The involvement of sand disturbance, cannibalism and intra-guild predation in competitive interactions among pit-building antlion larvae

Competition in trap-building predators such as antlion larvae is a complex biotic interaction, potentially involving exploitation competition, sand throwing (i.e., interference competition), cannibalism and intra-guild predation. We investigated the short-term behavioral and developmental responses of the strict sit-and-wait antlion predator Myrmeleon hyalinus to sand disturbance (i.e., quantification of the impact of severe sand throwing), and to con- and hetero-specific competition by a larger sit-and-pursue antlion species Lopezus fedtschenkoi. We found that antlions subjected to sand disturbances reduced their pit construction activity and relocated less often. Furthermore, the reduction in pit construction activity was stronger among antlions subjected to disturbances prior to feeding. Almost no death occurred during the sand disturbance experiment, but as expected, disturbances caused reductions in the relative growth rates of antlions. This negative effect was stronger in the group exposed to sand disturbances prior to feeding. The presence of the sit-and-pursue competitor led to reductions both in pit construction and in relocation activities of M. hyalinus. Although the per-capita food supply was identical in both experiments, only 48% of M. hyalinus larvae survived the competition experiment, and this pattern was consistent between the con- and hetero-specific treatments. However, in the presence of hetero-specific competitors, the relative growth rate of surviving larvae was significantly lower than that measured in the presence of con-specific competitors. Our study demonstrates that investigating the different components of complex biotic interactions can markedly improve our understanding of how these different factors interact to influence the behavior and life history of organisms.     

Functional and translational analyses of a beta-glucosidase gene (glycosyl hydrolase family 1) isolated from the gut of the lower termite Reticulitermes flavipes

This research focused on digestive beta-glucosidases from glycosyl hydrolase family (GHF) 1 from the gut of the lower termite Reticulitermes flavipes. In preceding studies on R. flavipes, we characterized beta-glucosidase activity across the gut and its inhibition by carbohydrate-based inhibitors, and subsequently we identified two partial beta-glucosidase cDNA sequences from a host gut cDNA library. Here, we report on the full-length cDNA sequence for one of the R. flavipes beta-glucosidases (RfBGluc-1), the expression of its mRNA in the salivary gland and foregut, the production of recombinant protein using a baculovirus–insect expression system, optimal recombinant substrate specificity profiles and parameters, and significant inhibition by the established beta-glucosidase inhibitor cellobioimidazole. We also report the partial cDNA sequence for a second gut beta-glucosidase (RfBGluc-2), and show that like RfBGluc-1 its mRNA is localized mainly in the salivary gland. Other results for RfBGluc-1 showing activity against laminaribose, a component of microbial cell walls, suggest that RfBGluc-1 may serve dual functions in cellulose digestion and immunity. These findings provide important information that will enable the testing of hypotheses related to collaborative host–symbiont lignocellulose digestion, and that contributes to the development of next-generation termiticides and novel biocatalyst cocktails for use in biomass-to-bioethanol applications.     

Selection for resistance to imidacloprid in the house fly (Diptera: Muscidae)

The house fly, Musca domestica L. (Diptera: Muscidae), continues to be a primary pest of livestock facilities worldwide. This pest also has shown a propensity for pesticide resistance development when under high selection pressures. In this study the house fly strain FDm was created by a 20% contribution from each of five colonies collected from dairies in Florida with known imidacloprid resistance. The FDm strain was used to evaluate the level ofimidacloprid resistance after five selections near the LC70 value of each selected generation. Overall, the mean selection mortality was 72.7, with males being considerably more susceptible than females. The unselected (F0) FDm strain showed considerable susceptibility to imidacloprid after its creation, compared with the five parental strains. Between 9500 and 14,000 virgin house flies were used in each selection. After the fifth and final selection, a 331-fold increase in imidacloprid resistance at the LC70 was observed over the parental FDm strain. In parallel studies, the FDm strain showed increasing tolerance of the commercial imidacloprid product QuickBayt. These results suggest that livestock producers should use caution when choosing pesticides and consider rotating fly baits, as is encouraged with other pesticide treatment regimes on farms.     

Proteomic analysis of doxorubicin‐induced changes in the proteome of HepG2cells combining 2‐D DIGE and LC‐MS/MS approaches

HepG‐2 cells are widely used as a cell model to investigate hepatocellular carcinomas and the effect of anticancer drugs such as doxorubicin, an effective antineoplastic agent, which has broad antitumoral activity against many solid and hematological malignancies. To investigate the effect of doxorubicin on the protein pattern, we used complementary proteomic workflows including 2‐D gel‐based and gel‐free methods. The analysis of crude HepG2 cell extracts by 2‐D DIGE provided data on 1835 protein spots which was then complemented by MS‐centered analysis of stable isotope labeling by amino acids in cell culture‐labeled cells. The monitoring of more than 1300 distinct proteins, including proteins of the membrane fraction provides the most comprehensive overview on the proteome of the widely used model cell line HepG2. Of the proteins monitored in total, 155 displayed doxorubicin‐induced changes in abundance. Functional analysis revealed major influences of doxorubicin on proteins involved in protein synthesis, DNA damage control, electron transport/mitochondrial function, and tumor growth. The strongest decrease in level was found for proteins involved in DNA replication and protein synthesis, whereas proteins with a function in DNA damage control and oxidative stress management displayed increased levels following treatment with doxorubicin compared with control cells. Furthermore, the doxorubicin‐associated increase in levels of multiple forms of keratins 8, 18, and 19 and other structural proteins revealed an influence on the cytoskeleton network.     

Time‐resolved quantitative proteome profiling of host–pathogen interactions: The response of Staphylococcus aureus RN1HG to internalisation by human airway epithelial cells

Staphylococcus aureus is a versatile Gram‐positive pathogen that gains increasing importance due to the rapid spreading of resistances. Functional genomics technologies can provide new insights into the adaptational network of this bacterium and its response to environmental challenges. While functional genomics technologies, including proteomics, have been extensively used to study these phenomena in shake flask cultures, studies of bacteria from in vivo settings lack behind. Particularly for proteomics studies, the major bottleneck is the lack of sufficient proteomic coverage for low numbers of cells. In this study, we introduce a workflow that combines a pulse‐chase stable isotope labelling by amino acids in cell culture approach with high capacity cell sorting, on‐membrane digestion, and high‐sensitivity MS to detect and quantitatively monitor several hundred S. aureus proteins from a few million internalised bacteria. This workflow has been used in a proof‐of‐principle experiment to reveal changes in levels of proteins with a function in protection against oxidative damage and adaptation of cell wall synthesis in strain RN1HG upon internalisation by S9 human bronchial epithelial cells.     

The influence of different surface treatments on the primary stability of cementless acetabular cups: an in vitro study]

INTRODUCTION: Long-term stability of cementless acetabular cups depends on osseointegration, which requires primary stability of the implant. The aim of this study was to determine the influence of different surface treatments on the primary stability of press-fit acetabular cups. Mechanical lever-out tests were performed to quantify the stability in vitro. MATERIALS AND METHODS: A hemispherical press-fit cup design with a flattened pole was used and different surface modifications were applied: smooth, corundum-blasted, titanium plasma spray, rough titan plasma spray, and titanium plasma spray with a rim. The outer diameter of all cups was kept constant. Polyurethane foam was selected as the test material and cup insertion was performed with a maximal force of 6000 N. The excess length between the cup and the surface of the foam blocks was measured. The maximum lever-out force was measured and the lever-out torque was calculated. RESULTS: The excess length of cups with a smooth surface was significantly less (p<0.001) than for the other cups, with no significant differences among the other surface modifications. The lever-out torque for cups with a smooth surface was significantly less (p<0.001) than for the other cups, with no significant differences among the other surface modifications. CONCLUSION: Only the cup with a smooth surface showed significant differences for excess length and lever-out torque. The other surface modifications exhibited the same stability. As long as a rough surface is chosen, cup design seems to have a greater influence on stability than surface modification. Although the study did not mimic real in vivo conditions and the lever-out-torques cannot be transferred to clinical situations, initial stability before bony ingrowth occurred could be clearly analysed.     

Phosphorylation of transitory starch is increased during degradation

The starch excess phenotype of Arabidopsis mutants defective in the starch phosphorylating enzyme glucan, water dikinase (EC 2.7.9.4) indicates that phosphorylation of starch is required for its degradation. However, the underlying mechanism has not yet been elucidated. In this study, two in vivo systems have been established that allow the analysis of phosphorylation of transitory starch during both biosynthesis in the light and degradation in darkness. First, a photoautotrophic culture of the unicellular green alga Chlamydomonas reinhardtii was used to monitor the incorporation of exogenously supplied (32)P orthophosphate into starch. Illuminated cells incorporated (32)P into starch with a constant rate during 2 h. By contrast, starch phosphorylation in darkened cells exceeded that in illuminated cells within the first 30 min, but subsequently phosphate incorporation declined. Pulse-chase experiments performed with (32)P/(31)P orthophosphate revealed a high turnover of the starch-bound phosphate esters in darkened cells but no detectable turnover in illuminated cells. Secondly, leaf starch granules were isolated from potato (Solanum tuberosum) plants grown under controlled conditions and glucan chains from the outer granule layer were released by isoamylase. Phosphorylated chains were purified and analyzed using high performance anion-exchange chromatography and matrix-assisted laser desorption/ionization mass spectrometry. Glucans released from the surface of starch granules that had been isolated from darkened leaves possessed a considerably higher degree of phosphorylation than those prepared from leaves harvested during the light period. Thus, in the unicellular alga as well as in potato leaves, net starch degradation is accompanied with an increased phosphorylation of starch.     

Characterization of general esterases from methyl parathion-resistant and -susceptible populations of western corn rootworm (Coleoptera: Chrysomelidae)

A consistent correlation between elevated esterase activity and methyl parathion resistance among Nebraska western corn rootworm, Diabrotica virgifera virgifera LeConte, populations has previously been documented. Characterization of general esterase activity using naphtholic esters as model substrates indicated that differences between resistant and susceptible strains could be maximized by optimizing assay conditions. The optimal conditions identified here were similar to those reported for other insect species. The majority of general esterase activity was found in the cytosolic fractions of resistant populations, whereas the activity was more evenly distributed between cytosolic and mitochondrial/nuclear fractions in the susceptible population. General esterase activity was predominately located in the adult thorax and abdomen. Although there were significant differences in general esterase activities between resistant and susceptible populations, the differences exhibited in single beetle activity assays did not provide sufficient discrimination to identify resistant individuals. In contrast, single larva activity assays provided greater discrimination and could be considered as an alternative to traditional bioassay techniques.