A case of osteomalacia: the pivotal role of the non-decalcified bone biopsy.
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Biopsy↗
Biomedical subjects
L V Avioli
Publications and source records attributed to L V Avioli.
Increasing osteoporosis screening referrals.
Numerous popular, trade, and scientific publications have warned that "routine screening" for osteoporosis is at best unwarranted and at worst a ruse of entrepreneurial practitioners attempting to get rich quick. However, given the prevalence of osteoporosis and the estimated medical and nursing costs it incurs (ranging from $7 to $10 billion annually, or 1.4% to 2.3% of health care expenditures in 1985), screening and identifying persons at risk for rapid bone loss should not be branded a ruse. Not all health care providers offering assessment of osteoporosis lie down with thieves. Such an insinuation undermines the necessity for aggressively and appropriately addressing a major health problem.
Adult↗
Socio-economic costs of osteoporosis and changing patterns.
Osteoporosis and its complications, especially hip and vertebral fractures, are a world-wide problem. Socio-economic costs and the need of hospital beds for acute and chronic care and for rehabilitation are ever-increasing. The health care system should take these demands into consideration.
Aged↗
Rationale for the use of calcitonin in postmenopausal osteoporosis.
Calcitonin has been used in the prevention and treatment of osteoporosis already for several years. The results have been promising. Especially patients with high-turnover osteoporosis respond satisfactorily to the treatment. In the immediate postmenopausal period calcitonin should be considered appropriate if estrogens are either contraindicated or refused by the patient.
Calcitonin↗
Calcium supplementation and postmenopausal bone loss.
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Calcium↗
Primary hyperparathyroidism: recognition and management.
Many cases may be missed, particularly those that are normocalcemic. The disease should be considered in all older patients with chronic mental or behavioral disturbances, nonspecific neuromuscular or GI complaints, and arthralgias--not only because hyperparathyroidism is eminently curable but also because it is virtually impossible to predict when the disease will become life threatening.
Calcium↗
Osteoporosis in rheumatoid arthritis.
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Arthritis, Rheumatoid↗
Effect of dietary acid and calcium on 25-hydroxyvitamin D metabolism by chick kidney.
Studies of the effects of acidosis and dietary calcium on 25-hydroxyvitamin D3 (25OHD3) metabolism were conducted utilizing assays of mitochondrial 1-hydroxylase and 24-hydroxylase activity following 96 hours of acid loading. The results showed decreased 1-hydroxylase (206 +/- 6 vs. 132 +/- 22 fmol min-1 mg/mitochondrial protein-1, p less than 0.01), augmented 24-hydroxylase (48 +/- 14 vs. 180 +/- 30 fmol min-1 mg-1, p less than 0.001) and increments in plasma calcium and phosphate following acidosis. High calcium diet also increased 24-hydroxylase activity (48 +/- 14 vs. 160 +/- 24 fmol min-1 mg-1, p less than 0.001) and plasma calcium, but decreased plasma phosphate. The extramitochondrial concentrations of calcium, potassium, and phosphate which maximally stimulated the hydroxylases in vitro were not altered by the in vivo dietary perturbations. The increments in 1-hydroxylase and 24-hydroxylase resulting from the presence of calcium, potassium, or phosphate in optimal concentrations (10(-5) M, 100 mM, and 100 mM, respectively) were changed by both acid loading and high calcium diet, decreasing in the case of 1-hydroxylase and increasing in that of 24-hydroxylase. The data indicate that the suppression of 1-hydroxylase and augmentation of 24-hydroxylase following these dietary perturbations may depend on both changed total enzyme capacity and altered enzyme sensitivity to extramitochondrial ions and are consistent with mediation by calcium of the effects of acidosis.
Acidosis↗
Membrane potential and cation content of osteoblast-like cells (UMR 106) assessed by fluorescent dyes.
