摘要:

AbstractA glycosyl-phosphatidylinositol (GPI) has been previously identified that serves as a precursor of the polar head group that mimics and may mediate some of the intracellular actions of insulin. Since many of the biological activities of insulin may depend upon the activity of the insulin receptor kinase, we evaluated the requirement for this activity in insulin-dependent GPI hydrolysis. For the analysis we used stably transfected CHO cell lines, expressing either the wild-type human insulin receptor or a mutant receptor that lacks tyrosine kinase activity (Chou et al., 1987) and a stably transfected CHO cell line, expressing the wild-type human insulin-like growth factor I (IGF-1) receptor (Steele-Perkins et al., 1988). A GPI was identified in both types of transfected cells and in both sets of parental cells by metabolic labeling with [3H]glucosamine or [3H]galactose. The isolated glycolipid was sensitive to hydrolysis by phospholipase C and to deamination by nitrous acid. Insulin induced a time- and dose-dependent hydrolysis of the GPI in the parental line and in the transfected cell types. Cells bearing normal human receptors hydrolyzed up to 70% of their radiolabeled GPI within 2 min of the addition of 0.1 nM insulin, whereas parental cells and-cells expressing the mutant receptor hydrolyzed only 20-30% in response to 100 nM insulin. IGF-1 (5-50 nM) had little effect on GPI hydrolysis in these cells as well as in CHO cells expressing the human IGF-1 receptor. It is concluded that insulin-dependent GPI hydrolysis is mediated by the normal but not by a kinase-deficient insulin receptor.

ISSN:0897-7194    

DOI:10.3109/08977199009071496

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor

摘要:

AbstractPrimary cultures of sheep thyroid cells have been used to study regulation of thyroid growth and function by growth factors and TSH. Cells were plated at low density to minimize contributions from the endogenously produced insulin-like growth factors and their binding proteins and other proteins or hormones secreted by thyroid cells in culture. Growth of the cells was followed for 7-11 days in medium without serum. We found that TSH by itself was unable to stimulate thyroid growth. However, the ability of insulin and IGF-I to stimulate thyroid cell growth was markedly potentiated by TSH. Thyroid function was assayed by measurement of uptake of pertechnetate and organification of iodide and also by synthesis of thyroglobulin mRNA. TSH alone was unable to stimulate thyroid function appreciably. Insulin and IGF-I were ineffective by themselves at stimulating thyroid differentiated function, but in the presence of TSH, all indices were stimulated markedly. We conclude that TSH by itself is not a growth factor for thyroid cells. However, in the presence of insulin or IGF-I, TSH potentiates the growth-stimulating properties of this hormone. Similarly, TSH by itself does not stimulate thyroid function but requires the presence of insulin or IGF-I. These data show the cooperative interactions between growth factors and TSH in regulating both thyroid growth and function.

ISSN:0897-7194    

DOI:10.3109/08977199009071497

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor

摘要:

AbstractThere is substantial evidence to suggest that transforming growth factor-β(TGF-β) plays an important role in wound healing and tissue repair as well as in carcinogenesis. It has also been observed that naturally occurring bovine papillomavirus type 1 (BPV-l)-induced bovine fibropapillomas occur predominantly at traumatized sites of the body, suggesting that humoral factors released in wounds might be important for papillomavirus infection. We have therefore investigated the possible role of TGF-β1 in BPV-1 infections. Two anti-peptide antibodies which recognize different epitopes in the N-terminus of TGF-β1 were used to localize TGF-β1 in bovine fibropapillomas and normal bovine skin using im-munohistochemical methods. Staining by anti-LC(l-30) is intracellular in suprabasal keratinocytes of the epidermis as well as the hair follicles and sebaceous glands and correlates with known sites of TGF-β1 mRNA synthesis. Anti-CC(l-30) staining is extracellular in the immediately underlying dermis. Neither the pattern nor intensity of TGF-β1 staining was affected by BPV-1 infection. C127 cells and BPV-1-transformed C127 cells were compared for TGF-β1 mRNA expression and secretion of TGF-β1 peptide. Although the levels of messenger RNA and secreted TGF-/51 peptide were similar in both cell types, five- to sixfold greater amounts of TGF-β-like activity per cell was detected in media conditioned by the uninfected cells. TGF-β1 treatment had no effect on the growth rate of either cell type or on BPV-1 gene expression in the transformed cells.

