Embryo Project Encyclopedia Articles

The Spemann-Mangold organizer, also known as the Spemann organizer, is a cluster of cells in the developing embryo of an amphibian that induces development of the central nervous system. Hilde Mangold was a PhD candidate who conducted the organizer experiment in 1921 under the direction of her graduate advisor, Hans Spemann, at the University of Freiburg in Freiburg, German. The discovery of the Spemann-Mangold organizer introduced the concept of induction in embryonic development. Now integral to the field of developmental biology, induction is the process by which the identity of certain cells influences the developmental fate of surrounding cells. Spemann received the Nobel Prize in Medicine in 1935 for his work in describing the process of induction in amphibians. The Spemann-Mangold organizer drew the attention of embryologists, and it spurred numerous experiments on the nature of induction in many types of developing embryos.

Congenital rubella syndrome (CRS) can occur in children whose mothers contracted the rubella virus, sometimes called German measles, during pregnancy. Depending on the gestational period when the mother contracts rubella, an infant born with CRS may be unaffected by the virus or it may have severe developmental defects. The most severe effects of the virus on fetal development occur when the mother contracts rubella between conception and the first trimester. Defects from maternal rubella in the first trimester are included in the term congenital rubella syndrome, but physicians and researchers specifically refer to those defects as rubella embryopathy. Developmental defects are less severe if the mother contracts rubella in the second trimester, and they are generally negligible if the infection occurs in the third trimester. Prenatal rubella infection can cause birth defects which include deafness, compromised vision, abnormal heart development, and damage to the central nervous system which can lead to compromised cognition and learning disabilities.

The concept Fetal Alcohol Syndrome (FAS) refers to a set of birth defects that occur in children born to mothers who abused alcohol during pregnancy. The alcohol-induced defects include pre- and post-natal growth deficiencies, minor facial abnormalities, and damage to the developing central nervous system (CNS). FAS is the most serious condition physicians group under the heading of Fetal Alcohol Spectrum Disorders, which also includes Alcohol-Related Birth Defects, like alcohol-induced congenital cardiac defects that are unrelated to a diagnosis of FAS, and Alcohol-Related Neurodevelopmental Disorders, which occur in the absence of any facial birth defects or growth delays. The severity of birth defects associated with FAS can vary depending on the intensity, duration, and frequency of exposure to alcohol during gestation. In addition to these dose-related concerns, maternal factors such as the mother's genetics or how quickly she metabolizes alcohol, and the timing of exposure during prenatal development also impact alcohol-induced abnormalities. As birth defects and anomalies can arise when pregnant women consume alcohol, alcohol is a teratogen, an environmental agent that negatively impacts the course of normal embryonic or fetal development.