Diphtheria toxin

disintegrins diphtheria toxin An AB exotoxin (62 kDa) coded by (3-corynephage of virulent Corynebacterium diphtheriae strains (that can produce a repressor of toxin production). The B-subunit binds to receptors on the surface of the target cell and facilitates the entry of the enzymically active A subunit (21 kDa) that ADP-ribosylates elongation factor 2, thereby halting mRNA translation.

diphtheria toxoid Diphtheria toxin treated with formaldehyde so as to destroy toxicity without altering its capacity to act as antigen. Used for active immunization against diphtheria.

dipicolinic acid 2,6-Pyridinedicarboxylic acid; DPA Dipicolinic acid (DPA) and the Ca2+ complex of DPA (CaDPA) are major chemical components of bacterial spores. DPA is a chelator of metal ions.

dipipanone hydrochloride A strong opioid analgesic used for treatment of moderate to severe pain, often in conjunction with an antiemetic. See Diconal.

diplococcus Bacterial strain in which two spherical cells (cocci) are joined to form a pair like a dumbbell or figure-of-eight.

Diplococcus pneumoniae See Streptococcus pneumoniae, the formal name for this organism.

diplohaplontic Organisms that show an alternation of generations; a haploid phase (gametophyte) exists in the life cycle between meiosis and fertilization (e.g. higher plants, many algae and fungi); the products of meiosis are spores that develop as haploid individuals from which haploid gametes develop and fuse to form a diploid zygote. See diplontic, haplontic.

diploid A diploid cell has its chromosomes in homologous pairs, and thus has two copies of each autosomal genetic locus. The diploid number (2n) equals twice the haploid number, and is the characteristic number for most cells other than gametes.

diplonema A stage in meiosis (diplotene stage) at which the chromosomes are clearly visible as double structures. More commonly diplotene.

diplont Organisms in which only the zygote is diploid and the vegetative cells are haploid.

diplontic Organisms with a life cycle in which the products of meiosis behave directly as gametes, fusing to form a zygote from which the diploid, or sexually reproductive polyploid, adult organism will develop. cf. haplontic, diplohaplontic.

diplornavirus Proposed family of all double-stranded RNA viruses: considered taxonomically unsound by many virologists.

diplotene The final stage of the first prophase of meio-sis. All four chromatids of a tetrad are fully visible, and homologous chromosomes start to move away from one another except at chiasmata.

Diptera Order of insects with one pair of wings, the second pair being modified into balancing organs, the halteres; the mouthparts are modified for sucking or piercing. The insects show complete metamorphosis in that they have larval, pupal and imaginal (imago, adult) stages. The order includes the flies and mosquitoes; best-known genera are Anopheles and Drosophila.

diptericin An 82-mer antimicrobial peptide, originally isolated from the dipteran Phormia terranovae (Flesh fly).

diptericins Inducible glycine-rich antibacterial peptides (about 8 kDa) from Dipteran haemolymph.

dipyridamole A coronary vasodilator and anti-platelet drug used to treat angina pectoris and prevent blood clotting.

direct B-cells Lymphocytes responding to a small range of antigens by antibody production without any requirement for T-cells. The antigens include flagellin and pokeweed mitogen.

directed evolution 1. An approach to developing molecules with specific desirable properties in which sequential rounds of synthesis are informed by data on the properties of the previous set. This approach has been applied, for example, to generating novel peptide ligands and enzymes with improved characteristics. 2. The creationist view that biological systems are so complex that there must have been an external director (a.k.a. deity). Evidence is unavailable for this belief which also masquerades as 'Intelligent design'.

disaccharide Sugar formed from two monosaccharide units linked by a glycosidic bond. The trehalose types are formed from two non-reducing sugars, the maltose type from two reducing sugars.

DISC Death-inducing signalling complex Activation of cas-pase 8 is preceded by the formation of a death-inducing signalling complex by recruitment of cytoplasmic death-domain (DD)-containing proteins to the death domain of a receptor that has bound its appropriate ligand. The best-studied death-inducing ligand-receptor pairs are TNF/TNF receptor-1 (TNF-R1) and CD95L/CD95 (Fas, Apo-1). See death-effector domain.

disc gel Confusingly, nothing to do with shape; gels in which there is a discontinuity in pH, or gel concentration, or buffer composition.

discodermolide Anti-tumour drug (a poly-hydroxylated alkatetraene lactone) that, like taxol, promotes formation of stable bundles of microtubules and competes with taxol for binding to polymerized tubulin. Isolated from the marine sponge, Discodermia dissoluta.

discoidin A lectin, isolated from the cellular slime mould Dictyostelium discoideum (see Acrasidae), that has a binding site for carbohydrate residues related to galactose. The lectin, which consists of two distinct species (discoidins I and II), is synthesized as the cells differentiate from vegetative to aggregation phase, and was originally thought to be involved in intercellular adhesion, but discoidin I is now thought to be involved in adhesion to the substratum by a mechanism resembling that of fibronectin in animals.

Discomycetes A class of Ascomycete fungi. Includes the Lecanorales (lichen-forming fungi) and many saprophytic and mycorrhizal species, e.g. morels and truffles.

Dishevelled Dvl Drosophila protein (Dvl) involved in both wingless (Wg) and Frizzled (Fz) signalling pathways. See wnt and axin.

disintegrins Peptides found in the venoms of various snakes of the viper family that inhibit the function of some integrins of the (31 and (33 classes. They were first identified as inhibitors of platelet aggregation, and were subsequently shown to bind with high affinity to integrins and

Getting Started With Dumbbells

Getting Started With Dumbbells

The use of dumbbells gives you a much more comprehensive strengthening effect because the workout engages your stabilizer muscles, in addition to the muscle you may be pin-pointing. Without all of the belts and artificial stabilizers of a machine, you also engage your core muscles, which are your body's natural stabilizers.

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