Lysosome mediated Kir2.1 breakdown directly influences inward rectifier current density

The inward rectifier current generated by Kir2.1 ion channel proteins is primarily responsible for the stable resting membrane potential in various excitable cell types, like neurons and myocytes. Tight regulation of Kir2.1 functioning prevents premature action potential formation and ensures optimal repolarization times. While Kir2.1 forward trafficking has been addressed in a number of studies, its degradation pathways are thus far unknown. Using three different lysosomal inhibitors, NH₄Cl, chloroquine and leupeptin, we now demonstrate involvement of the lysosomal degradation pathway in Kir2.1 breakdown. Upon application of the inhibitors, increased steady state protein levels are detectable within few hours coinciding with intracellular granular Kir2.1 accumulation. Treatment for 24 h with either chloroquine or leupeptin results in increased plasmamembrane originating inward rectifier current densities, while current-voltage characteristics remain unaltered. We conclude that the lysosomal degradation pathway contributes to Kir2.1 mediated inward rectifier current regulation.     

Cryptococcus cerealis sp. nov. a psychrophilic yeast species isolated from fermented cereals

Two yeast strains isolated in 2007 from fermented pig feed were studied, including the analysis of sequences of the D1/D2 and ITS-regions of the rDNA-repeats, their morphology and nutritional physiology. Sequence comparison of the D1/D2 and ITS regions demonstrated that the strains do not belong to any known species. Therefore, a new species, Cryptococcus cerealis with the type strain CBS 10505, is proposed. The species belongs to Filobasidiales (Agaricomycetes, Basidiomycota), and has Cryptococcus saitoi as the closest related species. The new species is psychrophilic, showing significant growth at 4 and 10°C.     

TNF‐α has both stimulatory and inhibitory effects on mouse monocyte‐derived osteoclastogenesis

Phenotypically different osteoclasts may be generated from different subsets of precursors. To what extent the formation of these osteoclasts is influenced or mediated by the inflammatory cytokine TNF‐α, is unknown and was investigated in this study. The osteoclast precursors early blasts (CD31^hiLy‐6C^?), myeloid blasts (CD31⁺Ly‐6C⁺), and monocytes (CD31^?Ly‐6C^hi) were sorted from mouse bone marrow using flow cytometry and cultured with M‐CSF and RANKL, with or without TNF‐α. Surprisingly, TNF‐α prevented the differentiation of TRAcP⁺ osteoclasts generated from monocytes on plastic; an effect not seen with early blasts and myeloid blasts. This inhibitory effect could not be prevented by other cytokines such as IL‐1β or IL‐6. When monocytes were pre‐cultured with M‐CSF and RANKL followed by exposure to TNF‐α, a stimulatory effect was found. TNF‐α also stimulated monocytes’ osteoclastogenesis when the cells were seeded on bone. Gene expression analysis showed that when TNF‐α was added to monocytes cultured on plastic, RANK, NFATc1, and TRAcP were significantly down‐regulated while TNF‐αR1 and TNF‐αR2 were up‐regulated. FACS analysis showed a decreased uptake of fluorescently labeled RANKL in monocyte cultures in the presence of TNF‐α, indicating an altered ratio of bound‐RANK/unbound‐RANK. Our findings suggest a diverse role of TNF‐α on monocytes’ osteoclastogenesis: it affects the RANK‐signaling pathway therefore inhibits osteoclastogenesis when added at the onset of monocyte culturing. This can be prevented when monocytes were pre‐cultured with M‐CSF and RANKL, which ensures the binding of RANKL to RANK. This could be a mechanism to prevent unfavorable monocyte‐derived osteoclast formation away from the bone.

     

Isolation of <Emphasis Type="Italic">Cryptococcus gattii</Emphasis> from a <Emphasis Type="Italic">Castanopsis argyrophylla</Emphasis> tree hollow (Mai-Kaw), Chiang Mai,Thailand

The pathogenic yeast Cryptococcus gattii was isolated from a tree hollow of a Castanopsis argyrophylla King ex Hook.f. (Fagaceae) in Chiang Mai, Thailand. Molecular characterization with amplified fragment length polymorphism analysis and multi-locus sequence typing showed that this isolate belonged to genotype AFLP4/VGI representing C. gattii sensu stricto. Subsequent comparison of the environmental isolate with those from clinical samples from Thailand showed that they grouped closely together in a single cluster.     

How radiation influences atherosclerotic plaque development: a biophysical approach in ApoE ¯/¯ mice

Atherosclerosis is the development of lipid-laden plaques in arteries and is nowadays considered as an inflammatory disease. It has been shown that high doses of ionizing radiation, as used in radiotherapy, can increase the risk of development or progression of atherosclerosis. To elucidate the effects of radiation on atherosclerosis, we propose a mathematical model to describe radiation-promoted plaque development. This model distinguishes itself from other models by combining plaque initiation and plaque growth, and by incorporating information from biological experiments. It is based on two consecutive processes: a probabilistic dose-dependent plaque initiation process, followed by deterministic plaque growth. As a proof of principle, experimental plaque size data from carotid arteries from irradiated ApoE\(^{{-/-}}\) mice was used to illustrate how this model can provide insight into the underlying biological processes. This analysis supports the promoting role for radiation in plaque initiation, but the model can easily be extended to include dose-related effects on plaque growth if available experimental data would point in that direction. Moreover, the model could assist in designing future biological experiments on this research topic. Additional biological data such as plaque size data from chronically-irradiated mice or experimental data sets with a larger variety in biological parameters can help to further unravel the influence of radiation on plaque development. To the authors’ knowledge, this is the first biophysical model that combines probabilistic and mechanistic modeling which uses experimental data to investigate the influence of radiation on plaque development.