Comparison of size distribution and (Pro249-Ser258) epitope exposure in in vitro and in vivo derived Tau fibrils

BACKGROUND

Although several studies demonstrate prion-like properties of Tau fibrils, the effect of size in the seeding capacity of these aggregates is not fully understood. The aim of this study is to characterize Tau seeds by their size and seeding capacity.

METHODS

Tau aggregates were isolated from postmortem AD brain tissue and separated from low molecular weight species by sucrose gradient ultracentrifugation. Biochemical characterization of the different fractions was done by non-reducing Western blotting and aggregate-specific immuno-assays using in house developed anti-Tau monoclonal antibodies, including PT76 which binds to an epitope close to the microtubule-binding domain and, hence, also to K18. Seeding efficiency was then assessed in HEK293 cells expressing K18 FRET sensors.

RESULTS

We observed that upon sonication of Tau aggregates different size-distributed tau aggregates are obtained. In biochemical assays, these forms show higher signals than the non-sonicated material in some aggregation-specific Tau assays. This could be explained by an increased epitope exposure of the smaller aggregates created by the sonication. By analyzing human brain derived and recombinant (K18) Tau aggregates in a cellular FRET assay, it was observed that, in the absence of transfection reagent, sonicated aggregates showed higher aggregation induction. Preparations also showed altered profiles on native PAGE upon sonication and we could further separate different aggregate species based on their molecular weight via sucrose gradients.

CONCLUSIONS

This study further elucidates the molecular properties regarding relative aggregate size and seeding efficiency of sonicated vs. non-sonicated high molecular weight Tau species. This information will provide a better knowledge on how sonication, a commonly used technique in the field of study of Tau aggregation, impacts the aggregates. In addition, the description of PT76-based aggregation specific assay is a valuable tool to quantify K18 and human AD Tau fibrils.

Anti-Tau Monoclonal Antibodies Derived from Soluble and Filamentous Tau Show Diverse Functional Properties in vitro and in vivo

The tau spreading hypothesis provides rationale for passive immunization with an anti-tau monoclonal antibody to block seeding by extracellular tau aggregates as a disease-modifying strategy for the treatment of Alzheimer's disease (AD) and potentially other tauopathies. As the biochemical and biophysical properties of the tau species responsible for the spatio-temporal sequences of seeding events are poorly defined, it is not yet clear which epitope is preferred for obtaining optimal therapeutic efficacy. Our internal tau antibody collection has been generated by immunizations with different tau species: aggregated- and non-aggregated tau and human postmortem AD brain-derived tau fibrils. In this communication, we describe and characterize a set of these anti-tau antibodies for their biochemical and biophysical properties, including binding, tissue staining by immunohistochemistry, and epitope. The antibodies bound to different domains of the tau protein and some were demonstrated to be isoform-selective (PT18 and hTau56) or phospho-selective (PT84). Evaluation of the antibodies in cellular- and in vivo seeding assays revealed clear differences in maximal efficacy. Limited proteolysis experiments support the hypothesis that some epitopes are more exposed than others in the tau seeds. Moreover, antibody efficacy seems to depend on the structural properties of fibrils purified from tau Tg mice- and postmortem human AD brain.

Optimization of lipid extraction from the oleaginous yeasts Rhodotorula glutinis and Lipomyces kononenkoae

The constant growing demand for vegetable oil for biodiesel and food is raising many environmental concerns about the sustainability of its production based on crops. Oleaginous yeasts show great potential to end with those concerns due to their high lipid productivity in small areas. To evaluate their productivity in lipids, an efficient and reproducible extraction process should be used. As no standard extraction process is available for the extraction of yeast lipids, an optimized extraction process is presented. In this work, the lipids extraction process for the yeasts Rhodotorula glutinis and Lipomyces kononenkoae is optimized using bead beating for cell rupture and introducing adaptations of the two most used extraction methods (Bligh and Dyer and Folch). For Rhodotorula g. the optimum extraction conditions are obtained by the Bligh and Dyer method applying 4.8 cycles of 47 s with 0.7 g of glass beads. For Lipomyces k. the optimum extraction conditions make use of the Folch method applying seven cycles of 42 s with 0.54 g of glass beads. These results reinforce the idea that, for each yeast, different extraction processes may be needed to correctly determine the lipid yield. The extraction procedure was further evaluated with less harmful solvents. Toluene was tested as a possible substitute of chloroform, and ethanol as a possible substitute of methanol. With the optimized extraction process, better results for Lipomyces k. were obtained using toluene and ethanol, while for Rhodotorula g. toluene proved to be a valid substitute of chloroform but ethanol is far less effective than methanol.

