Testing an invasion mechanism for Eucalyptus globulus: Is there evidence of allelopathy?

PREMISE: Sparse understory communities, in association with non-native tree species, are often attributed to allelopathy, the chemical inhibition of a plant by another. However, allelopathy is a difficult ecological phenomenon to demonstrate as many studies show conflicting results. Eucalyptus globulus, a tree native to Australia, is one of the most widely planted trees around the world. Sparse understories are common beneath E. globulus plantations and are often attributed to allelopathy, but the ecological impacts of E. globulus on native plant communities outside Austrialia are poorly understood. METHODS: To assess allelopathy as a mechanism of understory inhibition, we tested volatile- and water-soluble leaf extracts from E. globulus, Salvia apiana, and Quercus agrifolia on seed germination of California native plants. We also quantified germination rates and early seedling growth of California native plants grown in soil from E. globulus plantations versus soil from an adjacent native plant community. RESULTS: Volatile compounds from E. globulus did not significantly reduce germination for any species. Inhibition from water-soluble E. globulus compounds was comparable to that of a native tree, Quercus agrifolia (10%). Eucalyptus globulus soil supported germination and early seedling growth of native species equal to or better than coastal scrub soil, although species responses were variable. CONCLUSIONS: In contrast to previous studies, our results fail to support the hypothesis that E. globulus chemically inhibits germination of native species. California native plants germinate and grow well in soils from E. globulus plantations, which may have significant implications for management and restoration of land historically occupied by E. globulus plantations.

Effects From Continuous Infusions of Dexmedetomidine and Propofol on Hemodynamic Stability in Critically Ill Adult Patients With Septic Shock.

PURPOSE: To compare the development of clinically significant hemodynamic event (ie, hypotension or bradycardia) in adults with septic shock receiving either propofol or dexmedetomidine. MATERIALS AND METHODS: A retrospective cohort study of adults with septic shock admitted to an intensive care unit (ICU) at an academic medical center between July 2013 and July 2017. RESULTS: Patients in the propofol (n = 35) and dexmedetomidine (n = 37) groups developed a clinically significant hemodynamic event at similar frequencies (31.4 vs 29.7%, P = .99). All patients with an event experienced hypotension, whereas 2 (5.4%) patients in the dexmedetomidine group also experienced bradycardia. Most patients in both groups (70% vs 90%) received an escalating sedative dose, and almost half (42.9%) in the dexmedetomidine group had the sedative dosage increased more frequently than every 30 minutes. Patients in both groups had similar ICU (24.1 vs 24.3 days, P = .98) and hospital (37.9 vs 29.7 days, P = .29) lengths of stay. There was no difference in median time to hemodynamic event between the groups (propofol 1 hour [interquartile range, IQR: 0.5-9.9] vs dexmedetomidine 2 hours [IQR: 1.5-11.1 hours], P = .85). CONCLUSION: Patients with septic shock receiving propofol or dexmedetomidine experienced similar rates of clinically significant hemodynamic events. Most patients did not experience an event and those who did most frequently did so in the first couple of hours of therapy.

MicroRNAs and cancer: past, present, and potential future.

MicroRNAs (miRNAs) are a class of small RNAs that have revealed a new level of gene regulation in the cell. After being processed by Drosha and Dicer RNase III endonucleases, mature miRNAs can inhibit the translation of mRNA by directing a RNA-induced silencing complex (RISC) to the target mRNA. miRNAs are making an impact in our understanding of cancer biology. Acting as either tumor suppressors or oncogenes, miRNAs regulate several genes known to play important roles in cancer. With the discovery of miRNAs comes the need for new techniques to study their activity. Bioinformatic tools can be used to predict mRNA targets of miRNA, but validation of miRNA regulation of predicted targets is imperative. miRNAs are differentially expressed in normal and tumor cells as well as between tumor subtypes. These differences may be useful as prognostic and predictive markers in cancer patients. The study of miRNAs holds much promise for improving diagnosis and treatment of cancer.