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Biomedical subjects

Q Xiang

Publications and source records attributed to Q Xiang.

26 records · Page 2Linked to original sources
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↗
PubMed1996

Purification and characterization of a prokaryotic xanthine dehydrogenase from Comamonas acidovorans.

Xanthine dehydrogenase (XDH) is induced in Comamonas acidovorans cells incubated in a limited medium with hypoxanthine as the only carbon and nitrogen source. The enzyme has been purified to homogeneity using standard techniques and characterized. It contains two subunits with M(r) values of 90 and 60 kDa. Gel filtration studies show the enzyme to have an alpha 2 beta 2 native structure. No precursor form of the enzyme is observed on Western blot analysis of cell extracts obtained at various stages of enzyme induction. Metal analysis of the purified enzyme shows 1.1 Mo, 4.0 Fe, and 3.6 phosphorus atoms per alpha beta protomer. Cofactor analysis shows the enzyme to contain a single molybdopterin mononucleotide and one FAD per alpha beta protomer. Electron spin resonance and circular dichroism spectral studies of the oxidized and reduced forms of the enzyme suggest the Fe centers to be two nonidentical [2Fe-2S] clusters. Electron spin resonance signals due to Mo(V) and neutral FAD radical are also observed in the reduced form of the enzyme. Purified enzyme preparations ranged from 70% to 100% functionality. The enzyme is irreversibly inactivated by CN- and is inhibited on incubation with allopurinol. With xanthine and NAD+ as substrates the enzyme has a specific activity of 50 units/mg, a kcat value of 120 s-1, an activity/flavin ratio of 1930, and respective Km values of 66 and 160 mM. Using 8-D-xanthine as substrate, a DV value of 1.8 is found with no change in Km. Thus, the Km and KD values of the enzyme for xanthine are equal. These data show Comamonas XDH to exhibit structural properties similar to bovine milk xanthine oxidase/dehydrogenase and to chicken liver xanthine dehydrogenase. Although the bacterial enzyme exhibits a 6-7-fold greater turnover rate than bovine or avian enzymes, the catalytic efficiencies (as measured by V/K) are similar for all three enzymes.

Animals↗
PubMed1995

Studies on pathways of ring opening of benzene in a Fenton system.

Ring-opened products of benzene metabolism have been postulated to play a role in hematotoxicity and leukemogenesis. The reaction of benzene in the Fenton system was reexamined to determine the presence of compounds which might serve as intermediates in the formation of trans, trans-muconaldehyde (MUC), a microsomal hematotoxic metabolite of benzene. Benzene dihydrodiol (DHD) was found in this system based on coelution with authentic standard, ultraviolet (UV) absorption characteristics, and molecular weight. Incubation of DHD in the Fenton system resulted in the formation of phenol (PH), catechol (CAT), and products which reacted with thiobarbituric acid to form chromogens absorbing at 495 nm and 532 nm, consistent with products containing an alpha, beta-unsaturated aldehyde group. However, muconaldehyde was not detected in the Fenton system incubated with DHD, indicating that MUC is not formed via ring opening of DHD. When benzene was incubated in the Fenton system, MUC, cis,trans-muconaldehyde, PH, hydroquinone (HQ), and CAT were identified. Identification of cis,trans-muconaldehyde, an isomer which can quickly rearrange to MUC, suggests that cis,cis-muconaldehyde is originally formed from benzene and converted to cis,trans- and then trans,trans-muconaldehyde.

Aldehydes↗
PubMed1994

[Construction of the mammalian expression systems in hepatoma and non-liver cells with rat CPSI cDNA fragments].

Studies on recombination of 0.587 kb and 0.712 kb CPSI cDNA fragments with pSV2 vecter and recombinant pSV2-CPS505 and pSV2-CPS507 plasmid expression of CPSI in non-liver culture cells were presented. The results confirmed that the NIH/3T3 and 7402 hepatoma culture cells transfected individually with pSV2-CPS505 and pSV2-CPS507 plasmid were able to express CPSI effectively. The non-translational sequence is not indispensible to the highly tissue specific expression of CPS I. The studies provided experimental evidence and a cellular model for expression of novel CPSI in vitro, which has a great significance for carcinogenesis and differentiation.

3T3 Cells↗
PubMed1991

Correlation between gene expression and chromatin conformation of c-fos and N-ras in human liver and hepatoma.

In situ hybridization revealed an apparently higher expression of N-ras and c-fos in human hepatoma than in its adjacent liver tissue. When the isolated nuclei were partially digested with micrococcal nuclease followed by DNA extraction, gel electrophoresis and hybridization with labelled probes, it was shown that in hepatoma the c-fos and N-ras DNA sequences were mainly distributed on the nucleosomes of lower order structures, while these gene sequences in the adjacent liver tissue were found mainly on the nucleosomes of higher order structures. These results clearly indicate a close correlation between gene expression and chromatin conformation of c-fos and N-ras.

Carcinoma, Hepatocellular↗
PubMedDate not supplied

Reaction of (E,E)-muconaldehyde and its aldehydic metabolites, (E,E)-6-oxohexadienoic acid and (E,E)-6-hydroxyhexa-2,4-dienal, with glutathione.

(E,E)-Muconaldehyde (muconaldehyde) has been identified as a hematotoxic metabolite of benzene in vitro. It is metabolized in mouse liver cytosol to oxidized and reduced derivatives including the alpha, beta-unsaturated aldehydes (E,E)-6-oxohexadienoic acid and (E,E)-6-hydroxy-2,4-hexadienal. In this study we have synthesized the aldehydic metabolites of muconaldehyde. The reaction of glutathione with muconaldehyde and its aldehyde metabolites was investigated. Reactions were bimolecular and stoichiometric in aldehyde and glutathione in the initial phases. Second-order rate constants were determined, and the rates were in the order muconaldehyde > (E,E)-6-hydroxy-2,4-hexadienal > (E,E)-6-oxohexadienoic acid. Further investigation of the reaction of muconaldehyde with glutathione showed that the bimolecular reaction is reversible but the initial product decomposed irreversibly to two or more products, one of which had a red-shifted UV spectrum. Rate constants for these subsequent reactions were determined. The results are discussed in terms of the toxicity of muconaldehyde at tissues distal from the liver, where it is believed to be formed from the metabolism of benzene.

Aldehydes↗