Clavicular tunnel widening after acromioclavicular joint reconstruction: comparison between single and double clavicular tunnel techniques.

Acromioclavicular joint (ACJ) reconstruction using artificial ligaments is a common surgical treatment for Rockwood grade III or higher injuries. These techniques use bone tunnels in the clavicle and coracoid to insert the Tightrope implants. This multicenter retrospective study compares long term radiographic follow up of clavicular tunnel widening in two groups of patients with high-grade ACJ injury who underwent reconstruction using two different surgical techniques. The first group of 23 patients underwent an arthroscopic single clavicular tunnel ACJ reconstruction. The second group of 23 patiënts underwent an open double clavicular tunnel reconstruction. Inclusion criteria are Rockwood grade III or higher injury and minimum 18 months of follow-up. Exclusion criteria are distal clavicle fracture and additional stabilization techniques. Radiographic results were measured on anteroposterior shoulder radiographs taken at the first and last follow-up. Clavicular tunnel widening is the main outcome measurement. Secondary outcomes are heterotopic ligament calcifications, migration of buttons, tunnel fracture and loss of acromioclavicular reduction. The mean clavicular tunnel widening in the single clavicular tunnel technique is 1.91 mm. In the double clavicular tunnel technique, the widening of the medial tunnel is 2.52 mm and 3.59 mm in the lateral tunnel. The difference in widening between the single tunnel and the lateral tunnel is significant (p=0.003). A very clear observation on all follow-up X-rays was a reorientation of the clavicular tunnels towards the coracoid. The double clavicular tunnel technique has more tunnel widening in both tunnels compared to the single bundle technique.

Usage of digital, social and goal-setting functionalities to support health behavior change: A mixed methods study among disadvantaged women during or after pregnancy and their healthcare professionals.

OBJECTIVE: We aimed to gain insight into how and to what extent social (i.e. private/group chat) and goal-setting (e.g. rewards) functionalities in digital interventions for health behavior change were used by clients and nurses in a preventive care program for disadvantaged women during or after pregnancy, and which factors influenced usage. METHODS: We collected quantitative and qualitative data on usage of these functionalities in 'Kindle', a mHealth intervention to prepare for health behavior change. RESULTS: We found that nurses (n = 5) and clients (n = 20) scarcely used both functionalities. They sent 862 messages in the social functionality whose security they appreciated, but habitually used WhatsApp likewise. Moreover, nurses were hesitant to let their clients interact in the group chat. Clients formulated 59 personal goals, which they found difficult to do. Nurses rewarded 846 points for clients' progress on goal attainment, but found it hard to determine how many points to reward. Clients and nurses indicated that the functionality made it more fun and easy to discuss clients' personal goals. CONCLUSIONS: To conclude, digital, social and goal-setting functionalities were used to a limited extent by nurses and clients, and need optimization before implementation to support disadvantaged groups to change their health behavior.

Burn scar contracture release surgery effectively improves functional range of motion, disability and quality of life: A pre/post cohort study with long-term follow-up in a Low- and Middle-Income Country.

OBJECTIVE: Burn scar contractures limit range of motion (ROM) of joints and have substantial impact on disability and the quality of life (QoL) of patients, particularly in a Low- and Middle-Income Country (LMIC) setting. Studies on the long-term outcome are lacking globally; this study describes the long-term impact of contracture release surgery performed in an LMIC. METHODS: This is a pre-post cohort study, conducted in a referral hospital in Tanzania. Patients who underwent burn scar contracture release surgery in 2017-2018 were eligible. ROM (goniometry), disability (WHODAS 2.0) and QoL (EQ-5D) were assessed. The ROM data were compared to the ROM that is required to perform activities of daily living without compensation, i.e. functional ROM. Assessments were performed preoperatively and at 1, 3, 6 and 12 months postoperatively. RESULTS: In total, 44 patients underwent surgery on 115 affected joints. At 12 months, the follow-up rate was 86%. The mean preoperative ROM was 37.3% of functional ROM (SD 31.2). This improved up to 108.7% at 12 months postoperatively (SD 42.0, p < 0.001). Disability-free survival improved from 55% preoperatively to 97% at 12 months (p < 0.001) postoperatively. QoL improved from 0.69 preoperatively, to 0.93 (max 1.0) at 12 months postoperatively (p < 0.001). Patients who regained functional ROM in all affected joints reported significantly less disability (p < 0.001) and higher QoL (p < 0.001) compared to patients without functional ROM. CONCLUSIONS: Contracture release surgery performed in an LMIC significantly improved functional ROM, disability and QoL. Results showed that regaining a functional joint is associated with less disability and higher QoL.

Serious games for smoking prevention and cessation: A systematic review of game elements and game effects.

OBJECTIVE: Serious health games might have the potential to prevent tobacco smoking and its health consequences, depending on the inclusion of specific game elements. This review aimed to assess the composition of serious games and their effects on smoking initiation prevention and cessation and behavioral determinants. MATERIALS AND METHODS: We systematically searched MEDLINE, Embase, PsycINFO, and Web of Science for publications that evaluated serious games aimed at changing smoking behavior or behavioral determinants. A taxonomy by King et al was used to classify game elements. RESULTS: We identified 15 studies, evaluating 14 unique serious games. All games combined multiple game elements (mean 5.5; range, 3-10). Most frequently used were general and intermittent rewards, theme and genre features, and punishments. Six studies on smoking prevention together assessed 20 determinants and found statistically significant positive effects for 8 determinants (eg, attitude, knowledge, intention). Of 7 studies on smoking cessation, 5 found positive, statistically significant effects on smoking cessation or status. These studies found statistically significant positive effects for 6 of 12 determinants (eg, self-efficacy, attitude, intention). The majority of included studies had poor or fair methodological quality, lacked follow-up measures, and had fixed (as opposed to free, on-demand) play sessions. CONCLUSIONS: Serious games included multiple types of game elements. The evidence from a number of studies suggests that games may have positive effects on smoking-related outcomes, particularly smoking cessation. However, as most studies had important methodological limitations, stronger designs are needed to demonstrate, quantify, and understand the effects of serious games.

Participation rates of childhood cancer survivors to self-administered questionnaires: a systematic review.

This review aimed to assess participation rates of childhood cancer survivors (CCS) invited to fill out a health-related questionnaire. Additionally, effects of study and CCS characteristics on participation rates were examined. PubMed, Web of Science, Ovid (EMBASE) and CINAHL databases were searched. Publications included were questionnaire-based studies among CCS diagnosed with cancer before the age of 21, alive at least 5 years past diagnosis and aged 16 years or older at the time of study. Thirty-five studies were included; the median participation rate was 65%. Sixteen studies reported information about CCS actively declining participation (median rate 5%). Five study characteristics seemed to influence participation rates: the use of reminders and incentives, the option to answer a shortened questionnaire, the recruitment of participants through their general practitioner and a pre-notification before sending out the questionnaire. Furthermore, CCS characteristics related to improved participation were female gender, Caucasian ethnicity and a higher educational level. The results of this study will help to improve the (methodological) quality of future questionnaire-based studies among CCS, thereby increasing our knowledge about late effects among this group of survivors.

Uncovering healthcare practitioners' information processing using the think-aloud method: From paper-based guideline to clinical decision support system.

OBJECTIVE: To investigate whether the use of the think-aloud method with propositional analysis could be helpful in the design of a Clinical Decision Support System (CDSS) providing guideline recommendations about long-term follow-up of childhood cancer survivors. MATERIALS AND METHODS: The think-aloud method was used to gain insight into healthcare professionals' information processing while reviewing a paper-based guideline. A total of 13 healthcare professionals (6 physicians and 7 physician assistants) prepared 2 fictitious patient consults using the paper-based guideline. Propositional analysis was used to analyze verbal protocols of the think-aloud sessions. A prototype CDSS was developed and a usability study was performed, again with the think-aloud method. RESULTS: The analysis revealed that the paper-based guideline did not support healthcare practitioners in finding patient-specific recommendations. An information processing model for retrieving recommendations was developed and used as input for the design of a CDSS prototype user interface. Usability analysis of the prototype CDSS showed that the navigational structure of the system fitted well with healthcare practitioners' daily practices. CONCLUSIONS: The think-aloud method combined with propositional analysis of healthcare practitioners' verbal utterances while they processed a paper-based guideline was useful in the design of a usable CDSS providing patient-specific guideline recommendations.

Solid-state NMR characterization of tri-ethyleneglycol grafted polyisocyanopeptides.

