bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experimental analysis of Helicobacter pylori transcriptional terminators suggests this microbe uses both intrinsic and factor‐dependent termination
Authors: Castillo Andrea R. , Arevalo Sonia S. , Woodruff Andrew J. , Ottemann Karen M. 
Published: August 2010

SummaryIn this study, we report experimental analysis of transcriptional terminators in the human pathogen Helicobacter pylori. Previous bioinformatics approaches came to differing conclusions regarding transcriptional termination in this bacterium. We used a reporter construct, the tnpR‐encoded resolvase, to assess terminators. In our first experiments, we found that a subset of previously predicted intrinsic terminators for H. pylori are functional. In our second experiments, we used an unbiased screen to identify putative terminators and then characterized 18 of these. We found that these putative terminators overlap genomic regions that are either intergenic or intragenic. Using reverse transcription PCR, we showed that an intergenic terminator and an intragenic antisense terminator function at their endogenous loci. Additionally, we found that putative terminators contain features of both intrinsic and Rho‐dependent termination, but that intrinsic terminators define the majority. We were unable to delete rho, however, in H. pylori, suggesting that it is essential and likely important. Finally, we carried out a mutational analysis of one of our randomly identified terminators that has both intrinsic and Rho‐dependent features, and found that they are both functional. In conclusion, we found that H. pylori possesses numerous Rho‐dependent and intrinsic terminators including some found in intragenic regions.
Multiple Ku orthologues mediate DNA non‐homologous end‐joining in the free‐living form and during chronic infection of Sinorhizobium meliloti
Authors: Kobayashi Hajime , Simmons Lyle A. , Yuan Daniel S. , Broughton William J. , Walker Graham C. 
Published: August 2010

SummaryThe bacterial non‐homologous end‐joining (NHEJ) apparatus is a two‐component system that uses Ku and LigD to repair DNA double‐strand breaks. Although the reaction mechanism has been extensively studied, much less is known about the physiological role of bacterial NHEJ. Recent studies suggest that NHEJ acts under conditions where DNA replication is reduced or absent (such as in a spore or stationary phase). Interestingly, genes encoding Ku and LigD have been identified in a wide range of bacteria that can chronically infect eukaryotic hosts. Strikingly, Sinohizobium meliloti, an intracellular symbiont of legume plants, carries four genes encoding Ku homologues (sku1 to sku4). Deletion analysis of the sku genes indicated that all Ku homologues are functional. One of these genes, sku2, is strongly expressed in free‐living cells, as well as in bacteroid cells residing inside of the host plant. To visualize the NHEJ apparatus in vivo, SKu2 protein was fused to yellow fluorescent protein (YFP). Ionizing radiation (IR) induced focus formation of SKu2‐YFP in free‐living cells in a dosage‐dependent manner. Moreover, SKu2‐YFP foci formed in response to IR in non‐dividing bacteroids, indicating that NHEJ system is functional even during the chronic infection phase of symbiosis.
Gac/Rsm signal transduction pathway of γ‐proteobacteria: from RNA recognition to regulation of social behaviour
Authors: Lapouge Karine , Schubert Mario , Allain Frédéric H.‐T. , Haas Dieter 
Published: August 2010

SummaryIn many γ‐proteobacteria, the conserved GacS/GacA (BarA/UvrY) two‐component system positively controls the expression of one to five genes specifying small RNAs (sRNAs) that are characterized by repeated unpaired GGA motifs but otherwise appear to belong to several independent families. The GGA motifs are essential for binding small, dimeric RNA‐binding proteins of a single conserved family designated RsmA (CsrA). These proteins, which also occur in bacterial species outside the γ‐proteobacteria, act as translational repressors of certain mRNAs when these contain an RsmA/CsrA binding site at or near the Shine‐Dalgarno sequence plus additional binding sites located in the 5′ untranslated leader mRNA. Recent structural data have established that the RsmA‐like protein RsmE of Pseudomonas fluorescens makes specific contacts with an RNA consensus sequence 5′‐A/UCANGGANGU/A‐3′ (where N is any nucleotide). Interaction with an RsmA/CsrA protein promotes the formation of a short stem supporting an ANGGAN loop. This conformation hinders access of 30S ribosomal subunits and hence translation initiation. The output of the Gac/Rsm cascade varies widely in different bacterial species and typically involves management of carbon storage and expression of virulence or biocontrol factors. Unidentified signal molecules co‐ordinate the activity of the Gac/Rsm cascade in a cell population density‐dependent manner.
Characterization of the metalloactivation domain of an arsenite/antimonite resistance pump
Authors: Ruan Xiang , Bhattacharjee Hiranmoy , Rosen Barry P. 
Published: August 2010

SummaryThe ArsAB extrusion pump encoded by the ars operon of Escherichia coli plasmid R773 confers resistance to the toxic trivalent metalloids arsenite [As(III)] and antimonite [Sb(III)]. The ArsA ATPase, the catalytic subunit of the pump, has two homologous halves, A1 and A2. At the interface of these two halves are two nucleotide‐binding domains and a metalloid‐binding domain. Cys‐113 and Cys‐422 have been shown to form a high‐affinity metalloid binding site. The crystal structure of ArsA shows two other bound metalloid atoms, one liganded to Cys‐172 and His‐453, and the other liganded to His‐148 and Ser‐420. The contribution of those putative metalloid sites was examined. There was little effect of mutagenesis of residues His‐148 and Ser‐420 on metalloid binding. However, a C172A ArsA mutant and C172A/H453A double mutant exhibited significantly decreased affinity for Sb(III). These results suggest first that there is only a single high‐affinity metalloid binding site in ArsA, and second that Cys‐172 controls the affinity of this site for metalloid and hence the efficiency of metalloactivation of the ArsAB efflux pump.
A mitochondrial topoisomerase IA essential for late theta structure resolution in African trypanosomes
Authors: Scocca Jane R. , Shapiro Theresa A. 
Published: August 2010

SummaryTrypanosomes and Leishmania, protozoans that cause major human diseases, have a topologically intricate mitochondrial DNA (kinetoplast or kDNA) in the form of a network of thousands of interlocked circles. This unusual system provides a useful reporter for studying topoisomerase functions in vivo. We now find that these organisms have three type IA topoisomerases, one of which is phylogenetically distinctive and which we designate topoisomerase IAmt. In Trypanosoma brucei topoisomerase IAmt immunolocalizes within the mitochondrion close to the kDNA disk in patterns that vary with the cell cycle. When expression of TOPIAmt is silenced by RNAi there is a striking accumulation of kDNA late theta structure replication intermediates, with subsequent loss of kDNA networks and halt in cell growth. This essential enzyme provides clear molecular evidence for the obligatory role of a type IA enzyme in the resolution of late theta structures in vivo. With no close orthologue in humans it also offers a target for the rational development of selectively toxic new antiprotozoal therapies.
UV‐inducible cellular aggregation of the hyperthermophilic archaeon Sulfolobus solfataricus is mediated by pili formation
Authors: Fröls Sabrina , Ajon Malgorzata , Wagner Michaela , Teichmann Daniela , Zolghadr Behnam , Folea Mihaela , Boekema Egbert J. , Driessen Arnold J. M. , Schleper Christa , Albers Sonja‐Verena 
Published: August 2010

SummaryThe hyperthermophilic archaeon Sulfolobus solfataricus has been shown to exhibit a complex transcriptional response to UV irradiation involving 55 genes. Among the strongest UV‐induced genes was a putative pili biogenesis operon encoding a potential secretion ATPase, two pre‐pilins, a putative transmembrane protein and a protein of unknown function. Electron microscopy and image reconstruction of UV‐treated cells showed straight pili with 10 nm in diameter, variable in length, not bundled or polarized and composed of three evenly spaced helices, thereby clearly being distinguishable from archaeal flagella. A deletion mutant of SSO0120, the central type II/IV secretion ATPase, did not produce pili. It could be complemented by reintroducing the gene on a plasmid vector. We have named the operon ups operon for UV‐inducible pili operon of Sulfolobus. Overexpression of the pre‐pilins, Ups‐A/B (SSO0117/0118) in Sulfolobus resulted in production of extremely long filaments. Pronounced cellular aggregation was observed and quantified upon UV treatment. This aggregation was a UV‐dose‐dependent, dynamic process, not inducible by other physical stressors (such as pH or temperature shift) but stimulated by chemically induced double‐strand breaks in DNA. We hypothesize that pili formation and subsequent cellular aggregation enhance DNA transfer among Sulfolobus cells to provide increased repair of damaged DNA via homologous recombination.
Introduction of conventional microbial flora to germfree rats increases the frequency of migrating myoelectric complexes
Authors: HUSEBYE E. , HELLSTRÖM P. M. , MIDTVEDT T. 
Published: August 2010

