Production of amastigotes from metacyclic trypomastigotes of Trypanosoma cruzi

Attempts to recreate all the developmental stages of Trypanosoma cruzi in vitro have thus far been met with partial success. It is possible, for instance, to produce trypomastigotes in tissue culture and to obtain metacyclic trypomastigotes in axenic conditions. Even though T. cruzi amastigotes are known to differentiate from trypomastigotes and metacyclic trypomastigotes, it has only been possible to generate amastigotes in vitro from the tissue-culture-derived trypomastigotes. The factors and culture conditions required to trigger the transformation of metacyclic trypomastigotes into amastigotes are as yet undetermined. We show here that pre-incubation of metacyclic trypomastigotes in culture (MEMTAU) medium at 37°C for 48 h is sufficient to commit the parasites to the transformation process. After 72 h of incubation in fresh MEMTAU medium, 90% of the metacyclic parasites differentiate into forms that are morphologically indistinguishable from normal amastigotes. SDS-PAGE, Western blot and PAABS analyses indicate that the transformation of axenic metacyclic trypomastigotes to amastigotes is associated with protein, glycoprotein and antigenic modifications. These data suggest that (a) T. cruzi amastigotes can be obtained axenically in large amounts from metacyclic trypomastigotes, and (b) the amastigotes thus obtained are morphological, biological and antigenically similar to intracellular amastigotes. Consequently, this experimental system may facilitate a direct, in vitro assessment of the mechanisms that enable T. cruzi metacyclic trypomastigotes to transform into amastigotes in the cells of mammalian hosts

Aspectos funcionais, microbiológicos e morfológicos intestinais em crianças infectadas pelo vírus da imunodeficiência humana Functional, microbiological and morphological intestinal findings among human immunodeficiency virus infected children

RACIONAL: O trato gastrointestinal é freqüentemente acometido nas crianças infectadas pelo vírus da imunodeficiência humana, com importantes repercussões no seu estado nutricional e sobrevida. A maioria dos estudos relacionados a esse tema foi desenvolvida com adultos, sendo menos investigado o problema nas crianças OBJETIVOS: Estudar aspectos digestivo-absortivos, microbiológicos e morfológicos intestinais em crianças infectadas pelo vírus da imunodeficiência humana MATERIAL E MÉTODOS: Onze crianças infectadas pelo vírus da imunodeficiência humana, menores de 13 anos, pertencentes às categorias clínicas A, B ou C, divididas em dois grupos: cinco pacientes com relato atual ou recente de diarréia e seis pacientes sem diarréia nos 30 dias que antecederam à inclusão no estudo. Investigação proposta: biopsia de intestino delgado e reto para análise morfológica e microbiológica, coprocultura, protoparasitológico de fezes, pesquisa de rotavírus, micobactérias e Cryptosporidium; teste da D-xilose RESULTADOS: Todos os pacientes testados (9/11) apresentavam má absorção da D-xilose (8,4-24,4 mg/dL). Os achados histopatológicos de intestino delgado foram inespecíficos, representados em sua maioria, por enteropatia grau I a II (6/10). Em todos os casos foi constatado aumento do infiltrado celular do córion. As alterações histopatológicas do reto também foram inespecíficas, com presença de aumento do infiltrado celular do córion. A pesquisa de microorganismos enteropatogênicos só foi positiva em dois casos, sendo identificado Mycobacterium avium intracellulare e Cryptosporidium nas fezes CONCLUSÕES: Demonstrou-se alta prevalência (100%) de má absorção intestinal em crianças infectadas pelo vírus da imunodeficiência humana, com ou sem diarréia. Não foi possível estabelecer correlações quanto à presença de agentes enteropatogênicos, má absorção intestinal, alterações morfológicas intestinais e ocorrência ou não de diarréia. Não houve correlação entre os valores de D-xilose e os graus de atrofia vilositária.<br>BACKGROUD: Gastrointestinal tract disorders are frequent among human immunodeficiency virus infected children, with important repercussions on nutrition and survival. Most studies related to this subject were restricted to adults, being less investigated the problem in the children. AIMS: To study intestinal digestion, absorption, microbiological and morphological findings among human immunodeficiency virus infected children. MATERIAL AND METHODS: Eleven human immunodeficiency virus infected children under 13 years old, belonging to clinical categories A, B or C, separated in two groups: five patients with current or recent episode of diarrhea and six patients without diarrhea in the last 30 days preceding entering in study. Investigation proposed: microbiological and morphological analysis of small intestine and rectum biopsy; stool exams for bacterium, parasite, rotavirus, Mycobacterium species and Cryptosporidium; D-xylose test RESULTS: All tested subjects (9/11) had low D-xylose absorption (8,4 _ 24,4 mg d/L). Small intestinal mucosa histology findings were nonspecific, represented, in majority, of grade I/II enteropathy (6/10). Increased cellular infiltration of the chorion was observed in all specimens. Rectum histology alterations were also nonspecific, with chorion increased cellular infiltration. Mycobacterim avium intracellulare and Cryptosporidium were the solely microorganisms founded, both in stool CONCLUSIONS: Our study demonstrated high prevalence (100%) of intestinal malabsorption among human immunodeficiency virus infected children, despite the occurrence or not of diarrhea. It was not possible to establish relationships between the presence of microorganisms, intestinal malabsorption, intestinal morphologic findings and the occurrence or not of diarrhea. There was no correlation between D-xylose and intensity of villous atrophy