Role of hydrophobicity in adhesion of wild yeast isolated from the ultrafiltration membranes of an apple juice processing plant

The role of cell surface hydrophobicity in the adhesion to stainless steel (SS) of 11 wild yeast strains isolated from the ultrafiltration membranes of an apple juice processing plant was investigated. The isolated yeasts belonged to four species: Candida krusei (5 isolates), Candida tropicalis (2 isolates), Kluyveromyces marxianus (3 isolates) and Rhodotorula mucilaginosa (1 isolate). Surface hydrophobicity was measured by the microbial adhesion to solvents method. Yeast cells and surfaces were incubated in apple juice and temporal measurements of the numbers of adherent cells were made. Ten isolates showed moderate to high hydrophobicity and 1 strain was hydrophilic. The hydrophobicity expressed by the yeast surfaces correlated positively with the rate of adhesion of each strain. These results indicated that cell surface hydrophobicity governs the initial attachment of the studied yeast strains to SS surfaces common to apple juice processing plants.     

Studies on cell adhesion and recognition. III. The occurrence of α-mannosidase at the fibroblast cell surface, and its possible role in cell recognition

The occurrence of α-mannosidase activity at the surface of hamster embryo (NIL) fibroblasts is indicated by the following findings: (a) When NIL cells were incubated on the glass surfaces on which ovalbumin glycopeptides were covalently linked, a rapid release of free mannose from ovalbumin glycopeptides was observed as evidenced by analysis on gas chromatography/mass spectrometry. (b) Cell suspensions as well as intact cell monolayers hydrolyzed rapidly p-nitrophenyl-α-D-mannoside, and the time-course of the hydrolytic cleavage was linear from the moment of mixing of the substrate with the cells. The hydrolysis of the nitrophenyl glycosides of β-D-mannose, α-D-galactose, β-D-galactose, α-L-fucose, β-D-glucose, β-D-N-acetylgalactosamine and β-D-N-acetylglucosamine was negligible or more than ten times lower as compared with the hydolysis of α-D-mannoside. (c) No released or secreted activity of mannosidase could be detected under the conditions used. (d) Studies using known proportions of broken cells in the incubation mixture indicated that more than 90 percent of the mannosidase activity measured was attributable to intact cells and not to broken cells or cell fragments. (e) Hydrolysis of p-nitrophenyl-α-D-mannoside by cell monolayers was inhibited, in the order of decreasing inhibitory activity, by yeast mannan, ovalbumin, α-1,4-L-mannonolactone, α-methylmannoside, and mannose-6-phosphate. High inhibitory activity of the mannan polysaccharide and of ovalbumin favored the presence of the mannosidase activity at the cell surface, as these substrates may not penetrate rapidly into the cells. The following findings indicated that the cell surface mannosidase is mediating the cell adhesion based on the recognition of high-mannose-type glycopeptide: (a) Ovalbumin- coated plastic surfaces strongly promoted attachment and spreading of NIL fibroblasts, whereas the same ovalbumin coat did not promote attachment and spreading of some other cell types (BALB/c 3T3 fibroblasts and freshly prepared rat liver cells). (b) Digestion of ovalbumin with α-mannosidase greatly reduced the adhesion-mediating activity. (c) Cell adhesion to ovalbumin-coated surfaces was strongly inhibited by mannose tetrasaccharides, moderately by α-1,4-L-mannonolactone, and weakly by α- methylmannoside and mannose-6-phosphate. This order of the inhibitory activity for cell attachment is the same as that for the inhibition of mannosidic hydrolysis. The interpretation that the cell surface mannosidase is able to mediate cell adhesion is in agreement with previous studies suggesting that polyvalent glycosidase surfaces can promote cell adhesion to a degree similar to that caused by fibronectin and several lectins by interacting with their cell surface substrate site (the accompanying papers of this series).     

