Immunocytochemical localization of Tamm-Horsfall protein in the kidneys of normal and nephrolithic rats

Studies using in vitro systems have indicated that Tamm-Horsfall protein (THP) can interact with calcium oxalate (CaOx) crystals during kidney stone formation. However, information regarding the nature of its participation in this process remains controversial and unclear. In order to better understand the putative interaction of THP and crystals in vivo, we compared the localization of THP in normal rats and in chronic and semi-acute rat models of nephrolithiasis. In these rats, CaOx crystal deposits were induced in the kidneys by administering ethylene glycol (EG) in drinking water. The formation of CaOx mono- and dihydrate aggregates in the urine was confirmed by scanning electron microscopy. Immunohistochemical localization, as well as protein A-gold labeling at the ultrastructural level, demonstrated that in addition to its normal distribution, THP specifically associated with the renal crystal deposits. The THP-containing, organic matrix-like material consisted of a fine, fibrillar meshwork surrounding individual crystals and their aggregates. In addition, THP also appeared in the papilla, where it is normally absent, concurrent with the appearance of crystal deposits in the kidneys. These observations indicate that in nephrolithic rats the normal localization of THP is altered. Such an alteration may indicate an important physiological event related to crystal aggregation and kidney stone formation.

Increased urinary excretion of lipids by patients with kidney stones

OBJECTIVE

To test the hypothesis that patients with calcific kidney stones (stone formers) excrete more lipids and cell membranes in their urine than do normal individuals.

PATIENTS, SUBJECTS AND METHODS

Lipids were isolated from the urine of patients with calcific stones (four women and six men, age range 28-69 years) and from normal subjects (three men and three women, age range 31-54 years). Different phospholipids, neutral lipids and glycolipids were identified using thin layer chromatography and individual lipids were characterized by several assays after scraping the spots from the plates, or by densitometry.

RESULTS

Stone formers excreted more lipids and acidic phospholipids than did normal individuals; the urinary excretion of glycolipid, cholesterol and cholesterol esters was also increased.

CONCLUSIONS

The greater excretion of lipids may reflect the increased turnover of cells in the tubular epithelium and sloughing of cells into the urine in response to a challenge by oxalate and calcium oxalate crystals. Acidic phospholipids from cellular membranes of the sloughed epithelial cells may be involved in crystal nucleation and retention within the kidneys and thus the initial development of stone nidus and the continued growth thereafter.

Identification of uronic-acid-rich protein as urinary bikunin, the light chain of inter-alpha-inhibitor

Uronic-acid-rich protein (UAP) is a urinary glycoprotein that inhibits calcium oxalate crystallization in vitro. It shows a structural similarity to bikunin, a component of inter-alpha-inhibitor (IalphaI) known for its inhibition of the action of many serine proteinases like trypsin and chymotrypsin. To clarify the relationship between these macromolecules, UAP, IalphaI, urinary bikunin, and plasma bikunin were purified and studied. Their calcium oxalate crystallization inhibitory activity was assayed before and after treatment with chondroitinase AC and pronase. Their molecular mass was determined by using SDS/PAGE before and after these treatments. Polyclonal bikunin antibody was used on Western blots for immunological identification. The partial amino acid sequence of UAP before and after chondroitinase treatment was determined. Also, the antitryptic activity of UAP was measured and compared to that of bikunin, which is responsible for the antiprotease activity of IalphaI. UAP exhibited a strong calcium oxalate crystallization inhibitory activity. IalphaI and both bikunins were less inhibitory. Chondroitinase AC had no effect on inhibitory activity of these proteins even when their molecular mass changed. However, after pronase treatment, the inhibitory activity of both bikunins and UAP was completely destroyed. The antitryptic activity of UAP was found to be 0.78 U/mg which is lower than that of bikunin which is about 1.9 U/mg. On Western blotting, bikunin antibody immunoreacted with UAP and both urinary and plasma bikunins. Partial amino acid sequence confirmed the identity of UAP as urinary bikunin.

