The reduced folate carrier (RFC) is the dominant influx transporter for antifolates. A major mechanism of antifolate resistance is loss of RFC (SLC19A1) gene expression due to decreased GC-box-dependent transcription. However, despite the poor GC-box binding in multiple antifolate-resistant cell lines, normal Sp1 levels were retained. Here we explored the post-translational modifications that m...

Serotonin (5-HT) has been established as a regulator of ciliary beating in numerous systems. In early embryos of Helisoma trivolvis, a cilia-driven rotational movement is modulated by the release of endogenous serotonin from a pair of embryonic neurons, ENC1s, directly onto the ciliated epithelium. The present study was undertaken to examine the signal transduction mechanisms underlying seroton...

Spectrophotometric quantification of fluid phase endocytosis in the presence of different pharmacological compounds was performed in the model unicellular eukaryote Paramecium. The kinetics of Lucifer Yellow Carbohydrazide (LY) uptake in cells exposed to forskolin and isoproterenol--known to stimulate phagocytosis in this cell--was analyzed. Reduction in both the rate of endocytosis and total a...

The effects of the nonspecific cyclic nucleotide inhibitors 1-methyl-3-isobutylxanthine (IBMX) and dipyridamole, and the cGMP-specific phosphodiesterase inhibitor Zaprinast were studied on parallel fiber-Purkinje cell synaptic responses in rat cerebellar slices. Bath application of all three compounds, at concentrations shown to inhibit cGMP breakdown, led to stable and robust long-term depress...

The pharmacological activation of the cystic fibrosis gene protein cystic fibrosis transmembrane conductance regulator (CFTR) was studied in human airway epithelial Calu-3 cells, which express a high level of CFTR protein as assessed by Western blot and in vitro phosphorylation. Immunolocalization shows that CFTR is located in the apical membrane. We performed iodide efflux, whole cell patch-cl...

Recent studies have demonstrated that functionally discrete pools of phosphodiesterase (PDE) activity regulate distinct cellular functions. While the importance of localized pools of enzyme activity has become apparent, few studies have estimated enzyme activity within discrete subcellular compartments. Here we present an approach to estimate near-membrane PDE activity. First, total PDE activit...

Phototransduction in Drosophila is mediated by a G-protein-coupled phospholipase C transduction cascade in which each absorbed photon generates a discrete electrical event, the quantum bump. In whole-cell voltage-clamp recordings, cAMP, as well as its nonhydrolyzable and membrane-permeant analogs 8-bromo-cAMP (8-Br-cAMP) and dibutyryl-cAMP, slowed down the macroscopic light response by increasi...

Previously we observed that human adipose-derived stem cells (hADSCs) could form aggregation during culture in the presence of human serum (HS). In the present study, we have examined if the aggregation might result from the cell migration and analyzed the difference of cell adhesivity after culture in various conditions. When cells were cultured in fetal bovine serum (FBS) alone, there was no ...

Adrenaline, forskolin and ATP all evoked accumulation of cyclic AMP in equine sweat gland epithelial cells, although the response to adrenaline was more transient than that to forskolin and ATP. Cells preincubated in adrenaline (10 micromol l-1, 32 min) showed essentially complete, homologous desensitisation, and this phenomenon reversed slowly (half-time 6.3+/-0.9 h). After 10 min of recovery ...

Background: As the signal transduction of 5-HT4 receptors on cholinergic neurons innervating smooth muscle is controlled by phosphodiesterase (PDE) 4 in porcine stomach and colon, and human large intestine, the in vivo gastroprokinetic effects of a 5-HT4 receptor agonist might be enhanced by combination with a selective PDE4 inhibitor. The presence of 5-HT4 receptors on cholinergic neurons towa...