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Biomedical subjects

N A Wright

Publications and source records attributed to N A Wright.

At least 37 records · Page 2Linked to original sources
PubMed2002

Histogenesis of human colorectal adenomas and hyperplastic polyps: the role of cell proliferation and crypt fission.

BACKGROUND: The histogenesis of human colorectal hyperplastic polyps and colorectal adenomas is poorly understood even now. METHOD: Human colorectal adenomas, hyperplastic polyps, and normal colorectal mucosae (patients with familial adenomatous polyposis and hereditary non-polyposis colorectal carcinoma were excluded) were obtained during colonoscopy and microdissected into individual crypts. Morphology, cell proliferation characteristics, and fission indices of crypts isolated from these lesions were then studied. RESULTS: Crypts isolated from colorectal adenomas and colorectal hyperplastic polyps were significantly larger (p<0.001) than crypts from normal colorectal mucosae. Crypt fission was an uncommon event in normal colonic mucosae but common in crypts isolated from adenomas and hyperplastic polyps (p<0.001). Analysis of the distribution of mitoses suggested an upward expansion of the proliferation compartment in adenomas to the surface of the crypt with no reversal of proliferating cell distribution, as has previously been described. CONCLUSIONS: Sporadic human colorectal adenomas and hyperplastic polyps grow by the process of crypt fission. Expansion of the proliferative compartment was demonstrated in crypts from adenomas, consistent with deregulation of cell cycle control.

Adenoma↗
PubMed2002

Bone marrow derivation of pericryptal myofibroblasts in the mouse and human small intestine and colon.

BACKGROUND AND AIMS: In order to establish whether extraintestinal cells contribute to the turnover and repair of gastrointestinal tissues, we studied the colons and small intestines of female mice that had received a male bone marrow transplant, together with gastrointestinal biopsies from female patients that had developed graft versus host disease after receiving a bone marrow transplant from male donors. METHODS: Using in situ hybridisation to detect Y chromosomes and immunohistochemistry, we demonstrated that cells derived from injected bone marrow frequently engrafted into the intestine and differentiated into pericryptal myofibroblasts. RESULTS: In the human intestine, we confirmed by combining in situ hybridisation with immunostaining for smooth muscle actin that the bone marrow derived cells within the intestine exhibited a myofibroblast phenotype. In female mouse recipients of male bone marrow grafts, we observed colocalisation of Y chromosomes and clusters of newly formed marrow derived myofibroblasts. While few of these were present at seven days after bone marrow transplantation, they were numerous at 14 days, and by six weeks entire columns of pericryptal myofibroblasts could be seen running up the sides of crypts in both the small intestine and colon. These columns appeared to extend into the villi in the small intestine. Within the intestinal lamina propria, these Y chromosome positive cells were negative for the mouse macrophage marker F4/80 antigen and CD34. CONCLUSIONS: Bone marrow derived pericryptal myofibroblasts were present in the mouse intestine following irradiation and bone marrow transplant, and in the intestines of human patients suffering graft versus host disease following a bone marrow transplant. Our data indicate that bone marrow cells contribute to the regeneration of intestinal myofibroblasts and epithelium after damage, and we suggest that this could be exploited therapeutically.

Animals↗
PubMed2001

Use of ambulatory electrocardiography for detection of ventricular premature complexes in healthy dogs.

OBJECTIVE: To evaluate the use of 24-hour ambulatory electrocardiography (AECG) for the detection of ventricular premature complexes (VPC) in healthy dogs. DESIGN: Case series. ANIMALS: 50 healthy mature dogs. PROCEDURE: A 24-hour AECG was performed on each dog and evaluated for the presence of VPC. RESULTS: Fifty dogs weighing between 18.2 to 40.9 kg (40 and 90 lb) representing 13 breeds were evaluated; there were 4 sexually intact females, 21 spayed females, 4 sexually intact males, and 21 castrated males. Ages ranged from 1 to 12 years. Thirty-four dogs had no VPC; 16 dogs had between 1 and 24 VPC. The grade of arrhythmia ranged from 1 to 4, with 4 dogs having an arrhythmia with a grade > 1. Significant differences were not detected between the group of dogs with VPC and those without VPC with regard to sex, age, and minimum, maximum, or mean heart rate. CONCLUSIONS AND CLINICAL RELEVANCE: We conclude that healthy mature dogs have infrequent VPC, as detected by use of 24-hour AECG. The presence of numerous or sequential VPC may be suggestive of cardiac or systemic disease and may indicate the need for thorough clinical evaluation.

Animals↗
PubMed2001

Effect of ectopic expression of rat trefoil factor family 3 (intestinal trefoil factor) in the jejunum of transgenic mice.

To further examine the function of the trefoil factor family (TFF), the expression of which is up-regulated at sites of injury, we have produced transgenic mice that chronically express rat TFF3 within the jejunum (using a rat fatty acid-binding protein promoter). The expression of rat TFF3 was limited to the villi of the jejunum and had no effect on base-line morphology. Rat TFF3 expression did result, however, in a reduced sensitivity to indomethacin (85 mg/kg subcutaneously), which only caused a 29% reduction in villus height in transgenics versus 51% reduction in controls (p < 0.01). Indomethacin increased initial intestinal epithelial cell proliferation and migration, but the presence of rat TFF3 caused no additional change in proliferation (bromodeoxyuridine), cell migration ([(3)H]thymidine and bromodeoxyuridine), apoptosis (terminal deoxyuridine nucleotidyl nick end labeling), or E-cadherin immunostaining. In vitro studies following changes in resistance of intestinal strips in Ussing chambers (voltage-clamp technique) showed increased base-line resistance in the rat TFF3-expressing region (326 +/- 60 versus 195 +/- 48 ohm.cm(2) in controls, p < 0.05) and reduced the fall in resistance following HCl exposure by about 40% (p < 0.01). Overexpression of TFF3 stabilizes the mucosa against noxious agents, supporting its role in mucosal protection/repair. It may therefore provide a novel approach to the prevention and/or treatment of intestinal ulceration.

Animals↗
PubMed2001

Clinical features of dilated cardiomyopathy in Great Danes and results of a pedigree analysis: 17 cases (1990-2000).

OBJECTIVE: To determine clinical features of dilated cardiomyopathy (DCM) in Great Danes and to determine whether DCM is familial in this breed. DESIGN: Retrospective study. ANIMALS: 17 Great Danes with DCM. PROCEDURE: Medical records of Great Danes in which DCM was diagnosed on the basis of results of echocardiography (fractional shortening < 25%, end-systolic volume index > 30 ml/m2 of body surface area) were reviewed. Pedigrees were obtained for affected animals, as well as for other Great Danes in which DCM had been diagnosed. RESULTS: Dilated cardiomyopathy appeared to be familial and was characterized by ventricular dilatation, congestive heart failure (left-sided or biventricular), and atrial fibrillation. Pedigree analysis suggested that DCM was inherited as an X-linked recessive trait, but the mode of inheritance could not be definitively identified. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that DCM may be an X-linked recessive trait in Great Danes. Thus, dogs with DCM probably should not be used for breeding, and female offspring of affected dogs should be used cautiously. Male offspring of affected females are at an increased risk of developing DCM and should be evaluated periodically for early signs of disease. Results of pedigree analysis were preliminary and should be used only as a guide for counseling breeders, rather than as a basis for making breeding decisions.

Animals↗
PubMed2001

Comparison of in-hospital versus 24-hour ambulatory electrocardiography for detection of ventricular premature complexes in mature Boxers.

OBJECTIVE: To evaluate the use of in-hospital electrocardiography (ECG) for detection of ventricular premature complexes (VPC), compared with 24-hour ambulatory ECG. DESIGN: Original study. ANIMALS: 188 Boxers > 9 months old; 31 had a history of syncope, and 157 were healthy (no history of syncope). PROCEDURE: In-hospital ECG was performed on all Boxers for at least 2 minutes. Within 7 days after the in-hospital ECG was completed, 24-hour ambulatory ECG was performed. RESULTS: The specificity of in-hospital ECG was 100% for the detection of at least 50 VPC in a 24-hour period in dogs with syncope and 93% in healthy dogs. In-hospital ECG had poor sensitivity, although sensitivity increased as the number of VPC per 24 hours increased. CONCLUSIONS AND CLINICAL RELEVANCE: Use of in-hospital ECG is highly specific for detection of at least 50 VPC during a 24-hour period. However, in-hospital ECG is insensitive, and a lack of VPC does not suggest that the dog does not have a substantial number of VPC during that same period. The use of in-hospital ECG appears to be inadequate for screening purposes and therapeutic evaluations in mature Boxers with ventricular arrhythmic disease.

