Linear mixed model for weight analysis in mice infected by Trypanosoma cruzi

The use of linear mixed models for nested structure longitudinal data is called hierarchical linear modeling. Thismodeling takes into account the dependence of existing data within each level and between hierarchical levels. The process of modeling, estimating and analyzing diagnoses was illustrated through data on the weights of mice experimentally infected by Trypanosoma cruzi, divided into different treatment groups, with the purpose of verifying the evolution of their body weight as a result of usingdifferent types of biotherapeutics produced from Gallus gallus domesticus(chicken) serum to treat Trypanosoma cruzi. Through the model selection criteria AIC and BIC and the likelihood ratio test, a model was chosen to describe the data correctly. Model diagnoses were then performed by means of residual analysis for both levels and an analysis of influential observations to verify if any observations were signaled as influencing the fixed effects, the components of variance and the adjusted values. After the analysis, it was possible to notice that the observations that were signaled as influential had little impact on the Model chosen initially, so it was maintained, with no differences being evidenced between the treatments with the biotherapeutics tested; only the Time variable and the Random intercept were necessary to describe the weight of the mice.

Analyzing weight evolution in mice infected by Trypanosoma cruzi

Concerning the specificities of a longitudinal study, the trajectories of a subject's mean responses not always present a linear behavior, which calls for tools that take into account the non-linearity of individual trajectories and that describe them towards associating possible random effects with each individual. Generalized additive mixed models (GAMMs) have come to solve this problem, since, in this class of models, it is possible to assign specific random effects to individuals, in addition to rewriting the linear term by summing unknown smooth functions, not parametrically specified, then using the P-splines smoothing technique. Thus, this article aims to introduce this methodology applied to a dataset referring to an experiment involving 57 Swiss mice infected by Trypanosoma cruzi, which had their weights monitored for 12 weeks. The analyses showed significant differences in the weight trajectory of the individuals by treatment group; besides, the assumptions required to validate the model were met. Therefore, it is possible to conclude that this methodology is satisfactory in modeling data of longitudinal sort, because, with this approach, in addition to the possibility of including fixed and random effects, these models allow adding complex correlation structures to residuals.

The Association of Ponderal Benznidazole with its Ultra-high Diluted Formula Reduces the Toxic Effects and Allows Increasing of Dose in Dose-dependent Protocol in Mice Infected with Trypanosoma cruzi

Although several diseases are treated by toxic drugs, their side effects may hamper adherence to the therapy. The aim of this study is to evaluate the effect of the association of ponderal benznidazole (BZ) with its ultra-high diluted (UHD) formula on clinical and parasitological parameters of mice infected by Trypanosoma cruzi (T. cruzi). 24 non-isogenic Swiss mice were divided into groups: CI – infected animals treated with 7% alcohol; BZp – infected animals treated with BZ (500 mg/ kg) from the beginning of infection; BZp+d – infected animals treated with ponderal BZ and with UHD BZ, which started to be administered four days after the beginning of treatment with ponderal BZ; CNI - group of non-treated and non-infected animals. The UHD medicine was prepared according to Phamacopoeia until 30x. The different treatment schedules were statistically compared through parasitological and clinical parameters. The group BZp+d displayed more favorable clinical evolution than the group BZp, with improvement of mass gain, feed conversion and water intake, presenting data approximated to CNI group. The significant increase of the body temperature of BZp+d group indicates an activation of the immune system which was not observed in the other groups. Moreover, the anti-parasitic effect of the ponderal drug was maintained in all parasitological parameters of this group. By reducing the side effects and maintaining the action of the ponderal drug, the combination of toxic drugs with their UHD formula could be considered a way of improving efficacy of the treatment...

A infecção por Trypanossoma cruzi é um problema de saúde pública e o único medicamento disponível no Brasil é o benznidazol (BZ), com efeitos limitados e tóxicos. Estudos anteriores com BZ na dose de 200 mg/kg indicaram que a administração de BZ diluído (30d) controla os efeitos tóxicos da droga em dose ponderal, sem alterar a sua ação terapêutica. Sob essa perspectiva e considerando a ação do BZ dose dependente, aumentar a quantidade de droga administrada significaria uma melhora na eficácia do tratamento. Portanto, este trabalho teve como objetivo avaliar o efeito do BZ ponderal (BZP), na dose de 500 mg/kg associado com BZ diluído (BZD) nos parâmetros clínicos de camundongos infectados por T. cruzi. Em estudo cego, controlado e randomizado, foram utilizados 23 camundongos suíços, machos, com 8 semanas divididos em grupos: CNI - Não infectados e não tratados; CI - Infectados e tratados com álcool 7 %; BZP - Infectados tratados com BZ (500 mg/kg de peso/ animal) a partir do início da infecção; BZP + BZD - Infectados e tratados com a associação de BZP e BZD. Os medicamentos foram administrados por gavagem (0,2 mL/ dia/ animal). O BZP foi administrado a partir da constatação da infecção. O BZ diluído foi preparado de acordo com a Farmacopeia Homeopática Brasileira e administrado 4 dias após o início do tratamento com BZP. Os parâmetros clínicos, avaliados diariamente, incluíram: peso, consumo de ração e água, temperatura e quantidade de excretas. A análise clínica apontou melhores resultados nos grupos BZP e BZP + BZD, mostrando melhor evolução de peso, consumo de ração, água e excretas quando comparado aos grupos não tratados (p< 0.05)...