Dictionary of Cell & Molecular Biology (eBook)

antimorph A dominant negative mutant expressing some agent that antagonizes a normal gene product.

anti-Müllerian hormone AMH, Müllerian-inhibiting substance (MIS) A dimeric glycoprotein hormone belonging to the TGFβ superfamily. Synthesized as a large precursor with a short signal sequence followed by the prepro hormone that forms homodimers. Prior to secretion, the mature hormone undergoes glycosylation and dimerization to produce a 140-kDa dimer of identical disulphide-linked subunits. High levels of AMH are produced by Sertoli cells during foetal and postnatal testicular development. In the human female, AMH is produced by ovarian granulosa cells from 36 weeks of gestation to the menopause.

antimuscarinic drugs Anticholinergic drugs Class of drugs that block the action of acetylcholine at the muscarinic subclass of acetylcholine receptors. Effect is generally to relax smooth muscle of gut (antispasmodic) or airways (bronchodilatory). Example: tolterodine.

antimycin Inhibitor of QH2-cytochrome C reductase.

antineoplaston A naturally occurring cytodifferentiating agent that has been tested for antitumour activity and used to induce differentiation of astrocytes in rat models of neurodegenerative disease.

anti-oncogene See tumour suppressor gene.

antioxidant Any substance that inhibits oxidation, usually because it is preferentially oxidized itself. Common examples are vitamin E (a-tocopherol) and vitamin C. Important for trapping free radicals generated during the metabolic burst and possibly for inhibiting ageing.

antipain [(S)-1-Carboxy-2-Phenyl]-carbamoyl-Arg-Valarginal Peptidase inhibitor that inhibits papain, trypsin and, to a lesser extent, plasmin. More specific for papain and trypsin than leupeptin.

antiparallel Having the opposite polarity (e.g. the two strands of a DNA molecule).

antiplasmin α-2-Antiplasmin Plasma protein (65 kDa) that inhibits plasmin (and Factors XIa, XIIa, plasma kallikrein, thrombin and trypsin) and therefore acts to regulate fibrinolysis.

antiplectic Pattern of metachronal coordination of the beating of cilia, in which the waves pass in the opposite direction to that of the active stroke.

antipodal cells Three cells of the embryo sac in angiosperms, found at the end of the embryo, away from the point of entry of the pollen tube.

antiport A membrane protein that transports two different ions or molecules, in opposite directions, across a lipid bilayer. Energy may be required, as in the sodium pump, or may not, as in Na+/H+ antiport.

antiproteases Antiproteinases, antipeptidases Substances that inhibit proteolytic enzymes (peptidases).

antipsychotic drugs (neuroleptic drugs) Group of drugs sometimes referred to as major tranquillizers. Used short term to calm or sedate disturbed patients, to control acute symptoms of mania and relieve severe positive symptoms of schizophrenia. Most act by reducing levels of the neurotransmitter dopamine in the central nervous system (e.g. chlorpromazine, haloperidol, flupentixol), but the atypical antipsychotics (e.g. risperidone, clozapine) act by interfering with serotonin-based neurotransmission.

antipyretic Counteracting fever; a remedy for fever.

antiretroviral 1. Acting to counteract or control a retro-virus. 2. An antiretroviral agent or drug.

Antirrhinum majus A flowering plant (the common snapdragon), widely used as a model system for plant molecular genetics.

antisense In general, the complementary strand of a coding sequence of DNA or of mRNA. Antisense RNA hybridizes with and inactivates mRNA.

antisepsis Processes, procedures or chemical treatments that kill or inhibit microorganisms; in contrast with asepsis, where microorganisms are excluded.

antiserum Serum containing immunoglobulins against specified antigens.

antispasmodic drugs Drugs that relax smooth muscle of the gut wall and relieve symptoms of indigestion, irritable bowel syndrome and diverticular disease. Most are antimuscarinic drugs.

