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Biomedical subjects

M J Page

Publications and source records attributed to M J Page.

At least 19 recordsLinked to original sources
PubMed2005

Determinants of specificity in coagulation proteases.

Proteases play diverse roles in a variety of essential biological processes, both as non-specific catalysts of protein degradation and as highly specific agents that control physiologic events. Here, we review the mechanisms of substrate specificity employed by serine proteases and focus our discussion on coagulation proteases. We dissect the interplay between active site and exosite specificity and how substrate recognition is regulated allosterically by Na+ binding. We also draw attention to a functional polarity that exists in the serine protease fold, which sheds light on the structural linkages between the active site and exosites.

Allosteric Regulation↗
PubMed2001

Submillimeter evidence for the coeval growth of massive black holes and galaxy bulges.

The correlation, found in nearby galaxies, between black hole mass and stellar bulge mass implies that the formation of these two components must be related. Here we report submillimeter photometry of eight x-ray-absorbed active galactic nuclei that have luminosities and redshifts characteristic of the sources that produce the bulk of the accretion luminosity in the universe. The four sources with the highest redshifts are detected at 850 micrometers, with flux densities between 5.9 and 10.1 millijanskies, and hence are ultraluminous infrared galaxies. If the emission is from dust heated by starbursts, then the majority of stars in spheroids were formed at the same time as their central black holes built up most of their mass by accretion. This would account for the observed demography of massive black holes in the local universe. The skewed rate of submillimeter detection with redshift is consistent with a high redshift epoch of star formation in radio-quiet active galactic nuclei, similar to that seen in radio galaxies.

Journal Article↗
PubMed2000

Increased gelsolin expression and retarded collagen lattice contraction with smooth muscle cells from Crohn's diseased intestine.

Intestinal smooth muscle cells (SMC) produce the fibrotic tissue, strictures, that characterize Crohn's disease. These SMC change their phenotype from a contractile muscle form to an inflammation-responsive form that migrates and synthesizes a collagen matrix. It is postulated that the inflammatory responsive SMC form associates differently with its surrounding collagen matrix compared to the normal SMC form. SMC derived from Crohn's diseased and uninvolved bowel were sustained in cell culture. Cultured SMC incorporated in collagen lattices have the capacity to reduce the size of that lattice, referred to as lattice contraction. At day 2, Crohn's SMC-populated collagen lattices were reduced to 21% of their initial area, while non-Crohn's SMC collagen lattices were reduced to 8%. Crohn's SMC demonstrate retarded lattice contraction compared to non-Crohn's SMC. When grown in monolayer culture, Crohn's-derived SMC cover 30% more area than non-Crohn's SMC. By Western blot analysis Crohn's SMC express more gelsolin, an actin-binding protein found elevated in cells exhibiting increased cell motility. Was the increased expression of gelsolin related to retarded collagen lattice contraction? Intracellular levels of gelsolin were elevated by the electroporation of plasma gelsolin protein into suspended non-Crohn's SMC. When incorporated in collagen lattices, gelsolin loaded cells showed retarded lattice contraction compared to SMC loaded with albumin. Crohn's SMC show increased expression of gelsolin, which may be associated with a diminished capacity to reorganize collagen fiber bundles. It is suggested that increased concentrations of gelsolin in Crohn's SMC is consistent with enhanced cell migration as a consequence of the inflammatory state of Crohn's diseased intestine.

Blotting, Western↗
PubMed2000

Cd1d-restricted cellular lysis by peripheral blood lymphocytes: relevance to the inflammatory bowel diseases.

The CD1d molecule has been implicated to play a role in inflammatory bowel diseases (IBD), possibly through its presentation of an intestinal antigen trigger. To understand the role of the CD1d class I-like protein in IBD, we investigated the molecule's expression in diseased intestinal tissue and determined its potential to undergo specific recognition by intraepithelial and peripheral blood lymphocytes (PBLs) derived from IBD patients. We have observed an increase in precipitable CD1d in inflamed tissues, which suggests CD1d up-regulation in IBD; this was not accompanied by the occurrence of CD1d-specific cytotoxicity by lymphocytes isolated from the same tissue sites. In contrast, we have observed CD1d-specific cytotoxicity by PBLs from both patients and normal controls mediated by a possibly unique type of lymphocytic cell. These observations support a model in which intestinal inflammation may be initiated by circulating PBLs following the tissue-specific upregulation of CD1d. These activated PBLs may then be the source of the extraintestinal manifestations observed with IBD. We therefore propose that the cells responsible for this activity may play a role in regulating immune responses through the specific recognition of CD1d-specific antigen(s).

Antigens, CD↗
PubMed2000

Absence of GNAI2 codon 179 oncogene mutations in inflammatory bowel disease.

The human GNAI2 gene coding for G protein, Galphai2, is located on chromosome 3p21 in proximity to the region where an inflammatory bowel disease (IBD) locus has been suggested. Galphai2-deficient mice develop a lethal diffuse colitis that resembles human ulcerative colitis (UC) and frequently progresses to colon adenocarcinoma. Furthermore, the human GNAI2 gene is subject to point mutations at certain positions, including three at codon 179, all of which have been reported in human endocrine tumors. In order to evaluate the possible involvement of this gene in IBD pathogenesis, we have examined GNAI2 codon 179 sequences in 28 familial IBD patients, including 13 UC, 15 Crohn's disease (CD), and 7 patients with colon cancer/dysplasia, from 12 multiplex IBD families. The wildtype codon 179, CGC for arginine, plus the first G of the codon 180 engender a sequence recognizable by the enzyme BstUI. Mutations, therefore, can result in the abrogation of BstUI digestion of polymerase chain reaction (PCR) products containing the codon 179. Using the PCR-restriction fragment length polymorphism technique, all 28 IBD patients, including those with colon cancer, and 14 non-IBD family members show a BstUI-cleavable PCR-banding pattern indicating the presence of wildtype codon 179. We conclude that, in the familial IBD and colon cancer/dysplasia patients studied, there is no detectable mutation in the codon 179 of the GNAI2 gene.

Adult↗
PubMed1999

Proteomic definition of normal human luminal and myoepithelial breast cells purified from reduction mammoplasties.

Normal human luminal and myoepithelial breast cells separately purified from a set of 10 reduction mammoplasties by using a double antibody magnetic affinity cell sorting and Dynabead immunomagnetic technique were used in two-dimensional gel proteome studies. A total of 43,302 proteins were detected across the 20 samples, and a master image for each cell type comprising a total of 1,738 unique proteins was derived. Differential analysis identified 170 proteins that were elevated 2-fold or more between the two breast cell types, and 51 of these were annotated by tandem mass spectrometry. Muscle-specific enzyme isoforms and contractile intermediate filaments including tropomyosin and smooth muscle (SM22) alpha protein were detected in the myoepithelial cells, and a large number of cytokeratin subclasses and isoforms characteristic of luminal cells were detected in this cell type. A further 134 nondifferentially regulated proteins were also annotated from the two breast cell types, making this the most extensive study to date of the protein expression map of the normal human breast and the basis for future studies of purified breast cancer cells.

Adult↗
PubMed1999

A novel, orally administered nucleoside analogue, OGT 719, inhibits the liver invasive growth of a human colorectal tumor, C170HM2.

