GeneDn: for high-level expression design of heterologous genes in a prokaryotic system.

RESULTS: Based on the mathematical model of high-level expression of heterologous genes in prokaryotic vector pBV220, we developed a program GeneDn for high-level expression design of natural and synthetic genes. AVAILIBILITY: The program is written in Turbo Pascal 7.0. The source code and related material are available upon request. CONTACT: wujj@nic.bmi.ac.cn

Discovery of extracellular multiple form of Chlamydia trachomatis in the tissue culture.

A strain of Chlamydia trachomatis was isolated from a patient with nongonococcal urethritis (NGU). Alternate passages between chick embryo and McCoy cell culture were examined. From the Giemsa stained coverslips taken from the cell culture 96 hours after inoculation, we found, to our surprise, that elementary bodies (EBs) distributed over a large area, and several intact cells embedded in them. These pure EB particles are round, fairly uniform in size and often appeared in pair. According to their morphology, distribution, arrangement and relationship with host cells, they are not the remains after cell lysis or directly released from host cells. We considered that they consisted of EBs which continued to divide by binary fission after their release. The name "Extracellular Multiply Form" was designated and their formation mechanism was proposed. This discovery gives a great challenge to primary theory, i.e. Chlamydias are obligate intracellular prokaryotic parasites. If we can further reveal the law of their formation, it will be of great significance both theoretically and practically.

Expression of N-ras gene in human primary hepatocarcinoma.

Poly(A)+ RNA was isolated from 9 specimens of human primary hepatic carcinoma, 1 non-tumorous liver tissue adjacent to cancer and 1 normal liver tissue samples. The Oligo-dT cellulose-purified poly(A)+ RNAs were subjected to formaldehyde agarose gel electrophoresis, Northern transfer and hybridization with various oncogene probes. Two RNA species, 5.6 kb and 2.2 kb were identified by N-ras gene hybridization in 6 out of 9 mRNA samples from primary hepatic carcinoma specimen. N-ras specific mRNA was not detectable in mRNA samples from normal human liver and tumor surrounding cirrhotic tissue. No detectable hybridization of mRNA from hepatoma and normal liver with Ki-ras or Ha-ras was observed. As human N-ras gene has been identified in DNA of mouse transfectants transformed with PHC DNA, it strongly suggests that N-ras gene might be responsible for the transforming activity of part of cases of human liver cancer.