786 research outputs found
Mechanistic target of rapamycin (mTOR) implicated in plasticity of the reproductive axis during social status transitions
© 2019 Elsevier Inc. The highly conserved brain-pituitary-gonadal (BPG) axis controls reproduction in all vertebrates, so analyzing the regulation of this signaling cascade is important for understanding reproductive competence. The protein kinase mechanistic target of rapamycin (mTOR) functions as a conserved regulator of cellular growth and metabolism in all eukaryotes, and also regulates the reproductive axis in mammals. However, whether mTOR might also regulate the BPG axis in non-mammalian vertebrates remains unexplored. We used complementary experimental approaches in an African cichlid fish, Astatotilapia burtoni, to demonstrate that mTOR is involved in regulation of the brain, pituitary, and testes when males rise in rank to social dominance. mTOR or downstream components of its signaling pathway (p-p70S6K) were detected in gonadotropin-releasing hormone (GnRH1) neurons, the pituitary, and testes. Transcript levels of mtor in the pituitary and testes also varied when reproductively-suppressed subordinate males rose in social rank to become dominant reproductively-active males, a transition similar to puberty in mammals. Intracerebroventricular injection of the mTORC1 inhibitor, rapamycin, revealed a role for mTOR in the socially-induced hypertrophy of GnRH1 neurons. Rapamycin treatment also had effects at the pituitary and testes, suggesting involvement of the mTORC1 complex at multiple levels of the reproductive axis. Thus, we show that mTOR regulation of BPG function is conserved to fishes, likely playing important roles in regulating reproduction and fertility across all male vertebrates
Configuration for Micro pH Sensor
A fully integrated pH sensor with a built-in reference electrode is proposed. An iridium oxide microelectrode and a pH-insensitive field-effect transistor are used as a pH sensor and a reference electrode, respectively. The sensitivity of the proposed device matches well with the estimated value to within 0.3 mV/pH deviation
Emergence of robust 2D skyrmions in SrRuO3 ultrathin film without the capping layer
Magnetic skyrmions have fast evolved from a novelty, as a realization of
topologically protected structure with particle-like character, into a
promising platform for new types of magnetic storage. Significant engineering
progress was achieved with the synthesis of compounds hosting room-temperature
skyrmions in magnetic heterostructures, with the interfacial
Dzyaloshinskii-Moriya interactions (DMI) conducive to the skyrmion formation.
Here we report findings of ultrathin skyrmion formation in a few layers of
SrRuO3 grown on SrTiO3 substrate without the heavy-metal capping layer.
Measurement of the topological Hall effect (THE) reveals a robust stability of
skyrmions in this platform, judging from the high value of the critical field
1.57 Tesla (T) at low temperature. THE survives as the field is tilted by as
much as 85 degrees at 10 Kelvin, with the in-plane magnetic field reaching up
to 6.5 T. Coherent Bragg Rod Analysis, or COBRA for short, on the same film
proves the rumpling of the Ru-O plane to be the source of inversion symmetry
breaking and DMI. First-principles calculations based on the structure obtained
from COBRA find significant magnetic anisotropy in the SrRuO3 film to be the
main source of skyrmion robustness. These features promise a few-layer SRO to
be an important new platform for skyrmionics, without the necessity of
introducing the capping layer to boost the spin-orbit coupling strength
artificially.Comment: Supplementary Information available upon reques
Emergence of robust 2D skyrmions in SrRuO3 ultrathin film without the capping layer
Magnetic skyrmions have fast evolved from a novelty, as a realization of
topologically protected structure with particle-like character, into a
promising platform for new types of magnetic storage. Significant engineering
progress was achieved with the synthesis of compounds hosting room-temperature
skyrmions in magnetic heterostructures, with the interfacial
Dzyaloshinskii-Moriya interactions (DMI) conducive to the skyrmion formation.
Here we report findings of ultrathin skyrmion formation in a few layers of
SrRuO3 grown on SrTiO3 substrate without the heavy-metal capping layer.
