PKCζ mediates disturbed flow-induced endothelial apoptosis via p53 SUMOylation.

Atherosclerosis is readily observed in regions of blood vessels where disturbed blood flow (d-flow) is known to occur. A positive correlation between protein kinase C ζ (PKCζ) activation and d-flow has been reported, but the exact role of d-flow-mediated PKCζ activation in atherosclerosis remains unclear. We tested the hypothesis that PKCζ activation by d-flow induces endothelial cell (EC) apoptosis by regulating p53.

Suppression of prostate cancer cell rolling and adhesion to endothelium by 1α,25-dihydroxyvitamin D3.

Adhesion of circulating prostate cancer (PCa) cells to the microvascular endothelium is a critical step during cancer metastasis. To study PCa cell rolling and adhesion behavior, we developed a dynamic flow-based microtube system to mimic the microvascular environment. We found that PCa cell rolling capacity is mediated by E-selectin and can be enhanced by stromal cell-derived factor-1 under different wall shear stresses.

Analysis of human fibroadenomas using three-dimensional impedance maps.

Three-dimensional impedance maps (3DZMs) are virtual volumes of acoustic impedance values constructed from histology to represent tissue microstructure acoustically. From the 3DZM, the ultrasonic backscattered power spectrum can be predicted and model based scatterer properties, such as effective scatterer diameter (ESD), can be estimated. Additionally, the 3DZM can be exploited to visualize and identify possible scattering sites, which may aid in the development of more effective scattering models to better represent the ultrasonic interaction with underlying tissue microstructure.

Role of c-Abl in L-selectin shedding from the neutrophil surface.

L-selectin is a key molecule that participates in neutrophil tethering and subsequent rolling. It is cleaved from the surface of neutrophils activated in the presence of lipopolysaccharides, N-formyl-methionine-leucine-phenylalanine (fMLP), or Interleukin-8 (IL-8). We previously showed that L-selectin is also shed from the neutrophil surface during rolling on sialyl Lewis-x coated surfaces in a force-, ADAM-17 sheddase-, and p38 MAP kinase-dependent manner under flow.

Vascular Recruitment of Human Retinoblastoma Cells by Multi-Cellular Adhesive Interactions with Circulating Leukocytes.

Retinoblastoma (RB) is a retinal cancer of childhood. RB survivors tend to develop additional tumors later in life, although the physical mechanisms of RB metastatic spread are largely unknown. One step in metastasis through the blood stream is tumor cell adherence to the blood vessel wall through specific receptor:ligand interactions.

Knockdown of fucosyltransferase III disrupts the adhesion of circulating cancer cells to E-selectin without affecting hematopoietic cell adhesion.

Adhesive interactions between selectins and their ligands play an essential role during cancer extravasation. Fucosylation of these proteins by fucosyltransferases, or FUTs, is critical for their functions. Using quantitative RT-PCR, we demonstrated that FUT4 and FUT7 are the predominant FUTs expressed in hematopoietic cell line, while FUT3 is heavily expressed by multiple cancer cell lines including the prostate cancer cell line MDA PCa2b.

Ultrasonic backscatter coefficients for weakly scattering, agar spheres in agar phantoms.

Applicability of ultrasound phantoms to biological tissue has been limited because most phantoms have generally used strong scatterers. The objective was to develop very weakly scattering phantoms, whose acoustic scattering properties are likely closer to those of tissues and then compare theoretical simulations and experimental backscatter coefficient (BSC) results. The phantoms consisted of agar spheres of various diameters (nominally between 90 and 212 microm), containing ultrafiltered milk, suspended in an agar background.

Interlaboratory comparison of backscatter coefficient estimates for tissue-mimicking phantoms.

Ultrasonic backscatter is useful for characterizing tissues and several groups have reported methods for estimating backscattering properties. Previous interlaboratory comparisons have been made to test the ability to accurately estimate the backscatter coefficient (BSC) by different laboratories around the world. Results of these comparisons showed variability in BSC estimates but were acquired only for a relatively narrow frequency range, and, most importantly, lacked reference to any independent predictions from scattering theory.

Use of naturally occurring halloysite nanotubes for enhanced capture of flowing cells.

The development of individualized treatments for cancer can be facilitated by more efficient methods for separating cancer cells from patient blood in such a way that they remain viable for live cell assays. We have previously shown that immobilized P-selectin protein can be used on the inner surface of a microscale flow system to induce leukemic cells and leukocytes to roll at different velocities and relative fluxes, thereby creating a means for rapid cell fractionation without inflicting cellular damage. In this study, we explore a method to more efficiently capture leukemic and epithelial cancer cells from flow by altering the nanoscale topography of the inner surface of P-selectin-coated microtubes.

Platelets and megakaryocytes contain functional nuclear factor-kappaB.

Objective: To investigate the presence and role of NF-kappaB proteins in megakaryocytes and platelets. The nuclear factor-kappaB (NF-kappaB) transcription factor family is well known for its role in eliciting inflammation and promoting cell survival. We discovered that human megakaryocytes and platelets express the majority of NF-kappaB family members, including the regulatory inhibitor-kappaB (I-kappaB) and I-kappa kinase (IKK) molecules.

Nanoparticle coatings for enhanced capture of flowing cells in microtubes.

Recently, a flow-based selectin-dependent method for the capture and enrichment of specific types of cells (CD34+ hematopoetic stem and progenitor cells and human leukemia HL60) from peripheral blood was demonstrated. However, these devices depend on a monolayer of selectin protein, which has been shown to have a maximum binding efficiency as a function of surface area. A novel surface coating of colloidal silica nanoparticles was designed that alters the surface roughness resulting in increased surface area.

Rapid enrichment of biomolecules using simultaneous liquid and particulate dielectrophoresis.

Here we show that dielectrophoretic (DEP) liquid actuation can be used to dispense arrays of nanoliter-sized droplets loaded with biomolecules. Size-based enrichment of these biomolecules occurs rapidly and simultaneously with the droplet dispensing. The physical mechanism responsible for the effect is the positive DEP force directed toward the electrodes that is imposed by the non-uniform electric field during the very rapid DEP actuated flow before droplet formation.

An immobilized nanoparticle-based platform for efficient gene knockdown of targeted cells in the circulation.

It is well established that specific interaction between adhesion molecules of endothelial cells and receptors on leukocytes can separate and recruit leukocytes from the bloodstream to sites of inflammation and coagulation. Previously, we showed that P-selectin can be absorbed onto the surface of a blood-compatible microrenathane tube, and the P-selectin-coated surface could successfully capture P-selectin receptor-positive stem cells from physiological shear flow in vitro and from the bloodstream in vivo. In this paper, P-selectin was covalently attached to the surface of nanoscale liposomes to create targeting nanoparticles (NPs).

Adhesive dynamics simulations of the mechanical shedding of L-selectin from the neutrophil surface.

Here we accurately recreate the mechanical shedding of L-selectin and its effect on the rolling behavior of neutrophils in vitro using the adhesive dynamics simulation by incorporating the shear-dependent shedding of L-selectin. We have previously shown that constitutively expressed L-selectin is cleaved from the neutrophil surface during rolling on a sialyl Lewis x-coated planar surface at physiological shear rates without the addition of exogenous stimuli. Utilizing a Bell-like model to describe a shedding rate which presumably increases exponentially with force, we were able to reconstruct the characteristics of L-selectin-mediated neutrophil rolling observed in the experiments.

Who gets born? How did New Zealand's Bioethics Council arrive at its recommendations?

The Bioethics Council's Report Who Gets Born? elicited considerable public comment with its recommendation regarding the use of preimplantation genetic diagnosis (PGD) for sex selection for social reasons. The Report was based on a process of deliberative consultation, in which determined efforts had been expended to obtain the views of ordinary New Zealanders. Consequently, the manner in which the recommendations, including this particular one on sex selective PGD, were informed by the consultation is of considerable interest.

Microcontact printing of P-selectin increases the rate of neutrophil recruitment under shear flow.

The local variation of P-selectin expression on inflamed endothelial layers affects leukocyte recruitment in vivo. As an initial study of the spatially heterogeneous presentation of P-selectin in vitro, the influence of microcontact printing (microCP) of P-selectin on a planar surface in neutrophil recruitment was investigated using a parallel-plate flow chamber. Microline patterned and nonpatterned P-selectin were prepared using PDMS, Poly(dimethylsiloxane) (PMDS) stamps and isolated neutrophils perfused over the surface to quantify the level of neutrophil recruitment.

P-selectin-coated microtube for the purification of CD45+ hematopoietic cells directly from human peripheral blood.

Purified samples of CD45+ hematopoietic cells are a prerequisite for chimerism analysis in transplantation therapies, and are useful in various research and clinical settings such as functional and molecular analysis or disease diagnosis. Recently, we have established a flow-based adhesion molecule-dependent process for the purification of these cells from human bone marrow. However, for practical purposes, it is desirable to apply this approach to process small volumes of human blood.

Delivery of apoptotic signal to rolling cancer cells: a novel biomimetic technique using immobilized TRAIL and E-selectin.

The survival rate for patients with metastases versus localized cancer is dramatically reduced, with most deaths being associated with the formation of secondary tumors. Circulating cancer cells interact with the endothelial lining of the vasculature via a series of adhesive interactions that facilitate tethering and firm adhesion of cancer cells in the initial steps of metastasis. TNF-related apoptosis-inducing ligand (TRAIL) holds promise as a tumor-specific cancer therapeutic, by inducing a death signal by apoptosis via the caspase pathway.

Platelet adhesive dynamics. Part I: characterization of platelet hydrodynamic collisions and wall effects.

Abnormally high shear stresses encountered in vivo induce spontaneous activation of blood platelets and formation of aggregates, even in the absence of vascular injury. A three-dimensional multiscale computational model-platelet adhesive dynamics-is developed and applied in Part I and Part II articles to elucidate key biophysical aspects of GPIbalpha-von-Willebrand-factor-mediated interplatelet binding that characterizes the onset of shear-induced platelet aggregation. In this article, the hydrodynamic effects of the oblate spheroidal shape of platelets and proximity of a plane wall on the nature of cell-cell collisions are systematically investigated.

Platelet adhesive dynamics. Part II: high shear-induced transient aggregation via GPIbalpha-vWF-GPIbalpha bridging.

A three-dimensional multiscale computational model, platelet adhesive dynamics (PAD), is developed and applied in Part I and Part II articles to characterize and quantify key biophysical aspects of GPIbalpha-von-Willebrand-factor (vWF)-mediated interplatelet binding at high shear rates, a necessary and enabling step that initiates shear-induced platelet aggregation. In this article, an adhesive dynamics model of the transient aggregation of two unactivated platelets via GPIbalpha-vWF-GPIbalpha bridging is developed and integrated with the three-dimensional hydrodynamic flow model discussed in Part I. Platelet binding efficiencies predicted by PAD are in good agreement with platelet aggregation behavior observed experimentally, as documented in the literature.

Purification of CD45+ hematopoietic cells directly from human bone marrow using a flow-based P-selectin-coated microtube.

Recently, a flow-based selectin-dependent method for capture and enrichment of specific type blood cells (CD34+ hematopoietic stem and progenitor cells) from bone marrow and peripheral blood has been described. Using a similar approach, here we show isolation of CD45+ blood cells directly from human bone marrow to a high purity (90%-97%). The process mimics a ubiquitous mechanism of cell trafficking in the body for the recruitment of neutrophils during inflammation.

Microvascular endothelial cells exhibit optimal aspect ratio for minimizing flow resistance.

A recent analytical solution of the three-dimensional Stokes flow through a bumpy tube predicts that for a given bump area, there exists an optimal circumferential wavenumber which minimizes flow resistance. This study uses measurements of microvessel endothelial cell morphology to test whether this prediction holds in the microvasculature. Endothelial cell (EC) morphology was measured in blood perfused in situ microvessels in anesthetized mice using confocal intravital microscopy.

Capture and enrichment of CD34-positive haematopoietic stem and progenitor cells from blood circulation using P-selectin in an implantable device.

Clinical infusion of haematopoietic stem and progenitor cells (HSPCs) is vital for restoration of haematopoietic function in many cancer patients. Previously, we have demonstrated an ability to mimic physiological cell trafficking in order to capture CD34-positive (CD34+) HSPCs using monolayers of the cell adhesion protein P-selectin in flow chambers. The current study aimed to determine if HSPCs could be captured directly from circulating blood in vivo.

Nonmuscle myosin heavy chain IIA mediates integrin LFA-1 de-adhesion during T lymphocyte migration.

Precise spatial and temporal regulation of cell adhesion and de-adhesion is critical for dynamic lymphocyte migration. Although a great deal of information has been learned about integrin lymphocyte function-associated antigen (LFA)-1 adhesion, the mechanism that regulates efficient LFA-1 de-adhesion from intercellular adhesion molecule (ICAM)-1 during T lymphocyte migration is unknown. Here, we show that nonmuscle myosin heavy chain IIA (MyH9) is recruited to LFA-1 at the uropod of migrating T lymphocytes, and inhibition of the association of MyH9 with LFA-1 results in extreme uropod elongation, defective tail detachment, and decreased lymphocyte migration on ICAM-1, without affecting LFA-1 activation by chemokine CXCL-12.

Microfabrication of cavities in polydimethylsiloxane using DRIE silicon molds.

We present a novel method to create cavities in PDMS that is simple and exhibits wide process latitude allowing control over the radius of curvature to form shallow concave pits or deep spherical cavities.