Microparticle formulations alter the toxicity of fenofibrate to the zebrafish Danio rerio embryo

A wide variety of active pharmaceutical ingredients are released into the environment and pose a threat to aquatic organisms. Drug products using micro- and nanoparticle technology can lower these emissions into the environment by their increased bioavailability to the human patients. However, due to this enhanced efficacy, micro- and nanoscale drug delivery systems can potentially display an even higher toxicity, and thus also pose a risk to non-target organisms. Fenofibrate is a lipid-regulating agent and exhibits species-related hazards in fish. The ecotoxic effects of a fenofibrate formulation embedded into a hydroxypropyl methylcellulose microparticle matrix, as well as those of the excipients used in the formulation process, were evaluated. To compare the effects of fenofibrate without a formulation, fenofibrate was dispersed in diluted ISO water alone or dissolved in the solvent DMF and then added to diluted ISO water. The effects of these various treatments were assessed using the fish embryo toxicity test, acridine orange staining and gene expression analysis assessed by quantitative RT polymerase chain reaction. Exposure concentrations were assessed by chemical analysis. The effect threshold concentrations of fenofibrate microparticle precipitates were higher compared to the formulation. Fenofibrate dispersed in 20%-ISO-water displayed the lowest toxicity. For the fenofibrate formulation as well as for fenofibrate added as a DMF solution, greater ecotoxic effects were observed in the zebrafish embryos. The chemical analysis of the solutions revealed that more fenofibrate was present in the samples with the fenofibrate formulation as well as fenofibrate added as a DMF solution compared to fenofibrate dispersed in diluted ISO water. This could explain the higher ecotoxicity. The toxic effects on the zebrafish embryo thus suggested that the formulation as well as the solvent increased the bioavailability of fenofibrate.

Accelerating Drug Discovery Efforts for Trypanosomatidic Infections Using an Integrated Transnational Academic Drug Discovery Platform

According to the World Health Organization, more than 1 billion people are at risk of or are affected by neglected tropical diseases. Examples of such diseases include trypanosomiasis, which causes sleeping sickness; leishmaniasis; and Chagas disease, all of which are prevalent in Africa, South America, and India. Our aim within the New Medicines for Trypanosomatidic Infections project was to use (1) synthetic and natural product libraries, (2) screening, and (3) a preclinical absorption, distribution, metabolism, and excretion-toxicity (ADME-Tox) profiling platform to identify compounds that can enter the trypanosomatidic drug discovery value chain. The synthetic compound libraries originated from multiple scaffolds with known antiparasitic activity and natural products from the Hypha Discovery MycoDiverse natural products library. Our focus was first to employ target-based screening to identify inhibitors of the protozoan Trypanosoma brucei pteridine reductase 1 ( TbPTR1) and second to use a Trypanosoma brucei phenotypic assay that made use of the T. brucei brucei parasite to identify compounds that inhibited cell growth and caused death. Some of the compounds underwent structure-activity relationship expansion and, when appropriate, were evaluated in a preclinical ADME-Tox assay panel. This preclinical platform has led to the identification of lead-like compounds as well as validated hits in the trypanosomatidic drug discovery value chain.

Evaluation of potential environmental toxicity of polymeric nanomaterials and surfactants

Nanomaterials have gained huge importance in various fields including nanomedicine. Nanoformulations of drugs and nanocarriers are used to increase pharmaceutical potency. However, it was seen that polymeric nanomaterials can cause negative effects. Thus, it is essential to identify nanomaterials with the least adverse effects on aquatic organisms. To determine the toxicity of polymeric nanomaterials, we investigated the effects of poly(lactic-co-glycolid) acid (PLGA), Eudragit® E 100 and hydroxylpropyl methylcellulose phthalate (HPMCP) on zebrafish embryos using the fish embryo toxicity test (FET). Furthermore, we studied Cremophor® RH40, Cremophor® A25, Pluronic® F127 and Pluronic® F68 applied in the generation of nanoformulations to identify the surfactant with minimal toxic impact. The order of ecotoxicty was HPMCP < PLGA < Eudragit® E100 and Pluronic® F68 < Pluronic® F127 < Cremophor® RH40 < Cremophor® A25. In summary, HPMCP and Pluronic® F68 displayed the least toxic impact, thus suggesting adequate environmental compatibility for the generation of nanomedicines.

Fishing for contaminants: identification of three mechanism specific transcriptome signatures using Danio rerio embryos

In ecotoxicology, transcriptomics is an effective way to detect gene expression changes in response to environmental pollutants. Such changes can be used to identify contaminants or contaminant classes and can be applied as early warning signals for pollution. To do so, it is important to distinguish contaminant-specific transcriptomic changes from genetic alterations due to general stress. Here we present a first step in the identification of contaminant class-specific transcriptome signatures. Embryos of zebrafish (Danio rerio) were exposed to three substances (methylmercury, chlorpyrifos and Aroclor 1254, each from 24 to 48 hpf exposed) representing sediment typical contaminant classes. We analyzed the altered transcriptome to detect discriminative genes significantly regulated in reaction to the three applied contaminants. By comparison of the results of the three contaminants, we identified transcriptome signatures and biologically important pathways (using Cytoscape/ClueGO software) that react significantly to the contaminant classes. This approach increases the chance of finding genes that play an important role in contaminant class-specific pathways rather than more general processes.

