bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of flanking bases on quadruplex stability and Watson–Crick duplex competition
Authors: Arora Amit , Nair Divya R. , Maiti Souvik
Published: May 2009

Guanine‐rich DNA sequences have the ability to fold into four‐stranded structures called G‐quadruplexes, and are considered as promising anticancer targets. Although the G‐quadruplex structure is composed of quartets and interspersed loops, in the genome it is also flanked on each side by numerous bases. The effect of loop length and composition on quadruplex conformation and stability has been well investigated in the past, but the effect of flanking bases on quadruplex stability and Watson–Crick duplex competition has not been addressed. We have studied in detail the effect of flanking bases on quadruplex stability and on duplex formation by the G‐quadruplex in the presence of complementary strands using the quadruplex‐forming sequence located in the promoter region of the c‐kit oncogene. The results obtained from CD, thermal difference spectrum and UV melting demonstrated the effect of flanking bases on quadruplex structure and stability. With the increase in flank length, the increase in the more favorable ΔHvH is accompanied by a striking increase in the unfavorable ΔSvH, which resulted in a decrease in the overall ΔGvH of quadruplex formation. Furthermore, CD, fluorescence and isothermal titration calorimetry studies demonstrated that the propensity to attain quadruplex structure decreases with increasing flank length.
Intrinsic disorder and coiled‐coil formation in prostate apoptosis response factor 4
Authors: Libich David S. , Schwalbe Martin , Kate Sachin , Venugopal Hariprasad , Claridge Jolyon K. , Edwards Patrick J. B. , Dutta Kaushik , Pascal Steven M.
Published: May 2009

Prostate apoptosis response factor‐4 (Par‐4) is an ubiquitously expressed pro‐apoptotic and tumour suppressive protein that can both activate cell‐death mechanisms and inhibit pro‐survival factors. Par‐4 contains a highly conserved coiled‐coil region that serves as the primary recognition domain for a large number of binding partners. Par‐4 is also tightly regulated by the aforementioned binding partners and by post‐translational modifications. Biophysical data obtained in the present study indicate that Par‐4 primarily comprises an intrinsically disordered protein. Bioinformatic analysis of the highly conserved Par‐4 reveals low sequence complexity and enrichment in polar and charged amino acids. The high proteolytic susceptibility and an increased hydrodynamic radius are consistent with a largely extended structure in solution. Spectroscopic measurements using CD and NMR also reveal characteristic features of intrinsic disorder. Under physiological conditions, the data obtained show that Par‐4 self‐associates via the C‐terminal domain, forming a coiled‐coil. Interruption of self‐association by urea also resulted in loss of secondary structure. These results are consistent with the stabilization of the coiled‐coil motif through an intramolecular association.
Discovery of a large and bright bow shock nebula associated with low-mass X-ray binary SAX J1712.6–3739
Authors: Wiersema K. , Russell D. M. , Degenaar N. , Klein-Wolt M. , Wijnands R. , Heinz S. , Read A. M. , Saxton R. D. , Tanvir N. R.
Published: May 2009

In a multiwavelength programme dedicated to identifying optical counterparts of faint persistent X-ray sources in the Galactic bulge, we find an accurate X-ray position of SAX J1712.6–3739 through Chandra observations, and discover its faint optical counterpart using our data from EFOSC2 on the ESO 3.6-m telescope. We find this source to be a highly extincted neutron star low-mass X-ray binary (LMXB) with blue optical colours. We serendipitously discover a relatively bright and large bow shock shaped nebula in our deep narrow-band Hα imaging, most likely associated with the X-ray binary. A nebula like this has never been observed before in association with a LMXB, and as such provides a unique laboratory to study the energetics of accretion and jets. We put forward different models to explain the possible ways the LMXB may form this nebulosity, and outline how they can be confirmed observationally.
Geography and Election Results: Disproportionality and Bias at the 1993–2004 Elections to the Australian House of Representatives
Authors: JOHNSTON RON , FORREST JAMES
Published: May 2009

The Alternative Vote system used for elections to the Australian House of Representatives is generally believed to disadvantage the Australian Labor Party in contests with the Liberal and National parties. However, most analyses on which such conclusions are based over‐simplify the situation by not separating out the translation of votes into seats according to whether the election outcome in a district is determined using the first‐preference or two‐party preferred (2PP) votes. Analyses of bias at five recent elections which recognise that separation find little bias against either party in the districts where the determination used the 2PP votes (i.e. no candidate received a majority of the first preferences), but considerable bias in those where the outcome was decided on first‐preferences. Furthermore, that bias was not in one direction, but rather favoured the largest party in each of those contests. The reason for this is identified in the geography of support for the two parties, which produces the equivalent of a ‘cracked gerrymander’ in sufficient districts to have a significant impact on the outcome.
The relationship of pulp polyp with the presence and concentration of immunoglobulin E, histamine, interleukin‐4 and interleukin‐12
Authors: Sattari Mandana , Haghighi Ali K. , Tamijani Hasan D.
Published: May 2009

The aim of this study was to evaluate the relationship between pulp polyp formation and immunoglobulin E (IgE), histamine and interleukin‐4 (IL‐4) as the most important mediators which are involved in allergy. Thirty‐two samples including 16 pulp polyps and 16 normal pulps were gathered. After homogenising the pulpal tissue samples, enzyme‐linked immunosorbent assay (ELISA) techniques were used to assess the concentration of IgE, histamine, IL‐4 and IL‐12. The two groups showed statistically significant differences in terms of both the concentration and presence of IgE, histamine and IL‐4 (P < 0.001); both presence and concentration of IgE, histamine and IL‐4 were higher in pulp polyps than in normal pulps. There is not any significant difference between case and control groups regarding IL‐12. The results of this study give rise to the possibility of type I hypersensitivity reaction being involved in pulp polyp's pathogenesis.
Balance after stapedotomy: analysis of balance with computerized dynamic posturography
Authors: Özmen A.Ö. , Aksoy S. , Özmen S. , Saraç S. , Sennaroğlu L. , Gürsel B.
Published: May 2009

Objectives:  The aim of this study was to investigate vestibular symptoms and their effect on the balance in otosclerosis patients undergoing stapedotomy operations.

Design & setting:  Prospective study at an academic tertiary referral centre.

Participants:  Thirty‐three patients undergoing stapedotomy were included in the study.

Main outcome measures:  Sensory organisation test (SOT) protocol of computerized dynamic posturography was used to analyse the balance in patients preoperatively, in the first postoperative week and the first postoperative month. Postoperative vestibular symptoms were analysed with a grading system. Audiograms were obtained preoperatively and 1 month after the operation.

Results:  Preoperatively, all patients were asymptomatic when considering the vestibular system; however, eight of them got low SOT scores on vestibular examination. Postoperatively 82% of the patients had vestibular complaints in variable severity. In the first week, all but one patient become asymptomatic. This patient recovered by the end of postoperative second week. However, a significant drop in SOT scores was encountered at the first week testing (Student’s T‐test, P = 0.001). One month after the operation, all patients were asymptomatic and SOT scores recovered at least to preoperative level. Neither patient characteristics, nor audiological findings were found to be correlated with vestibular changes.

Conclusion:  Stapedotomy causes a temporary balance loss in a high percentage of patients which then recover to their former levels in the first postoperative month.
Effectiveness of multi‐channel unilateral cochlear implants for profoundly deaf children: a systematic review
Authors: Bond M. , Elston J. , Mealing S. , Anderson R. , Weiner G. , Taylor R.S. , Liu Z. , Stein K.
Published: May 2009

Background:  Annually an estimated 223 children in the UK are born with or acquire permanent profound bilateral deafness (PBHL ≥ 95 dB). These children may gain little or no benefit from acoustic hearing aids. However, cochlear implants might enable them to hear.

Objectives of the review:  To bring together the diverse research in this area under the rigor of a systematic review to discover the strength of evidence when comparing the effectiveness of unilateral cochlear implants with non‐technological support or acoustic hearing aids in children with PBHL.

Type of review:  Systematic review.

Search strategy:  This examined 16 electronic data bases, plus bibliographies and references for published and unpublished studies.

Evaluation method:  Abstracts were independently assessed against inclusion criteria by two researchers, results were compared and disagreements resolved. Included papers were then retrieved and further independently assessed in a similar way. Remaining studies had their data independently extracted by one of five reviewers and checked by another reviewer.

Results:  From 1,580 abstracts and titles 15 studies were included. These were of moderate to poor quality. The large amount of heterogeneity in design and outcomes precluded meta‐analysis. However, all studies reported that unilateral cochlear implants improved scores on all outcome measures. Additionally five economic evaluations found unilateral cochlear implants to be cost‐effective for profoundly deaf children at UK implant centres.

Conclusions:  The robustness of systematic review methods gives weight to the positive findings of 15 papers reporting on this subject that they individually lack; while an RCT to show this would be unethical.
Clopidogrel versus low‐dose aspirin as risk factors for epistaxis
Authors: Rainsbury J.W. , Molony N.C.
Published: May 2009

Objectives:  To quantify the relative risk of epistaxis for patients taking low‐dose aspirin or clopidogrel compared to patients taking neither drug.

Design:  Case‐control study.

Setting:  Primary care.

Participants:  10,241 patients from three GP practices in the West Midlands.

Main outcome measures:  Epistaxis resulting in presentation to the GP, attendance at Accident & Emergency, or referral to ENT outpatients.

Results:  There was a significant difference in the proportion of patients with epistaxis across the three groups (χ2 = 84.1; 2 degrees of freedom; P < 0.000001). Relative risk of epistaxis was increased in both the aspirin (RR = 9.04; 95% CI = 5.13–15.96) and clopidogrel (RR = 6.40; 95% CI = 2.33–17.56) groups compared to the no drug group. There was no increased risk of epistaxis with aspirin compared to clopidogrel (RR = 1.4; 95% CI = 0.6–3.4).

Conclusion:  There is an increased risk of troublesome epistaxis in patients taking aspirin or clopidogrel. There is no significant difference in risk of epistaxis between the two drug groups.
Enteral versus Parenteral Nutrition: Effect on Intestinal Barrier Function
Authors: Yang Hua , Feng Yongjia , Sun Xiaoyi , Teitelbaum Daniel H.
Published: May 2009

Total parenteral nutrition (TPN), or the complete absence of enteral nutrients, is commonly used in a clinical setting. However, a major consequence of TPN administration is the development of mucosal atrophy and a loss of epithelial barrier function (EBF); and this loss may lead to an increase in clinical infections and septicemia. Our laboratory has investigated the mechanism of this TPN‐associated loss of EBF using a mouse model. We have demonstrated that the mucosal lymphoid population significantly changes with TPN, and leads to a rise in interferon gamma (IFN‐γ) and decline in interleukin‐10 (IL‐10) expression—both of which contribute to the loss of EBF. Associated with these cytokine changes is a dramatic decline in the expression of tight junction and adherens junction proteins. This article discusses the potential mechanisms responsible for these changes, and potential strategies to alleviate this loss in EBF.
Modification of Tight Junction Structure and Permeability by Nutritional Means
Authors: Mullin James M. , Skrovanek Sonja M. , Valenzano Mary Carmen
Published: May 2009

The relative abundance of various claudin proteins of LLC‐PK1 renal epithelial tight junctions (TJs) is modulated by culturing the cells in a medium that is sharply reduced in the sulfur‐containing amino acids, cysteine, cystine, and methionine. The functional result is an epithelial barrier that has a higher transepithelial electrical resistance and a decreased paracellular leak to D‐mannitol (i.e., improved barrier function). This is accomplished without affecting the culture's confluent cell density, its short circuit current, or its hallmark differentiated property, Na+‐dependent sugar transport. The implications of being able to enhance epithelial TJ barrier function by nutritional means are discussed, particularly in light of the ability of methionine‐restrictive diets to enhance life span and forestall age‐related morbidity.
Probiotic Therapy in Radiation‐Induced Intestinal Injury and Repair
Authors: Ciorba Matthew A. , Stenson William F.
Published: May 2009

Intestinal injury from ionizing radiation is a clinically important entity, as enteritis symptoms occur commonly after radiotherapy for pelvic malignancies. Preventative or therapeutic options for radiation enteritis are mostly unsatisfactory; however, available data suggests that probiotic bacteria—those which confer health benefit—may have therapeutic value. Previous reports from both human trials and animal models have evaluated various end points for probiotic usage in limiting radiation‐associated intestinal damage. Newer data suggests that particular probiotics and/or their secreted or derived bacterial products may have unique radioprotective properties. We will review the area with a focus on new developments surrounding probiotic therapy in radiation‐induced intestinal injury and repair.
Corticotropin‐Releasing Hormone and Mast Cells in the Regulation of Mucosal Barrier Function in the Human Colon
Authors: Wallon Conny , Söderholm Johan D.
Published: May 2009

Corticotropin‐releasing hormone (CRH) is an important neuro‐endocrine mediator of the stress response. Local effects of CRH in the intestinal mucosa have become evident in recent years. We showed that CRH activates CRH receptor subtypes R1 and R2 on subepithelial mast cells, thereby inducing increased transcellular uptake of protein antigens in human colonic biopsies in Ussing chambers. Ongoing studies also implicate local cholinergic signaling in regulation of macromolecular permeability in the human colon. Since increased uptake of antigenic molecules is associated with mucosal inflammation, our findings may have implications for understanding stress‐related intestinal disorders.
Analysis of Claudin Genes in Pediatric Patients with Bartter's Syndrome
Authors: Chen Yan‐Hua , Lin Jen‐Jar , Jeansonne Beverly G. , Tatum Rodney , Lu Qun
Published: May 2009

Bartter's syndrome is a constellation of symptoms characterized by hyper‐reninemic hypokalemia, metabolic alkalosis, elevated renin and aldosterone, low or normal blood pressure, and hyperplasia of the juxtaglomerular apparatus. So far, five gene mutations in proteins regulating the sodium chloride transport in the thick ascending limb of Henle's loop have been described. However, the molecular mechanisms underlying the presentation of hypomagnesemia in some of these patients remains unclear. Claudins are a family of transmembranous proteins within the tight junctions that have been shown to be important for the paracellular movement of ions. Mutations in claudin‐16 have been identified in patients with familial hypomagnesemia with hypercalciuria and nephrocalcinosis. To test the hypothesis that mutations in claudin genes may be involved in the altered magnesium and calcium transport in Bartter's syndrome, we began to examine the genes of claudins known to be present in renal tubules in four pediatric patients with Bartter's syndrome. All four patients were African Americans with hypomagnesemia and hypercalciuria. In this study, we did not find any mutation in the coding regions of claudin‐2, ‐3, ‐4, ‐7, ‐8, ‐10, ‐11, or ‐16 genes in these patients. However, all patients had a single nucleotide substitution of C for T at the position of 451 of claudin‐8 gene sequence that changes amino acid residue from serine to proline at the position of 151 in the second extracellular domain of claudin‐8 protein. The significance of this known single nucleotide polymorphism remains to be determined.
Vertebrate Animal Models Unravel Physiological Roles for Zonula Occludens Tight Junction Adaptor Proteins
Authors: Hunziker Walter , Kiener Tania K. , Xu Jianliang
Published: May 2009

Tight junctions (TJs) contribute to the maintenance of epithelial cell polarity and endothelial and epithelial barrier functions. Structurally, TJs are composed of integral membrane proteins, which are tethered to the actin cytoskeleton through adaptor or scaffolding proteins. Three related members of the membrane associated guanylate kinase (MAGUK) protein family—ZO‐1, ZO‐2, and ZO‐3—have been extensively studied in cell culture systems, yet their relevance to TJ structure and function have only recently started to be elucidated. Vertebrate animal models—in particular, mouse and zebrafish—have contributed to the unraveling of the physiological importance of these proteins in vivo. Here we discuss recent findings on the importance of ZO‐2 in mouse development and the role of ZO‐3 in barrier function of the skin of zebrafish embryos.
Mechanisms of Outside‐in Signaling at the Tight Junction by Junctional Adhesion Molecule A
Authors: Severson Eric A. , Parkos Charles A.
Published: May 2009

