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[en] The aortic medial degeneration is the key histopathologic feature of Thoracic aortic dissection (TAD). The aim of this study was to identify the change of autophagic activity in the aortic wall during TAD development, and to explore the roles of autophagy on regulating functional properties of smooth muscle cells (SMCs). Firstly, compared with control group (n = 11), the increased expression of autophagic markers Beclin1 and LC3 was detected in the aortic wall from TAD group (n = 23) by immunochemistry and western blot. We found that more autophagic vacuoles were present in the aortic wall of TAD patients using Transmission electron microscopy. Next, autophagic activity was examined in AD mice model established by β-aminopropionitrile fumarate (BAPN) and angiotensin II. Immunochemistry proved that autophagic activity was dynamically changed during AD development. Beclin1 and LC3 were detected up-regulated in the aortic wall in the second week after BAPN feeding, earlier than the fragmentation or loss of elastic fibers. When AD occurred in the 4th week, the expression of Beclin1 and LC3 began to decrease, but still higher than the control. Furthermore, autophagy was found to inhibit starvation-induced apoptosis of SMCs. Meanwhile, blockage of autophagy could suppress PDGF-induced phenotypic switch of SMCs. Taken together, autophagic activity was dynamically changed in the aortic wall during TAD development. The abnormal autophagy could regulate the functional properties of aortic SMCs, which might be the potential pathogenesis of TAD. - Highlights: • Autophagy is up-regulated in aorta wall from thoracic aorta dissection (TAD) patient. • Autophagic activity is dynamically changed during TAD development. • Dynamically change of autophagy is associated with pathological process of TAD. • Autophagy participate in the development of TAD by regulating function of SMCs.
[en] Highlights: • We present a random-beam STEM acquisition-reconstruction framework that fully exploits the compressed sensing principles. • We demonstrate that RB-STEM acquisition associated with a wavelet basis fulfills the incoherence condition. • We present a regularized tomographic reconstruction framework to recover high-quality volumes from RB-STEM measurements. - Abstract: A central challenge in scanning transmission electron microscopy (STEM) is to reduce the electron radiation dosage required for accurate imaging of 3D biological nano-structures. Methods that permit tomographic reconstruction from a reduced number of STEM acquisitions without introducing significant degradation in the final volume are thus of particular importance. In random-beam STEM (RB-STEM), the projection measurements are acquired by randomly scanning a subset of pixels at every tilt view. In this work, we present a tailored RB-STEM acquisition-reconstruction framework that fully exploits the compressed sensing principles. We first demonstrate that RB-STEM acquisition fulfills the “incoherence” condition when the image is expressed in terms of wavelets. We then propose a regularized tomographic reconstruction framework to recover volumes from RB-STEM measurements. We demonstrate through simulations on synthetic and real projection measurements that the proposed framework reconstructs high-quality volumes from strongly downsampled RB-STEM data and outperforms existing techniques at doing so. This application of compressed sensing principles to STEM paves the way for a practical implementation of RB-STEM and opens new perspectives for high-quality reconstructions in STEM tomography.
[en] Amorphous carbon films have been routinely used to enhance the preparation of frozen-hydrated samples for transmission electron microscopy (TEM), either in retaining protein concentration, providing mechanical stability or dissipating sample charge. However, strong background signal from the amorphous carbon support obstructs that of the sample, and the insulating properties of thin amorphous carbon films preclude any efficiency in dispersing charge. Graphene addresses the limitations of amorphous carbon. Graphene is a crystalline material with virtually no phase or amplitude contrast and unparalleled, high electrical carrier mobility. However, the hydrophobic properties of graphene have prevented its routine application in Cryo-TEM. This Letter reports a method for rendering graphene TEM supports hydrophilic—a convenient approach maintaining graphene's structural and electrical properties based on non-covalent, aromatic functionalization
[en] It has long been assumed that basal dislocations were responsible for the deformation of layered, crystalline solids. Herein we make the case that, with the notable exception of some metals that kink, ripplocations - not basal dislocations - are the operative micromechanism. The reasons are: i) clear evidence for c-axis strain at multiple length scales including in transmission electron microscopy images; ii) strong influence of confining pressure on the compressive strengths of poly-, and especially single crystals; iii) ripplocations are a topological imperative if the layers are to move relative to each other, without breaking the in-plane bonds.
[en] Highlights: • No evidence for a dose-rate driven contrast reduction in HRTEM was found. • Experiments at high and medium dose rates do not show any dose-rate dependence. • Robust results for very low dose rates are missing. - Abstract: In a recent article  we examined the influence of the applied electron dose rate on the magnitude of the image contrast in high-resolution transmission electron microscopy (HRTEM). We concluded that the magnitude of the image contrast is not substantially affected by the applied electron dose rate. This result is in obvious contradiction to numerous earlier publications by Kisielowski and coworkers [2–7], who commented our recent article due to this contradiction. The present short communication is a response to the comment of Kisielowski and coworkers on our recent article, where we provide additional arguments supporting our initial findings and conclusions on the magnitude of the image contrast in HRTEM.
