bluuebunny/crossref_metadata_2025_split huggingface dataset:
Radial growth and climate responses of white oak (Quercus alba) and northern red oak (Quercus rubra) at the northern distribution limit of white oak in Quebec, Canada
Authors: Tardif J. C. , Conciatori F. , Nantel P. , Gagnon D. 
Published: June 2006

AbstractAim The objectives of this study were: (1) to compare radial growth patterns between white oak (Quercus albaL.) and northern red oak (Quercus rubraL.) growing at the northern distribution limit of white oak; and (2) to assess if the radial growth of white oak at its northern distribution limit is controlled by cold temperature.Location The study was conducted in three regions of the Ottawa valley in southern Québec. All stands selected were located at the northern limit of distribution ofQ. alba.Methods Twelve mixed red and white oak stands were sampled and increment cores were extracted for radial growth analyses. For each oak species, 12 chronologies were derived from tree‐ring measurement (residual chronologies). Principal components analysis and redundancy analysis were used to highlight the difference between radial growth in both species and to determine their radial growth–climate association.Results There was little difference between the radial growth of each species;Q. alba, however, exhibits more year‐to‐year variation in growth thanQ. rubra. More than 65% of the variance in radial growth was shared among sites and species. Both species showed a similar response to climate, which suggested that the limit of distribution ofQ. albamight not be determined by effects on growth. Both species had a classic response to climate and drought in the early growing season.Main conclusions The northern distribution limit ofQ. albadoes not appear to be directly controlled by effects on growth processes as indicated by the similarities in radial growth and response to climate between the two species. The location of the stands on southern aspects suggested that cold temperature could have been a major factor controlling the distribution limit ofQ. alba. However, it is speculated that stands growing on southern aspects may be more prone to forest fires or to drought, which would favour the maintenance and establishment of oaks, and ofQ. albain particular. Models relating the northern distribution limits of species to broad climate parameters like annual mean temperature will need to be reviewed to incorporate more biologically relevant information. Such assessments will in turn provide better estimates of the effect of climate changes on species distribution.
Evaluation of a nurse consultant's clinical activities and the search for patient outcomes in critical care
Authors: Fairley Debra , Closs S. Jose 
Published: June 2006

Aim.  To describe the actual clinical activities undertaken by a critical care nurse consultant in an eight‐bedded adult surgical high dependency unit within a large NHS Teaching Hospitals NHS Trust.Background.  In the United Kingdom, the first critical care nurse consultants were approved in 2000 following the Department of Health's (1999) revised career structure for nurses. Expert practice is a core function of the role although the nature of expert practice in the context of critical care is unclear. Expert practice is often deemed to be a feature of advanced practice and although a number of studies have investigated this in context of critical care, there is little insight into the nature of advanced practitioners’ clinical practice and how it might influence patient outcome.Design methods.  A diary was used by a critical care nurse consultant to record activity during scheduled clinical sessions. Data were collected for four months: 39 sessions were evaluated. Qualitative data were content analysed and coded into categories. Clinical activities were coded, categorized and analysed using SPSS 11.0 for windows (SPSS Inc., Chicago, IL, USA).Findings.  Clinical activities included direct care activities, clinical leadership, education and training. Two main themes emerged from the qualitative data and were categorized as clinical reasoning and clinical instruction. Clinical activities arising from clinical reasoning and clinical instruction were aimed at minimizing risk and the provision of quality care. In doing this, one of the outcomes was the detection and resolution of untoward clinical occurrences.Conclusion.  The level of achievement – or end point – of clinical activities was that the patient was established in ‘a state free from risk or harm that optimises rehabilitation’. ‘A state free from risk or harm that optimizes rehabilitation’ might be one outcome reflecting the needs of individual critically ill patients that is sensitive to individual nursing contribution.Relevance to clinical practice.  There is increasing pressure on health‐care professionals to identify and measure their individual impact on the outcome of patients. This study adds further insight into the complexities associated with evaluating the influence of individual contribution on patient outcome, especially when it is characterized by complex processes involving clinical judgement and decision‐making.
Change on the horizon: issues and concerns of neophyte advanced healthcare practitioners
Authors: Williamson Graham R , Webb Christine , Abelson‐Mitchell Nadine , Cooper Simon 
Published: June 2006

Aims and objectives.  The aim was to interview new entrants to a Master's level programme of educational preparation for advanced healthcare practice roles. The objectives were to gain an understanding of their issues and concerns as they looked ahead to their future development and to illuminate issues concerning their experiences as students and as employees.Background.  As advanced practice roles become more widespread in the United Kingdom and abroad, nurses and other healthcare professionals are becoming more involved in innovation and service development and experiencing greater autonomy in many areas, particularly in regard to clinical examination and diagnosis.Design.  A qualitative design was employed to illuminate issues and concerns of new students on a Master's degree programme of educational preparation for advanced healthcare practitioners.Methods.  Two focus group interviews were conducted in 2004. Sixteen students from two programme cohorts participated in the two groups.Findings.  Two main themes were outlined. These were: ‘opportunities for development’ and ‘time pressures’. Subcategories within these two themes are also discussed.Conclusions.  Students undertaking Master's level preparation for advanced healthcare practitioner roles perceive personal and professional benefits and opportunities to develop innovative services to improve patient care as accruing from the programme. These opportunities and benefits were related to the United Kingdom national health policy agenda. Some role difficulties were experienced. The additional burdens that the programme of study provided were an issue for some, but these were perceived as a temporary problem, worth undergoing for the likely long‐term benefits.Relevance to clinical practice.  Students undertaking educational preparation for advanced practice roles see themselves as innovators, specifically aiming to develop and improve aspects of service provision. Education for advanced practice roles should not be undertaken lightly, but can equip students with various skills, particularly regarding clinical assessment, and these skills should underpin practitioners’ autonomy.
The Legionella pneumophila IcmS–LvgA protein complex is important for Dot/Icm‐dependent intracellular growth
Authors: Vincent Carr D. , Vogel Joseph P. 
Published: June 2006

SummaryMany bacterial pathogens require a functional type IV secretion system (T4SS) for virulence. Legionella pneumophila, the causative agent of Legionnaires' disease, employs the Dot/Icm T4SS to inject a large number of protein substrates into its host, thereby altering phagosome trafficking. The L. pneumophila T4SS substrate SdeA has been shown to require the accessory factor IcmS for its export. IcmS, defined as a type IV adaptor, exists as a heterodimer with IcmW and this complex functions in a manner similar to a type III secretion chaperone. Here we report an interaction between IcmS and the previously identified virulence factor LvgA. Similar to the icmS mutant, the lvgA mutant appears to assemble a fully functional Dot/Icm complex. Both LvgA and IcmS are small, acidic proteins localized to the cytoplasm and are not exported by the Dot/Icm system, suggesting they form a novel type IV adaptor complex. Inactivation of lvgA causes a minimal defect in growth in the human monocytic cell line U937 and the environmental host Acanthamoeba castellanii. However, the lvgA mutant was severely attenuated for intracellular growth of L. pneumophila in mouse macrophages, suggesting LvgA may be a critical factor that confers host specificity.
An rplKΔ29‐PALG‐32 mutation leads to reduced expression of the regulatory genes ccaR and claR and very low transcription of the ceaS2 gene for clavulanic acid biosynthesis in Streptomyces clavuligerus
Authors: Gomez‐Escribano Juan Pablo , Liras Paloma , Pisabarro Agustín , Martín Juan F. 
Published: June 2006

SummaryThe transcriptional and translational control of the biosynthesis of the β‐lactamase inhibitor clavulanic acid is a subject of great scientific and industrial interest. To study the role of the ribosomal protein L11 on control of clavulanic acid gene transcription, the DNA region aspC‐tRNAtrp‐secE‐rplK‐rplA‐rplJ‐rplL of Streptomyces clavuligerus was cloned and characterized. An S. clavuligerus rplKΔPALG mutant, with an internal 12 nucleotides in‐frame deletion in the rplK gene, encoding the L11 (RplK) ribosomal protein lacking amino acids 29PALG32, was constructed by gene replacement. This deletion alters the L11 N‐terminal domain that interacts with the RelA and class I releasing factors‐mediated translational termination. The mutant grew well, showed threefold higher resistance to thiostrepton, did not form spores and lacked diffusible brown pigments, as compared with the wild‐type strain. The wild‐type phenotype was recovered by complementation with the native rplK gene. S. clavuligerus rplKΔPALG produced reduced levels of clavulanic acid (15–26% as compared with the wild type) and cephamycin C (40–50%) in cultures grown in defined SA and complex TSB media. The decreased yields resulted from an impaired transcription of the regulatory genes ccaR and claR and the cefD and ceaS2 genes for cephamycin and clavulanic acid biosynthesis respectively. Expression of ceaS2 encoding carboxyethylarginine synthase (CEAS), the precursor‐committing enzyme for clavulanic acid biosynthesis, was particularly affected in this mutant. In the wild‐type strain polyphosphorylated nucleotides peaked at 36–48 h of growth in SA cultures whereas expression of the cephamycin and clavulanic acid genes occurred 12–24 h earlier than the increase in ppGpp indicating that there is no strict correlation between the peak of ppGpp and the onset of transcription of the clavulanic acid and cephamycin C biosynthesis. The drastic effect of the rplKΔPALG mutation on the onset of expression of the ceaS2 and the regulatory ccaR and claR genes and the lack of correlation with ppGpp levels suggest that the onset of transcription of these genes is modulated by the conformational alteration of the N‐terminal region of L11 probably by interaction with the nascent peptide releasing factors and with RelA.
Effects of Rubisco kinetics and Rubisco activation state on the temperature dependence of the photosynthetic rate in spinach leaves from contrasting growth temperatures
Authors: YAMORI WATARU , SUZUKI KENSAKU , NOGUCHI KO , NAKAI MASATO , TERASHIMA ICHIRO 
Published: June 2006

ABSTRACTRecently, several studies reported that the optimum temperature for the initial slope [IS(Ci)] of the light‐saturated photosynthetic rate (A) versus intercellular CO2 concentration (Ci) curve changed, depending on the growth temperature. However, few studies compare IS(Ci) with ribulose 1,5‐bisphosphate carboxylase/oxygenase (Rubisco) properties. Here, we assessed Rubisco activation state and in vitro Rubisco kinetics, the main determinants of IS(Ci), in spinach leaves grown at 30/25 [high temperature (HT)] and 15/10 °C [low temperature (LT)]. We measured Rubisco activation state and A at a CO2 concentration of 360 µL L−1 (A360) at various temperatures. In both HT and LT leaves, the Rubisco activation state decreased with increasing temperatures above the optimum temperatures for A360, while the activation state remained high at lower temperatures. To compare Rubisco characteristics, temperature dependences of the maximum rate of ribulose 1,5‐bisphosphate (RuBP) carboxylation (Vcmax), specificity factor (Sc/o) and thermal stability were examined. We also examined Vcmax and thermal stability in the leaves that were transferred from HT to LT conditions and were subsequently kept under LT conditions for 2 weeks (HL). Rubisco purified from HT, LT and HL leaves are called HT, LT and HL Rubisco, respectively. Thermal stabilities of LT and HL Rubisco were similar and lower than that of HT Rubisco. Both Vcmax and Sc/o in LT Rubisco were higher than those of HT Rubisco at low temperatures, while these were lower at high temperatures. Vcmax in HL Rubisco were similar to those of LT Rubisco at low temperatures, and to those of HT Rubisco at high temperatures. The predicted photosynthetic rates, taking account of the Rubisco kinetics and the Rubisco activation state, agreed well with A360 in both HT and LT leaves. This study suggests that photosynthetic performance is largely determined by the Rubisco kinetics at low temperature and by Rubisco Kinetics and the Rubisco activation state at high temperature.
Mathematical review of literature to assess alternative electron transports and interphotosystem excitation partitioning of steady‐state C3photosynthesis under limiting light
Authors: YIN XINYOU , HARBINSON JEREMY , STRUIK PAUL C. 
Published: June 2006

ABSTRACTLinear whole‐chain electron (e–) transport plays a dominant role in generating NADPH and ATP required for carbon fixation in chloroplasts. However, other e–pathways may be present to contribute to the flexibility of e–transport in meeting demands by various downstream metabolic processes. The estimation of the fluxes of these alternative pathwaysin vivois difficult, as they are not amenable to direct experimental measurement. A recently developed model based on the generalized stoichiometry for the chloroplast e–transport pathways makes it possible to indirectly but quantitatively assess the fractions of e–that follow the alternative pathways. This model approach is used to review data from the literature on concurrent measurements of gas exchange and chlorophyll (Chl) fluorescence under steady‐state, limiting light, non‐photorespiratory conditions. The review suggests possiblein vivooccurrence of cyclic e–transport (CET) under such conditions. About 10% of e–from the reduced ferredoxin follow the pseudocyclic mode, notably in support of nitrate reduction. The estimated fraction of e–from the reduced plastoquinone that follows the Q‐cycle (fQ) depends on the number of protons required per ATP synthesis. Our model approach also allows the excitation partitioning to photosystem II (PSII) to be assessed quantitatively. Most important, the model helps assess the limit value to uncertain physiological parameters and answer the ‘what‐if’ question with regard to the effect of non‐measured processes or measurement uncertainties on the estimations of alternative e–transports.
On the induction of volatile organic compound emissions by plants as consequence of wounding or fluctuations of light and temperature
Authors: LORETO FRANCESCO , BARTA CSENGELE , BRILLI FEDERICO , NOGUES ISABEL 
Published: June 2006

ABSTRACTAmong the volatile organic compounds (VOCs) emitted by plants, some are characteristic of stress conditions, but their biosynthesis and the metabolic and environmental control over the emission are still unclear. We performed experiments to clarify whether (1) the emission following wounding can occur at distance from the wounding site, from VOC pools subjected to metabolic signals; and (2) the emission of biogenic VOCs generated by membrane damage (e.g. consequent to wounding or ozone exposure) can also be induced by exposure to high light and high temperature, recurrent in nature. In Phragmites australis, leaf cutting caused large and rapid bursts of acetaldehyde both at the cutting site and on parts of the cut leaf distant from the cutting site. This emission was preceded by a transient stomatal opening and did not occur in conditions preventing stomatal opening. This suggests the presence of a large pool of leaf acetaldehyde whose release is under stomatal control. VOCs other than isoprene, particularly acetaldehyde and (E)‐2‐hexenal, one of the C‐6 compounds formed by the denaturation of membrane lipids, were released by leaves exposed to high temperature and high light. The high‐temperature treatment (45 °C) also caused a rapid stimulation and then a decay of isoprene emission in Phragmites leaves. Isoprene recovered to the original emission level after suspending the high‐temperature treatment, suggesting a temporary deficit of photosynthetically formed substrate under high temperature. Emission of C‐6 compounds was slowly induced by high temperature, and remained high, indicating that membrane denaturation occurs also after suspending the high‐temperature treatment. Conversely, the emission of C‐6 compounds was limited to the high‐light episode in Phragmites. This suggests that a membrane denaturation may also occur in conditions that do not damage other important plant processes such as the photochemistry of photosynthesis of photoinhibition‐insensitive plants. In the photoinhibition‐sensitive Arabidopsis thaliana mutant NPQ1, a large but transient emission of (E)‐2‐hexenal was also observed a few minutes after the high‐light treatment, indicating extensive damage to the membranes. However, (E)‐2‐hexenal emission was not observed in Arabidopsis plants fumigated with isoprene during the high‐light treatment. This confirms that isoprene can effectively protect cellular membranes from denaturation. Our study indicates that large, though often transient, VOC emissions by plants occur in nature. In particular, we demonstrate that VOCs can be released by much larger tissues than those wounded and that even fluctuations of light and temperature regularly observed in nature can induce their emissions. This knowledge adds information that is useful for the parameterization of the emissions and for the estimate of biogenic VOC load in the atmosphere.
Variation in feeding rate of the intertidal mudsnail Hydrobia ulvae in relation to the tidal cycle
Authors: Barnes Richard S. K. 
Published: June 2006

AbstractDeposit feeding in the coastal epibenthic mudsnail Hydrobia ulvae, as estimated by egestion rate, varies in relation to the tidal cycle. In nature, feeding is maximal when the snails are covered by tidal water; after exposure, feeding reduces slightly but significantly whilst the sediment surface remains damp; and it is minor or ceases whilst the snails are buried in pits in the drying sediment. Within each of these three phases, however, egestion rate remains unchanged both in relation to phase duration, and with temperature over an ambient range of 18–30 °C (mean 24 °C). These findings form another example of disagreement between field and laboratory results on feeding in Hydrobia.
Variability in the nutritional value of the major copepods in Cape Cod Bay (Massachusetts, USA) with implications for right whales
Authors: DeLorenzo Costa Amy , Durbin Edward G. , Mayo Charles A. 
Published: June 2006

AbstractThe North Atlantic right whale, a seriously endangered species, is found in Cape Cod Bay (Massachusetts, USA) during the winter and early spring. During their residency in these waters, these whales are frequently observed feeding. This study evaluated spatial and temporal changes in the chemical composition (carbon weight and C/N ratio) of the food resource targeted by the right whales in Cape Cod Bay. The three taxa measured (Centropages typicus, Pseudocalanus spp., and Calanus finmarchicus) had highly variable chemical compositions resulting from the different life strategies and from fluctuations in their surrounding environment. The impact of seasonal variability in the energy densities of the food resource of right whales was calculated and compared to the energetic requirements of these whales. Calculations indicated that differences in the nutritional content of the zooplankton prey in Cape Cod Bay could have a considerable effect on the nutrition available to the right whales. Therefore, it is likely that using more precise estimates of the energetic densities of the prey of right whales would lead to a re‐evaluation of the adequacy of the food resource available to these whales in the North Atlantic.
A case study of mollusc and polychaete soft‐bottom assemblages submitted to sedimentary instability in the Mediterranean Sea
Authors: Cosentino Andrea , Giacobbe Salvatore 
Published: June 2006

AbstractIn the Strait of Messina (Sicily, Central Mediterranean Sea) strong tidal currents, very irregular hydrological regime and related solid load, and local seismic activity cause sediment instability; this area represents therefore a case‐study of a naturally disturbed soft‐bottom environment. In this paper, mollusc and polychaete assemblages of the northern part of the Strait were described. Composition, community structure, eco‐ethological features, trophic guilds and sediment‐type relationships were studied in 64 stations sampled located between 3.5 and 50 m depth in October 1992 by means of a Van Veen grab. A total of 131 species (65 molluscs and 66 polychaetes) were identified. A dense population of the tubicolous polychaete Ditrupa arietina was recognized, together with the occurrence of other species tied to a high sedimentation rate, such as Corbula gibba and Tellina distorta, as well as widespread, mud‐tolerant species (e.g.Chone spp., Hyalinoecia tubicola). Diversity (H′) showed a peak at intermediate depths (10/20 m) and a clear decrease beyond this depth, corresponding to the Ditrupa core population. Multivariate comparison between sediment features and community composition throughout the bathymetric gradient showed a narrow ecocline between two environments subjected to opposite hydrodynamic constraints. In the shallower zone, a wide typology of trophic‐ethological guilds was related to community patchiness, in contrast to a greater functional uniformity of the deeper assemblage, dominated by sessile, semi‐infaunal suspension feeders. A possible role played by a phase of increased rainfall to increase bottom instability, locally emphasized by a previous human activity, is also discussed.