Antigenic relatedness between phospholipases A2 from Naja naja venom and from mammalian cells

Polyclonal antiserum was prepared against phospholipase A2 from Naja naja and used to prepare a purified antibody. It cross-reacted with the antigen, and with intracellular mammalian PLA2. This antibody was immunoreactive and inhibited the PLA2 activity of Naja naja and of guinea pig alveolar macrophages or rat lymphocytes. By immunoblotting, this antiserum revealed one band of PLA2 from Naja naja (14 kDa) and 3 bands for guinea pig alveolar macrophages and rat lymphocytes (30, 45 kDa and a minor band of 14 kDa). These results show an antigenic relatedness between an extracellular PLA2 and membrane-bound PLA2 from two different mammalian species and cell types.     

Essential fatty acid uptake and esterification in primary culture of rat hepatocytes

Primary cultures of adult rat hepatocytes were used to compare the uptake and esterification of essential polyunsaturated fatty acids (18:2, 20:3 and 20:4 of the n-6 series) with those of palmitic and oleic acids. The uptake of unesterified fatty acids was linearly related to the free fatty acid/albumin molar ratio for 14 h and did not depend on the unbound free fatty acid level. Whatever the initial free fatty acid/albumin molar ratio, it dropped to 0.5 +/- 0.1 mM after 14 h, thus showing that hepatocytes have a high capacity for clearing free fatty acids from the medium at high free fatty acid/albumin molar ratios. The free fatty acid uptake become saturable when the free fatty acid and albumin concentrations were raised and the free fatty acid/albumin ratio remained constant. This strongly suggests that albumin-hepatocyte interaction mediates free fatty acid uptake. This uptake was identical whatever the fatty acid tested and did not depend on the relative amounts of fatty acids when they were added simultaneously. Triacylglycerol accumulation and synthesis, monitored by labelled fatty acids, were related to the free fatty acid/albumin molar ratio and exhibited no specificity for the series of fatty acids tested. Triacylglycerols were enriched in all the fatty acids tested by up to 60%, and fatty acid incorporation into diacylglycerols and triacylglycerols reflected the free fatty acid composition of the medium. By contrast, neither the level nor the synthesis of phospholipids varied with free fatty acid/albumin, but the rate of phospholipid turnover depended on the fatty acids tested. Accumulation of these acids was smaller in phospholipids than in triacylglycerols. When linoleic and arachidonic acids were added together, phospholipids (especially phosphatidylethanolamine and phosphatidylinositol) were more enriched in arachidonic acid than triacylglycerols. This might be due to the specificity for fatty acid of the enzymes involved in phospholipid metabolism.     

The feeding, growth and behaviour of juvenile cod, Gadus morhua L., in cold environments

Most studies on feeding-related activities of fish in cold water (0° C) have not used eurythermal species or examined a broad suite of activities. In this study we report on the feeding, growth, behaviour and conversion-efficiency of 0 + Atlantic cod in response to water temperature and food availability. In one experiment, activity, opercular beat and growth decreased with decreasing temperature over the range 8·3–0·6° C. However, the conversion efficiency increased with decreasing temperature, a result partly explained by the relative change in activity and opercular rate. In another experiment, temperature had a linear effect on growth in cod fed different food rations. Both food availability and temperature were found to influence growth in group 0 + cod. The specific growth rate of cod in this experiment exceeded 2% day^-1. Growth data collected from cod sampled in the field during the cold-water period showed a progressive increase of mean length over the season. Overall, these results demonstrate that 0 + cod have adapted to life in cold-water environments, in contrast to adult cod which mostly inhabit warmer environments.     

Low MHC DRB class II diversity in the mountain goat: past bottlenecks and possible role of pathogens and parasites

Major histocompatibility complex (MHC) genes are the most polymorphic in vertebrates and code for molecules playing a central role in pathogen resistance. We studied levels of MHC DRB class II diversity in a long-term study population of mountain goats (Oreamnos americanus) at Caw Ridge, Alberta, and two other populations from British Columbia, Canada. Only two alleles were found among the three populations sampled. The Caw Ridge population was fixed for one of the two MHC DRB alleles, but this lack of variation did not appear to have affected it negatively because the population doubled over two decades and had no history of any apparent infectious diseases. Past population bottlenecks during Pleistocene glaciations are thought to have been the main factor contributing to the low levels of MHC diversity in mountain goats, a hypothesis supported by our previous work reporting low polymorphism at neutral loci. Additionally, the limited MHC variability in mountain goats may be related to its northern distribution as we found that allelic diversity at MHC DRB class II in wild ungulates decreases with increasing latitude, possibly as a result of low parasite diversity at high latitudes. The low MHC variation in mountain goats and other northern ungulates such as muskoxen (Ovibos moschatus) may expose these species to population outbreaks that could be generated by introduced pathogens or northward shifts in the distribution of pathogens with global climate warming.     

Human cytomegalovirus UL44 concentrates at the periphery of replication compartments, the site of viral DNA synthesis

The formation of replication compartments, the subnuclear structures in which the viral DNA genome is replicated, is a hallmark of herpesvirus infections. The localization of proteins and viral DNA within human cytomegalovirus replication compartments is not well characterized. Immunofluorescence analysis demonstrated the accumulation of the viral DNA polymerase subunit UL44 at the periphery of replication compartments and the presence of different populations of UL44 in infected cells. In contrast, the viral single-stranded-DNA binding protein UL57 was distributed throughout replication compartments. Using "click chemistry" to detect 5-ethynyl-2'-deoxyuridine (EdU) incorporation into replicating viral DNA and pulse-chase protocols, we found that viral DNA synthesis occurs at the periphery of replication compartments and that replicated viral DNA subsequently localizes to the interior of replication compartments. The interiors of replication compartments also contain regions in which UL44 and EdU-labeled DNA are absent. The treatment of cells with a viral DNA polymerase inhibitor reversibly caused the dispersal of both UL44 and EdU-labeled viral DNA from replication compartments, indicating that ongoing viral DNA synthesis is necessary to maintain the organization of replication compartments. Our results reveal a previously unappreciated complexity of the organization of human cytomegalovirus replication compartments.     

Influence of habitat features and hunter behavior on white-tailed deer harvest

Sport hunting may help in controlling cervid populations over large areas. As with natural predators, several environmental factors can influence sport harvest. A better understanding of the environmental variables that limit the efficiency of sport hunting could provide guidelines for more efficient wildlife management using hunting. We studied white-tailed deer (Odocoileus virginianus) hunting on a high deer density island where hunting was the sole form of predation. Our objective was to study the behavior of sport hunters and determine the habitat characteristics (e.g., abundance of deer forage, visibility of the deer from the hunter's point of view, and accessibility of the territory to hunters) that are associated with a successful harvest. We collected movements and harvest site location data from 477 hunters equipped with handheld Global Positioning System (GPS) units. Harvest sites were visited and characterized, along with a paired random site, to determine the environmental conditions associated with a successful hunt. We also developed a model to predict the daily number of deer seen by hunters considering weather conditions, hunter characteristics (e.g., age, experience), and date of hunting. We used the mean number of deer seen per hunter per day as a relative index of local density in each hunted territory. At both the site and landscape scales, the combination of visibility and access had a positive effect on the distribution of harvested deer. Habitat types with less visual obstruction from vegetation enabled hunters to see more deer in a given day. At the site scale, harvested deer were located in areas with a lower density of access routes compared to areas where hunters travelled throughout the day. Using an innovative approach of studying hunter behavior with GPS technology, digital maps, and questionnaires, we highlighted the factors associated with hunter success. Our study suggests that habitat characteristics could be modified to increase harvest by improving accessibility and visibility near roads. Creating openings in mature and regenerating forest near access roads could make sport hunting a more efficient management tool, but the potential impact of increased forage availability in forest openings should not be overlooked. © 2012 The Wildlife Society.     

Tests of density dependence using indices of relative abundance in a deer population

A major question in animal ecology is explaining the causes of population fluctuations. Consensus about the most reliable method to detect density dependence (DD) or environmental effects from time‐series data, however, has not yet been achieved. Times series analyses have been used with indices of relative abundance in numerous studies, although these indices are rarely validated. Here, we used three different time series of relative abundance (number of deer seen per hunter per day, hunting success and proportion of males in the harvest) to explore direct and delayed DD in a white‐tailed deer Odocoileus virginianus population on Anticosti Island, Québec, Canada. Three mathematical approaches were tested: linear models, autoregressive (AR) models, and total DD in life history. Tests of DD using different indices of abundance on the same population should lead to similar results if all indices exhibit similar behaviour. Indices of relative abundance correlated with each other, although sometimes weakly, such that we obtained similar DD estimates with each index using detrended non‐stationary series. In most time series, linear regression of N_t?1 and N_t and AR models did not detect DD, while we obtained strong evidence for DD from the life‐history approach. This meant that contrasting conclusions about the role of density dependence within this population were reached depending on which method was used. We conclude that the method that incorporates most biological realism, the life‐history approach, provided a different result than classical interpretation of autoregressive coefficients. Only the life‐history interpretation supported our a priori belief that density dependence operating through competition for food regulates the Anticosti deer population. Phenomenological analysis aiming to investigate changes in abundance should be carefully conducted as the use of inappropriate indices or methods could lead to inappropriate conclusions or management strategies. Preferably, the method used should match the time scale of the population sampling regime and species life history.     

Massive breeding failures following a tsunami in a colonial seabird

Natural catastrophic events such as tsunamis may induce drastic decreases in breeding success of animal populations. We evaluate the impacts of flooding on the reproductive success of king penguins (Aptenodytes patagonicus) in the Crozet Archipelago. On 26 December 2004, a magnitude-9 earthquake created a large tsunami that flooded a colony at 6,500 km from the epicentre of the earthquake. On 30 January 2005, severe waves again flooded the colony. About 17–20% of the surface of the colony was impacted during each flood and 44% of the breeding birds abandoned their egg or chick following the two floodings. Although about 11% of birds laid another egg after the tsunami, none reproduced again after the second flood that happened later in the breeding season. Our results show that the tsunami directly affected the reproductive success of seabirds nesting near the coast.     

The fungal–mineral interface: challenges and considerations of micro-analytical developments

Over recent years, the role of fungi, especially mycorrhizal fungi, in the weathering of rock-forming minerals has been increasingly recognised. Much of our understanding of the effects of fungi on mineral weathering is based on macroscopic studies. However, the ability of fungi to translocate materials, including organic acids and siderophores, to specific areas of a mineral surface leads to significant spatial heterogeneity in the weathering process. Thus, geomycologists are confronted with unique challenges of how to comprehend and quantify such a high degree of diversity and complicated arrays of interactions. Recent advances in experimental and analytical techniques have increased our ability to probe the fungal–mineral interface at the resolution necessary to decouple significant biogeochemical processes. Modern microscopy, spectroscopy, mass spectrometry, wet chemistry, and scattering techniques allow for the selective extraction of physical, chemical, and structural data at the micro- to nano-scale. These techniques offer exciting possibilities to study fungal–mineral interactions at the scale of individual hyphae. In this review, we give an overview of some of these techniques with their characteristics, advantages and limitations, and how they can be used to further our understanding of biotic mineral weathering.     

Large-scale essential gene identification in Candida albicans and applications to antifungal drug discovery

Candida albicans is the primary fungal pathogen of humans. Despite the need for novel drugs to combat fungal infections [Sobel, J.D. (2000) Clin Infectious Dis 30: 652], antifungal drug discovery is currently limited by both the availability of suitable drug targets and assays to screen corresponding targets. A functional genomics approach based on the diploid C. albicans genome sequence, termed GRACETM (gene replacement and conditional expression), was used to assess gene essentiality through a combination of gene replacement and conditional gene expression. In a systematic application of this approach, we identify 567 essential genes in C. albicans. Interestingly, evaluating the conditional phenotype of all identifiable C. albicans homologues of the Saccharomyces cerevisiae essential gene set [Giaever, G., Chu, A.M., Ni, L., Connelly, C., Riles, L., Veronneau, S., et al. (2002) Nature 418: 387-391] by GRACE revealed only 61% to be essential in C. albicans, emphasizing the importance of performing such studies directly within the pathogen. Construction of this conditional mutant strain collection facilitates large-scale examination of terminal phenotypes of essential genes. This information enables preferred drug targets to be selected from the C. albicans essential gene set by phenotypic information derived both in vitro, such as cidal versus static terminal phenotypes, as well as in vivo through virulence studies using conditional strains in an animal model of infection. In addition, the combination of phenotypic and bioinformatic analyses further improves drug target selection from the C. albicans essential gene set, and their respective conditional mutant strains may be directly used as sensitive whole-cell assays for drug screening.