898 research outputs found
Endocytosis in filter-grown Madin-Darby canine kidney cells
The nitrogen-containing bisphosphonates used for management of the patients with osteoporosis were reported to influence the function of renal tubular cells. However, how nitrogen-containing bisphosphates exert any effects on ion currents remains controversial. The effects of ibandronate (Iban), a nitrogen-containing bisphosphonate, on ionic channels, including two types of Ca(2+)-activated K(+) (KCa) channels, namely, large-conductance KCa (BKCa) and intermediate-conductance KCa (IKCa) channels, were investigated in Madin-Darby canine kidney (MDCK) cells. In whole-cell current recordings, Iban suppressed the amplitude of voltage-gated K(+) current elicited by long ramp pulse. Addition of Iban caused a reduction of BKCa channels accompanied by a right shift in the activation curve of BKCa channels, despite no change in single-channel conductance. Ca(2+) sensitivity of these channels was modified in the presence of this compound; however, the magnitude of Iban-mediated decrease in BKCa-channel activity under membrane stretch with different negative pressure remained unchanged. Iban suppressed the probability of BKCa-channel openings linked primarily to a shortening in the slow component of mean open time in these channels. The dissociation constant needed for Iban-mediated suppression of mean open time in MDCK cells was 12.2\ua0μM. Additionally, cell exposure to Iban suppressed the activity of IKCa channels, and DC-EBIO or 9-phenanthrol effectively reversed its suppression. Under current-clamp configuration, Iban depolarized the cells and DC-EBIO or PF573228 reversed its depolarizing effect. Taken together, the inhibitory action of Iban on KCa-channel activity may contribute to the underlying mechanism of pharmacological or toxicological actions of Iban and its structurally similar bisphosphonates on renal tubular cells occurring in vivo
New High Field State of Flux Line Lattice in Unconventional Superconductor CeCoIn_5
Ultrasound velocity measurements of the unconventional superconductor
CeCoIn_5 with extremely large Pauli paramagnetic susceptibility reveal an
unusual structural transformation of the flux line lattice (FLL) in the
vicinity of the upper critical field. The transition field coincides with that
at which heat capacity measurements reveal a second order phase transition. The
lowering of the sound velocity at the transition is consistent with the
collapse of the FLL tilt modulus and a crossover to quasi two-dimensional FLL
pinning. These results provide a strong evidence that the high field state is
the Fulde-Ferrel-Larkin-Ovchinikov phase, in which the order parameter is
spatially modulated and has planar nodes aligned perpendicular to the vortices.Comment: 5 pages, 4 figure
Characterization of the early endosome and putative endocytic carrier vesicles in vivo and with an assay of vesicle fusion in vitro.
Structure of the Fulde-Ferrell-Larkin-Ovchinnikov state in two-dimensional superconductors
Nonuniform superconducting state due to strong spin magnetism is studied in
two-dimensional type-II superconductors near the second order phase transition
line between the normal and the superconducting states. The optimum spatial
structure of the orderparameter is examined in systems with cylindrical
symmetric Fermi surfaces. It is found that states with two-dimensional
structures have lower free energies than the traditional one-dimensional
solutions, at low temperatures and high magnetic fields. For s-wave pairing,
triangular, square, hexagonal states are favored depending on the temperature,
while square states are favored at low temperatures for d-wave pairing. In
these states, orderparameters have two-dimensional structures such as square
and triangular lattices.Comment: 11 pages (LaTeX, revtex.sty), 3 figures; added reference
Temperature dependence of the upper critical field of an anisotropic singlet superconductivity in a square lattice tight-binding model in parallel magnetic fields
Upper critical field parallel to the conducting layer is studied in
anisotropic type-II superconductors on square lattices. We assume enough
separation of the adjacent layers, for which the orbital pair-breaking effect
is suppressed for exactly aligned parallel magnetic field. In particular, we
examine the temperature dependence of the critical field H_c(T) of the
superconductivity including the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO or LOFF)
state, in which the Cooper pairs have non-zero center-of-mass momentum q. In
the system with the cylindrically symmetric Fermi-surface, it is known that
H_c(T) of the d-wave FFLO state exhibits a kink at a low temperature due to a
change of the direction of q in contrast to observations in organic
superconductors. It is shown that the kink disappears when the Fermi-surface is
anisotropic to some extent, since the direction of q is locked in an optimum
direction independent of the temperature.Comment: 5 pages, 5 figures, revtex.sty, submitted to J.Phys.Soc.Jp
Evidence of Andreev bound states as a hallmark of the FFLO phase in -(BEDT-TTF)Cu(NCS)
Superconductivity is a quantum phenomena arising, in its simplest form, from
pairing of fermions with opposite spin into a state with zero net momentum.
Whether superconductivity can occur in fermionic systems with unequal number of
two species distinguished by spin, atomic hyperfine states, flavor, presents an
important open question in condensed matter, cold atoms, and quantum
chromodynamics, physics. In the former case the imbalance between spin-up and
spin-down electrons forming the Cooper pairs is indyced by the magnetic field.
Nearly fifty years ago Fulde, Ferrell, Larkin and Ovchinnikov (FFLO) proposed
that such imbalanced system can lead to exotic superconductivity in which pairs
acquire finite momentum. The finite pair momentum leads to spatially
inhomogeneous state consisting of of a periodic alternation of "normal" and
"superconducting" regions. Here, we report nuclear magnetic resonance (NMR)
measurements providing microscopic evidence for the existence of this new
superconducting state through the observation of spin-polarized quasiparticles
forming so-called Andreev bound states.Comment: 6 pages, 5 fig
Late Endosomal Cholesterol Accumulation Leads to Impaired Intra-Endosomal Trafficking
Background Pathological accumulation of cholesterol in late endosomes is observed in lysosomal storage diseases such as Niemann-Pick type C. We here analyzed the effects of cholesterol accumulation in NPC cells, or as phenocopied by the drug U18666A, on late endosomes membrane organization and dynamics. Methodology/Principal Findings Cholesterol accumulation did not lead to an increase in the raft to non-raft membrane ratio as anticipated. Strikingly, we observed a 2–3 fold increase in the size of the compartment. Most importantly, properties and dynamics of late endosomal intralumenal vesicles were altered as revealed by reduced late endosomal vacuolation induced by the mutant pore-forming toxin ASSP, reduced intoxication by the anthrax lethal toxin and inhibition of infection by the Vesicular Stomatitis Virus. Conclusions/Significance These results suggest that back fusion of intralumenal vesicles with the limiting membrane of late endosomes is dramatically perturbed upon cholesterol accumulation
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