PubMed Health⌕ Search

Biomedical subjects

G X Chen

Publications and source records attributed to G X Chen.

At least 19 recordsLinked to original sources
PubMed2006

The 3C/3D line ratio in Ni XIX: New Ab Initio theory and experimental results.

We report a fully relativistic close-coupling calculation of the electron impact excitation of Ni xix to derive the 3C/3D line intensity ratio, with an uncertainty of 5%. Convergence of the calculation with respect to both channel coupling effects and the many interacting Rydberg series of resonances has been achieved. New measurements in an electron beam ion trap agree with our calculation. We show that the 3C/3D x-ray line ratio depends sensitively on both electron energy and beamwidth in an optically thin plasma. Accounting for this dependence improves the accuracy of the Ni abundance determination in astrophysical sources.

Journal Article↗
PubMed2005

Effect of petroleum-containing wastewater irrigation on bacterial diversities and enzymatic activities in a paddy soil irrigation area.

Effects of petroleum contamination on bacterial diversities and enzymatic activities in paddy soils were investigated in the Shenfu irrigation area, the largest area irrigated by oil-containing wastewater for more than 50 yr in northeastern China. Bacterial diversities were determined by conventional colony morphology typing techniques and 16S rDNA polymerase chain reaction (PCR)-denaturing gradient gel electrophoresis (DGGE). Dehydrogenase, hydrogen peroxidase, polyphenol oxidase, urease, and substrate-induced respiration (SIR) were measured to evaluate the effects of petroleum-containing wastewater irrigation on soil biochemical characteristics. Results showed that paddy soil total petroleum hydrocarbon (TPH) concentration in the irrigation area varied from 277.11 to 5213.37 mg kg(-1) dry soil. Soil TPH concentration declined along the gradient of the irrigation channel from up- to downstream. At the current pollution level, the paddy soil TPH concentration was positively correlated with the colony forming units (CFU) of aerobic heterotrophic bacteria (AHB) (r = 0.928, p < 0.001) and the genetic diversity based on DGGE profiles (r = 0.655, p < 0.05). The bacterial diversities in the soils based on colony morphotypes of AHB also increased with TPH concentration (r = 0.598), but not significant statistically (p = 0.052). Analysis of soil enzyme activities indicated a significant positive correlation between soil TPH concentration and activities of dehydrogenases (r = 0.974, p < 0.001), hydrogen peroxidases (r = 0.957, p < 0.001), polyphenol oxidases (r = 0.886, p < 0.001), and SIR (r = 0.916, p < 0.001). On the contrary, the urease activity showed a negative correlation with paddy soil TPH concentration (r = -0.814, p = 0.002), and could be used as a sensitive indicator of petroleum contamination.

Agriculture↗
PubMed2001

Effects of cultivation on N2O emission and seasonal quantitative variations of related microbes in a temperate grassland soil.

Laboratory and in situ experiments were done to investigate the influences of cultivation on temperate semi-arid grassland (for 17 years spring wheat planted once every two years without fertilisation) on soil N2O emission and quantitative variations of related soil microbes. In the laboratory (25 degrees C and soil moisture 18%), cultivation increased soil transformations of fertilizer nitrogen (100 micrograms N/g as NaNO3, urea, or as urea with dicyandiamide 1 microgram N/g). The N2O emissions from the cultivated and uncultivated soils with or without nitrogen additions were relatively low, and mainly originated from the nitrification. The soil N2O emission due to cultivation decreased somewhat upon no fertilization or NaNO3 addition, but significantly upon urea addition. The role of dicyandiamide as nitrification inhibitor was only considerable in the cultivated soil, and had small influence on decreasing N2O emission in the two soils. The influence of cultivation on soil N2O emission was also reflected by the number variations of microbes related with soil nitrogen transformation in the two soils. Compared to the uncultivated grassland, in situ ammonifiers and denitrifiers in the cultivated grassland quantitatively averagely increased, and aerobic no-symbiotic azotobacters were quantitatively similar, leading to the continued decrease of organic matter content and the decrease of N2O emission from the cultivated grassland soil.

China↗
PubMed2000

Expanded analysis of injury mortality among unionized construction workers.

BACKGROUND: To evaluate the utility of expanding the number and precision of injury categories used in previous occupational mortality studies, this study reanalyzed data from four previous studies of unionized construction workers (construction laborers, ironworkers, sheet metal workers, and operating engineers), by expanding the number of injury categories from 6 to 33. METHODS: Proportionate mortality ratios (PMRs) were computed using the distribution of deaths from the National Occupational Mortality Surveillance System, a mortality surveillance system from 28 states, as a comparison. A blue collar comparison group was also used in additional analyses to adjust for socioeconomic and other factors. RESULTS: This reanalysis identified significantly elevated PMRs in at least one of the four worker groups for falls, motor vehicle crashes, machinery incidents, electrocutions, being struck by falling objects, being struck by flying objects, explosions, suffocation, and water transport incidents. Limiting the comparison population to deaths among blue collar workers did not change the results substantially. CONCLUSIONS: This study demonstrates that increasing the precision of categories of death from injury routinely used in mortality studies will provide improved information to guide prevention. Am. J. Ind. Med. 37:364-373, 2000. Published 2000 Wiley-Liss, Inc.

