Cutaneous histoplasmosis in renal transplant recipients.

Cutaneous histoplasmosis is a rare entity, although it can be seen in a substantial portion of renal transplant recipients with disseminated disease. The prognosis of disseminated disease is worse than isolated cutaneous involvement, and significant delays in diagnosis are reported. We reviewed reports of cutaneous histoplasmosis with and without dissemination in the setting of renal transplantation to examine incidence, timing of diagnosis, clinical features, and prognosis. Remarkable morphologic variability and the non-specific appearance of skin findings suggest that tissue culture is required for definitive diagnosis. Cutaneous lesions represent an easily accessible source for early diagnosis.

In vitro differentiation of osteocytes and adipocytes from human placenta-derived cells.

OBJECTIVE: To investigate the capability of human placenta-derived adherent cells to differentiate into osteocytes and adipocytes. METHODS: Placenta-derived adherent cells were isolated by type IV collagenase digestion of a single freshly obtained human placenta and cultured under standard conditions. Cell surface markers of adherent cells from passages 3 - 9 were analysed by flow cytometry. Osteocytic differentiation was induced with ß-glycerol phosphate, vitamin C and dexamethasone and confirmed by Alizarin red staining. Adipocytic differentiation was induced with dexamethasone and insulin and confirmed by oil red O staining. RESULTS: Placenta-derived adherent cells were positive for high levels of CD44 and CD105 and very low levels of CD29 but were negative for CD34, CD45 and CD19. This pattern of cell surface markers is identical to human mesenchymal stem cells. Alizarin red-positive cells were detected 10 days after the induction of osteocyte differentiation. Oil red O-positive cells were detected 7 days after the induction of adipocyte differentiation. CONCLUSIONS: Placenta-derived adherent cells can differentiate into either osteocytes or adipocytes in vitro. The human placenta may provide an alternative source of mesenchymal stem cells for basic research and clinical use.

In vitro differentiation of human placenta-derived adherent cells into insulin-producing cells.

This study investigated the differentiation of placenta-derived adherent cells (PDACs) into insulin-producing cells (IPCs). PDACs were cultured and the cells characterized by analysis of cell surface markers using flow cytometry. The PDACs were then treated with induction media containing basic fibroblast growth factor (bFGF) and beta-mercaptoethanol (beta-ME). After induction, the presence of IPCs was demonstrated using dithizone staining, and the production of functional insulin was confirmed using immunocytochemistry and an enzyme-linked immunosorbent assay. Expression of the islet-associated genes PDX-1, Insulin 1, Insulin 2 and Glut 2 in the induced cells was measured using a reverse transcription-polymerase chain reaction; PDX-1 was expressed after 7 days of induction and PDX-1, Insulin 1 and Insulin 2 were all detected after 14 days. These results suggest that the placenta could be a new source of stem cells that can be induced to differentiate into IPCs following treatment with media containing bFGF and beta-ME.

A novel two-dimensional model for colloid transport in physically and geochemically heterogeneous porous media.

A two-dimensional model for colloid transport in geochemically and physically heterogeneous porous media is presented. The model considers patchwise geochemical heterogeneity, which is suitable to describe the chemical variability of many surficial aquifers with ferric oxyhydroxide-coated porous matrix, as well as spatial variability of hydraulic conductivity, which results in heterogeneous flow field. The model is comprised of a transient fluid flow equation, a transient colloid transport equation, and an equation for the dynamics of colloid deposition and release. Numerical simulations were carried out with the model to investigate the colloid transport behavior in layered and randomly heterogeneous porous media. Results demonstrate that physical and geochemical heterogeneities markedly affect the colloid transport behavior. Layered physical or geochemical heterogeneity can result in distinct preferential flow paths of colloidal particles. Furthermore, the combined effect of layered physical and geochemical heterogeneity may result in enhanced or reduced preferential flow of colloids. Random distribution of physical heterogeneity (hydraulic conductivity) results in a random flow field and an irregularly distributed colloid concentration profile in the porous medium. Contrary to random physical heterogeneity, the effect of random patchwise geochemical heterogeneity on colloid transport behavior is not significant. It is mostly the mean value of geochemical heterogeneity rather than its distribution that governs the colloid transport behavior.

Applications of numerical methods to simulate the movement of contaminants in groundwater.

This paper reviews mathematical models and numerical methods that have been extensively used to simulate the movement of contaminants through the subsurface. The major emphasis is placed on the numerical methods of advection-dominated transport problems and inverse problems. Several mathematical models that are commonly used in field problems are listed. A variety of numerical solutions for three-dimensional models are introduced, including the multiple cell balance method that can be considered a variation of the finite element method. The multiple cell balance method is easy to understand and convenient for solving field problems. When the advection transport dominates the dispersion transport, two kinds of numerical difficulties, overshoot and numerical dispersion, are always involved in solving standard, finite difference methods and finite element methods. To overcome these numerical difficulties, various numerical techniques are developed, such as upstream weighting methods and moving point methods. A complete review of these methods is given and we also mention the problems of parameter identification, reliability analysis, and optimal-experiment design that are absolutely necessary for constructing a practical model.