The influence of mating status and age on the induction of chromosome aberrations and dominant lethals in irradiated female mice

Young and old hybrid female mice were given 0.5 Gy or 2 Gy acute x-irradiation, followed by (i) in utero examination for dominant lethal mutations, or (ii) examination of metaphase I oocytes for chromosome aberrations 2-3 weeks after the irradiation. Some of the old females had been mated when young to males of a specific locus stock. Others were left unmated until after the irradiation when they, and the young females, were mated to the same specific locus stock and allowed to have 1 (if given 2 Gy) or 2 (if given 0.5 Gy) litters before the dominant lethal test. In both the 0.5-Gy and 2-Gy series, mean sizes of first litters in the old late-mated group were markedly lower than in the old early-mated or young groups, the differences being significant at the 2-Gy level. The intrauterine examinations showed that this difference was largely the result of a reduced ovulation rate in the old late-mated females. Preimplantation loss tended to be higher in all the old females than in the young ones, but differences between the groups in postimplantation lethality were less pronounced. In the chromosome studies, only about half as many oocytes were recovered from the ovaries of old females than from young ones. At both the 0.5-Gy and 2-Gy dose levels interchange frequencies were non-significantly higher in old than in young females (with no clear-cut effect of mating status), while the overall frequency of aberrations (interchanges + fragments) was significantly higher in oocytes of old than young females after 2 Gy X-rays (35.5% against 12.5%). No specific locus mutations were found in 5616 offspring of unirradiated females.     

Optimal dose of human chorionic gonadotropin for inducing ovulation in the ferret

The optimal dose of human chorionic gonadotropin (hCG) for induction of ovulation was determined by comparing the ovulatory response of 119 mated ferrets (controls) with that of estrous females induced to ovulate with five different dosages of hCG. Copulation induced formation of 12.7 ± 4.5 corpora lutea (CL) in all 119 females and resulted in a 90.7% conception rate as evidenced by finding approximately eight blastocysts/female in the uteri of 108 ferrets. All doses of hCG tested induced ovulation; however, the lower doses (50 and 75 IU) resulted in a lesser percentage of females ovulating. The highest doses of hCG (150 and 300 IU) resulted in fewer CL/female being formed. The optimal dose of hCG for simulating copulation induced ovulation was 100 IU. Tubal transport of unfertilized oocytes in pseudopregnant females was found to be significantly retarded when compared to the rate of transport of embryos in the control group.     

FSH-induced ovulation in intact and hypophysectomized mice

A single, ovulatory dose of 25 micrograms of a highly purified preparation of ovine FSH caused ovulation in 89% of hypophysectomized and 91% of intact female mice primed 48 h earlier with PMSG; the number of oocytes recovered (29.4 +/- 4.7 and 22 +/- 2.7/mouse ovulating, respectively) compared favourably with the 20.0 +/- 2.9 oocytes per ovulating female recovered from animals that received PMSG + hCG. After oFSH injection, 82% of oocytes released were fertilized and developed to blastocysts. That the trace contamination (less than 0.2%) of the oFSH with oLH was not responsible for the ovulation was shown by the markedly reduced number of oocytes collected from ovulating females that were injected with equivalent low levels of hCG (0.001 micrograms) or oLH (1 microgram) (9.0 +/- 3.3 and 8.0 +/- 3.1, respectively). These results demonstrate that oFSH is as effective as LH in inducing ovulation of competent oocytes in the mouse.     

Genetic consequences of irradiation of one or both parents (results of experiments on Wistar rats) Exitus lethalis in Wistar rat's progeny after irradiation of one or both parents

Examination of 2563 offsprings of Wistar rats after irradiation of one or both parents with doses of 0.25, 0.5, 1, 2, 3 and 4 Gy was carried out; the manifestation of lethal effects in the progeny of the first generation in ontogenesis was studied. The level of embryonic death was the highest after irradiation of germ cells of parents at stages of spermatids, spermatozoids and matured oocytes. Following irradiation of both parents with doses of 0.25, 0.5 and 1 Gy at these stages of gametogenesis and 4 Gy at the stage of spermatids and matured oocytes there was a trend of increasing radiation effects caused by the participation of two irradiated germ cells. After irradiation of both parents with doses of 2, 3 and 4 Gy the embryonic death F1 was essentially the same as rates for irradiated females and non-irradiated males. The F1 death rate in early postnatal development exceeded the control only after irradiation with doses of 2, 3 and 4 Gy. The increase in radiation effects in the F1 due to the mating of two irradiated parents appears to be associated with a mechanism demonstrating additivity or synergism.     

Gamma-ray-induced numerical and structural chromosome anomalies in mouse immature oocytes

Young female mice were given 1, 2 or 3 Gy of chronic gamma-irradiation. Metaphase II oocytes from these mice were sampled 8 weeks after the end of the treatment and screened for numerical and structural chromosome anomalies. The proportions of hyperhaploid (n + 1) metaphase II oocytes increased after 1 and 2 Gy (significantly after the latter) but remained at the control level after 3 Gy of gamma-rays. Structural chromosome anomalies were significantly increased above control levels at all doses and also showed an increase with dose to 2 Gy and a decline at 3 Gy. The cause of this unusual dose-response pattern for induced chromosome damage is uncertain. These results show that significant chromosome damage can be induced by irradiation of immature oocytes, a cell stage previously suggested to be resistant to induced genetic damage.     

Nondisjunction and chromosome breakage in mouse oocytes after various X-ray doses

Summary The effect of varying X-ray doses (0.05–0.80 Gy) on preovulatory mouse oocytes was studied by measuring nondisjunction during the first meiotic division, as well as structural chromosome anomalies in ovulated oocytes at metaphase stage II. The incidence of nondisjunction (0.1% hyperploid oocytes) found in oocytes from nonirradiated NMRI-Han female mice was in accordance with the results previously obtained with the same strain. Significantly (P<0.05) more hyperploid oocytes (0.9%) were ovulated following irradiation with 0.8 Gy. There was no statistically significant increase of nondisjunction after low doses. Structural chromosome anomalies occurred, however, even after an irradiation dose as low as 0.05 Gy. The dose response for structural chromosome anomalies is altogether different from that of radiation-induced hyperpoidy. We consider that irradiation of mature oocytes might well be less hazardous with regard to its potency for increasing nondisjunction during the first meiotic division when compared with the effect of chemical mutagens.     

Bimodal changes in germinability of pea seeds under the influence of low doses of gamma-radiation

Pea seeds (cv. 'Nemchinovskii-85', harvest of 2002, 80%-germination percentage) were exposed to gamma-radiation with doses ranging from 19 cGy to 100 Gy. One week after the irradiation with doses of 19 cGy and 3 Gy. the germination percentage decreased to 58 and 45%, respectively; at doses of 7 and 10 Gy it was 73 and 70% respectively. At greater doses (25, 50, and 100 Gy), germination percentage decreased in proportion. Anomalous changes in seed germination percentage (as a function of irradiation dose) were caused by the redistribution of irradiated seeds between fractions I and II. The measurements of room temperature phosphorescence in air-dry seeds and the phosphorescence of endogenous porphyrines of imbibing seeds showen that the germination decrease after the irradiation with low doses (19 cGy and 3 Gy) was caused by the increase in the number of weak seeds of fraction II, which had high rates of water uptake and suffered from hypoxia under seed coat. Some of these seeds suffocated from hypoxia, and other seeds produced seedlings with morphological defects (such seeds were considered incapable of germination). During storage of seeds irradiated at doses 19 cGy-10 Gy, the recovery of germination percentage (after its initial decrease) was caused by the decrease in seed number in fraction II. The subsequent germination decrease was caused by seed death. The higher was the irradiation dose, the faster were changes in germination percentage during storage of irradiated seeds. Bimodal changes in pea seed germination with the increase of y-irradiation dose has apparently the same origin as the changes in seed germination during accelerated ageing.     

Effect of gonadotrophin dose on oocyte retrieval in superovulated BALB/c mice

Mice are commonly used animal models in reproductive and developmental research. In order to get satisfying results from such experiments, large numbers of ova must be available and this can be achieved by using various ovulation induction protocols. To obtain an optimal response from these stimulation protocols, parameters such as breeding-housing conditions of the animal strains, the best age for superovulation, and type and dose of gonadotrophins must be optimized. The aim of this study was to investigate the impact of exogenous stimulation with increasing amounts of gonadotrophins on the number and quality of oocytes/pre-embryos recovered from outbred BALB/c mice. A dose-response analysis was performed by stimulating prepubescent (21- to 25-day-old) and sexually mature (6 to 8 weeks old) female mice with hMG, which contains equal amounts of follicle-stimulating hormone (FSH) and luteinizing hormone (LH). The stimulation dose contained 5, 10, 15, 20, 25 or 30 IU of FSH/LH. The effect of increasing stimulation was assessed by monitoring the number and maturity of ova recovered from the tubes. The data were analyzed by using a one-way Anova test and student t-test. Increasing stimulation doses in the prepubescent females resulted in an increased number of ova. A maximum of 55 ova per mouse was reached when stimulating with 20 IU of FSH/LH; higher stimulation doses showed no further increase in oocyte recovery. In the prepubescent group, a maximal number of recovered mature ova was reached with 15 IU of FSH/LH. In the sexually mature female group, 20 IU of FSH/LH gave the best quantitative and qualitative results. Positive effects of copulation on the number and maturity of oocytes in all induction doses were more evident in the prepubescent females and these parameters were significantly more improved (P < 0.05) in this group when compared to the pubertal females. Our findings led to the conclusion that ovulation induction of prepubescent outbred BALB/c mice with 15 IU FSH/LH and sexually mature ones with 20 IU FSH/LH give the best results in terms of oocyte number and maturity.     

Radiation-induced chromosome aberrations in guinea-pig growing oocytes, and their relation to follicular atresia

The female guinea-pig has been shown to represent a good model to investigate the genetic hazard of ionizing radiation in humans. The sensitivity of the guinea-pig oocytes to radiation-induced chromosome aberrations was, therefore, studied at different stages of oocyte and follicular growth. The sensitivity of oocytes enclosed in small follicles (15 weeks before ovulation) was found to be low and comparable to that of immature oocytes present at birth. The sensitivity of growing oocytes remained low and almost constant until 3 weeks before ovulation, from which time it began to increase. The most dramatic increase of sensitivity occurred during the last week preceding ovulation: about 90% of oocytes X-irradiated with 4Gy, 2 days before ovulation showed one or more chromatid interchanges, as compared to 20% for those irradiated with the same dose 1 week earlier. A comparison of our results with those found by others in the mouse shows that considerable differences of sensitivity exist between oocytes of these two species irradiated at similar stages of development. The possible reasons for these differences are discussed.     

High susceptibility for diploidy in ovulated oocytes from XO mice

Summary Adult female mice of the sensitive NMRI/Han strain ovulate diploid oocytes after gonadotropin treatment. Other mouse strains are non-sensitive with respect to the ovulation of such diploid oocytes. In this study we combined the impaired ovarian situation in the XO karyotype with the trait diploidy, which is determined genetically, by mating Ta/O (Ta=Tabby) females of C3Hx101 background to males of the NMRI/Han strain. The adult female F₁ hybrids were stimulated to ovulation by gonadotropins and identified by their karyotype (XX or XO). The cytogenetic analysis of ovulated oocytes revealed a low level of diploidy in the XX littermates (1.0%), but a very high level in females with the XO karyotype (24.6%). All of the XO females ovulated at least one diploid oocyte. We suggest that it is the XO status which drastically impairs meiosis I in our gonadotropin-sensitive F₁ females due to (1) alterations of the developmental program within the oocyte, (2) a disturbed communication between oocyte and follicle, (3) a preferential maturation and ovulation of follicles at risk, or (4) an exceptional recruitment of many such follicles, by, e.g., a premature responsiveness to gonadotropins in our XO females. An interdependence of several such mechanisms is possible.     

Reparable and irreparable damage in yeast cells induced by sparsely ionizing radiation.

It is shown that in diploid yeast there are significant differences in the extent of irreparable damage after irradiation with X-rays, 60Co-gamma-rays and 30 MeV electrons. At extremely low dose rates, 60Co-gamma-rays were found to produce almost no irreparable damage at least up to 1200 Gy. X-rays, however, at the same low dose rate caused irreparable damage in the same dose range yielding a surviving fraction of 0.25 at 1200 Gy. For irradiations at high dose rate followed by liquid holding recovery the relative biological effectiveness of X-rays amounted to at least 4 for absorbed doses of up to 1000 Gy. With 30 MeV electrons at high dose rates an accumulation of sublethal and potentially lethal damage resulting in irreparable damage occurred above 1000 Gy. It is suggested that irreparable damage in yeast is due to a cooperative effect of neighbouring track ends.     

Pattern and frequency of nondisjunction in oocytes from the Djungarian hamster are determined by the stage of first meiotic spindle inhibition

In order to study the mechanisms of nondisjunction at meiosis I in oocytes gonadotropin-stimulated Djungarian hamsters were treated at two stages [4.5 and 6 h post human chorionic gonadotropin (HCG)] during the preovulatory period with 1000 mg/kg Carbendazim (MBC). The compound, known to bind fast but reversibly to mammalian tubulin, was chosen to investigate whether the stage at which spindle function is inhibited affects the pattern of nondisjunction. Ovulated oocytes were cytologically prepared and scored for hyperhaploidy, diploidy and presegregation. Application at an early spindle phase, 4.5 h post HCG, to females stimulated with a low gonadotropin dose [3 IU pregnant mares serum (PMS); 2 IU HCG] caused a high frequency of nondisjunction (40.6%) with a more or less nonspecific pattern of malsegregated bivalents. Treatment at a late stage of spindle function (6 h post HCG) resulted in a less frequent (22.5%) but highly preferential malsegregation of those A-D group bivalents thought earlier to be late segregators. On the other hand, oocytes from females primed with a high (10 IU PMS and HCG) gonadotropin dose, a treatment assumed to delay meiosis by approximately 1.5 h, responded to MBC treatment at the late stage (6 h) with a nonspecific pattern and a high frequency (71.2%) of nondisjunction. The latter result is comparable to that in which MBC was given at the early stage (4.5 h) and after a low gonadotropin dose. The high nondisjunction response additionally indicates that spindles in hypergonadotropic stimulated oocytes are more susceptible and/or that the concentration of the inhibitor is higher in such oocytes. Only few oocytes with presegregation (3.1%; 0.0%; 1.7%) and few diploid oocytes (3.3%; 1.5%; 3.2%) with complete inhibition of meiosis I were observed. We conclude, that in Djungarian hamsters (1) the segregation of bivalents at meiosis I is asynchronous with the large A-D bivalents segregating last, (2) the phase in which spindle function is inhibited determines the pattern of nondisjunction, and (3) the resumption of meiosis I — from dictyotene to metaphase II — does not follow a rigidly timed programme but depends on the conditions of follicular maturation.     

Flow cytometric analysis of the effects of 0.4 MeV fission neutrons on mouse spermatogenesis

(C57Bl/Cne X C3H/Cne)F1 male mice were irradiated with single acute doses of 0.4 MeV neutrons ranging from 0.05 to 2 Gy, and testis cell suspensions were prepared for cytometric analysis of the DNA content 2-70 days after irradiation. Various cell subpopulations could be identified in the control histogram including mature and immature spermatids, diploid spermatogonia and spermatocytes, tetraploid cells and cells in the S-phase. Variations in the relative proportions of different cell types were detected at each dose and time, reflecting lethal damage induced on specific spermatogenetic stages. The reduction of the number of elongated spermatids 28 days after irradiation was shown to be a particularly sensitive parameter for the cytometrical assessment of the radiosensitivity of differentiating gonia. A D0 value of 0.13 Gy was calculated and compared with data obtained after X-irradiation, using the same experimental protocol. In the latter case a biphasic curve was obtained over the dose range from 0.25 to 10 Gy, possibly reflecting the existence of some cell population heterogeneity. RBE values were estimated at different neutron doses relative to the radiosensitive component of the X-ray curve, and ranged from 3.3 to 4, in agreement with data in the literature. Genotoxic effects were monitored 7 days after irradiation by a dose-dependent increase of the coefficient of variation (CV) values of the round spermatid peak, reflecting the induction of numerical and structural chromosome aberrations, and 14 or 21 days after irradiation by the detection of diploid elongated spermatids, probably arising from a radiation-induced complete failure of the first or second meiotic division.     

