Search PubMed⌕ Search

Biomedical subjects

D J Baylink

Publications and source records attributed to D J Baylink.

At least 217 records · Page 12Linked to original sources
PubMed1990

Theoretical physical chemical studies of the cause of fluoride-induced osteomalacia.

In this study we investigated the possibility of the formation of a calcium fluoride surface film on the new bone matrix in patients undergoing fluoride treatment for osteoporosis. This calcium fluoride film could interfere with the normal mineralization process and lead to hyperosteoidosis (osteomalacia), a well-documented complication seen in fluoride-treated patients. During treatment, fluoride circulating in the blood and extracellular fluid of patients, could interact with the components of the serum, but particularly calcium and magnesium ions. The interrelationships among serum components in the presence of fluoride ion may result, at thermodynamic equilibrium, in deposition on the apatitic bone surface of phases such as calcium fluoride, fluorapatite, or fluorhydroxyapatite. Differences in the phase deposited among patients could result in differences in response to fluoride treatment. A computer program based on equilibrium thermodynamic data was utilized to study the physicochemical calcium, fluoride, and phosphate interrelationships in serum. In all the computer calculations, fluorhydroxyapatite (FHAP), alone or in combination with hydroxyapatite (HAP), was determined to be the thermodynamically stable precipitating surface phase. These data strongly suggest that calcium fluoride surface film is not the reason for the delay of mineralization of fluoride-stimulated new bone. Based on these calculations, we now advance the hypothesis that the effect of fluoride to cause osteomalacia is due to an effect on osteoblasts and also on osteocytes.(ABSTRACT TRUNCATED AT 250 WORDS)

Biopsy↗
PubMed1990

Insulin-like growth factor-I and insulin-like growth factor-II induce c-fos in mouse osteoblastic cells.

We investigated the expression of c-fos in mouse osteoblast-like cultures treated with insulin-like growth factor (IGF)-I and IGF-II. The IGFs are present in bone, are produced by osteoblast-like cells in culture, and stimulate osteoblast cell proliferation. Quiescent, subconfluent cultures of the clonal osteoblast-like mouse calvarial cell line, MC3T3-E1, were treated with 10 ng/ml of IGF-I or IGF-II. RNA was extracted at 0, 15, 30, 60, 120 and 240 minutes, and c-fos messenger RNA (mRNA) was analyzed on Northern blots. Both IGFs transiently increased c-fos mRNA levels 25-28 fold at 15-30 min. To determine if c-fos induction was unique to the MC3T3-E1 cell line, effects of IGF-1 and IGF-II (3 ng/ml) were also tested in quiescent, serum-free primary mouse calvarial cells. Levels of c-fos mRNA were increased at 15 and 30 minutes (40-fold with IGF-I and 5-fold with IGF-II). These results indicate that IGF-I and IGF-II caused a rapid and transient induction of c-fos mRNA in murine osteoblasts.

Animals↗
PubMed1990

Insulin-like growth factors I and II are present in the skeletal tissues of ten vertebrates.

Previous studies have shown that insulin-like growth factor I and insulin-like growth factor II (IGF I and IGF II) constitute an important family of skeletal growth-regulating peptides. We undertook this study to determine if, as in the case of sera in various animals, IGF I and IGF II are conserved in the skeletal tissues of various vertebrates. Skeletal tissues of ten animals representing five of the six vertebrate classes were studied: monkey, dog, sheep, adult mice, neonatal mice, chicken, lizard, frog, trout, and shark. The skeletal tissues were pulverized and demineralized with 10% ethylenediaminetetraacetic acid (pH 7.0) to extract the soluble matrix proteins. The tissue extracts were concentrated, dialized, and subjected to specific human IGF assays. IGF I and IGF II were measured with a radioimmunoassay and a radioreceptor assay, respectively. We found that 1) there are detectable human IGF I- and II-like substances in all extracts, 2) IGF values obtained in the skeletal extracts were not caused by binding protein artifacts, 3) in general there is more IGF II than IGF I, and 4) the skeletal tissue levels of the IGFs are comparable with their respective serum levels. We conclude that, in the skeletal tissues of vertebrates, the IGFs are conserved and may be important regulators of osteogenesis.

