Multistep Photoluminescence Decay Reveals Dissociation of Geminate Charge Pairs in Organolead Trihalide Perovskites

Charge carrier dynamics in organolead iodide perovskites is analyzed by employing time‐resolved photoluminescence spectroscopy with several ps time resolution. The measurements performed by varying photoexcitation intensity over five orders of magnitude enable separation of photoluminescence components related to geminate and nongeminate charge carrier recombination and to address the dynamics of an isolated geminate electron–hole pair. Geminate recombination dominates at low excitation fluence and determines the initial photoluminescence decay. This decay component is remarkably independent of the material structure and experimental conditions. It is demonstrated that dependences of the geminate and nongeminate radiative recombination components on excitation intensity, repetition rate, and temperature, are hardly compatible with carrier trapping and exciton dissociation models. On the basis of semiclassical and quantum mechanical numerical calculation results, it is argued that the fast photoluminescence decay originates from gradual spatial separation of photogenerated weakly bound geminate charge pairs.     

Flow and Diffusion in Channel-Guided Cell Migration

Collective migration of mechanically coupled cell layers is a notable feature of wound healing, embryonic development, and cancer progression. In confluent epithelial sheets, the dynamics have been found to be highly heterogeneous, exhibiting spontaneous formation of swirls, long-range correlations, and glass-like dynamic arrest as a function of cell density. In contrast, the flow-like properties of one-sided cell-sheet expansion in confining geometries are not well understood. Here, we studied the short- and long-term flow of Madin-Darby canine kidney (MDCK) cells as they moved through microchannels. Using single-cell tracking and particle image velocimetry (PIV), we found that a defined averaged stationary cell current emerged that exhibited a velocity gradient in the direction of migration and a plug-flow-like profile across the advancing sheet. The observed flow velocity can be decomposed into a constant term of directed cell migration and a diffusion-like contribution that increases with density gradient. The diffusive component is consistent with the cell-density profile and front propagation speed predicted by the Fisher-Kolmogorov equation. To connect diffusion-mediated transport to underlying cellular motility, we studied single-cell trajectories and occurrence of vorticity. We discovered that the directed large-scale cell flow altered fluctuations in cellular motion at short length scales: vorticity maps showed a reduced frequency of swirl formation in channel flow compared with resting sheets of equal cell density. Furthermore, under flow, single-cell trajectories showed persistent long-range, random-walk behavior superimposed on drift, whereas cells in resting tissue did not show significant displacements with respect to neighboring cells. Our work thus suggests that active cell migration manifests itself in an underlying, spatially uniform drift as well as in randomized bursts of short-range correlated motion that lead to a diffusion-mediated transport.     

The role of patient expectations in predicting outcome after total knee arthroplasty

Introduction  

Patient's expectations are variably reported to influence self-rated outcome and satisfaction after medical treatment; this prospective study examined which of the following was the most important unique determinant of global outcome/satisfaction after total knee arthroplasty (TKA): baseline expectations; fulfilment of expectations; or current symptoms and function.     

Inhibition of palmitate‐induced GADD34 expression augments apoptosis in mouse insulinoma cells (MIN6)

Saturated fatty acids like palmitate induce endoplasmic reticulum (ER) stress in pancreatic beta‐cells, an event linked to apoptotic loss of β‐cells in type 2 diabetes. Sustained activation of the ER stress response leads to expression of growth arrest and DNA damage‐inducible protein 34 (GADD34), a regulatory subunit of protein phosphatase 1. In the present study, we have used small interfering RNA in order to knockdown GADD34 expression in insulin‐producing MIN6 cells prior to induction of ER stress by palmitate and evaluated its consequences on RNA‐activated protein kinase‐like ER‐localized eIF2alpha kinase (PERK) signalling and apoptosis. Salubrinal, a specific inhibitor of eukaryotic initiation factor 2α (eIF2α) dephosphorylation, was used as a comparison. Salubrinal treatment augmented palmitate‐induced ER stress and increased GADD34 levels. Both GADD34 knockdown and salubrinal treatment potentiated the cytotoxic effects of palmitate as evidenced by increased DNA fragmentation and activation of caspase 3, with the fundamental difference that the former did not involve enhanced levels of GADD34. The data from this study suggest that sustained activation of PERK signalling and eIF2α phosphorylation sensitizes insulin‐producing MIN6 cells to lipoapoptosis independently of GADD34 expression levels. Copyright © 2014 John Wiley & Sons, Ltd.     

