Colorado State University

About: Colorado State University is a education organization based out in Fort Collins, Colorado, United States. It is known for research contribution in the topics: Population & Laser. The organization has 31430 authors who have published 69040 publications receiving 2724463 citations. The organization is also known as: CSU & Colorado Agricultural College.

Integrative modelling reveals mechanisms linking productivity and plant species richness

Abstract: How ecosystem productivity and species richness are interrelated is one of the most debated subjects in the history of ecology. Decades of intensive study have yet to discern the actual mechanisms behind observed global patterns. Here, by integrating the predictions from multiple theories into a single model and using data from 1,126 grassland plots spanning five continents, we detect the clear signals of numerous underlying mechanisms linking productivity and richness. We find that an integrative model has substantially higher explanatory power than traditional bivariate analyses. In addition, the specific results unveil several surprising findings that conflict with classical models. These include the isolation of a strong and consistent enhancement of productivity by richness, an effect in striking contrast with superficial data patterns. Also revealed is a consistent importance of competition across the full range of productivity values, in direct conflict with some (but not all) proposed models. The promotion of local richness by macroecological gradients in climatic favourability, generally seen as a competing hypothesis, is also found to be important in our analysis. The results demonstrate that an integrative modelling approach leads to a major advance in our ability to discern the underlying processes operating in ecological systems.

Saturated Fatty Acids Promote Endoplasmic Reticulum Stress and Liver Injury in Rats with Hepatic Steatosis

Abstract: Nonalcoholic fatty liver disease is a relatively new hepatic sequela of obesity and type 2 diabetes. The pathogenesis of liver injury and disease progression in nonalcoholic fatty liver disease, however, is poorly understood. The present study examined the hypothesis that the composition of fatty acids in the steatotic liver promotes liver injury. Using dietary models of hepatic steatosis characterized by similar accumulation of total triglyceride but different composition of fatty acids, we show that hepatic steatosis characterized by increased saturated fatty acids is associated with increased liver injury and markers of endoplasmic reticulum stress (e.g. X-box binding protein-1 mRNA splicing and glucose-regulated protein 78 expression). These changes preceded and/or occurred independently of obesity and differences in leptin, TNFalpha, insulin action, and mitochondrial function. In addition, hepatic steatosis characterized by increased saturated fatty acids reduced proliferative capacity in response to partial hepatectomy and increased liver injury in response to lipopolysaccharide. These data suggest that the composition of fatty acids in the steatotic liver is an important determinant of susceptibility to liver injury.

Multidrug Pump Inhibitors Uncover Remarkable Activity of Plant Antimicrobials

Abstract: Plant antimicrobials are not used as systemic antibiotics at present. The main reason for this is their low level of activity, especially against gram-negative bacteria. The reported MIC is often in the range of 100 to 1,000 μg/ml, orders of magnitude higher than those of common broad-spectrum antibiotics from bacteria or fungi. Major plant pathogens belong to the gram-negative bacteria, which makes the low level of activity of plant antimicrobials against this group of microorganisms puzzling. Gram-negative bacteria have an effective permeability barrier, comprised of the outer membrane, which restricts the penetration of amphipathic compounds, and multidrug resistance pumps (MDRs), which extrude toxins across this barrier. It is possible that the apparent ineffectiveness of plant antimicrobials is largely due to the permeability barrier. We tested this hypothesis in the present study by applying a combination of MDR mutants and MDR inhibitors. A panel of plant antimicrobials was tested by using a set of bacteria representing the main groups of plant pathogens. The human pathogens Pseudomonas aeruginosa, Escherichia coli, and Salmonella enterica serovar Typhimurium were also tested. The results show that the activities of the majority of plant antimicrobials were considerably greater against the gram-positive bacteria Staphylococcus aureus and Bacillus megaterium and that disabling of the MDRs in gram-negative species leads to a striking increase in antimicrobial activity. Thus, the activity of rhein, the principal antimicrobial from rhubarb, was potentiated 100- to 2,000-fold (depending on the bacterial species) by disabling the MDRs. Comparable potentiation of activity was observed with plumbagin, resveratrol, gossypol, coumestrol, and berberine. Direct measurement of the uptake of berberine, a model plant antimicrobial, confirmed that disabling of the MDRs strongly increases the level of penetration of berberine into the cells of gram-negative bacteria. These results suggest that plants might have developed means of delivering their antimicrobials into bacterial cells. These findings also suggest that plant antimicrobials might be developed into effective, broad-spectrum antibiotics in combination with inhibitors of MDRs.