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At least 55 records · Page 3Linked to original sources
PubMed1989

Re-expression of 117 antigen, a cell surface glycoprotein of aggregating cells, during terminal differentiation of Dictyostelium discoideum prespore cells.

117 antigen is a glycoprotein expressed on the surface of D. discoideum cells at aggregation. It then disappears and is later re-expressed on the surface of a subpopulation of cells at culmination, the terminal differentiation stage (Sadeghi et al. 1987). A cDNA clone was used to show that the appearance of cell surface 117 antigen accurately reflects the expression of the 117 gene as measured by mRNA levels. It was also shown that during multicellular development there is a reciprocal relationship between the levels of 117 mRNA and the mRNA which codes for prespore surface glycoprotein, PsA. Dual parameter flow cytometry was used to demonstrate that the 117 antigen is found on the surface of maturing prespore cells after the PsA glycoprotein disappears, but that it is not found on mature spores. Using three monoclonal antibodies which identify respectively 117 antigen, PsA, and MUD3 antigen (a spore coat glycoprotein--probably Sp96), two new stages of final spore maturation were defined. These results indicate that there is a recapitulation of at least one aggregative cell surface glycoprotein in the prespore subpopulation of cells as they rise up the stalk during final spore development. This raises the possibility that culmination, which involves complex three dimensional morphogenetic movements not unlike those observed during animal embryogenesis, involves components of the two-dimensional pattern seen during aggregation.

Antigens, Differentiation↗
PubMed1994

Influence of folliculo-stellate cells on biphasic luteinizing hormone secretion response to gonadotropin-releasing hormone in rat pituitary cell aggregates.

Anterior pituitary cells cultured as three-dimensional cell aggregates and incubated with gonadotropin-releasing hormone (GnRH) show a biphasic pattern of luteinizing hormone (LH) release when steroid-free bovine follicle fluid is added to the culture medium. Initially, the GnRH-induced LH release is low (lag-phase response), but LH release increases during further incubations with GnRH (primed-state response). Also, in aggregates of dispersed cells from long-term ovariectomized rats cultured for 2 days in the presence of 1% bovine follicle fluid, a low initial LH responsiveness to GnRH could be restored. Cycloheximide was found to block the induction of the primed state, indicating the protein synthesis dependency of GnRH self-priming. In aggregates from gonadotroph-enriched cell populations obtained by velocity sedimentation in a bovine serum albumin gradient, addition of 1% bovine follicle fluid to the culture medium also restored a biphasic pattern of GnRH-induced LH release. However, co-culturing the gonadotroph-enriched cell aggregates with a folliculo-stellate (FS) cell-enriched population resulted in the attenuation of the differences in LH secretion rate between early and late responses to GnRH. The present example of the attenuation by folliculo-stellate cells of pituitary hormone secretion responses demonstrates that the cells regulate the cellular processes leading to a priming of the LH response to GnRH, rather than interfering with the access of GnRH to its receptor in gonadotrophs. Finally, it was found that stimulation of the adenylate cyclase enzyme with maximal effective doses of forskolin counteracted the inhibitory effect of bovine follicle fluid on the initial LH response to GnRH, but did not completely abolish the biphasic pattern of LH release. It is concluded that coupling to the adenylate cyclase enzyme is presumably involved in the LH surge inhibiting feedback action on the pituitary cells, but also other messenger pathways and intercellular interactions between pituitary cells may play a role in establishing a biphasic LH release at the pituitary level following GnRH administration.

Animals↗
PubMed1994

Expression of fusion regulatory proteins (FRPs) on human peripheral blood monocytes. Induction of homotypic cell aggregation and formation of multinucleated giant cells by anti-FRP-1 monoclonal antibodies.

Fusion regulatory proteins (FRPs) are newly defined cell surface molecules that enhance and/or induce virus-mediated cell fusion. Anti-FRP-1 Abs reacted with all of the established cells derived from humans and monkeys, whereas FRPs were found to be selectively expressed on a fraction of monocytes in human PBMCs. Granulocytes expressed no FRP-1 molecules, but approximately 18% of granulocytes expressed FRP-2 molecules. Alveolar macrophages also expressed FRP-1 molecules. FRP-1 expression was enhanced by culture of monocytes, but CD14 expression was not influenced by cultivation. Anti-FRP-1 Abs induced homotypic cell aggregation and multinucleated giant cell formation of monocytes. Anti-beta 2 integrin Ab blocked anti-FRP-1 Ab-induced cell aggregation, and anti-beta 1 integrin Ab and fibronectin inhibited anti-FRP-1 Ab-induced polykaryocyte formation. There was no competitive binding to monocytes between anti-FRP-1 Ab and anti-beta 1 or anti-beta 2 integrin Ab or fibronectin. Furthermore, there was no enhancement of beta 1 and beta 2 integrin expression by anti-FRP-1 Ab on monocytes. These findings suggest that anti-FRP-1 Ab activated integrin systems, and that the functions of anti-FRP-1 Ab were demonstrated through the activated integrin systems. Furthermore, it is inferred that integrin systems are involved in polykaryocyte formation of monocytes.

Amino Acid Sequence↗
PubMed1994

[Monoclonal antibody mNI-11 strongly induces homotypic cell aggregation of monocyte-like cell line U937: effects of conditioned medium and cytochalasin B].

A mouse monoclonal antibody (mAb), designated as mNI-11, has been produced. This mAb strongly induced homotypic cell aggregation (HCA) of monocyte-like cell line U937 cultured with conditioned medium derived from PHA-stimulated peripheral blood mononuclear cells and cytochalasin B. HCA occurred at an optimal temperature of 37 C but not 4 C. mAbs to CD18 (lymphocyte function-associated antigen-1 beta; LAF-1 beta) and CD54 (intercellular adhesion molecule-1; ICAM-1) completely inhibited this HCA. These results suggest that mNI-11 strongly induces HCA of the U937 cells in an activated form after stimulation with conditioned medium and cytochalasin B.

Animals↗
PubMed1980

Sponge cell aggregation.

Dissociated sponge cell system has proved to be a useful model to study the process of cell aggregation both on cellular and subcellular level. The purpose of this review is to discuss recent results obtained from experiments with the marine sponge Geodia cydonium. Dissociated cells form functional aggregates during a process which can be sub-divided into three phases: first, formation of small primary aggregates in the presence of Ca2+; second, formation of secondary aggregates in the presence of an aggregation factor and third, reconstitution of a functional system of water-containing channels by rearrangement in the secondary aggregates. On subcellular level a series of macromolecules are known which are involved in the control of aggregation and separation of sponge cells: Aggregation factor, aggregation receptor, anti-aggregation receptor, beta-glucuronidase, beta-glucuronosyltransferase, beta-galactosyltransferase, beta-galactosidase and a lectin. These components might be linked in the following sequence: (a) Activation of the aggregation receptor by its enzymic glucuronylation; (b) Adhesive recognition of the cells, mediated by the aggregation factor and the glucuronylated aggregation receptor; (c) Inactivation of the aggregation receptor by its deglucuronylation with the membrane-associated beta-glucuronidase; (d) Cell separation due to either the loss of the recognition site (glucuronic acid) of the aggregation receptor for the aggregation factor or to an inactivation of the aggregation factor by the anti-aggregation receptor. The activity of the anti-aggregation receptor is most likely controlled by the Geodia lectin. The events leading to cell-cell recognition cause a change in the following metabolic events: Increase of oxygen uptake, decrease of cyclic AMP level, increase of cyclic GMP level and stimulation of programmed syntheses.

Animals↗
PubMed1993

[Establishment of monoclonal antibody mNI-11 which induces homotypic cell aggregation of LPS-treated U937 cells].

