bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characteristics of parathyroid hormone-specific cyclic changes of glucose-6-phosphate dehydrogenase activity in the distal convoluted tubule of the guinea pig
Authors: Sakaguchi Kazushige , Fukase Masaaki , Kobayashi Ikuo , Fujita Takuo 
Published: February 2010

Abstract
The effect of parathyroid hormone (PTH) on the time course of glucose-6-phosphate dehydrogenase (G6PD) activity in the distal convoluted tubule of a vitamin D-depleted guinea pig was determined using quantitative cytochemistry. G6PD activity decreased to the stable basal level 5 hrs after the initiation of the kidney segment maintenance cultures. The exposure of the tissues to 1 pg/ml of bovine PTH-(1–84) induced a cyclic change of G6PD activity, whereas neither carboxyl-terminal PTH nor other hormones tested showed such activity. After a 16-min exposure to bovine PTH-(1–84), the peak height of each cycle began to decrease until it disappeared at 34 min. The second exposure to this hormone at 46 min reinduced a similar cyclic change with a similar peak, indicating full viability of the cells. When bovine PTH-(1–84) was incubated with an excess amount of anti-bovine PTH antibody, the PTH-induced G6PD activity was completely abolished. Throughout a 14-min exposure to either human PTH-(1–84), human PTH-(1–34) or bovine PTH-(1–84), similar cyclic changes were observed with the constant peak height regardless of the dose (10−16-10−12M), although the cycle length shortened progressively as the dose was increased. They were equipotent on a molar basis between the concentrations of 10−16 and 10−13M at 6 min of hormone exposure. The present data demonstrate that the cytochemical bioassay of PTH in a vitamin D-depleted animal is based on a dose-dependent difference in the time course of G6PD activity.
Frequency and partial characterization of adenylate cyclase-stimulating activity in tumors associated with humoral hypercalcemia of malignancy
Authors: Stewart Andrew F. , Insogna Karl L. , Burtis William J. , Aminiafshar Ahmad , Wu Terrence , Weir Eleanor C. , Broadus Arthur E. 
Published: February 2010

Abstract
Parathyroid hormone-like adenylate cyclase-stimulating activity (ACSA) has previously been identified in small numbers of tumors or tumor-conditioned tissue culture medium derived from patients or animals with humoral hypercalcemia of malignancy (HHM). We examined the frequency with which this ACSA occurred in a large group of tumor extracts derived from patients with HHM (n = 20), and compared this to three control groups: normocalcemia-associated tumors (n = 20), hypercalcemic control tumors (n = 7), and normal, nonmalignant tissue samples (n = 10). Eighteen of 20 HHM-associated tumor extracts displayed ACSA whereas only 4 of 37 controls contained detectable ACSA.
ACSA in one tumor was partially purified, using sequential extraction steps and reverse-phase, high-performance liquid chromatography. Highly purified ACSA (4800-fold) also contained potent in vitro bone-resorbing activity. The molecular weight as assessed by gel filtration was approximately 40,000 D.
These findings provide strong support for the thesis that the humoral factor which is responsible for the syndrome of HHM is a parathyroid hormone-like adenylate cyclase-stimulating protein.
Kinetics of calcitonin receptor internalization in lung cancer (BEN) and osteogenic sarcoma (UMR 106–06) cells
Authors: Findlay David M. , Martin T. John 
Published: February 2010

Abstract
The fate of 125I-labeled calcitonin and calcitonin receptors in BEN and UMR 106–06 cells was studied after binding of the ligand. At 37°C but not at 4°C, 125I-labeled salmon calcitonin bound to both cell types and was internalized as evidenced by increasing resistance to removal by acid pH. This process was dependent on de novo protein synthesis. Cells were pretreated with salmon calcitonin and washed with acidified buffer to release cell-surface bound hormone and to allow assessment of cell-surface receptor concentration. It was found that initially there was a temperature- and time-dependent calcitonin-induced loss of binding capacity after exposure to salmon calcitonin, suggestive of endocytosis of the calcitonin-receptor complex. In the continued presence of calcitonin, receptors were lost only at the same rate as the normal turnover of calcitonin receptors as assessed in the presence of cycloheximide. These data are consistent with the presence of two functional populations of calcitonin receptors, only one of which is induced to internalize by ligand binding.
Identification of the calcitonin receptor by chemical cross-linking and photoaffinity labeling in human cancer cell lines
Authors: Moseley J. M. , Smith P. , Martin T. J. 
Published: February 2010

