Interaction of human plasma fibronectin with cariogenic and non-cariogenic oral streptococci

The interaction of purified human plasma fibronectin (Fn) with bacteria was studied with a variety of oral streptococci. Each of the strains of Streptococcus mutans, Streptococcus salivarius, Streptococcus sanguis, and Streptococcus mitis tested was aggregated by Fn to various degrees, depending on the concentration of Fn added to the test mixtures. Binding assays performed with radiolabeled Fn and various strains of streptococci demonstrated various capabilities to bind Fn, and the amount of Fn bound by each strain was paralleled by its Fn-induced aggregation, with S. mutans 6715 giving the highest values in both assays. Because of the avid binding of Fn by certain strains of potentially cariogenic streptococci, we investigated the possibility that Fn may be present in human saliva and may be adsorbed from saliva onto artificial tooth pellicles. Immunoreactive Fn was detected in paraffin-stimulated whole saliva by enzyme-linked immunosorbent assays of saliva adsorbed onto gelatin-coated cuvettes and by immunoelectroblots (Western blots) of salivary components separated on sodium dodecyl sulfate-polyacrylamide slab gels. Furthermore, immunoreactive Fn was found to be present in artificial tooth pellicles formed by incubating hydroxyapatite beads with whole human saliva. These results demonstrate that certain strains of oral streptococci bind to and are aggregated by Fn. The presence of Fn in artificial tooth pellicles suggests that this macromolecule may play a role in the attachment of potentially cariogenic and other oral streptococci to dental tissues.     

Hypoesthesia after anterior cruciate ligament reconstruction: The relationship between proprioception and vibration perception deficits in individuals greater than one year post-surgery

Background

While surgical reconstruction restores mechanical stability following anterior cruciate ligament (ACL) rupture, many experience early-onset osteoarthritis despite surgery. Neurophysiological changes are hypothesized to contribute to knee osteoarthritis progression. Proprioceptive deficits have been reported following ACL injury/reconstruction; however, vibration perception threshold (VPT) has been less studied. This study explored relationships between pain, VPT, proprioception, function, and strength following ACL-reconstruction.

Binding of Streptococcus pyogenes to soluble and insoluble fibronectin.

The interaction of soluble and insoluble fibronectin with Streptococcus pyogenes was investigated. Soluble fibronectin bound to S. pyogenes in a dose-dependent and irreversible manner. Lipoteichoic acid competitively inhibited the binding of fibronectin to S. pyogenes but had little effect on the binding of fibronectin to staphylococci or pneumococci. The phase of growth of the streptococci had a slight effect on binding of fibronectin, with optimal binding occurring in the late log phase. S. pyogenes cells bound to fibronectin immobilized on microtiter plates in a dose-dependent and saturable manner. Both soluble fibronectin and lipoteichoic acid inhibited the binding of streptococci to immobilized fibronectin, suggesting that streptococci interact with soluble and insoluble fibronectin in a similar manner. Antibodies to fibronectin blocked the attachment of streptococci to immobilized fibronectin, whereas normal serum had no effect. Adherence of streptococci to buccal epithelial cells was inhibited by antibodies to fibronectin, but not by normal sera or by antibodies to buccal epithelial cells. The data suggest that lipoteichoic acid on the surface of S. pyogenes binds to fibronectin exposed on the host cell and that such binding mediates the attachment of streptococci to host cells.     

Up-regulated expression of zonula occludens protein-1 in human melanoma associates with N-cadherin and contributes to invasion and adhesion

During the process of malignant transformation, nascent melanoma cells escape keratinocyte control through down-regulation of E-cadherin and instead communicate among themselves and with fibroblasts via N-cadherin-based cell-cell contacts. The zonula occludens (ZO) protein-1 is a membrane-associated component of both the tight and adherens junctions found at sites of cell-cell contact. In most cancers, levels of ZO-1 are typically down-regulated, leading to increased motility. Here we report the novel observation that ZO-1 expression is up-regulated in melanoma cells and is located at adherens junctions between melanoma cells and fibroblasts. Immunofluorescence and co-immunoprecipitation studies showed co-localization of ZO-1 with N-cadherin. Down-regulation of ZO-1 in melanoma cells through RNA interference produced marked changes in cell morphology--leading to a less-dendritic, more rounded phenotype. Consistent with a role in N-cadherin-based adhesion, RNAi-treated melanoma cells were less adherent and invasive when grown in a collagen gel. These data provide the first evidence that increased ZO-1 expression in melanoma contributes to the oncogenic behavior of this tumor and further illustrate that protein products of genes, such as ZO-1, can function in either a pro- or anti-oncogenic manner when expressed in different cellular contexts.     

Inhibition of the in vitro growth of plasmodium falciparum by human polymorphonuclear neutrophil leucocytes

Polymorphonuclear neutrophil leucocytes (PMN) from children with acute Plasmodium falciparum malaria significantly inhibited parasite growth in homologous and in non-immune sera. Phagocytosis of schizonts in vitro was observed. PMN from uninfected children and uninfected adults had no effect on parasite growth.     

Characterization of lipoteichoic acid binding to polymorphonuclear leukocytes of human blood.

Human polymorphonuclear leukocytes (PMN) were shown to possess specific binding sites for lipoteichoic acid (LTA). LTA binding was reversible and time and temperature dependent. Scatchard plot analysis revealed an apparently single population of 6.6 X 10(6) LTA binding sites per PMN with a dissociation constant of 5.6 microM. Attachment of an avirulent, unencapsulated, M-negative strain of group A streptococci to PMN was inhibited by LTA, but not by other bacterial somatic antigens tested. Occupation of 30% of the LTA binding sites resulted in greater than 70% inhibition of streptococcal attachment to PMN. In contrast, LTA failed to block attachment of Escherichia coli or antibody-coated streptococci, indicating that binding sites for E. coli and the Fc portion of immunoglobulin G are distinct from those for LTA. Immunofluorescent studies demonstrated that LTA remained uniformly bound to PMN membranes for as long as 2 h at 37 degrees C. Cross-linking of PMN-bound LTA with anti-LTA resulted in rapid capping of LTA receptor sites. The results suggest that LTA is a monovalent ligand interacting with mobile receptors in the plasma membrane of PMN.     

Thymocyte expression of cathepsin L is essential for NKT cell development

CD1d antigen presentation to natural killer T (NKT) cells expressing the semi-invariant T cell receptor V(alpha)14J(alpha)18 requires CD1d trafficking through endosomal compartments; however, the endosomal events remain undefined. We show that mice lacking the endosomal protease cathepsin L (catL) have greatly reduced numbers of V(alpha)14(+)NK1.1(+) T cells. In addition, catL expression in thymocytes is critical not only for selection of these cells in vivo but also for stimulation of V(alpha)14(+)NK1.1(+) T cells in vitro. CD1d cell-surface expression and intracellular localization appear normal in catL-deficient thymocytes, as does the lysosomal morphology; this implies a specific role for catL in regulating presentation of natural CD1d ligands mediating V(alpha)14(+)NK1.1(+) T cell selection. These data implicate lysosomal proteases as key regulators of not only classical major histocompatibility complex class II antigen presentation but also nonclassical CD1d presentation.     

Isolation and characterization of a large molecular-weight polypeptide of herpes simplex virus type 1

Infection of human embryonic lung cells at the nonpermissive temperature (39°) with tsB2, a DNA-negative mutant of herpes simplex virus type 1 (HSV-1) resulted in the accumulation of a large molecular-weight (175,000) virus-induced polypeptide detectable by SDS-polyacrylamide gel electrophoresis. This polypeptide (VP175) was detectable only in small amounts and was found mainly in the nuclear fraction of cells infected with tsB2 at the permissive temperature (34°) or with wild-type HSV-1 at both 34° and 39°. However at 39° VP175 accumulated to become the major component in both the cytoplasmic and nuclear fractions of tsB2-infected cells. Identical results were obtained with a second mutant (tsB21) in the same complementation group. Temperature-shift studies suggest that the events responsible for the accumulation of VP175 at 39° occur early in the replicative cycle. With the use of a combination of SDS-preparative and analytical disc gel electrophoresis, VP175 was isolated and rabbit antisera to this polypeptide were prepared. By immunofluorescence assay, anti-VP175 sera reacted only with the nucleus of wild-type HSV-1-infected cells, whereas tsB2-infected cells cultured at 39° showed both cytoplasmic and nuclear immunofluorescence. In addition, the anti-VP175 serum reacted preferentially with HSV-1 as compared with HSV-2-infected cells, suggesting a possible type specificity for the reagent.