References of "Balthazart, Jacques"
     in
Bookmark and Share    
Peer Reviewed
See detailA two-step model for sexual differentiation.
Balthazart, Jacques ULg; Schumacher, M.

in Annals of the New York Academy of Sciences (1986), 474

Detailed reference viewed: 8 (0 ULg)
Full Text
Peer Reviewed
See detailA sexually dimorphic nucleus in the quail preoptic area.
Viglietti-Panzica, C.; Panzica, G. C.; Fiori, M. G. et al

in Neuroscience Letters (1986), 64(2), 129-34

The cytoarchitectural analysis of the preoptic-anterior hypothalamic region of the Japanese quail reveals a sexual dimorphism in the total volume of the medial preoptic nucleus (significantly larger in ... [more ▼]

The cytoarchitectural analysis of the preoptic-anterior hypothalamic region of the Japanese quail reveals a sexual dimorphism in the total volume of the medial preoptic nucleus (significantly larger in males than in females). Different nuclei of the region (dorsal preopticus, suprachiasmaticus) do not show any statistically significant difference. The sex-related difference is more consistent comparing the distribution of dark volume. This last is due to a larger number of cells containing high amount of Nissl's substance in male than in female. Present findings represent the first example of sexual dimorphism in the avian hypothalamus. [less ▲]

Detailed reference viewed: 13 (0 ULg)
Full Text
Peer Reviewed
See detailAltered endocrine and behavioral responses with reproductive aging in the male Japanese quail.
Ottinger, M. A.; Balthazart, Jacques ULg

in Hormones and Behavior (1986), 20(1), 83-94

Experiments were conducted to further characterize the age-related decline in reproductive capability previously described in the male Japanese quail. Behavioral testing of a large number of males in ... [more ▼]

Experiments were conducted to further characterize the age-related decline in reproductive capability previously described in the male Japanese quail. Behavioral testing of a large number of males in several age groups confirmed earlier results that showed a significant reduction in courtship and mating behavior by 80 weeks of age. Intact males, 78 weeks of age, that showed no reproductive behavior were given Silastic implants containing testosterone. This treatment restored behavior in 80% of the males. Gonadal regression induced by exposure to shortened photoperiod followed by transfer to a stimulatory photoperiod did not successfully restore the endocrine or behavioral components of reproduction. Males of two age groups, 42 and 208 weeks of age, were categorized as behaviorally active or inactive and then castrated. Eight weeks later they were given implants containing testosterone. Older males required longer exposure time to the exogenous steroid and in some cases, an additional implant to restore mating behavior as compared to younger males. The presence or absence of behavioral activity prior to castration did not affect the length of time required for restoration of behavior. Challenge with exogenous luteinizing hormone-releasing hormone revealed that there was reduced release of luteinizing hormone in aged, behaviorally inactive males as compared to young males. Results of these experiments in addition to previous data give evidence that age-related changes occur at the level of the hypothalamus and pituitary as well as at the level of the gonads. [less ▲]

Detailed reference viewed: 15 (0 ULg)
Full Text
Peer Reviewed
See detailDiurnal variations of sexual receptivity in the female Japanese quail (Coturnix coturnix japonica).
Delville, Y.; Sulon, J.; Balthazart, Jacques ULg

in Hormones and Behavior (1986), 20(1), 13-33

A series of experiments was performed to study the changes during the day of female receptivity in Japanese quail. In each experiment, the frequency of squatting and the percentage of male approaches ... [more ▼]

A series of experiments was performed to study the changes during the day of female receptivity in Japanese quail. In each experiment, the frequency of squatting and the percentage of male approaches which were followed by squatting increased at the end of the day, approximately 11 to 13 hr after lights on (in a photoperiod of 16L:8D). In some cases this increased receptivity was associated with a significant decrease of the long-avoid frequency. Analyses are presented which demonstrate that the increased receptivity at the end of the day is not directly caused by the oviposition and does not result directly from changes in the behavior of the male stimuli. This is strongly supported by the observation that the increase in receptivity was observed at the same time after lights on (but different clock times) in two groups of females which were raised in two different photoperiods shifted by 6 hr and tested with the same group of males raised in one of the two photoperiods. The increase in receptivity coincides with an increase in plasma estradiol and progesterone. Considering that this behavior is suppressed by ovariectomy, it is argued that the daily changes in receptivity could be controlled by the hormonal changes associated with the ovulatory cycle. [less ▲]

Detailed reference viewed: 13 (2 ULg)
Full Text
Peer Reviewed
See detailTestosterone-induced brain aromatase is sexually dimorphic.
Schumacher, M.; Balthazart, Jacques ULg

in Brain Research (1986), 370(2), 285-93

Female quail are less sensitive than males to the activating effects of testosterone (T) on behavior. Testosterone induces hypothalamic aromatase activity more efficiently in males than in females (higher ... [more ▼]

Female quail are less sensitive than males to the activating effects of testosterone (T) on behavior. Testosterone induces hypothalamic aromatase activity more efficiently in males than in females (higher Vmax but similar Km). As the conversion of T to estradiol (E2) is important for the activation of male sexual behavior, we propose that the incapacity of the female hypothalamus to produce behaviorally active E2 contributes to their insensitivity to T. The 5 alpha-reductase, which converts T into 5 alpha-dihydrotestosterone (5 alpha-DHT), is induced by T specifically in the anterior hypothalamus of both sexes. [less ▲]

Detailed reference viewed: 17 (0 ULg)
Peer Reviewed
See detailComparison of monoamine concentrations in the brains of adult male and female Japanese quail.
Ottinger, M. A.; Schumacher, M.; Clarke, R. N. et al

in Poultry Science (1986), 65(7), 1413-20

A fluorometric assay measuring brain tissue concentrations of norepinephrine, dopamine, and serotonin has been validated for Japanese quail. Accuracy, precision, specificity, and parallelism were ... [more ▼]

A fluorometric assay measuring brain tissue concentrations of norepinephrine, dopamine, and serotonin has been validated for Japanese quail. Accuracy, precision, specificity, and parallelism were determined. The sensitivity of the assays was 6 ng/tube, which allowed individual assay of 1 to 2 mg hypothalamic tissue. In Experiment 1, relatively large areas of brain from adult, reproductively active males and females were found to differ significantly in norepinephrine content in optic lobes and for dopamine in right telencephalon. A microdissection technique was used in Experiment 2 to sample small portions of hypothalamic tissue. Sex differences were observed for norepinephrine in the sections containing the lobus paraolfactorius and the preoptic, anterior, and medial hypothalamus. Differences in monoamine content were most apparent when smaller areas dissected by microdissection were analyzed. These results give evidence for sex differences in the monoamine content in specific areas of the brain. [less ▲]

Detailed reference viewed: 7 (0 ULg)
Full Text
Peer Reviewed
See detailEffects of metabolism inhibitors, antiestrogens and antiandrogens on the androgen and estrogen induced sexual behavior in Japanese quail.
Alexandre, Corine; Balthazart, Jacques ULg

in Physiology & Behavior (1986), 38(4), 581-91

The relative contribution of androgenic and estrogenic metabolites of testosterone to the activation of sexual behavior was studied in Japanese quail by using inhibitors of testosterone metabolism ... [more ▼]

The relative contribution of androgenic and estrogenic metabolites of testosterone to the activation of sexual behavior was studied in Japanese quail by using inhibitors of testosterone metabolism, antiestrogens and antiandrogens. These compounds were tested in castrated birds whose sexual behavior had been activated by silastic implants of testosterone (T) or daily injections of testosterone propionate (TP) or diethylstilboestrol (DES). The aromatase inhibitor ATD only depressed T-induced behavior when injected at high doses and the 5 alpha-reductase inhibitor, 4MA was inactive in this respect. The antiestrogens, tamoxifen (TAM) and nitromifene citrate (CI-628) strongly depressed sexual behavior but they also drastically reduced the crowing behavior which is typically androgen-dependent which throws some doubts on the specificity of their action. The antiandrogens, flutamide and cyproterone acetate (CA), only had limited inhibitory effects on the copulatory behavior but similarly decreased only marginally the crowing. As they strongly depressed the cloacal gland growth, it can be ascertained that they were injected in sufficient amounts and their lack of action on crowing questions the ability of these compounds to inhibit brain processes even when they are androgen-dependent. Taken together with the results of previous experiments which tested the behavioral effects of the testosterone metabolites, the present data confirm the implication of both androgenic and estrogenic metabolites of testosterone in the activation of behavior. Their interaction remains, however, poorly defined and its understanding will probably require the identification of the biochemical processes which in the brain mediate the behavior. [less ▲]

