bluuebunny/crossref_metadata_2025 huggingface dataset:
Linker histone H1 represses recombination at the ribosomal DNA locus in the budding yeast Saccharomyces cerevisiae
Authors: Li Chonghua , Mueller John E. , Elfline Megan , Bryk Mary
Published: August 2010

Several epigenetic phenomena occur at ribosomal DNA loci in eukaryotic cells, including the silencing of Pol I and Pol II transcribed genes, silencing of replication origins and repression of recombination. In Saccharomyces cerevisiae, studies focusing on the silencing of Pol II transcription and genetic recombination at the ribosomal DNA locus (rDNA) have provided insight into the mechanisms through which chromatin and chromatin‐associated factors regulate gene expression and chromosome stability. The core histones, H2A, H2B, H3 and H4, the fundamental building blocks of chromatin, have been shown to regulate silent chromatin at the rDNA; however, the function of the linker histone H1 has not been well characterized. Here, we show that S. cerevisiae histone H1 represses recombination at the rDNA without affecting Pol II gene silencing. The most highly studied repressor of recombination at the rDNA is the Silent information regulator protein Sir2. We find that cells lacking histone H1 do not exhibit a premature‐ageing phenotype nor do they accumulate the rDNA recombination intermediates and products that are found in cells lacking Sir2. These results suggest that histone H1 represses recombination at the rDNA by a mechanism that is independent of the recombination pathways regulated by Sir2.
Pseudomonas aeruginosa biofilm matrix polysaccharide Psl is regulated transcriptionally by RpoS and post‐transcriptionally by RsmA
Authors: Irie Yasuhiko , Starkey Melissa , Edwards Adrianne N. , Wozniak Daniel J. , Romeo Tony , Parsek Matthew R.
Published: August 2010

Extracellular polysaccharides are important components of biofilms. In non‐mucoid Pseudomonas aeruginosa strains, the Pel and Psl polysaccharides are major structural components of the biofilm matrix. In this study, we demonstrate that the alternative σ‐factor RpoS is a positive transcriptional regulator of psl gene expression. Furthermore, we show that psl mRNA has an extensive 5′ untranslated region, to which the post‐transcriptional regulator RsmA binds and represses psl translation. Our observations suggest that upon binding RsmA, the region spanning the ribosome binding site of psl mRNA folds into a secondary stem‐loop structure that blocks the Shine–Dalgarno sequence, preventing ribosome access and protein translation. This constitutes a novel mechanism for translational repression by this family of regulators.
A structural model of anti‐anti‐σ inhibition by a two‐component receiver domain: the PhyR stress response regulator
Authors: Herrou Julien , Foreman Robert , Fiebig Aretha , Crosson Sean
Published: August 2010

PhyR is a hybrid stress regulator conserved in α‐proteobacteria that contains an N‐terminal σ‐like (SL) domain and a C‐terminal receiver domain. Phosphorylation of the receiver domain is known to promote binding of the SL domain to an anti‐σ factor. PhyR thus functions as an anti‐anti‐σ factor in its phosphorylated state. We present genetic evidence thatCaulobacter crescentusPhyR is a phosphorylation‐dependent stress regulator that functions in the same pathway as σTand its anti‐σ factor, NepR. Additionally, we report the X‐ray crystal structure of PhyR at 1.25 Å resolution, which provides insight into the mechanism of anti‐anti‐σ regulation. Direct intramolecular contact between the PhyR receiver and SL domains spans regions σ2and σ4, likely serving to stabilize the SL domain in a closed conformation. The molecular surface of the receiver domain contacting the SL domain is the structural equivalent of α4‐β5‐α5, which is known to undergo dynamic conformational change upon phosphorylation in a diverse range of receiver proteins. We propose a structural model of PhyR regulation in which receiver phosphorylation destabilizes the intramolecular interaction between SL and receiver domains, thereby permitting regions σ2and σ4in the SL domain to open about a flexible connector loop and bind anti‐σ factor.
The Rectal Motor Complex
Authors: Orkin Bruce A. , Hanson Russell B. , Kelly Keith A.
Published: August 2010

To identify patterns of motility in the rectum of humans during the day while awake and at night during sleep, and to correlate the patterns with interdigestive duodenal motor complexes and sleep cycles, intraluminal rectal pressure was recorded in 12 healthy subjects (five female, seven male; mean age, 28 years) using a flexible, noncompliant, silastic catheter and an Arndorfer system with a single perfused rectal port 6 cm above the anorectal junction, duodenal motility was recorded via a perfused oroduodenal tube, and sleep stages were determined electroencephalographically. Discrete bursts of rectal motor waves, called rectal motor complexes (RMCs), were identified on 72 occasions in 11 of the 12 subjects during 157 hours of recording. The RMCs were found in daytime during fasting or after feeding (0.2 ± 0.1 RMCs/hour), but were more easily and frequently identified at night during sleep (0.8 RMCs/hour, p < .01). The complexes had a distinct onset, a mean duration ± SEM of 9.5 ± 1.0 minutes, and a distinct decline. Within each complex, the waves had a mean frequency of 3.8 ± 0.3 per minute and a mean amplitude of 19 ± 2.7 mm Hg. Complex‐to‐complex intervals at night averaged 74 ± 15 minutes. No clear‐cut temporal association was present between the complexes and phase III of interdigestive duodenal motor complex or the REM stage of sleep.
Influence of Stress on Gastric Emptying Depends on the Nature of Meals, Stressors, and Animal Species
Authors: Gué M. , Fioramonti J. , Buéno L.
Published: August 2010

This work evaluated the effects of 20‐minute exposures to acoustic stress, cold (10°C), or immobilization on gastric emptying of test meals containing 51Cr sodium chromate in rats and mice. Four diets were studied: one consisting of reconstituted cow's milk (diet A), a synthetic diet containing arabic gum, glucose, and casein (diet B), diet B with arachis oil (diet C), and a nonnutritive diet containing methylcellulose and saline (diet D). Test‐meal volumes were 0.5 ml in mice and 3 ml in rats. Gastric emptying, expressed as percentage of meal emptied, was measured 30 minutes after gavage with the test meal. Acoustic stress and cold, applied after gavage, increased (p > .05) the rate of gastric emptying of diet A by 46.8% and 70.7%, respectively, in mice and by 13.4% and 22.0% in rats. Immobilization did not affect (p > .05) the gastric emptying of diet A in either species. Cold significantly increased (p ≤ .05) the emptying rate of diets C and D in mice but not in rats. Gastric emptying of diet D was unaffected by the three stressors in mice but was increased (45.7%) by cold in rats. This study shows that the effects of stress on gastric emptying of a nutritive meal depend mainly on the type of stressor. Of the three tested, cold was the most powerful. These results also support the conclusion that stressor, diet, and species are all important in gastric emptying.
Relationship Between Gastroesophageal Reflux and Symptoms in Patients Referred for Ambulatory pH Monitoring
Authors: Howard Philip J. , Pryde Anne , Heading Robert C.
Published: August 2010

Ambulatory pH monitoring is regarded as the most objective means of detecting and quantifying gastroesophageal reflux. Nevertheless, the relationship between symptoms and distal esophageal acid exposure is unclear, especially in patients with atypical reflux symptoms or noncardiac chest pain. The aim of this study was to explore the relationship between symptoms and the indices of gastroesophageal reflux currently used. We examined 100 consecutive, unselected patients referred for ambulatory pH monitoring with suspected symptomatic gastroesophageal reflux (n = 65) or unexplained noncardiac chest pain (n = 35). A symptom‐reflux association (SRA) was defined as the percentage of episodes of pain, or heartburn, during pH monitoring that were reported within 5 minutes of a gastroesophageal reflux event (pH fall to < 4). The two most sensitive predictors of symptomatic reflux (defined as a SRA < 50%) were the frequency of erect reflux episodes per hour (sensitivity 90%, specificity 77%, and accuracy 85%) and the erect reflux time (sensitivity 61%, specificity 93%, and accuracy 75%). To identify gastroesophageal reflux as a cause of symptoms, it is important to seek a temporal relationship between symptoms and reflux events. Reliance on acid exposure times alone will result in “false negative” diagnoses in some patients with symptomatic reflux who do not have excess reflux.
Abdominal Surgery‐ and Trephination‐Induced Delay in Gastric Emptying is Prevented by Intracisternal Injection of CRF Antagonist in the Rat
Authors: Taché Y. , Barquist E. , Stephens R. L. , River J.
Published: August 2010

The role of endogenous corticotropin‐releasing factor (CRF) in mediating surgery‐induced delay in gastric emptying of a noncaloric solution was studied in rats using intracisternal injection of a CRF antagonist, α‐helical CRF9‐41. Intracisternal injections and surgery (abdominal or trephination) were performed under ether anesthesia. After rats recovered from anesthesia, a methylcellulose phenol red solution was administered oropharyngeally and gastric emptying was measured 20 minutes later. Laparotomy, followed by exteriorization of the cecum for 60 seconds (abdominal surgery), trephination, intracisternal injection, of CRF (130 pmol), and ether exposure alone for 120 to 140 or 70 to 80 seconds, inhibited gastric emptying by 83%, 81%, 60%, 56%, and 32%, respectively, as compared with an untreated control group. Intracisternal injection of α‐helical CRF9‐41 significantly enhanced gastric emptying by 27% and prevented by 79% to 87% the inhibition of gastric emptying induced by intracisternal injection of CRF and ether exposure (70–80 s) alone or combined with abdominal surgery. Intracisternal injection of the CRF antagonist (13–26 nmol) dose dependently prevented ether‐induced (120–140 s) and trephination‐induced inhibition of gastric emptying. These results suggest that central CRF may be involved in mediating the acute postoperative delay in gastric emptying.
Capsaicin‐Sensitive Vagal Afferent Fibers and Gastric Motility: Evidence for an “Axon Reflex” Mechanism
Authors: Laird Jennifer M. A. , Chang Bernard , Hoey Rachel , Cervero Fernando
Published: August 2010

The role of capsaicin‐sensitive afferent fibers in gastric motility has been studied in normal rats and in rats treated at birth with the sensory neurotoxin capsaicin, a procedure known to destroy up to 90% of unmyelinated afferent fibers. Gastric motility was measured as intragastric pressure changes evoked by the distention of the stomach with 8 to 10 ml of normal (154 mM) or 1 M saline solution. No differences were observed between the motility patterns evoked by gastric distention with these two solutions. Distention of the stomach evoked a significantly lower basal tone and a reduced number and amplitude of phasic contractions in capsaicin‐treated rats compared to control rats. Intravenous administration of the ganglionic blocker hexamethonium substantially reduced phasic motility in both groups of animals. Subsequent bilateral vagotomy had little extra effect. After bilateral vagotomy, electrical stimulation at supramaximal intensities of the peripheral end of the cut right vagus in the presence of hexamethonium produced an inhibition of the gastric basal tone in both groups of rats and, on cessation of stimulation, a series of rebound contractions in most control animals, but not in those treated at birth with capsaicin. These results provide evidence for an efferent role of vagal afferent fibers in the control of gastric motility, possibly via an axon reflex mechanism.
Role of Peptide YY in Intestinal and Gallbladder Motility in Dogs
Authors: Thor Piotr , Konturek Stanislaw J. , Laskiewicz Janusz , Domschke Wolfram
Published: August 2010

The purpose of this study was to characterize the action of exogenous PYY, an ileocolonic peptide released by fatty meal, and that released by Heal perfusion with oleate on intestinal and gallbladder motility patterns and the posssible role of the adrenergic pathway in this action. Dogs were equipped with chronic duodenal electrodes for recording myoelectric activity and with a cannula in the gallbladder fundus for measuring the gallbladders intraluminal pressure and volume and calculating its motility index (MI) and emptying rate. After intravenous infusion of PYY, there was a dose‐dependent prolongation of the migrating motor complex (MMC) interval and almost complete abolition of the contractions and emptying of gallbladder during the duodenal activity front. After meat feeding or during intravenous infusion of cerulein, 50 pmol/(kg · h), the MMC was interrupted and replaced by irregular spike activity, accompanied by a marked increase in the gallbladder MI and about 80% to 90% reduction of its volume. PYY, 200 pmol/(kg · h), reduced significantly the meal‐ or cerulein‐induced duodenal spike activity but failed to affect the MI and volume of the gallbladder. Similar changes in fasted and fed patterns of motility were observed after Heal oleate (16 mM/h), producing plasma PYY levels in a range similar to that observed after infusion of exogenous PYY. The inhibitory effects of PYY or Heal fat on intestinal myoelectric activity were reversed in part by α‐adrenergic blockade (phentolamine). We conclude that exogenous PYY or endogenous hormone released by Heal oleate inhibits the interdigestive and postprandial motility pattern of the small bowel but does not affect gallbladder motility, and that the inhibition of intestinal motility involves, at least in part, the adrenergic pathway.
The Relationship Between Clinical Factors and Gastrointestinal Dysmotility in Diabetes Mellitus
Authors: Kim C. H. , Kennedy F. P. , Camilleri M. , Zinsmeister A. R. , Ballard D. J.
Published: August 2010

Motility of the stomach and upper intestine was studied in 84 consecutive diabetic patients referred to the Mayo Clinic for evaluation of functional symptoms (nausea, vomiting, or epigastric pain in the absence of structural or mucosal abnormalities). Manometric abnormalities were found in 81 of 84 patients who successfully completed a 3‐hour fast and 2‐hour postprandial motility evaluation. Antral hypomotility was found in 9 patients, small intestinal dysmotility in 11, and gastric and small‐intestinal dysmotilities in 61. The most common abnormalities were the absence of a fed motility pattern after ingestion of the meal and the presence of abnormal intestinal bursts during the fasting period. Clinical factors such as type and duration of diabetes, fasting serum glucose and glycosylated hemoglobin levels, daily dose of insulin therapy, presence of autonomic neuropathy, peripheral neuropathy, retinopathy, and vascular disease were not significantly associated with the severity of gastrointestinal dysmotility. However, there was a significant association between the number of extraintestinal diabetic complications and the severity of gastrointestinal dysmotility (p < 0.05). We conclude that clinical factors, by and large, are not helpful in predicting the severity of gastrointestinal dysmotility among symptomatic diabetic patients.
Differences in longitudinal smooth muscle response along the length of the rabbit small intestine
Authors: SCOTT R. B. , TAN D. T. M.
Published: August 2010

To determine whether there is a gradient in the ability of longitudinal smooth muscle along the length of the small intestine to develop tension we prepared longitudinal muscle strips from proximal (P), medial (M) and distal (D) segments of small intestine removed from 900–1200 g New Zealand white rabbits (n = 9). Isometric tension was recorded in standard tissue baths perfused with oxygenated Krebs solution and 10−6m tetrodotoxin. Basal and active (the response to 10−5m carbachol) length‐tension curves were generated, and the length at which tissues developed maximal active tension (the optimum length or Lo) was determined for P, M and D tissues. Then the dose‐response to carbachol (over the range 10−2‐10−4m) was determined for each of the P, M and D tissues at Lo. Non‐linear regression was used to determine the dose at which the contractile response was half maximal (the ED so), and the maximum tension generated (Tm) by the tissue at each location. The basal tension generated in response to graded stretch increased exponentially between 100 and 140% of initial length and was not significantly different for P, M and D tissues. The active tension generated in response to 10−5m carbachol peaked at 125% of initial length; the Lo for P, M and D tissues was identical. With tissues equilibrated at Lo, dose‐response curves for carbachol and graded concentrations of KCl showed a significant increment in maximal tension generated, but no significant difference in ED50 in the more distal compared to proximal segments. Thus, the passive elastic properties and Lo were identical for the three regions of small intestine examined. However, there was a significant increase in active tension generated in distal compared to more proximal regions of the small intestine, which was not associated with a change in the ED50 value for carbachol. As the response occurs in the presence of tetrodotoxin and can be reproduced with KCl depolarization, it probably reflects post‐receptor changes in smooth muscle function.
Up and down the spinal cord: afferent and efferent innervation of the human external anal sphincter
Authors: ENCK P. , HERDMAN J. , BÖRGERMANN K. , THEISEN U. , ZACCHI P. , LÜBKE H. J.
Published: August 2010

