animal experiment controlled study male nonhuman 138 unclassified drug Animals 104 Male 104 priority journal 91 article 86 animal tissue 78 mouse 75 animal cell 70 animal model 70 animal 58 protein expression 56 Article 54 Mice 51 female 50 metabolism 45 human 34 rat 34 messenger RNA 33 in vitro study 32 in vivo study 32 Rats 30 Female 28 gene expression 25 Humans 24 physiology 24 genetics 23