ISSN:0897-7194    

DOI:10.3109/08977199308991570

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

Platelet derived growth factor (PDGF) induces activation of the protein tyrosine kinase domain of the PDGF receptor, resulting in receptor dimerization and the initiation of mitogenesis in responsive cells. In order to identify domains of the receptor involved in these processes, a panel of monoclonal antibodies (MAbs) against the extracellular region of the human PDGF receptor was developed and screened to identify which of these specifically block PDGF binding. One of these, MAb 2AlE2, binds PDGF beta receptor with high affinity and blocks PDGF BB binding in a whole cell binding assay with an IC 50 of 0.1 nM. Inhibition of binding results in the inhibition of ligand-induced receptor phosphorylation, dimerization and mitogenesis in cells expressing the PDGF beta receptor. MAb 2AlE2 has been mapped to the fifth Ig domain of the PDGF beta receptor, implying that this domain is important for ligand binding, dimerization and/or activation. The potency of MAb 2AlE2 for inhibiting PDGF BB binding indicates that this antibody is ideally suited to identify and characterize PDGF BB-induced biological responses.

ISSN:0897-7194    

DOI:10.3109/08977199308991571

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

Growth factors play an important role in the regulation of cell growth, division and differentiation. In this study the distribution and regulation of insulin-like growth factor-I (IGF-I) in the continuously erupting rat incisor was determined by immunohistochemistry. Results were evaluated both visually and with a computer-based image analysis system. The distribution and intensity of IGF-I immunoreactivity varied with developmental stage of the rat incisor. Strong IGF-I immunoreactivity was observed in differentiating odontoblasts and ameloblasts. The most intense immunoreactivity was observed in secretory ameloblasts, secretory odontoblasts and in maturation ameloblasts. Staining was weak or absent in post-secretory ameloblasts but persisted in post-secretory odontoblasts. Weak to moderate immunoreactivity was also seen in cells of the stratum intermedium and in the reduced enamel epithelium. Surrounding alveolar bone showed strong IGF-I immunoreactivity in osteoblasts and in the stratum basale and stratum spinosum of the adjacent labial gingival epithelium. In order to assess the role of GH in IGF-I expression, GH (65μg/100 g bw) was administered for six days to dwarf GH deficient rats, producing a significant increase in body weight (P<0.01). Measurements at different stages of odontogenesis showed that the staining intensity of secretory ameloblasts (P<0.01) and maturation ameloblasts (P<0.001) was significantly different between untreated and treated animals. These results indicate that IGF-I is present in cell populations of the enamel organ of the rat incisor found previously to exhibit growth hormone receptors, and that expression of IGF is GH dependent. These findings support the concept that paracrine or autocrine synthesis of IGF-I mediates the effects of growth hormone on the growth and secretory function of cells forming the rat mandibular incisor.

ISSN:0897-7194    

DOI:10.3109/08977199308991572

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

Acidic fibroblast growth factor (aFGF) lacks a classical signal sequence for secretion via the exocytic pathway but yet has to be released from cells in order to interact with high affinity receptors on the cell surface. To study the release process, we have expressed human aFGF in HeLa cells using a T7 RNA polymerase-driven vaccinia virus system. The high level of expression in combination with an efficient antibody allowed us to analyze the release of aFGF by pulse-chase experiments, and to immunolocalize the protein in transfected cells. In the absence of heparin, only negligible amounts of aFGF were detected in the medium during a IS hr chase period. However, if heparin was present during the chase, readily detectable amounts (about 10–20% of total) of aFGF were found in the medium during the 15 hr chase. Extracellular aFGF was first detected at 8 hr and increased during the chase. Concomitantly, only small amounts of lactate dehydrogenase activity, used as a cytoplasmic marker, was released from the cells. Further analyses indicated that heparin both stabilized the protein from degradation and prevented the binding of released aFGF to extracellular heparan-sulfate proteoglycans. Thus, both factors contributed to the increased recovery of aFGF in the presence of heparin. The slow and inefficient release of aFGF is consistent with our previous results obtained in insect cells expressing aFGF to a very high level, as well as with those obtained by others in cultured cells producing FGF.Immunolocalization using an affinity purified antibody made against native aFGF, showed strong fluorescence in the nuclei in most cells, while staining in the cytoplasm was usually weaker and varied between cells. The nuclear localization was confirmed by subcellular fractionation and immunoblot analysis. At an early time point following transfection (4 hr), aFGF was preferentially localized to the nuclei, while the distribution of the protein between cytoplasm and nuclei was about equal at later time points (12 hr). Thus, we conclude that aFGF is capable of efficiently entering the nucleus and apparently becoming trapped there.

