Inertial effects on trapped active matter.

In this work, the dynamics of inertial (mass and moment of inertia) active Brownian particles trapped in a harmonic well is studied. This scenario has seen success when characterizing soft passive and active overdamped matter. Motivated by the variety of applications of this system, we analytically find the effect of translational and rotational inertia on the mean-square displacement (MSD), mean-square speed (MSS), swim, Reynolds, and total pressures of a system of inertial active Brownian particles subject to a weak and a strong harmonic trap. Following a Langevin formalism, we explicitly find that as inertia grows, the systems' MSD and total pressure are enhanced, but its MSS and swim pressure decrease. The use of Langevin dynamics simulations enables us to observe that as inertia grows, inertial active matter under a strong trap no longer "condensates" at the "border" of the trap, but it rather tends to uniformly spread in space. Our analytical results are also numerically validated.

Intrauterine undernutrition in rats interferes with leukocyte migration, decreasing adhesion molecule expression in leukocytes and endothelial cells.

Experimental and epidemiologic data have shown that malnutrition predisposes individuals to infections. Immune responses are compromised, particularly in undernourished children. Therefore, we investigated the migratory capacity of leukocytes, using the intravital microscopy technique, in male Wistar rats (8-9 wk of age) that were undernourished in utero after their dams were fed 50% less food than the amount consumed by control dams. The number of leukocytes rolling along the venular endothelium, sticking after stimulation with leukotriene B4, tumor necrosis factor-alpha (TNF-alpha) or zymosan-activated plasma, or migrating after TNF-alpha stimulation was significantly reduced in the undernourished rat offspring. Compared with nourished rat offspring, undernourished offspring had significantly reduced numbers of circulating leukocytes, higher blood pressure, and higher leukocyte rolling velocity (V(WBC)), as well as a higher ratio between V(WBC) and RBC velocity (V(RBC)). Endothelial P-selectin and intercellular adhesion molecule-1 (ICAM-1) expression, analyzed by immunohistochemistry, and basal leukocyte L-selectin expression, analyzed by flow cytometry, were significantly reduced in the undernourished rat offspring. Because the groups did not differ in leukocyte CD11/18 expression, endothelial expression of platelet-endothelial cell adhesion molecule-1, or venular blood flow velocity and, consequently, venular shear rate, we conclude that intrauterine undernutrition in rats reduces leukocyte migration, downregulates endothelial expression of P-selectin and ICAM-1, as well as leukocyte expression of L-selectin, while reducing leukocyte counts. The higher V(WBC) and V(WBC)/V(RBC) ratio may also play a role in this reduced leukocyte migration. Our data suggest that this phenomenon is involved in the increased predisposition to infections in undernourished subjects.

Probucol restores the defective leukocyte-endothelial interaction in experimental diabetes.

Defective leukocyte-endothelial interactions have been observed in experimental type 1 diabetes. One of the mechanisms involved in the late complications of diabetes mellitus is the formation of free radicals species. Antioxidant treatment has been demonstrated to have beneficial effects on the complications observed in this pathology. Using intravital microscopy to visualize venules of the internal spermatic fascia, we demonstrated that the defective leukocyte-endothelial interactions in alloxan-induced diabetic rats could be corrected by probucol treatment. The defects were quantitated by the number of leukocytes rolling along the venular endothelium, sticking to the venular wall after topical application of zymosan-activated plasma (10%-0.1 ml) or leukotriene B4 (1 microM/0.1 ml) and migrated after the application of a local irritant stimulus (carrageenan, 100 microg/0.1 ml). Leukocyte counts, erythrocyte velocity and venular shear rate, unaltered in diabetic rats, were not modified by this treatment. Reactive oxygen species formation by endothelial cells increased in diabetic preparations, and the reduced expression of adhesion molecules such as intercellular adhesion molecule-1 (ICAM-1) and P-selectin in cross-sections of the whole testis of the animals, were both restored by the antioxidant agent. Therefore, antioxidant treatment improves leukocyte-endothelial interaction in diabetic rats at least in part by restoring the expression of adhesion molecules in venules of diabetic rats.