Enlarged Junctions Research Articles

Effect of miR-26b on gestational diabetes mellitus in rats via PI3K/Akt signaling pathway.

The aim of this study was to explore the influence of micro ribonucleic acid (miR)-26b on gestational diabetes mellitus in rats via the phosphatidylinositol 3-hydroxy kinase/protein kinase B (PI3K/Akt) signaling pathway. A total of 60 healthy pregnant female rats were randomly divided into three groups, including group A (normal group), group B (model group), and group C (model + miR-26b group). The differences in fasting blood glucose (FBG), C-reactive protein (CRP), and phosphatidylinositol 3-hydroxy kinase/protein kinase B (PI3K/AKT) among the three groups were analyzed via serum CRP test, morphological observation, quantitative Reverse Transcription-Polymerase Chain Reaction (qRT-PCR), and Western blotting, respectively. The levels of FBG ad CRP were significantly up-regulated in group B when compared with group A (p<0.01). Meanwhile, they increased significantly in group C when compared with group B (p<0.01). Rats in group A exhibited smooth and flat thoracic aortic intimas, as well as neatly arranged smooth muscle cells at the media layer. However, rats in group B showed fractured intimas with enlarged junction gaps, as well as necrotic and detached endothelial cells. Compared with group B, group C exhibited extremely poorly arranged cells at all the layers, rough and rugged intimas, larger areas of necrotic and detached endothelial cells, and markedly worsened lesions. QRT-PCR results indicated that the expression of phosphorylated-PI3K (p-PI3K) was significantly lower in group B than that of group A (p=0.04). Meanwhile, it was markedly lower in group C than that in group B (p=0.04). The expression of p-Akt was remarkably lower in group B than group A (p=0.04), which was also significantly lower in group C than group B (p=0.04). Compared with group A, the expressions of p-PI3K and p-Akt in the thoracic aorta of group B were evidently down-regulated (p<0.01). Furthermore, they decreased markedly in group C when compared with group B (p<0.01). MiR-26b accelerates the progression of gestational diabetes by inhibiting the PI3K/Akt signaling pathway.

An approach to the electronic structure of molecular junctions with metal clusters of atomic thickness.

TD-DFT calculations predict a linear dependence of the energies of charge transfer states of Agn-pyrazine-Agn molecular junctions on the inverse of the size (1/n) of the linear metal chains. The density of charge (qeff = q/n) in the metal-to-metal charge transfer excited states (CTMM: Agnq-pyrazine-Agn-q) smoothly tunes the electronic structure of the junction, especially the metal-to-molecule charge transfer states (CT0 and CT1) and the first excited singlet of pyrazine (S1,Pz). In enlarged junctions, pyrazine bonds preferably to one of the Agn clusters and this weak adsorption produces a significant unexpected asymmetry for forward and reverse charge transfer processes.

Comparative experimental and simulative investigations of radial p–n junction Si microwire array solar cells

We carried out experimental and simulative investigations of the electrical and optical characteristics of radial p–n junction Si microwire (MW) array solar cells (diameter: 4μm, height: 12μm, and period: 12μm) prepared by electroless etching (EE) methods. Due to its unique geometry, the MW array had an enlarged junction area, enabling efficient carrier collection and optical reflectance in the wavelength range from 400 to 1000nm, which is lower than that of its planar counterpart. Despite these advantages, the energy conversion efficiency (CE) of the MW array solar cell (3.2%) was lower than that of a planar solar cell (4.2%). This comparative study clearly reveals the inherent potential of MW-based solar cells and the importance of extrinsic trap state control to realize low-cost, high-efficiency devices.

Three-dimensional assembly and electrical properties of Cu2O/ZnO heterojunction via an electrochemical superfilling method

Three-dimensional (3D) heterojunctions consisting of Cu2O and ZnO nanorods were assembled via the electrochemical superfilling approach. This procedure included two electrochemical steps: the initial low-temperature nucleation of Cu2O on the surface of ZnO nanorods at high cathodic overpotential and the subsequent high-temperature growth at low cathodic overpotential. The structural morphologies, electrical properties and the interface features of the 3D heterojunction were characterized with SEM observation, I–V and Mott–Schottky testing and the impedance measurement. The bottom-up growth of Cu2O in ZnO nanorod arrays was realized. The filling depth was over 4.0μm. The dense structure had good electrical contact and large forward current, but the enlarged junction area and grain boundaries produced great interface state density, which contributed to the relative lower conversion efficiency of 0.08%.

