Expression profile of oestrogen receptors and oestrogen-related receptors is organ specific and sex dependent: the Japanese medaka Oryzias latipes model

Gene expression of all known subtypes of oestrogen receptor (ER) and oestrogen-related receptor (ERR) in multiple organs and both sexes of the Japanese medaka Oryzias latipes was profiled and systematically analysed. As revealed by statistical analyses and low-dimensional projections, the expressions of ERRs proved to be organ and sex dependent, which is in contrast with the ubiquitous nature of ERs. Moreover, expressions of specific ERR isoforms (ERRγ1, ERRγ2) were strongly correlated with that of all ERs (ERα, ERβ1 and ERβ2), suggesting the existence of potential interactions. Findings of this study shed light on the co-regulatory role of particular ERRs in oestrogen-ERs signalling and highlight the potential importance of ERRs in determining organ and sex-specific oestrogen responses. Using O. latipes as an alternative vertebrate model, this study provides new directions that call for collective efforts from the scientific community to unravel the mechanistic action of ER-ERR cross-talks, and their intertwining functions, in a cell and sex-specific manner in vivo.

Evaluation of biomarker potential of cytochrome P450 1A (CYP1A) gene in the marine medaka, Oryzias melastigma exposed to water-accommodated fractions (WAFs) of Iranian crude oil

CYP1A is involved in the metabolism of diverse chemicals, including polycyclic aromatic hydrocarbons and alkylated-PAHs, as a first line of detoxification mechanism. First, we identified and characterized the CYP1A gene from the marine medaka, Oryzias melastigma. O. melastigma CYP1A (Om-CYP1A) showed a high similarity of motifs/domains compared to those of vertebrates in their amino acid sequences. To check whether the Om-CYP1A would be inducible, we tested two strong CYP1A inducers, β-naphthoflavone (β-NF) and benzo[α]pyrene (B[α]P), and observed concentration-dependent transient expression on transcripts of Om-CYP1A for 96 h over a wide range of concentrations. Om-CYP1A mRNA level was significantly increased in exposure to different concentrations of β-NF and B[α]P, and its expression was highly transcribed within 12 h upon the exposure to low concentrations of both chemicals. Inducible transcript profiles revealed that Om-CYP1A would be associated with the toxicant metabolism via AhREs/DREs/XREs in its promoter region. To uncover the effects of the water-accommodated fraction (WAF) of crude oil on transcripts of Om-CYP1A, we measured mRNA expression of Om-CYP1A towards different concentrations of WAF for 24h. As a result, WAF exposure significantly increased Om-CYP1A transcripts at all concentrations as well as during time-course experiments for 96 h. In this paper, we demonstrated that WAF would trigger up-regulation of the CYP1A gene that would be associated with the initiation of the cellular defense systems. This finding provides a better understanding of the molecular mechanism of cellular protection particularly that involved in the WAF-mediated cellular response in O. melastigma.

Hollow superparamagnetic iron oxide nanoshells as a hydrophobic anticancer drug carrier: intracelluar pH-dependent drug release and enhanced cytotoxicity

With curcumin and doxorubicin (DOX) base as model drugs, intracellular delivery of hydrophobic anticancer drugs by hollow structured superparamagnetic iron oxide (SPIO) nanoshells (hydrodynamic diameter: 191.9 ± 2.6 nm) was studied in glioblastoma U-87 MG cells. SPIO nanoshell-based encapsulation provided a stable aqueous dispersion of the curcumin. After the SPIO nanoshells were internalized by U-87 MG cells, they localized at the acidic compartments of endosomes and lysosomes. In endosome/lysosome-mimicking buffers with a pH of 4.5-5.5, pH-dependent drug release was observed from curcumin or DOX loaded SPIO nanoshells (curcumin/SPIO or DOX/SPIO). Compared with the free drug, the intracellular curcumin content delivered via curcumin/SPIO was 30 fold higher. Increased intracellular drug content for DOX base delivered via DOX/SPIO was also confirmed, along with a fast intracellular DOX release that was attributed to its protonation in the acidic environment. DOX/SPIO enhanced caspase-3 activity by twofold compared with free DOX base. The concentration that induced 50% cytotoxic effect (CC(50)) was 0.05 ± 0.03 μg ml(-1) for DOX/SPIO, while it was 0.13 ± 0.02 μg ml(-1) for free DOX base. These results suggested SPIO nanoshells might be a promising intracellular carrier for hydrophobic anticancer drugs.

Complete mitochondrial genome of the marine medaka Oryzias melastigma (Beloniformes, Adrianichthyidae)

The complete mitochondrial genome was obtained from the assembled genome data sequenced by next-generation sequencer from the marine medaka Oryzias melastigma. The mitochondrial genome sequence was 16,864 bp in size, and the gene order and contents were identical with those of previously reported fish mitochondrial genomes. Of 13 protein-coding genes (PCGs), 4 genes (CO3, ND3, ND4, and Cytb) had incomplete stop codons. The base composition of O. melastigma mitogenome showed high A+T (59.65%) and anti-G bias (8.73%) on the 3rd position of PCGs.

Effect of membrane properties on the performance of a hybrid GAC and ultrafiltration process for water treatment

The performance of a hybrid granular activated carbon (GAC) and ultrafiltration (UF) process for water treatment was investigated using five types of UF membranes. The removal percentages for chemical oxygen demand (COD(Mn)), particles (> or = 2 microm) and total bacteria by the hybrid process were 30-40%, 98-99% and 76-92%, respectively. No invertebrates were detected in the hybrid process effluent. Transmembrane pressure and specific permeate flux (SPF) of the five types of membranes varied. With decreasing membrane pore sizes, removal of COD(Mn) and particles increased, whereas SPF firstly decreased and then increased. Hydrophilic membranes had a relatively high COD(Mn) removal potential, but did not obviously affect particle removal or SPF.

A high-throughput histoarray for quantitative molecular profiling of multiple, uniformly oriented medaka (Oryzias latipes) embryos

Embryos of aquatic animal model fish have proven to be useful organisms for developmental biology and for early life stage toxicity tests. By virtue of their transparent chorions, imaging of normal and abnormal development can be detected and related to exposure or to alterations due to environmental factors. However, the detection of changes at sub-individual levels of organization is hampered by time required to detect important events within cells and tissues of affected organisms. We describe herein development of a highly cost effective embryo chip enabling stringent inter-individual comparisons and multiplex detection in embryos and eleutheroembryos. As a proof of principle we examine cell proliferation and controlled cell death in normoxic and hypoxic conditions and relate these to tissue turnover in individual organisms. Coupled with a recently developed whole adult animal platform, we can now move beyond the common approach focusing on single target organ to the detection and characterization of systemic phenomena (syndromes) affecting the organism. Taken together, we can now determine adult consequences of early life stage exposure and assess ability of exposed individuals to respond to stresses superimposed along the axis of time.

Gender-specific modulation of immune system complement gene expression in marine medaka Oryzias melastigma following dietary exposure of BDE-47

BDE-47 is one of the most widely found congeners of PBDEs in marine environments. The potential immunomodulatory effects of BDE-47 on fish complement system were studied using the marine medaka Oryzias melastigma as a model fish. Three-month-old O. melastigma were subjected to short-term (5 days) and long-term (21 days) exposure to two concentrations of BDE-47 (low dose at 290 ± 172 ng/day; high dose at 580 ± 344 ng/day) via dietary uptake of BDE-47 encapsulated in Artemia nauplii. Body burdens of BDE-47 and other metabolic products were analyzed in the exposed and control fish. Only a small amount of debrominated product, BDE-28, was detected, while other metabolic products were all under detection limit. Transcriptional expression of six major complement system genes involved in complement activation: C1r/s (classical pathway), MBL-2 (lectin pathway), CFP (alternative pathway), F2 (coagulation pathway), C3 (the central component of complement system), and C9 (cell lysis) were quantified in the liver of marine medaka. Endogenous expression of all six complement system genes was found to be higher in males than in females (p < 0.05). Upon dietary exposure of marine medaka to BDE-47, expression of all six complement genes were downregulated in males at day 5 (or longer), whereas in females, MBl-2, CFP, and F2 mRNAs expression were upregulated, but C3 and C9 remained stable with exposure time and dose. A significant negative relationship was found between BDE-47 body burden and mRNA expression of C1r/s, CFP, and C3 in male fish (r = -0.8576 to -0.9447). The above findings on changes in complement gene expression patterns indicate the complement system may be compromised in male O. melastigma upon dietary exposure to BDE-47. Distinct gender difference in expression of six major complement system genes was evident in marine medaka under resting condition and dietary BDE-47 challenge. The immunomodulatory effects of BDE-47 on transcriptional expression of these complement components in marine medaka were likely induced by the parent compound instead of biotransformed products. Our results clearly demonstrate that future direction for fish immunotoxicology and risk assessment of immunosuppressive chemicals must include parallel evaluation for both genders.

