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Biomedical subjects

P D Howdle

Publications and source records attributed to P D Howdle.

At least 55 records · Page 3Linked to original sources
PubMed1994

Reperfusion injury, antioxidants and hemodynamics during orthotopic liver transplantation.

Endothelial injury occurs as a result of oxygen free radical production after ischemia and reperfusion of transplanted livers, causing hemodynamic disturbance. Patients with chronic liver disease generally have low levels of fat-soluble vitamins, which have important antioxidant roles. We therefore assessed circulating levels of the antioxidants vitamin A, vitamin E, beta-carotene and lycopene, indices of lipid peroxidation and hemodynamic changes during elective orthotopic liver transplantation in 12 patients. We found that initial antioxidant levels were severely depleted compared with healthy subjects, and in some patients carotene and lycopene levels were undetectable. Increased lipid peroxidation was also evident, as shown by thiobarbituric acid-reactive substances. On reperfusion of the liver graft, vitamin A and E levels fell (p < 0.01) and were associated with decreases in systemic vascular resistance (p < 0.02). These data show that patients undergoing liver transplant have lowered antioxidant defenses and evidence of free radical damage, which compound the additional insult of reperfusion injury. Antioxidant therapy in these patients before transplantation may ameliorate the effects of reperfusion.

Adult↗
PubMed1993

Rapid detection of enteric adenoviruses by means of the polymerase chain reaction.

A simple polymerase chain reaction (PCR) assay for detecting enteric adenoviruses (Ads 40 and 41) in faecal extracts is described. A pair of PCR primers designed to hybridise to the EIB genes of Ad40 and 41 was found to amplify only Ad40 and 41 DNA but not EIB genes or viral DNA from representative numbers of the other human adenovirus subgenera. The PCR assay was tested on a panel of 10 faecal extracts, all of which contained adenovirus particles (as judged by electron microscopy) but only four of which proved amenable to serotyping. Extracts in which enteric adenoviruses had been detected serologically yielded positive results in the PCR assay. These results suggest that this PCR assay may be useful for detecting enteric adenoviruses in clinical samples.

Adenovirus Infections, Human↗
PubMed1993

Expression of interleukin-6 by intestinal enterocytes.

AIMS: To investigate the cellular source of the cytokine interleukin-6 (IL-6) in the small and large intestines of patients with inflammatory bowel disease, coeliac disease, and in controls. METHODS: IL-6 was detected in frozen sections of bowel by single and double label indirect immunofluorescence using rabbit polyclonal and murine monoclonal anti-IL-6 antibodies. The murine monoclonal antibodies RFDR1 (anti-MHC class II) and UCHT1 (anti-CD3) were used to localise macrophages and T lymphocytes, respectively. Lipopolysaccharide stimulated peripheral blood monocytes were used as positive control cells for IL-6 protein. RESULTS: IL-6 was demonstrated in the small and large intestine of patients with inflammatory bowel disease, coeliac disease, and in controls. The protein was present predominantly in enterocytes and colocytes in normal and inflamed mucosa, but not in the infiltrating inflammatory cells of the lamina propria. There were no discernable differences between patients with inflammatory bowel disease or coeliac disease and controls, nor between small and large bowel mucosa. Incubation of antibody with recombinant human IL-6 protein abolished the labelling. IL-6 protein was also present in lipopolysaccharide stimulated peripheral blood monocytes. CONCLUSIONS: The data suggest that enterocytes and colocytes may play an active part in the immune response of the gut. The presence of IL-6 in both inflamed and non-inflamed small and large intestine requires further investigation into the function of this cytokine in the gut.

Celiac Disease↗
PubMed1992

Helicobacter pylori serology in patients with coeliac disease and dermatitis herpetiformis.