Junctional adhesion molecule A (JAM‐A) is a tight junction–associated, PDZ binding domain containing transmembrane protein that forms cis‐homodimers in endothelial and epithelial cells. In vivo, the function of JAM‐A in colonic mucosa has been examined using JAM‐A knockout mice, which have increased intestinal permeability, inflammation and cellular proliferation compared to wild‐type controls. In vitro studies have revealed that downregulation of JAM‐A leads to altered cell migration secondary to diminished levels of β1 integrin on the cell surface. Similar findings have been observed after transfection of epithelial cells with mutant JAM‐A, which is defective in dimerization or lacks the PDZ binding domain. The dominant‐negative effects of these mutant JAM‐A proteins are most likely secondary to the inability of mutant JAM‐A to form signaling complexes, the lack of which results in decreases in active or GTP‐bound Rap1. This review highlights findings that support a hypothetical model for JAM‐A mediated outside‐in signaling. In this model,  JAM‐A dimerization is required for close cytoplasmic apposition of complexes containing specific PDZ domain‐containing scaffold proteins that activate signaling molecules to serve as effectors for the regulation of cellular functions. The possibility of interactions of JAM‐A cis‐dimers between cells in trans is also discussed.
Mechanisms of Tight Junction Dysregulation in the SAMP1/YitFc Model of Crohn's Disease–like Ileitis
Authors: Reuter Brian K. , Pizarro Theresa T.
Published: May 2009

To date, the precise etiology of inflammatory bowel disease (IBD) remains largely unknown; however, it is well accepted that IBD results from a dysregulated mucosal immune response to environmental factors in genetically susceptible hosts. The primary defect, in at least a subpopulation of IBD patients, may be due to abnormal intestinal epithelial barrier function. The SAMP1/YitFc (SAMP) mouse strain is a spontaneous model of IBD, closely resembling Crohn's disease for its histologic features and localization to the terminal ileum. Dysregulated epithelial barrier function that precedes histologic evidence of ileitis has been reported to be the primary defect in SAMP mice. Data suggest that barrier dysfunction occurs in the absence of commensal bacteria and is accompanied by aberrant expression of the tight junction proteins claudin‐2 and occludin. Further investigation is needed to define the precise role of the intestinal epithelium, as well as the apical junctional complex and its associated proteins, in the pathogenesis of IBD in order to determine the etiology and aid in the development of novel treatment modalities for these devastating diseases.
Metabolic Stress Evokes Decreases in Epithelial Barrier Function
Authors: Lewis Kimberley , McKay Derek M.
Published: May 2009

The epithelial lining of the gastrointestinal tract is the major interface between the external world (e.g., the gut lumen) and the body, and as such the proper maintenance and regulation of epithelial barrier function is a key determinant of digestive health and host well‐being. Many enteropathies are associated with increased gut permeability, including inflammatory bowel disease (IBD). Maintaining the barrier function of the epithelium, independent of whether paracellular or transcellular permeation pathways are considered, is an energy‐dependent process. Here we present an overview of the impact that metabolic stress (e.g., reductions in epithelial ATP synthesis) can have on permeability characteristics of epithelial monolayers and show that metabolic stress in the presence of a commensal flora results in a significant loss of epithelial integrity, and that this increase in epithelial permeability can be enhanced by the presence of tumor necrosis factor‐α (TNFα). We speculate that the combination of these factors in vivo would result in significant perturbations in epithelial barrier function that could be of pathophysiological significance and contribute to the initiation of IBD or the induction of disease relapses.
Modulation of Intestinal Barrier Properties by Probiotics: Role in Reversing Colitis
Authors: Resta‐Lenert Silvia C. , Barrett Kim E.
Published: May 2009

Probiotic bacteria, commensals selected for their presumed therapeutic properties when ingested orally, have attracted increasing attention for their possible efficacy in a range of gastrointestinal disorders, including the inflammatory bowel diseases of Crohn's disease and ulcerative colitis. Since the barrier properties of the intestinal epithelium are believed to be compromised as a consequence (or perhaps as a cause) of intestinal inflammation, we hypothesized that probiotics might ameliorate such epithelial dysfunction as part of their spectrum of beneficial effects. We have used both cell line and animal models to test this hypothesis and show that two probiotics have significant effects on epithelial barrier properties, both at baseline and when deranged by inflammatory cytokines or in the setting of inflammation in a mouse model of colitis. Moreover, the probiotics also normalize epithelial ion transport function, which could also contribute to clinical efficacy. Overall, our studies extend the spectrum of functional effects attributable to probiotics, and may provide a rationale for their use in a range of gastrointestinal disorders associated with epithelial dysfunction.
Differential Phosphorylation of Occludin and Tricellulin by CK2 and CK1
Authors: Dörfel Max J. , Westphal Julie K. , Huber Otmar
Published: May 2009

In epithelial and endothelial cell layers tight junctions form selective apicolateral paracellular barriers separating luminal and extracellular spaces from the underlying tissues. Within the tight junctions the tetraspan transmembrane proteins occludin, claudins, and tricellulin form anastomosing strands of protein complexes, which interconnect opposing membranes of neighboring cells. Phosphorylation of tight junction components is critically involved in the regulation of tight junction assembly, maintenance, and function. This chapter compares occludin and tricellulin phosphorylation by the serine/threonine kinases CK2 and CK1.
Regulation of the Intestinal Anion Exchanger DRA (Downregulated in Adenoma)
Authors: Lamprecht Georg , Gaco Vera , Turner Jerrold R. , Natour Dorgam , Gregor Michael
Published: May 2009