Ageing-induced changes in the cortical granules of mouse eggs

The cortical cytoplasm and cortical granules (CGs) of mouse oocytes were analysed by electron microscopy. Oocytes were collected soon and 20h after ovulation from adult young females (3-4 months old). In addition, gametes collected soon after ovulation from 12- to 14-month-old females were used. Ultrastructural analyses were undertaken using the conventional procedures and the alcoholic PTA method. PTA selectively stains the CGs indicating the presence of lysine-rich proteins in these granules. Oocytes from young females showed CGs as dense granules 300-500 nm in diameter linearly arranged under the oolemma. In oocytes recovered 20h after ovulation 24.31% of CGs appeared vacuolated and 38.40% internalized in the cytoplasm. In gametes collected from old females several changes were observed in the cortical cytoplasm: (a) CGs appeared concentrated in some areas while others regions were devoid of granules; (b) groups of CGs appeared internalized in the egg cytoplasm; (c) the CG contents had swollen and changed, showing dense and clear areas; (d) numerous dense structures and vesicles (lysosome-like vesicles) were present; (e) cytoplasmic fragmentation was frequently seen. Fragments contained CGs, dense structures and vacuoles. These changes are closely related to the low fertilization rates shown by these oocytes when they were used for in vitro fertilization procedures.     

Ovulation and fertilization of primary and secondary oocytes in LT/Sv strain mice

In this study, the chromosome constitution of both unfertilized oocytes and fertilized eggs isolated from the oviducts of LT/Sv strain mice were analyzed. Air-dried chromosome preparations from unfertilized oocytes revealed that about one-third of those examined were ovulated as primary oocytes. These were arrested at metaphase of the first meiotic division and exhibited the characteristic “tetrad” chromosome configuration. The remaining two-thirds of the unfertilized oocytes were ovulated at metaphase of the second meiotic division. The fertilized eggs were isolated from the oviducts of LT/Sv females previously mated to (C57BL × CBA) F1 hybrid males. Analysis of the fertilized eggs at metaphase of their first cleavage mitosis revealed that about one-third of the eggs examined were digynic triploids, whereas the remaining two-thirds had the normal diploid chromsome constitution. In the triploids, the 40 female chromosomes present (mouse, n = 20) were derived from a single diploid pronucleus formed after the extrusion of a first polar body, and following the monospermic fertilization of primary oocytes. The female pronuclear-derived chromosomes invariably exhibited “homologous pairing,” and these were associated at their centromeres. The ovulation, penetration, and subsequent fertilization of primary oocytes is an extremely unusual phenomenon in mammals and only appears to occur on a regular basis in LT/Sv mice. The premature “cytoplasmic maturation” of these oocytes is of interest, as they clearly have the same developmental capacity as secondary oocytes. The significance of these observations in relation to folliculogenesis and litter size in LT/Sv mice is discussed.     

Effects of hyperstimulation with gonadotrophins and age of females on oocytes and their metaphase II status in rats

The present study was undertaken to evaluate the effects of hyperstimulation and aging on the number and proportion of oocytes in the metaphase II stage in female Wistar rats. It explored the validity of the hypothesis that a combination of hyperstimulation with pregnant mare serum gonadotrophins (PMSG) and age could compromise, to a greater extent, the oocyte quality as indicated by the proportion of ovulated oocytes in the metaphase II stage. Female Wistar rats were stimulated with varying doses of PMSG and human chorionic gonadotrophins (hCG) and the number and proportion of ovulated oocytes in the metaphase II stage were examined and compared between different groups of young adult (8-10 weeks old) and aging (30-32 weeks old) female rats. While spontaneous ovulation occurred in all young adult rats, only 50% of the aging rats did. The ovulation rate in aging rats was increased from 50 to 93% when non-PMSG-stimulated rats were given a dose of 10 IU of hCG at proestrus. The lower number of ovulated oocytes noted, even in those hyperstimulated with high doses of PMSG/hCG, also indicated a reduction in fertility in aging rats. Under the influence of high doses of PMSG, all aging rats ovulated, but as with the young adult rats, a higher dose of hCG was needed to achieve the maximum number of ovulated oocytes from the PMSG-induced expanded pool of preovulatory follicles. However, the average number of ovulated oocytes in aging rats was, nevertheless, still significantly lower than in young adult rats even when approximation of weight was considered. No consistent significant difference in proportion of normal oocytes was noted within groups and between young adult and aging rats. A lower proportion of ovulated oocytes was arrested at the metaphase II stages when rats, whether they were young adult or aging, were hyperstimulated with 40 IU of PMSG. However, this proportion was restored to normal (about 100%) when a higher dose of hCG, which is a signal responsible for initiating oocyte maturation, was used. Results of the present study showed that there appears to be an age-related reduction of sensitivity of the preovulatory follicles to the ovulation induction signal of hCG and thus higher doses of hCG were needed to ovulate the PMSG-induced expanded pool of dominant follicles. In older rats, apart from the obvious depletion of the pool of follicles, the evidence from the present study suggests that some of these older rats do have follicles, but that these were unable to develop to preovulatory follicles, probably because of the absence of sufficiently high levels of gonadotrophins essential for the initiation of folliculogenesis. PMSG-hyperstimulation can affect nuclear maturation; the proportion of ovulated oocytes not arrested at the metaphase II stage was higher. However, the proportion of ovulated oocytes at the metaphase II was restored to normal by increasing the dose of hCG use. Hence, meiotic aberration in rats is not age-dependent but rather dependent on the amplitude of the luteinizing hormone (LH)/hCG surge present. The results from this study nullified the hypothesis that hyperstimulation in combination with aging would lead to a higher proportion of abnormality in ovulated oocytes with respect to their being at inappropriate meiotic stages.     

Effects of azadirachtin on oogenesis in Aedes aegypti

ABSTRACT. . Azadirachtin in blood fed to adult female Aedes aegypti through an artificial membrane does not cause feeding inhibition over a wide dose range (0–200 ng/female), and high doses of ingested azadirachtin fail to inhibit or delay oviposition. However, significant, transient retardation of oocyte growth is observed for up to 72 h after feeding. Immature oocytes are observed in 86% of azadirachtin-fed females decapitated 10 h after a blood meal, whereas 96% of decapitated control females contain maturing oocytes. This suggests that azadirachtin delays the release of one or more factors from the head that regulate oogenesis. We propose that adult females overcome the effect of azadirachtin by rapid metabolism rather than by excretion of the compound, since by 2 h after a blood meal, only 0.1% of ingested azadirachtin was recovered from excreta and 5% recovered from the body.     

Superovulation of immature rats by continuous infusion of follicle-stimulating hormone

