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Vicki J Bennett

Publications and source records attributed to Vicki J Bennett.

5 recordsLinked to original sources
PubMed2006

Nitric oxide inhibits mitochondrial movement in forebrain neurons associated with disruption of mitochondrial membrane potential.

Nitric oxide (NO) has a number of physiological and pathophysiological effects in the nervous system. One target of NO is the mitochondrion, where it inhibits respiration and ATP synthesis, which may contribute to NO-mediated neuronal injury. Our recent studies suggested that impaired mitochondrial function impairs mitochondrial trafficking, which could also contribute to neuronal injury. Here, we studied the effects of NO on mitochondrial movement and morphology in primary cultures of forebrain neurons using a mitochondrially targeted enhanced yellow fluorescent protein. NO produced by two NO donors, papa non-oate and diethylamine/NO complex, caused a rapid cessation of mitochondrial movement but did not alter morphology. Movement recovered after removal of NO. The effects of NO on movement were associated with dissipation of the mitochondrial membrane potential. Increasing cGMP levels using 8-bromoguanosine 3',5'-cyclic monophosphate, did not mimic the effects on mitochondrial movement. Furthermore, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), an inhibitor of NO-induced activation of soluble guanylate cyclase, did not block the effects of NO. Thus, neither increasing nor decreasing cGMP levels had an effect on mitochondrial movement. Based on these data, we conclude that NO is a novel modulator of mitochondrial trafficking in neurons, which may act through the inhibition of mitochondrial function.

Animals↗
PubMed2003

Probing the binding pocket and endocytosis of a G protein-coupled receptor in live cells reported by a spin-labeled substance P agonist.

To probe the molecular nature of the binding pocket of a G protein-coupled receptor and the events immediately following the binding and activation, we have modified the substance P peptide, a potent agonist for the neurokinin-1 receptor, with a nitroxide spin probe specifically attached at Lys-3. The agonist properties and binding affinity of the spin-labeled substance P are similar to the native peptide. Using electron paramagnetic resonance (EPR) spectroscopy, the substance P analogue is capable of reporting the microenvironment found in the binding pocket of the receptor. The EPR spectrum of bound peptide indicates that the Lys-3 portion of the agonist is highly flexible. In addition, we detect a slight increase in the mobility of the bound peptide in the presence of a non-hydrolyzable analogue of GTP, indicative of the alternate conformational states described for this class of receptor. The down-regulation of neurokinin-tachykinin receptors is accomplished by a rapid internalization of the activated protein. Thus, it was also of interest to establish whether spin-labeled substance P could serve as a real time reporter for endocytosis. Our findings show the receptor agonist is efficiently endocytosed and the loss of EPR signal upon internalization provides a real time monitor of endocytosis. The rapid loss of signal suggests that endosomal trafficking vesicles maintain a reductive environment. Whereas the reductive capacity of the lysosome has been established, our findings indicate this capacity in early endosomes as well.

Animals↗
PubMed2003

Comparison of carbon dioxide and iodinated contrast for cavography prior to inferior vena cava filter placement.

BACKGROUND: The use of iodinated contrast in the critically ill trauma patient has been associated with the development of acute renal failure. The low incidence of nephrotoxicity associated with carbon dioxide (CO(2)) makes it an ideal contrast agent for cavography. However, the use of CO(2) has been limited, because reportedly it underestimates the diameter of the inferior vena cava (IVC). METHODS: During a 6-month period (January 2000 through June 2000), 25 adult trauma patients required IVC filter placement. Bedside cavagrams using CO(2) followed by iodinated contrast were employed to determine the diameter of the IVC and the anatomy of the renal veins. RESULTS: Using CO(2) injection for cavography, we were able to determine the diameter of the IVC and the anatomy of the renal veins in all patients. Furthermore, when CO(2) cavography was compared with the results obtained with iodinated contrast, the difference in diameter of the IVC was within 1 mm. CONCLUSIONS: Based on these data, it was determined that CO(2) cavagrams accurately reflect the diameter of the IVC and the anatomy of the renal veins. Additionally, CO(2) cavagrams can be safely performed in the intensive care unit during bedside placement of IVC filters.

Adolescent↗
PubMed2001

Analysis of fluorescently labeled substance P analogs: binding, imaging and receptor activation.

BACKGROUND: Substance P (SP) is a peptide neurotransmitter found in central and peripheral nerves. SP is involved in the control of smooth muscle, inflammation and nociception. The amino acid sequence of SP is Arg-Pro-Lys-Pro-Gln-Gln-Phe-Phe-Gly-Leu-Met-NH2. Five different forms of fluorescently labeled SP have recently been synthesized, in which Alexa 488, BODIPY Fl, fluorescein, Oregon Green 488 or tetramethylrhodamine has been covalently linked to SP at Lys3. Here, these novel analogs are characterized as to their ligand binding, receptor activation and fluorescence labeling properties. RESULTS: Competition binding studies, using radiolabeled [125I] SP, revealed that all of the labeled forms of SP, except for Alexa 488-SP, effectively competed with radiolabeled SP for binding at the rat SP receptor. With the exception of Alexa 488-SP, all of the SP analogs produced Ca++ elevations and fluorescence labeling of the SP receptor expressed in Chinese hamster ovary cells. In SP-responsive neurons, BODIPY Fl-SP and Oregon Green 488-SP were as effective as unlabeled SP in producing a reduction of the M-type K+ current. Fluorescein-SP produced variable results, while tetramethylrhodamine-SP was less potent and Alexa 488-SP was less effective on intact neurons. CONCLUSIONS: The above results show that fluorescent labeling of SP altered the biological activity and the binding properties of the parent peptide. Oregon Green 488 and BODIPY FL-SP are the most useful fluorophores for labeling SP without affecting its biological activity. Given these results, these probes can now be utilized in further investigations of the mechanisms of SPR function, including receptor localization, internalization and recycling.

Journal Article↗