Progesterone production and release in vitro, and mRNA expression for key steroidogenic enzymes, were studied in luteal tissue recovered in the immediate postovulatory period from cyclic gilts allocated to one of three treatments: moderate feed restriction during the first (RH) or second week of the estrous cycle, with (HR+I) or without (HR) concomitant injections of long-acting insulin. Time of feed restriction affected neither progesterone production or release, nor mRNA expression for several key steroidogenic enzymes. However, luteal tissue from RH but not from HR gilts responded to LH stimulation by increasing progesterone production and release (P: < 0.05). Insulin treatment increased progesterone production and release, restored luteal tissue responsiveness to LH, up-regulated steroidogenic enzyme mRNA expression, and down-regulated the tissue inhibitor of metalloproteinase-I mRNA expression in HR+I compared with HR gilts (P: < 0.05). In vitro progesterone production and gene expression were affected by time of tissue collection after ovulation in RH and HR gilts but not in HR+I gilts, and were correlated with temporal changes in oviductal and peripheral plasma progesterone concentrations. Inherent differences in luteal function therefore appear to mediate latent effects of nutrition and insulin treatment on circulating progesterone concentrations in the critical postovulatory period in gilts.

-The mechanisms regulating oviduct function were investigated. In Experiment 1, porcine oviductal secretory protein (pOSP) mRNA, and pOSP and insulin-like growth factor (IGF-I) in oviductal flushings, decreased through the peri-ovulatory period. In Experiment 2, higher plasma steroids in oviductal veins, ipsilateral (INT), rather than contralateral (OVX), to the remaining ovary in unilaterally ovariectomized gilts, were associated with higher pOSP in INT oviductal flushings. In Experiment 3, oviduct function was assessed as part of a collaborative study in cyclic gilts. Feed restriction in the late, compared to the early, luteal phase reduced estradiol concentrations in oviductal plasma, pOSP mRNA in oviductal tissue, and IGF-I concentrations and pOSP abundance in oviduct flushings. Previous insulin treatment differentially affected oviduct function. These data provide the first direct evidence for effects of previous feed restriction and insulin treatment on the oviduct environment in the peri-ovulatory period, which may contribute to nutritional effects on embryonic survival. oviduct / steroids / porcine oviduct secretory protein (pOSP) / IGF-I / pig Reprod. Nutr. Dev. 42 (2002) 355-372 355

A better understanding of the mechanisms mediating conceptus-reproductive tract interactions in pigs has important implications for breeding herd productivity and for understanding the effects of selection for reproductive merit on patterns of prenatal loss and associated changes in the uniformity and growth potential of offspring. Nutrition and metabolic state have an important impact on embryonic and fetal development, and there is extensive evidence for both direct and indirect effects of nutrition on the reproductive tract of pigs. Changes in progesterone status can be a key mediator of indirect effects on early embryonic development. Using the cyclic, unilaterally ovariectomized gilt model, we have initially confirmed steroid-dependent changes in the secretion of oviduct proteins (POSP 1-3) as one possible component of this effect. The identification of other genes that are differentially expressed in the oviduct in the peri-implantation period is progressing, using the DD-RT-PCR approach. At the uterine level, the study of the pattern of expression of matrix metalloproteinases (MMP) and their regulators during the periimplantation period has contributed to our understanding of the regulation of the noninvasive type placental development in pigs. A failure of the blastocyst to express MMP-9 may be a key factor and seems to be dependent on local inhibitory regulation within the uterus. The coexpression of MMP-2, tissue inhibitor of MMP-2, and MMP-14 may be linked to the morphological development of the extraembryonic tissues. Changes in plasminogen activator expression are consistent with an estrogenmodulated role in tissue remodeling during embryogenesis. Studies of the integrin family of adhesion molecules also revealed key mediators of the adhesion and attachment process that is fundamental to the development of the diffuse, epitheliochorial placenta of pigs. The lack of the αv subunits on the apical surface of the trophoblast, associated with uterine epithelial expression of both αvβ1 and αvβ3, suggests that attachment is directed from the maternal side. From the perspective of the trophoblast, the low expression of the αvβ1 subunit is consistent with noninvasive placentation. The temporal expression of other integrins is consistent with a role in the migation of both extraembryonic endoderm and mesoderm during embryogenesis.

cDNA and genomic clones of a new pollen-specific gene, Bnm1, have been isolated from Brassica napus cv. Topas. The gene contains an open reading frame of 546 bp and a single intron of 362 bp. A comparison of the deduced amino acid sequence with sequences in data banks did not show similarity with known proteins. Northern blot analysis of developing pollen showed that Bnm1 mRNA was first detected in bicellular pollen and accumulated to higher levels in tricellular pollen. Bnm1 mRNA was not detected in leaves, stems, roots, pistils, seeds or pollen-derived embryos. RNA in situ hybridization of whole flower buds confirmed that Bnm1 was pollen-specific and expressed late in development. A promoter fragment of the Bnm1 gene fused to the gusA reporter gene yielded similar patterns of tissue specificity and developmental regulation in transgenic B. napus cv. Westar plants; however, the promoter was also active during the early stages of pollen development. The Bnm1 gene, cloned in this study, was derived from the A genome of the allotetraploid species B. napus (AACC). Southern blot analysis indicated that sequences similar to the Bnm1 gene were found in both A and C Brassica genomes. Related sequences were found in all 10 members of the Brassiceae tribe examined, but were not present in all tribes of the Brassicaceae family.