Afferent and efferent pathways from the anal canal to the external anal sphincter muscle have been investigated in healthy volunteers by means of scalprecorded somatosensory‐evoked potentials following electrical stimulation within the anal canal and by means of motor‐evoked potentials recorded from the external anal sphincter muscle following transcranial magneto‐electrical stimulation of the motor cortex. Control recordings were obtained following posterior tibial‐nerve stimulation on the one hand and recordings form the anterior tibial muscle on the other hand. Latencies of both somatosensory‐evoked potentials following anal stimulation and motor‐evoked potentials recorded from the external anal sphincter were similar to those of the tibial muscle/nerve despite a longer distance. This may be due to slower conduction of the sensory and motor pathways from and to the pelvic floor in comparison to those pathways innervating the limbs, or to the fact that pelvic floor pathways comprise a larger number of neurons and synapses as has been shown in the motor pathways to the pelvic floor in animals.
Gastrointestinal motor activity associated with postoperative ileus and emesis
Authors: SMITH D. , WALDRON B. , LOUDON M. , SMALL P. , CAMPBELL F. C.
Published: August 2010

The gastrointestinal motor activity associated with post‐operative ileus and emesis has not been fully elucidated. This study has evaluated gastric and small‐bowel motility in six patients before and after cholecystectomy and in six healthy volunteers, by solid‐state manometry. Nausea and vomiting were recorded post‐operatively. After surgery, fasting motor abnormalities including (a) total gastric quiescence and (b) small‐bowel ‘phasic‐bursts’ of contractions were observed in all patients. Phasic bursts (PB) resembled phase III of the migrating motor complex (MMC) on initial visual inspection, but further analysis revealed that they were of shorter duration (3.4 ±.2 min [PB] vs 6.4 ± 0.8 min [MMC], [mean ± SEM] P < 0.01), lower contraction frequency (6.4 ± 0.1 contractions min −1 [PBj vs 10 ± 0.3 contractions min−1 [MMC] [mean ± SEM] P < 0.01) and shorter periodicity (36.4 ± 3 min [PB] vs 70.0 ± 6 min [MMC] [mean ± SEM] P < 0.01). Four patients experienced nausea during phasic burst activity. Vomiting was only observed in association with retrograde phasic‐bursts, which migrated through the duodenum to the stomach. This study has shown consistent gastrointestinal motor abnormalities in the immediate post‐operative state.
Colonic high‐amplitude propagated contractions (mass movements): repeated 24‐h manometric studies in healthy volunteers
Authors: Bassotti G. , Betti C. , Fusaro C. , Morelli A.
Published: August 2010

Abstract Colonic contractile activity in man is still poorly understood and reported to be highly variable. In particular, little is known about colonic mass movements. We sought to gain greater information on mass movements by manometrically recording high‐amplitude propagated contractions over three periods of 24 h in three healthy volunteers. Analysis of tracings showed that these events (a) are a relatively constant feature of the healthy colon (average [±SEM] number of mass movements for each subject was respectively 7 ± 1.7, 4 ± 1.5 and 6.3 ± 1.7); (b) display a diurnal variability, with a maximum of occurrence during the day and the waking state and a minimum during the night and the sleep; (c) are frequently related to specific physiological events
Effects of neurokinins on human colonic motility
Authors: KÖULBEL C. B. , MAYER E. A. , HOLTMANN G. , LAYER P. , PETSCHULAT W. , ERHARD J. , COEBELL H.
Published: August 2010

Abstract Neurokinins have been implicated as excitatory neuromessengers involved in the mediation of different reflexes in the mammalian gastrointestinal tract. However, marked interspecies variations in reported receptor distribution and in regional peptide content do not allow the extrapolation of results obtained in animals to the human gastrointestinal tract. To characterize the myogenic and neurogenic mechanical response of human colonic muscle to neurokinins, we studied the inotropic response of muscle strips from the proximal and distal human colon, and the rectum to the NK‐1 receptor agonists substance P (SP) and substance P methylester (SPME), to the NK‐2 receptor agonists neurokinin A (NKA) and neurokinin A 4–10 (NKA4–10) and to the NK‐3 receptor agonist neurokinin B (NKB). Even though all neurokinins caused a dose‐dependent inotropic response, NKA was 15–20 times more potent than SP or SPME in all areas of the colon. The efficacy and potency of NKA was highest in distal circular colon. The response to exogenous SP and NKA was partially mediated by actions of these peptides on myenteric nerves, as indicated by the sensitivity of the mechanical response to atropine, tetrodotoxin and hexamethonium. Densensitization to NKA, but not to SP significantly increased the atropine‐resistant part of the off response to electrical field simulation. These results suggest the following: (a) NKA is a potent agonist in human colon with a proximal to distal gradient in potency and in efficacy; (b) the response to NK‐I, NK‐2 and NK‐3 agonists involves cholinergic and nicotinic mechanisms; (c) the increase in the atropine resistant off‐response after desensitization with NKA is consistent with the existence of inhibitory NK‐2 receptors on non‐cholinergic myenteric neurons.
MMC‐related duodenojejunal antegrade and retrograde peristalsis in humans
Authors: BIORNSSON E. , ABRAHAMSSON H.
Published: August 2010

Abstract According to recent manometric studies the last part of phase III of the migrating motor complex (MMC) shows the features of a retroperistaltic pump in the proximal duodenum in most healthy humans. In the present study, individual contractions in phase II and phase III of the MMC were investigated in ten healthy subjects (four males, six females), focusing on the distal duodenum and the jejunum. Motility was recorded on two different days with eight‐channel catheters. On one day a standard antroduodenojejunal fasting recording was performed for 5 h, allowing detailed analysis of pressure waves in the proximal duodenum. On another day a two‐station measurement was performed in the proximal jejunum and the distal duodenum. The propagated pressure waves were analysed for late phase II (last 30 min) and for the first and the last part (I min) of phase III in the three intestinal segments. Antegrade peristalsis predominated at all levels in phase II and in the first part of phase III. In contrast, 84 ± 11% of all propagated contractions were retrograde in the last part of phase III in the proximal duodenum and 75 ± 16% in the distal duodenum. The proportions of retrograde contractions in early phase III and in late phase III differed significantly, from 11 ± 11% to 84 ± 11% and from 32 ± 16% to 75 ± 16% in the proximal and distal duodenum, respectively (P < 0.01 and P < 0.05). In the proximal jejunum such retroperistalsis was not observed, neither in the beginning nor at the end of phase III. In phase II the proportions of retrograde pressure waves were small (3–10%) in the three segments studied. The migration velocity of the pressure waves showed a gradient in this phase, with the lowest values in the jejunum.

It is concluded that the last part of phase III shows the pressure pattern of a retroperistaltic pump through out the duodenum. In contrast, no distinct MMC‐related retroperistalsis was observed in the jejunum.
Uncovering the complex relationship between pre‐eclampsia, preterm birth and cerebral palsy
Authors: Mann Joshua R. , McDermott Suzanne , Griffith Margaret I. , Hardin James , Gregg Anthony
Published: August 2010

Mann JR, McDermott S, Griffith MI, Hardin J, Gregg A. Uncovering the complex relationship between pre‐eclampsia, preterm birth and cerebral palsy. Paediatric and Perinatal Epidemiology 2010.

Pre‐eclampsia is a leading cause of preterm birth, which is strongly associated with cerebral palsy (CP). However, there is controversy about whether pre‐eclampsia is associated with increased risk of CP. We evaluated the association between pre‐eclampsia and CP in 122 476 mother–child pairs insured by the South Carolina Medicaid programme, with births between 1996 and 2002. Prenatal billing records were linked to the children's Medicaid billing records after birth until December 2008. The odds of CP were modelled using logistic regression with generalised estimating equations.

There were 337 children (0.28%) diagnosed with CP by at least two different health care providers, and 4226 (3.5%) women were diagnosed with pre‐eclampsia at least twice during pregnancy. Children whose mothers had pre‐eclampsia were almost twice as likely to have CP compared with children of mothers without pre‐eclampsia [odds ratio (OR) = 1.94, 95% confidence interval (CI) 1.25, 2.97]. The association was only significant for pre‐eclampsia diagnosed prior to 37 weeks' gestation. Full term (gestational age ≥37 weeks) infants whose mothers were diagnosed with pre‐eclampsia prior to 37 weeks had increased odds of CP compared with full term children whose mothers did not have pre‐eclampsia (OR = 3.41, 95% CI 1.40, 8.31). Preterm infants whose mothers had pre‐eclampsia were at significantly increased risk of CP compared with full term infants whose mothers did not have pre‐eclampsia (OR = 5.88, 95% CI 3.40, 10.17). The greatest risk for CP was in preterm infants whose mothers did not have pre‐eclampsia (OR = 8.12, 95% CI 6.49, 10.17 compared with full term infants without exposure to pre‐eclampsia). We conclude that pre‐eclampsia with onset before 37 weeks' gestation is a significant risk factor for CP. Some of the association is probably attributable to high risk of preterm birth because of early pre‐eclampsia, while a ‘direct’ effect of pre‐eclampsia on fetal brain development also seems likely.
The record of tidal cycles in mixed silici–bioclastic deposits: examples from small Plio–Pleistocene peripheral basins of the microtidal Central Mediterranean Sea
Authors: LONGHITANO SERGIO G.
Published: August 2010

The Pliocene–Pleistocene peripheral marine basins of the Mediterranean Sea in southern Italy, from Basilicata and western Calabria to northern and eastern Sicily, represent tectonically formed coastal embayments and narrow straits. Here, units of cross‐stratified, mixed silici–bioclastic sand, 25 to 80 m thick, record strong tidal currents. The Central Mediterranean Sea has had a microtidal range of ca 35 cm, and the local amplification of the tidal wave is attributed to tides enhanced in some of the bays and to the out‐of‐phase reversal of the tidal prism in narrow straits linking the Tyrrhenian and Ionian basins. The siliciclastic sediment was generated by local bedrock erosion, whereas the bioclastic sediment was derived from the contemporaneous, foramol‐type cool‐water carbonate factories. The cross‐strata sets represent small to medium‐sized (10 to 60 cm thick) two‐dimensional dunes with mainly unidirectional foreset dip directions. These tidalites differ from the classical tidal rhythmites deposited in mud‐bearing siliciclastic environments. Firstly, the foreset strata lack mud drapes and, instead, show segregation of siliciclastic and bioclastic sand into alternating strata. Secondly, the thickness variation of the successive silici–bioclastic strata couplets, measured over accretion intervals of 2 to 3 m and analysed statistically, reveal only the shortest‐term, diurnal and semi‐diurnal tidal cycles. Thirdly, the record of diurnal and semi‐diurnal tidal cycles is included within the pattern of neap‐spring cycles. Differences between these sediments and classical tidal rhythmites are attributed to the specific palaeogeographic setting of a microtidal sea, with the tidal currents locally enhanced in peripheral basins. It is suggested that this particular facies of mud‐free, silici–bioclastic arenite rhythmites in the stratigraphic record might indicate a specific type of depositional sub‐tidal environment of straits and embayments and the shortest‐term tidal cycles.
A novel aldose/aldehyde reductase protects transgenic plants against lipid peroxidation under chemical and drought stresses
Authors: Oberschall Attila , Deák Mária , Török Katalin , Sass László , Vass Imre , Kovács Izabella , Fehér Attila , Dudits Dénes , Horváth Gábor V.
Published: August 2010

