Browsing by Author "Rodgers, Allen"

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    Characterization of the physiochemical and biochemical properties of the urinary protein bikunin in South African black and white subjects with respect to calcium oxalate kidney stone formation
    (2006) Mabizela, Nontobeko; Rodgers, Allen; Sturrock, Edward D
    Approximately 12 % of males in the Western world are likely to suffer at least one kidney stone in their life. The incidence of kidney stone disease in South Africa is similar in white males; however stone occurrence in the South African black population is extremely rare. The difference between the incidences of kidney stones in the black and white populations in South Africa is unexplained. In general, the role of several urinary proteins in the pathogenesis of this disease has been established. Bikunin is an example. The primary aim of this study was to isolate bikunin from the urine of healthy black and white male subjects and to investigate whether the protein from the black group is a more powerful inhibitor of CaOx crystallization than that from the stone prone white group.
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    Dietry and microbiological investigation in South African black and white subjects as a key to understanding the difference in the incidence of kidney stone disease in the two race groups
    (2003) Lewandowski, Sonja; Rodgers, Allen
    Kidney stones occur in the South African white population to the same extent as in other westem countries. However, the incidence of this disease in the South African black population is extremely rare. In this thesis, investigations were undertaken to establish whether different renal handling mechanisms occur in the two race groups in response to different dietary challenges and whether there might be qualitative and quantitative differences in the colonization and utilization of oxalate-degrading bacteria in the two race groups which might account for this phenomenon.
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    The effect of inositol-hexakisphosphate (phytate) on urinary risk factors for calcium oxalate urolithiasis in South African population groups with different kidney stone risk profiles : theoretical modelling, in vitro crystallisation experiments and in vivo human studies
    (2015) Fakier, Saajidah; Rodgers, Allen; Jackson, Graham Ellis
    The principal aims of this thesis were to establish whether soluble calcium-phytate complexes inhibit calcium oxalate crystallisation and whether a higher dietary intake of phytate in South African black subjects compared to white subjects may contribute to the relative rarity of urolithiasis in this group. Potentiometric titrations were conducted to determine thermodynamic binding constants of soluble calcium-phytate complexes. Binding constants of seven complexes were identified. These were included in the data base of the Joint Experts Speciation System computer program to model the effect of phytate on the urinary supersaturation of calcium salts. Physiological concentrations of phytate failed to decrease ionized calcium and hence the urinary supersaturation of calcium salts. These theoretical predictions were then tested in an in vitro model. Calcium oxalate crystallisation experiments were conducted in simple salt solutions, artificial urine and real urine of the respective groups. The following parameters were measured: ionized calcium; calcium oxalate metastable limit; calcium oxalate particle volume-size distribution; calcium oxalate crystal nucleation, aggregation and growth kinetics. Deposited crystals were examined by scanning electron microscopy. The results confirmed those of the theoretical modelling. Furthermore, the results demonstrated that the inhibitory capacity of phytate is of a kinetic nature rather than a thermodynamic one. Phytate inhibited calcium oxalate crystal aggregation and the inhibition of calcium oxalate crystal growth was found to be independent of the physiological concentration of phytate. In vivo studies were conducted in which phytate-deficient, phytate-rich diets and a phytate supplement were administered in healthy black and white male volunteers. The baseline intake of phytate was assessed using food frequency questionnaires; urinary phytate was determined using a novel assay; biochemical and physiochemical urinary risk factors were measured. The black group had a significantly higher baseline intake of phytate culminating in a significantly higher urinary phytate excretion. No significant difference in urinary crystallisation kinetics was observed as being due to phytate per se. The findings of this thesis contribute to the pool of knowledge on urolithiasis and provide insight on the relative rarity of this disease in South Africa's black population.
