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Слова на букву isop-macr (375)

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isoprenylation
See prenylation.
isoproterenol
(= isoprenaline: isopropyl-noradrenaline) Synthetic b- adrenergic agonist; causes peripheral vasodilation, bronchodilation, and increased cardiac output.
isopycnic
Having equal density: thus in equilibrium density gradient centrifugation a particle (molecule) will cease to move when it reaches a level at which it is isopycnic with the ...
isosbestic
Wavelength at which the absorption coefficients of equimolar solutions of two different substances are identical.
isotonic
Of a fluid, having a concentration that will not cause osmotic volume changes of cells immersed in it. Note that an isotonic solution is not necessarily isosmotic. See ...
isotonic contraction
Contraction of a muscle, the tension remaining constant. Since the contractile force is proportional to the overlap of the filaments, and the overlap is varying, the numbers of ...
isotropic environments
Environments in which the properties are the same at all points, and there are no vectorial or axial cues.
isotype
(1) Applied to a set of macromolecules sharing some features in common. In immunology isotype describes the class, subclass, light chain type and subtype of an ...
isotype switching
The switch of immunoglobulin isotype that occurs, for example, when the immune response progresses (IgM to IgG). The switch from IgM to IgG involves only the constant region ...
isotypic variation
Variability of antigens common to all members of a species, for example the five classes of immunoglobulins found in humans. See idiotype and allotype.
isozyme
See isoenzyme.
ITAM
(= immunoreceptor tyrosine-based activation motif) When phosphorylated binds zap-70 and Syk and initiates T-cell activation. Contrast with ITIMs.
ITIM
(= immunoreceptor tyrosine-based inhibitory motif) Phosphorylation of the ITIM motif, found in the cytoplasmic tail of some inhibitory receptors (KIRs) that bind MHC Class I, ...
Ito cells
Hepatic stellate cells that become activated in liver fibrosis due to intoxication or hepatotoxic compounds such as carbon tetrachloride. Activation is associated with ...
ivermectin
Broad-spectrum anthelminthic drug used to treat eg. parasitic nematode worms such as Strongylus and Onchocerca.
J
(1) The joule, SI unit of energy. (2) Used in the single letter code for amino acids to represent trimethyl lysine, eg. in calmodulin.
J chain
(= J-piece) Polypeptide chain (15 kD), found in IgA and in IgM joining heavy chains (H chains) to each other to form dimers of IgA and pentamers of IgM. Disulphide bonds are ...
J gene
Gene(s) coding for the Joining segment of polypeptide chain which links the V (variable regions) to the C (constant) regions of both Light and Heavy chains of immunoglobulins. ...
J region
The polypeptide chains coded for by J genes.
J774.2 cells
Mouse (Balb/c) monocyte/macrophage cells with surface receptors for IgG and complement.
JAB
(= JAK-binding protein) Cytokine-inducible inhibitor of JAKs, probably negative regulator of cytokine signalling. See SOCS.
JAK
(= Janus kinase) Family of intracellular tyrosine kinases (120-140kD) that associate with cytokine receptors (particularly but not exclusively interferon receptors) and are ...
Jamin-Lebedeff system
Interference microscopy in which object and reference beams are split and later recombined by birefringent calcite plates, but pass through the same optical components (in ...
jaundice
Yellowing of the skin (and whites of eyes) by bilirubin, a bile pigment. Frequently because of a liver problem.
JC virus
A human retrovirus similar to polyoma virus, but which has not been found associated with any human cancer. Member of the Papovaviridae.
JE
See monocyte chemotactic and activating factor.
jelly roll
Complex protein topology in which 4 Greek key motifs form an 8-stranded beta sandwich. So called because the overall structure resembles a swiss (or jelly, USA) roll.
JH1 domain
Domain in JAKs that is probably the binding site for the SH2 domain of SOCS.
Jijoye cells
Human lymphoblastic cell line, CD23 positive. Model for B-lymphoctes. Derived from Burkitt&’s lymphoma.
Jimpy
Mouse mutant with reduced life-span due to a recessive sex-linked defect in PLP gene. Has a severe CNS myelin deficiency associated with complex abnormalities affecting all ...
JNK
(= Jun kinase; c-jun N-terminal kinase; stress-activated protein kinase; SAPK) Family of kinases involved in intracellular signalling cascades. JNKs are distantly related to ...
Job's syndrome
Thought to be due to a defect in neutrophil chemotaxis which predisposes to infection by staphylococci, often without the normal signs of inflammation ("cold abscesses"). At ...
jumping gene
Populist term for transposon.
jun
Oncogene from an avian sarcoma virus. Protein product, jun, dimerises with fos via a zipper motif to form the transcription factor AP1.
junction potential
Potential difference at the boundary between dissimilar solutions; arises from differences in diffusion constants between ions.
junctional basal lamina
Specialized region of the extracellular matrix surrounding a muscle cell, at the neuromuscular junction. May be responsible for localization of acetylcholine receptors in the ...
junctions
See adherens junction, desmosome, gap junction, zonula occludens.
junk DNA
Genomic DNA that serves, as yet, no known function.
Jurkat cells
Human T-lymphocyte line much used for studies of IL-2 production in vitro. Although a convenient model system they are not identical to real T cells, particularly in their ...
juvenile hormone
A hormone found in insects which affects the balance between mature and juvenile attributes of certain tissues at each moult. In particular, the imaginal discs of many larval ...
juxtacrine activation
Activation of target cells by membrane-anchored growth factors; also used for activation of leucocytes by PAF bound to endothelial cell surface.
K antigen
Capsular antigens of bacteria - usually polysaccharide.
K cells
See killer cells.
k-ras
Kirsten-ras; see also Kirtsen sarcoma virus.
Ka
(1) Acid dissociation constant. Often encountered as pKa (ie. -log10 Ka). (2) Association constant (Kass). The equilibrium constant for association, the reciprocal of Kd, ...
kainate
An agonist for the K-type excitatory amino acid receptor. It can act as an excitotoxin producing symptoms similar to those of Huntington\'s chorea, and is also used as an ...
kainic acid
See kainate.
kairomone
A subclass of pheromone, defined as an interspecific secretion which benefits the receiver. See allomone.
kalanin
Protein that provides adhesion between epidemal keratinocytes and dermis. Localizes to anchoring filaments of basement membrane; 400-440 kD with fragments of 165, 155, 130 and ...
kaliotoxin
Toxin from the scorpion, Androctonus mauretanicus m., (peptide, 4 kD) that blocks some potassium channels. Closely related to charybdotoxin and agitoxins.
kalirin
(= P-CIP10) Cytoplasmic protein with spectrin-like and guanine exchange factor (GEF) domains that interacts with peptidylglycine alpha-amidating mono-oxygenase (peptide ...
kallidin
Decapeptide (lysyl-bradykinin; amino acid sequence KRPPGFSPFR) produced in kidney. Like bradykinin, an inflammatory mediator (a kinin) ; causes dilation of renal blood vessels ...
kallikrein
Plasma serine proteases normally present as inactive prekallikreins which are activated by Hagemann factor. Act on kininogens to produce kinins. Contain an apple domain.
kanamycin
Aminoglycoside antibiotic.
Kaposi's sarcoma
A sarcoma of spindle cells mixed with angiomatous tissue. Usually classed as an angioblastic tumour. A fairly frequent concomitant to HIV infection or long-term ...
kappa chain
(= k-light chains) See L-chain.
kappa particle
Gram negative bacterial endosymbiont of Paramecium spp., ( Caedobacter taeniospiralis), that confers the "killer" trait; infected Paramecium are resistant to the toxin ...
kappa toxin
(= k-toxin) Exotoxin produced by Clostridium; a collagenase that presumably aids tissue infiltration.
Kar3
Protein of the kinesin family that, like NCD, differs from kinesin in that it moves towards the minus end of the microtubule (like cytoplasmic dynein). Has been implicated in ...
Kartagener's syndrome
(= situs inversus) Condition in which the normal left/right asymmetry of the viscera is reversed. Associated with a dynein defect (dynein is absent or dysfunctional in some ...
karyokinesis
(= mitosis) Division of the nucleus, whereas cytokinesis is the division of the whole cell.
karyopherins
Components of the nuclear pore responsible for regulating, in a ranGTP-dependent manner, transport of proteins with nuclear localization signals.
karyoplast
A nucleus isolated from a eukaryotic cell surrounded by a very thin layer of cytoplasm and a plasma membrane. The remainder of the cell is a cytoplast.
karyorrhexis
Degeneration of the nucleus of a cell. There is contraction of the chromatin into small pieces, with obliteration of the nuclear boundary.
karyotype
The complete set of chromosomes of a cell or organism. Used especially for the display prepared from photographs of mitotic chromosomes arranged in homologous pairs.