[en] Microscopic protrusions are shown to emerge from the Pd subsurface D-ion implanted at liquid-nitrogen temperature. Cross-sectional transmission electron microscopy has revealed that the protrusions were amorphous, suggesting that they were in a molten state during D-ion implantation. The amorphous area of the protrusion was commonly covered with a crystalline shell, the lattice of which expanded from the pure Pd lattice by around 5% that is in an agreement with previous works. The shell might have been of a deuteride structure stable in low-pressure ambiences.
[en] In the current work, we showed the synthesis of AuNPs using leaf extract of T. coriacea. The as prepared AuNPs were studied using microscopic and spectroscopic techniques. The absorption peaks of AuNPs were detected at 533 nm, which is a typical SPR peak for AuNPs, which also authenticates their successful preparation. TEM images confirmed that the size of prepared AuNPs were found to be in the range of 50–60 nm. Further, the T. coriacea extract in combination with AuNPs were studied for their anti-nociceptive activity in the rat model. The results of anti-nociceptive activity showed that the inhibition of glutamate treated paw licking in rats is higher in the combination of T. coriacea extract plus AuNPs when compared to pure T. coriacea extract indicating the enhanced inhibitory effect of AuNPs, which also indicates their future use in pain management. (paper)
[en] Cupriavidus metallidurans strain Ch34 (previously known as Ralstonia metallidurans, Ralstonia eutropha, and Alcaligenes eutrophus) is an ideal subject to study heavy metal disturbance of cellular processes. Moreover, the capacity of C. metallidurans Ch34 for in situ bioremediation was assessed and proved to be feasible on pilot scale. In this work, the molecular and physiological response to strontium cations (Sr2+) by C.metallidurans Ch34 was studied. Results showed that C. metallidurans Ch34 resisted to high concentrations of Sr (120 m M) and that this resistance is not linked to the presence of its 2 large plasmid pMOL30 or pMOL28. During this study, a tctCBA-dependent tripartite tricarboxylate transport (TTT) system in strain Ch34 was discovered. Transmission Electron Microscopy (TEM) observation of C.metallidurans challenged with strontium confirms the precipitation of Sr2+) directly onto the surface of cells, inside and in the microenvironment around the cells. These results highlight the potential of C. metalliduras Ch34 to endure environmental extremes and suggest that in situ bioremediation of Sr-containing waste with Ch34 might be feasible.
[en] Mitochondria play essential roles in both energy metabolism and cell signaling, which are critical for cell survival. Although significant efforts have been invested in understanding mitochondrial biology, methods for intact mitochondria preparation are technically challenging and remain to be improved. New methods for heterogeneous mitochondria purification will therefore boost our understanding on their physiological and biophysical properties. Herein, we developed a novel recycling free-flow isoelectric focusing (RFFIEF) with post-pH gradient sample injection (post-PGSI) for preparative separation of mitochondria. Crude mitochondria of rabbit liver obtained from differential centrifugation were purified by the developed method according to their pI values as six fractions. Transmission electron microscope images revealed that intact mitochondria existed in two fractions of pH 6.24 and 6.61, degenerative mitochondria were in two fractions of pH 5.46 and 5.72, and inner membrane vesicles (IMVs) appeared in the fractions of pH 4.70 and 5.04. Membrane potential measurement proved a dramatic difference between intact mitochondria and IMVs, which reflected the bioactivity of obtained populations. Particularly, proteomics analyses revealed that more number of proteins were identified in the intact fractions than that of IMVs or crude mitochondria, which demonstrated that RFFIEF could be powerful tool for the preparation of intact organelle as well as their proteomic and in-depth biological analysis. - Highlights: • Mitochondrial subpopulation was successfully separated according to their pIs via the developed RFFIEF method. • The post-PGSI method was introduced for the first time to achieve higher recovery of intact mitochondria. • Quick preparation of mitochondria subpopulation via the developed RFFIEF for both pI determination and downstream research.
[en] The effect of postgrowth rapid thermal annealing (RTA) on GaAs proximity-capped structures with self-assembled InAs/GaAs quantum dots (QDs) is investigated using transmission electron microscopy (TEM) and photoluminescence (PL). As can be seen from the TEM images, QDs increase their lateral sizes with increasing annealing temperature (up to 700 C). QDs cannot be distinguished after RTA at temperature 800 C or higher, and substantial thickening of the wetting layer can be seen instead. The main PL peak blueshifts as a result of RTA. We propose that in the as-grown sample as well, as in samples annealed at temperatures up to 700 C, the peak is due to the QDs. After RTA at 800 C and higher the PL peak is due to a modified wetting layer. Relatively fast dissolution of QDs is explained in terms of strain-induced lateral Ga/In interdiffusion. It is proposed that such a process may be of importance in proximity-capped RTA, when no group-III vacancy formation takes place at the sample/capping interface