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Biomedical subjects

J F Evans

Publications and source records attributed to J F Evans.

At least 19 recordsLinked to original sources
PubMed2004

Cancer and cyclooxygenase-2 (COX-2) inhibition.

Prior to the discovery of cyclooxygenase-2 (COX-2), a beneficial association was shown between chronic usage of non steroidal anti-inflammatory drugs (NSAIDs), that non-selectively inhibit both cyclooxygenase-1 (COX-1) and COX-2, and prevention of colorectal cancer. The cloning of COX-2 allowed the development of enzyme inhibitors that selectively inhibit COX-2 and also facilitated the expression profiling of COX-2 in many cancer tissues. COX-2 selective inhibitors have shown efficacy in vitro and in vivo in several animal cancer models and in limited human clinical trials. The potency of COX-2 inhibitors in vivo can be attributed to the inhibition of the enzyme in the tumor as well as in stromal cells, resulting in reduction of carcinogen production, anti-proliferative and pro-apoptopic actions within the tumor and anti-angiogenic and pro-immune surveillance activities in endothelial and myeloid cells. The combination of COX-2 inhibitor with standard cancer chemotherapeutic and/or radiation may provide additional therapeutic paradigms in the treatment of various human cancers.

Animals↗
PubMed2003

Expression of cysteinyl leukotriene synthetic and signalling proteins in inflammatory cells in active seasonal allergic rhinitis.

BACKGROUND: Cysteinyl leukotrienes (CysLTs) are bioactive lipids that have been shown to contribute to allergic and inflammatory diseases. Eosinophils and mast cells have the capacity to produce large amounts of CysLTs after allergic or non-allergic stimulation. Molecular identification of both the synthetic and signalling proteins in the CysLT pathway allows the investigation of expression of the CysLT enzymes and receptors in active allergic rhinitis. OBJECTIVE: We examined the expression of the proteins involved in the synthesis of CysLTs and the cysteinyl leukotriene-1 (CysLT1) and cysteinyl leukotriene-2 (CysLT2) receptors in inflammatory cells from patients with active seasonal allergic rhinitis. METHODS: Nasal lavage samples were obtained from patients during active seasonal allergic rhinitis. Specific cellular immunocytochemical techniques were used to detect the cysteinyl leukotriene synthetic proteins, namely 5-lipoxygenase (5-LO), 5-lipoxygenase-activating protein (FLAP) and leukotriene C4 synthase (LTC4S). In situ hybridization and immunocytochemical techniques were used to identify the mRNA and proteins for the CysLT1 and CysLT2 receptors. RESULTS: 5-LO, FLAP and LTC4S, and the CysLT1 and CysLT2 receptors were expressed in the majority of eosinophils and in subsets of mast cells and mononuclear cells. 5-LO, FLAP and the CysLT1 receptor, but not LTC4S or the CysLT2 receptor, were expressed in a subset of nasal neutrophils. CONCLUSIONS: Our study demonstrates the presence of CysLT pathway proteins in key allergic and inflammatory cells from the upper airway of patients with active seasonal allergic rhinitis. Our expression data highlight the potential of CysLT-modifying agents to treat both upper and lower airway symptoms in patients suffering from allergic rhinitis and asthma.

5-Lipoxygenase-Activating Proteins↗
PubMed2001

Discovery and mapping of ten novel G protein-coupled receptor genes.

