Validation of the type 1 diabetes distress scale (T1-DDS) in a large Danish cohort: Content validation and psychometric properties

Aim

To validate the Type 1 Diabetes Distress Scale (T1-DDS) in a large sample of adults with Type 1 diabetes (T1D) from diabetes clinics in Denmark.

Methods

Altogether 40 adults with T1D were interviewed to explore the content of T1-DDS in a Danish setting and to validate the translation of the T1-DDS into Danish. Subsequently, a survey including T1-DDS, the Problem Areas In Diabetes scale (PAID-20), fear of hypoglycemia, social support, and diabetes duration was answered by 2201 people with T1D. Other person characteristics were collected from the National Patient Register. HbA1c was obtained from the Clinical Laboratory Information System. Data distribution, internal consistency, convergent and construct validity, factor structure, three weeks retest, and cut-points were explored.

Results

Interview data supported the relevance of all T1-DDS items for the assessment of diabetes distress among adults with T1D. The T1-DDS showed good content and acceptable construct validity, and the ability to detect high diabetes distress levels. A high correlation between T1-DDS and PAID-20 (rho = 0.91) was found. The retest scores showed a good reliability (all rho ≥0.68) with the highest variability in the Friends/Family Distress and Physician Distress subscales and the lowest variability in the Powerlessness and Eating Distress subscales of the T1-DDS. Qualitative findings pointed out relevant concerns of people with T1D, which were not included in the T1-DDS.

Conclusion

The study supports the use of the Danish T1-DDS, but also highlights that existing diabetes distress questionnaires including T1-DDS do not cover all potential diabetes stressors and worries.

Microvascular complications, coronary artery disease and the risk of cardiovascular disease in diabetes patients undergoing coronary angiography: a cohort study from the Western Denmark Heart Registry

Background

Diabetes is associated with an increased risk of both microvascular macrovascular complications. The association between microvascular disease and cardiovascular risk, however, is less explored.

Aims

We aimed to estimate the cardiovascular risk associated with microvascular disease in diabetes patients with and without coronary artery disease.

Methods

We included every patient who underwent coronary angiography in Western Denmark between 2003–2016. Patients were stratified by microvascular disease (defined as diagnosis retinopathy, nephropathy, or peripheral neuropathy) and coronary artery disease by angiography. Outcomes included major adverse cardiovascular events (myocardial infarction, ischemic stroke, and cardiac death) as a combined outcome and as separate outcomes. Patients were followed for a maximum of 10 years. We estimated 10-year cumulative incidence of each outcome. Incidence rate ratios (IRR) were estimated by a modified Poisson regression model using diabetes patients with neither microvascular disease nor coronary artery disease as reference.

Results

We included 19,295 patients with diabetes, of whom 1,268 (6.6%) had microvascular disease, 10,161 (52.7%) had coronary artery disease, 3,113 (16.3%) had both microvascular disease and coronary artery disease, and 4,753 (24.6%) had neither microvascular nor coronary artery disease. Median follow-up was 5.9 years (interquartile range 3.3–9.0) Patients with microvascular disease had an increased risk of major adverse cardiovascular events compared to diabetes patients with neither microvascular disease nor coronary artery disease (13.6% versus 10.0%, adjusted IRR 1.45, 95% CI 1.19–1.77, Figure 1). This increased risk was driven by a 3.9% higher risk of ischemic stroke (adjusted IRR 1.53, 95% CI 1.14–2.05, Figure 2), while microvascular disease was not associated with an increased risk of myocardial infarction (adjusted IRR 1.08, 95% CI 0.72–1.62) or cardiac death (adjusted IRR 0.99, 95% CI 0.63–1.56). Patients with both microvascular disease and coronary artery disease had the highest risk of major adverse cardiovascular events (29.3%, adjusted IRR 3.06, 95% CI 2.67–3.50).

Conclusion

Microvascular disease in diabetes patients without angiographic coronary artery disease is associated with an increased cardiovascular risk. However, this was driven by a higher risk of ischemic stroke than by higher rates of myocardial infarction or cardiac death. In fact, diabetes patients with microvascular disease but no coronary artery disease had the same risk of ischemic stroke as those with combined microvascular disease and coronary artery disease.

Funding Acknowledgement

Type of funding sources: Public hospital(s). Main funding source(s): Aarhus University Hospital

Causes of excess mortality in diabetes patients without coronary artery disease

Background

Diabetes (DM) patients without coronary artery disease (CAD) by coronary angiography have a similar risk of myocardial infarction and cardiac death as non-DM patients without CAD. Yet, even with absence of CAD, patients with DM have higher mortality compared to non-DM patients.

Aims

To examine the underlying causes of death in patients undergoing coronary angiography depending on DM and CAD.

Methods

We included every patient with no previous history of CAD who underwent coronary angiography in Western Denmark between 2003–2016. Patients were stratified by DM and CAD and followed for a maximum of 10 years. We estimated the 10-year cumulative risk of all-cause death and cause-specific death. Causes of death were categorized as “cardiovascular”, “pulmonary”, “cancer”, “renal”, “bleeding-related”, and “other” based on ICD-10 codes listed as underlying causes of death obtained from death certificates. Deaths where DM was listed as the underlying cause of death (i.e. ICD-10 code DE1) were included in the category “other”.

Results

We included 132,432 patients, of whom 33% had neither DM nor CAD, 5% had DM only, 51% had CAD only, and 11% had both DM and CAD. Mean age was 64 years. Median follow-up was 6.3 year (inter-quartile range 3.8–10.0). During follow-up, 35,036 (26.5%) patients died. Patients with both DM and CAD had the highest 10-year mortality (47.4%, 95% CI 46.3–48.4), followed by CAD only (33.3%, 95% CI 32.8–33.7), DM only (30.7%, 95% CI 29.3–32.2), and patients with neither DM nor CAD (21.6%, 95% CI 21.1–22.1). The proportion of cardiovascular deaths were similar in patients with DM only (29.2%, 95% CI 27.0–31.5, Figure) and patients with neither DM nor CAD (29.7%, 95% CI 28.8–30.7). Patients with DM were more likely to die from causes categorized as “other” compared to patients with neither DM nor CAD [38.4% (95% CI 36.0–40.9) versus 30.2% (95% CI 29.3–31.2)]. Among patients with DM only, 43.7% of deaths classified as “other” were attributable to DM-related complications such as ketoacidosis and diabetic nephropathy.

