Biomedical subjects

Qing Liu

Publications and source records attributed to Qing Liu.

At least 109 records · Page 6Linked to original sources

PubMed2004

Sequence variability of human cytomegalovirus UL144 open reading frame in low-passage clinical isolates.

OBJECTIVE: To explore the relationship between human cytomegalovirus (HCMV) UL144 sequence variability and clinical disease. METHODS: HCMV UL144 open reading frame (ORF) was amplified by PCR assay in 72 low-passage isolates [65 congenitally infective children and 7 healthy children who were HCMV-DNA positive by quantitative PCR (qPCR)]. All positive PCR products were analyzed by heteroduplex mobility assay and single-stranded conformation polymorphism (HMA-SSCP) and 32 of them were sequenced. RESULTS: Fifty-five patient isolates and five healthy children isolates were HCMV-UL144 positive by PCR. Sequencing and HMA-SSCP analysis showed that significant strain-specific variability was present in the UL144 ORF. Phylogenetic analysis indicated that the nucleotide sequences could be separated into 3 major genotypes. Comparing between UL144 sequences and the corresponding symptoms showed that genotype 2 did not exist in megacolon isolates. And genotype 1 and 3 were the major types among microcephaly and jaundice isolates respectively. CONCLUSIONS: HCMV-UL144 existed in most of low passage isolates and sequences were hypervariable. The UL144 ORF and its predicted product with the high level of sequence variability in different kinds of isolates suggest that UL144 ORF might play a role in HCMV infectivity and subsequent diseases.

Amino Acid Sequence↗

PubMed2004

[Dynamics of litters in artificial restoration process of subalpine coniferous forest].

By adopting the concept of space as a substitute for time and taking the primitive subalpine coniferous forests as a reference, this paper investigated the forest litters in 10, 30, 40, 50 and 60-years subalpine Picea asperata stands to study the development process of litters in subalpine coniferous plantations with different restoration stages. The difference in litter development in artificial and natural stands was also discussed. The results indicated that in Picea asperata plantations with different ages, the litter pool on forest floor and the nutrient storage and maximum moisture holding capacity of litters showed a general trend of decrease at their earlier restoration stages, and of increase at the later stages. The trend of increase reached the maximum around 50 years of restoration, and then gradually leveled off or even slightly decreased. The observed litter pool (70.21 x 10(3) kg x hm(-2)), nutrient storage (4.73 x 10(3) kg x hm(-2)) and maximum moisture holding capacity (89.98 x 10(3) kg x hm(-2)) of 60-years plantations were considerably small, only accounted for 48.40%, 46.79% and 46.99% of the primitive forests, respectively. After 40 years of restoration, both artificial stands and naturally regenerated secondary forests showed similarity in litter dynamics, annual litterfall, and amount of annual nutrient returning to the soils, while a big difference in litter components, litter pool and structure on the forest floor, nutrient storage, and maximum moisture holding capacity. The difference which accounts for the difference in ecological functioning of the subalpine coniferous plantations lagging behind that of the secondary forests might be mainly caused by the less species diversity of the former.

Biodiversity↗

PubMed2004

[Determination of fifteen metal elements in Cynomorium songaricum by flame atomic absorption spectrophotometry (FAAS)].

A FAAS method was established for the determination of Na, K, Mg, Ca, Cu, Zn, Fe, Mn, Ni, Co, Pb, Cr, Cd, Ag and Au in Cynomorium songaricum after digestion with HNO3-HClO4 (phi 4:1) at 90-95 degrees C and at normal pressure. In this paper, the parameters in FAAS were studied. The analytical results of Na, K, Mg, Ca, Fe, Zn, Cu, Mn, Pb, Ni and Ag were 13,572.0, 14,260.0, 358.3, 168.3, 238.5, 19.4, 5.9, 3.4, 2.6, 1.3 and 0.4 microg x g(-1) respectively and Co, Cr, Cd and Au were not found in the samples. The results showed that the recovery of standard addition was 97.8%-104.5%, and the relative standard deviation (n = 9) was 0.2%-5.0%. The method is fast, simple and convenient. The results were satisfactory.

Adsorption↗

PubMed2004

[Effects of light and temperature on seed germination of Picea asperata and Betula albo-sinensis].

The effects of different light and temperature conditions on seed germination of two keystone species (Picea asperata and Betula albo-sinensis) in subalpine coniferous forests were studied by simulating environmental conditions in climatic chambers. The results indicated that the optimal temperature of seed germination for both species was 25 degrees C, with the germination rate of 88.8 +/- 8.4% and 30.8 +/- 10.4%, respectively. Through multiple comparisons with Tukey's HSD, B. albo-sinensis was more sensitive to temperature than P. asperata. Seeds of P. asperata could germinate when the temperature reached 10 degrees C, but those of B. albo-sinensis could not, which implied that the latter as a pioneer species of subalpine coniferous forest areas needed higher lowest temperature for seed germination. Day and night temperature difference (15 degreesC/10 degrees C, 20 degrees C/15 degrees C and 20 degrees C/10 degrees C) had significant effect on the germination rates of tested seeds, which was the highest under 20 degrees C/15 degrees C. A wide range of day and night temperature difference seemed to be unfavorable to the seed germination of B. albo-sinensis. Light intensity also had a marked effect on the germination rates of test seeds. Under 20% transmittance, the germination rate of P. asperata and B. albo-sinensis was the highest, being 83.0 +/- 6.6% and 29.2 +/- 5.5%, respectively, and the initiation time and regularity of germination were the best as well. Furthermore, B. albo-sinensis was less sensitive to light than P. asperata, which was determined by the life behavior of tree itself.

Betula↗

PubMed2003

Critical role of CXC chemokines in endotoxemic liver injury in mice.

Tissue accumulation of leukocytes constitutes a rate-limiting step in endotoxin-induced tissue injury. Chemokines have the capacity to regulate leukocyte trafficking. However, the role of CXC chemokines, i.e., macrophage inflammatory protein-2 (MIP-2) and cytokine-induced neutrophil chemoattractant (KC), in leukocyte recruitment, microvascular perfusion failure, cellular injury, and apoptosis in the liver remains elusive. Herein, mice were challenged with lipopolysaccharide (LPS) in combination with D-galactosamine, and intravital microscopy of the liver microcirculation was conducted 6 h later. It was found that immunoneutralization of MIP-2 and KC did not reduce LPS-induced leukocyte rolling and adhesion in postsinusoidal venules. In contrast, pretreatment with monoclonal antibodies against MIP-2 and KC abolished (83% reduction) extravascular recruitment of leukocytes in the livers of endotoxemic mice. Notably, endotoxin challenge increased the expression of CXC chemokines, which was mainly confined to hepatocytes. Moreover, endotoxin-induced increases of liver enzymes and hepatocellular apoptosis were decreased by more than 82% and 68%, respectively, and sinusoidal perfusion was restored in mice passively immunized against MIP-2 and KC. In conclusion, this study indicates that intravascular accumulation of leukocytes in the liver is independent of CXC chemokines in endotoxemic mice. Instead, our novel data suggest that CXC chemokines are instrumental in regulating endotoxin-induced transmigration and extravascular tissue accumulation of leukocytes. Indeed, these findings demonstrate that interference with MIP-2 and KC functions protects against septic liver damage and may constitute a potential therapeutic strategy to control pathological inflammation in endotoxemia.

Animals↗

PubMed2003

Small nucleolar RNA clusters in trypanosomatid Leptomonas collosoma. Genome organization, expression studies, and the potential role of sequences present upstream from the first repeated cluster.