We report the identification, cloning and tissue distributions of ten novel human genes encoding G protein-coupled receptors (GPCRs) GPR78, GPR80, GPR81, GPR82, GPR93, GPR94, GPR95, GPR101, GPR102, GPR103 and a pseudogene, psi GPR79. Each novel orphan GPCR (oGPCR) gene was discovered using customized searches of the GenBank high-throughput genomic sequences database with previously known GPCR-encoding sequences. The expressed genes can now be used in assays to determine endogenous and pharmacological ligands. GPR78 shared highest identity with the oGPCR gene GPR26 (56% identity in the transmembrane (TM) regions). psi GPR79 shared highest sequence identity with the P2Y(2) gene and contained a frame-shift truncating the encoded receptor in TM5, demonstrating a pseudogene. GPR80 shared highest identity with the P2Y(1) gene (45% in the TM regions), while GPR81, GPR82 and GPR93 shared TM identities with the oGPCR genes HM74 (70%), GPR17 (30%) and P2Y(5) (40%), respectively. Two other novel GPCR genes, GPR94 and GPR95, encoded a subfamily with the genes encoding the UDP-glucose and P2Y(12) receptors (sharing >50% identities in the TM regions). GPR101 demonstrated only distant identities with other GPCR genes and GPR102 shared identities with GPR57, GPR58 and PNR (35-42% in the TM regions). GPR103 shared identities with the neuropeptide FF 2, neuropeptide Y2 and galanin GalR1 receptors (34-38% in the TM regions). Northern analyses revealed GPR78 mRNA expression in the pituitary and placenta and GPR81 expression in the pituitary. A search of the GenBank databases with the GPR82 sequence retrieved an identical sequence in an expressed sequence tag (EST) partially encoding GPR82 from human colonic tissue. The GPR93 sequence retrieved an identical, human EST sequence from human primary tonsil B-cells and an EST partially encoding mouse GPR93 from small intestinal tissue. GPR94 was expressed in the frontal cortex, caudate putamen and thalamus of brain while GPR95 was expressed in the human prostate and rat stomach and fetal tissues. GPR101 revealed mRNA transcripts in caudate putamen and hypothalamus. GPR103 mRNA signals were detected in the cortex, pituitary, thalamus, hypothalamus, basal forebrain, midbrain and pons.

Amino Acid Sequence↗
PubMed2001

Suppression of intestinal polyps in Msh2-deficient and non-Msh2-deficient multiple intestinal neoplasia mice by a specific cyclooxygenase-2 inhibitor and by a dual cyclooxygenase-1/2 inhibitor.

Epidemiological studies suggest that nonsteroidal anti-inflammatory agents decrease the risk of colorectal cancer. This is believed to be mediated, at least in part, by inhibition of cyclooxygenase (COX) activity. There are two COX isoenzymes, namely the constitutively expressed COX-1 and the inducible COX-2. COX-2 is overexpressed in adenomas and colorectal cancers, and COX-2-specific inhibitors have been shown to inhibit intestinal polyps in Apc(Delta716) mice more effectively than dual COX-1/COX-2 inhibitors such as sulindac. Various Apc knockout mice, including the multiple intestinal neoplasia (Min) mouse and the Apc(Delta716) mouse, are limited by their lack of large numbers of colonic adenomas and aberrant crypt foci, the putative precursors of large-bowel polyps and cancers. Our DNA mismatch-repair-deficient Min mouse model (Apc+/-Msh2-/-) has genetic features of both familial adenomatous polyposis and hereditary nonpolyposis colorectal cancer, and most importantly, rapidly develops numerous small- and large-bowel adenomas, as well as colonic aberrant crypt foci. The purpose of this study was to determine the effects of COX inhibitors on intestinal adenomas and colonic aberrant crypt foci in this accelerated polyposis, mismatch-repair-deficient Min mouse model, in addition to a standard Min mouse model. Weanling Apc+/-Msh2-/- and Min mice were fed diets containing no drug, sulindac, or a specific COX-2 inhibitor (MF-tricyclic). Apc+/-Msh2-/- and Min mice were sacrificed after 4 weeks and 5 months on diet, respectively. Apc+/-Msh2-/- mice treated with MF-tricyclic had significantly fewer small-bowel polyps (mean +/- SD, 178 +/- 29) compared with mice on sulindac (278 +/- 80), or control diet (341 +/- 43; P < 0.001). There was no difference in numbers of large-bowel polyps or aberrant crypt foci in mice in the three groups. MF-tricyclic was also effective in reducing both small- and large-bowel polyps in Min mice. Western analysis demonstrated COX-2 expression in both large- and small-bowel polyps from mice of both genotypes. This study demonstrates that a specific COX-2 inhibitor is effective in preventing small-bowel polyps in mismatch-repair-deficient Min mice and both small- and large-bowel polyps in standard Min mice. Therefore, specific COX-2 inhibitors may be useful as chemopreventive and therapeutic agents in humans at risk for colorectal neoplasia.

Adenoma↗
PubMed2001

Chemoprevention of intestinal polyposis in the Apcdelta716 mouse by rofecoxib, a specific cyclooxygenase-2 inhibitor.