Accidental Falls↗
PubMed2000

Metabolites of Colletotrichum gloeosporioides, an endophytic fungus in Artemisia mongolica.

A new antimicrobial metabolite, named colletotric acid (1), was isolated from a liquid culture of Colletotrichum gloeosporioides, an endophytic fungus colonized inside the stem of Artemisia mongolica. The structure was determined using spectroscopic methods (EIMS and FABMS,(1)H and (13)C NMR, (1)H-(1)H COSY, HMBC, and HMQC). Compound 1 inhibited the growth of Bacillus subtilis, Staphylococcusaureus, and Sarcina lutea with minimal inhibitory concentrations (MICs) of 25, 50, and 50 microg/mL, respectively, and the crop pathogenic fungus Helminthosporium sativum (MIC: 50 microg/mL).

Anti-Bacterial Agents↗
PubMed1999

[Changes of potassium and sodium content in erythrocyte of rabbit cardiac blood after death and timing of death].

We studied the changes of potassium and sodium contents in erythrocytes and the activity of erythrocyte membrane Na(+)-K(+)-ATPase in 40 cardiac blood samples of rabbit corpses at different postmortem intervals (PMI). The erythrocyte potassium content (RBCK) decreased linearly as the PMI increased (R = -0.829, P < 0.025). during postmortem 48 hours. The erythrocyte potassium content and the time after death had significant correlation. The activity of erythrocyte membrane Na(+)-K(+)-ATPase had no significant changes over postmortem 48 hours.

Animals↗
PubMed1995

Superoxide contributes to the rapid inactivation of specific secondary donors of the photosystem II reaction center during photodamage of manganese-depleted photosystem II membranes.

The role of superoxide in the mechanism of photoinactivation of the secondary donors of the reaction center of photosystem II membranes depleted of Mn by extraction with NH2OH plus EDTA (NH2OH/EDTA-PSII) was assessed. EPR analyses (g = 2 region) in continuous light, optical kinetic spectrophotometric analyses of P680+ and Car+, and AT-band emission measurements were made after various durations of weak and strong light treatment of NH2OH/EDTA-PSII in the presence and absence of superoxide dismutase, or of PSII electron acceptors to suppress superoxide formation. Additionally, flash-induced variable fluorescence of chlorophyll a and the capabilities of the membranes of photooxidize Mn2+ (in the presence of H2O2) via a high-affinity site (Km approximately 180 nM) and to carry out the photoactivation of the Mn-cluster were determined. In the absence of any additions to the NH2OH/EDTA-PSII membranes which were highly depleted of Mn, weak light treatment caused rapid (t1/2 approximately 20 s) and parallel losses of (a) the approximately 10 microseconds phase of P680+ reduction, which reflects the TyrZ-->P680+ reaction, (b) the amplitude of chlorophyll a variable fluorescence, (c) the capability to accumulate the TyrZ(+)-radical in continuous light, and (d) the capability to photooxidize Mn2+/H2O2 in continuous light. As reported previously [Blubaugh et al. (1991) Biochemistry 30, 7586-7597], a dark-stable 12-G-wide featureless EPR signal centered at g = 2.004 was formed rapidly during illumination. This signal previously was tentatively identified as a Car+ radical and was suggested to contribute to the quenching of chlorophyll a variable fluorescence and to the slowing of the TyrZ-->P680+ reaction. However, we failed to detect Car+ formation by sensitive optical spectrophotometry and obtained no definable evidence for either a quencher of fluorescence other than P680+ itself or a slowing of the TyrZ-->P680+ reaction. Addition of a saturating concentration (96 units/mL) of superoxide dismutase diminished the rate of photodamage(s) by approximately 30-fold, but did not abolish it completely. Superoxide dismutase similarly suppressed strong light-induced photodamages, causing the loss of capability to photooxidize Mn2+/H2O2, to carry out photoactivation, and to generate the AT-band emission as well as TyrZ+ EPR signal. In contrast to others, we found no evidence that the initial target(s) of photodamage is (are) different in weak versus strong light treatment. The totality of the results suggests that the initial event in either weak light or strong light photodamage of NH2OH/EDTA-PSII is a decoupling of the redox activity of TyrZ from P680.(ABSTRACT TRUNCATED AT 400 WORDS)

Chlorophyll↗
PubMed1995

[Effects of composite xueliting on four gastric ulcer models in rats and mice].

Composite Xueliting (CXLT) was found to be an effective anti-ulcer agent in four experimental models in rats and mice, namely, the stress restraint-induced, histamin-induced, salicylic acid-induced and reserpine-induced ulcers. In above-mentioned models, CXLT (0.214-0.856 g/kg, 1/d x 5, per os) could inhibit gastric ulcer by 40%-63%, 48%-85%, 68%-87% and 27%-65% respectively. Among these, the salicylic acid-induced ulcer was more markedly inhibited. The result suggested that CXLT had the protective function against the gastric ulcer.

Animals↗
PubMed1994

Photoinactivation of photosystem II by in situ-photoproduced hydroxyurea radicals.

Oxygenic photosystem (PS) II complex from spinach photooxidized hydroxyurea (HU) to produce its aminoxy radical, which was identified by its electron spin resonance spectrum. HU was apparently photooxidized by the water-oxidizing enzyme (WOE) since the photooxidation reaction was blocked by carbonyl cyanide m-chlorophenylhydrazone (CCCP). HU radicals photoproduced by the WOE inhibited the electron transfer between the redox-active tyrosine residue (YZ), which is involved in electron transfer from the WOE to the reaction center chlorophyll of PS II, and the secondary quinone electron acceptor. Treatment of PS II complex with Tris resulted in the appearance of a CCCP-insensitive photooxidation site for HU. Photoproduced HU radicals in oxygenic and Tris-treated PS II complex decayed with first-order kinetics, an indication that the radicals reacted primarily with surrounding molecules rather than decayed through spontaneous dismutation or recombination. HU inhibited the diphenylcarbazide-supported photoreduction of 2,6-dichlorophenolindophenol (DCIP) in Tris-treated PS II complex preincubated only under illumination, but this inhibition was suppressed when ascorbate was added to scavenge HU radicals. If examined in darkness, HU radicals could not, however, inhibit subsequent photoreduction of DCIP. Therefore, the photoproduced HU radicals interact with a photogenerated site(s) in the PS II complex. The photoproduction of YZ., a radical of YZ, was suppressed to about 40% in Tris-treated PS II complex by the in situ-photogenerated HU radicals, and the yield of a cation radical of chlorophyll, close to the PS II reaction center, was increased, while the production of a radical of another redox-active tyrosine residue in PS II (YD.) was hardly affected.(ABSTRACT TRUNCATED AT 250 WORDS)

Binding Sites↗
PubMed1993

[Effect of intravenous atropine on the induction of paroxysmal supraventricular tachycardia].

Sixty nine patients with the history of paroxysmal supraventricular tachycardia (PSVT) or possible history of PSVT failed to have PSVT provoked by transesophageal atrial pacing (TEAP). After intravenous administration of 0.02 mg/kg atropine, 42 patients had PSVT provoked during the second TEAP. The electrophysiologic parameters showed that atropine could increase the inducibility of PSVT. The main effect was to decrease the anterograde AV node effective refractory period (ERP) or fast pathway ERP and provide an available condition for the reentry of impulses. The conclusion is that atropine could definitely increase the diagnostic value of TEAP.

Atropine↗
PubMed1993

[Pathomorphologic changes on 150 chronic atrophic gastritis patients by treatment based on syndrome differentiation].

Xiang-sha Warming (XSW) and Shashen Nourishing Decoction (SSN) were used in treating Yang Deficiency Syndrome (YaDS) and Yin Deficiency Syndrome (YiDS) of chronic atrophic gastritis (CAG) respectively. 121 cases with Spleen YaDS, and 29 cases with Spleen YiDS were selected. 26 and 30 specimens were taken from gastric mucosa for observation under the SEM and TEM, including 12 and 12 YaDS cases, 14 and 12 Spleen Qi Deficiency cases respectively, 2 cases of YiDS were also observed with TEM. The specimens were taken from the same site of the gastric mucosa directly under the gastroscope pre- and post-treatment. 43 patients (35.6%) with spleen YaDS and 5 cases (17.2%) in Spleen YiDS showed marked effect after 3-month treatment. It showed that the effect in Spleen YaDS was better than YiDS. The XSW was superior than that of SSN. The effects were related to the syndromes and the degrees of pathologic change. This showed that the recipe could somewhat reverse and restore the abnormal glands of gastric mucosa.

Biopsy↗
PubMed1992

Photoinhibition of hydroxylamine-extracted photosystem II membranes: studies of the mechanism.

