Cholesterol and phospholipid concentrations and phospholipase activity were measured in fluid from cannulae collected from the bovine oviductal isthmus and ampulla at different stages of the oestrous cycle. The cholesterol concentration and cholesterol normalized by protein were significantly (P = 0.03) greater in isthmic oviductal fluid (224.3 ± 42.7 μg ml⁻¹ over all stages) than in ampullary oviductal fluid (164.5 ± 11.3 μg ml⁻¹), and maximal concentrations (284.5 ± 25.5 μg ml⁻¹) were found during the luteal stage (serum progesterone concentration ≥ 1.5 ng ml⁻¹). The concentrations of the phospholipids sphingomyelin and lysophosphatidylcholine increased at different stages of the cycle and in different regions. In the ampulla, the concentration of sphingomyelin was significantly (P < 0.05) greater in oviductal fluid collected during the luteal phase (12.1 ± 2.7% of total phospholipids) than in fluid collected near oestrus and ovulation (7.5 ± 1.5% and 6.9 ± 1%, respectively). The concentration of lysophosphatidylcholine was greater (P < 0.01) in ampullary (19.2 ± 1.6% of total phospholipids) than in isthmic oviductal fluid (9.9 ± 1.1%) collected near ovulation. The ratio of cholesterol to total phospholipid was highest in oviductal fluid collected from the isthmus during all stages (2.3 μg ml⁻¹:% total phospholipid), while the minimal ratio was found in ampullary fluid collected near ovulation (1.5). Phospholipase activity was higher (P = 0.03) in isthmic oviductal fluid (20.4 ± 3.2% product formed) than in ampullary oviductal fluid (14.6 ± 1.4%); the lowest activity (12.6 ± 1.7% product formed) was in fluid collected during the phase of the oestrous cycle immediately before ovulation. We conclude that the regional and temporal differences in the concentrations of lipids in oviductal fluid provide general support for the concept that the isthmus serves as a sperm reservoir, while the ampulla is the site of the bovine sperm acrosome reaction.

The close relationship between cumulus cell function and oocyte developmental competence indicates that analysis of cumulus gene expression is a potential non-invasive method to aid embryo selection and IVF outcome. Cumulus was isolated from 674 oocytes from 75 women undergoing ICSI and gene expression analysed by quantitative RT-PCR. Cumulus expression of cyclooxygenase 2 (PTGS2) was higher with mature oocytes, whereas brain-derived neurotrophic factor (BDNF) was lower when fertilisation was normal. Expression levels of gremlin (GREM1) and BDNF were weak positive and negative predictors of embryo quality respectively. Ranking of GREM1 expression within cohorts of oocytes showed that oocytes associated with the highest GREM1 expression were more likely to be transferred or cryopreserved than discarded (49 vs 33%, P<0.02), although the clinical pregnancy rate was not significantly different. This study demonstrates both the feasibility and difficulties of this method of analysis in the largest such group studied thus far. Novel relationships between BDNF expression and fertilisation were identified, and the potential value of GREM1 expression as a marker of embryo quality supports the further assessment of GREM1 analysis in the context of embryo selection.