Image-guidance for transcatheter aortic valve implantation (TAVI) and cerebral embolic protection.

The study was aimed at evaluation of the feasibility and potential benefit of image fusion (IF) of pre-procedural CT angiography (CTA) and x-ray (XR) fluoroscopy for image-guided navigation in transfemoral transcatheter aortic valve implantation (TAVI) with the strong focus on guiding the double-filter cerebral embolic protection device and valve prosthesis placement. METHODS: In 31 patients undergoing TAVI, image registration of CTA-derived 3D anatomical models of the relevant cardiac anatomy and vasculature, and live XR was performed applying a commercially available navigation tool. The approach was evaluated in terms of the accuracy of the overlay. In 27 TAVI patients with IF receiving double-filter cerebral embolic protection device overall procedure time, fluoroscopy time, radiation dose, and total volume of intra-procedural iodinated contrast agent (CA) were registered and compared to those of a control group of prospectively enrolled during the same period of time N=27 patients receiving the same protection system but without IF. RESULTS AND CONCLUSIONS: Image co-registration and model-based guidance is feasible in TAVI procedures. The overlay facilitates placement of the embolic protection device, placement of the guide wire in the left ventricle and initial alignment of the valve prosthesis prior to final deployment, thus improving the confidence level of the operators during the procedure without compromising CA or XR dose.

Extracellular ATP induces assembly and activation of the myosin light chain phosphatase complex in endothelial cells.

OBJECTIVES: Extracellular ATP stabilizes the endothelial barrier and inactivates the contractile machinery of endothelial cells. This inactivation relies on dephosphorylation of the regulatory myosin light chain (MLC) due to an activation of the MLC phosphatase (MLCP). To date, activation and function of MLCP in endothelial cells are only partially understood. METHODS: Here, the mechanism of extracellular ATP-mediated activation of MLCP was analyzed in human endothelial cells from umbilical veins. Cells were transfected with the endogenous protein phosphatase 1 (PP1)-specific inhibitor-2 (I-2). RESULTS: Overexpression of I-2 led to inhibition of PP1 activity and abrogation of the ATP-induced dephosphorylation of MLC. This indicates that the PP1 catalytic subunit is the principal phosphatase catalyzing the MLC dephosphorylation induced by extracellular ATP. As demonstrated by immunoprecipitation analysis, extracellular ATP recruits the PP1delta catalytic subunit and the myosin phosphatase targeting subunit (MYPT1) to form a complex. ATP stimulated dephosphorylation of MYPT1 at the inhibitory phosphorylation sites threonine 850 and 696. However, extracellular ATP failed to stimulate MYPT1 dephosphorylation in I-2-overexpressing cells. CONCLUSIONS: The present study shows for the first time that, in endothelial cells, extracellular ATP causes activation of MLCP through recruitment of PP1delta and MYPT1 into a MLCP holoenzyme complex and PP1-mediated reduction of the inhibitory phosphorylation of MYPT1.

Opposite effect of cAMP signaling in endothelial barriers of different origin.

cAMP-mediated signaling mechanisms may destabilize or stabilize the endothelial barrier, depending on the origin of endothelial cells. Here, microvascular coronary [coronary endothelial cells (CEC)] and macrovascular aortic endothelial cell (AEC) monolayers with opposite responses to cAMP were analyzed. Macromolecule permeability, isometric force, activation state of contractile machinery [indicated by phosphorylation of regulatory myosin light chains (MLC), activity of MLC kinase, and MLC phosphatase], and dynamic changes of adhesion complex proteins (translocation of VE-cadherin and paxillin) were determined. cAMP signaling was stimulated by the adenosine receptor agonist 5'-N-(ethylcarboxamido)-adenosine (NECA), the beta-adrenoceptor agonist isoproterenol (Iso), or by the adenylyl cyclase activator forskolin (FSK). Permeability was increased in CEC and decreased in AEC on stimulation with NECA, Iso, or FSK. The effects could be inhibited by the PKA inhibitor Rp-8-CPT-cAMPS and imitated by the PKA activator Sp-cAMPS. Under cAMP/PKA-dependent stimulation, isometric force and MLC phosphorylation were reduced in monolayers of either cell type, due to an activation of MLC phosphatase. In CEC but not in AEC, FSK induced delocalization of VE-cadherin and paxillin from cellular adhesion complexes as indicated by cell fractionation and immunofluorescence microscopy. In conclusion, decline in contractile activation and isometric force contribute to cAMP/PKA-mediated stabilization of barrier function in AEC. In CEC, this stabilizing effect is overruled by cAMP-induced disintegration of cell adhesion structures.

Effect of codeine on gastrointestinal motility in relation to CYP2D6 phenotype.

BACKGROUND: Codeine is widely used as an analgesic and antitussive drug. The analgesic effect of codeine is mediated by its metabolite morphine, which is formed by the polymorphically expressed enzyme CYP2D6; therefore poor metabolizers have no analgesia after administration of codeine. Like other opiates, codeine causes a delay of gastric emptying and spastic constipation. It is not yet known whether the effect on gastrointestinal motility is mediated by codeine or its metabolite morphine. METHODS: To test the hypothesis that the metabolite morphine is responsible for the effects of codeine on gastrointestinal motility, a randomized, double-blind, two-way crossover study was performed. The orocecal transit time was studied in five extensive and five poor metabolizers of sparteine with the sulfasalazine-sulfapyridine method, assuming that no effects are observed in poor metabolizers because negligible amounts of morphine are formed. RESULTS: No differences of orocecal transit times were observed between extensive metabolizers and poor metabolizers after oral placebo administration. However, after oral codeine administration orocecal transit time was significantly prolonged in extensive metabolizer but not poor metabolizer subjects. All pharmacokinetic parameters of codeine showed no differences between extensive metabolizers and poor metabolizers. The pharmacokinetic parameters (mean +/- SD) of the metabolite morphine were significantly different between extensive metabolizer and poor metabolizer subjects (peak serum concentration, 13.9 +/- 10.5 versus 0.68 +/- 0.15 pmol/ml; area under the serum concentration-time curve, 27.8 +/- 16.0 versus 1.9 +/- 0.7 hr.pmol/ml; total amount of morphine excreted in urine, 0.160 +/- 0.036 versus 0.015 +/- 0.007 mumol). CONCLUSIONS: Because the orocecal transit time prolongation after codeine administration was observed only in extensive metabolizers, the effect of codeine on gastrointestinal motility, like the analgesia, is mediated by its metabolite morphine.