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PubMed2001

Cell adhesion peptide modification of gold-coated polyurethanes for vascular endothelial cell adhesion.

Gold-coated polyurethanes were chemisorbed with three cell-adhesion peptides having an N-terminal cysteine: cys-arg-gly-asp (CRGD), cys-arg-glu-asp-val (CREDV), and the cyclic peptide cys-cys-arg-arg-gly-asp-try-leu-cys (CCRRGDWLC). The peptides were selected based on their presumed preferential interactions with the cell-surface integrins on vascular endothelial cells. The ability of the surfaces to support the preferential adhesion of human vascular endothelial cells was studied by comparing in vitro adhesion results for these cells with those from mouse 3T3 fibroblasts. Surface modification with the peptides was confirmed by water-contact angles and XPS. Surface morphology was determined by AFM and SEM. In vitro cell-culture studies in conjunction with plasma-protein adsorption and immunoblotting were performed on the various modified surfaces. The data suggest that peptide-modified surfaces have significant potential for supporting cell adhesion. Little or no cell adhesion was noted on gold- or cysteine-modified control surfaces. Human vascular endothelial cells showed the greatest adhesion to the CCRRGDWLC-modified surfaces, and the 3T3 fibroblasts adhered best to the CREDV-modified surfaces. Protein adsorption studies suggest that the preferential adsorption of the cell-adhesive proteins fibronectin and vitronectin is not likely mediating the differences noted. It is concluded that the cell-adhesive peptide-modified gold-coated polymers have significant potential for further development both as model substrates for fundamental studies and for use in biomaterials applications.

3T3 Cells↗
PubMed1996

Interleukin-7 modulates intracytoplasmatic CD23 production and induces adhesion molecule expression and adhesiveness in activated CD4+CD23+ T cell subsets.

The low-affinity receptor for IgE, CD23, has been described in several pathological conditions. However, the factors involved in the upregulation or downregulation of this receptor are still debated. We studied the effect of interleukin 7 (IL-7) on the production of CD23 in normal PBT cells stimulated with PMA + Ca2. The results demonstrate that cytoplasmic CD23 level was significantly augmented by costimulation with PMA + Ca2 plus IL-7 (1000 U/ml). Using an intracytoplamatic cytometric analysis, an accumulation of intracellular CD23 was observed at 48 hr in the presence of IL-7. This appears to have a profile different from the CD23 surface expression peaking at 72 hr of culture. We were also able to show that sCD23 was specifically increased by IL-7 and occurred with an early peak at 72 hr and a late peak at 120 hr of culture. The increased release and the biphasic production of sCD23 may reside in an accelerated degradation of the receptor due to an excessive accumulation of it. Restimulation of CD4+ T cells with PMA + Ca2 without IL-7 changed the profile of sCD23 production showing a second peak at 144 hr of culture. The induction of IL-7 on CD23 production appears to be independent of IL-2, IL-4, IL-9, and IL-15. Indeed, the addition of specific mAbs anti-IL-2, -IL-4, -IL-9, -IL-15, or anti-IL-2R was unable to block the effect of IL-7 on CD23. The addition of IL-7 to specific subset CD4+CD23+ was able to augment the adhesiveness of T cells to parenchymal cell monolayers. The use of different cytokine (IL-2, IL-4, IL-9, IL-15) resulted in no increase of adhesiveness. In contrast, the addition of IL-7 to a different T cell subset (i.e., CD4+CD23-) was unable to rescue the lack of adhesiveness observed in these cells. The adhesion molecules LFA-1 and VLA-4 were responsible for the augmented adhesiveness of activated CD4+CD23+ T cells cultured in the presence of IL-7. Blocking experiments with anti-LFA-1beta, VLA-4alpha, anti-LFA-1beta plus VLA-4alpha mAbs, or anti-ICAM-1 mAb added to the monolayers resulted in a complete inhibition of adhesion to parenchymal monolayers. In contrast, the addition of anti-IL-7 or anti-IL-7R mAbs was able to block the augmented adhesiveness of CD4+CD23+ cells to monolayers observed in the presence of IL-7. A significant augmentation of LFA-1 and VLA-4 was observed in cells cultured in the presence of IL-7. Taken together these findings point to the likelihood that IL-7 is responsible for the observed quantitative difference in the level of adhesion molecules and may open a new role of CD23 in the immune regulations.

Adjuvants, Immunologic↗
PubMed2002

A Listeria adhesion protein-deficient Listeria monocytogenes strain shows reduced adhesion primarily to intestinal cell lines.

Listeria monocytogenes adheres and penetrates intestinal cell linings for systemic infection. A 104-kDa Listeria adhesion protein (LAP) from L. monocytogenes was previously demonstrated to be responsible for adhesion to intestinal enterocyte-like Caco-2 cells. We investigated the adhesion and invasion characteristics of a LAP-deficient mutant L. monocytogenes strain (A572) to various human intestinal and non-intestinal cell lines to assess the possible target host cells. Among the intestinal cell lines, A572 showed significantly reduced adhesion than the wild type (WT) strain to the cells of ileum-cecum (HCT-8) and colon (Caco-2 and HT-29), whereas A572 and WT did not show any significant differences in adhesion to other intestinal cell lines from duodenum (HuTu-80) or jejunum (Int-407). Differences in adhesion between A572 and WT were little or none in non-intestinal cell lines from liver, kidney, bladder, ovary, cervix, breast, larynx, or skin. Invasion data showed that A572 was invasive but the invasion efficiency was proportional to its adhesion characteristics to respective cell lines. In mouse bioassay, A572 was not found in liver following oral administration, suggesting that LAP mutant was possibly unable to pass through intestinal cell linings. Immuno-electron microscopy revealed that the LAP is localized in the bacterial surface as well as the cytoplasm. In summary, this study indicated that the LAP-mediated adhesion is associated with the intestinal cells originating from the lower part of small intestine and from the upper part of large intestine, and possibly plays an important role during the intestinal phase of infection.

Adhesins, Bacterial↗
PubMed1995

Reduction of ovarian adhesions by the use of Interceed. Ovarian Adhesion Study Group.

OBJECTIVE: To evaluate the efficacy of Interceed (TC7) Absorbable Adhesion Barrier, an oxidized regenerated cellulose fabric, as a barrier to the development of postsurgical ovarian adhesions after surgery involving the ovaries. METHODS: In a multicenter randomized study, 55 patients with bilateral ovarian disease were treated at initial laparotomy. At the end of the procedure, one ovary was assigned randomly to be wrapped with Interceed and the other was left uncovered. A second-look laparoscopy was performed 10-98 days later to evaluate the occurrence and severity of adhesions and the raw ovarian surface area exposed after lysis of adhesions. RESULTS: At second-look laparoscopy, 26 of 55 Interceed-treated ovaries were free of adhesions, compared with 14 of 55 untreated control ovaries, a statistically significant difference (P = .028, Fisher exact test). At second-look laparoscopy, ovaries treated with Interceed formed adhesions less extensively (1.66 +/- 0.34 cm2) than did untreated ovaries (2.75 +/- 0.60 cm2) and with a greater reduction of raw ovarian surface area (difference in area differential -1.89 +/- 0.96 cm2; P = .055, paired t test). Adhesion scores at second-look laparoscopy were reduced significantly for ovaries treated with Interceed compared with untreated ovaries (P = .02, Wilcoxon signed-rank test). No adverse events were recorded during the course of the study. CONCLUSION: Treatment of ovaries with Interceed significantly reduced the occurrence and severity of postsurgical ovarian adhesions.

Adult↗
PubMed2005

Adhesion of bacteria to resected human colonic tissue: quantitative analysis of bacterial adhesion and viability.