Association of urinary macromolecules with calcium oxalate crystals induced in vitro in normal human and rat urine

This study was undertaken to identify proteins which are found associated with calcium oxalate crystals induced in vitro in normal human and rat urine. Crystallization was initiated by adding sodium oxalate individually to each urine sample without centrifugation and filtration. Crystals were collected and analyzed by scanning electron microscopy and X-ray diffraction. Crystal matrix proteins (CMPs) were obtained by demineralization of the crystals with ethylenediaminetetra-acetic acid (EDTA) and analyzed by western blotting technique for immunological identification. Crystals produced in human urine were found to be a mixture of calcium oxalate monohydrate (COM) and calcium oxalate dihydrate (COD) while those produced in rat urine were exclusively COD. CMPs extracted from crystals in human urine comprised, in addition to prothrombin-related proteins, osteopontin and albumin. However, CMPs extracted from crystals in rat urine contained only osteopontin and albumin. Prothrombin-related proteins were found only in trace amounts. In a separate experiment, rat urine samples were supplemented with COM before inducing crystallization. Similar results were observed showing that CMP contained osteopontin, albumin and trace amounts of prothrombin-related proteins. We conclude that several urinary macromolecules including not only prothrombin-related proteins, but also osteopontin and albumin, become associated with CaOx crystals. The incorporation of these proteins in growing stones is not only due to the presence of gamma-carboxyglutamic acid as it was suggested for prothrombin-related proteins, but may be due to other factors such as urinary chemistry, presence of glutamic and aspartic acid residues, and calcium-binding sites.

Localization of tamm-horsfall protein and osteopontin in a rat nephrolithiasis model

The possibility of more than one urinary protein being simultaneously associated with calcium oxalate (CaOx) crystallization in vivo was investigated by examining the localization of Tamm-Horsfall protein (THP) and osteopontin (Opn) in a rat model of nephrolithiasis. CaOx crystal deposits were induced in male Sprague-Dawley rats by feeding 0.75% ethylene glycol in drinking water. THP and Opn were localized on kidney sections by immunoperoxidase technique, using specific polyclonal antibodies. When only occasional crystal deposits were seen in the kidney, THP showed a similar to normal pattern of distribution, with positive staining in the thick ascending limbs of the loop of Henle. Opn was localized in some nephrons in the thin limb of loop of Henle and on the papillary surface in the calyceal fornix. In contrast, in samples with a significantly increased number of deposits in the kidneys, the staining for both THP and Opn was strikingly enhanced and altered, with positive staining around the crystals as well as abnormal localization in the papilla. Interestingly, the occurrence of Opn was, however, more consistent than that of THP. This is a first study showing that in this nephrolithiasis model, normal localization of THP and Opn is altered and they are closely and concurrently associated with crystal deposits in vivo.

Ultrastructural immunodetection of osteopontin and osteocalcin as major matrix components of renal calculi

The organic matrix of renal calculi has long been considered to influence the crystal growth that occurs in these pathological mineral deposits. Recent advances in characterizing individual organic moieties from mineralized tissues in general and the combined use of antibodies raised against these molecules with different immunocytochemical approaches have allowed their precise distribution to be visualized in a variety of normal and pathological mineralized tissues. The present ultrastructural study reports on the epithelial expression and extracellular localization of several noncollagenous proteins in rat and human kidney stones using high-resolution colloidal-gold immunocytochemistry. To this end, we have examined in an ethylene glycol-induced calcium oxalate model of urolithiasis in the rat, and in human kidney stones, the distribution of certain noncollagenous and plasma proteins known to accumulate in bone and other mineralized tissues that include osteopontin, osteocalcin, bone sialoprotein, albumin, and alpha 2HS-glycoprotein. Of these proteins, osteopontin (uropontin) and osteocalcin (or osteocalcin-related gene/protein) were prominent constituents of the calcium oxalate-associated crystal "ghosts" found in the nuclei, lamellae, and striations of the organic matrix of lumenal renal calculi in the rat and of small crystal ghosts found within epithelial cells. Immunocytochemical labeling for both proteins of the content of secretory granules in tubular epithelial cells from treated rats, together with labeling of a similarly textured organic material in the tubular lumen, provides evidence for cosecretion of osteopontin and osteocalcin by epithelial cells, their transit through the urinary filtrate, and ultimately their incorporation into growing renal calculi. In normal rat kidney, osteopontin was localized to the Golgi apparatus of thin loop of Henle cells. In human calcium oxalate monohydrate stones, osteopontin was similarly detected in the lamellae and striations of the organic matrix. Based on these data, it is proposed that during urolithiasis, secretion of osteopontin (uropontin) and osteocalcin (or osteocalcin-related gene/protein), and the subsequent incorporation of these proteins into kidney stone matrix, may influence the nucleation, growth processes, aggregation, and/or tubular adhesion of renal calculi in mammalian kidneys.

