick-up. DESIGN: Prospective study. SETTING: Tertiary referral center. PATIENT(S): Fifty-five women undergoing controlled ovarian hyperstimulation for IVF/intracytoplasmic sperm injection (ICSI). INTERVENTION(S): [1] Ovarian stimulation with recombinant FSH, starting on day 2 of the cycle and GnRH antagonist, starting after a median of 6 days of recombinant FSH stimulation (range, 5-12 days); [2] hCG administration for ovulation induction; and [3] aspirational biopsy of endometrium at oocyte pick-up. MAIN OUTCOME MEASURE(S): Endometrial histology at oocyte pick-up by Noyes criteria. RESULT(S): Advancement of endometrial maturation (2.5 +/- 0.1 days) as compared to the expected chronological date was observed in all antagonist cycles at oocyte retrieval. Endometrial advancement at oocyte pick-up increased in line with values of LH at initiation of stimulation and the duration of recombinant FSH treatment before the antagonist was started. CONCLUSION(S): The higher the values of LH at initiation of stimulation and the longer the duration of recombinant FSH treatment before the antagonist is started, the more advanced the endometrial maturation at oocyte pick-up.

Adult↗
PubMed2002

Clinical validation of a fully automated 17beta-estradiol and progesterone assay (VIDAS) for use in monitoring assisted reproduction treatment.

Measurement of serum estradiol (E2) and progesterone (PRG) allows monitoring of follicular growth and prediction of the day of ovulation in natural cycles. In combination with vaginal ultrasonography, serum E2 and PRG are used for the monitoring of ovarian superovulation for assisted reproduction. We carried out a clinical evaluation of the VIDAS E2 and PRG assays on a fully automated random access analyzer (miniVIDAS, bioMérieux) by retrospective analysis of frozen serum samples obtained from 16 natural cycles monitored for frozen embryo transfer (FRET) and in superovulation cycles. The superovulation cycles consisted of 28 long gonadotropin-releasing hormone (GnRH) agonist protocol cycles and 15 GnRH antagonist protocol cycles. In FRET cycles we found a good correlation between serum E2 and the diameter of the dominant follicle measured by ovarian ultrasonography. Serum E2 values measured throughout the cycles and follicular phase PRG values were representative of normo-ovulatory cycles. In GnRH agonist long protocols, we found serum E2 and PRG values compatible with castration levels induced by pituitary desensitization. During gonadotropin treatment a close, highly significant correlation was observed between serum E2 and ultrasonographic follicle measurements with both GnRH analogue protocols. Serum PRG measured for 5 days prior to human chorionic gonadotropin (hCG) administration in the agonist cycles was compatible with the absence of premature luteinization. In conclusion, VIDAS E2 and PRG assays are precise and sensitivetoolsforevaluating natural cycles (based on the results in FRET cycles) and for monitoring ovarian superovulation.

Automation↗
PubMedDate not supplied

Ovarian follicle bioassay reveals adverse effects of diazepam exposure upon follicle development and oocyte quality.

A mouse ovarian follicle bioassay was used to study folliculogenesis and oocyte quality in vitro. Diazepam (DZ) was chosen as test compound to evaluate the system for its ability to detect possible effects of chemicals on reproduction. The bioassay is suitable to analyze the influence of DZ on each of the follicular components at any stage of development. A dose finding study revealed that follicle growth, differentiation and steroidogenesis were significantly disturbed by > or =5 microg/ml DZ. A transient exposure procedure was used to examine stage-specific sensitivities of oogenesis to DZ. The oocyte appeared to be most vulnerable during its growth process within the follicle. Resumption of meiosis was disturbed dose-dependently with reduced oocyte quality after chronic exposure to > or =2.5 microg/ml DZ. The bioassay is a highly efficient and informative tool to assess the hazards of chemical compounds for female fertility and to elucidate their mechanisms of action.

Animals↗