Maximum growth temperature ranges of Aeromonas Spp. isolated from clinical or environmental sources

Only a limited number of phenotypic tests are available for the differentiation of all 13 known hybridization groups (HG) of Aeromonas spp. These organisms have a wide spectrum of warm-blooded and cold-blooded hosts. In the present study, the maximum growth temperatures (t_max) of the most common HGs of Aeromonas spp. originating from human fecal samples, food, water, and healthy and diseased fish were determined with a plate-type continuous temperature-gradient incubator. We observed that determination of the t_max can be applied for differentiation of HG 1 from HG 2 and 3 (phenospecies A. hydrophila); HG 6 from HG 4, 5A, and 5B (phenospecies A. caviae); HG 7 from HG 8/10 (phenospecies A. sobria); and HG 11 from HG 8/10 (phenospecies A. veronii). HG 1, 4, 8/10, and 13 strains occurring also in human clinical samples had a high t_max, about 40°C or higher. Hybridization group 2, 3, 5A, and 5B strains, which in most cases originated from water or food, had t_max values in the range of about 36–39°C, while HG 6, 7, and 11 had t_max values in the range of about 33–37°C. Fish pathogenic strains of A. salmonicida subsp. salmonicida and subsp. achromogenes had the lowest t_max values from about 30 to 35°C. Correspondence to: M.-L. Hdnninen     

Anti-inflammatory effects of sodium butyrate on human monocytes: potent inhibition of IL-12 and up-regulation of IL-10 production.

Cytokines are critical in regulating unresponsiveness versus immunity towards enteric antigens derived from the intestinal flora and ingested food. There is increasing evidence that butyrate, a major metabolite of intestinal bacteria and crucial energy source for gut epithelial cells, also possesses anti-inflammatory properties. Its influence on cytokine production, however, is not established. Here, we report that butyrate strongly inhibits interleukin-12 (IL-12) production by suppression of both IL-12p35 and IL-12p40 mRNA accumulation, but massively enhances IL-10 secretion in Staphylococcus aureus cell-stimulated human monocytes. The effect of butyrate on IL-12 production was irreversible upon the addition of neutralizing antibodies to IL-10 or transforming growth factor b1 and of indomethacin. In anti-CD3-stimulated peripheral blood mononuclear cells, butyrate enhanced IL-10 and IL-4 secretion but reduced the release of IL-2 and interferon-g. The latter effect was in part a result of suppressed IL-12 production but also a result of inhibition of IL-12 receptor expression on T cells. These data demonstrate a novel anti-inflammatory property of butyrate that may have broad implications for the regulation of immune responses in vivo and could be exploited as new therapeutic approach in inflammatory conditions.     

Isolation and characterization of the plasma membrane from the yeast Pichia pastoris

Despite similarities of cellular membranes in all eukaryotes, every compartment displays characteristic and often unique features which are important for the functions of the specific organelles. In the present study, we biochemically characterized the plasma membrane of the methylotrophic yeast Pichia pastoris with emphasis on the lipids which form the matrix of this compartment. Prerequisite for this effort was the design of a standardized and reliable isolation protocol of the plasma membrane at high purity. Analysis of isolated plasma membrane samples from P. pastoris revealed an increase of phosphatidylserine and a decrease of phosphatidylcholine compared to bulk membranes. The amount of saturated fatty acids in the plasma membrane was higher than in total cell extracts. Ergosterol, the final product of the yeast sterol biosynthetic pathway, was found to be enriched in plasma membrane fractions, although markedly lower than in Saccharomyces cerevisiae. A further characteristic feature of the plasma membrane from P. pastoris was the enrichment of inositol phosphorylceramides over neutral sphingolipids, which accumulated in internal membranes. The detailed analysis of the P. pastoris plasma membrane is discussed in the light of cell biological features of this microorganism especially as a microbial cell factory for heterologous protein production.