Synthesis and conformation of the trimeric coiled-coil segment of laminin*

A disulfide linked 95-mer parallel hetero-trimeric active site segment of laminin was designed and synthesised. The three subunits, A (32-mer), B1 (30-mer) and B2 (33-mer), were prepared by Boc-based solid-phase peptide synthesis involving a two-step trimethylsilyl bromide-thioanisole and HF deprotection procedure. The interlinking of the three subunits was accomplished by the stepwise selective formation of two disulfide bridges using air-oxidation and thallium (III) trifluoroacetate oxidation. The conformations of the synthetic peptides were studied by circular dichroism (CD) spectroscopy, showing that the hetero-dimer, B1-B2, one of the homo-dimers, B1-B1, and the trinier are 30 to 40% in the α-helical conformation in aqueous buffer. Variable temperature CD studies demonstrated that the trimer is considerably more stable (melting temperature (Tm) = 61°) than the hetero-dimer, B1-B2 (Tm = 36°).     

Bisphosphonate induces apoptosis and inhibits pro-osteoclastic gene expression in prostate cancer cells

AIM: Bisphosphonates are well established for the management of cancer-induced skeletal complications. Recent studies suggest that bisphosphonates promote apoptosis of cancer cells as well as osteoclasts in bone metastatic sites. To determine the direct effects of bisphosphonate on prostate cancer, we examined the effects of minodronate on prostatic cancer cell growth and the expression of apoptosis-related proteins and osteoclastogenic factors. METHODS: PC-3, DU145 and LNCaP cells were treated with amino-bisphosphonate minodronate. Then proliferation, apoptosis and expression of bcl-2, bax, poly (ADP)-ribose polymerase (PARP), caspase-3, receptor activator of nuclear factor-kappaB ligand (RANKL), osteoprotegerin (OPG), matrix metalloproteinases-2 (MMP-2), and parathyroid hormone related protein (PTHrP) were assessed. RESULTS: The proliferation of prostatic cancer cells was inhibited by minodronate. DNA fragmentation and TUNEL-positive nuclei were observed in minodronate-treated PC-3 cells. Minodronate decreased bcl-2 expression and induced bax expression, caspase-3 activity and degradation of PARP in DU145 and PC-3 cells. Minodronate decreased expression of RANKL, PTHrP and MMP-2 in PC-3 cells. CONCLUSIONS: Our results suggest that bisphosphonate not only promotes apoptosis directly but also decreases pro-osteoclastic gene expression in prostate cancer cells.     

Electrophysiological Characteristics of Localized Reentrant Atrial Tachycardia Occurring After Catheter Ablation of Long-Lasting Persistent Atrial Fibrillation

Background: Mapping of recurrent atrial tachycardia (AT) after extensive ablation for long-lasting persistent atrial fibrillation (AF) is complex. We sought to describe the electrophysiological characteristics of localized reentry occurring after ablation of long-lasting persistent AF.
Methods: Out of 70 patients undergoing catheter ablation of long-lasting persistent AF, 9 patients (13%, 55 ± 8 years, 8 males) in whom localized reentry was demonstrated in a repeat ablation were studied. Localized reentry was defined as reentry in which the circuit was localized to a small area and did not have a central obstacle. The mechanism of AT was determined by electroanatomical and entrainment mapping.
Results: Nine localized reentries with cycle length of 243 ± 41 ms were mapped in 9 patients. The location of AT was the left atrial appendage in 4 patients, anterior left atrium in 2, left septum in 2, and mitral isthmus in 1. In all ATs, a critical isthmus of <10 mm in width was identified in the vicinity of the prior linear lesions or ostia of isolated pulmonary veins. Ablation of the critical isthmus, which was characterized by continuous low-voltage activity (median voltage: 0.15 mV, mean duration: 117 ± 31 ms), terminated AT and rendered it noninducible. Additionally, ablation was performed for all of inducible ATs. At 11 ± 7 months after the procedure, 8 of 9 patients (89%) were free from any arrhythmias.
Conclusions: After ablation of long-lasting persistent AF, localized reentry may arise from a site in the vicinity of the prior ablation lesions. Ablation of the critical isthmus eliminates the arrhythmia.     

Successful Prevention of Recurrent Ventricular Fibrillation by Intravenous Isoproterenol in a Patient with Brugada Syndrome

TANAKA, H., et al. : Successful Prevention of Recurrent Ventricular Fibrillation by Intravenous Isoproterenol in a Patient with Brugada Syndrome. Intravenous administration of isoproterenol restored the ST-segment configuration to nearly normal in the right precordial leads and completely prevented spontaneous VF attacks in a patient with Brugada syndrome. The formation of a Brugada-type ECG has been attributed to the transmural dispersion of repolarization of the right ventricular epicardium and related to modulation of the autonomic nervous system. Our case may provide clues to the pathophysiological mechanism of this syndrome.     

Analysis of Met235 to Thr variant of the angiotensinogen gene in relation to the blood pressure and family history of essential hypertension in Japanese children

A recent study reported a significant relationship between a T⁷⁰⁴→C (Met²³⁵→Thr) variant in exon 2 of the angiotensinogen gene in adults and essential hypertension. In the present study, this variant was detected in 131 Japanese children using a polymerase chain reaction. The allele frequency of the variant was 0.76. The genotype frequency of the homozygote for the allele was 0.59, and children who were homozygous had higher systolic blood pressure than those with the other two genotypes. No relationship was found between children's polymorphism and a family history of essential hypertension. These findings suggest that this molecular variant of the angiotensinogen gene may play some role in the regulation of blood pressure in Japanese children.