Conclusion

Despite absence of CAD, DM remained associated with increased mortality. Excess mortality was primarily driven by patients dying of DM-related microvascular complications and ketoacidosis. Thus, despite absence of CAD, patients with DM require continued preventative measures to reduce DM-related mortality.

Funding Acknowledgement

Type of funding sources: Public hospital(s). Main funding source(s): Aarhus University Hospital

Diabetes and coronary risk equivalency – a population-based cohort study from Western Denmark

Background

Diabetes is associated with an increased risk of cardiovascular disease. Accordingly, guidelines recommend extensive management of cardiovascular risk factors in patients with diabetes. Diabetes has previously thought to carry the same high cardiovascular risk as already having coronary heart disease. It is, however, unknown if the intensified focus on prophylactic treatment has changed the risk of myocardial infarction and ischemic stroke in contemporary practice.

Aims

We aimed to examine whether diabetes remains a cardiovascular risk equivalent to coronary heart disease under the contemporary treatment regimen.

Methods

We included every person residing in Western Denmark on January 1, 2012, aged 50–89 years. The cohort was stratified by diabetes and coronary heart disease (defined as previous myocardial infarction, percutaneous coronary intervention (PCI), coronary artery bypass grafting (CABG), or coronary artery disease documented by coronary angiography). The four groups were followed for up to seven years after inclusion. Outcomes were myocardial infarction, ischemic stroke, cardiac death, and all-cause death. Patients with coronary heart disease only were compared to patients with diabetes only using a multivariable Cox regression model.

Results

We included 1,111,456 persons residing in Western Denmark on January 1, 2012, of whom 86.1% had neither diabetes nor coronary heart disease, 7.5% had diabetes only, 5.0% only had history of coronary heart disease, 1.4% had both diabetes and coronary heart disease. Patients with diabetes only less likely to be in antithrombotic treatment, lipid-lowering treatment, and antihypertensive treatment compared to patients with coronary heart disease only. Compared to patients with diabetes only (Figure 1), coronary heart disease was associated with an increased risk of myocardial infarction (adjusted HR 1.73, 95% CI 1.65–1.82) and cardiac death (adjusted HR 1.40, 95% 1.32–1.48). However, coronary heart disease only was associated with a reduced risk of ischemic stroke (adjusted HR 0.83, 95% CI 0.79–0.87) and all-cause mortality (adjusted HR 0.76, 95% CI 0.74–0.77) compared to diabetes only (Figure 1).

Conclusions

In contemporary practice in Denmark, patients with diabetes only have a lower risk of myocardial infarction or cardiac death than observed in non-diabetic patients with verified coronary heart disease. On the contrary, patients with diabetes only have a greater risk ischemic stroke and al–cause mortality than coronary heart disease only. Thus, diabetes is not a uniform cardiovascular risk equivalent to coronary heart disease, but depends on the given outcome.

Funding Acknowledgement

Type of funding sources: Public hospital(s). Main funding source(s): Department of Cardiology, Aarhus University Hospital, Aarhus, Denmark

Spatiotemporal extracellular matrix modeling for in situ cell niche studies

Extracellular matrix (ECM) components govern a range of cell functions, such as migration, proliferation, maintenance of stemness, and differentiation. Cell niches that harbor stem-/progenitor cells, with matching ECM, have been shown in a range of organs, although their presence in the heart is still under debate. Determining niches depends on a range of in vitro and in vivo models and techniques, where animal models are powerful tools for studying cell-ECM dynamics; however, they are costly and time-consuming to use. In vitro models based on recombinant ECM proteins lack the complexity of the in vivo ECM. To address these issues, we present the spatiotemporal extracellular matrix model for studies of cell-ECM dynamics, such as cell niches. This model combines gentle decellularization and sectioning of cardiac tissue, allowing retention of a complex ECM, with recellularization and subsequent image processing using image stitching, segmentation, automatic binning, and generation of cluster maps. We have thereby developed an in situ representation of the cardiac ECM that is useful for assessment of repopulation dynamics and to study the effect of local ECM composition on phenotype preservation of reseeded mesenchymal progenitor cells. This model provides a platform for studies of organ-specific cell-ECM dynamics and identification of potential cell niches.

Characterization of Laminins in Healthy Human Aortic Valves and a Modified Decellularized Rat Scaffold

Aortic valve stenosis is one of the most common cardiovascular diseases in western countries and can only be treated by replacement with a prosthetic valve. Tissue engineering is an emerging and promising treatment option, but in-depth knowledge about the microstructure of native heart valves is lacking, making the development of tissue-engineered heart valves challenging. Specifically, the basement membrane (BM) of heart valves remains incompletely characterized, and decellularization protocols that preserve BM components are necessary to advance the field. This study aims to characterize laminin isoforms expressed in healthy human aortic valves and establish a small animal decellularized aortic valve scaffold for future studies of the BM in tissue engineering. Laminin isoforms were assessed by immunohistochemistry with antibodies specific for individual α, β, and γ chains. The results indicated that LN-411, LN-421, LN-511, and LN-521 are expressed in human aortic valves (n = 3), forming a continuous monolayer in the endothelial BM, whereas sparsely found in the interstitium. Similar results were seen in rat aortic valves (n = 3). Retention of laminin and other BM components, concomitantly with effective removal of cells and residual DNA, was achieved through 3 h exposure to 1% sodium dodecyl sulfate and 30 min exposure to 1% Triton X-100, followed by nuclease processing in rat aortic valves (n = 3). Our results provide crucial data on the microenvironment of valvular cells relevant for research in both tissue engineering and heart valve biology. We also describe a decellularized rat aortic valve scaffold useful for mechanistic studies on the role of the BM in heart valve regeneration.

