| single photon emission computed tomography | <radiology> Tomographic imaging of metabolic and physiological functions in tissues, the image being formed by computer synthesis of photons of a single energy emitted by radionuclides administered in suitable form to the patient. The method uses radionuclides which emit a single photon of a given energy. The camera is then rotated 180 or 360 degrees around the patient to capture images at multiple positions along the arc. The computer then reconstructs the transaxial, sagittal, and coronal images from the 3-dimensional distribution of radionuclides in the target area scanned. The advantages of SPECT are that it can be used to observe biochemical and physiological processes as well as the size and volume of the organ. The disadvantage is that, unlike positron emission tomography where the positron-electron annihilation results in the emission of 2 photons at 180 degrees from each other, SPECT requires physical collimation to line up the photons, which results in the loss of available photons and hence degrades the image. Acronym: SPECT (20 Jun 2000) |
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| single-strand break | A break in double-stranded DNA in which only one of the two strands has been cleaved; both strands have not separated from each other. (05 Mar 2000) |
| single stranded binding protein | <protein> SSB's are proteins responsiblefor holding the replication fork of DNAopen while polymerases readthe templates. (09 Oct 1997) |
| single stranded conformational polymorphism | Technique for detecting point mutations in genes by amplifying a region of genomic DNA (using asymmetric PCR) and running the resulting product on a high quality gel. Single base substitutions can alter the secondary structure of the fragment in the gel, producing a visible shift in its mobility. (18 Nov 1997) |
| single stranded DNA | <molecular biology> DNA that consists of only one chain of nucleotides rather than the two base pairing strands found in DNA in the double helix form. Parvoviridae have a single stranded DNA genome. Single stranded DNA can be produced experimentally by rapidly cooling heat denatured DNA. Heating causes the strands to separate and rapid cooling prevents renaturation. (18 Nov 1997) |
| single stranded DNA dependent ATPase | <enzyme> Probably involved in DNA replication Registry number: EC 3.6.1.- Synonym: ssdna-dependent atpase (26 Jun 1999) |
| single ventricle | Congenital absence or near total absence of the ventricular septum. (05 Mar 2000) |
| dental implants, single-tooth | Devices, usually alloplastic, surgically inserted into or onto the jawbone, which support a single prosthetic tooth and serve either as abutments or as cosmetic replacements for missing teeth. (12 Dec 1998) |
| diseases, single-gene | Hereditary disorders caused by a change (mutation) in a single gene. There are thousands of single-gene diseases including achondroplastic dwarfism, Huntington disease, cystic fibrosis, sickle cell disease, Duchenne muscular dystrophy, and haemophilia. Single-gene diseases typically describe classic simple Mendelian patterns of inheritance (as autosomal dominant, autosomal recessive, and X-linked traits) by comparison with polygenic diseases. (12 Dec 1998) |
| DNA, single-stranded | A single chain of deoxyribonucleotides that occurs in some bacteria and viruses. It usually exists as a covalently closed circle. (12 Dec 1998) |