Uterine media proteins in the rat during gestation

Uterine proteins secreted in response to estrogen and modulated by progesterone have previously been demonstrated in the immature rat. An in vitro radiolabeling technique with 35S-methionine was used to culture uteri from animals in estrus, pregnancy and the post partum period. Proteins released into the media (media proteins) were analyzed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis. On Days 1 and 2 of pregnancy, a 115,000 M.W.--protein similar in molecular weight to one previously described by this laboratory--is prominent. Its disappearance by Day 3 coincides with increased progesterone secretion. The appearance of a 43,000 M.W. protein is the most marked change at the time of blastocyst invasion of the uterine epithelium. A new 160,000 M.W. protein begins to emerge on Day 5 and is prominent in later gestation. The latter protein is thought to be a product of the uterine decidua. Its production in ovariectomized animals is increased in the presence of progesterone and a nonspecific decidual stimulus. In the immediate post partum period, a 115,000 M.W. protein reemerges, and the 160,000 M.W. protein disappears. It is believed that these proteins are influenced by the hormonal events of pregnancy and may represent an expression of the genetic control of gestation.     

Plasma gonadotrophins and oestradiol during oestrus in the cow

LH values between -2 and +4 h (0 h = LH peak) were higher than baseline. FSH values were also raised at this time and between +16 and +30 h. Oestradiol values between -20 and 0 h were higher than during +4 to +20h.     

Androgen level in the sheep fetus during gestation.

The androgen content of amniotic fluid, plasma, and gonads from 107 fetal lambs was determined by radioimmunoassay in an attempt to understand the ontogeny of gonadal function. Testosterone (T) was too low to be reliably measured in the amniotic fluid from fetuses of either sex. Ovaries were without T activity at any of the stages of gestation studied. Testicular T-5alpha-dihydrotestosterone (T-DHT) concentration steadily decreased from 1.4/ml near term. It is suggested that nongonadal testosterone production increases during fetal life and that T secretion by the fetal testis may contribute steadily less to the plasma pool of T as gestation proceeds.     

Decreased lipid peroxidation in the rat kidney during gestation

Renal malonaldehyde content and lipid peroxidation, induced by ascorbate, NADPH and cumene hydroperoxide, are significantly decreased during gestation in rats. Lipid peroxidation tends to reach normal levels in the kidney post partum. In the renal mitochondria lipid peroxidation without co-factors and that induced by cumene hydroperoxide, ascorbate and NADPH is decreased during pregnancy. However, in the microsomes, only lipid peroxidation induced by NADPH and cumene hydroperoxide is affected. The observed decrease in lipid peroxidation during gestation is reflected by low levels of total lipid and phospholipid. Endogenous inhibitors of lipid peroxidation also increase during pregnancy.     

Essential fatty acid interconversion during gestation in the rat

The synthesis of arachidonic acid has been investigated in fetal and pregnant rat liver microsomes in the course of the gestation. The delta 5-desaturase activity decreased 2-3 times in rat liver between the 19th and 22nd day of the pregnancy. During this period the delta 5-desaturate activity increased 3-fold in the fetal liver, exceeding the activity of the maternal liver. In contrast, the activity of the fetal delta 6-desaturase was in the same range as in pregnant rat liver and the liver of control animals and did not change between these two stages of the gestation. The elongation rate of linoleic acid in fetal liver was 2-3 times lower than in maternal liver but this increased during the pregnancy. The fatty acid activate rate was always higher than the activity of the desaturases. At the 19th day, the activity of the delta 5-desaturase was apparently the rate limiting step of arachidonic acid synthesis in fetal liver. We did not find any delta 5- and delta 6-desaturase activities or linoleic acid elongation in the placenta microsomes.     

Variation in macrophage-migration-inhibitory-factor immunoreactivity during porcine gestation

The localization and activity of macrophage migration inhibitory factor (MIF) was investigated in the interhemal region of the noninvasive, diffuse, folded epitheliochorial placenta and in the nonpregnant uterus of the pig. MIF, a proinflammatory cytokine with many actions on macrophages and monocytes, may play an important role in materno-fetal immuno-tolerance during placental establishment, modulation, and growth. Immunohistochemical staining with anti-human MIF polyclonal antibodies was carried out on placental sections from 11 stages of gestation (16-95 days postcoitus) and on nonpregnant uterus at 13 days postestrus. Western blot analysis confirmed the specificity of the anti-human MIF polyclonal antibodies on pig tissues. MIF staining was intense in both the trophoblast and maternal epithelium in the early stages; in the later stages, it decreased dramatically in the maternal epithelium but remained high in the trophoblast. The uterine glands showed immunoreactivity at all stages, and the maternal and fetal epithelial linings of the areolar cavity showed high reactivity at Day 25. The vasculature also showed staining for MIF, and an intense to moderate staining was shown in the nonpregnant uterus, mostly in the surface and glandular epithelium. The high activity of MIF in the maternal and fetal tissues throughout placentation and its expression in the nonpregnant uterus indicate a regulatory role for MIF during embryo receptivity and epitheliochorial placentation.     