ISSN:0897-7194    

DOI:10.3109/08977199308991573

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

Basic FGF is a multifunctional protein which promotes regeneration in several tissues. To investigate involvement in cardiac injury-repair, bFGF accumulation and localization was examined in hearts of rats injected with a single high dose of isoproterenol. The bFGF content of cardiac extracts was analyzed at 6 and 24 hours as well as 1, 4, and 6 weeks by western blotting of heparin-sepharose-bound fractions. The 18 kilodalton bFGF species showed an approximately 2-fold increase in extracts from treated animals compared to non-treated controls. A transient rise in a 21–23 kilodalton bFGF species was seen at 24 hours after treatment. An induction of bFGF mRNA was also observed in treated animals. To localize bFGFin vivo, immunofluorescent labelling with specific antibodies was used at 4–24 hours and 1–4 weeks after treatment. Simultaneous labelling for the cytoskeletal proteins vinculin or vimentin was employed to identify viable myocytes or non-muscle interstitial cells, respectively. Necrotic myocytes, identified by loss of vinculin, displayed a pronounced increase in cytoplasmic anti-bFGF staining compared to adjacent normal myocytes. This increase occurred prior to and may play a role in promoting mobile cell migration and proliferation in areas of necrosis. Viable cardiomyocytes adjacent to fibrotic regions displayed strong pericellular anti-bFGF staining and, occasionally, were also stained by anti-vimentin antibodies, suggesting reexpression of an embryonic phenotype and thus an attempt for regeneration. These data showing increased accumulation and distinct patterns of localization of bFGF in the hearts of isoproterenol-treated animals suggest that this growth factor plays a role in short-term as well as long term response of the myocardium to injury.

ISSN:0897-7194    

DOI:10.3109/08977199308991574

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

A guinea pig partial thickness skin excistoti model wx used to evaluatc the effects of recombinant human PDGF-BB, 1′17GF-AA, ECF, and bFGF on granuLition tissue (neodermis) formation. These growth factors tended to increcisr the thickness of the granulation tissue bed when assesstd histcilogitally at day 7. Using only four animals per group, PDGF-BB at 30 and 100μg/ml consistently and significantly incwaseil the thickness of the granulation bed 2–3 limits that of control. Except for the increased thickness, the granulation tissue appmred normal. I'DGF-AA and EGF also significantly increased the granulation tissue thickness, and bFGF gave indications of an effect. Therc was no evidence of synergistic effects bthwxi PDGF-BB, EGF, and/or bFCF.

ISSN:0897-7194    

DOI:10.3109/08977199308991575

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

Polyvinyl alcohol sponge implants were used in rats, mice, and guinea pigs to determine dose responses of growth factors. Eight differently treated sponges per rat or guinea pig (4/mouse) were injected with test material on alternate days and evaluated at day 8. Much of the observed response occurred in and around the capsule and was manifest as densely cellular granulation tissue. Including this capsular response in a single histologic slide ranking system provided a more sensitive and faster method of assessing growth factor effects than measurement of connective tissue ingrowth alone. Clear dose responsive effects were seen with recombinant human PDGF-BB, PDGF-AA, bFGF, and IL-1β, while EGF gave a lesser response. Lipopolysaccharide did not affect the connective tissue response, alone or in combination with PDGF-BB. PDGF-BB was tested in each species, and the dose response characteristics were qualitatively and quantitatively similar across species.

ISSN:0897-7194    

DOI:10.3109/08977199308991576

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor