[Topographic distribution of mitoses in the adrenal cortex of the rat]. / Distribution topographique des mitoses dans la cortico-surrénale du rat.

The situation of mitoses in the adrenal glands of the rat has been studied by measuring the distance between each of them (3,061 in the whole) at the surface. The curve of their distribution, logarithmic-normal type, shows that they are the most numerous in germinative zone classically described, but that they appear down to the depth of inner fascicula.

[Circadian variation of the mitotic activity of the adrenal cortex in male rats]. / Variation circadienne de l'activité mitotique du cortex surrénalien chez le rat mâle.

The mitotic activity in the adrenal cortex has been studied during a 24 hours-cycle in male rats that have been sacrificed by perfusion of fixative. A method of calculation of the thickness of the zona germinativa is proposed : it permits to compute mitotic densities in relation to surface, and mitotic index. Mitotic activity seems to be the combination of a relatively low and constant activity occurring from 7 a.m. (local time) to 11 p.m., and an hyperactivity from 0 to 6 a.m. Two maxima are demonstrated : one at 0 h, and another one, more important, at 5 a.m. (local time). Results are analyzed, discussed and compared with others obtained on different organs : each tissue seems to have its own characteristics according to horary and intensity in mitotic activity.

[Numerical arguments in favor of the existence of clone cells in the adenohypophysis]. / Arguments numériques en faveur de l'existence de clônes cellularies dans l'adénohypophyse.

In the rat's anterior pituitary, mitoses occur to be side by side, forming "pairs", the frequency of which is significant all the more as their number is underrated in sections. In 85% of the pairs the mitoses are synchronous. These paired synchronous mitoses are suggestive of the existence of cellular clones in the pituitary.

Variations of mitotic activity in the adenohypophysis of male rats during a 24-hour cycle.

The mitotic activity in the adenohypophysis of male rats during a 24 hours' cycle has been studied at the time of the spring equinox. The animals were killed by perfusion of fixative. The mitotic activity seems to be the combination of two elements: a relatively low and nearly constant activity with two peaks of high activity. The first one takes place at 6 o'clock (local time) with an index reaching 4.25; the second one occurs at 11 o'clock (local time) and its index is 2.09. The afternoon activity is weak with an average index of 0.56 between 1 p.m. and 9 p.m. The results are analyzed, discussed and compared with other results observed in different organs.

[Nycthemeral variations of mitotic activity in the adrenal cortex of the rat]. / Variations nycthémérales de l'activité mitotique dans la cortico-surrénale du rat mâle

Working on histologic sections 7 microns thick in the equatorial part of male rat adrenal cortex, we found two high mitotic activity periods. The first one stays at midnight and shows an average number of 42 mitoses per section; the second one occurs at 5 a.m. with an average number of mitoses of 70,1 per section. If we except these particular points, the mitotic activity is low, the average number of mitoses being 13,2 per section.