Articoli di riviste: "Ovine placental lactogen (oPL)"

1

Warren, W. C., R. Liang, G. G. Krivi, N. R. Siegel e R. V. Anthony. "Purification and structural characterization of ovine placental lactogen". Journal of Endocrinology 126, n. 1 (luglio 1990): 141–49. http://dx.doi.org/10.1677/joe.0.1260141.

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ABSTRACT Discrepancies exist in the reported purity and biological activity of ovine placental lactogen (oPL), and little structural characterization has been reported. Ovine PL was purified from fetal cotyledonary tissue (day 100 of gestation) by monitoring activity with a recombinant bovine GH (bGH) liver radioreceptor assay. Two hundred grams of tissue yielded 4·2 mg of oPL, with an ∼ 1000-fold purification of oPL specific activity following initial tissue extraction. The oPL was radioiodinated and used in an ovine fetal liver (day 100 of gestation) radioreceptor assay to examine competitive displacement of oPL, ovine GH (oGH) and ovine prolactin (oPRL). The potency of oPL (ED50 = 0·18 nmol/l; ED50 is the quantity of ligand necessary to displace 50% of specifically bound 125I-labelled oPL) was greater than that of oGH (ED50 = 4·1 nmol/l) and oPRL (ED50 = 1·1 μmol/l) in competing for 125I-labelled oPL-binding sites. Attempts to sequence the NH2 terminus of oPL by vapour-phase sequencing indicated that the NH2 terminus was blocked. Purified oPL was subjected to trypsin and CnBr digestion, and two CnBr and six tryptic peptides were sequenced. The peptide sequences were compared with other PLs, oPRL and bGH for sequence similarity, and found to be most similar to bovine PL (bPL; 68% overall identity) and oPRL (47% overall identity). Complementary DNA (cDNA) clones were isolated for oPL by screening a λZAP cDNA library with a cDNA coding for bPL. Three cDNAs were nucleotide sequenced, and their combined sequence included 41 nucleotides of 5'-untranslated region, the complete coding region of pre-oPL (708 nucleotides) and a portion of the 3' untranslated region (158 nucleotides). The predicted amino acid sequence derived from the nucleotide sequence confirmed homology to bPL (67%) and oPRL (48%). Little amino acid sequence existed with other PLs (≤29%) or GH proteins (≤27%). These results suggest that oPL and oGH are more biologically similar in their ability to compete for fetal liver binding sites, but that oPL is structurally more similar to oPRL. Elucidation of exact structure–function relationships for oPL will, however, require further investigation. Journal of Endocrinology (1990) 126, 141–149

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Wooding, F. B., G. Morgan, I. A. Forsyth, G. Butcher, A. Hutchings, S. A. Billingsley e P. D. Gluckman. "Light and electron microscopic studies of cellular localization of oPL with monoclonal and polyclonal antibodies." Journal of Histochemistry & Cytochemistry 40, n. 7 (luglio 1992): 1001–9. http://dx.doi.org/10.1177/40.7.1607634.

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Accurate knowledge of placental lactogen localization is fundamental to any hypothesis of its synthesis and secretion. We used locally generated monoclonal and polyclonal antibodies from three separate sources to localize ovine placental lactogen immunoreactivity on light and electron microscope Lowicryl K4M sections of ovine placentomes of 97-145 days of gestation, using immunogold techniques. All antibodies demonstrated that immunoreactivity was exclusively localized in the trophoectoderm binucleate cell Golgi body and granules and in granules in the syncytium derived from binucleate cell migration. No evidence was found to support a recent claim that monoclonal antibodies to oPL that were produced in Canada indicated a predominant localization of ovine placental lactogen to uninucleate trophectodermal cells.

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Huyler, S. E., W. R. Butler, A. Grandis, C. Mann, J. P. Figueroa, P. W. Nathanielsz, M. Mitchell e S. Handwerger. "Stimulation of ovine placental lactogen secretion by arachidonic acid". Journal of Endocrinology 106, n. 1 (luglio 1985): 43–47. http://dx.doi.org/10.1677/joe.0.1060043.

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ABSTRACT To determine whether arachidonic acid stimulates the secretion of ovine placental lactogen (oPL), arachidonic acid was infused as an intravenous bolus into pregnant ewes and fetuses. Plasma oPL concentrations were determined in mothers and fetuses before and for 5 h after infusion. The administration of 12·5 mg arachidonic acid (0·15−0·2 mg/kg, n = 11 experiments) to the pregnant ewes caused an increase in maternal plasma oPL concentrations of 73·9±15·6% (s.e.m.) and 60·8±18·1% above the pretreatment concentrations at 4 and 5 h respectively P<0·01 in each instance). The infusion of 25 mg arachidonic acid (n = 8) caused increases of 96·0±19·1% and 100·3±26·4% (P<0·005), and the stimulation was not inhibited by the cyclo-oxygenase inhibitors indomethacin and ibuprofen. In contrast to arachidonic acid, vehicle alone or palmitic acid had no effects on plasma oPL concentrations. Despite the increase in maternal plasma oPL concentrations, plasma oPL concentrations in the fetus remained unchanged after the maternal infusions. The infusion of arachidonic acid (0·5–1·5 mg/kg) directly into six fetuses had no effects on either fetal or maternal oPL concentrations. These studies indicate that (1) arachidonic acid stimulates maternal plasma oPL concentrations but has no effect on fetal oPL concentrations and (2) the stimulation of oPL secretion is not due to the conversion of arachidonic acid to prostaglandins or other cyclo-oxygenase products. J. Endocr. (1985) 106, 43–47

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Braun, Thorsten, Shaofu Li, Timothy J. M. Moss, John P. Newnham, John R. G. Challis, Peter D. Gluckman e Deborah M. Sloboda. "Maternal betamethasone administration reduces binucleate cell number and placental lactogen in sheep". Journal of Endocrinology 194, n. 2 (agosto 2007): 337–47. http://dx.doi.org/10.1677/joe-07-0123.

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The placenta may mediate glucocorticoid-induced fetal growth restriction. Previous studies have examined effects of fetal cortisol in sheep, which reduces placental binucleate cell (BNC) number; the source of ovine placental lactogen (oPL). The effects of maternal GC are unknown. Therefore, this study examined the effects of maternal betamethasone (BET) administration on BNC number, distribution, placental oPL protein levels, and maternal and fetal plasma oPL levels. Pregnant ewes were randomized to receive injections of saline or one (104 days of gestation; dG), two (104 and 111 dG), or three (104, 111, and 118 dG) doses of BET (0.5 mg/kg). Placental tissue was collected before, during, and after the period of BET treatment. Fetal (121–146 dG) and placental (121 dG) weights were decreased after BET when compared with controls. In controls, the mean number of BNCs increased until 132 dG and decreased thereafter. Placental oPL protein levels peaked at 109 dG and remained stable thereafter. Maternal plasma oPL levels in controls increased across gestation; fetal plasma oPL levels decreased. BNCs were reduced by 24% to 47% after BET when compared with controls at all ages studied. Placental oPL protein levels, maternal, and fetal plasma oPL levels were also reduced after BET injections, but recovered to values that were not different to controls near term. BET disrupted the normal distribution of BNCs within the placentome. These data may suggest a placental role in growth restrictive effects of prenatal maternal BET exposure through alterations in placental output of oPL, a key metabolic hormone of pregnancy.

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Freemark, M., M. Comer e S. Handwerger. "Placental lactogen and GH receptors in sheep liver: striking differences in ontogeny and function". American Journal of Physiology-Endocrinology and Metabolism 251, n. 3 (1 settembre 1986): E328—E333. http://dx.doi.org/10.1152/ajpendo.1986.251.3.e328.

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To determine whether changes in the relative biological potencies of ovine placental lactogen (oPL) and ovine growth hormone (oGH) during development derive from ontogenetic changes in the binding of these hormones to hepatic receptors, we have compared the binding of 125I-oPL and 125I-oGH to hepatic membranes from fetal lambs and pregnant sheep at mid- and late gestation and from postnatal sheep at 1 day to 7 mo of age. Specific high-affinity 125I-oPL binding sites in ovine fetal liver were detected as early as day 70 of gestation (term = 145 days), and the number of fetal 125I-oPL binding sites increased progressively throughout the latter half of gestation, reaching a maximum (11.2 fmol/mg protein) at 3-7 days before parturition. The potency of oPL (Kd 0.27 nM) in competing for 125I-oPL binding sites was 90 and 1,300 times greater than that of oGH and ovine prolactin, respectively. Although the number of fetal 125I-oPL binding sites increased throughout pregnancy, there was little or no specific binding of 125I-oGH noted in the fetus. Treatment of fetal liver membranes with 4 M MgCl2 did not enhance the subsequent specific binding of 125I-oGH, suggesting that the low specific binding of oGH did not result from occupation of hepatic receptors by endogenous circulating oPL or oGH. In contrast, MgCL2 treatment markedly increased the apparent number of fetal 125I-oPL binding sites, suggesting that oPL receptors in fetal liver are partly saturated in vivo by oPL.(ABSTRACT TRUNCATED AT 250 WORDS)

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6

Sakal, E., C. Bignon, J. Grosclaude, A. Kantor, R. Shapira, H. Leibovitch, D. Helman et al. "Large-scale preparation and characterization of recombinant ovine placental lactogen". Journal of Endocrinology 152, n. 2 (febbraio 1997): 317–27. http://dx.doi.org/10.1677/joe.0.1520317.

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Abstract To clone ovine placental lactogen (oPL) cDNA, total RNA from sheep placental cotyledon was reverse transcribed and the single-stranded cDNA was PCR-amplified with 5′ and 3′ primers containing, respectively, Ncol and PstI sites. The oPL cDNA fragment amplified between these two primers extended from A(−1) to the natural stop codon. The PCR product was gel-purified and subcloned into a Puc vector and the insert was sequenced on both strands, revealing several differences relative to the published sequence: S19N, S69N, D129E and R165Q. We assume that these differences can be accounted for by the high level of individual polymorphism, which has been described in detail for PLs of different species. The insert was subcloned into Ncol/PstI-digested pTrc99A procaryotic expression plasmid and protein expression was induced by isopropyl-1-thio-β-d-galactopyranoside. Because of low expression, oPL's cDNA was further subcloned into pET8 procaryotic expression plasmid. Its expression in E. coli strain BL21 transformed with this vector yielded 30–40 mg/l. The expressed protein, found in the inclusion bodies, was refolded into a monomer and purified on a Q-Sepharose column to homogeneity. Structural analysis using circular dichroism revealed a spectrum similar to that of human GH (hGH) thereby indicating proper refolding. Gel filtration and binding experiments, including real-time kinetic measurements using the surface plasmon resonance method revealed that oPL forms transient homodimeric complexes with extracellular domains of prolactin receptors from rabbit, rat and bovine and with hGH receptor. The purified oPL was biologically active in an Nb2-11C cell proliferation bioassay, in its ability to stimulate β-casein synthesis in explants of ovine and rabbit mammary gland and fat synthesis in explants of bovine mammary gland, and in a proliferation assay using FDC-P1 cells transfected with rabbit or hGH receptors. Journal of Endocrinology (1997) 152, 317–327

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Falconer, J., J. A. Owens, E. Allotta e J. S. Robinson. "Effect of restriction of placental growth on the concentrations of insulin, glucose and placental lactogen in the plasma of sheep". Journal of Endocrinology 106, n. 1 (luglio 1985): 7–11. http://dx.doi.org/10.1677/joe.0.1060007.

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ABSTRACT The effect of restricting placental growth on maternal glucose, insulin and placental lactogen was investigated in 16 ewes carrying singleton lambs. Uterine caruncles were removed from seven ewes (caruncle ewes) before pregnancy, resulting in reduced placental size and retarded intra-uterine fetal growth. The concentration of insulin in maternal plasma was similar in both control and caruncle ewes. The concentration of glucose was significantly higher in the caruncle than in the control ewes (3·26 ± 0·15 (s.e.m.) mmol/l, number of observations (n) = 9, vs 2·75 ± 0·1, n = 9, P<0·02, and 3·27 ±0·16, n = 7, vs 2·46± 0·11, n = 12, P<0·001, for the carotid artery and utero-ovarian vein respectively). The concentration of ovine placental lactogen (oPL) in the utero-ovarian vein was reduced in the caruncle compared with the control ewes (283± 65 μg/l, n = and 705±106 μg/l, n = 18, P<0·02, respectively). Restriction of placental growth by removal of endometrial caruncles similarly reduced the concentrations of oPL in maternal arterial plasma (231±54 μg/l, n = 9, and 621±96 μg/l, n = 18, P<0·002). Production of oPL by the placenta was also reduced by limiting placental growth to 30±11 μg/min, n = 8, compared with 133±43 μg/min, n = 15, P<0·05, for the controls. Production of oPL per gram of placenta in the caruncle group, although only 34% of the control value, was not reduced significantly. These observations are consistent with the hypothesis that oPL may be involved in the redirection of maternal glucose during pregnancy to maximize the amount available for the fetus. J. Endocr. (1985) 106, 7–11

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Ogawa, E., B. H. Breier, M. K. Bauer e P. D. Gluckman. "Ovine placental lactogen lacks direct somatogenic and anticatabolic actions in the postnatal lamb". Journal of Endocrinology 145, n. 1 (aprile 1995): 87–95. http://dx.doi.org/10.1677/joe.0.1450087.

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Abstract The metabolic effects of ovine placental lactogen (oPL) alone and in combination with bovine GH (bGH) were investigated in comparison with the identical dose of bGH alone in the well-fed postnatal lamb. The animals were treated by twice daily intramuscular injection for 5 days with oPL (n=7), bGH (n=7) or bGH+oPL (n=7) at a dose of 0·3 mg/kg per day or saline (n=9). bGH and bGH+oPL treatments, but not oPL treatment, resulted in significantly (P<0·01) higher plasma IGF-I levels than saline treatment. The rate of net protein catabolism (NPC) was significantly (P<0·05) reduced to the same extent by bGH and bGH+oPL treatment compared with saline treatment. In contrast, oPL did not affect the rate of NPC. Blood glucose and insulin:glucose ratio were significantly (P<0·05) elevated in the bGH+oPL group, whereas they were not significantly altered by either bGH or oPL treatment. These results suggest that oPL alone is not somatogenic or anticatabolic in the postnatal lamb despite the earlier evidence that oPL can bind to the oGH receptor (oGHR). However, oPL appeared to augment some of the effects of bGH when administered together, particularly with respect to carbohydrate metabolism. Potentiation of the diabetogenic effect of bGH by oPL may lead to insulin resistance during pregnancy. The lack of any obvious actions by oPL treatment alone may support the hypothesis that oGHR homo-dimerization is required for the full activation of GHR-mediated effects, since oPL binding does not initiate homo-dimerization of the oGHR. Journal of Endocrinology (1995) 145, 87–95

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Lea, Richard G., Peter Wooding, Ian Stewart, Lisa T. Hannah, Stephen Morton, Karen Wallace, Raymond P. Aitken et al. "The expression of ovine placental lactogen, StAR and progesterone-associated steroidogenic enzymes in placentae of overnourished growing adolescent ewes". Reproduction 133, n. 4 (aprile 2007): 785–96. http://dx.doi.org/10.1530/rep-06-0294.

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Overnourishing pregnant adolescent sheep promotes maternal growth but reduces placental mass, lamb birth weight and circulating progesterone. This study aimed to determine whether altered progesterone reflected transcript abundance forStAR(cholesterol transporter) and the steroidogenic enzymes (Cyp11A1,Hsd3bandCyp17). Circulating and placental expression of ovine placental lactogen (oPL) was also investigated. Adolescent ewes with singleton pregnancies were fed high (H) or moderate (M) nutrient intake diets to restrict or support placental growth. Experiment 1: peripheral progesterone and oPL concentrations were measured in H (n=7) and M (n=6) animals across gestation (days 7–140). Experiment 2: progesterone was measured to mid- (day 81; M:n=11, H:n=13) or late gestation (day 130; M:n=21, H:n=22), placental oPL,StARand steroidogenic enzymes were measured by qPCR and oPL protein by immunohistochemistry. Experiment 1: in H vs M animals, term placental (P<0.05), total cotyledon (P<0.01) and foetal size (P<0.05) were reduced. Circulating oPL and progesterone were reduced at mid- (P<0.001,P<0.01) and late gestation (P<0.01,P<0.05) and oPL detection was delayed (P<0.01). Experiment 2: placental oPL was not altered by nutrition. In day 81 H animals, progesterone levels were reduced (P<0.001) but not related to placental or foetal size. Moreover, placental steroidogenic enzymes were unaffected. Day 130 progesterone (P<0.001) andCyp11A1(P<0.05) were reduced in H animals with intrauterine growth restriction (H+IUGR). Reduced mid-gestation peripheral oPL and progesterone may reflect altered placental differentiation and/or increased hepatic clearance respectively. Restricted placental growth and reduced biosynthesis may account for reduced progesterone in day 130 H+IUGR ewes.

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Chan, John S. D., Z. R. Nie, N. G. Seidah e M. Chrétien. "Purification of ovine placental lactogen (oPL) using high-performance liquid chromatography". FEBS Letters 199, n. 2 (21 aprile 1986): 259–64. http://dx.doi.org/10.1016/0014-5793(86)80491-4.

