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Biomedical subjects

A G Byskov

Publications and source records attributed to A G Byskov.

At least 37 records · Page 2Linked to original sources
PubMed2000

Does anovulation induced by oral contraceptives favor pregnancy during the following two menstrual cycles?

OBJECTIVE: To compare IVF and pregnancy outcomes before and after anovulation induced by oral contraceptives. DESIGN: Observational clinical study. SETTING: Infertility clinic. PATIENT(S): Forty women with two intact ovaries (32 of 40 couples with male factor infertility and 8 with unknown causes of infertility) underwent 190 IVF treatment cycles (55 natural cycles and 135 clomiphene citrate-stimulated cycles). INTERVENTION(S): If the women failed to conceive after 2-4 IVF treatment cycles, oral contraceptives were used to induce anovulation for 1 month before IVF was performed in two consecutive cycles. MAIN OUTCOME MEASURE(S): Rates of oocyte retrieval, fertilization, cleavage, preembryo formation, pregnancy, and implantation were compared before and after a period of anovulation. RESULT(S): The pregnancy rate per cycle of the first and second cycle combined (23%) and that of the second cycle alone (30%) after a period of anovulation were significantly higher than that observed before a period of anovulation (9%). CONCLUSION(S): Anovulation induced by oral contraceptives, showing bilateral ovarian quiescence, enhances pregnancy rates in the following two menstrual cycles of IVF treatment.

Adult↗
PubMed2000

Effects of amphotericin B and ketoconazole on mouse oocyte maturation: implications on the role of meiosis-activating sterol.

Meiosis-activating sterol (MAS) has been shown to induce mouse oocytes cultured in the presence of hypoxanthine (HX) to resume meiosis. The present research was conducted to determine whether amphotericin B or ketoconazole (a promoter and an inhibitor of production of MAS), affected oocyte maturation. Mouse cumulus cell-enclosed oocytes (CEO) or denuded oocytes (DO) were cultured for 24 h in the presence of 4 mM HX with FSH or amphotericin B or ketoconazole. At the end of the culture, the frequency of germinal vesicle break down (GVBD) and polar body formation (PB) were recorded. The results demonstrated: (i) FSH (10-200 IU/l) induced dose-dependent oocytes maturation in CEO, but was without effect on DO. A maximum increase in GVBD and PB was observed with 25-50 IU/l FSH. The presence of FSH (50 IU/l) for 1 h was sufficient to induce meiotic resumption, which after 2 h reached a plateau similar to that of a continuous presence of FSH. (ii) CEO exposed to amphotericin B (0.0025-2.5 microg/l) underwent GVBD dose-dependently, whereas no effect was observed on DO. The presence of amphotericin B (0.025 microg/l) for 1 h stimulated oocyte resumption in a way similar to that of FSH. (iii) Amphotericin B (0.025 microg/l) and FSH (50 IU/l) did not show any additive effect on resumption of meiosis. (iv) Ketoconazole (10(-7)-10(-3) M) inhibited the effect of FSH on resumption of meiosis, but had no effect on oocyte spontaneous maturation. These results show that FSH and amphotericin B induce resumption of meiosis and indicate that they are likely to cause an accumulation of meiosis activating sterols in the CEO, but ketoconazole blocks the production of MAS. The present study supports the notion that MAS plays a physiological relevant role in triggering resumption of meiosis in mouse oocytes.

Amphotericin B↗
PubMed2000

Right-sided ovulation favours pregnancy more than left-sided ovulation.

