Publications by authors named "Zachary D Brown"

The complex and inaccessible space radiation environment poses an unresolved risk to astronaut cardiovascular health during long-term space exploration missions. To model this risk, healthy male c57BL/6 mice aged six months (corresponding to an astronaut of 34 years) were exposed to simplified galactic cosmic ray (GCR; 5-ion sim) irradiation at the NASA Space Radiation Laboratory (NSRL) at Brookhaven National Laboratories (BNL). Multi-modal cardiovascular functional assessments performed longitudinally and terminally revealed significant impairment in cardiac function in mice exposed to GCR compared to unirradiated controls, gamma irradiation, or single mono-energetic ions (Fe or O).

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Background: Atrial fibrillation (AF) and mitral regurgitation (MR) are closely interrelated in the setting of heart failure (HF). Here we investigate the prevalence and prognostic significance of AF in patients with acute decompensated HF (ADHF) stratified by MR severity.

Methods And Results: The Atherosclerosis Risk in Communities Study investigated ADHF hospitalizations in residents greater than or equal to 55 years of age in 4 US communities.

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The generation of an experimental animal model often requires considerable investment of both time and money. Typically, investigators are interested in specific organs and when experimental animals are euthanized, tissues that are not the focus of the research project are discarded. However, the remaining tissues from these animals could provide valuable scientific information if efficient, error-proof and economical approaches to collect and biobank them were available.

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Clinically, both percutaneous and surgical approaches to deliver viral vectors to the heart either have resulted in therapeutically inadequate levels of transgene expression or have raised safety concerns associated with extra-cardiac delivery. Recent developments in the field of normothermic ex vivo cardiac perfusion storage have now created opportunities to overcome these limitations and safety concerns of cardiac gene therapy. This study examined the feasibility of ex vivo perfusion as an approach to deliver a viral vector to a donor heart during storage and the resulting bio distribution and expression levels of the transgene in the recipient post-transplant.

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Mast cells (MCs) are strategically distributed at barrier sites and prestore various immunocyte-recruiting cytokines, making them ideal targets for selective activation to treat peripheral infections. Here, we report that topical treatment with mastoparan, a peptide MC activator (MCA), enhances clearance of from infected mouse skins and accelerates healing of dermonecrotic lesions. Mastoparan functions by activating connective tissue MCs (CTMCs) via the MRGPRX2 (Mas-related G protein-coupled receptor member X2) receptor.

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Article Synopsis
  • Chemists face challenges in manipulating white phosphorus to create new organophosphorus compounds through catalytic activation and functionalization.
  • Researchers utilized Lewis acidic transition metal moieties and AuCl to react with phosphorus derivatized with a low valent germanium compound, achieving bis-functionalized products but finding monosubstituted derivatives to be more stable.
  • Monitoring decomposition through P{H} NMR spectroscopy highlights the importance of selectively activating P-P bonds to advance the development of new organophosphorus compounds.
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Two unique systems based on low-coordinate main group elements that activate P4 are shown to quantitatively release the phosphorus cage upon short exposure to UV light. This reactivity marks the first reversible reactivity of P4, and the germanium system can be cycled 5 times without appreciable loss in activity. Theoretical calculations reveal that the LUMO is antibonding with respect to the main group element-phosphorus bonds and bonding with respect to reforming the P4 tetrahedron, providing a rationale for this unprecedented activity, and suggesting that the process is tunable based on the substituents.

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The reaction of phosphine gas with a low coordinate diaryl germylene or diarylstannylene results in both oxidative addition and arene elimination at the group 14 atom. The products were characterised by (31)P NMR spectroscopy and X-ray crystallography, and represent the first P-H bond activation by a heavy group 14 element compound.

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The main themes of this review are the mechanisms of the reactions of germanium and tin analogues of carbenes with isocyanides, CO, ammonia, and related molecules. The treatment of Ge(Ar(Me6))2 (Ar(Me6) = C6H3-2,6(C6H2-2,4,6-Me3)2) with MeNC or Bu(t)NC afforded 1:1 complexes, but the increase in the electron density at germanium leads to C-H activation at the isocyanide methyl or tert-butyl substituents. For MeNC, the initial adduct formation is followed by a migratory insertion of the MeNC carbon into a Ge-C(ipso) bond of an aryl substituent.

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An experimental and DFT investigation of the mechanism of the coupling of methylisocyanide and C-H activation mediated by the germylene (germanediyl) Ge(Ar(Me6))2 (Ar(Me6) = C6H3-2,6(C6H2-2,4,6-Me3)2) showed that it proceeded by initial MeNC adduct formation followed by an isomerization involving the migratory insertion of the MeNC carbon into the Ge-C ligand bond. Addition of excess MeNC led to sequential insertions of two further MeNC molecules into the Ge-C bond. The insertion of the third MeNC leads to methylisocyanide methyl group C-H activation to afford an azagermacyclopentadienyl species.

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Reaction of the diarylgermylene Ge(Ar(Me(6)))(2) [Ar(Me(6)) = C(6)H(3)-2,6-(C(6)H(2)-2,4,6-(CH(3))(3))(2)] with tert-butyl isocyanide gave the Lewis adduct species (Ar(Me(6)))(2)GeCNBu(t), in which the isocyanide ligand displays a decreased C-N stretching frequency consistent with an n → π* back-bonding interaction. Density functional theory confirmed that the HOMO is a Ge-C bonding combination between the lone pair of electrons on the germanium atom and the C-N π* orbital of the isocyanide ligand. The complex undergoes facile C-H bond activation to produce a new diarylgermanium hydride/cyanide species and isobutene via heterolytic cleavage of the N-Bu(t) bond.

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The reactions of Ar'GaGaAr' (Ar' = C(6)H(3)-2,6-(C(6)H(3)-2,6-(i)Pr(2))(2)) with alkenes revealed the addition of two olefins per Ar'GaGaAr' under ambient conditions for ethylene, propene, 1-hexene and styrene but no reactions with more hindered or cyclic olefins.

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Objective: Monocytic zinc finger (MOZ) maintains hematopoietic stem cells and, upon fusion to the coactivator CREB-binding protein (CBP), induces acute myeloid leukemia (AML). Leukemic stem cells in AML often exhibit excessive signal-dependent activity of the transcription factor nuclear factor (NF)-kappaB. Because aberrant interaction between NF-kappaB and coactivators represents an alternative mechanism for enhancing NF-kappaB activity, we evaluated whether MOZ and MOZ-CBP cooperate with NF-kappaB to activate transcription from NF-kappaB-dependent promoters.

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