Gastrointestinal tract capacity

Delivery of peptides and proteins via the gastrointestinal tract has not been successful because of poor penetration through the intestinal epithelium and high levels of proteolytic activity in the gastrointestinal tract. Liposomal encapsulation of proteins and peptides will not improve the efficiency and capacity of this absorption pathway considerably (e.g., Ryman et al., 1982 Machy and Leserman, 1987 Weiner and Chia-Ming Chiang, 1988). These difficulties in delivery via the oral route caused the parenteral route to remain the preferred route for the administration of therapeutic peptides... 

Only a subset of the parameter values in the O Flaherfy model require inputs from the user to simulate blood and tissue lead concentrations. Lead-related parameters for which values can be entered into the model include fractional absorption from the gastrointestinal tract partition coefficients for lead in nonbone tissues and in the surface region of bone maximum capacity and half-saturation concentration for capacity-limited binding in the erythrocyte elimination clearance fractional clearance of lead from plasma into forming bone and the restricted permeability coefficients for lead diffusion within bone, from plasma into bone, and from bone into plasma (O Flaherty 1991a). 

As regards respiratory apparatus, intoxication is manifested in the development of catarrh of upper air passages and bronchitis with dyspnea, but more often damage is limited to impaired vital capacity of lungs. Affection of gastrointestinal tract is manifested in gastritis and chronic colitis. 

Tolazoline is a weak, reversible a-adrenoblocker that lowers resistance of peripheral blood vessels and elevates venous capacity. However, it also exhibits 8-adrenomimetic activity, which consists of the stimulation of cardiac work and is manifest as tachycardia, chohn-ergic activity, which consists of stimulation of the gastrointestinal tract, and histamine-Uke activity, which consists of stimulation of gastric secretion. 

Absorption of a mycotoxin will occur when it crosses body membranes and enters the blood stream. The primary sites of mycotoxin absorption are the gastrointestinal tract (ingestion of contaminated food), lungs (inhalation of contaminated particles or toxin-containing fungal spores) and the skin (direct contact with contaminated materials or pure mycotoxins). When the mycotoxin enters the blood it is then available for distribution. Livers and kidneys have a high capacity to bind many mycotoxins while other mycotoxins are highly lipophilic and can concentrate in body fat. In the final outcome a toxic response by a mycotoxin will be critically influenced by the rate of absorption, distribution, biotransformation and excretion (Smith et al., 1994). 

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