PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “In vitro digestion model”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 91 records · Page 5Linked to original sources
PubMed1996

Carboxy-terminal sequence divergence and processing of the polyprotein antigen from Dirofilaria immitis.

A polyprotein composed of multiple units arranged in direct tandem arrays has been identified in parasitic and free living nematodes. Analysis of previously cloned units from the Dirofilaria immitis polyprotein antigen (DiPA) indicated the units were nearly identical but here we demonstrate that they segregate into two related families. The consensus repeats, DiPA-CR1 and CR2, derived for each family are 80% identical. However, the repeats at the C-terminus of the polyprotein have diverged from DiPA-CR1 and CR2. This was shown by DNA sequence and Southern blot analysis of a 1.9 kb cDNA clone that encodes 4.4 C-terminal repeats (DiPA-TR1 through TR5). DiPA-TR3 through TR5 show 27-52% amino acid identity with the consensus repeats and 31-35% amino acid identity with one another. Metabolic labeling studies have shown that cleavage of DiPA generates a protein "ladder' from 14 to > 200 kDa. RRKR, a cleavage motif of subtilisin-like proprotein convertases, was identified as the natural cleavage site. In vitro digestion experiments with proteinase K suggest a structural model for DiPA consisting of protease resistant cores joined by protease sensitive linkers containing the RRKR site. This motif is absent between DiPA-TR3 and TR4 and has been altered to KR between DiPA-TR4 and TR5. An immunoblot of D. immitis extract probed with anti-DiPA-TR4/5 serum demonstrates the absence of cleavage at these sites. These divergent repeats provide an opportunity to investigate processing of the D. immitis polyprotein in vivo.

Amino Acid Sequence↗
PubMed2005

The influence of associative effects on the in vitro-estimated utilizable crude protein (uCP) of feeds for ruminants.

Nineteen feed mixtures, formulated with 16 single feeds, were used to study the influence of associative effects on utilizable crude protein (uCP) of feed mixtures. The in vitro incubation technique of Zhao and Lebzien (2000) was used for uCP determination. It was found that the in vitro-determined uCP (D-uCP) was significantly higher than the weighted uCP (W-uCP) of feed mixtures and there was a significant regressive relationship between W-uCP (x) [g x kg(-1)DM] and D-uCP (y) [g x kg(-1)DM]: y=(0.94 +/- 0.23)x + (18.78 +/- 35.58), r2=0.49, n=19, p < 0.01. It was concluded that there exist significant associative effects of feed mixtures on uCP. In formulation of rations for ruminants the D-uCP should be used instead of W-uCP. Because of the low regression coefficient of the equation above, the D-uCP cannot be estimated from the W-uCP.

Animal Feed↗
PubMed1998

The use of an in vitro cellulase enzyme technique for predicting the digestibility of tropical feeds and fodders.

An attempt has been made to find out if the organic matter digestibility of tropical feeds and fodders can be predicted from the results of an in vitro cellulase enzyme technique. The in vivo digestibility coefficient of 27 tropical feeds and fodders was determined in wethers. The enzyme insoluble organic matter content of these feeds was determined using a cellulase enzyme technique. The indigestible OM (g/kg feed DM) in vivo (y) was plotted against enzyme insoluble organic matter (g/kg DM) (x). The equation is y = 60 + 0.817x, R2 = 0.95; RSD = 32 g/kg DM. Equations for predicting DOM (g/kg DM) and digestibility of OM (%) are calculated. The testing of the equation on an independent data base of 40 individual feeds and fodders showed that the validity of the equation is fairly general.

Animal Feed↗
PubMed2001

In vitro starch digestion correlates well with rate and extent of starch digestion in broiler chickens.

Current feed evaluation systems for poultry are based on digested components (fat, protein and nitrogen-free extracts). Digestible starch is the most important energy source in broiler chicken feeds and is part of the nitrogen-free extract fraction. Digestible starch may be predicted using an in vitro method that mimics digestive processes in the gastrointestinal tract of broiler chickens. An experiment was designed to use this method for predicting site, rate and extent of starch digestion in broiler chickens. In vitro starch digestion was studied in 12 experimental diets differing in starch sources. These diets were also used in a digestibility trial with broiler chickens. Correlations between in vitro and in vivo starch digestion were calculated. Starch digestion after 2 h incubation correlated well with in vivo starch digestion in the first half of the small intestine (r = 0.94). A 4-h incubation period resulted in a good correlation between in vitro starch digestion and ileal starch digestion (r = 0.96). In vitro starch digestion rate (h(-1)) correlated well with in vivo starch digestion rate (r = 0.87). In vitro starch digestion of individual starch sources was additive. It appeared that legume seeds and waxy corn contained two starch fractions, which were digested at different rates. We conclude that starch digestion rate in broiler chickens is well predicted by the in vitro method.

Animal Feed↗
PubMedDate not supplied

[Comparison of the resistance during proteolysis of the antigenic structure of bovine serum albumin, chicken ovalbumin and their carbohydrate-modified forms].

A study was made of the effect of Maillard reaction between epsilon-amino groups of proteins and sugar carbonyl groups on the resistance of protein antigens (AG) to proteolysis in model systems and in the course of digestion and absorption in the gastrointestinal tract of adult rats. It was found that in vitro pepsin and trypsin inactivate antigenic determinants of bovine serum albumin (BSA) modified by carbohydrate less readily than those of basic protein. At the same time in the course of studying the cleavage and absorption of 3H-proteins and their glucose derivatives in the rat body, lack of a significant stabilization of modified BSA and ovalbumin as compared with non-modified ones was discovered. The discrepancy of the data derived in vitro and in vivo is likely to be related to the inadequacy of the available enzymatic models with regard to real conditions of digestion in the gastrointestinal tract.

Animals↗
PubMed2001

Antimutagenic activity of green tea and black tea extracts studied in a dynamic in vitro gastrointestinal model.

An in vitro gastrointestinal model, which simulates the conditions in the human digestive tract, was used to determine potential antimutagenic activity of extracts of black tea and green tea. In this paper, results are presented on the availability for absorption of potential antimutagenic compounds present in tea and on the influence of the food matrix on this activity. Between 60 and 180min after the tea was introduced into the model, antimutagenic activity was recovered from the jejunal compartment by means of dialysis: the dialysate appeared to inhibit the mutagenicity of the food mutagen MeIQx in the direct plate assay with Salmonella typhimurium (Ames test). The maximum inhibition was measured at 2h after the start of the experiment and was comparable for black tea and green tea extract. To determine the influence of food matrices on the antimutagenic activity of tea, the model was loaded with black tea together with milk or a homogenized standard breakfast. The maximum inhibition observed with black tea was reduced by 22, 42 and 78% in the presence of whole milk, semi-skimmed milk, and skimmed milk, respectively. Whole milk and skimmed milk abolished the antimutagenic activity of green tea by more than 90%; for semi-skimmed milk the inhibition was more than 60%. When a homogenized breakfast was added into the model together with the black tea extract, the antimutagenic activity was completely eliminated. When tea and MeIQx were added together into the digestion model, MeIQx mutagenicity was efficiently inhibited, with green tea showing a slightly stronger antimutagenic activity than black tea. In this case, the addition of milk had only a small inhibiting effect on the antimutagenicity. Antioxidant capacity and the concentration of catechins were also measured in the jejunal dialysates. The reduction in antimutagenic activity corresponded with reduction in antioxidant capacity and with a decrease of concentration of three catechins, viz. catechin, epigallocatechin gallate and epigallocatechin. The in vitro gastrointestinal model appears to be a useful tool to study the antimutagenicity of food components.

Animals↗
PubMed2006

[An in vitro natural degeneration model of chondrocytes derived from endplate of intervertebral discs of rats].

OBJECTIVE: To set up a natural degeneration model of chondrocytes derived from endplate of intervertebral discs of rats in order to offer an appropriate carrier for the study on mechanism of intervertebral disc degeneration. METHODS: The method of enzyme digestion combined with natural subculture was used to set up the in vitro natural degeneration model of chondrocytes derived from the endplate of intervertebral disc of rats. The morphological appearances and microstructures of the chondrocytes of different generations were observed. The expression of collagen II in chondrocytes was detected by immunocytochemical method. RESULTS: The chondrocytes derived from the endplate of intervertebral disc expressed collagen II. After 13 days of culture, the chondrocytes of generation III showed that the ability of cell division descended, the nucleoli became unclear, the cells deformed obviously, fusiform shape with weak optical activity appeared, and the intercellular space was enlarged. There were vacuoles and lipid droplets in cytoplasm. The synthesis of collagen II, as well as the cell proliferation rate, descended notably. All results showed the natural degeneration process of the chondrocytes. CONCLUSION: The in vitro natural degeneration model of chondrocytes derived from endplate of intervertebral discs of rats was successfully established. This can offer the cytological basis for study on the mechanism of intervertebral disc degeneration.

Animals↗
PubMed2003

Estimates of starch digestion in the rat small intestine differ from those obtained using in vitro time-sensitive starch fractionation assays.

The objectives of this study were as follows: 1) to determine the rate and extent of starch disappearance from the small intestine of the rat fed selected starch sources, 2) to determine the ratios of the major starch fractions [rapidly digestible starch (RDS), slowly digestible starch (SDS), and resistant starch (RS)] in those starch sources using two in vitro methods and 3) to compare the two data sets to determine the accuracy of the in vitro methods. Diets were prepared using cornstarch, potato starch, amylomaize, maltodextrin, modified maltodextrin or pullulan. Starch sources and diets were analyzed for starch fractions by two in vitro methods. Diets were fed to rats, intestinal contents were collected and the ethanol-induced precipitate from the contents was analyzed to obtain a digestion curve that was mathematically modeled for comparison to results obtained using the two in vitro methods. Only the cornstarch diet had a defined amount of RDS, SDS and RS. The RDS concentration obtained from the intestinal contents of the rats fed the cornstarch diet differed (P < 0.05) from that determined by one in vitro method but was consistent with the value obtained using the other in vitro method. All other digestible starch values obtained differed (P < 0.05) among methods except for that of amylomaize. Starch fractions in starch sources obtained using in vitro procedures differed (P < 0.05) from values obtained for diets. The rate of disappearance differed (P < 0.05) between in vivo and in vitro procedures. There was minimal agreement between in vitro methods tested, and there was also minimal agreement between in vitro and in vivo results. Classification of starch into RDS and SDS components cannot be accomplished for a variety of starch sources, with cornstarch being the major exception.

Animals↗
PubMed1996

[Culture of endothelial cells as an in vitro model for experimental and clinical research].

Culture of endothelial cell is gotten from human umbilical cord by enzymatic digestion. For the growth of cells in culture, medial RPMI 1640 with 20% mixed human serum (NHS) or 20% fetal calf serum (FCS), endothelial cell growth factor (ECGF) and heparin have been used. Plastic, 0.1% gelatin and fibronectin have been used as a fundament. Immune identification of endothelial cells was culture is performed by monoclonal antibodies on vWF:Ag. Homogeneous cell line in culture might be used as in vitro model in both experimental and practice work.

Cell Culture Techniques↗
PubMed1993

Influence of particle size and sources of non-starch polysaccharides on postprandial glycaemia, insulinaemia and triacylglycerolaemia in pigs and starch digestion in vitro.

Physico-chemical properties of dietary fibres might be involved in metabolic control, particularly of the postprandial blood glucose response. The aim of the present study was to look at the effects of the content of soluble fibres and of the particle size of solid fibres on in vitro and in vivo starch hydrolysis and on the subsequent glucose absorption as well as the triacylglycerolaemia. Two sources of dietary fibres, one, with soluble fibres (beet pulp), the other with mostly insoluble fibres (wheat bran), were added at the rate of 60 g/kg to a meal simulating human food. The fibre sources were ground in order to obtain two different particle sizes (250 and 500 microns). Beet pulp decreased significantly (P < 0.05) initial in vitro hydrolysis whereas wheat bran increased starch hydrolysis in the first 10 min. Wheat bran and beet pulp, whatever its particle size, lowered the post-prandial triacylglycerol response. No significant effect was found with dietary fibre-supplemented diets on postprandial glycaemic and insulinaemic values. High correlation was found between initial in vitro starch hydrolysis and mean areas under the insulinaemic curves. This in vitro model can be used to predict initial in vivo digestion of carbohydrates from complex foods.

Animals↗
PubMed1993

Role of phospholipase A2 in pancreatic acinar cell damage and possibilities of inhibition: studies with isolated rat pancreatic acini.

Phospholipase A2 (PLA2) has been postulated to play an important role in the pathogenesis of acute pancreatitis. To study the mechanism through which PLA2 may cause cellular damage, we used an in vitro model of isolated rat pancreatic acini prepared by collagenase digestion. Newly synthesized proteins were labeled by [35S]methionine. Cellular destruction was measured by the degree of release of radiolabeled proteins. Incubation of pancreatic acini with PLA2 alone caused only minor damage when very high concentrations of this enzyme were used. However, when acini were incubated with PLA2 in combination with its substrate, lecithin, cells were destroyed in a time- and concentration-dependent manner. Incubating cells with pancreatic homogenates and lecithin caused damage only when there had been prior activation of homogenates with either trypsin or enterokinase. The damage could be simulated by incubating acini with pure lysolecithin. Alcohol and cerulein did not further increase the destruction caused by PLA2 and lecithin. When acini were incubated with supernatants from another set of acini to which oleic acid had been added, a similar degree of damage resulted as compared with acini incubated with oleic acid alone. However, adding PLA2 to supernatants from acini preincubated with fatty acids significantly increased the degree of cellular necrosis. The destruction by PLA2 and lecithin was inhibited by albumin but could not be inhibited by gabexate mesilate, nafamostat mesilate, or cytidine diphosphocholine. We conclude that PLA2 could play a role in pancreatic acinar cell damage, especially in the spread of cellular necrosis within the organ, provided that its substrate, lecithin, is present.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed2002

[A modified method for isolating and culturing peritoneal mesothelial cells in rats].

