Biomedical subjects

C Capo

Publications and source records attributed to C Capo.

At least 91 records · Page 5Linked to original sources

PubMed1987

Use of cell contour analysis to evaluate the affinity between macrophages and glutaraldehyde-treated erythrocytes.

Recently, several authors evaluated the affinity between lipid bilayers or erythrocyte membranes by analyzing the deformation of cells or vesicles they brought into close contact using micromanipulators. In the present report, we extend this approach in a study of the adhesive properties of rough nucleated cells. Rat peritoneal macrophages were made to bind human red cells modified with glutaraldehyde or glutaraldehyde and polylysine. Conjugates were examined with electron microscopy, and photomicrographs were digitized for quantification of cell surface roughness in and out of adhesion areas. Also, macrophages were subjected to micropipette aspiration to find a relationship between apparent surface tension and area increase. Assuming that this increase was a direct consequence of a smoothing of the cell surface on the submicrometer scale, the actual affinity between macrophages and erythrocytes was estimated. The obtained values ranged between 8.4 X 10(-5) and 18.2 X 10(-5) J/m2. It is concluded that cell surface roughness may be an important parameter of cell adhesion and perhaps deformation. This is made amenable to experimental study by the present approach.

Aldehydes↗

PubMed1987

Study of CTL and LAK contacts to target cells after treatment with mitomycin C and adriamycin.

We tried to understand the role of Mitomycin C and Adriamycin in the increased killing of target cells by Cytotoxic T lymphocytes (CTL) and lymphokine activated killers (LAK). For this purpose, we used an objective method allowing quantitative evaluation of the roughness of cell contours on electron micrographs. We compared the folding of the membranes of LAK and CTL as well as conjugated targets exposed to different treatments. We demonstrated first that CTL and LAK displayed similar morphological patterns: the killer cells were more villous than targets in the free areas, and second that the former cells exhibited significant smoothing on the areas of contact with these targets. These results suggest that the binding process (as distinct from the recognition step) is dependent on killer properties which are the same in CTL, LAK and probably NK cells.

Animals↗

PubMed1987

[Physiopathology of the mechanism of activation of neutrophils: a future pathway?].

Numerous agonists such as chemotactic factors, phorbol esters, calcium ionophores, arachidonic acid or particles induce a cascade of events associated to oxygen reduction, the oxidative burst, in phagocytes and specially in neutrophils. Diverse transductional pathways involved in the oxidative burst were described. Moreover, various pathologies of the transductional pathways in different cell systems were recently observed. We think that the study of neutrophils constitutes first an excellent model of Cell Biology and second a putative model of the physiopathology of the transductional pathways.

Acute Disease↗

PubMed1986

Primary structure of a cationic Cu,Zn superoxide dismutase. The sheep enzyme.

The complete amino acid sequence of Cu,Zn superoxide dismutase from sheep erythrocytes has been determined. The sequence is very similar to that of the bovine enzyme, having the same number of residues (151) and only two substitutions in the 'hypervariable' region (residues 17-30). The 5 overall substitutions confer a positive charge on the sheep enzyme at neutral pH (pI approximately equal to 8). This charge is localized outside the active site region. The catalytic efficiency of the sheep enzyme is 15% less than that of the cow enzyme, confirming the hypothesis that the enzyme activity is related to the concentration of positive surface charge near the active site channel.

Amino Acid Sequence↗

PubMed1986

Quantification of cell surface roughness; a method for studying cell mechanical and adhesive properties.

The presence on the surface of nucleated cells of a variety of asperities of different size and shape plays a prominent role in cell-cell and cell-substrate interaction. Also, the organization of these asperities is directly related to cellular cytoskeletal elements. In the present report, we describe a simple and objective method of studying electron micrographs to quantify the roughness of cell contours. Constant-length segments of cell boundaries are compared to reference circular segments with common extremities and enclosing the same area. This procedure was performed with a digitizer connected to a microcomputer, and it was used to analyse model contours or electron micrographs of (i) target tumour cells bound by cytotoxic T lymphocytes and (ii) thymocytes sticking to concanavalin A-coated surfaces. It is shown that this method allows precise quantification of cell deformation in adhesive zones, which may allow absolute evaluation of adhesive stimuli.

Animals↗

PubMed1986

Self-limitation of the oxidative burst of rat polymorphonuclear leukocytes.

