301 research outputs found
Recommended from our members
Diffuse optical spectroscopy and imaging to detect and quantify adipose tissue browning
Adipose (fat) tissue is a complex metabolic organ that is highly active and essential. In contrast to white adipose tissue (WAT), brown adipose tissue (BAT) is deemed metabolically beneficial because of its ability to burn calories through heat production. The conversion of WAT-resident adipocytes to “beige” or “brown-like” adipocytes has recently attracted attention. However, it typically takes a few days to analyze and confirm this browning of WAT through conventional molecular, biochemical, or histological methods. Moreover, accurate quantification of the overall browning process is not possible by any of these methods. In this context, we report the novel application of diffuse reflectance spectroscopy (DRS) and multispectral imaging (MSI) to detect and quantify the browning process in mice. We successfully demonstrated the time-dependent increase in browning of WAT, following its induction through β-adrenergic agonist injections. The results from these optical techniques were confirmed with those of standard molecular and biochemical assays, which measure gene and protein expression levels of UCP1 and PGC-1α, as well as with histological examinations. We envision that the reported optical methods can be developed into a fast, real time, cost effective and easy to implement imaging approach for quantification of the browning process in adipose tissue
Optical conductivity of CuO_2 infinite-layer films
The infrared conductivity of CaCuO_2, SrCuO_{2-y}, and
Sr_{0.85}Nd_{0.15}CuO_2 infinite-layer films is obtained from reflectivity
measurements by taking into account the substrate contribution. SrCuO_{2-y} and
Sr_{0.85}Nd_{0.15}CuO_2 exhibit extra-phonon modes and structured bands in the
midinfrared, not found in stoichiometric CaCuO_2. These features mirror those
observed in the perovskitic cuprates, thus showing that the polaronic
properties of high-T_c superconductors are intrinsic to the CuO_2 planes.Comment: File latex, 5 p. incl. 4 fig. in epsf. Submitted to Solid State Com
Electron effective mobility in strained Si/Si1-xGex MOS devices using Monte Carlo simulation
Based on Monte Carlo simulation, we report the study of the inversion layer
mobility in n-channel strained Si/ Si1-xGex MOS structures. The influence of
the strain in the Si layer and of the doping level is studied. Universal
mobility curves mueff as a function of the effective vertical field Eeff are
obtained for various state of strain, as well as a fall-off of the mobility in
weak inversion regime, which reproduces correctly the experimental trends. We
also observe a mobility enhancement up to 120 % for strained Si/ Si0.70Ge0.30,
in accordance with best experimental data. The effect of the strained Si
channel thickness is also investigated: when decreasing the thickness, a
mobility degradation is observed under low effective field only. The role of
the different scattering mechanisms involved in the strained Si/ Si1-xGex MOS
structures is explained. In addition, comparison with experimental results is
discussed in terms of SiO2/ Si interface roughness, as well as surface
roughness of the SiGe substrate on which strained Si is grown.Comment: 25 pages, 8 figures, 1 table, revised version, discussions and
references adde
Inter-planar coupling dependent magnetoresistivity in high purity layered metals
The magnetic field-induced changes in the conductivity of metals are the
subject of intense interest, both for revealing new phenomena and as a valuable
tool for determining their Fermi surface. Here, we report a hitherto unobserved
magnetoresistive effect in ultra-clean layered metals, namely a negative
longitudinal magnetoresistance that is capable of overcoming their very
pronounced orbital one. This effect is correlated with the inter-layer coupling
disappearing for fields applied along the so-called Yamaji angles where the
inter-layer coupling vanishes. Therefore, it is intrinsically associated with
the Fermi points in the field-induced quasi-one-dimensional electronic
dispersion, implying that it results from the axial anomaly among these Fermi
points. In its original formulation, the anomaly is predicted to violate
separate number conservation laws for left- and right-handed chiral- (e.g.
Weyl) fermions. Its observation in PdCoO, PtCoO and SrRuO
suggests that the anomaly affects the transport of clean conductors,
particularly near the quantum limit.Comment: Nature Communications (in press
A Model of Cancer Stem Cells Derived from Mouse Induced Pluripotent Stem Cells
Cancer stem cells (CSCs) are capable of continuous proliferation and self-renewal and are proposed to play significant roles in oncogenesis, tumor growth, metastasis and cancer recurrence. CSCs are considered derived from normal stem cells affected by the tumor microenvironment although the mechanism of development is not clear yet. In 2007, Yamanaka's group succeeded in generating Nanog mouse induced pluripotent stem (miPS) cells, in which green fluorescent protein (GFP) has been inserted into the 5′-untranslated region of the Nanog gene. Usually, iPS cells, just like embryonic stem cells, are considered to be induced into progenitor cells, which differentiate into various normal phenotypes depending on the normal niche. We hypothesized that CSCs could be derived from Nanog miPS cells in the conditioned culture medium of cancer cell lines, which is a mimic of carcinoma microenvironment. As a result, the Nanog miPS cells treated with the conditioned medium of mouse Lewis lung carcinoma acquired characteristics of CSCs, in that they formed spheroids expressing GFP in suspension culture, and had a high tumorigenicity in Balb/c nude mice exhibiting angiogenesis in vivo. In addition, these iPS-derived CSCs had a capacity of self-renewal and expressed the marker genes, Nanog, Rex1, Eras, Esg1 and Cripto, associated with stem cell properties and an undifferentiated state. Thus we concluded that a model of CSCs was originally developed from miPS cells and proposed the conditioned culture medium of cancer cell lines might perform as niche for producing CSCs. The model of CSCs and the procedure of their establishment will help study the genetic alterations and the secreted factors in the tumor microenvironment which convert miPS cells to CSCs. Furthermore, the identification of potentially bona fide markers of CSCs, which will help the development of novel anti-cancer therapies, might be possible though the CSC model
Majorana quantization and half-integer thermal quantum Hall effect in a Kitaev spin liquid
The quantum Hall effect (QHE) in two-dimensional (2D) electron gases, which
is one of the most striking phenomena in condensed matter physics, involves the
topologically protected dissipationless charge current flow along the edges of
the sample. Integer or fractional electrical conductance are measured in units
of , which is associated with edge currents of electrons or
quasiparticles with fractional charges, respectively. Here we discover a novel
type of quantization of the Hall effect in an insulating 2D quantum magnet. In
-RuCl with dominant Kitaev interaction on 2D honeycomb lattice, the
application of a parallel magnetic field destroys the long-range magnetic
order, leading to a field-induced quantum spin liquid (QSL) ground state with
massive entanglement of local spins. In the low-temperature regime of the QSL
state, we report that the 2D thermal Hall conductance
reaches a quantum plateau as a function of applied magnetic field.