Measurement of the topological Hall effect (THE) reveals a robust stability of
skyrmions in this platform, judging from the high value of the critical field
1.57 Tesla (T) at low temperature. THE survives as the field is tilted by as
much as 85 degrees at 10 Kelvin, with the in-plane magnetic field reaching up
to 6.5 T. Coherent Bragg Rod Analysis, or COBRA for short, on the same film
proves the rumpling of the Ru-O plane to be the source of inversion symmetry
breaking and DMI. First-principles calculations based on the structure obtained
from COBRA find significant magnetic anisotropy in the SrRuO3 film to be the
main source of skyrmion robustness. These features promise a few-layer SRO to
be an important new platform for skyrmionics, without the necessity of
introducing the capping layer to boost the spin-orbit coupling strength
artificially.Comment: Supplementary Information available upon reques
Mechanisms and energetics of free radical initiated disulfide bond cleavage in model peptides and insulin by mass spectrometry
We investigate the mechanism of disulfide bond cleavage in gaseous peptide and protein ions initiated by a covalently-attached regiospecific acetyl radical using mass spectrometry (MS). Highly selective SâS bond cleavages with some minor CâS bond cleavages are observed by a single step of collisional activation. We show that even multiple disulfide bonds in intact bovine insulin are fragmented in the MS2 stage, releasing the A- and B-chains with a high yield, which has been challenging to achieve by other ion activation methods. Yet, regardless of the previous reaction mechanism studies, it has remained unclear why (1) disulfide bond cleavage is preferred to peptide backbone fragmentation, and why (2) the SâS bond that requires the higher activation energy conjectured in previously suggested mechanisms is more prone to be cleaved than the CâS bond by hydrogen-deficient radicals. To probe the mechanism of these processes, model peptides possessing deuterated ÎČ-carbon(s) at the disulfide bond are employed. It is suggested that the favored pathway of SâS bond cleavage is triggered by direct acetyl radical attack at sulfur with concomitant cleavage of the SâS bond (S_H2). The activation energy for this process is substantially lower by ~9â10 kcal mol^(â1) than those of peptide backbone cleavage processes determined by density functional quantum chemical calculations. Minor reaction pathways are initiated by hydrogen abstraction from the α-carbon or the ÎČ-carbon of a disulfide, followed by ÎČ-cleavages yielding CâS or SâS bond scissions. The current mechanistic findings should be generally applicable to other radical-driven disulfide bond cleavages with different radical species such as the benzyl and methyl pyridyl radicals
A Case of Autoimmune Pancreatitis Manifested by a Pseudocyst and IgG4-Associated Cholangitis
Autoimmune pancreatitis (AIP) is a benign disorder and a unique form of chronic pancreatitis with several characteristic features. A cystic formation that mimics a pseudocyst is a rare finding. There have been a few reports of AIP complicated by pancreatic cysts. We present a case of AIP with multiple pseudocysts and obstructive jaundice caused by IgG4-associated cholangitis. We initially missed the diagnosis due to the pseudocyst. Based on the computed tomography images, laboratory findings and the therapeutic response to steroids, the case was diagnosed as AIP with pseudocysts and associated cholangiopathy
The Globular Cluster System of M60 (NGC 4649). I. CFHT MOS Spectroscopy and Database
We present the measurement of radial velocities for globular clusters in M60,
giant elliptical galaxy in the Virgo cluster. Target globular cluster
candidates were selected using the Washington photometry based on the deep
16\arcmin \times 16\arcmin images taken at the KPNO 4m and using the
photometry derived from the HST/WFPC2 archive images. The spectra of the target
objects were obtained using the Multi-Object Spectrograph (MOS) at the
Canada-France-Hawaii Telescope (CFHT). We have measured the radial velocity for
111 objects in the field of M60: 93 globular clusters (72 blue globular
clusters with and 21 red globular clusters with
), 11 foreground stars, 6 small galaxies, and the nucleus of
M60. The measured velocities of the 93 globular clusters range from
km s to km s, with a mean value of
km s, which is in good agreement with the velocity of the nucleus of M60
( km s). Combining our results with data in the
literature, we present a master catalog of radial velocities for 121 globular
clusters in M60. The velocity dispersion of the globular clusters in the master
catalog is found to be km s for the entire sample,
km s for 83 blue globular clusters, and
km s for 38 red globular clusters.Comment: 29 pages, 8 figures. To appear in Ap
The Globular Cluster System of M60 (NGC 4649). II. Kinematics of the Globular Cluster System
We present a kinematic analysis of the globular cluster (GC) system in the
giant elliptical galaxy (gE) M60 in the Virgo cluster. Using the photometric
and spectroscopic database of 121 GCs (83 blue GCs and 38 red GCs), we have
investigated the kinematics of the GC system. We have found that the M60 GC
system shows a significant overall rotation. The rotation amplitude of the blue
GCs is slightly smaller than or similar to that of the red GCs, and their
angles of rotation axes are similar. The velocity dispersions about the mean
velocity and about the best fit rotation curve for the red GCs are marginally
larger than those for the blue GCs. Comparison of observed stellar and GC
velocity dispersion profiles with those calculated from the stellar mass
profile shows that the mass-to-light ratio should be increased as the
galactocentric distance increases, indicating the existence of an extended dark
matter halo. The entire sample of GCs in M60 is found to have a tangentially
biased velocity ellipsoid unlike the GC systems in other gEs. Two subsamples
appear to have different velocity ellipsoids. The blue GC system has a modest
tangentially biased velocity ellipsoid, while the red GC system has a modest
radially biased or an isotropic velocity ellipsoid. From the comparison of the
kinematic properties of the M60 GC system to those of other gEs (M87, M49, NGC
1399, NGC 5128, and NGC 4636), it is found that the velocity dispersion of the
blue GC system is similar to or larger than that of the red GC system except
for M60, and the rotation of the GC system is not negligible. The entire sample
of each GC system shows an isotropic velocity ellipsoid except for M60, while
the subsamples show diverse velocity ellipsoids. We discuss the implication of
these results for the formation models of the GC system in gEs.Comment: 48 pages, 16 figures. To appear in Ap
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