Mastitis is associated with decreased fertility in dairy cows. In the current study, we created an experimental model to simulate shortterm mastitis by a single intramammary administration of Gram-negative endotoxin of Escherichia coli origin (GK), or Gram-positive toxin of Staphylococcus aureus origin (GC), to examine the effect of mastitis on oocyte developmental competence. Healthy Holstein cows were synchronized, and follicular fluid (FF) of cows treated with GC or GK and of uninfected cows (controls) was aspirated from the preovulatory follicles by transvaginal ultrasound procedure. The aspirated FF was used as maturation medium for in vitro embryo production. The distribution of matured oocytes into different cortical granule classes and meiotic stages was affected by GK administration (P!0.05) but not by GC administration. The proportion of oocytes that cleaved to two-and four-cell stage embryos (44 h postfertilization) was lower in both GC and GK groups than in controls (P!0.05). Blastocyst formation rate (7-8 days postfertilization) was lower in the GK group (P!0.05) and numerically lower in the GC group compared with their uninfected counterparts. The total cell number in blastocysts did not differ among groups; however, the apoptotic index was higher in the GC group (P!0.05), but not in the GK group, relative to controls. Examining mRNA relative abundance in oocytes and early embryos revealed mastitis-induced alterations in PTGS2 (COX2), POU5F1, and HSF1 but not in SLC2A1 (GLUT1) or GDF9. Results indicate a differential disruptive effect of mastitis induced by GK and GC on oocyte developmental competence in association with alterations in maternal gene expression.
PGS employing CMA is an efficient method to detect unrevealed chromosomal abnormalities, including complicated cases of CCR. The combined application of array CGH and FISH technologies enables the identification of an increased number of CCR carriers for which PGD is particularly beneficial.
Subclinical chronic mastitis was induced to examine the effects on oocyte developmental competence. Uninfected Holstein cows were intramammary administrated with serial (every 48h for 20 days) low doses of toxin of Staphylococcus aureus origin (Gram-positive; G+), endotoxin of Escherichia coli origin (Gram-negative; G-) or sterile saline (control). Follicular fluid of toxin- and saline-treated cows was aspirated from preovulatory follicles and used as maturation medium. Oocytes harvested from ovaries collected at the abattoir were matured and then fertilised and cultured for 8 days. The percentage of oocytes undergoing nuclear maturation, determined by meiotic nuclear stages, did not differ between groups. Cytoplasmic maturation, determined by cortical granule distribution, was affected by both toxins (PPPPTGS2) mRNA increased, whereas that of growth differentiation factor 9 (GDF9) decreased in matured oocytes. In addition, PTGS2 expression increased and POU class 5 homeobox 1 (POU5F1) expression decreased in 4-cell embryos developed from both G+ and G- oocytes. Thus, regardless of toxin type, subclinical mastitis disrupts oocyte cytoplasmic maturation and alters gene expression in association with reduced developmental competence.
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