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Biomedical subjects

C Y Pak

Publications and source records attributed to C Y Pak.

At least 307 records · Page 17Linked to original sources
PubMed1971

Spontaneous precipitation of brushite in urine: evidence that brushite is the nidus of renal stones originating as calcium phosphate.

Further evidence that brushite plays a regulatory role in renal stone formation was provided by the identification of brushite as the first precipitate that appears in supersaturated urine by spontaneous precipitation. Calcium chloride was added to induce supersaturation in urine specimens from twelve subjects with and twelve subjects without nephrolithiasis. The first precipitate in all specimens with pH below 6.9 was identified as brushite by x-ray diffraction and shown to have a calcium-phosphorus ratio of approximately 1.0. The activity product of [Ca(2+)] x [HPO(4) (2-)] necessary to produce a precipitate ranged from 2.2 to 3.5 times the solubility product of brushite, but the range and mean were the same for both groups of subjects. The activity product of [Ca(2+)] x [HPO(4) (2-)] in the supernatant (after spontaneous precipitation) was not significantly different from that obtained after incubation of the same urine specimen with synthetic brushite. These results provide conclusive evidence that brushite constitutes the solid phase formed by spontaneous precipitation from acidic urine supersaturated with respect to calcium and phosphorus; they suggest that the nidus for calcium-containing renal stones is brushite as well.

Calcium↗
PubMed1970

Calcification of collagen by urine in vitro: dependence on the degree of saturation of urine with respect to brushite.

A state of supersaturation of urine with respect to brushite is considered to be important in the formation of renal stones composed of calcium phosphate. 56 supersaturated urine specimens and 44 undersaturated specimens were incubated with collagen (Sigma collagen). Most of the supersaturated specimens calcified the collagen, whereas none of the undersaturated ones did so. Among samples which calcified the collagen, whereas none of the undersaturated ones did so. Among samples which calcified the collagen, the activity product of Ca(++) and HPO(4) (=) after incubation with collagen was essentially the same as that after incubation of the same specimen with brushite; it usually differed from that obtained after incubation with octacalcium phosphate or hydroxyapatite. The molar calcium-to-phosphorus ratio of the solid phase in collagen was approximately 1. These results suggested that the solid phase formed in collagen is brushite. This conclusion was confirmed by the direct identification of brushite in collagen by X-ray diffraction.

Adult↗