bluuebunny/crossref_metadata_2025 huggingface dataset:
Mycobacteriophage L5 infection of Mycobacterium bovis BCG: implications for phage genetics in the slow‐growing mycobacteria
Authors: Fullner Karla Jean , Hatfull Graham F.
Published: November 2003

Mycobacteriophage L5 is a well‐characterized temperate phage that forms stable lysogens in Mycobacterium smegmatis. The host range of L5 is, however, unclear because previous reports suggested that it does not infect slow‐growing mycobacteria such as Mycobacterium tuberculosis and bacille Calmette‐Guérin (BCG). Moreover, luciferase reporter phage derivatives of L5 failed to produce light from BCG, suggesting that infection is blocked at or before the stage of DNA injection. In this study, we demonstrate that L5 infection of slow growing mycobacteria specifically requires a high concentration of Ca2+, conditions that differs from those required for infection of M. smegmatis by L5 and for infection of BCG by the closely related phage D29. In addition, we show that there are specific genetic determinants of L5 that confer the ability to infect slow growing mycobacteria, without altering infection of M. smegmatis. These observations extend the use of phage L5 for the diagnosis and analysis of tuberculosis and other mycobacterial diseases.
Insertional mutagenesis of a peptide synthetase gene that is responsible for hepatotoxin production in the cyanobacterium Microcystis aeruginosa PCC 7806
Authors: Dittmann Elke , Neilan Brett A. , Erhard Marcel , Von Döhren Hans , Börner Thomas
Published: November 2003

Several bloom‐forming cyanobacterial genera produce potent inhibitors of eukaryotic protein phosphatases called microcystins. Microcystins are hepatotoxic cyclic heptapeptides and are presumed to be synthesized non‐ribosomally by peptide synthetases. We identified putative peptide synthetase genes in the microcystin‐producing strain Microcystis aeruginosa PCC 7806. Non‐hepatotoxic strains of M. aeruginosa lack these genes. Strain PCC 7806 was transformed to chloramphenicol resistance. The antibiotic resistance cassette insertionally inactivated a peptide synthetase gene of strain PCC 7806 as revealed by Southern hybridization and DNA amplification. This is the first report of genetic transformation and mutation, by homologous recombination, of a bloom‐forming cyanobacterium. Chemical and enzymatic analyses, including high‐performance liquid chromatography (HPLC), mass spectrometry, amino acid activation, and protein phosphatase inhibition, revealed the inability of derived mutant cells to produce any variant of microcystin while maintaining their ability to synthesize other small peptides. The disrupted gene therefore encodes a peptide synthetase (microcystin synthetase) that is specifically involved in the biosynthesis of microcystins. Our results confirm that microcystins are synthesized non‐ribosomally and that a basic difference between toxic and non‐toxic strains of M. aeruginosa is the presence of one or more genes coding for microcystin synthetases.
The outer membrane component, YscC, of the Yop secretion machinery of Yersinia enterocolitica forms a ring‐shaped multimeric complex
Authors: Koster Margot , Bitter Wilbert , De Cock Hans , Allaoui Abdelmounaaıamp;;uml;m , Cornelis Guy R. , Tommassen Jan
Published: November 2003

The YscC protein of Yersinia enterocolitica is essential for the secretion of anti‐host factors, called Yops, into the extracellular environment. It belongs to a family of outer membrane proteins, collectively designated secretins, that participate in a variety of transport processes. YscC has been shown to exist as a stable oligomeric complex in the outer membrane. The production of the YscC complex is regulated by temperature and is reduced in strains carrying mutations in the yscN‐U operon or in the virG gene. The VirG lipoprotein was shown to be required for efficient targeting of the complex to the outer membrane. Electron microscopy revealed that purified YscC complexes form ring‐shaped structures of ≈20 nm with an apparent central pore. Because of the architecture of the multimer, YscC appears to represent a novel type of channel‐forming proteins in the bacterial outer membrane.
The control of morphogenesis in Saccharomyces cerevisiae by Elm1 kinase is responsive to RAS/cAMP pathway activity and tryptophan availability
Authors: Garrett Jinnie M.
Published: November 2003

Many fungi undergo a morphological transition to filamentous growth in response to limiting nutrient conditions. Constitutively elongated Saccharomyces cerevisiae mutants (elm) have been isolated; the ELM1 gene encodes a putative serine/threonine protein kinase. A novel allele, elm1‐15, has been isolated in an S288C‐derived strain, which causes a pleiotropic phenotype, including media‐specific growth effects, abnormal morphology and altered stress response, in cells that are auxotrophic for tryptophan. elm1‐15 trp1 cells cannot use many nitrogen sources, are sensitive to amino acid analogues, have very low general amino acid permease activity and do not accumulate trehalose. In contrast, haploid elm1‐15 TRP1 cells grow well in budding form on all media, are stress resistant and overaccumulate trehalose. Several lines of evidence suggest that Elm1 acts on functions related to the RAS/cAMP pathway. Overexpression of Elm1 partially rescues the ts phenotype of cdc25 and cyr1 mutants. Deletion of ELM1 in low PKA activity mutants increased the severity of their phenotypes, and activation of Ras2 decreases the cell elongation phenotype of elm1 mutants. A ‘signal integration’ model for the complex relationship of Elm1 and the RAS/cAMP pathway in controlling morphogenesis in response to nutrients is proposed.
Requirement of topoisomerase IV parC and parE genes for cell cycle progression and developmental regulation in Caulobacter crescentus
Authors: Ward Doyle , Newton Austin
Published: November 2003

