Measurement of particle adhesion force and effective contact radius via centrifuge equipped with horizontal and vertical substrates

A centrifugal method was used to analyze and evaluate particle–surface interactions. Particles with count median diameters of 9.7, 14.5, and 32.8 μm were removed from horizontally and vertically mounted metal substrates. A point-mass model is conventionally used to analyze the forces exerted on particles during centrifugation. Conversely, in this study, a rigid-body model was employed considering the particle diameter and effective contact radius between a particle and substrate. As the moments of force exerted on the particles on the horizontal and vertical substrates were simultaneously formulated, the adhesion force and contact radius could be determined based on the particle diameter and angular velocities obtained at a given removal fraction. It was quantitatively demonstrated that as the particle diameter, relative humidity, and/or initial load increase and surface roughness decreases, the adhesion force increases. Furthermore, the contact radius increased as the particle diameter and/or surface roughness increased

Evaluation of mechanical properties of nanoparticles using a constant-volume shear tester

Nanoparticles have advantageous small-size and surface effects that impart them with unique mechanical properties. To evaluate these properties, a constant-volume shear tester that can precisely measure stresses on the shear plane was used. Six samples, namely, hydrophilic and hydrophobic silica, alumina, and titania nanoparticles, were prepared for the shear tests. For each sample, a single shear test provided the void fraction, stress relaxation ratio, stress transmission ratio, powder yield locus, consolidation yield locus, critical state line, shear cohesion, and flow function. All the tests were conducted under ambient conditions using powder beds, in which the void fractions were in the range of 0.89–0.96. A series of analyses demonstrated that the hydrophilic nanoparticles have lower flowability than the hydrophobic nanoparticles, indicating that moisture on the surface increases the cohesion and inhibits the flow

Detailed analysis of particle–substrate interaction based on a centrifugal method

The interaction between particles and inclined substrates in a centrifuge was investigated theoretically and experimentally. First, the balance of the force acting on a particle adhering to the substrate, with an inclination angle from 0 to 90° to the horizontal, was formulated separately in the normal and tangential directions. The adhesion force was then derived based on the point-mass model as a function of the angular velocity. Next, the balance of the moments of the forces acting on a particle adhering to the substrate was formulated; theoretical equations for the adhesion force and the effective contact radius were then derived from the angular velocities, obtained at any two inclination angles, based on the rigid-body model. Finally, the removal fraction curves of spherical/nonspherical particles with median diameters of less than 10 µm were experimentally obtained by increasing the angular velocity at each inclination angle. The experimentally obtained angular velocities were substituted into the theoretical equations to compare the point-mass and rigid-body models. The effects of the particle shape on the adhesion force and effective contact radius and that of the inclination angle on the removal fraction curves based on the theoretical equation were also investigated

Quantitative and Qualitative Urinary Cellular Patterns Correlate with Progression of Murine Glomerulonephritis

The kidney is a nonregenerative organ composed of numerous functional nephrons and collecting ducts (CDs). Glomerular and tubulointerstitial damages decrease the number of functional nephrons and cause anatomical and physiological alterations resulting in renal dysfunction. It has recently been reported that nephron constituent cells are dropped into the urine in several pathological conditions associated with renal functional deterioration. We investigated the quantitative and qualitative urinary cellular patterns in a murine glomerulonephritis model and elucidated the correlation between cellular patterns and renal pathology

Analysis of constant-volume shear tests based on precise measurement of stresses in powder beds

This study demonstrates a new constant-volume shear test configuration to analyze the stresses in powder beds and evaluate powder flowability. A novel cylindrical shear cell geometry and load cell arrangement allowed precise measurement of the normal stress acting on the shear planes of the powder beds. The stress transmission ratio between the top and shear planes decreased with increasing ratio of the powder bed height in the upper section of the shear cell to the shear cell diameter. This was due to friction between the powder bed and the side wall of the upper section of the shear cell. Using the measured values of the normal stress on the shear planes, the effects of the powder bed height and shear cell diameter were eliminated from the data. In addition, to evaluate the shear properties of the powder beds, the powder yield locus, consolidation yield locus, critical state line, shear cohesion, and void fraction were obtained from a single shear test. The powder yield locus data were used to obtain flow functions

The Structural and Functional Organization of the Podocyte Filtration Slits Is Regulated by Tjp1/ZO-1

<div><p>Blood filtration in the kidney glomerulus is essential for physiological homeostasis. The filtration apparatus of the kidney glomerulus is composed of three distinct components: the fenestrated endothelial cells, the glomerular basement membrane, and interdigitating foot processes of podocytes that form the slit diaphragm. Recent studies have demonstrated that podocytes play a crucial role in blood filtration and in the pathogenesis of proteinuria and glomerular sclerosis; however, the molecular mechanisms that organize the podocyte filtration barrier are not fully understood. In this study, we suggest that tight junction protein 1 (Tjp1 or ZO-1), which is encoded by <i>Tjp1</i> gene, plays an essential role in establishing the podocyte filtration barrier. The podocyte-specific deletion of <i>Tjp1</i> down-regulated the expression of podocyte membrane proteins, impaired the interdigitation of the foot processes and the formation of the slit diaphragm, resulting in glomerular dysfunction. We found the possibility that podocyte filtration barrier requires the integration of two independent units, the pre-existing epithelial junction components and the newly synthesized podocyte-specific components, at the final stage in glomerular morphogenesis, for which <i>Tjp1</i> is indispensable. Together with previous findings that <i>Tjp1</i> expression was decreased in glomerular diseases in human and animal models, our results indicate that the suppression of <i>Tjp1</i> could directly aggravate glomerular disorders, highlights <i>Tjp1</i> as a potential therapeutic target.</p></div

Podocyte-specific deletion of <i>Tjp1</i> results in glomerulosclerosis.

<p>(A) Kidney sections from <i>Tjp1^flox/flox</i> and <i>Nphs1-Cre: Tjp1^flox/flox</i> mice were examined with the antibody against Tjp1. Tjp1 was specifically eliminated from podocytes, while it was detected in endothelial cells in the glomerulus in the <i>Nphs1-Cre: Tjp1^flox/flox</i> mice (arrow). The expression of Tjp1 in the Bowman's capsule epithelial cells (double arrows) and in the renal tubules (arrowheads) was also unaffected. See also <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0106621#pone.0106621.s002" target="_blank">Fig. S2</a>. Scale bars, 10 µm. (B–I) Analyses of the control (<i>Tjp1^flox/flox</i>) and <i>Tjp1^△pod</i> (<i>Nphs1-Cre: Tjp1^flox/flox</i>) mice at 6 weeks of age. The <i>Tjp1^△pod</i> mice exhibited significant growth retardation (B) and developed massive proteinuria (C). (D) Gross appearance of the kidneys from the control and <i>Tjp1^△pod</i> mice at 6 weeks of age. (E) Histological analyses with periodic acid-Schiff (PAS) staining displayed disorder in the tissue architecture of the <i>Tjp1^△pod</i> mice kidney (top panels). Severe glomerulosclerosis and proteinaceous casts in the dilated renal tubules were observed in the <i>Tjp1^△pod</i> mice, but not in control mice (bottom panels). Scale bars, 200 µm (top panels), 20 µm (bottom panels). (F) The number of sclerosed glomeruli was expressed as a percentage of the total number of glomeruli (mean ± SEM of n = 3, <i>**p</i><0.001). (G) Transmission electron micrographs showing the loss of slit diaphragms, destruction of foot processes, and aberrant glomerular basement membranes in the <i>Tjp1^△pod</i> mice. Scale bars, 2 µm (top panels), 0.5 µm (bottom panels). (H and I) Histopathological analyses by Jones' silver (H) and Masson's trichrome (I) stain. Global sclerosis with extensive deposits of basement membrane components were observed with both stains. Scale bars, 10 µm.</p

The compromised foot process interdigitation and aberrant distribution of the slit diaphragm components in <i>Tjp1^△pod</i> mice.

<p>(A–C) SEM analyses of glomeruli from the control and <i>Tjp1^△pod</i> mice. Foot processes were severely disorganized in the <i>Tjp1^△pod</i> mice at 6 weeks of age (A). The loss of interdigitation and the impaired adhesion to the GBM of the podocyte foot processes was detected in the <i>Tjp1^△pod</i> mice at 2 weeks of age (B). At an earlier time point, 1 week of age, the foot processes were attached to the GBM but the interdigitation was disorganized in the <i>Tjp1^△pod</i> mice (C). Scale bars, 2 µm (A, B, C top panels), 0.5 µm (C bottom panels). (D) Immunofluorescence analyses of podocyte components: nephrin, podocin, Fyn, and synaptopodin (Synpo). The distribution of the slit diaphragm membrane proteins, nephrin and podocin, was fragmented and the signal intensity was reduced in the <i>Tjp1^△pod</i> mice at 1 week and 2 weeks of age. The signal of the actin-binding protein Synpo was increased in the <i>Tjp1^△pod</i> mice at 2 weeks of age. Fyn, a member of src family kinase, was not affected. See also <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0106621#pone.0106621.s004" target="_blank">Fig. S4A and C</a>. Scale bars, 10 µm.</p