Detailed reference viewed: 7 (0 ULg)
Full Text
Peer Reviewed
See detailBrain testosterone metabolism during ontogeny in the zebra finch.
Balthazart, Jacques ULg; Schumacher, M.; Prove, E.

in Brain Research (1986), 378(2), 240-50

The testosterone metabolism in different parts of the brain and in the syrinx was studied by an in vitro radioenzyme assay in male and female zebra finch (Taeniopygia guttata castanotis) at various ages ... [more ▼]

The testosterone metabolism in different parts of the brain and in the syrinx was studied by an in vitro radioenzyme assay in male and female zebra finch (Taeniopygia guttata castanotis) at various ages between 1 day post-hatch and adulthood. The 5 beta-reductase appeared in all experiments as the main enzyme involved in testosterone metabolism. Two experiments allowed to determine the kinetic parameters of the 5 beta-reductase. It was shown that the Vmax of the 5 beta-reduction is much higher in very young animals than in adults but that the Km of the enzyme is smaller (higher affinity) in the latter than in the former. A major decrease of 5 beta-reductase activity is observed during the ontogeny of both males and females in all the tissue samples which were studied including the hypothalamus and brain regions containing nuclei of the song system. This high reductase activity which produces behaviorally inactive compounds is likely to play a protective role during the sexual differentiation of the birds and in this way prevent the masculinization in females of the song system by the relatively high levels of circulating androgens. [less ▲]

Detailed reference viewed: 19 (0 ULg)
Peer Reviewed
See detailHormonal correlates of gonadal regression and spontaneous recovery in Japanese quail exposed to short day-lengths.
Delville, Y.; Sulon, J.; Balthazart, Jacques ULg

in Archives Internationales de Physiologie et de Biochimie (1985), 93(2), 123-33

Adult male Japanese quail were transferred from long to short days. Plasma testosterone and dihydrotestosterone quickly decreased and this endocrine response was followed by a regression of the cloacal ... [more ▼]

Adult male Japanese quail were transferred from long to short days. Plasma testosterone and dihydrotestosterone quickly decreased and this endocrine response was followed by a regression of the cloacal gland, an androgen-target organ. After about a month, a spontaneous recovery of gonadal activity was observed in some but not all birds. It was not associated with obvious shifts in the circadian system. The physiological bases of this spontaneous recovery are discussed as well as the detailed relationships between plasma testosterone and cloacal gland size. [less ▲]

Detailed reference viewed: 13 (0 ULg)
Full Text
Peer Reviewed
See detailInteraction of androgens and estrogens in the control of sexual behavior in male Japanese quail.
Balthazart, Jacques ULg; Schumacher, M.; Malacarne, G.

in Physiology & Behavior (1985), 35(2), 157-66

A series of 4 experiments was performed to study the relative contribution of androgens and estrogens in the activation of sexual behavior in castrated male quail. The synthetic androgen methyltrienolone ... [more ▼]

A series of 4 experiments was performed to study the relative contribution of androgens and estrogens in the activation of sexual behavior in castrated male quail. The synthetic androgen methyltrienolone (R 1881) which is not metabolized in androgen target tissues activated sexual behavior in castrated birds and at the dose level of 0.5-1 mg/day/animal had the same potency as testosterone (T). However R 1881 was much more active than T in the induction of cloacal gland growth and activation of crowing, two typically androgen-dependent responses. This suggests that sexual behavior is not controlled by exactly the same mechanism as crowing or cloacal gland growth. In another experiment, estradiol (E2) alone activated sexual behavior but it is only at very high doses which had clear toxic effects that a significant behavioral activation could be observed. This questions the role of E2 as the physiological agent stimulating copulation in intact birds unless it is assumed that centrally administered E2 would be much more active compared to peripheral E2 which is exposed to a very intense peripheral catabolism. In the last two experiments, a clear synergism could be detected between 5 alpha-dihydrotestosterone (5 alpha-DHT) and E2 in the activation of sexual activity and doses of hormones could be defined which had almost no activity by themselves but significantly stimulated sexual behavior when given simultaneously. It was however impossible to define a hormonal treatment with T metabolites which restored behavior to its precastration level, a result very easily achieved with T treatments. Taken together, these data suggest that activation of sexual behavior in quail does not depend only on E2, nor 5 alpha-DHT nor even on their combined action. Considering that specific T receptors which probably do not bind 5 alpha-DHT are present in the brain, it would seem justified to reconsider the possible role played by T itself in the activation of behavior. [less ▲]

