Regulation of hematopoietic stem and progenitor cell mobilization by cholesterol efflux pathways

Intact cholesterol homeostasis helps to maintain hematopoietic stem and multipotential progenitor cell (HSPC) quiescence. Mice with defects in cholesterol efflux pathways due to deficiencies of the ATP binding cassette transporters ABCA1 and ABCG1 displayed a dramatic increase in HSPC mobilization and extramedullary hematopoiesis. Increased extramedullary hematopoiesis was associated with elevated serum levels of G-CSF due to generation of IL-23 by splenic macrophages and dendritic cells. This favored hematopoietic lineage decisions toward granulocytes rather than macrophages in the bone marrow leading to impaired support for osteoblasts and decreased Cxcl12/SDF-1 production by mesenchymal progenitors. Greater HSPC mobilization and extramedullary hematopoiesis were reversed by raising HDL levels in Abca1(-/-)Abcg1(-/-) and Apoe(-/-) mice or in a mouse model of myeloproliferative neoplasm mediated by Flt3-ITD mutation. Our data identify a role of cholesterol efflux pathways in the control of HSPC mobilization. This may translate into therapeutic strategies for atherosclerosis and hematologic malignancies.     

Do Personalized Feedback Messages about Activity Patterns Stimulate Patients with Chronic Low Back Pain to Change their Activity Behavior on a Short Term Notice?

The aim of this study was to explore whether patients responded to personalized messages on top of continuous visual feedback by changes in activity patterns and whether this response is related to the stages of change and the pain intensity levels. Patients wore a movement sensor and a PDA for 2 weeks and received continuously feedback and time-related messages to influence activity behavior. The response was calculated by calculating the activity 30 min before and after a message. In addition, the readiness to change was measured with the Stage of Change questionnaire and pain intensity was measured on a visual analogue scale. Sixteen patients participated, receiving a total of 517 messages. Overall, patients responded to personalized messages (p < .049), with a higher response in the morning. Patients in different stages of change responded differently to the messages (p = .009) and the response was significantly related to the pain intensity levels (Pearson correlation −.226) in the second week of feedback. This study suggests that personalized messages have the potential to influence activity behavior. It seems relevant to take time of the day, the stages of change and pain intensity levels of the patient into account to further optimize the feedback strategy used.     

Rapid susceptibility testing and microcolony analysis of Candida spp. cultured and imaged on porous aluminum oxide

Background

Acquired resistance to antifungal agents now supports the introduction of susceptibility testing for species-drug combinations for which this was previously thought unnecessary. For pathogenic yeasts, conventional phenotypic testing needs at least 24 h. Culture on a porous aluminum oxide (PAO) support combined with microscopy offers a route to more rapid results.

Methods

Microcolonies of Candida species grown on PAO were stained with the fluorogenic dyes Fun-1 and Calcofluor White and then imaged by fluorescence microscopy. Images were captured by a charge-coupled device camera and processed by publicly available software. By this method, the growth of yeasts could be detected and quantified within 2 h. Microcolony imaging was then used to assess the susceptibility of the yeasts to amphotericin B, anidulafungin and caspofungin (3.5 h culture), and voriconazole and itraconazole (7 h culture).

Significance

Overall, the results showed good agreement with EUCAST (86.5% agreement; n = 170) and E-test (85.9% agreement; n = 170). The closest agreement to standard tests was found when testing susceptibility to amphotericin B and echinocandins (88.2 to 91.2%) and the least good for the triazoles (79.4 to 82.4%). Furthermore, large datasets on population variation could be rapidly obtained. An analysis of microcolonies revealed subtle effects of antimycotics on resistant strains and below the MIC of sensitive strains, particularly an increase in population heterogeneity and cell density-dependent effects of triazoles. Additionally, the method could be adapted to strain identification via germ tube extension. We suggest PAO culture is a rapid and versatile method that may be usefully adapted to clinical mycology and has research applications.     

Electrophysiological responses from neurons of antennal taste sensilla in the polyphagous predatory ground beetle Pterostichus oblongopunctatus (Fabricius 1787) to plant sugars and amino acids

The responses of antennal contact chemoreceptors, in the polyphagous predatory ground beetle Pterostichus oblongopunctatus, to twelve 1-1000mmoll(-1) plant sugars and seven 10-100mmoll(-1) amino acids were tested. The disaccharides with an alpha-1.4-glycoside linkage, sucrose and maltose, were the two most stimulatory sugars for the sugar-sensitive neuron innervating these contact chemosensilla. The firing rates they evoked were concentration dependent and reached up to 70impulses/s at 1000mmoll(-1). The stimulatory effect of glucose on this neuron was approximately two times lower. This can be partly explained by the fact that glucose exists in at least two anomeric forms, alpha and beta. These two forms interconvert over a timescale of hours in aqueous solution, to a final stable ratio of alpha:beta 36:64, in a process called mutarotation. So the physiologically active alpha-anomere forms only 36% of the glucose solution which was reflected in its relatively low dose/response curve. Due to the partial herbivory of P. oblongopunctatus these plant sugars are probably involved in its search for food, for example, for conifer seeds. Several carbohydrates, in addition to glucose, such as cellobiose, arabinose, xylose, mannose, rhamnose and galactose are known as components of cellulose and hemicelluloses. They are released by brown-rot fungi during enzymatic wood decay. None of them stimulated the antennal sugar-sensitive neuron. They are therefore not implicated in the search for hibernation sites, which include rotting wood, by this beetle. The weak stimulating effect (below 3impulses/s) of some 100mmoll(-1) amino acids (methionine, serine, alanine, glutamine) to the 4th chemosensory neuron of these sensilla was characterized as non-specific, or modulating the responses of non-target chemosensory neurons.     

Modulation of Lck function through multisite docking to T cell-specific adapter protein

T cell-specific adapter protein (TSAd), encoded by the SH2D2A gene, interacts with Lck through its C terminus and thus modulates Lck activity. Here we mapped Lck phosphorylation and interaction sites on TSAd and evaluated their functional importance. The three C-terminal TSAd tyrosines Tyr(280), Tyr(290), and Tyr(305) were phosphorylated by Lck and functioned as docking sites for the Lck Src homology 2 (SH2) domain. Binding affinities of the TSAd Tyr(P)(280) and Tyr(P)(290) phosphopeptides to the isolated Lck SH2 domain were similar to that observed for the Lck Tyr(P)(505) phosphopeptide, whereas the TSAd Tyr(P)(305) peptide displayed a 10-fold higher affinity. The proline-rich Lck SH3-binding site on TSAd as well as the Lck SH2 domain were required for efficient tyrosine phosphorylation of TSAd by Lck. Interaction sites on TSAd for both Lck SH2 and Lck SH3 were necessary for TSAd-mediated modulation of proximal TCR signaling events. We found that 20-30% of TSAd molecules are phosphorylated in activated T cells and that the proportion of TSAd to Lck molecules in such cells is approximately 1:1. Therefore, in activated T cells, a considerable number of Lck molecules may potentially be engaged by TSAd. In conclusion, Lck binds to TSAd prolines and phosphorylates and interacts with the three C-terminal TSAd tyrosines. We propose that through multivalent interactions with Lck, TSAd diverts Lck from phosphorylating other substrates, thus modulating its functional activity through substrate competition.     

The contribution of single and colonial cells of Phaeocystis pouchetii to spring and summer blooms in the north-eastern North Atlantic

Studies of the phytoplankton ecology in different localities in north-Norwegian fjords, the White Sea and the Barents Sea were carried out in spring and early summer to investigate the contribution of single and colonial stages of Phaeocystis pouchetii to phytoplankton abundance. Three different types of flagellated and four colonial cells were observed in all localities. P. pouchetii was rare under the ice of the Barents and White Seas, but their abundance increased rapidly during ice retreat. Single cell C dominated over colonial cell C, often by 50 times or more. The highest share of colonial cells was encountered in April in northern Norwegian fjords, in May in the Barents Sea and in May–June in the White Sea. At times the single cell dominated the total P. pouchetii biomass in Balsfjord (April 1999, 2001) with hardly any colonies present. In the White Sea colonies of P. pouchetii were less abundant than in the other regions. Cell carbon of P. pouchetii colonies appears never to be as dominating in the north-eastern North Atlantic as P. globosa blooms in coastal regions such as the southern North Sea. However, the lobal matrix of P. pouchetii colonies appears to be less solid than that of P. globosa and partly dissolution of the colony matrix during handling and storage of fixes samples induces uncertainty about the absolute numbers of P. pouchetii colonial cell counts. Despite of that, single cells of P. pouchetii seem to dominate significantly over colonial cell biomass at most sites and during some years and in some regions colonial cells seem rare. We speculate that top-down regulation of Phaeocystis spp. blooms possibly determines the ratio between single and colonial cells.     

Intrinsically disordered Meningioma-1 stabilizes the BAF complex to cause AML

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