Asian Science Citation Index is committed to provide an authoritative, trusted and significant information by the coverage of the most important and influential journals to meet the needs of the global scientific community.  
ASCI Database
308-Lasani Town,
Sargodha Road,
Faisalabad, Pakistan
Fax: +92-41-8815544
Contact Via Web
Suggest a Journal
 
Articles by Y Nakazawa
Total Records ( 2 ) for Y Nakazawa
  H Itoh , T Sakaguchi , W. G Ding , E Watanabe , I Watanabe , Y Nishio , T Makiyama , S Ohno , M Akao , Y Higashi , N Zenda , T Kubota , C Mori , K Okajima , T Haruna , A Miyamoto , M Kawamura , K Ishida , I Nagaoka , Y Oka , Y Nakazawa , T Yao , H Jo , Y Sugimoto , T Ashihara , H Hayashi , M Ito , K Imoto , H Matsuura and M. Horie
 

Background— Drugs with IKr-blocking action cause secondary long-QT syndrome. Several cases have been associated with mutations of genes coding cardiac ion channels, but their frequency among patients affected by drug-induced long-QT syndrome (dLQTS) and the resultant molecular effects remain unknown.

Methods and Results— Genetic testing was carried out for long-QT syndrome–related genes in 20 subjects with dLQTS and 176 subjects with congenital long-QT syndrome (cLQTS); electrophysiological characteristics of dLQTS-associated mutations were analyzed using a heterologous expression system with Chinese hamster ovary cells together with a computer simulation model. The positive mutation rate in dLQTS was similar to cLQTS (dLQTS versus cLQTS, 8 of 20 [40%] versus 91 of 176 [52%] subjects, P=0.32). The incidence of mutations was higher in patients with torsades de pointes induced by nonantiarrhythmic drugs than by antiarrhythmic drugs (antiarrhythmic versus others, 3 of 14 [21%] versus 5 of 6 [83%] subjects, P<0.05). When reconstituted in Chinese hamster ovary cells, KCNQ1 and KCNH2 mutant channels showed complex gating defects without dominant negative effects or a relatively mild decreased current density. Drug sensitivity for mutant channels was similar to that of the wild-type channel. With the Luo-Rudy simulation model of action potentials, action potential durations of most mutant channels were between those of wild-type and cLQTS.

Conclusions— dLQTS had a similar positive mutation rate compared with cLQTS, whereas the functional changes of these mutations identified in dLQTS were mild. When IKr-blocking agents produce excessive QT prolongation (dLQTS), the underlying genetic background of the dLQTS subject should also be taken into consideration, as would be the case with cLQTS; dLQTS can be regarded as a latent form of long-QT syndrome.

  H Kajiura , H Koiwa , Y Nakazawa , A Okazawa , A Kobayashi , T Seki and K. Fujiyama
 

N-Glycosylation is an important post-translational modification that occurs in many secreted and membrane proteins in eukaryotic cells. Golgi -mannosidase I hydrolases (MANI) are key enzymes that play a role in the early N-glycan modification pathway in the Golgi apparatus. In Arabidopsis thaliana, two putative MANI genes, AtMANIa (At3g21160) and AtMANIb (At1g51590), were identified. Biochemical analysis using bacterially produced recombinant AtMANI isoforms revealed that both AtMANI isoforms encode 1-deoxymannojirimycin-sensitive -mannosidase I and act on Man8GlcNAc2 and Man9GlcNAc2 structures to yield Man5GlcNAc2. Structures of hydrolytic intermediates accumulated in the AtMANI reactions indicate that AtMANIs employ hydrolytic pathways distinct from those of mammalian MANIs. In planta, AtMANI-GFP/DsRed fusion proteins were detected in the Golgi stacks. Arabidopsis mutant lines manIa-1, manIa-2, manIb-1, and manIb-2 showed N-glycan profiles similar to that of wild type. On the other hand, the manIa manIb double mutant lines produced Man8GlcNAc2 as the predominant N-glycan and lacked plant-specific complex and hybrid N-glycans. These data indicate that either AtMANIa or AtMANIb can function as the Golgi -mannosidase I that produces the Man5GlcNAc2 N-glycan structure necessary for complex N-glycan synthesis.

 
 
 
Copyright   |   Desclaimer   |    Privacy Policy   |   Browsers   |   Accessibility