Regulation of glutamine metabolism in vitro by bicarbonate ion and pH.

The effect of variations of medium pH and bicarbonate concentration on glutamine oxidation was studied in slices and mitochondria from dog renal cortex. Decreasing pH and bicarbonate concentration increased the rate of oxidation of glutamine-U-(14)C to (14)CO(2) in both slices and mitochondria, an effect comparable to the acute stimulation of glutamine utilization produced by metabolic acidosis. Decreases in the concentration of glutamate and alpha-ketoglutarate, which accompany metabolic acidosis in the intact animal, also occurred in tissue slices when pH and [HCO(3) (-)] were lowered; decrease in alpha-ketoglutarate but not in glutamate content occurred in mitochondria under these conditions. Study of independent variations of medium pH and [HCO(3) (-)] showed that simultaneous changes in both pH and [HCO(3) (-)] produced a greater effect on glutamine metabolism than did change in either of these parameters alone. The rate of glutamine oxidation was also compared in tissue preparations from pairs of litter-mate dogs with chronic metabolic acidosis and alkalosis. No significant difference in the rate of glutamine oxidation was present in mitochondria from the two sets of animals. Slices from animals with chronic metabolic acidosis consistently oxidized glutamine at a more rapid rate than slices from alkalotic dogs both at high and at low concentrations of bicarbonate in the medium. We believe this difference is a result of the same mechanism which leads to the delayed increase in ammonium excretion during induction of metabolic acidosis. The close parallel between the effects demonstrated here and the changes in ammonium production and glutamine utilization in the intact animal with metabolic acidosis suggest that the observed in vitro changes accurately represent the operation of the physiologic mechanism by which acid-base changes regulate ammonium excretion. The similarity between the changes in glutamine oxidation observed in this study and those described previously for citrate suggests that one control mechanism affects the metabolism of both citrate and glutamine. Thus, we believe that the increase in citrate clearance in metabolic alkalosis and the increase in glutamine utilization and ammonium production in metabolic acidosis reflect the operation of the same underlying biochemical mechanism. This mechanism permits changes in pH and [HCO(3) (-)] in the cellular environment to regulate the rate of mitochondrial uptake and oxidation of several physiologically important substrates.

Bone crystal maturation in renal osteodystrophy in humans.

Calcium, phosphorus, sodium, carbonate, magnesium, and hydroxyproline were measured in iliaccrest biopsies of 22 normal volunteers and 24 selected patients with renal osteodystrophy. Histologic classification revealed that 10 were mildly abnormal, 8 osteomalacic, and 6 osteofibrotic. Bone density measurements were performed on an additional 12 normal, 11 mildly abnormal, 6 osteomalacic, and 10 osteofibrotic subjects. The results revealed an increase in magnesium and adecrease in carbonate apparent in the minimal and osteomalacic lesions and a much greater change in osteofibrosis. The bone density was decreased in patients with osteofibrosis. These observations would appear to be explained by postulation of an impairment of the normal maturational process of bone whereby there is an increase in amorphous calcium phosphate and a decrease in apatite crystal. The data suggest that the maturational defect is present as soon as any abnormality can be identified histologically, is present to the same degree in osteomalacia, and is most severe in osteofibrosis. In comparison of two sets of six patients matched for age and duration of dialysis, neither acidosis nor vitamin D therapy appeared to influence the severity of the maturational defect.

Inert gas analysis of ventilation-perfusion matching during hemodialysis.

