Nutrition and colony investment in Solenopsis invicta workers

Dissertação de Mestrado em Biologia Celular e Molecular, apresentada ao Departamento de Ciências da Vida Da Faculdade de Ciências e Tecnologia da Universidade de Coimbra.A proteína Tau é responsável pela ligação e estabilização dos microtúbulos (MT) no citoesqueleto, sendo fundamental na função neuronal. A atividade desta proteína pode ser regulada por modificações pós-translacionais, como a fosforilação, que promovem a separação dos microtúbulos. A alteração na conformação da Tau provocada por uma deficiente regulação, como a híper-fosforilação, causa destabilização dos MT e agregação da mesma em filamentos helicoidais emparelhados e tranças neurofibrilares. Estas estruturas são uma das principais características na doença de Alzheimer (AD), e o seu processo de formação pode representar um dos principais motivos que leva a morte celular nas Tauopatias, inclusivamente AD e outras patologias neurodegenerativas. Nos últimos anos, recursos têm sido empregues na descoberta de novas estratégias que permitam diminuir a formação ou diminuam a quantidade de agregados da Tau dentro das células. Estudos recentes identificaram a indução da autofagia através da rapamicina como um dos potenciais alvos no aumento da remoção de agregados proteicos associados a doenças neurodegenerativas, melhorando também a esperança de vida em ratos e outros modelos. Recentemente, o nosso laboratório desenvolveu um modelo celular baseado no trabalho de Guo e Lee (2011) que mimetiza a agregação intracelular da Tau depois de induzida a expressão de uma forma mutada desta proteína seguido do seeding com fibrilas K18:P301L pré-agregadas. Neste estudo, foi possível demonstrar como a utilização destes modelos permite identificar novos compostos com atividade nas vias de redução da Tau. Curiosamente estas moléculas foram responsáveis pelo desenvolvimento de um fenótipo vesicular que identificámos como sendo lisossomas, derivados de um possível estímulo na via endócitica. As alterações na morfologia sub-celular foram acompanhadas por modificações em marcadores de autofagia, sem aumento no fluxo autofágico. Estes dados sugerem que o aumento na degradação de proteínas e estruturas por autofagia poderão ter origem em efeitos colaterais de outras vias em detrimento do estímulo direto. Para além disso, testamos uma série de moléculas com atividade reconhecida e validadas para induzir autofagia ou bloquear a degradação no lisossoma. Foi demonstrado que no nosso modelo, a ativação da autofagia não é responsável pela remoção de agregados. Por outro lado, provámos que os lisossomas são extremamente importantes da degradação de agregados da Tau. Por fim, usámos o fator de transcrição EB (TFEB) para aumentar a biogénese de lisossomas e a autofagia. Células transfectadas com este fator apresentaram menos agregados de Tau e um aumento na viabilidade celular. Quando considerados em conjunto, estes resultados demonstram que a biogénese de lisossomas seguida por estímulos na autofagia podem ser mais importantes do que a ativação da autofagia por si só. Concluindo, com este projeto foi não só possível identificar os mecanismos dos compostos responsáveis pela degradação dos agregados de Tau, como também foi possível validar o TFEB como um potencial novo alvo na descoberta de novos fármacos.Tau protein is responsible for binding and stabilizing microtubules (MT) in the cytoskeleton, thus supporting neuronal function. This protein activity can be regulated by post-translation modifications, such as phosphorylation, which promotes MT detachment. Tau misfolding provoked by abnormal regulation, like hyperphosphorilation, causes MT destabilization and Tau aggregation into paired helical filaments (PHF) and neurofibrillary tangles (NFTs). These structures are one of the main hallmarks in Alzheimer’s disease (AD), and its formation process may represent the principal motive for cell death in many Tauopathies, including AD and other neurodegenerative disorders. Over the last years, great efforts have been placed to find new strategies to either diminish the build-up or decrease the amount of aggregated Tau inside cells. Recent studies have identified induction of autophagy through rapamycin as a potential target in increasing the clearance of aggregated proteins associated with neurodegenerative diseases, as well as ameliorating life expectancy in rats and other animal models. Recently, our lab developed a cellular model based on the work by Guo and Lee (2011) that mimics the intracellular aggregation of Tau after overexpression of a mutated form of this protein and seeding with pre-aggregated K18:P301L fibrils. In this study, we have taken advantage of the developed model to discover new compounds active in Tau reduction pathways. Interestingly these molecules were responsible for the development of a vesicular phenotype that we identified as lysosomes due to a possible stimulation of the endocytic pathway. The change of the sub cellular morphology was followed by changes in autophagy markers, with no increase in the autophagic flux. This suggests an increment in the degradation of proteins and structures by autophagy as a collateral result from the activation of other pathways rather than a direct stimulus. Furthermore, we have tested a series of molecules with known and validated activity to induce autophagy or disable degradation via the lysosome. We showed that at least in our model, autophagy activation is not responsible for the clearance of aggregates. On the other hand, we have proven that lysosomes play a critical role in Tau aggregates degradation. Finally, we have used the transcription factor EB (TFEB) to intensify lysosomal biogenesis and autophagy. Cells transfected with this transcription factor had less Tau aggregates and cell viability was slightly increased. When considered together, these results show that lysosomal biogenesis followed by autophagy stimulation may be more important for clearance of Tau aggregates than autophagy by itself. In conclusion, we have not only determined the mechanisms targeted by the compounds responsible for the degradation of Tau aggregates, but also validated TFEB as a potential new target for drug discovery

