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Biomedical subjects

F R Singer

Publications and source records attributed to F R Singer.

At least 73 records · Page 4Linked to original sources
PubMed1987

Critical evaluation of viral antigen data in Paget's disease of bone.

This study evaluates previous viral antigen data obtained from fixed tissue sections and cells grown in culture from bone affected by Paget's disease. Finding antigens to both respiratory syncytial virus (RSV) and measles virus (MV) in the same osteoclasts of ten patients could not be explained on the basis of any previously known cross-reactivity. Therefore, possible causes for these observations were sought. Monoclonal antibodies to viral proteins of RSV and MV were used to label proteins. Polyclonal antibodies that were monospecific and were produced exclusively in nonhuman species were used to rule out nonspecific reaction with human proteins. Antivimentin antibody was used to test the possibility of cross-reactivity with a cytoskeletal protein, as a second antibody F(ab')2 conjugated to fluorescein was used to rule out nonspecific reactivity with Fc receptors. Electron microscopy was used to evaluate bone cell cultures derived from Paget's bone in comparison with Paget's osteoclasts. Results showed that the pattern of monoclonal viral antibody labeling followed different patterns in different patients. Nonspecific reactivity was ruled out by significant negative and positive controls. Cross-reactivity with vimentin could not account for the positive immunofluorescent results because of an entirely different pattern of fluorescence in the same samples of live and fixed cells after colchemid treatment. It was concluded that specific viral antigens are present in osteoclasts and in cells grown from Paget's bone and that the present data are compatible with the possibility that Paget's disease of bone is a slow virus infection.

Antibodies, Monoclonal↗
PubMed1987

Characterization and assay of tartrate-resistant acid phosphatase activity in serum: potential use to assess bone resorption.

We improved the spectrophotometric assay of tartrate-resistant acid phosphatase (TrACP; EC 3.1.3.2) activity in serum. During development of the assay we found that human serum contains a dialyzable, mixed-type noncompetitive inhibitor(s) of TrACP activity, the effects of which on the assay were substantially lessened by diluting the serum sample with water before assay and increasing the substrate concentration. Hemolysis releases into serum a significant amount of TrACP activity from erythrocytes, which can be inactivated by incubating the serum at 37 degrees C for 1 h before assay. Our improved assay was reproducible (CV = 5%), and measured within 10% of the amount of added bovine skeletal TrACP activity. Preliminary application of the assay revealed that the amount of serum TrACP activity in patients with skeletal diseases differed from normal values and changed in the same direction as the expected change in bone turnover, suggesting that TrACP activity in serum could be useful clinically as a marker of bone metabolism, possibly of bone resorption.

Acid Phosphatase↗
PubMed1986

The effects of metabolic acidosis on bone formation and bone resorption in the rat.

Metabolic acidosis (MA) has been implicated in the pathogenesis of both osteomalacia and osteopenia. Alterations in the secretion of parathyroid hormone and in the metabolism of vitamin D may contribute to such skeletal changes. To minimize the influence of these factors, quantitative bone histology and measurements of bone formation using double tetracycline labeling were done in thyroparathyroidectomized (TPTX) rats with MA induced by ammonium chloride (TPTX-A), and in both non-acidotic TPTX (TPTX-C) and intact (C) controls. To evaluate the response of both cortical and trabecular bone to MA, histologic studies were done at three separate sites in the tibia, cortical bone from the mid-shaft, and trabecular bone from the epiphysis and from the metaphysis. Plasma pH was lower in TPTX-A, 7.24 +/- 0.10, than in either TPTX-C, 7.39 +/- 0.03, or C, 7.43 +/- 0.04, P less than 0.01, and urinary hydroxyproline excretion increased from 89.8 +/- 8.7 in TPTX-C to 150.2 +/- 25.9 micrograms/mg/creatinine in TPTX-A, P less than 0.01. Resorption surface at the epiphysis increased from 1.8 +/- 0.6% in TPTX-C to 4.0 +/- 1.6% in TPTX-A, P less than 0.05, values not different from those in C, 3.1 +/- 1.1%. Resorption surface was unchanged at other skeletal sites, but total bone volume at the metaphysis fell from 15.5 +/- 5.6% in TPTX-C to 9.0 +/- 4.3% in TPTX-A, P less than 0.05. Bone formation was reduced at each skeletal site in TPTX-A vs. TPTX-C, P less than 0.05 for all values, but histologic evidence of osteomalacia was not observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Acidosis↗
PubMed1986

Relationship between urinary calcium and calcium intake during calcitriol administration.

