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E Pearlstein

Publications and source records attributed to E Pearlstein.

At least 55 records · Page 3Linked to original sources
PubMed1980

Correlation between spontaneous metastatic potential, platelet-aggregating activity of cell surface extracts, and cell surface sialylation in 10 metastatic-variant derivatives of a rat renal sarcoma cell line.

Several properties of 10 cell lines derived from the polyoma-induced PW20 Wistar-Furth rat renal sarcoma have been examined, including the ability of the tumor cells to metastasize spontaneously from subcutaneous sites in syngeneic hosts, the platelet-aggregating activity of material extracted by urea from the surface of cultured cells, the sialic acid content of the platelet-aggregating material, and the degree of sialylation of cell surface glycoconjugates in cultured cells. A correlation has been observed among all of these parameters. The results suggest a possible link between the degree of cell surface sialylation of tumor cells, their ability to aggregate platelets, and their ability to metastasize.

Acetylgalactosamine↗
PubMed1980

Plasma requirement for the aggregation of rabbit platelets by an aggregating material derived from SV40-transformed 3T3 fibroblasts.

Certain tumors require platelets for metastases, and many of these aggregate platelets in vitro. We have studied their in vitro interaction by extracting a PAM from SV40-transformed 3T3 fibroblasts. The preparation is enriched with membrane vesicles and requires an intact sedimentable sialolipoprotein for activity. PAM aggregates platelets after a lag period (J Lab Clin Med 93:332, 1979) and requires plasma as a cofactor(s). Two plasma components have been identified with the use of PRP or GFP. The first component shortens the platelet aggregation lag period after preincubation of PAM with plasma at 37 degrees C for 10 min prior to its addition to PRP or GFP and is labile to heating at 56 degrees C for 30 min. However, the activated PAM (formed by incubation with plasma at 37 degrees C) is stable at 56 degrees C for 30 min. This labile factor appears to be a component(s) of the complement alternative pathway, since it is inactivated by treatment of plasma with cobra venom or zymosan; and guinea pig PRP deficient in C' 4 can be aggregated by PAM. The second component is a plasma factor that is stable to heating at 56 degrees C. Activated PAM can be sedimented at 100,000 x g. The sediment, when suspended in Veronal buffer, pH 7.4, does not aggregate GFP, however, addition of plasma heated at 56 degrees C restores the platelet aggregation response. Thus a material extracted from SV40 3T3 fibroblasts aggregates platelets in vitro in the presence of two factors: (1) a component(s) of the alternative complement pathway that activates PAM and shortens the platelet aggregation lag period and (2) a heat-stable factor that is required for activated PAM to aggregate platelets.

Animals↗
PubMed1979

Stability of fibronectin biological activity following chemical modification.

Fibronectin isolated from human plasma functions in vitro as a mediator of adhesion and spreading of trypsinized fibroblasts on native or denatured collagen. As a means of elucidating structural characteristics which might contribute to fibronectin's biological activity, we have modified and digested the protein with several chemicals. Following various treatments, the protein was utilized to mediate cell adhesion and spreading on collagen to determine which alteration disrupted its activity. Fibronectin remained functionally intact after partial or complete reduction and alkylation, oxidation of 59% of the carbohydrates with sodium periodate, citraconylation, carbodiimide-catalyzed amide formation, and oxidation of 35.2 residues of tryptophan/molecule with N-bromosuccinimide. Dinitrofluorobenzene treatment, which phenylated ten residues/molecule of fibronectin, successfully inactivated fibronectin's in vitro biological function. Effective modification of the protein was determined by appropriate analytical procedures. Since fibronectin retained its biological function after several treatments that presumably affected its molecular conformation, we concluded that its secondary or tertiary structure appears not to be essential for its in vitro activity, or alternatively that the protein possesses a biologically active domain relatively resistant to chemical modification.

Bromosuccinimide↗
PubMed1979

Subtilisin and cyanogen bromide cleavage products of fibronectin that retain gelatin-binding activity.

The gelatin-binding region of fibronectin has been obtained by subtilisin digestion and cyanogen bromide cleavage of the molecule. Enzymatic digestion yielded two fragments of molecular weights 50,000 (S50K) and 30,000 (S30K) which were isolated by elution from gelatin-Sepharose affinity columns. Because the S50K fragment also mediated the adhesion of fibroblasts to collagen, it contains both the collagen and cell binding sites on the fibronectin molecule. Both fragments had valine as the NH2-terminal residue, were enriched in half-cystine and methionine residues compared to the whole molecule, and were identical by immunodiffusion. The S50K fragment begins with the sequence Val-Tyr-Gln-Pro-Gln-Pro-His-Pro-Gln-Pro-(Pro)-(Gly)-Tyr-Gly-His-( )-Val, a region with an extended conformation which is susceptible to proteolysis and connects this domain to the remainder of the fibronectin molecule. The S50K fragment appears to be located in the COOH-terminal one-third of the fibronectin molecule but does not contain the interchain disulfide bridge(s); the S30K fragment is probably derived from the NH2-terminal region of S50K.

