Fat absorption in cystic fibrosis mice is impeded by defective lipolysis and post-lipolytic events

Cystic fibrosis (CF) is frequently associated with progressive loss of exocrine pancreas function, leading to incomplete digestion and absorption of dietary fat. Supplementing patients with pancreatic lipase reduces fat excretion, but it does not completely correct fat malabsorption, indicating that additional pathological processes affect lipolysis and/or uptake of lipolytic products. To delineate the role of such ( post) lipolytic processes in CF-related fat malabsorption, we assessed fat absorption, lipolysis, and fatty acid uptake in two murine CF models by measuring fecal fat excretion and uptake of oleate- and triolein-derived lipid. Pancreatic and biliary function was investigated by determining lipase secretion and biliary bile salt (BS) secretion, respectively. A marked increase in fecal fat excretion was observed in cftr null mice but not in homozygous Delta F508 mice. Fecal BS loss was enhanced in both CF models, but biliary BS secretion rates were similar. Uptake of free fatty acid was delayed in both CF models, but only in null mice was a specific reduction in lipolytic activity apparent, characterized by strongly reduced triglyceride absorption. Impaired lipolysis was not due to reduced pancreatic lipase secretion. Suppression of gastric acid secretion partially restored lipolytic activity and lipid uptake, indicating that incomplete neutralization of gastric acid impedes fat absorption. We conclude that fat malabsorption in cftr null mice is caused by impairment of lipolysis, which may result from aberrant duodenal pH regulation

Thermoelectric properties of SiC/C composites from wood charcoal by pulse current sintering

SiC/C composites were investigated by sintering a mix of wood charcoal and SiO2 powder (32-45 mu m) at 1400, 1600 and 1800 degrees C under N-2 atmosphere with a pulse current sintering method. Thermoelectric properties of SiC/C composites were investigated by measuring the Seebeck coefficient and the electrical and thermal conductivities as a function of heat treatment temperature and reaction time. The Seebeck coefficient showed a p-type to n-type transition at a heat treatment temperature around 1600 degrees C. The electrical conductivity showed a steady increase with temperature for all three heat treatment temperatures. For the thermal conductivity, the samples heated at 1800 degrees C showed high values at room temperature which strongly decreased with increase in measurement temperature. In total, thermoelectric properties were improved with an increase in measurement temperature. A maximum in the figure of merit of 3.38 x 10(-7) K-1 was reached at 200 degrees C in the sample heated at 1400 degrees C for 30 min. (c) 2005 Elsevier Ltd. All rights reserved

SiC/C composites prepared from wood-based carbons by pulse current sintering with SiO2: Electrical and thermal properties

A powder mix of wood charcoal and SiO2 was sintered into a SiC/C composite. The heat treatment temperatures were 1400-1800 degreesC, the SiO2 concentration 0, 10, 30 and 50 wt.% with respect to the dry weight of wood charcoal. The microstructure, electrical resistance and thermal conductivity were studied. SEM and EDX confirmed that a 1 mum thick layer of beta-SiC was formed on the surface of the wood charcoal pieces. The bulk density did increase only slightly with temperature and SiC contents. The electrical resistance decreased slightly with temperature but increased with SiO2 contents. The thermal conductivity did increase both with temperature and SiC contents. By coating the wood charcoal in this rather natural way by such a ceramic layer we can use the SiC/C composite at least up to 1800 degreesC, far beyond the carbon oxidation limit of 500 degreesC. (C) 2004 Elsevier Ltd. All rights reserved

Studio 260 students of Caio Pagano : Debussy 24 preludes

Claude DebussyLast prelude not recorde