Immature female rats were infused s.c. continuously over a 60-h period with partially purified porcine pituitary follicle-stimulating hormone (FSH) preparations differing in degree of purity and having widely divergent luteinizing hormone (LH):FSH potency ratios as defined by radioreceptor assays. Rats infused with the more purified FSH preparation (FSH-A) ovulated a mean of 60-85 oocytes per rat on the morning of the third day (Day 1) after FSH infusion was begun (on Day -2). The same total dose of FSH administered as a single s.c. injection or as twice daily injections over the same 60-h period resulted in ovulation in only a minority of treated rats (3/16), with none achieving ovulation rates approaching those of rats infused continuously. High fertilization rates (80% of ovulated oocytes) were observed in superovulated rats joined with fertile males on the evening of the second day of infusion (Day 0). Of the 67 +/- 7 fertilized ova per rat retrieved from oviducts flushed on Day 1, 52 +/- 8, or 80%, were accounted for as morulae or blastocysts recovered when oviducts and uteri were flushed on the morning of Day 5, demonstrating essentially normal developmental rates and high survival rates in reproductive tracts of superovulated females during the preimplantation period. Infusion of rats with the same dose of a less well-purified FSH preparation (FSH-E) containing 20 times as much LH activity, or injection of rats with a superovulatory dose of pregnant mare's serum gonadotropin (PMSG) (40 IU), were much less effective in causing superovulation, with ovulation rates of 17 +/- 6 and 34 +/- 8 oocytes/rat, respectively, compared to 79 +/- 9 oocytes/rat infused with the FSH preparation (FSH-A) containing lower LH activity.(ABSTRACT TRUNCATED AT 250 WORDS)     

Triggering ovulation with 250 μg or 500 μg of r-hCG in oocyte donors treated with antagonist protocol has no effect on the number of mature oocytes retrieved: a randomized clinical trial

The aim of this study is to compare two r-hCG doses to trigger ovulation (250 μg vs. 500 μg of r-hCG) in an oocyte donation program. A prospective, randomized study was conducted in 118 oocyte donors. Group DI received 250 μg and Group DII received 500 μg of r-hCG. Both the groups were homogeneous. No significant differences were found in the total dose of gonadotropins, duration of the treatment, total number of oocytes, or Metaphase II (MII)oocytes. The pregnancy rate per embryo transfer in the corresponding recipients was similar for both the groups (58.2% for DII recipients and 56.1% for DI recipients). Mild hyperstimulation was observed in 17 donors in Group DI (29%) and in 23 donors in Group DII (39%). No cases of severe ovarian hyperstimulation syndrome (SOHSS) were observed. In conclusion, a double dose of r-hCG in oocyte donors to trigger ovulation after stimulation with r-FSH and antagonist does not translate into a higher number of MII oocytes retrieved or into higher pregnancy rates among recipients. Our results confirm that the optimal dose to induce the final oocyte maturation with r-hCG is 250 μg, and that a higher dose does not add any benefit.     

Gilts and sows produce similar rate of diploid oocytes in vitro whereas the incidence of aneuploidy differs significantly

Oocytes derived from prepubertal gilts show reduced developmental competence when compared to oocytes collected from adult sows. Therefore, the aim of the study was to investigate whether gilts (4-5 months old) and adult sows (average age 3.5 years) of the same breed (Polish Landrace x Polish Large White crossbred) differ with regard to the rate of chromosomally unbalanced oocytes after IVM. COCs derived from individual pairs of slaughterhouse ovaries were matured in vitro and analyzed cytogenetically by conventional staining (Giemsa) and FISH methods (probes corresponding to centromeric regions of pig chromosomes 1 and 10). Altogether, 72 females (31 sows, 41 gilts) and 430 secondary oocytes (194 and 236 oocytes of sows and gilts, respectively) were investigated. Cytogenetic analysis revealed diploid (Giemsa, FISH) and aneuploid (FISH) spreads. The incidence of diploid oocytes was similar for sows (26.0%) and gilts (24.5%) whereas the rate of aneuploid oocytes (nullisomic/disomic) was eight times higher in gilts (10.8%) than in sows (1.3%). Diploid and aneuploid oocytes were observed in 64% of investigated females. Pig chromosome 10 was more frequently disomic/nullisomic compared to chromosome 1 suggesting, that like in human, small porcine chromosomes are often involved in the nondisjunction process. In conclusion, chromosomal imbalance significantly contributes to in vitro embryo production in the pig, since over 60% of females produced diploid or aneuploid gametes. The significantly higher rate of aneuploidy among oocytes derived from gilt ovaries may contribute to the reduced developmental competence of gametes collected from nonmature female pigs.