Characteristics and Treatments of Patients with Peripheral Arterial Disease Referred to UK Vascular Clinics: Results of a Prospective Registry

BACKGROUND

Peripheral arterial disease (PAD) is often associated with risk factors including cigarette smoking, hypertension and hypercholesterolaemia, and patients have a high risk of future vascular events. Good medical management results in improved outcomes and quality of life, but previous studies have documented sub-optimal treatment of risk factors. We assessed the management of cardiovascular risk factors in patients with PAD referred to specialist vascular clinics.

METHODS

This was a prospective, protocol driven registry carried out in UK vascular clinics. Patients who were first-time referrals for evaluation of PAD were eligible if they had claudication plus ankle-brachial pressure index (ABPI) < or = 0.9. Statistical associations between key demographic and treatment variables were explored using a chi-squared test.

RESULTS

We enrolled 473 patients from 23 sites. Mean age was 68 years (SD 10) and 66% were male. Mean estimated claudication distance was 100 m, and ABPI was 0.74. Mean systolic blood pressure (SBP) was 155 mmHg, and 42% had a SBP >160 mmHg. Forty percent were current smokers and half had tried to give up in the prior 6 months, but there was no evidence of a systematic method of smoking cessation. Mean total cholesterol was 5.4 (SD1.2) mmol/l and 30% had levels >6 mmol/l. Antiplatelet therapy had been given to 70% and statins to 44%. Prior CHD was present in 29% and these patients had significantly higher use of antiplatelet therapy, statins and ACE-inhibitors.

CONCLUSIONS

In spite of attempts to raise awareness about PAD as an important marker of cardiovascular risk, patients are still poorly treated prior to referral to a vascular clinic. In particular, the use of evidence-based treatments is sub-optimal, while hypertension and cigarette smoking are poorly managed. More work needs to be done to educate health professionals about the detection and optimal medical management of PAD.

Ethnicity and cardiovascular disease prevention in the United Kingdom: a practical approach to management

The United Kingdom is a diverse society with 7.9% of the population from black and minority ethnic groups (BMEGs). The causes of the excess cardiovascular disease (CVD) and stroke morbidity and mortality in BMEGs are incompletely understood though socio-economic factors are important. However, the role of classical cardiovascular (CV) risk factors is clearly important despite the patterns of these risk factors varying significantly by ethnic group. Despite the major burden of CVD and stroke among BMEGs in the UK, the majority of the evidence on the management of such conditions has been based on predominantly white European populations. Moreover, the CV epidemiology of African Americans does not represent well the morbidity and mortality experience seen in black Africans and black Caribbeans, both in Britain and in their native African countries. In particular, atherosclerotic disease and coronary heart disease are still relatively rare in the latter groups. This is unlike the South Asian diaspora, who have prevalence rates of CVD in epidemic proportions both in the diaspora and on the subcontinent. As the BMEGs have been under-represented in research, a multitude of guidelines exists for the 'general population.' However, specific reference and recommendation on primary and secondary prevention guidelines in relation to ethnic groups is extremely limited. This document provides an overview of ethnicity and CVD in the United Kingdom, with management recommendations based on a roundtable discussion of a multidisciplinary ethnicity and CVD consensus group, all of whom have an academic interest and clinical practice in a multiethnic community.

Spontaneous pneumopericardium, pneumomediastinum and subcutaneous emphysema: unusual complications of asthma in a 2-year-old boy

A 2-year-old boy presented to the emergency department with a history of sudden onset of cough, dyspnoea and a slight expiratory wheeze on the right lung base. He also had subcutaneous emphysema on the left side of the chest anteriorly. Chest x ray confirmed subcutaneous emphysema and also revealed pneumomediastinum and pneumopericardium. He had had no previous episode and was not known to have asthma. He was apyrexial but had a raised white cell count. The eosinophil count was within normal limits. He was successfully treated with nebulised salbutamol, steroids, antibiotics and high flow oxygen. He made a good recovery and was discharged after 7 days. This case highlights the need for a high index of suspicion of asthma in very young children presenting for the first time with such complications.

Measuring the impact of venous leg ulcers on quality of life

OBJECTIVE

To identify health-related quality-of-life (HRQoL) issues in patients with venous leg ulcers, with the aim of generating items for a treatment outcome measure.

METHOD

Thirty-eight patients with venous leg ulcers were interviewed by a psychologist using a semi-structured guide; they also completed a HRQoL questionnaire (modified Skindex). Data from the questionnaire were examined to explore the impact of venous leg ulcers on patients' lives. Interview transcripts were analysed using qualitative methods to identify additional venous leg ulcer-specific HRQoL items.

RESULTS

Skindex scores indicated that older patients had worse HRQoL (p<0.05), as did those with pain and non-healing ulcers. Ulcer duration and size did not correlate with HRQoL. Interviews revealed the following effects of ulceration: pain (80.5%); itching (69.4%); altered appearance (66.7%); loss of sleep (66.6%); functional limitation (58.3%); and disappointment with treatment (50%). Based on the interview transcripts, items were generated and discussed with an expert panel, with a view to including them in a venous leg ulcer-specific HRQoL questionnaire.

CONCLUSION

Disease-specific HRQoL outcome measures should be considered when evaluating treatments for venous leg ulcers.

Strategies to improve the effectiveness of abdominal aortic aneurysm screening programmes

OBJECTIVE

Ruptured abdominal aortic aneurysms (rAAAs) occurring in patients with screen-detected aneurysms could be regarded as a failure of screening and reduce effectiveness of screening. To understand this issue, we studied the reasons why rAAAs occur in screened patients and estimated the cost-benefit ratio if these ruptures could be prevented.

METHODS

All rAAAs occurring in the Huntingdon district in the UK during the study period (1991-2000) were traced via a combination of hospital admission, accident and emergency attendance, and intensive therapy unit admission records, operating theatre registers and post-mortem reports. Cross-referencing with the aneurysm-screening database identified those patients who had attended screening. Previously used cost-effectiveness models were used to estimate the cost benefits to screening.

RESULTS

Ninety-three rAAAs occurred in men over the study period, of whom 23 (25%) had been invited for screening and 13 (14%) had accepted the invitation. All who had been screened (mean age 75 [65-82]) had abnormal aortic diameters (>30 mm) on their first scan. Of those invited, 10/23 (43%) did not attend their screening appointment, 4/23 (17%) were deemed not fit for open surgery, 4/23 (17%) ruptured whilst being assessed for aneurysm repair, 2/23 (9%) ruptured whilst under six-monthly surveillance, and 3/23 (13%) failed to attend scheduled six-monthly surveillance appointments. Reducing screened ruptures by one half could increase the cost-effectiveness of screening by 27%.

CONCLUSION

There were no failures of the screening test. The benefits of aneurysm screening can be improved by increasing the uptake of screening, the compliance with surveillance, and by streamlining the work-up process before surgery.

Mass screening for coeliac disease using antihuman transglutaminase antibody assay

AIMS

To determine coeliac disease prevalence by an anti-transglutaminase antibody assay in a large paediatric population; to evaluate acceptance of the screening programme, dietary compliance, and long term health effects.

METHODS

Cross-sectional survey of 3188 schoolchildren (aged 6-12) and prospective follow up of diagnosed cases. Main outcome measures were: prevalence of coeliac disease defined by intestinal biopsy or positivity to both human tissue transglutaminase and anti-endomysium antibodies in HLA DQ2-8 positive subjects; percentage of children whose families accepted screening; dietary compliance as defined by negativity for anti-transglutaminase antibodies; and presence of clinical or laboratory abnormalities at 24 month follow up.

RESULTS

The families of 3188/3665 children gave their consent (87%). Thirty biopsy proven coeliacs were identified (prevalence 1:106). Three other children testing positive for both coeliac related autoantibodies and HLA DQ2-8 but refusing biopsy were considered as having coeliac disease (prevalence 1:96). Of 33 cases, 12 had coeliac related symptoms. The 30 biopsy proven coeliacs followed a gluten-free diet. Of 28 subjects completing 18-24 months follow up, 20 (71.4%) were negative for anti-transglutaminase antibodies, while eight were slightly positive; symptoms resolved in all 12 symptomatic children.

CONCLUSIONS

Prevalence of coeliac disease is high in Italian schoolchildren. Two thirds of cases were asymptomatic. Acceptance of the programme was good, as was dietary compliance. Given the high prevalence and possible complications of untreated coeliac disease, the availability of a valid screening method, and evidence of willingness to comply with dietary treatment population mass screening deserves careful consideration.

Treatment of urinary incontinence in cystic fibrosis

BACKGROUND

Urinary incontinence (UI) is a newly recognised problem in cystic fibrosis. Whilst prevalence is well documented, there are no reports of assessment and treatment of the problem.

METHODS

A previous study reports the prevalence of UI in women with CF to be 51/75 (68%). Nineteen women subsequently requested help for the problem and were referred to a physiotherapist specialising in women's health. A digital assessment was performed to measure pelvic floor muscle strength and endurance. An individualised programme of pelvic floor muscle exercises (PFME) was taught based on the assessment. A questionnaire addressed issues of assessment and treatment.

RESULTS

12 women were assessed. The median (range) age, FEV1% predicted and BMI were 20.9 (19.3-46.1) years, 45.9 (14.8-82.7) and 20.5 (16.1-26.0), respectively. The median strength of the pelvic floor muscle was moderate (Oxford Scale grade 3) with a hold time (endurance) of 5 s. At reassessment (median time 13.1 weeks), there was an improvement in endurance (P = 0.04), with no change in strength. This was supported by a subjective improvement in symptoms. Patients found the exercises were difficult to perform, difficult to fit into their treatment programme and adherence was poor.

CONCLUSIONS

PFME are effective at improving endurance and reducing leakage over the short-term. Women are reluctant to be assessed and the CF team should provide support and encouragement with treatment. Long-term outcome and the mechanisms of UI in this group of patients need further evaluation.

A reliable screening procedure for coeliac disease in clinical practice

BACKGROUND

The main autoantigen recognized by the sera of patients with coeliac disease (CD) is tissue transglutaminase (tTG). A human-recombinant form of tTG was used to develop an ELISA to measure anti-tTG serum antibodies for the diagnosis of CD. Preliminary retrospective reports suggest that the human tTG-based ELISA could identify coeliac patients missed by the IgA-anti-endomysium antibody test (AEA). Whether the human recombinant tTG ELISA is sufficiently accurate to become the main diagnostic CD tool in everyday clinical practice is unknown. The objective was to determine, in a prospective study, the sensitivity and specificity of an ELISA test based on the use of human tTG compared with AEA, to analyse the discordant cases for HLA DQ2-8 and for clinical and intestinal biopsy characteristics.

METHODS

1106 patients referred to a gastrointestinal outpatient clinic for symptoms attributable to CD, 52 first-degree relatives of CD patients and 200 healthy controls were tested for both anti-human tTG and AEA antibodies.

