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Biomedical subjects

Y N Liu

Publications and source records attributed to Y N Liu.

At least 19 recordsLinked to original sources
PubMed2006

Exposure of traffic police to Polycyclic aromatic hydrocarbons in Beijing, China.

Exposure of on-duty traffic police in Beijing to polycyclic aromatic hydrocarbons (PAHs) was investigated during the summer, 2004 using a personal sampling technique in measuring both particulate and gaseous phase PAHs. The results were then compared with those from two control sites away from the street. Exposure levels to gaseous and particulate PAHs for the traffic police were found to be 1525 +/- 759 ngm(-3) and 148 +/- 118 ngm(-3), respectively, representing 2-2.5 times higher levels than those at the control sites. The daily inhalation exposure of the police was estimated to be 277 ngkg(-1)d(-1). Most of the PAHs exposure came from the vapor phase, particularly NAP, FLO and PHE. Based on calculated PAH diagnostic ratios, the major source of PAHs exposure was from vehicle exhaust. The effects of temperature, humidity and atmospheric stability on exposure levels are also discussed.

Air Pollutants, Occupational↗
PubMed2003

Trans-activation of heparanase promoter by ETS transcription factors.

The remodeling of extracellular matrix (ECM) is an important process required for cancer cells to turn into invasive and metastatic cancer cells. To dissolve the protein components of ECM, matrix metalloproteinases are some of the essential enzymes. Another ECM remodeling enzyme is the heparanase (Hpa) that digests the heparin sulfate component of the matrix. In metastatic cancer cells the Hpa gene is upregulated. To investigate the mechanism of why Hpa was upregulated in metastatic cancer cells, the regulatory sequence of heparanase gene was isolated and its function analysed in metastatic breast cancer cells. We found there are four ETS transcription factor binding sites. Two of them flanking the transcription initiation of the Hpa gene are nonfunctional, whereas two others are highly functional and responded to exogenously added ETS transcription factors. Mutation of these two ETS binding sites abolished the transcriptional activation of Hpa promoter by ETS transcription factors. Among four transcription factors tested (ETS1, ETS2, PEA3, and ER81), ETS1 and ETS2 are more potent in transactivating the human Hpa gene. Furthermore, dominant-negative ETS transcription factors failed to transactivate Hpa promoter and could abrogate the function of wild-type transcription factor in transactivation activity of ETS transcription factors on the Hpa promoter. These results suggest that ETS transcription factors play an important role in tumor invasion and metastasis by modulating the remodeling of ECM.

Binding Sites↗
PubMed2003

SARS: prognosis, outcome and sequelae.

Severe acute respiratory syndrome (SARS) is associated with considerable morbidity and mortality in the acute phase. Worldwide case fatality rate is 11% (range 7 to 27%) for the most severely affected regions. Several adverse prognostic factors have been identified, including advanced age, presence of comorbidity, higher lactose dehydrogenase levels and initial neutrophil count, but the impact of viral and other host factors on outcome is unknown. Published data on sequelae of SARS are limited. Clinical follow-up of patients who recovered from SARS has demonstrated radiological, functional and psychological abnormalities of varying degrees. In the early rehabilitation phase, many complained of limitations in physical function from general weakness and/or shortness of breath. In a small series of subjects who underwent CT scan of the chest, over half showed some patchy changes consistent with pulmonary fibrosis. Lung function testing at 6-8 weeks after hospital discharge showed mild or moderate restrictive pattern consistent with muscle weakness in 6-20% of subjects. Mild decrease in carbon monoxide diffusing capacity was detected in a minority of subjects. Preliminary evidence suggests that these lung function abnormalities will improve over time. Psychobehavioural problems of anxiety and/or depression were not uncommon in the early recovery phase, and improved over time in the majority of patients. Avascular necrosis of the hip has been reported as another complication. The long-term sequelae of SARS are still largely unknown. It is important to follow up these patients to detect and appropriately manage any persistent or emerging long-term sequelae in the physical, psychological and social domains.

