bluuebunny/crossref_metadata_2025_split huggingface dataset:
Expression, secretion and antigenic variation of bacterial S‐layer proteins
Authors: Boot Hein J. , Pouwels Peter H. 
Published: November 2003

Summary The function of the S‐layer, a regularly arranged structure on the outside of numerous bacteria, appears to be different for bacteria living in different environments. Almost no similarity exists between the primary sequences of S‐proteins, although their amino acid composition is comparable. S‐protein production is directed by single or multiple promoters in front of the S‐protein gene, yielding stable mRNAs. Most bacteria secrete S‐proteins via the general secretory pathway (GSP). Translocation of S‐protein across the outer membrane of Gram‐negative bacteria sometimes occurs by S‐protein‐specific branches of the GSP. O‐polysaccharide side‐chains of the lipopolysaccharide component of the cell wall of Gram‐negative bacteria appear to function as receptors for attachment of the S‐layer. Silent S‐protein genes have been found in Campylobacter fetus and Lactobacillus acidophilus. These silent genes are placed in the expression site in a fraction of the bacterial population via inversion of a chromosomal segment.
Different structures of selected and unselected araB‐lacZ fusions
Authors: Maenhaut‐Michel Genevieve , Blake Catherine E. , Leach David R. F. , Shapiro James A. 
Published: November 2003

SummaryFormation of araB‐lacZ coding‐sequence fusions is a key adaptive mutation system. Eighty‐four independent araB‐lacZ fusions were sequenced. All fusions carried rearranged MuR linker sequences between the araB and lacZ domains indicating that they arose from the standard intermediate of the well‐characterized Mu DNA rearrangement process, the strand transfer complex (STC). Five non‐standard araB‐lacZ fusions isolated after indirect sib selection had novel structures containing back‐to‐back inverted MuR linkers. The observation that different isolation procedures gave rise to standard and non‐standard fusions indicates that cellular physiology can influence late steps in the multi‐step biochemical sequence leading to araB‐lacZ fusions. Each araB‐lacZ fusion contained two novel DNA junctions. The MuR‐lacZ junctions showed‘hot‐spotting’according to established rules for Mu target selection. The araB‐MuR and MuR‐MuR junctions all involved exchanges at regions of short sequence homology. More extensive homology between MuR and araB sequences indicates potential STC isomerization into a resolvable four‐way structure analogous to a Holliday junction. These results highlight the molecular complexity of araB‐lacZ fusion formation, which may be thought of as a multi‐step cell biological process rather than a unitary biochemical reaction.
The Bacillus subtilis chromatin‐associated protein Hbsu is involved in DNA repair and recombination
Authors: Fernández Silvia , Rojo Fernando , Alonso Juan C. 
Published: November 2003

SummaryThe Bacillus subtilis hbs gene encodes an essential chromatin‐associated protein termed Hbsu. Hbsu, the counterpart of the Escherichia coli HU protein, binds DNA in a non‐specific way but has a clear preference for bent, kinked or altered DNA sequences. To investigate the role of Hbsu in DNA repair and DNA recombination we have constructed a series of site‐directed mutants in the hbs gene and used these mutant genes to substitute the wild‐type chromosomal hbs gene. The hbs47 mutation, which codes for a mutant protein in which residue Phe‐47 has been replaced by Trp, does not cause any discernible phenotype. Additional substitution of residue Arg‐55 by Ala (hbs4755 mutation) rendered cells deficient in DNA repair, homologous recombination and (i protein‐mediated site‐specific recombination. We have also tested the effect on DNA repair of the hbs4755 mutation in combination with mutations in different functions of homologous DNA recombination (recA, recF, recG, recti and addAB). The hbs4755 mutation did not modify the sensitivity of recH and addAB cells to the DNA‐damaging agents methylmethane sulphonate (MMS) or 4‐nitroquinoline‐1‐oxide (4NQO), and it only marginally affected recF and recG cells. The hbs4755 mutation blocked intermolecular recombination in recH cells and markedly reduced it (20‐ to 50‐fold) in recF and recG cells, but had no effect on addAB cells. Taken together, these data indicate that the Hbsu protein is required for DNA repair and for homologous DNA recombination.
Genetic evidence of separate repressor and activator activities of the XylR regulator of the TOL plasmid, pWWO, of Pseudomonas putida
Authors: Bertoni Giovanni , Perez‐Martfn Jose , de Lorenzo Victor 
Published: November 2003