Mutations in the human adenomatous polyposis (APC) gene are causative for familial adenomatous polyposis (FAP), a rare condition in which numerous colonic polyps arise during puberty and, if left untreated, lead to colon cancer. The APC gene is a tumor suppressor that has been termed the "gatekeeper gene" for colon cancer. In addition to the 100% mutation rate in FAP patients, the APC gene is mutated in >80% of sporadic colon and intestinal cancers. The Apc gene in mice has been mutated either by chemical carcinogenesis, resulting in the Min mouse Apcdelta850, or by heterologous recombination, resulting in the Apcdelta716 or Apedelta1368 mice (M. Oshima et al., Proc. Natl. Acad. Sci. USA, 92: 4482-4486, 1995). Although homozygote Apc-/- mice are embryonically lethal, the heterozygotes are viable but develop numerous intestinal polyps with loss of Apc heterozygosity within the polyps (M. Oshima et al., Proc. Natl. Acad. Sci. USA, 92: 4482-4486, 1995). The proinflammatory, prooncogenic protein cyclooxygenase (COX)-2 has been shown to be markedly induced in the Apcdelta716 polyps at an early stage of polyp development (M. Oshima et al., Cell, 87: 803-809, 1996). We demonstrate here that treatment with the specific COX-2 inhibitor rofecoxib results in a dose-dependent reduction in the number and size of intestinal and colonic polyps in the Apcdelta716 mouse. The plasma concentration of rofecoxib that resulted in a 55% inhibition of polyp number and an 80% inhibition of polyps > 1 mm in size is comparable with the human clinical steady-state concentration of 25 mg rofecoxib (Vioxx) taken once daily (A. Porras et al., Clin. Pharm. Ther., 67: 137, 2000). Polyps from both untreated and rofecoxib- or sulindac-treated Apcdelta716 mice expressed COX-1 and -2, whereas normal epithelium from all mice expressed COX-1 but minimal amounts of COX-2. Polyps from either rofecoxib- or sulindac-treated mice had lower rates of DNA replication, expressed less proangiogenic vascular endothelial-derived growth factor and more membrane-bound beta-catenin, but showed unchanged nuclear localization of this transcription factor. This study showing the inhibition of polyposis in the Apcdelta716 mouse suggests that the specific COX-2 inhibitor rofecoxib (Vioxx) has potential as a chemopreventive agent in human intestinal and colon cancer.

Animals↗
PubMed2001

Orphan G protein-coupled receptors in the CNS.

The majority of genes encoding G protein-coupled receptors were isolated by methods based on sequence similarities found throughout this family. Experimental techniques have exploited these similarities (including low-stringency hybridization, polymerase chain reaction and electronic database searching) to identify genes encoding many pharmacologically recognized receptors and their subtypes. Homology-based searches have revealed receptors for which the endogenous ligands were unknown and these were named orphan receptors. Many orphan receptors are expressed in the brain, suggesting the existence of unidentified neurotransmitters. Methods used to identify ligands for these orphan receptors resulted in the identification of novel ligands and succeeded in pairing previously identified ligands with their receptors. Similar successful strategies are required to characterize the physiological and pathological importance of the remaining orphan receptors to facilitate the discovery of novel drugs for these systems.

Animals↗
PubMed2001

Absorbed dose estimates to structures of the brain and head using a high-resolution voxel-based head phantom.

The purpose of this article is to demonstrate the viability of using a high-resolution 3-D head phantom in Monte Carlo N-Particle (MCNP) for boron neutron capture therapy (BNCT) structure dosimetry. This work describes a high-resolution voxel-based model of a human head and its use for calculating absorbed doses to the structures of the brain. The Zubal head phantom is a 3-D model of a human head that can be displayed and manipulated on a computer. Several changes were made to the original head phantom which now contains over 29 critical structures of the brain and head. The modified phantom is a 85 x 109 x 120 lattice of voxels, where each voxel is 2.2 x 2.2 x 1.4 mm3. This model was translated into MCNP lattice format. As a proof of principle study, two MCNP absorbed dose calculations were made (left and right lateral irradiations) using a uniformly distributed neutron disk source with an 1/E energy spectrum. Additionally, the results of these two calculations were combined to estimate the absorbed doses from a bilateral irradiation. Radiobiologically equivalent (RBE) doses were calculated for all structures and were normalized to 12.8 Gy-Eq. For a left lateral irradiation, the left motor cortex receives the limiting RBE dose. For a bilateral irradiation, the insula cortices receive the limiting dose. Among the nonencephalic structures, the parotid glands receive RBE doses that were within 15% of the limiting dose.

