RESUMO
We present a detailed analysis of the critical behavior close to the Mott-Anderson transition. Our findings are based on a combination of numerical and analytical results obtained within the framework of typical-medium theory-the simplest extension of dynamical mean field theory capable of incorporating Anderson localization effects. By making use of previous scaling studies of Anderson impurity models close to the metal-insulator transition, we solve this problem analytically and reveal the dependence of the critical behavior on the particle-hole symmetry. Our main result is that, for sufficiently strong disorder, the Mott-Anderson transition is characterized by a precisely defined two-fluid behavior, in which only a fraction of the electrons undergo a "site selective" Mott localization; the rest become Anderson-localized quasiparticles.
RESUMO
Several density gradients were tested for the isolation of parasitic nematode, Angiostrongylus costaricensis, first-stage larvae from rodent feces. With a 45/72% Percoll gradient, 83-99% (89.56+/-6.57%) of the larvae were recovered in a clean preparation.
Assuntos
Angiostrongylus/isolamento & purificação , Fezes/parasitologia , Doenças dos Roedores/parasitologia , Infecções por Strongylida/veterinária , Animais , Centrifugação com Gradiente de Concentração , Coloides , Larva , Camundongos , Camundongos Endogâmicos C3H , Povidona , Dióxido de Silício , Infecções por Strongylida/parasitologiaRESUMO
White rats were inoculated with 10(6) trypomastigotes of Trypanosoma lewisi, simultaneously or two days before and after inoculation with 10(5) oocysts of T. gondii. A greater number of cysts was found in the brain of the animals having concomitant inoculations, as compared with rats inoculated with either one of the two parasites. An apparent immunosuppressive effect is likely. Since both organisms can be found in rats, it is possible that infections with T. lewisi, could make this rodent another intermediate host for Toxoplasma infections.
Assuntos
Encefalopatias/parasitologia , Toxoplasma/imunologia , Toxoplasmose Animal/parasitologia , Trypanosoma lewisi/imunologia , Tripanossomíase/parasitologia , Animais , Encefalopatias/imunologia , Vetores de Doenças , Tolerância Imunológica , Ratos , Ratos Wistar , Toxoplasmose Animal/imunologia , Tripanossomíase/imunologiaRESUMO
To demonstrate that T. lewisi infection increases T. gondii multiplication in white rats, groups of five Wistar or Sprague Dawley rats were inoculated with 10(6) T. lewisi trypomastigotes and four or seven days later infected with Toxoplasma tachyzoites. Host survival time was monitored, and the presence of T. gondii was confirmed in all dead rats by studying peritoneal exudate smears and lung tissue sections stained with haematoxylin-eosin. The presence of Toxoplasma cysts or antibodies was checked in the brain of surviving rats. The increase is observed four days after trypanosome inoculation and is dependent on rat strain, but not on inoculum size or rat age. Humoral and cellular factors may have a role in the increase as has been reported for other experimental infections with African trypanosomes and T. cruzi.
Assuntos
Toxoplasmose Animal/parasitologia , Trypanosoma lewisi , Animais , Interações Hospedeiro-Parasita/imunologia , Tolerância Imunológica/imunologia , Ratos , Ratos Sprague-Dawley , Ratos Wistar , Toxoplasmose Animal/imunologiaRESUMO
To demonstrate that T. lewisi infection increases T. gondii multiplication in white rats, groups of five Wistar or Sprague Dawley rats were inoculated with 10(6) T. lewisi trypomastigotes and four or seven days later infected with Toxoplasma tachyzoites. Host survival time was monitored, and the presence of T. gondii was confirmed in all dead rats by studying peritoneal exudate smears and lung tissue sections stained with haematoxylin-eosin. The presence of Toxoplasma cysts or antibodies was checked in the brain of surviving rats. The increase is observed four days after trypanosome inoculation and is dependent on rat strain, but not on inoculum size or rat age. Humoral and cellular factors may have a role in the increase as has been reported for other experimental infections with African trypanosomes and T. cruzi
Assuntos
Animais , Ratos , Toxoplasmose Animal/parasitologia , Trypanosoma lewisi , Ratos Sprague-Dawley , Ratos Wistar , Interações Hospedeiro-Parasita/imunologia , Tolerância Imunológica/imunologia , Toxoplasmose Animal/imunologiaRESUMO
Presence of T. gondii in meat from several sources was determined by traditional methods and by a new simplified method in which animals are fed meat directly without any previous treatment with artificial gastric fluid. Tissues are ground and the animals ingest them naturally. Determination of Toxoplasma in lungs or brain (as well as by specific antibody test), showed no statistically significant differences between both methods.
Assuntos
Parasitologia de Alimentos , Carne/parasitologia , Toxoplasma/isolamento & purificação , Animais , Bovinos , Camundongos , Fatores de TempoRESUMO
Sigmodon hispidus, a cotton rat, was inoculated with tachyzoites or oocysts of Costa Rican strains of Toxoplasma gondii to demonstrate the resistance to this parasite, as compared with mice, hamster and white rat infection. Susceptibility to tachyzoite inoculation was higher in this animal than in white rats but lower than in the other animals. Independent to the Toxoplasma strain studied, oocyst infection was less lethal for S. hispidus when compared with mice and hamsters; the results were similar to those observed for white rats. There is a probable participation of this wild animal in the natural Toxoplasma life cycle.
Assuntos
Toxoplasma/fisiologia , Toxoplasmose Animal/imunologia , Animais , Cricetinae , Suscetibilidade a Doenças , Imunidade Inata , Mesocricetus , Camundongos , Camundongos Endogâmicos , Ratos , Ratos Sprague-Dawley , SigmodontinaeRESUMO
Groups of 1, 5, 10, 15 and 30 day old rats (Sprague Dawley) and Wistar mice were infected per os with different inocula of Toxoplasma gondii oocysts from an avirulent strain. Infection pattern was followed by determination of survival time, tissue lesions, parasite presence and serology. Although all the animals survived the total experimental period (30 day), there were important differences between both rodents regarding to Toxoplasma natural resistance. Brain cysts, as well as tachyzoites in other organs were regularly present in mice but not in rats. On the other hand, most of the organs from mice presented characteristic T. gondii lesions, while in rats a normal tissues were observed, with the exception of an acute reaction found in the brain of a 15d old animal.