1,720,990 research outputs found
Effects of trimethyltin on granule cells excitability in the in vitro rat dentate gyrus
No full textThe effects of trimethyltin (TMT) on passive properties and synaptic activity of dentate granule cell (GC) have been investigated in hippocampal slices in vitro. Intracellular recordings from GC indicated that TMT (1 and 10 microM) increased input resistance from 34.1 +/- 3.6 Mohms to 45.6 +/- 4.1 and 64.7 +/- 14.7 Mohms, respectively, 15 min after its application. This was accompanied by a 10-20 mV depolarization. A decrease in IPSP amplitude was also observed, but developed with longer delays (2-4 hr) following TMT exposure. Extracellular recording from the GC layer during paired pulse stimulation of the perforant path showed a decrease in the ratio of the amplitude of the first to the second population spikes (at an interpulse interval of 9 msec), from 1.8 +/- 0.14 to 0.8 +/- 0.08 (p less than 0.05). The amplitude of the first (conditioning) pulse remained unchanged, suggesting that TMT produced a specific decrease of inhibitory efficacy. These results add evidence to the hypothesis that TMT neurotoxicity is mediated by a decrease of inhibitory synaptic functions
Hyperpolarization-activated ion currents in cultured rat cortical and spinal cord astrocytes
No full textHyperpolarization-activated currents were recorded f r om r a t b r a i n c o r t i cal
and spinal cord astrocytes maintained i n culture. Spinal cord astrocytes expressed
pr i m a r i l y an i n w a r d rectifier potassium current characterized by time-dependent inactivation,
a strong dependence on extracellular N a + and insensitivity to i n t r a c e l l u l a r GTP-
-y-S ( 0 . 2 mM). I n cortical astrocytes voltage clamp protocols aimed to elicit currents
activated at, or negative to cell membrane potentials led to the development of two
distinct ion currents. The most prominent current resembled the inwar d rectifier potassium
current. This component was sensitive to blockade by extracellular cesium and
was greatly reduced d u r i n g recordings performed w i t h GTP-7-S ( 0 . 2 Mm) added to the
pipette solutions. The remaining current component was similar to the endothelial I h a
current. I h a conductance was enhanced by extracellular potassium and the current reversal
potential behaved as expected for a mixed cation, N a 7 K + current. I h a was nearly
abolished after removal of extracellular Na". These results are consistent w i t h the
expression of a novel mixed cation conductance i n g l i a l cells, possibly involved i n extracell
u l a r potassium bufferin
A dynamic model of the blood-brain barrier "in vitro"
No full textCell culture models have been widely used for screening of neurotoxicants and represent a viable alternative to direct in vivo experiments. We have developed a dynamic in vitro blood-brain barrier model designed to allow for extensive toxicological, pharmacological and physiological testing. Induction of blood-brain barrier properties in a tri-dimensional hollow fiber culturing apparatus was investigated by co-culturing a bovine aortic endothelial cell line (or rat brain endothelial cells) with rat brain astrocytes (or C6 rat glioma cells) under pulsatile flow conditions to mimic intraluminal blood flow. Cell growth was monitored over time by measuring glucose consumption and lactate production: these experiments confirmed that the hollow fiber cell culturing systems can maintain viable cells in culture for extended (> 1 month) periods of time. Cells were visually inspected after culturing and dissociation from the hollow fiber cartridge and identified as endothelial (by fluorescent Dil-Ac-LDL uptake) or glial (by GFAP immunoreactivity). Blood-brain barrier properties were tested by intraluminal injection of horse-radish peroxidase (HRP, mol. weight 44,000), glucose (m.w. 180) or potassium. Either procedure demonstrated that aortic cells co-cultured with astrocytes (or C6 cells) developed a selective barrier with an estimated electrical resistance of 2,900 omega/cm2. The electrophysiological and morphological properties of BAEC were also affected by the co-culturing process, suggesting that astrocytes induced CNS properties in these cells. These results demonstrate that the hollow fiber cell co-culturing system may be used as a dynamic model of the mammalian blood-brain barrier
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
Insulin permeability across an in vitro dynamic model of endothelium
No full textPurpose. Endothelium insulin permeability was investigated using in vitro, dynamic culture of endothelial cells. Methods. Endothelial cells were cultured in a hollow fiber apparatus and continuously exposed to a flow. Transendothelial electrical resistance and permeability to [C-14]sucrose and [C-14]inulin were used to monitor the integrity of the endothelial monolayer. Results. Under these experimental conditions, measurements of insulin permeability, investigated at increasing hormone concentrations, suggested that the predominant transendothelial insulin fluxes were attributable to bidirectional convective transport rather than to a saturable transport mechanism, in agreement with in vivo experiment results published earlier. Analytical determinations of insulin catabolism demonstrated a low percent of insulin degradation by the endothelium, leading to production of insulin metabolites qualitatively identical to those produced by human monocytes. Conclusions. The findings of this paper indicated that (a) insulin crosses the endothelial monolayer by paracellular "leak" and endothelial insulin receptors have a minor (if any) role in insulin transport; (b) degradation of the hormone by BAEC is minimal; (c) the in vitro, dynamic culture of endothelial cells presented here should represent a valuable transport model system to study permeability mechanisms of insulin and many other drugs
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
Brain dysfunction in COVID-19 and CAR-T therapy: cytokine storm-associated encephalopathy
Full text linkObjective: Many neurological manifestations are associated with COVID-19, including a distinct form of encephalopathy related to cytokine storm, the acute systemic inflammatory syndrome present in a subgroup of COVID-19 patients. Cytokine storm is also associated with immune effector cell-associated neurotoxicity syndrome (ICANS), a complication of chimeric antigen receptor T-cell (CAR-T) therapy, a highly effective treatment for refractory hematological malignancies. We investigated whether COVID-19-related encephalopathy, ICANS, and other encephalopathies associated with cytokine storm, share clinical and investigative findings. Methods: Narrative literature review. Results: Comparisons between COVID-19-related encephalopathy and ICANS revealed several overlapping features. Clinically, these included dysexecutive syndrome, language disturbances, akinetic mutism and delirium. EEG showed a prevalence of frontal abnormalities. Brain MRI was often unrevealing. CSF elevated cytokine levels have been reported. A direct correlation between cytokine storm intensity and severity of neurological manifestations has been shown for both conditions. Clinical recovery occurred spontaneously or following immunotherapies in most of the patients. Similar clinical and investigative features were also reported in other encephalopathies associated with cytokine storm, such as hemophagocytic lymphohistiocytosis, sepsis, and febrile infection-associated encephalopathies. Interpretation: COVID-19-related encephalopathy and ICANS are characterized by a predominant electro-clinical frontal lobe dysfunction and share several features with other encephalopathies associated with cytokine storm, which may represent the common denominator of a clinical spectrum of neurological disorders. Therefore, we propose a unifying definition of cytokine storm-associated encephalopathy (CySE), and its diagnostic criteria
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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