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Biomedical subjects

R Kent

Publications and source records attributed to R Kent.

At least 19 recordsLinked to original sources
PubMed2003

Outbreak of hepatitis A infection among intravenous drug users in Suffolk and suspected risk factors.

A prolonged outbreak of hepatitis A infection amongst drug users in Suffolk prompted a study of the natural immunity against hepatitis A in this population, and a retrospective analysis of the relationship between specific drug-taking behaviours and the risk of hepatitis A infection. Prior to the outbreak, age-specific seroprevalence of hepatitis A IgG in drug users was similar to that amongst blood donors in the region. Of those without effective immunity, intravenous drug users, multiple drug users and those injecting frequently were more likely to have developed hepatitis. The reported frequency of equipment sharing and the number of injecting partners were not related to the risk of infection. The potential for blood-to-blood, and a suggested faecal-blood transmission were considered to be important in propagating the outbreak in this population. We suggest that a single dose of hepatitis A vaccine administered opportunistically should be used in outbreaks involving drug users.

Adult↗
PubMed2002

Similarity of the oral microbiota of pre-school children with that of their caregivers in a population-based study.

This study evaluated the similarity between the oral microbiota of young children and that of their adult caregivers. Oral samples from children (174 dentate and 18 pre-dentate) aged 6-36 months and their caregivers in Saipan were assayed using a DNA probe assay. Many species including Streptococcus mutans, Streptococcus sobrinus, Actinomyces species, Campylobacter rectus, Fusobacterium nucleatum, Prevotella intermedia, and Porphyromonas gingivalis were detected in dentate and pre-dentate children, whereas Bacteroides forsythus was detected only in dentate children. A higher percentage of children were positive for the detection of an individual species if the caregiver was also positive. There were significant relative risks of species detection between dentate children and their caregivers. By logistic regression, there were significant positive associations between species detection in caregiver and in child, but not between species detection and child age or maternal education level. In conclusion, dental pathogens were detected in young, including pre-dentate, children. The microbial profiles of children were strongly associated with the microbiota of their caregivers.

Actinomyces↗
PubMed2002

The microbiota of young children from tooth and tongue samples.

This study determined the frequency with which 38 microbial species were detected in 171 randomly selected children from 6 to 36 months of age. Children were sampled and dental caries measured. Oral samples were assayed by means of a checkerboard DNA probe assay. The detection frequencies from tongue samples in children under 18 mos were: S. mutans 70%, S. sobrinus 72%, P. gingivalis 23%, B. forsythus 11%, and A. actinomycetemcomitans 30%, with similar detection frequencies in children over 18 mos. Thus, S. mutans and the periodontal pathogens, P. gingivalis and B. forsythus, were detected even in the youngest subjects. Species associated with caries included S. mutans (children ages 18-36 mos) and A. israelii (children ages < 18 mos), the latter species possibly reflecting increased plaque in children with caries. Species detection from tooth and tongue samples was highly associated, with most species detected more frequently from tongue than from tooth samples in children under 18 mos, suggesting that the tongue was a potential microbial reservoir.

Aggregatibacter actinomycetemcomitans↗
PubMed2001

Oral cancer in vivo gene expression profiling assisted by laser capture microdissection and microarray analysis.

Large scale gene expression profiling was carried out on laser capture microdissected (LCM) tumor and normal oral epithelial cells and analysed on high-density oligonucleotide microarrays. About 600 genes were found to be oral cancer associated. These oral cancer associated genes include oncogenes, tumor suppressors, transcription factors, xenobiotic enzymes, metastatic proteins, differentiation markers, and genes that have not been implicated in oral cancer. The database created provides a verifiable global profile of gene expression during oral carcinogenesis, revealing the potential role of known genes as well as genes that have not been previously implicated in oral cancer.

Aged↗
PubMed2001

Outcomes and costs of coronary artery bypass grafting: comparison between octogenarians and septuagenarians at a tertiary care centre.