Transfection of cells attached to selected cell based biosensor surfaces

Mammalian cell attachment studies were conducted on a variety of common microchip surfaces for potential use in cell based biosensors. COS-7 cell attachment to Au, Pt or ITO, per unit area was greater than to SiO(2) surfaces. The number of cells that would attach was essentially maximized 3 h after cell seeding. HL-1 cells attached more readily to surfaces precoated with fibronectin, but by 3 h equivalent number of cells had attached independent of fibronectin precoating. Inclusion of serum in media during the initial period of attachment decreased the number of COS-7 cells attached to SiO(2) surfaces, but no dependence on serum was seen for ITO surfaces. The number of cells attached per unit area varied with the composition of the surface. However, no differences were observed in the percentage of cells transfected with a green fluorescent protein gene, or in the level of reporter gene expression over the population of transfected cells on ITO, SiO(2), Pt, Ag, or Au surfaces. Similar FACS analysis of transfected Hep G2 cells revealed lower levels of both transfection efficiency and levels of GFP fluorescence. Hep G2 cells plated on Ag did not remain attached for analysis, but there were no significant differences between tissue culture plastic and the other biosensor surfaces in the percentage of cells transfected. This suggests that, in general, cells will attach to the various conducting and nonconducting biosensor surfaces studied and will provide comparable data in reporter gene expression assays.     

Prevention of pink-pigmented methylotrophic bacteria (Methylohacterium mesophilicum) contamination of plant tissue cultures

Pink-pigmented facultative methylotrophic bacteria (PPFMs) have been found on the surfaces of leaves of most plants tested. We found PPFMs on the leaf surfaces of all 40 plants (38 species) tested and on soybean pods by pressing onto AMS medium with methanol as the sole carbon source. The abundance ranged from 0.5 colony forming unit (cfu) /cm² to 69.4 cfu/cm² on the leaf surfaces. PPFMs were found in homogenized leaf tissues of only 4 of the species after surface disinfestation with 1.05% sodium hypochlorite and were rarely found in cultures initiated from surface disinfested Datura innoxia leaves or inside surface disinfested soybean pods. Of 20 antibiotics tested for PPFM growth inhibition, rifampicin was the most effective and of seven others which also inhibited PPFM growth, cefotaxime should be the most useful due to the expected low plant cell toxicity. These antibiotics could be used in concert with common surface sterilization procedures to prevent the introduction or to eliminate PPFM bacteria in tissue cultures. Thus, while PPFMs are present on the surfaces of most plant tissues, surface disinfestation alone can effectively remove them so that uncontaminated tissue cultures can be initiated in most cases.     

Studies on cell adhesion and recognition. I. Extent and specificity of cell adhesion triggered by carbohydrate-reactive proteins (glycosidases and lectins) and by fibronectin

The extent and the specificity of the initial cell attachment induced by various proteins coated on plastic surfaces have been studied with the following results: (a) Cell adhesion on the surfaces coated with sialidase and beta-galactosidase was as strong as on concanavalin A and limulus lectin-coated surfaces and the reactions were strongly inhibited by glycosidase inhibitors or by competitive substrates. The adhesion on sialidase was inhibited by 2-deoxy-2,3-dehydro-N- acetylneuraminic acid and by polysialoganglioside (GT1b) at low concentration (0.05-0.1 mM). The cell adhesion on beta-galactosidase coat was inhibited by 1,4-D-galactonolactone and beta-methylgalactoside but not by alpha-methylgalactoside. Thus, the initiation of cell adhesion on glycosidase surfaces could be mediated through the interactions of the specific binding sites of the enzyme surface with the cell surface substrates under physiological conditions. (b) Cell adhesion on various lectins could be blocked by various competing monosaccharides at the concentrations similar to the inhibitory concentrations for binding of lectins from solution to the cells. (c) Cell adhesion on fibronectin surfaces as well as on gelatin-coated surfaces was equally inhibited by GT1b at relatively high concentrations (0.25-0.5 mM). Lower concentrations of GT1b (0.05-0.1 mM) inhibited the cell adhesion on surfaces of Limulus lectin and sialidase. It is suggested that the cell adhesion mediated by fibronectin is based on yet unknown interactions in contrast to a specific cell adhesion through glycosidases and lectins.     

