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See detailLeptin Effects on Pulsatile Gonadotropin Releasing Hormone Secretion from the Adult Rat Hypothalamus and Interaction with Cocaine and Amphetamine Regulated Transcript Peptide and Neuropeptide Y
Parent, Anne-Simone ULg; Lebrethon, M. C.; Gerard, Arlette ULg et al

in Regulatory Peptides (2000), 92(1-3), 17-24

Leptin may act as a negative feedback signal to the hypothalamic control of appetite through suppression of neuropeptide Y (NPY) secretion and stimulation of cocaine and amphetamine regulated transcript ... [more ▼]

Leptin may act as a negative feedback signal to the hypothalamic control of appetite through suppression of neuropeptide Y (NPY) secretion and stimulation of cocaine and amphetamine regulated transcript (CART). We aimed at studying the effects of leptin, CART and NPY on the hypothalamic control of the pituitary-gonadal system. Pulsatile gonadotropin-releasing hormone (GnRH) secretion was studied in vitro using retrochiasmatic hypothalamic explants from adult rats. In the female, GnRH pulse amplitude was significantly increased by leptin (10(-7) M) and CART (10(-6) M) irrespective of the estrus cycle phase while no such effects were seen in the male. The GnRH interpulse interval was not affected in both sexes. Passive immunoneutralization against CART caused a reduction in GnRH pulse amplitude in the female. A slight but significant increase in GnRH pulse amplitude was caused by NPY (10(-7) M) in the female. However, GnRH pulse amplitude was not affected by a Y5-receptor antagonist (10(-6) M) while the interpulse interval was significantly increased as shown previously in the male. The increase in GnRH pulse amplitude caused by leptin was totally prevented by coincubation with an anti-CART antiserum whereas it was not affected by coincubation with the NPY Y5-receptor antagonist (10(-7) M). In conclusion, leptin and NPY show separate permissive effects on GnRH secretion in the adult rat hypothalamus. In both sexes, NPY is prominently involved in the control of the frequency of pulsatile GnRH secretion through the Y5 receptor subtype. Leptin causes a female-specific facilitatory effect on GnRH pulse amplitude which is mediated by CART and which occurs irrespective of the estrus cycle phase. [less ▲]

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See detailLeptin Reverts Pro-Apoptotic and Antiproliferative Effects of α-Linolenic Acids in BCR-ABL Positive Leukemic Cells: Involvement of PI3K Pathway
Beaulieu, Aurore ULg; Poncin, Géraldine ULg; Belaid-Choucair, Zakia et al

in PLoS ONE (2011), 6(10), 25651

It is suspected that bone marrow (BM) microenvironmental factors may influence the evolution of chronic myeloid leukaemia (CML). In this study, we postulated that adipocytes and lipids could be involved ... [more ▼]

It is suspected that bone marrow (BM) microenvironmental factors may influence the evolution of chronic myeloid leukaemia (CML). In this study, we postulated that adipocytes and lipids could be involved in the progression of CML. To test this hypothesis, adipocytes were co-cultured with two BCR-ABL positive cell lines (PCMDS and K562). T cell (Jurkat) and stroma cell (HS-5) lines were used as controls. In the second set of experiments, leukemic cell lines were treated with stearic, oleic, linoleic or α-linolenic acids in presence or absence of leptin. Survival, proliferation, leptin production, OB-R isoforms (OB-Ra and OB-Rb), phosphoinositide 3-kinase (PI3k) and BCL-2 expression have been tested after 24h, 48h and 72h of treatment. Our results showed that adipocytes induced a decrease of CML proliferation and an increase in lipid accumulation in leukemic cells. In addition, CML cell lines induced adipocytes cell death. Chromatography analysis showed that BM microenvironment cells were full of saturated (SFA) and monounsaturated (MUFA) fatty acids, fatty acids that protect tumor cells against external agents. Stearic acid increased Bcl-2 expression in PCMDS, whereas oleic and linoleic acids had no effects. In contrast, α-linolenic acid decreased the proliferation and the survival of CML cell lines as well as BCL-2 and OB-R expression. The effect of α-linolenic acids seemed to be due to PI3K pathway and Bcl-2 inhibition. Leptin production was detected in the co-culture medium. In the presence of leptin, the effect of α-linolenic acid on proliferation, survival, OB-R and BCl-2 expression was reduced.</p> [less ▲]

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See detailLa leptine et les hormones métaboliques chez trois races de bovins viandeux
Pirotte, Cécile ULg; Bister, J. L.; Cabaraux, Jean-François ULg et al

in 10èmes Rencontres autour des Recherches sur les Ruminants (2003)

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See detailLeptogenesis in flavor models with type I and II seesaws
Aristizabal Sierra, Diego ULg; Bazzocchi, Federica; de Medeiros Varzielas, Ivo

in Nuclear Physics B (2012), 858

In type I seesaw models with flavor symmetries accounting for the lepton mixing angles the CP asymmetry in right-handed neutrino decays vanishes in the limit in which the mixing pattern is exact. We study ... [more ▼]

In type I seesaw models with flavor symmetries accounting for the lepton mixing angles the CP asymmetry in right-handed neutrino decays vanishes in the limit in which the mixing pattern is exact. We study the implications that additional degrees of freedom from type II seesaw may have for leptogenesis in such a limit. We classify in a model independent way the possible realizations of type I and II seesaw schemes, differentiating between classes in which leptogenesis is viable or not. We point out that even with the interplay of type I and II seesaws there are generic classes of minimal models in which the CP asymmetry vanishes. Finally we analyze the generation of the lepton asymmetry by solving the corresponding kinetic equations in the general case of a mild hierarchy between the light right-handed neutrino and the scalar triplet masses. We identify the possible scenarios in which leptogenesis can take place. [less ▲]

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See detailLeptogenesis in the presence of exact flavor symmetries
Aristizabal Sierra, Diego ULg; Bazzocchi, Federica

in Journal of High Energy Physics [=JHEP] (2012)

In models with flavor symmetries in the leptonic sector leptogenesis can take place in a very different way compared to the standard leptogenesis scenario. We study the generation of a B−L asymmetry in ... [more ▼]

In models with flavor symmetries in the leptonic sector leptogenesis can take place in a very different way compared to the standard leptogenesis scenario. We study the generation of a B−L asymmetry in these kind of models in the flavor symmetric phase pointing out that successful leptogenesis requires (i) the right-handed neutrinos to lie in different irreducible representations of the flavor group; (ii) the flavons to be lighter at least that one of the right-handed neutrino representations. When these conditions are satisfied leptogenesis proceeds due to new contributions to the CP violating asymmetry and — depending on the specific model — in several stages. We demonstrate the validity of these arguments by studying in detail the generation of the B − L asymmetry in a scenario of a concrete A 4 flavor model realization. [less ▲]

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See detailLepton Flavor Equilibration and Leptogenesis
Aristizabal Sierra, Diego ULg; Losada, Marta; Enrico, Nardi

in Journal of Cosmology and Astroparticle Physics [= JCAP] (2009), 0912

We study the role played in leptogenesis by the equilibration of lepton flavors, as could be induced in supersymmetric models by off diagonal soft breaking masses for the scalar lepton doublets mαβ, or ... [more ▼]

We study the role played in leptogenesis by the equilibration of lepton flavors, as could be induced in supersymmetric models by off diagonal soft breaking masses for the scalar lepton doublets mαβ, or more generically by new sources of lepton flavor violation. We show that if mαβ>1GeV and leptogenesis occurs below ~100TeV, dynamical flavor effects are irrelevant and leptogenesis is correctly described by a one-flavor Boltzmann equation. We also discuss spectator effects in low scale leptogenesis by taking into account various chemical equilibrium conditions enforced by the reactions that are in thermal equilibrium. We write down the Boltzmann equation for low scale supersymmetric leptogenesis that includes flavor and spectator effects in the presence of lepton flavor equilibration, and we show how it reduces to a particularly simple form. [less ▲]

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See detailLepton flavor violation and seesaw symmetries
Aristizabal Sierra, Diego ULg

in Hyperfine Interactions (2013, February), 214

When the standard model is extended with right-handed neutrinos the symmetries of the resulting Lagrangian are enlarged with a new global U(1)R Abelian factor. In the context of minimal seesaw models we ... [more ▼]

When the standard model is extended with right-handed neutrinos the symmetries of the resulting Lagrangian are enlarged with a new global U(1)R Abelian factor. In the context of minimal seesaw models we analyze the implications of a slightly broken U(1)R symmetry on charged lepton flavor violating decays. We find, depending on the R-charge assignments, models where charged lepton flavor violating rates can be within measurable ranges. In particular, we show that in the resulting models due to the structure of the light neutrino mass matrix muon flavor violating decays are entirely determined by neutrino data (up to a normalization factor) and can be sizable in a wide right-handed neutrino mass range. [less ▲]

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See detailLepton flavor violation in SUSY left-right symmetric theories
Vicente, Avelino ULg

in Journal of Physics: Conference Series (2010), 259

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See detailLepton Flavor Violation in the Scotogenic Model
Toma, Takashi; Vicente, Avelino ULg

E-print/Working paper (2013)

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See detailLeptonic Charged Higgs Decays in the Zee Model
Aristizabal Sierra, Diego ULg; Restrepo, Diego

in Journal of High Energy Physics [=JHEP] (2006), 0608

We consider the version of the Zee model where both Higgs doublets couple to leptons. Within this framework we study charged Higgs decays. We focus on a model with minimal number of parameters consistent ... [more ▼]

We consider the version of the Zee model where both Higgs doublets couple to leptons. Within this framework we study charged Higgs decays. We focus on a model with minimal number of parameters consistent with experimental neutrino data. Using constraints from neutrino physics we (i) discuss the reconstruction of the parameter space of the model using the leptonic decay patterns of both of the two charged Higgses, h(1,2)→ℓj+νi, and the decay of the heavier charged Higgs, h2→h1+h0; (ii) show that the decay rate Γ(h1→μ+νi) in general is enhanced in comparision to the standard two Higgs doublet model while in some regions of parameter space Γ(h1→μ+νi) even dominates over Γ(h1→τ+νi). [less ▲]

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See detailLeptoquarks: Neutrino masses and accelerator phenomenology
Aristizabal Sierra, Diego ULg; Hirsch, M.; S.G., Kovalenko

in Physical Review. D : Particles and Fields (2008), 77

Leptoquark-Higgs interactions induce mixing between leptoquark states with different chiralities once the electro-weak symmetry is broken. In such LQ models Majorana neutrino masses are generated at 1 ... [more ▼]

Leptoquark-Higgs interactions induce mixing between leptoquark states with different chiralities once the electro-weak symmetry is broken. In such LQ models Majorana neutrino masses are generated at 1-loop order. Here we calculate the neutrino mass matrix and explore the constraints on the parameter space enforced by the assumption that LQ-loops explain current neutrino oscillation data. LQs will be produced at the LHC, if their masses are at or below the TeV scale. Since the fermionic decays of LQs are governed by the same Yukawa couplings, which are responsible for the non-trivial neutrino mass matrix, several decay branching ratios of LQ states can be predicted from measured neutrino data. Especially interesting is that large lepton flavour violating rates in muon and τ final states are expected. In addition, the model predicts that, if kinematically possible, heavier LQs decay into lighter ones plus either a standard model Higgs boson or a Z0/W± gauge boson. Thus, experiments at the LHC might be able to exclude the LQ mechanism as explanation of neutrino data. [less ▲]

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See detailLeptospira spp. prevalence in small mammal populations in Cotonou, Benin
Houemenou, Gualbert ULg; Ahmed, A.; Libois, Roland ULg et al

in ISRN Epidemiology (2013)

The aim of this study was to assess the Leptospira prevalence in small animals in Cotonou, the capital of Benin. Rodents and shrews were captured in urban and periurban settings and determined as species ... [more ▼]

The aim of this study was to assess the Leptospira prevalence in small animals in Cotonou, the capital of Benin. Rodents and shrews were captured in urban and periurban settings and determined as species of the genera Rattus, Mastomys, and Crocidura. Kidney specimens of 90 animals were examined using a real-time PCR assay specific for leptospires that belong to pathogenic species. Leptospiral DNA was amplified from kidney tissues ranging from 13.3% (8/60) in Rattus rattus to 100.0% (1/1) in Crocidura spp. with an average of 18.9% (17/90) of the animals caught at 15 locations. Clade-specific Taqman PCR on 10 samples placed six of these within clade 1 comprising the species L. kirschneri, L. interrogans, L. meyeri, and L. noguchii and four within clade 2 consisting of species L. weilii, L. alexanderi, L. borgpetersenii, and L. santarosai. Phylogenetic analysis of partial sequences of the amplicons of seven samples of these 10 samples revealed that four of the clade 1 samples could equally be assigned to L. interrogans and L. kirschneri and three samples fromclade 2 belonged to L. borgpetersenii. Results presented in the paper indicate that small mammals present a major public health risk for acquiring leptospirosis in Cotonou, Benin and will contribute to a raised awareness amongst health care workers and decision makers and hence promote appropriate clinical management of cases. [less ▲]

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See detailLernen lebender Fremdsprachen an den Schulen der europaïschen Union
Blondin, Christiane ULg

Book published by Amt für amtliche Veröffentlichungen der Europaïschen Gemeinschaften (1997)

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See detailLernout & Hauspie, Neuroplanet, SABENA ... ou quand les rêves indomptés s’écrasent contre les murs de la réalité
Van Caillie, Didier ULg

Article for general public (2002)

This chronicle analyses the reasons for some important recent firm failures in Belgium and insists on the crucial role played by growth management in the evolution of the firm

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See detailLeroi-Gourhan, l'art, la pensée et la main
de Villers Grand Champs, Bénédicte ULg

Conference given outside the academic context (2013)

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See detailLe lérot: Eliomys quercinus
Libois, Roland ULg

Learning material (1994)

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See detailLe lérot: trois études en une enquête
Libois, Roland ULg

Learning material (2003)

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