Hypothalamic and Thyroidal Regulation of Growth Hormone in Tilapia
; ; et al
in General and Comparative Endocrinology (1995), 97
A radioimmunoassay (RIA) for recombinant tilapia growth hormone (GH) was established and validated. The ability of various hypothalamic factors to regulate GH secretion in the tilapia hybrid (Oreochromis ... [more ▼]
A radioimmunoassay (RIA) for recombinant tilapia growth hormone (GH) was established and validated. The ability of various hypothalamic factors to regulate GH secretion in the tilapia hybrid (Oreochromis niloticus x Oreochromis aureus) was studied. Somatostatin1-14 (SRIF1-14; 10-100 micrograms/kg) was found to reduce circulating GH levels in a dose-dependent manner. SRIF1-14 (0.1-1000 nM) inhibited GH release from perifused pituitary fragments (ED50 0.83 nM). Human growth hormone-releasing hormone fragment 1-29 (hGHRH1-29; 100 micrograms/kg) doubled circulating GH levels and modestly stimulated GH secretion in vitro. Carp growth hormone-releasing hormone (cGHRH) stimulated GH secretion in vitro to a similar degree at the same dose (1 microM). Injection of salmon gonadotropin-releasing hormone (sGnRH) superactive analog (10-100 micrograms/kg) increased plasma GH levels sixfold. sGnRH also stimulated GH release in vitro (ED50 142.56 nM). Dopamine (0.1-10 microM) and the D1 DA receptor agonist SKF 38393 increased GH secretion from perifused pituitary fragments dose-relatedly. Thyrotropin-releasing hormone (TRH) had no effect on GH secretion from perifused pituitary fragments, but increased plasma GH levels, as did bovine thyroid stimulating hormone (bTSH). The increased plasma GH in the bTSH-treated fish coincided with a dramatic increase in T4; however, TRH increased GH without changing T4 levels. T3 increased the synthesis of GH by isolated pituitaries (incorporation of [3H]leucine). SRIF1-14 seems to be a most potent hypothalamic regulator of GH secretion in tilapia; sGnRH and DA both increased GH secretion, although sGnRH elicited considerably greater responses at lower doses. Two forms of GHRH increased GH levels, although the unavailability of the homologous peptide prevented an accurate evaluation of its importance in regulating GH secretion. The thyroid axis (TRH, TSH, and T3) stimulates both synthesis and release of GH, although TRH did not appear to have a direct effect on the level of the pituitary. [less ▲]Detailed reference viewed: 9 (0 ULg)
Absence of tiGh effect on adaptability to brackish water in Tilapia (Oreochromis niloticus)
; ; Rentier-Delrue, Françoise et al
in General and Comparative Endocrinology (1995)
The aim of this study was to investigate the possible role of growth hormone in the adaptation of tilapia (Oreochromis niloticus) to brackish water and to analyze its interactions with prolactin in this ... [more ▼]
The aim of this study was to investigate the possible role of growth hormone in the adaptation of tilapia (Oreochromis niloticus) to brackish water and to analyze its interactions with prolactin in this process. Plasma levels of growth hormone do not change upon transfer to brackish water. Treatment of intact tilapia in fresh water with growth hormone prior to transfer did not enable the fish to preadapt to brackish water: the duration of the hydromineral imbalance after transfer was the same in treated animals and controls. The major osmoregulatory role of prolactin in fresh water led us to test the hypothesis that prolactin might antagonize the effect of growth hormone on adaptation to brackish water. Growth-hormone-treated hypophysectomized animals, however, exhibited no increased osmoregulatory capacity as compared to hypophysectomized controls, confirming the absence of a growth-hormone-related osmoregulatory effect. When prolactin and growth hormone were coinjected, growth hormone also proved unable to oppose the Na+ retaining effect of prolactin, in both brackish and fresh water. Surprisingly, hypophysectomized animals adapt better to brackish water than do sham-operated animals. This result is discussed in light of the effects of prolactin and cortisol on osmoregulation in brackish water and we suggest that an important event which allows O. niloticus to adapt to hyperosmotic environment is the reduction of plasma PRL upon transfer to brackish water. [less ▲]Detailed reference viewed: 28 (6 ULg)
Immunocytochemical study of cell type distribution in the pituitary of Barbus barbus (Teleostei, Cyprindidae)
