Biomedical subjects

N Mordan

Publications and source records attributed to N Mordan.

5 recordsLinked to original sources

PubMed2003

Prevalence of Csh-like fibrillar surface proteins among mitis group oral streptococci.

The prevalence of Csh-like fibrillar surface proteins among oral streptococci was investigated by ELISA and by immunoelectron microscopy using antiserum raised to recombinant fragments of CshA of Streptococcus gordonii DL1. The majority of S. gordonii, Streptococcus sanguis and Streptococcus oralis strains tested elaborated short (ca. 50-80 nm long) surface fibrils and reacted with antiserum to the amino acid repeat region of CshA, demonstrating the widespread nature of Csh-like proteins among these species. In contrast, reactivity with antiserum raised to the adhesion-mediating non-repetitive region of CshA was more restricted. On the basis of the ELISA results, several isolates were selected for immunogold analysis using CshA antisera. Immunogold-negative staining showed a surface distribution of 10 nm gold particles consistent with antibody binding to short fibrils. Long fibrils (>150 nm long), where present, were not significantly labelled with gold. The results suggest that some of the short peritrichous fibrils on many mitis group streptococci comprise Csh-like fibrillar protein. Further, the data are consistent with our hypothesis that the antigenically conserved amino acid repeat region of Csh-like proteins forms a scaffold for cell-distal presentation of the amino-terminal non-repetitive region that, at least in S. gordonii DL1, functions as an adhesin.

Adhesins, Bacterial↗

PubMed2001

A new in vitro model for the study of microbial microleakage around dental restorations: a preliminary qualitative evaluation.

AIM: The aim of this study was to develop an in vitro model to replicate microbial microleakage at a tooth/ restoration interface using a constant depth film fermentor (CDFF). METHODOLOGY: Amalgam restorations were placed in machined bovine dentine cylinders and sealed externally with varnish, leaving a 1-mm perimeter exposed around the tooth/restoration interface. The dentine cylinders were housed in a CDFF and 300-microm thick microcosm dental plaques were grown over their exposed surfaces. The biofilms were maintained with a mucin-containing artificial saliva for up to 8 weeks. Cylinders were aseptically removed from the CDFF (at 1, 2, 4, & 8 weeks) and surface-decontaminated with validated protocols prior to splitting and sampling of apposing amalgam and dentine surfaces. Scanning electron microscopy (SEM) was used to ascertain the position and structure of the bacterial aggregates. Bacterial viability was determined by vital staining of the bacteria in situ. RESULTS: At all sampling times, SEM showed cocci, rods and filaments on both amalgam and dentine surfaces; some originated as cascades from the surface biofilm and extended into the tooth/restoration microspace. Vital staining showed the majority of bacteria from both dentine and amalgam surfaces to be viable. CONCLUSION: This preliminary investigation showed that the CDFF may be a valuable tool for the in vitro study of the dynamics of microbial microleakage around dental restorations.

Animals↗

PubMed2001

A transmission electron microscopy study of supragingival calculus.

In this study the ultrastructure of human dental calculus was investigated using transmission electron microscopy (TEM). The aim of the study was to observe and clarify the calcification process and the part played by dental plaque in this process. Supragingival calculus from 10 patients was harvested and processed. It was shown that both calculus, and dental plaque within non-mineralised lacunae in calculus, are heterogeneous. Furthermore it was shown that the calculus/dental plaque interface was distinct, although also variable. As calcification occurred apparently independently of dental plaque in some places and when calcification of dental plaque bacteria occurred, it was also varied, it was concluded that supragingival calculus is not simply 'mineralised plaque' but a complex heterogeneous material consisting of numerous phases of mineralisation and non-mineralised areas. The role of dental plaque in the mineralisation process is unclear. However, calculus was not observed arising out of mineralising dental plaque. Mineralising dental calculus and maturing dental plaque are two distinct and different phases occurring simultaneously, albeit with great variability.

Bacteria↗

PubMed1999

Mechanisms of internalization of Staphylococcus aureus by cultured human osteoblasts.

Staphylococcus aureus is an important bone pathogen, and evidence shows that this organism is internalized by chick osteoblasts. Here we report that S. aureus is internalized by human osteoblasts. Internalization was inhibited by monodansylcadaverine and cytochalasin D and to a lesser extent by ouabain, monensin, colchicine, and nocodazole. We propose that internalization occurs via a receptor-mediated pathway, requiring the participation of cytoskeletal elements, principally actin.

Actins↗

PubMed1993

Bone-derived growth factor release from poly(alpha-hydroxy acid) implants in vitro.

Matrix proteins were extracted from bovine cortical bone and polymer implant discs (13 mm x 2 mm composed of 50:50 poly DL-lactide-co-glycolide; mol. wt. approximately 9000) prepared by compression moulding granules with lyophilized bone matrix extracts (BMX) 10.1 (w/w). BMX-containing polymers were cultured for 5 wk in either serum-free Dulbecco's modification of Eagle's medium (DMEM) or phosphate buffer, and growth factor activity released into the media assayed by its ability to stimulate the proliferation of murine fibroblast BALB/c/3T3 cells. Approximately 60-75% of the biological activity was released during the first week of culture; however, less than half of the growth factor units originally incorporated into the implants retained biological activity. Scanning electron microscopy revealed the development of significant internal porosity by week 2; the size of the channels, pores and surface openings suggested they were of the right order for bone ingrowth. These preliminary findings suggest that poly(alpha-hydroxy acid) polymers containing bone-derived growth factors could have potential for stimulating osseous regeneration in vivo.

3T3 Cells↗