Cell population kinetics of 1,2-dimethylhydrazine-induced colonic neoplasms and their adjacent colonic mucosa in the mouse

Evidence for cell generation controlled proliferation in the small intestinal crypt

In this paper we discuss the hypothesis that cell proliferation is controlled by the number of generations after leaving an 'eternal' stem cell. The theory is based on a simulation of the kinetic behaviour of cells in the intestinal crypts. There is evidence of three, four and five generations of cells which are allowed to enter mitosis in the lower and upper part of the normal intestinal tract, and in some disease states, respectively. We suggest an internal proliferation control: some kind of knowledge that cells carry from generation to generation. It is an open question what sets and changes the generation counter: internal genetic information or external influences such as growth factors or chalones. The geometric shape of the epithelial tissue in the intestinal tract can be understood as the steady state of a highly dynamic process. Age and death are determined from the beginning; cell-cell interaction or communication is not necessary and can be neglected. Our theory will be illustrated using the intestinal crypts as they are easily accessible, of a simple structure and completely described in the literature.

Morphological basis of multistep process in experimental colonic carcinogenesis

Carcinogenesis has been shown to be a multistep process. However, the morphological basis of the multistep process in colonic carcinogenesis has not been adequately investigated. In the distal colon of adult female CF-1 mice given weekly injections of DMH, we are able to demonstrate that colonic adenocarcinomas develop and evolve in four distinct but continuous steps on morphological grounds. (1) A colonic neoplasm develops in a single crypt. A given crypt is first repopulated by atypical epithelial cells which have either originated at the cryptal base or occurred as an outpocketing pouch in the proliferative zone of the crypt. (2) In the atypical crypt thus repopulated by atypical cells, the epithelial lining becomes invaginated and/or evaginated in the upper half to form an earliest identifiable neoplastic glandular lesion there. (3) The neoplastic lesion thus formed keeps invaginating, evaginating and expanding in various directions by unceasing proliferation of neoplastic cells, giving rise to a polypoid or a discoid lesion. (4) As the neoplasm grows, its leading downward edge would eventually penetrate the muscularis mucosae, and the malignant behavior of the neoplasm becomes apparent with further invasion into the submucosa, muscularis externa and serosa. In the due process, we have also explored the mode of villous formation in some neoplasms and analyzed the possible regulatory mechanisms in the various steps of colonic carcinogenesis.