PubMed Health⌕ Search

Biomedical subjects

D Danielpour

Publications and source records attributed to D Danielpour.

70 records · Page 4Linked to original sources
PubMed1990

Antibodies to transforming growth factor-beta 2 peptides: specific detection of TGF-beta 2 in immunoassays.

Polyclonal antibodies have been raised to synthetic peptides corresponding to several regions of transforming growth factor-beta 2 (TGF-beta 2). All antisera were tested for their ability to react with either the native or reduced forms of both TGF-beta 1 and TGF-beta 2 in enzyme-linked immunosorbent assays, Western blots, and immunoprecipitation assays. On Western blots, antisera raised to a peptide corresponding to residues 50-75 of TGF-beta 2 specifically detected 5 ng TGF-beta 2, while antisera raised to regions 1-30 and 79-108 cross-reacted with TGF-beta 1. Anti-P 50-75(2) also localized TGF-beta 2 in murine placenta in immunohistochemical studies. In immunoprecipitation assays with either iodinated TGF-beta s or with media conditioned by cells labeled with [35S]cysteine, both anti-P 50-75(2) and anti-P 79-108(2) specifically immunoprecipitated TGF-beta 2 under reducing conditions only, while anti-P 79-108(2) also reacted with TGF-beta 1. None of the TGF-beta 2 peptide antibodies was able to block receptor binding of either TGF-beta 1 or 2. Analysis of the cross-reactivity patterns of these peptide antibodies suggests conformational differences between TGF-beta 1 and TGF-beta 2.

Amino Acid Sequence↗
PubMed1990

Isolation and characterization of TGF-beta 2 and TGF-beta 5 from medium conditioned by Xenopus XTC cells.

TGF-beta 2 and -beta 5 have been purified from medium conditioned by Xenopus cultured cells (XTC) and identified based on their N-terminal amino acid sequence analysis and biological activity. When applied in high concentrations, Xenopus TGF-beta 2, like porcine TGF-beta 2, induces expression of mesodermal markers from cultured Xenopus ectodermal explants, whereas TGF-beta 5 is inactive in this assay. However, the TGF-beta 's could be separated from the major mesoderm-inducing activity present in XTC medium. Xenopus TGF-beta 2 and -beta 5 are approximately equivalent to TGF-beta 1 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-beta 5 and suggest that more complex multicellular systems, in contrast to most isolated cells, discriminate between the different TGF-beta s.

Amino Acid Sequence↗
PubMed1990

Aberrant TGF-beta production and regulation in metastatic malignancy.

We have examined the possible role of transforming growth factor-beta (TGF-beta) in metastatic malignancy by analyzing the production and activation of TGF-beta 1 and -beta 2 and the regulation of TGF-beta-responsive genes in oncogene-transformed metastatic fibrosarcomas. All transformed lines derived from either 10T1/2 or NIH 3T3 by either H-ras or protein-kinase encoding oncogenes produced more TGF-beta than parental cells. However, only highly metastatic fibrosarcomas secreted activated TGF-beta at rates that were greater than parental fibroblasts. Immunohistochemical staining for TGF-beta 1 showed widespread intra- and extracellular distribution in metastatic lung nodules and adjacent tissue. Cells isolated from tumors successfully metastasizing to the lung had TGF-beta 1 mRNA levels which were increased 19-fold over in vitro controls. Despite the greatly enhanced rate of secretion of activated TGF-beta, metastatic cells exhibited markedly altered responses of TGF-beta 1 and TGF-beta 2, being unable to either increase collagen secretion or enhance collagen alpha 2(1) or TGF-beta 1 mRNA levels. This lack of response was not due to either altered TGF-beta receptor affinity or numbers. Metastatic progression was, therefore, associated with an increase in the secretion of activated TGF-beta 1 and a loss of the ability to deregulate TGF-beta-responsive genes.

Animals↗
PubMed1989

Immunodetection and quantitation of the two forms of transforming growth factor-beta (TGF-beta 1 and TGF-beta 2) secreted by cells in culture.

Transforming growth factor beta (TGF-beta), a potent modulator of cell growth, differentiation, and the expression of extracellular matrix components in a variety of cell types, exists as two distinct homodimers (TGF-beta 1 and TGF-beta 2), sharing 71% sequence homology. Radioreceptor and previously described radioimmunological assays using rabbit antibodies have not been able to distinguish between these two forms. We have developed antisera in turkeys against native TGF-beta 1 and TGF-beta 2, each of which specifically blocks both the receptor binding and biological activity of each of these peptides. With these immunological reagents we describe sensitive and specific immunological assays for TGF-beta 1 and TGF-beta 2 in complex biological fluids. Using these assays we show that both TGF-beta 1 and TGF-beta 2 are secreted by a variety of cultured cells, but that some cells secrete predominantly either TGF-beta 1 or TGF-beta 2 while others secrete both peptides in nearly equal amounts. Our results demonstrate that the expression of each of the two forms of TGF-beta is independently regulated.

