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