Small intestine description

In order to determine the optimal number of compartments, literature information on small intestinal transit times was utilized. A total of over 400 human small intestinal transit time data were collected and compiled from various publications, since the small intestinal transit time is independent of dosage form, gender, age, body weight, and the presence of food [70]. Descriptive statistics showed that the mean small intestinal transit time was 199 min with a standard deviation of 78 min and a 95% confidence interval of 7 min. The data set was then analyzed by arranging the data into 14 classes, each with a width of 40 min. Figure 9 shows the distribution of this data set. 

Cauxin is markedly different from previously reported mammalian CESs in term of urinary excretion. Other mammalian CESs comprise multigene families, and CES isozymes are highly and ubiquitously expressed in tissues such as the brain, liver, kidney, lung, and small intestine (Satoh and Hosokawa 1998). Our work on cauxin was the first description of a carboxylesterase excreted in urine. 

A group of 28 male Fischer rats, seven weeks of age, was treated by gavage with a single dose of 35 mg/kg bw 1,2-dimethylhydrazine hydrochloride dissolved in 0.1 M sodium acetate buffer. The animals were killed 1.5 years after treatment and 22/28 (78.6%) treated rats had colon epithelial tumours [detailed histological description not given]. One of the rats with colon tumours also developed a small intestinal tumour and another had a tumour of the Zymbal gland (Schiller et al., 1980). 

Description of the Model. The Keys et al. (1999) model simulates six tissue compartments small intestine, blood, liver, testis, slowly perfused tissues, and poorly perfused tissues. Conversion of DEHP to MEHP in the small intestine is simulated with km and Vmax terms, whereas conversion in liver and blood are simulated with separate first order rate constants, kj and kb, respectively. Elimination of DEHP and MEHP is assumed to be entirely by metabolism of DEHP to MEHP, and MEHP to unspecified metabolites the latter transformation is represented in the model by km and Vmax terms. 

Calcium is absorbed in the whole small intestine with the bulk preferentially from duodenum and the upper part of jejunum. The absorption consists of a passive diffusion as well as an active transport through the mucosa. A schematic description of the cellular and paracellular pathway for calcium absorption from the intestinal lumen to blood across the intestinal epithelium can be seen in Fig. 1. The higher rate of calcium transport in duodenum as compared to that in jejunum and ileum is probably not due to greater cellularity of duodenum but to a greater calcium transport by each duodenal cell. The molecular basis for calcium entry across the brushborder is not known in detail, but initial calcium binding may be an early step in the activation of a calcium channel or to increase membrane fluidity [3]. 

The first description of the use of plant stanols to lower plasma cholesterol levels in humans was by Heinemann etal (1986) in a small uncontrolled study. They showed that the administration of capsules of sitostanol dispersed in monoacylglycerol and sunflower oil at a dose of 1.5g/day lowered LDL cholesterol levels by 15%. Similar concentrations of sitosterol and sitostanol infused directly into the small intestine decreased cholesterol absorption by 50% and 85%, respectively (Heinemaim et al, 1991). Becker et al (1993) obtained impressive results with low-dose sitostanol in an uncontrolled study with 9 children suffering from familial hypercholesterolemia. LDL cholesterol levels decreased by 33% when the children consumed 1.5 g sitostanol daily, and by 20% when they consumed 6 g sitosterol daily, suggesting that sitostanol is more effective than sitosterol at lowering LDL cholesterol levels. 

The majority of the cell bodies of enteric neurons are found in the two plexuses, the myenteric (Auerbach s plexus) and the submucosal (Meissner s plexus). Because the enteric plexuses of the stomach have not been studied in as much detail as those of the small and large intestines, a description of the organization and function of the gastric enteric neurons relies often on information gleaned from other... 

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