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At least 1,207 records · Page 67Linked to original sources
PubMed1990

Role of prostaglandins and calcium in the effects of Entamoeba histolytica on colonic electrolyte transport.

We have previously shown that Entamoeba histolytica lysates contain the neurohormones serotonin, neurotensin, immunoreactive substance P, and probably acetylcholine, and that amebic lysates inhibit sodium and chloride absorption and stimulate chloride secretion in the rat descending colon as measured by the Ussing chamber-voltage clamp technique. We now demonstrate that these transport effects have both calcium-dependent and calcium-independent components. In addition, arachidonic acid metabolites of the cyclooxygenase pathway are probably involved in the Entamoeba histolytica-induced changes in colonic transport that are not dependent on Ca++ entry. Prostaglandin E2 (10(-5) M), indomethacin (10(-6) M), piroxicam (5 x 10(-5) M), and mepacrine (10(-4) M) partially inhibited the amebic lysate effect on active transport in the rat descending colon. In addition, verapamil (10(-4) M) partially inhibited the effect of amebic lysates. The effect of verapamil was additive with that of indomethacin, totally blocking the effect of amebic lysate on short-circuit current. However, amebic lysates do not contain prostaglandin E2 as measured by sensitive radioimmunoassay. Amebic lysates stimulated prostaglandin E2 release from rat colonic mucosal strips. Amebic lysate significantly increased colonic cyclic adenosine monophosphate content. Piroxicam inhibited the lysate-induced increase in colonic cyclic adenosine monophosphate content. These results indicate that although amebic lysate does not contain prostaglandin E2, it caused arachidonic acid metabolites to be produced by the cyclooxygenase pathway, and these are probably involved in the Entamoeba histolytica-induced changes in colonic transport. Neurohormones in Entamoeba histolytica may act directly on colonic tissue to stimulate intestinal secretion, probably via a Ca+(+)-dependent mechanism that is blockable by verapamil, or indirectly via stimulation of prostaglandin E2 generation and release from the rat colon via a cyclic adenosine monophosphate-dependent mechanism. These effects appear separate. The cyclic adenosine monophosphate-dependent secretion is the predominant mechanism in this model of colonic amebic diarrhea.

Amebiasis↗
PubMedDate not supplied

Amebiasis: introduction, current status, and research questions.

This series of five papers on the worldwide problem of amebiasis, its current status, research needs, and opportunities for progress has grown out of a renewal of investigative interest in amebiasis. The recent development of in vitro culture methods and of means to distinguish strain differences and the application of modern tools of cellular biology and biochemistry have raised new questions regarding strain definitions, virulence traits, host defenses, and the mechanism of invasive disease sometimes caused by Entamoeba histolytica. The clinical manifestations of amebic infections range from prolonged asymptomatic carriage to extensive, invasive intestinal and extraintestinal disease. The virulence traits of the parasite, whether stable in each strain or alterable by environmental or genetic factors, and the host factors involved in the development of disease and in protection have been investigated. From this series of reviews on the definition of amebiasis, its manifestations, its global magnitude, the methods for its detection, and the current understanding of its epidemiology, pathogenesis, cellular biology, and host defenses, a list of key questions that can now be addressed in work on amebiasis has been derived. Amebiasis is the third leading parasitic cause of death in the world. The need for work in this field is great, and the time is ripe for the application of new research tools to a better understanding of this remarkable tissue-lysing protozoan parasite and to the control of the disease it causes.

Amebiasis↗
PubMedDate not supplied

[Autochthonous amebiasis in the region of Nantes].

A retrospective study on amoebiasis observed in the central hospital in Nantes since twenty years, shows that, at least, 16 % of the intestinal cases and 1/6, 5 of 30 cases of hepatic amoebiasis are autochthonous.

Adult↗
PubMed2006

Oral infection of immunocompetent and immunodeficient mice with Balamuthia mandrillaris amebae.

Balamuthia mandrillaris is an opportunistic agent of lethal granulomatous amebic encephalitis (GAE). In mice, we have shown that intranasally instilled B. mandrillaris amebae infect the brain via the olfactory nerve pathway. In this study, we raised the question whether this ameba might also reach the brain after an oral/gastrointestinal infection. Immunocompetent (WT) and immunodeficient (RAG) mice received B. mandrillaris amebae by gavage into the esophagus. Mice of both groups became ill and some died (WT 20%, RAG 40%) within 42 days. All orally infected mice revealed B. mandrillaris amebae in the central nervous system. Outwardly intact amebae and/or specific antigen were found widely distributed in various organs and the stool. The data indicate that oral infection with B. mandrillaris leading to GAE is possible. Exit from the gastrointestinal tract and dissemination remains unresolved. Though stool cultures were negative, transmission of this highly pathogenic ameba via stool cannot be ruled out.

Amebiasis↗
PubMed1978

Chronic diarrhea. A practical approach.

Many patients who present with chronic diarrhea are not found to have an important organic disease. Most will have "functional" diarrhea. The history, the physical examination and the initial laboratory tests should lead to a provisional diagnosis, with respect to the organic or functional origin, and the location of disease in the small or the large bowel. Specific tests are then done to define particular organic causes of which malabsorption, inflammatory bowel diseases, carcinoma of the large bowel, parasitic infections, and metabolic disorders are most common. Patients with suspected functional diarrhea should be investigated at least by stool analysis, proctosigmoidoscopy, and barium enema. Functional diarrhea is common and these patients are no less susceptible to severe disease than is the rest of the population.

Adult↗
PubMed1991

Isolation of a strain-specific Entamoeba histolytica cDNA clone.

Entamoeba histolytica is an intestinal parasite causing significant morbidity and mortality worldwide. More tools are needed to understand the epidemiology and molecular pathogenesis of amebiasis. A cDNA library was constructed by using poly(A)+ RNA isolated from an axenic strain of E. histolytica, HM1:IMSS, which expresses a pathogenic isoenzyme pattern (zymodeme). Differential screening of the library yielded a strain-specific 3' polyadenylated cDNA clone, C2, possessing nine 26-nucleotide tandem repeats. RNA and DNA transfer blot analysis of four axenic strains of E. histolytica possessing the same pathogenic zymodeme revealed that the gene is present and expressed in pathogenic E. histolytica HM1:IMSS and 200:NIH but is not present in pathogenic strains HK-9 and Rahman. In addition, Southern blot analysis using the C2 clone showed heterogeneity of genomic organization between HM1:IMSS and 200:NIH. DNA dot blot hybridization analysis demonstrated that cDNA clone C2 was also able to distinguish axenically cultured E. histolytica strains possessing pathogenic zymodemes from those possessing nonpathogenic zymodemes and could detect as few as 100 amebic trophozoites. We conclude that C2 is a strain-specific E. histolytica cDNA clone that, in conjunction with other E. histolytica-specific probes, could serve as a useful epidemiologic tool.

Animals↗
PubMed1981

Amoebiasis as a cause of death in a Scottish resident.

An elderly woman, resident throughout her life in Scotland presented with abdominal pain and diarrhoea. A provisional diagnosis of ulcerative colitis was made on sigmoidoscopy. At post mortem Entamoeba Histolytica was demonstrated in considerable numbers in the mucosal ulcers. It would appear though extremely rare that amoebiasis should be considered in the differential diagnosis of colonic ulceration.

Aged↗