AIMS: To investigate whether Helicobacter pylori infection or autoimmune gastritis is responsible for the reported increase in gastric pathology and abnormalities of gastric function in patients with coeliac disease and dermatitis herpetiformis (DH). METHODS: Serum H pylori IgG antibodies were assayed by enzyme linked immunosorbent assay and intrinsic factor antibodies by radioimmunoassay in 99 patients with coeliac disease and 58 patients with dermatitis herpetiformis from two geographic areas. RESULTS: H pylori positivity in patients with coeliac disease and dermatitis herpetiformis increased with age, reaching 50% and 70%, respectively, in patients over 50 years. The percentage H pylori seropositivity in coeliac disease did not differ from the percentage positivity observed in 250 similarly aged blood donors from the same geographic area (Leeds). Seropositivity in patients with dermatitis herpetiformis was not significantly different from the level of positivity observed in 98 age matched patients without dermatitis herpetiformis attending the same Edinburgh dermatology clinic. Only one patient with coeliac disease had positive intrinsic factor antibodies. H pylori seropositivity in Edinburgh control subjects under 30 years of age (41.9%) was significantly higher (p less than 0.03) than in Leeds controls (18%) of corresponding age. An increasing prevalence of H pylori seropositivity with age in coeliac disease and dermatitis herpetiformis paralleled that of the control groups. CONCLUSIONS: Gastritis in coeliac disease and dermatitis herpetiformis is largely caused by H pylori infection at a level that is no different from that of the general population. Any increase in the prevalence of gastritis in these two diseases might be caused by lymphocytic gastritis rather than pernicious anaemia.

Adolescent↗
PubMed1992

Specific circulating anti-gliadin IgG-class antibody does not mediate intestinal enteropathy in gliadin-fed mice.

The effects of specific circulating IgG antibody on the uptake of dietary antigen and in the generation of intestinal enteropathy have been investigated in Balb/c mice bred on a gluten-free diet. A monoclonal IgG1 antibody (GD3) was prepared against gliadin. After adoptive transfer into mice, this antibody was capable of mediating a type III hypersensitivity response in vivo to footpad challenge with gliadin. The titres of circulating GD3, as estimated in vitro by ELISA, correlated well with the degree of inflammation at sites of type III responses in vivo. Following footpad challenge with gliadin, titres of circulating GD3 antibody were reduced. GD3 antibody was tested for its ability to mediate inflammatory responses in vivo in the intestinal mucosa of mice fed with gliadin. Circulating GD3 antibody was removed selectively and specifically by dietary gliadin, compared to feeding with bovine serum albumin or maintenance on a gliadin-free diet only. However, we were unable to demonstrate any pathological changes in the intestine as a result of possible local antigen-antibody complex formation or deposition. Using radio-iodinated gliadin as a trace marker, no significant retention of gliadin in the intestinal mucosa was found in mice pre-injected with GD3 antibody. These data suggest that circulating IgG antibody has little effect on dietary antigen uptake in the gut, and alone is insufficient to mediate an enteropathy.

Animals↗
PubMed1991

Expression of the LFA-1 beta 2 integrin (CD11a/CD18) and ICAM-1 (CD54) in normal and coeliac small bowel mucosa.

The leucocyte adhesion molecules (beta 2 integrins) comprise CD11 alpha-chains and a common beta-chain (CD18). CD11a (leucocyte function-associated antigen 1, LFA-1) is expressed by most T cells, and is involved in antigen presentation by macrophages via its counter-receptor, intercellular adhesion molecule (ICAM-1, CD54). By criteria of double-label immunofluorescence of cryostat tissue sections, virtually all lamina propria T cells of the normal small bowel were found to express LFA-1 strongly. By contrast, only 30-60% of intra-epithelial lymphocytes (IEL) expressed detectable LFA-1, most of which were LFA-1 weak and CD18-. ICAM-1 was expressed strongly only by vascular endothelium. In coeliac disease, there was a modest increase of diffuse ICAM-1 expression in the lamina propria, mainly in the subepithelial zone, where ICAM-1+ macrophages were occasionally seen. There was also a slight overall increase in CD11a expression by IEL, seen predominantly in surface epithelium and mainly by the CD4+ minority subset, but not by CD4-CD8- (TcR gamma delta +) cells. These data suggest that the LFA-1/ICAM-1-dependent antigen presentation pathway is of minor importance to IEL in the normal small bowel, and does not assume a major role in coeliac disease.

Antigens, CD↗
PubMed1991

Is persistent adenovirus 12 infection involved in coeliac disease? A search for viral DNA using the polymerase chain reaction.

It has been shown that partial amino acid sequence homology between alpha gliadin and an early region protein (E1B-58 kDa) of adenovirus 12 results in immunological cross reaction. This led to the proposal that prior infection by adenovirus 12 could be associated with the development of coeliac disease. To examine this hypothesis, evidence was sought of persistent adenovirus 12 infection in the small intestinal mucosa of patients with coeliac disease. DNA isolated from biopsy samples from 24 control and 18 coeliac disease patients was analysed by the polymerase chain reaction for adenovirus 12 DNA encoding the E1B-58 kDa protein. Four of 18 coeliac disease and two of 24 control patients were positive. There is thus a low prevalence of this infection on both groups of patients but certainly no significantly increased incidence in coeliac disease. These results suggest that persistent adenovirus 12 infection is not a major element in the pathogenesis of coeliac disease.