Animals↗
PubMed2001

Bone marrow contributes to renal parenchymal turnover and regeneration.

In order to establish whether extra-renal cells contribute to the turnover and repair of renal tissues, this study examined kidneys of female mice that had received a male bone marrow transplant and kidney biopsies from male patients who had received kidney transplants from female donors. By using in situ hybridization to detect Y-chromosomes it could be demonstrated that circulating stem cells frequently engraft into the kidney and differentiate into renal parenchymal cells. In the human renal grafts it was confirmed that some of the recipient-derived cells within the kidney exhibited a tubular epithelial phenotype, by combining in situ hybridization with immunostaining for the epithelial markers CAM 5.2 and the lectin Ulex europaeus. Female mouse recipients of male bone marrow grafts showed co-localization of Y-chromosomes and tubular epithelial markers Ricinus communis and Lens culinaris, and a specific cytochrome P450 enzyme (CYP1A2) indicating an appropriate functional capability of clustered newly formed marrow-derived tubular epithelial cells. Y-chromosome-containing cells were observed within glomeruli, with morphology and location appropriate for podocytes. Within the murine kidney, these Y-chromosome-positive cells were negative for the mouse macrophage marker F4/80 antigen and leukocyte common antigen, but were vimentin-positive. The presence of bone marrow-derived cells was noted in both histologically normal mouse kidneys and in human transplanted kidneys suffering damage from a variety of causes. These data indicate that bone marrow cells contribute to both normal turnover of renal epithelia and regeneration after damage, and it is suggested that this could be exploited therapeutically.

Animals↗
PubMed2001

Comprehensive analysis of SMAD4 mutations and protein expression in juvenile polyposis: evidence for a distinct genetic pathway and polyp morphology in SMAD4 mutation carriers.

Juvenile polyposis syndrome (JPS; OMIM 174900) is a rare disorder which is characterized by the presence of hamartomatous polyps throughout the gastrointestinal tract and an increased risk of gastrointestinal malignancy. Mutations of the SMAD4 gene on chromosome 18q21.1 have been shown to cause a subset of JPS cases, with estimates ranging from 20% to >50%. Characterization of the genes that cause the remainder of JPS cases relies on the certainty that SMAD4 is not the causative gene. We have undertaken a comprehensive analysis of germline SMAD4 mutations in a cohort of JPS patients to define the spectrum of mutations that cause JPS. We have analyzed a series of polyps from these patients for SMAD4 protein expression. We have also performed a blinded assessment of polyp material to look for morphological differences between polyps from patients with and without a germline SMAD4 mutation. The results indicate that almost all germline SMAD4 mutations are readily detectable by screening genomic DNA using polymerase chain reaction-based methods; SMAD4 can be excluded as the causative gene in the majority of our JPS cohort. Loss of SMAD4 expression occurs in most polyps from SMAD4 mutation carriers, even those with missense germline mutations. SMAD4 loss in polyps is, however, not a feature of cases that are not caused by SMAD4 mutations, indicating that these polyps develop along a SMAD4-independent pathway. The morphology of polyps from SMAD4 mutation carriers is subtly different from other JPS polyps, notably including a more prominent epithelial component in the former.

Amino Acid Sequence↗
PubMed2001

Glicentin, an active enteroglucagon, has a significant trophic role on the small intestine but not on the colon in the rat.

BACKGROUND: Many experiments have indicated that the gut glucagons (enteroglucagons) are associated with cell proliferation in the small intestine. However, recent studies have failed to show trophic effects of glicentin (enteroglucagon) on the intestine. AIMS: To examine the effects of glicentin on intestinal proliferation in vivo in the rat. METHODS: Rats were established on total parenteral nutrition for 6 days. Four experimental groups were given daily doses of 1, 4, 20 and 80 microg/rat of glicentin via the jugular vein. Rats fed by total parenteral nutrition and rats fed chow ad libitum were used as controls. Tissues taken from the duodenum, jejunum, ileum and colon were fixed in Carnoy's fluid and microdissected to determine the metaphase arrest scores and crypt fission ratios. RESULTS: The mean metaphase arrest scores per crypt of the small intestine were significantly increased in the rats given 4, 20 and 80 microg of glicentin. These responses were dose-dependent, and were most prominent in the ileum. Crypt fission of the ileum was significantly decreased in the 20 and 80 microg glicentin groups. Glicentin had no effects on proliferation or fission in the colon. CONCLUSIONS: Glicentin is trophic to the rat small intestine, but not the colon.

Animals↗
PubMed2000

Proliferative populations in intestinal metaplasia: evidence of deregulation in Paneth and goblet cells, but not endocrine cells.

In the small intestinal mucosa, four principal epithelial cell lineages are found - the Paneth, goblet, enterocytic, and endocrine cell lineages. These cell lineages are terminally differentiated, non-proliferative, and derive from multipotent stem cells near the bases of the crypts of Lieberkühn. Intestinal metaplasia of the stomach is considered to be a premalignant condition. Since proliferative populations in this condition are not well studied, this feature was examined using double-labelling immunohistochemical and histochemical methods; 20 paraffin blocks of small intestinal mucosa and 24 paraffin blocks of intestinal metaplasia of the human stomach were studied. Double-staining was carried out with MIB-1 as a proliferation marker, with Alcian blue for goblet cells, anti-chromogranin A for endocrine cells, and p-dimethylaminobenzaldehyde-nitrite for Paneth cells. Double-labelling showed that numerous Paneth cells and goblet cells in intestinal metaplasia were in the cell cycle, but endocrine cells appeared non-proliferative. Double-labelled Paneth or endocrine cells were not seen in the control small intestinal mucosa but scanty double-labelled goblet cells were observed in normal intestinal mucosa. In intestinal metaplasia of the stomach, there is evidence of cell-cycle deregulation in the goblet and Paneth cell lineages. These observations have considerable implications for the biology and histogenesis of Paneth cells, goblet cells, and endocrine cells, and the nature of intestinal metaplasia in the gastric mucosa.

Cell Division↗
PubMed2000

Clonality analysis of defined cell populations in paraffin-embedded tissue sections by RT-PCR amplification of X-linked G6PD gene.

This paper establishes a method of clonality analysis using the reverse transcription-polymerase chain reaction (RT-PCR) to amplify X-linked G6PD transcripts on defined cell populations microdissected from archival, paraffin-embedded tissue sections. Four known monoclonal low-grade B-cell lymphomas from females who were heterozygous (informative) at the 1131 exonic polymorphic locus of the G6PD gene were used to validate the method. Lymphoma and reactive lesions in each case were separated by microdissection. In order to preserve the intact RNA species in the lesion, sections were digested on the slides before microdissection. A one-step RT-PCR was performed with a single pair of primers, one of which contained a mismatched base adjacent to the polymorphic site, to generate a PvuI cutting site. Successful amplification and allele identification by PvuI digestion were achieved from all RNA samples studied. Three of four samples from non-neoplastic reactive lesions showed two bands with equal intensity, representing transcription of the two alleles of the G6PD gene, while the corresponding tumour samples demonstrated a biased intensity in one allele, indicating monoclonality. To assess the method further, the clonal nature of in situ and invasive breast cancers was examined, along with adjacent normal breast tissue and hyperplastic lesions from three informative females from our archives. Apart from the clusters of normal terminal duct-lobular units, all lesions were monoclonal. This result is in agreement with data derived from other X-linked gene studies and loss of heterozygosity (LOH) analyses of pre-invasive breast disease. The results suggest that the clonality analysis method presented here is simple and reliable, and is therefore potentially applicable in a wide range of pathological conditions.