AbstractThe present study demonstrates a direct stimulating influence of the viable conventional microbial flora on fasting myoelectric activity of the small intestine. Ten germfree AGUS rats were operated upon within sterile stainless steel isolators. Three bipolar electrodes were implanted into the muscular wall of the proximal small intestine, and fasting myoelectric recordings were performed one week later. Subsequently, the rats were transferred to the external conventional environment, and caecel content from conventional AGUS rats was given perorally and rectally. One week later, when the intestinal tract was colonized, myoelectric recordings were repeated. The frequency of activity fronts in proximal jejunum increased after introduction of conventional intestinal microflora, reflected by a decrease of the interval between activity fronts from median 17.6 min (15.2–23.4 min) (10th and 90th percentiles) to 13.9 min (11.4–17.6 min) (P < 0.05). The duration of activity fronts in proximal jejunum decreased from 4.9 min (3.8–5.9 min) to 3.6 min (3.2–3.9 min), respectively (P < 0.05). The propagation velocity of activity fronts was not significantly different. Stimulation of the fasting motility in the small intestine by conventional microbial flora may reflect activation of a physiological defense response in the host, in order to restrict bacterial colonization and avoid bacterial overgrowth of the small intestine.
Cisapride does not modify equine gastrointestinal motility disrupted byE. coliendotoxin or prostaglandin E2
Authors: KING J. N. , GERRING E. L. 
Published: August 2010

AbstractCisapride, E.coli endotoxin and prostaglandin E2were administered intravenously to ponies in which strain gauges had been attached to the stomach and proximal jejunum in order to test if cisapride could modify motility patterns induced by endotoxin or PGE2‐ Endotoxin at a dose of 0.1 μg kg−1and PGE2at a dose of 10 μg kg−1produced decreases in gastric motility and jejunal phase‐II motility with short intervals between jejunal phase‐Ill‐activity fronts. Cisapride at a dose of 0.2 mg kg1increased gastric motility and jejunal phase‐II activity with increased intervals between jejunal phase‐III‐activity fronts when given alone, but did not modify the motor effects of endotoxin or PGE2. Cisapride may be ineffective in improving gastrointestinal motility in clinical cases of equine ileus caused by endotoxaemia.
Development and validation of microcomputer analysis of gastric and small‐bowel manometry
Authors: WALDRON B. , SMITH D. , STOREY B. E. , WHITE G. , CAMPBELL F. C. 
Published: August 2010

AbstractA novel microcomputer method for analysis of gastric and small‐bowel motility was developed for recognition and measurement of inter‐digestive migrating motor complexes (MMC) and associated features as well as fed‐state contraction characteristics. Facilities for removal of signal artefacts were also provided. This microcomputer method was validated against observer findings in 24‐h ambulatory gastric and small‐bowel motility studies of six volunteers. No significant differences were found between microcomputer and observer motility analysis relating to MMC number, MMC migration velocity, fed‐state contraction characteristics or artefact recognition. This method provides an accurate automated method for measurement of gastric and small‐bowel motor physiology.
The non‐specific induction of mastocytosis in rat intestinal muscle
Authors: VERMILLION D. L. , COLLINS S. M. 
Published: August 2010

AbstractWe examined the effects of bowel manipulation on mast‐cell number and function in the rat. Mast cells were assessed histologically and by their ability to induce muscle contraction. Anaesthesia or abdominal incision did not alter mast‐cell number. However, laparotomy plus brief exteriorization of jejunal segments significantly increased mast‐cell number. Applying saline to the serosal surface by swab or droplet application increased mast‐cell number 16‐ and 3‐fold, respectively. Saline swabbing of jejunal segments from rats previously infected with Trichinella significantly reduced mast‐cell number. Functional integrity of mast cells was illustrated by muscle contraction in vitro following compound 48/80 or antigen and inhibition of cromoglycate. Serosal application of compound 48/80 in vivo increased mast‐cell number. This increase in mast‐cell number by compound 48/80 or by saline was prevented by prior treatment with cromoglycate. These data suggest that mast‐cell degranulation underlies the manipulation‐induced mastocytosis in gut muscle.
Effect of calcium antagonists on acetylcholine‐induced contractions in longitudinal smooth muscle strips from sheep duodenum
Authors: de PEDRO M.J. , PLAZA M. A. , ARRUEBO M. P. , MURILLO M. D. 
Published: August 2010

AbstractThe effect of several calcium antagonists on acetylcholine‐induced contractions has been examined in longitudinal smooth muscle strips from sheep duodenum. Contractions induced by 10−5M acetylcholine were inhibited up to 65% in Ca2+‐free solution and were blocked in the absence of extracellular Ca2+plus 1 mM EGTA; 10 mM lanthanum reduced acetylcholine‐induced contractions by 97%: 105mverapamil and W−4mnifedipine reduced contractions by 58 and 42%, respectively, but sodium nitroprusside did not modify these responses: 10−4mtrifluoperazine inhibited acetylcholine‐induced responses by 75%: 10−2mcaffeine produced a contraction; 2 mmprocaine antagonized acetylcholine responses by 85%. We suggest that acetylcholine‐induced contractions were mediated by extracellular Ca2+that enters through a potential‐dependent Ca2+channel by intracellular Ca2+release, probably from sarcoplasmatic reticulum because procaine inhibits the response.
Effect of cholecystokinin octapeptide and somatostatin on the mechanical and electrical activity of the colon of conscious dogs
Authors: ATANASSOVA E. , BOCHEVA A. , MILENOV K. 
Published: August 2010

AbstractIntraluminal pressure and electrical activity of the colon of conscious dogs were recorded using silver bipolar electrodes and a pressure transducer. Two phases in the mechanogram of the transverse colon were observed: a quiescent phase (lack of contractions) lasting 12.05 ± 0.54 min and a contractile phase lasting 14.46 ± 0.88 min. The electrical activity was characterized by a quiescent phase (only slow waves in the electrogram) with a duration of 13.55 ± 1.73 min. Groups of spike potentials bursting in the rhythm of the slow waves appeared during the activity phase lasting 15.60 ± 2.02 min. Cholecystokinin octapeptide (CCK8) (10–20 ng/kg i.v.) significantly increased the duration of 1–3 active phases and shortened the duration of the quiescent phases. The percentage of slow waves with spike potentials during the active phase in the electro‐gram increased. Colonic contractions also increased, i.e. CCK8 evoked an enhanced motility of the colon. Somatostatin (1–2 μg/kg i.v.) increased by two to three times the duration of the quiescent phases. Atropine (50–100 μg/kg i.v.) or somatostatin (1–2 μg/kg i.v.) inhibited both the spontaneous and the CCK8‐induced colonic motility. It is suggested that the inhibitory effect of somatostatin on spontaneous and CCAV induced colonic activity in conscious dogs is mediated by a decrease in cholinergic neurotransmission.
Psyche, personality and gut functions
Authors: STACHER G. 
Published: August 2010

AbstractPsychological factors are widely held to be important for the orderly function of the gastrointestinal tract as well as for the development and course of disorders affecting the gut. Evidence supporting these assumptions is scarce, although it has become clear that intestinal functions are influenced by the state of central nervous activation, i.e. by satiation, relaxation and sleep as well as hunger, tension and rage. Freud assumed that the accumulation of an unabreacted quota of affect induced defence or repression and a conversion of emotion into bodily symptoms. Subsequently, disorders such as globus sensation, diffuse oesophageal spasm and ‘cardiospasm’ were viewed as conversion symptoms. Other concepts claimed an aetiological role of specific conflicts, certain affective states and ‘inappropriate perpetuations of organ reactions adaptive to, or protective against, some stress in human life’. However, these and other psychosomatic concepts could not be verified. Conversely, an illness exacerbation may precipitate a disruption in a patient's adjustment to his/her environment and interfere with his/her ability to fight the disease. Psychotherapeutic interventions may help patients to cope with their illness and its consequences and possibly alter the course of disease. Psychosocial factors may determine a patient's reactions to, and handling of, a disease and thus should not escape the physician's attention.
Identification of mechanisms for duodenal contraction induced by tachykinins in the rat
Authors: KIM Y. C. , HELLSTRÖM P. M. 
Published: August 2010

