323 research outputs found
Hepatoxicity of aqueous extract and fractionated methanol extract of Phytolacca americana by isolated rat liver perfusion system
Recombinant retroviral vector containing human tissue inhibitor of matrix metalloproteinase-2 (TIMP-2) gene was constructed and investigation of the in vitro invasion and metastasis of gastric cancer cells transfected with TIMP-2 was carried out. Human TlMP-2 was isolated from recombinant vector Bluescript 1/TIMP-2(+), and then inserted into the retroviral vector pL-MT. Correct orientation was verified by restriction endonuclease digestion. Human full length TIMP-2 gene was ligated into a plasmid, which was then transfected into PA317 cell line. G418-resistant individual clones were selected to transfect human SGC-7901 cell line. Cell proliferation, cell electrophoresis, soft agar colony formation and in vitro invasion were detected to analyze the bio-behavioral changes of cancer cells. The results from restriction endonuclease digestion were as theoretically expected. The cell electrophoresis rate, colony number and invasion ability in SGC-7901 cells and MFC cells transfected with TIMP-2 gene were significantly decreased when compared with control group. However, no significant changes were noted in the proliferation of cancer cells. We successfully construct a recombinant retroviral vector containing human TIMP-2. TIMP-2 transfection could markedly alter the membrane charge of cancer cells, resulting in decreased electrophoresis capacity, cell migration and invasion. However, cell growth was not affected by TIMP-2. These results suggested TIMP-2 transfection might exert effects on the malignant phenotype of cancer cells through affecting extracellular environment, which provided a new way to investigate gene regulation of in vitro collagen metabolism
Magnetic hour-glass dispersion and its relation to high-temperature superconductivity in iron-tuned FeTeSe
High-temperature superconductivity remains arguably the largest outstanding
enigma of condensed matter physics. The discovery of iron-based
high-temperature superconductors has renewed the importance of understanding
superconductivity in materials susceptible to magnetic order and fluctuations.
Intriguingly they show magnetic fluctuations reminiscent of the superconducting
(SC) cuprates, including a 'resonance' and an 'hour-glass' shaped dispersion,
which provide an opportunity to new insight to the coupling between spin
fluctuations and superconductivity. Here we report inelastic neutron scattering
data on FeTeSe using excess iron concentration to tune
between a SC () and a non-SC () ground states. We find
incommensurate spectra in both samples but discover that in the one that
becomes SC, a constriction towards a commensurate hourglass shape develop well
above . Conversely a spin-gap and concomitant spectral weight shift happen
below . Our results imply that the hourglass shaped dispersion is most
likely a pre-requisite for superconductivity, whereas the spin-gap and shift of
spectral weight are consequences of superconductivity. We explain this
observation by pointing out that an inwards dispersion towards the commensurate
wave-vector is needed for the opening of a spin gap to lower the magnetic
exchange energy and hence provide the necessary condensation energy for the SC
state to emerge
Involving Young People in Healthy Ageing: A Crucial Facet to Achieving the Decade of Healthy Ageing (2021-2030)
Rotational dynamics in motor cortex are consistent with a feedback controller
Recent studies have identified rotational dynamics in motor cortex (MC), which many assume arise from intrinsic connections in MC. However, behavioral and neurophysiological studies suggest that MC behaves like a feedback controller where continuous sensory feedback and interactions with other brain areas contribute substantially to MC processing. We investigated these apparently conflicting theories by building recurrent neural networks that controlled a model arm and received sensory feedback from the limb. Networks were trained to counteract perturbations to the limb and to reach toward spatial targets. Network activities and sensory feedback signals to the network exhibited rotational structure even when the recurrent connections were removed. Furthermore, neural recordings in monkeys performing similar tasks also exhibited rotational structure not only in MC but also in somatosensory cortex. Our results argue that rotational structure may also reflect dynamics throughout the voluntary motor system involved in online control of motor actions
Electric-field control of the skyrmion lattice in Cu2OSeO3
Small-angle neutron scattering has been employed to study the influence of
applied electric (E-) fields on the skyrmion lattice in the chiral lattice
magnetoelectric Cu2OSeO3. In an experimental geometry with the E-field parallel
to the [111] axis, and the magnetic field parallel to the [1-10] axis, we
demonstrate that the effect of applying an E-field is to controllably rotate
the skyrmion lattice around the magnetic field axis. Our results are an
important first demonstration for a microscopic coupling between applied
E-fields and the skyrmions in an insulator, and show that the general emergent
properties of skyrmions may be tailored according to the properties of the host
system.Comment: 12 pages, 4 figures, published version (including final proof
corrections). Article is free to download at
http://iopscience.iop.org/0953-8984/24/43/432201
Mitigating Climate Biases in the Midlatitude North Atlantic by Increasing Model Resolution: SST Gradients and Their Relation to Blocking and the Jet