BACKGROUND: Decision-making related to coronary artery bypass grafting (CABG) in elderly patients is hampered by inadequate outcome data. We compared the clinical outcomes of octogenarians with those of septuagenarians who underwent CABG. Our secondary objective was to compare the costs associated with CABG in these groups. METHODS: We conducted a retrospective database review of patients 70 years of age and older who had undergone CABG at a regional cardiac surgical centre in Hamilton, Ont., between July 1, 1997, and Apr. 30, 2000. A total of 1034 patients were divided into 3 age groups: young septuagenarians (aged 70-74 years), old septuagenarians (aged 75-79) and those 80 and older. Costs were determined in a subset of 773 patients with the use of a case-costing system for cardiac surgery developed at our institution. RESULTS: The 3 groups were similar with respect to sex distribution and preoperative risk factors. Urgency scores at referral differed significantly between the groups, with the young septuagenarians demonstrating the lowest risk (mean score [and standard deviation] 4.48 [1.3] in that group, 4.28 [1.4] in the old septuagenarian group and 4.11 [1.2] in the octogenarian group). The rates of all complications combined were similar between the 3 groups (27.1%, 28.1% and 29.6% in the young and old septuagenarian groups and the octogenarian group respectively). There were no significant differences between the 3 groups in the mean number of grafts per patient (3.0, 3.1 and 3.0 respectively), the rate of postoperative death (3.3%, 5.7% and 4.2%), the mean length of stay (11.7, 13.4 and 12.6 days) or the incidence of postoperative myocardial infarction (4.5%, 3.4% and 4.2%). The total cost of CABG per patient did not differ significantly between the 3 groups. INTERPRETATION: Given that patients who are accepted for CABG represent a selected population, our findings suggest that, with careful triage, CABG in octogenarians is as safe as, and no more costly than, CABG in septuagenarians.

Age Factors↗
PubMed2001

Reduction of p12DOC-1 expression is a negative prognostic indicator in patients with surgically resected oral squamous cell carcinoma.

PURPOSE: p12DOC-1 is a growth suppressor that negatively regulates cyclin-dependent kinase 2 (CDK2) activities. Expression of p12DOC-1 is reduced and/or lost in tumor tissues. The purpose of this study is to correlate in vivo the expression of p12DOC-1 in oral cancer tissues by immunohistochemistry with clinical and pathological parameters. EXPERIMENTAL DESIGN: Twenty-five cases of normal oral mucosa and 127 cases of oral squamous cell carcinomas were evaluated. Patients' charts were reviewed for clinical, pathological, and 10-year survival data. Because p12DOC-1 is a growth suppressor and associates with CDK2, parallel immunostaining was done for proliferating cell nuclear antigen and CDK2 to evaluate cell proliferation and potential correlation with CDK2. RESULTS: Our results showed that strong p12DOC-1 staining was uniformly seen in normal oral mucosa. p12DOC-1 staining was reduced or absent in 81 cases (63.8%) of oral squamous cell carcinomas. Decreased p12DOC-1 staining (<25% of cells stained) correlated with tumor mode of invasion (P = 0.001) and higher proliferating cell nuclear antigen (P = 0.0028) and CDK2 (P = 0.0020) expression. Survival analysis showed significant correlation of low p12DOC-1 expression with the risk of cervical lymph node metastasis (P = 0.001) and patients' 10-year survival status (P = 0.0214). CONCLUSIONS: These results allow us to conclude that reduction of p12DOC-1 protein expression is a frequent event in oral cancers. Intratumor immunohistochemical evaluation of p12DOC-1 expression can be an adjunctive prognostic indicator for patients with oral cancer.

Adult↗
PubMed2000

Two-dimensional gel electrophoresis analyses of pH-dependent protein expression in facultatively alkaliphilic Bacillus pseudofirmus OF4 lead to characterization of an S-layer protein with a role in alkaliphily.

The large majority of proteins of alkaliphilic Bacillus pseudofirmus OF4 grown at pH 7.5 and 10.5, as studied by two-dimensional gel electrophoresis analyses, did not exhibit significant pH-dependent variation. A new surface layer protein (SlpA) was identified in these studies. Although the prominence of some apparent breakdown products of SlpA in gels from pH 10.5-grown cells led to discovery of the alkaliphile S-layer, the largest and major SlpA forms were present in large amounts in gels from pH 7.5-grown cells as well. slpA RNA abundance was, moreover, unchanged by growth pH. SlpA was similar in size to homologues from nonalkaliphiles but contained fewer Arg and Lys residues. An slpA mutant strain (RG21) lacked an exterior S-layer that was identified in the wild type by electron microscopy. Electrophoretic analysis of whole-cell extracts further indicated the absence of a 90-kDa band in the mutant. This band was prominent in wild-type extracts from both pH 7.5- and 10.5-grown cells. The wild type grew with a shorter lag phase than RG21 at either pH 10.5 or 11 and under either Na(+)-replete or suboptimal Na(+) concentrations. The extent of the adaptation deficit increased with pH elevation and suboptimal Na(+). By contrast, the mutant grew with a shorter lag and faster growth rate than the wild type at pH 7. 5 under Na(+)-replete and suboptimal Na(+) conditions, respectively. Logarithmically growing cells of the two strains exhibited no significant differences in growth rate, cytoplasmic pH regulation, starch utilization, motility, Na(+)-dependent transport of alpha-aminoisobutyric acid, or H(+)-dependent synthesis of ATP. However, the capacity for Na(+)-dependent pH homeostasis was diminished in RG21 upon a sudden upward shift of external pH from 8. 5 to 10.5. The energy cost of retaining the SlpA layer at near-neutral pH is apparently adverse, but the constitutive presence of SlpA enhances the capacity of the extremophile to adjust to high pH.