A number of cellular functions have recently been associated with alterations of the membrane potential in non-excitable cells. To assess the electrophysiologic regulation of osteoblast function, a method for measuring the membrane potential (Em) of a rat osteogenic sarcoma cell line (UMR 106) by the voltage-sensitive oxonol dye di-BA-C4(3) was developed. The fluorescent signal of di-BA-C4(3) was calibrated through a null point method using the protonophore FCCP. At null point, Em is equivalent to H+ equilibrium potential, and may be calculated by the Nernst equation. Intracellular pH (pHi) changes induced by the protonophore were monitored using BCECF, a pH-sensitive fluorescent probe. In the presence of FCCP, intracellular pH was found to be linearly correlated to extracellular pH (pHo). Therefore, the value of pHi at null point was extrapolated as well. With this technique, we estimated the plasma membrane potential of the "putative" rat osteoblasts (UMR 106) as -28.3 +/- 4.0 mV (n = 10). This method corrected the 16% overestimation of Em derived from the assumption that pHi does not change during the calibration procedure, as described in previous studies employing pH null point techniques. With null point methods, using BCECF and the carboxylic ionophores nigericin and monensin, intracellular concentrations of potassium and sodium were also measured and found to be 125 +/- 0.7 mM (n = 3) and 24 +/- 5.3 mM (n = 3), respectively. Although the Em of UMR 106 cells was dependent on extracellular potassium concentration, these cells did not behave as a potassium electrode. The sodium/potassium permeability ratio, calculated by the Goldman equation, was estimated at 0.317. This high membrane permeability to sodium may contribute to the genesis of the low plasma membrane potential of UMR 106 cells.
Animals↗
Cell density-dependent vitamin D effects on calcium accumulation in rat osteogenic sarcoma cells (ROS 17/2).
Rat osteogenic sarcoma cells have been used widely as a model system to study actions of 1,25(OH)2D3 and other hormones in osteoblastlike cells. However, some of the pleiotypic manifestations of hormones in these cells vary greatly dependent upon the cell population density and other conditions of culture. Therefore, we have studied the effect of cell density on the relationship between 1,25(OH)2D3 and the initial 45Ca accumulation in ROS 17/2 cells in order to establish conditions suitable for studying the effect of 1,25(OH)2D3 on calcium fluxes in these cells. Cells were grown in the presence and absence of 1,25(OH)2D3 for 48 hours and then incubated for 4 min in the culture medium containing 0.5 microCi/ml of 45CaCl2. In high population density cultures, 0.25-1.0 pg/ml of 1,25(OH)2D3 stimulated the intracellular accumulation of 45Ca (cpm/mg protein), whereas 80 pg/ml or higher concentrations inhibited accumulation of 45Ca. In low density cultures, concentrations less than 80 pg/ml had no effect, 80-120 pg/ml increased the intracellular accumulation, and as much as 200 pg/ml failed to show the inhibitory effect. These results indicate that the ROS 17/2 cell responses to 1,25(OH)2D3 are biphasic--low concentrations stimulating and high concentrations inhibiting 45Ca accumulation. The sensitivity of the cells to 1,25(OH)2D3 increases as the cell population density increases. These observations suggest that the culture density and dose-response relationship must be carefully defined in in vitro studies utilizing osteogenic cell culture systems.
Animals↗
Early manifestations of vitamin D effects in rat osteogenic sarcoma cells.
We have recently demonstrated that 48 hour exposure of ROS 17/2 cells to low concentrations of 1,25-dihydroxycholecalciferol (1,25-(OH)2D3) (1.0 pg/ml) stimulated the cellular accumulation of 45Ca, and exposure to high concentrations (160 pg/ml) inhibited such accumulation. In the present study, short-term (15 min) effects of the sterol on 45Ca accumulation in ROS 17/2 cells were compared with the long-term (48 hours) effects in order to clarify mechanisms responsible for 1,25(OH)2D3 control of calcium metabolisms in ROS 17/2 cells. ROS 17/2 cells were grown for 48 hours in the presence and absence of 1,25(OH)2D3 and then incubated for an additional 15 min in the presence and absence of 1,25(OH)2D3 immediately before measuring 45Ca accumulation. Cellular 45Ca was measured after incubating the cells in the medium containing 0.5 microCi/ml of 45CaCl2 for 4 min at 25 degrees C. The effect of actinomycin D was determined by preincubating the cells in 0.1 microgram/ml of actinomycin D for 45 min at 25 degrees C. Exposure to low concentrations (1.0 pg/ml) of 1,25(OH)2D3 for either 48 hours or 15 min increased 45Ca in the cells by 10-20%. An additional 15 min exposure following 48 hour exposure yielded an increase in the cellular 45Ca similar to that after 48 hours or 15 min exposure. Exposure to high concentrations (160 pg/ml) for either 48 hour or 15 min decreased cell 45Ca by approximately 20%. An additional 15 min exposure to the high concentrations did not change the 48 hour effect. Actinomycin D reversed early inhibitory effects of high concentrations, but had no effect on the early stimulatory effects of low concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Simulated acidosis does not impair 1,25-dihydroxyvitamin D3 production by cultured kidney cells.
Cultured mouse kidney cells grown in serum-free medium were used to assess the metabolism of 25-hydroxyvitamin D3 in the presence of simulated metabolic acidosis. Kidney epithelial cells isolated from 4-6 week old mice were grown to confluence in a defined serum-free medium at pH 7.4. The confluent monolayers were incubated with tritiated 25-hydroxyvitamin D3 for 6 hours, the samples were extracted, and vitamin D metabolites were separated and quantitated by high pressure liquid chromatography (HPLC). The pH of the incubation medium was set at 6.9, 7.1, 7.4, or 7.7 by adjusting the bicarbonate concentration, using chloride as the balancing anion at constant Pco2. When pH was altered at the beginning of the 6 hour assay, production of 1,25-dihydroxyvitamin D3 was the same at each pH. More prolonged pH perturbation for a total of 30 hours likewise had no influence on 1,25-dihydroxyvitamin D3 production. These results confirm that intact mammalian kidney cells in serum-free culture possess an active 25-hydroxyvitamin D3-1-hydroxylase and that the activity of the enzyme is unaffected by pH over the range 6.8-7.7. In experiments where acidosis has been shown to alter 1,25-dihydroxyvitamin D3 production, the mechanism was probably indirect.
25-Hydroxyvitamin D3 1-alpha-Hydroxylase↗
Adrenal responses to subtotal parathyroidectomy for primary hyperparathyroidism.
Although it is well known that hypertension is often associated with primary hyperparathyroidism and that parathyroidectomy reverses or reduces this abnormality, the etiology of elevated blood pressure in hyperparathyroidism is still conjectural. We have analyzed serum calcium, blood pressure, and metabolites of adrenal cortical hormones before and after surgical therapy for hyperparathyroidism in 10 normotensive and six hypertensive patients with primary hyperparathyroidism. Successful parathyroidectomy lowered serum calcium (P less than 0.01) and diastolic blood pressure (P less than 0.05) in all subjects. Mean urinary aldosterone and Porter-Silber chromagens were within normal limits preoperatively in normotensive as well as hypertensive subjects. After parathyroidectomy, aldosterone levels as well as Porter-Silber chromagens decreased significantly in all patients (P less than 0.01). However, when normotensive and hypertensive subjects were analyzed separately, the decrease in aldosterone levels was significant only in the normotensive group (P less than 0.05) whereas the decrease in Porter-Silber chromagens reached significancy only in the hypertensive group (P less than 0.01). The results indicate that surgical therapy for hyperparathyroidism lowers serum calcium and blood pressure and is associated with a decrease in the excretion of adrenal steroid metabolites. It is suggested that the temporal relationship which exists between ionized calcium and steroidogenesis in hyperparathyroid patients contributes at least in part to the generalized decrease in blood pressure observed after successful parathyroidectomy.
17-Hydroxycorticosteroids↗
Mineral homeostasis in neonates of streptozotocin-induced noninsulin-dependent diabetic rats and in their mothers during pregnancy and lactation.
