@article{corl_odle_niu_moeser_gatlin_phillips_blikslager_rhoads_2008, title={Arginine Activates Intestinal p70S6k and Protein Synthesis in Piglet Rotavirus Enteritis}, volume={138}, ISSN={0022-3166 1541-6100}, url={http://dx.doi.org/10.1093/jn/138.1.24}, DOI={10.1093/jn/138.1.24}, abstractNote={We previously showed that phosphorylation of p70 S6 kinase (p70(S6k)) in the intestine is increased during viral enteritis. In this study, we hypothesized that during rotavirus infection, oral Arg, which stimulates p70(S6k) activation, will further stimulate intestinal protein synthesis and mucosal recovery, whereas the p70(S6k) inhibitor rapamycin (Rapa) will inhibit mucosal recovery. Newborn piglets were fed a standard milk replacer diet supplemented with Arg (0.4 g x kg(-1) x d(-1), twice daily by gavage), Rapa (2 mg x m(-2) x d(-1)), Arg + Rapa, or saline (controls). They were infected on d 6 of life with porcine rotavirus. Three days postinoculation, we measured the piglets' body weight, fecal rotavirus excretion, villus-crypt morphology, epithelial electrical resistance in Ussing chambers, and p70(S6k) activation by Western blotting and immunohistochemistry. We previously showed a 2-fold increase in jejunal protein synthesis during rotavirus diarrhea. In this experiment, Arg stimulated jejunal protein synthesis 1.3-fold above standard medium, and the Arg stimulation was partially inhibited by Rapa. Small bowel stimulation of p70(S6k) phosphorylation and p70(S6k) levels were inhibited >80% by Rapa. Immunohistochemistry revealed a major increase of p70(S6k) and ribosomal protein S6 phosphorylation in the crypt and lower villus of the infected piglets. However, in Arg-treated piglets, p70(S6k) activation occurred over the entire villus. Jejunal villi of the Rapa-treated group showed inactivation of p70(S6k) and a decrease in mucosal resistance (reflecting increased permeability), the latter of which was reversed by Arg. We conclude that, early in rotavirus enteritis, Arg has no impact on diarrhea but augments intestinal protein synthesis in part by p70(S6k) stimulation, while improving intestinal permeability via a mammalian target of rapamycin/p70(S6k)-independent mechanism.}, number={1}, journal={The Journal of Nutrition}, publisher={Oxford University Press (OUP)}, author={Corl, Benjamin A. and Odle, Jack and Niu, Xiaomei and Moeser, Adam J. and Gatlin, Lori A. and Phillips, Oulayvanh T. and Blikslager, Anthony T. and Rhoads, J. Marc}, year={2008}, month={Jan}, pages={24–29} }
 @article{rhoads_niu_odle_graves_2006, title={Role of mTOR signaling in intestinal cell migration}, volume={291}, ISSN={["1522-1547"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-33748314634&partnerID=MN8TOARS}, DOI={10.1152/ajpgi.00189.2005}, abstractNote={An early signaling event activated by amino acids and growth factors in many cell types is the phosphorylation of the mammalian target of rapamycin (mTOR; FRAP), which is functionally linked to ribosomal protein s6 kinase (p70(s6k)), a kinase that plays a critical regulatory role in the translation of mRNAs and protein synthesis. We previously showed that intestinal cell migration, the initial event in epithelial restitution, is enhanced by l-arginine (ARG). In this study, we used amino acids as prototypic activators of mTOR and ARG, IGF-1, or serum as recognized stimulators of intestinal cell migration. We found that 1) protein synthesis is required for intestinal cell migration, 2) mTOR/p70(s6k) pathway inhibitors (rapamycin, wortmannin, and intracellular Ca(2+) chelation) inhibit cell migration, 3) ARG activates migration and mTOR/p70(s6k) (but not ERK-2) in migrating enterocytes, and 4) immunocytochemistry reveals abundant p70(s6k) staining in cytoplasm, whereas phospho-p70(s6k) is virtually all intranuclear in resting cells but redistributes to the periphery on activation by ARG. We conclude that mTOR/p70(s6k) signaling is essential to intestinal cell migration, is activated by ARG, involves both nuclear and cytoplasmic events, and may play a role in intestinal repair.}, number={3}, journal={AMERICAN JOURNAL OF PHYSIOLOGY-GASTROINTESTINAL AND LIVER PHYSIOLOGY}, author={Rhoads, J. Marc and Niu, Xiaomei and Odle, Jack and Graves, Lee M.}, year={2006}, month={Sep}, pages={G510–G517} }
