143 research outputs found

    Homing in Pigeons with Impaired Vision

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    Nanoformulation of the Superoxide Dismutase Mimic, MnTnBuOE-2-PyP5+, Prevents its Acute Hypotensive Response

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    Scavenging superoxide (O2•-) via overexpression of superoxide dismutase (SOD) or administration of SOD mimics improves outcomes in multiple experimental models of human disease including cardiovascular disease, neurodegeneration, and cancer. While few SOD mimics have transitioned to clinical trials, MnTnBuOE-2-PyP5+ (BuOE), a manganese porphyrin SOD mimic, is currently in clinical trials as a radioprotector for cancer patients; thus, providing hope for the use of SOD mimics in the clinical setting. However, BuOE transiently alters cardiovascular function including a significant and precipitous decrease in blood pressure. To limit BuOE\u27s acute hypotensive action, we developed a mesoporous silica nanoparticle and lipid bilayer nanoformulation of BuOE (nanoBuOE) that allows for slow and sustained release of the drug. Herein, we tested the hypothesis that unlike native BuOE, nanoBuOE does not induce an acute hypotensive response, as the nanoformulation prevents BuOE from scavenging O2•- while the drug is still encapsulated in the formulation. We report that intact nanoBuOE does not effectively scavenge O2•-, whereas BuOE released from the nanoformulation does retain SOD-like activity. Further, in mice, native BuOE, but not nanoBuOE, rapidly, acutely, and significantly decreases blood pressure, as measured by radiotelemetry. To begin exploring the physiological mechanism by which native BuOE acutely decreases blood pressure, we recorded renal sympathetic nerve activity (RSNA) in rats. RSNA significantly decreased immediately following intravenous injection of BuOE, but not nanoBuOE. These data indicate that nanoformulation of BuOE, a SOD mimic currently in clinical trials in cancer patients, prevents BuOE\u27s negative side effects on blood pressure homeostasis

    Pore size engineering of mesoporous silicon nitride materials

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    Nitrogen physisorption measurements of silicon nitride materials obtained from silicon diimide show the valuable porosity of these compounds in the mesopore regime and very high specific surface areas up to 1000 m(2) g(-1), suitable for catalytic applications. The pore size of the solids is effectively tailored by the variation of parameters in the manufacture of the diimide source. Si(NH)(2) is obtained by reacting silicon halides with gaseous ammonia in an organic solvent followed by sublimation of the by-products in an ammonia flow at elevated temperatures (773-1273 K). The nature of the solvent, halide source and precipitation temperature strongly affect the average pore size and specific surface area of the product. The pore size can be adjusted in a range from 5.6 to 9.1 nm, as derived from nitrogen physisorption isotherms. The elemental composition of the porous nitrides varies from Si2N2(NH) to Si3N4 and depends on the temperature of the heat treatment. IR measurements indicate a high number of amino groups present on the inner surface of the solids, suitable for further functionalization. The materials are amorphous according to XRD powder patterns and show broad Si-29 MAS NMR lines. The low sintering tendencies in vacuum, ammonia and under ammonothermal conditions are essential for development of the compounds as high temperature catalysts
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