摘要:

AbstractPorcine aortic endothelial cells expressing platelet-derived growth factor (PDGF)α- orβ-receptors after transfection of the corresponding cDNAs, were used to investigate whether PDGF receptor dimerization occurs in intact cells after ligand binding. Using three different methods—covalent cross-linking of125I-labeled ligand, cross-linking of metabolically labeled cells after ligand-binding followed by immunoprecipitation, and immunoblotting of cells after ligand binding and cross-linking—it was demonstrated thatα- as well asβ-receptors form ligand-induced dimeric complexes. Dimerization correlated with induction of receptor kinase activity, measured as receptor autophosphorylation. Heterodimeric complexes could furthermore be induced by PDGF-AB, when added to a mixture of lysates from theα- andβ-receptor expressing cell lines, or when added to human fibroblasts which express both receptor types.

ISSN:0897-7194    

DOI:10.3109/08977199209008867

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

AbstractHuman monocytes respond to IL-3 and GM-CSF with a similar range of functional activities, and at similar cytokine concentrations. We have recently shown, however, that the rate of monocyte activation is greater in response to GM-CSF than to IL-3. In order to understand the basis of this phenomenon we investigated the interaction of IL-3 and GM-CSF with their surface receptors by means of kinetic binding experiments.125I-GM-CSF showed very rapid association to monocytes at 37°C, with a half-time of only 40 sec. The pattern of binding with this ligand was complex, with a decline in overall cell-associated radioactivity after 2 min of incubation. In contrast,125I-IL-3 showed slower association, with a half-time at 37°C of 2.5 min. The different rates of association correlated well with the different rates of cell activation induced by the two cytokines. On the other hand, rates of internalisation were similar for the two cytokines, with half-times of 14-15 min.Competition binding experiments performed under high affinity conditions showed that IL-3 and GM-CSF cross-competed for binding on the surface of monocytes. In contrast, under low affinity conditions IL-3 did not compete for125I-GM-CSF binding while GM-CSF was a strong competitor of125I-IL-3 binding. In quantitative inhibition experiments GM-CSF showed inhibitory effects on low affinity125I-IL-3 binding at lower concentrations than those needed with unlabelled IL-3. It is suggested that current models of IL-3/GM-CSF receptor interactions need to be revised in order to accommodate the unique pattern of competition on human monocytes presented here.

ISSN:0897-7194    

DOI:10.3109/08977199209008868

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

AbstractWe describe the effect of soluble c-kit ligand (stem cell factor, SCF) on highly purified CD34-positive hemopoietic progenitors from human umbilical cord blood. Progenitor cells were purified from cord blood mononuclear cells by immune resetting with lineage specific antibodies and subsequent sorting of the rosette-negative population for CD34(BI3C5)-positive cells. This procedure enriched>100-fold for colony forming cells (CFC). Using optimal concentrations of colony-stimulating factors (CSF) without added SCF approximately 2.5% of cells formed colonies. SCF also had CSF activity on this population, up to 0.5% of cells forming small colonies in response to SCF alone. In contrast, the addition of SCF to optimal concentrations of the other growth factors produced a>10-fold increase in colony number. However, the most notable effect was an approximately 100-fold increase in the number of cells in each colony. Equally striking was the very high proportion (50-80%) of mixed colonies (CFU-MIX). These findings suggest the progenitor cell pool in cord blood is skewed towards very early cells. However, when day 14 colonies formed in response to SCF and other factors were assessed for their re-cloning potential they did not contain significant numbers of CFC, implying that SCF did not support the self-renewal of these CD34 positive cord blood progenitor cells. These findings support a role for SCF as an enhancing factor for hemopoietic progenitor cells but it does not promote self-renewal in these populations.

ISSN:0897-7194    

DOI:10.3109/08977199209008869

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

AbstractProfuse sprouting of sensory nerve fibers occurs in tooth pulp by 1-4 days following dentin injury. A possible role for nerve growth factor (NGF) in that neural response is suggested here by the demonstration that NGF mRNA and protein are increased 6 hr after injury to adult rat molars. The enhanced expression of NGF mRNA was localized to fibroblasts underlying the injury. A concomitant depletion of mRNA encoding the 75 Kd NGF receptor (NGFR) was observed in those fibroblasts. The increase in NGF mRNA was transitory and mRNA levels fell below normal levels by 2 days after injury. Both NGF and NGFR mRNA remained low thereafter in injured pulp. The inverse shifts in fibroblastic mRNA encoding NGF and NGFR were not affected by prior denervation of the tissue, or by pretreatment with dexamethasone. The regulatory mechanisms therefore must involve endogenous, non-neuronal, non-inflammatory factors that are released in response to injury.

