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Biomedical subjects

M Stoker

Publications and source records attributed to M Stoker.

At least 19 recordsLinked to original sources
PubMed1995

HGF/SF inhibits junctional communication.

Hepatocyte growth factor/scatter factor (HGF/SF) is a fibroblast-derived protein that affects the growth, motility, and differentiation of epithelial and endothelial cells. We have investigated the effect of HGF/SF on junctional communication in mouse keratinocytes (MK cells). HGF/SF inhibited cell communication in MK cells as assessed by the transfer of a low-molecular-weight dye, Lucifer Yellow. The inhibition was rapid, the earliest effects being apparent 5 to 10 min after addition of the factor, and was transient. The decrease in dye transfer correlated with a loss of the gap junction protein connexin 43 as measured by Western blotting, probably due to increased protein degradation. The results show that junctional communication is an early target of HGF/SF activity and they are consistent with the hypothesis that gap junctions are primary targets of the action of growth factors.

Animals↗
PubMed1993

Hepatocyte growth factor/scatter factor (HGF/SF), the c-met receptor and the behaviour of epithelial cells.

Hepatocyte growth factor/scatter factor (HGF/SF) is a multifunctional protein produced by fibroblasts and other mesenchymal cells and active on epithelial and endothelial cells. The factor shares the basic domain organization of plasminogen and other blood proteases and is produced as a single-chain high molecular weight precursor which is subsequently cleaved to produce a biologically active heterodimer. HGF/SF acts on target cells through binding to a cell surface, high-affinity receptor with tyrosine kinase activity encoded by the c-met proto-oncogene. Transduction of the HGF/SF signal in epithelial cells by the met receptor leads either to: (i) cell dissociation, with loss of adhesion and junctional communication, (ii) cell division or (iii) differentiation and morphogenesis. These responses depend on target cells and culture conditions. There is preliminary evidence for a role for HGF/SF in vivo, suggesting that the factor may be involved in the early stages of embryo development and in liver regeneration. A role in cancer growth or dissemination has been proposed but remains to be clarified.

Animals↗
PubMed1992

Down-regulation of scatter factor in MRC 5 fibroblasts by epithelial-derived cells. A model for scatter factor modulation.

Scatter factor/hepatocyte growth factor (SF/HGF) is a multifunctional cytokine produced by embryonic fibroblasts and other mesenchymal cells that affects the growth and/or the movement of certain epithelia. Here we report that expression of scatter factor activity by MRC 5 cells, a strain of normal human embryonic lung fibroblasts, is greatly reduced as a result of co-culture of these cells with SVK14, an SV40-transformed human keratinocyte cell line. Using a cDNA probe to the beta chain of human HGF, we have found that the fall in SF activity in MRC 5/SVK14 co-cultures is accompanied by the loss of SF/HGF transcripts. As the inhibition of SF activity coincides with the disappearance of SF/HGF transcript, we conclude that inhibition of the SF activity expressed by MRC 5 cells by co-culture with SVK14 involves transcriptional regulation.

Animals↗
PubMed1990

Epithelial scatter factor and development of the chick embryonic axis.

Scatter factor, a recently characterised protein secreted by certain embryonic fibroblasts, affects cultured epithelial by increasing cell motility, the breakdown of cell junctions and cell scattering. The process of gastrulation in higher vertebrate embryos, during which the primitive streak forms, involves an epithelial-to-mesenchymal transformation resembling the effects of the factor on cultured cells. The factor was applied locally to chick embryos, using both scatter-factor-secreting cell lines and inert carriers. We found that scatter factor can generate local supernumerary axial structures resembling primitive streak and/or neural plate and conclude that it may have primitive-streak and/or neural-inducing activity in chick embryos.

Animals↗
PubMed1989

Effect of scatter factor on motility of epithelial cells and fibroblasts.

The scatter factor is a protein released by fibroblasts that causes dispersal of epithelial cell colonies and disruption of intercellular junctions, as well as an alteration of morphology with ruffling and rapid extension and movement of pseudopodia. To find out if the scatter factor has a direct effect on cell migration, the Boyden chamber assay was used to determine the effect of partially purified factor on the migration of cells through 8 microns pore size filters. The results showed that the mobility of Madin-Darby canine kidney (MDCK) cells was stimulated, and usually maximal at 100 ng per ml, which is equivalent to 100 to 200 units of activity in the standard assay based on the morphology and arrangement of cells. The migration was due to chemotaxis and chemokinesis. A keratinocyte cell line was also sensitive as were, to a lesser extent, BSCl monkey kidney cells. The motility of freshly isolated fibroblasts and fibroblast cell lines, however, was not significantly affected. The results confirm the cell specificity and paracrine role of the scatter factor and show that this fibroblast-derived molecule can directly stimulate the movement of epithelial cells.

Animals↗
PubMed1989

Purification of scatter factor, a fibroblast-derived basic protein that modulates epithelial interactions and movement.

Scatter factor is a fibroblast-derived protein that causes separation of contiguous epithelial cells and increased local mobility of unanchored cells. Highly purified scatter factor has been obtained by a combination of ion-exchange and reverse-phase chromatography from serum-free medium conditioned by a ras-transformed clone (D4) of mouse NIH 3T3 fibroblasts. Under nonreducing conditions scatter factor has a pI of approximately 9.5 and migrates in SDS/polyacrylamide gels as a single band at approximately 62 kDa from which epithelial scatter activity can be recovered. Treatment with reducing agents destroys biological activity and is associated with the appearance of two major bands at approximately 57 and approximately 30 kDa. Whether both the 57-kDa and 30-kDa polypeptides are required for biological activity remains to be established. All the activities observed in crude medium conditioned by cells producing scatter factor are retained by highly purified preparations of scatter factor. These include (i) increased local movement, modulation of morphology, and inhibition of junction formation by single epithelial cells and (ii) disruption of epithelial interactions and cell scattering from preformed epithelial sheets. These changes occur with picomolar concentrations of purified scatter factor and without an effect on cell growth.

