1. Studies in vitro showed that sodium pentosan polysulphate (SPP) is an active inhibitor of calcium oxalate crystal growth and agglomeration and that it acts by increasing the negative zeta potential on the surface of calcium oxalate crystals. 2. Oral administration to human subjects resulted in an increase in the negative zeta potential, which is consistent with an increase in the polyanionic inhibitory activity of urine. SPP may offer a novel approach to the medical management of recurrent calcium oxalate stone disease.

1. Radio-calcium absorption, plasma 25-hydroxyvitamin D [25-(OH)D] and 1,25-dihydroxyvitamin D [1,25-(OH) 2 D] concentrations were measured in 19 elderly women with, and 21 without, vertebral fractures, before and after treatment with 25-hydroxyvitamin D 3 [25-(OH)D 3 ], to establish whether malabsorption of calcium in elderly women with vertebral fractures has a cause different from that in elderly women without vertebral fractures. 2. Malabsorption of calcium and low plasma 25-(OH)D and 1,25-(OH) 2 D concentrations were common in both groups of women but there was no significant difference in these variables between the two groups. 3. After treatment with 40 μg of 25-(OH)D 3 daily for 7 days, there was a significant increase in plasma 25-(OH)D and 1,25-(OH) 2 D in both groups of women, but radio-calcium absorption increased significantly only in the group without vertebral fractures. 4. Elderly women with vertebral fractures have malabsorption of calcium which is resistant to the action of vitamin D metabolites at concentrations which correct calcium malabsorption in elderly women without vertebral fractures.

1. Studies were carried out on six normal male subjects to determine the short-term effect of increasing the dietary consumption of animal protein on the urinary risk factors for stone-formation, namely, volume, pH, calcium, oxalate, uric acid and glycosaminoglycans. 2. An increase of 34 g/day of animal protein in the diet significantly increased urinary calcium (23%) and oxalate (24%). Total urinary nitrogen increased by an average of 368 mmol/day. The accompanying increase in dietary purine (11 mmol of purine nitrogen/day) caused a 48% increase in the excretion of uric acid. 3. The overall relative probability of forming stones, calculated from a combination of the risk factors, was markedly increased (250%) throughout the period of high animal protein ingestion.

1. A retrospective cross-sectional study was carried out on data derived from single 24 h urine collections from 246 male idiopathic calcium stone-formers. 2. The daily urine volume and pH and the excretions of calcium, oxalate, phosphate, creatinine and magnesium were related to the time of year when the urine was collected, and the saturation of urine with calcium oxalate and octocalcium phosphate calculated for each month. 3. There were significant seasonal variations in the urinary excretion of calcium and oxalate, each showing a maximum during the summer months and a minimum in the winter. There was no significant seasonal variation in urinary pH, volume, creatinine, phosphate or magnesium. 4. There was a significant increase in the saturation of urine with calcium oxalate and a trend towards higher saturation levels of octo-calcium phosphate in the summer. These changes were dependent only on the seasonal variation in urinary calcium and oxalate and not on urine volume. 5. A retrospective study of the seasonal incidence of stone episodes among these 246 stone-formers showed that the rate of stone passage per month was 50% higher in the summer than in the winter. There was no significant seasonal variation in the incidence of stones removed surgically.

1. The volume, size and type of calcium oxalate crystals excreted in the urine of a group of patients with recurrent ‘idiopathic’ stones were studied on a controlled basal diet, after an oral supplement of sodium oxalate and after oral administration of ethane-1-hydroxy-1,1-diphosphonate (EHDP) for 4 weeks. 2. Before administration of EHDP the stone-formers passed the large crystals and aggregates of calcium oxalate dihydrate characteristic of recurrent calcium oxalate stone-formers. For the same level of urine saturation and crystalluria EHDP caused a significant reduction in the proportion of large crystals and aggregates excreted. Studies by light-microscopy confirmed that EHDP caused a striking change in the size and habit of calcium oxalate crystals in some but not all of the urine samples examined. 3. The decrease in average crystal size during the administration of EHDP was attributed to the observed increase in the ability of urine to inhibit the growth and aggregation of calcium oxalate crystals as measured by a growth system in vitro. 4. The possible use of EHDP as a therapeutic agent in the treatment of calcium oxalate stone-formation is discussed.

