Arsenic alters global histone modifications in lymphocytes in vitro and in vivo

Arsenic, an established carcinogen and toxicant, occurs in drinking water and food and affects millions of people worldwide. Arsenic appears to interfere with gene expression through epigenetic processes, such as DNA methylation and post-translational histone modifications. We investigated the effects of arsenic on histone residues in vivo as well as in vitro. Analysis of H3K9Ac and H3K9me3 in CD4+ and CD8+ sorted blood cells from individuals exposed to arsenic through drinking water in the Argentinean Andes showed a significant decrease in global H3K9me3 in CD4+ cells, but not CD8+ cells, with increasing arsenic exposure. In vitro studies of inorganic arsenic-treated T lymphocytes (Jurkat and CCRF-CEM, 0.1, 1, and 100 μg/L) showed arsenic-related modifications of H3K9Ac and changes in the levels of the histone deacetylating enzyme HDAC2 at very low arsenic concentrations. Further, in vitro exposure of kidney HEK293 cells to arsenic (1 and 5 μM) altered the protein levels of PCNA and DNMT1, parts of a gene expression repressor complex, as well as MAML1. MAML1 co-localized and interacted with components of this complex in HEK293 cells, and in silico studies indicated that MAML1 expression correlate with HDAC2 and DNMT1 expression in kidney cells. In conclusion, our data suggest that arsenic exposure may lead to changes in the global levels of H3K9me3 and H3K9Ac in lymphocytes. Also, we show that arsenic exposure affects the expression of PCNA and DNMT1—proteins that are part of a gene expression silencing complex.     

The cytochrome system of Bacillus megaterium KM. The presence and some properties of two CO-binding cytochromes

1. Difference spectra of Bacillus megaterium KM membrane preparations indicate the presence of two pigments which bind CO and which exhibit the spectral characteristics of cytochromes a₃ and o. Relative amounts of the pigments vary with growth stage of the organism, but both are present at all stages which have been investigated. The pigments are believed to be metabolically active because they are completely reducible by substrate (NADH) and are reoxidizable in the presence of air. CO difference spectra of whole cell suspensions are in agreement with spectra of the isolated membrane fragments. In particulate preparations and in whole cells, CO difference spectra suggest that the a₃ component binds CO much more readily than the o component; this behavior offers a possible explanation for the fact that cytochrome o has been detected in only a few other microorganisms, since CO binding is by definition the property used to identify this cytochrome.

2. A separation of the two CO-binding pigments is obtained by incubation of membrane preparations with pancreatic lipase. This treatment selectively removes the o pigment from the membrane, leaving the a₃ component associated with an enzymatically active particulate fraction.     

The effects of electrical stimulation of posterior hypothalamus on activity of the nucleus pontis oralis' neurons

The nucleus pontis oralis' neurons were responsive to electrical stimulation of posterior hypothalamus. PS-on neurons showed an inhibitory response, and PS-off cells demonstrated an excitatory response. Neurons that discharged in association with phasic paradoxical sleep phenomena were found to have both the excitatory and the inhibitory responses. Evoked responses changed across sleep-waking cycle. The findings suggest that posterior hypothalamus is involved in the control of paradoxical sleep generation mechanisms located in the nucleus pontis oralis.     

Expression of peroxisomal proteins provides clear evidence for the presence of peroxisomes in the male germ cell line GC1spg

Peroxisomes are cell organelles that perform multiple functions in the metabolism of lipids and of reactive oxygen species. They are present in most eukaryotic cells. However, they are believed to be absent in spermatozoa and they have never been described in male germ cells. We have used the immortalized germ cell line GC1spg to investigate the expression of peroxisomal proteins in germ cells of mice. The GC1spg cells represent the differentiation state of type B spermatogonia or preleptotene spermatocytes. We could show that peroxisomal membrane proteins like Pmp70 and Pex14p as well as peroxisomal matrix proteins like catalase or acyl CoA oxidase are expressed in GC1spg cells. All these proteins were colocalized in the same structures within the cells. Furthermore, by electron microscopy we have identified subcellular particles with an ultrastructural appearance that is characteristic of peroxisomes. This is the first report demonstrating the peroxisomal compartment in male germ cells of mice.     

