Plasma Depletion Research Articles

One‐Step Local Acceleration Process of Ultra‐Relativistic Electrons in the Center of the Outer Radiation Belt: Observations

AbstractUltra‐relativistic (>3 MeV) electrons are considered as a novel, separate population in the Earth's radiation belts since their loss and acceleration features are distinct from relativistic (∼MeV) electrons. The dominant acceleration mechanism of ultra‐relativistic electrons remains a subject of ongoing debate. Some studies suggest that the acceleration mechanism of ultra‐relativistic electrons is energy‐dependent: local acceleration dominants the enhancement of ∼3–5 MeV electrons while two‐step acceleration process leading by radial diffusion effects for ∼7 MeV electrons. However, a recent study (https://doi.org/10.1126/sciadv.abc0380) theoretically demonstrated that local acceleration could accelerate electrons up to >7 MeV directly under the extreme plasma depletion. In this study, we report four enhancement events of ultra‐relativistic electrons that occurred in September and October 2017. Analysis of phase space density (PSD) radial profiles and contours demonstrate that local acceleration plays the dominant role in the enhancements of ∼7 MeV electrons in mid‐September and mid‐October, supported by persistently growing peaks in electron PSD. While enhancements of ultra‐relativistic electrons in other two events still show energy‐dependent phenomenon, our results provide the observation evidence that one‐step local acceleration process can lead to the enhancement of ∼7 MeV electrons in some events. We suggest that the acceleration process of ultra‐relativistic electrons may be subject to the efficiency of local acceleration.

Spatial distribution of plasma density and magnetic field amplitude in the dayside magnetosheath as a function of the IMF orientation

The properties of the magnetosheath are of pivotal importance in determining the coupling between the magnetosphere and interplanetary medium. In particular, the magnetic flux pileup and plasma depletion layer (PDL) modify the boundary conditions of magnetopause reconnection. However, the spatial distribution of the magnetic field strength and plasma density in the magnetosheath and their functional dependence on the interplanetary magnetic field (IMF) orientation remain poorly understood. This study characterizes these aspects in detail through the statistical processing of decades of data from Cluster, Double Star, THEMIS, and Magnetospheric Multiscale (MMS) missions. The first part of this study focuses on the poorly known variations across the magnetosheath, from the shock to the magnetopause. The magnetic pileup and PDL are significantly correlated, with a strong dependence on the IMF cone angle. Their dependence on the IMF clock angle is found only near the magnetopause, consistent with the expected effect of magnetic reconnection. The second part of this study examines the asymmetry in the magnetic field amplitude and density between the quasi-parallel and quasi-perpendicular sides of the equatorial magnetosheath. These asymmetries are characterized for different relative distances to the magnetopause and bow shock boundaries and for different IMF orientation. The magnetic field amplitude, observed to be higher on the quasi-perpendicular side of the magnetosheath, becomes more symmetric as it approaches the magnetopause. The quasi-parallel magnetosheath exhibits a higher plasma density near the magnetopause. However, this asymmetry reverses at approximately the mid-magnetosheath with a decreasing IMF cone angle.

PRIME‐SH: A Data‐Driven Probabilistic Model of Earth's Magnetosheath

AbstractA data‐driven model of Earth's magnetosheath is developed by training a recurrent neural network (RNN) with probabilistic outputs to reproduce Magnetospheric MultiScale (MMS) measurements of the magnetosheath plasma and magnetic field using measurements from the Wind spacecraft upstream of Earth at the first Earth‐Sun Lagrange point (L1). This model, called Probabilistic Regressor for Input to the Magnetosphere Estimation‐magnetosheath (PRIME‐SH) in reference to its progenitor algorithm PRIME, is shown to predict spacecraft observations of magnetosheath conditions accurately in a statistical sense with a continuous rank probability score of 0.227σ (dimensionless standard deviation units). PRIME‐SH is shown to be more accurate than many current analytical models of the magnetosheath. Furthermore, PRIME‐SH is shown to reproduce physics not explicitly enforced during training, such as field line draping, the dayside plasma depletion layer, the magnetosheath flow stagnation point, and the Rankine‐Hugoniot MHD shock jump conditions. PRIME‐SH has the additional benefits of being computationally inexpensive relative to global MHD simulations, being capable of reproducing difficult‐to‐model physics such as temperature anisotropy, and being capable of reliably estimating its own uncertainty to within 3.5%.

On the Formation Mechanism of Martian Dayside Ionospheric Plasma Depletion Events

AbstractPlasma Depletion Events (PDEs) are characterized by abrupt, localized reductions in ionospheric plasma density at least by an order of magnitude decrease. These events are observed over a limited range of altitudes, typically spanning a few tens of kilometers. We use Mars Atmosphere and Volatile Evolution spacecraft data to investigate the properties and possible formation mechanism of daytime PDEs, typically observed at altitudes above 250 km. We show, using two example events and statistical analysis, that the depletion events are associated with electrostatic fluctuations and increased electron temperatures. The events are further accompanied by enhanced fluxes of suprathermal electrons and light energetic ions. These are indicative of local plasma heating, possibly mediated by the electrostatic fluctuations. The heated plasma may eventually escape from the depletion region through the ambipolar diffusion.

Immuno-Hematologic Complexity of ABO-Incompatible Allogeneic HSC Transplantation.

ABO incompatibility is not considered a contraindication for hematopoietic stem cell transplantation (HSCT). Approximately 30% of transplants from related donors and up to 50% of transplants from unrelated donors are ABO incompatible. Immuno-hematologic investigations allow to estimate donor/recipient ABO mismatch and anti-A/B isohemagglutinin (IHA) titration in the pre-HSCT phase. Immediate hemolysis or delayed complications (passenger lymphocyte syndrome and pure red cell aplasia) can occur post HSCT. Some preventive measures take into consideration either decision-making algorithms based on the recipient's IHA titration or clinical protocols for the removal/reduction of IHAs through plasma exchange or immunoadsorption procedures. Product manipulation through red blood cell (RBC) and/or plasma depletion can also be taken into account. Currently, the best approach in the management of ABO-incompatible transplant is not defined in expert consensus documents or with solid evidence. In addition, the methods for IHA titration are not standardized. A transfusion strategy must consider both the donor's and recipient's blood group systems until the RBC engraftment catches on and ABO conversion (forward and reverse typing) is confirmed on two consecutive and independent samples. Therefore, ABO incompatibility in HSCT represents a demanding immuno-hematologic challenge and requires all necessary preventive measures, including the appropriate selection of ABO blood components for transfusion.

Exploring the link between convectively generated gravity waves and ionospheric anomalies: Insights from observations near the low-mid latitude geomagnetic transition region

In this paper, we examine the role of gravity waves (GWs) generated from tropospheric convection in initiating multiple nighttime ionospheric anomalies over Srinagar, located at 34.1°N, 74.8°E, and 25.91°N MLAT. Optical airglow observations during a geomagnetic quiet night (Ap = 4) of 29–30 June 2021, show the presence of plasma depletion tilted by an angle of ∼14.9° from the geographic North, quasi-periodic south eastward moving wave (QPSEMW), onset of two electrified MSTIDs and generation of plasma depletion channel between two MSTID phase fronts at ∼250 km altitude. GWs originating from deep convection in troposphere are detected at ∼85 and ∼97 km altitudes in OH and 557 nm filters respectively. The GWs in both the filters are propagating northward with almost similar characteristics. The intrinsic time period and vertical wavelength of GWs is estimated to be ∼11 min and ∼53 km respectively. We also present the observational indications of localised upliftment of F-layer ionosphere by ∼38 km, possibly initiated by polarization electric field generated through secondary GWs. The penetration of secondary GWs, generated by the dissipation of convective GWs, beyond the altitude of 500 km is also seen. FORMOSAT-7/COSMIC-2 RO data and SAMI3 model electron density suggest the occurrence of Sporadic-E (Es) layer at around 100 km altitude, caused by the negative gradient in eastward wind.

Assessment of the Origin of a Plasma Depletion Band Over the United States During the 8 September 2017 Geomagnetic Storm

AbstractThe development of an intense total electron content (TEC) depletion band over the United States during the 8 September 2017 geomagnetic storm was understood as the extension of an equatorial plasma bubble (EPB) to midlatitudes in previous studies. However, this study reports non‐EPB aspects within this phenomenon. First, the simultaneous emergence of the TEC depletion band at midlatitudes and EPBs in the equatorial region indicates that the midlatitude TEC depletion band is not initiated by an EPB. Second, the intensification of TEC depletion at midlatitudes during the decay of TEC depletion at intermediate latitudes is anomalous. Third, the location of the TEC depletion band at midlatitudes is inconsistent with the EPB location estimated from zonal plasma motion. Given ionospheric perturbations in North America from the beginning of the storm, it is plausible that the TEC depletion band was locally generated in association with these perturbations.

First evidence of a connection between cluster-scale diffuse radio emission in cool-core galaxy clusters and sloshing features

Radio observations of a few cool-core galaxy clusters have revealed the presence of diffuse emission on cluster scales, similar to what was found in merging clusters in the form of radio halos. These sources might suggest that a minor merger, while not sufficiently energetic to disrupt the cool core, could still trigger particle acceleration in the intracluster medium on scales of hundreds of kiloparsecs. We aim to verify the occurrence of cluster-scale diffuse radio emission in cool-core clusters and test the minor merger scenario. With the LOw Frequency ARray (LOFAR) at 144 MHz, we observed a sample of twelve cool-core galaxy clusters presenting some level of dynamical disturbances, according to X-ray data. We also performed a systematic search of cold fronts in these clusters, re-analysing archival Chandra observations. The clusters PSZ1G139.61+24, A1068 (new detection), MS 1455.0+2232, and RX J1720.1+2638 present diffuse radio emission on a cluster scale ($r $). This emission is characterised by a double component: a central mini-halo confined by cold fronts and diffuse emission on larger scales, whose radio power at 144 MHz is comparable to that of radio halos detected in merging systems with the same cluster mass. The cold fronts in A1068 are a new detection. We also found a candidate plasma depletion layer in this cluster. No sloshing features are found in the other eight clusters. Two of them present a mini-halo, with diffuse radio emission confined to the cluster core. We also found a new candidate mini-halo. Whereas, for the remaining five clusters, we did not detect halo-like emission. For clusters without cluster-scale halos, we derived upper limits to the radio halo power. We found that cluster-scale diffuse radio emission is not present in all cool-core clusters when observed at a low frequency, but it is correlated to the presence of cold fronts. The coexistence of cluster-scale diffuse radio emission and cold fronts in cool-core clusters requires a specific configuration of the merger and so it puts some constraints on the turbulence, which deserves to be investigated in the future with theoretical works.

An Automatic Method for Detection and Naive Classification of the Martian Ionospheric Irregularities

AbstractThe abundant observations and research established a detailed category of the terrestrial ionospheric irregularities, which significantly advanced our understanding of how the Earth system's complicated physical and chemical process generates the intermediate‐scale structures of the charged particles. Motivated by a future attempt at categorizing the Martian ionospheric irregularity, this study designs a method for naive classification of the plasma density depletion, enhancement, and oscillation based on the in situ measurements of the Martian ionosphere. The technique consists of several procedures: trend estimation, detrending and candidate extraction, and parameterization. The classification is achieved through a machine‐learning‐like process using some testing artificial density profiles. A preliminary credence test shows a good performance in separating the terrestrial low‐latitude Equatorial Plasma bubble (depletion) and mid‐latitude Median‐scale Traveling Ionospheric Disturbance (oscillation). Another detection experiment of the Martian plasma depletion events (collected by Basuvaraj et al. (2022a, https://doi.org/10.1029/2022je007302)) showed a recall rate (i.e., true positive) of 38% but with a high precision of 67.8%. Therefore, we believe the proposed method could convincingly extract different Martian ionospheric irregularities and help uncover the climatological characteristics in the future.

Growth factor and cytokine characterization of canine platelet lysate with variable leukocyte concentration, plasma content, and heat-sensitive proteins.

Platelet lysate is an acellular platelet product containing factors released from secretory granules, including cytokines and growth factors. This study aimed to evaluate different centrifugation methods used to prepare canine platelet lysate with variable content of leukocytes, plasma, and heat-sensitive proteins. Whole blood was collected from six dogs and two double-spin preparation methods were used to generate the platelet-rich plasma with reduced (PRP) and high (L-PRP) concentration of leukocytes. A portion of both methods underwent plasma depletion via centrifugation and platelet lysate was generated via freeze-thaw cycles. A portion of the generated platelet lysate underwent complement inactivation via heat treatment. Growth factors (TGF-β1, VEGF, TNF-α, PDGF-BB, HGF) were quantified in all different platelet lysate preparations using ELISAs. Both platelet-rich plasma preparations had a 6.7-fold increase in platelet concentration. White blood cell (WBC) concentration compared to whole blood increased 1.2-fold times in PRP and 1.9-fold times in L-PRP. Negligible concentrations of platelets, WBC, and hematocrit were identified in all lysate groups. Statistically significant differences were identified for PDGF, VEGF, and TNF-α, and not for TGF-β or HGF. No growth factor differences were noted between centrifugation methods. PDGF was significantly higher in platelet lysate that was plasma depleted. VEGF was significantly higher in heat-treated lysate groups. TNF-α concentrations were overall very low, though were noted to significantly increase following plasma depletion. These results support that growth factors and cytokine release can be affected by the platelet lysate preparation and processing.

Martian M2 peak behavior in the dayside near-terminator ionosphere during interplanetary coronal mass ejections

The interplanetary coronal mass ejections (ICMEs) can pose significant impacts on the Martian ionosphere, resulting in plasma depletion, variability, and escape to space. However, the connections between the ICMEs and the associated responses of the dayside near-terminator Martian ionospheric primary peak (M2) are not well understood. The present study primarily investigates the behavior of the ionospheric peak density (Nm) and height (hm) during the passage of ICMEs using observations from the Radio Occultation Science Experiment (ROSE) aboard MAVEN spacecraft. We have selected 8 such ICMEs (during 2017–2022) at Mars from the existing catalogs and studied the ROSE electron density profiles during quiet and disturbed time (ICMEs) for identical solar zenith angle range. We observed the elevation of the M2 peak (hm ∼ 4–16 km) during disturbed time (ICMEs) with a decrease in Nm (0.41–2.8 × 1010 m−3) in comparison to the quiet time. The present study, for the first time, addressed the influence of ICMEs on the M2 peak parameters (Nm and hm). We have proposed that the development of large vertical pressure gradient and electron temperature enhancement are plausible causes for ionospheric variability. Therefore, the present study provides new insights to understand peak plasma behavior in the dayside near-terminator ionosphere during ICMEs.

Modeling of Multi‐Ion Plasma Bubbles in the Equatorial Ionosphere

AbstractEquatorial plasma bubbles (spread F/ionospheric irregularities) are plasma density irregularities or depletion in the ionosphere. It can be observed by radio waves, optical and in situ instruments during postsunset in equatorial and low‐latitude regions. Severe scintillations in radio waves can be caused by the presence of plasma bubbles. Therefore, studies of plasma bubbles become one of the most important and hot topics. Many studies have been devoted to the physical mechanism and characteristics of plasma bubbles in the ionosphere. However, some critical issues (e.g., day‐to‐day variability, complex structures, and ions composition) are still not well known. In this study, a new two‐dimensional model of multi‐ion (H+, He+, N+, O+, N2+, NO+, and O2+) plasma bubbles was developed. The photoionization, chemical reaction, and recombination processes of multiple ions have been added to the new model. The present model was used to simulate the nonlinear evolutions of multiple plasma bubbles in the equatorial region. Results show that the merging, disconnection and connection processes of plasma bubbles can be reproduced in this simulation. In addition, simulations first present morphological structures of molecular ions (NO+, O2+) of multiple plasma bubbles, which are significantly different from plasma bubbles. Molecular ion NO+ is manifested as plasma blobs. However, molecular ion O2+ is manifested as bubbles at low altitudes but blobs at high altitudes. The complex structures of multiple plasma bubbles and morphological structures of molecular ions in the present simulation are mostly consistent with observations.

Absence of blood donors’ anti-SARS-CoV-2 antibodies in pre-storage leukoreduced red blood cell units indicates no role of passive immunity for blood recipients

Transfer of vaccine antibodies (Ab) from donors to recipients after transfusion of packed red blood cells (RBC) is supposed, thus affecting the recipients’ response to vaccinations. In this prospective study, SARS-CoV-2 IgG level in donors’ serum and RBC supernatant samples was assessed. Among 346 subjects, 280 were referred for hyperimmune plasma donation and 30 for whole blood donations. All units underwent pre-storage filtration, and residual plasma volume was 18±18 mL. The mean total IgG and IgM levels were 171.43 ± 48.79 and 11.43 ± 10.69 mg/dL respectively, with significant reduction after plasma depletion and filtration (IgG 5.86 ± 5.2 and IgM 1.43 ± 3.78, p < 0.05). Anti-COVID-19 Ab were identified in serum of 28/30 (93.5%) blood donors but were absent in all blood units. The mean value of anti-SARS-CoV-2 IgG level in donors’ serum samples and in RBC units was 8.80 S/C (range 0.01–23.4) and 0.11 (range 0.01–0.37) S/C, respectively (p<0.05). This study shows deplasmation and leukodepletion of RBC units ensured removal of IgG content and no red blood cell unit was reactive for anti-COVID-19 antibodies even from donors with high serum titre. These findings demonstrate that deplasmated and leukodepleted RBCs are not to be considered blood products containing substantial amounts of immune globulin, and differently from other blood derived-products containing Ab, transfusions with deplasmated and leukodepleted RBCs do not require delayed vaccinations and a revision of current recommendations is requested.

Response of the F2-peak electron density and height to plasma depletion bays in the equatorial nighttime ionosphere observed by FORMOSAT-7/COSMIC-2

FORMOSAT-7/COSMIC-2 (F7/C2) satellite cluster, launched in June 2019, performs radio occultation experiments observing the vertical electron density profiles in the low-latitude ionosphere. The F7/C2 F2-peak electron density (NmF2) and height (hmF2) are used to identify and examine the behavior of the plasma depletion bay (PDB) structures in the equatorial nighttime ionosphere. The NmF2 reveals three distinct PDBs within 60°W–15°E, 30−90°E, and 110−160°E during June solstice, while a single PDB appears within 150−60°W during December solstice. All the four PDBs’ features simultaneously appear during March and September equinoxes. Asymmetries in the hmF2 over the PDB regions suggests that the electron density increases (decreases) are related to the NmF2 ascending (descending) in the summer (winter) hemispheres. Agreements between F7/C2 observations and HWM93 results show that the asymmetry of vertical motions driven by the neutral wind is the main causal mechanism for the longitudinal variation of PDBs.

Unique observations and interactions over the low-mid latitude transition region: Simultaneous study of plasma blobs, MSTIDs and plasma irregularities

This paper presents the novel simultaneous observations of plasma blobs, MSTIDs and plasma depletions in OI 630 nm all sky airglow images over Srinagar, India (34.1 °N, 74.8 °E) during the night of July 29, 2019, obtained using an airglow imager. Notably, the MSTID bands that followed the plasma blob interacted with a plasma depletion structure and suddenly disappeared, resulting in a reduction in the intensity of the plasma depletion. The SWARM satellite observations during the airglow observations indicated the occurrence of the plasma blob event and showed the conjugate appearance of MSTIDs in both hemispheres. The ROTI maps indicated the absence of EPBs but the occurrence of irregularities near the transition zone just before the presence of plasma blobs in airglow images and at the time of plasma irregularity detection. These observations suggest potential interactions between these phenomena, indicating that the presence of one impacts the other. This paper discusses in detail the observed ionospheric features and time evolution of the occurrences of these events, in addition to their interactions.Utilizingthe satellite observations, including SABER, INSAT-3DR and AIRS, the presence of deep convective clouds and upward propagating gravity waves near the location of the plasma blob is demonstrated, suggesting that convective-generated gravity waves could possibly trigger the formation of plasma blobs.

Umbilical Cord Blood Processing Techniques and Their Comparative Advantages: A Review

Background: Umbilical Cord Blood (UCB) has steadily gained prominence in haematopoietic stem cell transplantation (HSCT). Despite UCB advantages, the main disadvantage of UCB in haematopoietic stem cell transplantation (HSCT) is its limited cell dose. Initially, UCB used to be processed and then made to undergo cryopreservation as whole cord blood banking leading to the problem of storing sufficiently large number of cryoprotected UCB units which requires vast amounts of costly storage space in liquid nitrogen. The sole purpose of processing is to concentrates the stem cells and reduce the volume for storage. Different UCB processing methods have been developed. &#x0D; Aim: This review is aimed at bringing together the literature on the different processing methods and highlighting the underlying principles of each method, the relative efficiency and advantages of the methods.&#x0D; Methodology: The work involved mainly the critical review of all available academic, professional and industry documents on cord blood processing. The relevant information was obtained from textbooks, academic journals, conference proceedings, the internet among others. The major UCB processing methods include Plasma Depletion, Density Gradient Centrifugation (DGC), Hetastarch, PrepaCyte-CB and Sepax. A study of the potential impact of Hetastarch and PrepaCyte processing methods on transplantation outcomes revealed no difference that was significant was observed between patients receiving cells after the processing regimens were compared.&#x0D; Results: A comparison of the engraftment time of PrepaCyte-CB with five other processing methods revealed a quicker engraftment time for PrepaCyte-CB processed cord blood units compared to other processing methods. PrepaCyte-CB also recovers significantly more viable stem cells than AutoXpress (AXP) and hydroxyethyl starch (HES) processing methods. Other workers demonstrated that Sepax depletion produces higher recovery of cells that are nucleated. The effect initial volume of cord blood had on the recovery of nucleated cells for the different method of processing were also compared. Recovery when using Sepax is reduced as the unit size processed increases. Hetastarch, which is a density gradient, and plasma depletion separation is also affected in like manner, however, processing done using PrepaCyte-CB was not affected by the initial volume of the collected unit. The advantage of Sepax is that it is fully automated and this allows for mass processing of samples, suitable for bigger cord blood banks. For erythrocyte removal, density gradient separation is a better method that is effective. PrepaCyte-CB is the second most efficient method for removing RBC. The result of Total Nucleated Cells (TNC) and Mono Nucleated Cells (MNC) recovery rate of Hespan and Sepax against AXP processing methods shows that both Hespan and Sepax reproducibly recover greater than 95% of the cord blood stem cells in a typical collection and result in a reduced final volume for final storage.&#x0D; Conclusion: The five most popular processing techniques are Plasma Depletion, Density Gradient, Hetastarch, PrepaCyte-CB and Automated Centrifugal Machine (Sepax). Most methods involve centrifugation, sedimentation and/or filtration for reducing the red cell content, plasma volume, or both. The different UCB processing methods each has its advantages and disadvantages.

Nighttime wavenumber-four and plasma depletion bays observed by FORMOSAT-5/AIP, ICON/IVM, and COSMIC-2/RO data

We examine nighttime longitudinal structures of ion density and ion velocity in wavenumber-four (WN4) and plasma depletion bays (PDBs) observed by FORMOSAT-5 (F5) and ICON, as well as electron density by FORMOSAT-7/COSMIC-2 (F7C2) in 2020. Three PDBs significantly occur in June and December solstices, while WN4 prominently appear in March and September equinox. F5/AIP (advanced ionospheric probe) ion velocities tend to be westward (eastward) at the PDB (WN4) longitudes, which shows that the ion density maximum and minimum are coincident with the eastward ion velocity maximum and minimum, respectively. ICON/IVM (ion drift meter) field-aligned velocities further reveal that the summer to winter trans-equatorial flow is essential to form PDBs, which further results in upward and downward ion drifts in the upstream and downstream areas (summer and winter hemisphere), respectively. Furthermore, F7C2 radio occultation electron density profiles reveal that three PDBs could prominently appear in June and December solstice in the upper ionosphere. F5/AIP and ICON/IVM ion velocities show that the zonal plasma drift is essential to form nighttime WN4 and PDBs, and the summer to winter trans-equatorial flow is important to PDBs.

Depletion of abundant plasma proteins for extracellular vesicle proteome characterization: benefits and pitfalls

Blood extracellular vesicles (EVs) play essential roles in cell–cell communication and their molecular cargo is a promising source of disease biomarkers. However, proteomic characterization of plasma-derived EVs is challenged by the presence of highly abundant plasma proteins, which limits the detection of less abundant proteins, and by the low number of EVs in biological fluids. The aim of this study was to investigate if the removal of abundant plasma proteins prior to EV isolation could improve plasma-derived EV characterization by LC–MS/MS and expand the proteome coverage. Plasma depletion was performed using a single-use spin column and EVs were isolated from only 100 µL of non-depleted and depleted plasma by size exclusion chromatography. Afterwards, EVs were characterized by nanoparticle tracking analysis and mass spectrometry–based proteomics using a data-independent acquisition approach. Depleted plasma-derived EVs had higher particle concentrations and particle-to-protein ratios. Depletion did increase the protein coverage with a higher number of identifications in EVs from depleted plasma (474 proteins) than from non-depleted (386 proteins). However, EVs derived from non-depleted plasma carried a slightly higher number of common EV markers. Overall, our findings suggest that plasma depletion prior to EV isolation by size exclusion chromatography provides higher yield and protein coverage, but slightly lower identification of EV markers. This study also showed the possibility to characterize the proteome of EVs derived from small plasma volumes, encouraging the clinical feasibility of the discovery of EV biomarkers.

A simple, time- and cost-effective, high-throughput depletion strategy for deep plasma proteomics.

We introduce a cost-effective, robust high-throughput-compatible plasma depletion method enabling in-depth profiling of plasma that detects >1300 proteins per run with a throughput of 60 samples per day. The method has been fully validated by processing >3000 samples with no apparent batch effect at a cost for the depletion step of ~$2.5 per sample.

Single vesicle analysis reveals the release of tetraspanin positive extracellular vesicles into circulation with high intensity intermittent exercise.

Small extracellular vesicles (sEVs) are released from all cell types and participate in the intercellular exchange of proteins, lipids, metabolites and nucleic acids. Proteomic, flow cytometry and nanoparticle tracking analyses suggest sEVs are released into circulation with exercise. However, interpretation of these data may be influenced by sources of bias introduced by different analytical approaches. Seven healthy participants carried out a high intensity intermittent training (HIIT) cycle protocol consisting of 4×30s at a work-rate corresponding to 200% of individual max power (watts) interspersed by 4.5min of active recovery. EDTA-treated blood was collected before and immediately after the final effort. Platelet-poor (PPP) and platelet-free (PFP) plasma was derived by one or two centrifugal spins at 2500g, respectively (15min, room temperature). Platelets were counted on an automated haemocytometer. Plasma samples were assessed with the Exoview R100 platform, which immobilises sEVs expressing common tetraspanin markers CD9, CD63, CD81 and CD41a on microfluidic chips and with the aid of fluorescence imaging, counts their abundance at a single sEV resolution, importantly, without a pre-isolation step. There was a lower number of platelets in the PFP than PPP, which was associated with a lower number of CD9, CD63 and CD41a positive sEVs. HIIT induced an increase in fluorescence counts in CD9, CD63 and CD81 positive sEVs in both PPP and PFP. These data support the concept that sEVs are released into circulation with exercise. Furthermore, platelet-free plasma is the preferred, representative analyte to study sEV dynamics and phenotype during exercise. KEY POINTS: Small extracellular vesicles (sEV) are nano-sized particles containing protein, metabolites, lipid and RNA that can be transferred from cell to cell. Previous findings implicate that sEVs are released into circulation with exhaustive, aerobic exercise, but since there is no gold standard method to isolate sEVs, these findings may be subject to bias introduced by different approaches. Here, we use a novel method to immobilise and image sEVs, at single-vesicle resolution, to show sEVs are released into circulation with high intensity intermittent exercise. Since platelet depletion of plasma results in a reduction in sEVs, platelet-free plasma is the preferred analyte to examine sEV dynamics and phenotype in the context of exercise.