Piscine Model Research Articles

Francisella sciaenopsi sp. nov. isolated from diseased red drum Sciaenops ocellatus in Florida, USA.

Piscine francisellosis is one of the most important bacterial diseases affecting various fish species worldwide. Francisella orientalis, F. noatunensis, and F. salimarina (F. marina) have been reported as etiological agents of disease in fish. A Francisella sp. was isolated from several diseased red drum Sciaenops ocellatus experiencing morbidity in Florida, USA, in 2008. In this study, molecular and phenotypic characterization of the recovered isolate was conducted. Phenotypically, the isolate showed a biochemical reaction profile distinct from that of F. orientalis and F. salimarina. Although the 16S rRNA sequence of this isolate shared 99.61% identity to the type strain of F. philomiragia O#319LT, whole genome analysis (average nucleotide identity <95%; digital DNA-DNA hybridization <70%) and a multilocus sequence analysis of 8 concatenated housekeeping genes in comparison with other Francisella spp. indicated that this isolate was a novel Francisella species, more closely related to F. orientalis. Immersion, intracoelomic injection, and co-habitation challenges using a Nile tilapia Oreochromis niloticus fingerling model of infection were done to investigate virulence in a piscine model. Variably pigmented granulomas and pigmented macrophage aggregates were observed in the kidneys and spleens of the challenged fish, but no mortality was recorded during the 15 d challenge period, suggesting that this novel Francisella sp. might be an opportunistic pathogen of fish. Based on the phenotypic and genotypic differences from other Francisella spp. observed in this study, we propose the name Francisella sciaenopsi sp. nov. for this novel isolate.

Melatonin ameliorates lipopolysaccharide induced brain inflammation through modulation of oxidative status and diminution of cytokine rush in Danio rerio

Lipopolysaccharide (LPS) is known to induce inflammation and immunonomodulation in a piscine model of Danio rerio. Present study aimed to explore the ability of melatonin in attenuating LPS-induced oxidative damages using this model. In LPS-exposed fish, activation of stress marker MDA was observed in brain with corresponding augmentation of multiple pro-inflammatory cytokines (IL1β, IL6, IL10 and TNFα). In addition, it also showed marked increase in the levels of heat shock factor (HSF) and heat shock proteins (HSPs) in association with transcription factors (NF-kB and NRF2) and mitogen-activated protein kinases (MAPKs). The changes in the levels of these mediators are highly correlated with the induction of pro-inflammatory cytokines. In melatonin-treated fishes, significant amelioration of oxidative stress was observed with reduced levels of MDA and pro-inflammatory cytokines. Melatonin also modulated expression of HSPs that facilitated the brain to overcome inflammation-induced stress by directly initiating NFkB/NRF2 translocation. In summary, melatonin effectively functions to reduce stress induced inflammatory signalling through modulation of oxidative stress and protects the brain from the neuropathological insult.

Molecular determinants regulating the release of the egg during ovulation: Perspectives in piscine models

Reproduction in bony fish, specifically in the female teleost, encompasses well-defined stages, including growth and development, final oocyte maturation and finally ovulation – a pre-requisite for forming fertilizable female gametes. The morphological changes encountered during ovulatory response engage a multitude of endocrine, autocrine, and paracrine factors. These include gonadal steroids, growth factors, inflammatory cytokines, prostaglandins, leukotrienes and matrix metalloproteinases. In recent years, the active participation of prostaglandins and their receptors in LH-dependent ovulatory action has received much attention. Considerable evidence also supports the participation of nitric oxide/nitric oxide synthase (NO/NOS) unit in regulating meiotic maturation and ovulatory cascade. However, relatively less information is available on physiological relevance, the inter-relationship and the conjoined efforts of these molecular candidates to trigger ovulation in the fish ovary. The prime objective of the present article is to summarize the potential cross-talk between major molecular candidates downstream of LH action in the follicular layer. Besides, the intraovarian role of prostaglandin (PG) vis-à-vis NO/NOS system on mammalian and teleost ovulatory response has been emphasised.