; ; et al
in General and Comparative Endocrinology (1991), 83(1), 35-47
Antisera to mammalian pituitary and placental hormones have been used to identify and localize the different cell types in the pituitary of the barbel (Barbus barbus, L.). The immunocytochemical labeling ... [more ▼]
Antisera to mammalian pituitary and placental hormones have been used to identify and localize the different cell types in the pituitary of the barbel (Barbus barbus, L.). The immunocytochemical labeling employed the immunoperoxidase technique or the immunogold silver staining procedure. Corticotrophic and prolactin cells, visualized using antisera to human adrenocorticotropic hormone and ovine prolactin (PRL), respectively, occur in the rostral pars distalis (RPD). Antisera against mammalian gonadotropins [ovine folliclestimulating hormone (FSH); bovine luteinizing hormone] or porcine growth hormone selectively cross-react with two different cell populations occupying the major part of the proximal pars distalis (PPD). Thyrotropic cells, stained by an antiserum to whole human thyroidstimulating hormone preabsorbed with porcine FSH, are scattered throughout the PPD and found amongst growth hormone and gonadotrophic cells. The majority of pars intermedia cells are stained with anti-melanophore stimulating hormone whereas the scattered PAS positive cells are revealed by both anti-ovine PRL and anti-bovine placental lactogen (or chorionic somatomammotropin). The latter antiserum also cross-reacts with the PRL cells of the RPD. Our results indicate that the distribution of the different cell types in Barbus barbus is similar to that described in other families of teleosts. This report is also the first demonstration of antigenic similarity between mammalian placental lactogen and fish prolactin. [less ▲]Detailed reference viewed: 39 (10 ULg)
Changes in Progesterone Metabolism in the Chicken Hypothalamus During Induced Egg Laying Stop and Molting
Balthazart, Jacques ; ; et al
in General and Comparative Endocrinology (1988), 72(2), 282-95
In the present study, we have established and validated a radioenzyme assay which permits us to quantify progesterone metabolism in the chicken brain. Progesterone metabolism was then studied in five ... [more ▼]
In the present study, we have established and validated a radioenzyme assay which permits us to quantify progesterone metabolism in the chicken brain. Progesterone metabolism was then studied in five brain areas obtained by microdissection from the telencephalon (part of the lobus paraolfactorius immediately rostral to the preoptic area), the preoptic area, and the hypothalamus. Three metabolites of progesterone were produced in large amounts in these brain regions and were quantified in this study: 5 beta-pregnane-3,20-dione (5 beta-DHP) as well as its metabolite 3 alpha-hydroxy-5 beta-pregnane-20-one (5 beta,3 alpha-ol) and 5 alpha-pregnane-3,20-dione (5 alpha-DHP). The unmetabolized progesterone was also recovered and quantified. The 5 beta-reduction of progesterone (production of 5 beta-DHP and 5 beta,3 alpha-ol) was very active but its 5 alpha-reduction (production of 5 alpha-DHP) was almost absent in the lobus paraolfactorius. An opposite pattern of metabolism was found in the preoptic area and the hypothalamus (higher 5 alpha- but lower 5 beta-reductase activity). The changes in progesterone metabolism in these brain areas were then studied in groups of hens submitted to induced egg laying stop and molting. A significant decrease in progesterone 5 alpha-reduction was found in the median hypothalamus of hens during the period of molt. Simultaneously, the experimental procedures induced significant decreases in the production of 5 beta-DHP by the lobus paraolfactorius, anterior, and medial hypothalamus but induced a significant increase in the production of this metabolite in the preoptic area. These changes are likely to be involved in the control of reproductive functions including sexual behavior and secretion of luteinizing hormone-releasing hormone, and a number of possible causal mechanisms are presented. These should now be tested experimentally especially in view of the very limited information which is now available on the biological effects of the metabolites of progesterone. [less ▲]Detailed reference viewed: 37 (2 ULg)
Effect of the injection solvent on steroid activity.
