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Biomedical subjects

J Ji

Publications and source records attributed to J Ji.

80 records · Page 5Linked to original sources
PubMed1991

[The structure of trijuganone C from Salvia trijuga].

From Salvia trijuga Diels 9 compounds were isolated and eight of them identified as ferruginol, sugiol, triacontanoic acid, tetratriacontanoic acid, octacosanoic acid, hexactecanoic acid, dl-homoserine and parahydroxybenzoic acid. Compound I a red needle crystal C20H20O5, mp 113-114 degrees C is a new diterpenoid related to methyltanshinonate named trijuganone C. Its structure has been proved to be 15, 16-dihydromethyltanshinoate by spectroscopic and chemical means.

Drugs, Chinese Herbal↗
PubMed1990

Scaling limitations of silicon multichannel recording probes.

This paper describes the scaling limitations of multichannel recording probes fabricated for use in neurophysiology using silicon integrated circuit technologies. Scaled silicon probe substrates 8 microns thick and 16 microns wide can be fabricated using boron etch-stop techniques. Theoretical expressions for calculating the thickness and width of silicon substrates have been derived and agree closely with experimental results. The effects of scaling probe dimensions on its strength and stiffness are described. The probe shank dimensions can be designed to vary the strength and stiffness for different applications. The scaled silicon substrates have a fracture stress of about 2 x 10(10) dyn/cm2, which is about six times that of bulk silicon, and are strong and very flexible. Scaling the feature sizes of recording electrode arrays down to 1 micron is possible with less than 1 percent electrical crosstalk between channels.

Electronics, Medical↗
PubMed1989

Molecular cloning of the outJ gene involved in pectate lyase secretion by Erwinia chrysanthemi.

The phytopathogenic enterobacterium Erwinia chrysanthemi secretes a number of enzymes involved in plant-tissue degradation, notably the five isoenzymes of pectate lyase. We have cloned a region involved in pectate lyase and cellulase secretion by complementation of non-secretory outJ mutants of E. chrysanthemi strain 3937 using the RP4::miniMu plasmid pULB110. The cloned region maps near the ade-22 marker on the E. chrysanthemi 3937 chromosome. An R-prime containing a chromosomal DNA insert of about 30kb was first obtained; subcloning into pBR325 permitted the isolation of a 4kb ClaI/SspI fragment able to complement outJ mutations in E. chrysanthemi. The isolation of phoA fusions in this fragment allowed us to determine the direction of transcription of the encoding region, which extends over about 2.5kb, and demonstrate that this region encodes exported protein(s). When the TnphoA insertions were transferred back into E. chrysanthemi chromosome, the recombined strains no longer secreted pectate lyases or cellulases. Identification of the products encoded by the ClaI/SspI fragment demonstrated that outJ encodes an 83 kD polypeptide which is processed to an 81 kD polypeptide by cleavage of a signal sequence. The cloned DNA fragment did not endow Escherichia coli with the ability to secrete pectate lyases.

Bacterial Proteins↗
PubMed1989

[Identification of tanshinones with related compounds by high performance thin layer chromatography and mass spectrometric analysis].

28 compounds isolated from Danshen (Salvia miltiorrhiza Bunge and S. przewalskii Maxium) were identified by both HPTLC and mass spectrometric analysis. The mass spectra of tanshinones and related terpenoids have been examined and a number of characteristic features noted which might be helpful in the identification of these compounds. The Rf values of five groups of tanshinones and related compounds in six solvent systems were given. They can be used for identifying several epimeric compounds which are difficult to identify by mass spectra alone.

Abietanes↗
PubMedDate not supplied

Suicide in contemporary China: a review of China's distinctive suicide demographics in their sociocultural context.

Suicide is a complex phenomenon--arguably a social and a moral deed--occurring within associated psychological, biological, and cultural contexts. We present data on suicide rates in China for 1988, 1990, and 1992 and provide an analysis of their social context. These figures, from the Chinese Public Health Annuals, have never before been publicly reported. These and other recent data indicate that suicide rates in China, although reportedly low in the past, are by global standards alarmingly high among certain demographic groups. They also reveal distinctive epidemiological patterns of suicide in China that contrast with the patterns characteristic of Western societies-for example, higher rates in rural than in urban areas and, among some demographic groups, higher among women than among men. As in the West, however, suicide among the elderly is a major problem in China. The sociocultural context of these data is examined as a means toward understanding their distinctive patterning.

Adolescent↗
PubMedDate not supplied

[Molecular evolution of AdoMet synthetase by DNA recombination with a novel separate-mixing method].

We describe a new approach to in vitro DNA recombination termed Separate-Mixing method in this study. The reaction process of this method consists of two stages: at the first stage the reaction was implemented in two parallel teams, which generated random recombination by template-switching of growing polynucleotides from primers in the presence of unidirectional single-stranded DNA fragments used as templates, and then both teams were mixed together for further extension and recombination of DNA sequences at the second stage. Because of the particular strategy, the reaction process was also accompanied by the other two processes of DNA shuffling and StEP simultaneously. Two AdoMet synthetase genes sam2 from Saccharomyces cerevisiae and metK from Escherichia coli, which have only 56% homology on the DNA level were used for recombination with Separate-Mixing method. DNA recombination was available after a single round of reaction. With sequencing of 10 randomly selected recombinants, no unshuffled parental clone was found, and also no unexpected insertion, deletion or rearrangement was detected. An evolved gene sam' was obtained after screen and selection, which could obviously increase the accumulation of AdoMet in S. cerevisiae.

Directed Molecular Evolution↗