Detailed reference viewed: 17 (0 ULg)
Peer Reviewed
See detailThe effect of pinealectomy on plasma levels of gonadotrophins and growth hormone in the pigeon (Columba livia).
Rintamaki, H.; Hissa, R.; Balthazart, Jacques ULg et al

in Journal of Pineal Research (1984), 1(4), 381-9

Detailed reference viewed: 9 (0 ULg)
Peer Reviewed
See detailSexual dimorphism in the hypothalamic metabolism of testosterone in the Japanese Quail (Coturnix coturnix japonica).
Schumacher, M.; Balthazart, Jacques ULg

in Progress in Brain Research (1984), 61

Detailed reference viewed: 10 (0 ULg)
Full Text
Peer Reviewed
See detailChanges in testosterone metabolism by the brain and cloacal gland during sexual maturation in the Japanese quail (Coturnix coturnix japonica).
Balthazart, Jacques ULg; Schumacher, M.

in Journal of Endocrinology (1984), 100(1), 13-8

Testosterone metabolism in the brain and pituitary and cloacal glands of male and female Japanese quail was studied in vitro during sexual maturation (from 1 day to 5 weeks after hatching). The production ... [more ▼]

Testosterone metabolism in the brain and pituitary and cloacal glands of male and female Japanese quail was studied in vitro during sexual maturation (from 1 day to 5 weeks after hatching). The production of 5 alpha-dihydrotestosterone in the hyperstriatum and cloacal gland and that of androstenedione in the cloacal gland of males was highest at 1 day after hatching, which could be related to the peak of plasma androgens previously demonstrated in neonatal quail. 5 beta-Reductase activity was very high in the brain, but not the pituitary or cloacal glands of young chicks and decreased markedly, especially in the hypothalamus, during sexual maturation. As 5 beta-reduced metabolites of testosterone are inactive androgens, it is suggested that the decrease of 5 beta-reductase activity with age corresponds to a potentiation of the effects of testosterone at the level of the brain. [less ▲]

Detailed reference viewed: 7 (0 ULg)
Full Text
Peer Reviewed
See detailRelative potencies of testosterone and 5 alpha-dihydrotestosterone on crowing and cloacal gland growth in the Japanese quail (Coturnix coturnix japonica).
Balthazart, Jacques ULg; Schumacher, M.; Malacarne, G.

in Journal of Endocrinology (1984), 100(1), 19-23

It has been suggested that testosterone is less effective at inducing crowing behaviour in young birds than in adults because of the presence of higher levels of steroid 5 beta-reductase in the young ... [more ▼]

It has been suggested that testosterone is less effective at inducing crowing behaviour in young birds than in adults because of the presence of higher levels of steroid 5 beta-reductase in the young brain, which converts testosterone to inactive 5 beta-reduced metabolites. This hypothesis was tested indirectly by comparing the relative potencies of 5 alpha-dihydrotestosterone (5 alpha-DHT), which cannot be converted to 5 beta-metabolites, and testosterone at inducing crowing in young gonadectomized male and female quail. The promotion of cloacal gland growth by these treatments was also assessed since there are no age-related changes in 5 beta-reductase in this organ. Silicone elastomer implants (2 X 5, 5 and 10 mm) containing 5 alpha-DHT were more effective at stimulating crowing than similar implants of testosterone whilst there was little difference in their potency at inducing cloacal gland growth. These results are consistent with the hypothesis that brain steroid 5 beta-reductase regulates the behavioural activity of testosterone in the brain of young birds. [less ▲]

