Formation of the smectic-B crystal from a simple monatomic liquid.

We report a molecular dynamics simulation demonstrating that the smectic-B crystalline phase (Cry-B), commonly observed in mesogenic systems of anisotropic molecules, can be formed by a system of identical particles interacting via a spherically symmetric potential. The Cry-B phase forms as a result of a first-order transition from an isotropic liquid phase upon isochoric cooling at appropriate number density. Its structure, determined by the design of the pair potential, corresponds to the Cry-B structure formed by elongated particles with the aspect ratio 1.8. The diffraction pattern and the real-space structure inspection demonstrate dominance of the ABC-type of axial layer stacking. This result opens a general possibility of producing smectic phases using isotropic interparticle interaction both in simulations and in colloidal systems.

Anisotropic pair correlations and structure factors of confined hard-sphere fluids: an experimental and theoretical study.

We address the fundamental question: how are pair correlations and structure factors of hard-sphere fluids affected by confinement between hard planar walls at close distance? For this purpose, we combine x-ray scattering from colloid-filled nanofluidic channel arrays and first-principles inhomogeneous liquid-state theory within the anisotropic Percus-Yevick approximation. The experimental and theoretical data are in remarkable agreement at the pair-correlation level, providing the first quantitative experimental verification of the theoretically predicted confinement-induced anisotropy of the pair-correlation functions for the fluid. The description of confined fluids at this level provides, in the general case, important insights into the mechanisms of particle-particle interactions in dense fluids under confinement.

Matrix metalloproteinase (MMP) expression in experimental choroidal neovascularization.

PURPOSE: Matrix metalloproteinases (MMP) are a family of proteolytic enzymes that degrade basement membrane and extracellular matrix proteins. To gain information on the possible role of MMPs in choroidal neovascularization (CNV), we have analyzed the mRNA expression of MMP-2 and MMP-9, two forms of MMPs implicated in ocular neovascularization, in a rat model. METHODS: Choroidal neovascularization was induced in pigmented rats by krypton laser photocoagulation of the fundus whereafter eyes were enucleated at 1, 3, 5, 7, 10 and 60 days. Antisense and sense riboprobes were generated using DNA complementary to MMP-2 and MMP-9, and mRNA expression was analyzed using in situ hybridization. RESULTS: In the untreated eyes MMP-2 mRNA expression was weakly detected in cells within the choroid. In laser-treated eyes MMP-2 mRNA expression was markedly increased and mainly localized to macrophage-like and retinal pigment epithelial (RPE)-like cells invading the choroid, subretinal space and inner retina. This increase in MMP-2 mRNA expression peaked at day 10 whereafter a decline was detected. MMP-9 mRNA expression was low in untreated eyes and did not increase following laser treatment. CONCLUSION: The results show that MMP-2 mRNA expression is increased in experimental CNV, and support of a role for MMP-2 in the development of CNV in age-related macular degeneration.

Expression of matrix metalloproteinase-2 (MMP-2) and vascular endothelial growth factor (VEGF) in inflammation-associated corneal neovascularization.

Matrix metalloproteinase-2 (MMP-2), matrix metalloproteinase-9 (MMP-9) and vascular endothelial growth factor (VEGF) are all implicated in the development of neovascularization. To investigate the possible role of these factors in corneal neovascularization we have analysed the expression of MMP-2, MMP-9 and VEGF in a rat model of inflammation-associated corneal neovascularization. In this model, corneal neovascularization was induced in Long-Evans rats by krypton laser photocoagulation whereafter eyes were enucleated at 1, 4, 7, 10 and 20 days. Slit-lamp biomicroscopy and histologic analysis revealed a gradual development of corneal neovascularization that peaked 7-10 days after treatment when newly formed vessels could be seen throughout the corneal surface reaching deep into the stroma. Antisense and sense riboprobes were generated using DNA complementary to MMP-2, MMP-9 and VEGF, and mRNA expression was analysed using in situ hybridization. The expression of MMP-2 and MMP-9 in untreated corneas was low or absent whereas VEGF was weakly expressed in the corneal epithelium. MMP-2 expression was increased during corneal neovascularization and was mainly localized to the cells infiltrating areas of new vessel formation. Many of these cells appeared to be inflammatory cells. VEGF expression had a similar overall distribution to MMP-2 during neovascularization with the exception that its expression in the corneal epithelium remained and even increased slightly. MMP-9 was prominently expressed at the border of regenerating corneal epithelium in areas with epithelial wounding but was not detected in the vascularized stroma. Together, the results of the present study support a role for MMP-2 and VEGF in inflammation-associated corneal neovascularization whereas MMP-9 instead appears to be involved in corneal epithelial wound-healing.