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Biomedical subjects

R Lim

Publications and source records attributed to R Lim.

At least 145 records · Page 8Linked to original sources
PubMed1984

Dual properties of cultured retinoblastoma cells: immunohistochemical characterization of neuronal and glial markers.

The dual properties of two human retinoblastoma cell lines, WERI-Rb1 and Y79, were investigated with immunohistochemistry. Two neuron-specific markers, dopamine-B-hydroxylase (DBH) and tetanus toxin, and an astrocyte-specific marker, the glial fibrillary acid protein (GFAP), were applied for immunohistochemical reactions. With peroxidase-antiperoxidase (PAP) and immunofluorescence techniques, all of the WERI-Rb1 and Y79 cells showed consistently positive results with both neuronal and glial markers. The findings demonstrate that cultured retinoblastoma cells WERI-Rb1 and Y79 have both neuronal and glial properties.

Cell Line↗
PubMed1983

Purification of rat Schwann cells from cultures of peripheral nerve: an immunoselective method using surfaces coated with anti-immunoglobulin antibodies.

We report a method for deriving purified rat Schwann cells by immunoselective removal of fibroblasts. Contaminating fibroblasts labeled with antibody against specific surface marker Thy 1.1 are bound on plastic surfaces coated with a second antibody. The efficacy of the method is demonstrated by flow cytometry and by specific Schwann cell Ran-1 immunofluorescence.

Animals↗
PubMed1983

Dual effect of glia maturation factor on astrocytes. Differentiation and release of interleukin-1 like factors.

C6 glioma cells, and primary cultures of mouse astrocytes, stimulated with lipopolysaccharide (LPS) release an interleukin-1 like factor (IL-1) which enhances lectin-induced T-lymphocyte proliferation and promotes the release of interleukin-2 (IL-2) by ConA-stimulated thymocytes. In the present study, the glia maturation factor (GMF) was found not only to induce differentiation of glioblasts, but also to elicit the secretion of IL-1 like factors by cultured mouse astrocytes and their precursor cells. GMF was also effective in triggering IL-1 release by macrophages. Contamination of the 23 000 MW GMF preparation with LPS was excluded by the Limulus lysate assay and by using C3H/HeJ LPS-nonresponder mice whose glia and macrophages responded to GMF but not to LPS, by IL-1 release. Through its ability to induce glial differentiation and IL-1 release, GMF may represent an important endogenous signal, triggering both reactive gliosis and the development of an immune response within the central nervous system.

Animals↗
PubMed1982

Interaction of glia maturation factor with the glial cell membrane.

Glia maturation factor (GMF) immobilized on agarose beads retained the same mitogenic and morphological transforming activities as free GMF when tested on glioblasts. The exposure of glioblasts to immobilized GMF for 5 min provoked the initiation of DNA synthesis and maximal stimulation was obtained within 30 min. Thiol-reducing agents, such as dithiothreitol and cysteine, increased the biological activity of GMF. These data suggest the presence of a surface receptor to GMF on the glioblasts, while the reduction of the thiol group(s) in GMF promotes the binding to its receptor. Repeated use of immobilized GMF decreased both the mitogenic and the morphological transforming activities. Immobilized GMF used for the third time lost its biological activity. This implies the existence of a certain kind of degradation system such as a proteolytic enzyme located close to the GMF receptor on the glial cell surface.

Animals↗
PubMed1982

Effect of glia maturation factor on glial fibrillary acidic protein and fibronectin: a comparative study on glioblasts and fibroblasts using immunofluorescence.

Glia maturation factor (GMF) was tested on separate cultures of glioblasts and fibroblasts isolated from the same rate fetuses. The astrocytic marker glial fibrillary acidic (GFA) protein and the fibroblast marker fibronectin were visualized with immunofluorescence. Before GMF stimulation, glioblasts showed only background fluorescence for GFA protein and fibronectin. After GMF stimulation, glioblasts showed intense fluorescence for GFA protein, especially in the processes and end-feet. GMF-stimulated glioblasts also showed a slight increase in intracellular fluorescence for fibronectin, mainly in the perinuclear cytoplasm but never in the process terminals. At no time was extracellular fibronectin observed in glioblast cultures. In contrast, fibroblast cultures formed an extensive extracellular network of fibronectin whether or not they were exposed to GMF. GFA protein never showed up in fibroblast cultures regardless of stimulation by GMF. The results indicate that GMF stimulates an increase of GFA protein in glial processes and confirms the astrocytic nature of these glioblasts.

Animals↗
PubMed1982

Enucleation blocks the morphological response of glioblasts to glia maturation factor.

Culture glioblasts obtained from rat fetuses were enucleated with cytochalasin B. The glia maturation factor stimulated the morphological differentiation of nucleated but not enucleated cells. In contrast, 8-bromo-cyclic AMP stimulated the morphological differentiation of both nucleated and enucleated cells. This distinction implies a difference in the mode of action of the two agents on cultured glioblasts, and suggests that an interaction between the nucleus and cytoplasm is required for expression of the morphological effect of the glia maturation factor.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1981

Glia maturation factor in bovine brain: partial purification and physicochemical characterization.

Glia maturation factor (GMF) is partially purified from bovine brains by the following procedure: extraction at physiologic pH, dialysis and freeze-drying of the extract, ethanol washing of the dried powder and re-extraction of the ethanol-washed residue with Tris-buffered saline, ion-exchange chromatography with DEAE Sephadex and molecular sieving with Bio-gel P-200. The partially purified protein has an apparent molecular weight of 23,000 and an isoelectric point of 4.75, and retains both morphological transforming and mitogenic activities when tested on glioblasts. Both activities are susceptible to protease digestion and heat inactivation. The procedure results in a 400-fold purification of the morphological activity and a 1400-fold purification of the mitogenic activity. Both activities are detectable when GMF is used in nanogram quantities. The possibility that both functions are expressions of the same factor and the possible role of GMF in the differential or sequential stimulation of cell growth and maturation are discussed.

Animals↗
PubMed1981

Biological effects of bovine glia maturation factor on glial cells in culture.

Optimal bioassay conditions for bovine glia maturation factor (GMF) were determined among glial cells from normal glioblasts to glioma cells. Rat glioblasts 4-8 days after subculture show the highest response t GMF with regard to morphological transformation and mitogenic activity. Bovine GMF enhances DNA synthesis of rat glioblasts at 12 h after stimulation; maximum incorporation of [methyl-3H]thymidine was detected at 18 h. GMF increases twofold the saturation density of rat glioblasts but does not alter that of C6 astrocytoma cells. The apparent inhibition of mitogenic activity of high doses of GMF is seen in both normal and malignant glial cells.

Animals↗
PubMed1981

Glia maturation factor promotes contact inhibition in cancer cells.

The effect of bovine glia maturation factor on the growth pattern of cancer cells was investigated in the rat glioma cell line 354A. When the cells were grown in the serum-free defined medium N2 in the absence of the factor, the cells proliferated with a doubling time of 24 hr without showing contact inhibition. After reaching confluency, the cell layer formed numerous foci from which heaps of cell colonies arose. The addition of glia maturation factor to the culture stimulated cell division in the logarithmic phase but prevented overgrowth once the cells arrived at confluency. The ability of glia maturation factor to restore contact inhibition suggests a regulatory role in normal and neoplastic cells.

Animals↗
PubMed1981

Distribution of glia maturation factor-like activity in organs and cells.

Glia maturation factor (GMF) is a protein first isolated from the adult pig brain. GMF-like activity can be demonstrated in rat organs, including brain, kidney and heart. The activity in these organs is low in newborn animals, but increases with development, reaching the adult level in 1 or 2 weeks. GMF-like activities in the various organs are similar in physicochemical properties, being heat-labile, susceptible to proteolytic enzymes, and are associated with an acidic molecule of large size. Cultured rat glioblasts and C6 glioma cells, but not their conditioned media, contain large amounts of endogenous GMF-like activity. GMF obtained from brains and cultured glial cells also possess mitogenic action. Subcellular fractionation localizes GMF-like activity in the cytosol and in microsomal and nerve ending fractions. GMF-like activity is also detectable in bovine, sheep, monkey and human brains. The results suggest that GMF is ubiquitous in distribution, and at least a portion of it may be associated with the structural components of the cells.

Animals↗
PubMed1980

Preliminary characterization of vasocontractile activities in erythrocytes.

The vasocontractile activities of washed red cell preparations hemolyzed by various methods were studied in vitro using isolated canine basilar arteries. Significant contractions were induced by each preparation. The maximum strength of contraction attained by the various preparations was similar. The contractile activity appeared to be dose-related, and molecular exclusion chromatography demonstrated that the activity migrated with the fraction of approximately 40,000 to 45,000 molecular weight. The vasocontractile effect of the active fraction was sustained in vitro when tested against basilar artery, but was inactive in peripheral arterial preparations. Preliminary biochemical characterization indicates that the contractile activity resides in a protein. Enzymatic digestion of the crude fraction appears to enhance the contractile activity significantly, and this observation suggests a possible mechanism for the delayed onset of ischemic symptoms encountered in the clinical situation.

Animals↗
PubMed1979

Multiple molecular forms of glia maturation factor.

Glia maturation factor from the pig brain can be detected in two molecular forms: the high molecular weight form which is 200 000 dalton in size and the low molecular weight form which is 40 000 dalton in size, as determined by Sephadex gel filtration. The former accounts for 85% of the total biological activity extracted at physiologic pH. The proportion of the low molecular weight form increases following freeze-thawing and ion-exchange chromatography. In addition to the morphological effects, both forms possess mitogenic activity but no esteropeptidase activity. Both forms show similar enzyme susceptibility, being inactivated by papain, ficin and pronase but resistant to subtilisin, thermolysin and trypsin. The high molecular weight form is more resistant to denaturation by low pH, heating and urea than the low molecular weight form. The high molecular weight factor has an isoelectric point of 4.27 whereas the low molecular weight factor has one of 5.04.

Animals↗
PubMed1979

Prolongation of pancuronium-induced neuromuscular blockade by intravenous infusion of nitroglycerin.

Based upon clinical observation of undue prolongation of pancuronium-induced blockade in the presence of intravenous infusion of nitroglycerin, neuromuscular blockades produced by pancuronium, succinylcholine and d-tubocurarine were studied in 51 cats using the sciatic-gastrocnemius nerve-muscle preparation. Pancuronium-induced blockade was found to be significantly prolonged (P less than 0.1) in the presence of a nitroglycerin infusion of 1 microgram/kg/min (65 vs. 127 min). Less, but still significant, prolongation occurred when nitroglycerin, 0.5 microgram/kg/min, was infused. The intravenous infusion of nitroglycerin must be started prior to the pancuronium injection for the block to be prolonged. Neuromuscular blocks produced by succinylcholine and d-tubocurarine were not altered by nitroglycerin. In experiments using the isolated rat diaphragm preparation, the depth of pancuronium-induced block was found not to be changed by nitroglycerin, suggesting an effect of nitroglycerin on the process of recovery from blockade. These findings indicate a selective pancuronium-nitroglycerin interaction.

Animals↗