Biomedical subjects

I Olsen

Publications and source records attributed to I Olsen.

At least 55 records · Page 3Linked to original sources

PubMed2000

Direct and indirect effects of P2O5 glass reinforced-hydroxyapatite composites on the growth and function of osteoblast-like cells.

Human osteoblast-like cells were plated on hydroxyapatite and P2O5-glass reinforced hydroxyapatite composite discs. They were also cultured in the presence of media obtained by incubating the discs in the absence of cells. The effects of these direct and indirect interactions were examined by measuring cell proliferation and the expression of certain key extracellular matrix antigens. One composite was found to initially delay cell growth, while the extract of a different composite appeared to down-regulate DNA synthesis. Flow cytometry analysis showed that growth directly on the discs had little effect on collagen type I, but reduced fibronectin and osteocalcin levels. The extracts of the materials generally had less effect, although one extract obtained from the glass-reinforced hydroxyapatite significantly down-regulated fibronectin. These in vitro studies thus suggest that there were only few differences overall in the growth of the cells directly on the glass-reinforced compared with the hydroxyapatite discs and also only relatively small effects of the extracts on the cells. However, the flow cytometry results suggest that both the materials and the extracts may have a potentially important influence on connective tissue production, and that these effects are both material- and antigen-specific.

Antigens↗

PubMed2000

Flow cytometry analysis of the effects of pre-immersion on the biocompatibility of glass-reinforced hydroxyapatite plasma-sprayed coatings.

Multilayered coatings composed of mixtures of HA and P2O5-based bioactive glasses are of potential clinical benefit in orthopaedic and dental surgery. Pre-immersion of these materials has been reported to further enhance their efficacy in vivo, although the precise biological effects of this treatment are not yet known. In this study we have therefore prepared double-layer plasma-sprayed coatings and evaluated the effects of pre-immersion on the growth and function of human osteosarcoma cells in vitro, using the MTT assay and flow cytometry analysis, respectively. The results showed that the increase in numbers of viable cells was the same or elevated following incubation on the pre-immersed HA and glass-reinforced HA coatings compared with the non-immersed materials. In addition, the expression of bone sialoprotein and fibronectin, two key connective tissue antigens, was up-regulated in cultures grown on the pre-immersed surfaces compared with the non-treated materials. Moreover, cell numbers and antigen expression both improved as the proportion of glass increased, particularly in the pre-immersed samples. Our findings thus suggest that the immersion treatment of these materials appeared to improve the response of these bone-like cells.

Biocompatible Materials↗

PubMed2000

Development of soluble glasses for biomedical use Part II: the biological response of human osteoblast cell lines to phosphate-based soluble glasses.

Soluble glasses are considered to be of potential clinical value in orthopaedic and dental surgery. However, the biological response to these materials is not well understood. To determine the effects of these glasses, two human osteoblast cell lines, MG63 and HOS (TE85), were incubated in vitro in the presence of increasing concentrations of extracts of the glasses. The effects of the extracts on cell growth was measured using the MTT assay and an ELISA assay was used to measure the expression of bone sialoprotein (BSP), osteonectin (ON) and fibronectin (FN), antigens which play a fundamental part in the integrity and function of hard connective tissue. The results showed that the proliferation of the cells was adversely affected only by the more soluble glasses, which also down-regulated the expression of the bone-associated proteins. In contrast, the extract of the glass with the lowest dissolution rate, which contains relatively elevated levels of Ca2+, was found to enhance bone cell growth and antigen expression. These findings suggest that the compositions of these glasses at least partly determine the response of cells and thus, that the glasses could be modified to elicit a more optimal biological response and clinical efficacy.

Journal Article↗

PubMed2000

Strain differentiation in Bacteroides fragilis by RAPD and Dendron computer-assisted gel analysis.

