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Biomedical subjects

H T Chang

Publications and source records attributed to H T Chang.

At least 55 records · Page 3Linked to original sources
PubMed1999

Molecular characterization of germline mutations in the BRCA1 and BRCA2 genes from breast cancer families in Taiwan.

A total of 18 families with multiple cases of breast cancer were identified from southern Taiwan, and 5 of these families were found to carry cancer-associated germline mutations in the BRCA1 and BRCA2 genes. One novel cryptic splicing mutation of the BRCA1 gene, found in two unrelated families, was shown to be a deletion of 10 bp near the branch site in intron 7. This mutation causes an insertion of 59 nucleotides derived from intron 7 and results in a frameshift, leading to premature translational termination of BRCA1 mRNA in exon 8. Deletions of 2670delC, 3073delT and 6696-7delTC in the BRCA2 gene were found in three other breast cancer families. All three deletions are predicted to generate frameshifts and to result in the premature termination of BRCA2 protein translation. Several genetic polymorphisms in both BRCA1 and BRCA2 genes were also detected in this investigation.

Adult↗
PubMed1999

Paired-associate learning in attention-deficit/hyperactivity disorder as a function of hyperactivity-impulsivity and oppositional defiant disorder.

A paired-associate learning (PAL) test was administered to 22 community volunteers without disruptive disorders and 197 children (7.5-13.5 years-old) presenting with the inattentive and combined subtypes of attention-deficit/hyperactivity disorder (ADHD) either in combination with or without oppositional defiant disorder (ODD). Participants were screened for learning disorders. In comparison to non-ADHD participants, children with ADHD achieved worse PAL and made errors rated as more acoustically and less semantically similar to the correct paired associates. These deficits were not related to hyperactivity-impulsivity or comorbid ODD. These results suggest that ADHD children are less competent at PAL and use less efficient learning strategies than their non-ADHD peers.

Adolescent↗
PubMed1999

Primary non-Hodgkin's lymphoma of the breast: breast conservation therapy in two patients.

We report two patients with primary non-Hodgkin's lymphoma of the breast who were treated with breast conservation therapy. These two patients were diagnosed with primary breast lymphoma by fine-needle aspiration cytology and underwent tumorectomy followed by adjuvant chemoradiation therapy. Follow-up studies showed that the two patients were free of disease for two and three years, respectively. To date, there exists no therapeutic standard for this disease and there is no survival advantage for patients who undergo radical mastectomy. Despite the rarity of lymphoma in the breast, a preoperative accurate diagnosis is essential so that unnecessary, extended breast ablation or delayed treatment is avoided. Cytologic diagnosis of breast lymphoma is an easy procedure and provides guidance for appropriate preoperative management. Early diagnosis combined with breast conservation therapy and systemic adjuvant therapy results in a favorable outcome for patients with breast lymphoma.

Adult↗
PubMed1999

Analysis of prognostic factors in Chinese women with breast cancer in southern Taiwan.

BACKGROUND: We conducted a retrospective review of all early-stage breast cancer patients treated at the Veterans General Hospital-Kaohsiung to determine overall and disease-free survival rates, and to evaluate prognostic factors for these outcomes. METHODS: During the period of October, 1990, to December, 1997, 332 patients with early-stage breast cancer were treated at our institution. Cox's multivariate regression analysis was used to select prognostic factors significant for overall survival and disease-free survival. RESULTS: The survival rate for breast cancer patients was 88.35% at five years. Prognostic factors predicting breast cancer mortality included poorly differentiated histologic grade, four or more lymph nodes positive for metastasis and negative progesterone-receptor status. For disease recurrence, prognostic factors included positive nodes, aneuploidy and poorly differentiated histologic grading. CONCLUSIONS: We conclude that a combination of lymph node status, DNA ploidy, histologic grading and progesterone-receptor status help to evaluate the possible outcomes for patients with breast cancer and to plan for optimal therapy.

Adult↗
PubMed1998

The band areas of proteins determined by fluorescent scanning in the commercial automated gel electrophoresis apparatus.

An automated gel electrophoresis apparatus, recently available commercially, allows one to follow the band during electrophoresis in real time, and lends itself therefore to an evaluation of bandwidth as a function of migration time (the dispersion coefficient), resolution and band shape. These determinations assume the constancy of band area with migration time and at various gel concentrations. The purpose of the present study was to verify these assumptions. Representative proteins and sodium dodecyl sulfate (SDS)-proteins, either natively fluorescent or fluorescein carboxylate labeled, were found to exhibit band areas which approach constancy as a function of migration time in both agarose and polyacrylamide gel electrophoresis, provided that (i) the protein concentration under the band was low enough to obviate self-quenching of fluorescence; (ii) the separation of the protein of interest from contaminants had progressed sufficiently during the time at which band areas were measured; (iii) the baseline under the peak was sufficiently well defined. However, band areas decrease with increasing gel concentration. Protein peaks exhibited leading and trailing tails. The ratio of the combined tail area to total area appeared to be near-constant at varying migration times. However, that ratio increases with increasing gel concentration. The tail area does not appear to be an artifact of fluorometric detection since it is reproduced upon fluorimetric analysis of the protein eluted from gel slices after electrophoresis. However, it may be due to photochemical destruction under the conditions of repetitive fluorometric peak detection.

Adsorption↗
PubMed1998

Capillary electrophoretic separation of 1 to 10 kbp sized dsDNA using poly(ethylene oxide) solutions in the presence of electroosmotic counterflow.

DNA fragments of 1 to 10 kbp in length were separated by capillary electrophoresis (CE), using poly(ethylene oxide) (PEO) solutions in the presence of electroosmotic flow. The technique requires filling the capillary with the polymer solution by means of electroosmotic flow (EOF). Separation times of 6-7 min in PEO solutions ranging from 0.3 to 8 x 10(6) Mr at 375 V/cm were sufficient to separate the 11 components of the dsDNA ladder (0.5 to 10 kbp) by size. The migration behavior of the double-stranded (ds)DNA fragments, interpreted by "Ferguson plot analysis", in the system is indistinguishable from that previously reported for capillary zone electrophoresis (CZE) in a polyacrylamide solution without EOF. Potential advantages of conducting CZE using polymer solutions in the presence of EOF are: (i) Possibility of long migration times on short columns; (ii) possibility of introducing relatively viscous, high Mr polymer solutions into narrow capillaries; (iii) possibility of establishing polymer concentration gradients in capillaries; (iv) possibility of concentrating the starting zone by balancing electrophoretic migration and electroosmotic transport.

DNA↗
PubMed1998

APACHE II score: a useful tool for risk assessment and an aid to decision-making in emergency operation for bleeding gastric ulcer.

BACKGROUND: Operating for bleeding gastric ulcer remains controversial. Gastric resection bears a higher surgical risk while limited operation may result in more postoperative hemorrhage. There has been little discussion of effective risk assessment of patients. The aim of this study is to define surgical risk by using the APACHE II scoring system, and to determine optimal management. STUDY DESIGN: Records from October 1990 to December 1996 were retrospectively reviewed for patients (n=101) with bleeding gastric ulcer who had undergone emergency operation after failed endoscopic therapy. Mortality rates were examined according to different APACHE II scores, and the surgical risk was defined. From January 1997 to December 1997, 35 consecutive patients were enrolled for prospective study. Partial gastric resection (PGR) was performed for patients with huge ulcers (>2 cm) and for low-risk patients with ulcers at the antrum or angularis, while limited operation (oversewing or excision of bleeding ulcer) was reserved for others. The results were compared with the retrospective study. RESULTS: In the retrospective study, the mortality rates for the group with a score < 15 and > or = 15 were 5% (3 of 63) and 58% (22 of 38), respectively (p < 0.05). In the group with a score < 15, PGR was performed on 27 patients, and one died. For those patients with a score > or = 15, PGR carried a lower mortality than limited operation, although this was not statistically significant (47% vs 65%). Limited operation resulted in an overall rate of 22% postoperative hemorrhage and 12% reoperation rate, in which all patients with a score > or = 15 died. In the prospective study, the mortality rates in those scoring <15 and > or = 15 were 6% and 50%, respectively. This is not significantly different than the retrospective study. However, the rate of postoperative hemorrhage was diminished (5%). CONCLUSIONS: APACHE II score is a useful tool for assessing risk in patients with bleeding gastric ulcer. The mortality is minimal in those with a score <15, and PGR can be performed with low risk. Although high-risk patients have dreadful outcomes, limited operation cannot improve them if postoperative hemorrhage occurs. Decision making in emergency operation for such patients should be based on the ulcer conditions and the patient's hemodynamic status.

APACHE↗
PubMed1998

Ocular metastases from breast carcinoma: a report of two cases.

Breast carcinoma metastases to the eye occur more frequently than is clinically recognized. The prevalence of this lesion is not appreciated because of the dominant clinical picture of metastases occurring in other organs or because a number of eye lesions are small and asymptomatic. With the increasing length of survival, more breast cancer patients will require care for ocular metastases. A thorough ophthalmic evaluation, aided by computed tomography or magnetic resonance imaging, usually confirms the diagnosis. Rapid progression of a lesion demands emergency therapy since the dysfunction produced by progressive disease may not otherwise be corrected. Early diagnosis of ocular metastases in patients with breast cancer is important because timely treatment may improve vision and quality of life in the time remaining to patients. Experience with two cases of metastases to the eye from breast cancer are presented, with a review of the literature.

Adult↗
PubMed1997

Distribution of neurons immunoreactive for parvalbumin and calbindin in the somatosensory thalamus of the raccoon.

The aim of this study was to assess the distribution of neurons immunoreactive for parvalbumin (PV), calbindin (CaBP), glutamic acid decarboxylase (GAD), and gamma-aminobutyric acid (GABA) in the somatosensory thalamus of the raccoon and to compare these features to those of other species, especially primates. Immunohistochemistry was used to study the location of these neurons in the ventroposterior nucleus (VP), ventroposterior inferior nucleus (VPI), posterior group of nuclei (Po), and reticular nucleus (Rt). A consistent differential pattern of PV-positive (PV+) and CaBP-positive (CaBP+) cells was found in the somatosensory thalamus. Many PV+ neurons were observed in VP and Rt, but very few were found in VPI or Po. In contrast, CaBP+ neurons were distributed throughout VP, VPI, and Po but were very sparse or absent in Rt. In the VP nucleus, PV+ cells were distributed in clusters separated by interclusteral regions with a sparse distribution of PV+ cell bodies. The distributions of PV+ and CaBP+ cells tended to be complementary to each other in VP; regions with a high density of PV+ neurons had a low density of CaBP+ cell bodies. Double-labeling experiments revealed very few neurons in which PV and CaBP immunoreactivities were colocalized. Cells immunoreactive for GAD or GABA were found in PV-dense clusters of VP; fewer GABAergic neurons were present in the CaBP-dense interclusteral regions of VP and in VPI and Po. GAD+ and GABA+ neurons were most prominently distributed in Rt. We conclude that the distributions of PV+ and CaBP+ cell bodies in the raccoon somatosensory thalamus are very similar to those in primates. The density of GABAergic neurons in the somatosensory thalamus of the raccoon is less than that in the cat and monkey, but the relative distribution of GABAergic neurons in the different somatosensory nuclei is very similar to that in the cat and monkey. These results are discussed in relation to findings in other species and are related to the functions of lemniscal and nonlemniscal somatosensory pathways.

Animals↗
PubMed1997

Preparative electrophoresis in a concentrated polymer solution: automated procedure for microsome isolation.

A recently introduced automated gel electrophoresis apparatus with an intermittent scanning of the migration path, the HPGE 1000 apparatus (LabIntelligence, Belmont, CA) has a unique preparative feature: A recovery cup can be automatically positioned on the band of interest, which is then electroeluted with fluorescence monitoring of recovery. Electroelution time is extended stepwise until quantitative recovery is attained. This preparative procedure has been extended from electrophoresis in gels to that of subcellularsized particles in concentrated polymer solutions Chang et al., Electrophoresis 17, 776-780, 1996). However, that application required manual rather than computer-directed positioning of the recovery chamber over the band. The present report details a modification of instrumentation and procedure by which automated operation was restored. The modified procedure extends the benefits of automation and known quantitative recovery to isolation of particles too large to enter into gels.

Animals↗
PubMed1997

Induction intraarterial chemotherapy for T4 breast cancer through an implantable port-catheter system.

Eleven patients with T4 breast cancer received induction intraarterial chemotherapy (IACT) as the first step in multidisciplinary therapy. The IACT agents (epirubicin and mitomycin C), were delivered weekly in the outpatient department by bolus injection through an implantable port-catheter system. A modified technique of port-catheter system implantation was used. The precise localization of the catheter was dually confirmed by angiography and dye test. The effectiveness of the treatment was evaluated by clinical appearance, image study, and microscopic examination. A 91% response rate was obtained, and the lesions were resectable in < or = 8 weeks. No obvious systemic toxicity resulted from the IACT. Our results show that weekly IACT by bolus injection through a port-catheter system for treating locally advanced T4 breast cancer is feasible and efficacious.

Adult↗
PubMed1996

The respiratory chain of Helicobacter pylori: identification of cytochromes and the effects of oxygen on cytochrome and menaquinone levels.

The quinone and cytochrome components of the respiratory chain of the microaerophilic bacterium Helicobacter pylori have been investigated. The major isoprenoid quinone was menaquinone-6, with traces of menaquinone-4; no methyl-substituted or unusual menaquinone species were found. Cell yield was highest after growth at 10% (v/v) oxygen and menaquinone levels (per dry cell mass) were maximal at 5-10% (v/v) oxygen. Helicobacter pylori cells and membranes contained b- and c-type cytochromes, but not terminal oxidases of the a- or d-types, as judged by reduced minus oxidised difference spectra. Spectra consistent with the presence of a CO-binding terminal oxidase of the cytochrome b- or o-type were obtained. The soluble fraction from disrupted cells also contained cytochrome c. There were no significant qualitative differences in the cytochrome complements of cells grown at oxygen concentrations in the range 2-15% (v/v) but putative oxidases were highest in cells grown at 5-10% (v/v) oxygen.

Cytochromes↗
PubMed1996

Application of gels of 0.5 mm thickness to electrophoresis in the automated HPGE-1000 apparatus: improved resolution.

Gel electrophoresis in commercial automated apparatus (HPGE-1000, LabIntelligence, Menlo Park, CA) is conventially conducted in gels of 3 mm thickness at about 15 V/cm. Since the intermittent scanning of the gel allows one to measure band width as a function of migration time, resolution may be evaluated quantitatively. Comparing the value of resolution between two proteins in electrophoresis on agarose gels of 0.5 and 3.0 mm thickness and at various field strengths, it was found that within the given Joule heat dissipation capacity of the apparatus, resolution between the proteins is improved when the gel thickness is reduced from 3.0 to 0.5 mm, which allows for an increase in field strength from 15 V/cm, conventional for that apparatus, to 45 V/cm.

Autoanalysis↗
PubMed1996

Reproducibility of mobility in gel electrophoresis.

The quantitative exploitation of gel electrophoresis to yield molecular and gel fiber properties rests on the assumption that mobility is characteristic of the macromolecule migrating as a band and is a physical constant for any system defined by pH, ionic strength and temperature. This assumption has not been tested intra-experimentally in previous literature. With the commercial introduction of automated gel electrophoresis apparatus, the collection of multiple mobility data during a single run without additional expense of labor has made it possible to test the assumption. As a start, we undertook that test for three proteins and their sodium dodecyl sulfate (SDS) derivatives, in agarose and polyacrylamide gel electrophoresis, various field strengths, continuous and discontinuous buffers, as well as intra- and interexperimentally. It was found that in agarose gel electrophoresis conducted in a single buffer, the standard deviation of mobility over a wide concentration range ranges intra-experimentally from 0.2 to 1.3% for two globular proteins and 1.4 to 5.3% for the same proteins derivatized with SDS. Interexperimentally, it was 3% in the single case tested to date. The standard deviation in polyacrylamide appears to be higher, varies in inverse relation to the mobility value, i.e. increases with gel concentration in the range of 11 to 19%T, and varies substantially between the two SDS-proteins investigated. Mobility in a discontinuous buffer system decreases continuously due to the decreasing leading phase/trailing phase ratio along the migration path. The decrease is sharpest in the "nonrestrictive" stacking gel.

Autoanalysis↗
PubMed1996

Separation and isolation of subcellular-sized particles by electrophoresis in polymer solution using the commercial scanning apparatus.

Electrophoresis of fluorescently labeled rat liver microsomes and polystyrene carboxylates of 10 and 30 nm radius was conducted in buffered 10-15% polyvinylpyrrolidone (M(r) = 10(6) solutions, using a horizontal gel electrophoresis apparatus with intermittent scanning of fluorescence (HPGE-1000, LabIntelligence). Banding, constant migration rates and Ferguson plots were obtained in these polymer solutions. The major microsome band detected by the automated scan was located visually on the gel by means of its fluorescein label and was isolated by volumetric withdrawal, recovery was monitored by scanning and ascertained to be near quantitative after three consecutive steps, in each of which 30 microL were withdrawn. This preparative method promises to be generally applicable to particles that are too large to enter into gels.

Animals↗
PubMed1995

Determination of optimally resolving gel concentration and migration time (path) in gel electrophoresis.

The notion of a mathematically defined optimally resolving gel concentration for components of a pair of molecular species of any given size was developed by Rodbard et al. (Electrophoresis and Isoelectric Focusing on Polyacrylamide Gel, pp. 28-62, de Gruyter, Berlin, 1974) 21 years ago. The mathematical treatment was incorporated into a computer program (T-OPT) for mainframe computers which upon input of the slope and intercept on the mobility axis of the Ferguson plots of the two components, electrophoresis time and temperature, yielded plots of resolution vs gel concentration. The same algorithms were later incorporated into the program ELPHOFIT for personal computers. Ideality of diffusion spreading and zero initial zone width were assumed along with a Gaussian peak distribution and an equal area for both components. Moreover, these programs failed to respond to the practical question of the migration time (or path) required for the resolution at the optimal gel concentration, although an independent program predicting the course of resolution under the assumption of free diffusion band spreading in gels (DAR-001) had been devised by Rodbard for application in preparative elution-PAGE. The present work advances the technology for predicting resolving conditions by presenting a computer program which allows the user (i) to predict the gel concentration which is optimal for obtaining the desired degree of resolution at any migration time, (ii) to prescribe the minimal degree of resolution between two band distributions one wishes to achieve, and (iii) to predict the migration time (or path) required at the optimal gel concentration for the resolution of the two components. The program is written in MATLAB and can be used by any computer that supports MATLAB language.

Algorithms↗
PubMed1995

Poly(ethyleneoxide) for high-resolution and high-speed separation of DNA by capillary electrophoresis.

Capillary electrophoresis (CE) with polyacrylamide gels has already been demonstrated to allow single-base resolution of single-stranded DNA. However, linear polyacrylamide is not an ideal matrix because of a high viscosity and difficulties in preparing the polymer with well defined pore sizes. Alternatively, poly(ethyleneoxide) (PEO) with a large range of molecular masses from 300,000 to 8,000,000 is available commercially. In addition, it is easy to prepare homogeneous solutions to provide highly reproducible separation performance with sufficient resolution. Single-base resolution of double-stranded DNA between 123 and 124 base pairs can be achieved by the use of homogeneous matrices prepared from PEO (2.5% M(r) 8,000,000), and even better resolution is achieved by using mixed polymer matrices. With further work, it should be possible to change the fractions and the total amounts of polymers to achieve even higher resolution for different samples with different size ranges of fragments. Another advantage of mixed polymer matrices is that relatively high resolution can be obtained while maintaining a relatively low viscosity compared to linear polyacrylamide with identical contents of formamide and urea, which makes it easier to fill these matrices into small capillaries.

DNA↗