Kawasaki disease
Acute inflammatory disease with systemic angiitis, most commonly occurring in infants and young children. Cause uncertain.
lactacystin
Specific inhibitor of proteasome.
lactadherin
Mucin-associated glycoprotein (46kD) found in human milk. Binds to rotavirus and inhibits replication.
lactalbumin
Milk protein fraction containing b -lactoglobulin and a -lactalbumin. a -lactalbumin is the regulatory subunit of lactose synthetase: thought to be related to lysozyme C.
lactate
(= 2-hydroxypropionic acid) Important as the terminal product of anaerobic glycolysis. Accumulation of lactate in tissues is responsible for the so-called oxygen debt.
lactate dehydrogenase
The enzyme that catalyses the formation and removal of lactate according to the equation: pyruvate + NADH = lactate + NAD. The appearance of LDH in the medium is often used ...
Lactobacillus
Genus of Gram positive anaerobic or facultatively aerobic bacilli, product of glucose fermentation is lactate. Important in production of cheese, yoghurt, sauerkraut and ...
lactoferrin
Iron-binding protein of very high affinity (Kd 10-19 at pH 6.4, 26-fold greater than that of transferrin) found in milk and in the specific granules of neutrophil leucocytes. ...
lactoperoxidase
Peroxidase enzyme from milk that finds an important use in generating active iodine as a non-permeant radiolabel for membrane proteins.
lactose
(= 4-O-b-D galactopyranosyl-b-D glucose) The major sugar in human and bovine milk. Conversion of lactose to lactic acid by Lactobacilli etc. is important in the production of ...
lactose carrier protein
The best known example is the product of the lacY gene, coded for in the lactose operon and responsible for the uptake of lactose by E. coli.
lactose operon
Group of adjacent and coordinately controlled genes concerned with the metabolism of lactose in E. coli. The lac operon was the first example of a group of genes under the ...
lactose repressor
Protein (tetramer of 37 kD subunits) that normally binds with very high affinity to the operator region of the lactose operon and inhibits transcription of the downstream ...
lacuna
Small cavity or depression, for example, the space in bone where an osteoblast is found.
LacZ
E. coli gene encoding beta-galactosidase. Part of the lac operon.
laddering
Apoptotic cells show a regular pattern of oligonucleotide sizes on electrophoretic gels; the ladder-like arrangement is a consequence of the cleavage of the DNA strand between ...
LAL test
See Limulus polyphemus.
lambda bacteriophage
(= l phage) Bacterial DNA virus, first isolated from E. coli. Its structure is similar to that of the T even phages. It shows a lytic cycle and a lysogenic cycle, and studies ...
lambda chain
See L-chain.
lamellar phase
See phospholipid bilayer.
lamellipodium
Flattened projection from the surface of a cell, often associated with locomotion of fibroblasts.
lamina
Flat sheet; as in basal lamina.
lamina propria
Fibrous layer of connective tissue underlying the basal lamina of an epithelium. May contain smooth muscle cells and lymphoid tissue in addition to fibroblasts and ...
laminarin
Storage polysaccharide of Laminaria and other brown algae; made up of b (1-3) -glucan with some b (1-6) linkages.
laminin
Link proteins of basal lamina; consist of an A chain (400 kD) and two B chains (200 kD). Each subunit contains at least 12 repeats of the EGF-like domain. The first laminin ...
lamins
Proteins that form the nuclear lamina, a polymeric structure intercalated between chromatin and the inner nuclear envelope. Lamins A and C (70 and 60 kD respectively) have ...
LAMP-1
(= lysosomal-associated membrane protein 1) Heavily glycosylated protein of lysosomal and plasma membrane. Depending on extent of glycosylation may have molecular weight ...
lampbrush chromosomes
Large chromosomes (as long as 1mm), actually meiotic bivalents, seen during prophase of the extended meiosis in the oocytes of some Amphibia. Segments of DNA form loops in ...
Landry-Guillain-Barre syndrome
See Guillain-Barre syndrome.
Langendorff perfused heart
Classic pharmacological organ preparation in which a rodent heart is maintained in vitro by perfusion of the aorta with oxygenated fluid so that the fluid passes into the ...
Langerhans
See Islets of Langerhans and Langerhans cells.
Langerhans cells
Cells of dendritic appearance, strongly MHC Class II positive and weakly phagocytic, found in the basal layers of the epidermis where they serve as accessory cells, ...
Langhans' giant cells
Multinucleate cells formed by fusion of epithelioid macrophages and associated with the central part of early tubercular lesions. Similar to foreign body giant cells, but with ...
