Pilot study of inflammatory responses following a negative imaginal focus in persons with chronic pain: Analysis by sex/gender

Background: Recent evidence suggests that differential stress and immune responses may play a role in the sex/gender disparity for pain. Pain pathology and psychological stress are both associated with elevated levels of proinflammatory cytokines.Objective: This pilot study tested a negative imaginal focus to assess whether it would elicit a proinflammatory cytokine response and whether responses would vary by sex/gender.Methods: Adults with chronic musculoskeletal pain were recruited from an outpatient, multidisciplinary pain clinic in Portland, Oregon, between 2007 and 2008. All participants underwent a psychologist-guided 10-minute focus on the negative aspects of their pain condition and the imagined worsening of their pain; no control group was used. Serum collected at baseline and postfocus (1, 2, and 2.5 hours) was assayed for interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α). Cortisol was assayed at each time point and at 15 minutes postfocus.Results: Thirty-six outpatients (aged 26-62 years; 23 women, 13 men) participated in the study. Compared with men, women displayed greater negative emotional expression during the experiment, and this in turn mediated their IL-6 inflammatory responses. Relative to men, the IL-6 response trajectory was delayed for women. The IL-6 and TNF-a findings suggest women's maximal cytokine responses were not captured by the final time point.Conclusions: This pilot study provides preliminary evidence that women with chronic pain may experience increased and delayed inflammatory responses following negative emotional expression induced by thinking negatively about their pain condition. The findings have implications for pain catastrophizing research. This early-phase research suggests that the timing and duration of the cytokine response are critical factors to consider in future pain research.     

Changes in power curve shapes as an indicator of fatigue during dynamic contractions

The purpose of this study was to analyze exercise-induced leg fatigue during a dynamic fatiguing task by examining the shapes of power vs. time curves through the combined use of several statistical methods: B-spline smoothing, functional principal components and (supervised and unsupervised) classification. In addition, granulometric size distributions were also computed to allow for comparison of curves coming from different subjects. Twelve physically active men participated in one acute heavy-resistance exercise protocol which consisted of five sets of 10 repetition maximum leg press with 120 s of rest between sets. To obtain a smooth and accurate representation of the data, a basis of 180 B-splines was used. Functional principal component (FPC) analysis was used to find the dominant modes of variation in the curves. A multivariate cluster over the FPC scores and a k-nearest neighbor classification led to three interpretable groups corresponding to different levels of fatigue. Fatigue-induced changes in the shapes of the power curves were evident, in which curves progressively flatten and develop a second power peak. In a practical setting FPC analysis greatly reduces dimensionality and the use of granulometries allows for comparison of the curve shapes without distorting the time scale.In contrast to the present methodology, which considers each curve as a datum, classical statistical approaches using summary parameters of time series may lead to limited information about the impact of dynamic fatiguing protocols on kinematic and kinetic time-course changes in curve shapes.     

Hydrogen peroxide removes TRPM4 current desensitization conferring increased vulnerability to necrotic cell death

Necrosis is associated with an increase in plasma membrane permeability, cell swelling, and loss of membrane integrity with subsequent release of cytoplasmic constituents. Severe redox imbalance by overproduction of reactive oxygen species is one of the main causes of necrosis. Here we demonstrate that H(2)O(2) induces a sustained activity of TRPM4, a Ca(2+)-activated, Ca(2+)-impermeant nonselective cation channel resulting in an increased vulnerability to cell death. In HEK 293 cells overexpressing TRPM4, H(2)O(2) was found to eliminate in a dose-dependent manner TRPM4 desensitization. Site-directed mutagenesis experiments revealed that the Cys(1093) residue is crucial for the H(2)O(2)-mediated loss of desensitization. In HeLa cells, which endogenously express TRPM4, H(2)O(2) elicited necrosis as well as apoptosis. H(2)O(2)-mediated necrosis but not apoptosis was abolished by replacement of external Na(+) ions with sucrose or the non-permeant cation N-methyl-d-glucamine and by knocking down TRPM4 with a shRNA directed against TRPM4. Conversely, transient overexpression of TRPM4 in HeLa cells in which TRPM4 was previously silenced re-established vulnerability to H(2)O(2)-induced necrotic cell death. In addition, HeLa cells exposed to H(2)O(2) displayed an irreversible loss of membrane potential, which was prevented by TRPM4 knockdown.     

