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Biomedical subjects

S Y Yang

Publications and source records attributed to S Y Yang.

At least 19 recordsLinked to original sources
PubMed1995

Glutamate 139 of the large alpha-subunit is the catalytic base in the dehydration of both D- and L-3-hydroxyacyl-coenzyme A but not in the isomerization of delta 3, delta 2-enoyl-coenzyme A catalyzed by the multienzyme complex of fatty acid oxidation from Escherichia coli.

Multienzyme complexes of fatty acid oxidation from Escherichia coli with either an alpha/Glu139-->Gln or an alpha/Arg134-->Gln mutation in the large alpha-subunit have been overproduced and characterized. The catalytic properties of the five different component enzymes of the alpha/Arg134-->Gln mutant complex showed no significant changes as compared with those of the wild type complex. In contrast, the 3-hydroxyacyl-coenzyme A (CoA) epimerase activity of the alpha/Glu139-->Gln mutant complex was not detected, and this mutant complex has lost almost all of the enoyl-CoA hydratase activity due to a greater than 3000-fold decrease in the kcat of the enoyl-CoA hydratase without a significant change in the Km value. The catalytic properties of 3-ketoacyl-CoA thiolase and L-3-hydroxyacyl-CoA dehydrogenase were virtually unaffected by the mutation. Together, these observations lead to the conclusion that the gamma-carboxylic group of Glu139 functions as a catalytic base in the dehydration of both D- and L-3-hydroxyacyl-CoA. These findings also support a dehydration/hydration mechanism for 3-hydroxyacyl-CoA epimerase but do not agree with an epimerase activity independent of enoyl-CoA hydratase as proposed for the glyoxysomal tetrafunctional protein [Preisig-Müller, R., Gühnemann-Schäfer, K., & Kindl, H. (1994) J. Biol. Chem. 269, 20475-20481]. Since this mutation caused the kcat of delta 3-cis-delta 2-trans-enoyl-CoA isomerase to decrease by only 60%, even though the Km value was significantly increased, it seems that Glu139 of the E. coli multifunctional protein does not function as a catalytic residue in the isomerization reaction.(ABSTRACT TRUNCATED AT 250 WORDS)

3-Hydroxyacyl CoA Dehydrogenases↗
PubMed1995

Reactivity of autologous CD4+ T lymphocytes against human melanoma. Evidence for a shared melanoma antigen presented by HLA-DR15.

Reactivity of CD8+ T lymphocytes against human melanoma has been extensively characterized, but little is known about melanoma Ags recognized by CD4+ lymphocytes. We have identified CD4+ CTL that recognize shared melanoma Ag(s) expressed by autologous melanoma cells and a subset of allogeneic melanomas. The same Ag(s) was shared by autologous and positive allogeneic melanomas by cross-blocking experiments. Cytotoxicity was directed against epitopes presented by HLA-DR on target melanoma cells, and allelic typing revealed that cytotoxicity was restricted through HLA-DR15. These CD4+ T cells released IFN-gamma, IL-4, and TNF-alpha, but not IL-2, in response to HLA-DR15+ target cells. CD4+ T cells did not lyse DR15+ nonmelanoma cell types, including melanocytes or fibroblasts (induced to express HLA-DR by IFN-gamma). Thus, by cytotoxicity assays, shared Ags were only recognized on melanoma cells but not on normal melanocytes. In summary, this analysis shows that melanoma cells share an Ag that is presented by HLA-DR15.

Antibodies, Monoclonal↗
PubMed1995

Epidemiology of measles in Taiwan: dynamics of transmission and timeliness of reporting during an epidemic in 1988-9.

We analysed nation-wide reported measles cases during the 1988-9 epidemic and found that longer duration and wider spread were two major characteristics of the outbreak. All the 22 county/city index cases were reported with a delay of > 4 days and 64% were aged 5-14 years. This epidemic occurred mainly among 5-14-year-old school-children (59%), infants under 1 year (19%), and pre-school children (18%). The overall attack rate was 0.63 cases per 10,000 population, with the highest attack rate (7.4 cases per 10,000 population) occurring in infants. Among 280 confirmed cases < 15 months of age, 9-month-old infants (42 cases) had a higher risk of measles and peaked at 10 months (49 cases). This epidemic started in March 1988 among 5-9-year-old children in the northern suburban area, then spread to Taipei City and neighbouring counties or cities. It continued to spread from the northern to southern and western areas during the summer vacation and New Year holidays. Multiple logistic regression analysis showed that the delay of measles reporting was strongly associated with the cases infected early in the epidemic (OR = 6.9, P < 0.001) and reported from teaching hospitals (OR = 2.6, P < 0.001). The reappearance of high attack rates among 5-9-year-old children in the 1985 and 1988-9 measles epidemics in Taiwan indicated the persistence of pockets of susceptible individuals even after mass immunization.

Adolescent↗
PubMed1995

Locus-specific amplification of HLA class I genes from genomic DNA: locus-specific sequences in the first and third introns of HLA-A, -B, and -C alleles.

We have identified locus-specific sequences in the first and third introns flanking the polymorphic second and third exons of HLA class I genes. PCR primers derived from these conserved sequences produced DNA fragments of the expected sizes for each of the HLA-A, -B, and -C loci in the amplification of genomic DNA. PCR products generated using each of the locus-specific sets of primers displayed exquisite locus specificity, as assessed by hybridization with oligonucleotide probes specific for ten classical and non-classical HLA class I genes. Amplification with these primer sets was effective and specific for the HLA alleles tested under the given PCR conditions. When hybridized with oligonucleotides derived from shared polymorphic sequence motifs, reaction patterns of PCR products from each locus were precisely as expected from published or database sequences. Chemiluminescent signals generated from digoxygenin-ddUTP-labeled probes were even for all samples and as strong as those obtained in MHC class II typing. These locus-specific primer sets derived from intron sequences provide an effective means to amplify genomic DNA which will facilitate PCR-based HLA class I typing methods. This will also allow HLA class I typing to be conducted with greater precision, at lower cost, and faster than previously described class I typing methodologies.

Alleles↗
PubMed1995

The relative distribution of B35 alleles and their IEF isotypes in a HLA-B35-positive population.

The HLA-B35 serotype represents a group of antigens detectable by IEF, cytotoxic T cells, and by sequencing analysis. Four isotypes and eight alleles have been thus far reported. We have determined the relative frequencies of these B35 subtypes in a group of 203 unrelated people. Dot blot hybridization of PCR amplified products was performed using 23 sequence-specific oligo probes designed based on the EMBL HLA class I sequence database. The amplification was achieved by a pair of group-specific primers, producing approximately 600 bp fragments. By hybridization pattern analysis, we found that four alleles represent over 95% of the B35+ population, with relative frequency of 48.2% for B*3501, 23.7% for B*3502, 15.2% for B*3503, and 8.0% for B*3508. We also identified 3 individuals with B*3504 and one with B*3505, and seven samples with new patterns. B*3501 and B*3503 exactly correlated with the most common isotype B35.3, B*3502 and B*3504 with B35.2, B*3508 may be the B35.1 IEF isotype. The B*3505 was identified from an individual with B35 IEF variant form. Our study shows that the B35 antigen has a wide distribution of alleles, and that many more B35-related alleles may yet to be uncovered.

Alleles↗
PubMed1994

The second kappa B element, kappa B2, of the HLA-A class I regulatory complex is an essential part of the promoter.

The MHC class I regulatory complex (CRC) contains the well characterized palindromic kappa B element, kappa B1, to which a number of nuclear factors are known to bind. This cis element plays an important role in controlling the transcription of MHC class I genes. In addition, the CRC contains a second kappa B element, kappa B2, which is located in tandem with the kappa B1 site, 5 bp upstream. In this study, from reporter gene transfection experiments, we present evidence that this kappa B2 site is as important as kappa B1 in regulating HLA-A locus transcription. Mutations introduced into either kappa B site reduced promoter activity to approximately the level obtained when the entire CRC was deleted. Electrophoretic mobility shift and supershift assays showed that the kappa B2-binding complex (BIII) contained a p65-like subunit, but apparently not the p50 subunit of NF-kappa B. Complex BIII also bound to the kappa B1 site, but the kappa B2 sequence was poorly recognized by the kappa B1-binding complex, BI, probably KBF1, the p50 homodimer. These results demonstrate that both kappa B sites are essential components of the promoter and suggest that they may function together to control MHC class I gene transcription.

Base Sequence↗
PubMed1994

Mid-P confidence intervals for the Poisson expectation.

Conventionally a confidence interval (CI) for the standardized mortality ratio is set using the conservative CI for a Poisson expectation, mu. Employing the mid-P argument we present alternative CIs that are shorter than the conventional ones. The mid-P intervals do not guarantee the nominal confidence level, but the true coverage probability is only lower than the nominal level for a few short ranges of mu. The implications for mid-P confidence intervals of various proposed definitions of two-sided tests for discrete data are discussed.

Confidence Intervals↗
PubMed1994

Transsphenoidal microsurgical management of pituitary adenomas.

The transsphenoidal microsurgical operation is the best choice for most pituitary adenomas, whether or not there is an extension into the sphenoid or a supra-sellar extension without lateral spread. The advantage of this approach is that it allows selective removal of the adenoma and therefore can preserve normal pituitary function. In our series of 249 cases 79% had achieved a remission at follow-up one year or more after surgery. The surgical failure rate was 21%, and the mortality rate 0.8%. Complications occurred in 5.6%; most were temporary and minimal. The recurrence rate after transsphenoidal microsurgery was lower than that quoted in the literature after craniotomy. The smaller the size of the adenomas and the less the hormone abnormality preoperatively, the better the outcome.

Adenoma↗
PubMed1994

Nonrandom allelic variation in the regulatory complex of HLA class I genes.

Recently, we have demonstrated that the HLA class I regulatory complex (CRC) is conserved in a locus-specific manner with limited allelic variation. In this study, we have analyzed the CRC sequences of the alleles that showed variation from a total of 22 well-characterized, HLA-homozygous B-LCLs, using PCR amplification of genomic DNA and direct sequencing. We compared the sequences of these alleles with their respective locus consensus sequence at kappa B1, kappa B2, the IRS, the putative NRE, and the HLA counterpart of the H-2RII region, the R x R beta-binding site. The palindromic kappa B1 sequence, an active enhancer, was found to be conserved in all HLA-A and -B alleles and in one HLA-C allele. The sequences of the kappa B2 site showed locus-specific divergence with almost no allelic variation. The IRS is strictly locus specific and HLA-B and -C have identical sequences in this region. Variation in the putative NRE sequence and RII-kappa B2 junctional sequence was apparently generated by gene conversion between B and C loci. Each locus had two sequence patterns at the putative RII site. Overall, sequence analysis of variant alleles demonstrated that there is limited variation in a nonrandom fashion. These results may provide a structural basis for locus and allele-specific modulation of these genes.

Alleles↗
PubMed1994

The large subunit of the pig heart mitochondrial membrane-bound beta-oxidation complex is a long-chain enoyl-CoA hydratase: 3-hydroxyacyl-CoA dehydrogenase bifunctional enzyme.

The subunit locations of the component enzymes of the pig heart trifunctional mitochondrial beta-oxidation complex are suggested by analyzing the primary structure of the large subunit of this membrane-bound multienzyme complex [Yang S.-Y. et al. (1994) Biochem. biophys. Res. Commun. 198, 431-437] with those of the subunits of the E. coli fatty acid oxidation complex and the corresponding mitochondrial matrix beta-oxidation enzymes. Long-chain enoyl-CoA hydratase and long-chain 3-hydroxyacyl-CoA dehydrogenase are located in the amino-terminal and the central regions of the 79 kDa polypeptide, respectively, whereas the long-chain 3-ketoacyl-CoA thiolase is associated with the 46 kDa subunit of this complex. The pig heart mitochondrial bifunctional beta-oxidation enzyme is more homologous to the large subunit of the prokaryotic fatty acid oxidation complex than to the peroxisomal trifunctional beta-oxidation enzyme. The evolutionary trees of 3-hydroxyacyl-CoA dehydrogenases and enoyl-CoA hydratases suggest that the mitochondrial inner membrane-bound bifunctional beta-oxidation enzyme and the corresponding matrix monofunctional beta-oxidation enzymes are more remotely related to each other than to their corresponding prokaryotic enzymes, and that the genes of E. coli multifunctional fatty acid oxidation protein and pig heart mitochondrial bifunctional beta-oxidation enzyme diverged after the appearance of eukaryotic cells.

3-Hydroxyacyl CoA Dehydrogenases↗
PubMed1994

SSOP typing of the Tenth International Histocompatibility Workshop reference cell lines for HLA-C alleles.

HLA-C gene products are the most poorly understood of the HLA class I molecules because they express at low level on the cell surface compared to HLA-A and -B. However, recent evidence shows that HLA-C molecules are functionally competent in eliciting T-cell responses and in controlling NK-cell recognition. Approximately 20 to 50% of HLA-C alleles type "blank" in most populations. To provide a better definition of the HLA-C alleles, we analyzed 98 extensively characterized B-cell lines from the 10th International Histocompatibility Workshop. Selective HLA-C-specific DNA amplification of exons 2 and 3 from DNA prepared from the cell panel was achieved with the use of two sets of locus-specific primers. We used 64 sequence-specific oligonucleotide probes (SSOPs) complementary to variable sites in exons 2 and 3 to generate hybridization patterns. Twenty-five alleles were found among these patterns, including seven new alleles in the homozygous cell lines and seven potential new alleles in heterozygous cell lines. Differences between the new alleles and known alleles were generally small. Five major groups were identified in the Cw "blank" cells by the SSOP patterns. In addition, linkage between HLA-B specificities and HLA-C alleles was similar to previous observations. The present study demonstrated that SSOP typing was effective in identifying new alleles in homozygous typing cells but not in the heterozygous cells. Also, DNA typing can facilitate the identification of all HLA-C alleles, including those that serologically type as blanks. The HLA-C locus may be more polymorphic than was previously recognized.

Amino Acid Sequence↗
PubMed1993

Differential effect of human and mouse beta 2-microglobulin on the induction and the antigenic profile of endogenous HLA-A and -B antigens synthesized by beta 2-microglobulin gene-null FO-1 melanoma cells.

beta 2-Microglobulin (beta 2-mu) gene-null human melanoma FO-1 cells display lower reactivity with anti-HLA class I monoclonal antibodies (mAb) following transfection with a wild-type mouse beta 2-mu gene (referred to as FO-1C cells) than following transfection with a wild-type human beta 2-mu gene (referred to as FO-1H cells). Furthermore, binding assays with a panel of anti-HLA class I mAb detected higher reactivity of FO-1C cells with mAb TP25.99 than with mAb CR1-S63, CR10-215, CR11-115, TP67, and W6/32 but similar reactivity of FO-1H cells with all the mAb tested. While mAb TP25.99 recognizes a determinant expressed on beta 2-mu-free and beta 2-mu-associated HLA class I heavy chains, the remaining mAb recognize determinants expressed only on beta 2-mu-associated HLA class I heavy chains. The differential effects of mouse and human beta 2-mu on the reactivity with anti-HLA class I mAb of FO-1 cells reflect more than one mechanism. Besides abnormalities in the processing of HLA class I heavy chains associated with mouse beta 2-mu, this molecular complex appears to be unstable on the plasma membrane of FO-1 cells. To analyze the interaction of mouse beta 2-mu with HLA-A and -B antigens, the HLA phenotype of FO-1 cells was determined, using a combination of isoelectric focusing analysis of antigens immunoprecipitated from radiolabeled cells with mAb to monomorphic determinants of HLA class I antigens, binding assays with a limited number of mAb recognizing HLA class I allospecificities, and sequence-specific oligonucleotide probe typing. Although association with mouse beta 2-mu does not cause marked differences in the expression of HLA-A25 and -B8 antigens on the cell surface of FO-1 cells, it causes a selective reduction in the expression of determinants recognized by anti-HLA-A mAb F4/72 and VF19-LL67 and by anti-HLA class I mAb W6/32 on HLA-A25 allospecificities. The differential effect of the association with mouse beta 2-mu on the antigenic profile of HLA-A25 and -B8 antigens may reflect the different characteristics of the amino acids at residue 12, which interact with residue 33 of beta 2-mu. The latter residue is the only one to differ between human and mouse beta 2-mu in the stretch of amino acids interacting with the alpha 1 and alpha 2 domains of HLA class I heavy chains.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1992

Inhibition of enoyl-CoA hydratase by long-chain L-3-hydroxyacyl-CoA and its possible effect on fatty acid oxidation.

The kinetics of bovine liver enoyl-CoA hydratase (EC 4.2.1.17) or crotonase with 2-trans-hexadecenoyl-CoA as a substrate were studied because different rates were obtained with two assay methods based on measurements of substrate utilization and product formation, respectively. L-3-Hydroxyhexadecanoyl-CoA, the product of the crotonase-catalyzed hydration of 2-trans-hexadecenoyl-CoA, was found to be a strong competitive inhibitor of the enzyme with a Ki of 0.35 microM. In contrast the short-chain product, L-3-hydroxybutyryl-CoA, is a weak competitive inhibitor with a Ki of 37 microM. L-3-Hydroxyhexadecanoyl-CoA is a much stronger inhibitor of crotonase than are other short-chain and long-chain intermediates of beta-oxidation and crotonase is more severely inhibited by this compound than are all beta-oxidation enzymes tested so far. Determination of true kinetic parameters for the crotonase-catalyzed hydration of long-chain substrates requires the removal of product in a coupled assay. When this was done, the Km for 2-trans-hexadecenoyl-CoA with bovine liver crotonase was found to be only 9 microM. It is suggested that under conditions of restricted beta-oxidation, when 3-hydroxyacyl-CoAs accumulate in mitochondria, the inhibition of crotonase by long-chain 3-hydroxyacyl-CoAs may limit the further degradation of medium-chain and short-chain intermediates of beta-oxidation.

Acyl Coenzyme A↗