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Biomedical subjects

K A Eaton

Publications and source records attributed to K A Eaton.

At least 55 records · Page 3Linked to original sources
PubMed1998

The role of gastric Helicobacter and N-methyl-N'-nitro- N-nitrosoguanidine in carcinogenesis of mice.

BACKGROUND: The aim of this study was to determine whether gastric epithelial proliferation due to gastric Helicobacter infection in mice represents a preneoplastic lesion. MATERIALS AND METHODS: Helicobacter heilmannii infected and uninfected mice were treated with 150 microg/ml N-methyl-N'-nitro-N-nitrosoguanidine in drinking water for either 20 or 38 weeks. Mice were killed 12 or 18 months after bacterial inoculation. RESULTS: All infected mice developed lymphoplasmocytic gastritis and epithelial hyperplasia. Proliferative gastric lesions were characterised by nodular hypertrophy of the glandular mucosa, multifocal epithelial hyperplasia, and elevated BrdU labeling index. Intestinal metaplasia and true atrophy were not present but proliferative glands were poorly differentiated, lined by mucus-type epithelial cells with no parietal, chief or other specialized cell types. Neoplasms developed only in MNNG-treated mice. of the 180 treated mice the following neoplasms developed: 14 squamous cell carcinomas of mouth and forestomach; 37 hemangiosarcomas of the intestinal serosa; and 15 splenic lymphomas. No tumors were present in the glandular gastric mucosa, and infection did not affect tumor incidence. p53 overexpression occurred in 79% of hemangiosarcomas and 71% of squamous cell carcinomas but not in normal or proliferative gastric glandular mucosa. CONCLUSIONS: Gastric proliferative lesions in Helicobacter-infected mice are not preneoplastic, and the combination of an alkylating agent and non-neoplastic proliferation does not result in gastric carcinogenesis in mice.

Animals↗
PubMed1998

Vaccination of gnotobiotic piglets against Helicobacter pylori.

To determine the effect of oral adjuvant-assisted and parenteral vaccination, germ-free piglets were vaccinated orally with and without labile toxin adjuvant or parenterally and challenged with viable Helicobacter pylori. All prechallenge vaccination regimens induced anti-H. pylori antibodies and suppressed bacterial colonization, but no vaccination regime completely prevented infection. Parenteral vaccination given after infection had no effect on bacterial colonization. Lymphocytic gastritis was present in all piglets challenged with live bacteria regardless of vaccination status. Neutrophilic gastritis was present in vaccinated challenged piglets but not in infected, unvaccinated piglets. Gastritis was not present in uninfected control piglets regardless of vaccination status. In gnotobiotic piglets, vaccination suppresses but does not prevent infection by H. pylori, and parenteral vaccination does not cure infected piglets. Vaccination does not ameliorate gastritis due to H. pylori in piglets but does induce neutrophilic gastric inflammation in some infected piglets.

Administration, Oral↗
PubMed1998

Awareness of periodontal diseases: the professional and the civil servant.

Newly qualified dentists and dental hygienists should have a good level of awareness of periodontal diseases. However, for a variety of reasons this knowledge may not be regularly updated or applied in practice. This paper considers how professional awareness can be influenced by such factors as: maintaining an up to date understanding of the nature of periodontal diseases, the routine use of appropriate screening and examination techniques, factors influencing assessment of treatment need, patient records, continuing professional education and an understanding of patient expectations. It goes on to describe how civil servants may help to stimulate improvements in awareness levels to periodontal diseases by promoting continuing education, epidemiological research and national oral health strategies as well as through legislation and regulation. The paper concludes that although a range of organisations can promote improvements in professional awareness, unless simultaneous efforts are made to improve the awareness of the general public to periodontal diseases, it is difficult to see how there can be an improvement in the periodontal health of the population.

Adolescent↗
PubMed1998

Antimicrobial therapies for Helicobacter pylori infection in gnotobiotic piglets.

Gnotobiotic piglets infected with Helicobacter pylori were treated with various antimicrobials as monotherapy and dual therapy, and the results were compared to those for piglets treated with a triple-therapy regimen (bismuth subsalicyclate at 5.7 mg/kg of body weight, metronidazole at 4.4 mg/kg, and amoxicillin at 6.8 mg/kg four times a day [QID]). Clearance of infection was assessed after 7 days of treatment, and eradication was assessed following 7 days of treatment and a 14-day posttreatment observation interval. Monotherapy with amoxicillin, clarithromycin, and ciprofloxacin cleared and eradicated the organism from porcine stomachs; monotherapy with metronidazole cleared the infection and eradicated it from some piglets. Metronidazole-resistant microbes were recovered from treated piglets which cleared but did not eradicate the infection. Monotherapy with bismuth subsalicylate, erythromycin, nitrofurantoin, and tetracycline in the dosage range of 5.0 to 7.1 mg/kg QID was less than 100% effective in clearance and eradication, in that these drugs cleared and/or eradicated the infection from some of the piglets but did not eradicate the infection from all of the piglets. Monotherapy with an H-2 receptor antagonist (ranitidine) or a proton pump inhibitor (omeprazole) was ineffective at either clearance or eradication. In vivo dose titrations with several effective monotherapies were performed to determine the lowest effective in vivo dose of drug. In piglets, eradication was associated with a statistically significant decline in serum H. pylori-specific immunoglobulin M (IgM) antibodies; the titers of both IgA and IgG also declined, but the values were not statistically significant. For many antimicrobials, piglets are more sensitive indicators of clearance and eradication than humans. These data establish the H. pylori-infected gnotobiotic piglet as a useful model for the identification of novel antimicrobials for the treatment of this disease and for drug assessment during preclinical evaluations.

Animals↗
PubMed1998

Production of gastroesophageal erosions and ulcers (GEU) in gnotobiotic swine monoinfected with fermentative commensal bacteria and fed high-carbohydrate diet.

Erosions and gastroesophageal ulcers (GEU) were produced in the pars esophagea of young gnotobiotic swine fed a carbohydrate-enriched liquid diet and monoinfected with two different fermentative commensal bacteria, Lactobacillus and Bacillus sp. In contrast, piglets, fed a similar diet and inoculated with Gastrospirillum sp. (Helicobacter heilmannii), a helicobacter species that colonizes the gastric mucosa, did not develop GEU. Experimental GEU likely develops secondary to epithelial damage mediated by microbial-origin acids whose production is potentiated by high dietary carbohydrate and parietal cell-origin hydrochloric acid.

Animals↗
PubMed1998

Changes in the numbers of dentists and dental caries levels in 12-year-olds in the countries of the European Union and economic area.

This study compares numbers of dentists in the countries of the European Union (EU) from 1970 to 1994 with dentist to population ratios and dental caries levels in 12-year-olds, sets the changes which have emerged against other changing dental disease patterns (including those unconnected with caries levels) and goes on to determine the significance of the findings to the problems of dental workforce planning. Data for the numbers of dentists and dentist to population ratios were obtained from published tables. Data for past caries levels in 12-years-olds were obtained from the WHO Global Data Bank. All other data were obtained from Chief Dental Officers in all countries of the EU. In 1994 there were 222,090 practising dentists in the EU and 12,853 other clinical workers of whom 11,493 were dental hygienists. Since 1970, the dentist:population ratios for Spain and Portugal have improved markedly, the improvement for other countries has been less marked and in Austria a small reduction has occurred. Six countries show a considerable reduction in caries levels for 12-year-olds between 1970 and the 1990s, five show smaller reductions and three show a deterioration. As a consequence of the general improvement in caries levels in most of these countries it is probable that workloads in relation to the treatment of caries are falling, particularly for younger age groups. However, because of the overall ageing of populations in many industrialised countries the workload for older age groups is increasing, as older adults increase in number, a greater proportion retain their teeth and are afflicted by a range of problems, which include, but are not exclusive to, dental caries. There are few data for these older age groups than for caries levels in 12-year-olds. It was concluded that those planning the EU dental workforce of the future should take account of reliable epidemiological data for all groups of the population and, as these are not currently available, that suitable periodic oral health surveys covering all population age groups should be carried out regularly in all EU member states.

