Bone Calcium Deposition Research Articles

Effect of low-dose methylprednisolone on calcium balance and bone composition in rats

Glucocorticoid induced osteoporosis has been associated with high doses and it has been partially attributed to decreased absorption and to increased calcium excretion. The present study examined the effect of low but effective doses of methylprednisolone (MP) on calcium balance and on skeleton in rats. Total duration of the experiment 29 days. Thirty-one male Wistar rats (MP group) were injected with 4mg/kg body weight MP s.c. at the 1st, 11th and 20th day of the experiment and 28 rats (C group) were used as matched controls. The 1st, 11th and 20th day of the experiment rats were placed in individual metabolic cages for three days. Food and water consumption were measured at the 2nd and 3rd days after each injection; urine and faeces were collected at the same days for calcium estimation. Calcium intake and excretion after each injection was significantly lower in the MP group as compared to controls. A statistically significant positive correlation between calcium consumption and calcium excretion was found in both groups resulting in a negative final balance. Rats were killed the 29th day. Adrenal weight was statistically significant lower in MP group (p<0.001). Morphometric properties were evaluated for the right femur. No significant difference was found between the two groups. Mineral and calcium content was slightly increased in the MP group. According to these results, it seems that methylprednisolone while effective on HPA axis did not have any effect on calcium absorption and on bone calcium deposition in rats.

Variables related to urinary calcium excretion in young girls.

The relations among dietary and calcium kinetic factors and 24-h urinary mineral excretion were evaluated in a group of 89 healthy girls (51 white and 38 black) aged 4.9-16.7 years. Nutrient intakes were calculated for each participant using a weighed intake of all food and beverage on the day of the 24-h urine collection study and two subsequent 24-h food records. A significant relation was noted between urinary calcium and sodium excretion (r = 0.55; p < 0.0001). No significant relations were found between urinary calcium and (a) calcium intake (r = 0.08), (b) protein intake (r = 0.14), or (c) phosphorus intake (r = 0.11). Urinary calcium was not significantly related to fractional calcium absorption (r = 0.03) or net calcium absorption (r = 0.11), but was significantly associated with the bone calcium deposition rate (r = 0.24; p < 0.03). Using a multiple regression model, both urinary sodium and the bone calcium deposition rate were independent predictors of urinary calcium excretion in this population (r = 0.57; p = 0.0001). A substantial number of the children in this population had urinary calcium excretion > 4 mg/kg/day (12%). The incidence of hypercalciuria differed between the racial groups and was markedly higher in the white than in the black children (17.6 vs. 5.3%). Over a range of usual calcium intakes, during the rapid-bone-growth period in childhood and early adolescence, urinary calcium appears relatively unaffected by calcium intake and is most strongly associated with urinary sodium levels.

Differences in calcium absorption and kinetics between black and white girls aged 5–16 years

To assess racial differences in calcium (Ca) metabolism, we measured Ca absorption and kinetics in 89 girls (38 black and 51 white) aged 4.9-16.7 years using a dual-tracer stable isotope technique. We found significantly greater rates of fractional (0.44 +/- 0.13 vs. 0.25 +/- 0.08, p < 0.0001) and total calcium absorption (406 +/- 142 vs. 234 +/- 82 mg/day, p < 0.0003) in black than in white postmenarcheal girls. Fractional absorption of Ca was also greater in black than in white premenarcheal girls (0.39 +/- 0.14 vs. 0.30 +/- 0.10, p = 0.01). Fractional absorption of Ca was more closely correlated to Ca intake in white (r = -0.42, p = 0.002) than in black girls (r = -0.25, p = 0.14). Urinary Ca excretion was significantly lower in pre- but not postmenarcheal black girls than in white girls. Calcium kinetic values associated with bone calcium deposition were greater in black girls, indicating a greater rate of bone Ca deposition in both pre- and postmenarcheal black girls. These results suggest that the greater bone mass accumulated during childhood and adolescence in black than in white females is due, in part, to greater rates of Ca absorption in black girls.