SummaryThe XylR protein encoded by pWWO, the TOL (toluene biodegradation) plasmid of Pseudomonas putida, activates at a distance the transcription of Pu and Ps, which are the two σ54‐dependent promoters of the plasmid, but it also downregulates its own σ70‐promoter, Pr, which divergently overlaps the upstream activating sites of Ps. All regulatory elements that control Pr activity have been faithfully reproduced in Escherichia coli, and the basis of the autoregulation of XylR transcription has been examined by monitoring the activity in vivo of different combinations of mutant proteins and promoters in rpoN+ and rpoN‐ genetic backgrounds. By using PsIPr regions bearing deleted or offset binding sites for XylR and the σ54‐containing RNA polymerase, we could show that formation of a nucleoprotein complex involving the polymerase bound to the divergent promoter Ps is not required for downregulation of Pr. Mutant XylR proteins, G268N and A311V (mutated within the NTP‐binding region of XylR) or R453H (affected in multi‐merization), which are unable to activate (‐dependent transcription from Ps, were indistinguishable from the wild‐type XylR in their ability to repress a reporter Pr‐lacZ fusion. Autoregulation of XylR is therefore due exclusively to the binding of the protein to its target sites at the Pr promoter. This allows one to define sensu stricto XylR as a transcriptional repressor, independently of its activator role in other promoters.
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.
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.
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.
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.
Secondary Echinococcus multilocularis infection in A/J mice: delayed metacestode development is associated with Th1 cytokine production
Authors: EMERY ISABELLE , LIANCE MARTINE , LECLERC CLAUDE 
Published: November 2003

The course of Echinococcus multilocularis infection was studied in four different strains of mice after intrahepatic inoculation of a metacestode homogenate. Among these strains of mice, A/J and BALB/c mice were characterized, respectively, as the most resistant and susceptible strains. Although there was no significant difference between the mean surface of hepatic metacestodes of these two strains of mice at any examination time, 13 weeks after infection, the mean metastatic burden of A/J mice was significantly lower than that of BALB/c mice. Moreover, at this time, some BALB/c mice spontaneously died from their infection whereas all A/J mice remained in good health. The relative resistance of A/J mice to parasite development was associated with a strong and sustained in vitro spleen cell proliferative response to a crude E. multilocularis extract as well as with a high parasite‐induced production of IFN‐γ and IL‐2. The susceptibility of BALB/c mice was on the contrary associated with a high IL‐4 production. Interestingly, the parasite extract also stimulated a significant IL‐4 production by spleen cells of uninfected susceptible BALB/c mice, but not by control A/J mouse spleen cells. Altogether, these results suggest that the relative resistance of A/J mice to E. multilocularis growth is associated with the development of T cell responses characterized by the production of high levels of Th1 cytokines.
Will elevated CO2 concentrations protect the yield of wheat from O3 damage?
Authors: MCKEE I. F. , BULLIMORE J. F. , LONG S. P. 
Published: November 2003

ABSTRACTThis study investigated the interacting effects of carbon dioxide and ozone concentrations on the growth and yield of spring whet (Triticum aestivum L. cv. Wembley). Plants were exposed from time of sowing to harvest to reciprocal combinations of two carbon dioxide and two ozone treatments: [CO2] at 350 or 700 μmol mol−1, and [O3] at < 5 or 60 nmol mol−1. Records of leaf emergence, leaf duration and tillering were taken throughout leaf development. At harvest, biomass, yield and partitioning were analysed. Our data showed that elevated [CO2] fully protected against the detrimental effect of elevated [O3] on biomass, but not yield.
Effects of elevated CO2 and temperature on photosynthesis and Rubisco in rice and soybean
Authors: VU J. C. V. , ALLEN L. H. , BOOTE K. J. , BOWES G. 
Published: November 2003

ABSTRACTRice (Oryza sativa L. cv. IR‐72) and soybean (Glycine max L. Merr. cv. Bragg), which have been reported to differ in acclimation to elevated CO2, were grown for a season in sunlight at ambient and twice‐ambient [CO2], and under daytime temperature regimes ranging from 28 to 40°C. The objectives of the study were to test whether CO2 enrichment could compensate for adverse effects of high growth temperatures on photosynthesis, and whether these two C3 species differed in this regard. Leaf photosynthetic assimilation rates (A) of both species, when measured at the growth [CO2], were increased by CO2 enrichment, but decreased by supraoptimal temperatures. However, CO2 enrichment more than compensated for the temperature‐induced decline in A. For soybean, this CO2 enhancement of A increased in a linear manner by 32–95% with increasing growth temperatures from 28 to 40°C, whereas with rice the degree of enhancement was relatively constant at about 60%, from 32 to 38°C. Both elevated CO2 and temperature exerted coarse control on the Rubisco protein content, but the two species differed in the degree of responsiveness. CO2 enrichment and high growth temperatures reduced the Rubisco content of rice by 22 and 23%, respectively, but only by 8 and 17% for soybean. The maximum degree of Rubisco down‐regulation appeared to be limited, as in rice the substantial individual effects of these two variables, when combined, were less than additive. Fine control of Rubisco activation was also influenced by both elevated [CO2] and temperature. In rice, total activity and activation were reduced, but in soybean only activation was lowered. The apparent catalytic turnover rate (Kcat) of rice Rubisco was unaffected by these variables, but in soybean elevated [CO2] and temperature increased the apparent Kcat by 8 and 22%, respectively. Post‐sunset declines in Rubisco activities were accelerated by elevated [CO2] in rice, but by high temperature in soybean, suggesting that [CO2] and growth temperature influenced the metabolism of 2‐carboxyarabinitol‐1‐phosphate, and that the effects might be species‐specific. The greater capacity of soybean for CO2 enhancement of A at supraoptimal temperatures was probably not due to changes in stomatal conductance, but may be partially attributed to less down‐regulation of Rubisco by elevated [CO2] in soybean than in rice. However, unidentified species differences in the temperature optimum for photosynthesis also appeared to be important. The responses of photosynthesis and Rubisco in rice and soybean suggest that among C3 plants species‐specific differences will be encountered as a result of future increases in global [CO2] and air temperatures.
The shade avoidance syndrome: multiple responses mediated by multiple phytochromes
Authors: SMITH H. , WHITELAM G. C. 
Published: November 2003

ABSTRACTIn recent years, the concept of shade avoidance has provided a functional meaning to the role of the phytochrome photoreceptor family in mature plants in their natural environment, and the question of which of these phytochromes is responsible for shade avoidance reactions has inevitably been raised. Unfortunately, a misconception has arisen that phytochrome B is solely responsible for detecting the environmental signal that initiates the shade avoidance syndrome. This view is too simplistic, and is based upon a selective interpretation of the available evidence. In this short Commentary, we review the concept of the shade avoidance syndrome, show how the misconception arose, and emphasize the plurality of perception and response that is crucial to successful competition for light.
UV and blue light signal transduction in Arabidopsis
Authors: JENKINS G. I. 
Published: November 2003

ABSTRACTThe application of genetic and biochemical approaches in Arabidopsis has generated new insights into the photoreceptors and signal transduction processes that mediate the effects of UV and blue light on gene expression and development. Biochemical studies with an Arabidopsis cell culture have provided information on the signal transduction events that couple UV‐B and UV‐A/blue light perception to transcription of the chalcone synthase (CHS) gene. Interactions between UV‐B and both UV‐A and blue light signalling pathways enhance the level of CHS transcription. Mutants which identify negative regulators of CHS transcription in response to UV and blue light have been isolated. The integration of biochemical and genetic approaches will further advance understanding of UV and blue light perception and signal transduction.
Fundamental and biotechnological applications of phytochrome transgenes
Authors: ROBSON P. R. H. , SMITH H. 
Published: November 2003

ABSTRACTIndividual phytochrome genes share regions of high homology which have facilitated the isolation of many phytochrome sequences from both higher and lower plants. Transgenes have been used to study the transcriptional control of phytochrome gene expression, and to create phytochrome‐deficient lines in polyploid species. Transgenically produced phytochrome apoproteins assemble with endogenous chromophore to become photoactive, and in most cases confer predictable light responses on the transgenic plants. The biological activity of transgenically produced phytochromes has been used to investigate the functions of domains within the phytochrome molecule. Physiological analysis of plants expressing phytochrome transgenes has revealed the potential of transgenic approaches to modifying the architecture of crop plants. Tobacco plants expressing to moderate levels an oat PHYA transgene exhibit proximity‐conditional dwarfing which leads to up to 20% improvement in harvest index in the field. These results provide prospects for a new genetic engineering approach to crop plant improvement.
Stomatal responses to jasmonic acid, linolenic acid and abscisic acid in wild‐type and ABA‐deficient tomato plants
Authors: HERDE O. , PEÑA‐CORTÉS H. , WILLMITZER L. , FISAHN J. 
Published: November 2003

ABSTRACTWild‐type and abscisic acid (ABA) ‐deficient (sitiens) tomato plants were used to analyse the effects of abscisic acid (ABA), butyric acid (BA), jasmonic acid (JA) and linolenic acid (LA) on assimilation and transpiration rates in detached leaves taking up those substances into the transpiration stream. BA did not affect assimilation and transpiration rates. ABA decreased assimilation and transpiration in both wild‐type and ABA‐deficient mutants. JA reduced the assimilation rate in both lines but induced a significant reduction of transpiration in the wild type only. The response to LA in both lines was slower than that to JA.
Photomorphogenesis and phyfohormones
Authors: KRAEPIEL Y. , MIGINIAC E. 
Published: November 2003

ABSTRACTThere are numerous reports of interactions between light and phytohormones. However, the exact nature of this interaction is not well understood. This article considers the possible roles played in the light signal transduction chain by four phytohormones (auxin, abscisic acid, gibberellins and cytokinins). As the involvement of phytohormones in this signalling mechanism is controversial, the major arguments in the debate are reported, including recently published results based on genetic, biochemical and physiological approaches.