Animals↗
PubMed1989

Retinoic acid induces transforming growth factor-beta 2 in cultured keratinocytes and mouse epidermis.

We have studied the functional interaction between retinoic acid and transforming growth factor-beta (TGF-beta), using the mouse epidermis as a model system. Treatment with retinoic acid increases expression of TGF-beta 2 in cultured keratinocytes in vitro, as well as in the epidermis in vivo. This TGF-beta 2 is secreted in a biologically active form that can bind to surface receptors, in contrast to most other conditions in which TGF-beta is secreted in a latent form. Specific antibodies to TGF-beta 2 partially reverse the ability of retinoic acid to inhibit DNA synthesis in cultured keratinocytes. The regulation of TGF-beta 2 expression by retinoic acid may have important physiological and pharmacological roles in the maintenance of epidermal homeostasis.

Animals↗
PubMed1989

Correlation of fibrosis and transforming growth factor-beta type 2 levels in the eye.

Approximately 1 out of every 10 eyes undergoing surgery for retinal detachment develops excessive intraocular fibrosis that can lead to traction retinal detachment and ultimate blindness. This disease process has been termed proliferative vitreoretinopathy (PVR). The ability to monitor and grade this fibrotic response accurately within the eye as well as the ability to aspirate vitreous cavity fluid bathing the fibrotic tissue makes this an ideal setting in which to investigate the development of fibrosis. Although laboratory studies have recently shown that transforming growth factor-beta (TGF-beta) can enhance fibrosis, little clinical evidence is yet available correlating the level of this or other growth factors with the degree of fibrosis in a clinical setting. We have found that vitreous aspirates from eyes with intraocular fibrosis associated with PVR have more than three times the amount of TGF-beta (1,200 +/- 300 pM [SEM]) found in eyes with uncomplicated retinal detachments without intraocular fibrosis (360 +/- 91 pM [SEM]). Using an in vitro assay, 84-100% of the TGF-beta activity could be blocked with specific antibodies against TGF-beta 2, whereas only 10-21% could be blocked by specific antibodies against TGF-beta 1. TGF-beta 1 was used in an animal model of traction retinal detachment. Since beta 1 and beta 2 have essentially identical biologic effects and only human beta 1 was available in quantities required, beta 1 was chosen for these in vivo studies. The injection of TGF-beta1 plus fibronectin (FN) but not TGF-beta1 alone into the vitreous cavity of rabbits resulted in the increased formation of intraocular fibrosis and traction retinal detachments as compared to control eyes. In previous studies, intravitreal FN levels were also found to be elevated in eyes with intraocular fibrosis.

Adolescent↗
PubMed1989

Sandwich enzyme-linked immunosorbent assays (SELISAs) quantitate and distinguish two forms of transforming growth factor-beta (TGF-beta 1 and TGF-beta 2) in complex biological fluids.

We have developed sandwich enzyme-linked immunosorbent assays (SELISAs) for TGF-beta 1 and TGF-beta 2 using both turkey and rabbit neutralizing polyclonal antibodies against native TGF-beta s. Each assay is based on the binding of two different antibodies to distinct epitopes of a single TGF-beta molecule. With these assays, TGF-beta types 1 and 2 can each be specifically quantitated in complex biological fluids, with detection limits of 2-5 pg. TGF-beta 3 and TGF-beta 5 either do not cross-react or cross-react very poorly in these assays. TGF-beta 1.2 heterodimer, although 50-80% neutralized by either TGF-beta 1 or TGF-beta 2 antibodies, shows only a 1.5 and 3.7% cross-reactivity in the TGF-beta 1 and TGF-beta 2 SELISAs, respectively. The SELISAs reported here represent the most specific, rapid, and precise assays for TGF-beta 1 and TGF-beta 2 reported thus far.

Animals↗
PubMed1989

Transforming growth factor-beta and suppression of carcinogenesis.

Transforming growth factor-beta (TGF-beta) plays an important role in controlling proliferation or differentiation in almost all epithelial tissues. The pathophysiology of TGF-beta during carcinogenesis is now an important area of investigation, since it appears that as the process of carcinogenesis progresses, epithelial cells often become refractory to the growth-regulatory actions of TGF-beta. In this article we consider the possible cellular and molecular bases for this phenomenon, and then discuss some pharmacological approaches to enhancing the synthesis or activity of TGF-beta. These approaches may provide new modalities for prevention of carcinogenesis, if they can be applied during the early stages of the disease process, before cells become refractory. We give particular attention to tamoxifen and retinoic acid, since it has been shown that these agents, which are of known efficacy for prevention of cancer, can markedly enhance the secretion of specific isotypes of TGF-beta by several types of cells.

