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M Centrella

Publications and source records attributed to M Centrella.

97 records · Page 6Linked to original sources
PubMed1986

Isolation of a nontransforming bone-derived growth factor from medium conditioned by fetal rat calvariae.

Previous studies have indicated that medium conditioned by 21-day-old fetal rat calvariae contains bioactive proteins termed bone-derived growth factors (BDGF) I and II. In the present studies we have purified the nontransforming BDGF II by dialysis, molecular sieving, three reverse phase HPLC steps, and preparative polyacrylamide gel electrophoresis. The second HPLC step (HPLC-2) yielded a recovery of 22% of the biological activity and achieved a 1500-fold purification, resulting in 20 micrograms protein/liter calvarial conditioned medium; the third HPLC step was of limited value in the purification of BDGF. Analytical PAGE revealed that the majority of the protein in HPLC-2-purified BDGF migrated with a relative molecular mass (Mr) of 11,000 and two additional proteins were seen at a Mr of 22,000-23,000. On preparative PAGE, the material migrating with a Mr of 11,000 stimulated parameters of bone and fibroblast growth in vitro, whereas the material with a Mr of 22,000-23,000 had less biological activity. Isoelectric focusing revealed that BDGF had an isoelectric point (pI) of 5. BDGF enhanced the incorporation of [3H]thymidine into DNA in fibroblast and calvarial cultures and of [3H]proline into collagen and noncollagen protein in calvariae. In conclusion, fetal rat calvariae secrete a BDGF with an estimated Mr of 11,000 and a pI of 5; this material stimulates bone and fibroblast growth in vitro.

Animals↗
PubMed1986

Human platelet-derived transforming growth factor-beta stimulates parameters of bone growth in fetal rat calvariae.

Human platelet-derived transforming growth factor type beta (TGF beta) is mitogenic for fetal rat calvariae in serum-free organ culture. It enhances DNA synthesis in short (24-h) and long (48- to 96-h) term cultures, but produces no significant stimulatory effects on bone collagen synthesis or alkaline phosphatase activity (two parameters of differentiated osteoblastic cell-type function) when present continuously in culture. Transitory treatment with TGF beta, however, induces a subsequent stimulation of collagen and noncollagen protein synthesis that depends on prior cell replication, suggesting an increase in the number of newly differentiated bone cells. In addition, TGF beta increases prostaglandin release, but this effect is probably unrelated to its mitogenic function. TGF beta activity is also found in culture medium conditioned by fetal rat calvariae, and the bone-derived factor produces effects similar to those of the human platelet factor. This polypeptide, therefore, may have an important function in early stages of bone development as well as bone repair after trauma-induced platelet degranulation.

Animals↗
PubMed1985

Transforming and nontransforming growth factors are present in medium conditioned by fetal rat calvariae.

Conditioned medium recovered from fetal rat calvarial cultures contains an autocrine factor termed bone-derived growth factor (BDGF); this factor has been purified by acid extraction, gel-permeation chromatography, and two reversed-phase HPLC steps and examined for mitogenicity on normal rat kidney fibroblasts (NRK, clone 49F). HPLC-purified BDGF caused a dose-related increase in cell number, DNA content, and [3H]thymidine incorporation into acid-insoluble material. Since highly purified BDGF appeared less mitogenic than cruder preparations, the latter were tested for additional growth factors, with particular attention to those required for anchorage-independent colony formation in soft agar. BDGF did not displace 125I-labeled epidermal growth factor (EGF) in a radioligand-receptor assay, indicating the absence of EGF and transforming growth factor alpha (TGF-alpha). Without EGF, no BDGF preparation induced NRK cells to form soft agar colonies. However, calvarial conditioned medium contained a factor which, like TGF-beta, induced large soft-agar colonies in the presence of EGF; this TGF-beta-like factor did not copurify with BDGF. Polyclonal antibodies against platelet-derived growth factor did not neutralize the effects of BDGF on NRK cells. BDGF is a potent mitogen for nonskeletal-tissue-derived fibroblasts. Although crude BDGF preparations do contain TGF-beta, BDGF is distinct from this factor and others necessary for NRK cell transformation to anchorage-independent growth.

Animals↗
PubMed1985

Effect of partially purified bone morphogenetic protein on DNA synthesis and cell replication in calvarial and fibroblast cultures.

The effects of bone morphogenetic protein (BMP), a molecule extracted from demineralized bone, were observed in organ cultures of 21-day fetal rat calvariae. The effects of BMP on cell replication in cultures of normal rat kidney (NRK) fibroblasts were studied for comparison. At concentrations of 0.1-10 micrograms/ml for periods of 24-96 hours, BMP stimulated the incorporation of 3H-thymidine into acid-insoluble residues (DNA) in calvariae by 25%-159%, and at 1-10 micrograms/ml it increased bone DNA content by 20%-23%. BMP at 1 micrograms/ml also increased the number of calvarial mitoses after colcemid arrest by 1.5-1.8-fold. The effect of BMP on calvarial DNA synthesis was observed in the periosteal bone. In contrast to its effects on DNA synthesis, BMP did not stimulate the incorporation of 3H-proline into collagenase-digestible and noncollagen protein and did not alter calvarial alkaline phosphatase activity. BMP at 1-10 micrograms/ml caused a marked increase in 3H-thymidine incorporation into DNA in cultured NRK fibroblasts and increased DNA content and cell number by 1.5-2-fold. These studies indicate that BMP stimulates DNA synthesis and cell replication in calvarial and fibroblast cultures but does not stimulate postdifferentiated bone cells in incubated calvariae.

Alkaline Phosphatase↗
PubMed1982

Regulation of protein synthesis in vesicular stomatitis virus-infected mouse L-929 cells by decreased protein synthesis initiation factor 2 activity.

Infection of mouse L-cell spinner cultures by vesicular stomatitis virus (VSV) effected the selective translation of viral mRNA by 4h after viral adsorption. Cell-free systems prepared from mock- and VSV-infected cells reflected this phenomenon; protein synthesis was reduced in the virus-infected cell lysate by approximately 75% compared with the mock-infected (control) lysate. This effect appeared to be specific to protein synthesis initiation since (i) methionine incorporation into protein from an exogenous preparation of initiator methionyl-tRNA gave completely analogous results and (ii) the addition of a ribosomal salt wash (containing protein synthesis initiation factors) stimulated protein synthesis by the infected cell lysate but had no effect on protein synthesis by the control. Micrococcal nuclease-treated (initiation-dependent) VSV-infected cell lysates were not able to translate L-cell mRNA unless they were supplemented with a ribosomal salt wash; a salt wash from ribosomes from uninfected cells effected a quicker recovery than a salt wash from ribosomes from infected cells. When salt wash preparations from ribosomes from uninfected and infected cells were tested for initiation factor 2 (eIF-2)-dependent ternary complex capacity with added GTP and initiator methionyl-tRNA, we found that the two preparations contained equivalent levels of eIF-2. However, initiation complex formation by the factor from virus-infected cells proceeded at a reduced initial rate compared with the control. When the lysates were supplemented with a partially purified eIF-2 preparation, recovery of activity by the infected cell lysate was observed. Mechanisms by which downward regulation of eIF-2 activity might direct the selective translation of viral mRNA in VSV-infected cells are proposed.

Animals↗