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Ogawa, Eishin, Bernhard H. Breier, Barbara Funk, Michael K. Bauer e Peter D. Gluckman. "Ovine Placental Lactogen (oPL) Lacks Anabolic Action in the Postnatal Lamb". Clinical Pediatric Endocrinology 3, Supple5 (1994): 181–82. http://dx.doi.org/10.1297/cpe.3.supple5_181.

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Limesand, Sean W., Kimberly M. Jeckel e Russell V. Anthony. "Purα, a Single-Stranded Deoxyribonucleic Acid Binding Protein, Augments Placental Lactogen Gene Transcription". Molecular Endocrinology 18, n. 2 (1 febbraio 2004): 447–57. http://dx.doi.org/10.1210/me.2003-0392.

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Abstract Placental lactogen (PL) is thought to alter maternal metabolism to increase the pool of nutrients available for the fetus and to stimulate fetal nutrient uptake. The ovine (o) PL gene is expressed in chorionic binucleate cells (oBNC) and cis-elements located within the proximal promoter (−124 to +16 bp) are capable of trophoblast-specific expression in human (BeWo) and rat (Rcho-1) choriocarcinoma cells. Protein-DNA interactions were identified with oBNC nuclear extracts, and mutational analysis of these regions revealed a previously undefined cis-element from −102/−123 bp that enhances promoter activity in BeWo cells but not Rcho-1 cells. Characterization of this region identified the nucleotide sequence CCAGCA (−105/−110; o110) as the responsible cis-acting element. Southwestern analysis with this element identified a binding protein with an apparent Mr of approximately 41,000. Expression screening of an ovine placental cDNA library identified six homologous cDNAs, which shared identity with human (97%) and mouse (95%) Purα, a single-stranded DNA binding protein. The Purα-o110 interaction was confirmed by electrophoretic mobility-supershift assays with oBNC and BeWo extracts but was absent with Rcho-1 extracts. Furthermore, overexpression of ovine Purα enhanced transactivation of the oPL gene proximal promoter in both choriocarcinoma cell lines through this novel cis-element. This study identified a previously undefined cis-element, which interacts with Purα to augment PL gene transcription.

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BOBOWIEC, RYSZARD, MARTA WÓJCIK, ANDRZEJ MILCZAK, URSZULA KOSIOR-KORZECKA, MONIKA GREGUŁA-KANIA e JAROSŁAW TATARCZAK. "Relationship between mammary blood flow, infrared thermography and ovine placental lactogen during the periparturient period in ewes". Medycyna Weterynaryjna 75, n. 05 (2019): 6245–2019. http://dx.doi.org/10.21521/mw.6245.

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The aim of the study to verify the hypothesis whether a drop in the oPL levels in the blood in the periparturient period is associated with changes in the right mammary vein blood flow (RMVBF) and udder skin temperature (UST). We were also interested in comparing variations in the above-mentioned parameters in single- and twin-pregnant ewes. Beginning six days before parturition (-6th day) until four days postpartum (4th day), every second day each of 15 experimental pregnant ewes was subjected to color Doppler ultrasound performed with continuous wave-equipment (My Lab One/Touch) and infrared thermography (IRT), which allowed for noninvasive collection of data. Plasma oPL levels were determined using quantitative sandwich ELISA Kit specified for sheep placental lactogen 1 (oPL). The measured values of UST were affected by the periparturient period but not by the number of lambs delivered. The highest udder temperatures were recorded at four days before parturition, which was followed by their gradual decrease. As a result, UST achieved the lowest values in single- and also in twin-pregnant ewes on the day of parturition (35.70 ± 0.65°C and 35.42 ± 0.45°C, respectively). Among all the time points of measuring IRT and oPL, a significant positive correlation (P≤0.01) was estimated at -4 and 0 days before parturition for single- (r= 0.99) and twin- (r= 0.59) pregnant ewes. In comparison to control ewes, right mammary vein blood flow (RMVBF) significantly (P≤0.05) increased in all pregnant ewes under study. Especially in twin-pregnant ewes, a positive correlation between the plasma concentration of oPL and blood flow occurred between the -4th and 0 day (r = 0.76). Maximal velocity of blood flow in the mammary vein in single- (25.90 ± 5.95 cm/s) and twin-pregnant ewes (24.62 ± 4.86 cm/s) was recorded at the 2nd and 4th day postpartum, respectively. The highest values of plasma oPL (0.56 ± 0.05 µg/ml) recorded at the beginning of the experimental period (-6 days before parturition) dropped significantly (P≤0.05) during the subsequent days, until parturition. The curve of the temporal changes in the concentrations of plasma oPL remains unchanged regardless of the number of fetuses. Three-phasic thermal changes in the periparturient period and an increase in blood flow parameters are related to the disappearance of oPL from the circulation, which should be taken into account when assessing a pathological state of this gland.

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Morgan, G., F. B. Wooding e M. R. Brandon. "Immunogold localization of placental lactogen and the SBU-3 antigen by cryoultramicrotomy at implantation in the sheep". Journal of Cell Science 88, n. 4 (1 novembre 1987): 503–12. http://dx.doi.org/10.1242/jcs.88.4.503.

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In the sheep, granulated trophectodermal binucleate cells (BNC) appear at implantation 16 days post coitum (dpc) and persist throughout pregnancy. Conventional immunocytochemical techniques at both light and electron microscope levels have indicated the presence of the ovine placental lactogen (oPL) hormone in the granules but no earlier than 22 dpc, when the level was very low. Immunofluorescent studies using glycolmethacrylate sections between 15 and 55 dpc suggest a completely different distribution of oPL restricted to uninucleate cells with none in the BNC. Using the most sensitive method available, immunocytochemistry on ultrathin frozen sections, the results in this paper demonstrate that BNC granules contain oPL at their earliest appearance (16–17 dpc). No significant localization was found in any uninucleate cell. In contrast, another molecule, the SBU-3 antigen, which is demonstrated in BNC granules later in pregnancy, is not present at the earliest stages but appears between 24 and 28 dpc coincident with the development of the foetal cotyledonary villi. The significance of these results for BNC function are discussed briefly.

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Kann, G., A. Delobelle-Deroide, L. Belair, A. Gertler e J. Djiane. "Demonstration of in vivo mammogenic and lactogenic effects of recombinant ovine placental lactogen and mammogenic effect of recombinant ovine GH in ewes during artificial induction of lactation". Journal of Endocrinology 160, n. 3 (1 marzo 1999): 365–77. http://dx.doi.org/10.1677/joe.0.1600365.

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The present study demonstrates that ovine placental lactogen (oPL) (ovine chorionic somatotrophin) may have an important role in the mammogenesis and/or lactogenesis of the ewe. Its effects were compared with that already described for ovine growth hormone (oGH). In the first experiment, 40 nulliparous ewes were induced to lactate by means of a 7 day (days 1-7) oestro-progestative treatment (E2+P4). The ewes from Group 1 (n=12) received no further treatment, while those of the other groups received either recombinant oGH (roGH, 28 micrograms/kg, i.m., twice daily, Group 2, n=12) or recombinant oPL (roPL, 79 micrograms/kg, i.m., twice daily, Group 3, n=12) from day 11 to 20. All ewes received 25 mg hydrocortisone acetate (HC) twice daily on days 18-20. Control Group 00 (n=2) received no steroid treatment at all, and the control Group 0 (n=2) received only the E2+P4 treatment. Thirteen ewes (three from each experimental group and the two of each control group) were slaughtered at the end of hormone treatments (day 21) before any milking stimulus. The 27 remaining ewes from Groups 1-3 were machine-milked and milk yields recorded daily from day 21 to 76. The E2+P4 treatment enhanced the plasma levels of oPRL, oGH and IGF-I between days 1 and 7 by 1.5, 2. 3 and 2.6 times respectively (P=0.002); roGH treatment induced a highly significant enhancement of IGF-I plasma levels from day 11 to 20, whereas a similar effect appeared for roPL-treated ewes only from day 17 to 20 (P<0.01). Eight weeks after the last exogenous hormone injections, milk yields of both roGH- and roPL-treated groups progressively rose to twice that of unsupplemented groups (P<0.001). The mammary DNA content on day 21 was higher for animals which received either oGH or oPL but, due to individual variations in so few samples (n=3), this difference was not significant. No beta-casein was measured in mammary tissue from control ewes, whereas steroid-treated ewes (E2+P4+HC) had higher casein concentrations regardless of subsequent hormonal treatment on days 11-20 (P<0.001). beta-Casein concentrations in mammary parenchyma of roGH-treated ewes did not differ from that of ewes which received only E2+P4+HC; roPL supplementation clearly enhanced expression of beta-casein (P<0.001). IGF-I stimulation by either roGH or roPL was more precisely examined during a second experiment, in which two twice-daily i.m. doses (58 or 116 micrograms/kg) of either roGH or roPL were administered to four groups of six ewes that were E2+P4 treated as those of Experiment 1. A control group (n=6) received no exogenous hormone from day 11 to 13. On day 13, hourly blood samples were taken from all ewes over 11 h. Both doses of roGH significantly stimulated IGF-I in a dose-dependent manner. The 58 micrograms/kg dose of roPL did not significantly stimulate IGF-I, but although being somewhat less efficient than the 58 micrograms/kg dose of roGH, the 116 micrograms/kg dose of roPL significantly stimulated IGF-I secretion (P<0. 001). These results suggest that mammogenesis and/or lactogenesis in the ewe is in part controlled by somatotrophic hormones such as oGH and oPL and that IGF-I could be one of the mediators of these hormones.