Differences in Caco-2 cell attachment, migration on collagen and fibronectin coated polyelectrolyte surfaces

Metastasis mechanisms depend on cell metabolism changes, migration and adhesion to different tissues. To understand their choice of interaction site, the tumoral cell adhesion to model surfaces was studied. The response of Caco-2 tumoral cells cultured on polyelectrolyte film-functionalized surfaces with or without adhesion proteins (fibronectin or collagen IV) was analyzed. Using the layer-by- layer method, multilayer films were prepared with cationic poly(allylamine hydrochloride) and anionic poly(sodium 4-styrenesulfonate) polyelectrolytes. Film surface wettability was evaluated. The electrochemical impedance spectroscopy analyses were carried out to control the elaborated surfaces on which Caco-2 tumoral cells were cultured. The cell velocity was studied by video-microscopy and a cell colorimetric assay (WST-1) was used to quantify cell viability. The film surface parameters as well as the protein nature and localization in the film were found to modulate cell response. Results demonstrated that the cancer cell motility and proliferation were higher when cultured onto pure collagen located above the polyelectrolyte film and that the reverse surprisingly was observed when proteins were inserted into the polyelectrolyte film. Data also showed that cell motility was correlated with a high charge transfer resistance (Rct) and a low surface free energy (SFE) polar component (electron donor character). This relationship was valid only for pure external proteins. Thus, fibronectin exhibited a low Rct and a high SFE polar component, which decreased cell motility and proliferation.     

Distribution of sialoglycoconjugates on acinar cells of the mammalian pancreas

Using the sialic acid-specific lectin, limulin (LPA; from Limulus polyphemus hemolymph), the distribution and nature of sialoglycoconjugates on the surface of rat pancreatic cells has been investigated. Binding of rhodaminated LPA (Rh-LPA) or horseradish peroxidase-conjugated LPA (HRP-LPA) to fixed-frozen sections of adult rat pancreas resulted in intense linear staining of the apical surface of acinar cells with fainter staining on the basal but not the lateral cell surfaces. LPA binding was specific in that it could be abolished by 1) pretreatment of tissue sections with neuraminidase or periodic acid; 2) competition with sialic acid; and 3) incubation in Ca2+ -free buffers. Pretreatment of sections with proteases abolished LPA binding to the apical surfaces of acinar cells and also enhanced LPA binding to the lateral cell surface. Lipid extraction of sections following protease treatment markedly reduced LPA binding to the acinar cell periphery. These results suggest that LPA binding sites on the acinar cell apical surface may be primarily sialoglycoproteins, while those on the basolateral surfaces may consist in part of gangliosides. Electron microscopy of collagenase-dispersed acini exposed to HRP-LPA confirmed binding of LPA to the basal plasmalemma and, in addition, revealed staining of basal lamina when present. LPA binding to the acinar cell surface was not affected by digestion of tissue sections with hyaluronidase, heparinase, collagenase, or 6 M guanidine-HCl. Control experiments indicated that rat pancreatic secretory proteins contain undetectable amounts of sialoglycoproteins and thus that the apical localization of LPA is not due to adherent secretory proteins. Islets of Langerhans were always uniformly and heavily stained with LPA conjugates; this staining was protease insensitive. Appearance of LPA binding sites was examined on embryonic pancreatic epithelia. At day 15 of gestation, Rh-LPA stained the entire periphery of the epithelial cells, including the lateral cell surface, although more intense staining was already noted on the apical surface. This pattern persisted through day 17 of gestation, but by day 19 an adult staining pattern was observed with loss of staining of the lateral cell surfaces.     

