Xylose absorption

SL Johnson, M Mayersohn, KA Conrad. Gastrointestinal absorption as a function of age xylose absorption in healthy adult subjects. Clin Pharmacol Ther 38 331-335, 1985. 

Nausea, vomiting, diarrhea (most common) malabsorption syndrome characterized by increased fecal fat, decreased serum carotene, and fall in xylose absorption. Clostridium difficile-assoaated colitis (following neomycin therapy) nephrotoxicity and ototoxicity (following prolonged and high-dosage therapy in hepatic coma). 

Craig RM, Murphy P, Gibson TP, Quintanilla A, Chao GC, Cochrane C, Patterson A, Atkinson AJ Jr. Kinetic analysis of D-xylose absorption in normal subjects and in patients with chronic renal failure. J Lab Clin Med 1983 101 496-506. 

A study of D-xylose absorption in renal failure found that the absorption rate of the xylose was slowed and the amount absorbed was decreased [38]. This is a water-soluble rather than a lipid-soluble substance. What relationship this impaired intestinal absorption of xylose has to usual drug absorption remains to be determined. 

Stool for occult blood testing Transrectal ultrasonography Upper gastrointestinal x-ray study Urea nitrogen blood test V ideofluoroscopy D-Xylose absorption test... 

White blood cell count and differential count D-Xylose absorption test... 

Xylose absorption test. Senim measurements of this. i-carbon sugar are made after an oral dose and provide an indication of intestinal ability to ab.sorb monosaccharides. 

Diagnosis of a malabsorption syndrome is based on the results of absorption tests such as xylose absorption, fat absorption balance study, the Schilling test for vitamin 6-12 absorption, and the folic acid test. Also gastrointestinal x ray studies, small intestine biopsy, prothrombin time, and serum levels of vitamin A are useful diagnostic tools. 

Hammon, H.M. and J.W. Blum. 1997. Prolonged colostrum feeding enhances xylose absorption in neonatal calves. 

Fig. 1 Absorption curve of a chromatogram track with 4 pg of each substance per chromatogram zone. Rhamnose (1), xylose (2), arabinose (3), fructose (4).

M Mayersohn, The xylose test to assess gastrointestinal absorption in the elderly a pharmacokinetic evaluation of the literature. J Gerontol 37 300-305, 1982. 

R3. Roberts, J. G., Neck, I. T., Kallos, J., and Kahn, D. S., D(-)-)-Xylose blood level time-curve as an index of intestinal absorption, with a description of a simplified method for estimation of blood xylose levels. Can. Med. Assoc. ]. 83, 112 (1960). 

Singh G, Chaudry KL, Chudler LC, Oneill PJ and Chaudry IH (1991) Measurement of D-Xylose Gut Absorptive-Capacity in Conscious Rats. Am J Physiol 261 pp R1313-R1320. 

Thus, the apparent membrane permeability characteristics of hydrophilic compounds listed in Table 3.4 indicate that colonic epithelium is different from small intestinal epithelium in selectivity, or size or density distribution of the paracellular pathway. This is further complicated because of the possible involvement of unidentified carriers or channels for some compounds, as suggested for glycerol and D-xylose. However, the colon-to-SI ratios of the apparent membrane permeability are generally comparable with (or lower than) those calculated considering the morphological surface area, suggesting that such factors are not in favor for colonic absorption in most cases. Matching... 

Note Data represent the mean S.E. (n = 3). MW, molecular weight P0/w, octanol-to-water partition coefficient CLapp, apparent membrane permeability clearance SI, midgut area of the small intestine NA, not available or applicable. Absorption was evaluated in our laboratory using the closed loop of the rat intestine in situ (urethane anesthesia, 1.125 g/4.5 ml/kg, i.p.) in 60 min for riboflavin and L-camitine and 30 min for the others. For those that are transported by carriers in part (riboflavin and glycerol in both colon and SI, and L-carnitine, 5-fluorouracil, and cephradine in SI), absorption was evaluated at higher concentrations where the contribution of carrier-mediated transport is negligible. Values of P0/w were obtained from a report by Leo et al. [30] except for that of D-xylose, which was determined in our laboratory. a Data by single-pass perfusion experiments. b Unpublished data from our laboratory. 

Pseudopterosin X (1) was isolated as a yellow colored gum. The UV spectrum of 1 showed maximum absorption at 280 nm due to the presence of a highly substituted benzene chromophore [10], Its IR spectmm displayed intense absorption bands at 3,470 (OH), 2,904 (CH), 1,705 (C = O), 1,595 (C = C) and 1,100 (C-0) cm . The high-resolution electron-impact mass spectmm (HREIMS) of 1 showed M+ at m/z 474.2622, and this mass provided molecular formula indicating the presence of nine double bond equivalents in 1. The C-NMR chemical shift assignments of 1 are shown around stracture 1. On the basis of the detailed NMR studies and comparison with the reported pseudopterosins in the literature and L-xylose [3-5], stmcture 1 was proposed for this new natural product. 

D-Xylose was found to yield 2-furaldehyde almost exclusively, but D-lyxose, D-ribose, and L-arabinose produce another, as yet unidentified, compound absorbing at 289 nm, which is the maximum absorption wavelength for reductic acid. D-Glucose, D-fructose, and sucrose give almost identical yields (—85%) of 5-(hydroxymethyl)-2-fural-dehyde, but D-galactose and D-mannose give much lower yields thereof. 

Fio. 2.—Curves for Light-absorption in the Disohe Test (A) 2-Desoxy-D-xylose (B) D-Xylal (C) w-Methoxylevulinaldehyde Dimethyl Acetal. 

Brown products from D-xylose-glycine showed an absorption peak at 320 m/3 and, in the infrared, a band at 6.2 n and also (sometimes), a second one at 5.9 n, which might be due to doubly-bonded atoms. However, no positive evidence of double bonds was obtained by treatment with... 

This is a term coined to denote a transport mechanism in which the rate of attainment of diffusion is accelerated without any direct expenditure of energy. It differs from active transport in being unable to operate against an electrochemical gradient. The absorption of D-xylose by the intestine comes under this heading. 

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