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Biomedical subjects

M Stoker

Publications and source records attributed to M Stoker.

At least 37 records · Page 2Linked to original sources
PubMed1984

Cultures of exfoliated mammary epithelial cells: variation between donors.

Human 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.

Africa↗
PubMed1983

Studies on differentiation of human mammary epithelial cells in culture: distinctive specificities of conditioned media.

Epithelium cultured from human milk contains cells of two types distinguishable by morphology and keratin pattern. First, the "open" type comprises cells which are isolated from one another, and which do not form typical epithelial sheets. Second, the "joined" type grow as tightly adjoining cell sheets. Clonal analysis shows that open cells, besides reproducing the same phenotype, can give rise to mixed colonies containing joined cells, thus indicating a pathway of in vitro differentiation. When conditioned medium was used to enhance colony growth it was found that human embryo lung fibroblasts release an activity which specifically enhances the open type of mammary epithelial cell. On the contrary the Nil 8 hamster fibroblast line and certain other cells release activities which primarily affect the joined cell type. This suggests that there are naturally occurring factors with specificities for distinct stages in mammary epithelial cell differentiation.

Animals↗
PubMed1982

Clonal analysis of morphological phenotype in cultured mammary epithelial cells from human milk.

Three main types of colony forming epithelial cell, termed elongated, cuboidal and open, are found in cultures of human milk. Subculture of identified colonies, and cloning from single cells shows that each cell type can maintain its morphological phenotype, but in addition the cuboidal and open cell types can give rise to the elongated type. The results, which suggest a differentiation pathway starting with open cell types, are discussed in relation to differentiation studies on mammary cancer cells.

Breast↗
PubMed1975

Dissociation by cytochalasin B of movement, DNA synthesis and transport in 3T3 cells.

Cytochalasin B was used as a tool to study the inter-relationships between cell movement, the reinitiated DNA synthesis and the enhanced transport of specific small molecules stimulated by serum in quiescent 3T3 cells. Cytochalasin at concentrations of less than 1 mug/ml inhibits serum-stimulated movement within the monolayer and migration into a wound. Even at ten times this concentration there is little effect on the increase in DNA in the culture, indicating that movement away from neighboring cells is not required for the initiation of DNA synthesis. While DNA synthesis is not inhibited by concentrations of cytochalasin up to 10 mug/ml, the increased thymidine transport which is associated with the onset of the S phase of the cell cycle is inhibited and DNA synthesis cannot be measured by the labelling of nuclei with radioactive thymidine. Cytochalasin has a differential effect on the early transport changes produced by serum addition. Glucose transport is inhibited by low concentrations of the drug (less than 1 mug/ml) while the enhanced uptake of phosphate and uridine is unaffected by a 10-fold increase in concentration. Although the doses of cytochalasin required for 50% inhibition of hexose uptake and of cell movement are the same, no causal relationship between sugar transport and locomotion can be demonstrated. Cytochalasin affects membrane functions in at least two different ways. The drug inhibits the uptake of glucose directly but affects only the S-phase associated increase in thymidine transport.

Animals↗
PubMed1975

The effects of topoinhibition and cytochalasin B on metabolic cooperation.

Metabolic cooperation was used to investigate the ability of 3T3 cells to form intercellular junctions under conditions of topoinhibition and topostimulation, respectively. A transformed BHK cell lacking hypoxanthine guanosine phosphoribosyl tranferase, which was used an an indicator, was found to incorporate 3H-hypoxanthine when in prolonged (20 hr) or brief (1 hr) contact with donor 3T3 cells, whether the latter were in a quiescent layer of in the region of stimulation at the edge of a wound. Cytochalasin B (1 mug/ml) prevented the development of metabolic cooperation and abolished most preexisting cooperation between donor 3T3 cells and recipient BHK cells. Cooperation was reestablished by removal of the drug. Cytochalasin B inhibited cooperation by the donor 3T3 cells in both the layer and wound edges, irrespective of topoinhibition and topostimulation. This provides further evidence that alteration in capacity to form stable intercellular junctions is not a necessary feature of the topoinhibition phenomenon.

Cell Division↗