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Biomedical subjects

T J Chang

Publications and source records attributed to T J Chang.

At least 19 recordsLinked to original sources
PubMed1996

Identification of a pseudorabies virus UL12 (deoxyribonuclease) gene.

We characterized the gene encoding the pseudorabies virus (PrV) homologue of the herpes simplex virus 1 UL12 open reading frame that encodes the alkaline nuclease. The deduced PrV UL12 product was 492 amino acid residues and exhibited three conserved regions among herpesviruses. Northern blot analysis indicated that three transcripts (3.2, 1.6 and 1 kb) were encoded in this region and the UL12 corresponds to the 1.6-kb transcript. Primer extension and UL12-specific cDNA cloning were performed to verify the precise location of the UL12 transcript. These data indicated that the transcription start site of UL12 was located at 47-62 nucleotides upstream of the UL12 translation start site and the polyadenylation cleavage site was located at 15 or 16 nucleotides downstream the typical polyadenylation signal. Furthermore, the 53-kDa UL12 product, which indeed has deoxyribonuclease activity, was evidenced by in vitro expression.

Amino Acid Sequence↗
PubMed1996

Analysis of pseudorabies virus genes by cDNA sequencing.

Cloning and sequencing of cDNA could provide a complementary approach to functional analysis of the pseudorabies virus (PrV) genome. Using colony hybridization, Southern hybridization, and DNA sequencing, four species of PrV-specific cDNA were identified. Among these four species of PrV-specific cDNA, three unidentified genes, UL26, UL29, and UL31, were mapped and a novel gI-11K bicistronic cDNA was confirmed. Thus, analysis of PrV-specific transcripts provided a way for identifying genes and a foundation to further study the roles of these transcripts in PrV infection.

Animals↗
PubMed1996

Rapid screening of pseudorabies virus-specific cDNAs from a cDNA library.

In order to reduce the time and cost for screening of pseudorabies virus (PRV)-specific cDNAs, a rapid and inexpensive method was developed that involved subtractive hybridization of the plasmid, which contained cDNA fragment, to PRV genomic DNA which was bound to nylon membranes. Ninety percent of DNA background was subtracted successfully by this method and the eluted DNA in the form of plasmid could be used to transform bacteria directly. Applying this technique, 200 colonies were screened from a cDNA library containing 30000 colonies. Furthermore, 17 colonies containing PRV-specific cDNAs, including PRV43, UL42, gII, DNase, EP0, 11K, gX, and RSP40, were identified from the 200 colonies by colony hybridization, Southern hybridization, and DNA sequencing. Thus, the subtractive hybridization can be used to construct and successfully establish the PRV cDNA library from PRV-infected cells.

Animals↗
PubMed1996

Cloning and sequencing of complete thyrotropin receptor transcripts in pretibial fibroblast culture cells.

Pretibial fibroblasts are considered to be targets of autoimmune attack in pretibial myxedema. A possibility of the pathogenesis of pretibial myxedema is that T cells, reacting with thyrotropin (TSH) receptor, will be targeting to the pretibial fibroblasts where, in the presence of antigen (TSH receptor), they will secrete various cytokines and stimulate fibroblasts to secrete glycosaminoglycans. We have demonstrated that TSH and TSH receptor antibody can bind to fibroblasts and the presence of RNA encoding the extracellular domain of the TSH receptor in fibroblasts derived from skin lesions of two patients with pretibial myxedema. The present study was designed to determine whether there are complete TSH receptor transcripts in pretibial fibroblasts obtained from patients with pretibial myxedema. RNA was prepared from pretibial fibroblasts obtained from 11 patients with pretibial myxedema and from four normal subjects, then reverse-transcribed by polymerase chain reaction using three sets of primers (-11/+8 and +754/+773; +353/+373 and +1265/+1285; +1000/+1017 and +2284/+2301). The overlapped 2312 bp cDNA sequence was expected to contain the genetic sequences of the signal peptide (+1/+60), extracellular domain (+61/+1254), transmembrane domain (+1255/+2046), and cytoplasmic domain (+2047/ +2292) of the TSH receptor. The sequences were determined using dideoxy sequencing method. All of the 2312 nucleotide sequences in 15 samples were consistent with the reported TSH receptor sequence of transcripts in thyroid. These data suggest that the complete TSH receptor transcripts are very possible to be present in the fibroblasts derived from pretibial skin.

Adult↗
PubMed1996

Analysis of upregulated cellular genes in pseudorabies virus infection: use of mRNA differential display.

Virus infection usually alters the host cell and shuts off the synthesis of cellular macromolecules. In order to screen the upregulated cellular transcripts during pseudorabies virus (PRV) infection, we employed the mRNA differential display technique. The screen is based on positive selection at the mRNA level for genes expressed in normal cells but increased in corresponding PRV-infected cells. Over 14000 species of mRNA, isolated from mock-infected and PRV-infected Madin-Darby bovine kidney cell at 1 h post infection, were screened, and 40 candidate clones were recovered. Southern blot analysis revealed that 17 out of 40 candidate clones, were enhanced in PRV-infected cells. Partial DNA sequences demonstrated that 17 clones were distinct cellular genes, including those encoding the modulators of signal transduction (saposin, 14-3-3, adenylate kinase, adenylyl cyclase, protein kinase C-alpha), those encoding the components of translation (fau, ribosomal proteins S11, L31, L36), other cellular genes (peptidase, cyclin E, rch1, oligo-C-rich single-stranded nucleic acid binding protein, rap, arginyl-tRNA synthetase), and two unknown genes. Thus, this study identifies successfully the transcriptionally regulated cellular genes which are associated with PRV infection. Furthermore, this study provides support for the use of mRNA differential display as a method to rapidly isolate differentially expressed genes in virus infection.

Animals↗
PubMed1996

Molecular cloning and nucleotide sequence determination of three envelope genes of classical swine fever virus Taiwan isolate p97.

A strain of classical swine fever virus (CSFV) has been isolated in Taiwan. The cDNA coding for three envelope glycoproteins E1, E2 and E3 were molecularly cloned from purified viral particles using the reverse transcription-polymerase chain reaction (RT-PCR) method and sequence-specific primers. The resulting PCR products (1113 bp for E1. 699 bp for E2 and 567 bp for E3) were cloned into the SmaI site of pUC19 and then subjected to DNA sequence analysis. Data showed that nucleotide sequence of the three envelope genes shared a 82-83% homology with the corresponding genes of three other strains (Alfort, Brescia and Weybridge). However, the homology of the deduced amino acid sequence was greater than 90% among the four strains. The potential asparagine-linked glycosylation sites for E1 (5 sites), E2 (7 sites) and E3 (2 sites) were conserved. This suggests that the Taiwan p97 strain is distinct from other three strains described. The variations may have implications for future vaccine development. The sequence has been submitted to GenBank. The accession numbers are U43924 and U03290.

Amino Acid Sequence↗
PubMed1996

Stepwise approach to hallux limitus. A surgical perspective.

Successful outcomes in hallux limitus surgery are still difficult to reproduce consistently. An attempt is made to improve these results by presenting a systematic approach to surgical reduction of this deformity by isolating several important steps. Emphasis is placed equally on both the soft-tissue and osseous structures. Cartilage grafting and replacement techniques may soon provide more options in joint salvage.

Arthroplasty↗
PubMed1995

Clinical experience with two-component first metatarsal phalangeal joint implants.

The development of the two-component implant systems has generated considerable interest over the past 5 years. It is important to critically document and record the clinical experiences with these devices as they occur. The authors present an objective evaluation of their early findings and comment on possible recommendations for the future.

Contraindications↗
PubMed1995

Metallic implants used in foot surgery.

Metallic materials have provided a tremendous advantage in the current treatment of many surgical specialties. Further studies on the long-term effects at both local and distant sites of implantation are essential. As this field continues to expand, the podiatric applications of these new devices will grow exponentially. Because all metallic implants in the human body will corrode, several recommendations can be made: 1. Beware of placing reactive components in the younger population. These should be followed accordingly because of latent periods of reported tumor findings in these metals. 2. Consideration should be made toward removal of implant devices when they are no longer effective. 3. The least reactive materials should be considered for implantation. At the present time, titanium alloys have been shown to be more inert than their metallic counterparts. As the search for the ideal human implant material continues, a few important lessons have been learned. First, mixtures of elements such as stainless steel have a higher incidence of antigenicity because they contain a number of different elements, each of which may be an allergen. The smaller the number of elements that are combined to form a metal, the more biocompatible the material will be. Second, certain elements have been found to have increased tissue reactivity, namely nickel, cobalt-chrome, and even vanadium. The less a metal contains these antigenic elements, the less likely the metal will be incompatible. Third, newer "pure" elements with a greater degree of chemical inertness, such as commercially pure titanium and titanium-alloy niobium, are being studied. This ongoing research may lead to a universally biocompatible human implant material that will be used exclusively for all types of implants.

Alloys↗
PubMed1994

TSH and TSH receptor antibody-binding sites in fibroblasts of pretibial myxedema are related to the extracellular domain of entire TSH receptor.

The role of TSH receptor antibodies in the pathogenesis of pretibial myxedema is still unclear. This study was designed to determine whether patients with pretibial myxedema had higher serum titers of TSH receptor antibodies, and whether there were TSH and TSH receptor antibody-binding sites on plasma membranes of fibroblasts derived from the skin of pretibial myxedema. If there were, were the binding sites similar to the TSH receptor? The TSH receptor antibodies were determined with radioreceptor assay in 20 normal subjects, 18 hyperthyroid Graves' disease patients without ophthalmopathy, 26 hyperthyroid Graves' disease patients with ophthalmopathy, and 11 patients with pretibial myxedema associated with Graves' ophthalmopathy. TSH and TSH receptor antibody-binding sites were studied on plasma membranes of fibroblasts cultured from the skin of pretibial myxedema with radioreceptor assay. RNA was also extracted from the fibroblasts of pretibial myxedema and reverse transcribed using random primers as the primers for cDNA synthesis. The resulting cDNAs were subjected to amplification by polymerase chain reaction with the use of a set of primers spanning the 5' region (+256/+275 and +616/+635) and the 3' region (+1819/+1838 and +2405/+2424) of the TSH receptor cDNA (+1 transcription start codon). They were further identified by Southern blot hybridization, with the probe spanning the 5' region (+272/+612) and the 3' region (+1908/+2268) of the TSH receptor cDNA (+ 1 transcription start codon), and sequencing. The results showed that patients with pretibial myxedema had higher titers of TSH receptor antibodies in the serum. TSH and TSH receptor antibody-binding sites were present on plasma membranes of fibroblasts derived from the skin of pretibial myxedema patients and related to the extracellular domain of the TSH receptor. These data suggest a common antigenic site in the skin and in the thyroid as a putative target for TSH receptor antibodies or lymphocytes of Graves' disease.

Adult↗
PubMed1994

Steroid hormone receptors in three human gastric cancer cell lines.

Steroid hormone receptors in three human gastric adenocarcinoma cell lines and their transplanted tumors (except nontumorigenic KATO-III) in nude mice were determined by dextran-coated charcoal assay. Progesterone receptors (PgR) were found in all cell lines, transplanted NUGC-3, and AZ 521 tumors. Estrogen receptors (ER) were found in KATO-III cells, transplanted NUGC-3, and AZ 521 tumors, whereas glucocorticoid receptors (GR) were found only in NUGC-3 tumor and no androgen receptor was found in any cell lines or transplanted tumors. Since NUGC-3 cells had ER, PgR, and GR, it was used for the study of the effects of steroid hormones on growth. The results showed the cell cycle phase distributions and growth rate of transplanted tumors were similar in hormone-treated and nontreated groups. The persistent expression of PgR in gastric cancer cell lines and tumors, and the slight increase of tumor volumes in the progesterone-treated group suggests that progesterone and its receptors may be important in the pathogenesis of gastric cancer, but their biological function remains to be elucidated.

Adenocarcinoma↗
PubMed1994

Lapidus arthrodesis. A different perspective.

Fusion of the first metatarsocuneiform joint may provide correction of positional deformities of the first metatarsal while offering significant structural stability to the medial column. The authors present a modification of the Lapidus procedure that uses well established internal fixation principles.

Arthrodesis↗
PubMed1993

Inhibition of mouse GATA-1 function by the glucocorticoid receptor: possible mechanism of steroid inhibition of erythroleukemia cell differentiation.

Treatment of mouse erythroleukemia (MEL) cells with hexamethylene bisacetamide induces a program of erythrodifferentiation, as judged by an increase in the synthesis of globins and other erythroid-specific products. This induction can be inhibited by glucocorticoids, e.g. dexamethasone. All globin and other erythroid-specific genes tested contain GATA response elements (GATA-RE) and can be transactivated by GATA-1, a transcription factor. GATA-1 is highly expressed in erythroid cells, including MEL cells. We noted a glucocorticoid receptor (GR) response element motif near a GATA-RE motif in the promoter region of the mouse beta-major and beta-minor globin genes and about 130 bases away from a GATA-RE in the alpha 1-globin gene promoter and, therefore, investigated the possibility that the dexamethasone-induced inhibition of induced MEL cell differentiation may involve effects of the GR on GATA-1 activity. Evidence obtained from transfection assays and DNA electrophoretic mobility shift assays indicates that the GR binds GATA-1 and interferes with its function before any interaction with DNA, but that the presence of a glucocorticoid response element near a GATA-RE augments the GR effect. The N-terminal 106-amino acid domain of the GR was found to be essential for the effect, possibly by binding to GATA-1. Since GATA-1 is autoregulatory, i.e. it has been shown by others to bind to its own promoter and up-regulate its own transcription, the finding that activated GR can interfere with GATA-1 function may provide an explanation for the inhibition by glucocorticoids of the entire program of erythroid differentiation in MEL cells. That is, by interfering with GATA-1 function, the GR inhibits not only the expression of erythroid structural genes, but may also inhibit the expression of a primary erythroid regulatory gene, GATA-1. It was also shown that the GATA-RE in each of the beta-globin promoters responds to mouse GATA-1 in a functional transfection assay.

Animals↗
PubMed1993

Analysis of glucocorticoid receptors in human hepatocellular carcinoma and HepG2 cells.

Hepatocellular carcinoma is the leading cause of male cancer death in Taiwan. We have found that the level of glucocorticoid receptor in hepatocellular carcinoma is significantly higher than that in the peritumoral tissue. In this study, we used a rat liver glucocorticoid receptor complementary DNA probe to examine the expression of glucocorticoid receptor gene in 15 paired samples of hepatocellular carcinoma and their peritumoral tissues. No differences in genomic DNA patterns of the glucocorticoid receptor gene were found between the tumor and peritumoral tissues. The amount of glucocorticoid receptor was found to be significantly higher in hepatoma samples than in peritumoral liver samples. The levels of glucocorticoid receptor messenger RNAs were increased in most tumors compared with their peritumoral samples. To examine the function of glucocorticoid receptors in hepatoma, we examined the expression of glucocorticoid receptor and its relation to cell-cycle progression in human HepG2 cells. Using specific monoclonal antibodies and flow cytometric study, we found glucocorticoid receptor to be expressed constitutively in all cell-cycle phases. In addition, hydrocortisone treatment of HepG2 cells resulted in increased expression of glucocorticoid receptors and increased secretion of alpha-fetoprotein. RU-486, a glucocorticoid antagonist, blocked the hydrocortisone effect, indicating that glucocorticoid receptors are functional in HepG2 cells. Taken together, our data suggest that glucocorticoids and their receptors play an important role in the growth of hepatoma.

Adult↗
PubMed1992

Clinicopathologic comparisons between estrogen receptor-positive and -negative gastric cancers.

We report that a modified dextran-coated charcoal (DCC) assay, including the addition of sodium molybdate and 5% DCC stripping of endogenous hormone, detected higher estrogen receptors (ERs) than those by the conventional assay. ERs in 21 gastric adenocarcinoma were determined by the modified DCC assay; 13 patients had ERs of 2.5 to 520.2 fmol/mg protein with a mean dissociation constant of 1.9 x 10(-10) M. The remaining 8 patients had no detectable amount of the receptor. There were no differences between the ER-positive and ER-negative groups in clinico-pathologic characteristics such as age, sex, tumor size, location, gross appearance, invasive depth, invasion of lymph vessel or vein of stomach wall, nodal involvement, peritoneal dissemination, liver metastasis, and curability. Histological analysis, using Japanese, Lauren's, or Ming's classifications, all revealed no differences between the ER-positive and -negative groups. The survival rate was identical for the 2 study groups. These results suggest that the presence or absence of ERs in gastric adenocarcinoma does not correlate to either biologic or clinicopathologic characteristics of this tumor; the role of ERs in human gastric cancer remains to be elucidated.

Adenocarcinoma↗
PubMed1992

Identification of autoantigen recognized by autoimmune ophthalmopathy sera with immunoblotting correlated with orbital computed tomography.

We have demonstrated that there is an antibody related to extraocular muscle enlargement in autoimmune ophthalmopathy (Graves' ophthalmopathy, thyroid-associated correlated with orbital computed tomography (CT). This study was designed to identify the autoantigen and to determine whether there are common antigens among the extraocular muscle, the lacrimal gland, and the thyroid. We prepared a 100,000g sediment fraction of porcine extraocular muscle, lacrimal gland, thyroid, and human thyroid, followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting with sera from patients with Graves' disease, with or without ophthalmopathy, classified by symptoms and signs combined with orbital CT and normal controls. The results showed there was an approximately 55-kDa protein band which was recognized by the sera in 32.1% (9/28) of patients with autoimmune ophthalmopathy and in 47.3% (9/19) of patients with extraocular muscle enlargement demonstrated by orbital CT. It was significantly higher than the positive rates in patients without autoimmune ophthalmopathy and normal controls (15.8 and 11.1%, respectively, P < 0.025). However, there was no common antigen among the extraocular muscles, the lacrimal gland, and the thyroid. To further confirm this eye muscle-specific antigen, the approximately 55-kDa protein band was cut and solubilized from the nitrocellulose paper after SDS-PAGE, and electrophoretically transferred and used as an antigen in enzyme-linked immunosorbent assay. The absorbance was significantly higher in patients with autoimmune ophthalmopathy than patients without ophthalmopathy (P < 0.005), and normal controls (P < 0.01). Our findings suggest that an approximately 55-kDa protein may be a possible antigen in the eye muscle related to autoimmune ophthalmopathy.

Animals↗
PubMed1991

Fixation devices in rearfoot surgery.

Numerous advances in biomaterials and fixation devices have improved the caliber of rearfoot surgical procedures. An understanding of the underlying physical properties of fixation devices along with the improvement in surgical technique have elevated complex foot surgery to a higher level of quality with improved results. Since the addition and continued improvement of rigid fixation to tarsal arthrodesis, more consistent osseus fusion with a decrease in nonunion has been found.

Bone Nails↗