Carp (Cyprinus carpio) vitellogenin: purification and development of a simultaneous chemiluminescent immunoassay

Synthesis, structure elucidation, and chemiluminescent activity of new 9-substituted 10-(ω-(succinimidyloxycarbonyl)alkyl)acridinium esters

Several new acridinium esters 2-9 having their central acridinium ring bearing a 9-(2,5-dimethylphenoxycarbonyl), 9-(2,6-bis(trifluoromethyl)phenoxycarbonyl) or 9-(2,6-dinitrophenoxycarbonyl) group, and a 10-methyl, 10-(3-(succinimidyloxycarbonyl)propyl), 10-(5-(succinimidyloxycarbonyl)pentyl), or 10-(10-(succinimidyloxycarbonyl)decyl) group, have been synthesized and their chemiluminescent properties have been tested. The 2,5-dimethylphenyl acridinium esters emit light slowly (glow) when treated with alkaline hydrogen peroxide, while the 2,6-dinitrophenyl and 2,6-bis(trifluoromethyl)phenyl esters emit light rapidly (flash). The substituent at the 10 position affects the hydrolytic stabilities of the compounds.

Physicochemical and bioinformatic characterization of Oreochromis niloticus vitellogenin as an endocrine disruption biomarker

Aquatic biota is increasingly being exposed to chemical pollutants due to human activities and the relationship between the level of environmental pollution and fish reproduction is a continuously ongoing issue. The vitellogenin (Vtg) protein synthesis can be induced in the liver of juvenile and male fish after stimulation of the estrogen receptor and therefore, Vtg has been used as a biomarker of xenoestrogen exposure in several fish species. The current study reported the first physicochemical characterization of Vtg from Oreochromis niloticus. Adult male fish were exposed to 17α-ethinylestradiol for Vtg induction. Purified vitellogenin from plasma showed low stability at 25 and 4 °C in saline conditions, and good stability in acidic (low pH) or in heated conditions. The 3D modeling provided useful information on the structure of O. niloticus Vtg showing conserved structural features. According to bioinformatics and experimental results, there are important structural differences between the two chemical forms of Vtg (VtgAb and VtgC) in a phylogenetic context. The present results add information about the development of ecotoxicological immunoassays to study the endocrine disruption in O. niloticus improving the Vtg performance as a biomarker of reproduction in fish.

Kinetic determination of vitellogenin induction in the epidermis of cyprinid and perciform fishes: Evaluation of sensitive enzyme-linked immunosorbent assays

Induction of vitellogenin (VTG) in male and immature fish is a standardized endpoint in endocrine-disruption testing. To establish a nondestructive swab sampling method, VTG induction in the epidermis of Cypriniformes and Perciformes species was investigated. Both VTG and estrogen receptor genes are expressed in epidermal cells. Immunoaffinity and mass fingerprint analyses show induction of identical VTG peptides in liver and epidermis. Induction of VTG by estradiol (E2) and bisphenol A (BPA) in the epidermis was quantified with homolog enzyme-linked immunosorbent assays. Initial values in juveniles and males were below 1 ng VTG/mL extraction buffer. Exposure to E2 led to values between 200 ng/mL and 4600 ng/mL in cyprinids and between 10 ng/mL and 81 ng/mL in perciforms. Exposure to BPA increased VTG amounts to 250 ng/mL in fathead minnows, 1360 ng/mL in goldfish, 100 ng/mL in zebrafish, and 12 ng/mL in bluegills. Serum VTG contents demonstrated a similar dose-response pattern in the epidermis and the blood. These results show that VTG induction may be reliably assessed in the skin mucus of fishes, demonstrating the suitability of this biological sample for investigating estrogenic activity in compliance with Organisation for Economic Co-operation and Development standard protocols. This broadens the perspectives in toxicological screening and environmental monitoring, reducing the number of tested animals and minimizing harmful effects for animals, allowing for follow-up of individual induction profiles. Environ Toxicol Chem 2016;35:2916-2930. © 2016 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals, Inc. on behalf of SETAC.

Development of a lipovitellin-based goldfish (Carassius auratus) vitellogenin ELISA for detection of environmental estrogens

The susceptibility of vitellogenin (Vtg) to degradation is a major problem affecting the robustness of enzyme-linked immunosorbent assay (ELISA) for goldfish (Carassius auratus) Vtg. In this study, a phospholipoglycoprotein with molecular mass of ∼420kDa was purified from goldfish egg extracts and it produced a single band corresponding to ∼112kDa in SDS-polyacrylamide gel electrophoresis (SDS-PAGE). Additionally, the amino acid composition of the purified protein was comparable to that of lipovitellin (Lv) from other fish species. Thus, the purified protein was identified as goldfish Lv. Purified Lv and anti-Lv polyclonal antiserum were used to develop an ELISA with a detection range between 31.25 and 1000ngmL(-)(1). The intra- and inter-assay coefficients of variation were 6.45% and 7.08%, respectively. The immunological similarity between goldfish Vtg and Lv was confirmed by immunoelectrophoresis and Western blot. Goldfish Lv showed higher stability than Vtg after -80°C storage, multiple freeze/thaw cycles, and heat treatment. Moreover, the use of treated Lv in the ELISA did not change the slopes of standard curves. Parallelism between the Lv standard curve and plasma dilution curves of vitellogenic females confirmed the validity of the assay for quantifying plasma Vtg. The Lv-based Vtg ELISA was further applied to evaluate the estrogenic activity of monocrotophos pesticide.

Preparation of a polyclonal antibody against goldfish (Carassius auratus) vitellogenin and its application to detect the estrogenic effects of monocrotophos pesticide

Goldfish (Carassius auratus) represents a good model to detect the estrogenic effects of chemicals, and vitellogenin (Vtg) is a vital indicator of estrogenic activity. The heterologous anti-carp Vtg antibody has previously been used for goldfish Vtg detection. Here, we report the preparation of an anti-goldfish Vtg antibody to improve the sensitivity and specificity of goldfish Vtg immunoassays. Vtg was purified from the plasma of 17β-estradiol (E2)-induced goldfish by gel filtration followed by anion-exchange chromatography. It was characterized as a phospholipoglycoprotein with an apparent molecular weight of ~460 kDa and separated into three major polypeptides corresponding to ~130, ~106, and ~81 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). A polyclonal antibody against goldfish Vtg was raised in rabbits and found to be specific for goldfish Vtg through immunoelectrophoresis and Western blot. A sensitive sandwich enzyme-linked immunosorbent assay (ELISA) was developed for the quantification of plasma Vtg, with a detection limit of 3.6 ng/mL and a detection range from 7.8 to 250 ng/mL. The intra- and inter-assay coefficients of variations were 2.4-6.8% and 6.7-10.8%, respectively. Additionally, we qualitatively and quantitatively detected the induction of Vtg in male fish exposed to 0.01, 0.01, and 1.00 mg/L monocrotophos pesticide by Western blot and ELISA. The homologous sandwich ELISA based on the anti-goldfish Vtg antibody could provide a valuable tool for the study of estrogenic effects of exogenous chemicals on goldfish.

Purification and partial characterization of vitellogenin from spotted wolffish (Anarhichas minor) and development of an enzyme-linked immunosorbent assay for the determination of gender and sexual maturity

Vitellogenin (VTG) from spotted wolffish, Anarhichas minor, a candidate species for cold-water marine aquaculture, was purified by MgCl₂/EDTA precipitation followed by a two-step chromatographic procedure. VTG had an apparent molecular mass of 470 kDa, as determined by gel filtration, and an amino acid composition similar to those of other teleosts. Sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis of the purified VTG revealed a major band with a relative molecular weight of 166 kDa and some minor bands. Spotted wolffish VTG (sw-VTG) is relatively robust to in vitro degradation, as shown when samples of purified VTG and plasma from mature females subjected to various storage conditions or multiple freeze/thaw cycles were analyzed by Western blot. We developed an indirect competitive enzyme-linked immunosorbent assay (ELISA) using an antibody against Atlantic wolffish (Anarhichas lupus) VTG and purified sw-VTG. The ELISA had a detection limit of 6.7 ng/ml and a working range of 16.2-787.5 ng/ml, with intra- and inter-assay coefficients of variation ranging from 1.5 to 7.3 % and 7.1 to 14.3 %, respectively. The assay could distinguish males from immature females and discriminate maturing females at different stage of oocyte development. These results suggest that the sw-VTG ELISA would be useful in spotted wolffish aquaculture to determine sex and monitor female maturation.

Effects of illegal cyanide fishing on vitellogenin in the freshwater African catfish, Clarias gariepinus (Burchell, 1822)

The effects of cyanide, used in illegal fishing, on one of the most economically important Nile fishes, the African catfish (Clarias gariepinus), were studied. Cyanide impacts were evaluated in terms of biochemical, molecular and histopathological characteristics. After exposure to sublethal concentration (0.05mg/l) of potassium cyanide (KCN) for two and four weeks, GOT (glutamate oxaloacetate transaminase) was significantly increased in both male and female, while GPT (glutamate pyruvate transaminase), total plasma protein, phosphoprotein phosphorus (Vgt) in serum, vitellogenin gene expression (Vtg mRNA) and estrogen receptors (ER mRNA) were significantly decreased in female. On the other hand, male C. gariepinus showed a significant increase in Vtg and Vtg mRNA. Liver, testis and ovaries showed distinct histopathological changes. It was concluded that, cyanide caused damaging effects to fish and can cause serious disturbance in the natural reproduction and a drastic decline in fish population. Therefore, it is recommended that, the use of cyanide compounds must be prohibited to conserve the fisheries resources.

Isolation and partial characterization of Asian sea bass (Lates calcarifer) Vitellogenin

A study was conducted to isolate, partial characterize Asian sea bass (Lates calcarifer) vitellogenin (vtg). Two-year-old juvenile L. calcarifer (n = 10) were given three intraperitoneal injections of 17-β estradiol (E2) at a dose of 2 mg/kg body weight to induce vitellogenesis. Blood was collected 3 days after the last injection, and plasma was purified through gel filtration chromatography. A broad single symmetrical peak consisting of vtg molecule was produced. Protein concentration was 0.059 mg/ml as determined by Bradfrod assay using bovine serum albumin as a standard. The protein appeared as one circulating form in Native PAGE considering the dimeric form of putative vtg with molecular weight of 545 kDa. In SDS-PAGE under reducing conditions, two major bands appeared at 232.86 and 118.80 kDa and minor bands at 100.60, 85.80 and 39.92 kDa, respectively. The purified vtg was used to generate a polyclonal antibody, and the specificity of antibody was assessed by Western blot analysis. Two major bands were immunoreacted, but no cross-reactivity was observed with plasma from non-induced males. The protein was characterized as phosphoglycolipoprotein as it positively stained for the presence of lipid, phosphorus and carbohydrate using Sudan Black B, methyl green and periodic acid/Schiff reagent solution, respectively. The amino acid composition was analyzed by high sensitivity amino acid analysis that showed high percentage of non-polar amino acids (~48 %). The results suggest the potential utilization of vtg as a basis tool to further study about reproductive physiology of this important economical species.

Characterization of vitellogenin and its derived yolk proteins in cloudy catshark (Scyliorhinus torazame)

Elasmobranchs (sharks and rays) exhibit unique reproductive characteristics and, in contrast to the situation in teleosts, very little is known about the identity, structure and physical characteristics of their egg yolk proteins. The aims of this study were to (1) detect and purify the vitellogenin (Vtg; egg yolk precursor) and yolk proteins (YPs) of the cloudy catshark (Scyliorhinus torazame), (2) examine the relationships between Vtg and YPs and (3) characterize and classify the deduced primary structure of the Vtg transcript (vtg). The apparent molecular weights of purified Vtg and putative Vtg-related YPs (lipovitellin: Lv, phosvitin: Pv) were determined by gel filtration and were ~560, >669 and ~58 kDa, respectively. Following SDS-PAGE, these purified products (i.e., Vtg, Lv and Pv) appeared as bands of ~210, ~110 and ~22 kDa, respectively. On Western blots, antisera against purified Vtg, Lv and Pv recognized the ~210 kDa Vtg band. Catshark Pv, in contrast to teleost Pvs, had a very low serine content. The catshark Vtg cDNA sequence (vtg) appeared to contain an open-reading frame consisting of domains encoding Lv, Pv and β'-component (β'-c). A phylogenetic analysis, with a consideration of genome duplication events, placed catshark vtg into the 'vtgAB type.' It is concluded that at least a single major type of Vtg protein, which is transcribed and translated from catshark vtgAB gene, is the precursor of three egg yolk proteins (Lv, Pv and β'-c) in catshark.

Induction of vitellogenin synthesis in immature male yellowfin seabream (Acanthopagrus latus) exposed to 4-nonylphenol and 17β-estradiol

In the present study, the effects of xenoestrogen 4-nonylphenol (4-NP) and 17β-estradiol (E2) on the synthesis of vitellogenin (VTG) in immature male yellowfin seabream (Acanthoparus latus) were assessed to determine the potential use of this species as a biological model for studying endocrine disrupters in the Musa estuary in southern seawaters of Iran. A total number of 104 fish were injected by 10, 50, 100, 150 and 200 µg g(-) (1) week(-) (1) of 4-NP and 2 µg g(-) (1) week(-) (1) of E2, and their blood plasma was obtained for biochemical analysis on days 0, 7 and 14. The hepatosomatic index (HSI) of each fish was also recorded at each sampling time. The results showed that 4-NP significantly induced VTG synthesis in A. latus, which was detected by gel electrophoresis as two major protein bands (∼210 and 191 KDa). The induction of VTG was also determined indirectly by measuring the alkali-labile phosphate, total plasma calcium and protein. All of these VTG indicators significantly increased in the plasma of 4-NP- and E2-treated fish. Meanwhile, a significant dose-dependent increase was observed in HSI, indicating the activation of hepatic VTG production in 4-NP- and E2-injected fish. Furthermore, the plasma alanine aminotransferase and aspartate aminotransferase concentrations significantly increased in 4-NP-treated fish, presumably reflecting a situation of hepatic tissue damage due to 4-NP toxicity. Based on the results, it is suggested that A. latus could be used successfully as a model species for future studies of endocrine disrupting contaminants in the Musa estuary.

