Gastrointestinal microbial

Effect of feed type on the gastrointestinal microbial ecosystem... 

Dogs, because of their relatively small gastrointestinal microbial population, are resistant to nitrate poisoning. The horse may succumb to nitrate poisoning because of the presence of microorganisms in the cecum in its posterior digestive tract. However, by the time nitrate reaches the cecum, more than 70% will have been absorbed little will be available for biotransformation into the toxic nitrite ion. Horses, therefore, require threefold higher nitrate concentrations to be poisoned than do cattle. 

An array of model systems of the gastrointestinal microbial environment of varying degrees of complexity have been developed and validated in recent years (Rumney and Rowland 1992 Molly et al. 1994). Such models, based around continuous flow culture, enable us to look at the human gut microflora under laboratory conditions and investigate such microflora-associated activities as fermentation of dietary constituents (e.g. dietary fibre, proteins and prebiotics). These models of the colonic microllora are invaluable in the development of efficacious or novel prebiotics. They may also be useful in conducting initial studies on the effect of antibiotics on the complex gut microllora and in DNA transfer studies between members of the gut microflora and genetically modified foods (Tuohy et al. 2002 Payne etal. 2003). 

Opapeju, F.O., D.O. Krause, R.L. Payne, M. Rademacher and C.M. Nyachoti, 2009. Effect of dietary protein level on growth performance, indicators of enteric health, and gastrointestinal microbial ecology of weaned pigs induced with postweaning colibacillosis. J. Anim. Sci. 87,2635-2643. 

This occurs in the seromucous secretions such as saliva, tears, nasal secretions, sweat, colostrum and secretions of the lung, urinogenital and gastrointestinal tracts. Its purpose appears to be to protect the external surfaces of the body from microbial attack. It occurs as a dimer in these secretions but as a monomer in human plasma, where its function is not known. The function of IgA appears to be to prevent the adherence of microorganisms to the surface ofmucosal cells thus preventing them entering the body tissues. It is protected from proteolysis by combination with another protein—the secretory component. 

It has recently been shown (14) that nitrate from food can be detected in the feces of germfree animals but not in the feces of conventional animals. This result and the results of Witter et al. (18-20) suggest that nitrate is available in the lower gastrointestinal tract and is metabolized by the microbial flora. The intestine may thus be a site for the endogenous formation of N-nitroso compounds. 

Savage DC Microbial ecology of the gastrointestinal tract. Annu Rev Microbiol 1977 31 107-133. 

Hill M Normal and pathological microbial flora of the upper gastrointestinal tract. Scand J Gastroenterol Suppl 1985 111 1-6. 

The studies on phospholipid bilayers with defined amounts of charged component are helpful to explain the partition characteristics in biological membranes. Liposome water partition data of propranolol in lipids from kidney epithelial cells (a common model system in pharmaceutical sciences for the uptake into the gastrointestinal tract) have been successfully described with partition models developed for pure bilayers or defined mixtures [159]. Since lipophilic cations and anions can be used as probes for the membrane potential, their interaction with microbial and mitochondrial membranes has been studied... 

Toxicology. Propionic acid is an irritant to skin, eyes, and mucous membranes. Propionic acid is a normal intermediary metabolite during the oxidation of fatty acids. It occurs ubiquitously in the gastrointestinal tract as an end product of microbial digestion of carbohydrates. It represents up to 4% of the normal total plasma fatty acids. ... 

Vitamin B12 consists of a porphyrin-like ring with a central cobalt atom attached to a nucleotide. Various organic groups may be covalently bound to the cobalt atom, forming different cobalamins. Deoxyadenosylcobalamin and methylcobalamin are the active forms of the vitamin in humans. Cyanocobalamin and hydroxocobalamin (both available for therapeutic use) and other cobalamins found in food sources are converted to the active forms. The ultimate source of vitamin Bi2 is from microbial synthesis the vitamin is not synthesized by animals or plants. The chief dietary source of vitamin Bi2 is microbially derived vitamin B12 in meat (especially liver), eggs, and dairy products. Vitamin Bi2 is sometimes called extrinsic factor to differentiate it from intrinsic factor, a protein normally secreted by the stomach that is required for gastrointestinal uptake of dietary vitamin B12. 

---