Child↗
PubMed1997

The evaluation of SafeQuest--a computer-assisted learning program on cross-infection control for the dental team.

OBJECTIVE: Evaluation of a computer-assisted learning (CAL) program (authored by a general dental practitioner-GDP) on cross-infection control (CIC) for the dental team. The aims of the evaluation were to determine how easy the program was to use, to determine if users found the information useful, to ensure that the content was accurate and to see what improvements could be made. METHODS: 96 questionnaires were distributed to dentists, 57 of whom responded (60%). 66% of the respondents were GDPs. RESULTS: Compared with earlier evaluations of hospital-produced CAL programs, SafeQuest was equally well received. 96% of respondents found it easy to use and 93% gave a positive score for their overall impression. 64% felt that the program had extended their knowledge, despite the fact that 74% rated their knowledge on CIC as being good/excellent before using SafeQuest. Suggestions on how the content and presentation of the program could be improved led to changes to the final version. CONCLUSIONS: The SafeQuest program on cross-infection control could be useful as a learning resource in general dental practice. The program, authored and produced by a GDP, compares favourably with those written in dental schools.

Adult↗
PubMed1997

The achievement and maintenance of inter-examiner consistency in the assessment of plaque and gingivitis during a multicentre study based in general dental practices.

This study set out to demonstrate that it was possible to train general dental practitioners (gdps) to achieve and maintain high levels of inter-examiner consistency in the use of simple periodontal indices over a 12-month period. The gdps were trained by one trainer in the use of the plaque index (PII) and a modified version of the gingival index (mGI) which assessed gingival bleeding only. All the gdps underwent intensive training and employed a technique, when assessing inter-examiner consistency in the use of the PII, such that the 1st examiner did not disturb in situ plaque from 50% of the circumference of a tooth. The problem of variation due to repeat probing, when assessing inter-examiner consistency for mGI, was overcome by one examiner lightly probing gingival margins and both examiners scoring the results. The problems relating to the multicentre nature of the study included: distance between the centres, the need for strict adherence to the study protocol, consistency in the use of forms and instruments, in the application of periodontal indices, and of inclusion and exclusion criteria. Techniques for overcoming these problems included: the planning and application of a coherent study design, which employed simple indices, a detailed protocol, the recruitment of very well-motivated gdps of similar age and experience as examiners, the recruitment of an experienced trainer who trained the gdps thoroughly and monitored their performance throughout the study, and repeat visits to the practices involved to explain the nature of the study to all their staff members. Initially, the gdps achieved inter-examiner kappa scores of 0.78-0.85 (mean 0.81) for PII and of 0.73-0.94 (mean 0.87) for mGI when assessing 168 sites for each variable. During the following 12 months, individual kappa scores, assessed every 3 months at 42 sites, ranged from 0.51-0.90 for PII and from 0.73-1.00 for mGI. Mean kappa for PII scores achieved by the five gdps fell during the study from 0.81 to 0.76, whereas that for mGI rose from 0.87 to 0.92. It is concluded that it is possible to train gdps to achieve high levels of inter-examiner consistency in the use of PII and mGI and for these high levels to be maintained during a 12-month multicentre study.

Calibration↗
PubMed1997

The effects of a 0.12% chlorhexidine-digluconate-containing mouthrinse versus a placebo on plaque and gingival inflammation over a 3-month period. A multicentre study carried out in general dental practices.

Several previous studies have evaluated the effects of 0.12% chlorhexidine digluconate (ChD) mouthrinses on plaque and gingival inflammation. However, previously, none have been based in general dental practices. The aim of this study was to evaluate the potential to conduct controlled periodontal clinical trials in co-operation with general dental practitioners (gdps). The project took place in 5 general dental practices in the South of England. 121 healthy subjects (24 at 4 sites and 25 at the 5th), aged 18-65 years, mean 35 +/- 12) years participated in a double-blind, randomised study during which they received full mouth assessments for plaque and gingival bleeding at baseline, 6 and 12 weeks. 60 subjects were randomly assigned to use the 0.12% ChD mouthwash and 61 the placebo. The assessments were carried out by 5 gpds, who had previously achieved inter-examiner kappa scores of 0.78-0.85 (mean 0.81) for the plaque index (PII), and of 0.73-0.94 (mean 0.87) for a modified gingival index (mGI), and who maintained kappa scores of 0.51-0.90 for PII and of 0.73-1.00 for mGI during the 12 months required to complete the study. 98 subjects (48 ChD and 50 placebo) completed the study. Even though the baseline levels of plaque and gingivitis were low, by week 12, mean whole mouth plaque score of the ChD mouthwash users had fallen from 1.33 at baseline to 0.96 and was significantly lower (p < 0.001) than for the placebo users, 1.31 at baseline to 1.13. Whole-mouth gingival bleeding score fell from 0.56 to 0.42 in the ChD mouthwash group but was unchanged (0.54-0.55) in the placebo group. A subsidiary data analysis which considered the effects at sites indicated that within these overall differences, the ChD users experienced almost 2 x the reduction from plaque score 2 at baseline at proximal molar sites over a 12-week period (50.6% ChD versus 27.6% placebo). It was concluded that 0.12% ChD mouthwash reduced plaque accumulation by 28% and gingival inflammation by 25% over a 12-week period, that it is feasible for a group of gdps to maintain high levels of inter-examiner consistency in the use of PII and mGI, that it is also feasible to carry out such a multicentre study in general dental practice, and that the use of mean mouth scores per subject to analyse the effects of mouthrinses may well mask variations in response throughout the mouth.

Adolescent↗
PubMed1997

Role of vacuolating cytotoxin in gastritis due to Helicobacter pylori in gnotobiotic piglets.

To investigate the role of the Helicobacter pylori cytotoxin in the pathogenesis of gastritis, gnotobiotic piglets were colonized with either toxigenic H. pylori or a nontoxigenic isogenic mutant. Only piglets given the toxigenic strain developed toxin-neutralizing antibodies (indicating that toxin is expressed in vivo), but there was no difference in bacterial colonization, epithelial vacuolation, or gastritis between the two groups of piglets.

Animals↗
PubMed1997

Autosomal dominant polycystic kidney disease in Persian and Persian-cross cats.

A form of autosomal dominant polycystic kidney disease (ADPKD) similar in clinical features to human ADPKD occurs in the Persian cat. We characterized the morphologic and immunohistochemical features of this disease in a colony of affected cats. Complete postmortem examinations were performed on 11 normal and 22 affected cats ranging in age from 3 months to 10 years. Kidneys were evaluated by gross and histologic examinations, ultrastructure, lectin staining, bromodeoxyuridine immunochemistry for labeling index and immunochemistry for distribution of Na/K ATPase. Feline ADPKD was characterized by variable numbers of cysts in the renal cortex and medullar. Ultrastructural examination and lectin staining suggested that cysts arose from proximal and distal nephron segments. Bromodeoxyuridine labeling demonstrated increased proliferation of epithelium lining some cysts in young cats. Immunohistochemical staining showed variable translocation of Na/K ATPase from the basolateral membranes of cyst-lining cells to the cytoplasm or luminal membranes. Cystic renal disease commonly was associated with chronic tubulointerstitial nephritis and hepatobiliary hyperplasia and fibrosis. Focal hyperplasia of renal tubular epithelium, hepatic cysts, and cardiac lesions were present in some cats. Feline ADPKD shares many morphologic and pathogenetic features with human ADPKD.

Animals↗
PubMed1997

Research in general dental practice--what is involved? Part 2. Specific considerations.

In the previous paper (Part 1. General Considerations), the problems which GDPs are likely to encounter when they embark on research were explored and an outline of the structure a GDP might use when planning to undertake a research project outlined. This paper explains how a recent mouthrinse study, carried out by five GDPs in five different practices, was planned and executed and how the principles described in the first paper were applied.

