Search PubMed⌕ Search

Biomedical subjects

D Huang

Publications and source records attributed to D Huang.

At least 145 records · Page 8Linked to original sources
PubMed1997

Pathophysiologic substrate for sustained ventricular tachycardia in coronary artery disease.

Sustained ventricular tachycardia (VT) in the presence of coronary artery disease (CAD) is almost always associated with prior infarction. Its mechanism is reentrant excitation and it can be initiated > 95% of the time. Disrupted and delayed endocardial activation and prolonged, fragmented electrograms recorded during sinus rhythm distinguish patients with VT from those with normal ventricles and those of prior infarction without VT. The extent of abnormalities of activation and number of abnormal, fragmented and late electrograms are greatest in patients with sustained VT. These abnormalities are associated with scar tissue separating the viable myocytes. Fragmented electrograms are due to discontinuous activation due to nonuniform anisotropy caused by the scar tissue. Patients with CAD demonstrate depressed excitability and prolonged relative refractory periods (ie, an upward shift in the strength-interval curve) at sites of infarction but effective refractory periods measured at 10 mA comparable to normals and dispersion of refractory periods. However the associated abnormalities of conduction and activation produce an abnormal dispersion of recovery. Intraoperative mapping of patients with CAD has shown that most of the abnormalities of endocardial activation and conduction are in the subendocardial layers and subendocardial resection of these areas cures VT and abolishes delayed, fragmented electrograms and split potentials and normalizes the electrograms recorded from the subjacent tissue. This supports the hypothesis that abnormalities of conduction are the critical pathophysiologic substrate of VT in CAD.

Arrhythmias, Cardiac↗
PubMed1997

[Comparison of defibrase and heparin in the prevention of thrombosis after coronary intervention].

To evaluate the effects of defibrase on thrombosis after coronary intervention. 12 dogs were randomized into group to be treated with defibrase (n = 6) and another group with heparin (n = 6) after coronary intervention. After implanting stents in coronary arteries, canine platelets labeled with 99mTc-hexamethyl propylene amine oxime were re-transfused into blood circulation. The stenting vessels were imaged with gamma-camera in vivo and in vitro at the 4th and 24th hour, then the relative radioactivity of stenting vessels was quantified. The isolated stenting vessels were weighted and measured with gamma-counter and the number of deposited platelets was calculated. The relative radioactivity and the number of deposited platelets were lower in the group of defibrase than in the group of heparin (P < 0.01). Compared with heparin, defibrase has more potent effect on the prevention of thrombus formation and may reduce the early-reocclusion after coronary intervention.

Angioplasty, Balloon, Coronary↗
PubMed1997

[Recurrent acoustic neuroma: report of 11 cases].

To improve the therapeutic effect of acoustic neuroma, 158 patients with acoustic neuroma treated in our hospital were retrospectively reviewed. Among them, 11 recurrent acoustic neuroma were found. The clinical analysis demonstrated that the recurrence of acoustic neuroma had close relationship with the size of the tumor, operative approach and extent of excision. All recurrent acoustic neuroma was large-sized when first operated. The more the tumor was excised, the lower the recurrent rate was. The recurrent rates were 19.4% for partial resection, 13.2% for near-total resection, 0% for total resection respectively. Retrolabyrinthine approach was more likely to recur than other approaches. The key to decrease recurrent rate was to excise as much tumor as possible. According to growth rate and double time of acoustic neuroma measured in this study, regular follow-up with CT or MRI at interval of 6 months was emphasized. X-knife was effective for early-diagnosed recurrent acoustic neuroma.

Adult↗
PubMed1997

Combined effect of noise and vibration on articulation of Chinese syllable.

To study combined effect of noise and vibration on articulation, changes of the speech features of Chinese single syllabic utterances were investigated under combined factors. The experiments were conducted under four conditions: combined noise and vibration, simple noise, simple vibration and control. A set of signal processing system was established, programs for speech signal analysis and statistics were developed. The results showed that, as compared with simple noise , simple vibration or control condition, the fundamental frequency, energy and duration of articulation under combined conditions increased significantly. It suggests that the effect of noise and vibration should be considered in the design of aerospace speech recognition system.

Aerospace Medicine↗
PubMed1996

Characterization and crystallization of the lumen side domain of the chloroplast Rieske iron-sulfur protein.

A soluble, 139-residue COOH-terminal polypeptide fragment of the Rieske iron-sulfur protein of the cytochrome b6f complex from spinach chloroplasts was obtained by limited proteolysis of the complex and a two-step chromatography purification protocol. The purified Rieske iron-sulfur protein fragment was characterized by: (i) a single NH2-terminal sequence, NH2-Phe-Val-Pro-Pro-Gly-Gly, starting with residue 41 of the intact Rieske protein; (ii) a single molecular weight species determined by mass spectrometry with a molecular weight of 14,620 +/- 2 without the [2Fe-2S] cluster; (iii) an optical absorbance spectrum with redox- and pH-dependent maxima and minima; and (iv) a reduced-oxidized optical difference spectrum characterized by DeltaepsilonmM = 3.8 mM-1 cm-1 for DeltaA at 394 versus 409 nm, which was used to determine the midpoint oxidation-reduction potential, which is +359 +/- 7 mV at 25 degrees C from pH 5.5-6.5, and +319 +/- 2 mV at pH 7, with an apparent pKox = 6.5 +/- 0.2 for the oxidized protein. The EPR spectrum measured at 17 K was characterized by the g values, gz = 2.03 and gy = 1.90, and a broad band centered at gx approximately 1.74, very similar or identical to those of the Rieske cluster in the b6f complex, implying that the environment of the [2Fe-2S] cluster is similar to that in the complex. Midpoint potential determination by low temperature EPR yielded a redox midpoint potential (Em) of +365-375 mV of the soluble Rieske fragment at pH 6 and 7 and an Em of +295-300 mV of the Rieske cluster in the cytochrome b6f complex at pH 6 and 7. The Em difference implies that the environment of the cluster in the soluble Rieske fragment is slightly more polar than that of the cluster in the intact complex. Single crystals of the Rieske polypeptide were obtained that are capable of x-ray diffraction to atomic resolution (<2.5 A), contain one molecule per asymmetric unit, a solvent content of approximately 30%, and belong to the triclinic space group P1 with cell dimensions, a = 29.1 A, b = 31.9 A, c = 35.8 A, alpha = 95.6 degrees, beta = 107.1 degrees, gamma = 117.3 degrees.

Amino Acid Sequence↗
PubMed1996

Markers on distal chromosome 2q linked to insulin-dependent diabetes mellitus.

Insulin-dependent diabetes mellitus (IDDM) is a multigenic autoimmune disease. An IDDM susceptibility gene was mapped to chromosome 2q34. This gene may act early in diabetogenesis, because "preclinical" individuals also showed linkage. Human leukocyte antigen (HLA)-disparate, but not HLA-identical, sibs showed linkage, which was even stronger in families with affected females. The genes encoding insulin-like growth factor-binding proteins 2 and 5 were mapped to a 4-megabase pair interval near this locus. These results indicate the existence of a gene that acts at an early stage in IDDM development, screening for which may identify a specific subset of at-risk individuals.

Alleles↗
PubMed1996

Complexometric determination of metal ions by microscopic diffusional titration.

Acid/base titrations of pico- and femtoliter microsamples have been performed previously using a diffusional microburet (DMB) for reagent delivery in a simple droplet-heptane system (Gratzl, M.; Yi, C. Anal. Chem. 1993, 65, 2085-2088). The lowest delivery rate achieved with a DMB was about 6 fmol/s, which would correspond to about a 1 microL/year volumetric flow rate with a hypothetical equivalent mechanical delivery scheme (Yi, C.; Gratzl, M. Anal. Chem. 1994, 66, 1976-1982). In this work, the feasibility of complexometric titrations in microscopic samples is explored. Stability of pH in the microdroplets required for different determinations and the effects of DMB shank geometry on titration characteristics are also studied. Diffusional microtitrations of Fe(III), Zn(II), and Cu(II) have been performed with EDTA. Xylenol orange and Eriochrome Black T provide clear color changes at the end point of the respective titrations, despite the microscopic size of the samples (between 16 and 1570 pL, corresponding to diameters between 30 and 144 microns). Random errors of the determinations relative to full scale were 6.6% for Fe(III), 5.8% for Cu(II), and 7.9% for Zn(II). The pH required for EDTA titrations of the individual metal ions stays stable in the acidic range. This makes the microscopic titration of a number of metal ions, such as Fe(III), Fe(II), Cu(II), and Pb(II), feasible in a simple droplet-heptane system without any modification. With a higher density of strongly alkaline buffer droplets (about 100 droplets/mm2) sprayed on the bottom of the Petri dish, or by flushing N2 above the heptane, the microscopic samples can also be kept alkaline despite ambient CO2 present. In this way, Zn(II) can also be titrated in microdroplets, requiring a pH around 10. This work renders it possible to perform a variety of complexometric titrations and other chemical manipulations in microdroplets even if they need to be kept alkaline. Similar titrations in single biological cells to assess intracellular buffer capacities of different metal ions, such as Ca(II) and Mg(II), are underway.

Diffusion↗
PubMed1996

Potential gastrointestinal tumor suppressor locus at the 3p14.2 FRA3B site identified by homozygous deletions in tumor cell lines.

A number of DNA fragments, identified by representational difference analysis, which were homozygously deleted in various cancer cell lines were previously mapped to human chromosomal arms. One of these, BE758-6, which was homozygously deleted in a number of colon carcinoma cell lines, had been mapped to chromosome region 3p. We have further localized the probe to 3p14.2, approximately 350kbp telomeric to the 3p14.2 break of the t(3;8) hereditary renal cell carcinoma chromosome translocation, within or near the 3p14.2 FRA3B, the most common human fragile site. We determined the sizes of the homozygous deletions in a number of cancer cell lines after isolation of a yeast artificial chromosome contig and development of STS markers which fall between D3S1234 and D2S1481, which flank the deletions. Homozygous deletions were observed and sized not only in the cell lines originally reported but also in a number of nasopharyngeal carcinoma cell lines and a gastric carcinoma cell line. About 50% of uncultured stomach and colon carcinomas were then shown to lose heterozygosity for alleles in the same region, with a common region of loss between the D3S1234 and D3S1481 markers. Thus, it is likely that the homozygous deletion observed in these cancer cell lines harbors an important tumor suppressor gene for several tumor types.

Base Sequence↗
PubMed1996

Morphological, biochemical, and genetic support for an apolipoprotein E effect on microtubular metabolism.

There are two distinct viewpoints on the association of the inheritance of apolipoprotein E (APOE) alleles and the age of onset distribution of Alzheimer's disease (AD): genetic and phenotypic expression. There have been multiple corroborations of the APOE-epsilon 4 association with Alzheimer's disease in populations around the world in clinic based studies as well as emerging epidemiological studies. The genetic data do not imply mechanism of pathogenesis. The phenotypic expression of AD has been based in theories based on amyloid plaques or neurofibrillary tangles. ApoE protein interacts with both beta-amyloid and tau in an isoform-specific manner. The interaction with tau had been thought to be an in vitro artifact, since apoE had not been previously localized to the neuronal cytoplasm. Immuno-EM studies have localized apoE in neuronal cytoplasm. ApoE3 interacts with both tau and MAP2c at the microtubule binding repeat domain under conditions in which apoE4 is less tightly bound. These data further support a hypothesis that apoE3 (and apoE2) protect the microtubule binding domain of tau from binding to itself to form paired helical filaments and neurofibrillary tangles, while protecting the site for microtubule stabilizing interactions with beta-tubulin. These data are supported by recent data from APOE knock-out mice demonstrating dendritic alterations leading to synaptic simplification similar to that observed in AD.

Age of Onset↗