Platelet Adhesion and Activation in an ECMO Thrombosis-on-a-Chip Model.

Use of extracorporeal membrane oxygenation (ECMO) for cardiorespiratory failure remains complicated by blood clot formation (thrombosis), triggered by biomaterial surfaces and flow conditions. Thrombosis may result in ECMO circuit changes, cause red blood cell hemolysis, and thromboembolic events. Medical device thrombosis is potentiated by the interplay between biomaterial properties, hemodynamic flow conditions and patient pathology, however, the contribution and importance of these factors are poorly understood because many in vitro models lack the capability to customize material and flow conditions to investigate thrombosis under clinically relevant medical device conditions. Therefore, an ECMO thrombosis-on-a-chip model is developed that enables highly customizable biomaterial and flow combinations to evaluate ECMO thrombosis in real-time with low blood volume. It is observed that low flow rates, decelerating conditions, and flow stasis significantly increased platelet adhesion, correlating with clinical thrombus formation. For the first time, it is found that tubing material, polyvinyl chloride, caused increased platelet P-selectin activation compared to connector material, polycarbonate. This ECMO thrombosis-on-a-chip model can be used to guide ECMO operation, inform medical device design, investigate embolism, occlusion and platelet activation mechanisms, and develop anti-thrombotic biomaterials to ultimately reduce medical device thrombosis, anti-thrombotic drug use and therefore bleeding complications, leading to safer blood-contacting medical devices.

Estimated mortality of the highly pathogenic avian influenza pandemic on northern gannets (Morus bassanus) in southwest Ireland.

The 2022 highly pathogenic avian influenza (HPAI) outbreak that occurred in many European countries affected several seabird species. Among them, northern gannets (Morus bassanus) were particularly impacted. We conducted aerial surveys in waters around the two largest gannet colonies in southwest Ireland (Little Skellig and Bull Rock, together representing 87% of the national population) in September 2022. During surveys dead and alive northern gannets were counted on survey effort. A total of 184 dead gannets were recorded on survey effort, representing 3.74% of the total number of gannets recorded. We estimated the abundance of dead gannets in the surveyed area at 1526 (95% confidence intervals (CIs) 1450-1605) individuals. The percentage of dead gannets observed was used to estimate a minimum local population mortality of 3126 (95% CIs 2993-3260) individuals across both colonies. Aerial surveys provided key information on gannet mortality from HPAI at sea. The study provides the first estimate of gannet mortality in the two largest gannetries in Ireland.

Killer whale (Orcinus orca) population dynamics in response to a period of rapid ecosystem change in the eastern North Atlantic.

This study investigates survival and abundance of killer whales (Orcinus orca) in Norway in 1988-2019 using capture-recapture models of photo-identification data. We merged two datasets collected in a restricted fjord system in 1988-2008 (Period 1) with a third, collected after their preferred herring prey shifted its wintering grounds to more exposed coastal waters in 2012-2019 (Period 2), and investigated any differences between these two periods. The resulting dataset, spanning 32 years, comprised 3284 captures of 1236 whales, including 148 individuals seen in both periods. The best-supported models of survival included the effects of sex and time period, and the presence of transients (whales seen only once). Period 2 had a much larger percentage of transients compared to Period 1 (mean = 30% vs. 5%) and the identification of two groups of whales with different residency patterns revealed heterogeneity in recapture probabilities. This caused estimates of survival rates to be biased downward (females: 0.955 ± 0.027 SE, males: 0.864 ± 0.038 SE) compared to Period 1 (females: 0.998 ± 0.002 SE, males: 0.985 ± 0.009 SE). Accounting for this heterogeneity resulted in estimates of apparent survival close to unity for regularly seen whales in Period 2. A robust design model for Period 2 further supported random temporary emigration at an estimated annual probability of 0.148 (± 0.095 SE). This same model estimated a peak in annual abundance in 2015 at 1061 individuals (95% CI 999-1127), compared to a maximum of 731 (95% CI 505-1059) previously estimated in Period 1, and dropped to 513 (95% CI 488-540) in 2018. Our results indicate variations in the proportion of killer whales present of an undefined population (or populations) in a larger geographical region. Killer whales have adjusted their distribution to shifts in key prey resources, indicating potential to adapt to rapidly changing marine ecosystems.

Growth and carbonate production of crustose coralline algae on a degraded turbid reef system.

Crustose coralline algae (CCA) and other encrusting calcifiers drive carbonate production on coral reefs. However, little is known about the rates of growth and calcification of these organisms within degraded turbid reef systems. Here we deployed settlement cards (N = 764) across seven reefs in Singapore for two years to examine spatio-temporal variation in encrusting community composition and CCA carbonate production. Our results showed that CCA was the dominant encrusting taxa (63.7% ± 18.3SD) across reefs. CCA carbonate production rates (0.009-0.052 g cm-2 yr-1) were less than half of those reported for most Indo-Pacific reefs, but similar to other turbid reef systems. Highest CCA carbonate production rates were observed furthest from Singapore's main shipping port, due to a relative increase in CCA cover on the offshore reefs. Our results suggest that proximity to areas of high industrialisation and ship traffic may reduce the cover of encrusting calcifying organisms and CCA production rates which may have negative, long-term implications for the stabilisation of nearshore reefs in urbanised settings.

Hemodynamic analysis for stenosis microfluidic model of thrombosis with refined computational fluid dynamics simulation.

Disturbed blood flow has been increasingly recognized for its critical role in platelet aggregation and thrombosis. Microfluidics with hump shaped contractions have been developed to mimic microvascular stenosis and recapitulate the prothrombotic effect of flow disturbance. However the physical determinants of microfluidic hemodynamics are not completely defined. Here, we report a refined computational fluid dynamics (CFD) simulation approach to map the shear rate (γ) and wall shear stress (τ) distribution in the stenotic region at high accuracy. Using ultra-fine meshing with sensitivity verification, our CFD results show that the stenosis level (S) is dominant over the bulk shear rate (γ0) and contraction angle (α) in determining γ and τ distribution at stenosis. In contrast, α plays a significant role in governing the shear rate gradient (γ') distribution while it exhibits subtle effects on the peak γ. To investigate the viscosity effect, we employ a Generalized Power-Law model to simulate blood flow as a non-Newtonian fluid, showing negligible difference in the γ distribution when compared with Newtonian simulation with water medium. Together, our refined CFD method represents a comprehensive approach to examine microfluidic hemodynamics in three dimensions and guide microfabrication designs. Combining this with hematological experiments promises to advance understandings of the rheological effect in thrombosis and platelet mechanobiology.

Evaluating medical device and material thrombosis under flow: current and emerging technologies.

Although blood-contacting medical devices are used widely, blood clot formation (thrombosis) leads to device failure and potentially catastrophic adverse thrombotic events for patients, such as stroke or pulomonary embolism. Systemic anti-thrombotic drugs aimed at reducing these complications do not always prevent device thrombosis and can cause increased bleeding risks. Therefore, our understanding of material thrombosis mechanisms needs to be improved in order to develop next generation blood-contacting medical devices and materials. Medical device development requires material thrombogenicity evaluation according to the International Standards 10993-4 Biological evaluation of medical devices-Selection of tests for interactions with blood, which highlights that one of the key aspects for testing is a clinically relevant flow system. In this review, we first provide an overview of the current knowledge regarding material thrombosis and important physical and biological aspects of blood flow in relation to thrombus formation. We then examine commonly used in vitro flow systems to evaluate material and medical device thrombosis, focusing on their capabilities, advantages and disadvantages. Finally, we explore recent advances in technology that will aid in improving the design and fabrication of flow systems, mechanistic analysis and computational modelling.