Streptococcus pneumoniae infection of host epithelial cells via polymeric immunoglobulin receptor transiently induces calcium release from intracellular stores

The pneumococcal surface protein C (PspC) is a major adhesin of Streptococcus pneumoniae (pneumococci) that interacts in a human-specific manner with the ectodomain of the human polymeric immunoglobulin receptor (pIgR) produced by respiratory epithelial cells. This interaction promotes bacterial colonization and bacterial internalization by initiating host signal transduction cascades. Here, we examined alterations of intracellular calcium ([Ca(2+)](i)) levels in epithelial cells during host cell infections with pneumococci via the PspC-hpIgR mechanism. The release of [Ca(2+)](i) from intracellular stores in host cells was significantly increased by wild-type pneumococci but not by PspC-deficient pneumococci. The increase in [Ca(2+)](i) was dependent on phospholipase C as pretreatment of cells with a phospholipase C-specific inhibitor U73122 abolished the increase in [Ca(2+)](i). In addition, we demonstrated the effect of [Ca(2+)](i) on pneumococcal internalization by epithelial cells. Uptake of pneumococci was significantly increased after pretreatment of epithelial cells with the cell-permeable calcium chelator 1,2-bis-(o-aminophenoxy)-ethane-N,N,N',N'-tetraacetic acid-tetraacetoxymethyl ester or use of EGTA as an extracellular Ca(2+)-chelating agent. In contrast, thapsigargin, an inhibitor of endoplasmic reticulum Ca(2+)ATPase, which increases [Ca(2+)](i) in a sustained fashion, significantly reduced pIgR-mediated pneumococcal invasion. Importantly, pneumococcal adherence to pIgR-expressing cells was not altered in the presence of inhibitors as demonstrated by immunofluorescence microscopy. In conclusion, these results demonstrate that pneumococcal infections induce mobilization of [Ca(2+)](i) from intracellular stores. This may constitute a defense response of host cells as the experimental reduction of intracellular calcium levels facilitates pneumococcal internalization by pIgR-expressing cells, whereas elevated calcium levels diminished bacterial internalization by host epithelial cells.     

Differential response of varying salinity and temperature on zoospore induction, regeneration and daily growth rate in Ulva fasciata (Chlorophyta, Ulvales)

Seaweed cultivation is imperative to augment increasing industrial demand. Ulva fasciata Delile is a potential seaweed for cultivation with applications in food industries. There is a renewed interest in large-scale aquaculture of this species in India due to its envisaged demand in snack food products. In the present study, we have successfully demonstrated the possibility of inducing zoospores in vegetative tissue, effective regeneration and improved growth in this seaweed by manipulating salinity (from 15 to 30 psu) and temperature (from 15 to 35°C). The optimum salinity and temperature requirement for zoospores induction were found to be 15 psu and 25°C, respectively. The quadriflagellate zoospores showed negative phototaxis and the settlement and germination pattern similar to several other green seaweeds. The optimum regeneration (78.53?±?10.05%) was recorded at 25°C and 30 psu salinity. The maximum daily growth rate (16.1?±?0.28%) was at 25°C and 30 psu salinity which corresponded to the field conditions. This method could be further refined at nursery culture to achieve artificial seeding essential for the success of commercial cultivation of this seaweed.     

Sparse learning and stability selection for predicting MCI to AD conversion using baseline ADNI data

ABSTRACT: BACKGROUND: Patients with Mild Cognitive Impairment (MCI) are at high risk of progression to Alzheimer's dementia. Identifying MCI individuals with high likelihood of conversion to dementia and the associated biosignatures has recently received increasing attention in AD research. Different biosignatures for AD (neuroimaging, demographic, genetic and cognitive measures) may contain complementary information for diagnosis and prognosis of AD. METHODS: We have conducted a comprehensive study using a large number of samples from the Alzheimer's Disease Neuroimaging Initiative (ADNI) to test the power of integrating various baseline data for predicting the conversion from MCI to probable AD and identifying a small subset of biosignatures for the prediction and assess the relative importance of different modalities in predicting MCI to AD conversion. We have employed sparse logistic regression with stability selection for the integration and selection of potential predictors. Our study differs from many of the other ones in three important respects: (1) we use a large cohort of MCI samples that are unbiased with respect to age or education status between case and controls (2) we integrate and test various types of baseline data available in ADNI including MRI, demographic, genetic and cognitive measures and (3) we apply sparse logistic regression with stability selection to ADNI data for robust feature selection. RESULTS: We have used 319 MCI subjects from ADNI that had MRI measurements at the baseline and passed quality control, including 177 MCI Non-converters and 142 MCI Converters. Conversion was considered over the course of a 4-year follow-up period. A combination of 15 features (predictors) including those from MRI scans, APOE genotyping, and cognitive measures achieves the best prediction with an AUC score of 0.8587. These results also demonstrate the effectiveness of stability selection for feature selection in the context of sparse logistic regression.     

A metric for phylogenetic trees based on matching

Comparing two or more phylogenetic trees is a fundamental task in computational biology. The simplest outcome of such a comparison is a pairwise measure of similarity, dissimilarity, or distance. A large number of such measures have been proposed, but so far all suffer from problems varying from computational cost to lack of robustness; many can be shown to behave unexpectedly under certain plausible inputs. For instance, the widely used Robinson-Foulds distance is poorly distributed and thus affords little discrimination, while also lacking robustness in the face of very small changes--reattaching a single leaf elsewhere in a tree of any size can instantly maximize the distance. In this paper, we introduce a new pairwise distance measure, based on matching, for phylogenetic trees. We prove that our measure induces a metric on the space of trees, show how to compute it in low polynomial time, verify through statistical testing that it is robust, and finally note that it does not exhibit unexpected behavior under the same inputs that cause problems with other measures. We also illustrate its usefulness in clustering trees, demonstrating significant improvements in the quality of hierarchical clustering as compared to the same collections of trees clustered using the Robinson-Foulds distance.     

Three-dimensional imaging and quantification of real-time cytosolic calcium oscillations in microglial cells cultured on electrospun matrices using laser scanning confocal microscopy

The development of a minimally invasive, robust, and inexpensive technique that permits real-time monitoring of cell responses on biomaterial scaffolds can improve the eventual outcomes of scaffold-based tissue engineering strategies. Towards establishing correlations between in situ biological activity and cell fate, we have developed a comprehensive workflow for real-time volumetric imaging of spatiotemporally varying cytosolic calcium oscillations in pure microglial cells cultured on electrospun meshes. Live HMC3 cells on randomly oriented electrospun fibers were stained with a fluorescent dye and imaged using a laser scanning confocal microscope. Resonance scanning provided high-resolution in obtaining the time-course of intracellular calcium levels without compromising spatial and temporal resolution. Three-dimensional reconstruction and depth-coding enabled the visualization of cell location and intracellular calcium levels as a function of sample thickness. Importantly, changes in cell morphology and in situ calcium spiking were quantified in response to a soluble biochemical cue and varying matrix architectures (i.e., randomly oriented and aligned fibers). Importantly, raster plots generated from spiking data revealed calcium signatures specific to culture conditions. In the future, our approach can be used to elucidate correlations between calcium signatures and cell phenotype/activation, and facilitate the rational design of scaffolds for biomedical applications.