bluuebunny/crossref_metadata_2025 huggingface dataset:
Estimating the internal conductance to CO2 movement
Authors: Warren Charles
Published: May 2006

The concentration of CO2 in the chloroplast is less than atmospheric owing to a series of gas-phase and liquid-phase resistances. For a long time it was assumed that the concentration of CO2 in the chloroplasts is the same as in the intercellular spaces (e.g. as measured by gas exchange). There is mounting evidence that this assumption is invalid and that CO2 concentrations in the chloroplasts are significantly less than intercellular CO2. It is now generally accepted that internal conductance (gi) is a significant limitation to photosynthesis, often as large as that due to stomata. Internal conductance describes this decrease in CO2 concentration between the intercellular spaces and chloroplasts as a function of net photosynthesis [gi = A / (Ci – Cc)]. Internal conductance is commonly estimated by simultaneous measurements of gas exchange and chlorophyll a fluorescence or instantaneous discrimination against 13CO2. These common methods are complemented by three alternative methods based on (a) the difference between intercellular and chloroplastic CO2 photocompensation points, (b) the curvature of an A / Ci curve, and (c) the initial slope of an A / Ci curve v. the estimated initial slope of an A / Cc curve. The theoretical basis and protocols for estimating internal conductance are described. The common methods have poor precision with relative standard deviations commonly > 10%; much less is known of the precision of the three alternative methods. Accuracy of the methods is largely unknown because all methods share some common assumptions and no truly independent and assumption-free method exists. Some assumptions can and should be tested (e.g. the relationship of fluorescence with electron transport). Methods generally require knowledge of either the kinetic parameters of Rubisco, or isotopic fractionation by Rubisco. These parameters are difficult to measure, and thus are generally assumed a priori. For parameters such as these a sensitivity analysis is recommended. One means of improving confidence in gi estimates is by using two or more methods, but it is essential that the methods chosen share as few common assumptions as possible. All methods require accurate and precise measurements of A and Ci — these are best achieved by minimising leaks, maximising the signal-to-noise ratio by using a large leaf area and moderate flow rate, and by taking into account cuticular and boundary layer conductances.
The accumulation of terpenoid oils does not incur a growth cost in Eucalyptus polybractea seedlings
Authors: King Drew J. , Gleadow Roslyn M. , Woodrow Ian E.
Published: May 2006

The deployment of secondary metabolites, such as terpenes, as anti-herbivore defences is thought to be costly for plants in terms of primary metabolism. Moreover, it is assumed that the cost of this deployment is modified by resource availability. In this study we examined the impact of terpenoid oil accumulation on the growth of Eucalyptus polybractea R.T.Baker seedlings from four maternal half-sib families, under conditions of sufficient and limiting nitrogen. The foliar oil concentration measured was extremely variable, varying almost 20-fold to a maximum of 13% (w / DW). Oil concentration was higher in plants grown under high nitrogen than in low-nitrogen plants, and it was positively correlated with foliar nitrogen concentration. Oil concentration was related to maternal concentration, although this relationship was weak because of the variation encountered. The composition of oil, dominated by monoterpenes, was also extremely variable, although this variation could not be adequately explained by either nitrogen availability or the seedling parentage. Importantly, we detected no negative correlations between oil concentration and relative growth rate (RGR), net assimilation rate (NAR), or leaf nitrogen productivity (LNP). Rather, under nitrogen limiting conditions, positive correlations were detected between oil concentration and all three indices. We conclude that oil accumulation is associated with factors that promote growth and if there is a cost to oil deployment, it could not be detected using the experimental design employed here.
Some like it wet — biological characteristics underpinning tolerance of extreme water stress events in Antarctic bryophytes
Authors: Wasley Jane , Robinson Sharon A. , Lovelock Catherine E. , Popp Marianne
Published: May 2006

Antarctic bryophyte communities presently tolerate physiological extremes in water availability, surviving both desiccation and submergence events. We investigated the relative ability of three Antarctic moss species to tolerate physiological extremes in water availability and identified physiological, morphological, and biochemical characteristics that assist species performance under such conditions. Tolerance of desiccation and submergence was investigated using chlorophyll fluorescence during a series of field- and laboratory-based water stress events. Turf water retention and degree of natural habitat submergence were determined from gametophyte shoot size and density, and δ13C signatures, respectively. Finally, compounds likely to assist membrane structure and function during desiccation events (fatty acids and soluble carbohydrates) were determined. The results of this study show significant differences in the performance of the three study species under contrasting water stress events. The results indicate that the three study species occupy distinctly different ecological niches with respect to water relations, and provide a physiological explanation for present species distributions. The poor tolerance of submergence seen in Ceratodon purpureus helps explain its restriction to drier sites and conversely, the low tolerance of desiccation and high tolerance of submergence displayed by the endemic Grimmia antarctici is consistent with its restriction to wet habitats. Finally the flexible response observed for Bryum pseudotriquetrum is consistent with its co-occurrence with the other two species across the bryophyte habitat spectrum. The likely effects of future climate change induced shifts in water availability are discussed with respect to future community dynamics.
Reexamining the empirical relation between plant growth and leaf photosynthesis
Authors: Kruger Eric L. , Volin John C.
Published: May 2006

Technological advances during the past several decades have greatly enhanced our ability to measure leaf photosynthesis virtually anywhere and under any condition. Associated with the resulting proliferation of gas-exchange data is a lingering uncertainty regarding the importance of such measurements when it comes to explaining intrinsic causes of plant growth variation. Accordingly, in this paper we rely on a compilation of data to address the following questions: from both statistical and mechanistic standpoints, how closely does plant growth correlate with measures of leaf photosynthesis? Moreover, in this context, does the importance of leaf photosynthesis as an explanatory variable differ among growth light environments? Across a wide array of species and environments, relative growth rate (RGR) was positively correlated with daily integrals of photosynthesis expressed per unit leaf area (Aarea), leaf mass (Amass), and plant mass (Aplant). The amount of RGR variation explained by these relationships increased from 36% for the former to 93% for the latter. Notably, there was close agreement between observed RGR and that estimated from Aplant after adjustment for theoretical costs of tissue construction. Overall, based on an analysis of growth response coefficients (GRCs), gross assimilation rate (GAR), a photosynthesis-based estimate of biomass gain per unit leaf area, explained about as much growth variation as did leaf mass ratio (LMR) and specific leaf area (SLA). Further analysis of GRCs indicated that the importance of GAR in explaining growth variation increased with increasing light intensity. Clearly, when considered in combination with other key determinants, appropriate measures of leaf gas exchange effectively capture the fundamental role of leaf photosynthesis in plant growth variation.
Phylloxera-infested grapevines have reduced chlorophyll and increased photoprotective pigment content — can leaf pigment composition aid pest detection?
Authors: Blanchfield Annette L. , Robinson Sharon A. , Renzullo Luigi J. , Powell Kevin S.
Published: May 2006

Grape phylloxera (Daktulosphaira vitifoliae Fitch) is a root-feeding pest of grapevines. In Australia, phylloxera-infested vineyards are subjected to quarantine restrictions and early detection remains vital for the timely implementation of post-outbreak quarantine protocols. Current detection methods rely on time-consuming ground surveying, which involves detailed examination of grapevine (Vitis vinifera L.) root systems. Leaf pigment composition is often a sensitive indicator of plant stress. The increasing popularity of remote sensing systems, which exploit those changes in pigments observed with plant stress, offers a real possibility for the development of a phylloxera-specific remote detection system. Our objective was to investigate changes in grapevine leaf pigments associated with phylloxera infestation and to relate any changes to appropriate reflectance indices. This was achieved with a glasshouse experiment in which the responses of two vine cultivars (Cabernet Sauvignon and Shiraz) to phylloxera infestation were compared with their responses to water and nitrogen deficiencies. The responses of leaf pigments to phylloxera infestation were also investigated in Pinot Noir and Cabernet Sauvignon grapevines grown under field conditions. A reduction in the leaf chlorophyll content and an increase in photoprotective pigment concentrations were observed in leaves of phylloxera-infested grapevines compared with uninfested vines. The photochemical reflectance index (PRI) was found to be most closely associated with the ratio of total carotenoid to chlorophyll in these vines.
Gradients of light availability and leaf traits with leaf age and canopy position in 28 Australian shrubs and trees
Authors: Wright Ian J. , Leishman Michelle R. , Read Cassia , Westoby Mark
Published: May 2006

Light availability generally decreases vertically downwards through plant canopies. According to optimisation theory, in order to maximise canopy photosynthesis plants should allocate leaf nitrogen per area (Narea) in parallel with vertical light gradients, and leaf mass per area (LMA) and leaf angles should decrease down through the canopy also. Many species show trends consistent with these predictions, although these are never as steep as predicted. Most studies of canopy gradients in leaf traits have concerned tall herbaceous vegetation or forest trees. But do evergreen species from open habitats also show these patterns? We quantified gradients of light availability, LMA, leaf N and phosphorus (P), and leaf angle along leaf age sequences and vertical canopy profiles, across 28 woody species from open habitats in eastern Australia. The observed trends in LMA, Narea and leaf angle largely conflicted with expectations from canopy optimisation models, whereas trends in leaf P were more consistent with optimal allocation. These discrepancies most likely relate to these species having rather open canopies with quite shallow light gradients, but also suggest that modelling the co-optimisation of resources other than nitrogen is required for understanding plant canopies.
Adaptations of strangler figs to life in the rainforest canopy
Authors: Schmidt Susanne , Tracey Dieter P.
Published: May 2006