Boron Neutron Capture Therapy↗
PubMed2001

Expression of the cysteinyl leukotriene 1 receptor in normal human lung and peripheral blood leukocytes.

The cysteinyl leukotrienes (CysLTs) are important mediators of human asthma. Pharmacologic and clinical studies show that the CysLTs exert most of their bronchoconstrictive and proinflammatory effects through activation of a putative, 7-transmembrane domain, G-protein-coupled receptor, the CysLT1 receptor. The initial molecular characterization of the CysLT1 receptor showed by in situ hybridization, the presence of CysLT1 receptor messenger RNA (mRNA) in human lung smooth-muscle cells and lung macrophages. We confirmed the results of these in situ hybridization analyses for the CysLT1 receptor, and produced the first immunohistochemical characterization of the CysLT1 receptor protein in human lung. The identification of the CysLT1 receptor in the lung is consistent with the antibronchoconstrictive and antiinflammatory actions of CysLT1 receptor antagonists. We also report the expression of CysLT1 receptor mRNA and protein in most peripheral blood eosinophils and pregranulocytic CD34+ cells, and in subsets of monocytes and B lymphocytes.

Blood↗
PubMed2001

Effect of circular motion exercise on bone modeling and bone mass in young rats: an animal model of isometric exercise.

The aims of the study are to develop a non-invasive animal model of circular motion exercise and to evaluate the effect of this type of exercise on bone turnover in young rats. The circular motion exercise simulates isometric exercise using an orbital shaker that oscillates at a frequency of 50 Hz and is capable of speeds from 0-400 rpm. A cage is fixed on top of the shaker and the animals are placed inside. When the shaker is turned on, the oscillatory movement should encourage the animals to hold on to the cage and use various muscle forces to stabilize themselves. Rats at 8 weeks of age were trained on the shaker for 6 weeks and static and dynamic histomorphometric analyses were performed for the proximal tibial metaphysis and the tibial shaft. The exercise resulted in no significant effect on animal body weight, gastrocnemius muscle weight and femoral weight. Although the bone formation rate of cancellous and cortical periosteum was increased by the exercise, trabecular bone volume was decreased. The exercise increased periosteal and marrow perimeters and the cross-sectional diameter of cortical bone from medial to lateral without a significant increase in the cortical bone area. These results suggest that circular motion exercise under force without movement or additional weight loading will cause bone-modeling drift with an increase in bone turnover to reconstruct bone shape in adaptation to the demand in strength. Since there is no additional weight loading during circular motion exercise, the net mass of bone is not increased. The bone mass lost in trabecular bone could possibly be due to a re-distribution of mineral to the cortical bone.

Journal Article↗
PubMed2000

Characterization of the human cysteinyl leukotriene 2 receptor.

The contractile and inflammatory actions of the cysteinyl leukotrienes (CysLTs), LTC(4), LTD(4), and LTE(4), are thought to be mediated through at least two distinct but related CysLT G protein-coupled receptors. The human CysLT(1) receptor has been recently cloned and characterized. We describe here the cloning and characterization of the second cysteinyl leukotriene receptor, CysLT(2), a 346-amino acid protein with 38% amino acid identity to the CysLT(1) receptor. The recombinant human CysLT(2) receptor was expressed in Xenopus oocytes and HEK293T cells and shown to couple to elevation of intracellular calcium when activated by LTC(4), LTD(4), or LTE(4). Analyses of radiolabeled LTD(4) binding to the recombinant CysLT(2) receptor demonstrated high affinity binding and a rank order of potency for competition of LTC(4) = LTD(4) LTE(4). In contrast to the dual CysLT(1)/CysLT(2) antagonist, BAY u9773, the CysLT(1) receptor-selective antagonists MK-571, montelukast (Singulair(TM)), zafirlukast (Accolate(TM)), and pranlukast (Onon(TM)) exhibited low potency in competition for LTD(4) binding and as antagonists of CysLT(2) receptor signaling. CysLT(2) receptor mRNA was detected in lung macrophages and airway smooth muscle, cardiac Purkinje cells, adrenal medulla cells, peripheral blood leukocytes, and brain, and the receptor gene was mapped to chromosome 13q14, a region linked to atopic asthma.

