UNSW Embryology

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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 [A.htm#apoptosis apoptosis])

Necrotizing Enterocolitis

(Greek, nekros = corpse) Gastrointestinal tract pathology occurring postnatally in mainly in premature and low birth weight infants (1 in 2,000 - 4,000 births). The underdeveloped gastointestinal tract appears to be susceptible to bacteria, normally found within the tract,to spread widely to other regions where they damage the tract wall and may enter the bloodstream.Pathological cell death from extrinsic injury. Cell lyses releasing cytoplasmic contents which may also have a role in initiating an inflammatory response.

(More? Gastrointestinal Tract Abnormalities | Medline Plus - Necrotizing Enterocolitis)

Neisseria gonorrhoeae

A gram-negative bacteria which causes the disease Gonorrhea, which is a sexually transmitted disease (STD).

(More? Abnormal Development - Bacterial)

nebenkern

(German, nebenkern = subsidiary nucleus) A mitochondrial aggregate formed during developemnt of the Drosophila spermatazoa. The individual mitochondria fuse into two giant mitochondria arranged in a sphere of many layers of "onion-like" wrapped mitochondrial membranes. This process appears to only occur in some insect spermatogenesis.

(More? Drosophila Development | Meiosis | Spermatogenesis)

neoplastic rest

In kidney development, a neoplastic rest can develop under either genetic or epigenetic influence from a hyperplastic rest, originating from an embryonic blastema cell. Normally the majority of nephrogenic rests either regress or become dormant.

(More? [W.htm#Wilms_tumour Wilm's tumour] | [N.htm#nephrogenic_rest nephrogenic rest] | Urogenital Abnormalities | Urogenital Notes)

nephroblastoma

A childhood kidney cancer see [W.htm#Wilmtumour Wilm's tumour]

nephrogenic rest

A kidney term used to describe the embryonic blastema cells which persist and under either genetic or epigenetic can change to become a neoplastic rest. These neoplastic rests can develop postnatally as a benign form (adenomatous rest) or a malignant [W.htm#Wilms_tumour Wilm's tumour] form. The rests are further characterised by the time of generation leading to different anatomical kidney locations: early intralobar nephrogenic rests (within the renal lobe) and late pelilobar nephrogenic rests (periphery of the renal lobe).

(More? [W.htm#Wilms_tumour Wilm's tumour] | Urogenital Abnormalities | Urogenital Notes)

nephron

(Greek, nephros = kidney) The functional unit of the kidney. Urogenital Notes

nephros

(Greek, nephros = kidney) Term used to describe features associated with the kidney. (pronephros, mesonephros, metanephros, nephric, nephron, nephroblastoma) Urogenital Notes

nestorone

A synthetic progesterone potentially used in postmenopausal women (with an intact [U.htm#uterus 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)

neuralation

The general term used to describe the early formation of the nervous system. It is often used to describe the early events of differentiation of the central ectoderm region to form the neural plate, then neural groove, then neural tube. The nervous system includes the central nervous system (brain and spinal cord) from the neural tube and the peripheral nervous system (peripheral sensory and sympathetic ganglia) from neural crest. In humans, early neuralation begins in week 3 and continues through week 4.

(More? Neural Notes | Neural Crest Notes | Development Week by Week)

neural crest

A 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), those that migrate ventrally form the sympatheitic ganglia. Neural crest cells also migrate into the somites and regions throught the entire embryo.

(More? Neural Crest Notes)

neural folds

The central region of the trilaminar embryo ectoderm called the neural plate region folds dorsally, generating two neural folds, which later fuse to form the neural tube. The mid-line depression between the two folds is described as the neural groove. In humans at approximately day 18-19 post-fertilization to form the neural groove, which then fuses to form an initially open at either end hollow [#neural_tube neural tube]. The neural tube forms the central nervous system (brain and spinal cord). Developmental sequence: neural plate ->(day 18-19) neural groove -> neural tube -> Central Nervous System -> brain and spinal cord.

(More? Neural Notes)

neural groove

The second stage in early development of the central nervous system. In the trilaminar embryo (ectoderm, mesoderm, endoderm) the central region of the ectoderm (in the midline above the mesodermal notochord) initially forms a columnar epithelium described as the [#neural_plate neural plate]. This epithelium will fold dorsally, beginning in humans at approximately day 18-19 post-fertilization to form the neural groove, which then fuses to form an initially open at either end hollow [#neural_tube neural tube]. The neural tube forms the central nervous system (brain and spinal cord). Developmental sequence: neural plate ->(day 18-19) neural groove -> neural tube -> Central Nervous System -> brain and spinal cord.

