1,721,181 research outputs found
When I show the Beatles then you say: ‛Ramones!’ : imaging semantic memory in Alzheimer’s disease and semantic dementia
No full textElderly people contacting the health care system because of suspected dementia very often report word forgetfulness, a clinical condition referred as anomia, often one of the first signs of cognitive decline. Considering the complexity of human language it is no wonder that dementia disorders can affect language processing, which in its turn relies heavily on the intactness of the semantic memory system. In an attempt to study language impairment in dementia, this thesis aimed to investigate semantic memory, from its normal degradation in healthy ageing, to its disruption in dementia, and from controlled to unconscious semantic processing. Moreover we chased the anatomical locus of semantic memory with the combination of several neurophysiological and neuroimaging techniques.In Study I we investigated controlled semantic retrieval together with pattern of blood perfusion through the performance of verb fluency (VF) and animal fluency (AF), combined with Single-Photon Emission Computed Tomography (SPECT) in patients suffering from Alzheimer’s disease (AD), Mild Cognitive Impairment (MCI), and Subjective Cognitive Impairment (SCI).In Study II we enquired automatic semantic retrieval in healthy young and healthy elderly, combining a novel semantic priming paradigm to Event Related Potential (ERP) Electroencephalography (EEG).In Study III we used the same semantic paradigm and ERP EEG measurement as in Study II to investigate automatic semantic retrieval in AD, Semantic Dementia (SD), and an healthy elderly population. The result was then correlated to measure of blood perfusion by means of Pulsed Continuous Arterial Spin Labelling (PCALS) Magnetic Resonance Imaging (MRI).In Study IV we chased the anatomical locus of semantic memory through the study of grey (GM) and white matter (WM) pathology in AD, SD, and healthy ageing, combining Voxel-Based Morphometry (VBM) MRI and Diffusion Tensor Imaging (DTI) MRI.We could show that controlled semantic retrieval, and in particular VF is impaired in dementia and that this correlates to hypoperfusion in particular anatomical regions. Moreover, we could prove the automatic semantic retrieval remains stable under the span of healthy adulthood while controlled retrieval is not, and that this processes activates neurophysiologically comparable neural networks for healthy young as well as for healthy elderly. In addition we could show that automatic spread of activation is spared in mild dementia despite the deviant result in measures of controlled semantic processes and we found a possible early marker differentiating SD from AD and healthy ageing. We could even associate patterns of hypoperfusion to impairment in controlled semantic memory processing, this indicating that the altered electrophysiology of dementia patients is closely related to their structural and baseline blood degeneration. Finally we could detect different patterns of GM and WM loss in the AD compared to the SD group. In particular we could detect a specific area of WM disruption significantly separating AD from SD.List of scientific papersI. Östberg P, Crinelli RM, Danielsson R, Wahlund L-O, Bogdanovic N, Fernaeus S-E. A temporal lob e factor in verb fluency. Cortex. 2007, 43: 607-15. https://doi.org/10.1016/S0010-9452(08)70491-X II. Grieder M, Crinelli RM, Koenig T, Wahlund L-O, Dierks T, Wirth M. Electrophysiological and behavioural correlates of stable automatic semantic retrieval in aging. Neuropsychologia. 2012, 50: 160-71. https://doi.org/10.1016/j.neuropsychologia.2011.11.014 III. Grieder M, Crinelli RM, Jann K, Federspiel A, Wirth M, Koenig T, Steirn M, Wahlund L-O, Dierks T. Topographic N400 anomaly correlates with reduced cerebral blood flow in the anterior temporal lobes of dementia patients. [Submitted]IV. Crinelli RM, Grieder M, Spulber G, Manzouri A, Östberg P, Dierks T, Wahlund L-O. A multimodal neuroimaing approach to Alzheimer’s disease and Semantic Dementia: a study in grey and white. [Manuscript]</p
Reactive oxygen species are involved in pollen tube initiation in kiwifruit
No full textThe role of reactive oxygen species (ROS) during pollen tube growth has been well
established, but its involvement in the early germination stage is poorly understood.
ROS production has been reported in germinating tobacco pollen, but evidence for
a clear correlation between ROS and germination success remains elusive. Here, we
show that ROS are involved in germination and pollen tube formation in kiwifruit.
Using labelling with dihydrofluorescein diacetate (H2FDA) and nitroblue tetrazolium
(NBT), endogenous ROS were detected immediately following pollen rehydration
and during the lag phase preceding pollen tube emergence. Furthermore,
extracellular H2O2 was found to accumulate, beginning a few minutes after pollen
suspension in liquid medium. ROS production was essential for kiwifruit pollen
performance, since in the presence of compounds acting as superoxide dismutase
⁄ catalase mimic (Mn-5,10,15,20-tetrakis(1-methyl-4-pyridyl)21H,23H-porphin,
Mn-TMPP) or as NADPH oxidase inhibitor (diphenyleneiodonium chloride, DPI),
ROS levels were reduced and pollen tube emergence was severely or completely
inhibited. Moreover, ROS production was substantially decreased in the absence of
calcium, and by chromium and bisphenol A, which inhibit germination in kiwifruit.
Peroxidase activity was cytochemically revealed after rehydration and during germination.
In parallel, superoxide dismutase enzymes, particularly the Cu ⁄ Zn-dependent
subtype – which function as superoxide radical scavengers – were detected by
immunoblotting and by an in-gel activity assay in kiwifruit pollen, suggesting that
ROS levels may be tightly regulated. Timing of ROS appearance, early localisation
at the germination aperture and strict requirement for germination clearly suggest
an important role for ROS in pollen grain activation and pollen tube initiation
Ubiquitin in plant cells: focus on sexual reproduction processes
No full textSi allega l'Introduction del libro, ad opera del Prof. V.K. Sawhney, University of Saskatchevan, Saskatoon, Canad
Il sistema ubiquitina-proteasoma 26S nella biologia del microgametofito di Actinidia deliciosa (kiwi)
No full textOverexpression of ubiquitin downregulates transcription of the endogenous UbC gene in HeLa cells
No full text32nd FEBS Congressw, MOLECULAR MACHINE
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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