Adolescent↗
PubMed1997

Treatment of gastritis in cheetahs (Acinonyx jubatus).

Three cheetahs (Acinonyx jubatus) had a clinical history of chronic spiral bacteria-associated gastritis and three cheetahs had no clinical history of gastritis. Gastric biopsies were obtained from all six cheetahs prior to treatment for gastritis and 3 wk and 1 yr posttreatment. The cheetahs were treated with tetracycline hydrochloride 500 mg p.o. q.i.d., metronidazole 250 mg p.o. q.i.d., and bismuth subsalicylate 300 mg p.o. q.i.d. Each drug was administered concurrently for 7 days. Following this treatment, each cheetah was maintained on 300 mg bismuth subsalicylate p.o. s.i.d. for 1 yr. The three cheetahs with a history of gastritis were culture positive for Helicobacter acinonyx and remained positive during the entire study. The three cheetahs with no clinical history of gastritis were culture negative for H. acinonyx, but gastric biopsies revealed Gastrospirillum-like bacteria (tentatively named Helicobacter heilmannii) pretreatment. Gastric biopsies were negative for H. heilmannii on subsequent examinations. Although the treatment did not eradicate H. acinonyx, it did provide symptomatic relief from the vomiting, anorexia, and weight loss associated with clinical gastritis. The use of endoscopically guided gastric mucosal biopsies for urease testing and histopathologic examination of Warthin-Starry-stained sections is a sensitive and specific method of diagnosing spiral bacteria-associated gastritis. Treatment of spiral bacteria-associated gastritis in cheetahs should include the rational use of antibiotics (tetracycline or amoxicillin and metronidazole), bismuth compounds, and omeprazole and evaluation of husbandry methods to reduce stress.

Acinonyx↗
PubMed1996

Manifestations of the local gastric immune response in gnotobiotic piglets infected with Helicobacter pylori.

Helicobacter pylori, a human gastric bacterial pathogen, was inoculated into gnotobiotic piglets and manifestations of the resultant gastric inflammation was analyzed by in situ immunochemistry and flow cytometric analysis of isolated lamina propria leukocytes (LPL) and peripheral blood leukocytes (PBL) recovered from infected and control piglets. Gastric mucosa tissue sections from uninfected control piglets were essentially negative for cluster differentiation- (CD-) positive leukocytes. Failure to isolate significant numbers of LPL from the gastric lamina propria confirmed this observation. A local and systemic immune response occurs in piglets after infection with H. pylori. This is manifest by the appearance of cells associated with a local immune response in gastric mucosa. In gastric tissue sections from H. pylori-infected piglets, CD4-positive leukocytes were sparse and closely associated with developing lymphoid follicles whereas the CD8-positive cellular phenotype was abundant. The latter formed a continuous band in the lamina propria just above the muscularis mucosa. Perivascular accumulations of lymphocytes in the outer muscular tunic(s) were strongly positive for expression of CD8 antigen. Class II-positive cells were prominent in CD8 lymphocytic infiltrates, developing follicles and vascular endothelia but were uniformly absent from gastric epithelia even in sites overlying areas of immunocyte proliferation and infiltration. Leukocytes possessing the monocyte and granulocyte markers were rare. Plasma cells containing IgA were common in the periphery of developing lymphoid follicles or distributed as discrete foci around individual gastric pits. Fewer numbers of IgG- and IgM-positive plasma cells were identified. When the LPL flow cytometry data were compared with the flow cytometry data obtained from PBL in these same H. pylori-infected piglets, leukocytes bearing the CD8 marker predominated in LPL whereas leukocytes bearing the CD4-reactive and MHC class II markers predominated in PBL. Finally, local ELISA antibody responses were measured in mucosal explant culture supernatants and compared with in vivo antibody levels in sera, bile, and gastric juice. Antibody activity, specific for H. pylori, was detected in supermatants and serum in all three isotypes in actively infected piglets whereas gastric juice lacked antibodies. Gastric explants prepared from piglets in which infection had been successfully eradicated failed to produce local antibody into supermatant fluids. These data support the concept that the gastric inflammation observed is mediated by local immunological events.