The aim of this study was to evaluate whether frequency of ovulation and fertility potential of oocytes from the two ovaries differed in regularly menstruating women (1057 cycles of 856 fertile women and 1033 cycles of 258 infertile women). For both fertile and infertile women ovulation from the right ovary occurred more often than from the left ovary (55 versus 45%; P: < 0.005). In infertile women follicular phase length was similar for right- and left-sided ovulation. However, infertile women treated with intrauterine insemination (IUI) or in-vitro fertilization (IVF) showed a pregnancy rate in connection with right-sided ovulation (13%) which was higher than that of left-sided (9%). The ratio of pregnancies deriving from the right ovary per total number of pregnancies was similar in infertile and fertile women (64.6%, 73/113 and 63.4%, 361/569 respectively). The ratio of pregnancies from right-sided ovulation (approximately 64%) per total number of pregnancies was higher than that of right-sided ovulation (approximately 55%) during non-pregnant cycles (P: < 0.0001). The implantation rate in right-sided ovulation seemed to be higher than in left-sided one, since IVF data showed a lower frequency (P: = 0.03) of pre-embryo formation from right-sided ovulation than left-sided. Mid-luteal serum oestradiol and testosterone were higher (P: < 0.05) in right-sided ovulation than left-sided. Taken together, in both fertile and infertile women the fertility potential of oocytes from the right ovary surpasses that of the left ovary.

Embryo Implantation↗
PubMed2000

Effect of inhibition of sterol delta 14-reductase on accumulation of meiosis-activating sterol and meiotic resumption in cumulus-enclosed mouse oocytes in vitro.

Two sterols of the cholesterol biosynthetic pathway induce resumption of meiosis in mouse oocytes in vitro. The sterols, termed meiosis-activating sterols (MAS), have been isolated from human follicular fluid (FF-MAS, 4,4-dimethyl-5 alpha-cholest-8,14,24-triene-3 beta-ol) and from bull testicular tissue (T-MAS, 4,4-dimethyl-5 alpha-cholest-8,24-diene-3 beta-ol). FF-MAS is the first intermediate in the cholesterol biosynthesis from lanosterol and is converted to T-MAS by sterol delta 14-reductase. An inhibitor of delta 7-reductase and delta 14 reductase, AY9944-A-7, causes cells with a constitutive cholesterol biosynthesis to accumulate FF-MAS and possibly other intermediates between lanosterol and cholesterol. The aim of the present study was to evaluate whether AY9944-A-7 added to cultures of cumulus-oocyte complexes (COC) from mice resulted in accumulation of MAS and meiotic maturation. AY9944-A-7 stimulated dose dependently (5-25 mumol l-1) COC to resume meiosis when cultured for 22 h in alpha minimal essential medium (alpha-MEM) containing 4 mmol hypoxanthine l-1, a natural inhibitor of meiotic maturation. In contrast, naked oocytes were not induced to resume meiosis by AY9944-A-7. When cumulus cells were separated from their oocytes and co-cultured, AY9944-A-7 did not affect resumption of meiosis, indicating that intact oocyte-cumulus cell connections are important for AY9944-A-7 to exert its effect on meiosis. Cultures of COC with 10 mumol AY9944-A-7 l-1 in the presence of [3H]mevalonic acid, a natural precursor for steroid synthesis, resulted in accumulation of labelled FF-MAS, which had an 11-fold greater amount of radioactivity incorporated per COC compared with the control culture without AY9944-A-7. In contrast, incorporation of radioactivity into the cholesterol fraction was reduced 30-fold in extracts from the same oocytes. The present findings demonstrate for the first time that COC can synthesize cholesterol from mevalonate and accumulate FF-MAS in the presence of AY9944-A-7. Furthermore, AY9944-A-7 stimulated meiotic maturation dose dependently, indicating that FF-MAS, and possibly other sterol intermediates of the cholesterol synthesis pathway, play a central role in stimulating mouse oocytes to resume meiosis. The results also indicate that oocytes may not synthesize steroids from mevalonate.

Animals↗
PubMed2000

Ontogeny of oestrogen receptor alpha in gonads and sex ducts of fetal and newborn mice.

