Placental Lactogen: A polypeptide hormone of approximately 25 kDa that is produced by the SYNCYTIOTROPHOBLASTS of the PLACENTA, also known as chorionic somatomammotropin. It has both GROWTH HORMONE and PROLACTIN activities on growth, lactation, and luteal steroid production. In women, placental lactogen secretion begins soon after implantation and increases to 1 g or more a day in late pregnancy. Placental lactogen is also an insulin antagonist.Placental Hormones: Hormones produced by the placenta include CHORIONIC GONADOTROPIN, and PLACENTAL LACTOGEN as well as steroids (ESTROGENS; PROGESTERONE), and neuropeptide hormones similar to those found in the hypothalamus (HYPOTHALAMIC HORMONES).Placenta: A highly vascularized mammalian fetal-maternal organ and major site of transport of oxygen, nutrients, and fetal waste products. It includes a fetal portion (CHORIONIC VILLI) derived from TROPHOBLASTS and a maternal portion (DECIDUA) derived from the uterine ENDOMETRIUM. The placenta produces an array of steroid, protein and peptide hormones (PLACENTAL HORMONES).Prolactin: A lactogenic hormone secreted by the adenohypophysis (PITUITARY GLAND, ANTERIOR). It is a polypeptide of approximately 23 kD. Besides its major action on lactation, in some species prolactin exerts effects on reproduction, maternal behavior, fat metabolism, immunomodulation and osmoregulation. Prolactin receptors are present in the mammary gland, hypothalamus, liver, ovary, testis, and prostate.Growth Hormone: A polypeptide that is secreted by the adenohypophysis (PITUITARY GLAND, ANTERIOR). Growth hormone, also known as somatotropin, stimulates mitosis, cell differentiation and cell growth. Species-specific growth hormones have been synthesized.Pregnancy: The status during which female mammals carry their developing young (EMBRYOS or FETUSES) in utero before birth, beginning from FERTILIZATION to BIRTH.Pregnancy-Specific beta 1-Glycoproteins: Glycoproteins with the electrophoretic mobility of BETA-GLOBULINS, secreted by the placental TROPHOBLASTS into the maternal bloodstream during PREGNANCY. They can be detected 18 days after OVULATION and reach 200 mg/ml at the end of pregnancy. They are associated with fetal well-being.Receptors, Prolactin: Labile proteins on or in prolactin-sensitive cells that bind prolactin initiating the cells' physiological response to that hormone. Mammary casein synthesis is one of the responses. The receptors are also found in placenta, liver, testes, kidneys, ovaries, and other organs and bind and respond to certain other hormones and their analogs and antagonists. This receptor is related to the growth hormone receptor.Pregnancy, Animal: The process of bearing developing young (EMBRYOS or FETUSES) in utero in non-human mammals, beginning from FERTILIZATION to BIRTH.Trophoblasts: Cells lining the outside of the BLASTOCYST. After binding to the ENDOMETRIUM, trophoblasts develop into two distinct layers, an inner layer of mononuclear cytotrophoblasts and an outer layer of continuous multinuclear cytoplasm, the syncytiotrophoblasts, which form the early fetal-maternal interface (PLACENTA).Estriol: A hydroxylated metabolite of ESTRADIOL or ESTRONE that has a hydroxyl group at C3, 16-alpha, and 17-beta position. Estriol is a major urinary estrogen. During PREGNANCY, a large amount of estriol is produced by the PLACENTA. Isomers with inversion of the hydroxyl group or groups are called epiestriol.Abortion, Threatened: UTERINE BLEEDING from a GESTATION of less than 20 weeks without any CERVICAL DILATATION. It is characterized by vaginal bleeding, lower back discomfort, or midline pelvic cramping and a risk factor for MISCARRIAGE.Sheep: Any of the ruminant mammals with curved horns in the genus Ovis, family Bovidae. They possess lachrymal grooves and interdigital glands, which are absent in GOATS.Choriocarcinoma: A malignant metastatic form of trophoblastic tumors. Unlike the HYDATIDIFORM MOLE, choriocarcinoma contains no CHORIONIC VILLI but rather sheets of undifferentiated cytotrophoblasts and syncytiotrophoblasts (TROPHOBLASTS). It is characterized by the large amounts of CHORIONIC GONADOTROPIN produced. Tissue origins can be determined by DNA analyses: placental (fetal) origin or non-placental origin (CHORIOCARCINOMA, NON-GESTATIONAL).Placental Extracts: Extracts prepared from placental tissue; they may contain specific but uncharacterized factors or proteins with specific activities.Animal Nutrition Sciences: The study of NUTRITION PROCESSES, as well as the components of food, their actions, interaction, and balance in relation to health and disease in animals.Radioligand Assay: Quantitative determination of receptor (binding) proteins in body fluids or tissue using radioactively labeled binding reagents (e.g., antibodies, intracellular receptors, plasma binders).Butoxamine: A beta-2 selective adrenergic antagonist. It is used primarily in animal and tissue experiments to characterize BETA-2 ANDRENERGIC RECEPTORS.Radioimmunoassay: Classic quantitative assay for detection of antigen-antibody reactions using a radioactively labeled substance (radioligand) either directly or indirectly to measure the binding of the unlabeled substance to a specific antibody or other receptor system. Non-immunogenic substances (e.g., haptens) can be measured if coupled to larger carrier proteins (e.g., bovine gamma-globulin or human serum albumin) capable of inducing antibody formation.Pregnancy Proteins: Proteins produced by organs of the mother or the PLACENTA during PREGNANCY. These proteins may be pregnancy-specific (present only during pregnancy) or pregnancy-associated (present during pregnancy or under other conditions such as hormone therapy or certain malignancies.)Receptors, Somatotropin: Cell surface proteins that bind GROWTH HORMONE with high affinity and trigger intracellular changes influencing the behavior of cells. Activation of growth hormone receptors regulates amino acid transport through cell membranes, RNA translation to protein, DNA transcription, and protein and amino acid catabolism in many cell types. Many of these effects are mediated indirectly through stimulation of the release of somatomedins.Chorionic Gonadotropin: A gonadotropic glycoprotein hormone produced primarily by the PLACENTA. Similar to the pituitary LUTEINIZING HORMONE in structure and function, chorionic gonadotropin is involved in maintaining the CORPUS LUTEUM during pregnancy. CG consists of two noncovalently linked subunits, alpha and beta. Within a species, the alpha subunit is virtually identical to the alpha subunits of the three pituitary glycoprotein hormones (TSH, LH, and FSH), but the beta subunit is unique and confers its biological specificity (CHORIONIC GONADOTROPIN, BETA SUBUNIT, HUMAN).Progesterone: The major progestational steroid that is secreted primarily by the CORPUS LUTEUM and the PLACENTA. Progesterone acts on the UTERUS, the MAMMARY GLANDS and the BRAIN. It is required in EMBRYO IMPLANTATION; PREGNANCY maintenance, and the development of mammary tissue for MILK production. Progesterone, converted from PREGNENOLONE, also serves as an intermediate in the biosynthesis of GONADAL STEROID HORMONES and adrenal CORTICOSTEROIDS.Receptors, Peptide: Cell surface receptors that bind peptide messengers with high affinity and regulate intracellular signals which influence the behavior of cells.Adrenergic beta-2 Receptor Antagonists: Drugs that bind to and block the activation of ADRENERGIC BETA-2 RECEPTORS.Pregnancy Trimester, Third: The last third of a human PREGNANCY, from the beginning of the 29th through the 42nd completed week (197 to 294 days) of gestation.Encyclopedias as Topic: Works containing information articles on subjects in every field of knowledge, usually arranged in alphabetical order, or a similar work limited to a special field or subject. (From The ALA Glossary of Library and Information Science, 1983)Electronic Mail: Messages between computer users via COMPUTER COMMUNICATION NETWORKS. This feature duplicates most of the features of paper mail, such as forwarding, multiple copies, and attachments of images and other file types, but with a speed advantage. The term also refers to an individual message sent in this way.Molecular Weight: The sum of the weight of all the atoms in a molecule.Periodicals as Topic: A publication issued at stated, more or less regular, intervals.Chorion: The outermost extra-embryonic membrane surrounding the developing embryo. In REPTILES and BIRDS, it adheres to the shell and allows exchange of gases between the egg and its environment. In MAMMALS, the chorion evolves into the fetal contribution of the PLACENTA.Gene Expression Profiling: The determination of the pattern of genes expressed at the level of GENETIC TRANSCRIPTION, under specific circumstances or in a specific cell.Transcription Factors: Endogenous substances, usually proteins, which are effective in the initiation, stimulation, or termination of the genetic transcription process.Gestational Trophoblastic Disease: A group of diseases arising from pregnancy that are commonly associated with hyperplasia of trophoblasts (TROPHOBLAST) and markedly elevated human CHORIONIC GONADOTROPIN. They include HYDATIDIFORM MOLE, invasive mole (HYDATIDIFORM MOLE, INVASIVE), placental-site trophoblastic tumor (TROPHOBLASTIC