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Depigmenting Agents
Published in Vineet Relhan, Vijay Kumar Garg, Sneha Ghunawat, Khushbu Mahajan, Comprehensive Textbook on Vitiligo, 2020
Vaccines using melanoma-associated antigen were reported by many authors to produce depigmentation by eliciting an autoimmune response directed against malignant but also normal melanocytes. 4-(p-hydroxyphenyl)-2-butanone and 4-n-butylresorcinol not only inhibit tyrosinase but also act as cytotoxic agents as they are oxidized to their quinonic forms, leading to a double effect. Hydroquinone in higher concentrations of more than 4%, IFN-gamma, and alkylating agent busulfan should be further investigated as topical depigmenting agents for use in human beings with vitiligo universalis. Some compounds like N-acetyl-4-S-cysteaminylphenol, N-2,4-acetoxyphenyl thioethyl acetamide, and N-hydroxycinnamoyl-phenalkylamides have been proposed as anti-melanoma drugs as well as for use as hypopigmenting agents. Ethanolic extracts of Myrica rubra dried leaves have shown good depigmenting effects in vitro and pseudo superoxide dismutase activity. They contain quercetin, myricetin, and some 3-O-rhamnoside derivatives. In vivo studies have been recommended to evaluate their potential use as depigmenting agents [39]. Taking into consideration recent findings on the possible role of immune adjuvants such as imiquimod, CpG oligonucleotides, and heat shock proteins in melanocyte destruction, supplementing the depigmenting effect of MBEH with such adjuvants has been suggested [40].
Sampling Techniques
Published in Jacques Derek Charlwood, The Ecology of Malaria Vectors, 2019
It has been used as a control tool against A. funestus on Rusinga Island, western Kenya, where it reduced transmission of malaria transmitted by A. funestus but was less effective against A. gambiae or A. arabiensis (Homan et al., 2016). A 12-volt battery drives a fan that sucks mosquitoes up through a tube with a 10 cm diameter opening into a collection bag. Netting can be placed between the tube and the fan so that collected mosquitoes are not damaged when caught. A non-return gate, that is activated when the fan is switched off, or when the tube is removed, means that under these circumstances the tube acts as a collection cage. The remainder of the base of the trap is perforated with numerous small holes through which the attractant is blown. There is also the possibility of adding carbon dioxide to the trap via an external source connected with a tube to an outlet in the trap. In the absence of gaseous carbon dioxide or dry ice, carbon dioxide can be generated using a sugar and yeast mixture in 2l of water in a 5l plastic bottle (Smallegange et al., 2010). In the trial in Rusinga Island, 2-butanone was included as a substitute for carbon dioxide. The trap is placed approximately 30 cms off the ground in places where mosquitoes might be expected to be present (Figure 13.6). In the trial in Rusinga Island the traps were suspended close to houses, and the battery was recharged by a solar panel supplied to householders (Homan et al., 2016).
Early Detection of Chronic Obstructive Pulmonary Disease: Influence on Lung Cancer Epidemiology
Published in Ayman El-Baz, Jasjit S. Suri, Lung Imaging and CADx, 2019
Amany F. Elbehairy, Ahmed Sadaka
Tobacco smoke contains over 4,000 chemicals, of which more than 70 are known to cause, initiate, or promote cancer and are called carcinogens. Of these, polycyclic aromatic hydrocarbons and the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone are likely to play major roles. COPD involves destruction of the lung parenchyma and airway inflammation, causing emphysema and chronic bronchitis, respectively. This invariably results in chronic airflow limitation, a hallmark feature of the disease. This not only is manifest as air trapping and poor clearance of secretions but also leads to chronic retention of airborne carcinogens. Persistent exposure to these carcinogens will create a continuous stimulus for the airway epithelial to undergo mesenchymal transformation and bronchoalveolar stem cell stimulation, which are two central components of the carcinogenesis process [21].
