A novel platform for in situ investigation of cells and tissues under mechanical strain.

The mechanical micro-environment influences cellular responses such as migration, proliferation, differentiation and apoptosis. Cells are subjected to mechanical stretching in vivo, e.g., epithelial cells during embryogenesis. Current methodologies do not allow high-resolution in situ observation of cells and tissues under applied strain, which may reveal intracellular dynamics and the origin of cell mechanosensitivity. A novel polydimethylsiloxane substrate was developed, capable of applying tensile and compressive strain (up to 45%) to cells and tissues while allowing in situ observation with high-resolution optics. The strain field of the substrate was characterized experimentally using digital image correlation, and the deformation was modeled by the finite element method, using a Mooney-Rivlin hyperelastic constitutive relation. The substrate strain was found to be uniform for >95% of the substrate area. As a demonstration of the system, mechanical strain was applied to single fibroblasts transfected with GFP-actin and whole transgenic Drosophila embryos expressing GFP in all neurons during live imaging. Three observations of biological responses due to applied strain are reported: (1) dynamic rotation of intact actin stress fibers in fibroblasts; (2) lamellipodia activity and actin polymerization in fibroblasts; (3) active axonal contraction in Drosophila embryo motor neurons. The novel platform may serve as an important tool in studying the mechanoresponse of cells and tissues, including whole embryos.

Biofilm formation by Candida albicans isolated from intrauterine devices.

Our survey revealed that infected intrauterine devices (IUDs) recovered from patients suffering from reproductive tract infections (RTIs) were tainted with Candida biofilm composed of a single or multiple species. Scanning electron microscopy (SEM) analysis of C. albicans biofilm topography showed that it consists of a dense network of mono- or multilayer of cells embedded within the matrix of extracellular polymeric substances (EPS). Confocal scanning laser microscopy (CSLM) and atomic force microscopy (AFM) images depicted that C. albicans biofilms have a highly heterogeneous architecture composed of cellular and noncellular elements with EPS distributed in the cell-surface periphery or at cell-cell interface. Biochemical analysis showed that EPS produced by C. albicans biofilm contained significantly reduced total carbohydrate (40%), protein (5%) and enhanced amount of hexosamine (4%) in contrast to its planktonic counterparts. The in vitro activity of antifungal agents amphotericin B, nystatin, fluconazole and chlorhexidine against pre-formed C. albicans biofilm, assessed using XTT (2,3-bis[2-methoxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-carboxanilide) reduction assay revealed increased resistance of these infectious biofilm (50% reduction in metabolic activity at a concentration of 8, 16, 64, 128 µg/ml respectively) in comparison to its planktonic form.

The role of meatal disinfection in preventing catheter-related bacteriuria in an intensive care unit: a pilot study in Turkey.

The purpose of this study was to investigate the efficacy of antiseptics meatal care in preventing catheter-related urinary tract infections (UTIs) in patients with an indwelling urinary catheter in the intensive care unit of Osmangazi University Medical School. One hundred patients were divided into four groups (25 per group) and treated with once or twice daily application of chlorhexidine gluconate or povidone-iodine. A control group was also studied (N=30). Urine samples were taken weekly and cultures were evaluated quantitatively. Meatal swabs were obtained on the first, fifth, and 10th day and determinated semiquantitatively. UTI was defined as bacteriuria with 10(5)cfu/L. Cultures showing no growth or mixed growths were stated as negative for UTI. UTI developed in 16 patients on days two, three, four, five and seven (including control group). Dominant micro-organisms in the meatal area were found to be Candida species. In nine cases the causative agents of UTI were Candida species. It was therefore decided that the use of antiseptics to clean the periurethral area provides no benefit in decreasing the rate of bacteriuria.