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Biomedical subjects

Y Xu

Publications and source records attributed to Y Xu.

At least 1,261 records · Page 70Linked to original sources
PubMed1989

Thermodynamic and spectroscopic characteristics of the cytochrome bc1 complex. Role of quinone in the behavior of cytochrome b562.

Cytochrome b562 does not behave as a single independent thermodynamic component in preparations of purified quinol cytochrome c reductase. This effect is much more pronounced in quinone sufficient preparations; in such preparations, the epr spectrum of the cytochrome is Eh sensitive, with a peak shift from g = 3.42 to 3.48 occurring as the potential is lowered from 100 mV to 0 mV. The peak shift is dependent on the presence of quinone and can be restored to quinone-depleted preparations by supplementation with ubiquinol 2 if phospholipid depletion is not too severe. The results suggest that cytochrome b562 is strongly interacting with the Qc quinone binding site.

Binding Sites↗
PubMed1989

Electrotonic modulation of parasystole in children.

This paper presents four cases of pediatric extrasystole which did not fulfil the diagnostic criteria for parasystole. By calculating various ectopic intervals, we established the phase-response curve demonstrating that sinus electrotonic activities modulated the parasystolic focus in each case. Our results showed these cases to be modulated parasystole.

Adolescent↗
PubMed1989

Solid-phase electrochemical enzyme immunoassay with attomole detection limit by flow injection analysis.

A sandwich electrochemical enzyme immunoassay with flow injection analysis for the model antigen mouse IgG has been developed with alkaline phosphatase as the enzyme label. The enzyme substrate, 4-aminophenyl phosphate and its enzymatic reaction product, 4-aminophenol have been studied by cyclic and hydrodynamic voltammetry. The determination of 4-aminophenol by flow injection analysis with electrochemical detection (FIAEC) has a linear range of 5.0 x 10(-8) to 1.0 x 10(-5) M, a detection limit of 2.4 x 10(-8) M, and a sample throughput of 72 samples/h. The detection limit is set by a background capacitance response, which depends on the ionic strength difference between the sample and the mobile phase. The sandwich immunoassay has been characterized with respect to substrate concentration for the enzymatic reaction, detection limit, dynamic range and sources of error. Mouse IgG can be determined with a detection limit of 0.81 pg ml-1 by a 30-min substrate incubation time and a six orders of magnitude linear dynamic range.

Aminophenols↗
PubMed1989

Restriction fragment length polymorphism analysis of major histocompatibility complex class II genes from inbred chicken lines.

High molecular weight DNA was extracted from sperm from chickens of 14 inbred lines. The DNA was digested with each of four restriction enzymes (Pvu II, Hind III, Bgl II, and Bam HI), electrophoresed for 18 or 45 h, blotted onto nitrocellulose, and hybridized to a chicken major histocompatibility complex (MHC, B complex) class II beta-chain probe (beta 2-exon specific). Restriction fragment length polymorphisms (RFLPs) were found with each of the restriction enzymes used. Birds with the same B haplotype always showed the same RFLP pattern; however, some birds of different B haplotypes also shared the same RFLP pattern. To test for the Mendelian inheritance of the RFLP patterns, the F2 progeny of an informative cross were analysed. The RFLP patterns corresponded with the serologically determined B haplotypes of the F2 birds, thereby showing the Mendelian inheritance of the polymorphic bands.

Animals↗
PubMed1989

Nucleotide sequence of the ADH2(3) gene encoding the human alcohol dehydrogenase beta 3 subunit.

All nine exons of the ADH2(3) allele, which encodes the human alcohol dehydrogenase beta 3 subunit, have been cloned and sequenced. Comparison of this sequence to the ADH2(1) nucleotide sequence revealed only a single difference that results in an amino acid change, thus proving that the significant kinetic differences between these two isozymes is due to the Cys for Arg substitution at position 369. There are also two silent polymorphisms, and two changes in noncoding regions.

Alcohol Dehydrogenase↗
PubMed1989

Dose-dependent expression of neuronopathy after experimental pyridoxine intoxication.

We examined the sequence of nervous system abnormalities that resulted when rats were given excess amounts of vitamin B6 (pyridoxine). High doses of pyridoxine (1,200 or 600 mg/kg/d) for 6 to 10 days caused a neuronopathy with necrosis of dorsal root ganglion (DRG) sensory neurons, accompanied by centrifugal axonal atrophy and breakdown of peripheral and central sensory axons. Large diameter neurons with long processes and large cytoplasmic volumes were especially affected. Smaller doses (300 to 150 mg/kg/d) for up to 12 weeks had minor effects on DRG neurons, but produced a neuropathy with axonal atrophy and degeneration. Guinea pigs given 1,800 mg/kg/d developed sensory neuronopathy, whereas mice given similar or higher doses did not have neuropathologic abnormalities. Multiple factors including rate of administration, differential neuronal vulnerability, and species susceptibility have bearing on the final expression of pyridoxine neurotoxicity.

Animals↗
PubMed1989

[Studies of the active constituents of the Chinese drug "duhuo" Angelica pubescents].

Eight coumarins isolated from the alcohol extract of the Chinese drug "Duhuo", the root of Angelica pubescents Maxim. f. biserrata Shan et Yuan (Umbelliferae) were elucidated to be columbianetin (I), columbianetin acetate (II), columbiadin (III), osthol (IV), isoimperatorin (V), bergapten (VI), xanthotoxin (VII), and columbianetin-beta-D-glucopyranoside (VIII), by chemical and spectral analysis, compound VIII was isolated from plant for the first time. All these coumarins were tested on platelet aggregation induced by 2 microns ADP. I, II, III, IV and VIII showed strong inhibiting activity against platelet aggregation.

Animals↗
PubMed1989

[Immunosuppresive effects of wilfortrine and euonine].

Wifortrine and Euonine isolated from Tripterygium wilfordii Hook. f. Wilfortrine and euonine (40.80 mg/(kg.d) x 4d ip) showed marked depressant effects on humoral mediated immunity using the hemolysin reaction as indices. Wilfortrine (160 mg/kg.d x 9d ip) exhibited a depressant effect on graft vs host reaction (GVHR), but wilfortrine (80 mg/(kg.d) x 9d ip) showed no definite effect. Euonine (80 mg/(kg.d) x 10d ip) showed marked suppressant effects on DNCB induced delayed hypersensitivity reaction on skin in mice. Wilfortrine and Euonine (80 mg/(kg.d) x 4d ip) significantly decreased the clearance rate of charcoal particles and the weights of spleen and thymus.

Alkaloids↗
PubMed1989

[The effect of Chinese teas on the occurrence of oesophageal tumor caused by N-nitrosomethylbenzylamine in rats].

Five groups of rats were given different varieties of Chinese tea as drinking water and on additional two groups of rats were given water with or without N-nitrosomethylbenzylamine (NMBzA) as controls. Except the control group, all the animals were intubated with NMBzA (5 mg.kg-1/wk) for 6 or 12 weeks. After 6 weeks, the incidence of oesophageal mucosa lesions was significantly lower in the tea-treated rats (16-59%) than the control group with NMBzA (100%). After 12 weeks, the incidence of oesophageal tumor was also significantly lower in the tea-treated groups (42-67%) than the control group with NMBzA (90%). Similar results were obtained in the tumor size and the number of tumors developed. The anti-carcinogenic effects of the 5 varieties of Chinese tea were also not the same the Fujian Oolong tea and Jasmine tea had the strongest effect. The results suggest that Chinese tea can inhibit the carcinogenesis caused by N-nitroso compound.

Animals↗
PubMed1989

Determination of E-rosette-forming lymphocytes in aged subjects with Taichiquan exercise.

T-lymphocytes were determined by rosette formation with sheep erythrocytes in the peripheral blood obtained from 30 healthy aged subjects who were practicing Taichiquan (88 style) exercise and 30 age-matched normal aged who served as a control group. At rest the total number of T-lymphocytes and the number of active T-lymphocytes were increased significantly in the exercise group compared with the controls. Immediately after a bout of Taichiquan exercise, a marked increase of active T-lymphocytes occurred. In conclusion, the results indicate that frequent Taichiquan exercise causes an increase of T-lymphocytes in the blood.

China↗
PubMed1989

[Quantitative DNA analysis in epithelial ovarian cancer].

The tumor cell nuclear DNA content was measured in 27 cases of epithelial ovarian cancer. The proliferative activity of the tumor was correlated with the prognosis of the patients. The proportion of G0 and G1 cells of the tumors of the same histologic type varied among individuals. There was a close relationship between the proliferative activity of the tumor and the remission rate, duration of survival and mortality of the patients. The heterogeneity of the proliferative activity of the tumor cells may explain the difference of response to chemotherapy. It is suggested that the quantitative analysis of DNA content may be used as an theoretical and experimental basis for the individualization of treatment.

Cell Cycle↗
PubMed1989

[Pulmonary encephalopathy and disturbance in amino acids metabolism].

18 kinds of serum free amino acids (SFAAs) were determined in 35 patients suffering from cor pulmonale (CP) with acute exacerbation of chronic obstructive pulmonary disease (COPD). We found that the branched-chain AAs/aromatic AAs ratio (BCAAs/AAAs) was smaller in patients with pulmonary encephalopathy (PE) than those with respiratory failure (RF) only. For the PE patients, this ratio was still smaller during unconscious period than during conscious period. Some SFAAs related to neurotransmitters were also altered during unconscious period. However, there was no significant difference between CP patients with simple RF and those without RF. When RF was controlled, the SFAAs remained unchanged. The above results suggested that disturbance in neutral AAs metabolism participates in the mechanism of PE formation.

Aged↗