Micro- and nanosystems for biology and medicine

The development of new tools and instruments for biomedical applications based on nano- (NEMS) or microelectromechanical systems technology (MEMS) are bridging the gap between the macro- and the nano-world. The well mastered microtechnique allows controlling many parameters of these instruments, which is essential for conducting reproducible and repeatable experiments in the life sciences. Examples are multifunctional scanning probe sensors for cell biology, an arthroscopic scanning force microscope for minimally invasive medical interventions and a nanopore sensor for single molecule experiments in biochemistry. This paper reviews some of the activities conducted in a fruitful interdisciplinary collaboration between physicists, engineers, biologists and physicians

An unusual case of persistent groin pain after total hip arthroplasty: a case report

ABSTRACT: INTRODUCTION: Arthroplasty is a well-established routine elective surgical procedure in orthopaedics. To a great extent, diagnosis, treatment and post-operative rehabilitation in these patients is standardised. In a busy clinic, surgeons from time to time tend to focus their attention on common causes of joint pain, but it may lead them to overlook sinister but less common pathologies. Here we report a case of a patient with groin pain due to pre-operatively undetected pelvic metastases from a pyeloureteral carcinoma who underwent total hip arthroplasty. There are several case reports which deal with primary or secondary tumours which were either discovered at the time of replacement surgery or developed at the site of prosthesis years after total hip or knee replacement. To the best of our knowledge, this is the first case report in which a metastatic cancer was missed pre-operatively and intra-operatively both by the radiologist and by the orthopaedic surgeon and should be reported so that surgeons are reminded to be careful when dealing with seemingly routine cases. CASE PRESENTATION: A 79-year-old Caucasian woman presented to the arthroplasty clinic with groin pain. Initial radiographs showed subtle bilateral abnormalities in the pelvis. Neither the radiologist nor the orthopaedic surgeon recognized it. A diagnosis of osteoarthritis of the hip was established, and she underwent total hip arthroplasty. Despite initial improvement, the patient came back with worsening hip pain three months later. Further radiological examination revealed multiple metastatic lesions throughout the pelvis due to a pyeloureteral carcinoma. CONCLUSIONS: This case report emphasizes the importance of meticulous, unbiased pre-operative assessment of patients and their radiographs, even in so-called routine clinical cases. Often subtle radiological changes are classed as normal, especially if they are bilateral. Further radiological imaging should be recommended in all cases where unexplained clinical features or radiological findings are present

Stress avulsion of the tibial tuberosity after tension band wiring of a patellar fracture: a case report

INTRODUCTION: To the best of our knowledge there is no other report of an elderly patient who was surgically treated for a patellar fracture with tension band wiring and who subsequently suffered from an avulsion fracture of the tibial tuberosity. The combination of a patellar fracture and avulsion of the patellar ligament has only been described as complication after bone-patellar tendon-bone anterior cruciate ligament reconstructions. However, due to demographic changes and more elderly patients treated this injury may become more frequent in future. CASE PRESENTATION: We present the case of an 81 year old female who sustained an oblique patellar fracture after a direct contact injury of the left knee when falling on ice. Consequently the patellar fracture was openly reduced and stabilized with tension band wiring. The follow-up was uneventful till three months after surgery when the patient noticed a spontaneous avulsion fracture of the tibial tuberosity (Ogden type 3). The tibial tuberosity fragment was reattached with two non-resorbable sutures looped around two modified AO cortical 3.5 mm long neck screws. Intraoperatively multiple bone cysts were seen. Biopsies were not taken to prevent further fragmentation of the tibial tuberosity. The patient was followed up with anteroposterior and lateral full weight bearing radiographs and clinical assessment at 6, 12 weeks and 6 months after surgery. Recovery was completely pain free with full satisfaction. CONCLUSION: In conclusion in elderly patients with a patella fracture a possible associated but not obvious fracture of the tibial tuberosity should be ruled out and the postoperative rehabilitation protocol after tension band wiring of the patella might have to be individually adjusted to bone quality and course of the fracture

Clinical value of SPECT/CT for evaluation of patients with painful knees after total knee arthroplasty- a new dimension of diagnostics?

