Search Results

You are looking at 1 - 3 of 3 items for

  • Author: Pedro Melo x
  • Refine by Access: All content x
Clear All Modify Search
Open access

Panayiota Ploutarchou, Pedro Melo, Anthony J Day, Caroline M Milner, and Suzannah A Williams

During follicle development, oocytes secrete factors that influence the development of granulosa and cumulus cells (CCs). In response to oocyte and somatic cell signals, CCs produce extracellular matrix (ECM) molecules resulting in cumulus expansion, which is essential for ovulation, fertilisation, and is predictive of oocyte quality. The cumulus ECM is largely made up of hyaluronan (HA), TNF-stimulated gene-6 (TSG-6, also known as TNFAIP6), pentraxin-3 (PTX3), and the heavy chains (HCs) of serum-derived inter-α-inhibitor proteins. In contrast to other in vivo models where modified expansion impairs fertility, the cumulus mass of C1galt1 Mutants, which have oocyte-specific deletion of core 1-derived O-glycans, is modified without impairing fertility. In this report, we used C1galt1 Mutant (C1galt1 FF :ZP3Cre) and Control (C1galt1 FF ) mice to investigate how cumulus expansion is affected by oocyte-specific deletion of core 1-derived O-glycans without adversely affecting oocyte quality. Mutant cumulus–oocyte complexes (COCs) are smaller than Controls, with fewer CCs. Interestingly, the CCs in Mutant mice are functionally normal as each cell produced normal levels of the ECM molecules HA, TSG-6, and PTX3. However, HC levels were elevated in Mutant COCs. These data reveal that oocyte glycoproteins carrying core 1-derived O-glycans have a regulatory role in COC development. In addition, our study of Controls indicates that a functional COC can form provided all essential components are present above a minimum threshold level, and thus some variation in ECM composition does not adversely affect oocyte development, ovulation or fertilisation. These data have important implications for IVF and the use of cumulus expansion as a criterion for oocyte assessment.

Free access

Pedro L J Monteiro, Roberto Sartori, Aurea M O Canavessi, Leonardo F Melo, Jessica C L Motta, Carlos E C Consentini, and Milo C Wiltbank

Inappropriate corpus luteum (CL) regression can produce pregnancy loss. An experimental model was utilized to investigate regression of accessory CL during pregnancy in dairy cows. Cows were bred (day 0) and treated with gonadotrophin-releasing hormone 6 days later to form accessory CL. Transrectal ultrasound (every other days) and blood samples for progesterone (P4; daily) were performed until day 56 of pregnancy. On day 28, 13 cows were confirmed pregnant, and accessory CL were found contralateral (n = 9) or ipsilateral (n = 4) to previous ovulation. On day 18, CL biopsy was performed to analyze mRNA expression for interferon-stimulated genes (ISGs). Luteolysis occurred more frequently in cows that had contralateral accessory CL (88.9% (8/9)) than in cows with ipsilateral accessory CL (0% (0/4)). Luteolysis of contralateral accessory CL occurred either earlier (days 19–23; 2/8) or later (days 48–53; 6/8) in pregnancy and occurred rapidly (24 h), based on daily P4. After onset of earlier or later accessory CL regression, circulating P4 decreased by 41.2%. There was no difference in luteal tissue mRNA expression for ISGs on day 18 between accessory and original CL and between CL that subsequently regressed or did not regress. On day 56, an oxytocin challenge dramatically increased prostaglandin F2α metabolite (PGFM) in all cows but produced no pregnancy losses, although cows with previous accessory CL regression had greater PGFM. In summary, ipsilateral accessory CL did not regress during pregnancy, whereas most contralateral CL regressed by 63 days of pregnancy, providing evidence for local mechanisms in regression of accessory CL and protection of CL during pregnancy.

Restricted access

Zachary K Seekford, Dylan B Davis, Mackenzie J. Dickson, Lucas Melo Goncalves, Samir Burato, Matthew P. Holton, Julie Gordon, Ky G. Pohler, G. Cliff Lamb, Timothy D. Pringle, Robert L. Stewart, Maria S. Ferrer, Pedro Fontes, and John J Bromfield

Bulls used in cattle production are often overfed to induce rapid growth, early puberty and increase sale price. While the negative consequences of undernutrition on bull sperm quality are known, it is unclear how a high gain diet influences embryo development. We hypothesized that semen collected from bulls fed a high gain diet would have a reduced capacity to produce blastocysts following in vitro fertilization. Eight mature bulls were stratified by body weight and fed the same diet for 67 d at either a maintenance level (0.5% body weight per day; n = 4) or a high gain rate (1.25% body weight per day; n = 4). Semen was collected by electroejaculation at the end of the feeding regimen and subjected to sperm analysis, frozen, and used for in vitro fertilization. The high gain diet increased body weight, average daily gain, and subcutaneous fat thickness compared to the maintenance diet. Sperm of high gain bulls tended to have increased early necrosis and had increased post-thaw acrosome damage compared with maintenance bulls, but diet did not affect sperm motility or morphology. Semen of high gain bulls reduced the percentage of cleaved oocytes that developed to blastocyst stage embryos. Paternal diet had no effect on the number of total or CDX2 positive cells of blastocysts, or blastocysts gene expression for markers associated with developmental capacity. Feeding bulls a high gain diet did not affect sperm morphology or motility, but increased adiposity and reduced the ability of sperm to generate blastocyst stage embryos.