Estradiol Cypionate

There have been some immunoassays reported for screening of the residues of estrogens in milk, but these methods can only determine one drug because of the limited recognition abilities of the used antibodies. Due to the broad specific recognition ability, receptor can be used as "special antibody" to develop pseudo immunoassay. However, there has been no article reporting the use of estrogen receptor for determination of estrogens in foods of animal origin so far. Furthermore, the recognition mechanism of estrogen receptor for estrogens have not been thoroughly studied.

In this study, a type of magnetic probe based on 17β-estradiol was synthesized that was used to produce the natural porcine estrogen receptor with ovarian as the source tissue. Then its recognition mechanisms for 13 estrogens were studied based on the optimal homological model. Results showed it only interacted with estrogens but did not interact with other steroid hormones. Then it was utilized as a broad specific recognition reagent to develop a direct competitive method on 96-well microplate for detection of the 13 drugs in milk. Due to the utilization of streptavidin-biotin labeled horseradish peroxidase as signal amplification system, the sensitivities for the 13 estrogens (limits of detection 0.007-0.0573 ng/mL) were improved for 33-100 folds in comparison with the use of conventional horseradish peroxidase system (limits of detection 0.31-3.53 ng/mL). This method showed no cross-reactivity with other steroid hormones, consistent with the docking result.

This is the first study reporting the use of magnetic probe to produce natural receptor from animal tissues, and this is also the first study reporting a natural estrogen-receptor-based method for multi-determination of estrogens in food sample. With the guidance of this study, more receptors and related analytical methods for other drugs or small molecules maybe are reported in the future.

While antral follicle count (AFC) has been associated with higher pregnancy rates, at present, our understanding of it as a reproductive parameter remains incomplete. This study aimed to characterize gene expression profile of oocytes from crossbred Bos taurus x Bos indicus heifers with high and low AFCs. Crossbred Nelore-Angus heifers (n = 50) with a mean (SD) age of 9.6 ± 0.55 months, a weight of 295.4 ± 32.6 kg, and a BCS of 3.44 ± 0.41 were studied in a feedlot system. The heifers received a hormonal protocol based on injectable progesterone and estradiol cypionate administered 12 days apart, and ovarian ultrasonography (US) was performed 12 days after to assess the AFC. Based on AFC, heifers were divided into low (≤14 follicles) and high (≥31 follicles) AFC, groups.Forty-five days after US, 14 heifers were slaughtered, and their ovaries were collected for morphological analysis and follicle aspiration. Cumulus-oocyte complexes (COCs) from the high and low AFC groups were graded according to their quality. Only best-quality COCs were stored for RNA-seq analysis. No differences were found in the presence or diameter of the dominant follicle and corpus luteum in the US, nor in the volume of the dominant follicle postmortem. The quantity of COCs recovered from high-AFC heifers was higher than that from low-AFC heifers (P < 0.05), and a tendency (P = 0.07) toward a higher amount of grade II COCs was observed. Thirty-two genes were differentially expressed between the groups, of which 30 were up-regulated and two down-regulated in the low AFC group. Among these, 22 % (7/32) were associated with fertility (CAB39, SLC2A6, CITED2, FDX1, HSD11B2, CD81, and PLA2G12B). Moreover, 9 and 2 exclusive genes were identified in the high and low AFC groups, respectively. Enrichment analyses showed that genes exclusive to oocytes from low-AFC heifers were associated with fundamental cellular processes, such as biosynthesis/biogenesis of ribosomes, peptides, amides, and nucleotides, and also with autophagy, mitophagy and mTOR signalling pathways.On the other hand, only one pathway was enriched in the high AFC group, but this cannot be related to the events studied No differences were observed in the ovarian structures after pre-synchronization of the estrus cycle of young Crossbred Nelore-Angus heifers. However, a tendency of a higher amount of grade II COCs was observed in heifers with high AFC than in those with low AFC. RNA sequencing results indicated that the main differences between high and low AFC heifers were not reflected in the genes directly related to fertility.