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Biomedical subjects

T J Wilson

Publications and source records attributed to T J Wilson.

At least 73 records · Page 4Linked to original sources
PubMed1988

Effects of urogastrone (epidermal growth factor) on the intestinal epithelium.

Recombinant urogastrone (human epidermal growth factor) was infused into rats in which intestinal cell proliferation was reduced to a steady state basal level by feeding them intravenously. Urogastrone elevated the augmented metaphase index and weight of all sections of the gastrointestinal tract in a dose-related manner. Infusion of urogastrone at a dose which has a minimal effect on gastric acid secretion significantly increased crypt cell production and tissue weights throughout the gastrointestinal tract. Intravenous urogastrone was also effective in restoring cell proliferation after the intestine had become hypoproliferative. Urogastrone administered luminally had no significant effect on either intestinal weight, crypt cell production rate, or metaphase collection.

Animals↗
PubMed1987

Dexamethasone selectively increases sodium-dependent alanine transport across neonatal piglet intestine.

1. Lysine and alanine uptake by pig enterocytes has been measured in piglet mid intestine both during normal development and 3 days after injection of dexamethasone and epidermal growth factor (EGF) into 3-day-old animals. 2. Alanine uptake measured in the presence of sodium increased markedly during the first 4 weeks of post-natal life. Similar effects on alanine uptake could be produced through injection of dexamethasone, but not EGF, into 3-day-old piglets. Alanine uptake measured in the absence of sodium and lysine uptake measured in the presence of sodium remained unchanged during development and unaffected by injection of dexamethasone or EGF. 3. Enterocytes capable of transporting alanine in the presence of sodium were found, by quantitative autoradiography, to cover the top 400 micron of the villus in 6-day-old and 3-4-week-old control pigs. Alanine concentrations in villus tip enterocytes in 3-4-week-old pigs were four times those found in 6-day-old animals. Qualitative examination of selected villi, however, showed alanine uptake taking place over a considerably greater area of villus surface in 6-day-old compared with 3-4-week-old animals. 4. Injection of dexamethasone and EGF into 3-day-old piglets caused an increase in crypt depth without apparent change in crypt cell proliferation. The rate at which enterocytes migrated out of the crypt and the length of individual villi also remained unchanged by dexamethasone or EGF injection. 5. Dexamethasone produces its effect on alanine uptake by acting on older enterocytes present on the upper part of the villus. These enterocytes can be shown, by calculations based on enterocyte migration rate, to have already been present on the villus at the time the pig was born. 6. The above findings are discussed in relation to the ability of villus as well as crypt enterocytes to change their programme of differentiation in response to external stimuli. The particular ability of dexamethasone to induce system A type carrier function is further discussed in relation to normal changes found to occur during neonatal development. It is finally suggested, as a working hypothesis, that endogenous glucagon might act as the final mediator of both developmentally controlled and dexamethasone-induced changes in amino acid transport.

Alanine↗
PubMed1987

Epidermal growth factor selectively increases maltase and sucrase activities in neonatal piglet intestine.

1. Pig intestinal sucrase and maltase activities increase markedly, and lactase activity decreases, during the second week of post-natal life. Correlations noted between the time course describing these changes and that found previously to describe a decline in the ability of the pig intestine to take up macromolecules suggest that both events are subject to the same type of developmental control. 2. Injection of epidermal growth factor (EGF) into 3-day-old piglets increase sucrase and maltase activities measured 3 days later. These increases, which are not seen when measuring other hydrolase enzymes, are confined to the mid and distal regions of the small intestine. 3. Dexamethasone injected into 3-day-old piglets inhibits lactase and, on occasion, sucrase activities without affecting other intestinal hydrolases. Significant increases in sucrase and maltase activities also occur in distal intestine following injection of EGF plus dexamethasone into 3-day-old pigs. 4. Cytochemical analysis shows EGF effects on sucrase and maltase activities to be exerted in crypt and basal villus enterocytes produced post-natally. Dexamethasone inhibits lactase activity mainly by acting on mid and upper villus enterocytes produced before birth. 5. EGF appears to increase sucrase and maltase activities by extending the time during which young enterocytes continue to accumulate these enzymes in their brush-border membranes. Dexamethasone appears to cause a more fundamental change in the biochemistry of older enterocytes. accompanied by an increasing ability of these cells to transport neutral amino acids through a sodium-dependent mechanism (see James, Smith, Tivey & Wilson, 1987a).

Animals↗
PubMed1987

Intravenous but not intragastric urogastrone-EGF is trophic to the intestine of parenterally fed rats.

The effects of beta-urogastrone/human epidermal growth factor (URO-EGF) on intestinal epithelial cell proliferation were studied in rats in which intestinal cell proliferation had been reduced to a steady state basal level, by maintaining the rats on total parenteral nutrition. The accumulation of arrested metaphases over a two hour time period was determined in a dose response study. Increasing doses of URO-EGF progressively raised the two hour collection of metaphases and intestinal weights. Intravenous infusion of URO-EGF was also effective in restoring cell proliferation when it was infused after the intestine had become hypoproliferative. beta-urogastrone/human epidermal growth factor administered through an intragastric cannulae thrice daily had no significant effect on intestinal weight or crypt cell production rate or metaphase collection. It is proposed that one of the in vivo actions of urogastrone-epidermal growth factor is the maintenance of gastrointestinal growth and that this occurs through a systemic rather than a luminal mechanism.

Animals↗
PubMed1987

Proliferative effects of urogastrone-EGF on the intestinal epithelium.

The effects of B-urogastrone/human epidermal growth factor on intestinal epithelial cell proliferation were studied in rats in which intestinal cell proliferation was reduced to a steady state basal level (by maintaining the rats on total parenteral nutrition). Increasing doses of urogastrone progressively raised the two hour collection of metaphases and intestinal weights. The crypt cell production rate was measured in animals maintained parenterally with or without urogastrone, and in rats fed a standard laboratory ration. Continuous infusion of 15 micrograms per rat per day of recombinant beta urogastrone (a dose which has a minimal effect on gastric acid secretion) significantly increased cell proliferation and intestinal tissue weights throughout the gastrointestinal tract. Intravenous infusion of urogastrone was also effective in restoring cell proliferation when it was infused after the intestine had become hypoproliferative. Urogastrone administered through an intragastric cannula thrice daily had no significant effect on either intestinal weight, crypt cell production rate, or metaphase collection.

Animals↗
PubMed1985

Urogastrone-epidermal growth factor is trophic to the intestinal epithelium of parenterally fed rats.

The weight of the stomach, small intestine and colon and the mucosal crypt cell production rate of these tissues were significantly decreased after 10 days on an isocaloric TPN diet when compared to orally fed controls. Continuous infusion of recombinant beta urogastrone, at a dose below that needed to inhibit gastric acid secretion, largely prevented this decrease in crypt cell production rate and gastrointestinal tissue weights.

Animals↗
PubMed1985

Use of a mouse chimaeric model to study cell migration patterns in the small intestinal epithelium.

The pattern of cells migration in the small intestinal epithelia of a RIII/ro----C57BL/6J mouse aggregation chimaera is demonstrated using Dolichos biflorus agglutinin-peroxidase (DBA) conjugate as a strain-specific marker. Using serial tangential sections of heterogeneously stained villi and plotting the distribution of labelled/unlabelled cells with a drawing tube, and by three-dimensional reconstruction with the aid of computer graphics, we show the migration pathway to be in tight cohorts of similar DBA-peroxidase staining type, which move upwards in straight lines. There is little cell mixing either on the villus or along the crypt-villus junctions. Our observations also show for the first time that a single crypt can feed cells to more than one villus. They also suggest that either cell loss is not confined to the villus tips but can take place from the villus sides, or that there is marked asynchrony of cell production between crypts.

Animals↗
PubMed1978

Relationship between platelet count and cardiotomy suction return.

A simple, inexpensive, accurate method of measuring the amount of blood returned by the cardiotomy suction system was devised and calibrated. Preoperative and postoperative platelet counts were obtained in 76 patients with congenital heart disease in whom the amount of cardiotomy suction return was measured. The mean percentage of total perfusate returned by the cardiotomy suction system was 8.9%. Both postoperative platelet count and the percentage change between preoperative and postoperative platelet counts correlated with the amount of blood returned by the cardiotomy suction system, time on bypass, and the percentage of total perfusate aspirated by the system.

Adolescent↗
PubMedDate not supplied

A locus determining pathogenicity of Xanthomonas campestris is involved in lipopolysaccharide biosynthesis.

A pathogenicity locus in Xanthomonas campestris pv. campestris has been shown to comprise two genes which mediate biosynthesis of the bacterial lipopolysaccharide (LPS) but not extracellular polysaccharide. Mutants with Tn5 insertions in either gene showed alterations in the electrophoretic patterns of both water-soluble and phenol-soluble LPS forms, which suggested defects in the biosynthesis of the core oligosaccharide component. On gel chromatography, core oligosaccharides of the mutants were of apparently lower molecular weight than those from the wild type. Furthermore, the content of mannose and glucose, sugars characteristic of the core oligosaccharide, were significantly lower in the water-soluble LPS of the mutants. Because of their role in LPS core biosynthesis, the two genes were called rfaX and rfaY. rfaX mutants show altered behavior in a range of host and non-host plants such that the number of recoverable bacteria drop within the first 24 h after inoculation. In contrast, the behavior of rfaY mutants only differed from the wild type in Datura, a non-host plant in which the growth of the wild type is severely attenuated. The predicted protein RfaY showed significant sequence homology to a sub-family of RNA polymerase sigma factors which are involved in extracytoplasmic functions.

Amino Acid Sequence↗
PubMedDate not supplied

Use of the Mycosep multifunctional cleanup column for liquid chromatographic determination of aflatoxins in agricultural products.

A liquid chromatographic (LC) technique has been developed that uses the Mycosep multifunctional cleanup (MFC) column. MFC columns provide a rapid 1-step extract purification. They are designed to retain particular groups of compounds that may create interferences in analytical methods. At the same time, MFC columns allow compounds of interest to pass through. In the method presented, test samples are extracted in a blender with acetonitrile-water (9 + 1). A portion of the extract is forced through an MFC column designed especially for analysis of numerous mycotoxins. Analytical interferences are retained, while aflatoxins pass through the column. Aflatoxins B1 and G1 are converted to their hemiacetals by heating a mixture of purified extract and water-trifluoroacetic acid-acetic acid (7 + 2 + 1) at 65 degrees C for 8.5 min. An aliquot of this mixture is analyzed by isocratic LC with acetonitrile-water mobile phase and fluorescence detection. A detection limit of less than 0.5 ng/g for aflatoxin B1 was obtained. Average recoveries greater than 95% total aflatoxins (B1, B2, G1, and G2) and coefficients of variation of less than 3% were obtained. The method was successfully applied to the following commodities: corn, almonds, pista-chios, walnuts, peanuts, Brazil nuts, milo, rice, cottonseed, corn meal, corn gluten meal, fig paste, and mixed feeds.

Aflatoxins↗