Trophic cul-de-sac, Pyrazus ebeninus, limits trophic transfer through an estuarine detritus-based food web

The importance to food‐webs of trophic cul‐de‐sacs, species that channel energy flow away from higher trophic levels, is seldom considered outside of the pelagic systems in which they were first identified. On intertidal mudflats, inputs of detritus from saltmarshes, macroalgae or microphytobenthos are generally regarded as a major structuring force underpinning food‐webs and there has been no consideration of trophic cul‐de‐sacs to date. A fully orthogonal three‐factor experiment manipulating the density of the abundant gastropod, Pyrazus ebeninus, detritus and macrobenthic predators on a Sydney mudflat revealed large deleterious effects of the gastropod, irrespective of detrital loading or the presence of predators. Two months after experimental manipulation, the standing‐stock of microphytobenthos in plots with high (44 per m²) densities of P. ebeninus was 20% less than in plots with low (4 per m²) densities. Increasing densities of P. ebeninus from low to high halved the abundance of macroinvertebrates and the average number of species. In contrast, the addition of detritus had differing effects on microphytobenthos (positively affected) and macroinvertebrates (negatively affected). Over the two‐months of our experiment, no predatory mortality of P. ebeninus was observed and high densities of P. ebeninus decreased impacts of predators on macroinvertebrate abundances. Given that the dynamics of southeast Australian mudflats are driven more by disturbance than seasonality in predators and their interactions with prey, it is likely that Pyrazus would be similarly resistant to predation and have negative effects on benthic assemblages at other times of the year, outside of our study period. Thus, in reducing microphytobenthos and the abundance and species richness of macrofauna, high abundances of the detritivore P. ebeninus may severely limit the flow of energy up the food chain to commercially‐important species. This study therefore suggests that trophic cul‐de‐sacs are not limited to the eutrophied pelagic systems in which they were first identified, but may exist in other systems as well.     

C-terminal tail phosphorylation of N-formyl peptide receptor: differential recognition of two neutrophil chemoattractant receptors by monoclonal antibodies NFPR1 and NFPR2

The N-formyl peptide receptor (FPR), a G protein-coupled receptor that binds proinflammatory chemoattractant peptides, serves as a model receptor for leukocyte chemotaxis. Recombinant histidine-tagged FPR (rHis-FPR) was purified in lysophosphatidyl glycerol (LPG) by Ni(2+)-NTA agarose chromatography to >95% purity with high yield. MALDI-TOF mass analysis (>36% sequence coverage) and immunoblotting confirmed the identity as FPR. The rHis-FPR served as an immunogen for the production of 2 mAbs, NFPR1 and NFPR2, that epitope map to the FPR C-terminal tail sequences, 305-GQDFRERLI-313 and 337-NSTLPSAEVE-346, respectively. Both mAbs specifically immunoblotted rHis-FPR and recombinant FPR (rFPR) expressed in Chinese hamster ovary cells. NFPR1 also recognized recombinant FPRL1, specifically expressed in mouse L fibroblasts. In human neutrophil membranes, both Abs labeled a 45-75 kDa species (peak M(r) approximately 60 kDa) localized primarily in the plasma membrane with a minor component in the lactoferrin-enriched intracellular fractions, consistent with FPR size and localization. NFPR1 also recognized a band of M(r) approximately 40 kDa localized, in equal proportions to the plasma membrane and lactoferrin-enriched fractions, consistent with FPRL1 size and localization. Only NFPR2 was capable of immunoprecipitation of rFPR in detergent extracts. The recognition of rFPR by NFPR2 is lost after exposure of cellular rFPR to f-Met-Leu-Phe (fMLF) and regained after alkaline phosphatase treatment of rFPR-bearing membranes. In neutrophils, NFPR2 immunofluorescence was lost upon fMLF stimulation. Immunoblotting approximately 60 kDa species, after phosphatase treatment of fMLF-stimulated neutrophil membranes, was also enhanced. We conclude that the region 337-346 of FPR becomes phosphorylated after fMLF activation of rFPR-expressing Chinese hamster ovary cells and neutrophils.     