To assess the affect of mild diabetes on calcium metabolism in an animal model, we evaluated calcium homeostasis before pregnancy and during gestation and lactation in non-insulindependent (NIDD) diabetic rat mothers and their neonates (NeoDM). Plasma glucose, calcium (Ca), magnesium (Mg), phosphate (Pi), and immunoreactive parathyroid hormone (iPTH) were measured in the NIDD rats and controls before pregnancy, during the first, second, and third gestational week, and during lactation 12, 24, 48 and 72 h postpartum. The same measurements were performed on NeoDM and controls 12, 24, 48, and 72 h after birth. In the mothers, plasma calcitonin was assayed before pregnancy and at 72 h postpartum. Higher plasma glucose values before pregnancy (216 +/- 9 mg/dl vs 126 +/- 4) and during the second (105 +/- 5 vs 73 +/- 6) and third (114 +/- 8 vs 91 +/- 3) gestational week were observed in diabetic mothers when compared to controls. Glucose values decreased during the second and third gestational week in both groups compared to pregestational values. Plasma Ca, Mg, and Pi were similar in both groups during gestation and lactation except for the third gestational week when plasma Mg was lower in the diabetic mothers (P less than 0.05). Plasma iPTH rose to similar values in both groups during pregnancy. During lactation, plasma iPTH levels were higher and plasma calcitonin levels were lower compared to controls (P less than .05, P less than 0.01, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Cytoplasmic pH regulation in canine renal proximal tubule cells.
The precise mechanisms by which the mammalian kidney proximal tubule transports H+ and HCO3- and regulates cytosolic pH (pHi) remain in doubt, though both a H+-ATPase pump and Na+/H+ exchange at the luminal membrane are known to function in the export of protons. The mechanisms of HCO3- transport are less clear though recent reports suggest an important role for an electrogenic Na+/HCO3- symport in the basolateral membrane. The importance of chloride-dependent bicarbonate transport is unknown. In the present studies, the pH-sensitive fluorescent dye, bis-(carboxyethyl)-carboxyfluorescein (BCECF) has been used to study pHi changes in suspensions of canine proximal tubule cells following acidification or alkalinization of the cytosol. Cells were acid-loaded to pH 6.5 by exposure to the H+/K+ ionophore, nigericin. Following removal of nigericin, pHi returned to basal levels (pHi = 7.1) when the cells were resuspended in a buffer containing 100 mM Na+. This recovery was blocked by removal of Na+ or addition of 0.2 mM amiloride to the cell suspension. In the presence of 0.2 mM amiloride and Na+, partial excretion of the acid load occurred if the buffer also contained HCO3-/CO2, but this effect was blocked by the removal of Na+ or the addition of 1 mM 4-acetomido-4'-isothiocyano-2,2'-stilbene disulfonic acid (SITS). When cell membrane potential was monitored in these experiments using the potential-sensitive fluorescent dye, bis-(1,3-dibutylbarbiturate) trimethine oxonol, the increase in pHi seen in the presence of Na+ was found to be electroneutral, whereas when that occurred in the presence of Na+, amiloride and HCO3-/CO2 was associated with membrane hyperpolarization.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Spontaneous release of interleukin 1 from human blood monocytes reflects bone formation in idiopathic osteoporosis.
Osteoporosis is a state of reduced skeletal mass characterized by various rates of bone remodeling. Multiple locally elaborated factors have been identified that appear to influence the cellular events in bone remodeling. The possible role(s) of these factors in the pathogenesis of osteoporosis is unknown. One such factor, interleukin 1 (IL-1), is of particular interest, as this protein is known to stimulate bone resorption and perhaps formation. Consequently, we have measured the spontaneous secretion of IL-1 activity by cultured peripheral blood monocytes obtained from 22 osteoporotic patients and 14 age-matched control subjects. Monocytes from osteoporotic patients produced more IL-1 than did monocytes from control subjects. When patients were grouped according to monocyte-produced IL-1 activity, dynamic parameters of bone formation, as judged by quantitative histomorphometric analysis of iliac crest bone biopsies and by circulating levels of bone 4-carboxyglutamic acid protein (BGP)--a marker of bone formation--were higher in subjects with elevated IL-1 activity; whereas, indices of bone resorption and static indices of bone formation were similar in subjects with either high or normal IL-1 activity. IL-1 activity released by peripheral blood monocytes appears to reflect bone formation rate in osteoporotic patients and may be of pathogenetic significance in a subset of individuals with osteoporosis.
