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Abstract

Enterotoxigenic Escherichia coli (ETEC) produces a heat-stable enterotoxin (STa) that binds to and activates a putative intestinal receptor, guanylate cyclase, causing an increase in the intracellular levels of cyclic guanosine monophosphate (cGMP). Using flow cytometry and 125I-STa binding assays, we studied the distribution of STa-receptors on enterocytes isolated from different segments of the newborn calf's intestinal tract. We also investigated the effect of STa on the intracellular levels of cGMP and ion transport to the intestinal lumen. More STa-receptors were found on enterocytes prepared from the ileum than on enterocytes obtained from the other segments of the intestinal tract. Guanylate cyclase activity was higher in the ileum of STa-challenged calves than in the ileum of control calves. No changes were observed in the guanylate cyclase activity of the other intestinal segments of the STa-challenged and control calves. Na+ levels, as measured by atomic absorption spectroscopy, were significantly increased in the luminal contents of the ileum of STa-challenged calves, whereas serum Cl- levels were significantly lower in the STa-challenged calves than in control calves. This study supports previous observations on the role of guanylate cyclase in the initiation of STa-induced secretory diarrhoea and suggests that Na+/Cl- coupling may be the major mechanism for the loss of ions in the diarrhoeal response that is mostly induced in the ileum of newborn calves.

Lentils and Yeast Fibers: A New Strategy to Mitigate Enterotoxigenic Escherichia coli (ETEC) Strain H10407 Virulence?

“…We also showed that the lentil extract and yeast cell walls were able to sustain ETEC growth in M9 minimal medium, most likely due to the presence of non-fiber components, as E. coli strains are not able to degrade complex polysaccharides on their own [ 84 , 85 ]. We argue that this positive effect on pathogen growth may not be an issue in the context of the complex nutritional and microbial background of the distal small intestine, the main site of ETEC colonization [ 3 , 4 , 86 , 87 , 88 , 89 ]. In the human gut, fibers are degraded into smaller carbohydrates by the endogenous gut microbiota, providing substrates for pathogens, such as ETEC, which generally behave as secondary degraders [ 90 ].…”

Electrolyte Concentrations and Blood Gas Values in Neonatal Calves With Diarrhea

“…Diarrhea is a major problem in calves less than one month of age and is of tremendous economic importance. Diarrhea results in electrolyte imbalance, dehydration, and metabolic acidosis [16][17][18][19][20]; however, only a few studies available have focused on acid−base balance, serum chemistries, and blood gas parameters associated with diarrhea caused by infectious agents in neonatal calves [21,22]. Unfortunately, because the information currently available for healthy young Korean native calves is not well documented, reference values for adult cattle have commonly been used to direct therapy.…”

Virulence Regulation and Innate Host Response in the Pathogenicity of Vibrio cholerae

“…NAG/O1-ST binds to guanylyl cyclase C (GC-C) on the apical surface of enterocytes, signals intracellular cGMP, and a cGMP-dependent kinase (PGKII) to phosphorylate CFTR on the apical membrane. The activation of cGMP and CFTR signaling stimulates chloride and fluid secretion (Al-Majali et al, 2000 ). PGKII plays an important role in regulating cGMP-dependent translocation of CFTR and ST-dependent anion secretion, which is independent of CT regulation (Golin-Bisello et al, 2005 ).…”