Abstract
Corpora lutea from the period of delayed implantation and from early postimplantation stages of the armadillo, mink, and rat were fixed in buffered osmium tetroxide-sucrose or potassium permanganate. After rapid dehydration, the portions of the corpora lutea were embedded in either methacrylate or epoxy resin. Examination of the lutein cells by electron microscopy revealed the presence, in the better preserved material, of an extensive development of tubular agranular endoplasmic reticulum. Although the membranes of the endoplasmic reticulum are the most striking feature of the lutein cells of both stages of the three animals examined, very numerous large mitochondria with cristae that exhibit a variety of forms tending toward villiform, and protrusions and foldings of the lutein cell margins on the pericapillary space are also characteristic of these cells. Certain minor differences in the lutein cells of the species examined are also noted. No indications of conversion of mitochondria into lipid, of accumulation of lipid in the Golgi area, or of the protrusion of lutein cells into spaces between the endothelial cells, as suggested by other authors, were noted in these preparations. Some of the difficulties inherent in the visualization of the secretory activity of cells producing steroid hormones are briefly discussed.
Highlights
Corpora lutea from the period of delayed implantation and from early postimplantation stages of the armadillo, mink, and rat were fixed in buffered osmium tetroxide-sucrose or potassium permanganate
Studies on lutein cells have been primarily concerned with the villiform nature of the cristae of the mitochondria [2, 23] and have not dealt extensively with the endoplasmic reticulum
With the appearance of Christensen and Fawcett's [5, 6] clear demonstration of an extensive network of agranular tubules of the endoplasmic reticulum in the interstitial cells of the opossum testis, it became apparent that a tubular form of endoplasmic reticulum might be a common feature of well preserved parenchymal cells of steroidproducing structures
Summary
Corpora lutea from armadillos, mink, and rats were used in this study. There are two sets of corpora present during delay of implantation; the corpora selected for study were those of the second pregnancy. These corpora were taken on the 7th to 13th day of the second pregnancy. The portions of the corpora lutea placed in cold Caulfield's [3] osmium-sucrose mixture or Dalton's [7] chrome-osmium mixture were fixed for I hour. Sections from epoxy-embedded material were generally placed on celloidin-coated grids without carbon. The lutein cells of the armadillo are large (36 /zmaximum diameter) and show little variation in size between the delay and early implantation periods. The lutein cells of even the more highly luteinized corpora are much smaller ( t 9 /z) t h a n the lutein cells from mink in which implantation has occurred (33 g)
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