RESULTS

Out of 1158 subjects, 146 were tested positive for anti-tTG antibodies and 140 were biopsy-proven coeliacs. The AEA test identified 126/1158 coeliacs who also tested positive for anti-tTG antibodies. The 14 patients missed by the AEA test carried the typical HLA-DQ for CD; they had normal levels of total serum IgA and had milder pathology than those with both anti-tTG and AEA positivity (P < 0001).

CONCLUSIONS

These results prove that human tTG-based ELISA is an excellent diagnostic tool for CD, for mass screening by both the specialist and the general clinic.

Mapping the C terminal epitope of the Alzheimer's disease specific antibody MN423

The mapping of monoclonal antibody epitopes is now predominantly carried out using molecular diversity techniques, phage display in particular. However, until very recently, phage display methods have been inappropriate for the analysis of epitopes that require a free carboxy terminus. Here we describe the use of two different techniques to analyze the known C terminal epitope specificity of MN423, a monoclonal antibody specifically staining truncated tau in Alzheimer's brain. Using a lambda phage based C-terminal random peptide library, and an intracellular expression library based on truncated tau, we show that this antibody has an absolute requirement for a glycine at position -3 with respect to the C terminus. Both methods give similar results, and identify other important residues in the binding site. However, affinity analysis of synthetic peptides revealed that the affinity of the antibody for identified tripeptides was far lower than the pentapeptide sequence in the native target, and that this in turn was considerably below the affinity for the native target itself. This suggests that molecular diversity methods may define minimum, but not necessarily complete epitopes. The methods described here have a general application to the analysis of antibody epitopes suspected to be found at the C terminus.

Using an in vivo phagemid system to identify non-compatible loxP sequences

The site-specific recombination system of bacteriophage P1 is composed of the Cre recombinase that recognizes a 34-bp loxP site. The Cre/loxP system has been extensively used to manipulate eukaryotic genomes for functional genomic investigations. The creation of additional heterologous loxP sequences potentially expands the utility of this system, but only if these loxP sequences do not recombine with one another. We have developed a stringent in vivo assay to examine the degree of recombination between all combinations of each previously published heterologous loxP sequence. As expected, homologous loxP sequences efficiently underwent Cre-mediated recombination. However, many of the heterologous loxP pairs were able to support recombination with rates varying from 5 to 100%. Some of these loxP sequences have previously been reported to be non-compatible with one another. Our study also confirmed other heterologous loxP pairs that had previously been shown to be non-compatible, as well as defined additional combinations that could be used in designing new recombination vectors.

Analyzing the peripheral blood antibody repertoire of a celiac disease patient using phage antibody libraries

Celiac disease (CD) is an autoimmune enteropathy characterized by intestinal malabsorption and immunological responses to dietary gliadins and an auto antigen located in the endomysium. The latter has recently been identified as the enzyme tissue transglutaminase (tTG). The linkage between gliadins, tTG and the autoimmune response has still to be clarified. In this work we report the production and analysis of a phage antibody library from the peripheral blood lymphocytes (PLB) of a CD patient. The library contained polyreactive and monoreactive antibodies to alpha-gliadin, to the dietary antigen beta-lactoglobulin, but not to tTG. The majority of the VH regions of the anti-alpha-gliadin antibodies belonged to the VH 4 family. The possibility of exploiting phage display antibodies as tools to study the molecular events associated with CD is discussed.

Antibodies in haystacks: how selection strategy influences the outcome of selection from molecular diversity libraries

Antibodies against most antigens can be isolated from high quality phage antibody libraries. However, not all antibodies binding a particular antigen are necessarily found when standard selections are performed. Here we investigate the effect of two different selection strategies on the isolation of antibodies against a number of different antigens, and find that these different strategies tend to select different antibodies, with little overlap between them. This indicates that the full diversity of these libraries is not tapped by a single selection strategy and that each selection strategy imposes different selective criteria in addition to that of antigen binding. To fully exploit such libraries, therefore, many different selection strategies should probably be employed for each antigen. The use of alternative strategies should be considered when selection apparently fails, or when the number of different antibodies recognizing an antigen needs to be maximised. Furthermore, the microtitre selection strategy developed is likely to prove useful in the application of phage antibody libraries to the human genome project, allowing the high throughput selection of antibodies against multiple antigens simultaneously.

Using an in vivo phagemid system to identify non-compatible loxP sequences

The site-specific recombination system of bacteriophage P1 is composed of the Cre recombinase that recognizes a 34-bp loxP site. The Cre/loxP system has been extensively used to manipulate eukaryotic genomes for functional genomic investigations. The creation of additional heterologous loxP sequences potentially expands the utility of this system, but only if these loxP sequences do not recombine with one another. We have developed a stringent in vivo assay to examine the degree of recombination between all combinations of each previously published heterologous loxP sequence. As expected, homologous loxP sequences efficiently underwent Cre-mediated recombination. However, many of the heterologous loxP pairs were able to support recombination with rates varying from 5 to 100%. Some of these loxP sequences have previously been reported to be non-compatible with one another. Our study also confirmed other heterologous loxP pairs that had previously been shown to be non-compatible, as well as defined additional combinations that could be used in designing new recombination vectors.

In vivo recombination as a tool to generate molecular diversity in phage antibody libraries

The creation of diversity in populations of polypeptides has become an important tool in the derivation of polypeptides with useful characteristics. This requires efficient methods to create diversity coupled with methods to select polypeptides with desired properties. In this review we describe the use of in vivo recombination as a powerful way to generate diversity. The novel principles for the recombination process and several applications of this process for the creation of phage antibody libraries are described. The advantage and disadvantages are discussed and possible future exploitation presented.

