17 research outputs found
DS Mice Undergo SUDEP.
<p>A. Kaplan-Meier survival curves for WT and DS mice (N = 75 for each group, p < 0.0001, Log-rank, Mantel-Cox, Survival Test). B. Percent survival in WT (N = 8) and DS (N = 13) mice implanted with radiotelemetry units. SUDEP or near-SUDEP in 3 DS mice (at P41, P45, and P51, respectively).</p
Dominant Frequency Analysis.
<p><i>A. Sinus</i> rhythm 1 day prior to SUDEP, which is consistent with heart rate (728 bpm) analysis. B. Muscle artifact embedded in the sinus ECG (same as <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0077843#pone-0077843-g009" target="_blank">Figure 9 C</a>) without any clear frequency peaks. C. High frequency electrical activity without any discernible sinus activity, consistent with VF (~25 Hz, same as <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0077843#pone-0077843-g009" target="_blank">Figure 9, D and E</a>). D. PTZ induced seizures lead to a lower frequency electrical signal (~10 - 20 Hz). <i>Inset</i>: Representative snapshots of the ECG signal included in the fast-fourier transformation.</p
mScn5a and Nav1.5 levels are unchanged in DS mutant hearts.
<p>A. Heart RNA from biological replicates (DS mice, n = 4; WT mice, n = 5) were used to generate two independent cDNAs per animal. The cDNAs were assayed using qPCR in quadruplicate with two independent <i>Scn5a</i> TaqMan primer sets and normalized to 18s RNA. B. Western blots of membrane proteins isolated from DS and WT ventricular CMs. 50 µg of protein was loaded in each lane, and probed with anti-Na<sub>v</sub>1.5 (Mohler 1:1000), and anti-α-actin (Sigma 1:500), which served as the loading control. C. Quantification of Na<sub>v</sub>1.5 expression normalized to α-actin expression.</p
Cardiac Arrhythmias Precede SUDEP in DS.
<p>Lead II ECG traces illustrating cardiac arrhythmias preceding death. A-C. In mouse DS-2, muscle artifact consistent with convulsive seizures was preceded by idioventricular rhythms, including premature ventricular complexes (PVCs), bundle branch block (BBB), altered QRS morphology, and R-R variability. D and E. Initiation of high frequency electrical activity without any discernible sinus activity, consistent with VF. F. Low amplitude wide complex focal bradycardia with a BBB morphology, and eventual asystole. </p
DS myocytes exhibit increased excitability and incidence of early after depolarizations (EADs).
<p>A. DS myocytes require significantly less injected current to fire APs. B. DS myocyte AP upstroke velocity is faster at all pacing cycle lengths (<i>p</i> = ns). C. Slight prolongation of the AP duration at 30%, 50%, and 75% repolarization at many pacing cycle lengths (<i>p</i> = ns). D. DS myocytes are significantly more susceptible to EADs, a substrate for arrhythmogenesis. <i>Inset</i>: Representative EADs from DS myocytes (red.) Panels A-C, unpaired t-test with Welch’s correction. Panel D χ<sup>2</sup> Test (WT, N = 9, n = 11, DS, N = 8, n = 17).</p
Isolation of TTX-R and TTX-S I<sub>Na</sub> Biophysical Properties.
<p>A. Boltzman curves for the voltage dependence of I<sub>Na</sub> availability and conductance for the total cardiac I<sub>Na</sub> (TTX-S + TTX-R I<sub>Na</sub>; reproduction of the curve-fits from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0077843#pone-0077843-g001" target="_blank">Figure 1C</a>). In both WT and DS myocytes the V<sub>½</sub> values of TTX-R I<sub>Na</sub> (closed circles, following blockade of TTX-S I<sub>Na</sub> with 100 nM TTX) and TTX-S I<sub>Na</sub> (open circles, defined as total I<sub>Na</sub> minus TTX-R I<sub>Na</sub>) are plotted. Pharmacological separation of TTX-S and TTX-R I<sub>Na</sub> was confirmed by the loss of difference in the V<sub>½</sub> values between WT vs DS, and the development of a significant difference between the TTX-S vs. TTX-R V ½ values for I<sub>Na</sub> availability and conductance. B. Zoom-in of the boxed region in A.</p
Altered Heart Rates Precede Death.
<p>A. DS mice exhibit significant QT prolongation (50 - 90%). B. Heart rates in DS mice decrease 100 min before death, followed by a sharp increase just prior to the terminal event, while the WT heart rates remains high and constant. (100 minutes = 10:16 PM in WT-1 and DS-1; 7:46 PM in WT-2 and DS-2). C. WT-3 and DS-3 HR cycling, followed by DS exhibiting sudden drops in heart rate in the 72 h preceding death. D and E. Increased R-R variability 60 min prior to SUDEP in DS-1 (blue) and DS-2 (red), respectively, with further increased variability immediately preceding the lethal arrhythmia, while 1 day prior at the same time the R-R interval was constant (black). F. Progressive bradycardia and increased R-R variability in DS-3 at several time points preceding an agonal state and euthanasia (denoted by colored arrows in C).</p
DS Mice Have Altered Cardiac I<sub>Na</sub> Properties.
<p>A. Current-voltage (I-V) relationship of transient I<sub>Na</sub>. Peak transient I<sub>Na</sub> density is increased 2-fold in the DS (N = 6, n = 14) vs WT cardiac myocytes (N = 8, n = 20, <i>p</i> < 0.0001). <i>Inset</i>: Representative traces from each group. B. I-V relationship for persistent I<sub>Na</sub> (pre- minus post-30 µM TTX) also shows a 2-fold increase in peak persistent I<sub>Na</sub> in the DS vs. WT groups. To further confirm these results we employed the P/4 method to measure the persistent I<sub>Na</sub>, yielding similar results (-60 mV, WT, -1.72 ± 0.50; DS, -3.88 ± 0.72, N = 2, n = 5-9, <i>p</i> = 0.02). C. Leftward shift (V<sub>½</sub> of Boltzman fit, <i>p</i> = 0.04) in the voltage dependence of I<sub>Na</sub> availability and conductance in the DS group. D. Similar percent change in peak transient I<sub>Na</sub> density upon administration of 100 nM TTX in the WT and DS groups. Unpaired t-test with Welch’s correction.</p
Decreased Threshold for PTZ Induced Seizures in DS Mice.
<p>WT and DS mice were administered incremental doses of pentylenetetrazole (PTZ), monitored for observable seizures, and classified on the Racine Scale.</p
Aberrant cellular mosaicism in <i>Pten</i> cKOs.
<p>(A–H) Immunolabeling of P21 wild-type (A) and <i>Pten</i> cKO (B) retinal flatmounts with TH. Voronoi diagrams depicting the distribution of TH<sup>+</sup> amacrine cells in P21 wild-type (C) and <i>Pten</i> cKO (D) retinae. Calculation of TH<sup>+</sup> Voronoi domain areas and their relative distributions in these two fields for P21 wild-type (C′) and <i>Pten</i> cKO (D′) retinae. Near neighbors of a TH<sup>+</sup> reference cell in P21 wild-type (E) and <i>Pten</i> cKO (F) retinae, with the nearest neighbour indicated in red. Frequency distribution of nearest neighbor distances between TH<sup>+</sup> amacrine cells in these two fields for P21 wild-type (E′) and <i>Pten</i> cKO (F′) retinae. Calculation of Voronoi domain (G) and Nearest Neighbor (H) regularity indices for TH<sup>+</sup> amacrine cells in wild-type and <i>Pten</i> cKO retinae. (I–P) Immunolabeling of P21 wild-type (I) and <i>Pten</i> cKO (J) retinal flatmounts with calbindin. Voronoi diagrams depicting the distribution of calbindin<sup>+</sup> horizontal cells in P21 wild-type (K) and <i>Pten</i> cKO (L) retinae. Calculation of TH<sup>+</sup> Voronoi domain areas and their frequency distributions in P21 wild-type (K′) and <i>Pten</i> cKO (L′) retinae in these two fields. Near neighbors of a calbindin<sup>+</sup> reference cell in P21 wild-type (M) and <i>Pten</i> cKO (N) retinae, with the nearest neighbour indicated in red. Frequency distribution of distances between TH<sup>+</sup> amacrine cells in P21 wild-type (M′) and <i>Pten</i> cKO (N′) retinae in these two fields. Calculation of Voronoi domain (O) and Nearest Neighbor (P) regularity indices for calbindin<sup>+</sup> horizontal cells in wild-type and <i>Pten</i> cKO retinae. p values are denoted as follows: <0.05 *, <0.01 **, <0.005 ***. Scale bars = 600 µm (A,B), 100 µm (C,D).</p