Molecular cloning and expression of novel metallothionein (MT) gene in the polychaete Perinereis nuntia exposed to metals

To report a novel metallothionein (MT) gene and evaluate its potency as a biomarker, we clone this MT gene and measured the expression levels in the metal-exposed polychaete Perinereis nuntia. Accumulated metal contents and metallothionein-like proteins (MTLPs), which have been recognized as potential biomarkers, were compared with the relative mRNA expressions of the MT gene of P. nuntia (Pn-MT). In addition, the metal-binding affinity was estimated by recombinant Pn-MT protein. Pn-MT having high cysteine residues with three metal response elements in the promoter region closely clusters with those of other invertebrates. The accumulation patterns of metals were dependent on the exposure times in lead (Pb), cadmium (Cd), and copper (Cu) exposure. Particularly, both MTLP levels and relative mRNA expressions of MT were increased with accumulated metal contents and exposure time in P. nuntia exposed to Pb and Cd. There was no significant modulation of the Pn-MT gene in polychaetes exposed to Zn and As. However, the metal-binding ability of the recombinant Pn-MT protein provides a clear evidence for a high affinity of MT to several metal elements. These results suggest that Pn-MT would play an important role in the detoxification and/or sequestration of specific metals (e.g., Pb and Cd) in P. nuntia and have potential as a molecular biomarker in the monitoring of the marine environment using a polychaete.

Unravelling the pathway of respiratory toxicity in goldlined seabream (Rhabdosargus sarba) induced by the harmful alga Chattonella marina

The harmful alga Chattonella marina has caused massive fish kills and economic losses worldwide. Suffocation is generally believed to be the major cause of fish death by C. marina. However, the specific mechanisms leading to respiratory disorder in fish and subsequent fish kills by C. marina remain unknown. The goldlined seabream, highly susceptible to C. marina, was employed to investigate temporal changes of physiological, histopathological and biochemical parameters related to respiratory function at different stages of exposure to C. marina. Hemoglobin oxidation and blood lyses were not found in goldlined seabream exposed to C. marina, which could not be the key reasons accounting for pO(2) drop in the stressed fish. Gill histopathology such as irregular organization of lamellae, mucous with algal cells trapped in interfilamental spaces, were typical in C. marina exposed fish. A surge of plasma lactate occurred in goldlined seabream shortly after exposure to C. marina (0.5h) and sustained throughout the exposure period, indicating rapid onset of and persistent anaerobic respiration in C. marina exposed fish. Depletion of plasma glucose was clearly evident in goldlined seabream showing stress symptoms and near death. Yet, fish alive in the C. marina bloom did not exhibit plasma glucose depletion. The results suggest that availability of fermentable fuel as indicated by glucose level is critical to determine fish survival in C. marina exposure. Overall, our findings have rebuked the involvement of hemolysins and/or nitric oxide as the culprits for C. marina toxicity to fish. This study is the first to demonstrate the pathway of respiratory toxicity induced by the harmful alga C. marina in fish.