We have identified the parC and parE genes encoding DNA topoisomerase IV (Topo IV) in Caulobacter crescentus. We have also characterized the effect of conditional Topo IV mutations on cell division and morphology. Topo IV mutants of C. crescentus are unlike mutants of Escherichia coli and S. typhimurium, which form long filamentous cells that are defective in nucleoid segregation and divide frequently to produce anucleate cells. Topo IV mutants of C. crescentus are highly pinched at multiple sites (cell separation phenotype) and they do not divide to produce cells lacking DNA. These results suggest unique regulatory mechanisms coupling nucleoid partitioning and cell division in this aquatic bacterium. In addition, distinctive nucleoid‐partitioning defects are not apparent in C. crescentus Topo IV mutants as they are in E. coli and S. typhimurium. However, abnormal nucleoid segregation in parE mutant cells could be demonstrated in a genetic background containing a conditional mutation in the C. crescentus ftsA gene, an early cell division gene that is epistatic to parE for cell division and growth. We discuss these results in connection with the possible roles of C. crescentus Topo IV in the regulation of cell division, chromosome partitioning, and late events in polar morphogenesis. Although the ParC and ParE subunits of Topo IV are very similar in sequence to the GyrA and GyrB subunits of DNA gyrase, we have used DNA sequence analysis to identify a highly conserved ‘GyrA box’ sequence that is unique to the GyrA proteins and may serve as a hallmark of the GyrA protein family.
Discrimination between structurally related ligands nitrate and nitrite controls autokinase activity of the NarX transmembrane signal transducer of Escherichia coli K‐12
Authors: Williams Stanly B. , Stewart Valley
Published: November 2003

Anaerobic respiratory gene expression in Escherichia coli is differentially controlled by nitrate and nitrite through dual interacting two‐component regulatory systems. The NarX sensor is one of two membrane‐spanning sensor kinases that control the phosphorylation state of two DNA‐binding response regulators. We have studied NarX autophosphorylation in crude membrane preparations from cells that overexpress NarX protein. The low basal autophosphorylation rate was stimulated about sixfold and threefold by nitrate and nitrite respectively. This demonstrates that nitrate and nitrite differentially activate NarX autokinase activity. We also isolated single‐residue substitutions in NarX that affect its ability to respond to or discriminate between nitrate and nitrite. Most of these substitutions affect residues within the conserved P‐box sequence in the periplasmic domain. We characterized several of the mutants in vivo, by monitoring ligand‐regulated gene expression, and in vitro, by monitoring ligand‐responsive autophosphorylation. At least one change, K49I (Lys at position 49 changed to Ile), resulted in a protein with greatly impaired ability to discriminate between nitrate and nitrite. Other changes (H45E and R59K) resulted in proteins that responded normally to nitrate but were unable to respond to nitrite. These results implicate the P‐box region in discrimination between subtly different small molecules.
The poison–antidote stability system of the broad‐host‐range Thiobacillus ferrooxidans plasmid pTF‐FC2
Authors: Smith Anthony S. G. , Rawlings Douglas E.
Published: November 2003

In plasmid pTF‐FC2, three small open reading frames (ORFs) are situated between the repB (primase) gene and the repA (helicase) gene of its IncQ‐type replicon. Disruption of each of the three ORFs followed by tests for plasmid stability and host cell growth indicated that the ORFs encoded a poison–antidote plasmid stability system. The three genes were named pasA, pasB and pasC (plasmid addiction system), in which PasA is the antidote, PasB the toxin and PasC a protein that appears to enhance the ability of the antidote to neutralize the toxin. Disruption of the pasA gene resulted in two different spontaneous deletions, which inactivated the stability system but did not alter the host range or plasmid copy number. This indicated that the three small ORFs were not involved in plasmid replication. When placed behind a tac promoter, induction of pasB was found to be highly lethal to host cells, which suggests that the Pas system acts by killing plasmid‐free host cells rather than by retarding the growth of plasmid‐free segregants, as occurs in the ParD system of R1. In spite of this, the presence of the Pas poison–antidote system resulted in a relatively modest threefold stabilization of the pTF‐FC2 host replicon and a similar increase in the stabilization of an unstable heterologous R1 plasmid replicon. The Pas system is a poison–antidote plasmid stability module, which appears to have become integrated within the pTF‐FC2 replicon module.
The Escherichia coli genome sequence: the end of an era or the start of the FUN?
Authors: Hinton Jay C. D.
Published: November 2003

Our dream of determining the entire Escherichia coli K12 genome sequence has been realized. This calls for new approaches for the analysis of gene expression and function in biology's best‐understood organism. Comparison of the E. coli genome sequence with others will provide important taxonomic insights and have implications for the study of bacterial virulence. Approximately 20% of E. coli genes have been designated FUN genes, because they have no known function or homologies to sequence databases. FUN genes promise to have an exciting impact on bacterial research. The post‐genome era requires novel strategies that address gene regulation at the level of the entire cell. These strategies need to supersede the reductionist approach to genetic analysis. Only then will the genome sequence lead us to an understanding of how a bacterial cell really works.
Expression of gpsA encoding biosynthetic sn‐glycerol 3‐phosphate dehydrogenase suppresses both the LB− phenotype of a secB null mutant and the cold‐sensitive phenotype of a secG null mutant
Authors: Shimizu Hisayo , Nishiyama Ken‐ichi , Tokuda Hajime
Published: November 2003