Abstract
Two methods have been used to covalently cross-link [125I]-salmon calcitonin to its receptor on a human lung carcinoma cell line, BEN, and the human breast cancer cell lines T47D and MCF 7. The first method was to use a specific photoaffinity derivative of salmon calcitonin and the second employed the chemical cross-linker, disuccinimidyl suberate. In both cases a cross-linked component of approximate molecular weight 80–90,000 on BEN cells was identified by polyacrylamide gel electrophoresis. This is consistent with the size of the cross-linked component found on T47D breast cancer cells using the photoactive salmon calcitonin as described in previous work. Disuccinimidyl suberate was unable to cross-link [125I]-salmon calcitonin either on T47D or MCF cells. However, photoactive salmon calcitonin cross-linked to a component of approximately 80–90,000 Mr on the MCF 7 cells. Thus, whereas the photoactive salmon calcitonin could cross-link a similar receptor component in all cell lines, the ability of disuccinimidyl suberate to do so was apparently cell specific. These data confirm that the calcitonin receptor comprises a component of approximately 85,000 Mr in cell lines examined thus far.
Vitamin D status and brush border membrane vesicles: 1,25-dihydroxyvitamin D3 induced destabilization
Authors: Putkey J. A. , Nemere I. , Dr. Norman A. W. 
Published: February 2010

Abstract
Purified chick duodenal brush border membrane vesicles (BBMV) were used to assess the effect of vitamin D on intestinal Ca2+ transport and membrane stability. BBMV preparations are right-side-out as judged by a nine-fold increase in accessibility of lactoperoxidase to core material actin in the presence of Triton X-100. Freshly prepared BBMV from vitamin D-deficient chicks support both sodium-dependent glucose transport and Ca2+ uptake. In vivo treatment with 1,25(OH)2D3 results in an 85% increase in the Vmax of Ca2+-uptake from 2.2 to 3.9 nmol/min/mg protein. The Km of Ca2+-uptake (0.9 mM) is independent of the vitamin D status of the chick. The majority of BBMV derived from vitamin D-replete chicks were destabilized and rendered incapable of supporting either sodium-dependent glucose uptake or Ca2+ uptake if they were held at 0–4°C for 2 to 24 h. In 40 separate experiments, 80% of membranes derived from vitamin D-replete chicks showed characteristics of destabilization, whereas only 24% of all control membranes exhibited a lack of viability.
Comparison of multinucleated cells elicited in rats by particulate bone, polyethylene, or polymethylmethacrylate
Authors: Dr. Glowacki J. , Jasty M. , Goldring S. 
Published: February 2010

