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Dietary triacylglycerols (TAGs) are the major lipid components in the human diet and they are carriers of energy as well as important fatty acids. Many factors affect the digestion and absorption of TAGs. Evidence is accumulating that, in addition to the overall fatty acid profile, the TAG structure and the species composition are of importance when considering the nutritional effects of a dietary fat. There is good evidence that in addition to its short-term effects in the intestine on absorption of fatty acids the TAG structure also has long-term effects resulting from differences in the profile of absorbed fatty acids. Observations on the different atherogenic potential of dietary fats have given us a clear indication of the importance of the TAG structure for absorption of saturated fatty acids. In this context, one may focus on the effects of the structure of dietary fats as such, or one may speculate additionally on the possibilities of modifying the structure of fats to affect their absorption and the distribution of the fatty acids in the body after digestion and uptake. In this review we will summarize diverse aspects of TAG digestion and absorption, as well as the influences of the fatty acid composition and the intramolecular structure of dietary TAGs on their digestion and absorption.  相似文献   

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The S1 thiol groups of heavy meromyosin (HMM) have been selectively spin labeled with a paramagnetic analog of iodoacetamide (10) and the effects of tryptic digestion on the ESR spectrum and ATPase activity have been studied. The loss of ATPase activity on tryptic digestion occurs at the same rate with spin-labeled or unlabeled HMM suggesting that spin labeling produces no major change in the conformation of HMM. ESR spectra indicate that spin labels bound to S1 groups of HMM are strongly immobilized; spectra of subfragment-1 isolated from tryptic digests of spin-labeled HMM are the same as those of labeled HMM. ESR spectra of S1-spin-labeled peptides produced by tryptic digestion of HMM indicate essentially no immobilization of labels, the spectra being similar to that of a solution of free labels. The ESR spectrum of an unfractionated digest of HMM exhibits a peak attributable to strongly immobilized labels on HMM and subfragment-1 and a peak attributable to weakly immobilized labels bound to peptides. The rate at which spin-labeled peptides are released on tryptic digestion can be measured on the unfractionated digest by the decrease in the ESR peak corresponding to HMM and subfragment-1. The appearance of peptides containing spin-labeled S1 groups parallels the loss of ATPase activity. No evidence has been found for the existence of an enzymatically active subfragment-1 lacking S1 thiol groups.  相似文献   

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Summary The ability of methanogenic bacteria to adapt to high concentrations of calcium was investigated using a 9 l Upflow Anaerobic Sludge Blanket (UASB) reactor fed semi-continuously with a synthetic waste. It was found that a calcium concentration of up to 7000 mg/l had no inhibitory effect on anaerobic digestion.  相似文献   

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The effect of iron on anaerobic digestion   总被引:1,自引:0,他引:1  
Summary The ability of methanogenic bacteria to adapt to high concentrations of iron was investigated using a 9l Upflow Anaerobic Sludge Blanket (UASB) reactor fed semi-continuously with a synthetic waste containing glucose as the organic carbon source. It was found that an iron concentration of up to 5 650 mg/l, which is well in excess of previously reported toxicity levels, had no inhibitory effects on anaerobic digestion, with the exception of a decrease in biogas production. The iron precipitated out and accumulated in the sludge bed of the digester, resulting in very low concentrations of iron in the digester effluent.  相似文献   

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Abstract All amniotes except birds and mammals have the ability to shunt blood past the lungs, but the physiological function of this ability is poorly understood. We studied the role of the shunt in digestion in juvenile American alligators in the following ways. First, we characterized the shunt in fasting and postprandial animals and found that blood was shunted past the lungs during digestion. Second, we disabled the shunt by surgically sealing the left aortic orifice in one group of animals, and we performed a sham surgery in another. We then compared postprandial rates of gastric acid secretion at body temperatures of 19 degrees and 27 degrees C and rates of digestion of bone at 27 degrees C. Twelve hours after eating, maximal rates of gastric acid secretion when measured at 19 degrees and 27 degrees C were significantly less in the disabled group than in sham-operated animals. Twenty-four hours postprandial, a significant decrease was found at 27 degrees C but not at 19 degrees C. For the first half of digestion, dissolution of cortical bone was significantly slower in the disabled animals. These data suggest the right-to-left shunt serves to retain carbon dioxide in the body so that it can be used by the gastrointestinal system. We hypothesize that the foramen of Panizza functions to enrich with oxygen blood that is destined for the gastrointestinal system to power proton pumps and other energy-demanding processes of digestion and that the right-to-left shunt serves to provide carbon dioxide to gastrointestinal organs besides the stomach, such as the pancreas, spleen, upper small intestine, and liver.  相似文献   

