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