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Copyright of European Poultry Science / Archiv für Geflügelkunde is the property of Verlag Eugen Ulmer and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The aim of this study was to analyse the effects of species (Muscovy and Pekin ducks) and age at the beginning of the overfeeding period on fatty liver production, carcass composition and lipid and moisture content of the liver and breast muscle. We reared four groups of 40 ducks per species for the study, starting at 2-week intervals in order to have four different ages together at the beginning of the overfeeding period (10, 12, 14 and 16 weeks). At the end of the overfeeding period, all ducks were slaughtered. Our results confirmed the high levels of difference in carcass composition and lipid content in the plasma, liver and breast muscle between Muscovy and Pekin ducks at all ages. Pekin ducks were not able to develop a high degree of hepatic steatosis, but had increased lipid storage in peripheral adipose and muscle tissues than Muscovy ducks. However, the fatty liver weight of Pekin ducks increased with age, with lipid deposition in the liver and peripheral tissues. The ability of Muscovy ducks to produce fatty livers remained unchanged with age in line, with lipid deposition in the liver and peripheral tissues. The sites of lipid deposition thus depend on species and not on the physiological maturity of ducks. [ABSTRACT FROM AUTHOR]

The difference in the ability of Pekin and Muscovy ducks to develop hepatic steatosis could result from a different peripheral lipoprotein lipase (LPL) activity, which hydrolyses triacylglycerol secreted by the liver. We studied the kinetics of plasma LPL activity in response to a meal at different ages in Pekin and Muscovy ducks. For that purpose, blood samples were taken at 5, 9, 12, 13, and 14 wk of age just before and 1, 2, 4, and 8 h after a meal. To release LPL into general circulation, an i.v. injection of heparin (400 lU/kg of BW) was administered 10 mm before blood collection. For that reason, different ducks per genotype were used for each point of measurement (n = 6). Plasma LPL activity measured before the meal was negatively correlated with the weight of the fatty liver measured in the same ducks at 14 wk of age (r = -0.58, P < 0.001). Plasma triacyiglycerol level measured before the meal was negatively correlated with plasma LPL activity measured in the same ducks (r = -0.31, P = 0.025) and was negatively correlated with plasma LPL activity measured in the same ducks for each age and each timing (r = -0.39, P < 0.001). At 14 wk of age for Muscovy and Pekin ducks, we observed that a high plasma LPL activity (>200 IU/L of plasma) corresponded to a relatively low development of fatty liver (190 g) induced by overfeeding, whereas a low plasma LPL activity (<150 lU/L of plasma) corresponded to a high propensity to develop fatty liver (470 g). In conclusion, plasma LPL activity measured just before the meal during the rearing period could be used as a marker of hepatic steatosis development during the overfeeding period. [ABSTRACT FROM AUTHOR]

This study compared models for growth (BW) before overfeeding period for male mule duck data from 7 families of a QTL experimental design. Four nonlinear models (Gompertz, logistic, Richards, and Weibull) and a spline linear regression model were used. This study compared fixed and mixed effects models to analyze growth. The Akaike information criterion was used to evaluate these alternative models. Among the nonlinear models, the mixed effects Weibull model had the best overall fit. Two parameters, the asymptotic weight and the inflexion point age, were considered random variables associated with individuals in the mixed models. In our study, asymptotic weight had a greater effect in Akaike's information criterion reduction than inflexion point age. In this data set, the between-ducks variability was mostly explained by asymptotic BW. Comparing fixed with mixed effects models, the residual SD was reduced in about 55% in the latter, pointing out the improvement in the accuracy of estimated parameters. The mixed effects spline regression model was the second best model. Given the piecewise nature of growth, this model is able to capture different growth patterns, even with data collected beyond the asymptotic BW. [ABSTRACT FROM AUTHOR]

The present study was designed to evaluate the effect of preslaughter transport (30 vs. 150 min) and holding of mule ducks in lairage in their transport crates (15 vs. 120 min) on the quality of the meat and fatty liver. A total of 120 birds were allocated in a 2 × 2 factorial design with a constant postprandial delay to slaughter (8 h), to avoid the confounding between the effects of the experimental treatments and those of fasting duration. Under such conditions, extending the transport or holding duration did not induce a loss in preslaughter live weight or liver weight. Similarly, breast muscle glycogen stores were not affected by the treatments, nor was the kinetics of postmortem pH decline affected. The mechanical resistance of raw meat obtained by the compression test significantly increased with holding duration. The gross chemical composition of the livers did not differ significantly among the preslaughter treatments. Residual blood in the liver, as indicated by heme pigment concentration, was enhanced with a longer transport, but this effect was more pronounced after the longest holding duration, as shown by a significant interaction. This, however, did not significantly affect the incidence of appearance defects or the commercial grading of the livers. The percentage of fat loss during the cooking of canned livers was significantly reduced when the transport duration was increased. This effect could not be explained on the basis of the current knowledge for determining the technological quality of fatty liver. The identification of biological markers of liver quality is currently underway in our laboratory. Further investigations studying the differential expression of these biological markers according to preslaughter conditions would provide a better understanding of the effect of transport duration on liver processing yield. [ABSTRACT FROM AUTHOR]