Detailed reference viewed: 4 (0 ULg)
Full Text
Peer Reviewed
See detailPartial characterization of testosterone-metabolizing enzymes in the quail brain.
Schumacher, M.; Contenti, E.; Balthazart, Jacques ULg

in Brain Research (1984), 305(1), 51-9

The properties of 5 beta-reductase, 5 alpha-reductase and aromatase, 3 testosterone metabolizing enzymes, were studied in the quail brain by an in vitro incubation technique. The results describe the ... [more ▼]

The properties of 5 beta-reductase, 5 alpha-reductase and aromatase, 3 testosterone metabolizing enzymes, were studied in the quail brain by an in vitro incubation technique. The results describe the changes in time of metabolite production and the effects of temperature, enzyme and cofactor concentrations. The apparent Km and Vmax were evaluated for the 3 enzymes. Aromatase and 5 alpha-reductase have a higher affinity but a lower capacity than 5 beta-reductase. The kinetics of the latter enzyme are complex and suggest the presence of two types of enzymes. These characteristics fit in well with the role probably played by the enzymes in vivo. [less ▲]

Detailed reference viewed: 6 (0 ULg)
Full Text
Peer Reviewed
See detailEffect of the presence of females on the pituitary-testicular activity in male Japanese quail (Coturnix coturnix japonica).
Delville, Y.; Sulon, J.; Hendrick, J. C. et al

in General and Comparative Endocrinology (1984), 55(2), 295-305

Five experiments were carried out to study the role of the presence of a female on the reproductive endocrinology of male Japanese quail. In the first three experiments, exposure of an adult male raised ... [more ▼]

Five experiments were carried out to study the role of the presence of a female on the reproductive endocrinology of male Japanese quail. In the first three experiments, exposure of an adult male raised in long days to a female for l0 min or l week failed to increase plasma testosterone and LH levels; in fact a significant transitory decrease in plasma testosterone was observed, associated with a preceding increase in plasma corticosterone. These changes are interpreted as a result of the stress caused by repeated bleeding or by the continuous presence of a female in a limited space. In the last two experiments, an increase in the maturation rate of immature males could be observed in birds maintained in the continuous presence of females by comparison with birds kept in isolation. The paired males had larger cloacal glands and testes and higher plasma levels of testosterone and LH than the isolated one. This effect of the female was observed in long days (l6L:8D) as well as in marginally stimulating short days (l2L:l2D). [less ▲]

Detailed reference viewed: 4 (0 ULg)
Full Text
Peer Reviewed
See detailAltered brain metabolism of testosterone is correlated with reproductive decline in aging quail.
Balthazart, Jacques ULg; Turek, R.; Ottinger, M. A.

in Hormones and Behavior (1984), 18(3), 330-45

In aging quail, an increasing proportion of males show no sexual behavior. A decrease in the mean size of the tests, cloacal gland, and sternotracheal muscles is also observed. In both sexually active and ... [more ▼]

In aging quail, an increasing proportion of males show no sexual behavior. A decrease in the mean size of the tests, cloacal gland, and sternotracheal muscles is also observed. In both sexually active and inactive males, plasma testosterone decreases with age but more so in inactive birds. The behavioral and morphological changes observed during aging are correlated with shifts in the intracellular testosterone metabolism resulting in a change in the ratio of active versus inactive metabolites. In the hypothalamus there is a steady decrease with age of 5 beta-reductase activity in all birds and an increase in 5 alpha-reductase activity only in the birds which remain sexually active. In the cloacal gland, the 5 beta-reductase activity markedly increases with age but more so in the birds which become sexually inactive. These data support the notion that the effects of testosterone are controlled by enzymatic shifts which could modulate the sensitivity to the hormone at the cellular level. [less ▲]

Detailed reference viewed: 7 (0 ULg)
Peer Reviewed
See detailOrganization and activation of behavior in quail: role of testosterone metabolism.
Balthazart, Jacques ULg; Schumacher, M.

in Journal of Experimental Zoology (The) (1984), 232(3), 595-604

In quail, the hypothalamus enzymatically transforms testosterone (T) into estradiol (E2), 5 alpha-dihydrotestosterone (5 alpha-DHT), and 5 beta-dihydrotestosterone (5 beta-DHT). During the embryonic life ... [more ▼]

