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Biomedical subjects

N A Wright

Publications and source records attributed to N A Wright.

At least 73 records · Page 4Linked to original sources
PubMed1998

Alterations in classical cadherins associated with progression in ulcerative and Crohn's colitis.

Human colitis is a condition associated with a spectrum of altered morphologic changes and cellular adhesion. The role of cadherins, which are powerful morphoregulatory cell adhesion molecules, in colitis is provocative and as yet unknown. Herein, we present results that suggest a strong correlation between the deregulation of two cadherin molecules, E- and P-cadherins, and the progression of human colitis. We examined the expression and structural integrity of E- and P-cadherins in inflamed, dysplastic, or neoplastic human ulcerative colitis (UC) (n=58), human Crohn's colitis (n = 30), and normal tissue (n = 20) to assess cadherin function in normal and abnormal epithelium. E-cadherin is strongly expressed in normal colorectal epithelium, whereas in left-sided UC it is either down-regulated or has a single-base pair mutation in exon 4 resulting in an amino acid alteration (6 of 58 UC cases). By contrast, P-cadherin is dramatically up-regulated in both Crohn's disease and ulcerative colitis and especially in dysplastic ulcerative tissue. In vitro transfected SW-480 colorectal cells containing E-cadherin mutations identical to those in vivo were associated with increased spontaneous disaggregation compared with cells transfected with wild-type E-cadherin. Based on this evidence, we hypothesize that a small subset of colorectal cells expressing mutant E-cadherin are associated with widespread ulceration, whereas those expressing P-cadherin are associated with a rapidly dividing immature phenotype that includes dysplasia. The differential expression of mutated and wild-type cadherins examined herein are associated with a broad spectrum of abnormal epithelial phenotypes, lymphocyte integrin binding, and resistance to denudation, as is seen in the colitis adenocarcinoma sequence.

Adult↗
PubMed1997

The incidence of aberrant crypt foci and colonic carcinoma in dimethylhydrazine-treated rats varies in a site-specific manner and depends on tumor histology.

In an attempt to demonstrate the relationship between aberrant crypt foci (ACF) and subsequent colonic neoplasms, we investigated the distribution of ACF in the dimethylhydrazine (DMH) model of colonic carcinogenesis in the rat. DMH was given to male Wistar rats by s.c. injection in a dosage of 15 mg/kg body weight once a week for 19 weeks. As a result, eight poorly differentiated, mucin-secreting carcinomas, two well-differentiated tubular adenocarcinomas, and four adenomas developed in 35 rats autopsied at 24 weeks after the first injection of DMH. The location of each type of tumor was site specific. Poorly differentiated, mucin-secreting carcinomas of signet-ring type occurred only in the proximal colon; the mean location of these lesions was 17.6 +/- 3.8% (SE; range, 0-39%) of the length of the colon. Well-differentiated tubular adenocarcinomas and adenomas developed in the distal colon; the mean location of these lesions was 76.7% +/- 4.9 (SE; range, 60-90%) of the length of the colon. There was a mean number of 276 +/- 29 (SE) ACF per colon; these were present at between 40 and 90% of the colonic length, peaking at 70%. We conclude that ACF are marker lesions for colonic neoplasms, but only in the distal colon where tumors follow the adenoma-carcinoma sequence; this is not so for the proximal colon, where poorly differentiated, mucin-secreting carcinomas are found. These findings suggest that these latter tumors well may arise de novo and indicate that studies that attempt to correlate ACF with subsequent tumor formation must take cognizance, not only of the site, but also of the tumor type.

Adenocarcinoma↗
PubMed1997

Rolling in the clover: trefoil factor family (TFF)-domain peptides, cell migration and cancer.

Trefoil factor family (TFF)-domain peptides 1-3 are mucin-associated molecules, largely found in epithelia of gastrointestinal tissues. Structurally similar, resistant to enzymatic degradation, they are up-regulated around areas of epithelial damage such as ulcers. Transgenic expression or exogenous peptide ameliorates or prevents gastric mucosal damage due to indomethacin and some are rapidly up-regulated after cryogenic burns. A role in promoting cell migration is strongly suggested. Knockout mice lacking TFF1 or TFF3 show significant pathology, with the former developing gastric tumours. A recent Conference Philippe Laudat agreed upon a new nomenclature for these peptides.

Animals↗
PubMed1997

Trefoil factor family domain peptides.

Within the past 15 years a new family of peptides has been identified, known as trefoil factor family (TFF) domain peptides; they are associated with mucin-secreting epithelial cells and synthesised predominantly in the gastrointestinal tract. They share a highly conserved physical structure, and their role in mucosal defence and healing is becoming increasingly clear, more recently a tumour suppressor function has been postulated. Outside the gastrointestinal tract, members of this group of peptides have also been identified in the normal hypothalamus and pituitary, and in normal breast tissue where it is responsive to oestrogen stimulation. Evidence of peptide expression has been found in a range of urological, gynaecological, gastrointestinal, pulmonary and breast carcinomas, and in the last two it appears to carry prognostic significance. The present review aims to summarise the rapidly expanding data on the role of these peptides in epithelial inflammation, repair and neoplasia.

Animals↗
PubMed1997

Differential expression of oestrogen receptor and oestrogen inducible genes in gastric mucosa and cancer.

BACKGROUND: Evidence exists for a role for oestrogen in gastric cancer. The incidence of gastric cancer is much higher in men than in woman, and a similar sex difference is also seen in a rat experimental model of gastric cancer. AIMS: Evidence for a functional oestrogen receptor in normal gastric mucosa and cancer has been sought. METHODS: Oestrogen receptor and the oestrogen inducible genes pS2 and ERD5 were sought by northern blot analysis and in situ hybridisation and immunohistochemistry. Oestrogen receptor protein was studied by enzyme immunoassay. RESULTS: mRNA for oestrogen receptor was detected in cancer and normal gastric mucosa. Enzyme immunoassay for oestrogen receptor showed a mean of 1.8 fmol/mg protein in cancer and 13.7 fmol/mg in paired normal mucosa. The oestrogen inducible genes pS2 and ERD5 were also detected in both cancer and normal mucosa, with expression localised to epithelium. Expression of pS2 was lower in cancer compared with normal mucosa, whereas ERD5 expression was higher in cancer. CONCLUSIONS: Significant amounts of oestrogen receptor were expressed in gastric mucosa with a lower amount in cancer. Oestrogen inducible genes were also expressed differentially but were not found to correlate closely with oestrogen receptor. Oestrogen receptor functionality remains to be demonstrated in the stomach.

Blotting, Northern↗
PubMed1997

T cell receptor-alpha beta-deficient mice fail to develop colitis in the absence of a microbial environment.

Mice with null mutations in cytokine or T cell receptor (TCR) genes develop intestinal inflammation. In the case of interleukin-2-/- and interleukin-10-/- mice it has been demonstrated that normal intestinal bacterial flora can cause gut pathology. TCR-alpha-/- mice not only develop colitis but also produce a strong antibody response to self-antigens, such as double-stranded DNA. It is therefore important to establish whether the intestinal inflammation develops spontaneously or is induced by luminal antigens. To address this issue, a germ-free colony of TCR-alpha-/- mice was derived and compared with TCR-alpha-/- mice kept in conventional specific-pathogen-free conditions. Although specific-pathogen-free animals developed colitis with a high level of penetrance, there was no evidence of intestinal pathology in germ-free animals. Furthermore, intestinal inflammation was not seen in TCR-alpha-/- mice colonized with a limited bacterial flora consisting of Lactobacillus plantarum, Streptococcus faecalis, S. faecium, and/or Escherichia coli. We conclude that intestinal inflammation in TCR-alpha-/- mice does not occur spontaneously nor does it result from the presence of bacteria, per se, but rather it is initiated by a specific organism or group of organisms normally present in the gut flora that have yet to be identified.

Animals↗
PubMed1997

Expression of oestrogen receptor and oestrogen-inducible genes in pancreatic cancer.

