animal experiment metabolism nonhuman protein expression unclassified drug Animals 56 animal 56 controlled study 56 animal cell 45 mouse 38 Mice 36 Article 34 animal model 34 priority journal 31 human 30 genetics 29 animal tissue 28 Humans 27 article 27 female 27 messenger RNA 27 Female 25 Male 24 male 24 pathology 24 protein function 20 human cell 18 in vivo study 18 physiology 18 RNA, Messenger 17