Re: the role of topical nasal steroids in the treatment of children with otitis media with effusion and/or adenoid hypertrophy.
Explore the source record for details and available documents.
Adenoids↗
Biomedical subjects
Adrian Lee
Publications and source records attributed to Adrian Lee.
Crystal structure of the SH3 domain of betaPIX in complex with a high affinity peptide from PAK2.
The p21-activated kinases (PAKs) are important effector proteins of the small GTPases Cdc42 and Rac and control cytoskeletal rearrangements and cell proliferation. The direct interaction of PAKs with guanine nucleotide exchange factors from the PIX/Cool family, which is responsible for the localization of PAK kinases to focal complexes in the cell, is mediated by a 24-residue peptide segment in PAKs and an N-terminal src homology 3 (SH3) domain in PIX/Cool. The SH3-binding segment of PAK contains the atypical consensus-binding motif PxxxPR, which is required for unusually high affinity binding. In order to understand the structural basis for the high affinity and specificity of the PIX-PAK interaction, we solved crystal structures for the N-terminal SH3 domain of betaPIX and for the complex of the atypical binding segment of PAK2 with the N-terminal SH3 domain of betaPIX at 0.92 A and 1.3A resolution, respectively. The asymmetric unit of the crystal contains two SH3 domains and two peptide ligands. The bound peptide adopts a conformation that allows for intimate contacts with three grooves on the surface of the SH3 domain that lie between the n-Src and RT-loops. Most notably, the arginine residue of the PxxxPR motif forms a salt-bridge and is tightly coordinated by a number of residues in the SH3 domain. This arginine-specific interaction appears to be the key determinant for the high affinity binding of PAK peptides. Furthermore, C-terminal residues of the peptide engage in additional interactions with the surface of the RT-loop, which significantly increases binding specificity. Compared to a recent NMR structure of a similar complex, our crystal structure reveals an alternate binding mode. Finally, we compare our crystal structure with the recently published betaPIX/Cbl-b complex structure, and suggest the existence of a molecular switch.
Amino Acid Sequence↗
Urea, fluorofamide, and omeprazole treatments alter helicobacter colonization in the mouse gastric mucosa.
BACKGROUND: Helicobacter pylori is a causative agent of gastric and duodenal ulcers and gastric cancer. Its urease enzyme allows survival in acid conditions and drives bacterial intracellular metabolism. We aimed to investigate the role of urease in determining the intragastric distribution of Helicobacter species in vivo. MATERIALS AND METHODS: The C57BL/6 mouse model of gastritis was used for infection with Helicobacter felis (CS1) or H. pylori (SS1). Urease-modulating compounds urea and/or fluorofamide (urease inhibitor) were administered to mice over 7 days. Concurrent gastric acid inhibition by omeprazole was also examined. Bacterial distribution in the antrum, body, antrum/body, and body/cardia transitional zones was graded "blindly" by histologic evaluation. Bacterial colony counts on corresponding tissue were also conducted. RESULTS: Urease inhibition by fluorofamide decreased H. pylori survival in most gastric regions (p < .05); however, there were no marked changes to H. felis colonization after this treatment. There was a consistent trend for decreased antral colonization, and an increase in antrum/body transitional zone and body colonization with excess 5% or 6% (w/v) urea treatment. Significant reductions of both Helicobacter species were observed with the co-treatment of urea and fluorofamide (p < .05). Collateral treatment with omeprazole did not alter H. pylori colonization patterns caused by urea/fluorofamide. CONCLUSIONS: Urease perturbations affect colonization patterns of Helicobacter species. Combined urea and fluorofamide treatment reduced the density of both Helicobacter species in our infection model.
Animals↗
GLUT4 distribution between the plasma membrane and the intracellular compartments is maintained by an insulin-modulated bipartite dynamic mechanism.
The GLUT4 glucose transporter is predominantly retained inside basal fat and muscle cells, and it is rapidly recruited to the plasma membrane with insulin stimulation. There is controversy regarding the mechanism of basal GLUT4 retention. One model is that GLUT4 retention is dynamic, based on slow exocytosis and rapid internalization of the entire pool of GLUT4 (Karylowski, O., Zeigerer, A., Cohen, A., and McGraw, T. E. (2004) Mol. Biol. Cell 15, 870-882). In this model, insulin increases GLUT4 in the plasma membrane by modulating GLUT4 exocytosis and endocytosis. The second model is that GLUT4 retention is static, with approximately 90% of GLUT4 stored in compartments that are not in equilibrium with the cell surface in basal conditions (Govers, R., Coster, A. C., and James, D. E. (2004) Mol. Cell Biol. 24, 6456-6466). In this model, insulin increases GLUT4 in the plasma membrane by releasing it from the static storage compartment. Here we show that under all experimental conditions examined, basal GLUT4 retention is by a bipartite dynamic mechanism involving slow efflux and rapid internalization. To establish that the dynamic model developed in studies of the extreme conditions of >100 nm insulin and no insulin also describes GLUT4 behavior at more physiological insulin concentrations, we characterized GLUT4 trafficking in 0.5 nm insulin. This submaximal insulin concentration promotes an intermediate effect on both GLUT4 exocytosis and endocytosis, resulting in an intermediate degree of redistribution to the plasma membrane. These data establish that changes in the steady-state surface/total distributions of GLUT4 are the result of gradated, insulin-induced changes in GLUT4 exocytosis and endocytosis rates.
3T3-L1 Cells↗
Full intracellular retention of GLUT4 requires AS160 Rab GTPase activating protein.
Insulin controls glucose flux into muscle and fat by regulating the trafficking of GLUT4 between the interior and surface of cells. Here, we show that the AS160 Rab GTPase activating protein (GAP) is a negative regulator of basal GLUT4 exocytosis. AS160 knockdown resulted in a partial redistribution of GLUT4 from intracellular compartments to the plasma membrane, a concomitant increase in basal glucose uptake, and a 3-fold increase in basal GLUT4 exocytosis. Reexpression of wild-type AS160 restored normal GLUT4 behavior to the knockdown adipocytes, whereas reexpression of a GAP domain mutant did not revert the phenotype, providing the first direct evidence that AS160 GAP activity is required for basal GLUT4 retention. AS160 is the first protein identified that is specially required for basal GLUT4 retention. Our findings that AS160 knockdown only partially releases basal GLUT4 retention provides evidence that insulin signals to GLUT4 exocytosis by both AS160-dependent and -independent mechanisms.
3T3-L1 Cells↗
The role of antigenic drive and tumor-infiltrating accessory cells in the pathogenesis of helicobacter-induced mucosa-associated lymphoid tissue lymphoma.
Gastric B-cell lymphoma of mucosa-associated lymphoid tissue type is closely linked to chronic Helicobacter pylori infection. Most clinical and histopathological features of the tumor can be reproduced by prolonged Helicobacter infection of BALB/c mice. In this study, we have addressed the role of antigenic stimulation in the pathogenesis of the lymphoma by experimental infection with Helicobacter felis, followed by antibiotic eradication therapy and subsequent re-infection. Antimicrobial therapy was successful in 75% of mice and led to complete histological but not "molecular" tumor remission. Although lympho-epithelial lesions disappeared and most gastric lymphoid aggregates resolved, transcriptional profiling revealed the long-term mucosal persistence of residual B cells. Experimental re-introduction of Helicobacter led to very rapid recurrence of the lymphomas, which differed from the original lesions by higher proliferative indices and more aggressive behavior. Immunophenotyping of tumor cells revealed massive infiltration of lesions by CD4(+) T cells, which express CD 28, CD 69, and interleukin-4 but not interferon-gamma, suggesting that tumor B-cell proliferation was driven by Th 2-polarized, immunocompetent, and activated T cells. Tumors were also densely colonized by follicular dendritic cells, whose numbers were closely associated with and predictive of treatment outcome.
Animals↗
Mucispirillum schaedleri gen. nov., sp. nov., a spiral-shaped bacterium colonizing the mucus layer of the gastrointestinal tract of laboratory rodents.
The mammalian gastrointestinal tract is covered by a layer of mucus that can harbour a range of bacterial species specifically adapted to colonize this ecological niche. Examination of 110 bacterial isolates cultivated from the gastrointestinal tract of 23 mice revealed the presence of a subgroup of 30 isolates that did not correspond genetically with genera commonly associated with this site, i.e. members of the epsilon-Proteobacteria such as Helicobacter and Campylobacter species. Instead this group of isolates was found to lie within the phylum Deferribacteres, a completely distinct lineage in the domain Bacteria. There was a high level of consensus in results obtained from the phenotypic and genotypic characterization of a number of the isolates, which showed they were distinct from other members of the Deferribacteres. As such, they are proposed to constitute a new genus and species, Mucispirillum schaedleri gen. nov., sp. nov. These organisms are anaerobic, Gram-negative, spiral-shaped rods with bipolar flagella. The type strain is HRI I17(T) (= ATCC BAA-1009(T) = ACM 5223(T)).
Anaerobiosis↗
Template DNA ratio can affect detection by genus-specific PCR-denaturing gradient gel electrophoresis of bacteria present at low abundance in mixed populations.
The detection of Helicobacter species by genus-specific polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) was compared with that by species-specific PCR in murine intestinal samples. Results suggest that, in samples containing multiple Helicobacter species, genus-specific PCR-DGGE may fail to detect all Helicobacter species present and that this relates to the initial template DNA ratio.
Animals↗
Visualization of Helicobacter species within the murine cecal mucosa using specific fluorescence in situ hybridization.
BACKGROUND: Members of the genus Helicobacter have been associated with colitis development in a number of immunodeficient animal models. While it is known that these organisms can initiate colitis development, the location and spatial distribution of these bacteria within the intestinal tract is currently unknown. In this study, we developed and optimized fluorescence in situ hybridization (FISH) probes specifically for Helicobacter species. MATERIALS AND METHODS: Based on 16S-RNA gene alignments, two probes specific for the entire family Helicobacteraceae and two probes specific for Helicobacter ganmani and Helicobacter hepaticus were designed. Evaluation of these probes was determined using ATCC reference strains and cecum samples from ten IL-10 knockout mice. The presence of Helicobacter species was determined using FISH and verified using PCR-DGGE and microscopic examination of silver stained sections. RESULTS: Analysis of the ATCC reference strains revealed that the probes HEL274/HEL717 were specific for the family Helicobacteraceae, while HEP642 was specific for H. hepaticus and GAN1237 for H. ganmani. Using these probes, a pattern of spatial localization of the two different Helicobacter species was observed in the cecum tissues of IL-10 knockout mice. This consistently showed that H. ganmani was localized to the lower regions and H. hepaticus to the mid-upper regions of the crypts. CONCLUSION: We have developed FISH probes specific for the family Helicobacteraceae as well as two individual Helicobacter species. This study will allow the future use of the FISH to better understand host-pathogen interactions in vitro.
Animals↗
Natural colonization with Helicobacter species and the development of inflammatory bowel disease in interleukin-10-deficient mice.
BACKGROUND: The interleukin-10-deficient (IL-10-/-) mice maintained in specific-pathogen-free (SPF) conditions develop typhlocolitis when experimentally infected with Helicobacter species. However, there is limited information regarding the role of Helicobacter species that naturally colonize IL-10-/- mice in typhlocolitis development. The aim of this study was to examine in SPF IL-10-/- mice the association between natural colonization specific Helicobacter species and typhlocolitis development. MATERIAL AND METHODS: Cecum and proximal colon from 72 C57BL/6 x 129/Ola IL-10-/- mice (8-20 weeks old) were removed for DNA extraction and histologic evaluation. Genus-specific polymerase chain reaction- denaturing gradient gel electrophoresis (PCR-DGGE) and species-specific PCR were used to detect Helicobacter species. Mice were grouped by age, sex, and Helicobacter colonization status, and their histologic scores were compared. The development of clinical typhlocolitis was observed in a further 12 mice. RESULTS: Species-specific PCR showed that mice were colonized with Helicobacter ganmani and/or Helicobacter hepaticus. The PCR-DGGE detected H. ganmani, H. hepaticus and an H. ganmani-like organism. The histologic scores in mice colonized with H. hepaticus were significantly higher than that in mice colonized with H. ganmani. Male mice showed significantly higher histologic scores than female mice. Four of the 12 mice developed clinical typhlocolitis in 38 weeks. CONCLUSION: Natural colonization with different Helicobacter species was found in IL-10-/- mice within the same breeding colony. The severity of typhlocolitis differed according to the colonizing Helicobacter species. Furthermore, the rate of typhlocolitis development in IL-10-/- mice naturally colonized with Helicobacter species was significantly slower than that reported in experimentally infected mice.
Animals↗
Immunisation against Helicobacter felis infection protects against the development of gastric MALT Lymphoma.
UNLABELLED: The formation of mucosa-associated lymphoid tissue (MALT) in response to Helicobacter pylori infection is closely associated with the development of primary gastric MALT lymphoma. AIM: To examine whether immunisation against Helicobacter felis can protect against development of MALT lymphoma. RESULTS: The majority of control infected mice demonstrated MALT formation (13/15) and five developed lymphoma. Fifteen immunised mice were protected against bacterial challenge, of which only five had evidence of MALT formation and none developed lymphoma. Interestingly, of the four mice in which immunisation failed, all developed MALT and two of these had lymphoma. CONCLUSION: Effective immunisation against Helicobacter infection can protect against gastric MALT lymphoma. To our knowledge this is the first demonstration of vaccination protecting against a bacteria-induced malignancy.
Animals↗
Description of 'Candidatus Helicobacter heilmannii' based on DNA sequence analysis of 16S rRNA and urease genes.
While Helicobacter pylori is accepted as the major bacterial agent of gastric disease in humans, some patients and many animals are infected with a larger, tightly helical-shaped bacterium previously referred to as 'Helicobacter heilmannii' or 'Gastrospirillum hominis'. Taxonomic classification of these bacteria has been hampered by the inability to cultivate them in vitro and by the inadequate discriminatory power of 16S rRNA gene sequence analysis. This study describes the detection and phylogenetic analysis of 26 different gastrospirillum isolates from humans and animals, which incorporates sequence data based on the 16S rRNA and urease genes. Fifteen gastrospirilla detected in humans, primates and pigs clustered with 'Candidatus Helicobacter suis', thus expanding the host range for this organism. By comparison, based on 16S rRNA data, the remaining 11 gastrospirilla could not be differentiated from Helicobacter felis, Helicobacter bizzozeronii and Helicobacter salomonis. However, urease gene sequence analysis allowed for the discrimination of this latter group into four discrete clusters, three of which contained the above recognized species. The fourth cluster contained isolates from human and feline hosts, and should provisionally be considered a unique bacterial species, for which the name 'Candidatus Helicobacter heilmannii' is proposed.
Adult↗
Chronic Helicobacter pylori infection with Sydney strain 1 and a newly identified mouse-adapted strain (Sydney strain 2000) in C57BL/6 and BALB/c mice.
The mouse model of Helicobacter pylori-induced disease using Sydney strain 1 (SS1) has been used extensively in Helicobacter research. Herein we describe the isolation and characterization of a new mouse-colonizing strain for use in comparative studies. One strain capable of persistent mouse colonization was isolated from a total of 110 clinical isolates and is named here SS2000 (Sydney strain 2000). Genome typing revealed a number of differences between SS1 and SS2000 as well as between them and the respective original clinical isolates. In particular, SS2000 lacked the entire cag pathogenicity island, while SS1 contained all 27 genes of the island. C57BL/6 and BALB/c mice were infected with SS1 or SS2000 or were treated with broth medium (controls). After 6 months host-specific effects were evident, including lower colonization levels in the BALB/c animals. Few pathological differences were observed between SS1- and SS2000-infected animals. However, by 15 months postinfection, SS1-infected C57BL/6 mice had developed more severe gastritis than the SS2000-infected animals. In contrast SS2000-infected BALB/c mice showed increased accumulation of mucosa-associated lymphoid tissue compared to those infected with SS1. This improved comparative model of H. pylori-induced disease allowed dissection of both host and strain effects and thus will prove useful in further studies.
Animals↗
Absence of mucosa-associated colonic Helicobacters in an Australian urban population.
Application of nested PCR for Helicobacter species to 416 samples obtained at colonoscopy from 15 patients with Crohn's disease, 12 with ulcerative colitis, and 43 controls revealed H. pylori DNA in only 6 individuals with no disease association. No other Helicobacter species were detected in ileal or colonic samples.
Australia↗
The erythropoietin receptor and its expression in tumor cells and other tissues.
Erythropoietin (EPO) is the primary regulator of erythropoiesis, stimulating growth, preventing apoptosis, and promoting differentiation of red blood cell progenitors. The EPO receptor belongs to the cytokine receptor superfamily. Although the primary role of EPO is the regulation of red blood cell production, EPO and its receptor have been localized to several nonhematopoietic tissues and cells, including the central nervous system (CNS), endothelial cells, solid tumors, the liver, and the uterus. The presence of EPO receptors and the possibility of EPO signaling in these tissues and cells have led to numerous studies of the effects of EPO at these sites. In particular, expression of EPO and the EPO receptor in cancer cells has generated much interest because of concern that administration of recombinant human erythropoietin (rHuEPO) to patients with breast and other cancer cells expressing the EPO receptor may promote tumor growth via the induction of cell proliferation or angiogenesis. However, evidence supporting a growth-promoting effect has been inconclusive. Moreover, several preclinical studies have shown a beneficial effect of EPO on delaying tumor growth. Further, it is conceivable that increased expression of EPO could reduce tumor hypoxia and ameliorate the deleterious effects of hypoxia on tumor growth, metastasis, and treatment resistance. On the other hand, EPO has also been shown to produce an angiogenic effect in vascular endothelial cells in vitro. However, there is no evidence that these effects occur in vivo to promote tumor growth. EPO and EPO receptors are expressed in neural tissue, and they are upregulated there by hypoxia. Animal studies have shown that administration of epoetin alfa (an rHuEPO) reduces tissue injury due to ischemic stroke, blunt trauma, and experimental autoimmune encephalomyelitis. These findings suggest that epoetin alfa may provide a therapeutic benefit in patients with stroke, trauma, epilepsy, and other CNS-related disorders. Clearly, further study of EPO and the EPO receptor in nonhematopoietic tissue is warranted to determine the potential therapeutic usefulness of rHuEPO as well as to determine the signaling pathway responsible for its effect in vivo.
Cell Hypoxia↗
Protective immunity against Helicobacter is characterized by a unique transcriptional signature.
Immunization with a whole-cell sonicate vaccine of Helicobacter felis in conjunction with cholera toxin as a mucosal adjuvant induces long-term protective immunity in a majority of laboratory mice. We have combined gene expression profiling and immunohistochemical analysis on a set of immunized animals to better understand the mechanism of protection. The stomachs of protected animals exhibited a strikingly different transcriptional profile compared with those of nonprotected or control mice, indicating that vaccination targets the appropriate site and leaves a molecular signature. Among the genes whose up-regulation is significantly correlated with protection are a number of adipocyte-specific factors. These include the fat-cell-specific cytokines adipsin, resistin, and adiponectin and the adipocyte surface marker CD36. Interestingly, potentially protective T and B lymphocytes can be found embedded in the adipose tissue surrounding protected stomachs but never in control or unprotected stomachs. Adipsin-specific immunohistochemical staining of protected stomach sections further revealed molecular cross-talk between adjacent lymphoid and adipose cell populations. We propose a mechanism of protection that involves the effector responses of either or both lymphocyte subclasses as well as the previously unappreciated paracrine functions of adipose tissue surrounding the resident lymphocytes.
Adipocytes↗
Distinct gene expression profiles characterize the histopathological stages of disease in Helicobacter-induced mucosa-associated lymphoid tissue lymphoma.
Long-term colonization of humans with Helicobacter pylori can cause the development of gastric B cell mucosa-associated lymphoid tissue lymphoma, yet little is known about the sequence of molecular steps that accompany disease progression. We used microarray analysis and laser microdissection to identify gene expression profiles characteristic and predictive of the various histopathological stages in a mouse model of the disease. The initial step in lymphoma development is marked by infiltration of reactive lymphocytes into the stomach and the launching of a mucosal immune response. Our analysis uncovered molecular markers of both of these processes, including genes coding for the immunoglobulins and the small proline-rich protein Sprr 2A. The subsequent step is characterized histologically by the antigen-driven proliferation and aggregation of B cells and the gradual appearance of lymphoepithelial lesions. In tissues of this stage, we observed increased expression of genes previously associated with malignancy, including the laminin receptor-1 and the multidrug-resistance channel MDR-1. Finally, we found that the transition to destructive lymphoepithelial lesions and malignant lymphoma is marked by an increase in transcription of a single gene encoding calgranulin AMrp-8.
ATP Binding Cassette Transporter, Subfamily B, Mem↗
Animal models of Helicobacter pylori infection and disease.
The acceptance of Helicobacter pylori as a major human pathogen has necessitated the development of animal models to help elucidate the pathogenic mechanisms of this bacterium and aid in the development of improved strategies for the treatment of gastric disease. Appropriate models, utilising a range of animal species, have been developed to examine factors such as the influence of host responses and bacterial factors in disease development and the success of new therapeutic regimens, including vaccination, to cure infection.
Animals↗