Hypoxia- and hyperoxia-related gene expression dynamics during developmental critical windows of the tropical gar Atractosteus tropicus

Aquatic hypoxia is both a naturally-occurring and anthropogenically-generated event. Fish species have evolved different adaptations to cope with hypoxic environments, including gill modifications and air breathing. However, little is known about the molecular mechanisms involved in the respiration of embryonic and larval fishes during critical windows of development. We assessed expression of the genes hif-1α, fih-1, nhe1, epo, gr and il8 using the developing tropical gar as a piscine model during three developmental periods (fertilization to hatch, 1 to 6 days post hatch (dph) and 7 to 12 dph) when exposed to normoxia (~7.43 mg/L DO), hypoxia (~2.5 mg/L DO) or hyperoxia (~9.15 mg/L DO). All genes had higher expression when fish were exposed to either hypoxia or hyperoxia during the first two developmental periods. However, fish continuously exposed to hypoxia had increased expression of the six genes by hatching and 6 dph, and by 12 dph only hif-1α still had increased expression. The middle developmental period was the most hypoxia-sensitive, coinciding with several changes in physiology and morphology. The oldest larvae were the most resilient to gene expression change, with little variation in expression of the six genes compared. This study is the first to relate the molecular response of an air-breathing fish to oxygen availability to developmental critical windows and contributes to our understanding of some molecular responses of developing fish to changes in oxygen availability.

In vivo immunostimulatory effect of the amoebocyte lysate and plasma of Asian horseshoe crab, Tachypleus gigas in a piscine model.

Antimicrobial proteins/peptides are becoming a new generation of immunostimulants for prevention and disease control in human and animals, including aquatic animals. As the haemolymph of horseshoe crabs (Tachypleus) contains broad ranges of bioactive compounds, we have explored the in vivo immunostimulating potential of amoebocyte lysate and plasma using a fish model. Indian major carp, Labeo rohita, yearlings were injected intraperitoneally with two doses of lysate and plasma at 50 and 100µg protein per fish. No abnormalities and/or mortalities were recorded in any group. L. rohita injected with 50µg lysate and 100µg plasma protein showed significant enhancement (P < 0.01) of various haematological and immunological parameters. There was a significant rise in the total protein and globulin content, myeloperoxidase and respiratory burst activity following injection with 50µg lysate and 100µg plasma protein. The agglutinating and haemagglutinating activities were increased albeit not significantly (P > 0.01) in any groups. On the contrary, a significantly high hemolysin titre was recorded in fish that received 100µg plasma protein. Following challenge with Aeromonas hydrophila, both lysate and plasma protein(s) cross protected the fish after 30days. The highest survival (50%) was recorded in group injected with 50µg lysate protein, followed by 45% in both 100µg lysate and plasma protein injected groups.

Nephroprotective effect of Emblica officinalis fruit extract against malachite green toxicity in piscine model: Ultrastructure and oxidative stress study.

Malachite green (MG) is a multi-application dye with raised concern as aquatic toxicant. Cyprinus carpio fingerlings were exposed to MG and simultaneously fed with Emblica officinalis (EO) fruit extract to mitigate the MG induced nephrotoxicity. MG exposure developed depressed activity of antioxidant enzymes such as catalase, superoxide dismutase, glutathione-s-transferase, and reduced glutathione, while levels of malondialdehyde got significantly (p < .05) elevated after 60 days MG exposure. H&E staining revealed increased intracellular space, vacuolation, fluid-filled spaces, damaged brush border lining of proximal convoluted tubule (PCT), focal necrosis, nuclear transformations and shrunken glomerulus. Further, Transmission electron microscope study detailed structural cytotoxicity with the appearance of the heterochromatic nucleus, electron-dense lysosomal bodies, damaged brush border lining of PCT, and necrosis; glomerulus exhibited erythrocyte infiltration and fused pedicels of podocyte. While, EO extract supplemented diet culminated in the restoration of the renal cytoarchitecture and significantly (p < .05) enhanced activity of antioxidant enzymes.

Corrigendum to “Elucidation of Malachite Green Induced Behavioural, Biochemical, and Histo-architectural Defects in Cyprinus carpio, as Piscine Model”

Corrigendum to “Elucidation of Malachite Green Induced Behavioural, Biochemical, and Histo-architectural Defects in Cyprinus carpio, as Piscine Model”

Elucidation of malachite green induced behavioural, biochemical, and histo-architectural defects in Cyprinus carpio, as piscine model

Colours are an indispensable portion of human survival. Malachite green (MG) is a dye with a bright hue of green, used in textile, paint, and confectionery industry. For the present study, healthy fingerlings of Cyprinus carpio were exposed to sub-lethal concentration (0.087 ​mg/L) of malachite green for 15, 30, and 60 days. Assessment of chronic toxicity was made through varied organs (cornea, erythrocytes, and liver) and analytical methods, comprising behavioural, histopathological, ultra-structural (transmission electron microscopy), biochemical (antioxidant and marker enzymes) and bioaccumulation studies. Behavioural aspects, comprised of opercular and fin (dorsal and caudal) movements, presented an inverse relation with MG treatment, and displayed escaping behaviour from the experimental tank. Scanning electron microscopy (SEM) of MG exposed fish peripheral erythrocytes demonstrated morphological anomalies in form of clubbing, budding, and appearance of the varied shaped cells as stomatocytes, acanthocytes, dacrocytes and fusiform cells in the exposure dependent manner, instead of regular elliptical erythrocytes in control. Corneal epithelium study conducted through SEM in MG treated fish reported damaged pavements cells, microridges, and microplicae, and increased intra-microplicae distance compared to control fish. Elevated levels of serum marker enzymes and disturbed levels of antioxidant enzymes were also evident; accompanied by abundance of MDA-TBARs level suggestive of oxidative stress in MG treated fish. Bioaccumulation studies conducted revealed up to 3.06 fold dye deposition, conferring the enhanced and prolonged toxicity of the dye in the fish. Consequently, MG can be inferred as a strong cellular toxicant even at sub-lethal concentration.

AMPK activation by dietary AICAR affects the growth performance and glucose and lipid metabolism in juvenile grass carp

Fish are poor users of dietary carbohydrates and considered to be glucose intolerant, and activating AMP‐activated protein kinase (AMPK) by 5‐aminoimidazole‐4‐carboxamide ribonucleoside (AICAR) has been shown to stimulate glucose uptake and utilization in skeletal muscle cells of rainbow trout. However, the effects of activating AMPK by dietary AICAR in the piscine model remain largely unexplored. In the present study, grass carp were fed purified diets including AICAR at a level of 0 or 200 mg/kg diet to chronically activate AMPK for 8 weeks, and the dietary effects on phenotypic and molecular responses related to glucose and lipid metabolism were examined. The results showed that activating AMPK by dietary AICAR significantly reduced fish growth performance, serum glucose and triacylglycerol contents, and liver lipid contents, while it increased hepatic glycogen contents (p 0.05). The results of AMPK signalling pathway in both the liver and muscle show that dietary AICAR increased the phosphorylation of AMPKα and acetyl‐CoA carboxylase (ACC; p < 0.05), while inhibiting the phosphorylation of sterol regulatory element‐binding transcription factor‐1(SREBP‐1) and target of rapamycin (p < 0.05). The activation of AMPK reduced the mRNA expression of lipogenesis enzymes in the liver and muscle (p < 0.05) and increased mRNA expression of gluconeogenesis enzymes in the liver and glycolysis enzymes in the heart (p < 0.05). Our results demonstrate that activating AMPK by AICAR reduces serum glucose and inhibits activities of ACC and SREBP‐1 to reduce lipogenesis in the liver and muscle, and AMPK could be used as an active target for its metabolic syndromes of grass carp.

Not going with the flow: Locomotor activity does not constrain immunity in a wild fish.

