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Biomedical subjects

M Yan

Publications and source records attributed to M Yan.

At least 127 records · Page 7Linked to original sources
PubMed1991

Ultrafast spectroscopy of the visual pigment rhodopsin.

We report on time-resolved absorption studies of the bovine visual pigment rhodopsin with subpicosecond resolution at room temperature. Our data show that bathorhodopsin, rhodopsin's early photoproduct, is photochemically formed in 3.0 +/- 0.7 ps. The data suggest that bathorhodopsin formation is kinetically preceded by two species along the rhodopsin-to-bathorhodopsin reaction coordinate. The first is identified with the vertically excited Franck-Condon state. This decays with an approximately 200-fs lifetime to an intermediate, which then decays to bathorhodopsin in 3.0 ps. We assign this intermediate to be an excited state transient near 90 degrees along the 11-12 torsional coordinate of rhodopsin's chromophore. Exchange of rhodopsin's exchangeable protons for deuterons does not affect the observed dynamics. These observations are both qualitatively and quantitatively consistent with molecular dynamics calculations, which model the rhodopsin to bathorhodopsin phototransition as a cis-trans isomerization along the 11-12 torsional coordinate of rhodopsin's chromophore.

Animals↗
PubMed1991

Changes in pulmonary Cu-Zn contents in superior mesenteric artery occlusion shock of rabbit.

Contents of Cu and Zn of into-pulmonary blood (IPB), out-pulmonary blood (OPB), Lung tissue, and supernatant and macrophages of Lung Lavage were determined in superior mesenteric artery occlusion (SMAO) shock of rabbits. Zn of pulmonary tissue was 11.42 +/- 0.60 and 14.52 +/- 1.78 (micrograms/g wet wt) in SMAO shock and control groups, respectively. Content of Zn was found to be lower, Cu was not changed, and Cu/Zn ratio increased in lung tissue in SMAO shock. Contents of Cu and Zn in other samples were not changed. The results suggest that lower Zn in lung tissue related to acute lung injury.

Animals↗
PubMed1991

[Primary color P-VEP in diabetic retinopathy].

148 normal eyes and 123 eyes of diabetic retinopathy patients were examined the red, green, blue primary color and black/white P-VEPs, with the conclusion that the latencies of P100 were significantly delayed in the diabetic group, particularly that of the blue color, which was also in positive correlation with the level of blood sugar and the duration of diabetes. The consistency of blue P-VEP with fluorescein angiographic examination in diabetic retinopathy was good, and the abnormality ratio of the former (73.0%) was higher than that of the latter (60.2%). The results indicated that S-wave cones were damaged more readily than were L-wave cones, and the blue P-VEP was sensitive in monitoring the injury to visual function in diabetes.

Adult↗
PubMed1990

The formation and structure of the sulfoxyl radicals RSO(.), RSOO(.), RSO2(.), and RSO2OO(.) from the reaction of cysteine, glutathione and penicillamine thiyl radicals with molecular oxygen.

This work reports an electron spin resonance study of the reactions of cysteine, glutathione and penicillamine thiyl radicals with molecular oxygen in frozen aqueous solutions at low temperatures. For all three thiols, the thiyl radical, RS., is found to react with oxygen to form the thiol peroxyl radical, RSOO(.). On the absorption of visible light, RSOO(.) photoisomerizes to the sulfonyl radical, RSO2(.), which subsequently reacts with molecular oxygen to form RSO2OO(.), the sulfonyl peroxyl radical. The identities of the sulfonyl and sulfonyl peroxyl radicals were confirmed by their production by a different route, from sulfinic acid. Sulfinyl radicals, RSO(.), are found as the final radical species in the reactions of thiyl radicals and oxygen. Parallel 17O hyperfine couplings (A parallel) are reported for each sulfoxyl radical and a correlation between the spin density on oxygen and the reactivity of the radical is suggested. As a result of this correlation sulfonyl peroxyl radicals are predicted to be far more reactive than thiol peroxyl radicals. We also report molecular orbital calculations on the nature of the spin density distribution and the molecular geometry of the model radicals CH3SO2(.) and CH3SO2OO(.).

Cysteine↗
PubMed1990

[Study on Ha-ras RFLPs in gastric carcinoma and normal tissue DNAs of Chinese individuals].

By using recombinant plasmid PHS-49 as a probe, BamHI restriction fragment length polymorphisms (RFLPs) was studied in tumour DNAs of 36 gastric carcinoma patients and normal tissue DNAs of 25 unaffected Chinese individuals. Ten alleles and eighteen genotypes for Ha-ras gene were found. Four "rare" restriction fragments of size less than 6 kilobase pairs (kb) are first reported for Ha-ras locus in present paper, we inferred that these alleles might be one of the characteristics of genetic polymorphisms in Chinese population. Moreover, the frequency of some "rare" alleles and genotypes occurred in gastric carcinoma samples is significantly higher than that occurred in normal individuals. The results of pedigree analysis for two patients showed that some heterozygotes carried three or four alleles. It suggested that there may be more than one copy of Ha-ras gene sequence existed in a chromosome. The possible causes of the phenomenon mentioned above were discussed.

Alleles↗
PubMed1990

[Effects of perioperative parenteral nutrition on immunocompetence in patients with gastric cancer].

To elucidate the effects of parenteral nutrition on the immunocompetence, we administrated parenteral nutritional support to the malnourished gastric cancer patients during perioperative periods. Changes of peripheral blood natural killer cytotoxicity (NKC) activity (LDH enzyme-release assay) and T lymphocyte subsets (OKT series monoclone antibody indirect fluorescent assay) were monitored before and after nutritional support. The results showed that one week of pre or postoperative parenteral nutrition significantly increased the NKC activity, T-helper, and T-helper/T-suppressor ratio. The total T lymphocytes count may also increase. T-suppressors remained unchanged no matter whether nutritional support was given or not. The authors believe that perioperative nutritional support could improve the immunocompetence of gastric cancer patients to some extent, and promote the restoration of immune depression caused by operation, but it could not eliminate the effects of immune depressing factor produced by the tumor. Intralipid can be used properly as non protein energy source without immunodepressing effects.

Adult↗
PubMed1990

[Congestive heart failure treated by a combination of cyclovirobuxine D with digoxin].

The patients with congestive heart failure which were treated by combination of digoxin with cyclovirobuxine D were described, with good result, of which prominating effect was 45.5%. Researchful result of 11 patients showed serum concentration of digoxin before and after combined treatment was not obviously different (P less than 0.05). Basis of pharmacokinetics was provided for using combined treatment of these drugs with long time and greater safeness.

Adult↗