Single Cell Adhesion Research Articles

Alteration of laminin production in small-cell lung carcinoma: possible correlation with the absence of the basement membrane.

Basement membranes are frequently absent in small-cell lung cancer (SCLC). To study this phenomenon, the production of laminin by SCLC cells, both in vitro and in vivo, has been investigated and compared with the laminin production by lung carcinomas of other histotypes (non-SCLC, NSCLC). Immunoradiometric and immunoperoxidase tests, respectively, carried out on culture supernatants and cells using antilaminin rabbit antiserum, revealed that in 1 (H446) out of 8 SCLC cell lines tested and in the NSCLC line Calu3, laminin was detectable both in the culture medium and in the cytoplasm of the cells. After treatment of an SCLC-negative cell line (N592) with monensin, a molecule which inhibits protein secretion, laminin became detectable in the cytoplasm. Similar results were obtained by FACS analysis on cells permeabilized with saponin. Northern analysis indicated that the laminin B1 gene was transcribed. The level of mRNA for the B1 laminin subunit in the N592 cells was twice and 4 times higher than that found in the laminin-secreting Calu3 and H446 cell lines. The production of laminin in SCLC and NSCLC surgically resected samples using immunoperoxidase staining of cryostatic sections was also investigated. The results indicate that 85% of the NSCLC cases tested showed diffuse staining in the cytoplasm of the tumor cells and strong staining at the basement membrane level, whereas a similar staining was only found in 15% of the SCLC cases tested. The treatment of SCLC cells with differentiating agents in vitro has been shown to induce the adhesion of these cells. In fact, n-butyric acid induced the disaggregation of floating-clump cells and single-cell adhesion in the N592 line, whereas after treatment with retinoids the clumps of the N592 cells were still present, but 30% of these were found to adhere to the plate. However, no increase in the laminin production was found in the cytoplasmic or culture medium under these conditions.

Single cell mobility and adhesion monitoring using extracellular electrodes

Cell attachment and activity on planar electrodes can be observed in real time by continuously monitoring the electrode impedance. The application of a low frequency a.c. field affects neither the electrode properties nor cell growth. The tightness of the cell/electrode junction can be quantified, and has been shown to be dependent on both cell type and electrode surface. Studies have been carried out on both large cell populations, and the single cell/microelectrode interface.

Neural cell adhesion molecules influence second messenger systems

We have investigated the influence of the neural cell adhesion molecules L1 and N-CAM on second messenger systems using a PC12 rat pheochromocytoma cell line as a model and triggering cell surface receptors by specific antibody binding. Antibodies directed against L1 and N-CAM, but not against other cell surface components, reduce intracellular levels of the inositol phosphates IP 2 and IP 3, while intracellular levels of CAMP are unaffected. Antibodies against L1 and N-CAM also reduce intracellular pH and increase intracellular Ca 2+ by opening Ca 2+ channels in a pertussis toxin-inhibi-table manner, suggesting the involvement of a G protein in the signal transduction process. Cross-linking of the adhesion molecules on the surface membrane is not required for the effects to occur. Furthermore, adhesion of single PC12 cells to each other elicits effects on intracellular pH and Ca 2+ similar to those seen after application, underscoring the physiological significance of the observed changes.

Major histocompatibility complex haplotypes and the cell physiology of peptide hormones

Speculations about the function of the major histocompatibility complex (MHC) have ranged widely over the years. Though the immune functions of the MHC have always been foremost in such speculations, there has always been a background of ideas and experiments about other functions of the complex [ 1]. While some associations of MHC and function are due to products of genes linked to the traditional MHC genes, most of the data on MHC/functional associations cannot be attributed to unknown genes, and, rather, must be explained in terms of unknown functions of known MHC gene products. The speculative basis for these unknown functions rests with a view that the products of the MHC complex evolved from primitive general systems for at the cell surface. This position was taken by Bodmer [2], Ohno [3], and Edelman [4] and, discussing the interactions of colonial tunicates, by Burnett [5] and by Scolfield and co-workers [6], by Dausset and Contu [7], and by Snell [8]. Their speculations on MHC origin appear to be better founded in truth today than they did at their first publication, because the sequence homologies between MHC antigens and a number of other proteins comprising the immunoglobulin superfamily suggest a common origin of the genes for all of these proteins, from an ancestral gene specifying a small membrane protein [9]. General properties then may be postulated as basic properties of MHC antigens. How readily can we detect such properties? A general approach to testing MHC dependence of cell phenomena has been through systems in which some aspects of can be quantitated. In such experiments, from our laboratory as well as from others, the assumption is made that while MHC antigens may modify or modulate recognition, they cannot act to abolish a specific system or to create a new, qualitatively distinct system. Thus all of the work in the area of nonimmune recognition has been on the quantitation of specific events such as cell-to-cell adhesion or the binding of hormones to specific receptors and subsequent cellular responses. Another good example of such work, on drug binding to cell surfaces, is presented by van Rood and co-workers in this volume [10]. Experiments on cell adhesion involve complicated multistage systems, but may be quantitated in vitro by measuring either the rate of single cell adhesion to

