Biomedical subjects
Yen-Ju Chen
Publications and source records attributed to Yen-Ju Chen.
Imaging strategies in intramuscular haemangiomas: an analysis of 20 cases.
The purpose of this study was to review the correlation between the imaging studies and the histological findings in the diagnosis of this disease. We retrospectively reviewed 21 lesions in 20 patients (median age, 23.7 years old) who had been diagnosed with cavernous haemangiomas (n=11), capillary (n=6), and mixed (n=3) types. The imaging studies were obtained with plain film radiography (n=20), Tc-99 m bone scans (n=5), angiography (n=7) and magnetic resonance imaging (MRI; n=20). All the patients underwent marginal to wide excision. Based on the imaging studies, the rate of accurate prediction of intramuscular haemangioma using MRI in our study was 90%. Using the preoperative imaging studies and surgical excisions, only one (5%) local recurrence happened 2 years after marginal excision. The remaining patients were free of disease. For the avoidance of recurrence, wide excision is necessary with the help of the imaging studies, which can provide more specific information, making possible the preoperative identification of characteristic features of the tumuor.
X-ray structure of the EmrE multidrug transporter in complex with a substrate.
EmrE is a prototype of the Small Multidrug Resistance family of efflux transporters and actively expels positively charged hydrophobic drugs across the inner membrane of Escherichia coli. Here, we report the x-ray crystal structure, at 3.7 angstrom resolution, of one conformational state of the EmrE transporter in complex with a translocation substrate, tetraphenylphosphonium. Two EmrE polypeptides form a homodimeric transporter that binds substrate at the dimerization interface. The two subunits have opposite orientations in the membrane and adopt slightly different folds, forming an asymmetric antiparallel dimer. This unusual architecture likely confers unidirectionality to transport by creating an asymmetric substrate translocation pathway. On the basis of available structural data, we propose a model for the proton-dependent drug efflux mechanism of EmrE.
Naphthazarin and methylnaphthazarin cause vascular dysfunction by impairment of endothelium-derived nitric oxide and increased superoxide anion generation.
The effects of the naphthoquinone analogue, naphthazarin (Nap), and its derivative, methylnaphthazarin (MetNap), on vascular reactivity were studied using isolated rat aortic rings and human umbilical vein endothelial cells (HUVECs). In this study, we determined vessel tension, nitric oxide (NO) formation, endothelial nitric oxide synthase (eNOS) activity, eNOS protein expression, and superoxide anion (O2*-) generation in an effort to evaluate the effect of Nap and MetNap on the impairment of the NO-mediated pathway. Lower concentrations of Nap (0.01-1 microM) and MetNap (1-10 microM) concentration-dependently enhanced phenylephrine (PE)-induced vasocontraction and abrogated acetylcholine (ACh)-induced vasorelaxation in an endothelium-dependent manner. On HUVECs, both Nap and MetNap concentration-dependently inhibited NO formation induced by A23187, and also partially inhibited nitric oxide synthase (NOS) activity. eNOS protein expression by HUVECs was not affected by treatment with Nap or MetNap, even within 24h. These data suggest that Nap and MetNap might act as inhibitors of nitric oxide synthesis in the endothelium. In addition, Nap and MetNap were also shown to generate O2*- on HUVECs with short-term treatment. We concluded that Nap and MetNap inhibited agonist-induced relaxation and induced vasocontraction in an endothelium-dependent manner, and these effects might have been due to modification of the NO content by inhibition of NOS activity and bioinactivation through O2*- generation.
Molecular epidemiology of severe acute respiratory syndrome-associated coronavirus infections in Taiwan.
BACKGROUND: In 2003, Taiwan experienced a series of outbreaks of severe acute respiratory syndrome (SARS) and 1 laboratory-contamination accident. Here we describe a new phylogenetic analytical method to study the sources and dissemination paths of SARS-associated coronavirus (SARS-CoV) infections in Taiwan. METHODS: A phylogenetic analytical tool for combining nucleotide sequences from 6 variable regions of a SARS-CoV genome was developed by use of 20 published SARS-CoV sequences; and this method was validated by use of 80 published SARS-CoV sequences. Subsequently, this new tool was applied to provide a better understanding of the entire complement of Taiwanese SARS-CoV isolates, including 20 previously published and 19 identified in this study. The epidemiological data were integrated with the results from the phylogenetic tree and from the nucleotide-signature pattern. RESULTS: The topologies of phylogenetic trees generated by the new and the conventional strategies were similar, with the former having better robustness than the latter, especially in comparison with the maximum-likelihood trees: the new strategy revealed that during 2003 there were 5 waves of epidemic SARS-CoV infection, which belonged to 3 phylogenetic clusters in Taiwan. CONCLUSIONS: The new strategy is more efficient than its conventional counterparts. The outbreaks of SARS in Taiwan originated from multiple sources.
Structural polymorphism of Methanothermobacter thermautotrophicus MCM.
The minichromosome maintenance (MCM) proteins are essential for replication initiation and elongation in eukarya and archaea. There are six MCM proteins in eukaryotes, and MCM complexes are believed to unwind DNA during chromosomal DNA replication. However, the mechanism and structure of the MCM complexes are not known. Only one MCM is found in the archaeon Methanothermobacter thermautotrophicus (mtMCM), and this provides a simpler system for study. The crystal structure of a mtMCM N-terminal fragment has been solved, but surprisingly only subtle structural changes were seen between the wild-type protein and one having a mutation corresponding to the yeast MCM5 bob1 mutation. The bob1 mutation bypasses the phosphorylation required for activation of MCM in yeast. We have used electron microscopy and three-dimensional reconstruction to examine a number of different fragments of mtMCM, and can visualize a large conformational change within the N-terminal fragment. This offers new insight into the conformational dynamics of MCM and the phosphorylation-bypass phenotype in yeast.
Protective effect of Mesona procumbens against tert-butyl hydroperoxide-induced acute hepatic damage in rats.
The protective effect of Hsian-tsao (Mesona procumbens Hemsl.) and its active compounds on liver damage was evaluated using the model of tert-butyl hydroperoxide (t-BHP)-induced acute hepatic damage in rats. Male Sprague-Dawley rats (200 +/- 10 g) were orally pretreated with a water extract of Hsian-tsao (WEHT) (0.1, 0.5, and 1.0 g/kg) or caffeic acid (0.1 g/kg of body weight) for 13 days before a single dose of t-BHP (0.2 mmol/kg, intraperitoneally) to each animal, and the rats were sacrificed 18 h later by decapitation; blood samples were collected for the assays of serum biochemical values. The livers were excised from the animals and assayed for oxidative injury, antioxidant enzyme, and pathological histology. The result showed that the oral pretreatment of WEHT (0.1, 0.5, and 1.0 g/kg) or caffeic acid (0.10 g/kg) before t-BHP (0.2 mmol/kg) treatment significantly lowered the serum levels of the hepatic enzyme markers (alanine aminotransferase, aspartate aminotransferase, and lactate dehydrogenase) and reduced oxidative stress of the liver by evaluation of malondialdehyde, glutathione, 8-hydroxy-2'-deoxyguanosine, glutathione peroxidase, and glutathione reductase. The histopathological evaluation of the rat livers showed that WEHT and caffeic acid reduced the incidence of liver lesions including cloudy swelling, pyknosis, and cytolysis induced by t-BHP in rats. On the basis of the results of this study, it can be speculated that M. procumbens protects liver against t-BHP-induced hepatic damage in rats.
The stalk region of dynamin drives the constriction of dynamin tubes.
The GTPase dynamin is essential for numerous vesiculation events including clathrin-mediated endocytosis. Upon GTP hydrolysis, dynamin constricts a lipid bilayer. Previously, a three-dimensional structure of mutant dynamin in the constricted state was determined by helical reconstruction methods. We solved the nonconstricted state by a single-particle approach and show that the stalk region of dynamin undergoes a large conformational change that drives tube constriction.
Zinc enhancement of nonviral salivary gland transfection.
Gene transfer to exocrine glands, including the major salivary glands, presents an attractive method to deliver proteins for therapeutic applications. Previous efforts using nonviral gene delivery to these glands have resulted in limited success. In this report, zinc and other divalent transitions were coadministered with plasmid DNA in an effort to improve nonviral salivary gland transfection efficiency. The inclusion of zinc into plasmid DNA solutions resulted in a 20-fold enhancement in transgene expression without noticeable inflammation compared to a solution of plasmid DNA only. This observed enhancement in transgene expression was dependent upon the DNA dose and correlated with the accumulation of plasmid DNA by salivary gland tissues.
The hexameric ring structure of the Escherichia coli RuvB branch migration protein.
The RuvB protein is part of the homologous recombination machinery in prokaryotic cells. Many studies have shown that RuvB is organized into hexameric rings functioning as DNA pumps at Holliday junctions, using ATP hydrolysis to drive branch migration. Structures now exist for two RuvB proteins, as well as for several structurally homologous proteins, including the replication factor-C small subunit (RFCS). Two models for the possible hexameric organization of RuvB subunits have been proposed, based upon the hexameric structures of NSF and HslU, two AAA-ATPases involved in vesicle fusion and proteolysis, respectively. We have used electron microscopy to generate an improved three-dimensional reconstruction of the double hexamers formed by Escherichia coli RuvB on double-stranded DNA. We find that an atomic model of the hexameric RFCS provides a significantly better fit to the RuvB hexamer than do the models for RuvB generated from NSF and HslU. This suggests that there may be a highly conserved structure for many proteins involved in different aspects of DNA replication, recombination, transcription and repair.
Anatomical location of T2-3 sympathetic trunk and Kuntz nerve determined by transthoracic endoscopy.
OBJECT: Bilateral subaxillary transthoracic endoscopic sympathectomy (TES) is a popular procedure of upper thoracic sympathectomy. The anatomical locations of the T-2 and T-3 sympathetic trunks, as viewed under the endoscope, are varied in the rib head areas. In this study, the authors investigated the more visible anatomical locations of the T-2 and T-3 sympathetic trunks, the so-called nerves of Kuntz, and intercostal rami by performing transthoracic endoscopy. METHODS: Seventy patients with palmar hyperhidrosis undergoing bilateral TES (140 sides) via the anterior subaxillary approach were included in this study. The operative findings and video images of the T-2 and T-3 sympathetic trunks and ganglia were recorded and analyzed. The anatomical locations of the T-2 and T-3 sympathetic trunks along the horizontal axes of the rib heads were determined using a three-region system constructed by the authors. The area between the rib neck and the medial border of the rib head was equally divided into Region E (external half) and Region M (medial half). The area between the medial border of the rib head and the paravertebral ligament was defined as Region I. The incidence of the T-2 and T-3 sympathetic trunks found in Regions E, M, and I were 31.4 to 42.9%, 50 to 57.1%, and 7.1 to 11.4%, respectively, on the left side, and 24.3 to 34.3%, 57.1 to 65.7%, and 8.6 to 10%, respectively, on the right side. One right (1.4%) and six left (8.6%) Kuntz nerves originating from the T-3 sympathetic trunk were found in seven patients (10%). The intercostal ramus was found around the T-2 rib neck in 24 patients (34.3%), with 18 cases (25.7%) for each side. The intercostal ramus around the T-3 rib neck was found in 17 patients (24.3%): 12 (17.1%) on the right and nine (12.9%) on the left. CONCLUSIONS: These results indicate that approximately 90% of the T-2 or T-3 sympathetic trunks are located on the rib head. These findings may also be used to assist the surgeon in fluoroscopic guidance for locating the T-2 and T-3 sympathetic trunks during posterior percutaneous sympathectomy.