ISSN:0897-7194    

DOI:10.3109/08977199009071498

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor

摘要:

AbstractUsing a simian transforming growth factor-β2 (TGF-β2) cDNA probe, we have isolated chicken cDNA clones for TGF-β2 from a chicken embryo chondrocyte cDNA library. The predicted precursor protein of chicken TGF-β2 is 412 amino acids long, two amino acids shorter than the human form to which it shows 90% identity. Cleavage of the chicken TGF-β2 precursor at a pentabasic Arg-Arg-Lys-Lys-Arg site would produce a 112-amino acid processed peptide differing by only one amino acid from the human TGF-β2 peptide. In contrast to TGF-β3 and 4 mRNAs, TGF-β2 mRNA is expressed in both cultured and non-cultured chicken embryo chondrocytes and at higher levels in chicken embryo fibroblasts. In chondrocytes and fibroblasts, the 3.9- and 4.3-kb TGF-β2 mRNAs are both expressed at higher levels than the 8-kb TGF-β2 mRNA; however, in developing chicken embryos, the level of expression of the 8-kb mRNA is higher than that of the 3.9- and 4.3-kb mRNAs.

ISSN:0897-7194    

DOI:10.3109/08977199009071499

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor

摘要:

AbstractTGF-β2 and -β5 have been purified from medium conditioned byXenopuscultured cells (XTC) and identified based on their N-terminal amino acid sequence analysis and biological activity. When applied in high concentrations,XenopusTGF-β2, like porcine TGF-β2, induces expression of mesodermal markers from culturedXenopusectodermal explants, whereas TGF-β5 is inactive in this assay. However, the TGF-β's could be separated from the major mesoderm-inducing activity present in XTC medium.XenopusTGF-β2 and -β5 are approximately equivalent to TGF-β1 in their abilities to inhibit the growth of mink lung CCL-64 cells, induce anchorage-independent growth of rat NRK cells, inhibit the proliferation and antibody secretion of human B-lymphocytes, and stimulate chemotaxis of human monocytes. These data establish the functional activity of TGF-β5 and suggest that more complex multicellular systems, in contrast to most isolated cells, discriminate between the different TGF-βs.

ISSN:0897-7194    

DOI:10.3109/08977199009071500

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor

摘要:

AbstractThe possible role of changes in TGF-βexpression in the multistage development of thyroid cancer was assessed. The presence of TGF-β1 in thyroid epithelial cells was analyzed in sections of normal and tumor tissue using an immunoperoxidase technique employing an antibody directed against the amino-terminal 30 amino acids of mature TGF-β1. Specific immunostaining was clearly detected in epithelial cells in 58% of malignant thyroid tumours (including follicular, papillary, and anaplastic variants). However, no positive cells were seen in any of 7 benign tumors nor in any normal thyroid epithelium. Within the cancer group as a whole, there was no significant correlation with pathological grade or clinical stage of tumor but in one subgroup–follicular carcinomas–a significant association was noted between TGF-βimmunostaining and the presence of a specific mutation of the H-ras oncogene (codon 61, glnarg). We conclude that a major alteration in expression of TGF-βoccurs specifically in the malignant stage of tumor development in thyroid follicular epithelium and speculate on its possible role in this process.

ISSN:0897-7194    

DOI:10.3109/08977199009071501

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor

摘要:

AbstractOncostatin M is a novel growth regulator originally isolated from differentiated human histiocytic lymphoma cells and activated T-lymphocytes based on its ability to inhibit the growth of A375 melanoma cells. We report here that oncostatin M is a widely acting regulator which alters the growth and/or morphology of cells derived from a variety of cancer cell types. At picomolar concentrations, recombinant oncostatin M inhibited the growth of 13/24 tumor cell lines. Six out of 7 lung cancer cell lines were inhibited by oncostatin M, but none of 6 colon cancer cell lines were affected. Oncostatin M also stimulated the growth of some normal cells (3/6), indicating that it, like many growth regulators, is bifunctional. Oncostatin M receptors appear necessary but not sufficient for a growth response to oncostatin M, since none of the cell lines lacking receptor responded to oncostatin M, whereas many but not all cell lines with receptor responded to oncostatin M. Receptor size(Mr= 150,000) was similar for cells in which growth was inhibited, stimulated, or unaffected by oncostatin M.

