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Слова на букву pert-prom (375)

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pertussis toxin
Protein complex (ca 117 kD). An AB toxin, the active subunit is a single polypeptide (28 kD), the binding subunit a pentamer (two heterodimers, 23 + 11.7 kD, 11.7 + 22 kD, and ...
PEST sequence
(= Pro-Glu-Ser-Thr) Amino acid motif that is thought to target cytoplasmic proteins for rapid proteolytic degradation.
petechia
(= petechiae (plural) ) Small round red-purple spot, not raised and caused by intradermal haemorrhage.
petite mutants
A class of yeast mutants, most studied in Saccharomyces cerevisiae. Mutants grow slowly and rely on anaerobic respiration: mitochondria, although present, have reduced cristae ...
Petromyzon
(= lamprey) Primitive marine vertebrate (Class Agnatha) with eel-like body and lacking true jaws. Their relatively simple nervous system has been studied in some detail.
Peyer's patches
Lymphoid organs located in the submucosal tissue of the mammalian gut containing very high proportions of IgA-secreting precursor cells. The patches have B- and T-dependent ...
PF 4
See cytokine.
Pfr
The form of phytochrome that absorbs light in the far red region, 730nm, and is thus converted to Pr. It slowly and spontaneously converts to Pr in the dark.
PGs
(= prostaglandins; PGA, PGB, PGD, PGE, PGF, PGG, PGH, PGI) PGA is prostaglandin A, etc. PGI is more commonly known as prostacyclin.
pH
(= -log10[H+]) A logarithmic scale for the measurement of the acidity or alkalinity of an aqueous solution. Neutrality corresponds to pH 7, whereas a 1 molar solution of a strong ...
PH domain
(= Pleckstrin homology domain) Domain found in various intracellular signalling cascade proteins (eg. tec family kinases). Seem to be involved in interactions with ...
PH-30
Heterodimeric sperm surface transmembrane protein involved in sperm-egg fusion. The a -subunit has some similarities to viral fusion proteins, and the b -subunit has a domain ...
PHA
See phytohaemagglutinin.
phaeochromocytoma
(= pheochromocytoma (USA) ) A normally benign neoplasia (neuroblastoma) of the chromaffin tissue of the adrenal medulla. In culture, the cells secrete enormous quantities of ...
Phaeophyta
(= Pheophyta (USA) ; brown algae) Division of algae, generally brown in colour, with multicellular, branched thalluses. Includes large seaweeds such as Laminaria and Fucus. ...
phage
See bacteriophage.
phage display library
Phage library in which the insert is expressed as a translational fusion with a phage coat protein. This makes it particularly easy to screen with antibodies. Widely used to ...
phage integrase family
See recombinases, site-specific recombination.
phage typing
Bacteria may be typed by their susceptibility to a range of bacteriophages though confusion may arise if the bacteria carry plasmids encoding restriction endonucleases.
phagemid
Bacteriophage whose genome contains a plasmid that can be excised by co-infection of the host with a Helper phage. Useful as vectors for library production, as the library ...
phagocyte
A cell that is capable of phagocytosis. The main mammalian phagocytes are neutrophils and macrophages.
phagocytic vesicle
Membrane-bounded vesicle enclosing a particle internalised by a phagocyte. The primary phagocytic vesicle (phagosome) will subsequently fuse with lysosomes to form a secondary ...
phagocytosis
Uptake of particulate material by a cell (endocytosis). See opsonization, phagocyte.
phakinin
Eye-lens specific protein, 47 kD, that co-assembles with filensin (3 phakinin molecules per filensin) to form beaded-chain intermediate filaments. Phakinin has very strong ...
phalangeal cells
Cells of the organ of Corti (in the inner ear).
phalloidin
Cyclic peptide (789D) from the Death Cap fungus ( Amanita phalloides ) that binds to, and stabilizes, F-actin. Fluorescent derivatives are used to stain actin in fixed and ...
pharate
Of an insect, having its new cuticle formed beneath its present cuticle, and thus ready for its next moult.
pharmacodynamics
The study of how drugs affect the body: contrast with pharmacokinetics.
pharmacokinetics
The study of what the body does to drugs, in contrast to pharmacodynamics.
phase contrast microscopy
A simple non-quantitative form of interference microscopy of great utility in visualizing live cells. Small differences in optical path length due to differences in refractive ...
phase separation
The separation of fluid phases that contain different concentrations of common components. Occurs with partially miscible solvents used in many biochemical separation methods. ...
phase variation
Alteration in the expression of surface antigens by bacteria. For example, Salmonella can express either of two forms of flagellin, H1 and H2, that are coded by different genes. ...
phaseollin
A phytoalexin produced by Phaseolus (bean) plants in response to pathogenic attack or other stress.
phasic
See adaptation.
