In vitro maturation of equine oocytes obtained from different age groups of sexually mature mares

Brinsko, S. P.; Ball, Barry A.; Ellington, J.E.

doi:10.1016/0093-691x(95)00218-w

Cited by 31 publications

(23 citation statements)

References 17 publications

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“…Nevertheless, this degeneration rate compares extremely unfavourably to that observed, for example, for bovine oocytes harvested and matured under similar conditions (Bevers, unpublished data). However, average rates of oocyte degeneration reported for in vitro matured horse oocytes vary greatly between laboratories (Willis et al, 1991;Alm and Torner, 1994;Brinsko et al, 1995;Del Campo et al, 1995) and it seems that this, at least in part, relates to the selection of follicles from which oocytes are collected. For example, Hinrichs and Schmidt (2000) reported recently that initial chromatin con®guration at the GV stage was strongly correlated with the meiotic competence of horse oocytes, and that the former was in¯uenced positively by increasing follicle size.…”

Section: Discussionmentioning

confidence: 93%

Organisation of the cytoskeleton during in vitro maturation of horse oocytes

Tremoleda¹,

Schoevers²,

Stout³

et al. 2001

Molecular Reproduction Devel

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Meiotic maturation of mammalian oocytes is a complex process during which microfilaments and microtubules provide the framework for chromosomal reorganisation and cell division. The aim of this study was to use fluorescence and confocal laser scanning microscopy to examine changes in the distribution of these important cytoskeletal elements and their relationship to chromatin configuration during the maturation of horse oocytes in vitro. Oocytes were cultured in M199 supplemented with pFSH and eLH and, at 0, 12, 24, and 36 hr after the onset of culture, they were fixed for immunocytochemistry and stained with markers for microtubules (a monoclonal anti-alpha-tubulin antibody), microfilaments (AlexaFluor 488 Phalloidin) and DNA (TO-PRO(3)). At the germinal vesicle stage, oocyte chromatin was amorphous and poorly condensed and the microfilaments and microtubules were distributed relatively evenly throughout the ooplasm. After germinal vesicle breakdown, the microtubules were aggregated around the now condensed chromosomes and the microfilaments had become concentrated within the oocyte cortex. During metaphase I, microtubules were detected only in the meiotic spindle, as elongated asters encompassing the aligned chromosomes, and, as maturation progressed through anaphase-I and telophase-I, the spindle assumed a more eccentric position and gradually rotated to assist in the separation of the homologous chromosomes and in the subsequent formation of the first polar body. During metaphase II, the meiotic spindle was a symmetrical, barrel-shaped structure with two poles and with the chromosomes aligned along its midline. At this stage, microtubules were found intermingled with chromatin within the polar body and, although, the bulk of the microfilaments remained within the oocyte cortex, a rich domain was found overlying the spindle. Thus, during the in vitro maturation of horse oocytes both the microfilament and microtubular elements of the cytoskeleton were seen to reorganise dramatically in a fashion that appeared to enable chromosomal alignment and segregation.

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Section: Discussionmentioning

confidence: 93%

Organisation of the cytoskeleton during in vitro maturation of horse oocytes

Tremoleda¹,

Schoevers²,

Stout³

et al. 2001

Molecular Reproduction Devel

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“…It has been reported that Ex horse oocytes take 24 h to reach maximum proportions at MII, whereas Cp oocytes take more than 30 h [17,18]. However, there is no standard classification or selection system for horse oocytes, and the duration of culture used for in vitro maturation of horse oocytes has ranged from 24 h [15,19,20] to 40 h or more [21,22].…”

Section: Introductionmentioning

confidence: 96%

Chromatin Configuration Within the Germinal Vesicle of Horse Oocytes: Changes Post Mortem and Relationship to Meiotic and Developmental Competence1