In aqueous media, ethylene glycol substituted polyisocyanopeptides (PICPs) change their state (undergo a sol-to-gel transition) as a response to temperature. This makes them promising materials for various biomedical applications, for instance, for controlled drug release and non-damaging wound dressing. To utilize PICP in biomedical applications, understanding of the origin of the gelation process is needed, but this is experimentally difficult because of the notoriously low gelator concentration in combination with the slow polymer dynamics in the sample. This paper describes a detailed characterization of the dried state of PICPs by solid-state NMR measurements. Both the (13) C and the (1) H NMR resonances were assigned using a combination of 1D cross-polarization magic angle spinning, 2D (13) C-(1) H heteronuclear correlation spectra and (1) H-(1) H single quantum-double quantum experiments. In addition, the chemical groups involved in dipolar interaction with each other were used to discuss the dynamics and spatial conformation of the polymer. In contrast to other PICP polymers, two resonances for the backbone carbon are observed, which are present in equal amounts. The possible origin of these resonances is discussed in the last section of this work. The data obtained during the current studies will be further used in elucidating mechanisms of the bundling and gelation. A comprehensive picture will make it possible to tailor polymer properties to meet specific needs in different applications. Copyright © 2015 John Wiley & Sons, Ltd.

A Concise and Practical Framework for the Development and Usability Evaluation of Patient Information Websites.

BACKGROUND: The Website Developmental Model for the Healthcare Consumer (WDMHC) is an extensive and successfully evaluated framework that incorporates user-centered design principles. However, due to its extensiveness its application is limited. In the current study we apply a subset of the WDMHC framework in a case study concerning the development and evaluation of a website aimed at childhood cancer survivors (CCS). OBJECTIVE: To assess whether the implementation of a limited subset of the WDMHC-framework is sufficient to deliver a high-quality website with few usability problems, aimed at a specific patient population. METHODS: The website was developed using a six-step approach divided into three phases derived from the WDMHC: 1) information needs analysis, mock-up creation and focus group discussion; 2) website prototype development; and 3) heuristic evaluation (HE) and think aloud analysis (TA). The HE was performed by three double experts (knowledgeable both in usability engineering and childhood cancer survivorship), who assessed the site using the Nielsen heuristics. Eight end-users were invited to complete three scenarios covering all functionality of the website by TA. RESULTS: The HE and TA were performed concurrently on the website prototype. The HE resulted in 29 unique usability issues; the end-users performing the TA encountered eleven unique problems. Four issues specifically revealed by HE concerned cosmetic design flaws, whereas two problems revealed by TA were related to website content. CONCLUSION: Based on the subset of the WDMHC framework we were able to deliver a website that closely matched the expectancy of the end-users and resulted in relatively few usability problems during end-user testing. With the successful application of this subset of the WDMHC, we provide developers with a clear and easily applicable framework for the development of healthcare websites with high usability aimed at specific medical populations.

Prevalence of severe subclinical coronary artery disease on cardiac CT and MRI in patients with extra-cardiac arterial disease.

OBJECTIVE: Patients with extra-cardiac arterial disease (ECAD) are at high risk of coronary artery disease (CAD). Prevalence of silent, significant CAD in patients with stenotic or aneurysmal ECAD was examined. Early detection and treatment may reduce CAD mortality in this high-risk group. MATERIALS AND METHODS: ECAD patients without cardiac complaints underwent computed tomography (CT) for calcium scoring, coronary CT angiography (cCTA) if calcium score was 1,000 or under, and adenosine perfusion magnetic resonance imaging (APMR) if there was no left main stenosis. Significant CAD was defined as calcium score over 1,000, cCTA-detected coronary stenosis of at least 50% lumen diameter, and/or APMR-detected inducible myocardial ischemia. In cases of left main stenosis (or equivalent) or myocardial ischemia, patients were referred to a cardiologist. RESULTS: The prevalence of significant CAD was 56.8% (95% CI 47.5 to 66.0). One-hundred and eleven patients were included. Eighty-four patients (76%) had stenotic ECAD, and 27 (24%) had aneurysmal disease. In patients with stenotic ECAD, significant coronary stenosis was present in 32 (38%) and inducible ischemia in eight (12%). Corresponding results in aneurysmal ECAD were eight (30%) and two (11%), respectively (p for difference >.05). Sixteen (19%) patients with stenotic and six (22%) with aneurysmal ECAD were referred to a cardiologist, with subsequent cardiac intervention in seven (44%) and three (50%), respectively (both p >.05). CONCLUSIONS: Patients with stenotic or aneurysmal ECAD have a high prevalence of silent, significant CAD.

Final height in survivors of childhood cancer compared with Height Standard Deviation Scores at diagnosis.

