1,720,955 research outputs found
The effects of methylene blue on learning and memory, plasticity, and oxidative stress in aged rats
No full textNormal aging in humans and animal models has been characterized, in large part, by declines and impairments in memory. Oxidative damage has been implicated in the process of aging. As an organism ages, the levels of reactive oxygen species (ROS) increase in the brain and can lead to an accumulation of oxidative damage. Methylene blue (MB) is a dye that has powerful antioxidant properties that prevent free radical damage and may help reduce the oxidative damage associated with aging. Low-dose MB improves memory, increases energy metabolism, enhances metabolic functions, and has antioxidant defenses for neuroprotection. It is not known whether MB has any beneficial effects in aged rats. In this dissertation, I investigated the effects of MB on trace-fear conditioning (TFC), a task known to be impaired in aged rats, and synaptic plasticity in the hippocampus. Levels of oxidative damage and protein conformational changes were also assessed.
MB was fed to F344/BN F1 rats separated into two age groups---young (6 months) and aged (24 months). They were fed either Methylene blue (MB) or the blue dye Indigo carmine (IC, control) for 4 weeks. Subjects underwent trace-fear conditioning (a hippocampus-related task) and 24 hours later they were tested for memory, or induction of long-term potentiation (LTP). At the end of the experiments, the hippocampi were extracted to measure levels of oxidative stress. We found that the young MB-treated animals learned faster during trace-fear training and the memory of TFC was rescued when compared to aged matched controls. In addition, the MB-treated rats showed less oxidative damage than their age-matched controls as measured by lipid peroxidation levels and the aged MB treated rats showed less protein conformation changes as measured by protein surface hydrophobicity. These results suggest that MB enhances learning and memory in young rats and reduces oxidative stress across the ages in the rat hippocampus. Furthermore, MB did not enhance LTP in either the young or aged MB-treated rats, but MB did decrease protein conformational changes in the hippocampus of aged rats.
These results suggest that MB, when given orally for 4 weeks, has a regional effect in the hippocampus and can work to reduce levels of oxidative damage. MB did not enhance LTP and this indicates that the treatment was not sufficient to have effects in LTP plasticity, or possibly, there was a ceiling effect in which all rats attained the maximum amount of LTP and there was no room for enhancement.Integrative Biolog
The effects of aging on neuronal morphology and on learning and memory in male mice
No full textThis item is available only to currently enrolled UTSA students, faculty or staff. To download, navigate to Log In in the top right-hand corner of this screen, then select Log in with my UTSA ID.The overall objective of this project was to investigate the effects of aging on the dendritic lengths, branch numbers, branch orders, average lengths per branch order, and spine densities on CA1 pyramidal neurons in behaviorally-characterized and non-behaviorally-characterized GFP-expressing male mice at 6, 18, and 24 months of age.
The first objective was to test the hypothesis that an increase in dendritic length, branch number, numbers of branch orders, and average lengths per branch order occurs with age in transgenic male mice expressing green fluorescent protein (GFP) in some neurons in the hippocampal formation. The results show that a decrease in apical dendritic length, branch number, number of branch orders, and average lengths per branch order occurs in middle-aged and old mice as compared to young adults. These data suggest an overall pruning and decrease in dendrite length with aging.
The second objective was to test the hypothesis that spine densities on CA1 pyramidal neurons decrease with age. The results show that no change in spine density occurs with age, which if viewed in isolation, would suggest synaptic number remains constant with age. However, these data in conjunction with the results showing that dendritic length decreases with age suggest that the overall number of synapses on CA1 pyramidal neurons decrease with age.
The third objective was to test the hypothesis that spatial learning and memory impairments in the Morris water maze (MWM) would occur in 18-month-old male, with more pronounced deficits observed at 24 months of age. In addition, it was hypothesized that aged animals with spatial-learning and memory impairments would have the same morphological characteristics hypothesized in the first and second objectives. The results showed that both 18- and 24-month-old mice have memory impairments, and that 24-month-old mice have learning and memory impairments more pronounced than those seen in the 18-month-olds. It was also observed the dendritic lengths, branch numbers, number of branch orders, and average lengths per branch order decreased on basal and distal apical dendrites in the older animals that were impaired, as compared to the younger animals that were not. Spine densities on basal dendrites in stratum oriens also decreased in the older learning and memory-impaired mice as compared to unimpaired young adults. These data show that impairments in learning and memory seem to correspond with decreases in dendritic length, branching patterns, and spine densities on basal dendrites.
The fourth objective was to test the hypothesis that the dendritic lengths do not change and spine densities increase on CA1 pyramidal neurons in mice trained and tested in the MWM as compared to controls. Training and testing resulted in a decrease in dendritic lengths and branch numbers in 6- and 24-month-old mice as compared to controls. Spine densities on distal apical dendrites in MWM trained and tested mice in stratum lacunosum-moleculare decreased in all three age groups as compared to controls. In addition, a decrease in spine density on dendrites in stratum radiatum was observed in 24-month-old trained and tested mice as compared to controls. Correlation analysis also showed that 6-month-old animals with a greater index of memory performance during probe trials had shorter dendritic lengths in distal apical dendrites of stratum lacunosum-moleculare. In contrast, 24-month-old male mice with a greater index of memory performance during probe trials had longer dendritic lengths in stratum-lacunosum moleculare. These data suggest that spatial learning tasks do affect CA1 pyramidal neuron morphology in specific ways depending on age group.Integrative Biolog
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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