No abstract

This paper reviews Cd exposure and consequences for the health and productivity of farmed ruminants. In farmed ruminants, Cd exposure may be associated with a number of different activities, including industrial processing, mining, and agricultural practices, and is also higher in soils in some geographic regions. Cd kidney concentrations increase with age and Cd exposure. Although Cd toxicity in farmed ruminants has been demonstrated experimentally, there are no published reports of naturally occurring Cd toxicity in farmed ruminants. Clinical signs of Cd intoxication are unlikely with a daily dietary Cd intake of less than 5 mg/kg feed, which is 5-10 times higher than the maximum permitted Cd concentration in ruminant feed in the European Union. In farmed ruminants, Cd levels in tissue are largely dependent on the Cd content of diet. However, many factors affect Cd availability, relating to soils, plants and the presence of other trace elements including Ca, Cu, Fe, Mn, Mo, Se and Zn. Experimental studies have highlighted the ability of Cd to alter trace element status, and the protective effect of good mineral status, however, there remain gaps in knowledge of the impact of these interactions on the health and productivity of farmed animals.

Dominant follicles are those that continue to develop and have the potential to ovulate while subordinate follicles regress. Characteristics of dominant follicles include a larger diameter, higher intrafollicular estradiol, and lower IGF-binding protein (IGFBP)-4 concentrations compared with other cohort follicles. Follicle development is regulated by endocrine hormones that act via intracellular signaling pathways. Here, we show the differences in Akt, Erk, c-Jun N-terminal protein kinase, and p-38 signaling pathways between dominant and subordinate follicles at the dominance stage of the follicle wave. However, earlier in the follicle wave (dominant follicle selection), there were only differences in the levels of Akt and Erk signal transduction proteins among dominant and subordinate follicles. Using this profile of Akt and Erk protein expression in granulosa and theca cells of selected dominant follicles compared with subordinate follicles, we suggest a predictive model to identify future dominant and subordinate follicles from the pool of otherwise similar cohort follicles at the time of follicle wave emergence. We conclude that the Erk and Akt signal transduction pathways are important for dominant follicle selection and development and, furthermore, that the observed differences in these pathways mark the future dominant follicle from subordinate follicles before differences in follicular diameter, follicular fluid estradiol, and IGFBP-4 concentrations are apparent.

No abstract

Transcription factors inhibit or assist RNA polymerases in the initiation and maintenance of transcription; however, the cell specific expression and roles of transcription factors within bovine ovarian follicles during development are unknown. The aim of present study was to determine if the expression of transcription factors in theca and granulosa cells differ between the dominant and the largest subordinate follicles at different stages of the follicle wave. We used a bovine cDNA microarray to screen granulosa and theca cells from dominant and subordinate follicles for differential expression of genes coding for transcription factors. Expression was confirmed using reverse transcription polymerase chain reaction and differences in mRNA abundance further examined at Emergence, Selection and Dominance stages of the follicle wave. We have identified five genes encoding for transcription factors that have not been previously described in developing follicles with greater mRNA abundance in subordinate compared to dominant follicles. The genes (and their putative roles) are CEBP-beta (responsible for luteinization), SRF (cell survival), FKHRL1 (stimulates apoptosis), NCOR1 (modulation of the actions of the oestradiol receptor) and Midnolin (control of development via regulation of mRNA transport in cells).