RESUMEN

For grass carp (Ctenopharyngodon idella) raised in the Ivory Coast (with water temperatures of 26-31 degrees C), induced spawning is obligatory for fry production. However, ovulation rates following hormonal treatment are often low. We hypothesized that high temperatures are an inhibiting factor for the reproductive axis (brain-pituitary-gonad) in these conditions. By in vivo and in vitro experiments, we tried to determine the thermosensitive steps during spawning induction. We compared gonadotropin and maturation-inducing steroid (MIS) profiles during a spawning induction at controlled temperatures of 24 and 28 degrees C in relation to ovulation success. We performed pituitary cell cultures and ovarian fragment incubations at controlled temperatures. The ovulation rate was lower at 28 degrees C (10%) than at 24 degrees C (36%). At the pituitary level, we found only minor thermal impacts on GnRH-stimulated LH release, but our data suggest an increase of the dopaminergic inhibition by high temperatures. The main effects were found at the ovary level, where ovary responsiveness to gonadotropin by MIS synthesis was disturbed, as well as oocyte responsiveness to MIS triggering final maturation, and probably ovulation. These results show the importance of regulating temperature during spawning induction to ensure a high rate of ovulation.

Asunto(s)

Carpas/fisiología , Reproducción , Temperatura , Animales , Células Cultivadas , Antagonistas de Dopamina/farmacología , Femenino , Hormona Liberadora de Gonadotropina/farmacología , Hormona Luteinizante/metabolismo , Ovulación , Pimozida/farmacología , Hipófisis/efectos de los fármacos , Hipófisis/metabolismo

RESUMEN

Various hormones were analyzed during the course of a reproductive cycle in the cichlid fish Oreochromis niloticus: plasma levels of the gonadal steroids 17beta-estradiol (E2), testosterone (T), 17, 20beta-OH progesterone (17,20beta-P), gonadotropin (taGtH), and plasma and pituitary concentrations of prolactin (tiPRL(I) and tiPRL(II)) and growth hormone (tiGH). Two categories of fish were sampled and sacrificed on days 1 and 3 postspawning and at 3-day intervals thereafter: typical incubating females (INC), and nonincubating females (NI), deprived of their eggs just after spawning. Such deprivation is known to suppress maternal behavior and to accelerate ovarian development and especially vitellogenesis, thus shortening the mean interspawning interval. In both groups, variations of the plasma concentrations of E2 and T appeared to depend on ovarian stages, and differences between groups appeared to reflect underlying differences in the kinetics of ovarian development. The observation of noticeable levels of 17,20beta-P in plasma before spawning, when high values of taGtH could also be detected in NI females, suggests the implication of this progestin in the control of final maturation events, as in some other teleosts. Moreover, 17,20beta-P, which was still detected a few days after spawning, but at low concentrations and only in the plasma of INC females, might play a role at the beginning of the reproductive cycle in incubating females (maternal behavior and/or slowing down of ovarian growth). The pituitary and plasma profiles of both tiPRLs isoforms appeared to depend mainly on the kinetics of ovarian development in each group of fish, suggesting a role during the beginning of vitellogenesis. However, the variance of plasma tiPRL(II), which was significantly enhanced during maternal behavior in INC females, also suggests an implication of this hormone in the control of that behavior. Concerning tiGH, comparison of the plasma profiles in INC and NI fish also suggest an influence on the control of maternal behavior, but a main effect of starvation of INC during mouthbrooding cannot be excluded.

Asunto(s)

Hormonas Esteroides Gonadales/sangre , Gonadotropinas/sangre , Hormona de Crecimiento Humana/sangre , Comportamiento de Nidificación/fisiología , Prolactina/sangre , Tilapia/fisiología , Animales , Estradiol/sangre , Femenino , Conducta Materna , Óvulo , Progesterona/sangre , Testosterona/sangre , Vitelogénesis

RESUMEN

Steroidogenesis in the gonad of the protandrous sea bass, Lates calcarifer, was examined in vitro in spermiating testis, previtellogenic ovary, and transitional gonads. Gonadal tissues were incubated with tritiated androstenedione. Metabolites were analyzed by thin-layer chromatography, high-performance liquid chromatography, microchemical reactions, and crystallization to constant specific activity. 17 beta-Hydroxysteroid dehydrogenase, 5 beta-reductase, and 3 alpha-hydroxysteroid dehydrogenase activities were found in all of the sex types. On the other hand, 11 beta-hydroxysteroid dehydrogenase and 11 beta-hydroxylase activities were found only when testicular tissue was present, i.e., in testis and early transitional gonad. A low aromatase activity leading to estrone synthesis was detected in the previtellogenic ovary. In late transitional gonads, a major metabolite (metabolite X) was suggestively identified as a 3-ester of 17 beta-estradiol according to its chemical and immunological characteristics. Levels of 17 beta-estradiol (E2), the metabolite X, testosterone (T), and 11-ketotestosterone (11KT) were also measured by radioimmunoassay in plasma, before (January and February) and during (March and April) the sex inversion process. Plasma E2 was virtually undetectable (means below 25 pg/ml), although higher levels of metabolite X were found in transitional fish (485 +/- 432 pg/ml in March). Throughout this period, plasma levels of T and 11KT and the androgens/estrogens ratio were significantly higher in males than in transitional fish, where these levels decreased during the sex inversion period. The level of in vitro synthesis of metabolite X was high in transitional gonads, but their concentrations were very low (0.07 +/- 0.09 ng of equivalent E2/g in transitional gonads against 0.22 +/- 0.37 ng of equivalent E2/g in testes and 2.16 +/- 2.7 ng of equivalent E2/g in ovaries).

Asunto(s)

Androstenodiona/metabolismo , Lubina/fisiología , Estradiol/sangre , Organismos Hermafroditas , Ovario/metabolismo , Procesos de Determinación del Sexo , Testículo/metabolismo , Testosterona/análogos & derivados , Testosterona/sangre , 11-beta-Hidroxiesteroide Deshidrogenasas , 17-Hidroxiesteroide Deshidrogenasas/análisis , 17-Hidroxiesteroide Deshidrogenasas/metabolismo , 17-Hidroxiesteroide Deshidrogenasas/fisiología , 3-Hidroxiesteroide Deshidrogenasas/análisis , 3-Hidroxiesteroide Deshidrogenasas/metabolismo , 3-Hidroxiesteroide Deshidrogenasas/fisiología , Animales , Lubina/embriología , Lubina/metabolismo , Cromatografía Líquida de Alta Presión , Estradiol/análisis , Estradiol/metabolismo , Femenino , Hidroxiesteroide Deshidrogenasas/análisis , Hidroxiesteroide Deshidrogenasas/metabolismo , Hidroxiesteroide Deshidrogenasas/fisiología , Masculino , Ovario/química , Ovario/enzimología , Radioinmunoensayo , Estaciones del Año , Testículo/química , Testículo/enzimología , Testosterona/análisis , Testosterona/metabolismo

RESUMEN

Plasma and gonadal levels of several gonadal steroids (testosterone, 11-ketotestosterone, androstenedione, 11 beta-hydroxyandrostenedione, 17 beta-estradiol, and estrone) were measured by RIA in the protandrous seabass, Lates calcarifer, throughout an annual reproductive cycle. Twenty to 25 fish were killed every month for gonadal and plasma sampling. Very low plasma levels of 11-ketotestosterone in females (monthly means always less than 75 pg/ml), and of 17 beta-estradiol (means always less than 68 pg/ml) and estrone (means always less than 42 pg/ml) in males did not fluctuate significantly during the cycle. Conversely, plasma concentrations of testosterone, estrone, and 17 beta-estradiol peaked during vitellogenesis in females (highest mean: 182 +/- 121, 182 +/- 32 and 598 +/- 369 pg/ml, respectively) and testosterone and 11-ketotestosterone peaked during spermiation in males (highest mean: 189 +/- 91 and 223 +/- 94 pg/ml, respectively). When sex type are compared over the whole cycle, females displayed higher 17 beta-estradiol (172 +/- 233.5 pg/ml) and estrone (79.5 +/- 72 pg/ml) levels than males (57 +/- 7.5 and 44 +/- 62.5 pg/ml, respectively), while males had higher 11-ketotestosterone levels (153 +/- 88 pg/ml) and, to a lesser extent, higher testosterone levels (128 +/- 82 pg/ml) than females (51.5 +/- 28 and 91.5 +/- 60 pg/ml, respectively). Transitional fish always exhibit low plasma levels for these four steroids (testosterone 56.5 +/- 12.5 pg/ml, 11-ketotestosterone 59 +/- 23.5 pg/ml, 17 beta-estradiol 65.6 +/- 36 pg/ml, and estrone 61 +/- 47.5 pg/ml). Among gonadal androgens, 11 beta-hydroxyandrostenedione predominated in testes (3.95 +/- 3 ng/g), except during spermiation (0.8 +/- 0.5 ng/g), and remained low in ovaries (1.05 +/- 1.4 ng/g). No differences were detected in gonads, for testosterone and 11-ketotestosterone whatever the sex type, but their concentrations were higher in vitellogenic and atretic ovaries. Androstenedione levels were slightly higher in testes (2.21 +/- 2 ng/g) than in ovaries (1.53 +/- 1.32 ng/g). Transitional gonads always showed low concentrations for these four androgens (testosterone 0.66 +/- 1.77 ng/g, 11-ketotestosterone 0.14 +/- 0.05 ng/g, androstenedione 0.3 +/- 0.34 ng/g, and 11 beta-hydroxyandrostenedione 0.2 +/- 0.23 ng/g). Gonadal 17 beta-estradiol was nearly undetectable in testes (0.06 +/- 0.07 ng/g), low in ovaries (0.42 +/- 0.46 ng/g), and strikingly high in transitional gonads (2.89 +/- 1.64 ng/g) even at the very beginning of sex inversion. This suggests an important role for this estrogen in the protandrous sex inversion process in the seabass L. calcarifer.