phasing of nucleosomes
A non-random arrangement of nucleosomes on DNA, in which, at certain segments of the genome, nucleosomes are positioned in the same way relative to the nucleotide sequence in ...
phasmid
Hybrid phage/plasmid formed by integration of plasmid containing the att site, and lambda phage, mediated by phage integrase site-specific recombination.
phelloderm
Tissue containing parenchyma-like cells, in the bark of tree roots and shoots. Produced by cell division in the phellogen.
phellogen
Meristematic tissue in plants, giving rise to cork (phellem) and phelloderm cells. Also termed "cork cambium".
phencyclidine
(= 1-(1-phenylcyclohexyl) piperidine; Angel dust; PCP) Anaesthetic and drug of a kind that can produce marked behavioural effects. Interacts with the NMDA receptor.
phenocopy
An environmentally produced phenotype simulating the effect of a particular genotype.
phenol red
Dye used as pH indicator: changes from yellow to red in range 6.8-8.4. Very commonly used in tissue culture medium though it can interfere with luminescence assays.
phenolphthalein
Indicator dye that is colourless at neutral pH and red-pink in slightly alkaline solutions. Also used as a laxative.
phenome
Phenotypic equivalent of the genome - the sum of all phenotypic characters.
phenothiazines
A group of antipsychotic drugs, thought to act by blocking dopaminergic transmission in the brain. Examples are chlorpromazine and trifluoperazine. Trifluoperazine binds to ...
phenotype
The characteristics displayed by an organism under a particular set of environmental factors, regardless of the actual genotype of the organism.
phenylalanine
(= Phe; F; 165D) An essential amino acid with an aromatic side chain.
phenylalanine ammonia lyase
Enzyme involved in the synthesis of ligninand other phenolic compounds from phenylalanine. Used as an enzymic marker for lignification and other developmental processes in plant ...
phenylephrine hydrochloride
An a1-adrenergic agonist (204 D).
phenylketonuria
Congenital absence of phenylalanine hydroxylase (an enzyme that converts phenylalanine into tyrosine). Phenylalanine accumulates in blood and seriously impairs early neuronal ...
pheo-
See phaeo-.
pheromone
A volatile hormone or behaviour modifying agent. Normally used to describe sex attractants (eg. bombesin for the moth Bombyx ) but includes volatile aggression stimulating ...
phi X-174
(= f X-174) Bacteriophage of E. coli with a single-stranded DNA genome and an icosahedral shell. This was the first DNA phage to be fully sequenced: the genome consists of 10 ...
Philadelphia chromosome
Characteristic chromosomal abnormality of chronic myelogenous leukaemia in which a portion of chromosome 22 is translocated to chromosome 9.
phlebotomy
The cutting of veins - fancy name for taking blood by venepuncture, usually with a needle not a knife.
phloem
Tissue forming part of the plant vascular system, responsible for the transport of organic materials, especially sucrose, from the leaves to the rest of the plant. Consists of ...
phorbol esters
Polycyclic compounds isolated from croton oil in which two hydroxyl groups on neighbouring carbon atoms are esterified to fatty acids. The commonest of these derivatives is ...
phormicin
Insect defensin produced by the blowfly, Phormia terranovae.
phosducin
Protein (33 kD) that inhibits Gs-GTPase activity (a GIP). Isolated from bovine brain and found in retina, pineal gland and many other tissues. Activity of phosducin is ...
phosphatases
Enzymes that hydrolyze phosphomonoesters. Acid phosphatases are specific for the single-charged phosphate group and alkaline phosphatases for the double-charged group. These ...
phosphatides
The family of phospholipids based on 1, 2 diacyl 3-phosphoglyceric acid. See phospholipids.
phosphatidic acid
(= PA; diacyl glycerol 3-phosphate) The ‘parent’ structure for phosphatidyl phospholipids, present in low concentrations in membranes. The acyl groups are derived from ...
phosphatidyl choline
The major phospholipid of most mammalian cell membranes where the 1-acyl residue is normally saturated and the 2-acyl residue unsaturated. Choline is attached to phosphatidic ...
phosphatidyl ethanolamine
A major structural phospholipid in mammalian systems. Tends to be more abundant than phosphatidyl choline in the internal membranes of the cell, and is an abundant component ...
phosphatidyl inositol
Very important minor phospholipid in eukaryotes, involved in signal transduction processes. Contains myo-inositol linked through the 1-hydroxyl group to phosphatidic acid. ...
phosphatidyl serine
An important ‘minor’ species of phospholipid in membranes. Serine is attached to phosphatidic acid by a phosphodiester linkage. Synthesis is from phosphatidyl ...
phosphocreatine
(= creatine phosphate) Present in high concentration (about 20mM) in striated muscle, and is synthesized and broken down by creatine phosphokinase to buffer ATP ...
