[Guided discontinuation of antidepressants: approach and first results of a Dutch multidisciplinary outpatient clinic]. / Werkwijze en eerste resultaten van multidisciplinaire afbouwpoli anti-depressiva.

BACKGROUND: Discontinuation of antidepressant medication can be difficult due to withdrawal symptoms and relapse risk. Scientific evidence on the questions of who, when, and how to stop antidepressants is limited. In Amsterdam a multidisciplinary outpatient clinic was started to provide advice and guidance. AIM: To substantiate the design of the clinic. Central questions relate to knowing which patients are referred, the background of their request, and their experiences with the outpatient clinic. METHOD: The first 51 patients of the clinic were described on the basis of file research, in addition a survey was conducted into patient experiences. RESULTS: Half of the patients (55%) actually started discontinuation, 39% were advised not to do so (yet). Patients at the clinic had used antidepressants for an average of 10 years, and 76% had previously attempted to stop. 21% had now successfully stopped and 25% were satisfied with a lower dose. One patient relapsed during tapering. CONCLUSION: So far, patients with long-term antidepressant use and multiple quit attempts have been referred. Our experiences are aimed at helping individual patients but can also result in more knowledge about who can stop at what moment, and how this should be done.

[Atypical fibroxanthoma and pleomorphic dermal sarcoma]. / Atypisches Fibroxanthom und pleomorphes dermales Sarkom.

Atypical fibroxanthoma (AFX) or undifferentiated pleomorphic sarcoma (UPS) is a rare malignant neoplastic disease of the skin. At the beginning of the 1960s AFX was described as an independent entity and superficial variant of malignant fibrous histiocytoma (MFH). Since then, many controversies on the classification have arisen mainly because in many cases dedifferentiated neoplasms from other origins were falsely diagnosed as AFX. A relevant deep expansion, the invasion of nerves and vessels or the presence of tumor necrosis are described as being typical for UPS; however, in the first-line they represent risk factors for recurrence. In view of the clinical and histological features it is meaningful to consider AFX and UPS as one disease. In recent years many studies on the molecular pathological background have attempted to make a better classification of the neoplasm, without being able to so far name a certain specific histopathological or molecular pathological characteristic. The AFX/UPS is still in essence a morphological and immunohistochemical diagnosis by exclusion.

Enamel: From brittle to ductile like tribological response.

OBJECTIVES: To identify the intrinsic nano-scale wear mechanisms of enamel by comparing it with that of highly brittle glass, and highly ductile copper and silver monocrystals. METHODS: A sharp cube corner indenter tip (20-50 nm radius) was used to abrade glass, enamel as well as copper and silver monocrystals. Square abraded areas (5 microm x 5 microm, 10 microm x 10 microm) were generated with loads of 50 microN for enamel and 100 microN for the remaining materials (2D abrasion). The normal load and displacement data were utilized in a complementary manner to support the comparison. In addition normal and lateral forces were simultaneously measured along 10 microm single scratched lines (1D abrasion). Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were also used to characterise the worn areas and debris. RESULTS: The sharp tip cuts into and ploughs the specimens creating a wedge or ridge of material ahead of itself which eventually detaches, for the ductile materials and at high loads in enamel. For glass and enamel at low loads, the indenter tip ploughs into the material and the removed material is redistributed and pressed back into the abraded area. CONCLUSIONS: The wear behaviour of enamel at the nano-level resembles that obtained with glass at low loads (50 microN) and that obtained with metal mono-crystals at high load (100 microN). The role of the microstructural heterogeneity in the wear behaviour of enamel is considered in the discussion. The relevance to clinical wear of enamel is also considered.

Individual MHC class I and MHC class IIB diversities are associated with male and female reproductive traits in the three-spined stickleback.

Genes of the major histocompatibility complex (MHC) are indispensable for pathogen defence in vertebrates. With wild-caught three-spined sticklebacks (Gasterosteus aculeatus) we conducted the first study to relate individual reproductive parameters to both MHC class I and II diversities. An optimal MHC class IIB diversity was found for male nest quality. However, male breeding colouration was most intense at a maximal MHC class I diversity. One MHC class I allele was associated with male redness. Similarly, one MHC class IIB allele was associated with continuous rather than early female reproduction, possibly extending the reproductive period. Both alleles occurred more frequently with increasing individual allele diversity. We suggest that if an allele is currently not part of the optimum, it had not been propagated by choosy females. The parasite against which this allele provides resistance is therefore unlikely to have been predominant the previous year - a step to negative frequency-dependent selection.

The "sticky chain": a kinetic model for the deformation of biological macromolecules.

The deformation behavior of certain biologic macromolecules is modeled by the "sticky chain," a freely jointed chain with weak bonds between subsequent joints. Straining the chain leads to thermally assisted breaking of the weak bonds, yielding a characteristic shape of the force-elongation curve, usually with a pronounced plateau, but sometimes displaying a pseudo-Hookean behavior over a wide range of deformations. The number of individual links is assumed to be large, so the stochastic time evolution of the individual events can be approximated by a differential equation. The cases of individual and collective bond breaking are treated and formulae given for various measurable quantities. A threshold strain rate is found, below which the deformation force no longer depends on the deformation velocity. The method is applied to experimental results for the deformation of single molecules like titin or DNA and the results agree with the parameters deduced from the same experiments by the original authors using Monte Carlo (MC) calculations. Despite its intrinsic continuous character, the model, therefore, is applicable even for the deformation of macromolecules with only a few discrete unfolding elements, yielding physical quantities from experimental results using simple formulae instead of a host of MC computations.

Mineralized collagen fibrils: a mechanical model with a staggered arrangement of mineral particles.

Both elastic modulus and fracture stress are known to increase with the amount of mineral deposited within collagen fibrils. Current mechanical models of mineralized fibrils, where mineral platelets are arranged in parallel arrays, reproduce the first effect but fail to predict an increase in fracture stress. Here, we propose a model with a staggered array of platelets that is in better agreement with results on molecular packing in collagen fibrils and that accounts for an increase of both elastic modulus and fracture stress with the amount of mineral in the fibril. Finally, we explore the dependence of the mechanical properties within the model, when the degree of mineralization and the thickness of the platelets as well as their distance varies.