Human dietary exposure to dioxins and dioxin-like PCBs through the consumption of Atlantic herring from fishing areas in the Norwegian Sea and Baltic Sea

The concentrations of dioxins [polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs)], and dioxin-like polychlorinated biphenyls (DL-PCBs) in Atlantic herring depend on the fishing area. These substances originate from various anthropogenic sources and accumulate in the environment and in food. The influence of country-specific contaminant concentrations on human dietary exposure was studied exemplary for herring to show the influence of fish origin. PCDD/F and DL-PCB concentrations in herring from the Norwegian Sea and the Baltic Sea were combined with country-specific herring consumption. Herring concentrations showed geographical variation. For herring consumers, the 50th percentile dietary exposure to the total sum of PCDD/Fs and DL-PCBs amounted to 1.2 and 8.9 pg WHO-2005-TEQ/kg BW/week for Norway and Germany, respectively. The different exposure was mainly related to higher concentrations in herring from the Baltic Sea, rather than in herring from the Norwegian Sea. If contaminant concentrations are influenced by geographical origin, this should be integrated into the dietary exposure assessments. For herring, relevant fishing areas should be integrated into the sampling strategy to generate concentration data. The usage of country-specific data could refine exposure assessments.publishedVersio

Physiological evidence of sensory integration in the electrosensory lateral line lobe of Gnathonemus petersii

Fechner S, Grant K, von der Emde G, Engelmann J. Physiological evidence of sensory integration in the electrosensory lateral line lobe of Gnathonemus petersii. PLOS ONE. 2018;13(4): e0194347.Mormyrid fish rely on reafferent input for active electrolocation. Their electrosensory input consists of phase and amplitude information. These are encoded by differently tuned receptor cells within the Mormyromasts, A- and B-cells, respectively, which are distributed over the animal’s body. These convey their information to two topographically ordered medullary zones in the electrosensory lateral line lobe (ELL). The so-called medial zone receives only amplitude information, while the dorsolateral zone receives amplitude and phase information. Using both sources of information, Mormyrid fish can disambiguate electrical impedances. Where and how this disambiguation takes place is presently unclear. We here investigate phase-sensitivity downstream from the electroreceptors. We provide first evidence of phase-sensitivity in the medial zone of ELL. In this zone I-cells consistently decreased their rate to positive phase-shifts (6 of 20 cells) and increased their rate to negative shifts (11/20), while E-cells of the medial zone (3/9) responded oppositely to I-cells. In the dorsolateral zone the responses of E- and I-cells were opposite to those found in the medial zone. Tracer injections revealed interzonal projections that interconnect the dorsolateral and medial zones in a somatotopic manner. In summary, we show that phase information is processed differently in the dorsolateral and the medial zones. This is the first evidence for a mechanism that enhances the contrast between two parallel sensory channels in Mormyrid fish. This could be beneficial for impedance discrimination that ultimately must rely on a subtractive merging of these two sensory streams

Physiological evidence of sensory integration in the electrosensory lateral line lobe of Gnathonemus petersii.

Mormyrid fish rely on reafferent input for active electrolocation. Their electrosensory input consists of phase and amplitude information. These are encoded by differently tuned receptor cells within the Mormyromasts, A- and B-cells, respectively, which are distributed over the animal's body. These convey their information to two topographically ordered medullary zones in the electrosensory lateral line lobe (ELL). The so-called medial zone receives only amplitude information, while the dorsolateral zone receives amplitude and phase information. Using both sources of information, Mormyrid fish can disambiguate electrical impedances. Where and how this disambiguation takes place is presently unclear. We here investigate phase-sensitivity downstream from the electroreceptors. We provide first evidence of phase-sensitivity in the medial zone of ELL. In this zone I-cells consistently decreased their rate to positive phase-shifts (6 of 20 cells) and increased their rate to negative shifts (11/20), while E-cells of the medial zone (3/9) responded oppositely to I-cells. In the dorsolateral zone the responses of E- and I-cells were opposite to those found in the medial zone. Tracer injections revealed interzonal projections that interconnect the dorsolateral and medial zones in a somatotopic manner. In summary, we show that phase information is processed differently in the dorsolateral and the medial zones. This is the first evidence for a mechanism that enhances the contrast between two parallel sensory channels in Mormyrid fish. This could be beneficial for impedance discrimination that ultimately must rely on a subtractive merging of these two sensory streams

Influence of the geographical origin on substance concentrations in herring as basis for dietary exposure assessments

Previous investigations on agricultural products showed that geographical origin influences concentrations of selected undesirable substances and ultimately dietary exposure assessment. This could also be relevant for fish from different catching areas, as substance concentrations have been found to vary between catching areas. Herring was chosen as an example. Norwegian and German data on consumption and substance concentrations were considered. To investigate if concentrations of substances are different in Norway and Germany, monitoring data between 2012 and 2017 were used. Norway provided data of commercial catching areas from the Norwegian Spring Spawning (NSS) herring stock, while Germany had market data available. Concentrations of cadmium, mercury and selenium tended to be higher in herring from Norway, while lead concentrations were higher in Germany. Polychlorinated dibenzo‐p‐dioxins/polychlorinated dibenzofurans (PCDD/Fs), dioxin‐like polychlorinated biphenyls (DL‐PCBs) and non‐dioxin‐like PCBs (NDL‐PCBs) tended to have higher concentrations in Germany, while perfluorinated alkylated substances (PFAS) were mostly below quantifiable levels in the two countries. These differences could be attributed to different herring stocks available on the market in Germany and Norway. Country‐specific data on consumption and substance concentrations give a basis for a refined exposure assessment covering both the Norwegian and the German situation. This is of special importance if European risk assessments are carried out combining concentration data recorded in several countries without taking origin into account

Human dietary exposure to dioxins and dioxin-like PCBs through the consumption of Atlantic herring from fishing areas in the Norwegian Sea and Baltic Sea

The concentrations of dioxins [polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs)], and dioxin-like polychlorinated biphenyls (DL-PCBs) in Atlantic herring depend on the fishing area. These substances originate from various anthropogenic sources and accumulate in the environment and in food. The influence of country-specific contaminant concentrations on human dietary exposure was studied exemplary for herring to show the influence of fish origin. PCDD/F and DL-PCB concentrations in herring from the Norwegian Sea and the Baltic Sea were combined with country-specific herring consumption. Herring concentrations showed geographical variation. For herring consumers, the 50th percentile dietary exposure to the total sum of PCDD/Fs and DL-PCBs amounted to 1.2 and 8.9 pg WHO-2005-TEQ/kg BW/week for Norway and Germany, respectively. The different exposure was mainly related to higher concentrations in herring from the Baltic Sea, rather than in herring from the Norwegian Sea. If contaminant concentrations are influenced by geographical origin, this should be integrated into the dietary exposure assessments. For herring, relevant fishing areas should be integrated into the sampling strategy to generate concentration data. The usage of country-specific data could refine exposure assessments

Example for an I-cell’s response in the medial zone to +10° (left, A-B) and -10° (right, C-D) phase-shifts.

<p>This cell responses reproducibly with a de- (10°) or an increased (-10°) rate to the phase shifts, whereas first-spike latency was not altered (not shown). For the full legend to the panels, refer to <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0194347#pone.0194347.g002" target="_blank">Fig 2</a>. See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0194347#pone.0194347.s001" target="_blank">S1 File</a> for data.</p

Example for an E-cell’s response in the dorsolateral zone to +10° (A, B) and -10° (C, D) phase-shifts.

<p>This cell responded with a reproducible de- (+10°) and increase (-10°) of its rate to the phase shifts, whereas first-spike latency was not systematically altered. Here and in the following figures four panels (A-D) are shown. <b>A, C</b>. Raster plots showing the change in spiking when switching from the undistorted (0°) to a phase-shifted (+ or -10°) EOD. Responses to phase shifted EODs are visualized by the coloured background. Significant differences between undistorted and phase-shifted conditions are indicated by the lines to the right (Kruskal-Wallis test with Dunn’s post-hoc analysis, <i>alpha</i> = 0.05). The raster plots on the right side of panels A and C depict the duration of the EODC for the corresponding raster plots. Note that EODC intervals were irregular and longer than the time at which spikes occurred. For better visualisation the raster plots are thus shown to match the longest interval after time zero at which spikes occurred in a given cell. <b>B, D</b>. Peri-stimulus time-histograms (PSTH) summarizing the data shown in A and C, phase shifts are plotted in colour, undistorted EOD-data in black. See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0194347#pone.0194347.s001" target="_blank">S1 File</a> for data.</p

Anatomical data on interzonal connectivity.

<p><b>A</b>. Low-magnification photomicrograph showing an ELL cross-section following a biocytin injection in the medial part of the medial zone. The section has been processed following the DAB procedure and counter stained with cresyl violet. The three zones are indicated on the slide and the different layers of the zones are indicated by the black lines at the borders between the MZ and DLZ. Note that the commissural projection connects the medial and dorsolateral zone such that the medial parts of the MZ connect with the lateral part of the DLZ. Likewise the lateral MZ is connected with the medial DLZ (see B, C). As the dorso-ventral topography of the sensory surface is represented along the medio-lateral axis in the MZ and the lateral to medial axis in the DLZ, this shows that somatotopically corresponding zones of the maps are connected. The higher magnification inset on the left shows the area surrounded by the stippled line in the DLZ. The red arrows point towards two retrogradely labelled somata in the granular layer. Abbreviations: deepf, deep fibre layer; gang, ganglionic layer; gran, granular layer; mol, molecular layer; plex, plexiform layer. <b>B</b>. Photomicrograph showing an injection site in the lateral part of the MZ using neurobiotin 488 (shown in green) and a fluorescent Nissl counterstain (blue). <b>C</b>. Interzonal projection to the DLZ originating from the injection shown in B. Note that in addition to the strong labelling of fibres some weakly stained large somata are present in the interzonal layer. The schematic inset in A and B shows a cross-section of the medulla with the injection site and the region where the close-up were taken indicated in green. deep, deep fibre layer; ggl, ganglionic layer, gran, granular layer, inter, intermediate layer; plex, plexiform layer.</p

Summary of effects of phase-shifted stimuli on E- and I-cells of DLZ & MZ.

<p>Summary of effects of phase-shifted stimuli on E- and I-cells of DLZ & MZ.</p