Impact of patient-centred diabetes self-management education targeting people with type 2 diabetes: an integrative review

AIMS

To synthesize primary research into the impact of person-centred diabetes self-management education, and support that targets people with type 2 diabetes, on behavioural, psychosocial and cardiometabolic outcomes and to identify effective mechanisms underlying positive outcomes of person-centred diabetes self-management education and support.

METHODS

Using Whittemore and Knafl's integrative review method, we conducted a systematic search of peer-reviewed literature published between January 2008 and June 2019 using PubMed, Scopus and CINAHL. After article selection according to established criteria, study quality was assessed using Critical Appraisal Skills Programme checklists for cohort studies, randomized controlled trials and qualitative research.

RESULTS

From 1901 identified records, 22 (19 quantitative, two qualitative, and one mixed methods) were considered eligible for inclusion. Interventions were categorized by content, medium of delivery, and outcomes. Qualitative studies, quantitative cohort studies and randomized controlled trials demonstrated positive outcomes, with no differences in success rates across study design. Interventions were largely successful in improving HbA_1c and patient-reported outcomes such as quality of life but had limited success in lowering cholesterol and weight, or initiating long-term improvements in lifestyle behaviours. Primary objectives were achieved more often than secondary objectives, and studies with fewer outcomes appeared more successful in achieving specific outcomes.

CONCLUSIONS

Person-centred diabetes self-management education and support has demonstrated a considerable impact on desired diabetes-related outcomes in people with type 2 diabetes. To advance the field further, new studies should take advantage of systematic and transparent approaches to person-centred diabetes self-management education.

Discrimination and stigma among people with type 2 diabetes in the workplace: prejudice against illness or obesity?

OBJECTIVES

Both obesity/overweight and type 2 diabetes (T2D) have been independently identified as being the basis for stigma and discrimination in the workplace. The study sought to test the hypothesis that people with T2D are at increased risk of discrimination and adverse self-reported psychosocial work environment.

STUDY DESIGN

This study was based on survey data from 2415 working Danes with T2D (n = 586) and without T2D (n = 1829) recruited from online panels. Single self-reported items were used to obtain information about diabetes status, exposure to discrimination and other individual factors.

METHODS

Descriptive statistics and linear regression were used for the data analysis.

RESULTS

Six percent of the participants with T2D had experienced some type of discrimination at work, which was ascribed to their diabetes. People with diabetes had higher levels of effort-reward imbalance. When adjusting for body mass index, differences in relation to effort-reward imbalance were accounted for.

CONCLUSIONS

People with T2D reported relatively poor psychosocial working environment compared with the general working population, but the difference was removed by adjusting for overweight/obesity. This indicates that T2D alone is not a source of stigma and discrimination in the context of work. Levels of perceived discrimination were notably lower than expected among people with diabetes as a whole, but a number of people, nonetheless, continue to be exposed to the destructive effects of discrimination in the context of work.

Health Literacy and self-care among visually impaired people with type 1 diabetes in Denmark

AIMS

The aim of this study was to investigate health literacy and self-care among visually impaired people with type 1 diabetes in Denmark.

METHODS

Survey data from 1425 Danes with type 1 diabetes were categorised in two groups according to visual status: visually impaired ( n = 38) and sighted ( n = 1387). Using the Health Literacy Questionnaire and the Summary of Diabetes Self-Care Activities Scale, health literacy and self-care activities were assessed. Visually impaired respondents were compared to sighted respondents using t-tests and chi-squared tests.

RESULTS

Visually impaired people were older, had higher diabetes duration and were more likely to live alone. Also they had a significant lower level of health literacy on two key dimensions of health literacy ('Ability to find good health information' and 'Understanding health information well enough to know what to do'), they monitored blood sugar less frequently than people that were sighted but had better self-care regarding feet examination.

CONCLUSIONS

Visually impaired people with type 1 diabetes are less able to find and understand health information than sighted people with type 1 diabetes. Our findings indicate need for interventions to promote better self-care and health literacy among visually impaired people with diabetes.

Reliability and validity of self-reported questionnaires to measure pain and disability in adults with neck pain and its associated disorders: part 3-a systematic review from the CADRE Collaboration

PURPOSE

To determine the reliability and validity of self-reported questionnaires to measure pain and disability in adults with grades I-IV neck pain and its associated disorders (NAD).

METHODS

We updated the systematic review of the 2000-2010 Bone and Joint Decade Task Force on Neck Pain and its Associated Disorders and systematically searched databases from 2005 to 2017. Independent reviewers screened and critically appraised studies using standardized tools. Evidence from low-risk-of-bias studies was synthesized according to best evidence synthesis principles. Validity studies were ranked according to the Sackett and Haynes classification.

RESULTS

We screened 2823 articles, and 26 were eligible for critical appraisal; 18 were low risk of bias. Preliminary evidence suggests that the Neck Disability Index (original and short versions), Whiplash Disability Questionnaire, Neck Pain Driving Index, and ProFitMap-Neck may be valid and reliable to measure disability in patients with NAD. We found preliminary evidence for the validity and reliability of pain measurements including the Body Pain Diagram, Visual Analogue Scale, the Numeric Rating Scale and the Pain-DETECT Questionnaire.

CONCLUSION

The evidence supporting the validity and reliability of instruments used to measure pain and disability is preliminary. Further validity studies are needed to confirm the clinical utility of self-reported questionnaires to assess pain and disability in patients with NAD. These slides can be retrieved under Electronic Supplementary Material.

