1,721,004 research outputs found
Increased brain temperature in Parkinson's disease
No full textThe maintenance of a stable temperature is of the utmost importance for the proper functioning of the brain. Brain temperature is tightly linked to mitochondrial energetics. Although Parkinson's disease is characterized by mitochondrial dysfunction, no data are available on brain temperature. We measured the temperature in the visual cortex and in the centrum semiovale at rest by proton magnetic resonance spectroscopy in patients with Parkinson's disease and in age-matched and sex-matched control participants. We report evidence of increased temperature in the visual cortex and, to a minor extent, in the centrum semiovale of patients with Parkinson's disease. The increase in brain temperature is best explained by an energy loss along the oxidative phosphorylation/respiratory chain
Human fetal brain chemistry as detected by proton magnetic resonance spectroscopy
No full textMagnetic resonance spectroscopy represents an invaluable tool for the in vivo study of brain development at the chemistry level. Whereas magnetic resonance spectroscopy has received wide attention in pediatric and adult settings, only a few studies were performed on the human fetal brain. They revealed changes occurring throughout gestation in the levels of the main metabolites detected by proton magnetic resonance spectroscopy (N-acetylaspartate, choline, myo-inositol, creatine, and glutamate), providing a reference for the normal metabolic brain development. Throughout the third trimester of gestation, N-acetylaspartate gradually increases, whereas choline undergoes a slow reduction during the process of myelination. Less clear are the modifications in creatine, myo-inositol, and glutamate levels. Under conditions of fetal distress, the meaning of lactate detection is unclear, and further studies are needed. Another field for investigation involves the possibility of early detection of glutamate levels in fetuses at risk for hypoxic-ischemic encephalopathy, because the role of glutamate excitotoxicity in this context is well-established. Because metabolic modifications may precede functional or morphologic changes in the central nervous system, magnetic resonance spectroscopy may likely serve as a powerful, noninvasive tool for the early diagnosis and prognosis of different pathologic conditions
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
PINK1 parkinsonism and Parkinson disease : distinguishable brain mitochondrial function and metabolomics
No full textMutations in the PINK1 gene are associated with early onset autosomal recessive parkinsonism (EOP), which is characterized by a phenotypic presentation that, although variable, generally overlaps with that of idiopathic Parkinson Disease (PD). The clinical features and brain metabolomics of a patient who was compound heterozygous for the novel association of PINK1 A168P/W437X mutations have been extensively characterized. Apart from a few typical EOP findings, the clinical features and SPECT mostly overlapped with typical idiopathic PD. Brain metabolomics, as examined by magnetic resonance spectroscopy and PET, were clearly distinguishable
Central hyperthermia, brain hyperthermia and low hypothalamus temperature
No full textIntroduction, Patients and Methods: We measured brain temperature in a case of central hyperthermia. Results Brain temperature was increased except for hypothalamus that was colder. Conclusion: We suppose that central hyperthermia is driven by cold hypothalamus
Variations on the Author
Full text link“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
Full text linkWe 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
Post-Activation Brain Warming: A 1-H MRS Thermometry Study.
Full text linkTemperature plays a fundamental role for the proper functioning of the brain. However, there are only fragmentary data on brain temperature (T(br)) and its regulation under different physiological conditions.We studied T(br) in the visual cortex of 20 normal subjects serially with a wide temporal window under different states including rest, activation and recovery by a visual stimulation-Magnetic Resonance Spectroscopy Thermometry combined approach. We also studied T(br) in a control region, the centrum semiovale, under the same conditions.Visual cortex mean baseline T(br) was higher than mean body temperature (37.38 vs 36.60, P<0.001). During activation Tbr remained unchanged at first and then showed a small decrease (-0.20 C°) around the baseline value. After the end of activation T(br) increased consistently (+0.60 C°) and then returned to baseline values after some minutes. Centrum semiovale T(br) remained unchanged through rest, visual stimulation and recovery.These findings have several implications, among them that neuronal firing itself is not a major source of heat release in the brain and that there is an aftermath of brain activation that lasts minutes before returning to baseline conditions
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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
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