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Waters, M. J., V. H. Oddy, C. E. McCloghry, P. D. Gluckman, R. Duplock, P. C. Owens e M. W. Brinsmead. "An examination of the proposed roles of placental lactogen in the ewe by means of antibody neutralization". Journal of Endocrinology 106, n. 3 (settembre 1985): 377–86. http://dx.doi.org/10.1677/joe.0.1060377.

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ABSTRACT The physiological role of placental lactogen (PL; chorionic somatomammotrophin) in the ewe has been investigated by infusion of ewes (n = 3) on day 131 of pregnancy with sufficient ovine PL (oPL) antibody to neutralize circulating oPL for at least 12 h. Effectiveness of the antibody neutralization was defined both in vitro and in vivo according to rigorous criteria. Control ewes (n = 3) were infused simultaneously with an equivalent amount of pooled goat gamma globulin. Since both sets of ewes had previously been catheterized with jugular, utero-ovarian and femoral vein catheters and a femoral arterial catheter, it was possible to measure whole body glucose kinetics as well as muscle and uterine glucose, free fatty acid (FFA) and 3-hydroxybutyrate extraction. In addition, plasma levels of insulin, GH, prolactin, insulin-like growth factor-I (IGF-I), IGF-II, progesterone and cholesterol were determined in femoral arterial samples. Neutralization of maternal oPL did not significantly affect whole body glucose metabolism, uterine and muscle glucose extraction, or 3-hydroxybutyrate extraction by muscle. A trend towards lower plasma FFA levels was observed after prolonged infusion, but was not statistically significant. However, plasma insulin levels rose significantly during antibody infusion after an early fall. These observations are rationalized in terms of the known requirements of ruminant metabolism during pregnancy, and contrasted with the accepted model for the role of human PL in the metabolic adjustments of pregnancy. No change in plasma IGF-I, IGF-II or GH was observed, providing no support for the concept that oPL is responsible for maternal somatomedin generation during pregnancy. Similarly, plasma prolactin did not differ between antibody-treated and control groups. Finally, antibody neutralization had no influence on either plasma progesterone or cholesterol, mitigating against a role for oPL in progesterone production during late pregnancy in the ewe. J. Endocr. (1985) 106, 377–386

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17

Biener, Eva, Cyril Martin, Nathalie Daniel, Stuart J. Frank, Victoria E. Centonze, Brian Herman, Jean Djiane e Arieh Gertler. "Ovine Placental Lactogen-Induced Heterodimerization of Ovine Growth Hormone and Prolactin Receptors in Living Cells Is Demonstrated by Fluorescence Resonance Energy Transfer Microscopy and Leads to Prolonged Phosphorylation of Signal Transducer and Activator of Transcription (STAT)1 and STAT3". Endocrinology 144, n. 8 (1 agosto 2003): 3532–40. http://dx.doi.org/10.1210/en.2003-0096.

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Abstract (sommario):

Abstract HEK-293T cells transiently transfected with ovine (o) GH receptor (GHR) and prolactin receptor (PRLR) constructs respectively tagged downstream with cyan or yellow fluorescent proteins were used to study ovine placental lactogen (oPL)-stimulated heterodimerization by fluorescence resonance energy transfer (FRET) microscopy. The oPL-stimulated transient heterodimerization of GHR and PRLR had a peak occurring 2.5–3 min after oPL application, whereas oGH or oPRL had no effect at all. The results indicate none or only little dimerization occurring before the hormonal stimulation. The effect of heterodimerization was studied by comparing activation of Janus kinase 2, signal transducer and activator of transcription (STAT)1, STAT3, STAT5, and MAPK in Chinese hamster ovary cells stably transfected with chimeric genes encoding receptors consisting of cytosolic and transmembrane parts of oGHR and oPRLR, extracellular domains of human granulocyte and macrophage colony-stimulating factor (hGM-CSF) receptor α or β, and cells transfected with the two forms (α or β) of PRLR and GHR. Functionality of those proteins was verified by hGM-CSF-induced phosphorylation of both intracellular PRLR and GHR domains and hGM-CSF-induced heterodimerization was documented by chimeric receptor coimmunoprecipitation. Homodimerization or heterodimerization of PRLRs and GHRs had no differential effect on activation of STAT5 and MAPK. However, heterodimerization resulted in a prolonged phosphorylation of STAT1 and in particular STAT3, suggesting that the heterodimerization of α-oGHR and β-oPRLR is able to transduce a signal, which is distinct from that occurring on homodimeric associations.

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18

Al-Gubory, K. H., S. Camous, G. Germain, P. Bolifraud, A. Nicole e I. Ceballos-Picot. "Reconsideration of the proposed luteotropic and luteoprotective actions of ovine placental lactogen in sheep: in vivo and in vitro studies". Journal of Endocrinology 188, n. 3 (marzo 2006): 559–68. http://dx.doi.org/10.1677/joe.1.06550.

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Abstract (sommario):

Ovine placental lactogen (oPL) is produced by the conceptus trophectoderm and is secreted into both the maternal and fetal circulations. The present study was designed to examine in vivo the luteotropic effect of recombinant oPL (roPL), as determined by monitoring progesterone concentration and cycle length (experiment 1), and the antioxidative and antiapoptotic effects of roPL, as determined respectively by monitoring antioxidant enzymatic activity and apoptosis in the corpus luteum (CL) of cyclic ewes (experiment 2). We also studied whether roPL is capable of stimulating progesterone secretion in vitro by cultured luteal tissue of functionally active CL obtained from day-10 cyclic ewes (experiment 3) and day-60 pregnant ewes (experiment 4). Circulating concentrations of progesterone and cycle length were not affected by treatment of ewes with 80 μg/kg body weight per day of roPL (n = 4 ewes) for 10 days beginning on day 11 post-estrus, as compared with saline-treated ewes (n = 4 ewes). Luteolysis occurred between days 15 and 16 post-estrus in the four saline-treated ewes and in 3/4 roPL-treated ewes. The activities of the key antioxidant enzymes copper-zinc superoxide dismutase (Cu,Zn-SOD), manganese SOD (Mn-SOD), glutathione peroxidase (GPX), glutathione reductase (GSR) and glutathione S-transferase (GST) were unaffected by treatment of ewes with 80 μg/kg per day of roPL (n = 4 ewes) for 3 days, between days 11 and 14 post-estrus, as compared with saline-treated ewes (n = 4 ewes). In situ TUNEL method revealed that the number of apoptotic cells was not different between the two groups of ewes. There was no significant change in progesterone secretion by explants from day-10 estrous cycle (n = 3 ewes) or day-60 pregnancy (n = 3 ewes) CL cultured with different concentrations (10, 100 and 1000 ng/ml) of roPL, whereas treatment with oLH at the concentration of 100 or 1000 ng/ml caused a significant increase in progesterone secretion by explants from day-10 estrous cycle CL (P < 0.05) and by explants from day-60 pregnancy CL (P < 0.01). In conclusion, our results demonstrate that oPL has no luteotropic and/or luteoprotective actions in sheep, either in vivo or in vitro.

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19

Gallaher, B. W., B. H. Breier, W. F. Blum, S. N. McCutcheon e P. D. Gluckman. "A homologous radioimmunoassay for ovine insulin-like growth factor-binding protein-2: ontogenesis and the response to growth hormone, placental lactogen and insulin-like growth factor-I treatment in sheep". Journal of Endocrinology 144, n. 1 (gennaio 1995): 75–82. http://dx.doi.org/10.1677/joe.0.1440075.