Qualitative and quantitative study of the growth and cell surface properties of Huntington's disease fibroblasts and age-matched controls

Different growth-and cell surface properties of cells grown from skin biopsy samples from 25 Huntington's chorea patients, 22 at risk patients, and agematched controls were examined in a blind study. The number of explants obtained from each biopsy was carefully controlled. The nature (epithelial or fibroblastic) of the initial outgrowth was scored on all explants and the mean number of cells obtained from each explant after 3 weeks in culture was determined after trypsinization. During the next 15 passages, various parameters characterizing cell growth were studied. Maximal cell densities and growth rates were examined using a standard plating density of cells at each passage. These growth properties were also examined in three media: DME-NCS, DME-FCS, and Ham's F10 fetal calf serum (FCS). In addition, the effects of high temperature (40°C) and the addition of insulin to the medium on the growth and protein content of the cells was examined. These results, containing 152 measurements on 81 cases, were examined using a phased multivariate analysis. Blind cluster analysis showed that the clusters were nonrandomly determined. Factor analysis indicated the initial growth parameters to be among the most discriminating. Discriminant analysis, however, did not prove to be of any diagnostic use, since the external factors masked any possible genetic difference. Two possible sources of bias were identified: the size of the biopsy and the type of culture medium. The cell surface properties of HD and control fibroblasts were further investigated using two different techniques. The adhesion of single HD cells to either HD cell layers or normal cell layers revealed no significant differences. Intradermal immunization of rabbits with whole fibroblasts resulted, with both cell lines, in a polyspecific antiserum containing antibodies directed against a number of surface components. When HD and control fibroblasts were compared with the two antisera, no qualitative or quantitative differences in the precipitation patterns obtained using crossed immunoelectrophoresis, (CIE) were found. Our investigations did not allow us to discriminate HD cultures from controls by any of the qualitative and quantitative parameters tested.

A quantitative assay for intercellular adhesion.

Intercellular adhesion is measured by a new method based on determination of the rates of attachment of single cells to confluent cell monolayers. The procedure is simple, rapid, and reproducible. Specific and nonspecific intercellular adhesions can be quantitated and distinguished from each other, and from the adhesion to glass (or plastic). The rate of adhesion of single cells to the monolayer is characteristic of more than 80% of the single-cell population. This method, therefore, provides a means for study of the molecular basis of intercellular adhesion.

Chapter 6 Toward A Molecular Explanation for Specific Cell Adhesion

Publisher Summary This chapter reviews the work directed at understanding the nature of chemical and molecular mechanisms involved in the formation of specific associations between embryonic cells. The studies summarized in this chapter provides convincing evidence that specific cellular adhesion in sponge and vertebrate cells is mediated by specific macromolecular constituents at the cell periphery. The preparation of such constituents opens to experimentation their molecular nature, organization at the cell periphery and role in morphogenesis. The aggregation of embryonic vertebrate cells can be separated into two phases: the adhesion of single cells to one another immediately following tryptic dissociation, and the subsequent adhesion of these clusters into tightly packed aggregates with a definite histological structure. The initial adhesion of single embryonic cells freshly dissociated by trypsin is nonspecific and insensitive to inhibitors of macromolecular synthesis. This phase in the sequence of reaggregation most probably reflects the modification or destruction of cell surface components during tissue dissociation by the enzyme. The second phase in the reaggregation of vertebrate cells is sensitive to inhibition of macromolecular synthesis.