Expression and localization of the contractile prostaglandin F receptor in pregnant rat myometrium in late gestation, labor, and postpartum

A polyclonal antibody was raised against amino acids 7-18 in the first extracellular loop of rat prostaglandin F (FP) receptor to monitor expression and localization in pregnant rat myometrium at Gestational Days 16, 18, 20, 21, 21.5, 22 (delivery), and 23 (1-day postpartum; n = 5 per group). The antibody recognized a protein of approximately 43 kDa on Western blot analysis in both membrane (soluble and nonsoluble) and cytosolic fractions of myometrium on each day of gestation. Expression of FP protein increased significantly (P < 0.05) during late gestation in both soluble membrane and cytosolic fractions, being significantly greater at Day 21.5 than at Day 20 of gestation in the soluble membrane fraction and in the cytosolic fraction of tissues collected during labor compared with those obtained before labor. The total concentration of FP receptor in the membrane (soluble plus nonsoluble) remained high throughout late gestation and fell significantly (P < 0.05) in the postpartum period. The FP receptor in the soluble membrane fraction (compared to the total membrane FP receptor) was significantly (P < 0.05) higher in late gestation than earlier, whereas the ratio of FP protein in cytosolic to that in the total membrane was significantly (P < 0.05) higher on Day 23 than earlier in gestation, suggesting a dynamic movement of FP with advancing gestational age. Immunoreactive FP receptor localized to circular and longitudinal smooth muscle at all gestational ages, but changes in intracellular localization were observed in late gestation with a staining pattern similar to alpha-actin, suggesting an association with myofibrils. Our study suggests an increase in FP-receptor protein in myometrium with advancing gestation and a marked elevation at term. This supports a role for uterine FP receptors in mediation of uterine contractility at term.     

Leptin in pregnancy: an update

Leptin influences satiety, adiposity, and metabolism and is associated with mechanisms regulating puberty onset, fertility, and pregnancy in various species. Maternal hyperleptinemia is a hallmark of mammalian pregnancy, although both the roles of leptin and the mechanisms regulating its synthesis appear to be taxa specific. In pregnant humans and nonhuman primates, leptin is produced by both maternal and fetal adipose tissues, as well as by the placental trophoblast. Specific receptors in the uterine endometrium, trophoblast, and fetus facilitate direct effects of the polypeptide on implantation, placental endocrine function, and conceptus development. A soluble isoform of the receptor may be responsible for inducing maternal leptin resistance during pregnancy and/or may facilitate the transplacental passage of leptin for the purpose of directly regulating fetal development. The steroid hormones are linked to the regulation of leptin and the leptin receptor and probably interact with other pregnancy-specific, serum-borne factors to regulate leptin dynamics during pregnancy. In addition to its effects on normal conceptus development, leptin is linked to mechanisms affecting a diverse array of pregnancy-specific pathologies that include preeclampsia, gestational diabetes, and intrauterine growth restriction. Association with these anomalies and with mechanisms pointing to a fetal origin for a range of conditions affecting the individual's health in adult life, such as obesity, diabetes mellitus, and cardiovascular disease, reiterate the need for continued research dedicated to elucidating leptin's roles and regulation throughout gestation.     

Relationship between placental vascular endothelial growth factor expression and placental/endometrial vascularity in the pig

We investigated the temporal association between placental vascular endothelial growth factor (VEGF), a potent stimulator of angiogenesis and vascular permeability, and changes in placental/endometrial vascularity on selected days throughout gestation in the pig. Placental and endometrial tissues were collected from sows on Days 25 (n = 4), 36 (n =6), 44 (n = 6), 70 (n =5), 90 (n =5 ), and 112 (n = 7) of gestation. Cross sections of the placental/endometrial interface of each conceptus were used to estimate the number of blood vessels per unit area via image analysis and the intensity of VEGF staining via immunohistochemistry. Placental tissues were also collected on these days to evaluate VEGF mRNA expression. Placental VEGF mRNA expression and the numbers of blood vessels per unit area of placental and adjacent endometrial tissue were low and decreasing from Day 25 to Day 44, before increasing (P < 0.05) markedly and progressively through Day 112. These data are consistent with the marked increase in VEGF immunostaining in the chorionic and uterine luminal epithelium from early to late gestation. Further, these increases in placental VEGF mRNA were positively correlated with fetal weight (r = 0.73; P < 0.0001) and placental efficiency (fetal weight/placental weight ratio; r = 0.66, P < 0.0001). These data are consistent with a role for VEGF in increasing the number of blood vessels at the placental endometrial interface, resulting in an increased capacity for nutrient transfer from the maternal to the fetal compartment.     

