Structural organization of pi conjugated highly luminescent molecular material

We report on striking evidence for a room temperature structural phase instability in p-hexaphenyl, inducing a nonplanar conformation of the molecules. Solid state proton NMR and single crystal x-ray diffraction allow the analysis of the organization, the individual dynamics and the involved symmetry breaking. The analysis of Raman spectra above and below room temperature reveals a singular behavior suggesting a modification of the overlap between the electronic wave function induced by the nonplanarity. These results provide a new basis to answer fundamental issues related to molecular and electronic materials and, in particular, luminescent organic devices.

Transcriptional analysis of testis maturation using trout cDNA macroarrays

The project seeks to identify genes involved in key stages of trout spermatogenesis and their regulation. Within the framework of the French project of farm animal genomics (AGENAE) we produced an original normalised trout testis cDNA library and obtained 1152 trout ESTs corresponding to 967 potential genes. To study the expression of those genes throughout first stages of spermatogenesis, we used nylon macroarray. Gonads in stage of immaturity (stage I), or at initiation of spermatogonial proliferation (stage II), meiosis (stage III) or spermiogenesis were selected by histological analysis. Total RNA was extracted and then used to produce complex targets labelled with [33P]dCTP and hybridised with cDNA arrays. After filtering and normalisation of hybridisation signals, genes presenting differential expression as revealed by ANOVA analysis were submitted to k-means clustering and hierarchical classification. Genes were separated into five clusters which presented distinct profiles. One cluster overexpressed in stage I could be involved in the initial events of spermatogenesis as seminiferous tubule organisation. The second cluster displays a transient increase at the beginning of testicular recrudescence (stage II). Three other clusters group several genes involved in cell proliferation and protein synthesis and modification. One is particularly down-expressed during stage I, the two others show increased expression during stages III and IV and appear to be involved in spermatogonial and meiotic proliferation and in protein metabolism linked to cellular growth. This allows us to plan further experiments to better understand the functional implication of some of the genes that are found to be significantly regulated like CDC2, hematological and neurological expressed gene 1-like protein, HCDI protein, Mago Nashi, a BMP-like, and a steroid receptor binding protein. These data demonstrate the applicability of the array based technology using our trout cDNA arrays and highlight genes that are potential targets for the control of puberty and fertility in farmed fish.

In vitro action of leptin on FSH and LH production in rainbow trout (Onchorynchus mykiss) at different stages of the sexual cycle

The short-term effect of recombinant human leptin (rhleptin) on FSH and LH production (release+intracellular content) was studied in vitro using pituitary cells from male and female rainbow trout during the first gametogenesis cycle. In our rearing conditions, we found a direct action of rhleptin at the pituitary level, which depends on the sexual stage of the fish. No effect of rhleptin on FSH or LH release and cellular content could be detected in immature fish and post-ovulatory females. However, throughout the process of spermatogenesis and ovogenesis, high concentrations (0.5 and 1 x 10(-6)M) of rhleptin stimulated FSH and LH release, without observable action on intracellular content of gonadotropins. A relatively constant response to rhleptin for FSH was observed throughout gonad maturation, while LH response tended to be higher at the first stages of gametogenesis (beginning of spermatogenesis and endogenous vitellogenesis). Preliminary results on the potential interaction of rhleptin and salmon GnRH (sGnRH) suggest a possible synergistic effect of high concentration of rhleptin (10(-6)M) and sGnRH only at restricted phases of gonadal development when the gametogenetic process was already fully started (full spermatogenesis and early vitellogenesis). The direct action of leptin on FSH and LH release, evident only when gametogenesis had already started suggests that leptin is not the unique signal for the activation of the gonadotropic axis but requires a combined action with other promoting factors.

In vivo and in vitro effects of prochloraz and nonylphenol ethoxylates on trout spermatogenesis

We investigated the effects of in vivo exposure to non-lethal concentrations of two chemicals commonly discharged into the aquatic environment, prochloraz and nonylphenol diethoxylate (NP2EO - Igepal(R) 210), on the development of spermatogenesis in trout. The in vitro effects on basal and insulin-like growth factor-1 (IGF-I) stimulated DNA synthesis by early germ cells were also studied. In vivo, rainbow trout were exposed for 2 or 3 weeks to waterborne prochloraz (21 and 175 nmol/l) and/or NP2EO (68-970 nmol/l) renewed continuously, or periodically. Only the highest concentrations of NP2EO (225-970 nmol/l) induced a significant increase in blood plasma vitellogenin in juvenile or maturing male trout. When prepubertal fish were exposed for 15 days to prochloraz, the spermatogenetic process was significantly inhibited as shown by the stage of gonadal development reached 3 weeks after exposure. This effect was, to a great extent, reversible within 9 weeks post-exposure. When fish in the initial stage of spermatogenesis were exposed for 21-27 days to 580 nmol/l NP2EO, a 20-40% reduction of the gonadosomatic index was observed 4.5 weeks post-exposure, and the spermatogenetic process was partly inhibited. In vitro, testicular cells obtained at different stages of spermatogenesis were cultured for 4.5 days in the presence or not of the tested molecules and with IGF-I or not. 3H-thymidine (3H-Tdr) incorporation was measured according to Loir (Mol. Reprod. Dev. 53 (1999) 424) and 125I-IGF-I specific binding was determined according to Le Gac et al. (Mol. Reprod. Dev. 44 (1996) 35). Irrespective of the spermatogenetic stage, basal 3H-Tdr incorporation was decreased by prochloraz concentrations > or =10 micromol/l. The presence of IGF-I (10-100 ng/ml) stimulated 3H-Tdr incorporation; this response to IGF-I began to decrease at 25-50 micromol/l prochloraz. In parallel, a dose-dependent increase of IGF-I specific binding was induced by prochloraz 1-100 micromol/l. Similarly, basal and IGF-I-stimulated 3H-Tdr incorporation was decreased by nonylphenol polyethoxylate (NpnEO; starting at 10 micromol/l), NP2EO and NP (30 micromol/l); a dose-dependent increase of IGF-I specific binding was also induced by NP and NPnEO. While 1-100 nmol/l 17beta-estradiol had no effect in our in vitro system, Triton(R) X-100 acted as NPnEO on 3H-Tdr incorporation. Beside their known endocrine disrupting effects on sex steroid production or action, these lipophilic molecules could act on germ cells by disrupting cell membrane receptivity to peptide hormones like growth factors.

Growth hormone receptors in ovary and liver during gametogenesis in female rainbow trout (Oncorhynchus mykiss)

Changes of growth hormone receptivity in the ovary during the reproductive cycle were studied in rainbow trout (Oncorhynchus mykiss). A method for characterizing growth hormone receptors in crude ovary homogenate was required for this. Binding of radiolabelled recombinant rainbow trout growth hormone (125I-labelled rtGH) to crude ovary preparation was dependent on ovarian tissue concentration. The sites were specific to growth hormone, with no affinity for prolactins and gonadotrophins. Similar high affinities for 125I-labelled rtGH were obtained with crude ovary (4.2 x 10(9) +/- 0.3 mol l-1) and crude liver preparations (4.9 x 10(9) +/- 0.1 mol l-1) at all stages of ovogenesis, and with ovarian membrane preparations (8.2 x 10(9) mol l-1) tested at the beginning of vitellogenesis. Ovarian growth hormone receptor concentration was highest during the early phases of follicular development (endogenous vitellogenesis: 315-310 fmol g-1 ovary) and decreased regularly during oocyte and follicular growth (exogenous vitellogenesis) to reach a minimal value at oocyte maturation (42 fmol g-1 ovary). In postovulated fish, binding was at a similar level (297 fmol g-1 ovary) to that found in endogenous vitellogenesis. Conversely, the absolute binding capacity of the whole ovary was low from immaturity to early exogenous vitellogenesis (0.1-0.6 pmol per pair of gonads), increased slowly during vitellogenesis and more markedly during rapid oocyte growth and at the time of final maturation (10.8 pmol per pair of gonads). In postovulated fish, the absolute binding capacity decreased partially (4.4 pmol per pair of gonads). Mean hepatic growth hormone receptor concentration did not vary with the reproductive stage for most of the cycle (3.0-4.5 pmol g-1 liver) except in endogenous vitellogenesis where significantly higher concentrations were observed (6.7 pmol g-1 liver). Individual ovarian growth hormone receptor concentrations were correlated with hepatic growth hormone receptor concentrations, indicating that they are regulated in a similar way. We conclude that growth hormone receptors are present in the ovary during the entire ovarian cycle in rainbow trout, probably mainly in somatic cells as indicated by the same concentration of binding sites in immature and in postovulated fish. Growth hormone is potentially important during oocyte recruitment in vitellogenesis and initiation of growth and during final follicular maturation.

Growth hormone (GH) and gonadotropin subunit gene expression and pituitary and plasma changes during spermatogenesis and oogenesis in rainbow trout (Oncorhynchus mykiss)

In order to evaluate potential interactions between somatotropic and gonadotropic axes in rainbow trout (Oncorhynchus mykiss), changes in pituitary content of the specific messenger RNA of growth hormone (GH) and gonadotropin (GTH) alpha- and beta-subunits were studied during gametogenesis with respect to pituitary and plasma hormone concentrations. Quantitative analyses of mRNA and hormones were performed by dot blot hybridization and homologous RIA on individual fish according to stage of spermatogenesis and oogenesis. All transcripts were detectable in 9-month-old immature fish. GH, GTH IIbeta, and GTH alpha increased moderately throughout most of gametogenesis and then more dramatically at spermiation and during the periovulatory period. GTH Ibeta mRNA increased first from stage I to V in males and more abruptly at spermiation, while in females GTH Ibeta transcripts increased first during early vitellogenesis and again around ovulation. Pituitary GH absolute content (microgram/pituitary, not normalized with body weight) increased slowly during gametogenesis and more abruptly in males during spermiation. In the pituitary of previtellogenic females and immature males, GTH I beta peptide contents were 80- to 500-fold higher than GTH II beta peptide contents. GTH I contents rose regularly during the initial phases of vitellogenesis and spermatogenesis and then more abruptly in the final stages of gonadal maturation, while GTH II contents show a dramatic elevation during final oocyte growth and maturation, in postovulated females, and during spermiogenesis and spermiation in males. Blood plasma GTH II concentrations were undetectable in most gonadal stages, but were elevated during spermiogenesis and spermiation and during oocyte maturation and postovulation. In contrast, plasma GTH I was already high ( approximately 2 ng/ml) in fish with immature gonads, significantly increased at the beginning of spermatogonial proliferation, and then increased again between stages III and VI to reach maximal levels ( approximately 9 ng/ml) toward the end of sperm cell differentiation, but decreased at spermiation. In females, plasma GTH I rose strongly for the first time up to early exogenous vitellogenesis, decreased during most exogenous vitellogenesis, and increased again around ovulation. Our data revealed that patterns of relative abundance of GTH Ibeta mRNA and pituitary and plasma GTH I were similar, but not the GTH II patterns, suggesting differential regulation between these two hormones at the transcriptional and posttranscriptional levels. Pituitary and plasma GH changes could not be related to sexual maturation, and only a weak relationship was observed between GH and gonadotropin patterns, demonstrating that no simple connection exists between somatotropic and gonadotropic axes at the pituitary level during gametogenesis.

Growth hormone receptors in testis and liver during the spermatogenetic cycle in rainbow trout (Oncorhynchus mykiss)

Changes in growth hormone (GH) receptivity in the testis during the reproductive cycle were studied in rainbow trout (Oncorhynchus mykiss). This necessitated setting up a method to characterize GH receptors (GH-R) in crude testis homogenate. Binding of radiolabeled recombinant rainbow trout GH (125I-rtGH) to crude testis preparation was dependent on testicular tissue concentration. The sites were specific to GH, with no affinity for prolactins, gonadotropins, or insulin. Similar high affinities for 125I-rtGH were obtained with crude testis (4.5 x 10(9) + 0.25 M(-1)) and crude liver preparations (5.1 x 10(9) +/- 0.06 M(-1)) at all stages of spermatogenesis, as well as with testicular membrane preparations (2.4 x 10(9) M(-1)). GH-R concentration in testis was high during the immature stage (590 fmol/g testis); it then decreased regularly from the beginning (stage II, spermatogonia proliferation: 706 fmol/g testis) to the end of spermatogenesis (stage VII: 158 fmol/g testis). Conversely, the absolute testicular capacity increased dramatically between stages IV and VI (1.2-16.2 pmol/2 gonads), when testicular growth is extremely rapid. GH-R concentration in the liver was highest in early stages (6.5-6.7 pmol/g liver); this value then significantly decreased during midspermatogenesis (stage VI: 3.5 pmol/g liver) and returned to immature levels at the end of the cycle. No significant correlation was found between GH-R in testis, GH-R in liver, and plasma GH concentration. Preliminary experiments performed on isolated populations of testicular cells revealed that binding of 125I-rtGH was detectable in Sertoli cell-enriched fractions but not in germ cell populations. We conclude that GH-R are present in the testis during the entire reproductive cycle in rainbow trout, probably in somatic cells and in particular in Sertoli cells.

Effect of 17 beta-estradiol, testosterone, and 11-ketotestosterone on 17,20 beta-dihydroxy-4-pregnen-3-one production in the rainbow trout testis

The principal hormone related to spermiation in Oncorhynchus mykiss is 17,20 beta-dihydroxy-4-pregnen-3-one (17,20 beta OHP). In the present study we analyzed the possible paracrine/autocrine effects of three other testicular steroids (17 beta-estradiol, 11-ketotestosterone, and testosterone) on the synthesis and secretion of this progestin in male rainbow trout. Pieces of testis at various stages of spermatogenesis were incubated for 24 or 48 hr with one of these steroids (5 to 800 ng ml-1) either alone or with the gonadotropin GtH II. Following incubation, 17,20 beta OHP was measured by RIA in the culture media. In vitro, only 17 beta-estradiol (E2) decreased 17,20 beta OHP secretion repeatedly and significantly when doses higher than or equal to 50 ng ml-1 were used. This effect was observed mainly at the spermiating stage and under gonadotropic stimulation. In turn, E2 did not seem to modify the testicular capacity to convert 17-hydroxyprogesterone into 17,20 beta OHP. In vivo, the circulating levels of E2 decreased at the beginning of spermiation, concomitantly with an increase of 17,20 beta OHP in plasma. These in vitro and in vivo data suggest a possible role for E2 in the regulation of 17,20 beta OHP secretion by testes, in particular during the spermiating period.

Insulin-like growth factor (IGF-I) mRNA and IGF-I receptor in trout testis and in isolated spermatogenic and Sertoli cells

Few data exist concerning the occurrence and potential role of an insulin-like growth factor (IGF) system in fish gonads. Using Northern and slot blot hybridization with a specific salmon IGF-I cDNA, we confirmed that IGF-I transcription occurs in trout testis. Testicular IGF-I mRNA abundance may be increased by long-term GH treatment in juvenile fish, while shorter treatment with growth hormone (GH) or a gonadotropin (GTH-II) in maturing males had no statistically significant effect. Radiolabelled recombinant human IGF-I binds with high affinity to crude trout testis preparation, to cultured isolated testicular cells, and to a membrane fraction of these cells (Ka = 0.2 to 0.7 x 10(10) M-1; Bmax = 10 to 20 fmol/10(7) cells, and 68 fmol/mg protein of membrane). The binding site was identified as type 1 IGF receptor by its binding specificity (IGF-I > IGF-II >>> insulin) and the molecular size of its alpha-subunit labelled with 125I-IGF-I (M(r)125-140 kDa). 125I-IGF-II also bound to the type 1 receptor whereas IGF-II/ mannose 6 phosphate receptors could not be detected. Separation of isolated testicular cells by Percoll gradient and centrifugal elutriation provided populations enriched in different types of intratubular cells. IGF-I mRNA (detected by reverse transcription + polymerase chain reaction [PCR]) and IGF-I receptors (measured by competitive binding) were observed to a greater extent in Sertoli cell-enriched populations and in spermatogonia with primary spermatocytes. Therefore, IGF-I is a potential paracrine/autocrine regulator inside the spermatogenic compartment and appears as a possible mediator of GH action at the gonadal level in fish.

20 beta-hydroxysteroid dehydrogenase activity in nonflagellated germ cells of rainbow trout testis

Nonflagellated germ cells were isolated from rainbow trout testis to determine their ability to synthesize 17,20 beta-dihydroxy-4-pregnen-3-one (17,20 beta OHP), a progestin involved in the control of the release of sperm. Germ cells were obtained by enzymatic dissociation (collagenase; 3 mg.ml-1, 4.5 h, 12 degrees C) from testes that were immature and at the beginning of spermatogenesis. Somatic cells were eliminated by adhesion to the culture plates. Dose-related amounts of 17,20 beta OHP were measured by RIA in culture media of germ cells incubated with increasing dosages of 17-hydroxyprogesterone (17OHP; 0.05-10 micrograms.ml-1) for 20 h at 12 degrees C. Furthermore, 3H-17,20 beta OHP was identified by chromatography and co-crystallization with a reference in incubating cells provided by 3H-17OHP (2.5 and 4 h, 12 degrees C). Other metabolites were detected but not identified. 11-Ketotestosterone (11KT) was either nondetectable by RIA in control cultures or, when detected, was found at very low levels. In no case was 11KT stimulated by addition of 17OHP or gonadotropin II (GtH II; 400 ng.ml-1); this indicated the absence of contamination by Leydig cells. Thus, to our knowledge, this report demonstrates steroidogenic activities in nonflagellated germ cells of fish testis for the first time. 20 beta-Hydroxysteroid dehydrogenase (20 beta HSD) activity was identified, showing that germ cells are able to synthesize 17,20 beta OHP at an early stage in rainbow trout testis.

Synthesis and regulation of 17α-hydroxy-20β-dihydroprogesterone in immature males of Oncorhynchus mykiss

Three experimental approaches were chosen to study the question if the progestin 17α-hydroxy-20β-dihydroprogesterone (17α20βOHP) is synthesised in testes of young Oncorhynchus mykiss, in which the absence of spermatozoa was verified histologically: first, in order to detect 20β-hydroxysteroid dehydrogenase activity (20βHSD), testes homogenates were incubated with (3)H-labeled 17αOHP.Metabolites were analysed by TLC, HPLC, and repeated crystallization to constant isotope ratios. One of the metabolites was identified as 17α20βOHP-(3)H, indicating that already immature testes contain 20βHSD activity and are able to produce 20β-reduced steroids. Second, 17α20βOHP was quantified by radioimmunoassay in incubates of testes fragments. The sensitivity of the gonads to gonadotropin II (GtH II) became evident when comparing incubations in the absence and presence of GtH II. Third, plasma levels of 17α20βOHP were significantly higher in animals injected with partially purified salmon gonadotropin, compared to controls. Thus, for the first time, it could be shown that 20βHSD is present in testicular cells other than spermatozoa. Furthermore, 17α20βOHP is indeed secreted at a very early stage of testicular development; 17α20βOHP secretion is also responsive to GtH II. Future studies will have to show if the functions of this progestin include the stimulation of spermatogenesis.

Insulin-like growth factor-I and -II binding and action on DNA synthesis in rainbow trout spermatogonia and spermatocytes

Radio-labeled recombinant human insulin-like growth factor (125I-rhIGF-I) bound specifically to total testicular cells and to spermatogonia plus primary spermatocytes (Go+CI) that had been prepared from trout testes at various maturation stages by centrifugal elutriation and then cleared of somatic cells by preculture in the presence of 2% Ultroser G. Binding sites showed high affinity (Ka = 0.5 +/- 0.2 x 10(10) M-1) and low capacity (1.1 +/- 0.8 fmol/10(6) testicular cells) for 125I-IGF-I. (Gln3, Ala4, Tyr15, Leu16)IGF-I ([QAYL]IGF-I) was equipotent to IGF-I in competing with 125I-IGF-I for site occupancy on Go+CI. Insulin-like growth factor-II (IGF-II) was to 10-fold less potent than IGF-I or (QAYL)IGF-I, while bovine insulin competed only about 300-fold higher concentrations. Go+CI were cultured for 3 days in the presence or absence of mammalian IGF-I, IGF-II, (QAYL)IGF-I, and salmon or bovine insulin. All these molecules stimulated the incorporation of [3H]thymidine (added during the last 24 h in culture) by Go+CI in a dose-dependent manner. The mean ED50, independent of testicular maturation stage, was 5.9 +/- 4.9 ng/ml and 29.1 +/- 15.8 ng/ml for IGF-I and IGF-II, respectively. (QAYL)IGF-I was as potent as IGF-I. Concentrations of salmon or bovine insulin 100- to 300-fold higher were required to produce effects similar to those of IGF-I. While recombinant human IGF binding protein (IGFBP-3) had no effect by itself of basal [3H]thymidine incorporation, it inhibited the effect of IGF-I in a dose-dependent manner; however, it had no effect on the stimulation by (QAYL)IGF-F. Although combinations of low concentrations of IGF-I and IGF-II or salmon insulin had additive effects, combinations of maximum concentrations did not. We conclude that, in vitro, IGFs stimulate DNA synthesis of trout male germ cells by interacting directly with these cells through one IGF receptor.

[Insulin-like growth factors and gonadal regulation in fish]

Recent data showing the occurrence of IGF in fish, mainly teleostean fish, and their biological activity in gonads are reviewed. IGF-I does occur in all vertebrates and first evidence of IGF-II occurrence in fish has been reported. IGF-I is expressed in the testis and the ovary, and receptors for the peptide have been demonstrated in both gonads. Besides, IGF-I seems implied in spermatogonial proliferation and in oocyte maturation. Both germinal cells and somatic cells could be responsive to IGF-I stimulation.

Growth hormone (GH) and reproduction: a review

Interaction between growth and reproduction occurs in many vertebrates and is particularly obvious at certain stages of the life cycle in fish. Endocrine interactions between the gonadotropic axis and the somatotropic axis are described, the potential role of GH being emphasised. A comparative analysis of these phenomena in mammals, amphibians and fish, suggests a specific role of GH in the physiology of puberty, gametogenesis and fertility. It also shows the original contribution made by studies on the fish model in this field of investigations.

Vitellogenin synthesis in cultured hepatocytes; an in vitro test for the estrogenic potency of chemicals

We describe here an in vitro technique to assess the estrogenic activity of chemicals. This technique is based on rainbow trout hepatocytes incubated in a basic medium free of any additional growth factors or estrogenic chemicals and uses the production of vitellogenin (VTG) as a marker for the estrogenic potency of the compounds tested. The system allows at least some of the metabolic transformations which are undertaken by the liver cells in vivo and could therefore be used for xenobiotic compounds which exhibit estrogenic activities after liver metabolic transformation. A dose-response curve was always consistently obtained using estradiol-17 beta (E2), with a mid point at around 100 nM E2 and a maximum response at around 1000 nM. Established estrogens such as 17 a 1 ethynylestradiol (EE2) or diethylstilboestrol (DES) were also tested. EE2 appeared to be equipotent with E2 and DES slightly less potent. E2 conjugates were, perhaps surprisingly, also very potent. Estradiol-3-sulfate was equipotent with E2 and estradiol-17 beta-glucuronide approx. 10% as potent. Other steroids such as androgens and progesterone, though active in the bioassay, were 3 orders of magnitude less potent than E2. Of the various steroids tested, only cortisol, at concentrations up to 50 microM, was completely inactive. Six different phytoestrogens were tested in the assay. All were weakly estrogenic, possessing approximately one thousandth the potency of E2 (they were as potent as the androgens and progesterone). All six phytoestrogens, as well as the androgens and progesterone, were tested in the presence of tamoxifen. In all cases tamoxifen reduced the production of VTG significantly, demonstrating that the estrogenic action of all of these compounds was most likely mediated by the E2 receptor. The potencies determined here may not reflect the situation in vivo but can provide complementary results about the activity of chemicals which need an hepatic metabolization to be estrogenic. Hepatocyte cultures would profitably be developed in other species to sustain these results.

Evidence for binding and action of growth hormone in trout testis

Growth hormone (GH) binding to testis tissue and GH action on trout testicular cells were studied in vitro. Labeled salmon GH (sGH) was able to bind to a trout testis membrane preparation. Binding sites showed high affinity (Ka = 1-2 x 10(9) M-1) and low capacity (11 fmol/g fresh tissue) for 125I-sGH. Salmon GH and bovine GH, but not salmon gonadotropin, could compete with 125I-sGH for site occupancy. The binding characteristics were similar to those of trout liver GH receptors that we previously described. Salmon GH (0.1 and 1 microgram/ml) and bovine GH (10 micrograms/ml) could modulate steroidogenesis in cultured testicular cells: 17 alpha-hydroxy, 20 beta-dihydroprogesterone (17 alpha 20 beta OHP) accumulation in culture medium was stimulated by GH addition, and this effect increased with duration of culture and/or stimulation; 11-ketotestosterone accumulation tended to be inhibited in the presence of GH at the beginning of culture. These effects were dependent on GH concentration and were observed both in the absence and presence of gonadotropin. The amplitude of the sGH effect varied between experiments, probably according to the physiological state of the cells used. In vivo, GH and 17 alpha 20 beta OHP plasma levels increased at the beginning of spermiation (sperm production) and decreased at the end of spermiation. This relationship suggests that, at the end of the reproductive cycle, high GH levels are associated with the production of 17 alpha 20 beta OHP, a progestin necessary for efficient spawning in this species. We conclude that GH may play a role in testicular physiology, at least at certain stages of spermatogenesis.

Influence of hypophysectomy, castration, fasting, and spermiation on SBP concentration in male rainbow trout (Oncorhynchus mykiss)

The influence of different experimental and physiological conditions on sex steroid binding protein (SBP) concentrations in the blood (and in hepatic and testicular cytosols) has been studied on male rainbow trout. SBP was measured with a specific binding assay. The aim was to further understanding of regulation of the SBP and in particular to determine the respective influences of reproductive and metabolic status. Twelve days after hypophysectomy, pituitary and steroid hormones were dramatically decreased and SBP concentrations were significantly lowered in blood (-32%) and in hepatic cytosol (-46%) while the binding protein concentration remained constant in testicular cytosol. Castration of maturing animals did not influence SBP concentration in blood and liver cytosol. Toward the end of the reproductive cycle, a dramatic decrease (-80%) of plasma SBP concentration occurred that appears independent of androgen changes that take place during this period, but is concomitant with a rapid increase of plasma growth hormone (GH) levels (and possibly secondary to a natural arrest of food intake). Long-term fasting that increases endogenous GH but decreases plasma IGFs (insulin-like growth factors) concentrations also induces a limited but significant decrease in SBP concentration. Treatment of intact control trout with recombinant bovine GH (1 microgram/g wt, twice a week, for 6 weeks) increased plasma IGF concentrations but did not significantly increase SBP levels. These results suggest that in mature male trout, testicular androgens have little or no influence on SBP regulation. GH levels or liver GH responsiveness and IGF might be involved in SBP regulation. This would, in part, explain the large decrease in SBP around spermiation in trout.

In vivo and in vitro studies on sex steroid binding protein (SBP) regulation in rainbow trout (Oncorhynchus mykiss): influence of sex steroid hormones and of factors linked to growth and metabolism

The respective roles of sex steroids and hormones related to growth and metabolism, on SBP regulation have been studied in rainbow trout. In vivo, oestradiol (E2) supplementation induces a slow but significant increase of plasma SBP concentration. Testosterone or cortisol injections have no effect. In vitro, the steroid binding protein that accumulates in incubation medium of hepatic cell primary cultures has been characterized and found to be similar to blood SBP. Its production is increased by addition of E2 (maximum: +300%). This effect develops slowly over several days of culture and is dose dependent; as little as 1-10 nM E2 is effective. Recombinant rainbow trout GH (rtGH)--0.01 to 1 microgram/ml--also increases SBP accumulation as compared to control cells and seems to maintain SBP production over culture duration. In preliminary experiments, (1) insulin-like growth factor (IGF) and SBP concentrations were found to change inversely after a 4 days stimulation with increasing concentrations of GH; (2) recombinant human IGF1 (250 ng/ml) tended to be inhibitory when SBP production was expressed per mg of total cellular protein, and a micromolar concentration of bovine insulin was clearly inhibitory. Other hormones tested in vitro: triiodothyronine (10-1000 nM), thyroxine (100 nM), 17 alpha, 20 beta-dihydroprogesterone (10-2000 nM), and testosterone (1-1000 nM) did not influence SBP concentration in hepatic cells culture media.

In vivo estrogen induction of hepatic estrogen receptor mRNA and correlation with vitellogenin mRNA in rainbow trout

We have previously described the cloning, sequencing and in vitro expression of a full-length rainbow trout estrogen receptor cDNA (rtER cDNA). This full cDNA randomly labelled was used to study the estrogen induction of hepatic rtER mRNA in correlation with vitellogenin (Vg) mRNA in different physiological situations. In this paper, we show that in the liver two mRNA species are under hormonal control and their level increases about 8-fold after estrogen stimulation. These two mRNAs are expressed and induced in the liver as early as the hatching stage in correlation with the expression of Vg mRNA. A long-term analysis of rtER mRNA after estradiol (E2) injection shows a transient induction of the nuclear ER and its mRNA which recover to the basal level after 2 weeks. Nevertheless, a memory effect was observed on the expression of the Vg gene which does not appear to be directly related to the estrogen receptor level.

