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Shoup, Timothy

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Shoup

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Timothy

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Shoup, Timothy
Author's Publications: search.filters.isAuthorOfPublication.e45a0ba8-2b0d-495e-8135-96a658d37485

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    Quantitative in vivo mapping of myocardial mitochondrial membrane potential
    (Public Library of Science, 2018) Alpert, Nathaniel; Guehl, Nicolas; Ptaszek, Leon; Pelletier-Galarneau, Matthieu; Ruskin, Jeremy; Mansour, Moussa; Wooten, Dustin; Ma, Chao; Takahashi, Kazue; Zhou, Yun; Shoup, Timothy; Normandin, Marc; El Fakhri, Georges
    Background: Mitochondrial membrane potential (ΔΨm) arises from normal function of the electron transport chain. Maintenance of ΔΨm within a narrow range is essential for mitochondrial function. Methods for in vivo measurement of ΔΨm do not exist. We use 18F-labeled tetraphenylphosphonium (18F-TPP+) to measure and map the total membrane potential, ΔΨT, as the sum of ΔΨm and cellular (ΔΨc) electrical potentials. Methods: Eight pigs, five controls and three with a scar-like injury, were studied. Pigs were studied with a dynamic PET scanning protocol to measure 18F-TPP+ volume of distribution, VT. Fractional extracellular space (fECS) was measured in 3 pigs. We derived equations expressing ΔΨT as a function of VT and the volume-fractions of mitochondria and fECS. Seventeen segment polar maps and parametric images of ΔΨT were calculated in millivolts (mV). Results: In controls, mean segmental ΔΨT = -129.4±1.4 mV (SEM). In pigs with segmental tissue injury, ΔΨT was clearly separated from control segments but variable, in the range -100 to 0 mV. The quality of ΔΨT maps was excellent, with low noise and good resolution. Measurements of ΔΨT in the left ventricle of pigs agree with previous in in-vitro measurements. Conclusions: We have analyzed the factors affecting the uptake of voltage sensing tracers and developed a minimally invasive method for mapping ΔΨT in left ventricular myocardium of pigs. ΔΨT is computed in absolute units, allowing for visual and statistical comparison of individual values with normative data. These studies demonstrate the first in vivo application of quantitative mapping of total tissue membrane potential, ΔΨT.
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    Mannose-Binding Lectin Binds to Amyloid \(\beta\) Protein and Modulates Inflammation
    (Hindawi Publishing Corporation, 2012) Larvie, Mykol; Shoup, Timothy; Chang, Wei-Chuan; Chigweshe, Lorencia; Hartshorn, Kevan; White, Mitchell R.; Stahl, Gregory L.; Elmaleh, David; Takahashi, Kazue
    Mannose-binding lectin (MBL), a soluble factor of the innate immune system, is a pattern recognition molecule with a number of known ligands, including viruses, bacteria, and molecules from abnormal self tissues. In addition to its role in immunity, MBL also functions in the maintenance of tissue homeostasis. We present evidence here that MBL binds to amyloid \(\beta\) peptides. MBL binding to other known carbohydrate ligands is calcium-dependent and has been attributed to the carbohydrate-recognition domain, a common feature of other C-type lectins. In contrast, we find that the features of MBL binding to A\(\beta\) are more similar to the reported binding characteristics of the cysteine-rich domain of the unrelated mannose receptor and therefore may involve the MBL cysteine-rich domain. Differences in MBL ligand binding may contribute to modulation of inflammatory response and may correlate with the function of MBL in processes such as coagulation and tissue homeostasis.