A mouse monoclonal antibody (mAb), designated as mNI-11, was produced. The reactivity of mNI-11 was assessed by immunofluorescence assay with various cells. Myelomonocytic cell line, U937, and lipopolysaccharide (LPS)-treated U937 (LPS-U937 cells) were found to bind strongly to the mAb. EBV-B cell line and peripheral blood mononuclear cells (PBMCs) were found to bind moderately to it. This mAb strongly induced homotypic cell aggregation of LPS-U937 cells. The mAbs to CD18 and CD54 completely inhibited the LPS-U937 cell aggregation induced by mNI-11. The surface antigens of the U937 and LPS-U937 cells recognized by mNI-11 had a molecular size of 95-97 kDa as determined by immunoblotting analysis.

Animals↗
PubMed1995

Cell aggregation and sedimentation.

The aggregation of cells into clumps or flocs has been exploited for decades in such applications as biological wastewater treatment, beer brewing, antibiotic fermentation, and enhanced sedimentation to aid in cell recovery or retention. More recent research has included the use of cell aggregation and sedimentation to selectively separate subpopulations of cells. Potential biotechnological applications include overcoming contamination, maintaining plasmid-bearing cells in continuous fermentors, and selectively removing nonviable hybridoma cells from perfusion cultures.

Animals↗
PubMed1980

Evaluation of flow cytometric data of human tumours. Correction procedures for background and cell aggregations.

Background signals and aggregation of cells affect flow cytometric DNA measurements to a great and mostly uncontrolled extent. These artefacts appear mainly in investigations of solid tumours leading to significant distortions in the results. Procedures are described that make possible quantitative corrections both of the background and of the cell aggregations.

Brain Neoplasms↗
PubMed1997

Neutral glycosphingolipids induce cell-cell aggregation of a variety of hematopoietic cell lines.

Exogenous neutral glycosphingolipids induced homotypic cell-cell aggregation of a variety of hematopoietic cell lines. A mouse cytotoxic T cell line, CTLL-2, was chosen to study the neutral glycosphingolipid-induced aggregation. Among neutral glycosphingolipids tested, galactosylceramide (GalCer) and glucosylceramide (GlcCer) were potent inducers, followed by lactosylceramide (LacCer); globotriaosylceramide (Gb3Cer) and neolactotetraosylceramide (nLc4Cer) were less effective. GalCer that contained a non-hydroxy fatty acid was more efficient than GalCer containing an alpha-hydroxy fatty acid. The minimum concentration of GalCer containing a non-hydroxy fatty acid that induced aggregation was 1 microM, and maximum aggregation occurred at 10-20 microM within 24 h. Cytochalasin B and a mixture of sodium azide and 2-deoxyglucose inhibited the aggregation, whereas cycloheximide, actinomycin D, and colchicine did not. Aggregated and dispersed cells, which were designated as competent cells, re-aggregated in the absence of neutral glycosphingolipids. Anti-GalCer polyclonal antibody inhibited GalCer-induced reaggregation. Furthermore, competent cells bound and aggregated non-competent cells in the absence of neutral glycosphingolipids. Cell-cell aggregatign was similar for CTLL-2 cells and the other hematopoietic cells that were tested. These findings suggest that the neutral glycosphingolipid-induced cell-cell aggregation of CTLL-2 cells was mediated by heterophilic interaction(s) between glycosphingolipids and other cell surface components. These properties are shared by a variety of hematopoietic cell lines.

Animals↗
PubMed1982

Tissue culture of chick embryonic choroidal cells: cell aggregation and pigment accumulation.

Cells originating from the chick embryo choroid were grown in culture for up to 1 month. The cells did not form coherent monolayer colonies but rather formed large transparent cell aggregates surrounded by a random, loose network of cells. The cell aggregates avidly took up and retained pigment granules while the individual cells did not. Choroidal cell aggregates were not similar to the "lentoid" bodies described by Okada and coworkers in cultures from other ocular tissues; they did not develop fiber cells and did not synthesize delta-crystallin. Thus aggregation of ocular cells appears to be a necessary but insufficient step for the formation of a "lentoid" body.