The oxidative response of rat polymorphonuclear leukocytes stimulated by phorbol myristate acetate and N-formyl-methionyl-leucyl-phenylalanine was studied. Ferricytochrome reduction and peroxidase-catalyzed decrease of scopoletin fluorescence were used to monitor O-2 and H2O2 release in the extracellular medium. Oxygen consumption was also measured in some experiments. Decrease of chlortetracyclin fluorescence after stimulation of dye-loaded cells was used to study an early step of cell stimulation. Finally, a possible relationship between cell responses and the medium redox potential was explored. Three major conclusions were obtained: Ferricytochrome reduction is dependent on the total cytochrome concentration, and a simple mathematical model allows a tentative estimate of total superoxide anion production by stimulated cells. Increasing cell concentration results in a decrease of individual cell response, and this may be accounted for by a direct inhibition of cell-released hydrogen peroxide on the reactivity of leukocytes. Further, H2O2 may be shown to inhibit an early step of cell response. The solution redox potential does not influence cell reactivity, since it may be dramatically decreased without inhibiting cell response.

Animals↗

PubMed1986

Determination of binding strength and kinetics of binding initiation. A model study made on the adhesive properties of P388D1 macrophage-like cells.

The adhesive properties of the mouse P388D1 macrophage-like line were explored. Cells were deposited in glass capillary tubes, and the kinetics of adhesion and spreading were studied. Binding involved the cell metabolism since it was decreased by cold, azide, or a divalent cation chelator. Glass-adherent cells were subjected to calibrated laminar shear flows with a highly viscous dextran solution. A tangential force of about 5 X 10(-3) dyn/cell was required to achieve substantial detachment. The duration of application of the shearing force strongly influenced cell-substrate separation when this was varied from 1-10 s. Further, this treatment resulted in marked cell deformation, with the appearance of an elongated shape. Hence, cell-substrate separation is a progressive process, and binding strength is expected to be influenced by cell deformability. The minimum time required for adhesion was also investigated by making cells adhere under flow conditions. The maximum flow rate compatible with adhesion was about 1000-fold lower than that required to detach glass-bound cells. A simple model was devised to provide a quantitative interpretation for the experimental results of kinetic studies. It is concluded that cell-to-glass adhesion required a cell-substrate contact longer than a few seconds. This first step of adhesion was rapidly followed by a large (about 1000-fold) increase of adhesion strength. It is therefore emphasized that adhesion is heavily dependent on the duration of cell-to-cell encounter, as well as the force used to remove so-called unbound cells.

Animals↗

PubMed1986

[Role of phagocytic cells in rheumatoid polyarthritis].

Three groups of subjects were selected for this study. Patients suffering from rheumatoid arthritis (RA) diagnosed according to the criteria of the ARA (mean: 6 criteria) and treated with gold salts. Control subjects treated with one type of non-steroidal anti-inflammatory agent (diclofenac). Healthy subjects receiving no treatment. The granulocytes and monocytes in the peripheral blood were tested separately for the ingestion of 3 types of particles and for the stimulation of the production of the superoxide anion. In the patients with rheumatoid arthritis, all of the phagocytic cells had a normal phagocytic response and a normal superoxide anion production. The serum of the patients did not inhibit the activity of these cells. Diclofenac did not act on phagocytosis or on the oxidative activity of the control cells. It is therefore logical to consider that the phagocytic cells are involved in RA via other mechanisms of action.

Adolescent↗

PubMed1985

Study of cell deformability by a simple method.

Cell deformability plays an important role in many immunological processes, such as phagocyte chemotaxis and endocytosis. The most widely used method of assay consists in aspirating cells into glass micropipettes and measuring the length of the protrusion induced by a given pressure, or the minimum pressure required to drive cells into the micropipette. This procedure requires specialized equipment and delicate manipulation. The present report describes a simpler procedure: cells are centrifuged in petri dishes floating on a water cushion, then fixed and coated with 0.8 micron diameter latex beads, which allows rapid and accurate determination of their height. This method is compared with the micropipette technique by studying lymphocyte and macrophage-like cell lines in physiological medium and in the presence of a divalent cation chelator or a microfilament inhibitor. In addition to simplicity, the main advantages of this technique are that (i) many cells may be examined within a reasonable period of time, which allows testing of heterogeneous cell populations, and (ii) unexpectedly, centrifugation was quite harmless under our experimental conditions, since it did not impair cell proliferative ability nor phagocytic ability. It is concluded that the method may be used in clinical laboratories to explore phagocyte dysfunctions, as well as in experimental studies.

Animals↗

PubMed1985

Monocytes and granulocytes in rheumatoid arthritis (RA): phagocytic activity and superoxide anion production.