Molecular dissection of the tissue transglutaminase autoantibody response in celiac disease

Celiac disease (CD) is an intestinal malabsorption characterized by intolerance to cereal proteins accompanied by immunological responses to dietary gliadins and tissue transglutaminase, an autoantigen located in the endomysium. Tissue transglutaminase belongs to the family of enzymes that catalyze protein cross-linking reactions and is constitutively expressed in many tissues as well as being activated during apoptosis. The role of gliadins in eliciting the immune response in CD and how transglutaminase is linked to the primary reaction are still unclear. In this work, we report the production and analysis of six phage Ab libraries from the peripheral and intestinal lymphocytes of three CD patients. We were able to isolate Abs to transglutaminase from all intestinal lymphocytes libraries but not from those obtained from peripheral lymphocytes. This is in contrast to Abs against gliadin, which could be obtained from all libraries, indicating that the humoral response against transglutaminase occurs at the local level, whereas that against gliadin occurs both peripherally and centrally. Abs from all three patients recognized the same transglutaminase epitopes with a bias toward the use of the V(H)5 Ab variable region family. The possible role of these anti-transglutaminase Abs in the onset of CD and associated autoimmune pathologies is discussed.

Early expression of GABA(A) receptor delta subunit in the neonatal rat hippocampus

The cDNA library screening strategy was used to identify the genes encoding for GABA(A) receptor subunits in the rat hippocampus during development. With this technique, genes encoding eleven GABA(A) receptor subunits were identified. The alpha5 subunit was by far the most highly expressed, followed by the gamma2, alpha2 and alpha4 subunits respectively. The expression of the beta2, alpha1, gamma1, beta1 and beta3 subunits was moderate, although that of the alpha3 and delta subunits was weak. In situ hybridization experiments, using digoxigenin-labeled cRNA probes, confirmed that the delta subunit was expressed in the neonatal as well as in the adult hippocampus, and is likely to form functional receptors in association with other subunits of the GABA(A) receptor. When the more sensitive RT-PCR approach was used, the gamma3 subunit was also detected, suggesting that this subunit is present in the hippocampus during development but at low levels of expression. The insertion of the delta subunit into functional GABA(A) receptors may enhance the efficacy of GABA in the immediate postnatal period when this amino acid is still exerting a depolarizing and excitatory action.

Development of a novel rapid non-invasive screening test for coeliac disease

BACKGROUND

Coeliac disease is one of the commonest underdiagnosed diseases in general practice. The autoantigen recognised by the sera of patients with coeliac disease has recently been identified as tissue transglutaminase.

AIMS

We evaluated a simple non-invasive immunological dot blot assay for coeliac disease, suitable for use by the general physician in the ambulatory setting. The sensitivity and specificity of this dot blot assay based on recognition of recombinant human transglutaminase were compared with those of antiendomysial antibodies and an enzyme linked immunosorbent assay.

METHODS

Serum samples were analysed from 64 healthy controls, 58 first degree relatives of coeliacs, 74 diseased controls, and 70 biopsy confirmed untreated patients with coeliac disease. Dot blot assay and enzyme linked immunosorbent assay were performed using recombinant human transglutaminase as antigen.

RESULTS

The dot blot assay, which can be performed in 20 minutes, was positive in all 70 untreated coeliacs (sensitivity 100%). Among the three control groups, there were three false positive tests by dot blot (specificity 98%), all belonging to the group of healthy subjects. The antiendomysial antibodies test missed five untreated coeliac patients (sensitivity 93%) and was negative in all three control groups (specificity 100%). The specificity of the immunosorbent assay was 99% for IgA and 98% for IgG, while sensitivity was 93% for IgA, 47% for IgG, and 100% for IgA and IgG combined.

CONCLUSIONS

The dot blot assay is highly accurate in detecting untreated subjects with coeliac disease and can be performed in the general physician's medical office during the course of a routine examination. This innovative test is a practical, reliable alternative to both the immunofluorescent based antiendomysial test and immunosorbent assay for detection of transglutaminase antibodies for the diagnosis of coeliac disease.

The relationship between lower limb symptoms and superficial and deep venous reflux on duplex ultrasonography: The Edinburgh Vein Study

BACKGROUND

Previous work from this group has demonstrated the relationships between lower limb symptoms and the presence and severity of trunk varicose veins as seen on clinical examination to be generally weak, symptom specific, and gender dependent.

OBJECTIVE

This study was undertaken to investigate the relationships in the general population between lower limb symptoms and the presence of superficial or deep venous reflux.

METHODS

A cross-sectional study was made of an age-stratified random sample of 1566 subjects (699 men and 867 women) aged 18 to 64 selected from 12 general practices in Edinburgh, Scotland. Subjects completed a self-administered questionnaire regarding symptoms (heaviness/tension, a feeling of swelling, aching, restless legs, cramps, itching, tingling) and underwent duplex ultrasound examination of the superficial and deep venous systems of both legs. Reflux of 0.5 seconds or greater was considered pathologic. Deep venous reflux was defined as reflux in at least the popliteal vein.

RESULTS

There was a significant positive relationship between isolated superficial reflux and the presence of heaviness/tension (P <.025, both legs) and itching (P =.002, left leg) in women. Isolated superficial reflux in men was not significantly positively associated with any symptom. Isolated deep venous reflux was not significantly related to any symptom in either leg in either sex. Combined reflux was related to a feeling of swelling (P =.018, right leg; P =.0022, left leg), cramps (P =.0049, left leg) and itching (P =.0043, left leg) in men, and aching (P =.03, right leg) and cramps (P =.026, left leg) in women.

CONCLUSION

In the general population, only certain lower limb symptoms were related to the presence of reflux on duplex ultrasound scanning. The strongest relationships were observed in the left legs of men with combined superficial and deep reflux.