Detection of vitellogenin incorporation into zebrafish oocytes by FITC fluorescence

BACKGROUND

Large volumes of lymph can be collected from the eye-sacs of bubble-eye goldfish. We attempted to induce vitellogenin (Vtg) in the eye-sac lymph of bubble-eye goldfish and develop a method for visualizing Vtg incorporation by zebrafish oocytes using FITC-labeling.

METHODS

Estrogen efficiently induced Vtg in the eye-sac lymph of goldfish. After FITC-labeled Vtg was prepared, it was injected into mature female zebrafish.

RESULTS

Incorporation of FITC-labeled Vtg by zebrafish oocytes was detected in in vivo and in vitro experiments. The embryos obtained from zebrafish females injected with FITC-labeled Vtg emitted FITC fluorescence from the yolk sac and developed normally.

CONCLUSION

This method for achieving Vtg incorporation by zebrafish oocytes could be useful in experiments related to the development and endocrinology of zebrafish oocytes.

Novel recombinant monoclonal antibodies for vitellogenin assays in cyprinid fish species

Various polyclonal and monoclonal antibodies have been developed for vitellogenin (Vtg) bioassays in different aquatic species. Preparation of these reagents is time-consuming and expensive. In the present study, a phage-displayed, recombinant, single-chain variable fragment (scFv) format antibody library was constructed using splenic mRNA from non-immunized mice. After 3 rounds of panning, 3 scFv antibodies with specificity for the highly conserved N-terminal region of cyprinid fish Vtg were isolated. One of these, antibody H4, bound purified Vtg from common carp Cyprinus carpio, zebrafish Danio rerio and Chinese rare minnow Gobiocypris rarus with similar affinities and detected Vtg in zebrafish plasma samples. This study provides a simple, low cost Vtg bioassay for plasma samples from a variety of cyprinid fish.

Hybrid ELISAs for vitellogenins of the endangered copper redhorse Moxostoma hubbsi and the shorthead redhorse Moxostoma macrolepidotum (Cypriniformes, catostomidae)

The shorthead redhorse (sr) Moxostoma macrolepidotum is endemic in North America, while in Canada the copper redhorse (cr) Moxostoma hubbsi is classified as endangered. A commercial heterologous carp vitellogenin (VTG) sandwich ELISA underestimates VTGs in these species. Hybrid ELISAs, using anti-carp VTG antibodies and purified sr- and cr-VTGs as standards, were validated to measure VTGs in plasma and surface mucus of redhorse species. The hybrid ELISAs showed good precision, sensitivity and accuracy. Following induction with beta-estradiol 3-benzoate (E2B), levels of plasma VTG (mean+/-SEM) in male sr increased from 2.7+/-1.5 microg/ml to 16.5+/-2.2mg/ml. In immature cr, plasma VTG increased to 70.1+/-13.8 mg/ml after induction, from an initial value of 37.7+/-51.0 microg/ml. Levels of VTG in mucus from E2B-injected fish were highly correlated (p<0.0001) with levels in plasma, but not in a non-induced mature female. Hybrid assays are a good compromise between homologous and heterologous assays, especially for small-bodied or endangered fish species. The performance of the hybrid assays strongly suggests they could be used to determine exposure of these species to estrogenic contaminants and contribute to restoration efforts of the copper redhorse.

Estrogenic effects of monocrotophos evaluated by vitellogenin mRNA and protein induction in male goldfish (Carassius auratus)

Monocrotophos (MCP) is listed as a Prior Informed Consent chemical, and it is still used extensively in developing countries. It has been seen that MCP shows high toxicity in fish and aquatic ecosystems. To confirm whether MCP shows estrogenic effects on fish, the induction of vitellogenin (VTG) in male goldfish (Carassius auratus) following a 21 day exposure to 0.01, 0.10 and 1.00 mg x L(-1) 40% MCP pesticide in a semi-static exposure system was evaluated by hepatic mRNA and plasma protein. Real-time reverse transcriptase polymerase chain reaction assay showed that MCP significantly increased hepatic mRNA expression of VTG in male goldfish in a dose-dependent manner. Western blot analysis revealed the presence of two VTG subunits with molecular masses of 134 kDa and 110 kDa in the plasma of the exposure groups, which were not observed in that of the control males, indicating the induction of VTG protein synthesis and secretion by MCP in male goldfish. Furthermore, the levels of plasma VTG protein in the control group and the 0.01, 0.10 and 1.00 mg x L(-1) 40% MCP pesticide exposure groups were quantified by enzyme-linked immunoassay, and revealed concentrations of 53.8+/-5.6 ng x mL(-1), 285.5+/-5.0 ng x mL(-1), 972.9+/-7.4 ng x mL(-1) and 678.4+/-38.0 ng x mL(-1), respectively. The overlapping results of VTG mRNA and protein indicated that MCP had significant estrogenic properties and was thus a potential endocrine disruptor.

Purification and partial characterization of vitellogenin from shorthead redhorse (Moxostoma macrolepidotum) and copper redhorse (Moxostoma hubbsi) and detection in plasma and mucus with a heterologous antibody

Vitellogenin (VTG), the egg yolk precursor protein, was purified from plasma of estradiol-3-benzoate (E2B)-treated male shorthead redhorse (Moxostoma macrolepidotum) and immature copper redhorse (Moxostoma hubbsi) by a two-step chromatographic procedure without precipitation. Intact VTGs appeared as dimers with apparent molecular masses, determined by gel filtration, of approximately 425 kDa (copper redhorse) and approximately 450 kDa (shorthead redhorse). In native polyacrylamide gel electrophoresis (PAGE), dimeric redhorse VTGs appeared as a 520 kDa band. Both VTGs were reduced to a single monomer of approximately 150 kDa in sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) under reducing and nonreducing conditions, indicating that monomers are not linked by disulfide bonds in the dimer form. The purified proteins were characterized as phospholipoglycoproteins. Isoelectric focusing of both VTGs revealed components with isoelectric points ranging from 5.3 to 6.0, suggesting charge heterogeneity. The amino acid composition of both VTGs contains a high proportion of nonpolar amino acids and was similar to those of other teleosts. An antibody developed against carp (Cyprinus carpio) VTG showed cross-reactivity with VTG from both redhorse species. Using this antibody, VTG was detected in plasma and surface mucus of E2B-treated redhorse. This is the most extensive report on purification and characterization of vitellogenin from catostomidid species.

Gender determination in the Paiche or Pirarucu (Arapaima gigas) using plasma vitellogenin, 17beta-estradiol, and 11-ketotestosterone levels

Arapaima gigas is an air-breathing giant fish of Amazonian rivers. Given its great economic and cultural importance, the aquaculture development of this species represents an evident solution to face the decline of wild populations. In captivity, reproduction occurs generally in large earthen ponds where stocks of a few tens of brooders are maintained together at the beginning of the rainy season (December-March in the Peruvian Amazon). Fry production relies on the spontaneous formation of male and female pairs, which build a nest, delimit a territory and guard the offspring for at least 20 days from other congeners and predators. However, as sex determination of A. gigas is not possible by morphological criteria, it is very difficult to optimize reproduction conditions and fry production in each pond, which seriously hampers the culture of this species. This situation prompted us to develop sexing methodologies based on (1) the detection of female specific plasma Vitellogenin (Vtg) using an enzyme immuno assay (EIA), and (2) the determination of plasma 17beta-estradiol and 11-ketotestosterone levels for immature specimens. The Vtg purification was performed by electro-elution after polyacrilamide gel electrophoresis (PAGE) from plasma of 17beta-estradiol treated A. gigas juveniles. Two different Vtg molecules were isolated, (Vtg(1) and Vtg(2)) with 184 and 112 kDa apparent molecular masses, respectively, and two antibodies were raised in rabbits for each Vtg molecule. Adult fish were 100% accurately sexed by Vtg EIA, while 100% of immature fish and 95% of adults were accurately sexed by 17beta-Estradiol and 11-Ketestosterone ratios. We also observed different color pattern development in male and female adult fish (6-year-olds) around the reproductive period.

Optical waveguide light-mode spectroscopy immunosensors for environmental monitoring

Coupling the high specificity of the immunoanalytical reaction with the high sensitivity of optical waveguide light-mode spectroscopy (OWLS) detection gives the possibility to develop immunosensors with in most cases a definitely lower detection limit than traditionally used immunoassays. Measurements were performed on the sensitized surface of optical waveguide grating coupler sensors (2400 lines/mm grating). The OWLS technique is based on the precise measurement of the resonance angle of a polarized laser light (632.8 nm), diffracted by a grating and incoupled into a thin waveguide. The effective refractive index, determined from the resonance incoupling angle detected at high accuracy, allows determination of layer thickness and coverage (or mass) of the adsorbed or bound material with ultrahigh sensitivity. OWLS immunosensors were developed as label-free immunosensors with an amino group modified SiO(2)-TiO(2) sensor surface on which the immunoreactants could be anchored. One of the components of the antibody-antigen complex was chemically bound on the sensor surface, allowing noncompetitive or competitive detection of the analytes. To illustrate that the resulting immunosensors are suitable for the determination of small and large molecular weight analytes, OWLS sensor formats were applied for quantitative detection of a herbicide active ingredient trifluralin, a Fusarium mycotoxin zearalenone, and an egg yolk protein of key importance in endocrine regulation, vitellogenin.

Structural and expression analyses of two vitellogenin genes in the carp, Cyprinus carpio

We cloned and sequenced two vitellogenin (vg) cDNAs of the carp, Cyprinus carpio, using a cDNA library constructed from estradiol-17 beta (E2)-treated livers. One was a novel, longer 5000 bp-long cDNA termed vg-B2 encoding 1624 amino acids in a single open reading frame. The other was a shorter cDNA (vg-B1), identical to that registered previously as carp vg cDNA in the international nucleotide sequence database. The deduced amino acid sequences of these two molecules were well-aligned with known vertebrate Vgs sharing common characteristics such as N-terminal lipovitellin I (LVI), phosvitin (PV) and C-terminal lipovitellin II (LVII). The novel Vg-B2 bore a highly conserved GL/ICG motif within the LVII region, in contrast to the shorter Vg-B1 that has a truncated C-terminal and lacks the beta-component within the LVII region including the GL/ICG motif. Both vg-B2 and vg-B1 genes were expressed in the livers of females and E2-injected males. Western blot analysis using anti-Vg and anti-vitellin (Vn) antisera demonstrated that both Vg-B2 and Vg-B1 were detected as polypeptides with an estimated molecular mass of 180 kDa and 160 kDa, respectively, in the blood of females and E2-injected males. The results suggest the potential utilization of these genes as sensitive xenoestrogenic markers.

Vertebrate Yolk Complexes and the Functional Implications of Phosvitins and Other Subdomains in Vitellogenins1

In nonplacental or nontrophotenic vertebrates, early development depends on the maternal provision of egg yolk, which is mainly derived from large multidomain vitellogenin (Vtg) precursors. To reveal the molecular nature of the protein pools in vertebrate oocytes, published data on the N-termini of yolk proteins has been mapped to the deduced primary structures of their parent Vtgs. The available evidence shows that the primary cleavage sites of Vtgs are conserved, whereas the cleavage products exist as multidomain variants in the yolk protein pool. The serine-rich phosvitin (Pv) domains are linearly related to the molecular masses of the lipovitellin heavy chain. The 3-D localization of Pv maps to the outer edges of the Vtg monomer, where it is proposed to form amphipathic structures that loop up over the lipid pocket. At this locus, it is proposed that Pv stabilizes the nascent Vtg while it receives its lipid cargo, thereby facilitating the hepatic loading and locking of lipid within the Vtg (C-sheet)-(A-sheet)-(LvL) cavity, and enhances its solubility following secretion to the circulating plasma. The C-terminal regions of Vtgs are homologous to human von Willebrand factor type D domains (Vwfd), which are conserved cysteine-rich molecules with homologous regions that are prevalent in Vtgs, lipophorins, mucins, integrins, and zonadhesins. Unlike human VWFD, lower vertebrate Vwfds do not contain RGD motifs, which are associated with extracellular matrix binding. Although its function in Vtg is unknown, the lubricant properties associated with mucins and the cell adhesion properties associated with integrins and zonadhesins implicate Vwfd in the genesis of hemostatic platelet aggregation. Similarly, the proteolytic inhibitory properties associated with the binding of factor VIII in humans suggest that Vwfd stabilizes Vtg during passage in the systemic circulation.

The pesticide heptachlor affects steroid hormone secretion in isolated follicular and luteal cells of rat

Heptachlor, a chlorinated hydrocarbon pesticide, suppresses the production of progesterone and estradiol in the female rat in vivo or in isolated ovaries in vitro. In this study the effect of heptachlor on steroid hormone production by isolated rat luteal and follicular cells, in the presence of two precursor hormones was investigated. Ovaries were isolated from anesthetized mature normocyclic virgin rats (3 to 4 months old), under sterile conditions. Corpora lutea and follicles were microscopically dissected out and separately enzymatically dispersed with collagenase at 37 degrees C. Viable cells collected after centrifugation were used at a concentration of approximately 2.5 x 10(5) cells/10 mL. Both luteal and follicular cell preparations were separately incubated overnight (15 h) at 37 degrees C in the presence of pregnenolone (P5) and androstenedione (A4) at a concentration of 6.0 nmol/L each, and heptachlor at either 0.12 microg/mL (low dose) or 1.20 microg/mL (high dose) (test cells) or in the absence of heptachlor (control cells). At the end of the incubations, progesterone and estradiol 17beta levels were analyzed in the incubation media. The results indicate that heptachlor significantly suppressed the production of both progesterone and estradiol in both cell types in a dose related manner even in the presence of A4 and P5 as precursor hormones (P<0.05).

Tilapia (Oreochromis niloticus) vitellogenins: development of homologous and heterologous ELISAs and analysis of vitellogenin pathway through the ovarian follicle

Vitellogenin (VTG) of Oreochromis niloticus was again purified, due to the conflicting results found in the literature. Three purification processes have been used: electrophoresis and electro-elution, double chromatography (gel filtration and ion-exchange chromatography) and single ion-exchange chromatography. Using SDS-PAGE we confirmed in all cases the presence of two polypeptidic forms of plasma VTG of 130 kDa (VTG1) and 170 kDa (VTG2). We raised polyclonal antibodies against each VTG form and we demonstrated the complete cross-reactivity of each antibody with both forms of VTG by Enzyme Immuno-Assay (EIA) and Western blots. The homologous ELISAs developed exhibited a detection limit of 6 ng x ml(-1), equivalent to 60 ng x ml(-1) of plasma VTG and allowed us to quantify the total plasma VTG of O. niloticus with high specificity and sensitivity. Using photonic and electron immunomicroscopy, we followed the pathway of VTG into the ovarian follicle (OF) demonstrating that VTG enters the oocyte at stage 3 of OF development, at the same time as cortical alveoli and lipid globules appear. Heterologous ELISAs performed on other cichlid species allowed us to quantify plasma VTG in Oreochromis aureus and Sarotherodon melanotheron and to detect it in Hemichromis fasciatus, Hemichromis bimaculatus and Tilapia zillii, constituting a reliable tool for monitoring the presence of xeno-estrogens in the environment of these fish species.

Vitellogenin induction in the endangered goodeid fish Girardinichthys viviparus: vitellogenin characterization and estrogenic effects of polychlorinated biphenyls

Vitellogenin (VTG) is a widely used biomarker in studies of endocrine disruption induced by xenobiotics such as polychlorinated biphenyls (PCBs). This study evaluates the estrogenic effects of these compounds on the black-fin goodeid Girardinichthys viviparus, an endangered fish species in Mexico with a reduced range of distribution due to pollution of its natural environment. Adult fish born in the laboratory were exposed to half the LC(0) of Inerteen commercial PCB mixture. VTG was determined through an inhibition enzyme-linked immunosorbent assay (ELISA) using a homologous-heterologous system. Male and female fish were killed after 1, 2, 4, 8 and 16 days of exposure. The distal third of each specimen was used for analysis. VTG was obtained from cultured hepatocytes and blood serum of males previously exposed to 17beta-estradiol. VTG molecular mass was 348 kDa. PCBs were found to elicit greater estrogenic effects on VTG induction in males than in females (p<0.05) and sex differences were noted. Time-dependent VTG induction kinetics in males and a stationary phase in females were also observed.

Rapid Determination of Vitellogenin in Fish Plasma by Anion Exchange High Performance Liquid Chromatography Using Postcolumn Fluorescence Derivatization with o-Phthalaldehyde

An analytical method involving anion exchange high performance liquid chromatographic determination of vitellogenin (Vtg) in fish plasma after postcolumn fluorescence derivatization with o-phthalaldehyde (OPA) was developed. The retention time of Vtg was about 11 min. The reagent variables for derivatization were optimized. The fluorophore was excited at 335 nm and detected at 435 nm. A calibration curve was established ranging from 0.13 to 11.28 microg. The determination limit of Vtg was found to be as low as 0.13 microg. The spiked recovery was 93.6% and interassay variability was less than 4%. The method developed was used to determine Vtg in fish plasma obtained from red sea bream (Pagrosomus major), black porgy (Sparus macrocephalus) and skew band grunt (Hapalogenys nitens), without complicated sample pretreatment. The results confirmed that the method showed advantages of being simple, rapid, reproducible and sensitive.

