Metformin Protects against NMDA-Induced Retinal Injury through the MEK/ERK Signaling Pathway in Rats

Metformin, an anti-hyperglycemic drug of the biguanide class, exerts positive effects in several non-diabetes-related diseases. In this study, we aimed to examine the protective effects of metformin against N-methyl-D-aspartic acid (NMDA)-induced excitotoxic retinal damage in rats and determine the mechanisms of its protective effects. Male Sprague–Dawley rats (7 to 9 weeks old) were used in this study. Following intravitreal injection of NMDA (200 nmol/eye), the number of neuronal cells in the ganglion cell layer and parvalbumin-positive amacrine cells decreased, whereas the number of CD45-positive leukocytes and Iba1-positive microglia increased. Metformin attenuated these NMDA-induced responses. The neuroprotective effect of metformin was abolished by compound C, an inhibitor of AMP-activated protein kinase (AMPK). The AMPK activator, AICAR, exerted a neuroprotective effect in NMDA-induced retinal injury. The MEK1/2 inhibitor, U0126, reduced the neuroprotective effect of metformin. These results suggest that metformin protects against NMDA-induced retinal neurotoxicity through activation of the AMPK and MEK/extracellular signal-regulated kinase (ERK) signaling pathways. This neuroprotective effect could be partially attributable to the inhibitory effects on inflammatory responses.     

Double Charge Polarity Switching in Sb-Doped SnSe with Switchable Substitution Sites

Tin mono-selenide (SnSe) is one of the most promising thermoelectric materials; however, it experiences difficulty in controlling the carrier polarity, which is inevitable for realizing p-n homojunction devices. Herein, double switching of charge polarity in (Sn_1−xSb_x)Se by varying x is reported; pure SnSe shows p-type conduction, whereas the polarity of (Sn_1−xSb_x)Se switches to n-type conduction for 0.005 < x < 0.05, and then re-switches to p-type conduction for x > 0.05. The major Sb substitution site switches from the Se (Sb_Se) to Sn site (Sb_Sn) with increasing x. Sb_Sn (Sb³⁺ at Sn²⁺) works as a donor, but Sb_Se (Sb³⁻ at Se²⁻) does not produce a hole because of the Sb–Sb dimer formation. The mechanism of double polarity switching is explained by native p-type conduction in pure SnSe due to Sn-vacancy formation, whereas (Sn_1−xSb_x)Se exhibits n-type behavior due to conduction through the Sb_Se impurity band formed above the valence band maximum, and finally re-switches to weak p-type, where the Fermi level approaches the midgap level between the Sb_Se band and conduction band minimum. Clarification of the Sb doping mechanism will provide a crucial guide for developing more sophisticated doping routes for SnSe and high-performance energy-related devices.     

Electroplastic behavior of doped poly(3-hexylthiophene)

Dynamic viscoelasticity of poly(3-hexylthiophene) (P3HT) doped with iodine or FeCI₃ under the influence of electric fields was studied. The doped P3HTs underwent a large decrease in elastic modulus under small electric fields on the order of 1 dc V/mm. The electric fields enhanced the loss tangent. The glass transition temperature decreased as the intensity of the applied fields was increased. This electroplastic behavior was observed also in ac excitation of less than 1 kHz. It was detected in both crystalline and amorphous P3HTs. Joule heating was a main process in the electroplastic behavior of doped P3HTs. We measured FTIR and X-ray diffraction spectra under electric fields to examine the possibility of other processes. The X-ray diffraction analysis suggested a possibility of another process caused by the formation of intraplanar packing of thiophene rings. © 1996 John Wiley & Sons, Inc.     

Chemical reaction between lead-free multicomponent alkali borosilicate glass frit and hematite during heat treatment

A mixture of a lead-free multicomponent alkali borosilicate glass frit containing zinc ions and hematite was heat-treated under various conditions to elucidate the reaction between the two components, which is essentially important for controlling the color of red overglaze enamels. Above the glass transition temperature, the interaction between the frit fluid and hematite was evident, as the viscosity of the frit decreased. Moreover, hematite dissolved, the iron ions diffused into the glass matrix and they precipitated on residual hematite, resulting in enhanced crystal growth through Ostwald ripening. Concurrently, the iron and zinc ions reacted to form zinc ferrite. During cooling, the supersaturated iron ions were consumed for precipitation of hematite and zinc ferrite. Because frit and hematite dramatically react during heat treatment, conventional modification of hematite alone is insufficient. Development of the frit exhibiting low reactivity toward hematite through precise control of physical properties is a future challenging issue.     

