Stomach, structure

Vane and co-workers isolated a new prostaglandin (initially called PGX) from microsomal fraction of stomach. The structure was established by chemical synthesis from PGP2a (Ref. 1). 

It will be appreciated that the delivery of nutrients from foods is attenuated by the structure of the food and the way in which it is digested. Thus, delivery from the food structure occurs over the same timescale as gastric emptying. Carotenoids, and other compounds, isolated from the food structure are generally emptied from the stomach and absorbed more rapidly. These different rates of delivery may have profound effects on subsequent metabolism. 

Milieu conditions in gastrointestinal tract can influence the pectin structure and properties. Under the acid conditions of the stomach (pH 2-4) extraction of pectin from plant cell walls and hydrolysis of side chains can occur. In small intestine (pH 5-6) -elimination of main chains or de-esterification seems to be possible. In caecum and colon (pH 6-8) a strong fermentation of pectin takes place causing depolymerization to oligomers and leading to formation of short chain fatty acids and gases. The presence of OligoGalA is not yet clarified. 

Recently, Tse et al. [73] and Orlowski et al. [74] have cloned a third isoform of Na /H exchanger (named NHE-3). The inferred 832-amino acid sequence of rabbit NHE-3 is 41% identical with NHE-1, 44% identical with NHE-2, and has a similar secondary structure. In contrast to NHE-1 and NHE-2, NHE-3 is only expressed in epithelia in intestine and kidney. Moreover, administration of glucocorticoids, which stimulates transport activity of the apical Na /H" exchanger in rabbit intestine, increased levels of NHE-3 transcripts but did not affect NHE-1 or NHE-2 [75]. Taken together, these results suggest that NHE-3 may encode a resistant-type Na /H exchanger of epithelia. A fourth Na /H exchanger isoform (NHE-4) is preferentially expressed in stomach [74]. 

Irritable bowel syndrome (IBS) is a disorder of the gastrointestinal tract that interferes with the normal functions of the colon. At various points in the past, IBS has been referred to as mucous colitis, spastic colon, irritable colon, or nervous stomach. IBS is generally described as afunctional disorder rather than a disease per se. A functional disorder involves symptoms that cannot be attributed to a specific injury, infection, or other physical problem. A functional disorder occurs because of altered physiologic processes rather than structural or biochemical defects and may be subject to nervous system influence. IBS is associated with frequent fluctuation in symptoms, loss of productivity, and decreased quality of life. Although IBS has been referred to as functional bowel disease, true functional bowel disease may be more indicative of widespread gastrointestinal involvement including (but not limited to) the colon. 

J. Deren, Development of structure and function of the fetal and newborn stomach, Am. J. Clin. Nutr, 24, 144 (1971). 

Did you know the average American consumes the equivalent of 20 teaspoons of sugar each day The non-nutritive sweetener industry is described as a billion-dollar industry with projections of even more rapid expansion in the next few years. What do chemists look for in their search for an ideal sweetener Consumers seek good-tasting, nontoxic, low-caloric sweeteners. Chemists in the sweetener industry add further demands an inexpensive, easy-to-synthesize product that is readily soluble in water and resists degradation by heat and light is of prime importance. The chemical structure of sucralose keeps the sweetener intact as it passes through the acidic environment of the stomach. Thus, sucralose is not... 

Kedishvili NY, Bosron WF, Stone CL, Hurley TD, Peggs CF, Thomasson HR, Popov KM, Carr LG, Edenberg HJ, Li T-K. Cloning and expression of a human stomach alcohol dehydrogenase Comparison of structure and catalytic properties with the liver isoenzymes. J Biol Chem 1995 280 3625-3630. 

Nomura and Ogata provided the first evidence that tunicates can produce PGs [17]. Using a rat stomach fundus bioassay, Halocynthia roretzi tissues were shown to possess low levels of PGs. The testes showed higher levels (9 ngg-1 wet tissue) than ovary and muscle tissue. The sea-squirt Styela clava did not show PGs by this method. No structures were determined in this work. Reexamination of the ability of H, roretzi to produce PGs was carried out by Ogata and coworkers [19]. Incubation of selected tissues with 14C-labeled eicosa-8,11,14-trienoic acid and subsequent isolation of PGE and PGF fractions after addition of carrier showed the branchial tissue to have the highest conversion levels. Quantitation was done by LSC. Using a TLC radioscanner, the authors determined that fractions with metabolites similar to PGE and PGF... 

A related type of reactive metabolite is formed from 3-methylindoles. Microorganisms in the stomach of ruminants can convert F-tryptophan into 3-methylindole, which can cause pulmonary edema and death in cattle (26). The reactive metabolite is shown in Figure 8.17. This basic structure also occurs in some drugs such as zafirlukast, and this is presumably responsible for the idiosyncratic adverse reactions associated with this drug (27). 

Epinephrine. Is adrenaline. This substance is highly psychotomimetic in small doses (1 to 5 mg), but is not orally active because enzymes in the stomach destroy its molecular structure. To keep from having to inject it, put a dose under your tongue and let it absorb into your blood stream in this manner. 

The main clinical use of H2 receptor antagonists is to inhibit gastric secretion in the treatment of stomach ulcers. These agents all contain features that relate to the histamine structure, in particular the heterocyclic ring. Cimetidine and ranitidine are the most widely used in this class. 

Omeprazole is an antiulcer drug. It is a proton pump inhibitor. This substituted benzimidazole inhibits gastric acid secretion to help acid/peptic disorders and duodenal ulcers. It interferes with the proton pump in the mucous lining of the stomach, the last stage of acid production. It can turn off stomach acid in as little as one hour. Lansoprazole (no. 12) has a similar structure. 

Traditional or Hj antihistamine drugs block many effects caused by histamine however, it turns out that they are not able to withstand events mediated by H2 receptors, in particular excess gastric juice secretion. In 1977 an H2-receptor antagonist, cimetidine, was proposed, which revolutionized stomach ulcer treatment. Later on, ranitidine was proposed, followed by drugs with minor structural and pharmacological differences such as famotidine and nizatidine. 

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