Animals↗
PubMed1989

Scatter factor and other regulators of cell mobility.

The scatter factor is a basic protein with an apparent molecular weight of about 62K, which is released from certain strains and lines of cultured fibroblasts. It affects the mobility, morphology, and cell to cell attachment of epithelial cells in culture and there is some evidence of an effect on early embryo development. Fibroblasts are unaffected by the factor and there is a negligible effect on cell growth. The scatter factor differs from a similar agent, the autocrine motility factor, in its paracrine role, its lack of association with tumour cells, and in some biochemical features, but both may be representatives of a group of cytokines which regulate cell motility.

Animals↗
PubMed1988

Split skin grafting using topical local anaesthesia (EMLA): a comparison with infiltrated anaesthesia.

The analgesic efficacy of EMLA cream was compared with that produced by infiltration of lignocaine solution when used to provide anaesthesia for cutting of skin grafts. The study was performed as an open parallel group comparison in 80 patients. Pain felt during administration of the anaesthetic and during cutting of the graft was assessed using visual analogue and verbal rating scales. During graft cutting, the anaesthesia produced by EMLA was at least as effective as infiltration. On administration, infiltration produced varying amounts of pain in all patients, but in contrast EMLA produced no discomfort. In view of this lack of discomfort and the consequent greater freedom afforded regarding the area of donor site anaesthetised, EMLA can be considered the treatment of choice when skin grafts are harvested under local anaesthetic.

Administration, Cutaneous↗
PubMed1987

Factors affecting epithelial interactions.

In an investigation of endogenous regulation of epithelial interaction, it was found that cultured embryo fibroblasts release an activity which causes loss of junctional attachment and separation of contiguous epithelial cells. This activity was originally observed in freshly cultured human mammary cells, but the MDCK cell line is also sensitive and has been used to develop an assay of activity. The activity is due to a protein that is heat-labile and sensitive to reducing agents and has a relative molecular mass of approximately 50,000 by gel filtration in the presence of 6 M-guanidinium hydrochloride or 8 M-urea. We term the agent 'epithelial scatter factor'. It is not known whether the factor acts directly or indirectly on junctional components. Besides its effect on cell relationships, the factor causes a change in cell morphology and local movement. In investigations so far, the scatter factor has been released only by fibroblasts of embryonic origin. Some but not all epithelial cells are sensitive; other cell types are not. The factor may be involved in morphogenetic changes involving the epithelium in embryonic or adult life. There is as yet no evidence for a role in the spread of tumour cells.

Animals↗
PubMed1985

An epithelial scatter factor released by embryo fibroblasts.

Medium conditioned by human embryo fibroblasts breaks structural junctions between several types of epithelial cells, leading to separation and scattering of the cells. An assay developed in MDCK cells shows activity up to a dilution of at least 1 in 64, equivalent to less than 100 ng of total protein. The activity is non-dialysable, heat-labile, and sensitive to trypsin, and it is assumed to be due to one or more proteins. After addition of the factor, separation of MDCK cells begins in about 15 min and is complete in 10 h. It increases migration of MDCK cells into wounds, and causes collapse of domes. Locomotion of isolated cells is not enhanced, but cell shape is affected by local membrane movement. Under the culture conditions used the factor, or an associated protein, causes a weak inhibition of cell growth without cytotoxic activity. The scattering factor has not been purified, nor has a physiological role been identified, but it might be concerned in the mobilization of epithelial cells.

Animals↗
PubMed1984

Junctional competence in clones of mammary epithelial cells, and modulation by conditioned medium.

Colony-forming epithelial cells exfoliated in human milk have been examined by immunofluorescence using antibodies to cytokeratins (tonofilaments), and to high molecular weight desmosomal core proteins. The cells may be classified by their ability to form junctional complexes with their neighbours. Those deficient in desmosomal junctions, called D- cells, grow into colonies of noncontiguous cells without desmosomes, and with a perinuclear network arrangement of cytokeratins. Junction forming, or D+ cells, grow as contiguous cell sheets with abundant desmosomes and well developed bundles of tonofilaments. D- cells may also segregate D+ cells among their progeny yielding mixed clones, and a gradual increase in the overall number of D+ cells during culture. Established D+ cells have surface markers characteristic of mammary epithelium and are presumably derived by exfoliation of luminal cells of the alveoli or ducts which contain desmosomal junctions. D- cells also possess mammary epithelial cell markers, but their origin is unknown. Medium conditioned by the Nil 8 line of hamster cells contains a junction-promoting activity that accelerates the rate, or frequency, of segregation of D+ cells from D- cells, so that milk cells grown in this medium predominantly give closed colonies of D+ cells. Medium conditioned by the MRC5 strain of human embryo lung cells, however, contains a junction-inhibiting activity, which prevents new junction formation and probably destroys existing junctions, so that cells in this medium mostly grow as open colonies of cells with D- phenotype. It is hoped that studies with this experimental system will assist in the better understanding of normal and abnormal regulation of desmosomal junctions and their role in tissue integrity.

Animals↗
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↗