The mechanism of hypoxemia during hemodialysis was investigated by the multiple inert gas elimination technique in anesthetized, paralyzed, mechanically ventilated dogs. Profound leukopenia occurred in the first hour of a 2-h hemodialysis with a cuprophan membrane and dialysate that contained acetate. Arterial partial pressure of O2 and CO2 and oxygen consumption remained unchanged during dialysis. Pulmonary carbon dioxide elimination and lung respiratory exchange ratio decreased with the initiation of dialysis, remained depressed throughout the duration of dialysis, and returned to predialysis levels after the cessation of dialysis. Cardiac output diminished during dialysis but did not return to base-line levels after dialysis. Multiple indices calculated from inert gas analysis revealed no ventilation-perfusion mismatching during dialysis. The shunt and perfusion to regions of low alveolar ventilation-to-perfusion ratio (VA/Q) were unchanged during dialysis. There was no change in the mean or standard deviation of the profile of the percentage of total perfusion to regions of the lung that had VA/Q near 1.0; nor was there any increase in the directly calculated arterial-alveolar partial pressure differences for the inert gases during dialysis. Dead space became mildly elevated during dialysis. These results show that during dialysis with controlled ventilation there is no ventilation-perfusion mismatching that leads to hypoxemia. During spontaneous ventilation any hypoxemia must occur due to hypoventilation secondary to the CO2 exchange by the dialyzer and subsequent reduction in pulmonary CO2 exchange.

Aluminum-associated bone disease in chronic renal failure: high prevalence in a long-term dialysis population.

Twenty-seven asymptomatic patients treated with hemodialysis longer than 8 years (mean 12.9 +/- 3.1 years) underwent bone biopsy to determine the prevalence of aluminum-associated bone disease. None had excess aluminum exposure from the dialysate. Ten patients (37%) had aluminum-associated bone disease as defined by a bone formation rate (BFR) below normal in the presence of stainable bone aluminum that covered more than 25% of the trabecular surface. The predominant type of bone histology in this group was the aplastic lesion characterized by low bone turnover, a decreased number of osteoblasts, and lack of excess unmineralized osteoid. Osteoblastic osteoid was highly correlated with stainable surface bone aluminum (r = -.82, p less than .001). Among the dynamic bone parameters, the double-tetracycline labeled surface was a more sensitive indicator of impaired bone function than was the bone apposition rate (BAR), since half of the patients with aluminum-associated bone disease had a normal BAR. In all of the biopsies the extent of double-labeled surfaces was inversely proportional to the amount of stainable aluminum on the bone surface (r = -.71, p less than .001), whereas stainable bone aluminum did not correlate with BAR. In seven of the patients with aluminum-associated bone disease, amino-terminal PTH levels were in the normal range while only one patient had a normal plasma mid-region PTH. PTH correlated directly with osteoblastic osteoid, BFR, and double-labeled surfaces. These results indicate that long-term oral aluminum intake in hemodialysis patients results in a high prevalence of aluminum-associated bone disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Bone histomorphometry of renal osteodystrophy in diabetic patients.

Bone biopsies and plasma parathyroid hormone (PTH) from 27 diabetic dialysis patients were compared to biopsies and PTH levels from matched patients without diabetes to determine if PTH has a role in preserving bone mass in diabetic renal osteodystrophy. Significantly lower values were present in the diabetic group for mineralized bone area (p less than 0.003), osteoblastic osteoid (p less than 0.01), resorptive surface (p less than 0.001), fibrosis (p less than 0.005), bone apposition rate (p less than 0.01), bone formation rate (BMU level) (p less than 0.04), and plasma PTH (p less than 0.05). Bone-surface aluminum was higher in the diabetic group (44 +/- 5% vs. 20 +/- 5%, p less than 0.005). Linear regression analysis revealed significant positive correlations of mineralized bone area with time on dialysis, bone formation rate, bone resorption, and PTH only in the group without diabetes. While both groups had significant positive correlations of PTH with osteoblastic osteoid and bone resorption, only in the nondiabetic group was there a positive correlation of PTH with bone apposition and bone formation rate (BMU level), observations suggesting that the lower bone formation in the diabetic patients may have arisen in part from a failure of PTH to promote bone mineralization. We conclude that relatively low PTH levels and high bone aluminum in diabetic patients with chronic renal failure may be responsible in part for low bone mass when compared to uremic patients without diabetes.