Adhesion to the intestinal mucosa is considered to be one of the main selection criteria of lactic acid bacteria for probiotic use. Adhesive probiotics are, for example, considered to provide better antagonism against pathogenic bacteria when compared to non-adhesive strains. Here a new model is described for studying adhesion and interaction of probiotic and pathogenic bacteria in the intestinal mucus in which the intestinal microbiota is present. The model is based on the use of human intestinal tissue, fluorescent-tagged bacteria and confocal laser scanning microscopy (CLSM) in adhesion measurements as well as human intestinal mucus and bioluminescent-tagged bacteria in viability measurements. Use of CLSM enabled, for the first time, real-time three-dimensional observations of live probiotic bacteria in their natural environment, the intestinal mucosa. When the real-time measurement of bacterial adhesion was combined with the real-time sensitive measurement of bacterial viability, it could be studied whether or not the adherent pathogens were alive. The model was used to study the interaction between Lactobacillus rhamnosus GG and Salmonella enterica serovar Typhimurium. We show that L. rhamnosus GG did not affect the adhesion or the viability of S. enterica serovar Typhimurium. Instead S. enterica serovar Typhimurium was shown to decrease the adhesion of L. rhamnosus GG in displacement assays. Moreover, the method is suitable for studies in which the interaction of two or more bacteria is examined in an environment in which other bacteria are present.

Bacterial Adhesion↗
PubMed2002

Tocotrienol is the most effective vitamin E for reducing endothelial expression of adhesion molecules and adhesion to monocytes.

Alpha-tocopherol and its esterified derivatives have been shown to be effective in reducing monocytic-endothelial cell adhesion. However, the effect of alpha-tocotrienol (alpha-T3) has not been characterized. In the present study, using human umbilical vein endothelial cells (HUVEC) as the model system, we examined the relative inhibitory effects of alpha-T3 and other vitamin E derivatives on cell surface adhesion molecule expression under TNF-alpha stimulation. Using enzyme-linked immunosorbent assay, we demonstrated that alpha-T3 markedly inhibited the surface expression of vascular cell adhesion molecule-1 in TNF-alpha activated HUVEC in a dose- and time-dependent manner. The optimal inhibition was observed at 25 micromol/l alpha-T3 within 24 h (77+/-5%) without cytotoxicity. In addition, the surface expression of intercellular adhesion molecule-1 and E-selectin were also reduced by 40+/-7 and 42+/-5%, respectively. In order to further evaluate the effects of alpha-T3 on the vascular endothelium, we investigated the ability of monocytes to adhere to endothelial cells. Interestingly, a 63+/-3% decrease in monocytic cell adherence was observed. Compared to alpha-tocopherol and alpha-tocopheryl succinate, alpha-T3 displayed a more profound inhibitory effect on adhesion molecule expression and monocytic cell adherence. This inhibitory action by alpha-T3 on TNF-alpha-induced monocyte adhesion was shown to be NF-kappaB dependent and was interestingly reversed with co-incubation with farnesol and geranylgeraniol, suggesting a role for prenylated proteins in the regulation of adhesion molecule expression. In summary, the above results suggest that alpha-T3 is a potent and effective agent in the reduction of cellular adhesion molecule expression and monocytic cell adherence.

Antioxidants↗
PubMed2001

A morphological and tensile bond strength evaluation of an unfilled adhesive with low-viscosity composites and a filled adhesive in one and two coats.

OBJECTIVE: The purpose of this study was to measure the tensile bond strength (TBS) testing of resin composite to dentin of three low-viscosity composites, in association with an unfilled adhesive, and a filled adhesive one and two coats respectively, and to evaluate and compare the SEM morphological observations. METHODS: The labial surface of 120 bovine lower incisors were ground to obtain a flat dentin surface allowing demarcation of a 4 mm diameter area with adhesive tape. The teeth were randomly divided in six groups of 20 each. The dentin of each ground surface was etched with 35% H(3)PO(4) for 15s, followed by application of the respective adhesive: Single Bond (SB) for Groups 1, 2, 3 and 6; Optibond Solo (OS) for Groups 4 and 5. In Groups 1 and 4, a resin composite rod with a wire loop was luted directly to the adhesive surface with Z100. Group 2 received an intermediate layer of Flow It (FI) composite; Group 3 received an intermediate layer of Protect Liner F (PLF) composite; Group 5 received a second coat of OS; and Group 6 received an intermediate layer of an experimental low-viscosity composite (EM). A resin composite rod was luted to the surface of each specimen with Z100 resin composite. All specimens were stored in distilled water at 37 degrees C for 24h prior to TBS testing. Each specimen was inspected by SEM and classified according to adhesive or cohesive failure mode. One specimen of each group was cut longitudinally, polished and prepared for SEM observation. RESULTS: The TBS values were: Group 1 (7.86MPa+/-2.28), Group 2 (7.62MPa+/-1.85), Group 3 (7.60MPa+/-2.14), Group 4 (7.96MPa+/-2.36), Group 5 (7.50MPa+/-2.70) and Group 6 (7.18MPa+/-2.40). No significant statistical differences were observed among the groups. However, the analyses of the failure mode presented a considerable variation. SIGNIFICANCE: The use of a filled adhesive or an unfilled adhesive along with a low-viscosity composite as an intermediate layer may provide a stress absorbing layer, whereby improving the preservation of the bonded interface area.

Adhesives↗
PubMed2000

A study of the adhesive-skin interface: correlation between adhesion and passage of a drug.

The phenomena taking place at the patch-skin interface, in particular the adhesion of a pressure sensitive adhesive (PSA) film loaded with drug and the partition of the drug between the patch and the skin were correlated. The kinetics of adhesion as well as those of drug passage were studied in detail. Adhesion data were collected from peel test either on skin or on a polymer model. Passage of the drug was studied in a simple system composed of PSA film stuck on skin. In some experiments the film was left on the skin throughout the experiment; in others, it was periodically removed and stuck on again to keep the adhesion force constant during the whole of the experiment. We observed a rapid increase of the drug content in the skin until a plateau was reached. One adhesion for the whole experiment or several adhesions gave a similar curve. The main difference was the rate of increase of skin drug content and the value of the plateau. Different hypotheses concerning the relationship between the adhesion of this PSA and changes in the flux of drug have been put forward. However, it is difficult to extrapolate from this model to the in vivo situation because of variation both between individuals and with time.

Adhesiveness↗
PubMed1995

Adhesion of Aeromonas sp. to cell lines used as models for intestinal adhesion.

Adhesion to HEp-2 cells has been shown to correlate with enteropathogenicity for Aeromonas species. Such adhesion is thought to reflect the ability of strains to adhere to human intestinal enterocytes, although HEp-2 cells are not of intestinal origin. In this study strains of Aeromonas veronii biotype sobria isolated from various sources were investigated in parallel assays for their ability to adhere to HEp-2 cells and to an intestinal cell line (Caco-2). Quantitative assays showed identical adhesion values were obtained with both cell lines. Adhesion was best when bacteria were grown at 22 degrees C compared with 37 degrees C and 7 degrees C. Some environmental isolates showed greater adhesion when grown at 7 degrees C than when grown at 37 degrees C. Filamentous structures on these strains are also optimally expressed under the above conditions (reported elsewhere). Mechanical shearing or trypsin treatment to remove surface structures from several adhesive strains grown at 22 degrees C decreased adhesion to cell lines by 50-80% providing further indirect evidence that filamentous adhesins may play a role in cell adhesion for this Aeromonas species.

Aeromonas↗
PubMed1997

Cell to substratum adhesion is involved in v-Src-induced cellular protein tyrosine phosphorylation: implication for the adhesion-regulated protein tyrosine phosphatase activity.

Protein tyrosine phosphorylation accompanies the integrin-mediated cell to substratum adhesion, and is essential for the progression of G1/S phase of the cell-cycle in normal fibroblasts. To examine how cellular protein tyrosine phosphatase (PTPase) activity is involved in regulating the adhesion-dependent protein tyrosine phosphorylation, we employed fibroblast cells bearing an active form of a protein tyrosine kinase (PTK), v-Src. We found that the v-Src induced tyrosine phosphorylation in certain proteins such as tensin, talin, p120, p80/85 (cortactin) and paxillin was greatly reduced when the cell to substratum adhesion was lost. Readhesion of the cells onto fibronectin restored these phosphorylation events, while this was inhibited by the addition of RGD peptide. The kinase activity of the v-Src was unchanged by the loss of cell to substratum adhesion. On the other hand, treatment with a protein tyrosine phosphatase inhibitor vanadate caused much the same increase in the v-Src-mediated cellular tyrosine phosphorylation between cells adhered to the culture environments and cells kept in suspension. These data suggest that PTPase(s) appears to be more critical than the v-Src PTK in determining the cell adhesion-dependent protein tyrosine phosphorylation. Moreover, most of the protein tyrosine phosphorylations that are mediated by the v-Src but still dependent on the cell adhesion were indeed greatly reduced during an anchorage-independent growth of v-Src cells. Thus our data collectively indicate that the v-Src induced high level of tyrosine phosphorylation in certain types of proteins are still under the control of the integrin(s) or the cell adhesion to culture substratum, and most of these adhesion-regulated high levels of tyrosine phosphorylations are not essential for the transformed phenotype.

Actins↗
PubMed2001

Glove powder promotes adhesion formation and facilitates tumour cell adhesion and growth.

BACKGROUND: The presence of foreign material in the abdominal cavity irritates the peritoneal surface, leading to an inflammatory response. This defensive mechanism can provoke adhesion formation. The same peritoneal defence cascade is thought to play a role in the process of intra-abdominal tumour recurrence. The aim of this study was to evaluate whether glove powder produced peritoneal adhesions in a rat adhesion model and whether it promoted intra-abdominal tumour recurrence in a rat tumour cell adhesion and growth model. METHODS: A reproducible model that allowed semiquantitative scoring of adhesion formation or tumour load was used in three different groups of rats. One group was treated by intra-abdominal application of powder obtained from starch-powdered gloves, one by application of pure starch and in one group no powder was used. RESULTS: Application of glove powder or pure starch on minimally and severely traumatized peritoneum gave rise to significantly greater adhesion formation and intra-abdominal tumour load than peritoneal trauma alone (both P < 0.001). CONCLUSION: Starch-induced peritoneal trauma leads not only to more adhesion formation but also to increased adhesion and growth of tumour cells. Since good powder-free alternatives are available there is no longer any justification for the use of powdered gloves during intra-abdominal surgery.

Adenocarcinoma↗
PubMed1984

Two antigenically related neuronal cell adhesion molecules of different specificities mediate neuron-neuron and neuron-glia adhesion.

Previous studies in this laboratory have led to the identification of the neural cell adhesion molecule, N-CAM, a homophilic ligand that mediates adhesion between neurons as well as between neurons and striated muscle precursors. By means of a similar immunological approach but with different assays, we have now identified a cell adhesion molecule on neurons (Ng-CAM) that mediates the heterotypic adhesion between neuronal membranes and glial cells. In this paper, we compare certain aspects of the structure and function of Ng-CAM and embryonic N-CAM from the chicken. Ng-CAM was localized by specific antibodies on neurons but not on glia, and double-staining methods showed that individual neurons contained both Ng-CAM and N-CAM. Embryonic Ng-CAM migrates primarily as a single component of Mr 135,000; its apparent Mr shifted to 127,000 after neuraminidase treatment. In contrast, the embryonic form of N-CAM migrates on NaDodSO4/polyacrylamide gels in the apparent Mr range of 200,000-250,000; after neuraminidase treatment, N-CAM migrates as two components of Mr 170,000 and Mr 140,000. Although both Ng-CAM and N-CAM have calcium-independent binding mechanisms, immunologically based cell adhesion assays suggested that they have different specificities in mediating cell adhesion. Whereas 0.25 micrograms of Ng-CAM partially neutralized the ability of 0.5 mg of polyspecific antineural Fab' fragments to inhibit the heterotypic binding of neuronal membrane vesicles to glial cells and larger amounts of Ng-CAM completely neutralized this inhibition, 20 micrograms of N-CAM had no neutralization activity in this assay. Reciprocally, 0.25 micrograms of N-CAM partially neutralized the ability of 0.5 mg of the same Fab' fragments to inhibit the direct homotypic aggregation of neuronal cells, but 20 micrograms of Ng-CAM had no detectable activity. Although peptide maps of the two cell adhesion molecules differed considerably and despite the differences in binding specificity of these molecules, two independently derived monoclonal antibodies were found to crossreact with both Ng-CAM and N-CAM. Therefore, these different neuronal cell adhesion molecules with distinct binding specificities share at least one antigenic determinant, raising the possibility that they arose from a common evolutionary precursor.

Animals↗
PubMed1976

Intercellular adhesive selectivity. I. An improved assay for the measurement of embryonic chick intercellular adhesion (liver and other tissues).

An improved assay for measuring intercellular adhesive selectivity of embryonic chick liver cells is described. Three major improvements over earlier procedures are noted: (a) enhanced reproducibility of liver cell-liver cell aggregate adhesion (homotypic adhesion) was achieved; (b) 25-70% of the input cells adhered to the collecting aggregates during the course of routine experiments as compared to the 0.25% in earlier assays. This increase in cellular adhesion suggests that the observed cell pick-up is a characteristic of the majority of the dissociated liver cell population; (c) the rate of intercellular adhesion was increased 1,000-fold. The main feature of the assay is that it measures the tissue adhesive selectivities of the dissociated cell population. Studies were undertaken on three embryonic chick tissues (liver, neural retina, and mesencephalon) to determine the tissue selectivity of intercellular adhesion of these dissociated cell types. Some general properties of liver cell homotypic adhesion have been studied and are reported.

Animals↗
PubMed1976

Intercellular adhesive selectivity. II. Properties of embryonic chick liver cell-cell adhesion.

Studies directed at understanding the molecular basis of liver cell homotypic adhesion are presented. An assay which measures the rate of adhesion of isotopically labeled (32PO4) embryonic chick liver cells to liver cell aggregates, described in a companion paper, has been used to investigate the problem of intercellular adhesive selectivity. Cation requirements, the effects of various inhibitors of metabolism and protein synthesis, of chelators (EDTA and EGTA), and the effects of temperature on liver cell adhesion are reported. Two mechanisms of inhibition of liver intercellular adhesion are suggested. One involves destruction of cell-surface adhesion receptors (sensitivity to proteases); the other is an energy-dependent step which may involve alterations in plasma membrane conformation and/or membrane fluidity. Finally, a model is suggested for liver cell-cell adhesion that incorporates the early tissue selectivity of intercellular adhesion previously reported, followed by a multistep process which leads to histogenic aggregation.

Animals↗
PubMed2004

Plasmodium falciparum-infected erythrocytes demonstrate dual specificity for adhesion to hyaluronic acid and chondroitin sulfate A and have distinct adhesive properties.

Hyaluronic acid (HA) and chondroitin sulfate A (CSA) have been identified as receptors for adhesion of Plasmodium falciparum-infected erythrocytes (IEs) and appear to be involved in mediating parasite accumulation in the placenta. We demonstrate here that some, but not all, parasite populations can adhere to both receptors, and we identify distinguishing features of adhesion. Adhesion to HA and CSA was greatest among pigmented trophozoite-infected erythrocytes and at physiologic pH and was associated with a lack of rosette formation and little adhesion to CD36 and intercellular adhesion molecule-1. Adhesion to HA was sensitive to trypsin cleavage of the IE surface, whereas trypsin-resistant and trypsin-sensitive CSA adhesion were both observed. Soluble HA, but not CSA, could cause aggregation or clumping of IEs. Different HA types varied in adhesion-inhibitory activity, which was altered by physical treatment, suggesting that structural features of HA influence IE interactions. These findings have important implications for understanding the pathogenesis of malaria, particularly in pregnancy.

Animals↗
PubMed1994

The value of an absorbable adhesion barrier, Interceed, in the prevention of adhesion reformation following microsurgical adhesiolysis.