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    Investigation of the effect of a solution of lime powder on urinary calcium oxalate kidney stone risk factors in artificial and real urines : in vitro and in vivo studies
    (2009) Bvumbi, Mpelegeng Victoria; Rodgers, Allen
    INTRODUCTION: Dietary factors in the form of citrus juices (e.g orange, grapefruits, cranberry, lemonade and lime) appear to affect the ability of urine to inhibit calcium oxalate crystallization. In South Africa, previous studies have demonstrated that black and white individuals respond differently to lithogenic and antilithogenic dietary supplements. OBJECTIVES: The current project was undertaken to study the inhibitory activity of lime in artificial urine and in the real urine of South African black and white subjects and also to assess the effects on urinary risk factors in these subjects after its ingestion. SUBJECTS AND METHODS: Experiments commenced with the preparation of artificial urine (AU) in which the effects of lime solutions (0.125-1.00 mglml) were tested by carrying out various crystallization experiments. These included the determination of the calcium oxalate (CaOx) metastable limit (MSL); particle volume-size distribution (PSD), nucleation, aggregation and growth assays. Crystal deposition was studied using scanning electron microscopy (SEM). In vitro experiments were then conducted in 24 hour urine samples from healthy South African black (n = 5) and white males (n = 5). The above-mentioned crystallization experiments were repeated in these urines. In addition, free Ca²⁺ values and the Bonn risk index (BRI) of CaOx crystallization were determined. Thereafter, a trial study in which 5 black and 4 white subjects ingested solutions of lime powder for 7 days was conducted. 24 hour urine samples were collected by subjects before and after the ingestion of lime. Urines were analysed for pH, sodium, potassium, calcium, oxalate, citrate, uric acid chloride, magnesium, phosphate, and creatinine. Urine composition values were used as input data for the calculation of relative supersaturation (RS) values for calcium oxalate monohydrate (COM), calcium oxalate dihydrate (COD), brushite and uric acid using the computer programme EQUIL and Tiselius Risk Index (TRI) was also determined. The above-mentioned CaOx crystallization experiments were also performed. Urine compositions, crystallization data and physicochemical risk indices were analyzed statistically using analysis of variance (ANOVA). RESULTS: None of the lime solutions did affect the CaOx MSL of the AU or the real urine (in vitro). However CaOx crystal nucleation was promoted while CaOx crystal growth and aggregation were inhibited. In the trial study, after ingestion of lime solutions, significant increases in urinary magnesium (1.80 vs 2.75 mmol/24h, p = 0.0001) and phosphate (20.9 vs 24.6 mmol/24h, p = 0.023) were observed in black subjects. On the other hand, in white subjects, a significant decrease in urinary oxalate (0.313 vs 0.205 mmol/24h, p = 0.023) and TRI (304 vs 187, p = 0.0102) were noted. However, lime did not increase citrate levels to a significant degree in either group. CONCLUSIONS: The results presented in this dissertation have shown that lime may be regarded as a potential therapeutic agent for reducing the risk of CaOx kidney stones in the white group based on the trial study. The results also provide further evidence in support of the hypothesis that there is a difference between the black and white populations with respect to their handling of lithogenic and antilithogenic dietary challenges. However, rigorous controlled trials in healthy subjects and in kidney stone patients need to be conducted in future studies to explicitly confirm these findings.
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    Investigation of the effect of hydroxycitric acid on urinary calcium oxalate risk factors for kidney stone formation in artificial urine: theoretical modelling and in vitro crystallisation experiments
    (2020) Ahmed, Amouna; Ravenscroft, Neil; Jackson, Graham; Rodgers, Allen
    Nephrolithiasis, or urolithiasis, commonly known as kidney stones, is a common medical problem. Kidney stones are composed of different mineral types. Calcium Oxalate is the most common kind of stone. The principal aim of this research was to establish whether hydroxycitrate (HCA) affects and/or inhibits calcium oxalate crystallisation. A three-pronged approach was adopted, involving the determination of thermodynamic binding constants for Ca, Mg and Zn-HCA complexes, theoretical modelling of HCA-complex formation in artificial urine and in vitro crystallisation experiments. A potentiometric analysis was conducted to determine thermodynamic binding constants. These were included in the database of the JESS computer program to model the effect of HCA on the urinary supersaturation of calcium salts. A 1 mM HCA concentrations successfully decreased the concentration of ionised calcium and hence the urinary supersaturation of calcium salts. The solution structures of H+ , Ca 2+, Mg 2+, and Zn 2+ -HCA complexes were investigated using 1H-NMR. For protonation, the results showed that the pKa values were too close to resolve and that several microstates were in rapid exchange. Similarly, for the metal complexes, several species were found to be in rapid exchange. Crystallisation experiments were conducted in artificial urine, to determine the effect of HCA on the thermodynamics and kinetics of crystallisation of calcium oxalate, which is the most common component of kidney stones. The effect of HCA on calcium oxalate metastable limit (MSL) and crystallisation kinetics were measured. The results confirmed those predicted by theoretical modelling. The MSL was significantly affected by 1 mM HCA. Also, 1 mM HCA increased the rate of CaOx crystallisation. Both these effects are favourable and decrease the risk of in vivo crystal and stone formation. This augurs well for the potential application of HCA as a therapeutic agent in the management of kidney stone disease. Such an outcome needs to be tested in human trials.
