252 resultados para Genetically selected mice


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Immunosuppression bp immunotolerance was obtained in mice by inoculating Trypanosoma cruzi avirulent PF strain in high doses to mice. Direct and indirect laboratory tests loere used to demoiistrate the above statements.

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Trypanosoma cruzi of the cultivated PF strain when injected in mice per subcutaneous route, in adequate doses, is able to induce an efficient sterile immunization in the animais (for at least one year) as determined by whole blood cultures and histopathology.

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A dialyzable transfer factor (TFd) was obtained from spleen cells, of mice vaccinated with the avirulent PF strain of Trypanosoma cruzi. This factor reduced significahtly the parasitemia of animals treated before or after the infection with a virulent strain of the same parasite, but does not reduced the mortality rate to a level lower than that of the control mice. It is expected that in a next future, new techniques in the use ofsuch factor will bring better resutts.

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Mice were infected with blood forms of 17 Trypanosoma cruzi strains recently isolated from chronic patients, which were dassified as of low, medium or high virulence on grounds of the prepatent period, parasitemia and mortality at the acute phase. A total of 212 mice were studied after 3, 6, 9 and 12 months of infection. In the chronic phase, intracellular parasites were detected in 11.0%,27.9%and 54.0,% of mice inoculated, respectively, with the low, medium and high virulent strains (r= 0.98, p < 0.005). Heart fibrosis was also related to virulence, affecting 5.7%, 11.6%and30.8% (r = 0.98, p < 0.001) of the mice inoculated with the above strains; a similar relationship was observed between intensity and frequency of the heart inflammatory reaction and the severity of infection at its early stage. Necrotizing arteritis was detected in 12.2% of the inoculated animals and this lesion was related to the infection duration rather than to strain characteristics. Inflammatory lesions and tissue parasitism were stable within the period of observation, whereas fibrosis was Progressive. The findings suggest that mice may reproduce heart lesions resembling human pathology and that organ damage apparently depends on the parasite virulence.

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Infection by Trypanosoma cruzi in mice depresses hepatic granuloma formation around Schistosoma mansoni eggs. This immunodepressive effect occurred in mice with Chagas' disease at the acute and/or chronic phases, granulomas being signijicantly smaller than those in Controls. Data suggest that Chagas ' disease depresses the delayed hypersensitivity immune response directly.

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Mice infected with 60 cercariae of Schistosoma mansoni were more resistant to the sarcoma 180 ascites tumor. Tumor inoculation was performed 50 days after schistosoma infection and the animals were observed and weighed at 48 hours intervals for development and progression of malignancy. In infected mice the weight gain (ascites formation) started later and was shorter than in uninfected Controls. Also, the number of tumor cells into the peritoneal cavity 72h after tumor implantation was shorter in infected group than incontrols. This in creased resistance against a transplantable tumor probably is related to the effect of endotoxin on tumoricidal activity of macrophages activated by the infection. The immunodepression induced by Schistosoma mansoni infection enhances the proliferation of endogenous bacteria increasing the amount of endotoxin absorbed from the gut.

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Levamisole (phenylimidothiazol), considered a strong immunostimulant, when administered to healthy Swiss mice did not cause a significant increase in -the weight of their thymus, liver and spleen, even though the drug was used at different times before removing such organs. High doses ofdrug used in the 4-day prophylactic scheme had no antimalarial effect. However, when given to malaria infected mice 24 hours before, at the same time, and 24 hours after the inoculation of a chloroquine-sensitive or a chloroquine-resistant strain of Plasmodium berghei small doses of the drug induced a somewhat decreased parasitemia, the dose of 1 mg/kg body weight before the inoculum being the best scheme. The mortality rates by malaria in the levamisole treated groups were also delayed although all mice finally died. The data suggest that levamisole may display a stimulant effect on the depressed immune response caused by malaria.

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Mice infected with adult Schistosoma mansoni were dosed with a single oral dose of 125 or 250 mg/kg oltipraz, 50 or 100 mg/kg oxamniquine, or 200 or 400 mg/kg praziquantel. The mortality rate of worms and oogram changes were determined between 1 and 16 weeks after dosing. The time required between dosing and postmortem to obtain maximum effectiveness was 1 week for praziquantel, 2 weeks for oxamniquine and 8 weeks for oltipraz. Changes in oograms persisted throughout most of the experiment, although relapse has been observed at the 4th week on.

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Body, liver and spleen weights; histopathology of the liver, spleen and intestines; hepatic and serum soluble proteins changes were the parameters studied in undernourished Swiss albino mice experimentally infected with S. mansoni. Non-infected deficient animab had lower liver/body weight and spleen/body weight ratios as compared to the controls (22.60% casein group). Infected mice showed higher values regardless the type of diet. Undernourished infected subgroup showed a persistent exudative periovular reaction in the liver. Soluble hepatic proteins content and serum protein fractions appeared to be lower in the deficient infected mice. A significant difference was detected in the gammaglobulin fraction between infected and non-infected animals fed the control diet with higher values for the former. Our data suggest that the effects of malnutrition, per se, are sometimes more detrimental to the host than those due to Manson 's schistosomiasis.

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Protein nutritionalstatus indicators were studied in weanling albino Swiss mice infected with S. mansoni andfed the Regional Basic Diet (RBD)from Northeast Brazil, a multideficient diet of low-protein content. Each mouse was infected percutaneously with 80 cercariae. The experiment lasted 63 days. The growth curve, food consumption, protein intake, weight gain, Protein Efficiency Ratio (PER) and Net Protein Ratio (NPR) were the parameters investigated. RBD-fed mice showed a marked weight loss, a lower food and protein intake, a slower body weight gain and lower rates of food protein utilization when compared to casein-fed animals. Differences between infected and non-infected mice were not consistent. The present results suggest that the effects of RBD-induced malnutrition on health and nutritional conditions of the mice are more severe than those of Manson's schistosomiasis, in the initial phase of the disease.

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Adult mice were submitted to different degrees of protein restriction for five weeks (4.75, 9.5,14.25 and 19% of protein in isocaloric diets with normal content of mineral and vitamins), being subsequently infected with two strains of Trypanosoma cruzi: 10(5) trypomastigotes of Y strain or 14(5) trypomastigotes of CL strain. The same diet was maintained for all animals and the infection wasfollowed up by evaluation of blood parasites, mortality and intensity of lesions in the heart and skeleton muscle. Only severe protein restriction (4.75%) induced decrease in resistance to the infection with both the Y and CL strains of T. cruzi, which resulted in higher parasitemia and mortality. The inflammatory lesions in heart and skeleton muscle were less extensive in groups with severe protein restriction despite the increased number of parasite in muscle cells. Depression of immune mechanisms could be responsiblefor the reduced resistance and reduced inflammatory reaction after T. cruzi infection in severely protein restricted animals.