ABSTRACT
We introduce relaxed dot plots as an improvement of nonlinear dot plots for unit visualization. Our plots produce more faithful data representations and reduce moiré effects. Their contour is based on a customized kernel frequency estimation to match the shape of the distribution of underlying data values. Previous nonlinear layouts introduce column-centric nonlinear scaling of dot diameters for visualization of high-dynamic-range data with high peaks. We provide a mathematical approach to convert that column-centric scaling to our smooth envelope shape. This formalism allows us to use linear, root, and logarithmic scaling to find ideal dot sizes. Our method iteratively relaxes the dot layout for more correct and aesthetically pleasing results. To achieve this, we modified Lloyd's algorithm with additional constraints and heuristics. We evaluate the layouts of relaxed dot plots against a previously existing nonlinear variant and show that our algorithm produces less error regarding the underlying data while establishing the blue noise property that works against moiré effects. Further, we analyze the readability of our relaxed plots in three crowd-sourced experiments. The results indicate that our proposed technique surpasses traditional dot plots.
ABSTRACT
Mouse cerebral cortical mini-slices were used in a superfusion system to monitor depolarization-induced (55 mM K(+)) release of preloaded [2,3-(3)H]GABA and to investigate the biosynthesis of glutamate, GABA and aspartate during physiological and depolarizing (55 mM K(+)) conditions from either [1,6-(13)C]glucose or [U-(13)C]glutamine. Depolarization-induced GABA release could be reduced (50%) by the GABA transport inhibitor tiagabine (25 microM) or by replacing Ca(2+) with Co(2+). In the presence of both tiagabine and Co(2+) (1 mM), release was abolished completely. The release observed in the presence of 25 microM tiagabine thus represents vesicular release. Superfusion in the presence of [1,6-(13)C]glucose led to considerable labeling in the three amino acids, the labeling in glutamate and aspartate being increased after depolarization. This condition had no effect on GABA labeling. For all three amino acids, the distribution of label in the different carbon atoms revealed on increased tricarboxylic acid (TCA) activity during depolarization. When [U-(13)C]glutamine was used as substrate, labeling in glutamate was higher than that in GABA and aspartate and the fraction of glutamate and aspartate being synthesized by participation of the TCA cycle was increased by depolarization, an effect not seen for GABA. However, GABA synthesis reflected TCA cycle involvement to a much higher extent than for glutamate and aspartate. The results show that this preparation of brain tissue with intact cellular networks is well suited to study metabolism and release of neurotransmitter amino acids under conditions mimicking neural activity.
