Mitotic Depression Research Articles

The effects of superior cervical ganglionectomy and/or bilateral adrenalectomy on the mitotic activity of the adult rat cornea

Superior cervical ganglionectomy inhibited mitotic activity in the cornea and increased mitotic duration. This effect was not eliminated by adrenalectomy. However, both operations appeared to lessen the marked mitotic depression found in the normal cornea in the late evening. Mitotic activity in the cornea was compared with that found previously in lenses from the same eyes. Although both tissues were affected by adrenal function and local sympathetic nerve activity the reactions bore no obvious relationship. Neither did the normal daytime mitotic variations found in the two tissues.

THE ROLE OF GLUCOCORTICOID HORMONES IN THE CONTROL OF EPIDERMAL MITOSIS

ABSTRACTIt has previously been established that the epidermal chalone inhibits epidermal mitotic activity more powerfully in the presence of adrenalin, although adrenalin itself is not a mitotic inhibitor. It is now shown that in low concentrations hydrocortisone has little if any antimitotic activity, that when it is present together with chalone and adrenalin it does not markedly increase their antimitotic activity, but that it does act to prolong the mitotic depression which they induce.It is known that, without hydrocortisone, adrenalin rapidly escapes from epidermal cells so that the chalone action is weakened. It appears that the role of hydrocortisone may be to reduce the rate of adrenalin loss and thus to prolong the chalone‐adrenalin activity.It is also shown that the rate of loss of adrenalin from epidermal cells is inhibited, though to a much lesser extent, in the presence of excess chalone.

Modification of radiation-induced intestinal injury in rats by chilling after irradiation.

SummaryChilling of the small intestine of the rat immediately after x-irradiation postponed depression of the mitotic count and degeneration of the crypt cells. Mitotic depression and cellular degeneration occurred, however, when the tissue was re-warmed. The effects of transient chilling at 18°c were essentially identical to those of chilling at 5°c. The inhibition of colchicine-induced metaphase arrest and of tritiated thymidine uptake in chilled crypt cells suggests that postponement of the signs of radiation injury resulted from suppression of metabolic activity and cell division at low temperature. Although there was some suggestion of reduced injury in the chilled tissues, the protective or recovery-promoting effectiveness of hypothermia remains to be established.

On Some Cellular Reactions to X-Radiation

ABSTRACT The wall of the developing neural tube of young chick embryos contains two types of cells; one type, the germinal cells, with nuclei conspicuously active in mitosis, is restricted to the innermost layer of the neural wall; the other type of cell with nuclei in the resting state and none in division, forms the main mass of the neural wall, the mantle layer. A study of the neural tube after radiation with a single non-lethal dose of X-rays reveals a series of cellular changes: an initial period of mitotic depression during which mitotic figures in the germinal cells disappear entirely; a period of pseudo-recovery during which mitotic activity reappears; a period of degeneration characterised by severe nuclear changes among the cells in the resting state; and a period of remarkable regeneration and recovery resulting in a return of the tissue to its normal condition.