Animals↗
PubMed1990

Development of valid methods to measure insulin-like growth factors-I and -II in bone cell-conditioned medium.

A variety of human cells and biological fluids have been shown to produce or contain insulin-like growth factor (IGF)-specific binding proteins (BPs). The existence of these BPs in serum and conditioned medium of cell and organ cultures has complicated radioligand assays for measurement of IGFs. Various strategies have been proposed to avoid interference of BPs with these assays, including acid-ethanol precipitation of BPs and acid-gel filtration. Many of these procedures are time consuming, exhibit low recoveries, and do not completely eliminate BP artifacts. In this study we have investigated interference of inhibitory IGF-BP (In-IGF-BP) purified from bone cell-conditioned medium in an IGF-II RRA and IGF-I RIA and developed methods to neutralize In-IGF-BP artifacts in IGF assays. In the IGF-II RRA, purified In-IGF-BP competed for [125I]IGF-II binding to H-35 cells in a dose-dependent manner and, thus, increased the apparent value for IGF-II in the medium. Fifty percent inhibition of [125I]IGF-II binding to H-35 cells was seen at 12.2 and 5.7 ng/ml unlabeled IGF-II and IN-IGF-BP, respectively. In-IGF-BP also competed for [125I]IGF-I in the IGF-I RIA; however, the interference was much less in the IGF-I RIA compared to the IGF-II RRA. Fifty percent displacement of [125I]IGF-I binding was seen at 0.25 and 5 ng/ml unlabeled IGF-I and In-IGF-BP, respectively. Our approach to eliminate BP artifacts was as follows. We knew that In-IGF-BP showed comparatively equal binding affinities with both IGF-I and IGF-II, and binding of these ligands to cell receptors (IGF-II) and antibodies (IGF-I) was very specific (2% and 0.5% cross-reactivity for IGF-I and IGF-II, respectively). Therefore, in the IGF-I RIA we blocked the In-IGF-BP artifacts by adding an excess of IGF-II, and in the IGF-II RRA we blocked the In-IGF-BP artifacts by adding an excess of IGF-I. By incubating purified In-IGF-BP with different amounts of IGF-I, we found that 30-min preincubation of 5 ng In-IGF-BP with 10 ng IGF-I completely blocked BP artifacts in the IGF-II RRA. Similarly, preincubation of In-IGF-BP with IGF-II blocked BP artifacts in the IGF-I RIA.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Multiple osteocalcin fragments in human urine and serum as detected by a midmolecule osteocalcin radioimmunoassay.

Reliable markers of bone formation are essential to the investigation of metabolic bone disorders. In this regard, evidence indicates that circulating levels of human osteocalcin (OC) correlate with the skeletal isoenzyme of alkaline phosphatase and can be used as an index of bone formation. A disadvantage of using serum OC as a marker of formation is its diurnal variation. To address this problem we carried out our studies to determine the usefulness of urine in the assessment of bone turnover. Using a midmolecule specific human OC RIA, we were able to detect OC in urine of normal adults (42 mugeq/g creatinine), normal children (849 mu/geq/g creatinine), and Paget's disease patients (613 mugeq/g creatinine). Immunoreactive fragments of OC in human urine and human serum were separated by high pressure liquid chromatography. Multiple fragments were found in normal adult urine that were not detected in normal adult serum. Uremic and Paget's disease sera contain several immunoreactive forms of OC, other than the intact molecule, not found in normal adult serum. Additionally, both Paget's disease sera and urine contained a specific peak of immunoreactive material, eluting at 25% acetonitrile, that was not found in any other serum or urine tested. Urinary OC (uOC) correlated with both skeletal alkaline phosphatase (r = 0.91) and serum OC (r = 0.83), indices of skeletal formation. While uOC has a diurnal variation similar to that of serum OC, determinations of 24-h uOC give integrated values of daily bone turnover rates. Z-Score analysis indicates that uOC (z = 14.04) is better able to distinguish between normal children with high bone turnover and normal adults than either skeletal alkaline phosphatase (z = 8.87) or serum OC (z = 9.01).