Exploring the links between natural products and bacterial assemblages in the sponge Aplysina aerophoba

The sponge Aplysina aerophoba produces a large diversity of brominated alkaloids (BAs) and hosts a complex microbial assemblage. Although BAs are located within sponge cells, the enzymes that bind halogen elements to organic compounds have been exclusively described in algae, fungi, and bacteria. Bacterial communities within A. aerophoba could therefore be involved in the biosynthesis of these compounds. This study investigates whether changes in both the concentration of BAs and the bacterial assemblages are correlated in A. aerophoba. To do so, we quantified major natural products using high-performance liquid chromatography and analyzed bacterial assemblages using denaturing gradient gel electrophoresis on the 16S rRNA gene. We identified multiple associations between bacteria and natural products, including a strong relationship between a Chloroflexi phylotype and aplysinamisin-1 and between an unidentified bacterium and aerophobin-2 and isofistularin-3. Our results suggest that these bacteria could either be involved in the production of BAs or be directly affected by them. To our knowledge, this is one of the first reports that find a significant correlation between natural products and bacterial populations in any benthic organism. Further investigating these associations will shed light on the organization and functioning of host-endobiont systems such as Aplysina aerophoba.     

A survey of Penstemon's genome size

Penstemon is the largest genus in North America with more than 270 reported species. However, little is known about its genome size. This information may be useful in developing hybrids for landscape use and for gaining insight into its current taxonomy. Using flow cytometry, we estimated the genome size of approximately 40% of the genus (115 accessions from 105 different species). Genome sizes for both reported and probable diploids range from P. dissectus 2C = 0.94 pg (1C = 462 Mbp) to P. pachyphyllus var. mucronatus 2C = 1.88 pg (1C = 919 Mbp), and the polyploids range from P. attenuatus var. attenuatus 2C = 2.35 pg (1C = 1148 Mbp) to P. digitalis 2C = 6.45 pg (1C = 3152 Mbp). Chromosome counts were done for ten previously published and four previously unreported Penstemon species (P. dissectus, P. navajoa, P. caespitosus var. desertipicti, and P. ramaleyi). These counts were compiled with all previously published chromosome data and compared with the flow cytometry results. Ploidy within this study ranged from diploid to dodecaploid. These data were compared and contrasted with the current taxonomy of Penstemon and previously published internal transcribed spacer and chloroplast DNA phylogenetic work. Based on genome size and previous studies, reassigning P. montanus to the subgenus Penstemon and P. personatus to the subgenus Dasanthera, would better reflect the phylogeny of the genus. Furthermore, our data concur with previous studies suggesting that the subgenus Habroanthus be included in the subgenus Penstemon. The DNA content of subgenus Penstemon exhibits high plasticity and spans a sixfold increase from the smallest to the largest genome (P. linarioides subsp. sileri and P. digitalis, respectively). Our study found flow cytometry to be useful in species identification and verification.     

Structural insights into the oligomerization and architecture of eukaryotic membrane pore-forming toxins

Pore-forming toxins (PFTs) are proteins that are secreted as soluble molecules and are inserted into membranes to form oligomeric transmembrane pores. In this paper, we report the crystal structure of Fragaceatoxin C (FraC), a PFT isolated from the sea anemone Actinia fragacea, at 1.8?? resolution. It consists of a crown-shaped nonamer with an external diameter of about 11.0?nm and an internal diameter of approximately 5.0?nm. Cryoelectron microscopy studies of FraC in lipid bilayers reveal the pore structure that traverses the membrane. The shape and dimensions of the crystallographic oligomer are fully consistent with the membrane pore. The FraC structure provides insight into the interactions governing the assembly process and suggests the structural changes that allow for membrane insertion. We propose a nonameric pore model that spans the membrane by forming a lipid-free α-helical bundle pore.     