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Abstract Although insulin-like growth factor-binding protein-2 (IGFBP-2) is an abundant IGFBP in fetal and postnatal plasma, its regulation is not yet clearly understood. To address this question in sheep, we purified ovine IGFBP-2 and developed a homologous radioimmunoassay. We have studied its ontogenesis and measured serum concentrations of ovine IGFBP-2 after bovine growth hormone (bGH), ovine placental lactogen (oPL) and IGF-I treatment. Concentrations of IGFBP-2 were high at 125 days of gestation (550 ± 15 μg/l) but fell after birth P<0·05) and plateaued after 1 year of age (340 ± 20 μg/l). In lactating ewes, bGH treatment for 7 days significantly reduced (21%; P<0·05) IGFBP-2 relative to the saline-treated group. Similarly, in neonatal lambs, bGH treatment from day 3 to day 23 of life reduced (P<0·05) IGFBP-2 by 23% relative to the saline-treated group. oPL had no effect on serum levels of IGFBP-2 in the ewe or the neonatal lamb. In well-fed yearling lambs, treatment with IGF-I reduced IGFBP-2 values by 27% (P<0·05) relative to control animals. In yearling lambs, reduced nutrition increased plasma IGFBP-2 (41%; P<0·05). However this increase was abolished by IGF-I treatment. The changes in plasma levels of IGFBP-2 were positively related to changes in IGF-II while there was a negative relationship between circulating IGF-I and IGFBP-2 such that both IGF-I and IGF-II may play a role in the regulation of IGFBP-2 in serum. Journal of Endocrinology (1995) 144, 75–82

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20

Regnault, TR, RJ Orbus, FC Battaglia, RB Wilkening e RV Anthony. "Altered arterial concentrations of placental hormones during maximal placental growth in a model of placental insufficiency". Journal of Endocrinology 162, n. 3 (1 settembre 1999): 433–42. http://dx.doi.org/10.1677/joe.0.1620433.

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Pregnant ewes were exposed chronically to thermoneutral (TN; 20+/-2 degrees C, 30% relative humidity; n=8) or hyperthermic (HT; 40+/-2 degrees C 12 h/day, 35+/-2 degrees C 12 h/day, 30% relative humidity, n=6) environments between days 37 and 93 of pregnancy. Ewes were killed following 56 days of exposure to either environment (days in treatment (dit)), corresponding to 93+/-1 day post coitus (dpc). Maternal core body temperatures (CBT) in HT ewes were significantly elevated above the TN ewes (HT; 39.86+/-0.1 degrees C vs TN; 39.20+/-0.1 degrees C; P<0.001). Both groups of animals displayed circadian CBT, though HT ewes had elevated amplitudes (HT; 0.181+/-0.002 degrees C vs TN; 0.091+/-0.002 degrees C; P<0.001) and increased phase shift constants (HT; 2100 h vs TN; 1800 h; P<0.001). Ewes exposed to chronic heat stress had significantly reduced progesterone and ovine placental lactogen (oPL) concentrations from 72 and 62 dpc respectively (P<0.05), corresponding to approximately 30 dit. However, when compared with the TN ewes, HT cotyledonary tissue oPL mRNA and protein concentrations were not significantly different (P>0.1). Prolactin concentrations rose immediately upon entry into the HT environment, reaching concentrations approximately four times that of TN ewes, a level maintained throughout the study (HT; 216.31+/-32.82 vs TN; 54. 40+/-10.0; P<0.0001). Despite similar feed intakes and euglycemia in both groups of ewes, HT fetal body weights were significantly reduced when compared with TN fetuses (HT; 514.6+/-48.7 vs TN; 703. 4+/-44.8; P<0.05), while placental weights (HT; 363.6+/-63.3 vs TN; 571.2+/-95.9) were not significantly affected by 56 days of heat exposure. Furthermore, the relationship between body weight and fetal length, the ponderal index, was significantly reduced in HT fetuses (HT; 3.01+/-0.13 vs TN; 3.57+/-0.18; P<0.05). HT fetal liver weights were also significantly reduced (HT; 27.31+/-4.73 vs TN; 45.16+/-6.16; P<0.05) and as a result, the brain/liver weight ratio was increased. This study demonstrates that chronic heat exposure lowers circulating placental hormone concentrations. The observation that PL mRNA and protein contents are similar across the two treatments, suggests that reduced hormone concentrations are the result of impaired trophoblast cell development, specifically trophoblast migration. Furthermore, the impact of heat exposure during maximal placental growth is great enough to restrict early fetal development, even before the fetal maximal growth phase (100 dpc-term). These data highlight that intrauterine growth retardation (IUGR) may result primarily from placental trophoblast cell dysfunction, and secondarily from later reduced placental size.

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21

Breier, B. H., B. Funk, A. Surus, G. R. Ambler, C. A. Wells, M. J. Waters e P. D. Gluckman. "Characterization of ovine growth hormone (oGH) and ovine placental lactogen (oPL) binding to fetal and adult hepatic tissue in sheep: evidence that oGH and oPL interact with a common receptor." Endocrinology 135, n. 3 (settembre 1994): 919–28. http://dx.doi.org/10.1210/endo.135.3.8070387.

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22

Helman, D., A. Herman, J. Paly, O. Livnah, PA Elkins, AM de Vos, J. Djiane e A. Gertler. "Mutations of ovine and bovine placental lactogens change, in different ways, the biological activity mediated through homologous and heterologous lactogenic receptors". Journal of Endocrinology 169, n. 1 (1 aprile 2001): 43–54. http://dx.doi.org/10.1677/joe.0.1690043.

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Abstract (sommario):

The biological activities of ovine (o) and bovine (b) placental lactogens (PLs) and their mutated analogues were compared using several binding and in vitro bioassays. In almost all cases, the biological activities of these analogues mediated through rat (r) prolactin receptor (PRLR) showed little or no change, despite a remarkable decrease in their capacity to bind to the extracellular domain of rPRLR and despite compromised stability of the 2:1 complexes. These results indicate that mutations impairing the ability of oPL or bPL to form stable complexes with lactogenic receptors do not necessarily lead to a decrease in the biological activity, because the transient existence of the homodimeric complex is still sufficient to initiate the signal transduction. In contrast, oPL and bPL analogues completely, or almost completely, lost their ability to activate homologous PRLRs, and some of them even acted as site-2 antagonists. To explain the difference between the activity transduced through homologous and that transduced through heterologous PRLRs, we propose the novel term 'minimal time of homodimer persistence'. This concept assumes that in order to initiate the signal transduction, the associated kinase JAK2 has to be transphosphorylated and this requires a 'minimal time' of homodimer existence. In the case of homologous interaction between ruminant PLs and homologous PRLRs, this 'minimal time' is met, though the interaction with homologous PRLRs has a shorter half-life than that with heterologous PRLRs. Therefore oPL or bPL are active in cells possessing both homologous and heterologous PRLRs. Mutations of oPL or bPL lead to reduced affinity and, consequently, the 'time of homodimer persistence' is shortened. Although in the case of heterologous interaction the 'minimal time' is still sufficient to initiate the biological activity, in homologous interactions, which are already weaker than heterologous interactions, further destabilization of the complex shortens its persistence to below the 'minimal time', leading to full or partial loss of biological activity.

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23

Oddy, VH, e PJ Holst. "Maternal-foetal adaptation to mid pregnancy feed restriction in single-bearing ewes". Australian Journal of Agricultural Research 42, n. 6 (1991): 969. http://dx.doi.org/10.1071/ar9910969.

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Abstract (sommario):

In two experiments, restriction of feed to levels below maintenance for periods of up to 4 weeks was imposed on groups of ewes bearing single foetuses at 79, 87 or 95 days post coitus. In the first experiment, carried out at pasture, measurements were made of concentration of ovine placental lactogen (oPL) and progesterone in ewe plasma. Effects on lamb birth weight and gestation length were also examined. The second experiment investigated the effect of maternal feed restriction of (i) feed intake, (ii) maternal oPL, (iii) maternal plasma glucose concentration, (iv) lamb birth weight and (v) gestation length. In the first experiment, there were no significant effects of feed restriction on lamb birth weight or gestation length, although foetal growth rate had been reduced in some treatment groups. There were significant interactions between time of sampling and treatment for oPL and progesterone concentration. Control group ewes had lower oPL (P< 0.001) and progesterone (P < 0.05) concentrations than restricted ewes at the end of feed restriction, but higher oPL (P < 0.001) and progesterone (P <0.05) concentrations at 144 days post coitus. In the second experiment, lamb birth weight and gestation length were not significantly affected by maternal feed restriction (birth weight: restricted 4.94 kg, control 4.87 kg av. s.e.m. 0.17 kg; gestation length: restricted 148.3 days, control 147.0 days, av. s.e.m. 0.76 days). Feed restriction was associated with increased (P < 0.05) oPL and decreased glucose (P < 0.05) concentration in plasma. Maternal feed intake was significantly higher (P <0.05) in the restricted group in the week preceding lambing. These results strongly suggest that continuation of maternal feed intake over the last week of pregnancy is the major contributor to maintenance of 'normal' lamb birth weight in previously feed restricted ewes.

