Dynamic mechanostimulation of live cells during real-time microscopy

Our body’s functioning depends on the ability of cells to sense and react to their local mechanical environment; this process is known as mechanotransduction. Despite the importance of understanding how cells interact with mechanical stimuli, the specific mechanisms governing such processes have yet to be elucidated. Using microscopy to detect the early responses of living cells to mechanical loads and forces would be a critical step towards further understanding cellular mechanotransduction. Dynamic and high-frequency cyclical loads are relevant to human physiology and disease. Yet, modern microscopy systems are not capable of delivering the appropriate mechanical stimuli to live cell cultures. To address this deficiency, we developed a suite of mechanostimulation platforms that provide precise and relevant loads and forces to cell cultures during simultaneous microscopic analysis. We developed a motion-control system capable of precisely delivering vibrations to live cells during real-time microscopy. Using this system, we found that vibration of osteoblastic cells does not elicit acute elevation of cytosolic free calcium, but did desensitize responses to later stimulation with extracellular ATP. We next developed and validated a technique for the practical fabrication of microfluidic channels. In contrast to the effect of vibration, osteoblastic cells were found to respond to changes in fluid shear stress with transient elevation in the concentration of cytosolic free calcium. Lastly, we developed a system to apply disturbed fluid flow to live cells during real-time imaging. This system was used to demonstrate changes in the concentration of cytosolic free calcium in human endothelial cells exposed to laminar and disturbed flow. Our findings indicate that different forms of mechanical stimuli activate distinct signaling pathways in cells. Moreover, these new technologies will facilitate investigations of the signaling pathways activated by dynamic mechanical stimulation of a variety of cell types, in particular those of the skeletal and vascular systems

Surface-confined molecular coolers for cryogenics

An excellent molecule-based cryogenic magnetic refrigerant, gadolinium acetate tetrahydrate, is here used to decorate selected portions of silicon substrate. By quantitative magnetic force microscopy for variable applied magnetic field near liquid-helium temperature, we demonstrate that the molecules hold intact their magnetic properties, and therefore their cooling functionality, after their deposition. Our result represents a step forward towards the realization of a molecule-based microrefrigerating device for very low temperatures.Comment: 16 pages, 4+1 figures, S.I. available from author

Open repair of type Ia endoleak in the aortic arch: three tailored approaches

Endoleaks are an important complication following hybrid thoracic endovascular aortic repair (TEVAR) with an incidence ranging from 20% to 25%. There are five different types of endoleaks, which are classified based on the source of vessels that cause the inflow into the aneurysm sac. Type I endoleaks (EL-I) occur at either the proximal (Ia) or distal (Ib) attachment sites and can be seen during insertion of the initial stent graft or during a follow-up surveillance imaging exam. EL-I may be secondary to incomplete dilatation or inaccurate sizing of the stent graft, diseased aortic wall or aortic tortuosity with angulations, leading to higher chances of rupture. However, EL-I represent a technical failure of endovascular repair that should be corrected promptly. However, endovascular EL-I repair at the level of aortic arch is not always possible due to an improper landing zone in the ascending aorta making it technically challenging. In the present paper, we describe three cases of EL-Ia following TEVAR and we address different repair techniques. Written informed consents were obtained from the patients for publication of the article and any accompanying images

Producing and Measuring Oscillatory Shear in a Novel Microfluidic Chip

Purpose: To demonstrate the effectiveness of a novel microfluidic device mimicking oscillatory blood flow, allowing cell biologists to examine how endothelial cells respond to a range of oscillatory shear stress levels. Methods: The microfluidic chip consists of a circular-shaped reservoir, leading to a rectangular channel that is examined under a microscope. The plunger is connected to a speaker system and oscilloscope, allowing the plunger to apply a range of frequencies (5-60Hz) and voltages (5-10 V, leading to a variety in oscillation amplitudes) to the reservoir region. 1.1 um fluorescent particles diluted in distilled water were used for tracking. Processing was done through particle image velocimetry (PIV) which uses a cross-correlation algorithm. We used matlab to plot average velocity profiles for a cycle, and extracted data points along the centre of the velocity profiles corresponding to the maximum velocities. Results: The oscillatory chip demonstrated the ability to effectively and accurately deliver oscillatory flow between 10-60Hz using 5-10V, resulting in a variety of oscillation frequencies and amplitudes. Plotting velocity maximum values vs. voltage for frequencies 10-60 Hz demonstrated a linear trend. 3D oscillatory-flow paraboloids can be used in calculating maximum shear stress values for oscillatory flow. Conclusions: Our analysis demonstrates that this microfluidic chip is able to execute controlled shear stress conditions to test how endothelial cells respond to oscillatory shear

ECMO during the COVID-19 pandemic: when is it unjustified?

No abstract was provided by the editors of this work

Aorto-atrial fistula formation and therapy

Aorta-atrial fistulas (AAF) are a rare but complex pathological condition. These fistulas are characterised by aberrant blood flow between the aorta and either atrium. In the present manuscript, we present a comprehensive overview of the clinical characteristics, formation and treatment of this condition. A literature review was conducted using PubMed. Aorta-Atrial Fistula was used as the primary search term. The clinical presentation of AAF encompasses a wide range of signs and symptoms of heart failure including dyspnoea, chest pain, palpitations, fatigue, weakness coughing or oedema. Causes of fistulas can be congenital or acquired, whilst diagnosis is normally achieved via echocardiography or MRI. Due to the low incidence of AAF, no clinical trials have been performed in AAF patients and treatment strategies are based on expert opinion and consensus amongst the treating physicians. Uncorrected AAF may continue to impose a risk of progression to overt heart failure. The repair of an AAF can either be surgical or percutaneous. AAF is a relatively rare but very serious condition. Clinicians should consider the possibility of AAF, when a new continuous cardiac murmur occurs, especially in patients with a history of cardiac surgery or with signs of heart failure. Closure of the AAF fistula tract is generally recommended. Further studies are required to define optimal therapeutic strategies, but these are hindered by the rarity of the occurrence of this disorde

Live Attenuated Influenza A Virus Vaccine Protects against A(H1N1)pdm09 Heterologous Challenge without Vaccine Associated Enhanced Respiratory Disease

Live-attenuated influenza virus (LAIV) vaccines may provide cross-protection against contemporary influenza A virus (IAV) in swine. Conversely, whole inactivated virus (WIV) vaccines have the potential risk of vaccine-associated enhanced respiratory disease (VAERD) when challenged with IAV of substantial antigenic drift. A temperature sensitive, intranasal H1N2 LAIV was compared to wild type exposure (WT) and an intramuscular WIV vaccine in a model shown to induce VAERD. WIV vaccinated swine challenged with pandemic A/H1N1 (H1N1pdm09) were not protected from infection and demonstrated severe respiratory disease consistent with VAERD. Lung lesions were mild and challenge virus was not detected in the respiratory tract of LAIV vaccinates. High levels of post-vaccination IgG serum antibodies targeting the H1N1pdm09 HA2 stalk domain were exclusively detected in the WIV group and associated with increased H1N1pdm09 virus infectivity in MDCK cells. In contrast, infection-enhancing antibodies were not detected in the serum of LAIV vaccinates and VAERD was not observed

How I manage drainage insufficiency on extracorporeal membrane oxygenation

No abstract was provided by the editors of this work

Aorto-atrial fistula formation and closure: a systematic review

Blood flow between the aorta and atrium is a rare but complex pathological condition, also known as aorto-atrial fistula (AAF). The exact incidence of this condition is unknown, as are the major precipitating factors and best treatment options. We carried out a systematic review of the available case report literature reporting AAF. We systematically reviewed literature on AAF formation and closure. Separate Medline (PubMed), EMBASE, and Cochrane database queries were performed. The following MESH headings were used: atrium, ventricle, fistula, cardiac, shunts, aortic, aorto-atrial tunnels and coronary cameral fistula. All papers were considered for analysis irrespective of their quality, or the journal in which they were published. Fistula formation from the ascending aorta to the atria occurred more often in the right atrium compared to the left. Endocarditis was the major cause of AAF formation, whilst congenital causes were responsible for nearly 12%. In a number of cases fistula formation occurred secondary to cardiac surgery, whilst chest traumas were a relatively rare cause of AAF. Correction via an open surgical approach occurred in 73.5% of cases, whilst percutaneous intervention was utilised in 10% of patients. In 74.3% of all studied cases the fistula repair was successful and patients survived the procedures. In 14.7% of the cases patients did not survive. Similar outcomes were observed between percutaneous and surgical interventions. Data from larger populations with AAF is lacking, meaning that specific data regarding incidence and prevalence does currently not exist