Alterations in MDCK and LLC-PK1 cells exposed to oxalate and calcium oxalate monohydrate crystals

Structural analysis of human kidney stones reveals the presence of cellular membranes and other cell fragments. Experimentally, calcium oxalate crystallization is facilitated when an exogenous nephrotoxin is given with ethylene glycol, thus providing cellular degradation products to act as heterogeneous nuclei. In this report, we tested whether oxalate alone could act as a cell toxin capable of producing damaged cells without the presence of an exogenous agent. Cultured LLC-PK1 and MDCK cells, when exposed to 1.0 mmol KOx, a concentration at the limit of metastability for calcium oxalate nucleation, were severely damaged as measured by specific lactate dehydrogenase (LDH) release in the spent media and by trypan blue exclusion. This effect was magnified by the addition of pre-formed calcium oxalate monohydrate crystals; the injury was significantly amplified when compared to exposure to oxalate alone. Scanning electron microscopy studies illustrated attachment of crystals to cells with loss of cell-to-cell and cell-to-substrate contact, as cells were released from the monolayer. In both oxalate and combined crystal-oxalate studies, more cells were released from the monolayer and exhibited considerably more damage when compared to controls. Oxalate, at the limit of metastability for calcium oxalate, is a cell toxin and can produce cellular degradation products. This effect is increased significantly by the addition of calcium oxalate monohydrate crystals.

Heterogeneous nucleation of calcium oxalate crystals in mammalian urine

It is generally recognized that calcium oxalate crystal formation in urine is induced by heterogeneous nucleation. However, there is no consensus as to the nature of the nucleation substrate. Evidence is provided in this paper that membranous cellular degradation products are the most likely candidates because they: (1) are ubiquitous in urine and urinary stones; (2) are found in close association with crystal deposits in the kidneys; and (3) can induce nucleation of crystals from a metastable solution of calcium oxalate in vitro and metastable urine in vivo.

Calcium oxalate crystal interaction with renal tubular epithelium, mechanism of crystal adhesion and its impact on stone development

The interaction between renal epithelial cells and calcium oxalate (CaOx) crystals and/or oxalate ions plays a critical role in the formation of urinary stones. Epithelial cells respond to hyperoxaluria and the presence of CaOx crystals in the kidneys by increased enzymuria and internalization of the crystals. Crystal cell interaction results in movement of crystals from the luminal to the basolateral side between the cells and the basement membrane. Once beneath the epithelium, crystals adhere to the basement membrane and become anchored inside the kidneys. Crystals anchored to basement membrane of the peripheral collecting duct aggregate with other crystals and move through an eroding epithelium to the papillary surface, furnishing an encrustation platform or a nidus for future development of a kidney stone. Thus interaction between renal epithelial cells and CaOx crystals and/or oxalate ions is an essential element in the development of urinary stone disease.

