| neuronal ceroid-lipofuscinosis | A heritable lipidosis with cytoplasmic inclusions staining for ceroid and lipofuscin. Clinically the patient has progressive dementia, retinal degeneration, seizures, and myoclonic jerks. It was formerly thought to be related to tay-sachs disease but the biochemical defect is as yet undetermined. Named according to age of onset: jansky-bielschowsky disease, 2-4 years; batten-spielmeyer-vogt disease, 5-11 years; and kufs disease, adult. (12 Dec 1998) |
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| neuronal differentiation | Acquisition during development of specific biochemical, physiological and morphological properties by nerve cells. (18 Nov 1997) |
| neuronal guidance | <cell biology> General term for mechanisms that ensure correct projections by nerve cells in developing and regenerating nervous systems. Implies accurate navigation by growth cones, the highly motile tips of growing neuronal processes. See: growth cone collapse. (12 Mar 1998) |
| neuronal hyperplasia | Increased numbers of ganglion cells with myenteric plexus hyperplasia and increased acetylcholinesterase activity in nerves of the mucosa and submucosa. Clinically, neuronal hyperplasia mimics Hirschprung's disease. Similar findings are seen in patients with multiple endocrine neoplasia syndrome, type IIB, and in neurofibromatosis. Synonym: hyperganglionosis, neuronal intestinal dysplasia. (05 Mar 2000) |
| neuronal intestinal dysplasia | Increased numbers of ganglion cells with myenteric plexus hyperplasia and increased acetylcholinesterase activity in nerves of the mucosa and submucosa. Clinically, neuronal hyperplasia mimics Hirschprung's disease. Similar findings are seen in patients with multiple endocrine neoplasia syndrome, type IIB, and in neurofibromatosis. Synonym: hyperganglionosis, neuronal intestinal dysplasia. (05 Mar 2000) |
| neuronal plasticity | Ability of nerve cells to change their properties for example by sprouting new processes, making new synapses or altering the strength of existing synapses. See: long-term potentiation. (18 Nov 1997) |
| neuronal polarity | Distribution of specific functions to discrete cellular domains: for example axons and dendrites that have different molecular composition, morphology and ultrastructure and perform different functions. (18 Nov 1997) |
| infantile neuronal degeneration | <neurology, paediatrics> Degenerative disorder of infants with widespread neuronal loss in thalamus, cerebellum, pons, and spinal cord, resembling infantile muscular atrophy. (05 Mar 2000) |
| A layer | <molecular biology> Right handed double helical DNA with approximately 11 residues per turn. Planes of base pairs in the helix are tilted 20 deg away from perpendicular to the axis of the helix. Formed from B DNA by dehydration. (18 Nov 1997) |
| ameloblastic layer | The internal layer of the enamel organ. Synonym: enamel layer. (05 Mar 2000) |
| anterior elastic layer | A transparent homogeneous acellular layer, 6 to 9 um thick, lying between the basal lamina of the outer layer of stratified epithelium and the substantia propria of the cornea; considered to be a basement membrane. Synonym: lamina limitans anterior corneae, anterior elastic layer, Bowman's membrane, lamina elastica anterior, limiting layers of cornea. (05 Mar 2000) |
| anterior layer of rectus abdominis sheath | The portion of the rectus sheath that lies anterior to the muscle, consisting in its upper two-thirds of contributions from the aponeuroses of the external and internal oblique muscles, and in its lower third (below the arcuralt line) of contributions from the aponeuroses of all three muscles of the anterolateral abdominal wall. Synonym: lamina anterior vaginae musculi recti abdominis. (05 Mar 2000) |
| anterior limiting layer of cornea | A transparent homogeneous acellular layer, 6 to 9 um thick, lying between the basal lamina of the outer layer of stratified epithelium and the substantia propria of the cornea; considered to be a basement membrane. Synonym: lamina limitans anterior corneae, anterior elastic layer, Bowman's membrane, lamina elastica anterior, limiting layers of cornea. (05 Mar 2000) |
| bacillary layer | The layer of the retina next to the pigment layer and containing the visual receptors. See: retina, granular layers of retina, neuroepithelial layer of retina. Synonym: bacillary layer. (05 Mar 2000) |
| basal cell layer | The deepest layer of the epidermis, composed of dividing stem cells and anchoring cells. Synonym: basal cell layer, columnar layer, germinative layer, palisade layer, stratum basale, stratum cylindricum, stratum germinativum. (05 Mar 2000) |