Requirements for invasion of epithelial cells by Actinobacillus actinomycetemcomitans.

Actinobacillus actinomycetemcomitans, an oral bacterium implicated in human periodontal disease, was recently demonstrated to invade cultured epithelial cells (D. H. Meyer, P. K. Sreenivasan, and P. M. Fives-Taylor, Infect. Immun. 59:2719-2726, 1991). This report characterizes the requirements for invasion of KB cells by A. actinomycetemcomitans. The roles of bacterial and host factors were investigated by using selective agents that influence specific bacterial or host cell functions. Inhibition of bacterial protein synthesis decreased invasion, suggesting the absence of a preformed pool of proteins involved in A. actinomycetemcomitans invasion. Inhibition of bacterial and eukaryotic energy synthesis also decreased invasion, confirming that A. actinomycetemcomitans invasion is an active process. Bacterial adherence to KB cells was indicated by scanning electron microscopy of infected KB cells. Further, the addition of A. actinomycetemcomitans-specific serum to the bacterial inoculum reduced invasion substantially, suggesting a role for bacterial attachment in invasion. Many of the adherent bacteria invaded the epithelial cells under optimal conditions. Inhibitors of receptor-mediated endocytosis inhibited invasion by A. actinomycetemcomitans. Like that of many facultatively intracellular bacteria, A. actinomycetemcomitans invasion was not affected by eukaryotic endosomal acidification. These are the first published observations describing the requirements for epithelial cell invasion by a periodontopathogen. They demonstrate that A. actinomycetemcomitans utilizes a mechanism similar to those used by many but not all invasive bacteria to gain entry into eukaryotic cells.     

Bioinspired mineralization and cell adhesion on surface functionalized poly(vinyl alcohol) films

Poly(vinyl alcohol) (PVA) films, when surface functionalized by phosphorylation, induced biomimetic nucleation and growth of calcium phosphate in a simulated physiological environment. The surface phosphorylation on PVA was ensured by attenuated total reflectance infrared spectroscopy. The morphology of the calcium phosphate phase grown on surface-phosphorylated PVA (PPVA) was analysed using scanning electron microscopy coupled with an energy-dispersive X-ray detector. The primary nucleation of calcium phosphate occurs in 3 days and secondary nucleation occurs after 10 days. The energy-dispersive X-ray analysis shows that the Ca/P ratio of the coating increases with time of exposure to the simulated physiological fluid and reaches 1.67 at 10 days. The PPVA supports in vitro cell adhesion and promotes in vitro biomineralization in the presence of cells, evaluated using human osteosarcoma cells.     

Frosted cylindrical lens induced artefact on Humphrey automated perimetry

Background: The aim of this study was to assess the effect of a cylindrical corrective lens with frosted sides on Humphrey automated perimetry performed with a translucent spectacle occluder in the contralateral eye. Methods: Ten healthy volunteers with cylindrical refractive errors of more than 1.50 DC had Humphrey visual fields (30‐2) measured with the contralateral eye occluded with either a translucent spectacle occluder or an opaque patch. The order of testing with each occluder was randomised. Additionally, visual field examination with the opaque patch was performed on three volunteer subjects with deep‐set eyes to establish the clinical significance of the frosted cylindrical lens induced artefact (CLA). The back vertex distances for the correcting lenses were measured for all tests. Results: Eight out of 10 volunteers tested with the translucent occluder demonstrated CLA, which was absent when the opaque patch was used. The presence of an artefact corresponding to the axis of the cylinder was observed, when the vertex distance was more than 15 mm. Three subjects with deep‐set eyes presented with CLA, even with the use of an opaque patch. Discussion: Cylindrical lens artefacts can occur with increasing vertex distance when using a translucent spectacle occluder instead of an opaque patch. CLA is also seen in subjects with deep‐set eyes.     

Oxidative and nitrosative stress mediated renal cellular damage induced by cyclosporine A: role of sulphated polysaccharides

Oxidative and nitrosative stress are known to exert various adverse effects on biological systems and this seems to be one of the major contributor of nephrotoxicity induced by cyclosporine A (CsA), which is a major clinical challenge, despite its potent immunosuppressive effect. Sulphated polysaccharides of marine origin are well known for its antioxidant properties, among its other biological applications. CsA administration (25 mg/kg body weight, orally, for 21 d) showed increased level of oxidants and xanthine oxidase activity. CsA induced nitrosative stress was evident from a marked elevation in the expression of inducible nitric oxide synthase mRNA in renal tissue and a concomitant increase in plasma nitric oxide level. Augmented levels of malondialdehyde, 8-hydroxy-2-deoxyguanosine and protein carbonyl coupled with diminished protein thiols; hallmarks of lipid peroxidation, DNA damage and protein oxidation were noted in CsA administered rats. Membrane damage was further confirmed by altered ATPase activities in the renal tissue. Simultaneous treatment with sulphated polysaccharides (5 mg/kg body weight, subcutaneously) remarkably prevented the above alterations mediated by oxidative and/or nitrosative stress during CsA induction. Hence, these findings conclude that the use of an antioxidant agent like sulphated polysaccharides could be a useful tool in reducing CsA-induced nephrotoxicity.