Biomedical subjects

Q Xiang

Publications and source records attributed to Q Xiang.

At least 19 recordsLinked to original sources

PubMed2002

Use of a quantitative real-time reverse transcription-polymerase chain reaction method to study the induction of CYP1A, CYP2B and CYP4A forms in precision-cut rat liver slices.

1. The aim was to employ real-time quantitative reverse transcription-polymerase chain reaction (RT-PCR) technology (TaqMan to examine the induction of some selected cytochrome P450 (CYP) forms in precision-cut rat liver slices. 2. Taqman primers and probe sets were developed for rat CYP1A1, CYP1A2, CYP2B1 and CYP4A1 forms. 3. Rat liver slices were cultured in control medium or medium containing either 10 micro g ml(-1) Aroclor 1254 (ARO), 500 micro M sodium phenobarbitone (NaPB) or 50 micro M Wy-14643 (WY) for 3, 6 and 24 h. 4. Compared with control liver slices, treatment with ARO for 3 and 6 h produced 24- and 184-fold increases, respectively, in CYP1A1 mRNA levels, and after 24h produced an 85-fold increase in CYP1A2 mRNA levels. Levels of CYP1A1 and CYP1A2 mRNA were not markedly affected by NaPB and WY. 5. Treatment with ARO and PB for 24 h produced 10.6- and 23.8-fold increases, respectively, in CYP2B1 mRNA. Levels of CYP2B1 mRNA were not markedly affected by WY. 6. Treatment with WY, but not ARO and NaPB, for 24h produced a 20.4-fold increase in levels of CYP4A1 mRNA. 7. These results demonstrate that cultured liver slices may be used to evaluate the effect of xenobiotics on CYP form mRNA levels.

Animals↗

PubMed2001

A flexible light-directed DNA chip synthesis gated by deprotection using solution photogenerated acids.

Oligonucleotide microarrays or oDNA chips are effective decoding and analytical tools for genomic sequences and are useful for a broad range of applications. Therefore, it is desirable to have synthesis methods of DNA chips that are highly flexible in sequence design and provide high quality and general adoptability. We report herein, DNA microarray synthesis based on a flexible biochip method. Our method simply uses photogenerated acid (PGA) in solution to trigger deprotection of the 5'-OH group in conventional nucleotide phosphoramidite monomers (i.e. PGA-gated deprotection), with the rest of the reactions in the synthesis cycle the same as those used for routine synthesis of oligonucleotides. The complete DNA chip synthesis process is accomplished on a regular DNA synthesizer that is coupled with a UV-VIS projection display unit for performing digital photolithography. Using this method, oDNA chips containing probes of newly discovered genes can be quickly and easily synthesized at high yields in a conventional laboratory setting. Furthermore, the PGA-gated chemistry should be applicable to microarray syntheses of a variety of combinatorial molecules, such as peptides and organic molecules.

DNA↗

PubMed2001

Proteomic detection of changes in protein synthesis induced by NGX6 transfected in human nasopharyngeal carcinoma cells.

In the previous study, we cloned a new gene, named NGX6, related to nasopharyngeal carcinoma (NPC) at 9p. To study its function in the pathogenesis of NPC, we have investigated changes in protein synthesis between NPC cell line HNE1 and that transfected with the gene. Using high-resolution two-dimensional electrophoresis, we found that 22 protein spots showed variations that were significant and reproducible. Analysis of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and database searches identified seven proteins that were upregulated and seven proteins that were downregulated. These proteins included Fas, zinc-finger protein (ZNF), RAB, and Ah receptor-interacting protein (AIP). The functional implications of the identified proteins are discussed.

Down-Regulation↗

PubMed2001

Kinetic dissection of the multistep process in L1.ltrB intron mobility.

A kinetic characterization is presented for intron insertion into a target duplex DNA site during L1.ltrB intron mobility. This reaction is catalyzed by a ribonucleoprotein particle (RNP), consisting of a lariat form of group II intron RNA and the intron-encoded LtrA protein. In the first stage of intron mobility, the RNA component of the enzyme by itself inserts directly into the target ds DNA site, and thus, the RNP enzyme does not carry out turnover. Using single-turnover kinetics, we established an in vitro kinetic assay system and investigated mechanism of the intron RNA insertion process.

DNA↗

PubMed2001

Production of oxychemicals from precipitated hardwood lignin.

Lignin is a major byproduct in the biomass-to-ethanol process. The lignin produced from acid treatment of biomass has characteristics suitable for further conversion to organic chemicals. It is free of contaminants and has a relatively low molecular weight. In this study, catalytic oxidative conversion of the acid-soluble lignin precipitated from acid hydrolysates of hardwood was investigated. The process is based on aqueous alkaline oxidation of lignin with dissolved O2 in the presence of Fe3+ and Cu2+ catalysts at moderate reaction temperatures (160-180 degrees C). Aromatic aldehydes, ketones, and organic acids are found to be the primary products identifiable on extraction with ether. The combined weight yield of the total ether extractable products is about 20-25% of the initial lignin. The yield of the aldehydes (vanillin + syringaldehyde) is in the vicinity of 15% with an additional 3 to 4% of aromatic ketones. The yields of aldehydes plus ketones observed in this work far exceeded those obtainable from the conventional alkaline air oxidation of spent sulfite liquors. This article also provides comprehensive batch reaction data on conversion and product distribution.

Aldehydes↗

PubMed2000

Oxidative cracking of precipitated hardwood lignin by hydrogen peroxide.

Precipitated hard-wood lignin (PHL) is a major byproduct in the biomass-to-ethanol process. Oxidative cracking of PHL by hydrogen peroxide in aqueous medium was investigated as a means to produce potentially useful chemicals. The cracking reaction takes place at moderate temperatures (80-160 degrees C), giving mono- and dicarboxylic acids as the main products. The yields of these products are in the range of 30-50% of initial lignin. The reaction mechanism and the product distribution are dependent upon the reaction conditions, especially the pH. The reaction under strong alkaline condition proceeds well even at low reaction temperatures (80-90 degrees C). Under acidic conditions, higher temperatures (130-160 degrees C) are required to attain the same degrees of cracking. The reaction patterns of the oxidative cracking reaction involve the cleavage of lignin ring, aryl ether bond, or other linkages within lignin. By using the findings of this investigation and those of previous work, we have illustrated the reaction pathways for degradation of PHL under alkaline and acidic conditions. Aldehydes and aromatic acids are intermediate products in the oxidative degradation of lignin. However, they were produced only in trace amounts owing to rapid degradation induced by hydrogen peroxide.

Biomass↗

PubMed2000

Use of a novel real-time quantitative reverse transcription-polymerase chain reaction method to study the effects of cytokines on cytochrome P450 mRNA expression in mouse liver.

In this study, we developed a real-time quantitative reverse transcription-polymerase chain reaction (RT-PCR) method to study cytochrome P450 (CYP) mRNA regulation by cytokines in mouse liver. The method combines standard RT-PCR with a fluorogenic probe in which the intensity of fluorescence is proportional to the amount of target template present. We show that this method provides very rapid, sensitive, and reproducible quantification of mouse Cyp mRNA with a wide dynamic range of starting target molecule. We validated the method by using several prototypic CYP inducers. As expected, the mRNA levels of Cyp3a11, Cyp2b10, and Cyp1a2 were induced by a single dose of dexamethasone (100 mg/kg), phenobarbital (80 mg/kg), and 3-methylcholanthrene (80 mg/kg), respectively. The method of real-time RT-PCR was then used to evaluate the effects of interleukin (IL)-6 (100 ng/mouse), IL-1beta (500 ng/mouse), and tumor necrosis factor (TNF)-alpha (2 microgram/mouse) on Cyp mRNA expression in the mouse. Constitutive Cyp2b10 mRNA was reduced to 40% by IL-6 and 15% by IL-1beta, whereas Cyp2d9 mRNA was reduced to 70% by TNF-alpha administration. The level of Cyp1a2 mRNA was suppressed to 67% by IL-6 and 59% by TNF-alpha. Cyp3a11 and Cyp2e1 mRNAs were not affected by any of the cytokines that were studied. We conclude that the real-time RT-PCR method is a powerful new tool to study CYP mRNA expression and regulation. Using this method, we are the first to report that the expression of constitutive Cyp2b10, 1a2, and 2d9 mRNAs was suppressed by proinflammatory cytokines.

Animals↗

PubMed2000

[Simultaneously corneal laceration repair, traumatic cataract removal and intraocular lens implantation].

OBJECTIVE: The study aimed to evaluate the outcome of patients who undrwent simultaneously corneal laceration repair, cataract extraction and posterior chamber lens implantation. METHODS: Traumatic cataract extraction and posterior chamber intraocular lens (PC IOL) implantation were performed in 36 eyes of 36 cases with corneal laceration. YAG laser was the postoperative procedure for embrane before the lens and after cataract. Penetrating keratoplasty was performed for central cicatrice of cornea. All the patients have been followed up for 3-12 months. RESULTS: The postoperative visual acuity s.c. was 0.1-0.3 in 8 cases(22.8%), 0.4-0.5 in 14 cases (40%) 0.6-0.8 in 13 cases (37.1%) on following up. There were no serious complication attributable to PC IOL implantation. CONCLUSION: As long as the range of surgical indication was known well, PC IOL implantation can get good clinical effects at the time of primary repair.

Adolescent↗

PubMed1999

Efficacy of levofloxacin for experimental aortic-valve endocarditis in rabbits infected with viridans group streptococcus or Staphylococcus aureus.

Levofloxacin is among the more active fluoroquinolones against streptococci and staphylococci. It is effective against moderately severe infections caused by these organisms, but its efficacy in the treatment of bacteremia and serious infections such as endocarditis is not well defined. We compared the efficacy of levofloxacin to those of standard agents in the rabbit model of aortic-valve endocarditis caused by fluoroquinolone-susceptible strains including a penicillin-susceptible strain of Streptococcus sanguis, a penicillin-resistant strain of Streptococcus mitis, a methicillin-resistant strain of Staphylococcus aureus, and a methicillin-susceptible strain of S. aureus. Levofloxacin administered intramuscularly at dosages of 20 to 40 mg/kg of body weight twice daily (b.i.d.) was completely ineffective against the penicillin-susceptible strain, with mean vegetation titers after 3 days of therapy not statistically significantly different from those for controls. Levofloxacin was no more effective than penicillin against the penicillin-resistant strain. Levofloxacin administered for 4 days at a dosage of 20 mg/kg b.i.d. was at least as effective as vancomycin administered intravenously at a dosage of 25 mg/kg b.i. d. against the methicillin-resistant S. aureus strain and was as effective as nafcillin administered intramuscularly at 100 mg three times daily against the methicillin-susceptible strain. Emergence of resistance to levofloxacin in vitro was less likely to occur than resistance to ciprofloxacin, and resistance to levofloxacin was not observed in vivo. Levofloxacin-rifampin combinations were antagonistic in vitro and in vivo. Levofloxacin was highly effective as a single agent against experimental staphylococcal endocarditis but was surprisingly ineffective against streptococcal endocarditis, suggesting that it has a potential role as treatment for serious S. aureus but not viridans group streptococcal infections in humans.

Animals↗

PubMed1998

Sequence specificity of a group II intron ribozyme: multiple mechanisms for promoting unusually high discrimination against mismatched targets.

Group II intron ai5 gamma was reconstructed into a multiple-turnover ribozyme that efficiently cleaves small oligonucleotide substrates in-trans. This construct makes it possible to investigate sequence specificity, since second-order rate constants (kcat/K(m), or the specificity constant) can be obtained and compared with values for mutant substrates and with other ribozymes. The ribozyme used in this study consists of intron domains 1 and 3 connected in-cis, together with domain 5 as a separate catalytic cofactor. This ribozyme has mechanistic features similar to the first step of reverse-splicing, in which a lariat intron attacks exogenous RNA and DNA substrates, and it therefore serves as a model for the sequence specificity of group II intron mobility. To quantitatively evaluate the sequence specificity of this ribozyme, the WT kcat/Km value was compared to individual kcat/Km values for a series of mutant substrates and ribozymes containing single base changes, which were designed to create mismatches at varying positions along the two ribozyme-substrate recognition helices. These mismatches had remarkably large effects on the discrimination index (1/relative kcat/K(m)), resulting in values > 10,000 in several cases. The delta delta G++ for mismatches ranged from 2 to 6 kcal/mol depending on the mismatch and its position. The high specificity of the ribozyme is attributable to effects on duplex stabilization (1-3 kcal/mol) and unexpectedly large effects on the chemical step of reaction (0.5-2.5 kcal/mol). In addition, substrate association is accompanied by an energetic penalty that lowers the overall binding energy between ribozyme and substrate, thereby causing the off-rate to be faster than the rate of catalysis and resulting in high specificity for the cleavage of long target sequences (> or = 13 nucleotides).

Base Composition↗

PubMed1998

[Effect of 7 d head down bed rest on cardiopulmonary circulation in human].

Changes of cardiopulmonary circulation in 6 healthy young men during 7 d head down bed rest (-6 degrees HDT) were observed with the XXH-2000 lesser circulation and cardiac function instrument. Decrease of Q-j and Q-j/j-z, increase of hz, hc, and hc/hz were found during the initial 24 h. After 24 h, j-z decreased and Q-j/j-z increased. The results showed that increased pulmonary arterial pressure, increased preload of left and right heart, increased right myocardial contractility and congestion of the lungs appeared during 24 h bed rest, after which right myocardial contractility decreased. It suggests that the lesser circulation and cardiac function testing is a sensitive method for evaluating the cardiopulmonary circulation function during HDT.

Adult↗

PubMed1998

[Changes in cerebral circulation function during head down bed rest for 7 days].