Rapid accumulation of toxic products from reactions of reactive oxygen species (ROS) with lipids and proteins significantly contributes to the damage of crop plants under biotic and abiotic stresses. Here we have identified a stress‐activated alfalfa gene encoding a novel plant NADPH‐dependent aldose/aldehyde reductase that also exhibited characteristics of the homologous human enzyme. The recombinant alfalfa enzyme is active on 4‐hydroxynon‐2‐enal, a known cytotoxic lipid peroxide degradation product. Ectopic synthesis of this enzyme in transgenic tobacco plants provided considerable tolerance against oxidative damage caused by paraquat and heavy metal treatment. These transformants could also resist a long period of water deficiency and exhibited improved recovery after rehydration. We found a reduced production of lipid peroxidation‐derived reactive aldehydes in these transformed plants under different stresses. These studies reveal a new and efficient detoxification pathway in plants.
Fatty acid ketodienes and fatty acid ketotrienes: Michael addition acceptors that accumulate in wounded and diseased Arabidopsis leaves
Authors: Vollenweider Sabine , Weber Hans , Stolz Stephanie , Chételat Aurore , Farmer Edward E.
Published: August 2010

Physical damage and disease are known to lead to changes in the oxylipin signature of plants. We searched for oxylipins produced in response to both wounding and pathogenesis in Arabidopsis leaves. Linoleic acid 9‐ and 13‐ketodienes (KODEs) were found to accumulate in wounded leaves as well as in leaves infected with the pathogen Pseudomonas syringae pv. tomato (Pst). Quantification of the compounds showed that they accumulated to higher levels during the hypersensitive response to Pst avrRpm1 than during infection with a Pst strain lacking an avirulence gene. KODEs are Michael addition acceptors, containing a chemically reactive α,β‐unsaturated carbonyl group. When infiltrated into leaves, KODEs were found to induce expression of the GST1 gene, but vital staining indicated that these compounds also damaged plant cells. Several molecules typical of lipid oxidation, including malonaldehyde, also contain the α,β‐unsaturated carbonyl reactivity feature, and, when delivered in a volatile form, powerfully induced the expression of GST1. The results draw attention to the potential physiological importance of naturally occurring Michael addition acceptors in plants. In particular, these compounds could act directly, or indirectly via cell damage, as powerful gene activators and might also contribute to host cell death.
Widely separated multiple transgene integration sites in wheat chromosomes are brought together at interphase
Authors: Abranches Rita , Santos Ana P. , Wegel Eva , Williams Sarah , Castilho Alexandra , Christou Paul , Shaw Peter , Stoger Eva
Published: August 2010

We have investigated the organization of transgenes delivered by particle bombardment into the wheat genome, combining conventional molecular analysis with fluorescence in situ hybridization (FISH) and three‐dimensional confocal microscopy. We selected a representative population of transformed wheat lines and carried out molecular and expression analysis. FISH on metaphase chromosomes showed that transgene integration sites were often separated by considerable lengths of genomic DNA (>1 Mbp), or could even be on opposite chromosome arms. Plants showing multiple integration sites on a single chromosome were selected for three‐dimensional confocal analysis of interphase nuclei in root and embryo tissue sections. Confocal microscopy revealed that these sites lay in close physical proximity in the interphase nuclei. Our results clearly show that multiple transgenes physically separated by large intervening regions of endogenous DNA at metaphase can be brought together at interphase. This may reflect the original physical organization of the endogenous DNA at the moment of transformation, with DNA strand breaks introduced into several co‐localized DNA loops by the intruding gold particles. Alternatively, the transgenes may be brought together after transformation, either by an ectopic homologous pairing mechanism, or by recruitment to a common transcription site.
Auxin induces mitogenic activated protein kinase (MAPK) activation in roots of Arabidopsis seedlings
Authors: Mockaitis Keithanne , Howell Stephen H.
Published: August 2010

Genome analyses have shown that plants contain gene families encoding various components of mitogen‐activated protein kinase (MAPK) signaling pathways. Previous reports have described the involvement of MAPK pathways in stress and pathogen responses of leaves and suspension‐cultured cells. Here we show that auxin treatment of Arabidopsis roots transiently induced increases in protein kinase activity with characteristics of mammalian ERK‐like MAPKs. The MAPK response we monitored was the result of hormonal action of biologically active auxin, rather than a stress response provoked by auxin‐like compounds. Auxin‐induced MAPK pathway signaling was distinguished genetically in the Arabidopsis auxin response mutant axr4, in which MAPK activation by auxin, but not by salt stress, was significantly impaired. Perturbation of MAPK signaling in roots using inhibitors of a mammalian MAPKK blocked auxin‐activated transgene expression in BA3‐GUS seedlings, while potentiating higher than normal levels of MAPK activation in response to auxin. Data presented here indicate that MAPK pathway signaling is positively involved in auxin response, and further suggest that interactions among MAPK signaling pathways in plants influence plant responses to auxin.
Indole alkaloid biosynthesis in Catharanthus roseus: new enzyme activities and identification of cytochrome P450 CYP72A1 as secologanin synthase
Authors: Irmler Stefan , Schröder Gudrun , St‐Pierre Benoit , Crouch Nicholas P. , Hotze Michael , Schmidt Jürgen , Strack Dieter , Matern Ulrich , Schröder Joachim
Published: August 2010

The molecular characterization of CYP72A1 from Catharanthus roseus (Madagascar periwinkle) was described nearly a decade ago, but the enzyme function remained unknown. We now show by in situ hybridization and immunohistochemistry that the expression in immature leaves is epidermis‐specific. It thus follows the pattern previously established for early enzymes in the pathway to indole alkaloids, suggesting that CYP72A1 may be involved in their biosynthesis. The early reactions in that pathway, i.e. from geraniol to strictosidine, contain several candidates for P450 activities. We investigated in this work two reactions, the conversion of 7‐deoxyloganin to loganin (deoxyloganin 7‐hydroxylase, DL7H) and the oxidative ring cleavage converting loganin into secologanin (secologanin synthase, SLS). The action of DL7H has not been demonstrated in vitro previously, and SLS has only recently been identified as P450 activity in one other plant. We show for the first time that both enzyme activities are present in microsomes from C. roseus cell cultures. We then tested whether CYP72A1 expressed in E. coli as a translational fusion with the C. roseus P450 reductase (P450Red) has one or both of these activities. The results show that CYP72A1 converts loganin into secologanin.
NEC1, a novel gene, highly expressed in nectary tissue of Petunia hybrida
Authors: Ge Ya‐Xin , Angenent Gerco C. , Wittich Peter E. , Peters Jeroen , Franken John , Busscher Marco , Zhang Le‐Min , Dahlhaus Ellen , Kater Martin M. , Wullems George J. , Creemers‐Molenaar Tineke
Published: August 2010

To study the molecular regulation of nectary development, we cloned NEC1, a gene predominantly expressed in the nectaries of Petunia hybrida, by using the differential display RT–PCR technique. The secondary structure of the putative NEC1 protein is reminiscent of a transmembrane protein, indicating that the protein is incorporated into the cell membrane or the cytoplast membrane. Immunolocalization revealed that NEC1 protein is present in the nectaries. Northern blot analyses showed that NEC1 is highly expressed in nectary tissue and weakly in the stamen. GUS expression driven by the NEC1 promoter revealed GUS activity in the outer nectary parenchyma cells, the upper part of the filament and the anther stomium. The same expression pattern was observed in Brassica napus. GUS expression was observed as blue spots on the surface of very young nectaries that do not secrete nectar and do accumulate starch. GUS expression was highest in open flowers in which active secretion of nectar and starch hydrolysis had taken place. Ectopic expression of NEC1 resulted in transgenic plants that displayed a phenotype with leaves having 3–4 times more phloem bundles in mid‐veins than the wild‐type Petunia. The possible role of NEC1 gene in sugar metabolism and nectar secretion is discussed.
AtSUC3, a gene encoding a new Arabidopsis sucrose transporter, is expressed in cells adjacent to the vascular tissue and in a carpel cell layer
Authors: Meyer Stefan , Melzer Michael , Truernit Elisabeth , Hümmer Carola , Besenbeck Rainer , Stadler Ruth , Sauer Norbert
Published: August 2010

The cDNA corresponding to the open reading frame T17M13.3 from Arabidopsis chromosome II was isolated and the encoded protein was characterized as a member of a subgroup of higher plant sucrose transporters. The AtSUC3 (Arabidopsis thaliana sucrose transporter 3) open reading frame encodes a protein with 594 amino acid residues, being 81 and 82 residues longer than the previously described Arabidopsis sucrose carriers AtSUC1 and AtSUC2. About 50 of these additional amino acids are part of an extended cytoplasmic loop separating the N‐terminal from the C‐terminal half of the protein. For functional characterization the AtSUC3 cDNA was expressed in baker's yeast. Substrate specificities, energy dependence and Km values of the recombinant protein were determined. Removal of the enlarged cytoplasmic loop and expression of the truncated cDNA caused no detectable change in the kinetic properties of the protein, suggesting a transport‐independent function for this cytoplasmic domain. Immunolocalization with an AtSUC3‐specific antiserum identified the protein in a cell layer separating the phloem from the mesophyll and in a single, subepidermal cell layer of the carpels that is important for pod dehiscence. These localizations suggest a possible role of AtSUC3 in the funnelling of sucrose from the mesophyll towards the phloem, and possibly in pod shatter.
Interactions betweenhy1andgunmutants ofArabidopsis, and their implications for plastid/nuclear signalling
Authors: Vinti Giovanna , Hills Alison , Campbell Shona , Bowyer John R. , Mochizuki Nobuyoshi , Chory Joanne , López‐Juez Enrique
Published: August 2010