attains a quantization value of ,
which is exactly half of in the integer QHE. This
half-integer thermal Hall conductance observed in a bulk material is a direct
signature of topologically protected chiral edge currents of charge neutral
Majorana fermions, particles that are their own antiparticles, which possess
half degrees of freedom of conventional fermions. These signatures demonstrate
the fractionalization of spins into itinerant Majorana fermions and
fluxes predicted in a Kitaev QSL. Above a critical magnetic field, the
quantization disappears and goes to zero rapidly,
indicating a topological quantum phase transition between the states with and
without chiral Majorana edge modes. Emergent Majorana fermions in a quantum
magnet are expected to have a major impact on strongly correlated topological
quantum matter.Comment: 7 pages, 8 figures. Submitted versio
Virally and physically transgenized equine adipose-derived stromal cells as a cargo for paracrine secreted factors
<p>Abstract</p> <p>Background</p> <p>Adipose-Derived Stromal Cells have been shown to have multiple lineage differentiation properties and to be suitable for tissues regeneration in many degenerative processes. Their use has been proposed for the therapy of joint diseases and tendon injuries in the horse. In the present report the genetic manipulation of Equine Adipose-Derived Stromal Cells has been investigated.</p> <p>Results</p> <p>Equine Adipose-Derived Stromal Cells were successfully virally transduced as well as transiently and stably transfected with appropriate parameters, without detrimental effect on their differentiation properties. Moreover, green fluorescent protein alone, fused to <it>neo </it>gene, or co-expressed as bi-cistronic reporter constructs, driven by viral and house-keeping gene promoters, were tested. The better expressed cassette was employed to stably transfect Adipose-Derived Stromal Cells for cell therapy purposes. Stably transfected Equine Adipose-Derived Stromal Cells with a heterologous secreted viral antigen were able to immunize horses upon injection into the lateral wall of the neck.</p> <p>Conclusion</p> <p>This study provides the methods to successfully transgenize Adipose-Derived Stromal Cells both by lentiviral vector and by transfection using optimized constructs with suitable promoters and reporter genes. In conclusion these findings provide a working platform for the delivery of potentially therapeutic proteins to the site of cells injection via transgenized Equine Adipose-Derived Stromal Cells.</p
A novel platform to enable the high-throughput derivation and characterization of feeder-free human iPSCs
Human induced pluripotent stem cells (hiPSCs) hold enormous potential, however several obstacles impede their translation to industrial and clinical applications. Here we describe a platform to efficiently generate, characterize and maintain single cell and feeder-free (FF) cultured hiPSCs by means of a small molecule cocktail media additive. Using this strategy we have developed an effective multiplex sorting and high-throughput selection platform where individual clonal hiPSC lines are readily obtained from a pool of candidate clones, expanded and thoroughly characterized. By promoting survival and self-renewal, the selected hiPSC clones can be rapidly expanded over multiple FF, single-cell passages while maintaining their pluripotency and genomic stability as demonstrated by trilineage differentiation, karyotype and copy number variation analysis. This study provides a robust platform that increases efficiency, throughput, scale and quality of hiPSC generation and facilitates the industrial and clinical use of iPSC technology
The Dynamin Chemical Inhibitor Dynasore Impairs Cholesterol Trafficking and Sterol-Sensitive Genes Transcription in Human HeLa Cells and Macrophages
Intracellular transport of cholesterol contributes to the regulation of cellular cholesterol homeostasis by mechanisms that are yet poorly defined. In this study, we characterized the impact of dynasore, a recently described drug that specifically inhibits the enzymatic activity of dynamin, a GTPase regulating receptor endocytosis and cholesterol trafficking. Dynasore strongly inhibited the uptake of low-density lipoprotein (LDL) in HeLa cells, and to a lower extent in human macrophages. In both cell types, dynasore treatment led to the abnormal accumulation of LDL and free cholesterol (FC) within the endolysosomal network. The measure of cholesterol esters (CE) further showed that the delivery of regulatory cholesterol to the endoplasmic reticulum (ER) was deficient. This resulted in the inhibition of the transcriptional control of the three major sterol-sensitive genes, sterol-regulatory element binding protein 2 (SREBP-2), 3-hydroxy-3-methyl-coenzymeA reductase (HMGCoAR), and low-density lipoprotein receptor (LDLR). The sequestration of cholesterol in the endolysosomal compartment impaired both the active and passive cholesterol efflux in HMDM. Our data further illustrate the importance of membrane trafficking in cholesterol homeostasis and validate dynasore as a new pharmacological tool to study the intracellular transport of cholesterol
- …