Asunto(s)

Lubina/metabolismo , Hormonas Esteroides Gonadales/metabolismo , Gónadas/metabolismo , Organismos Hermafroditas , Reproducción/fisiología , Procesos de Determinación del Sexo/fisiopatología , Animales , Lubina/sangre , Femenino , Hormonas Esteroides Gonadales/sangre , Gónadas/crecimiento & desarrollo , Masculino , Procesos de Determinación del Sexo/metabolismo , Diferenciación Sexual/fisiología

RESUMEN

Ovarian early postovulatory development and oestrogen production were studied in rainbow trout from a spring-spawning strain, 5 to 50 days postovulation (PO). Early postovulatory development was assessed by the ovarian development index, corresponding to the relative volume occupied in the ovary by oocytes in an advanced stage of differentiation (containing cortical alveoli). This index was shown to be related to the maximal oocyte diameter and to the time since ovulation, as well as to metabolic criteria. In contrast, gonadosomatic index was not correlated with any of these, confirming its unreliability for assessing the gonadal development, at least at this stage. Size of follicles and presence of vitellus (lipoprotein) in the oocytes of several animals indicate that ovarian development was more advanced in our females than in other studies. It is suggested that young follicles start developing before ovulation of the preceding batch of oocytes. Oestradiol (E2) plasma levels were low but detectable, and showed, in some females, peak values (max 5.5 ng/ml) within the first month PO. Besides, in vitro metabolism was studied using two isotopes of androstenedione as precursors. No sharp discrepancies were observed between the two types of incubation. Conjugation of the precursor or its metabolites was high but decreased with time postovulation. This suggests that it proceeds from postovulatory follicles. E2 production potential was demonstrated from the shortest time postovulation. Moreover, it increased with ovarian development, suggesting that E2 is synthesized in developing follicles.

Asunto(s)

Estrógenos/biosíntesis , Ovario/crecimiento & desarrollo , Ovulación , Salmonidae/fisiología , Maduración Sexual , Trucha/fisiología , Androstenodiona/sangre , Animales , Aromatasa/metabolismo , Estradiol/sangre , Femenino , Oocitos/citología , Ovario/fisiología

RESUMEN

Dietary administration of various estrogens for three months from swim-up stage resulted in excess of females, the remainder of the treated groups consisting of males and hermaphrodites. Mature hermaphrodites were self-fertilized or mated with standard males and females. These hermaphrodites and some of the estrogen-treated females proved to be genetic males; the frequencies of males obtained from their ova averaged 76.6%, suggesting viability of the YY genotype. Four of nine tested males of those progenies provided all male offspring when mated with standard females.

