A novel microscopic assay of transient platelet - von Willebrand Factor adhesion, kinetics, margination, and blood rheology

Platelets play a central role in hemostasis and arterial thrombosis. At high shear rates, von Willebrand factor (vWF) may recruit passive platelets to a growing thrombus via transient glycoprotein (GP) Ib binding, increasing platelet residence time to allow activation by stress or chemical agonists. Platelet accumulation also depends on dispersive transport driven by shear flow of red blood cells (RBC’s), platelet margination (a near-wall enrichment of platelet concentration due to persistent lateral drift), and flowinduced stresses.A new assay was developed that enables simultaneous measurement of platelet adhesion, platelet margination, wall shear stress, and non-Newtonian flow velocity profile, in blood flow through protein-coated capillaries. Transient platelet adhesion, translation, and embolization are measured by video microscopy. Translating-stage image sequences measure platelet concentration at 3 +/- 1 micron from the capillary surface and centerline flow velocity. The blood velocity profiles are fit to a Casson model based on flow rate, centerline velocity, and pressure gradient.In capillaries coated with plasma vWF, platelet adhesion was an increasing function of wall shear rate between 126 and 840 /s. Margination increased with shear rate, and decreased on vWF-coated capillaries compared to albumin controls. The characteristic time constant for transient binding on plasma vWF was 1.0 to 1.4 sec. A platelet flux balance was performed on a control volume within 2 μm of the vessel wall using near-wall concentration data, estimated convective flux, and surface net accumulation rate. Dispersive flux was an order of magnitude faster than the convective flux, meaning stronger contribution of shear-induced dispersion to the contact of platelet with thrombogenic surface, tethering or adhesion, accumulation, and aggregation of platelets than the convective motion. The new assay provides a wealth of data for celllevel computational modeling of platelet adhesion mechanics and kinetics under controlled flow.Ph.D., Mechanical Engineering -- Drexel University, 200

Measurement of beta-amyloid peptides in specific cells using a photo thin-film transistor

The existence of beta-amyloid [Aβ] peptides in the brain has been regarded as the most archetypal biomarker of Alzheimer's disease [AD]. Recently, an early clinical diagnosis has been considered a great importance in identifying people who are at high risk of AD. However, no microscale electronic sensing devices for the detection of Aβ peptides have been developed yet. In this study, we propose an effective method to evaluate a small quantity of Aβ peptides labeled with fluorescein isothiocyanate [FITC] using a photosensitive field-effect transistor [p-FET] with an on-chip single-layer optical filter. To accurately evaluate the quantity of Aβ peptides within the cells cultured on the p-FET device, we measured the photocurrents which resulted from the FITC-conjugated Aβ peptides expressed from the cells and measured the number of photons of the fluorochrome in the cells using a photomultiplier tube. Thus, we evaluated the correlation between the generated photocurrents and the number of emitted photons. We also evaluated the correlation between the number of emitted photons and the amount of FITC by measuring the FITC volume using AFM. Finally, we estimated the quantity of Aβ peptides of the cells placed on the p-FET sensing area on the basis of the binding ratio between FITC molecules and Aβ peptides

Application of PEEP using the i-gel during volume-controlled ventilation in anesthetized, paralyzed patients

PURPOSE: This prospective, randomized trial was designed to assess whether the i-gel supraglottic airway device is suitable for volume-controlled ventilation while applying positive end-expiratory pressure (PEEP) of 5 cmH(2)O under general anesthesia. It was believed that this device might improve arterial oxygenation. METHODS: Forty adult patients (aged 20–60 years) scheduled for elective orthopedic surgery were enrolled in this study. Twenty patients were ventilated without external PEEP [zero positive end-expiratory pressure (ZEEP) group], and the other 20 were ventilated with PEEP 5 cmH(2)O (PEEP group) after placing an i-gel device. Volume-controlled ventilation at a tidal volume (TV) of 8 ml/kg of ideal body weight, leak volume, and arterial blood gas analysis were investigated. RESULTS: The incidences of a significant leak were similar in the ZEEP and PEEP groups (3/20 and 1/20, respectively; P = 0.605), as were leak volumes. No significant PaO(2) difference was observed between the two groups at 1 h after satisfactory i-gel insertion (215 ± 38 vs. 222 ± 54; P = 0.502). CONCLUSIONS: The use of an i-gel during PEEP application at 5 cmH(2)O did not increase the incidence of a significant air leak, and a PEEP of 5 cmH(2)O failed to improve arterial oxygenation during controlled ventilation in healthy adult patients

Generation of a single-cycle pulse using a two-stage compressor and its temporal characterization using a tunnelling ionization method

A single-cycle laser pulse was generated using a two-stage compressor and characterized using a pulse characterization technique based on tunnelling ionization. A 25-fs, 800-nm laser pulse was compressed to 5.5 fs using a gas-filled hollow-core fibre and a set of chirped mirrors. The laser pulse was further compressed, down to the single-cycle limit by propagation through multiple fused-silica plates and another set of chirped mirrors. The two-stage compressor mitigates the development of higher-order dispersion during spectral broadening. Thus, a single-cycle pulse was generated by compensating the second-order dispersion using chirped mirrors. The duration of the single-cycle pulse was 2.5 fs, while its transform-limited duration was 2.2 fs. A continuum extreme ultraviolet spectrum was obtained through high-harmonic generation without applying any temporal gating technique. The continuum spectrum was shown to have a strong dependence on the carrier-envelope phase of the laser pulse, confirming the generation of a single-cycle pulse. © 2019, The Author(s