Biomedical subjects
Publications and source records attributed to B Finlayson.
The adsorption of pyrophosphate and citrate to whewellite was measured by solution depletion. At pH 6.5, the concentration for one-half surface coverage CE(1/2) by pyrophosphate is 15 micrometer. The estimated maximum coverage is 37.5 mumoles per m2. The CE (1/2) for citrate is 4 micrometer, and the estimated maximum coverage is 6.42 mumoles per m2.
In an effort to rationalize the difference between computed estimates of urinary calcium oxalate supersaturation and estimates obtained by equilibrating urine with solid calcium oxalate, we examined ultrasfiltered urine for the binding of urinary ions. Urine was passed through a filter with a nominal passage cutoff of 1000 Daltons. The average reduction in concentration of the ultrafiltrate was 12.7 per cent for oxalate, 11.9 per cent for phosphate, 9.4 percent for calcium, 7.6 per cent for magnesium, and 6.9 per cent for sodium. From these results we conclude that calculations of urinary ion equilibrium will give better estimates if the composition of ultrafiltered urine is used.
In an effort to evaluate the rate of stone disease, a questionnaire was sent to each hospital in the United States. On the basis of 1765 responses it is estimated that the average rate of hospital discharge diagnoses of urinary stone per all hospital discharges was 0.0102. It was calculated that the annual incidence of urolithiasis in the population is at least 16.41 per 10,000 and that approximately 12 per cent of the population is expected to have urinary stone disease at some time in their lives.
There is a paucity of literature concerning the origin of urinary stone disease. This report uses information currently available to examine the likelihood of urinary stone disease starting from free or fixed crystalluric particles. We conclude that stone disease in the renal tubules and renal pelvis cannot begin on unattached (free) particles. However, in conditions associated with stone formation, initiation of bladder stone disease on free particles seems quite likely.
This paper examines the kinetics of calcium deposition in rat kidneys after an intraperitoneal sodium oxalate injection. From the results we conclude that only a limited portion of tubular surface is available for adsorption of calcium oxalate crystals, that adsorpption of calcium oxalate crystals onto tubular epithelium is a process of greater than first order with regard to the dose, and that the washout of retained particles from the tubules is a first-order process as related to time. Also, we conclude that in these animals, which were subjected to a large oxalate challenge, the deposition of calcium oxalate crystals is virtually all intratubular.
On the basis of measurements of adsorption, solution depletion, zeta potential, solubility, seeded-crystal growth, nucleation, and intrarenal precipitation in rats, it was not possible to show that allopurinol retards the crystallization of calcium oxalate (whewellite).
A single intraperitoneal injection of sodium oxalate was used to induce intrarenal tubular precipitation of calcium oxalate in rats. This experimental model was used to screen the efficacy of hydrochlorothiazide, orthophosphate, methylene blue, trypan blue, retinal folic acid, neuraminidase, and lysozyme in retarding intratubular calcium oxalate precipitation. Orthophosphate caused a 53 per cent reduction in calcium oxalate precipitation relative to the control animals.
The adsorption of proteins and mucopolysaccharides on calcium oxalate crystals was measured by solution depletion. Anionic protein adsorption was found to be sensitive to calcium ion concentration. Adsorption of fibrinogen was anomalously large in the presence of 0.01 M Ca2+. Adsorption of cationic protein (histone) was sensitive to oxalate ion concentration. A small alteration in adsorption of protein as a result of pH or temperature change was also observed. Plots of adsorption versus concentration were interpreted in terms of a Langmuir adsorption isotherm. The derived Langmuir adsorption parameters were then used to investigate the contribution of protein, by physical adsorpti, to the quantity of matrix in urinary stones. It was concluded that physical adsorption can account for the deposition of part but not all of the matrix in calcium oxalate stones. It was also concluded that physical adsorption of mucopolysaccharides by calcium oxalate crystals could explain the inhibition of growth and aggregation of calcium oxalate crystals seen with in vitro precipitation systems. Recalculation of published data indicates that adsorption of protein on dental enamel (calcium hydroxyapatite) results in approximately the same extent of surface coverage as adsorption on calcium oxalate crystals, but protein has a much lower affinity for dental enamel than for calcium oxalate crystals.
An animal experimental model was used to study oxalate absorption from the gut. It was found that the initial rate of [14C]oxalate absorption is rapid (6.5 per cent per min), and that after 5 min the rate of absorption decreases to about 0.6 per cent per min. Absorption of [14C]oxalate was greatest in the jejunum and least in the colon. On the basis of linear coefficients derived from the data, it is estimated that at least 8.6 per cent of a challenge dose of oxalate should be absorbed from the small bowel during normal transit. The high absorption rate, compared with the normal absorption of oxalate, in this model is most likely attributable to the oxalate's being completely dissolved in the gut. Magnesium and calcium in the test solution did not cause large changes in the rate or amount of oxalate transfer in this experimental model.
The estimation of the degree of saturation of brushite and of calcium oxalate in urine of patients with disorders of calcium metabolism has been proved to be an effective tool in evaluating the patient's propensity to form renal stones. The methods used in three different laboratories have been compared and evaluated in 27 urine samples. Relative saturation ratio (ratio of activity product and thermodynamic solubility product of brushite) and activity product ratio (ratio of activity product of original sample and that obtained after incubation of sample with synthetic brushite) were determined. Similar studies were performed for calcium oxalate. The values for relative saturation ratio of brushite or calcium oxalate differed widely among the three techniques. However, nearly identical values for activity product ratio of brushite were obtained. The activity product ratios of calcium oxalate, obtained by different techniques, closely approximated each other except in sampels containing excessive amounts of calcium (greater than 5 mM) or oxalate (greater than 5 mM). The values for the relative saturation ratios for both brushite and calcium oxalate were usually higher than the corresponding values for activity product ratio. The results indicate that the use of activity product ratio provides a more simple and reliable estimate of the urinary state of saturation than does the relative saturation ratio.
The concentrations of sodium, potassium, calcium, magnesium, phosphorus, sulfate, citrate and oxalate in the urine of normal subjects were compared to the concentrations in urine of calcium oxalate stone-forming patients. Because of the large volume excreted by stone-forming patients the urine contained less concentrations of sodium, potassium, magnesium, phosphorus, sulfate and citrate than did the urine from normal subjects. The urinary concentrations of calcium and oxalate were similar in the 2 groups and, thus, the calculated supersaturation of calcium oxalate was greater in the urine of stone-forming patients than in the urine of normal subjects. Orthophosphate therapy increased the urinary concentration of alkali ions and phosphate but reduced urinary calcium concentration, thereby causing a reduction in urine supersaturation with calcium oxalate. There was no discernible correlation between the phosphate-induced changes in urine supersaturation and the presence or absence of continued calculus formation.
An explanation was sought as to why the ureter becomes tortuous with increased intraluminal pressure. Changes in ureteral diameter and length, secondary to increased intraluminal pressure, were measured in different pathologic conditions and these changes were compared to similar ones in a non-biologic material (latex rubber tubing). It was demonstrated that these changes were anisotropic and remarkably similar under quite different pathologic conditions. Ureteral tortusity occurring secondary to increased intraluminal pressure may be related to anisotropic expansion of a tube with both ends in a fixed position.
The stability constants of MgC204 and Mg2C204-2nCOmplexes were estimated at 37--38 C by four different techniques; there was good agreement among the results of the different techniques. The stability constant of MgC204 is (4019 plus or minus 76 M-minus 1). The stability constant of Mg2C204-2nWAS FOund to be less than 5 M-minus 1. These stability constant are needed in the evaluation of the stone-forming potential of urine.