UNSW Embryology

Glossary N

© Dr Mark Hill (2008)

Acknowledgements

nanog

homeodomain-containing transcription factor involved in maintaining embryonic stem (ES) cell self-renewal. Name is derived from Celtic "Tir Na Nog" a mythologic Celtic land of the ever young. (More? OMIM NANOG | Molecular Factors- Nanog)

nail-patella syndrome

(NPS) rare (1/50,000) autosomal dominant disorder characterized by hypoplastic or absent patellae, dystrophic nails, dysplasia of the elbows and iliac horns. Potentially due to mutations in LMX1B, a LIM-homeodomain transcription protein. (More? OMIM nail-patella syndrome | LMX1B)

necrosis

(Greek, nekros = corpse) pathological cell death from extrinsic injury. Cell lyses releasing cytoplasmic contents which may also have a role in initiating an inflammatory response. (See also apoptosis)

Neisseria gonorrhoeae

gram-negative bacteria which causes the disease Gonorrhea, which is a sexually transmitted disease (STD). (More? Abnormal Development - Bacterial)

nephroblastoma

a childhood kidney cancer see Wilm's tumour

nestorone

synthetic progesterone potentially used in postmenopausal women (with an intact uterus) in combination with estrogen as hormone-replacement therapy (HRT). (Other Progestins: levonorgestrel, 3-keto-desogestrel, dienogest, drospirenone, Nestorone and nomegestrol acetate) Trimegestone and Nestorone are currently the most potent fourth-generation progestins with no androgenic or estrogenic actions. (More? Human Menstrual Cycle)

neural crest

cell region at edge of neural plate, then atop the neural folds, that remains outside and initially dorsal to the neural tube when it forms. These paired dorsal lateral streaks of cells migrate throughout the embryo and can differentiate into many different cell types (= pluripotential). Those that remain on the dorsal neural tube form the sensory spinal ganglia (DRG). Neural crest cells also migrate into the somites. (More? Neural Crest Notes)

neural tube

in the trilaminar embryo (ectoderm, mesoderm, endoderm) the ectoderm in the midline (above the notochordin the mesoderm) initially forms a neural plate which folds and fuses to form a hollow ectodermal neural tube. The neural tube forms the central nervous system (brain and spinal cord) (More? Neural Notes)

neuroblastoma

tumour of neural crest derived cells. (More? Neural Crest - Abnormalities)

neurogenesis

the process of formation of the neural system. This begins with segregation of the neural plate from the ectoderm of the trilaminar embryo by folding to form initially the neural groove, which then fuses to form the neural tube (the central nervous system progenitor, brain and spinal cord) and associated neural crest. (More? Neural Notes)

neurogenin-3

(NEUROG3) expressed in endocrine progenitor cells (including pancrea islet cells) and required for endocrine cell development in pancreas and intestine. Mutation in this gene depletes intestinal enteroendocrine cells resulting in malabsorptive diarrhea. (More? Endocrine Notes | Endocrine Development - Pancreas)

neuropore

opening at either end of neural tube: cranial=rostral=anterior, caudal=posterior. The cranial neuropore closes (day 25) approx. 2 days (human) before caudal. (More? Neural Notes)

neutrophil

(neutrophil granulocytes) white blood cell granulocyte that has a central role in the inflammatory process, invade sites of infection in response to growth factors. Cell nucleus has a characteristic lobed appearance (3-5 lobes), the number of lobes increases with cell age. During the menstrual cycle, a cyclic change in neutrophil cell number in the endometrium is shown by vaginal smear. (More? Cardiovascular System - Blood| Human Vaginal Smear Cells)

nicotine

is a natural alkaloid ingredient in tobacco leaves, where it provides protection by acting as a botanical insecticide. There is an association between physical defects among newborns and maternal smoking tobacco during pregnancy. (More? Abnormal Development Smoking | Smoking Workshop)

nicotinamide

amide of vitamin B3 and is the precursor for the coenzyme beta-nicotinamide adenine dinucleotide (NAD+). Role in normal cellular function and metabolism and also recently identified as a protective agent against ethanol-induced cell death in the developing brain. (More? Neural Notes | Fetal Alcohol Syndrome | PLoS - Medicine Article)

nidation

means implantation within the uterus. (More? Week 2 Notes)