Animals↗
PubMed1978

Biochemical and morphological comparison of two tumour-cell-aggregation factors from rat ascites hepatoma cells.

Two tumour-cell-aggregation factors, derived from rat ascites hepatoma cells, had different antigenicity; one was not absorbed by immunoadsorbent chromatography with anti-rat serum antibody and the other was. Their activities were both lost by digestion with trypsin, but remained unchanged by oxidation with periodate, suggesting the role of the protein portions in their molecules. The potency of the unabsorbed factor was inhibited specifically by alpha-methyl-D-mannoside or D-mannose, while that of the absorbed factor was inhibited specifically by N-acetyl-D-glucosamine, suggesting that these carbohydrates may be concerned with the respective receptor structures at the tumour-cell surface. The unabsorbed factor induced not only cell aggregation (as shown in the form of simple apposition) but also cell adhesiveness characterized by development of intermediate junctions, desmosomes and tight junctions, while the absorbed factor produced only simple apposition, suggesting their functional difference.

Animals↗
PubMed1996

A region of the integrin VLA alpha 4 subunit involved in homotypic cell aggregation and in fibronectin but not vascular cell adhesion molecule-1 binding.

The VLA-4 (alpha 4 beta 1) integrin is involved in the adhesion of cells to fibronectin and vascular cell adhesion molecule-1 (VCAM-1). In order to study alpha 4 structure-function relationships, we have expressed mutated alpha 4 subunit by transfection into VLA-4-negative K562 cells. Substitutions at alpha 4 residues Arg89-Asp90, which show the highest surface probability indexes inside the N-terminal alpha 4/80 fragment, resulted in a reduction in the reactivity of all anti-alpha 4 epitope A monoclonal antibodies (mAbs) tested, compared with the reactivity with anti-alpha 4 epitopes B1, B2, and C mAb, both by transfectant flow cytometry, and by immunoprecipitation and SDS-polyacrylamide gel electrophoresis analysis of transfectant surface-iodinated proteins. In contrast, substitutions at nearby residues, Gln101, Pro102, and Ile105 did not affect the reactivity of any anti-alpha 4 mAb representing the known alpha 4 epitopes. Homotypic cell aggregation triggered by anti-alpha 4 epitope A mAb was prevented in the transfectants expressing mutated alpha 4 Arg89-Asp90Asp residues, while cell aggregation was fully achieved with either anti-alpha 4 epitope B2 or anti-beta 1 mAb. Mutations at alpha 4 residues Gln101, Pro102, and Ile108 did not affect the homotypic cell aggregation of the transfectants expressing these mutations. In addition, the adhesion of mutant Arg89-Asp90 alpha 4 transfectants to the connecting segment-1-containing fibronectin-40 (FN-40) fragment of fibronectin was diminished compared to wild type alpha 4 transfectants, as well as to other mutant alpha 4 transfectants. This adhesion to FN-40 was restored when the activating anti-beta 1 TS2/16 mAb was present in the adhesion assays. In contrast, adhesion to VCAM-1 was not affected by mutations at Arg89-Asp90, nor at Gln101, Pro102, and Ile108 alpha 4 residues. Altogether, these results indicate that alpha 4 residues Arg89 and Asp90 are included in a region involved in homotypic cell aggregation, as well as in adhesion to FN-40, but not to VCAM-1.

Animals↗
PubMed1979

Production of plasminogen activator and inhibition of embryonic cell aggregation by cultured human normal and neoplastic cells.

