No abstract

No abstract

1 Electrophysiological effects of MS-551, a new class III antiarrhythmic drug, were examined and compared with those of (+)-sotalol in rabbit ventricular cells. 2 In rabbit ventricular muscles stimulated at 1.0 Hz, MS-551 (0.1-10 LM) and (+)-sotalol (3-100I1M) prolonged action potential duration (APD) and effective refractory period without affecting the maximum upstroke velocity of phase 0 depolarization (V.,a). The class III effect of MS-551 was approximately 30 times more potent than that of (+)-sotalol. 3 Class III effects of MS-551 and (+)-sotalol showed reverse use-dependence, i.e., a greater prolongation of APD at a longer cycle length. 4 In rabbit isolated ventricular cells, 3 gM MS-551 and 100 JLM sotalol inhibited the delayed rectifier potassium current (IK) which was activated at more positive potentials than -50 mV and saturated around + 20 mV. 5 MS-551 at a higher concentration of 10 JAM decreased the transient outward current (Ito) and the inward rectifier potassium current (IKI) although 100 tLM sotalol failed to inhibit these currents.6 MS-551 is a non-specific class III drug which can inhibit three voltage-gated K+ channels in rabbit ventricular cells.

Type-I interferons (IFNs) and the interferon-stimulated genes (ISGs) play a major role in antivirus responses against hepatitis C virus (HCV) infection. In this study, we studied expression profiles of ISGs in cells supporting subgenomic HCV replication (Huh7/Rep), and screened their activities to suppress HCV replication. Real-time PCR analyses showed that the expression levels of 23 ISGs were significantly lower in Huh7/Rep than naive Huh7 cells due to transcriptional suppression of the interferon-stimulated response element (ISRE). Furthermore, the expression level of ISGs was also decreased in the cured Huh7 cells in which replicon had been eliminated (cHuh7), indicating adaptation of the cells to support HCV replication by downregulating ISGs. On the other hand, expression of HCV replicon was significantly suppressed by overexpression of several ISGs including PKR, MxA, IRF-9, GBP-1, IFI-6-16, IFI-27, 25OAS and IRF-1. Knock down of GBP-1, IFI-6-16 and IFI-27 by short hairpin RNA resulted in increase of HCV replication. Thus, we conclude that downregulation of ISG expression is required in the host cells supporting HCV replication and that several ISGs directly suppress HCV replication. The search for ISGs that regulate HCV replication may help to elucidate the cellular antiviral defence mechanisms against HCV infection.

ABSTRACT

IEffects of atrial natriuretic peptide (ANP) on the L-type Ca2+ channels were examined in rabbit isolated ventricular cells by use of whole-cell and cell-attached configurations of the patch clamp methods. ANP produced a concentration-dependent decrease (10-100 nM) in amplitude of a basal Ca2c hannel current. 2 The inactive ANP (methionine-oxidized ANP, 30nM) failed to decrease the current. 3 8-Bromo-cyclic GMP (300 ILM), a potent activator of cyclic GMP-dependent protein kinase (PKG), produced the same effects on the basal Ca2+ channel current as those produced by ANP. The cyclic GMP-induced inhibition of the Ca2+ channel current was still evoked in the presence of 1-isobutyl-3-methyl-xanthine, an inhibitor of phosphodiesterase. ANP failed to produce inhibition of the Ca2+ channel current in the presence of 8-bromo-cyclic GMP. 4 In the single channel recording, ANP and 8-bromo-cyclic GMP also inhibited the activities of the L-type Ca2+ channels. Both agents decreased the open probability (NP0) without affecting the unit amplitude. 5 The present results suggest that ANP inhibits the cardiac L-type Ca2+ channel activity through the intracellular production of cyclic GMP and then activation of PKG.

A green‐colored marine unicell has been grown in unialgal culture and its morphology, chloroplast fine structure, and chlorophyll composition investigated. The organism is typical of dinoflagellates in its shape, flagellation, nucleus, mitochondria, and trichocysts. It is similar to Gymnodinium but possesses fine body scales. Chloroplasts and two kinds of vesicles bounded by double membranes, but no organelles obviously identifiable as nuclei or mitochondria, are associated in ribosome‐dense cytoplasm separated by a double membrane from the dinophycean cytoplasm. The chloroplasts are unlike any previously reported for dinoflagellates. Each is enclosed by an envelope consisting of a double membrane. Chloroplast lamellae consist of three appressed thylakoids. Interlamellar pyrenoids are present. Pigment analysis reveals chlorophylls a and b but not chlorophyll c. It seems likely that the organism is an undescribed dinoflagellate containing an endosymbiont with chlorophylls a and b and that the reduction of the endosymbiont nucleus and mitochondria has permitted a more initmate symbiosis.

The occurrence of PIH may be related to the region of epileptic focus and the region of spread of epileptic discharges.