Batteroides fragilis is the anaerobe most frequently isolated from human infections. Strains of this species are not easily distinguished by phenotypic tests. It is important to make this distinction because virulence may vary between strains and because B. fragilis seems to be a heterogeneous species. The aim of this study was to assess the utility of randomly amplified polymorphic DNA (RAPD) analysis for differentiation of 46 strains of B. fragilis. Twenty-seven of the strains belonged to Johnson's DNA homology group I and 8 to group II, while 11 strains had not been assigned to any of these groups (NI group). The primers OPA16 and 18 were chosen among 30 primers tested for optimal RAPD analysis. OPA18 gave best discrimination, revealing a total of 15 genotypes while OPA16 gave 13. The gels obtained after RAPD analysis were evaluated with the Dendron computer-assisted program. Most strains showed similarity levels (S(AB)) within 70%. Strain clusters thus established were not always in agreement with DNA homology since strains from both homology groups fell in the same cluster. Similarly, strains of the NI group fell among the group I and II homology strains. RAPD was useful for differentiation of B. fragilis strains and thus probably suitable for epidemiological studies. On the other hand, DNA-DNA homology, comparing the entire genome of strains rather than a few random priming sites, would be more reliable for taxonomy. Computer-assisted gel analysis made it possible to objectively evaluate multiple banding patterns, thereby increasing the reliability of the RAPD analysis.

Bacteroides Infections↗

PubMed2000

Strain differentiation in Bacteroides fragilis by ribotyping and computer-assisted gel analysis.

It is important to distinguish between Bacteroides fragilis strains as their virulence may vary and as B. fragilis seems to be a heterogeneous species. The aim of our study was to evaluate ribotyping for differentiation of 46 strains of B. fragilis and for assessment of strain heterogeneity within and between the two DNA-DNA homology strain groups established in this species. Twenty-seven strains belonged to Johnson's DNA homology group I and eight to group II. Eleven strains had not been assigned to any group (NI group). DNA from all strains was cut with BglI, EcoRI and HindIII. Restriction fragment length polymorphisms were investigated using a non-radioactive digoxigenin-labelled cDNA probe transcribed from Escherichia coli 16S+23S rRNA. Ribotyping with BglI was most discriminatory, revealing a total of 26 different patterns by visual inspection of gels. EcoRI followed with 20 patterns and HindIII with 13 patterns. The gels from ribotyping were processed using the Dendron computer-assisted program. Strain clusters established using Dendron were not always in agreement with homology-based strain groups. Strains of the NI group fell into both homology groups. Ribotyping, as it is based on a relatively small portion of the genome, is useful for strain distinction in epidemiological studies with B. fragilis, whereas DNA-DNA homology, using the entire genome, is more reliable for taxonomy. The Dendron computer-assisted program, which enabled objective assessment of multiple banding patterns, increased the reliability of ribotyping.

Bacteroides fragilis↗

PubMed2000

Antimicrobial resistance with focus on oral beta-lactamases.

Over the last 10-15 yr antibiotic resistance has increased in the oral microflora. The beta-lactam antibiotics, i.e., penicillins and cephalosporins, are the most frequently used antimicrobial agents. Unfortunately, the efficiency of these drugs is increasingly being challenged by the emergence of resistant bacteria, which is mainly due to their production of beta-lactamases. In this paper, mechanisms of antibiotic resistance are reviewed, with emphasis on beta-lactamases. This review also discusses how the presence of beta-lactamases in oral microorganisms may affect the treatment of oral diseases. Dentists can influence the emerging global crisis of antibiotic resistance by carefully evaluating the indications for antibiotic treatment. General guidelines for when and how to use antibiotics in dentistry are reviewed.

Anti-Bacterial Agents↗

PubMed2000

Extraradicular infection: a methodological study.

Whether bacteria live or die in periapical lesions of endodontic origin is debated. Sampling of periapical bacteria is difficult due to possible contamination from the indigenous microflora. The aim of this study was to examine whether bacteria were present in periapical lesions of asymptomatic teeth before sampling or were transferred there during sampling. Thirty patients with root-filled teeth and periapical radiolucencies were divided into two groups, each containing 15 patients. In Group 1, a marginal incision was made to explore the periapical lesion. In Group 2, a submarginal incision was made. Before incision, the gingiva and mucosa were washed with 0.2% chlorhexidine gluconate. Bacterial samples were taken from the mucosa before reflecting the flap, and from the alveolar bone and the periapical lesion immediately after. All samples were cultured anaerobically on all-purpose and selective media. In Group 1, 12 of the 15 patients (80%) yielded bacteria from their mucosal samples despite the chlorhexidine wash. Bacterial growth was observed in all samples (100%) from the alveolar bone while the periapical lesions gave bacterial growth in 11 of 15 cases (73%). In Group 2, bacteria were cultured from the mucosa in 11 of 15 (73%) patients. Three samples (20%) from the alveolar bone and 10 from the periapical lesions (67%) gave positive growth. The predominant cultivable bacteria were anaerobic. Phenotypic profiling, performed with the data-based API bioMérieux system, indicated that the sampling technique used prevented mucosal bacteria from reaching the exposed bone and the periapical lesions. Profiling also indicated that following marginal incision, bacteria from the periodontal pocket might have reached the underlying tissues by surgeon-released bacteremia or direct translocation. Most organisms detected in the periapical lesions were clearly different from the bacteria present at neighboring sites and appeared to have been there before sampling.

Bacteria, Anaerobic↗

PubMed2000

Assessment of periradicular microbiota by DNA-DNA hybridization.

In the present study the "checkerboard" DNA-DNA hybridization technique was used to identify bacteria in periapical endodontic lesions of asymptomatic teeth. Thirty-four patients with root-filled teeth and apical periodontitis were divided into two groups, each containing 17 patients. In Group 1, a marginal incision was performed during surgery to expose the lesion, and in Group 2, a submarginal incision was applied. The gingiva and mucosa were swabbed with an 0.2% chlorhexidine gluconate solution prior to surgery. Bacterial DNA was identified in all samples from the two groups using 40 different whole genomic probes. The mean number (+/- SD) of species detected was 33.7 +/- 3.3 in Group 1 and 21.3 +/- 6.3 in Group 2 (P < 0.001). The majority of the probe-detected bacteria were present in more lesions from Group 1 than from Group 2. The differences were most notable for Campylobacter gracilis, Porphyromonas endodontalis, Propionibacterium acnes, Capnocytophaga gingivalis, Fusobacterium nucleatum ssp. nucleatum, Fusobacterium nucleatum ssp. polymorphum, Prevotella intermedia, Treponema denticola, Streptococcus constellatus and Actinomyces naeslundii I. Bacterial species such as Actinobacillus actinomycetemcomitans and Bacteroides forsythus were detected in more than 60% of the lesions from both groups. Also, P. endodontalis was abundant in periapical tissue. The data supported the idea that following a marginal incision, bacteria from the periodontal pocket might reach the underlying tissues by surgeon-released bacteremia. The study provided solid evidence that bacteria invade the periapical tissue of asymptomatic teeth with apical periodontitis. The detection of much more bacteria with the "checkerboard" DNA-DNA hybridization method than has previously been recovered by anaerobic culture indicated that the endodontic (and periodontal) microfloras should be redefined using molecular methods.

Actinomyces↗

PubMed2000

Genetic diversity of Porphyromonas gingivalis and its possible importance to pathogenicity.

During recent years much effort has been put into understanding the genetic composition of the oral populations of black-pigmented anaerobic bacteria. One of them, Porphyromonas gingivalis, is a putative periodontopathogenic organism considered to be particularly relevant in the etiology of adult periodontitis. It has been shown in studies using molecular typing methods that most bacterial populations consist of numerous genetic clones, and that only a small proportion of these clones cause disease. Elucidation of a possible association of genotypic profiles with either disease or clinical healthy condition is important for understanding the pathogenic characteristics of bacteria. Studies addressing this issue as it relates to P. gingivalis are reviewed in the present article. Genotypic characterization of P. gingivalis strains has revealed extensive heterogeneity in natural populations of this bacterium. Some of the potential virulence factors of P. gingivalis have been purified and cloned and methods have been established to identify their genes. Although no studies have clearly defined the relationship between a specific genotype of P. gingivalis and periodontal status of the host, it seems that molecular typing tools, which are undergoing rapid improvements, will allow us to distinguish between virulent and avirulent strains of the same species in the near future.