Characterization of uronic-acid-rich inhibitor of calcium oxalate crystallization isolated from rat urine

Human urine contains several macromolecules which inhibit calcium oxalate crystallization. Uronic-acid-rich protein (UAP), a glycoprotein with a molecular weight of approximately 35 kDa, is one such inhibitor. Here we report the characterization of UAP extracted from rat urine using three chromatographic steps including diethylaminoethanol (DEAE)-Sephacel, Sephacryl S-300 and Mono Q column and compare it with human UAP. The molecular weight of rat UAP (UAPr) is similar to that of human UAP (UAPh), being approximately 35 kDa as estimated by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Their amino acid compositions are identical, they contain a high percentage of aspartic and glutamic acids and they react positively in the carbazole reaction, suggesting that they contain uronic acid. The inhibitory activities of UAPh and UAPr were assayed on a calcium oxalate crystallization system in vitro using [45Ca]calcium chloride. Both exert a strong inhibition, suggesting that UAPr, like UAPh, plays an important role in preventing and reducing calcium oxalate crystallization in the urine. On Western blot analysis, both UAPh and UAPr immunoreact with inter-alpha-trypsin inhibitor (ITI) antibody. Nevertheless, using the Ouchterlony immunodiffusion technique, there was no precipitation line between ITI antibody and UAP. Therefore, we hypothesize that UAP is related to ITI and that they may have the same epitope but are not completely identical. We conclude that UAP belongs to the ITI superfamily of macromolecules which contribute to the regulation of the calcium oxalate crystallization process.

Articular chondrocalcinosis of the humeral head in greyhounds

Of 143 Greyhounds necropsied consecutively, 6 (4%) had chondrocalcinosis of the scapulohumeral joint; lesions were identified in 6 additional dogs. Lesions were seen exclusively in the humeral head, mainly in the plateau region. The lesions in the dogs of the initial group were unilateral, but 2 of the 6 additional dogs had bilateral lesions. Focal mineralization of articular cartilage appeared as a white raised nidus, sometimes surrounded by a translucent halo in the opaque cartilage. Circular, small translucent cartilage foci, with or without beginning mineralization, were adjacent to definitive chondrocalcinosis lesions. Chondrocyte necrosis and matrix degradation were considered to antedate appearance of matrical mineral granules; mineralization of the cartilage was considered a secondary process, but not necessarily an epiphenomenon. Scanning electron microscopy indicated that the chondrocalcinosis lesion was composed of deposits of irregularly fused stone material that, in scanning and transmission electron micrographs, was composed of irregular spheroids, 0.05 to 0.5 micron in diameter. The spheroids contained poorly formed needle-like crystals of apatite. Sparse transformation of the mineral phase into hydroxyapatite was considered to be attributable to a biological mechanism that inhibited phase transition. Cartilage degeneration and chondrocalcinosis of the plateau region of the humeral head appear to be unique lesions that develop in young Greyhounds. It is possible that these lesions are the result of the biomechanical stress of training and racing.

Experimental calcium oxalate nephrolithiasis and the formation of human urinary stones

Calcium oxalate nephrolithiasis in rats requires induction of hyperoxaluria which results in increased urinary calcium oxalate supersaturation. As a result of low to mild chronic hyperoxaluria, calcium oxalate crystals deposit first in the papillary collecting ducts. Crystal deposition in the kidneys is preceded by calcium oxalate crystalluria and starts with the retention of aggregated calcium oxalate crystals in the renal tubules. Retained crystals move from the tubules to the interstitium, and in the process, become anchored to the tubular basement membrane. Crystal aggregates present in the superficial peripheral collecting ducts of the renal papillae ulcerate through to the papillary surface and grow into the stones.

