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Biomedical subjects

Yan Wu

Publications and source records attributed to Yan Wu.

At least 127 records · Page 7Linked to original sources

[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↗

[Effect of qilong capsule on hemoreology in acute stress blood stasis rats].

OBJECTIVE: To study the influence of Qilong capsule (QLC) on the hemoreology in acute stress blood stasis model rats. METHOD: The model of acute stress blood stasis rats were induced by putting the rats into ice-water between hyodermic epinephrine twice of 1 mg x kg(-1). With the models, the effect of QLC on hemoreology such as whole blood viscosity, whole blood reduction viscosity, plasma viscosity, haematocrit (Hct), erythrocyte deformation and erythrocyte aggregation were observed. RESULT: QLC 0.6, 0.3, 0.15 g x kg(-1) could significantly reduce the increase of whole blood viscosity at high-middle-low shear rate, reduce the whole blood reduction viscosity at middle-low shear rate, reduce Hct and erythrocyte aggregation, and increase the erythrocyte deformation in acute stress blood stasis rats (P < 0.05, P < 0.01, compared with vehicle). QLC 0.6, 0.3 g x kg(-1) could also reduce plasma viscosity (P < 0.05, P < 0.01, compared with vehicle). CONCLUSION: QLC can significantly improve some indexes of hemoreology in acute stress blood stasis rats.

Animals↗

[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↗

Blockade of vascular endothelial growth factor receptor I (VEGF-RI), but not VEGF-RII, suppresses joint destruction in the K/BxN model of rheumatoid arthritis.

It was recently shown that vascular endothelial growth factor (VEGF), a growth factor for endothelial cells, plays a pivotal role in rheumatoid arthritis. VEGF binds to specific receptors, known as VEGF-RI and VEGF-RII. We assessed the physical and histological effects of selective blockade of VEGF and its receptors in transgenic K/BxN mice, a model of rheumatoid arthritis very close to the human disease. Mice were treated with anti-mouse VEGF Ab, anti-mouse VEGF-RI and -RII Abs, and an inhibitor of VEGF-RI tyrosine kinase. Disease activity was monitored using clinical indexes and by histological examination. We found that synovial cells from arthritic joints express VEGF, VEGF-RI, and VEGF-RII. Treatment with anti-VEGF-RI strongly attenuated the disease throughout the study period, while anti-VEGF only transiently delayed disease onset. Treatment with anti-VEGF-RII had no effect. Anti-VEGF-RI reduced the intensity of clinical manifestations and, based on qualitative and semiquantitative histological analyses, prevented joint damage. Treatment with a VEGF-RI tyrosine kinase inhibitor almost abolished the disease. These results show that VEGF is a key factor in pannus development, acting through the VEGF-RI pathway. The observation that in vivo administration of specific inhibitors targeting the VEGF-RI pathway suppressed arthritis and prevented bone destruction opens up new possibilities for the treatment of rheumatoid arthritis.

Animals↗

Antifungal diterpenoids of Pseudolarix kaempferi, and their structure-activity relationship study.

The in vitro antifungal activities of 19 structurally diversified analogues of pseudolaric acids tested against the major pathogenic fungus Candida albicans has led to the establishment of a very clear structure-activity relationship of pseudolaric acids derivatives. Pseudolaric acid A was first found to be a potent antifungal component comparable with pseudolaric acid B. Among the tested 19 diterpenoids, pseudolaric acids A2 (1), B2 (3), B3 (4) and methyl pseudolarate A2 (2) are new isolates of the root bark of Pseudolarix kaempferi, and their structures were elucidated mainly by 2D-NMR techniques and chemical methods. Compounds 12-19 were first semi-synthesized by efficient routines from pseudolaric acid B.

Animals↗

Algorithm and performance of a clinical IMRT beam-angle optimization system.

This paper describes the algorithm and examines the performance of an intensity-modulated radiation therapy (IMRT) beam-angle optimization (BAO) system. In this algorithm successive sets of beam angles are selected from a set of predefined directions using a fast simulated annealing (FSA) algorithm. An IMRT beam-profile optimization is performed on each generated set of beams. The IMRT optimization is accelerated by using a fast dose calculation method that utilizes a precomputed dose kernel. A compact kernel is constructed for each of the predefined beams prior to starting the FSA algorithm. The IMRT optimizations during the BAO are then performed using these kernels in a fast dose calculation engine. This technique allows the IMRT optimization to be performed more than two orders of magnitude faster than a similar optimization that uses a convolution dose calculation engine. Any type of optimization criterion present in the IMRT system can be used in this BAO system. An objective function based on clinically-relevant dose-volume (DV) criteria is used in this study. This facilitates the comparison between a BAO plan and the corresponding plan produced by a planner since the latter is usually optimized using a DV-based objective function. A simple prostate case and a complex head-and-neck (HN) case were used to evaluate the usefulness and performance of this BAO method. For the prostate case we compared the BAO results for three, five and seven coplanar beams with those of the same number of equispaced coplanar beams. For the HN case we compare the BAO results for seven and nine non-coplanar beams with that for nine equispaced coplanar beams. In each case the BAO algorithm was allowed to search up to 1000 different sets of beams. The BAO for the prostate cases were finished in about 1-2 h on a moderate 400 MHz workstation while that for the head-and-neck cases were completed in 13-17 h on a 750 MHz machine. No a priori beam-selection criteria have been used in achieving this performance. In both the prostate and the head-and-neck cases, BAO is shown to provide improvements in plan quality over that of the equispaced beams. The use of DV-based objective function also allows us to study the dependence of the improvement of plan quality offered by BAO on the DV criteria used in the optimization. We found that BAO is especially useful for cases that require strong DV criteria. The main advantages of this BAO system are its speed and its direct link to a clinical IMRT system.

Algorithms↗

Cleavage of the Pseudomonas syringae type III effector AvrRpt2 requires a host factor(s) common among eukaryotes and is important for AvrRpt2 localization in the host cell.

Many phytopathogenic bacteria use a type III secretion system to deliver type III effector proteins into the host plant cell. The Pseudomonas syringae type III effector AvrRpt2 is cleaved at a specific site when translocated into the host cell. In this study, we first demonstrate that the factor(s) required for AvrRpt2 cleavage is present in extracts from animal and yeast cells, as well as plant cells. The cleavage factor in animal and plant cell extracts was heat labile but relatively insensitive to protease inhibitors. Second, mutational analysis of AvrRpt2 was applied to identify features important for its cleavage. In addition to two of the amino acid residues in the immediate vicinity of the cleavage site, a large part of the region C-terminal to the cleavage site was required when AvrRpt2 was cleaved in animal cell extract. Most of these features were also important when AvrRpt2 was cleaved in plant cells. Third, we investigated the effect of cleavage in interactions of AvrRpt2 with plant cells. Cleavage of AvrRpt2 appeared to be important for proper interactions with Arabidopsis cells that lack the resistance gene product corresponding to AvrRpt2, RPS2. In addition, removal of the region N-terminal to the cleavage site was important for the correct localization of the C-terminal effector region of the protein in the host cell. We speculate that the virulence function of AvrRpt2 requires removal of the N-terminal region to redirect the effector protein to a specific subcellular location in the host cell after translocation of the protein.

Animals↗

[Exogenous rhCNTF inhibits myoblast differentiation of skeletal muscle of adult human in vitro].

To determine the role of recombinant human ciliary neurotrophic factor (rhCNTF) in myogenesis, we observed the effects of rhCNTF (0 10 ng/ml) on myoblast differentiation of adult human in vitro. The results showed that compared with the control group, the groups of 2.5 10 ng/ml rhCNTF treatment significantly inhibited myoblast differentiation (P<0.01), and the inhibition was dose-dependent and reversible. Western blots also indicated that compared with the control group, the expression of myogenin and p21, markers of myoblast differentiation phase, was significantly reduced (P<0.01), while Myf5 and desmin, markers of myoblast proliferative phase, significantly increased (P<0.01) in the groups of 2.5 10 ng/ml rhCNTF treatment. These findings demonstrate that exogenous rhCNTF can reversibly inhibit differentiation but permits proliferation of adult human myoblasts in vitro.

Adult↗

Quantitative quality control in microarray experiments and the application in data filtering, normalization and false positive rate prediction.

Data preprocessing including proper normalization and adequate quality control before complex data mining is crucial for studies using the cDNA microarray technology. We have developed a simple procedure that integrates data filtering and normalization with quantitative quality control of microarray experiments. Previously we have shown that data variability in a microarray experiment can be very well captured by a quality score q(com) that is defined for every spot, and the ratio distribution depends on q(com). Utilizing this knowledge, our data-filtering scheme allows the investigator to decide on the filtering stringency according to desired data variability, and our normalization procedure corrects the q(com)-dependent dye biases in terms of both the location and the spread of the ratio distribution. In addition, we propose a statistical model for false positive rate determination based on the design and the quality of a microarray experiment. The model predicts that a lower limit of 0.5 for the replicate concordance rate is needed in order to be certain of true positives. Our work demonstrates the importance and advantages of having a quantitative quality control scheme for microarrays.

Algorithms↗

A fast dose calculation method based on table lookup for IMRT optimization.

This note describes a fast dose calculation method that can be used to speed up the optimization process in intensity-modulated radiotherapy (IMRT). Most iterative optimization algorithms in IMRT require a large number of dose calculations to achieve convergence and therefore the total amount of time needed for the IMRT planning can be substantially reduced by using a faster dose calculation method. The method that is described in this note relies on an accurate dose calculation engine that is used to calculate an approximate dose kernel for each beam used in the treatment plan. Once the kernel is computed and saved, subsequent dose calculations can be done rapidly by looking up this kernel. Inaccuracies due to the approximate nature of the kernel in this method can be reduced by performing scheduled kernel updates. This fast dose calculation method can be performed more than two orders of magnitude faster than the typical superposition/convolution methods and therefore is suitable for applications in which speed is critical, e.g., in an IMRT optimization that requires a simulated annealing optimization algorithm or in a practical IMRT beam-angle optimization system.

Algorithms↗

Catalytic roles of arginine residues 82 and 92 of Escherichia coli 6-hydroxymethyl-7,8-dihydropterin pyrophosphokinase: site-directed mutagenesis and biochemical studies.

The roles of a pair of conserved positively charged residues R82 and R92 at a catalytic loop of Escherichia coli 6-hydroxymethyl-7,8-dihydropterin pyrophosphokinase (HPPK) have been investigated by site-directed mutagenesis and biochemical analysis. In the structure of HPPK in complex with ATP and a 6-hydroxymethyl-7,8-dihydropterin (HP) analogue, the guanidinium group of R82 forms two hydrogen bonds with the alpha-phosphate and that of R92 two hydrogen bonds with the beta-phosphate. In the structure of HPPK in complex with alpha,beta-methyleneadenosine triphosphate (AMPCPP, an ATP analogue) and HP, the guanidinium group of R82 has no direct interaction with AMPCPP and that of R92 forms two hydrogen bonds with the alpha-phosphate. Substitution of R82 with alanine caused a decrease in the rate constant for the chemical step by a factor of approximately 380, but there were no significant changes in the binding energy or binding kinetics of either substrate. Substitution of R92 with alanine caused a decrease in the rate constant for the chemical step by a factor of approximately 3.5 x 10(4). The mutation caused no significant changes in the binding energy or binding kinetics of MgATP. It did not cause a significant change in the binding energy of HP either but caused a decrease in the association rate constant for the binding of HP by a factor of approximately 4.5 and a decrease in the dissociation rate constant by a factor of approximately 10. The overall structures of the ternary complexes of both mutants were very similar to the corresponding structure of wild-type HPPK as described in the companion paper. The results suggest that R82 does not contribute to the binding of either substrate, and R92 is dispensable for the binding of MgATP but plays a role in facilitating the binding of HP. Both R82 and R92 are important for catalysis, and R92 plays a critical role in the transition state stabilization.

Amino Acid Substitution↗

Three color cDNA microarrays: quantitative assessment through the use of fluorescein-labeled probes.

Gene expression studies using microarrays have great potential to generate new insights into human disease pathogenesis, but data quality remains a major obstacle. In particular, there does not exist a method to determine prior to hybridization whether an array will yield high quality data, given good study design and target preparation. We have solved this problem through development of a three-color cDNA microarray platform where printed probes are fluorescein labeled, but are spectrally compatible with Cy3 and Cy5 dye-labeled targets when using confocal laser scanners possessing narrow bandwidths. This approach enables prehybridization evaluation of array/spot morphology, DNA deposition and retention and background levels. By using these measurements and the intra-slide coefficient of variation for fluorescence intensity we show that slides in the same batch are not equivalent and measurable prehybridization parameters can be predictive of hybridization performance as determined by replicate consistency. When hybridizing target derived from two cell lines to high and low quality replicate pairs (n = 50 pairs), a direct and significant relationship between prehybridization signal-to-background noise and post-hybridization reproducibility (R2 = 0.80, P < 0.001) was observed. We therefore conclude that slide selection based upon prehybridization quality scores will greatly benefit the ability to generate reliable gene expression data.

Carbocyanines↗

Nitrile biotransformations for the synthesis of enantiomerically enriched Baylis-Hillman adducts.

Catalysed by the nitrile hydratase/amidase-containing Rhodococcus sp. AJ270 cells, a number of beta-aryl- and beta-alkyl- beta-hydroxy-alpha-methylenepropiononitriles (the Baylis-Hillman nitriles) 1 underwent hydrolysis under mild conditions to produce the corresponding enantiomerically enriched Baylis-Hillman amides 2 and acids 3. The enantioselectivity of the biotransformations was strongly determined by the steric effect of the substituents at the beta-position of the substrates. The protection of the free hydroxy of beta-phenyl-beta-hydroxy-alpha-methylenepropiononitrile 1a by methylation led to the enhancement of enantiocontrol of the biohydrolysis.

Amides↗

Intensity-modulated radiotherapy optimization with gEUD-guided dose-volume objectives.

Currently, most intensity-modulated radiation therapy systems use dose-volume (DV)-based objectives. Although acceptable plans can be generated using these objectives, much trial and error is necessary to plan complex cases with many structures because numerous parameters need to be adjusted. An objective function that makes use of a generalized equivalent uniform dose (gEUD) was developed recently that has the advantage of involving simple formulae and fewer parameters. In addition, not only does the gEUD-based optimization provide the same coverage of the target, it provides significantly better protection of critical structures. However, gEUD-based optimization may not be superior once dose distributions and dose-volume histograms (DVHs) are used to evaluate the plan. Moreover, it is difficult to fine-tune the DVH with gEUD-based optimization. In this paper, we propose a method for combining the gEUD-based and DV-based optimization approaches to overcome these limitations. In this method, the gEUD optimization is performed initially to search for a solution that meets or exceeds most of the treatment objectives. Depending on the requirements, DV-based optimization with a gradient technique is then used to fine-tune the DVHs. The DV constraints are specified according to the gEUD plan, and the initial intensities are obtained from the gEUD plan as well. We demonstrated this technique in two clinical cases: aprostate cancer and ahead and neck cancer case. Compared with the DV-optimized plan, the gEUD plan provided better protection of critical structures and the target coverage was similar. However, homogeneities were slightly poorer. The gEUD plan was then fine-tuned with DV constraints, and the resulting plan was superior to the other plans in terms of the dose distributions. The planning time was significantly reduced as well. This technique is an effective means of optimizing individualized treatment plans.

Adenocarcinoma↗

Resolution of clonal origins for endometriotic lesions using laser capture microdissection and the human androgen receptor (HUMARA) assay.

OBJECTIVE: To determine the clonal origins of endometriotic lesions using laser capture microdissection and PCR-based HUMARA assay. DESIGN: Molecular genetic study of human tissue. SETTING: Molecular genetics laboratory in an academic setting. PATIENT(S): Twenty patients with endometriosis. Forty specimens of endometriotic lesions from these patients and one specimen of normal endometrium were analyzed. INTERVENTION(S): Laser capture microdissection was used to harvest epithelial cells from single and multifocal endometrial lesions from paraffin-embedded and frozen tissues, and their clonality was determined with the HUMARA assay. MAIN OUTCOME MEASURE(S): Polymerase chain reaction-based HUMARA assay of clonality. RESULT(S): Thirty-eight specimens were polymorphic and thus informative. Most specimens were monoclonal, as determined by the HUMARA assay. In four specimens of multifocal lesions, polyclonality was detected, but upon more refined microdissections and further analyses, we found that each focus was monoclonal individually. CONCLUSION(S): Previously reported polyclonality is very likely to be attributed to the pooling of multifocal lesions or contamination of normal tissues. These results suggest that endometriotic lesions were monoclonal in origin, and in the case of multifocal lesions, each focus originates monoclonally; hence, different foci have independent origins. The monoclonality of endometriotic lesions suggests that they may carry neoplastic potentials, and the apparent independent origins of multifocal lesions suggest that reconstruction of individual lesion histories may help us to understand the initiation and progression of endometriosis.

Adult↗

Direct delivery of bacterial avirulence proteins into resistant Arabidopsis protoplasts leads to hypersensitive cell death.

Many bacterial avirulence (Avr) proteins, including the Pseudomonas syringae proteins, AvrRpt2 and AvrB, appear to be recognized inside the host plant cell by resistance mechanisms mediated by the cognate resistance (R) genes. It is thought that Avr proteins are either delivered directly into the host cell via the bacterial type III secretion system (TTSS) or taken up by the plant cell following secretion into the apoplast through the TTSS. Recently, it was shown that the Xanthomonas campestris AvrBs2 protein can be delivered directly into the host plant cell by the TTSS. However, it is not known whether other type III effectors of phytopathogens behave similarly. Here, using a novel protein transfection method, we demonstrate that AvrRpt2 and AvrB must enter the plant cell to be recognized by R gene-mediated mechanisms. First, we established a hypersensitive cell death assay for protoplasts using the membrane-impermeable, nuclear-staining dye, YO-PRO-1, and transgenic Arabidopsis plants that carry an inducible avrRpt2 gene. Second, we transfected E. coli-produced AvrRpt2 or AvrB proteins into Arabidopsis protoplasts using a protein transfection kit based on the carrier peptide Pep-1, and demonstrated that hypersensitive cell death occurs in a gene-for-gene-specific manner. In contrast, these Avr proteins failed to elicit hypersensitive cell death when they were applied to protoplasts without the carrier peptide. We conclude that our preparations of E. coli-produced AvrRpt2 and AvrB are active, that AvrRpt2 and AvrB must be delivered into the plant cell to be recognized, and that a method based on a carrier peptide can be used to introduce proteins into plant cells.

Arabidopsis↗

The abi1-1 mutation blocks ABA signaling downstream of cADPR action.

Arabidopsis thaliana abscisic acid insensitive 1-1 (abi1-1) is a dominant mutant that is insensitive to the inhibition of germination and growth by the plant hormone, abscisic acid (ABA). The mutation severely decreases the catalytic activity of the ABI1 type 2C protein phosphatase (PP2C). However, the site of action of the abi1-1/ABI1 in the ABA signal transduction pathway has not yet been determined. Using single cell assays, we showed that microinjecting mutant abi1-1 protein inhibited the activation of RD29A-GUS and KIN2-GUS in response to ABA, cyclic ADP-ribose (cADPR), and Ca2+. The inhibitory effect of the mutant protein, however, was reversed by co-microinjection of an excess amount of the ABI1 protein. In transgenic Arabidopsis plants, overexpression of abi1-1 rendered the plants insensitive to ABA during germination, whereas overexpression of ABI1 did not have any apparent effect. Moreover, transgenic plants overexpressing abi1-1 were blocked in the induction of ABA-responsive genes; however, overexpression of ABI1 did not affect gene expression. Taken together, our results demonstrate that abi1-1 is likely to be a dominant negative mutation and ABI1 likely acts downstream of cADPR in the ABA-signaling pathway. Our results on ABI1 overexpression in Arabidopsis are not compatible with a negative regulatory role of this phosphatase in ABA responses.

Abscisic Acid↗

[Serum level and expression of vascular epithelial growth factor in ovarian epithelial carcinoma].

BACKGROUND & OBJECTIVE: This study was designed to examine the level of serum vascular epithelial growth factor (VEGF) and VEGF expression in the patients with ovarian epithelial carcinoma (EOC) and to evaluate the relationship between VEGF and the clinicopathological factors. METHODS: Seventy-three patients with ovarian epithelial tumor were selected as study group, including 24 benign epithelial ovarian tumor (BET), 7 borderline epithelial ovarian tumor (BOT), 42 EOC. Twenty women without obvious gynecologic diseases were selected as serum control group (CON). VEGF expression in the epithelial ovarian tumor tissues from 73 patients were analyzed immunohistochemically. Serum VEGF in 71 patients and ascite VEGF in 10 patients were detected by enzyme-linked immunosorbent assay (ELISA) and 7 cases with EOC were continuously determined after operation. RESULTS: (1) Positive immunostaining of VEGF was observed in 86.3% of EOC, which was significantly higher than that of BOT (66.67%, P < 0.005) and BET (37.5%, P < 0.005). (2) There were significant differences in serum VEGF level among BET, BOT, and EOC group (P < 0.01). Serum VEGF levels before operation in patients with EOC were significantly higher than those with BOT, BET, and CON (P < 0.01). Serum VEGF levels in EOC patients at advanced stage (stage III or IV), low differentiation (G3) were apparently higher than those at early stage (stage I or II) (P < 0.05) and high differentiation (G1, G2) (P < 0.01), respectively. Serum VEGF levels decreased after the successful removal of tumor in ovarian cancer patients. The serum VEGF levels were re-elevated during relapse in three patients. CONCLUSION: (1) The elevated serum VEGF levels and increased VEGF expression in EOC were associated with its maligment behavior. (2) Serum VEGF could be used as a marker for monitoring the clinical course of the patients with epithelial ovarian carcinoma.

Adult↗