controlled study nonhuman 2,338 article 2,264 priority journal 2,134 Animals 1,676 animal cell 1,136 protein expression 1,066 human 1,018 unclassified drug 998 animal experiment 934 Humans 920 mouse 856 metabolism 788 human cell 752 Mice 748 animal tissue 738 female 732 male 730 Article 646 Female 616 Male 596 animal 588 enzyme activity 512 signal transduction 494 animal model 482 rat 466 protein function 448 genetics 426 Rats 416 messenger RNA 370