Modulation of cytochrome biosynthesis in yeast by antimetabolite action of levulinic acid.

Levulinic acid, a competitive inhibitor of delta-aminolevulinic acid dehydratase, was used to inhibit cytochrome biosynthesis in growing yeast cells. In Saccharomyces cerevisiae the antimetabolite acts by inhibiting delta-aminolevulinic acid dehydratase in vivo, causing an accumulation of intracellular delta-aminolevulinic acid and simultaneous decreases in all classes of mitochondrial cytochromes. Changes in cellular cytochrome content with increasing levulinic acid concentration suggested the existence of different regulatory patterns in S. cerevisiae and Candida utilis. In C. utilis, cytochrome a.a3 formation is very resistant to the antimetabolite action of levulinic acid. In this aerobic yeast, cytochrome c+c1 is the most sensitive to levulinic acid, and cytochrome b exhibits intermediate sensitivity.     

Low levels of mercury inhibit the respiratory burst in human polymorphonuclear leukocytes

The objective of this investigation was to examine the effects of low levels of Hg(II) on the respiratory burst of PMNs by monitoring O2 consumption, superoxide radical formation, and chemiluminescence. Hg(II) at concentrations of 10-100 ng/ml profoundly inhibited zymosan-stimulated human cells. This inhibition was immediate in onset and occurred with minimal loss of cell viability. Effects of Hg(II) on the PMN respiratory burst were compared with those of Sn, Pb, Se, Au, Ag and Cu. Only in the case of Ag and Cu did the inhibitory effects approach those of Hg. The results indicate that Hg(II) may serve as a specific inhibitor of components of the respiratory burst.     

A checklist for choosing between R packages in ecology and evolution

1. The open source and free programming language R is a phenomenal mechanism to address a multiplicity of challenges in ecology and evolution. It is also a complex ecosystem because of the diversity of solutions available to the analyst.
2. Packages for R enhance and specialize the capacity to explore both niche data/experiments and more common needs. However, the paradox of choice or how we select between many seemingly similar options can be overwhelming and lead to different potential outcomes.
3. There is extensive choice in ecology and evolution between packages for both fundamental statistics and for more specialized domain‐level analyses.
4. Here, we provide a checklist to inform these decisions based on the principles of resilience, need, and integration with scientific workflows for evidence.
5. It is important to explore choices in any analytical coding environment—not just R—for solutions to challenges in ecology and evolution, and document this process because it advances reproducible science, promotes a deeper understand of the scientific evidence, and ensures that the outcomes are correct, representative, and robust.