Compartmental Analysis of Calcium Metabolism in Very-Low-Birth-Weight Infants

The calcium metabolism of 13 very-low-birth-weight infants fed a high-calcium diet was evaluated by means of stable isotope kinetic and balance studies. The studies used orally and i.v. administered stable isotopes, and the kinetic data were evaluated with the aid of a sequential, three-compartment model. The infants (postmenstrual age 33 +/- 1 wk, weight 1.34 +/- 0.03 kg) had higher bone calcium deposition rates (160 +/- 7 mg.kg-1.d-1 or 4.00 +/- 0.18 mmol.kg-1.d-1) than those previously reported for either older children or adults. Furthermore, when analyzed as a function of net calcium absorption, bone calcium deposition rates increased markedly and significantly as net calcium absorption increased (r = 0.70, p < 0.01), whereas in older individuals, bone calcium deposition is a relatively invariant function of absorption. A relatively smaller response of bone calcium removal to calcium absorption was found for the very-low-birth-weight infants in this study (r = -0.39, p = 0.18), whereas in adults, bone calcium removal constitutes the major regulatory response. It is suggested that the calcium kinetic results in the very-low-birth-weight infants reflect the high rate of bone growth typical of the third trimester of gestation.

Pubertal changes in calcium kinetics in girls assessed using 42Ca.

The rate of calcium deposition in bone (Vo+) and the size of the exchangeable calcium pool in bone (EP) were measured in 50 girls aged 4.9 to 16.7 y using i.v. administered 42Ca. Both Vo+ and EP reached a maximum during early puberty and decreased in late puberty and more than 2 y postmenarche. In contrast, the initial mass of calcium distribution did not decrease in late puberty. The ratio of calcium deposition in bone to the exchangeable pool size, i.e. ko+ = Vo+/EP, was more closely correlated with length of time since menarche (r = 0.83, p < 0.001) than with age (r = 0.65, p < 0.001), weight (r = 0.51, p < 0.001), or body mass index (r = 0.28, p = 0.05). The lower ko+ in late puberty indicates that as bone matures the fraction of the calcium pool that enters bone decreases.

Microgravity effects on sea urchin fertilization and development.

Gravity has been a pervasive influence on all living systems and there is convincing evidence to suggest that it alters fertilization and embryogenesis in several developmental systems. Notwithstanding the global importance of gravity on development, it has only been recently possible to begin to design experiments which might directly investigate the specific effects of this vector. The goal of this research program is to explore and understand the effects of gravity on fertilization and early development using sea urchins as a model system. Sea urchin development has several advantages for this project including the feasibility of maintaining and manipulating these cells during spaceflight, the high percentage of normal fertilization and early development, and the abundant knowledge about molecular, biochemical, and cellular events during embryogenesis which permits detailed insights into the mechanism by which gravity might interfere with development. Furthermore, skeletal calcium is deposited into the embryonic spicules within a day of fertilization permitting studies of the effects of gravity on bone calcium deposition.

Calcium and phosphorus balance in extremely low birthweight infants in the first six weeks of life.

The absorption and retention of calcium and phosphorus in infants of 28 weeks' gestation, or less, who were fed either breast milk or a preterm formula, were determined in 22 balance studies. Breast milk contained significantly lower amounts of calcium and phosphorus than the formula milk. The percentage absorption of calcium was similar in the two groups, but the infants fed breast milk had greater urinary calcium losses and significantly lower calcium retention than the group fed formula milk. The percentage phosphate absorption was also similar in the two groups but because of the higher phosphate intake in the formula milk this group retained a significantly greater amount of phosphate. The extremely low birthweight infants fed on breast milk were phosphorus depleted, with low plasma phosphate concentrations, and seemed to retain as much phosphate as possible. The hypophosphataemia may result in reduced deposition of calcium in bone and explain the calciuria in the breast fed infants. Substrate deficiency may be an important factor in the aetiology of rickets of prematurity and, particularly if breast milk is used, preterm infants may require calcium and phosphate supplements from an early age.