Possible involvement of IFNT in lymphangiogenesis in the corpus luteum during the maternal recognition period in the cow

The corpus luteum (CL), which secretes large amounts of progesterone and is thus essential for establishing pregnancy, contains various types of immune cells that may play essential roles in CL function by generating immune responses. The lymphatic system is the second circulation system and is necessary for immune function, but the lymphatic system of the bovine CL has not been characterized in detail. We collected bovine CLs on days 12 and 16 of the estrous cycle (C12 and C16) and days 16 and 40 of early pregnancy (P16 and P40). Lymphatic endothelial hyaluronan receptor 1 (LYVE1) protein was detected in the CL by immunohistochemistry and western blotting and increased at P40 compared with C16. The mRNA expression levels of lymphangiogenic factors, such as vascular endothelial growth factor-C (VEGFC), VEGFD, and their common receptor VEGFR3, as well as the lymphatic endothelial cell (LyEC) marker podoplanin, increased in P16 and P40 CLs. Thus, it is suggested that the lymphatic system of the bovine CL reconstitutes during early pregnancy. Interferon tau (IFNT) from the conceptus in the uterus is a candidate for activating luteal lymphangiogenesis during the maternal recognition period (MRP). We found that treatment of LyECs isolated from internal iliac lymphatic vessels with IFNT stimulated LyEC proliferation and significantly increased mRNA expression of VEGFC and IFN-stimulated gene 15. Moreover, both IFNT and VEGFC induced LyECs to form capillary-like tubes in vitro. In conclusion, it is suggested that new lymphangiogenesis in the bovine CL begins during the MRP and that IFNT may mediate this novel phenomenon.     

Construction of an in vitro model system for the anatomical reentry phenomenon of cardiac tissues by using microfabrication techniques

Anatomical reentry has been identified as a major cause of clinical cardiac arrhythmia. The probability for anatomical reentry is strongly dependent on the structures and cell characteristics of the causal cardiac regions. In this paper, we propose a simple in vitro model system for analyzing and simulating the anatomical reentry phenomenon in cardiac tissues. Rat ventricular myocytes were cultured and aligned in predesigned structures by using a microcontact printing method. Excitation propagation in the cultures was visualized and evaluated by applying electrical stimulation and the calcium imaging technique. We confirmed that differences between passage times along the two excitation pathways were modulated by changing the structures of cultured myocytes. This simple in vitro model system will be useful for studying the anatomical reentry phenomenon. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Role of boric acid for a poly (vinyl alcohol) film as a cross-linking agent: Melting behaviors of the films with boric acid

We have investigated the role of boric acid as a cross-linking agent for a poly (vinyl alcohol) (PVA) film when the film is immersed in boric acid aqueous solution. DSC results show that the films with boric acid exhibit the higher glass transition temperatures than that of the PVA film without boric acid, when the films are dried after immersing in boric acid aqueous solutions with various boric acid concentrations, implying that boric acid penetrating into the films slows down the PVA molecular motion. Furthermore, simultaneous small-angle X-ray scattering and wide-angle X-ray diffraction measurements were performed on the melting processes of the PVA films with boric acid. We found that the crystallite size increase originated from melting and recrystallization do not occur for the PVA films with boric acid, whereas in the case of the PVA without boric acid the crystallite size is enlarged in both directions parallel and perpendicular to the chain axis via melting and recrystallization on melting. These indicate that chemical reactions of boric acid to the PVA molecular chains in amorphous regions resulted in cross-linking points take place in boric acid aqueous solutions, inhibiting recrystallization on melting, because the cross-links slow down the PVA molecular motion and must not be included in the crystalline domains.     

AFM observation of OMVPE grown ErP on InP (0 0 1), (1 1 1)A and (1 1 1)B substrates

ErP has been grown on InP (0 0 1), (1 1 1)A and (1 1 1)B substrates by low-pressure organometallic vapor-phase epitaxy. The morphological change with growth temperature has been explored by atomic force microscope. On all the substrates, ErP is grown in island structure. Height and area size of the ErP islands on (1 1 1)A substrate exhibit an obvious dependence on growth temperature. ErP islands grown at 540°C, that is the suitable temperature for ErP formation, gather to step edges to make wires.     

NO/CH4 reaction over nanodispersed Pt particles

The catalytic behavior of the cubic (≈70%) Pt nanoparticles supported on alumina, with an average diameter of 132 nm, was investigated for NO/CH₄ reaction. It was observed that the formation of reaction products (N₂O, CO and NH₃) is related to the size as well to the shape (facet) of the Pt nanoparticles.

     

Energy-dispersive XAFS study on the decarbonylation process of Mo(CO)6 in NaY zeolite

The temperature-programmed decarbonylation process of Mo(CO)₆ in NaY zeolite was studied by means of a time-resolved energy-dispersive XAFS method. The XANES analysis demonstrated that the decarbonylation proceeded by two successive steps via a stable intermediate which existed between 440 and 490 K. The curve fitting analysis of the EXAFS data revealed that the intermediate was a molybdenum monomer subcarbonyl species Mo(CO)₃(O_L)₃ coordinated by three CO ligands and three oxygen atoms of zeolite framework (O_L). Molybdenum dimer subcarbonyl species were not observed. This study demonstrated that the DXAFS technique is a powerful method to study the dynamic behavior of the Mo carbonyl species during decarbonylation process.