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    Investigation of the in vitro and in vivo effects of some herbal preparations on risk factors for calcium oxalate kidney stone disease
    (2012) Ramsout, Ronica; Rodgers, Allen
    Several herbal preparations (Folium pyrrosiae , Desmodium styracifolium, Hylocereus trigonus, Phyllanthus niruri, Orthosiphon stamineus and Cystone®) were investigated as potential therapeutic and prophylactic agents for kidney stone disease. These studies were executed in the context of the existence of a virtually stone-free (black) and a stone-prone (white) population group in South Africa, with a view of establishing whether their respective renal responses are different. The independent in vitro effects of six plant extracts were tested on the crystallization characteristics of calcium oxalate (CaOx), the predominant stone-forming salt in urine. These investigations were performed in synthetic urine and real urine collected from healthy black and white South African males and the following parameters were assessed: urine composition; CaOx metastable limit; particle size-volume distribution; 14 [C]-oxalate deposition kinetics; CaOx crystal nucleation, aggregation and growth kinetics; examination of crystalluria by scanning electron microscopy and calculation of various physicochemical risk indices (Bonn Risk Index, Tiselius Risk Index and the relative urinary supersaturation of several stone-forming salts). All plant extracts inhibited one or more of the crystallization processes. Furthermore, crystal-cell binding, another risk factor for stone formation, was investigated in the presence of plant extracts. Madin-Darby canine kidney (MDCK)-I cells were used for this experiment. Crystals (inorganic and urinary) were bound to cells incubated in both aqueous media and real urine. Results showed that plant extracts reduced crystal binding under some but not all conditions. One of the extracts (Folium pyrrosiae) was administered to healthy South African black (n=9) and white (n=9) males in a double-blind placebo-controlled study. No significant effects on urine chemistry were found and there were no significant differences between the race groups post- treatment. Compounds from this herb were isolated and purified by the use of sequential liquid-liquid extractions and gel-permeation chromatography. A novel compound, 5 - (3 -(5,5 -dihydroxy-3- oxopentyl)phenoxy)-2-hydroxy-5H-indene-6-carboxylic acid , was identified using mass spectrometry and nuclear magnetic resonance imaging spectroscopy. The findings in this thesis have contributed to the body of knowledge about kidney stone disease. It has been demonstrated that some herbal preparations may be potentially useful in treating and managing this disease, but further clinical testing is required prior to the implementation of such an approach.
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    Investigation of the potential beneficial effects of supplemental polyunsaturated fatty acids and glycosaminoglycans on the risk factors for calcium oxalate kidney stone formation using theoretical, experimental and human models
    (2014) Gogwana, Pumeza Christine; Rodgers, Allen; Ravenscroft, Neil
    Introduction: Two hypotheses with regard to calcium oxalate (CaOx) renal stone formation were tested in this thesis. The first hypothesis is that fatty acid (FA) supplementation (n-6 and n-3) and chondroitin sulphate (CS) supplementation may reduce the plasma (FA) and urinary (FA and CS) risk factors for CaOx renal stone formation, and ultimately serve as therapeutic agents in the management of this disease. The notion that FAs may reduce plasma risk factors is based on previous studies which have shown that n-6 and n-3 FA supplementation reduces the concentrations of arachidonic acid, while the notion of an effect on urinary risk factors is based on reports of these supplements decreasing urinary calcium and/or oxalate excretion in animal and human studies. The notion of CS playing a role in reducing CaOx stone risk is based on its chemical structure which presents potential binding sites for calcium and magnesium. The second hypothesis is that black and white healthy South African subjects may respond differently to these dietary supplements and that these differences may provide insights which could account for the lower stone incidence in the former group compared to the latter. This hypothesis is based on the observation in many previous studies of different renal responses in the two race groups, to different dietary and supplemental challenges. FA’s and CS have not been previously investigated in this regard. Methods: These hypotheses were tested simultaneously by administering n-6 and n-3 FA supplements individually and in combination, and supplemental CS, to different groups of black and white healthy male subjects. For the FA studies, blood samples were analyzed for serum biomarkers (25-hydroxyvitamin 03 and triglycerides) for CaOx stone formation and FA profiles in plasma total phospholipids since arachidonic acid regulates calcium excretion. Urine samples were analyzed for individual CaOx stone risk factors, risk indices (Tiselius risk index and supersaturation (SS) of calcium oxalate, brushite and uric acid); crystallization experiments (metastable limit and crystal growth kinetics) were also conducted. For the CS studies, thermodynamic binding constants for calcium-CS and magnesium-CS complexes were determined by isothermal titration calorimetry. These constants were then used to model speciation in different urines using the computer program Joint Expert Speciation System (JESS), and to calculate supersaturation values under different urinary conditions. This was followed by in vitro crystallization experiments in which the effects of exogeneous CS on the CaOx metastable limit and CaOx crystallization kinetics were investigated in artificial and real urine samples. Finally, human studies were performed in which CS supplements were administered to subjects to test their efficacy on reducing the urinary risk factors for CaOx stone formation. Urines were analyzed and crystallization experiments were performed as described for the FA supplementation studies. Results: In the FA studies, favourable changes in the plasma CaOx stone risk factors were achieved by the supplementation of n-3 FA alone. Post-supplementation, the concentration of arachidonic acid in plasma total phospholipids was significantly reduced in both groups, thereby implying a reduction in urinary calcium excretion. However, FA supplementation had no positive effect on the urinary risk factors or on CaOx metastable limits and CaOx crystallization kinetics. In the CS studies, theoretical modelling showed that the reduction of ionized calcium concentrations can only be attainable at 100 times physiological concentrations of urinary CS and that the formation of the calcium-CS complex does not influence the urinary supersaturation of CaOx. The formation of the magnesium-CS complexes was unfavourable because it resulted in an increase in the concentrations of ionized oxalate, a risk factor for CaOx stone formation. The in vitro crystallization experiments showed that exogeneous CS at physiological and above physiological concentrations had no favourable effect on the metastable limit and crystal growth kinetics in all the tested urine samples. Finally, the human study showed that CS supplementation had no effect on urine chemistry and crystallization kinetics. Speciation calculations also showed that the SS values of CaOx and the concentrations of ionized calcium were not significantly changed by supplementation. Within groups, the effects of FA supplementation on the urinary risk factors were different. n-6 FA supplementation significantly increased magnesium and significantly decreased urate in the black group whereas in whites citrate, oxalate and potassium were significantly increased while ionized calcium was significantly reduced. In the n-3 FA study, magnesium was significantly increased and SS value of brushite was significantly decreased in whites. In the black group, there was no significant difference in the urinary risk factors after supplementation compared to baseline values. With regards to n-6 & n-3 FA supplementation, citrate was significantly increased while oxalate and SS CaOx were significantly decreased in the black group whereas in the white group, magnesium was significant increased. With regards to the CS study, SS values for brushite, tribasic calcium phosphate, hydroxylapatite and octacalcium phosphate decreased significantly in black subjects after CS supplementation, whereas the SS value for hydroxylapatite increased significantly in the white group. These effects could not be attributed to complexation of CS with calcium or magnesium. However, they are noteworthy because they are different in the two groups. Discussion: The results of these studies do not support the hypothesis that supplemental fatty acids or chondroitin sulfate have significant beneficial effects for reducing blood and urinary risk factors for calcium oxalate stone formation. Although the response to FA and CS supplementation was different between the two race groups, these findings did not provide new information to explain the difference in the incidence of calcium oxalate stone disease in the two population groups. The work described in this thesis provides a foundation for future studies in which CaOx stone patients, rather than healthy individuals are investigated.
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    Investigation of the role of dietary myo-inositol hexakisphosphate (phytate) on the relative risk of calcium oxalate kidney stone formation in black and white male South African subjects
    (2005) Lesotho, Ntlama; Rodgers, Allen; Ravenscroft, Neil
    Previous studies have shown that caJclum oxalate (CaOx) stone-formers have lower urinary concentrations of myo-inositol hexakisphosphate (phytate or IPe) than healthy individuals, that dietary intake of this substance leads to its increased urinary excretion and that it is an inhibitor of CaOx nucleation and growth In South Africa it has been reported that the black population has a higher dietary phytate intake than whites. The present study was undertaken to test the hypothesis that South African black subjects have higher urinary phytate levels than their white cOLlflterparts and that this contributes to the relative rarity of caOx kidney stone disease in this population group A modified indirect extraction/photometry method to measure urinary IPe was designed, developed and tested in the present study. This assay was then used to measure IPo in the urine of rural black and urban white subjects while on their free unrestricted diets In addition, urban black and white subjects each followed IPo-restricted followed by lPG-rich dietary protocols for a period of three days Urines were collected after administration of each protocol and were again analysed for IPe using the newly developed assay. Urines were then used in several crystallization experiments to measure the CaOx metastable limit, "C-oxalate deposition kinetics and inhiOition of CaOx crystal aggregation. The results showed that while on their free diets, rural blacks excreted significantly less IPs than urban whites despite their previously reported higher dietary intake of this substance This suggests that the renal handling of dietary IP
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    Kidney stone rarity in South Africa's black population : investigation of the biochemical and physico-chemical properties of Tamm Horsfall Mucoprotein as a possible contributory factor
    (2004) Craig, Tracy-Ann; Rodgers, Allen
    Tamm Horsfall mucoprotein (THP) is a powerful inhibitor of calcium oxalate crystallisation. Since urolithiasis in South African blacks is extremely rare, this study was undertaken to compare the relative inhibitory and biochemical properties of this protein in South African black and white healthy and stone—forn1ing male subjects. THP was isolated by salt precipitation, purified by column chromatography and verified by electrophoresis on SDS-polyacrylamide gels. MALDI-TOF mass spectroscopy was used to determine the molecular weights of the protein from each group and their respective amino acids were analysed. All four THP groups were subjected to tryptic finger printing digestion and matched those of the database. The secondary structures of the four THP proteins were also determined using circular dichroism. The carbohydrate moeities of the four THP groups were analysed for and O-linked oligosaccharides. THP from each of the four groups were subjected to a series of crystallisation experiments using a crossover design in which the protein was added to the urine from which it had been originally isolated, as well as to the urines from the other three groups. This process generated a 4x4 protein-urine grid for investigation of the inhibitory properties of THP in different urine environments. Calcium oxalate crystallization was induced by administration of aqueous sodium oxalate and was monitored Using a Coulter Counter. In another series of experiments 14C-oxalate was used to initiate crystallization. Monitoring in these experiments was achieved by scintillation counter techniques. Calcium oxalate crystal aggregation was investigated in the presence and absence of THP using zeta potential measurements and crystal sedimentation experiments.
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    The Quartz Conundrum : understanding the role of quartz in the composition of late Pleistocene and Holocene lithic assemblages from the Verlorenvlei area, Western Cape
    (2004) Orton, Jayson; Rodgers, Allen; Sturrock, Edward D
    This research explores the related roles of quartz and bipolar reduction in the composition of Later Stone Age (LSA) lithic assemblages from the Verlorenvlei area, Western Cape Province. With few exceptions, these two elements strongly dominate the assemblages from this area, and the attitudes to and reasons for their continuous use are considered here. Discussions on typology and raw material classification illustrate and attempt to solve problems existing in current systems, and a comprehensive classification scheme for the western Cape area is provided. The use of an innovative analytical technique, in which each raw material is assessed individually, allows considerable variation in the flaking and subsequent use of each material to be demonstrated. While fine~grained rocks are undoubtedly preferred for artefact manufacture, overall raw material proportions are clearly determined by the ubiquitous availability of quartz in the study area, but less important factors, virtually impossible to differentiate from the lithics alone, are undoubtedly also implicated. Technological change related to the use of quartz and bipolar flaking is explored through three critical periods, the late Holocene, the terminal Pleistocene/early Holocene, and the late Pleistocene. In order to ascertain the factors governing assemblage composition, the frequencies of various artefact types are compared with those of quartz and bipolar cores by means of scatter plots. Correlation coefficients are calculated to assist the analysis of the data, but due to the small sample sizes some visual interpretation of the graphs based on intuitive archaeological knowledge is also essential. Considerably different approaches to the reduction of quartz are demonstrated for each period, with distinct strategies of raw material conservation, each operating in a different manner, existing throughout most of the LSA. These promoted the variable use of bipolar and non-bipolar reduction techniques and microlithic technology in order to make best use of the relatively intractable quartz on offer in the local landscape. Such strategies only broke down during the late Holocene, possibly due to the changing social relations that must have occurred with the introduction of pastoralism to the area some 2000 years ago. The nature of industrial change is also explored, and it is evident that in this area the LSA lithic sequence constitutes a continuous progression of sporadic change with no distinct breaks or periods of absolute stability being apparent. It is recommended that larger sample sizes be used in similar future analyses in order to alleviate the difficulties inherent in drawing general conclusions from small sets of data. The frequency of chips in any assemblage is shown to be unreliable and their exclusion from comparative typological data will lend greater validity to all lithic analyses.
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    Rarity of kidney stones in South Africa's black population : studies of urinary macromolecules, crystal matrix extract containing osteopontin, and bone turnover markers in urine and serum from black and white subjects as a key to understanding this paradox
    (2007) Deppa, Ntsapokazi; Rodgers, Allen; ; Sturrock, Edward
    The work described in this thesis was undertaken to investigate physicochemical, biochemical and physiological factors contributing towards the rarity of kidney stone disease in the South African black population. Healthy, age-matched male subjects from the black and white population groups were recruited for this purpose. In several of the studies, subjects followed a standardized diet and were required to provide 24 hour urine collections. These were analyzed for sodium, potassium, calcium, oxalate, uric acid, citrate, chloride, magnesium, phosphate, sulphate and creatinine using standard laboratory techniques. Urine composition values were used as input data for the calculation of relative supersaturation (RS) values for calcium oxalate (CaOx), calcium phosphate (CaP, or brushite) and uric acid (U A) using the computer programme EQUIL and for the calculation of the Tiselius Risk Index (TRI). CaOx crystallization experiments were performed. These included CaOx metastable limit (MSL) and BONN Risk Index (BRI) determinations, particle formation kinetics, 14 C-oxalate cry stal deposition kinetics and CaOx crystal aggregation and nucleation inhibition. Crystallizati on experiments were also supplemented with scanning electron microscopy (SEM) and zeta potential measurements. Urine compositions, crystallization data and physicochemical risk indices were analyzed statisitically using ANOV A. Several different investigations were undertaken. These included crystallization experiments involving urinary macromolecules from both race groups, crystal matrix extract isolation (with osteopon tin as its major component) from both race groups and its testing for inhibitory capacity in ultrafiltered urine from both race groups. Similar crystallization experiments were conducted with commercially available osteopontin. In addition, a comprehensive trial was conducted in which the ingestion of three sodium salts (sodium chloride, sodium bicarbonate and sodium citrate) was investigated for their effects on urinary risk factors of CaOx stone formation and for their effects on bone turnover markers in urine and in serum. For the biochemical isolation of crystal matrix extract, COD-CME was precipitated in urine from both black and white subjects. The proteins included in COD-CME were detected using sodium dodecyl sulfate polyacryalamide gel electrophoresis (SDS-PAGE). Western Blotting was used for semi-quantitative analysis of OPN v For the trial involving different sodium salts, four experimental protocols were investigated. The four protocols included low NaCl (3 g/day), high NaCl (12 g/day), sodium bicarbonate (6 g/day) and sodium citrate in the form of Citro-Soda (16 g/day). A Latin Square Design was followed for the random assignment of participants to sequences of protocols. The studies on macromolecules showed that those in the urine of black subjects were more potent inhibitors of CaOx crystal deposition and aggregation than those in the urine of white subjects. Isolation and characterization of the crystal matrix extract in COD crystals confirmed that osteopontin is the main intracrystalline protein in the extract. The crystallization experiments performed on the crystal matrix extract isolated from the urine of both race groups demonstrated that the extract isolated from the urine of black subjects was a superior inhibitor of CaOx deposition, growth and aggregation. Crystallization studies performed on commercially available osteopontin in urine from black and white subjects showed that this protein is a more effective inhibitor of CaOx crystal deposition, growth and nucleation in the urine from the former group compared to that from the latter. The studies on supplemental sodium salts demonstrated that the two race groups respond differently to lithogenic and anti-lithogenic dietary challenges. High NaCl protocol resulted in a favourable and counter-intuitive significant decrease in free unbound calcium in samples from black subjects whereas no such change was observed in white subjects. Supplemental sodium bicarbonate and sodium citrate induced favourable decreases in urinary total calcium, urinary ionized calcium, BRI, RS of CaOx, RS of uric acid and RS of brushite, and a favourable increase in urinary citrate and pH in both groups. Interestingly and more importantly, these factors were more prominent in samples from black subjects than those from white subjects. Bone turnover measurements showed that urinary deoxypyridinoline (DPD) levels were lower while serum osteocalcin (OC) levels were higher in blacks than in whites at baseline, but these differences were not statistically significant. Smaller increases in urinary DPD levels after high aCl and sodium bicarbonate and corresponding bigger increases in serum osteocalcin (OC) levels after these protocols (and sodium citrate) in black subjects than in white subjects indicate less bone resorption and higher bone formation, respectively, in the former group. Vl The results presented in this thesis have provided convincing evidence that in the context of CaOx kidney stone formation, several physicochemical, biochemical and physiological factors are different in black and white South African subjects and that these factors are more effective in the former group with respect to providing protective mechanisms against CaOx kidney stone formation
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    Studies of genetic, gastrointestinal, renal and dietary factors in white and black South African subjects as a possible key to understanding the relative absence of calcium oxalate kidney stone disease in the black population
    (2009) Theka, Takalani P; Rodgers, Allen; Ravenscroft, Neil; O'Ryan, Colleen
    The incidence of urolithiasis in South Africa's black population is extremely rare «1%) while in the white population it is similar to that of western countries (-15%). The present thesis was aimed at shedding more light on the complex nature of the physicochemical, biochemical and physiological mechanisms in black South Africans which provide this group with a natural protection against urolithiasis in contrast to their white compatriots. Four studies comprise this thesis.
