E. coli O104:H4: social media and the characterization of an emerging pathogen

The 2011 German E. coli O104:H4 outbreak resulted in thousands of cases of enterohaemorrhagic illness, with approximately 25% of these progressing to develop haemolytic uraemic syndrome (HUS). This high rate of progression to HUS was the first indicator that the bacterial cause of illness was not a typical enterohaemorrhagic E. coli (EHEC) strain. Collaborative bioinformatic analysis while the outbreak was still in progress indicated that the O104:H4 strain was in fact an enteroaggregative E. coli (EAEC) strain which had acquired genes for the production of Shiga - like toxin.     

Characterization of a Vibrio fischeri aminopeptidase and evidence for its influence on an early stage of squid colonization

Vibrio fischeri cells are the sole colonists of a specialized light organ in the mantle cavity of the sepiolid squid Euprymna scolopes. The process begins when the bacteria aggregate in mucus secretions outside the light organ. The cells eventually leave the aggregate, enter the light organ, and encounter a rich supply of peptides. The need to dissociate from mucus and presumably utilize peptides led us to hypothesize that protease activity is integral to the colonization process. Protease activity associated with whole cells of Vibrio fischeri strain ES114 was identified as the product of a putative cell membrane-associated aminopeptidase (PepN). To characterize this activity, the aminopeptidase was cloned, overexpressed, and purified. Initial steady-state kinetic studies revealed that the aminopeptidase has broad activity, with a preference for basic and hydrophobic side chains and k(cat) and K(m) values that are lower and smaller, respectively, than those of Escherichia coli PepN. A V. fischeri mutant unable to produce PepN is significantly delayed in its ability to colonize squid within the first 12 h, but eventually it establishes a wild-type colonization level. Likewise, in competition with the wild type for colonization, the mutant is outcompeted at 12 h postinoculation but then competes evenly by 24 h. Also, the PepN-deficient strain fails to achieve wild-type levels of cells in aggregates, suggesting an explanation for the initial colonization delay. This study provides a foundation for more studies on PepN expression, localization, and role in the early stages of squid colonization.     

Distinct intracellular signaling mediates C‐MET regulation of dendritic growth and synaptogenesis

Hepatocyte growth factor (HGF) activation of the MET receptor tyrosine kinase influences multiple neurodevelopmental processes. Evidence from human imaging and mouse models shows that, in the forebrain, disruptions in MET signaling alter circuit formation and function. One likely means of modulation is by controlling neuron maturation. Here, we examined the signaling mechanisms through which MET exerts developmental effects in the neocortex. In situ hybridization revealed that hgf is located near MET‐expressing neurons, including deep neocortical layers and periventricular zones. Western blot analyses of neocortical crude membranes demonstrated that HGF‐induced MET autophosphorylation peaks during synaptogenesis, with a striking reduction in activation between P14 and P17 just before pruning. In vitro analysis of postnatal neocortical neurons assessed the roles of intracellular signaling following MET activation. There is rapid, HGF‐induced phosphorylation of MET, ERK1/2, and Akt that is accompanied by two major morphological changes: increases in total dendritic growth and synapse density. Selective inhibition of each signaling pathway altered only one of the two distinct events. MAPK/ERK pathway inhibition significantly reduced the HGF‐induced increase in dendritic length, but had no effect on synapse density. In contrast, inhibition of the PI3K/Akt pathway reduced HGF‐induced increases in synapse density, with no effect on dendritic length. The data reveal a key role for MET activation during the period of neocortical neuron growth and synaptogenesis, with distinct biological outcomes mediated via discrete MET‐linked intracellular signaling pathways in the same neurons. © 2016 Wiley Periodicals, Inc. Develop Neurobiol 76: 1160–1181, 2016     

Epidemiology of Acute Pancreatitis in Hospitalized Children in the United States from 2000–2009

Background

Single-center studies suggest an increasing incidence of acute pancreatitis (AP) in children. Our specific aims were to (i) estimate the recent secular trends, (ii) assess the disease burden, and (iii) define the demographics and comorbid conditions of AP in hospitalized children within the United States.

Methods

We used the Healthcare Cost and Utilization Project Kids’ Inpatient Database, Agency for Healthcare Research and Quality for the years 2000 to 2009. Extracted data were weighted to generate national-level estimates. We used the Cochrane-Armitage test to analyze trends; cohort-matching to evaluate the association of AP and in-hospital mortality, length of stay, and charges; and multivariable logistic regression to test the association of AP and demographics and comorbid conditions.

Results

We identified 55,012 cases of AP in hospitalized children (1–20 years of age). The incidence of AP increased from 23.1 to 34.9 (cases per 10,000 hospitalizations per year; P<0.001) and for all-diagnoses 38.7 to 61.1 (P<0.001). There was an increasing trend in the incidence of both primary and all-diagnoses of AP (P<0.001). In-hospital mortality decreased (13.1 to 7.6 per 1,000 cases, P<0.001), median length of stay decreased (5 to 4 days, P<0.001), and median charges increased ($14,956 to $22,663, P<0.001). Children with AP compared to those without the disease had lower in-hospital mortality (adjusted odds ratio, aOR 0.86, 95% CI, 0.78–0.95), longer lengths of stay (aOR 2.42, 95% CI, 2.40–2.46), and higher charges (aOR 1.62, 95% CI, 1.59–1.65). AP was more likely to occur in children older than 5 years of age (aORs 2.81 to 5.25 for each 5-year age interval). Hepatobiliary disease was the comorbid condition with the greatest association with AP.

Conclusions

These results demonstrate a rising incidence of AP in hospitalized children. Despite improvements in mortality and length of stay, hospitalized children with AP have significant morbidity.     

A high frequency of distinct ATM gene mutations in ataxia-telangiectasia.

The clinical features of the autosomal recessive disorder ataxia-telangiectasia (AT) include a progressive cerebellar ataxia, hypersensitivity to ionizing radiation, and an increased susceptibility to malignancies. Epidemiological studies have suggested that AT heterozygotes may also be at increased risk for malignancy, possibly as a consequence of radiation exposure. A gene mutated in AT patients (ATM) has recently been isolated, making mutation screening in both patients and the general population possible. Because of the relatively large size of the ATM gene, the design of screening programs will depend on the types and distribution of mutations in the general population. In this report, we describe 30 mutations identified in a panel of unrelated AT patients and controls. Twenty-five of the 30 were distinct, and most patients were compound heterozygotes. The most frequently detected mutation was found in three different families and had previously been reported in five others. This corresponds to a frequency of 8% of all reported ATM mutations. Twenty-two of the alterations observed would be predicted to lead to protein truncation at sites scattered throughout the molecule. Two fibroblast cell lines, which displayed normal responses to ionizing radiation, also proved to be heterozygous for truncation mutations of ATM. These observations suggest that the carrier frequency of ATM mutations may be sufficiently high to make population screening practical. However, such screening may need to be done prospectively, that is, by searching for new mutations rather than by screening for just those already identified in AT families.     

A multigene framework for polychaete phylogenetic studies

Producing a robust phylogenetic reconstruction for Polychaeta using either morphological or molecular data sets has proven very difficult. There remain many conflicts between morphological analyses and hypotheses based on DNA data, the latter principally derived from 18S rRNA sequences. For the present study a data set covering a broad range of polychaete diversity was assembled, including 38 new sequences from 21 species. Besides available 18S rRNA data, five additional gene segments were examined: the D1 and D9-10 expansion regions of 28S rRNA, histone H3, snU2 RNA and cytochrome c oxidase subunit I. Maximum parsimony, maximum likelihood and Bayesian analyses were conducted.Annelida and Mollusca were reciprocally monophyletic in maximum likelihood analyses, but Polychaeta included a cephalopod in maximum parsimony analyses, and a patellogastropod in Bayesian analyses. When rooted on the Mollusca, optimal topologies from maximum likelihood analyses showed a recognisable basal group of taxa, including Oweniidae, Chaetopteridae and Amphinomidae. The six studied phyllodocidan families plus Orbiniidae (as the sister group of the scale-worms) formed the next most basal group. All analyses support the inclusion of Echiura, Clitellata and Siboglinidae within polychaetes. Bayesian analyses show Echiura as the sister group of Capitellidae, in agreement with previous 18S rRNA results, In contrast, Echiura formed the sister group to Trichobranchidae in maximum likelihood and maximum parsimony analyses.Supra-familial groupings consistently recovered within Polychaeta in the analyses are: (i) Terebellida without Ampharetidae; (ii) Scolecida (excepting Orbiniidae); (iii) Eunicidae, Lumbrineridae and Clitellata; and (iv) “Cirratuliformia” (including Sternaspidae) plus Sabellidae, Serpulidae and Spionidae.     

Failure modelling of trabecular bone using a non-linear combined damage and fracture voxel finite element approach

Trabecular bone tissue failure can be considered as consisting of two stages: damage and fracture; however, most failure analyses of 3D high-resolution trabecular bone samples are confined to damage mechanisms only, that is, without fracture. This study aims to develop a computational model of trabecular bone consisting of an explicit representation of complete failure, incorporating damage criteria, fracture criteria, cohesive forces, asymmetry and large deformation capabilities. Following parameter studies on a test specimen, and experimental testing of bone sample to complete failure, the asymmetric critical tissue damage and fracture strains of ovine vertebral trabecular bone were calibrated and validated to be compression damage ?1.16 %, tension damage 0.69 %, compression fracture ?2.91 % and tension fracture 1.98 %. Ultimate strength and post–ultimate strength softening were captured by the computational model, and the failure of individual struts in bending and shear was also predicted. This modelling approach incorporated a cohesive parameter that provided a facility to calibrate ductile–brittle behaviour of bone tissue in this non-linear geometric and non-linear constitutive property analyses tool. Finally, the full accumulation of tissue damage and tissue fracture has been monitored from range of small magnitude (normal daily loading) through to specimen yielding, ultimate strength and post–ultimate strength softening.     

A comparison of dynamic-state-dependent models of the trade-off between growth, damage, and reproduction

Fast growth can be costly, so trade-offs between growth and fitness are to be predicted when organisms adjust their growth to compensate for earlier environmental conditions. We developed four generic models of increasing complexity with different processes to predict the indeterminate growth of vertebrate ectotherms, which is sensitive to ambient temperature even when food is not limiting. We contrast the predictions of the models with observed experimental data on growth trajectories, feeding activity, and reproductive investment of three-spined sticklebacks and inferred patterns of accumulation of biomolecular damage arising from activity and growth. All models predicted observed patterns of compensatory growth (both accelerating and decelerating) in response to earlier temperature perturbations, but the more complex models provided the best fit to experimental data. Growth trajectories influenced future reproductive investment regardless of final body size at breeding. Our findings suggest that while models with fewer parameters can predict basic patterns of growth in stable conditions, they cannot capture the costly long-term effects of deviations from steady growth trajectories. In contrast, models in which foraging activity is assumed to carry costs are capable of predicting the complex patterns of feeding, growth, and reproductive investment seen in animals, with the cost of a heightened mortality risk (e.g., through predation) being more important than the cost of increased physiological damage.     

Molecular genetic advances in tuberous sclerosis

Over the past decade, there has been considerable progress in understanding the molecular genetics of tuberous sclerosis, a disorder characterised by hamartomatous growths in numerous organs. We review this progress, from cloning and characterising TSC1 and TSC2, the genes responsible for the disorder, through to gaining insights into the functions of their protein products hamartin and tuberin, and the identification and engineering of animal models. We also present the first comprehensive compilation and analysis of all reported TSC1 and TSC2 mutations, consider their diagnostic implications and review genotype/phenotype relationships.     

Differentially Expressed miRNAs Influence Metabolic Processes in Pituitary Oncocytoma

Neurochemical Research - Spindle cell oncocytomas (SCO) of the pituitary are rare tumors accounting for 0.1–0.4% of all sellar tumors. Due to their rarity, little information is available...