Specific pattern of ionic channel gene expression associated with pacemaker activity in the mouse heart

Even though sequencing of the mammalian genome has led to the discovery of a large number of ionic channel genes, identification of the molecular determinants of cellular electrical properties in different regions of the heart has been rarely obtained. We developed a high-throughput approach capable of simultaneously assessing the expression pattern of ionic channel repertoires from different regions of the mouse heart. By using large-scale real-time RT-PCR, we have profiled 71 channels and related genes in the sinoatrial node (SAN), atrioventricular node (AVN), the atria (A) and ventricles (V). Hearts from 30 adult male C57BL/6 mice were microdissected and RNA was isolated from six pools of five mice each. TaqMan data were analysed using the threshold cycle ( C _t) relative quantification method. Cross-contamination of each region was checked with expression of the atrial and ventricular myosin light chains. Two-way hierarchical clustering analysis of the 71 genes successfully classified the six pools from the four distinct regions. In comparison with the A, the SAN and AVN were characterized by higher expression of Navβ1, Navβ3, Cav1.3, Cav3.1 and Cavα2δ2, and lower expression of Kv4.2, Cx40, Cx43 and Kir3.1. In addition, the SAN was characterized by higher expression of HCN1 and HCN4, and lower expression of RYR2, Kir6.2, Cavβ2 and Cavγ4. The AVN was characterized by higher expression of Nav1.1, Nav1.7, Kv1.6, Kvβ1, MinK and Cavγ7. Other gene expression profiles discriminate between the ventricular and the atrial myocardium. The present study provides the first genome-scale regional ionic channel expression profile in the mouse heart.     

Intracellular calcium does not directly modulate cardiac pacemaker (if) channels

A study on the cardiac pacemaker current if in inside-out macro-patches of sino-atrial (SA) node cells has recently demonstrated that i_f channels are directly activated by intracellular cAMP [4]. Using the same preparation, here we investigate the possibility that internal Ca²⁺ ions play a role in the modulation of i_f channels. Our results indicate that Ca²⁺ ions do not have a direct activating effect on i_f.     

Clonidine in essential tremor: preliminary observations from an open trial

Summary The authors present ten cases of essential tremor, studied before and after administration of clonidine with clinical tests and electrophysiological recordings. Improvement due to the desynchronizing effect of clonidine on tremor was observed in all cases. Possible mechanisms acting on the central and peripheral nervous system are discussed.     

Glycolipids from sponges. Part 17. Clathrosides and isoclathrosides, unique glycolipids from the Caribbean sponge Agelas clathrodes

Two families of unique glycolipids, clathrosides A-C (2a-4a) and isoclathrosides A-C (5a-7a) were isolated from the Caribbean sponge Agelas clathrodes. Clathrosides and isoclathrosides are glycosides of a very-long-chain alcohol derived from fatty acids, a new class of glycolipids that appears to be characteristic of marine sponges. The six compounds differ in configuration and in the branching of alkyl chains. Stereostructures of the clathrosides were determined by NMR and CD spectroscopy, mass spectrometry, and chemical degradation. Location of the methyl branch on the proper alkyl chain required an exceptional 1-D TOCSY experiment, in which coherence was transferred through as many as 13 vicinal couplings.     

In vitro restoration of polyclonal hematopoiesis in a chronic myelogenous leukemia after in vitro treatment with 4- hydroperoxycyclophosphamide

Bone marrow cells of a 45-year-old female with Philadelphia chromosome (Ph1)-positive, early-phase chronic myelogenous leukemia (CML), who was heterozygous for the glucose-6-phosphate dehydrogenase (G6PD) locus, were pretreated in vitro with 4-hydroperoxycyclophosphamide (4-HC) and tested for G6PD activity in several colony formation assays and for karyotypic abnormalities. All cells within the mixed (CFU-GEMM), the erythroid burst (BFU-E), and the granulocyte-macrophage (CFU-GM) colonies expressed type A and type B G6PD activity and a normal karyotype, whereas untreated cells expressed type A G6PD and the Ph1 chromosome. This reversal of G6PD activity type and the disappearance of the Ph1 chromosome in colonies grown from 4-HC-treated cells indicate that this cytotoxic agent spares a residual normal stem cell population in bone marrow cells of early-phase CML patients. This finding, in turn, suggests a therapeutic approach in CML based on in vitro chemotherapy of autologous bone marrow grafts.     

Adefovir treatment for chronic hepatitis B in heart transplant recipients

Chronic hepatitis B is prevalent in the transplant setting and may cause significant complications. Effective control of viral replication is needed. Besides lamivudine, very little data are available on safety and efficacy of other drugs. We describe our experience with adefovir dipivoxil (ADV) in eight heart transplant recipients. Studies included a baseline liver biopsy, thrice‐monthly clinical, biochemical, and virological evaluations, including genotyping and viral load, polymerase gene sequencing for resistance mutations, liver and kidney function tests, and liver ultrasound. Of eight patients, six had fibrosis score ≤2 and negative HBeAg and seven had hepatitis B virus (HBV) genotype D. Upon ADV start, median HBV‐DNA was 5.8 logs IU/mL and alanine aminotransferase (ALT) levels were mostly normal. All patients had prior mild‐to‐moderate renal functional impairment. Seven of eight patients started ADV after a previous course of lamivudine. Five of these seven patients became HBV‐DNA undetectable within eight months. One patient with low baseline viremia started ADV de novo and suppressed HBV‐DNA. Median treatment duration was 66 months. ADV daily dose was halved in one patient due to renal function worsening. No ALT flares, hypophosphatemia, liver decompensation, liver cancer, or emergence of resistance was observed. Our data suggest that ADV may be a safe and effective rescue treatment for heart transplant recipients with lamivudine‐resistant chronic hepatitis B.     

Influence of comorbidities and medication use on tilt table test outcome in elderly patients

BACKGROUND: The tilt table test (TTT) is a useful diagnostic tool in people with unexplained syncope, dizziness, and falls. However, preexisting comorbidities and medications affecting hemodynamic response might affect TTT outcome (i.e. presence or absence of vasomotor syncope). We studied the influence of these compounding factors on TTT outcome. METHODS: One hundred and sixty-four elderly patients with a mean (+/-SD) age of 80.0 +/- 6.1 years (M:F 104:60) underwent TTT. Heart rate and blood pressure were recorded continuously using a noninvasive device (Task Force Monito, CNS systems, Graz, Austria). Predictors of TTT outcome in a backward regression analysis included age, gender, comorbidities (chronic heart failure, hypertension, diabetes, and cerebrovascular disease), and drugs (beta-blockers, angiotensin-converting enzyme inhibitors, calcium channel blockers, diuretics, digoxin, opioids, antidepressants, and nonsteroidal antiinflammatory agents). RESULTS: TTT was positive in 30 patients (18.3%). None of the above factors were a significant predictor of TTT outcome. The use of calcium channel blockers predicted a drop in systolic blood pressure after 2 minutes of TTT (P = 0.048, R(2)= 0.018). However, this was not associated with significant changes in heart rate and did not influence TTT outcome. CONCLUSION: The TTT outcome was not influenced by comorbidities or medications. TTT is a reliable diagnostic tool in a population characterized by significant comorbidities and polypharmacy.