Mass spectral analysis of a protein complex using single-chain antibodies selected on a peptide target: applications to functional genomics

Genome projects are identifying an ever-increasing number of genes, accelerating the need for reagents to study the expression of these genes and elucidate the function and cellular location of the gene products. Our goal was to develop a strategy to allow human single-chain variable fragment (scFv) antibodies to be used for these endeavors. A library containing 7x10(9) individual variants was displayed by bacteriophage and selected against a biotinylated peptide corresponding to the C-terminal 15 amino acid residues of Ku86, one component of a heterodimer involved in double-stranded DNA break repair. Four unique scFv antibodies were recovered that not only recognized the selected peptide, but also the intact protein. Three of the scFv antibodies were expressed in soluble form and recognized Ku86 by Western analysis. The affinity of one of the scFv antibodies for Ku86 was 16 nM as measured by BIAcore analysis. scFv immunoprecipitation of Ku86 also isolated the other component of the heterodimer, Ku70, as determined by Western analysis and mass spectrometry. These results demonstrate the utility of scFv antibodies as invaluable reagents for functional genomics.

The neuronal microtubule-associated protein tau is a substrate for caspase-3 and an effector of apoptosis

We have identified a class of tau fragments inducing apoptosis in different cellular contexts, including a human teratocarcinoma-derived cell line (NT2 cells) representing committed human neuronal precursors. We have found a transition point inside the tau molecule beyond which the fragments lose their ability to induce apoptosis. This transition point is located around one of the putative caspase-3 cleavage sites. This is the only site that can be effectively used by caspase-3 in vitro, releasing the C-terminal 19 amino acids of tau. These results establish tau as a substrate for an apoptotic protease that turns tau itself into an effector of apoptosis. Accordingly, tau may be involved in a self-propagating process like what has been predicted for the pathogenesis of different neurodegenerative disorders.

'Specific' oligonucleotides often recognize more than one gene: the limits of in situ hybridization applied to GABA receptors

As exquisite probes for gene sequences, oligonucleotides are one of the most powerful tools of recombinant molecular biology. In studying the GABA receptor subunits in the neonatal hippocampus we have used oligonucleotide probes in in situ hybridization and cloning techniques. The oligonucleotides used and assumed to be specific for the target gene, actually recognized more than one gene, leading to surprising and contradictory results. In particular, we found that a GABA(A)-rho specific oligonucleotide recognized an abundant, previously unknown, transcription factor in both in situ and library screening, while oligos 'specific' for GABA(A) subunits were able to recognize 30 additional unrelated genes in library screening. This suggests that positive results obtained with oligonucleotides should be interpreted with caution unless confirmed by identical results with oligonucleotides from different parts of the same gene, or cDNA library screening excludes the presence of other hybridizing species.

Human recombinant tissue transglutaminase ELISA: an innovative diagnostic assay for celiac disease

OBJECTIVE

Tissue transglutaminase is the autoantigen recognized by the sera of celiac patients. An enzyme-linked immunosorbent assay (ELISA) based on guinea-pig tissue transglutaminase was recently used to measure serum tissue transglutaminase antibodies for the diagnosis of celiac disease. We determine the sensitivity and specificity of an ELISA test based on the use of human recombinant transglutaminase, compared with the guinea pig transglutaminase ELISA and IgA antiendomysium antibodies.

METHODS

Serum samples were tested from 65 patients with intestinal biopsy proven celiac disease, from 10 patients with Crohn's disease, and from 150 healthy blood donors.

RESULTS

Human transglutaminase ELISA identified 64 of 65 celiac patients, whereas the guinea pig transglutaminase ELISA and IgA antiendomysium antibodies identified 58 of 65 and 60 of 65 subjects, respectively. The three tests showed comparable specificity.

CONCLUSIONS

These results proved that the human tissue transglutaminase-based ELISA represents a cost-effective strategy for identifying both symptomatic and atypical forms of celiac disease and could mean that intestinal biopsy need no longer be the gold standard for diagnosing this clinical condition. Furthermore, early identification and treatment of patients with celiac disease in an outpatient setting could have significant implications for reducing long-term morbidity and can produce major savings in future health care costs.

Exploiting recombination in single bacteria to make large phage antibody libraries

The creation of large phage antibody libraries has become an important goal in selecting antibodies against any antigen. Here we describe a method for making libraries so large that the complete diversity cannot be accessed using traditional phage technology. This involves the creation of a primary phage scFv library in a phagemid vector containing two nonhomologous lox sites. Contrary to the current dogma, we found that infecting Cre recombinase-expressing bacteria by such a primary library at a high multiplicity of infection results in the entry of many different phagemid into the cell. Exchange of Vh and Vl genes between such phagemids creates many new V h/Vl combinations, all of which are functional. On the basis of the observed recombination, the library is calculated to have a diversity of 3x1011. A library created using this method was validated by the selection of high affinity antibodies against a large number of different protein antigens.

Elective repair of type IV thoraco-abdominal aortic aneurysms; experience of a subcostal (transabdominal) approach

OBJECTIVE

preoperative pulmonary function has been shown by univariate analysis to be an independent predictor of outcome following Crawford Type IV thoraco-abdominal aortic aneurysm repair. The aim of this study was to determine if outcome had been improved by the introduction of a subcostal approach for the elective repair of these aneurysms.

METHODS

39 patients studied (19 subcostal, 20 thoracolaparotomy) all operated on between 1993 and 1998 by a single surgeon using a standard technique. No significant difference in median age (69 years) or weight (64 kg vs. 69 kg) between the two groups.