BACKGROUND: Previous studies have not been able to demonstrate convincingly whether the human pancreas expresses oestrogen receptor and whether there is any benefit from antioestrogen therapy in advanced pancreatic cancer. METHODS: Oestrogen receptor expression was assessed in normal human pancreas and pancreatic cancer tissue by enzyme immunoassay, Northern blot analysis, in situ hybridization and immunohistochemistry. The expression of the oestrogen-inducible proteins, progesterone receptor, pS2 and ERD5 was also examined. RESULTS: A mean of 1.0 (range 0-2.4) fmol oestrogen receptor per mg protein was detected in normal pancreas and 0.5 (range 0-1.2) fmol mg-1 in pancreatic cancer. Messenger RNA for oestrogen receptor was detected in both normal and cancerous pancreas. In situ hybridization and immunohistochemistry, however, failed to localize oestrogen receptor expression. Mean (range) expression of progesterone receptor in normal and neoplastic pancreas was 1.9 (0.5-3.5) and 2.5 (0.3-9.3) fmol mg-1 respectively. pS2 and ERD5 were also expressed in normal tissue and pancreatic cancer, and expression was localized to ductular epithelium. CONCLUSION: The amount of oestrogen receptor detected in pancreatic tissue was small, and may account for previous difficulties in its detection. The extent to which it is functional in both the normal and malignant pancreas warrants further investigation.

Adult↗
PubMed1997

Effects of epidermal growth factor and dimethylhydrazine on crypt size, cell proliferation, and crypt fission in the rat colon. Cell proliferation and crypt fission are controlled independently.

Crypt fission is now established as an important mechanism of intestinal growth and regeneration. It has been proposed that increased crypt size is the stimulus for crypt fission, because crypts preparing for fission are generally larger. Consequently, we investigated the effects of epidermal growth factor (EGF) and dimethylhydrazine, which are both known to stimulate crypt cell proliferation, on crypt fission in the rat intestine. We also examined whether the effects of EGF on both proliferation and crypt fission are modified by the pretreatment with dimethylhydrazine for 16 weeks, dimethylhydrazine was then discontinued for 8 weeks, followed by intravenous infusion of EGF for 1 week. There were four groups: vehicle alone, EGF alone, dimethylhydrazine alone, and dimethylhydrazine followed by EGF infusion. The rats were killed at 25 weeks and rates of intestinal crypt cell production, crypt size, and crypt fission were determined. Intravenously infused EGF significantly increased crypt cell production rate, but the magnitude of the effect decreased from the proximal to the distal colon. EGF caused an increase in crypt area, possibly reflecting an increase in crypt size. Importantly dimethylhydrazine had no significant effect on crypt cell production rate nor on crypt area in the distal colon, but it did cause an increase in crypt area in the mid-colon. The crypt fission index was significantly decreased by EGF and increased by dimethylhydrazine. There was no qualitative interaction between EGF and dimethylhydrazine. These results demonstrate the marked proliferative effect of intravenously infused EGF in the colon of orally fed rats, with significant site effects (P = 0.0007); the effect was greatest in the proximal colon and disappeared in the distal colon. The observation that EGF reduced crypt fission indicates that increased cell proliferation, per se, is not a stimulus for crypt fission. This is further supported by the observation that dimethylhydrazine increases crypt fission in crypts of normal size in the distal colon without significantly increasing cell proliferation. These results suggest that increasing crypt cellularity by proliferation is not sufficient to induce crypt fission, and factors other than increased crypt size by proliferation can control crypt fission. It is also probable that cell proliferation and crypt fission are independently regulated. Crypt fission appears to play a considerable role in the intestinal response to carcinogens.

Animals↗
PubMed1997

Duodenal content reflux esophagitis in the rat: an animal model for the ulcer-associated cell lineage (UACL)?

We have studied the histological changes observed in the mucosa of 10 rats in the region of a esophagojejunostomy to evaluate it as a model for the ulcer-associated cell lineage (UACL). In man, the UACL has a distinctive morphology, proliferative organization, and pattern of trefoil peptide localization. We have therefore examined these aspects aided by immunohistochemistry and in situ hybridization to the trefoil peptides TFF1, TFF2, and TFF3. Only TFF2 was studied by immunohistochemistry, whereas the mRNAs for all three peptides were examined by in situ hybridization using 35S-labeled riboprobes. The marker MIB-1 to the Ki67 proliferation-related antigen was used to examine the proliferative organization of UACL-like changes. In all cases, columnar epithelialization of the distal esophagus was seen, and in all, glands with morphological and gene expression attributes of the UACL were identified. TFF3 mRNA localized patchily throughout the UACL, whereas TFF1 mRNA was found in the upper portions of the lineage and TFF2 mRNA and its product in the acini. These lineages showed virtually no intrinsic proliferative activity. These appearances are similar to those seen in early human UACL, and we therefore propose this that this represents the first published animal model of this lineage.

Animals↗
PubMed1996

Analysis of foetal expression sites of human type II DNA topoisomerase alpha and beta mRNAs by in situ hybridisation.

We present the first analysis of the sites of expression of DNA topoisomerase II alpha and II beta mRNAs in human foetal tissues by in situ hybridisation, using 35S-radiolabelled probes. This revealed differential localisation of topoisomerase II alpha and II beta mRNAs in a range of foetal organs, including foetal kidney (developing structures within the neogenic zone), brain (cortical layers), small intestine (crypt epithelium and muscle), liver (hepatocytes), lung (smooth muscle, and epithelium in the lining of primitive lung buds) and placenta (trophoblastic epithelium). The intensity of expression of topoisomerase II alpha mRNA appeared higher than that of topoisomerase II beta, although topoisomerase II beta mRNA was expressed in a broader range of cell types. The distinct patterns of expression of topoisomerase II alpha and beta mRNAs indicate differential regulation of these genes, suggesting that the two isoforms may play important but different roles in foetal development, with topoisomerase II alpha being expressed most strongly in zones of proliferation.

Antigens, Neoplasm↗
PubMed1996

Polyclonal origin of colonic adenomas in an XO/XY patient with FAP.

It is widely accepted that tumors are monoclonal in origin, arising from a mutation or series of mutations in a single cell and its descendants. The clonal origin of colonic adenomas and uninvolved intestinal mucosa from an XO/XY mosaic individual with familial adenomatous polyposis (FAP) was examined directly by in situ hybridization with Y chromosome probes. In this patient, the crypts of the small and large intestine were clonal, but at least 76 percent of the microadenomas were polyclonal in origin.

Adenomatous Polyposis Coli↗
PubMed1996

Effects of pancreatic spasmolytic Polypeptide (PSP) on epithelial cell function.

Trefoil peptides are expressed near endodermal ulcerations and may modulate epithelial repair. The trefoil pancreatic spasmolytic polypeptide (PSP) was tested for growth activity in vitro on epithelial cells and in vivo following intragastric or intravenous infusion in parenterally fed intact rats. Ion transport was assessed as changes in short-circuit current in rat intestine and adenocarcinoma cells in Ussing chambers. PSP stimulated growth of MCF-7 and Colo-357 cells, but only in the presence of extracellular glutathione (GSH). The effect was attenuated by GSH depletion with buthionine sulphoximine, even in GSH-containing media. When GSH-reduced PSP was carboxymethylated with iodoacetic acid, it still depended on extracellular GSH for its growth effect. Intestinal epithelial proliferation in rats was not affected by either intravenous or intraluminal infusion. PSP had no effect on basal or stimulated ion flux in rat jejunum or epithelial monolayers. The peptide did not compete with 125I-labeled epidermal growth factor for its receptor. [14C]Iodoacetamide treatment of PSP, followed by prolonged tryptic digestion yielded predominantly a 14C-labeled tetrapeptide fragment containing Cys1O4, with a lesser quantity of a 14C-labeled 15-amino-acid peptide containing Cys95 (molar ratio 15:1). GSH may predominantly reduce the Cys6-Cys1O4 terminal disulphide bond in PSP. We conclude that some epithelia may exhibit a growth response to PSP if extracellular GSH is present. Reduction of PSP by GSH is not necessary for this response, suggesting that the trefoil receptor or its signal transduction is GSH sensitive. PSP could assist wound healing by interactions with epithelial cells exposed concurrently to a local high GSH concentration.

