Follicular size affects the meiotic competence of in vitro matured prepubertal and adult oocytes in sheep

Ledda, Sergio; Bogliolo, Luisa; Leoni, Giovanni; Naitana, Salvatore

doi:10.1051/rnd:19990409

Cited by 42 publications

(24 citation statements)

References 13 publications

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“…Thus, the nucleus organizes prior to oocyte development to full size. In fact, these oocytes have diameters of approximately 100 2m and they are largely incompetent (Ledda et al, 1999). Therefore, on the basis of these results in the present research, and in agreement with the indirect results of other authors, it can be asserted that nuclear competence, which is a crucial determinant for a correct embryo development, increases during the transition from PAs to EAs.…”

Section: Discussionsupporting

confidence: 92%

Nuclear Remodelling in Growing Oocytes of Sheep

et al. 2007

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Section: Discussionsupporting

confidence: 92%

Nuclear Remodelling in Growing Oocytes of Sheep

et al. 2007

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“…In fact, only sheep oocytes derived from antral follicles of *2 mm in diameter of adult ovaries can progress in meiosis in high percentage and 70% of total oocytes reach metaphase II (Ledda et al, 1999;Moor and Tounson, 1997).…”

Section: Discussionmentioning

confidence: 99%

Modifications in chromatin morphology and organization during sheep oogenesis

Russo

Martelli

Berardinelli

et al. 2007

Microscopy Res & Technique

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This research has been designed to study the major events of nuclear remodeling that characterize sheep oocytes during the early stage of folliculogenesis (transition from preantral to antral stage). In particular, the modifications in large-scale chromatin configuration, the global DNA methylation, and the process of telomere elongation have been investigated as crucial events of oocyte nuclear maturity. In addition, the spatio-temporal distribution of the major enzymes involved in DNA methylation, the DNA methyltransferase 1 (Dnmt1), and in telomere elongation, telomerase catalytic subunit (TERT), have been described. To these aims, the nuclei of isolated oocytes were investigated using immunocytochemistry and Q-FISH analyses. In absence of preliminary information, these nuclear determinants were compared with those of fully competent germ cells obtained from medium and preovulatory antral follicles. The nuclei of sheep oocytes acquired a condensed chromatin configuration, stable high levels of global DNA methylation, and a definitive telomere length already in the majority of late growing stage oocytes (110 microm) derived from early antral follicles. In addition, while the process of methylation resulted strictly related to oocyte diameter, the telomeric program appeared to be highly chromatin configuration-dependent. The translocation of Dnmt1 and TERT from the nucleus to the cytoplasm in the oocytes derived from early antral follicles seems to confirm the definitive chromatin asset of these germ cells. In conclusion, changes in large-scale chromatin structure, epigenesis, and telomere size in the sheep are established prior to oocyte acquires the ability to resume meiosis.

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“…In vitro evidence suggests that, although appreciable amounts of estradiol are detected in follicles of > 0.5 mm diameter, small antral follicles respond individually and not identically to gonadotrophins indicating a hierarchical development [31]. In sheep, the ability to progress to meiotic cycle and gain the ability to develop up to the blastocyst stage is achieved progressively as follicle diameter increases [7,18]. These negative effects due to eCG can occur before ovulation, as a consequence of an unbalanced hormonal profile during oocyte maturation or later, during early embryonic development as an inadequate capacity to cleave.…”

Section: Discussionmentioning

confidence: 99%

Sheep embryos derived from FSH/eCG treatment have a lower in vitro viability after vitrification than those derived from FSH treatment

et al. 2001

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-In the non breeding period, the effect of two superovulatory treatments (eCG/FSH in single dose or FSH alone in four decreasing doses) on the production of embryo quality following in vitro viability after vitrification procedures was investigated using forty-four adult Sarda breed ewes. In sheep treated with eCG/FSH, the mean number of corpora lutea was significantly (P < 0.05) higher (11.8 ± 4.0 vs. 8.05 ± 3.8), although the recovery rate was significantly (P < 0.01) lower (74.6 vs. 59.9) than with FSH alone. After vitrification (ethylene glycol and glycerol) was repeated three times, the rates of re-expansion at first and second warming were significantly (P < 0.01) higher in embryos derived from FSH alone than in those with both gonadotrophins (94.9 and 41.9 vs. 72.8 and 18.6) and after the last vitrification the hatched blastocyst rates were 22.5 and 7.6. After differential stain, blastocysts derived from FSH alone showed a mean number of cells significantly higher than blastocysts from eCG/FSH (184.2 vs. 157.7). It was concluded that superovulatory treatment with eCG/FSH may increase the ovarian responses compared with FSH alone, but these embryos showed a reduction in viability rates after repeated vitrification. superovulation / embryo quality / ovine / vitrification / viabilityRésumé -Les embryons ovins obtenus après un traitement de superovulation associant FSH et eCG ont une viabilité in vitro plus faible après vitrification que les embryons obtenus avec un traitement séquentiel de FSH. Pendant la saison non reproductive, on a évalué, chez 44 brebis adultes de race Sarde, l'effet de deux traitements de superovulation (le premier avec les eCG/FSH en une seule administration, le deuxième avec la FSH administrée en quatre doses décroissantes) sur la qualité des embryons produits et sur la viabilité in vitro après vitrification. Dans le groupe traité avec les eCG/FSH, le nombre moyen d'ovulations était plus élevé (11,8 ± 4,0 vs. 8,05 ± 3,8, P < 0,05) tandis que le taux de récupération était plus faible (74,6 vs. 59,9, P < 0,01) par rapport au groupe traité avec la FSH seule. Les embryons ont suivi 3 vitrifications successives (éthylène glycol et glycérol). Reprod. Nutr. Dev. 41 (2001) [239][240][241][242][243][244][245][246] 239

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Follicular size affects the meiotic competence of in vitro matured prepubertal and adult oocytes in sheep

Abstract: -Non-atretic follicles dissected from prepubertal and adult ovaries were allocated in three groups: a) < 1 mm; b) 1-2 mm; c) >

Cited by 42 publications

References 13 publications

Nuclear Remodelling in Growing Oocytes of Sheep

Nuclear Remodelling in Growing Oocytes of Sheep

Modifications in chromatin morphology and organization during sheep oogenesis

Sheep embryos derived from FSH/eCG treatment have a lower in vitro viability after vitrification than those derived from FSH treatment

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