RESULTS

preoperative co-morbidities, pulmonary function and predictors of respiratory failure did not vary significantly between the two groups, despite a trend towards greater respiratory, cardiac and renal disease in the subcostal group. Preoperative median pulmonary function in both groups was 80% of that predicted for age, sex and height. The subcostal approach did not significantly reduce blood loss (3500 ml vs. 4500 ml) or anaesthetic time (255 min vs. 253 min). Overall 30 day mortality was 10.2%. The rate of re-operation was significantly higher in the subcostal group (21% vs. 0%, p=0.05). No differences were observed in intensive care unit stay, total hospital stay or respiratory complications, despite earlier extubation of the subcostal group (47% vs. 10% extubated at 12 h, p=0.01).

CONCLUSION

the introduction of a subcostal approach for type IV thoraco-abdominal aneurysm repair in selected "high risk" patients has been associated with an unacceptably high rate of complications requiring early re-operation. We feel that this relates to the problems inherent in the introduction of a new technique and reduced exposure in patients of inappropriate body habitus. The predicted benefit to pulmonary function is realised in shorter intubation times, but has not translated into earlier recovery or improved outcome. Operation duration and blood loss have not been significantly reduced. Based on these outcomes, we do not currently recommend the general adoption of this approach in all type IV repairs. We will continue to evaluate this approach in patients with poor pulmonary function and a suitable body habitus.

Low expression of the ClC-2 chloride channel during postnatal development: a mechanism for the paradoxical depolarizing action of GABA and glycine in the hippocampus

In early postnatal development, during the period of synapse formation, gamma-aminobutyric acid (GABA) and glycine, the main inhibitory transmitters in the adult brain, paradoxically excite and depolarize neuronal membranes by an outward flux of chloride. The mechanisms of chloride homeostasis are not fully understood. It is known that in adult neurons intracellular chloride accumulation is prevented by a particular type of chloride channel, the ClC-2. This channel strongly rectifies in the inward direction at potentials negative to ECl thus ensuring chloride efflux. We have tested the hypothesis that in the developing hippocampus, a differential expression or regulation of ClC-2 channels may contribute to the depolarizing action of GABA and glycine. We have cloned a truncated form of ClC-2 (ClC-2nh) from the neonatal hippocampus which lacks the 157 bp corresponding to exon 2. In situ hybridization experiments show that ClC-2nh is the predominant form of ClC-2 mRNA in the neonatal brain. ClC-2nh mRNA is unable to encode a full-length protein due to a frameshift, consequently it does not induce any currents upon injection into Xenopus oocytes. Low expression of the full-length ClC-2 channel, could alter chloride homeostasis, lead to accumulation of [Cl-]i and thereby contribute to the depolarizing action of GABA and glycine during early development.

Disruption of anthrax toxin binding with the use of human antibodies and competitive inhibitors

The protective antigen (PA83) of Bacillus anthracis is integral to the mechanism of anthrax toxicity. We have isolated a human single-chain Fv antibody fragment (scFv) that blocks binding of a fluorescently tagged protective antigen (PA) moiety to cell surface receptors. Several phage-displayed scFv were isolated from a naive library biopanned against PA83. Soluble, monomeric scFv were characterized for affinity and screened for their capacity to disrupt receptor-mediated binding of PA. Four unique scFv bound to PA83, as determined by surface plasmon resonance, the tightest binder exhibiting a Kd of 50 nM. Two scFv had similar affinities for natural PA83 and a novel, recombinant, 32-kDa carboxy-terminal PA fragment (PA32). Binding of scFv to green fluorescent protein fused to the amino-terminal 32-kDa fragment of B. anthracis edema factor, EGFP-EF32, was used to confirm specificity. Fusion of EGFP to PA32 facilitated development of a novel flow cytometric assay that showed that one of the scFv disrupted PA receptor binding. This method can now be used as a rapid assay for small molecule inhibitors of PA binding to cell receptors. The combined data presented suggest the potential utility of human scFv as prophylactics against anthrax poisoning. Moreover, recombinant PA32 may also be useful as a therapeutic agent to compete with anthrax toxins for cellular receptors during active infection.

What are the symptoms of varicose veins? Edinburgh vein study cross sectional population survey

OBJECTIVE

To define the relations between age, sex, lower limb symptoms, and the presence of trunk varicose veins on clinical examination.

DESIGN

Cross sectional population study.

SETTING

12 general practices with catchment areas geographically and socioeconomically distributed throughout Edinburgh.

PARTICIPANTS

An age stratified random sample of 1566 people (699 men and 867 women) aged 18-64 selected from the computerised age-sex registers of participating practices.

MAIN OUTCOME MEASURES

Self administered questionnaire on the presence of lower limb symptoms and physical examination to determine the presence and severity of varicose veins.

RESULTS

Women were significantly more likely than men to report lower limb symptoms such as heaviness or tension, swelling, aching, restless legs, cramps, and itching. The prevalence of symptoms tended to increase with age in both sexes. In men, only itching was significantly related to the presence and severity of trunk varices (linear test for trend, P=0.011). In women there was a significant relation between trunk varices and the symptoms of heaviness or tension (P</=0.001), aching (P</=0.001), and itching (P</=0.005). However, the level of agreement between the presence of symptoms and trunk varices was too low to be of clinical value, especially in men.

CONCLUSIONS

Even in the presence of trunk varices, most lower limb symptoms probably have a non-venous cause. Surgical extirpation of trunk varices is unlikely to ameliorate such symptoms in most patients.

Single-chain variable fragments selected on the 57-76 p21Ras neutralising epitope from phage antibody libraries recognise the parental protein

Phage antibodies have been widely prospected as an alternative to the use of monoclonal antibodies prepared by traditional means. Many monoclonal antibodies prepared against peptides are able to recognise the native proteins from which they were derived. Here we show that the same is also true for phage antibodies. We have selected a number of single-chain variable fragments (scFv) from a large phage scFv library against a peptide from the switch region II of p21Ras. This peptide is known to reside in a mobile area of the native protein and is the epitope of a well characterised monoclonal antibody. Selected scFvs were able to recognise native p21Ras in both ELISA and Western blots, indicating that peptides are also likely to be very useful in selecting from phage antibody libraries.

Tau cleavage and dephosphorylation in cerebellar granule neurons undergoing apoptosis

Cerebellar granule cells undergo apoptosis in culture after deprivation of potassium and serum. During this process we found that tau, a neuronal microtubule-associated protein that plays a key role in the maintenance of neuronal architecture, and the pathology of which correlates with intellectual decline in Alzheimer's disease, is cleaved. The final product of this cleavage is a soluble dephosphorylated tau fragment of 17 kDa that is unable to associate with microtubules and accumulates in the perikarya of dying cells. The appearance of this 17 kDa fragment is inhibited by both caspase and calpain inhibitors, suggesting that tau is an in vivo substrate for both of these proteases during apoptosis. Tau cleavage is correlated with disruption of the microtubule network, and experiments with colchicine and taxol show that this is likely to be a cause and not a consequence of tau cleavage. These data indicate that tau cleavage and change in phosphorylation are important early factors in the failure of the microtubule network that occurs during neuronal apoptosis. Furthermore, this study introduces new insights into the mechanism(s) that generate the truncated forms of tau present in Alzheimer's disease.

Relationship between abdominal aortic aneurysm wall compliance and clinical outcome: a preliminary analysis

BACKGROUND

Aortic compliance, as measured by the pressure-strain elastic modulus (Ep) and stiffness (B), may allow a more precise estimate of abdominal aortic aneurysm rupture risk than size alone.

AIM

To determine the relationships between AAA compliance, size, growth, and clinical outcome.

METHODS

One-hundred and twelve patients with initially non-operated AAA (86 men, 26 women, mean age 73 years), recruited from five centres, underwent baseline compliance measurements and were then followed for a median of 7 (range 2-18) months; 85 patients underwent repeated measurements (median 3, range 2-5) 3-6-monthly over a median of 12 (range 3-18 months).

RESULTS

Seven patients have ruptured and 16 have undergone repair of non-ruptured AAA. AAA that ruptured had significantly lower Ep and B (more compliant). In AAA that ruptured or required repair there was an inverse relationship between diameter and Ep and B. In those undergoing repeated measurements AAA expansion was only associated with a significant increase in Ep and B in non-operated patients.

CONCLUSIONS

Baseline AAA compliance was significantly related to rupture and the future requirement for operative repair. Failure of compliance to increase with size may be a marker for rapid growth, developmental symptoms and rupture.

A definitive set of oligonucleotide primers for amplifying human V regions

BACKGROUND

The creation of large diverse phage antibody libraries from natural sources relies on primers which are able to amplify as many V genes as possible. All functional germline V genes have recently been catalogued in a database, V BASE [1]. Previously published primer sets are unable to recognise all these V genes.

OBJECTIVES

The design of a human primer set able to recognise all functional human V genes which can be used to create diverse phage antibody libraries.

STUDY DESIGN

A new set of primers able to recognise all functional V genes were designed using the following criteria: at least 16 bp homology of the 3' end of the primer to the V gene, no more than 8-fold total degeneracy and minimum primer dimer formation. These primers were tested in all possible combinations in PCR using cDNA from human peripheral blood lymphocytes or from human cord blood lymphocytes.

RESULTS

By computer analysis, all V genes in V BASE could be amplified using this primer set. This theoretical result was tested practically by PCR and all primer pairs were shown to be functional, producing PCR products of the expected size. The intensity of the PCR products reflected information available on the expression of the different V gene families recognised and their expression in these two different V gene sources.

CONCLUSIONS

This new primer set will facilitate the creation of more diverse phage antibody libraries than has been hitherto possible using presently available primer sets.

Phage display of Bacillus thuringiensis CryIA(a) insecticidal toxin

The display of proteins or peptides on the surface of filamentous phages or phagemids has been shown to be a very powerful technology for the rescue of specific binders from large combinatorial libraries, as well as to select derivatives of known proteins with altered binding properties. The Bacillus thuringiensis (Bt) crystal proteins are a large family of insecticidal toxins which bind to receptors found on the brush border of larval midgut cells, different crystal toxins having different larval specificities. Here we describe the display of different CryIA(a) toxin regions on the surface of phagemids using the display vector pHEN1, the purpose being the identification of toxin sequences suitable for mutagenesis and selection using phage display. We show that CryIA(a) domain II, in which the receptor binding activity is located, is efficiently displayed as well as being secreted as soluble protein into the periplasm of bacterial cell. This forms the basis of a simple means for the modification of toxin specificity and the selection of toxin proteins with novel or expanded host ranges.

Changes in platelet count, coagulation and fibrinogen associated with elective repair of asymptomatic abdominal aortic aneurysm and aortic reconstruction for occlusive disease

BACKGROUND

Mortality and morbidity following aortic surgery, particularly repair of ruptured abdominal aortic aneurysm (AAA), is frequently associated with the development of coagulopathy.

OBJECTIVES

To examine changes in platelet count (PC), fibrinogen, and coagulation in patients undergoing elective repair of asymptomatic abdominal aortic aneurysm (AAA) and aortic surgery for occlusive disease.

DESIGN

Prospective clinical study in a University Department of Vascular Surgery.

PATIENTS

Thirty-three patients undergoing elective repair of asymptomatic AAA and 19 patients undergoing aortic surgery for occlusive disease.

METHODS

Full blood count (FBC), clotting screen, and fibrinogen measured pre-operatively; 6, 12, 24, 48 h postoperatively; and thereafter as clinically indicated in 23 consecutive patient's undergoing AAA repair (Group 1). Pre- and postoperative PC measured weekly for 4 weeks following operation in a further 10 consecutive patients undergoing AAA repair (Group 2) and perioperative PC measured in 19 consecutive patients undergoing aortic surgery for occlusive disease (Group 3).

RESULTS

Group 1: Preoperative haematological parameters were normal. There was no mortality. Postoperatively, 21 (91%) patients developed thrombocytopenia (PC < 150 x 10(9)/l). The postoperative fall in PC (median 90, range 12-160 x 10(9)/l) was significantly related to the duration of aortic cross-clamp (median 46, range 20-127 min, r2 = 0.33, p < 0.01). At 10 days all patients had developed thrombocytosis (PC > 350 x 10(9)/l) Postoperatively, by 48 h, 17 (74%) patients had developed hyperfibrinogenaemia. One patient suffered a myocardial infarction associated with a PC of 105 x 10(9)/l and a fibrinogen of 7.2 g/l. GROUP 2: In a further 10 patients undergoing AAA repair postoperative thrombocytosis was found to persist for several weeks in five of nine survivors. GROUP 3: Patients undergoing aortic surgery for occlusive disease had significantly higher preoperative PC than AAA patients (median 292, range 179-251 x 10(9)/l vs. median 204, range 140-293 x 10(9)/l, p < 0.01).

CONCLUSIONS

Patients undergoing elective repair of AAA demonstrate similar, albeit less dramatic, changes in platelet count to those we have previously reported in patients undergoing repair of ruptured AAA. Aortic clamping leads to platelet sequestration and thrombocytopenia in the early postoperative period. Later, patients develop hyperfibrinogenaemia and thrombocytosis which may persist for several weeks. Similar changes are seen in patients undergoing aortic surgery for occlusive disease. These changes may represent a hypercoagulable state that predisposes these patients to thrombotic complications.

Kinetics of drug metabolism in rat liver slices. III. Relationship between metabolic clearance and slice uptake rate

The time course for distribution of five compounds (caffeine, tolbutamide, phenytoin, ondansetron, and diazepam) was studied in precision-cut rat liver slices. Transport of these compounds differed greatly, with caffeine being distributed rapidly, but not accumulating above the media concentration. Although tolbutamide similarly was not accumulated within the tissue, its uptake rate was slower. The rate of phenytoin, ondansetron, and diazepam distribution (with appropriate corrections for metabolism) was slower still; yet, these drugs were accumulated within the cells of the slice to a concentration approximately 15-fold that of the media. Examination of the physicochemical properties of these compounds demonstrated that the extent of accumulation positively correlated with lipophilicity, whereas the rate of uptake was not statistically correlated with log D. The extent of accumulation within the slice was assessed by an apparent volume of distribution parameter (ranging from 26 to 195 microliters/slice). Using cell:media partition coefficients determined in hepatocytes and the intra- and extracellular spaces within the slice (as measured with the markers tritiated water and sucrose), it was possible to predict apparent volumes of distribution for each drug in the liver slice. Comparison of observed and predicted apparent volumes of distribution gave ratios of 0.34-1. Intrinsic clearance values for these five drugs are available for slices and cells (slice: cell intrinsic clearance ratios 0.05-0.43; Worboys et al., Drug Metab. Dispos. 24, 676-681, 1996). Drugs that demonstrate low intrinsic clearance ratios also have low apparent volume ratios, thus indicating that reduced drug uptake and clearance in slices, relative to hepatocytes, are interdependent. Both phenomena may be rationalized by the existence of a drug concentration gradient within the slice. At very high drug concentrations, Vmax operates, and the consequence of the gradient is minimal. Therefore, it is possible to speculate upon the fraction of hepatocytes within the slice contributing to clearance by considering Vmax values. For six pathways of metabolism, Vmax in slices averages 35% of the corresponding parameter in isolated hepatocytes. This is most likely due to limited oxygen and compromised metabolic function of the core cells. These distribution phenomena severely complicate the possibility of using a scaling factor based on the theoretical number of slices obtainable from a liver to predict in vivo intrinsic clearance.

An integrated vector system for the eukaryotic expression of antibodies or their fragments after selection from phage display libraries

Phage display is now an established method to select antibody fragments specific for a wide range of diverse antigens. In particular, isolation of human monoclonal antibodies has become a reality and for most purposes bacterial expression of the selected recombinant antibody fragments is sufficient. However, there are some cases where the expression of complete human immunoglobulin in mammalian cells is, if not essential, at least desirable. For this reason we have designed and constructed a set of mammalian expression vectors which permit facile and rapid cloning of antibody genes for both transient and stable expression in mammalian cells. Immunoglobulin genes may be cloned into these expression vectors as V regions or as Fabs for expression as either complete antibodies or as Fab fragments, using restriction sites which are rare in human V genes. All the important elements in the vectors--promoter, leader sequence, constant domains and selectable markers--are flanked by unique restriction sites, allowing simple substitution of elements. The vectors have been evaluated using the variable regions from the neutralizing anti-nerve growth factor (NGF) antibody, alphaD11, and the V regions from 2E10, a scFv selected from a scFv phagemid library.