We conducted a study to evaluate the effects of intramuscular fat levels on the sensory characteristics of duck breast meat. Combining duck genotypes (Muscovy, Pekin, and their crossbreed hinny and mule ducks) and feeding levels (overfeeding between 12 and 14 wk of age vs. ad libitum feeding) enabled us to obtain a wide range of lipid levels in breast muscle. The average values were between 2.55 and 6.40 g per 100 g of muscle. Breast muscle from overfed ducks showed higher lipid and lower water levels than breast muscle from ducks fed ad libitum. Muscle from the overfed ducks was also paler in color and exhibited greater yellowness and cooking loss values. Juiciness was judged lower and flavor more pronounced in overfed ducks. Muscovy ducks exhibited higher breast weight and lower lipid levels than the other genotypes. At the other extreme, Pekin ducks exhibited the highest lipid levels and the lowest breast weights; values for these criteria were intermediate in hinny and mule ducks. Breast muscle of Muscovy ducks was paler, less red, and more yellow than that of other genotypes. Breast muscle of Pekin ducks exhibited the lowest values for lightness, yellowness, and energy necessary to shear meat, as well as the highest cooking loss values, and was judged more tender, juicy and less stringy than that of other genotypes. In contrast, scores for breast muscle of Muscovy ducks were the lowest for tenderness, juiciness, and flavor, and the highest for stringiness. Breast muscle of hinny and mule ducks scored the highest values for redness. Hinny ducks also scored the highest values for flavor. Genotype exerted a higher effect on the sensory quality of breast muscle than did feeding levels. Finally, increasing lipid levels in breast muscle increased lightness, yellowness, cooking loss, tenderness, and flavor, with correlation coefficients of 0.49, 0.47, 0.54, 0.43, and 0.28, respectively. However, breast meat color and tenderness were mainly influenced by genotype. [ABSTRACT FROM AUTHOR]

Context: In a cohort of 95 women with multiple breast fibroadenomas (MFAs), we recently identified patients harboring germline heterozygous variants of the prolactin receptor (PRLR) exhibiting constitutive activity (PRLR I146L and PRLR I176V )., Objective: This study sought to better delineate the potential role of PRLR gain-of-function variants in benign and malignant mammary tumorigenesis., Design: This was an observational study and transgenic mouse model analysis., Setting: The study took place at the Department of Endocrinology, Reproductive Disorders and Rare Gynecologic Diseases, Pitié Salpêtrière, Paris, and Inserm Unit 1151, Paris., Patients or Other Participants: We generated a second MFA cohort (n = 71) as well as a group of control subjects (n = 496) and a cohort of women with breast cancer (n = 119). We also generated two transgenic mouse models carrying the coding sequences of human PRLR I146L or PRLR WT ., Intervention: We aimed to determine the prevalence of PRLR variants in these three populations and to uncover any association of the latter with specific tumor pattern, especially in patients with breast cancer., Results: This study did not highlight a higher prevalence of PRLR variants in the MFA group and in the breast cancer group compared with control subjects. Transgenic mice expressing PRLR I146L exhibited very mild histological mammary phenotype but tumors were never observed., Conclusion: PRLR I146L and PRLR I176V variants are not associated with breast cancer or MFA risk. However, one cannot exclude that low but sustained PRLR signaling may facilitate or contribute to pathological development driven by oncogenic pathways. Long-term patient follow-up should help to address this issue.

Cytokine receptors elicit several signaling pathways, but it is poorly understood how they select and discriminate between them. We have scrutinized the prolactin receptor as an archetype model of homodimeric cytokine receptors to address the role of the extracellular membrane proximal domain in signal transfer and pathway selection. Structure-guided manipulation of residues involved in the receptor dimerization interface identified one residue (position 170) that in cell-based assays profoundly altered pathway selectivity and species-specific bio-characteristics. Subsequent in vitro spectroscopic and nuclear magnetic resonance analyses revealed that this residue was part of a residue quartet responsible for specific local structural changes underlying these effects. This included alteration of a novel aromatic T-stack within the membrane proximal domain, which promoted selective signaling affecting primarily the MAPK (ERK1/2) pathway. Importantly, activation of the MAPK pathway correlated with in vitro stabilities of ternary ligand·receptor complexes, suggesting a threshold mean lifetime of the complex necessary to achieve maximal activation. No such dependence was observed for STAT5 signaling. Thus, this study establishes a residue quartet in the extracellular membrane proximal domain of homodimeric cytokine receptors as a key regulator of intracellular signaling discrimination., (© 2015 by The American Society for Biochemistry and Molecular Biology, Inc.)

PRLR(I146L) is the first identified gain-of-function variant of the prolactin receptor (PRLR) that was proposed to be associated with benign breast tumorigenesis. Structural investigations suggested this hydrophobic core position in the extracellular D2 domain to be linked to receptor dimerization. Here, we used a mutational approach to address how the conservative I-to-L substitution induced constitutive activity. Using cell-based assays of different I146-PRLR variants in combination with spectroscopic/nuclear magnetic resonance analyses we found that chemical manipulation of position 146 profoundly altered folding, PRL-responsiveness, and ligand-independent activity of the receptor in a mutation-specific manner. Together, these data further add to the critical role of position 146, showing it to also be crucial to structural integrity thereby imposing on the biological PRLR properties. When stably introduced in MCF-7 (luminal) and MDA-MB231 (mesenchymal) breast cancer cells, the most potent of the PRL-insensitive mutants (PRLR(I146D)) had minimal impact on cell proliferation and cell differentiation status., (Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.)

Anterior pituitary cell turnover occurring during female sexual cycle is a poorly understood process that involves complex regulation of cell proliferation and apoptosis by multiple hormones. In rats, the prolactin (PRL) surge that occurs at proestrus coincides with the highest apoptotic rate. Since anterior pituitary cells express the prolactin receptor (PRLR), we aimed to address the actual role of PRL in the regulation of pituitary cell turnover in cycling females. We showed that acute hyperprolactinemia induced in ovariectomized rats using PRL injection or dopamine antagonist treatment rapidly increased apoptosis and decreased proliferation specifically of PRL producing cells (lactotropes), suggesting a direct regulation of these cell responses by PRL. To demonstrate that apoptosis naturally occurring at proestrus was regulated by transient elevation of endogenous PRL levels, we used PRLR-deficient female mice (PRLRKO) in which PRL signaling is totally abolished. According to our hypothesis, no increase in lactotrope apoptotic rate was observed at proestrus, which likely contributes to pituitary tumorigenesis observed in these animals. To decipher the molecular mechanisms underlying PRL effects, we explored the isoform-specific pattern of PRLR expression in cycling wild type females. This analysis revealed dramatic changes of long versus short PRLR ratio during the estrous cycle, which is particularly relevant since these isoforms exhibit distinct signaling properties. This pattern was markedly altered in a model of chronic PRLR signaling blockade involving transgenic mice expressing a pure PRLR antagonist (TGΔ1-9-G129R-hPRL), providing evidence that PRL regulates the expression of its own receptor in an isoform-specific manner. Taken together, these results demonstrate that i) the PRL surge occurring during proestrus is a major proapoptotic signal for lactotropes, and ii) partial or total deficiencies in PRLR signaling in the anterior pituitary may result in pituitary hyperplasia and eventual prolactinoma development, as observed in TGΔ1-9-G129R-hPRL and PRLRKO mice, respectively.

The mule duck, an interspecific hybrid obtained by crossing common duck (Anas platyrhynchos) females with Muscovy (Cairina moschata) drakes, is widely used for fatty liver production. The purpose of the present study was to detect and map single and pleiotropic QTL that segregate in the common duck species, and influence the expression of traits in their overfed mule duck offspring. To this end, we generated a common duck backcross (BC) population by crossing Kaiya and heavy Pekin experimental lines, which differ notably in regard to the BW and overfeeding ability of their mule progeny. The BC females were mated to Muscovy drakes and, on average, 4 male mule ducks hatched per BC female (1600 in total) and were measured for growth, metabolism during growth and the overfeeding period, overfeeding ability, and the quality of their breast meat and fatty liver. The phenotypic value of BC females was estimated for each trait by assigning to each female the mean value of the phenotypes of her offspring. Estimations allowed for variance, which depended on the number of male offspring per BC and the heritability of the trait considered. The genetic map used for QTL detection consisted of 91 microsatellite markers aggregated into 16 linkage groups (LG) covering a total of 778 cM. Twenty-two QTL were found to be significant at the 1% chromosome-wide threshold level using the single-trait detection option of the QTLMap software. Most of the QTL detected were related to the quality of breast meat and fatty liver: QTL for meat pH 20 min post mortem were mapped to LG4 (at the 1% genome-wide significance level), and QTL for meat lipid content and cooking losses were mapped to LG2a. The QTL related to fatty liver weight and liver protein and lipid content were for the most part detected on LG2c and LG9. Multitrait analysis highlighted the pleiotropic effects of QTL in these chromosome regions. Apart from the strong QTL for plasma triglyceride content at the end of the overfeeding period mapped to chromosome Z using single-trait analysis, all metabolic trait QTL were detected with the multitrait approach: the QTL mapped to LG14 and LG21 affected the plasma cholesterol and triglyceride contents, whereas the QTL mapped to LG2a seemed to impact glycemia and the basal plasma corticosterone content. A greater density genetic map will be needed to further fine map the QTL.