Willingness to pay for flexible working conditions of people with type 2 diabetes: discrete choice experiments

BACKGROUND

The increasing number of people with chronic diseases challenges workforce capacity. Type 2 diabetes (T2D) can have work-related consequences, such as early retirement. Laws of most high-income countries require workplaces to provide accommodations to enable people with chronic disabilities to manage their condition at work. A barrier to successful implementation of such accommodations can be lack of co-workers' willingness to support people with T2D. This study aimed to examine the willingness to pay (WTP) of people with and without T2D for five workplace initiatives that help individuals with type 2 diabetes manage their diabetes at work.

METHODS

Three samples with employed Danish participants were drawn from existing online panels: a general population sample (n = 600), a T2D sample (n = 693), and a matched sample of people without diabetes (n = 539). Participants completed discrete choice experiments eliciting their WTP (reduction in monthly salary, €/month) for five hypothetical workplace initiatives: part-time job, customized work, extra breaks with pay, and time off for medical consultations with and without pay. WTP was estimated by conditional logits models. Bootstrapping was used to estimate confidence intervals for WTP.

RESULTS

There was an overall WTP for all initiatives. Average WTP for all attributes was 34 €/month (95% confidence interval [CI]: 27-43] in the general population sample, 32 €/month (95% CI: 26-38) in the T2D sample, and 55 €/month (95% CI: 43-71) in the matched sample. WTP for additional breaks with pay was considerably lower than for the other initiatives in all samples. People with T2D had significantly lower WTP than people without diabetes for part-time work, customized work, and time off without pay, but not for extra breaks or time off with pay.

CONCLUSIONS

For people with and without T2D, WTP was present for initiatives that could improve management of diabetes at the workplace. WTP was lowest among people with T2D. Implementation of these initiatives seems feasible and may help unnecessary exclusion of people with T2D from work.

Characteristics associated with non-disclosure of Type 2 diabetes at work

AIM

To explore factors associated with non-disclosure of Type 2 diabetes to employers among Danish workers with Type 2 diabetes.

METHODS

A total of 705 workers with Type 2 diabetes completed a Danish cross-sectional survey. Logistic regression models were used to estimate the associations between background characteristics and probability of non-disclosure of diabetes to the employer. The models were mutually adjusted for background characteristics, socioeconomic-, diabetes- and work-related factors.

RESULTS

Among the participants, 23% had not disclosed their Type 2 diabetes to their current employer. Non-disclosure was associated with more sickness absence, more years with diabetes, greater use of diabetic medication, higher educational level and a perception of not being respected by superior. Personal traits such as gender, age and well-being were not associated with disclosure.

CONCLUSIONS

Among the feasible targets for interventions, good psychosocial work environment was associated with disclosure.

Risk of depressive disorder following disasters and military deployment: systematic review with meta-analysis

BACKGROUND

Numerous studies describe the occurrence of post-traumatic stress disorder following disasters, but less is known about the risk of major depression.

AIMS

To review the risk of depressive disorder in people surviving disasters and in soldiers returning from military deployment.

METHOD

A systematic literature search combined with reference screening identified 23 controlled epidemiological studies. We used random effects models to compute pooled odds ratios (ORs).

RESULTS

The average OR was significantly elevated following all types of exposures: natural disaster OR = 2.28 (95% CI 1.30-3.98), technological disaster OR = 1.44 (95% CI 1.21-1.70), terrorist acts OR = 1.80 (95% CI 1.38-2.34) and military combat OR = 1.60 (95% CI 1.09-2.35). In a subset of ten high-quality studies OR was 1.41 (95% CI 1.06-1.87).

CONCLUSIONS

Disasters and combat experience substantially increase the risk of depression. Whether psychological trauma per se or bereavement is on the causal path is unresolved.

UWB Wind Turbine Blade Deflection Sensing for Wind Energy Cost Reduction

A new application of utilizing ultra-wideband (UWB) technology to sense wind turbine blade deflections is introduced in this paper for wind energy cost reduction. The lower UWB band of 3.1–5.3 GHz is applied. On each blade, there will be one UWB blade deflection sensing system, which consists of two UWB antennas at the blade root and one UWB antenna at the blade tip. The detailed topology and challenges of this deflection sensing system are addressed. Due to the complexity of the problem, this paper will first realize the on-blade UWB radio link in the simplest case, where the tip antenna is situated outside (and on the surface of) a blade tip. To investigate this case, full-blade time-domain measurements are designed and conducted under different deflections. The detailed measurement setups and results are provided. If the root and tip antenna locations are properly selected, the first pulse is always of sufficient quality for accurate estimations under different deflections. The measured results reveal that the blade tip-root distance and blade deflection can be accurately estimated in the complicated and lossy wireless channels around a wind turbine blade. Some future research topics on this application are listed finally.

Controlled Delivery of Human Cells by Temperature Responsive Microcapsules

Cell therapy is one of the most promising areas within regenerative medicine. However, its full potential is limited by the rapid loss of introduced therapeutic cells before their full effects can be exploited, due in part to anoikis, and in part to the adverse environments often found within the pathologic tissues that the cells have been grafted into. Encapsulation of individual cells has been proposed as a means of increasing cell viability. In this study, we developed a facile, high throughput method for creating temperature responsive microcapsules comprising agarose, gelatin and fibrinogen for delivery and subsequent controlled release of cells. We verified the hypothesis that composite capsules combining agarose and gelatin, which possess different phase transition temperatures from solid to liquid, facilitated the destabilization of the capsules for cell release. Cell encapsulation and controlled release was demonstrated using human fibroblasts as model cells, as well as a therapeutically relevant cell line-human umbilical vein endothelial cells (HUVECs). While such temperature responsive cell microcapsules promise effective, controlled release of potential therapeutic cells at physiological temperatures, further work will be needed to augment the composition of the microcapsules and optimize the numbers of cells per capsule prior to clinical evaluation.

