Annual changes in plasma and liver in relation to vitellogenesis in the female rainbow trout, Salmo gairdneri

Molecular cloning of insulin-like growth factor 3 (igf3) and its expression in the tissues of a female damselfish, Chrysiptera cyanea, in relation to seasonal and food-manipulated reproduction

Food availability is a permissive determinant that drives gonadal activity in fish. The present study aimed to clarify the interactions between reproductive and nutritive statuses in the sapphire devil (Chrysiptera cyanea), a tropical damselfish with a long-day preference for reproduction. Insulin-like growth factor 3 (IGF3), a novel IGF that likely plays a role in gonadal maturation, was closely monitored in the sapphire devil. The cDNA of sapphire devil igf3 had an open reading frame of 443 base pairs (146 amino acid residues). Phylogenetic analyses revealed that sapphire devil IGF3 was clustered within the teleost IGF3 family. The transcript levels of sapphire devil igf3 increased in the brain, liver, and ovary of the fish during the late vitellogenic phase, suggesting that it plays a role in reproduction. Immersion of the fish in seawater containing estradiol-17β suppressed transcript levels of sapphire devil igf3 in the liver, but not in the brain, suggesting that intensive protein synthesis in relation to vitellogenesis negatively impacts somatic metabolism in this tissue. When fish were reared with high or low food under conditions of photoperiod (LD = 14:10) and temperature (at 25-28 °C) during the non-reproductive season, ovarian development was induced in high-food fish. Furthermore, prior to ovarian development in the high-food fish, the transcript levels of sapphire devil igf3 increased in the brain, liver, and ovary. These results indicated crosstalk between the reproductive and growth networks and suggested that a metabolic shift, from growth mode to reproductive mode, occurs in peripheral tissues when nutritive status is improved under suitable conditions of photoperiod and water temperature.

Histological evaluation of vital organs of the livebearer Jenynsia multidentata (Jenyns, 1842) exposed to glyphosate: A comparative analysis of Roundup® formulations

Roundup formulations are herbicides whose active principle is glyphosate. However, these formulations are potentially more toxic to non-target organisms than pure glyphosate. This study aimed to evaluate and compare the toxic potential of the Roundup formulations through histological alterations in fish. Thus, males and females of the neotropical fish species Jenynsia multidentata (Jenyns, 1842) were exposed for 24 or 96 h to the Roundup Original® (RO), Roundup Transorb® (RT) or Roundup WG® (RWG) formulations, at a fixed concentration of 0.5 mg/L of glyphosate. This concentration is close to the maximum glyphosate limits found in the environment and is non-lethal to J. multidentata. The three formulations caused histological damage to the liver, gills and brain of J. multidentata, which increased over the exposure time. Differences in the histological alterations between females and males were observed in the liver and brain. Females were more tolerant to RO and RT than RWG. Males did not exhibit these differences in sensitiveness with formulations. The RWG caused more damage in the liver and gills and RT in the brain. Overall, there were differences in the toxicity of RO, RT and RWG and the toxic effect was presented through histological damage, reinforcing the usefulness of histological biomarkers for Roundup® toxicity. The comparison of the toxic potential of glyphosate-based herbicides is important because it could give support to the governmental organizations to set protective rules for the water ecosystems and human health, as well as to reduce the use of highly toxic formulations in agriculture.

Changes in mRNA abundance of insulin-like growth factors in the brain and liver of a tropical damselfish, Chrysiptera cyanea, in relation to seasonal and food-manipulated reproduction

Food availability can become a factor driving the reproductive activity of tropical fish, particularly when primary production within their habitats fluctuates with tropical monsoons. The present study examined the involvement of insulin-like growth factors (IGF) in controlling the reproduction of the sapphire devil Chrysiptera cyanea, a reef-associated damselfish that is capable of manipulating its reproductive activity based on food availability. We cloned and characterized the cDNAs of igf1 and igf2 and determined their transcript levels in relation to seasonal and food-manipulated reproduction. The partial cDNAs of sapphire devil igf1 and igf2 had open reading frames (ORFs) composed of 600 bp (155 amino acid residue) and 636 bp (211 aa), respectively. Phylogenetic analyses revealed that IGF1 and IGF2 of the sapphire devil were clustered into those of teleosts. The gonadosomatic index increased from March to June. Vitellogenic oocytes and ovulatory follicles were observed in ovaries from May to June, which suggests that the spawning season lasts for at least 2 months. The hepatosomatic index, but not the condition factor, increased in March and June. The transcript levels of igf1 in the brain, but not in the liver, increased in April, June (vitellogenesis) and July (post vitellogenesis). Ovarian activity during the spawning season was maintained by high food supply (HH) for 30 days, although it was suppressed in the food-restriction treatment (LL) and restored in the re-feeding treatment (LH). The transcript levels of igfs in the brain, but not in the liver, in LH were lower than those in HH and LL. Moreover, immersing fish in seawater containing estradiol-17β suppressed transcript levels of igfs in the liver, but not in the brain. We conclude that reproductive activity during the spawning season is influenced by nutritive conditions and that crosstalk exists between the reproductive and growth network in the neural and peripheral tissues, thus controlling the reproductive activity of this species.

Purification and development of ELISAs for two forms of vitellogenin in Indian walking catfish, Clarias batrachus (L.)

Two forms of vitellogenin (Vg: Vg1 and Vg2) were purified from the plasma of estradiol-17β (E₂)-treated Indian walking catfish, Clarias batrachus, by gel filtration and adsorption chromatography. Native Vg1 and Vg2 had apparent molecular masses of 375 and 450 kDa, respectively, and both Vgs resolved into two similar major bands (95 and 67 kDa) in SDS-PAGE under reducing condition. Polyclonal antisera raised against each form of Vg were absorbed with a combination of hypophysectomized male catfish serum proteins and alternate Vg to ensure specificity. Immunological analyses verified the presence of Vg1 and Vg2 in the plasma of female catfish. Homologous ELISAs were developed for Vg1 and Vg2 using their respective harvested antisera, which exhibited the detection limit of 100 ng ml^-1 for Vg1 and 40 ng ml^-1 for Vg2, and low level of cross-reactivity (not parallel to the standard) was found with alternate Vg in each assay. Treatment of male catfish with E₂ induced both Vgs showing a proportionate ratio of Vg1 to Vg2 at 5.6:1. Plasma concentrations of both Vgs measured by ELISAs at different reproductive phases of field collected female catfish increased in accordance with the ovarian development, keeping the proportionate ratio of Vg1 to Vg2 at about 2:1 in fish undergoing vitellogenesis during prespawning period and 1:20 during spawning period, suggesting that Vg1 may be the major Vg to contribute in yolk formation, whereas Vg2, besides its role in yolk formation, may facilitate other physiological functions. The present study, thus, demonstrates the occurrence of two unequally synthesized Vgs in the catfish.

Sex-specific food intake in whiting Merlangius merlangus

In this study, the topic of sexual growth dimorphism in whiting Merlangius merlangus is examined. To understand the magnitude and underlying mechanisms, North Sea International Bottom Trawl Survey (IBTS) data and two additional datasets from the third quarter of 2007 and the first quarter of 2012 were analysed. Merlangius merlangus displays distinct differences in growth parameters between males and females, with females reaching a higher asymptotic length (L∞ ) than males. To identify the mechanisms which lead to higher growth in females, the quantity and the quality of the diet of M. merlangus in the North Sea were investigated to compare the sex-specific energy uptake levels. The diet composition did not differ between the sexes, but females had higher stomach content masses than males of the same total length (LT ), and showed lower proportions of empty stomachs. Moreover, female M. merlangus had higher liver and empty stomach masses compared with males of the same size, which indicates additional sex-specific differences in the metabolic costs and energy allocation patterns. Finally, interannual differences were found in the stomach contents, the share of empty stomachs and liver masses of M. merlangus in the North Sea.

Assessment of reproductive biomarkers in three-spined stickleback (Gasterosteus aculeatus) from sewage effluent recipients

The aim of this study was to examine the occurrence of endocrine disruption close to sewage treatment plant effluent discharges along the Finnish Baltic Sea coast using a set of reproductive biomarkers present in adult three-spined stickleback (Gasterosteus aculeatus). Possible variation and sensitivity of the biomarkers during an entire reproductive period were also examined. The analysis of vitellogenin (VTG) for estrogenic activity and spiggin for androgenic activity, together with histopathological analysis indicated that sticklebacks were exposed to estrogenic loads sufficient to cause inappropriate production of VTG and to disrupt normal testicular structure in adult male sticklebacks. No androgenic disruption was observed. The results emphasize the need of a combination of several reproductive biomarkers in fish and repeated sampling for the detection of potential endocrine modulating substances under field condition.

The hepatocytes of the brown trout (Salmo trutta fario): a stereological study of some cytoplasmic components with the breeding cycle

Sex differences exist in fish hepatocytes, but studies for characterizing their cytology throughout the breeding cycle are still scarce; suggesting changes, but most lacking quantitative data. To address this limitation, to complement baseline data generated from the brown trout model, and to prove that sex-specific seasonal changes exist, we made an unbiased stereological evaluation of the hepatocytic cytoplasm. Unprecedentedly for fish liver, the stereological design was exempt from model (biased) assumptions. Five (3 years old) animals per sex were studied in endogenous vitellogenesis, exogenous vitellogenesis, and spawning season end. Liver pieces for analysis were systematically sampled. Stereology was done in transmission electron microscopy (TEM) micrographs. Primary data generated relative volume estimates of the major cytoplasmic components. Such values were used for deriving absolute volumes (per cell and per liver). Lipid droplets did not show changes. As to other targets, trends at cell and liver levels were not always equal. If the hepatocyte was the reference space, the contents in mitochondria, dense bodies, glycogen, and cytosol changed seasonally, in both sexes. If taking the liver as the reference, changes attained the Golgi apparatus and rough endoplasmic reticulum (RER), besides dense bodies, glycogen (in females), and cytosol. The components volumes (namely per liver) were often positively (negatively for glycogen) correlated with the ovary weight, disclosing new associations and implications in fish. While also offering gold-standard data for backing morphofunctional correlations and pathology, we revealed a new process by which females increase the amount of RER and Golgi throughout vitellogenesis, breaking from the idea on how this event happens in fish.

Effects of exposure to the xenoestrogen octylphenol and subsequent transfer to clean water on liver and gonad ultrastructure during early development of Zoarces viviparus embryos

Female eelpouts (Zoarces viviparus L.) are exposed during early pregnancy to nominal concentrations of 100 microg/L of 4-tert-octylphenol (OP) or 0.5 microg/L of 17beta-estradiol (E2). Effects on maternal metabolism and on liver and gonad development in embryos were examined and compared with controls (C) during exposure and after transfer to clean water (depuration). In the mother fish, significantly higher concentrations of plasma vitellogenin (vtg) and calcium were found in the two exposed groups, when compared with the C group after exposure and depuration. When compared, however, with the respective values after exposure, vtg had decreased significantly after depuration. The hepatosomatic index was normalized after depuration. In both exposed groups, the hepatocytes were rounded and not distinctly polygonal as in the controls. The amount of glycogen was considerably less while the number of mitochondria increased, and the rER significantly proliferated after exposure as well as after depuration. The gonads of nine of more than 28 embryos in the group treated with OP exhibited a number of abnormalities as compared with the normal gonad development in both sexes. Feminization of the male gonads in the exposed specimens and a number of histopathological features were observed in all the abnormal gonads, whereas reliable male features, such as formation of seminiferous tubules or spermioduct, were not observed. This study showed that 4t-tert-OP and 17beta-estradiol exert estrogenic effects during very early development of the embryos and that depuration had a positive effect on the motherfish and her embryos.

Seasonal and gender variation of peroxisome proliferator activated receptors expression in brown trout liver

PPAR isotypes have been previously identified in the teleost brown trout (Salmo trutta f. fario) and their organ distribution pattern established. Being that the liver is a vital metabolic organ presenting expression of all isotypes and also knowing that estrogens/estrogen receptors seem to interact with PPARs, we hypothesized that the latter may very well change seasonally. So, we studied the expression of these receptors in the liver, along the annual reproductive cycle and in both genders. According to real-time RT-PCR, PPARalpha mRNA expression in females was significantly higher in May and lower in September than in other seasons. No significant variation was observed along the year in males. A significant difference between genders occurred in May, when PPARalpha expression was higher for females. PPARbeta expression showed little variation along the reproductive cycle in females, but in males it was significantly higher in December than in the other seasons. No significant differences existed between genders. PPARgamma was more expressed in February than in September and December, for females. As to males, it was more expressed in February than in all other seasons. No significant differences were observed between genders. The study proved our hypothesis that PPARs gene expression varies along the year. Moreover, PPARalpha expression in females followed the same annual variation pattern as peroxisome volumes and enzyme activities, and an inverse pattern relatively to the salmonid type annual plasma estradiol levels. The data agrees with the idea that PPARalpha is under estradiol modulation and that cross-talk between this receptor and the estrogen receptor possibly exists.

Effects of 17alpha-ethynylestradiol on EROD activity, spiggin and vitellogenin in three-spined stickleback (Gasterosteus aculeatus)

The three-spined stickleback (Gasterosteus aculeatus) has quantifiable biomarkers of exposure to estrogens (vitellogenin), androgens (spiggin) and aryl hydrocarbon receptor (AhR) agonists (EROD activity) and is therefore a promising test species for biomonitoring of reprotoxic chemicals in aquatic environments. In this study we evaluated the effects of 17alpha-ethynylestradiol (EE(2)) on EROD activity, induction of vitellogenin and spiggin, hepatosomatic index (HSI), ovarian somatic index (OSI) and nephrosomatic index (NSI). Adult male and female three-spined sticklebacks were exposed to concentrations of 0-170 ng EE(2)/l (measured concentrations) in a flow-through system for 21 days. Exposure to 170 ng EE(2)/l resulted in a significant 8- and 9-fold induction of gill EROD activity in males and females, respectively. In livers, EROD activity expressed in relation to microsomal protein content was suppressed due to a significant increase in microsomal protein content. Hepatic EROD activity per se expressed as picomol/min was not affected by exposure to EE(2). The lowest observed effect concentration for induction of vitellogenin in males was 53.7 ng EE(2)/l. In females, vitellogenin levels were significantly higher in those exposed to 170 ng EE(2)/l compared to controls. Spiggin production was significantly inhibited and NSI lower in males exposed to 170 ng EE(2)/l. In both females and males LSI was significantly higher in fish exposed to 170 ng EE(2)/l than in controls. In females exposed to 170 ng EE(2)/l, OSI was significantly lower and NSI higher than controls. The observed results from this study show that a synthetic estrogen can affect the well-known biomarker of exposure for dioxin-like compounds, EROD activity, and further that this response can differ between tissues. These findings are important for interpretation of biomonitoring data.

Ultrastructural changes in female hepatocytes during ovarian maturation of Steindachnerina insculpta (Pisces: Curimatidae)

During gonadal maturation the females of Steindachnerina insculpta, a teleost of the Furnas reservoir, Minas Gerais, Brazil, show low hepatosomatic and high gonadossomatic indexes, suggesting possible transference of hepatic substances to the ovaries. In comparison to the resting phase, in the maturation/mature one the hepatocytes show greater development of both smooth and rough endoplasmic reticula, increased electron density in the mitochondria, and glycogen scattered throughout the cytoplasm. In both resting and maturation/mature phases, the hepatic parenchyma contains melanomacrophagic centers that consist of degenerating cellular debris and are surrounded by capsules formed by cells, resembling fibroblasts, joined by desmosomes. No physiological relation of these centers with ovarian maturation was found.

Interactive effects of naphthalene treatment and the onset of vitellogenesis on energy metabolism in liver and gonad, and plasma steroid hormones of rainbow trout Oncorhynchus mykiss

The purpose of the study was to assess in female fish the possible interaction between treatment with a polycyclic aromatic hydrocarbon (PAH) like naphthalene and the onset of vitellogenesis. In a first experiment, female rainbow trout (Oncorhynchus mykiss) at stages 2-3 (previtellogenesis) or 4 (early vitellogenesis) were intraperitoneally injected (2 microl g(-1)) with vegetable oil alone (control) or containing naphthalene (50 mg kg(-1)) to be sampled 3 h later. A second experiment was similarly designed but using fish intraperitoneally implanted (10 microl g(-1)) with slow-release coconut oil implants alone (control) or containing 50 mg naphthalene kg(-1) body mass that were sampled 3 days after injection. On each sampling time, plasma levels of cortisol and 17beta-estradiol, and several metabolic parameters in plasma, liver and gonad were assessed. In controls, early vitellogenic fish compared with previtellogenic fish displayed changes that in some cases are confirmatory of previous studies whereas in other cases provide new information in plasma (increased amino acid levels), liver (decreased capacity for exporting glucose and reduced amino acid levels) and gonad (decreased amino acid levels). Naphthalene treatment produced in previtellogenic fish decreased 17beta-estradiol levels in plasma, increased plasma glucose or decreased liver gluconeogenic capacity whereas no major effects were noticed on parameters involved in lipid, amino acid and lactate metabolism. Differential effects of naphthalene treatment were noticed in early vitellogenic fish such as decreased 17beta-estradiol and glucose levels in plasma, increased hexokinase and glucokinase and lack of changes in fructose 1,6-bisphosphatase activities in liver, and a lower decrease of amino acid levels in gonad. Those alterations produced by naphthalene treatment resulted in a decreased capacity for covering the energy demand of vitellogenesis in liver and gonad that could contribute to a delay and/or impairment of the onset of maturation.

Cloning and characterization of vitellogenin cDNA from the common Japanese conger (Conger myriaster) and vitellogenin gene expression during ovarian development

The major yolk protein precursor, vitellogenin (VTG) was detected in plasma from vitellogenic females and estradiol-17beta (E2)-treated immature females, but not in males and immature females by Western blotting in common Japanese conger Conger myriaster. Its molecular mass was approximately 180 kDa under denaturing and reducing conditions. The common Japanese conger VTG cDNA was cloned from the liver of vitellogenic female. It contains 5110 nucleotides including an open reading frame that encodes 1663 amino acids. The deduced amino acid sequence of the common Japanese conger VTG shares 80% identity with that of eel Anguilla japonica VTG-1, and 45-55%, 32-34% and 27-29% identity with the deduced amino acid sequences of other fish, amphibian and avian VTG with polyserine domain, respectively. In female common Japanese conger, VTG gene was highly expressed in the liver of this species similar with other oviparous vertebrates. The expression levels of VTG gene in the liver increased from the oil droplet stage to the tertiary yolk globule stage and were maintained until the migratory nucleus stage.

Sex reversal in medaka treated in vitro with 17alpha-methyldihydrotestosterone during oocyte maturation

Using the S-rR strain of the medaka Oryzias latipes, we examined the effect of a non-aromatizable androgen on sex determination. Intrafollicular immature oocytes isolated before breakdown of the germinal vesicle were incubated in the presence of 17alpha-methyldihydrotestosterone (MDHT) for about 10 h during their maturational period. At the end of incubation, mature oocytes were rinsed and then artificially inseminated in regular saline. The fertilized eggs were then allowed to develop in tap water, and the fry were reared on a regular powdered diet until adulthood. Sex reversal of female to male was observed in a manner dependent on the dose of MDHT. In the solvent control group in which intrafollicular oocytes were matured in medium containing no exogenous androgen, no sex reversal was observed. The present finding, that the sex of medakas can be reversed by a single in vitro exposure of immature oocytes to androgen during the preovulatory period, suggests the existence in the oocyte of a sex determinant sensitive to sex steroids. This method for controlling the sex of eggs before fertilization may establish sex-determined eggs as potent material for investigating the mechanism of sex determination in the medaka.

Temperature and gender influences on the hepatic stroma (and associated pancreatic acini) of Nile tilapia,Oreochromis niloticus (Teleostei, Cichlidae): A stereological analysis by light microscopy

The normal organ morphology and function in fishes varies according to several natural factors, and such variability is found in liver. Knowledge about the normal liver microanatomy is fundamental to pathological evaluation. Even though gender and temperature are important factors for modulating morphophysiological processes in fishes, their influences on liver stroma are virtually unknown. Because temperature- and gender-related changes exist in liver parenchyma, we predict both factors should also influence the normal stromal structure. Using Nile tilapia as a model, we undertook a study to: 1) establish baseline quantitative structural data on the hepatic stroma (and intimately associated pancreatic acini); 2) compare data with those available from other species, namely, salmonids that do not have a liver with pancreatic acini; and 3) test our hypothesis that, within normal healthy limits, the stroma and its structural components may vary significantly with temperature and gender. We used 1-year-old male and female specimens acclimated to 17 degrees C (breeding noncompatible) and 27 degrees C (breeding compatible) for 45 days. Basic morphometric fish parameters were recorded. After estimation of liver volume, the organ was sliced and pieces systematically sampled for light microscopy. Stereology allowed estimation of the relative volumes of organ components. The total volumes were computed by combining the relative volumes with the total liver volumes. Nile tilapia of both genders, held at 17 vs. 27 degrees C, showed structural quantitative differences in the relative volumes of stroma and most of its components, and in the total volumes of certain stromal elements. The total volume of the stroma and of associated pancreatic acini did not differ. We first established that, in fishes, the total amount (volume) of liver biliary ducts and of eosinophilic granule cells might significantly change (increase and decrease, respectively) with a higher acclimation temperature. Indeed, virtually all the stereological changes were, essentially, temperature- and not gender-related. At 27 degrees C, parallel changes in the parenchyma caused a decreased liver volume and hepatic-somatic index (HSI). The relative volumetric proportion of stroma vs. parenchyma in tilapia is higher than in salmonids. The differences found in this study could not be detected with a qualitative approach, thus stressing the importance of using stereology for analyzing histological patterns and for establishing reliable baseline values in healthy conditions. It was also anticipated that in experimental settings with fish the baseline liver stromal architecture may be different according to temperature and breeding status; in consequence, the effects of the tested variable may also diverge. Our data do not fully explain the lower liver volume and HSI at 27 degrees C, thus justifying studies on the parenchyma, particularly on cell size and number.

The effects of 17β-estradiol injections on thyroid hormone deiodination pathways in liver and other tissues of female and male rainbow trout (Oncorhynchus mykiss) at different stages of sexual maturity

The effects of two intraperitoneal injections of 17β-estradiol (E2) over 7 days were studied on thyroid hormone plasma levels and on activities of thyroxine (T4), 3,5,3'-triiodothyronine (T3), and 3,3',5'-triiodothyronine (rT3) outer-ring deiodination (ORD) and inner-ring deiodination (IRD) pathways in various tissues of female and male rainbow trout (Oncorhynchus mykiss (Walbaum, 1792)). E2 administered to adult females and males at different stages of sexual maturity increased liver mass, depressed plasma T3 levels with no change in plasma T4 levels, and severely decreased liver T4ORD activity. E2 also modestly depressed hepatic rT3ORD activity, but only at low substrate levels, and had no consistent effect on the hepatic IRD pathways. There were no E2-induced changes in brain, gill, or heart deiodination, but E2 increased kidney T3IRD activity. In contrast, an all-female stock of trout with rudimentary ovaries responded to E2 with an increase in liver mass but without change in plasma T4 and T3 levels or liver and brain deiodination activities. In conclusion, the decrease in plasma T3 levels in both male and female adult E2-injected trout may be due to both decreased hepatic T3 production and increased renal T3 degradation. However, thyroidal responses to E2 depend on physiological/developmental state and were absent in a highly immature all-female trout stock.

Effects of husbandry practices, gender, and normal physiological variation on growth and reproduction of Japanese medaka, Oryzias latipes

Japanese medaka, Oryzias latipes, are currently used in a variety of research applications for toxicological and carcinogenesis research, yet the impact of certain husbandry factors on study outcome has received limited attention. In this study, we demonstrated significant effects of stocking density (SD), dietary restriction (DR) and photoperiod on somatic growth in medaka. Higher stocking densities significantly inhibited somatic and hepatic growth in females, while having no similar effects on males. Daily egg production declined in a step-wise manner in groups of fish stocked at densities ranging from 0.38 to 2.6 fish per l. Significantly slower somatic growth was observed in fish fed on a mildly restrictive dietary protocol compared with those fish fed to excess. Further significant declines were observed in somatic growth of fish fed at a rate comparable to that used in research studies (3-4% body weight (BW) per day). Fish reared at an 8-h light:16-h dark (8L/16D) photoperiod were significantly smaller than cohorts reared at a 16-h light:8-h dark (16L/8D) photoperiod and female sexual maturity was delayed in the short photoperiod cohort. In normal female medaka, a high degree of individual variation was observed in daily egg production, as well as diurnal fluctuations in ovarian weight, gonadosomatic index (GSI) and hepatosomatic index (HSI). These results indicate some husbandry factors affect growth, sexual maturation and egg production in medaka and should be taken into consideration in studies evaluating endpoints that may be impacted by growth and reproductive performance, i.e. carcinogenesis and endocrine disruption studies. The high degree of individual variation among normal females and daily fluctuations in organ weights should also be considered in study design.

Induction of vitellogenesis in 17alpha-ethinylestradiol-exposed rainbow trout (Oncorhynchus mykiss): a method comparison

Juvenile rainbow trout, Oncorhynchus mykiss, were exposed to the synthetic estrogen 17alpha-ethinylestradiol (EE(2)) through injection (1, 10, 25 and 50 microg EE(2)/g fish/week) and via water exposure (1, 10 and 100 ng EE(2)/l). After seven (injection and water exposure) and 14 days (only for water exposure), blood and plasma vitellogenin concentrations were quantified using indirect endpoints, i.e. plasma alkaline-labile phosphorus (ALP), plasma protein and plasma calcium. In addition, the relative gonad (GSI) and liver weight (HSI) were recorded. Actual plasma vitellogenin concentrations were measured with an enzyme immunoassay. Only fish injected with 50 microg EE(2)/g fish had a significantly higher gonad weight. No concentration-dependent changes in the HSI were detected in fish exposed via the water, but a significant dose-dependent increase of the HSI was observed in fish injected with EE(2). Exposure of rainbow trout to EE(2) had a significant effect on all tested plasma parameters. Plasma protein, phosphoprotein and calcium concentrations were significantly higher after two weeks exposure to 100 ng EE(2)/l. Fish injected with 10, 25 and 50 microg EE(2)/g fish exhibited increased plasma protein concentrations after 1 week. Compared to the controls, plasma ALP and calcium levels were significantly higher in all injected fish. A significant and positive correlation was observed between all three plasma parameters and between these indirect parameters and the actual plasma vitellogenin concentrations. These findings indicate that both the plasma ALP and the plasma calcium assay have a similar sensitivity as that of available antibody-based assays (EIA), at least in EE(2) exposure studies, and thus these assays can provide a rapid, simple and cost-effective alternative to available immunoassays.

Selenium biotransformations into proteinaceous forms by foodweb organisms of selenium-laden drainage waters in California

Selenium contamination represents one of the few clear cases where environmental pollution has led to devastation of wildlife populations, most notably in agricultural drainage evaporation and power plant coal-fly ash receiving ponds. Complex biogeochemistry, in particular extensive biotransformations and foodchain transfer, governs Se ecotoxicology and toxicology, for which the mechanism(s) are still elusive. However, total waterborne Se concentration has been widely used as a criterion for regulating and mitigating Se risk in aquatic ecosystems, which does not account for Se biogeochemistry and its site-dependence. There is a need for more reliable indicator(s) that encompass Se ecotoxicity and/or toxicity. Selenomethionine warrants special attention since it simulates Se toxicosis of wildlife in laboratory feeding studies. While low in free selenomethionine, microphytes isolated from Se-laden agricultural evaporation ponds were abundant in proteinaceous selenomethionine. This prompted a more extensive survey of Se speciation in foodchain organisms including microphytes, macroinvertebrates, fish, and bird embryos residing mainly in the agricultural drainage systems of the San Joaquin Valley, California. Total Se in biomass, water-soluble fractions, and protein-rich fractions were measured along with GC-MS analysis of proteinaceous selenomethionine. In all foodchain organisms, water-soluble Se constituted the major fraction of total biomass Se, while proteinaceous Se was a substantial, if not dominant, fraction of the water-soluble Se. In turn, proteinaceous selenomethionine comprised an important fraction of proteinaceous Se. In terms of total biomass Se, an average 1400-fold of Se biomagnification from water to microphytes was observed while subsequent transfer from microphytes to macroinvertebrates exhibited an average of only 1.9-fold. The latter transfer was more consistent and greater in extent for proteinaceous Se and proteinaceous selenomethionine, which is consistent with their importance in foodchain transfer. Proteinaceous Se in the omnivorous carp (Cyprinus carpio) liver also demonstrated a relation to ovarian lesions, while deformed stilt (Himantopus mexicanus) embryo was more abundant in proteinaceous selenomethionine than were normal embryos. Although limited in the number of organisms surveyed, these findings provide an impetus for further field and laboratory feeding studies to substantiate the hypothesis that proteinaceous selenomethionine underlies Se ecotoxicity, which may in turn prove to be a reliable indicator of Se risk in aquatic ecosystems.

Vitellogenin from female and estradiol-stimulated male river lampreys (Lampetra fluviatilis L.)

The influence of estradiol-17beta (E(2)) on vitellogenesis is well documented for a number of oviparous craniates. We have examined the role that estradiol-17beta plays in the induction and regulation of vitellogenin synthesis in the maturing European river lamprey, Lampetra fluviatilis. In both females and males the estradiol-17beta concentrations in the plasma reached comparable maximum values in March, only a few weeks before spawning. Throughout the spawning run, the vitellogenin titer in the blood of females remains rather constant while the ovary volume increases. In contrast, we never found circulating VTG in untreated male lampreys. The synthesis and secretion of the yolk precursor molecule can be induced in males, however, by high doses of estradiol injected into the coelom. Lamprey vitellogenin was isolated from the blood of maturing females as well as from hormone-stimulated males and identified by its immunological and electrophoretic properties. In the blood plasma of both maturing female and estradiol-treated male lampreys it always appears simultaneously in two different molecular forms: a vitellogenin monomer with an apparent molecular weight of 310-330kDa and a dimer. After SDS treatment, vitellogenin is represented as a 212-kDa polypeptide.

Some aspects of hepatic function in feral brown trout, Salmo trutta, living in metal contaminated water

Brown trout, Salmo trutta, exposed to heavy metals (mainly Cd and Zn) for at least 2 years in the Eagle River, Colorado, were examined for liver size and activity of the growth-promoting enzyme, ornithine decarboxylase (ODC) and compared to trout living in an uncontaminated site. Liver-somatic index (LSI) was greater for trout living in the uncontaminated site with the LSI of females being significantly greater than that of males. The LSI for females at the uncontaminated site was greater than that of females at the contaminated site, but males were not different statistically. ODC activity in the livers of both males and females was lower at the contaminated site. However, males and females did not differ with respect to ODC activity. These data suggest that chronic exposure to heavy metals may have important implications for growth and reproduction and possibly survival. The activity of ODC in liver might serve as a useful biomarker when assessing chronic toxicity of metals to naturally reproducing fish populations.

Relationship between hepatic deiodination of thyroxine and early oocyte development in rainbow trout, Oncorhynchus mykiss

We examined the relationship between five stages of ovarian growth and development and hepatic microsomal thyroxine (T4) deiodinating activity in rainbow trout, Oncorhynchus mykiss, held in the laboratory at 11.5°C. Thyroxine outer-ring deiodination (T4ORD) activity, which forms biologically active 3,5,3'-triiodothyronine (T3), was low when the gonadosomatic index (GSI = (ovary mass X 100) / body mass) was below 0.2 (stage I, previtellogenesis), but rose sharply between GSI values of 0.2 and 0.3 (stage II), when oocyte Balbiani activity, RNA synthesis, and endogenous vitellogenesis were maximal. Hepatic T4ORD activity was again low during exogenous vitellogenesis at GSI values of 0.3-12, which correspond to stages III-V. Hepatic T4 inner-ring deiodination (T4IRD), which forms biologically inactive 3,3',5'-triiodothyronine, was detected only at stage II. Plasma T3 concentrations were significantly higher at stage II than at stage IV (primary yolk globule formation). Our data indicate changes in systemic thyroidal status at stage II and are consistent with a role for T3 in early oogenesis in trout. Enhanced hepatic T3 production at the late Balbiani stage may be required for oocyte development.

Plasma vitellogenin levels during the annual reproductive cycle of the female rainbow trout (Oncorhynchus mykiss): establishment and validation of an ELISA

Rainbow trout, Oncorhynchus mykiss, vitellogenin (Vtg) was purified from plasma of E2-treated male by direct anion exchange chromatography and some of its biochemical characteristics were studied. Our results demonstrated that, under SDS-PAGE conditions, rainbow trout Vtg was composed of two molecular forms of 390 and 176 kDa representing, respectively, the dimeric form and the monomeric from of the molecule. The purified Vtg was used to raise a polyclonal antibody for Vtg (anti-Vtg). Using this anti-Vtg, a competitive enzyme-linked immunosorbent assay (ELISA) was developed for the quantification of rainbow trout Vtg. The practical sensitivity range of this ELISA was 20-320 ng/ml (80-20% of binding) and the detection limit was 9 ng/ml. The intra- and the inter-assay coefficients of variation (at 50% of binding) were estimated at 1.8% (n = 10) and 3.9% (n = 13), respectively. This ELISA was validated by detecting changes in Vtg levels in rainbow trout at different physiological stages, as well as in 2-year-old female rainbow trout throughout the reproductive cycle.

Liver of the brown trout, Salmo trutta (Teleostei, Salmonidae): a stereological study at light and electron microscopic levels

BACKGROUND

A quantitative study was undertaken for the first time on the normal liver of male and female 2-year-old brown trout, Salmo trutta.

METHODS

Liver was fixed by controlled perfusion. Organ-level morphometry provided weight and volume. A two-stage stereological approach was performed at light and electron microscopy levels. Systematic sampling and point-counting morphometry were used for estimating the relative volumes of the structural compartments. Total absolute volumes of these components were obtained by multiplying each volume density by the volume of its reference space.

RESULTS

Liver volume was 3,423.6 mm3 for males and 3,657.4 mm3 for females. Parenchyma accounted for 95% of hepatic volume. Veins and bile ducts occupied, respectively, 76% and 17% of the stroma, whereas arteries, connective tissue, and melanomacrophages together composed only 6%. Hepatocytes occupied 88% of the parenchyma. Nonhepatocytic cells (endothelium, biliary epithelial cells, Ito cells, and macrophages) composed 4% of the parenchyma, the capillary lumen 6%, and other spaces (Disse space, canaliculi, and lumina of preductules and ductules) composed 2%. Significant sexual differences were found: (1) Females showed a greater parenchymal volume density (0.85% vs. 0.35%) and absolute volume (29.5 mm2 vs. 11.7 mm3) of Ito cells; (2) macrophages of females also presented a greater parenchymal volume density (0.94% vs. 0.46%), but not absolute volume.

CONCLUSIONS

The need to analyze both relative and absolute stereological data was stressed. Similarities and differences were detected between brown trout and other species (fishes and mammals); the findings suggest that, despite architectural differences, some quantitative parameters of liver microanatomy were retained during phylogeny. Factors mediating sexual differences in Ito cells and macrophages were discussed and the need for further studies was highlighted.

Plasma vitellogenin of grouper (Epinephelus malabaricus): isolation and properties

Radiolabelled vitellogenin produced by juvenile grouper following injection of 3H-leucine, 32P-orthophosphate and estradiol-stimulation was purified by anion-exchange and gel filtration chromatography and characterized by electrophoresis and chemical analysis. The radiolabelled product was found to exist in two heterogeneous molecular weight forms by electrophoresis under nondenaturing conditions on polyacrylamide gel with M(r), of 260,000 and 525,000. It showed two protein monomers (M(r) 113,000 and 140,000) on electrophoresis under denaturing condition on a sodium dodecyl sulphate-polyacrylamide gel. The purified material contained 17.2% total lipid with 1.3% cholesterol and 2.1% triglycerides, 8-21 micrograms/mg protein total carbohydrate and 6.8 micrograms phosphate/mg protein; amino acid analysis showed a profile comparable to that found for vitellogenins isolated from the grouper, medaka, goldfish and rainbow trout. The study showed grouper vitellogenin to be a glycophospholipoprotein similar in composition to vitellogenins from other teleosts and demonstrated that vitellogenins can be induced in juveniles by injection with estradiol-17 beta.

Enzyme-linked immunosorbent assay (ELISA) for rainbow trout (Oncorhynchus mykiss) vitellogenin

1. A specific and simple enzyme-linked immunoassay for rainbow trout (Onchorynchus mykiss) vitellogenin (Vtg) is described. This assay is performed using a rabbit antiserum for Vtg purified from trout plasma. 2. This assay is based upon the competition between soluble Vtg and Vtg adsorbed on microtiter plates, for the rabbit anti-Vtg antibody binding sites. 3. The adsorbed Vtg-antibody complexes are revealed through the peroxidase-antiperoxidase antibody, which is colored by o-phenylendiamin. This assay can be performed in a day and a night. 4. Under our conditions, 90-20% of binding gave a sensibility range of 33-1473 ng/ml. With almost a 50% binding yield (335 ng/ml) the intra-assay coefficient of variation (CV) was 5.2% (n = 26) and the inter-assay CV was 12.5% (n = 5). 5. There was low immunological cross-reactivity with sera from other salmonids and with ovary extracts. Extracts of liver from oestrogenized male rainbow trout yielded displacements parallel to the vitellogenin standard and to mature female serum or oestrogenized male serum. 6. This enzyme immunoassay is simple and easy to use. Its great specificity allows its use only for the rainbow trout species.

Sex differences in hepatic monooxygenases in winter flounder (Pseudopleuronectes americanus) and scup (Stenotomus chrysops) and regulation of P450 forms by estradiol

Details concerning the endogenous regulation of hepatic cytochrome P450 monooxygenases in teleosts, and the features of this regulation common among fish species, are poorly known. Gonadally mature female winter flounder (Pseudopleuronectes americanus) have been reported to have severalfold lower levels of microsomal cytochromes P450 and b5 and NADPH-cytochrome c reductase than do males (Stegeman and Woodin ('84) Mar. Environ. Res., 14:422-425). These strong sex differences prompted more detailed study of P450 regulation in winter flounder liver, and a comparison with sex differences in another marine teleost, scup (Stenotomus chrysops). Ethoxyresorufin O-deethylase (EROD) activity/nmol P450 was less in gonadally mature females than in males of both species. Immunoblot analysis with MAb 1-12-3 to P450E (the EROD catalyst) showed that the content of P450E counterpart was also much less in females of both species. Aminopyrine N-demethylase (APND) and testosterone 6 beta-hydroxylase (6 beta-OHase) activities per nmol P450 were higher in gonadally mature female than in mature male flounder, differences not seen in scup. Polyclonal antibodies to scup P450A were shown to detect proteins in a number of teleosts. The levels of anti-P450A cross-reacting protein were greater in mature female than in male flounder, but as with 6 beta-OHase activity, the content of this protein was not sexually differentiated in scup. Estradiol treatment of winter flounder depressed the rates of EROD, APND, 6 beta-OHase, and estradiol 2-OHase activities per mg protein, but APND and 6 beta-OHase activities per nmol P450 were unchanged. Thus, E2 promotes general decreases in some hepatic P450-catalyzed activities, but in achieving sex differences there is also specific regulation of the P450E counterpart, and possibly of the 6 beta-OHase (P450A?). Other factors, temporal or hormonal, can modify the effect of E2 treatment, and may contribute to the specific regulation of P450 forms in naturally maturing fish, and to species differences in this regulation.

Plasma zinc as an index of vitellogenin production and reproductive status in the domestic fowl

1. A technique is described for the accurate determination of circulating vitellogenin concentrations by measurement of plasma zinc concentrations before and after selective precipitation of lipoproteins in the domestic fowl. 2. Vitellogenin zinc concentrations exhibit a high degree of correlation with those of another major egg yolk precursor, very low density lipoprotein (VLDL) in immature female birds, during developing and maximum egg production in mature birds and following cessation of egg laying. 3. Mature female patterns of plasma vitellogenin and VLDL were induced by injection of oestradiol 17 beta (5 mg/kg body weight per day for 3 days) into adult cockerels. 4. It is suggested that measurement of plasma zinc provides a simple and accurate technique for the estimation of vitellogenin production and reproductive status in the domestic fowl and that this may be applied to other oviparous vertebrates.

Functional units in rainbow trout (Salmo gairdneri, Richardson) liver: III. Morphometric analysis of parenchyma, stroma, and component cell types

Hepatic stroma and parenchyma with its component cell types were quantitatively described in adult male and female actively-spawning 5-year-old rainbow trout (Salmo gairdneri, Richardson). Point-count morphometry of glycol methacrylate sections estimated volume compartments for stroma and parenchyma. Veins composed 85% of the stroma while arteries and bile ducts occupied approximately 6-7% each. Parenchyma accounted for 95% of hepatic volume. Point-count morphometry of transmission electron micrographs estimated volume compartments as well as numerical and surface density measurements for parenchymal components. Within the hepatic parenchymal compartment, hepatocytes occupied 85% and showed significant sex differences. Female hepatocytes were significantly more numerous but were smaller, only 60% of the volume of male hepatocytes. Since hepatocyte nuclear volume was equal in both sexes, differences were due to reduced cytoplasmic volume in females. Perisinusoidal macrophages of females occupied larger volumes of their respective parenchymal compartments, and their larger mean cytoplasmic volumes suggested activation. Biliary epithelial cells of preductules and ductules were numerous. Ratios of numerical density of hepatocytes to biliary epithelial cells were consistent with a tubular arrangement of hepatocytes. Factors possibly mediating the sexual dimorphism are discussed.

