ABCA1 transporter reduces amphotericin B cytotoxicity in mammalian cells.

Amphotericin B (AmB) belongs to a group of polyene antibiotics commonly used in the treatment of systemic mycotic infections. A widely accepted mechanism of action of AmB is based on the formation of an oligomeric pore structure within the plasma membrane (PM) by interaction with membrane sterols. Although AmB binds preferentially to ergosterol, it can also bind to cholesterol in the mammalian PM and cause severe cellular toxicity. The lipid content and its lateral organization at the cell PM appear to be significant for AmB binding. Several ATP-binding cassette (ABC) transporters, including ABCA1, play a crucial role in lipid translocation, cholesterol redistribution and efflux. Here, we demonstrate that cells expressing ABCA1 are more resistant to AmB treatment, while cells lacking ABCA1 expression or expressing non-active ABCA1MM mutant display increased sensitivity. Further, a FLIM analysis of AmB-treated cells reveals a fraction of the antibiotic molecules, characterized by relatively high fluorescence lifetimes (> 6 ns), involved in formation of bulk cholesterol-AmB structures at the surface of ABCA1-expressing cells. Finally, lowering the cellular cholesterol content abolishes resistance of ABCA1-expressing cells to AmB. Therefore, we propose that ABCA1-mediated cholesterol efflux from cells induces formation of bulk cholesterol-AmB structures at the cell surface, preventing AmB cytotoxicity.

Interpretation of the LHCb P_{c}(4312)

We study the nature of the new signal reported by LHCb in the J/ψp spectrum. Based on the S-matrix principles, we perform a minimum-bias analysis of the underlying reaction amplitude, focusing on the analytic properties that can be related to the microscopic origin of the P_{c}(4312)^{+} peak. By exploring several amplitude parametrizations, we find evidence for the attractive effect of the Σ_{c}^{+}D[over ¯]^{0} channel, which is not strong enough, however, to form a bound state.

Determination of the Pole Position of the Lightest Hybrid Meson Candidate.

Mapping states with explicit gluonic degrees of freedom in the light sector is a challenge, and has led to controversies in the past. In particular, the experiments have reported two different hybrid candidates with spin-exotic signature, π_{1}(1400) and π_{1}(1600), which couple separately to ηπ and η^{'}π. This picture is not compatible with recent Lattice QCD estimates for hybrid states, nor with most phenomenological models. We consider the recent partial wave analysis of the η^{(')}π system by the COMPASS Collaboration. We fit the extracted intensities and phases with a coupled-channel amplitude that enforces the unitarity and analyticity of the S matrix. We provide a robust extraction of a single exotic π_{1} resonant pole, with mass and width 1564±24±86 and 492±54±102 MeV, which couples to both η^{(')}π channels. We find no evidence for a second exotic state. We also provide the resonance parameters of the a_{2}(1320) and a_{2}^{'}(1700).

Plantar pressure reduction in step-to gait: a biomechanical investigation and clinical feasibility study.

BACKGROUND: Protection of the foot may necessitate reduction of peak pressures in specific plantar regions. The study focuses on the unloading effects that exercising step-to gait may have. METHODS: 20 healthy volunteers were recruited and completed three pedobarographic examinations measuring peak pressures in different gait patterns: normal, half-step length, step-to gait with normal step length on the leading side and zero step length on the trailing side--all gait patterns with an individual but constant cadence. To test clinical feasibility 10 diabetic-neuropathic patients were studied in normal and step-to gait without any restrictions regarding speed or cadence. FINDINGS: Volunteers exercising step-to gait exhibit a significant (P<1%) reduction of peak pressures under the heels and central metatarsals by 9% and 67% on the leading side and of 32% and 19% on the trailing side, respectively. In the diabetic-neuropathic patients unloading effects of the same magnitude but less significant were observed. INTERPRETATION: Reduction of speed reduces peak pressures in all plantar regions. Asymmetry of step patterns reduces peak pressures in the heel and forefoot regions of that foot where heel strike and push-off are suppressed, respectively. However, pressures on the contralateral side are increased. The result is an asymmetric distribution of pressure that is reduced in all regions. Step-to gait may be an option, if pressure protection is required in selected plantar regions. This is confirmed by a feasibility study done with diabetic-neuropathic patients. Protection of the foot, however, is balanced at the cost of harmony of gait, impeding clinical application.

Stiff, light, strong and ductile: nano-structured High Modulus Steel.

Structural material development for lightweight applications aims at improving the key parameters strength, stiffness and ductility at low density, but these properties are typically mutually exclusive. Here we present how we overcome this trade-off with a new class of nano-structured steel - TiB2 composites synthesised in-situ via bulk metallurgical spray-forming. Owing to the nano-sized dispersion of the TiB2 particles of extreme stiffness and low density - obtained by the in-situ formation with rapid solidification kinetics - the new material has the mechanical performance of advanced high strength steels, and a 25% higher stiffness/density ratio than any of the currently used high strength steels, aluminium, magnesium and titanium alloys. This renders this High Modulus Steel the first density-reduced, high stiffness, high strength and yet ductile material which can be produced on an industrial scale. Also ideally suited for 3D printing technology, this material addresses all key requirements for high performance and cost effective lightweight design.

Crystal structure of chloroplast cytochrome f reveals a novel cytochrome fold and unexpected heme ligation.

BACKGROUND: Cytochrome f is the high potential electron acceptor of the chloroplast cytochrome b6f complex, and is the electron donor to plastocyanin. The 285-residue cytochrome f subunit is anchored in the thylakoid membrane of the chloroplast by a single membrane-spanning segment near the carboxyl terminus. A soluble redox-active 252-residue lumen-side polypeptide with native spectroscopic and redox properties, missing the membrane anchor and carboxyl terminus, was purified from turnip chloroplasts for structural studies. RESULTS: The crystal structure of cytochrome f, determined to 2.3 A resolution, has several unexpected features. The 252-residue polypeptide is organized into one large and one small domain. The larger heme-binding domain is strikingly different from known structures of other c-type cytochromes and has the same fold as the type III domain of the animal protein, fibronectin. Cytochrome f binds heme with an unprecedented axial heme iron ligand: the amino terminus of the polypeptide. CONCLUSION: The first atomic structure of a subunit of either the cytochrome b6f complex or of the related cytochrome bc1 complex has been obtained. The structure of cytochrome f allows prediction of the approximate docking site of plastocyanin and should allow systematic studies of the mechanism of intra- and inter-protein electron transfer between the cytochrome heme and plastocyanin copper, which are approximately isopotential. The unprecedented axial heme iron ligand also provides information on the sequence of events (i.e. cleavage of signal peptide and ligation of heme) associated with translocation of the cytochrome across the membrane and its subsequent folding.

Glutamic acid mimicking of synaptic inhibition on the giant serotonin neurone of the snail.

Stimulation of the snail's tentacle nerves results in hyperpolarization and inhibition of the 'giant serotonin-containing neurone'located in the brain. Glutamic acid mimics this effect. Available data indicate that the reversal potential for the glutamic acid effect is very similar to that of the synaptic action being about 5 to 8 mV more negative than the resting potential in each case.

The Rieske protein from purple sulfur bacteria is an extrinsic protein.

The mode of membrane attachment of the Rieske iron-sulfur protein from cytochrome bc1 complex of Rhodospirillum rubrum has been studied using biochemical approaches. In contrast to cytochrome c1 the bacterial Rieske protein was extracted from chromatophores using chaotropic agents (NaSCN, urea, guanidine), an alkaline pH and relatively low concentration of Triton X-100. The results presented here lead to the conclusion, that the Rieske protein from chromatophores is extrinsic and that their association with the rest of the complex involves hydrophobic interactions.

Membrane association of the Rieske iron-sulfur protein.

The mode of membrane attachment of the Rieske iron-sulfur proteins from cytochrome b6f complex of pea thylakoids and from cytochrome bc1 complex of yeast mitochondria has been studied using biochemical approaches. The relative sensitivity of the Rieske protein to trypsin in the thylakoid membrane shows that all trypsin sites of the Rieske protein are on the lumen side of the thylakoid membrane. In contrast to cytochrome f the chloroplast Rieske protein was extracted from thylakoids using chaotropic agents (NaSCN, urea), an alkaline pH and relatively low concentrations of Trinon X-100. The cytochrome bc1 complex Rieske protein from mitochondrial membranes of yeast was also released by NaSCN and alkaline treatment. The results presented here led us to the conclusion that the mitochondrial and chloroplast Rieske proteins are extrinsic and that their association with the rest of the complex involves hydrophobic interactions.

Topography of the chloroplast cytochrome b6: orientation of the cytochrome and accessibility of the lumen-side interhelix loops.

The topography of chloroplast cytochromes f and b6 was probed with proteases carboxypeptidase A (CpA), trypsin, and Staph, aureus V8. The cytochrome and its proteolytic products were detected by heme stain and, in most experiments, by immunoreaction. In thylakoids, the only protease that significantly affected the intactness of cytochrome f was CpA that caused a small (delta Mr = -1-2000) decrease in the apparent molecular weight. In SDS-treated thylakoids, both trypsin and V8 degraded cytochrome f. The inferred topography of cytochrome f., with the COOH-terminus on the stromal (n) side, one membrane-spanning alpha-elix near the COOH-terminus, and most of the Cyt f mass on the lumen (p) side, is consistent with that previously inferred by others. Cytochrome b6 was not sensitive to CpA, but was more sensitive to trypsin and V8 protease than cytochrome f, cytochrome b-559, or the 17 kDa OEC extrinsic protein. Trypsin caused a small decrease in size of cytochrome b6, which was observed using whole protein antibody as a single smaller band (delta Mr approximately 2000) or two smaller discrete bands (delta Mr = -1000 and 2500, respectively) which, unlike the untreated protein, did not react with antibody generated to a peptide mimicking Asp-5-Gln-14 near the NH2-terminus. These shortened tryptic fragments were attributed to cleavage after R-10 and K-23 near the NH2-terminus, implying an orientation with the NH2-terminus on the stromal side of the membrane. The sensitivity of cytochrome b6 toward this trypsin cleavage was increased if the membranes were first incubated with CpA, showing that the NH2-terminal region of cytochrome b6 is masked by the COOH-terminal domain of one or more thylakoid proteins.(ABSTRACT TRUNCATED AT 250 WORDS)

[Central venous lines in children with cancers]. / Centralne drogi dozylne w leczeniu dzieci z chorobami rozrostowymi.

Authors analyzed clinical aspects of central venous lines in children with cancer. In 25 patients central venous catheters with subcutaneous ports and in 34 patients lines with external ending were inserted. Catheters were left in place respectively 62-836 days and 4-365 days. During that time 10 catheters were removed due to occlusion, leakage, local infection or sepsis. The causes of these complications were analyzed in discussion.