Publication Date


Document Type


First Advisor

Graves, Lynn B.||Frampton, Elon W.

Degree Name

M.S. (Master of Science)

Legacy Department

Department of Biological Sciences


Mice; Epidermis


Diurnal variation in the number of cells in DNA synthesis was studied in the dorsal epidermis of the hairless mouse, using thymidine labeled with carbon-14 or tritium. Mice were initially injected with ¹⁴C-thymidine and after a two or three hour interval, were injected again, with ³H-thymidine. An improved double-layered autoradiographic method was used, which clearly identified cells labeled with carbon-14 only, or tritium only, and those cells labeled with both isotopes. This distinction allowed the simultaneous determination of the relative rate of flow of cells into and out of the S-compartment, using the same animal, during the same period of the diurnal cycle. During the different periods of the day studied, cells synthesizing DNA were found only in the basal layer of the epidermis, and the distribution of these cells was random. The results show that, in the two periods of the diurnal cycle studied, there was a continuous decrease in the number of cells observed in S and, concurrently, a significant decrease in the influx of cells as compared to the efflux, with both decreasing. During both periods, the time cells which remained in the S-compartment was relatively constant. It is concluded that the diurnal rhythmicity in the number of cells in DNA synthesis, reflects changes in the rate proliferating cells are entering into S from the G₁ compartment. A graphic analysis is consistent with the observed data only when it is assumed that, the duration of S is constant and that, the flux of cells into S is the changing parameter.


Includes bibliographical references.||"Research supported by the United States Atomic Energy Commission."--Title page.||Includes illustrations.


ix, 54 pages




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