Remarks on oxygen effects

Oxygen concentration will influence the alpha- and beta-effect (two-component theory of radiation effects) independently. The beta-effect is reduced by a dose-modifying factor gamma. Oxygen, in competition with enzyme repair actions fortifies a part of the beta-lesions and this model leads to a simple equation for the factor gamma. The alpha-effect is also enhanced by oxygen. Measurements of OER indicate that the reduction of the effect from aerobic to anoxic condition might be about 70%. The functional dependence of oxygen concentration has not been investigated. For small oxygen concentrations of 0.15 to 0.5 muM/l and doses below 1000 R Révész and Littbrand have found that oxygen can protect the irradiated cells and thus increase survivals with about 10%. This is explained as a scavenger action where radical hydrogen atoms are oxidized and hydrated electrons captured by oxygen moelcules. When the oxygen concentration is increased, or with higher doses, the usual sensitizing effect of oxygen exceeds the protection effect. The influence of oxygen on alpha-effects are mainly connected with indirect radiation effects and thus depend on temperature and milieu.     

Application of modified Salmonella/microsome prescreen to petroleum-derived complex mixtures and polynuclear aromatic hydrocarbons (PAH)

In some cases, the Salmonella mutagenicity assay may fail to predict the carcinogenic potential of PAH (and of complex mixtures containing PAH) because of nonoptimal in vitro metabolic activation parameters. In this study, 7 petroleum-derived complex mixtures, as well as a number of individual PAH which were representative constituents of such mixtures, were tested in a Salmonella prescreen using quadrant plates with rat or hamster S9 at concentrations approximately 2-8 times those used in the standard assay. Some PAH (perylene, quinoline, benzo[b]chrysene, phenanthrene, anthracene) were optimally activated to mutagens by S9 at 400 microliters/plate. Rat S9 was similar to hamster S9 for most tested PAH, but anthracene and quinoline mutagenicity was enhanced by hamster S9. All 7 complex mixtures were more mutagenic with 200-400 microliters/plate S9; rat was generally slightly more efficient than hamster. Modifying this assay to include a prescreen using a range of S9 concentrations (and perhaps from species other than rat) may improve prediction of the potential carcinogenicity of complex petroleum-derived mixtures.     

The ecology of chronic wasting disease in wildlife

Prions are misfolded infectious proteins responsible for a group of fatal neurodegenerative diseases termed transmissible spongiform encephalopathy or prion diseases. Chronic Wasting Disease (CWD) is the prion disease with the highest spillover potential, affecting at least seven Cervidae (deer) species. The zoonotic potential of CWD is inconclusive and cannot be ruled out. A risk of infection for other domestic and wildlife species is also plausible. Here, we review the current status of the knowledge with respect to CWD ecology in wildlife. Our current understanding of the geographic distribution of CWD lacks spatial and temporal detail, does not consider the biogeography of infectious diseases, and is largely biased by sampling based on hunters' cooperation and funding available for each region. Limitations of the methods used for data collection suggest that the extent and prevalence of CWD in wildlife is underestimated. If the zoonotic potential of CWD is confirmed in the short term, as suggested by recent results obtained in experimental animal models, there will be limited accurate epidemiological data to inform public health. Research gaps in CWD prion ecology include the need to identify specific biological characteristics of potential CWD reservoir species that better explain susceptibility to spillover, landscape and climate configurations that are suitable for CWD transmission, and the magnitude of sampling bias in our current understanding of CWD distribution and risk. Addressing these research gaps will help anticipate novel areas and species where CWD spillover is expected, which will inform control strategies. From an ecological perspective, control strategies could include assessing restoration of natural predators of CWD reservoirs, ultrasensitive CWD detection in biotic and abiotic reservoirs, and deer density and landscape modification to reduce CWD spread and prevalence.     

Integrating management techniques to restore subtropical forests invaded by Hedychium coronarium J. Köenig (Zingiberaceae) in a biodiversity hotspot

The restoration of areas invaded by non‐native plants is challenging as invasive plants may affect both biotic and abiotic components of ecosystems, leading to impacts that constrain recolonization by native species after invaders are eliminated. In such a scenario, restoration techniques as topsoil transposition might accelerate colonization by native species in forests. Hedychium coronarium J. Koenig (Zingiberaceae) is a Himalayan herbaceous rhizomatous plant recognized as invasive in several countries. This study aimed to experimentally evaluate the response of plant assemblages to topsoil transposition on a site invaded by H. coronarium after chemical control. Four treatments were applied: chemical control integrated with topsoil transposition, chemical control of H. coronarium alone, topsoil transposition alone, and no intervention (control). Plots were evaluated prior to the application of treatments and then monthly for 11 months after treatments. Parameters were measured for H. coronarium (number of ramets, ramet height, and cover) and other species (species richness, abundance, and cover). Plots treated with chemical control (regardless of topsoil transposition) were similar in terms of all parameters measured and species composition, with dominance of herbs and shrubs. Plots managed solely with topsoil transposition had lower species richness, abundance, and cover, but more diverse life‐forms, being equally rich in climbers, trees, and herbs. Chemical control was effective to control invasion by H. coronarium and increase species richness and abundance on the managed site. Topsoil transposition promoted colonization by species that might accelerate restoration.     

From endosperm to triploid plants: a stepwise characterization of the de novo shoot organogenesis and morpho-agronomic aspects of an ornamental passion fruit (Passiflora foetida L.)

Plant Cell, Tissue and Organ Culture (PCTOC) - Somaclonal variation during in vitro culture is often an undesirable phenomenon but may also be a source of genetic variation useful for breeders. The...     

The pollination seesaw of Rhynchospora cephalotes (L.) Vahl (Cyperaceae): Influence of plant location on the role of wind and insects as pollen vectors

Ambophily (wind and insect pollination) has been reported for some genera of the typically wind-pollinated family Cyperaceae, including the genus Rhynchospora. The significance of wind and insect pollination can vary, depending on local microclimatic conditions. Rhynchospora cephalotes is an ambophilous species that can grow under different environmental conditions, either along forest edges or inside forest fragments. This study, therefore, tests the hypothesis that (a) there is greater contribution by wind than insects to fruit set of the individuals at the forest edge and (b) there is greater contribution by insects than wind to fruit set of the individuals inside the forest. Field work was carried out in a fragment of Atlantic Forest in northeastern Brazil. We quantified the number of visits by insects, wind velocity and the reproductive success (fruit set) of R. cephalotes provided by wind and insects through exclusion experiments performed at the edge of and inside the forest. We observed a greater number of visits per day by pollinating bees to individuals inside the forest (36.83 ± 7.46) than to individuals at the edge (16.66 ± 6.53). The wind speed was significantly higher at the edge (1.71 ± 0.46 m/s) than inside the forest (0.97 ± 0.18 m/s). Bees and wind are both pollen vectors of R. cephalotes, but bees were the pollen vector that contributed most to fruit set (63.3%) for individuals inside the forest, whereas wind was the primary vector for individuals at the forest edge (76.6%). This seesaw in importance of each pollen vector in the two different environments guarantees high fruit set in R. cephalotes under different microclimatic conditions.     

Evaluation of Antioxidant,Antibacterial and Enhancement of Antibiotic Action by Punica granatum Leaves Crude Extract and Enriched Fraction against Multidrug-Resistant Bacteria

The aim of this study was to evaluate the phytochemical composition, antioxidant, and antimicrobial potential of crude extract and fractions of Punica granatum leaves. The extract was produced by turbo extraction, after which hexanic, ethyl acetate, and aqueous fractions were obtained by partitioning. The chemical analyses were performed by thin layer chromatography and high-performance liquid chromatography, and the antioxidant activities were assayed by DPPH^. and ABTS^.+. Minimal inhibitory and bactericidal concentrations (MIC/MBC) were applied to twenty-two bacteria. Most strains susceptible to extract/fractions and resistant to antibiotics were selected, and ampicillin, azithromycin, ciprofloxacin, and gentamicin were associated with the ethyl acetate fraction (EAF) against multidrug-resistant strains in modulatory and checkboard models. The data from chromatographic analyses showed flavonoids and tannins in the extract, as well as the enrichment of EAF in phenols, mainly flavonoids. The flavonoids were connected to the electron transfer activity demonstrated in the DPPH^. and ABTS^.+ assays. Gram-positive strains are more susceptible to EAF. The subinhibitory concentrations of P. granatum enhanced the antimicrobial activity of the agents and reduced the EAF individual MIC, and the combination of EAF and antibiotics demonstrated a synergistic effect. These results present a promising approach for developing a therapy in which antioxidant extracts and fractions can be used in combination with antibiotics.