 @article{rhoads_brunner-neuenschwander_levings_siedow_1998, title={Cross-linking and disulfide bond formation of introduced cysteine residues suggest a modified model for the tertiary structure of URF13 in the pore-forming oligomers}, volume={354}, ISSN={["0003-9861"]}, DOI={10.1006/abbi.1998.0671}, abstractNote={URF13 is a mitochondrially encoded protein in the inner mitochondrial membrane of maize (Zea mays L.) carrying the cms-T cytoplasm. This protein is responsible for Texas-type cytoplasmic sterility and is a ligand-gated, pore-forming receptor for the pathotoxins of fungal pathogens Bipolaris maydis race T and Phyllosticta maydis. URF13 contains three transmembrane alpha-helices, with amphipathic helices II and III likely involved in pore formation, and is present as oligomers in cms-T maize mitochondria and when expressed in Escherichia coli cells. To study tertiary and quaternary structures of URF13 oligomers, we employed combinations of site-directed mutagenesis and chemical cross-linking. We introduced Cys residues individually into consecutive positions 78-82, believed to be in helix III. We expressed these proteins in E. coli cells and tested for cross-linking through disulfide bond formation or by using Cys-Cys cross-linkers. URF13-R79C, URF13-R81C, and URF13-T82C were cross-linked using Cys-Cys-specific cross-linkers, as were double mutants URF13-C27R/R79C, URF13-C27R/R81C, and URF13-C27R/T82C, indicating that the cross-linking was between introduced Cys residues on adjacent URF13 molecules. Disulfide bond formation, induced by diamide, was seen only in URF13-T82C and URF13-C27R/T82C, indicating that Cys residues introduced into position 82 are closely juxtaposed in the oligomers. Based on these observations, we modified the models for the secondary structure of URF13 and the tertiary structure of the URF13 oligomers. Sequential cross-linking of URF13-R81C oligomers with bismaleimidohexane (Cys-Cys cross-linker) and N,N'-dicyclohexylcarbodiimide (Lys-Asp/Glu cross-linker) suggests that URF13 oligomers consist of an even number of monomers.}, number={1}, journal={ARCHIVES OF BIOCHEMISTRY AND BIOPHYSICS}, author={Rhoads, DM and Brunner-Neuenschwander, BB and Levings, CS and Siedow, JN}, year={1998}, month={Jun}, pages={158–164} }
 @article{ahdieh_blikslager_bhat_coleman_argenzio_rhoads_1998, title={L-Glutamine and Transforming Growth Factor-α Enhance Recovery of Monoacylglycerol Acyltransferase and Diacylglycerol Acyltransferase Activity in Porcine Postischemic Ileum}, volume={43}, ISSN={0031-3998 1530-0447}, url={http://dx.doi.org/10.1203/00006450-199802000-00012}, DOI={10.1203/00006450-199802000-00012}, abstractNote={Recovery of the ability to digest and absorb lipids is essential to the maintenance of normal nutrition in infants with bowel damage. Two intrinsic microsomal enzymes, monoacylglycerol acyltransferase (MGAT) and diacylglycerol acyltransferase (DGAT), catalyze the major pathway for intestinal triacylglycerol biosynthesis. This study describes the effects of intestinal ischemia on epithelial DGAT and MGAT activities and their recovery in response to two luminal treatments: L-glutamine (Gln), the primary intestinal fuel, and transforming growth factor-alpha (TGF-alpha), a mitogenic hormone similar to epidermal growth factor present in breast milk. Ischemic damage and recovery were analyzed in mucosa from Thiry-Vella loops in the mid-ileum of 7-wk-old pigs. Loops were subjected to 2-h occlusion of local mesenteric arteries, followed by 6 or 72 h of recovery in the presence of luminal glucose (control), Gln, or TGF-alpha. Ischemic tissue followed by 6-h recovery exhibited an approximate 50% decrease in both MGAT and DGAT activities compared with nonischemic loop tissue. At 72 h, MGAT and DGAT recovery in Gln plus TGF-alpha-treated loops was significantly greater than their corresponding 6-h peak damage levels (p < 0.05). From 6 to 72 h, MGAT increased 4-fold and DGAT increased 3.6-fold after Gln plus TGF-alpha treatment. With other treatments, MGAT and DGAT activities increased <2.5-fold from 6 to 72 h. This study shows that intestinal MGAT and DGAT activities decrease after ischemic damage, yet recover rapidly in bowel exposed to Gln and/or TGF-alpha. By stimulating the rate of recovery of the villi and lipid synthesizing enzymes, these treatments could improve the efficacy of enteral feeding in infants recovering from bowel damage.}, number={2}, journal={Pediatric Research}, publisher={Springer Nature}, author={Ahdieh, Navid and Blikslager, Anthony T and Bhat, B Ganesh and Coleman, Rosalind A and Argenzio, Robert A and Rhoads, J Marc}, year={1998}, month={Feb}, pages={227–233} }