Structure–function studies of blood and air capillaries in chicken lung using 3D electron microscopy

Avian pulmonary capillaries differ from those of mammals in three important ways. The blood-gas barrier is much thinner, it is more uniform in thickness, and the capillaries are far more rigid when their transmural pressure is altered. The thinness of the barrier is surprising because it predisposes the capillaries to stress failure. A possible mechanism for these differences is that avian pulmonary capillaries, unlike mammalian, are supported from the outside by air capillaries, but the details of the support are poorly understood. To clarify this we studied the blood and air capillaries in chicken lung using transmission electron microscopy (EM) and two relatively new techniques that allow 3D visualization: electron tomography and serial block-face scanning EM. These studies show that the pulmonary capillaries are flanked by epithelial bridges composed of two extremely thin epithelial cells with large surface areas. The junctions of the bridges with the capillary walls show thickening of the epithelial cells and an accumulation of extracellular matrix. Collapse of the pulmonary capillaries when the pressure outside them is increased is apparently prevented by the guy wire-like action of the epithelial bridges. The enlarged junctions between the bridges and the walls could provide a mechanism that limits the hoop stress in the capillary walls when the pressure inside them is increased. The support of the pulmonary capillaries may also be explained by an interdependence mechanism whereby the capillaries are linked to a rigid assemblage of air capillaries. These EM studies show the supporting structures in greater detail than has previously been possible, particularly in 3D, and they allow a more complete analysis of the mechanical forces affecting avian pulmonary capillaries.

Isolation and Ultrastructural Study of the Flagellar Basal Body Complex fromRhodobacter sphaeroidesWS8 (Wild Type) and a Polyhook Mutant PG

Filament-Hook-Basal Body (FHBB) complexes were isolated from the purple non-sulphur facultative anaerobic bacteriumRhodobacter sphaeroides(WS8) by lysozyme digestion of the cells followed by an alkaline treatment and ultracentrifugation, and they were analysed by electron microscopy. The structure is composed of a filament linked through an enlarged junction to the hook and a basal body composed of L and P rings, a rod, and a less well-defined cytoplasmic ring that has evidence of additional attached structures. Hook-basal body complexes isolated from a mutant (PG) which produces an extended hook but no filament shows basal body structures identical to those of wild-type FHBBs.

Synaptic structural dynamics and aging.

Synaptic junctional areas are not immutable structures, on the contrary, they are remodelled throughout the individual's lifespan as a consequence of environmental stimulations. This adaptive capacity of the synapses is discussed from a morphological standpoint with reference to aging. In old subjects, the number of contacts and the total surface area of synaptic appositions per unit volume of tissue decrease significantly, while the average synaptic size increases at a different extent according to the CNS area taken into account. This increase in synaptic average area is due to a higher percent of a subpopulation of enlarged contacts supposed to represent either the degenerating junctional zones or a compensatory phenomenon counteracting the synaptic reduction in number. Recent studies on perforated synapses support that the enlarged junctions are possible intermediates in synaptic physiological restructuring, thus the higher percentage of this type of contacts in the old CNS may witness unaccomplished synaptic turnover cycles. Taking into account the high metabolic rate of nerve cells, an age-related impairment in energy provision at synaptic terminal regions may constitute an early and subtle alteration affecting synaptic dynamic morphology in aging.

Structural Events in the Caries Process in Enamel, Cementum, and Dentin

The structural events observed in enamel, cementum, and dentin during the caries process have been reviewed. In incipient enamel lesions, the prevailing concept of an almost intact surface layer has been seriously challenged by SEM and TEM observations demonstrating structural pathways (such as enlarged prism junctions or sheaths) from the enamel surface to the sub-surface lesion. The destruction in this latter location consisted of (1) enlarged prism junctions, (2) diffuse mineral destruction in the prism cores, and (3) destruction of the interprismatic substance. In root caries, the destruction of cementum started along junctions between calcified layers of extrinsic (Sharpey) and intrinsic collagen fibers as well as along incremental lines. Invasion of Gram-positive micro-organisms followed these enlarged junctions. Dentin caries was similar in coronal and root caries. It consisted of sclerosis of the lumens of the dentinal tubules, followed by an important gradient of demineralization of intertubular dentin and destruction of occluded tubular lumens and peritubular dentin. Bacterial penetration occurred initially in the dentinal tubules and was followed by bacterial invasion and destruction of the intertubular dentin. Various phenomena of crystalline remineralization were described in enamel and dentin. Whereas in enamel and dentin caries, an important gradient of demineralization was observed before bacterial invasion, a simultaneous destruction of the mineral and organic components seemed to occur in cementum.