OBJECTIVE: To determine whether Interceed, an absorbable adhesion barrier, confers any additional benefit over conventional microsurgery, including the use of an adjuvant (hydrocortisone), in the prevention of adhesion reformation after pelvic microsurgery. DESIGN: A prospective, randomised, controlled study. SETTING: Jessop Hospital for Women, Sheffield, UK. SUBJECTS: Twenty-eight women who underwent pelvic microsurgery for infertility or for chronic pelvic pain and who had bilateral pelvic adhesions and deperitonealised areas following adhesiolysis. INTERVENTIONS: Following microsurgical adhesiolysis, one side of the pelvis was randomised to have its deperitonealised areas covered with Interceed, whereas the contralateral side served as the control. A second look laparoscopy was carried out 3 to 14 weeks after microsurgery to evaluate adhesion reformation. MAIN OUTCOME MEASURE: The amount of adhesion reformation at second look laparoscopy compared with the amount of deperitonealised area exposed following microsurgical adhesiolysis. RESULTS: The use of Interceed resulted in a significant reduction of adhesion reformation over and above that achieved by conventional microsurgical techniques with hydrocortisone as an adjuvant. CONCLUSION: Interceed, an absorbable adhesion barrier, is of value in the prevention of adhesion reformation and may be used in conjunction with hydrocortisone instilled intraperitoneally at the conclusion of microsurgery.

Adult↗
PubMed1993

Adhesion of CHO cells to fibronectin is mediated by functionally and structurally distinct adhesion plaques.

We have investigated the dynamics between free fibronectin receptors and clusters of them organized into adhesion plaques on CHO cells using the ability of these free integrins to be endocytosed and recycled to the plasma membrane. Indirect inhibition of the endocytic cycle by monensin resulted in the subsequent internalization of free receptors, which we followed by indirect immunostaining and confocal microscopy. Consequently, all the adhesive structures that were in equilibrium with free integrins became progressively disorganized. The cellular morphological changes were analyzed and correlated with the distribution of cell-substratum contacts viewed by confocal images obtained after immunostaining with antibodies raised against the fibronectin receptor, talin, vinculin and actin. After cell adhesion to fibronectin, blockage of the endocytic cycle induced disruption of the adhesion plaques that were mainly localized at the cell periphery, and disappearance of the stress fibers. However, the cells remained firmly attached to the substratum through focal contacts localized in the central part of the cell. These central focal contacts, but not the peripheral adhesion plaques, could form when the vesicular traffic was blocked prior to adhesion and they allowed the cells to attach and flatten onto the substratum. Whereas both adhesive structures contained the same receptors linked to talin and vinculin, the central adhesive structures were attached to a short stretch of actin but never permitted the organization of stress fibers.

Animals↗
PubMed1980

Adhesive and non-adhesive membrane domains of amphibian embryo cells.

Superficial blastomeres of mid-cleavage stage amphibian embryos (32- and 64-cell stage) display regional cell-surface differences in adhesiveness. The cells are adhesive on the lateral and basal cell surfaces and non-adhesive on the apical surface. These adhesive differences are maintained by single cells which have been dissociated from the intact embryo. Pigmentation differences afford a means of distinguishing apical surface from basal/lateral surface in dissociated cells. The apical surface is underlain by melanin granules and so appears dark, whereas the lateral and basal surfaces lack pigment and are white. Scanning electron-micrograph observations of isolated superficial cells reveal striking morphological differences between the adhesive and non-adhesive regions. The apical (non-adhesive) portion of the cell surface has a convoluted appearance and is almost entirely devoid of microvilli. The lateral and basal (adhesive) surfaces lack the convolutions of the apical surface and bear scattered microvilli. The isolated superficial cells continue to divide in culture. The cells display a unilateral or one-sided furrow which begins in the basal surface and progresses toward the apical surface. The plane of cleavage of most of the cells is oriented such that the pigmented cap is bisected, with very few cells having the plane of the furrow pass parallel to the apical surface. The direction of furrowing in the isolated cells from the 32- to 64-cell embryo represents a direction of furrow progression in the intact embryo from the interior to the surface. Since the early cleavages are initiated at the surface and progress into the interior, it is suggested that a reversal in direction of furrowing occurs by mid-cleavage stages.

Animals↗