IL-6 trans-signaling system in intra-amniotic inflammation, preterm birth, and preterm premature rupture of the membranes

Classic IL-6 signaling is conditioned by the transmembrane receptor (IL-6R) and homodimerization of gp130. During trans-signaling, IL-6 binds to soluble IL-6R (sIL-6R), enabling activation of cells expressing solely gp130. Soluble gp130 (sgp130) selectively inhibits IL-6 trans-signaling. To characterize amniotic fluid (AF) IL-6 trans-signaling molecules (IL-6, sIL-6R, sgp130) in normal gestations and pregnancies complicated by intra-amniotic inflammation (IAI), we studied 301 women during second trimester (n = 39), third trimester (n = 40), and preterm labor with intact (n = 131, 85 negative IAI and 46 positive IAI) or preterm premature rupture of membranes (PPROM; n = 91, 61 negative IAI and 30 positive IAI). ELISA, Western blotting, and real-time RT-PCR were used to investigate AF, placenta, and amniochorion for protein and mRNA expression of sIL-6R, sgp130, IL-6R, and gp130. Tissues were immunostained for IL-6R, gp130, CD15(+) (polymorphonuclear), and CD3(+) (T cell) inflammatory cells. The ability of sIL-6R and sgp130 to modulate basal and LPS-stimulated release of amniochorion matrix metalloprotease-9 was tested ex vivo. We showed that in physiologic gestations, AF sgp130 decreases toward term. AF IL-6 and sIL-6R were increased in IAI, whereas sgp130 was decreased in PPROM. Our results suggested that fetal membranes are the probable source of AF sIL-6R and sgp130. Immunohistochemistry and RT-PCR revealed increased IL-6R and decreased gp130 expression in amniochorion of women with IAI. Ex vivo, sIL-6R and LPS augmented amniochorion matrix metalloprotease-9 release, whereas sgp130 opposed this effect. We conclude that IL-6 trans-signaling molecules are physiologic constituents of the AF regulated by gestational age and inflammation. PPROM likely involves functional loss of sgp130.     

Differential suppression of endometrial prostaglandin F2alpha by the equine conceptus

Prostaglandin F2alpha secretion by the uterine endometrium between Days 13 and 14 postovulation causes luteal regression in mares. A mechanism involving interruption or suppression of this secretion causes pregnancy to be maintained. The present study was designed to determine the age of the conceptus when maximal suppression of PGF2alpha secretion occurs. Mares were examined daily during estrus with ultrasonography (day 0 = day of ovulation). Conceptus tissues were recovered nonsurgically on Days 9 (n = 7), 12 (n = 5), 13 (n = 5), and 16 (n = 7) and uterine biopsies on Day 14. Both uterine and conceptus tissues were washed in phosphate-buffered saline (PBS) with 100 units penicillin G/ml + 100 microg streptomycin/ml, pH 7.4. Endometrial tissue (approximately 200 mg) plus conceptus tissues were incubated in 15 ml of tissue culture medium 199 (M199) + 10% fetal calf serum and 10 units penicillin G/ml and 10 microg streptomycin/ml at 37 degrees C under 5% CO(2): 5% O(2) : 90% N(2). Samples were taken at 4, 8, and 24 h. Two plates that contained only endometrial tissue and two additional plates with 25 mg flunixin meglumine added along with endometrial tissue were also included in the incubations. Concentrations of PGF2alpha were measured in all samples using radioimmunoassay. There was a trend toward suppression of PGF2alpha secretion by conceptus tissues, regardless of age. However, Day 12 concepti significantly suppressed PGF2alpha secretion compared with that of endometrial tissue incubated alone (P = 0.03).     

