bluuebunny/crossref_metadata_2025_split huggingface dataset:
Retinoic acid modulation of mrna levels in malignant, nontransformed, and immortalized osteoblasts
Authors: Zhou Hong , Hammonds Glenn R. , Findlay David M. , Fuller Peter J. , Martin John T. , Dr. Ng Kong Wah 
Published: February 2010

Abstract
Clonal cell lines presumably “arrested” at a particular stage of differentiation are useful models to study the processes of differentiation in osteoblasts. UMR-201 is a presumptive preosteoblastic nontransformed rat clonal cell line with a limited life span in culture. Two immortalized cell lines, UMR-201-10A (10A) and UMR-201-10B (10B), were derived from UMR-201 by stable transfection with simian virus (SV) 40 large T antigen. This study compares the growth and profile of gene expression of the immortalized cell lines with those of UMR-201 and UMR-106-06, a rat clonal cell line with well-defined osteoblast-like phenotypic characteristics. All four cell lines constitutively expressed the mRNA for the γ, α, and β receptors for retinoic acid (RA), the growth hormone receptor, pro-α1(I) collagen, osteonectin, bone proteoglycan I, and bone morphogenetic proteins (BMP) 1 and 2A. Alkaline phosphatase mRNA was absent in the preosteoblast cell lines but was induced by treatment with 10−6 M RA, which also increased the steady-state levels of mRNA for osteopontin and BMP1. mRNA for matrix gla protein was constitutively present and further induced by RA in UMR-201 and 10B only. Messenger RNA for bone sialoprotein and bone morphogenetic protein 3 were constitutively expressed in UMR-106-06 and UMR-201 but absent in the immortalized cell lines. None of the cell lines expressed measurable mRNA for bone gla protein or bone proteoglycan II. 10B grew more rapidly than UMR-201, but unlike UMR-201, it was also able to proliferate in serum-free medium and exhibit anchorage-independent growth. In summary, this study identifies novel retinoic acid effects on gene expression in these cells. Differences noted in the expression of mRNAs between UMR-106-06 and the other cell lines may provide some insight into the sequence of expression of these phenotypic characteristics as osteoblasts differentiate.
Bradykinin-induced burst of prostaglandin formation in osteoblasts is mediated via B2 bradykinin receptors
Authors: Ljunggren Östen , Vavrek Raymond , Stewart John M. , Lerner Ulf H. 
Published: February 2010

AbstractThe receptor subtype mediating the bradykinin (Bk)-induced burst of prostaglandin formation in osteoblasts has been studied. Bk, but not des-Arg9-Bk, induced the formation of prostaglandin E2 and prostacyclin in neonatal mouse calvarial bones incubated for 30 minutes. Bk-induced prostaglandin synthesis in neonatal mouse calvarial bones was significantly inhibited by the B2 Bk receptor antagonist D-Arg0[Hyp3, Thi5,8, D-Phe']-Bk. The B2 Bk receptor agonists Bk and Lys-Bk, but not the B1 Bk receptor agonist des-Arg9-Bk, caused a rapid burst (5 minutes) of prostaglandin E2 and prostacyclin formation in isolated osteoblast-like cells from neonatal mouse calvarial bones and in the murine osteoblastic cell lineage MC3T3-E1. When comparing the relative potency of different kinin analogs on their stimulatory effect on prostaglandin formation in isolated osteoblast-like cells and in MC3T3-E1 cells, we found that Bk = Lys-Bk &gt; Met-lys-Bk &gt;&gt;&gt; Des-Arg9-Bk. Bk-induced prostaglandin synthesis in isolated osteoblast-like cells and in MC3T3-E1 cells was inhibited by D-Arg0[Hyp3, Thi5,8, D-Phe7]-Bk, whereas the B1 Bk receptor antagonist des-Arg9-Leu8-Bk had no effect. Total binding of 3H-Bk (3–20 nM; 4°C) to whole MC3T3-E1 cells reached a maximum after 4–5 h. An excess of nonradioactive Bk (1 μM) reduced cell-associated radioactivity by 20–30%. The B2 Bk receptor agonist Bk and the B2 Bk receptor antagonist D-Arg0[Hyp3, Thi5,8, D-Phe7]-Bk were able to reduce specific binding, but the B1 Bk receptor agonist des-Arg9-Bk was unable to reduce the specific binding of 3H-Bk to whole MC3T3-E1 cells. These findings indicate the presence of B2 Bk receptors on osteoblasts coupled to enhanced prostaglandin synthesis.
Bone mass is related to creatinine clearance in normal elderly women
Authors: Dr. Yendt Edmund R. , Cohanim Moussa , Jarzylo Stanley , Jones Glenville , Rosenberg Gilbert 
Published: February 2010

Abstract
We determined the relationship between bone mass and age, anthropometric variables, creatinine clearance (Ccr), and serum and urine biochemical variables in 77 normal white women (aged 41–86, mean = 67) living in their own homes. A total of 74 women were postmenopausal. Skeletal status was assessed in all subjects by x-rays of the hand with measurement of the mean combined cortical thickness (CCT) of the second metacarpal bones. In 53 women, bone mineral content of the radial shaft (RMBC) was also measured by single-photon absorptiometry (SPA) and lumbar bone mineral density (LBMD) was measured by dual-photon absorptiometry (DPA). Serum and urine biochemical variables were measured under standardized conditions on the sixth and seventh days of a controlled diet. There was a strong positive correlation between Ccr and bone mass. Although our subjects showed the expected linear decline in Ccr with age, we found that the relationship between Ccr and bone mass in the radius and lumbar spine was independent of age. On the other hand, the relationship between Ccr and CCT was not independent of age. We concluded that the relationship between Ccr and lumbar and radial bone mass is probably indicative of a relationship between glomerular filtration rate and bone mass, although this requires validation with a noncreatinine method for measurement of glomerular filtration rate. Age per se does not appear to be a cause of declining lumbar bone mass after the menopause.
Preexisting bone loss associated with ovariectomy in rats is reversed by parathyroid hormone
Authors: Liu Chung C. , Kalu Dike N. , Salerno Elena , Echon Rosanno , Hollis Bruce W. , Ray Michelle 
Published: February 2010

Abstract
Previous studies have demonstrated that when parathyroid hormone (PTH) administration to rats is started immediately following ovariectomy, it prevents bone loss due to ovarian hormone deficiency. In this study, we examined whether bone loss induced by ovariectomy could be reversed by pasrathyroid hormone if hormone therapy is started after the bone loss had already occurred. In the first experiment, two groups of animals were ovariectomized or sham operated, killed after 40 days, and their bones examined to ensure that bone loss occurred. In the second experiment, three groups of rats were studied. Group 1 rats were sham operated, and rats in groups 2 and 3 were ovariectomized. Each rat in group 3 received a single subcutaneous injection of 8 μg parathyroid hormone [hPTH-(1–34); Bachem, CA] per 100 g body weight per day, starting 40 days following ovariectomy. Rats in groups 1 and 2 received solvent vehicle, and all animals were sacrificed on day 60. Ovariectomized rats had lost an appreciable amount of bone 40 days after surgery, as indicated by a significant decrease in femoral and vertebral densities and calcium and an over 55% loss of cancellous bone in the tibial metaphysis. The loss of bone was reversed by intermittent PTH administration. Increased cancellous bone in the parathyroid hormone-treated ovariectomized rats was associated with increased trabecular osteoblasts, decreased trabecular osteoclasts, and increased serum osteocalcin and urinary hydroxyproline. Our findings indicate that parathyroid hormone can substantially augment bone mass after the loss due to ovarian hormone deficiency has already occurred. The hormone caused positive bone balance in vivo in ovarian hormone-deficient animals by increasing bone formation and decreasing bone resorption.
Stimulation of 1,25-dihydroxyvitamin D3 receptor gene expression in cultured cells by serum and growth factors
Authors: Krishnan Aruna V. , Feldman David 
Published: February 2010