The hypercalciuria that occurs when 1,25 (OH)2D3 (calcitriol) is given to humans with normal renal function depends on dietary Ca absorption and may also relate, in part, to enhanced bone resorption. To evaluate the relationship between urinary and dietary Ca during treatment with calcitriol, 12 metabolic balance studies were performed in normal volunteers ingesting a diet containing 350 mg/day of Ca, to which Ca gluconate was added. After 10 days on either 350 mg/day or 1550 mg/day of Ca, calcitriol, 0.5 microgram every 12 hr, was given. Then diet Ca was changed in successive 5-day treatment periods from 350 to 650, 950 and 1550 mg/day (group A) or from 1550 to 950, 650 and 350 mg/day (group B). On the lowest diet Ca, urinary Ca was less than Ca intake during calcitriol treatment (group A, 220 +/- 50 mg/day; group B, 247 +/- 40). As diet Ca was changed during calcitriol treatment, urinary Ca correlated with diet Ca (r = 0.60) until diet Ca reached 950 mg/day. With calcitriol, serum iPTH fell by 18 to 25% (P less than 0.01) and urinary hydroxyproline fell by 11 to 19% (P less than 0.05 to 0.01). Baseline serum levels of 1,25(OH)2D were 47 +/- 8 and 34 +/- 5 pg/ml in group A and B, respectively, and the values increased to 51 +/- 12 and 45 +/- 7.4 pg/ml during treatment with calcitriol. Serum Ca from fasted subjects was not affected by calcitriol, but the mean postabsorptive serum Ca (moon) was increased by 0.35 mg/dl.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

A viral antigen-bearing cell line derived from culture of Paget's bone cells.

This study documents the characteristics of a viral antigen-bearing cell line derived from co-culture of the bone from a 71-year-old woman with Paget's disease of bone and HEp-2 cells. The cell line has survived in continuous culture for 3 1/2 years and 185 subcultures. The cells are epithelioid in appearance, produce alkaline and acid phosphatase, increase alkaline phosphatase activity in response to 1,25-(OH)2-D3 and contain receptors for 1,25-(OH)2-D3. Immunofluorescent studies utilizing antisera to respiratory syncytial virus and measles virus reveal antigens of both viruses in the cells. These cells do not produce bone in culture and the adenylate cyclase activity found in their plasma membrane does not increase significantly in response to parathyroid hormone or calcitonin. The cells are not contact inhibited and form spherical colonies in agarose. They are aneuploid and have a modal number of 62-74 as well as HeLa markers. When injected into athymic mice, osteosarcomas are produced. These tumors continue to bear viral antigens. The availability of this cell line should aid in further studies of the viral antigens associated with Paget's disease of bone.

Aged↗
PubMed1985

Estrogen and progestin effects on urinary calcium and calciotropic hormones in surgically-induced postmenopausal women.

Seventeen surgically-induced postmenopausal (PM) women were randomized to receive either 0.625 mg of conjugated estrogens (CE) daily or 150 mg of intramuscular depomedroxyprogesterone acetate (DMPA) every 3 months. Urinary calcium/creatinine ratios were significantly higher than ratios of premenopausal controls before treatment, but were lower in all patients 2 months after both types of treatment. Compared to controls, all PM patients had similar levels of serum PTH and 25 hydroxy vitamin D before and after treatment. As a group, PM patients had lower levels of 1.25-dihydroxyvitamin D. In 5 patients who had levels which were below the normal range, 3 were treated with CE and 2 received DMPA. These patients all had significant increases in 1,25-dihydroxyvitamin D after treatment. Serum calcitonin did not change with either CE or DMPA treatment. These data suggest that, while both CE and DMPA lower calcium excretion in PM women, the mechanism(s) for the effects of hormonal treatment on bone resorption remain unsettled.

Adult↗
PubMed1985

Alpha and beta human transforming growth factors stimulate prostaglandin production and bone resorption in cultured mouse calvaria.

Human alpha and beta transforming growth factors (TGF-alpha and TGF-beta) stimulated the production of prostaglandin E2 (PGE2) and bone resorption in neonatal mouse calvaria in organ culture. Significant stimulation of bone resorption by TGF-alpha was observed with a concentration of 0.2 ng/ml (35 pM) and by TGF-beta with 0.2 ng/ml (8.0 pM). Enhanced production of PGE2 and bone resorption stimulated by either TGF-alpha or TGF-beta were both inhibited by indomethacin. We conclude that TGF-alpha and TGF-beta are potent and powerful stimulators of the resorption of mouse bone by a mechanism that involves the enhanced local production of PGE2.

6-Ketoprostaglandin F1 alpha↗
PubMed1985

Magnesium deficiency in a medical ICU population.

The serum magnesium level was measured in 94 consecutive patients admitted to the medical ICU of Los Angeles County/University of Southern California Medical Center over a 2-month period. Sixty-five percent of patients with serum creatinine concentrations of 1.1 mg/dl or less were hypomagnesemic. Of these, one third had hypocalcemia that was corrected with magnesium supplementation. Physicians should be alert to the high incidence of magnesium deficiency in critically ill patients.

California↗
PubMed1985

Isolation and structural identification of 1,25-dihydroxyvitamin D3 produced by cultured alveolar macrophages in sarcoidosis.

Hypercalcemia and hypercalciuria in sarcoidosis are thought to result from the endogenous overproduction of an active vitamin D metabolite. We employed primary cultures of pulmonary alveolar macrophages from two patients with biopsy-proven pulmonary sarcoidosis and a recent or current clinical abnormality in calcium metabolism to synthesize in vitro a 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3]-like metabolite from 25-hydroxyvitamin D3 (25OHD3). The macrophage metabolite cochromatographed with [3H]1,25-(OH)2D3 on normal phase and reverse phase high performance liquid chromatography and was bound with high affinity by the chick intestinal receptor for 1,25-(OH)2D3. On UV spectroscopy, the metabolite possessed the carbon-5,7,10 (19) cis-triene chromophore characteristic of a vitamin D sterol. Electron impact mass spectrometry of trimethylsilyl ether derivatives of the metabolite revealed a mass fragmentation pattern similar to that of the trimethylsilyl ether derivative of authentic 1,25-(OH)2D3. The incubation of cultured macrophages from two patients with idiopathic pulmonary fibrosis and two with scleroderma with [3H]25OHD3 did not result in production of a metabolite with the chromatographic identity of 1,25-(OH)2D3. These data indicate that the metabolite of 25OHD3 synthesized by sarcoid macrophages in vitro is 1,25-(OH)2D3 and that the macrophage is a synthetic source of the sterol metabolite in sarcoidosis.

Adult↗
PubMed1985

Low serum concentrations of 1,25-dihydroxyvitamin D in human magnesium deficiency.

The effect of magnesium deficiency on vitamin D metabolism was assessed in 23 hypocalcemic magnesium-deficient patients by measuring the serum concentrations of 25-hydroxyvitamin D (25OHD) and 1,25-dihydroxyvitamin D [1,25-(OH)2D] before, during, and after 5-13 days of parenteral magnesium therapy. Magnesium therapy raised mean basal serum magnesium [1.0 +/- 0.1 (mean +/- SEM) mg/dl] and calcium levels (7.2 +/- 0.2 mg/dl) into the normal range (2.2 +/- 0.1 and 9.3 +/- 0.1 mg/dl, respectively; P less than 0.001). The mean serum 25OHD concentration was in the low normal range (13.2 +/- 1.5 ng/ml) before magnesium administration and did not significantly change after this therapy (14.8 +/- 1.5 ng/ml). Sixteen of the 23 patients had low serum 1,25-(OH)2D levels (less than 30 pg/ml). After magnesium therapy, only 5 of the patients had a rise in the serum 1,25-(OH)2D concentration into or above the normal range despite elevated levels of serum immunoreactive PTH. An additional normocalcemic hypomagnesemic patient had low 1,25-(OH)2D levels which did not rise after 5 days of magnesium therapy. The serum vitamin D-binding protein concentration, assessed in 11 patients, was low (273 +/- 86 micrograms/ml) before magnesium therapy, but normalized (346 +/- 86 micrograms/ml) after magnesium repletion. No correlation with serum 1,25-(OH)2D levels was found. The functional capacity of vitamin D-binding protein to bind hormone, assessed by the internalization of [3H]1,25-(OH)2D3 by intestinal epithelial cells in the presence of serum was not significantly different from normal (11.42 +/- 1.45 vs. 10.27 +/- 1.27 fmol/2 X 10(6) cells, respectively). These data show that serum 1,25-(OH)2D concentrations are frequently low in patients with magnesium deficiency and may remain low even after 5-13 days of parenteral magnesium administration. The data also suggest that a normal 1,25-(OH)2D level is not required for the PTH-mediated calcemic response to magnesium administration. We conclude that magnesium depletion may impair vitamin D metabolism.

Calcifediol↗
PubMed1985

Pharmacokinetics and biologic effects of calcitriol in normal humans.

The dose response and pharmacokinetics of orally administered calcitriol were investigated in normal humans. In one protocol, six volunteers received calcitriol 0.25 micrograms twice a day, 0.5 micrograms daily, and 0.5 micrograms twice a day, in successive weeks. Peak plasma levels of 1,25(OH)2D occurred 4 to 8 hours after ingestion of a single dose of 0.5 micrograms, with a return to baseline within 24 hours. The 8:00 AM calcitriol plasma levels were raised only when the drug was given twice daily. Urinary calcium excretion (UCa) was significantly increased from 199 +/- 19 mg/24 hr during the control period to similar levels of 302 +/- 26 mg/24 hr after 0.25 microgram twice a day and 284 +/- 31 mg/24 hr after 0.50 microgram daily. With 0.50 microgram twice a day, UCa was 417 +/- 36 mg/24 hr, a value greater than after the lower doses (p less than 0.05). In another protocol, fourteen volunteers received calcitriol 0.25 microgram, 0.5 microgram, and 1.0 microgram twice a day each for 14 days with intervening control periods of 2 weeks. A dose-related response in urinary calcium/creatinine excretion occurred. Thus, UCa (milligrams calcium per milligram creatinine) increased with calcitriol from 0.13 +/- 0.014 mg to 0.15 +/- 0.018 mg with 0.25 microgram twice a day, from 0.13 +/- 0.010 mg to 0.22 +/- 0.022 mg with 0.5 microgram twice a day, and from 0.12 +/- 0.012 mg to 0.23 +/- 0.012 mg with 1 microgram twice a day (p less than 0.05 with 0.25 microgram, p less than 0.01 with 0.5 and 1 microgram twice a day).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Hypercalcemia in leprosy.

We report a case of hypercalcemia in a patient with leprosy. Aminoterminal parathyroid hormone and 25-hydroxy-cholecalciferol concentrations were suppressed. Urinary hydroxyproline concentrations were elevated. There was no evidence of malignancy. The hypercalcemia resolved with corticosteroid therapy.

Arthritis, Rheumatoid↗
PubMed1985

Parenteral magnesium tolerance testing in the evaluation of magnesium deficiency.

Magnesium deficiency is a common clinical condition, frequently present even with normal serum magnesium (S-Mg) concentrations. We have studied retention of a low-dose (0.2 mEq/kg lean body weight), intravenously administered magnesium load in 6 hypomagnesemic patients and 18 normomagnesemic alcoholics as compared with 16 normal subjects. Both normomagnesemic and hypomagnesemic subjects retained significantly greater amounts of the administered magnesium than did the normal subjects. In patients who were restudied following parenteral magnesium repletion, retention of the magnesium load normalized. We conclude that increased retention of a magnesium load is a more sensitive index of magnesium deficiency than is the S-Mg concentration, and suggest that low-dose magnesium tolerance testing be used more frequently as a clinical tool in the evaluation of states of normomagnesemic magnesium deficiency.

