bluuebunny/crossref_metadata_2025_split huggingface dataset:
Retrotransposition of the Ll.LtrB group II intron proceeds predominantly via reverse splicing into DNA targets
Authors: Ichiyanagi Kenji , Beauregard Arthur , Lawrence Stacey , Smith Dorie , Cousineau Benoit , Belfort Marlene 
Published: March 2003

SummaryCatalytic group II introns are mobile retroelements that invade cognate intronless genes via retrohoming, where the introns reverse splice into double‐stranded DNA (dsDNA) targets. They can also retrotranspose to ectopic sites at low frequencies. Whereas our previous studies with a bacterial intron, Ll.LtrB, supported frequent use of RNA targets during retrotransposition, recent experiments with a retrotransposition indicator gene indicate that DNA, rather than RNA, is a prominent target, with both dsDNA and single‐stranded DNA (ssDNA) as possibilities. Thus retrotransposition occurs in both transcriptional sense and antisense orientations of target genes, and is largely independent of homologous DNA recombination and of the endonuclease function of the intron‐encoded protein, LtrA. Models based on both dsDNA and ssDNA targeting are presented. Interestingly, retrotransposition is biased toward the template for lagging‐strand DNA synthesis, which suggests the possibility of the replication folk as a source of ssDNA. Consistent with some use of ssDNA targets, many retrotransposition sites lack nucleotides critical for the unwinding of target duplex DNA. Moreover, in vitro the intron reverse spliced into ssDNA more efficiently than dsDNA substrates for some of the retrotransposition sites. Furthermore, many bacterial group II introns reside on the lagging‐strand template, hinting at a role for DNA replication in intron dispersal in nature.
Intracellular localization modulates targeting of ExoS, a type III cytotoxin, to eukaryotic signalling proteins
Authors: Pederson Kristin J. , Krall Rebecca , Riese Matthew J. , Barbieri Joseph T. 
Published: March 2003

SummaryExoS is a bifunctional type III cytotoxin produced by Pseudomonas aeruginosa. Residues 96–232 comprise the Rho GTPase activating protein (Rho GAP) domain, whereas residues 233–453 comprise the 14‐3‐3‐dependent ADP‐ribosyltransferase domain. Earlier studies showed that the N‐terminus targeted ExoS to intracellular membranes within eukaryotic cells. This N‐terminal targeting region is now characterized for cellular and biological contributions to intoxications by ExoS. An ExoS(1–107)–green fluorescent protein (GFP) fusion protein co‐localized with α‐mannosidase, which indicated that the fusion protein localized near the Golgi. Residues 51–72 of ExoS (termed the membrane localization domain, MLD) were necessary and sufficient for membrane localization within eukaryotic cells. Deletion of the MLD did not inhibit type III secretion of ExoS from P. aeruginosa or type III delivery of ExoS into eukaryotic cells. Type III‐delivered ExoS(ΔMLD) localized within the cytosol of eukaryotic cells, whereas type III‐delivered ExoS was membrane associated. Although type III‐delivered ExoS(ΔMLD) stimulated the reorganization of the actin cytoskeleton (a Rho GAP activity), it did not ADP‐ribosylate Ras. Type III‐delivered ExoS(ΔMLD) and ExoS showed similar capacities for eliciting a cytotoxic response in CHO cells, which uncoupled the ADP‐ribosylation of Ras from the cytotoxicity elicited by ExoS.
A role for division‐site‐selection protein MinD in regulation of internucleoid jumping of Soj (ParA) protein in Bacillus subtilis
Authors: Autret Sabine , Errington Jeffery 
Published: March 2003

SummaryThe Bacillus subtilis soj‐spo0J locus encodes two proteins belonging to a family of proteins (the ParAB proteins) with dual roles in plasmid or chromosome segregation and transcriptional regulation. Soj protein was previously shown to be capable of abrupt subcellular relocation. The movement was highly co‐operative and at any moment, most of the Soj in any cell formed a single large ‘patch’ covering all or part of one nucleoid. Movement, and co‐operativity, in the sense of formation of a single patch, was dependent on Spo0J. Movement, but not co‐operativity, was also shown to be dependent, directly or indirectly, on FtsZ protein. We now report that the ftsZ effect arises because jumping onto a nucleoid is promoted by proximity to a cell pole. Studies of other mutants affected in cell division suggest that the attraction to the cell pole is mediated by the division‐site‐selection protein, MinD (which localizes at the cell poles). It does not require MinC, the main effector of the division site selection system. A mutant form of Soj, putatively locked in the ATP form of the protein, interacts with the cell pole (dependent on MinD) but not with the nucleoid. These results identify a novel function for MinD and demonstrate an intriguing link between proteins involved in the cell division and chromosome segregation machineries.
AraC/XylS family members, HilD and HilC, directly activate virulence gene expression independently of HilA in Salmonella typhimurium
Authors: Akbar Samina , Schechter Lisa M. , Lostroh C. Phoebe , Lee Catherine A. 
Published: March 2003

Summary Salmonella typhimurium
is a Gram‐negative enteric pathogen that can infect intestinal epithelial cells and induce inflammation of the intestinal mucosa. These processes are mediated by a type III secretion system (TTSS), which is encoded on
Salmonella
pathogenicity island 1 (SPI1). Previous studies showed that four SPI1‐encoded transcriptional regulators, HilD, HilC, HilA and InvF, act in an ordered fashion to co‐ordinately activate expression of the SPI1 TTSS. HilD and HilC derepress
hilA
transcription. HilA activates
invF
as well as SPI1 genes that encode components of the TTS apparatus. InvF then activates genes that encode proteins secreted by the SPI1 TTS apparatus. In this scheme, HilD and HilC indirectly activate expression of the SPI1 TTS apparatus and its secreted substrates by affecting
hilA
expression. Here, we report that HilD and HilC can also activate expression of a subset of SPI1 genes independently of HilA. Our studies show that HilD and HilC activate transcription of
invF
from a promoter that is far upstream of its HilA‐dependent promoter. This activation is most probably through direct binding of HilD and HilC to sequences upstream and downstream of this alternative HilA‐independent promoter. We conclude that HilD and HilC have a second role in SPI1 gene regulation that is separate from their role in co‐ordinating expression of the SPI1 TTSS through
hilA .
SseA acts as the chaperone for the SseB component of the Salmonella Pathogenicity Island 2 translocon
Authors: Zurawski Daniel V. , Stein Murry A. 
Published: March 2003

SummaryThe Salmonella Pathogenicity Island 2 (SPI2) encodes a type III secretion system (TTSS) shown to be critical for adaptation to the intracellular environment within both phagocytic and epithelial cell types. Within SPI2, the Effector region encodes several exported proteins that comprise the SPI2 translocon (SseB, C, D). SseA is the first protein encoded within the Effector region but remains an unclassified factor that is essential for SPI2 function. In the present study, we determined that SseA shares several features with TTSS chaperones: it is small (12.5 kDa), located directly upstream of a TTSS export target (SseB), and contains an amphipathic, C‐terminal α‐helix. Construction and analysis of a ΔsseA mutant demonstrated that the total amount of SseB is significantly reduced and SPI2 export of SseB to the bacterial surface is prevented. SseB accumulation and export were restored when SseA was provided in trans. Loss of SseA does not cause a generalized defect in SPI2 secretory function as export of SseC, encoded downstream of SseB, still occurs in the ΔsseA strain. Quantitative PCR indicates that the loss of SseB in ΔsseA does not occur at the transcriptional level. Co‐purification studies demonstrate that SseA directly binds to SseB. Collectively, these results demonstrate that SseA functions as a TTSS chaperone for the SPI2 translocon component, SseB.
A hexA homologue from Photorhabdus regulates pathogenicity, symbiosis and phenotypic variation
Authors: Joyce Susan A. , Clarke David J. 
Published: March 2003

Summary Photorhabdus
is a genus of entomopathogenic Gram‐negative bacteria that belong to the family Enterobactericeae. Remarkably, at the same time as being pathogenic to insect larvae,
Photorhabdus
also have a mutualistic relationship with entomophagous nematodes of the family Heterorhabditiae.
Photorhabdus
can be isolated in two phenotypically distinct forms, termed the primary and secondary variant. Both variants grow equally well and are equally virulent when injected into insect larvae. However, only the primary variant can colonize the intestinal tract of the IJ stage of the nematode and support nematode growth and development. The primary variant expresses several phenotypes that are absent from the secondary variant, including the production of extracellular enzymes, pigments, antibiotics and light. In this study, we use
Photorhabdus temperata
strain K122 to show that these primary‐specific products are symbiosis factors, i.e. factors that are required for nematode growth and development. We also show that, in
P. temperata
K122, the production of these symbiosis factors is repressed in the secondary variant by the protein encoded by a gene with homology to
hexA
from
Erwinia
. Moreover, the derepression of the symbiosis factors in the secondary variant results in a significant attenuation of virulence to larvae of the greater wax moth,
Galleria mellonella . This suggests that, during a normal infection, pathogenicity and symbiosis must be temporally separated and that HexA is involved in the regulation of this pathogen–symbiont transition.
Streptococcus dysgalactiae‐derived mitogen (SDM), a novel bacterial superantigen: characterization of its biological activity and predicted tertiary structure
Authors: Miyoshi‐Akiyama Tohru , Zhao Jizi , Kato Hidehito , Kikuchi Ken , Totsuka Kyoichi , Kataoka Yasushi , Katsumi Masanori , Uchiyama Takehiko 
Published: March 2003