Linking the response of endocrine regulated genes to adverse effects on sex differentiation improves comprehension of aromatase inhibition in a Fish Sexual Development Test

The Fish Sexual Development Test (FSDT) is a non-reproductive test to assess adverse effects of endocrine disrupting chemicals. With the present study it was intended to evaluate whether gene expression endpoints would serve as predictive markers of endocrine disruption in a FSDT. For proof-of-concept, a FSDT according to the OECD TG 234 was conducted with the non-steroidal aromatase inhibitor fadrozole (test concentrations: 10μg/L, 32μg/L, 100μg/L) using zebrafish (Danio rerio). Gene expression analyses using quantitative RT-PCR were included at 48h, 96h, 28days and 63days post fertilization (hpf, dpf). The selection of genes aimed at finding molecular endpoints which could be directly linked to the adverse apical effects of aromatase inhibition. The most prominent effects of fadrozole exposure on the sexual development of zebrafish were a complete sex ratio shift towards males and an acceleration of gonad maturation already at low fadrozole concentrations (10μg/L). Due to the specific inhibition of the aromatase enzyme (Cyp19) by fadrozole and thus, the conversion of C19-androgens to C18-estrogens, the steroid hormone balance controlling the sex ratio of zebrafish was altered. The resulting key event is the regulation of directly estrogen-responsive genes. Subsequently, gene expression of vitellogenin 1 (vtg1) and of the aromatase cyp19a1b isoform (cyp19a1b), were down-regulated upon fadrozole treatment compared to controls. For example, mRNA levels of vtg1 were down-regulated compared to the controls as early as 48 hpf and 96 hpf. Further regulated genes cumulated in pathways suggested to be controlled by endocrine mechanisms, like the steroid and terpenoid synthesis pathway (e.g. mevalonate (diphospho) decarboxylase (mvd), lanosterol synthase (2,3-oxidosqualene-lanosterol cyclase; lss), methylsterol monooxygenase 1 (sc4mol)) and in lipid transport/metabolic processes (steroidogenic acute regulatory protein (star), apolipoprotein Eb (apoEb)). Taken together, this study demonstrated that the existing Adverse Outcome Pathway (AOP) for aromatase inhibition in fish can be translated to the life-stage of sexual differentiation. We were further able to identify MoA-specific marker gene expression which can be instrumental in defining new measurable key events (KE) of existing or new AOPs related to endocrine disruption.

Persistence of endocrine disruption in zebrafish (Danio rerio) after discontinued exposure to the androgen 17β-trenbolone

The aim of the present study was to investigate the effects of the androgenic endocrine disruptor 17β-trenbolone on the sexual development of zebrafish (Danio rerio) with special emphasis on the question of whether adverse outcomes of developmental exposure are reversible or persistent. An exposure scenario including a recovery phase was chosen to assess the potential reversibility of androgenic effects. Zebrafish were exposed to environmentally relevant concentrations of 17β-trenbolone (1 ng/L-30 ng/L) from fertilization until completion of gonad sexual differentiation (60 d posthatch). Thereafter, exposure was either followed by 40 d of recovery in clean water or continued until 100 d posthatch, the age when zebrafish start being able to reproduce. Fish exposed for 100 d to 10 ng/L or 30 ng/L 17β-trenbolone were masculinized at different biological effect levels, as evidenced from a concentration-dependent shift of the sex ratio toward males as well as a significantly increased maturity of testes. Gonad morphological masculinization occurred in parallel with decreased vitellogenin concentrations in both sexes. Changes of brain aromatase (cyp19b) mRNA expression showed no consistent trend with respect to either exposure duration or concentration. Gonad morphological masculinization as well as the decrease of vitellogenin persisted after depuration over 40 d in clean water. This lack of recovery suggests that androgenic effects on sexual development of zebrafish are irreversible.

Species-specific considerations in using the fish embryo test as an alternative to identify endocrine disruption

A number of regulations have been implemented that aim to control the release of potentially adverse endocrine disrupters into the aquatic environment based on evidence from laboratory studies. Currently, such studies rely on testing approaches with adult fish because reliable alternatives have not been validated so far. Fish embryo tests have been proposed as such an alternative, and here we compared two species (medaka and zebrafish) to determine their suitability for the assessment of substances with estrogenic and anti-androgenic activity. Changes in gene expression (in here the phrase gene expression is used synonymously to gene transcription, although it is acknowledged that gene expression is additionally regulated, e.g., by translation and protein stability) patterns between the two species were compared in short term embryo exposure tests (medaka: 7-day post fertilization [dpf]; zebrafish: 48 and 96h post fertilization [hpf]) by using relative quantitative real-time RT-PCR. The tested genes were related to the hypothalamic-gonadal-axis and early steroidogenesis. Test chemicals included 17α-ethinylestradiol and flutamide as estrogenic and anti-androgenic reference compounds, respectively, as well as five additional substances with endocrine activities, namely bisphenol A, genistein, prochloraz, linuron and propanil. Estrogenic responses were comparable in 7-dpf medaka and 48/96-hpf zebrafish embryos and included transcriptional upregulation of aromatase b, vitellogenin 1 as well as steroidogenic genes, suggesting that both species reliably detected exposure to estrogenic compounds. However, anti-androgenic responses differed between the two species, with each species providing specific information concerning the mechanism of anti-androgenic disruption in fish embryos. Although small but significant changes in the expression of selected genes was observed in 48-hpf zebrafish embryos, exposure prolonged to 96hpf was necessary to obtain a response indicative of anti-androgenic activity. In contrast, for medaka clear anti-androgenic response, e.g. transcriptional downregulation of 11β-hydroxylase, 3β-hydroxysteroid-dehydrogenase, gonadotropin-releasing hormone receptor 2, was already observed at the pre-hatch stage. Together, this data suggests that medaka and zebrafish embryos would provide a beneficial alternative testing platform for endocrine disruption that involves additive information on interspecies and exposure time variability when using both species.

Transgenic fluorescent zebrafish Tg(fli1:EGFP)y¹ for the identification of vasotoxicity within the zFET

The fish embryo toxicity test (FET) is currently one of the most advocated animal alternative tests in ecotoxicology. To date, the application of the FET with zebrafish (zFET) has focused on acute toxicity assessment, where only lethal morphological effects are accounted for. An application of the zFET beyond acute toxicity, however, necessitates the establishment of more refined and quantifiable toxicological endpoints. A valuable tool in this context is the use of gene expression-dependent fluorescent markers that can even be measured in vivo. We investigated the application of embryos of Tg(fli1:EGFP)(y1) for the identification of vasotoxic substances within the zFET. Tg(fli1:EGFP)(y1) fish express enhanced GFP in the entire vasculature under the control of the fli1 promoter, and thus enable the visualization of vascular defects in live zebrafish embryos. We assessed the fli1 driven EGFP-expression in the intersegmental blood vessels (ISVs) qualitatively and quantitatively, and found an exposure concentration related increase in vascular damage for chemicals like triclosan, cartap and genistein. The fluorescence endpoint ISV-length allowed an earlier and more sensitive detection of vasotoxins than the bright field assessment method. In combination with the standard bright field morphological effect assessment, an increase in significance and value of the zFET for a mechanism-specific toxicity evaluation was achieved. This study highlights the benefits of using transgenic zebrafish as convenient tools for identifying toxicity in vivo and to increase sensitivity and specificity of the zFET.

The toxicity of silver nanoparticles to zebrafish embryos increases through sewage treatment processes

Silver nanoparticles (AgNPs) are widely believed to be retained in the sewage sludge during sewage treatment. The AgNPs and their derivatives, however, re-enter the environment with the sludge and via the effluent. AgNP were shown to occur in surface water, while evidence of a potential toxicity of AgNPs in aquatic organisms is growing. This study aims to examine the toxicity of AgNPs to the embryos of the aquatic vertebrate model zebrafish (Danio rerio) before and after sewage treatment plants (STPs) processes. Embryos were treated with AgNP (particle size: >90 % <20 nm) and AgNO3 in ISO water for 48 h and consequently displayed effects such as delayed development, tail malformations and edema. For AgNP, the embryos were smaller than the controls with conspicuously smaller yolk sacs. The corresponding EC50 values of 48 hours post fertilization (hpf) were determined as 73 μg/l for AgNO3 and 1.1 mg/l for AgNP. Whole-mount immunostainings of primary and secondary motor neurons also revealed secondary neurotoxic effects. A TEM analysis confirmed uptake of the AgNPs, and the distribution within the embryo suggested absorption across the skin. Embryos were also exposed (for 48 h) to effluents of AgNP-spiked model STP with AgNP influent concentrations of 4 and 16 mg/l. These embryos exhibited the same malformations than for AgNO3 and AgNPs, but the embryo toxicity of the sewage treatment effluent was higher (EC50 = 142 μg/l; 48 hpf). On the other hand, control STP effluent spiked with AgNPs afterwards was less toxic (EC50 = 2.9 mg/l; 48 hpf) than AgNPs in ISO water. This observation of an increased fish embryo toxicity of STP effluents with increasing AgNP influent concentrations identifies the accumulation of AgNP in the STP as a potential source of effluent toxicity.

Transcriptome alterations in zebrafish embryos after exposure to environmental estrogens and anti-androgens can reveal endocrine disruption

Exposure to environmental chemicals known as endocrine disruptors (EDs) is in many cases associated with an unpredictable hazard for wildlife and human health. The identification of endocrine disruptive properties of chemicals certain to enter the aquatic environment relies on toxicity tests with fish, assessing adverse effects on reproduction and sexual development. The demand for quick, reliable ED assays favored the use of fish embryos as alternative test organisms. We investigated the application of a transcriptomics-based assay for estrogenic and anti-androgenic chemicals with zebrafish embryos. Two reference compounds, 17α-ethinylestradiol and flutamide, were tested to evaluate the effects on development and the transcriptome after 48h-exposures. Comparison of the transcriptome response with other estrogenic and anti-androgenic compounds (genistein, bisphenol A, methylparaben, linuron, prochloraz, propanil) showed commonalities and differences in regulated pathways, enabling us to classify the estrogenic and anti-androgenic potencies. This demonstrates that different mechanism of ED can be assessed already in fish embryos.