Adult↗
PubMed1990

Effects of short term administration of recombinant human growth hormone to elderly people.

We evaluated the effects of recombinant human GH (rhGH) in 16 men and women more than 60 yr of age. After 10 days of dietary equilibration and control collections, subjects were randomly assigned to receive 0.03, 0.06, or 0.12 mg/kg rhGH by daily injection for 7 days. A brisk rise in circulating somatomedin-C (insulin-like growth factor-I) occurred in all subjects, and this rise was dose dependent. rhGH produced striking changes in nitrogen retention, sodium excretion, and the parathyroid-vitamin D axis. Twenty-four-hour urinary nitrogen excretion decreased from 8.00 +/- 0.33 to 5.01 +/- 0.33 g (P less than 0.001), and sodium excretion decreased from 45.9 +/- 2.96 to 21.2 +/- 3.48 mmol/day (P less than 0.001). Serum calcium concentrations did not change, but serum inorganic phosphorus levels of 1.08 +/- 0.04 mmol/L at baseline increased significantly after rhGH treatment to 1.33 +/- 0.04 mmol/L (P less than 0.001). Increases were also observed in circulating PTH (53.2 +/- 6 vs. 39.5 +/- 4.2 ng/L; P less than 0.01) and calcitriol (82.8 vs. 65.8 pmol/L; P less than 0.05). A rise in serum osteocalcin (10.3 +/- .86 vs. 8.0 +/- 0.5 micrograms/L; P less than 0.05) was accompanied by increased urinary excretion of hydroxyproline (628 +/- 63 vs. 406 +/- 44 mumol/day; P less than 0.01). Despite the reduction in sodium excretion, marked increases were observed in urinary calcium (6.04 +/- 0.97 vs. 3.27 +/- 0.40 mmol/day; P less than 0.01). rhGH significantly impaired oral glucose tolerance and reduced insulin sensitivity, but was otherwise well tolerated and produced no systematic changes in weight or blood pressure. The results of this study indicate that rhGH requires further study as a potential agent for attenuating or reversing the loss of muscle and bone in elderly people.

Age Factors↗
PubMed1990

Increased monocyte interleukin-1 activity and decreased vertebral bone density in patients with fasting idiopathic hypercalciuria.

Idiopathic hypercalciuria (IH) is a heterogeneous disorder frequently observed in patients with nephrolithiasis. At one extreme of its clinical spectrum is fasting hypercalciuria (FH), a condition characterized by increased bone resorption and turnover. In previous studies we have shown that monocytes from patients with high turnover osteoporosis and from women in early postmenopause elaborate increased amounts of interleukin-1 (IL-1), a cytokine that stimulates bone resorption in vitro and in vivo. Since IL-1 could also mediate the resorptive mechanism of FH and cause a clinically significant bone loss, we have studied the relationship of IH, vertebral mineral density, bone turnover, and monocyte IL-1 activity in 47 patients with absorptive hypercalciuria (AH), 23 with FH, and 38 nonhypercalciuric subjects with recurrent nephrolithiasis (controls). Vertebral mineral density, as measured by quantitative computer tomography, was decreased in each of the three patient groups, but was significantly lower in FH patients than in AH patients or control subjects. Twenty-four-hour total urinary hydroxyproline excretion was increased in FH patients compared to that in AH patients or controls, but blood levels of osteocalcin were not. Monocytes from FH subjects yielded significantly more IL-1 (alpha + beta) activity than those from AH patients or controls; levels of IL-1 activity in monocytes of AH and control patients were similar. In IH subjects, significant correlations were found between IL-1 and hydroxyproline (r = 0.70; P less than 0.0001), IL-1 and quantitative computer tomography values (r = -0.49; P less than 0.005), and IL-1 and urinary calcium (r = -0.36; P less than 0.05). Serum PTH levels were within normal limits in all subjects and were similar in the three study groups, 1,25-Dihydroxyvitamin D3 levels, although higher in IH patients than in controls, were not significantly different in FH and AH subjects. Increased IL-1 activity and decreased vertebral mineral density are features of a subset of patients with IH. Although a cause-effect relationship remains to be established, increased monocytic IL-1 activity, rather than elevated PTH or 1,25-dihydroxyvitamin D3 levels, could underlie the resorptive component of FH.