ISSN:0897-7194    

DOI:10.3109/08977199009071502

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor

摘要:

AbstractThe kinetics of uptake and processing of recombinant human interferon-a2a (IFN) and recombinant human tumor necrosis factor-a (TNF) were studied in human epithelial rumor cell lines differing in sensitivity to growth inhibition by IFN and TNF. Concentrations of [125I]IFN or [125I]TNF at the cell surface and internalized by confluent cell monolayers incubated at 37°C were measured as a function of time. Cells incubated with [125I]IFN exhibited transient maxima of surface-associated and internalized [I25I]IFN after 1-2 hr of incubation followed by a steady-state attained after approximately 6 hr of exposure to [125I]IFN. Concentration of [125I]TNF associated with the plasma membrane displayed a maximum within 20 min of incubation. Internalized radioactivity increased with time and did not achieve a steady state. We analyzed the time-dependent concentrations of membrane-associated and internalized cytokines by use of a compartmental model. This model describes changes in concentrations of free surface receptors, of ligand-receptor complex at the membrane and of internalized ligand and contains a term for receptor recycling. The rate constants for concentration changes were evaluated by fitting model functions to data. The best fits for IFN were obtained without receptor recycling. The best-fit values for the endo-cytotic rate constant(ktlFN)varied among cell lines from 2.4x10−4to 7.8 x10−4sec−1. To obtain fits to time-dependent concentrations of surface-associated and internalized [125I]TNF, introduction of a term for receptor recycling was required. Best-fit values fork,TNFranged among cell lines from 8.4x10−4to 2.5x10−3sec−1. For every cell line, the value ofklTNFwas larger than the value ofkclFN.We tested the significance of these differences by substitutingK.IFNtorK.TNTasfixed parameters in fits to data for TNF andv.v., respectively. Under these conditions, fits were significantly worse. Our data indicate that recycling is insignificant in kinetics of Type-I IFN receptor; recycling is necessary to explain the kinetics of TNF receptor. Upon binding, TNF is taken up by cells faster than IFN and is eliminated from cells more slowly than IFN.

ISSN:0897-7194    

DOI:10.3109/08977199009071503

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor

摘要:

AbstractParacrine growth factors probably stimulate the pathologic proliferation of synovial fibro-blast-like cells (synoviocytes) in rheumatoid arthritis (RA), but the relative importance of various factors is highly controversial. To address this problem, we compared the effects of highly purified or recombinant cytokines, in serum-free medium, on thein vitrolong-term growth of synoviocytes from patients with RA and rats with streptococcal cell wall (SCW) arthritis. Of the factors tested (PDGF, aFGF, bFGF, EGF, TGF-β, IL-l-a, TNF-αand IFN-γ), PDGF, was clearly the most potent stimulant of long-term growth of both rat and human synoviocytes. The strong mitogenic activity of rheumatoid synovial fluids was significantly inhibited by neutralizing anti-PDGF antibody, thus confirming the importance of PDGF. EGF, TGF-β, IL-l-α, TNF-α, and IFN-γhad minimal effects. Similar to the effects on anchorage-independent growth, TGF-β1 and 2, inhibited serum- or PDGF-stimulated anchorage-dependent growth. Considered in the context of other reports, these data support the view that cytokines such as PDGF, and possibly aFGF and bFGF, play major roles in stimulating synoviocyte hyperplasia in RA and SCW arthritis, whereas TGF-βmay inhibit synoviocyte growth.

ISSN:0897-7194    

DOI:10.3109/08977199009071504

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor

摘要:

AbstractSeveral HTLV-I-infected T-cell lines express the two genes encoding platelet-derived growth factor (PDGF). Therefore, we examined the question of a possible self-stimulatory mechanism of proliferation involving PDGF in these cells. Using a nucleic acid probe and an antibody specific for the PDGF-B receptor (PDGFR-B), we examined four established human T-cell lines infected with HTLV-I, as well as several noninfected T-cell lines for expression of the PDGF-B receptor. Previous reports indicate that lymphocytes do not display receptors for PDGF; our results show that two noninfected T-cell lines (HUT-78, CCRF-HSB-2) expressed the canonical 5.5-kb PDGFR mRNA, and two HTLV-I-infected T-cell lines (C10/ MJ, MT-2) expressed a novel PDGFR mRNA of 4.8 kb. Concomitantly, the cell lines expressing PDGFR mRNA also synthesize PDGFR proteins immunoprecipitated by the antibody to PDGFR-B. Differences were observed in the molecular weight of PDGFR molecules immunoprecipitated from uninfected and HTLV-infected T-cells. Immunofluorescence studies demonstrated that the PDGFR-B proteins are localized primarily on the cell external membrane. The results suggest that the HTLV-I-infected T-cells acquire an autostimulatory mechanism of cell proliferation that involves PDGF.

ISSN:0897-7194    

DOI:10.3109/08977199009071505

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor