Search PubMed⌕ Search

Biomedical subjects

G H Morrison

Publications and source records attributed to G H Morrison.

At least 55 records · Page 3Linked to original sources
PubMed1986

Imaging intracellular elemental distribution and ion fluxes in cultured cells using ion microscopy: a freeze-fracture methodology.

A freeze-fracture methodology was standardized for tissue culture cells to study intracellular distribution of diffusible elements with ion microscopy. Chinese hamster ovary (CHO) and normal rat kidney (NRK) cells grown on a silicon substrate were sandwiched using another smooth surface (silicon, glass, mica) in the presence of spacers and fast frozen in liquid nitrogen slush. The sandwich was fractured by prying the two halves apart under liquid nitrogen. This procedure produced large areas on the silicon substrate containing hundreds of cells grouped together and fractured at the apical cell surface. After freeze-drying, these cells revealed a subcellular distribution of Na, K, Ca, Mg, P, Cl and S with the approximately 0.5 micron lateral resolution of the ion microscope. Between the nuclei and the cytoplasm of cells, no major differences were observed for Na, K, Mg, P, Cl and S intensities. Calcium alone, however, exhibited a remarkable distribution. Calcium accumulated more in the cytoplasm than in the nuclei of cells. Even within the cytoplasm its distribution was heterogeneous, suggesting Ca binding sites. The fractured cells consistently exhibited high K-low Na intensities. The injured or dead cells were easily recognized among the healthy ones due to their abnormal ion composition. This simple freeze-fracture methodology allowed fracturing of cells without removing the cells from the substrate. In addition, it eliminated the need for washing the nutrient media away and cryo-sectioning before ion microanalysis. The methodology was successfully extended to 3T3 mouse fibroblast, PtK2 rat kangaroo and L5 rat myoblast cultures.

Animals↗
PubMed1985

Imaging elemental distribution and ion transport in cultured cells with ion microscopy.

Both elemental distribution and ion transport in cultured cells have been imaged by ion microscopy. Morphological and chemical information was obtained with a spatial resolution of approximately 0.5 micron for sodium, potassium, calcium, and magnesium in freeze-fixed, cryofractured, and freeze-dried normal rat kidney cells and Chinese hamster ovary cells. Ion transport was successfully demonstrated by imaging Na+-K+ fluxes after the inhibition of Na+- and K+ -dependent adenosine triphosphatase with ouabain. This method allows measurements of elemental (isotopic) distribution to be related to cell morphology, thereby providing the means for studying ion distribution and ion transport under different physiological, pathological, and toxicological conditions in cell culture systems.

Animals↗
PubMed1984

Distribution of calcium during interphase and mitosis as observed by ion microscopy.

The ion microscope, based on secondary ion mass spectrometry, has been used to demonstrate the distribution of calcium in the root tip cells of two plant species, Allium cepa and Vicia faba. Interphase nuclei showed higher intensities of calcium than cytoplasm, while nucleoli exhibited higher calcium intensities than the rest of the nucleoplasm. The chromosomes showed high intensities of calcium at all stages of mitosis. Calcium was also detected in the cell plate and phragmoplast region of dividing cells. It appears that during prophase calcium concentrates in the condensing chromosomes, and during telophase it is transferred to nucleoli. These observations suggest that chromosomes may serve as a reservoir of calcium during mitosis.

Calcium↗
PubMed1980

Diffusible ion localization by ion microscopy: a comparison of chemically prepared and fast-frozen, freeze-dried, unfixed liver sections.

The necessity of low temperature preparative procedures for diffusible ion localization using the ion microscope has been established with rat liver as the test material. Using conventional fixation procedures, significant ion loss and redistribution were observed which exceeded the 1 micrometer lateral resolution of the direct imaging ion microanalyser. The compositional morphology evidenced in chemically prepared versus fast-frozen, freeze-dried, unfixed material was compared and evaluated in terms of ion retention, ion redistribution and morphological integrity. A mass spectral analysis of both preparations has been presented and discussed with regard to spectral interferences and elemental sensitivities. Ion images of sodium and potassium were recorded for chemically prepared liver sections and compared with the ion distributions obtained for unfixed, fast-frozen, freeze-dried 1 micrometer thick sections. The magnitude of ion loss during preparation of samples removed at different stages in the course of chemical processing was determined by atomic absorption and flame emission spectrophotometry.

Animals↗