Van Der Laan Research Articles

Peripheral Blood Monocyte-expressed ANXA2 Gene is Involved in Pathogenesis of Osteoporosis in Humans

Low bone mineral density (BMD) is a risk factor of osteoporosis and has strong genetic determination. Genes influencing BMD and fundamental mechanisms leading to osteoporosis have yet to be fully determined. Peripheral blood monocytes (PBM) are potential osteoclast precursors, which could access to bone resorption surfaces and differentiate into osteoclasts to resorb bone. Herein, we attempted to identify osteoporosis susceptibility gene(s) and characterize their function(s), through an initial proteomics discovery study on PBM in vivo, and multiscale validation studies in vivo and in vitro. Utilizing the quantitative proteomics methodology LC-nano-ESI-MS(E), we discovered that a novel protein, i.e. ANXA2, was up-regulated twofold in PBM in vivo in Caucasians with extremely low BMD (cases) versus those with extremely high BMD (controls) (n = 28, p < 0.05). ANXA2 gene up-regulation in low BMD subjects was replicated at the mRNA level in PBM in vivo in a second and independent case-control sample (n = 80, p < 0.05). At the DNA level, we found that SNPs in the ANXA2 gene were associated with BMD variation in a 3(rd) and independent case-control sample (n = 44, p < 0.05), as well as in a random population sample (n = 997, p < 0.05). The above integrative evidence strongly supports the concept that ANXA2 is involved in the pathogenesis of osteoporosis in humans. Through a follow-up cellular functional study, we found that ANXA2 protein significantly promoted monocyte migration across an endothelial barrier in vitro (p < 0.001). Thus, elevated ANXA2 protein expression level, as detected in low BMD subjects, probably stimulates more PBM migration through the blood vessel walls to bone resorption surfaces in vivo, where they differentiate into higher number of osteoclasts and resorb bone at higher rates, thereby decreasing BMD. In conclusion, this study identified a novel osteoporosis susceptibility gene ANXA2, and suggested a novel pathophysiological mechanism, mediated by ANXA2, for osteoporosis in humans.

Current status observation of a three‐state counting process with application to simultaneous accurate and diluted HIV test data

AbstractThe authors examine multistate current status data defined by two survival times of interest where one only observes whether or not each of the individual survival times exceed a common observed monitoring time. An individual can therefore belong to one of three states. The authors are interested in whether current status information on the second event can be used to improve estimation of the distribution function of time to the first event. For both single and multiple monitoring time scenarios, in the fully nonparametric setting, one cannot improve the naïve estimator, using information on the first event only, when estimating “smooth” functionals of the distribution of time to the first event (van der Laan &amp; Jewell, 2003). Therefore, improving the naïve estimator is examined when parametric assumptions about the waiting time between the two events are made. For situations where this waiting time is modifiable by design, the issue of determining the optimal length of the waiting time for estimation of the cumulative hazard of the distribution of time to the first event in the recent past is also addressed. The ideas are motivated by and applied to an example on simultaneous accurate and diluted assay HIV test data. The Canadian Journal of Statistics 39: 475–487; 2011 © 2011 Statistical Society of Canada

The Effect of Prolapse Surgery on Vaginal Sensibility

Prolapse surgery has been shown to have major impact on sexual function. Since prolapse surgery not only influences psychological factors but might also influence physiological conditions such as vaginal innervation, there is a need for objective outcome measurements to better understand the effects of prolapse surgery on sexual function. To assess the effects of prolapse surgery with or without stress incontinence surgery on vaginal sensibility and to assess the relationship between vaginal wall sensibility and sexual well-being. This study was performed parallel to a randomized controlled trial comparing vaginal and abdominal prolapse surgery with or without incontinence surgery in women with uterine prolapse stage 2 or more. Vaginal wall sensibility was defined as mean sensation threshold to electrical stimulation of the vaginal wall at four standardized places, measured before and 6 months after surgery. Higher sensation thresholds postsurgery relative to presurgery indicate diminished vaginal wall sensibility. Sexual function was assessed at the same time points using a questionnaire. Data on vaginal wall sensibility were obtained from 65 patients. The sensibility of the distal posterior (P = 0.02) and distal anterior (P = 0.10) vaginal wall decreased after vaginal surgery compared to abdominal surgery. Abdominal prolapse surgery with incontinence surgery decreased sensibility of the distal part of the anterior vaginal wall significantly more than abdominal prolapse surgery only (P = 0.01). Before surgery, vaginal wall sensibility was lower in women who reported vaginal dryness or anorgasmia. The presence of genital pain was associated with higher vaginal wall sensibility. Postoperative vaginal wall sensibility was similar in women with and without sexual problems. Vaginal prolapse surgery as well as abdominal prolapse surgery with additional incontinence surgery resulted in decreased vaginal wall sensibility. This pilot study shows no influence of the decreased vaginal wall sensibility on sexual well-being. Larger studies are needed to better understand the association between changes in vaginal wall sensibility and changes in sexual well-being.

Aligned Collagen Is a Prognostic Signature for Survival in Human Breast Carcinoma

Evidence for the potent influence of stromal organization and function on invasion and metastasis of breast tumors is ever growing. We have performed a rigorous examination of the relationship of a tumor-associated collagen signature-3 (TACS-3) to the long-term survival rate of human patients. TACS-3 is characterized by bundles of straightened and aligned collagen fibers that are oriented perpendicular to the tumor boundary. An evaluation of TACS-3 was performed in biopsied tissue sections from 196 patients by second harmonic generation imaging of the backscattered signal generated by collagen. Univariate analysis of a Cox proportional hazard model demonstrated that the presence of TACS-3 was associated with poor disease-specific and disease-free survival, resulting in hazard ratios between 3.0 and 3.9. Furthermore, TACS-3 was confirmed to be an independent prognostic indicator regardless of tumor grade and size, estrogen or progesterone receptor status, human epidermal growth factor receptor-2 status, node status, and tumor subtype. Interestingly, TACS-3 was positively correlated to expression of stromal syndecan-1, a receptor for several extracellular matrix proteins including collagens. Because of the strong statistical evidence for poor survival in patients with TACS, and because the assessment can be performed in routine histopathological samples imaged via second harmonic generation or using picrosirius, we propose that quantifying collagen alignment is a viable, novel paradigm for the prediction of human breast cancer survival.

Is Each NPMLE of a Continuous Bivariate Distribution Function with Singly Right-Censored Data Really Inconsistent?

We consider non-parametric estimation of a continuous cdf of a random vector (X 1, X 2). With bivariate RC data, it is stated in van der Laan (1996, p. 59810, Ann. Statist.), Quale et al. (2006, JASA) etc. that “it is well known that the NPMLE for continuous data is inconsistent (Tsai et al. (1986)).” The claim is based on a result in Tsai et al. (1986, p.1352, Ann. Statist.) that if X 1 is right censored but not X 2, then common ways for defining one NPMLE lead to inconsistency. If X 1 is right censored and X 2 is type I right-censored (which includes the case in Tsai et al.), we present a consistent NPMLE. The result corrects a common misinterpretation of Tsai's example (Tsai et al., 1986, Ann. Statist.).

Differential expression of the nuclear receptors farnesoid X receptor (FXR) and pregnane X receptor (PXR) for grading dysplasia in patients with Barrett’s oesophagus

To investigate expression of nuclear receptors farnesoid X receptor (FXR) and pregnane X receptor (PXR) as a diagnostic tool to improve grading of dysplasia in Barrett's oesophagus patients. Immunostaining was analysed on a total of 192 biopsy samples of 22 Barrett's patients with no dysplasia (ND), 17 with low-grade dysplasia (LGD), 20 high-grade dysplasia (HGD) and 24 with adenocarcinoma (AC). Nuclear FXR expression was observed in 15 of 22 (68%) ND cases versus none of 19 HGD; 3 of 17 (18%); LGD; 5 of 60 (8%) patients with AC (P<0.001). FXR expression was highly specific for non-dysplastic tissue. Nuclear PXR was expressed in 16 of 20 (80%) HGD cases versus two of 16 (13%) LGD cases (PPV 89%). Upon examining adjacent tissue taken from HGD and AC patients, PXR expression was high in samples of all tissue types. Nuclear receptors are expressed differentially during neoplastic progression, with FXR positivity being useful to distinguish ND from dysplasia and AC. PXR nuclear expression is able to separate HGD from LGD and ND. The combination of FXR and PXR also appears to have diagnostic and possibly prognostic value, but future prospective studies are required to investigate their predictive power for neoplastic progression in Barret's oesophagus.

Evolutionary Constraints of Phosphorylation in Eukaryotes, Prokaryotes, and Mitochondria

High accuracy mass spectrometry has proven to be a powerful technology for the large scale identification of serine/threonine/tyrosine phosphorylation in the living cell. However, despite many described phosphoproteomes, there has been no comparative study of the extent of phosphorylation and its evolutionary conservation in all domains of life. Here we analyze the results of phosphoproteomics studies performed with the same technology in a diverse set of organisms. For the most ancient organisms, the prokaryotes, only a few hundred proteins have been found to be phosphorylated. Applying the same technology to eukaryotic species resulted in the detection of thousands of phosphorylation events. Evolutionary analysis shows that prokaryotic phosphoproteins are preferentially conserved in all living organisms, whereas-site specific phosphorylation is not. Eukaryotic phosphosites are generally more conserved than their non-phosphorylated counterparts (with similar structural constraints) throughout the eukaryotic domain. Yeast and Caenorhabditis elegans are two exceptions, indicating that the majority of phosphorylation events evolved after the divergence of higher eukaryotes from yeast and reflecting the unusually large number of nematode-specific kinases. Mitochondria present an interesting intermediate link between the prokaryotic and eukaryotic domains. Applying the same technology to this organelle yielded 174 phosphorylation sites mapped to 74 proteins. Thus, the mitochondrial phosphoproteome is similarly sparse as the prokaryotic phosphoproteomes. As expected from the endosymbiotic theory, phosphorylated as well as non-phosphorylated mitochondrial proteins are significantly conserved in prokaryotes. However, mitochondrial phosphorylation sites are not conserved throughout prokaryotes, consistent with the notion that serine/threonine phosphorylation in prokaryotes occurred relatively recently in evolution. Thus, the phosphoproteome reflects major events in the evolution of life.

The Carboxyl-terminal End of Cox1 Is Required for Feedback Assembly Regulation of Cox1 Synthesis in Saccharomyces cerevisiae Mitochondria

Synthesis of the largest cytochrome c oxidase (CcO) subunit, Cox1, on yeast mitochondrial ribosomes is coupled to assembly of CcO. The translational activator Mss51 is sequestered in early assembly intermediate complexes by an interaction with Cox14 that depends on the presence of newly synthesized Cox1. If CcO assembly is prevented, the level of Mss51 available for translational activation is reduced. We deleted the C-terminal 11 or 15 residues of Cox1 by site-directed mutagenesis of mtDNA. Although these deletions did not prevent respiratory growth of yeast, they eliminated the assembly-feedback control of Cox1 synthesis. Furthermore, these deletions reduced the strength of the Mss51-Cox14 interaction as detected by co-immunoprecipitation, confirming the importance of the Cox1 C-terminal residues for Mss51 sequestration. We surveyed a panel of mutations that block CcO assembly for the strength of their effect on Cox1 synthesis, both by pulse labeling and expression of the ARG8(m) reporter fused to COX1. Deletion of the nuclear gene encoding Cox6, one of the first subunits to be added to assembling CcO, caused the most severe reduction in Cox1 synthesis. Deletion of the C-terminal 15 amino acids of Cox1 increased Cox1 synthesis in the presence of each of these mutations, except pet54. Our data suggest a novel activity of Pet54 required for normal synthesis of Cox1 that is independent of the Cox1 C-terminal end.

Marginal Structural Models: unbiased estimation for longitudinal studies

In this article, we introduce Marginal Structural Models, which yield unbiased estimates of causal effects of exposures in the presence of time-varying confounding variables that also act as mediators. We describe estimation via inverse probability weighting; estimation may also be accomplished by g-computation (Robins in Latent Variable Modeling and Applications to Causality, Springer, New York, pp 69-117, 1997; van der Wal et al. in Stat Med 28:2325-2337, 2009) or targeted maximum likelihood (Rosenblum and van der Laan in Int J Biostat 6, 2010). When both time-varying confounding and mediation are present in a longitudinal setting data, Marginal Structural Models are a useful tool that provides unbiased estimates.

Corporate social disclosures in the context of national cultures and stakeholder theory

Purpose – The purpose of this study is to investigate whether corporate social disclosure levels relate to national cultures.Design/methodology/approach – The sample consisted of 600 large companies from 22 countries. Cultural measures were applied: a measure for secrecy, as proposed by Hope et al. and a newly constructed measure for generic types of cultures (Gannon), both derived from Hofstede's national culture dimensions. Two other dimensions, masculinity and long‐term orientation, not part of secrecy and generic types of culture measures, were also tested separately.Findings – A number of significant statistical relationships between corporate social disclosures and cultural measures are identified. The results are consistent with the associations suggested by stakeholder theory and a country‐specific stakeholder orientation. It is concluded that corporate social disclosure levels are likely to be influenced by national cultures.Research limitations/implications – The results of Van der Laan Smith et...

Rooted-tree solutions for tree games

In this paper, we study cooperative games with limited cooperation possibilities, represented by a tree on the set of agents. Agents in the game can cooperate if they are connected in the tree. We introduce natural extensions of the average (rooted)-tree solution (see [Herings, P., van der Laan, G., Talman, D., 2008. The average tree solution for cycle free games. Games and Economic Behavior 62, 77–92]): the marginalist tree solutions and the random tree solutions. We provide an axiomatic characterization of each of these sets of solutions. By the way, we obtain a new characterization of the average tree solution.

Hotline update of clinical trials and registries presented at the American College of Cardiology Congress 2010: ACCORD, INVEST, NAVIGATOR, RACE II, SORT OUT III, CSP-474, DOSE, ASPIRE and more.

This article gives an overview on a number of novel clinical trials in the field of cardiovascular medicine, which were presented during the Late Breaking Clinical Trial Sessions at the 59th annual meeting of the American College of Cardiology in Atlanta, USA, from 14th March to 16th March 2010. The data were presented by leading experts in the field with relevant positions in the trials. These comprehensive summaries should provide the readers with the most recent data on diagnostic and therapeutic developments in cardiovascular medicine similar as previously reported (Schirmer SH, van der Laan AM, Bohm M, Mahfoud F in Clin Res Cardiol 98:691–699, 2009; Maier LS, Schirmer SH, Walenta K, Jacobshagen C, Bohm M in Clin Res Cardiol 98:413–419, 2009).

Gain of Function Mutations in Membrane Region M2C2 of KtrB Open a Gate Controlling K+ Transport by the KtrAB System from Vibrio alginolyticus

KtrB, the K(+)-translocating subunit of the Na(+)-dependent bacterial K(+) uptake system KtrAB, consists of four M(1)PM(2) domains, in which M(1) and M(2) are transmembrane helices and P indicates a p-loop that folds back from the external medium into the cell membrane. The transmembrane stretch M(2C) is, with its 40 residues, unusually long. It consists of three parts, the hydrophobic helices M(2C1) and M(2C3), which are connected by a nonhelical M(2C2) region, containing conserved glycine, alanine, serine, threonine, and lysine residues. Several point mutations in M(2C2) led to a huge gain of function of K(+) uptake by KtrB from the bacterium Vibrio alginolyticus. This effect was exclusively due to an increase in V(max) for K(+) transport. Na(+) translocation by KtrB was not affected. Partial to complete deletions of M(2C2) also led to enhanced V(max) values for K(+) uptake via KtrB. However, several deletion variants also exhibited higher K(m) values for K(+) uptake and at least one deletion variant, KtrB(Delta326-328), also transported Na(+) faster. The presence of KtrA did not suppress any of these effects. For the deletion variants, this was due to a diminished binding of KtrA to KtrB. PhoA studies indicated that M(2C2) forms a flexible structure within the membrane allowing M(2C3) to be directed either to the cytoplasm or (artificially) to the periplasm. These data are interpreted to mean (i) that region M(2C2) forms a flexible gate controlling K(+) translocation at the cytoplasmic side of KtrB, and (ii) that M(2C2) is required for the interaction between KtrA and KtrB.

Experts' opinions on ethical issues of genetic research into Alzheimer's disease: results of a Delphi study in the Netherlands

Most publications on the ethical aspects of genetic research into Alzheimer's Disease (AD) concentrate on the differences between the opinions of professionals and non-professionals. Differences in rating of morally relevant issues between groups of professionals have not yet been described. A modified Delphi study in two rounds was held to identify differences between groups of experts (i.e. clinicians, representatives of patient organisations, ethicists and persons with a commercial background). The strongest correlation was found between the opinions of ethicists and representatives of patient organisations (0.67) and between clinicians and ethicists (0.62). Moderate correlation (0.55) was found between the opinions of clinicians and representatives of patient organisations. Persons with a commercial background showed a weak correlation with clinicians (0.41), ethicists (0.35) and representatives of patient organisations (0.30). These differences in rating of morally relevant issues between various professional groups are relevant for clinical practice and dementia care, particularly the different rating of prenatal diagnosis found between clinicians and representatives of patient organisations. Interdisciplinary consultations between various professional groups -including at least researchers, clinicians and ethicists -are recommended to guarantee that all considerations will be incorporated into the debate on ethical issues of genetic research into AD.

ATPase Domain and Interdomain Linker Play a Key Role in Aggregation of Mitochondrial Hsp70 Chaperone Ssc1

The co-chaperone Hep1 is required to prevent the aggregation of mitochondrial Hsp70 proteins. We have analyzed the interaction of Hep1 with mitochondrial Hsp70 (Ssc1) and the determinants in Ssc1 that make it prone to aggregation. The ATPase and peptide binding domain (PBD) of Hsp70 proteins are connected by a linker segment that mediates interdomain communication between the domains. We show here that the minimal Hep1 binding entity of Ssc1 consists of the ATPase domain and the interdomain linker. In the absence of Hep1, the ATPase domain with the interdomain linker had the tendency to aggregate, in contrast to the ATPase domain with the mutated linker segment or without linker, and in contrast to the PBD. The closest homolog of Ssc1, bacterial DnaK, and a Ssc1 chimera, in which a segment of the ATPase domain of Ssc1 was replaced by the corresponding segment from DnaK, did not aggregate in Delta hep1 mitochondria. The propensity to aggregate appears to be a specific property of the mitochondrial Hsp70 proteins. The ATPase domain in combination with the interdomain linker is crucial for aggregation of Ssc1. In conclusion, our results suggest that interdomain communication makes Ssc1 prone to aggregation. Hep1 counteracts aggregation by binding to this aggregation-prone conformer.

Conserved Negative Charges in the Transmembrane Segments of Subunit K of the NADH:Ubiquinone Oxidoreductase Determine Its Dependence on YidC for Membrane Insertion

All members of the Oxa1/Alb3/YidC family have been implicated in the biogenesis of respiratory and energy transducing proteins. In Escherichia coli, YidC functions together with and independently of the Sec system. Although the range of proteins shown to be dependent on YidC continues to increase, the exact role of YidC in insertion remains enigmatic. Here we show that YidC is essential for the insertion of subunit K of the NADH:ubiquinone oxidoreductase and that the dependence is due to the presence of two conserved glutamate residues in the transmembrane segments of subunit K. The results suggest a model in which YidC serves as a membrane chaperone for the insertion of the less hydrophobic, negatively charged transmembrane segments of NuoK.

Dipping Into a Shallow Pool or Beginning a Deeper Conversation: A Case Study of a Minister's Engagement With the Internet for Preaching

The study considers the question “What is the pastor's experience of engagement with the Internet for preaching?” The study responds to van der Laan's work on the potential negative impact of Internet use by Protestant Christian ministers for sermon preparation. My case study ethnographically explores one minister's experience of Internet seeking (IS) for sermon preparation alongside earlier research on clergy information behavior. The respondent recounted being actively engaged with the Internet in the course of his devotional and intentional IS. He appeared to use online sources critically, and his formal IS activities for sermon preparation were comparable to earlier descriptions of clergy IS. The negative impact of the Internet, feared by van der Laan, was not apparent in this study. I found that Internet use did offer interesting possibilities for feedback and engagement during the sermon-construction process.

Contribution of Public Relations (PR) to Corporate Social Responsibility (CSR): A Review on Malaysia Perspective