OBJECTIVE: To establish a culture model of peritoneal mesothelial cells in vitro separated by infusing the digestive fluid in the rat abdominal cativity. METHODS: Peritoneal mesothelial cells (PMC) were digested with 0.125% trypsin-0.01% EDTA Na2 in the abdominal cavity. We collected coelio-perfusate and cultured it. The isolated cells were identified by the phase contrast microscope, electron microscope and immunohistochemical analysis. RESULTS: The confluent cells showed a uniform cobblestone-like appearance under the phase contrast microscope; numerous surface microvilli could be found under the electron microscope and the purity of the cells was over 95%. Immunohistochemical studies revealed a positive staining for cytokeratin and vimentin, but a negative staining for Factor VIII associated antigen and CD45. CONCLUSION: The model of rat peritoneal mesothelial cells has been established successfully and it will provide an experimental basis of studying the fibrosis in peritoneal dialysis.

Animals↗
PubMed1999

Digestibility of the hydrogenated derivative of an isomaltooligosaccharide mixture by rats.

The digestibility of the hydrogenated derivative of an isomaltooligosaccharide mixture (IMO-H) was investigated. In an in vitro experiment, the digestibility of IMO-H was examined by models of the digestive system. IMO-H was resistant to two types of alpha-amylase and to artificial gastric juice. Enzymes in the rat small intestinal mucosa hydrolyzed tri-, tetra- and higher saccharide alcohols to disaccharide alcohol, removing successive glucose units from the non-reducing ends of the chains. The hydrolysis ratio for IMO-H was intermediate between the values for maltose and maltitol. In an in vivo study, growing rats were fed on an experimental diet containing IMO-H, maltitol, or hydrogenated palatinose in the range from 5% to 20%. The growth parameters of the rats fed on the test sugar show that the availability of IMO-H was about 1.2 to 1.25 times that of maltitol or hydrogenated palatinose.

Animals↗
PubMed2004

Sequences of B-chain/domain 1-10/1-9 of insulin and insulin-like growth factor 1 determine their different folding behavior.

Although insulin and insulin-like growth factor-1 (IGF-1) belong to one family, insulin folds into one thermodynamically stable structure, while IGF-1-folds into two thermodynamically stable structures (native and swap forms). We have demonstrated previously that the bifurcating folding behavior of IGF-1 is mainly controlled by its B-domain. To further elucidate which parts of the sequences determine their different folding behavior, by exchanging the N-terminal sequences of mini-IGF-1 and recombinant porcine insulin precursor (PIP), we prepared four peptide models: [1-9]PIP, [1-10]mini-IGF-1, [1-4]PIP, and [1-5]mini-IGF-1 by means of protein engineering, and their disulfide rearrangement, V8 digestion, circular dichroic spectra, disulfide stability, and in vitro refolding were investigated. Among them only [1-9]PIP, like mini-IGF-1/IGF-1, was expressed in yeast as two isomers: isomer 1 (corresponding to swap IGF-1) and isomer 2 (corresponding to native IGF-1), which are supported by the experimental results of disulfide rearrangements, peptide mapping of V8 endoprotenase digests, circular dichroic analysis, in vitro refolding, and disulfide stability analysis. The other peptide models, [1-10]mini-IGF-1, [1-4]PIP, and [1-5]mini-IGF-1, fold into one stable structure as PIP does, which indicates that sequence 1-4 of mini-IGF-1 is important for the folding behavior of mini-IGF-1/IGF-1 but not sufficient to lead to a bifurcating folding. The results demonstrated that the folding information, by which mini-IGF-1/IGF-1-folds into two thermodynamically structures, is encoded/written in its sequence 1-9, while sequences 1-10 of B chain in insulin/PIP play an important role in the guide of its unique disulfide pairing during the folding process.

Amino Acid Sequence↗
PubMed2004

[Primary culture of human periodontal ligament fibroblasts by explants with enzymatic digestion].