Binding and phagocytosis of fibronectin-coated beads by BHK cells: receptor specificity and dynamics

Studies on the receptor specificity and dynamics involved in fibroblast phagocytosis of latex beads revealed the following: 1) Ligands other than fibronectin such as concanavalin A (ConA) and serum spreading factor, when coated on latex beads, were found to promote phagocytosis of the beads. This indicates that fibroblast phagocytosis, like spreading, is a ligand-receptor mediated phenomenon not specifically requiring fibronectin (pFN); 2) Anti-pFN antibodies were found to inhibit the ability of cells to ingest pFN-coated beads that previously were bound on the cell surfaces. Consequently, binding of beads to the cell surfaces per se is not a sufficient signal to promote ingestion of the beads; 3) Finally, divalent cations protected receptor function necessary for phagocytosis of pFN-coated beads from proteolysis by trypsin, as previously was found for receptors involved in cell attachment and spreading on pFN-coated culture dishes. Recovery experiments carried out with cells whose surface receptors had been destroyed indicated that there was an internal (or cryptic cell surface) pool of receptors that amounted to at least 50% of the receptors normally found on the cell surface. After complete destruction of the cell surface and cryptic pools of receptors, reappearance of receptors required for bead binding and phagocytosis required several hours and did not occur in the absence of new protein synthesis.     

The electrokinetic surface of five enteropathogenicEscherichia coli serogroups

The surface ionogenicity of five enteropathogenicEscherichia coli serogroups (O111:H2, O111:H12, O125:H9, O119:H6, and O26:H11) was investigated by electrokinetical approaches. All of the studied surfaces are negatively charged with their mean values of zeta potential (ZP) varying from −9.0 (O26:H11) to −11.9 mV (O111:H2). The populational behavior of the all bacteria are similar since very high ZP values varying from −26 to −30 mV were obtained in experiments carried out with the slip plane calculated at 6.83 nm from the cell surface. All the surfaces are extremely acidic, because the isoelectrophoretic points are localized at pH values below 3.0. Treatment of the microorganisms with neuraminidase did not alter their surface anionogenicity, while treatment with trypsin or phospholipase C reduced their negative charge.     

Effect of cytochalasins on the surface topography of neoplastic cells in suspension

The effect of cytochalasins B or D on the surface topography of mouse neoplastic fibroblasts of L line (detached from glass by trypsin-EDTA solution) or of its LS subline (adapted to the growth in suspension in vitro), as well as on that of Ehrlich's ascites tumor cells was investigated by screening electron microscopy. Incubation of suspended cells with cytochalasin B (2 micrograms/ml) or cytochalasin D (0.2 microgram/ml) for 30-180 min led to the following changes: (I) progressive decrease of the proportion of the cells with a microvillous surface relief and simultaneous increase in the percentage of the cells with a blebbed microrelief; (2) shortening of the microvilli and decrease of their density on the cell surface; (3) appearance of surface areas with a rough folded relief; (4) formation of very large blebs on the LS or L cell surfaces; (5) unusual "polar" distribution of blebs on Ehrlich's tumor and L cells: the blebs were concentrated in one locus on the cell surface. The data show that normal organization of the actin microfilament system in the cell cortex is necessary for formation of the microvilli but not for the blebs.     

Studies on cell adhesion and recognition. II. The kinetics of cell adhesion and cell spreading on surfaces coated with carbohydrate- reactive proteins (glycosidases and lectins) and fibronectin