Langmuir trough
A device for studying the properties of lipid monolayers at an air/water interface. A moveable barrier connected to a balance allows measurement of surface pressure.
Langmuir-Blodgett film
In biophysics, an ordered monolayer of molecules produced on the surface of water. An amphipathic molecule is floated at low concentration on the surface of the water, and ...
lanthanum
Lanthanum salts are used as a negative stain in electron microscopy, and as calcium-channel blockers.
LAR
(= leucocyte antigen-related protein) LAR is the prototype for a family of transmembrane protein tyrosine phosphatases with extracellular domains composed of Ig and ...
large T-antigen
See T-antigen.
large-cell lymphoma
Highly malignant group of tumours arising from transformed lymphocytes or myeloid precursors. Cell of origin often obscure.
Laron dwarfism
Human growth defect in which cells do not respond to growth hormone - the defect is due to mutation in the growth hormone receptor gene.
Lassa fever
See Lassa virus.
Lassa virus
Virulent and highly transmissible member of the Arenaviridae whose normal host is a rodent (Mastomys natalensis ) ; first recorded from Nigeria.
late gene
Gene expressed relatively late after infection of a host cell by a virus, usually structural proteins for the viral coat.
latency
(1) In electrophysiology: the time between onset of a stimulus and peak of the ensuing action potential. (2) Of an infection, a period in which the infection is present in the ...
latent virus
Virus integrated within host genome but inactive: may be reactivated by stress such as ultraviolet irradiation.
lateral diffusion
Diffusion in two dimensions, usually referring to movement in the plane of the membrane, such as the motion of fluorescently labelled lipids or proteins measured by the ...
lateral inhibition
A simple form of information processing. The classic example is found in the eye, whereby ganglion cells are stimulated if photoreceptors in a well defined field are ...
lathyrism
Disorder of collagen cross-linking as a result of copper sequestration by nitriles. (Lysyl oxidase is a copper-containing metalloenzyme). In animals, caused by eating toxic ...
Laticauda semifasciata
Sea snake. See erabutotoxins.
Latrodectus
Genus of spiders, Black Widows. See alpha-latrotoxin.
latroinsectotoxin
(= a-latroinsectotoxin) See latrotoxin.
latrotoxin
(= a-latrotoxin; a-LTx) Major toxin from Latrodectus spp. (1401 residues). Causes release of neurotransmitters from all synapses. An insect-specific toxin, a ...
lavage
Washing out of a cavity (eg.peritoneal cavity) in order to remove loosely adherent cells.
lazy leucocyte syndrome
A rare human complaint in which neutrophils display poor locomotion towards sites of infection.
Lbc
Oncoprotein of Dbl-like family. See Lfc.
LD50
That dose of a compound which causes death in 50% of the organisms to which it has been administered. Routine use of LD50 tests is now being replaced by more sensitive (and less ...
LDH
(= lactate dehydrogenase) LDH release from cells was often used as a test for cytolysis - as a cytoplasmic enzyme it should not leak from normal undamaged cells.
LDL
See low density lipoprotein.
LE body
A globular mass of nuclear material that stains with haematoxylin; associated with lesions of systemic lupus erythematosus.
LE cell
Phagocyte that has ingested nuclear material of another cell: characteristic of systemic lupus erythematosus.
leader peptide
See leader sequence.
leader sequence
In the regulation of gene expression for enzymes concerned with amino acid synthesis in prokaryotes, the leader sequence codes for the leader peptide that contains several ...
leading lamella
Anterior region of a crawling cell, such as a fibroblast, from which most cytoplasmic granules are excluded.
leaky mutation
Mutation in which sub-normal function exists - for example if a mutation leads to instability in a protein rather than its complete absence or there is reduced expression of a ...
LECAM
(= CD62L; LAM-1; L-selectin; MEL-14 antigen; leu-8) Leucocyte-endothelial cell adhesion molecule (37 kD polypeptide), a selectin, expressed on most haematopoietic cells and ...
lecithin
Phospholipids of egg yolk (usually hen\'s eggs). A mixture of phosphatidyl choline and phosphatidyl ethanolamine, but usually refers to phosphatidyl choline.
lecithinase
See phospholipases.
lectin
Proteins obtained particularly from the seeds of leguminous plants, but also from many other plant and animal sources, that have binding sites for specific mono- or ...
leghaemoglobin
Form of haemoglobin found in the nitrogen-fixing root-nodules of legumes. Binds oxygen, and thus protects the nitrogen-fixing enzyme, nitrogenase, that is oxygen sensitive.
Legionella
Genus of Gram negative asporogenous bacteria. Most species are pathogenic in humans, causing pneumonia-like disease, eg. Legionnaires\' disease, named after an outbreak in ...
legumin
Major storage protein of the seeds of peas and other legumes.
Leidig cells
See Leydig cells.
leiomyoma
Benign tumour of smooth muscle in which parallel arrays of smooth muscle cells form bundles which are arranged in a whorled pattern. The amount of fibrous connective tissue ...
leiotonin
Smooth-muscle analogue (homologue?) of troponin. Two subunits, leiotonins A and C, the latter similar in size, and homologous, to calmodulin and troponin C.
Leishman stain
Romanovsky-type stain; a mixture of basic and acid dyes used to stain blood smears and that differentially stains various classes of leucocytes.
leishmaniasis
Disease caused by protozoan parasites of the genus Leishmania. The parasite lives intracellularly in macrophages. Various forms of the disease are known, depending upon the ...
Leiurus quinquestriatus hebraeus
Scorpion. See scyllatoxin and charybdotoxin.
lentigo
Relatively common pigmented lesion of the skin in which melanocytes replace the basal layer of the epidermis.
Lentivirinae
Subfamily of non-oncogenic retroviruses that cause "slow diseases" that are characterized by horizontal transmission, long incubation periods and chronic progressive phases. ...
lentoid
Spherical cluster of retinal cells, formed by aggregation in vitro, that has a core of lens-like cells inside which accumulate proteins characteristic of normal lens. The ...
Lepidoptera
Order of insects that comprises butterflies and moths
Lepore haemoglobin
Variant haemoglobin in a rare form of thalassemia: there is a composite d-b chain as a result of an unequal crossing-over event. The composite chain is functional but ...
leprosy
Disease caused by Mycobacterium leprae, an obligate intracellular parasite that survives lysosomal enzyme attack by possessing a waxy coat. Leprosy is a chronic disease ...
leptin
Product (16 kD) of the ob (obesity) locus. Found in plasma of mouse and man: reduces food uptake and increases energy expenditure.
leptin receptor
Receptor for leptin. G-protein coupled, highly expressed in the hypothalamus, the site of appetite regulation in the brain; downstream regulates a K+ ATP channel similar to ...
leptinotarsins
(= b-leptinotarsins; leptinotoxin) Toxic proteins (45- 47 kD) present in the haemolymph of potato beetles ( Leptinotarsa spp.) Causes release of neurotransmitters from synapses ...
leptinotoxin
See beta-leptinotarsin.
leptonema
See leptotene.
Leptospira
Genus of spirochaete bacteria that cause a mild chronic infection in rats and many domestic animals. The bacteria are excreted continuously in the urine and contact with ...
leptospirosis
Weil\'s Disease, caused by infection with Leptospira.
leptotene
Classical term for the first stage of prophase I of meiosis, during which the chromosomes condense and become visible.
Lepus
The common European hare.
Lesch-Nyhan syndrome
A sex-linked recessive inherited disease in humans that results from mutation in the gene for the purine salvage enzyme HGPRT, located on the X chromosome. Results in severe ...
lethal mutation
Mutation that eventually results in the death of an organism carrying the mutation.
LETS
(= large extracellular transformation/trypsin sensitive protein) Originally described as a cell-surface protein that was altered on transformation in vitro : now known to be ...
Leu enkephalin
A natural peptide neurotransmitter; see enkephalins.
leucine
(= leu; L; 2-amino-4-methylpentanoic acid; 131 D) The most abundant amino acid found in proteins. Confers hydrophobicity and has a structural rather than a chemical role.
leucine aminopeptidase
An exopeptidase that removes neutral amino acid residues from the N-terminus of proteins.
leucine zipper
Motif found in certain DNA-binding proteins. In a region of around 35 amino acids, every seventh is a leucine. This facilitates dimerisation of two such proteins to form a ...
leucine-rich repeat
Short motif (around 24 residues) with 5-7 leucines generally at positions 2, 5, 7, 12, 21, 24. Forms an amphipathic region and is probably involved in protein-protein ...
leucinopine
(= dicarboxypropyl leucine) An analogue of nopaline found in crown gall tumours (induced by Agrobacterium tumefasciens) that do not synthesize octopine or nopaline.
leucocidin
Exotoxins from staphylococcal and streptococcal species of bacteria that cause leucocyte killing or lysis. There are two subunits, S and F, each inactive alone but ...
