[Quantitative and qualitative studies of the Auerbach and Meissner plexuses of the esophagus in dogs inoculated with Trypanosoma cruzi]

Dogs as a Model for Chemotherapy of Chagas Disease and Leishmaniasis

BACKGROUND

Dogs are natural reservoir of Chagas disease (CD) and leishmaniasis and have been used for studies of these infections as they develop different clinical forms of these diseases similar to humans.

OBJECTIVE

This article describes publications on the dog model relative to CD and leishmaniasis chemotherapy.

METHODS

The search of articles was based on PubMed, Scopus and MESH using the keywords: dog, Trypanosoma cruzi, treatment (T. cruzi chemotherapy analysis), Leishmania chagasi, Leishmania infantum, canine visceral leishmaniasis, treatment (Leishmania chemotherapy evaluation).

RESULTS

Benznidazole and nifurtimox were used as a reference in the treatment of CD and in combination with other compounds. Eleven out of the fifteen studies have authors from the same team, using similar protocols and post-treatment evaluations, which assured more reproducibility and credibility. Twenty leishmaniasis studies, especially on visceral leishmaniasis, presenting at least one parasitological analysis tested in distinct monochemotherapy and polychemotherapy approaches were accessed. Data demonstrated that polychemotherapy was more effective in improving the clinical signs and parasitism control.

CONCLUSION

The benefits of treatment in terms of reducing or eliminating lesions and/or cardiac dysfunctions were demonstrated at acute and/or chronic phases relative to parasite load and/or the T. cruzi strain resistance to treatment. BZ presented better therapeutic results than the two EBI compounds evaluated. Although treatment of the canine visceral leishmaniasis was not able to induce complete parasite clearance, it can improve clinical recovery. Thus, the dog is a good model for CD and leishmaniasis studies of chemotherapy and may be indicated for pre-clinical trials of new treatments.

Myenteric plexus is differentially affected by infection with distinct Trypanosoma cruzi strains in Beagle dogs

Chagasic megaoesophagus and megacolon are characterised by motor abnormalities related to enteric nervous system lesions and their development seems to be related to geographic distribution of distinct Trypanosoma cruzi subpopulations. Beagle dogs were infected with Y or Berenice-78 (Be-78) T. cruzi strains and necropsied during the acute or chronic phase of experimental disease for post mortem histopathological evaluation of the oesophagus and colon. Both strains infected the oesophagus and colon and caused an inflammatory response during the acute phase. In the chronic phase, inflammatory process was observed exclusively in the Be-78 infected animals, possibly due to a parasitism persistent only in this group. Myenteric denervation occurred during the acute phase of infection for both strains, but persisted chronically only in Be-78 infected animals. Glial cell involvement occurred earlier in animals infected with the Y strain, while animals infected with the Be-78 strain showed reduced glial fibrillary acidic protein immunoreactive area of enteric glial cells in the chronic phase. These results suggest that although both strains cause lesions in the digestive tract, the Y strain is associated with early control of the lesion, while the Be-78 strain results in progressive gut lesions in this model.

Morphological and quantitative study of ganglionated plexus of Calomys callosus trachea

Calomys callosus is a wild, native forest rodent found in South America. In Brazil, this species has been reported to harbour the parasitic protozoan Trypanosoma cruzi. The ganglionated plexus of this species was studied using whole-mount preparations of trachea that were stained using histological and histochemical methods. The histological methods were used to determine the position of the ganglia with respect to the trachea muscle and to determine the presence of elastic and collagen fibers. The histochemical method of NADH-diaphorase was used for morphometric evaluations of the plexus. The tracheal plexus lies exclusively over the muscular part of the organ, dorsal to the muscle itself. It varies in pattern and extent between animals. The average number of neurons was 279 and the cellular profile area ranged from 38.37 microm2 to 805.89 microm2. Acetylcholinesterase (AChE) histochemistry verified that both ganglia and single neurons lie along nerve trunks and are reciprocally interconnected with the plexus. Intensely AChE-reactive neurons were found to be intermingled with poorly reactive ones. Two longitudinal AChE-positive nerve trunks were also observed and there was a diverse number of ganglia along the intricate network of nerves interconnecting the trunks. A ganglion capsule of collagen and elastic fibers surrounding the neurons was observed. Under polarized light, the capsule appeared to be formed by Type I collagen fibers.

