Behavioral changes in Rattus norvegicus experimentally infected by Toxocara canis larvae

Toxocara canis is a common canine nematode parasite and one of its possible transmission mechanisms is the predation of infected rodents by canids. Fifty Rattus norvegicus were used to study behavioral alterations in rodents infected by T. canis larvae. The rats were divided into three groups: G1, 20 rats infected with 300 T. canis eggs; G2, 20 rats infected with 2,000 T. canis eggs; and G3, 10 non-infected rats. Thirty and 60 days post-infection, rats from all the groups were submitted to an open-field apparatus for five min and subsequently, to an elevated plus-maze apparatus, again for five min. The data obtained indicated improvement in mobility (total locomotion time and rearing frequency) and exploratory behavior in infected rats, principally in G2, which provides some support for the hypothesis that behavioral alterations in rodents infected by Toxocara canis larvae enhance the transmission rate of this ascarid to dogs.Toxocara canis é um nematódeo parasita habitual do intestino delgado de cães. Um dos mecanismos conhecidos de transmissão para cães é representado pela predação de pequenos roedores que, como hospedeiros paratênicos albergam larvas de Toxocara canis em seus tecidos. Para avaliar a ocorrência de alterações de comportamento em roedores infectados por Toxocara canis 50 exemplares de Rattus norvegicus foram utilizados no experimento. Os animais foram divididos em três grupos: G1 - 20 ratos infectados com 300 ovos de Toxocara canis; G2 - 20 ratos infectados com 2.000 ovos de Toxocara canis e G3 - 10 ratos sem infecção. Trinta e 60 dias após a infecção avaliou-se a ocorrência de alterações comportamentais nos três grupos submetendo os animais, primeiramente, a uma arena de campo aberto durante cinco minutos e, a seguir, a labirinto em cruz elevado por mais cinco minutos. Os resultados obtidos indicaram aumento significativo da mobilidade (tempo total de movimentação e número de vezes em que os animais se levantaram nas patas traseiras) e comportamento exploratório nos ratos infectados, principalmente nos pertencentes ao G2, sugerindo a ocorrência de alterações comportamentais que favoreceriam a transmissão de Toxocara canis para canídeos por meio de relação presa-predador

Hypermutable myotonic dystrophy CTG repeats in transgenic mice

Myotonic dystrophy (DM) is one of a growing number of inherited human disorders associated with the expansion of triplet repeat DNA sequences. Expanded alleles are highly unstable in both the germline and soma, accounting in large part for the unusual genetics of this disorder, its phenotypic variability and probably, the progressive nature of the symptoms. However, the molecular mechanisms and the genetic factors modulating repeat stability in DM and the other human disorders associated with expanded repeats are not well understood. To provide a model system in which the turnover of triplet repeats could be studied throughout mammalian development, we have generated five transgenic mouse lines incorporating expanded CTG/CAG arrays derived from the human DM locus. Transgene analysis has revealed germline hypermutability, including expansions, deletions and parent-of-origin effects, somatic and early embryonic instability and segregation distortion. Mutational differences between lines and sexes demonstrate that stability, as in humans, is modulated by as yet unidentified cis and trans acting genetic elements