Presence of specific growth hormone binding sites in rainbow trout (Oncorhynchus mykiss) tissues: characterization of the hepatic receptor

The present work outlines the presence of specific binding for chinook salmon growth hormone (sGH) in different tissue preparations of rainbow trout. Optimal incubation conditions (pH, Tris, MgCl2) were determined. Specific binding was very sensitive to salt concentration during incubation. The specific binding reached a plateau after 15 and 25 hr of incubation at 12 and 4 degrees. At 20 degrees, specific and nonspecific binding were not stable. Specific binding dissociation was slower than association and was only partial. The binding was saturable (Bmax = 187 +/- 167 pmol), of high affinity (Ka = 2.4 +/- 0.8 10(9) M-1), and very specific for GH, properties which are in agreement with the characteristics of hormonal receptors. Sea bream and mammalian GH appeared 2- and 30-fold, respectively, less potent than cold sGH2 for displacing 125I-sGH2. Tissue preparations from ovary, testis, fat, skin, cartilage, gill, blood pellet, brain, spleen, kidney, and muscle showed significant saturable binding.

Full-length sequence and in vitro expression of rainbow trout estrogen receptor cDNA

We previously reported the isolation of a partial cDNA clone encoding the rainbow trout estrogen receptor (rtER). A 0.4 kb 5'-end insert of this cDNA was used to screen the trout liver lambda gt10 cDNA library, and a full-length cDNA was isolated and sequenced. The principal structural characteristics of the complete coding sequence of the rtER are: first a remarkable homology of the DNA binding (C) and hormone binding (E) domains with those of other species, and second the lack of an A region, the function of which is not yet known but which is well conserved in other species. In vitro expression of the full-length rtER cDNA was carried out after transcription by T7 RNA polymerase and translation in rabbit reticulocyte lysate. Translation product analysis shows three major proteins, the largest one of which probably corresponds to the translation of the complete open reading frame of mRNA. The rtER in vitro translation products specifically bind estrogens (estradiol and diethylstilbestrol), without competition from testosterone or cortisol. The equilibrium dissociation constant (Kd), deduced from the Scatchard plot, is in the same order of magnitude as those determined heretofore in salmon livers during classical experiments. The tissue distribution of rtER mRNA shows that the same mRNA size (3.5 kb) is also present in the pituitary and hypothalamus. However, in the pituitary, a smaller sized mRNA (1.4 kb) is also detected.

Evidence for an androgen binding protein in the testis of a teleost fish (Salmo gairdneri R.): a potential marker of Sertoli cell function

A factor binding tritiated testosterone was detected using "steady-state" polyacrylamide-gel electrophoresis, in rainbow trout genital tract. It migrated with a Rf identical to that of rat ABP. This binding was thermolabile, and was competitively inhibited by unlabelled testosterone. The steroid binding protein was found in cytosols from trout testes which had been previously perfused to avoid blood contamination, trout seminal plasma and in testicular explants incubation media. Using a quantitative assay and a Scatchard analysis, 25-50 pmol binding sites per gram gonad were found in testis cytosol. Binding affinity constant for testosterone in the various samples was close to 4 x 10(8) M(-1). The dissociation of steroid-protein complex was rapid (t 1/2 approximately 1.5 min). Hormonal specificity was studied by the competition of 3H-T binding with several concentrations of unlabelled competitors and the following order for affinities was obtained: dihydrotestosterone approximately androstenedione greater than testosterone greater than oestradiol greater than 17 alpha, 20 beta DHP greater than 11KT greater than cyproterone acetate greater than cortisol. High testicular cytosol and seminal plasma concentrations and apparent in vitro production indicate that the testis may synthesize an ABP-like protein in the trout. Such a factor would provide a unique marker of Sertoli cell activity and regulation in various physiological or experimental situations.

Gonadotropic hormone (GtH) receptors in the testis of the troutSalmo gairdneri: in vitro studies

A particulate fraction obtained from trout testis at the time of spermiation shows saturable binding sites for(125)I-labeled salmon gonadotropin ((125)I-GtH). Non-gonadal tissues (liver, muscle and spleen) did not demonstrate specific(125)I-GtH binding. The tracer's specific activity was determined by the self-displacement method (18 to 30 μCi/μg). Maximal specific binding ability of(125)I-GtH varied from 20 to 30% of the labelled ligand added, depending on the hormone preparation. Specific binding of(125)I-GtH to 20 mg of the testis membrane varied from 40 to 85% of the total binding depending on the method of membrane prepratation, and was competitively inhibited by concentrations of unlabelled GtH ranging from ca 1 to 1000 ng/ml of incubate. Gonadotropin of mammalian origin, ovine TSH or salmon prolactin competed only weakly, or not at all, for testicular gonadotropin binding sites (relative potencies s-GtH>>FSH=hCG>s-PRL>bTSH). Scatchard analysis of equilibrium binding studies shows that saturable gonadotropin binding was due to a class of high affinity binding sites (sites I Ka≊3×10(10) M(-1)) and possibly to a second class of lower affinity binding sites (sites II Ka=5 to 14×10(8) M(-1)). The binding capacity of sites I, as measured in enriched membrane preparations, was 45±18 fmoles/g of testis during the period of spermiation. The concentration of GtH required to obtain half maximal displacement of(125)I-GtH in the binding studies was of the same order of magnitude as the apparent ED50 for GtH stimulation of 11-Cetotestosterone (11KT) secretion by trout testesin vitro. Mammalian LH and FSH were 100 to 1000 folds less potent than salmor GtH to increase 11 KT secretion.

Gonadotropin hormone (GtH) receptors in the ovary of the brown trout Salmo trutta L. in vitro studies

A method has been developed suitable for the study of the binding of salmon (Oncorhynchus tsawytscha) gonadotropic hormone (GtH) to brown trout (Salmo trutta) ovarian particulate fractions. Several proteolytic enzyme inhibitors were tested to preserve the binding capacity of particulate fractions (1000, 20,000, and 110,000g) from yolky oocytes. The best preservation was obtained with trypsin inhibitor. The effects on binding of the pH, time, and temperature of the incubation were investigated. Binding increased linearly with amount of particulate fraction, and is saturable. In both the 20,000 and 110,000g fractions, there are two classes of receptors: one with a high-affinity constant (3.14 and 0.95 10(10) M-1 for the 20,000 and 110,000g fractions, respectively) and a low capacity (1.76 and 0.63 fmol/g of ovary), the other with a higher-affinity constant (3.44 and 1.78 10(9) M-1) but a higher capacity (7.37 and 7.42 fmol/g of ovary). GtH binding was not affected by ovine luteinizing hormone (oHL), ovine follice-stimulating hormone (oFSH), and human chorionic gonadotropin (hCG), but was partially inhibited by 1 micrograms of bovine thyroid-stimulating hormone (bTSH) and salmon prolactin (sPRL). The results are discussed in relation to the biological specificity of fish GtH and to the unsolved problem concerning the number of gonadotropins in fish.

