Decreased Cell Production Research Articles

Cell kinetics of urethane induced murine pulmonary adenomata: I. The growth rate.

A single injection of urethane into adult male A2G mice produced an increase in the proliferative rate of alveolar wall cells, reaching a peak at 2 weeks post urethan (PU) and declining to control levels by 2 months PU. During this urethane induced proliferative response the single and double labelling indices and the native metaphase index were all elevated although there was no corresponding alteration in the arrested metaphase index. This proliferative response may not be restricted to hyperplasia of potentially neoplastic cells, such as type II epithelium, but may also include type I epithelial cells and alveolar macrophage precursors. However, it was impossible to identify individual cell populations by methods used. The growth rate of adenomata decrease with time and cell kinetic techniques showed that the rates of entry of adenoma cells into DNA synthesis and into metaphase were decreasing concurrently with the growth rate. Thus the rate of cell production falls as adenomata age but how much cell loss contributes to the decrease in growth rate is not yet known. Decreasing cell production could be due to an increased cell cycle time and/or a decreased growth fraction. The duration of DNA synthesis in adenomata increased markedly as the mice survived, suggesting that the cell cycle time might be increased, but further experiments are required to determine whether the growth fraction changes. Attention is drawn to a complication that Colcemid introduces into kinetic studies on alveolar wall cells.

Cell kinetics and morphology of the growth plate in the normal and hypophysectomized rat

The width of the proximal growth plate of the tibia, its undifferentiated and columnar zone and the size of the degenerative cell close to the metaphysis, were determined in normal and hypophysectomized Sprague-Dawley rats. The cell production in the growth plate was calculated from the longitudinal bone growth determined with oxytetracycline and the degenerative cell size. It was found that the decrease in longitudinal bone growth with increasing age and after hypophysectomy, is due partly to a decrease in cell production, and partly to a decrease in degenerative cell size in the growth plate. The influence of cell production and thus the mitotic activity predominates.

Effect of antifoam agents on oxygen transfer in deep tank fermentations

AbstractDevelopment of a foam breaker which operates on the principle of rapid acceleration of foam through a nozzle has allowed large‐scale aerobic fermentations to be run without addition of antifoam agents. Fermentations have been investigated over a wide range of aeration levels in which oxygen supplied to the organisms was the limiting growth factor.With Torulopsis utilis grown in a 5 per cent molasses medium. oxygen utilization followed an exponential pattern during the early phase of growth, with carbon dioxide production equal to the consumption of oxygen. At the point where oxygen supply to the organism became limiting, anaerobic fermentation began, and the consumption of oxygen remained constant. The level of oxygen absorption beyond which the respiratory quotient exceeded unity was used as a measure of limiting oxygen supply.Addition of three types of antifoam compounds to T. utilis fermentations resulted in a marked depression of oxygen consumption, and a decrease in cell production. Incremental addition of small quantities of antifoam to maintain a constant foam level in the fermentor depressed the oxygen absorption rate to a lesser extent. Sulphite oxidation rates did not reflect the true value of oxygen absorption rates found for fermentations without addition of antifoam.