The kinetics of cell attachment and cell spreading on the coated surfaces of two classes of carbohydrate-reactive proteins, enzymes and lectins, have been compared with those on fibronectin-coated surfaces with the following results: (a) A remarkable similarity between the kinetics of cell attachment to fibronectin-coated and glycosidase- coated surfaces was found. In contrast, cell attachment kinetics induced by lectin- and galactose oxidase-coated surfaces, in general, were strikingly different from those on fibronectin and glycosidase surfaces. The distinction between fibronectin- or glycosidase- and lectin- or galactose oxidase (an enzyme with lectin-type characteristics)-coated surfaces was further supported by the finding that cytochalasin B and EDTA inhibited cell attachment to fibronectin- and glycosidase-coated surfaces but not lectin-coated surfaces. (b) Fibronectin, if labeled and added to a cell suspension, showed only low or negligible interaction with the cell surface. However, fibronectin absorbed on plastic surfaces showed a high cell-attaching activity. It is assumed that fibronectin coated on plastic surfaces may form polyvalent attachment sites in contrast to its lower valency in aqueous solution. (c) Various inhibitors of cell attachment to both fibronectin- , galactose oxidase-, and lectin-coated surfaces were effective only during the first few minutes of the adhesion assay, after which time the attached cells became insensitive to the inhibitors. It is suggested that the initial specific recognition on either lectin-type or fibronectin-type surfaces is followed by an active cell-dependent attachment process. The primary role of the adhesion surface is to stimulate the cell-dependent attachment response. (d) Cells attached on tetravalent concanavalin A (Con A) spread very rapidly and quantitatively, whereas divalent succinyl Con A and monovalent Con A were effective stimulators of cell attachment but not cell spreading. Cross-linking of succinyl Con A restored the cell spreading activity. Tetravalent Con A surfaces specifically bind soluble glycoproteins, whereas succinyl Con A has a greatly reduced ability to bind the same glycoproteins. These results suggest that cross-linking of cell surface glycoproteins by the multivalent adhesive surface may trigger the cellular reaction leading to cell spreading.     

The relative importance of topography and RGD ligand density for endothelial cell adhesion

The morphology and function of endothelial cells depends on the physical and chemical characteristics of the extracellular environment. Here, we designed silicon surfaces on which topographical features and surface densities of the integrin binding peptide arginine-glycine-aspartic acid (RGD) could be independently controlled. We used these surfaces to investigate the relative importance of the surface chemistry of ligand presentation versus surface topography in endothelial cell adhesion. We compared cell adhesion, spreading and migration on surfaces with nano- to micro-scaled pyramids and average densities of 6×10(2)-6×10(11) RGD/mm(2). We found that fewer cells adhered onto rough than flat surfaces and that the optimal average RGD density for cell adhesion was 6×10(5) RGD/mm(2) on flat surfaces and substrata with nano-scaled roughness. Only on surfaces with micro-scaled pyramids did the topography hinder cell migration and a lower average RGD density was optimal for adhesion. In contrast, cell spreading was greatest on surfaces with 6×10(8) RGD/mm(2) irrespectively of presence of feature and their size. In summary, our data suggest that the size of pyramids predominately control the number of endothelial cells that adhere to the substratum but the average RGD density governs the degree of cell spreading and length of focal adhesion within adherent cells. The data points towards a two-step model of cell adhesion: the initial contact of cells with a substratum may be guided by the topography while the engagement of cell surface receptors is predominately controlled by the surface chemistry.     

Different titanium surfaces modulate the bone phenotype of SaOS-2 osteoblast-like cells

Commercially pure titanium implants presenting a relatively smooth, machined surface or a roughened endosseous surface show a large percentage of clinical success. Surface properties of dental implants seem to affect bone cells response. Implant topography appears to modulate cell growth and differentiation of osteoblasts affecting the bone healing around the titanium implant. The aim of the present study was to examine the effects of 1cm diameter and 1mm thick titanium disks on cellular morphology, adhesion and bone phenotypic expression of human osteoblast-like cells, SaOS-2. SaOS-2 cells were cultured on commercially 1 cm pure titanium disks with three different surface roughness: smooth (S), sandblasted (SB) and titanium plasma sprayed (TPS). Differences in the cellular morphology were found when they were grown on the three different surfaces. An uniform monolayer of cells recovered the S surface, while clusters of multilayered irregularly shaped cells were distributed on the rough SB and TPS surfaces. The adhesion of SaOS-2 cells, as measured after 3h of culture, was not affected by surface roughness. ECM components such as Collagen I (CoI), Fibronectin (FN), Vitronectin (VN) and Tenascin (TN) were secreted and organized only on the SB and TPS surfaces while they remained into the cytoplasm on the S surfaces. Osteopontin and BSP-II were largely detected on the SB and TPS surfaces, while only minimal production was observed on the S ones. These data show that titanium surface roughness affects bone differentiation of osteoblast like-cells, SaOS-2, indicating that surface properties may be able to modulate the osteoblast phenotype. These observations also suggest that the bone healing response around dental implants can be affected by surface topography.     