Asunto(s)

Salmonidae/genética , Trucha/genética , Cromosoma Y , Animales , Trastornos del Desarrollo Sexual , Estrona/farmacología , Etinilestradiol/farmacología , Femenino , Fertilización , Genitales Masculinos/efectos de los fármacos , Genotipo , Masculino , Razón de Masculinidad

RESUMEN

The changes in cAMP were followed in trout oocytes incubated in vitro after defolliculation performed by either enzymatic or manual dissection. Both defolliculation methods induced a highly significant rise in oocyte cAMP level (4.5 times the basal level of control [follicle-enclosed oocytes], after 6 h). Treatment of defolliculated oocytes with 17 alpha-hydroxy, 20 beta-dihydroprogesterone (17 alpha, 20 beta-OH-P) (10(-6) M), which induced oocyte maturation (germinal vesicle breakdown [GVBD]) was able, first, to interrupt the increase of oocyte cAMP level promoted by defolliculation and then to lower this level significantly down to values that still remained higher than folliculated controls. Very low concentrations of 17 alpha, 20 beta-OH-P (1.38-55.6 10(-9) M), or physiological doses of testosterone (0.35 10(-6) M, in the range found in vivo before ovulation) were able to induce a similar decrease of oocyte cAMP level without inducing GVBD. Under the same experimental conditions estradiol (0.35 10(-6) M) exhibited no action. These results suggest that some factor(s) originating in the follicle (FIF), inhibit the oocytes' tendency to accumulate cAMP before the final surge of 17 alpha, 20 beta-OH-P. This factor might be a follicular steroid such as testosterone or nonmaturing concentrations of 17 alpha, 20 beta-OH-P. Moreover our data favour the hypothesis that the final surge of 17 alpha, 20 beta-OH-P could induce distinct intraoocyte mechanisms: the first induces an irreversible blockage of cAMP level before the inhibitory action of the FIF is suppressed by ovulation, and the second mechanism leads to GVBD.

Asunto(s)

AMP Cíclico/metabolismo , Hidroxiprogesteronas/farmacología , Oocitos/metabolismo , Folículo Ovárico/fisiología , Salmonidae/metabolismo , Trucha/metabolismo , Animales , Femenino , Oocitos/efectos de los fármacos , Ovulación , Testosterona/farmacología

RESUMEN

The plasma levels of estradiol-17ß (E2), 17α, 20ß-dihydroxy-4-pregnen-3-one (17,20-P) and gonadotropin (GTH) were measured in brook trout (Salvelinus fontinalis) during the period from the end of vitellogenesis to postovulation. Blood samples were taken according to specific stages of maturation, including germinal vesicle breakdown (GVBD) and ovulation. E2 levels were quite high (∼45 ng/ml) at the end of vitellogenesis (and prior to GVBD) and dropped precipitously by GVBD (∼2 ng/ml). They remained low through ovulation and postovulation. 17,20-P levels were low prior to GVBD (∼0.7 ng/ml) and increased dramatically at GVBD (∼148 ng/ml). The levels of 17,20-P remained high at ovulation (∼142 ng/ml) and then dropped significantly within 24 h to approximately half of the ovulatory values. They decreased even further by 7 days postovulation. GTH levels rose gradually through GVBD and ovulation from a postvitellogenic level of approximately 3 ng/ml to a 7 day postovulatory value of approximately 10 ng/ml. The overall results; 1) decrease in estradiol prior to GVBD, 2) increase in 17,20-P at GVBD and 3) gradual GTH rise through GVBD and ovulation, are similar to those reported for other salmonids.

RESUMEN

In fish, oocyte maturation (resumption of meiosis after completion of vitellogenesis and before ovulation) is triggered by maturation inducing steroids (MIS) which generally appear to be secreted in the ovary in response to stimulation by a pituitary maturational gonadotropin. Converging data from different laboratories show that 17α-hydroxy, 20ß-dihydroprogesterone (17α, 20ß-OH-P) is the principal MIS in salmonoids; but clear identification remains to be done in other taxonomic groups.The experiments reported here in the rainbow troutSalmo gairdneri examine the possible involvement of oocyte cAMP on the mechanism of MIS action. The action of 17α, 20ß-OH-P, on germinal vesicle breakdown (GVBD) in oocytes incubatedin vitro within the follicle, was inhibited by various substances expected to elevate the intraoocyte concentrations of cAMP: cAMP (≥ 1 mM) or dibutyril cAMP (≥ 2 mM), phosphodiesterase inhibitors such as theophylline (≥ 0.2 mM) or 3-isobutyl-1 methylxanthine (IBMX ≥ 0.1 mM), adenylate cyclase activators such as cholera toxin (> 100 nM) or forskolin (≥ 0.03 mM). In fact, the combined action of IBMX (1 mM) and forskolin (0.01 or 0.05 mM)in vitro was to promote accumulation of intraoocyte cAMP within 1 to 5 hours. Oocyte cAMP concentrations exhibited a large variability between different females, depending on the stage of oocyte development; a significant positive correlation between oocyte cAMP concentration and the follicular weight, and a significant negative correlation between oocyte cAMP concentration and the median efficient dose of 17α, 20ß-OH-P for induction of GVBD, were observed. Finally, when intrafollicular oocytes were incubatedin vitro, the addition of a maturation-inducing concentration of 17α, 20ß-OH-P (3×10(-6)M) induced a significant decrease of oocyte cAMP within the first 10 hours of incubation. These results show that cAMP appears to play a central role in the regulation of oocyte sensitivity to 17α, 20ß-OH-P and in the intraoocyte mechanisms leading to GVBD in trout.These data are discussed together with the few indications available in fish concerning the mechanism of MIS action which can be compared to some extent with the amphibian model.

RESUMEN

In order to specify the timing of some changes in ovarian steroid production during the transition from vitellogenesis to ovulation, plasma hormones levels andin vivo andin vitro responses of the ovary to salmon gonadotropin (s-GtH) or dibutyryl-cyclic adenosine mono-phosphate (db-cAMP) were recorded in relationship with the state of germinal vesicle migration in the oocyte.In vivo, a small, but significant, increase of plasma 17α-hydroxy-20ß-dihydroprogesterone (17α, 20ß-OH-P) level was detected earlier (at the "subperipheral germinal vesicle" stage) than the increase of GtH level (detectable at the "peripheral germinal vesicle" stage) and the decline of oestradiol-17ß (E2-17ß) (also detectable at the "peripheral germinal vesicle" stage). Negative correlations were established between E2-17ß levels and GtH (ρ=-0.53) or 17α,20ß-OH-P (ρ=-0,43) levels while a positive correlation occurred between 17α,20ß-OH-P and GtH levels (ρ=+0,54).In vivo no action of GtH on the decline of E2-17ß levels was detected GtH did not stimulate 17α,20ß-OH-P production, within 72h, in females at the "end of vitellogenesis" stage. It had significant effect in females at other stages closer to ovulation, but the pattern of responses changed according to the stage.In vitro db-cAMP like GtH was able to stimulate 17α,20ß-OH-P output from ovarian follicles. The greatest response was observed at the later stage. (GVBD). Testosterone output was also increased by GtH, but the lowest response was observed at the later stage (GVBD). Androstenedione output was lower than testosterone output.In vitro, a small but significant decline of E2-17ß output was induced by GtH. We conclude that substantial changes occur during the very last stages prior to ovulation, both in the steroidogenic potential of the ovary and in the ovarian sensitivity to GtH. 20ß-oxydoreductase is probably progressively induced during GV migration when GtH basal levels are increasing but still relatively low. Without minimizing the role of discrete pulses of GtH on this induction, we could expect synergic actions of other hormones. Thus a high testosterone/oestradiol ratio in the follicle environment favours 17α,20ß-OH-P secretion.

RESUMEN

The number of germ cells in fry gonads was determined from histological sections sampled periodically over a 10-week post-hatching period. Several successive types of germ cells were identified: primordial germ cells (PGC), two kinds of gonocytes (G1 and G2) and all the stages of female meiotic prophase. The mean diameters are shown in table 1. The number of germ cells increased regularly from 47 +/- 35 (SD) after hatching (PGC) to 166 +/- 25 at 2 post-hatching weeks (G1). At 5 post-hatching weeks, two groups of fish could be distinguished by the number of their germ cells (G2) - one group had less than 926 cells and the other more than 1 577 - and by their gonadal morphology (Filiform or with an enlarged anterior part due to germ cell concentration). At 6 post-hatching weeks, the ovary differentiated with organization of the ovarian lamellae and the appearance of oocytes in meiotic prophase (4 out of 10 trout). The gonads of the other fish stayed at the indifferent stage. The number of germ cells was significantly higher in female-type gonads (6 335 +/- 3 558) than in indifferent gonads (1 696 +/- 467). The situation was the same at 8 to 10 weeks.

Asunto(s)

Células Germinativas/citología , Gónadas/citología , Salmonidae/anatomía & histología , Trucha/anatomía & histología , Animales , Peso Corporal/efectos de los fármacos , Femenino , Meiosis , Ovario/citología , Factores de Tiempo

RESUMEN

The plasma concentrations of the glycoproteic gonadotropin (GTH) and of the 17 alpha hydroxy-20 beta dihydroprogesterone (17 alpha 20 beta OHP) have been followed in the course of ovulation in 6 rainbow trout, using radioimmunoassays on samples taken every two days. A first slow and limited GTH increase (10 to 20 ng/ml) is detected before and during the ovulation, while the 17 alpha 20 beta OHP rises sharply (up to three to five hundreds nanogrammes per millilitre). Then the progestagen levels drop back to their previous values, for about three weeks after ovulation. At the same time, a second higher GTH increase (25 to 20 ng/ml) is taking place. The relations between these two hormones, maturation and ovulation are discussed.

Asunto(s)

Glicoproteínas/sangre , Gonadotropinas/sangre , Hidroxiprogesteronas/sangre , Ovulación , Maduración Sexual , Animales , Femenino , Radioinmunoensayo , Trucha

RESUMEN

17 alpha-Hydroxy-20 beta-dihydroprogesterone and 17 alpha-hydroxyprogesterone were found in higher concentrations in serum from female Salmo gairdneri undergoing final oocyte maturation immediately before ovulation than in serum from spermiating male trout. Other steroids (11-deoxycorticosterone, 11-deoxycortisol and progesterone) which have been implicated in oocyte maturation and/or ovulation in lower vertebrates were not identified at such high concentrations and the differences between the serum of both sexes were not so great. These results confirm that 17 alpha-hydroxy-20 beta-dihydroprogesterone and 17 alpha-hydroxyprogesterone, the most potent inducers of trout oocyte maturation in vitro, are present in the blood when oocyte maturation occurs. The concentration of testosterone was found to be higher in serum from female than from male trout indicating that testosterone is unlikely to be the principal androgen in trout. High concentrations of 11-oxotestosterone in male and barely detectable levels in female fish support the hypothesis that 11-oxotestosterone is an important androgen in the regulation of testicular activity.

Asunto(s)

Hidroxiprogesteronas/sangre , Salmonidae/sangre , Trucha/sangre , Animales , Femenino , Masculino , Oocitos/crecimiento & desarrollo , Progesterona/sangre , Espermatogénesis , Testosterona/sangre

RESUMEN

Using radioimmunoassays, plasma levels of carp gonadotropin (c-GTH) and oestradiol-17 beta (E2) are measured every day in Carp, during induced spawning (water temperature = 15 degrees C). Ten Carps injected twice intraperitonealy with a total extract of Carp hypophysis (0,6 mg/kg BW at Jo and 5,4 mg/kg BW at J1) are compared to a lot receiving only saline solution. No evolution is detected in that last group when in the experimental one E2 level increases with exogenous c-GTH (see table). Even if E2 levels are low at the end of vitellogenesis, steroidogenic structures remain sensitive to an exogenous hypophysial stimulation. Secretion ability differs within individuals (correlation coefficient between total estimated c-GTH and E2 = 0,15).

Asunto(s)

Carpas/fisiología , Cyprinidae/fisiología , Estradiol/metabolismo , Ovario/fisiología , Hipófisis/fisiología , Animales , Estradiol/sangre , Femenino , Gonadotropinas Hipofisarias/sangre

RESUMEN

Ovulation occurred 5 to 9 days after injection of 2 mg/kg 17 alpha-hydroxy-20 beta dihydroprogesterone (17 alpha-20 beta Pg) in rainbow trout with oocytes in which the germinal vesicle was subperipheral. Whereas oocyte maturation was initiated by 17 alpha-20 beta Pg without an immediate increase in the concentration of t-GtH, in controls an increased level was found to coincide with initiation of the process and the concentration of t-GtH was higher at all stages. Progesterone treatment was less effective.

Asunto(s)

20-alfa-Dihidroprogesterona/análogos & derivados , Oocitos/efectos de los fármacos , Ovulación/efectos de los fármacos , Óvulo/efectos de los fármacos , Progesterona/análogos & derivados , Progesterona/farmacología , Salmonidae/fisiología , Trucha/fisiología , 20-alfa-Dihidroprogesterona/farmacología , Animales , Femenino , Gonadotropinas/sangre , Oogénesis/efectos de los fármacos , Estimulación Química , Factores de Tiempo

RESUMEN

10 In the rainbow trout and the tench, at the time of spermatogonia divisions a rise in the plasma gonadotropin levels was observed. Just before or during the spawning period, E217 beta and plasma gonadotropin reach their maximum levels. 20 When the effects of raising the natural cycle temperature of the tench were studied (deltat + 3 degrees C and + 6 degrees C), in conditions where nycthemeral and seasonal rythmicity were maintained, a significant increase in fertility was observed with the increase in temperature (the first spawning period was earlier and there was a rise in the number of spawnings). This effect of temperature seems to act at the level of the hypothalamo-pituitary system.

Asunto(s)

Estradiol/sangre , Peces/fisiología , Gonadotropinas Hipofisarias/sangre , Reproducción , Salmonidae/fisiología , Trucha/fisiología , Animales , Relojes Biológicos , Frío , Femenino , Masculino , Espermatogénesis , Temperatura

RESUMEN

The efficiency of 17 alpha-hydroxy-20 beta-dihydroprogesterone (17 alpha-20 beta Pg) or of a Trout pituitary gonadotropic extract to induce intrafollicular maturation of trout oocytes can be modulated by some steroids which do not present any direct maturing action: gonadotropic extract efficiency is lowered by estradiol and estrone, and enhanced by testosteron. As these steroids do not present a significant effect on 17 alpha-20 beta Pg induced maturation, their site of action may be located in the follicular tissues. The corticosteroids, particularly cortisol and cortisone enhance the maturing efficiency of gonadotropin and stimulate much more strongly the efficiency of 17 alpha-20 beta Pg. This suggests a direct effect on oocyte sensitivity to 17 alpha-20 beta Pg.

Asunto(s)

Gonadotropinas/farmacología , Hidroxiprogesteronas/análogos & derivados , Oogénesis/efectos de los fármacos , Salmonidae/fisiología , Trucha/fisiología , 20-alfa-Dihidroprogesterona/análogos & derivados , 20-alfa-Dihidroprogesterona/farmacología , Animales , Corticosterona/farmacología , Cortisona/farmacología , Sinergismo Farmacológico , Estradiol/farmacología , Estrona/farmacología , Hidrocortisona/farmacología , Hidroxiprogesteronas/farmacología , Testosterona/farmacología

RESUMEN

Ovulation (active expulsion of oocyte from the mature follicle) of trout follicles matured in vivo can be induced in vitro by adding PGF2alpha at doses of 1 and 5 mug/ml. PGE2 is ineffective. The in vitro induction of ovulation by PGF2alpha is inhibited in a calcium free medium or by inhibitors of calcium influx, particularly by Mn++ and La+++, suggesting the ovulation process implies active contraction of the smooth muscle cells of the theca. A significant but partial inhibition is also observed with cytochalasin B (1 and 5 mug/ml) demonstrating that contraction of other cell types than muscle, containing actin-like filaments, may also participate in the process.

Asunto(s)

Oocitos/efectos de los fármacos , Folículo Ovárico/efectos de los fármacos , Ovulación/efectos de los fármacos , Óvulo/efectos de los fármacos , Prostaglandinas E/farmacología , Prostaglandinas F/farmacología , Salmonidae/fisiología , Células Tecales/efectos de los fármacos , Trucha/fisiología , Animales , Calcio/farmacología , Citocalasina B/farmacología , Femenino , Contracción Muscular/efectos de los fármacos , Músculo Liso/efectos de los fármacos , Oxitocina/farmacología , Estimulación Química , Inhibidores de Tripsina/farmacología , Vasopresinas/farmacología

Asunto(s)

Carpas/fisiología , Clomifeno/farmacología , Cyprinidae/fisiología , Gonadotropinas Hipofisarias/sangre , Animales , Relación Dosis-Respuesta a Droga , Femenino , Cinética , Masculino

Asunto(s)

Gonadotropinas Hipofisarias/metabolismo , Hipotálamo , Hipófisis/metabolismo , Animales , Carpas , Cromatografía en Gel , Dopamina/farmacología , Femenino , Hipotálamo/efectos de los fármacos , Hipotálamo/metabolismo , Técnicas In Vitro , Cinética , Masculino , Peso Molecular , Concentración Osmolar , Oxitocina/farmacología , Hipófisis/efectos de los fármacos , Neurohipófisis , Vasopresinas/farmacología