Barrier function and transepithelial transport are intimately linked and are sometimes disturbed in parallel. DRA (downregulated in adenoma) is an intestinal chloride/bicarbonate exchanger that is functionally coupled to CFTR (cystic fibrosis transmembrane regulator) in the upper gastrointestinal tract to mediate chloride and bicarbonate secretion and to NHE3 (Na/H exchanger‐ isoform 3) in the lower gastrointestinal tract to mediate electroneutral NaCl absorption. All three transport proteins possess PDZ domain binding motifs that facilitate binding to members of the NHERF (Na/H exchanger regulatory factor) family of adapter proteins [NHERF, E3KARP (NHE3 kinase A regulatory protein), PDZK1 (PDZ protein kidney 1) and IKEPP (intestinal and kidney enriched PDZ protein)]. Regulation of DRA appears to depend on the presence of a partner transport protein, and this may involve the assembly of different complexes of transporters, adapter proteins, and signaling molecules. We have established stable expression of DRA in HEK cells. In these cells, that do not express significant amounts of CFTR or NHE3, DRA is inhibited by intracellular calcium but not by protein kinase C or protein kinase A. At high calcium concentrations induced by 4Br‐A23187 this inhibition is independent of the PDZ interaction of DRA. These data show that DRA can be individually regulated and may be confirmed in a more physiologically relevant expression system (i.e., Caco‐2/BBE cells) using natural agonists of the intracellular calcium signal.
The Role of the NHERF Family of PDZ Scaffolding Proteins in the Regulation of Salt and Water Transport
Authors: Seidler Ursula , Singh Anurag Kumar , Cinar Ayhan , Chen Mingmin , Hillesheim Jutta , Hogema Boris , Riederer Brigitte
Published: May 2009

The four members of the NHERF (Na+/H+exchanger regulatory factor) family of PDZ adapter proteins bind to a variety of membrane transporters and receptors and modulate membrane expression, mobility, interaction with other proteins, and the formation of signaling complexes. All four family members are expressed in the intestine. The CFTR (cystic fibrosis transmembrane regulator) anion channel and the Na+/H+exchanger NHE3 (Na/H exchanger‐ isoform 3) are two prominent binding partners to this PDZ‐adapter family, which are also known key players in the regulation of intestinal electrolyte and fluid transport. Experiments in heterologous expression systems have provided a number of mechanistic models how NHERF protein interactions can affect the function of their targets at the molecular level. Recently, NHERF1, 2, and 3 knockout mice have become available, and this review summarizes the reports on electrolyte and fluid transport regulation in the native intestine of these mice.
Occludin Phosphorylation in Regulation of Epithelial Tight Junctions
Authors: Rao Radhakrishna
Published: May 2009

Occludin is the first transmembrane protein of the tight junction to be discovered. While numerous studies emphasized the important role of occludin in assembly and maintenance of tight junctions, occludin knockout studies indicated that it was not required for tight junction assembly in different epithelia. However, a detailed characterization of the occludin knockout mouse concluded that the occludin gene is indispensable, and plays a complex role in regulation of epithelial tight junctions in different organs. This article describes the role of occludin phosphorylation in the regulation of its assembly into the tight junctions. Occludin is highly phosphorylated on Ser and Thr residues, while Tyr‐phosphorylation is kept at minimum in the intact epithelium. During the disruption of tight junctions by various factors, occludin undergoes dephosphorylation on Ser/Thr residues and elevated phosphorylation on Tyr residues. The phosphorylation of occludin on Tyr, Ser, and Thr residues appears to be regulated by the balance between protein kinases such as c‐Src, PKCζ, and PKCλ/ι, and protein phosphatases such as PP2A, PP1, and PTP1B. The precise mechanism of regulation of the tight junction by occludin phosphorylation is unclear at this time. However, an in vitro study indicated that Tyr‐phosphorylation of occludin C‐terminal domain attenuates its interaction with ZO‐1. Therefore, phosphorylation of specific Ser/Thr/Tyr residues in occludin may regulate its interactions with ZO‐1 and possibly other tight junction proteins. It is likely that occludin plays a regulatory role in tight junctions rather than a role in the de novo assembly of tight junctions.
Regulation of Intestinal Electroneutral Sodium Absorption and the Brush Border Na+/H+ Exchanger by Intracellular Calcium
Authors: Zachos Nicholas C. , Kovbasnjuk Olga , Donowitz Mark
Published: May 2009

The intestinal electroneutral Na+ absorptive processes account for most small intestinal Na+ absorption in the period between meals and also for the great majority of the increase in ileal Na+ absorption that occurs postprandially. In most diarrheal diseases, there is inhibition of neutral NaCl absorption. Elevated levels of intracellular calcium ([Ca2+]i) are known to inhibit NaCl absorption and involve multiple components of the Ca2+ signaling pathway. The BB Na+/H+ exchanger NHE3 accounts for most of the recognized digestive changes in neutral NaCl absorption, as well as most of the changes in Na+ absorption that occur in diarrheal diseases. Previous studies have examined several aspects of Ca2+ regulation of NHE3 activity. These include phosphorylation, protein trafficking, and multiprotein complex formation. In addition, recent studies have demonstrated the role of the NHERF family of PDZ domain–containing proteins in Ca2+ regulation of NHE3 activity, thereby adding a new level of complexity to understanding Ca2+‐dependent inhibition of Na+ absorption. In this article, we will review the current understanding of (1) Ca2+ signaling events in intestinal epithelial cells; (2) Ca2+ regulation of intestinal electroneutral sodium absorption, which includes NHE3; and (3) the role of the NHERF family of PDZ domain–containing proteins in Ca2+ regulation of NHE3 activity. We will also present new data on using advanced imaging showing rapid BB NHE3 endocytosis in response to elevated [Ca2+]i.
Tight Junctions and Enteropathogenic E. coli
Authors: Weflen Andrew W. , Alto Neal M. , Hecht Gail A.
Published: May 2009

