Such changes may be {HEAD ~ the result} of {TAIL ~ exposure} of the cells to environmental toxins 
of
Such changes may be { HEAD ~ the result } of { TAIL ~ exposure } of the cells to environmental toxins
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH