Variation of mouse oocyte sensitivity to griseofulvin-induced aneuploidy and meiotic delay during the first meiotic division

The effects of varying the time of chemical treatment on the induction of areuploidy and meiotic delay in metaphase II (Mll) oocytes were studied by administering 1,500 mg/kg griseofulvin (GF) at 0, 2, 4, 6, or 8 hr after on injection of human chorionic gonadotrophin (HCG). The results show that the oocytes have a different sensitivity to GF-induced aneuploidy and meiotic delay during the course of meiotic maturation. Although not restricted to a particular period of meiotic maturation, the frequency of aneuploidy was highest (P < 0.05) when GF was given at 2, 4, or 6 hr after HCG. The maximum frequency of hyperploidy (42.4%) occurred at the 4-hr treatment time. Also, GF treatment resulted in the induction of meiotic delay as demonstrated by ovulated metaphase I (Ml) and polyploid Mll oocytes. The meiotic delay data depict a period of relative resistance between two periods of sensitivity in that the percentages of ovulated Ml oocytes were 53.3, 21.3, 3.5, 6.7, and 25.7 when GF was given at 0, 2, 4, 6, and 8 hr after HCG, respectively. Also, at these treatment times the percentages of polyploid oocytes were 0.6, 1.7, 7.7, 20.1, and 15.4, respectively. Therefore, the oocytes seem to be more sensitive to GF-induced meiotic delay during the periods preceding and following meiotic spindle assembly. In conclusion, the results demonstrate that the time of chemical treatment influences the frequency of aneuploidy and the degree of meiotic delay. Also, the results emphasize that to thoroughly characterize the aneugenic potential of a specific chemical several treatment times may be needed. © 1994 Wiley-Liss, Inc.     

Dose-response study and threshold estimation of griseofulvin-induced aneuploidy during female mouse meiosis I and II

The relative sensitivity of the two meiotic divisions of mouseoogenesis to griseofulvin (GF)-induced aneuploidy was investigated.The first meiotic division was studied by administering GF 4h after human chorionic gonadotrophin (HCG) injection and analyzingmetaphase II (MII) oocytes, whereas study of the second meioticdivision involved treating the females 10 h after HCG and analyzingone-cell (1-Cl) zygotes. Data from previous studies have shownthat these treatment times represented the most sensitive timesfor aneuploidy induction during meioses I and II. The statisticalanalyses of the data showed that the dose-response curves foraneuploidy induction did not differ quantitatively or qualitativelybetween the two meiotic divisions. The percentages of hyperploidMil oocytes and 1-Cl zygotes were significantly higher (P <0.001) than in the controls for all doses except 125 mg/kg GF.The highest percentages of hyperploid cells were found afteradministering 1500 mg/kg GF. However, these percentages werenot different (P > 0.05) from those observed after 500 or1000 mg/kg GF, suggesting saturation of the GF aneuploid target(s).These results suggest that the relative sensitivity to GF-inducedaneuploidy between the two meiotic divisions of oogenesis aresimilar. They also suggest the presence of a lower (125 mg/kg)and an upper (500 mg/ kg) threshold for GF-induced aneuploidy. ³To whom correspondence should be addressed at: Biology and Biotechnology Research Program, Lawrence Livermore National Laboratory L-452, PO Box 808, Livermore, CA 94550, USA     

Numerical and structural chromosome aberrations induced by etoposide (VP16) during oocyte maturation of mice: transmission to one-cell zygotes and damage to dictyate oocytes

