RESUMO
The in vitro cytopathic effect of four strains of Trichomonas vaginalis on cultured epithelial monolayers was analyzed through electrophysiology and electron microscopy. Interaction of trichomonads of two virulent strains (GT-10 and GT-13) with cultured MDCK cell monolayers mounted in Ussing chambers produced a rapid decrease in transepithelial resistance to less than 30% of control values after only 15 min. By 30 min the electrical resistance was practically abolished by the virulent parasites. In contrast, of two attenuated strains of trichomonads (GT-3 and GT-7) analyzed under similar conditions, GT-3 trophozoites required 180 min to reduce transepithelial resistance to 9% of control values, while monolayers in contact with GT-7 parasites still showed 28% of control values at this time of incubation. Sequential scanning electron microscopy confirmed the much faster and widespread cytopathic effect of virulent parasites. In contrast, the slow lytic process produced by attenuated trophozoites was reduced to focal areas of direct contact with epithelial cells. Another difference was found by measurement of the surface charge of the four strains of T. vaginalis by means of cell microelectrophoresis. While the two virulent strains showed a negative surface charge, the two attenuated strains had no detectable surface charge at neutral pH. When parasites were incubated with cationized ferritin and studied with transmission electron microscopy the surface of virulent trichomonads appeared heavily labeled, whereas the surface of attenuated parasites had only sparse and irregular ferritin binding.
Assuntos
Extensões da Superfície Celular/ultraestrutura , Propriedades de Superfície , Trichomonas vaginalis/patogenicidade , Trichomonas vaginalis/ultraestrutura , Fatores de Virulência , Animais , Linhagem Celular , Impedância Elétrica , Eletroforese , Eletrofisiologia , Feminino , Humanos , Camundongos , Microscopia Eletrônica de Varredura , Especificidade da Espécie , Vaginite por Trichomonas/parasitologia , Trichomonas vaginalis/classificaçãoRESUMO
The in vitro cytopathic effect of Trichomonas vaginalis on epithelial cells was explored through the interaction of trophozoites of the virulent strain GT-10 with MDCK monolayers. The interaction was analyzed through electrophysiology, video microscopy, and transmission and scanning electron microscopy. Electrical measurements revealed that living parasites produced severe damage to the cell monolayers within 30 min, manifested as a rapid decrease in transepithelial resistance. Microscopic observations demonstrated that when placed in contact with epithelial cells, trichomonas formed clumps through interdigitations and transient plasma membrane junctions between adjacent parasites. Also, attached trophozoites adopted an ameboid shape. The in vitro cytopathic action of T. vaginalis on MDCK cells was initially evident by modifications of the plasma membrane, resulting in opening of tight junctions, membrane blebbing, and monolayer disruption. After 15 min of interaction the damage was focal, concentrating at sites where parasite clumps adhered to the monolayer. At 30 min practically all MDCK cells were dead, whether or not trichomonas were attached to them. These events were followed by detachment of lysed cells and complete disruption of the monolayer at 60 min. Electron microscopy demonstrated a peculiar form of adhesion that appears to be specific for trichomonas, in which the basal surface of T. vaginalis formed slender channels through which microvilli and cytoplasmic fragments of epithelial cells were internalized. The same sequence of lytic events was found with the less virulent GT-3 strain. However, the time course of cytolysis with GT-3 parasites was much slower, and lysis was limited to areas of attachment of T. vaginalis.
Assuntos
Morte Celular , Trichomonas vaginalis/patogenicidade , Trichomonas vaginalis/ultraestrutura , Adulto , Animais , Adesão Celular , Linhagem Celular , Membrana Celular/parasitologia , Cães , Impedância Elétrica , Células Epiteliais , Epitélio/parasitologia , Epitélio/ultraestrutura , Feminino , Humanos , Rim , Microscopia Eletrônica , Microscopia Eletrônica de Varredura , Vaginite por Trichomonas/parasitologia , Trichomonas vaginalis/fisiologia , VirulênciaRESUMO
A morphological analysis of an experimental model of invasive intestinal amebiasis was carried out using the washed-closed cecal loop model in hamsters and guinea-pigs. By light microscopy, few amebic trophozoites adhered to the intestinal epithelium, whereas many associated to the mucus blanket. Some trophozoites attached to the interglandular epithelium, during the first 10 to 15 hours of interaction. Hereafter, the parasites destroyed gradually the epithelium and were associated with normal and lysed inflammatory cells. Some amebas have cell debris and erythrocytes in their cytoplasms. Typical amebic ulcer contained abundant trophozoites at the basolateral area. The results suggest that intestinal mucus and muscularis mucosa are temporal barriers to amebic invasion and extension of the ulcer. At the mucosal and submucosal levels, lysis of inflammatory cells produced by amebas seems to play an important role in the extension of the ulcer.
Assuntos
Disenteria Amebiana/patologia , Animais , Ceco/parasitologia , Ceco/patologia , Cricetinae , Disenteria Amebiana/parasitologia , Entamoeba histolytica/crescimento & desenvolvimento , Entamoeba histolytica/isolamento & purificação , Feminino , Cobaias , Inflamação , Mucosa Intestinal/parasitologia , Mucosa Intestinal/patologia , Masculino , Músculo Liso/parasitologia , Músculo Liso/patologiaRESUMO
Some strains of mice are known to be relatively resistant to hepatic or intestinal amebic infections. In order to know if the intestinal resistance is expressed few hours after infection, we inoculated axenic amebae in three inbred strains of mice either by direct intracecal injection or by infection of a washed-closed cecal loop. We found that amebae do not survive in conventional animals but they colonize longer in animals with the cecal loop. However, the survival was low after 24 hours postinfection. Balb/c mice were more susceptible and CBA mice more resistant. Our results suggest that genetic resistance to intestinal amebiasis is expressed in mice in the early phases of infection.
Assuntos
Disenteria Amebiana/genética , Camundongos Endogâmicos BALB C/parasitologia , Camundongos Endogâmicos C3H/parasitologia , Camundongos Endogâmicos CBA/parasitologia , Animais , Ceco/parasitologia , Sobrevivência Celular , Entamoeba histolytica/crescimento & desenvolvimento , Feminino , Interações Hospedeiro-Parasita/genética , Imunidade Inata/genética , Camundongos , Camundongos Endogâmicos BALB C/genética , Camundongos Endogâmicos C3H/genética , Camundongos Endogâmicos CBA/genéticaRESUMO
The morphological features of early intestinal ulcerations induced in rodents with axenic cultures of Entamoeba histolytica were studied by scanning and transmission electron microscopy. Amebas did not attach to the luminal surface of the mucosa except at interglandular regions, where parasites penetrated apparently through pseudopodial movement. Once in the lamina propria, trophozoites multiplied and destroyed mucosal components. Damage extended laterally through the mucosa, but progression to deeper layers of the intestinal wall was prevented by the muscularis mucosae, which acted as a partial barrier. This was eventually breached at focal points where amebas invaded the submucosa. Electron microscopy clearly showed the lysis of abundant polymorphonuclear neutrophil leukocytes (PMNs) by the amebas at the periphery of intestinal ulcerations as well as the lack of bacteria at these sites. This study demonstrates that recruitment and destruction of inflammatory cells following intestinal amebic invasion may take place in the absence of bacterial multiplication. The observations provide histological support to the hypothesis that lysis of PMNs by trophozoites participates in the genesis of amebic intestinal lesions.
Assuntos
Ceco/ultraestrutura , Disenteria Amebiana/patologia , Entamoeba histolytica/ultraestrutura , Mucosa Intestinal/ultraestrutura , Animais , Ceco/parasitologia , Cricetinae , Modelos Animais de Doenças , Disenteria Amebiana/parasitologia , Cobaias , Mucosa Intestinal/parasitologia , Microscopia Eletrônica , Microscopia Eletrônica de VarreduraRESUMO
The in vitro activity of the antibacterial agent nalidixic acid (HNal) and its iron (III) complex (FeNal) against Entamoeba histolytica HM1 strain trophozoites in axenic or monoxenic (associated with Clostridium symbiosum) cultures was investigated. Using a dilution test with TYI-S-33 medium, this protozoan was found to be susceptible to both drugs, but FeNal showed amoebicidal activity only at concentrations higher than those used with HNal.