Studying the effects of genistein on gene expression of fish embryos as an alternative testing approach for endocrine disruption

Assessment of endocrine disruption currently relies on testing strategies involving adult vertebrates. In order to minimize the use of animal tests according to the 3Rs principle of replacement, reduction and refinement, we propose a transcriptomics and fish embryo based approach as an alternative to identify and analyze an estrogenic activity of environmental chemicals. For this purpose, the suitability of 48 h and 7 days post-fertilization zebrafish and medaka embryos to test for estrogenic disruption was evaluated. The embryos were exposed to the phytoestrogen genistein and subsequently analyzed by microarrays and quantitative real-time PCR. The functional analysis showed that the genes affected related to multiple metabolic and signaling pathways in the early fish embryo, which reflect the known components of genistein's mode of actions, like apoptosis, estrogenic response, hox gene expression and steroid hormone synthesis. Moreover, the transcriptomic data also suggested a thyroidal mode of action and disruption of the nervous system development. The parallel testing of two fish species provided complementary data on the effects of genistein at gene expression level and facilitated the separation of common from species-dependent effects. Overall, the study demonstrated that combining fish embryo testing with transcriptomics can deliver abundant information about the mechanistic effects of endocrine disrupting chemicals, rendering this strategy a promising alternative approach to test for endocrine disruption in a whole organism in-vitro scale system.

Implications of the solvent vehicles dimethylformamide and dimethylsulfoxide for establishing transcriptomic endpoints in the zebrafish embryo toxicity test

Current aquatic chemical testing guidelines recognize that solvents can potentially interfere with the organism or environmental conditions of aquatic ecotoxicity tests and therefore recommend concentration limits for their use. These recommendations are based on evidence of adverse solvent effects in apical level tests. The growing importance of subapical and chronic endpoints in future test strategies, however, suggests that the limits may need reassessment. To address this concern, microarrays were used to determine the effects of organic solvents, dimethylformamide (DMF) and dimethylsulfoxide (DMSO), on the transcriptome of zebrafish (Danio rerio) embryos. Embryos were exposed for 48 h to a range of concentrations between 0.025 and 32.0 ml/L. Effects on survival and development after 24 and 48 h were assessed microscopically, with no effects on mortality or morphology up to 2.0 and 16.0 ml/L for DMF and DMSO. However, analysis of 48-h embryonic RNA revealed large numbers of differentially expressed genes at concentrations well below the 0.1 ml/L solvent limit level. The enrichment of differentially expressed genes was found for metabolic, developmental, and other key biological processes, some of which could be linked to observed morphological effects at higher solvent concentrations. These findings emphasize the need to remove or lower as far as possible the concentrations of solvent carriers in ecotoxicology tests.

Estrogen-induced alterations in amh and dmrt1 expression signal for disruption in male sexual development in the zebrafish

Dmrt1 and amh are genes involved in vertebrate sex differentiation. In this study, we cloned dmrt1 and amh cDNAs in zebrafish (Danio rerio) and investigated the effects of exposure to 17a-ethinylestradiol (EE2), during early life on their patterns of expression and impact on the subsequent gonadal phenotype. Expression of both amh and dmrt1 in embryos was detected as early as at 1 day post fertilization (dpf) and enhanced expression of amh from 25 dpf was associated with the period of early gonadal differentiation. Sex-dependent differences in enhanced green fluorescent protein transgene expression driven by the promoter of the germ cell-specific vas gene were exploited to show that at 28dpf and 56dpf both amh and dmrt1 mRNA were overexpressed in males compared with females. Exposure during early life to environmentally relevant concentrations of EE2 had a suppressive effect on the expression of both amh and dmrt1 mRNAs and this was associated with a cessation/retardation in male gonadal sex development. Our findings indicate that estrogen-induced suppression in expression of dmrt1 and amh during early life correlate with subsequent disruptive effects on the sexual phenotype in males.

Concentration- and time-dependent effects of the synthetic estrogen, 17alpha-ethinylestradiol, on reproductive capabilities of the zebrafish, Danio rerio

Partial or full life-cycle tests are needed to assess the potential of endocrine-disrupting compounds (EDCs) to adversely affect development and reproduction of fish. Small fish species such as zebrafish, Danio rerio, are under consideration as model organisms for appropriate test protocols. The present study examines how reproductive effects resulting from exposure of zebrafish to the synthetic estrogen 17alpha-ethinylestradiol (EE2) vary with concentration (0.05 to 10 ng EE2 L(-1), nominal), and with timing/duration of exposure (partial life-cycle, full life-cycle, and two-generation exposure). Partial life-cycle exposure of the parental (F1) generation until completion of gonad differentiation (0-75 d postfertilization, dpf) impaired juvenile growth, time to sexual maturity, adult fecundity (egg production/female/day), and adult fertilization success at 1.1 ng EE2 L(-1) and higher. Lifelong exposure of the F1 generation until 177 dpf resulted in lowest observed effect concentrations (LOECs) for time to sexual maturity, fecundity, and fertilization success identical to those of the developmental test (0-75 dpf), but the slope of the concentration-response curve was steeper. Reproduction of zebrafish was completely inhibited at 9.3 ng EE2 L(-1), and this was essentially irreversible as a 3-mo depuration restored fertilization success to only a very low rate. Accordingly, elevated endogenous vitellogenin (VTG) synthesis and degenerative changes in gonad morphology persisted in depurated zebrafish. Full life-cycle exposure of the filial (F2) generation until 162 dpf impaired growth, delayed onset of spawning and reduced fecundity and fertilization success at 2.0 ng EE2 L(-1). In conclusion, results show that the impact of estrogenic agents on zebrafish sexual development and reproductive functions as well as the reversibility of effects, varies with exposure concentration (reversibility at < or = 1.1 ng EE2 L(-1) and irreversibility at 9.3 ng EE2 L(-1)), and between partial and full life-cycle exposure (exposure to 10 ng EE2 L(-1) during critical period exerted no permanent effect on sexual differentiation, but life-cycle exposure did).