The distribution of nuclear oestrogen receptor alpha (ER-alpha) in the sex organs of fetal and newborn mice has been investigated immunohistochemically. There was no visible ER-alpha immunoreaction in the sexually undifferentiated gonads, whereas a faint immunoreaction was detected in a few cells surrounding the sex ducts, the Müllerian and Wolffian ducts. After sex differentiation, the immunoreaction of ER-alpha was observed in various cell types, with the exception of both the male and female germ cells. In the fetal ovary, immunoreaction was restricted to the surface epithelium and a few stroma cells without any preferential localization. In the testis, the number of ER-alpha-immunopositive cells, identified as Leydig and peritubular cells, increased with age. Immediately after sex differentiation, cells surrounding the sex ducts were ER-alpha-immunopositive, but no immunoreaction was detected in the epithelium in either sex. During development, the epithelium of the sex ducts attained a topographic difference in ER-alpha immunoreaction. In females, immunoreaction was detected in the epithelium of the oviduct, but not in the uterus. In males, the immunoreaction of ER-alpha was intense in the epithelium of the efferent ducts, weak in the epididymis and absent in the vas deferens. ER-alpha immunoreaction in the cells surrounding the sex duct differed between the sexes, being high in all these cells in females, but of varying intensity in males. ER-alpha may not play an important role in the development and function of ovarian cells, but may be involved in the development of Leydig and peritubular cells. Furthermore, substances that react with ER-alpha may influence the male germ cells indirectly through the ER-alpha-immunopositive peritubular cells. In addition, in both sexes, ER-alpha-immunopositive cells surrounding the sex ducts may be involved in the mediation of growth and functional differentiation of the ductal epithelium.

Animals↗
PubMed2000

Regulation of spontaneous and induced resumption of meiosis in mouse oocytes by different intracellular pathways.

The mitogen-activated protein kinase-dependent and the cAMP-protein kinase A-dependent signal transduction pathways were studied in cultured mouse oocytes during induced and spontaneous meiotic maturation. The role of the mitogen-activated protein kinase pathway was assessed using PD98059, which specifically inhibits mitogen-activated protein kinase 1 and 2 (that is, MEK1 and MEK2), which activates mitogen-activated protein kinase. The cAMP-dependent protein kinase was studied by treating oocytes with the protein kinase A inhibitor rp-cAMP. Inhibition of the mitogen-activated protein kinase pathway by PD98059 (25 micromol l(-1)) selectively inhibited the stimulatory effect on meiotic maturation by FSH and meiosis-activating sterol (that is, 4,4-dimethyl-5alpha-cholest-8,14, 24-triene-3beta-ol) in the presence of 4 mmol hypoxanthine l(-1), whereas spontaneous maturation in the absence of hypoxanthine was unaffected. This finding indicates that different signal transduction mechanisms are involved in induced and spontaneous maturation. The protein kinase A inhibitor rp-cAMP induced meiotic maturation in the presence of 4 mmol hypoxanthine l(-1), an effect that was additive to the maturation-promoting effect of FSH and meiosis-activating sterol, indicating that induced maturation also uses the cAMP-protein kinase A-dependent signal transduction pathway. In conclusion, induced and spontaneous maturation of mouse oocytes appear to use different signal transduction pathways.

Analysis of Variance↗
PubMed2000

Octylphenol does not mimic diethylstilbestrol-induced oestrogen receptor-alpha expression in the newborn mouse uterine epithelium after prenatal exposure.

This study examined whether the endocrine disruptor octylphenol (OP) mimics the synthetic oestrogen diethylstilbestrol (DES) in ability to induce oestrogen receptor-alpha (ER-alpha) expression in the newborn mouse uterine epithelium after prenatal exposure. Pregnant mice were given daily s.c. injections with DES (10 or 100 microgram DES/kg maternal wt) or OP (100 or 250 mg/kg maternal wt) or with vehicle alone from day 11.5 to 16.5 of pregnancy. ER-alpha expression was evaluated on histological sections by detecting ER-alpha mRNA with the in situ hybridization technique and ER-alpha protein using immunohistochemistry. The immunostaining was quantitated using a microspectrophotometer. Oestrogen-like activity of the DES and OP batches used for in vivo exposure was confirmed in an in vitro assay based on transient gene expression of an oestrogen-dependent reporter plasmid. In mice exposed prenatally to vehicle alone, the uterine epithelium did not express either ER-alpha mRNA or protein, while both were highly expressed in the stroma. Exposure to either DES dose induced the expression of both ER-alpha mRNA and protein in the epithelium, whereas it was unchanged in the stroma. In contrast, neither OP dose induced the expression of ER-alpha mRNA or protein in the epithelium and expression was unchanged in the stroma. Our data stress the importance of in vivo studies when investigating endocrine disruptors.

Animals↗
PubMed1999

Meiosis activating sterols (MAS) and fertility in mammals and man.

In mammals two meiosis activating sterols (MAS) have been found to activate meiotic resumption in mouse oocytes, in vitro. FF-MAS (4, 4-dimethyl-5alpha-cholesta-8,14,24-triene-3beta-ol) was extracted from human preovulatory follicular fluid and T-MAS (4, 4-dimethyl-5alpha-cholest-8,24-diene-3beta-ol) from bull testicular tissue. Quite unexpected, these two sterols, which introduce the cholesterol biosynthetic pathway from lanosterol, may be locally acting substances with important physiological function for reproduction. FF-MAS and T-MAS are present in the preovulatory follicular fluid of different mammalian species and have the capacity to initiate resumption of meiosis in mouse oocyte cultured in the presence of hypoxanthine, a natural meiosis maturation inhibitor. FF-MAS is produced by the cumulus cells of intact oocyte-cumulus complexes upon FSH-stimulation and provides the oocyte with a go-signal for the resumption of meiosis. T-MAS constitutes the vast majority of MAS found in the mammalian testis and in the human ejaculate; in particular a high concentration is found in the spermatozoa. T-MAS may be produced by the spermatids and the presence of T-MAS in spermatozoa may suggest that T-MAS plays a role in fertilization by affecting the second meiotic division.J. Exp. Zool. (Mol. Dev. Evol.) 285:237-242, 1999.

Animals↗
PubMed1999

Protein kinase C and intracellular calcium are involved in follicle-stimulating hormone-mediated meiotic resumption of cumulus cell-enclosed porcine oocytes in hypoxanthine-supplemented medium.

The present experiments were conducted to examine the hypothesis that follicle-stimulating hormone (FSH) can stimulate the hydrolysis of phosphoinositide, generating the intracellular second messengers to activate protein kinase C and mobilizing intracellular calcium, thus inducing oocyte meiotic resumption. Pig cumulus cell-enclosed oocytes (CEO) were cultured for 24 hr in 4 mM hypoxanthine (HX)-supplemented medium and treated with different agents in the following designs: (1) CEO were treated with neomycin (an inhibitor of phosphoinositide hydrolysis) in the presence of FSH or only treated with 7,12-dimethylbenzin(a) anthracene (DMBA, a tumor promoter which can cause phosphorylation of phospholipase C (PLC), formation of inositol triphophate, and mobilization of intracellular calcium) to mimic the direct activation of PLC; (2) CEO were challenged by FSH, together with sphingosine or staurosporine (two kinds of PKC inhibitors); or treated with phorbol myristate acetate (PMA, an activator of PKC) separately; (3) CEO were primed with BAPTA/AM (an intracellular calcium chelator) or BAPTA/AM +FSH for 60 min, and then transferred into a new culture medium supplemented with FSH but without BAPTA/AM; total culture time was 24 hr. At the end of the culture, the incidence of germinal vesicle breakdown (GVBD) was calculated. The results showed that: (1) FSH (100 U/liter) could stimulate pig CEO to override the arrest of HX and resume meiosis; DMBA (10(-8)-10(-5) M) itself also had such a kind of effect; whereas neomycin, at the level of 10-20 mM, could dramatically inhibit the stimulatory effect of FSH. (2) Staurosporine (10(-9)-10(-6) M) or sphingosine (10(-8)-10(-5) M) could also inhibit the effect of FSH in a dose-dependent manner on stimulating CEO to resume meiosis. However, PMA (10(-8)-10(-5) M) alone had a dual effect on the meiotic resumption of pig CEO. PMA, at the level of 10(-8)-10(-6) M, could stimulate CEO to resume meiosis, and at high concentration of 10(-5) M , it could even enhance the inhibitory effect of HX. (3) Priming CEO with BAPTA/AM only or BAPTA/AM +FSH for 60 min could significantly inhibit the effect of FSH in a dose-dependent manner. These results indicate that in the process of ligand-mediated meiotic resumption of pig CEO, FSH can stimulate the hydrolysis of phosphoinositide leading to the activation of PKC and mobilization of intracellular calcium; and suggest that multiple signaling pathways and signal interaction are involved in this process.

Animals↗
PubMed1999

Quantitation of meiosis activating sterols in human follicular fluid using HPLC and photodiode array detection.

A chromatographic assay for 4,4-dimethyl-5alpha-cholesta-8,14, 24-triene-3beta-ol (FF-MAS), and its reduced species, 4, 4-dimethyl-5alpha-cholesta-8,24-triene-3beta-ol (T-MAS), has been established for analysis of human follicular fluid (huFF). The assay also quantifies lanosterol, free cholesterol and progesterone. It was established using a pool of more than 100 individual follicular fluids from women undergoing in vitro fertilization treatment. Both FF-MAS and T-MAS were found in huFF, and can be quantified with HPLC equipped with photodiode array (PDA) detection. The examination wavelength for each analyte was chosen at the absorption maximum between 200 and 300 nm. Spike-recovery experiments revealed mean recoveries of 91 +/- 7.3% for lanosterol, 103 +/- 5.1% for FF-MAS, 104 +/- 5.5% for T-MAS, 103 +/- 4.5% for free cholesterol and 85 +/- 5.1% for progesterone. The lower recovery value for progesterone was due to a sub-optimal extraction procedure for this particular analyte, as indicated by re-extraction. The minimum amounts of FF-MAS required for quantification were 4 ng/mL and 23 ng/mL for T-MAS and lanosterol. FF-MAS was assayed to approximately 1.6 microM. T-MAS and lanosterol was assayed to about half of this value. No esterification of either MAS or lanosterol could be detected in huFF. Less than 10% of cholesterol was underivatized cholesterol, as more than 10 times the amount of free cholesterol could be assayed after extended saponification. This method can be used for evaluating the accumulation of MAS in huFF and its correlation to oocyte quality and fertilization parameters in in vitro fertilization programmes.

Cholestenes↗
PubMed1999

Requirements for human chorionic gonadotropin and recombinant human luteinizing hormone for follicular development and maturation.

PURPOSE: Our purpose was to evaluate the requirements for human chorionic gonadotropin (hCG) and recombinant luteinizing hormone (rec-LH) for follicular development and maturation in mice. METHODS: We carried out ovarian stimulation of immature mice. Output parameters were the preembryos created in vivo and frequency of blastocyst formation in vitro. RESULTS: hCG at 0 to 1 IU resulted in a dose-dependent recovery of preembryos (0 to 39.7 +/- 4.3; mean +/- SE) per mouse. hCG at 1 and 10 hCG gave similar results, whereas higher doses significantly reduced the number of preembryos. Potential for blastocyst formation was independent of hCG dose. hCG and rec-LH together exerted a synergistic effect on the recovery of preembryos. CONCLUSIONS: Optimal follicular development required a combination of 20 IU follicle stimulating hormone and 1-10 IU hCG. The potency of hCG was higher than that of rec-LH, but a synergistic effect of rec-LH and hCG was observed. The results may be pertinent for the development of strategies for ovarian stimulation of women with low levels of endogenous LH.

Animals↗
PubMed1999

Anovulations in an ovary during two menstrual cycles enhance the pregnancy potential of oocytes matured in that ovary during the following third cycle.