Immunity is a central component of fitness in wild animals, but its determinants are poorly understood. In particular, the importance of locomotory activity as a constraint on immunity is unresolved. Using a piscine model (Gasterosteus aculeatus), we combined a 25‐month observational time series for a wild lotic habitat with an open flume experiment to determine the influence of locomotor activity (countercurrent swimming) on natural variation in immune function. To maximize the detectability of effects in our flume experiment, we set flow velocity and duration (10 cm/s for 48 hr) just below the point at which exhaustion would ensue. Following this treatment, we measured expression in a set of immune‐associated genes and infectious disease resistance through a standard challenge with an ecologically relevant monogenean infection (Gyrodactylus gasterostei). In the wild, there was a strong association of water flow with the expression of immune‐associated genes, but this association became modest and more complex when adjusted for thermal effects. Our flume experiment, although statistically well‐powered and based on a scenario near the limits of swimming performance in stickleback, detected no countercurrent swimming effect on immune‐associated gene expression or infection resistance. The field association between flow rate and immune expression could thus be due to an indirect effect, and we tentatively advance hypotheses to explain this. This study clarifies the drivers of immune investment in wild vertebrates; although locomotor activity, within the normal natural range, may not directly influence immunocompetence, it may still correlate with other variables that do.

Risk assessment of low arsenic exposure using biomarkers of oxidative and genotoxic stress in a piscine model.

The high level exposure to arsenic induces marked oxidative and genotoxic stress. However, information on the potential of low level arsenic exposure in this context is still scanty. In the present study, the extent of oxidative stress and genetic toxicity induced by low arsenic exposure was explored in freshwater fish Channa punctatus. Fish were exposed to low levels of arsenic (10 and 50 µg L-1) as well as to its high level (500 µg L-1) using sodium arsenite in aquaria water for 14 consecutive days. The TBARS assay for lipid peroxidation exhibited the increased occurrence of oxidative damage in the erythrocytes of fish at both the lower and higher levels of arsenic exposure. The level of reduced glutathione was also elevated in all the three arsenic exposed groups of fish compared to control. In contrast, significant decline was observed in the levels of three major antioxidant enzymes namely, superoxide dismutase, catalase and glutathione peroxidase, upon exposure to higher as well as lower levels of arsenic. Significant increases in micronucleus induction were found in the erythrocytes of fish even at the low levels of arsenic exposure. The study further revealed the occurrence of DNA fragmentation in the erythrocytes of fish at low arsenic exposures as well. The low level exposure to arsenic (using sodium arsenite), therefore, appeared to be capable of inducing noticeable oxidative stress as well as potential genotoxic effect in Channa punctatus. Moreover, the ability of arsenic to induce oxidative stress invariably appeared correlated with its genotoxic potential.

Evaluating the protective efficacy of Silybum marianum against deltamethrin induced hepatotoxicity in piscine model

With the known facts of deltamethrin toxicity in aquaculture, efforts have been made to ameliorate its toxicity with supplementation of Silybum marianum plant extract in Cyprinus carpio. For validating its efficacy, standard techniques of histopathology, anti-oxidant profile and RAPD-PCR were used. By performing acute toxicity bioassay, 96 h LC50 of the pesticide to C. carpio was determined and was found to be 2 μg/L. Histopathological alterations were comprised of nuclear alterations, vacuolisation and oedema in the hepatocytes. Chronic exposure to the toxicant induced significant changes in antioxidant defense system (CAT, SOD, GSH and GST levels), lipid peroxidation being prominent. Diet supplementation with silymarin appeared to modulate the oxidative stress, histopathological alterations and genotoxic damage caused by the pesticide in the fish. RAPD-PCR studies revealed deltamethrin induced toxicity and its effective amelioration in form of restoration of bands which were lost in toxicant exposed DNA profile.

Physical Cues Controlling Seasonal Immune Allocation in a Natural Piscine Model.

Seasonal patterns in immunity are frequently observed in vertebrates but are poorly understood. Here, we focused on a natural piscine model, the three-spined stickleback (Gasterosteus aculeatus), and asked how seasonal immune allocation is driven by physical variables (time, light, and heat). Using functionally-relevant gene expression metrics as a reporter of seasonal immune allocation, we synchronously sampled fish monthly from the wild (two habitats), and from semi-natural outdoors mesocosms (stocked from one of the wild habitats). This was repeated across two annual cycles, with continuous within-habitat monitoring of environmental temperature and implementing a manipulation of temperature in the mesocosms. We also conducted a long-term laboratory experiment, subjecting acclimated wild fish to natural and accelerated (×2) photoperiodic change at 7 and 15°C. The laboratory experiment demonstrated that immune allocation was independent of photoperiod and only a very modest effect, at most, was controlled by a tentative endogenous circannual rhythm. On the other hand, experimentally-determined thermal effects were able to quantitatively predict much of the summer–winter fluctuation observed in the field and mesocosms. Importantly, however, temperature was insufficient to fully predict, and occasionally was a poor predictor of, natural patterns. Thermal effects can thus be overridden by other (unidentified) natural environmental variation and do not take the form of an unavoidable constraint due to cold-blooded physiology. This is consistent with a context-dependent strategic control of immunity in response to temperature variation, and points to the existence of temperature-sensitive regulatory circuits that might be conserved in other vertebrates.

Glutathione and zebrafish: Old assays to address a current issue

Several xenobiotic agents (e.g. metals, polycyclic aromatic hydrocarbons, nanoparticles, etc.) commonly involve the generation of reactive oxygen species (ROS) and oxidative stress as part of their toxic mode of action. Among piscine models, the zebrafish is a popular vertebrate model to study toxicity of various xenobiotic agents. Similarly to other vertebrates, zebrafish possess an extensive antioxidant system, including the reduced form of glutathione (GSH), which is an important antioxidant that acts alone or in conjunction with enzymes, such as glutathione peroxidase (GPx). Upon interaction with ROS, GSH is oxidized, resulting in the formation of glutathione disulfide (GSSG). GSSG is recycled by an auxiliary antioxidant enzyme glutathione reductase (GR). This article outlines detailed methods to measure the concentrations of GSH and GSSG, as well as the activities of GPx and GR in zebrafish larvae as robust and economical means to assess oxidative stress. The studies that have assessed these endpoints in zebrafish and alternative methods are also discussed. We conclude that the availability of these robust and economical methods support the use of zebrafish as a model organism in studies evaluating redox biology, as well as the induction of oxidative stress following exposure to toxic agents.

Podophyllum hexandrum ameliorates endosulfan-induced genotoxicity and mutagenicity in freshwater cyprinid fish crucian carp

Context: Medicinal plants continue to act as a repository for novel drug leads with novel mechanisms of action. Podophyllum hexandrum Royale (Berberideceae) treats diverse conditions in folk medicine.Objective: The antimutagenic potential of P. hexandrum was evaluated against endosulfan-induced clastogenicity in a piscine model by cytogenetic endpoints.Materials and methods: Podophyllum hexandrum rhizomes were subjected to successive solvent extraction. Fish were exposed to hexane, chloroform, ethyl acetate, methanol and aqueous extracts (15 mg/L each) of plant and endosulfan (0.05 mg/L) alone followed by their combination for antimutagenicity estimates. Chromosomal aberrations (CA) were made from kidney cells and micronuclei (MN) slides from peripheral blood erythrocytes at 48, 72 and 96 h. Antioxidant activity was analyzed by the DPPH assay. Phytochemical analyses were carried out using chromatographic and spectroscopic techniques.Results: Endosulfan induced significant (p < .05) MN, authenticated by scanning electron microscopy, and CA in a time-dependent manner. However, methanol and ethyl acetate extracts revealed ameliorating effects. The column eluted methanolic fraction-2 (ME-F2) showed highest reduction profile of 83 and 84% in CA and MN, followed in its extent (73 and 72%) by ethyl acetate fraction-4 (EE-F4). ME-F2 and EE-F4 showed three and six major peaks when analyzed by GC-MS. To explore possible mechanism of action, ME-F2 showed potent antioxidant potential and strong correlation (R2 = .900) with antimutagenic activity, whereas EE-F4 seemed to act through a different mechanism.Discussion and conclusion: This study confirms the antimutagenic potential of the subject plant with the identification of some novel compounds, justifying their use in folk medicine, and their corresponding benefit to mankind.

Seasonal immunoregulation in a naturally-occurring vertebrate.

BackgroundFishes show seasonal patterns of immunity, but such phenomena are imperfectly understood in vertebrates generally, even in humans and mice. As these seasonal patterns may link to infectious disease risk and individual condition, the nature of their control has real practical implications. Here we characterize seasonal dynamics in the expression of conserved vertebrate immunity genes in a naturally-occurring piscine model, the three-spined stickleback.ResultsWe made genome-wide measurements (RNAseq) of whole-fish mRNA pools (n = 36) at the end of summer and winter in contrasting habitats (riverine and lacustrine) and focussed on common trends to filter habitat-specific from overarching temporal responses. We corroborated this analysis with targeted year-round whole-fish gene expression (Q-PCR) studies in a different year (n = 478). We also considered seasonal tissue-specific expression (6 tissues) (n = 15) at a third contrasting (euryhaline) locality by Q-PCR, further validating the generality of the patterns seen in whole fish analyses. Extremes of season were the dominant predictor of immune expression (compared to sex, ontogeny or habitat). Signatures of adaptive immunity were elevated in late summer. In contrast, late winter was accompanied by signatures of innate immunity (including IL-1 signalling and non-classical complement activity) and modulated toll-like receptor signalling. Negative regulators of T-cell activity were prominent amongst winter-biased genes, suggesting that adaptive immunity is actively down-regulated during winter rather than passively tracking ambient temperature. Network analyses identified a small set of immune genes that might lie close to a regulatory axis. These genes acted as hubs linking summer-biased adaptive pathways, winter-biased innate pathways and other organismal processes, including growth, metabolic dynamics and responses to stress and temperature. Seasonal change was most pronounced in the gill, which contains a considerable concentration of T-cell activity in the stickleback.ConclusionsOur results suggest major and predictable seasonal re-adjustments of immunity. Further consideration should be given to the effects of such responses in seasonally-occurring disease.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-2701-7) contains supplementary material, which is available to authorized users.

An introduction about Genotoxicology Methods as Tools for Monitoring Aquatic Ecosystem: Present status and Future perspectives

Pesticide residues with genotoxic potential reach the aquatic environment and constitute a major issue that give rise to concerns at local, regional, national and global scales. Fish serves as an excellent genetic model for the genetic hazard assessment as they are very sensitive to changes in their environment. As there is a close consortium of DNA damage, mutation and induction of various types of genetic disorders, genotoxicity tests like chromosomal aberration test, micronuclei and comet assay are gaining credence and since past few decades many tests have been developed for evaluating genetic alterations in aquatic organisms. These tests rely on the premise that any change to DNA may have enduring and ardent consequences. Thus, the first aim of the genotoxicology is to describe the outcome produced by toxic substances in various test species, but only from the genetic point of view and to draw conclusions that can be extrapolated to man. This review summarizes the genotoxicity tests developed till date and the role of piscine model in genotoxicology. The text also delves the latest knowledge and thinking on these cardinal approaches for the assessment of aquatic environmental health, management and conservation, besides providing useful repository for the researchers especially dealing with aquatic genotoxicity tests. The perspectives for further research on the use of genotoxicology tests were also highlighted.

The metabolic consequences of hepatic AMP-kinase phosphorylation in rainbow trout.

AMP-activated protein kinase (AMPK), a phylogenetically conserved serine/threonine protein kinase, is proposed to function as a “fuel gauge” to monitor cellular energy status in response to nutritional environmental variations. However, in fish, few studies have addressed the metabolic consequences related to the activation of this kinase. This study demonstrates that the rainbow trout (Oncorhynchus mykiss) possesses paralogs of the three known AMPK subunits that co-diversified, that the AMPK protein is present in the liver and in isolated hepatocytes, and it does change in response to physiological (fasting-re-feeding cycle) and pharmacological (AICAR and metformin administration and incubations) manipulations. Moreover, the phosphorylation of AMPK results in the phosphorylation of acetyl-CoA carboxylase, a main downstream target of AMPK in mammals. Other findings include changes in hepatic glycogen levels and several molecular actors involved in hepatic glucose and lipid metabolism, including mRNA transcript levels for glucokinase, glucose-6-phosphatase and fatty acid synthase both in vivo and in vitro. The fact that most results presented in this study are consistent with the recognized role of AMPK as a master regulator of energy homeostasis in living organisms supports the idea that these functions are conserved in this piscine model.