<p>Abstract</p> <p>Background</p> <p>The purpose of our study was to evaluate the clinical value of hybrid SPECT/CT for the assessment of patients with painful total knee arthroplasty (TKA).</p> <p>Methods</p> <p>Twenty-three painful knees in patients following primary TKA were assessed using Tc-99m-HDP-SPECT/CT. Rotational, sagittal and coronal position of the TKA was assessed on 3D-CT reconstructions. The level of the SPECT-tracer uptake (0-10) and its anatomical distribution was mapped using a validated localization scheme. Univariate analysis (Wilcoxon-Mann-Whitney, Spearmean`s-rho test, p < 0.05) was performed to identify any correlations between component position, tracer uptake and diagnosis.</p> <p>Results</p> <p>SPECT/CT imaging changed the suspected diagnosis and the proposed treatment in 19/23 (83%) knees. Progression of patellofemoral OA (n = 11), loosening of the tibial (n = 3) and loosening of the femoral component (n = 2) were identified as the leading causes of pain after TKA.</p> <p>Patients with externally rotated tibial trays showed higher tracer uptake in the medial patellar facet (p = 0.049) and in the femur (p = 0.051). Patients with knee pain due to patellofemoral OA showed significantly higher tracer uptake in the patella than others (p < 0.001).</p> <p>Conclusions</p> <p>SPECT/CT was very helpful in establishing the diagnosis and guiding subsequent management in patients with painful knees after TKA, particularly in patients with patellofemoral problems and malpositioned or loose TKA.</p

Capture, Reconstruction, and Representation of the Visual Real World for Virtual Reality

We provide an overview of the concerns, current practice, and limitations for capturing, reconstructing, and representing the real world visually within virtual reality. Given that our goals are to capture, transmit, and depict complex real-world phenomena to humans, these challenges cover the opto-electro-mechanical, computational, informational, and perceptual fields. Practically producing a system for real-world VR capture requires navigating a complex design space and pushing the state of the art in each of these areas. As such, we outline several promising directions for future work to improve the quality and flexibility of real-world VR capture systems

Biodiversity effects on ecosystem functioning in a 15-year grassland experiment: Patterns, mechanisms, and open questions

In the past two decades, a large number of studies have investigated the relationship between biodiversity and ecosystem functioning, most of which focussed on a limited set of ecosystem variables. The Jena Experiment was set up in 2002 to investigate the effects of plant diversity on element cycling and trophic interactions, using a multi-disciplinary approach. Here, we review the results of 15 years of research in the Jena Experiment, focussing on the effects of manipulating plant species richness and plant functional richness. With more than 85,000 measures taken from the plant diversity plots, the Jena Experiment has allowed answering fundamental questions important for functional biodiversity research. First, the question was how general the effect of plant species richness is, regarding the many different processes that take place in an ecosystem. About 45% of different types of ecosystem processes measured in the ‘main experiment’, where plant species richness ranged from 1 to 60 species, were significantly affected by plant species richness, providing strong support for the view that biodiversity is a significant driver of ecosystem functioning. Many measures were not saturating at the 60-species level, but increased linearly with the logarithm of species richness. There was, however, great variability in the strength of response among different processes. One striking pattern was that many processes, in particular belowground processes, took several years to respond to the manipulation of plant species richness, showing that biodiversity experiments have to be long-term, to distinguish trends from transitory patterns. In addition, the results from the Jena Experiment provide further evidence that diversity begets stability, for example stability against invasion of plant species, but unexpectedly some results also suggested the opposite, e.g. when plant communities experience severe perturbations or elevated resource availability. This highlights the need to revisit diversity–stability theory. Second, we explored whether individual plant species or individual plant functional groups, or biodiversity itself is more important for ecosystem functioning, in particular biomass production. We found strong effects of individual species and plant functional groups on biomass production, yet these effects mostly occurred in addition to, but not instead of, effects of plant species richness. Third, the Jena Experiment assessed the effect of diversity on multitrophic interactions. The diversity of most organisms responded positively to increases in plant species richness, and the effect was stronger for above- than for belowground organisms, and stronger for herbivores than for carnivores or detritivores. Thus, diversity begets diversity. In addition, the effect on organismic diversity was stronger than the effect on species abundances. Fourth, the Jena Experiment aimed to assess the effect of diversity on N, P and C cycling and the water balance of the plots, separating between element input into the ecosystem, element turnover, element stocks, and output from the ecosystem. While inputs were generally less affected by plant species richness, measures of element stocks, turnover and output were often positively affected by plant diversity, e.g. carbon storage strongly increased with increasing plant species richness. Variables of the N cycle responded less strongly to plant species richness than variables of the C cycle. Fifth, plant traits are often used to unravel mechanisms underlying the biodiversity–ecosystem functioning relationship. In the Jena Experiment, most investigated plant traits, both above- and belowground, were plastic and trait expression depended on plant diversity in a complex way, suggesting limitation to using database traits for linking plant traits to particular functions. Sixth, plant diversity effects on ecosystem processes are often caused by plant diversity effects on species interactions. Analyses in the Jena Experiment including structural equation modelling suggest complex interactions that changed with diversity, e.g. soil carbon storage and greenhouse gas emission were affected by changes in the composition and activity of the belowground microbial community. Manipulation experiments, in which particular organisms, e.g. belowground invertebrates, were excluded from plots in split-plot experiments, supported the important role of the biotic component for element and water fluxes. Seventh, the Jena Experiment aimed to put the results into the context of agricultural practices in managed grasslands. The effect of increasing plant species richness from 1 to 16 species on plant biomass was, in absolute terms, as strong as the effect of a more intensive grassland management, using fertiliser and increasing mowing frequency. Potential bioenergy production from high-diversity plots was similar to that of conventionally used energy crops. These results suggest that diverse ‘High Nature Value Grasslands’ are multifunctional and can deliver a range of ecosystem services including production-related services. A final task was to assess the importance of potential artefacts in biodiversity–ecosystem functioning relationships, caused by the weeding of the plant community to maintain plant species composition. While the effort (in hours) needed to weed a plot was often negatively related to plant species richness, species richness still affected the majority of ecosystem variables. Weeding also did not negatively affect monoculture performance; rather, monocultures deteriorated over time for a number of biological reasons, as shown in plant-soil feedback experiments. To summarize, the Jena Experiment has allowed for a comprehensive analysis of the functional role of biodiversity in an ecosystem. A main challenge for future biodiversity research is to increase our mechanistic understanding of why the magnitude of biodiversity effects differs among processes and contexts. It is likely that there will be no simple answer. For example, among the multitude of mechanisms suggested to underlie the positive plant species richness effect on biomass, some have received limited support in the Jena Experiment, such as vertical root niche partitioning. However, others could not be rejected in targeted analyses. Thus, from the current results in the Jena Experiment, it seems likely that the positive biodiversity effect results from several mechanisms acting simultaneously in more diverse communities, such as reduced pathogen attack, the presence of more plant growth promoting organisms, less seed limitation, and increased trait differences leading to complementarity in resource uptake. Distinguishing between different mechanisms requires careful testing of competing hypotheses. Biodiversity research has matured such that predictive approaches testing particular mechanisms are now possible

