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H Y Chang

Publications and source records attributed to H Y Chang.

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

Cosuppression of recF, recR and recO mutations by mutant recA alleles in Escherichia coli cells.

The ability of recA718, recA720, recA730, recA750 and two known recA(Srf) alleles (recA2020 and recA441) to act as suppressors of recF, recR and recO mutations was examined by studying their UV radiation sensitivity in uvrA cells of Escherichia coli. With the exception of recA718, all the mutant recA alleles examined were able to suppress the UV radiation sensitivity caused by recF, recR or recO mutations, but not by the recB mutation. The suppression by recA750 was minimal. The suppression of recF, recR and recO mutations by other recA alleles was more pronounced, but none of them could exert full suppression. Heterozygotes containing a mutant recA allele (recA720, recA730 or recA441) and recA2020 (or recA803, another known recA(Srf) allele) failed to produce any additive or synergistic suppression of recF, indicating that these suppressors did not use different mechanisms for their suppression. Similar to a requirement of recJ+ in the suppression of recF, the suppression of recR and recO mutations by mutant recA alleles also required recJ+. The similar phenotypes conferred by recF, recR, and recO mutations and the observations that a number of mutant recA alleles can cosuppress these three mutations suggest that the recF, recR and recO gene products may function together as a complex.

Alleles↗
PubMed1993

Analysis of the Drosophila gene for the laminin B1 chain.

We have isolated and sequenced a Drosophila genomic DNA that encodes the entire coding region of the laminin B1 chain. The genomic DNA sequenced spans 11,787 bp, including a 1.1-kb 5'-flanking region, 5 exons, 4 introns, and a 1.4-kb 3'-flanking region. The open reading frame is within the two largest exons, the exons 3 and 4, while the first two and the last exons are much smaller and are untranslated. The structure of the Drosophila laminin B1 gene is similar to the Drosophila laminin B2 gene. Their exon-intron lengths and Eco RI, Pst I restriction maps are quite conserved. Both of their open reading frames are very compact, and their first introns are much larger than all of the rest of the introns. These results are consistent with the suggestion that the B1 and B2 genes could be derived from an ancestral gene. The similarity of the proximal 5'-flanking regions of the Drosophila B1 and B2 genes is 46.6%. Also, similar sequences of transcriptional regulatory elements, even though not site conserved, are found in both proximal 5'-flanking regions of the B1 and B2 genes. When transfected into Drosophila SL-2 cells, pCAT plasmid containing 1,048 bp of 5'-flanking region shows a strong expression of chloramphenicol acetyltransferase (CAT) activity. The deletion clones that contain sequences between nucleotides -462 to +150, and -282 to +150 all show strong CAT activity. These results suggest that this 5'-flanking promoter region may contain DNA sequences that can promote the expression of the laminin B1 gene.

Amino Acid Sequence↗
PubMed1993

Regulation of diaphragmatic oxygen uptake by endothelium-derived relaxing factor.

The role of endogenous nitric oxide (NO) in the regulation of phrenic blood flow (Qphr) and O2 consumption (VO2) of the in situ isolated left hemidiaphragms was assessed in two groups of anesthetized, mechanically ventilated dogs. Saline was infused into the phrenic artery for 20 min in one group, whereas N omega-nitro-L-arginine (L-NNA, 6 x 10(-4) M) was infused in the other (L-NNA) group. Qphr and diaphragmatic VO2 were measured at rest and during 2 min of continuous 3-Hz stimulation of the left phrenic nerve. The animals were progressively hemorrhaged, and the measurements were repeated at various arterial pressures (Pa). For the resting diaphragm, Qphr at a mean Pa of 145 mmHg was lower in the L-NNA group than in the saline group; however, diaphragmatic VO2 values were similar in both groups. Qphr decreased with the decline in Pa in both groups, but O2 extraction ratios obtained at mean Pa of 25-45 mmHg were similar in both groups (71 vs. 73%). For the contracting diaphragm, Qphr and diaphragmatic VO2 values at a given Pa were lower in the L-NNA group than in the saline group (except at mean Pa < 75 mmHg). O2 extraction ratios obtained at a given Pa were similar in both groups. We concluded that 1) EDRF inhibition limits diaphragmatic blood flow both at rest and during 3-Hz stimulation; 2) diaphragmatic O2 extraction is unaffected by EDRF inhibition; and 3) the effect of EDRF release on diaphragmatic VO2 is dependent on the level of metabolic demands.

Animals↗
PubMed1993

Bronchoprovocation test by forced oscillation technique: airway hyperresponsiveness in chronic cough and psychogenic dyspnea subjects.

By measuring the respiratory resistance (Rrs) with the forced oscillation technique, we evaluated the airway responsiveness to methacholine in four groups of subjects (30 normal, 21 asthmatic, 60 chronic cough, and 30 psychogenic dyspnea subjects). After evaluating the airway responsiveness of normal and asthmatic subjects, four patterns of dose-response curves were found. All of the asthmatic subjects were responders (types III and IV), whereas all but two of the normal subjects were nonresponders (types I and II). The responders had more bronchoconstriction than the nonresponders who presented with a significant decrease in FEV1 after the test. If airway hyperresponsiveness to methacholine was defined as Cmin < or = 12.5 mg/mL, then this test showed 100% sensitivity, 97% specificity, a positive predictive value of 95.5%, and a negative predictive value of 100%. According to these criteria, 18 of 60 (30%) chronic cough subjects and six of 30 (20%) psychogenic dyspnea subjects had airway hyperresponsiveness. We conclude that bronchoprovocation test by the forced oscillation technique is a simple, safe and time-saving tool for measuring airway hyperresponsiveness. We also found that airway hyperresponsiveness is a common finding in subjects with chronic cough, and is also present in some subjects with psychogenic dyspnea.

Adult↗
PubMed1992

Cloning, sequencing and heterologous expression of a Klebsiella pneumoniae gene encoding an FAD-independent acetolactate synthase.

The gene encoding the valine-resistant and FAD-independent acetolactate synthase of Klebsiella pneumoniae was isolated and expressed in Escherichia coli. The nucleotide sequence of this gene was determined and it exhibited an open reading frame of 1680 bp in length. In vivo expression of the acetolactate synthase-encoding gene in E. coli revealed a single 60-kDa protein which is consistent with the molecular weight calculated from the deduced amino acid sequence of the gene product. The gene product shares about 20-30% homology with the acetolactate synthases of E. coli, yeast and higher plants.

Acetolactate Synthase↗
PubMed1992

Cyclosporin-mediated inhibition of bovine calcineurin by cyclophilins A and B.

The Ca(2+)- and calmodulin-dependent protein phosphatase calcineurin is inhibited by the immunosuppressant drug cyclosporin A in the presence of cyclophilin A or B. Of the two isoforms, cyclophilin B is more potent by a factor of 2-5 when either the phosphoprotein [32P]casein or the [32P]phosphoserine [Ser(32P)] form of the 19-residue bovine cardiac cAMP-dependent protein kinase regulatory subunit peptide RII, [Ser(32P)15]RII, is used as substrate. With [Ser(32P15]RII as substrate, the concentrations of the cyclosporin A.cyclophilin A and cyclosporin A.cyclophilin B complexes, which cause 50% inhibition of calcineurin activity, are 120 and 50 nM, respectively. Lowering the concentration of calcineurin 80% with [32P]casein as substrate lowered the apparent inhibition constant for each complex even further; 50% inhibition of calcineurin was observed at 40 nM for cyclosporin A.cyclophilin A, whereas it was less than 10 nM for cyclosporin A.cyclophilin B. In all inhibition assays with [32P]casein or [Ser(32P)15]RII, the concentration of calcineurin required for measurable phosphatase activity is such that these complexes behave as tight-binding inhibitors of calcineurin, and steady-state kinetics cannot be used to assess inhibition patterns or Ki values. Limited trypsinization of calcineurin produces a fragment that is still inhibited, indicating that the interaction of cyclosporin.cyclophilin with calcineurin does not require either calmodulin or Ca2+.

Amino Acid Isomerases↗
PubMed1992

The hydrolysis of natural phosphatidylethanolamines by phospholipase A2 from rat serum: a degree of selectivity is shown for docosahexaenoate release.

The selectivity of phospholipase A2 from serum was evaluated using radioassays and mass analyses of fatty acids liberated from phosphatidylcholine and phosphatidylethanolamine. These natural phospholipid substrates were labelled at the sn-2 position with radioactive oleate, linoleate and arachidonate. The rates of release of fatty acids were compared with their abundance at the sn-2 position of these phospholipid substrates. While there was little or no selectivity in the liberation of these fatty acids from phosphatidylcholine, there was some evidence for a preferential release of arachidonate with respect to linoleate from phosphatidylethanolamine. Mass analyses of free fatty acid products revealed that docosahexaenoate was consistently liberated at levels that exceeded its abundance at the sn-2 position of phosphatidylethanolamine. Three different, natural phosphatidylethanolamines with varying levels of docosahexaenoate showed a 1.2-1.8-fold enrichment of this polyunsaturate in the free fatty acid products compared with its abundance at the sn-2 position. This preference could also be shown when phosphatidylethanolamine was mixed with synthetic phosphatidylcholine as co-sonicated substrates. This preferential release of docosahexaenoate by serum phospholipase A2 is of considerable significance in the nervous system which is enriched in this polyunsaturate. The potential competition between liberated docosahexaenoate and arachidonate may be of fundamental importance in the response of brain to hemorrhage.

Animals↗
PubMed1992

Effects of an eight-hour advance of the light-dark cycle on sleep-wake rhythm in the rat.

We observed effects of an 8-h advance of the light-dark (LD) cycle on the sleep-wake rhythm in the rat. On the day phase-advanced, rapid eye movement (REM) sleep increased with its enhanced diurnal amplitude. Non-REM (NREM) sleep gradually increased in parallel with the decrease of its diurnal amplitude. Although the acrophase of NREM sleep gradually advanced after the phase advance, that of REM sleep did not significantly change. We confirmed that diurnal rhythm of REM sleep was hardly shifted and dissociated from the rhythm of NREM sleep under the eight-hour advance of the LD cycle in the rat.

Animals↗
PubMed1992

Active site mutants of human cyclophilin A separate peptidyl-prolyl isomerase activity from cyclosporin A binding and calcineurin inhibition.

Based on recent X-ray structural information, six site-directed mutants of human cyclophilin A (hCyPA) involving residues in the putative active site--H54, R55, F60, Q111, F113, and H126--have been constructed, overexpressed, and purified from Escherichia coli to homogeneity. The proteins W121A (Liu, J., Chen, C.-M., & Walsh, C.T., 1991a, Biochemistry 30, 2306-2310), H54Q, R55A, F60A, Q111A, F113A, and H126Q were assayed for cis-trans peptidyl-prolyl isomerase (PPIase) activity, their ability to bind the immunosuppressive drug cyclosporin A (CsA), and protein phosphatase 2B (calcineurin) inhibition in the presence of CsA. Results indicate that H54Q, Q111A, F113A, and W121A retain 3-15% of the catalytic efficiency (kcat/Km) of wild-type recombinant hCyPA. The remaining three mutants (R55A, F60A, and H126Q) each retain less than 1% of the wild-type catalytic efficiency, indicating participation by these residues in PPIase catalysis. Each of the mutants bound to a CsA affinity matrix. The mutants R55A, F60A, F113A, and H126Q inhibited calcineurin in the presence of CsA, whereas W121A did not. Although CsA is a competitive inhibitor of PPIase activity, it can complex with enzymatically inactive cyclophilins and inhibit the phosphatase activity of calcineurin.

Amino Acid Isomerases↗
PubMed1992

Cloning and expression of the Klebsiella pneumoniae galactose operon.

The entire galactose (gal) operon of Klebsiella pneumoniae was isolated and functionally analyzed in Escherichia coli. The genes encoding galactokinase (galK), galactose-1-phosphate uridyltransferase (galT), and UDP-galactose-4-epimerase (galE) were mapped by complementation analysis. The gene order E-T-K was found to be identical to that of Salmonella spp. and E. coli. Analysis of the nucleotide sequence in the control region revealed significant homology with that of E. coli. Two major sites for transcriptional initiation, both mapped to a cytosyl residue, were identified by primer extension. When the operon is expressed in E. coli, the K. pneumoniae gal gene products make up about 30% of the total cellular proteins. The presence of a powerful promoter responsible for high level synthesis of the gal proteins was also demonstrated using beta-galactosidase as reporter.

Amino Acid Sequence↗
PubMed1992

Comparison of hemagglutinating pili of Haemophilus influenzae type b with similar structures of nontypeable H. influenzae.

Thirty-eight clinical isolates of nontypeable Haemophilus influenzae were tested for the presence of hemagglutinating pili similar to those of H. influenzae type b (Hib) that mediate buccal epithelial cell adherence. Four endogenously hemagglutinating (HA+) strains were identified, and eight additional HA+ variants were obtained from HA- strains by erythrocyte enrichment. All 12 HA+ nontypeable H. influenzae isolates bound antisera directed against denatured pilins of Hib, but none bound antisera against assembled native pili of Hib. In erythrocyte- and buccal-cell-binding assays, HA+ nontypeable H. influenzae binding was reduced compared with HA+ Hib binding and was not significantly different from HA- nontypeable H. influenzae binding. Both HA- and HA+ nontypeable H. influenzae binding was increased over binding of HA- Hib. HA+ nontypeable H. influenzae strains agglutinated adult erythrocytes that possess the Anton antigen, which is thought to be the receptor for Hib pili, and did not agglutinate cord or Lu(a-b-) dominant erythrocytes, which lack the Anton antigen. Electron microscopy of HA- and HA+ variants of three nontypeable H. influenzae strains showed few or no surface appendages on the HA- organisms, but piluslike structures were seen on many organisms from two HA+ nontypeable H. influenzae strains and on a few organisms from one strain. Thus, nontypeable H. influenzae appears to possess structures that are immunologically similar to the pilins that make up the hemagglutinating pili of Hib. However, nontypeable H. influenzae appears to also possess mechanisms for erythrocyte and buccal cell adherence that are not directly correlated with the presence of a hemagglutinating pilus.

Bacterial Adhesion↗
PubMed1992

Adult bacteremic pneumonia: bacteriology and prognostic factors.

Bacteremic pneumonia is a highly specified subgroup of pneumonia that is potentially life-threatening. In order to find out the prognostic factors in this subgroup of pneumonia, we conducted a 40-month retrospective analysis of 70 cases in our hospital. The male to female ratio was 54:16. Forty-one cases were community-acquired bacteremic pneumonia (CABP), and 29 cases were nosocomial bacteremic pneumonia (NBP). Both CABP and NBP were predominated by gram-negative bacteria. Klebsiella pneumoniae was the most common microorganism isolated in both CABP and NBP. The overall mortality was 62.9% (44/70). There was no significant difference in the mortality between CABP (61.0%) and NBP (65.5%). After univariate analysis of all possible prognostic factors, 10 variables were found to have significantly poor prognostic values. They were: 1) the presence of septic shock; 2) the use of ventilatory support; 3) the presence of radiologic spread; 4) treatment in an intensive care unit; 5) male gender; 6) the development of adult respiratory distress syndrome; 7) Klebsiella bacteremic pneumonia in patients with an alcohol habit; 8) patients with ultimately fatal underlying diseases; 9) an initial AaDO2 > 200 mmHg; and 10) an initial arterial pH < 7.25.

Adult↗
PubMed1992

Occupational exposure and respiratory morbidity among asbestos workers in Taiwan.

To determine the prevalence of asbestos-related lung disease and the impairment of lung function among asbestos workers, we conducted a cross-sectional health survey of 459 workers in 33 asbestos-related factories in Taiwan. Each worker was asked about his medical and occupational history and was given a medical examination, chest roentgenogram and pulmonary function test. Manufacturing processes included production of asbestos cements, textiles, friction materials and insulation products. Exposure assessments were based on asbestos sampling and counting using a phase contrast microscope. The average age of the participants in the study was 41.6 years. They had an average of 8.1 years of dust exposure, with a range of one to 42 years. The majority had a cumulative asbestos exposure of less than 20 fiber years/mL. No case of asbestos-related lung disease was found during our investigation. No roentgenogram showed unequivocal changes of asbestosis. However, a multiple linear regression analysis of the pulmonary function test showed that both FVC and FEV1 decreased significantly with an increasing cumulative dose of exposure after controlling for age, height and smoking effects during analysis. FEV1/FVC and FEF25-75% were not affected by exposure dose. The absence of asbestosis and other asbestos-related lung diseases may be due to an inadequate induction time of asbestos exposure and a possible healthy selection of workers. We conclude that among workers in Taiwan, there is a significant effect on the respiratory system, especially pulmonary function, due to asbestos exposure.

Adolescent↗
PubMed1991

Effect of rec mutations on viability and processing of DNA damaged by methylmethane sulfonate in xth nth nfo cells of Escherichia coli.

The role of recombination genes in the processing of DNA damaged by methlymethane sulfonate (MMS) was examined in an xth nth nfo strain of Escherichia coli K-12. Introduction of a recQ mutation did not increase the cell's sensitivity to MMS treatment. The presence of recF, recJ or recN mutation slightly increased the cell's sensitivity to MMS treatment. The introduction of recA or recB mutation into the cells led to inviability. Taken together, we suggest that replication of DNA containing apurinic/apyrimidinic (AP) sites in vivo will lead to the formation of secondary lesions. The repair of these secondary lesions requires the function of recA and recB genes, but does not appear to require recF, recJ, recQ or recN genes.

DNA Damage↗
PubMed1991

Ras-like genes and gene families in the mouse.

Four human RAS-like cDNAs and a mouse genomic DNA fragment were used to define novel mouse Ras-like genes and gene families. Inheritance of DNA restriction fragment length variants associated with these genes in recombinant inbred and backcross mice allowed definition of 12 genetic loci, nine of which were mapped, to chromosomes (Chr) 2, 4, 7, 8, 9, and 17. Two possible clusters of Ras-like and/or G protein genes were identified, on Chrs 9 and 17.

Animals↗
PubMed1991

Molecular epidemiology of Klebsiella pneumoniae.

Plasmid profile, restriction fragment length polymorphism (RFLP) patterned by an rRNA probe, and capsule serotyping of 143 Taiwan local bacteriemic isolates of Klebsiella pneumoniae were analyzed. Our results indicate that K1 and K2 are probably the most prevalent serotypes in Taiwan, accounting for 39% of total isolates tested. A remarkable genotypic heterogeneity was observed among these isolates by the analysis of rRNA gene RFLP patterns and plasmid profile, which highlighted differences that were not discerned by the serological tests used to differentiated these strains. On the basis of these analyses, 27 rRNA gene restriction patterns and 57 plasmid profiles were identified.

Humans↗