Deposition of calcium phosphate and calcium oxalate crystals in the kidneys

Calcium phosphate (CaP) and calcium oxalate (CaOx) are the two most common crystalline constituents of human urinary stones. Calcium phosphate is often recognized as the nucleator of CaOx crystals, but the relationship between the two is not yet clearly understood. Using rat models of nephrolithiasis, we studied the role of CaP in renal deposition of CaOx. Calcium oxalate nephrolithiasis was brought about by inducing hyperoxaluria, while CaP CaOx nephrolithiasis was produced by dietary manipulation. Under similar urinary CaOx or CaP supersaturations, male rats were prone to form CaOx deposits while female rats were susceptible to produce CaP deposits in their kidneys. Crystal deposition in females was generally localized to the corticomedullary junction and in males to the renal papillae. The results indicate that gender plays an important role in the type and location of crystal deposition in the kidneys. In addition, deposition of CaP does not appear to influence the deposition of CaOx.

Calcium oxalate nephrolithiasis, a free or fixed particle disease

The chances of stone formation occurring through a free particle mechanism were calculated using the approach of Finlayson and Reid [1]. For these calculations we used new data on nephron dimensions, supersaturation and crystal growth rates in urine, and also incorporated the size increasing effect of crystal agglomeration. The calculations were performed assuming different levels of oxalate excretion, simulating the diurnal variation and acute hyperoxaluria following a dietary load. In addition urinary flow conditions were varied according to changes in daily urinary volume. It is shown that during the normal transit time of urine through the nephron, particles can obtain a size big enough to be retained in the nephron. This is mainly due to the size-increasing effect of the agglomeration process. The precipitable amount of oxalate present is not limiting for the maximum attainable particle size. However, acute increases in oxalate excretion do pose a risk because supersaturation is reached earlier in the nephron and consequently the crystal particles are allowed more time to increase in size. In conclusion, the present calculations demonstrate that during the normal transit time through the kidney, crystalline particles can be formed which are large enough to be retained because of their size and thus form the nidus of a stone. The highest risk is encountered at the end of those collecting ducts where crystals formed in nephrons with a long loop of Henle meet and agglomerate.

Madin-Darby canine kidney cells are injured by exposure to oxalate and to calcium oxalate crystals

The reaction of Madin-Darby canine kidney cells (MDCK) to potassium oxalate (KOx), calcium oxalate monohydrate (COM) crystals, or a combination of the two was studied. The most noticeable effect of exposure of the cells to either KOx or COM crystals was loss of cells from the monolayer ranging from 20% to 30%, depending upon the particular treatment. Cellular enzyme values in the media were elevated significantly by 12 h of exposure, although in specific instances, elevated levels occurred at earlier time periods. As regards the monolayer, trypan blue exclusion was decreased significantly, although amounting to only a 4-5% reduction. Specific tritiated release occurred at 4 and 12 h after exposure to KOx and at 12 h after exposure to crystals. Structurally, COM-cell interactions were complex and extensive endocytosis was noted. Cells were released from culture either as cell-crystal complexes or from the intercellular spaces after exocytosis. When treatments were combined the effects were only slightly additive, but the two treatments potentiated each other: all media enzyme levels (with one exception) were elevated at 2 h, tritiated adenine release was present at 4 h, and there was more extensive cell loss from the culture monolayer. These data suggest that both KOx and COM crystals damage MDCK cells when applied alone, and in concert they act synergistically.

Early child health in Lahore, Pakistan: VIII. Microbiology

The causative agents of acute diarrhoea were investigated in children under the age of five years from 1985-1991 in three socio-economically different areas in Lahore, Pakistan. The aim was to determine the frequencies of the most common enteropathogens in faeces. The total isolation rate was 73.4%; two thirds (53.5%) were of bacterial and one third (19.9%) of viral origin. ETEC-LT (23.4%), Rota virus (19.9%), EPEC (15%) and Campylobacter (12%) were the single most frequent pathogens in all age groups and areas of living. The positivity of Campylobacter increased from 1.6% to 12% after the change of isolation technique. Shigella was isolated significantly (p > 0.001) more in children over than under one year of age. The incidence of bacterial infections was high during all seasons, while in certain years Rota virus was relatively low in the summer compared to the cooler months. The prevalence of ETEC-LT diarrhoea was higher in the periurban slum as compared to the village and the urban slum. The study is the first of its kind in Pakistan, and the results are similar to other comparable studies. It is thus possible to establish a well functioning and reliable microbiological laboratory in developing countries in a setting with restricted trained personnel and material resources.

