The motion of rigid twisted ribbon-like particles in shear flow is studied by computer simulation. It is shown that the twisted ribbon migrates in the vorticity direction in strong shear flow with the sign determined by the chirality: the right-handed particles and their mirror-imaged particles move in opposite directions. This enables the separation of chiral particles from the racemic mixture. The average migration velocity in the vorticity direction is studied as a function of the shear rate, the length, and the pitch of the particle.

These results suggest that increased expression of the cadherin-catenin cell-cell adhesion system in metastatic foci may play an important role in progression of metastatic colorectal carcinomas.

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The expression of CD44v6 is well known as a useful marker of tumor progression and prognosis in colorectal cancer. In this study, we evaluated the serum levels of soluble CD44 splice variants containing exon v6 (sCD44v6) and examined the histological expression of CD44v6 in patients with colorectal cancer. Serum samples were obtained from 44 primary colorectal cancer patients before surgery. We used enzyme-linked immunosorbent assay to determine the serum levels of sCD44v6. The expression of CD44v6 was examined by immunohistochemical staining of the primary tumors obtained from the same patients. Both the serum concentration of sCD44v6 and the expression of CD44v6 were significantly associated with lymph node metastasis (p < 0.05). Furthermore, the serum level of sCD44v6 was higher in those patients with CD44v6-positive tumor tissues (154.4 ± 34.8 ng/ml) than in those with CD44v6-negative ones (130.7 ± 32.3 ng/ml; p < 0.05). The 5-year survival rate was significantly lower in patients with high serum levels of sCD44v6 (52.4%) than in those with low levels of sCD44v6 (78.0%; p < 0.05), and it was also significantly lower in patients with CD44v6-positive cancer (42.1%) than in those with CD44v6-negative cancer (84%; p < 0.01). We concluded that preoperative elevation in the serum levels of sCD44v6 might be a prognostic indicator for patients with colorectal cancer.

The pathologic characteristics of gastric cancer in 57 patients with hematogenous recurrence were pathologically analyzed by the site of recurrence. In recurrence of gastric cancer that developed in the liver, macroscopic observation revealed that cancers of Borrmann type 2 and 3 were most frequent. Microscopic examination revealed that the rate of occurrence of the medullary type of differentiated or poorly differentiated adenocarcinoma were high and that there were relatively frequent invasion by cancerous cells of the blood vessel that were closely related to the hematogenous metastasis. On the other hand, with respect to recurrence of gastric cancer that had developed in the lung or bone, Borrmann type 3 and 4, respectively, were more frequently observed. In these cases, microscopic analysis revealed that these cancers were poorly differentiated adenocarcinomas. In gastric cancer with bone recurrence, the rate of recurrence of the scirrhous type of tumor were higher than that of other types. It is important, for the management of patients after gastric cancer surgery, to predict possible hematogenous recurrence and its site by evaluation of the pathologic characteristics of the gastric cancer.

The lateral migration properties of a rigid spherical particle suspended in a pressure-driven flow through channels with square cross-sections were investigated numerically, in the range of Reynolds numbers (Re) from 20 to 1000. The flow field around the particle was computed by the immersed boundary method to calculate the lateral forces exerted on the particle and its trajectories, starting from various initial positions. The numerical simulation showed that eight equilibrium positions of the particle are present at the centres of the channel faces and near the corners of the channel cross-section. The equilibrium positions at the centres of the channel faces are always stable, whereas the equilibrium positions at the corners are unstable until Re exceeds a certain critical value, Re c . At Re ≈ Re c , additional equilibrium positions appear on a heteroclinic orbit that joins the channel face and corner equilibrium positions, and the lateral forces along the heteroclinic orbit are very small. As Re increases, the channel face equilibrium positions are shifted towards the channel wall at first, and then shifted away from the channel wall. The channel corner equilibrium positions exhibit a monotonic shift towards the channel corner with increasing Re. Migration behaviours of the particle in the cross-section are also predicted for various values of Re. These numerical results account for the experimental observations of particle distributions in the cross-section of micro and millimetre scale channels, including the characteristic alignment and focusing of the particles, the absence of the corner equilibrium positions at low Re and the progressive shift of the equilibrium positions with Re.

The authors propose a method to simulate the DNA motion in microchannels of complex geometry. It is based on stochastic rotation dynamics using a new scheme for the boundary condition. The method enables them to define a boundary wall of arbitrary shape and to describe a wall moving at an arbitrary velocity. As an application, they simulate the motion of DNA in Poiseuille flow between two parallel planes and show that DNA molecules tend to concentrate near the center of the channel in agreement with experimental results.

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