; Balthazart, Jacques
in General and Comparative Endocrinology (1987), 65(2), 199-202
The effects of testosterone, 5 alpha-dihydrotestosterone, and androstenedione on cloacal gland and sternotracheal muscle growth and on luteinizing hormone plasma levels were studied in Japanese quail. The ... [more ▼]
The effects of testosterone, 5 alpha-dihydrotestosterone, and androstenedione on cloacal gland and sternotracheal muscle growth and on luteinizing hormone plasma levels were studied in Japanese quail. The steroids were given to the animals in daily intramuscular injections and were dissolved either in propylene glycol or in ethanol:saline (1:1). The three steroids had significant effects on the responses which were measured, but the magnitude of this effect was clearly related to the type of vehicle in which the steroids were dissolved. Furthermore there was a significant interaction between the effects of solvents and of steroid; for example, testosterone was much less androgenic than 5 alpha-dihydrotestosterone when dissolved in propylene glycol, but both had similar effects when dissolved in ethanol:saline. The effects of the mode of administration of different steroids on a given physiological response should be taken into consideration. [less ▲]Detailed reference viewed: 10 (1 ULg)
Effect of the presence of females on the pituitary-testicular activity in male Japanese quail (Coturnix coturnix japonica).
; ; 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)
Annual variation in the concentrations of circulating hormones in capercaillie (Tetrao urogallus).
; ; Balthazart, Jacques et al
in General and Comparative Endocrinology (1983), 51(2), 183-90
Seasonal variation in the levels of immunoreactive lutropin (LH), follitropin (FSH), prolactin (PRL), corticosterone (B), thyroxine (T4), and triiodothyronine (T3) was measured in the plasma of male and ... [more ▼]
Seasonal variation in the levels of immunoreactive lutropin (LH), follitropin (FSH), prolactin (PRL), corticosterone (B), thyroxine (T4), and triiodothyronine (T3) was measured in the plasma of male and female capercaillies (Tetrao urogallus, Galliformes) in captivity (latitude N 67 degrees). In male capercaillies there was an increase in the concentrations of LH and FSH beginning in March and reaching their maxima in May, which correlated with the nesting period. The concentration of plasma PRL increased from the end of April and reached its highest level simultaneously with the rapid fall of plasma LH and FSH concentrations. It remained elevated until August, Plasma T4 level was depressed after levels of plasma FSH and LH had reached their maxima and was correlated to simultaneous elevation of plasma PRL level. No dramatic seasonal changes in plasma T3 level were noted. In the female capercaillie no marked changes in plasma FSH and LH concentrations were observed. Although four of six females laid eggs only one of them managed to terminate its nesting successfully; five eggs hatched. Changes in prolactin concentration in females parallel those in males. No marked variations were observed in plasma corticosterone concentrations. On the basis of these results it seems probable that captive female capercaillie show depressed gonadotrophin secretion, resulting in unsuccessful nesting. On the other hand it has to be emphasized that gonadotrophin assays may not be sensitive enough, especially in the female, to measure LH and FSH in the volumes of plasma put in the assays. [less ▲]Detailed reference viewed: 10 (0 ULg)
Sexual differences in the Japanese quail: behavior, morphology, and intracellular metabolism of testosterone.