(More? Neural Notes)

neural plate

The first stage in early development of the central nervous system. In the trilaminar embryo (ectoderm, mesoderm, endoderm) the central region of the ectoderm (in the midline above the mesodermal notochord) initially forms a columnar epithelium described as the neural plate. This epithelium will fold dorsally to form the [#neural_groove neural groove], which then fuses to form an initially open at either end hollow [#neural_tube neural tube]. The neural tube forms the central nervous system (brain and spinal cord). Developmental sequence: neural plate -> neural groove -> neural tube -> Central Nervous System -> brain and spinal cord.

(More? Neural Notes)

neural stem cell

(NSC) A stem cell within the central nervous system (CNS) that can proliferate indefinitely and give rise to either neurons, astrocytes, and oligodendrocytes.

(More? Neural Stem Cell Notes | Neural Notes | Stem Cell Notes)

neural stem cell niche

Locations within the nervous system that multipotent stem cells reside and participate in specialized microenvironments that support cell self-renewal and differentiation.

(More? Neural Stem Cell Notes | Neural Notes | Stem Cell Notes)

neural tube

The third stage in early development of the central nervous system. In the trilaminar embryo (ectoderm, mesoderm, endoderm) the central region of the ectoderm (in the midline above the mesodermal notochord) initially forms a columnar epithelium described as the [#neural_plate neural plate]. This epithelium will fold dorsally to form the [#neural_groove neural groove], which then fuses to form an initially open at either end hollow neural tube. The neural tube forms the central nervous system (brain and spinal cord). Developmental sequence: neural plate -> neural groove -> neural tube -> Central Nervous System -> brain and spinal cord.

(More? Neural Notes)

neuroblastoma

A tumour derived from neural crest cells.

(More? Neural Crest - Abnormalities)

neuroenteric canal

The canal or opening existing early in trilaminar embryo development that provides transient communication between the amnion and the yolk sac. Canal forms as part of axial process development, the precursor to the notochord.

(More? Neural Notes)

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) Gene 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)

neuron

(neurone) The cell forming the unit basis of the nervous system (both central and peripheral) capable of generating an action potential and releasing neurotransmitter. There are many different types of neuronal cells.

(More? Neural Notes)

neuropore

The initial two openings at either end of neural tube are the neuropores: cranial=rostral=anterior, caudal=posterior. The cranial neuropore closes (day 25) approx. 2 days (human) before caudal. The developmental abnormality classed as Neural Tube Defects (NTDs) are mainly dure to failure of these two neuropores to developmentally close.

(More? Neural Notes | Neural Abnormalities | Folic Acid and Neural Tube Defects)

neutrophil

(neutrophil granulocytes) A 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

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

The 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 | [doi:10.1371/journal.pmed.0030101 PLoS - Medicine Article])

nidation

Term used to clinically describe implantation within the [U.htm#uterus uterus].

(More? Week 2 Notes)

Nitabuch's layer

(fibrinoid layer) The 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 Nogo-A] | Neural Notes | OMIM - Reticulon 4)

Nogo-A

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

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

A 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) The rod of cells lying in the midline of the trilaminar embryo mesoderm layer ventral to the neural tube. Thought to have at least 2 early roles in development and later roles in patterning surrounding tissues. 1. Mechanical, influencing the folding of the early embryo; 2. Morphogenic, secreting sonic hedgehog a protein which regulates the development of surrounding tissues (neural plate, somites, endoderm and other organs). In humans, the notochord forms in week 3 and is eventually lost during the formation of the vertebral column.

(More? Mesoderm Notes | Neural Notes | Molecular Development- Sonic Hedgehog)

Non-Hodgkin's lymphoma

(NHL) A 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 ===N===icotine ===R===eplacement ===T===herapy, 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)

Comments

Use this page to access brief definitions of specific 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 this glossary list includes: texts listed on page 1 Reading of each notes section, Department of Anatomy Publications, WWW resources from NCBI, NIH, OMIM, NHMRC (Australia), AMA (USA), Office of Rare Diseases (USA), PubMed Medline Dictionaries, MSDS, Merck Manual home edn.

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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