Dynamic self-assembly of DNA minor groove-binding ligand DB921 into nanotubes triggered by an alkali halide.

We describe a novel self-assembling supramolecular nanotube system formed by a heterocyclic cationic molecule which was originally designed for its potential as an antiparasitic and DNA sequence recognition agent. Our structural characterisation work indicates that the nanotubes form via a hierarchical assembly mechanism that can be triggered and tuned by well-defined concentrations of simple alkali halide salts in water. The nanotubes assembled in NaCl have inner and outer diameters of ca. 22 nm and 26 nm respectively, with lengths that reach into several microns. Our results suggest the tubes consist of DB921 molecules stacked along the direction of the nanotube long axis. The tubes are stabilised by face-to-face π-π stacking and ionic interactions between the charged amidinium groups of the ligand and the negative halide ions. The assembly process of the nanotubes was followed using small-angle X-ray and neutron scattering, transmission electron microscopy and ultraviolet/visible spectroscopy. Our data demonstrate that assembly occurs through the formation of intermediate ribbon-like structures that in turn form helices that tighten and compact to form the final stable filament. This assembly process was tested using different alkali-metal salts, showing a strong preference for chloride or bromide anions and with little dependency on the type of cation. Our data further demonstrates the existence of a critical anion concentration above which the rate of self-assembly is greatly enhanced.

An evaluation of the International Standards to Document Remaining Autonomic Function after Spinal Cord Injury: input from the international community.

STUDY DESIGN: Interactive workshops with a presurvey-postsurvey. OBJECTIVES: To describe a series of workshops held at international meetings to inform the spinal cord injury (SCI) community about the International Standards to Document Remaining Autonomic Function after Spinal Cord Injury (ISAFSCI) and to obtain feedback on both the workshop and the ISAFSCI assessment. SETTING: Three international conferences of SCI practitioners in Toronto, Las Vegas and Vancouver held between 2012 and 2013. METHODS: The workshops included an overview of the ISAFSCI, sharing experiences using it in clinical practice and interactive cases illustrating how to complete the scoring. A presurvey-postsurvey was administered to obtain feedback on the workshops and the ISAFSCI assessment. RESULTS: One hundred and fourteen participants completed the workshop surveys and 96% (109/114) completed both presurvey and postsurvey. Prior to the workshop, 41% (47/114) of those who had completed the survey reported assessing autonomic function in their practice, and of those, 53% (25/47) reported using the ISAFSCI. After the workshop, 74% (84/114) of participants reported that the case studies were helpful, and 57% (65/114) reported that they wanted to start or continue to use the ISAFSCI in their clinical practice. Suggestions for improving the ISAFSCI included providing further areas to consider when performing the assessment, addressing ambiguity of terms and reporting foreseeable implementation challenges. CONCLUSION: Results from this workshop suggest that more work is needed to inform the SCI community on the ISAFSCI assessment and to further clarify its language. Results from this study will inform future revisions to the ISAFSCI.

Structural and mechanistic insights into Helicobacter pylori NikR activation.

NikR is a transcriptional metalloregulator central in the mandatory response to acidity of Helicobacter pylori that controls the expression of numerous genes by binding to specific promoter regions. NikR/DNA interactions were proposed to rely on protein activation by Ni(II) binding to high-affinity (HA) and possibly secondary external (X) sites. We describe a biochemical characterization of HpNikR mutants that shows that the HA sites are essential but not sufficient for DNA binding, while the secondary external (X) sites and residues from the HpNikR dimer-dimer interface are important for DNA binding. We show that a second metal is necessary for HpNikR/DNA binding, but only to some promoters. Small-angle X-ray scattering shows that HpNikR adopts a defined conformation in solution, resembling the cis-conformation and suggests that nickel does not trigger large conformational changes in HpNikR. The crystal structures of selected mutants identify the effects of each mutation on HpNikR structure. This study unravels key structural features from which we derive a model for HpNikR activation where: (i) HA sites and an hydrogen bond network are required for DNA binding and (ii) metallation of a unique secondary external site (X) modulates HpNikR DNA binding to low-affinity promoters by disruption of a salt bridge.

Synchrotron-based in vivo tracking of implanted mammalian cells.