Development of a quantitative enzyme-linked immunosorbent assay for vitellin in the mysid Neomysis integer (Crustacea: Mysidacea)

Mysid crustaceans have been put forward by several regulatory bodies as suitable test organisms to screen and test the potential effects of environmental endocrine disruptors. Despite the well-established use of mysid reproductive endpoints such as fecundity, egg development time, and time to first brood release in standard toxicity testing, little information exists on the hormonal regulation of these processes. Control of vitellogenesis is being studied intensively because yolk is an excellent model for studying mechanisms of hormonal control, and vitellogenesis can be chemically disrupted. Yolk protein or vitellin is a major source of nourishment during embryonic development of ovigorous egg-laying invertebrates. The accumulation of vitellin during oocyte development is vital for the production of viable offspring. In this context, we developed a competitive enzyme-linked immunosorbent assay (ELISA) for vitellin of the estuarine mysid Neomysis integer. Mysid vitellin was isolated using gel filtration, and the purified vitellin was used to raise polyclonal antibodies. The ELISA was sensitive within a working range of 4 to 500 ng vitellin/mL. Serial dilutions of whole body homogenates from female N. integer and the vitellin standard showed parallel binding curves, validating the specificity of the ELISA. The intra- and interassay coefficients of variation were 8.2% and 13.8%, respectively. Mysid vitellin concentrations were determined from ovigorous females and eggs at different developmental stages. The availability of a quantitative mysid vitellin ELISA should stimulate further studies on the basic biology of this process in mysids. Furthermore, it could provide a means to better understand and predict chemically induced reproductive effects in mysids.

An environmentally relevant concentration of estrogen induces arrest of male gonad development in zebrafish, Danio rerio

The aim of the present study was to elucidate how full life-cycle exposure to estrogens impacts zebrafish development and reproduction, compared to partial life-cycle exposure only, and whether the estrogen-induced effects in zebrafish are reversible or irreversible. Zebrafish were exposed in a flow-through system to an environmentally relevant concentration (3 ng/L) of the synthetic estrogen 17alpha-ethinylestradiol (EE2) either from fertilization until the all-ovary stage of gonad development (i.e., 42 d postfertilization [DPF] in our experiment) or from fertilization until the reproductive stage (i.e., 118 DPF). Reversibility of the estrogen-induced effects was assessed after 58 d of depuration in EE2-free water until 176 DPE Early life exposure led to a lasting induction of plasma vitellogenin (VTG) in adult females but altered neither the sex ratio nor the reproductive capabilities. Full life-cycle exposure resulted in elevated VTG concentrations and caused gonadal feminization in 100% of exposed fish and thus inhibited reproduction. Two types of ovaries were observed in continuously exposed adult fish, immature ovaries with primary growth stage oocytes only and mature ovaries containing the full range of all oocyte maturation stages. Fish with immature ovaries had plasma VTG levels like control males, while fish with mature ovaries had female-like VTG levels. The effects of full life cycle exposure were at least partly reversible, and 26% of fish of the previous all-female cohort developed fully differentiated testes. These findings suggest that continuous estrogen exposure had arrested the developmental transition of the gonads of genetic males from the early all-ovary stage to functional testes. After the exposure had ceased, however, these males apparently were able to accomplish testicular differentiation.

Aromatase modulation alters gonadal differentiation in developing zebrafish (Danio rerio)

This study investigated whether gonadal sex differentiation of zebrafish (Danio rerio) is susceptible to compounds that interfere with cytochrome P450 aromatase (P450arom). Treatment of zebrafish during the period of gonadal differentiation with either the non-steroidal aromatase inhibitor fadrozole or 17alpha-methyltestosterone (MT) changed gonad morphological differentiation and altered the pattern of P450arom gene (CYP19) expression. Application of fadrozole (500 microg/g of food) between days 35 and 71 post-fertilisation (pf) resulted in 100% masculinisation, i.e. the gonads of all individuals examined ( n = 40) showed testicular morphology. At the same time, fadrozole treatment suppressed gonadal CYP19A (gonad-derived CYP19 gene) mRNA expression, as assessed by means of semi-quantitative RT-PCR. After termination of fadrozole treatment at day 71 pf and subsequent rearing of zebrafish under control conditions until 161 days pf, the gonads of all individuals still displayed testicular morphology. Gonadal CYP19A expression, however, showed a dimorphic pattern, with 14 out of 22 individuals having low CYP19A mRNA levels similar to those found in testes of control fish, while eight fish showed high, ovary-like levels of gonadal CYP19A mRNA. MT treatment (10 microg/l) during the period of gonadal differentiation (days 35 to 71 pf) resulted in phenological feminisation, i.e., all fish examined (n = 28) showed an ovarian gonadal morphology. While gonadal CYP19A expression was suppressed compared to control fish, cerebral CYP19B (brain-derived CYP19 gene) mRNA expression was increased in 71-day-old MT-treated fish. The results from this study provide evidence that exogenous compounds interfering with the P450arom system are able to disrupt, even persistently, gonadal sex differentiation of the protogynic zebrafish.

