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Abstract. The present study determined vascular changes in the bovine corpus luteum (CL) at Day 16 (early maternal recognition period) and Day 40 in early pregnancy and compared them to the CL from Day 12 and Day 16 of the estrous cycle. The CLs were analyzed in the central and peripheral regions, where site-depending features of vessels and angiogenic factors are evident. The same protein level of the endothelial cell marker von Willebrand factor was retained in the CL from Day 16 of the estrous cycle to Day 40 of early pregnancy. The protein level of pericytes and smooth muscle cells was determined using smooth muscle α-actin; the level decreased at Day 40 of early pregnancy in both regions of the CL. No significant change in the expressions of vascular endothelial growth factors VEGF164 and VEGF120 mRNA occurred from Day 16 of the estrous cycle until Day 40 of early pregnancy. Angiopoietin (ANGPT)-2 / ANGPT-1 mRNA ratio (an index of instability of vasculature) increased in the periphery at Day 16 of the estrous cycle and then decreased until Day 40 of early pregnancy. The results suggest that there is no difference in vascular structure between non-pregnant and pregnant luteal tissue during the early maternal recognition period (Day 16). Also, luteal rescue by early pregnancy may be not associated with further blood vessel formation but rather may be related to the decrease of blood vessels per unit of area and blood vessel stabilization in the bovine CL. he corpus luteum (CL) is temporarily formed in the ovary following ovulation and secretes progesterone (P) to regulate the estrous cycle and to support the establishment of pregnancy. In cows, the CL begins to regress within 17-18 days after ovulation during the estrous cycle but retains a functional lifespan of more than 200 days during pregnancy [1]. Up to 40% of total embryonic loss occurs between Days 7 and 17 of pregnancy [2,3], which is a period associated with inadequate P concentrations. Thus, some changes of function and morphology in the CL to approve conception are critical during the estrous cycle, the early maternal recognition period and early pregnancy in the cow.Several distinct cell types, such as small and large luteal cells, vascular endothelial cells and pericytes, are distributed in the bovine CL [4]. More than 50% of cells in the mature CL are of vascular origin [4]. Alterations in luteal vascularity are associated with the luteinization and formation of the CL [5]. Angiogenesis is critical to development of the CL, as an inadequate microvasculature compromises luteal function [6]. The formation of a dense capillary network in the ovary enables the hormone-producing cells to obtain the oxygen, nutrients and also precursors necessary to synthesize and release different hormones essential for maintenance of the ovarian functions. Large luteal blood vessels, i.e., arteriolovenous vessels, have a smooth muscle cell layer and exist in the peripheral, but not central, region of the rabbit CL [7]. Indeed, in the bovine CL, the arteriolovenous ...

Luteolysis is caused by a pulsatile release of prostaglandin F(2alpha) (PGF(2alpha)) from the uterus in ruminants, and a positive feedback between endometrial PGF(2alpha) and luteal oxytocin (OXT) has a physiologic role in the promotion of luteolysis. The bovine corpus luteum (CL) produces vasoactive substances, such as endothelin 1 (EDN1) and angiotensin II (Ang II), that mediate and progress luteolysis. We hypothesized that luteal OXT has an additive function to ensure the CL regression with EDN1 and Ang II, and that it has an active role in the luteolytic cascade in the cow. Thus, the aim of the present study was to observe real-time changes in the local secretion of luteal OXT and to determine its relationship with other local mediators of luteolysis. Microdialysis system (MDS) capillary membranes were implanted surgically into each CL of six cyclic Holstein cows (18 lines total among the six cows) on Day 15 (estrus == Day 0) of the estrous cycle. Simultaneously, catheters were implanted to collect ovarian venous plasma ipsilateral to the CL. Although the basal secretion of OXT by luteal tissue was maintained during the experimental period, the intraluteal PGF(2alpha) secretion gradually increased up to 300% from 24 h after the onset of luteolysis (0 h; time in which progesterone started to decrease). In each MDS line (microenvironment) within the CL, the local releasing profiles of OXT were positively associated with PGF(2alpha) and EDN1 within the CL in all 18 MDS lines implanted in the six CLs (OXT vs. PGF(2alpha), 50.0%; OXT vs. EDN1, 72.2%; P < 0.05). On the other hand, the intraluteal OXT was weakly related to Ang II (OXT vs. Ang II, 27.7%). In the ovarian vein, the peak concentration of PGF(2alpha) increased significantly when the peak of PGF(2alpha) coincided with the peak of OXT after the onset of spontaneous luteolysis (P < 0.05). In conclusion, intraluteal OXT may locally modulate secretion of vasoactive substances, particularly EDN1 and PGF(2alpha) within the CL, and thus might be one of the luteal mediators of spontaneous luteolysis in the cow.

