摘要:

AbstractThere is significant evidence that the insulin-like growth factors (IGF) play a role in both murine and human hemopoiesis. In order to better define the nature and mechanisms of these effects, we have used a serum-free system to examine DNA synthesis and cell replication in murine hemopoietic cells. Cell preparations from 13-day fetal mice livers were incubated in serum-free DMEM alone or with erythropoetin (Epo) 0.5 U/ml, recombinant human IGF-I, purified IGF-II, or recombinant human growth hormone (GH) in various doses, and [3H]thymidine added for the last 3 hr of 21-hr incubation. Cell distribution was over 80% erythroid or erythroblasts. IGF-I and IGF-II promoted thymidine incorporation into cells at a half-maximal dose of 3 and 1 nM respectively, IGF-II with a maximum potency 65% of IGF-I; insulin stimulated at a half-maximum dose of 100 nM, with similar maximum effect to IGF-I, and their effects were not additive. GH was stimulatory at 1μM. Epo was 2–9 times as effective as IGF-I and their effects were not additive. A monoclonal antibody to IGF-I reduced the effect of IGF-I by 50–80%, had no effect on Epo, and abolished the GH effect. Separation of erythroid cells and precursors from accessory and other liver cells did not alter the response to IGF-I. Cell counts increased in response to IGF-I or Epo, and cell viability was maintained by IGF-I compared to control medium.We demonstrate that (1) physiologic levels of IGF-I and IGF-II promote DNA synthesis in these cells, (2) their effects are primarily on erythroid precursors, (3) insulin's effects are probably via the IGF-I receptor, (4) the effects of IGF-I are specific and direct, and primarily not generated by a product of accessory cells, (5) high-dose GH has effects which are probably via local IGF production. It is concluded that IGF plays a role in fetal hemopoiesis, both by promoting cell growth and by maintenance of viability.

ISSN:0897-7194    

DOI:10.3109/08977199009043902

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor

摘要:

AbstractAdult rat arterial smooth muscle cells were shown to express mRNA for the platelet-derived growth factor (PDGF)α- andβ-receptors and to bind radioiodinated PDGF-AA and PDGF-BB in a phenotype-dependent and growth state-dependent manner. PDGFα-receptor mRNA was not detected in the intact aortic media, but appeared as the cells converted from a contractile to a synthetic phenotype during serum-free primary culture. PDGFβ-receptor mRNA was expressed already in vivo, and increased further as the cells were isolated and cultured in vitro. Exposure of the cells to human platelet PDGF resulted in increased PDGFα-receptor mRNA levels, decreased PDGFβ-receptor mRNA levels, and decreased binding of both PDGF-AA and PDGF-BB. Following removal of the exogenous mitogen, the content of PDGFα- andβ-receptor mRNA increased, as did the binding of PDGF-AA and PDGF-BB. Subsequently, the content of PDGF A-chain mRNA started to rise, and the cells retained a high rate of DNA synthesis in a serum-free medium. As a result of this autocrine stimulation, the PDGF receptors were down-regulated. Although smooth muscle cells in serum-free primary cultures bound the different PDGF isoforms to a varying extent (AA

ISSN:0897-7194    

DOI:10.3109/08977199009043904

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor

摘要:

AbstractThe effects of treatment with L-thyroxine (T4; 20 ng/g body weight, given subcutaneously on days 1, 3, 5, 7 and 9., 2.5 S nerve growth factor (NGF; 2 ngJmg brain wet weight, given intracerebroventricularly on days 1, 3, 5, 7 and 9), monoclonal anti-NGF (2 ng/mg wet weight, given intracerebroventricularly on days 1, 3, 5, 7 and 9), and monoclonal anti-NGF receptor (192 IgG; 2 ngJmg wet weight, injected daily from day 1 to day 9) antibodies, separately or together, were studied on the biochemical development of hippocampal formation, olfactory bulbs and cerebellum in 10-day-old and 15-day-old normal and hypothyroid rats. The results provide the following information: (1) CNS structures other than the basal fore-brain are sensitive to NGF during early development. (2) Both normal and hypothyroid rats are more sensitive to NGF deprivation than NGF supplementation. (3) The effects of anti-NGF antibodies in normal rats are similar to those induced by anti-NGFr antibodies. (4) NGF alone had little or no effect, but interacts with T4in promoting cell maturation, especially in hypothyroid rats. (5) Hypothyroid rats are more sensitive to T4and to T4plus NGF than are normal ones. (6) The synergistic action of both trophic factors, but not that of T4, tend to disappear at long term in hypothyroid rats. (7) The differential sensitivity of the brain areas to T4, NGF, or both trophic factors correlates with their cell acquisition rate, especially in hypothyroid rats. (8) T4and NGF together act more markedly (but not exclusively) on the cholinergic structures in both normal and hypothyroid rats. (9) RNA appears to be very sensitive to NGF, especially in hypothyroid rats. In close correlation with preliminary morphological observations, the results clearly demonstrate that an interaction between T4and NGF regulates the ontogeny of a number of neuronal structures in CNS independently of their neurotransmitter phenotype, but with a regional specificity. The possibilities of accounting for this interaction, in particular the major role of thyroxine, are discussed.

