Abstract
Proliferation and hyperplasia of cells are phenomena observed widely in various biologic systems. In such effects of overgrowth, it is obvious that the dimensions of the involved tissue exceed those established by normal controls on growth. Very little, however, is understood about this, even as to initiating circumstances (1–3).
One phenomenon that might be explored for possible significance in proliferative overgrowth is the biologic reaction of repair, that is, regeneration after loss of part of a given tissue. In other words, it may be asked whether hyperplasia could be a quite regular result of the regenerative repair response, a result brought out even more when the damage is chronic or repeated.
More specifically, it may be asked whether one or more adequately harmful stimuli to a group of cells would be followed regularly by a rise above normal in the quantity and size of the cells and subsequently by a return to normal. It was felt that the answer to this was desirable first in simple histologic terms as preparation for a biochemical exploration of the mechanisms and effects of regenerative response to damage. Histologic evidence presented here indicates that any of a large number of harmful substances regularly produce a proliferative response in the skin of mouse and guinea pig. Various characteristics of the effect are reported, together with certain related biologic principles.
The constancy of a hyperplastic response to harmful substances reported here raises a second, early question: Is the repletiveproliferation response, after application of a harmful agent, associated with the development of increased resistance in the involved tissue to later invasion by the originally inciting agent? Histologic evidence for the presence of such resistance is given below.
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