Balthazart, Jacques ; ;
in General and Comparative Endocrinology (1983), 51(2), 191-207
Three experiments were carried out to study whether differences in the intracellular metabolism of testosterone (T) can explain sexually differential responses to T in Japanese quail. In the first ... [more ▼]
Three experiments were carried out to study whether differences in the intracellular metabolism of testosterone (T) can explain sexually differential responses to T in Japanese quail. In the first experiment, a series of dose-response curves in which length of Silastic testosterone implants was related to effects on several behavioral and physiological variables was established. In Experiment 2, adult males and females were assigned to six experimental groups: intact males and females (I-males and I-females), castrated males and females implanted subcutaneously with 40-mm Silastic implants of T (T-males and T-females), and castrated males and females without hormone treatment (CX-males and CX-females). No CX-bird (male or female) and no I-female exhibited male sexual behavior. However, I-males and T-males regularly copulated during the behavioral tests. No crowing was ever heard in CX-animals and I-females. T-females crowed less than T-males and their crowing sounded weaker than those of males. The cloacal glands of T-females were less developed than those of males. Radioimmunoassay of T and 5 alpha-DHT showed that T-males and T-females have similar plasma levels of androgens. No striking differences were observed in the way testosterone is metabolized by the pituitary gland and central nervous tissues of males and females. By contrast, the production of 5 alpha-dihydrotestosterone (5 alpha-DHT) and 5 alpha-androstane-3 alpha, 17 beta-diol (5 alpha, 3 alpha-diol) was higher in the cloacal glands of males than in those of females. These sex differences were not detected between T-males and T-females. In experiment 3, the cloacal gland of males produced more 5 alpha-reduced metabolites than those of females. The pituitary gland of females also produced more 5 beta-androstane-3 alpha, 17 beta-diol (5 beta, 3 alpha-diol). In syringeal muscles, the production of 5 beta-dihydrotestosterone (5 beta-DHT) and 5 beta, 3 alpha-diol was higher in females compared to males. [less ▲]Detailed reference viewed: 7 (0 ULg)
5 beta-Dihydrotestosterone is weakly androgenic in the adult Japanese quail (Coturnix coturnix japonica).
; ; Balthazart, Jacques
in General and Comparative Endocrinology (1982), 48(4), 421-4Detailed reference viewed: 12 (0 ULg)
Effects of in vivo corticosterone treatment on the in vitro metabolism of testosterone in the comb and brain of the young male chicken.
; Balthazart, Jacques ; et al
in General and Comparative Endocrinology (1982), 48(3), 398-402Detailed reference viewed: 8 (0 ULg)
Diurnal variations of plasma FSH, LH, and testosterone in male ring doves kept under different photoperiods.
Balthazart, Jacques ; ;
in General and Comparative Endocrinology (1981), 44(2), 202-6Detailed reference viewed: 8 (0 ULg)
Circulating concentrations of growth hormone during growth, maturation, and reproductive cycles in ring doves (Streptopelia risoria).
; Balthazart, Jacques
in General and Comparative Endocrinology (1981), 45(3), 381-5Detailed reference viewed: 3 (0 ULg)
Endocrine effects of castration followed by androgen replacement and ACTH injections in the male domestic duck (Anas platyrhynchos L.).
; Balthazart, Jacques ; et al
in General and Comparative Endocrinology (1980), 41(1), 53-61Detailed reference viewed: 10 (0 ULg)
Photoperiodic control of testosterone metabolism, plasma gonadotrophins, cloacal gland growth, and reproductive behavior in the Japanese quail.
Balthazart, Jacques ; ;
in General and Comparative Endocrinology (1979), 39(2), 222-35Detailed reference viewed: 4 (2 ULg)
Diurnal variations of plasma gonadotrophins in male domestic ducks during the sexual cycle.
Balthazart, Jacques ; ;
in General and Comparative Endocrinology (1977), 32(4), 376-89Detailed reference viewed: 2 (0 ULg)
Annual variation in reproductive behavior, testosterone, and plasma FSH levels in the Rouen duck, Anas platyrhynchos.
Balthazart, Jacques ;
in General and Comparative Endocrinology (1976), 28(2), 171-83Detailed reference viewed: 16 (0 ULg)