Adult↗
PubMed1984

Specific internalization and action of 1,25-dihydroxyvitamin D3 in cultured dermal fibroblasts from patients with X-linked hypophosphatemia.

An abnormality in the interaction of 1,25-dihydroxyvitamin D [1,25-(OH)2D] with its specific intracellular receptor has been postulated to explain the resistance of patients with X-linked hypophosphatemia (XLH) to treatment with vitamin D. To investigate this possibility, the specific internalization of [3H]1,25-(OH)2D3 by suspensions of cultured dermal fibroblasts from six patients with XLH was evaluated. Scatchard analysis of the specific uptake of [3H]1,25-(OH)2D3 by intact XLH fibroblasts revealed a mean internalization constant (Kin) of 0.72 +/- 0.10 nM (mean +/- SE) and a cellular capacity for hormone (Nmax) of 61.5 +/- 5.4 fmol/mg protein. The Kin and Nmax for XLH cells were similar to the mean values obtained for normal fibroblasts (0.59 nM and 72 fmol/mg protein, respectively) and cells from a patient with acquired hypophosphatemia (0.67 nM and 73 fmol/mg protein, respectively). Conversely, cultured fibroblasts from a patient with vitamin D-dependent rickets type II demonstrated a marked reduction of sterol uptake when compared to that in cells from either a hypophosphatemic or normal host. Neither the affinity nor the capacity of XLH fibroblasts for [3H]1,25-(OH)2D3 was influenced by exposure of proliferating or confluent monolayer cultures to a low phosphate concentration (2.0 mg/dl) in the extracellular medium before or during assay. In addition, the normal responsiveness of cultured fibroblasts from three patients with XLH to 1,25-(OH)2D3 was confirmed by the provocative induction of the cellular 25-hydroxyvitamin D3-24-hydroxylase. These data suggest that 1,25-(OH)2-D3-receptor binding as well as postreceptor events are normal in patients with XLH.

Adolescent↗
PubMed1984

Postpartum resolution of hypocalcemia in a lactating hypoparathyroid patient.

A 24 year old woman with post-surgical hypoparathyroidism was studied during pregnancy and lactation. During pregnancy the patient required less vitamin D therapy for control of her hypoparathyroidism and, while lactating, maintained a normal serum calcium without any supplemental vitamin D. The serum parathyroid hormone concentration and plasma 1,25 (OH)2 vitamin D concentration were undetectable and low normal respectively at a time when the serum calcium concentration was normal and the patient was not on vitamin D therapy. Urinary calcium excretion was low during this period and may explain the normalization of the serum calcium. The mechanism by which the improvement in calcium metabolism occurred is unknown, but may be secondary to a direct effect of prolactin on calcium homeostasis.

Adult↗
PubMed1984

Evidence for both respiratory syncytial virus and measles virus antigens in the osteoclasts of patients with Paget's disease of bone.

Recent ultrastructural and immunohistochemical evidence supports the hypothesis that Paget's disease of bone is a slow viral infection of the Paramyxoviridae family. Conflicting evidence for the presence of respiratory syncytial virus (RSV), a pneumovirus, or measles, a morbillivirus, has been reported. By the indirect fluorescent antibody assay, four RSV antisera were compared with four measles antisera on serial sections of pagetic bone or replicate coverslips of cells from pagetic bone grown in culture from 30 patients. Results produced positive immunofluorescence for RSV in 28 of 29 patients and positive immunofluorescence for measles in 11 of 22 patients. Of the 20 patients from whom comparable samples could be tested for antigens, 11 were found to harbor both antigens. These studies support the hypothesis that Paget's disease of bone is a slow viral infection of the Paramyxoviridae family more closely related to the pneumoviruses than the morbilliviruses.

Antigens, Viral↗