 @article{blikslager_roberts_rhoads_argenzio_1997, title={Is reperfusion injury an important cause of mucosal damage after porcine intestinal ischemia?}, volume={121}, ISSN={["0039-6060"]}, DOI={10.1016/S0039-6060(97)90107-0}, abstractNote={Intestinal ischemic injury is exacerbated by reperfusion in rodent and feline models because of xanthine oxidase-initiated reactive oxygen metabolite formation and neutrophil infiltration. Studies were conducted to determine the relevance of reperfusion injury in the juvenile pig, whose low levels of xanthine oxidase are similar to those of the human being.Ischemia was induced by means of complete mesenteric arterial occlusion, volvulus, or hemorrhagic shock. Injury was assessed by means of histologic examination and measurement of lipid peroxidation. In addition, myeloperoxidase, as a marker of neutrophil infiltration, and xanthine oxidase-xanthine dehydrogenase were measured.Significant ischemic injury was evident after 0.5 to 3 hours of complete mesenteric occlusion or 2 hours of shock or volvulus. In none of these models was the ischemic injury worsened by reperfusion. To maximize superoxide production, pigs were ventilated on 100% O2, but only limited reperfusion injury (1.2-fold increase in histologic grade) was noted. Xanthine oxidase-xanthine dehydrogenase levels were negligible (0.4 +/- 0.4 mU/gm).Reperfusion injury may not play an important role in intestinal injury under conditions of complete mesenteric ischemia and low-flow states in the pig. This may result from low xanthine oxidase-xanthine dehydrogenase levels, which are similar to those found in the human being.}, number={5}, journal={SURGERY}, author={Blikslager, AT and Roberts, MC and Rhoads, JM and Argenzio, RA}, year={1997}, month={May}, pages={526–534} }
 @article{rhoads_argenzio_chen_rippe_westwick_cox_berschneider_brenner_1997, title={L-glutamine stimulates intestinal cell proliferation and activates mitogen-activated protein kinases}, volume={272}, ISSN={["0193-1857"]}, DOI={10.1152/ajpgi.1997.272.5.g943}, abstractNote={We studied the mechanisms by which L-glutamine (Gln), a major fuel for enterocytes, signals proliferation in intestinal epithelial cell lines. Gln was additive to epidermal growth factor (EGF) and insulin-like growth factor I (IGF-I) in stimulating DNA synthesis, as assessed by [3H]thymidine incorporation. Extracellular signal-regulated kinases (ERKs) p42mapk and p44mapk and Jun nuclear kinases (JNKs) phosphorylate and activate nuclear transcription factors. Proteins of the c-Jun, ATF-2, and c-Fos families aggregate to form DNA-binding homodimers or heterodimers called activating protein 1 (AP-1). In vitro assays and functional assays of phosphorylation demonstrated that Gln activates both ERKs and JNKs, resulting in a fourfold increase in AP-1-dependent gene transcription. Gln was required for EGF signaling through ERKs. Maximal stimulation of proliferation required approximately 2.5 mM Gln. c-Jun mRNA levels responded to Gln in "Gln-starved" porcine IPEC-J2 cells and in rat IEC-6 cells. Although Gln metabolism is required for the proliferative response, several Gln by-products did not stimulate [3H]thymidine incorporation, with the exception of arginine. Gln may be a unique nutrient for enterocytes, capable of dual signaling and augmenting the effects of growth factors that govern cellular proliferation and repair.}, number={5}, journal={AMERICAN JOURNAL OF PHYSIOLOGY-GASTROINTESTINAL AND LIVER PHYSIOLOGY}, author={Rhoads, JM and Argenzio, RA and Chen, WN and Rippe, RA and Westwick, JK and Cox, AD and Berschneider, HM and Brenner, DA}, year={1997}, month={May}, pages={G943–G953} }
 @article{argenzio_armstrong_blikslager_rhoads_1997, title={Peptide YY inhibits intestinal Cl- secretion in experimental porcine cryptosporidiosis through a prostaglandin-activated neural pathway}, volume={283}, number={2}, journal={Journal of Pharmacology and Experimental Therapeutics}, author={Argenzio, R. A. and Armstrong, M. U. and Blikslager, A. and Rhoads, J. M.}, year={1997}, pages={692–697} }
 @article{blikslager_roberts_rhoads_argenzio_1997, title={Prostaglandins I2 and E2 have a synergistic role in rescuing epithelial barrier function in porcine ileum.}, volume={100}, ISSN={0021-9738}, url={http://dx.doi.org/10.1172/JCI119723}, DOI={10.1172/JCI119723}, abstractNote={Prostaglandins (PG) are cytoprotective for gastrointestinal epithelium, possibly because they enhance mucosal repair. The objective of the present studies was to assess the role of prostaglandins in intestinal repair. Intestinal mucosa from porcine ileum subjected to 1 h of ischemia was mounted in Ussing chambers. Recovery of normal transepithelial electrical resistance occurred within 2 h, and continued to increase for a further 2 h to a value twice that of control. The latter response was blocked by inhibition of prostaglandin synthesis, and restored by addition of both carbacyclin (an analog of PGI2) and PGE2, whereas the addition of each alone had little effect. Histologically, prostaglandins had no effect on epithelial restitution or villous contraction, indicating that elevations in transepithelial resistance were associated with increases in paracellular resistance. Furthermore, prostaglandin-stimulated elevations in resistance were inhibited with cytochalasin D, an agent known to stimulate cytoskeletal contraction. Synergistic elevations in transepithelial resistance, similar to those of carbacyclin and PGE2, were also noted after treatment with cAMP and A23187 (a calcium ionophore). We conclude that PGE2 and PGI2 have a synergistic role in restoration of intestinal barrier function by increasing intracellular cAMP and Ca2+, respectively, which in turn signal cytoskeletal-mediated tight junction closure.}, number={8}, journal={Journal of Clinical Investigation}, publisher={American Society for Clinical Investigation}, author={Blikslager, A T and Roberts, M C and Rhoads, J M and Argenzio, R A}, year={1997}, month={Oct}, pages={1928–1933} }
 @article{argenzio_rhoads_1997, title={Reactive oxygen metabolites in piglet cryptosporidiosis}, volume={41}, ISSN={["1530-0447"]}, DOI={10.1203/00006450-199704000-00011}, abstractNote={Piglet cryptosporidiosis is characterized by intestinal villous damage and malabsorption, and by reduced NaCl absorption in response to prostaglandins(PGs), which act directly on the epithelium and indirectly through enteric nerves. We hypothesized that phagocyte-derived reactive oxygen metabolite(ROM) production contributed to PG synthesis and altered transport in inflamed ileum. Ileal mucosa from control and infected piglets was analyzed for villous height, PGE2, catalase (an endogenous antioxidant), and malondialdehyde(MDA, a by-product of lipid peroxidation) from d 2-8 after infection. The response of control ileal mucosa to exogenous ROM and infected mucosa to antioxidant treatment was also studied in tissues mounted in Ussing chambers. Increased levels of MDA on d 2 preceded increased PGE2 on d 3-4, which correlated with the acute diarrheal phase; however the most severe villous atrophy (d 8) correlated with the highest levels of catalase and MDA but low levels of PGE2. Control mucosa responded to H2O2 with indomethacin- and tetrodotoxin-sensitive transient increases in short circuit current (Isc), which were accompanied by increased tissue production of 6-keto-PGF1a, the stable metabolite of PGI2; however, no increased PGE2 production was detectable. A stable analog of PGI2, carbacyclin, mimicked the transient Isc response to H2O2; however, several antioxidants failed to alter the abnormal Isc of infected tissue. These results suggest that there is evidence of increased ROM production in cryptosporidial infection and that intestinal PG synthesis and inhibited NaCl absorption may be mediated partially by ROM in this model. Additional, cooperative factors, such as PGE2 production, however, are likely needed to induce the alterations in ion transport seen in this infection.}, number={4}, journal={PEDIATRIC RESEARCH}, author={Argenzio, RA and Rhoads, JM}, year={1997}, month={Apr}, pages={521–526} }