Bone disease in burn patients.

Burn patients are at risk for bone disease due to aluminum (Al) exposure from use of antacids and albumin, partial immobilization, and increased production of endogenous glucocorticoids. Moreover, severely burned children are growth impaired up to 3 years after the burn. To determine the extent of bone disease, we studied nine men and three women, ages 18-41 years, with greater than 50% body surface area burn. Seven patients underwent iliac crest bone biopsy following double tetracycline labeling, one additional patient expired after a single label, and three others had postmortem specimens obtained for quantitative Al only. Serial serum and urine samples were obtained weekly until biopsy or death. All biopsied patients had reduced bone formation and osteoid area, surface, and width, with mineral apposition rate, osteoblast surface, and osteoclast number with normal eroded surfaces compared to age- and sex-matched normal ambulatory volunteers. Burn patients also had reduced bone formation, mineral apposition rate, osteoid area, and surface compared to age-matched volunteers at short-term bed rest. Serum levels of osteocalcin were low. Most patients had mild hypercalcemia but only a third had hypercalciuria. All patients had elevated Al in blood or urine; urine Al correlated inversely with serum osteocalcin. In 60% significant bone Al was detectable by stain or quantitation. Our data are compatible with burn patients having markedly reduced bone turnover. Al loading, partial immobilization, endogenous corticosteroids, and cytokine production may be among the etiologic factors.

Adipose tissue lipoprotein lipase in chronic hemodialysis: role in plasma triglyceride metabolism.

The role of adipose tissue lipoprotein lipase (LPL) in the pathogenesis of hypertriglyceridemia in uremic patients receiving maintenance hemodialysis was evaluated. The fasting level of adipose tissue LPL activity was reduced below normal (3.4 +/- 2.5 microU/106 cells; n = 23; mean +/- SD) in hypertriglyceridemic dialysis patients (1.5 +/- 0.8; P less than 0.01; n = 15) and did not differ from normal in normotriglyceridemic dialysis patients (2.5 +/- 2.4; P = NS; n = 13). The enzyme activity increased as a function of relative body weight in normotriglyceridemic hemodialysis patients (r = 0.21; P less than 0.05) but not in the hypertriglyceridemic group (r = 0.21; P = NS). There was an abnormal response of LPL to feeding in the hypertriglyceridemic dialysis patients. The postprandial level of LPL was significantly lower in hypertriglyceridemic dialysis patients (2.2 +/- 1.0; n = 9) than in normotriglyceridemic dialysis patients (3.9 +/- 1.9; P less than 0.05; n = 10) or normal controls (4.8 +/- 1.8; P less than 0.01; n = 12). Whereas the postprandial change in LPL was inversely related to the fasting enzyme activity in normotriglyceridemic dialysis patients (r = 0.74; P less than 0.02; n = 10) and in normal controls (r = 0.58; P less than 0.05; n = 12), no such relationship existed in hypertriglyceridemic dialysis patients (r = 0.17; P = NS; n = 9). Furthermore, fasting plasma triglyceride levels in the entire group of dialysis patients were a function of the postprandial level of LPL activity (rs = 0.574; P less than 0.02; n = 19). Since the level of LPL 1) is below normal in both the fasted and fed state in the hypertriglyceridemic hemodialysis patients, 2) is normal in both the fasted and fed state in the normotriglyceridemic hemodialysis patients, and 3) in the fed state is inversely correlated with the fasting plasma triglyceride concentration in the entire group of hemodialysis patients, it is proposed that adipose tissue LPL plays a role in the etiology of hypertriglyceridemia in hemodialysis patients.

Serum immunoreactive parathyroid hormone and 25-hydroxyvitamin D in patients with uremic bone diseases.