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24

Rueda, BR, TG Dunn, RV Anthony e GE Moss. "Influence of fetal death and fetectomy on gestation and the initiation of parturition in the ewe". Reproduction, Fertility and Development 7, n. 5 (1995): 1221. http://dx.doi.org/10.1071/rd9951221.

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Abstract (sommario):

Depressed function of the fetal hypothalamic-pituitary-adrenal axis results in prolonged gestation, and fetal death causes premature parturition. The objective of this experiment was to determine effects of death in utero of a sibling, or its removal, on the duration of gestation and concomitant changes in maternal serum concentrations of oestradiol (E) and progesterone (P). Ovine placental lactogen (oPL) was also determined as an index of placental viability. Blood samples were collected in the morning, beginning 3 days prior to surgery on Day 115 +/- 3 of gestation and continuing daily until 3 days post partum. Surgeries were performed via mid-ventral laparotomy to induce fetal death or to remove the fetus. Fetal death was induced by ligating the umbilicus. Duration of gestation was similar (P > 0.05) in control (C, n = 6) and sham-operated (S, n = 3) ewes (148 +/- 1.0 and 148.6 +/- 0.7 days, respectively). On the day of parturition, concentrations of P, E and oPL were 5.2 +/- 1.9 ng mL-1, 135 +/- 22 pg mL-1 and 153 +/- 54 ng mL-1, respectively, in ewes from combined C and S groups. Total fetectomy (n = 3) resulted in a rapid decrease (P < 0.05) in maternal serum concentrations of P, E, and oPL. Ligation of the umbilicus of both fetus(es) in utero (n = 4) induced fetal death, decreased (P < 0.05) length of gestation to 118.8 +/- 1.8 days and decreased (P < 0.05) serum concentrations of P and oPL prior to parturition and oPL on the day of parturition. In addition, maternal serum concentrations of E failed (P > 0.05) to increase at parturition. Length of gestation and concentrations of P, E and oPL at parturition were not affected (P > 0.05) by removal of one fetus when its sibling was undisturbed (n = 4) compared to control ewes. In contrast, death of one fetus with its sibling undisturbed (n = 5) decreased (P < 0.01) length of gestation (139.2 +/- 2.8 days), but did not affect P, E and oPL (P > 0.05) on all days tested. In conclusion, death of one fetus reduced the duration of gestation, but changes prepartum in maternal serum concentrations of P and oPL were similar to ewes delivering only live fetuses. The increase in maternal concentrations of E that normally occur at parturition was absent in ewes giving birth to only dead fetuses and, therefore, was not a prerequisite to parturition.

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25

Oliver, M. H., J. E. Harding, B. H. Breier, P. C. Evans, B. W. Gallaher e P. D. Gluckman. "The effects of ovine placental lactogen infusion on metabolites, insulin-like growth factors and binding proteins in the fetal sheep". Journal of Endocrinology 144, n. 2 (febbraio 1995): 333–38. http://dx.doi.org/10.1677/joe.0.1440333.

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Abstract (sommario):

Abstract It has been suggested, but not shown, that in the fetus placental lactogen (PL) may affect the regulation of the IGFs and fetal metabolism. To examine the effects of PL on the circulating concentrations of the IGFs, IGF-binding proteins (IGFBPs), glucose, free fatty acids (FFAs) and amino nitrogen (AN), we infused late gestation sheep fetuses with recombinant ovine PL (roPL). Five chronically-catheterised sheep fetuses were infused intravenously with three 24 h infusions of saline, roPL (100 μg bolus then 500 μg over 24 h) and then saline again. Fetal roPL infusion increased plasma oPL from 0·4 ± 0·1 to 3·3 ± 0·5 nm (mean ± s.e.m.; P<0·05; factorial analysis of variance and Scheffé's test). Fetal plasma IGF-I, IGF-II, insulin, FFAs and blood glucose were unaffected by the roPL infusion. Fetal plasma IGFBP-3, as measured by Western ligand blotting, decreased by 30% during fetal roPL infusion while other fetal plasma IGFBPs were unaffected. Fetal roPL infusion decreased fetal blood AN from 7·3 ± 0·5 to 6·6 ± 0·2 mm (P<0·05). Maternal plasma IGF-I, IGF-II, IGFBPs, insulin, FFAs, blood glucose and AN were unaffected by the fetal roPL infusion. Saline infusion had no effect on any parameter. The data suggest that PL is not a significant determinant of plasma IGFs in the late gestation sheep fetus although there may be an indirect effect via alterations in levels of IGFBP-3. The effect of fetal roPL infusion on fetal blood AN concentrations may suggest some role for PL in the regulation of fetal amino acid metabolism. Journal of Endocrinology (1995) 144, 333–338

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26

Breier, B. H., G. R. Ambler, H. Sauerwein, A. Surus e P. D. Gluckman. "The induction of hepatic somatotrophic receptors after birth in sheep is dependent on parturition-associated mechanisms". Journal of Endocrinology 141, n. 1 (aprile 1994): 101–8. http://dx.doi.org/10.1677/joe.0.1410101.

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Abstract (sommario):

Abstract While the GH receptor (GHR) plays a key role during adult life, its role during fetal development is not well understood. Recent data suggest that GHRs are present in ovine fetal hepatic tissue at mid-gestation. However, the levels of GHR expression are markedly lower in fetal hepatic tissue in comparison with postnatal values. The present study investigates whether the neonatal induction of the hepatic GHR and plasma levels of IGF-I follow a pattern of strictly age-related development or whether birth-associated processes stimulate this increase. Stereotaxic electrolytic lesioning of the fetal paraventricular nuclei was employed to prolong gestation markedly. We compared the hepatic binding of ovine placental lactogen (oPL) and oGH and plasma levels of IGF-I in these post-mature fetuses with those in pre-term fetuses, pregnant mothers and lambs which were of the same conceptional age as the post-mature fetuses. While specific binding of both 125I-labelled oGH and 125I-labelled oPL to hepatic microsomal membranes was fully reversible in all groups, the specific binding of 125I-labelled oGH was significantly (P<0·001) lower than specific binding of 125I-labelled oPL in all groups of animals. There was no difference in specific I-labelled oGH or 125I-labelled oPL binding in livers or plasma levels of IGF-I in post-mature fetuses in comparison with pre-term fetuses. In contrast, a major increase (P<0·001) in 125I-labelled oGH and 125I-labelled oPL binding and plasma IGF-I levels was observed in lambs. In pregnant females, specific 125I-labelled oGH and 125I-labelled oPL binding and plasma IGF-I levels were significantly (P<0·01) higher compared with the two fetal groups. A significant (P<0·001) correlation was observed between specific binding with 125I-labelled oGH and 125I-labelled oPL (r=0·95, intercept=4·5, slope=2·36). Detailed competitive binding studies showed that the potency of unlabelled oPL in competing with 125I-labelled oPL or 125I-labelled oGH was consistently higher in comparison with unlabelled oGH. The differences in cross-reactivity of oPL and oGH at the distinct developmental stages were related to the differences in affinity between the two ligands and major developmental increases in capacity. The present study shows major parallel induction of oPL and oGH binding to hepatic microsomal membranes and plasma IGF-I concentrations after birth. The postnatal increase in the hepatic GHR is inhibited if delivery is prevented by stereotaxic destruction of the fetal paraventricular nuclei. Our observation that oGH and oPL binding is co-ordinately induced after birth in hepatic tissue supports the emerging evidence that the two ligands may bind to the same membrane receptor or to related protein(s). Journal of Endocrinology (1994) 141, 101–108

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27

Gertler, Arieh, Eva Biener, Krishnan V. Ramanujan, Jean Djiane e Brian Herman. "Fluorescence resonance energy transfer (FRET) microscopy in living cells as a novel tool for the study of cytokine action". Journal of Dairy Research 72, S1 (28 luglio 2005): 14–19. http://dx.doi.org/10.1017/s0022029905001123.