Alkalies↗
PubMed2000

The pH of dental plaque in its relation to early enamel caries and dental plaque flora in humans.

Dental caries appears to result from the action of multiple, interrelated factors. A companion study dealt with the plaque-flora/caries relationship (van Ruyven et al., 2000). The plaque-pH/caries relationship is the subject of this study. Since both studies involve the same subjects, plaques, and tooth surfaces, data on the examined factors have also been integrated. In vivo plaque pH determinations (microelectrode) were done on buccal sound (s) and "white-spot" (ws) caries surfaces in a selected dentition area in a low-caries (no ws) and higher-caries subject group. The pH response to sugar was evaluated before and after a sugar rinse, a local sugar application, or sucking on a sugary lozenge. pH profiles with sugar rinsing and normal or limited salivary flow conditions, showed progressively decreasing plaque pH values at various time points in the order of: low-caries subjects (s sites), higher-caries subjects (s sites), higher-caries subjects (s + ws sites), and higher-caries subjects (ws sites). The minimum pH values showed the same trend. Analyses of all data indicated only a statistical difference for minimum values for s sites in low-caries subjects vs. ws sites in higher-caries subjects, and for s and ws sites in the latter. Local sugar application and sucking on a sugary lozenge induced smaller pH drops than sugar rinsing; such suboptimal sugar exposure caused a disappearance of the difference between the minimum pH values for s and ws sites observed with sugar rinsing in the higher-caries subjects. Initial plaque pH values were similar regardless of subject or tooth caries status. The values were also not correlated with the plaque levels of strongly iodophilic polysaccharide-storing bacteria. Collectively, both studies indicate that increasing subject caries status is characterized by increasing plaque levels of highly-acid-tolerant, acidogenic bacteria and an increasing plaque-pH-lowering potential and support the dynamic relationship between these parameters.

Administration, Topical↗
PubMed2000

Relationship among mutans streptococci, "low-pH" bacteria, and lodophilic polysaccharide-producing bacteria in dental plaque and early enamel caries in humans.

Multiple interactions occur among major determinants of dental caries. We have studied the bacterial flora and pH-lowering capacity of the same dental plaques in relation to caries. The findings on the plaque flora are reported here. The buccal surfaces of upper teeth in each subject were selected for study. A low-caries group had no "white spot" caries (ws) in the selected dentition area; a higher-caries group averaged 4.1 ws in this area. The latter group was divided into subjects with 2, 3, or 4 ws and subjects with 5, 6, or 7 ws. Enumerated organisms in plaque samples (sound and ws sites) from all subjects were: (1) mutans streptococci (MS) on mitis-salivarius-bacitracin and mitis-salivarius agar; (2) non-mutans streptococci (non-MS) on mitis-salivarius agar; (3) organisms that were categorized according to their minimum pH in sugar broth, i.e., the predominant undifferentiated total flora on blood agar or the predominant non-MS flora on mitis-salivarius agar; and (4) iodophilic polysaccharide-storing organisms on trypticase-yeast extract-salts agar. Plaques covering ws lesions contained generally only low proportions (< 0.1%) of MS. The plaque proportions of all the above 4 bacterial groups were increased in the higher-caries group but were similar for s and ws sites in this group. Over half of the total plaque flora in subjects with 5, 6, or 7 ws consisted of "low-pH"-type organisms (minimum pH < 4.4). Many of these were neither MS nor "low-pH" non-MS. The numerical emergence of MS in plaque appeared to be preceded often by other types of "low-pH" bacteria, including the non-MS. Caries development in the absence or presence of MS as well as different bacterial successions in plaque can be explained readily by the dynamic and positive relationship among the factors carbohydrate consumption, plaque flora composition, plaque acidogenic potential, and caries activity.

Adolescent↗
PubMed2000

An evaluation of ontology exchange languages for bioinformatics.

