Search

Age‐related macular degeneration (AMD) is a major cause of vision loss in older adults. AMD is caused by degeneration in the macula of the retina. The retina is the highest oxygen consuming tissue in our body and is prone to oxidative damage. DNA damage is one hallmark of aging implicated in loss of organ function. Genome instability has been associated with several disorders that result in premature vision loss. We hypothesized that endogenous DNA damage plays a causal role in age‐related retinal changes. To address this, we used a genetic model of systemic depletion of expression of the DNA repair enzyme ERCC1‐XPF. The neural retina and retinal pigment epithelium (RPE) from Ercc1−/Δ mice, which models a human progeroid syndrome, were compared to age‐matched wild‐type (WT) and old WT mice. By 3‐months‐of age, Ercc1−/Δ mice presented abnormal optokinetic and electroretinogram responses consistent with photoreceptor dysfunction and visual impairment. Ercc1−/Δ mice shared many ocular characteristics with old WT mice including morphological changes, elevated DNA damage markers (γ‐H2AX and 53BP1), and increased cellular senescence in the neural retinal and RPE, as well as pathological angiogenesis. The RPE is essential for the metabolic health of photoreceptors. The RPE from Ercc1−/Δ mice displayed mitochondrial dysfunction causing a compensatory glycolytic shift, a characteristic feature of aging RPE. Hence, our study suggests spontaneous endogenous DNA damage promotes the hallmarks of age‐related retinal degeneration. [ABSTRACT FROM AUTHOR]

Rod and cone photoreceptors use similar but distinct sets of phototransduction proteins to achieve different functional properties, suitable for their role as dim and bright light receptors, respectively. For example, rod and cone visual pigments couple to distinct variants of the heterotrimeric G protein transducin. However, the role of the structural differences between rod and cone transducin [alpha] subunits (T[alpha]) in determining the functional differences between rods and cones is unknown. To address this question, we studied the translocation and signaling properties of rod T[alpha] expressed in cones and cone T[alpha] expressed in rods in three mouse strains: rod T[alpha] knockout, cone T[alpha] [GNAT2.sup.cpfl3] mutant, and rod and cone T[alpha] double mutant rd17 mouse. Surprisingly, although the rod/cone T[alpha] are only 79% identical, exogenously expressed rod or cone T[alpha] localized and translocated identically to endogenous T[alpha] in each photoreceptor type. Moreover, exogenously expressed rod or cone T[alpha] rescued electroretinogram responses (ERGs) in mice lacking functional cone or rod T[alpha], respectively. Ex vivo transretinal ERG and single-cell recordings from rd17 retinas treated with rod or cone T[alpha] showed comparable rod sensitivity and response kinetics. These results demonstrate that cone T[alpha] forms a functional heterotrimeric G protein complex in rods and that rod and cone T[alpha] couple equally well to the rod phototransduction cascade. Thus, rod and cone transducin [alpha]-subunits are functionally interchangeable and their signaling properties do not contribute to the intrinsic light sensitivity differences between rods and cones. Additionally, the technology used here could be adapted for any such homoIogue swap desired. photoreceptor | phototransduction | signaling property | translocation doi/ 10.1073/pnas.0901382106

One-dimensional-magnetic nanostructures have recently attracted much attention because of their intriguing properties that are not displayed by their bulk or particle counterparts. One of the commonly used methods for generating ID-nanostructures is based on the electrodeposition of various materials in porous membranes. This technique has been applied to fabricate metallic nanowires as arrays of wires perpendicular to the substrate. They display unique magnetic properties (e.g., anisotropic magnetization). Electrodeposition is, however, of limited use for oxide-based magnetic materials, due to the difficulty involved in the formation of oxides through electrochemical deposition. We obtained zinc ferrite nanowires inside an anodic aluminum oxide (AAO) template using a novel technology fundamentally different from electrodeposition. First, fabricated zinc ferrite nanopartiles were injected in the AAO template and then annealed in air. The process of embedding particles into the pores was assisted by the magnetic field of a permanent magnet placed under the substrate. The physical and chemical properties of these zinc ferrite nanowires have been investigated by thermogravimetric analysis, infrared, X-ray diffraction, scanning electron microscope, and superconducting quantum interference device. The nanopartiles embedded into the pores exhibited superparamagnetic behavior with the blocking temperature of 15 K. After annealing, the particles formed nanowires and the hysteresis of the annealed samples increased significantly. Index Terms--Ferrites, ferromagnetic resonance.

The agglomeration behavior of Cu and Au films each with a thickness of 5 and 50 nm, deposited on thermally grown SiO[sub 2] by dc magnetron sputtering, was investigated with scanning electron microscopy. The size of Cu islands formed by agglomeration increased with increasing annealing temperature. Also, the agglomeration of Cu films seem to follow the grain boundary grooving process. On the other hand, Au islands have an identical size at different annealing temperatures. Au films were observed to agglomerate via nucleation of voids followed by the fractal growth of voids. The fractal dimension was determined to be 1.7 indicating that the fractal growth of voids can be described with a diffusion limited aggregation model. Finally, the kinetics of agglomeration of the Au films was described with an Avrami-type equation. [ABSTRACT FROM AUTHOR]

Synthetic ferrimagnet-based spin-valve (SV) films comprising Ta 5/NiFe 2/IrMn 9/CoFe (P1) 1.5/ Ru 0.7/CoFe (P2) 3/Cu 2.8/CoFe 1.6/NiFe 3.2/Ta 5 (in nanometers) were examined with an emphasis given on understanding the interface evolution of IrMn/CoFe (P1) upon postdeposition annealing. A 300 °C, 5 h annealing resulted in 12% and 42% decreases in effective pinning field and 29% and 53% decreases in MR ratio for the bottom (B) and top (T) SV, respectively. Because both structures exhibit different thermal degradation behaviors, we were curious to uncover the underlying causes by employing various analytical methods. The column sizes of the B--SV and T--SV were about 30 and 15 nm, respectively. No major difference in the (111) crystal texture was observed. We found that the main cause was due to the interlayer diffusion of atomic constituents such as Mn, most likely through grain boundaries and IrMn/CoFe interface, where the degree of the diffusion was considerably higher for the T--SV. Due to the surface free energy differences depending on the deposition sequence, two types of SV structures behaved differently upon exposure to annealing. The B--SV featuring less grain boundaries and nonabrupt IrMn/CoFe (P1) interface could effectively impede interlayer diffusion and, as a result, exhibited less thermal degradation in MR properties. [ABSTRACT FROM AUTHOR]