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See detailOntogeny of Aromatase and Tyrosine Hydroxylase Activity and of Aromatase-Immunoreactive Cells in the Preoptic Area of Male and Female Japanese Quail
Balthazart, Jacques ULg; Tlemcani, O.; Harada, N. et al

in Journal of Neuroendocrinology (2000), 12(9), 853-66

The aromatization of testosterone into oestrogens plays a key role in the control of many behavioural and physiological aspects of reproduction. In the quail preoptic area (POA), aromatase activity and ... [more ▼]

The aromatization of testosterone into oestrogens plays a key role in the control of many behavioural and physiological aspects of reproduction. In the quail preoptic area (POA), aromatase activity and the number of aromatase-immunoreactive (ARO-ir) cells are sexually differentiated (males > females). This sex difference is implicated in the control of the sexually dimorphic behavioural response of quail to testosterone. We analysed the ontogenetic development of this sex difference by measuring aromatase activity and counting ARO-ir cells in the POA of males and females from day 1 post hatch to sexual maturity. We investigated in parallel another enzyme: tyrosine hydroxylase, the rate limiting step in catecholamine synthesis. Between hatching and 4 weeks of age, aromatase activity levels were low and equal in males and females. Aromatase activity then markedly increased in both sexes when subjects initiated their sexual maturation but this increase was more pronounced in males so that a marked difference in aromatase activity was present in 6 and 8 week-old subjects. Tyrosine hydroxylase activity progressively increased with age starting immediately after hatching and there was no abrupt modification in the slope of this increase when birds became sexually mature. No sex difference was detected in the activity of this enzyme. The number of ARO-ir cells in the POA progressively increased with age starting at hatching. No sex difference in ARO-ir cell numbers could be detected before subjects reached full sexual maturity. The analysis of the three-dimensional organization of ARO-ir cells in the POA revealed that, with increasing ages, ARO-ir cells acquire a progressively more lateral position: they are largely periventricular in young birds but they are found at higher density in the lateral part of the medial preoptic nucleus in adults. These data indicate that aromatase activity differentiates sexually when birds reach sexual maturity presumably under the activating effects of the increased testosterone levels in males. The number of ARO-ir cells, however, begins to increase in a non sexually differentiated manner before the rise in plasma testosterone in parallel with the increased tyrosine hydroxylase activity. Whether this temporal coincidence results from a general ontogenetic pattern or from more direct causal links remains to be established. [less ▲]

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See detailOntogeny of GABA-ergic and dopaminergic mediation of gnawing behavior in the mouse
Tirelli, Ezio ULg

in Psychopharmacology (1987), 92(1), 89-95

Examined the ontogenetic course of dopaminergically mediated gnawing and the potentiation of this behavior by muscimol (a gamma-aminobutyric acid receptor agonist) in developing and young adult mice using ... [more ▼]

Examined the ontogenetic course of dopaminergically mediated gnawing and the potentiation of this behavior by muscimol (a gamma-aminobutyric acid receptor agonist) in developing and young adult mice using a time-sampling or a corrugated paper procedure. In Exp I, the older group (14-53 days), displayed a dose-dependent gnawing behavior after intraperitoneal injections of methylphenidate ([MTPD], 20, 30, 50 mg/kg). In 5-, 8-, 11-, and 14-day-old pups, MTPD (10, 20, 50 mg/kg) evoked stereotyped gnawing. Muscimol pretreatment (0.025-2.3 mg/kg) induced a clear-cut potentiation of gnawing elicited by MTPD (10 or 20 mg/kg) as early as 8 days of age. It is argued that the effectiveness of MTPD in inducing gnawing-licking among 5-day-old pups confirms the early maturation of central dopamine receptors reported in the literature. ((c) 1997 APA/PsycINFO, all rights reserved) [less ▲]

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See detailOntogeny of radial and other astroglial cells in murine cerebral cortex
Misson, Jean-Paul ULg; Takahashi, Takao; Caviness, V. S.

in Glia (1991), 4

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See detailontogeny of radial and other astroglial cells in murine cerebral cortex
Misson, Jean-Paul ULg; takahashi, takao; caviness, verne S

in Glia (1991), 4

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See detailOntogeny of sex differences in steroid-sensitive regions in the quail brain (Coturnix Japonica)
Mouriec, Karen ULg; Bardet, Sylvia; Balthazart, Jacques ULg

Poster (2010, May)

Sex differences affecting the expression of sexual behavior are observed in many species. In quail, expression of the male-typical copulatory pattern is androgen-dependent. This behavior disappears within ... [more ▼]