Animals↗
PubMed1996

Characterization of monoclonal antibodies raised to C-terminal peptides of pS2: a major trefoil peptide and motility factor expressed in adenocarcinomas and regions of mucosal injury.

Two novel monoclonal antibodies, GE1 and GE2 raised against the C-terminal 31 and 28 amino acids of the estrogen-inducible trefoil peptide pS2, are described. Both antibodies are able to detect pS2 in formalin-fixed, paraffin-embedded tissues. Conditions are presented under which pS2 can be shown in cell lines by immunohistochemistry that has previously been problematic. The antibodies can specifically show the presence of pS2 in cell lysates by Western blotting and immunoprecipitation. In the form of an affinity column, the GE1 monoclonal antibody can be used to purify pS2 from MCF-7 supernatants. The eluted peptide from the GE1 affinity column shows a single band at 6,600 Da (predicted size for pS2) on Western blotting. These antibodies are valuable reagents in the analysis of the role of trefoil peptides in the maintenance of mucosal integrity, and may have applications in the assessment of pS2 expression in chronic gastrointestinal ulceration and adenocarcinomas that secrete pS2, where it may serve as a prognostic marker.

Adenocarcinoma↗
PubMed1996

Epidermal growth factor (EGF).

Despite the wealth of information concerning EGF and its related peptides, its precise role in the control of gastrointestinal functions is still not fully resolved. However, there is no doubt that it can have some very potent effects on the gastrointestinal tract. These may be related to the control of growth and development and to the regular control of cell renewal. Nevertheless, in the adult, EGF may only be active in response to luminal damage and repair, and furthermore this may also only occur if the luminal EGF is protected from proteolytic degradation. Notwithstanding this, 'EGF'-like responses may be evoked in the gut by intestinal TGF-alpha. The possible therapeutic use of EGF and members of its family in ulcer therapy will be discussed in later Chapters of this volume, other potential uses are in the control of necrotising enteritis and in the alleviation of the mucositis associated with cancer treatment.

Adult↗
PubMed1996

Right ventricular volume estimation using an ellipsoidal shell model and single-plane magnetic resonance imaging.

RATIONALE AND OBJECTIVES: To investigate whether accurate right ventricular volumes could be obtained using an ellipsoidal shell model with magnetic resonance (MR) image measurements from a single imaging plane. METHODS: An initial retrospective patient study included 10 patients with congenital cardiac defects who had undergone same-day or next-day radiographic contrast ventriculography. An expanded study included MR scans of a total of 29 patients with congenital cardiac defects. Magnetic resonance scans of 10 healthy volunteers were also included in part of the study. Right ventricular volumes were calculated from (1) model-based calculations using single-plane cine MR imaging, and (2) multislice calculations based on contrast angiography. RESULTS: Regression of angiography-based volumes against MR-based volumes showed high correlation (r = 0.97, see = 12.5 mL) and slope near unity. Regression of right against left stroke volumes, both calculated from MR data, showed excellent correlation (r = 0.90, see = 11.6 ml) and slope near unity. CONCLUSIONS: The ellipsoidal shell model can be used to reliably estimate right ventricular volume using single-plane MR images.

Adolescent↗
PubMed1996

Why is epidermal growth factor present in the gut lumen?

The jury is still out on the role of luminal EGF in the normal gastrointestinal tract. Recent evidence, however, suggests that its major function is to act as a 'luminal surveillance' peptide, which is available to stimulate repair and that it is not of major importance in maintaining normal gut growth. Recombinant EGF administered via the gut lumen could still prove a valuable tool for the treatment of gastrointestinal ulceration. Perhaps the old term for EGF, 'epidermal healing factor' or EHF, was more appropriate after all!

Animals↗