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PubMed2003

Highly concentrated Si1-xCx alloy with an ordered superstructure.

An ordered Si-C alloy was observed in the products resulting from thermal reduction of molybdenum disilicide heating rods. High-resolution transmission electron microscopy measurements indicate that the Si1-xCx alloy with x approximately 25% is pure, single crystalline, and possesses a superlattice structure. The superlattice periodicity occurs along the diamond [001] direction and corresponds to the quintupling of the primary (002) periodicity. The possible growth mechanism is discussed. The Mo element is likely to play a crucial role in the growth process of the Si1-xCx alloy, since it can both reduce the energy required for breaking up C clusters and contribute to surface modification, which are of great benefit to enhance the carbon concentration and induce an ordered structure.

Journal Article↗

PubMed2006

Ring of C60 polymers formed by electron or hole injection from a scanning tunneling microscope tip.

Carrier (electron or hole) injection from a scanning tunneling microscope tip causes various surface modifications on the molecular scale. We report that injection into C60 close-packed layers forms a ring-shaped distribution of C60 polymers. This can be explained on the basis of the radial propagation and energy dissipation of carriers. Subsequent electron or hole injections enlarge the ring, showing that both carriers can induce both polymerization and depolymerization. Furthermore, we demonstrate visualization of carrier scattering by injecting carriers into C60 layers with grain boundaries.

Journal Article↗

PubMed1992

Thrombus with infection in total artificial heart animals.

From January 1980 to December 1990, several types of total artificial hearts were implanted into 378 animals. In a retrospective study of these animals, 147 (39%) were found to have thrombus with infection (T&I). The criteria for diagnosis was thrombus formation in the artificial heart and a positive blood culture. The most common pathogen isolated from T&I animals was Pseudomonas species. Concurrent skin lesions and contamination from the pressure lines may be the primary sources of infection, but bacterial translocation from the intestine is another possible route. The main pathological findings at necropsies of artificial heart animals with T&I were associated with sepsis, congestive heart failure, infected thrombus, thromboembolism, and multiple organ infarctions. Most thrombi appeared to have originated from valve junctions and connectors. On the basis of these observations, a possible mechanism for pathogenesis of T&I has been proposed. The results suggest that design improvements and surface modifications to reduce thrombosis are important factors that should be carefully considered. Similarly, it is important to eliminate the route of entry of pathogenic microorganisms. These findings imply that bacterial interaction with thrombus, device related bacterial colonization, and host immunomodulation and gut barrier function following artificial heart implantation need further investigation.

Animals↗

PubMed2001

Substantial reduction of platelet adhesion by heparin-coated stents.

Although optimized antiplatelet medication has improved the clinical outcome after coronary stenting, vessel occlusion and restenosis still remain a relevant clinical problem. Platelets play a key role in this process. Therefore, the authors compared the platelet adhesion on different stent surface modifications (electropolished without coating or coated with carbon, carbon and additional heparin, silicon carbide, or heparin alone) to investigate their role in reducing platelet adhesion. All stents and additional stainless steel plates were incubated in heparinized whole blood with radiolabeled platelets. After washing the stents and plates four times, radioactivity caused by the adhesion of radiolabeled platelets was measured. The adhesion of radiolabeled platelets, compared to uncoated, electropolished stents, was reduced through silicon carbide coating to 58.6%, by carbon coating with additional heparin to 32.9%, and heparin coating alone to 7.7%. Stent coating with heparin is the most effective among the examined coatings in reducing platelet adhesion in vitro.

Anticoagulants↗

PubMed1997

The effects of CO2, Nd:YAG and Er:YAG lasers with and without surface coolant on tooth root surfaces. An in vitro study.

