Occurrence and a possible mechanism of penetration of natural killer cells into k562 target cells during the cytotoxic interaction

The cytotoxic interaction between cloned human Natural Killer (NK) cells and K562 target cells was studied using confocal laser scanning microscopy (CLSM) and conventional fluorescence microscopy. We observed, using fixed as well as living cells, the occurrence of (pseudo)emperipolesis during the interaction. About 30% of conjugated NK cells penetrated, partly or completely, into the target cells (in-conjugation). Virtually all in-conjugated target cells exhibited polymerized actin. Killer cells of in-conjugates were frequently seen approaching the target cell nucleus or aligning along it. If the cytotoxic process was inhibited by the absence of calcium neither actin polymerization nor in-conjugation were observed. A kinetic study showed that in-conjugation starts somewhat later than actin polymerization but still within a few minutes after addition of calcium to conjugates previously formed in the absence of calcium. The presence of cytochalasin D (an inhibitor of actin polymerization) completely inhibited in-conjugation and partly reduced the cytotoxic activity. Zinc ions (endonuclease inhibition) inhibited in-conjugation and decreased the total number of target cells with polymerized actin in a concentration dependent manner. Cytotoxic activity was also reduced but not as efficiently as in-conjugation. \ud Our study demonstrates that in-conjugation represents a significant fraction of the cytotoxic interaction. The results indicate that it may be a consequence of an actin polymerization and endonuclease activity dependent part of a cytotoxic mechanism. \u

A fast strong coupling algorithm for the partitioned fluid–structure interaction simulation of BMHVs

The numerical simulation of Bileaflet Mechanical Heart Valves (BMHVs) has gained strong interest in the last years, as a design and optimisation tool. In this paper, a strong coupling algorithm for the partitioned fluidstructure interaction simulation of a BMHV is presented. The convergence of the coupling iterations between the flow solver and the leaflet motion solver is accelerated by using the Jacobian with the derivatives of the pressure and viscous moments acting on the leaflets with respect to the leaflet accelerations. This Jacobian is numerically calculated from the coupling iterations. An error analysis is done to derive a criterion for the selection of useable coupling iterations. The algorithm is successfully tested for two 3D cases of a BMHV and a comparison is made with existing coupling schemes. It is observed that the developed coupling scheme outperforms these existing schemes in needed coupling iterations per time step and CPU time

Measuring adaptive expertise: development and validation of an instrument

Individuals with adaptive expertise possess the skills to deal with novel problems. Whereas this concept has been around since the mid-1980s, no instrument exists that provides a good operationalization of the theoretical construct. This inhibits the further development of research on adaptive expertise and the evaluation of employees' adaptive expertise levels. Adaptive expertise has been unanimously described as a composition of domain-specific and innovative skills. Some researchers argue that metacognitive skills are also crucial. This study aimed to establish whether an instrument measuring adaptive expertise is composed of these three dimensions. In addition, it was tested whether such an instrument is influenced by task variety and work experience, as previously reported in literature. A sample of 383 professionals and graduates were used to test the Adaptive Expertise Inventory. Through exploratory factor analysis (EFA), (E/CFA), and confirmatory factor analysis (CFA), the quality of the instrument was evaluated. Good model fit was achieved. The final instrument consisted of two dimensionsi.e., domain-specific and innovative skillswith five items each. Regression analysis showed that not work experience, but task variety is related to level of adaptive expertise. The Adaptive Expertise Inventory proved to be a valid instrument for measuring adaptive expertise

Aging is associated with an earlier arrival of reflected waves without a distal shift in reflection sites

Background-Despite pronounced increases in central pulse wave velocity (PWV) with aging, reflected wave transit time (RWTT), traditionally defined as the timing of the inflection point (T-INF) in the central pressure waveform, does not appreciably decrease, leading to the controversial proposition of a "distal-shift" of reflection sites. T-INF, however, is exceptionally prone to measurement error and is also affected by ejection pattern and not only by wave reflection. We assessed whether RWTT, assessed by advanced pressure-flow analysis, demonstrates the expected decline with aging. Methods and Results-We studied a sample of unselected adults without cardiovascular disease (n=48; median age 48 years) and a clinical population of older adults with suspected/established cardiovascular disease (n=164; 61 years). We measured central pressure and flow with carotid tonometry and phase-contrast MRI, respectively. We assessed RWTT using wave-separation analysis (RWTTWSA) and partially distributed tube-load (TL) modeling (RWTTTL). Consistent with previous reports, T-INF did not appreciably decrease with age despite pronounced increases in PWV in both populations. However, aging was associated with pronounced decreases in RWTTWSA (general population -15.0 ms/decade, P<0.001; clinical population -9.07 ms/decade, P=0.003) and RWTTTL (general -15.8 ms/decade, P<0.001; clinical -11.8 ms/decade, P<0.001). There was no evidence of an increased effective reflecting distance by either method. TINF was shown to reliably represent RWTT only under highly unrealistic assumptions about input impedance. Conclusions-RWTT declines with age in parallel with increased PWV, with earlier effects of wave reflections and without a distal shift in reflecting sites. These findings have important implications for our understanding of the role of wave reflections with aging

Forces on a boiling bubble in a developing boundary layer, in microgravity with g-jitter and in terrestrial conditions

Terrestrial and microgravity flow boiling experiments were carried out with the same test rig, comprising a locally heated artificial cavity in the center of a channel near the frontal edge of an intrusive glass bubble generator. Bubble shapes were in microgravity generally not far from those of truncated spheres,which permitted the computation of inertial lift and drag from potential flow theory for truncated spheres approximating the actual shape. For these bubbles, inertial lift is counteracted by drag and both forces are of the same order of magnitude as g-jitter. A generalization of the Laplace equation is found which applies to a deforming bubble attached to a plane wall and yields the pressure difference between the hydrostatic pressures in the bubble and at the wall, p. A fully independent way to determine the overpressure p is given by a second Euler-Lagrange equation. Relative differences have been found to be about 5% for both terrestrial and microgravity bubbles. A way is found to determine the sum of the two counteracting major force contributions on a bubble in the direction normal to the wall from a single directly measurable quantity. Good agreement with expectation values for terrestrial bubbles was obtained with the difference in radii of curvature averaged over the liquid-vapor interface, (1/R2 − 1/R1), multiplied with the surface tension coefficient, σ. The new analysis methods of force components presented also permit the accounting for a surface tension gradient along the liquid-vapor interface. No such gradients were found for the present measurements

Contrast enhancement by differently sized paramagnetic MRI contrast agents in mice with two phenotypes of atherosclerotic plaque

Interest in the use of contrast-enhanced MRI to enable in vivo specific characterization of atherosclerotic plaques is increasing. In this study the intrinsic ability of three differently sized gadolinium-based contrast agents to permeate different mouse plaque phenotypes was evaluated with MRI. A tapered cast was implanted around the right carotid artery of apoE-/- mice to induce two different plaque phenotypes: a thin cap fibroatheroma (TCFA) and a non-TCFA lesion. Both plaques were allowed to develop over 6 and 9 weeks, leading to an intermediate and advanced lesion, respectively. Signal enhancement in the carotid artery wall, following intravenous injection of Gd-HP-DO3A as well as paramagnetic micelles and liposomes was evaluated. In vivo T1-weighted MRI plaque enhancement characteristics were complemented by fluorescence microscopy and correlated to lesion phenotype. The two smallest contrast agents, i.e. Gd-HP-DO3A and micelles, were found to enhance contrast in T1-weighted MR images of all investigated plaque phenotypes. Maximum contrast enhancement ranged between 53 and 70% at 6¿min after injection of Gd-HP-DO3A with highest enhancement and longest retention in the non-TCFA lesion. Twenty-four hours after injection of micelles maximum contrast enhancement ranged between 24 and 35% in all plaque phenotypes. Administration of the larger liposomes did not cause significant contrast enhancement in the atherosclerotic plaques. Confocal fluorescence microscopy confirmed the MRI-based differences in plaque permeation between micelles and liposomes. Plaque permeation of contrast agents was strongly dependent on size. Our results implicate that, when equipped with targeting ligands, liposomes are most suitable for the imaging of plaque-associated endothelial markers due to low background enhancement, whereas micelles, which accumulate extravascularly on a long timescale, are suited for imaging of less abundant markers inside plaques. Low molecular weight compounds may be employed for target-specific imaging of highly abundant extravascular plaque-associated target