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A L Rodgers

Publications and source records attributed to A L Rodgers.

36 records · Page 2Linked to original sources
PubMed1988

Quantitative X-ray diffraction analysis of urinary calculi by use of the internal-standard method and reference intensity ratios.

The internal-standard method and the powder diffractometer have been applied here to the quantitative determination of urinary stone constituents by x-ray diffraction (XRD). Reference intensity ratios determined for six stone substances were used in the reduction of intensity data. Constituent concentrations calculated for 21 stones were compared with values obtained from an element-sensitive technique. We conclude that XRD analysis alone cannot be regarded as a routine technique for the quantitative characterization of uroliths, but that semiquantitative XRD analysis supplemented by accurate quantitative elemental data is more suitable for the precise determination of true stone composition.

Calcium Oxalate↗
PubMed1987

Fluoride concentrations in a collection of urinary calculi.

Fluoride concentrations in 42 urinary calculi were determined using a microdiffusion procedure in conjunction with a fluoride sensitive electrode. Mean values of 56, 230 and 1112 ng./mg. fluoride were obtained for uric acid, calcium oxalate monohydrate and apatite/struvite stones, respectively. Fluoride concentration was found to be related to calcium oxalate dihydrate levels as well as to apatite content. It is suggested that the former has zeolithic properties which might trap fluoride while formation and growth of the latter appears to be enhanced by elevated urinary fluoride levels.

Apatites↗
PubMed1986

Crystalluria in marathon runners. 1. Standard marathon--males.

Epidemiological evidence suggests that marathon runners have a higher incidence of renal stone formation than occurs in the general population. Since crystalluria and stone disease are thought to be related, we subjected urine samples from a group of marathon runners to particle counting and sizing in a Coulter Counter equipped with a population accessory unit. The volume-size distribution curves so obtained were bimodal with one peak occurring in the 2-5 micron diameter range and a second in the 15-32 micron diameter range - a pattern that is remarkably similar to the distributions reported for recurrent idiopathic stone formers and distinctly different to those recorded for control subjects. Analyses by scanning electron microscopy and X-ray powder diffraction revealed other features which are regarded as typical of stone formers' crystalluria. These physicochemical data indicate that marathon runners may be at increased risk of urinary stone formation.

Adult↗
PubMed1986

Pancreatic calculi containing brushite: ultrastructure and pathogenesis.

Six pancreatic calculi were analyzed by X-ray powder diffraction and scanning electron microscopy. All were found to contain calcite; however, small amounts of two other morphologically distinct deposits containing only Ca were also detected in some of the stones. It is suggested that these substances may be vaterite and aragonite. In addition, significant deposits of brushite, CaHPO4 X 2H2O, were identified on the outer surfaces of three of the stones. This substance has not been previously reported as a constituent of pancreatic calculi, and its presence is surprising since physico-chemical factors such as phosphate concentration and fluid pH do not favor its deposition. We suggest that precipitation of calcite in the pancreatic duct occurs as the primary event in the formation of pancreatic calculi and that it may continue until the duct is completely occluded. Thereafter, further growth causes injury to the duct wall resulting in the calcite core being exposed to phosphate in the tissue fluid. Deposition of brushite follows.

Calcium Carbonate↗
PubMed1986

Crystalluria and urolithiasis in a relatively stone-free population.

The occurrence of renal stone in South African blacks is extremely rare. Whites however are prone to calculi to the same extent as that reported in other Western communities. The nature of the particulate material and crystalluria in urine samples from the two population groups were investigated using a Coulter Counter and scanning electron microscope. In addition, 10 calculi obtained from black patients over a 5 year period were analysed. The particle size distribution curves obtained for normal black and white males were identical. The curves for normal black and white females were also identical but different from those for males. Black male stone formers had larger particles than their controls while the single black female stone former investigated had particles of the same size as female controls, but in greater numbers. Scanning electron microscopy revealed profuse amounts of crystalline NaCl, KCl and other salts in the urinary sediments of blacks. These were not observed in the specimens from whites nor in the black stone formers' urines. Analysis of the calculi identified chemical and ultrastructural features similar to those observed in stones from whites. The hypothesis that the lower incidence of stone disease in blacks may be due to a high Na/Ca ratio is supported by our findings. It is suggested that various salts play a role in lowering the stone forming potential of such urines by a competitive substitution mechanism in which lattice calcium is displaced by sodium. It is also suggested that when urinary stone formation does occur in blacks, it does so via the same physicochemical mechanisms as in any other race group.

Adolescent↗
PubMed1986

Struvite crystalluria and urolithiasis in cross Labradors.

Recurrent struvite crystalluria and urolithiasis in a cross-Labrador bitch was studied using a combined Coulter-Counter and scanning electron microscope (SEM) approach. Staphylococcus bacteria were cultured from the patient's urine as well as from the calculi themselves. Urine samples were subjected to particle counting and sizing during active and non-active periods of stone formation. Size distribution curves so obtained were identical as were those derived from sterile and non-sterile specimens. These showed a peak incidence at a diameter of 5 microns. Particle sizes for 6 controls were also determined and showed an even distribution over a much wider range with small peaks occurring at 3, 10, and 20 microns diameters. SEM studies of urine sediments revealed the presence of struvite crystals in all the controls as well as in the stone-former. These occurred in a variety of shapes and sizes but were generally larger in the controls. SEM also revealed intimate admixtures of struvite and apatite in calculi surgically removed from the patient. The results of this study indicate that crystal numbers are of greater significance than crystal size. It is also suggested that Cross-Labradors may be unusually predisposed to struvite crystalluria. The repeated recurrence of struvite urolithiasis in the subject indicates a possible inherent physiological malfunction in the animal's ability to cope with this crystalluria. The absence of a nucleation inhibitor in the stone-former's urine is also postulated.