The aim of this study was to test whether ovulation from an ovary affects the health of oocytes from dominant follicles in that ovary two cycles later. A total of 80 women each with two intact ovaries underwent 270 treatment cycles (155 natural cycles and 115 clomiphene citrate cycles) all showing unilateral ovulation. The results from the in-vitro fertilization (IVF) treatment were grouped according to whether ovulation (O) or anovulation (A) (no ovulation) was observed in the ovary with dominant follicle during the treatment cycle in the previous two cycles: O-O, A-O, O-A and A-A (previous second cycle-previous first cycle). The rate of pre-embryo formation in A-A was significantly higher than that of O-A. The pregnancy rate in A-A (29%) was also higher than those of O-A (13%), A-O (9%) and O-O (5%). These rates increased from O-O to A-A as the number of previous ovulations in an ovary decreased. The presence of a corpus luteum and/or a dominant follicle is likely to exert local negative effects on the health of the oocyte contained in the follicle selected to ovulate up to two cycles later. Anovulations in an ovary for two menstrual cycles may therefore provide improved conditions for the development of a healthier oocyte with an increased pregnancy potential.

Adult↗
PubMed1999

FSH-induced resumption of meiosis in mouse oocytes: effect of different isoforms.

The ability of different isoforms of follicle stimulating hormone (FSH) to induce the resumption of meiosis in cultured mouse oocytes was evaluated. Oocytes were cultured in the presence of hypoxanthine to prevent spontaneous resumption of meiosis. Using serial dilutions of the isoform fractions representing less acidic isoforms (pI 6. 43-5.69), mid-acidic (pI 5.62-4.96) and acidic (pI 4.69-3.75), the concentration which caused 50% of the oocytes to resume meiosis and undergo germinal vesicle breakdown (GVBD) after a culture period of 24 h (i.e. ED(50%) GVBD) was determined. The FSH concentration of the isoform fractions was determined by radioimmunoassay, radio-receptor assay or through cAMP release in a Chinese hamster ovary-cell line expressing the human FSH-receptor. Determined by radioimmunoassay, the (ED(50%) GVBD) values were: less acidic 6.4 +/- 0.3 IU/l (mean +/- SD), mid-acidic 6.1 +/- 0.7 IU/l and acidic 12.2 +/- 0.7 IU/l. The less and mid-acidic isoforms were significant lower than the acidic (P < 0.0005). Similar relationships between the isoform fractions were obtained by the two other FSH assays. The results demonstrate that FSH isoforms with a pI of >5.0 induced resumption of meiosis significantly more efficiently than acidic isoforms. Less and mid-acidic isoforms may exert an important physiological function by inducing the resumption of meiosis in oocytes from pre-ovulatory follicles during the mid-cycle gonadotrophin surge.

Animals↗
PubMed1999

Anti-MIC2 as a tool in examination of testicular biopsies.

MIC2 is a pseudoautosomal gene localized on X and Y chromosomes. The MIC2 gene product is a glycoprotein expressed on the cell membranes of a number of somatic cells, including Sertoli cells of the testis, but not on the cell membranes of germ cells. In cases of cryptorchidism, a testicular biopsy is recommended in order to evaluate future fertility potential. The spermatogonia are identified on histological sections and the number per tubular transverse section is compared with normal values for age. The patient is at 33-100% risk of subsequent infertility when the number of spermatogonia per tubular transverse section is lower than 1% of the lowest normal age-matched value. Besides Sertoli cells the seminiferous tubules in undescended testes contain only a few germ cells, and it may be difficult to pinpoint the germ cells in small biopsies. Especially in nonpalpable testes their number may be heavily reduced. A reliable identification of germ cells may also be difficult in cultures of testicular biopsies from undescended testes. Against this background, we tried the use of an immunohistochemical method with DAKO antibody to the MIC2 gene product (MIC2, 12 E7, code no. M3601) in order to obtain a "negative reaction" of germ cells, contrasting with the stained Sertoli cells. The material comprised: 44 specimens of testicular parenchyma taken at time of surgery for cryptorchidism from 24 cryptorchid boys with nonpalpable testes and 14 testicular biopsies from 13 cryptorchid patients with palpable testes which had been cultured in vitro for 7, 14 or 21 days. In all cases the immunohistochemical method with DAKO antibody to the MIC2 gene product was helpful for identification of Sertoli cells and germ cells, and we therefore recommend the use of anti-MIC2 in all testicular biopsies where it is difficult to pinpoint the germ cells.