SecB maintains the structures of a subset of precursor proteins competent for translocation across the Escherichia coli cytoplasmic membrane. SecG, a membrane component of the translocation machinery, stimulates protein translocation by undergoing the cycle of membrane topology inversion. Null mutants of secB and secG are unable to form isolated colonies on rich medium and at low temperature respectively. A 3.2 kb DNA fragment carrying the secB–gpsA region on a multicopy plasmid was found to suppress the null mutation of either gene. However, subcloning of the DNA fragment revealed that secB is not involved in the suppression of either mutation. Instead, gpsA located downstream from the secB gene was found to be responsible for the suppression of both mutations. The activity of the gpsA‐encoded sn‐glycerol‐3‐phosphate dehydrogenase, which is involved in phospholipid synthesis, was significantly lower in the secB null mutant than in the wild type, presumably because of a polar effect. Suppression of the secB null mutation required the wild‐type level of GpsA activity. In contrast, overexpression of the enzyme was essential for suppression of the secG null mutation. Moreover, the gpsA‐dependent suppression of the secG null mutation occurred only on rich medium, i.e. not on minimal medium. These results indicate that the SecB function is dispensable even in rich medium, and further demonstrate that overexpression of enzymes involved in phospholipid synthesis partly compensates for the SecG function.
Characterization of hapR, a positive regulator of the Vibrio cholerae HA/protease gene hap, and its identification as a functional homologue of the Vibrio harveyi luxR gene
Authors: Jobling Michael G. , Holmes Randall K.
Published: November 2003

The Vibrio cholerae HA/protease gene (hap) promoter is inactive in Escherichia coli. We cloned and sequenced the 0.7 kb hap promoter fragment from strain 3083‐2 and showed that hap is located immediately 3′ of ompW, encoding a minor outer membrane protein. A clone from a genomic library of strain 3083‐2 was isolated, which was required for activation of the hap promoter in E. coli. Expression from the hap promoter only occurred late in the growth phase. A single complete open reading frame (ORF) designated HapR was identified on a 1.7 kb DNA fragment that was required for activation. Allelic replacements showed that hapR was also essential for hap expression in V. cholerae. In El Tor, but not in classical biotypes of V. cholerae, hapR mutations also produced a rugose colonial phenotype. HapR was shown to encode a 203‐amino‐acid polypeptide with 71% identity to LuxR of V. harveyi, an essential positive regulator of the lux operon that has no previously identified homologues. The amino‐terminal domain (residues 21–68) showed significant homology to the TetR family of helix–turn–helix DNA‐binding domains and was 95% identical to the same domain of LuxR. HapR and LuxR activated both the hap and the lux promoters at near wild‐type levels, despite only limited homology in the promoter sequences (46% identity with 12 gaps over 420 bp). DNA sequences and ORFs 5′ (but not 3′) of the hapR and luxR loci were homologous, suggesting a common origin for these loci, and hapR‐hybridizing sequences were found in other vibrios. We conclude that HapR is absolutely required for hap expression and that HapR and LuxR form a new family of transcriptional activator proteins.
The FliP and FliR proteins of Salmonella typhimurium, putative components of the type III flagellar export apparatus, are located in the flagellar basal body
Authors: Fan Fan , Ohnishi Kouhei , Francis Noreen R. , Macnab Robert M.
Published: November 2003

Most of the structural components of the flagellum of Salmonella typhimurium are exported through a flagellum‐specific pathway, which is a member of the family of type III secretory pathways. The export apparatus for this process is poorly understood. A previous study has shown that two proteins, about 23 and 26 kDa in size and of unknown genetic origin, are incorporated into the flagellar basal body at a very early stage of flagellar assembly. In the present study, we demonstrate that these basal body proteins are FliP (in its mature form after signal peptide cleavage) and FliR respectively. Both of these proteins have homologues in other type III secretion systems. By placing a FLAG epitope tag on FliR and the MS‐ring protein FliF and immunoblotting isolated hook basal body complexes with anti‐FLAG monoclonal antibody, we estimate (using the FLAG‐tagged FliF as an internal reference) that the stoichiometry of FliR is fewer than three copies per basal body. An independent estimate of stoichiometry was made using data from an earlier quantitative radiolabelling analysis, yielding values of around four or five subunits per basal body for FliP and around one subunit per basal body for FliR. Immunoelectron microscopy using anti‐FLAG antibody and gold–protein A suggests that FliR is located near the MS ring. We propose that the flagellar export apparatus contains FliP and FliR and that this apparatus is embedded in a patch of membrane in the central pore of the MS ring.
The Bacillus subtilis division protein DivIC is a highly abundant membrane‐bound protein that localizes to the division site
Authors: Katis V. L. , Harry E. J. , Wake R. G.
Published: November 2003

The Bacillus subtilis divIC gene is involved in the initiation of cell division. It encodes a 14.7 kDa protein, with a potential transmembrane region near the N‐terminus. In this paper, we show that DivIC is associated with the cell membrane and, in conjunction with previously published sequence data, conclude that it is oriented such that its small N‐terminus is within the cytoplasm and its larger C‐terminus is external to the cytoplasm. DivIC is shown to be a highly abundant division protein, present at approximately 50 000 molecules per cell. Using immunofluorescence microscopy, DivIC was seen to localize at the division site of rapidly dividing cells between well‐segregated nucleoids. Various DivIC immunostaining patterns were observed, and these correlated with different cell lengths, suggesting that the DivIC localization takes on various forms during the cell cycle. The DivIC immunolocalization patterns are very similar to those of another membrane‐bound B. subtilis division protein, DivIB.
Evidence for two chemosensory pathways in Rhodobacter sphaeroides
Authors: Hamblin Paul A. , Maguire Bruce A. , Grishanin Ruslan N. , Armitage Judith P.
Published: November 2003

In contrast to enteric bacteria, chemotaxis in Rhodobacter sphaeroides requires transport and partial metabolism of chemoattractants. Although a chemotaxis operon has been identified containing homologues of the enteric cheA, cheW, cheR genes and two homologues of the cheY gene, deletion of the entire chemotaxis operon had only minor effects on chemotactic behaviour under the conditions tested. Responses to sugars were enhanced in tethered cells but in all other chemotaxis assays behaviour of the operon deletion mutant was wild type. The mutant also showed wild‐type responses to weak organic acids such as acetate and propionate, the dominant chemoattractants for this organism, under all conditions. This is in direct contrast to the enterics in which CheA, CheW and CheY are absolutely essential for taxis to PTS sugars, oxygen and MCP‐dependent chemoeffectors. The operon deletion mutant was subjected to Tn5 transposon mutagenesis and new mutants selected using a chemotaxis and phototaxis screen. One mutant, JPA203, was non‐chemotactic on swarm plates and showed inverted responses when tethered or subjected to changes in light intensity. Characterization of the Tn5 insertion in JPA203 identified a second chemotaxis operon in R. sphaeroides that contains homologues of cheY, cheA and cheR, the first homologue of cheB and two homologues of cheW. The new genes were labelled orf10, cheYIII, cheAII, cheWII, cheWIII, cheRII, cheB and tlpC. When introduced into a wild‐type background, deletion of cheAII produced a chemotaxis minus phenotype in R. sphaeroides, suggesting that cheAII forms part of a dominant chemotactic pathway, whereas the earlier identified operon plays only a minor role under laboratory conditions. The data presented here support the existence of two chemosensory pathways in R. sphaeroides, a feature that so far is unique in bacterial chemotaxis.
ATP‐dependent ferric hydroxamate transport system in Escherichia coli: periplasmic FhuD interacts with a periplasmic and with a transmembrane/cytoplasmic region of the integral membrane protein FhuB, as revealed by competitive peptide mapping
Authors: Mademidis Athanasios , Killmann Helmut , Kraas Wolfgang , Flechsler Insa , Jung Günther , Braun Volkmar
Published: November 2003

The Escherichia coli iron transport system via ferrichrome belongs to the group of ATP‐dependent transporters that are widely distributed in prokaryotes and eukaryotes. Transport across the cytoplasmic membrane is mediated by three proteins: FhuD in the periplasm, FhuB in the cytoplasmic membrane and FhuC (ATPase) associated with the inside of the cytoplasmic membrane. Interaction of FhuD with FhuB was studied in vitro with biotinylated synthetic 10 residue and 20–24 residue peptides of FhuB by determining the activity of β‐galactosidase linked to the peptides via streptavidin. Peptides identical in sequence to only one of the four periplasmic loops (loop 2), predicted by a transmembrane model of FhuB, and peptides representing a transmembrane segment and part of the adjacent cytoplasmic loop 7 of FhuB bound to FhuD. Decapeptides were transferred into the periplasm of cells through a FhuA deletion derivative that forms permanently open channels three times as large as the porins in the outer membrane. FhuB peptides that bound to FhuD inhibited ferrichrome transport, while peptides that did not bind to FhuD did not affect transport. These data led us to propose that the periplasmic FhuD interacts with a transmembrane region and the cytoplasmic segment 7 of FhuB. The transmembrane region may be part of a pore through which a portion of FhuD inserts into the cytoplasmic membrane during transport. The cytoplasmic segment 7 of FhuB contains the conserved amino acid sequence EAA…G (in FhuB DTA…G) found in ABC transporters, which is predicted to interact with the cytoplasmic FhuC ATPase. Triggering of ATP hydrolysis by substrate‐loaded FhuD may occur by physical interaction between FhuD and FhuC, which bind close to each other on loop 7. Although FhuB consists of two homologous halves, FhuB(N) and FhuB(C), the sites identified for FhuD‐mediated ferrichrome transport are asymmetrically arranged.
Identification of amdX, a new Cys‐2–His‐2 (C2H2) zinc‐finger gene involved in the regulation of the amdS gene of Aspergillus nidulans
Authors: Murphy Rachael L. , Andrianopoulos Alex , Davis Meryl A. , Hynes Michael J.
Published: November 2003

The acetamidase‐encoding amdS gene of Aspergillus nidulans has been shown to be controlled by multiple regulatory genes. A new gene, amdX, involved in amdS regulation was identified during the characterization of a translocation affecting amdS control. The amdX gene is predicted to encode a 1150‐amino‐acid polypeptide which contains two Cys‐2–His‐2 (C2H2) zinc finger DNA‐binding motifs. Insertional inactivation of amdX and the phenotypes of transformants containing multiple copies of the amdX gene show that it is an activator of amdS expression. A fusion protein containing the AmdX zinc fingers was found to bind to sequences in the 5′ region of amdS which overlap binding sites for the CreA and AmdA regulatory proteins. Evidence is presented for AmdX acting at these sites in vivo.
Meal‐induced secretion of gastrointestinal regulatory peptides is not affected by sleep
Authors: SOFFER E. E. , ADRIAN T. E. , LAUNSPACH J. , ZIMMERMAN B.
Published: November 2003

The mechanisms responsible for the disruption of the migrating motor complex (MMC) by feeding are not fully understood. Sleep reduces the duration of the postprandial or fed pattern of motility in the intestine. This study was set out to determine if this effect is associated with sleep‐induced changes in the secretion of regulatory peptides in response to food. Methods: Duodenojejunal motility was studied in 15 healthy ambulant subjects for 2 consecutive days. On one day identical solid meals were consumed in the morning and late in the evening, the latter followed by sleep. On the other day, identical liquid meals were infused into the stomach and the duodenum in the morning and late in the evening, the latter after the onset of sleep. Plasma concentrations of gastrin, neuro­tensin, peptide YY (PYY), pancreatic polypeptide (PP), motilin and glucose were monitored before and after meals.

Sleep significantly shortened the duration of the fed pattern after the solid meal and even more so after the liquid meal. The plasma concentrations of all peptides, except motilin, increased significantly following each meal. Blood glucose levels rose after each meal, the changes being similar with all meals.

Food‐induced gastrointestinal regulatory peptides secretion and intestinal absorption of glucose are not affected by sleep. The vagal response to a meal, as indicated by PP release, is intact during sleep. The results support the importance of neural mechanisms in the modulation of the postprandial pattern of intestinal motility.
The effect of gravity on oesophageal peristalsis inhumans
Authors: Allen M. L. , Zamani S. , Dimarino, Jr A. J.
Published: November 2003

Many mammalian species including non‐human primates consume water in a body position not aided by gravity and it has been conjectured that oesophageal peristalsis overcomes gravity in humans. The purpose of this study was to determine the effects of gravity on oesophageal peristalsis in humans in response to water swallows. Six females (30–43 years old) and six males (27–46 years old) without oesophageal symptoms underwent oesophageal motility testing with intraluminal microtransducers placed 5, 7.5, 10 and 15 cm above the lower oesophageal sphincter. Subjects received ten 5 mL water swallows every 30 sec in the supine, standing, and head down (30 degrees) prone positions which were counterbalanced. Oesophageal contractile pressure (115, 98, 126 mmHg), duration (3.5, 3.0, 3.7 sec), onset velocity (4.7, 4.9, 4.7 cm sec−1), peak velocity (5.1, 4.8, 4.1 cm sec−1), average upstroke (dP/dT) (78, 75, 84 mmHg sec−1), or maximum upstroke (132, 120, 141 mmHg sec−1) were not significantly different among the head down prone, upright and supine positions, respectively. The frequency of abnormal contractile activity was statistically different among the positions. More abnormal contractions (i.e. simultaneous, retrograde, non‐transmitted) occurred in the upright position (26%) when compared to either the supine (12%, P = 0.005) or head down prone (13%, P = 0.013) positions. The oesophagus tends to function normally to water swallows when unassisted by gravity. Oesophageal peristaltic dysfunction to water swallows may be more pronounced when assisted by the force of gravity.
Difficult defaecation and/or faecal incontinence as a presenting feature of neurologic disorders in four patients
Authors: BARDOUX N. , LEROI A. M. , TOUCHAIS J.‐Y. , WEBER J. , DENIS P.
Published: November 2003

We report four cases of difficult defaecation and/or faecal incontinence revealing a neurologic disease. These anorectal symptoms were associated with urinary disorders, but urinary symptoms always appeared several years after anorectal complaints. Clinical neurologic examination immediately led us to suspect a neurologic aetiology in two patients with the following signs: perineal hypoesthesia, absence of vol­untary anal contraction and anal reflexes in one subject (final diagnosis: L1 neurinoma), and in the other a weakness in both thighs with absent tendon reflexes in the four limbs (final diagnosis: amiodarone neuropathy). In the two other patients with multiple cerebral infarction or multiple system atrophy, the neurologic aeti­ology was suspected on the absence of anal voluntary contraction contrasting with a normal perineal an­atomy, but the final diagnosis was made only two years later when orthostatic arterial hypotension occurred.
Colonic transit time in patients with myelomeningocele
Authors: Pigeon N. , Leroi A. M. , Devroede G. , Watier A. , Denis P. , Weber J. , Arhan P.
Published: November 2003

To evaluate colonic motility in patients with myelomeningocele, the transit time of radiopaque markers was studied in 22 patients with myelomeningocele and 22 age and sex matched controls. Mean colonic transit time was significantly longer in patients than in controls (103.2 ± 49 h versus 23.3 ± 13 h; P < 10−7). Thirteen of 22 patients with myelomeningocele were severely constipated. Six patients had constipation secondary to delayed colonic transit, particularly in the left colon, and seven had increased rectosigmoïd transit. The clinical questionnaire and particularly the frequency of bowel movements did not predict colonic transit. Among 13 patients with increased colonic transit, eight had more than five bowel movements per week and, thus, six of them did not use laxatives or enemas, despite the presence of faecal incontinence. There was no relationship between colonic transit time and the level of the spinal lesion or patient mobility in patients with myelomeningocele. Rectoanal dyssynergia was found in 14 of the 22 patients, but equally often in patients with delayed rectosigmoid transit (4/7) as in the other patients (10/15) (P = ns). Uninhibited detrusor contractions were observed more often in patients with increased colonic transit time than in others (8/12 versus 1/8, P = 0.05). In the absence of a correlation between colonic transit time, clinical symptoms, anorectal motility, level of spinal lesion, patient mobility, evaluation of colonic transit of radiopaque markers should be assessed routinely in all patients with myelomeningocele to plan the most appropriate treatment, mainly in case of unhibited detrusor contractions.
The cerebral response to electrical stimuli in the oesophagus is altered by increasing stimulus frequencies
Authors: Hollerbach S. , Kamath M. V. , Fitzpatrick D. , Shine G. , Fallen E. , Upton A. R. M. , Tougas G.
Published: November 2003

Recording of cerebral evoked responses (EP) allows the assessment of visceral afferent pathways and gut–brain communication, but the optimal stimulation parameters remain to be established. The present study determined the optimal stimulation frequency of electrical stimulation of the oesophagus to elicit EP responses. In 13 healthy male volunteers (24.1 ± 5.9 years), a 5 mm stainless‐steel electrode was placed in the distal oesophagus for electrical stimulation (ES). EP were recorded from 21 scalp electrodes placed according to the 10/20 International system. ES (15 mA, 200 μs) were delivered in repeated series of 24 stimuli. Stimulus frequency was randomly altered in different series using a pseudologarithmic range (0.1, 0.2, 0.3, 0.5, and 1 Hz). Two series of stimuli were applied using each stimulation frequency. Two‐dimensional topographic brain maps were created using interpolation techniques at each stimulation frequency. With increasing stimulus frequency, a significant and progressive decrease of EP amplitudes was observed between frequencies of 0.1 Hz and 1.0 Hz (P1/N2: 7.6 ± 1.2 vs 1.4 ± 0.3* μV, N2/P2: 17.2 ± 1.7 vs 4.6 ± 0.4* μV, P2/N3: 6.9 ± 0.7 vs 4.2 ± 0.5* μV; * = P < 0.05). In addition, there was a significant shortening of the mean peak latency of the intercalated P2 peak (P < 0.0005), with a similar trend for the P3 peak (P < 0.06), with increasing stimulus frequency from 0.1–1.0 Hz. Topographic brain maps localized the maximal early peaks (N1,P1,N2) in the paracentral cortical region (C3, Cz, C4), whereas the later peaks (P2 to P3) were symmetrically spread over the centro‐parietal and temporal regions (Cz, Pz, T5, T4). There was no difference in the cortical location of maximal EP amplitudes with increasing stimulus frequency. In conclusion, there is a clear relationship between stimulus frequency and amplitude of EP, suggesting rapid attenuation of the cerebral autonomic neural responses with increased electrical stimulation frequency. The effect of increased frequency on peak latencies suggests an alteration of stimulus processing in the thalamocortical region due to an altered perception of stimuli. Early EP peaks originate from basal structures of primarily the dominant hemisphere, while later peaks are localized in centroparietal cortical regions.
The effect of intravenous vasopressin on gastric myoelectrical activity in human subjects
Authors: Caras S. D. , Soykan I. , Beverly V. , Lin Z. , McCallum R. W.
Published: November 2003

Vasopressin's role in the sensation of nausea is incompletely understood. In this study, our goals were to investigate whether high intravenous vasopressin levels in normal subjects would induce nausea and vomiting and to determine the electrogastrographic (EGG) pattern which would develop at these concentrations. Methods: EGG recordings were made on five fasting healthy subjects (three females, mean age: 27 years). Vasopressin was infused (0.15 or 0.3 U kg−1 h−1) for 1 h after a 30‐min baseline recording. Serum vasopressin levels were measured every 15 min. Symptoms of nausea, cramping, retching, vomiting and bloating were graded from 0 to 5 (0 = none, 5 = most severe). Normal saline at the same rate was then infused for 1 h, with recording of symptoms and measuring blood levels of vasopressin as done previously. Results: EGG data showed a 43% reduction in the percentage of normal slow waves (96–53%) at a vasopressin rate of 0.3 U kg−1 h−1. A 29% reduction (88–59%) occurred at 0.15 U kg−1 h−1. The EGG dominant frequency decreased by 0.8 cpm (3.07–2.25) for the high dose, while only 0.2 cpm reduction (2.9–2.7) occurred at the lower dose. Bradygastria (< 2.4 cpm) rather than tachygastria (> 3.7 cpm) was the predominant abnormality with the high dose. Symptoms of nausea correlated with the infusion of vasopressin and significantly increased with the higher dose. Conclusions: (i) At supraphysiological vasopressin levels, nausea was present in 80% of subjects but there was no retching or vomiting, (ii) bradygastria was the predominant dysrhythmia at these high vasopressin concentrations, (iii) increasing vasopressin levels correlated symptomatically with increases in nausea.
Measurement of gastric emptying by intragastric gamma scintigraphy
Authors: Malbert C. H. , Mathis C. , Bobillier E. , Laplace J. P. , Horowitz M.
Published: November 2003

Gastric emptying is usually measured in animals and humans by dilution/sampling or external scintigraphy. These methods are either time consuming or require expensive equipment. The capacity of a miniature gamma counter positioned in the stomach to measure emptying of liquid and solid meals was evaluated. In eight conscious pigs fitted with gastric and duodenal cannulae, gastric emptying of saline (500 mL), dextrose (20%, 500 mL), porridge (300 g) and scrambled eggs (300 g), all labelled with 3.5 MBq 99mTc, was evaluated. When positioned in the antrum the probe was unable to quantify gastric emptying. In contrast, measurements of the fractional emptying of saline over 4‐min periods by the probe positioned in the corpus and quantification of radioactivity in the duodenal effluent correlated closely (r = 0.88, P < 0.05). Gastric emptying (50% emptying time) of saline and both solid meals measured by the probe was not significantly different from quantification of the duodenal effluent volume. No difference was observed also for the dextrose meal but only while gastric acid secretion was suppressed by omeprazole. We conclude that an intragastric gamma counter permits measurement of gastric emptying of homogeneous meals provided meal stimulation of gastric secretion was not extensive. This was possible probably by monitoring emptying from the proximal stomach.
Comparison of lower oesophageal sphincter pressure measurement using circumferential vs unidirectional transducers
Authors: Pursnani K. G. , Oeffner C. , Gideon R. M. , Castell D. O.
Published: November 2003

Average values from unidirectional (UND) transducers have traditionally been used in standard manometric evaluation of lower oesophageal sphincter pressures (LOSPs). A single circumferential (CMF) transducer has recently become popular. Our aim was to compare LOSP measurements made using the two techniques. Ten healthy volunteers were intubated with a Konigsberg manometry catheter containing five solid‐state transducers (four unidirectional at 90° angles radially and 2.5‐cm intervals and one circumferential, 3 cm distal). LOSP was measured using the station pull‐through technique in the supine and upright positions with Synectics Polygram software for computerized analysis. Mean UND pressures were plotted against CMF pressures and a linear regression and correlation analysis was performed. A similar analysis was done for LOS length. A significant difference (P < 0.01) was found between mean (±SE) supine and upright LOSPs for both mean UND (20.21 ± 1.36 vs 15.56 ± 1.28 mmHg) and CMF (20.41 ± 1.96 vs 16.17 ± 1.61 mmHg); however no difference was shown between supine and upright lengths. There was a high degree of correlation between LOSP (r = 0.83) and a weaker correlation (r = 0.65) between LOS lengths when measured by CMF and UND transducers. Conclusion: UND and CMF transducers provide identical measurements when evaluating the LOS.
Sodium azide induces relaxation of the canine gastric body by activating a guanylate cyclase‐dependent pathway
Authors: Sano I. , Mizumoto A. , Sakai T. , Tamura T. , Itoh Z.
Published: November 2003

In order to study the inhibitory mechanism by which sodium azide eliminates smooth muscle contraction in vivo and in vitro, gastrointestinal motility was monitored via chronically implanted force transducers in the stomach and duodenum of conscious dogs. Circular smooth muscle strips with myenteric plexus from the canine gastric body were used for in vitro measurement of isometric tension. In conscious dogs, sodium azide (50 μg kg−1, i.v.) abolished both the spontaneously occurring phase III contractions and postprandial motility. Exogenous motilin (100 ng kg−1)‐ and bethanechol (50 μg kg−1)‐induced contractions were also abolished by sodium azide. In vitro, sodium azide and electrical field stimulation (EFS) caused a concentration‐ or frequency‐dependent nonadrenergic noncholinergic relaxation in the gastric body strips. The relaxation induced by EFS, but not sodium azide, was abolished by tetrodotoxin. NG‐nitro‐l‐arginine and oxyhaemoglobin failed to attenuate the relaxant effect of sodium azide, but strongly inhibited EFS‐induced relaxation. Methylene blue inhibited both sodium azide‐ and EFS‐induced relaxation. cGMP concentrations in muscle strips were markedly increased by sodium azide. These findings indicate that sodium azide induces relaxation in the canine gastric body through a direct action on smooth muscle, by activating a guanylate cyclase‐dependent pathway; endogenous NO synthesis does not participate in this inhibitory mechanism.
Effect of 5‐hydroxytryptamine on gastrointestinal motility in conscious guinea‐pigs
Authors: Nakajima M. , Shiihara Y. , Shiba Y. , Sano I. , Sakai T. , Mizumoto A. , Itoh Z.
Published: November 2003

Many studies have suggested that 5‐hydroxytryptamine (5HT, serotonin) plays an important role in the control of gastrointestinal motility. However, most of these studies have been carried out on guinea‐pig ileum in vitro. Therefore, we investigated the mechanisms of action of 5HT on gastrointestinal motility in conscious guinea‐pigs.

In order to investigate the effects of 5HT on gastrointestinal motility, extraluminal force transducers were sutured onto the serosal surfaces of the gastric antrum, duodenum and ileum and 5HT was infused intravenously. One of three types of 5HT antagonist or atropine was given before a 5HT infusion of 3.0 μg kg−1 min−1 was started.

Regular cyclic patterns were observed from the gastric antrum to the ileum in both the fasted and fed states. 5HT increased the contraction amplitudes at all sites. 5HT‐induced contractions in the gastric antrum and duodenum were significantly inhibited by methysergide, ondansetron and atropine, but not by ketanserin. In the ileum, only atropine inhibited 5HT‐induced contractions.

These results suggest that 5HT increases the gastrointestinal contraction amplitude mainly via a cholinergic pathway. 5HT3 receptors and 5HT1‐like and/or 5HT2C receptors appear to be responsible for 5HT‐induced gastric antral and duodenal contractions, but 5HT receptors other than 5HT1‐like, 5HT2A, 5HT2C and 5HT3 receptors induce ileal contractions.
Calcitonin gene‐related peptide (CGRP), a potent regulator of biliary flow
Authors: Rasmussen T. N. , Harling H. , Rehfeld J. F. , Holst J. J.
Published: November 2003

This study was designed to investigate the effect of porcine calcitonin gene‐related peptide (CGRP) on the motility of the porcine biliary tract in vivo. We measured the pressure in the gallbladder and sphincter of Oddi and, in separate experiments, the biliary flow into the duodenum during local intra‐arterial infusions of CGRP. To determine if the observed effect could be caused by release of cholecystokinin (CCK), we measured the CCK release. The basal pressure in the sphincter of Oddi increased dose‐dependently from 5.9 ± 0.5 mmHg to 11.5 ± 2.1 mmHg and the motility index of phasic contractions (amplitude × frequency) from 47 ± 8 to 347 ± 64 mmHg s−1, at an infusion rate of 32.6 pmol kg−1 min−1. No effect was observed on the gallbladder pressure. CGRP at 6.5 pmol kg−1 min−1 significantly reduced the biliary flow into the duodenum to 47.7 ± 6% of the basal level. Atropine, injected intravenously, completely abolished the contractile effect of CGRP. CGRP had no effect on the release of CCK.