High mobility group proteins in ram spermatids

The four major high mobility group proteins HMG 1, 2, 14 and 17, HMG 19B and histone H1(0) were identified in the ram testis by their extraction and solubility characteristics and by their electrophoretic mobilities. HMG 14 and 17 were isolated by chromatography and amino acid analysis revealed that they were similar to their calf thymus analogues. A protein, named 2R and co-extracted with HMG 14, was also purified and analysed. Electrophoretic analyses of the proteins extracted by 0.75 M perchloric acid (PCA) or by 0.35 M NaCl from round and non-round spermatids, separated by centrifugal elutriation, showed that the four major HMG proteins disappear from nuclei in the oldest round spermatids, at the time the nuclear content of protein 2R and histone H1(0) increases in spermatids. Ubiquitin and HMG 19B were present in the round and elongating spermatids, but not in elongated spermatids which contained only protamine. The relation was considered between several protein changes and genetic inactivation and structural reorganization of the spermatid chromatin.

Stimulation of rat Sertoli cell secretory activity in vitro by germ cells and residual bodies

The direct influence of germ cells and residual bodies on Sertoli cell basal and FSH-stimulated secretion of androgen-binding protein (ABP) was studied using Sertoli cells, recovered from 20-day-old rats, cultured alone or cocultured with a crude germ cell preparation from adult rats or with pachytene spermatocytes, round spermatids or populations of residual bodies enriched by centrifugal elutriation. The effect of a rat liver epithelial cell line (LEC) on Sertoli cell function was also tested. Addition of a crude germ cell preparation increased basal and FSH-stimulated ABP secretion. Pachytene spermatocytes and residual bodies adhered to the Sertoli cell monolayer to a much greater extent than did round spermatids. Addition of pachytene spermatocytes markedly enhanced basal and FSH-stimulated ABP secretion over 12 days of culture. Round spermatids and residual bodies stimulated ABP secretion although to a lesser extent than did spermatocytes. Furthermore, the increase of FSH-stimulated ABP levels was not maintained after 4 or 8 days of culture. LEC also enhanced basal and FSH-induced ABP levels but the increase of FSH-induced ABP production was only observed until Day 8 of culture. The influence of LEC on Sertoli cell secretion could be mediated through the production of an extracellular matrix. It is concluded that germ cells, particularly pachytene spermatocytes, can directly stimulate Sertoli cell secretory activity in vitro.

Use of pituitary cells in primary culture to study the regulation of gonadotropin hormone (GtH) secretion in rainbow trout: setting up and validating the system as assessed by its responsiveness to mammalian and salmon gonadotropin releasing hormone

To study the regulation of gonadotropin secretion in rainbow trout in vitro, a method for preparing primary cultures of dispersed pituitary cells is described. Cells were dispersed by collagenase 0.1% in Hank's saline solution for 20 hr at 12 degrees and a high yield of viable cells was obtained. Attempts to improve cell functioning were made by varying culture conditions (density of cells initially plated, age of the culture). Cell functioning was assessed by their ability to respond to increasing doses of mammalian and salmon GnRH. Pituitaries were collected from spermiating males whose pituitaries are known to be sensitive to mammalian GnRH in vivo. Using 96-well plates, optimal conditions for good biological activity, are initial plating with 6.2 X 10(4) cells, incubation with GnRH for 24 hr on the third day after plating. In these conditions mammalian analog and salmon GnRH induced an increase in GtH release for doses ranging from 10(-9) to 10(-6) M. The GtH released during the GnRH incubation period does not decrease the sensitivity of the system since addition of 20 ng of GtH at the beginning of incubation does not modify the response profile.

Studies on the mechanism of follicle-stimulating hormone-induced desensitization of Sertoli cell adenylyl cyclase in vitro

When Sertoli cells were cultured in the presence of follicle-stimulating hormone (FSH), a time-and concentration-dependent desensitization of FSH-responsive adenylyl cyclase (AC) was observed. Maximal desensitization (80%) was attained after 6-9 h of incubation with FSH (10 micrograms/ml; NIH-FSH-S12). During 24 h of incubation the concentration of FSH causing a half-maximal desensitization was about 100 ng/ml. Removal of the hormone from the culture medium was associated with a gradual reappearance of the FSH response. Follicle-stimulating hormone-induced desensitization of Sertoli cell AC was specific for homologous hormone, since AC activation by isoproterenol was unaffected. Furthermore, AC activity of control and FSH-desensitized cells was equally activated by GTP and fluoride, showing that the interaction of the guanyl nucleotide regulatory (N) component with the catalytic subunit is not affected during FSH-induced desensitization. A loss in specific FSH binding was detected after 9 and 24 h of exposure to FSH, but not at shorter times of incubation. Desensitization of Sertoli cell AC to both FSH and isoproterenol stimulation could also be achieved by dibutyryl cyclic AMP (dbcAMP); however, a 30-40% desensitization required a high nucleotide concentration (1 mM) and a long incubation time (24 h). These results show that desensitization of Sertoli cell AC by FSH is associated with normal function of the N component, and precedes any significant loss in specific FSH binding sites. Furthermore, exogenous addition of dbcAMP (1 mM) did not cause the same effects on Sertoli cell AC as did FSH.

