Michael Stoker

The fine structure of polyoma virus.

Abstract Preparations of polyoma virus were examined by electron microscopy, using the negative contrast method. Spherical particles identified as viruses were found to have a mean diameter of 453 A. All the particles showed a shell (capsid) of elongated hollow subunits (capsomeres). In the majority, these surrounded a central core; but some particles appeared to be empty. Though there is no evidence of icosahedral shape, the capsomere arrangement showed 5:3:2 axial symmetry. It has been deduced that the particle contains 42 capsomeres, each aligned radially along an axis of symmetry.

Changes in nucleic acid content of HeLa cells infected with herpes virus

Abstract The nucleic acid content of HeLa cells was determined at various times after exposure to a high multiplicity of herpes virus. The DNA content rose 6 to 9 hours after infection, before any increase in infective virus, which was just detectable at 12 hours. By 72 hours the cells contained nearly double their normal content of DNA. This increase in DNA was confined to the nucleus. No significant change in RNA content was observed.

The Effect of Herpes Virus on HeLa Cells dividing Parasynchronously.

Abstract HeLa cells dividing parasynchronously have been used to study the effect of the HFEM strain of herpes virus upon mitosis. Mitosis of the HeLa cells is inhibited, and this inhibition is prevented by serum containing virus neutralizing antibody. The damage to mitosis occurs rapidly relative to the cycle of virus growth, probably less than 1 hour after virus adsorption. Virus particles which adsorb to, but do not infect, the HeLa cells fail to inhibit mitosis. Similar rates of virus growth were found in both synchronously and asynchronously dividing cells when the former were infected 7 hours before expected division.

Cultures of exfoliated mammary epithelial cells: variation between donors

SummaryHuman milk contains clonogenic epithelial cells which give rise to three distinct colony types, namely, joined elongated, joined cuboidal, and open (i.e. unjoined). Previous studies have shown that these may be interrelated and may reflect stages in cell differentiation in the human mammary gland. This paper reports an analysis of paired milk samples from a series of donors, and shows that the predominant clonogenic cell type varies from donor to donor. This could reflect individual variation in the cell population of the lactating human breast.

FUNDAMENTALS OF CANCER CELL BIOLOGY

Publisher Summary This chapter focuses on the fundamentals of cancer cell biology. Cell biology can be described as the study of individual cells—in contrast to tissues—individual molecules, and individual genes. Much of cell biology has been cancer cell biology, because in the early days, cancer cells were easier to study than normal cells. One of the most important advances in an understanding of cancer has been the realization that cancer does not arise as an abnormality of an individual or even a tissue. Nearly all cancers originate from one single abnormal cell—that is, they are clonal. The authors slow path toward cell biology was influenced both by local events in Cambridge and distant developments overseas. The chapter also discusses about foundations of cell culture. One of the most active and exciting fields of research in cell biology has been concerned with the adhesion of cells to one another and to the extracellular substrate. This is now known to be because of the families of cell adhesion molecules (CAMs) and substrate adhesion molecules (SAMs) that bind specifically, either homotypically to one another or hetereotypically to a receptor molecule. A great deal of cancer research is at present centered on the protooncogenes and tumor suppressor genes, and the way in which their perturbation as oncogenes, for example, gives rise to cancer itself.

Juxtapositional regions of human breast epithelium and fibroblasts in vitro

Abstract Previous studies of junctional intercellular communication, using the [ 3 H]uridine nucleotide transfer method, have shown that although both human mammary epithelial cells and human mammary fibroblasts are capable of communication with a variety of other cell types, these cells do not communicate directly with one another in heterologous combination. In order to investigate this phenomenon of selective communication, the juxtapositional regions between cultured human breast epithelial cells and human breast fibroblasts have been examined by transmission electron microscopy (TEM). There was no detectable difference in relative lengths of close apposition (less than 20 nm), between homologous or heterologous cell pairs respectively. Calf lens epithelial cells, which behave as non-selective communicators, transferring [ 3 H]uridine to and from all cells capable of communication, have much tighter apposition between homologous cell pairs, with formation of membrane spirals containing gap junctions. However, in heterologous communicating combinations, the calf lens cells did not produce spirals, nor was the membrane apposition any closer than that between breast epithelia or breast fibroblasts in homologous or heterologous combination. These results suggest that selectivity in junctional communication does not result from variations in the ability of cells to approach one another, due for example to the presence of ground substance which prevents the formation of junctions. The inability of human breast fibroblasts and epithelia to communicate directly with one another is therefore more likely to be due to intrinsic cell membrane incompatibility of the two cell types so that intercellular gap junctions do not form, or alternatively have a low probability of formation.