Statistics of active transport in Xenopus melanophores cells

The transport of cell cargo, such as organelles and protein complexes in the cytoplasm, is determined by cooperative action of molecular motors stepping along polar cytoskeletal elements. Analysis of transport of individual organelles generated useful information about the properties of the motor proteins and underlying cytoskeletal elements. In this work, for the first time (to our knowledge), we study collective movement of multiple organelles using Xenopus melanophores, pigment cells that translocate several thousand of pigment granules (melanosomes), spherical organelles of a diameter of ∼1 μm. These cells disperse melanosomes in the cytoplasm in response to high cytoplasmic cAMP, while at low cAMP melanosomes cluster at the cell center. Obtained results suggest spatial and temporal organization, characterized by strong correlations between movement of neighboring organelles, with correlation length of ∼4 μm and pair lifetime ∼5 s. Furthermore, velocity statistics revealed strongly non-Gaussian velocity distribution with high velocity tails demonstrating exponential behavior suggestive of strong velocity correlations. Depolymerization of vimentin intermediate filaments using a dominant-negative vimentin mutant or actin with cytochalasin B reduced correlation of behavior of individual particles. Based on our analysis, we concluded that steric repulsion is dominant, but both intermediate filaments and actin microfilaments are involved in dynamic cross-linking organelles in the cytoplasm.     

Experimental stress in inflammatory rheumatic diseases: a review of psychophysiological stress responses

Introduction  

Stressful events are thought to contribute to the aetiology, maintenance and exacerbation of rheumatic diseases. Given the growing interest in acute stress responses and disease, this review investigates the impact of real-life experimental psychosocial, cognitive, exercise and sensory stressors on autonomic, neuroendocrine and immune function in patients with inflammatory rheumatic diseases.     

Use of the flux model of amino acid metabolism of Escherichia coli

A program implementing a flux model of Escherichia coli metabolism was used to analyze the effects of the addition of amino acids (tryptophan, tyrosine, phenylalanine, leucine, isoleucine, valine, histidine, lysine, threonine, cysteine, methionine, arginine, proline) to minimal medium or media lacking nitrogen, carbon, or both. The overall response of the metabolic system to the addition of various amino acids to the minimal medium is similar. Glycolysis and the synthesis of pyruvate with its subsequent degradation to acetate via acetyl-CoA become more efficient, whereas the fluxes through the pentose phosphate pathway and the TCA cycle decrease. If amino acids are used as the sole source of carbon, nitrogen, or both, the changes in the flux distribution are determined mainly by the carbon limitation. The phosphoenolpyruvate to glucose-6-phosphate flux increases; the flux through the pentose phosphate path is directed towards ribulose-5-phosphate. Other changes are determined by the compounds that are the primary products of catabolism of the added amino acid.     

A future for models and data in environmental science

Together, graphical models and the Bayesian paradigm provide powerful new tools that promise to change the way that environmental science is done. The capacity to merge theory with mechanistic understanding and empirical evidence, to assimilate diverse sources of information and to accommodate complexity will transform the collection and interpretation of data. As we discuss here, we specifically expect a shift from a focus on simple experiments with inflexible design and selection among models that embrace parts of processes to a synthesis of integrated process models. With this potential come new challenges, including some that are specific and technical and others that are general and will involve reexamination of the role of inference and prediction.     

The leukotriene B4 receptor (BLT1) is required for effector CD8+ T cell-mediated, mast cell-dependent airway hyperresponsiveness

Studies in both humans and rodents have suggested that CD8+ T cells contribute to the development of airway hyperresponsiveness (AHR) and that leukotriene B4 (LTB4) is involved in the chemotaxis of effector CD8+ T cells (T(EFF)) to the lung by virtue of their expression of BLT1, the receptor for LTB4. In the present study, we used a mast cell-CD8-dependent model of AHR to further define the role of BLT1 in CD8+ T cell-mediated AHR. C57BL/6+/+ and CD8-deficient (CD8-/-) mice were passively sensitized with anti-OVA IgE and exposed to OVA via the airways. Following passive sensitization and allergen exposure, C57BL/6+/+ mice developed altered airway function, whereas passively sensitized and allergen-exposed CD8-/- mice failed to do so. CD8-/- mice reconstituted with CD8+ T(EFF) developed AHR in response to challenge. In contrast, CD8-/- mice reconstituted with BLT1-deficient effector CD8+ T cells did not develop AHR. The induction of increased airway responsiveness following transfer of CD8+ T(EFF) or in wild-type mice could be blocked by administration of an LTB4 receptor antagonist confirming the role of BLT1 in CD8+ T cell-mediated AHR. Together, these data define the important role for mast cells and the LTB4-BLT1 pathway in the development of CD8+ T cell-mediated allergic responses in the lung.     

Initial Neurite Outgrowth in Drosophila Neurons Is Driven by Kinesin-Powered Microtubule Sliding

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