China 
Africa 
Explore chapters and articles related to this topic
Cell Line Development
Published in Wei-Shou Hu, Cell Culture Bioprocess Engineering, 2020
Selectable markers fall into two categories: dominant and recessive (Panel 6.10). A recessive marker resides in cells with a particular genetic background and causes a growth deficiency. The introduction of a compensatory gene leads to overcoming the deficiency. For example, cells without a functional dihydrofolate reductase (DHFR) gene will require the additional supplementation of thymidine and glycine in the culture medium for growth. The introduction of a functional DHFR enables them to grow without the supplements. Therefore, after the transfection of a plasmid containing DHFR, only the transfectants that express the newly acquired DHFR will grow in the absence of thymidine/glycine. Similarly, thymidine kinase (TK)-defective mutants require thymidine to be included to the culture medium. The introduction of a functional TK gene allows for cell growth in the absence of thymidine. Conversely, the presence of a dominant selectable marker is protective to the cell under selective conditions. By introducing the selectable gene to the cell, the cell is endowed with a resistance to a given lethal condition.
Glossary of scientific and technical terms in bioengineering and biological engineering
Published in Megh R. Goyal, Scientific and Technical Terms in Bioengineering and Biological Engineering, 2018
Thymidine kinase (tk) is an enzyme that allows a cell to utilize an alternate metabolic pathway for incorporating thymidine into DNA. It is used as a selectable marker to identify transfected eukaryotic cells.
Evaluation of the carcinogenicity of carbon tetrachloride
Published in Journal of Toxicology and Environmental Health, Part B, 2023
Samuel M. Cohen, Christopher Bevan, Bhaskar Gollapudi, James E. Klaunig
In strain A mice dosed with 2550 mg/kg of CCl4 in olive oil, necrosis was detectable in half the hepatocytes at 24 hr and mitotic activity appeared 48 hr after dosing (Eschenbrenner and Miller 1946). Wistar rats treated with 5 ml/kg (7,970 mg/kg) exhibited peak ALT levels at 24 hr, peak AST levels at 48 hr, and significantly elevated levels for activities of DNA-synthesizing enzymes thymidine kinase and thymidylate synthetase at 48 and 72 hr (Nakata et al. 1985). Activity of these DNA-synthesizing enzymes were reduced 96 hr after treatment. Doolittle, Muller, and Scribner (1987) examined the relationship between hepatic toxicity induced by CCl4 and DNA synthesis in the liver of male CD-1 mice. Mice were dosed by gavage with CCl4 at a dose of 20 or 25 mg/kg for either one day (25 mg/kg) or daily for 7 days (20 mg/kg). A single dose of CCl4 at 25 mg/kg did not markedly alter DNA replication, or activities of AST and ALT. However, treatment with 20 mg/kg CCl4 daily for 7 days produced a 10-fold increase in hepatocyte replication as well as the levels of liver enzymes (AST, ALT). Data indicate that induction of replicative DNA synthesis in liver after CCl4 treatment is a consequence of hepatotoxicity.
Biosynthesis, antimicrobial spectra and applications of silver nanoparticles: current progress and future prospects
Published in Inorganic and Nano-Metal Chemistry, 2022
Nimisha Tehri, Amit Vashishth, Anjum Gahlaut, Vikas Hooda
Viruses also constitute one of the important microbial group that are known to cause numerous diseases in different life forms. Till date, only a fewer no. of studies have focused on evaluating the antiviral activity of biosynthesized silver nanoparticles. The biosynthesized silver nanoparticles of a marine actinomycete, Nocardiopsis alba have been reported to show significant antiviral activity against new castle viral disease (NDV) of cattle.[136] Recently, plant mediated synthesis of spherical silver nanoparticles from the aqueous and hexane extracts of Lampranthus coccineus and Malephora lutea have shown significant antiviral activity against HAV-10 virus, HSV-1 virus, and CoxB4 virus. In this study, molecular docking of extracts predicted the patterns of interactions between identified compounds of both plant extarcts with hepatitis A 3c proteinase, herpes simplex thymidine kinase and Coxsackievirus B4 3c protease indicating the potential antiviral activity of aqueous and nano-extract.[137]
Genetic toxicity assessment using liver cell models: past, present, and future
Published in Journal of Toxicology and Environmental Health, Part B, 2020
Xiaoqing Guo, Ji-Eun Seo, Xilin Li, Nan Mei
Genetic damage is considered an important underlying mechanism for toxicity, specifically for the carcinogenicity of chemical substances. Currently, genotoxicity is evaluated using a battery of short-term genetic toxicity tests that are recommended by several international authoritative organizations, such as the Organization for Economic Co-operation and Development (OECD) and International Council for Harmonization (ICH, formerly the International Conference on Harmonization) (ICH 2015; OECD 2015). According to the ICH S2(R1) Guideline, the standard genotoxicity test battery includes two equally acceptable options. Option 1 consists of a gene mutation test in bacteria (the Ames test), a cytogenetic test for chromosomal damage [the in vitro micronucleus (MNvit) assay or chromosomal aberration (CA) assay] or the mouse lymphoma Thymidine kinase (Tk) gene mutation assay, and an in vivo chromosomal damage test using rodent hematopoietic cells. Option 2 includes the Ames test and two in vivo tests in two different tissues, usually a micronucleus (MN) assay using rodent hematopoietic cells and a DNA strand breakage assay (the Comet assay) in the liver (ICH 2011). These assays play a significant role in assessing the safety of various products such as industrial chemicals, prescribed human drugs, cigarettes, and cosmetics.