SummaryA mitogenic substance, designated Streptococcus dysgalactiae‐derived mitogen (SDM), was purified from S. dysgalactiae culture supernatant, and the gene encoding the mitogen was cloned. Both native and recombinant SDM expressed in Escherichia coli significantly activated human Vβ1+ and Vβ23+ T cells in association with major histocompatibility complex (MHC) class II molecules on accessory cells, indicating that SDM possesses superantigenic properties. The sdm gene consists of two segments encoding a signal peptide and a mature 25 kDa protein composed of 212 amino acids. Three of 34 S. dysgalactiae strains but none of 28 Streptococcus pyogenes strains examined carried sdm. Phylogenetic analysis indicated that SDM belongs to a family distinct from established bacterial superantigens. SDM showed around 30% homology with other superantigens at the amino acid sequence level. The tertiary structure of SDM was predicted by modelling onto streptococcal pyrogenic exotoxin C and streptococcal mitogenic exotoxin Z‐2, both of which share highly homologous structure‐determining regions. SDM showed overall structural similarity to both these superantigens. This is the first study to characterize fully a bacterial superantigen from S. dysgalactiae.
Serotonin stimulates migrating myoelectric complex via 5‐HT3‐receptors dependent on cholinergic pathways in rat small intestine
Authors: LÖRDAL  , HELLSTRÖM  
Published: March 2003

We have investigated the effect of 5‐hydroxytryptamine (5‐HT) and different 5‐HT‐receptor antagonists and atropine on the migrating myoelectric complex in the rat small intestine.Infusion of 5‐HT dose‐dependently shortened the interval between phase III of the migrating myoelectric complex (MMC). In untreated animals the interval in upper jejunum was 19.1 (16.0–22.1) min. At doses of 10 and 20 nmol kg–1 min–1, the interval decreased to 15.2 (12.0–18.4) and 10.2 (9.4–11.0) min, respectively. The 5‐HT3‐receptor antagonist ondansetron (0.5 mg kg–1) alone increased the MMC interval from 20.8 (15.1–26.5) to 33.9 (19.4–48.4) min. Neither methiothepin (0.5 mg kg–1) nor ketanserin (0.5 mg kg–1), selective for 5‐HT15‐HT2‐and 5‐HT2‐receptors, respectively, changed the MMC interval. The 5‐HT4‐receptor antagonist GR 113808 (0.5 mg kg–1) disrupted the MMC and induced irregular spiking activity.Ondansetron and atropine antagonized the 5‐HT‐induced shortening of the MMC interval. Neither methiothepin nor ketanserin affected the response to 5‐HT. GR 113808 did not block the response to 5‐HT in half of the animals; however, in the remaining ones MMC was disrupted and irregular spiking induced.In conclusion, these results show that 5‐HT dose‐dependently stimulates the cycling of the MMC in the small intestine via 5‐HT3‐receptors and a cholinergic final pathway. Our findings encourage further studies on the role of the 5‐HT3‐receptor in the control of gastrointestinal motility.
Rectal visceral sensitivity in healthy volunteers: influences of gender, age and methods
Authors: Sloots  , Felt‐Bersma  , Cuesta  , Meuwissen  
Published: March 2003

The barostat is a device that maintains a constant pressure within an air‐filled polyethylene bag by means of a feedback mechanism. The system measures variations in rectal tone by recording changes in the intrarectal pressure and volume. Different procedures, such as ramp distension or intermittent distension, are used to test visceral sensitivity and rectal wall compliance. It is not quite clear which method is preferable and how the barostat measurements compare with those of the conventional latex balloon. In 28 healthy volunteers (11 males, mean age 36, range 22–67 years) rectal distension was performed in two ways: 1  Pressure‐controlled distension, by both intermittent and ramp methods, with measurement on the Visual Analogue Scale (VAS, 0–5) at 8, 12, 16, 20, 24, 28, 32 and 36 mmHg. Hysteresis (comparing area under the curve during deflation and inflation with ramp pressure distension) and compliance were calculated. 2  Volume‐controlled distension, with registration of first sensation, urge to defecate and maximal tolerated distension. This procedure was compared to conventional water‐filled latex balloon distension.No differences were found between intermittent and ramp distension comparing VAS scores at the same pressures. Gender or age did not affect the VAS score. Males had larger volumes at the same pressures than females. Females had larger hysteresis than males. Older females had larger hysteresis than younger females. The pressure volume curves were S‐shaped. Compliance at maximal tolerated distension (V/p) and maximal dynamic compliance (ΔV/Δp) was higher in males than females. The polyethylene bag had higher MTV and MTP compared to the latex balloon. In conclusion, no differences were found in volumes, compliance or VAS between the intermittent and the ramp pressure‐controlled inflation, indicating potential for simplification of the procedure. Males had larger rectal volumes and compliances; females had more pronounced hysteresis. A systemic difference was found between distension with the water‐filled latex balloon and with the air‐filled polyethylene bag. This should be taken into account when interpreting results.
Lower oesophageal sphincter relaxation evoked by stimulation of the dorsal motor nucleus of the vagus in ferrets
Authors: Abrahams T. P. , Partosoedarso E. R. , Hornby P. J. 
Published: March 2003

