Extreme heat stress-induced gastrointestinal injury and dysfunction may occur during summer. We investigated possible mechanisms of heat stress-induced damage in the small intestine using male Sprague-Dawley rats subjected to 2 h of heat stress (40 °C, 60% relative humidity) daily for 10 consecutive days. Rats were killed at specific times immediately following heat treatment to determine: morphological changes by optical and electron microscopy; intestinal permeability using fluorescein isothiocyanate-dextran; production of reactive oxygen species (ROS), malondialdehyde (MDA), and activities of superoxide-dismutase and glutathione-peroxidase by specific assays; phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2), c-Jun N-terminal kinase (JNK), and p38 mitogen-activated protein kinase (MAPK) by immunocytochemistry and western-blot analysis. The rat intestinal epithelial cell line (IEC-6) and specific MAPK inhibitors were used for in vitro investigation of effects of activation of MAPKs by heat stress. Heat stress caused marked morphological damage to the small intestine and significantly increased intestinal permeability. Heat stress increased ROS and MDA production, and significantly reduced anti-oxidase activity. MAPK activity in small intestine was increased by heat stress. In vitro, heat stress caused damage and apoptosis in IEC-6 cells; inhibition of ERK1/2 activation (by U0126) exacerbated these effects, which were attenuated by inhibition of JNK (by SP600125) and p38 (by SB203580) activation. Hence, heat stress caused severe small intestine injury, increased oxidative stress, and activated MAPK signaling pathways. The in vitro studies indicated that ERK1/2 activation is anti-apoptotic, and JNK and p38 activation are pro-apoptotic in heat stressed intestinal epithelial cells.

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Heat stress damages rat intestinal mechanical and mucosal immune barriers, and reduces immune function of the intestinal mucosa and mesenteric lymphoid tissues, leading to bacterial translocation.

Prevalence and risk analysis of mobile colistin resistance and extended-spectrum βlactamase genes carriage in pet dogs and their owners: a population based cross-sectional study, Emerging Microbes & Infections,

Recent studies have shown that C-type natriuretic peptide (CNP; encoded by the natriuretic peptide C (NPPC) gene) plays an essential role in maintaining meiotic arrest of mouse and porcine oocytes. However, whether CNP inhibits feline meiotic resumption is not known. In the present study we used a domestic cat model to explore the role played by CNP in feline oocyte meiotic resumption. We determined mRNA expression of genes encoding CNP and its cognate receptor natriuretic peptide receptor 2 (NPR2) in antral follicles. NPPC mRNA was primarily expressed in mural granulosa cells, whereas NPR2 mRNA was predominantly expressed in cumulus cells. Following in vitro culture for 24h, 100nM CNP increased cGMP levels, and maintained meiotic arrest of oocytes associated with cumulus cells. When the duration of in vitro culture increased from 24h to 36h, the ability of CNP to maintain meiotic arrest decreased, and this was accompanied by a decrease in the steady state levels of NPR2 mRNA in cumulus cells. In addition, CNP decreased the rate of degeneration of oocytes. These results indicate that CNP is required to maintain meiotic arrest and prevent degeneration in domestic cat oocytes.