Orientational behavior of phosphatidylcholine bilayers in the presence of aromatic amphiphiles and a magnetic field.

A number of aromatic-containing additives which can influence the orientation of fragments of lipid bilayer membranes by a magnetic field have been investigated. Two properties of these additives prove important: (1) sufficient detergency to facilitate reorganization of bilayer components and (2), sufficient anisotropy in magnetic susceptibility the preferred direction of fragment orientation. Triton X-100 is identified as effective in terms of facilitating magnetic field ordering of bilayer fragments but does not alter the preferred direction of orientation. A combination of the detergent CHAPSO (3-[(3-cholamidopropyl)-dimethylammonio]-1-propane sulfonate) and the aromatic alcohol 1-naphthol facilitates both ordering and alters the preferred direction of bilayer orientation. As mixtures of dimyristoylphosphatidylcholine (DMPC) and CHAPSO, which orient with bilayer normals perpendicular to the magnetic field, were titrated with 1-naphthol, the assemblies underwent transitions, first to random orientation, and then to an orientation with bilayer normals parallel to the field. Based on temperature-induced phase transitions and the extent of motional averaging of the 31P shielding tensor of the DMPC headgroup, the DMPC in these oriented samples appears to maintain a bilayer morphology during transitions. The insight provided in this study regarding factors which influence fragment stability and orientation lays the groundwork for the design of improved field-oriented media for spectroscopic investigation of membrane components.     

Human caco-2 motility redistributes FAK and paxillin and activates p38 MAPK in a matrix-dependent manner

The signals involved in restitution during mucosal healing are poorly understood. We compared focal adhesion kinase (FAK) and paxillin protein and phosphorylation, extracellular signal-regulated kinase (ERK) 1, ERK2, and p38 activation, as well as FAK and paxillin organization in static and migrating human intestinal Caco-2 cells on matrix proteins and anionically derivatized polystyrene dishes (tissue culture plastic). We also studied effects of FAK, ERK, and p38 blockade in a monolayer-wounding model. Compared with static cells, cells migrating across matrix proteins matrix-dependently decreased membrane/cytoskeletal FAK and paxillin and cytosolic FAK. Tyrosine phosphorylated FAK and paxillin changed proportionately to FAK and paxillin protein. Conversely, cells migrating on plastic increased FAK and paxillin protein and phosphorylation. Migration matrix-dependently activated p38 and inactivated ERK1 and ERK2. Total p38, ERK1, and ERK2 did not change. Caco-2 motility was inhibited by transfection of FRNK (the COOH-terminal region of FAK) and PD-98059, a mitogen-activated protein kinase-ERK kinase inhibitor, but not by SB-203580, a p38 inhibitor, suggesting that FAK and ERK modulate Caco-2 migration. In contrast to adhesion-induced phosphorylation, matrix may regulate motile intestinal epithelial cells by altering amounts and distribution of focal adhesion plaque proteins available for phosphorylation as well as by p38 activation and ERK inactivation. Motility across plastic differs from migration across matrix.     

Homer modulates NFAT-dependent signaling during muscle differentiation

While changes in intracellular calcium are well known to influence muscle contraction through excitation contraction coupling, little is understood of the calcium signaling events regulating gene expression through the calcineurin/NFAT pathway in muscle. Here, we demonstrate that Ca(+2) released via the inositol trisphosphate receptor (IP3R) increases nuclear entry of NFAT in undifferentiated skeletal myoblasts, but the IP3R Ca(+2) pool in differentiated myotubes promotes nuclear exit of NFAT despite a comparable quantitative change in [Ca(+2)]i. In contrast, Ca(+2) released via ryanodine receptors (RYR) increases NFAT nuclear entry in myotubes. The scaffolding protein Homer, known to interact with both IP3R and RYR, is expressed as part of the myogenic differentiation program and enhances NFAT-dependent signaling by increasing RYR Ca(+2) release. These results demonstrate that differentiated skeletal myotubes employ discrete pools of intracellular calcium to restrain (IP3R pool) or activate (RYR pool) NFAT-dependent signaling, in a manner distinct from undifferentiated myoblasts. The selective expression of Homer proteins contributes to these differentiation-dependent features of calcium signaling.     

CLIMTREG: Detecting temporal changes in climate–growth reactions – A computer program using intra-annual daily and yearly moving time intervals of variable width

Analysing climate–growth relationships is one of the key areas in dendrochronological research. One problem however remained unsolved – the discrepancy between the trees continuous growth over the vegetation period and the mean climate variables stretching over much longer periods. Here we present the possibility to calculate climate–growth correlations based on daily climate data using variable temporal width together with moving correlations to accommodate for short term as well as long term influences on tree growth. For the first time this offers the opportunity to acknowledge annual changes in the growing seasonal length and effects of short extreme events. Numerous outputs in data- and graphic-files allows a comparison of varying periods with significant correlations between climate and tree growth. Furthermore the use of climate scenarios is an optional tool for growth predictions.     

Disruption of ant-seed dispersal mutualisms by the invasive Asian needle ant (<Emphasis Type="Italic">Pachycondyla chinensis</Emphasis>)

By disrupting the structure of native ant assemblages, invasive ants can have effects across trophic levels. Most studies to date, however, have focused on the impacts just two species (Linepithema humile and Solenopsis invicta). The impacts of many other invasive ant species on ecological processes in their introduced range are unknown. In this study we tested the hypothesis that the invasive ant Pachycondyla chinensis disrupts ant-seed dispersal mutualisms by displacing native ant species, especially the keystone mutualist Aphaenogaster rudis, while failing to disperse seeds itself. In a paired design we measured the impact of P. chinensis on the native ant-plant seed dispersal mutualism. The number of A. rudis workers was 96% lower in invaded than in intact plots, and the number of seeds removed was 70% lower in these plots. Finally, in invaded plots the abundance of Hexastylis arifolia, a locally abundant myrmecochorous plant, was 50% lower than in plots where P. chinensis was absent. A parsimonious interpretation of our results is that P. chinensis causes precipitous declines in the abundance of A. rudis within invaded communities, thereby disrupting the ant-plant seed dispersal mutualisms and reducing abundances of ant-dispersed plants. In sum, the magnitude of the effects of P. chinensis on seed dispersal is quantitatively similar to that documented for the intensively studied invasive Argentine ant. We suggest that more studies on the impacts of less-studied invasive ant species on seed dispersal mutualisms may increase our knowledge of the effects of these invaders on ecosystem function.     

Site-directed mutagenesis of UDP-galactopyranose mutase reveals a critical role for the active-site, conserved arginine residues

The flavoenzyme UDP-galactopyranose mutase (UGM) is a mediator of cell wall biosynthesis in many pathogenic microorganisms. UGM catalyzes a unique ring contraction reaction that results in the conversion of UDP-galactopyranose (UDP-Galp) to UDP-galactofuranose (UDP-Galf). UDP-Galf is an essential precursor to the galactofuranose residues found in many different cell wall glycoconjugates. Due to the important consequences of UGM catalysis, structural and biochemical studies are needed to elucidate the mechanism and identify the key residues involved. Here, we report the results of site-directed mutagenesis studies on the absolutely conserved residues in the putative active site cleft. By generating variants of the UGM from Klebsiella pneumoniae, we have identified two arginine residues that play critical catalytic roles (alanine substitution abolishes detectable activity). These residues also have a profound effect on the binding of a fluorescent UDP derivative that inhibits UGM, suggesting that the Arg variants are defective in their ability to bind substrate. One of the residues, Arg280, is located in the putative active site, but, surprisingly, the structural studies conducted to date suggest that Arg174 is not. Molecular dynamics simulations indicate that closed UGM conformations can be accessed in which this residue contacts the pyrophosphoryl group of the UDP-Gal substrates. These results provide strong evidence that the mobile loop, noted in all the reported crystal structures, must move in order for UGM to bind its UDP-galactose substrate.     

Plasma proteomic signature of decline in gait speed and grip strength

The biological mechanisms underlying decline in physical function with age remain unclear. We examined the plasma proteomic profile associated with longitudinal changes in physical function measured by gait speed and grip strength in community‐dwelling adults. We applied an aptamer‐based platform to assay 1154 plasma proteins on 2854 participants (60% women, aged 76 years) in the Cardiovascular Health Study (CHS) in 1992–1993 and 1130 participants (55% women, aged 54 years) in the Framingham Offspring Study (FOS) in 1991–1995. Gait speed and grip strength were measured annually for 7 years in CHS and at cycles 7 (1998–2001) and 8 (2005–2008) in FOS. The associations of individual protein levels (log‐transformed and standardized) with longitudinal changes in gait speed and grip strength in two populations were examined separately by linear mixed‐effects models. Meta‐analyses were implemented using random‐effects models and corrected for multiple testing. We found that plasma levels of 14 and 18 proteins were associated with changes in gait speed and grip strength, respectively (corrected p < 0.05). The proteins most strongly associated with gait speed decline were GDF‐15 (Meta‐analytic p = 1.58 × 10⁻¹⁵), pleiotrophin (1.23 × 10⁻⁹), and TIMP‐1 (5.97 × 10⁻⁸). For grip strength decline, the strongest associations were for carbonic anhydrase III (1.09 × 10⁻⁷), CDON (2.38 × 10⁻⁷), and SMOC1 (7.47 × 10⁻⁷). Several statistically significant proteins are involved in the inflammatory responses or antagonism of activin by follistatin pathway. These novel proteomic biomarkers and pathways should be further explored as future mechanisms and targets for age‐related functional decline.     

Expression of an onco-developmental antegen among avian species.

Rabbit antisera directed against an onco-developmental antigen on chicken red blood cells have been serologically dissected through specific adsorptions. It is now possible to detect 13 antigenic determinants with the fractionated antisera. The onco-developmental antigen referred to as chicken fetal-leukemic antigen (CFA) is fetal-specific in the white Leghorn chicken, being present on the embryonic but not adult peripheral red blood cells of non-being present on the embryonic but not adult peripheral red blood cells of non-leukemic birds. However, one or more of the onco-developmental antigenic determinants have been detected on adult peripheral red blood cells of non-Gallus avian species, as well as on red blood cells from two adult chicken varieties. For phylogenetic purposes, red blood cells from avian species were characterized for their combinations of CFA determinants. Comparisons among species revealed specific patterns of antigenic expression within phylogenetic groups. Several CFA determinants were restricted in their occurrence to species within a single family, and one determinant was found in all cases where CFA was expressed. The distribution of CFA determinants was used to determine immunological distances among four Galliform species. These distances agreed with the immunological relationships established using different serological markers.     

Analyzing Spatial Heterogeneity in DCE- and DW-MRI Parametric Maps to Optimize Prediction of Pathologic Response to Neoadjuvant Chemotherapy in Breast Cancer

The purpose of this study is to investigate the ability of multivariate analysis of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and diffusion-weighted MRI (DW-MRI) parametric maps, obtained early in the course of therapy, to predict which patients will achieve pathologic complete response (pCR) at the time of surgery. Thirty-three patients underwent DCE-MRI (to estimate K^trans, v_e, k_ep, and v_p) and DW-MRI [to estimate the apparent diffusion coefficient (ADC)] at baseline (t₁) and after the first cycle of neoadjuvant chemotherapy (t₂). Four analyses were performed and evaluated using receiver-operating characteristic (ROC) analysis to test their ability to predict pCR. First, a region of interest (ROI) level analysis input the mean K^trans, v_e, k_ep, v_p, and ADC into the logistic model. Second, a voxel-based analysis was performed in which a longitudinal registration algorithm aligned serial parameters to a common space for each patient. The voxels with an increase in k_ep, K^trans, and v_p or a decrease in ADC or v_e were then detected and input into the regression model. In the third analysis, both the ROI and voxel level data were included in the regression model. In the fourth analysis, the ROI and voxel level data were combined with selected clinical data in the regression model. The overfitting-corrected area under the ROC curve (AUC) with 95% confidence intervals (CIs) was then calculated to evaluate the performance of the four analyses. The combination of k_ep, ADC ROI, and voxel level data achieved the best AUC (95% CI) of 0.87 (0.77–0.98).