Regulation of calcium metabolism in streptozotocin-induced diabetes.

Sixty-nine-day-old female Wistar rats that had been made diabetic 9 days earlier by an intraperitoneal injection of streptozotocin were studied by a combination radioisotope and balance technique that evaluates calcium absorption, excretion, and bone calcium deposition and resorption rates. Streptozotocin-induced diabetes was associated with a marked drop in calcium absorption and a threefold rise in urinary calcium excretion, changes that greatly exceeded the expected effects from the hyperphagia and increased calcium intake of the experimental animals. Bone calcium deposition was halved in the diabetic rats, with bone resorption unchanged and equal to the deposition rate. As a result, the bone and body calcium balances were zero in the experimental animals. To maintain plasma calcium near normal under these circumstances, the diabetic animals turned over their skeletal calcium in relationship to the central pool much more rapidly than the controls. Although the skeleton in the normal animals serves as both storehouse and regulator of the plasma calcium, in short-term streptozotocin-induced diabetes there is no calcium storage in bone, with the skeleton only playing the role of regulator of calcium homeostasis.

Histological Alterations in Tryptophan-deficient Rainbow Trout

Tryptophan-deficient and nondeficient synthetic amino acid test diets were prepared using D, L-amino acids. The diets were fed to three groups of rainbow trout (Salmo gairdneri) for 8 weeks. Experimental control fish fed well and grew from 1.3 to 2.5 g. Deficient fish fed poorly and did not gain weight. Scoliosis was observed in the deficient fish after 1 week of feeding. Daily transitory scoliosis was noted in some fish. Histological studies of trypthophan-deficient scoliotic fish revealed hyperemia, disorganization of myomere septa, and protrusions of the fibrous matrix sheath, which invests the notochord. Abnormal deposition of calcium was noted in the kidney and the bony plates surrounding the notochord and sheath. Fish with mechanically induced scoliosis had disorganization of myomere septa, but did not have protrusions of fibrous matrix sheath, nor did they have abnormal calcium deposition in bone or kidney. Scoliotic fish returned to normal within 1 week upon replacement of tryptophan in the ration.

The effect of sodium fluoride on otosclerotic activity as determined by strontium.

Sodium fluoride (NaFl) has the effect of changing active foci of otosclerosis to quiescence. Strontium85 (Sr85) was used to determine the process of calcium deposition in normal canal wall bone and in the footplates of patients with bilateral otosclerosis before and after the administration of NaFl. The first surgery was performed on the poorer hearing ear. Fragments from oval window bone initially showed up to 34 times as much radioactivity as fragments from canal wall bone. The patients then took 25 mg of NaFl daily for six months. None failed to close and maintain gap closure within 11 dB for five months. The same evaluation was done on the bone of the footplate after surgery on the second ear. There was little or no more radioactivity in the footplate bone than in the ear canal wall bone used as a control, indicating cessation or diminution of activity at the otosclerotic focus. Prior to initiating this study, other patients with familial, progressive, purely sensorineural loss showed little or no hearing loss progression after undergoing fluoride therapy. We now recommend 25 mg daily for individuals with progressive hereditary sensorineural hearing loss and evidence of otosclerosis by polytomography.

The influence of dieldrin on tibial bone calcium deposition in domestic chicks.

The influence of dieldrin on tibial bone calcium deposition in domestic chicks.