Adult↗
Parathyroid hormone acutely elevates intracellular calcium in osteoblastlike cells.
Changes in cytoplasmic calcium concentration ([Ca2+]i) activate numerous cellular processes thus mediating the effects of a number of hormones, but whether this mechanism is involved in the activation of osteoblasts by parathyroid hormone (PTH) remains uncertain. To examine this question, [Ca2+]i has been measured in suspensions of UMR 106 cells, a rodent osteosarcoma cell line with an osteoblastic phenotype. Basal [Ca2+]i was 137 +/- 3.7 nM (n = 60) and after the addition of rat PTH-(1-34) [rPTH-(1-34)] there was a rapid, dose-related increase with return to base line within 1 min. Half-maximal stimulation was produced by 5 X 10(-8) M rPTH-(1-34). Complexing of intracellular calcium by EGTA addition immediately before that of rPTH did not affect the calcium transient; neither did MnCl2 (10(-4) M) nor diltiazem (10(-4) M). Verapamil (10(-5) M) reduced the [Ca2+]i peak height after rPTH to 0.48 +/- 0.14 of control (n = 7). 8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoic acid and dantrolene both reduced the [Ca2+]i response to rPTH (0.65 +/- 0.08 and 0.29 +/- 0.13 of control, respectively). Forskolin (10(-6) and 10(-5) M) produced a slight [Ca2+]i transient smaller in amplitude than seen with PTH. It is concluded that PTH mobilizes an intracellular calcium pool in these osteoblastlike cells, and the predominant mechanism for this is independent of cAMP.
Animals↗
Stimulation of phosphatidylcholine biosynthesis in diabetic hypertrophic kidneys.
Choline metabolism and phosphatidylcholine biosynthesis were studied in renocortical slices of rats rendered diabetic with streptozotocin. The rates of [14C]choline incorporation into both acid-soluble and acid-insoluble fractions were increased in diabetic relative to control kidneys. While choline uptake into the control kidneys reached a plateau after 30 min of incubation, the tissue uptake of choline by the diabetic kidneys showed a time-dependent increase over 120 min, rising to a level exceeding that of control kidneys. In the control kidney, the oxidation of choline to betaine was similar to the level of phosphocholine accumulation during the first 30 min, while the formation of phosphocholine in the diabetic kidney was 1.9-fold higher than that in the control kidney (P less than 0.02) and 1.4-fold higher than the formation of betaine in diabetics (P less than 0.05). These data suggest that most of the choline transported into cells enters the Kennedy pathway by phosphorylation to phosphocholine in diabetic kidneys. The diabetic kidney also demonstrated a marked increase in the formation of three choline-containing phospholipids; phosphatidylcholine, lysophosphatidylcholine, and sphingomyelin. The treatment of diabetes with insulin restored these abnormalities toward normal. The absolute content of phosphatidylcholine significantly increased in diabetic kidneys (P less than 0.05) while contents of other major phospholipids and total lipid phosphorus in diabetic kidneys were not different from those in control kidneys. Our results indicate that renal hypertrophy in experimental diabetes is associated with a stimulation of the biosynthesis of renal phosphatidylcholine, presumably caused by an enhanced tissue uptake of choline and a stimulation of choline kinase. Since an enhancement of the membrane phosphatidylcholine biosynthesis is one of the early responses to growth signals, an alteration in phosphatidylcholine biosynthesis may contribute to the development of renal hypertrophy in experimental diabetes.
Animals↗