bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effects of ovariectomy and 17β-estradiol on cortical bone histomorphometry in growing rats
Authors: Turner Russell T. , Vandersteenhoven Jacob J. , Bell Norman H. 
Published: February 2010

Abstract
The effects of ovariectomy for four weeks and of 17β-estradiol for three weeks on histomorphometry of the tibial diaphysis were determined in young rats. The effects of ovariectomy on histomorphometry of subcutaneous implants of demineralized bone matrix were also examined. Groups of young female rats were either ovariectomized or sham operated. After surgery, the animals were weight matched and pair fed. Despite the same caloric intake, ovariectomized rats grew more rapidly than pair-fed, sham-operated controls but were significantly heavier at sacrifice in only one of three experiments. Ovariectomy did not change mean serum calcium, phosphate, 25-hydroxyvitamin D (25-OHD), or 1,25-dihydroxyvitamin D [1,25(OH)2D] but significantly lowered mean serum magnesium. Serum estradiol was not detectable in ovariectomized animals. 17β-Estradiol in ovariectomized animals significantly increased mean serum estradiol and lowered mean serum phosphate but did not change mean serum calcium, magnesium, 25-OHD, or 1,25(OH)2D, as compared to values in sham-operated controls. Bone formation rate was significantly enhanced in ovariectomized animals at both the endosteal and periosteal surfaces of the tibial diaphysis as compared to values in sham-operated controls. The increase in bone formation rate was reversed by 17β-estradiol at the periosteal but not endosteal surface. Ovariectomy increased the bone apposition rate, mineralization rate, and osteoid thickness of the tibial diaphysis. These increases were reversed by 17β-estradiol. In implants, ovariectomy increased the resorption of implant matrix and enhanced the formation of new matrix. Ovariectomy resulted in increases in forming surface and resorbing surface in the implants. The results of these short-term studies indicate (a) that ovariectomy in growing rats leads to increases in both bone formation and resorption, and (b) that these increases are reversed by treatment with 17β-estradiol.
Incidence of hip fractures in osteoporotic women treated with sodium fluoride
Authors: Riggs B. Lawrence , Baylink David J. , Kleerekoper Michael , Lane Joseph M. , Melton L. Joseph , Meunier Pierre J. 
Published: February 2010

Abstract
It has been suggested recently that, although fluoride therapy may decrease the occurrence of vertebral fractures, it could increase the risk of hip fractures. To evaluate this possibility, we combined retrospective data from five medical centers that have had a large experience with this therapeutic regimen. In 416 osteoporotic patients who were followed for more than 1,000 patient-years of fluoride treatment, there were 17 nontraumatic hip fractures. This incidence of 1.6% per year is similar to the incidence, 1.9% per year, for 120 of the patients in this series who had been followed prospectively for 3 years prior to initiation of fluoride therapy. The expected incidence for women of the same age in the general community is 0.5% per year. Thus, untreated osteoporotic women are at increased risk for hip fracture, but treatment with fluoride seems neither to decrease nor to increase the incidence of hip fracture substantially.
A tissue-specific protein in rat osteogenic tissues
Authors: Mardon Helen J. , Dr. Triffitt James T. 
Published: February 2010

Abstract
A tissue-specific protein fraction has been detected in rat osteogenic tissue. Dissociative extraction of adult rat bone matrix with 4 M guanidinium chloride solution was followed sequentially by gel chromatography and Polyacrylamide gel electrophoresis. By the latter procedure a prominent protein component of molecular weight 19,000 was isolated from the low molecular weight fraction, and antibodies directed against this protein were raised in rabbits. The antibodies were mainly against antigenic sites on this protein, as shown by protein blotting techniques. By embedding rat tissues in hydrophilic plastic and by using immunohistochemical procedures the presence of this protein was demonstrated specifically in bone matrix in vivo, in osteogenic tissue developing in diffusion chamber culture, and in a malignant osteoblast cell line (UMR 106). Soft tissues (liver, kidney, spleen, gut, skin, thymus, eye) showed no reactivity with the antiserum and in vitro a further malignant osteoblast cell line (ROS 17/2.8) did not synthesize the 19,000 molecular weight protein. This protein appears to be expressed solely by osteogenic tissue and may be used as a biochemical criterion of osteogenic differentiation.
Ability of four different techniques of measuring bone mass to diagnose vertebral fractures in postmenopausal women
Authors: Ott Susan M. , Kilcoyne R.F. , Chesnut Charles H. 
Published: February 2010

Abstract
Since bone mass has been shown to be an important determining factor of fractures in vitro, we undertook a study to evaluate whether bone mass measurements could separate postmenopausal women with vertebral compression fractures from women of a similar age without fractures. We also wanted to see if methods of measuring bone mass at the spine would be more sensitive or specific than methods that measured bone at the wrist or the entire skeleton. The techniques used were: total body calcium by neutron activation analysis (TBC), single photon absorptiometry (SPA), dual photon absorptiometry (DPA), and quantitative computed tomography (QCT). Normal women aged 20–85 were measured, but only those &gt;50 yr were used in the analysis. Mean values for women with fractures were significantly lower than normals (p &lt; .001): TBC 642 ± 103 g vs. 764 ± 114; SPA .658 ± .134 g/cm vs. .779 ± .142; DPA 3.75 ± .82 g/cm vs. 4.37 ± .86; QCT 59.0 ± 25.7 mg/cc vs. 92.6 ± 36.0. However, each of the methods showed considerable overlap between women with and without fractures. At 90% specificity the sensitivities of the tests were: TBC 34%; SPA 29%; DPA 33%; QCT 36%. When values were expressed as the % expected (based on age and height) then the sensitivities were: TBC 52%; SPA 36%; DPA 35%; QCT 44%. Using Bayes' theorem, we constructed curves showing the posttest probability of these tests at a prevalence of 20%. None of these bone mass measuring techniques showed complete separation between normal and osteoporotic women with fractures; about one-half of the women with fractures were below the normal range. The risk of having a fracture increases as bone mass declines, but our data suggest that bone mass is not the only factor leading to vertebral fractures in postmenopausal women.
Parathyroid hormone stimulation of mitosis in rat thymic lymphocytes is independent of cyclic AMP
Authors: Atkinson M.J. , Hesch R.-D. , Cade C. , Wadwah M. , Perris A.D. 
Published: February 2010

Abstract
The in vitro mitotic response of rat thymic lymphocytes to hPTH(1–34), hPTH (1–38), and 8,18 NIe hPTH(1–34) exhibits a dependency upon extracellular calcium. Removal of extracellular calcium or the addition of Verapamil (5 μg/ml) or trifluoroperazine (10 μM) abrogated the mitotic response. Mitogenic concentrations of 8,18 NIe hPTH(1–34) increased calcium 45 uptake from 4.49 ± 0.25 to 8.23 ± 0.75 pMol/106 cells/min. The intracellular calcium concentration, measured by Quin 2 fluorescence, also increased after addition of 8,18 NIe hPTH(1–34).
Parathyroid hormone-induced activation could not be demonstrated in an otherwise responsive thymocyte membrane adenylate cyclase. In intact cells mitogenic levels of 8,18 NIe hPTH(1–34) decreased intracellular cyclic AMP content. This response was blocked by both 3-isobutyl 1-methyl xanthine and trifluoroperazine, and may indicate activation of calcium-dependent phosphodiesterase.
We conclude that PTH stimulates thymic lymphocyte proliferation independently of cyclic AMP, and that changes in cellular calcium homeostasis are intimately involved in the action of PTH. In all of the assays employed, the hitherto antagonistic analogue 8,18 NIe 34 Tyr bPTH(3–34)amide proved to be an agonist. We postulate that the receptor utilized for this PTH action may not exhibit classical PTH structure-activity specificities.
Effects of extracellular calcium and magnesium on cytosolic calcium concentration in fura-2-loaded bovine parathyroid cells
Authors: Chen Chu J. , Anast Constantine S. , Posillico James T. , Brown Edward M. 
Published: February 2010