The pYC plasmids, a series of cassette-based yeast plasmid vectors providing means of counter-selection

A series of 24 general-purpose yeast plasmid vectors has been constructed. The plasmid series is composed of inter-replaceable cassettes, allowing for easy interconversion of plasmid types. In addition to the usual replication origins, selectable markers and multiple cloning sites (MCS), cassettes dedicated to counter-selection have been constructed. A pair of unique 8 bp restriction enzyme recognition sites flank each type of cassette, FseI in the case of yeast replication origins, AscI in the case of selectable markers, PacI in the case of counter-selectable markers and NotI in the case of the MCS. Thus, any given cassette can be replaced by another cassette of the same type, facilitating interconversion of any given plasmid from one type to another, even after the insertion of DNA into the MCS. Hence, the plasmids have been named pYC for 'yeast cassettes'. The cassettes consist of either NONE, CEN4/ARS or 2micro as replication origin, either URA3, MET2-CA (Lg-MET2) or the G418 resistance gene (the apt1 gene from bacterial transposon Tn903, encoding aminoglycoside phosphotransferase) as selectable markers, either NONE, PMET25-PKA3 or PCHA1-PKA3 as counter-selectable marker, and the MCS, containing recognition sites for AflII, AvrII, BspEI, PmeI, SacII, SalI, SunI, BamHI, EcoRI, HindIII, KpnI, MluI, NarI and SacI (of which the seven first are unique in all plasmids). The counter-selectable markers consist of the PKA3 gene under control of the conditional MET25 or CHA1 promoters. At activating conditions these promoters express the PKA3 gene at toxic levels, facilitating easy selection for loss of plasmid or 'loop-out' of plasmid DNA sequence after genomic integration.

4. Preliminary Findings of a Prospective Study of FDG-PET in Patients with Possible Lung Cancer

Purpose: To examine the value of PET in diagnosis and staging of suspected lung cancer.Methods: 20 (13 male; mean age: 56 yr., range: 22-83 yr.) patients with chest X-ray findings suspicious of malignancy were staged a) "clinically" (X-ray, history/physical examination, lung function), b) by chest CT of thorax/upper abdomen, and c) by whole-body PET (GE Advance, visual analysis). The CT and PET studies were performed within 2 weeks of admission and read blinded to all information except the chest X-ray report. The decision to refer to mediastinoscopy/thoracotomy was made by a tumor board using clinical information, CT and PET findings. In principle, suspected metastatic lesions were biopsied before surgery. The gold standard was histology from biopsy or thoracotomy, or resolution of the X-ray findings and symptoms.Results: One patient was excluded because of uncertain diagnosis. In 3 (15%) patients surgery was avoided mainly because of the PET findings. In one SCLC patient and one lymphoma patient, PET showed extensive disease, which changed the chemotherapy regime. Accuracy was 83% for clinical stage, 79% for CT and 77% for PET. Four (20%) false positive PET findings were caused by granuloma, pneumonia and BOOP. These nodules were only 1 to <3 cm, while malignant nodules were 2-8 cm. There were no false negative PET or CT studies.Conclusion: FDG-PET is valuable in patients suspected for pulmonary malignancy, since thoracotomy was avoided in 15% of patients and in 10% of patients more extensive disease was found which changed the chemotherapy regime.

Electron transfer to photosystem 1 from spinach plastocyanin mutated in the small acidic patch: ionic strength dependence of kinetics and comparison of mechanistic models

A set of plastocyanin (Pc) mutants, probing the small acidic patch (Glu59, Glu60, and Asp61) and a nearby residue, Gln88, has been constructed to provide further insight into the electron transfer process between Pc and photosystem 1. The negatively charged residues were changed into their neutral counterparts or to a positive lysine. All mutant proteins exhibited electron transfer kinetics qualitatively similar to those of the wild type protein over a wide range of Pc concentrations. The kinetics were slightly faster for the Gln88Lys mutant, while they were significantly slower for the Glu59Lys mutant. The data were analyzed with two different models: one involving a conformational change of the Pc-photosystem 1 complex that precedes the electron transfer step (assumed to be irreversible) [Bottin, H., and Mathis, P. (1985) Biochemistry 24, 6453-6460] and another where no conformational change occurs, the electron transfer step is reversible, and dissociation of products is explicitly taken into account [Drepper, F., Hippler, M., Nitschke, W., and Haehnel, W. (1996) Biochemistry 35, 1282-1295]. Both models can account for the observed kinetics in the limits of low and high Pc concentrations. To discriminate between the models, the effects of added magnesium ions on the kinetics were investigated. At a high Pc concentration (0.7 mM), the ionic strength dependence was found to be consistent with the model involving a conformational change but not with the model where the electron transfer is reversible. One residue in the small acidic patch, Glu60, seems to be responsible for the major part of the ionic strength dependence of the kinetics.

The central lysine in the P-loop motif of the Escherichia coli DnaA protein is essential for initiating DNA replication from the chromosomal origin, oriC, and the F factor origin, oriS, but is dispensable for initiation from the P1 plasmid origin, oriR

The Escherichia coli DnaA protein is essential for initiation of DNA replication from the chromosomal origin, oriC, and from certain plasmid origins such as oriR of P1, oriS of F, and ori of pSCS101. The DnaA protein binds ATP with high affinity and contains a P-loop motif assumed to be the binding site. Three mutations in the E. coli dnaA gene were constructed by oligonucleotide-directed mutagenesis that changed amino acids in the P-loop. A DnaA protein, K178T, in which the central lysine was changed to the smaller amino acid threonine, was able to initiate DNA replication from P1 oriR, but was unable to initiate replication from E. coli oriC or F oriS in vivo. Mutant and wild-type DnaA proteins were overexpressed, partially purified, and tested for replication activity in vitro. The K178T DnaA protein could initiate replication from oriR, although with a decreased activity compared to the wild-type DnaA protein. No replication activity was detected for this mutant protein from oriC. The different responses of the oriR and oriC replicons to the K178T DnaA protein indicate that the role of DnaA is different in the two systems.