We have developed an X-ray imaging protocol that permits 3D visualisation of a small number of implanted cells within bulk tissue. The cells are marked using natural endocytosis of inert gold nano-particles. The resulting local increase in electron density allows high imaging contrast to be obtained from small clusters of these marked cells. Using this technique we have imaged C6 glioma cells within the brain of a model animal. The cells were marked by exposing them to colloidal gold incorporated in the growth media. Gold-loaded glioma cells were implanted into the brains of adult male Wistar rats. After tumours had been allowed to develop for up to 2 weeks, the animals were sacrificed and images of the intact cranium were acquired at the SYRMEP imaging station on the Elettra synchrotron in Italy. Computed tomography was performed using mixed absorption and phase contrast techniques at an X-ray energy of 24 keV. In the resulting volume datasets the tumour bulk is clearly visible and the infiltrating nature of the malignant growth is well demonstrated. Although the protocol was developed using this particular model of malignant brain tumour, it is believed that it will be possible to use it with other cell lines.

Automated sample-changing robot for solution scattering experiments at the EMBL Hamburg SAXS station X33.

There is a rapidly increasing interest in the use of synchrotron small-angle X-ray scattering (SAXS) for large-scale studies of biological macromolecules in solution, and this requires an adequate means of automating the experiment. A prototype has been developed of an automated sample changer for solution SAXS, where the solutions are kept in thermostatically controlled well plates allowing for operation with up to 192 samples. The measuring protocol involves controlled loading of protein solutions and matching buffers, followed by cleaning and drying of the cell between measurements. The system was installed and tested at the X33 beamline of the EMBL, at the storage ring DORIS-III (DESY, Hamburg), where it was used by over 50 external groups during 2007. At X33, a throughput of approximately 12 samples per hour, with a failure rate of sample loading of less than 0.5%, was observed. The feedback from users indicates that the ease of use and reliability of the user operation at the beamline were greatly improved compared with the manual filling mode. The changer is controlled by a client-server-based network protocol, locally and remotely. During the testing phase, the changer was operated in an attended mode to assess its reliability and convenience. Full integration with the beamline control software, allowing for automated data collection of all samples loaded into the machine with remote control from the user, is presently being implemented. The approach reported is not limited to synchrotron-based SAXS but can also be used on laboratory and neutron sources.

Myelin structure is a key difference in the x-ray scattering signature between meningioma, schwannoma and glioblastoma multiforme.

Small angle x-ray scattering (SAXS) patterns of benign and malignant brain tumour tissue were examined. Independent component analysis was used to find a feature set representing the images collected. A set of coefficients was then used to describe each image, which allowed the use of the statistical technique of flexible discriminant analysis to discover a hidden order in the data set. The key difference was found to be in the intensity and spectral content of the second and fourth order myelin scattering peaks. This has clearly demonstrated that significant differences in the structure of myelin exist in the highly malignant glioblastoma multiforme as opposed to the benign: meningioma and schwannoma.

Offspring birthweight is not associated with paternal insulin resistance.

AIMS/HYPOTHESIS: Low birthweight is associated with insulin resistance and other insulin resistance-related phenotypes: diabetes, hypertension, and vascular disease in later life. The underlying mechanism is unclear. The foetal insulin hypothesis proposes that a single genetic predisposition to beta cell dysfunction/insulin resistance results in both reduced insulin-dependent foetal growth in utero, hence low birthweight, and predisposition to type 2 diabetes. The aim of this study was to test whether, as predicted by the foetal insulin hypothesis, there is an association between measures of paternal insulin resistance and offspring birthweight. SUBJECTS AND METHODS: The Exeter Family Study of Childhood Health (EFSOCH) is a community-based study within central Exeter (UK), established to test the foetal insulin hypothesis prospectively. Associations were tested between offspring birthweight and paternal insulin resistance, calculated by homeostasis model assessment analysis in 986 families using data relating to singleton, non-diabetic, UK white pregnancies. Ethics approval was given by the North and East Devon local ethics committee. RESULTS: Offspring birthweight was not significantly correlated with log paternal insulin resistance (r=0, p=0.91), log HDL cholesterol concentration (r=-0.02, p=0.47) or log triglyceride concentration (r=0, p=0.99) when corrected for paternal BMI and common confounders. Multiple linear regression analysis confirmed that paternal insulin resistance was not an independent predictor of offspring birthweight. CONCLUSIONS/INTERPRETATION: Results from a young, adult, non-diabetic population do not support the foetal insulin hypothesis as an explanation for the association of low birthweight with insulin resistance.

An epidemiological study of head injuries in a UK population attending an emergency department.