Variable responses of natural enemies to Salix triandra phenotypes with different secondary chemistry

Plant phenotypes often differ in their resistance to natural enemies, but the mechanism for this has seldom been identified. The aim of this study was to determine if the spatial patterns of phenotype use of a highly specialized insect herbivore (the galling sawfly Pontania triandrae ) in a natural willow population can be related to phenotypic variation in plant secondary chemistry. Furthermore, we tested if traits that confer resistance to one type of natural enemy, i.e. the galling sawfly, also confer resistance to others, in our case a leaf beetle Gonioctena linnaeana and the rust fungus Melampsora amygdalinae . We identified 18 phenotypes with high and 18 phenotypes with low gall density in our field population and determined gall densities, the degree of leaf damage and rust infection on each phenotype and collected leaves for chemical analyses. The concentration of phenolics was higher in phenotypes with high density of galls suggesting that this galling sawfly may use phenolics as oviposition cues. Rust infection showed the opposite pattern, with lower levels on clones with high concentration of phenolics, while leaf damage by G. linnaeana did not differ between clone types. This indicates that these important natural enemies may assert divergent selection on willow phenotypes and that this might provide a mechanism for maintaining phenotypic variation within willow populations.     

Forest History as a Basis for Ecosystem Restoration—A Multidisciplinary Case Study in a South Swedish Temperate Landscape

Basic knowledge of the previous forest types or ecosystem present in an area ought to be an essential part of all landscape restoration. Here, we present a detailed study of forest and land use history over the past 2,000 years, from a large estate in southernmost Sweden, which is currently undergoing a restoration program. In particular, the aim was to identify areas with long continuity of important tree species and open woodland conditions. We employed a multidisciplinary approach using paleoecological analyses (regional and local pollen, plant macrofossil, tree ring) and historical sources (taxation documents, land surveys, forest inventories). The estate has been dominated by temperate broad‐leaved trees over most of the studied period. When a forest type of Tilia, Corylus, and Quercus started to decline circa 1,000 years ago, it was largely replaced by Fagus. Even though extensive planting of Picea started in mid‐nineteenth century, Fagus and Quercus have remained rather common on the estate up to present time. Both species show continuity on different parts of the estate from eighteenth century up to present time, but in some stands, for the entire 2,000 years. Our suggestions for restoration do not aim for previous “natural” conditions but to maintain the spatial vegetational pattern created by the historical land use. This study gives an example of the spatial and temporal variation of the vegetation that has historically occurred within one area and emphasizes that information from one methodological technique provides only limited information about an area’s vegetation history.     

Antifungal compounds from cultures of dairy propionibacteria type strains

Antifungal compounds from cultures of five type strains of dairy propionibacteria, as well as from the cultivation medium, were studied. Cell-free supernatants and medium were fractionated by C(18) solid phase extraction. The aqueous 95% acetonitrile fractions were analyzed by GC-MS or subjected to reversed-phase HPLC, to identify, quantify or isolate antifungal substances. The resulting HPLC fractions were screened for antifungal activity against the mold Aspergillus fumigatus and the yeast Rhodotorula mucilaginosa. Active fractions were further separated by HPLC and the structures of the compounds were determined by spectroscopic and chromatographic methods. All five strains produced 3-phenyllactic acid, at concentrations ranging from 1.0 microg mL(-1) (Propionibacterium freudenreichii ssp. shermanii) to 15.1 microg mL(-1) (Propionibacterium thoenii), and at L/D -ratios ranging from 2 : 3 (Propionibacterium acidipropionici) to 9 : 1 (Propionibacterium freudenreichii). A number of active compounds found in cultures of propionibacteria were also present in noninoculated growth medium: two antifungal diketopiperazines, cyclo(L-Phe-L-Pro) and cyclo(L-Ile-L-Pro), and seven antifungal linear peptides. Three of the linear peptides corresponded to sequences found in the medium component casein, suggesting their origin from this component, whereas the diketopiperazines were suggested to be formed from medium peptides by heat treatment.     

Polyethylene glycol and electric field treatment of plant protoplasts: characterization of some membrane properties

Petiolar protoplasts of a dihaploid line of winter oilseed rape Brassica napus L. ssp. oleifera were exposed to fusogenic polyethylene glycol (PEG) and electric field treatments. The surface properties and stability of membrane components of the treated protoplasts were investigated by contact angle measurements in aqueous two-phase systems and differential scanning calorimetry, respectively. The leakage of intracellular components was estimated with respect to amino acids, proteins and DNA. Both fusogenic treatments resulted in the same apparent changes in membrane surface hydrophobicity and the same destabilization of membrane components. However, the PEG-treated protoplasts were more leaky than both the control and the electric field-treated protoplasts. The results indicate that the molecular mechanisms of PEG- and electrical field-induced fusion are similar. However, the effects of the latter appear to be less harmful presumably because the parameters for electric field treatment are more easily controlled.