The antineoplastic drug etoposide (ET) inhibits topoisomeraseII (topo II) activity by forming a ternary complex (DNA–ET–topoII). This complex prevents the DNA-strandrejoining activityof topo II and may result in structural chromosome aberrations.Inhibition of topo II activity may also predispose cells toaneuploidy because this enzyme is needed for removing regionsof DNA catenation prior to chromosome segregation. Our objectiveswere to study the dose response for ET-induced numerical andstructural chromosomal aberrations in mouse one-cell zygotes,to compare these data with those obtained from a contemporarymetaphase II (MII) oocyte study and to evaluate the sensitivityof dictyate oocytes to ET-induced aneuploidy. ICR female micewere superovulated and injected i.p. with either 6% dimethylsulphoxide(controls) or 20, 40 or 60 mg/kg ET 2 h after human chorionicgonadotrophin (HCG). ICR males were paired (1:1) with femalesimmediately after treatment. After 17 h the males were removed,and after 24 h the females with a vaginal plug were given colchicine.One-cell zygotes were harvested for cytogenetic analysis 17h after colchicine. The percentages of hyperploid zygotes were1.1, 5.7, 13.8 and 20.7 and of zygotes with structural aberrationswere 2.5, 16.3, 37.7 and 64.7, for control, 20, 40 and 60 mg/kgET respectively. The differences between each succeeding dosefor both structural and numerical aberrations were statisticallysignificant (P < 0.01). When the ET dose response aneuploidydata from zygotes were compared with similar data from a contemporarystudy involving metaphase II oocytes, the frequencies of hyperploidywere greater in zygotes than in oocytes. We conclude that whenET is administered during the preovulatory phase of meiosis,it is both an aneugen and a clastogen in mouse one-cell zygotes. ³To whom correspondence should be addressed     

Sensitivity of mouse oocytes to nicotine-induced perturbations during oocyte meiotic maturation and aneuploidy in vivo and in vitro

Oocyte meiosis is sensitive to endogenous and exogenous perturbations that upset the temporal sequence of biochemical reactions during oocyte maturation (OM) and predispose oocytes to aneuploidy. Nicotine is an alkaloid that has been reported to disrupt the rate of OM, reduce ovulation and fertilization rates, and increase diploidy. The objective of this study was to test the hypothesis that nicotine perturbs the rate of OM and induces aneuploidy in mouse oocytes in vivo and in vitro. Female mice were given 7.5 IU pregnant mare's serum and either 0, 5.0, 7.5, or 10 mg/kg nicotine in vivo at -3, 0, and +3 h relative to a 5 IU injection of HCG. Oocytes were also cultured in vitro in the presence of 0, 1.0, 5.0, or 10.0 mmol/l nicotine. In vivo, significant (P < 0.05) differences in the proportions of oocytes with premature centromere separation and premature anaphase were found at 10.0 mg/kg nicotine suggesting that the rate of OM was advanced. Also, at this dose the proportion of ovulated oocytes was reduced by approximately 50% relative to controls. In vitro, only non-significant differences were found among the parameters measured. Although nicotine reduced the ovulation rate and perturbed the rate of OM in vivo, these data show that the rate of aneuploidy was not significantly elevated.     

The incidence of chromosomal aneuploidy in stimulated and unstimulated (natural) uninseminated human oocytes.

The incidence of chromosomal aneuploidy in human oocytes is higher than for various animal species. Since this estimate for aneuploidies is based on data obtained from in-vitro fertilization (IVF) patients, it is possible that superovulation could be contributing to this phenomenon. In this study we determine the incidence of chromosomal aneuploidy in nonstimulated uninseminated human oocytes donated by IVF patients. Furthermore, we compare this incidence of aneuploidy to that obtained after superovulation using two different protocols for induction of multiple follicular growth. The rate of aneuploidy in non-stimulated oocytes was 20% (4/20). This is not significantly different from the rate of aneuploidy in oocytes obtained after superovulation with clomiphene/human menopausal gonadotrophin (HMG)/(HCG) (15/43 = 35%, chi 2 = 1.11; P > 0.20), buserelin-flare (8/25 = 32%; chi 2 = 0.32; P > 0.05), and the rate of aneuploidy in the total number of superovulated oocytes (23/68 = 34%; chi 2 = 82; P < 0.30). Furthermore, the incidence of chromosome aneuploidy in non-stimulated uninseminated oocytes (20%) was well within the range and not significantly different from that reported in the literature for both superovulated uninseminated oocytes (range, 21-57%; total aneuploidy rate, 67/216 = 31%; P < 0.30) and superovulated inseminated oocytes (range, 3-56%; total aneuploidy, 339/1480 = 23%; P < 0.95). Consequently, the data provide evidence that superovulation protocols used in IVF may not be responsible for the higher rate of aneuploidy in human oocytes. These results are discussed in relation to hypotheses on the occurrence of meiotic non-disjunction.     

Karyotyping of human oocytes by cenM-FISH, a new 24-colour centromere-specific technique

BACKGROUND: Metaphase II (MII) chromosome complements are difficult to karyotype. The objective of this study was to investigate the efficiency and limitations of centromere-specific multiplex fluorescence in situ hybridization (cenM-FISH), a new 24 colour FISH technique using centromere-specific probes, to analyse the whole chromosome complement within human oocytes. METHODS: Oocytes were donated by 34 patients undergoing ovarian stimulation and IVF. The MII oocytes were analysed by means of cenM-FISH, while the confirmation of results was performed by FISH and/or by analysing the corresponding first polar bodies using comparative genomic hybridization (CGH). RESULTS: A total of 30 cells, corresponding to 16 oocytes and 14 first polar bodies, were successfully karyotyped by either cenM-FISH or CGH. The incidence of aneuploidy was 25%, and eight out of nine aneuploidy events were confirmed by CGH and FISH. CONCLUSIONS: We demonstrate here for the first time that the identification of any numerical abnormality in oocytes is feasible using cenM-FISH. Despite the fact that the fixation efficiency remains low, the present results confirm the advantage of analysing the whole set of chromosomes to make an accurate estimation of the aneuploidy rate in human oocytes.     

Effects of low O2 and ageing on spindles and chromosomes in mouse oocytes from pre-antral follicle culture

To assess their quality, spindles were analysed in mouse oocytes from pre-antral follicle culture. High or low oxygen tension was present during the last 16 or 20 h post human chorionic gonadotrophin (HCG)/epidermal growth factor (EGF) addition. Most oocytes from pre-antral follicle culture possessed typical anastral spindles with flat poles resembling those of ovulated, in-vivo-matured oocytes of sexually mature mice, while denuded oocytes in-vitro matured to metaphase II (MII) formed significantly longer, slender spindles with pointed, narrow poles. Spindles in oocytes from follicle culture were only slightly shorter and less compact at the equator as compared with those of oocytes matured in vivo. Chromosomes were well aligned at the equator in MII oocytes obtained from follicle culture with high oxygen. Maturation rate was significantly reduced by lowering oxygen tension to 5% O2. Prolonged culture and the presence of only 5% O2 dramatically increased the percentage of MII oocytes with unaligned chromosomes. These observations indicate that sufficient oxygen supply and time of retrieval after initiation of resumption of maturation by HCG as well as the microenvironment and cell-cell interactions between oocytes and their somatic compartment are critical in affecting the oocyte's capacity to mature to MII, to form a functional spindle, and to align chromosomes correctly.     

Thiabendazole-induced cytogenetic abnormalities in mouse oocytes

Of the various classes of human genetic disorders, aneuploidy is the most prevalent. Besides its association with maternal age and its predominant origin during maternal meiosis I, little is known about the etiology of aneuploidy. Although various classes of chemicals have been shown to induce aneuploidy in experimental systems, there is no definitive evidence for the role of chemically induced aneuploidy and adverse human health effects, particularly germ cell effects. Thus, it is important to understand the potential of chemicals for inducing aneuploidy in germ cells. There are conflicting data in the literature about the ability of thiabendazole (TBZ) to induce aneuploidy; therefore, we investigated the potential of TBZ for inducing aneuploidy in oocytes. Superovulated ICR female mice were administered 0, 50, 100, or 150 mg/kg TBZ by intraperitoneal injection. The frequencies and percentages of hyperploid oocytes were 0/472 (0), 2/410 (0.5), 6/478 (1.3), and 3/427 (0.7) for control, 50, 100, and 150 mg/kg TBZ, respectively. The difference between controls and the 100 mg/kg dose was statistically significant. Also, the proportions of ovulatory mice and the number of oocytes collected per ovulatory female were reduced in the TBZ groups relative to controls. Based on these results, we conclude that TBZ induces a small, but significant increase in the frequency of aneuploid oocytes at toxic doses that also impair ovulation. Environ. Mol. Mutagen. 29:367–371, 1997. © 1997 Wiley-Liss, Inc.     