Vitellogenin expression in zebrafish Danio rerio: evaluation by histochemistry, immunohistochemistry, and in situ mRNA hybridisation

Several histological methods were tested for their potential to detect the in vivo induction of vitellogenin in zebrafish, after exposure to 17beta-oestradiol (E2), and validated by correlating semi-quantitative measurements on digital images to vitellogenin plasma values measured by ELISA and morphological criteria. All methods, except for vitellogenin-specific immunohistochemistry on liver, detected vitellogenin production in male zebrafish at the exposure level of 1 nM E2/l, and correlated well to each other and to ELISA results on plasma, thus indicating their specificity. The level of sensitivity is in the range of the induction of clinical (histopathological) effects, although slightly below the level of sensitivity of the plasma ELISA. Vitellogenin specific in situ mRNA hybridisation on liver appeared laborious and not applicable on routinely prepared material. Vitellogenin specific immunohistochemistry on plasma and basophilia of male liver are cost- and effort-effective detection methods of vitellogenin production, and can be applied routinely on standard histological sections. These methods are, therefore, suitable to evaluate vitellogenin production as an indicator of exposure to compounds with estrogenic activity, at the level of induction of clinical effects. They are a useful tool for hazard identification of endocrine disruption, especially when combined with routine histopathology.

Identification of endocrine-disrupting effects in aquatic vertebrates and invertebrates: report from the European IDEA project

The EU-funded project IDEA aimed to evaluate (a) what parameters and endpoints allow the detection of endocrine-mediated developmental and reproductive effects of (xeno)estrogens in life cycle- and life stage-specific toxicity tests with the zebrafish Danio rerio, a small laboratory fish used in many ecotoxicity test guidelines, and (b) whether substances that act as estrogens in vertebrates may also adversely affect the development, differentiation, and reproduction of aquatic invertebrates. The invertebrate species investigated included Hydra vulgaris, Gammarus pulex, Chironomus riparius, Hyalella azteca, and Lymnaea stagnalis. The animals were exposed to the model estrogenic chemicals ethynylestradiol (EE2), bisphenol A (BPA), and octylphenol (OP), which exert their endocrine activity in vertebrates through the estrogen receptor. As endpoints, developmental and reproductive parameters at the organism level as well as molecular and cellular parameters were measured. Life cycle exposure of zebrafish to (xeno)estrogens induced a specific, partly irreversible response pattern, consisting mainly of (a) induction of vitellogenin (VTG), (b) alterations of gonad differentiation, (c) delay of first spawning, and (d) reduced fertilization success. The effects of EE2 on zebrafish were expressed at environmentally realistic concentrations, while BPA and OP became effective at concentrations higher than those usually found in the environment. The vitellogenic response was equally sensitive as the reproductive parameters in the case of EE2, but VTG was more sensitive in the case of BPA. Partial life cycle exposure of zebrafish had lasting effects on fish development and reproduction only when the fish were exposed during the stage of juvenile bisexual gonad differentiation. In (partial) life cycle and multigeneration studies with invertebrates, (xeno)estrogenic impact was assessed by a range of developmental and reproductive parameters including hatching, growth, moulting, mating behavior, and egg number. Several parameters were found to be responsive to (xeno)estrogens; however, most effects were induced only at higher, probably nonphysiological concentrations. Low-dose effects were observed in full life cycle experiments, particularly in the second generation. It remains to be established whether the estrogen-induced alterations in the invertebrate species indeed do result from disturbances of the endocrine system. The findings of the present research project support the development of appropriate testing methodologies for substances with estrogenic activity.

Development and validation of a homologous zebrafish (Danio rerio Hamilton-Buchanan) vitellogenin enzyme-linked immunosorbent assay (ELISA) and its application for studies on estrogenic chemicals

Vitellogenin (VTG) was isolated by anion exchange chromatography from plasma of female zebrafish (Danio rerio) induced with 17alpha-ethinylestradiol (EE2). The purity of the VTG isolate was confirmed by polyacrylamide gel electrophoresis (SDS-PAGE). Purified VTG was used to raise polyclonal antibodies in rabbits and the specificity of the antisera for VTG confirmed by Western blot analysis of plasma proteins separated by SDS-PAGE. The antibodies cross-reacted with two proteins in the plasma of female zebrafish, with molecular masses of approximately 142 and 171 kDa. No cross-reactivity was observed with any other plasma proteins. A competitive enzyme-linked immunosorbent assay (ELISA) was developed using the polyclonal zebrafish VTG (z-VTG) antibodies and purified z-VTG as ligand and standard, respectively. The z-VTG ELISA was sensitive with a detection limit of between 2.0 and 3.0 ng purified VTG/ml, and a working range between 3 and 500 ng/ml (30-85% binding). The ELISA demonstrated precision, with inter- and intra-assay variations of 7.5+/-2.7 and 4.9+/-1.4%, respectively. Plasma from adult zebrafish and whole body homogenates from juvenile zebrafish diluted parallel with the z-VTG standard in the ELISA, validating the assay for quantifying z-VTG in both of these tissues. Exposure of adult male zebrafish to EE2 via water induced a concentration-dependent induction of VTG with a lowest observed effect concentration (LOEC) < or =1.67 ng EE2/l (for a 21-day exposure). The homologous z-VTG ELISA provides a valuable tool for the study of environmental estrogens in zebrafish.

