Bacterial Footprints in Elastic Pillared Microstructures.

Soft substrates decorated with micropillar arrays are known to be sensitive to deflection due to capillary action. In this work, we demonstrate that micropillared epoxy surfaces are sensitive to single drops of bacterial suspensions. The micropillars can show significant deformations upon evaporation, just as capillary action does in soft substrates. The phenomenon has been studied with five bacterial strains: S. epidermidis, L. sakei, P. aeruginosa, E. coli, and B. subtilis. The results reveal that only droplets containing motile microbes with flagella stimulate micropillar bending, which leads to significant distortions and pillar aggregations forming dimers, trimers, and higher order clusters. Such deformation is manifested in characteristic patterns that are left on the microarrayed surface following evaporation and can be easily identified even by the naked eye. Our findings could lay the ground for the design and fabrication of mechanically responsive substrates, sensitive to specific types of microorganisms.

The protein tyrosine phosphatase-BL, modulates pancreatic beta-cell proliferation by interaction with the Wnt signalling pathway.

In pancreatic beta-cells, increased expression of the MODY5 gene product, HNF1 beta, leads to enhanced rates of apoptosis and altered regulation of the cell cycle, suggesting that control of HNF1 beta expression may be important for the control of beta-cell proliferation and viability. It is unclear how these effects of HNF1 beta are mediated, but previously we have identified a protein tyrosine phosphatase, (PTP)-BL, as an HNF1 beta-regulated protein in beta-cells and have now studied the role of this protein in INS-1 beta-cells. Stably transfected cells were generated, which express either wild-type (WT) or a phosphatase-deficient mutant (PTP-BL-CS) of PTP-BL conditionally under the control of a tetracycline-regulated promoter. Enhanced expression of WT PTP-BL inhibited INS-1 cell growth dose dependently, but this effect was not observed when PTP-BL-CS was expressed. Neither construct altered the rate of apoptosis. PTP-BL has been reported to interact with components of the Wnt signalling pathway, and we observed that addition of exogenous Wnt3a resulted in an increase in cell proliferation and a rise in beta-catenin levels, consistent with the operation of this pathway in INS-1 cells. Up-regulation of WT PTP-BL antagonised these responses but PTP-BL-CS failed to inhibit Wnt3a-induced proliferation. The rise in beta-catenin caused by Wnt3a was also suppressed by over-expression of HNF1 beta, suggesting that HNF1 beta may interact with the Wnt signalling pathway via an increase in PTP-BL levels. We conclude that PTP-BL plays an important role in the regulation of cell cycle progression in pancreatic beta-cells, and that it interacts functionally with components of the Wnt signalling pathway.

Macroporous gel particles as robust macroporous matrices for cell immobilization.

A new design of robust matrices for cell immobilization is described. Macroporous gels (MGs) with immobilized microbial cells were prepared at subzero temperatures and were formed inside a plastic core (so-called, protective housing). Due to the protective housing the macroporous gel particles with immobilized cells can be used in well-stirred bioreactors. High retained activity of yeast (77-92%) and Escherichia coli (50-91%) cells immobilized in MGs after drying and storage in the dried state was due to the high structural stability and heterogeneous porous structure of the MGs.

Long-term regulation of cyclic nucleotide phosphodiesterase type 3B and 4 in 3T3-L1 adipocytes.

Phosphodiesterase 3B (PDE3B), is known to play an important role in acute insulin and cAMP-mediated regulation of lipid metabolism, and PDE4 are the main PDE types expressed in adipocytes. Here, we show that members of all PDE4 isoforms are expressed in 3T3-L1 and primary mouse adipocytes. Long-term treatment of 3T3-L1 adipocytes with insulin induced up-regulation of PDE3B and PDE4D in a phosphatidylinositol 3-kinase-dependent manner whereas long-term treatment with beta-adrenergic agonists induced down-regulation of PDE3B and up-regulation of PDE4D. Thus, PDE3B and PDE4D can be added to the list of genes regulated by insulin and cAMP-increasing hormones. Altered expression of PDE3B and PDE4D in response to long-term treatment with insulin and catecholamines may contribute to altered regulation of metabolism in diabetes.

Role of PDE3B in insulin-induced glucose uptake, GLUT-4 translocation and lipogenesis in primary rat adipocytes.

In adipocytes, phosphorylation and activation of PDE3B is a key event in the antilipolytic action of insulin. The role of PDE4, another PDE present in adipocytes, is not yet known. In this work we investigate the role of PDE3B and PDE4 in insulin-induced glucose uptake, GLUT-4 translocation and lipogenesis. Inhibition of PDE3 (OPC3911, milrinone) but not PDE4 (RO 20-1724) lowered insulin-induced glucose uptake and lipogenesis, especially in the presence of isoproterenol (a general beta-adrenergic agonist), CL316243, a selective beta3-adrenergic agonist, and pituitary adenylate cyclase-activating peptide. The inhibitory effect of OPC3911 was associated with reduced translocation of GLUT-4 from the cytosol to the plasma membrane. Both OPC3911 and RO 20-1724 increased protein kinase A (PKA) activity and lipolysis. H89, a PKA inhibitor, did not affect OPC3911-mediated inhibition of insulin-induced glucose uptake and lipogenesis, whereas 8-pCPT-2'-O-Me-cAMP, an Epac agonist which mediates PKA independent cAMP signaling events, mimicked all the effects of OPC3911. Insulin-mediated activation of protein kinase B, a kinase involved in insulin-induced glucose uptake, was apparently not altered by OPC3911. In summary, our data suggest that PDE3B, but not PDE4, contributes to the regulation of insulin-induced glucose uptake, GLUT-4 translocation, and lipogenesis presumably by regulation of a cAMP/Epac signalling mechanisms.