leucocyte
(= leukocyte (USA) ) Generic term for a white blood cell. See basophil, eosinophil, lymphocyte, monocyte, neutrophil.
leucocytosis
An excess of leucocytes in the circulation.
leucopenia
An abnormally low count of circulating leucocytes.
leucoplast
Colourless plastid, that may be an etioplast or a storage plastid (amyloplast, elaioplast or proteinoplast).
leukaemia
(= leukemia (USA) ) Malignant neoplasia of leucocytes. Several different types are recognized according to the stem cell that has been affected, and several virus-induced ...
leukaemia inhibitory factor
Polypeptide growth factor or cytokine with wide range of activities. Regulates growth and differentiation of primordial germ cells and embryonic stem cells but has effects on ...
leukemia
See leukaemia.
leuko-
See leuco-.
leukosialin
(= CD43; sialophorin) Widely distributed membrane-associated mucin, the major sialoglycoprotein of thymocytes and mature T-cells. Transmembrane protein with extensive O-linked ...
leukosis
The correct term for an excess of leucocytes in the circulation and other parts of the body, preferable in place of the term leucocytosis.
leukosulfakinin
Cockroach peptide hormones, that affect gut motility. Related to gastrin.
leukotrienes
(= LTA4, LTB4, LTC4, LTD4, LTE4) A family of hydroxyeicosatetraenoic (HETE) acid derivatives. LTA4 and LTB4 are modified lipids; leukotrienes C, D and E have the lipid ...
leupeptin
Family of modified-tripeptide protease inhibitors. Commonest is N-acetyl-Leu-Leu-argininal.
Lewis blood group
A pair of blood group activities associated with the A, B, H substances. Lewis Lea is a separate gene, whereas Leb arises from the combined activity of the enzymes specified by ...
Lewy body
Hyaline eosinophilic concentrically-laminated inclusions found in the substantia nigra and locus ceruleus of patients with Parkinsonism and Lewy body dementia.
LexA
E. coli repressor of the SOSsystem for response to DNA damage.
Leydig cell
Interstitial cells of the mammalian testis, involved in synthesis of testosterone.
LFA-1
(= CD11a/CD18; lymphocyte function-related antigen-1) Heterodimeric lymphocyte plasma-membrane protein ( aL 180 kD, b 95 kD) that binds ICAM-1, particularly involved in ...
LFA-3
(= lymphocyte function-related antigen-3) Ligand for the CD2 adhesion receptor that is expressed on cytolytic T-cells. LFA-3 is expressed on endothelial cells at low levels. The ...
Lfc
Oncoprotein of the Dbl-related family. Contains a Dbl-homology domain in tandem with a PH domain and is similar to Lsc, Lbc, Tiam-1 and Dbl. Has rho-GEF activity.
LH
See luteinizing hormone.
LHRF
See luteinizing hormone releasing factor.
library
See genomic library.
lichen
A large group of symbiotic associations between fungi and green and occasionally blue-green algae. Several genera of algae and of fungi are involved and the associations are ...
lichen planus
Rare skin disorder in which there is marked hyperkeratosis and extensive infiltration of lymphocytes into the lower epidermis.
Liddle&’s disease
Hereditable (autosomal dominant) form of salt-sensitive human hypertension caused by mutation in the beta or gamma subunit of the multi-subunit epithelial sodium channel ...
lidocaine
(= lignocaine) Commonly used local anaesthetic.
LIF
See leukaemia inhibitory factor
ligand
Any molecule that binds to another; in normal usage a soluble molecule such as a hormone or neurotransmitter, that binds to a receptor. The decision as to which is the ligand ...
ligand-gated ion channel
A transmembrane ion channel whose permeability is increased by the binding of a specific ligand, typically a neurotransmitter at a chemical synapse. The permeability change ...
ligand-induced endocytosis
The formation of coated pits and then coated vesicles as a consequence of the interaction of ligand with receptors, which then interact with clathrin and associated proteins ...
ligases
(= synthetases) Major class of enzymes that catalyse the linking together of two molecules (category 6 in the E classification) eg. DNA ligases that link two fragments of DNA by ...
ligatin
Polypeptide (10 kD monomer) that forms 3-4.5nm polymeric fibrils on the outside of chick neural retina cells.
light chain
Nonspecific term used of the smaller subunits of several multimeric proteins, for example immunoglobulin, myosin, dynein, clathrin. See also L-chain.
