Biomedical subjects

Y S Chang

Publications and source records attributed to Y S Chang.

At least 19 recordsLinked to original sources

PubMed1992

Detection of mutations in the p53 gene in human head and neck carcinomas by single strand conformation polymorphism analysis.

Using the polymerase chain reaction (PCR)-based single strand conformation polymorphism (SSCP) analysis, we have examined the highly conserved regions of the p53 gene in 58 biopsy samples of head and neck tumors. Mutations were found in 13/58 (23%) tumor specimens, but not in 6 normal tissues. Ten of 13 mutations were due to single base changes and the remaining 3 were 1- or 8-base deletion mutants. These mutations were clustered in exons 5 and 7 and resulted in amino acid changes. Our results seem to indicate that mutations in the p53 gene contribute to a significant number of cases of the head and neck tumors including 20% of nasopharyngeal carcinoma biopsies. The relationship of Epstein-Barr virus or human papillomavirus and p53 gene mutations in this group of cancers was also analyzed and discussed.

Base Sequence↗

PubMed1992

Cigarette smoking and other risk factors for progression of precancerous stomach lesions.

BACKGROUND: Stomach cancer is generally thought to evolve through a series of gastric mucosal changes, but the determinants of the precancerous lesions are not well understood. PURPOSE: Our purpose was to assess risk factors for intestinal metaplasia and gastric dysplasia arising from chronic atrophic gastritis in a general population at high risk for stomach cancer. METHODS: A population-based gastroscopic screening of more than 3000 residents was conducted in a county in China with one of the world's highest rates of stomach cancer. Information on the lifestyle and other characteristics of the participants was obtained by interview, and responses were compared between those in whom the most advanced gastric lesion was dysplasia or intestinal metaplasia versus those with chronic atrophic gastritis. RESULTS: Cigarette smoking was found to nearly double the risk of transition to dysplasia and to be a mild risk factor for intestinal metaplasia. Smoking accounted almost entirely for the 55% higher prevalence of dysplasia among men than among women. Risk of transition to dysplasia had a weak association with several dietary factors and was increased among those participants with a family history of stomach cancer and with blood type A. CONCLUSIONS: The findings provide strong evidence for a role of tobacco consumption and offer clues to other environmental and genetic factors involved in the process of gastric carcinogenesis.

Adult↗

PubMed1992

Peptidoglycan composition in heterogeneous Tn551 mutants of a methicillin-resistant Staphylococcus aureus strain.

It was shown that Tn551 inactivation of two chromosomal (so-called auxiliary) loci other than the mec gene result in a dramatic reduction of methicillin resistance and decreased cell wall turnover and autolytic capacity in a methicillin-resistant Staphylococcus aureus strain (de Jonge, B. L. M., de Lencastre, H., and Tomasz, A. (1990) J. Bacteriol. 173, 1105-1110). To understand the mechanistic basis of these phenomena we have examined the status of the autolytic enzymes and the muropeptide composition of peptidoglycan using reversed-phase high-performance liquid chromatography and mass spectral analyses. While no differences could be detected in the number of autolytic hydrolases, the mutants showed major changes in peptidoglycan composition. Nine prominent muropeptides of the parental strain each carrying a pentaglycyl substituent were missing from the cell wall of one group of mutants. The second mutant lacked four parental muropeptides which were composed of the unsubstituted disaccharide pentapeptide and its alanyl-tetraglycine derivative. The auxiliary genes are genetic determinants involved with the biosynthesis of peptidoglycan precursors, the presence of which in the cell wall may be needed for optimal cell wall turnover.

Amino Acid Sequence↗

PubMed1992

Peptidoglycan composition of a highly methicillin-resistant Staphylococcus aureus strain. The role of penicillin binding protein 2A.

All clinical isolates of methicillin-resistant Staphylococcus aureus contain an extra penicillin binding protein (PBP) 2A in addition to four PBPs present in all staphylococcal strains. This extra PBP is thought to be a transpeptidase essential for the continued cell wall synthesis and growth in the presence of beta-lactam antibiotics. As an approach of testing this hypothesis we compared the muropeptide composition of cell walls of a highly methicillin-resistant S. aureus strain containing PBP2A and its isogenic Tn551 derivative with reduced methicillin resistance, which contained no PBP2A because of the insertional inactivation of the PBP2A gene. Purified cell walls were hydrolyzed into muropeptides which were subsequently resolved by reversed-phase high-performance liquid chromatography and identified by chemical and mass spectrometric analysis. The peptidoglycan composition of the two strains were identical. Both peptidoglycans were highly cross-linked mainly through pentaglycine cross-bridges, although other, chemically distinct peptide cross-bridges were also present including mono-, tri-, and tetraglycine; alanine; and alanyl-tetraglycine. Our experiments provided no experimental data for a unique transpeptidase activity associated with PBP2A.

Amino Acid Sequence↗

PubMed1992

Increased expression of alpha IIb beta 3 integrin in subpopulations of murine melanoma cells with high lung-colonizing ability.

Four subpopulations of B16 amelanotic melanoma cells, possessing different abilities to induce platelet aggregation (TCIPA) and to form lung colonies, were isolated by centrifugal elutriation. The expression of alpha IIb beta 3, alpha v beta 3 and alpha 5 beta 1 integrins was examined in the 4 subpopulations in order to determine the relationship between integrin receptor expression and tumor-cell metastatic potential. The mRNA of alpha IIb, alpha 5, beta 1 and beta 3 was detectable in the 4 subpopulations by Northern blotting. A gradual increase in mRNAs and cell-surface immunoreactivity of the alpha IIb beta 3 receptor, but not in their gene copies, was observed from the low to the high metastatic subpopulations. The ability of tumor cells to adhere to fibronectin and subendothelial matrix (SEM) increased in parallel. In the high metastatic cells, the alpha IIb beta 3 receptors, but not the alpha 5 beta 1 receptors, were localized to focal adhesion plaques. Incubation of the high metastatic cells with alpha IIb beta 3-specific antibodies reduced their matrix adhesion, TCIPA and lung-colonizing abilities. In contrast, in the low met- astatic cells, SEM adhesion and lung-colony formation were not affected by anti-alpha IIb beta 3 antibody treatment. Incubation of either the low or the high metastatic subpopulation with an alpha 5 beta 1-specific antibody had no effect in vitro and showed a slight inhibition of lung colonization in vivo. Our results suggest that several phenotypic characteristics of the enhanced metastatic potential of B16a subpopulations may be mediated by increased expression of alpha IIb beta 3 receptors and that expression of these receptors may be regulated at the transcriptional level.

Blood Platelets↗

PubMed1992

Organization and nucleotide sequence of carp gonadotropin alpha subunit genes.

We have used PCR to amplify and align the sequence of two genes encoding cGTH alpha. Both genes comprise four exons and three introns. The organization of cGTH alpha genes is very similar to that of mammalian GTH alpha genes. However, the cGTH alpha genes only span a region of 1.2 kb which is much smaller than those mammalian GTH alpha genes.

Amino Acid Sequence↗

PubMed1992

Direct sequencing of tobacco chloroplast genome by the polymerase chain reaction.

We have developed a polymerase chain reaction (PCR) method for sequencing of tobacco chloroplast genome. In a mixture containing chloroplast DNA, 5'-end-labeled oligonucleotide primer, Taq DNA polymerase and reaction buffer, we were able to sequence a segment of chloroplast 16S rRNA gene. The results showed that the 750 bp of DNA sequenced were identical to the sequence reported, indicating that direct sequencing method that we have developed is useful for the sequencing of chloroplast genome. To analyze the chloroplast genome more rapidly in those in vitro grown plantlets, we also developed a simple method which is applicable for the amplifications and sequencing of chloroplast 16S rRNA fragment from either 0.15 g of tobacco leaf or stem tissue. The readable sequences obtained from the presented methods were consistent with the published sequence.

Base Sequence↗

PubMed1992

Chromosomal assignments of mouse connexin genes, coding for gap junctional proteins, by somatic cell hybridization.

The connexin genes Cx31 and Cx45 coding for proteins of gap junctional subunits have been assigned to mouse chromosomes 4 and 11 by Southern blot hybridization of specific gene probes to DNA from mouse x Chinese hamster somatic cell hybrids. In addition, our results confirm the recent assignment of mouse connexin genes Cx26, Cx32, Cx37, Cx40, Cx43, and Cx46 to mouse chromosomes 14, X, 4, 3, 10, and 14, respectively, by analysis of interspecific backcrosses and by somatic cell hybridization. Our assignment of the Cx31 gene to mouse chromosome 4 locates the fourth connexin gene on this mouse chromosome to which the genes for Cx31.1, Cx37, and Cx30.3 have previously been assigned. Interestingly three of them (coding for Cx31, Cx31.1, and Cx30.3) are preferentially expressed in skin. Possibly some of the connexin genes clustered on mouse chromosome 4 may be regulated coordinately.

Animals↗

PubMed1992

Molecular cloning of silver carp and bighead carp prolactin.

The cDNAs encoding the prolactin of silver carp (scPRL) and bighead carp (bcPRL) have been cloned. Deduced from the nucleotide sequences, both scPRL and bcPRL are composed of 187 amino acid residues. Only one residue is different between scPRL and bcPRL. Homology analysis indicates that scPRL and bcPRL are highly homologous to carp PRL (97%), relatively conserved in relation to PRLs of salmon, trout, and tilapia (64-69%), and diversified from avian and mammalian PRL (30-35%). Similar to PRLs of other species of fish, scPRL and bcPRL lack the first 12 N-terminal residues of avian and mammalian PRLs.

Amino Acid Sequence↗

PubMed1992

The primary structures of growth hormones of three cyprinid species: bighead carp, silver carp, and grass carp.

The primary structures of growth hormone (GH) of three cyprinid species, bighead carp, silver carp, and grass carp, were determined by a chemical method and/or by molecular cloning. The bighead carp GH was extracted from pituitary tissue by use of an alkaline medium, then successively purified by gel filtration, hydrophobic interaction column chromatography, and reverse-phase high-pressure liquid chromatography. The primary structure of bighead carp GH determined chemically is identical to that deduced from the cDNA nucleotide sequence. By molecular cloning, the primary structures of silver carp and grass carp GHs were also determined. The GHs of these three cyprinid species all contain 188 amino acid residues and their sequences are identical. When four of the five cysteines of cyprinid GHs were arranged to match the same positions of cysteines of other vertebrate GHs, a maximally matched alignment was achieved. Among fishes, GHs are relatively conserved within the same order (82 to 100% identity) but they are more diversified between orders (49 to 68% identity). In further comparison, fish GHs are even more different from tetrapod GHs (37 to 58% identity). Although the primary structures of vertebrate GHs are relatively variable, four homologous sequences, notably one located at the C-terminal, are found.

Amino Acid Sequence↗

PubMed1992

Distribution of type A and type B EBV in normal individuals and patients with head and neck carcinomas in Taiwan.

The subtypes of Epstein-Barr virus (EBV) according to the EBNA 2 gene were investigated in Taiwan by the polymerase chain reaction (PCR) and by Southern blot hybridization. The materials included 53 nasopharyngeal carcinoma (NPC) biopsies, 49 other head and neck cancers and 32 throat washings of normal individuals. EBV DNA was found in all NPC biopsies, 27 of 49 other head and neck carcinomas and 81% of normal individuals. Type A EBV was the predominant type of EBV in both normal individuals and patients with head and neck carcinomas in Taiwan. Type B EBV or coexistence of the A and B types comprised a small number of samples in this study.

Base Sequence↗

PubMed1992

Comparison of the anatomic distribution of stomach cancer and precancerous gastric lesions.

The anatomic distribution of precancerous gastric lesions among 3,400 residents in Linqu, Shandong Province of China, was compared with the anatomic distribution of stomach cancer (SC) among 959 patients in Tokyo, Japan. The incidence of SC is high in both areas, and locations within the stomach of the precancerous and malignant lesions were classified using similar criteria. Chronic atrophic gastritis (CAG) affected 98% of the population in Linqu, with intestinal metaplasia (IM) the most severe diagnosis in 33% and dysplasia (DYS) in 20%. Neither the SC nor precancerous lesions were uniformly distributed in the stomach. Among the DYS 3% were along the greater curvature of the body, 15% along the lesser curvature of the body, 25% in the angulus, 22% along the lesser curvature of the antrum, and 34% elsewhere in the antrum. Among the SC the corresponding percentages were 2, 16, 28, 25 and 29. The similarity to the SC distribution increased gradually from CAG to IM to DYS, providing further evidence for the multistage progression of precancerous gastric lesions.

Adult↗

PubMed1992

Cloning of an Erwinia herbicola gene necessary for gluconic acid production and enhanced mineral phosphate solubilization in Escherichia coli HB101: nucleotide sequence and probable involvement in biosynthesis of the coenzyme pyrroloquinoline quinone.

Escherichia coli is capable of synthesizing the apo-glucose dehydrogenase enzyme (GDH) but not the cofactor pyrroloquinoline quinone (PQQ), which is essential for formation of the holoenzyme. Therefore, in the absence of exogenous PQQ, E. coli does not produce gluconic acid. Evidence is presented to show that the expression of an Erwinia herbicola gene in E. coli HB101(pMCG898) resulted in the production of gluconic acid, which, in turn, implied PQQ biosynthesis. Transposon mutagenesis showed that the essential gene or locus was within a 1.8-kb region of a 4.5-kb insert of the plasmid pMCG898. This 1.8-kb region contained only one apparent open reading frame. In this paper, we present the nucleotide sequence of this open reading frame, a 1,134-bp DNA fragment coding for a protein with an M(r) of 42,160. The deduced sequence of this protein had a high degree of homology with that of gene III (M(r), 43,600) of a PQQ synthase gene complex from Acinetobacter calcoaceticus previously identified by Goosen et al. (J. Bacteriol. 171:447-455, 1989). In minicell analysis, pMCG898 encoded a protein with an M(r) of 41,000. These data indicate that E. coli HB101(pMCG898) produced the GDH-PQQ holoenzyme, which, in turn, catalyzed the oxidation of glucose to gluconic acid in the periplasmic space. As a result of the gluconic acid production, E. coli HB101(pMCG898) showed an enhanced mineral phosphate-solubilizing phenotype due to acid dissolution of the hydroxyapatite substrate.

Acinetobacter calcoaceticus↗

PubMed1992

Thrombotic thrombocytopenic purpura-like syndrome associated with systemic lupus erythematosus--combined treatment with plasmapheresis and fresh frozen plasma infusion.

We report on a patient with systemic lupus erythematosus, who, during the course of the illness, developed thrombotic thrombocytopenic purpura. In this case, the coexistence of these two conditions was confirmed by laboratory and pathologic findings. The infusion of fresh frozen plasma with plasmapheresis reversed the course of thrombotic thrombocytopenic purpura.

Adult↗

PubMed1992

'Pauci-immune' rapidly progressive glomerulonephritis associated with systemic vasculitis.

'Pauci-immune' glomerulonephritis has been recognized as an important cause of rapidly progressive glomerulonephritis. The paucity of immune deposits can be separated from the other two major immunohistologic variants of crescentic glomerulonephritis, ie, antiglomerular basement membrane (GBM) antibody-mediated and immune complex-mediated glomerulonephritis. Here we describe the case of a 42-year-old woman with pauci-immune' glomerulonephritis and vasculitis presenting as rapidly progressive renal failure with characteristic pathologic and immunohistologic findings. And in this case, despite oliguria and rapid deterioration of renal function, the renal function recovered partially and continued to be stabilized with a favourable response to hemodialysis and combined system immunosuppressive therapy.

Adult↗

PubMed1992

Isolation and sequence analysis of carp gonadotropin beta-subunit gene.

Using the cDNA encoding the beta subunit of carp gonadotropin (cGTH-beta) as a probe, 14 clones containing cGTH-beta gene have been isolated from a carp genomic library. Nucleotide sequence analysis indicated that the transcriptional unit of the cGTH-beta gene is 1.2 Kb. Similar to mammalian GTH-beta genes, cGTH-beta gene contains three exons and two introns. The locations of the exon/intron junctions also correspond to those of mammalian GTH-beta gene. Using the primer extension assay, the start site of transcription was determined to be 35 or 37 bp upstream from the translation initiation codon. The TATAA box is present in the 5' flanking region of the gene, 21 bp upstream from the start site of transcription. Three polyadenylation signals, AATAAA, are located in the 3' noncoding region, 111, 430, and 442 bp downstream from the stop codon of translation, respectively.

Amino Acid Sequence↗

PubMed1992

Cloning and characterization of the latent membrane protein (LMP) of a specific Epstein-Barr virus variant derived from the nasopharyngeal carcinoma in the Taiwanese population.

A DNA fragment containing Epstein-Barr virus (EBV) terminal fragment sequence was obtained from a genomic library of nasopharyngeal carcinoma (NPC). One of the clones (clone 1510) contained the gene encoding latent membrane protein (LMP). Sequence analysis revealed that this gene had 95% homology with the LMP sequence of the B95-8 strain. Among the sequence variations, there was a change from G to T at nucleotide position 169,426, resulting in the loss of an XhoI site in exon 1 of the LMP gene. A pair of primers bracketing the XhoI site were designed to synthesize the EBV DNA fragment from nucleotides 169,081-169,577 by using the polymerase chain reaction (PCR) method. The PCR products were then subject to XhoI digestion and to DNA sequencing analysis. This restriction enzyme site polymorphism along with the sequence variations were also observed in 50 biopsy tissues as well as in the throat washings of 6 out of 20 healthy individuals that we examined, indicating that the EBV strain predominantly existing in these biopsy tissues was different from strains of B95-8, Jijoye or nude mouse passaged cells (C15) with an African origin, but closely resembled other nude mouse passaged CAO cells which were originally derived from China. Balb/c 3T3 cells carrying this NPC-LMP gene showed a transformed cell morphology and were tumorigenic in nude mice. The relationship between this unique type of EBV and NPC has yet to be established.

3T3 Cells↗

PubMed1992

[The comparison of microleakage among three different dentin bonding agents in class V cavities].

The use of the etching technique and an enamel bonding agent may effectively reduce microleakage of the cavity wall. However, the reduction of marginal leakage relating to class V cavities, is still unsatisfactory according to the dental literature. Due to the structural difference between the dentin and the enamel, though many new dentin bonding agents have been developed lately, none of them work perfectly. In this experiment, the "silver staining technique" was used to investigate the degree of microleakage in class V resin restorations which were bonded with 3 different dentin bonding agents (Scotchbond, Scotchbond 2 and Denthesive). The sample consists of 21 caries free human molars which were divided into 3 groups: 1) Scotchbond v. s. Scotchbond 2, 2) Scotchbond v. s. Denthesive, 3) Scotchbond 2 v. s. Denthesive. Both buccal and lingual surfaces were prepared for class V cavities. The cavities were then filled with composite resin Silux, and immersed in 50% silver nitrate solution for 2 hours, and followed by washing with distilled water. After that these teeth were immersed in photodeveloping solution under the fluorescent light for 3 hours. On finishing, they were washed again, sectioned vertically into mesial and distal halves with a Isomet sectioner and put under a microscope and evaluated for the degree of microleakage with Dr. Going's method. On statistical analysis, the results of this study showed that the degree of microleakage was not significantly different among the 3 dentin bonding agents in class V resin restorations, either on the gingival wall or the occlusal wall.

Dental Caries↗