130,576 research outputs found
IMPACT OF PHENYLPROPANOIDS ON HEAT STRESS PROTECTION
No full textI metaboliti secondari sono composti organici non direttamente coinvolti nella crescita e nello sviluppo della pianta. Queste sostanze sono spesso prodotte e accumulate dopo stress biotici e abiotici, ma le loro precise funzioni in vivo sono ancora poco chiare. Le colture cellulari in vitro possono essere utilizzate al fine di chiarire il ruolo biologico di specifici metaboliti secondari dopo un particolare tipo di stress. In una precedente tesi di dottorato, uno stress termico di 1 ora a 44°C è stato applicato ad una linea cellulare di carota chiamata R3M, una linea pigmentata, in grado di accumulare derivati della cianidina e degli acidi idrossicinnamici, molecole appartenenti alla classe dei fenilpropanoidi. Il trattamento termico causava la comparsa di strutture circolari citoplasmatiche dopo 24 ore di recupero dallo stress, ed è stato dimostrato che le cellule mostranti queste strutture erano destinate ad una lenta morte cellulare, con caratteristiche tipiche di una morte cellulare programmata. Somministrando alle cellule R3M alcuni precursori molecolari (approccio chimico), quali gli acidi idrossicinnamici, prima del trattamento termico, si è osservata una riduzione del numero di cellule con strutture circolari citoplasmatiche e una riduzione del numero di cellule morte. Questo progetto ha come obiettivo la caratterizzazione dei danni morfologici causati dallo stress termico, al fine di chiarire il possibile ruolo biologico di specifici fenilpropanoidi accumulati nella coltura R3M. Inoltre, un tentativo per valutare la possibilità di sfruttare l'approccio chimico, ovvero di somministrare i precursori molecolari in pianta per osservare l’eventuale assorbimento e modificazione degli stessi in piante intere, è stato provato. La doppia colorazione con fluoresceina di acetato e ER tracker blue white delle cellule stressate al calore, ha permesso di investigare la natura di queste strutture circolari citoplasmatiche, rivelando che esse sono circondate dal reticolo endoplasmatico. Questa organizzazione è tipica degli autofagosomi, strutture coinvolte nel processo di macroautofagia e spesso indotte da uno stress. Ulteriori analisi di microscopia hanno mostrato come queste strutture circolari citoplasmatiche contengano anche gocce lipidiche e organelli, per esempio cromoplasti, supportando fortemente l'ipotesi che queste strutture circolari siano autofagosomi. La colorazione con il marcante di endocitosi “FM 1-43” ha permesso di osservare che, nelle cellule stressate, l'arresto dei movimenti endocellulari avveniva immediatamente dopo l’esposizione allo stress termico e che, anche dopo due ore di recupero, la ripresa dei movimenti vescicolari non avveniva. Questo risultato ha suggerito che il citoscheletro, o qualche componente implicato nel trasporto vescicolare, poteva essere stato danneggiato dal calore. Dato che il citoscheletro è formato da diverse strutture, due tossine, colchicina e citocalasina D, agenti contro i microtubuli e microfilamenti, sono state addizionate alla coltura cellulare di carota per provare a mimare i danni causati dallo stress termico. Solo la citocalasina D perfettamente fenocopiava, in una parte della popolazione cellulare, la morfologia stressata, suggerendo che uno dei target dello stress termico erano i microfilamenti, i quali, una volta danneggiati, determinavano, direttamente o indirettamente, la comparsa di putativi autofagosomi nelle cellule stressate. Poiché l'approccio di somministrazione degli acidi idrossicinnamici determinava l'aumento di specifiche antocianine e derivati di acidi idrossicinnamici, prevenendo parzialmente la comparsa di putativi autofagosomi nelle cellule stressate, è stato concluso che questi fenilpropanoidi agiscono contro lo stress termico, prevenendo la morte cellulare programmata, probabilmente mediante un effetto protettivo, non caratterizzato, sui microfilamenti. Rispetto a molte pubblicazioni scientifiche che suggeriscono il ruolo dei metaboliti secondari sulla base di una correlazione tra accumulo/diminuzione di gruppi/classi di metaboliti e uno specifico stress, questo lavoro dimostra chiaramente che alcune molecole specifiche, in particolare la cianidina acilata con acido caffeico e l’acido cumarico coniugato con l’acido quinico, hanno un ruolo biologico di protezione contro lo stress termico in questa linea cellulare carota, risultando in una diminuzione della morte cellulare. Infine, la somministrazione di precursori molecolari è stata condotta su piante intere, rivelando che le piantine di Arabidopsis thaliana sono in grado di assorbire precursori molecolari e convertirli in altri prodotti. Questo risultato dimostra che l’approccio chimico può essere eseguito non solo in colture cellulari in vitro, ma anche in piante intere, permettendo future indagini sui ruoli biologici dei metaboliti secondari.Secondary metabolites are organic compounds not directly involved in growth and development. These substances are often produced by plants after biotic and abiotic stresses, but their precise in vivo functions are still unclear. In vitro cell culture can be used in order to clarify the role of certain secondary metabolites after stress. In a previous work, a heat stress (1 hour at 44°C) was applied to R3M carrot cell line, a purple pigmented line that is able to accumulate cyanidin derivatives and hydroxycinnamic acid derivatives, molecules belonging to the phenylpropanoid class. The heat treatment caused the appearance of cytoplasmic circular structures after 24 hours of recovery. It has been shown that cells developing these structures were committed to a slow cell death, which showed some morphological markers of a programmed cell death. Feeding R3M cells with hydroxycinnamic acids before the heat treatment caused a reduction of the number of cells with cytoplasm circular structures and a reduction of cell death. The aim of this project is the characterization of the morphological damages caused by heat stress in order to clarify the possible