Pathogenesis of Helicobacter pylori Infection

Although Helicobacter pylori infection is highly prevalent in the global human population, the majority of infected individuals remain asymptomatic. A complex combination of host, environmental, and bacterial factors are considered to determine susceptibility and severity of outcome in the subset of individuals that develop clinical disease. These factors collectively determine the ability of H.?pylori to colonize the gastric mucosa and profoundly influence the nature of the interaction that ensues. Many studies over the last year provide new insight into H.?pylori virulence strategies and the activities of critical bacterial determinants that modulate the host environment. These latter include the secreted proteins CagA and VacA and adhesins BabA and OipA, which directly interact with host tissues. Observations from several studies extend the functional repertoire of CagA and the cag type IV secretion system in particular, providing further mechanistic understanding of how these important determinants engage and activate host signalling pathways important in the development of disease.     

Functional Heterogeneity within the CD44 High Human Breast Cancer Stem Cell–Like Compartment Reveals a Gene Signature Predictive of Distant Metastasis

The CD44^hi compartment in human breast cancer is enriched in tumor-initiating cells; however, the functional heterogeneity within this subpopulation remains poorly defined. We used a triple-negative breast cancer cell line with a known bilineage phenotype to isolate and clone CD44^hi single cells that exhibited mesenchymal/basal B and luminal/basal A features, respectively. Herein, we demonstrate in this and other triple-negative breast cancer cell lines that, rather than CD44^hi/CD24⁻ mesenchymal-like basal B cells, the CD44^hi/CD24^lo epithelioid basal A cells retained classic cancer stem cell features, such as tumor-initiating capacity in vivo, mammosphere formation and resistance to standard chemotherapy. These results complement previous findings using oncogene-transformed normal mammary cells showing that only cell clones with a mesenchymal phenotype exhibit cancer stem cell features. Further, we performed comparative quantitative proteomic and gene array analyses of these cells and identified potential novel markers of breast cancer cells with tumor-initiating features, such as lipolysis-stimulated lipoprotein receptor (LSR), RAB25, S100A14 and mucin 1 (MUC1), as well as a novel 31-gene signature capable of predicting distant metastasis in cohorts of estrogen receptor–negative human breast cancers. These findings strongly favor functional heterogeneity in the breast cancer cell compartment and hold promise for further refinements of prognostic marker profiling. Our work confirms that, in addition to cancer stem cells with mesenchymal-like morphology, those tumor-initiating cells with epithelial-like morphology should also be the focus of drug development.     

The Limits of Mean-Field Heterozygosity Estimates under Spatial Extension in Simulated Plant Populations

Computational models of evolutionary processes are increasingly required to incorporate multiple and diverse sources of data. A popular feature to include in population genetics models is spatial extension, which reflects more accurately natural populations than does a mean field approach. However, such models necessarily violate the mean field assumptions of classical population genetics, as do natural populations in the real world. Recently, it has been questioned whether classical approaches are truly applicable to the real world. Individual based models (IBM) are a powerful and versatile approach to achieve integration in models. In this study an IBM was used to examine how populations of plants deviate from classical expectations under spatial extension. Populations of plants that used three different mating strategies were placed in a range of arena sizes giving crowded to sparse occupation densities. Using a measure of population density, the pollen communication distance (P(cd)), the deviation exhibited by outbreeding populations differed from classical mean field expectations by less than 5% when P(cd) was less than 1, and over this threshold value the deviation significantly increased. Populations with an intermediate mating strategy did not have such a threshold and deviated directly with increasing isolation between individuals. Populations with a selfing strategy were influenced more by the mating strategy than by increased isolation. In all cases pollen dispersal was more influential than seed dispersal. The IBM model showed that mean field calculations can be reasonably applied to natural outbreeding plant populations that occur at a density in which individuals are less than the average pollen dispersal distance from their neighbors.     

Similarities of Drosophila rab GTPases Based on Expression Profiling: Completion and Analysis of the rab-Gal4 Kit

We recently generated rab-Gal4 lines for 25 of 29 predicted Drosophila rab GTPases. These lines provide tools for the expression of reporters, mutant rab variants or other genes, under control of the regulatory elements of individual rab loci. Here, we report the generation and characterization of the remaining four rab-Gal4 lines. Based on the completed 'rab-Gal4 kit' we performed a comparative analysis of the cellular and subcellular expression of all rab GTPases. This analysis includes the cellular expression patterns in characterized neuronal and non-neuronal cells and tissues, the subcellular localization of wild type, constitutively active and dominant negative rab GTPases and colocalization with known intracellular compartment markers. Our comparative analysis identifies all Rab GTPases that are expressed in the same cells and localize to the same intracellular compartments. Remarkably, similarities based on these criteria are typically not predicted by primary sequence homology. Hence, our findings provide an alternative basis to assess potential roles and redundancies based on expression in developing and adult cell types, compartment identity and subcellular localization.     

Hypoglycemia in Non-Diabetic In-Patients: Clinical or Criminal?

Background and Aim

We wished to establish the frequency of unexpected hypoglycemia observed in non diabetic patients outside the intensive care unit and to determine if they have a plausible clinical explanation.

Methods

We analysed data for 2010 from three distinct sources to identify non diabetic hypoglycaemic patients: bedside and laboratory blood glucose measurements; medication records for those treatments (high-strength glucose solution and glucagon) commonly given to reverse hypoglycemia; and diagnostic codes for hypoglycemia. We excluded from the denominator admissions of patients with a diagnosis of diabetes or prescribed diabetic medication. Case notes of patients identified were reviewed. We used capture-recapture methods to establish the likely frequency of hypoglycemia in non-diabetic in-patients outside intensive care unit at different cut-off points for hypoglycemia. We also recorded co-morbidities that might have given rise to hypoglycemia.

Results

Among the 37,898 admissions, the triggers identified 71 hypoglycaemic episodes at a cut-off of 3.3 mmol/l. Estimated frequency at 3.3 mmol/l was 50(CI 33–93), at 3.0 mmol/l, 36(CI 24–64), at 2.7 mmol/l, 13(CI 11–19), at 2.5 mmol/l, 11(CI 9–15) and at 2.2 mmol/l, 8(CI 7–11) per 10,000 admissions. Admissions of patients aged above 65 years were approximately 50% more likely to have an episode of hypoglycemia. Most were associated with important co-morbidities.

Conclusion

Significant non-diabetic hypoglycemia in hospital in–patients (at or below 2.7 mmol/l) outside critical care is rare. It is sufficiently rare for occurrences to merit case-note review and diagnostic blood tests, unless an obvious explanation is found.     

Modeling and experimental analyses reveals signaling plasticity in a bi-modular assembly of CD40 receptor activated kinases

Depending on the strength of signal dose, CD40 receptor (CD40) controls ERK-1/2 and p38MAPK activation. At low signal dose, ERK-1/2 is maximally phosphorylated but p38MAPK is minimally phosphorylated; as the signal dose increases, ERK-1/2 phosphorylation is reduced whereas p38MAPK phosphorylation is reciprocally enhanced. The mechanism of reciprocal activation of these two MAPKs remains un-elucidated. Here, our computational model, coupled to experimental perturbations, shows that the observed reciprocity is a system-level behavior of an assembly of kinases arranged in two modules. Experimental perturbations with kinase inhibitors suggest that a minimum of two trans-modular negative feedback loops are required to reproduce the experimentally observed reciprocity. The bi-modular architecture of the signaling pathways endows the system with an inherent plasticity which is further expressed in the skewing of the CD40-induced productions of IL-10 and IL-12, the respective anti-inflammatory and pro-inflammatory cytokines. Targeting the plasticity of CD40 signaling significantly reduces Leishmania major infection in a susceptible mouse strain. Thus, for the first time, using CD40 signaling as a model, we show how a bi-modular assembly of kinases imposes reciprocity to a receptor signaling. The findings unravel that the signalling plasticity is inherent to a reciprocal system and that the principle can be used for designing a therapy.