Amino Acids↗
PubMed1978

Substrate activation of cell adhesion factor as a prerequisite for cell attachment.

Cell Adhesion Factor, complexed to insoluble collagen-coated tissue culture dishes, is required for the attachment of fibroblasts to this substrate. In solution, the factor has no demonstrable affinity for cells in suspension following trypsin-EDTA removal of cells from monolayer. Cell surface receptors for the factor are present during the assay period since cells allowed to recover for 1 h at 37 degrees C, 4 degrees C or in the presence of 10(-6) M cycloheximide show exactly the same kinetics of adhesion as control cells. It is demonstrated that Cell Adhesion Factor acquires affinity for the cell surface only following its binding to collagen.

Animals↗
PubMed1978

Identification of macrophage external membrane proteins and their possible role in cell adhesion.

Starch-activated mouse peritoneal macrophages (STpMAC) plated on plastic demonstrate the adhesive properties typical for activated pMAC: attaching as round cells and, within 15 min, spreading out with marginal membrane ruffles. These attached STpMAC were labeled by lactoperoxidase-catalysed 125I surface iodination, sodium dodecyl-sulfate-lysed, and the lysates electrophoresed on polyacrylamide gels which were examined by autoradiography. The STpMAC morphological phenotype correlates with the labeling of a particular protein (195,000, estimated mol wt). Normal pMAC (NpMAC), from unstimulated mice, do not spread and do not display the 195,000 band. Both pMAC band patterns, including the 195,000 band, are relatively resistant to trypsin digestion, as is pMAC adhesion itself trypsin-resistant. Neither class of pMAC exhibits fibronectin (Cell Adhesion Factor, LETS protein) which is a component in the adhesive matrix of cells forming trypsin-sensitive monolayers. When pMAC are tested against antifibronectin antibody, these cells do not give immunofluorescent staining. In summary, two functions in pMAC adhesion, enzyme resistance and the ability to spread, appear related to molecular properties distinctive for pMAC surface protein.

Cell Adhesion↗
PubMed1977

Expression of protein HC on the plasma membrane of different human cell types.

The surface expression of a recently described plasma glycoprotein called human complex-forming glycoprotein, hetergeneous in charge (protein HC) on a number of different human cell types was investigated. By means of direct and indirect immunofluorescence, protein HC was shown to be associated with the surface of virtually all cells of the investigated normal cell types including erythrocytes, peripheral blood B and T lymphocytes, and the human fibroblast lines HE 81, HE 31, and WI 38. When transformed and malignant cell populations were studied, it was found that some populations (e.g., the T cell line Molt-4) carried protein HC on the surfaces of very few cells, whereas other cell populations (e.g., chronic lymphocytic leukemia lymphocytes) carried the protein on most cells. Malignant cell populations with intermediary percentages of protein HC-positive cells were also found. Protein HC on the cell surface of normal peripheral blood lymphocytes could be redistributed by incubation of the cells with anti-protein HC-antiserum at 37 degrees C, and this reaction could be inhibited by sodium azide.

Animals↗
PubMed1976

Non-lytic, non-ionic detergent extraction of plasma membrane constituents from normal and transformed fibroblasts.

A technique has been developed for the selective extraction of plasma membrane protein constituents from normal and transformed cell employing non-ionic detergents. The extraction procedure does not damage cells as judged by cell viability, 51Cr release, and trypan blue staining. Lactoperoxidase-catalyzed iodination followed by detergent extraction permits demonstration of a 100,000 dalton protein which is found on the surface of normal but not transformed hamster and mouse fibroblasts.

Cell Fractionation↗
PubMed1976

Surface proteins and fibrinolytic activity of cultured mammalian cells.

Surface proteins and fibrinolysis were investigated in a variety of cell types. A large external transformation-sensitive protein was demonstrated by lactoperoxidase-catalyzed iodination. Electron microscope autoradiography confirmed that the technique labeled surface material only. The protein was present in explants of normal tissues was well as in nontumor-producing cultured cell lines. It was not lost during long-term culture. Neoplastic transformation in vitro, whether spontaneous or induced by a chemical carcinogen or virus, led to the loss of the material in most but not all cases. The protein was also absent from many but not all spontaneous and induced tumors of the different types tested. Elevated fibrinolytic activity was demonstrated in a number of normal tissues and non-tumor-producing cell lines. It was also present in most sarcomas but absent from most carcinomas that we have examined, except for a cell line from a well-differentiated bladder tumor. The correlation between absence of large external transformation-sensitive protein and fibrinolysis was examined, and it was found that activation of plasminogen was not sufficient to cause the absence of this surface protein.

9,10-Dimethyl-1,2-benzanthracene↗