phosphodiester bond
Not a precise term. Refers to any molecule in which two parts are joined through a phosphate group. Examples are found in RNA, DNA, phospholipids, cyclic nucleotides, nucleotide ...
phosphodiesterase
An enzyme that cleaves phosphodiesters to give a phosphomonoester and a free hydroxyl group. Examples include RNAase, DNAase, phospholipases C and D and the enzymes that ...
phosphoenolpyruvate
An important metabolic intermediate. The enol (less stable) form of pyruvic acid is trapped as its phosphate ester, giving the molecule a high phosphate transfer potential. ...
phosphofructokinase
The pacemaker enzyme of glycolysis. Converts fructose 6-phosphate to fructose 1,6-bisphosphate. A tetrameric allosteric enzyme that is sensitive to the ATP/ADP ratio.
phosphoglycerate
The molecules 2-phosphoglycerate and 3-phosphoglycerate are intermediates in glycolysis. 3-phosphoglycerate is the precursor for synthesis of phosphatidic acid and diacyl ...
phospholipases
Enzymes that hydrolyze ester bonds in phospholipids. They comprise two types: aliphatic esterases (phospholipase A1, A2 and B) that release fatty acids, and phosphodiesterases ...
phospholipid
The major structural lipid of most cellular membranes (except the chloroplast, which has galactolipids). Contain phosphate, usually as a diester. Examples include phosphatidyl ...
phospholipid bilayer
A lamellar organization of phospholipids that are packed as a bilayer with hydrophobic acyl tails inwardly directed and polar head groups on the outside surfaces. It is this ...
phospholipid transfer protein
Cytoplasmic proteins that bind phospholipids and facilitate their transfer between cellular membranes. May also cause net transfer from the site of synthesis.
phosphomannose
See mannose-6-phosphate.
phosphoprotein
Proteins that contain phosphate groups esterified to serine, threonine or tyrosine (S,T or Y). The phosphate group usually regulates protein function.
phosphoramidite
Nucleotide derivative used in oligonucleotide synthesis.
phosphorescence
(1) Emission of light following absorption of radiation. Emitted light is of longer wavelength than the exciting radiation and is a result of decay of electrons from the triplet ...
phosphorylase
(= glycogen phosphorylase) Enzyme that catalyses the sequential removal of glycosyl residues from glycogen to yield one glucose-1-phosphate per reaction. Its activity is ...
phosphorylase kinase
The enzyme that regulates the activity of phosphorylase and glycogen synthetase by addition of phosphate groups. A large and complex enzyme, itself regulated by ...
phosphorylation of proteins
Addition of phosphate groups to hydroxyl groups on proteins (to the side chains of serine, threonine or tyrosine) catalysed by a protein kinase (often specific) with ATP as ...
phosphotransferase
An enzyme that transfers a phosphate group from a donor to an acceptor. Very important in metabolism.
phosphotyrosine
Strictly speaking, tyrosine phosphate, but normally refers to the phosphate ester of a protein tyrosine residue. Present in very small amounts in tissues, but believed to be ...
photoaffinity labelling
A technique for covalently attaching a label or marker molecule onto another molecule such as a protein. The label, which is often fluorescent or radioactive, contains a group ...
photobleaching
Light-induced change in a chromophore, resulting in the loss of its absorption of light of a particular wavelength. A problem in fluorescence microscopy where prolonged ...
photodynamic therapy
Therapeutic approach in which a light-sensitive prodrug is given and then the target area (usually a tumour) is illuminated to generate the active drug in the right place.
photodynesis
Initiation of cytoplasmic streaming by light. Uncommon usage.
photolyase
(= DNA photolyase) Family of ubiqitous enzymes found in bacteria, archaebacteria and eukaryotes that can repair UV-induced DNA damage. The protein (between 454 to 614 residues) ...
photolysis
Light-induced cleavage of a chemical bond, as in the process of photosynthesis.
photoperiodism
Events triggered by duration of illumination or pattern of light/dark cycles: often the wavelength of the illuminating light is important - as for example in control of ...
photophosphorylation
The synthesis of ATP that takes place during photosynthesis. In non-cyclic photophosphorylation the photolysis of water produces electrons that generate a proton motive ...
photopigment
Pigment involved in photosynthesis in plants. Includes chlorophyll, carotenoids and phycobilins.
photoreceptor
A specialized cell type in a multicellular organism that is sensitive to light. This definition excludes single-celled organisms, but includes non-eye receptors, such as snake ...
photorespiration
Increased respiration that occurs in photosynthetic cells in the light, due to the ability of RuDP carboxylase to react with oxygen as well as carbon dioxide. Reduces the ...
