Adult virgin female Syrian hamsters were killed at known stages of the estrous cycle, and mast cells were counted in the myometrium, endometrium, and mesometrial-triangle region of the uterus and in the pinna. Tissues were fixed in Helly's solution, and mast cells were stained using 0.06% toluidine blue in 0.12 M Michaelis' veronal acetate-hydrochloric acid buffer, pH 4.5. The number of mast cells in the myometrium and endometrium was found to vary with the estrous cycle, whereas the number in the mesometrial-triangle region and the pinna showed no such variation. The number of mast cells in the myometrium and endometrium was lowest on day 4 of the cycle (the day before the night during which ovulation would occur) and increased approximately twofold to maximal levels found on days 1 and 2. Intermediate levels were seen on day 3. The origin of the increase in mast cell numbers from day 4 to day 1 was investigated using a combined alcian blue--safranin stain to differentiate between immature and mature mast-cell granules. The results obtained did not support the hypothesis that the increase was due to de novo differentiation of mast cells from precursors, but, equally, no evidence was obtained to refute this hypothesis.

Antibodies to differentiation markers have made it possible to identify macrophages in murine tissues. Macrophages are potent mediators of immunological reactions and it has been proposed that they are pivotal cells at the maternal-fetal interface. Studies of macrophage distribution in murine decidual tissue have provided conflicting evidence for and against the presence of significant numbers of macrophages at the maternal-fetal interface. The study described here used three independent macrophage differentiation antigens to examine the macrophage distribution in decidual tissue from day 6 to day 19 of pregnancy. Macrophage distribution was defined initially using a polyclonal antiserum to the plasma membrane differentiation antigen F4/80. Macrophages were virtually absent from antimesometrial decidual tissue until degenerating tissue was invaded by macrophages from about day 15. The resident population of macrophages in the mesometrial stroma was retained when this area decidualized but these cells did not survive beyond day 13. Mesometrial decidual tissue was virtually devoid of macrophages after this time. The metrial gland contained many macrophages until degeneration set in, but few were seen by day 15 of pregnancy. These distributions were confirmed using monoclonal antibodies (mAb) to F4/80, macrosialin, a monocyte- and macrophage-specific membrane sialoprotein (mAb FA/11), and the leucocyte beta 2-integrin CR3 (CD11b/CD18; Mac-1), which is expressed on neutrophils as well as monocytes and some tissue macrophages. CR3+, F4/80- and FA/11- neutrophils were found to be more widely distributed in decidual tissue than were F4/80+ or FA/11+ macrophages.(ABSTRACT TRUNCATED AT 250 WORDS)

Since the endometrial area in the immediate vicinity of nodules is inimical to implantation and nodules consist of a group of macrophages, it can be implied that nodule macrophages are exerting some influence on the endometrium in their vicinity.

Summary. Systemic administration to rats of a combination of mepyramine, a histamine H1-, and burimamide, a histamine H2-receptor antagonist, over a period which included the time of implantation (late Day 5 to early Night 5), increased the number of blastocysts recovered from the uterus and reduced the number and intensity of Pontamine Sky Blue (PSB) sites obtained at autopsy on Night 5. Histological examination of the PSB sites taken on Night 5 from animals receiving the histamine antagonists revealed that the stromal oedema, which is characteristic of the attachment phase of pregnancy, had been inhibited.

No abstract

Summary. Unilaterally ovariectomized mice were allowed to complete one pregnancy before the second ovary was removed and sensitivity to decidualization was induced by hormone administration. The virgin uterine horn and the post-partum horn were stimulated to decidualize by the intraluminal injection of arachis oil. A greater decidual response was found in post-partum horns than in virgin horns. The foci of decidual induction in post-partum horns were regularly spaced reflecting the regular spacing of used and unused areas of the uterus. A focus of decidual induction occurred in 68% of the recently used uterine areas observed, i.e. areas associated with post-partum nodules. When compared with foci of decidualization in adjacent unused areas of the uterus, none of the decidualized used zones showed more decidual tissue, about half showed less decidual tissue and half showed the same amount of decidual tissue. The remaining 32% of used zones were not associated with foci of decidual induction. The results indicate that decidualization can be induced in recently used zones of the uterus using a non-traumatic method of induction, but that used zones are associated with less decidual tissue than unused zones of the post-partum uterus.

No abstract

The vole, Microtus agrestis, was chosen for this study of mast cells during early pregnancy because this species does not show spontaneous estrous cycles. Mast cell numbers in the uterus are known to vary during the estrous cycle in some species (rat, cow, Syrian hamster). Mast cell changes during early pregnancy in the vole could not reflect hormonal changes which had occurred during a preceding estrous cycle. Mast cells in the uterus (myometrium, endometrium, and mesometrial triangle) and ear skin were examined at 0 hours (virgin, estrus) and at 24, 48, 72 and 96 hours postcoitum (p.c.). The stain used was 0.06% toluidine blue in 0.12 M Michaelis's veronal acetate-hydrochloric acid buffer at pH 4.5. The number of mast cells observed in the uterus was not significantly affected when the nondehydrating fixative used routinely ( Helly 's solution) was substituted by a dehydrating fixative (Carnoy's solution without chloroform). The number of mast cells in the myometrium decreased from 0 to 72 hours p.c. and increased from 72 to 96 hours p.c. There was no significant variation in mast cell numbers in the endometrium. The number of mast cells in ear skin and in the mesometrial triangle decreased from 0 to 48 hours p.c. An increase occurred from 48 to 96 hours p.c. in ear skin and from 72 to 96 hours p.c. in the mesometrium.