23,494 research outputs found
Angiotensin II and VEGF are Involved in Angiogenesis Induced by Short-Term Exercise Training
Results from our laboratory have suggested a pathway involving angiotensin II type 1 (AT1) receptors and vascular endothelial growth factor (VEGF) in angiogenesis induced by electrical stimulation. The present study investigated if similar mechanisms underlie the angiogenesis induced by short-term exercise training. Seven days before training and throughout the training period, male Sprague-Dawley rats received either captopril or losartan in their drinking water. Rats underwent a 3-day treadmill training protocol. The tibialis anterior and gastrocnemius muscles were harvested under anesthesia and lightly fixed in formalin (vessel density) or frozen in liquid nitrogen (VEGF expression). In controls, treadmill training resulted in a significant increase in vessel density in all muscles studied. However, the angiogenesis induced by exercise was completely blocked by either losartan or captopril. Western blot analysis showed that VEGF expression was increased in the exercised control group, and both losartan and captopril blocked this increase. The role of VEGF was directly confirmed using a VEGF-neutralizing antibody. These results confirm the role of angiotensin II and VEGF in angiogenesis induced by exercise
Coexistence of Antiferromagnetism and Superconductivity in Electron-doped High-Tc Superconductors
We present magnetotransport evidence for antiferromagnetism in films of the
electron-doped cuprates PrCeCuO. Our results show clear
signature of static antiferromagnetism up to optimal doping x=0.15, with a
quantum phase transition close to x=0.16, and a coexistence of static
antiferromagnetism and superconductivity for 0.12x0.15
Steep-Spectrum Radio Emission from the Low-Mass Active Galactic Nucleus GH 10
GH 10 is a broad-lined active galactic nucleus (AGN) energized by a black
hole of mass 800,000 Solar masses. It was the only object detected by Greene et
al. in their Very Large Array (VLA) survey of 19 low-mass AGNs discovered by
Greene & Ho. New VLA imaging at 1.4, 4.9, and 8.5 GHz reveals that GH 10's
emission has an extent of less than 320 pc, has an optically-thin synchrotron
spectrum with a spectral index -0.76+/-0.05, is less than 11 percent linearly
polarized, and is steady - although poorly sampled - on timescales of weeks and
years. Circumnuclear star formation cannot dominate the radio emission, because
the high inferred star formation rate, 18 Solar masses per year, is
inconsistent with the rate of less than 2 Solar masses per year derived from
narrow Halpha and [OII] 3727 emission. Instead, the radio emission must be
mainly energized by the low-mass black hole. GH 10's radio properties match
those of the steep-spectrum cores of Palomar Seyfert galaxies, suggesting that,
like those Seyferts, the emission is outflow-driven. Because GH 10 is radiating
close to its Eddington limit, it may be a local analog of the starting
conditions, or seeds, for supermassive black holes. Future imaging of GH 10 at
higher resolution thus offers an opportunity to study the relative roles of
radiative versus kinetic feedback during black-hole growth.Comment: 7 pages; 2 figures; emulateapj; to appear in Ap
Lack of evidence for decreased protein stability in the 2397 (Met) haplotype of the leucine rich repeat kinase 2 protein implicated in Parkinson’s disease
Missense mutations in the leucine rich repeat kinase 2 (LRRK2) gene are the leading genetic cause of autosomal dominant familial Parkinson’s disease. We previously reported that two mutations within the ROC domain, namely R1441C and A1442P, exhibit increased protein degradation leading to lowered steady state LRRK2 protein levels in HEK293 cells. More recently, the common WD40 domain LRRK2 haplotype, Met2397, which is a risk factor for Crohn’s disease, has been shown to lower steady state protein levels in HEK293 cells. In view of recent evidence implicating LRRK2 and inflame-mation in PD, we investigated the effects of Met2397 on LRRK2 expression, and compared them to the Thr2397 variant and other LRRK2 mutants. In this study, we transfected HEK293 cells with plasmid constructs encoding the different LRRK2 variants, and analyzed the resulting protein levels by Western blot and flow cytometry. Here we found that both the Met2397 and Thr2397 haplotypes yield similar levels of LRRK2 protein expression and do not appear to impact cell viability in HEK293 cells, compared to other LRRK mutants. Thus, we have concluded that the Met2397 haplotype is unlikely to play a role in LRRK2 mediated or idiopathic PD
Hybridization, Inter-Ion Correlation, and Surface States in the Kondo Insulator SmB6
As an exemplary Kondo insulator, SmB6 has been studied for several decades;
however, direct evidence for the development of the Kondo coherent state and
the evolution of the electronic structure in the material has not been obtained
due to the rather complicated electronic and thermal transport behavior.
Recently, these open questions attracted increasing attention as the emergence
of a time-reversal invariant topological surface state in the Kondo insulator
has been suggested. Here, we use point-contact spectroscopy to reveal the
temperature dependence of the electronic states in SmB6. We demonstrate that
SmB6 is a model Kondo insulator: below 100 K, the conductance spectra reflect
the Kondo hybridization of Sm ions, but below ~ 30 K, signatures of inter-ion
correlation effects clearly emerge. Moreover, we find evidence that the
low-temperature insulating state of this exemplary Kondo lattice compound
harbors conduction states on the surface, in support of predictions of
nontrivial topology in Kondo insulators.Comment: Accepted for publication in Physical Review
Spectroscopic Detection of a Stellar-like Photosphere in an Accreting Protostar
We present the first spectrum of a highly veiled, strongly accreting
protostar which shows photospheric absorption features and demonstrates the
stellar nature of its central core. We find the spectrum of the luminous (L_bol
= 10 L_sun) protostellar source, YLW 15, to be stellar-like with numerous
atomic and molecular absorption features, indicative of a K5 IV/V spectral type
and a continuum veiling r_k = 3.0. Its derived stellar luminosity (3 L_sun) and
stellar radius (3.1 R_sun) are consistent with those of a 0.5 M_sun
pre-main-sequence star. However, 70% of its bolometric luminosity is due to
mass accretion, whose rate we estimate to be 1.6 E-6 M_sun / yr onto the
protostellar core. We determine that excess infrared emission produced by the
circumstellar accretion disk, the inner infalling envelope, and accretion
shocks at the surface of the stellar core of YLW 15 all contribute signifi-
cantly to its near-IR continuum veiling. Its projected rotation velocity v sin
i = 50 km / s is comparable to those of flat-spectrum protostars but
considerably higher than those of classical T Tauri stars in the rho Oph cloud.
The protostar may be magnetically coupled to its circumstellar disk at a radius
of 2 R_*. It is also plausible that this protostar can shed over half its
angular momentum and evolve into a more slowly rotating classical T Tauri star
by remaining coupled to its circumstellar disk (at increasing radius) as its
accretion rate drops by an order of magnitude during the rapid transition
between the Class I and Class II phases of evolution. The spectrum of WL 6 does
not show any photospheric absorption features, and we estimate that its
continuum veiling is r_k >= 4.6. Together with its low bolometric luminosity (2
L_sun), this dictates that its central core is very low mass, ~0.1 M_sun.Comment: 14 pages including 9 figures (3 figures of 3 panels each, all as
separate files). AASTeX LaTex macros version 5.0. To be published in The
Astronomical Journal (tentatively Oct 2002
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