Adenoviridae↗
PubMed1991

Gamma delta T cell receptor-positive cells of the human gastrointestinal mucosa: occurrence and V region gene expression in Heliobacter pylori-associated gastritis, coeliac disease and inflammatory bowel disease.

T cells expressing the gamma delta heterodimer of the T cell receptor (TCR) were studied with respect to their occurrence and expression of gamma delta TCR variable region (V) genes in the normal gastrointestinal mucosa and in a variety of inflammatory conditions. In controls, gamma delta TCR+ cells were a minority population confined to the epithelial compartment of stomach, small bowel and colonic mucosae. Unlike in the periphery, gastro-intestinal gamma delta TCR+ intraepithelial lymphocytes (IEL) were mainly V delta 1+ (89.98 +/- 17.70%); few were V delta 2+ (6.04 +/- 13.8%) or V gamma 9+ (11.38 +/- 10.73%). All gamma delta TCR+ IEL were CD5low; nearly half were CD8+ and the remainder were CD4-CD8- 'double negatives'. There was no significant change from normal in percentages of gamma delta TCR+ IEL in H. pylori-associated gastritis, Crohn's disease and ulcerative colitis. However, in coeliac disease, gamma delta TCR+ IEL were elevated from 2.54% (+/- 1.71) in controls to 29.6% (+/- 16.1) in untreated patients (P less than 0.001) and 18.5% (+/- 7.2) in treated patients (P less than 0.001) and more were CD4-CD8-. Otherwise, gamma delta TCR+ IEL phenotypes were little changed: the majority remained V delta 1+V delta 2-V gamma 9- and all were CD5low. These data suggest that increased gamma delta TCR+ IEL are not a generalized response to intestinal inflammation or to stress proteins, although the typical V delta 1+V delta 2-V gamma 9- CD5low phenotype is retained.

Adult↗
PubMed1989

Responses of antigen-specific long-term murine T cell lines to wheat gliadin fractions.

Recent evidence suggests that the four electrophoretically defined gliadin subfractions (alpha, beta, gamma and omega) of wheat can induce the typical pathological finding of coeliac disease. We have prepared long-term murine T cell lines to gliadin and its four major subfractions. The cell lines were tested in proliferative assays with each homologous gliadin subfraction, and to the other gliadin subfractions. There was some cross-reactivity, with unfractionated gliadin and its alpha-subfraction being the most antigenic, while omega-gliadin was the least. These data demonstrate that gliadin components are effective stimuli for specific T cell responses, and further suggest that the alpha-gliadin subfraction generates the highest specific responses. This accords with observations in man that all four gliadin subfractions exacerbate coeliac mucosa, but that the alpha-subfraction is the most active.

Animals↗
PubMed1989

Lack of a serologic response to an E1B protein of adenovirus 12 in coeliac disease.

The description of an amino acid sequence homology between the E1B-58-kDa protein of adenovirus 12 and gliadin has led to the suggestion that previous infection by this virus and subsequent exposure to gliadin could trigger the development of coeliac disease in susceptible individuals as a result of immunologic cross-reactivity. We have sought to measure specific antibodies to the E1B-58-kDa protein in 23 coeliac patients and 10 normal subjects. The sera were analysed by radioimmunoprecipitation with metabolically labelled adenovirus-12-transformed rat cells (which express the E1B-58-kDa protein), followed by separation on polyacrylamide gels. None of the coeliac sera had evidence of antibodies to the E1B-58-kDa protein. These data suggest that coeliac patients show little evidence of humoral immunity to the specific adenovirus 12 E1B-58-kDa protein implicated in the aetiology of coeliac disease.

Adenovirus Early Proteins↗
PubMed1989

Expression of T-cell receptors TcR1 (gamma/delta) and TcR2 (alpha/beta) in the human intestinal mucosa.