Amino Acid Sequence↗
PubMed1988

Mesoderm induction in amphibians: the role of TGF-beta 2-like factors.

Mesoderm induction in the amphibian embryo can be studied by exposing animal region explants (destined to become ectoderm) to appropriate stimuli and assaying the appearance of mesodermal products like alpha-actin messenger RNA. Transforming growth factor beta 2 (TGF-beta 2), but not TGF-beta 1, was active in alpha-actin induction, while addition of fibroblast growth factor had a small synergistic effect. Medium conditioned by Xenopus XTC cells (XTC-CM), known to have powerful mesoderm-inducing activity, was shown to contain TGF-beta-like activity as measured by a radioreceptor binding assay, colony formation in NRK cells, and growth inhibition in CCL64 cells. The activity of XTC-CM in mesoderm induction and in growth inhibition of CCL64 cells was inhibited partially by antibodies to TGF-beta 2 but not by antibodies to TGF-beta 1. Thus, a TGF-beta 2-like molecule may be involved in mesoderm induction.

Actins↗
PubMed1988

Growth of MTW9/PL2 estrogen-responsive rat mammary tumor cells in hormonally defined serum-free media.

Growth of the estrogen-responsive MTW9/PL2 rat mammary tumor cells was demonstrated in serum-free defined medium (designated DDM-1) formulated with F12-DME (1:1 vol/vol) supplemented with 15 mM HEPES pH 7.4, insulin 10 micrograms/ml, transferrin 10 micrograms/ml, sodium selenite 10 ng/ml, triiodo-L-thyronine 0.3 nM, phosphoethanolamine 5 microM, epidermal growth factor (20 ng/ml), 17 beta-estradiol 2 nM, and bovine serum albumin 20 micrograms/ml. In DDM-1, the growth rate was about one-half that seen in serum-containing medium. When ethanolamine (50 microM), glutathione (20 micrograms/ml), and linoleic acid/bovine serum albumin (150 micrograms/ml) were added (formulation DDM-2), the growth rate was 80% of serum-containing medium and not seed-density dependent. Deletion of estradiol from DDM-1 or DDM-2 had no effect on growth rate. Also, cells grown in steroid hormone deficient medium for 4 mo. continued to form estrogen-responsive tumors in rats as did cells cultured for the same period in 2 nM estradiol. To investigate autocrine growth factor secretion, a third medium (DDM-3) was prepared by deleting insulin, epidermal growth factor, phosphoethanolamine, estradiol, and both forms of bovine serum albumin from DDM-2. Growth in mitogen-free medium equaled 86% of the serum-stimulated rate and was seed-density dependent; phenol red deletion from DDM-3 had no effect on growth rate. Evidence presented suggests that autocrine factors stimulate growth of the MTW9/PL2 cells in DDM-3, and that this secretion may support the growth of estrogen-responsive cells in culture in the absence of steroid hormone.

Animals↗
PubMed1984

Characterization of a sheep pituitary-derived growth factor for rat and human mammary tumor cells.

A growth factor for rat and human mammary tumor cells (MTGF-Pit) was isolated from lyophilized powders of whole sheep pituitaries by a rapid four-step procedure utilizing acetic acid extraction, heating at 93 degrees C, and sequential chromatography in 0.10 M acetic acid on sulphopropyl Sephadex and Sephadex G-50. From 10 g of pituitary powder, 8-10-mg amounts of MTGF-Pit were isolated. By 8 M urea, 0.1% SDS-12.5% polyacrylamide gel electrophoresis analysis followed by Coomassie blue staining, this preparation was shown to be one major stained band. When assayed for growth effects on cells maintained in serum-free medium, 5.1-19.2 nM MTGF-Pit half replaced the growth of MTW9/PL rat and MCF-7 and T-47D human mammary tumor cells in response to 2% to 10% serum. MTGF-Pit shows mitogenic activity toward normal human diploid fibroblasts only at concentrations in excess of 2.5 X 10(-4) M, while rat fibroblasts are unresponsive even at this high concentration. From data available, we conclude that a mitogenic activity for epithelial-type mammary cells has been isolated, and this growth factor appears to be a previously undetected acid- and heat-stable activity that is highly abundant (estimated at 0.16% or more of the total dry weight of the pituitary powder). The isolated ovine MTGF-Pit (3,900 +/- 200 daltons) does not share the molecular weight of native prolactin (24,000 daltons), "cleaved" prolactin (16,000 daltons), or growth hormone (22,000 daltons), and by all tests applied cannot be replaced with other known hormones and purified growth factors. We conclude a potent new mammary tumor cell mitogenic activity has been identified from sheep pituitaries.