ISSN:0897-7194    

DOI:10.3109/08977199209008870

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

AbstractMuscle growth and regeneration is controlled by locally produced growth factors which activate satellite cells and stimulate their proliferation, differentiation and fusion to form mature myotubes. Basic fibroblast growth factor (bFGF) has been previously shown to promote proliferation and inhibit differentiation of myoblastsin vitro.In comparison, thein vivorole of this growth factor is less well documented. In the present investigation on the role of bFGF in muscle regeneration, bFGF mRNA levels were studied in two experimental systems: (1) primary cell cultures derived from rat skeletal muscles, and (2) anin vivorat muscle injury model. bFGF mRNA was detected in myoblasts just prior to fusion and in myotubes of primary muscle cell cultures. In the non-injured muscle, bFGF mRNA transcripts were detected in myotubes but not satellite cells. In thein vivomuscle injury model bFGF mRNA was observed in myoblasts and in degenerating and regenerated myotubes. The significance of these experimental results in terms of the role played by bFGF in the myogenic programin vivoare discussed.

ISSN:0897-7194    

DOI:10.3109/08977199209008871

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

AbstractFrom medium conditioned by 3T3 cells, we had previously purified an inhibitory factor of Mr 45 kDa which we termed IDF45 (inhibitory diffusible factor). The protein was able to 100% inhibit stimulation induced in CEF by 1% calf serum and to reversibly prevent cell growth. We then demonstrated that IDF45 was an IGF-binding protein. Our results suggested that IDF45 was a bifunctional molecule able to bind IGF and to inhibit DNA synthesis stimulated by this hormone, but also to inhibit stimulation of DNA synthesis induced by another growth factor in serum. Indeed, its N terminal amino acid sequence has great homology with that of IGFBP-3 and IDF45 is now proposed to be named IGFBP-3 (mouse IGF binding protein). Present results show that Ha-ras transfected 3T3 cells (EJ cells), like 3T3 cells, secrete a mIGFBP-3 molecule. In addition, transfected cells secrete a doublet of an IGF-binding protein (IGFBP-28) of Mr 28 kDa which is not secreted by untransformed 3T3 cells. IGFBP-28 has been purified and characterized in this work. Various results suggest that IGFBP-28 is not a degradation product of mIGFBP-3. Its N terminal amino acid sequence was different from that of mIGFBP-3. IGFBP-28 inhibited DNA synthesis stimulated by IGF-I, but much more IGFBP-28 protein than mIGFBP-3 was required to prevent this stimulation. In agreement with this result, IGFBP-28 has low affinity for IGF-I. In contrast, IGFBP-28 has high affinity for IGF-II. Like mIGFBP-3, IGFBP-28 was able to inhibit the stimulation induced by serum in CEF and to reversibly prevent growth, though with a specific activity lower than that of mIGFBP-3. It has also the capacity to inhibit stimulation of DNA synthesis induced by high molecular weight serum proteins depleted in IGF-I and II.In conclusion we have shown that transformation of 3T3 cells with Ha-ras induced the synthesis of a new IGF binding protein in medium conditioned by normal 3T3 cells. Our results suggest that IGFBP-28 like mIGFBP-3 is a bifunctional protein able to inhibit stimulation induced by IGF and by serum proteins different from IGFs.

ISSN:0897-7194    

DOI:10.3109/08977199209008872

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

AbstractAngiogenesis induced by transforming growth factor beta (TGFB) implanted in the rabbit cornea is accorripanied by an influx of inflammatory cells. To determine if the inflammatory cells are the mediators of the neovascularization, they were depleted by local administration of methylprednisolone acetate (MPA). Subconjunctival injections of 16 mg of MPA immediately following implantation of 50 ng of TGFB in the cornea prevented the inflammation and subsequent formation of capillaries. If the injections of MPA were delayed by 48 hr and the inflammatory cells were allowed to enter the cornea, angiogenesis occured, demonstrating that MPA had no adverse effects on the ability of endothelial cells to form capillaries. These results confirm the hypothesis that TGFB induces angiogenesis indirectly by recruiting inflammatory cells capable of stimulating direct angiogenesis.

ISSN:0897-7194    

DOI:10.3109/08977199209008873

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

AbstractLevels of transforming growth factor-β(TGF-β) activity in the conditioned medium of blood lymphocytes of twelve patients with aplastic anemia (AA), nine patients with myelodysplastic syndromes (MDS) and five normal volunteers were investigated. We were able to observe growth inhibitory activity on porcine endothelial cells only after acidification of the materials. The growth inhibitory activity is neutralized by anti-TGF-βantibody. It indicates that TGF-βexists as a latent form in the conditioned medium. On the basis of growth inhibition assay, the mean level of TGF-βproduction of MDS patients was estimated to be 188·199 pg/1·107cells and that of normal volunteers was 668·314 pg/1·107cells. In contrast, the lymphocytes of almost all of the AA patients failed to produce detectable amounts of TGF-β. No correlation between TGF-βlevels and peripheral blood parameters could be detected. Stimulation of lymphocytes by phytohemagglutinin is known to increase the production of TGF-β. Induction of TGF-βproduction was also observed in AA (45% of normal controls). Possible roles of the decreased production of TGF-βin the pathogenesis of AA were discussed.

ISSN:0897-7194    

DOI:10.3109/08977199209008874

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

AbstractGrowth Factors in Cell and Developmental Biology. [Edited by M.D. Waterfield; Published by The Company of Biologists Ltd, Cambridge; Supplement 13 to J. Cell Science, 1990]

ISSN:0897-7194    

DOI:10.3109/08977199209008875

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor