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Biomedical subjects

T H Huang

Publications and source records attributed to T H Huang.

At least 37 records · Page 2Linked to original sources
PubMed2000

Hypermethylation of ribosomal DNA in human breast carcinoma.

We examined the methylation status of the transcribed domain of ribosomal DNA (rDNA) in 58 patients with breast cancer. The mean percent of methylation was significantly higher in breast tumours than that of normal control samples (P < 0.0001). This increased rDNA methylation was associated with oestrogen receptor non-expression (P < 0.0273) and with moderately or poorly differentiated tumours as compared to well differentiated tumours (P < 0.0475). Our results suggest that rDNA can be a useful marker for monitoring aberrant methylation during breast tumour progression.

Adult↗
PubMed2000

Lactate dehydrogenase leakage of hepatocytes with AH26 and AH Plus sealer treatments.

Numerous root canals filling materials are available in the field of dentistry, based on various formulas that contain a variety of different and partly mutagenic components, such as epoxy resin sealers, Ca(OH)2-based materials, and zinc oxide-eugenol cements. AH Plus root canal sealer will not release formaldehyde according to the manufacturer, although AH26 does. The purpose of this study was to analyze the leakage of lactate dehydrogenase (LDH) from rat hepatocytes after treatment with AH26 and AH Plus root canal sealers in vitro. Hepatocytes from male Sprague-Dawley rats were used to test the cytotoxicity of AH26 and AH Plus. The root canal sealers were mixed and then dissolved in the dimethyl sulfoxide to final concentrations of 0.01%, 0.04%, and 0.1% (wt/vol), with a dimethyl sulfoxide concentration of < 0.05%. Dosage-dependent and time-dependent lactate dehydrogenase leakage values were measured and tested by one-way ANOVA. The results showed that both AH26 and AH Plus are toxic to rat hepatocytes. At a low concentration, AH26 had a higher toxicity than AH Plus to rat hepatocytes.

Analysis of Variance↗
PubMed2000

CpG island arrays: an application toward deciphering epigenetic signatures of breast cancer.

CpG island hypermethylation is a frequent epigenetic event in cancer. We have recently developed an array-based method, called differential methylation hybridization (DMH), allowing for a genome-wide screening of CpG island hypermethylation in breast cancer cell lines (T. H-M. Huang et al., Hum. Mol. Genet., 8: 459-470, 1999). In the present study, DMH was applied to screen 28 paired primary breast tumor and normal samples and to determine whether patterns of specific epigenetic alterations correlate with pathological parameters in the patients analyzed. Amplicons, representing a pool of methylated CpG DNA derived from these samples, were used as hybridization probes in an array panel containing 1104 CpG island tags. Close to 9% of these tags exhibited extensive hypermethylation in the majority of breast tumors relative to their normal controls, whereas others had little or no detectable changes. Pattern analysis in a subset of CpG island tags revealed that CpG island hypermethylation is associated with histological grades of breast tumors. Poorly differentiated tumors appeared to exhibit more hypermethylated CpG islands than their moderately or well-differentiated counterparts (P = 0.041). This early finding lays the groundwork for a population-based DMH study and demonstrates the need to develop a database for examining large-scale methylation data and for associating specific epigenetic signatures with clinical parameters in breast cancer.

Adult↗
PubMed1999

Manipulating the amyloid-beta aggregation pathway with chemical chaperones.

Amyloid-beta (Abeta) assembly into fibrillar structures is a defining characteristic of Alzheimer's disease that is initiated by a conformational transition from random coil to beta-sheet and a nucleation-dependent aggregation process. We have investigated the role of organic osmolytes as chemical chaperones in the amyloid pathway using glycerol to mimic the effects of naturally occurring molecules. Osmolytes such as the naturally occurring trimethylamine N-oxide and glycerol correct folding defects by preferentially hydrating partially denatured proteins and entropically stabilize native conformations and polymeric states. Trimethylamine N-oxide and glycerol were found to rapidly accelerate the Abeta random coil-to-beta-sheet conformational change necessary for fiber formation. This was accompanied by an immediate conversion of amorphous unstructured aggregates into uniform globular and possibly nucleating structures. Osmolyte-facilitated changes in Abeta hydration also affected the final stages of amyloid formation and mediated transition from the protofibrils to mature fibers that are observed in vivo. These findings suggest that hydration forces can be used to control fibril assembly and may have implications for the accumulation of Abeta within intracellular compartments such as the endoplasmic reticulum and in vitro modeling of the amyloid pathway.

Alzheimer Disease↗
PubMed1999

Loss of heterozygosity of p53 gene of oral cancer detected by exfoliative cytology.

The p53 tumor suppressor gene is a 16-20-kb section of cellular DNA located on the short arm of human chromosome 17 at position 17 P 13.1. Allelic deletions and/or point mutations in p53 gene are now known to be associated with the development of carcinogenesis. A hallmark of p53 is that both alleles are generally altered during transformation, which usually represents a loss of heterozygosity (LOH). In this study 30 normal dental students and 22 oral cancer patients were collected from the affiliated hospital of Chung Shan Medical and Dental College, Taichung, Taiwan. Extractions of DNA from the buccal mucosa or cancer surface were sampled by cytology brush. The two polymorphic restriction sites exon 4 and intron 6 within the p53 gene were amplified with polymerase chain reactions followed by restriction fragment length polymorphism assay. In heterozygous individuals, 66% of oral cancers demonstrated loss of p53 gene heterozygosity at the exon 4 site, and 50% showed LOH at the intron 6 site. These results indicate that inactivation of p53 gene is associated with development and/or progression of oral cancer. The essential advantages of oral exfoliative cytology are the non-invasiveness, painlessness, rapidity, ease and cost-effectiveness of cell sampling and DNA extraction. Furthermore, this experimental assay might be useful for preliminary screening of carcinogenesis in human beings.

Carcinoma, Squamous Cell↗
PubMed1999

Hypermethylation of the Wilms' tumor suppressor gene CpG island in human breast carcinomas.

CpG island hypermethylation is known to be associated with transcriptional silencing of tumor suppressor genes in neoplasia. We have previously detected aberrantly methylated sites in the first intron of the Wilms' tumor suppressor (WT1) gene in breast cancer. In the present study, we extended the investigation to a CpG island located in the promoter and first exon regions of WT1. Methylation of this CpG island was found to be extensive in MCF-7 and MDA-MB-231 breast cancer cells, as well as in 25% (five of 20 patients) of primary breast tumors. While levels of the known 3.0-kb WT1 mRNAs were decreased or not detected in these cell lines, the expression could be partially restored following treatment with a demethylation agent, 5-aza-2'-deoxycytidine. Surprisingly, a novel 2.5-kb WT1 transcript was expressed at high levels in both untreated and treated MDA-MB-231 cells. This novel transcript was likely a WT1 variant missing the first exon, and therefore escaped the methylation control present in the normal transcript. Our study implicates the future need to investigate the significance of this aberrant transcript as well as the role of WT1 CpG island hypermethylation in breast neoplasia.

Breast Neoplasms↗
PubMed1999

A simple splinting method for correction of supple congenital clasped thumbs in infants.

A splint has been designed to correct the congenital clasped thumb. It is like a short opponens splint that can keep the thumb in a position of abduction and extension without limiting wrist movement. The application of the splint was easy and adjustment for fit could be made at each visit if necessary. The device has been used in 11 infant patients (17 thumbs) with congenital clasped thumb of the supple type. The functional results were excellent in 15 of 17 thumbs, and the other two were good according to the grading system of Weckesser et al. (1968).

Female↗
PubMed1999

Methylation profiling of CpG islands in human breast cancer cells.

CpG island hypermethylation is known to be associated with gene silencing in cancer. This epigenetic event is generally accepted as a stochastic process in tumor cells resulting from aberrant DNA methyltransferase (DNA-MTase) activities. Specific patterns of CpG island methylation could result from clonal selection of cells having growth advantages due to silencing of associated tumor suppressor genes. Alternatively, methylation patterns may be determined by other, as yet unidentified factors. To explore further the underlying mechanisms, we developed a novel array-based method, called differential methylation hybridization (DMH), which allows a genome-wide screening of hypermethylated CpG islands in tumor cells. DMH was used to determine the methylation status of >276 CpG island loci in a group of breast cancer cell lines. Between 5 and 14% of these loci were hypermethylated extensively in these cells relative to a normal control. Pattern analysis of 30 positive loci by Southern hybridization indicated that CpG islands might differ in their susceptibility to hypermethylation. Loci exhibiting pre-existing methylation in normal controls were more susceptible to de novo methylation in these cancer cells than loci without this condition. In addition, these cell lines exhibited different intrinsic abilities to methylate CpG islands not directly associated with methyltransferase activities. Our study provides evidence that, aside from random DNA-MTase action, additional cellular factors exist that govern aberrant methylation in breast cancer cells.

Base Sequence↗
PubMed1999

A reliable technique of nuclear transplantation for immature mammalian oocytes.

Transplanting a germinal vesicle (GV) to another enucleated oocyte provides a possible way to avoid age-related aneuploidy in metaphase II (MII) oocytes from older women. This study was conducted to examine the efficiency of each step of nuclear transplantation as reflected in the survival and maturation capacity of immature mouse oocytes subjected to this procedure. GV stage oocytes were retrieved from unstimulated ovaries. A GV removed with a small amount of cytoplasm (karyoplast) was transferred subzonally into a previously enucleated oocyte, which was then exposed to direct current to promote fusion. Such reconstituted oocytes were placed in culture to allow maturation, and some that had extruded a first polar body were fixed and processed for chromosome analysis. Each step of nuclear transplantation - survival, enucleation, grafting, and reconstitution - was successful in >90%, with the overall efficiency of reconstitution being 80%. The observation of normal karyotypes confirmed that the procedure did not increase chromosomal aneuploidy. An electrolytic medium, revealed to be superior for the reconstitution procedure, also allowed haploidization of the transplanted nucleus. These findings suggest that this technique can be applied to study the effects of a 'younger' woman's ooplasm on the disjunction of an 'older' woman's chromosomes during meiosis I.

Aneuploidy↗
PubMed1998

The solution structure of a cytotoxic ribonuclease from the oocytes of Rana catesbeiana (bullfrog).

RC-RNase is a pyrimidine-guanine sequence-specific ribonuclease and a lectin possessing potent cell cytotoxicity. It was isolated from the oocytes of Rana catesbeiana (bull frog). From analysis of an extensive set of 1H homonuclear 2D NMR spectra we have completed the resonance assignments. Determination of the three-dimensional structure was carried out with the program X-PLOR using a total of 951 restraints including 814 NMR-derived distances, 61 torsion angles, and 76 hydrogen bond restraints. In the resultant family of 15 best structures, selected from a total of 150 calculated structures, the root-mean-square deviation from the average structure for the backbone heavy-atoms involved in well-defined secondary structure is 0.48 A, while that for all backbone heavy-atoms is 0.91 A. The structure of RC-RNase consists of three alpha-helices and two triple-stranded anti-parallel beta-sheets and folds in a kidney-shape, very similar to the X-ray crystal structure of a homolo gous protein, onconase isolated from Rana pipiens. We have also investigated the interaction between RC-RNase and two inhibitors, cytidylyl(2'-->5')guanosine (2',5'-CpG) and 2'-deoxycytidylyl(3'-->5')-2'-deoxyguanosine (3',5'-dCpdG). Based on the ligand-induced chemical shift changes in RC-RNase and the NOE cross-peaks between RC-RNase and the inhibitors, the key residues involved in protein-inhibitor interaction have been identified. The inhibitors were found to bind in a "retro-binding" mode, with the guanine base bonded to the B1 subsite. The His103 residue was found to occupy the B state with the imidazole ring pointing away from the active site. The structure coordinates and the NMR restraints have been deposited in the Brookhaven Protein Data Bank (1bc4 and 1bc4mr, respectively).

Amphibian Proteins↗
PubMed1998

pH measurement of root canal sealers.

The purpose of this study was to compare the surface pH level of three different type sealers after mixing at various time intervals in vitro. The cements were mixed according to the manufacturer's instructions. They were incubated to set in 100% humidity at 37 degrees C for 1 h, 24 h, 5 days, 8 days, 2 wk, 3 wk, 4 wk, 5 wk, and 7 wk. pH was calculated by a Twin pH meter. The pH levels of the three sealers were different at various time intervals (p < 0.0001). The resin-based cement had a acid pH level (pH < 7.0). The calcium hydroxide-based cement showed a higher alkalinity pH level (pH > 7.0). The zinc oxide-eugenol-based cement showed a similar pH level to the calcium hydroxide cement at the end of the measurement. We postulated that, in endodontic therapy when those healing is needed, the alkaline-based sealer is the choice.

Analysis of Variance↗
PubMed1998

Multinuclear NMR resonance assignments and the secondary structure of Escherichia coli thioesterase/protease I: a member of a new subclass of lipolytic enzymes.

Escherichia coli thioesterase/protease I is a 183 amino acid protein with a molecular mass of 20,500. This protein belongs to a new subclass of lipolytic enzymes of the serine protease superfamily, but with a new GDSLS consensus motif, of which no structure has yet been determined. The protein forms a tetramer at pH values above 6.5 and exists as a monomer at lower pH values. Both monomer and tetramer are catalytically active. From analysis of a set of heteronuclear multidimensional NMR spectra with uniform and specific amino acid labeled protein samples, we have obtained near-complete resonance assignments of the backbone 1H, 13C and 15N nuclei (BMRB databank accession number 4060). The secondary structure of E. coli thioesterase/protease I was further deduced from the consensus chemical shift indices, backbone short- and medium-range NOEs, and amide proton exchange rates. The protein was found to consist of four beta-strands and seven alpha-helices, arranged in alternate order. The four beta-strands were shown to form a parallel beta-sheet. The topological arrangement of the beta-strands of -1x, +2x, +1x appears to resemble that of the core region of the alpha beta hydrolase superfamily, typically found in common lipases and esterases. However, substantial differences, such as the number of beta-strands and the location of the catalytic triad residues, make it difficult to give a definitive classification of the structure of E. coli thioesterase/protease I at present.

Amino Acid Sequence↗
PubMed1998

Anti-idiotype antibody directly interferes with glomerular IgA immune complex deposition.

Data from both animal and clinical studies suggest that anti-idiotype antibodies deposited in glomeruli may be involved in the pathogenesis of glomerulonephritis. This study was conducted to examine the role of a hybridoma-AB1-2-derived IgG anti-T15 idiotype (IgG anti-T15) in the immunopathogenesis of a short-term experimental IgA nephropathy. BALB/c mice (12/group) were administered intravenously with: (1) an equal mass (1 mg) of T15-hybridoma-derived IgA antiphosphorylcholine (PC) and PC-conjugated bovine serum albumin (BSA-PC) antigen; (2) 1 mg of IgA anti-PC, 1 mg of BSA-PC antigen, and 3 mg of IgG anti-T15, or (3) 1 mg of BSA-PC antigen alone. The mice were sacrificed 6 h after the injection. A 6-hour clearance study was performed. The initial phase of elimination of BSA-PC antigen in mice receiving IgA anti-PC/BSA-PC/IgG anti-T15 or those receiving the antigen alone was significantly faster than that in those receiving IgA anti-PC/BSA-PC (p < 0.001). There was no significant difference in the elimination rate of BSA-PC antigen between mice receiving IgA anti-PC/BSA-PC/IgG anti-T15 and those receiving BSA-PC antigen alone. The late phases of elimination of the BSA-PC antigen in mice receiving IgA anti-PC/BSA-PC/IgG anti-T15 showed somewhat similar to those of BSA-PC antigen in mice receiving IgA anti-PC/BSA-PC. Moreover, mice injected with IgA anti-PC/BSA-PC/IgG anti-T15 showed a significantly less glomerular BSA-PC antigen deposition than those injected with IgA anti-PC/BSA-PC (positive control), as demonstrated by light microscopy, autoradiography, and immunohistochemistry (each p < 0.001). It is inferred that the injected IgG anti-T15 could react with the IgA anti-PC in vivo, directly interfering with immune complex formation by the IgA anti-PC and BSA-PC antigen, thereby resulting in diminished glomerular deposition of the BSA-PC antigen. These findings suggest that an anti-idiotype antibody may be protective in the immunopathogenesis of IgA nephropathy, because of its inhibitory effect on glomerular trapping of an antigen.

Animals↗
PubMed1998

[Synthesis of multifunctional surfactants for elaboration of micellar model systems of enzymes].

In order to provide a closer analogy between micelles and enzymes, the design of functionalized micellar systems have been undertaken. This paper presents the synthesis of surfactant cationic molecules which contains either a free or a protected aldehyde group. An ammonium quaternary surfactant with two functional groups, aldehyde dimethyl acetal and imidazole, has also been synthesized.

Chymotrypsin↗