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Labeling Studies (labeling + studies)

Distribution by Scientific Domains

Chemistry	75%

Selected Abstracts

Differential effects of arachidonoyl trifluoromethyl ketone on arachidonic acid release and lipid mediator biosynthesis by human neutrophils

FEBS JOURNAL, Issue 15 2002
Evidence for different arachidonate pools
The goal of this study was to determine the effects of a putative specific cytosolic phospholipase A2 inhibitor, arachidonyl trifluoromethyl ketone (AACOCF3), on arachidonic acid (AA) release and lipid mediator biosynthesis by ionophore-stimulated human neutrophils. Initial studies indicated that AACOCF3 at concentrations 0,10 µm did not affect AA release from neutrophils. In contrast, AACOCF3 potently inhibited leukotriene B4 formation by ionophore-stimulated neutrophils (IC50 , 2.5 µm). Likewise, AACOCF3 significantly inhibited the biosynthesis of platelet activating factor. In cell-free assay systems, 10 µm AACOCF3 inhibited 5-lipoxygenase and CoA-independent transacylase activities. [3H]AA labeling studies indicated thatthe specific activities of cell-associated AA mimicked that of leukotriene B4 and PtdCho/PtdIns, while the specific activities of AA released into the supernatant fluid closely mimicked that of PtdEtn. Taken together, these data argue for the existence of segregated pools of arachidonate in human neutrophils. One pool of AA is linked to lipid mediator biosynthesis while another pool provides free AA that is released from cells. Additionally, the data suggest that AACOCF3 is also an inhibitor of CoA-independent transacylase and 5-lipoxygenase. Thus, caution should be exercised in using AACOCF3 as an inhibitor of cytosolic phospholipase A2 in whole cell assays because of the complexity of AA metabolism. [source]

Insertion of Molecular Oxygen in Transition-Metal Hydride Bonds, Oxygen-Bond Activation, and Unimolecular Dissociation of Metal Hydroperoxide Intermediates.

HELVETICA CHIMICA ACTA, Issue 3 2008
Short Communication
Abstract Thermal activation of molecular oxygen is observed for the late-transition-metal cationic complexes [M(H)(OH)]+ with M=Fe, Co, and Ni. Most of the reactions proceed via insertion in a metalhydride bond followed by the dissociation of the resulting metal hydroperoxide intermediate(s) upon losses of O, OH, and H2O. As indicated by labeling studies, the processes for the Ni complex are very specific such that the O-atoms of the neutrals expelled originate almost exclusively from the substrate O2. In comparison to the [M(H)(OH)]+ cations, the ionmolecule reactions of the metal hydride systems [MH]+ (M=Fe, Co, Ni, Pd, and Pt) with dioxygen are rather inefficient, if they occur at all. However, for the solvated complexes [M(H)(H2O)]+ (M=Fe, Co, Ni), the reaction with O2 involving OO bond activation show higher reactivity depending on the transition metal: 60% for the Ni, 16% for the Co, and only 4% for the Fe complex relative to the [Ni(H)(OH)]+/O2 couple. [source]

Effects of axotomy on telomere length, telomerase activity, and protein in activated microglia

JOURNAL OF NEUROSCIENCE RESEARCH, Issue 2 2005
Barry E. Flanary
Abstract The adult central nervous system (CNS) is generally thought of as a postmitotic organ. However, DNA labeling studies have shown that one major population of nonneuronal cells, called microglia, retain significant mitotic potential. Microglial cell division is prominent during acute CNS injury involving neuronal damage or death. Prior work from this laboratory has shown that purified microglia maintained in vitro with continual mitogenic stimulation exhibit telomere shortening before entering senescence. In the current study, we sought to investigate whether telomere shortening occurs in dividing microglia in vivo. For this purpose, we used a nerve injury model that is known to trigger localized microglial proliferation in a well-defined CNS region, the facial motor nucleus. Adult Sprague-Dawley rats underwent facial nerve axotomy, and facial motor nuclei were microdissected after 1, 4, 7, and 10 days. Whole tissue samples were subjected to measurements of telomere length, telomerase activity, and telomerase protein. Results revealed a tendency for all of these parameters to be increased in lesioned samples. In addition, microglial cells isolated directly from axotomized facial nuclei with fluorescence-activated cell sorting (FACS) showed increased telomerase activity relative to unoperated controls, suggesting that microglia are the primary cell type responsible for the increases observed in whole tissue samples. Overall, the results show that microglia activated by injury are capable of maintaining telomere length via telomerase during periods of high proliferation in vivo. We conclude that molecular mechanisms pertaining to telomere maintenance are active in the injured CNS. © 2005 Wiley-Liss, Inc. [source]

Primary events in dim light vision: a chemical and spectroscopic approach toward understanding protein/chromophore interactions in rhodopsin

THE CHEMICAL RECORD, Issue 2 2004
Nathan Fishkin
The visual pigment rhodopsin (bovine) is a 40,kDa protein consisting of 348 amino acids, and is a prototypical member of the subfamily A of G protein-coupled receptors (GPCRs). This remarkably efficient light-activated protein (quantum yield = 0.67) binds the chromophore 11- cis -retinal covalently by attachment to Lys296 through a protonated Schiff base. The 11- cis geometry of the retinylidene chromophore keeps the partially active opsin protein locked in its inactive state (inverse agonist). Several retinal analogs with defined configurations and stereochemistry have been incorporated into the apoprotein to give rhodopsin analogs. These incorporation results along with the spectroscopic properties of the rhodopsin analogs clarify the mode of entry of the chromophore into the apoprotein and the biologically relevant conformation of the chromophore in the rhodopsin binding site. In addition, difference UV, CD, and photoaffinity labeling studies with a 3-diazo-4-oxo analog of 11- cis -retinal have been used to chart the movement of the retinylidene chromophore through the various intermediate stages of visual transduction. © 2004 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 4: 120,135; 2004: Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/tcr.20000 [source]