To further understand the effects and regulation of brain circulation before, during and after short-term -6 degrees head down bed rest (HDT), 6 healthy young men aged 19-21 years, were subjected to HDT for 7 d. Cerebral blood flow velocity in the middle cerebral arteries of both sides was measured with a TC2000TCD instrument in 6 young adults before, during, and after 7d HDT. The results showed that cerebral blood flow velocity in the middle cerebral arteries increased throughout HDT, the increase was obvious in 24 h. They reached the highest value at the 4th hour and the lowest value on the 5 th day, and then, there were a tendency to rise on the 6th day and 7th day. The changes were about the same on both sides.

Adult↗

PubMed1997

Beta-globin haplotypes from blood spots for follow-up of newborn hemoglobinopathy screening.

The inheritance of sickle-cell anemia upon the background of the major beta-globin gene cluster haplotypes has been associated with differing risks for major organ failure, and more recently with response to hydroxyurea treatment. Early identification of beta-globin haplotypes in individuals with sickle-cell anemia may be a clinically useful prognostic factor for severity of disease expression. This report describes the use of whole-blood spots on filter papers from newborn hemoglobinopathy screening for beta-globin gene cluster haplotyping by the polymerase chain reaction.

Filtration↗

PubMed1997

[Tolerance of human and rhesus monkey elbow joints].

In order to study tolerance transfer relationships between human and rhesus monkey elbow joints, torsional and bending tests were conducted on human and rhesus monkey elbow joints under the same condition, and the tolerance transfer relationships between their elbow joints were obtained by comparing and analysing their biomechanical properties. The results show that the mean load transfer ratios between human and rhesus monkey elbow joints were 3.65 and 4.28 for torsional and bending injury respectively.

Animals↗

PubMed1997

[Changes of microcirculation in nasal mucosa during -15 degrees head-down tilt].

Changes of microcirculation in nasal mucosa in 19 young men during 2.5 h head-down -15 degrees tilt (DHT) were observed with Laser Doppler Flowmetry. The results showed that the change of microcirculation in nasal mucosa was significant, blood volume, concentration and the velocity of blood flow increased, and distinct periodical wave of microvessels appeared during HDT. The results suggest that the change of microcirculation in nasal mucosa caused by fluid shift from the lower to the upper body is one of the important factors causing stuffy nose and breathe with a little difficulty.

Aerospace Medicine↗

PubMed1997

Effects of Chinese herb medicine on improving the circulation of rabbits under simulated weightlessness.

In order to find out the effects of Chinese herb medicine on improving the functional state of blood circulation under weightlessness (WL) or simulated weightlessness (SWL), five experiments (building the SWL animal model and determining the treatment based on the differentiation of symptoms and signs, selecting herb medicine, determining the dosage of Chinese herb medicine, pharmacological text and toxicological experiment of (DH) were accomplished. Two kinds of Chinese herb medicine(CQ and DH) having the effects of improving the circulatory conditions of rabbits in SWL were selected. SWL animal model, space blood stasis and mechanism and effects of Chinese herb medicine were discussed.

Animals↗

PubMed1997

Effects of simulated weightlessness on erythrocyte deformability in rats.

In order to investigate the mechanism of space anemia, the erythrocyte deformability membrane fluidity and cell shape in 7, 15, 30 day tail-suspended rats were observed. The results were: (1) erythrocyte deformability (DImax and IDI) in suspended rats was significantly lower than that in the control on the 7th day (P<0.05), and had a further decrease on the 15th day (P<0.01), but a recovery was found on the 30th day (P<0.05). (2) membrane fluidity in suspended rats was markedly lower than that in the control group on the 15th and 30th day, degrees of fluorescence polarization was increased (P<0.01), but there was no change on the 7th day. (3) percentage of erythrocytes with abnormal shape in suspended rats was higher than that in the control group during the whole experimental period. The results indicate that the changes of rheological and morphological properties of red cell were induced by simulated weightlessness (SWL), which may be an important cause of space anemia.

Anemia↗

PubMed1997

[Observation of changes of cardiovascular function during 2.5h HDT (-15 degrees) with sphygmogram method].

To understand the changes of cardiovascular functions in the initial stage of space flight, the changes in 19 healthy young men during 2.5h head down tilt (HDT) (15 degrees) were observed with CF-II cardiovascular function detecting and diagnosing equipment. The blood pressure and sphygmogram of left radial arterial were recorded in sedentary condition and at 10th, 30th, 60th, 90th, 120th and 140th minute of HDT. The results showed that changes of cardiovascular indices during HDT can be divided into acute regulation stage (< 1h) and the regulation stage (1-2.5 h); circulatory blood volume, stroke volume and cardiac output were increased, while heart rate, pre and after load of the heart, CVP, coronary circulatory function, blood pressure and systemic vascular resistance were decreased; the vagus feedback index increased and the regulation function of vasscule decreased. Most of the changes of cardiovascular indices as reflected in the sphygmogram are in consistent with the reported result in space flight or simulated micro-G, so the sphygmogram method might be applied to space medical research.

Aerospace Medicine↗