Ontologies are specifications of the concepts in a given field, and of the relationships among those concepts. The development of ontologies for molecular-biology information and the sharing of those ontologies within the bioinformatics community are central problems in bioinformatics. If the bioinformatics community is to share ontologies effectively, ontologies must be exchanged in a form that uses standardized syntax and semantics. This paper reports on an effort among the authors to evaluate alternative ontology-exchange languages, and to recommend one or more languages for use within the larger bioinformatics community. The study selected a set of candidate languages, and defined a set of capabilities that the ideal ontology-exchange language should satisfy. The study scored the languages according to the degree to which they satisfied each capability. In addition, the authors performed several ontology-exchange experiments with the two languages that received the highest scores: OML and Ontolingua. The result of those experiments, and the main conclusion of this study, was that the frame-based semantic model of Ontolingua is preferable to the conceptual graph model of OML, but that the XML-based syntax of OML is preferable to the Lisp-based syntax of Ontolingua.

Computational Biology↗
PubMed2000

Rib fracture patterns and radiologic detection--a restraint-based comparison.

This paper presents a study of the rib fracture patterns generated in simulated frontal collisions and the visibility of the rib fractures on plain film radiographs. Using 29 cadaver subjects, rib fractures were identified on oblique, lateral, and anteroposterior chest films by five radiologists independently and were compared with fractures found during a detailed necropsy. Physical, geometric, and experimental factors demonstrated an influence on the ability of a radiologist to identify rib fractures on an x-ray. Specifically, the restraint system configuration, the total number of fractures, the circumferential location of the fracture, the rib number, and the aspect (right or left) affected fracture identification. The results verify that torso belt loading produces rib fractures generally located along the path of the belt whereas superimposed airbag loading results in a more distributed and posterolateral fracture pattern. A higher proportion of rib fractures was identified on x-ray for occupants restrained by only a belt (44% of fractures) than for occupants restrained by both a belt and an airbag (24% of fractures). Overall, less than 40% of the rib fractures were detected upon an initial examination of radiographs. After being provided with the location of all fractures, detection increased to 49%. On average, occult rib fractures resulted in an average underreporting of injury severity of more than one AIS level.

Acceleration↗
PubMed1999

Cyclin D1 overexpression combined with N-nitrosomethylbenzylamine increases dysplasia and cellular proliferation in murine esophageal squamous epithelium.

We previously described the oral-esophageal tissue-specific expression of cyclin D1 with the Epstein-Barr virus ED-L2 promoter in transgenic mice, and resulting dysplasia. Given the evidence for an interplay between environmental and genetic factors in esophageal squamous carcinogenesis, the aim of this study was to determine the potential cooperation of the nitrosamine compound N-nitrosomethylbenzylamine (NMBA), an esophageal specific carcinogen, in the cyclin D1 transgenic mice. NMBA was first demonstrated to induce dysplasia in two strains of inbred mice, C57BL/6 and FVB/N. Subcutaneous NMBA was then administrated to wild type and transgenic mice beginning at 4 weeks of age. Mice were monitored for the duration of the study for general appearance, activity and weight, and were euthanized at 12 and 15 months. Histopathologic analysis revealed increased severity of dysplasia in cyclin D1 mice treated with NMBA compared with treated age-matched wild-type mice and untreated mice. There was also increased proliferating cell nuclear antigen (PCNA) expression in the esophagi of NMBA treated cyclin D1 mice. Taken together, these findings suggest that a genetic alteration, specifically cyclin D1 overexpression and a chemical carinogen, NMBA, may cooperate to increase the severity of esophageal squamous dysplasia, a prominent precursor to carcinoma.

Animals↗
PubMed1999

Double blind clinical trial of a remineralizing dentifrice in the prevention of caries in a radiation therapy population.

OBJECTIVES: The purpose of this study is to determine the efficacy and safety of a specially formulated remineralizing toothpaste in controlling caries in a group of high risk, head and neck radiation patients. DESIGN: The study compares the performance of the remineralizing toothpaste with a leading conventional fluoride dentifrice using double-blind randomization. TEST PRODUCTS: The products compared both contain equivalent quantities of fluoride (1150 ppm). The remineralizing toothpaste also delivers soluble calcium and phosphate ions, the essential components of teeth. SUBJECTS: On completion, 50 subjects who received > 50 Gy of radiation to the head and neck. MEASUREMENTS: Examinations include coronal and root caries using the Pitts Diagnostic Criteria, salivary flow rate, plaque and gingival indices and microbiological counts over one year. RESULTS: At this point subjects are enrolled in the study at various phases. However, the current average for the net increment per month per subject is -0.12 (+/- 1.30) for coronal caries and 0.06 (+/- 0.73) for root caries in subjects using the remineralizing toothpaste and 0.53 (+/- 1.62) for coronal caries and 0.45 (+/- 0.98) for root caries in subjects using the conventional fluoride dentifrice. Non-parametric analysis of rank scores for net root surface increments/month was statistically significant (p = 0.02), suggesting lower net root surface increment/month for the remineralizing toothpaste relative to the conventional toothpaste. No significant differences were noted on coronal surfaces. CONCLUSIONS: The results to date indicate that the remineralizing toothpaste is significantly superior to the conventional fluoride dentifrice in preventing root caries in high risk patients.

Adult↗
PubMed1999

Effectiveness of rehabilitation following amputation.

For many patients, the outcome of rehabilitation following amputation depends substantially on comorbidity. This is particularly so where amputation is performed because of peripheral vascular disease which may involve other end-organs, but also applies in trauma where loss of limb may not be the only injury. In evaluating outcome, measures must take account of the very different goals for rehabilitation. These may range from cosmesis or the simple ability to transfer from bed to chair, to successful competition in the Para-Olympics. Rehabilitation programmes for amputees are not simply prosthetic services, but must take account of the whole patient, their goals and ambitions. Research to date has made a contribution in identifying prognostic factors for prosthetic rehabilitation, thus helping to target limited resources. Controlled studies are still required, however, to establish the optimum services to offer to different groups of patients.

Amputees↗
PubMed1998

Cat allergen levels in public places in New Zealand.

AIMS: Cat allergen (Fel d 1) is a known risk factor for asthma. Studies have demonstrated Fel d 1 in both public buildings and domestic dwellings where cats have never been. The aims of this study were to measure reservoir Fel d 1 levels in public buildings in New Zealand, to examine determinants of these levels and to compare them with previously measured domestic levels. METHODS: Dust was obtained in two centres (Wellington and Christchurch) from hotels, hospitals, rest homes, churches, primary schools, childcare centres, cinemas, bank head offices and aeroplanes; and from North Island ski lodges. Measurements of temperature and relative humidity were taken. Information was collected on building characteristics. Fel d 1 levels (microg/g of fine dust) for floors (n=203), beds (n=64) and seats (n=24) were expressed as geometric means (95% confidence intervals). RESULTS: Detectable Fel d 1 levels were found in 95% of floor samples, 91% of bed samples and 100% of seat samples. Fel d 1 levels [geometric mean (95% confidence intervals)] were significantly higher on cinema and domestic aircraft seats [36.8 (20.8-65.3) microg/g and 33.3 (28.0-39.7) microg/g respectively] than on floors [3.6 (2.5-5.1) microg/g and 2.4 (1.8-3.0) microg/g respectively]. Floor Fel d 1 levels in the public buildings sampled were lower than those of domestic dwellings without cats [0.9 (0.6-1.4) microg/g vs 1.7 (1.2-2.4)] microg/g in Wellington and [2.0 (1.6-2.6) microg/g vs 4.0 (2.7-6.0] microg/g in Christchurch. After controlling for potential confounders, floor Fel d 1 levels were higher with carpeted floors (p<0.001) and lower in banks and hospitals (p<0.001). CONCLUSION: Fel d 1 levels in public buildings are low in New Zealand public places except for cinema and domestic aircraft seats where all but one sample had Fel d 1 levels potentially high enough to precipitate asthma symptoms in sensitised individuals.

Air Pollution, Indoor↗
PubMed1998

Identification of bacterial species on or in crevicular epithelial cells from healthy and periodontally diseased patients using DNA-DNA hybridization.

The purpose of this investigation was to identify bacterial species present on or in crevicular epithelial cells in healthy and diseased sites using DNA probes. In order to achieve this aim, further improvements were made in the separation of unattached bacteria from those adherent to epithelial cells isolated from the human gingival crevice or periodontal pocket. Then the DNA probes were used to determine the prevalence of detectable DNA from 15 microbial species on or in crevicular epithelial cells. One sample was taken from a single subgingival site in each of 51 individuals ranging in age from 19 to 45 years. Samples were taken from 27 sites of clinically healthy subjects and 24 samples were taken from subjects having periodontally diseased sites. DNA-DNA hybridization indicated that a majority of epithelial cells from healthy sites (63%) were in contact with or harbored Streptococcus oralis. On the other hand, species such as Bacteroides forsythus, Prevotella intermedia, Capnocytophaga ochracea and Campylobacter rectus were more frequently detected in elevated numbers in periodontally diseased sites. Cluster analysis of the microbial profiles generally aggregated subjects with and without periodontitis into separate cluster groups. The cluster patterns suggest the possibility that microbial complexes will be, in part, determined by the receptors available on the epithelial cells.

Adult↗