Can current moisture responses predict soil CO2 efflux under altered precipitation regimes? A synthesis of manipulation experiments

As a key component of the carbon cycle, soil CO2 efflux (SCE) is being increasingly studied to improve our mechanistic understanding of this important carbon flux. Predicting ecosystem responses to climate change often depends on extrapolation of current relationships between ecosystem processes and their climatic drivers to conditions not yet experienced by the ecosystem. This raises the question of to what extent these relationships remain unaltered beyond the current climatic window for which observations are available to constrain the relationships. Here, we evaluate whether current responses of SCE to fluctuations in soil temperature and soil water content can be used to predict SCE under altered rainfall patterns. Of the 58 experiments for which we gathered SCE data, 20 were discarded because either too few data were available or inconsistencies precluded their incorporation in the analyses. The 38 remaining experiments were used to test the hypothesis that a model parameterized with data from the control plots (using soil temperature and water content as predictor variables) could adequately predict SCE measured in the manipulated treatment. Only for 7 of these 38 experiments was this hypothesis rejected. Importantly, these were the experiments with the most reliable data sets, i.e., those providing high-frequency measurements of SCE. Regression tree analysis demonstrated that our hypothesis could be rejected only for experiments with measurement intervals of less than 11 days, and was not rejected for any of the 24 experiments with larger measurement intervals. This highlights the importance of high-frequency measurements when studying effects of altered precipitation on SCE, probably because infrequent measurement schemes have insufficient capacity to detect shifts in the climate dependencies of SCE. Hence, the most justified answer to the question of whether current moisture responses of SCE can be extrapolated to predict SCE under altered precipitation regimes is 'no' - as based on the most reliable data sets available. We strongly recommend that future experiments focus more strongly on establishing response functions across a broader range of precipitation regimes and soil moisture conditions. Such experiments should make accurate measurements of water availability, should conduct high-frequency SCE measurements, and should consider both instantaneous responses and the potential legacy effects of climate extremes. This is important, because with the novel approach presented here, we demonstrated that, at least for some ecosystems, current moisture responses could not be extrapolated to predict SCE under altered rainfall conditions