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Biomedical subjects

C Wu

Publications and source records attributed to C Wu.

At least 199 records · Page 11Linked to original sources
PubMed2000

Topoisomerase I associates specifically with simian virus 40 large-T-antigen double hexamer-origin complexes.

Topoisomerase I (topo I) is required for releasing torsional stress during simian virus 40 (SV40) DNA replication. Recently, it has been demonstrated that topo I participates in initiation of replication as well as in elongation. Although T antigen and topo I can bind to one another in vitro, there is no direct evidence that topo I is a component of the replication initiation complex. We demonstrate in this report that topo I associates with T-antigen double hexamers bound to SV40 origin DNA (T(DH)) but not to single hexamers. This association has the same nucleotide and DNA requirements as those for the formation of double hexamers on DNA. Interestingly, topo I prefers to bind to fully formed T(DH) complexes over other oligomerized forms of T antigen associated with the origin. High ratios of topo I to origin DNA destabilize T(DH). The partial unwinding of a small-circular-DNA substrate is dependent on the presence of both T antigen and topo I but is inhibited at high topo I concentrations. Competition experiments with a topo I-binding fragment of T antigen indicate that an interaction between T antigen and topo I occurs during the unwinding reaction. We propose that topo I is recruited to the initiation complex after the assembly of T(DH) and before unwinding to facilitate DNA replication.

Animals↗
PubMed2000

RGS proteins inhibit Xwnt-8 signaling in Xenopus embryonic development.

RGS family members are GTPase activating proteins (GAPs) that antagonize signaling by heterotrimeric G proteins. Injection of Xenopus embryos with RNA encoding rat RGS4 (rRGS4), a GAP for G(i) and G(q), resulted in shortened trunks and decreased skeletal muscle. This phenotype is nearly identical to the effect of injection of either frzb or dominant negative Xwnt-8. Injection of human RGS2, which selectively deactivates G(q), had similar effects. rRGS4 inhibited the ability of early Xwnt-8 but not Xdsh misexpression to cause axis duplication. This effect is distinct from axin family members that contain RGS-like domains but act downstream of Xdsh. We identified two Xenopus RGS4 homologs, one of which, Xrgs4a, was expressed as a Spemann organizer component. Injection of Xenopus embryos with Xrgs4a also resulted in shortened trunks and decreased skeletal muscle. These results suggest that RGS proteins modulate Xwnt-8 signaling by attenuating the function of a G protein.

Adaptor Proteins, Signal Transducing↗
PubMed2000

XCS-1, a maternally expressed gene product involved in regulating mitosis in Xenopus.

The regulation of the cell cycle during early development is an important and complex biological process. We have cloned a cDNA, XCS-1, that may play an important role in regulating mitosis during early embryogenesis in Xenopus laevis. XCS-1 is a maternally expressed gene product that is the Xenopus homologue of the human cleavage signal protein (CS-1). XCS-1 transcripts were detected in oocytes with the titer decreasing just prior to the MBT. During development the XCS-1 protein was detected on the membrane and in the nucleus of blastomeres. It was also detected on the mitotic spindle in mitotic cells and on the centrosomes in interphase cells. Overexpression of myc-XCS-1 in Xenopus embryos resulted in abnormal mitoses with increased numbers of centrosomes, multipolar spindles, and abnormal distribution of chromosomes. Also, we observed incomplete cytokinesis resulting in multiple nuclei residing in the same cytoplasm with the daughter nuclei in different phases of the cell cycle. The phenotype depended on the presence of the N terminus of XCS-1 (aa 1-73) and a consensus NIMA kinase phosphorylation site (aa159-167). Mutations in this site affected the ability of the overexpressed XCS-1 protein to produce the phenotype. These results suggest that XCS-1 is a maternal factor playing an important role in the regulation of the cell cycle during early embryogenesis and that its function depends on its state of phosphorylation.

Age Factors↗
PubMed2000

Exposure assessment of trichloroethylene.

This article reviews exposure information available for trichloroethylene (TCE) and assesses the magnitude of human exposure. The primary sources releasing TCE into the environment are metal cleaning and degreasing operations. Releases occur into all media but mostly into the air due to its volatility. It is also moderately soluble in water and can leach from soils into groundwater. TCE has commonly been found in ambient air, surface water, and groundwaters. The 1998 air levels in microg/m(3) across 115 monitors can be summarized as follows: range = 0.01-3.9, mean = 0.88. A California survey of large water utilities in 1984 found a median concentration of 3.0 microg/L. General population exposure to TCE occurs primarily by inhalation and water ingestion. Typical average daily intakes have been estimated as 11-33 microg/day for inhalation and 2-20 microg/day for ingestion. A small portion of the population is expected to have elevated exposures as a result of one or more of these pathways: inhalation exposures to workers involved in degreasing operations, ingestion and inhalation exposures occurring in homes with private wells located near disposal/contamination sites, and inhalation exposures to consumers using TCE products in areas of poor ventilation. More current and more extensive data on TCE levels in indoor air, water, and soil are needed to better characterize the distribution of background exposures in the general population and elevated exposures in special subpopulations.

Body Burden↗
PubMed2000

Dopamine transporter transmembrane domain polar mutants: DeltaG and DeltaDeltaG values implicate regions important for transporter functions.

Polar residues in dopamine transporter (DAT) transmembrane domains (TMs) are likely to act individually and even interactively in recognizing cocaine and dopamine. We initially evaluated the effects of alanine substitution mutants that remove the polar side chains from residues in each of the 12 putative DAT TMs on the recognition of dopamine and the cocaine analog CFT. Eleven combination mutants with multiple substitutions in DAT TMs 4, 5, 7, or 11 were then selected as candidates for more detailed evaluation based on mutation effects on dopamine and cocaine analog affinities. An evaluation of Gibbs free energy changes displayed by single and combined TM mutants (DeltaG(o) and DeltaDeltaG(o)(int)) reveals three categories of potential interactions among mutants: 1) independent, noncooperative interactions (five influenced CFT and two influenced dopamine affinities), 2) synergistic influences (two for CFT and four for dopamine), and 3) complementation of influences on CFT recognition (four mutants) or on dopamine affinity (five). Combined mutations in TMs 4 and 5 yield the largest DeltaDeltaG(o)(int) values for dopamine uptake. TMs 4 and 11 mutants provide the largest DeltaDeltaG(o)(int) for CFT binding. Interactions between residues lying in DAT TMs 4 and 5 support current DAT structural models that suggest the juxtaposition of these two TMs. These data also support contributions of TM 4 and 11 residues to a polar pocket important for cocaine recognition. These candidate interactive DAT polar domains provide larger target sites for compounds that could modulate specific DAT functions than those provided by single mutations alone.

Alanine↗
PubMed2000

Interleukin-12 induces gene expression in interleukin-2 stimulated human T lymphocytes.

IL-12 is a critical immunoregulatory cytokine that promotes cell-mediated immune responses by inducing the differentiation of Th1 cells. To better clarify the molecular basis of IL-12 action, we compared the gene expression in human T lymphocytes activated by IL-2 and IL-12. mRNAs from T lymphocytes activated by either IL-2 alone or IL-2 plus IL-12 were transcribed into cDNAs. A differential mRNA display was conducted. As a result, differential display of five cDNA fragments was obtained. Sequence analysis suggests that they had high homology with recorded genes as found by a computer search against GenBank. Two full genes of the five fragments were cloned, which activation-induced C-type lectin and glucose transporter-like protein. Interestingly, these proteins were expressed in the T cells stimulated by IL-2 and IL-12, but not in the T cells stimulated by IL-2 alone. These results suggest that C-type lectin and glucose transporter-like protein may play an important role in the T lymphocyte activation induced by IL-12.

Base Sequence↗
PubMed2000

[Skeletal dysplasia and osteoporosis due to inadequate athletic].

Athletic load is an important factor that has an influence on the growth, development and mature of skeleton. In patients who had the functional disorder of hip joint resulting from hip diseases during their teen-ages, skeletal dysplasia and osteoporosis would occur. The present paper reported 30 cases of unilateral hip disorder. The patients were 20 men and 10 women whose age ranged from 2 to 20 years. The course of disease lasted 2 to 49 years. Their primary diseases included suppurant hip arthritis (16 cases), tuberculous arthritis of hip (10 cases), and others (4 cases). The follow-up study revealed fixed hip joint in 18 cases, positive Thomas sign in 22 cases, limited motion of hip joint in 12 cases, and unequal length of lower extremities in 25 cases; at the same time X-ray films showed ankylosis of hip at normal position in 10 patients, dislocation with ankylosis of hip in 13 patients, arthritic disorder of hip in 7 patients, skeletal dysplacia of ischium and pubis in 18 patients, and skeletal dysplasia of femur in 22 patients. All patients had osteoporosis. A discussion about the basic mechanism for skeletal dysplasia and osteoporosis following inadequate athletic load is presented. We believe that the skeletal dysplasia and osteoporosis in our group were caused by the diseases that led to inadequate athletic load. Therefore it is important to provide a thorough treatment and help the patients to their strength to be loaded in time.

Adolescent↗
PubMed2000

[Neural network based on modified simplex method and its application in studying forest self-thinning].

The mechanism of forest self-thinning is generally nonlinear and dynamic, and the artificial neural network has the characteristic of expressing arbitrary nonlinear mapping. In this paper, the feasibility and limitation of artificial neural network used to simulating forest self-thinning was expounded, and the principle and algorithms of the neural network model based on modified simplex method (BP-MSM mixed algorithms) for modeling forest self-thinning were described. Its applications in self-thinning of Populus tremula natural forest Cunninghamia lanceolata plantation were illustrated. The results of forest self-thinning examples show the BP-MSM mixed algorithms were satisfactory in simulating forest self-thinning, and its precision was higher, which develops the method and theory of artificial neural network, and enriches the simulating method of forest self-thinning.

Algorithms↗
PubMed2000

[Quantitative characteristics of rare and endangered Castanopsis kawakamii population].

In this paper, a new self-adaptive model for population growth, i.e. S = exp(alpha ln2(1 + ce-rt) + beta ln(1 + ce-rt) + gamma) was established, which combined Logistic, Smith, Gompertz, Gui-Lawson, Zhang-Logistic and Liu-Logistic models. Estimations with genetic algorithm showed that the new model was more suitable than other models to simulate the actual growth trend of Castanopsis kawakamii population.

China↗
PubMed2000

[Energy distribution of Phyllostachys pubescens ecosytem in north Fujian].

Based on the data obtrained from 40 Phyllostachys pubescens plots in Jianou City of Fujian Province, the distribution of energy was studied in this paper. The results showed that the energy contained in stems, branches and leaves, and underground parts of P. pubescens ecosystem were 4.2322 x 10(8) kJ.hm-2, 0.9230 x 10(8) kJ.hm-2 and 1.7643 x 10(8) kJ.hm-2, accounting for 61.32%, 13.11% and 25.57% of the total energy respectively.

China↗
PubMed2000

[Life table analysis of Tsuga longibracteata population].

Tsuga longibracteata is a rare and endangered tree species in China. Based on the life table of population and the theory of survival analysis, the authors worked out the life table of Tsuga longibracteata population drew the curves of mortality density function, hazard rate function and survival, and analyzed the population dynamics. The results show that the population had two peaks of mortality, and the survival curve of the population trended to the type of Deevey II.

China↗
PubMed2000

[The clinical significance of true insulin and proinsulin levels in subjects with different glucose tolerance].

OBJECTIVE: To examine the levels of serum true insulin (TI) and proinsulin (PI) in individuals with different glucose tolerance and to assess its clinical significance. METHODS: The levels of true insulin and proinsulin during oral glucose tolerance test (OGTT) were determined with specific BA-ELISA in 135 normal glucose tolerance (NGT) and 86 impaired glucose tolerance (IGT) subjects as well as 101 type II diabetes mellitus (DM) patients. RESULTS: The fasting TI levels showed no significant difference (P > 0.05) among the groups of NGT, IGT and type II DM, but the immunoreactive insulin (IRI) concentration increased significantly in type II DM patients as compared with that in NGT (P < 0.01). Both of the fasting PI levels and the ratio of PI/(PI + TI) were significantly higher in type II DM patients as compared with those in NGT or IGT. The area under the curve of TI (AUC(TI)) was significantly higher (P < 0.05) in IGT than NGT and type II DM. Obese subjects had higher TI levels (P < 0.01) and lower insulin sensitivity (P < 0.05) than those in non-obese, while the ratio of PI/(PI + TI) and AUC(TI) was not significantly different statistically (P > 0.05) between the obese and non-obese subjects. CONCLUSION: Type II DM patients present hyperproinsulinemia rather than hyperinsulinemia and have higher ratio of PI/(PI + TI) as compared with NGT and IGT subjects. Higher TI level and significant insulin resistance were observed in obese subjects, but there is no difference of the PI/(PI + TI) ratio. The fasting PI level and PI/(PI + TI) ratio tend to be the indexes of beta-cell dysfunction.

Adult↗
PubMed2000

[The relationship among proinsulin and true insulin to coronary artery disease].

OBJECTIVE: Whether proinsulin (PI) and true insulin (TI) are independently related to coronary artery disease (CAD). METHODS: 54 patients with CAD diagnosed by coronary angiography and/or intravascular ultrasound, 37 patients without CAD by coronary angiography and/or intravascular ultrasound and 23 healthy volunteers. All subjects had oral glucose tolerance test after an overnight 14 h fast. PI and TI concentrations were detected at different phases by BA-ELISA in which PI cross -reactivity is less than 0.1%. RESULTS: Fasting and post-glucose loading PI and TI levels in both CAD and non-CAD groups significantly increased when compared with the control group (P < 0.05), after adjustment for age, body mass index and waist hip ratio, all statistically significant associations weakened or disappeared among three groups; but there was no significant difference of all the above variables between CAD group and non-CAD group (P > 0.05). CONCLUSION: PI and TI, whether fasting or post-glucose loading, may not be independently related to CAD.

Adult↗
PubMed2000

[The prevention of infection complicating acute necrotizing pancreatitis:an experimental study].

OBJECTIVE: To observe the effects of 5 intervention measures on infection complicating acute necrotizing pancreatitis (ANP) in dogs and rats. METHODS: A lethal model of ANP was reproduced by infusion of artificial bile into the biliopancreatic duct. Animals were divided randomly into: ANP group (no treatment); Chinese medicine group ("Qing Yi Tang"); Bifidobacterium mixture group; purgation group (MgSO(4)); selective decontamination of the digestive tract (SDD) group; and somatostatin group. The pancreas and intestine were observed morphologically and tight junction on ileum epithelia was assessed on cryofracture replicas. Blood and/or tissue levels of DAO and D-lactic acid and uric contents of lactulose/mannitol (L/M), served as indicators of gut barrier function, were measured at various time points. Intestinal flora and incidence of bacterial translocation (BT) to organs were examined. RESULTS: In early stage of ANP, mucosal and epithelial tight junction damage and flora disturbance occurred in the gut. In addition, the gut barrier function indicators deteriorated. The BT rates were as high as 78.6% (canine) and 59.5% (rat). Treatment with Chinese medicine markedly improved gut barrier function and reduced BT rate (32.1% - 37.0%). Having similar purgative response as Chinese medicine, MgSO4 did not show any beneficial effect on gut barrier protection and the incidence of BT was not reduced. In bifidobacterium mixture and SDD group, flora balance was preserved well and similar results as Chinese medicine were obtained. The BT rates of these two groups decreased to 33.9% and 33.3%, respectively. Somatostatin markedly blunted pancreatic tissue injury and ameliorated gut barrier damage during early phase of ANP. All intervention measures except for purgation also decreased mortalities (14.3% - 35.3%, compared with 58.8% of the no treatment group). CONCLUSIONS: Treatment with Chinese medicine, bifidobacterium mixture, SDD and somatostatin attenuated gut barrier damage and BT after ANP, and could be used to prevent secondary infection after ANP, but purgation alone is not effective.

Animals↗
PubMed2000

[Detection of trisomy 8 with interphase fluorescence in situ hybridization in myelodysplastic syndromes].

OBJECTIVE: To explore the value of interphase fluorescence in situ hybridization (FISH) in the detection of trisomy 8 in myelodysplastic syndromes (MDS). METHODS: Conventional cytogenetics (CC) and interphase FISH using SpectrumGreen labelled chromosome 8 centromere specific probe were simultaneously carried out to detect trisomy 8 in 69 MDS and 6 normal individuals. RESULTS: Two hundred interphase cells were counted and cells with three green hybridization spots > 3% was assigned. Eleven cases displayed trisomy 8 by CC and were confirmed in 10 by FISH. In 7 cases, the percentage of trisomy 8 cells was significantly lower by FISH than by CC. Seven cases displayed trisomy 8 by FISH in 58 cases who did not show trisomy 8 by CC. Of the 7 cases, two had 2 and 3 marker chromosomes respectively, 4 had normal karyotypes. CONCLUSIONS: Interphase FISH was a useful method for the detection of trisomy 8 in MDS, especially in patients with normal karyotype or marker chromosome. It was a important complement to CC.

Adult↗