bluuebunny/crossref_metadata_2025_split huggingface dataset:
VirD4‐independent transformation by CloDF13 evidences an unknown factor required for the genetic colonization of plants via Agrobacterium
Authors: Escudero Jesús , Den Dulk‐Ras Amke , Regensburg‐Tuïnk Tonny J. G. , Hooykaas Paul J. J. 
Published: March 2003

Summary Agrobacterium
uses a mechanism similar to conjugation for
trans
‐kingdom transfer of its oncogenic T‐DNA. A defined VirB/VirD4 Type IV secretion system is responsible for such a genetic transfer. In addition, certain virulence proteins as VirE2 can be mobilized into host cells by the same apparatus. VirE2 is essential to achieve plant but not yeast transformation. We found that the limited host range plasmid CloDF13 can be recruited by the virulence apparatus of
Agrobacterium
for transfer to eukaryotic hosts. As expected the VirB transport complex was required for such
trans
‐kingdom DNA transfer. However, unexpectedly, the coupling factor VirD4 turned out to be necessary for transfer to plants but not for transport into yeast. The CloDF13 encoded coupling factor (Mob) was essential for transfer to both plants and yeast though. This is interpreted by the different specificities of Mob and VirD4. Hence, Mob being required for the transport of the CloDF13 transferred DNA (to both plants and yeast) and VirD4 being required for transport of virulence proteins such as VirE2. Nevertheless, the presence of the VirE2 protein in the host plant was not sufficient to restore the deficiency for VirD4 in the transforming bacteria. We propose that Mob functions encoded by the plasmid CloDF13 are sufficient for DNA mobilization to eukaryotic cells but that the VirD4‐mediated pathway is essential to achieve DNA nuclear establishment specifically in plants. This suggests that other
Agrobacterium virulence proteins besides VirE2 are translocated and essential for plant transformation.
Identification and characterization of genomic loci unique to the Brazilian purpuric fever clonal group of H. influenzae biogroup aegyptius: functionality explored using meningococcal homology
Authors: Li Ming‐Shi , Farrant Jayne L. , Langford Paul R. , Kroll J. Simon 
Published: March 2003

SummaryBrazilian purpuric fever (BPF) is a fulminant septicaemic infection of young children, caused by a clonal group of strains of Haemophilus influenzae biogroup aegyptius (Hae), an organism previously solely associated with conjunctivitis. Their special capacity to invade from the initial site of conjunctival infection is unexplained. A polymerase chain reaction (PCR)‐amplified subtractive hybridization technique was used to identify genes specific to the BPF clonal group. A copy of bacteriophage HP1 and 46 further chromosomal loci were identified in the BPF but not in the conjunctivitis strain of Hae. Sixteen were characterized further, and one – encoding an analogue of the Legionella pneumophila epithelial cell entry‐enhancing protein EnhC – was investigated in depth. Two genes, bpf001 and bpf002, unique to the BPF clonal group were identified between homologues of HI1276 and HI1277 in a complex locus close to H. influenzae genetic island 1, recently identified in pathogenic H. influenzae type b. Bpf001 encodes a protein homologous to EnhC and to the previously uncharacterized product of the meningococcal gene NMB0419. Functional studies of bpf001 proving intractable, NMB0419 was chosen as a surrogate for investigation and shown to modulate bacterial interaction with monolayers of human respiratory epithelial cells, promoting invasion, the first stage (for Hae) in the pathogenesis of BPF.
Effects of ileal bile salts on fasting small intestinal and gallbladder motility
Authors: Van Ooteghem N. A. M. , Samsom M. , Van Erpecum K. J. , Van Berge‐Henegouwen G. P. 
Published: March 2003

Abstract
In the fasting state, gallbladder emptying is related to phase III of the intestinal migrating motor complex. The effects of ileal infusion of mixed taurocholate‐phospholipid micelles on fasting small intestinal motility (by a 17‐channel catheter with side holes located in duodenum, jejunum and ileum) and gallbladder motility (by ultrasound) were investigated in eight healthy volunteers. After bile salt depletion by cholestyramine, 0.9% NaCl or mixed micelles were infused in the ileum during phase II of the migrating motor complex. Time to onset of subsequent phase III was significantly shorter after infusion of mixed micelles compared with 0.9% NaCl (32 ± 5 min vs. 60 ± 5 min, P = 0.01). Distal to the infusion port, numbers of pressure waves and their amplitudes were significantly lower during bile salt infusion compared with 15 min before infusion (11 ± 6 per 15 min vs. 21 ± 8 per 15 min, and 2.4 ± 0.6 kPa vs. 2.8 ± 0.5 kPa, respectively). Micellar infusions increased fasting gallbladder volumes to 170 ± 5% of starting volumes (P < 0.0001). In conclusion, ileal infusion of mixed micelles influences the timing of phase III of the intestinal migrating motor complex, inhibits ileal motility and increases fasting gallbladder volumes. These findings may have important consequences for enterohepatic circulation of bile salts.
Ileal manometry in children following ileostomies and pull‐through operations
Authors: Sood M. R. , Cocjin J. , Di Lorenzo C. , Narasimha Reddy S. , Flores A. F. , Hyman P. E. 
Published: March 2003

Abstract Our aim was to analyse the patterns of ileal contractions in children. We reviewed the charts of 23 children who had ileal manometry studies (16 males), mean age 7 years (range 2 months to 17 years). We positioned the manometry catheters with 4–8 recording sites, 5 or 15 cm apart, through ileostomies fashioned for clinically indicated reasons. We studied six additional children with persistent faecal soiling following endorectal pull through for Hirschsprung's disease; the catheters were positioned through the anus and colon into the ileum. We recorded phasic and tonic intermittent contractions in all the subjects, clustered contractions (rate 5–9 min−1, duration 20–120 s) in 19 subjects with ileostomies and four with endorectal pull throughs. In 13 children there were prolonged propagated contractions, > 60 mmHg in amplitude, > 15 s in duration, propagating at rates of 2–6 cm s−1 over at least 20 cm. The migrating motor complex was rare; in 55 h of fasting recording there were two phase III sequences. There are four distinctive features of ileal manometry recordings in children: random intermittent contractions, clustered contractions, prolonged propagated contractions and tonic contractions. The features of ileal motility differ from motility in the proximal small bowel.
Fully automated analysis of colonic manometry recordings
Authors: De Schryver A. M. P. , Samsom M. , Akkermans L. M. A. , Clemens C. H. M. , Smout A. J. P. M. 
Published: March 2003

Abstract The purpose of this study was to develop a computer program for fully automated analysis of all presently known motor patterns in human colonic motility recordings. Colonic pressure recordings obtained from 24 healthy volunteers were used. Algorithms were developed for the detection and numerical analysis of five types of pressure waves: antegrade, retrograde, simultaneous, high‐amplitude and isolated pressure waves. Furthermore, periodical motor activity was quantified. Validation was performed by comparison with visual analysis by two experienced observers. Patterns recorded during day‐ and night‐time were compared using multiple‐factor analysis of variance with Bonferroni correction. Automated analysis correlated well with visual peak detection (r = 0.98, P <0.01) and detection of antegrade pressure waves (r = 0.98, P <0.01). Most motor patterns showed a diurnal variation. During the night, prevalences of antegrade (938 vs 455; P <0.05), retrograde (112 vs 81; P <0.05), high‐amplitude (12.9 vs 1.3; P <0.05), isolated pressure waves (1114 vs 765; P <0.05), and periodic motor activity were decreased (7.33 vs 4.47%; P <0.05). However, when expressed as percentage of absolute numbers of pressure waves, prevalences remained constant. In conclusion, fully automated analysis of all hitherto described colonic motility patterns is feasible. During the night, overall wave prevalences markedly decreased, but the distribution over the various motor patterns was preserved.
Green leaf volatile‐detecting olfactory receptor neurones display very high sensitivity and specificity in a scarab beetle
Authors: Hansson BilL. S. , Larsson Mattias C. , Leal Walter S. 
Published: March 2003

SummaryIn the Japanese scarab beetle, Phyllopertha diversa, olfactory receptor neurones specific for the detection of so‐called general green leaf volatiles (GLV) display a high specificity and sensitivity. Three main types of green‐leaf‐volatile‐detecting receptor neurones specific to (Z)‐3‐hexenyl acetate, (E)‐2‐hexenal and (Z)‐3‐hexenol, respectively, were identified. Each type responded at a very low stimulus concentration to the key stimulus, and required at least a thousand‐fold increase in concentration to respond to any of the other GLVs tested. Flower‐odour‐and pheromone‐detecting receptor neurones were also identified. Olfactory sensilla housing plant‐odour‐ or pheromone‐detecting receptor neurones displayed clear morphological differences, and were also separated into different antennal regions.
Agonistic behaviour of female Tegenaria atrica in the presence of different aged spiderlings
Authors: Pourié Grégory , Trabalon Marie 
Published: March 2003

SummaryThe agonistic behaviour of adult female T. atrica increases with increasing age of spiderlings until 80 days post‐emergence, then decreases. In all cases, cannibalism of spiderlings increases markedly after completion of their pre‐dispersal period with a correlation between the switch of behaviour, from tolerance to cannibalism, and a modification of individual’s cuticular compounds. Experiments that compare spiderlings weight and mobility indicate that female agonistic behaviour are always low with spiderlings in pre‐dispersal period, and high with spiderlings in post‐dispersal period. Female reproductive state and the weight/mobility of spiderlings are not the only factors controlling the adult female’s agonistic behaviour towards spiderlings on her web, as tactochemical information plays an important role in modulating agonistic behaviour after close contact between female spiders and spiderlings. The agonistic behaviour of females appears to correspond with a change in the increase of polar compound levels (methylesters and fatty acids) and the decrease of apolar compound levels (hydrocarbons) in spiderlings of different ages.
Two‐dimensional pattern discrimination by the honeybee
Authors: Horridge Adrian 
Published: March 2003

SummaryFor a reward of sugar, bees will learn to prefer a pattern rather than an alternative similar one. This visual discrimination allows us to measure resolution, and to search for the cues that the bees remember and later use to recognize the rewarded pattern. Two systems in parallel, analogous to low pass and high pass filters, are distinguished. The first system discriminates the location and size of at least one area of contrast on each side of the target, with inputs from blue and green receptors, but the ability to discriminate the location of colour depends upon fixation. The bees remember less than a low resolution copy of the image, even when they fixate on a vertical pattern.The second system amplifies the contrast at edges in the pattern, ignoring the direction of contrast, and controls fixation upon the target. Edges are discriminated according to their orientation and radial or tangential arrangement. An axis of bilateral symmetry is detected. However, the relative locations of cues within the image are lost, apparently because the relevant neurones have very large fields. Only the cues, not the whole patterns, are preserved in memory. This system is colour blind because its input is restricted to the receptors with peak sensitivity in the green. The two systems together discriminate many simple patterns, but not all, because the filters are limited in variety.
Effects of ovariectomy and mating on the activity of the corpora allata in adult female Blattella germanica (L.) (Dictyoptera: Blattellidae)
Authors: Holbrook Glenn L. , Bachmann J.A.N.E. A. S. , Schal C.O.B.Y. 
Published: March 2003

SummaryIn adult female cockroaches, the ovary greatly affects the synthesis of Juvenile Hormone (JH) by the corpora allata, and in females of some cockroach species, removal of the ovaries results in a permanent depression of JH synthesis. We report that the corpora allata in ovariectomised, adult virgins of the German cockroach, Blattella germanica (L.), increase and then decrease in activity, as they do in intact females. Moreover, the distal tubules in the left colleterial glands of ovariectomised females accumulate abundant protein, the production of which is regulated by JH. In both ovariectomised and sham‐operated females, the activity of the corpora allata more than tripled between days 1 and 4 of adulthood, during which the oöcytes of sham‐operated females grew considerably in length. The corpora allata of sham‐operated females produced even more JH on day 7, but very little on day 10, by which time all females had oviposited. The glands of ovariectomised females, by constrast, produced a similar amount of JH on day 7 as on day 4, but much less on day 10. Beginning on day 13, the activity of the corpora allata increased again in ovariectomised females, an increase that did not occur until day 22 in sham‐operated females. Mating of ovariectomised females on day 6 resulted in a significant increase in the activity of the corpora allata by day 10. We conclude that both the ovary and mating stimulate the synthesis of JH early in the reproductive cycle, but that neither is needed for the occurrence of a complete cycle of JH synthesis.
Partial purification of the aminopeptidase from the midgut of the human body louse, Pediculus humanus humanus
Authors: Ochanda James O. , Oduor Eva A. C. , Galun Rachel , Imbuga Mabel O. , Mumcuoglu Kosta Y. 
Published: March 2003

SummaryThe midgut of the human body louse Pediculus humanus humanus contains a thermally stable leucine aminopeptidase, which was detected by agarose gel electrophoresis using
l‐amino oxidase. Midgut extracts were homogenized in saline or in 1% Triton X‐100 and the aminopeptidase was purified by Superose 6 gel filtration chromatography. A peak with enzyme activity that was extracted with or without Triton X‐100 was eluted at a molecular weight 67–69 kDa. Non‐denaturing polyacrylamide gel electrophoresis resolved one band of molecular weight of 69 kDa for samples that were extracted in a saline buffer. Two closely linked bands of molecular weight 67 kDa and 69 kDa were observed in samples that were extracted in 1% Triton X‐100.
CO2 is the main inorganic C species entering photosynthetically active leaf protoplasts of the freshwater macrophyte Ranunculus penicillatus ssp. pseudofluitans
Authors: Newman J. R. , Raven J. A. 
Published: March 2003

ABSTRACTSubmerged aquatic macrophytes growing in water where free CO2 is unavailable (above pH 8·2) must use mechanisms to supply external dissolved inorganic carbon in a form available to chloroplasts (CO2). Active transport of HCO3– across the plasmalemma has not been proven to be widespread in aquatic macrophytes and catalytic conversion of HCO3– to CO2 is the usual supply mechanism in submerged macrophytes. The interaction of leaf form and function in this respect was investigated in the linear, submerged leaves of Ranunculus penicillatus (Dumort.) Bab ssp. pseudofluitans (Syme) S.Webster. Viable protoplasts were isolated using a mixture of cell wall degrading enzymes optimized for this species. Protoplast viabilities greater than 80% after 5 h of isolation were achieved. Photosynthetic rates of isolated protoplasts were comparable with that of intact plant tissue. Results of carbon isotopic disequilibrium experiments showed that CO2 was the preferred species of dissolved inorganic carbon for photosynthesis by protoplasts and that HCO3– which predominates in the plant’s natural environment mainly contributes by supplying CO2 outside the cells.
Sodium/potassium selectivity and pleiotropy in stl2, a highly salt‐tolerant mutation of Ceratopteris richardii
Authors: Warne T. R. , Hickok L. G. , Sams C. E. , Vogelien D. L. 
Published: March 2003

ABSTRACTThe roles of Na+ and K+ (Rb+) uptake were further studied in a NaCl‐tolerant strain of Ceratopteris richardii containing the stl2 mutation by direct comparison with the wild‐type strain. In addition to Na+ tolerance, stl2 also confers tolerance to Mg2+ and sensitivity to K+. In addition to higher K+ (Rb+) uptake at concentrations commonly associated with low‐affinity K+ transport, stl2 maintained higher uptake down to 0·1 mol m–3 Rb+. Up to a 25‐fold excess of Na+ had little effect in either genotype on K+ (Rb+) uptake at low concentrations, i.e. 0·2 and 0·5 mol m–3 RbCl. Pretreatment with K+ (20 mol m–3) inhibited uptake of K+ (Rb+) in the wild type, whereas concurrent inclusion of K+ inhibited uptake of Rb+ more in stl2. In the absence of K+, Na+ uptake (0·01–60 mol m–3) was nearly identical in the wild type and stl2. K+ inhibited Na+ uptake more effectively in stl2 than the wild type, especially at 60 mol m–3 Na+. Greater inhibition of K+ uptake in stl2 occurred with MgCl2 or TEA (tetraethylammonium chloride) preincubation or with simultaneous inclusion of Al3+ (Al2SO4). The higher effective velocity of K+ uptake at a wide range of concentrations and the enhanced selectivity for K+ and against Na+ contribute to the preservation of higher cytosolic K+ and lower Na+ under salinity stress.
Imbibitional leakage from anhydrobiotes revisited
Authors: Hoekstra F. A. , Golovina E. A. , Aelst A. C. Van , Hemminga M. A. 
Published: March 2003

ABSTRACTDry desiccation‐tolerant organ(ism)s leak cellular solutes when placed in water. Elevated temperatures at imbibition and elevated initial moisture contents reduce the leakage and promote growth. We have re‐examined the effects of imbibitional stress imposed on cattail (Typha latifolia L.) pollen as a model anhydrobiotic system. A nitroxide spin probe technique and electron microscopy were used, allowing study of the permeability of the plasma membrane together with its visual intactness. Imbibitional leakage can be transient, or prolonged when associated with membrane damage. During the first 15 s of rehydration in medium, plasma membranes of pre‐humidified pollen were highly permeable but became less permeable thereafter. The resulting transient leakage may affect vigour as measured by the rate of fresh weight increase, but did not reduce germination. A permanent, high permeability was observed when dry pollen was plunged into medium at low temperatures. This led to cell death and is associated with a phase change of the membranes from gel to liquid crystalline during imbibition. Freeze‐fracture images indicate that the damage to plasma membranes is mechanically imposed by the pressure of the penetrating water rather than occurring structurally by a phase separation of membrane components. We suggest that a high rigidity of the plasma membranes in the gel phase at imbibition underlies imbibitional damage.
Leaf cuticular waxes are arranged in chemically and mechanically distinct layers: evidence from Prunus laurocerasus L.
Authors: Jetter R. , Schäffer S. , Riederer M. 
Published: March 2003

ABSTRACTThe composition and spatial arrangement of cuticular waxes on the leaves of Prunus laurocerasus were investigated. In the wax mixture, the triterpenoids ursolic acid and oleanolic acid as well as alkanes, fatty acids, aldehydes, primary alcohols and alcohol acetates were identified. The surface extraction of upper and lower leaf surfaces yielded 280 mg m−2 and 830 mg m−2, respectively. Protocols for the mechanical removal of waxes from the outermost layers of the cuticle were devised and evaluated. With the most selective of these methods, 130 mg m−2 of cuticular waxes could be removed from the adaxial surface before a sharp, physically resistant boundary was reached. Compounds thus obtained are interpreted as ‘epicuticular waxes’ with respect to their localization in a distinct layer on the surface of the cutin matrix. The epicuticular wax film can be transferred onto glass and visualized by scanning electron microscopy. Prunus laurocerasus epicuticular waxes consisted entirely of aliphatic compounds, whereas the remaining intracuticular waxes comprised 63% of triterpenoids. The ecological relevance of this layered structure for recognition by phytotrophic fungi and herbivorous insects that probe the surface composition for sign stimuli is discussed.
Physiological and photosynthetic plasticity in the amphibious, freshwater plant,Littorella uniflora, during the transition from aquatic to dry terrestrial environments
Authors: Robe W. E. , Griffiths H. 
Published: March 2003

ABSTRACTThe physiological and photosynthetic responses ofLittorella uniflora(L.) Ascherson, an amphibious macrophyte of isoetid life form, to rapid and prolonged emersion onto dry land, was studied at a reservoir. Water relations were little affected in the short term, but declining water potential and turgor pressure indicated water stress after flowering. High leaf lacunal CO2concentrations suggested continued CO2uptake from sediments. In contrast, a switch from Crassulacean acid metabolism (CAM) to C3photosynthesis was indicated by much lower levels of ΔH+(down minus dusk titratable acidity) and phosphoenolpyruvate carboxylase (PEPC) activity in new terrestrial leaves, 7–8‐fold higher activity of ribulose bisphosphate carboxylase oxygenase (Rubisco), and increased chlorophyll and soluble protein contents. Accumulated nitrate and amino acid pools were depleted, whereas storage of carbohydrates as soluble sugars, fructan and starch increased. Plant carbon and nitrogen isotope ratios (δ13C and δ15N) declined, perhaps reflecting changes in C fixation processes, N metabolism, and source C and N. In leaves of plants grown half‐emersed for an extended period, contrasting activities of PEPC and Rubisco were found in submersed and emersed portions. Overall,L. uniflorashowed considerable phenotypic plasticity, yet seemed to remain poised for re‐submersion; these characteristics could be adaptive in the unpredictable water margin habitat.
Strategies providing success in a variable habitat: II. Ecophysiology of photosynthesis of Cladophora glomerata
Authors: Ensminger I. , Hagen C. , Braune W. 
Published: March 2003

ABSTRACT Cladophora glomerata (L.) Kütz. is the dominant filamentous algae of the river Ilm, Thuringia, Germany. For most of the year it can be found at open as well as at shaded sites. Photosynthetic acclimation of C. glomerata to different light intensities was detected by chlorophyll fluorescence measurements and pigment analysis. Cladophora glomerata from highlight sites showed decreased values of efficiency of open photosystem II (Fv/Fm) as compared with C. glomerata from low‐light sites. Winter populations revealed higher Fv/Fm values than summer populations. A light‐induced decrease in efficiency of the closed photosystem II was observed at increasing irradiance intensities. The decrease was higher in C. glomerata from shaded sites compared with plants from open sites. Differences in the photosynthetic electron transport rate of different populations of C. glomerata were shown by photosynthesis–irradiance curves. Summer populations from high‐light sites yielded higher maximum electron transport rates than plants from low‐light sites, whereas winter populations exhibited significantly decreased values compared with the summer populations. Results of the analysis of photosynthetic pigments corresponded with data from chlorophyll fluorescence measurements. In addition to these long‐term acclimation effects, C. glomerata expressed its ability to cope with rapid changes in the light environment by the de‐epoxidation of violaxanthin during exposure to high light intensities.