Assessment of ecological risks in weed biocontrol: Input from retrospective ecological analyses

Prediction of the outcomes of natural enemy introductions remains the most fundamental challenge in biological control. Quantitative retrospective analyses of ongoing biocontrol projects provide a systematic strategy to evaluate and further develop ecological risk assessment. In this review, we highlight a crucial assumption underlying a continued reliance on the host specificity paradigm as a quantitative prediction of ecological risk, summarize the status of our retrospective analyses of nontarget effects of two weevils used against exotic thistles in North America, and discuss our prospective assessment of risk to a federally listed, threatened species (Cirsium pitcheri) based on those studies. Our analyses quantify the fact that host range and preference from host specificity tests are not sufficient to predict ecological impact if the introduced natural enemy is not strictly monophagous. The implicit assumption when such use is made of the host specificity data in risk assessment is that population impacts are proportional to relative preference and performance, the key components of host specificity. However, in concert with shifting awareness in the field, our studies demonstrate that the environment influences and can alter host use and population growth, leading to higher than expected direct impacts on the less preferred native host species at several spatial scales. Further, we have found that straightforward, easily anticipated indirect effects, on intraguild foragers as well as on the less preferred native host plant species, can be both widespread and significant. We conclude that intensive retrospective ecological studies provide some guidance for the quantitative prospective studies needed to assess candidate biological control agent dynamics and impacts and, so, contribute to improved rigor in the evaluation of total ecological risk to native species.     

Arachidonic acid metabolism in the murine eosinophil. III. Effect of nonsteroid anti-inflammatory drugs on lymphokine-directed eosinophil migration in vivo

In vitro studies of murine eosinophils indicated that lymphokine-stimulated metabolism of arachidonic acid by a lipoxygenase pathway was required for a migration response. In this study we tested the effects of drugs that affect arachidonic acid metabolism on lymphokine-dependent eosinophil accumulation in vivo by the use of 111In-labeled eosinophils. Indomethacin at different dosages either stimulated (1 mg/kg) or partially inhibited (5 to 25 mg/kg) eosinophil accumulation. Aspirin had no significant effects in doses up to 50 mg/kg. BW755C, a drug that inhibits both cyclooxygenase and lipoxygenase, dramatically inhibited eosinophil accumulation at 25 to 125 mg/kg. Pretreatment in vitro of 111In-labeled eosinophils with some drugs known to inhibit lipoxygenase reduced their subsequent accumulation at a lymphokine-injected site in vivo, but the high concentrations required for inhibition suggested that the effects of the drugs were at least partially reversible. Pretreatment with indomethacin did not inhibit the ability of 111In-labeled eosinophils to accumulate at the site of lymphokine injection in vivo. It may be anticipated from these results that drugs inhibiting lipoxygenase will have critical effects on manifestations of immunologic reactions that recruit eosinophils.     

Increased Adiposity,Dysregulated Glucose Metabolism and Systemic Inflammation in Galectin-3 KO Mice

Obesity and type 2 diabetes are associated with increased production of Galectin-3 (Gal-3), a protein that modulates inflammation and clearance of glucose adducts. We used Lean and Diet-induced Obese (DIO) WT and Gal-3 KO mice to investigate the role of Gal-3 in modulation of adiposity, glucose metabolism and inflammation. Deficiency of Gal-3 lead to age-dependent development of excess adiposity and systemic inflammation, as indicated by elevated production of acute-phase proteins, number of circulating pro-inflammatory Ly6C^high monocytes and development of neutrophilia, microcytic anemia and thrombocytosis in 20-week-old Lean and DIO male Gal-3 KO mice. This was associated with impaired fasting glucose, heightened response to a glucose tolerance test and reduced adipose tissue expression of adiponectin, Gal-12, ATGL and PPARγ, in the presence of maintained insulin sensitivity and hepatic expression of gluconeogenic enzymes in 20-week-old Gal-3 KO mice compared to their diet-matched WT controls. Expression of PGC-1α and FGF-21 in the liver of Lean Gal-3 KO mice was comparable to that observed in DIO animals. Impaired fasting glucose and altered responsiveness to a glucose load preceded development of excess adiposity and systemic inflammation, as demonstrated in 12-week-old Gal-3 KO mice. Finally, a role for the microflora in mediating the fasting hyperglycemia, but not the excessive response to a glucose load, of 12-week-old Gal-3 KO mice was demonstrated by administration of antibiotics. In conclusion, Gal-3 is an important modulator of glucose metabolism, adiposity and inflammation.     

Hopf bifurcation in a stomatal oscillator

Stomata are microscopic openings in leaves of green plants which permit gas exchange. This paper presents a parameter study of a model of a stomatal oscillator first derived by Delwiche and Cooke in 1977. We prove the existence of an unstable limit cycle by using the theory of the Hopf bifurcation. Other bifurcations exhibited by the model are also discussed.