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    Studies of the effects of various lithogenic and antilithogenic dietry supplements on calcium oxalate kidney stone risk factors in South African black and white subjects
    (2008) Bungane, Ntombovuyo; Rodgers, Allen
    In South Africa, the incidence of urolithiasis in the white population occurs to the same extent as in other western societies. However, in the black population, this disease is extremely rare. Differences in the gastrointestinal and renal handling of several lithogenic and antilithogenic agents in the two ethnic groups have been reported, but the rarity of kidney stone disease in the black group remains a riddle. The studies described in this thesis were undertaken to address aspects of this phenomenon. Carbohydrate and oxalate-containing dietary agents were identified as being of interest since surveys have paradoxically demonstrated that the consumption of these potentially lithogenic substances is significantly higher in the black group. The carbohydrates selected for study were glucose, sorbitol and xylitol, while the oxalatecontaining agents were rhubarb, spinach and an aqueous solution of sodium oxalate itself. Finally, taurine, which has been shown to reduce urinary glycolate and oxalate in animal models, was also selected for investigation in the two population groups. In all studies, similar protocols were adopted. These were approved by the Research and Ethics Committee of the University of Cape Town.
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    Sulfate but not thiosulfate reduces calculated and measured urinary ionized calcium and supersaturation: implications for the treatment of calcium renal stones
    (Public Library of Science, 2014) Rodgers, Allen; Gauvin, Daniel; Edeh, Samuel; Allie-Hamdulay, Shameez; Jackson, Graham; Lieske, John C
    BACKGROUND: Urinary sulfate (SO 4 2− ) and thiosulfate (S 2 O 3 2− ) can potentially bind with calcium and decrease kidney stone risk. We modeled the effects of these species on the concentration of ionized calcium (iCa) and on supersaturation (SS) of calcium oxalate (CaOx) and calcium phosphate (CaP), and measured their in vitro effects on iCa and the upper limit of stability (ULM) of these salts. METHODS: Urine data from 4 different types of stone patients were obtained from the Mayo Nephrology Clinic (Model 1). A second data set was obtained from healthy controls and hypercalciuric stone formers in the literature who had been treated with sodium thiosulfate (STS) (Model 2). The Joint Expert Speciation System (JESS) was used to calculate iCa and SS. In Model 1, these parameters were calculated as a function of sulfate and thiosulfate concentrations. In Model 2, data from pre- and post STS urines were analyzed. ULM and iCa were determined in human urine as a function of sulfate and thiosulfate concentrations. RESULTS: Calculated iCa and SS values for all calcium salts decreased with increasing sulfate concentration. Thiosulfate had no effect on these parameters. In Model 2, calculated iCa and CaOx SS increased after STS treatment, but CaP SS decreased, perhaps due to a decrease in pH after STS treatment. In confirmatory in vitro experiments supplemental sulfate, but not thiosulfate, significantly increased the calcium needed to achieve the ULM of CaP and tended to increase the oxalate needed to reach the ULM of CaOx. Sulfate also significantly decreased iCa in human urine, while thiosulfate had no effect. CONCLUSION: Increasing urinary sulfate could theoretically reduce CaOx and CaP stone risk. Although STS may reduce CaP stone risk by decreasing urinary pH, it might also paradoxically increase iCa and CaOx SS. As such, STS may not be a viable treatment option for stone disease.