Serum and milk concentrations of leptin in gilts fed a high- or low-energy diet during gestation

Concentrations of leptin in serum and milk were assessed in gilts fed diets during gestation that differed in energy level. Beginning at day 45 and continuing throughout pregnancy, gilts received either a high-energy (6882 kcal metabolizable energy (ME) per day) or low-energy (5221 kcal ME per day) diet (n = 9 per group). All gilts had ad libitum access to a standard lactation diet throughout a 21 day lactation. During gestation, gilts consuming the high-energy diet gained more body weight (P < 0.01) and backfat thickness (P = 0.03) than gilts fed the low-energy diet; however, serum concentrations of leptin remained similar between groups (P = 0.35). Within 24 h after farrowing, gilts fed the high-energy diet had greater levels of leptin in serum and milk than gilts that consumed the low-energy diet during gestation (P < 0.07); Across treatments, backfat thickness and leptin levels in serum were positively correlated (r(2) = 0.51; P = 0.03). At weaning, backfat thickness (P < 0.07), but not body weights or serum and milk levels of leptin (P > 0.1), were greater for gilts fed the high-energy, versus the low-energy, diet during gestation. Gilts that were fed the low-energy diet during gestation consumed more feed during week 2 of lactation (P = 0.06). Our results suggest that altering the level of energy in the diets of gestating swine can influence circulating and milk concentrations of leptin, as well as feed consumption, during lactation.     

Maturational differences between vascular and bladder smooth muscle during ovine development

Maturation rates of vascular and visceral smooth muscle (SM) during ovine development were compared by quantifying contractile protein, myosin heavy chain (MHC) isoform contents, and contractile properties of aortas and bladders from female fetal (n = 19) and postnatal (n = 21) sheep. Actin, myosin, and protein contents rose progressively throughout development in both tissues (P 相似文献   

Circulating leptin concentrations are positively related to leptin messenger RNA expression in the adipose tissue of fetal sheep in the pregnant ewe fed at or below maintenance energy requirements during late gestation

We have investigated the effects of maternal undernutrition during late gestation on maternal and fetal plasma concentrations of leptin and on leptin gene expression in fetal perirenal adipose tissue. Pregnant ewes were randomly assigned at 115 days of gestation (term = 147 +/- 3 days [mean +/- SEM]) to either a control group (n = 13) or an undernourished group (n = 16) that received approximately 50% of the control diet until 144-147 days of gestation. Maternal plasma glucose, but not leptin, concentrations were lower in the undernourished ewes. A significant correlation was found, however, between mean maternal plasma leptin (y) and glucose (x) concentrations (y = 2.9x - 2.4; r = 0.51, P < 0.02) when the control and undernourished groups were combined. Fetal plasma glucose and insulin, but not fetal leptin, concentrations were lower in the undernourished ewes, and no correlation was found between mean fetal leptin concentrations and either mean fetal glucose or insulin concentrations. A positive relationship, however, was found between mean fetal (y) and maternal (x) plasma leptin concentrations (y = 0.18x + 0.45; r = 0.66, P < 0.003). No significant difference was found in the relative abundance of leptin mRNA in fetal perirenal fat between the undernourished (0.60 +/- 0.09, n = 10) and control (0.70 +/- 0.08, n = 10) groups. Fetal plasma concentrations of leptin (y) and leptin mRNA levels (x) in perirenal adipose tissue were significantly correlated (y = 1.5x +/- 0.3; r = 0.69, P < 0.05). In summary, the capacity of leptin to act as a signal of moderate maternal undernutrition may be limited before birth in the sheep.     

