The pathogenesis of cholera and some wider implications

Drug Repositioning with GraphSAGE and Clustering Constraints Based on Drug and Disease Networks

The understanding of therapeutic properties is important in drug repositioning and drug discovery. However, chemical or clinical trials are expensive and inefficient to characterize the therapeutic properties of drugs. Recently, artificial intelligence (AI)-assisted algorithms have received extensive attention for discovering the potential therapeutic properties of drugs and speeding up drug development. In this study, we propose a new method based on GraphSAGE and clustering constraints (DRGCC) to investigate the potential therapeutic properties of drugs for drug repositioning. First, the drug structure features and disease symptom features are extracted. Second, the drug–drug interaction network and disease similarity network are constructed according to the drug–gene and disease–gene relationships. Matrix factorization is adopted to extract the clustering features of networks. Then, all the features are fed to the GraphSAGE to predict new associations between existing drugs and diseases. Benchmark comparisons on two different datasets show that our method has reliable predictive performance and outperforms other six competing. We have also conducted case studies on existing drugs and diseases and aimed to predict drugs that may be effective for the novel coronavirus disease 2019 (COVID-19). Among the predicted anti-COVID-19 drug candidates, some drugs are being clinically studied by pharmacologists, and their binding sites to COVID-19-related protein receptors have been found via the molecular docking technology.

Oral rehydration therapy

Diarrhea is a major cause of mortality and morbidity affecting infants and children in many parts of the world. Research and understanding of normal and abnormal gastrointestinal physiology allowed the development of oral electrolyte solutions to treat dehydration. These solutions were initially used for treatment of cholera in areas with poor access to medical care and are now used extensively by the WHO. Therapy with OES has expanded to other nonsecretory causes of diarrhea. Two types of solutions are available in the United States. Maintenance solutions contain 40 to 60 mEq per liter of sodium and are used for prevention of dehydration or after rehydration. Rehydration solutions contain 60 to 90 mEq per liter of sodium and are effective for the oral repletion of fluid and electrolyte deficits in both secretory and nonsecretory diarrhea.

Effect of heat stable and heat labile Escherichia coli enterotoxins and cholera toxin in combination with theophylline on unidirectional sodium and chloride flux in the small intestine of weanling swine

The effect of heat stable and heat labile Escherichia coli enterotoxins or cholera toxin in combination with theophylline on net water, sodium and chloride and unidirectional sodium and chloride fluxes was examined in acute isolated loops of jejunum of weanling swine. The effect of heat stable enterotoxin in combination with theophylline was determined in loops located in the proximal jejunum, while combinations of theophylline and either heat labile enterotoxin or cholera toxin were studied in the distal jejunum. In each situation the addition of theophylline resulted in an additive rather than a synergistic increment of intestinal secretory activity. This study implies that the intestinal adenyl cyclase system and enterotoxin induced intestinal secretion may not be directly related in the swine small intestine.

Influence of staphylococcal enterotoxin on water and electrolyte transport in the small intestine

The direct and indirect effects of staphylococcal enterotoxins A and C on the flux of water, sodium, and potassium have been studied in paired Thiry Vella fistulae in dogs. Administration of toxin resulted in a significant decrease in absorption, both in the loop to which the toxin had been administered and its pair. This decrease in absorption was associated with a decrease in movement out of the lumen, movement into the lumen remaining relatively unchanged. The mechanism of action of staphylococcal enterotoxins is discussed, and comparisons made with other enterotoxins.

The response of small intestinal villous and crypt epithelium to choleratoxin in rat and guinea pig. Evidence against a specific role of the crypt cells in choleragen-induced secretion

1. Some kinetic properties of adenylate cyclase in separately isolated upper villous and crypt cells from rat and guinea pig small intestine were compared. An apparent Km of 0.4 mM was found for both enzymes in the rat. The slight difference between the V-values measured in the fluoride-stimulated state (132 and 165 pmoles cyclic AMP formed per min per mg protein respectively) indicated an approximately equal enzyme content of both cell populations and argues strongly against a preferential localization in the brushborder region of the epithelial cell. 2. Prolonged contact of the small intestine with luminally administered choleragen led to an irreversible activation of adenylate cyclase in both villous and crypt compartments. The maximal stimulation of the upper villous enzyme (4-7 times) exceeded the maximal effect on the crypt enzyme by two-fold. 3. A lag phase of at least 30 min was found between the first luminal contact with the purified choleragen and a significant activation of the adenylate cyclase associated with isolated intestinal brushborders from the upper villous region. 4. By using a short exposure time (2 min) of the luminal surface to high amounts of choleragen, adenylate cyclase activity in the upper villus could be optimally stimulated in the absence of any alteration of crypt cell activity. 5. By comparing, in vivo, the effects of short and prolonged contact with choleratoxin on the unidirectional and net flux of ions and water in ileal and jejunal segments, it was concluded that both villous and crypt regions contribute to the secretion of water and electrolytes (sodium, chloride and bicarbonate ions) during cholera. The serosal to mucosal flux of sodium and chloride ions increased without a significant alteration of the opposite flux. These results imply that absorptive and secretory processes occur within the same epithelial compartment. 6. The view that the crypt epithelium fulfills a specific role during the choleragen-induced secretion of ions and water is incompatible with the results of the present study.

Electron microscopic study on the jejunal mucosa in human cholera

Small intestinal mucosa obtained from six fasting patients with cholera by a peroral biopsy technique was studied with the electron microscope. The cultures of their rectal swabs were all positive for Vibrio cholerae. In the absorptive cells, large pseudopod-like cytoplasmic processes with deformed microvilli or without microvilli (blebs) projected into the intestinal lumen from the apical cell surface, interrupting the microvillous border. In the crypts some of the undifferentiated crypt cells possessed pseudopod-like cytoplasmic projections which extended into the crypt lumen. The swelling of mitochondria, the disappearance of their cristae, an increase in the number of vesicles of the Golgi apparatus, and the dilatation and vesiculation of endoplasmic reticulum were observed in the epithelial cells. The apical portion of the cells became oedematous in some of the epithelial cells. Cytoplasmic fragments enclosed by a plasma membrane, desquamated epithelial cells, cytoplasmic organelles, and secretory granules were lying free in the intestinal lumen.Marked irregular widening of the interepithelial spaces in the jejunal mucoa was observed at the midvillous area. Many cystic vacuoles were present in the cytoplasm of epithelial cells. The possibility of fluids being transported from blood vessels to intestinal lumina through the interepithelial spaces, and the significance of these pathological findings in human cholera are discussed in this study.