Identification and analysis of a Sciaenops ocellatus ISG15 homologue that is involved in host immune defense against bacterial infection

ISG15 is an interferon-stimulated gene that encodes a ubiquitin-like protein. ISG15 homologues have been identified in a number of fish species, some of which are known to be regulated at expression level by virus infection and lipopolysaccharide (LPS) treatment. However, the relationship between ISG15 and live bacterial infection has not been investigated in piscine models. In this study, an ISG15 homologue, SoISG15, was identified from red drum Sciaenops ocellatus and analyzed at expression and functional levels. The open reading frame of SoISG15 is 477 base pairs (bp) and intronless, with a 5′-untranslated region (UTR) of 91 bp and a 3′-UTR of 415 bp. The deduced amino acid sequence of SoISG15 shares 60–67% overall identities with the ISG15 of several fish species. SoISG15 possesses two conserved ubiquitin-like domains and the canonical ubiquitin conjugation motif, LRGG, at the C-terminus. Expressional analysis showed that constitutive expression of SoISG15 was highest in blood and lowest in kidney. Experimental challenges with LPS and bacterial pathogens induced significant SoISG15 expression in the kidney but not in the liver. Similar differential induction was also observed at cellular level with primary hepatocytes and head kidney (HK) lymphocytes. Poly(I:C), however, effected drastic induction of SoISG15 expression in kidney and liver at both tissue and cellular levels. Immunoblot analysis showed that SoISG15 was secreted by cultured HK lymphocytes into the extracellular milieu. Recombinant SoISG15 expressed in and purified from Escherichia coli was able to enhance the respiratory burst activity, acid phosphatase activity, and bactericidal activity of HK macrophages. Taken together, the results of this study indicated that SoISG15 possesses apparent immunological property and is likely to be involved in host immune defense against bacterial infection.

Overview of Developmental Heart Defects by Dioxins, PCBs, and Pesticides

The developing cardiovascular system is a sensitive target of many environmental pollutants, including dioxins, dioxin-like polychlorinated biphenyls (PCBs), and some pesticides such as methyl parathion. Laboratory research has utilized a variety of vertebrate models to elucidate potential mechanisms that mediate this cardioteratogenicity and to establish the sensitivity of different species for predicting potential risk to environmental and human health. Studies of dioxin and dioxin-like PCBs have illustrated that piscine, avian, and mammalian embryos exhibit cardiovascular structural changes and functional deficits, although the specific characteristics vary among the individual models. Piscine models typically exhibit reduced blood flow, altered heart looping, and reduced heart size and contraction rate. The chick embryo exhibits extensive cardiac dilation, thinner ventricle walls, and reduced responsiveness to chronotropic stimuli, while the murine embryo exhibits reduced heart size. It is notable that in all models the dioxin-associated cardioteratogenicity is associated with increases in cardiovascular apoptosis and decreases in cardiocyte proliferation. While the cardiotertogenicity in piscine and avian species is associated with overt morbidity and mortality, that is not the case for the murine embryo. However, murine offspring exposed during development to dioxin exhibit cardiac hypertrophy and an increased sensitivity to a second cardiovascular insult in adulthood. Thus, although the mammalian embryo is less sensitive to cardiovascular defects by dioxin and dioxin-like compounds, developmental exposure increases the risk of cardiovascular disease later in life. The impact of developmental exposure to dioxin-like chemicals on human cardiovascular disease susceptibility is not known. However, recent animal research has confirmed human epidemiology studies that dioxin exposure in adulthood is associated with hypertension and cardiovascular disease.