Long-term hypoxia increases leptin receptors and plasma leptin concentrations in the late-gestation ovine fetus

This study was designed to test the hypothesis that long-term hypoxia (LTH) increases fetal plasma leptin and fetal adipose or placental leptin expression and alters hypothalamic and adrenocortical leptin receptor (OB-R) expression. Pregnant ewes were maintained at high altitude (3,820 m) from day 30 to approximately 130 days of gestation. Reduced Po2 was maintained in the laboratory by nitrogen infusion through a maternal tracheal catheter. On day 132, normoxic control and LTH fetuses underwent surgical implantation of vascular catheters (n=6 for each group). Five days after surgery, maternal and fetal arterial blood samples were collected for leptin, insulin, and glucose analysis. Placental tissue, periadrenal fat, and fetal hypothalami and adrenal glands were collected from additional control (n=7) and LTH (n=8) fetuses for analysis of leptin mRNA by quantitative, real-time, RT-PCR (qRT-PCR). There was a significant (P<0.03) elevation in fetal plasma leptin in the LTH fetuses (3.5+/-0.7 ng/ml) vs. control (1.1+/-0.1 ng/ml). There were no differences in either glucose or insulin concentrations between the two groups. Periadrenal adipose leptin mRNA was significantly higher in the LTH group compared with control, as was placental leptin expression. The levels of leptin mRNA in adipose were approximately 70 times higher vs. placenta. LTH significantly reduced expression of OB-Ra (short-isoform) in the hypothalamus (P=0.0156), while resulting in a significant increase in adrenal OB-Rb (long-form) expression (P<0.03). Our data suggest that leptin is a hypoxia-inducible gene in the ovine fetus and OB-R expression is altered by LTH. These changes may be responsible in part, for our previously observed alterations in fetal hypothalamic-pituitary-adrenal function following LTH.     

Developmental changes in polyamine levels and synthesis in the ovine conceptus

Polyamines (putrescine, spermidine, and spermine) are essential for placental growth and angiogenesis. However, little is known about changes in polyamine synthesis associated with development of the ovine conceptus (embryo/fetus and associated placental membranes). We hypothesized that rates of placental polyamine synthesis were maximal during the rapid placental growth that occurs in the first half of pregnancy. This hypothesis was tested using ewes between Days 30 and 140 of gestation. Columbia cross-bred ewes were hysterectomized on Days 30, 40, 60, 80, 100, 120, or 140 of gestation (Day 0 = mating; n = 4 ewes/day) to obtain placentomes, intercotyledonary placenta, intercaruncular endometrium, and allantoic as well as amniotic fluids. The tissues were analyzed for ornithine decarboxylase (ODC) and arginase activities; arginine, ornithine, and polyamine concentrations; and polyamine synthesis using radiochemical and chromatographic methods. Maximal ODC and arginase activities and the highest rates of polyamine synthesis were observed in all tissues on Day 40 of gestation. Concentrations of ornithine and polyamines in placentomes and intercaruncular endometrium also peaked on Day 40 of gestation. In ovine allantoic and amniotic fluids, polyamines were most abundant during early (Days 40-60) and late (Days 100-140) gestation, respectively. Amniotic fluid spermine increased progressively with advancing gestation. Results of the present study indicate metabolic coordination among the several integrated pathways that support high rates of polyamine synthesis in the placenta and endometrium during early pregnancy. Our findings may have important implications for both intrauterine growth retardation and fetal origins of diseases in adults.     

173 Role of free cysteines in leptin receptor

Leptin, a 16-kDa adipocytic peptide hormone (product of ob gene), is known to play a key role in the control of body weight and exerts its influence by binding to its long-form receptor (Ob-Rb). Ob-Rb belongs to class I cytokine receptor superfamily and consists of an extracellular, transmembrane, and an intracellular domain. Cysteines including free and disulphide-bonded are known to play a significant role in recognition of leptin by its receptor and are known to be highly conserved in different organisms including human, macaca, mouse, dog, sheep, zebrafish, and medaca. Recently, the crystal structure of leptin-binding domain of human leptin receptor has been determined (1). Using the structural data, we analyzed the role of free cysteines in leptin-binding domain of leptin receptor through docking studies using Rosettadock. The conserved free cysteines namely Cys-604 and Cys-613 were mutated to alanines and this resulted in drastic change in the binding orientation of leptin and its receptor. Based on computational analysis, we propose that cysteines either free or involved in disulphide bridges might play a crucial role during signaling and might be the primary determinant of leptin-receptor interactions, the details of which will be discussed. Currently, understanding the structural basis of leptin and its binding to leptin receptor gains much significance since it might pave the way for designing inhibitors that might be used in controlling obesity.     

