Pathogenesis and pharmacology of diarrhea

Gut modulatory and butyrylcholinesterase inhibitory activities of Gaultheria trichophylla

CONTEXT

Gaultheria trichophylla Royle (Ericaceae) and related species have been used in the traditional system of medicine for the treatment of diarrhoea, pain and inflammation.

OBJECTIVE

The present investigation explores G. trichophylla for its potential activity in hyperactive gut disorders.

MATERIALS AND METHODS

Antidiarrheal activity was evaluated on castor oil induced diarrhoea in mice with reference to standard drug verapamil. Gut modulatory activity was performed on isolated jejunum tissue preparations on spontaneous and high potassium induced contractions. Butyrylcholinesterase (BChE) inhibitory activity was performed with an in vitro study. Extract was tested for toxicity in mice.

RESULTS

In the in vivo studies, the methanol extract of G. trichophylla and verapamil significantly (p < 0.05, 0.01, 0.001) inhibited the frequency of defecation as well as wetting of faeces when compared with the negative control. The methanol (Gt. MeOH) extract of G. trichophylla caused a dose-dependent inhibitory effect on spontaneous contractions in isolated rabbit jejunum preparations and exhibited a partial inhibitory effect against high K⁺(80 mM) induced precontractions. Gt. MeOH shifted the Ca²⁺concentration-response curves (CRCs) to the right, suggesting calcium channel blocking like constituents. In an in vitro assay Gt. MeOH inhibited BChE enzyme with an IC₅₀ values of 35.52 ± 1.17 μg/mL. The extract showed no toxicity in mice at the dose of 3 g/kg.

DISCUSSION AND CONCLUSION

This study provides evidence that G. trichophylla possesses combinations of inhibitory and stimulatory effects mediated through possible cholinergic and less potent calcium blocking constituents, respectively. The latter may be responsible for the antidiarrheal effect.

Evaluation of an oral electrolyte solution for treatment of mild to moderate dehydration in dogs with hemorrhagic diarrhea

OBJECTIVE

To determine the safety and efficacy of an electrolyte solution for oral administration (OES) for the correction of mild to moderate dehydration associated with hemorrhagic diarrhea in dogs.

DESIGN

Nonrandomized, noncontrolled clinical trial.

ANIMALS

20 dogs that had hemorrhagic diarrhea with < 3 episodes of vomiting.

PROCEDURES

All dogs underwent testing for parvovirus infection, were given maropitant citrate to control emesis, and were offered an OES. Intravenous crystalloid fluid administration was performed when dogs refused the OES or had vomiting, a 5% increase in PCV, 5% decrease in body weight, serum creatinine or BUN concentration higher than at admission, or clinically important alterations in blood electrolyte or serum glucose concentrations.

RESULTS

13 (65%) dogs voluntarily consumed the OES; 7 (35%) dogs refused the OES and received a balanced electrolyte solution IV instead. All 13 dogs in the OES group consumed the solution ≤ 5 hours after hospital admission. Eight and 16 hours after admission, PCV and serum total protein and BUN concentrations were significantly lower than at hospital admission in the OES group, whereas no significant changes were identified in venous blood pH, base excess, and concentrations of sodium, potassium, chloride, ionized calcium, ionized magnesium, and lactate. The cost of treatment was significantly less for the OES group than for the IV treated group.

CONCLUSIONS AND CLINICAL RELEVANCE

Rehydration therapy with an OES was effective and safe in dogs with mild to moderate dehydration associated with hemorrhagic diarrhea. Potential benefits of this treatment approach for gastroenteritis in dogs, compared with traditional IV fluid administration, include lower owner-related veterinary costs and decreased staff time associated with treatment.

Experimental inoculation of foals and pigs with an enterotoxigenic E. coli isolated from a foal

Hemolytic E. coli strain 807-13, O149:NM:K88(STb+, LT+), was isolated from the feces of a neonatal diarrheic foal. E. coli 807-13 was examined for adhesion to brush border membranes (BBM) from foals, adult horses and pigs, and its pathogenicity was assessed in neonatal foals and pigs. E. coli 807-13 did not adhere to equine BBM but adhered to pig BBM. It did not cause diarrhea nor did it colonize the intestinal epithelium of 3 colostrum-deprived and 3 suckled foals challenged at 24 h of age. Acute ulcerative gastritis and acute suppurative gastritis were observed in 2 colostrum-deprived challenged foals, and acute neutrophilic enteritis was observed in 1 colostrum-deprived and in 1 suckled challenged foal. No similar histopathologic lesions were detected in the control foals. Both gnotobiotic and suckled pigs developed diarrhea after challenge exposure to E. coli 807-13 and the intestinal epithelium of the pigs was colonized. Histopathologic evidence of gastritis and enteritis among the foals indicated some complicity of E. coli 807-13 in foal enteric disease.

Characterization of Escherichia coli isolated from foals

Serotype, biotype, antibiogram, hemolysin production, fimbrial hemagglutinins, select toxin genes (STb, STaP, LT, slt1 and slt2) and the attaching effacing (eae) gene were determined for 99 foal strains of E. coli. E. coli from diarrheic and normal foals could not be distinguished by serotype, biotype, or antibiogram. Differences (P < or = 0.05) were observed in hemolysin production (11.5% vs 0%) and the expression of mannose-resistant hemagglutinins (23% vs 13%) among E. coli from diarrheic and healthy foals, respectively. Three of the E. coli strains from diarrheic foals were positive with probes for slt genes and one was positive for STb and LT genes. One strain from a healthy foal possessed the STb gene. As determined by the polymerase chain reaction, 8 strains possessed the eae gene. Seven of the 8 strains were from diarrheic foals and one eae-positive strain was from a healthy foal. The slt-positive strains did not possess eae genes and the eae-positive strains did not possess slt genes. These results indicate that enterotoxigenic strains of E. coli are not implicated in any substantial degree in sporadic foal diarrhea. However, the identification of slt-positive and eae-positive strains in foal feces indicate the presence of potentially virulent strains among foals.

Inhibitory activity of camptothecin derivatives against acetylcholinesterase in dogs and their binding activity to acetylcholine receptors in rats

A camptothecin derivative, 7-ethyl-10-[4-(1-piperidino)-1-piperidino]carbonyloxycamptothecin (CPT-11), shows a potent antitumour activity in experimental tumour models and in clinical trials. However, CPT-11 induced early diarrhoea and vomiting at high dose levels in clinical studies and showed an acetylcholine-like action on the guinea-pig ileum and trachea. In the present study, we investigated the activities of camptothecin derivatives in inhibiting acetylcholinesterase (AChE) and in binding to muscarinic acetylcholine receptors (AChR). CPT-11 inhibited AChE and binding of the specific ligand to AChR with respective 50% inhibition concentrations of 0.2 and 5 microM. These inhibitions were induced by camptothecin derivatives having an amino group at the C-10 position (or the C-4 position of hexacyclic derivatives), but were not or were only slightly induced by the others. Early defecation and vomiting in dogs were observed after intravenous injection of DU-6596 and DU-6888, two hexacyclic derivatives having the aminomethyl group at the C-4 position, and of CPT-11. DU-6174, however, which has a hydroxy group at this position, induced no early defecation and little vomiting. Plasma concentrations of CPT-11, DU-6596 and DU-6888 after intravenous treatment at doses causing such early adverse effects were maintained for 1 h or longer at levels sufficient to inhibit AChE. These results suggest that the inhibition of AChE by camptothecin derivatives with an amino group at the C-10 position (or the C-4 position) relates to the early defecation or diarrhoea and vomiting.

Some infectious causes of diarrhea in young farm animals

Escherichia coli, rotaviruses, and Cryptosporidium parvum are discussed in this review as they relate to enteric disease in calves, lambs, and pigs. These microorganisms are frequently incriminated as causative agents in diarrheas among neonatal food animals, and in some cases different strains or serotypes of the same organism cause diarrhea in humans. E. coli causes diarrhea by mechanisms that include production of heat-labile or heat-stable enterotoxins and synthesis of potent cytotoxins, and some strains cause diarrhea by yet undetermined mechanisms. Rotaviruses and C. parvum induce various degrees of villous atrophy. Rotaviruses infect and replicate within the cytoplasm of enterocytes, whereas C. parvum resides in an intracellular, extracytoplasmic location. E. coli, rotavirus, and C. parvum infections are of concern to producers, veterinarians, and public health officials. These agents are a major cause of economic loss to the producer because of costs associated with therapy, reduced performance, and high morbidity and mortality rates. Moreover, diarrheic animals may harbor, incubate, and act as a source to healthy animals and humans of some of these agents.

Physiological aspects of absorption and secretion in intestine

Two differently oriented approaches in intestinal physiology can be distinguished. One, mainly based on in vitro experiments, seeks explanations at the level of the epithelium itself. The other, mainly based on in vivo experiments, looks for explanations at the level of regulatory nervous and endocrine mechanisms and their interaction. These two approaches complement each other.