1,721,035 research outputs found
Management of a ruptured cerebral aneurysm in infancy.—Report of a case of a ten-month-old boy
No full textA ten month old unconscious boy with hemiplegia (Hunt and Hess IV) was first admitted to a district hospital without a CT scanner or a neurosurgical service (Glasgow-Coma-Score 4, no pathological pupillary signs). Therefore, he was transferred to the Pediatric Department of the University Hospital the same night. An emergency CT scan that night showed intracerebral and subarachnoid hemorrhage with enlarged ventricle (Fisher grade 5). Angiography was not available within reasonable time. Thus in the stage of progressively increasing clinical deterioration, still without pupillary signs, an external ventricular drain-age was placed. Immediately after reduction of the cerebrospinal fluid volume, arterial hypertension was noticed--the right pupil was mydriatic and fixed. Without further apparative diagnosis an emergency craniotomy was performed for decompression under the suspicion of a secondary hemorrhage due to a rerupture of a middle cerebral artery aneurysm. A bleeding aneurysm of the right middle cerebral artery was found and clipped. A mass transfusion was necessary and a pulmonary air embolism occurred. The infant died in tabula. The histological specimens revealed disruption of the internal elastic membrane of both MCA. This emphasizes a congenital nature of the aneurysm. We conclude that cerebral arterial aneurysms have to be considered in the differential diagnosis of stroke-like symptoms in infancy and early childhood, although the incidence of reported cases is less than one case per year. Since no valid screening parameter is available, diagnosis is often made only after rupture of the aneurysm. This causes problems for emergency management. Infants and children with stroke or stroke-like symptoms should immediately be transferred to a hospital with a neurosurgical unit
Neuroprotection by 21-aminosteroids: insights from latencies of anoxic terminal negativity in hippocampus slices of guinea pig
No full textThe protection of neuronal function by 21-aminosteroids against a hypoxic challenge was tested in guinea pig hippocampal slices. 21-aminosteroids, which apart from a protective mechanism against membrane lipid peroxidation, provide direct membrane stabilizing effects, are reported. We tested whether the 21-aminosteroid U-74389G delays the anoxic terminal negativity (ATN) of the DC-potential during hypoxia. Hippocampal slices were placed at the interface of artificial cerebrospinal fluid (aCSF) and gaseous phase (normoxic: 95% O2, 5% CO2; hypoxic: 95% N2, 5% CO2). Population spikes obtained by stimulation of Schaffer-collaterals as well as the DC-Potential were recorded in the CA1 region. The latency of appearance of ATN after oxygen deprivation was determined. In control experiments, the latency of ATN was 12.6 +/- 3.1 min (n = 6, mean +/- SEM). With application of U-74389G, the ATN-latency was 8.8 +/- 3.2 min (n = 6). We conclude that the cerebroprotective effect of the 21-aminosteroid is not mediated via direct membrane stabilization
Hypothermia as cerebroprotective measure. Experimental hypoxic exposure of brain slices and clinical application in critically reduced cerebral perfusion pressure
No full textAn in vitro human neocortical and rodent hippocampus brain slice technique was used under repeated hypoxia to investigate the cerebroprotective effect of hypothermia. As a hallmark of the neuronal hypoxic reaction anoxic terminal negativity (ATN) was registered to test whether hypothermia delays the onset of ATN. The experiments clearly confirm an assumed protective effect of hypothermia in vitro and in vivo and give for the first time evidence of the lack of the protective effect of hypothermia once hypoxia has occurred under normothermic conditions, probably by a critical depletion of cellular ATP-stores. In patients with severe traumatic brain injury and critically low cerebral perfusion pressure mild hypothermia is able to improve clinical outcome
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
Neuroprotection of mild hypothermia: differential effects
No full textTo estimate whether mild hypothermia during repetitive hypoxia provides a neuroprotective effect on brain tissue, hippocampal slice preparations were subjected to repetitive hypoxic episodes under different temperature conditions. Slices of guinea pig hippocampus (n=40) were placed at the interface of artificial cerebrospinal fluid (aCSF) and gas (normoxia: 95% O2, 5% CO2; hypoxia: 95% N2, 5% CO2). Evoked potentials (EP) and direct current (DC) potentials were recorded from hippocampal CA1 region. Slices were subjected to two repetitive hypoxic episodes under the following temperature conditions: (A) 34 degrees C/34 degrees C, (B) 30 degrees C/30 degrees C and (C) 34 degrees C/30 degrees C. Hypoxic phases lasted until an anoxic terminal negativity (ATN) occurred. The recovery after first hypoxia lasted 30 min. Tissue function was assessed regarding the latency of ATN and the recovery of evoked potentials. The ATN latencies with protocol A (n = 25) for the first and second hypoxia were 5.9+/-1.3 min (mean+/-S.E.M., 1st hypoxia) and 2.4+/-0.9 min (2nd hypoxia), with protocol B the latencies (n = 7) were significantly longer: 25.2+/-7.1 min and 15.6+/-7.7 min. With protocol C (n=8), the latencies were 5.6+/-1.8 and 3.3+/-0.5 min. No differences were seen in the recovery of the EPs with protocols A-C. Our results suggest that a mild hypothermia is only neuroprotective if applied from an initial hypoxia onwards
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