The feasibility of using Chinese hamsters as an animal model for aneuploidy

The utility of Chinese hamsters as a test species for aneuploidy analysis was studied using four chemicals--vincristine, methyl 2-benzimidazole carbamate (MBC), nocodazole, and cyclophosphamide. Ten or more male Chinese hamsters were used per dose and bone marrow was removed at intervals of 6-96 hr. Slides were coded and 50-100 metaphases were analyzed per animal. A metaphase with more than 22 chromosomes was classified as a hyperploid cell, and the data were evaluated by using a one-tailed Fisher's exact test. In experiments using vincristine, MBC, and nocodazole, the frequencies of hyperploid cells were 0.43, 1.14, and 0.91%, respectively, for the control groups. In the experiment using cyclophosphamide, the control value frequency was 3.75%. The treated groups showed no significant increase in hyperploid frequencies when compared to concurrent controls at each of the treated times, except the value at 24 hr for the group that had been treated with vincristine at 0.75 mg/kg. However, this increase was not significant when compared to the overall value for pooled controls, with or without the cyclophosphamide control. Therefore, no significant effects due to chemical treatment were obtained in the present study. The results illustrate the extent of animal-to-animal as well as experiment-to-experiment variability in hyperploid frequencies and the importance of incorporating concurrent controls in assays for aneuploidy.     

A cytogenetic study of in-vitro matured murine oocytes after ICSI by human sperm

BACKGROUND: The purpose of this study was to investigate the chromosomal complement and developmental potential of in-vitro matured murine oocytes following ICSI by human sperm. METHODS: Heterologous ICSI fertilization between mouse oocytes and human sperm was employed in order to overcome the reduced fertilization rates observed after conventional IVF due to zona hardening during in-vitro maturation, and to assess separately maternal and paternal chromosome complements. Cytogenetic analyses were performed in four types of oocytes: (i) in-vitro matured metaphase II (MII) oocytes; (ii) in-vivo matured MII oocytes; (iii) in-vitro matured oocytes after ICSI; (iv) in-vivo matured oocytes after ICSI. RESULTS: Activation rates after ICSI of in-vitro matured oocytes was lower than that of in-vivo matured oocytes (69.9 versus 97.2%, P < 0.01), and premature chromosomal condensation was only observed in in-vitro matured oocytes. However, there were no significant differences in developmental rates after successful activation between in-vivo and in-vitro matured ICSI oocytes (69.7 versus 76.6%). The incidences of aneuploidy and structural aberrations were similar between the ICSI embryos and non-ICSI (MII) oocytes. Furthermore, the frequency of chromosomal aberrations was not associated with in-vitro or in-vivo maturation. Similar analyses of paternal chromosomes indicated that there were no significant differences in the incidence of chromosomal aberrations between the embryos derived from in-vitro and in-vivo matured oocytes. CONCLUSIONS: These results suggest that in-vitro matured oocytes following ICSI do not lead to an increase in the frequency of aneuploidy and structural aberrations when human sperm are injected into mouse oocytes.     

Methylmercury effects on Syrian hamster metaphase II oocyte chromosomes

Methylmercury (MM) denatures DNA and can induce chromosomal aberrations. In addition, it destroys microtubules and increases the incidence of aneuploidy and mitotic arrest. Although MM is distributed to gonads, data relating the cytogenetic effects of MM on mammalian germ cells in vivo have not been found. To determine whether MM increases the incidence of cytogenetic damage in oocytes, Syrian hamsters were divided into three groups: (1) negative controls; (2) positive controls, 0.25 mg Trenimon (T)/kg; and (3) 10 mg methylmercury chloride (MMC)/kg. Superovulation was utilized and metaphase II oocytes analyzed for numerical and structural chromosome aberrations. A highly significant (P = .015, Fisher's exact test) difference in the incidence of hyperploid (N = 23) oocytes was obtained between negative controls (0/150) and the MMC group (6/150). The incidence of hypoploid (N = 21) oocytes in negative controls and the MMC group was 12/150 and 21/150, respectively (P = .069). Structural aberrations were not observed. Of 281 oocytes analyzed in the T group, 42.7% had structural aberrations. These results primarily indicate that MMC increases the incidence of hyperploidy and not structural aberrations.     

