The origin and fate of Paneth cells were examined in duodenum, jejunum and ileum of adult female mice, using radioautography after administration of Wthymidine either in a single injection or in drinking water for four days or as a continuous infusion for up to ten days.The tissues were fixed by perfusion with 4% paraformaldehyde. One-micron thick, Eponembedded single or serial sections were stained with Regaud's hematoxylin, radioautographed, and counterstained with safranin 0.Mitosis of Paneth cells is never observed, nor are these cells ever labeled one hour after 3H-thymidine. Hence, Paneth cells do not divide.However, a few days after single injection or prolonged administration of "-thymidine, labeled Paneth cells appear. The first labeled cells have tiny granules but, as the cells age, larger and larger granules are observed.Adjacent to Paneth cells are slender undifferentiated cells which show frequent mitoses and early labeling. The evidence points to some of these cells transforming into Paneth cells. Since occasionally Paneth cells degenerate, the newly-formed ones would provide replacement for those which die, thus insuring the steady state of the Paneth cell population. The renewal of this population is characterized by a turnover time of about three weeks.

The epithelium of duodenum, jejunum and ileum was investigated in adult female mice given an injection of H-thymidine and sacrificed at times varying from one hour to 14 days later. The tissues were fixed by perfusion with paraformaldehyde and embedded in Epon. One micron thick sections were cut singly or serially, radioautographed and stained with iron hematoxylin and safranin 0. In addition, reconstruction of a crypt was made from serial sections of jejunum.The reconstruction of a crypt shows the well known columnar, goblet, Paneth, and argentaffin cells. There are also little known cell types referred to as oligomucous and granulo-mucous and pale cells with or without mucus. Of these cells, the only numerous ones are the oligomucous cells, which are located in the lower half of the crypts and contain a few or even only one mucous globule. In the electron microscope, they display long cisterns of rough endoplasmic reticulum parallel to the lateral cell membrane and similar to those observed in goblet cells.

No abstract

Cyclosporin A is a selective immunosuppressant, used in organ transplants to prevent graft rejection. Cyclosporin A can cause various side effects including gingival overgrowth. The aim of this work was to evaluate gingival overgrowth of rats treated daily with 10 mg/kg bodyweight of cyclosporin A for 60 days, as well as the regression after the interruption of treatment. All rats treated with cyclosporin A developed gingival overgrowth, with increased thickness of the epithelium, height and width of the connective tissue. The density of fibroblasts and collagen fibers also increased. Five to 90 days after the interruption of treatment with cyclosporin A, there was a progressive reduction of the gingival volume and of collagen fibers and fibroblast densities. The reduction was more pronounced in the initial periods and after 90 days did not return to the normal values.

No abstract