ISSN:0897-7194    

DOI:10.3109/08977199009043905

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor

摘要:

AbstractFibroblast growth factors (FGFs) are a family of structurally related proteins that influence the growth and differentiation of a variety of cell types, including the cells of the vascular system. Due to the lack of signal sequence, basic FGF is not actively secreted. However, it has been detected in the extracellular matrix bound, at least in some cases, via heparin-like molecules. Heparin has been shown to displace FGF from cells and matricesin vitro, and we have investigated the possibility that a similar phenomenon might occurin vivo.Heparin was infused intravenously into anesthesized rabbits; plasma samples taken 30 min later and monitored using [3H] thymidine incorporation into BALB/c 3T3 cells were found to contain 3-fold more stimulatory activity than control plasma samples. Addition of heparin directly to the 3T3 cells or to the plasma samples following their collection did not affect the level of stimulatory activity. A time course of stimulatory activity in rabbit plasma following heparin administration revealed that 3T3 cell stimulatory activity rapidly increased following heparin infusion, peaked at 30 min, and declined to control levels by 90–120 min. The anticoagulant action of heparin followed a different time course, providing evidence that these two effects of heparin are functionally distinct. The binding affinity of the plasma-derived stimulatory activity for heparin was used to demonstrate that the activity is FGF-like in nature. Additionally, administration of [125IJbFGF to rabbits that had been“precleared”by heparin infusion resulted in an immediate peak of circulating labeled bFGF that decreased to plateau level by 20–45 min following injection. Subsequent infusion of heparin led to an elevation of plasma [125I]bFGF levels for 20 min before returning to baseline. These results demonstrate that plasma contains an FGF-like activity whose levels can be significantly increased by thein vivoadministration of heparin. Our findings indicate that cell-associated heparin-like molecules may act as a reservoir for heparin-binding molecules, including potent vaso-regulators such as the FGFs.

ISSN:0897-7194    

DOI:10.3109/08977199009043906

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor

摘要:

AbstractBasic fibroblast growth factor (bFGF) is a potent mitogen for human bone marrow stromal cells. Normally, large numbers of human bone marrow stromal cells are difficult to obtain. However, nanogram/ml concentrations of bFGF stimulate the growth of passaged bone marrow stromal cells both in media formulated for optimal growth of stromal cells and in a simple mixture of RPMI-1640 and 10% fetal calf serum facilitating the successive expansion of stromal cells through multiple passages. bFGF also greatly accelerates the formation of a primary stromal cell layer following inoculation of newly harvested bone marrow cells into dishes. In the presence of bFGF, the stromal cells attain high densities, lose their contact inhibition and grow in multilayered sheets. Heparin greatly potentiates the stimulatory effect of low concentrations of bFGF. The effects of bFGF are fully reversible: cells cultured in the presence of this factor for multiple passages revert to normal growth rates following trypsinization and subculture. A short (4 h) exposure of the cells to bFGF elicits profound growth stimulation. This supports the hypothesis that this factor binds to glycosaminogly-cans in the cell matrix which act as a storage reservoir for this cytokine.

ISSN:0897-7194    

DOI:10.3109/08977199009043907

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor

摘要:

AbstractTransforming growth factor-beta 1 (TGFβ1) and basic fibroblast growth factor (bFGF) are known to be potent inhibitors and stimulators, respectively, of endothelial cell growth in vitro. In the present study we examined the effect of bFGF on endothelial cell growth inhibitory activity of TGFβ1 and on the binding of (l25I)-TGFβl to these cells. The concentration of TGFβ1 required for half-maximal inhibition of endothelial cell growth was increased in a dose-dependent manner by bFGF (a 20–100 fold increase at 1 ng/ml of bFGF). A 24 h-pretreatment of cells with bFGF resulted in abolition of the TGFβ1 inhibitory effect on DNA synthesis. Moreover, the binding of (l25I)-TGFβl to the endothelial cell surface was decreased in a concentration-dependent and time-dependent manner after a preincubation of these cells with bFGF. Analysis of the binding parameters showed that bFGF decreased by two-fold the number of TGFβreceptors (to approximately 6000 receptors per cell). Cross-linking experiments with disuccinimidyl suberate demonstrated the presence of two TGFβreceptor subtypes, a predominant 85 kDa form and a minor 65 kDa form. Basic FGF decreased selectively the labeling of the 85 kDa TGFβreceptor subtype. These findings suggest that the growth stimulator bFGF can attenuate the cell's response to the growth inhibitor TGFβ1.

ISSN:0897-7194    

DOI:10.3109/08977199009043908

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor

摘要:

AbstractStudies were conducted with chicken granulosa cells to evaluate the relative efficacy of human recombinant transforming growth factor alpha (TGFα) versus murine epidermal growth factor (EGF) to affect cyclic adenosine monophosphate (cAMP) accumulation and progesterone production stimulated by luteinizing hormone (LH) or steroid output induced by a cAMP analogue, and to modulate plasminogen activator (PA) activity.Increasing concentrations of EGF (33–328 nM) and TGFα(0.04–18'nM) were found to inhibit cAMP formation stimulated by LH in a dose-dependent manner, with calculated half-maximal inhibitory doses (ID30s) of 97.1 and 0.27 nM, respectively. Similarly, a 470-fold difference in the ability of TGFa (ID30= 0.13 nM) versus EGF (ID30= 61.3 nM) to half-maximally suppress LH-induced progesterone production was observed in the same cells. Progesterone production stimulated by a cAMP analogue (8-bromo-cAMP, 1 mM) was also attenuated by EGF (ID30= 75.9 nM) and TGFa (ID30= 0.08 nM), suggesting a post-cAMP site of inhibition by these growth factors on steroidogenesis. Finally, a 260-fold to 330-fold difference in the efficacy of TGFαversus EGF to half-maximally stimulate cell-associated and secreted PA activity was observed.From these data, we propose that TGFαmay serve an important role in regulating follicular growth and maturation in the domestic hen via its ability to affect granulosa cell steroidogenesis and plasminogen activator activity.

ISSN:0897-7194    

DOI:10.3109/08977199009043909

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor