31 research outputs found

    Additional file 4: Figure S4. of Somato-dendritic decoupling as a novel mechanism for protracted cortical maturation

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    Dormant cells are neuronal in nature. A: A biocytin-filled dormant neuron (left) and NeuN co-staining of the same section (right) illustrating the nuclear region of the same cell (dotted circle). Scale bar = 25 μm. B: Summary data (t (4) = 6.83 p = 0.0024 n = 5; one-sample t test) of NeuN immunoreactivity. To make individual fluorescence measurements comparable, we normalized the ’co-labelled’ NeuN signals to the highest NeuN signals (i.e. pixel density) obtained from the same sections. Co-labelled cells generally had a less dense and more diffuse NeuN staining pattern. C: To ensure that diffuse NeuN staining was not due to recording conditions, NeuN signals were analysed for a population of TeA neurons and normalized for comparison in the same way as in panel B: a high percentage of TeA neurons have moderate to low levels of NeuN staining. **p < 0.01. (PDF 673 kb

    Additional file 2: Figure S2. of Somato-dendritic decoupling as a novel mechanism for protracted cortical maturation

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    Recordable currents from TeA dendrites. A: Differential interference contrast (DIC) microscopy images of the same pyramidal neuron illustrating recordings targeted to a dendrite (left) and to that of the soma (right). Scale bar = 20 μm. B: Corresponding current traces from somatic (red) and dendritic (black) recordings in response to a voltage ramp from –120 to +50 mV. The corresponding traces from panel A are shown in purple and blue for the dendrite and soma respectively for the same cell example. Note that a total of four traces have been shown for each group (i.e. soma and dendrite). C–D: Summary data demonstrating significantly lower membrane conductance (G) at both hyperpolarized (–100 mV; t (5) = 3.18 Welch-corrected p = 0.024) and depolarized (+50 mV; t (5) = 3.29 Welch-corrected p = 0.022) potentials from somatic (n = 11) compared to dendritic (n = 6) recordings. *p < 0.05. (PDF 184 kb

    Additional file 7: Figure S7. of Somato-dendritic decoupling as a novel mechanism for protracted cortical maturation

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    Presence of anionic but not cationic membrane current. A: Representative current traces (left) for both low free bicarbonate (red; n = 15; pH 3.5–4; 50 mM NaHCO3) and high free bicarbonate ion (black; n = 14; pH 8–8.5; 50 mM NaHCO3) internal pipette recording conditions are shown in A. Cells were held at –60 mV and a voltage command ramp from –120 to +50 mV was applied. (Right) Group data illustrating a significant larger slope conductance (G) under alkaline conditions (t (13) = 3.80 Welch-correction p = 0.0022 on square rooted-transformed data to minimize distribution skew). Importantly, under these conditions, cells still failed to demonstrate action potential and rectifying currents under both ramp or step protocols. B: Given the lack of any observable current under acidic recording conditions, the membrane impermeable amphipathic dye FM1-43 (≈40 μM) was included in the pipette (n = 10). Scale bar = 20 μm. C: Current traces (left) from the same cell under high free bicarbonate internal recording conditions before (black) and after (orange) bath application of the anionic (chloride and electrogenic NBC co-transporter) channel blockers SITS and DIDS (≈1 mM). Cells were held at a holding potential of –60 mV and a voltage command ramp from –160 to +80 mV was applied. (Right) Summary data showing that the high free bicarbonate internal recording condition membrane current is sensitive to both SITS and/or DIDS. Bath application of SITS and/or DIDS led to a significant decrease in recordable current (Wilcoxon signed-rank test W = –36.0, p = 0.0039 n = 8). When stratified into individual or combined drug application, similar findings were observed (t (3) = 5.60 p = 0.011 one-sample t test and t (3) = 33.38 p < 0.0001 one-sample t test for either and both blockers respectively), with almost 90 % of the recordable current being blocked with SITS and DIDS application. *p < 0.025; **p < 0.01. (PDF 1103 kb

    Additional file 8: Figure S8. of Somato-dendritic decoupling as a novel mechanism for protracted cortical maturation

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    Optical changes driven by the imposed pipette tonicity. A–B: A schematic illustration of the experiments to confirm a whole-cell configuration based on the characteristic feature that, under whole-cell conditions, the properties of the pipette solution are imposed to the cytosol through dialysis. Here a hypotonic pipette solution was used to provide a driving force for the movement of ions from the cell interior to the pipette during dialysis (red arrow; panel A). Following dialysis (e.g. >3 min) the interior of the cell becomes like the pipette solution (i.e. hypotonic), thus leading to a crenation-like effect in cell shape as water moves out of the cell (panel A). Conversely, using a hypertonic pipette solution will result in the opposite effect; ions move into the cell and ultimately lead to cell swelling membrane dimpling (panel B). C: Representative examples of these types of responses, which were quite robust occurring in 100 % of cells tested. Under these conditions cells still failed to demonstrate action potential and rectifying currents. D: This response can be partially quantified using an ImageJ profile analysis where the grey value represents regions of high contrast (e.g. edges) from the DIC image region of interest (orange line; the coloured arrows correspond to the same spatial locations as in panel C). It should be mentioned that unlike the XY planes of the cell which are associated with the coverslip, changes could also be observed in the Z plane but were difficult to quantify. The colors correspond to the initial condition (green) and the dialyzed condition (orange) for both panels C and D. E: The summarized data represent the proportional change in cross-sectional distance of dormant cells for both the hypertonic (light grey; n = 6; t (5) = 4.28, one-sampled t test p = 0.0079) and hypotonic (dark grey; n = 5; t (4) = 10.51, one-sampled t test p = 0.0005) conditions. Note that volume increases non-linearly with distance. * denotes p < 0.05. Scale bar = 5 μm. (PDF 148 kb

    Additional file 6: Figure S6. of Somato-dendritic decoupling as a novel mechanism for protracted cortical maturation

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    TTX-sensitive spikes in spiking neurons from mature tissue. A: Representative current-clamp step-protocol traces from a spiking neuron under pre (Control) and post-tetrodotoxin (sodium channel blocker) application (TTX). The step protocol consisted of an initial –200 pA step followed by eight 50 pA steps (750 ms in duration) from an initial V m of –70 mV. B: Summarized data (n = 5) on the effect of TTX (1–0.1 μM) on the number of spikes per second (normalized) under control and TTX conditions in spiking neurons from tissue slices around 1 month old (t (4) = –29.7; p < 0.0001). (PDF 200 kb

    Additional file 5: Figure S5. of Somato-dendritic decoupling as a novel mechanism for protracted cortical maturation

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    Lack of age-dependent increase in cell number in TeA. A: Representative images of juvenile and mature tissue sections illustrating a comparable pattern of DAPI (blue) and NeuN (green) staining. Neurofilament-200 (red) was also included here to illustrate the surrounding neuropil. Note that the intensity of DAPI staining appears, in general, weaker and more dispersed in older animals. Scale bar = 50 μm. B–C: Summarized cell count data based on DAPI (B) and NeuN (C) staining normalized for comparison. Note that there does not appear to be an increase in cell number for both the total number of cells and NeuN positive cells between juvenile (P19; n = 3 animals) and mature (P57; n = 3 animals) animals using both counting methods (t (4) = 1.45 p = 0.22 for DAPI and t (4) = 1.69 p = 0.17 for NeuN). These results are consistent with the general notion that the postnatal neocortex does not appear to produce more neurons [51]. (PDF 695 kb

    Additional file 3: Figure S3. of Somato-dendritic decoupling as a novel mechanism for protracted cortical maturation

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    BDNF can stimulate TeA maturation and somato-dendritic coupling. A: DIV20 cultures immunocytochemically labelled with the dendritic-associated marker MAP2 under control (TeA) and BDNF treatment (TeA + BDNF) on DIV6 (50 ng/ml). Scale bar = 50 μm. B: Summary data showing the density of MAP2 positive dendrites in DIV12–20 cultures between control and BDNF treatment (t (12) = 5.28 p = 0.0002; n = 7 cultures). C: Single-cell GFP-labelled neurons under control (left) and BDNF-treated (right) conditions. TeA neurons were transfected with GFP plasmid on DIV12 and visualized on DIV13. Scale bar = 20 μm. D: Summary data of TeA neurite length between control and BDNF conditions (control n = 34 and BDNF-treated n = 29; t (61) = 7.31 p < 0.0001). E: Summary data of the proportion of dormant neurons. The first two bars (Juvenile and Mature) represent re-plotted data from intact tissue at different ages representing the total proportion of neurons that exhibit the dormant phenotype (P10-28 vs. P29-49; 78 % (n = 157) in mature vs. 41 % (n = 94) in juvenile; p < 0.0001, Fisher’s exact test), while the last two bars (TeA and TeA + BDNF) represent TeA cultures without (n = 16; DIV12–15) and with BDNF treatment (n = 15; DIV13–14, 75 % without and 33 % with; p = 0.032, Fisher’s exact test) respectively. F: Left; a DIC image of the dimensions of a TeA pyramidal cell indicating the long and short somatic axes. Note that dendrites could always be observed under DIC microscopy. With a lack of any significant voltage-gated conductances (e.g. Additional file 1: Figure S1), the specific membrane capacitance is expected to be ≈ 0.4–0.75 μF/cm2 [104–106]. Given the approximate dimensions of the soma, we can thus estimate the theoretical somatic capacitance (diameter equal to the average of the long and short axes). Inset; the theoretical and measured C m values for this cell using a value of 0.5 μF/cm2. Middle and right; images represent Alexa488 (40 μM) fluorescence images of a small capacitance pyramidal cell characteristic of the TeA and that of a spiking cell following BDNF application with confirmed aqueous dye diffusing into dendrites respectively. Scale bar = 20 μm. Colours correspond to summary data on the far right (purple n = 13; blue n = 9; orange n = 10; F (2,29) = 119.51, p < 0.0001; ANOVA and Games-Howell post-test, BDNF p < 0.0001). (PDF 232 kb

    Microbubbles Loaded with Nickel Nanoparticles: A Perspective for Carbon Sequestration

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    This work reports a microfluidic study investigating the feasibility of accelerating gaseous carbon dioxide (CO<sub>2</sub>) dissolution into a continuous aqueous phase with the use of metallic nickel (Ni) nanoparticles (NPs) under conditions specific to carbon sequestration in saline aquifers. The dissolution of CO<sub>2</sub> bubbles at different pH levels and salinities was studied to understand the effects that the intrinsic characteristics of brine in real reservoir conditions would have on CO<sub>2</sub> solubility. Results showed that an increased shrinkage of CO<sub>2</sub> bubbles occurred with higher basicity, while an increased expansion of CO<sub>2</sub> bubbles was observed with a proportional increase in salinity. To achieve acceleration of CO<sub>2</sub> dissolution in acidic brine containing high salinity content, the catalytic effect of Ni NPs was investigated by monitoring change in CO<sub>2</sub> bubble size at various Ni NPs concentrations. The optimal concentration for the Ni NPs suspension was determined to be 30 mg L<sup>–1</sup>; increasing the concentration up to 30 mg L<sup>–1</sup> showed a significant increase in the dissolution of CO<sub>2</sub> bubbles, but increasing from 30 to 50 mg L<sup>–1</sup> displayed a decrease in catalytic potential, due to the decreased translational diffusion coefficient that occurs at higher concentrations. The optimal additive concentration of Ni NPs was tested with variations of solution at acidic and basic conditions and different levels of salinity to reveal how effectively the Ni NPs behave under real reservoir conditions. At the acidic level, Ni NPs proved to be more effective in catalyzing CO<sub>2</sub> dissolution and can sufficiently alleviate the negative impact of salinity in brine

    Synthesis of Oxidation-Resistant Cupronickel Nanowires for Transparent Conducting Nanowire Networks

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    Nanowires of copper can be coated from liquids to create flexible, transparent conducting films that can potentially replace the dominant transparent conductor, indium tin oxide, in displays, solar cells, organic light-emitting diodes, and electrochromic windows. One issue with these nanowire films is that copper is prone to oxidation. It was hypothesized that the resistance to oxidation could be improved by coating copper nanowires with nickel. This work demonstrates a method for synthesizing copper nanowires with nickel shells as well as the properties of cupronickel nanowires in transparent conducting films. Time- and temperature-dependent sheet resistance measurements indicate that the sheet resistance of copper and silver nanowire films will double after 3 and 36 months at room temperature, respectively. In contrast, the sheet resistance of cupronickel nanowires containing 20 mol % nickel will double in about 400 years. Coating copper nanowires to a ratio of 2:1 Cu:Ni gave them a neutral gray color, making them more suitable for use in displays and electrochromic windows. These properties, and the fact that copper and nickel are 1000 times more abundant than indium or silver, make cupronickel nanowires a promising alternative for the sustainable, efficient production of transparent conductors
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