China 
Africa 
Explore chapters and articles related to this topic
Alkylated Naphthalenes
Published in Leslie R. Rudnick, Lubricant Additives, 2017
The alkylating agents may be linear or branched olefins, alcohols, and alkyl halides. Often, alpha-olefins are used because the double bond is located at one terminus of the alkyl chain, which enhances the reactivity of the compound. Chain lengths of 6–16 carbons are commonly used because these produce high-molecular-weight products with low volatility and good viscometric properties.
Selection and Improvement of Industrial Organisms for Biotechnological Applications
Published in Nduka Okafor, Benedict C. Okeke, Modern Industrial Microbiology and Biotechnology, 2017
Nduka Okafor, Benedict C. Okeke
Some chemical mutagens, such as nitrous acid and nitrosoguanidine, work by causing chemical modifications of purine and pyrimidine bases that alter their hydrogen-bonding properties. For example, nitrous acid converts cytosine to uracil which then forms hydrogen bonds with adenine rather than guanine. These chemicals act on the non-dividing cell and include nitrous acid, alkylating agents, and nitrosoguanidine (NTG, also known as MNNG).Nitrous acid: This acid is rather harmless and the mutation can be easily performed by adding 0.1 to 0.2 M of sodium nitrate to a suspension of the cells in an acid medium several times. The acid is neutralized after suitable intervals by the addition of appropriate amounts of sodium hydroxide. The cells are plated out subsequently.Alkylating agents: These are compounds with one or more alkyl groups which can be transferred to DNA or other molecules. Many of them are known but the following have been routinely used as mutagens: EMS (ethyl methane sulfonate), EES (ethyl ethane sulfonate), and DES (Diethyl sulfonate). They are liquids and easy to handle. Cells are treated in solutions of about 1% concentration and allowed to react from ¼ hour to ½ hour, and thereafter are plated out. Experimentation has to be done to decide the amount of kill that will provide a suitable amount of mutation. While some are carcinostatic (i.e. stop cancers), some are carcinogenic and must be handled carefully.NTG—nitrosoguanidine: also known as 1-methyl-3-nitro-1-nitrosoguanidine— MNNG: It is one of the most potent mutagens known and should be handled with care. Amounts ranging from 0.1 to 3.0 mg/ml have been used, but for most mutations, the lower quantity is used. It is reported to induce mutation in closely linked genes. It is widely used in industrial microbiology.Nitrogen mustards: The most commonly used of this group of compounds is methyl- bis (Beta-chlorethyl) amine also referred to as ‘HN2’. Nitrogen mustards were used for chemical warfare in World War I. Other members of the group are ‘HN’, ‘HN1’, or ‘HN3’ from the wartime code name for mustard gas, H. The number after the H denotes the number of 2-chloroethyl groups which have replaced the methyl groups in tri-methylamine. A spore or cell suspension is made in HN2 (methyl-bis [Beta-chlorethyl amine]), and after exposure to various concentrations for about 30 minutes each, the reaction is ended by a decontaminating solution containing 0.7% NaHCO3 and 0.6% glycine. The solution is then plated out to identify survivors. Between 0.05 and 0.1% HN2 solutions in 2% sodium bicarbonate solutions have been found satisfactory for Streptomyces.
A male germ cell assay and supporting somatic cells: its application for the detection of phase specificity of genotoxins in vitro
Published in Journal of Toxicology and Environmental Health, Part B, 2020
Khaled Habas, Martin H. Brinkworth, Diana Anderson
Chemotherapy drugs such as alkylating agents affect male fertility via targeting the DNA of proliferative cells (Beaud, van Pelt, and Delbes 2017). Alkylating agents are a group of electrophilic compounds that are capable of affecting nucleophilic centers of DNA, leading to base mismatch within DNA replication and proteins (Friedberg et al. 2005). N-ethyl-N-nitrosourea (ENU) and N- methyl-N-nitrosourea (MNU) were reported to induce primarily mutations in spermatogonia (Russell, Hunsicker, and Russell 2007). O’Brien et al. (2014) noted that ENU induced a significant increase in the mutant frequency (MF) in spermatogonial stem cells. Wyrobek et al. (2007) showed that exposure to ENU induces single base-pair alterations and enhanced rates of apoptosis in spermatogonial cells. Sotomayor, Ehling, and Sega (1999) also found that spermatogonial cells display high mutational sensitivity to ENU and MNU. Ehling and Neuhauser-Klaus (1991) also demonstrated that the highest mutational yield was induced in differentiating spermatogonia after treated with MNU. Several investigations in germ cells from adult rodents found that isolated germ cells treatment with ENU and MNU exhibit the greatest response in spermatogonial stem cells in vitro (Habas, Anderson, and Brinkworth 2016; Habas, Brinkworth, and Anderson 2017c). The loss of sperm production is associated with rapidly dividing differentiating spermatogonia which are sensitive to lethality via many cytotoxic chemotherapeutic drugs than are the later stage male germ cells (Meistrich et al. 1982; Oakberg 1955). Spermatogonia are a mitotic component of spermatogenesis and the main male germ cell phase not protected by the blood testes barrier (BTB), suggesting that are most susceptible to genotoxins effects (Aslam et al. 2000). Wang et al. (2010), using Big Blue mice, reported that the spermatogonia were more sensitive to ENU induced mutagenesis than permatocytes, spermatids, and spermatozoa. Several investigators confirmed that spermatogonia were significantly more affected by hydrogen peroxide and doxorubicin than the spermatocytes and spermatids, respectively (Habas, Anderson, and Brinkworth 2014, 2017a). Exami-nation of the biology and molecular mechanisms of SSCs provides a better understanding of the reproductive biology of future gametes of spermatogonial stem cell regulation in the testis (Habas, Anderson, and Brinkworth 2017a).