Bone histologic parameters and serum iPTH and 25-OHD were measured in 20 patients with end-stage renal failure treated with hemodialysis. By bone histologic criteria, the patients were divided into three groups: mild, osteomalacic, and fibrotic. The increase in serum iPTH was much greater in the fibrotic group than in the mild or osteomalacic groups. In the uremic patients as a group, there were significant correlations between serum iPTH and both percent marrow fibrosis and percent resorbing surface. In the mild and fibrotic groups together, serum iPTH was also correlated with percent forming surface. This and other findings suggested that most of the bone changes in the mild and fibrotic groups could be explained by excess PTH. The difference in bone changes and in serum iPTH between the mild and fibrotic groups could be related to our eariler findings that duration of renal disease was much greater in the fibrotic than in the mild group. The lowest increment in serum iPTH was found in the osteomalacic group. In this group, percent resorbing surface was not increased and there was only a slight increase in marrow fibrosis. Thus in all three groups, serum iPTH appeared to reflect parathyroid status. The cause of the elevated serum iPTH and for the intergroup differences was not apparent inasmuch as serum calcium was normal in all three groups. Serum 25-OHD was significantly elevated in the osteomalacic and fibrotic groups. Because none of our patients had received preparations containing vitamin D, the elevated serum 25-OHD in the osteomalacic and fibrotic groups is consistent with altered vitamin D metabolism in these two groups. There was a direct relationship between percent osteroid area and serum 25-OHD. However, whether or not altered vitamin D metabolism contributed to the mineralization defect in uremic bone disease could not be established.

Osteomalacia and aplastic bone disease in aluminum-related osteodystrophy.

The bone histology in patients with chronic renal failure and aluminum-related bone disease does not always show the excess accumulation of unmineralized osteoid (matrix) characteristic of osteomalacia. Frequently, bone aluminum accumulation is associated with normal or reduced amounts of unmineralized osteoid and low bone formation and is referred to as aplastic bone disease. In this study, we compared static and dynamic bone histomorphometric parameters and plasma PTH and aluminum levels in 12 patients with osteomalacia and 18 patients with aplastic bone disease who had been receiving dialysis for the same duration to determine if the difference in osteoid accumulation in these 2 lesions might be explained by differences in aluminum accumulation or PTH levels. The stainable bone surface aluminum level was significantly higher in the patients with osteomalacia compared to that in the group with aplastic bone [61 +/- 5% (+/- SEM) vs. 43 +/- 4%; P less than 0.02]. The rates of bone apposition and bone formation were lower in the group with osteomalacia (P less than 0.01). Plasma amino-terminal PTH was not significantly different in the 2 groups. The increment in plasma aluminum levels after a single infusion of deferoxamine was higher in the osteomalacic group than in the aplastic group, suggesting that the patients with osteomalacia accumulated more total body chelatable aluminum than did those with aplastic bone disease during a comparable length of time on dialysis. We conclude that the excess unmineralized osteoid in aluminum-related osteomalacia results from the high rate of total body aluminum accumulation, which directly causes uncoupling of matrix mineralization and matrix production, independent of PTH levels. Patients with aplastic bone disease who have accumulated lesser amounts of total body aluminum fail to develop excess unmineralized osteoid because production and mineralization of matrix are more closely coupled than in the osteomalacic lesion, despite a decline in osteoblast numbers.

Bone aluminum and histomorphometric features of renal osteodystrophy.