Animals↗
PubMed1985

The application of physico-chemical procedures in the analysis of urinary calculi.

All physico-chemical techniques used in the analysis of urinary calculi have inherent advantages and limitations. Although x-ray powder diffraction can identify constituents unambiguously, certain minor components can be missed. Infrared spectroscopy is more sensitive but band assignment at low concentrations is difficult. Scanning electron microscopy together with energy dispersive x-ray analysis permits the simultaneous investigation of morphology and chemical microstructure. However, microanalysis of elements lighter than sodium is not possible and constituents are prone to irradiation damage. With the electron microprobe, minor constituents can be detected but tedious sample preparation procedures are required. Transmission electron microscopy is extremely useful in determining constituent inter-relationships and ultrastructure but ultramicrotomy is very difficult. Thermal gravimetric analysis gives quantitative information easily but does not satisfactorily distinguish between struvite and brushite. In an attempt to assess the accuracy of chemical analyses, 62 calculi were investigated applying several chemical tests. Those for Mg2+, PO4(3-), NH4+ and uric acid proved highly reliable while that for Ca2+ often yielded an incorrect result. The test for oxalate was totally unsatisfactory. Investigators of stone composition and structure should include x-ray diffraction (or infrared spectroscopy) and scanning electron microscopy as their methods of first choice. In addition, chemical or thermogravimetric analyses should be utilized in an auxiliary capacity.

Chemistry, Physical↗
PubMed1982

A multiple technique approach to the analysis of urinary calculi.

10 urinary calculi have been qualitatively and quantitatively analysed using X-ray diffraction, infra-red, scanning electron microscopy, X-ray fluorescence, atomic absorption and density gradient procedures. Constituents and compositional features which often go undetected due to limitations in the particular analytical procedure being used, have been identified and a detailed picture of each stone's composition and structure has been obtained. In all cases at least two components were detected suggesting that the multiple technique approach might cast some doubt as to the existence of "pure" stones. Evidence for a continuous, non-sequential deposition mechanism has been detected. In addition, the usefulness of each technique in the analysis of urinary stones has been assessed and the multiple technique approach has been evaluated as a whole.

Densitometry↗
PubMed1981

The nucleation and growth kinetics of calcium oxalate in the presence of some synthetic urine constituents.

We determined quantitative nucleation and growth kinetics of calcium oxalate in the presence of various combinations of urine constituents, using a continuous mixed suspension mixed product removal crystallizer and a Coulter counter. Nucleation rates of calcium oxalate from the pure component system were approximately an order of magnitude higher than those from an artificial urine. The presence of citrate inhibited nucleation rates under high conditions. The ions Na+, K+, NH4+, Cl-, and SO42- did not affect the overall kinetics in the synthetic urine. Di- and tri-hydrate products were formed, except when crystallizing from pure components, when only the thermodynamically stable monohydrate was observed.

Animals↗
PubMed1981

Analysis of renal calculi by X-ray diffraction and electron microprobe: a comparison of two methods.

We analyzed 48 renal calculi by X-ray powder diffraction and electron microprobe techniques. In 35 of these, the presence of a minor constituent, not detected by X-ray diffraction, was revealed--hydroxyapatite was found in 24 stones, struvite in 6, and calcium oxalate in 5. The results of this study, as well as others, show that incomplete assignment of the crystalline constituents of urinary calculi is an inherent risk of the X-ray method and that conclusions concerning total chemical composition should be based on X-ray diffraction analyses coupled with data obtained from other analytical procedures.

Calcium Oxalate↗
PubMed1981

Developmental aspects of calcium oxalate tubular deposits and calculi induced in rat kidneys.

We employed an experimental hyperoxaluric protocol involving the administration of 1 per cent ethylene glycol drinking water to rats to determine (i) the location and mechanism of retention of renal tubular calcium oxalate crystals, and (ii) how this tubular deposition is modified by magnesium deficiency and contributes to stone formation. Calcium oxalate monohydrate deposition was found predominantly within the lumina of proximal tubules, and was markedly accelerated by magnesium deficiency. Sheet- and strandlike mucoid appearing material attached the crystals to the luminal surface of the renal tubules. The structure of stones found in the renal pelvis suggested that tubular deposits aggregate to form the nidus of the calculus.

Animals↗
PubMed1981

Application of several physical techniques in the total analysis of a canine urinary calculus.

A single calculus from the bladder of a Beagle bitch has been analyzed by a multiple technique approach employing x-ray diffraction, infrared spectroscopy, scanning electron microscopy, x-ray fluorescence spectrometry, atomic absorption spectrophotometry and density gradient fractionation. The qualitative and quantitative data obtained showed excellent agreement, lending confidence to such an approach for the evaluation and understanding of stone disease.

Animals↗