Endocytotic activity in the endometrium during conceptus attachment in the cow

The uptake of horseradish peroxidase tracer injected into the uterine lumen of the cow was studied during the period of conceptus attachment (Days 18-21; Day 0 = oestrus) and also in cyclic animals. Endocytosis occurred in pregnant and non-pregnant cows but was especially marked when circulating progesterone concentrations were high. By 20 min after injection, the tracer was located in apical endocytotic vesicles and in organelles of the lysosomal system. In addition, some of the horseradish peroxidase-containing vesicles were associated with the lateral membranes of the cells and the tracer was also present in the intercellular spaces and beneath the basal membrane, especially in pregnant animals by the time of conceptus attachment. There was no evidence that pinopod-like functions could be attributed to large cytoplasmic protrusions from endometrial cells. Rather, the protrusions seemed to be involved in secretory processes. The presence of clear vesicles among the endocytotic vesicles suggested a coupled secretory-endocytotic activity of the cells, the significance of which remains to be determined.     

Oxytocin receptor binding in the hypothalamus during gestation in rats

Central oxytocin receptors (OTR) may be involved in adaptations of the brain oxytocin (OT) system during gestation, which are critical for systemic release of OT during parturition and lactation. We used quantitative autoradiography to determine changes in OTR binding in numerous brain sites during the course of gestation in the rat. Furthermore, to evaluate the importance of ovarian steroids in mediating pregnancy-related changes in OTR binding, we measured binding in ovariectomized animals treated with progesterone and/or estrogen, and in pregnant animals treated with exogenous progesterone during late gestation. We found that OTR binding was significantly increased in the paraventricular nucleus (PVN) and supraoptic nucleus (SON) by midgestation (day 15) compared with control. In addition, there was a further significant increase in OTR binding in these nuclei by late gestation (day 20). The bed nucleus of the stria terminalis (BNST) and the medial preoptic area (MPOA) also showed significant gestation-associated increases in OTR binding, which were similar during mid- and late pregnancy. Treatment with exogenous progesterone throughout pregnancy did not alter the increase in OTR binding characteristic of late gestation in any of these brain sites. Finally, estrogen treatment in ovariectomized animals resulted in increased OTR binding in the SON, BNST, and MPOA, but not the PVN. These data demonstrate that OTR binding in the hypothalamus is increased during mid- and late-gestation, compared with ovariectomized control animals, which may be mediated by increased estradiol.     

Mammary extraction of plasma triglycerides in the cow during lactogenesis

• 1.1. In control cows, extraction of triglycerides from the circulation by the mammary gland increased abruptly and markedly, and the concentration of triglycerides in arterial plasma fell, on the day of parturition.
• 2.2. In cows that had fluid regularly removed from the mammary glands before parturition, these changes occurred at varying times from more than 4 days before parturition in an animal that secreted triglyceride copiously to 24 hr before parturition in an animal that secreted little triglyceride pre-partum
• 3.3. In all animals, the time when triglyceride extraction increased was close to the time when K⁺ concentration in the mammary secretion became maximal.

     

Glucose tolerance tests during gestation in the unanesthetized rat.

To establish the temporal stages at which changes in insulin/glucose interactions may appear during gestation in the rat, unanesthetized animals were subjected to oral glucose tolerance tests (2 g glucose/kg) at days 15 and 21 of gestation and were compared to virgin female controls. On day 15 glucose tolerance is enhanced in the pregnant rat whereas plasma insulin levels are like those in control animals. On day 21 glucose tolerance does not differ between the two groups although insulin is higher in the pregnant animals. Results show 2 differentiated stages of insulin/glucose relationships throughout gestation in the rat with enhanced insulin sensitivity on day 15 and enhanced insulin resistance during late gestation. It is suggested that these changes contribute to the anabolic tendencies of the mother during mid gestation and her catabolic condition during late gestation.     

Development of the pancreas during gestation and lactation in swine

This study examined the development of the pancreas during gestation and lactation in swine. Forty-two mated sows and 42 unmated controls were sacrificed after 30, 70, and 110 days of gestation; 7, 14, and 28 days of lactation; and 11 days after weaning. Their pancreas were excised, weighed, and fragments homogenized for evaluation of protein, amylase, chymotrypsin, RNA, and DNA contents. Data indicate that all these parameters were reduced at the end of the gestation period when compared with controls. During lactation, pancreatic weights, enzyme, protein, and RNA contents showed regular increases. DNA contents were significantly increased after weaning, an indication of pancreatic hyperplasia. A return to control values is not complete 11 days after weaning. These changes in the pancreas can be related to increased food intake during lactation and are probably mediated by the endogenous release of the gastrointestinal hormones cholecystokinin and secretin.