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Query: UMLS:C0027960 (mole)
 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

It is suggested that the melanocytic series is characterized by a differentiation pathway (MDP) that has four discrete stages during normal development and in postnatal tissue maintenance--nerve sheath precursor (nsp), dermal migratory, junctional migratory, and dendritic--and that congenital melanocytic nevi (CMN) derive from cells in the nsp stage of the MDP. This concept accounts satisfactorily for morphologic variations and clinicopathologic correlations in CMN. It also permits a unified explication of both similarities and differences between congenital and acquired melanocytic nevi (AMN), which are thought to arise by transformation of nsp cells in the MDP during postnatal tissue maintenance. This perspective suggests that answers to many basic questions about CMN may require meticulous study of the interrelations of CMN with peripheral nerve elements. Such research may be necessary to resolve current controversies about optimal criteria for distinguishing small CMN from AMN, thereby permitting an accurate assessment of the risk of malignant melanoma in association with small CMN.
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PMID:The melanocytic differentiation pathway in congenital melanocytic nevi: theoretical considerations. 317 7

We have investigated the in vitro adsorption of three C-14-labeled diphosphonates on calcium phosphate. The three are 1-hydroxy[1-14C]ethylidene diphosphonate (C-14 HEDP), [14C]methylenediphosphonate (C-14 MDP), and hydroxy[14C]methylenediphosphonate (C-14 HMDP). All three adsorbed significantly more, per mole of calcium, on amorphous calcium phosphate than on crystalline hydroxyapatite. Among the three diphosphonates, C-14 HMDP adsorbed--on both amorphous and crystalline calcium phosphate--to a greater degree than did the other two bone-seeking agents. Moreover, when HMDP was complexed with Sn(II) and Tc-99m, it produced a significantly higher uptake of Tc-99m, per mg of calcium, in an isolated in vivo site of osteogenesis. The mechanisms of adsorption are discussed relative to the hydroxyl group on the diphosphonate, to the solubility of the calcium salts to the diphosphonates, and to the form of the calcium phosphate. These studies form a working rationale for the clinically observed high contrast obtained with Tc-99m HMDP between normal bone and soft tissue, and between normal and abnormal bone.
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PMID:Comparative evaluation of three diphosphonates: in vitro adsorption (C- 14 labeled) and in vivo osteogenic uptake (Tc-99m complexed). 644 67

Thermostable dipeptidase from Bacillus stearothermophilus, a typical metalloenzyme containing 1.0g atom of Zn per mole of subunit of the dimeric enzyme was markedly activated by exogenous divalent metal ions such as Mn(2+), Co(2+), and Cd(2+) . In contrast, several others including Ba(2+), Hg(2+), and Cu(2+) considerably inhibited the enzyme, even the inherent metal, Zn(2+), being slightly inhibitory. To study the metal-binding properties of this dipeptidase, the enzyme was completely resolved to the inactive, Zn-free apoenzyme by treatment with EDTA in the presence of guanidine hydrochloride in a weakly acidic buffer. The apoenzyme was readily reconstituted by incubation with either Zn(2+), Mn(2+), or Co(2+), restoring the catalytic activity. The Mn-reconstituted enzyme had nearly twice the activity of the original Zn-enzyme. Combined with kinetic analyses of reconstitution of the apoenzyme with metal ions, these results show that the enzyme has two non-identical metal-binding sites, each with a different property. Furthermore, substitution of Mn(2+) or Co(2+) for Zn(2+) considerably lowered the thermostability of the enzyme without affecting the overall conformation of the enzyme protein, suggesting that the prosthetic Zn is playing dual roles in conformational stability and catalysis of the thermostable dipeptidase.
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PMID:Role of Divalent Metal Ions on Activity and Stability of Thermostable Dipeptidase from Bacillus stearothermophilus. 2739 65