Fine surface structure of enterotoxemic Escherichia coli O139:K12 strains associated with swine edema disease

The fine structure of the cell surface of seven enterotoxemic Escherichia coli (ETEEC) O139:K12 strains isolated from piglets with edema disease were examined electron microscopically using both the negative-staining method and the freeze-substitution fixation method. Densely packed, fine fibers were observed; they consisted of a capsule layer approximately 25 nm thick around the cell surfaces of strains 107/86, IW-2, ED-3, ED-43, and ED-61, all of which have a capacity to adhere strongly to HEp-2 cells. In contrast, no such structure was observed on the surface of strains RK-O139 or ED-1, both of which adhere only weakly to HEp-2 cells. These results suggest that the capsule structure might be associated with the ability to adhere to HEp-2 cells and, as a result, also potentially play some role in ETEEC infection. Received: 29 April 1996 / Accepted: 13 August 1996     

Directional secretion of prostaglandin F(2alpha) by polarized luminal epithelial cells from pig endometrium

In swine, endometrial prostaglandin F(2alpha) (PGF(2alpha)) is the luteolysin. The capacity of luminal epithelial cells isolated from the endometrium of day 16 cyclic pigs, to secrete PGF(2alpha)500 Omega/cm(2)), they were treated on the apical, basal or both surfaces with 0 or 100 nM oxytocin (OT) in Experiment 1 or phorbol 12-myristate 13-acetate (PMA) in Experiment 2. In the absence of OT or PMA, PGF(2alpha) secretion occurred primarily from the basal surface and was approximately 12-fold greater (P < 0.001) than from the apical surface. Treatment with OT did not stimulate PGF(2alpha) secretion from either surface regardless of which surface was treated. In contrast, PMA increased PGF(2alpha) secretion from both surfaces. Treatment of the apical surface or both surfaces with PMA increased (P < 0.001) PGF(2alpha) secretion similarly from both surfaces. Treatment of only the basal surface with PMA increased (P < 0.01) PGF(2alpha) secretion from both surfaces, but tended (P = 0. 06) to increase its secretion from the basal surface more than from the apical surface. These results indicated that PGF(2alpha) secretion by luminal epithelial cells obtained from cyclic pigs occurs primarily toward a basal direction and is not stimulated by oxytocin. Activation of protein kinase C stimulates directional secretion of PGF(2alpha) from both surfaces of the epithelial cells.     

Localized insertion of new S-layer during growth of Bacillus stearothermophilus strains

Bacillus stearothermophilus strains PV 72 and ATCC 12980 carry a crystalline surface layer (S-layer) with hexagonal (p6) and oblique (p2) symmetry, respectively. Sites of insertions of new subunits into the regular lattice during cell growth have been determined by the indirect fluorescent antibody technique and the protein A/colloidal gold technique.During S-layer growth on both bacillus strains the following common features were noted: 1. shedding of intact S-layer or turnover of individual subunits was not seen; 2. new S-layer was deposited in helically-arranged bands over the cylindrical surface of the cell at a pitch angle related to the orientation of the lattice vectors of the crystalline array; 3. little or no S-layer was inserted into pre-existing S-layer at the poles, and 4. septal regions and, subsequently, newly formed cell poles were covered with new S-layer protein.     