Light Green
A stain often used for counterstaining cytoplasm following iron haematoxylin; a component of Masson&’s trichrome.
light microscopy
In contrast to electron microscopy. See bright field, phase contrast, interference, interference contrast, interference reflection, dark field, confocal and fluorescence ...
light scattering
Particles suspended in a solution will cause scattering of light, and the extent of the scattering is related to the size and shape of the particles (in a somewhat complex ...
light-dependent reaction
The reaction taking place in the chloroplast in which the absorption of a photon leads to the formation of ATP and NADPH.
light-harvesting system
Set of photosynthetic pigment molecules that absorb light and channel the energy to the photosynthetic reaction centre, where the light reactions of photosynthesis occur. In ...
lignin
Complex polymer of phenylpropanoid subunits, laid down in the walls of plant cells such as xylem vessels and sclerenchyma. Imparts considerable strength to the wall, and also ...
LIM domain
Domain found in proteins required for developmental decisions. Contain 60-residue conserved, cysteine-rich, repeats. Named after first 3 genes in group: Lin-11 ( Caenorhabditis ...
limb bud
The limbs of vertebrates start as outpushings of mesenchyme surrounded by a simple epithelium. The distal region is referred to as the progress zone. There has been extensive ...
limbic system
Those regions of the central nervous system responsible for autonomic functions and emotions. Includes hippocampus, amygdaloid nucleus and portions of the mid-brain.
limit of resolution
See resolving power.
Limulus polyphemus
Now renamed Xiphosura, though Limulus is still in common usage as a name. The king crab or horseshoe crab, found on the Atlantic coast of North America. It is more closely ...
lincomycin
Antibiotic active against Gram positive bacteria. Acts by blocking protein synthesis by binding to the 50S subunit of the ribosome and blocking peptidyl transferase reaction. ...
linear dichroism
See circular dichroism.
Lineweaver-Burke plot
A plot of 1/v against 1/S for an enzyme-catalyzed reaction, where v is the initial rate and S the substrate concentration. From the equation: 1/v = 1/Vmax(1+Km/S) the parameters ...
lining epithelium
An epithelium lining a duct, cavity or vessel, that is not particularly specialized for secretion or as a mechanical barrier. Not a precise classification.
linkage
Tendency for certain genes tend to be inherited together, because they are on the same chromosome. Thus parental combinations of characters are found more frequently in ...
linkage disequilibrium
The occurrence of some genes together, more often than would be expected. Thus, in the HLA system of histocompatibility antigens, HLA-A1 is commonly associated with B8 and DR3, ...
linkage equilibrium
Situation that should exist in a population undisturbed by selection, migration, etc., in which all possible combinations of linked genes should be present at equal frequency. ...
linoleic acid
An essential fatty acid(9, 12, octadecadienoic acid) ; occurs as a glyceride component in many fats and oils.
linolenic acid
An 18-carbon fatty acid with three double bonds (9, 12, 15, octadecatrienoic acid) and a - and g -isomers. Essential dietary component for mammals. See fatty acids.
lipaemia
Presence in the blood of an abnormally large amount of lipid.
lipases
Enzymes that break down mono-, di- or tri-glycerides to release fatty acids and glycerol. Calcium ions are usually required.
lipid A
The lipid associated with polysaccharide in the lipopolysaccharide of Gram negative bacterial cell walls.
lipid bilayer
See phospholipid bilayer.
lipidoses
Storage diseases in which the missing enzyme is one that degrades sphingolipids (sphingomyelin, ceramides, gangliosides). In Tay-Sachs disease the lesion is in hexosiminidase A, ...
lipids
Biological molecules soluble in apolar solvents, but only very slightly soluble in water. They are an heterogenous group (being defined only on the basis of solubility) and ...
lipoamide
The functional form of lipoic acid in which the carboxyl group is attached to protein by an amide linkage to a lysine amino group.
lipoamide dehydrogenase
An enzyme that regenerates lipoamide from the reduced form dihydrolipoamide.
lipocalin
Family of proteins that transport small, hydrophobic molecules, such as retinol, porphyrins, odorants. Characterized by two orthogonally-stranded beta sheets. Examples: ...
lipocortin
The name given to calcium-binding protein believed to be secreted by macrophages that acts as an inhibitor of phospholipase A2 enzymes and has a possible role in mediating the ...
lipofectamine
(= lipofect amine) Proprietary formulation for lipid-mediated tranfection of cultured cells.
lipofuscin
Brown pigment characteristic of ageing. Found in lysosomes and is the product of peroxidation of unsaturated fatty acids and symptomatic, perhaps, of membrane damage rather than ...
