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Abstract Background Altruism can be favored by high relatedness among interactants. We tested the effect of relatedness in experimental populations of the social amoeba Dictyostelium discoideum, where altruism occurs in a starvation-induced social stage when some amoebae die to form a stalk that lifts the fertile spores above the soil facilitating dispersal. The single cells that aggregate during the social stage can be genetically diverse, which can lead to conflict over spore and stalk allocation. We mixed eight genetically distinct wild isolates and maintained twelve replicated populations at a high and a low relatedness treatment. After one and ten social generations we assessed the strain composition of the populations. We expected that some strains would be out-competed in both treatments. In addition, we expected that low relatedness might allow the persistence of social cheaters as it provides opportunity to exploit other strains. Results We found that at high relatedness a single clone prevailed in all twelve populations. At low relatedness three clones predominated in all twelve populations. Interestingly, exploitation of some clones by others in the social stage did not explain the results. When we mixed each winner against the pool of five losers, the winner did not prevail in the spores because all contributed fairly to the stalk and spores. Furthermore, the dominant clone at high-relatedness was not cheated by the other two that persisted at low relatedness. A combination of high spore production and short unicellular stage most successfully explained the three successful clones at low relatedness, but not why one of them fared better at high relatedness. Differences in density did not account for the results, as the clones did not differ in vegetative growth rates nor did they change the growth rates over relevant densities. Conclusions These results suggest that social competition and something beyond solitary growth differences occurs during the vegetative stage when amoebae eat bacteria and divide by binary fission. The high degree of repeatability of our results indicates that these effects are strong and points to the importance of new approaches to studying interactions in D. discoideum.

A production facility shutdown related to containment measures during the COVID-19 pandemic has resulted in a global shortage of iodinated contrast media. This article describes the strategies implemented at one large U.S. health system to maintain care continuity during the ongoing shortage. The strategies have included attempts to procure additional stock, repackage existing stock for use in larger numbers of patients, use noncontrast CT or alternative imaging modalities in place of contrast-enhanced CT, and collaborate with specialties outside of radiology to participate in conservation efforts. In addition, individual CT protocols underwent tailored modifications to use dual-energy technique and/or lower tube voltages, to allow lower contrast media doses with maintained visualization of tissue enhancement. The experiences during this period provide insights to facilitate long-term reductions in contrast media doses and ongoing CT protocol optimization after supplies return to normal levels. Critical throughout the efforts to mitigate the impact of the shortage have been system-level action, operational flexibility, and close communication by the health system's radiologists, technologists, physicists, pharmacists, and ordering providers.

Alterations in membrane lipid composition during temperature acclimation of poikilotherms is hypothesized to compensate for direct effects of temperature on membrane fluidity. Temperature also influences disposition and actions of some xenobiotics. This suggests the potential for complex interactions between temperature and metabolism of chemical carcinogens. Whole livers and hepatic microsomes from rainbow trout acclimated at 18 degrees C have more saturated fatty acids and less mono- and polyunsaturated fatty acids than those from fish acclimated at 10 degrees C. Such changes are consistent with a role for membrane lipid fluidity in temperature compensation. When 10 and 18 degrees C acclimated fish are ip injected with 0.4 mg/kg [3H]aflatoxin B1 (AFB1) at their respective acclimation temperatures, hepatic disposition of AFB1, DNA adduction, and biliary metabolites are similar. An acute shift of 18 degrees C acclimated trout to 14 degrees C reduces [3H]AFB-DNA adduct formation, while [3H]AFB1 adduction after acute shift of 10 degrees C acclimated fish to 14 degrees C is no different than in non-shifted fish. Hepatic microsomes isolated from 10 or 18 degrees C acclimated trout, incubated with 10 microM [3H]AFB1 and calf thymus DNA between 6 and 22 degrees C exhibit no differences in the "break points" of Arrhenius plots (16 degrees C in both groups). There is, however, more in vitro DNA adduction of [3H]AFB1 by microsomes from 18 degrees C acclimated fish, a difference abolished by 0.5 mM alpha-naphthoflavone (ANF). These results suggest that temperature acclimation of trout differentially modifies activities of cytochrome P-450 isozymes. When assayed at respective acclimation temperatures, hepatic cytosol from 18 degrees C fish produces more aflatoxicol, a detoxication product of AFB1, than cytosol from 10 degree C fish. Therefore, this soluble enzyme does not exhibit ideal temperature compensation. Such temperature-induced differences in microsomal cytochrome P-450 isozymes and cytosolic dehydrogenase partially explain temperature-modulated AFB1 genotoxicity.