Trypanosomatid small nucleolar RNA (snoRNA) genes are clustered in the genome. snoRNAs are transcribed polycistronically and processed into mature RNAs. In this study, we characterized four snoRNA clusters in Leptomonas collosoma. All of the clusters analyzed carry both C/D and H/ACA RNAs. The H/ACA RNAs are composed of a single hairpin, a structure typical to trypanosome and archaea guide RNAs. Using deletion and mutational analysis of a tagged C/D snoRNA situated within the snoRNA cluster, we identified 10-nucleotide flanking sequences that are essential for processing snoRNA from its precursor. Chromosome walk was performed on a snoRNA cluster, and a sequence of 700 bp was identified between the first repeat and the upstream open reading frame. Cloning of this sequence in an episome vector enhanced the expression of a tagged snoRNA gene in an orientation-dependent manner. However, continuous transcript spanning of this region was detected in steady-state RNA, suggesting that snoRNA transcription also originates from an upstream-long polycistronic transcriptional unit. The 700-bp fragment may therefore represent an example of many more elements to be discovered that enhance transcription along the chromosome, especially when transcription from the upstream gene is reduced or when enhanced transcription is needed.

Amino Acid Sequence↗

PubMed2003

Involvement of the ubiquitin-proteasome system in the early stages of wallerian degeneration.

Local axon degeneration is a common pathological feature of many neurodegenerative diseases and peripheral neuropathies. While it is believed to operate with an apoptosis-independent molecular program, the underlying molecular mechanisms are largely unknown. In this study, we used the degeneration of transected axons, termed "Wallerian degeneration," as a model to examine the possible involvement of the ubiquitin proteasome system (UPS). Inhibiting UPS activity by both pharmacological and genetic means profoundly delays axon degeneration both in vitro and in vivo. In addition, we found that the fragmentation of microtubules is the earliest detectable change in axons undergoing Wallerian degeneration, which among other degenerative events, can be delayed by proteasome inhibitors. Interestingly, similar to transected axons, degeneration of axons from nerve growth factor (NGF)-deprived sympathetic neurons could also be suppressed by proteasome inhibitors. Our findings suggest a possibility that inhibiting UPS activity may serve to retard axon degeneration in pathological conditions.

Amino Acids↗

PubMed2003

Small nucleolar RNA interference induced by antisense or double-stranded RNA in trypanosomatids.

In trypanosomes the C/D- and H/ACA-like small nucleolar RNAs (snoRNAs) are clustered and repeated in the genome. The snoRNAs studied to date are transcribed as polycistronic transcripts by RNA polymerase II and then processed, resulting in mature snoRNAs. In this study we demonstrated that snoRNA genes can be silenced in three trypanosomatid species: Leptomonas collosoma, Leishmania major, and Trypanosoma brucei. Silencing was achieved in L. collosoma and L. major by the expressing of an antisense transcript complementary to the snoRNA gene and was accompanied by the accumulation of small interfering RNA. Silencing eliminated the mature snoRNA but not its precursor and abolished the specific 2'-O-methylation guided by the snoRNA. In T. brucei, silencing was achieved by using the inducible synthesis of double-stranded RNA from T7 opposing promoters. Silencing varied between the different snoRNA genes, which may reflect the accessibility of small interfering RNA to the target RNAs. This study suggests that RNA interference can degrade snoRNAs. This study has further implications in elucidating the function of nucleolar RNAs and specific modifications guided by these RNAs in trypanosomatids and perhaps in other eukaryotes as well.

Animals↗

PubMed2003

Docosahexaenoic acid inhibits cytokine-induced expression of P-selectin and neutrophil adhesion to endothelial cells.

Dietary polyunsaturated fatty acids, such as docosahexaenoic acid, may inhibit pathological processes involving endothelial cell activation. Herein, it was found that treatment of endothelial cells with docosahexaenoic acid dose dependently reduced neutrophil adhesion provoked by tumor necrosis factor-alpha (TNF-alpha). In fact, pretreatment with 100 microM of docosahexaenoic acid for 24 h decreased TNF-alpha-induced neutrophil adhesion by 50%. Moreover, this pretreatment with docosahexaenoic acid (100 microM, 24 h) down-regulated TNF-alpha-induced endothelial cell surface expression of P-selection by 75%. Importantly, immunoneutralization of P-selectin reduced neutrophil adhesion to TNF-alpha-activated endothelial cells by more than 50%, indicating a significant role of P-selectin in this model. On the other hand, CXC chemokines, i.e. macrophage inflammatory protein-2 (MIP-2) and cytokine-induced neutrophil chemoattractant (KC), are also important regulators of neutrophil activation and adhesion. However, pretreatment with docosahexaenoic acid had no effect on TNF-alpha-provoked production of MIP-2 and KC in endothelial cells. Our study provide evidence that docosahexaenoic acid inhibits expression of P-selectin and subsequent adhesion of neutrophils to endothelial cells in response TNF-alpha, which may help explain the anti-inflammatory effects exerted by docosahexaenoic acid.

Animals↗

PubMed2003

Human gamma/delta T-cell proliferation and IFN-gamma production induced by hexamethylene diisocyanate.

BACKGROUND: The human immune response to isocyanate, a leading cause of occupational asthma, remains incompletely characterized, including the cell types involved and the form of the chemical that acts as an antigen. OBJECTIVE: The purpose of this investigation was to characterize human T cells that respond to hexamethylene diisocyanate (HDI), an aliphatic isocyanate routinely used in the automobile body industry. METHODS: Human T-cell lines were generated and characterized from peripheral blood of HDI-exposed and HDI-unexposed subjects, using two different HDI antigens, HDI-conjugated albumin and HDI-exposed human airway epithelial cells (NCI-H292). Flow cytometry was used to characterize the phenotype of HDI-responsive T cells. ELISA and intracellular staining techniques were used to evaluate HDI-induced cytokine production. DNA sequence analysis of T-cell receptors was used to further define clonal populations of HDI-responsive T cells. RESULTS: HDI antigen preparations but not "mock exposed" control antigens lead to increased proliferation of specific cell types, CD3+CD4-CD8(dim) and/or CD3+CD4-CD8- cells, from HDI-exposed but not from HDI-unexposed subjects. These HDI-responsive T cells expressed unique oligoclonal gamma/delta rather than alpha/beta T-cell receptors, with characteristics suggestive of antigen-mediated selection and specificity. The HDI-stimulated gamma/delta T cells were associated with T(H)1-like cytokines and produce IFN-gamma but not IL-5 or IL-13. CONCLUSIONS: These data are the first to demonstrate that HDI can selectively stimulate gamma/delta T cells with the potential to modulate the human immune response to exposure.

Allergens↗

PubMed2003

Practical midcourse sample size modification in clinical trials.

Power calculations are very important in the planning of a well-designed clinical trial. Sometimes there is limited information available before the trial, making it highly desirable to adjust the sample size after seeing actual trial data. Indeed, there has been a recent proliferation of papers promising great flexibility in midcourse correction of sample size and other design features, such as choice of primary endpoint. We point out the difficulty in accurately estimating the treatment effect midway through a trial, and we encourage the use of a simple, conservative approach whereby sample size can be increased but not decreased from what was originally planned. We show how to compute the p value and confidence interval for this two-stage procedure. If the original sample size is maintained, analysis of the data is the same as for a fixed sample procedure.

Bayes Theorem↗

PubMed2003

Recent developments in diisocyanate asthma.

OBJECTIVE: To summarize the latest experimental findings on diisocyanate asthma and discuss the impact of these data on our understanding of disease pathogenesis and diagnosis. DATA SOURCES: The literature reviewed includes articles from PubMed (National Library of Medicine) published within the last 3 years (1999-2001). In addition, pertinent older references are discussed to provide a historical perspective and background. STUDY SELECTION: The data discussed were chosen to highlight key concepts relevant to diisocyanate asthma pathogenesis and are grouped accordingly. RESULTS: In many ways, diisocyanate-induced asthma mirrors allergic asthma caused by other stimuli; however, the immune-mediated pathways believed to be central to the disease have been difficult to define. Recent studies on the human immune response to diisocyanates provide additional evidence supportive of an immune basis for pathogenesis but also highlight well-recognized differences between diisocyanate asthma and common atopic asthma. Studies on the antigenic form of diisocyanates and their interaction with epithelial tissues provide new insights that may help explain these apparent immunologic differences. Genetic factors that influence disease have begun to be identified but remain poorly characterized. Associations of particular major histocompatibility complex class II alleles with diisocyanate asthma further fuel the hypothesis that immune-dependent mechanisms underlie pathogenesis, whereas associations of glutathione S-transferase polymorphisms (in conjunction with recent studies defining the effects of diisocyanates on thiol-redox homeostasis) may implicate additional antigen-independent mechanisms. Long-term follow-up studies of diisocyanate asthma patients have confirmed the prognostic value of early removal of symptomatic patients from exposure and highlight the need for effective diagnostic tests of sensitivity and susceptibility. CONCLUSIONS: Diisocyanate-induced asthma appears to be a multifactorial disease involving the immune system, airway epithelium, and genetic factors. The potential long-term adverse effects of diisocyanate exposure in sensitized patients underscore the need for further studies to elucidate the pathogenesis of this disease and identify biomarkers for sensitization and susceptibility.

Asthma↗

PubMed2003

Sequence diversity in the amino-terminal region of the malaria-vaccine candidate serine repeat antigen in natural Plasmodium falciparum populations.

The amino-terminal region of the serine repeat antigen (SERA) of Plasmodium falciparum is a major malaria-vaccine candidate. Variation in this molecule is essentially dimorphic and alleles may be grouped into the types FCR3, K1 and Honduras1. The Honduras1-type is thought to be the product of homologous recombination between FCR3 and K1 alleles. Here we have examined patterns of sequence diversity in exon II of SERA gene, which encodes most of the amino-terminal region of the antigen, in wild P. falciparum isolates from Indonesia (n=60), Myanmar (n=10) and Thailand (n=14). Among the Indonesian isolates the FCR-3 type predominated (56/60), twenty of which we characterized as novel alleles. A new K1-type allele was also found. In Myanmar, however, all isolates displayed K1-type SERA sequences, which included one new allele. The Honduras1-type was not detected in both countries. In contrast, the 14 isolates from Thailand displayed all three allelic types, with one new Honduras1-type and three new K1-type alleles. On examining the global distribution of SERA alleles by combining previously published sequence data with our results, the FCR3-type alleles predominated in Indonesia, Brazil, and Solomon Islands, but were not found in wild isolates from Myanmar and Africa. Brazil was the only area where K1-type alleles were not found. The distribution of Honduras1-type alleles seems to be mostly restricted to parasite populations from Vietnam, Thailand and Africa. In the allelic families FCR3 and K1, most diversity resulted from variation in sequence and number of octamer repeat units and of allotypes encoding the stretch of serine residues. Sequence analysis indicated that both insertions and deletions of repetitive motifs (creating variation within dimorphic allelic families) and homologous recombination between alleles belonging to different allelic families (creating Honduras1-type alleles) play a role in generating new SERA alleles. Since repeat motifs in the amino-terminal region of SERA contain epitopes recognized by parasite-inhibitory antibodies, sequence variation in exon II may represent one of the parasite's immune-evasion strategies.

Alleles↗

PubMed2003

Solvent effects on infrared spectra of 2-acetylthiophene in organic solvents.

Infrared spectroscopy studies of 2-acetylthiophene (ACTH) in 18 different organic solvents, both polar and non-polar, were undertaken to investigate the solvent-solute interactions. The frequencies of carbonyl stretching vibration upsilon(C=O) of ACTH were correlated with the properties such as the solvent acceptor number (AN) and the linear solvation energy relationships (LSER). The solvent-induced stretching vibration frequency shifts showed a better correlation with the LSER than the AN. A six-membered ring-like hydrogen bonding structure was presented and the solvent effects of ACTH in alcohol solvents were investigated in detail.

Hydrogen Bonding↗

PubMed2003

CC chemokines induce P-selectin-dependent neutrophil rolling and recruitment in vivo: intermediary role of mast cells.

1. Based on in vitro chemotaxis experiments, it is widely held that CC chemokines, such as macrophage inflammatory protein-1alpha (MIP-1alpha) and macrophage chemotactic protein-1 (MCP-1) mainly support lymphocyte trafficking. 2. The objective of the present study was to examine the role of MIP-1alpha and MCP-1 in neutrophil recruitment in vivo by use of intravital microscopy of the mouse cremaster microcirculation. 3. MIP-1alpha and MCP-1 caused a dose-dependent increase in leukocyte rolling, adhesion and recruitment. Indeed, neutrophils comprised more than 85% of the leukocyte response to MIP-1alpha and MCP-1. An anti-P-selectin antibody reduced MIP-1alpha and MCP-1-provoked leukocyte rolling by more than 94%. Concomitantly, firm adhesion and extravasation of neutrophils in response to MIP-1alpha and MCP-1 challenge were significantly decreased by more than 78 and 84%, respectively. In contrast, an anti-E-selectin antibody had no influence on CC chemokine-induced neutrophil recruitment. 4. Flow cytometric analysis revealed that MIP-1alpha and MCP-1 had no effect on P-selectin expression on endothelial cells, suggesting that neutrophil recruitment elicited by CC chemokines in vivo is not mediated via a direct effect on the endothelium but rather via an indirect effect involving activation of an intermediary tissue cell. Indeed, it was found that MIP-1alpha-induced neutrophil accumulation was significantly decreased by 58% in mast cell-deficient mice. 5. These findings demonstrate that CC chemokines trigger P-selectin-dependent rolling and tissue recruitment of neutrophils via tissue mast cells in vivo and suggest that CC chemokines may also be important targets in neutrophil-mediated tissue damage in multicellular organs.

Animals↗

PubMed2003

Custom knock-outs with hairpin RNA-mediated gene silencing.

Hairpin (hpRNA)-mediated gene silencing exploits a cellular mechanism that recognizes double-stranded RNA (dsRNA) and subjects it and its corresponding mRNA to a sequence-specific degradation. This phenomenon is known as posttranscriptional gene silencing (PTGS) in plants and RNA interference (RNAi) in animals. dsRNA, when introduced into plant cells through hpRNA constructs, results in severe reduction of the target mRNA-the silencing effect being stably inherited over many generations. While hpRNA constructs can be made using conventional plasmids, use of generic vectors such as pHANNIBAL makes it more convenient to silence a number of genes simultaneously. Vectors, such as pHELLSGATE, that are based on the Gateway(R) technology are suitable for high-throughput gene silencing. The specificity of dsRNA silencing, it's ability to simultaneously silence multiple genes combined with the availability of high-throughput silencing vectors enables the researcher to generate custom knockout plants.

Base Sequence↗

PubMed2003

[Researches into the modernization of tongue diagnosis: in retrospect and prospect].

With the further development of clinical modernization of traditional Chinese medicine (TCM), new request to tongue diagnosis for objectivity and quantification is raised. Many researchers have devoted themselves to this field and have achieved some accomplishments since 1950's. Especially in recent years, the revolution of information technique derived from computer industry brings the research new chances. The research history of the past five decades can be divided into three stages: (1) looking for micro-markers by newly-developed medical technique; (2) quantifying traditional markers by new technique; (3) further development based on information technique and corporation of multiple subjects. This article reviewed the three stages and described its prospect.

Humans↗

PubMed2003

[Study on decomposed recipes of traditional Chinese medicine].

OBJECTIVE: To introduce and analyze the present status of research on decomposed recipes of traditional Chinese medicine (TCM). METHODS: The relevant literature on the study of the decomposed recipes of TCM in the past five years was collected and analyzed. RESULTS AND CONCLUSION: Studies on the decomposed recipes of TCM have been made from the whole body level to the organ, cell and molecular research level. The pharmacological research in vitro is the main way and quantitative changes of the chemical ingredients have been measured before and after composition. It is very important to combine the modern science and technology in exploring the composing mechanisms of TCM remedies.

Biomedical Research↗