Hinrichs

Choi

Love

et al. 2005

Biology of Reproduction

133

129

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We evaluated the relationship of initial chromatin configuration to time of oocyte recovery and to nuclear maturation after culture in horse oocytes having compact (Cp) and expanded (Ex) cumuli. In addition, we evaluated the effect of oocyte type, time of recovery, and duration of culture on blastocyst development after intracytoplasmic sperm injection. In oocytes collected within 1 h of slaughter, fibrillar and intermediate chromatin configurations were more prevalent in Cp than in Ex oocytes (68% and 12%, respectively). In Cp oocytes collected after a 5- to 9-h delay, the proportions in the fibrillar and intermediate configurations decreased significantly, and the proportions of degenerating and homogeneously fluorescent configurations increased. When cultured, 20% of oocytes classified as having fibrillar chromatin resumed meiosis, whereas 82% of intermediate and 81% to 86% of condensed chromatin oocytes did so. Meiotic resumption was higher in oocytes recovered immediately after slaughter, but these oocytes took longer to mature. Duration of maturation significantly affected blastocyst development rates in Cp oocytes recovered after a delay (13% and 38% for oocytes matured 24 and 36 h, respectively). Oocytes recovered after a delay had higher blastocyst development rates than did those collected immediately after slaughter. We conclude that the fibrillar and intermediate chromatin configurations may degenerate during ovary storage, resulting in decreased maturation rates, especially of Cp oocytes. Time of oocyte recovery and duration of maturation significantly affect the rate of blastocyst development. Oocytes with Cp and Ex cumuli have similar developmental competence to the blastocyst stage.

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“…The proportion of horse oocytes maturing in vitro has varied among laboratories and is generally lower than those reported for other domestic species [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. Typically, 40%-70% of equine oocytes reach metaphase II (MII) after culture for in vitro maturation, whereas in goats, sows, and cows, more than 90% of oocytes progress to MII (for a review, see Goudet et al [15]).…”

Section: Introductionmentioning

confidence: 99%

Meiotic Competence of Equine Oocytes and Pronucleus Formation after Intracytoplasmic Sperm Injection (ICSI) as Related to Granulosa Cell Apoptosis1

Dell’Aquila¹,

Albrizio²,

Maritato³

et al. 2003

Biology of Reproduction

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Follicle atresia and granulosa cell apoptosis may be related to oocyte meiotic and developmental competence. We analyzed the relationships among granulosa cell apoptosis, initial cumulus morphology, oocyte nuclear maturation in vitro, and pronucleus formation after intracytoplasmic sperm injection (ICSI) in the horse. For each follicle, the size was measured and granulosa cells were used for DNA laddering analysis. Oocytes were evaluated for cumulus morphology, cultured for in vitro maturation, and submitted to ICSI. Apoptosis was categorized as absent, intermediate, or advanced according to the relative concentrations of two DNA fragments at 900 and 360 base pairs (bp). In 98 oocyte-follicle pairs, 52 oocytes were classified as expanded (Exp), 39 as compact (Cp), and 7 as having a partial (P) cumulus. Advanced apoptosis was detected in 55% (54/98) of follicles; 37% (36/98) of follicles showed an intermediate level of apoptosis; and 8 follicles (8%) were nonapoptotic. Follicle size was not significantly correlated with granulosa cell apoptosis (P > 0.05). Significantly more Exp than Cp oocytes originated from follicles with advanced apoptosis (P < 0.001). The proportion of oocytes maturing in vitro was significantly higher in oocytes issuing from apoptotic follicles than in oocytes issuing from healthy follicles (P < 0.05). The proportion of normally (two pronuclei) or abnormally fertilized oocytes (one or greater than two pronuclei, or partially decondensed sperm) did not differ in relation to granulosa cell apoptosis. We conclude that, in the mare, granulosa cell apoptosis is related to cumulus expansion and an increase in oocyte meiotic competence but has no effect on the proportion of meiotically competent oocytes that activate after ICSI. These results provide selection criteria for horse oocytes used in assisted reproductive techniques so that embryo production may be maximized.

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In vitro maturation of equine oocytes obtained from different age groups of sexually mature mares

Cited by 31 publications

References 17 publications

Organisation of the cytoskeleton during in vitro maturation of horse oocytes

Organisation of the cytoskeleton during in vitro maturation of horse oocytes

Chromatin Configuration Within the Germinal Vesicle of Horse Oocytes: Changes Post Mortem and Relationship to Meiotic and Developmental Competence1

Meiotic Competence of Equine Oocytes and Pronucleus Formation after Intracytoplasmic Sperm Injection (ICSI) as Related to Granulosa Cell Apoptosis1

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