Antioxidants reveal an inverted U‐shaped dose‐response relationship between reactive oxygen species levels and the rate of aging in Caenorhabditis elegans

Reactive oxygen species (ROS) are potentially toxic, but they are also signaling molecules that modulate aging. Recent observations that ROS can promote longevity have to be reconciled with the numerous claims about the benefits of antioxidants on lifespan. Here, three antioxidants [N‐acetylcysteine (NAC), vitamin C, and resveratrol (RSV)] were tested on Caenorhabditis elegans mutants that alter drug uptake, mitochondrial function, and ROS metabolism. We observed that like pro‐oxidants, antioxidants can both lengthen and shorten lifespan, dependent on concentration, genotypes, and conditions. The effects of antioxidants thus reveal an inverted U‐shaped dose–response relationship between ROS levels and lifespan. In addition, we observed that RSV can act additively to both NAC and paraquat, to dramatically increase lifespan. This suggests that the effect of compounds that modulate ROS levels can be additive when their loci of action or mechanisms of action are sufficiently distinct.     

Vitreoscilla hemoglobin renders Enterobacter aerogenes highly susceptible to heavy metals

When expressed in heterologous microorganisms Vitreoscilla hemoglobin (VHb) acts as oxygen storage and causes a higher oxygen uptake. In this study, the effect of this protein on growth, sensitivity and antioxidant properties of Enterobacter aerogenes exposed to metal stress was investigated. The strain expressing VHb was more sensitive to mercury and cadmium as the minimal inhibitory concentration (MIC) for these metals was up to 2-fold lower in this strain than the host and the recombinant strain carrying a comparable plasmid. At lower concentrations than MIC, the metals partially limited growth and caused an inhibition proportional to metal concentration applied. The growth pattern of VHb expressing strain was also distinctly different from other two non-hemoglobin strains. The hemoglobin containing strain showed substantially higher superoxide dismuates (SOD) activity than the non-hemoglobin strains, while catalase levels were similar in all strains. All strains exposed to copper, however, showed similar MIC values, growth patterns, and SOD and catalase levels.     

TAR-cloning of the short arm of human chromosome 7 in yeast and search for terminal sequences

A partial clone library of the short arm of human chromosome 7 was created in yeast artificial chromosomes (YAC) using TAR-cloning. The DNA of monochromosome somatic hybrid cells (mouse/human) RuRag 14-4-7-44 containing short arm human chromosome 7 was used for cloning. The clone library was screened for YACs with the human DNA; the mitotic stability of these YACs, the sizes of cloned fragments, and an independent clonal distribution in the chromosome were determined. Human YACs were tested for the presence of chromosome 7p telomeric sequences.     

Cutting Edge: Allele-specific and peptide-dependent interactions between KIR3DL1 and HLA-A and HLA-B

Although it is clear that KIR3DL1 recognizes Bw4(+) HLA-B, the role of Bw4(+) HLA-A allotypes as KIR3DL1 ligands is controversial. We therefore examined the binding of tetrameric HLA-A and -B complexes, including HLA*2402, a common Bw4(+) HLA-A allotype, to KIR3DL1*001, *005, *007, and *1502 allotypes. Only Bw4(+) tetramers bound KIR3DL1. Three of four HLA-A*2402 tetramers bound one or more KIR3DL1 allotypes and all four KIR3DL1 allotypes bound to one or more HLA-A*2402 tetramers, but with different binding specificities. Only KIR3DL1*005 bound both HLA-A*2402 and HLA-B*5703 tetramers. HLA-A*2402-expressing target cells were resistant to lysis by NK cells expressing KIR3DL1*001 or *005. This study shows that HLA-A*2402 is a ligand for KIR3DL1 and demonstrates how the binding of KIR3DL1 to Bw4(+) ligands depends upon the bound peptide as well as HLA and KIR3DL1 polymorphism.     

Dietary classification of extant kangaroos and their relatives (Marsupialia: Macropodoidea)

Kangaroos and kin (superfamily Macropodoidea) are the principal endemic herbivores of Australia and the most diverse radiation of marsupial herbivores ever to have evolved. As is typical of other herbivore groups (e.g. bovids), dietary niches span fruit, fungi, dicot leaves and monocot grasses in both specialists and generalists, but to date dietary classification has been largely ad hoc and poorly tied to actual dietary ecological data. Here we provide a simple dietary classification of the Macropodoidea based on an extensive literature survey. Intake of four major dietary items – grasses, dicot leaves, fruits and seeds, and fungi – was assessed using proportional intake for 19 species and categorical (ranked intake) data for 37 species. Statistical comparisons with cluster and principal components analyses aligned species into four dietary groups. Members of the first group have diets that primarily consist of fungi and fruits. Relative proportions of grasses to dicot leaves separate the remaining species into browser (more than 70% dicots), grazer (more than 70% grasses) and mixed feeder groups. Comparison of our diet‐based classification with a prevailing scheme based on dental morphology suggests that most species with what has traditionally been viewed as a ‘browser‐grade dentition’ are actually mixed feeders. This suggests that either morphology and diet are not tightly linked or that morphological differences between the dentitions of browsers and mixed feeders are subtle and have been overlooked. A positive correlation was found between body mass and average proportional intake of grass in the diet of macropodoids. This parallels the situation found in bovids, as well as the percentage cut‐off between dietary groups. These trends suggest that some underlying ecophysiological constraints may influence food choice in mammalian herbivores providing useful pointers to the diets of extinct taxa.     

ARS-activity of a DNA fragment from Bombyx mori in Saccharomyces cerevisiae cells]

A previously cloned autonomous transgene (pr8a) of silkworm Bombyx mori inherited without changes in the structure was used to clarify the activity of its ARS in yeast cells. ARS of pr8a was also shown to maintain autonomous replication of hybrid plasmids in yeast cells. The same was true for its central 2.4-kb fragment devoid of flanking sequences.     

Identification of the proteins interacting with neuroprotective peptide humanin in a yeast two-hybrid system

Humanine is a human neuroprotective peptide with a wide action spectrum. To analyze molecular mechanisms of humanin functioning, a search for proteins interacting with this peptide was conducted using yeast two-hybrid system. Screening of human fetal brain cDNA library identified seven proteins with different functions that specifically interacted with humanin.