The plasminogen activator (PA) production and the capacity to inhibit embryonic neural retina (NR) cell aggregation by human normal and neoplastic cell lines have been studied. The PA production was detected by both iodinated fibrin and casein lysis assays, and by changes in cell morphology at the presence of activated PA, using dog serum. Since the casein lysis assay and morphological changes proved to be less sensitive than 125I-fibrin lysis assay, a good correlation between these three assays could be observed provided that PA production measured by fibrinolysis exceeded 10--20%. The neoplastic cell lines exhibited the PA production to quite a large extent. The highest fibrinolytic activity (78%) was found in the case of bladder carcinoma cells T24, while the B-5GT cells from giant cell tumor of bone failed to produce any detectable amount of the PA. The cells from synovial sarcoma and both glioma lines exhibited fibrinolytic activity of about 10% and four sarcoma cell lines over the range 20--50%. Out of 13 normal cell lines tested, 7 were negative or exhibited very low fibrinolysis not exceeding 3% of total radioactivity. Four cell lines derived from kidneys, lungs, intestines, and from mixed embryonic tissues showed a marked fibrinolytic activity of about 10--37%, a slightly elevated fibrinolysis being found in embryonic lung cells LEP and cells from fetal skin tissue only at the presence of dog serum. The fibrinolysis detected in the neoplastic cloned cell populations showed considerable differences in the PA production between individual cell clones isolated from the same parental cell line. Unlike the normal fibroblastic cells B-41FB derived from bone, all neoplastic cell lines tested possess the capability to inhibit embryonic NR cell aggregation significantly. The results suggest the effect not to be dependent upon the PA production.

Animals↗
PubMed1997

A novel human monoclonal antibody rapidly induces homotypic cell aggregation and promotes antibody-secreting activity by human B lymphoblastoid cell line IM-9.

A human monoclonal antibody (mAb), designated mNKES, was generated by fusing B cells isolated from an enlarged cervical lymph node of a patient with a carotid body tumor (CBT), with human myeloma cell line KR-12 (6TG). The reactivity of mNKES was tested by the indirect immunofluorescence method. The antigen defined by mNKES was expressed on Burkitt's lymphoma cell lines Raji, Daudi, and Ramos and on B lymphoblastoid cell line IM-9. In addition, mNKES reacted with T cells stimulated with recombinant interleukin-2 (rIL-2) obtained from normal healthy donors. However, mNKES did not react with normal resting human T, B, or adherent cells (monocytes/macrophages). When the reactivity of mNKES and mouse mAbs recognizing the human adhesion-associated antigen (CD10, CD11a, CD11b, CD11c, CD14, CD16, CD18, CD23, CD28, CD29, CD31, CD43, CD44, CD45RA, CD50, CD54, CD58, CD80, CD102, CD106, and HLA class I, and HLA class II antigen) with various cell lines was compared, mNKES reactivity was found to be unique, not resembling that of any of these mouse mAbs. Interestingly, mNKES specifically and rapidly (within 2 hr) induced homotypic cell aggregation of IM-9 cells. This mNKES-induced cell aggregation was completely blocked by the addition of EDTA and when incubated at 4 degrees C. The mAbs reactive with CD11a/CD18 (leukocyte function-associated antigen-1; LFA-1) and CD54 (intercellular adhesion molecule-1; ICAM-1) completely blocked the IM-9 cell aggregation induced by mNKES, and induction of IM-9 cell aggregation by mNKES was significantly blocked in the presence of the protein kinase C inhibitors sphingosine and H-7 and completely blocked by cytochalasin B and cytochalasin D, which inhibit microfilament formation. Regarding biological function, IM-9 cells bearing surface IgG (sIgG) effectively promoted IgG-secreting activity underlying the homotypic cell aggregation induced by mNKES. The surface antigen recognized by mNKES has a molecular size of about 55 kDa, as determined by immunoblotting analysis. These findings indicate that mNKES recognizes a novel adhesion-associated antigen distinct from any previously reported adhesion-associated antigens in terms of pattern of cellular distribution and biological function and that mNKES is the first human mAb found that rapidly induces homotypic cell aggregation and effectively promotes the IgG-secreting activity of human B lymphoblastoid cell line IM-9.

Adolescent↗
PubMed1982

Teratocarcinoma cell adhesion: identification of a cell-surface protein involved in calcium-dependent cell aggregation.