Abstract. This study was undertaken to produce trophoblastic vesicles (TVs) by using blastocysts of in vitro origin and to estimate the effect on the interestrous interval after transfer of 4 TVs into the uteri of heifers on Day 7. Morphological examination under a stereoscopic microscope revealed that the total formation rate of TVs prepared from IVP expanded blastocysts was 80.5% and that there was no difference in the formation rates of TVs derived from blastocysts between Day 7 (83.5%) and Day 8 (78.5%). After intrauterine transfer of TVs, observation of the corpus luteum (CL) by transrectal ultrasonography together with measurement of the plasma progesterone concentration confirmed that 2 of 4 recipients (50%) had a longer interestrous interval, 33.5 and 35.0 days, while the other 2 recipients had normal cycles, 20.0 and 24.5 days. In the control group transferred D-PBS, all 4 heifers had a normal cycles, 24.0-24.5 days. Consequently, the average number of days after intrauterine transfer of TVs compared with the 2 consecutive cycles just before the treatment was longer than in the controls (6.1 ± 2.4 days vs. -0.8 ± 1.1 days, P<0.05). These results indicate that preparation of TVs from blastocysts of in vitro origin is a useable method and that TVs from blastocysts may have the capacity to maintain CL function after intrauterine transfer. Key words: Blastocyst, Corpus luteum, Estrous cycle, Trophoblastic vesicle (J. Reprod. Dev. 55: [454][455][456][457][458][459] 2009) mbryo transfer makes it possible to obtain more than one offspring per year from valuable cattle. In Japan, 80% of embryo transfers are conducted using frozen-thawed embryos [1]. However, the pregnancy rate of frozen-thawed embryo transfer is still low (45%) compared with that of fresh embryo transfer (50%) [2]. Improving fertility is necessary because of the efficiency of frozenthawed embryo transfer for control of reproduction and breeding in cattle.In ruminants, Interferon-tau (IFN-τ) is recognized as the pregnancy recognition signal [3] to maintain progesterone (P4) secretion from the corpus luteum (CL) during the pre-implantation period. The CL is a prerequisite for establishing pregnancy [4]. IFN-τ is secreted from the embryonic trophectoderm, which will develop into the main part of the future placenta [3,5]. Previously, it has been reported that the pregnancy rates following transfer of biopsied fresh, vitrified and frozen embryos are 50, 44 and 23%, respectively [6]. The pregnancy rate may tend to decrease since the level of manipulation for storage of the embryos may produce inadequate IFN-τ as result of by damage to the embryonic trophectoderm. In addition, up to 40% of total embryonic losses occur between Day 7 and 17 of pregnancy [7]. The bovine conceptus must secrete the highest amount of IFN-τ as signal for maternal recognition pregnancy between Day 15 and 17 [8]. Thus, less IFN-τ may be one reason for early embryonic loss.A prolonged cycle and delay of luteolysis has been confirmed by injection of homogenates of Day 17-18 ...

This study was conducted to evaluate the negative regulation of enkephalinase by an endogenously produced peptide, namely transforming growth factor-beta 1 (TGF beta 1). We found that TGF beta 1 acts in human endometrial stromal cells and sex skin fibroblasts in culture to cause a striking decrease (60% to > 90% in 3-7 days) in the specific activity of enkephalinase (membrane metalloendopeptidase; EC 3.4.24.11) by reducing the levels of enkephalinase mRNA and protein. Platelet-derived growth factor caused a slight reduction in enkephalinase specific activity in endometrial stromal cells; epidermal growth factor caused a slight decrease in enkephalinase specific activity in sex skin fibroblasts. In studies in which TGF beta 1 treatment and [35S]methionine labeling were conducted simultaneously, radiolabeling of enkephalinase was decreased. When proteins were radiolabeled with [35S] methionine before treatment with TGF beta 1, the extent of enkephalinase radiolabeling was similar to that in nontreated cells. These findings are indicative that TGF beta 1 acts to decrease enkephalinase activity by a reduction in gene transcription or mRNA stability and not by accelerated degradation of enkephalinase protein.