Lactose and Calcium Metabolism: A Review

Four main hypotheses have been presented in the last four decades to explain the mode of action of lactose on calcium metabolism, but not one of these has been widely accepted. Three of them relate the effect of lactose to enhanced calcium absorption and one to improved calcium deposition in bone. These hypotheses listed in chronological order state that the ingested lactose improves calcium metabolism as a result: A, of providing an acidic pH in the intestinal tract which increases the solubility and the availability of calcium for absorption; B, of chelating calcium in the lumen of the small intestine as a soluble chelate which increases calcium absorption; C, of inhibiting a metabolic system which is responsible for controlling the uptake of divalent cations at the absorption sites in the small intestine and results in an increased calcium absorption; and D, of stimulating certain metabolic steps at the ossification sites which increase the deposition of calcium and improve the efficiency of calcium utilization. Findings by the authors (1,2,3,4,18) agree with hypothesis A and suggest that diet composition affects the mode of action of lactose on calcium absorption. Dietary lactose produced a more acid pH in the intestine, increased calcium retention, raised serum calcium and enhanced bone calcification. The effect on calcium retention and osteogenesis appears to be indirect as lactose-fed rats maintain a relatively younger body composition, i.e., a lower body fat with higher water, protein, ash and calcium, compared to rats receiving no lactose in their diet.

ACTION OF BONE HÆMODYNAMICS ON LACUNÆ-WALL CALCIFICATION

Increase in the venous pressure of a limb produced by venous ligation or by the creation of an arteriovenous fistula accelerates fracture consolidation and bone growth. In contrast, factors which should reduce the bony intramedullary venous pressure, such as paralysis, bed rest, or exposure to zero gravity, tend to decalcify bone or retard its growth. It is suggested that changes in a limb venous pressure produce alterations in bone calcium deposition. An increase in venous pressure should increase capillary filtration. This would cause œdema in most organs. Bone, because of its rigid structure, cannot swell; therefore, excess interstitial fluid production in this organ should produce an increase in interstitial-space pressure. Changes in the pressure of a crystallising solution would alter the rate of crystal formation and dissolution. Therefore, increases in the bony interstitial-space pressure should increase the crystallisation-rate at the lacunæ wall, and lowering the lacunæ pressure by a reduction in limb venous pressure should induce crystal dissolution. This hypothesis will only be valid if all other factors involved in bone metabolism (i.e., hormonal, ionic, &c.) are present and functioning normally.

Further studies on the role of thyrocalcitonin in calcium homeostatis and metabolism

1. 1. Net calcium absorption from the gut, S i , can be considered the input that disturbs plasma Ca which in turn is regulated by the net calcium balance of bone, Δ, and urinary calcium excretion, v u . A comparison of the plasma calcium level as a function of S i in thyroidectomized (TX) and control (C) animals, both groups bearing parathyroid autografts and supplied with three levels of calcium intake, the TX animals receiving l-thyroxin, failed to reveal differences in either their capacity for or intensity of plasma calcium regulation. 2. 2. Net calcium balance in bone is the difference between calcium deposition in bone, v 0 + , and removal from bone, v 0 − . Lack of endogenous thyrocalcitonin failed to affect the intensity of v 0 + or v 0 − or the relationships between S i and v 0 + or v 0 − . Hence, thyrocalcitonin has no effect on the relative or absolute importance of v 0 + and v 0 − in regulation. Moreover, there were no differences in bone calcium between C and TX animals. 3. 3. Lack of endogenous thyrocalcitonin also had no effect on urinary calcium excretion nor on the relative importance of the kidney in regulating plasma calcium. Thus the lack of thyrocalcitonin can be seen to have had no steady state effect on the calcium metabolism of the rat and it is unlikely that this hormone plays a steady state role. 4. 4. Similar detailed comparisons of control (C) animals with normal intact (N) rats revealed differences which, though small, were often of greater magnitude than the differences between C and TX animals. The differences between C and N animals were of the type and direction observed in a comparable study of N and parathyroidectomized rats. The differences between C and N animals thus point to the profound steady state role played by parathyroid hormone in the regulation of calcium metabolism and further indicate why the nature of the control exerted by thyrocalcitonin cannot be comparable to that exerted by parathyroid hormone.

Corpuscles of Stannius and Renal Physiology in the Eel (Anguilla rostrata)

In freshwater eels there is a significant correlation between glomerular filtration rates (GFR) and urine flow rates suggesting that changes in GFR rather than tubular water reabsorption lead to the major adjustments in urine flow rates accompanying changes in environmental salinity.Removal of the corpuscles of Stannius was not followed by a significant change in GFR indicating that an adequate (normal) effective filtration pressure is independent of a corpuscular pressor substance.In 8 of 17 Stanniectomised eels urine flow rates exceeded GFR demonstrating that, under these experimental conditions, eel renal tubules secrete water.Multiple tissue electrolyte changes followed Stanniectomy; the 75% increase in the plasma calcium concentration is of particular interest. This increase was probably due to a reduction in the net rate of calcium deposition in bone and not to a change in the renal handling of calcium.

Effect of coenzyme Q administration on the periodontal lesions in citrated rats

Citrate may play a role in the transport, mobilization and perhaps deposition of calcium in bone. It is capable of rendering soluble the insoluble calcium salts. Tanner (1967) has observed that citrated rats disclosed severe porosity with alveolar atrophy and myelofibrosis accompanied by bone resorption and hyperemia of the gingiva. This indicated citrates to be directly attributed to loss of alveolar bone and intimately related to advanced alveolar atrophy. This study was designed to confirm the histopathological changes in periodontal tissues in citrated rats and simultaneously to evaluate the calcium and citrate levels in blood. Since it is known that coenzyme Q which is now generally recognized to have an important role in the electron transport system has a profound influence on the citric acid metabolism, the effect of coenzyme Q on the changes in blood and periodontal tissues found in the citrated rats were also studied.Male albino rats of the Wistar strain, 5 to 7 weeks old and weighing 120-140 gm. were initially fed on powdered normal diet. All animals were given this diet for two weeks before the beginning of the experiment. The animals were then alloted to two groups; one group continuing with the normal diet and another group with the citrate diet which consisted of 10 gm. of sodium citrate and 10 gm. of citric acid homogenized with 80 gm. of powdered normal diet. Both normal and citrated rats were further assigned to subgroups. One subgroup of both groups served as a control. Animals in the second subgroup of both groups were given the diet added coenzyme Q7 powder; each subgroup was fed on normal diet contained 0.005% coenzyme Q7 and citrate diet contained 0.005% coenzyme Q7, respectively. The experimental period lasted three months. At the end of that time the animals were given water but received no food for 15 to 18 hours before the blood was collected. After the blood collection by heart puncture the animals were stunned by a sudden blow on the head and decapitated. The mandibles were fixed to 10% formalin, and then decalcified in a solution of 5% nitric acid and formalin. They were then imbedded in paraffin, and stained with hematoxylin and eosin. The citric acid content of blood was determined by the method of Ettinger et al. (1952) and the serum calcium by the method of Kingsley and Robnett (1957).In the citrated rats, marked osteoporosis of the alveolar bone and atrophy of the periodontal membrane accompanied by myelofibrosis were observed. These histopathological findings were alleviated by prolonged administration of coenzyme Q. Hypercitricemia with hypercalcemia found in the citrated animals were also restored to the normal level by coenzyme Q administration.

The treatment of adult phosphate diabetes and Fanconi syndrome with neutral sodium phosphate

