Heterologous expression of rat testis GABA_A receptor P3t variant in Chinese hamster ovary cells

Aim: To study the characteristics and possible retention function of specific sequence in the 5'-end of rat testis GABAA receptor β 3t variant. Methods: Rat testis GABAA receptor β 3t variant cDNA was cloned and inserted into two eukaryotic expression vectors of pEGFP-Nl and pEGFP-Cl respectively, which have EGFP reporter gene. The recombinant plasmids were transfected into Chinese hamster ovary (CHO) cells with the calcium phosphate co-precipitation method. Fluorescence microscope and laser confocal microscope were used to analyze the transfected cells. ConA-Texas-Red was used to label cell endoplasmic reticulum (ER) and study the located area of rat testis β 3t variant in the CHO cells. Results: When the rat testis β 3t variant express in CHO cells, there were two expression pattern, the even and the concentrated expression pattern. Although rat brain β 3 can reach cell membrane, the rat testis β 3t variant can't target to the cell membrane. It may be retained in the ER of CHO cells. Conclusion: There may exist an ER retention signal in the 25 specific amino acid sequence in the N terminal of rat testis β 3t variant.

A Study on Antitoxic Role of Vesicular Monoamine Transporter 2 in Transgenic Chinese Hamster Overy Cells

Objective : To study the antitoxic role of vesicular monoamine transporter 2 (VMAT2) in transgenic Chinese Hamster ovary (CHO) cell. Methods :With the technology of trans-gene from PC 12 to CHO, MTT reduction assay was used to detect MPP+ toxic effect on wild type CHO (wtCHO) and transgenic CHO. Meanwhile, the role of reserpine was also observed in MPP+ toxic effects. Results :The sensitivity of transgenic CHO to MPP+ was much less than that of wtCHO with 0. 5 mmol/L MPP+. Transgenic CHO had the same sensitivity as wtCHO if rotenone was given. WtCHO, by given reserpine alone, didn't change its sensitivity to MPP+. Conclusions :VMAT2 has protective effect on transgenic CHO by transporting MPP+ to vesicles.

Effect of Matrine on Human Ether à go-go Related Gene (HERG) Channels Expressed in Chinese Hamster Ovary Cells

Objective： To observe the effect of matrine on human ether à go-go related gene （HERG） potassium channels expressed in Chinese hamster ovary （CHO） cells and investigate whether HERG channel is a new target of the pharmacological effect of matrine on arrhythmia and tumor. Methods： HERG channel potassium current in CHO cell was recorded using whole-cell patch-clamp technique, and the influence of matrine on the current was explored. Results： Matrine inhibited HERG potassium current in a dose-dependent manner, and the 50% inhibitory concentration （IC50） was 411±23 μmol/L. Matrine had no significant effect on the activation kinetics, and mainly blocked HERG channels in their closed state. Conclusions： The blocking effect of matrine on HERG channels might be one of the mechanisms against arrythmias and tumors. Unlike most other blockers exerting blocking effect at the intracellular sites by entering the cell with the opening of HERG channel, matrine blocked HERG channels at the extracellular sites.

Cytotoxicity of six copper-bearing intrauterine devices on Chinese hamster ovary cells: the influence of frame, shape and copper surface area

Objective To evaluate the cytotoxicity of six commonly used copper-bearing intrauterine devices （Cu-IUDs） on Chinese hamster ovary （CHO-K1） cells and to investigate the influence of frame, shape and copper surface area of Cu-IUDs on cell toxicity.Methods Cu-IUDs were incubated in 10% FBS-DMEM/F12 culture medium at 37 ℃ for 24 h. The extracts were analyzed by flame atomic absorption spectrometer and were then diluted into different concentrations with culture medium. Finally, cytotoxicity of these original and diluted extracts on CHO-K1 cells was detected by cell counting kit-8 （CCK-8） assay.Results The viabilities of cells treated with the original extracts of six Cu-IUDs （TCu220C bulb, TCu220C, GCu220, GCu300, Yuangong Cu270 and Yuangong Ⅱ- 300） were all below 10% and the cupric ion concentrations in these extracts were 28.22 mg/L, 31.80 mg/L, 92.80 mg/L, 99.74 mg/L, 114.90 mg/L and 119.20 mg/L, respectively. After these original extracts were diluted, significant differences in cytotoxicity were exhibited. IUDs with larger copper surface areas （GCu300 and Yuangong Ⅱ-300） showed more cytotoxicity than those with smaller areas （GCu220 and Yuangong Cu270） respectively; When different shapes of Cu-IUDs were compared, TCu220C bulb showed lower cytotoxicity than TCu220C, and GCu300 exhibited higher toxicity than Yuangong Ⅱ-300; TCu220C displayed significantly lower cytotoxicity than GCu220 due to their differences in frames.Conclusion We presented evidence on the cytotoxic effects of copper ions released from Cu-IUDs on CHO-K1 cells and found that shape, frame together with copper surface area of Cu-IUDs had obvious influence on the cytotoxicity.

