Thymosin β10 Expression Driven by the Human TERT Promoter Induces Ovarian Cancer-Specific Apoptosis through ROS Production

Thymosin β10 (Tβ10) regulates actin dynamics as a cytoplasm G-actin sequestering protein. Previously, we have shown that Tβ10 diminishes tumor growth, angiogenesis, and proliferation by disrupting actin and by inhibiting Ras. However, little is known about its mechanism of action and biological function. In the present study, we establish a new gene therapy model using a genetically modified adenovirus, referred to as Ad.TERT.Tβ10, that can overexpress the Tβ10 gene in cancer cells. This was accomplished by replacing the native Tβ10 gene promoter with the human TERT promoter in Ad.TERT.Tβ10. We investigated the cancer suppression activity of Tβ10 and found that Ad.TERT.Tβ10 strikingly induced cancer-specific expression of Tβ10 as well as apoptosis in a co-culture model of human primary ovarian cancer cells and normal fibroblasts. Additionally, Ad.TERT.Tβ10 decreased mitochondrial membrane potential and increased reactive oxygen species (ROS) production. These effects were amplified by co-treatment with anticancer drugs, such as paclitaxel and cisplatin. These findings indicate that the rise in ROS production due to actin disruption by Tβ10 overexpression increases apoptosis of human ovarian cancer cells. Indeed, the cancer-specific overexpression of Tβ10 by Ad.TERT.Tβ10 could be a valuable anti-cancer therapeutic for the treatment of ovarian cancer without toxicity to normal cells

Identification of Molecular Pathologies Sufficient to Cause Neuropathic Excitability in Primary Somatosensory Afferents Using Dynamical Systems Theory

Pain caused by nerve injury (i.e. neuropathic pain) is associated with development of neuronal hyperexcitability at several points along the pain pathway. Within primary afferents, numerous injury-induced changes have been identified but it remains unclear which molecular changes are necessary and sufficient to explain cellular hyperexcitability. To investigate this, we built computational models that reproduce the switch from a normal spiking pattern characterized by a single spike at the onset of depolarization to a neuropathic one characterized by repetitive spiking throughout depolarization. Parameter changes that were sufficient to switch the spiking pattern also enabled membrane potential oscillations and bursting, suggesting that all three pathological changes are mechanistically linked. Dynamical analysis confirmed this prediction by showing that excitability changes co-develop when the nonlinear mechanism responsible for spike initiation switches from a quasi-separatrix-crossing to a subcritical Hopf bifurcation. This switch stems from biophysical changes that bias competition between oppositely directed fast- and slow-activating conductances operating at subthreshold potentials. Competition between activation and inactivation of a single conductance can be similarly biased with equivalent consequences for excitability. “Bias” can arise from a multitude of molecular changes occurring alone or in combination; in the latter case, changes can add or offset one another. Thus, our results identify pathological change in the nonlinear interaction between processes affecting spike initiation as the critical determinant of how simple injury-induced changes at the molecular level manifest complex excitability changes at the cellular level. We demonstrate that multiple distinct molecular changes are sufficient to produce neuropathic changes in excitability; however, given that nerve injury elicits numerous molecular changes that may be individually sufficient to alter spike initiation, our results argue that no single molecular change is necessary to produce neuropathic excitability. This deeper understanding of degenerate causal relationships has important implications for how we understand and treat neuropathic pain

Supernova remnants: the X-ray perspective

Supernova remnants are beautiful astronomical objects that are also of high scientific interest, because they provide insights into supernova explosion mechanisms, and because they are the likely sources of Galactic cosmic rays. X-ray observations are an important means to study these objects.And in particular the advances made in X-ray imaging spectroscopy over the last two decades has greatly increased our knowledge about supernova remnants. It has made it possible to map the products of fresh nucleosynthesis, and resulted in the identification of regions near shock fronts that emit X-ray synchrotron radiation. In this text all the relevant aspects of X-ray emission from supernova remnants are reviewed and put into the context of supernova explosion properties and the physics and evolution of supernova remnants. The first half of this review has a more tutorial style and discusses the basics of supernova remnant physics and thermal and non-thermal X-ray emission. The second half offers a review of the recent advances.The topics addressed there are core collapse and thermonuclear supernova remnants, SN 1987A, mature supernova remnants, mixed-morphology remnants, including a discussion of the recent finding of overionization in some of them, and finally X-ray synchrotron radiation and its consequences for particle acceleration and magnetic fields.Comment: Published in Astronomy and Astrophysics Reviews. This version has 2 column-layout. 78 pages, 42 figures. This replaced version has some minor language edits and several references have been correcte

Mortality and pulmonary complications in patients undergoing surgery with perioperative SARS-CoV-2 infection: an international cohort study

Background: The impact of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) on postoperative recovery needs to be understood to inform clinical decision making during and after the COVID-19 pandemic. This study reports 30-day mortality and pulmonary complication rates in patients with perioperative SARS-CoV-2 infection. Methods: This international, multicentre, cohort study at 235 hospitals in 24 countries included all patients undergoing surgery who had SARS-CoV-2 infection confirmed within 7 days before or 30 days after surgery. The primary outcome measure was 30-day postoperative mortality and was assessed in all enrolled patients. The main secondary outcome measure was pulmonary complications, defined as pneumonia, acute respiratory distress syndrome, or unexpected postoperative ventilation. Findings: This analysis includes 1128 patients who had surgery between Jan 1 and March 31, 2020, of whom 835 (74·0%) had emergency surgery and 280 (24·8%) had elective surgery. SARS-CoV-2 infection was confirmed preoperatively in 294 (26·1%) patients. 30-day mortality was 23·8% (268 of 1128). Pulmonary complications occurred in 577 (51·2%) of 1128 patients; 30-day mortality in these patients was 38·0% (219 of 577), accounting for 81·7% (219 of 268) of all deaths. In adjusted analyses, 30-day mortality was associated with male sex (odds ratio 1·75 [95% CI 1·28–2·40], p\textless0·0001), age 70 years or older versus younger than 70 years (2·30 [1·65–3·22], p\textless0·0001), American Society of Anesthesiologists grades 3–5 versus grades 1–2 (2·35 [1·57–3·53], p\textless0·0001), malignant versus benign or obstetric diagnosis (1·55 [1·01–2·39], p=0·046), emergency versus elective surgery (1·67 [1·06–2·63], p=0·026), and major versus minor surgery (1·52 [1·01–2·31], p=0·047). Interpretation: Postoperative pulmonary complications occur in half of patients with perioperative SARS-CoV-2 infection and are associated with high mortality. Thresholds for surgery during the COVID-19 pandemic should be higher than during normal practice, particularly in men aged 70 years and older. Consideration should be given for postponing non-urgent procedures and promoting non-operative treatment to delay or avoid the need for surgery. Funding: National Institute for Health Research (NIHR), Association of Coloproctology of Great Britain and Ireland, Bowel and Cancer Research, Bowel Disease Research Foundation, Association of Upper Gastrointestinal Surgeons, British Association of Surgical Oncology, British Gynaecological Cancer Society, European Society of Coloproctology, NIHR Academy, Sarcoma UK, Vascular Society for Great Britain and Ireland, and Yorkshire Cancer Research

25th annual computational neuroscience meeting: CNS-2016

The same neuron may play different functional roles in the neural circuits to which it belongs. For example, neurons in the Tritonia pedal ganglia may participate in variable phases of the swim motor rhythms [1]. While such neuronal functional variability is likely to play a major role the delivery of the functionality of neural systems, it is difficult to study it in most nervous systems. We work on the pyloric rhythm network of the crustacean stomatogastric ganglion (STG) [2]. Typically network models of the STG treat neurons of the same functional type as a single model neuron (e.g. PD neurons), assuming the same conductance parameters for these neurons and implying their synchronous firing [3, 4]. However, simultaneous recording of PD neurons shows differences between the timings of spikes of these neurons. This may indicate functional variability of these neurons. Here we modelled separately the two PD neurons of the STG in a multi-neuron model of the pyloric network. Our neuron models comply with known correlations between conductance parameters of ionic currents. Our results reproduce the experimental finding of increasing spike time distance between spikes originating from the two model PD neurons during their synchronised burst phase. The PD neuron with the larger calcium conductance generates its spikes before the other PD neuron. Larger potassium conductance values in the follower neuron imply longer delays between spikes, see Fig. 17.Neuromodulators change the conductance parameters of neurons and maintain the ratios of these parameters [5]. Our results show that such changes may shift the individual contribution of two PD neurons to the PD-phase of the pyloric rhythm altering their functionality within this rhythm. Our work paves the way towards an accessible experimental and computational framework for the analysis of the mechanisms and impact of functional variability of neurons within the neural circuits to which they belong

Simulation and dynamical explanation of change in spiking pattern.

<p>(<b>A</b>) Spiking pattern during sustained depolarization was converted from onset-only (normal, β_w = −21 mV) to repetitive (neuropathic, β_w = −13 mV) by varying a single parameter. Onset-only spiking was observed in the neuropathic model but for only a narrow stimulus range. (<b>B</b>) According to bifurcation analysis in which stimulation (<i>I</i>_stim) was systematically varied, repetitive spiking was produced by the neuropathic model when <i>I</i>_stim exceeded a critical value required for a subcritical Hopf bifurcation. In contrast, the normal model did not undergo a bifurcation, which means spiking was limited to single spikes generated through a QS-crossing (see below). Generation of a single spike does not constitute a change in steady-state behavior, consistent with the absence of a bifurcation. (<b>C</b>) Phase planes show the fast activation variable <i>V</i> plotted against the slower recovery variable <i>w</i>. Nullclines (color) indicate where <i>V</i> or <i>w</i> do not change. Excitatory stimulation shifts the <i>V</i>-nullcline upward without affecting the <i>w</i>-nullcline. In the neuropathic model, <i>V</i>- and <i>w</i>-nullclines intersect at a stable (<i>s</i>) fixed point prior to stimulation, but that point becomes unstable (<i>u</i>) during stimulation – this corresponds to a Hopf bifurcation and is responsible for repetitive spiking. In the normal model, the fixed point remains stable during stimulation despite the <i>V</i>-nullcline shifting upward, but a single spike can nonetheless be generated depending on how the system moves to the newly positioned fixed point. The trajectory can be predicted by reference to a quasi-separatrix (QS), which corresponds to a manifold in phase space from which trajectories diverge. Quasi-separatrices were plotted here by integrating with a negative time step with initial values indicated by * on the phase planes (see <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1002524#s4" target="_blank">Methods</a>). Like the <i>V</i>-nullcline, the QS shifts instantaneously with stimulation. If, as shown, the original fixed point ends up below the shifted QS, the trajectory to the newly positioned fixed point must follow an indirect route around the end of the QS (*), thus producing a spike; a more direct, subthreshold route would require the trajectory to cross back over the QS, which is not possible. If the original fixed point remained above the shifted QS, the trajectory would follow a direct route and no spike would be produced (not illustrated).</p

Simulation and dynamical explanation of bursting.

<p>(<b>A</b>) Sample responses at different average membrane potentials in the neuropathic model (β_w = −13 mV) with slow adaptation mediated by <i>I</i>_AHP. Noise was included in all simulations and makes the bursting irregular (and thus more realistic) but noise is not necessary for bursting. Duration and frequency of bursts increased with average depolarization. (<b>B</b>) Bursting depends on hysteresis caused by bistability associated with the subcritical Hopf bifurcation. Inset shows <i>V</i> and <i>z</i> during sample burst, where <i>z</i> controls activation of <i>I</i>_AHP. The same response, with its differently colored burst and interburst phases, was projected onto the bifurcation diagram created by treating <i>z</i> as a bifurcation parameter. The model tracks the stable limit cycle branch, spiking repetitively as <i>z</i> increases until the end of the branch is reached, at which point the burst stops. The model then tracks the stable fixed point as <i>z</i> decreases (during which noise-dependent MPOs wax and wane) until the fixed point becomes unstable, at which point another burst starts. Hysteresis is evident from the bursts starting and stopping at different values of <i>z</i>. This bifurcation diagram is flipped horizontally relative to those shown in other figures because the bifurcation parameter here controls <i>I</i>_AHP, which is an inhibitory current, whereas <i>I</i>_stim (the bifurcation parameter used elsewhere) is excitatory.</p

Relating parameter changes in the 2-D model with more biologically meaningful changes in a 3-D model.

<p>(<b>A</b>) Changing β_w from −21 mv to −13 mV shifts the <i>I</i>_slow-<i>V</i> curve to the right, which corresponds to a rightward shift in the <i>w</i>-nullcline on the <i>V-w</i> phase plane (inset) and switches the spike initiation mechanism (see <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1002524#pcbi-1002524-g002" target="_blank"><b>Fig. 2</b></a>). In the 2-D model, β_w represents the voltage-dependency of <i>I</i>_slow which, in reality, comprises multiple currents with slow kinetics. The biological realism of the model can be increased by “ungrouping” <i>I</i>_slow into two (or more) components, one representing the delayed-rectifier potassium current <i>I</i>_K,dr and one representing a subthreshold current <i>I</i>_sub that can be inward or outward depending on the reversal potential. (<b>B</b>) Voltage-dependent activation curve for <i>I</i>_sub. Parameter values (indicated on the figure) were determined as explained below. In the 3-D model, the (<i>I</i>_K,dr+<i>I</i>_sub)−<i>V</i> curve was shifted the same as the <i>I</i>_sub-<i>V</i> curve in A by increasing inward <i>I</i>_sub (<b>C</b>) or by decreasing outward <i>I</i>_sub (<b>D</b>) on the basis of varying <i>g</i>_sub. Bifurcation diagrams demonstrate the change in spike initiation mechanism. With <i>I</i>_K,dr properties fixed, maximal conductance and voltage-sensitivity of <i>I</i>_sub were adjusted to recreate the shift shown in A; derived parameters illustrate the importance of the modulated conductance activating at subthreshold potentials. Adding or removing the same subthreshold currents to a Hodgkin-Huxley model (rather than to our starting 2-D Morris-Lecar model) produces equivalent changes in excitability (data not shown). By comparison, modulating current that activates only at suprathreshold potentials (β_y = 0 mV) had no effect on the (<i>I</i>_K,dr+<i>I</i>_supra)−<i>V</i> curve in the perithreshold voltage range, and thus the spike initiation dynamics were unchanged (see <b><a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1002524#pcbi.1002524.s004" target="_blank">Fig. S4</a></b>).</p

Simulating the continuum of pathological change.

<p>(<b>A</b>) Summary of <i>I</i>_stim thresholds to elicit onset-only or repetitive spiking for different values of β_w in our standard 2-D model. Reduction in threshold equates with an increase in excitability. Summary of peak MPO power (<b>B</b>) and peak frequency (<b>C</b>) across a range of β_w values. All simulations included noise. For each β_w value, <i>I</i>_stim was chosen relative to the threshold for repetitive spiking: <i>high</i> and <i>low I</i>_stim were 1.3 and 4 µA/cm² below threshold, respectively. Those values were chosen in order to include or exclude, respectively, noise-independent MPOs when a supercritical Hopf bifurcation occurs. Peak MPO amplitude and frequency decreased as β_w was increased. That trend is not attributable to noise-independent MPOs occurring at certain β_w values since noise-independent MPOs were excluded when testing with <i>low I</i>_stim (see above). Moreover, re-setting γ_m from 18 mV to 15 mV prevented the supercritical Hopf bifurcation from occurring at any β_w, but the same trend in MPO power and frequency was observed (data not shown). Dotted curve in C shows minimum sustainable firing rate. * indicates data points that include a noise-independent MPO component.</p