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Biomedical subjects

A Allen

Publications and source records attributed to A Allen.

At least 73 records · Page 4Linked to original sources
PubMed1998

The MUC2 gene product: a human intestinal mucin.

The MUC2 gene product is the first human secretory mucin protein core to be fully sequenced. Like the other eight human MUC genes identified to date, MUC2 is characterised by tandem and irregular repeat sequences rich in threonine and serine, the potential sites of attachment of the oligosaccharide chains. The MUC2 gene product is more than 5100 amino acids in its commonest allelic form and accounts for one fifth by weight of the mucin glycoprotein molecule (80% oligosaccharide side chains). The MUC2 product is polymerised end to end through disulphide bridges to form large secreted polymeric gel-forming mucins (Mr approximately 10(7)). The primary function of the MUC2 gene product is to provide a protective barrier between the epithelial surfaces and the gut lumen. There is decreased expression of MUC2 in colonic cancer and defective polymerisation of secreted mucin in ulcerative colitis. Elucidation of the MUC2 and other mucin gene sequences has opened the way for a full structural characterisation and an improved understanding of the structure and function of these complex mucus gel secretions.

Amino Acid Sequence↗
PubMed1998

IgG subclass responses to pigeon intestinal mucin are related to development of pigeon fanciers' lung.

BACKGROUND: Pigeon fanciers' lung (PFL) is a form of extrinsic allergic alveolitis. Affected individuals produce antibodies to various pigeon antigens, and the resulting immune complexes are thought to initiate the disease. However, high antibody titres also occur in some asymptomatic individuals. Previously attention has focused on protein antigens, but we have recently identified pigeon intestinal mucin as a novel antigen in PFL. OBJECTIVE: To determine the relationship between IgG subclass antibodies to pigeon intestinal mucin and the development of pigeon fanciers' lung. METHODS: Sera were collected from 250 pigeon fanciers, who also completed a clinical questionnaire. Sera were screened for precipitating antibodies to pigeon serum and droppings. Individuals with symptoms and precipitating antibodies were considered to have classical PFL. Serum IgG and IgG subclass antibodies to pigeon intestinal mucin and pigeon serum proteins were investigated by quantitative enzyme-linked immunosorbent assay (ELISA). RESULTS: Very high titres of IgG antibodies against pigeon mucin were found in all precipitin-positive individuals. A strong positive correlation was seen between titres of antibodies to mucin and to serum proteins, but this was not due to crossreactivity. No significant differences in IgG titres to either mucin or pigeon serum proteins were found between individuals with PFL and asymptomatic precipitin positive fanciers. IgG1 and IgG2 were the major subclasses of anti-mucin, with lower titres of IgG3. Patients with PFL had significantly higher titres of IgG1 to mucin than asymptomatic, precipitin-positive individuals. In contrast, no significant differences were seen between PFL and asymptomatic precipitin-positive sera with respect to the subclass titres against pigeon serum proteins. CONCLUSION: The high titres of anti-mucin IgG in sera of all individuals with PFL, together with the finding that high IgG1 titres to mucin are associated with the development of disease confirm pigeon intestinal mucin as an important antigen in PFL.

Adult↗
PubMed1998

Pigeon fanciers' lung: effects of smoking on serum and salivary antibody responses to pigeon antigens.

A reduced prevalence of pigeon fanciers' lung has been reported in pigeon breeders who smoke cigarettes. Serum and salivary antibodies to pigeon intestinal mucin and pigeon serum proteins were investigated in 227 pigeon fanciers, subdivided according to smoking habit and clinical status. Smokers had a lower incidence of precipitating antibodies to pigeon antigens and lower titres of serum IgG and IgA antibodies to mucin and to pigeon serum proteins in ELISA compared with non-smokers and ex-smokers. In contrast, IgG antibody titres to tetanus toxoid were similar in smoking and non-smoking groups. In contrast to serum antibodies, salivary IgA antibody titres to pigeon antigens were similar in smokers and non- or ex-smokers. Approximately one third of the smokers reported symptoms consistent with pigeon fanciers' lung but did not have precipitating antibodies. Only some individuals with precipitating antibodies had disease symptoms, and IgG antibody titres in these individuals were not significantly higher than in many asymptomatic individuals. Salivary IgA titres against pigeon mucin were significantly higher in asymptomatic individuals, consistent with a protective role for these antibodies. The results confirm that smoking is associated with a decreased serum antibody response to inhaled pigeon antigens, affecting IgG1, IgG2 and IgA responses, but this impairment does not extend to salivary IgA or to antibody responses to a parenterally administered protein antigen. The fact that responses to pigeon serum proteins and to pigeon intestinal mucin were similarly affected suggests that cigarette smoking depresses both T-independent and T-dependent responses to inhaled antigens.

Animals↗
PubMed1998

Helicobacter pylori in vivo causes structural changes in the adherent gastric mucus layer but barrier thickness is not compromised.

BACKGROUND: It has been proposed that a pathogenic effect of Helicobacter pylori is a weakening of the protective mucus barrier; however, this remains controversial. AIMS: To clarify the effects of H pylori infection on the mucus gel barrier in vivo. METHODS: Mucus gel polymeric structure and the thickness of the adherent mucus barrier were measured in endoscopic biopsy samples in subjects with and without H pylori infection. RESULTS: There was a significant 18% reduction in the proportion of polymeric gel forming mucin in the adherent mucus layer in H pylori positive compared with negative subjects. There was no change in the adherent mucus thickness between H pylori positive and negative subjects without gastric atrophy (mean (SD): 104 (26) micron, 106 (30) micron, respectively). There was however a significant reduction in mucus thickness in those H pylori positive subjects with underlying gastric atrophy (84 (13) micron, p=0.03) compared with those without atrophy. CONCLUSIONS: A partial breakdown in gel forming structure of the gastric mucus barrier does occur in H pylori infection per se but this is insufficient to cause a collapse of the mucus barrier.

