The activities of copper, zinc-superoxide dismutase (SOD1), manganese SOD (SOD2), glutathione peroxidase (GPX), glutathione reductase (GSSG-R) and glutathione S-transferase (GST) were studied in sheep corpora lutea (CL) obtained on days 15, 40, 60, 80 and 128 of pregnancy. Maintained enzymatic activity of SOD1, SOD2, GPX, GSSG-R and GST were found in the sheep CL throughout pregnancy. Enzymatic activity of SOD1, GPX and GST increased significantly from day 15 to day 40 of pregnancy, and thereafter remained constant until day 128. SOD2 and GSSG-R activities were not different between any days of pregnancy examined. Apoptotic luteal cells identified by the terminal deoxynucleotidyl transferase-mediated fluoresceindUTP nick-end labelling were very rarely observed, and their incidence (less than 0.5%) was not different between days of pregnancy. These results showed that the activities of antioxidant enzymes in the sheep CL are subject to major changes during early pregnancy, suggesting that the CL of early pregnancy may be rescued from luteolysis through increasing activities of key antioxidant enzymes and inhibition of apoptosis. Maintained levels of antioxidant enzymes in the CL throughout pregnancy may be linked to reactive oxygen species continuously generated in the steroidogenically active luteal cells, and may be involved in the maintenance of luteal steroidogenic activity and cellular integrity.
RNA fragments containing the complete R region and the beginning of the U5 region ('R') from the human T cell leukaemia virus 1 (HTLV-1) stimulated the translation of the second eistrons in bicistronic mRNAs. The 5' untranslated region from SV40 early genes (SU) which was unable to stimulate translation of second cistrons amplified markedly the internal ribosome entry site (IRES) effect of the HTLV-1 'R' fragments. The 'R' regions from HTLV-1 have therefore properties similar to internal ribosome entry sites (IRES) originally found in picornavirus. The beginning of the U5 region from HTLV-1 contains a polypyrimidine sequence which is known to play an essential role in the IRES activity in picornavirus. The same experiments carried out using the 'R' region from bovine leukaemia virus (BLV) showed that this sequence has at most a weak IRES effect. One retroviruses HTLV-1 and perhaps others contain therefore an IRES activity. Interestingly, the combined SU 'R' sequence worked efficiently with different cistrons, different promoters and in all tested cell lines, whereas the poliovirus IRES was active in CHO cells but not in the mouse mammary cell line HCll. The SU 'R' sequence may therefore preferably be used to generate active bicistronic mRNAs.
It is established that the conceptus-endometrium dialogue involves cytokines, growth factors and hormones. Given the crucial functions of the suppressor of cytokine signaling (SOCS) family proteins in cytokine signalling, we analyzed the expression and the regulation of CIS and SOCSs 1-3 transcripts during early pregnancy in the ovine endometrium. An overall stimulation of the SOCS transcripts was described in the pregnant ewes with two specific patterns. Unilaterally pregnant ewes confirmed the conceptus-produced factors as regulators of the SOCSs 1-3 expression at day 16 of pregnancy. Intrauterine injection of recombinant ovine interferon (IFN ) in cyclic ewes stimulated the expression of the SOCS mRNA with various potencies, therefore suggesting that the SOCS could take part in the negative regulation of the IFN signalling pathway.
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