Enteropathogenic E. coli (EPEC) are a leading cause of infantile diarrhea in developing countries, resulting in millions of deaths each year. EPEC secrete virulence factors, also called effectors, directly into host intestinal epithelial cells via type three secretion systems. Secreted effectors then affect host signaling pathways to induce several phenotypes, which ultimately lead to disease. Among the over 20 secreted effectors is E. coli secreted protein F (EspF), a 206 amino acid protein believed to be central to EPEC pathogenesis, as it disrupts tight junction structure and function. Although the mechanism by which this occurs is unknown, EspF has recently been found to contain several protein–protein interaction domains that may be involved. We have shown EspF to interact with the endocytic regulators sorting nexin 9 (SNX9) and N‐WASP via non‐exclusive binding sites. These interactions induce actin polymerization in vitro, and interaction with SNX9 alters its endocytic activity, as EspF induces the formation of tubular vesicles in a manner dependent upon its interaction with SNX9. EspF, therefore, appears to hijack endocytic regulation via SNX9 and possibly N‐WASP interaction, to affect an as yet unidentified pathogenic phenotype.
Barrier Effects of Nutritional Factors
Authors: Amasheh Maren , Andres Susanne , Amasheh Salah , Fromm Michael , Schulzke Jörg‐Dieter
Published: May 2009

High dietary intake of fruits and vegetables is associated with a reduced disease risk. Therefore, clinical interest is growing in therapies based on dietary supplements and effects of food components. Immune‐modulatory and barrier‐protective effects have been described for the amino acid glutamine and the trace element zinc. In Caco‐2‐cells, zinc is necessary to maintain the expression of proteins like ZO‐1 and occludin, and experimental evidence exists that glutamine has enterocyte‐protective effects and modulates intestinal barrier function in stressed animals and humans. Polyunsaturated fatty acids (PUFA) improve paracellular permeability after IL‐4 incubation. Enhancement of barrier properties by long‐chain PUFA is discussed controversially, but a beneficial role preventing the redistribution of occludin and ZO‐1 and reduction of epithelial resistance by IFN‐γ and TNF‐α exists. In addition, a group of secondary plant compounds, the polyphenols, are supposed to be important in this respect. The flavonoid quercetin and its metabolite DHBA increased epithelial resistance of Caco‐2‐cells to 157 ± 4% of control values, and DHBA up to 119 ± 4% of control values, respectively. This is due to a 2.3 ± 0.1‐fold expression rate of the tight junction protein claudin‐4.
Tight Junction Proteins as Channel Formers and Barrier Builders
Authors: Amasheh Salah , Milatz Susanne , Krug Susanne M. , Markov Alexander G. , Günzel Dorothee , Amasheh Maren , Fromm Michael
Published: May 2009

Tight junctions form the paracellular barrier for ions and uncharged solutes not only in “tight” but also in “leaky” epithelia. In the premolecular era of tight junction research, this was believed to be achieved in a perfect or less perfect way, depending mainly on the amount of horizontally oriented tight junction strands. During the past decade it emerged that tight junction molecules, such as claudin‐1 and many others, strengthen the barrier, while a few claudins, such as claudin‐2 or ‐10, weaken it. This report focuses on three claudins: one channel former and two barrier builders. Claudin‐2 represents the prototype of a paracellular, channel‐forming, tight junction protein responsible for specific transfer of solutes across the epithelium without entering the cells. This channel is selective for small cations but nearly impermeable to anions and uncharged solutes of any size. In contrast, claudin‐5, a tight junction protein typical for all endothelia but also found in some epithelia, was characterized as a potent barrier builder. Claudin‐8, another barrier builder, was demonstrated to be regulated by Na+ uptake in surface epithelial cells of human colon. Here, aldosterone enhanced Na+ absorption by dual action: transcellularly by inducing the epithelial sodium channel and paracellularly by preventing back leakage of absorbed Na+ by upregulating claudin‐8.
Zonula Occludens‐1 and ‐2 Are Cytosolic Scaffolds That Regulate the Assembly of Cellular Junctions
Authors: Fanning Alan S. , Anderson James M.
Published: May 2009

The integrity of the tight junction barrier in epithelial and endothelial cells is critical to human health, but we still lack a detailed mechanistic knowledge of how the barrier is formed during development or responds to pathological and pharmacological insults. This limits our understanding of barrier dysfunction in disease and slows the development of therapeutic strategies. Recent studies confirm the long‐maintained but previously unsupported view that the zonula occludens (ZO) proteins ZO‐1 and ZO‐2 are critical determinants of barrier formation. However, ZO proteins can also be components of adherens junctions, and recent studies suggest that ZO proteins may also promote the assembly and function of these junctions during epithelial morphogenesis. We review these studies and outline several recent observations that suggest that one role of ZO proteins is to regulate cytoskeletal dynamics at cell junctions. Finally, we propose a model by which the functional activities of ZO proteins in the adherens junction and tight junction are differentiated by a novel regulatory motif known as the U6 or acidic motif.
A New Insight into Pathophysiological Mechanisms of Zinc in Diarrhea
Authors: Hoque Kazi Mirajul , Sarker Rafiquel , Guggino Sandra E. , Tse Chung‐Ming
Published: May 2009