Adrenal Medulla↗
PubMed2000

Identification of receptors for neuromedin U and its role in feeding.

Neuromedin U (NMU) is a neuropeptide with potent activity on smooth muscle which was isolated first from porcine spinal cord and later from other species. It is widely distributed in the gut and central nervous system. Peripheral activities of NMU include stimulation of smooth muscle, increase of blood pressure, alteration of ion transport in the gut, control of local blood flow and regulation of adrenocortical function. An NMU receptor has not been molecularly identified. Here we show that the previously described orphan G-protein-coupled receptor FM-3 (ref. 15) and a newly discovered one (FM-4) are cognate receptors for NMU. FM-3, designated NMU1R, is abundantly expressed in peripheral tissues whereas FM-4, designated NMU2R, is expressed in specific regions of the brain. NMU is expressed in the ventromedial hypothalamus in the rat brain, and its level is significantly reduced following fasting. Intracerebroventricular administration of NMU markedly suppresses food intake in rats. These findings provide a molecular basis for the biochemical activities of NMU and may indicate that NMU is involved in the central control of feeding.

Amino Acid Sequence↗
PubMed2000

Studies of retention and stability of a horizontally polymerized bonded phase for reversed-phase liquid chromatography.

We have studied the novel horizontally polymerized mixed trichloropropyl-trichlorooctadecyl silane bonded phase described by Wirth. These materials can be reproducibly prepared and give very high bonded phase density (>7.5 micromol m(-2)). They show significantly improved alkaline stability and chromatographic selectivity towards PAHs similar to conventional monomeric phases. Study of retention by the Linear Solvation Energy Relationship approach as well as measurement of dead volume and retention of methanol indicate that less mobile phase is sorbed by a horizontally polymerized phase than by conventional phases. Silanophilic interaction of amines are decidedly weaker on a silica modified by horizontal polymerization compared to a conventionally modified phase. In addition, this work provides additional support for the "partition-like" retention mechanism of bonded phase RPLC.

Chromatography, Liquid↗
PubMed2000

Osteoblast-like cells of the hypophysectomized rat: a model of aberrant osteoblast development.

In a previous work, we demonstrated that the osteoprogenitors derived from the marrow stroma of the hypophysectomized (HX) rat demonstrate enhanced proliferative and differentiation capacities when placed in an optimal microenvironment. In this study, we sought to investigate the potential of the trabecular osteoblast-like cells of the HX rat. These cells represent a more mature pool of osteoblasts than the progenitors derived from the marrow stroma. We examined all three stages of osteoblast development using trabecular osteoblast-like cells derived from age-matched intact rats as a control. Using thymidine incorporation and cell number as indicators of proliferation, we found that these cells, like the osteoprogenitors derived from the HX rat, demonstrate augmented proliferation when placed in culture. Additionally, type I collagen expression remained at significant levels past the end stages of proliferation, at which point it is expected to be downregulated. Matrix maturation markers, such as alkaline phosphatase activity and bone sialoprotein expression, however, were significantly lower than in the controls. Mineralization potential, as measured by mineralized nodule formation, Ca(2+) content, and OPN and OCN expression, was also significantly reduced. Our results have uncovered an aberrant model of osteoblast development in which proliferation is deregulated, resulting in a minimal capacity of these cells to develop into fully differentiated mineralizing osteoblasts.

Animals↗
PubMed1999

Identification of urotensin II as the endogenous ligand for the orphan G-protein-coupled receptor GPR14.