Regulation of mammalian cell growth by autocrine growth factors: analysis of consequences for inoculum cell density effects

Effects of inoculum cell density on mammalian cell growth in culture have been observed in a variety of experimental systems. Although these effects have been attributed generally to medium conditioning by the cells, there has previously been no quantitative theory proposed for this phenomenon based on developments in molecular and cell biology. In this article, we offer such a theory founded on the regulatory action of autocrine growth factors. A particularly relevant example of these is platelet- derived growth factor (PDGF), which is produced by fibroblastic cells in response to stimulation by transforming growth factor beta (TGFbeta), a common serum constituent, and provides a mitogenic signal for the same cells. A simple mathematical model for the production, diffusive transport, and binding of autocrine growth factors to cell surface receptors, coupled to a model for the dependence of cell proliferation on growth factor receptor binding allows prediction of initial cell population growth rate as a function of inoculum cell density. We focus on situations involving anchorage-dependent cell growth, in which the cells are attached to a surface. A number of clear results are obtained, most notably the following: 1) for cells cultured on spherical microcarrier bead surfaces, the inoculum cell density needed to produce a given growth rate is linearly proportional to the bead radius; and 2) all other factors being equal, the inoculum cell density on a unit surface area basis needed to produce a given growth rate is greater for spherical microcarrier surfaces than for flat culture dish surfaces. These two results are consistent with the experimental observations of Hu and coworkers(1,2) for fibroblast growth in minimal medium plus serum. The model also allows elucidation of the influence of other system parameters, both biological and physical, on initial cell proliferation rate and the inoculum cell density dependence.     

Impact of surface energy and roughness on cell distribution and viability

Abstract

The aim of this study was to assess the respective impacts of the surface energy and surface roughness of bare and coated steels on biofouling and sanitisation. Bioadhesion of Staphylococcus aureus CIP 53.154 was studied on two stainless steel surfaces with smooth or specific micro-topography. Two coatings were also studied: silicon oxide (hydrophilic) and polysiloxane (hydrophobic). On smooth surfaces, adhesion was reduced on an apolar coating and cell viability increased with the surface polarity. A specific micro-topography decreased the level of bacterial adhesion on bare surfaces by a factor ten. On this surface, only single adherent cells were observed, contrasting with cells in clusters on smoother surfaces. As a consequence, cell repartition influenced bacterial viability. Most isolated adherent cells were dead whereas cells in clusters were still alive. In addition, the quaternary ammonium chloride used in sanitisation, acted at once both as a tensio-active molecule and a biocide. It only displaced adherent cells but did not remove them.     

Leukocyte cell surface proteinases: regulation of expression, functions, and mechanisms of surface localization

A number of proteinases are expressed on the surface of leukocytes including members of the serine, metallo-, and cysteine proteinase superfamilies. Some proteinases are anchored to the plasma membrane of leukocytes by a transmembrane domain or a glycosyl phosphatidyl inositol (GPI) anchor. Other proteinases bind with high affinity to classical receptors, or with lower affinity to integrins, proteoglycans, or other leukocyte surface molecules. Leukocyte surface levels of proteinases are regulated by: (1) cytokines, chemokines, bacterial products, and growth factors which stimulate synthesis and/or release of proteinases by cells; (2) the availability of surface binding sites for proteinases; and/or (3) internalization or shedding of surface-bound proteinases. The binding of proteinases to leukocyte surfaces serves many functions including: (1) concentrating the activity of proteinases to the immediate pericellular environment; (2) facilitating pro-enzyme activation; (3) increasing proteinase stability and retention in the extracellular space; (4) regulating leukocyte function by proteinases signaling through cell surface binding sites or other surface proteins; and (5) protecting proteinases from inhibition by extracellular proteinase inhibitors. There is strong evidence that membrane-associated proteinases on leukocytes play critical roles in wound healing, inflammation, extracellular matrix remodeling, fibrinolysis, and coagulation. This review will outline the biology of membrane-associated proteinases expressed by leukocytes and their roles in physiologic and pathologic processes.