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J E DeLarco

Publications and source records attributed to J E DeLarco.

6 recordsLinked to original sources
PubMed1991

Specific binding of vascular permeability factor to endothelial cells.

Vascular permeability factor (VPF), also known as vascular endothelial cell growth factor, has recently been purified from guinea pig, human, and bovine sources. We show that various fetal or adult endothelial cell strains originating from either capillary or large vessels possess specific high affinity and saturable binding sites for guinea pig tumor-derived [125I]VPF. Two classes of sites with KDs of approximately 10 pM and 1 nM were detected for all endothelial cell types examined. Guinea pig [125I]VPF binding to endothelial cells was inhibited by human VPF (ID50 = 0.8 ng/ml) and by suramin (ID50 = 75 micrograms/ml) but not by heparin. Cross-linking experiments revealed specific [125I]VPF-receptor complexes of two types. Most of the complexes migrated very slowing in SDS-PAGE, indicating that they were of very high molecular weight and probably highly cross-linked. A portion of the molecules migrated as 270 kDa complexes, indicating that the molecular weight of the endothelial cell VPF receptor is about 230 kDa.

Animals↗
PubMed1988

An improved method of purification of transforming growth factor, type beta from platelets.

Platelets contain high concentrations of TGF-beta and for this reason have been the primary source of materials for its purification. The yield from acid-ethanol extracts of platelets has been reported to be 0.5 microgram/unit of platelets. We have developed a method which yields approximately 2 micrograms/unit of platelets from acid-ethanol extracts. The use of an ion-exchange column followed by RPLC results in a homogeneous product in less time and with fewer manipulations than the previously published methods. A tritiated thymidine incorporation assay using the CC164 cell line is described for the quantitation of TGF-beta.

Blood Platelets↗
PubMed1983

Antibodies to the epidermal growth factor receptor block the biological activities of sarcoma growth factor.

The role of the epidermal growth factor (EGF) receptor system in mediating the biological activities of sarcoma growth factor (SGF) has been assessed by using specific anti-EGF receptor antibodies. There are two classes of anti-EGF receptor antibodies, those that block binding of 125I-labeled EGF (125I-EGF) and those that do not block binding but do interact with a portion of the EGF receptor on the surface of intact cells. Antisera of both types have been assayed for their capacity to affect the biological activities of SGF. The antisera that block 125I-EGF binding to its receptor block the induction of DNA synthesis in human fibroblasts by either EGF or SGF but not by other polypeptide mitogens. Titration of the anti-EGF receptor antiserum indicates the presence of one population of antibody that blocks the site of both EGF and SGF action. Antisera to the EGF receptor that block 125I-EGF binding also inhibited the SGF-dependent anchorage-independent growth of normal cells in soft agar. The antisera to the EGF receptor that does not block 125I-EGF binding or EGF activity did not inhibit any of the biological activities of SGF. The results suggest that occupation of the EGF receptor is required for both the mitogenic and colony-forming activity of SGF.

Animals↗
PubMed1982

Affinity labeling of a transforming growth factor receptor that does not interact with epidermal growth factor.

Membrane components that interact with epidermal growth factor (EGF) and transforming growth factors (TGFs) have been identified by covalent crosslinking to their respective 125I-labeled ligands. Under appropriate conditions, disuccinimidyl suberate or hydroxysuccinimidyl p-azidobenzoate cross-link receptor-bound 125I-labeled EGF to a 140- to 170-kilodalton (kDal) receptor species in membranes from both A431 human carcinoma cells and normal rat kidney cells. 125I-Labeled sarcoma growth factor (SGF), a TGF from virally transformed mouse 3T3 cells, also can be affinity-crosslinked to the 140- to 170-kDal EGF receptor species in membranes from A431 and rat kidney cells. The labeling of this receptor is inhibited when either excess unlabeled EGF or SGF is present during incubation of membranes with either 125I-labeled EGF or 125I-labeled SGF. In contrast, a second receptor species of 60 kDal is affinity-labeled with 125I-labeled SGF but not with 125I-labeled EGF in membranes from both A431 and rat kidney cells. SGF and a TGF from virally transformed rat embryo cells inhibit the labeling of the 60-kDal species when present in excess during incubation of membranes with 125I-labeled SGF, whereas EGF is completely ineffective in inhibiting the labeling of this receptor. The data suggest that a specific 60-kDal receptor that displays high affinity for TGFs but not for EGF may mediate induction of the transformed phenotype. In addition, SGF and other TGFs interact with the 140- to 170-kDal EGF receptor that appears to mediate normal cell growth effects.

Affinity Labels↗
PubMed1980

In vitro production of immunosuppressive factors by murine sarcoma virus-transformed mouse fibroblasts.

Murine sarcoma virus-transformed mouse fibroblasts produce potent immunosuppressive factors (ISF) in vitro. The partially purified ISF inhibited thymocyte proliferation induced by concanavalin A or phytohemagglutinin plus lymphocyte activating factor (Interleukin 1), lipopolysaccharide-induced spleen cell proliferation, the in vitro splenic anti-sheep erythrocyte plaque-forming cell response, and the generation of alloantigen-specific cytotoxic T cells. The effect of ISF on thymocyte proliferation was not readily reversible and required only a 4-hr exposure of the thymocytes to ISF to inhibit cell proliferation. Although ISF shares several biochemical properties with a murine sarcoma virus-transformed cell-derived sarcoma growth factor (e.g., acetic acid solubility and sensitivity to dithiothreitol), the two factors could be resolved by gel filtration on Bio-Gel P-60. Two peaks of ISF activity were found with apparent molecular weights of 12,000 and 8000. The results described here support the hypothesis that at least some of the ISF obtained from the serum of tumor-bearing hosts may be released by the tumor cells themselves. In view of the potent in vitro activity of the murine sarcoma virus-transformed fibroblast-derived ISF, it is quite possible that ISF-like molecules may play a role in subverting in vivo tumor rejection processes involving the immune system.

Animals↗