A GDI (AGS3) and a GEF (GIV) regulate autophagy by balancing G protein activity and growth factor signals

Autophagy is the major catabolic process responsible for the removal of aggregated proteins and damaged organelles. Autophagy is regulated by both G proteins and growth factors, but the underlying mechanism of how they are coordinated during initiation and reversal of autophagy is unknown. Using protein-protein interaction assays, G protein enzymology, and morphological analysis, we demonstrate here that Gα-interacting, vesicle-associated protein (GIV, a. k. a. Girdin), a nonreceptor guanine nucleotide exchange factor for Gα(i3), plays a key role in regulating autophagy and that dynamic interplay between Gα(i3), activator of G-protein signaling 3 (AGS3, its guanine nucleotide dissociation inhibitor), and GIV determines whether autophagy is promoted or inhibited. We found that AGS3 directly binds light chain 3 (LC3), recruits Gα(i3) to LC3-positive membranes upon starvation, and promotes autophagy by inhibiting the G protein. Upon growth factor stimulation, GIV disrupts the Gα(i3)-AGS3 complex, releases Gα(i3) from LC3-positive membranes, enhances anti-autophagic signaling pathways, and inhibits autophagy by activating the G protein. These results provide mechanistic insights into how reversible modulation of Gα(i3) activity by AGS3 and GIV maintains the delicate equilibrium between promotion and inhibition of autophagy.     

Electromyographic models to assess muscle fatigue

Muscle fatigue is a common experience in daily life. Many authors have defined it as the incapacity to maintain the required or expected force, and therefore, force, power and torque recordings have been used as direct measurements of muscle fatigue. In addition, the measurement of these variables combined with the measurement of surface electromyography (sEMG) recordings (which can be measured during all types of movements) during exercise may be useful to assess and understand muscle fatigue. Therefore, there is a need to develop muscle fatigue models that relate changes in sEMG variables with muscle fatigue. However, the main issue when using conventional sEMG variables to quantify fatigue is their poor association with direct measures of fatigue. Therefore, using different techniques, several authors have combined sets of sEMG parameters to assess muscle fatigue. The aim of this paper is to serve as a state-of-the-art summary of different sEMG models used to assess muscle fatigue. This paper provides an overview of linear and non-linear sEMG models for estimating muscle fatigue, their ability to assess power loss and their limitations due to neuromuscular changes after a training period.     

Landscape Genetics for the Empirical Assessment of Resistance Surfaces: The European Pine Marten (Martes martes) as a Target-Species of a Regional Ecological Network

Coherent ecological networks (EN) composed of core areas linked by ecological corridors are being developed worldwide with the goal of promoting landscape connectivity and biodiversity conservation. However, empirical assessment of the performance of EN designs is critical to evaluate the utility of these networks to mitigate effects of habitat loss and fragmentation. Landscape genetics provides a particularly valuable framework to address the question of functional connectivity by providing a direct means to investigate the effects of landscape structure on gene flow. The goals of this study are (1) to evaluate the landscape features that drive gene flow of an EN target species (European pine marten), and (2) evaluate the optimality of a regional EN design in providing connectivity for this species within the Basque Country (North Spain). Using partial Mantel tests in a reciprocal causal modeling framework we competed 59 alternative models, including isolation by distance and the regional EN. Our analysis indicated that the regional EN was among the most supported resistance models for the pine marten, but was not the best supported model. Gene flow of pine marten in northern Spain is facilitated by natural vegetation, and is resisted by anthropogenic landcover types and roads. Our results suggest that the regional EN design being implemented in the Basque Country will effectively facilitate gene flow of forest dwelling species at regional scale.