Association of the cyclic AMP chemotaxis receptor with the detergent-insoluble cytoskeleton of Dictyostelium discoideum

Treatment of 6-h differentiated Dictyostelium discoideum cells with the nonionic detergent Triton X-100 dissolves away membranes and soluble components, as judged by marker enzyme distributions, leaving intact a cytoskeletal residue that contains approximately 10% of the cell protein and 50% of the actin. Nitrobenzooxadiazo-phallacidin staining for F-actin and electron microscopy of detergent-extracted whole-mounts indicate that the cytoskeletons retain the size and shape of intact cells and contain F-actin in cortical meshworks. The cytoskeletons contain little if any remaining membrane material by morphological criteria, and the plasma membrane enzymes cyclic nucleotide phosphodiesterase and alkaline phosphatase are absent from the insoluble residue, which retains only 15% of the membrane concanavalin A-binding glycoproteins. This detergent-insoluble residue retains a specific [3H]cAMP-binding site with the nucleotide specificity, rapid kinetics and approximate affinity of the cAMP receptor on intact cells. Upon detergent extraction of cells, the number of cAMP-binding sites increases 20-70%. The binding site is attached to the insoluble residue whether or not the cAMP receptor is occupied at the time of detergent addition. The pH dependence for recovery of the insoluble cAMP-binding site is much sharper than that on intact cells or membranes with an optimum at pH 6.1. Conditions of pH and ionic composition that lead to disruption of the cytoskeleton upon detergent treatment also result in the loss of cAMP binding. During differentiation, the detergent- insoluble cAMP binding increases in parallel with cell surface cAMP receptors and chemotaxis to cAMP.     

世居及移居高原青少年最大有氧能力的特征

本文报道海拔３４１７ｍ和４２８０ｍ地区世居藏族和移居汉族青少年运动状态下心肺功能的对比研究。结果显示：３４１７ｍ和４２８０ｍ世居藏族的最大氧耗量、无氧阈值及最大心输出量都明显大于汉族,血氧饱和度（Ｓａｏ２）随运动负荷的增加而降低。海拔３４１７ｍ藏、汉族的△Ｓａｏ２分别为７．４６％和１０．０３％,４２８０ｍ处为８．５７％和１３．７５％,最大心率随海拔升高而下降。研究提示,藏族青少年有较高的最大有氧能力,反映了他们对低氧环境的适应优势。     

The phylogeny of the ant tribe Formicini (Hymenoptera: Formicidae) with the description of a new genus

Abstract. The holarctic ant tribe Formicini is revised, the new genus Bajcaridris described, and possible phylogenetic relationships are discussed. The subgenus Iberoformica is synonymized with Formica. A synopsis, diagnosis and keys to the genera are provided.     

Re-structuring of marine communities exposed to environmental change: a global study on the interactive effects of species and functional richness

Species richness is the most commonly used but controversial biodiversity metric in studies on aspects of community stability such as structural composition or productivity. The apparent ambiguity of theoretical and experimental findings may in part be due to experimental shortcomings and/or heterogeneity of scales and methods in earlier studies. This has led to an urgent call for improved and more realistic experiments. In a series of experiments replicated at a global scale we translocated several hundred marine hard bottom communities to new environments simulating a rapid but moderate environmental change. Subsequently, we measured their rate of compositional change (re-structuring) which in the great majority of cases represented a compositional convergence towards local communities. Re-structuring is driven by mortality of community components (original species) and establishment of new species in the changed environmental context. The rate of this re-structuring was then related to various system properties. We show that availability of free substratum relates negatively while taxon richness relates positively to structural persistence (i.e., no or slow re-structuring). Thus, when faced with environmental change, taxon-rich communities retain their original composition longer than taxon-poor communities. The effect of taxon richness, however, interacts with another aspect of diversity, functional richness. Indeed, taxon richness relates positively to persistence in functionally depauperate communities, but not in functionally diverse communities. The interaction between taxonomic and functional diversity with regard to the behaviour of communities exposed to environmental stress may help understand some of the seemingly contrasting findings of past research.     

Sex differences in the rate of fatigue development and recovery

Background

Many musculoskeltal injuries in the workplace have been attributed to the repetitive loading of muscle and soft tissues. It is not disputed that muscular fatigue is a risk factor for musculoskeltal injury, however the disparity between gender with respect to muscular fatigability and rate of recovery is not well understood. Current health and safety guidelines do not account for sex differences in fatiguability and may be predisposing one gender to greater risk. The purpose of this study was to quantify the sex differences in fatigue development and recovery rate of lower and upper body musculature after repeated bouts of sustained isometric contractions.

Methods

Twenty-seven healthy males (n = 12) and females (n = 15) underwent bilateral localized fatigue of either the knee extensors (male: n = 8; female: n = 8), elbow flexors (male: n = 8; female: n = 10), or both muscle groups. The fatigue protocol consisted of ten 30-second sub-maximal isometric contractions. The changes in maximum voluntary contraction (MVC), electrically evoked twitches, and motor unit activation (MUA) were assessed along with the ability to control the sustained contractions (SLP) during the fatigue protocol using a mixed four-factor repeated measures ANOVA (gender × side × muscle × time) design with significance set at p < 0.05.

Results

There was a significant loss of MVC, MUA, and evoked twitch amplitude from pre- to post-fatigue in both the arms and legs. Males had greater relative loss of isometric force, a higher rate of fatigue development, and were less capable of maintaining the fatiguing contractions in the legs when compared to the females.

Conclusion

The nature of the induced fatigue was a combination of central and peripheral fatigue that did not fully recover over a 45-minute period. The results appear to reflect sex differences that are peripheral, and partially support the muscle mass hypothesis for explaining differences in muscular fatigue.

     

Anti-inflammatory Effects of Mapracorat,a Novel Selective Glucocorticoid Receptor Agonist,Is Partially Mediated by MAP Kinase Phosphatase-1 (MKP-1)

Mapracorat is a novel selective glucocorticoid receptor agonist (SEGRA), structurally distinct from corticosteroids. In preclinical studies, mapracorat potently inhibits the production of a variety of inflammatory mediators including cytokines and prostaglandin E2 (PGE₂), with limited side effects associated with traditional corticosteroids. The objective of this study was to delineate the mechanisms underlying the anti-inflammatory properties of mapracorat. We found that mapracorat potently inhibited the production of GM-CSF and TNF-α in LPS-stimulated Raw 264.7 macrophages. Mapracorat also substantially attenuated the expression of COX-2 and the production of PGE₂. The inhibition of mapracorat on the inflammatory response was dose-dependent, and substantially inhibitory effects were observed at concentrations in the 10–100 nm range. Examination of the activation kinetics of p38 and its downstream target MAPK-activated protein kinase-2 (MK-2) revealed a shortened activation course after LPS stimulation in cells pretreated with mapracorat. Supporting the notion that mapracorat augments a feedback control mechanism restraining the p38 pathway, we found that mapracorat enhanced the expression of MAPK phosphatase-1 (MKP-1), a critical negative regulator of MAPKs that drive the production of cytokines and other inflammatory mediators. While mapracorat alone did not stimulate MKP-1 expression, it markedly enhanced the expression of MKP-1 in cells stimulated by LPS, in a similar manner and potency to the augmenting effect of dexamethasone. Blocking MKP-1 expression by triptolide also abolished the accelerating effects of mapracorat on p38 and MK-2 deactivation, further supporting a role of MKP-1 in the anti-inflammatory mechanism of mapracorat. Taken together, these results indicate that mapracorat exerts its anti-inflammatory effects, at least in part, by augmenting MKP-1 expression.     

18F-FET MicroPET and MicroMRI for Anti-VEGF and Anti-PlGF Response Assessment in an Orthotopic Murine Model of Human Glioblastoma

BackgroundConflicting data exist for anti-cancer effects of anti-placental growth factor (anti-PlGF) in combination with anti-VEGF. Still, this treatment combination has not been evaluated in intracranial glioblastoma (GBM) xenografts. In clinical studies, position emission tomography (PET) using the radiolabeled amino acid O-(2-¹⁸F-fluoroethyl)-L-tyrosine (¹⁸F-FET) and magnetic resonance imaging (MRI) add complementary but distinct information about glioma growth; however, the value of ¹⁸F-FET MicroPET combined with MicroMRI has not been investigated preclinically. Here we examined the use of ¹⁸F-FET MicroPET and MicroMRI for evaluation of anti-VEGF and anti-PlGF treatment response in GBM xenografts.MethodsMice with intracranial GBM were treated with anti-VEGF, anti-PlGF + anti-VEGF or saline. Bioluminescence imaging (BLI), ¹⁸F-FET MicroPET and T2-weighted (T2w)-MRI were used to follow tumour development. Primary end-point was survival, and tumours were subsequently analysed for Ki67 proliferation index and micro-vessel density (MVD). Further, PlGF and VEGFR-1 expression were examined in a subset of the xenograft tumours and in 13 GBM patient tumours.ResultsAnti-VEGF monotherapy increased survival and decreased ¹⁸F-FET uptake, BLI and MVD, while no additive effect of anti-PlGF was observed. ¹⁸F-FET SUV_max tumour-to-brain (T/B) ratio was significantly lower after one week (114±6%, n = 11 vs. 143±8%, n = 13; p = 0.02) and two weeks of treatment (116±12%, n = 8 vs. 190±24%, n = 5; p = 0.02) in the anti-VEGF group as compared with the control group. In contrast, T2w-MRI volume was unaffected by anti-VEGF. Gene expression of PlGF and VEGFR-1 in xenografts was significantly lower than in patient tumours.Conclusion¹⁸F-FET PET was feasible for anti-angiogenic response evaluation and superior to T2w-MRI; however, no additive anti-cancer effect of anti-PlGF and anti-VEGF was observed. Thus, this study supports use of ¹⁸F-FET PET for response evaluation in future studies.     

Pyrazole C-region analogues of 2-(3-fluoro-4-methylsulfonylaminophenyl)propanamides as potent TRPV1 antagonists

A series of 1-substituted 3-(t-butyl/trifluoromethyl)pyrazole C-region analogues of 2-(3-fluoro-4-methylsulfonamidophenyl)propanamides were investigated for hTRPV1 antagonism. The structure activity relationship indicated that the 3-chlorophenyl group at the 1-position of pyrazole was the optimized hydrophobic group for antagonistic potency and the activity was stereospecific to the S-configuration, providing exceptionally potent antagonists 13S and 16S with K_i(CAP) = 0.1 nM. Particularly significant, 13S exhibited antagonism selective for capsaicin and NADA and not for low pH or elevated temperature. Both compounds also proved to be very potent antagonists for rTRPV1, blocking in vivo the hypothermic action of capsaicin, consistent with their in vitro mechanism. The docking study of compounds 13S and 16S in our hTRPV1 homology model indicated that the binding modes differed somewhat, with that of 13S more closely resembling that of GRT12360.