Commonly used techniques for trace-element analysis in human biological material are flame atomic absorption spectrometry (FAAS), graphite furnace atomic absorption spectrometry (GFAAS), inductively coupled plasma atomic emission spectrometry (ICP-AES) and inductively coupled plasma mass spectrometry (ICP-MS). Elements that form volatile hydrides, first of all mercury, are analysed by hydride generation techniques. In the absorption techniques the samples are vaporized into free, neutral atoms and illuminated by a light source that emits the atomic spectrum of the element under analysis. The absorbance gives a quantitative measure of the concentration of the element. ICP-AES and ICP-MS are multi-element techniques. In ICP-AES the atoms of the sample are excited by, for example, argon plasma at very high temperatures. The emitted light is directed to a detector, and the optical signals are processed to values for the concentrations of the elements. In ICP-MS a mass spectrometer separates and detects ions produced by the ICP, according to their mass-to-charge ratio. Dilution of biological fluids is commonly needed to reduce the effect of the matrix. Digestion using acids and microwave energy in closed vessels at elevated pressure is often used. Matrix and spectral interferences may cause problems. Precautions should be taken against trace-element contamination during collection, storage and processing of samples. For clinical problems requiring the analysis of only one or a few elements, the use of FAAS may be sufficient, unless the higher sensitivity of GFAAS is required. For screening of multiple elements, however, the ICP techniques are preferable.

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Betanodavirus infects both larvae and juvenile fish and can cause the disease viral encephalopathy and retinopathy (VER). During an acute outbreak of VER, infected individuals display several clinical signs of infection, i.e. abnormal swimming pattern and loss of appetite. Betanodaviruses can also cause chronic or persistent infection where the infected individuals show no clinical signs of infection. During infection the viral sub-genomic RNA3 and the RNA3-encoded B2 protein are expressed. Antibodies against the B2 protein from Atlantic halibut nodavirus were raised and used together with antibodies against the capsid protein to detect the presence of these 2 viral proteins in infected cells in culture and at different stages of infection in Atlantic halibut Hippoglossus hippoglossus and Atlantic cod Gadus morhua. The B2 protein was detected in recently infected, but not in chronically infected fish. Results suggest that the detection of B2 may be used to discriminate a recent and presumably active infection from a chronic and presumably persistent infection. KEY WORDS: Fish nodavirus · Atlantic halibut · Atlantic cod · B2 protein · Viral nervous necrosis Resale or republication not permitted without written consent of the publisherDis Aquat Org 83: [97][98][99][100][101][102][103] 2009 for both alpha-and betanodavirus replication (Johnson et al. 2004, Fenner et al. 2006b).RNA interference (RNAi) is a conserved evolutionary mechanism widely found in nature and is considered to be a cellular defense mechanism against foreign genes and viral infection (Cullen 2002, Plasterk 2002. The B2 proteins from the alphanodaviruses Flock House virus (FHV) and Nodamura virus (NoV) and the betanodavirus greasy grouper nervous necrosis virus (GGNNV) have been shown to suppress RNAi by binding to double stranded RNA, thus preventing cleavage, leading to enhanced accumulation of viral RNAs in plant, insect and mammalian cells (Johnson et al. 2004, Lingel et al. 2005, Sullivan & Ganem 2005, Fenner et al. 2006a.Atlantic halibut nodavirus (AHNV) was first isolated from hatchery-reared larvae of Atlantic halibut in 1995 (Grotmol et al. 1995). The clinical signs of AHNV infection are loss of appetite, abnormal swimming pattern, and changes in pigmentation (Munday et al. 2002). Mass mortality in farmed Atlantic cod and diseased juveniles with similar clinical signs to AHNV-infected Atlantic halibut led to the identification of Atlantic cod nodavirus (ACNV) , Nylund et al. 2008. The RdRp and capsid protein of AHNV and ACNV are more than 97% identical (GenBank accession nos. AJ401165, AJ245641, EF617332, EF617326), and both strains belong to the barfin flounder genotype of nodavirus (Nishizawa et al. 1997). Diagnosis of VER is performed by histopathology with identification of necrosis and vacuolation in the brain and retina, often combined with immunohistochemistry (IHC) using antibodies against the capsid protein (Grotmol et al. 1997). Other diagnostic tests, including enzyme-linked immunosorbant assays (ELISA) and rever...