Since anterior pituitary expresses prolactin receptors, prolactin secreted by lactotropes could exert autocrine or paracrine actions on anterior pituitary cells. In fact, it has been observed that prolactin inhibits its own expression by lactotropes. Our hypothesis is that prolactin participates in the control of anterior pituitary cell turnover. In the present study, we explored the action of prolactin on proliferation and apoptosis of anterior pituitary cells and its effect on the expression of the prolactin receptor. To determine the activity of endogenous prolactin, we evaluated the effect of the competitive prolactin receptor antagonist Δ1-9-G129R-hPRL in vivo, using transgenic mice that constitutively and systemically express this antagonist. The weight of the pituitary gland and the anterior pituitary proliferation index, determined by BrdU incorporation, were higher in transgenic mice expressing the antagonist than in wild-type littermates. In addition, blockade of prolactin receptor in vitro by Δ1-9-G129R-hPRL increased proliferation and inhibited apoptosis of somatolactotrope GH3 cells and of primary cultures of male rat anterior pituitary cells, including lactotropes. These results suggest that prolactin acts as an autocrine/paracrine antiproliferative and proapoptotic factor in the anterior pituitary gland. In addition, anterior pituitary expression of the long isoform of the prolactin receptor, measured by real-time PCR, increased about 10-fold in transgenic mice expressing the prolactin receptor antagonist, whereas only a modest increase in the S3 short-isoform expression was observed. These results suggest that endogenous prolactin may regulate its own biological actions in the anterior pituitary by inhibiting the expression of the long isoform of the prolactin receptor. In conclusion, our observations suggest that prolactin is involved in the maintenance of physiological cell renewal in the anterior pituitary. Alterations in this physiological role of prolactin could contribute to pituitary tumor development.

The lipoprotein-lipase (LPL) hydrolyses the triacylglycerols (TG) secreted by the liver and, thus, allows the storage of lipids onto the extrahepatic tissues. The LPL activity has been studied by injection of LPL antibodies in three genotypes of ducks (Muscovy (Cairina moschat), Pekin (Anas plathyrhynchos) and Mule (hybrids of male Muscovy ducks and female Pekin ducks)) under overfeeding condition. The results show a similar weight gain between injected and control animals. A higher liver steatosis is observed in Mule ducks (616+/-18 g; 8.79% of body mass (BW)) and Muscovy ducks (514+/-13 g; 7.05% BW) compared to Pekin ducks (353+/-21 g; 5.89% BW, p<0.05). Pekin ducks showed a much marked extrahepatic fattening of abdominal and subcutaneous adipose tissues. The LPL activity was evaluated by comparing the evolution of the plasma TG concentrations after injections of saline (control animals) or injections of specific LPL-antibodies. Inhibition of LPL activity performed by intravenous injections of LPL-antibodies showed a spectacular increase in the plasma TG concentrations in the three genotypes. That increase was considerably higher in Pekin ducks (98+/-10 g/L) compared to Muscovy ducks (35+/-2 g/L, p<0.01) and Mule ducks (30+/-4 g/L, p<0.01). Those data suggest that a high export of lipids synthesized in liver and a high LPL activity occur in overfed Pekin ducks, which can favour the extrahepatic fattening to the detriment of the liver steatosis, and conversely in overfed Muscovy and Mule ducks.