photosynthesis
Process by which green plants, algae, and some bacteria absorb light energy and use it to synthesize organic compounds (initially carbohydrates). In green plants, occurs in ...
photosynthetic bacteria
Bacteria that are able to carry out photosynthesis. Light is absorbed by bacteriochlorophyll and carotenoids. Two principal classes are the green bacteria and the purple ...
photosynthetic unit
Group of photosynthetic pigment molecules (chlorophylls and carotenoids) that supply light to one reaction centre in photosystem I or II.
photosystem I
Photosynthetic system in chloroplasts in which light of up to 700nm is absorbed and its energy used to bring about charge separation in the thylakoid membrane. The electrons are ...
photosystem II
Photosynthetic system in chloroplasts in which light of up to 680nm is absorbed and its energy used to split water molecules, giving rise to a high energy reductant, Q-, and ...
phototaxis
Movement of a cell or organism towards (positive phototaxis) or away from (negative p.) a source of light.
phototransduction
The transformation by photoreceptors (eg. retinal rods and cones) of light energy into an electrical potential change.
phototrophic
Any organism that can utilize light as a source of energy.
phototropism
Movement or growth of part of an organism (eg. a plant shoot) towards (positive phototropism) a source of light, without overall movement of the whole organism.
phox
(= phox47; phox67) Components of the NADPH oxidase system in phagocytes, the system responsible for generating an oxidative burst and thus bacterial killing. Phox47 and phox67 ...
phragmoplast
Central region of mitotic spindle of a plant cell at telophase, in which vesicles gather and fuse to form the cell plate, apparently guided by spindle microtubules.
phragmosome
In plant cells, the region of the cytoplasm in which the nucleus is located during nuclear division. Can also refer to microbodies associated with the developing cell plate ...
phycobilins
Photosynthetic pigments found in certain algae, especially red algae (Rhodophyta) and cyanobacteria.
phycobilisome
An accessory light energy harvesting structure in cyanobacteria. They have cores of allophycocyanin with radiating rods composed of discs of phycocyanin and phycoerythrin. ...
phycocyanin
Blue phycobilin found in some algae, and especially in cyanobacteria.
phycoerythrin
Red phycobilins found in some algae, especially red algae (Rhodophyta).
Phycomycetes
A group of fungi possessing hyphae that are usually non-septate (without cross walls).
physaliphorous cells
Cells of chordoma (tumour derived from notochordal remnants) that appear vacuolated because they contain large intracytoplasmic droplets of mucoid material.
Physarum
A member of the Myxomycetes or acellular slime moulds. Normally exists as a multinucleate plasmodium that may be many centimetres across, but if starved and stimulated by ...
physical mapping
The process of assembling genomic DNA clones that completely cover a genetic locus. In genome projects, this is an essential prerequisite for sequencing; in positional ...
phytic acid
Inositol hexaphosphate, found in plant cells, especially in seeds, where it acts as a storage compound for phosphate groups.
phytoalexins
Toxic compounds produced by higher plants in response to attack by pathogens and to other stresses. Sometimes referred to as plant antibiotics, but rather nonspecific, having a ...
phytochelatins
Metallothionein-type peptides of plants that bind heavy metals such as cadmium, zinc, lead, mercury and copper. General form is ( g-glutamyl-cysteinyl) n-glycine where n is from ...
phytochrome
Plant pigment protein that absorbs red light and then initiates physiological responses governing light-sensitive processes such as germination, growth and flowering. Exists in ...
phytohaemagglutinin
Sometimes used as synonym for lectins in general, but more usually refers to lectin from seeds of the red kidney bean Phaseolus vulgaris. Binds to oligosaccharide containing ...
phytohormones
See plant growth substances.
phytol
Long-chain fatty alcohol (C20) forming part of chlorophyll, attached to the protoporphyrin ring by an ester linkage.
pi protein
(= p protein) Polypeptide (35 kD) that is required for the initiation of DNA replication in the R6K antibiotic-resistance plasmid, of which there are 12-18 copy equivalents in ...
PI-3-kinases
(= phosphatidyl inositol-3-kinases; PI kinases) Lipid kinases that phosphorylate phosphatidylinositol phosphate on the 3 position.Now recognised to be key enzymes acting ...
pia mater
Innermost of the three meningeal membranes that surround the brain, lying between the dura mater and the arachnoid layer. Contains a plexus of small blood vessels.
Pick&’s disease
Rare neurodegenerative disease similar in clinical symptoms to Alzheimer&’s disease. Affects mostly frontal and temporal lobes.
Picornaviridae
Class IV viruses, with a single positive strand of RNA and an icosahedral capsid. There are two main classes: enteroviruses, which infect the gut and include poliovirus, and ...
pigment cells
Cells that contain pigment: see melanocytes, chromatophores.
pigmented retinal epithelium
(= PRE; retinal pigmented epithelium, RPE) Layer of unusual phagocytic epithelial cells lying below the photoreceptors of the vertebrate eye. The dorsal surface of the PRE ...
pigtail
One name for the covalent assembly of sugars linked to phosphatidyl inositol joined to the C-terminal residue of many proteins by a modified ethanolamine residue. Also called ...
PIIF
(= proteinase-inhibitor inducing factor) Factor produced by a plant in response to attack by insects. Induces the formation of a substance that inhibits the proteinase that the ...
pilin
(1) General term for the protein subunit of pilus. (2) Protein subunit (7.2 kD) of F-pili, sex pili coded for by the F-plasmid.
pilocarpine
Alkaloid with muscarinic cholinomimetic activity isolated from Pilocarpus jaborandi.
pilus
(= pili (plural) ; fimbrium, fimbria (plural) ) Hair-like projection from surface of some bacteria. Involved in adhesion to surfaces (may be important in virulence), and ...
pim-1
Oncogene from murine T-cell lymphomas, encoding a serine/threonine protein kinase.
pinacocyte
Flattened polygonal cell that lines ostia and form the epidermis of sponges.Capable of synthesizing collagen.
pinocytosis
Uptake of fluid-filled vesicles into cells (endocytosis). Macro-pinocytosis and micro-pinocytosis are distinct processes, the latter being energy independent and involving the ...
pinocytotic vesicle
Fluid-filled endocytotic vesicle, usually less than 150 m m diameter. Micropinocytotic vesicles are around 70nm diameter.
pinosome
A pinocytotic vesicle.
PIP2
(= phosphatidyl inositol 4,5,bisphosphate)
piroplasm
Class of Protista, Phylum Apicomplexa (Sporozoa or Telosporidea), which includes the tick-transmitted parasite, Babesia.
Pisaster
Echinoderm of the Class Asteroidea, a starfish.
pisatin
Phytoalexin produced by peas.
pit
Region of the plant cell wall in which the secondary wall is interrupted, exposing the underlying primary cell wall. One or more plasmodesmata are usually present in the ...
pituicytes
Dominant intrinsic cells of the neural lobe of the hypophysis. Have long branching processes and resemble neuroglia: secrete antidiuretic hormone.
pituitary
(= hypophysis) Possibly the most important of the vertebrate endocrine glands. Located below the brain to which it is attached by a stalk. Has two lobes, the anterior ...
Pitx2
Bicoid-type homeobox gene that is expressed asymmetrically in the left lateral plate mesoderm and may be involved in determining left-right asymmetry in mouse and chick.
pKa
See association constant.
PKC
Protein kinase C
PLA2
(= phospholipase A2) See phospholipases.
placental calcium-binding protein
(= 18a2; nerve growth factor-induced protein 42a; pE2-9d; calvasculin p9k) Calcium-binding protein of placenta, uterus and vasculature containing the EF-hand motif.
placode
Area of thickened ectoderm in the embryo from which a nerve ganglion, or a sense organ will develop.
plakalbumin
Fragment of ovalbumin produced by subtilisin cleavage: more soluble than ovalbumin itself.
plakoglobin
Polypeptide (83 kD) present at cell-cell but not cell-substratum contacts. Associated with desmosomes and with adherens junctions: soluble 7S form present in cytoplasm.
planapochromat
Expensive microscope objective that is corrected for spherical aberration and chromatic aberration at three wavelengths.
plant growth substances
Substances that, at low concentration, influence plant growth and differentiation. Formerly referred to as plant hormones or phytohormones, these terms are now suspect because ...
plaque assay
(1) Assay for virus in which a dilute solution of the virus is applied to a culture dish containing a layer of the host cells; convective spread is prevented by making the ...
plaque-forming cell
Antibody-secreting cell detected in a plaque assay.
plaque-forming unit
Number of Ig-producing cells or infectious virus particles per unit volume. Of a virus like bacteriophage l, the number of viable viral particles, established by counting the ...
plasma
Acellular fluid in which blood cells are suspended. Serum obtained by defibrinating plasma (plasma-derived serum) lacks platelet-released factors and is less suitable to ...
plasma cell
A terminally differentiated antibody-forming, and usually antibody-secreting, cell of the B-cell lineage.
plasma kallikrein
A plasma serine protease with an apple domain.
plasma membrane
The external, limiting lipid bilayer membrane of cells.
plasmacytoma
Malignant tumour of plasma cells, very similar to a myeloma (plasmacytomas usually develop into multiple myeloma). Can easily be induced in rodents by the injection of complete ...
plasmal reaction
Long-chain aliphatic aldehydes occurring in plasmalogens react with Schiff\'s reagent in the so-called plasmal reaction, to form eg. palmitaldehyde, stearaldehyde.
plasmalemma
Archaic name for the plasma membrane of a cell (the term often included the cortical cytoplasmic region). Adjectival derivative (plasmalemmal) still current.
plasmalogens
A group of glycerol-based phospholipids in which the aliphatic side chains are not attached by ester linkages. Widespread distribution. Less easily studied than the acyl ...
plasmid
(= episome) A small, independently-replicating, piece of cytoplasmic DNA that can be transferred from one organism to another. Linear or circular DNA molecules found in both ...
plasmid prep
Generic term for the isolation of recombinant plasmids from liquid bacterial culture, usually by alkaline/detergent lysis, selective precipitation of other components, and ...
plasmin
(= fibrinolysin) Trypsin-like serine protease that is responsible for digesting fibrin in blood clots. Generated from plasminogen by the action of another protease, ...
plasminogen
Inactive precursor of plasmin; occurs at 200 mg/l in blood plasma. Contains multiple copies of the kringle domain.
plasminogen activator
Serine protease that acts on plasminogen to generate plasmin. Has also been implicated in invasiveness, and is produced by many normal and invasive cells. The vascular form ...
plasmodesma
(= plasmodesmata (plural) ) Narrow tube of cytoplasm penetrating the plant cell wall, linking the protoplasts of two adjacent cells. A desmotubule runs down the centre of the ...
Plasmodium
Genus of parasitic protozoa that cause malaria. The life-cycle is complex, involving several changes in cellular morphology and behaviour. Intermediate host is female mosquito ...
plasmodium
Multinucleate mass of protoplasm bounded only by a plasma membrane; the main vegetative form of acellular slime moulds (eg. Physarum).
plasmolysis
Process by which the plant cell protoplast shrinks, so that the plasma membrane becomes partly detached from the wall. Occurs in solutions of high osmotic potential, due to ...
plastid
Type of plant cell organelle, surrounded by a double membrane and often containing elaborate internal membrane systems. Partially autonomous, containing some DNA, RNA and ...
plastin
Microfilament-bundling protein from mammalian cells very similar to fimbrin with two actin binding domains. Two forms, l-plastin (627 residues, may be identical to acumentin) ...
plastocyanin
An electron-carrying protein present in chloroplasts, forming part of the electron transport chain. Contains two copper atoms per molecule. Associated with photosystem I.
plastoglobuli
Globules found in plastids, containing principally lipid, including plastoquinone.
plastoquinone
A quinone present in chloroplasts, forming part of the photosynthetic electron transport chain. Closely associated with photosystem II. May be stored in plastoglobuli.
platelet
Anucleate discoid cell (3 m m diameter) found in large numbers in blood; important for blood coagulation and for haemostasis. Platelet a -granules contain lysosomal enzymes; ...
platelet activating factor
(= PAF; PAFacether; 1-0-hexadecyl-2-acetyl-sn-glycero-3-phosphorylcholine) Potent activator of many leucocyte functions, not just platelet activation.
platelet basic protein
Protein that is the precursor of connective tissue-activating peptide III and beta-thromboglobulin.
platelet factor 3
Phospholipid associated with the platelet plasma membrane that contributes to the blood clotting cascade by forming a complex (thromboplastin) with other plasma proteins and ...
platelet factor 4
Platelet-released protein that promotes blood clotting by neutralising heparin.
platelet-derived growth factor
(= PDGF) The major mitogen in serum for growth in culture of cells of connective tissue origin. It consists of 2 different but homologous polypeptides A and B ...
PLCPI
(= porcine leucocyte cysteine protease inhibitor) Stefin type protease inhibitor (103 residues, 11 kD) that co-purifies with cathelin. Inhibits papain and cathepsins L and ...
pleckstrin
Protein of 47 kD, the major substrate for protein kinase C in platelets. Pleckstrin homology domains (PH domains) are being identified in a number of proteins.
plectin
Abundant protein of cytomatrix (apparent 300 kD but 466 kD on basis of cDNA sequence). Co-localises with various intermediate filament proteins and may be involved in their ...
pleiomorphic
Having more than one body shape during the life cycle or having the ability to change shape or to adopt a variety of shapes.
pleiotropic
Having multiple effects. For example, the cyclic-AMP concentration in a cell will have a variety of effects because the cAMP acts to control a protein kinase that in turn ...
Pleurobrachia
Small free-swimming marine organism, member of the Phylum Ctenophora. Roughly spherical and transparent with most of the body made up from transparent jelly-like material. The ...
Pleurodeles
Genus of salamanders.
pleuropneumonia-like organism
(= PPLO) See mycoplasmas.
PLGF
(= placental growth factor) Growth factor similar in activity to VEGF.
pluripotent stem cell
Cells in a stem cell line capable of differentiating into several different final differentiated types, eg. there may be a pluripotent stem cell line for erythrocytes, ...
pluteus
Free-swimming ciliated larval stage of some echinoderms.
PMA
(= TPA; tumour promotor activity) Phorbol myristate acetate, a phorbol ester.
PMF
(= proton motive force) The proton gradient across a prokaryote membrane that provides the coupling between oxidation and ATP synthesis, and is used to drive the flagellar ...
PMN
(= PMNL) Polymorphonuclear leucocyte: could be an eosinophil, basophil or neutrophil granulocyte, but usually intended to mean the latter (an idle habit).
PMSF
(= phenylmethylsulphonyl fluoride) Broad spectrum protease inhibitor.
pneumococci
Gram positive pyogenic organisms (about 1 m m diameter), usually encapsulated, closely related to streptococci; associated with diseases of the lung.
Pneumocystis carinii
Organism that commonly causes pneumonia in immunocompromised patients (eg. with AIDS). Apparently most closely related to ustomycetous yeasts.
pneumolysin
Cholesterol binding toxin from Streptococcus pneumoniae.
PNMT
(= phenylethanolamine N-methyl transferase) Terminal enzyme in the catecholamine biosynthetic pathway; it converts noradrenaline to adrenaline.
podocalyxin
Major sialoprotein (140 kD) of renal glomerular epithelial cells (podocytes).
podocytes
Cells of the visceral epithelium that closely invest the network of glomerular capillaries in the kidney. Most of the cell body is not in contact with the basal lamina, but is ...
podophyllotoxin
Toxin (414D) that binds to tubulin and prevents microtubule assembly.
podosomes
Punctate substratum-adhesion complexes in osteoclasts. Contain vinculin, talin, fimbrin and F-actin. Podosomes form a broad ring of contacts with the underlying bone and the ...
poikilocytosis
Irregularity of red cell shape.
poikilotherm
Organism whose body temperature varies with environment, opposite of homeotherm. Though poikilothermic animals are often referred to as cold-blooded this is not necessarily true.
point mutation
Mutationthat causes the replacement of a single base pair with another pair.
pokeweed mitogen
Any of the lectins derived from the pokeweed, Phytolacca americana, all of which will stimulate T-cells. Binds b -D-acetylglucosamine.
pol genes
Genes coding for DNA polymerases of which there are three in E. coli, polA, polB, and polC coding for polymerases I, II, and III respectively. Pol genes in oncogenic ...
polar body
In animals each meiotic division of the oocyte leads to the formation of one large cell (the egg) and a small polar body as the other cell. Polar body formation is a consequence ...
polar granules
Granules containing a basic protein found in insect eggs that induce the formation of and become incorporated into germ cells.
polar group
Any chemical grouping in which the distribution of electrons is uneven enabling it to take part in electrostatic interactions.
polar lobe
In some molluscs a polar lobe appears as a clear protrusion close to the vegetal pole of the cell prior to the first cleavage, and becomes associated with only one of the ...
polar plasm
Differentiated cytoplasm associated with the animal or vegetal pole of an oocyte, egg or early embryo.
polarity
Literally "having poles" (like a magnet), but used to describe cells that have one or more axes of symmetry. In epithelial cells, the polarity meant is between apical and ...
polarization microscopy
Any form of microscopy capable of detecting birefringent objects. Usually performed with a polarizing element below the stage to produce plane-polarized light, and an analyser ...
pole cell
A cell at or near the animal or vegetal pole of an embryo.
pole fibres
Microtubules inserted into the pole regions of the mitotic spindle (each pole is the product of the division of the centrioles and constitutes a microtubule organizing centre. ...
polehole
Drosophila homologue of the raf oncogene.
poliovirus
A member of the enterovirus group of Picornaviridae that causes poliomyelitis.
pollen mother cell
A diploid plant cell that forms four microspores by meiosis; the microspores give rise to pollen grains in seed plants.
poly(ADP-ribose) polymerase
(= PARP) (EC 2.4.2.30) An abundant nuclear protein activated by DNA nicks and important in DNA repair. PolyADP ribosylation, brought about by ADP-ribosyl protein ligase, is a ...
poly-A
See polyadenylic acid.
poly-A tail
Polyadenylic acid sequence of varying length found at the 3\' end of most eukaryotic mRNAs. Histone mRNAs do not have poly-A tail. The poly-A tail is added ...
polyacrylamide gel electrophoresis
(= PAGE) Analytical and separative technique in which molecules, particularly proteins, are separated by their different electrophoretic mobilities in a hydrated gel. The gel ...
polyadenylic acid
Polynucleotide chain consisting entirely of residues of adenylic acid (ie. the base sequence is AAAA....AAAA). Polyadenylic chains of various lengths are found at the 3\' end of ...
polyamine
Polycations at physiological pH, polyamines can bind and interact with various other molecules within the cell. In particular interact with DNA but also may modulate ion channels ...
polyanion
Macromolecule carrying many negative charges. The commonest in cell-biological systems is nucleic acid.
polycation
Macromolecule with many positively charged groups. At physiological pH the most commonly used in cell biology is poly-L-lysine; this is often used to coat surfaces thereby ...
polycistronic mRNA
A single mRNA molecule that is the product of the transcription of several tandemly arranged genes; typically the mRNA transcribed from an operon.
polyclonal antibody
An antibody produced by several clones of B-lymphocytes as would be the case in a whole animal. Usually refers to antibodies raised in immunized animals, whereas a monoclonal ...
polyclonal compartment
When the progeny of several cells occupy an area or volume with a defined boundary, it is referred to as a polyclonal compartment, eg. clones lying close to the mid-line of the ...
polycloning site
(= multiple cloning site; MCS) Region of a phage or plasmid vector that has been engineered to contain a series of restriction sites that are usually unique within the ...
Polycomb
Drosophila gene, which when mutated leads to extra sex combs on the legs of male flies, suggesting that the posterior legs have become anterior legs. There are at least 10 genes ...
polycythemia
Increase in the haemoglobin content of the blood, either because of a reduction in plasma volume or an increase in red cell numbers. The latter may be a result of abnormal ...
polyelectrolyte
An ion with multiple charged groups.
polyendocrine syndrome
Autoimmune disorder (the antigen to which the response is mounted is in the B cells of the pancreas) in which there is involvement of several organ systems.
polyethylene glycol
A hydrophilic polymer that interacts with cell membranes and promotes fusion of cells to produce viable hybrids. Often used in producing hybridomas.
polygalacturonan
Plant cell wall polysaccharide consisting predominantly of galacturonic acid. May also contain some rhamnose, arabinose and galactose. Those with significant amounts of ...
polygalacturonase
Enzyme that degrades polygalacturonan by hydrolysis of the glycosidic bonds that link galacturonic acid residues. Important in fruit ripening and in fungal and bacterial attack ...
polygenic
Something that is controlled or caused by the action of many genes. Thus many of the major non-infectious diseases (for example arthritis, cardiovascular disease, asthma, ...
polyisoprenylation
See geranylation.
polylysine
A polymer of lysine, it carries multiple positive charges and is used to mediate adhesion of living cells to synthetic culture substrates, or of fixed cells to glass slides ...
polymer
A macromolecule made of repeating (monomer) units or protomers.
polymerase chain reaction
The first practical system for in vitro amplification of DNA, and as such one of the most important recent developments in molecular biology. Two synthetic oligonucleotide ...
polymerization
The process of polymer formation. In many cases this requires nucleation and will only occur above a certain critical concentration.
polymorphism
(1) The existence, in a population, of two or more alleles of a gene, where the frequency of the rarer alleles is greater than can be explained by recurrent mutation alone ...
polymorphonuclear leucocyte
(= PMNL; PMN) Mammalian blood leucocyte (granulocyte) of myeloid series in distinction to mononuclear leucocytes: see neutrophil, eosinophil, basophil.
polymyxins
Group of peptide antibiotics produced by Bacillus spp. Molecular weights are around 1000-1200 D and the molecules are cyclic. Act against many Gram negative bacteria, working ...
polynucleotide
Linear sequences of nucleotides, in which the 5\'-linked phosphate on one sugar group is linked to the 3\' position on the adjacent sugars. In the polynucleotide DNA the sugar ...
polyomavirus
A DNA tumour virus with very small genome (of the Papovaviridae). Polyoma was isolated from mice, in which it causes no obvious disease, but when injected at high titre into ...
polyp
(1) Growth, usually benign, protruding from a mucous membrane. (2) The sessile stage of the Cnidarian (coelenterate) life-cycle; the cylindrical body is attached to the ...
polypeptide
Chains of a -amino acids joined by peptide bonds. Distinction between peptides, oligopeptides and polypeptides is arbitrarily by length; a polypeptide is perhaps more than 10 ...
polyploid
Of a nucleus, cell or organism that has more than two haploid sets of chromosomes. A cell with three haploid sets (3n) is termed triploid, four sets (4n) tetraploid and so ...
polypodial
Adjective describing an amoeba with several pseudopods.
polyposis coli
(= adenomatous polyposis coli; Familial adenomatous polyposis; FAP) Hereditary disorder (Mendelian dominant) characterized by the development of hundreds of adenomatous polyps ...
polyprotein
Protein that, after synthesis, is cleaved to produce several functionally distinct polypeptides. Some viruses produce such proteins, and some polypeptide hormones seem to be ...
polyribosome
Functional unit of protein synthesis consisting of several ribosomes attached along the length of a single molecule of mRNA.

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