\begin{tikzpicture}[x=1ex,y=1ex,baseline={([yshift=-.5ex]current bounding box.center)}]
    \coordinate (vm);
    \coordinate [left=1 of vm] (v0);
    \coordinate [right=1 of vm] (v1);
    \draw (v0) -- (v1);
    \draw (vm) circle(1);
    \filldraw (v0) circle (1pt);
    \filldraw (v1) circle (1pt);
\end{tikzpicture}%