antitermination During transcription, failure of an RNA polymerase to recognize a termination signal: can be of significance in regulation of gene expression.

antithymocyte globulin ATG A polyclonal IgG fraction that selectively targets and destroys T-lymphocytes; used as an immunosuppressive agent.

antithrombins Plasma glycoproteins of the α-2-globulin class that inhibit the proteolytic activity of thrombin and serve to regulate the process of blood clotting. See also Table F1.

antitoxin An antibody reacting with a toxin, e.g. anticholera toxin antibody.

antitrypsin α-1-Antitrypsin; alpha-1-peptidase inhibitor; serpin A1 A major protein (54 kDa) of blood plasma (3 mg/ml in human), part of the α-globulin fraction and able to inhibit a wide spectrum of serine peptidases.

antitussive drug A cough suppressant. Most work by suppressing the cough reflex, rather than treating the cause of the cough.

antiviral drugs Drugs that inhibit viral infection. Two main categories have been developed so far; those which inhibit or interfere with the replication of viral nucleic acid (nucleoside analogues such as acyclovir and AZT), and those that interfere with virus-specific enzymes such as proteases (e.g. Saquinavir, Ritonavir, Indinavir) or neuraminidases (e.g. Relenza, Tamiflu) which are important for processing of viral proteins to produce infective particles.

antizyme Repressor of ornithine decarboxylase (ODC). Antizyme (29 kDa) is a polyamine-inducible protein involved in feedback regulation of cellular polyamine levels. The N-terminus of antizyme is not required for the interaction with ODC but is necessary to induce its degradation. Antizyme can be induced by IL-1. The elaborate regulation of ODC activity in mammals still lacks a defined developmental role but an antizyme-like gene in Drosophila, gutfeeling (guf), is required for proper development of the embryonic peripheral nervous system.

Antp See antennapedia.

antral Relating to an antrum.

antral mucosa Pyloric mucosa Type of mucosa found in the gastric antrum which has coiled and branching antral glands that are lined by mucus cells interspersed with endocrine cells (chiefly G and D types) and a few parietal (oxyntic) cells.

antrum 1. A cavity or chamber, especially in bone. 2. The lower third of the stomach which lies between the body of the stomach and the pyloric canal. 3. In the ovary, the fluid-filled space within the follicle.

Antrycide Proprietary name for an antitrypanocidal drug used in veterinary practice.

anucleate Having no nucleus.

anucleolate Literally, having no nucleoli. An anucleolate mutant of Xenopus (viable when heterozygous) is used in nuclear transplantation experiments because nuclei are of identifiable origin.

Anura Class of amphibians; the frogs and toads.

anuresis Failure to secrete urine.

anxiogenic Causing anxiety; something that enhances fear/anxiety reactions.

anxiolytic Drug that reduces anxiety, for example benzodiazepines and barbiturates.

AP-1 1. A transcription factor, formed from a heterodimer of the products of the proto-oncogenes fos and jun. Binds the palindromic DNA sequence TGACTCA. See also Table O1. 2. Adaptor protein found in the trans-Golgi network that links membrane proteins to clathrin (see AP-2).

AP-2 1. Cis-acting transcription activator. 2. One of the multimeric adaptor proteins (APs; ca. 270 kDa) found in clathrin-associated complexes. AP-2 is found at the plasma membrane and may bind preferentially to the cytoplasmic tail of the EGF receptor. Also associates with the EGF-R tyrosine kinase substrate eps15. See adaptins.

AP3, AP4, AP5 Amino-3-phosphonopropanoate, 2-amino-4-phoshonobutanoate, 2-amino-5-phosphonopentanoic acid Selective antagonists for NMDA receptors.

APA Amino pimelic acid Low affinity, rapidly dissociating competitive antagonist of NMDA receptors.

APAF-1 Apoptosis protease activating factor 1 Protein which binds to cytochrome c that has been released from mitochondria and links with caspase-9, which then activates caspase-3, initiating a cascade of events that...