Animals↗
PubMed1996

Colonization of gnotobiotic piglets by Helicobacter pylori deficient in two flagellin genes.

Helicobacterpylori possesses two flagellin molecules, MA, the major species, and FlaB, which is expressed in minor amounts. This study sought to determine if one or both flagellin species are necessary for colonization or persistence by H. pylon. Thirty-six gnotobiotic piglets from six litters were given one of four isogenic strains of H. pylon orally. The bacterial strains used were strain N6, the wild type, which produced both FlaA and FlaB and was fully motile; N6flaB::km, which produced FlaA but not FlaB and was weakly motile; N6flaA::km, which expressed FlaB but not FlaA and was nonmotile; and N6flaA::cat/flaB::km, which produced neither flagellin and was nonmotile. Strain N6 colonized all piglets and persisted for 2, 4, and 10 days after inoculation. Both N6flaA::km and N6flaB::km colonized for 2 and 4 but not 10 days, and colonization was weak. N6flaA::cat/flaB:: km colonized for 2 days but did not persist for 4 or 10 days after inoculation. These findings demonstrate that both flagellin species are necessary for full colonization by H. pylon. Colonization for up to 4 days is possible in the absence of either flagellin species but not both.

Animals↗
PubMed1996

Prevalence and varieties of Helicobacter species in dogs from random sources and pet dogs: animal and public health implications.

Gastric bacteria of a variety of ultrastructural morphologies have been identified in or isolated from domestic carnivores, but their prevalence in different populations of animals and their clinical significance are still unknown. The purposes of this study were (i) to evaluate the prevalence and morphologic types of gastric bacterial in three different populations of dogs; (ii) to determine which of the organisms were culturable, and if the cultured organisms were morphologically similar to the organisms seen in situ; (iii) to identify the isolated organisms; and (iv) to determine if gastric bacteria were associated with gastritis. Three groups of dogs were examined: healthy laboratory dogs, healthy dogs from an animal shelter, and pet dogs with various nongastric illnesses. Of these, 100% of laboratory and shelter dogs and 67% of pet dogs were colonized by large, tightly coiled gastric spiral bacteria morphologically similar to Gastrospirillum hominis or Helicobacter felis (referred to as gastrospirilla). Regardless of the presence or density of gastric bacteria, all of the dogs in the study except one had mild to moderate gastritis. Helicobacter spp. were isolated from only 6 of 39 stomachs cultured, and only three of the organisms isolated were morphologically similar to the bacteria seen in situ. Five helicobacters were identified by 16S rDNA (genes coding for rRNA) sequence analysis. Three were strains of H. felis, one was H. bilis, and one was a novel helicobacter morphologically similar to "Flexispira rappini." Gastrospirilla are almost universal in the stomachs of domestic dogs, and in most infected dogs, they do not appear to be associated with clinical signs or histologic lesions compared with uninfected dogs. Nongastrospirillum helicobacters are rare in dogs and are not histologically detectable. Helicobacter pylori was not isolated from domestic dogs.

Animals↗
PubMed1996

Discontinued orthodontic treatment in the general dental service and community dental service in England and Wales during the summer of 1991.

This paper reports on two studies which investigated levels of discontinued orthodontic treatment amongst patients under 18 years, who had been treated in the General Dental Service (GDS) and Community Dental Service (CDS) of the National Health Service during June and July 1991. These complement the study of discontinued Hospital Dental Service treatment already reported. The studies indicated that, at the time, the levels were 13.1 per cent in the GDS and 12.5 per cent in the CDS. The figure for the GDS was much lower than that of 20 per cent reported in the Schanschieff Report. There was little difference in the levels of discontinued treatment between those working in the GDS with an orthodontic qualification (12.1 per cent) and those without (13.5 per cent). The results suggest that the levels for discontinued orthodontic treatment in those aged under 18 years of age may be lower than previously reported.

Adolescent↗