In quail, the hypothalamus enzymatically transforms testosterone (T) into estradiol (E2), 5 alpha-dihydrotestosterone (5 alpha-DHT), and 5 beta-dihydrotestosterone (5 beta-DHT). During the embryonic life, the 5 beta-reductase activity is very high, which probably protects the brain of males from being behaviorally demasculinized by their endogenous T. 5 beta androstanes are inactive androgens. The decrease of 5 beta reductase with age during sexual maturation corresponds to a potentiation of the effects of T as shown by experiments that compared the effects of T and 5 alpha-DHT in adult and young quail. T metabolism is also involved in the activation of male behavior in the adult. T aromatization is probably essential for behavioral activation, but nonaromatizable androgens such as methyltrienolone, and to some extent 5 alpha-DHT, can also stimulate sexual behavior in castrates. These enzymatic activities show a clear neuroanatomical localization and are sexually dimorphic. Males produce more active metabolites (E2, 5 alpha-DHT) than females, which could explain the male's greater sensitivity to T treatments. It thus appears that T metabolism is involved in the differentiation and activation of behavior in quail. [less ▲]

Detailed reference viewed: 15 (1 ULg)
Full Text
Peer Reviewed
See detailThe postnatal demasculinization of sexual behavior in the Japanese quail (Coturnix coturnix japonica).
Schumacher, M.; Balthazart, Jacques ULg

in Hormones and Behavior (1984), 18(3), 298-312

Three experiments were performed to analyze the time course of demasculinization in the Japanese quail and to test the activating and organizing effects of estradiol (E2) in adult sexually active birds ... [more ▼]

Three experiments were performed to analyze the time course of demasculinization in the Japanese quail and to test the activating and organizing effects of estradiol (E2) in adult sexually active birds. In Experiment 1, males and females were castrated at the age of 1 day or 1, 2, 4, and 6 weeks and treated as adults with testosterone (T). The age of castration had no effect on behavior and morphology in males. Plasma gonadotrophins (LH and FSH) were, however, higher in males castrated at or before than in those castrated after 2 weeks of age. This suggests that postnatal testicular secretions have organizing effects on the pituitary activity. Females which were castrated before 1 week of age were less sensitive to the activating effects of T than males, but were not fully demasculinized. The demasculinization of different reproductive characteristics such as male sexual behavior, cloacal gland size, and weight of the syringeal muscles is achieved in females at different times posthatching. In Experiment 2, castration of male and female quail at the ages of 4 days or 4 weeks confirmed that postnatal ovarian secretions contribute to the full behavioral and morphological demasculinization of females. It is easier to elicit mounting in T-treated females when they are tested in their home cage instead of a test arena. This difference was not observed in males. During Experiment 3, it was impossible to demasculinize sexually active adult males or females by treatment with Silastic implants of E2. E2 did not maintain sexual behavior in ovariectomized females showing male sexual behavior when treated with T but maintained the behavior in males. [less ▲]

Detailed reference viewed: 20 (1 ULg)
Full Text
Peer Reviewed
See detailEstradiol contributes to the postnatal demasculinization of female Japanese quail (Coturnix coturnix japonica).
Balthazart, Jacques ULg; Schumacher, M.

in Hormones and Behavior (1984), 18(3), 287-97

Two experiments were performed to characterize the process of postnatal demasculinization in Japanese quail. In the first experiment, it was shown that estradiol (E2) can complete female demasculinization ... [more ▼]

Two experiments were performed to characterize the process of postnatal demasculinization in Japanese quail. In the first experiment, it was shown that estradiol (E2) can complete female demasculinization during the first 4 weeks of life. By contrast, E2 did not demasculinize sexual behavior and cloacal gland in neonatally castrated males. Neonatally gonadectomized females preferentially performed mount attempts when tested in their home cage by comparison to a test arena. In Experiment 2, E2 Silastic implants (40-mm) maintained full copulatory behavior in castrated males but not in females. This large dose of E2 did not demasculinize adult sexually active birds (males or females) even if treatment lasted for 1 month. It is concluded that E2 can demasculinize sexual behavior only in females and only if treatment is performed in very young birds. [less ▲]

Detailed reference viewed: 16 (1 ULg)