Growth and metabolism of the placenta after unilateral fetectomy in twin pregnant ewes.

Twin-pregnant ewes underwent unilateral fetectomy (Fetx) at 50 days of gestation and were studied at 136 days. Aspects of conceptus growth and placental cellularity and metabolism in vitro were compared to those of unoperated control groups of twin-pregnant or single-pregnant ewes. Mean fetal weight in Fetx ewes tended to be greater than that of twin-pregnant ewes and was similar to that of single-pregnant ewes. Mean placental wet and dry weights were intermediate between those for naturally single- and twin-pregnant animals. Fetectomy caused a significant increase in placental protein:DNA ratio but an unchanged DNA concentration, apparently due to cellular hypertrophy in the placenta of the remaining fetus. Weight-specific rate of oxygen consumption (VO2) of fetal placental tissue in twin-pregnant ewes was higher than in Fetx or singles while maternal placental VO2 in twins tended to be lower than in either of the other two groups. These results highlight the plasticity of placental metabolism and growth, perhaps in response to altered trophic signals from the fetus. Unilateral fetectomy should prove useful in studies designed to identify these signals.     

Relationship between maternal plasma progesterone concentration and interferon-tau synthesis by the conceptus in cattle

The objective of this study was to determine the relationship between maternal progesterone concentration and conceptus synthesis of interferon-tau as an index of conceptus viability at the time of maternal recognition of pregnancy. Heifers of mixed beef breeds were randomly assigned to receive 1 of 2 treatments: 1) intramuscular injection of 1500 IU hCG on Day 5 after artificial insemination (AI; n = 12) or 2) intramuscular injection of saline on Day 5 after AI (n = 17). Ovaries were scanned daily by transrectal real-time ultrasonography. Progesterone concentrations were determined from daily blood samples collected from the jugular vein. Heifers were slaughtered on Day 18 after AI and conceptus tissues were collected. These were incubated individually at 37 degrees C in RPMI medium, and supernatant collected after 24 h. Conceptus secretory products in the supernatant were analyzed for interferon concentration by antiviral assay using vesicular stomatitis virus. Transrectal ultrasonography showed all heifers that received hCG had at least 1 extra corpus luteum (CL) in addition to the spontaneous CL formed from the previous ovulation (10 with 2 CL, 2 with 3 CL). A significant increase in plasma progesterone concentration was detected in pregnant heifers treated with hCG (n = 9) vs pregnant control heifers (n = 11; P < 0.001). There was a tendency for an increase (P = 0.059) in synthesis of interferon-tau by conceptuses from hCG-treated heifers compared to control heifers. Maternal plasma progesterone concentrations were correlated with interferon-tau production by the conceptuses (r = 0.593, P < 0.006), suggesting that higher maternal progesterone may provide a more suitable environment for the developing conceptus.     

Fetectomy alters maternal pituitary-adrenal function in pregnant rhesus macaques.

The interplay between the fetus and mother may play a key role in the regulation of primate pregnancy and parturition. This study was designed to test the hypothesis that fetectomy alters maternal pituitary-adrenal function. Between 117 and 122 days of gestation (term = 167 days), six rhesus macaques underwent surgery for catheter implantation. At surgery the fetuses were removed while the membranes and placenta were left in situ. Six additional intact catheterized pregnant animals served as controls. Animals were maintained under a 12L:12D cycle with lights-on from 0700 to 1900 h. Beginning at least 1 wk after surgery, maternal arterial blood samples were collected at 3-h intervals for 24 h for hormone and catecholamine analysis. This sampling protocol was repeated at weekly intervals until cesarean delivery at 151-157 days of gestation. Following fetectomy, plasma ACTH, dehydroepiandrosterone sulfate (DHEAS), and cortisol levels were significantly lower (36%, 35%, and 44%, respectively) compared with control animals (P;lt 0.05). Despite a significant reduction in overall levels, the rhythm in maternal plasma cortisol was maintained following fetectomy. Plasma dopamine and norepinephrine were also depressed (P;lt 0.05), whereas epinephrine remained unaffected. Our data clearly demonstrate the role of the fetus in the regulation of the maternal pituitary-adrenal axis during gestation. This interaction plays a significant role in the regulation of maternal endocrine function that may influence the initiation of labor.     

