Linden, D R

AbstractBackgroundRAD21 is a double‐strand‐break repair protein and component of the cohesin complex with key roles in cellular functions. A RAD21 loss‐of‐function mutation was found in cases of chronic intestinal pseudo‐obstruction (CIPO) with associated enteric neuronal loss. Analysis of RAD21 expression in the enteric nervous system is lacking, thus we aimed to characterize RAD21 immunoreactivity (IR) in myenteric ganglia.MethodsDouble labeling immunofluorescence in mouse and human jejunum was used to determine colocalization of RAD21 with HuC/D, PGP9.5, neuronal nitric oxide synthase (nNOS), neuropeptide Y (NPY), choline acetyl transferase (ChAT), Kit, platelet‐derived growth factor receptor‐α (PDGFRα), and glial fibrillary acid protein (GFAP) IRs.ResultsA subset of PGP9.5‐ and HuC/D‐IR neuronal cell bodies and nerve fibers in the myenteric plexus of human and mouse small intestine also displayed cytoplasmic RAD21‐IR Cytoplasmic RAD21‐IR was found in 43% of HuC/D‐IR neurons in adult and neonatal mice but did not colocalize with nNOS. A subset of ChAT‐positive neurons had cytoplasmic RAD21‐IR Punctate RAD21‐IR was restricted to the nucleus in most cell types consistent with labeling of the cohesin complex. Cytoplasmic RAD21‐IR was not detected in interstitial cells of Cajal, fibroblast‐like cells or glia. Subsets of neurons in primary culture exhibited cytoplasmic RAD21‐IR Suppression of RAD21 expression by shRNA knockdown abolished RAD21‐IR in cultured neurons.ConclusionsOur data showing cytoplasmic RAD21 expression in enteric neurons provide a basis toward understanding how mutations of this gene may contribute to altered neuronal function/survival thus leading to gut‐motor abnormalities.

Abstract Background Gastric emptying is a complex physiological process regulating the division of a meal into smaller partitions for the small intestine. Disrupted gastric emptying contributes to digestive disease, yet current measures may not reflect different mechanisms by which the process can be altered. Methods We have developed high temporal resolution solid and liquid gastric emptying breath tests in mice using [ 13 C]‐octanoic acid and off axis‐ integrated cavity output spectroscopy ( OA ‐ ICOS ). Stretched gamma variate and 2‐component stretched gamma variate models fit measured breath excretion data. Key Results These assays detect acceleration and delay using pharmacological (7.5 mg/kg atropine) or physiological (nutrients, cold exposure stress, diabetes) manipulations and remain stable over time. High temporal resolution resolved complex excretion curves with 2 components, which was more prevalent in mice with delayed gastric emptying following streptozotocin‐induced diabetes. There were differences in the gastric emptying of Balb/c vs C57Bl6 mice, with slower gastric emptying and a greater occurrence of two‐phase gastric emptying curves in the latter strain. Gastric emptying of C57Bl6 could be accelerated by halving the meal size, but with no effect on the occurrence of two‐phase gastric emptying curves. A greater proportion of two‐phase gastric emptying was induced in Balb/c mice with the administration of PYY (8‐80 nmol) 60 min following meal ingestion. Conclusions and Inferences Collectively, these results demonstrate the utility of high temporal resolution gastric emptying assays. Two‐phase gastric emptying is more prevalent than previously reported, likely involves intestinal feedback, but contributes little to the overall rate of gastric emptying.