Astrocytes are thought to have important roles after brain injury, but their behavior has largely been inferred from postmortem analysis. To examine the mechanisms that recruit astrocytes to sites of injury, we used in vivo two-photon laser-scanning microscopy to follow the response of GFP-labeled astrocytes in the adult mouse cerebral cortex over several weeks after acute injury. Live imaging revealed a marked heterogeneity in the reaction of individual astrocytes, with one subset retaining their initial morphology, another directing their processes toward the lesion, and a distinct subset located at juxtavascular sites proliferating. Although no astrocytes actively migrated toward the injury site, selective proliferation of juxtavascular astrocytes was observed after the introduction of a lesion and was still the case, even though the extent was reduced, after astrocyte-specific deletion of the RhoGTPase Cdc42. Thus, astrocyte recruitment after injury relies solely on proliferation in a specific niche.

Background: Tau aggregation is a multistep process. The identity of Tau species compromising cell viability remains largely unknown. Results: Analysis of Tau aggregation dynamic identifies oligomeric Tau aggregates as toxic species that impair viability. Conclusion: Membrane leakage induced by oligomeric Tau is a mechanism for toxicity. Significance: Tau belongs to the class of amyloidogenic proteins that share a common toxicity-mediating mechanism.

A series of peptide mutants was studied to understand the influence of local physical interactions on the fibril formation mechanism of amyloid β (Aβ)(1-40). In the peptide variants, the well-known hydrophobic contact between residues phenylalanine 19 and leucine 34 was rationally modified. In single site mutations, residue phenylalanine 19 was replaced by amino acids that introduce higher structural flexibility by a glycine mutation or restrict the backbone flexibility by introduction of proline. Next, the aromatic phenylalanine was replaced by tyrosine or tryptophan, respectively, to probe the influence of additional hydrogen bond forming capacity in the fibril interior. Furthermore, negatively charged glutamate or positively charged lysine was introduced to probe the influence of electrostatics. In double mutants, the hydrophobic contact was replaced by a putative salt bridge (glutamate and lysine) or two electrostatically repelling lysine residues. The influence of these mutations on the fibrillation kinetics and morphology, cross-β structure as well as the local structure and dynamics was probed using fluorescence, transmission electron microscopy, X-ray diffraction, and solid-state NMR spectroscopy. While the fibrillation kinetics and the local structure and dynamics of the peptide variants were influenced by the introduction of these local fields, the overall morphology and cross-β structure of the fibrils remained very robust against all the probed interactions. Overall, 7 out of the 8 mutated peptides formed fibrils of very similar morphology compared to the wildtype. However, characteristic local structural and dynamical changes indicate that amyloid fibrils show an astonishing ability to respond to local perturbations but overall show a very homogenous mesoscopic organization.

Recent studies demonstrated that primary immune responses can be induced within the brain depending on vessel-associated cells expressing markers of dendritic cells (DC). Using mice transcribing the green fluorescent protein (GFP) under the promoter of the DC marker CD11c, we determined the distribution, phenotype, and source of CD11c+ cells in non-diseased brains. Predilection areas of multiple sclerosis (MS) lesions (periventricular area, adjacent fibre tracts, and optical nerve) were preferentially populated by CD11c+ cells. Most CD11c+ cells were located within the juxtavascular parenchyma rather than the perivascular spaces. Virtually all CD11c+ cells co-expressed ionized calcium-binding adaptor molecule 1 (IBA-1), CD11b, while detectable levels of major histocompatibility complex II (MHC-II) in non-diseased mice was restricted to CD11c+ cells of the choroid plexus. Cellular processes project into the glia limitans which may allow transport and/or presentation of intraparenchymal antigens to extravasated T cells in perivascular spaces. In chimeric mice bearing CD11c-GFP bone marrow, fluorescent cells appeared in the CNS between 8 and 12 weeks after transplantation. In organotypic slice cultures from CD11c-GFP mice, the number of fluorescent cells strongly increased within 72 h. Strikingly, using anti-CD209, an established marker for human DC, a similar population was detected in human brains. Thus, we show for the first time that CD11c+ cells can not only be recruited from the blood into the parenchyma, but also develop from an intraneural precursor in situ. Dysbalance in their recruitment/development may be an initial step in the pathogenesis of chronic (autoimmune) neuroinflammatory diseases such as MS.