Abstract

An understanding of the neural control of lower oesophageal sphincter (LOS) relaxation is clinically relevant because transient LOS relaxations (TLOSRs) are a mechanism of acid reflux into the oesophagus. Preganglionic motor neurones innervating the LOS are localized in the dorsal motor nucleus of the vagus (DMV). Based on a single study in cats, it is now widely accepted that these neurones are functionally organized into two separate populations, such that stimulation of the caudal and rostral DMV evokes LOS relaxation and contraction, respectively. Our goal was to map the functional LOS responses to chemical stimulation in the DMV and nucleus tractus solitarius (NTS) of ferrets, an animal model commonly used for conscious studies on TLOSRs, and to test whether DMV‐evoked LOS relaxation is mediated through hexamethonium‐sensitive vagal‐inhibitory pathways to the LOS. We used miniaturized manometry with Dentsleeve to monitor LOS and oesophageal pressures in decerebrate unanaesthetized ferrets. LOS relaxation was evoked readily in response to gastric insufflation, which shows that the vago–vagal reflex was intact in this preparation. Microinjections of l‐glutamate (12.5 nmol L−1in 25 nL) were made into the DMV from approximately − 1.5 to + 2.0 mm relative to the obex. Microinjections into the caudal (− 1.5 to + 0.0 mm behind obex) and intermediate (+ 0.1 to + 1.0 mm rostral to obex) DMV both significantly decreased LOS pressure, and complete LOS relaxation was noted in 28/32 and 11/18 cases, respectively. LOS relaxation responses to DMV microinjection were highly reproducible and abolished by bilateral vagotomy or hexamethonium (15 mg kg−1intravenously). A nitric oxide synthase inhibitor (l‐NAME 100 mg kg−1intramuscularly) significantly increased the time taken to reach the maximal response. Increases in LOS pressure (24 ± 4 mmHg; n = 3) were obtained only when stimulation sites were located equal to greater than 1.5 mm rostral to the obex. LOS relaxation (− 78 ± 10%; n = 6) was evoked by stimulation of the NTS but not immediately outside of the NTS (11 ± 27%; n = 5). We conclude that there is a very extensive population of ‘inhibitory’ motor neurones in the DMV that may account for the predominant vagal‐inhibitory tone in ferrets. As NTS stimulation evokes LOS relaxation and the predominant response to DMV stimulation is also LOS relaxation, this vago–vagal reflex may involve an excitatory interneurone between the NTS and DMV vagal inhibitory output.
Relationship between colonic motility and cholinergic mechanosensory afferent synaptic input to mouse superior mesenteric ganglion
Authors: Miller S. M. , Szurszewski J. H. 
Published: March 2003

Abstract
Abdominal prevertebral ganglion neurones receive excitatory synaptic input from intestinofugal neurones. To better understand the physiological significance of this input, we examined the relationship between synaptic input to mouse superior mesenteric ganglion (SMG) neurones and intracolonic pressure and volume changes that accompany spontaneous colonic contractions in vitro. Electrical activity was recorded intracellularly from SMG neurones in ganglia attached to a segment of distal colon. The majority of neurones examined received ongoing fast excitatory potentials (F‐EPSPs). F‐EPSP frequency increased when the colon was distended with fluid and during spontaneous increases in colonic volume that accompanied colonic relaxation. In contrast, F‐EPSP frequency in SMG neurones decreased when the colon emptied, and remained at a reduced frequency until the colon refilled and volume increased. Nicotinic blockade of the colon abolished spontaneous colonic contractions and reduced or abolished synaptic input to SMG neurones, suggesting that most of the synaptic input arose from second or higher order neurones. Retrograde labelling identified cell bodies of intestinofugal neurones in myenteric ganglia. Most had short, club‐like dendritic processes and appeared uni‐axonal. These results show that mechanosensory intestinofugal afferent nerves monitor intracolonic volume changes.
SCN5A is expressed in human jejunal circular smooth muscle cells
Authors: Ou Y. , Gibbons S. J. , Miller S. M. , Strege P. R. , Rich A. , Distad M. A. , Ackerman M. J. , Rae J. L. , Szurszewski J. H. , Farrugia G. 
Published: March 2003

