In vitro assessment of the toxicity of metal compounds

A review of in vitro mutagenesis assessment of metal compounds in mammalian and nonmammalian test systems has been compiled. Prokaryotic assays are ineffective or inconsistent in their detection of most metals as mutagens, with the notable exception of hexavalent chromium. Mammalian assay systems appear to be similarly inappropriate for the screening of metal compounds based upon the limited number of studies that have employed those compounds having known carcinogenic activity. Although of limited value as screening tests for the detection of potentially carcinogenic metal compounds, the well-characterized in vitro mutagenesis systems may prove to be of significant value as a means to elucidate mechanisms of metal genotoxicity.     

The role of arctic zooplankton in biogeochemical cycles: respiration and excretion of ammonia and phosphate during summer

The study of the structural and functional properties of key components of polar marine ecosystems has received increased attention in order to better understand the ecological consequences of future sea temperature rise and seasonal ice retraction. Owing to this purpose, during the ATOS-Arctic cruise, held in July 2007 in the framework of the 2007–2008 International Polar Year, we studied the respiratory carbon demand of mesozooplankton as well as their contribution to the regeneration of inorganic nitrogen and phosphorus (NH₄-N and PO₄-P) via excretion. The studied area comprised several stations along a latitudinal gradient in the East Greenland current, plus a network of stations NW of the Svalbard islands. The specific respiratory carbon losses and phosphorus (PO₄-P) excretion rates were similar or slightly higher than some reports for Arctic mesozooplankton, but the nitrogen (NH₄-N) excretion rates were higher by a factor of 3 when compared with previous data sets. The mesozooplankton respiratory losses were equivalent to 23% of primary production, and at turn zooplankton contributed by excretion to more than 50% of the N and P required by phytoplankton. Although C:N, C:P and N:P metabolic atomic quotients almost coincided with the average Redfield’s stoichiometric ratios, the low C:N values when compared to previous reports suggested a predominance of protein-related metabolic substrates. The potential consequences of changes observed in the C:N, N:P and C:P metabolic ratios of mesozooplankton for Arctic marine ecosystems are discussed.     

An “orientation sphere” visualization for examining animal head movements

1. Animal behavior is elicited, in part, in response to external conditions, but understanding how animals perceive the environment and make the decisions that bring about these behavioral responses is challenging.
2. Animal heads often move during specific behaviors and, additionally, typically have sensory systems (notably vision, smell, and hearing) sampling in defined arcs (normally to the front of their heads). As such, head‐mounted electronic sensors consisting of accelerometers and magnetometers, which can be used to determine the movement and directionality of animal heads (where head “movement” is defined here as changes in heading [azimuth] and/or pitch [elevation angle]), can potentially provide information both on behaviors in general and also clarify which parts of the environment the animals might be prioritizing (“environmental framing”).
3. We propose a new approach to visualize the data of such head‐mounted tags that combines the instantaneous outputs of head heading and pitch in a single intuitive spherical plot. This sphere has magnetic heading denoted by “longitude” position and head pitch by “latitude” on this “orientation sphere” (O‐sphere).
4. We construct the O‐sphere for the head rotations of a number of vertebrates with contrasting body shape and ecology (oryx, sheep, tortoises, and turtles), illustrating various behaviors, including foraging, walking, and environmental scanning. We also propose correcting head orientations for body orientations to highlight specific heading‐independent head rotation, and propose the derivation of O‐sphere‐metrics, such as angular speed across the sphere. This should help identify the functions of various head behaviors.
5. Visualizations of the O‐sphere provide an intuitive representation of animal behavior manifest via head orientation and rotation. This has ramifications for quantifying and understanding behaviors ranging from navigation through vigilance to feeding and, when used in tandem with body movement, should provide an important link between perception of the environment and response to it in free‐ranging animals.

     

Trace elements in rock salt and their bioavailability estimated from solubility in acid

In this study, 18 partly commercially available samples of rock salt from Austria, Germany, Pakistan, Poland, Switzerland, and Ukraine were investigated with respect to their content of trace elements using instrumental neutron activation analysis. Elements detected were Al, Ba, Br, Ca, Ce, Cl, Co, Cr, Cs, Eu, Fe, Hf, La, Mn, Na, Rb, Sb, Sc, Sm, Sr, Ta, Tb, Th, and Zn, some of them only in individual cases. An estimation of the bioavailability of these trace elements was performed by dissolving an equivalent of the sodium chloride samples in diluted hydrochloric acid (simulating stomach acid), filtering off the insoluble components, and analyzing the evaporated filtrate. It could be shown that in most cases bioactive trace elements like Fe can be found in rock salt in the form of almost insoluble compounds and are therefore not significantly bioavailable, whereas thorium, for example, was partly bioavailable in two cases. A significant contribution to the recommended daily intake of metal trace elements by using rock salt for nutrition can be excluded.