that stop more from entering

Context:
But this could be a bad idea as small doses of free radicals trigger changes in most cells that stop more from entering.

stop more from entering = stop more (what?) from entering (where?)



More context:
GENES that protect yeast DNA from oxidising free radicals could one day lead to drugs that prevent cancer and ageing in people.

Produced by the body, free radicals damage DNA, so some people take supplements to mop them up. But this could be a bad idea as small doses of free radicals trigger changes in most cells that stop more from entering.

Now Trey Ideker at the University of California, San Diego, and colleagues have found genes that control this response in yeast. If similar genes are found in people, drugs that mimic their protective effects could be a better strategy against cancer and ageing than simply mopping up all free radicals (PLoS