Abstract
Osteoclasts, the multinucleated resorbing cells of bone, are identified by their characteristic morphology, unique cell membrane specializations, and more recently by the presence of cell surface antigens recognized by monoclonal antibodies. They are derived from mononuclear precursor cells of hematogenous origin. The precise relationship between osteoclasts and other types of tissue giant cells is unknown. This study was designed to examine factors involved in the recruitment and differentiation of multinucleated cells and to investigate the relationship between so-called foreign body giant cells and bone-resorbing osteoclasts.
Particles of various materials were implanted into subcutaneous pockets in rats. Histological, histochemical, and electron microscopic evaluations were made of specimens harvested 12 days after implantation. Large, foamy multinucleated cells were evident around particles of devitalized bone, polyethylene, and polymethylmethacrylate. Bone particles showed scalloped surfaces and were partially resorbed. Those cells adjacent to the bone particles stained positive for tartrate-resistant acid phosphatase, in contrast to the multinucleated cells adjacent to the other materials. All the cell types had extensive rough endoplasmic reticulum, abundant mitochondria, cytoplasmic vacuoles and dense bodies, giant centrospheres, and areas of fusion of plasma membranes. Cells in lacunae on the surface of the bone particles showed a clear zone of attachment to the bone substrate and ruffled borders, a feature characteristic of in osso osteoclasts. Although the giant cells occasionally displayed an extensive clear zone of attachment to the polyethylene and polymethylmethacrylate particles, no ruffled borders were detected.
The results of these studies show that the multinucleated cells elicited in response to different materials, although sharing many common features, do demonstrate certain features that are substrate specific. This model can be used to investigate the relationship between osteoclasts and other types of multinucleated giant cells and to help elucidate factors involved in osteoclast recruitment, differentiation, and regulation.
Isolation and characterization of highly serum-dependent cells released early from collagenase digested calvaria
Authors: Wong Glenda L. , Frantz K. , Lam C. 
Published: February 2010

Abstract
A subclass of highly serum-dependent bone cells has been identified among the cells released early from calvaria following digestion in collagenase. Partial purification for these cells has been carried out based on the observation that they require serum for attachment to polystyrene culture flasks. This subclass of bone cells differs from adherent cells and late released osteoblasts, in that they express almost no cAMP response to PTH, require high levels of serum (10%) for initial growth and proliferation, and do not increase DNA synthesis in response to PTH. In common with adherent cells and late released osteoblasts, their proliferation is decreased by 1,25(OH)2D3 at doses above 0.2 ng/ml and they respond to PGE2 with increased DNA synthesis. These similarities suggest an ontogenic relationship with osteoblasts. Based on their differences, however, provisional identification of these cells as relatively undifferentiated mesenchymal cells is suggested.
Redox studies of the epiphyseal growth cartilage: Pyridine nucleotide metabolism and the development of mineralization
Authors: Kakuta Saburo , Golub Ellis E. , Haselgrove John C. , Chance Britton , Frasca Peter , Dr. Shapiro Irving M. 
Published: February 2010

Abstract
The objective of this investigation was to examine the redox status of chondrocytes in normal and rachitic growth cartilages and to relate energy metabolism to cell maturation and the initiation of mineralization. The redox status was evaluated by chemical analysis and by microfluorimetric scanning of rapidly frozen, freeze-fractured tibial growth cartilages. In the normal epiphysis, the redox pattern of both avian and lagomorph cartilages were very similar. Thus, in the proliferative tissue zone the NAD/NADH ratio was high; in the hypertrophic zone, the cells appeared to be reduced. The sharp border between the two zones suggested that the redox shift may be associated with development of hypoxia. Induction of rickets resulted in a fivefold decrease in the total concentration of pyridine nucleotides in the proliferating and hypertrophic zones. Furthermore, the NAD/NADH ratio was profoundly disturbed. In the mineralizing zone, there was an accumulation of reduced pyridine nucleotide. Healing, initiated by administration of vitamin D to the rachitic birds, caused a rapid increase in NAD and NADH in all zones of the growth cartilage. It was concluded that vitamin D deficiency leads to changes in the energy metabolism of growth cartilage and that these changes were related to the defective mineralization of the rachitic tissue.
Effect of 1,25-dihydroxyvitamin D3 on mouse mammary tumor (GR) cells: Evidence for receptors, cellular uptake, inhibition of growth and alteration in morphology at physiologic concentrations of hormone
Authors: Gross Myron , Kost Susan Bollman , Ennis Bruce , Stumpf Walter , Kumar Rajiv 
Published: February 2010