Two-stroke scooters are a dominant source of air pollution in many cities.

Fossil fuel-powered vehicles emit significant particulate matter, for example, black carbon and primary organic aerosol, and produce secondary organic aerosol. Here we quantify secondary organic aerosol production from two-stroke scooters. Cars and trucks, particularly diesel vehicles, are thought to be the main vehicular pollution sources. This needs re-thinking, as we show that elevated particulate matter levels can be a consequence of 'asymmetric pollution' from two-stroke scooters, vehicles that constitute a small fraction of the fleet, but can dominate urban vehicular pollution through organic aerosol and aromatic emission factors up to thousands of times higher than from other vehicle classes. Further, we demonstrate that oxidation processes producing secondary organic aerosol from vehicle exhaust also form potentially toxic 'reactive oxygen species'.This work was supported by the Swiss Federal Office for the Environment (FOEN), the Federal Roads Office (FEDRO), the Swiss National Science Foundation (Ambizione PZ00P2_131673, SAPMAV 200021_13016), the EU commission (FP7, COFUND: PSI-Fellow, grant agreement n.° 290605), the UK Natural Environment Research Council (NERC), the French Environment and Energy Management Agency (ADEME, Grant number 1162C00O2) and the Velux Foundation.This is the accepted manuscript version. The final version is available from http://www.nature.com/ncomms/2014/140513/ncomms4749/full/ncomms4749.html

TDP-43 as a potential biomarker for amyotrophic lateral sclerosis:a systematic review and meta-analysis

Abstract Background Frontotemporal dementia (FTD) and Amyotrophic Lateral Sclerosis (ALS) are incurable, progressive and fatal neurodegenerative diseases with patients variably affected clinically by motor, behavior, and cognitive deficits. The accumulation of an RNA-binding protein, TDP-43, is the most significant pathological finding in approximately 95% of ALS cases and 50% of FTD cases, and discovery of this common pathological signature, together with an increasing understanding of the shared genetic basis of these disorders, has led to FTD and ALS being considered as part of a single disease continuum. Given the widespread aggregation and accumulation of TDP-43 in FTD-ALS spectrum disorder, TDP-43 may have potential as a biomarker in these diseases. Methods We therefore conducted a systematic review and meta-analysis to evaluate the diagnostic utility of TDP-43 detected in the cerebrospinal fluid (CSF) of patients with FTD-ALS spectrum disorder. Results From seven studies, our results demonstrate that patients with ALS have a statistically significantly higher level of TDP-43 in CSF (effect size 0.64, 95% CI: 0.1–1.19, p = 0.02). Conclusions These data suggest promise for the use of CSF TDP-43 as a biomarker for ALS

Behavioral Mechanism during Human Sperm Chemotaxis: Involvement of Hyperactivation

