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Biomedical subjects

Q Yu

Publications and source records attributed to Q Yu.

At least 91 records · Page 5Linked to original sources
PubMed2001

[The fluorescent properites of the complexes of 1,3-diphenyl-4-acyl-5-pyrazolones with Eu(III)].

The binary and ternary Eu(III) complexes have been prepared with four 1,3-diphenyl-4-acyl-5-pyazolones as ligands (where the four acyls are benzoyl, phenylacetyl, butyryl and choroacetyl, and the compounds are represented by DPBZP, DPPAP, DPBTP, DPCAP respectively). The composition of the complexes was determined by chemical and elementary analysis, and the structure of the complexes was characterized by FTIR spectra. The fluorescence spectra of the complexes were measured. It is indicated that the complexes emit with the characteristic fluorescence of Eu(III), the fluorescence intensity of the complexes are closely related to the substituents at the acyl at 4-position in pyrazolone ring of the ligands, depending on the ligands, the descending order of the fluorescence intensity is DPBZP > DPPAP > DPBTP > DPCAP, and that the second ligand, 1, 10-phenanthroline, remarkably intensifies the fluorescence of the complexes.

English Abstract↗
PubMed2001

[Fluorescence spectra of the rare earth complex-PAA-g-PE films].

The acrylic acid (AA) was grafted onto the PE film surface through UV photograft polymerization. With certain pH value, the grafted films were made to react with the alcohol-water solution of Eu3+ and alpha-thenoyltrifluoroacetone (TTA) or with the chloroform-water solution of Tb3+ and acetyl actone (AcAc), thus causing the preparation of the red or green fluorescent films. As compared with the corresponding Eu(TTA)3.(H2O)2 or Tb(AcAc)3.(H2O)2 solid complexes, both the excitation and emission spectra of the fluorescent films changed remarkably. It's predictable that chemical bond combination has occurred between the rare earth complexes and the macromolecular material. In addition, the IR spectra of the fluorescent films were also observed.

Acrylates↗
PubMed2001

[MRI artifacts caused by keepers in a dental arch].

OBJECTIVE: This research was designed to observe the degree of artifacts caused by 1-4 keepers. METHODS: Samples were imaged in a living human subject by 0.15 Tesla MR devices in sagital plane. Results were analyzed and the maximal diameters of artifacts were measured. RESULTS: The maximal diameters of the artifacts caused by 1-4 keepers were 101-109.6mm. CONCLUSION: Even with four keepers in the dental arch, the degree of artifact is still limited.

English Abstract↗
PubMed2001

[The predictive value of plasma fibronectin concentration on fetal growth retardation and preeclampsia at earlier stage of the third trimester].

OBJECTIVE: To evaluate the predictive value of maternal plasma fibronectin concentration at 24-34 weeks on fetal growth retardation (FGR) and preeclampsia. METHODS: The maternal plasma fibronectin concentrations were measured by rate nephelometric procedure in the 130 initial normal nulliparous pregnant woman at 24-34 gestational weeks. The outcomes of pregnancies were followed. The predictive values of FN predicting on 3 kinds of outcome of pregnancy with FGR, preeclampsia, or FGR complicated preeclampsia were compared. RESULTS: (1) In a cohort of 130 initially normal nulliparous pregnant women, 10 cases of FGR, 10 cases of preeclampsia, and 4 cases of FGR complicated with preeclampsia were developed, and 106 cases with no complication. The maternal age, gravidity, sampling gestational ages, delivering gestational ages were not significantly different among the 4 groups (P > 0.05). (2) The plasma fibronectin levels in women with FGR, preeclampsia or FGR complicated preeclampsia [(486.45 +/- 122.69) mg/L, (428.38 +/- 118.71) mg/L and (443.66 +/- 68.13) mg/L, respectively] were significantly higher than that in the control [(284.41 +/- 93.83) mg/ L, P < 0.01]. (3) The areas under ROC of predicting on three outcomes of FGR, preeclampsia, or FGR complicated preeclampsia were 0.893, 0.818 and 0.867 respectively. (4) At the best cut point, the sensitivity, specificity, positive predictive value, negative predictive value and Kappa index of FN level predicting on the outcomes of pregnancy with three groups were 57.14%, 95.69%, 61.54%, 94.87%, 0.545 5 (on FGR); 91.27%, 50.00%, 15.38%, 98.29%, 0.1975 (on preeclampsia) and 42.86%, 91.38%, 37.50%, 92.98%, 0.3221 (on FGR complicated with preeclampsia), respectively. CONCLUSION: The maternal plasma fibronectin may be used as an earlier predictor for screening of FGR and the predictive value of FN on FGR is better than on preeclampsia.

Area Under Curve↗
PubMed2001

[The endocrine activity and clinical characteristics of benign ovarian fibro-epithelial tumors].

OBJECTIVE: To investigate the endocrine activity and clinical characteristics of benign ovarian fibro-epithelial tumors. METHODS: A retrospective analysis was done on 16 cases of benign fibro-epithelial tumor collected from the department of obstetrics and gynecology, Peking Union Medical College Hospital from 1981 to 2000. RESULTS: The examinations of endocrine activity was measured in 15 cases. Serum estradiol and follicle-stimulating hormone levels in 4 cases, it was (166.5 +/- 83.0) pmol/L and (39.4 +/- 12.6) IU/L respectively; low to moderate level of estrogen influence was observed in 8 cases by vaginal cytology; endometrium proliferation was observed in 10/15 cases by pathological examination. CLINICAL MANIFESTATIONS: post-menopausal vaginal bleeding in 10 cases, lower abdominal recessive pain in 3 cases, pelvic mass in all of the 16 cases with both pelvic examination and ultrasonography. CONCLUSION: Most of the benign fibro-epithelial tumor have endocrine activity and related clinical manifestations.

Abdominal Pain↗
PubMed2000

Microfluidic tectonics: a comprehensive construction platform for microfluidic systems.

A microfluidic platform for the construction of microscale components and autonomous systems is presented. The platform combines liquid-phase photopolymerization, lithography, and laminar flow to allow the creation of complex and autonomous microfluidic systems. The fabrication of channels, actuators, valves, sensors, and systems is demonstrated. Construction times can be as short as 10 min, providing ultrarapid prototyping of microfluidic systems.

Journal Article↗
PubMed2000

Essential regions of the tRNA primer required for HIV-1 infectivity.

Human immunodeficiency virus (HIV), like all retroviruses, requires a cellular tRNA as a primer for initiation of reverse transcription. In a previous study, we demonstrated that an HIV-1 with a primer binding site complementary to yeast tRNA(Phe) (psHIV-Phe) was not infectious unless yeast tRNA(Phe) was supplied in trans. This unique in vivo complementation system has now been used to define the elements of the tRNA required for HIV-1 replication. Mutant tRNA(Phe) with deletions in TPsiC stem-loop, anticodon stem-loop or D stem-loop of the tRNA were generated and assessed for the capacity to rescue psHIV-Phe. Mutant tRNA(Phe) with disrupted TPsiC stem-loop did not rescue psHIV-Phe. In contrast, a mutant tRNA(Phe) without the D stem-loop was fully functional for the rescue. The tRNA anticodon stem-loop region was found to be important for efficient complementation. The results of our studies demonstrate for the first time the importance of specific structural and sequence elements of the tRNA primer for HIV-1 reverse transcription and define new targets for interruption of HIV-1 replication.

Base Sequence↗
PubMed2000

Stabilization of neoclassical tearing modes by an externally applied static helical field.

The effect of a static helical magnetic field on the nonlinear growth of the neoclassical tearing mode (NTM) is investigated. The NTM is found to be stabilized by an externally applied helical field of a different helicity if the field magnitude is sufficiently large, suggesting a very simple method for stabilizing the NTM. The mechanism responsible for this stabilization is the decreased fundamental harmonic pressure perturbation of the NTM in the presence of the helical field.

Journal Article↗
PubMed2000

Hypoxia augments conversion of big-endothelin-1 and endothelin ET(B) receptor-mediated actions in rat lungs.

We have examined the effect of endothelin-1, sarafotoxin-6C, big-endothelin-1 and other agents on perfused lungs from chronically hypoxic rats. Increases in pulmonary perfusion pressure induced by big-endothelin-1, endothelin-1, phenylephrine and potassium chloride were enhanced in hypoxic lungs, while the constrictor action of sarafotoxin-6C was not increased. When basal pulmonary perfusion pressure was raised, low doses of endothelin-1 and sarafotoxin-6C produced decreases in pulmonary perfusion pressure which were significantly greater in chronically hypoxic lungs, whereas responses to sodium nitroprusside were unchanged. Endothelin ET(B) receptor-mediated bronchoconstrictor responses were also potentiated in hypoxic lungs, whereas responses to carbachol were not. In hypoxic lungs, conversion of big-endothelin-1 to endothelin-1 was significantly increased. These data provide evidence for a generalised increase in vasomotor activity in chronically hypoxic lungs, and a more selective increase in endothelin ET(B) receptor-mediated vasodilator and bronchoconstrictor responses. Hypoxia also augments the conversion of big-endothelin-1 to endothelin-1.

Animals↗
PubMed2000

Complete suppression of neoclassical tearing modes with current drive at the electron-cyclotron-resonance frequency in ASDEX upgrade tokamak

Noninductive current drive has been performed in the tokamak ASDEX upgrade by injection of radiofrequency waves at the second harmonic of the electron-cyclotron frequency in order to suppress unwanted disturbances of the magnetic-field configuration. The current has been driven parallel [co-electron cyclotron current drive (ECCD)] and antiparallel (counter-ECCD) to the plasma current to compare the effect of heating with direct current drive in the magnetic island. For the first time it has been shown experimentally that total stabilization of neoclassical tearing modes is possible with co-ECCD. The experiments verify the role of direct current drive as opposed to local heating.

Journal Article↗
PubMed2000

Phase-contrast X-ray imaging with a large monolithic X-ray interferometer.

To increase the field of view for large objects in phase-contrast X-ray imaging, a large monolithic X-ray interferometer has been fabricated using an available silicon ingot of diameter 10 cm. A performance study of this interferometer has been carried out using a synchrotron X-ray source. The view size of the interference pattern obtained with this interferometer was 25 mm wide and 15 mm high and its visibility was 79%. Various structures of a sliced human hepatocellular carcinoma were identified as necrosis, hemorrhagic necrosis, normal liver tissue and blood vessel. The performance of this interferometer was sufficient for phase-contrast X-ray imaging.

Journal Article↗
PubMed2000

Specific inhibition of FGF-induced MAPK activation by the receptor-like protein tyrosine phosphatase LAR.

LAR is a widely expressed receptor-like protein tyrosine phosphatase that is implicated in regulation of intracellular signaling triggered by both cell adhesion and peptide growth factors. Genetic studies revealed that LAR regulates neuron axon path finding in Drosophila and mammary gland epithelial cell differentiation in mice. The molecular mechanism underlying the tissue specific function of LAR has not been clearly understood. We investigated the role and mechanism of LAR in peptide growth factors EGF and FGF signaling in human tissue culture cells in which the expression of LAR is under the control of an inducible promoter. We found that although both EGF and FGF induce activation of mitogen-activated protein kinase (MAPK), LAR only inhibits FGF-induced MAPK activation. LAR does not interact directly with the peptide growth factor receptors, since the ligand-induced autophosphorylation of growth factor receptors was not affected by induction of LAR. The specific effect of LAR on FGF-induced MAPK activation appeared to be mediated by specific inhibition of the phosphorylation of two signal transducers that act downstream of the FGF receptor, FRS2 and a 180 kDa protein, and by prevention of their interaction with the adaptor protein GRB2. In contrast, LAR selectively inhibited the epidermal growth factor (EGF)-induced phosphorylation of p130CAS and the formation of the complex between p130CAS and GRB2 but this effect did not influence the activation of MAPK by EGF. These data suggest that LAR and similar receptor-like protein tyrosine phosphatases may contribute to the regulation of transmembrane signaling by selectively inhibiting the tyrosine phosphorylation of specific signal transducers that act downstream of the plasma membrane-associated tyrosine kinases. The consequent inhibition of the formation of signaling complexes by these proteins may contribute to the specificity of the signals generated by specific peptide growth factors as well as extracellular matrix proteins.

Adaptor Proteins, Signal Transducing↗
PubMed2000

Functional hydrogel structures for autonomous flow control inside microfluidic channels

Hydrogels have been developed to respond to a wide variety of stimuli, but their use in macroscopic systems has been hindered by slow response times (diffusion being the rate-limiting factor governing the swelling process). However, there are many natural examples of chemically driven actuation that rely on short diffusion paths to produce a rapid response. It is therefore expected that scaling down hydrogel objects to the micrometre scale should greatly improve response times. At these scales, stimuli-responsive hydrogels could enhance the capabilities of microfluidic systems by allowing self-regulated flow control. Here we report the fabrication of active hydrogel components inside microchannels via direct photopatterning of a liquid phase. Our approach greatly simplifies system construction and assembly as the functional components are fabricated in situ, and the stimuli-responsive hydrogel components perform both sensing and actuation functions. We demonstrate significantly improved response times (less than 10 seconds) in hydrogel valves capable of autonomous control of local flow.

Journal Article↗
PubMed2000

Fast (3 Hz and 10 Hz) and slow (respiratory) rhythms in cervical sympathetic nerve and unit discharges of the cat.

1. In seven decerebrate cats, recordings were taken from the preganglionic cervical sympathetic (CSy) nerves and from 74 individual CSy fibres. Correlation and spectral analyses showed that nerve and fibre discharges had several types of rhythm that were coherent (correlated) between population and unit activity: respiratory, '3 Hz' (2-6 Hz, usually cardiac related), and '10 Hz' (7-13 Hz). 2. Almost all units (73/74) had respiratory modulation of their discharge, either phasic (firing during only one phase) or tonic (firing during both the inspiratory (I) and expiratory (E) phases). The most common pattern consisted of tonic I-modulated firing. When the vagi were intact, lung afferent input during I greatly reduced CSy unit and nerve discharge, as evaluated by the no-inflation test. 3. The incidence of unit-nerve coherent fast rhythms (3 Hz or 10 Hz ranges) depended on unit discharge pattern: they were present in an appreciable fraction (30/58 or 52 %) of tonic units, but in only a small fraction (2/15 or 13 %) of phasic units. 4. When baroreceptor innervation (aortic depressor amd carotid sinus nerves) was intact, rhythms correlated to the cardiac cycle frequency were found in 20/34 (59 %) of units. The cardiac origin of these rhythms was confirmed by residual autospectral and partial coherence analysis and by their absence after baroreceptor denervation. 4. The 10 Hz coherent rhythm was found in 7/34 units when baroreceptor innervation was intact, where it co-existed with the cardiac-locked rhythm; after barodenervation it was found in 9/50 neurones. Where both rhythms were present, the 10 Hz component was sometimes synchronized in a 3:1 ratio to the 3 Hz (cardiac-related) frequency component. 5. The tonic and phasic CSy units seem to form distinct populations, as indicated by the differential responses to cardiac-related afferent inputs when baroreceptor innervation is intact. The high incidence of cardiac-related correlation found among tonic units suggests that they are involved in vasomotor regulation. The high incidence of respiratory modulation of discharge suggests that the CSy units may be involved in regulation of the nasal vasculature and consequent ventilation-related control of nasal airway resistance.

Action Potentials↗
PubMed2000

A truncated cytoplasmic topoisomerase IIalpha in a drug-resistant lung cancer cell line is encoded by a TOP2A allele with a partial deletion of exon 34.

To study the problem of acquired resistance to widely used anti-cancer drugs that target the 170 kDa topoisomerase IIalpha (topo IIalpha), a drug-resistant human small-cell lung cancer cell line, H209/VP, was selected in VP-16. H209/VP cells express reduced levels of the 170 kDa topo IIalpha that is localized normally in the nucleus and also express lower levels of a 160 kDa topo IIalpha-related protein that is located predominantly in the cytoplasm. Band depletion immunoblotting experiments suggest that the H209/VP nuclear 170 kDa topo IIalpha is able to form ternary complexes with DNA and VP-16 in intact cells, but the ability of the cytoplasmic 160 kDa protein to do so is greatly diminished. Sequence analysis of the 3; end of the H209/VP mutant topo IIalpha mRNA and the TOP2A gene indicates that the mRNA is missing 200 nt that corresponds to exon 34 because the partial loss of the minimal 3; splice-acceptor sequence at the beginning of exon 34 results in splicing of exon 33 to exon 35. The protein predicted to be encoded by this mutant mRNA does not contain the COOH-terminal 109 amino acids of the wild-type enzyme that we have demonstrated contain a strongly functional nuclear localization signal sequence. Consequently, our data explain both the size and the cytoplasmic localization of the H209/VP mutant topo IIalpha. The mutant TOP2A allele in H209/VP cells differs from those in previously characterized cell lines with cytoplasmic topo IIalpha and extends the number of types of resistance-associated deletions in this region to 4. These findings indicate that this region of the TOP2A gene may be a hot spot for mutations.

3' Untranslated Regions↗
PubMed2000

Engineered salt-insensitive alpha-defensins with end-to-end circularized structures.

We designed a retro-isomer and seven circularized "beta-tile" peptide analogs of a typical rabbit alpha-defensin, NP-1. The analogs retained defensin-like architecture after the characteristic end-to-end, Cys(3,31) (C I:C VI), alpha-defensin disulfide bond was replaced by a backbone peptide bond. The retro-isomer of NP-1 was as active as the parent compound, suggesting that overall topology and amphipathicity governed its antimicrobial activity. A beta-tile design with or without a single cross-bracing disulfide bond sufficed for antimicrobial activity, and some of the analogs retained activity against Escherichia coli and Salmonella typhimurium in NaCl concentrations that rendered NP-1 inactive. The new molecules had clustered positive charges resembling those in protegrins and tachyplesins, but were less cytotoxic. Such simplified alpha-defensin analogs minimize problems encountered during the oxidative folding of three-disulfide defensins. In addition, they are readily accessible to a novel thia zip cyclization procedure applicable to large unprotected peptide precursors of 31 amino acids in aqueous solutions. Collectively, these findings provide new and improved methodology to create salt-insensitive defensin-like peptides for application against bacterial diseases.

Amino Acid Sequence↗