Abstract
A newly developed calcium-sensitive dye, Fura-2, was employed in dispersed bovine parathyroid cells to study the effects of extracellular calcium and magnesium on cytosolic calcium concentration and parathyroid hormone (PTH) release. In comparison with control cells, Fura-2-loaded parathyroid cells showed the same maximal rate of PTH release, set-point for extracellular Ca++ (the calcium concentration producing half of the maximal inhibition of PTH release), and maximal inhibition of PTH release (71.6%) by high extracellular Ca++. At an extracellular Mg++ concentration of 0.5 mM, raising extracellular Ca++ in a stepwise fashion from 0.5 mM to 2.0 mM produced a dose-dependent, statistically significant (p &lt; 0.01) increase in cytosolic Ca++ from 198 ± 24 nM (0.5 mM Ca++) to 411 ± 21 nM (2.0 mM Ca++) which closely paralleled the concomitant decrease in PTH release. An elevation of extracellular Mg++ from 0.5 mM to 5 mM, at an extracellular Ca++ of 0.5 mM, resulted in a transient spike of cytosolic Ca++ which lasted for approximately 30 seconds, followed by a small but stable increase in the cytosolic Ca++ concentration (174 ± 7 nM vs. 237 ± 10 nM, n = 4, p &lt; 0.01). Prior removal of extracellular calcium by addition of an excess of EGTA did not abolish the transient spike induced by high extracellular magnesium concentrations in Fura-2-loaded cells, suggesting that this rapid increase in cytosolic Ca++ arises, at least in part, from intracellular stores of Ca++. This is supported by the observation that pretreating cells with ionomycin resulted in disappearance of the magnesium-induced spike. In parallel experiments, the values for cytosolic calcium concentration at high and low extracellular calcium and magnesium concentrations in cells loaded with Fura-2 were comparable to those in cells loaded with Quin-2. These results show that Fura-2 may be employed to measure the cytosolic Ca++ concentration in dispersed bovine parathyroid cells and that extracellular Ca++ and Mg++ produced sustained increases in cytosolic Ca++ in cells loaded with this dye which are comparable to those seen with Quin-2-loaded cells. In addition, however, probably because of the lower loading concentrations possible with Fura-2, cells loaded with this dye show Mg++-induced spikes in intracellular Ca++, resulting, in part, from release of intracellular Ca++. These Ca++ transients support other data suggesting the possibility of an extracellular divalent cation receptor on parathyroid cells, which may produce some of its effects on parathyroid function by mobilizing intracellular Ca++.
Age-related rise in parathyroid hormone in man: The use of intact and midmoleeule antisera to distinguish hormone secretion from retention
Authors: Young Gloria , Marcus Robert , Minkoff Jerome R. , Kim Lance Y. , Segre Gino V. 
Published: February 2010

Abstract
Circulating levels of parathyroid hormone (PTH) rise with age in normal men and women. To resolve the basis for this observation we measured iPTH in 137 normal men and women, age 23 to 85 years, using two antisera which responded to different portions of the PTH molecule. A midmoleeule assay (Mid-PTH) employed antiserum NG-5, which recognizes mid- and carboxy-terminal portions of hPTH, whereas antiserum CK-67, which recognizes determinants in the 1–34 hPTH sequence, was used to measure intact PTH (NH2-PTH). Two-hour fasting urine was collected for measurement of creatinine clearance and excretion indices of phosphorus and cyclic AMP. Serum was analyzed for 25-hydroxyvitamin D (25-OHD) in addition to iPTH. Mid-PTH rose significantly with age in the 72 women (r = 0.38, p &lt; 0.001) and in the 65 men (r = 0.40, p &lt; 0.001). NH2-PTH rose with age in women (r = 0.23, p &lt; 0.05), but a change in men was not significant (r = 0.19, n.s.). Cyclic AMP excretion rose significantly with age in both women (r = 0.42) and men (r = 0.41), whereas phosphorus excretion rose significantly in women only (r = 0.32, p &lt; 0.01). 25-OHD levels were 27.5 ± 1.3 ng/ml for women and 26.1 ± 1.2 ng/ml for men. No change in 25-OHD was observed with age in women, and a significant decrease in men was due entirely to extremely high values in three young subjects. Endogenous creatinine clearance decreased with age in women (r = -0.65, p &lt; 0.001) and men (r = -0.46, p &lt; 0.001). In women, creatinine clearance correlated significantly with Mid-PTH (r = 0.21, p &lt; 0.05), but the relationship of Mid-PTH to age remained significant when the effect of renal function was eliminated in the multiple regression. Creatinine clearance did not correlate significantly with NH2-PTH. Fourteen women with the highest values of NH2-PTH were compared with 12 women with the lowest NH2-PTH levels for multiple indices of PTH action and bone turnover, including urinary excretion indices for calcium, phosphorus, cyclic AMP, and hydroxyproline, and serum alkaline phosphatase activity and 25-OHD. In no case were significant differences observed between the two groups of elderly women. We conclude that increased iPTH with age in women reflects an increase in steady-state levels of intact hormone. Although a similar phenomenon probably occurs in men, results from men in this study did not reach significance. Although it is considered likely that elevated PTH levels may contribute to age-related bone loss, we found no correspondence of iPTH to several measures of PTH action and bone turnover. These results point out the need for a prospective evaluation of the relationship of iPTH to bone loss in elderly men and women.
Modifications of the mouse calvarial technique improve the responsiveness to stimulators of bone resorption
Authors: Lerner Ulf H. 
Published: February 2010

Abstract
The effect of a preincubation period, in basic medium or in medium with inhibitors of prostaglandin biosynthesis, on the response to different stimulators of bone resorption has been studied in an organ culture system using calvarial bones from neonatal mice. Bone resorption was assessed either by the release of 45Ca or by the release of 3H from [3H]-proline labeled bones. Preincubated bones were cultured for 18–24 hr in medium, with and without indomethacin, hydrocortisone, and dexamethasone, and then extensively washed before being transferred to culture medium containing different stimulators of bone resorption. Preincubation in medium containing indomethacin or corticosteroids resulted in an increased response to parathyroid hormone (PTH), prostaglandin E2 (PGE2), 1-alpha-hydroxyvitamin-D3 and thrombin as compared to the response in bones which were exposed to the stimulants directly after dissection. Preincubation in basic medium did not enhance the subsequent response to PTH. By using a preincubation period in indomethacin, the dose-response curves for the stimulatory effect of PTH and PGE2 on mineral mobilization could be sensitized as compared to the curves obtained with fresh bones. Thus, the concentration of agonists causing 50% stimulation of 45Ca release was decreased by a factor of 10. The threshold for actions of PTH and PGE2 on 45Ca release was 0.01–0.03 and 1–3 nmol/l, respectively.
Biphasic effects of epidermal growth factor on bone nodule formation by isolated rat calvaria cells in vitro
Authors: Dr. Antosz Mark E. , Bellows C.G. , Aubin J.E. 
Published: February 2010

Abstract
Osteoblast-like cells isolated from fetal rat calvaria (RC) form three-dimensional nodules in vitro having the morphological and immunohistochemical characteristics of bone. When administered continually over 21 days of culture, EGF caused a dose-related inhibition of nodule formation, as well as a reduction in the proportion of mineralized nodules, at concentrations between 10−12 to 10−7M. The same conditions caused an increase in both cell proliferation and saturation density in the cultures, suggesting that decreased nodule formation was not the result of general cell toxicity. Inhibitory concentrations of EGF caused a reversible alteration in cell shape, although changes in protein synthesis were not detectable. Indomethacin (5 × 10−7M) did not affect either nodule formation or its inhibition by EGF. When cultures were pretreated for various time periods with 10−8M EGF followed by its removal and continued culture in supplemented medium for 21 days, the number of bone nodules formed with brief exposures to EGF (4 hr up to 48 hr) was increased compared to the numbers formed in supplemented medium alone, whereas exposures to EGF of 4 days or longer decreased the number of nodules formed. These data indicate that EGF can either increase or decrease the osteogenic potential of RC cells in vitro depending on the duration of exposure to the factor.
The influence of sex steroid hormones on plasma calcitonin response to the calcium clamp in normal subjects
Authors: Tørring O. , Bucht E. , Sjöberg H.E. 
Published: February 2010

Abstract
The influence of sex steroid hormones on plasma calcitonin levels in healthy subjects was studied in 15 males and 10 premenopausal (PREMF) and 12 postmenopausal females (PMF). A standardized ionized calcium stimulus was achieved by means of the calcium clamp technique, and a sensitive RIA was used to determine immunoreactive CT (iCT) in plasma. Plasma iCT levels increased in response to the calcium clamp with an initial peak at 15 or 30 min. The iCT levels then declined but remained at an elevated level for the rest of the 180-min infusion period in all three groups. In males a positive correlation was found between the serum testosterone levels at 0 min and the estimates for initial iCT response, i.e., the change between 0 and 15 min (r = 0.80, n = 11, p &lt; 0.01), between 0 and 30 min (r = 0.56, n = 15, p &lt; 0.05) and between 0 and the maximum value (r = 0.68, n = 15, p &lt; 0.01). In the two female groups no such correlation was found. Serum 17 β-estradiol or dehydroepiandrosterone sulfate concentrations were not correlated either to basal iCT levels or to the iCT response to the calcium clamp. PMF had lower levels of 17 β-estradiol than PREMF (p &lt; 0.001), while the testosterone levels were similar. The iCT levels and response to the calcium clamp showed no significant difference in the two groups. The results indicate that sex difference in the plasma CT levels may be related to different testosterone levels. In addition, physiological levels of serum 17 β-estradiol seem to bear no direct relation to basal or Ca-stimulated iCT levels in pre- and postmenopausal females.
Biological activity of 19-nor, 10-keto, 25-hydroxyvitamin D3
Authors: Gray T.K. , Kleckner N.W. , Malloy P.J. , Feldman D. , Sivam G. , Dodd R.C. , Cohen M.S. 
Published: February 2010

Abstract
19 nor, 10 keto, 25-hydroxyvitamin D3 (19/10–25OHD3) is a metabolite of 25-OHD3 produced in vitro by various phagocytes including normal human blood monocytes and transformed cell lines, U937 and HL-60. We recently reported that 19/10–25OHD3 induced differentiation of U937 cells. In these studies, 19/10–25OHD3 alone produced no detectable effect on the growth rates, surface adherence, and oxidative metabolism of U937 and HL-60 cells. When combined with lymphocyte-conditioned medium (LCM), 19/10–25OHD3 reduced proliferation, increased surface adherence and stimulated luminol-dependent luminescence (LDL) of the U937 cells. In contrast, the combination of 19/10–25OHD3 and LCM had no effect on the growth of HL-60 cells but did increase the surface adherence and the expression of a complement receptor component. 19/10–25OHD3 competed for tritium-labeled 1,25(OH)2D3 binding to receptors extracted from cultured human skin fibroblasts. This displacement capacity was 600 times weaker than that of unlabeled 1,25(OH)2D3. Incubation of human skin fibroblasts for 24 hr with 19/10–25OHD3 induced 25OHD3-24-hydroxylase activity in the fibroblasts. The inductive potency of 19/10–25OHD3 was 1/50 that of 1,25(OH)2D3. These results demonstrate bioactivity of 19/10–25OHD3 in several systems. At least one of these responses, the induction of 25OHD3-24-hydroxylase, is a receptor-mediated event. Some of the other responses may be independent of the cellular receptor for 1,25(OH)2D3. Interestingly, the potency of 19/10–25OHD3 was highest in the receptor-mediated response (1:50) and lower in the other parameters, ranging from 1: 100 to 1:600 compared to 1,25(OH)2D3. This range of bioactivity in phagocytes and fibroblasts is presently unexplained.
A simple spectrophotometric assay for micromolar amounts of lanthanum in the presence of calcium and phosphate
Authors: Fernandez-Gavarron Federico , Brand Joseph G. , Rabinowitz Joseph L. 
Published: February 2010

Abstract
A sensitive spectrophotometric assay for micromolar amounts of lanthanum in the presence of calcium and phosphate (as hydroxyapatite) was developed utilizing the change in absorption (at 652 nm) when the dye arsenazo III was complexed with lanthanum. Arsenazo III was used at a level of 25 μM and the solution pH was maintained at 3.1 with 0.2 M sodium acetate. Lanthanum concentrations down to 0.5 μM could be reliably assayed. Calcium ion did not complex well with arsenazo III at pH 3.1. With calcium present at 100 μM and lanthanum at 10 μM, the assay was 115 times more sensitive for lanthanum. The assay is simple, rapid, reproducible and, unlike the assay using radioactive lanthanum, can be performed at any time.
Biological activity of chicken calcitonin: Effects on neonatal rat and embryonic chick osteoclasts
Authors: Dempster D.W. , Murrills R.J. , Horbert W.R. , Arnett T.R. 
Published: February 2010

Abstract
Chicken calcitonin (cCT) has recently been synthesized according to nucleotide sequence data. We have investigated the in vitro effects of this hormone on the activity of disaggregated, neonatal rat and embryonic chick osteoclasts. While synthetic cCT inhibited bone resorption by neonatal rat osteoclasts at concentrations as low as 0.1 pg/ml, it failed to produce a significant reduction in bone resorption by embryonic chick osteoclasts, even at concentrations as high as 1 μg/ml. Similarly, cCT at 1 pg/ml reproducibly produced the rapid and dramatic inhibition of rat osteoclast motility characteristic of other calcitonins, as judged by time-lapse video recording, but did not impair the motile behavior of chick osteoclasts at concentrations up to a million-fold higher. Previous studies showing that embryonic chick osteoclasts were unresponsive to synthetic salmon calcitonin left open the possibility that the native hormone was required to produce an inhibitory effect. We conclude that the osteoclast is not a target cell for calcitonin in the embryonic chick; further studies will be required to define a role, if any, for this potent but enigmatic hormone in birds.