Iron and gallium increase iron uptake from transferrin by human melanoma cells: further examination of the ferric ammonium citrate-activated iron uptake process

AbstractPreviously we showed that preincubation of cells with ferric ammonium citrate (FAC) resulted in a marked increase in Fe uptake from both 59Fe-transferrin (Tf) and 59Fe-citrate (D.R. Richardson, E. Baker, J. Biol. Chem. 267 (1992) 13972–13979; D.R. Richardson, P. Ponka, Biochim. Biophys. Acta 1269 (1995) 105–114). This Fe uptake process was independent of the transferrin receptor and appeared to be activated by free radicals generated via the iron-catalysed Haber-Weiss reaction. To further understand this process, the present investigation was performed. In these experiments, cells were preincubated for 3 h at 37°C with FAC or metal ion solutions and then labelled for 3 h at 37°C with 59Fe-Tf. Exposure of cells to FAC resulted in Fe uptake from 59Fe-citrate that became saturated at an Fe concentration of 2.5 μM, while FAC-activated Fe uptake from Tf was not saturable up to 25 μM. In addition, the extent of FAC-activated Fe uptake from citrate was far greater than that from Tf. These results suggest a mechanism where FAC-activated Fe uptake from citrate may result from direct interaction with the transporter, while Fe uptake from Tf appears indirect and less efficient. Preincubation of cells with FAC at 4°C instead of 37°C prevented its effect at stimulating 59Fe uptake from 59Fe-Tf, suggesting that an active process was involved. Previous studies by others have shown that FAC can increase ferrireductase activity that may enhance 59Fe uptake from 59Fe-Tf. However, there was no difference in the ability of FAC-treated cells compared to controls to reduce ferricyanide to ferrocyanide, suggesting no change in oxidoreductase activity. To examine if activation of this Fe uptake mechanism could occur by incubation with a range of metal ions, cells were preincubated with either FAC, ferric chloride, ferrous sulphate, ferrous ammonium sulphate, gallium nitrate, copper chloride, zinc chloride, or cobalt chloride. Stimulation of 59Fe uptake from Tf was shown (in order of potency) with ferric chloride, ferrous sulphate, ferrous ammonium sulphate, and gallium nitrate. The other metal ions examined decreased 59Fe uptake from Tf. The fact that redox-active Cu(II) ion did not stimulate Fe uptake while redox-inactive Ga(III) did, suggests a mechanism of transporter activation not solely dependent on free radical generation. Indeed, the activation of Fe uptake appears dependent on the presence of the Fe atom itself or a metal ion with atomic similarities to Fe (e.g. Ga)

Robust low loss splicing of hollow core photonic bandgap fiber to itself

Robust, low loss (0.16dB) splicing of hollow core photonic band gap fiber to itself is presented. Modal content is negligibly affected by splicing, enabling penalty-free 40Gbit/s data transmission over > 200m of spliced PBGF

AN EXPLORATORY STUDY OF LONG SUPPLY CHAIN COMPETITION: SELECTED CASES IN THE SOUTH AFRICAN AEROSPACE SECTOR

<p>ENGLISH ABSTRACT: This article investigates how supply chains, especially long supply chains, compete in the South African aerospace industry. A multiple case study methodology is employed, involving six selected firms. Semi-structured interviews provide the primary source of data. Multiple case analysis identifies similarities in competitive dimension criteria for supplier-firm and customer-firm units in the supply chain. Results indicate that supplier-firm units compete on the basis of speed, dependability, quality, flexibility, and cost. Customer-firm units compete on the basis of speed, quality, and flexibility. The results also identify focus areas for future research into how long supply chains compete in the South African aerospace industry.</p><p>AFRIKAANSE OPSOMMING: Hierdie artikel ondersoek hoe voorsieningskettings, veral uitgerekte kettings, meeding in die Suid-Afrikaanse lugvaartindustrie. ‘n Meervoudige gevallestudie-metodologie is gevolg waartydens ses ondernemings bestudeer is. Semi-gestruktureerde onderhoude was die primêre bron van data. Meervoudige gevalle-analise identifiseer ooreenkomste in die mededingingskriteria vir leweransiers- en kliëntefirmas. Die resultate toon dat leweransiers kompeteer op spoed, betroubaarheid, kwaliteit, aanpasbaarheid en koste. Kliëntefirmas ding mee op grond van spoed, kwaliteit en aanpasbaarheid. Die resultate identifiseer fokusareas vir verdere navorsing op hierdie terrein.</p&gt

Mitigating spectral leakage and sampling errors in spatial and spectral (S2) imaging

We present a novel method for validating the relative power value (MPI) of the Spatial and Spectral (S2) imaging technique. By applying corrections for spectral leakage and sampling errors we found the MPI determinations to be accurate within 1dB

The potential of effective field theory in NN scattering

We study an effective field theory of interacting nucleons at distances much greater than the pion's Compton wavelength. In this regime the NN potential is conjectured to be the sum of a delta function and its derivatives. The question we address is whether this sum can be consistently truncated at a given order in the derivative expansion, and systematically improved by going to higher orders. Regularizing the Lippmann-Schwinger equation using a cutoff we find that the cutoff can be taken to infinity only if the effective range is negative. A positive effective range---which occurs in nature---requires that the cutoff be kept finite and below the scale of the physics which has been integrated out, i.e. O(m_\pi). Comparison of cutoff schemes and dimensional regularization reveals that the physical scattering amplitude is sensitive to the choice of regulator. Moreover, we show that the presence of some regulator scale, a feature absent in dimensional regularization, is essential if the effective field theory of NN scattering is to be useful. We also show that one can define a procedure where finite cutoff dependence in the scattering amplitude is removed order by order in the effective potential. However, the characteristic momentum in the problem is given by the cutoff, and not by the external momentum. It follows that in the presence of a finite cutoff there is no small parameter in the effective potential, and consequently no systematic truncation of the derivative expansion can be made. We conclude that there is no effective field theory of NN scattering with nucleons alone.Comment: 25 pages LaTeX, 3 figures (uses epsf

Complementary analysis of modal content and properties in a 19-cell hollow core photonic band gap fiber using Time-of-Flight and S2 techniques

We study the rich multimode content of an ultra-low loss hollow core photonic bandgap fiber using two complementary techniques which allow us to investigate both short and long propagation distances. Several distinct vector modes are clearly identified, with evidence of low intermodal coupling and distributed scattering

1.45 Tbit/s low latency data transmission through 19-cell hollow core photonic band gap fibre

We report transmission of 37 x 40 Gbit/s C-band channels over 250 m of hollow core band gap fibre, at 99.7% the speed of light in vacuum. BER penalty below 1 dB as compared to back-to-back was measured across the C-band

Discrete eddies in the northern North Atlantic as observed by looping RAFOS floats

Author Posting. © The Authors, 2004. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part II: Topical Studies in Oceanography 52 (2005): 627-650, doi:10.1016/j.dsr2.2004.12.011.RAFOS float trajectories near the 27.5 density level were analyzed to investigate discrete eddies in the northern North Atlantic with the objective of determining their geographical distribution and characteristics. Floats that made two or more consecutive loops in the same direction (loopers) were considered to have been in an eddy. Overall 15% (24 float years) of the float data were in loopers. One hundred and eight loopers were identified in 96 different eddies. Roughly half of the eddies were cyclonic (49%) and half were anticyclonic (51%), although the percentages varied in different regions. A few eddies were quasi-stationary for long times, one for over a year in the Iceland Basin, and many others clearly translated, often in the direction of the general circulation as observed by non-looping floats. Several floats were trapped in eddies in the vicinity of the North Atlantic Current just upstream (west) of the Charlie Gibbs (52ºN) and Faraday (50ºN) Fracture Zones, which seem to be preferred routes for flow crossing the mid-Atlantic ridge. Five floats looped in four anticyclones which translated southwestward away from the eastern boundary near the Goban Spur (47ºN-50ºN). These could have been weak meddies forming from remnants of warm salty Mediterranean Water advected northward along the eastern boundary.Funds for this research were provided by National Science Foundation grants OCE-9531877 to WHOI and OCE-9906775 to URI. This work was also supported by a grant from the WHOI Associates

Vortex Plastic Flow, B(x,y,H(t)),M(H(t)),Jc(B(t))B(x,y,H(t)), M(H(t)), J_c(B(t)), Deep in the Bose Glass and Mott-Insulator Regimes

We present simulations of flux-gradient-driven superconducting vortices interacting with strong columnar pinning defects as an external field $H(t)$ is quasi-statically swept from zero through a matching field $B_{\phi}$. We analyze several measurable quantities, including the local flux density $B(x,y,H(t))$, magnetization $M(H(t))$, critical current $J_{c}(B(t))$, and the individual vortex flow paths. We find a significant change in the behavior of these quantities as the local flux density crosses $B_{\phi}$, and quantify it for many microscopic pinning parameters. Further, we find that for a given pin density $J_c(B)$ can be enhanced by maximizing the distance between the pins for $B < B_{\phi}$.Comment: 4 pages, 4 PostScript Figure

Surface Roughness and Effective Stick-Slip Motion

The effect of random surface roughness on hydrodynamics of viscous incompressible liquid is discussed. Roughness-driven contributions to hydrodynamic flows, energy dissipation, and friction force are calculated in a wide range of parameters. When the hydrodynamic decay length (the viscous wave penetration depth) is larger than the size of random surface inhomogeneities, it is possible to replace a random rough surface by effective stick-slip boundary conditions on a flat surface with two constants: the stick-slip length and the renormalization of viscosity near the boundary. The stick-slip length and the renormalization coefficient are expressed explicitly via the correlation function of random surface inhomogeneities. The effective stick-slip length is always negative signifying the effective slow-down of the hydrodynamic flows by the rough surface (stick rather than slip motion). A simple hydrodynamic model is presented as an illustration of these general hydrodynamic results. The effective boundary parameters are analyzed numerically for Gaussian, power-law and exponentially decaying correlators with various indices. The maximum on the frequency dependence of the dissipation allows one to extract the correlation radius (characteristic size) of the surface inhomogeneities directly from, for example, experiments with torsional quartz oscillators.Comment: RevTeX4, 14 pages, 3 figure