Sex differences affecting the expression of sexual behavior are observed in many species. In quail, expression of the male-typical copulatory pattern is androgen-dependent. This behavior disappears within a week after castration and is restored after a few days of treatment with exogenous testosterone. In contrast, ovariectomized females treated with testosterone never show the sequence of male-typical copulatory behavior. This sex difference in responsiveness to testosterone results from organizational effects of embryonic estrogens secreted by the female ovary. The behavioral phenotype can be completely reversed by treatment, before embryonic day 12, of male embryos with estrogens or of female embryos with an aromatase inhibitor. In the quail brain, the medial preoptic nucleus (POM) is a necessary and sufficient site for the activation by testosterone of sexual behavior. Aromatase, the enzyme converting testosterone into estradiol, is densely expressed in POM and its activity is sexually differentiated (males>females) even when birds are treated with a same dose of testosterone. Aromatase and other neuroendocrine systems are thus, like sexual behavior, differentially activated by testosterone in adult quail but the cellular basis of these sexually differentiated features presumably organized in early life by steroid action have not been identified. To analyze the ontogeny of steroid sensitive regions that control behavioral sex differences in the quail brain, we injected 5-bromo-2-deoxyuridine (BrdU) in eggs at different stages of the embryonic (E) development (E8, E10, E12, E14 and E16) and sacrificed the animals at postnatal (PN) day 56. Large numbers of BrdU-positive cells were observed throughout the POM of males and females injected on E8-E10 but most cells were post-mitotic in both sexes on E14-E16. E12 injections resulted in a larger number of BrdU cells in females than in males. This differential number of BrdU-positive cells seen at PN56 in birds injected on E12 could result from a) a difference in the age at which cells become post-mitotic (males before females or alternatively females before males, so that male cells labeled by BrdU on E12 dilute their label in subsequent divisions) or b) a differential apoptosis between E13 and PN56. However, no sex differences in the number of BrdU positive cells was observed in embryos injected with BrdU on E12 and killed on E13. Furthermore, BrdU injections on E14 labeled very few cells at PN 56 suggesting that the POM is essentially post-mitotic at that age. The sex difference observed in birds injected at E12 should result from a differential apoptosis after E13. Double-label immunohistochemistry for BrdU and the neuronal marker Hu (C/D) indicated that all BrdU-positive cells born between E8 and E16 are not neurons (no double label) suggesting that these are glial cells. This sex difference in (glial?) proliferation around the end of the critical period of sexual differentiation may play a key role in the differentiation of brain and behavior. The specific phenotype of these cells and the mechanisms mediating their differential development are currently under investigation. [less ▲]

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See detailOntogeny of sound production and sonic muscle morphology in Pygocentrus nattereri
Millot, Sandie; Parmentier, Eric ULg

Conference (2012)

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See detailOntogeny of swimming movement in bronze corydoras (Corydoras aeneus)
Mauguit, Quentin; Olivier, Damien ULg; Vandewalle, Nicolas ULg et al

in Canadian Journal of Zoology (2010), 88(4), 378-389

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See detailOntogeny of swimming movements in the catfish Clarias gariepinus
Mauguit, Quentin ULg; Gennotte, Vincent ULg; Becco, Christophe ULg et al

in Open Fish Science Journal (2010), 3

The swimming movements of C. gariepinus larvae were recorded with a high-speed camera (400, 500 and 800 fps) from 0 to 336 hours post-hatching. Movements of adult fish were also recorded to provide ... [more ▼]

The swimming movements of C. gariepinus larvae were recorded with a high-speed camera (400, 500 and 800 fps) from 0 to 336 hours post-hatching. Movements of adult fish were also recorded to provide information on the last developmental stage. Seven landmarks positioned on the fish midline were used during tail beating to determine various parameters during ontogeny and, on the basis of these parameters, to describe the first appearance of swimming movements and their development and efficiency during growth. Larvae were unable to swim at hatching (4 mm total length). Swimming movements were established at 48 hours posthatching when the fish measured between 7 and 8 mm total length and the yolk sac was more than 95% absorbed. At this stage, lateral excursion of the head appeared strongly reduced (from 13% to 6% of the total length). The efficiency of swimming movements increased throughout ontogeny, as did the homogeneity of the speed of the propulsive wave. Spontaneous swimming speed of 1 to 10 TLs-1 were observed in early stage (8-12 hPH). The various speed induced significant variations in parameters such as the amplitude of lateral head movements, swimming efficiency, and body rigidity. No major change was observed at the theoretical flow-regime transition. [less ▲]

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See detailOntogeny of T-Cell Surface Molecules and Receptors in the Thymus
Defresne, Marie-Paule ULg; Humblet, Chantal ULg; Deman, J. et al

in Progress in Histochemistry and Cytochemistry (1992), 26(1-4), 194-200

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See detailOntogeny of the radial glial fiber system of the developing murine cerebrum
Caviness, Verne S; Misson, Jean-Paul ULg; Takahashi, Takao et al

in Finlay, B. L.; Innocenti, G. (Eds.) The neocortex: Ontogeny and Phylogeny (1989)

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See detailOntogeny of the stimulant and sedative effects of ethanol in male and female Swiss mice: gradual changes from weaning to adulthood
Quoilin, Caroline ULg; Didone, Vincent ULg; Tirelli, Ezio ULg et al

in Psychopharmacology (2010), 212(4), 501-512

Rationale: The adolescent period is characterized by a specific sensitivity to the effects of alcohol, which is believed to contribute to the enhanced risks of alcohol dependence when drinking is ... [more ▼]

Rationale: The adolescent period is characterized by a specific sensitivity to the effects of alcohol, which is believed to contribute to the enhanced risks of alcohol dependence when drinking is initiated early during adolescence. In adolescent rodents, while the reduced sensitivity to the sedative effects of ethanol has been well characterized, its stimulant effects have not yet been extensively studied. Objectives: The present study characterized the development of the stimulant and sedative effects of acute ethanol in male and female Swiss mice from weaning to early adulthood and tested whether both effects are interrelated. Methods: In a first experiment, mice aged 21, 28, 35, 42 and 60 days were injected with various ethanol doses and tested for ethanol-induced locomotor activity. In an independent experiment, mice of the same groups of age were injected with 4 g/kg ethanol and ethanol-induced sedation was quantified with the loss of righting reflex procedure. Results: In male and female mice, the stimulant effects of ethanol gradually decreased, whereas its sedative effects increased with age. When the sedation was statistically controlled using a covariance analysis, the differences between adult and juvenile mice in the locomotor stimulation were significantly reduced. Conclusions: From weaning to early adulthood, the acute stimulant and sedative effects of ethanol show gradual changes that are similar in male and female mice. Although the initial tolerance to the sedative effects of ethanol contribute to the changes in ethanol-induced locomotor activity, young mice also show a higher sensitivity to the stimulant effects of ethanol. [less ▲]

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See detailL'ontologia materiale di Franz Brentano
Boccaccini, Federico ULg

Master's dissertation (2005)

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See detailOntología y fenomenología en el pensamiento de Saussure
Badir, Sémir ULg

in Topicos del Seminario (2002), 8

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See detailL'ontologie critique de Heinrich Rickert
Dewalque, Arnaud ULg

in Philosophie (2005), 87

Cet article vise à mettre en évidence les outils conceptuels fournis par le néokantien Heinrich Rickert en vue de fonder l'ontologie dans une certaine analyse logique de la proposition - analyse qui est ... [more ▼]

Cet article vise à mettre en évidence les outils conceptuels fournis par le néokantien Heinrich Rickert en vue de fonder l'ontologie dans une certaine analyse logique de la proposition - analyse qui est développée dans son traité intitulé "Die Logik des Prädikats und das Problem der Ontologie" (1930). [less ▲]

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See detailOntologie et cosmologie chez Heidegger
Dewalque, Arnaud ULg

Scientific conference (2002, November 02)

A partir de certains cours de Heidegger publiés dans la "Gesamtausgabe", j'interroge le rapport qu'il y a, dans l'oeuvre heideggérienne, entre l'enquête ontologique et le concept de "monde". Je suggère qu ... [more ▼]

A partir de certains cours de Heidegger publiés dans la "Gesamtausgabe", j'interroge le rapport qu'il y a, dans l'oeuvre heideggérienne, entre l'enquête ontologique et le concept de "monde". Je suggère qu'ontologie et cosmologie forment deux aspects inséparables de son oeuvre dite de maturité. [less ▲]

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See detailOntologie et phénoménologie dans la pensée de Saussure
Badir, Sémir ULg

in Bouquet, Simon (Ed.) Saussure (2003)

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See detailL’«ontologie fondamentale» est-elle une ontologie ou une sémantique ? Note sur la lecture néokantienne de Heidegger
Dewalque, Arnaud ULg

in Daimon : Revista de Filosofia (2007), 40

My aim is to clarify Heidegger's foundational program called "Fundamentalontologie". I show that the critical interpretation given by the neo-Kantian philosopher Rudolf Zocher (a heir of Heinrich Rickert ... [more ▼]

My aim is to clarify Heidegger's foundational program called "Fundamentalontologie". I show that the critical interpretation given by the neo-Kantian philosopher Rudolf Zocher (a heir of Heinrich Rickert) has the merit to emphasize some ambiguities of thos program. Three theses are under examination: 1. the concept of "Fundamentalontologie" is equivocal; 2. the distinction between "grounding theory" and "grounded theory" helps to overcome this equivocity; 3. the "Fundamentalontologie" mainly is a theory of meaning or a semantics. [less ▲]

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See detailL’ontologie politique de Sein und Zeit et le destin de la technique
Zincq, Aurélien ULg

Conference (2013, April 22)

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See detailOntologies for an Improved Communication in Urban Development Projects
Teller, Jacques ULg

in Teller, Jacques; Lee, John; Roussey, Catherine (Eds.) Ontologies for an Improved Communication in Urban Development Projects (2007)

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