OGT 719 is a novel p.o. bioavailable nucleoside analogue in which galactose is incorporated onto the fluoropyrimidine moiety of the cytotoxic agent 5-fluorouracil (5-FU). OGT 719 has been designed to reduce the systemic toxicity normally associated with 5-FU while retaining activity against disease localized in the liver, in which it may be preferentially localized through the asialoglycoprotein receptor (ASGP-R). We report studies confirming the activity of OGT 719 in inhibiting growth of metastatic human colorectal tumors in the liver of nude mice. The human colorectal cancer cell line C170HM2 readily forms liver metastases in vivo. Oral administration of 1500 mg/kg/day OGT 719 inhibited liver tumor burden by 95% compared with vehicle control, without any observable signs of toxicity. When the tumor burden was increased and the same OGT 719 treatment was compared with a standard clinical dose regimen of 25 mg/kg/day 5-FU/leucovorin given i.v., both treatments were equally efficacious, although 5-FU/leucovorin treatment started 7 days earlier. In contrast to 5-FU, OGT 719 is p.o. bioavailable and has a plasma half-life between 1.5 and 3 h. Several colorectal cancer cell lines express the asialoglycoprotein receptor, although no significant levels can be detected in C170HM2 cells, consistent with the observation that OGT 719 is approximately 3 log orders of magnitude less potent in vitro than 5-FU. Flux through thymidylate synthase, as measured by 3H release from [3H]dUrd, was inhibited by OGT 719 at 4 h. The notable difference in the potency of OGT 719 efficacy on C170HM2 cells in vitro and in vivo supports our model of liver-specific activation of OGT 719. As our data suggest, OGT 719 may significantly inhibit growth of metastatic colorectal tumors in the liver in vivo. This hypothesis is presently being explored in clinical trials for primary hepatocellular carcinoma and colorectal liver metastases.

Administration, Oral↗
PubMed1999

New model of ErbB-2 over-expression in human mammary luminal epithelial cells.

The ErbB-2 receptor has been strongly implicated in the development of breast cancer. To establish a new model system to investigate the role of erbB-2 in tumorigenesis of the breast, the conditionally immortalised human mammary luminal epithelial cell line HB4a was transfected with erbB-2 cDNA. Biological and biochemical characterisation of the resulting cell lines demonstrated that high levels of ErbB-2 expression were sufficient to cause transformation in vitro but did not cause tumours in vivo. Transformation by overexpression of ErbB-2 correlated with ligand-independent tyrosine phosphorylation of ErbB-2 and the adaptor protein Shc. Over-expression of ErbB-2 also resulted in the ligand-independent constitutive association between Shc and another adaptor protein, Grb2, indicating that receptor activation was sufficient to activate downstream signalling pathways. Using the model described, it was found that elevation of ErbB-2 expression levels caused marked quantitative and qualitative alterations in responses to the ligands epidermal growth factor and heregulin. Data indicate a central role for ErbB-2 in mediating the responses induced by these ligands and suggest that these altered ligand-dependent responses play an important role in tumorigenesis in vivo.

Breast↗
PubMed1999

Gamma delta intraepithelial lymphocytes drive tumor necrosis factor-alpha responsiveness to intestinal iron challenge: relevance to hemochromatosis.

The dependence of intestinal epithelial cell (IEC) growth and differentiation on intraepithelial lymphocytes (IELs) expressing the gamma/delta (gamma delta) T-cell receptor (TCR), suggested a potential role for gamma delta + IELs in the regulation of iron absorption. We therefore examined the levels of hepatic iron and the IEL cytokine responses in C57BL/6J control and class I and TCR knockout lines (placed on a C57BL/6J genetic background) following the administration of supplemental dietary iron. The highest level of liver iron was found in the beta 2-microglobulin knockout (beta 2m-/-) mice followed by the TCR-delta knockout (TCR delta-/-) animals. TCR-alpha knockout (TCR alpha-/-) and control animals did not differ in their iron levels. Liver iron loading correlated inversely with the ability of the mice to generate an IEL tumor necrosis factor (TNF)-alpha response. These observations suggest a model in which IEC iron loading is communicated to IELs via the HFE class I protein. The result of this communication is the initiation of TNF-alpha release by gamma delta + IELs (sustained by macrophages and dendritic cells) contributing to the upregulation of ferritin expression and possibly to the normal maintenance of the IEC apoptotic pathway.

Amino Acid Sequence↗
PubMed1999

Applying proteomics to drug discovery.

Proteomics is a technology that has come to prominence over the last few years largely as a result of the advances that have been made in the equipment and software associated with the performance and analysis of two dimensional (2D) gel electrophoresis. With this technique it is now possible to resolve and identify proteins on 2D gels with a high degree of reproducibility and sensitivity. This facilitates the detection and quantification of thousands of proteins from complex biological samples in a single analysis and, more significantly, the comparison of these data accurately and reproducibly between samples. Thus, qualitative and quantitative assessments of changes are possible between the healthy and diseased state, in the presence and absence of drug, or between responders and non-responders. The added ability of carrying out such analysis at a high throughput opens up the possibilities for using proteomics to great effect throughout the drug discovery process. This review outlines the proteomic process and indicates areas where its potential has begun to be realised.

Journal Article↗
PubMed1998

Amelioration of graft versus host disease with anti-ICAM-1 therapy.

We have previously demonstrated an increase in the adhesion molecule lymphocyte function-associated antigen-1 (LFA-1) in GVHD after small bowel transplantation (SBTx) and a therapeutic effect for the monoclonal antibody (MoAb) to LFA-1 in the same model. The present study evaluated the role of MoAb to LFA-1's ligand, intercellular adhesion molecule-1 (ICAM-1) in GVHD. Methods. GVHD was created in LBNF1 rats by heterotopic vascularized SBTx from Lewis donors. Saline treated SBTx-GVHD and sham-operated control animals were compared to animal groups treated with MoAb to ICAM-1 or MoAb to ICAM-1 and LFA-1. GVHD was evaluated by measuring spleen index, white blood cell count, bowel permeability, weight loss, and animal survival. RESULTS. Animals treated with the MoAb to ICAM-1 appeared clinically to have almost as severe GVHD as untreated animals; however, they had improved spleen indices, less neutropenia and weight loss, and survived longer than untreated animals (range 15-22 days in treated animals vs 12-16 days in untreated animals, P < 0. 01). Treatment with MoAb to both ICAM-1 and LFA-1 appeared to have a synergistic beneficial effect on GVHD (range 19-29 days, P < 0.001 vs untreated animals). Conclusion. MoAb to ICAM-1 alone or in combination with MoAb to LFA-1 ameliorates GHVD after SBTx and prolongs survival.

Animals↗
PubMed1998

Cytomegalovirus enteritis: a highly lethal condition requiring early detection and intervention.

UNLABELLED: Cytomegalovirus infection causing symptomatic enteritis is most usually associated with immunosuppressed transplant patients or patients positive for human immunodeficiency virus. Most reports studying this illness are small and do not clearly define the risk factors or mortality rates. METHODS: The present study retrospectively reviewed the charts of 67 patients with biopsy-proven cytomegalovirus enteritis (esophageal, gastric, small bowel, and colonic) to define and to investigate factors that influence survival. Patients were classified into four groups based on underlying medical condition: 1) patients positive for human immunodeficiency virus; 2) transplant patients receiving immunosuppressive medications; 3) immunosuppressed nontransplant patients; and 4) otherwise healthy individuals. Mortality rates based on underlying medical condition, location of intestinal cytomegalovirus infection, cytomegalovirus therapy, age, and average days to institution of treatment were defined and statistically assessed. RESULTS: Mortality was significantly greater in the normal patient group (80 percent) than in the transplant (21 percent), other immunosuppressed (44 percent), or human immunodeficiency virus-positive (75 percent) groups (P = 0.0006, Cochran-Mantel-Haenszel statistics). There was no difference in mortality based on intestinal location of disease or treatment modality (surgery, medical therapy, or both). Cohorts of patients older than 65 years had a statistically higher mortality rate vs. those younger than 65 years old (68 vs. 38 percent; P = 0.05, Cochran-Mantel-Haenszel statistics). Statistically increased mortality was also associated with increased time from hospital admission to institution of cytomegalovirus treatment, whether therapy was medication alone or medication and surgery (P < 0.05, exact Wilcoxon's test). CONCLUSIONS: 1) Lethal cytomegalovirus enteritis can arise in patient populations not typically identified as being at risk for this disorder, including normal individuals. 2) Mortality in cytomegalovirus enteritis is adversely associated with age older than 65 years and increased time to institution of therapy but is not affected by anatomic site of infection or particular form of treatment. Paradoxically, in this study, normal patients had the highest mortality, which we attribute to a low index of suspicion and relatively late institution of therapy.

