| GAP protein | <molecular biology> Originally purified as a 125 kD protein from bovine brain (1044 amino acids), stimulates the GTPase activity of ras p21 and thereby switches it to the inactive state. GAP may itself be regulated by phospholipids and by phosphorylation on a tyrosine residue by growth factor receptors (PDGF R, EGF R). The neurofibromatosis type 1 gene NF1) codes for a protein homologous to GAP. GAP has both SH2 and SH3 domains. Another example is sar 1 (from yeast). (18 Nov 1997) |
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| chromosomal gap | A localised area of thinning in a chromatid which may simulate a complete break. (05 Mar 2000) |
| silent gap | The period during which Korotkoff sounds indicating true systolic pressure fade away and reappear at a lower pressure point; responsible for errors made in recording falsely low systolic blood pressure, especially in hypertensive patients, of up to 25 mm Hg, and avoided by pumping the cuff 30 mm Hg beyond palpable systolic pressure. Synonym: silent gap. (05 Mar 2000) |
| DNA gap | A localised loss of one of the two strands in the double helix of DNA. (05 Mar 2000) |
| interocclusal gap | The space between the occluding surfaces of the maxillary and mandibular teeth when the mandible is in physiologic resting position. Synonym: interocclusal clearance, interocclusal distance, interocclusal gap, interocclusal rest space. (05 Mar 2000) |
| excitable gap | A short period in the cycle of the atrioventricular or intraventricular conduction allowing passage of an impulse which at other times would be blocked in transit. Synonym: excitable gap. (05 Mar 2000) |
| adhering junction | <cell biology> A type of junction between cells forming tissues that are subjected to stretching and pulling, such as the skin. This type of junction provides very tight contact between adjacent cells and allows the cells to fuction as a unit. Belt desmosomes are attachment sites that circle the cell, and spot desmosomes are small points of attachment across the cells surface. (15 Jan 1998) |
| amelodental junction | Amelodentinal junction, rarely used terms for dentinoenamel junction. (05 Mar 2000) |
| amnioembryonic junction | The line of amniotic attachment to the periphery of the embryonic disk. (05 Mar 2000) |
| anorectal junction | Transition from rectum to anal canal; corresponds to the perineal flexure, or the level at which the gut perforates the pelvic diaphragm; here the rectal ampulla narrows abruptly into a narrow slip. (05 Mar 2000) |
| anterior junction line | Radiographic projection of the mediastinal tissue septum between the upper lobes behind the sternum. (05 Mar 2000) |
| A-V junction | Imprecisely defined zone surrounding and including the A-V node and the adjacent atrial and ventricular myocardium. (05 Mar 2000) |
| cardioesophageal junction | The abrupt transition from oesophageal mucosa to that of the cardiac portion of stomach, demarcated internally in the living by the z-line, and approximated externally by the cardiac notch. (05 Mar 2000) |
| manubriosternal junction | The angle between the manubrium and the body of the sternum at the manubriosternal junction. Marks the level of the second costal cartilage (rib) for counting ribs or intercostal spaces. Denotes level of aortic arch, bifurcation of trachea, and T4/T5 intervertebral disc. Synonym: angulus sterni, Louis' angle, Ludwig's angle, manubriosternal junction. (05 Mar 2000) |
| rectosigmoid junction | <anatomy> The site where the sigmoid colon becomes the rectum; usually takes the form of an acute angle, demarcated externally by a discontinuation of appendices epiploicae, a spreading out of the teniae coli to completely encircle the rectum, and consequently, termination of the sacculations (haustrae) between the teniae. (05 Mar 2000) |