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Abstract (sommario):

Fluorescence resonance energy transfer (FRET) microscopy was used to study interactions between proteins in intact cells. We showed that growth hormone (GH) causes transient homodimerization of GH receptors tagged with yellow or cyan fluorescent proteins. The peak of FRET signaling occurred 2 to 4 min after hormonal stimulation and was followed by a decrease in FRET signal. Repeating those experiments in cells pretreated with the inhibitor of internalization methyl-β-cyclodextrin, or in potassium-depleted cells showed no difference in the kinetics of FRET signaling as compared with the non-treated cells, indicating that the decrease in FRET signal does not result from receptor internalization by the pathways inhibited by methyl-β-cyclodextrin or potassium depleted but might occur by other pathways of internalization. Using a similar methodology, we also demonstrated that ovine placental lactogen (oPL) causes transient heterodimerization of GH and prolactin (PRL) receptors 2·5 to 3 min after oPL application. On the other hand, oGH or oPRL had no effect at all, further substantiating the finding the oPL, which lacks a specific receptor, acts in homologous systems by heterodimerization of GH and PRL receptors. We also demonstrated that both PRL and leptin (LEP) are capable of transactivation of the oncogenic receptors erbB2 and erbB3. Upon PRL or LEP stimulation of HEK-293T cells transfected with LEP or PRL receptors and erbB2 or erbB3, erbB proteins are first phosphorylated and then activate MAPK (erk1/erk2). However, the FRET experiments failed to document any evidence of a direct interaction between erbB2 and the PRL or LEP receptors, suggesting that erbB activation probably occurs via activated JAK2, translocated from the respective receptors to erbB2.

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28

Klempt, M., BH Breier, SH Min, DDS MacKenzie, SN McCutcheon e PD Gluckman. "IGFBP-2 expression in liver and mammary tissue in lactating and pregnant ewes". Acta Endocrinologica 129, n. 5 (novembre 1993): 453–57. http://dx.doi.org/10.1530/acta.0.1290453.

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Abstract (sommario):

Binding proteins for the insulin-like growth factors (IGFBPs) modulate the actions of IGF I and IGF II. IGFBP-2 is particularly high in plasma of pregnant and fetal animals and in milk. We investigated the peri-lactational control of IGFBP-2 expression and secretion. Fifteen singleton-bearing pregnant ewes at day 101 of gestation were injected sc twice daily for 8 days with bovine growth hormone (bGH) or ovine placental lactogen (oPL) both at 0.15 mg·kg−1·d−1 or saline. A further fifteen ewes at day 17 of lactation were injected sc twice daily for 5 days with bGH or oPL at 0.1 mg·kg−1·d−1 or saline. On the last day of injection blood samples were taken and the animals were sacrificed. Liver and mammary tissue samples were immediately frozen and subsequently extracted to provide total RNA for evaluation by Northern blot analysis using a rat IGFBP-2 cDNA probe. Plasma samples were analysed by Western ligand blotting for IGFBP-2. The comparison of the two saline-treated groups (pregnant vs lactating ewe) revealed no difference in the plasma concentrations of IGFBP-2. IGFBP-2 mRNA expression in the liver of the lactating ewes was markedly increased compared to that in the pregnant ewes. In contrast, in mammary tissue the expression was significantly lower in lactating than in pregnant sheep. In pregnant animals treatment with bGH, but not oPL, decreased the expression of IGFBP-2 in liver. There was a similar trend in the lactating ewe. GH treatment, but not PL treatment, moderately reduced IGFBP-2 levels in the lactating but not the pregnant ewes. bGH but not oPL induced hyperinsulinaemia. We conclude that GH has actions in pregnancy and lactation which are not mimicked by oPL. The regulation of hepatic IGFBP-2 expression by GH is similar in pregnant and postpartum animals. However, there are distinct differences in the tissue-specific regulation of IGFBP-2 between pregnancy and lactation. The liver might be the major source of circulating IGFBP-2.

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29

Colosi, Peter, Gudmundur Thordarson, Renate Hellmiss, Kuljeet Singh, Isabel A. Forsyth, Peter Gluckman e William I. Wood. "Cloning and Expression of Ovine Placental Lactogen". Molecular Endocrinology 3, n. 9 (settembre 1989): 1462–69. http://dx.doi.org/10.1210/mend-3-9-1462.

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30

Forsyth, IA, A. Hutchings e GW Butcher. "A panel of monoclonal antibodies to ovine placental lactogen". Journal of Endocrinology 165, n. 2 (1 maggio 2000): 435–42. http://dx.doi.org/10.1677/joe.0.1650435.

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Abstract (sommario):

A panel of 11 rat monoclonal antibodies (mAbs) has been raised to ovine placental lactogen (PL). By competitive enzyme-linked immunoabsorbent assay (ELISA), confirmed by two-site ELISA, the antibodies were shown to recognize six antigenic determinants on the ovine PL molecule, two of which overlap. One antigenic determinant (designated 1) was shared by other members of the prolactin/growth hormone (GH)/PL family in ruminants, humans and rodents. The binding of (125)I-labelled ovine PL to crude receptor preparations from sheep liver (somatotrophic) or rabbit mammary gland (lactogenic) was inhibited by mAbs recognizing antigenic determinants 2-6. Both types of receptor preparation were affected similarly. In the local in vivo pigeon crop sac assay, mAbs directed against determinants 3 and 6 enhanced the biological activity of ovine PL.

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31

Thordarson, G., G. H. McDowell, S. V. Smith, S. Iley e I. A. Forsyth. "Effects of continuous intravenous infusion of an ovine placental extract enriched in placental lactogen on plasma hormones, metabolites and metabolite biokinetics in non-pregnant sheep". Journal of Endocrinology 113, n. 2 (maggio 1987): 277–83. http://dx.doi.org/10.1677/joe.0.1130277.

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Abstract (sommario):

ABSTRACT Continuous intravenous infusions of saline or of a placental extract containing ovine placental lactogen were given to three non-pregnant, non-lactating ewes over periods of 36 h, 1 week apart. During saline infusion no placental lactogen was detected in jugular vein plasma, but infusion of the placental extract raised the placental lactogen concentration from undetectable to 40-50 μg/l, similar to concentrations in ewes with one fetus on day 90 of pregnancy. By comparison with the saline control period, infusion of the placental extract consistently increased both plasma concentrations and irreversible loss of non-esterified fatty acids. Plasma concentrations of glucose and urea, but not irreversible loss of these metabolites, were consistently increased. Although the placental extract was not subjected to extensive purification, it was enriched in placental lactogen and contained no detectable contamination with insulin, prolactin or growth hormone. The results are suggestive of a role for placental lactogen in modifying metabolism and acting during pregnancy to provide nutrients for fetal metabolism. J. Endocr. (1987) 113, 277–283

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32

Fernández, M. Laura, Gisela D. Cymes, Lucrecia M. Curto e Carlota Wolfenstein-Todel. "Ovine placental lactogen and ovine prolactin: partial proteolysis and conformational stability". International Journal of Biochemistry & Cell Biology 32, n. 6 (giugno 2000): 597–608. http://dx.doi.org/10.1016/s1357-2725(00)00012-1.

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33

Noel, Sekoni, Asael Herman, Greg A. Johnson, C. Allison Gray, M. David Stewart, Fuller W. Bazer, Arieh Gertler e Thomas E. Spencer. "Ovine Placental Lactogen Specifically Binds to Endometrial Glands of the Ovine Uterus1". Biology of Reproduction 68, n. 3 (1 marzo 2003): 772–80. http://dx.doi.org/10.1095/biolreprod.102.009183.

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34

Chan, John S. D., Z. R. Nie e S. C. Pang. "Cellular localization of ovine placental lactogen using monoclonal antibodies". Animal Reproduction Science 23, n. 1 (agosto 1990): 33–40. http://dx.doi.org/10.1016/0378-4320(90)90013-6.

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35

Cymes, Gisela D., M. Mercedes Iglesias e Carlota Wolfenstein-Todel. "Selective modification of tryptophan-150 in ovine placental lactogen". Comparative Biochemistry and Physiology Part B: Comparative Biochemistry 106, n. 3 (novembre 1993): 743–46. http://dx.doi.org/10.1016/0305-0491(93)90157-z.

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36

Yossefi, S., e E. Gootwine. "A PvuII RFLP at the ovine placental lactogen CSH1 locus". Animal Genetics 27, n. 4 (24 aprile 2009): 285–86. http://dx.doi.org/10.1111/j.1365-2052.1996.tb00493.x.

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37

CARIDAD, J. J., e C. WOLFENSTEIN-TODEL. "Selective reduction of the disulfide bonds of ovine placental lactogen". International Journal of Peptide and Protein Research 31, n. 1 (12 gennaio 2009): 71–76. http://dx.doi.org/10.1111/j.1399-3011.1988.tb00008.x.

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38

Liang, Rongti, Sean W. Limesand e Russell V. Anthony. "Structure and transcriptional regulation of the ovine placental lactogen gene". European Journal of Biochemistry 265, n. 3 (25 dicembre 2001): 883–95. http://dx.doi.org/10.1046/j.1432-1327.1999.00790.x.

