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Pars intermedia and pars distalis of the rat hypophysis were examined, following experimentally induced alterations in ACTH secretion. The concentration of ACTH in the pars inter-media is considerably greater than that in the pars distalis. At 1 month after adrenalectomy, the ACTH concentration in the pars distalis increased 3-fold, while that in the pars intermedia remained unchanged. Following chronic administration of cortisol, the ACTH concentration in the pars distalis fell to 27% of the control, while the fall in ACTH concentration in the pars intermedia was not significant. The immunoglobulin-peroxidase bridge technique, employing 17–39 ACTH antiserum, demonstrated the presence of ACTH-containing cells, both in the pars intermedia and in the pars distalis. Following adrenalectomy or chronic administration of cortisol, there was no change in the immunostaining or in the electron microscopic appearance of the cells of the pars intermedia. These findings suggest that although a relation between the pars intermedia and ACTH is established, this relation is different from that between the pars distalis and ACTH.

Cytological changes in uterine stromal cells of the rat during induced primary decidua formation have been examined electron microscopically. Decidua forming stroma was examined at daily intervals for the five days during which the reaction reaches maximal hypertrophy and hyperplasia and was compared with pseudopregnant, non-decidual (control) endometrium. Stromal cells of control uteri resemble embryonic fibroblasts. They appear to be of two types, depending on whether they contain rough -or smooth-surfaced endoplasmic reticulum. As the decidual reaction progresses, the cells enlarge and become binucleate; cells which contain exclusively rough surface endoplasmic reticulum no longer are evident. Glycogen and fat become abundant, the former in association with smooth-surfaced membranes of the endoplasmic reticulum. Mitochondria become more numerous, smaller, and show evidence of a rearrangement in internal organization. There is a pronounced increase in a fine intracytoplasmic fibrillar component; and a spectrum of "microbodies" and lysosomes appears. At the height of the reaction, the stroma appears epithelioid. The possible functional signikance of these changes is discussed.Implantation of the mammalian blastodermic vesicle is considered the result of an interreaction between endometrium and trophoblast. The precise role of each during implantation, however, remains poorly understood (Eckstein, Shelesnyak and Amoroso, '59). Tissue relationships during implantation have been studied to advantage in rodents where embryonic and uterine contributions to this process are readily dissociated (Loeb, '07; Krehbiel, '37; Shelesnyak, '57; Jollie, '61). The initial maternal contribution is the transformation of the uterine stroma into primary decidua at the site of implantation.Although the decidual reaction has been studied extensively, descriptions of the sequential histologic features of the process at the site of implantation have been restricted by the limits of light microscopy. The decidual cells described at an ultrastructural level in the rat (Wislocki and Dempsey, '55) are not the primary decidual cells dealt with in this paper. The fine structure of human decidual cells has been described (Hamperl, '58; De Palo and Stoppelli, '60) and a comparison made with non-decidual stroma (Dubrauszky and Schmitt, '58). Because of differences in modes of implantation, however, homologies between human decidual cells and primary decidual cells of the rat are uncertain.The purpose of the present investigation is to describe at an electron microscopic level the changes in stromal cells which accompany decidual cell formation at the site of implantation in the rat. In order to eliminate extrinsic structural changes in the forming decidua imposed by trophoblast, we have confined the investigation to an examination of induced decidua formation during pseudopregnancy.When the cervix of a virgin rat in estrus is stimulated electrically, the action of coitus is duplicated in that, through a reflex pathway to the hypothalamu...

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