Spectroscopic, kinetic, and electrochemical characterization of heterologously expressed wild-type and mutant forms of copper-containing nitrite reductase from Rhodobacter sphaeroides 2.4.3

We report the development of a high-yield heterologous expression system for the copper-containing nitrite reductase from a denitrifying variant of Rhodobacter sphaeroides. Typical yields of wild-type protein are 20 mg L-1, which can be fully loaded with copper. Nitrite reductase contains an unusual blue-green Type 1 copper center with a redox/electron transfer function and a nearby Type 2 center where nitrite binds and is reduced to nitric oxide. The wild-type enzyme was characterized by: (1) its blue-green Type 1 optical spectrum; (2) its EPR spectrum showing rhombic character to its Type 1 center and nitrite perturbation to its Type 2 center; (3) its 247-mV Type 1 midpoint potential which is low relative to other Type 1 centers; and (4) its kinetics as measured by both steady-state and stopped-flow methods. The Type 2 copper reduction potential as monitored by EPR in the absence of nitrite was below 200 mV so that reduction of the Type 2 center by the Type 1 center in the absence of nitrite is not energetically favored. The mutation M182T in which the methionine ligand of Type 1 copper was changed to a threonine resulted in a blue rather than blue-green Type 1 center, a midpoint potential that increased by more than 100 mV above that of the wild-type Type 1 center, and a somewhat reduced nitrite reductase activity. The blue color and midpoint potential of M182T are reminiscent of plastocyanin, but the Type 1 cupric HOMO ground-state electronic g value and copper hyperfine properties of M182T (as well as cysteine and histidine ENDOR hyperfine properties; see next paper) were unchanged from those of the blue-green native Type 1 center. His287 is a residue in the Type 2 region whose imidazole ring was thought to hydrogen bond to the Type 2 axial ligand but not directly to Type 2 copper. The mutation H287E resulted in a 100-fold loss of enzyme activity and a Type 2 EPR spectrum (as well as ENDOR spectra; see next paper) which were no longer sensitive to the presence of nitrite.

Electronic structural information from Q-band ENDOR on the type 1 and type 2 copper liganding environment in wild-type and mutant forms of copper-containing nitrite reductase

Q-band ENDOR elucidated proton and nitrogen hyperfine features to provide spin density information at ligands of blue-green Type 1 and catalytic Type 2 copper centers in nitrite reductase. The blue-green Type 1 center of nitrite reductase has a redox, electron-transfer role, and compared to the blue center of plastocyanin, it has the following structural differences: a shortened Cu-Smet bond length, a longer Cu-Scys bond length, and altered ligand-copper-ligand bond angles (Adman, E. T., Godden, J. W., and Turley, S. (1995) J. Biol. Chem. 270, 27458-27474). The hyperfine couplings of the two Type 1 histidine (N delta) ligands showed a larger percentage difference from each other in electron spin density than previously reported for other blue Type 1 proteins, while the cysteine beta-proton hyperfine couplings, a measure of unpaired p pi spin density on the liganding cysteine sulfur, showed a smaller electron spin density. A mutation of the Type 1 center, M182T, having the copper-liganding Met182 transformed to Thr182, caused the center to revert to an optically "blue" center, raised its redox potential by approximately 100 mV, and led to the loss of activity (prior paper). Surprisingly, in M182T there was no change from native Type 1 copper either in the histidine or cysteine hyperfine couplings or in g values and Cu nuclear hyperfine couplings. The conclusion is that the optical and redox alterations due to changed Type 1 methionine ligation need not be concurrent with electron spin delocalization changes in the HOMO as reported from its essential cysteine and histidines. A detailed picture of the nitrogen couplings from the three histidine (N epsilon) ligands of the Type 2 center indicated a substantial ( approximately 200%) electronic hyperfine inequivalence of one of the histidine nitrogens from the other two within the Type 2 HOMO and thus provided evidence for electronic distortion of the Type 2 site. In the presence of the nitrite substrate, hyperfine couplings of all histidines diminished. We suggest that this nitrite-induced decreased covalency would correlate with an increased Type 2 redox potential to assist electron transfer to the Type 2 center. Dipole-coupled, angle-selected exchangeable proton features, observed over a range of g values, predicted a ligand-water proton distance of 2.80 A from copper, and these water protons were eliminated by nitrite. His287 is not a Type 2 ligand but is positioned to perturb an axial water or a nitrite of Type 2 copper. In the presence of nitrite the mutant H287E showed no evidence for the loss of water protons and no diminished ligand histidine covalency. H287E has vastly diminished activity (prior paper), and the ENDOR information is that NO2- does not bind to Type 2 copper of H287E. In summary, the electronic information from this study of native and suitably chosen mutants provided a test of the highest occupied molecular orbital (HOMO) wave function at Type 1 and Type 2 coppers and an intimate electronic insight into functional enzymatic properties.

The involvement of the two acidic patches of spinach plastocyanin in the reaction with photosystem I

Six different spinach plastocyanin mutants have been constructed by site-directed mutagenesis and expressed in Escherichia coli to probe the importance of the two acidic patches in the interaction with photosystem I. The mutants were: Asp42Lys, Glu43Asn, Glu43Lys, Glu43Gln/Asp44Asn, Glu59Lys/Glu60Gln and Glu43Asn/Glu59Lys/Glu60Gln and they have been characterised by optical absorption and EPR spectroscopy, redox titrations and isoelectric focusing. The electron transfer to photosystem I was investigated by flash-induced time-resolved absorption measurements at 830 nm. The kinetics were interpreted with a model that incorporates a rate-limiting conformational change from inactive to active forms of the plastocyanin-photosystem I complex. All mutations resulted in a displacement of the equilibrium towards the inactive conformation. The strongest impairment of the electron transfer was found for mutations in the larger acidic patch, in particular upon modification of residues 43 or 44. However, mutations of residues 59 and 60 in the smaller acidic patch also resulted in a lower reactivity.

