Running gels backwards to select DNA molecules larger than a minimum size.
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DNA↗
Biomedical subjects
D S Parker
Publications and source records attributed to D S Parker.
Probiotics shown to change bacterial community structure in the avian gastrointestinal tract.
Culturing and molecular techniques were used to monitor changes in the bacterial flora of the avian gastrointestinal (GI) tract following introduction of genetically modified (GM) and unmodified probiotics. Community hybridization of amplified 16S ribosomal DNA demonstrated that the bacterial flora of the GI tract changed significantly in response to the probiotic treatments. The changes were not detected by culturing. Although both GM and non-GM strains of Enterococcus faecium NCIMB 11508 changed the bacterial flora of the chicken GI tract, they did so differently. Probing the community DNA with an Enterococcus faecalis-specific probe showed that the relative amount of E. faecalis in the total eubacterial population increased in the presence of the non-GM strain and decreased in the presence of the GM probiotic compared with the results obtained with an untreated control group.
Aging↗
Gene transfer in the gastrointestinal tract.
The maximum in vivo transfer rate of plasmid pAMbeta1 in the gut was 0.03 transconjugant per recipient cell, and this rate could be simulated in vitro only by forced filter mating. Transfer was not detected in liquid culture matings. Our findings demonstrate that in vitro methods, such as forced filter mating and liquid mating, underestimate the in vivo rates of gene transfer.
Animals↗
Term domain distribution analysis: a data mining tool for text databases.
In this paper, we give a case history illustrating the real-world application of a useful technique for data mining of text databases. The technique, which we call Term Domain Distribution Analysis (TDDA), consists of keeping track of term frequencies for specific finite domains and announcing significant differences from standard frequency distributions over these domains as a hypothesis. TDDA is part of a larger framework, the Digital Filter Model, for data mining of text documents. In the case study presented, the domain of terms was the pair {right, left}, over which we expected a uniform distribution. In analyzing term frequencies in a thoracic lung cancer database, the TDDA technique led to the surprising discovery that primary thoracic lung cancer tumors appear in the right lung more often than the left lung, with a ratio of 3:2. Treating the text discovery as a hypothesis, we verified this relationship against the medical literature in which primary lung tumor sites were reported, using a standard chi 2 statistic. We subsequently developed a working theoretical model of lung cancer that may explain the discovery. This discovery and our model may change how oncologists view the mechanisms of primary lung tumor location.
Humans↗
The metabolic fate of the amido-N group of glutamine in the tissues of the gastrointestinal tract in 24 h-fasted sheep.
Whole-body and gastrointestinal tract (GIT) metabolism of [5-(15)N]glutamine were monitored in lambs (33 kg live weight) fasted for 24 h. Animals were previously prepared with vascular catheters across the mesenteric-(MDV) and portal-drained viscera (PDV) to permit quantification of mass and isotopic transfers of metabolites by arterio-venous difference. Continuous infusions of [5-(15)N]glutamine into the jugular vein were conducted for 10 h and integrated blood samples withdrawn over 75 min intervals for the last 5 h of infusion. The lambs were then killed and portions from various tissues of the digestive tract and other body organs removed for determination of 15N enrichment in RNA, DNA and protein (the latter obtained by difference using total acid-precipitable N). Whole-body glutamine flux was 108 mumol/min of which 23 and 47% could be attributed to MDV and PDV metabolism (P < 0.001) respectively. There was a small net production of glutamine across the MDV. GIT blood-flows and NH3 production were partitioned 3:2 between MDV and non-MDV components. Less than 5% of the NH3 produced was derived from the amido-N of glutamine, while across the small intestine (MDV) 26% of the glutamine flux was converted to NH3, compared with 18% for non-MDV transfers. The 15N enrichments in protein were of the order jejunum > duodenum > ileum with mucosal cells more labelled than serosal (P < 0.001). Lesser enrichments were observed for other GIT tissues (abomasum > caecum > rumen) while liver and lymph were comparable with the abomasum; kidney, spleen and muscle were lower still (P < 0.05). Enrichments of RNA were similar to that of protein and followed the same pattern, except for higher relative values for liver, spleen and lymphoid tissue. The lowest enrichments were observed for DNA, but again the pattern order was similar except for increased label in lymph, caecum and the spleen. For the MDV there was reasonable agreement between 15N-disappearance as glutamine and appearance in NH3 (24%), protein (81%), RNA (3.6%) and DNA (2.1%). For the total PDV there was a shortfall (-12%), however, which may be due to losses in lumen components. These results show the importance of the GIT as a contributor to total glutamine plasma flux, but indicate a lesser reliance on glutamine metabolism by the digestive tract of the ruminant compared with observations from non-ruminants.
Ammonia↗
Glucose and [13C]leucine metabolism by the portal-drained viscera of sheep fed on dried grass with acute intravenous and intraduodenal infusions of glucose.
The effect of exogenous glucose supply by either intrajugular (IJG) or intraduodenal (IDG) infusion at 2.0 mg glucose/kg body weight per min was investigated in four wether sheep (average weight 44 (SD 4) kg) chronically catheterized in the carotid artery and portal veins. Sheep were fed on a dried grass pellet diet hourly using continuous belt feeders. Whole-body glucose irreversible loss (IL) rate, measured with [6-3H]glucose, was increased by 0.5 and 0.8 of exogenous supply for IJG and IDG infusions respectively. Portal glucose utilization, measured by isotope dilution across the portal-drained viscera, was unaffected by additional glucose regardless of the route of glucose supply (P = 0.76 for control v. glucose infusions) and was a constant proportion of glucose IL (0.28) for all treatments. Portal plasma flow was higher during IDG infusions compared with IJG infusions (1.65 v. 1.44 litres/min, P = 0.055). Circulating total free amino acid concentrations fell during glucose infusions (2146, 1808 and 1683 mumol/l for control, IJG and IDG treatments respectively, P = 0.067 for treatment effect) but net portal absorption was not affected by increased glucose supply. Recovery in the portal vein of [1-13C]leucine infused into the duodenum averaged 0.65 and was not affected by increasing glucose supply to the gut tissues. The results show that glucose utilization by gut tissues is responsive to changes in both vascular and luminal glucose supply. The effects of changing gut tissue use of glucose and increased whole body glucose IL on metabolism of nutrients is discussed.
Amino Acids↗
Effect of intraruminal propionic acid infusion on metabolism of mesenteric- and portal-drained viscera in growing steers fed a forage diet: II. Ammonia, urea, amino acids, and peptides.
This experiment investigated the effect of intraruminal infusion of propionic acid on the net flux of nitrogenous compounds across the mesenteric- (MDV) and portal-(PDV) drained viscera of seven Friesian steers, average BW 127 kg (SEM 4.6), fed a grass-pellet diet. Each received by random allocation 0 (control), .5, or 1.0 mol of propionic acid/d for 7 d. Blood flow in mesenteric and portal veins was determined by downstream dilution of p-aminohippuric acid in order to determine net appearance rates across the gastrointestinal tissues. Net urea and ammonia flux was unaffected by propionic acid supply. Circulating plasma free amino acid concentrations were increased (P < .05) by propionic acid infusion (2,235, 2,428, and 2,427, error mean square [EMS] 44,370 microM, for control, .5, and 1.0 mol of propionic acid/d, respectively). Net amino acid flux rates were increased at the highest rate of propionic acid infusion across MDV and PDV (4.66, 3.69, and 6.11, EMS 2.98 mol/d for MDV [P < .05] and 2.98, 2.45, and 3.73, EMS 1.69 mol/d for PDV [P < .10] for control, .5, and 1.0 mol of propionic acid/d respectively). Positive venous-arterio concentration differences for peptide-bound amino acids (PBAA) across the MDV and PDV indicated net appearance across the gastrointestinal tissues, but this was not affected by propionic acid infusion. The data show that amino acid flux across postruminal tissues can be influenced by ruminal propionic acid supply and that this does not affect PBAA appearance.
Amino Acids↗
Metabolic implications of ammonia production in the ruminant.
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Amino Acids↗
Effect of intravenous glucose infusion on metabolism of portal-drained viscera in sheep fed a cereal/straw-based diet.
This experiment investigated the effect of intrajugular infusion of glucose on whole-body glucose metabolism and the absorption of nutrients by the portal-drained viscera of four Suffolk-cross sheep, average BW 46 +/- 7 kg, fed a cereal/straw-based pelleted diet. Each sheep received by random allocation 0 (control), 1.0, or 2.0 mg of glucose.kg BW-1.min-1 for 8 h infused into the jugular vein. Glucose irreversible loss rate, measured by simultaneous infusion of 6-[3H]-glucose, increased approximately stoichiometrically during glucose infusion (.51, .75, and 1.09 error mean square [EMS] .032 mmol/min for control, 1.0, and 2.0 mg of glucose infused.kg BW-1.min-1, respectively). Utilization of glucose increased in portal tissues (P = .089) as a result of glucose infusion (.17, .18, and .33 EMS .008 mmol/min) and was a constant proportion of glucose irreversible loss (.28). Portal blood flow was not affected by glucose infusion (overall mean 1.13 L/min EMS .034). Net portal absorption of acetate increased during glucose infusion although ruminal VFA concentrations were not affected. In contrast, net free amino acid absorption by portal-drained tissues was reduced during glucose infusion (291, 115, and 4 EMS 33,816 mumol/min, P = .054). These results show that metabolism of nutrients across the gut wall is influenced by glucose availability to gastrointestinal tissues and affects the pattern of nutrients available to the liver and peripheral tissues.
Absorption↗
Glucose and L-lactate metabolism in pregnant and in lactating ewes fed barley- or ground maize-based diets.
The contribution of glucose absorbed from the small intestine to whole-body glucose metabolism was examined in ewes during late pregnancy and early lactation, using diets based on ground barley or ground maize. Glucose and L-lactate turnover in the whole body and the mesenteric-drained viscera were investigated in these ewes using isotope dilution techniques. The net absorption of glucose by the mesenteric-drained viscera and whole-body glucose turnover were unaffected by diet or reproductive status. Arterial and mesenteric venous blood glucose concentrations, arterial and mesenteric venous L-lactate concentrations and whole-body lactate turnover were all significantly higher in lactation than in pregnancy. The whole-body rates of lactate conversion to glucose and to other products were significantly higher in lactation than in pregnancy. Using a two-pool model of whole-body glucose and lactate metabolism, a relatively high percentage of glucose was converted to lactate (64-84%), accounting for 60-80% of whole-body lactate turnover. A model of glucose and lactate metabolism by the mesenteric-drained viscera was constructed. Both the calculated endogenous glucose production and the visceral conversion of glucose to lactate were greater in lactation than in pregnancy when barley was fed. Calculated total glucose absorption was relatively constant, contributing between 26 and 59% of whole-body glucose turnover. Diet had little effect on glucose and lactate metabolism in either the mesenteric-drained viscera or the whole-body of breeding ewes.
Animals↗
Effect of intraruminal propionic acid infusion on metabolism of mesenteric- and portal-drained viscera in growing steers fed a forage diet: I. Volatile fatty acids, glucose, and lactate.
This experiment investigated the effect of intraruminal infusion of propionic acid on ruminal VFA metabolism and the absorption of nutrients by the mesenteric- and portal-drained viscera of seven Friesian steers, average BW 127 kg, fed a dried grass-pellet diet. Each received by random allocation 0 (control), .5, or 1.0 mol of propionic acid/d for 7 d. Ruminal acetate and propionate irreversible loss rates and carbon exchange between VFA and CO2 were measured during continuous intraruminal infusions of 2-14C-acetic acid and 2-14C-propionic acid. Ruminal acetate irreversible loss rate was not affected by propionic acid infusion (overall mean 8.09, error mean square [EMS] 2.68 mol/d), whereas propionate irreversible loss increased incrementally with PA supply (3.22 vs 4.16, EMS .61 mol/d, for control and 1.0 mol of propionic acid/d, respectively, P = .09). Glucose irreversible loss rate was increased at the highest level of PA infusion (2.84, 2.83, and 3.22, EMS .06 mol/d, for control, .5, and 1.0 mol of propionic acid/d, respectively; P = .02 for control vs .5 + 1.0), although the proportion of glucose irreversible loss derived from propionate remained constant (.6). Net absorption into venous blood showed that propionate was extensively metabolized in the rumen wall and that the tissues of the small intestine utilized acetate. Utilization of glucose was reduced in portal tissues as a result of intraruminal infusion, and the data were used to derive a model of glucose and lactate interrelationships in gut tissues.
Absorption↗
Simultaneous determination of allantoin and oxypurines in biological fluids by high-performance liquid chromatography.
A high-performance liquid chromatographic method is described for the separation and quantification of allantoin and oxypurines in plasma and urine samples. Urine was analyzed directly and plasma after acid deproteinisation with perchloric acid. Separation and quantification of purine derivatives was achieved using two Spherisorb ODS-5 column (250 mm x 4.6 mm I.D.) connected in series together with a NH4H2PO4-NH4H2PO4-acetonitrile (80:20) gradient and monitoring the effluent at 205 nm. The average recoveries of standard compounds added to urine and plasma samples were 96 and 97%, respectively, using allopurinol as internal standard. The within-day variability was less than 7% and the day-to-day coefficient of variation less than 11% indicating a good precision of the method.
Allantoin↗
Purine metabolite concentrations in portal and peripheral blood of steers, sheep and rats.
1. The concentration of purine derivatives in portal and peripheral blood of steers, sheep and rats was measured by reverse-phase high performance liquid chromatography. 2. Nucleotides, nucleosides (apart from inosine), adenine and guanine were not found in the plasma samples. Allantoin, uric acid, hypoxanthine and xanthine accounted for virtually all purine metabolites in plasma samples. 3. Non-oxidized derivatives (hypoxanthine and xanthine) were consistently detected in sheep but not in steer or rat plasma samples showing a differential availability of reutilizable purine derivatives between species.
Animals↗
The effect of forage and forage-concentrate diets on rumen fermentation and metabolism of nutrients by the mesenteric- and portal-drained viscera in growing steers.
Growing Friesian steers chronically catheterized in the anterior mesenteric and portal veins were used to study the influence of feeding with either a forage or forage-concentrate diet on nutrient utilization by mucosal tissue. When animals were consuming the forage-concentrate diet the molar proportion of propionate in rumen fluid was significantly increased, although production rate as measured by isotope dilution was not altered. Net rates of absorption of VFA into portal blood when compared with rumen production rates underlined the extent to which metabolism within mucosal tissue modifies the propionate supply to the liver. Net glucose utilization by splanchnic tissue was shown to be significantly lower on the forage-concentrate diet. There were no effects of diet on whole-body glucose turnover or on the proportion of glucose derived from propionate. Animals fed on the forage-concentrate diet had significantly lower concentrations of circulating essential amino acids, due mainly to a reduction in branched-chain amino acid levels. There was net absorption of all amino acids by animals on both diets except for glutamate, glutamine and taurine in forage-fed animals.
Amino Acids↗
Isolation and characterization of circulating low molecular weight peptides in steer, sheep and rat portal and peripheral blood.
1. Low mol. wt peptides in plasma were isolated by reverse-phase HPLC from steer and sheep carotid arterial and rat heart blood and portal blood from all three species. 2. Elution profiles for peptide fractions were similar but the concentration of peptide-bound amino acids (PBAA) in fractions corresponding to different mol. wt peptides was not constant across species. 3. PBAA contributed between 65 and 78% to the plasma amino acid pool in steer and sheep but only 52% in the rat (P less than 0.05). 4. The percentage of many individual amino acids present in either free amino acid (FAA) or PBAA pools was different for ruminant compared with rat plasma but it was similar for steer and sheep apart from branch-chain amino acids (P less than 0.05).
Amino Acids↗
The influence of inclusion of either an antibiotic or a probiotic in the diet on the development of digestive enzyme activity in the pig.
The aim of the present experiment was to determine the influence of either probiotic or antibiotic inclusion in the diets of pigs from birth on the development of enzyme activity in the small intestine. Pigs were fed on creep feed and grower diets containing either a probiotic, an antibiotic or no added growth promoter. At 7, 17, 42 and 80 d of age pigs from each treatment group were sampled to investigate the development of carbohydrase and peptidase activity in the mucosa at five sites along the small intestine. Inclusion of either the probiotic or antibiotic had a significant effect on the development of sucrase (sucrose alpha-D-glucohydrolase; EC 3.2.1.48), lactase (beta-D-galactoside galactohydrolase; EC 3.2.1.23) and tripeptidase (EC 3.4.11.4) activities before weaning but had no effect on depeptidase (EC 3.14.13.11) activity. The study of the distribution of enzyme activity along the small intestine showed significant differences between the proximal and distal sections associated with weaning.
Aging↗
Manipulation of the functional activity of the gut by dietary and other means (antibiotics/probiotics) in ruminants.
The mucosa of the gut is some of the most metabolically active tissue in the body. This paper discusses the methodology used to assess enterocyte cell metabolism and nutrient uptake in the reticulorumen and small intestine of ruminant species. Metabolism of volatile fatty acids and glucose by this tissue may limit the availability of essential nutrients to peripheral tissues, and the extent to which this may vary between concentrate-based and forage-based diets is discussed. Factors that affect the development and expression of metabolite uptake by the enterocyte are considered in addition to the influence that manipulation of the microbial flora of the gut by the use of antibiotic growth promoters or probiotics may have upon this process. Data are presented to show that the use of antibiotic compounds in ruminant feeds can influence the rate of cell turnover in the small intestine and the rate of glucose uptake by isolated brush border vesicles.
Animal Nutritional Physiological Phenomena↗
Mechanisms in the transformation of IL3-dependent hematopoietic stem cells.
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Animals↗