To evaluate the relationship between aluminum and the characteristics of bone disease in uremia, bone aluminum content and quantitative histomorphometric analysis of bone were evaluated in bone biopsies from 59 uremic patients undergoing maintenance hemodialysis. Biopsies were classified as showing 1) pure osteomalacia (OM) in 23 cases, 2) osteitis fibrosa (OF) in 13, 3) mixed in 7, and 4) mild lesions in 16. There were no significant differences in levels of serum calcium or alkaline phosphatase between the groups, but serum phosphorus levels were slightly higher in those with OF. Serum immunoreactive parathyroid hormone levels were greater in the patients with OF and mixed lesions than in patients with OM or mild lesions (P less than 0.01). Bone aluminum exceeded normal in all groups (P less than 0.01), with values of 175 +/- 18 mg/kg dry wt in OM patients, 46 +/- 7 of OF patients, 81 +/- 29 in mixed subjects, and 67 +/- 7 in patients with mild lesions. Bone aluminum was significantly higher in the OM patients than in any other group (P less than 0.01); also, bone aluminum correlated with the quantitative measure of unmineralized osteoid in OM (r = 0.67; P less than 0.001); no correlations existed for the other groups. There were inverse correlations between bone aluminum and the serum immunoreactive parathyroid hormone (r = -0.35; P less than 0.01) and resorbing surface on biopsy (r = -0.44; P less than 0.001). Bone aluminum correlated with the duration of hemodialysis in patients with OF with mixed and mild lesions (r = 0.49); no relation was seen in OM patients, and bone aluminum was higher for the duration of dialysis, suggesting that aluminum may accumulate more rapidly in OM subjects. These findings are consistent with but do not prove the hypothesis that aluminum plays a pathogenic role in dialysis osteomalacia; the mechanism by which aluminum accumulates remains unknown.

Comparison of parathyroid hormone assays with bone histomorphometry in renal osteodystrophy.

Bone biopsies were studied in 67 dialysis patients to determine if a PTH RIA specific for intact plasma PTH is a better predictor of osteitis fibrosa than a RIA that measures inactive carboxy-terminal/midregion plasma PTH fragments. An amino-terminal-specific antiserum that cross-reacts with intact PTH, but not midregion or carboxy-terminal fragments, and an antiserum that cross-reacts with the 44-68 region of the PTH molecule and measures both intact and midregion/carboxy-terminal PTH fragments were used in the comparisons. Plasma PTH concentrations measured by both assays correlated positively with bone formation rate, bone apposition rate, osteoblastic osteoid, osteoclast number, and marrow fibrosis. The optimum predictive value of the amino-terminal PTH assay for osteitis fibrosa was 88%, compared to 74% for the midregion PTH assay. This difference in predictive value could be attributed to the highly significant correlation of marrow fibrosis with plasma amino-terminal PTH. In conclusion, these data suggest that a PTH RIA that uses an amino-terminal-specific antiserum may be a better predictor of osteitis fibrosa in patients undergoing maintenance hemodialysis.

Control of clofibrate toxicity in uremic hypertriglyceridemia.

A daily dose of 1.5 to 2.0 gm of clofibrate lowers serum triglyceride (TG) levels in patients with normal renal function but causes muscle toxicity and elevated creatine phosphokinase (CPK) levels in patients with long-term renal failure. Plasma clofibrate disappearance is prolonged as much as seven times normal in severely uremic patients. A marked reduction in the standard 14 gm/wk clofibrate dose to a total dose of 1.0 to 1.5 gm/wk effectively lowered serum TG levels (--28%, p less than 0.02) in hypertriglyceridemic hemodialysis patients without toxicity. The serum clofibrate level at this dose was comparable to that in hypertriglyceridemic nonuremic patients receiving 14 gm/wk of clofibrate. The dose of clofibrate administered to hemodialysis patients can be adjusted to avoid toxicity and provide the desired therapeutic effect by monitoring serum CPK and TG levels.

Effect of high carbohydrate feeding with dextrose or sucrose on adipose tissue lipoprotein lipase activity and plasma triglyceride levels in hemodialysis patients.