Adult↗

PubMed2000

Bulleidia extructa gen. nov., sp. nov., isolated from the oral cavity.

Five strains of anaerobic non-sporing Gram-positive bacilli isolated from advanced periodontitis (four strains) and a dentoalveolar abscess (one strain) that did not correspond to existing species were subjected to phenotypic and genetic characterization. Following 16S rDNA sequence analysis, they were found to constitute a novel branch of the low G+C Gram-positive division of the phylogenetic tree related to Erysipelothrix rhusiopathiae and Holdemania filiformis. A new genus Bulleidia, and the species Bulleidia extructa, are proposed. Growth of B. extructa in broth media was poor but was enhanced by the addition of fructose, glucose or maltose together with Tween 80. Glucose and maltose were fermented and arginine was hydrolysed. Acetate, lactate and trace amounts of succinate were the end products of glucose fermentation. The G+C content of the DNA of the type strain is 38 mol%. The type strain of Bulleidia extructa is DSM 13220T.

Bacteria, Anaerobic↗

PubMed2000

Dysgonomonas gen. nov. to accommodate Dysgonomonas gadei sp. nov., an organism isolated from a human gall bladder, and Dysgonomonas capnocytophagoides (formerly CDC group DF-3).

Results of a polyphasic taxonomic study on an unknown Gram-negative, facultatively anaerobic, coccobacillus-shaped organism isolated from an infected human gall bladder are presented. Phenotypic and molecular taxonomic studies revealed the organism to be close to, but distinct from, organisms designated CDC (Centers for Disease Control and Prevention) group DF-3. The unknown bacterium was readily distinguished from reference strains of Bacteroides, Prevotella, Porphyromonas and related taxa by 16S rRNA gene sequencing, biochemical tests, analysis of cellular long-chain fatty acids and electrophoretic analysis of whole-cell proteins. Based on the results of the present study, it is proposed that the unknown bacterium be classified in a new genus, Dysgonomonas, as Dysgonomonas gadei sp. nov. (type strain CCUG 42882T = CIP 106420T). In addition, a new species, Dysgonomonas capnocytophagoides sp. nov., is proposed to accommodate strains previously belonging to CDC group DF-3. The type species of the genus Dysgonomonas is Dysgonomonas gadei.

Aged↗

PubMed2000

Systemic diseases caused by oral infection.

Recently, it has been recognized that oral infection, especially periodontitis, may affect the course and pathogenesis of a number of systemic diseases, such as cardiovascular disease, bacterial pneumonia, diabetes mellitus, and low birth weight. The purpose of this review is to evaluate the current status of oral infections, especially periodontitis, as a causal factor for systemic diseases. Three mechanisms or pathways linking oral infections to secondary systemic effects have been proposed: (i) metastatic spread of infection from the oral cavity as a result of transient bacteremia, (ii) metastatic injury from the effects of circulating oral microbial toxins, and (iii) metastatic inflammation caused by immunological injury induced by oral microorganisms. Periodontitis as a major oral infection may affect the host's susceptibility to systemic disease in three ways: by shared risk factors; subgingival biofilms acting as reservoirs of gram-negative bacteria; and the periodontium acting as a reservoir of inflammatory mediators. Proposed evidence and mechanisms of the above odontogenic systemic diseases are given.

Cardiovascular Diseases↗

PubMed2000

Alkyl hydroperoxide reductases C and D are major antigens constitutively expressed by Mycobacterium avium subsp. paratuberculosis.

Antigens characteristic for Mycobacterium avium subspecies paratuberculosis were identified by crossed immunoelectrophoresis (CIE) and by absorbing out cross-reactive antigens by using a polyclonal and polyvalent Mycobacterium avium subspecies avium antiserum. Two antigens were present in M. avium subsp. paratuberculosis and not detected in Mycobacterium avium subsp. avium. They were identified as antigens 17 and 20 in a CIE reference system for M. avium subsp. paratuberculosis antigens. Purified antigen 20 was identified as alkyl hydroperoxide reductase C (AhpC) while the N-terminal part of purified antigen 17 showed 80% homology with alkyl hydroperoxide reductase D (AhpD) of Mycobacterium tuberculosis. AhpC had a nonreduced mobility in sodium dodecyl sulfate-polyacrylamide gel electrophoresis corresponding to a molecular mass of 45 kDa and is probably a homodimer linked with disulfide bridges in its native form. AhpD had a mobility corresponding to 19 kDa. Monospecific rabbit antiserum against AhpC and AhpD reacted with 9 strains of M. avium subsp. paratuberculosis but not with 20 other mycobacterial strains except for a Mycobacterium gordonae strain, against which a weak cross-reactive band was produced. Goats experimentally infected with M. avium subsp. paratuberculosis had strong gamma interferon (IFN-gamma) responses toward both AhpC and AhpD, and they also had antibodies against AhpC. The ability of AhpC and AhpD to induce IFN-gamma production shows that these proteins potentially could be used in future vaccines or in diagnostic assays. These results further show that AhpC and AhpD are immunologically important proteins which are constitutively and highly expressed in M. avium subsp. paratuberculosis without the bacteria being submitted to oxidative stress and that the specificities of antigens can be a matter of different levels of protein expression in various species as well as distinct structural differences.

Amino Acid Sequence↗

PubMed2000

Distinct differences in repertoires of low-molecular-mass secreted antigens of Mycobacterium avium complex and Mycobacterium tuberculosis.

Antigens in a 4-week-old culture filtrate (CF) of Mycobacterium avium subsp. avium were separated in sodium dodecyl sulfate-polyacrylamide gel electrophoresis and identified by Western blotting. The culture had minimal lysis of bacilli, giving a CF preparation consisting mainly of secreted proteins. Comparison with a similar CF of Mycobacterium tuberculosis with almost no contamination with intracellular proteins showed the presence of cross-reactive antigens homologous to the four components of the antigen 85 complex, as well as MPT32. These were major constituents of the M. avium subsp. avium CF. In addition, there were several low-molecular-mass bands (<15 kDa) in both species that did not cross-react with polyclonal and polyvalent rabbit antibodies in Western blotting. Furthermore, these bands were not detected in corresponding sonicate preparations, indicating high localization indexes, which is typical of soluble secreted proteins. A 14-kDa protein was selected for purification and more detailed characterization. The N-terminal amino acid sequence was determined, and a matching gene was found within the genomic sequence of M. avium subsp. avium which was highly homologous to Rv0455c of M. tuberculosis. The gene encoded a signal peptide typical of secreted mycobacterial proteins. A rabbit antiserum was raised against the purified protein, and the antigen was demonstrated by Western blotting in CFs of M. avium subsp. avium, Mycobacterium avium subsp. paratuberculosis, Mycobacterium intracellulare, and Mycobacterium scrofulaceum but was not detected in M. tuberculosis. This is a new example of a highly homologous gene being differentially expressed by different mycobacterial species.

Amino Acid Sequence↗

PubMed2000

Genetic structure of population of Bacillus cereus and B. thuringiensis isolates associated with periodontitis and other human infections.

The genetic diversity and relationships among 35 Bacillus cereus and Bacillus thuringiensis isolates recovered from marginal and apical periodontitis in humans and from various other human infections were investigated using multilocus enzyme electrophoresis. The strains were isolated in Norway, except for three strains isolated from periodontitis patients in Brazil. The genetic diversity of these strains was compared to that of 30 isolates from dairies in Norway and Finland. Allelic variation in 13 structural gene loci encoding metabolic enzymes was analyzed. Twelve of the 13 loci were polymorphic, and 48 unique electrophoretic types (ETs) were identified, representing multilocus genotypes. The mean genetic diversity among the 48 genotypes was 0.508. The genetic diversity of each source group of isolates varied from 0.241 (periodontal infection) to 0.534 (dairy). Cluster analysis revealed two major groups separated at a genetic distance of greater than 0.6. One cluster, ETs 1 to 13, included solely isolates from dairies, while the other cluster, ETs 14 to 49, included all of the human isolates as well as isolates from dairies in Norway and Finland. The isolates were serotyped using antiflagellar antiserum. A total of 14 distinct serotypes were observed. However, little association between serotyping and genotyping was seen. Most of the strains were also analyzed with pulsed-field gel electrophoresis, showing the presence of extrachromosomal DNA in the size range of 15 to 600 kb. Our results indicate a high degree of heterogeneity among dairy strains. In contrast, strains isolated from humans had their genotypes in one cluster. Most strains from patients with periodontitis belonged to a single lineage, suggesting that specific clones of B. cereus and B. thuringiensis are associated with oral infections.

Adult↗

PubMed2000

Soluble and cell-associated forms of the adhesion molecule LFA-3 (CD58) are differentially regulated by inflammatory cytokines.

The adhesion molecule lymphocyte function-associated antigen 3 (LFA-3) (CD58) is an important regulator of immune cell function which occurs as both surface-associated and 'soluble' forms. This study has investigated the inter-relationship and the effects of cytokines on the expression of LFA-3 isoforms. The surface antigen was found to be relatively unaffected by cytokines, but the release of soluble LFA-3 (sLFA-3) was highly responsive to interleukin 1beta (IL-1beta), interferon gamma (IFN-gamma) and tumour necrosis factor alpha (TNF-alpha). This modulation was cell-specific, particularly with regard to IFN-gamma, which up-regulated sLFA-3 release by A431 cells but down-regulated the release of the soluble form from HEp2 and HepG2 cells. We further demonstrated that LFA-3 is also present in a cytoplasmic 'pool' in each of the cells and, moreover, that cleavage of LFA-3 from the cell surface by phospholipase C resulted in an increase in the levels of the intracellular LFA-3 and replacement of the membrane-associated antigen. These observations suggest that the expression of the surface, soluble and intracellular forms of LFA-3 may be linked by regulatory mechanisms which are likely to exert an important influence on inflammatory interactions.

CD58 Antigens↗

PubMed1999

Flow cytometry analysis of effects of glass on response of osteosarcoma cells to plasma-sprayed hydroxyapatite/CaO-P(2)O(5) coatings.

Multilayered coatings composed of mixtures of hydroxyapatite (HA) and P(2)O(5)-based bioactive glasses offer potential clinical benefits in orthopedic and dental surgery. In this study double-layer plasma-sprayed coatings were prepared and the biological response evaluated in tissue culture using two human osteosarcoma cell lines, MG63 and HOS TE85 (HOS). The cells were cultured on the materials and the effects on cell growth were determined using a spectrophometric assay of a mitochondrial enzyme that is active in viable cells. While none of the materials influenced the growth of the MG63 cells, the HOS cells appeared to undergo less proliferation on all the HA materials. Flow cytometry analysis was carried out using rabbit antibodies against osteonectin, osteopontin, bone sialoprotein, fibronectin, and collagen type I to measure the effects of the materials on key cellular functions. The results showed that the materials downregulated the expression of these extracellular matrix antigens by MG63 cells whereas they had less effect on the HOS cells compared to the same cells incubated on a plastic surface. Notably, with both cell lines the composite with the higher percentage of glass restored the production of connective tissue proteins to levels that were more similar to those present in the control cells.

Animals↗

PubMed1999

Intrafamilial transmission of black-pigmented, putative periodontal pathogens.

Porphyromonas gingivalis and Prevotella intermedia are black-pigmented, putative periodontopathogenic bacteria considered to cause some forms of periodontal disease. Porphyromonas gingivalis and P. intermedia can be transmitted between humans and produce periodontal disease in susceptible hosts. In this article, studies using molecular typing methods for determining the transmission of black-pigmented, putative periodontopathogens between family members are reviewed. As individuals living close to each other are more prone to transmit bacteria, the studies on transmission of periodontopathogens have been performed on family members. It has been shown that black-pigmented bacteria are not only transferred between spouses but also between parents and child. Since only a limited number of studies have been done, longitudinal and controlled studies should be carried out to elucidate further the transmittance potential of these bacteria.

Journal Article↗