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Animals in agroecosystems
Published in Stephen R. Gliessman, V. Ernesto Méndez, Victor M. Izzo, Eric W. Engles, Andrew Gerlicz, Agroecology, 2023
Stephen R. Gliessman, V. Ernesto Méndez, Victor M. Izzo, Eric W. Engles, Andrew Gerlicz
The alimentary canal ends in the large intestine, which includes the colon, cecum, and rectum. The small intestine connects to the large intestine at a fork that goes one way to the colon—and then to the rectum and the anus for elimination of the final wastes of the digestive system—and the other way to the cecum. In animals that eat large amounts of plant matter, the cecum is important for fermenting ingested material before it can be fully digested. The size of the cecum varies from animal to animal; in humans it is a vestigial organ called the appendix. The major function of the colon is to recover water that entered the alimentary canal and served as the solvent for the digestive juices. On the average, almost 90% of the fluid secreted into the digestive system is reabsorbed in the small intestine and colon.
Improving the predictive value of bioaccessibility assays and their use to provide mechanistic insights into bioavailability for toxic metals/metalloids – A research prospectus
Published in Journal of Toxicology and Environmental Health, Part B, 2021
Jennifer L. Griggs, David J. Thomas, Rebecca Fry, Karen D. Bradham
In the case of SHIME ® studies, standardizing gut bacteria communities presents a unique challenge, because these highly diverse microbial communities are in flux until the system stabilizes as bacteria-generated metabolic byproducts become less variable over time. Selective pressures such as microbiota interactions, aging of the in vitro system, environmental conditions, competition for nutrients, and inability to culture select bacteria in the lab result in a fluctuating and evolving bacteria community (Justice et al. 2017) that has not been well-characterized despite common use of this in vitro system. Simply controlling the overall bacterial concentration and volume of the inoculum may not dampen the force of these selective pressures. Further research may enable researchers to characterize these pressures and their relationship with contaminant fate in the GI tract. In addition, fecal bacteria are primarily used to inoculate the system due to the ease of fecal collection. However, cecal bacteria may be a better representation of the bacteria colonizing the mammalian colon. The cecum is the site of bacteria propagation and metabolism of various nutrients by a different community of bacteria than the community characterized in feces (Gu et al. 2013; Marteau et al. 2001). Differences in microbial community structure between fecal and cecal sources may be reflected in differential dissolution and transformation of metals. Developing methods and coming to a consensus on the use of those methods enables researchers to achieve optimal inter- and intra-lab assay performance for all commonly used assays.