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Biomedical subjects

J X Chen

Publications and source records attributed to J X Chen.

At least 55 records · Page 3Linked to original sources
PubMed1990

Preparative slab electrofocusing of methane monooxygenase from a type I methanotroph Methylomonas GYJ3.

The isolation and purification of methane monooxygenase from a type I methanotroph Methylomonas GYJ3 to near homogeneity is reported. The isoelectric focusing in flat-bed granulated gels has resolved the methane monooxygenase into three protein components. The specific activity of the enzyme is 198.4 n mol per min per mg protein, degree of purification 4.13-fold. Recovery of the focused proteins is high and elution simple. Several purification steps may be omitted from the previously published scheme by other techniques.

Isoelectric Focusing↗
PubMed1990

[Protective effects of Panax notoginseng saponins on experimental myocardial injury induced by ischemia and reperfusion in rat].

Effects of total saponins of Panax notoginseng (PNS) and purified ginsenosides Rb1 and Rg1 from PNS on myocardial injury induced by cardiac ischemia and reperfusion were studied with rat hearts in situ and in vitro. In pentobarbital-anesthetized rats, PNS pretreatment (100 and 200 mg/kg) provided significant reduction in myocardial infarct size after left descending coronary artery ligation (40 min) and reperfusion (120 min) in comparison with the control. PNS 12.5 and 25 mg/L, Rb1 10 mg/L, and Rg1 10 mg/L significantly decreased cardiac CPK release, attenuated myocardial Ca2+ accumulation, reduced malondialdehyde (MDA) production and prevented reduction of superoxide dismutase (SOD) activity in comparison with the control in perfused isolated rat hearts with global ischemia (40 min) and reperfusion (15 min). The results show that PNS, Rb1, and Rg1 prevent cardiac ischemia and the action is considered to be related to the inhibition of lipid peroxidation.

Animals↗
PubMed1989

[Effects of Panax notoginseng saponins on cardiac action potentials and slow inward current].

The effects of total saponins of Panax notoginseng (PNS) on contraction force, normal and slow response action potentials and slow inward current of guinea pig papillary muscles were studied by intracellular microelectrodes and voltage clamp techniques. The contraction force was decreased and the APD20, APD90 of normal AP were shortened in the presence of PNS 1 mg/ml, while the RP, APA and Vmax remained unchanged. The APA of slow AP induced with high K+ was decreased to 85% of its normal value after 20 min of perfusion with PNS solution. Isi was decreased from a peak value of 9.8 +/- 2.0 to effects of PNS on slow affecting INa. The 6.9 +/- 3.6 microA without AP and Isi were reversed by increasing calcium concentration. The results indicate that PNS has a selective blocking effect on calcium channels.

Action Potentials↗
PubMed1988

Isolation and characterization of auxotrophic mutants of Legionella pneumophila that fail to multiply in human monocytes.

Attempts to isolate auxotrophic mutants of Legionella pneumophila have been hampered by the complex nutritional composition of the media used to cultivate this organism. We developed a semidefined medium, designated CAA, to facilitate the isolation and characterization of Legionella auxotrophs. Unlike previously described chemically defined media for this organism, L. pneumophila formed colonies on CAA agar. Using this medium, we isolated several independent tryptophan auxotrophs of strain Philadelphia-1 after ethyl methanesulfonate mutagenesis and penicillin enrichment. Trimethoprim selection was used to isolate several independent thymidine-requiring mutants of the same strain. The thymidine auxotrophs exhibited a marked decrease in viability when they were deprived of thymidine. The results of monocyte infection experiments with both the tryptophan and thymidine auxotrophs indicated that the thymidine auxotrophs were incapable of intracellular survival or multiplication. In contrast, the tryptophan auxotrophs grew well in monocyte cultures. The isolation of additional auxotrophic mutants will facilitate the study of the nutritional requirements of L. pneumophila for growth in human mononuclear phagocytes.

Culture Media↗
PubMed1983

Studies on antihepatitic drugs. Total synthesis of (+/-)schizandrin C and its analogs.

This paper reports the total synthesis of (+/-) schizandrin, C, namely 5,6,7,8-tetrahydro-1, 12-dimethoxy-2, 3, 10, 11-bismethylenedioxy-6, 7-cis-dimethyldibenzo (a, c) cyclooctene (12B), a new active SGPT lowering principle isolated from the Chinese medical plant Schizandra chinensis, and its 6, 7-trans-dimethyl isomer (16B). We also synthesized two more isomers, namely 5, 6, 7, 8-tetrahydro-3, 10-dimethoxy-1, 2, 11, 12-bismethylenedioxy-6, and 7-cis-(and trans-) dimethyldibenzo (a, c) cyclooctene (12A and 16A). The NMR, UV and mass spectra of these four isomers are discussed. IR (in chloroform), UV, NMR and MS of synthetic schizandrin C (12B) are identical with those of the natural compound.

Animals↗