Abstract
The abundance of 1,25-dihydroxyvitamin D3 receptors (VDR) in bone cells has been shown to vary in direct relation to the rate of cell proliferation. In this study we further explored this upregulation of VDR as it relates to the mitogenic response using NIH-3T3 mouse fibroblasts and MCF-7 human breast cancer cells as model systems. Serum and growth factors, such as EGF, high concentrations of insulin (2 μM), and IGF-I, were mitogenic and stimulated the proliferation of both cells types. These factors also caused significant increases in VDR levels as measured by ligand binding assays, which preceded the rise in cell proliferation rate measured by [3H]thymidine incorporation. Serum and growth factors increased the abundance of VDR but did not affect the concentrations of other steroid receptors in MCF-7 cells. Mouse cells have been reported to have several VDR mRNA transcripts. Our northern blot analysis revealed three mRNA species at approximately 7.5, 4.4, and 3 kb of which the 4.4 kb species was the most prominent and the 7.5 kb the least. Serum and growth factor stimulation of quiescent 3T3 cells led to significant increases in all the transcripts, suggesting that the upregulation occurs at the level of VDR mRNA expression. A time course analysis of serum stimulation in 3T3 cells showed that the mRNA species reached peak levels 4 h after serum addition. When serum stimulation was carried out in the presence of the protein synthesis inhibitor cycloheximide, the 3 kb transcript as well as the 7.5 kb transcript were superinduced but the stimulation of the 4.4 kb transcript was inhibited. Hydroxyurea (an inhibitor of DNA synthesis) and colchicine (a microtubule disruptive agent) had no effect on serum stimulation of the mRNA species, indicating that the enhanced expression of the VDR gene is not dependent upon the S, G2, or M phase of the cell cycle. The results suggest that the VDR gene appears to be one of a set of early genes activated when quiescent cells are stimulated by a mitogenic signal.
Voltage-dependent phosphate transport in osteoblast-like cells
Authors: Luong KHANH V.Q. , Green Jacob , Kleeman Charles R. , Yamaguchi Dean T. 
Published: February 2010

Abstract
Phosphate ion (Pi) in sufficient concentrations is crucial for bone mineralization. The osteoblast (OB) may be responsible for the transport of Pi into the bone interstitium, where mineralization occurs. We previously characterized a Na+-dependent Pi transporter (NaPi) in the osteoblastic UMR-106–01 cell line. In the present study, the alteration of Na+-dependent Pi transport by changes in membrane potential was investigated. Depolarizing the cells with increasing concentrations of ambient K+ and valinomycin resulted in a progressive decline in Na+-dependent Pi uptake to a maximum of 28% at a membrane potential of −18 mV compared to control Na+-dependent Pi uptake at a membrane potential of approximately −60 mV. Hyperpolarizing the cells with SCN− increased Na+-dependent Pi uptake over control by 50% at an SCN− concentration of 70 mM. Determination of membrane potential by using the fluorescent probe, DiSC3(5), showed that the addition of Pi to cells in Na+-containing medium resulted in a small depolarization. These data show that NaPi activity can be altered by membrane potential changes and that the initiation of Na+-dependent Pi uptake is associated with depolarization of the plasma membrane of UMR-106–01 cells. Taken together, the cotransport of Na+ and Pi results in the movement of a net positive charge into the cell.
Effects of 17β-estradiol on calcitonin secretion and content in a human medullary thyroid carcinoma cell line
Authors: Lazaretti-Castro Marise , Grauer Andreas , Mekonnen Yalem , Raue Friedhelm , Ziegler Reinhard 
Published: February 2010

Abstract
The presence of a direct estrogen effect on calcitonin secretion is controversial. Because most of the data available were obtained from complex in vivo systems, we chose an in vitro approach to assess the problem. Using a human C cell carcinoma cell line (TT cells) with well-documented estrogen receptors, we investigated the effect of 17β-estradiol (E2) on basal and stimulated calcitonin secretion, on calcitonin content, and on total cellular protein. After short (30 and 180 minutes) and long-term (24 h to 6 days) incubation of the cells with different concentrations of E2 (from 0.01 to 100 nM) we observed no stimulatory but a transient dose-dependent inhibitory effect on CT secretion and content. The nadir of the effect on CT secretion appeared at 24 h, demonstrating a reduction to 80.5 ± 7.8% of control at 1 nM and to 59.1 ± 15% of control at 100 nM E2. After 72 h, the CT levels of the E2-exposed groups returned to control levels. The acute stimulation of the cells with TPA plus forskolin after preincubation with E2 up to 6 days showed no difference in the increment of CT release compared to the control groups. Additionally, E2 had a dose-dependent stimulatory effect on cell protein content. The data demonstrate the absence of a direct stimulatory effect of E2 on CT secretion, revealing a dose-dependent inhibitory effect on CT secretion and content.
Lack of effects of neutralization of parathyroid hormone-related protein on calcium homeostasis in neonatal mice
Authors: Kukreja Subhash C. , D'Anza James J. , Melton Mary E. , Wimbiscus Sarah A. , Grill Vivian , Martin John T. 
Published: February 2010

Abstract
Large quantities of parathyroid hormone-related protein (PTHrP) are present in the milk of various species. It has been suggested that PTHrP may play a role in neonatal calcium homeostasis. In the present study we evaluated the effect of neutralization of amino-terminal PTHrP activity by passive immunization in 1-day-old mouse pups. Neutralization of amino-terminal PTHrP activity had no significant effect on serum calcium or whole-body calcium content in the neonatal mice. In additional studies, we demonstrated that subcutaneous administration of PTHrP-(1–34) increased serum calcium, whereas oral administration had no significant effect in 3-day-old pups. The studies therefore demonstrate that the amino terminus of PTHrP may not play a significant role in neonatal calcium homeostasis. Local effects of PTHrP cannot be excluded by the results of the present study.
Regulation of osteoblast proliferation by leukemia inhibitory factor
Authors: Lowe Carolyn , Cornish Jill , Callon Karon , Martin John T. , Dr. Reid Ian R. 
Published: February 2010

Abstract
We recently showed that leukemia inhibitory factor (LIF) stimulates 45Ca release from neonatal mouse calvariae in vitro and that it increases DNA and protein synthesis in this model. To elucidate further the actions of LIF on bone we now report the effects of this cytokine on DNA synthesis and cell proliferation in isolated fetal rat osteoblasts and in the osteogenic sarcoma cell line, UMR-106. In both actively growing and growth-arrested rat osteoblasts, LIF stimulated [3H]thymidine incorporation in a dose-dependent manner. The increase in DNA synthesis was time dependent, was associated with an increase in the number of osteoblasts, and was not blocked by indomethacin. LIF-treated cells showed reduced [3H]thymidine incorporation in comparison with control, as they approached confluence, possibly because of the increased cell density in the LIF-treated cultures.
In UMR-106 cells, treatment with LIF inhibited [3H]thymidine incorporation in both actively growing and growth-arrested cultures. The effect was dose dependent and sustained with time. There was a corresponding decrease in cell numbers. It is concluded that although LIF causes an early stimulation of proliferation in isolated osteoblasts, it has opposing effects on UMR-106 cells. It is not possible to determine which of these effects is more relevant to the actions of LIF in vivo. The demonstration of a LIF effect on both these cell types, however, provides further evidence that this cytokine acts directly on osteoblasts.
Interleukin-6 messenger RNA expression and interleukin-6 protein secretion in cells isolated from normal human bone: Regulation by interleukin-1
Authors: Linkhart Thomas A. , Linkhart Susan G. , MacCharles Daniel C. , Long Dana L. , Strong Donna D. 
Published: February 2010

Abstract
Recent evidence suggests that cytokines, in addition to regulating hematopoiesis and immune functions, may be important paracrine regulators of bone turnover. Interleukin-1 (IL-1) and IL-6 are cytokines that are produced by and affect both hematopoietic and nonhematopoietic cell types. IL-1 stimulates bone resorption and inhibits osteoblast proliferation and collagen production. Previous reports that IL-6 was secreted in murine osteoblast and bone organ cultures in response to IL-1 and PTH suggested that IL-6 has paracrine effects on bone resorption or formation. To determine whether IL-6 has a paracrine function in human bone, IL-6 expression in cells isolated from normal human bone was investigated. IL-6 mRNA levels in untreated cultures were low and variable, and IL-6 secretion was undetectable. PTH had no effect on IL-6 mRNA levels or IL-6 secretion. IL-1β increased IL-6 mRNA levels, maximally 40-fold at 12 h. IL-1β increased IL-6 secretion to 0.13 nM, more than 80-fold that of untreated controls at 12 h. IL-1β also increased IL-1β mRNA levels, maximally 9-fold at 12 h, but did not increase cellular levels or secretion of IL-1β protein. Recombinant human IL-6 at 0.5–5 nM stimulated resorption in neonatal mouse calvarial organ cultures but had no effect on human bone-derived cell DNA synthesis or type I procollagen mRNA levels. The results suggest that IL-6 production by human osteoblasts may function to enhance osteolytic activity of IL-1 but does not affect proliferative and matrix biosynthetic aspects of bone formation that were tested. Because osteoblasts and bone marrow cells are in close proximity, IL-6 produced by osteoblasts may also function to amplify IL-1 stimulation of immune responses and hematopoiesis in bone marrow.
Effects of a combined estrogen-gestagen regimen on serum levels of the carboxy-terminal propeptide of human type I procollagen in osteoporosis
Authors: Hasling Claus , Eriksen Erik F. , Melkko Jukka , Risteli Leila , Charles Peder , Mosekilde Leif , Risteli Juha 
Published: February 2010

Abstract
Estrogen stimulates osteoblastic collagen production in vitro, but whether the same stimulation takes place in vivo is still unknown. To test the stimulatory effects of a combined estrogen-gestagen regimen in vivo we monitored serum levels of the carboxy-terminal propeptide of human type I procollagen (S-PICP) in a group of 12 osteoporotic women over a 150 week treatment period. Spinal bone mineral content (BMC) increased to a maximum of 5% over pretreatment values around week 90. Serum alkaline phosphatase (S-AP) and serum bone gla protein (S-BGP) both fell from initial values of 220 U/liter and 39 ng/ml, respectively, to 146 U/liter (p &lt; 0.01) and 27.2 ng/ml (NS) around week 60 and remained reduced over the remaining treatment period. S-PICP also fell from 117 to 68 μg/liter at week 60 and 70 μg/ml at week 150 (P &lt; 0.01). This is equal to a reduction to 32 ± 10% pretreatment levels. The reduction in S-PICP was not significantly different from that of the other two markers of bone formation (S-AP and S-BGP). Thus, provided the metabolic clearance of PICP remains unaltered after hormone replacement therapy, no major stimulation of osteoblastic collagen type I synthesis was demonstrable during estrogen-gestagen treatment in this population of osteoporotic women. The changes in bone markers seen in this study are therefore consistent with an estrogen-mediated reduction in the frequency of remodeling activation. Because of the reduction in bone turnover and methodologic limitations of bone marker assays, however, smaller increases in the amount of bone formed per activation could remain undetectable.
Effects of acid and basic fibroblast growth factor and heparin on resorption of cultured fetal rat long bones
Authors: Simmons Hollis A. , Raisz Lawrence G. 
Published: February 2010

Abstract
We tested acid and basic fibroblast growth factor (aFGF and bFGF), members of the heparin binding FGF family, for their ability to stimulate bone resorption as measured by the release of previously incorporated 45Ca from cultured fetal rat long bones in the presence and absence of heparin. Purified low-molecular-weight heparin (LMW heparin) at 5–125 μg/ml had no direct stimulatory effect. There was little effect from aFGF (10−11-10−8 M) alone, but increased resorption was observed in the presence of LMW heparin. With bFGF, increased bone resorption was observed at 10−9 M but not at 10−8 M. The stimulatory effects of aFGF and bFGF in the presence of LMW heparin were not blocked by the addition of indomethacin (10−6 M), which blocks prostaglandin production, or hydroxyurea (10−3 M), which blocks DNA synthesis. However, pretreatment with aphidicolin (3 × 10−5 M), a potent inhibitor of DNA synthesis, blocked the effect of acid FGF and diminished the effect of bFGF. These results indicate that both aFGF and bFGF can stimulate bone resorption by a prostaglandin-independent mechanism, particularly in the presence of heparin. The activation of FGF-mediated bone resorption by heparin could play a role in producing the osteoporosis that has been described with heparin therapy and mastocytosis.
Actions of calcipotriol (MC 903), a novel vitamin D3 analog, on human bone-derived cells: Comparison with 1,25-dihydroxyvitamin D3
Authors: Evans Dean B. , Thavarajah Mannicam , Binderup Lise , Kanis John A. 
Published: February 2010

Abstract
The actions of a novel vitamin D3 analog calcipotriol (MC 903), on human bone-derived cells were compared to those of 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3]. Both calcipotriol and 1,25-(OH)2D3 inhibited the proliferation of human osteoblast-like cells in a dose-dependent manner (10−10-10−6 M), an effect observed at different cell densities. Lower concentrations of either agent exerted no marked effect on the growth of the cells compared to untreated cultures. Calcipotriol and 1,25-(OH)2D3 were equipotent in stimulating the activity of alkaline phosphatase and the synthesis of osteocalcin in human osteoblast-like cells. The stimulation of alkaline phosphatase activity and osteocalcin synthesis by both compounds was evident by 24 h and was increased progressively up to 96 h in a dose-dependent manner over the concentration range of 10−10-10−6 M. The increment in both proteins was dependent on cell density and was attenuated at higher cell densities. In contrast to these actions, neither calcipotriol nor 1,25-(OH)2D3 (10−14-10−6 M) affected the synthesis of prostaglandin E2. These studies indicate that calcipotriol and 1,25-(OH)2D3 exhibit a similar spectrum of activity on human osteoblast-like cells in vitro.