Reconstitution Properties of Thymus Stem Cells in Murine Fetal Liver

Injection of day-12 murine fetal liver cells into thymus lobes of Thy-1 congenic adult recipients results in a wave of thymocyte development. The kinetics of repopulation by donor cells reaches a peak after 20–25 days. The frequency of thymic stem cells (TSC) in day-12 fetal liver was estimated, by limit dilution, as 1 in 4x104 cells. Within 8 hr of injection into a thymus lobe, fetal liver TSC commit to T-cell development, losing stem-cell activity. When fetal liver cells are maintained in culture for 7 days, with no exogenous cytokines added, and then injected intra-thymically (I.T.), thymus recolonization is not observed. However, TSC can be maintained in culture for 7 days with IL-1β, IL-3, IL-6, or LIF added, alone or in combination, with steel factor (SLF). Poisson analysis of fetal liver cells cultured with SLF and IL-3 together revealed a precursor frequency of 1 in 1.8x 105 cells. In contrast, the frequency of TSC in adult bone marrow was estimated by limit dilution as 1 in 12,000 cells

Respiratory simulator for robotic respiratory tract treatments

Robotic healthcare is a growing and multi-faceted field where robots help perform surgery, remotely provide care to patients, aid in supplying various physical therapies and further medical research. Robotic simulators of human physiology provide a powerful platform to advance the development of novel treatments, prostheses and therapies. This study focuses on the design, building, testing and characterisation of a novel simulator of the human respiratory system. The comparison between healthy subjects breathing and coughing physiological values and the values achieved utilising our novel bioinspired respiratory simulator shows that the latter is able to reproduce peak flow rates and volumes

Prediction of larynx function using multichannel surface EMG classification

Total laryngectomy (TL) affects critical functions such as swallowing, coughing and speaking. An artificial, bioengineered larynx (ABL), operated via myoelectric signals, may improve quality of life for TL patients. To evaluate the efficacy of using surface electromyography (sEMG) as a control signal to predict instances of swallowing, coughing and speaking, sEMG was recorded from submental, intercostal and diaphragm muscles. The cohort included TL and control participants. Swallowing, coughing, speaking and movement actions were recorded, and a range of classifiers were investigated for prediction of these actions. Our algorithm achieved F1-scores of 76.0 ± 4.4 % (swallows), 93.8 ± 2.8 % (coughs) and 70.5 ± 5.4 % (speech) for controls, and 67.7 ± 4.4 % (swallows), 71.0 ± 9.1 % (coughs) and 78.0 ± 3.8 % (speech) for TLs, using a random forest (RF) classifier. 75.1 ± 6.9 % of swallows were detected within 500 ms of onset in the controls, and 63.1 ± 6.1 % in TLs. sEMG can be used to predict critical larynx movements, although a viable ABL requires improvements. Results are particularly encouraging as they encompass a TL cohort. An ABL could alleviate many challenges faced by laryngectomees. This study represents a promising step toward realising such a device

Using Raman Spectroscopy to Improve Hyperpolarized Noble Gas Production for Clinical Lung Imaging Techniques

Spin-exchange optical pumping (SEOP) can be used to “hyperpolarize” 129Xe for human lung MRI. SEOP involves transfer of angular momentum from light to an alkali metal (Rb) vapor, and then onto 129Xe nuclear spins during collisions; collisions between excited Rb and N2 ensure that incident optical energy is nonradiatively converted into heat. However, because variables that govern SEOP are temperature-dependent, the excess heat can complicate efforts to maximize spin polarization—particularly at high laser fluxes and xenon densities. Ultra-low frequency Raman spectroscopy may be used to perform in situ gas temperature measurements to investigate the interplay of energy thermalization and SEOP dynamics. Experimental configurations include an “orthogonal” pump-and-probe design and a newer “inline” design (with source and detector on the same axis) that has provided a >20-fold improvement in SNR. The relationship between 129Xe polarization and the spatiotemporal distribution of N2 rotational temperatures has been investigated as a function of incident laser flux, exterior cell temperature, and gas composition. Significantly elevated gas temperatures have been observed—hundreds of degrees hotter than exterior cell surfaces—and variances with position and time can indicate underlying energy transport, convection, and Rb mass-transport processes that, if not controlled, can negatively impact 129Xe hyperpolarization

The Incidence of X-ray selected AGN in Nearby Galaxies

We present the identification and analysis of an unbiased sample of AGN that lie within the local galaxy population. Using the MPA-JHU catalogue (based on SDSS DR8) and 3XMM DR7 we define a parent sample of 25,949 local galaxies ($z \leq 0.33$). After confirming that there was strictly no AGN light contaminating stellar mass and star-formation rate calculations, we identified 917 galaxies with central, excess X-ray emission likely originating from an AGN. We analysed their optical emission lines using the BPT diagnostic and confirmed that such techniques are more effective at reliably identifying sources as AGN in higher mass galaxies: rising from 30% agreement in the lowest mass bin to 93% in the highest. We then calculated the growth rates of the black holes powering these AGN in terms of their specific accretion rates ($\propto L_X/M_*$). Our sample exhibits a wide range of accretion rates, with the majority accreting at rates $\leq 0.5\%$ of their Eddington luminosity. Finally, we used our sample to calculate the incidence of AGN as a function of stellar mass and redshift. After correcting for the varying sensitivity of 3XMM, we split the galaxy sample by stellar mass and redshift and investigated the AGN fraction as a function of X-ray luminosity and specific black hole accretion rate. From this we found the fraction of galaxies hosting AGN above a fixed specific accretion rate limit of $10^{-3.5}$ is constant (at $\approx 1\%$) over stellar masses of $8 < \log \mathrm{M_*/M_\odot} < 12$ and increases (from $\approx 1\%$ to $10\%$) with redshift.Comment: 18 pages, 10 figures, 2 appendices. Accepted for publication in MNRA

The incidence of AGN in galaxies with different stellar population ages

It has been argued that recycled gas from stellar mass loss in galaxies might serve as an important fuelling source for black holes (BHs) in their centers. Utilizing spectroscopic samples of galaxies from the Sloan Digital Sky Survey (SDSS) at $z = 0-0.35$ and the Large Early Galaxy Astrophysics Census (LEGA-C) survey at $z = 0.6-1$ that have X-ray coverage from XMM-Newton or Chandra, we test this stellar mass loss fuelling scenario by investigating how AGN activity and BH growth vary with the break strength at 4000 $\r{A}$, $\rm D_{n}4000$ (which is closely related to the age of stellar populations), as younger galaxies are considered to have higher stellar mass loss rates. We found that when controlling for host-galaxy properties, the fraction of log $L_{\rm X}$/$M_\star$ > 32 (which roughly corresponds to Eddington ratios $\gtrsim 1$%) AGN and sample-averaged black hole accretion rate ($\rm \overline{BHAR}$) decrease with $\rm D_{n}4000$ among $\rm D_{n}4000$ $\lesssim$ 1.9 galaxies, suggesting a higher level of AGN activity among younger galaxies, which supports the stellar mass loss fuelling scenario. For the oldest and most massive galaxies at $z = 0-0.35$, this decreasing trend is not present anymore. We found that, among these most massive galaxies at low redshift, the fraction of low specific-accretion-rate (31 $<$ log $L_{\rm X}$/$M_\star$ $<$ 32) AGNs increases with $\rm D_{n}4000$, which may be associated with additional fuelling from hot halo gas and/or enhanced accretion capability.Comment: 24 pages, 28 figures. Accepted for publication in MNRA

Improving cellular migration in tissue-engineered laryngeal scaffolds

ObjectiveTo modify the non-porous surface membrane of a tissue-engineered laryngeal scaffold to allow effective cell entry.MethodsThe mechanical properties, surface topography and chemistry of polyhedral oligomeric silsesquioxane poly(carbonate-urea) urethane were characterised. A laser technique introduced surface perforations. Micro computed tomography generated porosity data. Scaffolds were seeded with cells, investigated histologically and proliferation studied. Incubation and time effects were assessed.ResultsLaser cutting perforated the polymer, connecting the substructure with the ex-scaffold environment and increasing porosity (porous, non-perforated = 87.9 per cent; porous, laser-perforated at intensities 3 = 96.4 per cent and 6 = 89.5 per cent). Cellular studies confirmed improved cell viability. Histology showed cells adherent to the scaffold surface and cells within perforations, and indicated that cells migrated into the scaffolds. After 15 days of incubation, scanning electron microscopy revealed an 11 per cent reduction in pore diameter, correlating with a decrease in Young's modulus.ConclusionIntroducing surface perforations presents a viable method of improving polyhedral oligomeric silsesquioxane poly(carbonate-urea) urethane as a tissue-engineered scaffold

A Bioinspired Active Robotic Simulator of the Human Respiratory System

Pathologies affecting the respiratory system can lead to a debilitating decrease in quality of life and can be fatal. To test medical devices and implants for the human respiratory system, a simulation system that can reproduce multiple respiratory features is necessary. Currently available respiratory simulators only focus on reproducing flow rate profiles of breathing while coughing simulators focus on aerosol analysis. In this paper we propose a novel, bioinspired robotic simulator that can physically replicate both breathing and coughing flow rate characteristics of healthy adults. We conducted a study on 31 healthy adult participants to gather the flow rate measurement of normal breathing, deep breathing, breathing while running and coughing. Coughing flow rate profiles vary considerably between participants, making an accurate simulation of coughs a challenge. To enable cough flow rate simulation, a new methodology based on the identification of four cough phases, Attack, Decay, Sustain and Release (ADSR) and their parametrization was devised. This methodology leads to the unprecedented ability to reproduce diverse and complex coughing flow rate profiles. Our simulator is able to reproduce respiratory flows with a root mean square error (RMSE) of 1.8 L/min between normal participant breathing and its simulation, 5% of the maximum flow rate simulated for that participant (pMFR), an RMSE of 10.08 L/min for deep breathing, 18% of the pMFR and an RMSE of 13.29 L/min for exertion breathing, 17% of pMFR. For the simulation of an average cough we recorded an RMSE of 51.43 L/min, 13% of the pMFR and for a low flow rate cough an RMSE of 12.38 L/min, 9.5% of the pMFR. The presented simulator matches the fundamentals of human breathing and coughing, advancing the current capability of respiratory system simulators