When mammalian spermatozoa become capacitated they acquire, among other activities, chemotactic responsiveness and the ability to exhibit occasional events of hyperactivated motility—a vigorous motility type with large amplitudes of head displacement. Although a number of roles have been proposed for this type of motility, its function is still obscure. Here we provide evidence suggesting that hyperactivation is part of the chemotactic response. By analyzing tracks of spermatozoa swimming in a spatial chemoattractant gradient we demonstrate that, in such a gradient, the level of hyperactivation events is significantly lower than in proper controls. This suggests that upon sensing an increase in the chemoattractant concentration capacitated cells repress their hyperactivation events and thus maintain their course of swimming toward the chemoattractant. Furthermore, in response to a temporal concentration jump achieved by photorelease of the chemoattractant progesterone from its caged form, the responsive cells exhibited a delayed turn, often accompanied by hyperactivation events or an even more intense response in the form of flagellar arrest. This study suggests that the function of hyperactivation is to cause a rather sharp turn during the chemotactic response of capacitated cells so as to assist them to reorient according to the chemoattractant gradient. On the basis of these results a model for the behavior of spermatozoa responding to a spatial chemoattractant gradient is proposed

Gastrointestinal complaints in runners are not due to small intestinal bacterial overgrowth

<p>Abstract</p> <p>Background</p> <p>Gastrointestinal complaints are common among long distance runners. We hypothesised that small intestinal bacterial overgrowth (SIBO) is present in long distance runners frequently afflicted with gastrointestinal complaints.</p> <p>Findings</p> <p>Seven long distance runners (5 female, mean age 29.1 years) with gastrointestinal complaints during and immediately after exercise without known gastrointestinal diseases performed Glucose hydrogen breath tests for detection of SIBO one week after a lactose hydrogen breath test checking for lactose intolerance. The most frequent symptoms were diarrhea (5/7, 71%) and flatulence (6/7, 86%). The study was conducted at a laboratory.</p> <p>In none of the subjects a pathological hydrogen production was observed after the intake of glucose. Only in one athlete a pathological hydrogen production was measured after the intake of lactose suggesting lactose intolerance.</p> <p>Conclusions</p> <p>Gastrointestinal disorders in the examined long distance runners were not associated with small intestinal bacterial overgrowth.</p

Tropical Stratospheric Circulation and Ozone Coupled to Pacific Multi-Decadal Variability

Observational and modeling evidence suggest a recent acceleration of the stratospheric Brewer-Dobson circulation (BDC), driven by climate change and stratospheric ozone depletion. However, slowly varying natural variability can compromise our ability to detect such forced changes over the relatively short observational record. Using observations and chemistry-climate model simulations, we demonstrate a link between multi-decadal variability in the strength of the BDC and the Interdecadal Pacific Oscillation (IPO), with knock-on impacts for composition in the stratosphere. After accounting for the IPO-like variability in the BDC, the modeled trend is approximately 7%–10% dec−1 over 1979–2010. Furthermore, we find that sea surface temperatures explain up to 50% of the simulated decadal variability in tropical mid-stratospheric ozone. Our findings demonstrate strong links between low-frequency variability in the oceans, troposphere and stratosphere, as well as their potential importance in detecting structural changes in the BDC and future ozone recovery

Drosophila Sperm Swim Backwards in the Female Reproductive Tract and Are Activated via TRPP2 Ion Channels

Sperm have but one purpose, to fertilize an egg. In various species including Drosophila melanogaster female sperm storage is a necessary step in the reproductive process. Amo is a homolog of the human transient receptor potential channel TRPP2 (also known as PKD2), which is mutated in autosomal dominant polycystic kidney disease. In flies Amo is required for sperm storage. Drosophila males with Amo mutations produce motile sperm that are transferred to the uterus but they do not reach the female storage organs. Therefore Amo appears to be a mediator of directed sperm motility in the female reproductive tract but the underlying mechanism is unknown.Amo exhibits a unique expression pattern during spermatogenesis. In spermatocytes, Amo is restricted to the endoplasmic reticulum (ER) whereas in mature sperm, Amo clusters at the distal tip of the sperm tail. Here we show that flagellar localization of Amo is required for sperm storage. This raised the question of how Amo at the rear end of sperm regulates forward movement into the storage organs. In order to address this question, we used in vivo imaging of dual labelled sperm to demonstrate that Drosophila sperm navigate backwards in the female reproductive tract. In addition, we show that sperm exhibit hyperactivation upon transfer to the uterus. Amo mutant sperm remain capable of reverse motility but fail to display hyperactivation and directed movement, suggesting that these functions are required for sperm storage in flies.Amo is part of a signalling complex at the leading edge of the sperm tail that modulates flagellar beating and that guides a backwards path into the storage organs. Our data support an evolutionarily conserved role for TRPP2 channels in cilia