Abstract
Tetrodotoxin‐resistant Na+currents are expressed in a variety of muscle cells including human jejunal circular smooth muscle (HJCSM) cells. The aim of this study was to determine the molecular identity of the pore‐forming α‐subunit of the HJCSM Na+channel. Degenerate primers identified a cDNA fragment of 1.5 kb with 99% nucleotide homology with human cardiac SCN5A. The identified clone was also amplified from single smooth muscle cells by reverse transcriptase–polymerase chain reaction (RT–PCR). Northern blot analysis showed expression of full‐length SCN5A. Laser capture microdissection was used to obtain highly purified populations of HJCSM cells. RT–PCR on the harvested cells showed that SCN5A was present in circular but not in longitudinal muscle. A similar result was obtained using a pan‐Na+channel antibody. The full‐length sequence for SCN5A was obtained by combining standard polymerase chain reaction with 5′ and 3′ rapid amplification of cDNA end techniques. The intestinal SCN5A was nearly identical to the cardiac SCN5A. The data indicate that SCN5A is more widely distributed than previously thought and encodes the pore‐forming α‐subunit of the tetrodotoxin‐resistant Na+current in HJCSM cells.
Model of rapid gastrointestinal transit in dogs: effects of muscarinic antagonists and a nitric oxide synthase inhibitor
Authors: Chiba T. , Bharucha A. E. , Thomforde G. M. , Kost L. J. , Phillips S. F. 
Published: March 2003

Abstract
Our aims were to establish a canine model of rapid gastrointestinal transit, and to test the effects of muscarinic receptor antagonists (atropine, pirenzepine, AF‐DX116, and darifenacin), and an NOS inhibitor, l‐nitro‐N‐arginine (l‐NNA) in this model. For gastric emptying and small bowel transit,99mTc‐labelled DTPA were added to a meal of skimmed milk (236 mL) that contained 2.4 g of magnesium hydroxide. Regional colonic transit was measured by111In‐labelled beads placed in a capsule that released isotope in the proximal colon. Scintiscans were taken at regular intervals and indices of transit were calculated. Drugs were administrated intravenously. Gastric emptying, small bowel and colonic transit were rapid. Atropine and darifenacin (a selective M3antagonist) delayed gastric emptying and colonic transit, the selective M1and M2muscarinic antagonists did not. The muscarinic blockers did not slow small bowel transit. l‐NNA delayed small bowel and colonic transit but did not slow gastric emptying. A model suitable for the preclinical study of antidiarrhoeals was established. M3receptors are important in the control of gastric emptying and colonic transit, and NOS inhibition slowed small bowel and colonic transit.
Intraduodenal capsaicin inhibits gastric migrating motor complex via an extrinsic neural reflex in conscious dogs
Authors: Shibata C. , Naito H. , Ueno T. , Jin X.‐L. , Funayama Y. , Fukushima K. , Matsuno S. , Sasaki I. 
Published: March 2003

Abstract
The aim was to study the effect of intraduodenal capsaicin on interdigestive gastric contractions. Mongrel dogs were equipped with strain‐gauge force transducers to measure gastroduodenal motility. The effects of intraduodenal capsaicin with or without pharmacological antagonists on spontaneous and motilin‐induced interdigestive gastric contractions and on plasma motilin were studied in dogs with intact stomachs. The effect of intraduodenal capsaicin on gastric contractions was also studied in vagally denervated gastric (Heidenhain) pouch and vagally innervated antral pouch. Intraduodenal capsaicin inhibited spontaneous and motilin‐induced gastric contractions. The spontaneous peak in plasma motilin was inhibited by intraduodenal capsaicin. The effect of intraduodenal capsaicin on motilin‐induced gastric contractions was not affected by blockade of nitric oxide synthase, or by β‐adrenoceptor antagonist. Administration of α‐adrenergic blocker inhibited basal interdigestive gastric motility. Intraduodenal capsaicin had no effect on contractions in the Heidenhain pouch but inhibited those in vagally innervated antral pouch. Duodenal afferent fibres stimulated by capsaicin inhibit gastric contractions via a nitric oxide‐independent extrinsic neural reflex.