Starting to resolve the oceanic mesoscale in climate models is a step change in model fidelity. This study examines how certain obstinate biases in the midlatitude North Atlantic respond to increasing resolution (from 18 to 0.258 in the ocean) and how such biases in sea surface temperature (SST) affect the atmosphere. Using a multimodel ensemble of historical climate simulations run at different horizontal resolutions, it is shown that a severe cold SST bias in the central North Atlantic, common to many ocean models, is significantly reduced with increasing resolution. The associated bias in the time-mean meridional SST gradient is shown to relate to a positive bias in low-level baroclinicity, while the cold SST bias causes biases also in static stability and diabatic heating in the interior of the atmosphere. The changes in baroclinicity and diabatic heating brought by increasing resolution lead to improvements in European blocking and eddy-driven jet variability. Across the multimodel ensemble a clear relationship is found between the climatological meridional SST gradients in the broader Gulf Stream Extension area and two aspects of the atmospheric circulation: the frequency of high-latitude blocking and the southern-jet regime. This relationship is thought to reflect the two-way interaction (with a positive feedback) between the respective oceanic and atmospheric anomalies. These North Atlantic SST anomalies are shown to be important in forcing significant responses in the midlatitude atmospheric circulation, including jet variability and the storm track. Further increases in oceanic and atmospheric resolution are expected to lead to additional improvements in the representation of Euro-Atlantic climate
Rational design of hypoallergenic vaccines: Blocking ige-binding to polcalcin using allergen-specific igg antibodies
Chenopodium album polcalcin (Che a 3) is characterized as a major cause of cross-reactivity inallergic patients to the Chenopodiaceae family. Therefore, the present study was conducted to develop a hypoallergenic Che a 3 derivatives as the candidate vaccine for type 1 allergy. Four derivatives were generated from Che a 3. The first was a mosaic peptide derivative computationally identified in Che a 3 which was coupled to keyhole limpet hemocyanin (KLH). The second one was a mutant Che a 3, and the other two derivatives included N-and C-Terminal halves of Che a 3 that both coupled to KLH. The IgE-binding capacity of Che a 3 and its derivatives and also their ability to induce there combinant Che a 3 (rChe a 3)-specific IgG antibody, were determined using the enzyme-linked immune sorbent assay (ELISA). Moreover, the lymphopro liferative capacity of rChe a 3 or its derivatives and their pro-inflammatory cytokine response interleukin (IL)-5 and IL-13 were measured in the human peripheral blood mononuclear cells (PBMCs). Among all derivatives, the N-Terminal half peptide and mosaic peptide exhibited the lowest IgEbinding capacity. In addition, in comparison to other antigens, KLH-coupled mosaic peptide induced the highest level of the recombinant Che a 3 (rChe a 3)-specific IgG antibody and ther Che a 3 specific-blocking IgG antibody in mice. Moreover, the mosaic peptide lacked lymphopro liferative capacity and down-regulated expression of pro-Allergic IL-5 and IL-13 cytokines. Therefore, a peptide-carrier fusion vaccine, composed of the B-cell epitope coupled to the carrier, could be considered as one of the promising hypoallergenic vaccines to treat patients with allergy to low molecular weight allergens such as Che
Electrons imitating light: Frustrated supercritical collapse in charged arrays on graphene
The photon-like electronic dispersion of graphene bestows its charge carriers
with unusual confinement properties that depend strongly on the geometry and
strength of the surrounding potential. Here we report bottom-up synthesis of
atomically-precise one-dimensional (1D) arrays of point charges aimed at
exploring supercritical confinement of carriers in graphene for new geometries.
The arrays were synthesized by arranging F4TCNQ molecules into a 1D lattice on
back-gated graphene devices, allowing precise tuning of both the molecular
charge state and the array periodicity. Dilute arrays of ionized F4TCNQ
molecules are seen to behave like isolated subcritical charges but dense arrays
show emergent supercriticality. In contrast to compact supercritical clusters,
extended 1D charge arrays exhibit both supercritical and subcritical
characteristics and belong to a new physical regime termed frustrated
supercritical collapse. Here carriers in the far-field are attracted by a
supercritical charge distribution, but have their fall to the center frustrated
by subcritical potentials in the near-field, similar to the trapping of light
by a dense cluster of stars in general relativity
Genetically engineered fusion of allergen and viral-like particle induces a more effective allergen-specific immune response than a combination of them
Abstract: Chimeric virus-like particles (VLPs) were developed as a candidate for allergen-specific immunotherapy. In this study, hepatitis B core antigen (HBcAg) that genetically fused to Chenopodium album polcalcin (Che a 3)–derived peptide was expressed in E. coli BL21, purified, and VLP formation was evaluated using native agarose gel electrophoresis (NAGE) and transmission electron microscopy (TEM). Chimeric HBc VLPs were characterized in terms of their reactivity to IgE, the induction of blocking IgG and allergen-specific IgE, basophil-activating capacity, and Th1-type immune responses. Results from IgE reactivity and basophil activation test showed that chimeric HBc VLPs lack IgE-binding capacity and basophil degranulation activity. Although chimeric HBc VLPs induced the highest level of efficient polcalcin-specific IgG antibody in comparison to those induced by recombinant Che a 3 (rChe a 3) mixed either with HBc VLPs or alum, they triggered the lowest level of polcalcin-specific IgE in mice following immunization. Furthermore, in comparison to the other antigens, chimeric HBc VLPs produced a polcalcin-specific Th1 cell response. Taken together, genetically fusion of allergen derivatives to HBc VLPs, in comparison to a mix of them, may be a more effective way to induce appropriate immune responses in allergen-specific immunotherapy. Key points: • The insertion of allergen-derived peptide into major insertion region (MIR) of hepatitis B virus core (HBc) antigen resulted in nanoparticles displaying allergen-derived peptide upon its expression in prokaryotic host. • The resultant VLPs (chimeric HBc VLPs) did not exhibit IgE reactivity with allergic patients’ sera and were not able to degranulate basophils. • Chimeric HBc VLPs dramatically improved protective IgG antibody response compared with those induced by allergen mixed either with HBc VLPs or alum. • Chimeric HBc VLPs induced Th1 responses that were counterparts of Th2 responses (allergic). • Chimeric HBc VLPs increased IgG2a/ IgG1 ratio and the level of IFN-γ compared to those induced by allergen mixed with either HBc VLPs or alum. [Figure not available: see fulltext.
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