Patterns of trace metal accumulation in Swedish marine nemerteans

Total body burdens of Zn, Pb, Al and Cu were measured in Swedish marine nemerteans sampled from an area close to a major source of pollution. Accumulation patterns varied both seasonally and spatially. The results suggest that nemerteans may be useful bioindicator species in environmental monitoring programmes.     

Initial soil organic carbon stocks govern changes in soil carbon: Reality or artifact?

Changes in soil organic carbon (SOC) storage have the potential to affect global climate; hence identifying environments with a high capacity to gain or lose SOC is of broad interest. Many cross-site studies have found that SOC-poor soils tend to gain or retain carbon more readily than SOC-rich soils. While this pattern may partly reflect reality, here we argue that it can also be created by a pair of statistical artifacts. First, soils that appear SOC-poor purely due to random variation will tend to yield more moderate SOC estimates upon resampling and hence will appear to accrue or retain more SOC than SOC-rich soils. This phenomenon is an example of regression to the mean. Second, normalized metrics of SOC change—such as relative rates and response ratios—will by definition show larger changes in SOC at lower initial SOC levels, even when the absolute change in SOC does not depend on initial SOC. These two artifacts create an exaggerated impression that initial SOC stocks are a major control on SOC dynamics. To address this problem, we recommend applying statistical corrections to eliminate the effect of regression to the mean, and avoiding normalized metrics when testing relationships between SOC change and initial SOC. Careful consideration of these issues in future cross-site studies will support clearer scientific inference that can better inform environmental management.     

Hydrology shapes microbial communities and microbiome-mediated growth of an Everglades tree island species

Plant-associated microbiomes can improve plant fitness by ameliorating environmental stress, providing a promising avenue for improving outplantings during restoration. However, the effects of water management on these microbial communities and their cascading effects on primary producers are unresolved for many imperiled ecosystems. One such habitat, Everglades tree islands, has declined by 54% in some areas, releasing excess nutrients into surrounding wetlands and exacerbating nutrient pollution. We conducted a factorial experiment, manipulating the soil microbiome and hydrological regime experienced by a tree island native, Ficus aurea, to determine how microbiomes impact growth under two hydrological management plans. All plants were watered to simulate natural precipitation, but plants in the “unconstrained” management treatment were allowed to accumulate water above the soil surface, while the “constrained” treatment had a reduced stage to avoid soil submersion. We found significant effects of the microbiomes on overall plant performance and aboveground versus belowground investment; however, these effects depended on hydrological treatment. For instance, microbiomes increased investment in roots relative to aboveground tissues, but these effects were 142% stronger in the constrained compared to unconstrained water regime. Changes in hydrology also resulted in changes in the prokaryotic community composition, including a >20 log₂fold increase in the relative abundance of Rhizobiaceae, and hydrology-shifted microbial composition was linked to changes in plant performance. Our results suggest that differences in hydrological management can have important effects on microbial communities, including taxa often involved in nitrogen cycling, which can in turn impact plant performance.     

Inoculation with native soil improves seedling survival and reduces non-native reinvasion in a grassland restoration

Losses of grasslands have been largely attributed to widespread land-use changes, such as conversion to row-crop agriculture. The remaining tallgrass prairie faces further losses due to biological invasions by non-native plant species, often with resultant ecosystem degradation. Of critical concern for conservation, restoration of native grasslands has been met with little success following eradication of non-native plants. In addition to the direct and indirect effects of non-native invasive plants on beneficial soil microbes, management practices targeting invasive species may also negatively affect subsequent restoration efforts. To assess mechanisms limiting germination and survival of native species and to improve native species establishment, we established six replicate plots of each of the following four treatments: (1) inoculated with freshly collected prairie soil with native seeds; (2) inoculated with steam-pasteurized soil with native seeds; (3) noninoculated with native seeds; or (4) noninoculated/nonseeded control. Inoculation with whole soil did not improve seed germination; however, addition of whole soil significantly improved native species survival, compared to pasteurized soil or noninoculated treatments. Inoculation with whole soil significantly decreased reestablishment of non-native invasive Bothriochloa bladhii (Caucasian bluestem); at the end of the growing season, plots receiving whole soil consisted of approximately 30% B. bladhii cover, compared to approximately 80% in plots receiving no soil inoculum. Our results suggest invasion and eradication efforts negatively affect arbuscular mycorrhizal hyphal and spore abundances and soil aggregate stability, and inoculation with locally adapted soil microbial communities can improve metrics of restoration success, including plant species richness and diversity, while decreasing reinvasion by non-native species.     

Second messenger and protein phosphorylation mechanisms underlying opiate addiction: Studies in the rat locus coeruleus

We have studied the role of second messenger and protein phosphorylation pathways in mediating changes in neuronal function associated with opiate addiction in the rat locus coeruleus. We have found that chronic opiates increase levels of the G-protein subunits Gi and Go, adenylate cyclase, cyclic AMP-dependent protein kinase, and a number of phosphoproteins (including tyrosine hydroxylase) in this brain region. Electrophysiological data have provided direct support for the view that this up-regulation of the cyclic AMP system contributes to opiate tolerance, dependence, and withdrawal exhibited by these neurons. As the adaptations in G-proteins and the cyclic AMP system appear to occur at least in part at the level of gene expression, current efforts are aimed at identifying the mechanisms, at the molecular level, by which opiates regulate the expression of these intracellular messenger proteins in the locus coeruleus. These studies will lead to an improved understanding of the biochemical basis of opiate addiction.Special issue dedicated to Dr. Paul Greengard     

Drug resistance in rat colon cancer cell lines is associated with minor changes in susceptibility to cytotoxic cells

The development of resistance to anticancer drugs urges the search for different treatment modalities. Several investigators have reported the concomitant development of drug resistance and resistance to natural killer (NK), lymphokine-activated killer (LAK) or monocyte/macrophage cell lysis, while others described unchanged or even increased susceptibility. We investigated this subject in the rat colon carcinoma cell line, CC531-PAR, which is intrinsically multidrug-resistant (MDR), and in three sublines derived from this parental cell line: a cell line with an increased MDR phenotype (CC531-COL), a revertant line from CC531-COL (CC531-REV), which demonstrates enhanced sensitivity to anticancer drugs of the MDR phenotype, and an independently developed cisplatin-resistant line (CC531-CIS). In a 4-h⁵¹Cr-release assay we found no difference in susceptibility to NK cell lysis. No significant differences in lysability by adherent LAK (aLAK) cells were observed in a 4-h assay. In a prolonged 20-h⁵¹Cr-release assay an enhanced sensitivity to aLAK-cell-mediated lysis was observed in the revertant, P-glycoprotein-negative cell line and in the cisplatin-resistant cell line (CC531-CIS). None of the cell lines was completely resistant to lysis by aLAK cells. Therefore, a role for immunotherapy in the treatment of drug-resistant tumors remains a realistic option.