Astroglia See astrocytes

astrogliosis Hypertrophy of the astroglia, usually in response to injury.

Astropectinidae Family of echinoderms that includes many starfish species with long spines.

astrotactin Neuronal surface glycoprotein (100-105 kDa; three EGF-like repeat domains, two íibronectin III repeats) that functions in murine cerebellar granule cell migration in vitro, acting as the ligand for neuron-glial cell binding. Message has been detected in neuronal precursors in the cerebellum, hippocampus, cerebrum and olfactory bulb in the brain. See weaver mutant.

astroviruses Astroviridae Spherical viruses with five- or six-pointed star-shaped surface pattern. May be associated with enteritis in various vertebrates. Genome is a single molecule of linear, positive-sense, single-stranded RNA.

AT hook An AT-rich DNA-binding domain that occurs three times in mammalian high-mobility-group chromosomal proteins and in DNA-binding proteins from plants.

ataxia Imbalance of muscle control. See ataxia telangiec-tasia.

ataxia telangiectasia Louis-Bar syndrome A hereditary autosomal recessive disease in humans characterized by a high frequency of spontaneous chromosomal aberrations, neurological deterioration and susceptibility to various cancers. In part an immune deficiency disease and in part one of DNA repair; it is believed to be due to hypersensitivity to background ionizing radiation as a result of mutations in the ATM gene.

ATCase EC; aspartate transcarbamylase Enzyme that catalyses the first step in pyrimidine biosynthesis, condensation of aspartate and carbamyl phosphate. Positively allosterically regulated by ATP and negatively by CTP; classic example of an allosterically regulated enzyme. Bacterial ATCases exist in three forms: class A (ca. 450500 kDa), class B (ca. 300 kDa) and class C (ca. 100 kDa).

ATCC The American Type Culture Collection, repository of many eukaryotic cell lines (which may be purchased). Comparable collections of microorganisms, protozoa, etc. are kept.

atelocollagen A highly purified pepsin-treated type I collagen from calf dermis which is of low immunogenicity because telopeptides are absent. It is used clinically for a wide range of purposes, including wound healing, vessel prosthesis and as a bone cartilage substitute, and more recently has been used as a complex with DNA or siRNA because these complexes are efficiently transduced into cells.

atenolol Beta adrenoreceptor antagonist or blocker with greater affinity for (1-receptors. It has more cardiac effects and less effect on airway tone.

ATF Activating transcription factor Commonly: 1. Member of the CREB/ATF family of bZip transcription factors. A number of ATF variants (ATF-1, ATF-2, etc.) have been described and are, in general, involved in mediating transcription in response to intracellular signalling. Occasionally: 2. Artificial transcription factor. 3. Amino-terminal fragment.

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