Biomedical subjects

D Hsieh

Publications and source records attributed to D Hsieh.

10 recordsLinked to original sources

PubMed2006

Complete d-band dispersion relation in sodium cobaltates.

We utilize fine-tuned polarization selection coupled with excitation-energy variation of photoelectron signal to image the complete d-band dispersion relation in sodium cobaltates. A hybridization gap anticrossing is observed along the Brillouin zone corner and the full quasiparticle band is found to emerge as a many-body entity lacking a pure orbital polarization. At low dopings, the quasiparticle bandwidth (Fermion scale, many-body E(F) approximately 0.25 eV) is found to be smaller than most known oxide metals. The low-lying density of states is found to be in agreement with bulk-sensitive thermodynamic measurements for nonmagnetic dopings where the 2D Luttinger theorem is also observed to be satisfied.

Journal Article↗

PubMed2006

Low-lying quasiparticle states and hidden collective charge instabilities in parent cobaltate superconductors.

We report a state-of-the-art photoemission (angle-resolved photoemission spectroscopy) study of high quality single crystals of NaxCoO2 the series focusing on the fine details of the low-energy states. The Fermi velocity is found to be small (<0.5 eV A) and only weakly anisotropic over the Fermi surface at all dopings, setting the size of the pair wave function to be on the order of 10-20 nm. In the low-doping regime, the exchange interlayer splitting vanishes and two-dimensional collective instabilities such as 120 degrees -type fluctuations become kinematically allowed. Our results suggest that the unusually small Fermi velocity and the unique symmetry of kinematic instabilities distinguish cobaltates from most other oxide superconductors.

Journal Article↗

PubMed2006

Quasiparticle dynamics in the vicinity of metal-insulator phase transition in NaxCoO2.

Layered cobaltates embody novel realizations of correlated matter on a spin-1/2 triangular lattice. We report a high-resolution systematic photoemission study of the insulating cobaltates. The observation of a single-particle gap opening and band folding provides direct evidence of anisotropic particle-hole instability on the Fermi surface due to its unique topology. Overlap of the measured Fermi surface is observed with the square root 3xsquare root 3 charge-order Brillouin zone near x=1/3 but not at x=1/2 where the insulating transition is actually observed. Unlike conventional density waves, charge stripes, or band insulators, the onset of the gap depends on the quasiparticle's quantum coherence which is found to occur well below the disorder-order symmetry breaking temperature of the crystal (the first known example of its kind).

Journal Article↗

PubMed2001

Development and deployment of a web-based physician order entry system.

The computer-based Physician Order Entry System (POES) has been employed in many clinical institutes in Taiwan. Most of the POES systems are developed in the two-tier client-server architecture, and a large portion of the systems are constructed on a mainframe or even a single PC. The exponential growth of the Internet has had a tremendous impact on our society in recent years. In consideration of the future user interface and system architecture, we have developed a three-tier web-based Physician Order Entry System and successfully deployed it in the Wang-Fang Hospital in Taipei. The system is the first POES based on three-tier and World Wide Web (WWW) in Taiwan. The system provides the Subjective, Objective, Assessment, and Plan (SOAP) structure for the physician to enter subject, object, diagnoses, medicine dosage, treatment and laboratory test request, and prints out the prescription and necessary document. The doctor can also retrieve the patient's medical record on the system. One of the special characteristics of the system is its personalized design. The doctor can define their own diagnosis, medicine and treatment database and any combination of these to facilitate their clinical work. The system has been reviewed since February 1999. The result shows that the clinical procedure has become more efficient, and the chances of omission have been reduced. The system is very stable and the Open Database Connectivity (ODBC) database access did not show any delay in the network. Since we have incorporated many new web-programming techniques, the progress of the techniques will improve the system performance in the future.

Computer Systems↗

PubMed2000

The estrogen replacement therapy of the Women's Health Initiative promotes the cellular mechanisms of memory and neuronal survival in neurons vulnerable to Alzheimer's disease.

OBJECTIVES: The current study investigated the neurotrophic and neuroprotective action of the complex formulation of conjugated equine estrogens (CEEs), the most frequently prescribed estrogen replacement therapy in the United States and the estrogen replacement therapy of the Women's Health Initiative. METHODS: Videomicroscopic, morphologic and biochemical analyses were conducted in primary cultures of hippocampal neurons to determine the neurotrophic and neuroprotective properties of CEEs. RESULTS: Results of these analyses demonstrated that CEEs significantly increased hippocampal neuronal outgrowth, a cellular marker of memory formation. Dose response analyses indicated that the lowest effective concentration of CEEs exerted the maximal neurotrophic effect. Results of neuroprotection studies demonstrated that CEES induced highly significant neuroprotection against beta amyloid(25-35), hydrogen peroxide and glutamate-induced toxicity. CONCLUSIONS: CEEs induced cellular markers of memory function in neurons critical to memory and vulnerable to negative effects of aging and Alzheimer's disease. In addition, CEEs significantly and potently protected neurons against toxic insults associated with Alzheimer's disease. Because CEEs are the estrogen replacement therapy of the Women's Health Initiative, results of the current study could provide cellular mechanisms for effects of CEEs on cognitive function and risk of Alzheimer's disease derived from this prospective clinical trial.

Alzheimer Disease↗

PubMed1994

Association of the catalytic subunit of aspartate transcarbamoylase with a zinc-containing polypeptide fragment of the regulatory chain leads to increases in thermal stability.

The regulatory enzyme aspartate transcarbamoylase (ATCase), comprising 2 catalytic (C) trimers and 3 regulatory (R) dimers, owes its stability to the manifold interchain interactions among the 12 polypeptide chains. With the availability of a recombinant 70-amino acid zinc-containing polypeptide fragment of the regulatory chain of ATCase, it has become possible to analyze directly the interaction between catalytic and regulatory chains in a complex of simpler structure independent of other interactions such as those between the 2 C trimers, which also contribute to the stability of the holoenzyme. Also, the effect of the interaction between the polypeptide, termed the zinc domain, and the C trimer on the thermal stability and other properties can be measured directly. Differential scanning microcalorimetry experiments demonstrated that the binding of the zinc domain to the C trimer leads to a complex of markedly increased thermal stability. This was shown with a series of mutant forms of the C trimer, which themselves varied greatly in their temperature of denaturation due to single amino acid replacements. With some C trimers, for which tm varied over a range of 30 degrees C due to diverse amino acid substitutions, the elevation of tm resulting from the interaction with the zinc domain was as large as 18 degrees C. The values of tm for a variety of complexes of mutant C trimers and the wild-type zinc domain were similar to those observed when the holoenzymes containing the mutant C trimers were subjected to heat denaturation.(ABSTRACT TRUNCATED AT 250 WORDS)

Aspartate Carbamoyltransferase↗

PubMed1980

Bovine peripheral nervous system myelin P2 protein: chemical and immunological characterization of the cyanogen bromide peptides.

Cleavage of bovine P2 protein by cyanogen bromide (CNBr) produced peptide fractions CN1, CN2, and CN3 which were isolated by gel filtration chromatography. CN2 was found to contain two NH2-terminals (lysine and valine) and accounted for both of the cysteine residues of P2. When reduced carboxymethylated P2 (RCM-P2) was digested with CNBr, peptides CN1 and CN3 were obtained as were (1) a peptide with NH2-terminal lysine (Lys) that contained no homoserine and only one cysteine residue and (2) a peptide with NH2-terminal valine (Val) that was co-eluted with CN3. These data and the chemical characterization of all the CNBr peptides obtained from P2 and RCM-P2 suggest that isolated P2 protein has a structure composed of the CNBr peptides in the order CN3-CN1-CN2(Val)-CN2(Lys) with an intrachain disulfide bond between the cysteine residues located in the two constituent peptides of CN2, CN2(Lys) and CN2(Val). To locate the neuritogenic region(s) within the P2 protein structure, CN1, CN2, and CN3 were tested for the ability to induced experimental allergic neuritis (EAN) in Lewis rats. The disease-inducing sites of P2 protein were found only in CN1; neither CN2 nor CN3 produced disease. EAN induced by CN1 was comparable to that induced with P2 protein as determined by disease onset, clinical symptoms, and histologic lesions.

Amino Acids↗

PubMed1973

Automatic screening of biological specimens by optical correlation.

An optical analog correlation technique was used to detect morphologic abnormalities in rat liver cells. The method employs an optical matched filter for correlating a test pathological specimen with a control specimen. Experimental results show appreciable promise that such an optical correlator can be employed as a tool for rapid mass screening of a variety of pathological specimens.

Animals↗

PubMedDate not supplied

Aflatoxin content of foods served to a population with a high incidence of hepatocellular carcinoma.

During three seasons, 36 samples of foods served to mentally retarded clients with a high incidence of hepatocellular carcinoma were analyzed for aflatoxin. Aflatoxin was not detected (less than 5 ppb) by thin-layer liquid chromatography in 35 food samples containing peanuts, corn, wheat or milk. One peanut butter sample contained 20 ppb aflatoxin. Aflatoxin content of these foods was at or below the level permitted by the Food and Drug Administration. Aflatoxin is probably not responsible for liver disease in this population.

Aflatoxins↗

PubMedDate not supplied

The women's health initiative estrogen replacement therapy is neurotrophic and neuroprotective.

The current study investigated the neurotrophic and neuroprotective action of the complex formulation of conjugated equine estrogens (CEEs), the most frequently prescribed estrogen replacement therapy in the United States and the estrogen replacement therapy of the Women's Health Initiative. Morphologic analyses demonstrated that CEEs significantly increased neuronal outgrowth in hippocampal, basal forebrain, occipital, parietal and frontal cortex neurons. Dose-response analyses indicated that the lowest effective concentration of CEEs exerted the maximal neurotrophic effect with greatest potency occurring in hippocampal and occipital cortex neurons. CEES induced highly significant neuroprotection against beta amyloid(25-35), hydrogen peroxide and glutamate-induced toxicity. Rank order of potency and magnitude of CEE-induced neuroprotection in the brain regions investigated was hippocampal neurons > basal forebrain neurons > cortical neurons. In hippocampal neurons pre-exposed to beta amyloid(25-35), CEEs halted Abeta(25-35)-induced cell death and protected surviving neurons from further cell death induced by Abeta(25-35). Because CEEs are the estrogen replacement therapy of the Women's Health Initiative, results of the current study could provide cellular mechanisms for understanding effects of CEEs on cognitive function and risk of Alzheimer's disease derived from this prospective clinical trial.

Adenosine Triphosphate↗