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Immunocompetence in Invertebrates
Published in C. S. Giam, Lee E. Ray, Pollutant Studies in Marine Animals, 2018
The effects of HCB and PCP on components of the defense system of a polychaete, G. dibranchiata, were also determined. Although both pollutants were markedly concentrated in the tissues, the levels reached in these studies produced no mortality or morbidity. Certain parameters (in vitro phagocytosis by amebocytes, total and differential coelomocyte counts, hemolysin, hemagglutinin, and bacterial agglutinin activity) were not affected. However, the activity of a bactericidal glycoprotein was consistently induced in PCP- or HCB-exposed Glycera. Release of this factor from coelomocytes may be increased by a mechanism similar to that of macrophage activation, a characteristic of the leukocytes of higher animals. Exposure to PCP caused an apparent reduction in the numbers of amebocytes capable of forming rosettes with formaldehyde-treated rabbit erythrocytes. This was interpreted as an impairment in the ability of the cells to recognize foreign material, a process required for the normal functioning of these potentially protective blood phagocytes.
Xenobiotic metabolism and transport in Caenorhabditis elegans
Published in Journal of Toxicology and Environmental Health, Part B, 2021
Jessica H. Hartman, Samuel J. Widmayer, Christina M. Bergemann, Dillon E. King, Katherine S. Morton, Riccardo F. Romersi, Laura E. Jameson, Maxwell C. K. Leung, Erik C. Andersen, Stefan Taubert, Joel N. Meyer
C. elegans might also be exposed to xenobiotic compounds through ingestion. C. elegans feeds on microbes in the lab, either bacterial lawns or suspension in liquid cultures, through pharyngeal pumping. The pharynx is the neuromuscular pump that connects the mouth to the intestine and contracts and relaxes in order to take in bacteria and expel liquids (Avery and You 2012). The pharynx is lined with a specialized cuticle that helps to form structural elements of the pharynx such as the flaps, sieve, and the grinder, all of which are necessary for initial processing as well as transport of food to the intestine, and protection against diffusion of compounds in the pharynx (Page 2007; Altun and Hall 2009a). The pharyngeal cuticle and the pumping mechanism that expels liquids might serve as a protective barrier from xenobiotic uptake. However, xenobiotics that are bound to or taken up by bacterial food source would still be ingested by the worm. For chemicals that make their way into the intestine, uptake through epithelial cells lining the intestine might occur, as well as transport and trafficking to other locations in the organism. The intestine exhibits high expression of P-glycoproteins, involved in trafficking hydrophobic molecules, as well as cytochrome P450s, metallothioneins, and other phase I–III enzymes (McGhee 2013). It is important to note the availability and uptake of xenobiotics in the intestine varies by physicochemical properties and the chemical properties of the gut. As previously noted, membrane permeability to these compounds in the gut is determined by chemical structure, pKa, and pH of the environment (Casarett, Doull, and Klaassen 2008). Alterations in the C. elegans diet and microbiome also lead to changes in intestine pH or metabolites, which might alter the availability of certain compounds (Höss, Schlottmann, and Traunspurger 2011). Other cell types may also play specialized roles; for example, the six coelomocytes are macrophage-like cells that occupy the body cavity, are highly endocytotic, and may, similar to intestinal cells, play a “liver-like” role. Investigators demonstrated their importance in metal detoxification via endocytosis and metal transport and binding proteins (Maurer et al. 2016; Schwartz et al. 2010; Tang et al. 2020).