Publications by authors named "Anniek Visser"

A 66-year-old patient was seen at the emergency department with a skin infection of the left leg, probably erysipelas, which worsened despite the use of antibiotics. The symptoms had started 5 days earlier. The patient was respiratory and haemodynamically stable, he was not clinically ill and had relatively little pain.

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Purpose: Sigma-1 receptor ligands modulate the release of several neurotransmitters and intracellular calcium signaling. We examined the binding of a radiolabeled sigma-1 agonist in the aging rat brain with positron emission tomography (PET).

Procedures: Time-dependent uptake of [(11)C]SA4503 was measured in the brain of young (1.

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Individual differences in coping style emerge as a function of underlying variability in the activation of a mesocorticolimbic brain circuitry. Particularly serotonin seems to play an important role. For this reason, we assessed serotonin-2A receptor (5-HT2A R) binding in the brain of rats with different coping styles.

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Many patients with major depression do not respond to selective serotonin reuptake inhibitors (SSRIs). Lack of response could be due to inhibition of dopamine (DA) release by serotonin (5-HT) through 5-HT2C receptors. Combining an SSRI with a 5-HT2C antagonist may result in improved efficacy by causing simultaneous increases of 5-HT and DA.

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Objective: Point-of-care testing (POCT) cardiac troponin (cTn) measurements are being used increasingly, despite the fact that evidence on the safety of their use is outdated, not taking into account current 'gold standard' high-sensitivity cardiac troponin (hs-cTn) assays. In the present study, we aimed to compare the analytical and diagnostic performance of the AQT90-flex POCT cTnT assay (which is the POCT assay with the lowest reported 99th percentile cutoff currently available) with the laboratory-based Roche Modular E170 hs-cTnT assay.

Materials And Methods: During a 4-month prospective observational cohort study, laboratory-based hs-cTnT and POCT cTn were measured simultaneously in 261 undifferentiated chest-pain patients presenting to the emergency department (ED) of the Medical Centre Leeuwarden to determine the diagnostic accuracy of both assays in predicting acute myocardial infarction (AMI) at presentation.

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Background: Acute coronary syndrome (ACS) can be a diagnostic challenge in the emergency department (ED). Recently, the HEART score was developed, a simple bedside scoring system that quantifies risk of ischaemic events in patients with undifferentiated chest pain presenting in the ED.

Objective: In this prospective cohort study, we compared the diagnostic accuracy of HEART score and clinical gestalt (clinical judgement) for diagnosing ACS in an unselected population of patients with chest pain presenting to the ED.

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It has been hypothesized that effects of uncontrollable stress on serotonin receptor expression contribute to the etiology of stress-related disorders like depression. While the serotonin-2A receptors (5-HT2A R) are thought to be important in this context, only few studies examined effects of stress on this receptor subtype. In this study, we therefore assessed acute and long-term changes in 5HT2A R binding after social defeat stress in rats.

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Rationale: Sigma-1 receptor agonists are under investigation as potential disease-modifying agents for several CNS disorders. Donepezil, an acetylcholinesterase inhibitor used for the symptomatic treatment of Alzheimer's disease, is also a high-affinity sigma-1 agonist.

Objectives: The objectives of the present study were to investigate if the sigma-1 agonist tracer (11)C-SA4503 and microPET can be used to determine sigma-1 receptor occupancy (RO) of donepezil in the rat brain; to establish RO of donepezil at doses commonly used in rodent behavioural studies; and to determine the effective plasma concentration of donepezil required for 50 % of max-min occupancy (EC50).

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The PET tracer [(11)C]5-hydroxytryptophan ([(11)C]5-HTP), which is converted to [(11)C]5-hydroxytryptamine ([(11)C]5-HT) by aromatic amino acid decarboxylase (AADC), is thought to measure 5-HT synthesis rates. But can we measure these synthesis rates by kinetic modeling of [(11)C]5-HTP in rat? Male rats were scanned with [(11)C]5-HTP (60 minutes) after different treatments. Scans included arterial blood sampling and metabolite analysis.

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Unlabelled: Pituitary tumors are often detected only after death or at late stages of the disease when they are macroadenomas with a low surgical cure rate. Spontaneous pituitary tumors occur in rats over 1 y of age. In an ongoing study of changes in σ-1 agonist binding related to aging, several of our rats developed such tumors.

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Purpose: Preclinical positron emission tomography studies are important to follow disease progression and develop new pharmacological agents. We investigated whether kinetic modeling of 5-HT2A tracer [(11)C]MDL 100907 is possible in rats.

Procedures And Results: Kinetic modeling with either metabolite-corrected plasma curve or with the cerebellum as a reference tissue resulted in a good correlation of nondisplaceable binding potential (BPND) calculated from a two-tissue compartment model (2TCM) or different reference tissue models.

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Unlabelled: Determination of the residual β-cell mass using noninvasive tools might help to follow up the efficacy of new treatments in both type 1 (insulin-dependent) and type 2 (non-insulin-dependent) diabetes mellitus, including islet transplantation. β-cells are neuroendocrine cells that can take up and metabolize the serotonin precursor 5-hydroxytryptophan. The serotonin pathway may therefore be an attractive target for the development of an imaging tracer for residual β-cell mass.

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The serotonergic system of the brain is complex, with an extensive innervation pattern covering all brain regions and endowed with at least 15 different receptors (each with their particular distribution patterns), specific reuptake mechanisms and synthetic processes. Many aspects of the functioning of the serotonergic system are still unclear, partially because of the difficulty of measuring physiological processes in the living brain. In this review we give an overview of the conventional methods of measuring serotonin synthesis and methods using positron emission tomography (PET) tracers, more specifically with respect to serotonergic function in affective disorders.

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This article presents our experience in managing a series of consecutive patients with arteriovenous malformation (AVM) referred to our Vascular Anomalies Centre over a 14-year period. These patients were culled from our prospective Vascular Anomalies Database 1996-2010. The medical records of these patients were reviewed to supplement the data collected.

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The multi-drug efflux transporter P-glycoprotein is expressed in high concentrations at the blood-brain barrier and has a major function in the transport of drugs. In a recent PET-study evidence was found for an increased function of P-glycoprotein at the blood-brain barrier in medicated patients suffering from major depressive disorder. We used small-animal PET and [(11)C]-verapamil to study P-glycoprotein function at the blood-brain barrier of rats, either being administered as venlafaxine, an antidepressant, or subjected to chronic stress, a factor contributing to the development of depression.

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It is unclear whether protein phosphatases, which counteract the actions of protein kinases, play a beneficial role in the formation and extinction of previously acquired fear memories. In this study, we investigated the role of the calcium/calmodulin dependent phosphatase 2B, also known as calcineurin (CaN) in the formation of contextual fear memory and extinction of previously acquired contextual fear. We used a temporally regulated transgenic approach, that allowed us to selectively inhibit neuronal CaN activity in the forebrain either during conditioning or only during extinction training leaving the conditioning undisturbed.

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