Biomedical subjects

Y Bao

Publications and source records attributed to Y Bao.

126 records · Page 7Linked to original sources

PubMed1993

A strong-stop DNA in rice plants infected with rice tungro bacilliform virus.

A virus-specific small nucleic acid (strong-stop DNA) was identified in rice plants infected with rice tungro bacilliform virus, but not in the virus particles. This nucleic acid was shown to consist of about 595 deoxyribonucleotides with about 70 ribonucleotides covalently linked at the 5' end. Hybridization with sequence-specific oligonucleotides showed that the ribonucleotides were from the plant cytoplasmic tRNA(iMet) sequence. PCR analysis detected hairpin structures at the 3' end of the DNA.

Base Sequence↗

PubMed1993

[Preparation of digoxigenin labeled virG DNA probe of Shigella and its homology analysis].

Using hapten digoxigenin labeled 1. 4kb virG DNA probe of S. flexneri 2a YSH6000. We examined the DNA homology among 73 strains of Shigella, 32 strains of EIEC, 17 strains of Yersinia, 5 strains of S. typhi and 5 strains of E. coli. At the same time strains of Shigella, EIEC and Yesinia were tested by Sereny assay. We concluded that virG DNA is conserved both in Shigella and EIEC and is related to Sereny test only in Shigella and EIEC but not in Yesinia. The coincidence rate of hybridization and Sereny test was 87.5% and 90.9% for S. sonni and EIEC respectively.

Bacterial Proteins↗

PubMed1992

A surface protease and the invasive character of plague.

A 9.5-kilobase plasmid of Yersinia pestis, the causative agent of plague, is required for high virulence when mice are inoculated with the bacterium by subcutaneous injection. Inactivation of the plasmid gene pla, which encodes a surface protease, increased the median lethal dose of the bacteria for mice by a millionfold. Moreover, cloned pla was sufficient to restore segregants lacking the entire pla-bearing plasmid to full virulence. Both pla+ strains injected subcutaneously and pla- mutants injected intravenously reached high titers in liver and spleen of infected mice, whereas pla- mutants injected subcutaneously failed to do so even though they establish a sustained local infection at the injection site. More inflammatory cells accumulated in lesions caused by the pla- mutants than in lesions produced by the pla+ parent. The Pla protease was shown to be a plasminogen activator with unusual kinetic properties. It can also cleave complement C3 at a specific site.

Amino Acid Sequence↗

PubMed1992

Molecular cloning and nucleotide sequence of cDNA encoding human muscle glycogen debranching enzyme.

cDNA comprising the entire length of the human muscle glycogen debranching enzyme was cloned and its nucleotide sequence determined. The debrancher mRNA includes a 4545-base pair coding region and a 2371-base pair 3'-nontranslated region. The calculated molecular mass of the debrancher protein derived from cDNA sequence is 172,614 daltons, consistent with the estimated size of purified protein (Mr 165,000 +/- 500). A partial amino acid sequence (13 internal tryptic peptides with a total of 213 residues) determined on peptides derived from purified porcine muscle debrancher protein confirmed the identity of the cDNA clone. Comparison of the amino acid sequence predicted from the human glycogen debrancher cDNA with the partial protein sequence of the porcine debrancher revealed a high degree (88%) of interspecies sequence identity. RNA blot analysis showed that debrancher mRNA in human muscle, lymphoblastoid cells, and in porcine muscle are all similar in size (approximately 7 kilobases). Two patients with inherited debrancher deficiency had a reduced level of debrancher mRNA, whereas two other patients had no detectable abnormality in RNA blots. The isolation of the debrancher cDNA and determination of its primary structure is an important step toward defining the structure-function relationship of this multifunctional enzyme and in understanding the molecular basis of the type III glycogen storage disease.

Amino Acid Sequence↗

PubMed1992

Characterization of the discontinuities in rice tungro bacilliform virus DNA.

The dsDNA of rice tungro bacilliform virus (RTBV) has two discontinuities, one on each strand, each in a specific position as found in other pararetroviruses. The 5' end of discontinuity 1 was mapped to nucleotide 1 of the published RTBV DNA sequence which suggests that tRNAiMet serves as a primer for negative strand DNA synthesis. This 5' terminus contains up to two ribonucleotides and the 3' terminus overlaps it by five to 25 nucleotides. The discontinuity 2 (D2) did not map to a purine-rich region as has been found in other similar viruses. Both the 5' and 3' termini of D2 were heterogeneous in position giving structures varying from a gap of 10 nucleotides to an overlap of 103 nucleotides.

Base Sequence↗

PubMed1992

Identification of a new mutation in medium-chain acyl-CoA dehydrogenase (MCAD) deficiency.

A mutation involving an A-to-G nucleotide replacement at position 985 of the medium-chain acyl-CoA dehydrogenase (MCAD) cDNA was found in homozygous form in 18 unrelated MCAD-deficient families and in heterozygous form in 4 families. By PCR amplification and sequencing of cDNA from a compound heterozygote, we have detected a new mutation in an MCAD-deficient patient in whom one MCAD allele produces mRNA that is missing 4 bp in the MCAD cDNA, while the other allele carries the A-to-G-985 mutation. The presence of this 4-bp deletion was confirmed in the patient's genomic DNA by dot-blot hybridization with allele-specific oligonucleotide probes and by restriction analysis of PCR products. A rapid screening test for this 4-bp deletion was developed, based on mismatched primer PCR amplification. The deletion created a new restrictive-enzyme site which yielded two DNA fragments. The 4-bp deletion was not found in the three remaining MCAD chromosomes not harboring the A-to-G-985 mutation, nor it was present in 20 chromosomes from 10 unrelated normal Caucasians. The PCR-based method for screening these two mutations can detect over 93% of all MCAD mutations.

Acyl-CoA Dehydrogenases↗

PubMed1991

An improved Tn7-based system for the single-copy insertion of cloned genes into chromosomes of gram-negative bacteria.

A system is described for the single-copy, stable insertion of cloned DNA sequences into the chromosomes of Gram- bacteria. Two narrow-host-range plasmids form the basis of this system: the 'carrier' plasmid contains the mini Tn7-Km transposon, into which foreign DNA can be cloned; the 'helper' plasmid provides the Tn7 transposition functions in trans. Both plasmids are readily transferred into Gram- bacteria by conjugation. The functionality of this system has been demonstrated in Rhodospirillum rubrum.

Chromosomes, Bacterial↗

PubMed1991

The gene for von Recklinghausen neurofibromatosis (NF1) maps to the pericentromeric region of chromosome 17 in Chinese families.

Linkage analysis of six Chinese families with neurofibromatosis type 1 (NF1) confirms the location of the NF1 gene to the region of the proximal long arm of chromosome 17, as in Caucasian populations. The diagnosis of NF1 was made according to internationally accepted criteria. The markers used were D17S71, D17S58, D17S33, and EVI2A. The overall odds in favor of NF1 lying within this linkage group in the families studied are over 150,000:1, with a maximum location score of 5.112 for the interval D17S58-EVI2A.

Centromere↗

PubMed1991

Self-splicing of the Chlamydomonas chloroplast psbA introns.

We used alpha-32P-GTP labeling of total RNA preparations to identify self-splicing group I introns in Chlamydomonas. Several RNAs become labeled with alpha-32P-GTP, a subset of which is not seen with RNA from a mutant that lacks both copies of the psbA gene. Hybridization of the GTP-labeled RNAs to chloroplast DNA indicates that they originate from the psbA and rrn 23S genes, respectively, the only genes known to contain group I introns in this organism. Introns 1, 2, and 3 of psbA (with flanking exon sequences) were subcloned and transcribed in vitro. The synthetic RNAs were found to self-splice; splicing required Mg2+, GTP, and elevated temperature. In addition, the accuracy of self-splicing was confirmed for introns 1 and 2, and intermediates in the splicing reactions were detected. These results, together with our recent data on the 23S intron, indicate that the ability to self-splice is a general feature of Chlamydomonas group I introns. These findings have significant implications for the mechanism of group I intron splicing and evolution in Chlamydomonas and other chloroplast genomes.

Animals↗

PubMed1991

Nitrosation of tertiary aromatic amines related to sunscreen ingredients.

Possible routes to the formation of the sunscreen contaminant, 2-ethylhexyl 4-N-methyl-N-nitrosoaminobenzoate, have been investigated in a study of the nitrosation chemistry of 2-ethylhexyl 4-N,N-dimethylaminobenzoate (Padimate-O) and related tertiary and secondary amines. Padimate-O and the corresponding ethyl ester nitrosate rapidly at 25 degrees C in either N2O3:ether or HNO2:HOAc to produce a mixture of alkyl 4-N-methyl-N-nitrosoaminobenzoate and alkyl 4-N,N-dimethylamino-3-nitrobenzoate, the former of which is the major product. The nitrosative dealkylation of these amines at this low temperature is unusual. Asymmetrical amines exhibit a preference for nitrosative demethylation (methyl versus ethyl or benzyl), but the cleavage ratios in N2O3:ether are time-dependent, suggesting competing mechanisms with different reactant kinetic orders. A radical cation route would explain the unusual reactivity, which may compete with the established nitrosative dealkylation mechanism. 2-Ethylhexyl 4-N-methyl-N-nitrosoaminobenzoate was mutagenic in two strains of Salmonella typhimurium in the Ames assay.

4-Aminobenzoic Acid↗

PubMed1991

[Two biotin-labeled probes of gentamicin resistance genes].

A 2.0 kb BamHI-HindIII fragment of pDG0103 from Australia containing gentamicin 2"-o-adenylytransferase [ANT(2")] gene and a 4.9 kb PstI-EcoRI fragment of pBY102 were recovered from low-temperature-melting agarose by the slot method. Both fragments were labeled with biotin-7-dATP by nick translation with a commercial kit. The result of colony and Southern hybridization was that: the 2.0 kb probe from Australia hybridized with that containing ANT(2") from America, while no hybridization occurred between the 2.0 kb probe and the 4.9 kb probe constructed in our lab. Furthermore, the above two fragments were used as probes for detection of 106 strains of gentamicin resistant Enterobacteriaceae. It revealed that there were more than one gentamicin resistance gene in the tested strains.

Biotin↗

PubMed1991

[Purification and immunological behavior of beta-lactamase from Bacteroides fragilis].

The beta-lactamase crude extract of Bacteroides fragilis 55 was chromatographed with DEAE-sepharose CL-6B and sephadex G-100. The partial purified enzyme proteins was further purified by cutting the band on PAGE in which the beta-lactamase was distinguishable from other proteins by our method of fluorescent staining. Using purified preparations to be mixed with liposome-CPS-K, prepared specific antisera against the purified beta-lactamase. Serological reactions were carried out by IgG-ELISA together with western blotting. The results revealed that Bacteroides fragilis beta-lactamase possessed its species-specificity.

Bacteroides fragilis↗

PubMed1990

[Dynamic changes of myocardial beta, alpha 1-adrenergic and muscarinic cholinergic receptors in endotoxic rats].

The dynamic changes of myocardial beta, alpha 1-adrenergic and muscarinic cholinergic receptors (beta AR, alpha 1AR, MAchR) were investigated in endotoxic rats by radiolabelled ligand binding assay. It was found that the number of beta AR increased, while its affinity decreased progressively following endotoxin injection. The number of alpha 1AR reduced significantly during the whole course of the experiment but no change was found in its affinity. The affinity of MAchR was not changed and the number of MAchR reduced only at agonal stage. The up regulation of beta AR in early stage might indicate a compensatory mechanism, while the attenuation in affinity of beta AR and/or the number of alpha 1AR might result in the decreased responsiveness of heart to catecholamine stimulation. Since the affinity of beta AR reduced prominently at the agonal stage, the up regulation of beta AR seemed to be discompensated. The down regulation of MAchR at agonal stage of endotoxic rats might share some light of its compensatory action to the discompromised relationship between the adrenergic and cholinergic system sbut it seemed to be with no effect, which might correlate with myocardial failure.

Animals↗

PubMed1990

[Physico-chemical and enzymological properties of beta-lactamase from Bacteroides fragilis].

Bacteroides fragilis 55 from clinical specimens was selected at random for beta-lactamase investigation of physico-chemical and enzymological properties. The enzyme was characterized as a cell-associated cephalosporinase with some penicillinase activity, the molecular weight of the enzyme being 43,000 and the pI 4.95. It could be inhibited by cefoxitin, PCMB, carbenicillin, sulbactam, clavulanic acid and cloxacillin. The optimum pH and temperature for enzyme reactions have been found to be 7.2 and 37 degrees C, respectively. The analysis of amino acid composition and parameters of enzyme kinetics has been described.

Amino Acids↗

PubMed1986

Esters and lactones of phenolic amino carboxylic acids: prodrugs for iron chelation.

The new iron chelator N,N'-bis(2-hydroxyphenyl)ethylenediamine-N,N'-diacetic acid (1), its dilactone 2, N,N'-bis(2-hydroxybenzyl)-2-hydroxypropylene-1,3-diamine-N,N'- diacetic acid (3), and its methyl ester lactone 4 and a series of esters of N,N'-bis(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid (5) were prepared and their iron chelating efficacy and toxicity determined by using the hypertransfused mouse model of iron overload. The biological activities were compared with results obtained with use of the hypertransfused rat. Esterification enhanced the oral iron chelating activity but also increased toxicity. The diisopropyl ester of 5 exhibited the highest therapeutic index. In vitro measurements showed that the rate of ester hydrolysis at pH 7.5 increased by a factor of 10(4) in the presence of 5 X 10(-4) M ferric ion, which may account for the utility of esters and lactones as prodrugs. Seventeen other chelating agents were screened but showed no intraperitoneal or oral activity.

Animals↗

PubMedDate not supplied

alpha-Tocopherol enhances the peroxidase activity of hemoglobin on phospholipid hydroperoxide.

We have used direct separation of phospholipid hydroperoxide and phospholipid hydroxide by high performance liquid chromatography to examine the phospholipid hydroperoxide peroxidase activity of hemoglobin (Hb) in the presence of hydrogen donors. Hb exhibits phospholipid hydroperoxide peroxidase activity and rapidly breaks down phospholipid hydroperoxide to thiobarbituric acid-reactive substances. However, in the presence of alpha-tocopherol, some phospholipid hydroperoxide is converted to phospholipid hydroxide, which is more stable than the hydroperoxide and is much less reactive with thiobarbituric acid. Other electron donors such as glutathione and ascorbate are less effective than alpha-tocopherol. Free cysteine also shows some ability to reduce phospholipid hydroperoxides to corresponding hydroxides, but cys-93 beta of Hb did not participate in the reaction, as shown by N-ethylmaleimide modification. Hemin alone catalysed the reaction, in the absence of protein. The results therefore show that Hb catalyses an apparent phospholipid hydroperoxide alpha-tocopherol peroxidase reaction due to bound hemin, and that the reduction depends on the ability of hydrogen donors to react with the intermediate phospholipid alkoxyl radical and does not involve reduction by deprotonated sulfhydryl groups.

Hemoglobins↗

PubMedDate not supplied

Heparin-bonded circuits improve clinical outcomes in emergency coronary artery bypass grafting.

Compared to patients undergoing elective or urgent coronary artery bypass grafting (CABG), those undergoing emergency CABG (EM-CABG) have a higher morbidity and mortality. The use of heparin-bonded circuits (HBC) has been shown to improve clinical outcomes in nonemergent CABG patients. It is not known, however, whether the improved hemostasis and attenuation of the inflammatory response to cardiopulmonary bypass, conferred by HBC, can overcome the high incidence of comorbid risk factors in (EM-CABG) patients and improve their outcomes. A retrospective analysis of 206 consecutive patients undergoing EM-CABG over 4 years (1993-1997) at one institution was performed. Eighty-one patients were treated with conventional non-heparin-bonded circuits (NHBC) with full anticoagulation protocol (FAP, activated clotting time [ACT] > 480 sec); 125 patients were treated with HBC and a lower anticoagulation protocol (LAP, ACT > 280 seconds). Outcomes and results were collected prospectively and are presented as mean +/- SD. Preoperative risk profiles were similar in both treatment groups. Postoperatively, compared with the NHBC group, patients treated with HBC/LAP required fewer homologous donor units (4.1 +/- 10.7 vs 8.2 +/- 13.6 units, p = 0.005), were less likely to require inotropic support (18.6% vs 38.3%, p = 0.005), and had a lower incidence of perioperative myocardial infarction (MI, 3.2% vs 12.3%, p = 0.04) and pulmonary complications (4.0% vs 12.3%, p = 0.04). The use of HBC/LAP resulted in a decreased incidence of postoperative complications (12.8% vs 28.4%, p = 0.01, odds ratio 0.37 with 95% confidence interval [CI] 0.18-0.76). This resulted in a shorter duration of ventilatory support (30.5 +/- 54.0 vs 72.8 +/- 16.7 hours, p = 0.009), ICU stay (38.2 +/- 36.5 vs 91.5 +/- 68.7 hours, p = 0.009), hospital stay (8.0 +/- 7.1 vs 11.0 +/- 8.9 days, p = 0.008), and therefore cost. In conclusion, the use of HBC/LAP in EM-CABG resulted in a reduction of homologous transfusion and postoperative complications associated with decreased hospital stays and cost.

Aged↗

PubMedDate not supplied

Dura mater maintains rat cranial sutures in vitro by regulating suture cell proliferation and collagen production.

Craniosynostosis, the premature osseous obliteration of cranial vault sutures, can result from mutations in genes encoding components of growth factor signaling systems or the extracellular matrix (ECM). Little is known of the capacity of osteoprogenitor cells of the cranial sutures to divide or to synthesize ECM in situ. Osteoblasts derived from patients with prematurely fused sutures were reported to express alkaline phosphatase and osteocalcin at elevated levels, while proliferating at a rate comparable to control cells [DePollack et al., JBMR, 1996]; however, the suture osteoprogenitors, the population most likely to show proliferative abnormalities, were not present in the fused sutures used for this study. A model in which rat coronal sutures and associated bones develop normally in vitro, but in which sutures can be induced to fuse in the absence of dura mater, was used to examine cell proliferation and total protein synthesis in unfused sutures cultured in the presence of dura mater or in sutures induced to fuse in the absence of dura mater. Significantly increased cell proliferation was seen in suture cells prior to sutural obliteration, which returned to control levels as sutural fusion proceeded. Collagen synthesis in fusing sutures was elevated compared to non-fusing sutures and comparable to that seen in bone. Results indicated that in the absence of intercellular signals provided by the dura mater, suture cell proliferation increased initially, followed by increased synthesis of collagenous ECM within the suture and subsequent osseous obliteration of the suture. Thus factors originating in the dura mater affected suture cell proliferation and ECM production and were required for the maintenance of suture patency.

Animals↗