Early child health in Lahore, Pakistan: I. Study design

In this paper, details are given of a community based follow up study of four areas: a village, a periurban slum, an urban slum and an upper middle class control group living in and around Lahore, Pakistan. The aim was to characterize the determinants of child health in a rapidly urbanizing community. The study was undertaken in two steps. An initial cross-sectional survey collecting socio-economic and demographic background information was carried out between March to August 1984. This was followed by a longitudinal study of 1476 infants representing the outcome of the pregnancies registered continuously between September 1984 to March 1987 among the 3242 families in the study. These infants were followed monthly from birth to 3 years of age and thereafter less frequently. In this communication we describe the study design, the study population, the organization and the research methodology used, including the reasons for drop outs from birth to 24 months of age. The internal consistency of the data is also presented. After the initial examination of the newborns within between 0-7 days of birth, the infants were visited monthly for 24 months making a total of 20911 examinations. At 24 months of age 70% of the infants were still in the study, 11% had died before reaching this age, 13% had moved from the area and 6% had refused to participate in the study. The economic, conditions, social structure, and the quality of life were found, not surprisingly, to vary significantly among the four areas. This community-based project provides new, critical and reliable information for local health planners. The study highlights the importance of the development of a useful model for research collaboration between institutions in developed and developing countries.

Early child health in Lahore, Pakistan: IX. Perinatal events

In Pakistan there are a number of acute problems related to maternal and infant health in the perinatal period. There is also lack of reliable data needed for the formulation of action strategies. To provide a database 1490 women have been followed from the 5th month of pregnancy in four different areas at various levels of urbanization and socio-economic development. After adjusting for gestational age, the proportion of newborns with weight for length < -2SDS in relation to the Swedish National Standard was 12-31% for boys and 12-25% for girls, the figure being highest in the most deprived area. Preterm birth was infrequent compared with IUGR. The overall prevalence rate of birth defects was 21% out of which 8% were severe defects. The overall perinatal mortality rate was 56/1000 births, with rates of 60, 75, 36 and 33/1000 births for the village, periurban slum, urban slum and the upper middle class. Two thirds of the deaths were related to either a continuation of intrauterine disturbances or severe congenital defects incompatible with life. One third of the deaths were due to infection; mostly diarrhoea, clinical sepsis and ARI. Neonatal mortality was significantly related to birth length (< -2SDS, odds ratio 5.5) and length of gestation (< 37 weeks, odds ratio 5.6) and was to a lesser extent related to weight (< -2SDS, odds ratio 2.0) and weight for length (< -2SDS, odds ratio 1.3). Forty percent of the mothers had weight for height below -2SDS, 23-35% had height < -2SDS. Forty percent of mothers from a subset within the cohort had a hemoglobin < 10 gm/dl and 20% showed signs of pre-eclampsia. This presentation raises the issue of expanding the current Child Survival Programs into the perinatal period as well.

Early child health in Lahore, Pakistan: X. Mortality

Mortality during the first two years of life among 1476 Pakistani infants born between September 1984 and March 1987 is described according to age, causes of death, area of living, season of the year and sex. The mortality rate (deaths under two years/1000 live births) projected over the whole population of Pakistan was 127 and under one year 114. During the first two years of life, the mortality rate was 133/1000 in the village, 159 in the periurban slum, 107 in the urban slum and 17 in the upper middle class group. In the latter group all deaths had occurred within 72 hours after birth. The overall major causes of death were acute and prolonged diarrhoea (36%), asphyxia neonatorum (13%), respiratory infections (13%), septicaemia (11%) and tetanus (9%). A clear age dependency was noted with 14% of deaths occurring during the first 24 hours of life (asphyxia neonatorum in 86%), and 57% dying within the first 28 days of life. In the later age groups, infections were mainly responsible for 82% of total deaths. Early mortality was therefore extremely high in the poorer areas studied and the cause of death was highly age dependent. Any interventions for reducing mortality must therefore be directed towards better antenatal care and safe delivery and postnatally, towards preventing infections, especially during the first six months of life.