The influence of fasting on blood and plasma composition of herring gulls (Larus argentatus)

Populations of scavenging seabird species in the North Sea may fluctuate with an artificial food source: the availability of fishery waste. To document this impact, it is necessary to assess the birds' nutritional status during periods with decreased fishing activity. Reference data for this purpose was collected from 22 herring gulls investigated during laboratory fasting. After 6 d of food deprivation and body mass losses exceeding 15%, the first birds entered starvation phase 3. Comparatively, this is a rather weak fasting capacity. Plasma levels of total protein and thyroid hormones decreased and beta-hydroxybutyrate increased with fasting duration. The leucocyte proportions were shifted from lymphocytes to heterophils. After 3 d of refeeding, most of the fasting changes were reversed. Plasma enzyme activities increased and hematocrit, hemoglobin, and erythrocyte numbers decreased in both fasting and control birds, most likely as a result of experimental stress and repeated blood sampling. Glucose, cholesterol, monocytes, basophils, and glycosylated hemoglobin remained fairly constant. Triglycerides, free fatty acids, uric acid, and urea varied significantly, but changes were not as clearly a result of fasting. Therefore, total protein, beta-hydroxybutyrate, triiodothyronine, thyroxine, and lymphocyte and heterophil percentages may be the most reliable indicators of the nutritional status and the condition of free-living herring gulls.

Extramedullary facial plasmacytomas with anaplastic features: a diagnostic dilemma with implications for treatment

Extramedullary plasmacytomas (EMPs) are rare plasma-cell tumors of the soft tissue that occur predominantly in the nasal sinuses and oropharynx. Subcutaneous and cutaneous plasmacytomas of the face are distinctly unusual. The authors report a case of rapidly expanding EMP involving the lip and contralateral nasolabial fold of a native Alaskan man with a 25-year history of recurring solitary bone plasmacytomas (SBP). An incisional biopsy revealed sheets of monotypic plasmablasts with anaplastic features. The pathologic and clinical findings were most consistent with a Richter transformation from a low-grade to a high-grade malignancy, or anaplastic myeloma (AM). With combined chemotherapy and radiation therapy, he achieved a complete response. The clinical and laboratory features of this most unusual plasma-cell dyscrasia are reviewed with an emphasis placed on diagnosis and treatment.

Role of cortisol in the ACTH-induced suppression of testicular steroidogenesis in guinea pigs

In order to investigate the role of cortisol in the regulation of testicular function, adult male guinea pigs were challenged with ACTH (20 IU), cortisol (8 or 16 mumol), or with ACTH plus dexamethasone (DEX, 2 mumol). The amounts of cortisol, testosterone, progesterone, and androstenedione present in the plasma or secreted by incubated adrenals or testes were determined by radioimmunoassay. The plasma concentrations of LH were determined using a radioimmunoassay for rat LH. ACTH treatment elevated cortisol plasma concentrations to 999% of control values, whereas it reduced testosterone plasma levels to 43% of control values. ACTH treatment did not affect LH plasma levels. A significant negative correlation was found in ACTH-treated animals, when the cortisol and testosterone plasma concentrations in serially taken blood samples (30-240 min after treatment) were compared (rs = -0.90 and rs = -0.99, P < 0.05). In addition to cortisol, ACTH raised progesterone and androstenedione plasma concentrations. If animals were treated with 2 mumol DEX + ACTH, the plasma levels of cortisol and androstenedione but not of progesterone, testosterone or LH were changed. ACTH stimulated the in vitro secretion of cortisol, progesterone and androstenedione by the adrenals but reduced the in vitro release of androstenedione and testosterone by the testes. In summary, treatment of guinea pigs resulted in elevated cortisol and in reduced testosterone plasma concentrations. The mechanism of the cortisol-induced inhibition of testicular function was independent of the LH plasma concentrations. The in vitro experiments indicate that cortisol directly interacts with the Leydig cells, presumably by inhibiting the activity of the testicular 17 alpha-hydroxylase and/or C17,20-lyase. Taking into account the results of comparable investigations in the rat, the inhibition of the testicular 17 alpha-hydroxylase and/or C17,20-lyase takes place if the intracellular cortisol exceeds the capacity of the 11 beta-hydroxysteroid dehydrogenase to inactivate it.

Clean-up and re-use of kieselguhr (Extrelut) for liquid-liquid extraction of urinary cortisol

Cortisol was isolated from human urine using kieselguhr (Extrelut)-filled columns. After use, Extrelut was cleaned-up once with distilled water and twice with ethanol. Before re-use, the cleaned-up kieselguhr was dried for 24 h by a warm air stream. The comparison of cortisol recovery from human urine and HPLC chromatograms of urinary extracts show that Extrelut can be repeatedly used for liquid-liquid extraction of urinary cortisol.

The use of salivary cortisol measurements for the non-invasive assessment of adrenal cortical function in guinea pigs

For collection of saliva, cotton buds (Q-tips) were inserted into the guinea pig's cheek pouch, parallel with the cheek teeth. The recovery of saliva from the buds increased with the volume applied: whereas the recovery was 63% when 20 microliters were applied, it increased to 85% when 120 microliters were applied. The recovery of cortisol was closely related to the volume of saliva obtained by centrifugation (r = 0.99, p < 0.001). The mean value of salivary cortisol concentrations in untreated animals was 6.6 ng/ml, with relatively large variations across minutes and days within and between animals. Salivary cortisol was significantly increased if animals were singly caged, either in their familiar housing room or in an unfamiliar empty test room. In comparison to these changes, a much more pronounced increase of salivary cortisol occurred after the intramuscular (i.m.) administration of 20 IU ACTH: while the pretreatment value was 2.2 ng/ml, cortisol concentrations increased to 47 ng/ml (1 h), 72 ng/ml (2 h), 137 ng/ml (3 h) and 170 ng/ml (4 h), respectively. Similarly, i.m. administration of 2 IU insulin resulted in a significant increase of salivary cortisol (2 h: 37 ng/ml, 3 h: 24 ng/ml, 4 h: 25 ng/ml). The present study shows that the cortisol concentrations in the saliva of guinea pigs can be used as an index of adrenal cortical function in preference to the more commonly measured concentrations in the plasma. The advantages of the saliva method are: Firstly, cortisol values reflect the biologically active, unbound fraction in the plasma and are thus less affected by concentration changes of the corticosteroid-binding globulin. Secondly, saliva is easy to collect and the collection method is non-invasive; thus, no handling- or stress-induced changes of the adrenal gland occur. Thirdly, the ease of collection facilitates investigations which require frequent sampling.

Saliva cortisol and testosterone in the guinea pig: measures for the endocrine function of adrenals and testes?

For collection of saliva, cotton buds (Q-tips) were inserted into the guinea pig's cheek pouch, parallel with the cheek teeth. Within 5 min, sufficient fluid was collected for cortisol and testosterone measurements. In saline-treated animals, saliva cortisol and testosterone were about 15 ng/mL and 1.5 ng/mL, corresponding to plasma levels of 52 ng/mL and 5.9 ng/mL. Within 2-4 h after administration of 20 IU ACTH, saliva and plasma cortisol concentrations were strikingly elevated: saliva: 125 ng/mL (2 h), 157 ng/mL (4 h); plasma: 458 ng/mL (2 h), 736 ng/mL (4 h). This treatment did not influence testosterone in saliva, but reduced it in plasma (2.4 ng/mL (4 h)). In animals receiving 100 IU HCG, saliva testosterone remained unchanged, whereas its plasma levels were markedly raised (9.6 ng/mL (2 h), 12.5 ng/mL (4 h)). These results show that saliva cortisol offers promise as a noninvasive method of monitoring changes in guinea pig adrenocortical function. Saliva testosterone, on the other hand, does not correlate with plasma values; hence it cannot be used to assess testicular function in the guinea pig.

Measurement of salivary cortisol in guinea pigs

For collection of saliva, cotton buds (Q-tips) were inserted into the guinea pig's cheek pouch, parallel with the cheek teeth. Within 5 minutes, sufficient fluid was collected for salivary cortisol measurements. Salivary cortisol was about 7 ng/ml after intramuscular (i.m.) injection of 0.2 ml saline. Compared with saline treatment, it was drastically increased after i.m. injection of ACTH or cortisol. Taking into account the close relationship between the amounts of cortisol in saliva and plasma in cortisol- or ACTH-treated animals, we conclude that measuring saliva cortisol offers promise as a noninvasive method to monitor the changes of adrenocortical function in guinea pigs.

Dissociation of plasma and urinary steroid values after application of stressors, insulin, vasopressin, ACTH, or dexamethasone in the Mongolian gerbil

The amounts of cortisol and testosterone in the plasma or urine of Mongolian gerbils exposed to stress factors or treated subcutaneously with insulin (2 IU), vasopressin (1 IU), ACTH (6 IU) or dexamethasone (50 micrograms) were determined. Increased plasma cortisol was observed in animals stressed by ether anesthesia or immobilisation (1-4 hours), or treated with insulin, vasopressin or ACTH. Cortisol levels were reduced after dexamethasone administration. Plasma testosterone was elevated in animals stressed by ether anesthesia or handling plus seizure; no other treatment altered testosterone levels. An augmented cortisol excretion, which lasted one day, occurred in gerbils immobilised for one as well as for four hours. A much more prolonged stimulation of cortisol excretion, lasting three days, was seen in animals receiving ACTH or dexamethasone plus ACTH. Testosterone excretion was stimulated by ACTH and dexamethasone plus ACTH; it was not influenced by any other treatment. The present study shows that analysis of circulating steroid levels is the only reliable approach to assess the secretory activity of Mongolian gerbil adrenals or testes. In some experimental conditions (e.g. after stressor application or ACTH treatment) cortisol excretion may be used as an index of adrenal secretory function. In contrast, the striking differences between cortisol values present in plasma and urine of peptide-or dexamethasone-treated gerbils indicate that urinary cortisol does not reflect short-term changes of adrenal function. Similarly, the striking differences of testosterone values in plasma and urine indicate that urinary testosterone monitoring cannot be used to determine the secretory activity of gerbil testes.