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Y F Chang

Publications and source records attributed to Y F Chang.

At least 19 recordsLinked to original sources
PubMed1992

Amplification and characterization of an inverted repeat from the Chlamydomonas reinhardtii mitochondrial genome.

Based on the nucleotide (nt) sequences of cob and L2a, two oligodeoxyribonucleotides (oligos) were synthesized and used in the polymerase chain reaction (PCR) to amplify the termini of the Chlamydomonas reinhardtii mitochondrial (mt) genome. A 0.8-kb PCR product was detected by agarose-gel electrophoresis when using unligated mt DNA as the template for PCR. This may have indicated the presence of a naturally occurring circular mt DNA molecule that acted as the PCR template. The 0.8-kb DNA could also be amplified from the linear mt DNA via an intramolecular jump during PCR. The sequence data from the 0.8-kb PCR product, and the right 0.6-kb and left 1-kb terminal fragments of the linear mt DNA, along with Southern hybridization analysis, indicated that a 0.49-kb inverted repeat (IR) sequence is present at the right and left termini of the linear mt DNA. The IR contains A+T-rich clusters, as well as numerous short direct repeats (DR) and IR, and might be involved in the recombination, replication and expression of the C. reinhardtii mt genome.

Animals↗
PubMed1992

Assay for L-pipecolate oxidase activity in human liver: detection of enzyme deficiency in hyperpipecolic acidaemia.

A direct assay method is described for L-pipecolate oxidase. The assay uses NaHSO3 to trap the L-alpha-amino [3H]adipate delta-semialdehyde (AAS) formed as a direct reaction product of L-pipecolate oxidase from L-[3H]pipecolic acid. The adduct so formed was separated from the substrate on Dowex 50 (H+) column. The product was identified as [3H]AAS by amino acid analysis after breaking down the adduct by boiling under acidic conditions. The assay is simpler and more specific than fluorometric methods; it is also more sensitive, requiring at most 16 micrograms of liver peroxisome-enriched protein per assay. We have used this assay procedure to detect L-pipecolate oxidase in skin fibroblasts obtained from a control subject and from patients of hyperpipecolic acidaemia and Zellweger syndrome and found that this enzyme activity is present in the control, but absent or decreased in the patients with the peroxisomal disorders.

Humans↗
PubMed1992

Developmental changes of L-lysine-ketoglutarate reductase in rat brain and liver.

1. Developmental aspects of L-lysine-ketoglutarate reductase, the first enzyme in saccharopine pathway of L-lysine degradation in rat liver and brain tissues were studied. 2. Although the adult rat brain shows negligible activity, the enzyme activity was shown to be highly active during the early stages of development. 3. The enzyme activity gradually decreased through development in the brain, whereas it gradually increased in the liver, establishing the fact that the saccharopine pathway is the major pathway in liver. 4. Our results also show that glucagon stimulated the induction of this enzyme by 2-3-fold in both adult liver and brain tissues.

Aging↗
PubMed1992

Sequence analysis of the ROB-1 beta-lactamase gene from Actinobacillus pleuropneumoniae.

The ROB-1 beta-lactamase gene from Actinobacillus pleuropneumoniae was cloned and sequenced. The structural gene encodes a 305 amino acid polypeptide. The ROB-1 beta-lactamase gene sequence is identical to that derived from Pasteurella haemolytica and only one amino acid different from that of Haemophilus influenzae, suggesting that they are derived from the same ancestor, and transformed from one to another.

Actinobacillus pleuropneumoniae↗
PubMed1992

Regional localization of human beta-casein gene (CSN2) to 4pter-q21.

Milk proteins are crucial for the development of all newborn mammals. Caseins that constitute the bulk of the protein in mammalian milk have been shown to be members of a multigene family in at least two species. They are among the most rapidly diverging groups of proteins, and their numbers vary widely among species. beta- and kappa-Caseins are the only caseins present in human milk. Using polymerase chain reaction on genomic DNA from somatic cell hybrids, we have localized the human beta-casein gene (CSN2) to 4pter----q21.

Blotting, Southern↗
PubMed1992

Exon skipping in human beta-casein.

Earlier amino acid alignments of mature beta-caseins showed that the human protein was shifted in alignment relative to other species, with amino acid deletions in the N-terminal region and others inserted in the C-terminal region. Our alignment, based on cDNA sequences and their translation products, has shown that the amino acid deletions correspond exactly to exon 3 in the other species. Cloning and sequencing of a segment of the human beta-casein gene between exons 2 and 4 revealed the presence of an intact exon 3 sequence in the gene. An interruption of the polypyrimidine tract adjacent to the 5' end of exon 3 sequence may account for the omission of the exon from human beta-casein mRNA.

Amino Acid Sequence↗
PubMed1992

Separable domains define target cell specificities of an RTX hemolysin from Actinobacillus pleuropneumoniae.

The leukotoxin (LktA) from Pasteurella haemolytica and the hemolysin (AppA) from Actinobacillus pleuropneumoniae are members of a highly conserved family of cytolytic proteins produced by gram-negative bacteria. Despite the extensive homology between these gene products, LktA is specific for ruminant leukocytes while AppA, like other hemolysins, lyses erythrocytes and a variety of nucleated cells, including ruminant leukocytes. Both proteins require activation facilitated by the product of an accessory repeat toxin (RTX) C gene for optimal biological activity. We have constructed six genes encoding hybrid toxins by recombining domains of ltkA and appA and have examined the target cell specificities of the resulting hybrid proteins. Our results indicate that the leukocytic potential of AppA, like that of LktA, maps to the C-terminal half of the protein and is physically separable from the region specifying erythrocyte lysis. As a consequence, we were able to construct an RTX toxin capable of lysing erythrocytes but not leukocytes. The specificity of one hybrid was found to be dependent upon the RTX C gene used for activation. With appC activation, this hybrid toxin lysed both erythrocytes and leukocytes, while lktC activation produced a toxin which could attack only leukocytes. This is the first demonstration that the specificity of an RTX toxin can be determined by the process of C-mediated activation.

Actinobacillus pleuropneumoniae↗
PubMed1992

Characterization of plasmids with antimicrobial resistant genes in Pasteurella haemolytica A1.

Two R plasmids, pYFC1 and pYFC2, from Pasteurella haemolytica A1 encoding sulfonamide, streptomycin (pYFC1), and ampicillin (pYFC2) resistances have been characterized by restriction endonuclease digestions, subcloning or DNA sequencing. pYFC1 consists of 4225 bp and is 51.9% in AT content. Physical mapping indicated a highly conserved region of restriction sites among pYFC1, RSF1010, pGS05, pFM739, pHD148 and pGS03B. pYFC1 encoded a dihydropteroate synthase (29.8 kDa), and streptomycin kinase (29.6 kDa) which is homologous in nucleotide sequences or deduced amino acid sequence to that encoded by a broad-host range IncQ plasmid RSF1010. Based on the primary structure of pYFC1, the sulfonamide and streptomycin genes are derived from the same ancestor of RSF1010. pYFC2 is similar to the plasmid from P. haemolytica LNPB51 isolated in France by partial restriction enzyme mapping. pYFC1 and pYFC2 have the same size of 4.2 kbp.

Amino Acid Sequence↗
PubMed1992

Effect of sodium butyrate on glucocorticoid-sensitive and -resistant P1798 lymphosarcoma.

This study aims to examine the effect of sodium butyrate on the viability and the level of glucocorticoid receptors and cells cycle progression in glucocorticoid-sensitive and -resistant P1798 cells. Our results indicated that low levels of sodium butyrate had no effect on either the viability or the receptor level. However, high-level (5 mM) sodium butyrate appeared to reduce cell viability as well as the glucocorticoid receptor level. On the other hand, sodium butyrate inhibited cell cycle progression in a dose-dependent manner. This response was similar in both the glucocorticoid-sensitive and -resistant P1798 cells. Results from this study suggested that the sodium butyrate induced effect may be cell cycle related.

Butyrates↗
PubMed1991

Correlation between enhancement of [3H]flunitrazepam binding and suppression of pentylenetetrazol-induced seizures by L-lysine.

L-Lysine enhanced the specific [3H]flunitrazepam (FTZ) binding of bovine brain membranes in vitro. Inhibition of specific [3H]FTZ binding to brain membranes in vitro by pentylenetetrazol (PTZ) at concentrations 0.46 mM and below was reversed by increasing L-lysine concentrations in the incubation mixture; further increase of L-lysine concentration enhanced this binding. However, inhibition of [3H]FTZ binding by PTZ higher than 2.3 mM was reversed only partially by L-lysine. L-Lysine enhanced specific [35S]t-butylbicyclophosphorothionate (TBPS) binding on mouse brain membranes in a dose-dependent manner (EC approximately 5 microM). This enhancement was inhibited by PTZ dose dependently. Inhibition of [35S]TBPS binding by PTZ was attenuated slightly by L-lysine. L-Lysine enhanced [3H]FTZ binding in intact mice in a dose- or concentration-dependent manner with an ED50 of 6 mmol/kg body weight or EC50 of 3 mumol/g brain tissue, respectively. Similar effect was observed for L-lysine in ex vivo [3H]FTZ binding study when [3H]FTZ was incubated in vitro with an ED50 of 1 mmol/kg mouse or EC50 of 0.7 mumol/g brain. PTZ not only induced seizures, but also inhibited specific [3H]FTZ binding to brain membranes in a dose-dependent manner. L-Lysine, in a dose-dependent manner, suppressed seizures caused by PTZ at 50 or 60 mg/kg, or prolonged the time of seizure onset (seizure latency) caused by higher doses of PTZ (90 or 100 mg/kg). Pretreatment with L-lysine at 1, 5, 10 or 20 mmol/kg not only reversed the inhibition of the specific [3H]FTZ binding caused by PTZ at 50, 90 or 100 mg/kg, but also enhanced this binding above control level.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Analysis of monoamines in the cerebrospinal fluid of Chinese patients with Alzheimer's disease.

We have established HPLC assay conditions that could measure the levels of 14 monoamines and their metabolites simultaneously. Monoamine levels in cerebrospinal fluids of 12 Chinese patients with Alzheimer's disease were compared with those in samples from patients with benign prostate hyperplasia. Of the 14 monoamines and metabolites, only three were found to be present in all samples. Although the levels of 5-hydroxy-3-indoleacetic acid (HIAA) and homovanillic acid (HVA) in cerebrospinal fluid of patients with Alzheimer's disease were lower, and the levels of 3-methoxy-4-hydroxyphenylglycol (MHPG) higher, as compared to control patients, no significant differences were found between these two groups.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1991

The Actinobacillus pleuropneumoniae hemolysin determinant: unlinked appCA and appBD loci flanked by pseudogenes.

The appBD genes encoding the secretion functions for the 110-kDa RTX hemolysin of Actinobacillus pleuropneumoniae have been cloned and sequenced. Unlike analogous genes from other RTX determinants, the appBD genes do not lie immediately downstream from the hemolysin structural gene, appA. Although isolated from a diverse group of gram-negative organisms, the appBD genes and the characterized RTX BD genes from other organisms all exhibit a high degree of homology at both the DNA and predicted amino acid sequence levels. Analysis of the DNA sequences 3' to appA and 5' to appB suggests that these regions harbor remnant RTX B and A pseudogenes, respectively. Although the appA gene is most similar to the lktA gene from Pasteurella haemolytica (Y. F. Chang, R. Young, and D. K. Struck, DNA 8:635-647, 1989), the RTX A pseudogene upstream from appB most closely resembles the hlyB gene from Escherichia coli, suggesting that the appCA and appBD operons were derived from different ancestral RTX determinants.

Actinobacillus↗
PubMed1990

L-pipecolic acid metabolism in human liver: detection of L-pipecolate oxidase and identification of its reaction product.

L-Pipecolate oxidase, an enzyme that oxidizes L-pipecolic acid in the human liver has been demonstrated in the peroxisomal preparation. This enzyme oxidizes L-pipecolic acid with concomitant production of H2O2 in the peroxisome of the normal human liver. The immediate product of L-pipecolic acid oxidation has been identified as L-alpha-aminoadipate delta-semialdehyde. This reaction product was directly, and also after conversion to pipecolic acid by NaBH4 reduction, characterized by use of an amino acid analyzer and thin-layer chromatography. The pit fall of an indirect assay of L-pipecolate oxidase by means of the assay of alpha-aminoadipic acid formation was discussed.

2-Aminoadipic Acid↗
PubMed1990

L-pipecolic acid metabolism in human liver: L-alpha-aminoadipate delta-semialdehyde oxidoreductase.

A soluble enzyme that catalyzes the oxidation of L-alpha-aminoadipate delta-semialdehyde to L-alpha-aminoadipic acid in the presence of NAD+ has been isolated and characterized from human liver. This enzyme L-alpha-aminoadipic delta-semialdehyde oxidoreductase has been found to be localized in the cytosol using subcellular fractionation and marker enzyme assays. The reaction product of this enzyme has been identified as L-alpha-aminoadipic acid by use of an amino acid analyzer and thin layer chromatography. The enzymatic reaction was irreversible and has a pH optimum of 8. The enzyme was stimulated by Mg2+, Cu2+ and Mn2+, and has a requirement of free -SH groups. The Km and Vmax values for its substrate L-alpha-aminoadipate delta-semialdehyde were shown to be 181 microM and 71.4 pmol.min-1.mg-1, respectively, and for its coenzyme NAD+ to be 454 microM and 142.9 pmol.min-1.mg-1, respectively. The characteristics of the oxidoreductase obtained from the human liver and Pseudomonas putida were compared.

2-Aminoadipic Acid↗
PubMed1990

Deletion analysis resolves cell-binding and lytic domains of the Pasteurella leukotoxin.

A series of internal deletions in the lktA gene of Pasteurella haemolytica has been constructed. All of the deletions eliminated the lytic activity of the leukotoxin towards the bovine lymphoma cell line, BL-3. Deletions removing segments of the amino-proximal hydrophobic region, which is thought to constitute an essential membrane-spanning domain, were found to agglutinate BL-3 cells. Agglutination was similar to lysis by the wild-type toxin in that it was dependent upon the presence of calcium and required expression of the lktC gene. The agglutinating deletion proteins protected BL-3 cells from lysis by the wild-type toxin in a competitive fashion. This suggests that these mutants bind to a surface feature of the leukocyte which interacts with the native leukotoxin. These findings demonstrate that the cell-binding and lytic domains of the leukotoxin are separable.

Animals↗
PubMed1989

Enhancement of benzodiazepine receptor binding by L-lysine is chloride-dependent and due to increase in binding affinity.

L-Lysine enhanced specific [3H]flunitrazepam binding dose dependently on extensively washed bovine brain membrane in vitro. This enhancement was stimulated by chloride ions dose dependently. Scatchard analysis indicated this enhancement by L-lysine to be due to increase in binding affinity (KD) with no change in receptor density (Bmax). Since enhancement of [3H]flunitrazepam binding by L-lysine was partially inhibited by picrotoxinin, L-lysine may act on a distinct picrotoxinin-sensitive site which was distinct from the gamma-aminobutyric acid receptor site. This binding site, however, appears to have some features resembling that of the central nervous system-depressant barbiturates.

Animals↗
PubMed1989

Secretion of the Pasteurella leukotoxin by Escherichia coli.

Nucleic acid sequence analysis has indicated that the leukotoxin determinant from Pasteurella haemolytica is related to the hemolysin determinant from E. coli. The cloning and expression in E. coli of the lktCA genes has been previously reported, but the existence of leukotoxin secretory genes equivalent to hlyBD has not been documented. In this report we demonstrate that a 4.0 kb segment of P. haemolytica genomic DNA distal to the lktA gene, when expressed in trans to the previous cloned lktCA genes, allow the synthesis and secretion of active leukotoxin from E. coli. Complementation analysis using the cloned hlyB and hlyD genes indicates that this secretory locus derived from P. haemolytica contains two genes which we designate, by analogy, lktB and lktD.

Amino Acid Sequence↗