Teratocarcinoma cells have a Ca2+-dependent cell-cell adhesion site (t-CDS) that is unique in being inactivated with trypsin in the absence of CA2+ but not in the presence of Ca2+. Fab fragments of antibodies raised against teratocarcinoma F9 cells dissociated by treatment with trypsin and calcium (anti-TC-F9) inhibit the aggregation of teratocarcinoma cells mediated by t-CDS. This inhibitory effect of Fab is removed when anti-TC-F9 is absorbed with F9 cells treated with trypsin and calcium (TC-F9), but not when it is absorbed with F9 cells treated with trypsin and EGTA (TE-F9). Comparisons of cell-surface antigens reactive to anti-TC-F9 in TC-F9 cells with those in TE-F9 cells reveal that only one component, with an approximate molecular weight of 140,000 (p140), is detected specifically on the surface of TC-F9 cells. When TC-F9 cells are retrypsinized in the absence of CA2+, a substance with an approximate molecular weight of 34,000 (p34) is released that can neutralize the aggregation-inhibitory effect of the Fab. This p34 interferes with the immunoprecipitation of p140 with anti-TC-F9, suggesting that p34 is a tryptic fragment of p140. Anti-TC-F9 Fab causes the dissociation of the monolayers of teratocarcinoma cells. This effect is removed by absorption of the Fab with p34 as well as with TC-F9 cells, but not with TE-F9 cells. These results suggest that p140 is essential for the function of t-CDS, and that this is an actual cell-adhesion molecule active in the establishment of monolayers of teratocarcinoma cells.

Antigens, Surface↗
PubMed1995

CD23 molecule acts as a galactose-binding lectin in the cell aggregation of EBV-transformed human B-cell lines.

Epstein-Barr virus (EBV)-transformed human B-cell lines, L-KT9 and DH3 cells express CD23 antigen, and grow in a mixture of single and aggregated cells. The CD23 molecule has high amino acid sequence homology with C-type lectin and recently we have shown that the solubilized CD23 molecule can really interact with galactose residues on glycoproteins. In this study, therefore, we tested whether CD23 antigen on the cell surface really acts as a galactose-binding lectin in the aggregation of these cells. The EBV-transformed cells (L-KT9) were separated into an aggregated-cell-rich fraction and a single-cell-rich fraction. Aggregated cells disaggregated after removal of galactose by beta-galactosidase treatment, whereas single cells made large aggregation on sialidase treatment, and this aggregation was inhibited in the presence of asialo-fetuin. On the other hand, naturally aggregated cells become single cells with anti-CD23 monoclonal antibody (mAB) as well as the soluble form of CD23, but not with anti-CD21 mAB. In addition, L-KT9 and DH3 cells bound to asialo-fetuin-coupled Sepharose (ASF-Sepharose) and this binding was significantly inhibited by pre-treatment of cells with anti-CD23, but not with anti-CD21 or other anti-adhesion molecules. From these results, we conclude that the naturally aggregated state of EBV-transformed cells occurs mainly through the interaction of CD23 as a lectin molecule and galactose residues as its ligand.

Antibodies, Monoclonal↗
PubMed1982

Cell-surface discoidin in aggregating cells of Dictyostelium discoideum.

Both discoidin I and discoidin II have been detected on the surface of aggregating (10 h developmental stage) cells of Dictyostelium discoideum NC4 by radioiodination of the cell-surface followed by immunoprecipitation and sodium dodecyl sulphate/polyacrylamide-gel-electrophoretic analysis. Approx. 92% of cell-surface discoidin I and 72% of cell-surface discoidin II can be eluted with 0.5 M-galactose, showing that most of each endogenous lectin is not present as integral membrane protein but rather is bound to cell-surface discoidin receptors. Two-dimensional polyacrylamide-gel-electrophoretic analysis of discoidin I suggests that the native tetramer may be a hetero-multimer composed of both Ia and Ib subunits. Cell-surface discoidin I also contains both types of subunit, but it is not clear whether both subunits have corresponding cell-surface receptors.

Carrier Proteins↗