Aged↗
PubMed1998

Pigeon fanciers' lung: the mucin antigen is present in pigeon droppings and pigeon bloom.

BACKGROUND: Pigeon intestinal mucin has been implicated as an important antigen pigeon fanciers' lung. This study investigated whether mucin is detectable in pigeon droppings and bloom, the likely antigenic sources in disease. METHODS: Soluble extracts of a number of materials found in a pigeon loft were prepared and specific IgG subclass antibodies to these antigens were measured in 14 antibody-positive pigeon fanciers. Cross-reactivity between these materials and purified pigeon intestinal mucin was investigated by inhibition of anti-mucin ELISA. Mucin was purified from the soluble extracts of these crude antigen mixtures by CsCl density gradient centrifugation. RESULTS: The patterns of IgG subclass responses to purified pigeon intestinal mucin and to the four materials collected from the pigeon loft were similar. Subclass differences between symptomatic and asymptomatic individuals, demonstrable against purified mucin, were similarly seen against pigeon droppings and pigeon bloom. Both pigeon droppings and pigeon bloom were capable of inhibiting IgG binding to purified pigeon mucin, and mucin inhibited substantially the binding of IgG to these materials. Glycoprotein with a density similar to that described for pigeon intestinal mucin was purified from each source. CONCLUSION: Pigeon intestinal mucin is present in a variety of materials found in the environment of the pigeon loft in a form capable of reacting with anti-mucin antibodies in the sera of exposed individuals. Reduction in exposure to these materials may decrease the likelihood of developing pigeon fanciers' lung and minimise reactions in sensitised individuals.

Animals↗
PubMed1998

A joint US-UK study of home telenursing.

Nursing notes for patients nursed at home in the USA and the UK were reviewed using an abstraction instrument developed and tested in the US. More than 1700 episodes of patient care at home were reviewed: 906 in the US and 839 in the UK. Preliminary data suggest that in the US approximately 45% of home nursing visits could be done via telemedicine, while the figure is lower in the UK, less than 15%. Pilot trials of an analogue video-telephone in Kansas City and Belfast suggest that even relatively low-quality compressed video may be useful for home nursing. Clearly, there are differences between the two countries which merit further study, but there is evidence to suggest that telemedicine may have a role in the delivery of home health care.

Aged↗
PubMed1998

A cost measurement study for a tele-oncology practice.

The costs of providing oncology services in three different ways were measured. Services were provided to a peripheral hospital by: conventional clinics, in which the oncologist worked at the hospital concerned; outreach clinics, in which an oncologist was flown in periodically from a central hospital; telemedicine clinics, in which the oncologist at the central hospital practised via a video-link. During a one-year study period, 2400 patients were seen in conventional clinics, 81 in outreach clinics and 103 in telemedicine clinics. At these workloads the average costs per patient were $149, $897 and $812, respectively. However, the average costs cannot be compared directly without further information about the shape of the unit cost curves.

Cost-Benefit Analysis↗
PubMed1998

The potential for telemedicine in home nursing.

We assessed the proportion of home nursing visits that could be replaced by home telenursing in the UK. A retrospective review of nursing notes in the UK was undertaken using an abstraction instrument developed and tested in the US. A total of 1951 episodes of patient care at home were reviewed: 1450 from Liverpool and 501 from Belfast. A total of 1626 (83%) of the episodes involved 'hands-on' interventions. In Belfast two observers estimated that 14% of home nursing visits could be done via telemedicine while in Liverpool two more observers gave an estimate of 16%. Inter-rater agreement was high (kappa = 0.93 for the Belfast observers and 0.79 for the Liverpool observers). Pilot trials of an analogue video-phone in Belfast suggested that even relatively low-quality compressed video might be useful for home nursing. These findings suggest that telemedicine may have a significant role in the delivery of home health care in the UK.

Adult↗
PubMed1998

Outcome of renal replacement therapy in antineutrophil cytoplasmic antibody-associated systemic vasculitis.

Antineutrophil cytoplasmic antibody-associated systemic vasculitis (AASV) frequently leads to end-stage renal disease (ESRD). Potentially fatal disease activity can continue after the onset of ESRD in both dialysis and transplant patients, despite the immunosuppressive effects of uremia and rejection prophylaxis, leading to concerns that such patients have greater morbidity and mortality. To assess the outcome of AASV patients receiving renal replacement therapy, a retrospective analysis of 59 patients from our unit who received chronic dialysis, renal transplantation, or both, was performed. The survival of AASV patients with ESRD was comparable to national registry controls, as were both graft and patient survival after renal transplantation. Ther is no evidence that standard immunosuppressive protocols should be altered for AASV patients receiving renal transplants. The rate of relapse of vasculitis for patients on chronic dialysis and after transplantation was 0.09 and 0.02 per patient per year, respectively. These rates are lower than those of other series and support the contention that continued immunosuppression after ESRD, as practiced in our unit, is warranted. Relapses usually responded to cyclophosphamide and high-dose prednisolone treatment. Significantly, vasculitic flare-ups in dialysis patients were sometimes initially misdiagnosed as dialysis complications, leading to fatal delays in effective treatment. Follow-up by physicians experienced in the diagnosis and treatment of vasculitis activity should continue in these patients.

Adolescent↗
PubMed1998

Telemedicine in Latin America.

Latin America, stretching 6,000 miles from Mexico to Tierro del Fuego, is comprised of twenty countries totaling nearly 1/2 billion people. There are wide variations in median income levels, medical access, telecommunications infrastructures, and levels of rurality. The great variety of settings precludes any simple approach to telemedicine deployment.

Computer Communication Networks↗