368 research outputs found
Protein kinase C inhibitor and irradiation-induced apoptosis: Relevance of the cytochrome c-mediated caspase-9 death pathway
Caspases are a family of cysteine proteases that constitute the apoptotic cell death machinery, We report the importance of the cytochrome c-mediated caspase-9 death pathway for radiosensitization by the protein kinase C (PKC) inhibitors staurosporine (STP) and PKC-412. In our genetically defined tumor cells, treatment with low doses of STP or the conventional PKC-specific inhibitor PKC-412 in combination with irradiation (5 Gy) potently reduced viability, enhanced mitochondrial cytochrome c release into the cytosol, and specifically stimulated the initiator caspase-9. Whereas treatment with each agent alone had a minimal effect, combined treatment resulted in enhanced caspase-3 activation. This was prevented by broad-range and specific caspase-9 inhibitors and absent in caspase-9-deficient cells. The tumor suppressor p53 was required for apoptosis induction by combined treatment but was dispensable for dose-dependent STP-induced caspase activation. These results demonstrate the requirement for an intact caspase-9 pathway for apoptosis-based radiosensitization by PKC inhibitors and show that STP induces apoptosis independent of p53
Charge-Fluctuation-Induced Non-analytic Bending Rigidity
In this Letter, we consider a neutral system of mobile positive and negative
charges confined on the surface of curved films. This may be an appropriate
model for: i) a highly charged membrane whose counterions are confined to a
sheath near its surface; ii) a membrane composed of an equimolar mixture of
anionic and cationic surfactants in aqueous solution. We find that the charge
fluctuations contribute a non-analytic term to the bending rigidity that varies
logarithmically with the radius of curvature. This may lead to spontaneous
vesicle formation, which is indeed observed in similar systems.Comment: Revtex, 9 pages, no figures, submitted to PR
A lattice model for the kinetics of rupture of fluid bilayer membranes
We have constructed a model for the kinetics of rupture of membranes under
tension, applying physical principles relevant to lipid bilayers held together
by hydrophobic interactions. The membrane is characterized by the bulk
compressibility (for expansion), the thickness of the hydrophobic part of the
bilayer, the hydrophobicity and a parameter characterizing the tail rigidity of
the lipids. The model is a lattice model which incorporates strain relaxation,
and considers the nucleation of pores at constant area, constant temperature,
and constant particle number. The particle number is conserved by allowing
multiple occupancy of the sites. An equilibrium ``phase diagram'' is
constructed as a function of temperature and strain with the total pore surface
and distribution as the order parameters. A first order rupture line is found
with increasing tension, and a continuous increase in proto-pore concentration
with rising temperature till instability. The model explains current results on
saturated and unsaturated PC lipid bilayers and thicker artificial bilayers
made of diblock copolymers. Pore size distributions are presented for various
values of area expansion and temperature, and the fractal dimension of the pore
edge is evaluated.Comment: 15 pages, 8 figure
HLA-J, a Non-Pseudogene as a New Prognostic Marker for Therapy Response and Survival in Breast Cancer
The human leukocyte antigen (HLA) genes are cell-surface proteins, essential for immune cell interaction. HLA-G is known for their high immunosuppressive effect and its potential as predictive marker in breast cancer. However, nothing is known about the HLA-J and its immunosuppressive, prognostic and predictive features, as it is assumed to be a pseudogene by in silico sequence interpretation. HLA-J, ESR1, ERBB2, KRT5 and KRT20 mRNA expression were analysed in 29 fresh frozen breast cancer biopsies and their corresponding resectates obtained from patients treated with neoadjuvant chemotherapy (NACT). mRNA was analysed with gene specific TaqMan-based Primer/Probe sets and normalized to Calmodulin 2. All breast cancer samples did express HLA-J and frequently increased HLA-J mRNA levels after NACT. HLA-J mRNA was significantly associated with overexpression of the ESR1 mRNA status (Spearman Ï 0,5679; p = 0.0090) and KRT5 mRNA (Spearman Ï 0,6121; p = 0.0041) in breast cancer core biopsies and dominated in luminal B subtype. Kaplan Meier analysis revealed that an increase of HLA-J mRNA expression after NACT had worse progression free survival (p = 0,0096), indicating a counterreaction of tumor tissues presumably to prevent elimination by enhanced immune infiltration induced by NACT. This counterreaction is associated with worse prognosis. To our knowledge this is the first study identifying HLA-J as a new predictive marker in breast cancer being involved in immune evasion mechanisms.Humane Leukozyten-Antigene (HLA) sind Proteine auf der ZelloberflĂ€che, die essenziell fĂŒr die Immunzellinteraktion sind. HLA-G ist fĂŒr seine hohe immunosuppressive Wirkung sowie als potenzieller prĂ€dikativer Marker fĂŒr Brustkrebs bekannt. Dagegen ist kaum etwas ĂŒber HLA-J und seine immunosuppressiven, prognostischen und prĂ€diktiven Eigenschaften bekannt, da es basierend auf In-silico-Sequenzanalysen als âPseudogenâ interpretiert wurde. Die Expression von HLA-J, ESR1, ERBB2, KRT5 und KRT20 mRNA wurde in 29 frisch gefrorenen Brustkrebsbiopsien analysiert und mit den klinisch-pathologischen Daten von Patientinnen, welche mit neoadjuvanter Chemotherapie behandelt wurden, verglichen. Die mRNA-Expression wurde mit genspezifischen TaqMan-basierten Primer/Probe-Sets analysiert und auf Calmodulin 2 normalisiert. Alle Gewebeproben von Patientinnen mit Brustkrebs exprimierten HLA-J, und der HLA-J-mRNA-Spiegel war nach NACT oft erhöht. In den Brustkrebsstanzbiopsien war die HLA-J-mRNA-Expression signifikant mit der Ăberexpression von ESR1-mRNA (Spearmans Ï 0,5679; pâ=â0,0090) und KRT5-mRNA (Spearmans Ï 0,6121; pâ=â0,0041) assoziiert und dominierte im Luminal-B-Subtyp. Die Kaplan-Meier-Analyse zeigte, dass ein Anstieg der HLA-J-mRNA-Expression nach NACT mit einem schlechteren progressionsfreien Ăberleben einhergeht (pâ=â0,0096), womöglich als Gegenreaktion des Tumorgewebes, um eine Eliminierung durch tumorinfiltrierende Lymphozyten, welche durch eine NACT induziert wurden, zu verhindern. Diese Gegenreaktion ist mit einer schlechteren Prognose assoziiert. Soweit uns bekannt, handelt es sich hierbei um die erste Studie, die HLA-J als neuen prĂ€diktiven Marker im Brustkrebs identifiziert hat und möglicherweise zur Immunevasion beitrĂ€gt
Magnetospheric Emission from Extrasolar Planets
The magnetospheric emissions from extrasolar planets represent a science
frontier for the next decade. All of the solar system giant planets and the
Earth produce radio emissions as a result of interactions between their
magnetic fields and the solar wind. In the case of the Earth, its magnetic
field may contribute to its habitability by protecting its atmosphere from
solar wind erosion and by preventing energetic particles from reaching its
surface. Indirect evidence for at least some extrasolar giant planets also
having magnetic fields includes the modulation of emission lines of their host
stars phased with the planetary orbits, likely due to interactions between the
stellar and planetary magnetic fields. If magnetic fields are a generic
property of giant planets, then extrasolar giant planets should emit at radio
wavelengths allowing for their direct detection. Existing observations place
limits comparable to the flux densities expected from the strongest emissions.
