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Potassium channel activators protect the N-methyl-D-aspartate-induced cerebral vascular dilation after combined hypoxia and ischemia in piglets
Background and Purpose-Cerebral arteriolar dilation to N-methyl-D-aspartate (NMDA) is a neuronally mediated multistep process that is sensitive to cerebral hypoxia and ischemia (H/I). We tested the hypothesis that topical pretreatment with the selective potassium channel agonists NS1619 and aprikalim preserves the vascular response to NMDA after consecutive WI.
Methods-Pial arteriolar diameters were measured in anesthetized piglets with the use of a closed cranial window and intravital microscopy, Arteriolar responses to NMDA (10(-5), 5 x 10(-5), and 10(-4) mol/L) were recorded before and 1 hour after 10 minutes of hypoxia (8.5% O-2 in N-2) plus; 10 minutes of ischemia (WI), Ischemia was induced by increasing intracranial pressure, Subgroups were topically pretreated with 10(-5) mol/L NS1619, 10(-6) mol/L aprikalim, 10(-6) mol/L calcitonin gene-related peptide (CGRP), or 10(-5) mol/L papaverine. We also examined the effects of H/I on vascular responses to kainate (10(-4) mol/L) to assess specificity of neuronal injury.
Results-Arteriolar responses to NMDA were significantly attenuated after WI. Baseline compared with post-WI arteriolar diameters were 9+/-4% versus 3+/-2% at 10(-5) mol/L, 22+/-4% versus 4+/-2% at 5 x 10(-5) mol/L, and 33+/-4% versus 7+/-2% at 10(-4) mol/L (mean+/-SE; all P<.05, n=7), Pretreatment with NS1619 and aprikalim preserved the arteriolar responses to NMDA after WI, For NS1619 (n=6), values were as follows: 9+/-2% versus 6+/-4% at 10(-5) mol/L, 19+/-6% versus 21+/-5% at 5x10(-5) mol/L, and 35+/-3% versus 31+/-5% at 10(-4) mol/L, For aprikalim (n=7), values were as follows: 6+/-2% versus 8+/-2% at 10(-5) mol/L, 22+/-6% versus 15+/-3% at 5x10(-5) mol/L, and 41+/-5% versus 32+/-6% at 10(-4) mol/L. In contrast, piglets pretreated with CGRP (n=6) or papaverine (n=5) showed no preservation of the vascular response to NMDA after WI, although these compounds dilated the arterioles to an extent similar to that with NS1619/aprikalim. Kainate-induced arteriolar dilation (n=6) was largely preserved after H/I compared with preischemic responses,
Conclusions-(1) Vascular responses of cerebral arterioles to NMDA after H/I are preserved by pretreatment with NS1619 or aprikalim, indicating a neuroprotective effect, (2) CGRP and papaverine do not preserve the vascular response to NMDA despite causing vasodilation similar to that with NS1619 or aprikalim, This suggests that activation of potassium channels on neurons accounts for the protective effect of potassium channel agonists, (3) Preserved arteriolar dilation to kainate suggests largely intact functioning of neuronal nitric oxide synthase after H/I
Complex Hadamard matrices and Equiangular Tight Frames
In this paper we give a new construction of parametric families of complex
Hadamard matrices of square orders, and connect them to equiangular tight
frames. The results presented here generalize some of the recent ideas of
Bodmann et al. and extend the list of known equiangular tight frames. In
particular, a (36,21) frame coming from a nontrivial cube root signature matrix
is obtained for the first time.Comment: 6 pages, contribution to the 16th ILAS conference, Pisa, 201
On the Paradox of the Adder
Sometimes it is worth using Tarski’s solution rather than merely mentioning it
Combination of analysis techniques for efficient track reconstruction in high multiplicity events
A novel combination of established data analysis techniques for
reconstructing all charged-particle tracks in high energy collisions is
proposed. It uses all information available in a collision event while keeping
competing choices open as long as possible. Suitable track candidates are
selected by transforming measured hits to a binned, three- or four-dimensional,
track parameter space. It is accomplished by the use of templates taking
advantage of the translational and rotational symmetries of the detectors.
Track candidates and their corresponding hits, the nodes, form a usually highly
connected network, a bipartite graph, where we allow for multiple hit to track
assignments, edges. The graph is cut into very many minigraphs by removing a
few of its vulnerable components, edged and nodes. Finally the hits are
distributed among the track candidates by exploring a deterministic decision
tree. A depth-limited search is performed maximising the number of hits on
tracks, and minimising the sum of track-fit . Simplified models of LHC
silicon trackers, as well as the relevant physics processes, are employed to
study the performance (efficiency, purity, timing) of the proposed method in
the case of single or many simultaneous proton-proton collisions (high pileup),
and for single heavy-ion collisions at the highest available energies.Comment: 11 pages, 12 figures, submitted to EPJ
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