Calcium entry through stretch-inactivated ion channels in mdx myotubes.

Recent advances in understanding the molecular basis of human X-linked muscular dystrophies have come from the identification of dystrophin, a cytoskeletal protein associated with the surface membrane. Although there is little or virtually no dystrophin in affected individuals, it is not known how this causes muscle degeneration. One possibility is that the membrane of dystrophic muscle is weakened and becomes leaky to Ca2+. In muscle from mdx mice, an animal model of the human disease, intracellular Ca2+ is elevated and associated with a high rate of protein degradation. The possibility that a lack of dystrophin alters the resting permeability of skeletal muscle to Ca2+ prompted us to compare Ca2(+)-permeable ionic channels in muscle cells from normal and mdx mice. We now show that recordings of single-channel activity from mdx myotubes are dominated by the presence of Ca2(+)-permeable mechano-transducing ion channels. Like similar channels in normal skeletal muscle, they are rarely open at rest, but open when the membrane is stretched by applying suction to the electrode. Other channels in mdx myotubes, however, are often open for extended periods of time at rest and close when suction is applied to the electrode. The results show a novel type of mechano-transducing ion channel in mdx myotubes that could provide a pathway for Ca2+ to leak into the cell.     

耐碱性芽孢杆菌碱性淀粉酶研究Ⅰ──菌种的分离与筛选

从１５份土样中筛选出一株产碱性淀粉酶的耐碱性芽孢杆菌９－Ａ２，经菌学鉴定为耐碱性巨大芽孢杆菌。９－Ａ２菌株可在ｐＨ１０以上的环境中生长，在ｐＨ９～１０条件下产生较高的碱性淀粉酶。碱性淀粉酶在ｐＨ６～１１范围内比较稳定，酶反应的最适ｐＨ为９，最适温度为５０℃     

双光子过程的修饰Hamiltonians

采用规范变换技术给出描述双光子过程的修饰Hamiltonian.并得到了对于给定任一组参量ω_0,ω和ε_4时,系统Hamiltonian本征值谱。此外还讨论了真空基态的稳定性问题。     

Pelagic tunicates in the China Seas

The biogeography of pelagic tunicates belonging to the two taxonomic classes Larvacea and Thaliacea was analysed using seven sampling stations along the coastal regions of Taiwan which contribute to all the China Seas surrounding Taiwan. The collected data were then compared with the information in the available literature about pelagic tunicate species diversity in the China Seas (Bohai Sea, North Yellow Sea, East China Sea and South China Sea) and previous studies on these organisms in Taiwan waters to get a better understanding of their biodiversity, abundance and distribution. A total of 19 species of pelagic tunicates were observed and identified to the speciel level: five species belonging to the class Larvacea, in the two families Oikopleuriidae and Fritillariidae; 14 species belonging to the class Thaliacea, in the families Salpidae and Doliolidae. We summarised morphological characteristics of the recorded species which were found to be useful for identification, and we provided further information about their global distribution and ecological preferences. Our results revealed that pelagic tunicates occurred in the China Seas with high species richness throughout the year. This is the first account on the class Larvacea from Taiwan. Comparing our results with available records from all China Seas, Taiwan proved to be a species diversity hotspot for pelagic tunicates, especially for the family Salpidae. The waters of southern Taiwan showed a higher species richness compared to the northern counterpart. The doliolid Doliolum denticulatum can be designated as an indicator of the low-temperature China Coastal Current species.     

Heterodimeric adenosine receptors: a device to regulate neurotransmitter release

Since 1990 it has been known that dimers are the basic functional form of nearly all G-protein-coupled receptors (GPCRs) and that homo- and heterodimerization may play a key role in correct receptor maturation and trafficking to the plasma membrane. Nevertheless, homo- and heterodimerization of GPCR has become a matter of debate especially in the search for the precise physiological meaning of this phenomenon. This article focuses on how heterodimerization of adenosine A₁ and A_2A receptors, which are coupled to apparently opposite signalling pathways, allows adenosine to exert a fine-tuning modulation of striatal glutamatergic neurotransmission, providing a switch mechanism by which low and high concentrations of adenosine inhibit and stimulate, respectively, glutamate release. Received 8 May 2006; received after revision 19 June 2006; accepted 17 July 2006     

Kallmann syndrome gene on the X and Y chromosomes: implications for evolutionary divergence of human sex chromosomes.

The recently identified gene for X-linked Kallmann syndrome (hypogonadotropic hypogonadism and anosmia) has a closely related homologue on the Y chromosome. The X and Y copies of this gene are located in a large region of X/Y homology, on Xp22.3 and Yq11.2, respectively. Comparison of the structure of the X-linked Kallmann syndrome gene and its Y homologue shed light on the evolutionary history of this region of the human sex chromosomes. Our data show that the Y homologue is not functional. Comparative analysis of X/Y sequence identity at several loci on Xp22.3 and Yq11.2 suggests that the homology between these two regions is the result of a complex series of events which occurred in the recent evolution of sex chromosomes.     

Multiple ADH genes are associated with upper aerodigestive cancers

Alcohol is an important risk factor for upper aerodigestive cancers and is principally metabolized by alcohol dehydrogenase (ADH) enzymes. We have investigated six ADH genetic variants in over 3,800 aerodigestive cancer cases and 5,200 controls from three individual studies. Gene variants rs1229984 (ADH1B) and rs1573496 (ADH7) were significantly protective against aerodigestive cancer in each individual study and overall (P = 10(-10) and 10(-9), respectively). These effects became more apparent with increasing alcohol consumption (P for trend = 0.0002 and 0.065, respectively). Both gene effects were independent of each other, implying that multiple ADH genes may be involved in upper aerodigestive cancer etiology.     

Genome-wide association study identifies a susceptibility locus for thoracic aortic aneurysms and aortic dissections spanning FBN1 at 15q21.1

Although thoracic aortic aneurysms and dissections (TAAD) can be inherited as a single-gene disorder, the genetic predisposition in the majority of affected people is poorly understood. In a multistage genome-wide association study (GWAS), we compared 765 individuals who had sporadic TAAD (STAAD) with 874 controls and identified common SNPs at a 15q21.1 locus that were associated with STAAD, with odds ratios of 1.6-1.8 that achieved genome-wide significance. We followed up 107 SNPs associated with STAAD with P < 1 × 10(-5) in the region, in two separate STAAD cohorts. The associated SNPs fall into a large region of linkage disequilibrium encompassing FBN1, which encodes fibrillin-1. FBN1 mutations cause Marfan syndrome, whose major cardiovascular complication is TAAD. This study shows that common genetic variants at 15q21.1 that probably act via FBN1 are associated with STAAD, suggesting a common pathogenesis of aortic disease in Marfan syndrome and STAAD.     

A functional variant of lymphoid tyrosine phosphatase is associated with type I diabetes

We report that a single-nucleotide polymorphism (SNP) in the gene (PTPN22) encoding the lymphoid protein tyrosine phosphatase (LYP), a suppressor of T-cell activation, is associated with type 1 diabetes mellitus (T1D). The variants encoded by the two alleles, 1858C and 1858T, differ in a crucial amino acid residue involved in association of LYP with the negative regulatory kinase Csk. Unlike the variant encoded by the more common allele 1858C, the variant associated with T1D does not bind Csk.