Human gastrointestinal tract

Rafii F, W Franklin, RH Hetlich, CE Cerniglia (1991) Reduction of nitroaromatic compounds by anaerobic bacteria isolated from the human gastrointestinal tract. Appl Environ Microbiol 51 962-968. 

Webb LM, Taylor DM, Williams DR. 1998. Computer modeling of the chemical speciation of lanthanide and actinide elements in the human gastrointestinal tract Mouth and stomach. Radiat Prot Dosim 79(l/4) 219-222. 

Food-grade or medicinal mineral oil, a mixture of aliphatic hydrocarbons that also may be found in mineral oil hydraulic fluids, is known to be absorbed only to a limited extent by the human gastrointestinal tract and has a laxative effect (Anonymous 1967 Brunton 1985), thus suggesting that mineral oil hydraulic fluids may behave likewise. 

Table 1 Approximate Lengths of Various Regions of the Human Gastrointestinal Tract... 

PE Warner, KLR Brouwer, EK Hussey, GE Dukes, WD Heizer, KH Donn, IM Davis, JR Powell. Sumatriptan absorption from different regions of the human gastrointestinal tract. Pharmaceut Res 12 138-143, 1995. 

The medium selected for the dissolution test must consider the drug solubility. Aqueous media with a typical plT range between 1 and 7 to mimic the human gastrointestinal tract are preferred over organic solvents. The operating parameters of the dissolution setting should be optimized to ensure complete dissolution. ... 

The structure of vitamin K is characterized by methylnaphthoquinone rings with a side chain at position 3. It exists naturally in two forms phylloquinone (vitamin Kt 6.13) occurs only in plants, while menaquinones (vitamin K2 6.14) are a family of compounds with a side chain consisting of between 1 and 14 isoprene units. Menaquinones are synthesized only by bacteria (which inhabit the human gastrointestinal tract and thus provide some of the vitamin K required by the body). Menadione (vitamin K3 6.15) is a synthetic compound with vitamin K activity. Unlike Kj and K2, menadione is water soluble and is not active until it is alkylated in vivo. 

The 1997 consultation addressed the topic of safety factors, which is vitally important for die protection of public health. Setting MRLs is in fact based on a series of assumptions. One assumption is that humans are at least as sensitive as the most sensitive laboratory animal to a potentially toxic residue. Another assumption is diat all the residues covered by the MRLs are as toxic as the parent substance. A third assumption is that residues free from the human gastrointestinal tract are all totally bioavailable. A fourth assumption is the safety factor used to infer an ADI from a NOEL, including the additional safety factor, generally with a value of 2, to establish a provisional ADI until further information is available to convert this into a definite ADI. Other assumptions are the overestimation of consumer exposure to drug residues and the reduction of MRL values to take account of normal conditions under which the veterinary drugs are administered. 

Rahle R, Huemmer W, Rempf M, Scheppach W, Erk T, Richling E. 2007. Polyphenols are intensively metabolized in the human gastrointestinal tract after apple juice consumption. J Agric Food Chem 55 10605-10614. 

Peppercorn MA, Goldman P. 1971. Caffeic acid metabolism by bacteria of the human gastrointestinal tract. J Bacteriol 108 996-1000. 

In 1960, Volkheimer [31] elegantly demonstrated resorption of starch from the human gastrointestinal tract and its appearance in blood and urine as early as 30-60 min after ingestion reaching peak concentrations after approximately 2 h. 

Maletskos CJ, Keane AT, Telles NC, et al. 1966. The metabolism of intravenously administered radium and thorium in human beings and the relative absorption from the human gastrointestinal tract. In Radium and mesothorium poisoning and dosimetry and instrumentation techniques in applied radioactivity. Cambridge, MA Massachusetts Institute of Technology, Physics Department, 202-317. MIT-952- 3. 

Using an in vitro model of the human gastrointestinal tract, it was found that TAC of jejunal dialyzates (subjected to enzymatic treatment equivalent to that encountered in the human stomach and jejunum) was the highest when green tea was introduced. When the green tea was mixed with whole milk or semiskimmed milk, TAC of the dialyzates decreased by about one half, and with skimmed milk by almost two thirds. Similar effects were noted for the black tea, but the initial TAC values were lower (K17). 

Netherwood, Trudy, Susana M. Martin-Orue, Anthony G. O Donnell, Sally Gockling, Julia Graham, John C. Mathers, and Harry J. Gilbert. 2004. Assessing the survival of transgenic plant DNA in the human gastrointestinal tract. Nature Biotechnology 22 204—209. 

Thorn M, Finnstrom N, Lundgren S, et al. Cytochromes P450 and MDR1 mRNA expression along the human gastrointestinal tract. Br J Clin Pharmacol 2005 60 54-60. 

Sabolovic N, Humbert AC, Radominska-Pandya A, et al. Resveratrol is efficiently glucuronidated by UDP-glucuronosyltransferases in the human gastrointestinal tract and in Caco-2 cells. Biopharm Drug Dispos 2006 27(4) 181—189. 

The purpose of this chapter is to document the nature of the enzyme barrier that macromolecular drugs will encounter during their passage down the human gastrointestinal tract. I will discuss the peptidases that digest peptides and proteins and the nucleases that will hydrolyse nucleic acids and also briefly consider other enzymes that may affect the behaviour of the newer generation of pharmaceutical formulations. It is very important to consider both the qualitative aspects of the problem, that is, the specificity of the digestive... 

Table 3.1 Biological and physical parameters of the human gastrointestinal tract. Adapted from Daugherty and Mrsny (1999)...

Most foods are heat processed prior to consumption. Although heat processing increases the availability of starch to enzyme, a fraction of starch remains resistant to amylase hydrolysis in the human gastrointestinal tract. This fraction is called resistant starch (RS). RS has been classified107 into three groups (a) RSI starch that is physically inaccessible to digestive enzymes due to enclosure in structures such as... 

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