It is suggested by many tests that phagocytic cells were implied in inflammation which occurred during rheumatoid arthritis (RA). Further, three subject populations were selected for this study: Rheumatoid arthritis patients diagnosed according to American Rheumatism Association criteria (ARA mean = 6) and treated with gold compounds. Control subjects treated with the same non-steroidal anti-inflammatory drug (NSAID), diclofenac (75 mg per day). Normal subjects without disease or treatment. Blood granulocytes and monocytes were separately tested for ingestion of three different particle species (opsonized zymosan, immunoglobulin G sheep red cells, glutaraldehyde-treated sheep red cells) and stimulation of superoxide anion production by these particles. All phagocytic cells in RA patients have normal phagocytic response and superoxide anion production. Autologous serum does not inhibit the activity of these cells. In addition the NSAID (diclofenac) does not act upon phagocytosis and oxidative burst of control cells.

Adolescent↗

PubMed1985

T-cell-fibroblast hybridoma deformability and concanavalin A-induced agglutination.

Cell adhesion influences many important immunological functions such as phagocytosis or T-cell-mediated cytotoxicity. Previous work suggested that the ease of inducing intercellular bonds (i.e. binding efficiency) and the difficulty to separate bound cells with mechanical forces (i.e. binding strength) might be parameters of different significances. The present report describes a study made on two T-lymphocyte/polyoma virus transformed fibroblast hybrid subclones (3D1c and 3D1n) with markedly different adhesive properties: indeed, 3D1c cells were at the same time more readily agglutinated with concanavalin A and more easily disagglutinated than 3D1n. In order to understand these differences, a systematic comparison of various properties of 3D1c and 3D1n cells was undertaken. The following parameters were studied: surface density of concanavalin A binding sites, surface electrostatic charge, hydrophobicity, fluorescence polarization measured on individual cells, and ability to spread on a flat substrate in response to volume or surface forces. It is concluded that cell deformability and/or spreading ability might be an important determinant of binding strength, but the factors governing binding efficiency remained incompletely understood. It is suggested that the methods described in the present report might help understanding differences between various tumor cell lines with different malignant potential.

Animals↗

PubMed1984

Nonspecific cell surface properties: contact angle of water on dried cell monolayers.

Measuring contact angle of water on dried cell or bacterium monolayers allowed van Oss (1) and others (2) to find a correlation between particle hydrophobicity and ingestion by phagocytic cells. The present study was undertaken to understand what was actually assayed with this method. Monolayers were prepared with different cell types at different densities, and they were dried under atmospheres with varying humidity before being studied with scanning electron microscopy and contact angle techniques. It is concluded that a) contact angles are independent of the cell density and substrate structure when more than 30% of the substrate area is covered with cells. b) Initial cell shape should not influence contact angle. c) Contact angles are markedly dependent on the nature of tested cells. d) Contact angles are substantially influenced by the cell drying procedure. e) A very small fraction of the energies we measured would be sufficient to account for cell-cell interactions. Hence these might play a role in some situations of biological interest.

Animals↗

PubMed1983

Dimethylsulphoxide induction of the murine macrophage-like line P388D1: change of phagocytic ability and cell surface properties.

The murine macrophage-like cell line P388D1 ingests immunoglobulin-coated sheep red cells (IgG-SRC) poorly, but after 3 days incubation in the presence of 1.5% dimethyl sulphoxide (DMSO), it becomes highly phagocytic. We used this model to correlate triggering of phagocytosis with some surface properties of P388D1 cells, possibly involved in recognition or engulfment of particles. The accessibility of Fc receptors on the cell membranes did not seem to be affected by DMSO treatment since the binding of IgG-SRC to cells was the same before and after treatment with DMSO. A technique allowing quantitative determination of the stability of cell-particle binding showed that binding strength was not the only essential factor in triggering ingestion. Hydrophobicity and surface charge were postulated to play a role in phagocytic recognition. No change in hydrophobicity, as assayed by contact-angle measurement, and in net surface charge evaluated by cell electrophoresis, was observed for normal and DMSO-treated P388D1 cells. On the other hand, the fluorescence polarization of a membrane lipophilic probe (1,6-diphenyl-1,3,5-hexatriene) was significantly (P less than 0.01) decreased when P388D1 cells were treated with DMSO. Since the effect of DMSO on P388D1 function was delayed, our results were consistent with the view that enhancement of phagocytosis might be a consequence of some modification of membrane dynamics, due to changes in lipid composition.

Animals↗

PubMed1983

Dissociation between phagocytosis and phagosome-lysosome fusion.