Effects of leptin on fetal plasma adrenocorticotropic hormone and cortisol concentrations and the timing of parturition in the sheep

We investigated whether leptin can suppress the prepartum activation of the fetal hypothalamus-pituitary-adrenal (HPA) axis and delay the timing of parturition in the sheep. First, we investigated the effects of a 4-day intravascular infusion of recombinant ovine leptin (n = 7) or saline (n = 6) on fetal plasma adrenocorticotropic hormone (ACTH) and cortisol concentrations, starting from 136 days gestation (i.e., at the onset of the prepartum activation of the fetal HPA axis. The effects of a continuous intrafetal infusion of leptin (n = 7) or saline (n = 5) from 144 days gestation on fetal plasma ACTH and cortisol concentrations and the timing of delivery were also determined in a separate study. There was an increase in fetal plasma ACTH (P < 0.01) and cortisol (P < 0.001) concentrations when saline was infused between 136-137 and 140-141 days gestation. Plasma ACTH and cortisol concentrations did not rise, however, when leptin was infused during this period of gestation. When leptin was infused after 144 days gestation, there was no effect of a 4- to 5-fold increase in circulating leptin on fetal ACTH concentrations. In contrast, leptin infusion from 144 days gestation suppressed (P < 0.05) fetal plasma cortisol concentrations by around 40% between 90 and 42 h before delivery. There was no difference, however, in the length of gestation between the saline- and leptin-infused groups (saline infused, 150.2 +/- 0.5 days; leptin infused, 149.8 +/- 1.0 days). In saline-infused fetuses, there was a significant negative relationship between the plasma concentrations of cortisol (y) and leptin (x) between 138 and 146 days gestation (y = 81.4 - 7.7x, r = 0.38, P < 0.005). This study provides evidence for an endocrine negative feedback loop between leptin and the HPA axis in fetal life.     

Differential regulation of suppressor of cytokine signaling-3 in the liver and adipose tissue of the sheep fetus in late gestation

It is unknown whether the JAK/STAT/suppressor of cytokine signaling-3 (SOCS-3) intracellular signaling pathway plays a role in tissue growth and metabolism during fetal life. We investigated whether there is a differential profile of SOCS-3 expression in the liver and perirenal adipose tissue during the period of increased fetal growth in late gestation and the impact of fetal growth restriction on SOCS-3 expression in the fetal liver. We also determined whether basal SOCS-3 expression in the fetal liver and perirenal adipose tissue is regulated by endogenous fetal prolactin (PRL). SOCS-3 mRNA abundance was higher in the liver than in the pancreas, spleen, and kidney of the sheep fetus during late gestation. In the liver, SOCS-3 mRNA expression was increased (P < 0.05) between 125 (n = 4) and 145 days (n = 7) gestation and lower (P < 0.05) in growth-restricted compared with normally grown fetal sheep in late gestation. The relative expression of SOCS-3 mRNA in the fetal liver was directly related to the mean plasma PRL concentrations during a 48-h infusion of either a dopaminergic agonist, bromocriptine (n = 7), or saline (n = 5), such that SOCS-3 mRNA expression was lower when plasma PRL concentrations decreased below approximately 20 ng/ml [y = 0.99 - (2.47/x) + (4.96/x(2)); r(2) = 0.91, P < 0.0001, n = 12]. No relationship was shown between the abundance of phospho-STAT5 in the fetal liver and circulating PRL. SOCS-3 expression in perirenal adipose tissue decreased (P < 0001) between 90-91 (n = 6) and 140-145 days (n = 9) gestation and was not related to endogenous PRL concentrations. Thus SOCS-3 is differentially expressed and regulated in key fetal tissues and may play an important and tissue-specific role in the regulation of cellular proliferation and differentiation before birth.     

Effect of fetal mass, number and stage of gestation on pregnancy-specific protein B concentrations in the bovine

In this study we characterized the peripheral plasma pregnancy-specific protein-B (PSPB) profile throughout gestation and examined the effect of stage of gestation, fetal mass and number on this profile in Holstein cows after non surgical embryo transfer. Cows (n = 12) were divided into 2 groups: Group 1 = single embryo recipient cows (n = 5), Group 2 = twin-embryo recipient cows (n = 7). Blood was collected approximately every third day from Day 0 (Day 0 = first day of standing estrus), then daily for the last 10 d of gestation, and sampling was stopped 1 d post partum. Two twin-embryo recipient cows had abnormal pregnancies; therefore, their data were excluded from the group. The time trend concentrations of plasma PSPB were significantly affected by the stage of gestation (P < 0.001) and fetal number (P < 0.001). In both groups PSPB increased gradually, with the mean levels being significantly higher (P < 0.01) in the twin-bearing group from Day 50 onwards (0.7 +/- 0.2 vs 9.2 +/- 4.5 ng/ml, singleton and twin-bearing cows, respectively) except for Day 10 pre-partum. By mid-gestation (Day 140), mean PSPB levels increased in the singleton (P < 0.001) cows by thirty-fold (21.2 +/- 3.2 ng/ml) as opposed to a ten-fold (98.4 +/- 13.2 ng/ml) increase in the twin-bearing (P < 0.001) group. The mean PSPB concentrations between Days 30 to 20 prepartum dramatically increased by about 700 to 200% in singleton (128.8 +/- 46.3 to 745.6 +/- 66.7 ng/ml) and twin-bearing cows (375.6 +/- 130.4 to 861.5 +/- 127.9 ng/ml), respectively. The PSPB levels between Day 10 prepartum to parturition were significantly higher (P < 0.001) in the twin-bearing group than in the singleton group (745.6 +/- 66.7 to 1627.4 +/- 238.9 ng/ml vs 861.5 +/- 127.9 to 3103.0 +/- 643.0 ng/ml in singleton and twin-bearing groups, respectively). Calf birthweight was correlated (P < 0.01) to peripheral PSPB concentration in singleton cows; however, this relationship decreased with the subsequent increase in fetal number. Cows giving birth prematurely to stillborn calves or to a schistosomus reflexus calf exhibited abnormal PSPB profiles. These results indicate that peripheral PSPB levels are correlated to the stage of gestation and fetal number. In addition, the peripheral pattern of PSPB is a valuable guage for predicting fetoplacental viability.     

Declining fertility in the lethal yellow mouse is related to progressive hyperleptinemia and leptin resistance

Mice possessing the lethal yellow mutation (C57BL/6J A(y)/a) become obese and develop hyperleptinemia and leptin resistance as they age. To determine the relationship between altered leptin physiology and reproductive function in these mice, we compared body weight (BW), serum leptin concentration, ovulation rate, and in vitro blastocyst development among 120- and 180-d-old lethal yellow and black non-mutant (a/a) mice. Estrous female yellow and black mice were mated with fertile black males. Oviducts were flushed approximately 36 h after mating and the recovered embryos were cultured for 96 h. BW, serum leptin levels, and the leptin:BW ratio differed among groups as follows: 180-d yellow > 120-d yellow > 180-d black = 120-d black. Ovulation rate was similar among 120-d yellow and black, and 180-d black mice. Among 180-d yellow mice, five of twelve mice failed to ovulate, but the other seven mice ovulated a similar number of oocytes as their black counterparts (8.4 +/- 0.9 versus 8.0 +/- 1.3). Non-ovulators had higher (P < 0.05) leptin levels (56.6 +/- 1.8 ng x mL(-1)) than ovulators (46.2 +/- 3.5), but BW did not differ significantly. Fewer embryos from 180-d yellow mice reached the blastocyst stage in culture than did the embryos from black mice (55% versus 83%, P < 0.05). Moreover, blastocyst development in 180-d old yellow mice negatively correlated with leptin levels (r = -0.797, P = 0.032) and leptin:BW ratio (r = -0.847, P = 0.016), but not with BW. Declining reproductive function in lethal yellow mice appears to be related to increasing levels of leptin and progression of leptin resistance.