A role of metallothionein in zinc regulation after oestradiol induction of vitellogenin synthesis in rainbow trout, Salmo gairdneri

The regulation of metallothionein (MT) biosynthesis in rainbow-trout liver was studied after a single intraperitoneal injection of oestradiol-17 beta. Sampling was performed after 2, 7, 14, 21, 28 and 35 days. Following induction of vitellogenin synthesis in the liver, liver somatic index (LSI) rose from 1.25 to 2.00 in 14 days. Associated with the increase in LSI was an elevation of hepatic vitellogenin mRNA and zinc concentrations. The vitellogenin mRNA concentrations peaked at 7 days after treatment. The zinc concentrations increased to a peak at day 14. MT was analysed by using differential pulse polarography and a rainbow-trout MT RNA probe. The MT mRNA concentrations rose after 14 days and remained elevated at 21 and 28 days. The MT concentrations increased after 14 days and remained elevated throughout the experimental period. The concentrations of MT-bound zinc increased in association with the elevation in MT concentrations in the oestradiol-treated rainbow trout. These findings indicate that MT is involved in the regulation of zinc during the period of vitellogenin induction and that MT may function by maintaining the pool of available zinc at an appropriate concentration.

High-affinity binding of [3H]estradiol-17 beta by an estrogen receptor in the liver of the turtle

Specific [3H]estradiol-17 beta ([3H]E2) binding activity (EBA) with characteristics of an estrogen receptor (ER) was demonstrated in cytosols and nuclear extracts of the female turtle, Chrysemys picta. Three different receptor assays (dextran-coated charcoal assay, hydroxylapatite batch procedure, and DNA-cellulose chromatography) were evaluated in terms of their applicability in analyzing large numbers of samples. For the measurement of cytosolic EBA, the hydroxylapatite batch procedure was found to be the most reliable assay. On the other hand, the dextran-coated charcoal assay was found to be the most appropriate method for the measurement of nuclear EBA. Turtle hepatic EBA binds [3H]E2 with high affinity (cytosolic, 17.4 +/- 2.8 X 10(9) M-1; nuclear, 17.7 +/- 1.9 X 10(9) M-1), limited capacity (cytosolic, 133.7 +/- 4.6 fmol/g tissue; nuclear, 81.1 +/- 9.0 fmol/g tissue), and strict steroid specificity. The EBA bound natural estrogens (E2, estrone, estriol) as well as the nonsteroidal estrogen, diethylstilbestrol, but exhibited little affinity for androgens, progesterone, or corticosterone. The turtle hepatic EBA resembled mammalian and avian ERs in terms of binding characteristics; however, unlike mammalian and avian ERs it was shown to be heat-labile. Incubation at 30 degrees caused rapid loss of [3H]E2 binding activity in both cytosolic and nuclear fractions. The exchange between [3H]E2 and the endogenously bound estrogen was slow at 4 and 15 degrees, but the exchange process was facilitated in the presence of the chaotropic salt, NaSCN. Establishment of quantitation methods for both cytosolic and nuclear forms of EBA will enable future investigation of the mechanism and regulation of estrogen action in the liver of this turtle species.

An investigation of an estrogen-binding component in the liver and plasma of brook char, Salvelinus fontinalis

1. Estrogen-binding activity was investigated in liver nuclear and cytosolic preparations of sexually mature female brook char, Salvelinus fontinalis. Nuclear salt extracts of estrogen-injected fish were found to contain high affinity binding sites (Kd = 1.6 nM, capacity = 2.8 fM/ug DNA). 2. Low levels of high-affinity specific binding activity were found in the cytosol of both injected and untreated fish (Kd = 7.5 nM, capacity = 16.1 fM/mg protein). 3. Binding sites in both preparations were specific for estrogens with no significant competition by 5 alpha-dihydrotestosterone, progesterone, or cortisone. 4. A plasma-binder was found to have distinctive differences with regard to structural specificity compared to the estrogen-binding component in liver. It was found to have no affinity for diethylstilbestrol while having some affinity for both 5 alpha-dihydrotestosterone and progesterone. 5. The brook char liver estrogen-binding component was observed to have characteristics in common with estrogen receptors found in other vertebrates.

Morphologic and histochemical analysis of the newt (Notophthalmus viridescens) liver

Architectural arrangement, ultrastructure, and selected histochemical properties of the newt (Notophthalmus viridescens) liver were examined. Although hematopoietic tissue (1-4 cells thick) invested the liver, direct vascular communication between this tissue and hepatic parenchyma was not observed. The liver was intensely positive when stained with Oil-red-O and periodic acid-Schiff reagent and connective tissue was limited to large vascular channels and the capsule. A distinctive polarity was observed in the hepatic vascular system when lobes were viewed in cross section. Dorsally, portal venules accompanied arterioles and branches of the biliary system, while tributaries of hepatic veins were observed ventrally. Following perfusion fixation, hepatocytes appeared as sheets of cells 1-5 cells thick; however, lobules as defined in adult mammalian liver were absent. Hepatocytes contained abundant smooth endoplasmic reticulum, mitochondria, electron-dense lysosomes, patches of granular endoplasmic reticulum, and lipid droplets. Continuous endothelial cells lined sinusoids and exhibited fenestrae organized into structures similar to sieve plates observed in mammalian liver. Variable numbers of melanin-containing macrophages and subendothelial macrophages were observed; however, Kupffer cells and lipid containing perisinusoidal fat-storing cells were not seen. Patterns of reaction product for glucose-6-phosphatase (G-6-Pase), glucose-6-phosphate dehydrogenase (G-6-PDH), and succinic dehydrogenase (SDH) were localized in the newt liver. All enzymes exhibited a uniform distribution pattern; however, small punctate regions of intensely positive G-6-PDH cells were noted within hepatic parenchyma. Cells comprising the hematopoietic tissue were intensely positive for G-6-Pase, G-6-PHD, and negative for SDH.