The acridine orange technique was used to explore phagosome-lysosome fusion (P-L fusion) in thioglycollate-elicited rat peritoneal macrophages. Sheep red blood cells were coated with IgG or IgM plus complement, or treated with neuraminidase, tannic acid or glutaraldehyde; then both their capacity to be ingested by macrophages and their ability to induce P-L fusion after ingestion were assayed. Their capacity to be engulfed by macrophages was similar, but glutaraldehyde-treated erythrocytes were far more efficient than the other particles in triggering P-L fusion. Hence, both processes must be driven by different mechanisms. No correlation was found between the surface charge of test particles (as assayed by cell electrophoresis) and their ability to trigger phagocytosis or P-L fusion. However, glutaraldehyde-treated erythrocytes were found to be more hydrophobic than the other particles, as previously reported. Hence, particle hydrophobicity might favor P-L fusion. The implication of these findings are discussed.

Animals↗

PubMed1982

Adhesion, phagocytosis and cell surface energy. The binding of fixed human erythrocytes to rat macrophages and polymethylpentene.

Fixed human erythrocytes were used as model particles for the study of adhesion and phagocytosis by rat peritoneal macrophages. Erythrocytes were fixed with various concentrations of glutaraldehyde or tannic acid, or were treated with neuraminidase. Adhesion and phagocytosis of these cells were measured. In addition, the surface energy of these erythrocytes and macrophages was estimated by the contact angle technique. Free energies of adhesion, based on the cell surface energies, were correlated with both adhesion and phagocytosis.

Animals↗

PubMed1982

Concanavalin-A-mediated thymocyte agglutination: a model for a quantitative study of cell adhesion.

This report describes a quantitative study of the agglutination of rat thymocytes with concanavalin A (ConA). The probability that two ConA-coated cells remain bound after centrifugation was determined over a wide range of lectin concentrations. The minimal force required to separate agglutinated cells and the number of ConA molecules bound per cell were measured in similar experimental conditions. Agglutinated cells were examined by electron microscopy to estimate the area of membrane involved in adhesion. The dependence of agglutination on cell metabolism was studied: cold (4 degrees C), sodium azide (15 mM) and cytochalasin B (10 micrograms/ml) inhibited thymocyte adhesion. The importance of lateral movements of ConA molecules was assayed by measuring the adhesion of ConA-coated glutaraldehyde-fixed thymocytes to untreated cells: substantial binding occurred, but at a reduced level relative to untreated cells. A mathematical analysis of experimental data allowed the following conclusions. (1) At least 10(3) ConA bonds were involved in cross-linking two bound cells, which required the lectin molecules to be concentrated in the binding area, at least when low ConA concentrations (0.5 microgram/ml or less) were used. (2) The dependence of the binding probability on lectin concentration was fairly linear when the latter was small, which implied that the limiting step in cell-cell adhesion was the formation of a bond between a single ConA molecule and a ligand on the other cell. (3) The mean intercellular-contact time for the formation of this first bond was about 10 S for high concentrations of ligand (8 micrograms/ml). It was possible to fit the above data into a physically consistent quantitative model of cell adhesion.

Animals↗

PubMed1982

Nonspecific binding by macrophages: different modulation of adhesive properties of rat peritoneal cells after plating on a glass or a plastic surface.

Rat peritoneal cells can bind immunoglobulin-coated sheep red cells (IGSRC), glutaraldehyde-treated sheep red cells (GSPC), Leishmania, latex beads, and autologous thymocytes in a serum-deprived medium. When macrophages were plated on plastic Petri dishes, their ability to bind thymocytes and GSRC was decreased ninefold and fourfold, respectively, as compared to macrophages adhering to glass coverslips. However, the binding of IGSRC, Leishmania, and latex was not significantly dependent on the nature of the surface where peritoneal cells were plated. Sequential adhesion to plastic and glass did not reveal any cell subpopulation adhering only to one substrate. The ability of plastic-bound macrophages to bind thymocytes or GSRC was not restored after a 16 hr culture. Hence, some cell properties may be strikingly dependent on the nature of the surface where these cells are plated.

Animals↗

PubMed1981

Non-specific binding by macrophages: evaluation of the influence of medium-range electrostatic repulsion and short-range hydrophobic interaction.

Rat peritoneal macrophages can bind glutaraldehyde-treated human rat cells (GHRC), but not normal human red cells (HRC). When the surface charge of HRC was reduced by treating them with neuraminidase (to remove some negative sialic acid residues) or coating them with polylysine (a positively charged polymer), no substantial binding to macrophages was obtained. However, a similar reduction of the surface charge of GHRC resulted in sevenfold enhancement of their binding of macrophages. All erythrocyte batches were tested with a phase partition technique: only glutaraldehyde-treated cells were found hydrophobic. It is concluded that: i) Short range hydrophobic interactions are responsible for macrophage-GSRC adhesion. ii) Medium range electrostatic repulsion may substantially hamper any close approach of the macrophage and particle surface in physiological conditions.

Animals↗