The presence of glucokinase (GK), a critical enzyme controlling glucose homeostasis, particularly liver glucose utilization in mammals, has long been a matter of debate in avian species because a number of investigators have failed to detect GK activity in the livers of chickens and several other avian species. In this study, we cloned a partial GK cDNA from mule duck livers and measured GK-like activity in the livers of mule ducks and broiler chickens under 2 nutritional states. Liver samples from 5-wk-old meal-fed male broiler chickens (Ross) were obtained from overnight-fasted chickens (BC) and 5 h after an oral saccharose load (6 mL/kg of BW of a 50% saccharose solution) given just before the meal (BS). Liver samples from 15-wk-old mule ducks were collected after an overnight fast (DC) and 12 h after the last overfeeding meal (DO). A partial cDNA ( approximately 600 bp) was obtained from duck livers. It presented 99% identity with chicken partial GK cDNA (gi 44888789) and 82% identity with human GK (gi 15967158). Chicken liver weights represented 1.8 and 3.3% of BW, respectively, for BC and BS (n = 8, P < 0.05). Glucokinase and low-Michaelis constant hexokinase (HK) activity levels were similar in BC (respectively, 0.88 and 1.00 mU/mg of protein). In response to the meal load, GK activity increased significantly (+57%), whereas HK decreased (-46%) in BS. Duck liver weights represented 1.4 and 7.6% of BW, respectively, for DC and DO (n = 8, P < 0.05). In DC livers, GK activity was significantly higher than HK activity (respectively, 1.76 and 0.63 mU/mg of protein). Both activities were significantly increased in DO (2 times, n = 8, P < 0.05). In conclusion, GK is present in ducks as well as chickens, and it is nutritionally regulated in avian species as well as in mammals. Further work will determine whether the higher liver GK activity and GK:HK ratio in DC compared with BC is related to age or BW or linked to the high lipogenic capacity of the duck liver.

The effects of age (from 1 day post-hatch to 98 days of age) and feeding levels (feed restriction followed by overfeeding v. ad libitum feeding) on lipid deposition in breast muscle (quantity and quality, localisation) of mule ducks were determined in relation to muscle energy metabolism (glycolytic and oxidative), plasma levels of lipids, glucose and insulin, and muscle capacity for lipid uptake (characterised by lipoprotein lipase (LPL) activity). Two periods were defined for age effects on intramuscular lipids in breast muscle: - 1 to 42 days of age when lipids (mainly phospholipids and cholesterol provided by egg yolk) stored in the adipocytes during embryonic life were transferred to the muscle fibres and used for growth and energy requirements, - 42 to 98 days of age when the muscle again stored lipids (mainly triglycerides provided by liver lipogenesis), first in fibres and then in adipocytes.Plasma glucose and insulin levels were not affected by age. Plasma levels of lipids and LPL activity in breast muscle were high at 1 and 14 days of age and then decreased, remaining stable until 98 days of age. Energy metabolism activity in the breast muscle (mainly glycolytic activity) increased with age.Feed restriction, corresponding to 79% of ad libitum intake, applied between 42 and 75 days of age only resulted in decreases in plasma insulin concentration and total lipid content of breast muscle, mainly affecting triglyceride and mono-unsaturated fatty acid (MUFA) levels. Overfeeding increased plasma levels of insulin and lipids while glycaemia remained stable. LPL activity and total lipid levels increased in breast muscle, mainly induced by deposition of triglycerides and MUFA occurring particularly during the 2nd week of this period. Glycolytic energy metabolism decreased.In response to age or feeding levels, muscle lipid levels and composition reflect plasma lipid levels and composition and high muscle lipid levels stimulate oxidative energy metabolism.

Poaceae species present a conserved distichous phyllotaxy (leaf position along the stem) and share common properties with respect to leaf initiation. The goal of this work was to determine if these common traits imply common genes. Therefore, homologues of the maize TERMINAL EAR1 gene in Poaceae were studied. This gene encodes an RNA-binding motif (RRM) protein, that is suggested to regulate leaf initiation. Using degenerate primers, one unique tel (terminal ear1-like) gene from seven Poaceae members, covering almost all the phylogenetic tree of the family, was identified by PCR. These genes present a very high degree of similarity, a much conserved exon-intron structure, and the three RRMs and TEL characteristic motifs. The evolution of tel sequences in Poaceae strongly correlates with the known phylogenetic tree of this family. RT-PCR gene expression analyses show conserved tel expression in the shoot apex in all species, suggesting functional orthology between these genes. In addition, in situ hybridization experiments with specific antisense probes show tel transcript accumulation in all differentiating cells of the leaf, from the recruitment of leaf founder cells to leaf margins cells. Tel expression is not restricted to initiating leaves as it is also found in pro-vascular tissues, root meristems, and immature inflorescences. Therefore, these results suggest that TEL is not only associated with leaf initiation but more generally with cell differentiation in Poaceae.