Blocking the QB‐binding site of photosystem II by tenuazonic acid,a non–host‐specific toxin of Alternaria alternata,activates singlet oxygen‐mediated and EXECUTER‐dependent signalling in Arabidopsis

Necrotrophic fungal pathogens produce toxic compounds that induce cell death in infected plants. Often, the primary targets of these toxins and the way a plant responds to them are not known. In the present work, the effect of tenuazonic acid (TeA), a non–host‐specific toxin of Alternaria alternata, on Arabidopsis thaliana has been analysed. TeA blocks the Q_B‐binding site at the acceptor side of photosystem II (PSII). As a result, charge recombination at the reaction centre (RC) of PSII is expected to enhance the formation of the excited triplet state of the RC chlorophyll that promotes generation of singlet oxygen (¹O₂). ¹O₂ activates a signalling pathway that depends on the two EXECUTER (EX) proteins EX1 and EX2 and triggers a programmed cell death response. In seedlings treated with TeA at half‐inhibition concentration ¹O₂‐mediated and EX‐dependent signalling is activated as indicated by the rapid and transient up‐regulation of ¹O₂‐responsive genes in wild type, and its suppression in ex1/ex2 mutants. Lesion formation occurs when seedlings are exposed to higher concentrations of TeA for a longer period of time. Under these conditions, the programmed cell death response triggered by ¹O₂‐mediated and EX‐dependent signalling is superimposed by other events that also contribute to lesion formation.     

Differential effects of aging on estrogen negative and positive feedback

Recent studies have demonstrated an age-related decline in gonadotropins and a decrease in pituitary responsiveness to GnRH, indicating that aging influences the neuroendocrine components of the female reproductive axis independently of changes in ovarian function. To determine whether aging might also affect the luteinizing hormone (LH) negative and positive feedback responses to gonadal steroids, we administered a controlled, graded sex steroid infusion to 11 younger (45-56 yr) and nine older (70-80 yr) postmenopausal women (PMW) in whom endogenous ovarian steroids and peptides are uniformly low. The doses of estradiol (E(2)) and progesterone (P) were chosen to mimic levels across the normal follicular phase and have been shown previously to induce negative followed by positive feedback on LH. Similar E(2) and P levels were achieved in younger and older PMW (P = 0.4 and 0.3, respectively) and produced a biphasic LH response in all subjects. The early decline in LH to 53% of baseline was not different in older vs. younger PMW. However, the positive feedback effect was attenuated in older compared with younger PMW (peak LH 144.4 ± 19.5 vs. 226.8 ± 22.3 IU/l, respectively, P = 0.01). In conclusion, these studies in PMW demonstrate preservation of short-term steroid negative and positive feedback in response to exogenous E(2) and P with aging. Attenuation of positive feedback in older compared with younger PMW is consistent with previous reports of declining GnRH responsiveness with aging.     

Determining the effect of the incorporation of unnatural amino acids into antimicrobial peptides on the interactions with zwitterionic and anionic membrane model systems

Circular Dichroism (CD), isothermal calorimetry (ITC) and calcein fluorescence leakage experiments were conducted to provide insight into the mechanisms of binding of a series of antimicrobial peptides containing unnatural amino acids (Ac-XF-Tic-Oic-XK-Tic-Oic-XF-Tic-Oic-XK-Tic-KKKK-CONH₂) to zwitterionic and anionic micelles, SUVs and LUVs; where X (Spacer# 1) is either Gly, β-Ala, Gaba or 6-aminohexanoic acid. It is the intent of this investigation to correlate these interactions with the observed potency and selectivity against several different strains of bacteria. The CD spectra of these compounds in the presence of zwitterionic DPC micelles and anionic SDS micelles are very different indicating that these compounds adopt different conformations on binding to the surface of anionic and zwitterionic membrane models. These compounds also exhibited very different CD spectra in the presence of zwitterionic POPC and anionic mixed 4:1 POPC/POPG SUVs and LUVs, indicating the formation of different conformations on interaction with the two membrane types. This observation is also supported by ITC and calcein leakage data. ITC data suggested these peptides interact primarily with the surface of zwitterionic LUVs and was further supported by fluorescence experiments where the interactions do not appear to be concentration dependent. In the presence of anionic membranes, the interactions appear more complex and the calorimetric and fluorescence data both imply pore formation is dependent on peptide concentration. Furthermore, evidence suggests that as the length of Spacer# 1 increases the mechanism of pore formation also changes. Based on the observed differences in the mechanisms of interactions with zwitterionic and anionic LUVs these AMPs are potential candidates for further drug development.     

DNA evolutionary rates in nine-primaried passerine birds

Differences in single-copy nuclear-DNA sequences among 13 species of passerine birds were measured using DNA-DNA hybridization. A matrix of pairwise dissimilarity values (delta mode distances) was constructed from analysis of fitted thermal dissociation curves. A least-squares method of phylogenetic estimation was used to construct two topologies from the distance matrix, one constraining branch lengths of sister taxa to be equal and the other permitting such lengths to vary. These topologies were identical in the pattern of branching of taxa, and the difference in their sums of squares was not statistically significant, suggesting that rates of DNA evolution in sister groups of nine- primaried oscines are equal. A nonparametric test for nonrandom variation in distances of sister groups to outgroup taxa revealed no statistically significant deviation from random variation that would be expected as a result of measurement error. However, the level of measurement error was such that rates of DNA evolution in sister taxa could vary by as much as 10% without being detected with the statistical methods used here.      

脑电信号数据压缩及棘波识别的小波神经网络方法

本文在对小波神经网络及其算法研究的基础上,提出了一种对脑电信号压缩表达和痫样脑电棘波识别的新方法。实验结果显示,小波网络在大量压缩数据的同时,能够较好的恢复原有信号,另外,在脑电信号的时频谱等高线图上,得到了易于自动识别的棘波和棘慢复合波特征,说明此方法在电生理信号处理和时频分析方面有着光明的应用前景。     

14-3-3 proteins double the number of outward-rectifying K+ channels available for activation in tomato cells

Outward-rectifying K+ channels are modulated in response to environmental stimuli by a range of intracellular factors, such as cytoplasmic Ca2+, pH, kinases and phosphatases. Here we report that voltage-dependent outward-rectifying K+ channels in tomato cells are also targets for modulation by 14-3-3 proteins. In whole-cell patch-clamp experiments, recombinant 14-3-3 protein (tomato isoform TFT7) was introduced into tomato cell protoplasts via the patch pipette. As a result the steady-state outward K+ current increased twofold and this increase was not dependent upon the presence of cytoplasmic ATP. A phosphorylated peptide that contained a phosphorylated 14-3-3 target-binding motif (RSTS*TP), derived from nitrate reductase, blocked the effect of 14-3-3, thus showing the specific nature of 14-3-3 action. Kinetic parameters of the conductance, like (de)activation kinetics, voltage dependence of gating and activation potential, were not significantly different between control and 14-3-3 infused cells. Analysis of single-channel activity and whole-cell noise indicated that the single-channel conductance was not affected by 14-3-3 infusion. We conclude that 14-3-3 proteins recruit 'sleepy' channels into a voltage-activatable state. The molecular mechanism underlying the 1 : 1 ratio of constitutively active and 14-3-3 recruited channels is discussed in the light of known functions of 14-3-3 dimers.     

Longitudinal proxy measurements in multiple sclerosis: patient-proxy agreement on the impact of MS on daily life over a period of two years

Background  

The use of self-report measurements in clinical settings is increasing. However, in patients with limitations that interfere with reliable self-assessment such as cognitive impairment or mood disturbances, as may be the case in multiple sclerosis (MS), data collection might be problematic. In these situations, information obtained from proxy respondents (e.g. partners) may replace self-ratings. The aim of this study was to examine the value of proxy ratings at separate points in time and to assess patient-proxy agreement on possible changes in disease impact of MS.     

Molecular function prediction for a family exhibiting evolutionary tendencies toward substrate specificity swapping: Recurrence of tyrosine aminotransferase activity in the Iα subfamily

The subfamily Iα aminotransferases are typically categorized as having narrow specificity toward carboxylic amino acids (AATases), or broad specificity that includes aromatic amino acid substrates (TATases). Because of their general role in central metabolism and, more specifically, their association with liver‐related diseases in humans, this subfamily is biologically interesting. The substrate specificities for only a few members of this subfamily have been reported, and the reliable prediction of substrate specificity from protein sequence has remained elusive. In this study, a diverse set of aminotransferases was chosen for characterization based on a scoring system that measures the sequence divergence of the active site. The enzymes that were experimentally characterized include both narrow‐specificity AATases and broad‐specificity TATases, as well as AATases with broader‐specificity and TATases with narrower‐specificity than the previously known family members. Molecular function and phylogenetic analyses underscored the complexity of this family's evolution as the TATase function does not follow a single evolutionary thread, but rather appears independently multiple times during the evolution of the subfamily. The additional functional characterizations described in this article, alongside a detailed sequence and phylogenetic analysis, provide some novel clues to understanding the evolutionary mechanisms at work in this family. Proteins 2013. © 2013 Wiley Periodicals, Inc.     

ACUTE EFFECTS OF MOVEMENT VELOCITY ON BLOOD LACTATE AND GROWTH HORMONE RESPONSES AFTER ECCENTRIC BENCH PRESS EXERCISE IN RESISTANCE-TRAINED MEN

This study aimed to compare the effects of different velocities of eccentric muscle actions on acute blood lactate and serum growth hormone (GH) concentrations following free weight bench press exercises performed by resistance-trained men. Sixteen healthy men were divided into two groups: slow eccentric velocity (SEV; n = 8) and fast eccentric velocity (FEV; n = 8). Both groups performed four sets of eight eccentric repetitions at an intensity of 70% of their one repetition maximum eccentric (1RMecc) test, with 2-minute rest intervals between sets. The eccentric velocity was controlled to 3 seconds per range of motion for SEV and 0.5 seconds for the FEV group. There was a significant difference (P < 0.001) in the kinetics of blood lactate removal (at 3, 6, 9, 15, and 20 min) and higher mean values for peak blood lactate (P = 0.001) for the SEV group (9.1 ± 0.5 mM) compared to the FEV group (6.1 ± 0.4 mM). Additionally, serum GH concentrations were significantly higher (P < 0.001) at 15 minutes after bench press exercise in the SEV group (1.7 ± 0.6 ng · mL⁻¹) relative to the FEV group (0.1 ± 0.0 ng · mL⁻¹). In conclusion, the velocity of eccentric muscle action influences acute responses following bench press exercises performed by resistance-trained men using a slow velocity resulting in a greater metabolic stress and hormone response.     

Protein structure analysis of mutations causing inheritable diseases. An e-Science approach with life scientist friendly interfaces

Background  

Many newly detected point mutations are located in protein-coding regions of the human genome. Knowledge of their effects on the protein's 3D structure provides insight into the protein's mechanism, can aid the design of further experiments, and eventually can lead to the development of new medicines and diagnostic tools.