Aneuploidy in mouse metaphase II oocytes exposed in vivo and in vitro in preantral follicle culture to nocodazole

Aneuploidy tests are important in evaluating genetic hazards especially when chemical exposures are suspected to affect the fidelity of chromosome segregation in oocytes and embryos. In the current study, a newly established method, mouse preantral follicle culture, was employed to grow oocytes in vitro within follicles. The sensitivity of in vitro grown follicle enclosed oocytes was compared with oocytes maturing in vivo in the ovary. In both the cases, oocytes were exposed to the cytostatic chemical, nocodazole, from the time of hormonally stimulated resumption of meiosis. The in vivo study revealed a significant decrease in the number of ovulated mouse oocytes and an increase in meiosis I-arrested and hyperploid metaphase II oocytes at a single i.p. dose of 70 mg/kg body weight of nocodazole. A significant increase was also observed in the number of meiosis I-arrested and hyperploid mouse oocytes from preantral follicle culture, when they were cultured in the presence of >or=30 nM nocodazole during the final stages of maturation. This concentration is slightly lower than that previously shown to induce nondisjunction in denuded mouse oocytes or in cultured human lymphocytes. The higher sensitivity of the in vitro matured oocytes from preantral follicle culture than that of denuded oocytes may be related to a synergistic adverse influence of nocodazole on the oocyte, on somatic cell integrity and on cell-cell communication, which possibly also affects ovulation in vivo. When expressed in molarity relative to the mouse weight, the effective dose of the acute exposure in vivo is 3-4 orders of magnitude higher than the lowest effective concentration employed continuously in vitro. Reduced bioavailability of nocodazole to the target cells due to its poor water solubility may contribute to this difference. Preantral follicle culture can be helpful in analysing mechanisms in chemically induced aneuploidy in mammalian oogenesis, and in predicting the consequences of chemical exposures in vivo.     

Blunted LH surge after HCG administration in cycles superovulated for in-vitro fertilization

The preovulatory pattern of serum luteinizing hormone (LH) was investigated in cycles superovulated for in-vitro fertilization (IVF). The method used was immunoradiometric assay which shows no cross-reactivity with human chorionic gonadotrophin (HCG) at concentrations usually found after HCG administration. Of the 245 cycles stimulated by clomiphene citrate + human menopausal gonadotrophin, an endogenous LH surge was observed in 29.8% of the patients shortly prior to the HCG injection. In the post-HCG period, 49.4% of the cycles exhibited a blunted LH rise, whereas in the remaining 20.8% the LH level did not exceed twice the mean preovulatory value. According to the oestradiol-17 beta (E2) and progesterone concentrations, different hormonal patterns were found in patients with pre-HCG and post-HCG elevation of LH. However, the occurrence of a blunted LH surge following HCG administration cannot be attributed to different, HCG-induced secretory patterns of progesterone. There were no significant differences in clinical parameters, the pregnancy rate was slightly but not significantly higher (19.0%) in the post-HCG LH surge group than in the two other groups (13.7%). It is presumed that various factors may contribute to the suspension of preovulatory LH suppression. The possible beneficial influence of a post-HCG surge of LH requires further investigation.     

Spindle imaging: a new marker for optimal timing of ICSI?

BACKGROUND: The LC Polscope facilitates visualization of the meiotic spindle in human oocyte. This study aimed to investigate meiotic spindle assembly in correlation to time elapsed after HCG administration, and to determine whether spindle imaging may serve to indicate the likelihood of fertilization and embryo cleavage. METHODS: Metaphase II (MII) oocytes from 103 couples who were being treated for male infertility were imaged with the Polscope prior to sperm injection. Spindle imaging was correlated to time elapsed from HCG administration, fertilization rate and embryo cleavage. The main outcome measures were spindle visualization, fertilization and embryo cleavage on day 3. RESULTS: A total of 770 MII oocytes were imaged. A spindle was imaged in a significantly higher number of oocytes from >or=38 h after HCG administration compared with those in the <38 h group (78.1-81.5% versus 61.6%; P < 0.001). The fertilization rate in oocytes with a visible spindle was statistically higher compared with oocytes in which spindle could not be detected (70.4% versus 62.2%; P = 0.035). We found no relationship between spindle imaging and embryo cleavage on day 3. CONCLUSIONS: Spindle imaging, in addition to first polar body appearance, is an accurate indicator for oocyte maturity. We suggest that spindle imaging be performed prior to sperm injection.     

Aneuploidy study of human oocytes first polar body comparative genomic hybridization and metaphase II fluorescence in situ hybridization analysis

BACKGROUND: The object of this study was to determine the mechanisms that produce aneuploidy in oocytes and establish which chromosomes are more prone to aneuploidy. METHODS: A total of 54 oocytes from 36 women were analysed. The whole chromosome complement of the first polar body (1PB) was analysed by comparative genomic hybridization (CGH), while the corresponding metaphase II (MII) oocyte was analysed by fluorescence in situ hybridization (FISH) to confirm the results. RESULTS: Matched CGH-FISH results were obtained in 42 1PB-MII doublets, of which 37 (88.1%) showed reciprocal results. The aneuploidy rate was 57.1%. Two-thirds of the aneuploidy events were chromatid abnormalities. Interestingly, the chromosomes more frequently involved in aneuploidy were chromosomes 1, 4 and 22 followed by chromosome 16. In general, small chromosomes (those equal to or smaller in size than chromosome 13) were more prone to aneuploidy (chi2-test, P=0.07); 25% of the aneuploid doublets would have been misdiagnosed as normal using FISH with probes for nine-chromosomes. CONCLUSIONS: The combination of two different techniques, CGH and FISH, for the study of 1PB and MII allowed the identification and confirmation of any numerical chromosome abnormality, as well as helping to determine the mechanisms involved in the genesis of maternal aneuploidy.     

Analysis of nine chromosome probes in first polar bodies and metaphase II oocytes for the detection of aneuploidies

We used fluorescent in situ hybridisation (FISH) to detect nine chromosomes (1, 13, 15, 16, 17, 18, 21, 22 and X) in 89 first Polar Bodies (1PBs), from in vitro matured oocytes discarded from IVF cycles. In 54 1PBs, we also analysed the corresponding oocyte in metaphase II (MII) to confirm the results; the other 35 1PBs were analysed alone as when preimplantation genetic diagnosis using 1PB (PGD-1PB) is performed. The frequency of aneuploid oocytes found was 47.5%; if the risk of aneuploidy for 23 chromosomes is estimated, the percentage rises to 57.2%. Missing chromosomes or chromatids found in 1PBs of 1PB/MII doublets were confirmed by MII results in 74.2%, indicating that only 25.8% of them were artefactual. Abnormalities observed in 1PBs were 55.8% whole-chromosome alterations and 44.2% chromatid anomalies. We observed a balanced predivision of chromatids for all chromosomes analysed. Differences between balanced predivision in 1PB and MII were statistically significant (P&<0.0001, chi(2) test); the 1PB was most affected. The mean abnormal segregation frequency for each chromosome was 0.89% (range 0.52-1.70%); so, each of the 23 chromosomes of an oocyte has a risk of 0.89% to be involved in aneuploidy. No significant differences were observed regarding age, type of abnormality (chromosome or chromatid alterations) or frequency of aneuploidy. Nine of the 35 patients (25.7%) whose 1PB and MII were studied presented abnormalities (extra chromosomes) that probably originated in early oogenesis. Analysis of 1PBs to select euploid oocytes could help patients of advanced age undergoing in vitro fertilization (IVF) treatment.     

The oxidizing agent tertiary butyl hydroperoxide induces disturbances in spindle organization, c-meiosis, and aneuploidy in mouse oocytes

It has been recently proposed that a concomitant generationof oxidative stress of oocytes with increasing maternal agemay be a major factor responsible for the age-related increasein aneuploid conceptions. As a preliminary step in the testingof this hypothesis, we need to confirm that oxidative stressin itself can induce errors in chromosome segregation. In orderto achieve this goal, germinal vesicle (GV)-stage mouse oocytesfrom unstimulated ICR and (C57BLxCBA) F₁ hybrid female micewere matured in vitro for 9 h for metaphase I (MI) oocytes or16 h for metaphase II (MII) oocytes in the presence of varyingconcentrations of the oxidizing agent tertiary-butyl hydroperoxide(tBH). MII oocytes from (C57BLxCBA) F₁ hybrid mice were fixedand C-banded for karyotyping analysis. MI and MII oocytes fromICR mice were fixed and stained with the DNAfluorescent probe4',6-diamidino-2-phenylindole (DAPI) to detect abnormalitiesin chromosomal distribution. Meiosis I and meiosis II spindlesfrom ICR mice were visualized by confocal immunofluorescencemicroscopy. Data from these experiments demonstrate that in-vitroexposure of mouse oocytes to tBH during meiosis I reduces thelength (pole-to-pole distance) and width (diameter at the equatorof the spindle) of meiosis I and meiosis II spindles. This reductionis associated with an increase in the percentage of oocytesshowing chromosome scattering and clumping on the MII plate,and of aneuploidy (hyperhaploidy) in MII oocytes. However, tBHat the concentrations used in the present study has only a minimalnegative effect on the frequency of meiotic maturation. Theseresults suggest that oxidative stress during meiotic maturationin vitro may induce chromosomal errors that are undetectablein the living oocyte and whose developmental consequences maybecome manifest after fertilization. aneuploidy/meiosis/mouse oxidative stress/spindle/tertiary butyl hydroperoxide     

Investigation of aneuploidy induction in mouse oocytes following exposure to vinblastine-sulfate,pyrimethamine, diethylstilbestrol diphosphate,or chloral hydrate

The various causative and mechanistic phenomena associated with aneuploidy induction require considerable investigation to better understand the etiology of chromosome missegregation. We investigated the potential of vinblastine sulfate, pyrimethamine, diethylstilbestrol diphosphate, and chloral hydrate to induce numerical and structural chromosome changes in female mouse germ cells. Superovulated ICR mice were administered the compounds either by intraperitoneal injection or oral gavage, and oocytes were collected and processed for cytogenetic analysis 17 hr later. Vinblastine sulfate, administered i.p., induced a significant increase in the frequency of ovulated Ml oocytes and of hyperploid Mll oocytes compared to controls, but did not increase the frequency of structural aberrations. Pyrimethamine, diethylstilbestrol diphosphate, and chloral hydrate did not increase the frequency of numerical or structural chromosome changes in female mouse germ cells. © 1993 Wiley-Liss, Inc.     

Evidence from a salvaged treatment cycle supports an aetiology for the empty follicle syndrome that is related to terminal follicular developmental events

Oocyte retrieval in a stimulated in-vitro fertilization treatment cycle was unsuccessful when inadvertently carried out 12 h after the administration of human chorionic gonadotrophin (HCG) injection. Repeat follicular aspiration at 36 h post-HCG injection recovered 20 oocytes, out of which 16 metaphase-II eggs were subjected to intracytoplasmic sperm injection and eight became fertilized. Uterine transfer of three cleaving embryos resulted in a singleton pregnancy which went to term and a healthy female infant was delivered. Our experience shows that in addition to issues of HCG bioavailability to the developing follicles, the temporal relationship between HCG administration (or the luteinizing hormone surge) and follicular aspiration is also an important consideration in the determination of the aetiology of the empty follicle syndrome.