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Summary The digestion ofSaccharomyces cerevisiae byAcanthamoeba castellanii, at different times after feeding, has been examined by cytochemical techniques at electron microscope level and by measurement of yeast viability. The measurement of viability, combined with cytochemistry is presented as a novel method of examining the progress of digestion. Particular attention has been given to the temporal development of digestion.Vacuoles, probably primary lysosomes, have been identified containing acid phosphatase activity within minutes of feeding and these accumulate around and fuse with phagocytic vacuoles. Acid phosphatase levels in the digestive vacuoles appeared highest at 20 to 40 minutes. Yeast digestion was observed and yeast viability began to decline at this time. Mixing of autophagic and heterophagic material was also observed. At least half of the yeast population was still viable after 90 minutes.Our method (p-nitrophenyl phosphate) of enzyme localization has demonstrated plasma membrane associated acid phosphatase activity.  相似文献   

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The effects of detergents on anaerobic digestion   总被引:1,自引:0,他引:1  
Summary The anionic detergent sodium dodecylbenzene sulphonate (SDBS) inhibited mesophilic fermentation in anaerobic digesters. Total gas production and methanogenesis from glucose were reduced to half maximal rates at between 20 and 50 ppm SDBS during the initial phase of digestion, and over 20 days the pH declined from 7.4 to 6.0 in inhibited cultures. As well as accentuating the accumulation of propionic, iso-butyric and iso-valeric acids, a most remarkable effect of this anionic detergent observed only at high concentrations (100 ppm) was to divert the pathway of fermentation with transient accumulation of ethanol. Methanogenesis from cellulose was also inhibited. In thermophilic populations degrading glucose, SDBS was less toxic, and ethanol was not produced. Both the non-ionic detergent Tergitol (nonyl phenyl polyethylene glycol ether) and soap were virtually without effect on the mesophilic anaerobic digestion of glucose.  相似文献   

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Summary The ability of methanogenic bacteria to adapt to high concentrations of aluminium was investigated using a 9 Upflow Anaerobic Sludge Blanket (UASB) reactor fed semi-continuously with a synthetic waste containing glucose as the organic carbon source. It was found that an influent concentration of 2500 mg/ Al3+ could be tolerated by acclimatized methanogenic bacteria. However, if the concentration in the synthetic waste was further increased, inhibition of the methanogens resulted, with a corresponding decrease in digester performance. The aluminium precipitated as Al(OH)3 and accumulated in the sludge bed of the digester.  相似文献   

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The physiology of digestion in fish larvae   总被引:22,自引:0,他引:22  
Synopsis The acquisition, digestion, and assimilation of food is critical for the growth and survival of fish larvae; a fish larva either grows or it perishes. Fish larvae are characterized by digestive systems and diets that differ from adults. Larvae undergo a pattern of trophic ontogeny, changing diet with increasing size, and these changes result in differences in digestive requirements. At first feeding, the larval alimentary canal is functional, but is structurally and functionally less complex than that of adults. The larval alimentary canal remains unchanged histologically during the larval period before transformation. During transformation, major changes that result in the development of the adult alimentary canal occur. The ontogeny of the alimentary canal differs in different taxa, and experimental evidence suggests that functional differences exist as well. Assimilation efficiency may be lower in larvae than it is in adult fishes, due to a lack of a morphological and functional stomach in larvae, but the question of improving assimilation efficiencies during larval development before transformation remains unresolved.  相似文献   

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The enzymatic degradation of insoluble elastin has been studied at several pH values using purified pepsin and cathepsin D, and neutrophil extracts. Pepsin degraded elastin throughout the pH range of 1.2-4.0 with the optimum pH below 2.0. Molecular sieve chromatography and gel electrophoresis indicated that a spectrum of molecular weight degradation products was produced. The degradation by pepsin was inhibited by sodium dodecyl sulfate (SDS), NaCl and pepstatin. Cathepsin D, which, like pepsin, degrades hemoglobin at acid pH and is inhibited by pepstatin, had no activity against insoluble elastin in the pH range of 3.2-7.2. Extracts of neutrophils degraded elastin above pH 4.0. The pH profile of elastin degradation by neutrophil extracts generally followed that of purified human leukocyte elastase. Our results suggest that during alimentation or pulmonary aspiration of gastric contents, extracellular elastin may be digested by gastric juice at acid pH. Inflammatory cells would not appear to be capable of contributing to such actions until local pH approaches neutrality. Cathepsin D, a major constituent of inflammatory cells, does not digest all types of connective tissue proteins.  相似文献   

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