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    The effects of calcium, magnesium and citrate health supplements on urinary risk factors for calcium oxalate kidney stone formation
    (2004) Allie-Hamdulay, Shameez; Rodgers, Allen
    [Pages missing] This thesis was undertaken to investigate the effects of various health supplements on the risk of calcium oxalate (CaOx) kidney stone formation. Four separate studies comprised the entire project. In the first study, a new approach was implemented to investigate the individual, additive and synergistic effects of calcium, magnesium and citrate health supplements on the urinary risk factors for CaOx kidney stone formation in eight healthy males. · While previous studies have examined the effects of individual preparations, few (if any) have addressed the issue of chemical interactions or synergism between different agents. The experimental design which was employed was a "Complete Latin Square Design" in which each subject was allocated to a randomized sequence of seven supplemental protocols in addition to the normal diet. These protocols comprised of calcium, magnesium and citrate supplements and combinations thereof. Supplementation lasted for 1 week. 24-hour urines were collected at baseline and during the final day of each supplemental protocol. The urine composition, relative supersaturation (RS), Tiselius risk index, metastable limit (MSL) and particle volume-size distributions were measured for each urine sample. The results showed that the activity of citrate-containing protocols in reducing several physicochemical risk factors for CaOx stone formation was superior to those containing calcium or magnesium alone and also that it behaves this way irrespective of whether the latter two components are present or not. The study also identified three interactions, viz. magnesium enhances citrate's ability to lower RS brushite (favourable synergistic interaction) and attenuates its ability to raise urinary pH (unfavourable synergistic interaction) and finally, calcium enhances citrate's ability to lower RS uric acid (additive effect). In the second study, the potential prophylactic and therapeutic properties of a South African product (CitroSoda: sodium citrate bicarbonate tartrate), previously untested in the management of CaOx urolithiasis, was investigated. 30 healthy males (MC), 30 male CaOx stone formers (MSF), 30 healthy females (FC) and 30 female CaOx stone formers (FSF) participated in the study. The experimental design which was implemented was a placebo controlled, randomized, "within-patient" design. All the subjects were required to provide two 24h urine collections prior to the commencement of the trial which were used as baseline samples. Twenty subjects in each group ingested CitroSoda and ten subjects V ~•~=•w~,-~,~~==w in each group ingested a blinded placebo. Supplementation lasted for 7 days. In addition to the baseline 24h urine samples, subjects provided 24h collections on day 7 (final day of supplementation) and on day 10 (3 days after supplementation was suspended). The urine composition, relative supersaturation (RS), Tiselius risk index, metastable limit (MSL), particle volume-size distribution and [ 14C]-oxalate deposition were measured for each urine sample. Scanning electron microscopy was also performed on selected samples. The results showed that CitroSoda favourably altered four biochemical risk factors in all four groups: pH and citrate excretion increased and the RS of uric acid and the RS of CaOx decreased. No unfavourable changes occurred in any of the risk factors. These results demonstrated that CitroSoda has the potential to be an effective preparation for the prophylactic and therapeutic management of CaOx urolithiasis. Since the question of whether there is a stone forming risk associated with the ingestion of calcium supplements with meals or between meals remains unanswered, the third study was undertaken under strictly controlled conditions, to investigate urinary oxalate excretion as a function of the time at which a calcium supplement is ingested relative to an oxalate-rich meal. 20 healthy males participated in the study in which six different protocols were investigated over a six-hour time period. Subjects provided a fasting overnight urine sample on the morning of trial and thereafter ingested a standardized oxalate-rich meal. In the first protocol no calcium supplement was administered; in the 2nd protocol the calcium supplement was given with the meal and in the 3rd , 4th , 5th and 6th protocol, the supplement was given 1 hr, 2hrs, 3hrs and 4hrs respectively after the meal. Subjects were required to provide urine samples at hourly intervals throughout the protocol, after which the urine composition and ion activity product of calcium oxalate (AP(CaOx) index) for each sample was calculated. The study demonstrated that calcium supplements taken 1 hour after an oxalate-rich meal produced the lowest total oxalate excretion over the 6-hour period following the ingestion of the oxalate-rich meal, relative to other protocols. The urinary calcium excretion was fairly steady in this protocol whereas for the other protocols, a dramatic surge was observed at some stage during the 6 hour test period. The AP(CaOx) index values supported the choice of this protocol as the optimum one because it displayed a level trend which was relatively lower (or equal) to that of the other protocols. In the final study, a speciation program (JESS) which is not well-known in urolithiasis research, was firstly used to compare RS outputs with those of the more familiar EQUIL2.