12E7 Antigen↗
PubMed1999

Assessment of the follicular cortisol:cortisone ratio.

Cortisol and cortisone concentrations in serum and follicular fluid (FF) from women undergoing in-vitro fertilization (IVF) treatment were monitored. Four groups were included: group 1, women in their natural menstrual cycle having an endogenous mid-cycle surge of gonadotrophins; group 2, women in their natural menstrual cycle receiving human chorionic gonadotrophin (HCG) for ovulation induction; group 3, women receiving exogenous gonadotrophins for ovarian stimulation and HCG for ovulation induction; and group 4, women receiving exogenous gonadotrophins for ovarian stimulation, follicles being aspirated immediately before administration of HCG. In this study, 12 follicles contained oocytes which resulted in clinical pregnancy after IVF. Cortisone concentrations were significantly higher in FF compared with that of matched serum samples, while the opposite was observed for cortisol, resulting in cortisol:cortisone ratios being significantly lower in FF compared with serum. FF from group 4 showed significantly higher cortisone concentrations than FF from each of the other three groups. FF from group 1 showed significantly higher cortisone concentrations and significantly lower cortisol:cortisone ratios in comparison with groups 2 and 3. None of the observed parameters pinpointed any of the follicles containing oocytes which resulted in a clinical pregnancy. The intrafollicular concentrations of cortisol and cortisone suggest that pre-ovulatory follicles actively convert cortisol to cortisone. Neither FF concentrations of cortisol and cortisone nor the cortisol:cortisone ratio seem to reflect implantation potential of the derived pre-embryos.

Adult↗
PubMed1998

Contralateral ovulation shortens follicular phase length and favours pre-embryo development during ovarian stimulation with clomiphene citrate.

The present study was undertaken to evaluate whether the site of ovulation affects the following follicular phase length and pre-embryo development during infertility treatment with ovarian stimulation using clomiphene citrate. A total of 363 cycles in 97 patients undergoing infertility treatment (182 intrauterine insemination (IUI) cycles in 60 patients and 181 in-vitro fertilization (IVF) cycles in 52 patients) were studied. The cycles were divided into two main groups: preceding unilateral ovulation (PUO) and preceding bilateral ovulation (PBO). In the PUO group, the cycles were subdivided into contralateral ovulation, bilateral ovulation and ipsilateral ovulation. In IVF cycles alone, bilateral ovulations were further divided into bilateral ovulation-contralateral side and bilateral ovulation, ipsilateral side. Contralateral ovulations were seen in 134 of 240 cycles (56%), excluding bilateral ovulation and PBO. The follicular phase length in contralateral ovulation (16.2 +/- 2.6 days, mean +/- SD) was significantly (P < 0.05) shorter than that of ipsilateral ovulation (16.9 +/- 2.8). There were no significant differences of follicular phase length among contralateral ovulation, bilateral ovulation and PBO. Of IVF cycles including contralateral ovulation-ipsilateral ovulation and bilateral ovulation a total of 107 preovulatory follicles was assessed in the contralateral side (contralateral ovulation + bilateral ovulation-contralateral side) and 97 in the ipsilateral side (ipsilateral ovulation + bilateral ovulation, ipsilateral side). The oocyte retrieval rate (88%), fertilization rate (84%), cleavage rate (95%), embryo transfer rate (70%) of contralateral follicles were higher than those of ipsilateral follicles (71, 62, 86, 38% respectively) and those of PBO (76, 62, 87, 41% respectively). The total pregnancy rate of both IUI and IVF did not differ among contralateral ovulation (15%), ipsilateral ovulation (8%), bilateral ovulation (11%) and PBO (10%). The results confirm and extend our previous findings in natural cycles, suggesting that local ovarian factors, e.g. from corpus luteum, affect the health of preovulatory follicle and the enclosed oocyte in the same ovary (ipsilateral) negatively. Contralateral selection of preovulatory follicles in the succeeding cycle shortens the follicular phase length and favours pre-embryo development. The chance of conceiving during ovarian stimulation with clomiphene citrate may thus be affected by the site of ovulation in the previous cycle.

