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K. F. DeBOER, L. L. ANDERSON and R. M. MELAMPY

The mode of action of intra-uterine devices (IUDs) has been postulated by several investigators to involve a pharmacologically active substance capable of inhibiting the uterine decidual response or of actively cytolysing the pre-implantation blastocysts (Marston & Chang, 1965; Marston & Kelly, 1969; Doyle & Margolis, 1963; Batta & Chaudhury, 1968a, b; Parr, Schaedler & Hirsch, 1967). An investigation of the effect of uterine secretions on ovarian function and embryonic survival in the rat is reported here.Rats (180 to 250 g; Holtzman Co.) were maintained as previously described (Anderson, Melampy & Chen, 1967). Daily vaginal smears were taken. Day 1 was characterized by the appearance of spermatozoa in mated animals. In the first series of experiments (Table 1), laparotomies were carried out under ether anaesthesia, using clean but not sterile technique,
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L. L. ANDERSON, J. J. FORD and R.M. MELAMPY

Summary.

After mating, rats were fed one of the following diets: 100% sucrose, 100% vitamin-free casein, purified protein-free or purified with 20% casein. Fetal survival and weight changes in the maternal adrenal glands, uterus, ovaries and gastrocnemius muscle were determined at Day 20. Pregnancy failed in all animals fed sucrose or a protein-free diet and in half of those fed purified casein. Daily injections of progesterone (5 mg) increased both the number of rats remaining pregnant and fetal survival rates in those fed sucrose, a protein-free diet or casein. Pregnancy maintenance in these animals was characterized by larger adrenal glands and smaller gastrocnemius weights. The failure of pregnancy in rats fed only vitamin-free casein or a protein-free diet was associated with a significant increase in loss of total body weight. The minimum period of progesterone treatment for the maintenance of pregnancy was Days 5 to 9 in dams fed only sucrose after mating. In animals fed sucrose, treated with progesterone from Days 5 to 9 and killed on Days 6, 9, 12, 15 and 18, the weights of the uterus and conceptuses began to increase, the weight of the liver declined, followed by a decrease in gastrocnemius weight. Exogenous ACTH or prolactin was inadequate for maintaining viable embryos in ovariectomized rats given a diet of sucrose.

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R. P. RATHMACHER, L. L. ANDERSON, K. KAWATA and R. M. MELAMPY

Experimental control of fertility has been accomplished by inserting foreign objects in the uterus. Doyle & Margolis (1963) found that a suture in the uterine lumen of the rat prevented implantation of blastocysts. This was soon followed by similar studies on the rabbit (Adams & Eckstein, 1964), cow (Hawk, Conley, Brinsfield & Righter, 1965) and ewe (Hawk, 1965). A local inhibitory effect on luteal function has been demonstrated by inserting plastic coils in an anterior portion of a uterine horn in the ewe (Ginther, Pope & Casida, 1966) and heifer (Ginther, Woody, Janakiraman & Casida, 1966). Uterine distention does not alter oestrous cycles in the pig (Anderson, 1962); however, a local uterine luteolytic effect has been observed during pregnancy (du Buisson, 1961). This investigation concerns the effect of an intra-uterine foreign body

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L. L. ANDERSON, J. B. PETERS, R. M. MELAMPY and D. F. COX

Summary.

Percentages of cell types in the adenohypophysis were compared with the content of sth and prolactin at different reproductive stages (e.g. immature, oestrous cycle, pregnancy, lactation and after hysterectomy) in the pig. Acidophils represent sth and prolactin activities. Chromophobes are undifferentiated, inactive or depleted cells.

Acidophils represented half (53·5%) the cell population. Percentages of sth cells were higher in 17-day-old pigs than in mature animals. This is a period of rapid growth in the young pig. During the cycle, during pregnancy and after hysterectomy, the percentages of prolactin cells were higher than those found in immature or lactating pigs.

The chromophobes represented 13·1% of the cell population. Chromophobes were the predominant cell type during lactation, but these seemingly inactive cells may have been active acidophils that were synthesizing and secreting prolactin. By rapid turnover of hormone, the cytoplasmic granules in prolactin cells lack differentiation.

The sth activity was similar in pigs during pregnancy and lactation and after hysterectomy. There were no significant correlations in the percentages of sth cells and the concentration or content of sth during pregnancy and lactation. There was a trend of increased percentages of prolactin cells in later stages of pregnancy and after hysterectomy. Exogenous oestrogen caused a marked increase in the pituitary content of sth and prolactin in hysterectomized pigs as compared with uninjected hysterectomized animals. Prolactin levels remained relatively constant during pregnancy and after hysterectomy, but declined during lactation. Exogenous oestrogen caused a consistently higher trend in prolactin activity in hysterectomized animals.