Publications by authors named "Yi-Hsien Chen"

35 Publications

Retropharyngeal abscess with descending necrotizing mediastinitis.

J Emerg Med 2012 Jul 20;43(1):114-5. Epub 2010 Jun 20.

Department of Emergency Medicine, Chi-Mei Medical Center, Yong Kang City, Tainan, Taiwan, R.O.C.

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http://dx.doi.org/10.1016/j.jemermed.2010.04.028DOI Listing
July 2012

A conserved mechanism for vertebrate mesoderm specification in urodele amphibians and mammals.

Dev Biol 2010 Jul 13;343(1-2):138-52. Epub 2010 Apr 13.

Institute of Genetics, Queens Medical Centre, University of Nottingham, NG7 2UH, UK.

Understanding how mesoderm is specified during development is a fundamental issue in biology, and it has been studied intensively in embryos from Xenopus. The gene regulatory network (GRN) for Xenopus is surprisingly complex and is not conserved in vertebrates, including mammals, which have single copies of the key genes Nodal and Mix. Why the Xenopus GRN should express multiple copies of Nodal and Mix genes is not known. To understand how these expanded gene families evolved, we investigated mesoderm specification in embryos from axolotls, representing urodele amphibians, since urodele embryology is basal to amphibians and was conserved during the evolution of amniotes, including mammals. We show that single copies of Nodal and Mix are required for mesoderm specification in axolotl embryos, suggesting the ancestral vertebrate state. Furthermore, we uncovered a novel genetic interaction in which Mix induces Brachyury expression, standing in contrast to the relationship of these molecules in Xenopus. However, we demonstrate that this functional relationship is conserved in mammals by showing that it is involved in the production of mesoderm from mouse embryonic stem cells. From our results, we produced an ancestral mesoderm (m)GRN, which we suggest is conserved in vertebrates. The results are discussed within the context of a theory in which the evolution of mechanisms governing early somatic development is constrained by the ancestral germ line-soma relationship, in which germ cells are produced by epigenesis.
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http://dx.doi.org/10.1016/j.ydbio.2010.04.002DOI Listing
July 2010

Rare presentations of hyperthyroidism--Basedow's paraplegia and pancytopenia.

Am J Emerg Med 2009 Feb;27(2):258.e1-2

Emergency Department, Chi-Mei Medical Center, Tainan, Yungkang 710, Taiwan.

Typical presentations of hyperthyroidism are palpitation, nervousness, tremor, malaise, and weight loss. Hyperthyroidism affects nearly every system in the body, and some patients may manifest neurologic or hematologic symptoms. Atypical presentations of hyperthyroidism often pose a great challenge in diagnosis and treatment. We report a case of Basedow's paraplegia and pancytopenia that was precipitated by hyperthyroidism. The unusual manifestations led to unnecessary examinations and delayed the treatment of hyperthyroidism. The classical symptoms of Basedow's paraplegia are subacute symmetric weakness of the lower extremities with areflexia and sparing sensation or sphincter involvement. Control of the hyperthyroidism mitigated the neurologic and hematologic complications and prevented unnecessary studies.
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http://dx.doi.org/10.1016/j.ajem.2008.06.038DOI Listing
February 2009

Cr:Forsterite-laser-based fiber-optic nonlinear endoscope with higher efficiencies.

Microsc Res Tech 2008 Aug;71(8):559-63

Department of Electrical Engineering and Graduate Institute of Electro-Optical Engineering, National Taiwan University, Taipei 10617, Taiwan, Republic of China.

We demonstrate a beam-scanning nonlinear light endoscope based on a flexible fiber bundle. Excited with a femtosecond Cr:Forsterite laser, the degradation in multiphoton multiharmonic excitation efficiency due to the pulse-broadening effect is significantly reduced without utilizing any external devices. The system resolution has been characterized to be 5.4 microm in the two-photon fluorescence endoscope, limited by the sampling theory. Finally, several image examples have been given.
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http://dx.doi.org/10.1002/jemt.20586DOI Listing
August 2008

Selenite-induced survival of HuH7 hepatoma cells involves activation of focal adhesion kinase-phosphatidylinositol 3-kinase-Akt pathway and Rac1.

J Biol Chem 2003 Oct 1;278(41):39615-24. Epub 2003 Aug 1.

Institute of Genetics, School of Life Sciences, National Yang-Ming University, Shih-Pai, Taipei 112, Taiwan, Republic of China.

Selenium has been shown to sustain the growth of selected human hepatocellular carcinoma cell lines under serum-free conditions, but the detailed mechanism remained undetermined. In the present study, the molecular mechanism(s) involving sodium selenite (Na2SO3, Se) as a survival agent were determined. Selenite not only protects HuH7 cells from serum deprivation-induced apoptosis, it also supports its long-term growth in sodium selenite (10(-7)m) supplemented serum-free medium. The anti-apoptotic effect correlates with activation of focal adhesion kinase and the phosphatidylinositol 3-kinase (PI3K)-Akt kinase pathway. Using HuH7 cells stably transfected with a constitutively active Akt kinase and PI3K inhibitor LY294002, selenite-induced cell survival was shown to be PI3K-Akt-dependent. Parallel changes included a significant reduction in the intracellular reactive oxygen species content, the reversal of DNA fragmentation, and the suppression of caspase and apoptosis signal-regulating kinase 1 activities. HuH7 cells stably expressing a Rac1 mutant N17 (Rac1N17-HuH7) are refractory to selenite treatment. In these cells selenite supplement neither triggers Akt activation nor supports cell proliferation. Participation of Rac1 activation in this event is supported by the fact that selenite treatment drastically enhanced activation of Rac1. The exact link between selenite treatment, Rac1 activation, and activation of the focal adhesion kinase-PI 3-kinase, however, remains to be characterized. The mitogenic signaling mediated by selenite may involve unconventional growth stimuli including higher glutathione peroxidase 1 activity and higher transcription levels of selenoprotein P. The selenium-HuH7 system we have established thus provides a unique tool that will allow the biological role of selenite in growth regulation of hepatocytes to be studied in detail.
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http://dx.doi.org/10.1074/jbc.M304095200DOI Listing
October 2003
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