biological role of specific phenylpropanoids accumulated in R3M cells. Finally, an effort to evaluate the possibility to exploit the feeding chemical approach in in vitro whole plants has been pursuit. The double staining of the heat stressed cells with fluorescein di-acetate and ER tracker blue-white allowed at observing the appearance of cytoplasmic circular structures surrounded by endoplasmic reticulum. This organization is typical of autophagosomes, structures involved during the macroautophagy process, which are often stress induced. Further microscope investigations revealed that these circular structures included lipid droplets and also organelles, for instance chromoplasts, strongly supporting that these structures are autophagosomes. The staining of the heat stressed cells with the endocytosis tracker FM 1-43 allowed to observe the arrest of endocellular movements just after heat stress, suggesting that cytoskeleton could have been damaged by heat. Toxins towards microtubules and microfilaments were used in order to phenocopy the damages induced by the heat treatment, but only Cytochalasin D, an anti-microfilament agent, caused the formation of structures similar to the heat induced putative-autophagosomes. Since the feeding approach determined the increase of anthocyanins and hydroxycinnamic acid derivatives, thus partially preventing the putative autophagosome-containing cell phenotype after heat stress, it can be concluded that these phenylpropanoids prevent programmed cell death possibly through an uncharacterized protective effect on microfilaments. Respect to other public researches that show the correlations between groups or classes of molecules and stresses, this work clearly demonstrates that specific molecules, i.e. the cyanidin acylated with caffeic acid and coumaroyl quinic acid, have a protective role against heat stress in this carrot cell line. Finally, the administration of molecular precursors has been investigated on in vitro whole plants revealing that Arabidopsis thaliana seedlings are able to absorb molecular precursors and immediately convert them in other plant products. This finding demonstrates that the chemical approach can be performed also in whole plants, allowing future investigations on secondary metabolite biological roles
MeSH term explosion and author rank improve expert recommendations
No full textInformation overload is an often-cited phenomenon that reduces the productivity, efficiency and efficacy of scientists. One challenge for scientists is to find appropriate collaborators in their research. The literature describes various solutions to the problem of expertise location, but most current approaches do not appear to be very suitable for expert recommendations in biomedical research. In this study, we present the development and initial evaluation of a vector space model-based algorithm to calculate researcher similarity using four inputs: 1) MeSH terms of publications; 2) MeSH terms and author rank; 3) exploded MeSH terms; and 4) exploded MeSH terms and author rank. We developed and evaluated the algorithm using a data set of 17,525 authors and their 22,542 papers. On average, our algorithms correctly predicted 2.5 of the top 5/10 coauthors of individual scientists. Exploded MeSH and author rank outperformed all other algorithms in accuracy, followed closely by MeSH and author rank. Our results show that the accuracy of MeSH term-based matching can be enhanced with other metadata such as author rank
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Scholarly Communication and Publishing Lunch and Learn Talk #11: The ULS Open Access Author Fee Fund
No full textAt the May 2014 talk, you will learn about the ULS Open Access Author Fee Fund--what it is, why we do it, how it works, and how the program is going so far
The R&D Tax Incentives
No full textThis article sets out some background information and reflections of the author on the R&D tax incentive schemes included in the Common Corporate Tax Base (CCTB) Proposal. In particular the author analyzes the stimulus to private R&D through ad hoc tax incentives included in the CCTB Proposal and dives into the actual provisions included in the Proposal highlighting the most relevant issues connected with their design and interpretation. Moreover, the author explores the interaction between the CCTB Proposal and the granting by Member States of domestic R&D tax incentives
Morphologic and functional correlates of synaptic pathology in the cathepsin D knockout mouse model of congenital neuronal ceroid lipofuscinosis
No full textMutations in the cathepsin D (CTSD) gene cause an aggressive neurodegenerative disease (congenital neuronal ceroid lipofuscinosis) that leads to early death. Recent evidence suggests that presynaptic abnormalities play a major role in the pathogenesis of CTSD deficiencies. To identify the early events that lead to synaptic alterations, we investigated synaptic ultrastructure and function in presymptomatic CTSD knockout (Ctsd) mice. Electron microscopy revealed that there were significantly greater numbers of readily releasable synaptic vesicles present in Ctsd mice than in wild-type control mice as early as postnatal day 16. The size of this synaptic vesicle pool continued to increase with disease progression in the hippocampus and thalamus of the Ctsd mice. Electrophysiology revealed a markedly decreased frequency of miniature excitatory postsynaptic currents (mEPSCs) with no effect on paired-pulse modulation of the evoked excitatory post synaptic potentials in the hippocampus of Ctsd mice. The reduced mEPSCs frequency was observed before the appearance of epilepsy or any morphologic sign of synaptic degeneration. Taken together, these data indicate that CTSD is required for normal synaptic function and that a failure in synaptic trafficking or recycling may bean early and important pathologic mechanism in Ctsd mice; these presynaptic abnormalities may initiate synaptic degeneration in advance of subsequent neuronal loss
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