Análise até a Deformação de dois Sistemas Rotatórios Com Tratamento da Fase R na Instrumentação de Condutos Radiculares Curvos

É sabido que a incidência de curvaturas em condutos radiculares é elevada, principalmente em dentes molares, e que a não instrumentação destas pode comprometer o tratamento endodôntico. Esta pesquisa foi submetida ao Comitê de Ética em Pesquisa com parecer nº 1.197.375 e teve como objetivo analisar, por meio de um ensaio laboratorial, a durabilidade até a deformação de 2 sistemas rotatórios com tratamento da Fase R, quando utilizados em condutos radiculares curvos de molares extraídos. Foram selecionados inicialmente 150 molares, apresentando curvaturas, estes, foram acessados, e radiografados com a lima 15 posicionada até o forame, determinando suas curvaturas. Dentes que apresentavam 1 ou mais condutos curvos foram incluídos no presente trabalho. Dividiu-se, por meio de uma análise estatística os 120 condutos selecionados em 6 conjuntos de 20 condutos cada. Foi analisada a durabilidade dos 2 sistemas rotatórios, K3 XF (sequência RCS) e Twisted File (Kit Large), acionados por motor elétrico. Foram utilizados 3  kits de cada sistema, sendo, que cada kit totalizou a instrumentação 20 condutos curvos ou até ocorrer a deformação das espiras da lima utilizada. A análise estatística se deu pelo teste ANOVA (p>0,05) e uma avaliação qualitativa foi realizada. Como resultados, constatou-se que, não houve diferença estatística entre os sistemas K3 XF e TF quanto ao número de condutos instrumentados até a deformação, tendo o sistema TF instrumentado 5,72 condutos até a deformação e o sistema K3 XF 6,12.Palavras-chave: Endodontia. Fadiga. Instrumentação.

Modular multipin electrodes for comfortable dry EEG

Electrode and cap concepts for continuous and ubiquitous monitoring of brain activity will open up new fields of application and contribute to increased use of electroencephalography (EEG) in clinical routine, neurosciences, brain-computer-interfacing and out-of-the-lab monitoring. However, mobile and unobtrusive applications are currently hindered by the lack of applicable convenient and reliable electrode and cap systems. We propose a novel modular electrode concept based on a flexible polymer substrate, coated with electrically conductive metallic films. The overall concept enables design adaptation to different head regions and cap designs. We describe the single modules of the system and investigate the influence of electrode pin number, coating material and adduction force on electrode-skin impedance and perceived wearing comfort. Our results contribute to rapid and comfortable multichannel dry EEG.

Heterotypic seeding of Tau fibrillization by pre-aggregated Abeta provides potent seeds for prion-like seeding and propagation of Tau-pathology in vivo

Genetic, clinical, histopathological and biomarker data strongly support Beta-amyloid (Aβ) induced spreading of Tau-pathology beyond entorhinal cortex (EC), as a crucial process in conversion from preclinical cognitively normal to Alzheimer‘s Disease (AD), while the underlying mechanism remains unclear. In vivo preclinical models have reproducibly recapitulated Aβ-induced Tau-pathology. Tau pathology was thereby also induced by aggregated Aβ, in functionally connected brain areas, reminiscent of a prion-like seeding process. In this work we demonstrate, that pre-aggregated Aβ can directly induce Tau fibrillization by cross-seeding, in a cell-free assay, comparable to that demonstrated before for alpha-synuclein and Tau. We furthermore demonstrate, in a well-characterized cellular Tau-aggregation assay that Aβ-seeds cross-seeded Tau-pathology and strongly catalyzed pre-existing Tau-aggregation, reminiscent of the pathogenetic process in AD. Finally, we demonstrate that heterotypic seeded Tau by pre-aggregated Aβ provides efficient seeds for induction and propagation of Tau-pathology in vivo. Prion-like, heterotypic seeding of Tau fibrillization by Aβ, providing potent seeds for propagating Tau pathology in vivo, as demonstrated here, provides a compelling molecular mechanism for Aβ-induced propagation of Tau-pathology, beyond regions with pre-existing Tau-pathology (entorhinal cortex/locus coeruleus). Cross-seeding along functional connections could thereby resolve the initial spatial dissociation between amyloid- and Tau-pathology, and preferential propagation of Tau-pathology in regions with pre-existing ‘silent’ Tau-pathology, by conversion of a ‘silent’ Tau pathology to a ‘spreading’ Tau-pathology, observed in AD.

Templated misfolding of Tau by prion-like seeding along neuronal connections impairs neuronal network function and associated behavioral outcomes in Tau transgenic mice

Prion-like seeding and propagation of Tau-pathology have been demonstrated experimentally and may underlie the stereotyped progression of neurodegenerative Tauopathies. However, the involvement of templated misfolding of Tau in neuronal network dysfunction and behavioral outcomes remains to be explored in detail. Here we analyzed the repercussions of prion-like spreading of Tau-pathology via neuronal connections on neuronal network function in TauP301S transgenic mice. Spontaneous and GABA(A)R-antagonist-induced neuronal network activity were affected following templated Tau-misfolding using synthetic preformed Tau fibrils in cultured primary neurons. Electrophysiological analysis in organotypic hippocampal slices of Tau transgenic mice demonstrated impaired synaptic transmission and impaired long-term potentiation following Tau-seed induced Tau-aggregation. Intracerebral injection of Tau-seeds in TauP301S mice, caused prion-like spreading of Tau-pathology through functionally connected neuroanatomical pathways. Electrophysiological analysis revealed impaired synaptic plasticity in hippocampal CA1 region 6 months after Tau-seeding in entorhinal cortex (EC). Furthermore, templated Tau aggregation impaired cognitive function, measured in the object recognition test 6 months post-seeding. In contrast, Tau-seeding in basal ganglia and subsequent spreading through functionally connected neuronal networks involved in motor control, resulted in motoric deficits reflected in clasping and impaired inverted grid hanging, not significantly affected following Tau-seeding in EC. Immunostaining, biochemical and electron microscopic analysis in the different models suggested early pathological forms of Tau, including Tau-oligomers, rather than fully mature neurofibrillary tangles (NFTs) as culprits of neuronal dysfunction. We here demonstrate for the first time using in vitro, ex vivo and in vivo models, that prion-like spreading of Tau-misfolding by Tau seeds, along unique neuronal connections, causes neuronal network dysfunction and associated behavioral dysfunction. Our data highlight the potential relevance of this mechanism in the symptomatic progression in Tauopathies. We furthermore demonstrate that the initial site of Tau-seeding thereby determines the behavioral outcome, potentially underlying the observed heterogeneity in (familial) Tauopathies, including in TauP301 mutants.

Models of β-amyloid induced Tau-pathology: the long and "folded" road to understand the mechanism

The amyloid cascade hypothesis has been the prevailing hypothesis in Alzheimer’s Disease research, although the final and most wanted proof i.e. fully successful anti-amyloid clinical trials in patients, is still lacking. This may require a better in depth understanding of the cascade. Particularly, the exact toxic forms of Aβ and Tau, the molecular link between them and their respective contributions to the disease process need to be identified in detail. Although the lack of final proof has raised substantial criticism on the hypothesis per se, accumulating experimental evidence in in vitro models, in vivo models and from biomarkers analysis in patients supports the amyloid cascade and particularly Aβ-induced Tau-pathology, which is the focus of this review. We here discuss available models that recapitulate Aβ-induced Tau-pathology and review some potential underlying mechanisms. The availability and diversity of these models that mimic the amyloid cascade partially or more complete, provide tools to study remaining questions, which are crucial for development of therapeutic strategies for Alzheimer’s Disease.

Intracerebral injection of preformed synthetic tau fibrils initiates widespread tauopathy and neuronal loss in the brains of tau transgenic mice

Neurofibrillary tangles composed of hyperphosphorylated fibrillized tau are found in numerous tauopathies including Alzheimer's disease. Increasing evidence suggests that tau pathology can be transmitted from cell-to-cell; however the mechanisms involved in the initiation of tau fibrillization and spreading of disease linked to progression of tau pathology are poorly understood. We show here that intracerebral injections of preformed synthetic tau fibrils into the hippocampus or frontal cortex of young tau transgenic mice expressing mutant human P301L tau induces tau hyperphosphorylation and aggregation around the site of injection, as well as a time-dependent propagation of tau pathology to interconnected brain areas distant from the injection site. Furthermore, we show that the tau pathology as a consequence of injection of tau preformed fibrils into the hippocampus induces selective loss of CA1 neurons. Together, our data confirm previous studies on the seeded induction and the spreading of tau pathology in a different tau transgenic mouse model and reveals neuronal loss associated with seeded tau pathology in tau transgenic mouse brain. These results further validate the utility of the tau seeding model in studying disease transmission, and provide a more complete in vivo tauopathy model with associated neurodegeneration which can be used to investigate the mechanisms involved in tau aggregation and spreading, as well as aid in the search for disease modifying treatments for Alzheimer's disease and related tauopathies.