Adult↗
PubMed1997

Cumulus cells of oocyte-cumulus complexes secrete a meiosis-activating substance when stimulated with FSH.

The effect of the different follicular cell types on resumption of meiosis was studied during stimulation with FSH. Cumulus enclosed oocytes (CEO), denuded oocytes (DO), and cumulus and mural granulosa cells were used. The resumption of meiosis and oocyte maturation were assessed by the determination of the germinal vesicle breakdown (GVBD) and polar body formation (PB) at the end of a 24 hr culture period in the presence of 4 mM hypoxanthine (HX). The effects of recombinant LH (r-LH) and hCG were also evaluated. Oocyte exposure to the gonadotrophins varied from 5 min to 24 hr (i.e., priming time). Oocytes were obtained from immature gonadotrophin-stimulated and -unstimulated mice. 1. FSH (1 IU/L-75 IU/L) provoked a dose-dependent increase in GVBD and PB in CEO, but not in DO, in stimulated and unstimulated mice. Eight IU/L was sufficient for inducing resumption of meiosis. In contrast, LH and hCG (both 1 IU/L-1500 IU/L) were without effect on GVBD and PB in CEO and DO of oocytes from stimulated and unstimulated mice. A combination of 8 IU/L FSH and 4-8 IU/L hCG produced an additive effect, whereas combinations with LH and higher concentrations of hCG had no such effect. 2. A 2 hr priming with FSH (8 IU/L-75 IU/L) induced a dose-dependent oocyte maturation in CEO. Thirty minutes of priming with FSH (75 IU/L) was sufficient for induction of meiotic resumption in CEO. 3. Priming CEO with FSH for 2 hr followed by the separation and repooling of oocytes and cumulus cells induced oocyte maturation. GVBD of new, unprimed DO added to cumulus cells of primed CEO increased slightly but was significant, whereas GVBD in DO isolated from the primed CEO only increased marginally. DO cocultured with FSH-primed cumulus masses seem to be prevented from resuming meiosis. 4. Priming a coculture of granulosa cells and DO with FSH for 2 hr caused a significant increase in GVBD compared to the control, evaluated after 24 hr. In contrast, a 24 hr FSH-priming of a coculture of granulosa cells and DO was without effect on GVBD. 5. A spent medium in which unstimulated cumulus cells or mural granulosa cells had grown was without effect on GVBD in DO. However, a small fraction of the DO resumed meiosis after culture in a spent medium derived from a 2 hr priming of CEO and spent media from 24 hr priming of CEO induced a 2-3 times higher GVBD frequency in the DO compared to the controls. Heat treatment of spent media (70 degrees C, 30 min) from a 24 hr FSH-priming of CEO still induced GVBD in naive DO. The results showed that FSH, in a concentration of as little as 8 IU/L, but not r-LH and hCG, induced within 30 minutes the cumulus cells to produce and after 2 hr to secrete a diffusible heat stable meiosis activating substance. This substance overcame, in a paracrine fashion, the inhibiting effect of HX and induced oocyte maturation directly in DO. The production of this substance, however, was dependent on the initial connection between the cumulus cells and the oocyte, indicating an important 2-way communication between these 2 cell types. The mural granulosa cells did not produce a meiosis inducing activity by stimulation with FSH, but significantly, more DO matured after coculture with the nonstimulated granulosa cells for 24 hr than for 2 hr. It is proposed that the heat stable meiosis activating component of the spent media from the FSH-stimulated CEO belongs to the meiosis activating sterols, MAS, previously isolated from human follicular fluid and from adult bull testes.

Animals↗