Robert Powers

• Doctor of Philosophy
• University of North Georgia, United States, Dahlonega

Hypergastrinemia, induced by sustained suppression of gastric acid secretion, is associated with gastric enterochromaffin-like (ECL) cell hyperplasia and carcinoid tumor formation. We examined the effect of a selective H1-histamine antagonist, terfenadine, on gastric mucosal cell proliferation to determine whether histamine might modulate ECL cell...

With the availability of increasingly potent acid-suppressing medications, questions continue to rise concerning the safety of these compounds in regards to carcinogenetic potential. In this review, we examine current concepts and procedures relating to genotoxicity, the potential for a chemical agent to interact with and alter the genomic informat...

This review examines recent concepts of gastric mucosal cell biology in relation to acid inhibition. Powerful acid-inhibitory drugs have been associated with the production of enterochromaffin-like (ECL) cell proliferation and the induction of ECL-cell carcinoids in rats. The ECL-cell lineage and its renewal is discussed, and the factors that regul...

Cholecystokinin and its analogues such as cerulein, muscarinic cholinergic agonists, and gastrin-releasing peptide (bombesin) bind to distinct receptors on the surface of pancreatic acinar cells and stimulate digestive protein secretion by a calcium-dependent mechanism. The mechanisms of the calcium-dependent secretagogue classes has been assumed t...

Phase I clinical trials of the purine analog 2',3'-dideoxyinosine (ddl) revealed that 10% of the patients developed pancreatitis, yet there was no clear relationship between increasing doses of ddl and the development of pancreatitis. To test the effects of chronic ddl administration on the structure and function of the rat pancreas, male Wistar ra...

The role of oxygen-derived free radicals was evaluated in two models of experimental acute pancreatitis by testing the effects of agents which either reduce oxygen-derived free radical generation or scavenge those free radicals. Those agents (catalase, superoxide dismutase, polyethylene glycol-superoxide dismutase, dimethylsulfoxide, and allopurino...

A degree of caution is both necessary and desirable when assessing the safety profile of any new drug. In comparative clinical trials, the reporting of adverse events by patients given omeprazole has been of the same order as for the H2RA. With the exception of a few anecdotal case reports, omeprazole has so far been shown to be safe in short- and...

Current methods for the study of the toxicological effects of antisecretory medications on the gastric mucosa possess disadvantages or limitations. A novel assay has been proposed to assess gastric mucosal genotoxicity in which the proton-pump inhibitor omeprazole has been reported to induce direct damage to cellular DNA, raising questions about th...

Despite the proposal that somatostatin or its stable analogue, octreotide (SMS-201,995), may exert an ameliorating effect on acute pancreatitis, data concerning its beneficial effect in this situation are conflicting. This study examines the effects of octreotide on acute pancreatitis, resulting from the retrograde injection of a bile salt (tauroch...

It is generally believed that the activation of various cell surface receptors results in the phospholipase C-catalyzed production of inositol trisphosphate which, in turn, increases the intracellular concentration of free Ca2+ by stimulating its release from nonmitochondrial sources. We have investigated both the production of inositol trisphospha...

The development of acute pancreatitis involves a number of pathophysiological changes which result in pancreatic tissue damage. Data from several models of acute pancreatitis suggest that the in vivo conversion of the enzyme xanthine dehydrogenase to xanthine oxidase may cause tissue damage by the subsequent generation of oxygen-derived free radica...

The subcellular distribution of the lysosomal enzymes cathepsin B and D in the pancreas was evaluated in rats infused with saline (control) or a maximal (0.25 microgram . kg-1 . h-1) or a supramaximally stimulating dose (5 micrograms . kg-1 . h-1) of the secretagogue caerulein. The latter results in acute edematous pancreatitis, inhibition of diges...

The role of oxygen-derived free radicals in the pathogenesis of acute pancreatitis was studied by evaluating the effects of catalase, allopurinol, and dimethylsulfoxide on diet-induced acute hemorrhagic pancreatic necrosis in mice. The mortality rate and degree of hyperamylasemia associated with this model of pancreatitis were reduced by catalase b...

Young female mice fed a choline-deficient, ethionine-supplemented (CDE) diet rapidly develop acute hemorrhagic pancreatitis. We have observed that pancreatic acini prepared from these mice are unable to secrete amylase in response to addition of the cholinergic agonist carbachol, although they retain the ability to secrete amylase in response to th...

The basal rate of amylase secretion from rat pancreatic lobules was found to diminish with time. This decline, which is not due to depletion of amylase stores or loss of tissue integrity, has been attributed to the build-up of amylase in the extracellular space [Ho and Rothman, Am. J. Physiol. 245 (Cell Physiol. 14): C21-C27, 1983]. This accumulati...

Infusion of a supramaximal dose of caerulein results in acute interstitial pancreatitis in rats. We report studies of in vivo pancreatic acinar cell function during the initial 3.5 h of supramaximal stimulation with caerulein (5 micrograms X kg-1 X h-1). Amino acid [( 3H]phenylalanine) uptake was not altered, and there was no change in the rate or...

Rats were treated with reserpine (0.2 mg/kg) on days 1, 3, and 5. On day 6, binding parameters for alpha-1 adrenergic receptors (3H-prazosin) and putative voltage dependent calcium channels, VDCC (3H-nitrendipine), were determined. There was an increase in both the number (2.1 fold) and affinity (1.8 fold) of alpha-1 adrenergic receptors following...

Dispersed mouse pancreatic acini prelabelled with (3H)-myoinositol generated (3H)-inositol trisphosphate (3H-IP3), (3H)-IP2 and (3H)-IP1 in response to both cholinergic and cholecystokinin analogues. The generation of (3H)-IP3 was very rapid, reaching a maximal value within 5 seconds following hormone stimulation. Stimulation with 10(-3)M carbachol...

Dispersed mouse pancreatic acini were loaded with the Ca2+-sensitive fluorescence probe Quin 2. Stimulation with carbamylcholine or cholecystokinin-octapeptide (CCK-OP) resulted in a rapid increase in Quin 2 fluorescence, which returned to a lower and sustained plateau level within 2 min of secretagogue stimulation. The magnitude of the initial ris...

The concentrations of PGE, PGF, and 6-keto-PGF1 alpha were increased in rat seminal vesicle tissue following mating activity. Likewise, synthesis of PGE and PGF was stimulated by epinephrine (3 X 10(-7) to 3 X 10(-6) M) in tissues and media from in vitro incubations of intact rat seminal vesicles. The in vitro stimulation was inhibited by phentolam...

Oxytocin when administered intravenously had no detectable effect on sperm count, seminal volume, or total ejaculated sperm number in oligospermic males.

Prostacyclin (PGI2) caused a dose-dependent increase in the tonus of the rat seminal vesicle (RSV) in vitro. The sensitivity of the RSV to the prostaglandins examined was: PGE2 > PGI2 > 6-keto PGF1α.

Thesis (M. Div.)--Emory University, 1996. Includes bibliographical references (leaves 111-113). Photocopy of printout copy.

Thesis (Ph. D.)--Medical University of South Carolina, 1981.