lipoic acid
(= thioctic acid; 1,2-dithiolane-3-valeric acid) Regarded as a coenzyme in the oxoglutarate dehydrogenase complex of the tricarboxylic acid cycle. Involved generally in ...
lipomodulin
The name originally given to lipocortin from neutrophils.
lipophorin
A family of high-density lipoproteins (6-700 kD) from insect haemolymph, that transport diacyl glycerols. The molecule comprises heavy (250 kD) and light (85 kD) subunits, the ...
lipopolysaccharide
The major constituents of the cell walls of Gram negative bacteria. Highly immunogenic and stimulates the production of endogenous pyrogen interleukin-1 and tumour necrosis ...
lipoproteins
An important class of serum proteins in which a lipid core with a surface coat of phospholipid monolayer is packaged with specific proteins (apolipoproteins). Classified ...
liposome
Artificially formed single or multi-layer spherical lipid bilayer structures. Made from solutions of lipids etc. in organic solvents dispersed in aqueous media. Under ...
lipoteichoic acid
Compounds formed from teichoic acid linked to glycolipid and found in the walls of most Gram positive bacteria. The lipoteichoic acid of streptococci may function as an ...
lipotropin
(= LPH; lipotropic hormone; adipokinetic hormone) Polypeptide hormone ( b form: 9894D, 91 residues; g form has only residues 1-58 of b ) from the pituitary hypophysis, that ...
lipoxygenase
(= 5-lipoxygenase; 5-LO) Enzyme that catalyses the addition of a hydroperoxy group to the 5-position of arachidonic acid, the first step in leukotriene synthesis.
liprins
Family of proteins that interact with LAR family phosphatases. C-terminal portion of liprins binds to membrane-distal phosphatase domain of LAR and N-terminal region may be ...
Listeria monocytogenes
Rod-shaped Gram positive bacterium. Wide-spread and can grow over an unusually wide range of temperatures (0-45°C). Normally saprophytic but is an opportunistic parasite, in ...
listeriolysin O
Cholesterol binding toxin from Listeria monocytogenes.
lithium
The lightest alkali metal, although it has the largest hydrated cation. Important as an antidepressant and is thought to act by inhibiting the regeneration of inositol from ...
lithotroph
Cell or organism that depends upon inorganic compounds as electron donors for energy production.
litorin
A peptide that mimics bombesin in its mitogenic effects, and has a carboxy-terminal octapeptide in common with bombesin.
liver cells
Usually implies hepatocytes, even though other cell types are found in the liver (Kupffer cellsfor example). Hepatocytes are relatively unspecialised epithelial cells and are the ...
LMM
(= light meromyosin)
lobopodia
Hemispherical protrusions from the front of a moving tissue cell.
local circuit theory
A generally accepted model for neuronal conduction, by which depolarization of a small region of a neuronal plasma membrane produces transmembrane currents in the neighbouring ...
locomotion
Term used by some authors to distinguish movement of cells from place-to-place from movements such as flattening, shape-change, cytokinesis etc.
locus
(= loci (plural) ) The site in a linkage map or on a chromosome where the gene for a particular trait is located. Any one of the alleles of a gene may be present at this site. ...
locus control region
(= control region; LCR) Region of DNA which contains the promoters and enhancers that regulate the expression of a particular gene. Often taken to be a single region 0-2kb ...
Lod score
‘Logarithm of the odds’ score: a statistical test for the probability that there is linkage. For non-X-linked genetic disorders a Lod score of +3 (1000:1) is usually taken ...
Loeffler&’s syndrome
Acute but mild and self-limiting eosinophilic pneumonia.
Loeffler's medium
Suboptimal coagulated-serum medium used to culture Corynebacterium diphtheriae in diagnostic bacteriology.
Loligo
Squid. Source of giant axons for electrophysiologists.
lomasome
Membranous structure, often containing internal membranes, located between the plasma membrane and cell wall of plant cells. Included in the more general term, paramural ...
long-term potentiation
Increase in the strength of transmission at a synapse with repetitive use that lasts for more than a few minutes. As a form of long-term synaptic plasticity it is important as ...
long-terminal repeat
Identical DNA sequences, several hundred nucleotides long, found at either end of transposons and the proviral DNA, formed by reverse transcription of retroviral RNA. They are ...
lophocytes
Cells found beneath the dermal membrane of a few species of sponges. Have been postulated to constitute a primitive nervous system though this is uncertain.

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