Platelet dysfunction reversal with cold-stored vs room temperature-stored platelet transfusions.

ABSTRACT: Platelets are stored at room temperature for 5 to 7 days (room temperature-stored platelets [RSPs]). Because of frequent and severe shortages, the US Food and Drug Administration recently approved up to 14-day cold-stored platelets (CSPs) in plasma. However, the posttransfusion function of CSPs is unknown and it is unclear which donors are best suited to provide either RSPs or CSPs. In this study, we sought to evaluate the posttransfusion platelet function and its predictors for platelets stored for the maximum approved storage times (7-day RSPs and 14-day CSPs) in healthy volunteers on acetylsalicylic acid (ASA). We conducted a randomized crossover study in 10 healthy humans. Individuals donated 1 platelet unit, stored at either 22°C or 4°C based on randomization. Before transfusion, participants ingested ASA to inhibit endogenous platelets. Transfusion recipients were tested for platelet function and lipid mediators. Platelet units were tested for lipid mediators only. A second round of transfusion with the alternative product was followed by an identical testing sequence. RSPs reversed platelet inhibition significantly better in αIIbß3 integrin activation-dependent assays. In contrast, CSPs in recipients led to significantly more thrombin generation, which was independent of platelet microparticles. Lysophosphatidylcholine-O species levels predicted the procoagulant capacity of CSPs. In contrast, polyunsaturated fatty acid concentrations predicted the aggregation response of RSPs. In summary, we provide, to our knowledge, the first efficacy data of extended-stored CSPs in plasma. Our results suggest that identifying ideal RSP and CSP donors is possible, and pave the way for larger studies in the future. This trial is registered at www.ClinicalTrials.gov as #NCT0511102.

Evaluating stored platelet shape change using imaging flow cytometry.

Platelets are routinely stored at room temperature for 5-7 days before transfusion. Stored platelet quality is traditionally assessed by Kunicki's morphology score. This method requires extensive training, experience, and is highly subjective. Moreover, the number of laboratories familiar with this technique is decreasing. Cold storage of platelets has recently regained interest because of potential advantages such as reduced bacterial growth and preserved function. However, platelets exposed to cold temperatures change uniformly from a discoid to a spherical shape, reducing the morphology score outcomes to spheroid versus discoid during cooling. We developed a simpler, unbiased screening tool to measure temperature-induced platelet shape change using imaging flow cytometry. When reduced to two dimensions, spheres appear circular, while discs are detected on a spectrum from fusiform to circular. We defined circular events as having a transverse axis of >0.8 of the longitudinal axis and fusiform events ≤0.8 of the longitudinal axis. Using this assay, mouse and human platelets show a temperature and time-dependent, two-dimensional shape change from fusiform to circular, consistent with their three-dimensional change from discs to spheres. The method we describe here is a valuable tool for detecting shape change differences in response to agonists or temperature and will help screening for therapeutic measures to mitigate the cold-induced storage lesion.

What is the context? Platelets for transfusion are currently stored for 5­7 days at room temperature, increasing the risk for bacterial growthCold storage reduces the risk for bacterial growth but reduces circulation timeStored platelet quality can be assessed by the light microscopy-based Morphology Score, first described in the 1970sDownsides of the Morphology Score include subjectivity, extensive training, and reduced availability in platelet laboratories.What is new? In this study, we provide data showing that the Morphology score is reduced to a binary spheres versus discs response in cold-exposed plateletsWe developed an imaging flow cytometry-based approach to quantify platelets' response to cold based on the two-dimensional projection of the three-dimensional shapes, i.e., fusiform (discoid) versus circular (discoid and spherical)We provide validation of this approach in mouse and human plateletsWhat is the impact?This study provides an easy and unbiased tool for laboratories working on circumventing the cold-induced storage lesion or documenting spherical shape change in general.

Black dots: High-yield traction force microscopy reveals structural factors contributing to platelet forces.

Measuring the traction forces produced by cells provides insight into their behavior and physiological function. Here, we developed a technique (dubbed 'black dots') that microcontact prints a fluorescent micropattern onto a flexible substrate to measure cellular traction forces without constraining cell shape or needing to detach the cells. To demonstrate our technique, we assessed human platelets, which can generate a large range of forces within a population. We find platelets that exert more force have more spread area, are more circular, and have more uniformly distributed F-actin filaments. As a result of the high yield of data obtainable by this technique, we were able to evaluate multivariate mixed effects models with interaction terms and conduct a clustering analysis to identify clusters within our data. These statistical techniques demonstrated a complex relationship between spread area, circularity, F-actin dispersion, and platelet force, including cooperative effects that significantly associate with platelet traction forces. STATEMENT OF SIGNIFICANCE: Cells produce contractile forces during division, migration, or wound healing. Measuring cellular forces provides insight into their health, behavior, and function. We developed a technique that calculates cellular forces by seeding cells onto a pattern and quantifying how much each cell displaces the pattern. This technique is capable of measuring hundreds of cells without needing to detach them. Using this technique to evaluate human platelets, we find that platelets exerting more force tend to have more spread area, are more circular in shape, and have more uniformly distributed cytoskeletal filaments. Due to our high yield of data, we were able to apply statistical techniques that revealed combinatorial effects between these factors.

Effect of bedside filtration on aggregates from cold-stored whole blood-derived platelet-rich plasma and apheresis platelet concentrates.

BACKGROUND: The current approach to manufacture cold-stored platelets (CSP) replicates that of room temperature-stored platelets (RSP). However, this production method is associated with aggregate formation in CSP, a major pitfall that leads to significant wastage. We hypothesized that isolating platelets from whole blood as platelet-rich plasma (PRP) and storing them at a lower concentration reduces aggregates and that conventional bedside transfusion filtration removes CSP aggregates. METHODS: We collected platelets from healthy humans by apheresis (AP) and by phlebotomy, from which we generated platelet-rich plasma (PRP). We split each AP and PRP platelets into two equal aliquots, storing one at 22°C (RT-PRP and RT-AP) and the other at 4°C (4C-PRP and 4C-AP). We evaluated platelets on day 0 and day 7 of storage. After storage, we measured platelet counts, aggregates, and other key characteristics before and after filtration by a bedside filter. RESULTS: After storage, the 4C-AP platelet counts decreased significantly. 4C-PRP preserved glucose better and prevented a significant increase in lactate contrary to 4C-AP. Filtration led to significantly lower platelet counts in both 4C-PRP and 4C-AP but not in their RT counterparts. Post filtration, we observed 50% fewer aggregates only in 4C-AP, whereas 4C-PRP showed an unexpected but significant increase in aggregates. Testing confirmed activation during storage but filtration did not further activate platelets. CONCLUSION: We provide evidence that 4C-PRP is an alternative to 4C-AP and that bedside filters reduce aggregates from 4C-AP. Further studies are needed to evaluate the hemostatic potential of 4C-PRP and the management of aggregates.

Storage temperature determines platelet GPVI levels and function in mice and humans.

Platelets are currently stored at room temperature before transfusion to maximize circulation time. This approach has numerous downsides, including limited storage duration, bacterial growth risk, and increased costs. Cold storage could alleviate these problems. However, the functional consequences of cold exposure for platelets are poorly understood. In the present study, we compared the function of cold-stored platelets (CSP) with that of room temperature-stored platelets (RSP) in vitro, in vivo, and posttransfusion. CSP formed larger aggregates under in vitro shear while generating similar contractile forces compared with RSP. We found significantly reduced glycoprotein VI (GPVI) levels after cold exposure of 5 to 7 days. After transfusion into humans, CSP were mostly equivalent to RSP; however, their rate of aggregation in response to the GPVI agonist collagen was significantly lower. In a mouse model of platelet transfusion, we found a significantly lower response rate to the GPVI-dependent agonist convulxin and significantly lower GPVI levels on the surface of transfused platelets after cold storage. In summary, our data support an immediate but short-lived benefit of cold storage and highlight the need for thorough investigations of CSP. This trial was registered at www.clinicaltrials.gov as #NCT03787927.

Cold-Stored Platelets: Review of Studies in Humans.

Although numerous reviews and editorials have been published about the biologic features of platelets exposed to cold temperature and their in vitro function, none has focused on the data from studies after transfusion in healthy human participants and patients. This may, in part, be due to the paucity of well-controlled in vivo investigations of cold-stored platelets. Although numerous studies are looking into the recovery and survival of cold-stored platelets (ie, the percentage of infused platelets maintained in circulation over time), very few assess in vivo platelet function. Another caveat is that most studies were performed in the 1960s and 1970s, at a time when platelet collection and storage were different compared to today. Despite these limitations, we believe the transfusion community can take valuable information from these studies. This review is limited to data on cold-stored platelets in plasma or additive solution and does not include data on whole blood or resuspended whole blood from components because the hemostatic properties of whole blood are likely very different (the interested reader is referred to the review article focused on the hemostatic properties of platelets stored in whole blood by van der Meer et al in this special edition of Transfusion Medicine Reviews). In this review, we report that room temperature storage consistently results in a longer in vivo platelet circulation time at the expense of bacterial growth and shorter storage duration, resulting in expiration, wastage, and regional and national shortages. Cold storage of platelets universally results in moderately reduced recovery and markedly reduced survival. We found inconsistent data about the efficacy of cold-stored platelets likely due to study design differences. The analysis of the available data suggests that there is a short-lasting hemostatic effect of cold-stored platelets. Storage time or choice of anticoagulant did not have a clear effect on platelet efficacy after cold storage. In summary, more data and clinical trials are needed to better understand the effect of cold-stored platelets after transfusion into humans.

The Influence of Goal Commitment and Partner Status on Team Assignment Outcomes.

The present study replicated and extended research on the influence of team assignment methods on task performance and fairness perceptions. This study examined the influence of team assignment methods, goal commitment, and partner status on team member performance and fairness perceptions in a laboratory setting. The assignment conditions were comprised of three variables: assignment method (random, self-decision, and ability), performer status (assigned or unassigned), and partner status (unassigned team member stayed or left during task performance). A significant interaction was found between assignment method and performer status when the unassigned team member left during task performance, but not when the unassigned team member stayed. Random and self-decision assignment methods resulted in higher levels of goal commitment and task performance than did ability-based assignment conditions. Lastly, goal commitment was found to mediate the relationship between assignment method and task performance. The implications of these findings for the task performance and organizational justice literatures, as well as for managers in general, are discussed.

Pre- and postdoctoral dental education compared to practice patterns in special care dentistry.

There has been limited research into the impact of predoctoral experiences and postdoctoral general dentistry residencies on the practice patterns of dentists in the care of patients with special or complex needs. This study was undertaken to determine if educational experiences with special populations had a relationship to practice patterns after graduation or residency. University of the Pacific alumni who graduated between 1997 and 2007 were surveyed regarding their pre- and postdoctoral dental education and their practice patterns for the care of patients categorized as medically compromised, frail elders, and developmentally disabled. Definitions for each patient category were provided. Alumni were asked about their practice setting and postdoctoral education. Thirty-one percent (n=526) of those surveyed responded. Regression analyses showed respondents not in private practice were more likely to have completed a postdoctoral general dentistry program (Advanced Education in General Dentistry or General Practice Residency) after dental school compared to respondents in private practice (p<0.001). Across all age groups, respondents not in private practice treated significantly more patients with developmental disabilities than those in private practice (p<0.001). Respondents not in private practice treated more medically compromised patients younger than age sixty-five compared to respondents in private practice (p<0.01). Interestingly, those in private practice treated significantly more patients over sixty-five who were also classified as medically compromised (p<0.05). Pacific alumni who completed postdoctoral training in general dentistry were found to practice more often in non-private practice settings. Alumni in non-private practice settings reported treating a higher percentage of medically compromised patients below age sixty-five than their counterparts in a typical private practice. The pre- and postdoctoral experiences of treating special needs populations appear to have a relationship to graduates' practice setting and patient population.

Spatial correlation in the ambient core noise field of a turbofan engine.

An acoustic transfer function relating combustion noise and turbine exit noise in the presence of enclosed ambient core noise is investigated using a dynamic system model and an acoustic system model for the particular turbofan engine studied and for a range of operating conditions. Measurements of cross-spectra magnitude and phase between the combustor and turbine exit and auto-spectra at the turbine exit and combustor are used to show the presence of indirect and direct combustion noise over the frequency range of 0-400 Hz. The procedure used evaluates the ratio of direct to indirect combustion noise. The procedure used also evaluates the post-combustion residence time in the combustor which is a factor in the formation of thermal NO(x) and soot in this region. These measurements are masked by the ambient core noise sound field in this frequency range which is observable since the transducers are situated within an acoustic wavelength of one another. An ambient core noise field model based on one and two dimensional spatial correlation functions is used to replicate the spatially correlated response of the pair of transducers. The spatial correlation function increases measured attenuation due to destructive interference and masks the true attenuation of the turbine.

Perceptions of predoctoral dental education and practice patterns in special care dentistry.

The objective of this research project was to compare alumni perceptions of predoctoral dental education in the care and management of patients with complex needs to alumni practice patterns. Alumni from the University of the Pacific Arthur A. Dugoni School of Dentistry who graduated from 1997 to 2007 were surveyed regarding perceptions of their predoctoral education in the care of patients categorized and defined as medically compromised, frail elders, and developmentally disabled, as well as their practice patterns. Perceptions were rated on a Likert scale. Regression analyses were utilized. Three primary relationships were identified: 1) positive relationships emerged between perceptions of educational value, as students and practitioners, of the training they received compared to percentages of medically compromised patients they currently treat (p≤0.05); 2) after practice experience, 2003-07 graduates reported significantly higher value of their education in this area compared to 1997-2002 graduates; and 3) alumni who reported treating more patients with complex needs during school reported treating significantly more of these patients in practice (p≤0.05). We conclude that alumni who reported educational experiences as more valuable treat more patients with complex needs compared to those who valued them less. Alumni who reported having more opportunities to treat patients with complex needs as students treat a higher percentage of those patients than those reporting fewer. Even positive perceptions may underestimate the value of educational experiences as they relate to future practice.

Estimation of signal coherence threshold and concealed spectral lines applied to detection of turbofan engine combustion noise.

Combustion noise from turbofan engines has become important, as the noise from sources like the fan and jet are reduced. An aligned and un-aligned coherence technique has been developed to determine a threshold level for the coherence and thereby help to separate the coherent combustion noise source from other noise sources measured with far-field microphones. This method is compared with a statistics based coherence threshold estimation method. In addition, the un-aligned coherence procedure at the same time also reveals periodicities, spectral lines, and undamped sinusoids hidden by broadband turbofan engine noise. In calculating the coherence threshold using a statistical method, one may use either the number of independent records or a larger number corresponding to the number of overlapped records used to create the average. Using data from a turbofan engine and a simulation this paper shows that applying the Fisher z-transform to the un-aligned coherence can aid in making the proper selection of samples and produce a reasonable statistics based coherence threshold. Examples are presented showing that the underlying tonal and coherent broad band structure which is buried under random broadband noise and jet noise can be determined. The method also shows the possible presence of indirect combustion noise.

Pulp capping with mineral trioxide aggregate (MTA): a retrospective analysis of carious pulp exposures treated by undergraduate dental students.

The current study estimated pulpal vitality after MTA pulp caps were performed by undergraduate student clinicians. At recall after 12 to 27 months, 51 pulp caps were clinically and radiographically assessed. Kaplan-Meier analyses were used to estimate overall success at 12 and 24 months, determined as the presence of a vital pulp, as well as impact of preoperative variables on pulp vitality at recall. Overall, one-year pulp survival was 67.7%, while the two-year survival rate was 56.2%. Tarone-Ware statistics indicated that neither age of the patient nor size of the exposure ("minimal" or "moderate") and the amount of bleeding ("none," "minimal" or "moderate") had a significant effect on survival rates. Within the limitations of the current study on procedures performed by student clinicians, it may be concluded that, for MTA pulp caps applied to carious exposures in adults, certain preoperative conditions--patient age, exposure size and amount of bleeding--are not predictive of clinical outcome. Considering the comparatively low success rate for the current cohort, more research is needed to define predictive criteria for successful pulp capping with MTA.

Perception in consequences of free riding.

This study examined the relationships between perceptions of group members' free riding and group outcomes using Mulvey and Klein's 1998 perceived free riding scale. In a laboratory study, three free riding conditions were created (no free riding, free riding, free riding with justification) in which 97 college students performed two short number-finding tasks as members of temporary ad hoc three-person groups. 55% of the students were male and the average age was 22.9 yr. (SD= 3.0). Participants' perceptions of free riding were negatively related to commitment to the assigned group goal, task performance, and goals for group performance and individual performance. In the condition wherein free riding was justified by low ability, participants set lower goals for their future task performance than did those in the other two conditions.