An increasing amount of data showing the beneficial use of zinc (Zn) in treating diarrhea continues to emerge from epidemiological and clinical trials. However, without a thorough understanding of physiological mechanisms of Zn, it does not support policy recommendation to advocate the therapeutic use of Zn. Our data demonstrate that Zn is a potential antidiarrheal agent that provides substantial benefit by stimulating sodium absorption and inhibiting chloride secretion in intestinal epithelial cells. Thus, inclusion of Zn in oral rehydration solution (ORS) has the potential to markedly augment the effectiveness of ORS in the treatment of diarrhea.
Q Fever in Dairy Animals
Authors: Rodolakis Annie
Published: May 2009

This review evaluates the threat to human health—with the shedding of C. burnetii in dairy animals with reproductive disorders or those without clinical signs. The review also discusses the diagnosis of Q fever in livestock and the possibility of Coxiella‐free herds, and it reports the available methods for controlling Q fever. C. burnetii shedding seems to occur frequently in milk taken from asymptomatic dairy cows. The number of Coxiella shed in milk is generally low. The phase I vaccine prevented abortion and greatly decreased the shedding of C. burnetii in milk.
Coxiella burnetii Glycomics and Proteomics—Tools for Linking Structure to Function
Authors: Toman Rudolf , Skultety Ludovit , Ihnatko Robert
Published: May 2009

Coxiella burnetii, the causative agent of Q fever, is an obligate intracellular bacterium and a highly infectious pathogen. The disease is a widespread zoonosis and is endemic throughout the world. An easy aerosol dissemination, environmental persistence, and high infectivity make the bacterium a serious threat for humans and animals. Lipopolysaccharide is considered one of the major factors of virulence expression and infection of the bacterium. Detailed glycomic studies enabled to better understand structural and functional peculiarities of this biopolymer and its role in pathogenesis and immunity of Q fever. Recent proteomic studies of C. burnetii have brought new approaches in accurate detection of the infectious agent and offered new insights into the inter‐ or intra‐species relatedness. Thus, structure/function relationship studies are currently of utmost importance in the field. This paper will focus on glycomic and proteomic approaches providing information on unique glycan and protein species of the microorganism as the candidate molecules for the use in detection/diagnosis, therapy, and prophylaxis.
Mitochondrial Porin VDAC 1 Seems to Be Functional in Rickettsial Cells
Authors: Emelyanov Victor V.
Published: May 2009

We have recently shown that Rickettsia prowazekii (typhus group rickettsiae) cells incorporate human mitochondrial porin VDAC1. Here, I report on the import of porin by rickettsiae of spotted fever group. It was shown that rickettsial cells of heavy band of Renografin density gradient, known as permeabilized rickettsiae, contain much more VDAC 1 compared to the cells of light band, that is, non‐permeabilized rickettsiae. These data hint at a functionality of mitochondrial porin in rickettsial cells. The cells of Rickettsia canadensis were broken in French‐press, and total membranes were fractionated on linear sucrose density gradient. In this way, previous data were confirmed that an outer rickettsial membrane does not contain porin, while fraction of intermediate density, which likely represents Bayer's adhesion zones, is enriched in VDAC 1. This is consistent with earlier results and their interpretation that imported porin seems to localize to contact sites between inner and outer rickettsial membranes. Based on well‐known phylogenetic relationship of Rickettsiales and mitochondria, an evolutionary scenario for the origin of protein import machinery is proposed. A dependence of rickettsiae upon essential protein(s), destined to organelle, is also viewed as a nature of their obligate endosymbiotic lifestyle.
Epidemiology and Clinical Aspects of Rickettsioses in Thailand
Authors: Suputtamongkol Y. , Suttinont C. , Niwatayakul K. , Hoontrakul S. , Limpaiboon R. , Chierakul W. , Losuwanaluk K. , Saisongkork W.
Published: May 2009

Scrub typhus and murine typhus are widespread in Thailand. Clinical manifestations of both diseases are nonspecific and vary widely. Acute undifferentiated fever (AUF), with or without organ dysfunction, is a major clinical presentation of these two diseases. The epidemiology and clinical manifestations including severe complications of scrub typhus and murine typhus in Thailand are summarized. Sixteen hundred and sixty‐three patients with AUF were studied in six hospitals in Thailand between 2000 and 2003. Scrub typhus and murine typhus were diagnosed in 16.1% and 1.7% of them, respectively. Clinical spectrum of murine typhus was similar to scrub typhus. Hepatic dysfunction and pulmonary involvement were common complications. Multi‐organ dysfunction mimicking sepsis syndrome occurred in 11.9% of patients with scrub typhus. The mortality of severe scrub typhus varied from 2.6% to 16.7%. Awareness that scrub typhus and murine typhus are prominent causes of AUF in adults in Thailand improves the probability of an accurate clinical diagnosis. Early recognition and appropriate treatment reduces morbidity and mortality. Results from recent clinical studies from Thailand indicated that rational antimicrobial therapy would be doxycycline in mild cases and a combination of either cefotaxime or ceftriaxone and doxycycline in severe cases. Azithromycin could be considered as an alternative treatment when doxycycline allergy is suspected. This would be either curative, or have no ill effect, in the majority of instances. Failure to improve or defervesce within 48 hours would indicate the need to perform a thorough re‐evaluation of clinical findings and initial laboratory investigation results, as well as a need to change antibiotic.
Ecology of Rickettsia in South America
Authors: Labruna Marcelo B.
Published: May 2009

