No abstract

[Ca 2ϩ ]i from 0.1 to 0.3, 0.6, and 1.0 M increased I Na.L in a concentration-dependent manner from 0.221 Ϯ 0.038 to 0.554 Ϯ 0.045 pA/pF (n ϭ 10, P Ͻ 0.01) and was associated with an increase in mean Na ϩ channel open probability and prolongation of channel mean open-time (n ϭ 7, P Ͻ 0.01). In the presence of 0.6 M [Ca 2ϩ ]i, KN-93 (10 M) and bisindolylmaleimide (BIM, 2 M) decreased I Na.L by 45.2 and 54.8%, respectively. The effects of KN-93 and autocamtide-2-related inhibitory peptide II (2 M) were not different. A combination of overload, is a pathological occurrence in the heart and is reported to be related to ischemia, hypoxia, oxidative stress, cardiac hypertrophy, heart failure, and elevated catecholamine levels (7,11,28,35,49). Intracellular Ca 2ϩ overload results in cardiac mechanical and electrical dysfunction (44). Many pathological conditions that lead to intracellular Ca 2ϩ overload in ventricular myocytes are also associated with an increase in the late or persistent sodium current (I Na.L ) (1, 17, 18, 21, 23, 24, 26, 40 -42, 47, 48, 53). I Na.L is created when inactivation-resistant sodium channels continue to open for long periods during the action potential plateau. Maltsev et al. (25) reported that an increase in the level of [Ca 2ϩ ] i from baseline to 1 M increased the amplitude of I Na.L in dog ventricular myocytes via a mechanism involving activation of Ca 2ϩ -calmodulin-dependent protein kinase II (CaMKII). Elevated [Ca 2ϩ ] i is also reported to activate protein kinase C (PKC) and mitogen-activated protein kinase (MAPK) (31, 39, 52), and the PKC activation is associated with an increase in I Na.L (3,4,10,14,27,29,48,50,51).An increase in the amplitude of I Na.L may prolong action potential duration, increase the transmural dispersion of repolarization, and cause cardiac arrhythmias (2). An increase in I Na.L also raises the intracellular sodium concentration and subsequently increases [Ca 2ϩ ] i via the reverse mode of the Na ϩ -Ca 2ϩ exchanger to cause further Ca 2ϩ influx (18,20). Reduction of the extracellular Na ϩ concentration or inhibition of I Na.L was shown to attenuate the increase in [Ca 2ϩ ] i (8,12,15,22,32,36,37,43). Inhibition of I Na.L is therefore a potential therapeutic target for the treatment of cardiac arrhythmias and myocardial dysfunction associated with intracellular Ca 2ϩ overload (5,6,16,33,34,45,46). In this study we tested the hypothesis that both CaMKII and PKC mediate the augmentation of I Na.L in the presence of an increased [Ca 2ϩ ] i . Using rabbit ventricular myocytes, we measured whole cell Na ϩ current and single Na ϩ channel activities, the latter with a novel open cell-attached patch technique. I Na.L and single Na ϩ channel activities were investigated under conditions mimicking the physiological and pathological conditions of normal and increased [Ca 2ϩ ] i . In cells with increased [Ca 2ϩ ] i , agents that modulate the functions of CaMKII, PKC, and MAPK were used to determine the relative contributions of these signali...

3‐Deoxyfortalpinoid F, fortalpinoid A, and cephinoid H are members of the Cephalotaxus diterpenoids class of natural products, which feature diverse chemical structures and valuable biological activities. We report herein the development of a diastereoselective Pauson–Khand reaction as an effective pathway to access the core tetracyclic skeleton, which is found widely in Cephalotaxus diterpenoids. Furthermore, we enabled the construction of the tropone moiety through a ring‐closing metathesis/elimination protocol. Based on the developed strategy, asymmetric synthesis of the title compounds has been achieved for the first time.

Streptococcus suis serotype 2 (SS2) is widely recognized in the veterinary world as the cause of rapidly progressive and fatal sepsis in infant pigs, manifested with meningitis, polyarthritis and pneumonia. It has evolved into a highly infectious strain, and caused two large-scale outbreaks of human epidemic in China, characterized bytypical toxic-shock syndrome and invasive infection. However, the molecular basis of virulence of this emerging zoonotic pathogen is still largely unknown. The present study shows that the sequence type (ST)7 epidemic strain S. suis 05ZYH33 causes higher mortality, higher necrosis of polymorphonuclear neutrophils and a significantly higher damage to human umbilical vein endothelial cells compared to the non-epidemic strain S. suis 1940. These differences appear to associate with the enhanced secretion of suilysin (sly) by S. suis 05ZYH33 compared to the non-epidemic strain 1940. Inclusion of additional strains confirmed that the epidemic ST7 strains produce more sly protein (mean, 1.49 g/ml; range, 0.76–1.91 g/ml) than non-epidemic strains (mean, 0.33 g/ml; range, 0.07–0.94 g/ml), and this difference is significant (P<0.001). The nonpolar mutant strain S. suis Δsly, constructed from the epidemic ST7 strain S. suis 05ZYH33 confirmed the role of sly on the enhanced virulence of S. suis ST7 strains. These findings suggest that increased sly production in S. suis 05ZYH33 facilitates penetration to the epithelium and its survival in the bloodstream, thereby contributing to the invasive infection.