Susceptibility of fish to Chattonella marina is determined by its tolerance to hypoxia

The harmful alga Chattonella marina has caused massive fish kills and economic losses worldwide. However, the fish kill mechanisms by C. marina have not been identified. The present study has confirmed that a significant elevation of blood osmolality is the universal response in moribund fish exposed to C. marina and the possible reasons leading to contradictory reports were identified. Both osmotic distress and respiratory impairment are important mechanisms leading to fish kill by C. marina. The susceptibility of marine fish to C. marina appears to be inversely related to their tolerance to hypoxia, with the hypoxia intolerant goldlined seabream being the most susceptible, and the hypoxia tolerant green grouper being the most tolerant to C. marina. Further studies in the marine medaka (Oryzias melastigma) showed that fish susceptibility to C. marina is directly related to susceptibility of the fish to hypoxia, but not related to its tolerance to hypersalinity stress.

The marine medaka Oryzias melastigma--a potential marine fish model for innate immune study

The objective of this study is to develop the marine medaka Oryzias melastigma as a potential marine fish model for innate immune and immunotoxicological studies. Hepcidin plays an important role in innate immune system. Two hepcidin genes (OM-hep1 and OM-hep2) were identified and characterized in the O. melastigma, which were highly conserved with other reported hepcidins. During embryogenesis, significant elevation of OM-hep1 and OM-hep2 transcripts were coincided with liver development in the embryos. In adult medaka, differential tissue expressions of both hepcidin transcripts were evident: high in liver, moderate in spleen and low in non-immune tissues. After bacterial challenge, the two hepcidin mRNAs were rapidly and remarkably induced in liver and spleen, suggesting the two OM-hepcidins in O. melastigma play a complementary role in innate defense. Gender difference in time of induction and extent of the two hepcidin mRNAs elevation in infected O. melastigma should be considered in immunotoxicological studies.

Use of medaka in toxicity testing

Small aquarium fishes are increasingly used as animal models, and one of these, the Japanese Medaka (Oryzias latipes), is frequently utilized for toxicity testing. While these vertebrates have many similarities with their terrestrial counterparts, there are differences that must be considered if these organisms are to be used to their highest potential. Commonly, testing may employ either the developing embryo or adults; both are easy to use and work with. To illustrate the utility and breadth of toxicity testing possible using medaka fish, we present protocols for assessing neurotoxicity in developing embryos, evaluating toxicant effects on sexual phenotype after treatment with endocrine-disrupting chemicals by sexual genotyping, and measuring hepatotoxicity in adult fish after treatment with a model hepatotoxicant. The methods run the gamut from immunohistology through PCR to basic histological techniques.

Investigation of microbial safety of a full-scale ozonation and biological activated carbon process under high humidity and temperature conditions

Microbial safety of a full-scale ozonation and biological activated carbon (BAC) process was investigated by examining pathogens, microbial community and particle counts, with emphasis on the BAC effluent. The process is located at South China, where the average humidity and air temperature were 70-80% and 22-24 °C, respectively. A high diversity of microbial community existed on the BAC media. Three types of dominant bacteria were identified, including Chryseobacterium indologenes, Bacillus brevis and Pseudomonas stutzeri, accounting for 90-95% of total bacteria number. As to pathogenic bacteria and viruses, an opportunistic pathogen, Bacillus cereus, was detected on the BAC. Six types of invertebrates were also observed on the medium, including rotifer, cyclops, nematode, clodecera, nauplius and blood worm. Diversity and number of invertebrates in the BAC effluent were higher than those in the BAC influent. Particle counts were generally less than 50 CNT/mL, with the maximum of 500 CNT/mL during the initial filtration stage after backwashing.

Ethoxyresorufin-O-deethylase enzyme activities and accumulation of secondary/tertiary lysosomes in rabbitfish Siganus oramin as biomarkers for xenobiotic exposures

The sensitivities of using hepatic and intestinal ethoxyresorufin-O-deethylase (EROD) activities and hepatic accumulation of secondary/tertiary (2 degrees/3 degrees) lysosomes to detect xenobiotic exposures were assessed in the rabbitfish Siganus oramin in a metropolitan harbour, subtropical Hong Kong, over a complete seasonal cycle of one year. Additional information on the body-burden pollutants and physiological indices in S. oramin, and seasonal variables in seawater quality, were extracted from published data and re-analyzed. Under the influences of pollutant cocktail and seasonal factors, neither the hepatic nor intestinal EROD activity was indicative of total polycyclic aromatic hydrocarbons (Sigma PAH), total polychlorinated biphenyls, condition factor and hepatosomatic index (HSI) in S. oramin. However, the relative ratio of hepatic to intestinal EROD activities provided an indication to differentiate the xenobiotic intake route in the fish through diffusion via gills/skin or consumption of contaminated food. In addition, the elevated hepatic accumulation of 2 degrees/3 degrees lysosomes was closely associated with the dominant temporal trends of zinc and Sigma PAH, as well as reduced HSI, in S. oramin. Being minimally influenced by any investigated seasonal factors, the hepatic 2 degrees/3 degrees lysosomes in S. oramin was recommended as an effective biomarker of xenobiotic exposures and toxic effects for use in coastal pollution monitoring programmes.

Polybrominated diphenylethers (PBDEs) alter larval settlement of marine benthic polychaetes

Polybrominated diphenylethers (PBDEs) are found ubiquitously in marine environments worldwide. Sediment is the major sink of PBDEs, with the congener BDE 47 being most abundant. In this study, laboratory experiments were carried out to test the hypothesis that contamination of BDE 47 at environmentally realistic sediment concentrations can alter polychaete larval settlement. Using multiple-choice experiment, settlement of three polychaete species (Pseudopolydora vexillosa, Polydora cornuta, and Capitella sp. I) on four types of spiked sediment was studied and compared: (i) low BDE 47 concentration (0.5 ng g(-1) dry weight); (ii) high BDE 47 concentration (3.0 ng g(-1) dry weight), (iii) hexane (solvent control), and (iv) natural sediment (control). Our results showed that settlement of P. vexillosa and Capitella sp. I larvae was significantly promoted, while settlement of P. cornuta reduced, at high BDE 47 concentration in sediment compared with the respective controls under both short- (24 h) and long-term (4 week) exposures. After 4 weeks, body burden of BDE 47 in all polychaete species was directly related to the spike concentration, and body length of settled juveniles of P. vexillosa and Capitella sp. I at the high-concentration treatment was significantly longer compared with that of other treatments and controls. For the first time, we demonstrated that environmentally realistic concentrations of BDE 47 in sediment can affect polychaete settlement in species-specific and dose-dependent manners. Given the global contamination of PBDE in marine sediment, BDE 47 may potentially alter the settlement pattern of marine polychaetes and hence their benthic composition over large areas.

Toxicity comparison between Chattonella marina and Karenia brevis using marine medaka (Oryzias melastigma): Evidence against the suspected ichthyotoxins of Chattonella marina

The marine alga Chattonella marina is often associated with massive fish mortality worldwide. Here, we challenge brevetoxins and free fatty acids as the ichthyotoxins of C. marina by comparing the toxicity of C. marina with a brevetoxins-producing alga Karenia brevis as well as their organic solvent extracts using the seawater medaka Oryzias melastigma. Opposite to K. brevis, toxicity of C. marina was highly correlated with its growth rate and exhibited no dose response relationship between cell density and fish mortality. Fish exposed to C. marina developed significant hyperventilation response, but K. brevis induced hypoventilation response in medaka. Moreover, the organic extracts from C. marina showed no toxicity to fish whereas organic extracts from K. brevis showed significantly higher toxicity than the whole K. brevis culture. The toxins produced by C. marina may be protein in nature or small and labile molecular compounds which are not able to be extracted by traditional organic extraction methods.

The initial and subsequent inflammatory events during calcium oxalate lithiasis

BACKGROUND

Crystallization is believed to be the initiation step of urolithiasis, even though it is unknown where inside the nephron the first crystal nucleation occurs.