Adult↗
PubMed1990

Development of an immunoassay for human serum osteoclastic tartrate-resistant acid phosphatase.

A tartrate-resistant acid phosphatase (TrACP), which has been suggested to be very similar to the osteoclastic TrACP, was partially purified from the spleen of a patient with hairy cell leukemia. The purification procedure consisted of carboxymethyl-Sepharose, phosphocellulose, Sephacryl S-200, and phenyl-Sepharose chromatographies. Polyclonal antibodies were generated in guinea pigs with a titer of at least 1:6000. Immunohistochemical staining of fetal rat tibia with the antisera revealed that only the lysosomes of osteoclasts, but not osteoblasts, were stained. An enzyme-linked immunosorbent assay (ELISA) was developed with the antisera. There was no cross-reactivity with 1) partially purified acid phosphatases (ACPs) from normal human and beef spleens, 2) ACPs in extracts of human osteoblastic cells, 3) purified bovine bone matrix TrACP, or 4) commercial prostatic ACP. However, extracts of giant cell bone tumors, containing large amounts of bona fide osteoclasts, showed large amounts of cross-reactive material, which diluted in parallel with the partially purified hairy cell leukemic TrACP in the ELISA. Commercial serum band 5b TrACP also displaced in parallel with the partially purified hairy cell leukemic TrACP. Immunoblotting studies revealed that the antiserum, but not nonimmune guinea pig serum, reacted with the homogeneous hairy cell leukemia splenic band 5 TrACPs, which were recently purified by our laboratory. Preliminary application of the ELISA to sera of patients with metabolic bone diseases revealed that normal healthy individuals had measurable amounts of the immunoreactive material, and patients with Paget's disease or hyperparathyroidism, who should have high bone turnover, had elevated levels of this immunoreactive material in their sera. In contrast, the level of serum osteoclastic TrACP in a patient with an acute lymphatic leukemia was normal. In summary, 1) we have shown that hairy cell leukemia splenic TrACP shares significant immunological similarity with the osteoclastic TrACP and with the serum band 5b TrACP, and 2) the ELISA holds promise for a sensitive and specific assay for bone resorption.

Acid Phosphatase↗
PubMed1990

An inhibitory insulin-like growth factor binding protein (In-IGFBP) from human prostatic cell conditioned medium reveals N-terminal sequence identity with bone derived In-IGFBP.

Insulin-like growth factor binding proteins (IGFBPs), are produced by several cell types, are present in biological fluids, and may function in modulating insulin-like growth factor (IGF) biological activities. Recently the presence of multiple IGFBPs was reported in seminal fluid, suggesting that IGFBPs are produced by prostatic epithelium. We have found that human prostatic tumor cells of the PC3 cell line produce an IGFBP. PC3-IGFBP was purified to homogeneity using sequential IGF I affinity and HPLC C4 reverse phase chromatographies. Chemical cross-linking of PC3-IGFBP to 125I-IGF I revealed a molecular weight of 25 kDa. Its N-terminal sequence and amino-acid composition were highly homologous to that of a recently described 25 kDa inhibitory IGFBP (In-IGFBP), produced by osteoblasts in vitro. PC3-IGFBP inhibited basal and IGF II-stimulated bone cell DNA synthesis. We conclude that the PC3-IGFBP is very similar, if not identical to the osteoblast-derived In-IGFBP. Expression of PC3-IGFBP by metastatic human prostate tumor cells thus might affect the osteoblast proliferation that is induced by metastatic prostatic carcinoma. The PC3-IGFBP may be similar to a 24 kDa IGFBP described in seminal fluid and thus may be important in the regulation of cell proliferation in the male reproductive tract.

Amino Acid Sequence↗
PubMed1990

Inhibitory insulin-like growth factor-binding protein: cloning, complete sequence, and physiological regulation.

In this study we report the preparation of a human osteosarcoma cell cDNA library and describe the isolation and sequence determination of a clone encoding the complete sequence of a novel human insulin-like growth factor (IGF)-binding protein (hIGFBP-4). Previous work indicated that hIGFBP-4 is the predominant IGFBP expressed by human osteoblast-like cells, and that IGFBP-4 binds and inhibits the mitogenic activities of IGF-I and IGF-II. Sequence determination revealed that hIGFBP-4 is a unique gene product with significant amino- and carboxy-terminal sequence similarity to three other known IGFBPs. Identical alignment of 18 cysteines in IGFBP-4 and the three other IGFBPs is a key structural feature of this protein family. In vitro studies of human osteoblast-like cells suggest that PTH regulates the expression of hIGFBP-4 and that the PTH effect is mediated through a cAMP mechanism. hIGFBP-4 mRNA was also expressed in skin fibroblasts, and thus, this inhibitory IGFBP could be an important physiological regulator of IGF actions in bone cells and other cell types as well.

Amino Acid Sequence↗
PubMed1990

Interactions of growth factors present in bone matrix with bone cells: effects on DNA synthesis and alkaline phosphatase.

It has been shown that bone cells produce and secrete several growth factors (GFs) which are also found in the bone matrix. To investigate the role of these growth factors in bone cell metabolism, we compared the effects of different factors separately and in combination with respect to osteoblastic cell proliferation and differentiation. While basic fibroblast GF (FGF), transforming GF beta-1 (TGF beta), and platelet-derived GF (PDGF) enhance DNA synthesis, they had the opposite effect on alkaline phosphatase (ALP) activity in cell extracts: FGF, TGF beta, and PDGF inhibited cell ALP but strongly stimulated DNA synthesis. The IGFs had little effect on cell ALP but increased the release of ALP into the conditioned medium. In mitogenic tests of combinations of GFs, most had at least additive effects at low concentrations, and FGF, TGF beta, and IGF2 produced synergistic effects. Evidence is presented for (1) the modulation of the effects of one GF by the action of other GF, (2) synergistic interactions between FGF, TGF beta, and IGF2, and (3) a possible role for the observed interactions among GF for the mitogenic effect of human bone extract.

Alkaline Phosphatase↗
PubMed1990

Effect of estrone sulfate on postmenopausal bone loss.

Estrogen replacement therapy confers many beneficial effects to postmenopausal women, such as slowing the rate of bone loss and decreasing the risk of coronary artery disease. This multicenter, placebo-controlled study evaluated the lowest effective daily dose of estrone sulfate (0.3, 0.625, or 1.25 mg) combined with 1000 mg elemental calcium supplementation for preventing bone loss in the immediate supplementation for preventing bone loss in the immediate postmenopausal period. Spinal bone mineral density was measured using quantitative computed tomography. Compared with baseline, bone mineral density increased significantly (P less than .05) after 12 months of 0.625 mg daily (+ 1.9%) or 1.25 mg daily (+ 2.5%). The difference between the 0.625-mg and 1.25-mg doses was not statistically significant. Estrone sulfate administration (0.625 and 1.25 mg) produced significant changes in various lipid measurements at both the 6- and 12-month observation points. The prevalence rates for adverse events were comparable among the estrone sulfate groups and the placebo group. Estrone sulfate 0.625 mg daily, combined with 1000 mg elemental calcium supplementation, was the minimum effective dosage to prevent loss of spinal bone mineral density in postmenopausal women over a 12-month period.

Bone Density↗
PubMed1989

Purification and N-terminal sequence of two tartrate-resistant acid phosphatases type-5 from the hairy cell leukemia spleen.