Beta-adrenergic regulation of Sertoli cell adenylyl cyclase: desensitization by homologous hormone

Incubation of Sertoli cell-enriched cultures with D,L-isoproterenol caused a time- and concentration-dependent, homologous desensitization of isoproterenol-responsive adenyl cyclase, whereas the response to FSH was unaffected. Half-maximal desensitization was achieved within 1 h of preincubation, after which a more gradual loss of response was observed. Preincubation of Sertoli cells for 24 h with increasing concentrations of D,L-isoproterenol demonstrated that the concentration required to obtain half-maximal densensitization was approximately 10-fold lower than the Km for activation of adenylyl cyclase. The function of the guanine nucleotide regulatory component (N-component) of the adenylyl cyclase complex in hormonally desensitized Sertoli cells, as evaluated by activation of adenylyl cyclase by GTP, GMPP(NH)P, fluoride and Mg2+, was not affected by the hormone pretreatment. Preincubation of Sertoli cells with a high concentration of dbcAMP (10(-3) M) for 24 h was associated with a 45% reduction in adenylyl cyclase activation by both FSH and isoproterenol. Also in this case fluoride- and GTP-stimulated adenylyl cyclase activities were normal. However, the effects of dibutyryl cyclic AMP occurred much more slowly than agonist-induced desensitization, indicating that cAMP may not be the primary mediator of homologous desensitization of Sertoli cell adenylyl cyclase by isoproterenol.

Studies on seminiferous tubule fluid production in the adult rat: effect of hypophysectomy and treatment with FSH, LH and testosterone

Seminiferous tubule fluid production in adult rats was studied using the technique of unilateral efferent duct ligation (EDL), the production rate representing the difference in testis weight over the time since ligation. Following EDL, fluid production increases linearly for 6 h and linearly at a slightly slower rate for a further 18 h with a sharp decrease thereafter. No differences in fluid production were noted for rats aged between 90-310 days. Forty-eight hours after hypophysectomy there was a significant fall (26%) in fluid production prior to any significant decrease in testis weight. Fluid production continued to decline with time after hypophysectomy eventually reaching a plateau 16-44 days later at levels approximately 15% of those found in control rats. Treatment of rats hypophysectomized 4 days earlier with ovine FSH for 3 days did not restore fluid production, but treatment with ovine LH, testosterone propionate (TP) or FSH together with TP for a similar duration all restored fluid production to normal. On the other hand, treatment of intact adult rats with ovine LH significantly increased fluid production but the effect of treatment with testosterone alone did not reach significance. The results indicate that in the adult rat, seminiferous tubule fluid production is controlled principally by testosterone secreted by the Leydig cell in response to LH stimulation.

Effects of FSH, isoproterenol, and cyclic AMP on the production of lactate and pyruvate by cultured Sertoli cells

We have examined the hormonal regulation of the secretion of lactate and pyruvate from cultured rat Sertoli cells. FSH and isoproterenol caused 3-6-fold stimulation of lactate and pyruvate secretion, whereas ovine LH, TSH, and prolactin were ineffective. Dibutyryl cyclic AMP (10(-4) M) stimulated the secretion of lactate and pyruvate to the same extent as FSH. Much lower stimulation was observed when Sertoli cells from 43-day old rats were exposed to FSH or isoproterenol. FSH increased lactate secretion in a concentration-dependent manner. The concentration of FSH (NIH-S14) causing half-maximal stimulation of lactate secretion (150 ng/ml) was similar to that causing 50% maximal stimulation of Sertoli cell adenylyl cyclase. Both FSH and isoproterenol caused a time-dependent increase in lactate levels in the incubation medium during the first 6-9 hr after the addition of hormones, after which levels were constant or decreased. Thus, the production of lactate and pyruvate by cultured Sertoli cells is stimulated both by FSH and isoproterenol and these effects are exerted via cyclic AMP.

Inhibin production by Sertoli cell cultures

The production of inhibin by cultures of Sertoli cells from 21-day-old rats was assessed by the use of an in vitro bioassay using rat pituitary cells in culture. Sertoli cell culture media (SCCM) caused a dose-dependent suppression of the pituitary cell FSH content which was parallel with that of an ovine testis lymph preparation used as an inhibin standard. SCCM also caused a dose-dependent inhibition of FSH secreted by pituitary cells in response to 10 nM GnRH stimulation. The FSH-inhibitory activity in SCCM was destroyed by heat or trypsin digestion and could not be attributable to the steroid content of the medium, since ether extraction caused no change in the inhibitory activity. The inhibin activity in SCCM was not due to cytotoxicity in the bioassay, since the LH cell content was unchanged and the media produced no change in the release of 51Cr from labelled pituitary cells, a parameter which has been shown to be a useful test of cytotoxicity. Sertoli cell cultures produced inhibin for the 8-day duration of the cultures. The amount of inhibin produced was proportional to the number of Sertoli cells initially plated. If foetal calf serum was included for more than the initial 48 h, the spent medium caused toxic effects in the pituitary cells as evidenced by an increase in 51Cr release from 51Cr-labelled pituitary cells. Similar toxic effects were found if the lyophilized spent media contained cellular debris. A dose-dependent increase in inhibin activity was observed in the presence of graded doses of FSH (0.05-5 micrograms/ml NIH-FSH-S13).

Seminiferous tubule fluid and interstitial fluid production. I. Effects of age and hormonal regulation in immature rats

Efferent duct ligation was used to assess seminiferous tubule fluid (TF) production and studies of the kinetics of TF production following this procedure were performed on 25-day-old rats. The rate of TF production was linear for 48 h, thereafter reached a plateau until 72 h and began decreasing at 96 h post-ligation. Using a 16-h ligation period, the onset of TF production was investigated in groups of immature rats from 15 days of age. TF secretion was not detected prior to 15 days but rose rapidly after Day 20 coincident with the prepubertal rise in serum FSH. The acute effect of hormone on TF production following unilateral efferent duct ligation (EDL) was evaluated in 25-day-old rats in which interstitial fluid production (IF) was also assessed in the unligated testis by the method of Sharpe (1977). Single subcutaneous injections of the following hormones were given to groups of rats at the time of EDL: a) NIH follicle-stimulating hormone (FSH) S13 (20 micrograms/rat); b) NIH luteinizing hormone (LH) S22 (200 micrograms/rat); c) testosterone propionate (2 mg/rat); d) human chorionic gonadotropin (hCG) (10 IU/rat); or e) NIH prolactin (Prl) 14 (200 micrograms/rat). A significant rise in TF production occurred following FSH treatment but no effect was noted in any of the other groups. In contrast, a marked stimulation of IF production occurred in rats treated with LH or hCG.