Additional sensitivity at low radio frequencies coupled with algorithmic
improvements likely will enable a new means of detection and characterization
of extrasolar planets within the next decade.Comment: Science white paper for Astro2010; submitted to PSF pane
Plasma Depletion and Mirror Waves Ahead of Interplanetary Coronal Mass Ejections
We find that the sheath regions between fast interplanetary coronal mass
ejections (ICMEs) and their preceding shocks are often characterized by plasma
depletion and mirror wave structures, analogous to planetary magnetosheaths. A
case study of these signatures in the sheath of a magnetic cloud (MC) shows
that a plasma depletion layer (PDL) coincides with magnetic field draping
around the MC. In the same event, we observe an enhanced thermal anisotropy and
plasma beta as well as anti-correlated density and magnetic fluctuations which
are signatures of mirror mode waves. We perform a superposed epoch analysis of
ACE and Wind plasma and magnetic field data from different classes of ICMEs to
illuminate the general properties of these regions. For MCs preceded by shocks,
the sheaths have a PDL with an average duration of 6 hours (corresponding to a
spatial span of about 0.07 AU) and a proton temperature anisotropy -1.3, and are marginally unstable to the
mirror instability. For ICMEs with preceding shocks which are not MCs, plasma
depletion and mirror waves are also present but at a reduced level. ICMEs
without shocks are not associated with these features. The differences between
the three ICME categories imply that these features depend on the ICME geometry
and the extent of upstream solar wind compression by the ICMEs. We discuss the
implications of these features for a variety of crucial physical processes
including magnetic reconnection, formation of magnetic holes and energetic
particle modulation in the solar wind.Comment: fully refereed, accepted for publication in J. Geophys. Re
Negative electrostatic contribution to the bending rigidity of charged membranes and polyelectrolytes screened by multivalent counterions
Bending rigidity of a charged membrane or a charged polyelectrolyte screened
by monovalent counterions is known to be enhanced by electrostatic effects. We
show that in the case of screening by multivalent counterions the electrostatic
effects reduce the bending rigidity. This inversion of the sign of the
electrostatic contribution is related to the formation of two-dimensional
strongly correlated liquids (SCL) of counterions at the charged surface due to
strong lateral repulsion between them. When a membrane or a polyelectrolyte is
bent, SCL is compressed on one side and stretched on the other so that
thermodynamic properties of SCL contribute to the bending rigidity.
Thermodynamic properties of SCL are similar to those of Wigner crystal and are
anomalous in the sense that the pressure, compressibility and screening radius
of SCL are negative. This brings about substantial negative correction to the
bending rigidity. For the case of DNA this effect qualitatively agrees with
experiment.Comment: 8 pages, 2 figure
A Statistical Study on the Morphology of Rays and Dynamics of Blobs in the Wake of Coronal Mass Ejections
In this paper, with a survey through the Large Angle and Spectrometric
Coronagraph (LASCO) data from 1996 to 2009, we present 11 events with plasma
blobs flowing outwards sequentially along a bright coronal ray in the wake of a
coronal mass ejection. The ray is believed to be associated with the current
sheet structure that formed as a result of solar eruption, and the blobs are
products of magnetic reconnection occurring along the current sheet. The ray
morphology and blob dynamics are investigated statistically. It is found that
the apparent angular widths of the rays at a fixed time vary in a range of
2.1-6.6 (2.0-4.4) degrees with an average of 3.5 (2.9) degrees at 3 (4) Rs,
respectively, and the observed durations of the events vary from 12 h to a few
days with an average of 27 h. It is also found, based on the analysis of blob
motions, that 58% (26) of the blobs were accelerated, 20% (9) were decelerated,
and 22% (10) moved with a nearly-constant speed. Comparing the dynamics of our
blobs and those that are observed above the tip of a helmet streamer, we find
that the speeds and accelerations of the blobs in these two cases differ
significantly. It is suggested that these differences of the blob dynamics stem
from the associated magnetic reconnection involving different magnetic field
configurations and triggering processes.Comment: 12 pages, 6 figures, accepted by Solar Physic
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