Abstract
Mammary glands are target tissues for 1,25-dihydroxyvitamin D3 (1,25(OH)2D3). We have examined a mouse mammary tumor cell line (GR) for receptors of 1,25(OH)2D3 and have examined alterations in the growth and morphology of these cells in response to 1,25(OH)2D3. GR cells contain a high affinity (Kd ∼ 10−11), lowcapacity receptor with a high specificity for 1,25(OH)2D3. The 1,25(OH)2D3 receptor in GR cells has a sedimentation coefficient of 3.5 and elutes from DEAE cellulose columns with ∼ 0.15 M KCI. These properties of the receptor are similar to those reported for other 1,25(OH)2D3 receptors. 1,25(OH)2D3 is internalized by GR cells in situ and specifically bound 1,25(OH)2D3 is found predominantly, if not entirely, in the nucleus as determined by cell fractionation and autoradiographic techniques. The incubation of GR cells in culture for 7 days with 1,25(OH)2D, markedly alters cell growth. Cell growth is retarded in a dose-dependent manner; physiologic concentrations (10−10M) of l,25(OH)2D3 retard cell growth by approximately 50%. In addition, GR cells incubated with 10−9 to 10−8M 1,25(OH)2D3 undergo marked morphological changes. The incubation of GR cells with other vitamin D metabolites such as 25-hydroxyvitamin D3 (25(OH)D3) at a concentration of 10−9M does not significantly alter cell growth or morphology. The presence of high affinity receptors for 1,25(OH)2D3, the specific internalization of 1,25(OH)2D3 predominantly into the nuclei, and the significant effects of physiological concentrations of 1,25(OH)2D3 on cell growth suggest a direct, specific, nuclear effect of 1,25(OH)2D3 on GR cells. The mouse mammary tumor model might be useful in examining the effect of 1,25(OH)2D3 on tumor formation.
Parathyroid cell surface autoantibodies that inhibit parathyroid hormone secretion from dispersed human parathyroid cells
Authors: Posillico James T. , Wortsman Jacobo , Srikanta Sath , Eisenbarth George S. , Mallette Lawrence E. , Brown Edward M. 
Published: February 2010

Abstract
Serum autoantibodies directed toward antigenic determinants on the surface of human parathyroid cells (PTAb-CS) have been demonstrated in a subset (8 of 23) of adult patients with idiopathic hypoparathyroidism (IHP). In sera from 3 of 8 patients with PTAb-CS, binding of these autoantibodies to their respective parathyroid cell surface antigen(s) resulted in marked inhibition of parathyroid hormone (PTH) secretion in an in vitro dispersed human parathyroid cell (dPTC) system. In 1 subject evaluated longitudinally, circulating levels of PTAb-CS, and the magnitude of the inhibitory effect on PTH secretion, temporally correlated with the clinical course of the hypoparathyroidism. These findings suggest a causative role for antibodies directed against cell surface antigens in parathyroid dysfunction in some cases of “autoimmune” hypoparathyroidism.
Effect of vitamin D metabolites on the expression of alkaline phosphatase activity by epiphyseal hypertrophic chondrocytes in primary cell culture
Authors: Hale Laura V. , Kemick Mary Lynn S. , Dr. Wuthier Roy E. 
Published: February 2010

Abstract
The effects of three vitamin D3 metabolites, 25-hydroxyvitamin D3 (25-(OH)D3), 1α,25-dihydroxyvitamin D3 (1α,25-(OH)2D3), and 24R,25-dihydroxyvitamin D3 (24R,25-(OH)2D3) on the activity of alkaline phosphatase (AP), a key enzyme involved in biomineralization, have been studied in primary cultures of chicken epiphyseal growth plate chondrocytes. Dosages of 1α,25-(OH)2D3 (10−12 to 10−7M) caused a progressive, dosage-and time-dependent decrease in cellular AP levels, IC50 occurring at approximately 10−12M. In contrast, 24R,25-(OH)2D3 at 10−13 to 10−10M stimulated cellular AP activity, half-maximal stimulation occurring at about 10−13M. At higher levels (10−10 to 10−7M), 24R,25-(OH)2D3 caused progressive reduction in AP activity. Maximal effects of 24R,25-(OH)2D3 were evident 48 h after administration of the metabolite. 25-(OH)D3 initially (24 h) caused a weak, dosage-dependent decrease in cellular AP activity, but after 48–72 h, low levels (10−13 to 10−11M) caused a dosage-dependent increase in AP activity. Higher levels of 25-(OH)D (&gt; 10−10M) were clearly inhibitory to AP. These findings reveal that the AP activity of growth plate chondrocytes is exquisitely sensitive to both 1α,25- and 24R,25-(OH)2D3 but the response to each is in opposite directions. The paradoxical response of the cells to 25-(OH)D3 can be explained if the metabolite is slowly metabolized by a 24-hydroxylase to 24R,25-(OH)2D3 leading to stimulation of cellular AP. The inhibitory effects of all metabolites at higher levels (10−8 to 10−7M) may be explained if both 25-(OH)D3 and 24R,25-(OH)2D3 act as weak agonists for the 1α,25-(OH)2D3 receptor, mimicking its inhibitory action. The data show that vitamin D metabolites exert a direct effect on the growth plate chondrocytes. Studies are in progress to elucidate the mechanism of this AP response.
Differential effects of 1,25-dihydroxyvitamin D3 on cytosolic calcium in two human cell lines (HL-60 and U-937)
Authors: Desai Sanjay S. , Appel Michael C. , Dr. Baran Daniel T. 
Published: February 2010

Abstract
1,25-Dihydroxyvitamin D3 (1,25-(OH)2D3) has been shown to induce maturational changes in the human promyelocytic leukemia cell line HL-60 and in the human monocytic cell line U-937. Changes in cytosolic calcium have been reported to regulate cellular processes. We used the fluorescent dye Quin 2 to examine the effects of vitamin D metabolites on cytosolic calcium levels in HL-60 and U-937 cells. 1,25-(OH)2D3 (20 nM) increases cytosolic calcium by 24% over a 5-min period in HL-60 but not in U-937 cells. 1,25-(OH)2D3 (0.2 nM and 4 nM) has no effect on cytosolic calcium levels in either cell type. 24,25-(OH)2D3 (20 nM) has no effect on cytosolic calcium in HL-60 cells. Nifedipine (1 m M) has no effect on cytosolic calcium levels over 30 min and likewise does not block the 1,25-(OH)2D3-induced increase in cytosolic calcium in HL-60 cells. However, chelation of extracellular calcium with EGTA (10 m M) blocks the 1,25-(OH)2D3-induced increment in cytosolic calcium, but does not block the 1,25-(OH)2D3-induced maturational changes in HL-60 cells. The data suggest that 1,25-(OH)2D3 but not 24,25-(OH)2D3 increases cytosolic calcium in HL-60 cells within 5 min and the increment is due to increased influx of calcium. 1,25-(OH)2D3 modifies membrane permeability to calcium independent of calcium channels sensitive to nifedipine. Finally, 1,25-(OH)2D3-induced maturational changes in HL-60 cells can take place without an increase in cytosolic calcium.
Isolation of EGF-dependent transforming growth factor (TGFβ-like) activity from culture medium conditioned by fetal rat calvariae
Authors: Centrella Michael , Canalis Ernesto 
Published: February 2010

Abstract
A transforming growth factor of the beta class (TGF-β), defined by its ability to induce normal rat kidney cells (NRK, clone 49F) to form anchorage-independent large colonies in soft agar in the obligate presence of epidermal growth factor, has been prepared from culture medium conditioned by fetal rat calvariae. This activity was purified by acetic acid extraction, gel permeation chromatography, and two reversed-phase HPLC (rpHPLC) steps. Bone culture derived-TGFβ-like activity was soluble in 1.0 M acetic acid, eluted from Sephadex G-75 at relative molecular mass (Mr) 25,000, from μBondapak C18 rpHPLC at 63 ± 5% methanol in 0.1 M acetic acid, and from μBondapak CN rpHPLC at 36 ± 2% n-propanol in 0.1% trifluoroacetic acid. Based on specific activity estimations at each stage of purification, TGFβ-like activity was purified 2500-fold with a 14% recovery, and 1 I of conditioned medium yielded 1–2 μg of factor. Silver-stained polyacrylamide gels of this material after CN μBondapak rpHPLC revealed a predominant band of (Mr) 24,000.
The relative potency of a human tumor-derived PTH-like adenylate cyclase-stimulating preparation in three bioassays
Authors: Stewart Andrew F. , Wu Terence , Burtis William J. , Weir Eleanor C. , Broadus Arthur E. , Insogna Karl L. 
Published: February 2010

Abstract
Three bioassays are widely employed for the measurement of PTH-like adenylate cyclase-stimulating factors (ACSFs) drived from tumors associated with humoral hypercalcemia of malignancy. These include renal cortical adenylate cyclase (RAC) assays, rat osteosarcoma (ROS) adenylate cyclase assays, and fetal bone resorption (FBR) assays. A previous study has suggested that the potency of one human tumor-derived ACSF, expressed in PTH equivalents, was 30-fold higher in the ROS assay than in the RAC assay, but no study has directly compared all three bioassays using a single PTH standard and a single ACSF preparation.
We compared one partially purified ACSF preparation to a single lot of bPTH 1–34 in all three bioassays. The results indicate that the relative potency of this ACSF as compared to the PTH standard varied with the assay employed, with the ROS assay yielding a specific activity estimate 47.5-fold higher than the RAC, and the FBR 6.7-fold higher than the RAC but 7.1-fold lower than the ROS.
These findings support the possibility that distinct subpopulations of PTH receptors exist on different PTH target tissues. Further, they underscore the importance of bioassay choice when estimating the specific activity of tumor-derived ACSF preparations.
Evidence that low plasma 1,25-dihydroxyvitamin D causes intestinal malabsorption of calcium and phosphate in juvenile X-linked hypophosphatemic mice
Authors: Meyer Ralph A. , Meyer Martha H. , Gray Richard W. , Bruns M. Elizabeth 
Published: February 2010

Abstract
X-linked hypophosphatemic (Hyp) mice are a model for human sex-linked vitamin D-resistant rickets. We have reported intestinal malabsorption of calcium in young Hyp mice, and in this report we have explored the mechanism for it. To test for resistance of the intestine to 1,25(OH)2 vitamin D3, this hormone was continually infused via osmotic minipumps into 4-week-old normal and Hyp mice at 0,17, 50 or 150 ng/kg/day. After 3 days, 45Ca and inorganic 32P were administered by gavage, and the mice were sacrificed on the fifth day. The Hyp mice showed responses to the hormone equivalent to the normal mice in terms of increased intestinal absorption of both 45Ca and 32P, increased plasma isotope levels, increased femoral isotope content, and increased duodenal and renal 9 kD vitamin D-dependent calcium-binding protein (calbindin-D9K; CaBP). Plasma 1,25(OH)2D was measured in these mice. There were significant correlations of plasma 1,25(OH)2D to the intestinal absorption of 45Ca and 32P and to duodenal and renal CaBP. Plasma 1,25(OH)2D was also measured in stock normal and Hyp mice and was found to be lower in 4-week-old Hyp mice than in 4-week-old normal mice (113 ± 10 pM (n = 18) vs. 67 ± 10 (n = 20), normal vs. Hyp, p &lt; .01), but unchanged at 13 weeks of age (77 ± 13 (n = 13) vs. 70 ± 15 (n = 15), NS). This observed difference in plasma 1,25(OH)2D between normal and Hyp mice at 4 weeks of age was sufficient to explain the observed normal-to-Hyp differences in intestinal absorption of 45Ca and duodenal and renal CaBP. It also explained 72 ± 18% of the observed difference in 32P absorption. We conclude that Hyp mouse intestine is not resistant to 1,25(OH)2D and that the lower plasma 1,25(OH)2D of 4-week-old Hyp mice causes intestinal malabsorption of calcium and phosphate.