AbstractMechanisms for contractile effects of tachykinins on muscle strips of rat duodenum were studied using substance P (SP), neurokinin A (NKA), neurokinin B (NKB) and neuropeptide K (NPK), and the tachykinin analogues SP methyl ester (SPME), Nle10‐NKA(4–10) (NleNKA) and senktide (SENK) selective for neurokinin (NK)‐1, NK‐2 and NK‐3 receptors, respectively. NK receptors responsible for smooth muscle contraction were identified using selective ligands to protect NK receptors combined with inactivation of residual receptors with N‐ethylmaleimide. Tachykinins (10−9to 10−5M) caused dose‐related contractions of the muscle strips. The order of potency of native tachykinins was NKA > NKB > SP > NPK in circular, and NKB > NKA > NPK > SP in longitudinal muscle, whereas that of selective tachykinin analogues was SENK > NleNKA > SPME. NKA, NleNKA and SENK were equieffective as acetylcholine, whereas SP, SPME, NKB and NPK were less effective. Spantide decreased the sensitivity to all tachykinin analogues. Atropine reduced the sensitivity to SENK only, whereas hexamethonium reduced the sensitivity to SENK and SPME, but not to NleNKA. Selective receptor protection with SPME, NleNKA or SENK protected contractions induced by SPME, NleNKA and SENK, respectively. Responses to tachykinin analogues were reduced in Ca2+‐free medium. Thus, NKA is suggested to be the dominating tachykinin to stimulate contraction of the rat duodenum via NK receptors coupled to Ca2+‐dependent signal transduction pathways. Of the receptors available, the NK‐1 subtype involves a nicotinic transmission step, and the NK‐3 subtype also a muscarinic step, whereas the NK‐2 receptor subtype is not dependent on cholinergic mechanisms.
The relationship between gastric pH and the emptying of solid, semisolid and liquid meals
Authors: CLARK G. W. B. , JAMIESON I. R. , HINDER R. A. , POLISHUK P. V. , DEMEESTER T. R. , GUPTA N. , CHENG S.C. 
Published: August 2010

AbstractThe effect of three different meal constituents, solid, semisolid and liquid, on gastric pH, recorded in the proximal and distal stomach, was evaluated in a prospective study of 20 normal volunteers. The solid and liquid were ingested together as one meal and the semisolid as another. Simultaneous recordings of the rate of gastric emptying of the isotopically labelled meal constituents and the gastric pH were made. The rate of gastric emptying was more rapid for the liquid and semisolid constituents (t1/2= 35.6, range 9.8–103.3 min and 47.4, range 33.5–120 min, respectively) than for the solid meal constituent (t1/2= 72.0, range 45.0–103.8 min), P < 0.01. Both the combined meal of solid and liquid and the semisolid meal produced a higher pH response in the proximal stomach than in the distal stomach (5.2, range 2.4–6.1 vs 2.9, range 0.8–5.3 and 5.9, range 4.3–6.6 vs 4.3, range 1.1–5.9), P < 0.01. There were significant correlations between the rate of gastric emptying of all three meal constituents and the decline phase in the gastric pH recorded at both the proximal and distal probes, P < 0.01 (Pearson's correlation). The strongest correlations were found between the rate of gastric emptying and the gastric pH recorded in the proximal stomach. The decline phase of gastric pH followed the emptying of semisolid more closely than the emptying of either solid or liquid.
Loxiglumide abolishes the effects of intraduodenal oleic acid on gastric motility and emptying in the pig
Authors: ANVARI M. , MALBERT C.‐H. , HOROWITZ M. , JAMIESON G. G. 
Published: August 2010

AbstractThe role of cholecystokinin in mediating the effects of intraduodenal fat infusion on gastric motility and gastric emptying and the pattern of transpyloric flow was evaluated in conscious pigs. Concurrent measurements of antropyloroduodenal motility with an eight‐channel sleeve/sidehole catheter, transpyloric flow and gastric emptying after instillation of 1000 ml of saline into the stomach, were made during intraduodenal infusion of either normal saline or oleic acid at 5 ml min−1. Studies with intraduodenal oleic acid were performed with and without intravenous infusion of loxiglumide (30 mg kg−1intravenous bolus 15 min before intraduodenal oleic acid, followed by intravenous infusion of 10 mg kg−1h−1), Intraduodenal oleic acid was associated with stimulation of isolated pyloric pressure waves (P < 0.05), inhibition of antral pressure waves (P < 0.05), reduced pulsatile transpyloric flow (P < 0.05) and retardation of gastric emptying (P < 0.05). when compared to intraduodenal saline. Loxiglumide prevented retardation of gastric emptying by intraduodenal oleic acid (P < 0.05), and maintained it at values that were not significantly different from saline. After loxiglumide there were more antral pressure waves (P < 0.05) and less isolated pyloric pressure waves (P < 0.05) when compared to oleic acid.These results indicate that the effects of intraduodenal oleic acid on gastric and pyloric motility, and gastric emptying are largely mediated by CCK‐dependent mechanisms.