bluuebunny/crossref_metadata_2025_split huggingface dataset:
THE INFLUENCE OF BURIAL AND DRY‐STORAGE UPON CYCLIC CHANGES IN DORMANCY, GERMINATION AND RESPONSE TO LIGHT IN SEEDS OF VARIOUS ARABLE WEEDS
Authors: FROUD‐WILLIAMS R. J. , DRENNAN D. S. H. , CHANCELLOR R.J. 
Published: May 2006

SummarySeeds of Alopecurus myosuroides, Bromus sterilis, Capsella bursa‐pastoris, Papaver rhoeas, Stellaria media, Veronica arvensis, Veronica persica and Viola arvensis were sown in soil at depths of 0, 25 and 150 mm. Seeds buried at 150 mm were exhumed at intervals of 3, 6, 12 and 15 months and incubated at an alternating temperature regime of 10/20 °C (16/8 h) or irradiated with light of various wavelengths prior to incubation.In general, shallow burial (25 mm) reduced seedling emergence except in the case of B. sterilis, which also germinated at a depth of 150 mm but failed to emerge.Cyclic changes in dormancy of buried seeds were observed. Although sensitivity to light was enchanced by burial, germination and response to light quality varied between seasons. Dormancy of most species, including the winter annuals A. myosuroides, Veronica persica and Viola arvensis, was least in autumn and most in summer. Papaver rhoeas was least dormant in spring and S. media was least dormant in summer. Generally, red light promoted germination whereas far‐red light or darkness was not stimulatory. However, A. myosuroides was more sensitive to far‐red light in autumn than at other times of the year.Natural day‐light promoted germination of A. myosuroides, S. media and Veronica arvensis. Germination of B. sterilis was delayed in natural daylight. Transfer of A. myosuroides, Papaver rhoeas, Veronica arvensis and Viola arvensis from darkness to daylight increased germination above that obtained under natural daylight.Germination of freshly collected seeds of Alopecurus myosuroides, Arrhenatherum elatius, Poa annua, Poa trivialis, Plantago major and Viola arvensis was promoted by short irradiations of red light. Dry‐storage did not affect germination of Alopecurus myosuroides, Poa annua, Plantago major or Viola arvensis, but did affect dormancy and light requirement of Poa trivialis. Burial of seeds of Alopecurus myosuroides, Poa trivialis and Plantago major increased their sensitivity to far‐red light.It is concluded that cyclic changes in seed dormancy and associated light sensitivity are determined seasonally and result from changing environmental factors and that they are of adaptive importance for survival.
FRANKIA SOURCE AFFECTS GROWTH, NODULATION AND NITROGEN FIXATION IN CASUARINA SPECIES
Authors: REDDELL PAUL , BOWEN G. D. 
Published: May 2006

SummaryTwo species of Casuarina [C. equisetifolia ssp. incana (Benth.) L.J. and C. cunninghamiana Miq.] differed in growth responses to inoculation with Frankia from five sources. Casuarina equisetifolia ssp. incana formed nodules with all five Frankia inocula whereas C. cunninghamiana formed nodules with only two. A range of response from ineffectiveness in N2 fixation to high effectiveness was observed between Casuarina species ‐ Frankia source combinations. Strains of Frankia highly effective on one species were frequently ineffective on the other. Effectiveness was related to nodule development after infection and to the ability of developed nodules to fix N2.
FORMATION OF EXTERNAL HYPHAE IN SOIL BY FOUR SPECIES OF VESICULAR‐ARBUSCULAR MYCORRHIZAL FUNGI
Authors: ABBOTT L. K. , ROBSON A. D. 
Published: May 2006

SummaryThe ability of several species of vesicular–arbuscular (VA) mycorrhizal fungi to form hyphae in soil was compared in two glasshouse experiments. We measured the length of hyphae in soil and related this to the length of infected root. Species of VA mycorrhizal fungi differed in the length of external hyphae produced per cm of infected root. Glomus fasciculatum (Thaxter sensu Gerd.) Gerd. and Trappe produced less external hyphae per cm infected root than did Gigaspora calospora (Nicol. and Gerd.) Gerd. at all harvest times and when inoculum was either placed in a band below the seed or mixed throughout the soil. Glomus tenue (Greenall) Hall and Acaulospora laevis Gerd. and Trappe both produced similar lengths of external hyphae per cm infected root to that formed by G. calospora.Differences among isolates of VA mycorrhizal fungi in the distribution of hyphae in soil may be as important as differences in the length of external hyphae when selecting fungi that are effective at increasing nutrient uptake.
FUNCTIONING OF VESICULAR–ARBUSCULAR MYCORRHIZAS UNDER FIELD CONDITIONS
Authors: FITTER A. H. 
Published: May 2006

SummaryAlthough VA mycorrhizas are easily demonstrated as mutualistic associations in pot culture, on the basis of reciprocal exchange of carbon and (mainly) phosphorus, unequivocal field demonstrations are less numerous. This may be due to incompetence of widely occurring fungal types, to inter‐plant connections by hyphae, which dissipate the benefit, to grazing of external hyphae, or to problems associated with root longevity. The action of mycorrhizal roots in improving plant water relations and promoting phosphate uptake under field conditions is considered in the light of these constraints. It is suggested that much greater effort is required in the investigation of mycorrhizal associations in the field.
EVIDENCE FOR AN ENDOGENOUS CYCLE OF DORMANCY IN DRY STORED SEEDS OF POA TRIVIALIS L.
Authors: FROUD‐WILLIAMS R. J. , HILTON JANET R. , DIXON J. 
Published: May 2006

SummarySeeds of Poa trivialis L. (rough meadow‐grass) were collected from two contrasting habitats during the summer of 1982. Collections from an arable population were obtained on three occasions and seeds from a grassland population were collected once. Although both populations responded similarly to various combinations of light, temperature and nitrate, the arable collections were markedly more dormant.Loss of dormancy of the grassland and early arable populations one month after collection was rapid in seeds stored at ambient temperatures and at 4 °C but more delayed in those stored at 23 °C. Despite a gradual loss of dormancy during storage, cyclic changes in dormancy were also evident, especially at 23 °C. The percentage germination of the various collections 7 d after incubation following storage at 23 °C increased over the first three months, but declined following six and 12 months storage and increased again after 15 months storage. At 4 °C the late arable collection lost dormancy more slowly than the other two collections and germination was greatest after six months storage; a reduction in percentage germination occurred after twelve months.Seeds buried at 5 and 15 cm showed cyclic changes of dormancy, being least dormant in autumn and spring, but most dormant in summer, corresponding to the natural periodicity of germination.It is proposed that cyclic changes in dormancy are regulated by endogenous rhythms and seasonal changes of temperature. The ecological implications of the germination behaviour of this species in various habitats are discussed.
EROSION OF WAXES FROM LEAF SURFACES BY SIMULATED RAIN
Authors: BAKER E. A. , HUNT GRACE M. 
Published: May 2006

SummaryEffects of simulated rain on the epicuticular wax of glaucous leaves have been studied. Droplets (250 to 400 μm) travelling at low or medium velocity (0.25 to 5 m s−1) fractured the dendrites and tubes on leaves of Brassica spp., the tubes on Eucalyptus globulus Labillardere and the ribbons on the adaxial surfaces of Pisum sativum L. and Fragaria ananassa Duchesne. Rates of erosion for Brassica and E. globulus leaves were high during an initial application equivalent to 1 mm rainfall but declined markedly with extended exposure. In contrast, erosion from P. sativum and F. ananassa proceeded at a fairly uniform rate throughout the exposure period. The composition of the detached wax deposits was identical with that of the intact leaf wax for Brassica species but differed for the other species. The practical consequences of wax erosion of field crops are considered.
CALCIUM‐CONTAINING CRYSTALS IN TELFAIRIA HOOKER (CUCURBITACEAE)
Authors: OKOLI 'BOSA E. , McEUEN A. R. 
Published: May 2006

SummaryPolarized light and scanning electron microscopy were used to examine the distribution, location and form of crystals in the leaves, probracts, stems, flowers and seed‐coats of Telfairia pedata (Sims) Hooker and T. occidentalis Hooker fil. Energy‐dispersive X‐ray analysis showed that calcium is the primary crystal cation. Histochemical tests confirmed that the crystals are mainly calcium oxalate and these are particularly abundant around and within the vascular tissues. Cystolith ‐ like crystals of calcium carbonate are also numerous at the bases of macrohairs and as heavy incrustations within the midrib and major veins of mature leaves. The crystal types include solitary, acicular, druse (cluster) and combinations of two or more of these. Substantial amounts of soluble oxalate were also found to be present, especially in the leaf laminae of T. occidentalis. The total oxalate contents of the edible portions of T. occidentalis were determined and compared with values published for other vegetables.
MODIFICATION OF RESPIRATION AND CARBOHYDRATE STATUS OF BARLEY ROOTS BY SELECTIVE PRUNING
Authors: FARRAR J. F. , JONES C. L. 
Published: May 2006

SummaryBarley plants were pruned selectively to give root systems with relative growth rates that varied two‐fold. Rates of elongation of the seminal root axes were unaffected. Respiration rate was highest in the fast‐growing roots, but there was no change in the proportion of carbon entering the root that was subsequently lost in respiration. Soluble sugar contents were greater in fast than in slow growing plants, but the rate of uptake of exogenously supplied sucrose and glutamine was highest where root growth rate was reduced by pruning of the shoot. Turnover of sugars in the vacuole was slower in roots with reduced growth rate.
ABSORPTION OF NITROGEN DIOXIDE BY SUNFLOWER PLANTS GROWN AT VARIOUS LEVELS OF NITRATE
Authors: OKANO K. , TOTSUKA T. 
Published: May 2006

SummaryThe effect of varied levels of nitrate on the absorption of atmospheric nitrogen dioxide (NO2) by sunflower (Helianthus annus L.) plants was investigated by using a 15N dilution method. Growth of the plants was greatest at 5 mM nitrate, with less growth at 15 mM nitrate and a considerable reduction at zero nitrate. The total amount of NO2‐nitrogen absorbed by the plant depended on the plant size and total leaf area.Nitrate supply did not influence the rate of absorption of NO2 by the plants when exposed to 0.3 μl l−1 NO2. On the contrary, when the plants were exposed to 2.0 μl l−1 NO2, the absorption rate was significantly lower for the plants grown at zero nitrate compared with those grown at 5 or 15 mM nitrate. The lower rate of NO2 absorption in the nitrate‐deficient plants was not due to the changes in stomatal resistance or stomatal density of the leaves, but could have been due to an increase in mesophyll resistance resulting from accumulation of high levels of nitrite in the leaf tissues. Nitrogen dioxide at 0.3 μl l−1 exerted a nutritional effect on the nitrate‐deficient plants, while NO2 at 2.0 μl l−1 acted as a toxic air pollutant on the plants at all the levels of nitrate supplied.
PATTERNS IN THE GEOGRAPHICAL DISTRIBUTION OF THE EARLY FLANDRIAN CORYLUS RISE IN SOUTHWEST SCOTLAND
Authors: BOYD W. E. , DICKSON J. H. 
Published: May 2006

SummaryThe timing of the early Flandrian Corylus rise in southwest Scotland is discussed, with reference to radiocarbon dates from nine sites. These sites cover a range of geomorphological regions and sediment types.The Corylus rise on the mainland of southwest Scotland appears to have occurred with some degree of synchroneity over a wide area at around 9200 to 9300 radiocarbon years before present. However, two dates from the island of Arran in the Firth of Clyde are considerably younger, and the Corylus rise on Arran appears to have occurred approximately half a millenium later than on the surrounding mainland. This is explicable in terms of the relative isolation of Arran from the mainland; the surrounding deep‐water troughs effectively halted the migration of Corylus. The later, apparently ‘normal’Corylus rise on Arran may relate to Mesolithic human activity. A similar, but shorter interval separates the date of the late Corylus rise on the island of Mull from that of the Corylus rise on the surrounding mainland.
Incidence of Atrial Fibrillation in Heart Transplant Patients: Long‐Term Follow‐Up
Authors: KHAN MOHAMMED , KALAHASTI VIDYASAGAR , RAJAGOPAL VIVEK , KHAYKIN YAARIV , WAZNI OUSSAMA , ALMAHAMEED SOUFIAN , ZUZEK RYAN , SHAH TEHMEENA , LAKKIREDDY DHANUMJAYA , SALIBA WALID , SCHWEIKERT ROBERT , CUMMINGS JENNIFER , MARTIN DAVID O , NATALE ANDREA 
Published: May 2006

Background: The incidence of atrial fibrillation (AF) in heart transplant patients has not been well documented. Methods: To determine the incidence of AF in a cohort of patients undergoing cardiac transplantation, clinical data were obtained from a prospectively collected database for all consecutive orthotopic heart transplantation (OHT) patients and for all consecutive coronary artery bypass graft (CABG) surgery patients between January 1984 and March 2004 at our institution. A cohort of 1,714 OHT patients and low‐risk CABG (normal ejection fraction [EF] and no left ventricular hypertrophy [LVH]) patients were age‐ and sex‐matched. Results: The average age in the two groups was 56 ± 7 years with 87% male and 81% white race and body mass index (BMI) of 26 ± 4. There were 3 cases of AF (0.3%) in the OHT group and 757 cases of AF (21%) in the low‐risk CABG group. The strongest independent predictor of freedom from postoperative AF was having had a transplant (odds ratio [OR] 96, 95% confidence interval [CI] 13–720). The incidence of AF, atrial flutter (AFL), and supraventricular tachycardia (SVT) in OHT was 0.33, 2.8%, and 1.3%, respectively. Given that incidence of AF, AFL, and SVT in historical post‐CABG population is 25%, 17%, and 4.3%, transplanted patients appear to have lower incidence of AF, AFL, and SVT than the reference population. Consistent with this, transplanted patients underwent few ablation procedures for atrial arrhythmias. Additionally, the three patients with AF had bicaval anastomoses suggesting the possibility of PACs originating in the donor superior vena cava (SVC) or IVC (inferior vena cava) initiating AF in these patients. Conclusions: In a cohort study of transplant and low‐risk CABG patients, the strongest independent predictor of freedom from AF is having undergone transplant surgery. One potential explanation for the markedly lower incidence of AF may be effective isolation of thoracic veins with documented cases retaining the native SVC.
Dental implants placed in expanded narrow edentulous ridges with the Extension Crest® device
Authors: Chiapasco Matteo , Ferrini Francesco , Casentini Paolo , Accardi Stefano , Zaniboni Marco 
Published: May 2006

AbstractObjective: This study has been designed to evaluate the capability of a new surgical device (Extension Crest®) to widen narrow edentulous alveolar ridges and to allow a correct placement of endosseous implants in horizontally atrophied sites.Material and methods: Forty‐five patients, 20 males and 25 females, aged 20–66 years, affected by edentulism associated to horizontal resorption of the ridges, were treated by means of a sagittal osteotomy and expansion of the ridge with a new surgical device (Extension Crest®) to obtain a wider bony base for ideal implant placement. In the same procedure in 33 patients, and 1 week afterwards in 12 patients, 110 endosseous titanium implants (ITI TE®) were placed. Three to four months later, the patients were rehabilitated with implant‐supported prostheses.Results: The success rate of the expansion technique was 97.8%. A total of 110 implants were inserted in the expanded ridges. The mean follow‐up after the start of prosthetic loading was 20.4 months. Three implants were removed before the start of prosthetic loading, because of non‐integration, while no other implants failed after the completion of the prosthetic rehabilitation. Three implants, although integrated and in function, did not fulfill success criteria: cumulative success and survival rates at the end of the observation period were 95.4% and 97.3%, respectively.Conclusion: Within the limits of this study, this technique appeared to be reliable and simple, with reduction of morbidity and times of dental rehabilitation as compared with other techniques such as autogenous bone grafts and guided bone regeneration. Survival and success rates of implants placed in the treated areas are consistent with those placed in native bone.
Gnathostomiasis: Import from Laos
Authors: Hennies Felix , Jappe Uta , Kapaun Annette , Enk Alexander 
Published: May 2006

SummaryGnathostomiasis is a nematode infestation endemic in Southeast Asia, which can involve multiple organs including the liver, eyes, gastrointestinal tract and CNS. The most common manifestation is recurrent migratory subcutaneous swellings which can appear anywhere on the body and are accompanied by pruritus and systemic symptoms such as low‐grade fever, loss of appetite and nausea. The diagnosis is based on the clinical picture, history of travel, peripheral blood eosinophilia and the determination of agent‐specific antibody levels. The standard treatment is albendazole. We present a 37‐year‐old Laotian woman, who had lived in Germany for 17 years, but developed recurrent swelling of the cheek following a visit to Laos. Because of the typical clinical findings, the history of a visit to Laos, and the presence of specific anti‐Gnathostoma antibodies on Western blot, the diagnosis of cutaneous gnathostomiasis was made.
Diffusion of Green Fluorescent Protein in Three Cell Environments in
Escherichia Coli
Authors: Mullineaux Conrad W. , Nenninger Anja , Ray Nicola , Robinson Colin 
Published: May 2006

ABSTRACT

Surprisingly little is known about the physical environment inside a prokaryotic cell. Knowledge of the rates at which proteins and other cell components can diffuse is crucial for the understanding of a cell as a physical system. There have been numerous measurements of diffusion coefficients in eukaryotic cells by using fluorescence recovery after photobleaching (FRAP) and related techniques. Much less information is available about diffusion coefficients in prokaryotic cells, which differ from eukaryotic cells in a number of significant respects. We have used FRAP to observe the diffusion of green fluorescent protein (GFP) in cells of
Escherichia coli
elongated by growth in the presence of cephalexin. GFP was expressed in the cytoplasm, exported into the periplasm using the twin-arginine translocation (Tat) system, or fused to an integral plasma membrane protein (TatA). We show that TatA-GFP diffuses in the plasma membrane with a diffusion coefficient comparable to that of a typical eukaryotic membrane protein. A previous report showed a very low rate of protein diffusion in the
E. coli
periplasm. However, we measured a GFP diffusion coefficient only slightly smaller in the periplasm than that in the cytoplasm, showing that both cell compartments are relatively fluid environments.
Ecf, an Alternative Sigma Factor from
Neisseria gonorrhoeae
, Controls Expression of
msrAB
, Which Encodes Methionine Sulfoxide Reductase
Authors: Gunesekere Ishara C. , Kahler Charlene M. , Ryan Catherine S. , Snyder Lori A. S. , Saunders Nigel J. , Rood Julian I. , Davies John K. 
Published: May 2006

ABSTRACT

A DNA microarray was used to identify genes transcribed in
Neisseria gonorrhoeae
using Ecf, an alternative sigma factor. No differences between the transcriptional profiles of strain FA1090 and a mutant where
ecf
had been inactivated could be detected when both were grown in vitro. We therefore constructed a gonococcal strain in which Ecf can be overexpressed. Some differentially expressed genes are clustered with
ecf
on the genome and appear to form a single transcriptional unit. Expression of the gene encoding MsrAB, which possesses methionine sulfoxide reductase activity, was also dependent on Ecf, suggesting that the regulon responds to oxidative damage. Western blotting confirmed that the increased level of MsrAB protein is dependent on the presence of Ecf.
Loss- and Gain-of-Function Mutations in the F1-HAMP Region of theEscherichia coliAerotaxis Transducer Aer
Authors: del Carmen Burón-Barral Maria , Gosink Khoosheh K. , Parkinson John S. 
Published: May 2006

ABSTRACTTheEscherichia coliAer protein contains an N-terminal PAS domain that binds flavin adenine dinucleotide (FAD), senses aerotactic stimuli, and communicates with the output signaling domain. To explore the roles of the intervening F1 and HAMP segments in Aer signaling, we isolated plasmid-borne aerotaxis-defective mutations in a host strain lacking all chemoreceptors of the methyl-accepting chemotaxis protein (MCP) family. Under these conditions, Aer alone established the cell's run/tumble swimming pattern and modulated that behavior in response to oxygen gradients. We found two classes of Aer mutants: null and clockwise (CW) biased. Most mutant proteins exhibited the null phenotype: failure to elicit CW flagellar rotation, no aerosensing behavior in MCP-containing hosts, and no apparent FAD-binding ability. However, null mutants had low Aer expression levels caused by rapid degradation of apparently nonnative subunits. Their functional defects probably reflect the absence of a protein product. In contrast, CW-biased mutant proteins exhibited normal expression levels, wild-type FAD binding, and robust aerosensing behavior in MCP-containing hosts. The CW lesions evidently shift unstimulated Aer output to the CW signaling state but do not block the Aer input-output pathway. The distribution and properties of null and CW-biased mutations suggest that the Aer PAS domain may engage in two different interactions with HAMP and the HAMP-proximal signaling domain: one needed for Aer maturation and another for promoting CW output from the Aer signaling domain. Most aerotaxis-defective null mutations in these regions seemed to affect maturation only, indicating that these two interactions involve structurally distinct determinants.
WrbA fromEscherichia coliandArchaeoglobus fulgidusIs an NAD(P)H:Quinone Oxidoreductase
Authors: Patridge Eric V. , Ferry James G. 
Published: May 2006

ABSTRACTWrbA (tryptophan [W] repressor-binding protein) was discovered inEscherichia coli, where it was proposed to play a role in regulation of the tryptophan operon; however, this has been put in question, leaving the function unknown. Here we report a phylogenetic analysis of 30 sequences which indicated that WrbA is the prototype of a distinct family of flavoproteins which exists in a diversity of cell types across all three domains of life and includes documented NAD(P)H:quinone oxidoreductases (NQOs) from theFungiandViridiplantaekingdoms. Biochemical characterization of the prototypic WrbA protein fromE. coliand WrbA fromArchaeoglobus fulgidus, a hyperthermophilic species from theArchaeadomain, shows that these enzymes have NQO activity, suggesting that this activity is a defining characteristic of the WrbA family that we designate a new type of NQO (type IV). ForE. coliWrbA, theKmNADHwas 14 ± 0.43 μM and theKmbenzoquinonewas 5.8 ± 0.12 μM. ForA. fulgidusWrbA, theKmNADHwas 19 ± 1.7 μM and theKmbenzoquinonewas 37 ± 3.6 μM. Both enzymes were found to be homodimeric by gel filtration chromatography and homotetrameric by dynamic light scattering and to contain one flavin mononucleotide molecule per monomer. The NQO activity of each enzyme is retained over a broad pH range, and apparent initial velocities indicate that maximal activities are comparable to the optimum growth temperature for the respective organisms. The results are discussed and implicate WrbA in the two-electron reduction of quinones, protecting against oxidative stress.