Microparticle image velocimetry approach to flow measurements in isolated contracting lymphatic vessels

We describe the development of an optical flow visualization method for resolving the flow velocity vector field in lymphatic vessels, in vitro. The aim is to develop an experimental protocol for accurately estimating flow parameters, such as flow rate and shear stresses, with high spatial and temporal resolution. Previous studies in situ have relied on lymphocytes as tracers, but their low density resulted in a reduced spatial resolution whereas the assumption that the flow was fully developed in order to determine the flow parameters of interest may not be valid, especially in the vicinity of the valves, where the flow is undoubtedly more complex. To overcome these issues, we have applied the time-resolved micro-Particle Image Velocimetry technique, a well-established method that can provide increased spatial and temporal resolution that this transient flow demands. To that end, we have developed a custom light source, utilizing high-power light-emitting diodes, and associated control and image processing software. This manuscript reports the performance of the system and the results of a series of preliminary experiments performed on vessels isolated from rat mesenteries, demonstrating, for the first time, the successful application of the micro-PIV technique in these vessels

Constructive Aggression? Multiple Roles of Aggressive Content in Political Discourse on Russian YouTube

Abstract Today, aggressive verbal behavior is generally perceived as a threat to integrity and democratic quality of public discussions, including those online. However, we argue that, in more restrictive political regimes, communicative aggression may play constructive roles in both discussion dynamics and empowerment of political groups. This might be especially true for restrictive political and legal environments like Russia, where obscene speech is prohibited by law in registered media and the political environment does not give much space for voicing discontent. Taking Russian YouTube as an example, we explore the roles of two under-researched types of communicative aggression—obscene speech and politically motivated hate speech—within the publics of video commenters. For that, we use the case of the Moscow protests of 2019 against non-admission of independent and oppositional candidates to run for the Moscow city parliament. The sample of over 77,000 comments for 13 videos of more than 100,000 views has undergone pre-processing and vocabulary-based detection of aggression. To assess the impact of hate speech upon the dynamics of the discussions, we have used Granger tests and assessment of discussion histograms; we have also assessed the selected groups of posts in an exploratory manner. Our findings demonstrate that communicative aggression helps to express immediate support and solidarity. It also contextualizes the criticism towards both the authorities and regime challengers, as well as demarcates the counter-public

Unhealthy communication on health: Discursive and ecosystemic features of opinion cumulation in the anti-vaccination discourse on Russian Telegram

With the advent of social networking sites, the so-called health dissidents have received unprecedented possibilities for online community building and spreading their views. In particular, the combination of social uncertainty and the platform affordances that bordered antivaxxer communities from outer communication led to formation of (allegedly) closed-up online milieus where vaccination denialists’ (‘antivaxxers’) irrational views resided and grew. The deliberative counter-productivity of such communities needs to be investigated. In this respect, Russia is a special case, characterized by low trust in the public sphere as a ground for the spread of conspiracy theories, and by ‘mixed’ trust to the healthcare system, thanks to highly-reputable Soviet-time medical services but negative attitudes to the current ones. We look at @anti_ covid21, the largest Russian pandemic antivaxxer community on Telegram, to explore by what means destructive opinions accumulate in this community. We investigate the combination of three discursive elements usually studied separately in research on COVID-19 denialism: 1) distrust, including its addressees, and interconnectedness of the destructive features of the antivaxxer discourse, namely distrust, aggression, and conspiracy thinking; 2) the patterns of micro-opinion cumulation that lead to general growth of distrust; 3) content sourcing that supports ‘the discourse of distrust.’ We follow the conceptual framework of cumulative deliberation; it implies that micro-acts of opinionated participation matter both en masse and in deliberative micro-patterns. Our sample includes all posts and comments from @anti_covid21 of six months of 2021, with 1,185 posts and 282,000+ comments altogether. Out of this sample, three datasets were formed. In particular, Dataset 1 was received by semi-automatedly reducing from 282,000+ to 12,188+ texts and then coded by 28 coders. Dataset 2 comprised comment threads of three most active days in terms of commenting, of 411 comments altogether, that were coded as continuous samples by 6 additional coders. Dataset 3 consisted of the 1,185 posts in which the available attracted content (text, photo, or video) was coded by 4 coders on its formal belonging to certain media types and countries of origin. Our results show that @anti_covid21 was a reactive community centered around one-sided anti-vaccination content that left no room for multi-view discussing. Content sourcing united user-generated evidence, criticized mainstream media pieces, and publications of blurred origin of many countries, making the community open to world experience but of highly biased nature. The ‘discourse of distrust’ that emerged in response was politicized, distrust to national and global actors potentially being a mediator to vaccine distrust. We identified two stable micro-patterns of accumulation of distrust triggered by both the published content and user behavior. Altogether, our conclusions differ from other countries’ experiences and call for pre-emptive resolution of the multi-faceted issue of social distrust before new health crises erupt

Structure and physiology of the lymphatic vasculature

The lymphatic vascular system is a highly organized network of structurally and functionally connected specialized lymphatic vessels of various sizes and lymph nodes that perform metabolic and transport functions. Lymph is a blood plasma filtrate that comprises antigen-presenting cells and lymphocytes. Via lymph, excess fluid and extravasated proteins are removed from the tissues. The lymphatic system supports an extracellular fluid homeostasis that is favorable for optimal tissue functioning by removing substances that result from metabolism or cell death, as well as optimizing immunity against bacteria, viruses and other antigens. Although the lymphatic vasculature is not formally considered part of the immune system, it is crucial for the traffic of antigens and immune cells. In addition, lymphatic endothelial cells can supply antigens and express factors that modulate immune responses. After an inflammatory stimulus, endothelial cells produce chemokines, which recruit immune cells to the lymph nodes. Unlike the circulatory system with a centralized pump, the movement of lymph through the network of lymphatic vessels is provided by forces that stimulate the initial formation of lymph in the tissues and the ability of the lymphatic vessels and nodes to rhythmically contract, providing increased pressure and lymph movement in the proximal direction. Since the metabolic rate in various organs and tissues varies significantly depending on the functional state of the tissue, the blood flow through the tissue and the amount of lymph formed also change significantly. The lymphatic vasculature has several circuits for regulating lymph flow. This review provides a comprehensive overview of the important results obtained over the past century and discusses the molecular and physiological control of the transport function of lymphatic vessels and nodes.</jats:p

Automated detection and measurement of isolated retinal arterioles by a combination of edge enhancement and cost analysis

Pressure myography studies have played a crucial role in our understanding of vascular physiology and pathophysiology. Such studies depend upon the reliable measurement of changes in the diameter of isolated vessel segments over time. Although several software packages are available to carry out such measurements on small arteries and veins, no such software exists to study smaller vessels (<50 µm in diameter). We provide here a new, freely available open-source algorithm, MyoTracker, to measure and track changes in the diameter of small isolated retinal arterioles. The program has been developed as an ImageJ plug-in and uses a combination of cost analysis and edge enhancement to detect the vessel walls. In tests performed on a dataset of 102 images, automatic measurements were found to be comparable to those of manual ones. The program was also able to track both fast and slow constrictions and dilations during intraluminal pressure changes and following application of several drugs. Variability in automated measurements during analysis of videos and processing times were also investigated and are reported. MyoTracker is a new software to assist during pressure myography experiments on small isolated retinal arterioles. It provides fast and accurate measurements with low levels of noise and works with both individual images and videos. Although the program was developed to work with small arterioles, it is also capable of tracking the walls of other types of microvessels, including venules and capillaries. It also works well with larger arteries, and therefore may provide an alternative to other packages developed for larger vessels when its features are considered advantageous

Entrainment of Lymphatic Contraction to Oscillatory Flow

AbstractLymphedema, a disfiguring condition characterized by an asymmetrical swelling of the limbs, is suspected to be caused by dysfunctions in the lymphatic system. A possible source of lymphatic dysfunction is the reduced mechanosensitivity of lymphangions, the spontaneously contracting units of the lymphatic system. In this study, the entrainment of lymphangions to an oscillatory wall shear stress (OWSS) is characterized in rat thoracic ducts in relation to their shear sensitivity. The critical shear stress above which the thoracic ducts show a substantial inhibition of contraction was found to be significantly negatively correlated to the diameter of the lymphangion. The entrainment of the lymphangion to an applied OWSS was found to be significantly dependent on the difference between the applied frequency and the intrinsic frequency of contraction of the lymphangion. The strength of the entrainment was also positively correlated to the applied shear stress when the applied shear was less than the critical shear stress of the vessel. The ejection fraction and fractional pump flow were also affected by the difference between the frequency of the applied OWSS and the vessel's intrinsic contraction frequency. The results suggest an adaptation of the lymphangion contractility to the existing oscillatory shear stress as a function of its intrinsic contractility and shear sensitivity. These adaptations might be crucial to ensure synchronized contraction of lymphangions through mechanosensitive means and might help explain the lymphatic dysfunctions that result from impaired mechanosensitivity.</jats:p