THINDOWN IN RADIOBIOLOGY：E．COLI B／r，Bs－1，B．SUBTILUS SPORES，AND V－79 CHINESE HAMSTER CELLS

Track theory rested on the foundation of the radial distribution of dose from δ rays as the central contribution of atomic physics to heavy ion radiobiology.Here,a new calculation of the radial distribution of dose is applied, in which the classical angular distribution of dose of delta rays and a logarithmic polynomial representation of the electron range-energy relation are used,to form the basis of the present thindown calculation.Calculations of inactivation cross sections for heavy ions in the track width regime displaying thindown for E.Colt B/r and Bs-1,and for Bacillus Subtilus are straightforward for these are 1-hit detectors,Calculations for V-79 hamster cells are more complex.They follow the original development of this model for eucaryotic cells,and make use of the cross sections calculated for hypothetical internal targets which are then asserted to be proportional to the measured cellular inactivation cross sections.The results are in reasonable agreement with experimental data.

Detection and quantitation of host cell proteins in monoclonal antibody drug products using automated sample preparation and data-independent acquisition LC-MS/MS

Ensuring the removal of host cell proteins(HCPs) during downstream processing of recombinant proteins such as monoclonal antibodies(m Abs) remains a challenge.Since residual HCPs might affect product stability or safety,constant monitoring is required to demonstrate their removal to be below the regulatory accepted level of 100 ng/mg.The current standard analytical approach for this procedure is based on ELISA;however,this approach only measures the overall HCP content.Therefore,the use of orthogonal methods,such as liquid chromatography-mass spectrometry(LC-MS),has been established,as it facilitates the quantitation of total HCPs as well as the identification and quantitation of the individual HCPs present.In the present study,a workflow for HCP detection and quantitation using an automated magnetic bead-based sample preparation,in combination with a data-independent acquisition(DIA) LC-MS analysis,was established.Employing the same instrumental setup commonly used for peptide mapping analysis of m Abs allows for its quick and easy implementation into pre-existing workflows,avoiding the need for dedicated instrumentation or personnel.Thereby,quantitation of HCPs over a broad dynamic range was enabled to allow monitoring of problematic HCPs or to track changes upon altered bioprocessing conditions.

Synthesis of Novel Hydrophobic Media and Purification of Recombinant HBsAg

A novel hydrophobic medium with propyl as functional group and Sepharose 6B as matrix was designed and synthesized. The comparison of the hydrophobic medium synthesized with the commercial products was made by hydrophobic interaction chromatography(HIC) in isolating recombinant hepatitis B surface antigen(r HBsAg). r HBsAg was further purified to the final products by following a downstream procedure . The results indicate that the synthesized hydrophobic medium possesses a stable structure and desired physical and chemical properties. They were used to purify r HBsAg with a high yield and purity. Both the immunity and stability of hepatitis vaccine made by the r HBsAg products have reached the same level as other similar kinds of products.

Expression of Porcine Growth Hormone Gene in CHO Cell

An expressive plasmid pSMTPCH was constructed from porcine growth hormone gene,sheep metallothionein promoter (MT-011)and the vector,pUC19. The linear pSMTPGH and circular pSV2-dhfr were cotransfected into CHO-dhfr cell by calcium phosphate coprecipitation. Positive clones made up 74% of total clones, which were identified with ELISA. The expression of pSMTPGH was induced by 0.5 μM of Cd￣++. The clone 1-C-3 was found to secrete hGH at the level of 3800 μg/10￣6 cells/24 hrs in media containing 10 μMTX. After 20 generations in culture, the clone was still stable with hGH expression.The molecular weight of secreted protein was the same as that of the natural pGH, 22KD;the identity was further supported by Western blot.

High-level expression of recombinant IgG1 by CHO K1 platform

The Chinese Hamster Ovary （CHO K1） cell was used to express a targeted anti-cancer monoclonal antibody by optimizing the platform of the construction of production cell line in this study. The adherent CHO K1 was first adapted to suspension culture in chemical defined medium. Then the glutamine synthetase （GS） vector was applied to construct a single plasmid to overexpress a monoclonal antibody IgG1. Post transfection, the produc- tion of cell pool was optimized by glutamine-free selection and amplification using various concentrations of methio- nine sulfoximine. The best cell pool ofCHO K1/IgG1 was used to screen the top single clone using the limiting dilution cloning. Finally, a high IgG1 production of 780 mg/L was obtained from a batch culture. This study demonstrated that the construction of high producing cell line, from gene to clone, could be completed within six month and the gene amplification improved protein production greatly.