1. Bovine parathyroid hormone at a concentration of 1 unit/ml caused an immediate transient uptake of calcium from the bathing medium by 5-day-old mouse calvaria in tissue culture. 2. The uptake of calcium by bone was followed by the release of calcium into the medium over the subsequent 3–4 h. 3. The results support the conclusion that the primary action of the hormone on calcium transport in bone is to cause an increase in the intracellular concentration of calcium before producing the characteristic release of calcium from bone.

1. The particle size distributions of calcium oxalate crystals were measured at 37°C in fresh urine from recurrent, idiopathic stone-formers and their controls under the same conditions of dietary and fluid intake. The crystals excreted by the controls were small and belonged to a unimodal distribution, whereas those excreted by the stone-formers belonged to a distribution which contained a second peak of much larger particles. The proportion of large crystals in the urines of the stone-formers was significantly higher than in the urines of the controls. 2. The difference in the proportion of large particles passed by the two groups was accentuated by adding a small quantity of sodium oxalate to their diets. Whereas the controls continued to excrete only small crystals of calcium oxalate, the stone-formers passed most of their crystals as large particles. 3. Further investigations showed that the urines of the controls contained a potent inhibitor of the growth and aggregation of calcium oxalate crystals in vitro and that the inhibitor was deficient in the urines of the recurrent stone-formers. 4. It is suggested that the inhibitor in normal urine may allow calcium oxalate to be passed harmlessly in the form of small particles, whereas the lower inhibitory activity in the urines of the recurrent stone-formers is insufficient to prevent the growth of the primary crystals into the large aggregates seen in these urines. By blocking the formation of abnormally large crystals and aggregates the inhibitor may therefore play an important role in preventing crystalluria leading to stone formation.

1. The degree of saturation with calcium oxalate has been determined in fresh urine samples from six patients with recurrent calcium oxalate-containing renal stones and six normal control subjects who were studied under the same conditions of diet and fluid intake. 2. The degree of saturation of urine with calcium oxalate was significantly higher in the group of stone-formers than in the control series and more often exceeded the amount needed for spontaneous crystallization of calcium oxalate (formation product). This was accounted for by the higher concentration of calcium and oxalate in the urine of the stone-formers. 3. Crystals of calcium oxalate were observed in all freshly examined urines in which the formation product of calcium oxalate was exceeded. Since the formation product of calcium oxalate was exceeded more often in the urines of stone-formers than in the urines of the control subjects, this accounted for the greater calcium oxalate crystalluria of the stone-formers. 4. Addition of a small quantity of sodium oxalate to the basal diets of the two groups resulted in a greater increase in the urine saturation and calcium oxalate crystalluria of the stone-formers, thus accentuating the difference observed between the two groups when they were given the basal diet. 5. Calcium oxalate crystalluria was related quantitatively to the degree of over-saturation of urine with calcium oxalate, although uric acid solubility may play a small role at low pH values. 6. The results are consistent with a ‘hyperexcretion—crystallization’ mechanism of stone formation.

1. Variations with age in body weight, urine volume and calcium and creatinine excretion were determined in 246 normal subjects and 305 patients with calcium-containing renal stones. 2. Body weight, urine volume and creatinine excretion increased with age to a maximum in the third decade in both male and female controls and stone-formers. Thereafter body weight and urine volume did not change appreciably but creatinine excretion decreased. 3. In normal subjects the daily excretion of calcium and calcium concentration increased in the first two decades and remained relatively constant thereafter until the eighth decade when they decreased. The calcium/creatinine ratio was high in the first decade and fell during the second and third decades. Thereafter it remained relatively constant in men until the eighth decade when it fell. In women, however, there was a second rise in the fifth and sixth decades. The calcium/body weight ratio remained relatively constant with age until the eighth decade, when it fell. 4. Patients with renal calculus showed similar variations in calcium excretion with age. The mean values, however they were expressed, were higher than those in normal subjects of the same age and sex. 5. The daily excretion of calcium was higher in men than women, whether normal subjects or stone-formers. This difference was abolished when calcium excretion was related to body weight and reversed when excretion was related to creatinine. 6. Comparison of the present data with previous data from the same population indicated that the mean daily excretion of calcium by both normal subjects and patients with renal calculi has increased during the last decade. 7. The significance of these observations in relation to calcium homeostasis and renal calculus formation is discussed.