Tartrate-resistant acid phosphatases types 5a and 5b were purified from human hairy cell leukemia spleen by sequential chromatography on Phenyl-Sepharose, CM-Sepharose, concanavalin A-Sepharose, FPLC Superose-12 and FPLC Mono-S. The purification over the original tissue extract was 1150- and 3300-fold, with a yield of 2.1% and 2.5%, respectively. Gel filtration indicated an Mr of about 30000 for both forms. There was a N-terminal sequence identity between the two enzymes. However, they appeared to be different as assessed by cation exchange chromatography and amino acid composition.

Acid Phosphatase↗
PubMed1989

Estradiol stimulates in vitro the secretion of insulin-like growth factors by the clonal osteoblastic cell line, UMR106.

UMR106 cells, a rat osteosarcoma derived clonal line, secreted insulin-like growth factors (IGF) in vitro. The IGF-II levels corrected for the cell numbers were 7-8 times higher than the IGF-I levels in the medium. Both growth factors were higher by 4-5 fold in medium conditioned by rapidly growing cells than in medium conditioned by confluent cells. The addition of 17-beta-estradiol (E) to the culture medium was associated with a statistically significant increase in the IGF concentrations. This increment was metabolite specific, not occurring with 17-alpha-E, the inactive epimer of E. 1,25(OH)2D3 also increased the IGF-I concentration but prior treatment with E blocked the response to 1,25(OH)2D3, demonstrating antagonistic actions of these two hormones on IGF secretion by osteoblast-like cells.

Animals↗
PubMed1989

Copurification of osteolytic and transforming growth factor beta activities produced by human lung tumor cells associated with humoral hypercalcemia of malignancy.

The SK-Luci-6 cell line, established from a large-cell anaplastic lung tumor of a patient with humoral hypercalcemia of malignancy (HHM), was investigated to identify osteolytic factors produced that might mediate HHM. Most HHM-associated tumors are thought to produce parathyroid hormone-related proteins or transforming growth factor (TGF) alpha. SK-Luci-6 cells formed s.c. tumors and induced hypercalcemia in athymic nude mice. Serum-free conditioned medium from SK-Luci-6 cultures induced bone resorption in neonatal mouse calvariae in vitro, and also contained TGF-beta activity and mitogenic activity. SK-Luci-6 cell conditioned medium did not displace [125I]epidermal growth factor binding to cell receptors or stimulate cyclic AMP formation in rat osteosarcoma cells, suggesting that the conditioned medium did not contain TGF-alpha or parathyroid hormone-related proteins. The osteolytic, TGF-beta, and mitogenic activities copurified in several chromatographic separations: gel filtration in acid and then in guanidine HCl; ion exchange; and reverse phase. The results suggest that in the HHM-associated SK-Luci-6 tumor, the causative osteolytic factor produced by the tumor cells is not a parathyroid hormone-related protein or TGF-alpha but, rather, may be a TGF-beta.

Animals↗
PubMed1989

Frequency dependence of increased cell proliferation, in vitro, in exposures to a low-amplitude, low-frequency electric field: evidence for dependence on increased mitogen activity released into culture medium.

In order to investigate the mechanism(s) through which an electric field can increase bone cell proliferation, we have developed an in vitro model incorporating a low-amplitude (estimated 10(-7) V/cm in the serum-free culture medium), low-frequency, capacitively coupled electric field. In previous studies with this model, we have shown that electric field exposure can increase bone cell proliferation both in chick tibiae organ cultures and in calvaria-derived monolayer cell cultures. The current in vitro studies demonstrate that skeletal tissue responses to a 30 min electric field exposure are characterized by a) a frequency window for both increased cell proliferation and increased release of mitogen activity into the cell-conditioned medium, with a peak near 16 Hz; b) a dependence on conditioned medium from exposed cells for increased cell proliferation; and c) a correlation between the alkaline phosphatase content of the bone cell cultures and effects of electric field exposure on both cell proliferation and release of mitogen activity into the conditioned medium.

Alkaline Phosphatase↗