Animals↗
PubMed1984

New perspectives in hormone-dependent (responsive) and autonomous mammary tumor growth: role of autostimulatory growth factors.

In this report, we present evidence that estrogen-dependent rat mammary tumor cells produce autostimulatory (autocrine) growth factors in response to estrogens, and that hormone autonomous cells produce autocrine activities that are no longer under estrogen regulation. Confirmation of the in vivo significance of autostimulatory factors was sought by inoculating rats with mixed populations of estrogen-dependent, responsive, and autonomous MTW9/PL mammary tumor cells, and showing that after 16 weeks growth in castrated male rats, the estrogen-dependent and responsive mammary tumor cells not only survived, but continued to grow. Three out of seven of the clones derived from apparently autonomous tumors were shown to be estrogen-dependent or responsive. These are the first data establishing that estrogen-dependent (responsive) mammary tumor cells are able to grow in the absence of physiological concentrations of sex steroid hormones in vivo, and that autocrine factors secreted from adjacent autonomous cells are able to substitute for the steroid hormone requirement.

Animals↗
PubMed1984

Identification of an autostimulatory growth factor in the extracts and conditioned medium of GH3/C14 rat pituitary cells in culture.

An acid- and heat-stable low molecular weight (Mr 2,500-6,200) autostimulatory growth factor has been identified in extracts of GH3/C14 rat pituitary tumors, in extracts of these cells in culture and in their serum-free conditioned medium. The concentrations of autostimulatory activity required to achieve ED50 in serum-free culture were 4.3, 4.0 and 85 micrograms/ml for extracts of tumors, the cultured cells, and from the conditioned medium of the cells in culture, respectively. To characterize this activity, we have used an isolation method that included 0.1 M acetic acid extraction, heating at 95 C, SP-Sephadex chromatography, and finally, Sephadex G-50 chromatography. The identification of this activity if rapidly growing, relatively autonomous GH3/C14 tumors suggests an autostimulatory role in the conversion from estrogen-responsive growth to autonomy.

Animals↗
PubMed1982

Identification of estrogen-inducible growth factors (estromedins) for rat and human mammary tumor cells in culture.

The role of polypeptide growth factors (estromedins) as mediators of estrogen-responsive mammary tumor growth is studied in this report. Three possible new mechanisms were investigated that include endocrine, autocrine, and paracrine related growth factors. The first hypothesis being tested is whether estrogens interact with target tissues and cause the biosynthesis and secretion of polypeptide growth factors, which then act as mitogens for normal and neoplastic mammary tissues. Data presented suggest that this mechanism involves estrogen interaction with uterus, kidney, and pituitary gland causing production of growth factors, which then enter the general circulation and promote growth of distant target tissues. This is an endocrine type mechanism. Another type of estromedin control (autocrine control) may be exerted in an autostimulatory way in which the target tissue produces the polypeptide factors for its own growth in response to estrogen stimulation. A variation of the autocrine mechanism may be a paracrine mechanism in which some cells of an estrogen-responsive normal or neoplastic tissue produce growth factors that act on adjacent or neighboring cells. From the data available, all three possible types of growth factors could be functioning synergistically to yield the final result of continuous estrogen responsive tumor growth in vivo.

Animals↗
PubMedDate not supplied

Wound healing in the fetus. Possible role for inflammatory macrophages and transforming growth factor-beta isoforms.

Macrophages are believed to play a crucial role in wound healing by synthesizing and secreting numerous cytokines. Some of these cytokines, such as transforming growth factor-beta and tumor necrosis factor-alpha, promote fibrosis and repair. We have shown that macrophages are recruited to sterile fetal wounds and have the potential to regulate repair by synthesizing transforming growth factor-beta(1), transforming growth factor-beta(2), and tumor necrosis factor-alpha. Transforming growth factor-beta was present in fetal lamb wounds in higher amounts than in adult sheep wounds. Furthermore, the concentrations and ratios of the transforming growth factor-beta isoforms in wounds that healed without scarring were different from those in wounds that scarred; transforming growth factor-beta(2) was highest in fetal wounds that did not scar and lowest in adult wounds. These data suggest that concentrations of transforming growth factor-beta isoforms rather than total transforming growth factor-beta concentration may be important in the regulation of fibrosis in prenatal and postnatal wound healing.

Journal Article↗