The long‐term influence of repetitive cellular cardiac rejections on left ventricular longitudinal myocardial deformation in heart transplant recipients

The aim of the study was to evaluate the long‐term influence of repeated acute cellular rejections on left ventricular longitudinal deformation in heart transplantation (HTX) patients. One hundred and seventy‐eight HTX patients were included in the study. Rejections were classified according to the International Society of Heart and Lung Transplantation (ISHLT) classification (0R–3R). Patients were divided into three groups according to rejection scores (RSs). Group 1: <50% of biopsies with 1R rejection and no ≥2R rejections; Group 2: ≥50% of biopsies with 1R rejection or one biopsy with ≥2R rejection; Group 3: ≥Two biopsies with ≥2R rejections. All patients had a comprehensive echocardiographic examination and coronary angiography. We found significantly decreasing global longitudinal strain (GLS) comparing to rejection groups (GLS group 1: ?16.8 ± 2.4 (%); GLS group 2: ?15.9 ± 3.3 (%); GLS group 3: ?14.5 ± 2.9 (%), P = 0.0003). After excluding patients with LVEF < 50% or vasculopathy, GLS was still significantly reduced according to RS groups (P = 0.0096). Total number of 1R and 2R rejections correlated significant to GLS in a linear regression model. In contrast, we found fractional shortening and LVEF to be unaffected by repeated rejections. In conclusion, repeated cardiac rejections lead to impaired graft function as detected by decreasing magnitude of GLS. In contrast, traditional systolic graft function surveillance by LVEF did not correlate to rejection burden.     

Identification of hepoxilin A3 in inflammatory events: a required role in neutrophil migration across intestinal epithelia

The mechanism by which neutrophils [polymorphonuclear leukocyte (PMNs)] are stimulated to move across epithelial barriers at mucosal surfaces has been basically unknown in biology. IL-8 has been shown to stimulate PMNs to leave the bloodstream at a local site of mucosal inflammation, but the chemical gradient used by PMNs to move between adjacent epithelial cells and traverse the tight junction at the apical neck of these mucosal barriers has eluded identification. Our studies not only identify this factor, previously termed pathogen-elicited epithelial chemoattractant, as the eicosanoid hepoxilin A(3) (hepA(3)) but also demonstrate that it is a key factor promoting the final step in PMN recruitment to sites of mucosal inflammation. We show that hepA(3) is synthesized by epithelial cells and secreted from their apical surface in response to conditions that stimulate inflammatory events. Our data further establish that hepA(3) acts to draw PMNs, via the establishment of a gradient across the epithelial tight junction complex. The functional significance of hepA(3) to target PMNs to the lumen of the gut at sites of inflammation was demonstrated by the finding that disruption of the 12-lipoxygenase pathway (required for hepA(3) production) could dramatically reduce PMN-mediated tissue trauma, demonstrating that hepA(3) is a key regulator of mucosal inflammation.     

Flow disturbances generated by feeding and swimming zooplankton

Interactions between planktonic organisms, such as detection of prey, predators, and mates, are often mediated by fluid signals. Consequently, many plankton predators perceive their prey from the fluid disturbances that it generates when it feeds and swims. Zooplankton should therefore seek to minimize the fluid disturbance that they produce. By means of particle image velocimetry, we describe the fluid disturbances produced by feeding and swimming in zooplankton with diverse propulsion mechanisms and ranging from 10-µm flagellates to greater than millimeter-sized copepods. We show that zooplankton, in which feeding and swimming are separate processes, produce flow disturbances during swimming with a much faster spatial attenuation (velocity u varies with distance r as u ∝ r⁻³ to r⁻⁴) than that produced by zooplankton for which feeding and propulsion are the same process (u ∝ r⁻¹ to r⁻²). As a result, the spatial extension of the fluid disturbance produced by swimmers is an order of magnitude smaller than that produced by feeders at similar Reynolds numbers. The “quiet” propulsion of swimmers is achieved either through swimming erratically by short-lasting power strokes, generating viscous vortex rings, or by “breast-stroke swimming.” Both produce rapidly attenuating flows. The more “noisy” swimming of those that are constrained by a need to simultaneously feed is due to constantly beating flagella or appendages that are positioned either anteriorly or posteriorly on the (cell) body. These patterns transcend differences in size and taxonomy and have thus evolved multiple times, suggesting a strong selective pressure to minimize predation risk.Zooplankters move to feed, find food, and find mates, so moving is critical to the efficient execution of essential functions. However, moving comes at a predation risk: Swimming increases the predator encounter velocity (encounter rate increases with prey velocity to a power ≤1), and feeding and swimming generate fluid disturbances that may be perceived by rheotactic predators, thus increasing the predator’s detection distance (encounter rate increases with detection distance squared) (1–5). So, the advantages of moving and feeding must be traded off against the associated risks, and organisms should aim at moving and foraging in ways that reduce the predation risk and optimize the trade-off (6, 7). They may do so by moving in patterns that minimize encounter rates (8) and/or they may feed and propel themselves in ways that generate only small fluid disturbances (9). For example, theoretical models suggest that zooplankton that swim by a sequence of jumps may create a smaller fluid disturbance than similar-sized ones that swim smoothly (9), that a hovering zooplankter generates a larger fluid signal than one that cruises through the water (10, 11), and that a zooplankter moving at low Reynolds numbers will generate a relatively larger fluid signal than one moving at higher Reynolds numbers (11). Thus, motility patterns and propulsion modes may strongly influence predation risk and must be subject to strong selection pressure during evolution.Zooplankton span a huge taxonomic diversity and a large size range (from microns to centimeters) and their propulsion mechanisms vary substantially (12). Unicellular plankton may use one or more flagella or cilia, and the flagella may be smooth or plumose, which has implications for whether the cell is pulled or pushed by the beating flagellum (13). Ciliates may have the cilia rather evenly distributed on the cell surface or concentrated on certain parts of the cell, typically either anteriorly or as an equatorial band. Small animals may have an anterior “corona” of cilia (e.g., rotifers and many pelagic invertebrate larvae) to generate feeding currents and propulsion, or they may have beating or vibrating appendages that can be positioned anteriorly, ventrally, or laterally. The implications and potential adaptive value of this diversity of propulsion modes for feeding and survival are largely unexplored.Various idealized models, simplifying the swimming organisms to combinations of point forces acting on the water, have been used to describe the fluid disturbance generated by moving and feeding plankton. A self-propelled plankton is often described by a so-called stresslet (two oppositely directed point forces of equal magnitude), a hovering one by a stokeslet (a stationary point force), and a jumping animal by an impulsive stresslet (a stresslet working impulsively) (9, 11, 12). These highly idealized models yield very different predictions of the spatial attenuation of the fluid disturbance and, thus, of how far away the feeding and swimming animal can be detected. A few studies have compared observed flow patterns with those predicted from these simple models and in some cases found fair comparisons (4, 14–17). However, numerical simulations as well as observations of self-propelled microplankton have demonstrated that the distribution of propulsion forces, i.e., the position of flagella, cilia, or appendages on the (cell) body, may have a profound effect on the imposed fluid flow (18, 19). Also, most of the idealized models ignore the fact that swimming in most cases is unsteady, which leads to fluctuating flows at scales smaller than the Stokes length scale (ν/ω, where ν is the kinematic viscosity and ω is the beat frequency) (e.g., ref. 19). The simple, idealized models hitherto applied may be insufficient to represent the diverse propulsion modes observed in real organisms and to understand the associated trade-offs.Feeding and swimming are often part of the same process in zooplankton. Many zooplankton generate a feeding current that at the same time propels the animal through the water. In others, feeding and swimming are separate processes. For example, ambush feeding “sit-and-wait” zooplankters do not move as part of feeding but may swim to undertake vertical migration or to search for mates or patches of elevated food availability. Also, many of the plankton that generate a feeding current by vibrating appendages may in addition swim by using the same appendages in a different way (e.g., the nauplius larvae of most crustaceans) or by using other swimming appendages dedicated to propel themselves (most pelagic copepods and cladocerans).Whereas feeding and swimming may both compromise the survival of the organism, the trade-offs may be different. To get sufficient food, zooplankters need to daily clear a volume of water for prey that corresponds to about 10⁶ times their own body volume (20, 21) and hence, implicit in the feeding process is the need to examine or process large volumes of water. In contrast, dedicated swimming should translate the organism through the water as quietly as possible. Thus, we hypothesize that in microplankton, dedicated swimming produces flow fields that attenuate more readily and/or have a smaller spatial extension than the cases in which feeding and propulsion are intimately related.In this study we use particle image velocimetry (PIV) to describe the flow fields generated by micron- to millimeter-sized feeding and swimming zooplankton that use a variety of propulsion modes. We show that—across taxa and sizes—dedicated swimming produces flow fields with a much smaller spatial extension and a faster spatial attenuation than those produced by the plankton for which feeding and swimming are integrated, and we characterize the propulsion modes that minimize susceptibility to rheotactic predators.     

Increased thrombin generation in splanchnic vein thrombosis is related to the presence of liver cirrhosis and not to the thrombotic event

Introduction

In recent years there have been increasing evidence associating liver disease with hypercoagulability, rather than bleeding. The aim of the study was to evaluate the haemostatic potential in patients with liver disease.

Patients and methods

We measured thrombin generation in the presence and absence of thrombomodulin in patients with portal vein thrombosis (PVT, n = 47), Budd-Chiari syndrome (BCS, n = 15) and cirrhosis (n = 24) and compared the results to those obtained from healthy controls (n = 21). Fifteen patients with PVT and 10 patients with BCS were treated with warfarin and were compared to an equal number of patients with atrial fibrillation matched for prothrombin time-international normalized ratio. We assessed resistance to thrombomodulin by using ratios [marker measured in the presence/absence of thrombomodulin].

Results

There were no differences in thrombin generation between patients on warfarin treatment and their controls. Cirrhotic patients generated more thrombin in the presence of thrombomodulin and exhibited thrombomodulin resistance compared to controls [p = 0.006 for endogenous thrombin potential (ETP) and p < 0.001 for peak thrombin and both ratios ETP and peak] and patients with non-cirrhotic PVT (p = 0.001, p = 0.006, p < 0.001, p < 0.001 for ETP, peak, ratio ETP, ratio peak, respectively). The patients with cirrhotic PVT exhibited higher ETP (p = 0.044) and peak (p = 0.02) in the presence of thrombomodulin than controls, as well as thrombomodulin resistance (ETP and peak ratios: p = 0.001).

Conclusions

Hypercoagulability and thrombomodulin resistance in patients with cirrhosis were independent of the presence of splanchnic vein thrombosis. The hypercoagulability in patients with cirrhotic PVT could have implications for considering longer or more intensive treatment with anticoagulants in this group.