Lhcband other nuclear genes for chloroplastic proteins are regulated by several signals. Among them, light and retrograde signals from the plastid itself appear to act through closely related mechanisms. To investigate this interaction, we analysed anArabidopsismutant,hy1, deficient in plastidic heme oxygenase.hy1is defective in phytochrome chromophore biosynthesis, which has other indirect effects on tetrapyrrole metabolism. We generated double mutants betweenhy1‐6.2, genetically a null mutation, and three knowngun(genome uncoupled) mutants, defective in retrograde plastid signalling. Recent molecular evidence showsGUN5to be involved in tetrapyrrole metabolism (N. Mochizuki and J. Chory, manuscript in preparation). We observedhy1gun4to be semi‐albino plants, andhy1gun5albino lethal, in a high‐light‐sensitive manner. Both double mutants showed defective greening and chloroplast development, and expressedLhcbat reduced levels specifically in high light. Their degree of ‘genome uncoupling’ (Lhcbexpression in the absence of functional chloroplasts) was similar to that observed in single mutants. These results can be interpreted as a metabolic (rather than genetic) interaction betweenHY1andGUN4orGUN5, and this in turn supports the involvement of tetrapyrroles as plastid signals. The tetrapyrrole precursor 5‐aminolevulinic acid (ALA) inhibitedLhcbexpression inhy1. Surprisingly, ALA also rescued photomorphogenesis ofhy1. We speculate that either one tetrapyrrole intermediate, which can accumulate anomalously inhy1, or an altered ratio between two intermediates, plays a role as a repressor ofLhcbexpression.gun1did not exacerbate the plastid orLhcbexpression phenotype ofhy1. This can be interpreted as a role forgun1strictly on the same pathway ashy1or, more likely, as evidence for the existence of at least one separate, non‐tetrapyrrole related plastid signal.
Two kinesin‐related proteins associated with the cold‐stable cytoskeleton of carrot cells: characterization of a novel kinesin, DcKRP120‐2
Authors: Barroso Consuelo , Chan Jordi , Allan Viki , Doonan John , Hussey Patrick , Lloyd Clive
Published: August 2010

We have previously described the biochemical isolation of 65 kDa and 120 kDa microtubule‐associated proteins from carrot cytoskeletons. The 65 kDa MAPs have subsequently been shown to be structural MAPs that reconstitute 30 nm cross‐bridges of the kind that maintain cortical microtubules in parallel groups. By exploiting its avid binding to microtubules, we have now devised a method for isolating MAP120 from protoplast extracts, and shown that it has properties of a kinesin‐related protein. MAP120 segregates with the cold stable pool of microtubules in carrot cytoskeletons, whilst the 65 kDa MAPs are also associated with the cold‐sensitive microtubules. On gradient gels, MAP120 resolves as two kinesin‐like bands. We report the isolation of a carrot cDNA, DcKRP120‐2, corresponding to a novel kinesin of the BimC class known to move to the plus ends of microtubules. Antibodies raised against specific expressed sequences recognize the upper band, while the lower band is recognized by antibodies to the tobacco kinesin‐related protein, TKRP125. We have also isolated a partial genomic carrot DNA, DcKRP120‐1, homologous to the motor region of tobacco TKRP125. Immunofluorescence of the two proteins produces different staining patterns. Anti‐TKRP125 labels the cortical microtubules and the pre‐prophase band, but anti‐DcKRP120–2 does so only weakly. Both clearly stain the spindle and the phragmoplast, but in a proportion of cells anti‐DcKRP120‐2 strongly decorates the phragmoplast mid‐line where the plus ends of the microtubules overlap. We discuss the potential roles of these proteins during the microtubule cycle.
Cell death of barley aleurone protoplasts is mediated by reactive oxygen species
Authors: Bethke Paul C. , Jones Russell L.
Published: August 2010

The barley aleurone layer is a terminally differentiated secretory tissue whose activity is hormonally controlled. The plant hormone gibberellic acid (GA) stimulates the secretion of hydrolytic enzymes and triggers the onset of programmed cell death (PCD). Abscisic acid (ABA) antagonizes the effects of GA and inhibits enzyme secretion and PCD. Reactive oxygen species (ROS) are key players in many types of PCD, and data presented here implicate ROS in hormonally regulated death of barley aleurone cells. Incubation of aleurone layers or protoplasts in H2O2‐containing media results in death of GA‐treated but not ABA‐treated aleurone cells. Cells that are programmed to die are therefore less able to withstand ROS than cells that are programmed to remain alive. Illumination of barley aleurone protoplasts with blue or UV‐A light results in a rapid increase in intracellular H2O2 production. GA‐treated protoplasts die rapidly in response to this increase in intracellular H2O2 production, but ABA‐treated protoplasts do not die. The rate of light‐induced death could be slowed by antioxidants, and incubating protoplasts in the dark with the antioxidant butylated hydroxy toluene reduces the rate of hormonally induced death. Taken together, these data demonstrate that GA‐treated aleurone protoplasts are less able than ABA‐treated protoplasts to tolerate internally generated or exogenously applied H2O2, and strongly suggest that ROS are components of the hormonally regulated cell death pathway in barley aleurone cells.
Survey of transposable elements from rice genomic sequences
Authors: Turcotte Kime , Srinivasan Sujatha , Bureau Thomas
Published: August 2010

Oryza sativa L. (domesticated rice) is a monocotyledonous plant, and its 430 Mb genome has been targeted for complete sequencing. We performed a high‐resolution computer‐based survey for transposable elements on 910 Kb of rice genomic DNA sequences. Both class I and II transposable elements were present, contributing 19.9% of the sequences surveyed. Class II elements greatly outnumbered class I elements (166 versus 22), although class I elements made up a greater percentage (12.2% versus 6.6%) of nucleotides surveyed. Several Mutator‐like elements (MULEs) were identified, including rice elements that harbor truncated host cellular genes. MITEs (miniature inverted‐repeat transposable elements) account for 71.6% of the mined transposable elements and are clearly the predominant type of transposable element in the sequences examined. Moreover, a putative Stowaway transposase has been identified based on shared sequence similarity with the mined MITEs and previously identified plant mariner‐like elements (MLEs). Members of a group of novel rice elements resembling the structurally unusual members of the Basho family in Arabidopsis suggest a wide distribution of these transposons among plants. Our survey provides a preview of transposable element diversity and abundance in rice, and allows for comparison with genomes of other plant species.