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Biomedical subjects

S Yuan

Publications and source records attributed to S Yuan.

At least 19 recordsLinked to original sources
PubMed2006

Soil organic carbon decomposition and carbon pools in temperate and sub-tropical forests in China.

Decomposition of soil organic carbon (SOC) is a critical component of the global carbon cycle, and accurate estimates of SOC decomposition are important for forest carbon modeling and ultimately for decision making relative to carbon sequestration and mitigation of global climate change. We determined the major pools of SOC in four sites representing major forest types in China: temperate forests at Changbai Mountain (CBM) and Qilian Mountain (QLM), and sub-tropical forests at Yujiang (YJ) and Liping (LP) counties. A 90-day laboratory incubation was conducted to measure CO(2) evolution from forest soils from each site, and data from the incubation study were fitted to a three-pool first-order model that separated mineralizable soil organic carbon into active (C(a)), slow (C(s)) and resistant (C(r)) carbon pools. Results indicate that: (1) the rate of SOC decomposition in the sub-tropical zone was faster than that in the temperature zone, (2) The C(a) pool comprised approximately 1-3% of SOC with an average mean residence time (MRT) of 219 days. The C(s) pool comprised approximately 25-65% with an average MRT of 78 yr. The C(r) pool accounted for approximately 35-80% of SOC, (3) The YJ site in the sub-tropical zone had the greatest C(a) pool and the lowest MRT, while the QLM in the temperature zone had the greatest MRT for both the C(a) and C(s) pools. The results suggest a higher capacity for long-term C sequestration as SOC in temperature forests than in sub-tropical forests.

Carbon↗
PubMed2006

Quantification of atelectatic lung volumes in two different porcine models of ARDS.

BACKGROUND: Cyclic recruitment during mechanical ventilation contributes to ventilator associated lung injury. Two different pathomechanisms in acute respiratory distress syndrome (ARDS) are currently discussed: alveolar collapse vs persistent flooding of small airways and alveoli. We compare two different ARDS animal models by computed tomography (CT) to describe different recruitment and derecruitment mechanisms at different airway pressures: (i) lavage-ARDS, favouring alveolar collapse by surfactant depletion; and (ii) oleic acid ARDS, favouring alveolar flooding by capillary leakage. METHODS: In 12 pigs [25 (1) kg], ARDS was randomly induced, either by saline lung lavage or oleic acid (OA) injection, and 3 animals served as controls. A respiratory breathhold manoeuvre without spontaneous breathing at different continuous positive airway pressure (CPAP) was applied in random order (CPAP levels of 5, 10, 15, 30, 35 and 50 cm H(2)O) and spiral-CT scans of the total lung were acquired at each CPAP level (slice thickness=1 mm). In each spiral-CT the volume of total lung parenchyma, tissue, gas, non-aerated, well-aerated, poorly aerated, and over-aerated lung was calculated. RESULTS: In both ARDS models non-aerated lung volume decreased significantly from CPAP 5 to CPAP 50 [oleic acid lung injury (OAI): 346.9 (80.1) to 96.4 (48.8) ml, P<0.001; lavage-ARDS: 245 17.6) to 42.7 (4.8) ml, P<0.001]. In lavage-ARDS poorly aerated lung volume decreased at higher CPAP levels [232 (45.2) at CPAP 10 to 84 (19.4) ml at CPAP 50, P<0.001] whereas in OAI poorly aerated lung volume did not vary at different airway pressures. CONCLUSIONS: In both ARDS models well-aerated and non-aerated lung volume respond to different CPAP levels in a comparable fashion: Thus, a cyclical alveolar collapse seems to be part of the derecruitment process also in the OA-ARDS. In OA-ARDS, the increase in poorly aerated lung volume reflects the specific initial lesion, that is capillary leakage with interstitial and alveolar oedema.

Animals↗
PubMed2006

Calmodulin concentrates at the apex of growing hyphae and localizes to the Spitzenkörper in Aspergillus nidulans.

The calmodulin (CaM) localization pattern in the growing hyphal tip of Aspergillus nidulans was studied with the functional GFP::CaM fusion protein. A faint tip-high gradient of CaM was found in the growing hyphal tip, with CaM highly localized in the region corresponding to the Spitzenkörper forming a bright granule. The position of highly concentrated CaM in the extreme apex seemed to determine the orientation of the hypha. The normal pattern of CaM localization was also shown to be dependent on the integrated actin cytoskeleton. When the growth of the hyphal tip ceased, CaM failed to localize in the bright granule and was evenly distributed in the hyphal tip. These findings suggest that CaM may play an important role in establishing and maintaining apical organization, morphogenesis, and growth in Aspergillus nidulans.

Actins↗
PubMed2006

Quantitative structure-property relationship studies on electrochemical degradation of substituted phenols using a support vector machine.

A quantitative structure-property relationship (QSPR) model has been developed for the electrochemical degradation of substituted phenols using a support vector machine (SVM). Thirty descriptors, including quantum chemical parameters, steric effect descriptors and half wave potential (E1/2), were used for describing twelve substituted phenols, including mono- and multi-substituent phenols. A leave-one-out (LOO) cross validation procedure resulted in the selection of three descriptors, the total of electron and nuclear energies of the two-center terms for the carbon-chlorine or carbon-nitrogen bond (TE2), the net atomic charges on the chlorine or nitrogen (qx), and the largest negative atomic charge on an atom (q-). The model based on SVM yielded a Q2 value of 0.892, indicating a high predictive ability. Compared with models developed with partial least squares (PLS) and multiple linear regression (MLR), where Q2 were 0.804 and 0.799 respectively, SVM showed higher performances.

Chlorine↗
PubMed2005

An optical differential scanning calorimeter cryomicroscope.

An optical-DSC system was designed, built, tested, calibrated and verified to incorporate into a single device the capability for simultaneous optical cryomicroscopy and differential scanning calorimetry (DSC). This instrument can be used to obtain both visual and thermal data for an individual specimen subjected to a defined freezing and thawing protocol with very little compromise in quality or range of data available in comparison with dedicated single instruments. Temperature and caloric calibrations were performed based on phase transition states in water, n-dodecane and n-decane. The instrument has proven effective for process analysis in living cells and in foodstuffs.

Journal Article↗
PubMed2005

Case report: massive postpartum transfusion of Jr(a+) red cells in the presence of anti-Jra.

Jr(a) is a high-prevalence antigen. The rare Jr(a-) individuals can form anti-Jr(a) after exposure to the Jr(a) antigen through transfusion or pregnancy. The clinical significance of anti-Jr(a) is not well established. This study reports a case of a 31-year-old woman with a previously identified anti-Jr(a) who required massive transfusion of RBCs after developing life-threatening postpartum disseminated intravascular coagulopathy. Despite the emergent transfusion of 15 units of Jr(a) untested RBCs, she did not develop laboratory or clinical evidence of acute hemolysis. The patient's anti-Jr(a) had a pretransfusion titer of 4 and a monocyte monolayer assay (MMA) reactivity of 68.5% (reactivity > 5% is considered capable of shortening the survival of incompatible RBCs). The titer increased fourfold to 64 and the MMA reactivity was 72.5% on Day 10 posttransfusion. Review of laboratory data showed evidence of a mild delayed hemolytic transfusion reaction by Day 10 posttransfusion. Despite rare reports of hemolytic transfusion reactions due to anti-Jr(a) in the literature, most cases, including this one, report that this antibody is clinically insignificant or causes only mild delayed hemolysis. Clinicians should be advised to balance the risks of withholding transfusion with the small chance of significant hemolysis after transfusion of Jr(a+) RBCs in the presence of anti-Jr(a).

Adult↗
PubMed2004

Determination of an endothelin receptor antagonist in rat plasma by radioimmunoassay.

A quantitative method based on radioimmunoassay for the determination of an endothelin receptor antagonist (C(31)H(33)NO(7), I) has been developed and validated. The immunogen was prepared by coupling I to the bovine serum albumin via the N-hydroxysuccinimide ester of I from which the radioligand was also prepared by the reaction with [125I]-iodotyrosine. The method was specific and no immunoactive material other than the parent drug was detectable in mammalian plasma. This direct assay, using 50 microl of rat plasma is sensitive (0.4 ng/ml), without matrix interference, and has sufficient sensitivity, specificity, accuracy and precision for the analysis of dosed rat plasma samples.

Animals↗
PubMed2004

A functional genomic study on NCI's anticancer drug screen.

Pharmacogenomics requires massive computer exploration on heterogeneous databases. COMPARE, the gateway to the NCI's anticancer drug screen database, allows users to correlate drug-sensitivity profiles with a functional genomic database. However, most drugs of known molecular mechanism turn out to be uncorrelated with their molecular-target gene expression. Based on a novel statistical concept, liquid association, we develop an on-line system to identify candidate genes that intervene, confound and weaken the drug-gene correlation. The system takes queries and returns button-clickable tables of functionally associated genes for rerouting to knowledgebases such as Locus Link, OMIM and PubMed. We report results that link methotrexate resistance to DNA component biosynthesis, and taxol sensitivity to genes associated with human immunodeficiency virus infection. The drug-sensitivity database can be synergistically coanalyzed with gene expression data to study proteins of poorly understood physiological roles. When applied to the human prion, a cellular context embroidered with the gene expression network of Alzheimer disease is revealed.

Databases, Nucleic Acid↗
PubMed2002

Isolation and identification of Streptomyces sp. and assay of its exocellular water-soluble blue pigments.

A bacterial strain producing a great amount of blue pigment during submerse fermentation was isolated and identified. Based on morphological characteristics, cell-wall chemotype and sequence of 16S rRNA gene, the strain should belong to the genus Streptomyces; it had 99.4% homology of 16S rRNA gene sequence with that of Streptomyces indigocolor. The pigment production by the strain was affected by carbon and nitrogen sources. The main components of the pigment mixture (detected by HPLC and TLC) were tentatively classified as actinorhodin-related compounds. The pigment was relatively stable against light and higher temperature but was sensitive to low pH. The preliminary acute-toxicity determination showed that the pigment was nontoxic (LD50 > 15 mg/g).

Animals↗
PubMed2002

A gene therapy for cancer based on the angiogenesis inhibitor, vasostatin.

The growth and persistence of solid tumors and their metastasis are angiogenesis-dependent. Vasostatin, the N-terminal domain of calreticulin inclusive of amino acids 1-180, is a potent angiogenesis inhibitor. To investigate whether intramuscular administration of vasostatin gene has the antitumor activity in mouse tumor models, we constructed a plasmid DNA encoding vasostatin and a control vector. Production and secretion of vasostatin protein by COS cells transfected with the plasmid DNA encoding vasostatin (pSecTag2B-vaso) were confirmed by Western blot analysis and ELISA. Conditioned medium from vasostatin-transfected COS cells apparently inhibited human umbilical vein endothelial cell (HUVEC) and mouse endothelial cell (SVEC4-10) proliferation, compared with conditioned medium from the COS cells transfected with control vector or non-transfected cells. Treatment with pSecTag2B-vaso twice weekly for 4 weeks resulted in the inhibition of tumor growth and the prolongation of the survival of tumor-bearing mice. The sustained high level of vasostatin protein in serum could be identified in ELISA. Angiogenesis was apparently inhibited in tumor by immunohistochemical analysis. Angiogenesis was also inhibited in the chicken embryo CAM assay and mouse corneal micropocket assay. The increased apoptotic cells were found within the tumor tissues from the mice treated with plasmid DNA encoding vasostatin. Taken together, the data in the present study indicate that the cancer gene therapy by the intramuscular delivery of plasmid DNA encoding vasostatin, is effective in the inhibition of the systemic angiogenesis and tumor growth in murine models. The present findings also provide further evidence of the anti-tumor effects of the vasostatin, and may be of importance for the further exploration of the application of this molecule in the treatment of cancer.

Angiogenesis Inhibitors↗
PubMed2001

Complete genome comparison of porcine reproductive and respiratory syndrome virus parental and attenuated strains.

Two full-length porcine reproductive and respiratory syndrome virus (PRRSV) genomes, strain VR-2332 and its cell culture passaged descendent RespPRRS vaccine strain, were compared and analyzed in order to identify possible sites of attenuation. Of the 41 nucleotide changes, 12 resulted in conservative changes and 18 produced non-conservative changes. The results suggest that key amino acids in ORF1 may contribute to the phenotype of RespPRRS, which includes increased growth rate on MA-104 cells and decreased virulence in swine. The results provide a genetic basis for future manipulation of a PRRSV reverse genetics system.

5' Untranslated Regions↗
PubMed2001

DNA microarray analysis of gene expression in endothelial cells in response to 24-h shear stress.

The recently developed DNA microarray technology provides a powerful and efficient tool to rapidly compare the differential expression of a large number of genes. Using the DNA microarray approach, we investigated gene expression profiles in cultured human aortic endothelial cells (HAECs) in response to 24 h of laminar shear stress at 12 dyn/cm(2). This relatively long-term shearing of cultured HAECs led to the modulation of the expression of a number of genes. Several genes related to inflammation and EC proliferation were downregulated, suggesting that 24-h shearing may keep ECs in a relatively noninflammatory and nonproliferative state compared with static cells. Some genes were significantly upregulated by the 24-h shear stress; these includes genes involved in EC survival and angiogenesis (Tie2 and Flk-1) and vascular remodeling (matrix metalloproteinase 1). These results provide information on the profile of gene expression in shear-adapted ECs, which is the case for the native ECs in the straight part of the aorta in vivo.

Adult↗
PubMed2001

A novel parasite-derived suicide gene for cancer gene therapy with specificity for lung cancer cells.

The enzyme hypoxanthine-guanine phosphoribosyltransferase (HGPRT) expressed by the parasite Trypanosoma brucei (Tb) can convert allopurinol, a purine analogue, to corresponding nucleotides with greater efficiency than its human homologue. We have developed a retroviral system that expresses the parasitic enzyme and tested its capacity to activate the prodrug allopurinol to a cytotoxic metabolite. Cytotoxicity assays demonstrated that five non-small cell lung carcinoma cell lines transduced with the construct were sensitized to the prodrug by 2.1- to 7.6-fold compared with control values. This selectivity was not observed in seven other cell lines also expressing the construct, such as breast carcinoma. Assays indicated that enhanced cytotoxicity to allopurinol correlated with induction of apoptosis in lung cancer cells. The selectivity of this suicide gene was not explained either by the TbHGPRT expression or by the allopurinol accumulation. Our study shows that this novel system may represent a therapeutic tool for gene prodrug targeting of lung cancer, considering the fact that allopurinol is well tolerated in humans.

Allopurinol↗
PubMed2001

Identification of a new fibroblast growth factor receptor, FGFR5.

A novel fibroblast growth factor receptor (FGFR), designated FGFR5, was identified from an EST database of a murine lymph node stromal cell cDNA library. The EST has approximately 32% identity to the extracellular domain of FGFR1-4. Library screening with this EST identified two full-length alternative transcripts which we designated as FGFR5 beta and FGFR5 gamma. The main difference between these transcripts is that FGFR5 beta contains three extracellular Ig domains whereas FGFR5 gamma contains only two. A unique feature of FGFR5 is that it does not contain an intracellular tyrosine kinase domain. Predictive structural modelling of the extracellular domain of FGFR5 gamma suggested that it was a member of the I-set subgroup of the Ig-superfamily, consistent with the known FGFRs. Northern analysis of mouse and human FGFR5 showed detectable mRNA in a broad range of tissues, including kidney, brain and lung. Genomic sequencing identified four introns but identified no alternative transcripts containing a tyrosine kinase domain. Extracellular regions of FGFR5 beta and 5 gamma were cloned in-frame with the Fc fragment of human IgG(1) to generate recombinant non-membrane bound protein. Recombinant FGFR5 beta Fc and R5 gamma Fc demonstrated specific binding to the ligand FGF-2, but not FGF-7 or EGF. However, biological data suggest that FGF-2 binding to these proteins is with lower affinity than its cognate receptor FGFR2C. The above data indicate that this receptor should be considered as the fifth member of the FGFR family.

3T3 Cells↗
PubMed2001

Spindle-cell lesions of the liver: diagnosis by fine-needle aspiration biopsy.

Rarely, spindle-cell lesions in liver fine-needle aspiration biopsies (FNABs) are encountered. A retrospective review of our experience with lesions that are mesenchymal in origin or appearance was undertaken to elucidate the frequency and spectrum of these lesions. Image-guided liver FNABs performed over a 3-year period (n = 585) at our institution (1996-1998) were retrospectively evaluated. Cytologic smears, cell block preparations, and clinical follow-up of lesions with spindle-cell morphology were reviewed. Twenty-nine of 585 cases were of spindle-cell morphology (5%). Hemangiomas (n = 12, 41%) and metastatic sarcomas (n = 6, 21%) comprised the largest categories, followed by granulomatous inflammation (n = 3, 10%). Other cases included primary angiosarcoma and fibrolamellar hepatocellular carcinoma. The most frequent spindle-cell liver lesion encountered is hemangioma, followed by metastatic leiomyosarcoma and granulomatous hepatitis. Awareness of diagnostic possibilities, special attention to specimen adequacy, and use of ancillary procedures can maximize diagnostic yield.

Adolescent↗