Humans↗
PubMed2001

[Cloning of gene related to salt tolerance from Sinorhizobium fredii RT19 and its expression in Escherichia coli].

A 4.4 kb DNA fragment related to salt tolerance containing three open reading frames was isolated from the gene library of S. fredii strain RT19. By subcloning and functional analysis, only ORF2 related to salt tolerance was obtained. The ORF2 was ligated to expression vectors pThioHisA, B and C, respectively, and recombinant expression vectors pGA, pGB and pGC containing 1.5 kb DNA fragment related to salt tolerance were constructed. These recombinant expression vectors were transformed into E. coli DH5 alpha. Inducing by IPTG and analyzing with SDS-PAGE, it was found that the fusion protein encoded by pGC was expressed, and its molecular weight was equal to the sum of thioredoxin encoded by trxA and ORF2 putative protein molecular weight. The Western blot demonstrated that the target gene was successfully expressed in E. coli.

Cloning, Molecular↗
PubMed1999

[Scanning electron microscope observation on endosperm starch grain characters in multiplasmic maize].

In this article, endosperm starch grains of eleven lines in multiplasmic maize were studied by scanning electron microscope. The results show that different cytoplasm has different effects on the characters of starch grain. The starch grains of three sweet corn cytoplasmic lines (su1, sh2, btl) are mainly spherical and packed tightly, which means they have some degree of similarity. While the grains of four cytolasmic male sterility lines (T, S, C, 21A) are mostly irregular and packed loosely except (T) Mo17, in which grains are tightly packed. The average diameter of these eleven varieties is ranged from 9.78 microns to 14.69 microns. Through the study of endosperm starch grain shape and size, we tried to explore the relationship between the property of starches and the quality of seeds. And this will significantly prompt the development of maize genetics and breeding.

Fertility↗
PubMed1994

Molecular analysis of the immune response to human cytomegalovirus glycoprotein B (gB). II. Low gB-specific T and B cell responses are associated with expression of certain HLA-DR alleles.

Human cytomegalovirus (HCMV) is a common cause of congenital infection leading to birth defects and a leading cause of serious illness in patients with immunodeficiencies. Studies in this laboratory have focused on a molecular analysis of the immune response to glycoprotein B (gB) of HCMV. This protein has been shown to elicit B cell, helper T cell (Th), and cytotoxic T cell responses, suggesting that it may be useful as a subunit HCMV vaccine. However, previous studies showed that although peripheral blood mononuclear cells (PBMC) from all HCMV-seropositive donors proliferate in response to stimulation with whole HCMV, not all donors respond to purified recombinant gB. In the present study, PBMC from HCMV-seropositive donors homozygous for HLA-DR were tested for proliferative responses to whole HCMV and to purified gB expressed in vaccinia virus. PBMC from all donors proliferated in response to HCMV, but those from multiple donors expressing the HLA-DR3Dw3 and -DR4Dw4 specificities, and single donors expressing the -DR15Dw2, -DR13Dw19 and -DR14Dw9 specificities, failed to respond to gB. These results suggested a possible HLA-DR association with low proliferative responses to gB. In further studies, PBMC from donors expressing both putative gB-high responder and low responder HLA-DR alleles were stimulated multiple times with gB to generate gB-specific T cell lines. These cells were then tested for proliferative responses to gB presented by irradiated PBMC sharing only one DR allele with the responder cells. Cells from the gB-specific lines proliferated only when antigen was presented in the context of a responder DR allele but not when presented in the context of a low responder DR allele. Analysis of immune sera revealed that those from donors with PBMC proliferative responses always contained antibodies reactive with B cell epitopes on both the N-terminal gp93 and C-terminal gp55 portions of gB. In contrast, many of the sera from donors with low gB-specific proliferative responses had gp55-specific antibodies but lacked antibodies to gp93. These results suggest that immunogenetic differences in Th responsiveness to gB may lead to lack of antigen-specific help for antibody responses to gp93 in some cases. The prevalence of these low responder HLA alleles in the population, and the central importance of the T cell response to the generation of antibodies suggest that native gB alone may not be an attractive candidate for an HCMV subunit vaccine.

Adult↗
PubMed1994

[Antibiotic treatment for pneumonia caused by Flavobacterium meningosepticum].

Two cases of critical nosocomial pneumonia caused by flavobacterium meningosepticum (FM) were reported and both of them were successfully cured. There were 2 other cases of FM pneumonia reported in Chinese literature previously, but none of them survived. It has been found that the treatment for FM respiratory infection was very difficult because of its resistance to majority of antibiotics, including the third generation cephalosporins. The symptoms of FM pneumonia are similar to those of other gram-negative bacillus pneumonias, such as Klebsiella pneumoniae pneumonia. Definite diagnosis depends principally on etiological examination and clinical manifestations of pneumonia. Cefoperazone, Cefsulodin, Astreonam and Ciprofloxacin are valuable drugs in saving the lives of patients with FM Pneumonia.

Aged↗
PubMed1993

Molecular analysis of the immune response to human cytomegalovirus glycoprotein B. I. Mapping of HLA-restricted helper T cell epitopes on gp93.

Human cytomegalovirus (HCMV) is one of the most common causes of congenital infection leading to birth defects, and a leading cause of serious illness in patients with impaired cell-mediated immunity. Helper T cell (Th) responses to HCMV proteins are likely to be important in limiting viral replication and preventing disease. Previous studies from this laboratory have demonstrated that the amino-terminal 513 amino acids of HCMV glycoprotein B (gB) can stimulate both B and T cell responses in humans. In the present study, the proliferative responses of HCMV-specific Th clones to recombinant proteins and synthetic peptides were examined to identify four Th epitopes on gp93, which represents the amino-terminal 460 amino acids of the gB polypeptide. Using clones of known HLA restriction specificity from several donors, it was shown that each HLA class II allele preferentially associates with a different epitope on gB. Five clones from two different donors recognized an epitope in the region of amino acids 250 to 264 restricted by DR4Dw14, two clones from different donors recognized an epitope in the region of amino acids 420 to 434 restricted by DR7Dw17, two clones from different donors recognized an epitope in the region of amino acids 178 to 194 restricted by DQw1 and a single clone recognized an epitope in the region of amino acids 190 to 204 restricted by DPw4. Although all peripheral blood mononuclear cells (PBMCs) expressing a particular HLA class II allele were able to present the appropriate HLA-restricted gB peptide to gB-specific Th clones, not all individuals expressing a given HLA allele exhibited PBMC responses to the corresponding gB peptide. The HLA-related differences in Th recognition of specific epitopes on gB described in this report may have important implications in virus-host interactions and vaccine strategies.

Adult↗
PubMed1993

[Application of bedside monitoring with arterized capillary blood, transcutaneous and end tidal carbon dioxide during mechanical ventilation].

Arterial blood, arterialized capillary blood, transcutaneous, end tidal carbon dioxide pressure (PaCO2, PcCO2, PtcCO2, PetCO2) and physiological respiratory deadspace to tidal volume ratio (VD/VT) were observed in 12 patients with chronic obstructive pulmonary disease (group A), 17 postoperative patients of cardiac surgery (group B), and 16 healthy subjects (group C) under three mechanical ventilatory patterns. PcCO2, PtcCO2 and PetCO2 were found to correlate well with PaCO2 (r = 0.99, 0.97 and 0.88 respectively); P(a-et) CO2 correlated with age (year) in group B and C (r = 0.77 and 0.76), and all P(a-et) CO2 measurements of each of three groups highly correlated with VD/VT (r = 0.96 0.91 and 0.87 for group A,B,C respectively). The results suggested that the trend of PaCO2 variation can be deduced from PcCO2, PtcCO2 and PetCO2 with fair accuracy under various ventilatory patterns in subjects with stable circulatory function, and P(a-et) CO2 is a simple quantitative index for evaluating physiological deadspace.

Aged↗
PubMed1993

[The mechanism of water and sodium retention during positive end-expiratory pressure (PEEP) ventilation].

To investigate the mechanism of water and sodium retention during PEEP ventilation, ten dogs were studied at 0, 1.33Kpa, 2.67Kpa PEEP and at spontaneous breathing. Hemodynamics, renal excretory function parameters and plasma hormonal parameters were recorded at the end of each period. Compared with spontaneous breathing, PEEP induced a significant reduction of diuresis (from 31.8 +/- 17.9 to 11.2 +/- 6.4ml/h, P < 0.01) and natriuresis (from 5.21 +/- 4.93 to 1.09 +/- 1.22 mmol/h, P < 0.01), whereas plasma atrial natriuresis factor (ANF) fell from 1219 +/- 446 to 713 +/- 344 pg/ml (P < 0.05) and esophageal pressure increased from 0.13 +/- 0.42 to 1.22 +/- 0.66Kpa (P < 0.01), serum aldosterone (ALD) increased from 295 +/- 281 to 1012 +/- 685 pg/ml (P < 0.05). There was a significant correlation between ANF and ALD (r = -0.647, P < 0.001). We suggest that changes in ANF in response to intrathoracic pressure may contribute to alteration of renal excretory function during PEEP.

Aldosterone↗
PubMed1992

[Effect of enoxacin on theophylline pharmacokinetics].

The effect of a multiple-dose regimen of oral Enoxacin on Theophylline pharmacokinetics was evaluated in 10 hospitalized patients with COPD. It was found that mean Theophylline concentrations in serum significantly increased 144% (P < 0.01), AUC increased 350.4% (P < 0.01), T1/2K increased 204% (P < 0.01), clearance decreased 76.8% (P < 0.01) during coadministration of enoxacin than before. This results suggested that a multidose regimen of enoxacin significantly slowed the clearance of theophylline and elevated theophylline concentrations in serum. The careful monitoring of serum theophylline level and modification of theophylline dosage in patients receiving enoxacin and theophylline were recommended.

Adult↗
PubMed1992

Comparison of serum bactericidal activity of 4 fluoroquinolones in healthy volunteers.

In vitro antibacterial activities (MBCs) and serum bactericidal activities (SBAs) of fluoroquinolones were compared. The MBCs were measured by the agar disk dilution test. The 40 tested strains belonging to 8 species were isolated from hospitalized patients. Against Gram positive cocci, Ciprofloxacin (CPLX) and ofloxacin (OFLX) were the more active and nefloxacin (NFLX) was less potent than the others. Against Ps. aeruginosa, CPLX had the highest activity, enoxacin (ENX) as well as OFLX had powerful activity, whereas NFLX was less active. All the 4 agents showed high activity against Gram negative bacilli. In the self-controlled, randomized crossover study, 4 fluoroquinolones were given to 10 healthy volunteers and then SBAs were determined using microdilution method. The peak SBAs of CPLX and OFLX were significantly higher than NFLX, and those of ENX were comparatively low, but there was no difference between ENX and OFLX against most of the strains tested. The percentages of peak SBAs greater than 1:8 of the 4 fluoroquinolones suggest that in the treatment of serious infections, CPLX and OFLX are more effective and ENX can also achieve high cure rate. The trough SBAs of the 4 fluoroquinolones suggest that the time interval of administration of CPLX and OFLX should be more than 8 hours, but increase of the dosage or shortening of the time interval between the administrations is recommended for ENX and NFLX.

Adult↗
PubMed1991

Genetic and molecular analysis of a cluster of rpf genes involved in positive regulation of synthesis of extracellular enzymes and polysaccharide in Xanthomonas campestris pathovar campestris.

The cosmid clone pIJ3020 containing DNA from the plant pathogenic bacterium Xanthomonas campestris pathovar campestris has previously been shown to complement a non-pathogenic mutant defective in synthesis of extracellular enzymes. The DNA cloned in pIJ3020 was analysed by mutagenesis with Tn5 and Tn5lac and by nucleotide sequencing. The results indicate that this region of the genome contains a cluster of genes, mutation in any of which results in failure of the enzymes and extracellular polysaccharide to be synthesized. The designation rpf (regulation of pathogenicity factors) is proposed for these genes. The nucleotide sequence of one gene (rpfC) predicts a protein product with homology to conserved domains of both sensor and regulator proteins of prokaryotic two-component regulatory systems, which are usually involved in regulating gene expression in response to environmental stimuli.

Amino Acid Sequence↗
PubMed1991

The N-terminal 513 amino acids of the envelope glycoprotein gB of human cytomegalovirus stimulates both B- and T-cell immune responses in humans.

Host defense against human cytomegalovirus (HCMV) involves both humoral and cell-mediated immunity. In this report, human immune responses to glycoproteins encoded by the HCMV gB homolog gene have been examined by using glycoproteins purified by immunoaffinity from HCMV virions and recombinant proteins expressed by vaccinia viruses containing either the entire gB open reading frame or a C-terminal deletion mutant, gBm165, coding for the N-terminal 513 amino acids of gB. Neutralizing antibodies, helper T cells, and cytotoxic T cells reactive with epitopes on the N-terminal portion of gB were detected in some seropositive individuals, suggesting that this region of gB may be important in eliciting protective immunity during natural infection for some individuals.

Antibodies, Monoclonal↗
PubMed1991

[Complications of mechanical ventilation. A clinical analysis of 82 cases].

The complications of mechanical ventilation were analysed retrogradely in 82 cases with respiratory failure treated in ICU in recent 5 years. There were 48 males and 34 females ranging from 28 to 82 years of age (mean age: 57.1 +/- 16.8). In 82 cases, 6 cases had complications of barotrauma, 39 cases, of infections, 15 cases, of hypotension, 24 cases, of arrhythmia, 14 cases, of upper gastrointestinal hemorrhage and 10 cases, of multiple organ failure. The total incidence of complication was 76.8%. Exactly within three days of mechanical ventilation, the incidence of complication was 31.3%, while beyond three days, it was 87.9%. It was indicated that the mortality increased significantly in the cases with severe complications such as, multiple organ failure. The causes of all kinds of complications and their prevention as well as treatments were discussed.

Adult↗
PubMed1991

[Application of positive end expiratory pressure (PEEP) and continuous positive airway pressure (CPAP) in the treatment of asthma].

Two intubated young adults with respiratory failure and acidosis due to severe asthma attack were treated by mechanical ventilation with PEEP. Two hours after using of PEEP the expiratory resistance decreased from 35 to 14 cmH2O/L/Sec and 56 to 18 cmH2O/L/Sec respectively, and within two days they were successfully weaned from mechanical ventilation. Another fifteen patients with moderate asthmatic attack were treated with CPAP via a mask from Siemens 900C ventilator. Twenty minutes later the FEV1 and VC were significantly increased from 1.19 +/- 0.69 L to 1.36 +/- 0.73 L and 2.41 +/- 0.97 to 2.65 +/- 0.94 L respectively. We concluded that, PEEP and CPAP have mechanical bronchodilative effect on spasm bronchi, and could be used as a effective way to treat severe asthma attack.

Acidosis, Respiratory↗
PubMed1990

A multipurpose broad host range cloning vector and its use to characterise an extracellular protease gene of Xanthomonas campestris pathovar campestris.

A multipurpose broad host range plasmid, pIJ3200, was constructed by inserting the polylinker-containing 445 bp PvuII fragment of Bluescript M13 into the EcoRI site of the cosmid pLAFR1. Using this vector a protease gene of Xanthomonas campestris pathovar campestris, previously cloned in the recombinant plasmid pIJ3070, was located by deletion to a 2.2 kb DNA region. Sequencing of the protease gene revealed an open reading frame encoding a 580 amino acid polypeptide with molecular weight of 57,000. The deduced amino acid sequence showed strong homology with the subtilisin family of serine proteases. This, together with its sensitivity to inhibition by phenylmethylsulphonyl fluoride, suggests that the enzyme belongs to this family of proteases.

Amino Acid Sequence↗