BACKGROUND: Our study aimed to evaluate final height in a cohort of Dutch childhood cancer survivors (CCS) and assess possible determinants of final height, including height at diagnosis. PATIENTS AND METHODS: We calculated standard deviation scores (SDS) for height at initial cancer diagnosis and height in adulthood in a cohort of 573 CCS. Multivariable regression analyses were carried out to estimate the influence of different determinants on height SDS at follow-up. RESULTS: Overall, survivors had a normal height SDS at cancer diagnosis. However, at follow-up in adulthood, 8.9% had a height ≤-2 SDS. Height SDS at diagnosis was an important determinant for adult height SDS. Children treated with (higher doses of) radiotherapy showed significantly reduced final height SDS. Survivors treated with total body irradiation (TBI) and craniospinal radiation had the greatest loss in height (-1.56 and -1.37 SDS, respectively). Younger age at diagnosis contributed negatively to final height. CONCLUSION: Height at diagnosis was an important determinant for height SDS at follow-up. Survivors treated with TBI, cranial and craniospinal irradiation should be monitored periodically for adequate linear growth, to enable treatment on time if necessary. For correct interpretation of treatment-related late effects studies in CCS, pre-treatment data should always be included.

Proclets in healthcare.

Healthcare processes can be characterized as weakly-connected interacting light-weight workflows coping with different levels of granularity. Classical workflow notations fall short in supporting these kind of processes. Although these notations are able to describe the life-cycle of individual cases and allow for hierarchical decomposition, they primarily support monolithic processes. However, they are less suitable for healthcare processes. The Proclets framework is one formalism that provides a solution to this problem. Based on a large case study, describing the diagnostic process of the gynecological oncology care process at the Academic Medical Center (AMC), we identify the limitations of "monolithic workflows". Moreover, by using the same case study, we investigate whether healthcare processes can be described effectively using Proclets. In this way, we provide a comparison between the Proclet framework and existing workflow languages and identify research challenges.

Training inter-physician communication using the Dynamic Patient Simulator.

PURPOSE: Clear and adequate communication between physicians is essential in modern medicine. Nevertheless, the medical curricula in The Netherlands lack an identifiable part in their education concerning inter-physician communication training. To train medical students in inter-physician communication skills using the Dynamic Patient Simulator (DPS), the Academic Medical Center at the University of Amsterdam and the Leiden University Medical Center joined in a 2-year project sponsored by the Dutch government. DPS is an educational computer program to create and simulate virtual patients with a wide variety of medical conditions in different clinical settings and over different time frames. To evaluate whether DPS is a suitable method for training medical students in inter-physician communication, we assessed if medical students felt that they had improved their inter-collegial communication skills after the pilot with DPS. Besides, we inquired students on DPS' usability and their satisfaction with DPS. METHODS: We first developed and implemented 20 patient simulations in DPS to be practiced upon by two students asynchronously during a week. These students were situated in different medical institutions, geographically spread over The Netherlands and had to treat the virtual patient as a team supported by DPS. The students had to report their findings and treatment plan in the electronic referral form of DPS. A total of 134 students participated in the pilot. To evaluate inter-physician communication training using DPS we conducted a survey amongst these students who were entering their internships. The evaluation focused on self-assessment of their communication skills, usability of the DPS program, and their satisfaction with DPS as educational format, using multiple questionnaires. DISCUSSION: The outcome of the evaluation showed significant progression in students' feeling of improvement of their skills in different aspects concerning the referral of a patient after participating in the pilot. Besides, students evaluated the usability of DPS positive and were highly satisfied with the education in inter-physician communication training using DPS. Based on these outcomes, nowadays this form of training is incorporated in the curricula on a regular basis.

Development of a national protocol to screen Dutch cancer survivors on late cancer treatment effects.

PURPOSES: The development of a national protocol to formalize the screening of Dutch cancer survivors on potential late cancer treatment effects and the medical terminology used in describing the patient follow up procedures. METHODS: A combined evidence-based and qualitative approach, the Glaser's State of the Art Strategy, was used to reach consensus on how to screen Dutch cancer survivors on late cancer treatment effects. A core working group set up a first proposal of a screening protocol and a handbook of medical term definitions by incorporating available research evidence (1980-2003), clinical expertise and definitions from Dutch medical dictionaries and textbooks. External experts reviewed this proposal in a cycle of two postal and two discussion rounds. The follow-up procedures and medical term definitions described in the draft screening protocol were to be accepted if consensus among external experts was > or =50%. RESULTS: A protocol for screening cancer survivors on late cancer treatment effects was developed describing the follow-up procedures for cancer survivors according to previous therapeutic exposures. Four hundred and twenty one medical terms were used in describing these follow-up procedures. One hundred and fifteen of these terms were classified as multi-interpretable and 101 of these terms were defined. No definitions could be found for the remaining 14 medical terms. CONCLUSIONS: We succeeded in reaching consensus throughout The Netherlands on a protocol to screen cancer survivors on late cancer treatment effects. This protocol is now in use by all Dutch outpatient clinics and warrants that the screening of cancer survivors is consistent across The Netherlands. The screening protocol specifies in detail how screening of cancer survivors should take place and can therefore be used by clinicians who were not involved in the consensus study.