Until the year 2000, only three Rickettsia species were known in South America: (i) Rickettsia rickettsii, transmitted by the ticks Amblyomma cajennense, and Amblyomma aureolatum, reported in Colombia, Argentina, and Brazil, where it is the etiological agent of Rocky Mountain spotted fever; (ii) Rickettsia prowazekii, transmitted by body lice and causing epidemic typhus in highland areas, mainly in Peru; (iii) Rickettsia typhi, transmitted by fleas and causing endemic typhus in many countries. During this new century, at least seven other rickettsiae were reported in South America: Rickettsia felis infecting fleas and the tick‐associated agents Rickettsia parkeri, Rickettsia massiliae, Candidatus“Rickettsia amblyommii,”Rickettsia bellii, Rickettsia rhipicephali, and Candidatus“Rickettsia andeanae.” Among these other rickettsiae, only R. felis, R. parkeri, and R. massiliae are currently recognized as human pathogens. R. rickettsii is a rare agent in nature, infecting ≤1% individuals in a few tick populations. Contrastingly, R. parkeri, Candidatus“R. amblyommii,” R. rhipicephali, and R. bellii are usually found infecting 10 to 100% individuals in different tick populations. Despite rickettsiae being transmitted transovarially through tick generations, low infection rates for R. rickettsii are possibly related to pathogenic effect of R. rickettsii for ticks, as shown for A. aureolatum under laboratory conditions. This scenario implies that R. rickettsii needs amplifier vertebrate hosts for its perpetuation in nature, in order to create new lines of infected ticks (horizontal transmission). In Brazil, capybaras and opossums are the most probable amplifier hosts for R. rickettsii, among A. cajennense ticks, and small rodents for A. aureolatum.
Advances in Rickettsia Pathogenicity
Authors: Balraj Premanand , Renesto Patricia , Raoult Didier
Published: May 2009

One century after the first description of rickettsiae as human pathogens, the rickettsiosis remained poorly understood diseases. These microorganisms are indeed characterized by a strictly intracellular location which has, for long, prohibited their detailed study. Within the last ten years, the completion of the genome sequences of several strains allowed gaining a better knowledge about the molecular mechanisms involved in rickettsia pathogenicity. Here, we summarized available data concerning the critical steps of rickettsia‐host cell interactions that should contribute to tissue injury and diseases, that is, adhesion, phagosomal escape, motility, and intracellular survival of the bacteria.
BartonellaEndocarditis
Authors: Chomel Bruno B. , Kasten R.W. , Williams C. , Wey A.C. , Henn J.B. , Maggi R. , Carrasco S. , Mazet J. , Boulouis H.J. , Maillard R. , Breitschwerdt E.B.
Published: May 2009

Bartonellae were first recognized to cause endocarditis in humans in 1993 when cases caused byBartonella quintana,B. elizabethae,andB. henselaewere reported. Since the first isolation ofBartonella vinsoniisubspeciesberkhoffiifrom a dog with endocarditis, this organism has emerged as an important pathogen in dogs and an emerging pathogen in people. Subsequently, four types ofB. vinsoniisubsp.berkhoffiihave been described, all of which have been associated with endocarditis in dogs. A limited number of dog endocarditis cases have also been associated withB. clarridgeiae,B. washoensis,B. quintana,andB. rochalimae. The second canineB. clarridgeiaeendocarditis case is presented. The clinical and pathological characteristics ofBartonellaendocarditis in dogs are similar to disease observed in humans, more often affecting the aortic valve, presenting with highly vegetative lesions with accompanying calcification, and in most instances high antibody titers. Pathological features in dogs include a combination of fibrosis, mineralization, endothelial proliferation, and neovascularization with variable inflammation. Endocarditis has also been described in animal species, which are the natural reservoir of specificBartonellaspecies, once thought to be solely healthy carriers of these pathogens. A fewBartonellaendocarditis cases, includingB. henselae, have been reported in cats in the USA and Australia. The second case ofB. henselaetype Houston I identified in the USA is presented. Furthermore, two cases ofB. bovisendocarditis were recently described in adult cows from France. Finally, on‐going investigation of valvular endocarditis in free‐ranging Alaskan sea otters suggests the involvement ofBartonellaspecies.
Rickettsioses in Australia
Authors: Graves Stephen , Stenos John
Published: May 2009

The rickettsial diseases of Australia are described in their chronological order of discovery. The include epidemic typhus (R. prowazekii); murine typhus (R. typhi) found Australia‐wide; scrub typhus (O. tsutsugamushi) only in tropical, northen Australia; Q. fever (C. burnetti) found Australia‐wide; Queensland tick typhus (R. australis) along the east coast of Australia; Flinders Island spotted fever (R. honei) in southeast Australia; Variant Flinders Island spotted fever (R. honei, strain “marmionii”) in eastern Australia; Rickettsia felis, Western Australia; eight new RFG rickettsiae from ticks (of unknown pathogenicity); and two nonhuman pathogens in A. platys (dogs) and A. marginale (cattle).