TUMOR, PLACENTAL SITE), and CHORIOCARCINOMA. These neoplasms have varying propensities for invasion and spread.Trophoblastic Neoplasms: Trophoblastic growth, which may be gestational or nongestational in origin. Trophoblastic neoplasia resulting from pregnancy is often described as gestational trophoblastic disease to distinguish it from germ cell tumors which frequently show trophoblastic elements, and from the trophoblastic differentiation which sometimes occurs in a wide variety of epithelial cancers. Gestational trophoblastic growth has several forms, including HYDATIDIFORM MOLE and CHORIOCARCINOMA. (From Holland et al., Cancer Medicine, 3d ed, p1691)Hydatidiform Mole: Trophoblastic hyperplasia associated with normal gestation, or molar pregnancy. It is characterized by the swelling of the CHORIONIC VILLI and elevated human CHORIONIC GONADOTROPIN. Hydatidiform moles or molar pregnancy may be categorized as complete or partial based on their gross morphology, histopathology, and karyotype.Uterine Neoplasms: Tumors or cancer of the UTERUS.Hydatidiform Mole, Invasive: A uterine tumor derived from persistent gestational TROPHOBLASTS, most likely after a molar pregnancy (HYDATIDIFORM MOLE). Invasive hyadatiform mole develops in about 15% of patients after evacuation of a complete mole and less frequently after other types of gestation. It may perforate the MYOMETRIUM and erode uterine vessels causing hemorrhage.Canada: The largest country in North America, comprising 10 provinces and three territories. Its capital is Ottawa.Biotin: A water-soluble, enzyme co-factor present in minute amounts in every living cell. It occurs mainly bound to proteins or polypeptides and is abundant in liver, kidney, pancreas, yeast, and milk.Nonsuppressible Insulin-Like Activity: A blood protein (NSILA) which mimics the biological activity of insulin in serum, but is not suppressed by insulin antibodies. During acid-ethanol extraction of Cohn fraction III, 10% of the activity is found in the supernatant (NSILA-S) and the remaining activity in the precipitate (NSILA-P). The latter is a large molecular compound, much less stable than the soluble fraction. NSILA-S is a more potent growth factor than insulin and exhibits sulfation activity.Somatomedins: Insulin-like polypeptides made by the liver and some fibroblasts and released into the blood when stimulated by SOMATOTROPIN. They cause sulfate incorporation into collagen, RNA, and DNA synthesis, which are prerequisites to cell division and growth of the organism.Insulin-Like Growth Factor I: A well-characterized basic peptide believed to be secreted by the liver and to circulate in the blood. It has growth-regulating, insulin-like, and mitogenic activities. This growth factor has a major, but not absolute, dependence on GROWTH HORMONE. It is believed to be mainly active in adults in contrast to INSULIN-LIKE GROWTH FACTOR II, which is a major fetal growth factor.Insulin-Like Growth Factor II: A well-characterized neutral peptide believed to be secreted by the LIVER and to circulate in the BLOOD. It has growth-regulating, insulin-like and mitogenic activities. The growth factor has a major, but not absolute, dependence on SOMATOTROPIN. It is believed to be a major fetal growth factor in contrast to INSULIN-LIKE GROWTH FACTOR I, which is a major growth factor in adults.Receptor, IGF Type 1: A protein-tyrosine kinase receptor that is closely related in structure to the INSULIN RECEPTOR. Although commonly referred to as the IGF-I receptor, it binds both IGF-I and IGF-II with high affinity. It is comprised of a tetramer of two alpha and two beta subunits which are derived from cleavage of a single precursor protein. The beta subunit contains an intrinsic tyrosine kinase domain.Genes, Synthetic: Biologically functional sequences of DNA chemically synthesized in vitro.Lactation: The processes of milk secretion by the maternal MAMMARY GLANDS after PARTURITION. The proliferation of the mammary glandular tissue, milk synthesis, and milk expulsion or let down are regulated by the interactions of several hormones including ESTRADIOL; PROGESTERONE; PROLACTIN; and OXYTOCIN.Milk, HumanMammary Glands, Animal: MAMMARY GLANDS in the non-human MAMMALS.Swallows: The family Hirundinidae, comprised of small BIRDS that hunt flying INSECTS while in sustained flight.X Chromosome Inactivation: A dosage compensation process occurring at an early embryonic stage in mammalian development whereby, at random, one X CHROMOSOME of the pair is repressed in the somatic cells of females.Milk: The white liquid secreted by the mammary glands. It contains proteins, sugar, lipids, vitamins, and minerals.