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C R Birdwell

Publications and source records attributed to C R Birdwell.

25 records · Page 2Linked to original sources
PubMed1976

Cellular interactions in the metastatic process.

Tumor metastasis is a multistep process which is dependent on both host and tumor properties. It is proposed that the interaction of normal host blood and endothelial cells with circulating malignant cells result in tumor cell arrest leading to subsequent metastases at specific secondary sites. In experimental animal models the frequency and location of metastatic foci can be manipulated by repeated in vivo selection for tumor cell variants showing altered preference for organ-specific implantation and survival. These tumor cell variants can be used to determine the cell surface structures and enzymes involved in the various steps of the metastatic process.

Animals↗
PubMed1974

Replication of Sindbis virus. IV. Electron microscope study of the insertion of viral glycoproteins into the surface of infected chick cells.

The appearance of Sindbis virus-envelope glycoproteins in the surfaces of chicken embryo fibroblasts was studied by an indirect labeling technique. This technique involved treating infected cells sequentially with rabbit immunoglobulin G (IgG) specific for Sindbis virus followed by hemocyanin-conjugated goat (anti-rabbit IgG) IgG; surface replicas of these cells were then prepared and examined in the electron microscope. As early as 2 h after infection (and at least 1 h before mature virions were released), newly synthesized virus-envelope glycoproteins were detected at the cell surface. By 3 h after infection, cell surface membranes were extensively modified by the insertion of the Sindbis glycoproteins. When infected cells were prefixed with glutaraldehyde before labeling, the glycoproteins were distributed fairly evenly over the cell surface, although a slight clustering was observed on cells labeled early in infection. However, no evidence for large-scale clustering of virus glycoproteins corresponding to patches of budding virus was observed. Similar results were found with unfixed cells labeled at 4 C. However, when unfixed cells were labeled at 37 C, the glycoproteins were shown to be in discrete clusters, demonstrating that these glycoprotein antigens can diffuse laterally through the cell membrane at this temperature.

Animals↗
PubMed1974

Distribution of the receptor sites for Sindbis virus on the surface of chicken and BHK cells.

Sindbis virus was adsorbed to chicken cells or to BHK cells, and the distribution of virus over the surface of the cell was examined by electron microscopy of surface replicas. The distribution of virus particles on the cell was used to indicate the position of virus receptors at the cell surface. When purified Sindbis virus was adsorbed at 37 C to cells prefixed with glutaraldehyde, the virus particles were evenly distributed over the surface of most cells. There was a large variability from cell to cell, however, in the number of virus particles adsorbed, and regions with different concentrations of virus particles were sometimes observed on the same cell. The concentration of virus receptors observed varied from 20 to 160/mum(2) of cell surface, and, thus, the total number of virus receptors per chicken cell is on the order of 10(5). When virus was adsorbed to unfixed cells at 4 C, the virus particles were clustered into aggregates varying from a few particles to large crystalline arrays (the latter seen only in chicken cells). These conditions are apparently conducive to virus aggregation, and this, coupled with free lateral diffusion of the virus-receptor complex in the cell membrane at 4 C, leads to the observed clustering.

Adsorption↗
PubMed1973

Agglutination of Sindbis virus and of cells infected with Sindbis virus by plant lectins.

We have examined the agglutination of Sindbis virus and of chick and hamster cells infected with Sindbis virus by two of the plant lectins, concanavalin A and Ricinus communis agglutinin. Both lectins agglutinate the virus by binding to the polysaccharide chains of the envelope glycoproteins. Both chick and hamster cells exhibit increased agglutination by the lectins after infection by Sindbis virus. In the case of chick cells infected with Sindbis virus, this increase in agglutinability occurs between 3 and 5 h after infection. Infected and mock-infected cells bind the same amount of (3)H-labeled concanavalin A, which suggests that the increase in agglutination after infection is due to rearrangements at the cell surface rather than to insertion of new lectin binding sites per se.

Agglutination↗
PubMedDate not supplied

Biochemical changes in endothelial cell monolayers induced by fibrin deposition in vitro.

Endothelial cells in vivo come into contact with fibrin during numerous physiological and pathological processes, but the nature of this interaction is poorly understood. The interaction of fibrin and endothelial cells was examined by incubating bovine aortic endothelial cell monolayers in vitro with fibrinogen (100 micrograms/ml) in medium supplemented with 10% calf serum. This treatment produced a layer of fibrin above the endothelial cell monolayer, which induced disorganization of the monolayer and remained associated with the monolayer even after washing. Endothelial cell pinocytosis of 14C-sucrose was elevated by 25% and 60% after incubation with fibrin for 8 hours and 2 days, respectively. Fibrin deposition on endothelial cell monolayers increased the rate of DNA synthesis (3H-thymidine incorporation) for 1 to 3 days by as much as 60% over controls. Concomitant with the lysis of fibrin above endothelial cells and the reorganization of the monolayer at Days 4 or 5 was a reduction of endothelial cell pinocytosis and DNA synthesis to control values. In contrast, there was no effect on the cell density at any time after incubation with fibrin. These results indicate that fibrin interacts with endothelial cells and induces a disorganization of the monolayer that is accompanied by changes in the rate of pinocytosis and in the rate of DNA synthesis.

Animals↗