Showing papers by "Fergus Shanahan published in 1995"

Discontent with dysplasia surveillance in ulcerative colitis

Abstract: Dysplasia surveillance by microscopic examination of endoscopic biopsy sections from patients with ulcerative colitis is a subjective and insensitive method of identifying those at particular risk of developing cancer. The need for better molecular and cytochemical markers of cancer risk is well recognized. The search for such markers has included examination of mucin and other glycoprotein expression, flow cytometric profile of DNA content, and molecular analysis of oncogene mutations and tumor suppressor genes. Although promising, these approaches have not yet yielded a validated, reliable cancer marker of high predictive value. Light microscopy is still the most practical and conveniently available approach. Debate, therefore, focuses on the effectiveness of the current practice and whether it can be improved.

Irish Society of Gastroenterology: Proceedings for summer meeting – 26th/27th May 1995 in Galway

Abstract: Endothelin isopeptides (ET-1, -2, -3) and sarafotoxin 6c (SX6c) are potent contractors of the guinea-pig isolated gallbladder. Based on the relative potencies of ET agonists and the effects of several ET receptor antagonists, we have reported that two receptors, an ETB and an additional uncharacterised receptor , media te these con t rac t ions . Here, we have characterized the binding of ET to guinea-pig gallbladder membranes. Guinea-pigs (250-350g) were killed by cervical dislocation and the gallbladder rapidly excised, trimmed free of connec t ive t i ssue and fat, minced to smal l p ieces and homogenized for 10min in 10 volumes of ice-cold assay buffer. The homogenate was centrifuged for 15 min at 1500g (4~ the supernatant collected and centrifuged for 60 rain at 100,000g (4~ The.pellet formed was resuspended in 3 ml of ice-cold assay buffer (as above) and its protein content determined. The membranes (20~tg of protein) were incubated in binding buffer with 125I-ET-1 (2000 Ci/mmol) in the presence of 1015M to 106M ET-I, ET-3 or SX6c. After 240 min at room temperature, the binding was stopped by filtering the incubate through a Whatman glass filter followed by washing with 3 x 4 ml of ice-cold binding buffer. The amount of radioactivity present on the filter was measured in a gamma counter for 60 sec. In competition binding studies using membranes prepared from the guinea-pig gallbladder 10 11 M and 10 -6 M ET-1 inhibited by 76.9+3.1 and 95.7+1.1% respectively, the binding of [I25I]ET-I (n=3). The displacement of 125I-ET-1 by ET-I was biphasic. A very high affinity site (ICs0: 35fM) and a high affinity site (IC5o: 0.18 nM) were observed. They represented 75% and 25% respectively, of the total population of ET receptors. Using ET-3 as the cold ligand, a biphasic displacement was also observed (IC50:0.10 nM and 70 nM, each representing about 50% of total binding). Using SX6c, a monophasic curve was observed with one site of low affinity (IC50:>70 nM). This study shows that ET agonists in the guinea-pig gallbladder act through at least two high affinity sites and one lower affinity site. This supports our previous reports showing the existence of at least two receptors in this tissue. Further studies will be conducted to determine the exact nature of these receptors. This work was suppor t ed in par t by Pa rke -Dav i s Pharmaceutical.