Variation of Total and Speciated Arsenic in Commonly Consumed Fish and Seafood

This article compiles available data and presents an approach for predicting human intakes of inorganic arsenic (As_i), monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA) from marine, estuarine, and freshwater seafood when only total arsenic (As_tot) concentrations are reported. Twenty studies provided data on total arsenic (As_tot) and As_i. Mean As_i concentrations were approximately 10 to 20 ng/g wet weight (ww) in freshwater, anadromous, and marine fish, whereas crustaceans and molluscs had mean As_i concentrations of 40 to 50 ng/g ww. Thirteen studies provided data for MMA and DMA. MMA was seldom detected, whereas DMA averaged 10 ng/g ww in freshwater fish, and 45 to 95 ng/g ww in anadromous fish, marine fish, crustaceans, and molluscs. There was little correlation between As_tot concentrations and As_i concentrations; however, when only As_tot data are available to assess health risks from arsenic in seafood, these data could support conservative, upper end estimates of the percent of As_tot likely to be As_i. For marine and estuarine fish, and crustaceans and molluscs 2–3% of As_tot was As_i at the 75th percentile of the dataset. For freshwater fish As_i was 10% of As_tot at the 75th percentile. Due to the nonlinearity and low carcinogenic potency of DMA, the reported DMA concentrations should not contribute substantially to potential health risks from arsenic in seafood.     

Directional characteristics of tuberous electroreceptors in the weakly electric fish,Hypopomus (Gymnotiformes)

This paper is an electrophysiological study of the directionality of the tuberous electroreceptors of weakly electric fish. We recorded from two classes of tuberous electroreceptors known for pulse gymnotiforms: Burst Duration Coders (BDCs), and Pulse Markers (PMs). Both code for stimulus amplitude, although the dynamic range for BDCs is greater, and both exhibit strong directional preferences. Polar plots of spike number (for BDCs) or spike threshold (for PMs) versus electric field azimuth, are figure-8 shaped with two asymmetrical, elliptical lobes separated by 180°. The best azimuth of these two types of receptors from a given body region correlate with each other and with measures of best azimuth for transepidermal current flow. The shape and asymmetry of the directionality profiles appear to be caused by filter dynamics of the receptors. Pulse Markers are located on the anterior part of the body surface while Burst Duration Coders are located all over. The best directions of receptors in the anterior third of the body vary systematically with location from 0° to 180°. This region is probably critical for determining the direction of local electric fields. Together these receptors provide the CNS with sufficient information to construct a map of horizontal plane electric field directions.Abbreviations BDC Burst Duration Coder - ELL electrosensory lateral line lobe - EOD electric organ discharge - nALL anterior lateral line nerve - PM Pulse Marker     

Ectopic expression of Hox-2.3 induces craniofacial and skeletal malformations in transgenic mice.

To better understand the role of the Hox-2.3 murine homeobox gene during development, a dominant gain-of-function mutation was generated. The developmental malformations that resulted when the chicken beta-actin promoter was used to direct widespread expression of the Hox-2.3 gene in transgenic mice included early postnatal death as well as craniofacial abnormalities, including open eyes and cleft palate. Ventricular septal defects were also observed in the hearts of three transgenic mice. Skeletal malformations were seen in the bones of the craniocervical transition, with the occipital, basisphenoid, and atlas bones deficient or misshapen. Interestingly, one mutant exhibited an extra pair of ribs as well as alterations in cervical vertebrae identities. Some of the malformations observed in Hox-2.3 gain-of-function mutants overlap with those seen in Hox-1.1 and Hox-2.2 misexpression mutants which suggests functional similarities between paralogous homeobox genes. The results of these experiments are consistent with a role for Hox-2.3 in specifying positional information during development.     

A sensitive method to measure physical and chemical carcinogen-induced "unscheduled DNA synthesis" in rapidly dividing eukaryotic cells

A sensitive assay for quantitating ‘unscheduled DNA synthesis’ (repair synthesis) in transformed human amnion (AV₃) cells has been developed. The combined use of hydroxyurea and arginine-deficient culture medium enabled the detection of 10–20 fold increases in ‘unscheduled DNA synthesis’ after treatment with N-acetoxy-2-acetylaminofluorene or ultraviolet light. The technique allows the detection of ‘DNA repair synthesis’ following treatment with extremely low doses of mutagens and carcinogens.     

A Comparison of Two Serological Methods for Detecting the Immune Response after Rabies Vaccination in Dogs and Cats being Exported to Rabies-free Areas

Levels of rabies virus neutralizing antibody in sera from dogs and cats were titrated to endpoint by the Rapid Fluorescent Focus Inhibition Test (RFFIT) and retested by the RFFIT and the Fluorescent Antibody Virus Neutralization test (FAVN). The two tests were compared for their ability to detect the 0.5 international units/ml (I.U.) of antibody required by the World Health Organization and the Office International des Epizooties as the minimum response for proof of rabies immunization. No difference was observed in sensitivity or specificity for either method in tests of 168 sera from unvaccinated animals or 70 sera from vaccinated animals with high levels of neutralizing antibody (an initial RFFIT titre of > or = 1.0 I.U.). Test to test variation occurred for results obtained by both RFFIT and FAVN for 95 sera from vaccinated animals with low to moderate levels of neutralizing antibody (RFFIT titre < 1.0 I.U.). No significant differences were detected for the 95 sera in the frequency for one methodology more often than the other to have a positive response (> or = 0.5 I.U.), nor were significant differences detected for the symmetry (P = 0.43) or the marginal homogeneity (P = 0.39) of results obtained by the two methods. Both methods can adequately identity unvaccinated animals, but false positive and false negative results are possible for either method when a single test is used to measure the antibody response of low-responding vaccinated animals. Nucleotide sequence analysis identified several amino acid differences in stocks of the challenge rabies virus from different laboratories. The small differences in neutralizing antibody titre that may result from mutations in the challenge virus are not important for evaluating immunity induced by vaccines which are themselves prepared from a variety of different rabies virus strains, but differences in the challenge virus, rather than differences in methodology, may account for at least some of the discrepant results reported in inter-laboratory surveys. Comparative studies of serological methods for measuring rabies antibodies should use well-characterized unpassaged virus stocks obtained from a single reference laboratory.