A novel enzyme-linked immunosorbent assay system for the quantitative analysis of Carassius auratus vitellogenin

A sandwich enzyme-linked immunosorbent assay (ELISA) was developed to quantitatively detect Carassius auratus vitellogenin (VTG) levels. The protein levels in fish plasma are useful aquatic biomarkers of estrogenic compounds. This procedure involved an ELISA using monoclonal antibodies of CVmA2 and CVmA7 against Carassius auratus VTG, and CVmA7 conjugated to horseradish peroxidase as the detection antibody. The assay range was between 1 and 401.5 ng/ml and the recovery of the VTG added to Carassius auratus plasma was 92.5-109%. An in vitro assay was performed to measure low levels of the VTG, using primary hepatocytes of Carassius auratus induced by 17-beta estradiol (E2). The detection limit was 1 ng/ml and 137 ng/ml at the maximum. Within each sex of wild Carassius auratus, VTG levels from the river next to sewage treatment works (STWs) were much higher than those from the feeding stream. The Carassius auratus VTG bioassay could be a sensitive and useful tool for quantification of estrogenic principles in aquatic environments.

Transcript and protein environmental biomarkers in fish--a review

The levels of contaminant-affected gene products (transcripts and proteins) are increasingly utilized as environmental biomarkers, and their appropriate implementation as diagnostic tools is discussed. The required characteristics of a gene product biomarker are accurate evaluation using properly normalized absolute units, aiming at long-term comparability of biomarker levels over a wide geographical range and among many laboratories. Quantitative RT-PCR and competitive ELISA are suggested as preferred evaluation methods for transcript and protein, respectively. Constitutively expressed RNAs or proteins which are part of the examined homogenate are suggested as normalizing agents, compensating for variable processing efficiency. Essential characterization of expression patterns is suggested, providing reference values to be compared to the monitored levels. This comparison would enable estimation of the intensity of biological effects of contaminants. Contaminant-independent reference expression patterns should include natural fluctuations of the biomarker level. Contaminant-dependent patterns should include dose response to model contaminants chronically administered in two environmentally-realistic routes, reaching extreme sub-lethal affected levels. Recent studies using fish as environmental sentinel species, applying gene products as environmental biomarkers, and implementing at least part of the depicted methodologies are reviewed.

Effect of nonylphenol on plasma vitellogenin of male adult guppies (Poecilia reticulata)

Adult male guppies (Poecilia reticulata) were exposed to 4-nonylphenol (NP) at nominal concentrations of 10, 60, and 150 microg/L for 7, 14, or 21 days. Significant induction of vitellogenin (VTG) was found in male guppies exposed to 1 microg/L of 17beta-estradiol and 60 or 150 microg/L of NP after 7, 14, or 21 days. Maximum induction was seen after 14 days of treatment at these concentrations. On the other hand, significant induction of VTG in male guppies exposed to 10 microg/L of NP was observed only after 21 days of treatment. A time-dependent tendency of reduction of the gonadosomatic index (GSI) in male guppies treated with 17beta-estradiol or NP was observed, but no corresponding concentration-dependent tendency was detected. There were also no differences in the liver somatic index (LSI) of male fish treated with various concentrations of NP during the above-mentioned exposure periods. Preliminary data presented in this study strongly suggests that measurement of plasma VTG induction in male guppies is a suitable and rather sensitive indicator of exposure to estrogenic chemicals.

Reproductive responses of common carp (Cyprinus carpio) exposed in cages to influent of the Las Vegas Wash in Lake Mead, Nevada, from late winter to early spring

The Las Vegas Wash (LW) delivers tertiary-treated municipal wastewater effluent, nonpotable shallow groundwater seepage, and runoff from the urbanized Las Vegas Valley to Las Vegas Bay (LX) of Lake Mead. To investigate the potential for contaminants in LW influent to produce effects indicative of endocrine disruption in vivo, adult male and female common carp (Cyprinus carpio) were exposed in cages for 42-48 d at four sites in Lake Mead: LW, LX, and two reference locations in the lake. End points examined included gonadosomatic index; gonad histology; concentrations of plasma vitellogenin (VTG) and plasma sex steroids (17beta-estradiol (E2), testosterone (T), 11-ketotestosterone (11-KT)); plasma estrogen:androgen ratios (E2:T, E2:11-KT), in vitro production of T by gonad tissue, and hepatopancreas ethoxyresorufin O-deethylase activity. Few differences among fish caged at different sites were potentially attributable to exposure to contaminants