Passage
Neurulation refers to the early formation of the nervous system in vertebrate embryos and begins when the notochord, a rodlike mesodermal structure, induces neural tube and neural crest cell formation in the ectoderm. Neural tube defects (NTDs) arise from abnormalities in the development of the neural tube and can range from mild to severe, depending on which portion of the tube is affected. Spina bifida, a form of NTD, is divided into three categories. The most serious subclassification of spina bifida is myelomeningocele, which occurs when the lower spine fails to close, which leaves the spinal cord and nerve roots in the lower back damaged and exposed.NTDs are thought to be caused in part by folate deficiency. Folate plays a critical role in normal cell division and growth as it is a necessary coenzyme for DNA synthesis and methylation. Mutations in several genes involved in folate metabolism have been associated with an increased risk for NTDs. It has been hypothesized that folate decreases NTD risk by ameliorating oxidative stress, thereby reducing damage to developing cells in the embryo. Certain maternal conditions, such as high blood glucose, increase the risk of NTD development by enhancing embryonic oxidative stress during crucial developmental periods.A study was conducted to examine how supplementation with folic acid, the dietary form of folate, affected pregnant women who were identified to have preexisting diabetes, pregestational obesity (another risk factor for NTD), or no preexisting conditions (control group). Higher folic acid intake decreased the incidence of embryonic NTDs among pregnant women with diabetes, but no significant effect was found for pregnant women who were obese.
Adapted from Parker SE, Yazdy MM, Tinker SC, Mitchell AA, Werler MM. The impact of folic acid intake on the association among diabetes mellitus, obesity, and spina bifida. Am J Obstet Gynecol. 2013;209(3):239.e1-8.
-Assume that neural stem cells are considered to be multipotent. Which of the following best describes this classification of stem cells?

Question

Passage
Neurulation refers to the early formation of the nervous system in vertebrate embryos and begins when the notochord, a rodlike mesodermal structure, induces neural tube and neural crest cell formation in the ectoderm.  Neural tube defects (NTDs) arise from abnormalities in the development of the neural tube and can range from mild to severe, depending on which portion of the tube is affected.  Spina bifida, a form of NTD, is divided into three categories.  The most serious subclassification of spina bifida is myelomeningocele, which occurs when the lower spine fails to close, which leaves the spinal cord and nerve roots in the lower back damaged and exposed.NTDs are thought to be caused in part by folate deficiency.  Folate plays a critical role in normal cell division and growth as it is a necessary coenzyme for DNA synthesis and methylation.  Mutations in several genes involved in folate metabolism have been associated with an increased risk for NTDs.  It has been hypothesized that folate decreases NTD risk by ameliorating oxidative stress, thereby reducing damage to developing cells in the embryo.  Certain maternal conditions, such as high blood glucose, increase the risk of NTD development by enhancing embryonic oxidative stress during crucial developmental periods.A study was conducted to examine how supplementation with folic acid, the dietary form of folate, affected pregnant women who were identified to have preexisting diabetes, pregestational obesity (another risk factor for NTD), or no preexisting conditions (control group).  Higher folic acid intake decreased the incidence of embryonic NTDs among pregnant women with diabetes, but no significant effect was found for pregnant women who were obese.
Adapted from Parker SE, Yazdy MM, Tinker SC, Mitchell AA, Werler MM. The impact of folic acid intake on the association among diabetes mellitus, obesity, and spina bifida. Am J Obstet Gynecol. 2013;209(3):239.e1-8.
-Assume that neural stem cells are considered to be multipotent.  Which of the following best describes this classification of stem cells?

Quizplus · Accepted Answer

11ecba2d_0fc1_3e9d_a3bf_c10aa9a55b9f_MD0008_00 The cells of the human body are derived from the zygote, the single diploid cell formed by the joining of two gametes at fertilization. This cell undergoes a series of mitotic divisions (cleavage) that eventually lead to the development of the fetus. Totipotent stem cells, which are found only in the zygote and up to the eight-cell stage of its mitotic division, have the greatest potency as they alone can autonomously give rise to an entire organism. Consequently, totipotent cells can differentiate into any cell type from either an embryonic or extraembryonic (placental) lineage (Choice B). Following the eight-cell stage, the blastocyst forms. This hollow structure contains an outer cell layer (trophoblast), which forms the placenta, and an inner cell mass, which forms the embryo. The cells of the inner cell mass are said to be pluripotent as these are able to differentiate into any cell found in the body. Pluripotent cells can give rise to any of the three primary germ layers found in the embryo but not the cells found in placental structures (Choice A). Therefore, pluripotent cells are more specialized (differentiated) than totipotent cells. As the ectoderm, mesoderm, and endoderm cell lineages mature and become more specialized, specific resident stem cells are preserved in each developing tissue and function to replace damaged/aged cells throughout the organism's life span. These cells, which are found in both the fetus and the adult, are multipotent because they can differentiate into cells with many specialized functions but are limited in that they are "committed" to a specific lineage (Choice D). For example, multipotent neural stem cells can give rise to the various cells of nervous tissue but cannot give rise to cells found in other tissue types. Educational objective: Totipotent stem cells are the least specialized cells and can give rise to both placental and fetal cells. Pluripotent stem cells can give rise to only fetal cells (ie, all cell lineages from the three germ layers). Multipotent cells are able to differentiate only into the specialized cells of certain tissues and are also found in adults.

Passage Neurulation Refers to the Early Formation of the Nervous System