the efficacy of clindamycin and monensin were evaluated in the prevention of oocyst shedding of kittens with toxoplasma gondii (tehran strain). in this study, 28 healthy kittens aged 1.5 – 2 months old divided randomly into 4 groups of seven. in group 1, kittens were fed with the infected brain tissues of mice, all of seven kittens (100 %), shed oocyst, nearly 1 week after infection, which last...

An evolutionary constraint is a bias or limitation in phenotypic variation that a biological system produces. One can distinguish physicochemical, selective, genetic and developmental causes of such constraints. Here, I discuss these causes in three classes of system that bring forth many phenotypic traits and evolutionary innovations: regulatory circuits, macromolecules and metabolic networks....