Anti-myelin immunity is commonly thought to drive multiple sclerosis, yet the initial trigger of this autoreactivity remains elusive. One of the proposed factors for initiating this disease is the primary death of oligodendrocytes. To specifically test such oligodendrocyte death as a trigger for anti-CNS immunity, we inducibly killed oligodendrocytes in an in vivo mouse model. Strong microglia-macrophage activation followed oligodendrocyte death, and myelin components in draining lymph nodes made CNS antigens available to lymphocytes. However, even conditions favoring autoimmunity-bystander activation, removal of regulatory T cells, presence of myelin-reactive T cells and application of demyelinating antibodies-did not result in the development of CNS inflammation after oligodendrocyte death. In addition, this lack of reactivity was not mediated by enhanced myelin-specific tolerance. Thus, in contrast with previously reported impairments of oligodendrocyte physiology, diffuse oligodendrocyte death alone or in conjunction with immune activation does not trigger anti-CNS immunity.

When walking in open space, collision avoidance with other pedestrians is a process that successfully takes place many times. To pass another pedestrian (an interferer) walking direction, walking speed or both can be adjusted. Currently, the literature is not yet conclusive of how humans adjust these two parameters in the presence of an interferer. This impedes the development of models predicting general obstacle avoidance strategies in humans’ walking behavior. The aim of this study was to investigate the adjustments of path and speed when a pedestrian is crossing a non-reactive human interferer at different angles and speeds, and to compare the results to general model predictions. To do so, we designed an experiment where a pedestrian walked a 12 m distance to reach a goal position. The task was designed in such a way that collision with an interferer would always occur if the pedestrian would not apply a correction of movement path or speed. Results revealed a strong dependence of path and speed adjustments on crossing angle and walking speed, suggesting local planning of the collision avoidance strategy. Crossing at acute angles (i.e. 45° and 90°) seems to require more complex collision avoidance strategies involving both path and speed adjustments than crossing at obtuse angles, where only path adjustments were observed. Overall, the results were incompatible with predictions from existing models of locomotor collision avoidance. The observed initiations of both adjustments suggest a collision avoidance strategy that is temporally controlled. The present study provides a comprehensive picture of human collision avoidance strategies in walking, which can be used to evaluate and adjust existing pedestrian dynamics models, or serve as an empirical basis to develop new models.

Background-The aim of this prospectively randomized study was to evaluate left ventricular hypertrophy and its regression after stentless versus conventional biological aortic valve replacement. Methods and Results-From March 1996 through April 1998, 180 patients were prospectively selected; 106 patients received a stentless aortic valve (SAV), and 74 received a conventional stented bioprosthesis (CSB). Of these patients, 95% and 96%, respectively, had aortic stenosis. Their mean age was 72.3 and 74.8 years, and there were no significant differences in left ventricular function, preoperative pressure gradients, and NYHA functional status. Aortic annulus diameter indexes were comparable at 13.46 (SAV) versus 13.55 (CSB) mm (PϭNS). Larger SAVs were implanted because of the oversizing technique. In-hospital mortality (nϭ3 and 1 for SAV and CSB) was not valve related. At follow-up, all patients were in NYHA class 1 or 2. Baseline end-diastolic left ventricular posterior wall thickness was 15.6 (SAV) and 14.8(CSB) mm (PϭNS) and decreased to 11.8 (SAV) and 13.2 (CSB) mm (PϽ0.05) at 6 months. Left ventricular mass index was 213 and 202 g/m 2 at baseline (PϭNS), whereas after 6 months, it was 141 (SAV) and 170 (CSB) g/m 2 (PϽ0.05). Conclusions-Regression of left ventricular hypertrophy occurs in all patients after aortic valve replacement but is significantly enhanced after SAV implantation. This possibly is due to improved transvalvular hemodynamics.

Lead optimization of a high-throughput screening hit led to the rapid identification of aminopyrimidine ZK 304709, a multitargeted CDK and VEGF-R inhibitor that displayed a promising preclinical profile. Nevertheless, ZK 304709 failed in phase I studies due to dose-limited absorption and high inter-patient variability, which was attributed to limited aqueous solubility and off-target activity against carbonic anhydrases. Further lead optimization efforts to address the off-target activity profile finally resulted in the introduction of a sulfoximine group, which is still a rather unusual approach in medicinal chemistry. However, the sulfoximine series of compounds quickly revealed very interesting properties, culminating in the identification of the nanomolar pan-CDK inhibitor BAY 1000394, which is currently being investigated in phase I clinical trials.