Ultrastructural and functional fate of recycled vesicles in hippocampal synapses

Efficient recycling of synaptic vesicles is thought to be critical for sustained information transfer at central terminals. However, the specific contribution that retrieved vesicles make to future transmission events remains unclear. Here we exploit fluorescence and time-stamped electron microscopy to track the functional and positional fate of vesicles endocytosed after readily releasable pool (RRP) stimulation in rat hippocampal synapses. We show that most vesicles are recovered near the active zone but subsequently take up random positions in the cluster, without preferential bias for future use. These vesicles non-selectively queue, advancing towards the release site with further stimulation in an actin-dependent manner. Nonetheless, the small subset of vesicles retrieved recently in the stimulus train persist nearer the active zone and exhibit more privileged use in the next RRP. Our findings reveal heterogeneity in vesicle fate based on nanoscale position and timing rules, providing new insights into the origins of future pool constitution

The association between leukocytes and sperm quality is concentration dependent

<p>Abstract</p> <p>Background</p> <p>To evaluate the association between leukocytes (polymorphonuclear granulocytes -PMNL) and semen parameters at different leukocyte concentrations.</p> <p>Methods</p> <p>This was a retrospective clinical study at a university hospital andrology clinic. Semen samples from infertile men were analyzed for sperm morphology and motility according to seminal leukocytes (PMNL) concentration (category A: >0 to <0.25 × 10(6)/mL; category B: >0.25 to <0.5 × 10(6)/mL; category C: >0.5 to <0.75 × 10(6)/mL; category D: >0.75 to <1.0 × 10(6)/mL, category E: >1 × 10(6)/mL).</p> <p>Results</p> <p>The percentage of sperm with normal morphology increased significantly from category A (14%) to category D (19%) but decreased in category E to levels (14%) similar to those in category A. Motility grades a and a+b (combined) also increased from category A (12%, 20%) to category D (18.0%, 28.5%) and decreased in category E (11%, 20.5%) to levels similar to those in category A. Sperm deformities and motility grades c and d increased progressively in all categories.</p> <p>Summary</p> <p>Leukocytes had a positive association with normal morphology and progressive motility in semen samples at a concentration of 0-1 × 10(6)/mL. The findings suggest that the association between leukocytes (PMNL) and semen quality might be concentration dependent.</p

Trabalho de consenso de força-tarefa da WFSBP sobre marcadores biológicos das demências: contribuição da análise do LCR e do sangue para o diagnóstico precoce e diferencial das demências

Aging of population, and increasing life expectancy result in an increasing number of patients with dementia. This symptom can be a part of a completely curable disease of the central nervous system (e.g, neuroinflammation), or a disease currently considered irreversible (e.g, Alzheimer's disease, AD). In the latter case, several potentially successful treatment approaches are being tested now, demanding reasonable standards of pre-mortem diagnosis. Cerebrospinal fluid and serum analysis (CSF/serum analysis), whereas routinely performed in neuroinflammatory diseases, still requires standardization to be used as an aid to the clinically based diagnosis of AD. Several AD-related CSF parameters (total tau, phosphorylated forms of tau, Aß peptides, ApoE genotype, p97, etc.) tested separately or in a combination provide sensitivity and specificity in the range of 85%, the figure commonly expected from a good diagnostic tool. In this review, recently published reports regarding progress in neurochemical pre-mortem diagnosis of dementias are discussed with a focus on an early and differential diagnosis of AD. Novel perspectives offered by recently introduced technologies, e.g, fluorescence correlation spectroscopy (FCS) and surface enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI-TOF MS) are briefly discussed.O envelhecimento da população e o aumento da expectativa de vida resultam em um número cada vez maior de pacientes com demência. Os déficits cognitivos podem ser manifestações de uma doença curável do sistema nervoso central (por exemplo, neuroinflamação), como também de uma doença atualmente considerada irreversível, como a doença de Alzheimer (DA). Tendo em vista as novas abordagens terapêuticas para a DA, em que se avalia o potencial modificador da patogenia, torna-se necessário o estabelecimento de um diagnóstico confiável em vida. Embora a análise do líquido cefalorraquidiano (LCR) e do soro seja realização de rotina em doenças neuroinflamatórias, ainda necessita de padronização para ser usada como instrumento auxiliar no diagnóstico clínico da DA. Vários parâmetros relacionados à DA (tau total, formas fosforiladas de tau, peptídeos A&#946;, genótipo ApoE, p97 etc.) podem ser determinados no LCR. A combinação de alguns desses parâmetros proporciona sensibilidade e especificidade na faixa de 85% para o diagnóstico da DA, um valor usualmente atribuído a um bom instrumento de diagnóstico. Nesta revisão, são discutidas as publicações mais recentes sobre os marcadores neuroquímicos para o diagnóstico clínico das demências, com ênfase no diagnóstico precoce e diferencial da DA. Discutem-se brevemente as novas perspectivas oferecidas por tecnologias recentes, tais como a FCS (fluorescence correlation spectroscopy) e a técnica de espectrometria de massa pelo método SELDI-TOF (surface enhanced laser desorption/ionization time-of-flight mass spectrometry)

Verbal Reports and "Real' Reasons" : Confabulation and Conflation

This document is the Accepted Manuscript version of a published work that appeared in final form in Ethical Theory and Moral Practice after peer review and technical editing by the publisher. Constantine Sandis, ‘Verbal Reports and “Real” Reasons: Confabulation and Conflation’, Ethical Theory and Moral Practice, Vol. 18(2): 267-280, first published online 18 March 2015. The final publication is available at Springer via http://dx.doi.org/10.1007/s10677-015-9576-6 © Springer Science+Business Media Dordrecht 2015This paper examines the relation between the various forces which underlie human action and verbal reports about our reasons for acting as we did. I maintain that much of the psychological literature on confabulations rests on a dangerous conflation of the reasons for which people act with a variety of distinct motivational factors. In particular, I argue that subjects frequently give correct answers to questions about the considerations they acted upon while remaining largely unaware of why they take themselves to have such reasons to act. Pari passu, experimental psychologists are wrong to maintain that they have shown our everyday reason talk to be systematically confused. This is significant because our everyday reason-ascriptions affect characterizations of action (in terms of intention, knowledge, foresight, etc.) that are morally and legally relevant. I conclude, more positively, that far from rendering empirical research on confabulations invalid, my account helps to reveal its true insights into human nature.Peer reviewe

Lipid Metabolites Enhance Secretion Acting on SNARE Microdomains and Altering the Extent and Kinetics of Single Release Events in Bovine Adrenal Chromaffin Cells

Lipid molecules such as arachidonic acid (AA) and sphingolipid metabolites have been implicated in modulation of neuronal and endocrine secretion. Here we compare the effects of these lipids on secretion from cultured bovine chromaffin cells. First, we demonstrate that exogenous sphingosine and AA interact with the secretory apparatus as confirmed by FRET experiments. Examination of plasma membrane SNARE microdomains and chromaffin granule dynamics using total internal reflection fluorescent microscopy (TIRFM) suggests that sphingosine production promotes granule tethering while arachidonic acid promotes full docking. Our analysis of single granule release kinetics by amperometry demonstrated that both sphingomyelinase and AA treatments enhanced drastically the amount of catecholamines released per individual event by either altering the onset phase of or by prolonging the off phase of single granule catecholamine release kinetics. Together these results demonstrate that the kinetics and extent of the exocytotic fusion pore formation can be modulated by specific signalling lipids through related functional mechanisms

Academic artisans in the research university

In the changing context of universities, organisational structures for teaching and research problematize academic roles. This paper draws on a critical realist analysis of surveys and interviews with academics from universities in England and Australia. It identifies important academic work, not captured simply in descriptions of teaching or research. It shows that many academics, who are not research high flyers nor award-winning teachers, carry out this essential work which contributes to the effective functioning of their universities. That work is referred to as academic artisanal work and the people who do it as academic artisans. Characteristics and examples of academic artisans are presented and the nature of artisanal work is explored. Implications for higher education management and for future studies are discussed. The paper points to an urgent need to better understand the complex nature of academic work

Multiple sclerosis drug FTY-720 toxicity is mediated by the heterotypic fusion of organelles in neuroendocrine cells

FTY-720 (Fingolimod) was one of the first compounds authorized for the treatment of multiple sclerosis. Among its other activities, this sphingosine analogue enhances exocytosis in neuroendocrine chromaffin cells, altering the quantal release of catecholamines. Surprisingly, the size of chromaffin granules is reduced within few minutes of treatment, a process that is paralleled by the homotypic fusion of granules and their heterotypic fusion with mitochondria, as witnessed by dynamic confocal and TIRF microscopy. Electron microscopy studies support these observations, revealing the fusion of several vesicles with individual mitochondria to form large, round mixed organelles. This cross-fusion is SNARE-dependent, being partially prevented by the expression of an inactive form of SNAP-25. Fused mitochondria exhibit an altered redox potential, which dramatically enhances cell death. Therefore, the cross-fusion of intracellular organelles appears to be a new mechanism to be borne in mind when considering the effect of FTY-720 on the survival of neuroendocrine cells

Key Physiological Parameters Dictate Triggering of Activity-Dependent Bulk Endocytosis in Hippocampal Synapses

To maintain neurotransmission in central neurons, several mechanisms are employed to retrieve synaptically exocytosed membrane. The two major modes of synaptic vesicle (SV) retrieval are clathrin-mediated endocytosis and activity-dependent bulk endocytosis (ADBE). ADBE is the dominant SV retrieval mode during intense stimulation, however the precise physiological conditions that trigger this mode are not resolved. To determine these parameters we manipulated rat hippocampal neurons using a wide spectrum of stimuli by varying both the pattern and duration of stimulation. Using live-cell fluorescence imaging and electron microscopy approaches, we established that stimulation frequency, rather than the stimulation load, was critical in the triggering of ADBE. Thus two hundred action potentials, when delivered at high frequency, were sufficient to induce near maximal bulk formation. Furthermore we observed a strong correlation between SV pool size and ability to perform ADBE. We also identified that inhibitory nerve terminals were more likely to utilize ADBE and had a larger SV recycling pool. Thus ADBE in hippocampal synaptic terminals is tightly coupled to stimulation frequency and is more likely to occur in terminals with large SV pools. These results implicate ADBE as a key modulator of both hippocampal neurotransmission and plasticity