Autoantibodies in patients with gut motility disorders and enteric neuropathy

OBJECTIVE

Enteric neuropathy with mild inflammation (ganglionitis) has been described in several motility disorders including irritable bowel syndrome (IBS), enteric dysmotility (ED), slow-transit constipation (STC) and chronic intestinal pseudo-obstruction (CIPO). The purpose of this study was to test the hypothesis that autoantibodies directed against specific neural antigens including ion channels may be associated with this finding.

MATERIAL AND METHODS

Comprehensive routine and immunohistochemical analyses of full-thickness jejunal laparoscopic biopsies were performed on patients fulfilling the international criteria for IBS, ED, STC and CIPO. Patients with ganglionitis had sera screened for specific antibodies to voltage-gated calcium channels (VGCCs) of P/Q- and N-type, voltage-gated potassium channels (VGKCs), glutamic acid decarboxylase (GAD) and neuronal alpha3-AChR by validated immunoprecipitation assays.

RESULTS

Thirty-three patients were included in the study. Two of them, both with IBS, were found to have positive antibody titres. One had anti-VGKC antibodies and one had anti-alpha3-AChR antibodies. No antibodies were detected in GAD or VGCCs (case reports presented).

CONCLUSIONS

A small proportion of patients with inflammatory enteric neuropathy have antibodies directed towards neuronal ion channels. The pathogenic role of such antibodies requires determination but may represent a possible aetiology of severe functional symptoms in these groups of patients.

Human enteric neuropathies: morphology and molecular pathology

The aim of this study is to review current understanding of the molecular and morphological pathology of the enteric neuropathies affecting motor function of the human gastrointestinal tract and to evaluate the described pathological entities in the literature to assess whether a new nosology may be proposed. The authors used PUBMED and MEDLINE searches to explore the literature pertinent to the molecular events and pathology of gastrointestinal motility disorders including achalasia, gastroparesis, intestinal pseudo-obstruction, colonic inertia and megacolon in order to characterize the disorders attributable to enteric gut neuropathies. This scholarly review has shown that the pathological features are not readily associated with clinical features, making it difficult for a patient to be classified into any specific category. Individual patients may manifest more than one of the morphological and molecular abnormalities that include: aganglionosis, neuronal intranuclear inclusions and apoptosis, neural degeneration, intestinal neuronal dysplasia, neuronal hyperplasia and ganglioneuromas, mitochondrial dysfunction (syndromic and non-syndromic), inflammatory neuropathies (caused by cellular or humoral immune mechanisms), neurotransmitter diseases and interstitial cell pathology. The pathology of enteric neuropathies requires further study before an effective nosology can be proposed. Carefully studied individual cases and small series provide the basic framework for standardizing the collection and histological evaluation of tissue obtained from such patients. Combined clinical and histopathological studies may facilitate the translation of basic science to the clinical management of patients with enteric neuropathies.

Morphometry of submucous and myenteric esophagic plexus of dogs experimentally reinfected with Trypanosoma cruzi

We carried out a morphometric study of the esophagus of cross-bred dogs experimentally infected or consecutively reinfected with Trypanosoma cruzi 147 and SC-1 strains, in order to verify denervation and/or neuronal hypertrophy in the intramural plexus. The animals were sacrificed in the chronic stage, 38 months after the initial infection. Neither nests of amastigotes, nor myositis or ganglionitis, were observed in all third inferior portions of esophageal rings analyzed. No nerve cell was identified in the submucous of this organ. There was no significant difference (p>0.05) between the number, maximum diameter, perimeter, or area and volume of the nerve cells of the myenteric plexus of infected and/or reinfected dogs and of the non-infected ones. In view of these results we may conclude that the 147 and SC-1 strains have little neurotropism and do not determine denervation and/or hypertrophy in the intramural esophageal plexuses in the animals studied, independent of the reinfections.