The radioautographic transfer function and its implications for radioautographic methodology

Cell flux through S phase in the mouse duodenal epithelium determined by cell sorting and radioautography

An accumulation of cells in early S phase was observed in normal mouse duodenal epithelium studied with flow cytometry (Cheng and Bjerknes, 1982). To determine if this accumulation of cells was the result of a lower rate of DNA synthesis, animals were given a single injection of 3H-thymidine and the epithelium collected one hour later. The epithelium was processed for flow cytometry. Seven sort windows were established in different portions of the DNA histogram. Cells from each window were sorted onto glass slides that were then processed for radioautography. The number of silver grains over the nuclei of each sorted population was counted. It was found that cells in early S phase had significantly fewer grains over their nuclei than did mid- or late-S phase cells. We conclude that the accumulation of cells in early S phase is due, at least in part, to a lower rate of DNA synthesis in early than in mid or late S phase.

Small cell anaplastic carcinoma of the lung. A review of growth characteristics and implications for chemotherapy

Small cell anaplastic lung cancer is increasingly considered to be potentially curable. The opinion that this tumor is a rapidly proliferating one has not been substantiated by kinetic studies, and for this reason late relapse may occur in complete remitters. Differential rates of response/relapse in different tumor sites may be explained on the basis of heterogeneity in tumor kinetics.

Effects of theophylline and dibutyryl cyclic AMP on proliferation and keratinization of human keratinocytes

Recent evidence suggested that cyclic adenosine 3',5'-monophosphate (cAMP) may be involved in the regulation of cell proliferation and differentiation. The effects of theophylline and dibutyryl cAMP on cell division and keratinization of human epidermal cultures were examined. Nine to 12-day-old cultures were treated with these agents, separately and in combination, for various intervals. Both agents, either singly or in combination, depressed mitoses. The maximum mitotic inhibition was obtained in cultures treated with theophylline or theophylline plus dibutyryl cAMP. Tritiated thymidine studies showed that the test agents had no effect on labelling index (LI) at 4 h, but a 74% inhibition of LI was observed at 24 h. The maximum inhibition of LI (93%) occurred at 96 hours. In contrast to the control cultures, which rarely contain keratohyaline granules (KG), a marked increase in the production of these granules occurred in cultures treated with dibutyryl cAMP plus theophylline. The KG were present over the whole outgrowth. Theophylline alone also stimulated the production of KG, whereas dibutyryl cAMP had no effect. These data show that these agents inhibit cell division and this inhibition may be accompanied by an increased production of KG.