Two adults with untreated phosphate diabetes and severe osteomalacia as demonstrated by wide osteoid seams on bone biopsy, multiple pseudofractures and marked skeletal rarefaction were studied using metabolic balance technics, radiocalcium kinetics and urinary hydroxyproline excretion. Negative calcium balance with high fecal calcium, low normal rates of deposition of calcium in bone and normal rates of hydroxyproline excretion were found. The acute as well as long-term effects of phosphate supplements as the only therapy were investigated by these methods. Healing of the bone disease resulted, as judged by clinical, roentgenologic and histologic criteria, and was accompanied by a striking increase in bone turnover (increased calcium deposition rate in bone and, to a lesser extent, increased calcium removal rate from bone; increased urinary hydroxyproline excretion and increased levels of serum alkaline phosphatase). This increase in bone turnover was accompanied by increased absorption of calcium and phosphorus from the gastrointestinal tract. There was a good correlation between the radiocalcium kinetics and hydroxyproline excretion, less correlation between these two parameters and the levels of alkaline phosphatase. Acute and long-term withdrawal of phosphate supplements was associated with fall of the first two parameters toward pretreatment levels; long-term withdrawal was accompanied by a decrease in the levels of serum alkaline phosphatase as well. Phosphate therapy also produced changes in skeletal retention of an acute load of sodium fluoride, and in the urinary excretion of hydroxylysine which paralleled those obtained using the other parameters of bone turnover. A similar response to phosphate therapy was observed in a subject with the adult Fanconi syndrome, partially treated with vitamin D. In another subject with normal serum phosphate levels and idiopathic osteoporosis, therapy with phosphate for five months produced only minor changes in the aforementioned parameters although the direction was similar to that in the other subjects. In a patient with mild phosphate diabetes, short-term phosphate supplements elicited responses in the same direction, although of lesser magnitude, as in patients with more severe osteomalacia. It is concluded that phosphate treatment of patients with phosphate diabetes and osteomalacia results in stimulation of initially low-normal rates of bone formation by a mechanism as yet undefined. The stimulation of bone resorption which also accompanied phosphate therapy in these subjects may result in part from secondary hyperparathyroidism.

Effect of alkali administration on calcium metabolism.

ABSTRACT In 12 patients with hypoparathyroidism, administration of calcium carbonate (10.0–18.0 g/day) was effective in increasing serum calcium by 2.5 to 4.0 mg/100 ml. Tracer studies with 47Ca were performed one or more times in 6 individuals before or after treatment with calcium carbonate or other salts. With these isotope data, and utilizing a 2-compartment open-ended model to describe calcium distribution, compartment sizes and rates of movement of miscible calcium were calculated. The results indicated that increasing serum calcium by use of calcium carbonate in hypoparathyroid patients expanded the size of fast- and slow-exchanging compartments, but decreased calcium interchange between these compartments and reduced calcium deposition in bone. Alkali administration to a single normal individual whose serum calcium was stable also decreased calcium interchange between fast- and slow-exchanging compartments, and, in addition, decreased size of these compartments. The effect of acid salts on calcium...

Action of thyrocalcitonin on bone.

A CONSIDERABLE amount of evidence has been presented which suggests that thyrocalcitonin, the hypocalcemic, hypophosphatemic hormone first described by Hirsch et al.1, promotes the deposition of calcium in bone. Aliapoulias et al.2 indicated that in tissue culture, thyrocalcitonin exerted a direct positive effect on the deposition of calcium into mouse calvariae. Foster et al.3 have also recently indicated that thyrocalcitonin promoted calcium uptake by perfused isolated bone. Investigations from these laboratories4 indicated that perfusion of rats over a period of 1 h with thyrocalcitonin and calcium-45 resulted in an increased isotopic concentration in the bones as compared to the isotopic concentration of the bones of rats perfused with calcium-45 only. Further, we4 have demonstrated that the administration of thyrocalcitonin to rats over a period of 5 days led to an increased positive calcium balance and a reduction of endogenous calcium.

Promotion of Bone Calcification by Sodium Fluoride: Short-Term Experiments on Newborn Rats Using Tetracycline Labeling

PROMOTION of calcium deposition in otosclerotic bone by administration of large doses of sodium fluoride has been proposed in an effort to hasten maturation and inactivation of an actively growing otosclerotic focus.1This proposition was based on a number of theoretical considerations, including the resemblance of the active spongy stage of otosclerosis to the gnarly young bone found in callus formation and to the spongy bone of Paget's disease. Recent observations have demonstrated a beneficial effect of large doses of sodium fluoride on the symptoms of Paget's disease and on the negative calcium balance of this condition.2We have confirmed this observation in a 57-year-old female patient with stapes fixation produced by Paget's disease of the middle ear and labyrinth capsule. Severe pain and lameness of the femur and hip joint produced by Paget's disease were markedly improved by the administration of sodium fluoride, 60 mg daily for