METHODS

Direct nucleation of calcium oxalate and subsequent events including crystal retention, cellular damage, endocytosis, and hyaluronan (HA) expression, were tested in a two-compartment culture system with intact human proximal tubular HK-2 cell monolayer.

RESULTS

Calcium oxalate dihydrate (COD) was nucleated and bound onto the apical surface of the HK-2 cells under hypercalciuric and hyperoxaluric conditions. These cells displayed mild cellular damage and internalized some of the adhered crystals within 18h post-COD-exposure, as revealed by electron microscopy. Prolonged incubation in complete medium caused significant damage to disrupt the monolayer integrity. Furthermore, hyaluronan disaccharides were detected in the harvested media, and were associated with HAS-3 mRNA expression.

CONCLUSION

Human proximal cells were able to internalize COD crystals which nucleated directly onto the apical surface, subsequently triggering cellular damage and HAS-3 specific hyaluronan synthesis as an inflammatory response. The proximal tubule cells here demonstrate that it plays an important role in facilitating urolithiasis via endocytosis and creating an inflammatory environment whereby free hyaluronan in tubular fluid can act as crystal-binding molecule at the later segments of distal and collecting tubules.

Durable mesenchymal stem cell labelling by using polyhedral superparamagnetic iron oxide nanoparticles

Small polyhedral superparamagnetic iron oxide (SPIO) nanoparticles (<10 nm) coated with a thin layer of silica were prepared (SPIO@SiO(2) and SPIO@SiO(2)-NH(2)). Surface modification of the small polyhedral silica-coated SPIO nanoparticles with amines led to substantially higher mesenchymal stem cell (MSC) labelling efficiency without the use of additional transfecting agents. Therefore, amine surface-modified nanoparticles (SPIO@ SiO(2)-NH(2)) appeared to be the preferred candidate for MSC labelling. In vitro studies demonstrated that controlled labelling of SPIO@SiO(2) and SPIO@SiO(2)-NH(2) did not cause MSC death or proliferation inhibition. MSCs labelled with SPIO@SiO(2)-NH(2) nanoparticles retained differentiation potential and showed osteogenic, adipogenic and chondrogenic differentiations. The noncytotoxic polyhedral SPIO@SiO(2)-NH(2) nanoparticle-labelled MSCs were successfully implanted in rabbit brain and erector spinae muscle, and demonstrated long-lasting, durable MRI labelling efficacy after 8-12 weeks.

The effects of sub-lethal UV-C irradiation on growth and cell integrity of cyanobacteria and green algae

The effects of UV-C irradiation on algal growth and cell integrity were investigated to develop a potential method for preventing cyanobacterial blooms. The toxic cyanobacterium Microcystis aeruginosa and three common freshwater green algae Chlorella ellipsoidea, Chlorella vulgaris, and Scenedesmus quadricanda were exposed to UV-C irradiation at 0-200mJcm(-2) and subsequently incubated for 9-15 d under normal culture conditions. Cell density and cell integrity were assessed using flow cytometry. The results suggested that UV-C irradiation at 20-200mJcm(-2) can suppress M. aeruginosa growth for 3-13 d in a dose-dependent manner. UV-C irradiation at 20 and 50mJcm(-2) is sub-lethal to M. aeruginosa cells as over 80% of the exposed cells remained intact. However, UV-C irradiation at 100 and 200mJcm(-2) induced severe cell disintegration in more than 70% of the irradiated cells. Neither significant suppression nor disintegration effects on green algae were observed for UV-C irradiation at 20-200mJcm(-2) in this study. Taken together, the sensitivity of M. aeruginosa to UV-C irradiation was significantly higher than that of the non-toxic C. ellipsoidea, C. vulgaris, and S. quadricauda, suggesting the potential application of sub-lethal UV-C irradiation for M. aeruginosa bloom control with a predictable low ecological risk.

