Priority effects transcend scales and disciplines in biology.

Although primarily studied through the lens of community ecology, phenomena consistent with priority effects appear to be widespread across many different scenarios spanning a broad range of spatial, temporal, and biological scales. However, communication between these research fields is inconsistent and has resulted in a fragmented co-citation landscape, likely due to the diversity of terms used to refer to priority effects across these fields. We review these related terms, and the biological contexts in which they are used, to facilitate greater cross-disciplinary cohesion in research on priority effects. In breaking down these semantic barriers, we aim to provide a framework to better understand the conditions and mechanisms of priority effects, and their consequences across spatial and temporal scales.

Plasma testosterone free index: a better indicator of plasma androgen activity?

Testosterone, quantitatively the most important androgen in the circulation, must enter cells to exert an androgenic effect. It is accepted that it is that fraction of the hormone not bound to the specific, binding, beta-globulin which is available for entry into the cells. By equilibrium dialysis we obtained an in vitro measurement of the unbound fraction. The product of this fraction and the total testosterone level gave us a testosterone free index (TFI). In normal men and women, our ranges were 24.6 to 93.6 and 0.8 to 3.8 ng/100 ml, respectively. Of 54 hirsute women, 24 had an elevated TFI; 4 of these had normal plasma testosterone levels. Thirteen men with hypogonadism had a decreased TFI. Nine of ten women and two men with hyperthyroidism had a normal TFI, although there was an elevated plasma testosterone level in most instances. The calculated TFI, which reflects both the extent of binding and the total testosterone level, may therefore be a better indicator of circulating androgen activity.