Effects of fluoxetine on the activity of phagocytosis in stressed mice

We studied the effects of 1, 2, 5, 10 and 20 mg/kg of fluoxetine on the activity of phagocytosis in mice subjected to a chronic auditory stressor. Both the in vitro and in vivo activity of phagocytosis, measured using the zymosan-particle uptake method and the carbon clearance test, respectively, were reduced after 2, 4, 8 and 16 days of stress exposure. A partial recovery on the in vivo activity of phagocytosis was found on day 16th. Daily treatment with fluoxetine partially reversed the adverse effects of stress in a dose-dependent manner on both parameters but did not significantly affect the activity of phagocytosis in unstressed mice. Significant differences appeared when fluoxetine was administered at 2 mg/kg. Maximum effect was reached at 5 mg/kg.     

Reverse genetic approaches in plants and yeast suggest a role for novel,evolutionarily conserved,selenoprotein-related genes in oxidative stress defense

Oxidation of methionine residues during periods of oxidative stress can lead to loss of protein function. Organisms have developed defense strategies to minimize such damage. The PilB protein, which is involved in pilus formation in the pathogen Neisseria gonorrhoeae, is composed of three functional protein domains (I-III) with putative roles in oxidative stress defense. These domains are evolutionarily conserved and homologs have been discovered in diverse prokaryotes and eukaryotes. Domain III shows similarities to selenoproteins which contain selenium instead of sulfur in a conserved cysteine residue. The substitution of selenium for sulfur alters the redox properties of such proteins. Knock-out mutants were used to elucidate the function of these novel selenoprotein-like domains in yeast and in Arabidopsis thaliana. We show that organisms with non-functional genes for selenoprotein-like polypeptides accumulate higher levels of oxidized methionine residues on exposure to oxidative stress. The behavior of the mutants suggests that these novel selenoprotein-like gene products are part of a ubiquitous detoxification system that interacts with other redox-related proteins such as the thioredoxin-related protein and methionine sulfoxide reductase which are encoded by domains I and II of PilB. These proteins may be encoded by one gene as in the case of several prokaryotes, or by separate genes as in the eukaryotes examined here.     

Analysis of Genomic DNA from Medieval Plague Victims Suggests Long-Term Effect of Yersinia pestis on Human Immunity Genes

Pathogens and associated outbreaks of infectious disease exert selective pressure on human populations, and any changes in allele frequencies that result may be especially evident for genes involved in immunity. In this regard, the 1346-1353 Yersinia pestis-caused Black Death pandemic, with continued plague outbreaks spanning several hundred years, is one of the most devastating recorded in human history. To investigate the potential impact of Y. pestis on human immunity genes, we extracted DNA from 36 plague victims buried in a mass grave in Ellwangen, Germany in the 16th century. We targeted 488 immune-related genes, including HLA, using a novel in-solution hybridization capture approach. In comparison with 50 modern native inhabitants of Ellwangen, we find differences in allele frequencies for variants of the innate immunity proteins Ficolin-2 and NLRP14 at sites involved in determining specificity. We also observed that HLA-DRB1*13 is more than twice as frequent in the modern population, whereas HLA-B alleles encoding an isoleucine at position 80 (I-80+), HLA C*06:02 and HLA-DPB1 alleles encoding histidine at position 9 are half as frequent in the modern population. Simulations show that natural selection has likely driven these allele frequency changes. Thus, our data suggest that allele frequencies of HLA genes involved in innate and adaptive immunity responsible for extracellular and intracellular responses to pathogenic bacteria, such as Y. pestis, could have been affected by the historical epidemics that occurred in Europe.     

Effects of Changing Rainfall on the Limnology of a Mediterranean,Flowthrough‐Seepage Chain of Lakes

Relationships between groundwater and lake ecology are often overlooked, but they may be strong, particularly in seepage lakes. As a result, the nature and degree of groundwater effects on lakes are usually neglected. In this study interactions among rainfall, groundwater and surface water and their limnological effects were traced seasonally for two years of changing rainfall in a Spanish flowthrough, seepage lake complex. Cumulative rainfall dictated recharge of groundwater with delays of nine months. Groundwater discharge, in turn, increased surface discharge downstream. Mediated by the geographical setting of lakes, both fluxes impinged on lake water renewal time, but effects of the latter on limnological variables were much stronger at the district scale than at the single lake scale. These water‐renewal effects included the following: decreasing salinity, total phosphorus concentration and phytoplankton biomass and increasing water transparency and total nitrogen concentration as water renewal shortened, the nitrogen effect arising because of nitrate‐rich water entering the lakes as groundwater levels rose. This complex response of a Mediterranean lake district to water availability may also be expected in cold temperate lakes as climate change effects become stronger. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Specialized breeding in plants affects diversification trajectories in Neotropical frogs

Many animals breed exclusively in plants that accumulate rainwater (phytotelma; e.g., bromeliad, bamboo, fruit husk, and tree hole), to which they are either physiologically or behaviorally specialized for this microhabitat. Of the numerous life-history modes observed in frogs, few are as striking or potentially consequential as the transition from pond- or stream-breeding to the deposition of eggs or larvae in phytotelmata. Such specialization can increase offspring survivorship due to reduced competition and predation, representing potential ecological opportunity for adaptive radiation, yet few lineages of phytotelma-breeding frogs appear to have diversified extensively after such a transition, at least in the New World. We use a phylogeny of Neotropical frogs and data on breeding microhabitat to understand the evolutionary transitions involved with specialized phytotelma-breeding. First, we find that phytotelma-breeding is present in at least 168 species in 10 families of frogs. Across the phylogeny, we estimate 14 origins of phytotelma-breeding and 115 reversals, showing that phytotelma-breeding is a highly labile character. Second, phytotelma-breeding lineages overall have higher net diversification than nonphytotelma-breeding ones. This specialization represents an ecological opportunity resulting in increased diversification in most families with phytotelma-breeding lineages, whereas phytotelma-breeding toads have restricted diversification histories.