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H GREEN

Publications and source records attributed to H GREEN.

At least 37 records · Page 2Linked to original sources
PubMed1963

Quantitative studies of the growth of mouse embryo cells in culture and their development into established lines.

Disaggregated mouse embryo cells, grown in monolayers, underwent a progressive decline in growth rate upon successive transfer, the rapidity of the decline depending, among other things, on the inoculation density. Nevertheless, nearly all cultures developed into established lines within 3 months of culture. The first sign of the emergence of an established line was the ability of the cells to maintain a constant or rising potential growth rate. This occurred while the cultures were morphologically unchanged. The growth rate continued to increase until it equaled or exceeded that of the original culture. The early established cells showed an increasing metabolic autonomy, as indicated by decreasing dependence on cell-to-cell feeding. It is suggested that the process of establishment involves an alteration in cell permeability properties. Chromosome studies indicated that the cells responsible for the upturn in growth rate were diploid, but later the population shifted to the tetraploid range, often very rapidly. Still later, marker chromosomes appeared. Different lines acquired different properties, depending on the culture conditions employed; one line developed which is extremely sensitive to contact inhibition.

Animals↗
PubMed1962

Immune cytolysis: electron microscopic localization of cellular antigens with ferritin-antibody conjugates.

Immune gamma globulin has been coupled to ferritin by the diisocyanate method of Singer. The final product ("ferroglobulin") had approximately 13 per cent of its gamma globulin coupled to ferritin, and roughly half of its ferritin coupled to gamma globulin. The uncoupled gamma globulin could be removed by ultracentrifugal sedimentation of the free ferritin and the ferritin-antibody conjugates. The characteristics of the native antibody were retained by the ferritin-antibody conjugates, for they could be precipitated by anti-gamma globulin antisera, and when used as antibodies, they reacted specifically with soluble and cellular antigens. Ferroglobulin preparations made from rabbit antisera against whole ascites tumor cells were incubated with the cells, and the location of ferritin determined by electron microscopy of thin-sectioned material. It was found that the immune ferroglobulins localized specifically on antigens of the cell membrane. Some of the ferritin label entered the cells by pinocytosis, but the ferritin-antibody units did not appear able to pass directly through the cell membrane into the cytoplasmic matrix. When cells were incubated with ferritin-labeled antibody and complement, antibody could be located in the cytoplasmic matrix, and it therefore appeared that complement action was required before antibody could pass directly through the cell membrane. This finding was consistent with previous observations that the plasma membrane of an antibody-complement treated cell becomes permeable to large molecules. In broken cell preparations incubated with ferroglobulin, antibody combined with amorphous material and with structures derived from cell membranes and from smooth membranes of the endoplasmic reticulum. The data favor the concept that antigens contained within the membranous structures are most important in the formation of cytotoxic antibodies. The reported experiments support the view that cytotoxic antibodies fix primarily to surface antigens of the cell membrane. The subsequent action of complement establishes the permeability defect that induces the osmotic lysis of the cell and permits antibody to pass into the cell where it may act in a similar fashion on intracellular organelles.

Animals↗
PubMed1960

Immune cytolysis. 1. The release of ribonucleoprotein particles. 2. Membrane-bounded structures arising during cell fragmentation.

It has been shown that Krebs ascites tumor cells incubated in vitro with immune gamma globulin and complement lose the bulk of their cytoplasmic RNA to the suspending medium, although the cell membrane remains visibly intact. The present experiments show that about four-fifths of the lost RNA is sedimented by centrifugation of the cell-free medium at 105,000 g. Electron microscopic and chemical analyses of the pellets show them to consist of 150 A ribonucleoprotein particles. It is concluded that most of the RNA passes from the cells in this form. Antibody-complement action causes osmotic swelling of the tumor cells and they become quite fragile. Fragmentation of such preparations yields large numbers of membrane-bounded spheres which may be separated from the heavier nuclei by differential centrifugation. Electron microscopic study of the spheres provides evidence that they can arise from segments of the cell surface as well as from mitochondria and the endoplasmic reticulum.

Animals↗