The acute effect of feeding high concentration carbohydrate meals containing equicaloric amounts of dextrose or sucrose on the activity of adipose tissue lipoprotein lipase and the concentration of plasma triglyceride was assessed in 11 hemodialysis patients. Dextrose feeding resulted in higher postprandial glucose levels and a greater insulin response than sucrose. The relationship between the postprandial change in the activity of adipose tissue lipoprotein lipase and the insulin response to feeding almost reached statistical significant (rs = 0.40, P = 0.08, n = 20), and the increase in the activity of the enzyme after dextrose feeding was greater than after sucrose (P less than 0.01). There was a significant decrease in plasma triglyceride levels after dextrose feeding (P less than 0.01), but no change was observed after the ingestion of sucrose. These results indicate that the inability of the administered sucrose to raise the plasma insulin concentration to the same level as isocaloric amounts of dextrose probably accounts for the smaller increase in the activity of adipose tissue lipoprotein lipase after sucrose. The failure of plasma triglyceride levels to fall after sucrose feeding suggests that the extent to which the activity of adipose tissue lipoprotein lipase increases postprandially may be important in the regulation of triglyceride metabolism in hemodialysis patients.

Aluminum loading during total parenteral nutrition.

Patients on long-term total parenteral nutrition were found to have elevated aluminum (AI) levels in bone, and plasma, with the casein in the total parenteral nutrition solution the source of A1. Substitution of amino acids for casein was followed by a fall in urinary and plasma A1. Thus, parenteral loading with A1 increases tissue A1, particularly in bone. Whether A1 accumulation contributes to bone disease remains unclear, but the prolonged use of casein in total parenteral nutrition solutions may be inadvisable.

Metabolic bone disease of total parenteral nutrition: course after changing from casein to amino acids in parenteral solutions with reduced aluminum content.

Bone disease with total parenteral nutrition (TPN) has been attributed to aluminum loading or vitamin D therapy. We studied 17 patients who first received TPN containing casein hydrolysate with high Al and ergocalciferol (25 micrograms/d) for 6-72 mo followed by TPN containing amino acids with reduced Al and ergocalciferol (5 micrograms/d) for 9-58 mo. We also did a cross-sectional study of 22 patients receiving casein and ergocalciferol (25 micrograms/d) compared with 46 patients receiving amino acids and ergocalciferol (5 micrograms/d) for 6-58 mo. Bone formation was higher and osteoid area, bone-surface stainable Al and total bone Al were lower with amino acid TPN than with casein TPN. Bone formation varied inversely with both plasma Al and bone-surface Al, suggesting that plasma or bone-surface Al, acquired during TPN, can reduce bone formation and lead to patchy osteomalacia. Serum levels of iPTH and 1,25-dihydroxyvitamin D were higher with amino acid TPN.

Avascular necrosis following bone marrow transplantation: a case-control study.

The role of specific immunosuppressive agents in the development of avascular necrosis (AVN) following hematopoietic stem cell and solid organ transplantation remains unclear. To further explore this question, we conducted a case-control study of patients who underwent bone marrow transplantation (BMT) at the Fred Hutchinson Cancer Research Center. 96 of 1939 long-term survivors transplanted between May 1976 and October 1993 were identified as having AVN. Eight patients were excluded because AVN developed before transplant and one was excluded due to restrictions on reviewing follow-up records. The remaining 87 patients developed AVN a mean of 26.3 +/- 2 months posttransplant and were matched for age, gender, and date of transplant to other BMT recipients. Records were reviewed for corticosteroid and cyclosporine use, pretransplant conditioning with total body irradiation (TBI), and other information including disease for which the transplant was indicated, type of transplant, the occurrence of acute and chronic graft-vs.-host disease, and steroid use prior to transplant. Adjusted odds ratios (ORs) were obtained from conditional logistic regression for 87 matched pairs. Posttransplant steroid use was a risk factor for the occurrence of AVN (adjusted OR, 14.4; 95% CI, 2.8-73.2), with the greatest risk associated with those receiving steroids at the time of diagnosis of AVN (adjusted OR, 31.9; 95% CI, 4.4-248.9). There was no further increasing risk associated with increasing duration of steroid use. Conditioning with TBI was also associated with the occurrence of AVN (adjusted OR, 3.2; 95% CI, 1.1-9.7); however, cyclosporine was not a risk factor for AVN (adjusted OR, 0.5; 95% CI, 0.1-1.9). Our results support the hypothesis that AVN following BMT has a strong association with the administration of corticosteroids. TBI may be an additional risk factor, and cyclosporine does not appear to contribute to an increased incidence of AVN.