OBJECTIVE: To increase the success rate of primary culture of human periodontal ligament fibroblasts (HPLF), and to establish an experimental model for studying HPLF in vitro. METHODS: The primary cells were isolated from human periodontal ligament by explants with enzymatic digestion method. Morphological analysis and immunocytochemical staining were used to characterize the cell lineage, and growth curve assay to evaluate the biological features of HPLF. RESULTS: The success rate of primary culture of HPLF was 77.8%. Cultured cells were spindle-shaped, and had a positive reaction to antibodies against vimentin, and a negative reaction to antibodies against keratin. Their morphological and biological characteristics were similar to those of typical HPLF. Growth of HPLF obtained by this method was satisfactory. CONCLUSION: The success rate of primary culture of HPLF is significantly increased by explants combined with enzymatic digestion. The method is simple and feasible.

Cell Culture Techniques↗
PubMed1996

Mobilization of PAH and PCB from contaminated soil using a digestive tract model.

Environmental contaminants are mainly incorporated by ingestion. In general only those contaminants mobilized by the digestive juices are available for absorption in the digestive tract, while pollutants still fixed to indigestible particles leave the body without any effect. To evaluate the different health risks arising from the ingestion of individual types of polluted soil or other materials, we developed an in vitro test system which simulates the transition of pollutants from contaminated materials into digestive juices by means of a standardized artificial gastro-intestinal model. The test system simulates the influence of the acidic environment of the stomach (gastric model) followed by the neutral or slightly alkaline environment of the small intestine (gastro-intestinal model). Investigations on small amounts of polluted soil, sewage sludge, asphalt, metal scrap and blast sand showed that the mobilization of polycyclic aromatic hydrocarbons (PAH) and polychlorinated biphenyls (PCB) by artificial gastric juice reaches 3% up to 22% of the pollutant concentration introduced into the test system. Elutions of the contaminated materials under gastric and subsequently under intestinal conditions with bile concentrations of 3 g/l resulted in PAH- and PCB-mobilizations in the range of 5% up to 40%. The degree of mobilization depends considerably on supplementary food material added to the test system. Lyophilized milk increased the fraction of mobilized PAH and PCB to 40%-85%. Application of the test system on 22 different contaminated soils showed that the mobilization of PAH under gastro-intestinal conditions with the addition of lyophilized milk ranged from 7% up to 95%, and the mobilization of PCB ranged from 32% up to 83%. This indicates that the test system can be a useful tool for evaluating the individual health risks arising from polluted soil or other materials.

Animals↗
PubMed1987

cAMP elevation modulates physiological activity of pyloric neurons in the lobster stomatogastric ganglion.

1. We analyzed the physiological effects of the adenylate cyclase activator forskolin, and other adenosine 3',5'-cyclic monophosphate (cAMP)-elevating agents, on neurons of the pyloric circuit from the stomatogastric ganglion of the lobster Panulirus interruptus. Agents were bath applied to pyloric neurons either in the synaptically intact pyloric circuit or following isolation from all known synaptic input. 2. Several cAMP-elevating agents, including forskolin, 3-isobutyl-1-methylxanthine, Ro20-1724, and 8-bromo-cAMP, generated similar motor patterns from the pyloric circuit. The motor patterns exhibited an increased cycle frequency and enhanced spike activity from all classes of pyloric neurons. Since these agents differ both in structure and site of action in the cAMP pathway, their physiological effects on the motor pattern probably result from increased cAMP levels in pyloric neurons. 3. When forskolin was applied to synaptically isolated neurons, it caused a strong activation or enhancement of activity of all pyloric cells. However, it induced different types of activity in different cells, including the induction of bursting pacemaker potentials in one cell type, activation of plateau potentials in another, and depolarization with activation or enhancement of tonic spike activity in the remaining cells. Thus there is no single physiological response to cAMP elevation in the pyloric circuit; its effects can be quite diverse, mediating several activity states, in different cells. 4. Radioimmunoassays were performed on whole stomatogastric ganglia to determine whether known neuromodulators can affect cAMP concentrations. Both forskolin and octopamine increased cAMP levels, whereas dopamine, serotonin, proctolin, and FMRFamide did not appreciably affect cAMP levels. The physiological effects of octopamine and forskolin are similar in most, but not all, pyloric cells. Octopamine is thus a candidate neuromodulator whose actions may be mediated, at least in part, by increased cAMP in some pyloric cells; however, forskolin does not completely mimic the physiological effects of octopamine on all pyloric neurons, suggesting that octopamine can also act by other biochemical mechanisms.

1-Methyl-3-isobutylxanthine↗