We aimed to identify the attendance rate for all head injuries, and for moderate to severe head injury (MSHI), in an emergency department (ED), and related risk factors for MSHI, including age, sex, area of residence, and socioeconomic status (SES). This was a retrospective descriptive epidemiological study of an ED database of head injury attendances over 6 years, carried out in an ED that serves both urban and mixed rural and urban areas, with a wide socioeconomic range, and a total population of 344,600. The main outcome measure was rates of attendance for head injury. Head injury presentations accounted for 3.4% of all attendances per year. An overall rate of 453 per 100,000 was found for all head injuries, of which 40 per 100,000 were moderate to severe (10.9%). Urban residents had significantly greater risk of presenting with MSHI compared with residents of mixed/rural areas. Males were more at risk than females, and children and adolescents had higher risk of MSHI. A high attendance rate of MSHI was found in the <5 year old age group in urban areas for both sexes. A gradient, with higher attendance in groups with lower SES, was observed for children in urban areas, while the gradient was reversed in mixed/rural areas. Head injuries are a relatively common cause of attendance at ED. There is significant variation in attendance with MSHI with regard to sex, age, socioeconomic factors, and type of area of residence. The planning and delivery of preventative and management services may be improved by such analyses.

What are the clinical features of lung cancer before the diagnosis is made? A population based case-control study.

BACKGROUND: Over 38,000 new cases of lung cancer occur each year in the UK. Most are diagnosed after initial presentation to primary care, but the relative importance of the various clinical features is largely unknown. METHODS: A population based case-control study was undertaken in all 21 general practices in Exeter, Devon, UK (population 128 700). 247 primary lung cancers were studied in subjects aged over 40 years diagnosed between 1998 and 2002 and 1235 controls matched by age, sex and general practice. The entire primary care record for 2 years before diagnosis was coded using the International Classification of Primary Care-2. Univariable and multivariable conditional logistic regression analyses were used to identify and quantify clinical features independently associated with lung cancer. The main outcome measures were odds ratios and positive predictive values for these variables. RESULTS: Seven symptoms (haemoptysis, loss of weight, loss of appetite, dyspnoea, thoracic pain, fatigue and cough), one physical sign (finger clubbing), and two abnormal investigation results (thrombocytosis and abnormal spirometry) were associated with lung cancer in multivariable analyses, as was cigarette smoking. After excluding variables reported in the final 180 days before diagnosis, haemoptysis, dyspnoea and abnormal spirometry remained independently associated with cancer. CONCLUSIONS: This study provides an evidence base for selection of patients for investigation of possible lung cancer, both for clinicians and for developers of guidelines.

A preliminary study of breast cancer diagnosis using laboratory based small angle x-ray scattering.

Breast tissue collected from tumour samples and normal tissue from bi-lateral mastectomy procedures were examined using small angle x-ray scattering. Previous work has indicated that breast tissue disease diagnosis could be performed using small angle x-ray scattering (SAXS) from a synchrotron radiation source. The technique would be more useful to health services if it could be made to work using a conventional x-ray source. Consistent and reliable differences in x-ray scatter distributions were observed between samples from normal and tumour tissue samples using the laboratory based 'SAXSess' system. Albeit from a small number of samples, a sensitivity of 100% was obtained. This result encourages us to pursue the implementation of SAXS as a laboratory based diagnosis technique.

Clinical features of colorectal cancer before diagnosis: a population-based case-control study.

Most colorectal cancers are diagnosed after the onset of symptoms. However, the risk of colorectal cancer posed by particular symptoms is largely unknown, especially in unselected populations like primary care. This was a population-based case-control study in all 21 general practices in Exeter, Devon, UK, aiming to identify and quantify the prediagnostic features of colorectal cancer. In total, 349 patients with colorectal cancer, aged 40 years or more, and 1744 controls, matched by age, sex and general practice, were studied. The full medical record for 2 years before diagnosis was coded using the International Classification of Primary Care-2. We calculated odds ratios for variables independently associated with cancer, using multivariable conditional logistic regressions, and then calculated the positive predictive values of these variables, both individually and in combination. In total, 10 features were associated with colorectal cancer before diagnosis. The positive predictive values (95% confidence interval) of these were rectal bleeding 2.4% (1.9, 3.2); weight loss 1.2% (0.91, 1.6); abdominal pain 1.1% (0.86, 1.3); diarrhoea 0.94% (0.73, 1.1); constipation 0.42% (0.34, 0.52); abnormal rectal examination 4.0% (2.4, 7.4); abdominal tenderness 1.1% (0.77, 1.5); haemoglobin <10.0 g dl(-1) 2.3% (1.6, 3.1); positive faecal occult bloods 7.1% (5.1, 10); blood glucose >10 mmol l(-1) 0.78% (0.51, 1.1): all P < 0.001. Earlier diagnosis of colorectal cancer may be possible using the predictive values for single or multiple symptoms, physical signs or test results.