Employing in vitro metabolism to guide design of F-labelled PET probes of novel α-synuclein binding bifunctional compounds
Published in Xenobiotica, 2021
Chukwunonso K. Nwabufo, Omozojie P. Aigbogun, Kevin J.H Allen, Madeline N. Owens, Jeremy S. Lee, Christopher P. Phenix, Ed S. Krol
Furthermore, previous studies suggest that nicotine and some of its metabolites (such as cotinine) have neurotherapeutic effects for Parkinson’s disease (Barreto et al. 2014). This suggests that M4 may have similar neuroprotective effect as the parent compound (C8-6-N). More so, 2′-hydroxylation of nicotine is an important step in the formation of 4-(methylamino)-1-(3- pyridyl)-1-butanone, 4-oxo-4-(3-pyridyl) butanoic acid and 4-hydroxy-4-(3-pyridyl) butanoic acid (Hecht et al. 2000); however, this is a minor pathway in nicotine metabolism. In fact, this pathway is toxicologically significant since 4-(methylamino)-1-(3- pyridyl)-1-butanone can be biotransformed to carcinogenic 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) (Benowitz et al. 2009). Fortunately, this pathway was not observed in the biotransformation of C8-6-N in HLM, RLM, and MLM.
Toluene and methylethylketone: effect of combined exposure on their metabolism in rat
Published in Xenobiotica, 2018
Frédéric Cosnier, Hervé Nunge, Élodie Bonfanti, Stéphane Grossmann, Anne-Marie Lambert-Xollin, Samuel Muller, Sylvie Sébillaud, Aurélie Thomas, Laurent Gaté, Pierre Campo
Recently, interactions between TOL and methylethylketone (MEK) (also known as butanone), a presumed nontoxic (or low-toxic) solvent used in large amounts in factories (8 h-OEL = 200 ppm = 600 mg/m3), were highlighted as potentially leading to differences between blood concentrations of the parent compounds and levels of their metabolites excreted in urine (Cosnier et al., 2014). This observation was of concern because these solvents are frequently used together in industry. Indeed, according to the COLCHIC database (Mater et al., 2016), 9473 individual measurements of TOL were performed in 1209 companies in France between 2005 and 2014. Of these measurements, 64% revealed a multiple exposure context, and the TOL/MEK mixture was present in almost 44% of companies. Statistical analysis of long-term measurements in manufacturing industry (which covers the vast majority of measurements) revealed that the 8 h-OEL for TOL and MEK were exceeded in 3.3% and 0.6% of cases, respectively, with peaks exceeding 1400 ppm in both cases.
Metabolism of inhaled methylethylketone in rats
Published in Drug and Chemical Toxicology, 2018
Frédéric Cosnier, Stéphane Grossmann, Hervé Nunge, Céline Brochard, Samuel Muller, Anne-Marie Lambert-Xolin, Sylvie Sebillaud, Benoît Rieger, Aurélie Thomas, Marie-Josèphe Décret, Manuella Burgart, Laurent Gaté, Benoît Cossec, Pierre Campo
Methylethylketone (MEK) (or 2-butanone) (CAS no. 78-93-3) is commonly used as a solvent in the manufacture of adhesives and coatings (especially vinyl, nitrocellulose and acrylic), dewaxing agents of mineral oils, and extraction agents for foodstuffs, and also as a synthesis intermediate (INRS, 2009). In these contexts, it is often associated with other substances (Yoshikawa et al., 1995). MEK exposure alone shows low acute and subchronic toxicity but, when combined with other substances, it can make the other chemicals harmful (ATSDR, 1992; INRS, 2009; Yang, 1986). Indeed, it has been demonstrated that MEK potentiates the hepatotoxic effects of carbon tetrachloride (Dietz & Traiger, 1979), and the neurotoxicity of ethanol, n-hexane, ethyl-n-butyl ketone (EnBK) and methyl-n-butyl ketone (MnBK) (Noraberg & Arlien-Soborg, 2000; O'Donoghue et al., 1984; Yang, 1986).