Publications by authors named "T D Hexum"

Adenosine triphosphate (ATP) is coreleased with catecholamines from adrenal medullary chromaffin cells in response to sympathetic nervous system stimulation and may regulate these cells in an autocrine or paracrine manner. Increases in extracellular signal-regulated kinase (ERK) 1/2 phosphorylation were observed in response to ATP stimulation of bovine chromaffin cells. The signaling pathway involved in ATP-mediated ERK1/2 phosphorylation was investigated via Western blot analysis.

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ATP and neuropeptide Y (NPY) are examples of agents co-secreted with catecholamines from neuronal and neuroendocrine cells which may regulate the function of the cells from which they are released. For example, ATP and NPY could influence chromaffin cell activity in an autocrine or paracrine manner. The primary recognized function of chromaffin cells is the synthesis and secretion of catecholamines; therefore, we hypothesize that ATP and NPY can regulate catecholamine synthesis in chromaffin cells.

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Mononuclear phagocyte (macrophages and microglia) dysfunction plays a significant role in the pathogenesis of human immunodeficiency virus (HIV) associated dementia (HAD) through the production and release of soluble neurotoxic factors including glutamate. The mechanism of glutamate regulation by HIV-1 infection remains unclear. In this report, we investigated whether the enzyme glutaminase is responsible for glutamate generation by HIV-1 infected monocyte-derived macrophages.

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Neuropeptide Y (NPY) enhances ATP-stimulated inositol phosphate (InsP) formation in bovine chromaffin cells through an unknown mechanism. Chromaffin cells were transduced with the carboxyl terminus of beta-adrenergic receptor kinase 1 (betaARK1CT), a Gbetagamma subunits scavenger, using a recombinant adenovirus system. The adenovirus also expresses a green fluorescent protein (GFP) which serves as an index of transduction.

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Bovine chromaffin cells contain an ecto-ATPase (K(m)=1.57 +/- 0.27 x 10(-4) M) which can hydrolyze ATP present in the culture media.

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