Substrates with charged P1 residues are efficiently hydrolyzed by serine carboxypeptidases when S3-P1 interactions are facilitated

The high activity of carboxypeptidase S1 with substrates having basic P1 residues is predicted to depend on the size of residue 312 in combination with the presence of a counter-charge in an alpha-helix above the S1 binding pocket. This hypothesis is tested by the construction of 32 mutant forms of carboxypeptidase Y that combines a reduction in size of residue 312 and the introduction of either a basic or an acidic residue at either position 241 or position 245. Kinetic characterization using substrates with Leu, Arg, Lys, Glu, or Asp in P1 demonstrates that most of these enzymes exhibit drastically altered catalytic properties. One mutant enzyme, N241D + W312L, hydrolyzes FA-Arg-Ala-OH with a kcat/KM value of 13 000 min-1 mM-1 corresponding to a 930-fold increase relative to the wild-type enzyme. This increased activity is due to an increase in kcat and is independent of ionic strength. The pH profile of kcat/KM exhibits an optimum around pH 5.5 similar to that observed for CPD-S1. Another mutant enzyme, L245R + W312S, hydrolyzes FA-Glu-Ala-OH and FA-Asp-Ala-OH with kcat/KM values of 5100 and 5300 min-1 mM-1, respectively, corresponding to 120 and 170-fold increases relative to wild-type values. With the latter substrate, a 280-fold reduction of KM is observed. The activity of L245R + W312S is also independent of ionic strength and displays a virtually unaltered dependence on pH. The P1 substrate preference of these two mutant enzymes for Arg versus Asp differs 2.5 x 10(6)-fold. values of single and double mutants demonstrate that the effects of reducing the size of Trp312 and introducing a charged residue at position 241 or 245 in some cases exceed 100% additivity. Thus, the double mutant enzyme gains more activation energy than can be accounted for by each individual single mutation.

C-terminal incorporation of fluorogenic and affinity labels using wild-type and mutagenized carboxypeptidase Y

The ability to carry out specific C-terminal modification or labeling of peptides and proteins has a broad range of applications. It is well established that this may be achieved by protease-catalyzed transacylation reactions and that carboxypeptidase Y (CPD-Y) is suitable for this due to its broad specificity and stability in the presence of denaturants. Furthermore, CPD-Y is characterized by a S'1 binding site that is open to solvent and, thus, capable of catalyzing a transpeptidation reaction with nucleophiles that extend beyond the perimeter of the active site. However, one major drawback with CPD-Y is that the yield of the reaction is highly dependent on the nature of the leaving group; e.g., with large apolar leaving groups the yield of the reaction does not exceed 15%. In the present publication it is demonstrated that mutants of CPD-Y, designed for low leaving group dependence, efficiently incorporate biocytin amide as well as a new fluorescent nucleophile, N'-Abz-Lysine amide (ablysin amide), into peptides and proteins.

The histone-like protein H-NS acts as a transcriptional repressor for expression of the anaerobic and growth phase activator AppY of Escherichia coli

The transcriptional activator AppY is required for anaerobic and stationary-phase induction of the cyx-appA and hya operons of Escherichia coli, and expression of the appY gene itself is induced by these environmental conditions. The sequence of the appY gene and its promoter region is unusually AT rich. The nucleoid-associated protein H-NS has a DNA-binding specificity for intrinsically curved AT-rich DNA. Using a single-copy transcriptional appY-lacZ fusion, we have shown that appY gene expression is derepressed in hns mutants during aerobic exponential growth. In the hns mutant, growth phase and growth rate regulation under aerobic conditions was maintained, while ArcA-dependent anaerobic induction was greatly diminished. Judged by two-dimensional gel electrophoresis, the appY promoter fragment exhibits the features characteristic of curved DNA. Gel retardation assays showed that purified H-NS protein bound with high affinity to two different segments of the appY promoter region. The role of H-NS in the AppY regulatory cascade is discussed and compared with its function in the regulatory cascades of the AppY homologs CfaD and VirF.

Increase of the P1 Lys/Leu substrate preference of carboxypeptidase Y by rational design based on known primary and tertiary structures of serine carboxypeptidases

The P1 substrate preference of serine carboxypeptidases, as expressed by the Lys/Leu ratio, differs by up to 10(5)-fold. Predictions of the major determinants of this preference are made by correlating primary and tertiary structures to substrate preferences. In carboxypeptidase Y from yeast it is predicted that Trp312 constitutes such a determinant, reducing the P1 Lys/Leu substrate preference of this enzyme. The predictions are tested by the construction and kinetic characterization of ten mutant enzymes of carboxypeptidase Y. All of these enzymes exhibit changes in their P1 substrate preference. Generally, small decreases in activity (kcat/Km) are observed with substrates containing uncharged P1 side chains. With substrates containing acidic P1 side chains, i.e., FA-Glu-Ala-OH, the activity generally increases slightly, 7-fold in the case of W312K. The most dramatic effects of the Trp312 substitutions are observed with substrates containing basic P1 side chains, i.e., kcat/Km for the hydrolysis of Fa-Lys-Ala-OH with W312E has increased 1150-fold, exclusively as a result of increased kcat values. Similar results have previously been obtained by mutational substitution at position 178 of carboxypeptidase Y. The construction and kinetic characterization of position 178 + 312 double mutants demonstrate that the kinetic effects of substitutions at these two positions are not additive. The P1 Lys/Leu substrate preference of one double mutant, L178D + W312D, has changed 380,000-fold as compared to the wild type enzyme, and the overall P1 substrate preference of this enzyme closely resembles that of carboxypeptidase WII from wheat.

