National Center for Biotechnology Information NCBI NLM MEDLINE Mice review animals humans pubmed abstract nih national institutes of health national library of medicine models Neuronal Plasticity / physiology Cell Division / physiology biological cellular senescence / physiology transcription factors / physiology learning brain chemistry synapses / physiology xenopus laevis joel d richter pmid:17481902 doi:10.1016/j.tibs.2007.04.004 memory / physiology oogenesis / physiology protein biosynthesis / drug effects rna-binding proteins / physiology xenopus proteins / physiology mrna cleavage and polyadenylation factors / physiology*