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39

FREEMARK, MICHAEL, e STUART HANDWERGER. "The Glycogenic Effects of Placental Lactogen and Growth Hormone in Ovine Fetal Liver Are Mediated through Binding to Specific Fetal Ovine Placental Lactogen Receptors*". Endocrinology 118, n. 2 (febbraio 1986): 613–18. http://dx.doi.org/10.1210/endo-118-2-613.

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40

Christinger, Hans W., Patricia A. Elkins, Yael Sandowski, Edna Sakal, Arieh Gertler, Anthony A. Kossiakoff e Abraham M. de Vos. "Crystallization of ovine placental lactogen in a 1:2 complex with the extracellular domain of the rat prolactin receptor". Acta Crystallographica Section D Biological Crystallography 54, n. 6 (1 novembre 1998): 1408–11. http://dx.doi.org/10.1107/s0907444998005794.

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Abstract (sommario):

Growth hormone and prolactin control somato-lactogenic biology. While high-resolution crystal structures have been determined for receptor complexes of human growth hormone, no such information exists for prolactin. A stable 1:2 complex was formed between ovine placental lactogen, a close prolactin homologue, and two copies of the extracellular portion of the rat prolactin receptor. Using synchrotron radiation, native data have been collected to 2.3 Å. Crystals contain one complex per asymmetric unit. The crystal structure of this complex will shed light on the structural reasons for cross-reactivity and specificity among the endocrine hormones, placental lactogen, prolactin and growth hormone.

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41

Schoknecht, P. A., W. B. Currie e A. W. Bell. "Kinetics of placental lactogen in mid- and late-gestation ovine fetuses". Journal of Endocrinology 133, n. 1 (aprile 1992): 95–100. http://dx.doi.org/10.1677/joe.0.1330095.

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ABSTRACT Placental lactogen (PL) is found in fetal plasma throughout gestation, and PL receptors occur on many types of fetal cells. In this study, the entry rate of PL into the fetal circulation was estimated by injection of 125I-labelled ovine PL into two mid- and four late-gestation fetuses. At both ages, PL appears to be distributed into two body pools. One pool has a rapid half-life (approximately 9 min) and a volume of distribution approximately 8% of body weight, while the second pool has a longer half-life (approximately 45 min) and a distribution volume only 4% of body weight. The first pool is presumably blood plasma, but the physiological identity of the second pool is unknown. The effective half-life of PL is approximately 15 min, and the liver is suggested as a probable major site of degradation. These estimates were confirmed in late gestation by measuring fetal plasma concentrations of PL in response to a continuous infusion of unlabelled PL. The kinetic parameters estimated in this study can be used to determine the quantity of exogenous hormone required to alter PL concentration in fetal plasma in a predictable manner. Journal of Endocrinology (1992) 133, 95–100

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42

FREEMARK, MICHAEL, e STUART HANDWERGER. "Ovine Placental Lactogen Inhibits Glucagon-Induced Glycogenolysis in Fetal Rat Hepatocytes*". Endocrinology 116, n. 4 (aprile 1985): 1275–80. http://dx.doi.org/10.1210/endo-116-4-1275.

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43

Braun, Thorsten, Wenbin Meng, Hongkai Shang, Shaofu Li, Deborah Sloboda, Loreen Ehrlich, Huaisheng Xu et al. "Early maternal dexamethasone administration and the effect on ovine placental lactogen". Placenta 34, n. 9 (settembre 2013): A92. http://dx.doi.org/10.1016/j.placenta.2013.06.273.

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44

Warren, W. C., D. H. Keisler e R. V. Anthony. "Synthesis and secretion of ovine placental lactogen and its biochemical properties". Domestic Animal Endocrinology 7, n. 3 (luglio 1990): 331–42. http://dx.doi.org/10.1016/0739-7240(90)90039-3.

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45

Spencer, Thomas E., Allison Gray, Greg A. Johnson, Kristin M. Taylor, Arieh Gertler, Elisha Gootwine, Troy L. Ott e Fuller W. Bazer. "Effects of Recombinant Ovine Interferon Tau, Placental Lactogen, and Growth Hormone on the Ovine Uterus1". Biology of Reproduction 61, n. 6 (1 dicembre 1999): 1409–18. http://dx.doi.org/10.1095/biolreprod61.6.1409.

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46

Freemark, M., M. Comer, T. Mularoni, A. J. D'Ercole, A. Grandis e L. Kodack. "Placental lactogen receptors in maternal sheep liver: effects of fasting and refeeding". American Journal of Physiology-Endocrinology and Metabolism 258, n. 2 (1 febbraio 1990): E338—E346. http://dx.doi.org/10.1152/ajpendo.1990.258.2.e338.

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Abstract (sommario):

In a recent study we demonstrated that fasting of the pregnant ewe reduces the number of placental lactogen (PL) receptors in fetal sheep liver. In the present study we examined the effects of a 72-h fast on the number and affinity of PL receptors in maternal sheep liver. Fasting caused a 57% reduction in the number of hepatic ovine PL receptors; this effect was reversed by refeeding. There were no changes in the affinity of the PL receptor, the subunit structure of the receptor, or the extent of occupancy of the receptor by endogenous circulating maternal hormones. The number of hepatic PL receptors was correlated positively with the maternal plasma concentrations of glucose and insulin, suggesting that these factors may regulate PL binding to maternal tissues during pregnancy. In addition, PL receptor number was correlated positively with maternal plasma insulin-like growth factor I (IGF-I) concentrations, suggesting that a reduction in hepatic ovine PL binding may contribute to the reduction in maternal IGF-I during fasting. Fasting produced a 72% reduction in the number of ovine growth hormone receptors in maternal liver and an 83% increase in hepatic insulin binding. These findings indicate that fasting of the pregnant ewe reduces the number of PL receptors in maternal and fetal liver. The reduction in PL binding may contribute to maternal and fetal hyposomatomedinemia and may play a role in the pathogenesis of the intrauterine growth retardation that accompanies maternal nutritional deprivation.

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47

Battista, P. J., A. W. Bell, D. R. Deaver e W. B. Currie. "Differential control of placental lactogen release and progesterone production by ovine placental tissue in vitro". Placenta 11, n. 4 (luglio 1990): 337–48. http://dx.doi.org/10.1016/s0143-4004(05)80225-5.

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48

Herman, Asael, Christophe Bignon, Nathalie Daniel, Jeanne Grosclaude, Arieh Gertler e Jean Djiane. "Functional Heterodimerization of Prolactin and Growth Hormone Receptors by Ovine Placental Lactogen". Journal of Biological Chemistry 275, n. 9 (25 febbraio 2000): 6295–301. http://dx.doi.org/10.1074/jbc.275.9.6295.

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49

Sakal, E., C. Bignon, N. Chapnik-Cohen, N. Daniel, J. Paly, L. Belair, J. Djiane e A. Gertler. "Cloning, preparation and characterization of biologically active recombinant caprine placental lactogen". Journal of Endocrinology 159, n. 3 (1 dicembre 1998): 509–18. http://dx.doi.org/10.1677/joe.0.1590509.

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Abstract (sommario):

Caprine placental lactogen (cPL) cDNA was cloned by reverse transcription (RT)-PCR from total RNA of goat placenta. The PCR product encoding for the mature protein was gel purified, ligated to pGEM-T and finally subcloned into a pET8c prokaryotic expression vector. E. coli cells (BL-21) transformed with this vector overexpressed large amounts of cPL upon induction with Isopropyl-1-thio-beta-D-galactopyranoside. The expressed protein, found in the inclusion bodies, was refolded and purified to homogeneity on Q-Sepharose and SP-Sepharose columns, yielding two electrophoretically pure fractions (cPL-Q and cPL-S), composed of over 98% of monomeric protein of the expected molecular mass of approximately 23 kDa. Binding of cPL to the extracellular domain (ECD) of prolactin receptors (PRLR) from rat (r), rabbit (rb), and bovine (b), growth hormone receptors (GHR) from human (h) and rabbit, and binding to rabbit mammary gland membranes revealed similar binding profiles for cPL-Q, cPL-S and ovine (o)PL. Caprine PL was capable of forming 1:2 complexes with hGHR-ECD, rbGHR-ECD, rPRLR-ECD and rbPRLR-ECD whereas with bPRLR-ECD only a 1:1 complex was detected. The biological activity of both cPL fractions resulting from proper renaturation was further evidenced by their ability to stimulate proliferation of Nb2 cells, FDC-P1 cells transfected with rabbit or human GHRs and by stimulation of beta-casein synthesis in rabbit and ovine mammary gland acini cultures.

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50

Jeckel, K. M., S. W. Limesand e R. V. Anthony. "Specificity protein-1 and -3 trans-activate the ovine placental lactogen gene promoter". Molecular and Cellular Endocrinology 307, n. 1-2 (agosto 2009): 118–24. http://dx.doi.org/10.1016/j.mce.2009.04.006.

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