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October, 2006
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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.

Endocrine Signaling

JoVE 10719

Endocrine cells produce hormones to communicate with remote target cells found in other organs. The hormone reaches these distant areas using the circulatory system. This exposes the whole organism to the hormone but only those cells expressing hormone receptors or target cells are affected. Thus, endocrine signaling induces slow responses from its target cells but these effects also last longer. There are two types of endocrine receptors: cell surface receptors and intracellular receptors. Cell surface receptors work similarly to other membrane bound receptors. Hormones, the ligand, bind to a hormone specific G-protein coupled receptor. This initiates conformational changes in the receptor, releasing a subunit of the G-protein. The protein activates second messengers which internalize the message by triggering signaling cascades and transcription factors. Many hormones work through cell surface receptors, including epinephrine, norepinephrine, insulin, prostaglandins, prolactin, and growth hormones. Steroid hormones, like testosterone, estrogen, and progesterone, transmit signals using intracellular receptors. These hormones are small hydrophobic molecules so they move directly past the outer cell membrane. Once inside, and if that cell is a target cell, the hormone binds to its receptor. Binding creates a conformational change in the receptor

 Core: Biology

Parental Care

JoVE 10921

Many animals exhibit parental care behavior, including feeding, grooming, and protecting young offspring. Parental care is universal in mammals and birds, which often have young that are born relatively helpless. Several species of insects and fish, as well as some amphibians, also care for their young.

Parental care can occur even before hatching in birds, when parents sit on their eggs to incubate them. After hatching, the parents provide food for their offspring, and may continue to brood their young to keep them warm. Both male and female birds provide parental care, depending on the species. In marsupial mammals, such as kangaroos, the embryos are often born at a very early stage and then crawl into their mother’s pouch. Here, the mother nurses and protects her offspring—sometimes for many months—until it can function more independently. Placental mammals are born more developed than marsupials, but they still require a lot of care. Mammalian parental care is mostly provided by the mother, triggered by the hormones of pregnancy and birth and the necessity of lactation for providing nutrients. Nursing is an essential kind of mammalian parental care since the mother’s milk is the primary source of food for the young. Mammals also often lick their newborns and carry them around—grooming, protecting, and bonding wi

 Core: Biology
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