The activity of carboxypeptidase Y toward substrates with basic P1 amino acid residues is drastically increased by mutational replacement of leucine 178

A random mutagenesis study on carboxypeptidase Y has previously suggested that Leu178 is situated in the S1 binding pocket, and this has later been confirmed by the three-dimensional structure. We here report the mutational replacement of Leu178 with Trp, Phe, Ala, Ser, Cys, Asn, Asp, or Lys and the kinetic characterization of each mutant, using substrates systematically varied at the P1 position. The general effect of these substitutions is a reduced kcat/Km for substrates with uncharged amino acid residues in the P1 position, little effect on those with acidic residues, and an increased kcat/Km for those with basic amino acid residues. There is a clear correlation between the reduction in kcat/Km for substrates with uncharged P1 side chains and the nature of the residue at position 178. A small reduction is observed when Leu178 is replaced by another hydrophobic amino acid residue, a larger reduction when it is replaced by a polar residue, and a very large reduction when it is replaced by a charged residue. When Leu178 is replaced by Asp, kcat/Km is reduced by a factor of 2200 for a substrate with Val in the P1 position. The kcat/Km values for the hydrolysis of substrates with charged P1 side chains are increased when Leu178 is replaced by an amino acid residue with the opposite charge, and they are decreased when it is replaced by a residue with the same charge. Surprisingly, all mutants (except L178K) exhibit increased activity with substrates with basic P1 side chains.(ABSTRACT TRUNCATED AT 250 WORDS)

Improvement of the applicability of carboxypeptidase Y in peptide synthesis by protein engineering

Asn51 and Glu145 of (serine) carboxypeptidase Y function as binding sites for the C-terminal carboxylate group of peptide substrates, and Glu65 is involved in orienting these two amino acid residues. A series of mutants of carboxypeptidase Y where these three amino acid residues have been replaced were investigated for their applicability in transacylation reactions with amino acid esters as acceptors. With H-Val-OMethyl as the nucleophile, the fraction of aminolysis is significantly higher than with the corresponding amino acid, suggesting a beneficial effect of blocking the alpha-carboxylate group. Increasing the size of the alcohol moiety, i.e., -OEthyl, -OPropyl or OButyl, has an adverse effect on the binding of the nucleophile and on the maximum yield of aminolysis. Replacement of Asn51 and Glu145 with Ala or Gly has a pronounced beneficial effect both on binding and the maximum fraction of aminolysis. However, the results do not establish a specific type of interaction between the enzyme and these valine esters. It is probable that the rotational freedom around the ester bond allows multiple binding modes, depending on both the leaving group and type of structural change within the binding site. From a synthetic point of view, some of the mutant enzymes are much better than the wildtype enzyme when amino acid esters are used as nucleophiles.

Altering substrate preference of carboxypeptidase Y by a novel strategy of mutagenesis eliminating wild type background

To change the substrate preference of carboxypeptidase Y the putative substrate binding pocket was subjected to random mutagenesis. Based upon the three-dimensional structure of a homologous enzyme from wheat, we hypothesized that Tyr147, Leu178, Glu215, Arg216, Ile340 and Cys341 are the amino acid residues of carboxypeptidase Y that constitute S1, the binding pocket for the penultimate amino acid side chain of the substrate. We developed a new and generally applicable mutagenesis strategy to facilitate efficient screening of a large number of mutants with multiple changes in carboxypeptidase Y. The key feature is the elimination of wild type background by introducing a nonsense codon at each target site for subsequent mutagenesis by degenerate oligonucleotides. The entire hypothesized S1 binding pocket and subsets of it were subjected to saturation mutagenesis by this strategy, and screening yielded a number of mutant enzymes which have up to 150 times more activity (kcat/Km) towards CBZ-Lys-Leu-OH than the wild type enzyme. All selected mutants with increased activity have mutations at position 178. Mutagenesis of positions 215 and 216 has virtually no effect on the activity, while mutating positions 340 and 341 generally reduces activity.

Correlation of abdominal ultrasound and computed tomography scans with second- or third-look laparotomy in patients with ovarian carcinoma

To determine the best noninvasive means of evaluating response in patients with advanced ovarian carcinoma, 50 abdominal ultrasound (US) and computed tomography (CT) scans were performed in clinically disease-free ovarian cancer patients. The scans were correlated with the results obtained at a subsequent second- or third-look laparotomy. CT and US were not complementary, and only metastases larger than 2 cm were detected. The overall positive predictive value of nonconcordant scans was 57% compared with 100% for concordant CT and US (95% confidence limits: 18.4-90.1 and 29.2-100%, respectively). The corresponding negative predictive values were 45 and 47% (30.2-59.9 and 30.4-61.2%, respectively), if undetected microscopic disease was classified as a false-negative result. The negative predictive value of US and CT increased only to 60% in both cases, if undetected microscopic disease was registered as a true-negative result. Compared with the pelvic examination CT and US added positive information for 4 of 22 (18%) patients with macroscopic residual disease. In this study neither CT nor US was sensitive enough to preclude second-look laparotomy.

Distamycin inhibition of topoisomerase I-DNA interaction: a mechanistic analysis

Inhibition of eukaryotic DNA topoisomerase I by the minor groove binding ligand, distamycin A, was investigated. Low concentrations of the ligand selectively prevented catalytic action at a high affinity topoisomerase I binding sequence. A restriction enzyme protection assay indicated that the catalytic cycle was blocked at the binding step. Distamycin binding sites on DNA were localized by hydroxyl radical footprinting. A strongly preferred site mapped to a homopolymeric (dA).(dT)-tract partially included in the essential topoisomerase I binding region. Mutational elimination of the stable helix curvature associated with this ligand binding site demonstrated that (i) the intrinsic bend was unessential for efficient binding of topoisomerase I, and (ii) distamycin inhibition did not occur by deformation of a stable band. Alternative modes of inhibition are discussed.

Endoprosthesis for internal drainage of the biliary tract. Technique and results in 48 cases

In 48 patients with obstructive jaundice caused by unresectable lesions, a polyethylene tube was inserted into the biliary tract using a percutaneous transhepatic technique. This endoprosthesis provided permanent internal drainage without an external catheter. In 27 patients, bilirubin declined to anicteric or subicteric levels and pruritus subsided. In six patients, endoprosthesis had an intermediate effect, with moderate falls in bilirubin and improvement of their general condition. This method does not seem to increase the risk of percutaneous transhepatic cholangiography, which precedes insertion. It is recommended for patients with inoperable bile duct obstruction and may replace surgical biliodigestive anastomoses in patients with unresectable lesions.