The main objectives of this study are to review on current public relations (PR) contributions to corporate socialresponsibility (CSR) programs, and also to review the current CSR activities applied in Malaysia. Numbers of researchhave been done on PR and CSR (examples Freeman, 1984; Grunig and Hunt, 1984; Hooghiemstra, 2000; Cutlip et. al,2006; Golob and Barlett, 2007; Harrison, 2007; and Argenti, 2007), and also impacts on the business (examples Cannon,1992; Gray et al., 1995; Woodward et. al, 1996; Johnson & Johnson, 2000; Volkswagen AG, 2000; Doane, 2002; AbdulRashid and Ibrahim, 2002; Van der Laan, 2004; Orlizty et. al, 2004; Kotler and Lee, 2005; Savitz and Weber, 2006;Porter and Kramer, 2006; Golob and Bartlett, 2007; and Janggu et. al, 2007). The objectives of the application of PRand CSR mainly related to “social responsibility of business which is encompasses the economic, legal, ethical anddiscretionary expectations that society has of organisations at a given point of time” (Carroll, 1979). The concept of PRand CSR are also concern for society, communities, environment, employees and ethics. CSR attracted great attention of the government, public-listed and private companies in Malaysia. This can be seen from various governmental and non-governmental efforts in creating awareness and provide initiatives to public listed and private companies to align their business objectives with CSR concerns (example The Malaysia Institute of Integrity (IIM), The Institute of Corporate Social Responsibility Malaysia (ICRM), Sahabat Alam Malaysia, and Federation of Malaysian Consumers Association and Consumers Association of Penang).

The average tree solution for cooperative games with communication structure

We study cooperative games with communication structure, represented by an undirected graph. Players in the game are able to cooperate only if they can form a network in the graph. A single-valued solution, the average tree solution, is proposed for this class of games. The average tree solution is defined to be the average of all these payoff vectors. It is shown that if a game has a complete communication structure, then the proposed solution coincides with the Shapley value, and that if the game has a cycle-free communication structure, it is the solution proposed by Herings, van der Laan and Talman in 2008. We introduce the notion of link-convexity, under which the game is shown to have a non-empty core and the average tree solution lies in the core. In general, link-convexity is weaker than convexity. For games with a cycle-free communication structure, link-convexity is even weaker than super-additivity.

Side Effects of Oral Dexamethasone Pulse Therapy for Idiopathic Sudden Sensorineural Hearing Loss

To the Editor: In reaction to clinical practice article by Steven D. Rauch (1) in the August 21 issue of the New England Journal on sudden deafness and the following correspondence in Otology Neurotology on intratympanic treatment of this disease, we would like to comment on the use of a dexamethasone 3-day pulse therapy as studied by Westerlaken et al. (2) in comparison to a 7-day prednisolone taper in a double-blind, randomized, controlled trial as mentioned on page 836 by Rauch (1). Rauch comments rightly on the possible severe side effects of corticosteroid treatment, including elevated blood sugar levels, elevated blood pressure, mood change, sleep disturbances, flushing, gastritis, and weight gain. As we implemented the 3-day dexamethasone pulse therapy treatment in our hospital after the study by Westerlaken, a former colleague of ours, we would like to stress the importance of utter care in following the exclusion criteria, like diabetes mellitus, cardiac history, hypertension, pregnancy, stomach ulcer, renal failure, use of oral anticoagulant or corticosteroids, and Cushing syndrome. We have experienced patients with raising blood pressures, mood disturbances, sleep disturbances, and flushes and observed that this seems to be more often the case in the 3-day dexamethasone treatment than in the prednisolone taper therapy. Also, 1 patient treated with the 3-day dexamethasone course developed a myocardial infarction while his previously existing diabetes mellitus derailed, without regaining the lost hearing. Obviously, that is too high a price to be paid, especially for a disease from which 45 to 65% show spontaneous improvement (3,4). Perhaps because of his preexisting (well-regulated) diabetes mellitus, our patient should not have started the treatment in the first place; however, only badly regulated insulin-dependent diabetes mellitus is one of our exclusion criteria for this type of treatment. We would like to urge physicians to take the severe risks of oral dexamethasone pulse therapy and prednisolone taper therapy seriously and refrain from prescribing this treatment to the group of patients known with exclusion criteria as previously mentioned. A hopeful but expensive alternative could be the intratympanic corticosteroid treatments that are currently being studied and discussed (5,6). However, also doing nothing might be an interesting type of treatment, although difficult for physicians; as the Cochrane Review of Wei pointed out, the efficacy of corticosteroid therapy for sudden sensorineural hearing loss remains unproven (3). Rolien H. Free, M.D., Ph.D.* Noor D. Smale, M.D.* Emile de Kleine, Ph.D.† Bernard F. A. M. van der Laan, M.D., Ph.D.* *Department of Otorhinolaryngology-Head and Neck Surgery and †University Audiological Center Groningen University Hospital Groningen The Netherlands