The objective of this study was to compare and contrast the morphologic changes in tooth root surfaces treated in vitro by scaling and root planing followed by irradiation with the Er:YAG laser using air/water surface cooling and the CO2 and Nd:YAG lasers, both with and without surface coolant. The experimental unit consisted of 42 freshly extracted teeth which were divided equally and randomly assigned to the following 7 treatment groups: untreated control, S/RP only, CO2 laser with and without air/water surface cooling, Nd:YAG laser with and without/air water surface cooling, and Er:YAG laser with air/water surface coolant. Specimens treated with CO2 laser irradiation were subjected to energy densities ranging from 100 to 400 J/cm2; those treated with the Nd:YAG from 286 to 1857 J/cm2; and the Er:YAG was used within a range of 20 to 120 J/cm2. The degree of morphologic change following CO2 and Nd:YAG irradiation appeared directly related to energy density but unrelated to the use of surface coolant. Laser induced surface changes included cavitation, globules of melted and resolidified mineral, surface crazing, and production of a superficial char layer. In contrast, the Er:YAG laser produced root surface changes that might be expected from acid etching, i.e., removal of the smear layer and exposure of the collagen matrix. In addition, sharply defined microfractures of the mineralized structure were noted and unlike the CO2 and Nd:YAG lasers, there was no evidence of melting or surface char. Given the parameters of this study, it appears that both the CO2 and Nd:YAG lasers alter the root surface in an undesirable manner. The Er:YAG laser, however, when used at low energy densities shows sufficient potential for root surface modification to warrant further investigation.

Acid Etching, Dental↗

PubMed1989

Cell membrane and volume changes during red cell development and aging.

This paper provides a summary of our understanding of cell membrane and volume changes during red cell development and aging. Cytoskeletal structures which include microtubules and microfilaments appear to play key roles in the genesis of the anucleate reticulocyte from its nucleated precursor cell, as well as in the early stages of reticulocyte development. The maturation of reticulocyte into red cell is accompanied by marked changes in cell shape and extensive remodeling of the membrane skeleton, resulting in the mature red cell acquiring a highly deformable yet remarkably stable membrane. The volume and cell density heterogeneity seen for circulating red cells also appears to be the result of the membrane changes that occur during reticulocyte maturation. Following its genesis from reticulocyte, the mature red cell undergoes further membrane and volume changes during its life span of 120 days. While it is clear that surface area loss, decrease in cell volume and cell surface modifications leading to binding of immunoglobulins accompany red cell aging, the cardinal cellular modification responsible for the removal of senescent red cells from the circulation is yet to be defined.

Cytoskeleton↗

PubMed1983

Specific absence of type 2 fimbriae on a coaggregation-defective mutant of Actinomyces viscosus T14V.

The coaggregation-defective (COG-) mutant Actinomyces viscosus T14V(PK455), which is unable to participate in lactose-sensitive adherence, and its COG+ parent were compared to structurally define the mutational loss of cell-associated lectin activity. Immunoelectrophoretic comparisons of crude extracts or isolated fimbriae from both strains demonstrated type 2 fimbriae (previously designated Ag2) in preparations obtained from the parent but none in those obtained from the mutant. This result was verified by the immunoelectron-microscopic identification of type 1 (previously designated Ag1 or VAl) and type 2 fimbriae on the parent organism but only type 1 fimbriae on the mutant. A comparison of the amounts of extractable fimbriae of each type and the capacity of the cells to bind 14C-labeled monoclonal antibodies specific for each fimbrial component showed that the mutational loss of type 2 fimbriae had no significant quantitative effect on fimbriation of the COG- mutant with type 1 structures. Cells of A. viscosus T14AV, a mutant with various adherence defects that include the COG- phenotype, displayed fimbriae of both types, but in greatly reduced amounts. Thus, the properties of mutant strain T14V(PK455) associated the lectin activity with type 2 fimbriae, whereas those of strain T14AV provided little insight into the mechanism of lactose-sensitive adherence. In addition, the precise nature of the cell surface modification displayed by strain T14V(PK455) provides clear evidence for the existence of distinct and independent fimbriae on A. viscosus T14V.

Actinomyces↗

PubMed1989

Role of adherence in pathogenesis of Enterococcus faecalis urinary tract infection and endocarditis.

Enterococcus faecalis strains isolated from urinary tract infections (UTIs) and endocarditis were analyzed for their ability to adhere to urinary tract epithelial cells (ECs) and Girardi heart (GH) and human embryonic kidney (HEK) cell cultures. UTI isolates adhered to urinary tract ECs more efficiently than to the cultured cells, at the same time showing the least affinity for GH cells. In contrast, endocarditis isolates adhered to GH cell cultures more readily than to urinary tract ECs. Moreover, although strains isolated from endocarditis adhered to GH cells more efficiently than those derived from UTI, the latter strains adhered to urinary tract cells better than the former. Studies of the ability of GH and HEK cells to internalize E. faecalis showed that for UTI isolates, 9 to 74% of adhered bacteria were internalized, while for endocarditis isolates, the percentage varied from 76 to 82%. All strains were able to associate with human neutrophils; endocarditis strains, however, associated less efficiently than UTI isolates. Growth in serum raised the adherence of all tested strains by at least 1.5- to 3-fold, with the greatest increase being observed in UTI strain adherence to GH cells (8-fold). In contrast, the association of serum-grown cells with polymorphonuclear leukocytes was reduced by two- to fivefold. In both cases, the observed serum-dependent alterations were cancelled by a few subcultures in brain heart infusion broth. These results indicate that adhesive properties are important virulence factors in the pathogenesis of UTI and endocarditis and also suggest that UTI strains showing the highest invasion and adhesive potential invade the kidneys, cause bacteremia, and, after having expressed the serum-dependent surface modification, colonize the heart.

Adult↗

PubMed1996

Bovine herpesvirus 1 UL49.5 homolog gene encodes a novel viral envelope protein that forms a disulfide-linked complex with a second virion structural protein.

We previously reported that the genome of bovine herpesvirus 1 (BHV-1) contains an open reading frame (ORF) homologous to the herpes simplex virus UL49.5 ORF, and as with the herpes simplex virus UL49.5 ORF, the deduced amino acid sequence of the BHV-1 UL49.5 homolog (UL49.5h) contains features characteristic of an integral membrane protein, implying that it may constitute a functional gene encoding a novel viral envelope protein. This communication reports on the identification of the BHV-1 UL49.5h gene product. By employing an antibody against a synthetic BHV-1 UL49.5h peptide and an UL49.5h gene deletion mutant, the primary product of BHV-UL49.5h gene was identified as a polypeptide with a size of approximately 9 kDa; in both infected cells and isolated virions, the UL49.5h products were found to exist in three forms; monomer, disulfide-linked homodimer, and disulfide-linked heterodimer containing a second viral protein with a size of about 39 kDa. O-Glycosidase digestion and [3H]glucosamine labelling experiments showed that the UL49.5h protein is not glycosylated. Although the deduced amino acid sequence contains putative sites for myristylation and phosphorylation, we were unable to detect either modification. Surface labelling and trypsin digestion protection experiments showed that the BHV-1 UL49.5h protein was present on the surface of infected cells and on the surface of mature virions. Nonionic detergent partition of isolated virions revealed that the UL49.5h protein is more tightly associated with the virion tegument-nucleocapsid structure than envelope protein gD. The results from this study demonstrate that the BHV-1 UL49.5h gene encodes a nonglycosylated virion envelope protein which may associate with virion internal structures by forming a complex with the 39-kDa virion structural protein.

Animals↗

PubMed1979

Adaptive differences of the surface organization of horny cells.

The existence of a peculiar structural pattern of complementary villi and pores was observed on the squamous surfaces of palms and soles. These features, which might be considered as acquired and adaptive cell surface modifications, proved to be more conspicuous during a period of rat and human postnatal development.

Animals↗

PubMed1986

Scanning electron microscopy of pulmonary vascular endothelium in rats with hypoxia-induced hypertension.

Scanning electron microscopy was used to study the endothelial surface of the pulmonary trunk, artery, and vein in normobaric control rats as well as in rats exposed to hypobaric hypoxia for 7 and 21 days. The individual endothelial cells of the normobaric pulmonary trunk and hilar artery were flat and slightly elongated with elevated nuclear regions, and those of the intermediate-sized artery were more elongated and had more microvilli than the large arteries studied. Their endothelial cell boundaries were outlined by beaded cytoplasmic projections. The surfaces of the normobaric hilar and intermediate-sized veins were smooth and demonstrated numerous longitudinal streaks. These venous endothelial cells were elongated and their cell boundaries were outlined by low discontinuous marginal folds. Exposure to hypobaric hypoxia caused the following changes on the arterial surface: elevation of the endothelial cells; formation of microvilli-rich cell clusters; formation of hollow defects; and the attachment of leukocytes. Hypobaric hypoxia also caused the disappearance of the longitudinal streaks and the occurrence of microvilli-rich cells in the hilar veins. The endothelial surface modifications in the hypobaric rats could be related to thickening of the endothelium, intimal edema, increased intimal connective tissue, luminal invasion of leukocytes, and increased endothelial cell proliferation, known to occur in systemic arteries of hypertensive animals.

Animals↗

PubMed1990

Scanning-electron-microscopic studies on the pathogenesis of exencephaly and cranioschisis induced in the rat after neural tube closure.

Following a single-dose (15 mg/kg) administration of cyclophosphamide on day 12 of gestation to Wistar rats, fetuses were collected at various intervals of time and studied under the scanning electron microscope. Comparisons were made with age-matched controls. Disorganization of the neuro-epithelium (NE) was characterized by expansion of the intercellular space (ICS), appearance of abundant cellular debris, extravascular red blood cells and formation of haemorrhagic cysts in the subependymal zone. Proliferation of the choroid plexus and its surface modifications parallelled the changes in the NE. The ventricular system dilated progressively. Supra-ependymal elements appeared earlier and in greater abundance in the experimental than in the control embryos. The mesenchymal cells of the cyclophosphamide-treated embryos were scanty, poorly organized, had less numerous cytoplasmic processes than the corresponding controls and failed to develop into the primordium of the skull vault. Degenerative changes in the NE, ventricular dilatation and the absence of a supporting skull vault primordium appeared to underlie the reopening of the closed neural tube.

Animals↗

PubMed1983

Differential agglutination of P388 adriamycin-sensitive and P388 adriamycin-resistant leukemia cells.

Cell surface modification was studied in a subline of murine leukemia resistant to adriamycin (P388/ADR). Lectin-induced agglutination was used as a probe. Agglutination was studied using two plant lectins, wheat germ agglutinin (WGA) and Ricinus communis agglutinin-I (RCA-I). A 7-fold higher amount of WGA and 14-fold higher amount of RCA-I were required to bring about minimum agglutination of P388/S as compared to P388/ADR. The present studies clearly indicate a change in the plasma membrane of P388/ADR cells.

Agglutination↗

PubMed1999

Denucleation promotes neovascularization of ePTFE in vivo.

Expanded polytetrafluoroethylene (ePTFE) implants are being increasingly used as vascular prostheses and other devices. However the tissue response associated with this and other polymer implants continues to limit any long-term function. One of the major approaches currently being investigated to improve biocompatibility involves surface modification of the base polymer. In this report, we attempted to alter the healing characteristics of ePTFE by denucleation, a process which removes air trapped within the interstices of the material. Additionally, adsorption of extracellular proteins on the denucleated polymer was also tested. After 5 weeks implanted in subcutaneous and epididymal fat sites of rats, the material was explanted and the healing around the implant evaluated histologically. We found that in skin implants, denucleation alone resulted in a substantial reduction in the fibrous capsule which has been previously reported for untreated ePTFE, and an increase in blood vessel development around and within the polymer. Absorption of extracellular matrix proteins prior to implantation resulted in a reduced vascularity of the implants compared with denucleation-only implants. Implants in fat tissue, regardless of treatment, showed very little tissue reaction, either in the number of inflammatory cells, development of a fibrous capsule or neovascularization. These results suggest that the presence of air nuclei within porous material may contribute to the inappropriate healing response associated with these polymers. In addition, they confirm earlier reports that healing around implanted polymers is tissue-specific.

Adipose Tissue↗

PubMedDate not supplied

Human vascular endothelial cells in primary cell culture for the evaluation of nanoparticle bioadhesion.

Nanoparticles (NP) are employed in various therapeutic approaches for innovative drug delivery strategies. Among them, there is drug delivery to the brain and sustained release forms for intravenous drug delivery. In order to optimize drug carriers and to elucidate involved mechanisms such as bioadhesion and cellular uptake, NP were surface modified and analyzed for their interaction with human endothelial cells in cell culture. Fluorescently labeled NP of different diameters (50 to 1000 nm) were surface modified either by simple adsorption of chitosan or by covalent binding to the lectin ulex europaeus agglutinin and thereafter applied to human endothelial cells for different incubation periods. After incubation with NP the binding of NP was quantified directly by the fluorescence emission signals from the cell layers. In order to visualize the binding behaviour, NP were localized three-dimensionally in the cell layer by confocal laser scanning microscopy. Cell binding experiments in phosphate buffer were observed to be particle size dependent with the 50 nm NP showing the highest binding percentage over all experiments. Binding decreased with increasing particle diameter and shorter incubation interval. The adhesion was further enhanced by NP surface modifications in the order blank < chitosan < lectin. The presence of plasma proteins enhanced the adhesiveness of chitosan coated NP, while the binding of lectin coated NP was inhibited. Experiments at 4 degrees C indicated the involvement of an active process in the binding of NP to endothelial cells.

Adhesiveness↗

PubMed2006

Synthesis of SiO2-coated Bi2S3/poly(styrene) nanocomposites by in-situ polymerization.

New nanocomposites containing silica-coated Bi2S3 nanofibers were synthesised by in situ polymerization using two distinct synthetic strategies: emulsion and suspension polymerization. Transmission and scanning electron microscopy of the nanocomposite particles showed that in both cases the Bi2S3/SiO2 nanoparticles were densely coated with poly(styrene). In situ emulsion polymerization afforded nanocomposites in which the nanofibers were coated with polymer spheres whilst suspension polymerization gives rise to a homogeneous polymer layer coat. The morphology of the poly(styrene) coating observed is discussed considering the surface modification of the nanofibers and the polymerization technique involved.

Bismuth↗

PubMed2006

The development of a serum-free derived bioengineered conjunctival epithelial equivalent using an ultrathin poly(epsilon-caprolactone) membrane substrate.

PURPOSE: To evaluate the use of an ultrathin poly(epsilon-caprolactone) (PCL) membrane as a substrate for the development of a serum-free-derived conjunctival epithelial equivalent. METHODS: Ultrathin PCL membranes 6 microm in thickness were prepared by solvent casting and biaxial stretching and analyzed by atomic force microscopy (AFM), scanning electron microscopy (SEM), tensile testing, and water-contact angle measurement. Rabbit conjunctival epithelial cells were cultivated on sodium hydroxide (NaOH)-treated PCL membranes and untreated PCL membranes in serum-free medium. The proliferative capacity of cultivated cells was analyzed with a bromodeoxyuridine (BrdU) ELISA proliferation assay. Conjunctival equivalents were xenografted into severe combined immune-deficient (SCID) mice. Immunostaining for tissue-specific and basement membrane-related proteins was performed. RESULTS: After biaxial stretching, the tensile strength of PCL membranes increased from 21 to 42 MPa, with a Young's modulus of 225 MPa. AFM and SEM showed that biaxially stretched PCL membranes consisted of closely packed microfibrils. PCL membranes supported the attachment and proliferation of conjunctival epithelial cells to form confluent stratified epithelial sheets. Surface modification with NaOH resulted in greater hydrophilicity and cellular proliferation than that of untreated membranes. Transplanted conjunctival equivalents underwent greater proliferation and stratification in vivo. Cultivated conjunctival cells expressed K4, K19, MUC5AC, and Ki67, whereas collagen IV and integrin beta4 were detected at the basement membrane junction. CONCLUSIONS: An ultrathin PCL membrane was shown to be biocompatible, mechanically strong enough to stand up to handling, and able to support conjunctival epithelial cell proliferation. This membrane may have potential for use as a scaffold matrix for tissue-engineered conjunctival equivalents.

Amnion↗

PubMed2005

Decreased bacterial adhesion to surface-treated titanium.

Osteointegrative dental implants are widely used in implantology for their well-known excellent performance once implanted in the host. Remarkable bacterial colonization along the transgingival region may result in a progressive loss of adhesion at gum-implant interface and an increase of the bone area exposed to pathogens. This phenomenon may negatively effect the osteointegration process and cause, in the most severe cases, implant failure. The presence of bacteria at implant site affect the growth of new bone tissue and consequently, the achievement of a mechanically stable bone-implant interface, key parameters for a suitable implant osteointegration. In the present work, a novel surface treatment has been developed and optimized in order to convert the amorphous titanium oxide in a crystalline layer enriched in anatase capable of providing not only antibacterial properties but also of stimulating the precipitation of apatite when placed in simulated body fluid. The collected data have shown that the tested treatment results in a crystalline anatase-type titanium oxide layer able to provide a remarkable decrease in bacterial attachment without negatively effecting cell metabolic activity. In conclusion, the surface modification treatment analyzed in the present study might be an elegant way to reduce the risk of bacterial adhesion and increase the lifetime of the transgingival component in the osteointegrated dental implant.

Animals↗