Cryostat sections of normal human adult gastrointestinal mucosae were studied by double-label immunofluorescence with antibodies to CD3, CD4, CD8, CD5 and CD6, in parallel with antibodies beta F1 and TCR delta 1 against beta-chains and delta-chains of the T-cell receptor (TcR) types TcR2 (alpha/beta) and TcR1 (gamma/delta), respectively. Virtually no TcR1+ were found within the lamina propria. In the epithelial compartment, TcR1+ cells were infrequent: in the small bowel, congruent to 2% of T cells were TcR1+. In the colonic epithelium, the percentage of T cells expressing gamma/delta-chains was higher, with a mean value approximating 15-20%, although this apparently large percentage increase compared with small bowel reflects in part a much lower density of colonic IEL, as absolute numbers of TCR delta 1+ cells were comparable. Of the TcR1+ population, about half were CD4- CD8-, 'double negatives' and the remainder were CD8+. TcR1+ cells were also CD5- CD6-, irrespective of expression of CD8. No CD4+ cells expressing TcR1 were observed: essentially all CD4+ cells were beta F1+, with some variability of labelling intensity. Approximately 30-50% of the CD8+ subset expressed the beta F1 antigen strongly. However, in the remaining TcR1- CD8+ cells, which were all of the CD5- CD6- phenotype, expression of the beta F1 antigen was only detectable when streptavidin and biotin conjugates were used for amplification of labelling. Thus, the CD8+ CD5- subset, a prominent population of the epithelial compartment of the small bowel, was either TcR2dull in the majority or TcR1+ in a minority. Our data imply that gamma/delta TcR1 cells may be actively excluded from intestinal lamina propria, and that any preferential localization that does occur is limited and is rather a feature of the colonic mucosa, rather than the small bowel.

Humans↗
PubMed1989

Serum interleukin-2-receptor in coeliac disease: response to treatment and gluten challenge.

Concentrations of the soluble interleukin-2 receptor (sIL-2R) in the serum of 33 patients with coeliac disease were measured by ELISA. The levels of sIL-2R were significantly raised in 15 patients with untreated coeliac disease compared with treated patients and age- and sex-matched symptomatic and non-symptomatic control groups. Longitudinal studies in individual coeliac patients showed that serum sIL-2R fell following commencement of a gluten-free diet. Gluten challenge of 16 treated coeliac patients for 1 week resulted in a significant increase in serum sIL-2R, which returned to prechallenge levels within 4 weeks of recommencement of a gluten-free diet. We suggest that serum sIL-2R levels in patients with coeliac disease reflect specific immunological activation in response to gluten ingestion. Measurement of serum sIL-2R may therefore be useful in the assessment of response to treatment in patients with coeliac disease.

Adolescent↗
PubMed1987

The immunology of coeliac disease.

Coeliac disease is defined as that disorder in which there is an abnormality of the small intestinal mucosa manifested by contact with the gluten of wheat and certain other cereal grains. In the immunological theory of the pathogenesis of coeliac disease, gluten, or a component, is viewed as the antigen responsible for the immune response. The search for the gluten component responsible for 'toxicity' and, by implication, antigenicity, is described. The antigen may be presented differently to the immune system by an abnormal cell membrane, either of the enterocyte, lymphocyte or macrophage. Alternatively, increased amounts of antigen may be absorbed due to increased membrane binding or permeability, either of which could be genetically determined. As a further possibility, coeliac disease may occur because the patients are immunologically hyperresponsive and this too appears to be genetically determined. The perturbations which occur in the mucosal immune system and the systemic immune system are described. It is conceivable that the major complications described (intestinal ulceration, malignancy and splenic atrophy) result from immunological disturbances. The incidence of childhood coeliac disease is declining, which may be due to altered exposure to, or increased protection from, the antigen in infancy, or to changes in environmental factors. The immunological mystery of coeliac disease continues to excite interest and fascination, and has certainly been a stimulus to our deeper understanding of gastrointestinal immunology.

Celiac Disease↗
PubMed1987

Chronic hepatitis B carriers found at blood donation: do they need regular follow-up?

It is recommended by the Department of Health and Social Security that hepatitis B virus (HBV) carriers found at blood donation should be followed up by specialist liver units. We attempted to do this in 74 such patients found by the Yorkshire Regional Blood Transfusion Service during a 4.5-year period. Only 32 of the patients eventually attended for further investigation and follow-up. However, 43 chronic HBV carriers found at blood donation have been followed for varying periods from 2 to 14 years, and the prognosis has been good. Although this raises the question as to whether such carriers need to be seen routinely in a specialist unit, we suggest that there are good reasons to continue to advocate this policy.

Biopsy↗