DSL ligand endocytosis physically dissociates Notch1 heterodimers before activating proteolysis can occur

Cleavage of Notch by furin is required to generate a mature, cell surface heterodimeric receptor that can be proteolytically activated to release its intracellular domain, which functions in signal transduction. Current models propose that ligand binding to heterodimeric Notch (hNotch) induces a disintegrin and metalloprotease (ADAM) proteolytic release of the Notch extracellular domain (NECD), which is subsequently shed and/or endocytosed by DSL ligand cells. We provide evidence for NECD release and internalization by DSL ligand cells, which, surprisingly, did not require ADAM activity. However, losses in either hNotch formation or ligand endocytosis significantly decreased NECD transfer to DSL ligand cells, as well as signaling in Notch cells. Because endocytosis-defective ligands bind hNotch, but do not dissociate it, additional forces beyond those produced through ligand binding must function to disrupt the intramolecular interactions that keep hNotch intact and inactive. Based on our findings, we propose that mechanical forces generated during DSL ligand endocytosis function to physically dissociate hNotch, and that dissociation is a necessary step in Notch activation.     

Dispersal of the estuarine gastropod Pyrazus ebeninus is only weakly influenced by pneumatophore density

Studies on rocky intertidal gastropods indicate habitat complexity and body size to be major determinants of dispersal patterns. Considerations of effects of habitat complexity and body size on soft sediment gastropods are, however, less common. In neither habitat has the interaction between habitat complexity and body size been considered despite the increasing recognition in the general ecological literature that complexity effects are body-size-dependent. We tested independent and interacting effects of habitat complexity and body size on movement of the mud-whelk, Pyrazus ebeninus, by marking large (61-85 mm) and small (31-55 mm) snails in sites with low and high densities of pneumatophores and determining the distance and direction of their dispersal over periods of 1 week, 2 weeks and 1 month. Contrary to our expectation, we found no effect of pneumatophore density on the distance of snail migration over each of the temporal scales; net distance travelled by snails was determined only by body size and idiosynchratic, site-specific factors. The direction of snail movement was, by contrast, influenced on some temporal scales by both pneumatophore density and snail size. Over 1 week, site effects dominated patterns of movement and neither size of snail nor density of pneumatophore produced statistically significant effects. As the temporal scale increased, effects of size and pneumatophore density became increasingly apparent. Over the 1-month period, large snails at all sites and small snails at sites with high pneumatophore density migrated down the shore, while small snails at sites with low pneumatophore displayed non-directional movement. Thus, overall this study provides only weak support for effects of pneumatophore density on snail movement. In combination with other studies, our results suggest that, in comparison to on rocky shores where habitat complexity has strong effects on the distribution, abundance and behaviour of gastropods in soft-sediment systems habitat complexity is a less important structuring agent.     

Irradiation Sensitivity of Planktonic and Biofilm-Associated Escherichia coli O157:H7 Isolates Is Influenced by Culture Conditions

Ionizing radiation effectively inactivates Escherichia coli O157:H7, but the efficacy of the process against biofilm cells versus that against free-living planktonic cells is not well documented. The radiation sensitivity of planktonic or biofilm cells was determined for three isolates of E. coli O157:H7 (C9490, ATCC 35150, and ATCC 43894). Biofilms were formed on sterile glass slides incubated at 37°C for either 24 h, 48 h, or 72 h. The biofilm and planktonic cultures were gamma irradiated at doses ranging from 0.0 (control) to 1.5 kGy. The dose of radiation value required to reduce the population by 90% (D₁₀) was calculated for each isolate, culture, and maturity based on viable populations at each radiation dose. For each of the times sampled, the D₁₀ values of isolate 43894 planktonic cells (0.454 to 0.479 kGy) were significantly (P < 0.05) higher than those observed for biofilm cells (0.381 to 0.385 kGy), indicating a significantly increased sensitivity to irradiation for cells in the biofilm habitat. At the 24-h sampling time, isolate C9490 showed a similar pattern, in which the D₁₀ values of planktonic cells (0.653 kGy) were significantly higher than those for biofilm cells (0.479 kGy), while isolate 35150 showed the reverse, with D₁₀ values of planktonic cells (0.396 kGy) significantly lower than those for biofilm cells (0.526 kGy). At the 48-h and 72-h sampling times, there were no differences in radiation sensitivities based on biofilm habitat for C9490 or 35150. Biofilm-associated cells, therefore, show a response to irradiation which can differ from that of planktonic counterparts, depending on the isolate and the culture maturity. Culture maturity had a more significant influence on the irradiation efficacy of planktonic cells but not on biofilm-associated cells of E. coli O157:H7.     

Results from the pediatric European register for treatment of Helicobacter pylori (PERTH)

BACKGROUND AND AIM: Data on the eradication treatment for childhood Helicobacter pylori are scanty. A register was established on the European Society for Pediatric Gastroenterology Hepatology and Nutrition (ESPGHAN) website to collect data on treatment performed by European pediatricians to ascertain what is practiced in the field. SUBJECTS: From January 2001 to December 2002, information on 597 children were entered by 23 European Centers, but only data of 518 treated children were completed and analyzed (86.7%, 262 male subjects, median age 9 years, range 1-14). According to their nationality, 226 children were from Southern Europe, 132 from Eastern Europe, 68 from Western Europe, and 4 from northern Europe, 68 from North Africa, and 20 from Asia. At endoscopy, 454 children had gastritis and 64 had ulcer (12.3%). Antibiotic sensitivity, tested in 361 cases, revealed 18% clarithromycin-resistant and 19% metronidazole-resistant H. pylori strains. RESULTS: Treatment was performed for 1 week in 388 and for 2 weeks in 130 children. Antibiotics were associated with proton pump inhibitors (PPI) in 345 and with bismuth in 121 children. Triple therapy was given to 485 children, dual therapy to 26, quadruple to 7. Follow-up data, by (13)C-Urea-Breath Test or histology or both, were available for 480 children. Overall eradication rate was 65.6%, significantly higher in children with ulcer (79.7%) than without (63.9%, p = .001). When given as first treatment, bismuth-containing triple therapies were more efficacious than PPI-containing ones (77% versus 64%, p = .02, OR 1.88, 95% CI 1.1-3.3). Twenty-seven different treatment regimens were used, but only six were administered to at least 18 children (range 18-157). There was no difference between treatments given for 1 or 2 weeks, or given as first or second therapies. CONCLUSION: European pediatricians entering data in the register used 27 different regimens. Bismuth-containing therapies resulted in higher eradication rate. Omeprazole-containing triple therapies were the most used although their efficacy was low. Therapies recommended for adults do not appear to be suitable for children.     

Mathematical Models of Cell Motility

Cell motility is an essential biological action in the creation, operation and maintenance of our bodies. Developing mathematical models elucidating cell motility will greatly advance our understanding of this fundamental biological process. With accurate models it is possible to explore many permutations of the same event and concisely investigate their outcome. While great advancements have been made in experimental studies of cell motility, it now has somewhat fallen on mathematical models to taking a leading role in future developments. The obvious reason for this is the complexity of cell motility. Employing the processing power of today’s computers will give researches the ability to run complex biophysical and biochemical scenarios, without the inherent difficulty and time associated with in vitro investigations. Before any great advancement can be made, the basics of cell motility will have to be well-defined. Without this, complicated mathematical models will be hindered by their inherent conjecture. This review will look at current mathematical investigations of cell motility, explore the reasoning behind such work and conclude with how best to advance this interesting and challenging research area.     

Virus-host interactions in salt lakes

Natural hypersaline waters are widely distributed around the globe, as both continental surface waters and sea floor lakes, the latter being maintained by the large density difference between the hypersaline and overlying marine water. Owing to the extreme salt concentrations, close to or at saturation (approximately 35%, w/v), such waters might be expected to be devoid of life but, in fact, maintain dense populations of microbes. The majority of these microorganisms are halophilic prokaryotes belonging to the Domain Archaea, 'haloarchaea'. Viruses infecting haloarchaea are a vital part of hypersaline ecosystems, in many circumstances outnumbering cells by 10-100-fold. However, few of these 'haloviruses' have been isolated and even fewer have been characterised in molecular detail. In this review, we explore the methods used by haloviruses to replicate within their hosts and consider the implications of haloviral-haloarchaeal interactions for salt lake ecology.     

Nasopharyngeal carcinoma-associated Epstein-Barr virus-encoded oncogene latent membrane protein 1 potentiates regulatory T-cell function

Sequence variation in the Epstein-Barr virus (EBV) latent membrane protein 1 (LMP1) oncogene structure may affect antigen-presenting cell (APC) function of infected B cells and immune escape by EBV-specific T cells and thus contribute to the development of malignancy. Normal B cell-associated LMP1 (B-LMP1) upregulates B cell APC function through activation of the necrosis factor (NF)-kappaB subunit, RelB. We examined the ability of B-LMP1 and a nasopharyngeal carcinoma-associated LMP1 (NPC-LMP1) to modulate B cell APC function and T-cell responses. B lymphoma cells transfected with NPC-LMP1 stimulated resting T cells in mixed lymphocyte reaction less efficiently than B-LMP1 transfectants. Unexpectedly, antigen presentation to CD4(+) T helper cells was reduced owing to potentiation of regulatory T-cell function by NPC-LMP1 transfectants, which produce increased levels of interleukin-10, rendering CD4(+) T cells hyporesponsive. Thus, after primary EBV infection, T cells may escape activation by NPC-LMP1. These observations have important implications for the establishment of EBV-associated malignancy in the context of infection with tumour-associated EBV LMP1 variants.