Tauopathy contributes to synaptic and cognitive deficits in a murine model for Alzheimer's disease

Tau alterations are now considered an executor of neuronal demise and cognitive dysfunction in Alzheimer's disease (AD). Mouse models combining amyloidosis and tauopathy and their parental counterparts are important tools to further investigate the interplay of abnormal amyloid-β (Aβ) and Tau species in pathogenesis, synaptic and neuronal dysfunction, and cognitive decline. Here, we crossed APP/PS1 mice with 5 early-onset familial AD mutations (5xFAD) and TauP301S (PS19) transgenic mice, denoted F(+)/T(+) mice, and phenotypically compared them to their respective parental strains, denoted F(+)/T(-) and F(-)/T(+) respectively, as controls. We found dramatically aggravated tauopathy (~10-fold) in F(+)/T(+) mice compared to the parental F(-)/T(+) mice. In contrast, amyloidosis was unaltered compared to the parental F(+)/T(-) mice. Tauopathy was invariably and very robustly aggravated in hippocampal and cortical brain regions. Most important, F(+)/T(+) displayed aggravated cognitive deficits in a hippocampus-dependent spatial navigation task, compared to the parental F(+)/T(-) strain, while parental F(-)/T(+) mice did not display cognitive impairment. Basal synaptic transmission was impaired in F(+)/T(+) mice compared to nontransgenic mice and the parental strains (≥40%). Finally, F(+)/T(+) mice displayed a significant hippocampal atrophy (~20%) compared to nontransgenic mice, in contrast to the parental strains. Our data indicate for the first time that pathological Aβ species (or APP/PS1) induced changes in Tau contribute to cognitive deficits correlating with synaptic deficits and hippocampal atrophy in an AD model. Our data lend support to the amyloid cascade hypothesis with a role of pathological Aβ species as initiator and pathological Tau species as executor.

Study on the impact of exposure to noise in professional snipers

Facing an increasing violence level and higher firepower in the hands of criminal organizations (especially those related to drug trafficking), the Military Police of Pernambuco has created, in 1989, the "1a Companhia Independente de Operações Especiais" (1st Independent Company of Special Operations), as a tactical last resort of the Police to be used on special, complex situations. The CIOE progressively makes use of Negotiation measures, of less-than-lethal maneuvers, of Precision Shots and Tactical Assaults. When all possibilities are drained, the Precision Shot will bring the crisis perpetrator down. This study had as an objective to assess the level of impact noise suffered by the elite snipers of the 1st CIOE-PE in their training. The working conditions of the snipers were evaluated through the use of a semi-structured questionnaire. Noise measuring was done on four (4) .308 IMBEL AGLC (with ammo from the same lot) rifles. Six (6) shots were fired off each gun, separated by a 30-second pause. In the end, it has been concluded that the noise level the 1st CIOE snipers are submitted to is considered to be normal by Brazilian legislation.

Development of temporomandibular joint ankylosis in rats: a preliminary experimental study

The objective of this study was to evaluate a model for the development of temporomandibular joint ankylosis in rats using disc removal and articular damage. In 30 adult male Wistar rats, articular damage was induced and disc removal performed in the right joint to induce ankylosis. The rats were divided into groups according to the time of killing (7, 15, 30, 60 and 90 days). Maximal mouth opening, mandibular deviation, initial and final weights, and duration of surgery were recorded and evaluated. After death, the joints were submitted to histological study in order to score the ankylosis. The mean duration of surgery was 14.23 min. Mean difference between initial and final maximal mouth opening was 3.38 mm, being greatest at the 15-day evaluation and lowest at 90 days, and was statistically significant at 15 days (p=0.043), 30 days (p=0.027) and 60 days (p=0.027). No mandibular deviation was observed at any of the evaluation times. Histological scores increased with time of evaluation from 7 to 30 days, when they started to fall. This study model permitted the development of fibrous ankylosis in the majority of the animals, and no bony bridge was observed between the mandibular condyle and the temporal bone.