The hypoxia inducible factor 1 (HIF-1) and the cyclic AMP-responsive element binding protein (CREB) are two transcription factors that have been studied in the context of neuronal survival and neurodegeneration. HIF-1 upregulation and CREB activation have been observed not only in neurons but also in astrocytes under conditions of hypoxia. We hypothesized that activation of CREB regulate HIF-1α expression in the nucleus of cortical astrocytes under in vitro ischemic condition. To test the hypothesis, we determined the effects of inhibiting the CREB activation pathway on the expression of HIF-1α protein in astrocytes exposed to CoCl and severe hypoxia (near anoxia, 0.1% O). The results demonstrated that inhibition of CaMKII and CaMKIV had no effect on both HIF-1α and pCREB expression in cortical astrocytes exposed to CoCl and anoxia. In contrast, PKA inhibition lowered the expression of HIF-1α and pCREB expression. Furthermore, the inhibition of PKA but not CaMKII or CaMKIV increased cell death of astrocytes exposed to near anoxia. The results suggest that PKA plays an important role in the cell survival signaling pathways in astrocytes.
Objectives:
Clinical research is a collaborative enterprise; researchers benefit from the expertise, experience, and resources of their collaborators. We sought to describe the extent and patterns of collaboration among pediatric critical care trialists, and to identify the most influential individuals, centers, and countries.
Design:
Social network analysis of coauthorship.
Data Sources:
Publications of pediatric critical care randomized controlled trials (1986–2018).
Data Extraction:
We manually extracted the names of all authors and their affiliations. We used productivity (number of randomized controlled trials), influence (number of citations), and four measures of prominence in the social network (degree, betweenness, closeness, and eigenvector centrality) to identify the most influential individuals.
Measurements and Main Results:
From 415 randomized controlled trials in pediatric critical care, we identified 2,176 trialists from 377 centers in 43 countries. The coauthorship network is highly disconnected and dominated by a single large cluster of trialists publishing 142 (34%) of the randomized controlled trials. However, 119 (29%) of the randomized controlled trials were published by 28 smaller clusters—a median (interquartile range) of 3 (2–4) randomized controlled trials each. The remaining 154 (37%) randomized controlled trials were coauthored by researchers publishing a single randomized controlled trial each. This overall structure has remained constant with the publication of new randomized controlled trials over 33 years. The most influential trialists and centers varied according to the metric we used; only one trialist and three centers ranked in the top 10 for all measures of influence. Thirty-five of the 40 trialists (88%) ranking in the top 10 of any of the measures were from the United States, the United Kingdom, and Canada.
Conclusions:
Pediatric critical care has made considerable progress in the number of trialists and randomized controlled trials, but the research enterprise remains highly clustered and fragmented, particularly geographically. Efforts to further increase the quantity and quality of research in the field should include steps to increase the level and range of collaboration.
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