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Papers by Caroline Dean
Clinical Science, 2000
The bikunin peptide chain of the protease inhibitor inter-α-inhibitor (IαI) has been reported to ... more The bikunin peptide chain of the protease inhibitor inter-α-inhibitor (IαI) has been reported to be an inhibitor of calcium oxalate (CaOx) crystallization, and hence has been proposed as having a role in CaOx kidney stone formation. However, further experimental evidence is required to assess if fragments of IαI other than bikunin may play a role in the regulation of crystallization events in stone formation. The aim of the present study was to assess the effects of IαI and several of its derivatives on CaOx crystallization in a seeded inorganic system and to compare these effects with those of a known inhibitor of crystallization, prothrombin. IαI was purified from a preparation of human plasma and fragmented by alkaline hydrolysis, and two of its peptide chains, bikunin and heavy chain 1 (H1), were purified further by HPLC. Their purity was confirmed by SDS/PAGE. Using Coulter counter and [ 14 C]oxalate analysis and scanning electron microscopy, IαI, its H1 chain and bikunin from urine and from plasma were shown to be relatively weak inhibitors of CaOx crystallization in vitro at expected physiological concentrations. It was concluded that members of the IαI family may not be as important in kidney stone formation as has been generally proposed, although further studies are required before a possible role for IαI and its fragments in stone formation can be unambiguously discounted.
Journal of Structural …, 2001
The external appearance of urinary calcium oxalate (CaOx) crystals suggests that they are solid, ... more The external appearance of urinary calcium oxalate (CaOx) crystals suggests that they are solid, homogeneous structures, despite their known association with proteins. Our aim was to determine whether proteins comprising the organic matrix of CaOx crystals are superficial or intracrystalline in order to clarify the role of urinary proteins in the formation of kidney stones. CaOx crystals were precipitated from centrifuged and filtered, or ultrafiltered, healthy human urine. They were then treated with dilute NaOH to remove bound proteins, partially demineralized with EDTA, or fractured and subjected to limited proteolysis before examination by low-resolution scanning electron microscopy or field emission scanning electron microscopy. Crystals precipitated from centrifuged and filtered urine had a complex interior network of protein distributed throughout the mineral phase, which appeared to comprise closely packed subcrystalline particles stacked in an orderly array among an amorphous organic matrix. This ultrastructure was not evident in crystals deposited in the absence of macromolecules, which were completely solid. This is the first direct evidence that crystals generated from cell-free systems contain significant amounts of protein distributed throughout a complex internal cribriform ultrastructure. Combined with mineral erosion in the acidic lysosomal environment, proteins inside CaOx crystals would render them susceptible to attack by urinary and intracellular renal proteases and facilitate their further dissolution or disruption into small particles and ions for removal by exocytosis. The findings also have broader ramifications for industry and the materials sciences, as well as the development and resorp-tion of crystals in biomineralization systems throughout nature.
Clinical Science, 2000
The bikunin peptide chain of the protease inhibitor inter-α-inhibitor (IαI) has been reported to ... more The bikunin peptide chain of the protease inhibitor inter-α-inhibitor (IαI) has been reported to be an inhibitor of calcium oxalate (CaOx) crystallization, and hence has been proposed as having a role in CaOx kidney stone formation. However, further experimental evidence is required to assess if fragments of IαI other than bikunin may play a role in the regulation of crystallization events in stone formation. The aim of the present study was to assess the effects of IαI and several of its derivatives on CaOx crystallization in a seeded inorganic system and to compare these effects with those of a known inhibitor of crystallization, prothrombin. IαI was purified from a preparation of human plasma and fragmented by alkaline hydrolysis, and two of its peptide chains, bikunin and heavy chain 1 (H1), were purified further by HPLC. Their purity was confirmed by SDS/PAGE. Using Coulter counter and [ 14 C]oxalate analysis and scanning electron microscopy, IαI, its H1 chain and bikunin from urine and from plasma were shown to be relatively weak inhibitors of CaOx crystallization in vitro at expected physiological concentrations. It was concluded that members of the IαI family may not be as important in kidney stone formation as has been generally proposed, although further studies are required before a possible role for IαI and its fragments in stone formation can be unambiguously discounted.
Journal of Structural …, 2001
The external appearance of urinary calcium oxalate (CaOx) crystals suggests that they are solid, ... more The external appearance of urinary calcium oxalate (CaOx) crystals suggests that they are solid, homogeneous structures, despite their known association with proteins. Our aim was to determine whether proteins comprising the organic matrix of CaOx crystals are superficial or intracrystalline in order to clarify the role of urinary proteins in the formation of kidney stones. CaOx crystals were precipitated from centrifuged and filtered, or ultrafiltered, healthy human urine. They were then treated with dilute NaOH to remove bound proteins, partially demineralized with EDTA, or fractured and subjected to limited proteolysis before examination by low-resolution scanning electron microscopy or field emission scanning electron microscopy. Crystals precipitated from centrifuged and filtered urine had a complex interior network of protein distributed throughout the mineral phase, which appeared to comprise closely packed subcrystalline particles stacked in an orderly array among an amorphous organic matrix. This ultrastructure was not evident in crystals deposited in the absence of macromolecules, which were completely solid. This is the first direct evidence that crystals generated from cell-free systems contain significant amounts of protein distributed throughout a complex internal cribriform ultrastructure. Combined with mineral erosion in the acidic lysosomal environment, proteins inside CaOx crystals would render them susceptible to attack by urinary and intracellular renal proteases and facilitate their further dissolution or disruption into small particles and ions for removal by exocytosis. The findings also have broader ramifications for industry and the materials sciences, as well as the development and resorp-tion of crystals in biomineralization systems throughout nature.