Effect of improving flue gas cleaning on characteristics and immobilisation of APC residues from MSW incineration.

The flue gas cleaning system of a MSW incinerator with a capacity of 350 kt/year was changed to improve the HCl elimination efficiency. Instead of the semi-wet operating spray reactor and subsequent baghouse, a two-step wet flue gas cleaning was added behind the baghouse. Elemental composition, X-ray powder diffraction patterns and TGA measurements showed that the resulting APC residue was totally different from the former residue. As a consequence, leaching characteristics of both residues also differed and another treatment was required prior to disposal. For the former residue, mainly leaching of Pb (>100 mg/l), necessitated treatment prior to landfilling. The lower alkalinity of the new residue resulted in a leachate pH of 9.7 and a Pb concentration of 0.8 mg/l. The leachate pH of the former residue was 12.4. The leaching of Pb and Zn increased above 100 mg/l when immobilising the new residue with cement. Better results were obtained when immobilising with micro silica. The high CaCl2 x 2H2O content of the new residue brought along clogging of the bag filter system. Adding 1.4% of CaO (or 1.9% of Ca(OH)2) to the residue already improved these inconveniences but again significantly changed the leaching behaviour of the residue.

[The use of a self-expanding stent as palliation or before elective surgery in patients with obstructive colorectal carcinoma]. / Zelfexpanderende stent bij obstruerend colorectaal carcinoom als palliatie of als overbrugging naar electieve chirurgie.

OBJECTIVE: To evaluate the use of colorectal stents. DESIGN: Retrospective. METHOD: Data were collected on all patients treated at the Deventer Hospital, the Netherlands, between 1 April 1996 and 31 December 2003 in whom the placement of a self-expanding colorectal stent was attempted. Each patient's physician was contacted to inquire about the patient's status, including quality of life with the stent in situ. RESULTS: Stent placement was attempted in 57 patients as palliation (n = 45) or before elective surgery (n = 12). Of the 57 patients, 29 were men and 28 were women, and the mean age was 71 years (range: 46-94). All patients had colorectal carcinoma, except 1 patient with stenosis following ischaemic colitis. Passage of air and faeces occurred immediately after stent expansion in 55 of the 57 patients (96%). Perforation during stent placement occurred in 2 patients, who subsequently underwent colostomy. 4 additional patients required a colostomy due to stent migration within a few hours or days after placement (n = 3) or obstruction by tumor growth after 65 days (n = 1). Patients in the palliative group had an acceptable quality of life. Those who received a stent before elective surgery were able to undergo resection, did not require colostomy, and had no postoperative complications. One patient did not undergo surgery because of extensive metastases. CONCLUSION: A colorectal stent can be used in the palliative treatment of terminal patients with colorectal carcinoma before colostomy is considered. Experiences with stents before elective surgery were also positive.

Genotype/phenotype correlation of the G85E mutation in a large cohort of cystic fibrosis patients.

In this European study, the phenotype in 68 patients, homozygous or compound heterozygous for the G85E mutation, was investigated. Each index case was compared with two cystic fibrosis (CF) patients from the same clinic, matched for age and sex: one with pancreatic sufficiency (PS) and one with pancreatic insufficiency (PI). When comparing 31 G85E/F508del and F508del/F508del patients, there were no differences in median age at diagnosis, mean sweat chloride value, most recent weight for height, most recent forced expiratory volume in one second % predicted, prevalence of chronic Pseudomonas aeruginosa colonisation and typical CF complications. However, PI was less frequent in the G85E/F508del group. Comparison of 55 G85E patients (with second mutation known and not classified as mild) with PS controls (n=44) showed that the G85E patients had a significantly higher sweat chloride, more often failure to thrive at diagnosis, higher prevalence of PI, worse current weight for height, higher prevalence of chronic P. aeruginosa colonisation and liver cirrhosis. Pulse-chase experiments revealed that G85E cystic fibrosis transmembrane conductance regulator failed to mature on a M470 as well as on a V470 background. Therefore, G85E is a class II mutation. Although there is variability in its clinical presentation, G85E mutation results in a severe phenotype.