Urotensin II (UII) is a neuropeptide with potent cardiovascular effects. Its sequence is strongly conserved among different species and has structural similarity to somatostatin. No receptor for UII has been molecularly identified from any species so far. GPR14 was cloned as an orphan G protein-coupled receptor with similarity to members of the somatostatin/opioid receptor family. We have now demonstrated that GPR14 is a high affinity receptor for UII and designate it UII-R1a. HEK293 cells and COS-7 cells transfected with rat GPR14 showed strong, dose-dependent calcium mobilization in response to fish, frog, and human UII. Radioligand binding analysis showed high affinity binding of UII to membrane preparations isolated from HEK293 cells stably expressing rat GPR14. In situ hybridization analysis showed that GPR14 was expressed in motor neurons of the spinal cord, smooth muscle cells of the bladder, and muscle cells of the heart. The identification of the first receptor for UII will allow better understanding of the physiological and pharmacological roles of UII.

Amino Acid Sequence↗
PubMed1999

Characterization of the human cysteinyl leukotriene CysLT1 receptor.

The cysteinyl leukotrienes-leukotriene C4(LTC4), leukotriene D4(LTD4) and leukotriene E4(LTE4)-are important mediators of human bronchial asthma. Pharmacological studies have determined that cysteinyl leukotrienes activate at least two receptors, designated CysLT1 and CysLT2. The CysLT1-selective antagonists, such as montelukast (Singulair), zafirlukast (Accolate) and pranlukast (Onon), are important in the treatment of asthma. Previous biochemical characterization of CysLT1 antagonists and the CysLT1 receptor has been in membrane preparations from tissues enriched for this receptor. Here we report the molecular and pharmacological characterization of the cloned human CysLT1 receptor. We describe the functional activation (calcium mobilization) of this receptor by LTD4 and LTC4, and competition for radiolabelled LTD4 binding to this receptor by the cysteinyl leukotrienes and three structurally distinct classes of CysLT1-receptor antagonists. We detected CysLT1-receptor messenger RNA in spleen, peripheral blood leukocytes and lung. In normal human lung, expression of the CysLT1-receptor mRNA was confined to smooth muscle cells and tissue macrophages. Finally, we mapped the human CysLT1-receptor gene to the X chromosome.

Amino Acid Sequence↗
PubMed1999

Identification of a GABAB receptor subunit, gb2, required for functional GABAB receptor activity.

G protein-coupled receptors are commonly thought to bind their cognate ligands and elicit functional responses primarily as monomeric receptors. In studying the recombinant gamma-aminobutyric acid, type B (GABAB) receptor (gb1a) and a GABAB-like orphan receptor (gb2), we observed that both receptors are functionally inactive when expressed individually in multiple heterologous systems. Characterization of the tissue distribution of each of the receptors by in situ hybridization histochemistry in rat brain revealed co-localization of gb1 and gb2 transcripts in many brain regions, suggesting the hypothesis that gb1 and gb2 may interact in vivo. In three established functional systems (inwardly rectifying K+ channel currents in Xenopus oocytes, melanophore pigment aggregation, and direct cAMP measurements in HEK-293 cells), GABA mediated a functional response in cells coexpressing gb1a and gb2 but not in cells expressing either receptor individually. This GABA activity could be blocked with the GABAB receptor antagonist CGP71872. In COS-7 cells coexpressing gb1a and gb2 receptors, co-immunoprecipitation of gb1a and gb2 receptors was demonstrated, indicating that gb1a and gb2 act as subunits in the formation of a functional GABAB receptor.

Amino Acid Sequence↗
PubMed1999

Interpreting the clinical significance of the differential inhibition of cyclooxygenase-1 and cyclooxygenase-2.

The International Consensus Meeting on the Mode of Action of COX-2 Inhibition (ICMMAC) brought together 17 international experts in arthritis, gastroenterology and pharmacology on 5 6 December 1997. The meeting was convened to provide a definition of COX-2 specificity and to consider the clinical relevance of COX-2-specific agents. These compounds are a new class of drugs that specifically inhibit the enzyme COX-2 while having no effect on COX-1 across the whole therapeutic dose range. The objectives of the meeting were to review the currently available data regarding the roles and biology of COX-1 and COX-2, and to foster a consensus definition on COX-2 specificity. At the present time, no guidelines exist for the in vitro and in vivo assessment of COX specificity, and it was felt that consensus discussion might clarify some of these issues. The meeting also reviewed recent clinical data on COX-2-specific inhibitors. The following article reflects discussion at this meeting and provides a consensus definition of COX-2-specific inhibitors.

Anti-Inflammatory Agents, Non-Steroidal↗