Early child health in Lahore, Pakistan: V. Feeding patterns

The feeding practices of children (n = 1476) from birth to 24 months, as determined in a longitudinal study, in Lahore, Pakistan, are presented. Four socioeconomic groups at various levels of urbanization were included; a village, periurban slum, urban slum and an upper middle class. Initiation of breastfeeding was delayed in all the neonates. Sixty-five percent of the periurban slum mothers and 45% of the village mothers had not started breastfeeding at 48 hours after the birth of the infant. Prelacteal feedings, especially of herb water and honey, were the norm. Breastfeeding was highly prevalent. Eighty-seven to 98% of the infants in all the areas were breastfed at one month of age. Exclusive breastfeeding was rare, with 9% at one month, declining rapidly with age and being highly influenced by season. Partial breastfeeding was the most common mode of feeding. Water in addition to human milk was given by 45-73% of the mothers living in the urban slum, village and periurban slum at one month of age. Fresh animal milk and/or commercial formula was already being given at 1 month by 22-64% of the mothers in all areas. Commercial formula was the preferred food in the upper middle class, while in the other three areas it was rare and fresh animal milk was mainly used. More than 50% of the mothers in the village and in the periurban slum gave diluted animal milk even beyond the age of 10-15 months. In the upper middle class 50% of the infants were fed semisolids at the age of four months, while in the village, the periurban and the urban slum at 6 months of age only 10%, 12% and 47% of the infants received semisolids. The results of this study indicate that breastfeeding was highly prevalent in the three poorest areas. However, in all the areas initiation of breastfeeding was delayed and prelacteal feeding was the norm. Exclusive breastfeeding was rare, feeding bottles were used by 82-100% of the mothers to feed supplements and human milk substitutes, in the four areas.

Role of organic matrix in urinary stone formation: an ultrastructural study of crystal matrix interface of calcium oxalate monohydrate stones

Human calcium oxalate monohydrate (COM) urinary stones were decalcified by treatment with a mixture of ethylenediaminetetraacetic acid (EDTA) solution and Karnovsky's fixative after embedding in bactoagar. Decalcified stones were examined by light microscopy, and also by scanning and transmission electron microscopy. Stones had distinct nuclei that were occupied by amorphous or apatitic calcium phosphate or aggregates of spherulitic COM crystals. EDTA insoluble matrix was ubiquitous in stones and consisted largely of finely matted fibrous material. It was organized in concentric laminations in the peripheral area of the stone but appeared highly disorganized in the stone center. Crystals were replaced by crystal ghosts. Organic matrix was present both inside the crystals and in the intercrystalline spaces. The study indicates a very close association between crystals and organic matrix. The relationship appears to begin early in crystal formation and persists throughout the formative and growth phases of the urinary stones.

Magnesium oxide administration and prevention of calcium oxalate nephrolithiasis

We studied the effect of oral administration of magnesium oxide (MgO) on calcium oxalate (CaOx) nephrolithiasis in rats. Nephrolithiasis was induced by administration of 1.0% ethylene glycol (EG) in drinking water. Magnesium oxide was given mixed with food at 500 mg./100 g. rat chow. Dispensation of MgO resulted in a significant increase of urinary pH and a modest increase in urinary excretion of citrate. Urinary excretion of oxalate started to decline by day 14 and was significantly reduced on days 21 and 28. All rats receiving EG displayed crystalluria. From the group receiving EG only, 3 of 4 rats sacrificed on day 15 and 2 of 4 rats sacrificed on day 29 had CaOx crystal deposits in their kidneys. None of the 8 rats who received both EG and MgO had CaOx nephrolithiasis. Thus our findings indicate that dispensation of magnesium as MgO can be beneficial against calcium oxalate nephrolithiasis.