Properties of ivabradine-induced block of HCN1 and HCN4 pacemaker channels

Ivabradine is a 'heart rate-reducing' agent able to slow heart rate, without complicating side-effects. Its action results from a selective and specific block of pacemaker f-channels of the cardiac sinoatrial node (SAN). Investigation has shown that block by ivabradine requires open f-channels, is use dependent, and is affected by the direction of current flow. The constitutive elements of native pacemaker channels are the hyperpolarization-activated cyclic nucleotide-gated (HCN) channels, of which four isoforms (HCN1–4) are known; in rabbit SAN tissue HCN4 is expressed strongly, and HCN1 weakly. In this study we have investigated the blocking action of ivabradine on mouse (m) HCN1 and human (h) HCN4 channels heterologously expressed in HEK 293 cells. Ivabradine blocked both channels in a dose-dependent way with half-block concentrations of 0.94 μ m for mHCN1 and 2.0 μ m for hHCN4. Properties of block changed substantially for the two channels. Block of hHCN4 required open channels, was strengthened by depolarization and was relieved by hyperpolarization. Block of mHCN1 did not occur, nor was it relieved, when channels were in the open state during hyperpolarization; block required channels to be either closed, or in a transitional state between open and closed configurations. The dependence of block upon current flow was limited for hHCN4, and not significant for mHCN1 channels. In summary our results indicate that ivabradine is an 'open-channel' blocker of hHCN4, and a 'closed-channel' blocker of mHCN1 channels. The mode of action of ivabradine on the two channels is discussed by implementing a simplified version of a previously developed model of f-channel kinetics.     

Establishment and characterization of two new pig cell lines for use in virological diagnostic laboratories

Two pig cell lines derived from kidney and trachea tissues and referred to as newborn swine kidney (NSK) and newborn pig trachea (NPTr) were established following serial culture of primary cells. They were characterized by an epithelial-like morphology, high capacity to replicate and stability of the cell monolayer for several days after seeding. Their modal chromosome number was modified in comparison to that of primary swine cells and they both displayed a transforming potential in vitro and displayed oncogenicity in nude mice. Infection with pig endogenous retroviruses was detected. Almost all the swine viruses tested, i.e., pseudorabies virus, pig parvovirus, hog cholera virus, transmissible gastroenteritis virus of swine, encephalomyocarditis virus, swine vesicular disease virus and the enteroviruses, except pig reproductive respiratory syndrome virus, were capable of replicating in the new cell lines with titres similar to the ones detected in the reference culture systems. Furthermore, all the selected influenza virus sub-types isolated from human, swine and avian species replicated with cytopathic effect in NSK and NPTr cells, whereas, of all the equine influenza viruses tested only the Miami and Suffolk sub-types replicated.     

The technicon H6000 automated hematology analyzer in the diagnosis and classification of the myelodysplastic syndromes

The Technicon H6000 hematology blood counter is a fully automated analyzer which provides, in addition to conventional hematological blood values (i.e. RBC, PLT, etc.), a differential count of WBCs based on a combination of cytochemistry (peroxidase content) and cell volume analysis. Because of these characteristics, the H6000 quantitizes, as part of the full differential count, the number and percentage of "large unstained cells" (LUCs), i.e. large peroxidase-negative circulating elements with a cell volume above a predetermined threshold established for the lymphocytes of normal subjects. We evaluated the H6000 printouts (scattergrams) of 29 patients with myelodysplastic syndromes and of 12 other patients with transient cytopenias. The most important and constant diagnostic features for myelodysplastic syndromes were the increased proportion of LUCs and, in some cases, the high monocyte count, which are both automatically provided by the instrument.     

Local immunotherapy (β-IFN) and systemic chemotherapy in primary glial tumors

Dosage and schedules for the treatment of malignant glial tumors using IFN (interferon) are still uncertain and controversial. In this study we give the preliminary results of treatment in 28 patients with glioblastoma multiforme (GBM). 6 patients were treated with local injection of β-IFN through an Ommaya reservoir; 4 patients with β-IFN followed by systemic chemotherapy (Cisplatin+Etoposide), and 18 patients with chemotherapy only. Two end points were evaluated: 1) Whether or not the patients responded to treatment. 2) Length of Time to Tumor Progression(TTP) after surgery. We found that IFN alone was ineffective. Results were improved when local immunotherapy was associated with systemic chemotherapy. New drugs and investigation of possible pharmacological synergism are needed.     

Transapical aortic balloon valvuloplasty in a 890‐gram infant: Hybrid is better!

Balloon aortic valvuloplasty has become in many centers the treatment of choice for neonates with critical or severe aortic stenosis. Usual approaches both antegrade and retrograde can be problematic in preterms extremely low birth weight babies. We describe a novel approach for dilating the aortic valve in an 890 grams baby. © 2010 Wiley‐Liss, Inc.     

17Beta-estradiol abrogates apoptosis in murine skeletal muscle cells through estrogen receptors: role of the phosphatidylinositol 3-kinase/Akt pathway

Estrogens can regulate apoptosis in various cellular systems. The present study shows that 17beta-estradiol (E2), at physiological concentrations, abrogates DNA damage, poly (ADP-ribose) polymerase cleavage, and mitochondrial cytochrome c release induced by H2O2 or etoposide in mouse skeletal muscle C2C12 cells. This protective action, which involved PI3K/Akt activation and Bcl-2 associated death agonist (BAD) phosphorylation, was inhibited by antibodies against the estrogen receptor (ER) alpha or beta isoforms, or transfecting siRNA specific for each isoform. The inhibition of the antiapoptotic action of E2 at the mitochondrial level was more pronounced when ER-beta was immunoneutralized or suppressed by mRNA silencing, whereas transfection of C2C12 cells with either ER-alpha siRNA or ER-beta siRNA blocked the activation of Akt by E2, suggesting differential involvement of ER isoforms depending on the step of the apoptotic/survival pathway evaluated. These results indicate that E2 exerts antiapoptotic effects in skeletal muscle cells which are mediated by ER-beta and ER-alpha and involve the PI3K/Akt pathway.