Pseudohyperparathyroidism. Syndrome associated with aluminum intoxication in patients with renal failure.

Aluminum intoxication is an increasingly frequent complication of chronic renal failure. Because hypercalcemia, elevated parathyroid hormone levels, and radiologic changes said to be typical of osteitis fibrosa commonly occur with aluminum intoxication, it is frequently confused with hyperparathyroidism. In this report, examples of this dilemma are described. The pathophysiology leading to the confusing clinical picture is discussed, with a suggested approach to the problem.

Preliminary trials with 24,25-dihydroxyvitamin D3 in dialysis osteomalacia.

Fifteen patients with dialysis osteomalacia were treated with 24,25-dihydroxyvitamin D3 in dosages up to 10 micrograms per day for two to 24 months. All had previously had no improvement during treatment with calcitriol but had been remarkably susceptible to hypercalcemia. When 24,25-dihydroxyvitamin D3 was given with either calcitriol or dihydrotachysterol, serum calcium levels were significantly lower than during treatment with calcitriol or dihydrotachysterol alone. Eight of nine patients who received combined therapy with 24,25-dihydroxyvitamin D3 and calcitriol for longer than two months had clinical improvement; six patients underwent repeated bone biopsy and showed evidence of improved bone mineralization. Patients who received 24,25-dihydroxyvitamin D3 alone did not improve clinically. Since 24,25-dihydroxyvitamin D3 appears to improve calcium homeostasis and bone mineralization in some patients with severe dialysis osteomalacia when administered with 1-hydroxylated vitamin D metabolites, further controlled studies are warranted.

Reactivation of inhibited bone acid phosphatase and its significance in bone histomorphometry.

Despite biochemical demonstration of acid phosphatase (AcP) activation or reactivation in bone, few attempts have been made to show similar effects histochemically. Bones from growing rats, when fixed in 4% buffered formaldehyde at room temperature and demineralized in 5% formic acid, exhibited expected inactivation of AcP. The inhibited AcP, however, was reactivated by pre-incubation of sections for 1 hr at 37 degrees C in the following buffers: 0.2 M Tris, 0.2 M glycine, 0.2 M NaHCO3, or 0.1 M borax, as well as in alkaline water, but not in 0.2 M Na2HPO4 (all at pH 9). The reactivation was (a) site-specific (e.g., osteoclasts, osteoblasts, osteocytes, and cement lines), (b) temperature- and pH-dependent, (c) unaffected by OH- or SH--binding agents or by an alkaline phosphatase inhibitor, and (d) inhibited completely by 10 mM Na2HPO4. The reactivation process, much simplified and/or more effective than with the methods previously reported, was observed in all 83 human biopsy bones embedded in methyl methacrylate and in human bones stored in cold buffered formaldehyde for 7 months. This study demonstrates a unique method for reactivating and thus localizing the inhibited AcP in bones, and suggests possible applications in bone histomorphometry.

Periarticular tumoral calcinosis and hypercalcemia in a hemodialysis patient without hyperparathyroidism: a case report.

We present a case of a 58-yr-old male to illustrate the scintigraphic, roentgenographic, clinical, and pathologic features of periarticular tumoral calcinosis that occurred in a hemodialysis patient. Soft-tissue calcifications developed 3 yr after onset of hemodialysis, became progressively larger during the ensuing five years, and culminated in voluntary withdrawal from dialysis because of the extreme discomfort and lack of mobility that resulted from the calcinosis. Histologically, an aplastic disorder was present with very low bone formation. On bone scintigraphy, intense calcium uptake in soft tissues implied that it was metabolically active. We hypothesize that this high metabolic activity contributed to the persistent hypercalcemia observed during the patient's last year of life.