Adult↗
PubMed1998

Bowel permeability is improved in Crohn's disease after ileocolectomy.

PURPOSE: Numerous investigators have shown increased bowel permeability in patients with Crohn's disease. It is unclear whether this is a precondition affecting the entire intestine or a consequence of the inflammation and, therefore, only affecting the diseased bowel. The present study tested the hypothesis that resection of diseased bowel in patients with ileocolonic Crohn's disease would correct abnormalities in bowel permeability. METHODS: Ten patients (5 females; mean age, 33 +/- 2 years) with ileocolonic Crohn's disease who underwent elective ileocolic resections had bowel permeability measured preoperatively and postoperatively by the relative urinary clearance of orally consumed lactulose and rhamnose. RESULTS: Mean preoperative bowel permeability in patients with Crohn's disease was significantly elevated relative to healthy volunteers (0.172 +/- 0.04 vs. 0.046 +/- 0.01; P < 0.05, unpaired t-test). After ileocolectomy, bowel permeability decreased in patients with Crohn's disease and reached a normal range by postoperative day 30. CONCLUSIONS: Bowel permeability is increased in patients with ileocolic Crohn's disease because of the presence of diseased bowel and decreases to a normal range in these patients after resection of gross intestinal disease. This suggests that bowel permeability may be a quantitative and clinically effective method with which to assess the presence and severity of diseased bowel in patients with Crohn's disease.

Adult↗
PubMed1998

Monoclonal antibody to lymphocyte function associated antigen-1 improves graft-versus-host disease.

UNLABELLED: We previously showed that intestinal tissue expression of lymphocyte function associated antigen-1 is increased in animals with graft-versus-host disease after small-bowel transplantation. HYPOTHESIS: Treatment of rats with monoclonal antibody to lymphocyte function associated antigen-1 after small-bowel transplantation will lessen the severity of graft-versus-host disease. METHODS: Graft-versus-host disease was created in Lewis X Brown-Norway F1 rats by heterotopic vascularized small-bowel transplantation from Lewis donors. Transplanted rats were treated with either saline or various regimens of monoclonal antibody to lymphocyte function associated antigen-1. Clinical characteristics, weight loss, spleen index, white blood cell counts, native intestinal histology, bowel permeability, and survival were then compared between groups and appropriate sham-operated and lymphocyte function associated antigen-1-treated controls. RESULTS: Lymphocyte function associated antigen-1-treated rats lost less weight, had larger spleen indexes, more normal white blood cell counts, more normal native intestinal histology, less alteration in bowel permeability, and longer survival than untreated small-bowel transplantation rats. CONCLUSIONS: In this model of graft-versus-host disease after small-bowel transplantation, monoclonal antibody to lymphocyte function associated antigen-1 treatment decreased the severity of graft-versus-host disease and prolonged rat survival.

Animals↗
PubMed1998

Factor V Leiden mutation: a nursing perspective.

The factor V Leiden mutation is a recently described autosomal dominant genetic risk factor for venous thromboembolism (VTE). Persons who are heterozygous or homozygous for this disorder are at 4 to 7 times and 50 to 100 times increased risk, respectively, for VTE. In particular, women have unique challenges because the presence of the Leiden mutation in combination with pregnancy or use of oral contraceptives results in an even greater increased risk for VTE. This article will review the factor V Leiden mutation, its association with VTE, and the genetic inheritance pattern and ethnic distribution. Oral contraceptive use, pregnancy, and hormone replacement therapy in women with the Leiden mutation will be discussed. Screening issues and management for all patients, and women in particular, will be addressed. Nursing implications for care management of this group of patients is complex and requires evaluation of the significance of newly defined genetic disorders such as the factor V Leiden mutation. Nurses need to be knowledgeable about genetic screening, risk factors, risk-reduction counseling, and considerations for long-term therapy, which include quality of life issues. Two case studies exemplify many of the issues that will be discussed.

Adult↗