The effects of photosystem II (PSII) exogenous electron donors and acceptors on the kinetics of weak light photoinhibition of NH2OH/EDTA-extracted spinach PSII membranes were examined. Under aerobic conditions, Mn2+ (approximately 1 Mn/reaction center; Km approximately 400 nM) inhibited photoinactivation and approximately 1 Mn/reaction center plus 100 microM NH2NH2 gave almost complete protection. In the absence of electron donors, strict anaerobiosis greatly inhibited photoinactivation even in the presence of an electron acceptor. Under aerobic conditions, the addition of electron acceptors (FeCN, DCIP), oxyradical scavengers, or superoxide dismutase strongly suppressed rates of photodamages. Increase in the concentrations of superoxide above those produced by illuminated NH2OH/EDTA-photosystem II membranes increased the rates of damage in the light but gave no damage in the dark. Scavengers of hydroxyl radicals and singlet oxygen did not suppress the rates of aerobic photoinhibition. These findings, along with others, lead us to conclude that photodamage of the secondary donors of the PSII reaction center occurs by two mechanisms: (1) a rapid superoxide and tyrosine YZ+ dependent process and (2) a slower process in which P680+/Chl+ catalyze the damages.

Free Radical Scavengers↗
PubMed1992

The pregnane glycoside marsdekoiside A from Marsdenia koi.

A new pregnane glycoside, marsdekoiside A was isolated from the stems of Marsdenia koi (Asclepiadaceae) and its structure was elucidated from chemical and spectral data as 12-cinnamoyl-dihydrosarcostin-3-O-methyl-6-deoxy-beta-D-allopyr ano syl-(1----4)-O-beta-D-oleandropyranosyl-(1----4)-O-beta-D-++ +cymar opyranoside.

Carbohydrate Sequence↗
PubMed1991

A Plasmodium falciparum-specific reverse target capture assay.

Plasmodium falciparum DNA is detected with an assay modeled according to the reverse target capture assay described by Morrissey et al. [19] for the detection of Listeria cells. A poly(A)-tailed oligonucleotide (pWZ34), derived from the partial sequence of a 4-kb repetitive unit of P. falciparum, functions as a capture probe and the labelled 21-bp repetitive units specific for P. falciparum serve as a reporter probe. Both probes are complementary to non-overlapping regions of the target DNA and in the presence of high concentration of chaotropic salts, hybridization efficiently takes place at relatively low temperatures (15 min. 37 degrees C). The addition of poly(dT)-derivatized ferromagnetic beads allows the formation of A:T base pairing between the tailed beads and the tailed capture probe. Upon applying magnetic force, the target-capture-reporter-probe complex attached to the beads is removed from the reaction mixture, leaving the bulk of unreacted reporter molecules behind. Subsequent washings of the immobilized complex reduces the amount of non-specifically bound reporter probe. After elution of the complex from the beads a new cycle of capture, washing and release of the target-capture-reporter-probe complex is initiated by the additions of unused (dT)-tailed beads. After 3 cycles, the signal-to-noise ratio with 0.1 pg of P. falciparum DNA as a target was as high as 21-27, with a background of 8-10 cpm. The assay is unique in its speed, well suited for large sample numbers, and allows the manipulation of the background at will by simply increasing the number of capture rounds.

Animals↗
PubMed1991

Etiological investigation of farmer's lung disease: a serological study.

To confirm the main etiological antigen of farmer's lung in Dafeng County, Jiangsu Province, People's Republic of China, precipitins in serum from 30 patients with farmer's lung were tested with several strains of antigens. Reactions against two strains of T.vulgaris were shown in 46.7% and 66.7% of the patients group, which were significantly higher than in the controls, while the percentage of reactions against Faenia rectivirgula and A. fumigates were low in the patients group and had no significant difference with the controls. The results indicate that the main etiological agents were some strains of T. vulgaris. This finding was consistent with the microbiological study of sputum of the patients and moldy hay samples from the working area.

Adult↗
PubMed1991

The cytochemical changes and the adherence of neutrophil during cross-linked agarose encapsulated activated charcoal hemoperfusion.

After one hour cross-linked agarose encapsulated activated charcoal hemoperfusion, there was slight increase of total white cells and neutrophil count, but the neutrophil adherence was 16.87 +/- 5.26% and marked lower than that before hemoperfusion (59.91 +/- 5.26%, p less than 0.05). Using glassball hemoperfusion as control, the neutrophil adherence also decreased but not so obvious as the former. Adherence is a cell property that may affect granulocyte margination, diapedesis, chemotaxis and phagocytic function, so the above investigations showed that both the hemoperfusion process and the charcoal itself may reduce the host defence mechanism. There were no change of the peroxidase and alkaline phosphatase activities of neutrophils during one hour cross-linked agarose encapsulated activated charcoal hemoperfusion.

Alkaline Phosphatase↗
PubMed1991

[Structure determination of marsdekoiside C].

A pregnane glycoside ester was isolated from Marsdenia koi Tsiang by column chromatography. The structure was identified on the basis of IR, 1H-NMR, 13C-NMR and FAB-MS. It is a new compound obtained from this plant for the first time and named as marsdekoiside C.

Animals↗