We conclude that CGRP increases biliary motility and hereby reduces bile flow, an effect which involves cholinergic but not cholecystokininergic mechanisms.
Physiological variations in blood glucose concentration affect oesophageal motility and sensation in normal subjects
Authors: BOECKXSTAENS G. E. , HOROWITZ M. , BERMINGHAM H. , HOLLOWAY R. H.
Published: November 2003

Background/aims: a marked elevation in the blood glucose concentration (≈ 15 mmol L−1) slows oesophageal peristalsis. Recent studies indicate that changes in blood glucose within the normal postprandial range affect gastric motility and emptying. The aim of this study was to investigate whether such alterations in blood glucose also affect oesophageal motility. Methods: in eight healthy subjects oesophageal motility and sensation to balloon distension were measured on two separate days while blood glucose concentrations were stabilized with an insulin‐glucose clamp at 4 mmol L−1 and 8 mmol L−1. Results: peristaltic velocity in the proximal oesophagus and over the oesophagus as a whole was faster at a plasma glucose concentration of 8 mmol L−1 compared with those at 4 mmol L−1 (proximal 3.3 ± 0.3 cm s−1 vs 2.6 ± 0.2 cm s−1, P < 0.05, total 3.1 ± 0.2 cm s−1 vs 2.7 ± 0.2 cm s−1, P < 0.005) but there were no differences in wave amplitude or duration, or basal lower oesophageal sphincter pressure (LOSP). The threshold for initial perception of oesophageal distension was lower at a plasma glucose of 8 mmol L−1 (2.9 ± 0.5 mL vs 4.9 ± 1.0 mL, P < 0.05). Conclusions: physiological variations in plasma glucose concentration influence oesophageal motility and sensation. These observations suggest that in order to minimize effects of varying plasma glucose levels on oesophageal motility, manometry should be performed under the same fasting or fed conditions when oesophageal motor function is evaluated.
Gastric secretion but not nitric oxide is involved in pentagastrin‐induced gastric relaxation in conscious dogs
Authors: Meulemans A. L. , Wellens A. L. Y. , Schuurkes J. A. J.
Published: November 2003

Gastrin delays gastric emptying of liquids probably by reducing gastric tone. The mechanism responsible for the relaxatory effect induced by pentagastrin was unknown. The aim of this study was to investigate the effects of pentagastrin and the underlying mechanisms responsible for these effects. Could nitric oxide (NO) be involved as a mediator? Gastric tone was monitored with a flaccid bag introduced into the stomach via a gastric cannula and connected to a barostat. A series of pressure–volume curves with a 30‐min interval were constructed by increasing intragastric pressure to a maximum of 14 mmHg (2‐mmHg steps).

Pentagastrin (4 μg kg−1 s.c.) facilitated the volume increases induced by isobaric gastric distension. This effect could be completely blocked by pretreatment with cimetidine (10 mg kg−1 s.c.) or by omeprazole (10 mg kg−1 p.o.). The effect induced by pentagastrin could be mimicked by histamine (0.16 mg kg−1 s.c.) and to a lesser extent by insulin (0.2 IU kg−1 i.v.). Cimetidine and omeprazole had no intrinsic effect on gastric tone. With an opened cannula, allowing the gastric secretions to leave the stomach, no increased gastric relaxation could be observed either in the presence of pentagastrin or in the presence of histamine or insulin.

Nitro‐l‐arginine (L‐NNA, 5 mg kg−1 i.v.) reduced the volume increases induced by distension. Unexpectedly, even in the presence of L‐NNA, pentagastrin remained effective.

In conclusion, pentagastrin induces a gastric relaxation via a mechanism which involves gastric secretion but not nitric oxide.
Recent history and status of the Mongolian gazelle in Inner Mongolia, China
Authors: Wang Xiaoming , Sheng Helin , Bi Junghui , Li Ming
Published: November 2003

In 1994 and 1995 the authors studied Mongolian gazelle Procapra gutturosa populations in Inner Mongolia, China, conducting interviews and making field observations in eight counties along the national boundary between Mongolia and China. Mongolian gazelle distribution was estimated to cover approximately 73, 152 sq km, which was only 25.2 per cent of that in 1950–70. The adult malefemale sex ratio was 1: 4, and the average herd size 923.3 individuals in November/December 1994 and 23.1 in March/April 1995. The gazelles regularly migrate from Mongolia into China from October onwards and return to Mongolia in late February. Hunting is a major threat to the survival of the species.
The decline and impending extinction of the South China tiger
Authors: Tilson Ronald , Traylor-Holzer Kathy , Jiang Qiu Ming
Published: November 2003

The South China tiger Panthera tigris amoyensis is the rarest of the five living tiger subspecies, the most critically threatened and the closest to extinction. No wild South China tigers have been seen by officials for 25 years and one was last brought into captivity 27 years ago. The 19 reserves listed by the Chinese Ministry of Forestry within the presumed range of the tiger are spatially fragmented and most are too small to support viable tiger populations. Over the last 40 years wild populations have declined from thousands to a scattered few. Despite its plight and occasional anecdotal reports of sightings by local people, no intensive field study has been conducted on this tiger subspecies and its habitat. The captive population of about 50 tigers, derived from six wild-caught founders, is genetically impoverished with low reproductive output. Given the size and fragmentation of potential tiger habitat, saving what remains of the captive population may be the only option left to prevent extinction of this tiger subspecies, and even this option is becoming increasingly less probable. This precarious dilemma demands that conservation priorities be re-evaluated and action taken immediately to decide if recovery of the wild population will be possible.