Gretchen Williams
= Gretchen Williams
{c}
\b[Gretchen Williams] coauthored the 1971 investigation with <Judah Folkman>, <Ezio Merler> and <Charles Abernathy> that isolated angiogenic activity from <tumours>.<Isolation of a Tumor Factor Responsible for Angiogenesis by Judah Folkman and others>[Byline, Abstract and printed p.275]{ref} The collaboration helped turn <tumour angiogenesis> into an experimentally testable interaction between <tumours> and surrounding <blood vessels>.
The important distinction is between growth of a <tumour>'s own <cells> and growth of host <endothelial cells>. A substance released by one population can change the behaviour of the other. Thus a vascular response outside an implanted <tumour> cannot be interpreted simply as movement of the implanted <cells>.
An original measurement example illustrates the distinction. Suppose a marked tissue region initially contains 20 vessel branch points, and later contains 32. The increase is $32-20=12$, or 60 percent of the initial count. That observation alone does not give a <cell proliferation> rate: vessel branching, length and endothelial <cell> number are different measurements. It also does not establish effective <perfusion>. A convincing experiment therefore defines its vascular readout and compares it with a matched <negative control>. These numbers illustrate the reasoning, not the paper's data.