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Biomedical subjects

S Y Yang

Publications and source records attributed to S Y Yang.

At least 127 records · Page 7Linked to original sources
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↗
PubMed1993

Association of both enoyl coenzyme A hydratase and 3-hydroxyacyl coenzyme A epimerase with an active site in the amino-terminal domain of the multifunctional fatty acid oxidation protein from Escherichia coli.

An Escherichia coli mutant multienzyme complex of fatty acid oxidation, composed of two 41-kDa beta-subunits and two 79-kDa mutant alpha-subunits with the alpha/Gly116-->Phe substitution, has been overproduced and purified. The catalytic properties of 3-ketoacyl-coenzyme A (CoA) thiolase and L-3-hydroxyacyl-CoA dehydrogenase were found to be virtually identical with those of the wild type, whereas both enoyl-CoA hydratase and 3-hydroxyacyl-CoA epimerase activities were eliminated by the alpha/Gly116-->Phe mutation. delta 3-cis-delta 2-trans-Enoyl-CoA isomerase was only slightly affected by the mutation. The results of this study, together with the sequence analysis of the large alpha-subunit of the E. coli complex (Yang, X.-Y. H., Schulz, H., Elzinga, M., and Yang, S.-Y. (1991) Biochemistry 30, 6788-6795) and a demonstration of the epimerization of D-3-hydroxyacyl-CoAs in E. coli via a dehydration/hydration mechanism (Smeland, T. E., Cuebas, D., and Schulz, H. (1991) J. Biol. Chem. 266, 23904-23908), lead to the conclusion that enoyl-CoA hydratase and 3-hydroxyacyl-CoA epimerase are associated with a common active site in the amino-terminal domain of the multifunctional fatty acid oxidation protein. Thus the E. coli hydratase and epimerase activities represent two functions of a unique crotonase that converts both L- and D-3-hydroxyacyl-CoAs to 2-trans-enoyl-CoAs. Moreover, the results suggest that the amino-terminal domain of the large alpha-subunit is also involved in the isomerase activity but the key residue(s) required for catalyzing the isomerization is distinct from the crotonase.

Acetyl-CoA C-Acyltransferase↗
PubMed1993

Cloning and chromosome mapping of human retinoid X receptor beta: selective amino acid sequence conservation of a nuclear hormone receptor in mammals.

The murine retinoid X receptor beta (mRXR beta) is a nuclear hormone receptor that activates transcription of murine major histocompatibility complex (MHC) class I genes in response to retinoic acid. In this study, the human RXR beta gene was mapped onto the short arm or centromeric region of chromosome 6 (6pter-q13), which also harbors the MHC. Chromosomal localization was performed by Southern hybridization of genomic DNA from human rodent cell hybrids with the mRXR beta gene as a probe. In addition, a full-length cDNA clone encoding a human RXR beta was isolated by nucleic acid screening of a human cDNA library with a fragment of the mRXR beta gene as a probe. Comparison of the nucleotide-coding sequences of the human and the murine RXR beta revealed a predominance of third base substitutions, resulting in selective conservation of the predicted amino acid sequence of the proteins. The overall sequence homology was 97.6% on the amino acid level as opposed to 91.6% on the nucleotide level. In Northern hybridization experiments with the human cDNA as a probe, RXR beta gene transcripts were detected in a variety of human tumor cell lines, regardless of whether these cell lines expressed MHC class I genes.

Amino Acid Sequence↗
PubMed1993

Review of 140 patients with brain abscess.

There were 140 cases of brain abscess treated between 1980 (when CT scanning became available) and June 1991. These arose by spread of a contiguous area of infection in 37%, and from another identified cause in 22%; the origin was undetermined in 41%. There were multiple abscesses in 11%. The abscess was < 2 cm in diameter in 21%. In two-thirds of the patients, the intracranial pressure was raised, there were localizing neurologic signs in 33%, and in 28% there were epileptic seizures. The computed tomographic (CT) feature of an abscess in the capsular stage was a thin, regular, and uniform, ring-like enhancement. In the cerebritis stage, nine out of 17 patients showed a uniform enhancement throughout the lesion. Since 1989, 14 cases have been investigated with magnetic resonance imaging (MRI). In 11, the abscess was in the capsular stage. In both T1- and T2-weighted images, the abscess and the surrounding inflammatory area were well demonstrated, and with T2-weighting, the capsule showed a low-intensity signal clearly. In the three abscesses in the cerebritis stage, there was a uniform abnormality with indistinct margins between the abscess, inflammatory edema, and surrounding grey and white matter. All cases received a combination of wide-spectrum antibiotics before the organism was identified; and later the medication was administered according to bacteriologic indication of the organism of 112 cases, organisms were identified in 71%, with anaerobic organisms occurring in 30% of these. In 127 cases, surgical treatment was used: either repeated aspiration, excision or both. We treated 13 cases that had small, early, or multiple abscesses with antibiotics only. The mortality with surgical treatment was 7.9%, and no case treated conservatively died.

Adult↗
PubMed1993

Isoelectric focusing subtypes of HLA-A can be defined by oligonucleotide typing.

This study describes a simple and direct method for sequence-specific oligonucleotide probe (SSOP) typing of the A locus of HLA class I genes. Genomic DNA from a panel of over 200 cells which have been characterized by the methods of serology and isoelectric focusing (IEF) for the HLA class I antigens was used for locus-specific PCR amplification of HLA-A sequences. Dot blot hybridization of the amplified products was performed with 28 SSOPs derived from hypervariable regions in exon 2 and 3. Co-amplification of three alleles of HLA-H pseudogene in apparent linkage disequilibrium with HLA-A2 and A10 was observed but did not interfere with the typing of HLA-A alleles. Using short SSOPs (15 nucleotides each) in single temperature tetramethylammonium chloride (TMAC) hybridization and washing steps, 30 IEF-definable isotypes of HLA-A antigens could be unambiguously defined by their hybridization patterns. Moreover, comparison of the typing results with available nucleotide sequences of HLA-A alleles showed that the conditions used allowed faithful detection of single codon mismatches between probe and template. Thus, these alleles can be identified by their unique hybridization patterns generated by the SSOPs. Nucleotide sequence analysis of any new HLA-A allele will further permit its rapid and unambiguous characterization by SSOP typing.

Amino Acid Sequence↗
PubMed1993

DNA-binding proteins for transcription enhancing region of HLA class I gene.

Class I regulatory complex (CRC) located in the 5'-upstream region of MHC class I gene contains transcriptional enhancing sequences, called Enh A. This Enh A region contains tandem-arranged kappa B-like sites, one of which has a well-conserved perfect palindromic sequence. The second kappa B-like site, juxtaposed to the perfect palindrome, contains an imperfect palindromic sequence. In B-cell nuclear extracts, we have identified at least four sequence-specific protein complexes; three shared the repeated kappa B enhancer as their binding motifs. The perfect palindromic sequence facilities the binding of a complex termed BI, while the imperfect palindrome provides the binding sites for two other complexes, BII and BIII. The BII and BIII complexes exhibited binding crossreactivity with other kappa B-related motifs and recognized both the perfect and imperfect palindromic sequences, whereas the BI complex was specific for the perfect palindromic sequence which is unique to the class I promoters. A DNA segment outside the repeated kappa B enhancers probably binds the fourth complex, BIV. These complexes, except for the perfect palindrome-binding complex, differ from those described for the murine class I promoter. The binding characteristics of these factors suggest that the mechanism controlling the class I transcription may be quite complex.

Animals↗
PubMed1993

Influence of strain on [3H]thymidine incorporation, surfactant-related phospholipid synthesis, and cAMP levels in fetal type II alveolar cells.

Episodic fetal breathing movements occur in utero; however, their purpose is not known. While some evidence indicates these movements produce distention of the fetal lung, the effects of eliminating the movements on lung development are not clear. Using preparations of the surfactant-producing fetal rabbit lung type II cells, we have examined the hypothesis that distention is involved in maturation of these cells as determined by replication rate and phospholipid synthesis. Differentiating type II cells were isolated from fetal rabbit lungs on gestational day 24. After allowing 24 h for the cells to attach, distention (10%) was applied using a Flexercell apparatus at a rate of 3 s of strain and 57 s of rest for 24 or 48 h. Cells were concurrently incubated with [3H]thymidine. Autoradiography showed that [3H]thymidine-labeled nuclei of fetal type II cells and fibroblasts could be identified. Strain significantly increased incorporation of the radioisotope into DNA. In the remaining studies, cells were grown to confluence prior to use. Cell viability after straining (3 or 50 cycles per minute [cpm] for 48 h) was assessed by incubating with diacetyl fluorescein/ethidium bromide and viewing by fluorescence microscopy. Straining did not alter cellular viability. Lactate dehydrogenase was also assayed in the culture medium. Straining did not cause release of lactate dehydrogenase. Ultrastructural examination showed typical cellular appearance in the strained cells. Extracellular lamellar body material was also observed. The incorporation of [3H]choline (3 or 50 cpm) into cellular phospholipids was measured under static conditions or under distention. [3H]choline-labeling of phosphatidylcholine and disaturated phosphatidylcholine was significantly increased by distention at either 3 or 50 cpm.(ABSTRACT TRUNCATED AT 250 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↗
PubMed1992

Effect of age-related lipid peroxidation on membrane fluidity and phospholipase A2: modulation by dietary restriction.

Age-related changes in membrane property are generally accepted phenomena. In this report, using the anti-lipoperoxidative measure of dietary restriction on membranes, the age-related effects of lipid peroxidation on membrane fluidity are explored in conjunction with the membrane-associated phospholipase A2. The fluidity of mitochondrial and microsomal membranes from ad libitum fed rats shows a progressive decline with age as indicated by a substantial decrease in two parameters, l/polarization and l/anisotropy. In contrast, the membrane fluidity of dietary restricted rats shows slight changes between 6 and 24 months of age. Evidence is presented to support the possibility that age-related peroxidation of membrane lipids may play a significant role in bringing about fluidity changes in aged membranes. The findings on the increased phospholipase A2 with age is also consistent with this conclusion.

Aging↗
PubMed1992

Biochemical analysis of MHC and non-MHC lymphocyte membrane antigens.

Basic biochemical techniques have been skillfully used to characterize MHC-bound peptides and to examine the changes that occur in MHC molecules and lymphocyte membrane receptor complexes upon ligand binding. The fine tuning of these experimental approaches was possible because of the availability of a variety of biochemical and biological reagents.

Affinity Labels↗
PubMed1992

[Changes in serum endogenous digitalis-like factor concentration in patients with renal impairment].

Measurement of serum endogenous digitalis-like factor (EDF) concentration was carried out in 58 patients with renal impairment with radioimmunoassay. The results showed that serum EDF concentration in patients with renal impairment was markedly higher than that of normal cases. The serum EDF concentration was significantly elevated with decrease of renal function and was positively correlated with the levels of BUN and blood creatinine. The serum EDF concentration in patients with primary and secondary renal impairment was of no difference. It was found that the difference between patients with and without hypertension was statistically significant. The serum EDF concentrations were markedly decreased after hemodialysis but still higher than those of normal cases.

Adult↗
PubMed1991

Nucleotide sequence of the promoter and fadB gene of the fadBA operon and primary structure of the multifunctional fatty acid oxidation protein from Escherichia coli.

The primary structure of a multifunctional protein, the large alpha-subunit of the Escherichia coli fatty acid oxidation complex, was determined by sequencing the fadB region of the fadBA operon. The amino-terminal sequence of this protein had been established by Edman degradation. The transcription start site of the fadBA operon was located 42 nucleotides upstream of the initiator codon of the fadB gene by primer extension analysis. Sequences of -10 and -35 regions of the promoter responsible for interaction with RNA polymerase were found to be CACACT and TTTGCA, respectively. The location of the promoter of the fadBA operon was defined, and the transcription direction of this operon, from fadB to fadA, as previously proposed [Yang, S.-Y., et al. (1990) J. Biol. Chem. 265, 10424-10429], was corroborated. The multifunctional protein is composed of 729 amino acid residues and has a calculated Mr of 79,593. A putative NAD-binding beta alpha beta-fold necessary for L-3-hydroxyacyl-CoA dehydrogenase function was found in the central region of the fadB gene product. Sequence analyses suggest that the functional domains of the multifunctional protein are arranged in the order enoyl-CoA hydratase:L-3-hydroxyacyl-CoA dehydrogenase: delta 3-cis-delta 2-trans-enoyl-CoA isomerase and suggest that the genes of the E. coli multifunctional protein and rat peroxisomal trifunctional beta-oxidation enzyme evolved from a common ancestral gene.

3-Hydroxyacyl CoA Dehydrogenases↗
PubMed1991

Transcatheter double-blade valvotomy for the treatment of valvar pulmonary stenosis.

A transcatheter double-blade valvotome for cutting a stenotic pulmonary valve has been devised. The valvotome consists of a retractable rhomboid structure at its tip, with a blade on each side of its proximal half. By tugging the extended blades from the pulmonary artery to the right ventricle it is possible to tear the stenotic valve. After animal experiments proved the feasibility and safety of this method, it was used in three children with pulmonary stenosis. The results were encouraging.

Adolescent↗
PubMed1991

Differential modulation of the CD-2 and CD-3 T cell activation pathways by a monoclonal antibody to Leu-13.

MAb anti-Leu-13 reacts with a 16-kDa-interferon-responsive lymphocyte-endothelial cell surface antigen and has been demonstrated to induce lymphocyte aggregation by an undefined adhesion pathway. While anti-Leu-13 inhibits proliferation triggered by CD3 antibodies it was found to consistently augment proliferation induced by a pair of CD2 antibodies at suboptimally mitogenic concentrations. The latter mechanism of T cell activation may represent an antigen-nonspecific activation pathway requiring extensive cell-cell interaction. Proliferation induced via the CD2 pathway was very sensitive to the presence of monocytes whose inhibitory effect was reversed by indomethacin. While the potent inhibitory effect of PGE2 on proliferation induced via the CD2 pathway was weakly antagonized by anti-Leu-13, the combined effects of anti-Leu-13 and PGE2 on the CD3 pathway were additive and very inhibitory. The possibility that the Leu-13 signal reflects a mechanism by which a monocyte/macrophage-sensitive T cell activation pathway might be selectively amplified in vivo is discussed.

Antibodies, Monoclonal↗