Do the findings of case series studies vary significantly according to methodological characteristics?

OBJECTIVES: To review the use of case series in National Institute for Clinical Excellence (NICE) Health Technology Assessment (HTA) reports, to review systematically the methodological literature for papers relating to the validity of aspects of case series design, and to investigate characteristics and findings of case series using examples from the UK's Health Technology Assessment programme. DATA SOURCES: Electronic databases. NICE website. Reports produced as part of the UK's HTA programme. REVIEW METHODS: NICE HTAs that used information from case series studies were obtained from the NICE website and a range of quality criteria applied. Searches of electronic databases, handsearched journals and the bibliographies of papers were made in order to find studies that assessed aspects of case series design, analysis or quality in relation to study validity. Hypotheses relating to the design of case series studies were developed and empirically investigated using four case examples from existing reports produced as part of the UK's HTA programme (functional endoscopic sinus surgery for nasal polyps, spinal cord stimulation for chronic back pain, percutaneous transluminal coronary angioplasty and coronary artery bypass grafting for chronic angina). Analysis was undertaken comparing studies within each review. RESULTS: There was no consensus on which case series to include in HTAs, how to use them or how to assess their quality, despite them being used in 30% of NICE HTAs. No previous studies empirically investigating methodological characteristics of case series were found. However, it is possible that the search strategy failed to find relevant studies. Poor reporting of case series characteristics severely constrained analysis and there were insufficient data to investigate all the hypotheses. Findings were not consistent across the different topics and were subject to considerable uncertainty. All the examples in our analysis were surgical interventions, which are prone to additional confounding factors due to difficulties of standardisation compared with drug treatment. Our findings may not be generalisable outside the interventions studied. The case series reports included generally exhibited poor reporting of methodological characteristics. This constrained our analysis. The use of several methods of analysis has led to apparently discrepant results. Given the number of analysis performed, the usual level of significance (p = 0.05) should be viewed with caution. The most important limitation of this study is the small number of cases on which the findings are based. The results are therefore tentative and should be viewed with caution. CONCLUSIONS: Case series are incorporated in a significant proportion of health technology assessments. Quality criteria have been used to appraise the quality of case series and decide on their inclusion in reviews of studies using this design. In this small series of case studies drawn from HTAs carried out for the NHS HTA programme, little evidence was found to support the use of many of the factors included in quality assessment tools. Importantly, no relationship was found between study size and outcome across the four examples studied. Isolated examples of a potentially important relationship between other methodological factors and outcome were shown, such as blinding of outcome measurement, but these were not shown consistently across the small number of examples studied. This study is based on a very small sample of studies and should therefore be considered as exploratory. Further investigation of the relationship between methodological features and outcome is justified given the frequency of use of case series in health technology assessments. Further research into the methodological features of case series and their outcome is justified in a wider sample of technologies and larger sets of case series. Value of information analyses including case series could be explored. Further exploration of the differences between case series and randomised controlled trial results, preferably using registry or comprehensive case series data, would be valuable.

Effectiveness and cost-effectiveness of imatinib for first-line treatment of chronic myeloid leukaemia in chronic phase: a systematic review and economic analysis.

