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Biomedical subjects

X Yan

Publications and source records attributed to X Yan.

177 records · Page 10Linked to original sources
PubMed1992

Susceptibility of Aedes albopictus from China to insecticides, and mechanism of DDT resistance.

Aedes albopictus collected from urban districts of China (12 strains) has developed high levels of DDT resistance, while 2 strains collected from rural areas remain susceptible. The mechanism of DDT resistance was due to intensified activity of DDT-dehydrochlorinase, but the penetration of DDT into the mosquito body is also different. This may possibly have had some influence on the resistance levels of some strains, but it seems unlikely that was the main mechanism of DDT resistance.

Aedes↗
PubMed1987

Submitochondrial localization of kidney 25-hydroxycholecalciferol 1 alpha-hydroxylase in vitamin D repleted weanling guinea pigs.

We have studied the submitochondrial localization of guinea-pig kidney 25-hydroxycholecalciferol 1 alpha-hydroxylase. Treatment of the mitochondrial-enriched fraction with recrystallized digitonin produced mitoplasts bordered by a single membrane and with intact matrix. They contained nearly 90% of the 25-hydroxycholecalciferol 1 alpha-hydroxylase activity and nearly 100% of the cytochrome-c:oxygen oxidoreductase. Amine:oxygen oxidoreductase activity remained mainly in the outer membrane fraction. These data show that 25-hydroxycholecalciferol 1 alpha-hydroxylase has a distribution similar to that of steroid hydroxylases.

25-Hydroxyvitamin D3 1-alpha-Hydroxylase↗
PubMedDate not supplied

The spatial dimension of Chinese urbanization.

"This paper focuses on four interrelated aspects of the spatial dimension of city development [in China]. Attention is paid initially to the basic geography of urbanization, before turning to an analysis of recent trends in the pattern of urbanization. Spatial biases throughout the present-day hierarchy are then investigated and, finally, the relationships between urbanization patterns and economic planning belts are considered."

Asia↗
PubMedDate not supplied

Structural analysis of ricin and implications for inhibitor design.

Ricin is a potent cytotoxin with experimental and clinical uses; it has also been used as a poison. There is considerable interest in identifying or designing inhibitors of the toxin that could be administered as antidotes. The X-ray structure of ricin A-chain is known and a plausible mechanism of action has been proposed. This provides a structural and chemical framework around which inhibitors could be designed; such a structure-based project is underway. Computer programs such as DOCK, GRID, SYBYL, and CHEMX have been used to map the ricin A-chain binding site and to search for potential inhibitors. Inhibitor candidates can be assayed kinetically in a protein synthesis assay and binding can be observed crystallographically. Taken together, a workable search algorithm has been developed and initial tests indicate that at least one ricin A-chain inhibitor, pteroic acid, has been identified.

Animals↗
PubMedDate not supplied

Traditional Chinese medicine database and application on the Web.

To study traditional Chinese medicines and exchange related information through the worldwide Web, we developed a traditional Chinese medicine database and a program for searching and displaying data in the database on the Web. In this paper, the traditional Chinese medicine database is briefly introduced; the methods used in developing the program, including ISAPI (Microsoft Internet Server Application Programming Interface), VRML (Virtual Reality Model Language), and JavaScript are described; and three application examples are also given.

Databases, Factual↗
PubMedDate not supplied

Concept design of computer-aided study on traditional Chinese drugs.

Traditional Chinese drugs (TCDs) have played a key role for Chinese people in the treatment of diseases since ancient times. The use of TCDs has generated a great amount of information in the past thousand years about the relationship between natural products and the human body. However, up to now, our understanding on the mode of action of the TCD is still limited. Considering that the basic mechanism of all drug function involves the interaction between the drug and biological receptors at the molecular level, we propose to connect TCDs with modern medicine theory through molecular structures. We propose to explain functions of TCDs by using the knowledge developed in modern molecular biology, pharmacology, computer chemistry, and biochemistry. We are working on a computer-aided Chinese drug study that is discussed in this paper. A short introduction on the progress of our research is also given.

Artificial Intelligence↗
PubMedDate not supplied

[Cloning, sequence analysis and heterologous expression of a beta-mannanase gene from Bacillus subtilis Z-2].

Mannanase, an extracellular enzyme catalyzes the hydrolysis of hemicelluloses to produce oligosaccharides, has a potential to be applied in food industries. In this study, a mannanase gene from B. subtilis Z-2 was isolated through PCR screening of a genomic DNA library. The nucleotide sequence of the mannanase gene, man, contained an open reading frame of 1.080 bp, which codes for a deduced 26 amino-acid signal peptide and a mature protein with the deduced molecular mass of 38 KDa. The man gene can both be expressed heterologously into the periplasm in plasmid pET22b(+) containing intact signal peptide (pET-NdeI18) and the pelB signal peptide of the pET22b(+)vector (pET-NcoI3). The Escherichia coli BL21 (DE3) containing pET-NcoI3 secreted about twice as much mannanase as that harboring pET-NdeI18. In E. coli DH5alpha, expression of man was under the control of the lac promoter in the pRK415 vector and was much more effective when the Shine-Dalgamo (SD) sequence was changed from GGGGAG to AAGGAG and the start codon was changed from TTG to ATG, respectively. These results suggest that genetic modification of the SD sequence and start codon is practical for high-level expression of mannanase in different bacterial strains.

Bacillus subtilis↗