Functional interaction between TRP4 and CFTR in mouse aorta endothelial cells.

BACKGROUND: This study describes the functional interaction between the putative Ca2+ channel TRP4 and the cystic fibrosis transmembrane conductance regulator, CFTR, in mouse aorta endothelium (MAEC). RESULTS: MAEC cells express CFTR transcripts as shown by RT-PCR analysis. Application of a phosphorylating cocktail activated a Cl- current with characteristics similar to those of CFTR mediated currents in other cells types (slow activation by cAMP, absence of rectification, block by glibenclamide). The current is present in trp4 +/+ MAEC, but not in trp4 -/- cells, although the expression of CFTR seems unchanged in the trp4 deficient cells as judged from RT-PCR analysis. CONCLUSIONS: It is concluded that TRP4 is necessary for CFTR activation in endothelium, possibly by providing a scaffold for the formation of functional CFTR channels.

Suppressive interactions between mutations located in the two nucleotide binding domains of CFTR.

The S1235R locus in CFTR was studied in combination with alleles found at the M470V and G628R loci. While R628 caused a maturational defect, R1235 did not. The impact of R1235 was found to be influenced by the alleles present at the G628R and M470V loci. At the single channel level, R1235-V (R1235 on a V470 background) was characterized by an open probability significantly higher than V470-wildtype CFTR. M470, which on its own increases CFTR chloride transport activity when compared to V470-wildtype CFTR, suppressed the activity of R1235 in such a way that a protein with an open probability not significantly different from V470-wildtype CFTR was obtained. While R628-V CFTR had similar current densities as V470-wildtype CFTR in Xenopus laevis oocytes, R1235-V resulted in current densities that were more than twofold higher than those of V470-wildtype CFTR. However, the current densities generated by R1235/R628-V (R1235 and R628 on a V470 background) CFTR were significant lower than R1235-V or R628-V CFTR.

The development of a new information model for a pediatric cancer registry on late treatment sequelae in The Netherlands.

Worldwide, the need is felt for life time follow up of survivors of childhood cancer and for the establishment of registries of the late effects of pediatric oncology treatments. There is however little consensus about how this all should take place. For example, agreement on the nature of this follow up and the type of data to be collected in view of the earlier diagnosis and treatment of the patient is lacking. In a close collaboration between the 'Late Effects Study Group' (consisting of the Pediatric Oncology department of the Emma Children's Hospital and the department of Medical Oncology at the Academic Medical Center), the Netherlands Cancer institute/Antoni van Leeuwenhoek Hospital, and the department of Medical Informatics of the University of Amsterdam, consensus was reached on a new dataset on adverse late effects of pediatric oncology treatment. This dataset was used in developing an information model for the design of a computerized documentation system, PLEKsys. PLEKsys covers both standardized documentation of all relevant data items for evaluating late effects and review facilities on individual patient basis and on patient cohorts. We will install PLEKsys at all Dutch pediatric oncology centers and use the information model as a starting point in developing a National Pediatric Oncology Follow up Registry. A national programme encompassing all Dutch pediatric oncology centers has already been set up to co-ordinate the construction of this national registry.

Functional characterization of the CFTR R domain using CFTR/MDR1 hybrid and deletion constructs.

To improve our insight into the structure and function of the CFTR R domain, deletion and hybrid constructs in which different parts of the R domain were deleted or replaced by the MDR1 linker domain, and vice versa, were made. Replacement of the linker domain by the R domain did not result in a decrease and replacement of the CFTR R domain by the linker domain did not result in an increase of maturation efficiency, when compared to the respective wild-type proteins. This indicates that the R domain is not responsible for the high degree of degradation observed for CFTR translation products in the ER, but rather the overall structure or sequences located outside the R domain. Replacing the C-terminal part of the R domain (amino acids 780-830) by the MDR1 linker domain resulted in the appearance of PKA-dependent whole cell chloride currents which were not significantly different from wild-type CFTR currents. This might indicate that the PKA sites present in the linker domain are functional and that not the exact sequence of the C-terminal part of the R domain is important, but rather the presence of PKA sites and the length. Moreover, when this hybrid construct was PKC-stimulated, chloride currents were activated. Although these PKC-induced currents were lower than the PKA-induced ones, this again indicates that the linker domain is functional in this hybrid construct. Taken together, these results suggest that the MDR1 linker domain can substitute for part of the regulatory domain of the CFTR protein.