Nitabuch's layer

(fibrinoid layer) layer formed at maternal/fetal interface during placentation and is thought to act to prevent excessively deep conceptus implantation. Fibrin-type fibrinoid (maternal blood-clot product) and matrix-type fibrinoid (secreted by invasive extravillous trophoblast cells). (More? Placenta)

Nogo

(= Reticulon 4, RTN4, Neurite Growth Inhibitor 220) one of several myelin-associated proteins with inhibitory effects for neuronal neurite outgrowth. Nogo exists as 3 splice transcript variants (NOGO-A, NOGO-B and NOGO-C) which are differentially expressed in the developing central nervous system. Also associated with autoimmune demyelination, shown in models of multiple sclerosis (MS) such as experimental autoimmune encephalomyelitis (EAE). (More? Nogo-A | Neural Notes | OMIM - Reticulon 4)

Nogo-A

myelin-associated protein which can inhibit neurite outgrowth and prevent regeneration in the adult central nervous system. Secreted by oligodendrocytes in the central nervous system, but not by Schwann cells in the peripheral nervous system. (More? Neural Notes | OMIM - Reticulon 4)

nosocomial

is an infection acquired with medical treatment, generally associated with hospitals. Some forms of acquired infections may impact on fetal development either directly, by transmission to the fetus, or indirectly through maternal effects such as fever. (More? Abnormal Development)

notch

cell surface single-pass transmembrane receptor family (1-4) required for asymmetric cell division. Acts as a receptor for Jagged (1,2) and Delta-like (1,3,4) proteins and also interacts with a negative regulator (Numb) which is down-regulated by notch. Asymmetry of cell division allows generation of distinct progeny from a single cell division required in many developmental processes including neurogenesis. (More? OMIM - NOTCH | OMIM - NUMB)

notochord

(= axial mesoderm) rod of cells lying in trilaminar embryo mesoderm layer ventral to the neural tube, induces neural tube and secretes sonic hedgehog which "ventralizes" the neural tube and also influences somite development. (More? Mesoderm Notes | Neural Notes)

Non-Hodgkin's lymphoma

(NHL) type of cancer where the cause is unknowm and may develop in people with suppressed immune system. Treatment may cause premature ovarian failure. A recent study has shown CHOP therapy (cyclophosphamide 750 mg/m2, doxorubicin 50 mg/m2, vincristine 1.4 mg/m2 (maximum 2 mg) and prednisone 100 mg/day for 5 days) does not affect the ovarian function or fertility. (More? Medline Encyclopedia | Dann EJ, Epelbaum R, Avivi I, Ben Shahar M, Haim N, Rowe JM, Blumenfeld Z. Fertility and ovarian function are preserved in women treated with an intensified regimen of cyclophosphamide, adriamycin, vincristine and prednisone (Mega-CHOP) for non-Hodgkin lymphoma. Hum Reprod. 2005 Aug;20(8):2247-9.

NRT

acronym for Nicotine Replacement Therapy, a method of replacing cigarette nicotine by either nicotine transdermal patches, nicotine gum, nicotine lozenges or nicotine inhalers. (More? Abnormal Development Smoking | Smoking Workshop)

numb

a membrane-associated protein (also Numblike) involved in asymmetric cell division along with notch. Acts as a negative regulator of notch which can also down-regulate numb expression. Asymmetry of cell division allows generation of distinct progeny from a single cell division required in many developmental processes including neurogenesis. (More? JCB - Notch and Numb | OMIM - NUMB | | OMIM - NUMBL | OMIM - NOTCH)

Alphabetical Links

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External Resources

Comments

Use this page to access brief definitions of specific alphabetically listed embryology terms. Additional information can be accessed from links listed at the end of each definition. Glossary from the UNSW Embryology program compiled and written by Dr Mark Hill. Reference Material used in preparing Glossary List: Texts listed on page 1 Reading of each notes section, Department of Anatomy Publications, WWW resources from NCBI, AMA (USA), Office of Rare Diseases (USA), PubMed Medline Dictionaries, MSDS, Merck Manual home edn., NHMRC (Australia). These notes are for Educational Purposes Only. Please email Dr Mark Hill if you wish to make a comment about this current project.

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