Advanced fluorescence in situ hybridization to localize and quantify gene expression in Japanese medaka (Oryzias latipes) exposed to endocrine-disrupting compounds

In an earlier study, we described the development of fluorescence in situ hybridization (FISH) using confocal microscopy to localize and quantify gene expression in fish. Here, we report the results of FISH application to investigate effects of model endocrine-disrupting chemicals (EDCs), 17alpha-ethinylestradiol (EE2) and 17beta-trenbolone (TB), on expressions of EDC-responsive genes in Japanese medaka (Oryzias latipes) at the cellular/tissue level paired with histological observation. Gene expressions of vitellogenin-II (Vit-II), androgen receptor (AR), and cytochrome P450 gonadal aromatase (CYP19a) were determined after exposure to 5, 50, or 500 ng/L of EE2 or 50, 500, or 5,000 ng/L of TB for 7 d. Exposure to the greatest concentration of EE2 or TB significantly reduced fecundity and caused histological alterations in gonads. 17alpha-Ethinylestradiol induced Vit-II expression in both male gonads and liver relative to controls and resulted in greater intensity of hematoxylin staining in hepatocytes, which was significantly correlated with Vit-II induction in liver. When exposed to EE2 at less than 50 ng/L, CYP19a expression associated with early stage oocytes was greater than that in controls. However, at 500 ng/L, this trend was reversed. The greater Vit-II expression in testis from all EE2 groups, and the lesser expression of CYP19a in ovaries from the 500 ng/L group, likely is related to changes in the number of cells in which these genes are predominantly expressed rather than to an increase in expression per cell. 17beta-Trenbolone significantly induced AR expression in ovaries but did not alter AR expression in female liver. It was concluded that FISH combined with histology enables advanced elucidation of molecular effects of chemicals by associating changes in gene expression with certain tissues and/or cell types and allows these changes to be related to histological effects.

The use of muscle burden in rabbitfish Siganus oramin for monitoring polycyclic aromatic hydrocarbons and polychlorinated biphenyls in Victoria Harbour, Hong Kong and potential human health risk

Muscle concentrations of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) were determined in rabbitfish Siganus oramin collected from Victoria Harbour and its vicinity, Hong Kong from 2004 to 2007. Spatially, relatively higher levels of [summation operator]PAH (1.05-4.26 microg g(-1)) and [summation operator]PCB (45.1-76.9 ng g(-1)) were determined in the central and western sites inside the harbour. Temporally, upward trend of [summation operator]PAH, accompanied with a proportion shift from high molecular weight to low molecular weight PAHs, was detected during the three-year study period, suggesting a heavier marine traffic in Victoria Harbour and its western region. However, human health risk assessment based on five individual PAHs indicated that PAHs in fish muscles posed minimal health risk through consumption. In contrast, a downward trend of [summation operator]PCB was registered as the open use of PCBs has been banned. Despite this, the level of [summation operator]PCB in fish muscles still posed a health risk on the local people who have a high fish consumption rate. While seasonal influences on [summation operator]PAH/[summation operator]PCB accumulation in S. oramin seemed to be negligible, our findings in S. oramin were in line with the established PAH and PCB levels in sediments and/or mussels from the harbour, suggesting S. oramin can be used as a model fish species for monitoring PAHs and PCBs in the region.

In situ hybridization to detect spatial gene expression in medaka

A whole-animal tissue section in situ hybridization (ISH) system with radio-labeled probes was developed to detect differential gene expression among tissues of the small, oviparous teleost fish, Japanese medaka (Oryzias latipes). Because of its tissue- and gender-specific expression, gonadal aromatase (CYP19a) was selected as a model gene to demonstrate the potential of the system. The ISH system was validated with a 7d exposure to the model aromatase inhibitor, fadrozole. Fadrozole did not affect the magnitude of gene expression in testes, but significantly up-regulated CYP19a gene expression in ovaries. These results were confirmed with quantitative real-time-polymerase chain reaction (RT-PCR). Histological evaluation revealed that females exposed to 100microg/L fadrozole lacked mature oocytes. Male gonadal morphology was normal in all treatments. The ISH method developed in this study allowed tissue-specific resolution of gene expression in a whole animal model, as well as the ability to analyze cellular morphological detail in the same organism.