Advances in DNA sequencing technologies have enabled scientists to reconstruct the human fetal genome from genetic material isolated from maternal blood and paternal saliva. Fetal genome sequencing tools are valuable particularly in the area of prenatal diagnosis , where noninvasive testing methods, such as those based on the analysis of parental blood or saliva, could significantly reduce the risk of miscarriage associated with the collection of fetal or placental tissue in procedures such as amniocentesis and chorionic villus sampling.
Immunity wears off over time. So, the current recommendation is that everyone needs a booster shot for tetanus and diphtheria every 10 years after first being immunized. That booster comes in the form of a vaccine called Td . But since immunity to pertussis also wears off during childhood, a weaker form of the pertussis vaccine has been added to the booster to make the vaccine Tdap. The current recommendation is that one dose of the Tdap vaccine be substituted for one dose of the Td vaccine between the ages of 11 and 64. Pregnant women are also advised to get the Tdap vaccine, preferably between 27 and 36 weeks' gestation.
The secretion of hypothalamic, pituitary, and target tissue hormones is under tight regulatory control by a series of feedback and feed- forward loops. This complexity can be demonstrated using the growth hormone (GH) regulatory system as an example. The stimulatory substance growth hormone releasing hormone (GHRH) and the inhibitory substance somatostatin (SS) both products of the hypothalamus, control pituitary GH secretion. Somatostatin is also called growth hormone-inhibiting hormone (GHIH). Under the influence of GHRH, growth hormone is released into the systemic circulation, causing the target tissue to secrete insulin-like growth factor-1, IGF-1. Growth hormone also has other more direct metabolic effects; it is both hyperglycemic and lipolytic. The principal source of systemic IGF-1 is the liver, although most other tissues secrete and contribute to systemic IGF-1. Liver IGF-1 is considered to be the principal regulator of tissue growth. In particular, the IGF-1 secreted by the liver is believed to synchronize growth throughout the body, resulting in a homeostatic balance of tissue size and mass. IGF-1 secreted by peripheral tissues is generally considered to be autocrine or paracrine in its biological action.
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