OBJECTIVES: To evaluate the effectiveness of imatinib as first-line treatment for chronic myeloid leukaemia (CML) compared with interferon-alpha (IFN-alpha), hydroxyurea and bone marrow transplantation (BMT), and the cost-effectiveness of imatinib compared with IFN-alpha and hydroxyurea. DATA SOURCES: Electronic databases. REVIEW METHODS: Selected studies and full-text articles were screened and rigorously selected. Survival was the key outcome measure. Surrogate outcome measures included haematological (blood) response and cytogenetic (bone marrow) response (CR). As no published cost-effectiveness studies were found that compared imatinib and IFN-alpha, an independent Markov model was constructed and this was compared with models submitted to the National Institute for Clinical Excellence by the manufacturer of imatinib. RESULTS: Intention-to-treat analysis showed that imatinib was associated with complete CR at 12 months follow-up of 68% compared with 20% for the IFN-alpha plus Ara-C group. The estimated proportion of people taking imatinib who had not progressed to accelerated or blast phases at 12 months was 98.5%, and 93.1% for IFN-alpha plus Ara-C. Overall survival was not statistically significantly different. Withdrawal due to side-effects was 2% for imatinib and 5.6% for IFN-alpha plus Ara-C. Cross-over due to intolerance was 0.7% and 22.8% for imatinib and for IFN-alpha plus Ara-C, respectively. Quality of life was better in the imatinib group than the IFN-alpha group when assessed at 1, 3 and 6 months. Median survival across the four IFN-alpha versus hydroxyurea studies was 66 and 56.2 months, respectively. Median complete CR was 6% for IFN-alpha and 0 for hydroxyurea. Median withdrawal due to side-effects was 24% and 4% for IFN-alpha and hydroxyurea, respectively. Four out of the five studies comparing BMT and IFN-alpha showed a long-term survival advantage for BMT over IFN-alpha, but a short-term disadvantage. In four of the five studies comparing BMT and IFN-alpha, median survival had not yet been reached in the BMT groups in 6--10 years. Median survival in the IFN-alpha arms ranged from 5.2 to 7 years. The BMT group gained a survival advantage over IFN-alpha at 3--5.5 years. In the BMT group death due to transplant-related complications ranged from 36 to 45%. The incremental cost-effectiveness ratio (ICER) of imatinib compared with IFN-alpha from the independent model was GBP26,180 per quality-adjusted-life-years (QALY) gained and was relatively robust. Imatinib was less cost-effective than hydroxyurea with an ICER of GBP86,934. CONCLUSIONS: Imatinib appears to be more effective than current standard drug treatments in terms of cytogenetic response and progression-free survival, with fewer side-effects. However, there is uncertainty concerning longer term outcomes, the development of resistance to imatinib, the duration of response and the place of imatinib relative to BMT. New issues are continually arising, such as optimal management pathways and combination therapies. Recommendations for research include: long-term follow-up data from the first- and second-line imatinib trials; investigation into specific subgroups, e.g. high-risk patients, the elderly, children or those eligible for BMT; long-term comparisons of imatinib with BMT performed in early stages of CML; the use of imatinib in combination with other therapies, and further detailed economic studies. Investigation of the impact of CML and imatinib on quality of life is also important.

The effectiveness and cost-effectiveness of microwave and thermal balloon endometrial ablation for heavy menstrual bleeding: a systematic review and economic modelling.

OBJECTIVES: To estimate the clinical effectiveness and cost-effectiveness of microwave endometrial ablation (MEA) and thermal balloon endometrial ablation (TBEA) for heavy menstrual bleeding (HMB), compared with the existing (first-generation) endometrial ablation (EA) techniques of transcervical resection (TCRE) and rollerball (RB) ablation, and hysterectomy. DATA SOURCES: Electronic databases, bibliographies of articles, and also experts in the field and relevant industry bodies were asked to provide information. REVIEW METHODS: A detailed search strategy was carried out to identify systematic reviews and controlled trials of MEA and TBEA versus first-generation techniques for EA. In addition to electronic database searching, reference lists were hand-searched and information sought from manufacturers of EA devices and by experts in the field. A deterministic Markov model was developed to assess cost-effectiveness. Data for the model were taken from a range of sources. RESULTS: The systematic review of first-generation EA techniques versus hysterectomy found that EA offered an alternative to hysterectomy for HMB, with fewer complications and a shorter recovery period. Satisfaction and effectiveness were high for both MEA and TBEA. Costs were lower with EA although the difference narrows over time. Second-generation EA techniques are an alternative treatment to first-generation techniques for HMB, and first-generation techniques are known to offer an alternative to hysterectomy. Although no trials of second-generation techniques and hysterectomy have been undertaken, it seems reasonable to assume that second-generation techniques also offer an alternative surgical treatment. Using the model to assess cost-effectiveness, costs were very slightly higher for MEA when compared to TBEA, and differences in quality-adjusted life-years (QALYs) were negligible. For MEA compared with transcervical resection of the endometrium (TCRE) and RB ablation, costs were slightly lower with MEA and MEA accrued very slightly more QALYs. Compared with hysterectomy, MEA costs less and accrues slightly fewer QALYs. For TBEA compared with TCRE and RB ablation, costs were lower with TBEA and TBEA accrued slightly more QALYs. Compared with hysterectomy, TBEA costs moderately less and accrues moderately fewer QALYs. CONCLUSIONS: Overall, there were few significant differences between the outcomes of first- and second-generation techniques including bleeding, satisfaction and QoL measures and repeat surgery rates. Second-generation techniques had significantly shorter operating and theatre times and there appear to be fewer serious perioperative adverse effects with second-generation techniques and postoperative effects are similar. Compared with hysterectomy, TCRE and RB are quicker to perform and result in shorter hospitalisation and faster return to work. Hysterectomy results in more adverse effects and is more expensive, although the need for retreatment leads this difference to decrease over time. Satisfaction with hysterectomy is initially higher, but there is no significant difference after 2 years. The economic model suggests that second-generation techniques are more cost-effective than first-generation techniques of EA for HMB. Both TBEA and MEA appear to be less costly than hysterectomy, although the latter results in more QALYs. Further research is suggested to make direct comparisons of the cost-effectiveness of second-generation EA techniques, to carry out longer term follow-up for all methods of EA in RCTs, and to develop more sophisticated modelling studies. Further research is also recommended into HMB to establish health-state utility values, its surgical treatment, convalescence, complications of treatment, symptoms and patient satisfaction.

Systematic review of endoscopic sinus surgery for nasal polyps.

OBJECTIVES: To provide a systematic review of the clinical effectiveness of endoscopic sinus surgery (ESS) for the removal of nasal polyps. DATA SOURCES: Searches of electronic databases, websites and reference lists were made to identify relevant studies. REVIEW METHODS: An extensive search was performed to identify all articles where FESS is used for the excision of nasal polyps. Two reviewers independently screened articles for inclusion according to predefined criteria. Comparative studies were included if they were primary research, focused on FESS for the removal of nasal polyps, reported patient relevant outcomes and were published in English. In addition, case series studies were included if they met the above criteria and enrolled more than 50 patients with polyps. Data were then extracted by one reviewer and checked by a second. A structured form was used to assess the internal and external validity of included studies. Comparative data were reported where available. Excluded case series and case reports were grouped and described. A group of nine ear, nose and throat (ENT) experts were selected, then using the literature and their own experience, they generated a list of priority research questions. Existing economic evaluations were sought and described. RESULTS: Of the 33 studies included, the randomised controlled trials and controlled trials reported overall symptomatic improvement that ranged from 78 to 88% for FESS compared with 43 to 84% for similar techniques (including polypectomy, Caldwell-Luc and intranasal ethmoidectomy). Disease recurrence was 8% for FESS compared with 14% for Caldwell-Luc and polyp recurrence was 28% for endoscopic ethmoidectomy compared with 35% for polypectomy. Revision surgery was reported in one study only and was the same for FESS and Caldwell-Luc procedures. Percentage of overall complications was reported in only one comparative study and was 1.4% for FESS compared with 0.8% for conventional procedures. The case series studies reported overall symptomatic improvement for patients with nasal polyps ranging from 37 to 99% (median 89%). For the mixed patient groups (with and without polypoid disease) overall symptomatic improvement ranged from 40 to 98% (median 88%). Total complications in the case series studies ranged from 22.4 to 0.3% (median 6%). CONCLUSIONS: The majority of studies report that symptoms improve following FESS with relatively few complications; however, only a small proportion of evidence is comparative. Results from non-comparative studies do not inform the choices that need to be made by ENT surgeons and commissioners. Health economics data are also lacking and therefore cannot inform these decisions. FESS may offer some advantages in effectiveness over comparative techniques, but there is enormous variation in the range of results reported and there are severe methodological limitations. There is a clear need for quality-controlled trials in order to answer questions regarding the effectiveness of FESS. A number of priority research questions from a selection of ENT surgeons within the UK are identified and presented.

Heterogeneity and persistence length in human ocular mucins.

Atomic force microscopy (AFM) has been used to investigate the heterogeneity and flexibility of human ocular mucins and their subunits. We have paid particular attention, in terms of theory and experiment, to the problem of inducing the polymers to assume equilibrium conformations at a surface. Mucins deposited from a buffer containing Ni(2+) ions adopt extended conformations on mica akin to those observed for DNA under similar conditions. The heterogeneity of the intracellular native mucins is evident from a histogram of contour lengths, reflecting, in part, the diversity of mucin gene products expressed. Reduction of the native mucin with dithiothreitol, thereby breaking the S==S bonds between cysteine residues, causes a marked reduction in polymer length. These results reflect the modes of transport and assembly of newly synthesized mucins in vivo. By modifying the worm-like chain model for applicability to two dimensions, we have confirmed that under the conditions employed mucin adsorbs to mica in an equilibrated conformation. The determined persistence length of the native mucin, 36 nm, is consistent with that of an extended, flexible polymer; such characteristics will influence the properties of the gels formed in vivo.