Breast↗
PubMed2000

The clonal origin and clonal evolution of epithelial tumours.

While the origin of tumours, whether from one cell or many, has been a source of fascination for experimental oncologists for some time, in recent years there has been a veritable explosion of information about the clonal architecture of tumours and their antecedents, stimulated, in the main, by the ready accessibility of new molecular techniques. While most of these new results have apparently confirmed the monoclonal origin of human epithelial (and other) tumours, there are a significant number of studies in which this conclusion just cannot be made. Moreover, analysis of many articles show that the potential impact of such considerations as patch size and clonal evolution on determinations of clonality have largely been ignored, with the result that a number of these studies are confounded. However, the clonal architecture of preneoplastic lesions provide some interesting insights --many lesions which might have been hitherto regarded as hyperplasias are apparently clonal in derivation. If this is indeed true, it calls into some question our hopeful corollary that a monoclonal origin presages a neoplastic habitus. Finally, it is clear, for many reasons, that methods of analysis which involve the disaggregation of tissues, albeit microdissected, are far from ideal and we should be putting more effort into techniques where the clonal architecture of normal tissues, preneoplastic and preinvasive lesions and their derivative tumours can be directly visualized in situ.

Cell Transformation, Neoplastic↗
PubMed2000

Epithelial stem cell repertoire in the gut: clues to the origin of cell lineages, proliferative units and cancer.

Gastrointestinal stem cells are shown to be pluripotential and to give rise to all cell lineages in the epithelium. After damage, gut stem cells produce reparative cell lineages that produce a wide range of peptides with important actions on cell proliferation and migration, and promote regeneration and healing. Increase in stem cell number is considered to induce crypt fission, and lead to increases in the number of crypts, even in the adult; it is also the mode of spread of mutated clones in the colorectal mucosa. Stem cell repertoire is defined by both intrinsic programming of the stem cell itself, but signalling from the mesenchyme is also vitally important for defining both stem cell progeny and proliferation. Carcinogenesis in the colon occurs through sequential mutations, possibly occurring in a single cell. A case is made for this being the stem cell, but recent studies indicate that several stem cells may need to be so involved, since early lesions appear to be polyclonal in derivation.

Animals↗
PubMed2000

Coordinated localisation of mucins and trefoil peptides in the ulcer associated cell lineage and the gastrointestinal mucosa.

BACKGROUND AND AIMS: Trefoil factor family (TFF) peptides and the chromosome 11p15.5 mucin glycoproteins are expressed and secreted in a site specific fashion along the length of the gastrointestinal tract. Evidence for coexpression of mucins and trefoil peptides has been suggested in numerous gastrointestinal mucosal pathologies. The ulcer associated cell lineage (UACL) occurs at sites of chronic ulceration in Crohn's disease, expresses all three trefoil peptides, and is implicated in mucosal restitution. We tested the hypothesis that individual trefoil peptides are uniquely localised with specific mucins in the UACL and normal gastrointestinal epithelia. METHODS: Expression of mucin genes in the UACL from small bowel tissue of patients with Crohn's disease was detected by in situ hybridisation, and localisation of the products by immunohistochemistry. Colocalisation of mucins and trefoil peptides was demonstrated by immunofluorescent colabelling in UACL and normal gastrointestinal epithelia. RESULTS: MUC5AC and TFF1 were colocalised in distal ductular and surface elements of the UACL and in foveolar cells of the stomach, whereas MUC6 and TFF2 were colocalised to acinar and proximal ductular structures in the UACL, in the fundus and deep antral glands of the stomach, and in Brunner's glands of the duodenum. MUC5B was found sporadically throughout the UACL and gastric body. MUC2 was absent from the UACL, Brunner's glands, and stomach. MUC2 and TFF3 were colocalised throughout the large and small bowel mucosa. CONCLUSIONS: The UACL has a unique profile of mucin gene expression. Coordinated localisation of trefoil peptides and mucins in UACL and normal gastrointestinal epithelia suggests they may assist each others' functions in protection and repair of gastrointestinal mucosa.

Crohn Disease↗