Figs are rainforest keystone species. Non-strangler figs establish on the forest floor; strangler figs establish epiphytically, followed by a dramatic transition from epiphyte to free-standing tree that kills its hosts. Free-standing figs display vigorous growth and resource demand suggesting that epiphytic strangler figs require special adaptations to deal with resource limitations imposed by the epiphytic environment. We studied epiphytic and free-standing strangler figs, and non-strangler figs in tropical rainforest and in cultivation, as well as strangler figs in controlled conditions. We investigated whether the transition from epiphyte to free-standing tree is characterised by morphological and physiological plasticity. Epiphyte substrate had higher levels of plant-available ammonium and phosphate, and similar levels of nitrate compared with rainforest soil, suggesting that N and P are initially not limiting resources. A relationship was found between taxonomic groups and plant N physiology; strangler figs, all members of subgenus Urostigma, had mostly low foliar nitrate assimilation rates whereas non-strangler figs, in subgenera Pharmacocycea, Sycidium, Sycomorus or Synoecia, had moderate to high rates. Nitrate is an energetically expensive N source, and low nitrate use may be an adaptation of strangler figs for conserving energy during epiphytic growth. Interestingly, significant amounts of nitrate were stored in fleshy taproot tubers of epiphytic stranglers. Supporting the concept of plasticity, leaves of epiphytic Ficus benjamina L. had lower N and C content per unit leaf area, lower stomatal density and 80% greater specific leaf area than leaves of conspecific free-standing trees. Similarly, glasshouse-grown stranglers strongly increased biomass allocation to roots under water limitation. Epiphytic and free-standing F. benjamina had similar average foliar δ13C, but epiphytes had more extreme values; this indicates that both groups of plants use the C3 pathway of CO2 fixation but that water availability is highly variable for epiphytes. We hypothesise that epiphytic figs use fleshy stem tubers to avoid water stress, and that nitrate acts as an osmotic compound in tubers. We conclude that strangler figs are a unique experimental system for studying the transition from rainforest epiphyte to tree, and the genetic and environmental triggers involved.
Proteomic identification of oncogenic chromosomal translocation partners encoding chimeric anaplastic lymphoma kinase fusion proteins
Authors: Elenitoba-Johnson Kojo S. J. , Crockett David K. , Schumacher Jonathan A. , Jenson Stephen D. , Coffin Cheryl M. , Rockwood Alan L. , Lim Megan S.
Published: May 2006

The anaplastic lymphoma kinase (ALK) on 2p23 is a tyrosine kinase that forms chimeric fusions with numerous translocation partners. We describe a mass spectrometry-based approach for the identification of ALK fusion partners. This approach accurately identified the nucleophosmin (NPM)–ALK fusion protein in an anaplastic large cell lymphoma (ALCL)-derived cell line carrying the t(2;5)(p23;q35), and the TPM3–ALK in a clinical biopsy of inflammatory myofibroblastic tumor (IMT) carrying the t(1;2)(q21;p23). This study shows the ability of mass spectrometry to identify oncogenic chimeric proteins resulting from chromosomal rearrangements. This strategy can be adapted for the identification of known and unknown translocation partners of chimeric ALK fusion proteins involved in oncogenesis.
The brain-specific carnitine palmitoyltransferase-1c regulates energy homeostasis
Authors: Wolfgang Michael J. , Kurama Takeshi , Dai Yun , Suwa Akira , Asaumi Makoto , Matsumoto Shun-ichiro , Cha Seung Hun , Shimokawa Teruhiko , Lane M. Daniel
Published: May 2006

Fatty acid synthesis in the central nervous system is implicated in the control of food intake and energy expenditure. An intermediate in this pathway, malonyl-CoA, mediates these effects. Malonyl-CoA is an established inhibitor of carnitine palmitoyltransferase-1 (CPT1), an outer mitochondrial membrane enzyme that controls entry of fatty acids into mitochondria and, thereby, fatty acid oxidation. CPT1c, a brain-specific enzyme with high sequence similarity to CPT1a (liver) and CPT1b (muscle) was recently discovered. All three CPTs bind malonyl-CoA, and CPT1a and CPT1b catalyze acyl transfer from various fatty acyl-CoAs to carnitine, whereas CPT1c does not. These findings suggest that CPT1c has a unique function or activation mechanism. We produced a targeted mouse knockout (KO) of CPT1c to investigate its role in energy homeostasis. CPT1c KO mice have lower body weight and food intake, which is consistent with a role as an energy-sensing malonyl-CoA target. Paradoxically, CPT1c KO mice fed a high-fat diet are more susceptible to obesity, suggesting that CPT1c is protective against the effects of fat feeding. CPT1c KO mice also exhibit decreased rates of fatty acid oxidation, which may contribute to their increased susceptibility to diet-induced obesity. These findings indicate that CPT1c is necessary for the regulation of energy homeostasis.
Post-Miocene expansion, colonization, and host switching drove speciation among extant nematodes of the archaic genus
Trichinella
Authors: Zarlenga D. S. , Rosenthal B. M. , La Rosa G. , Pozio E. , Hoberg E. P.
Published: May 2006

Parasitic nematodes of the genus
Trichinella
cause significant food-borne illness and occupy a unique evolutionary position at the base of the phylum Nematoda, unlike the free-living nematode
Caenorhabditis elegans
. Although the forthcoming genome sequence of
Trichinella spiralis
can provide invaluable comparative information about nematode biology, a basic framework for understanding the history of the genus
Trichinella
is needed to maximize its utility. We therefore developed the first robust and comprehensive analysis of the phylogeny and biogeographic history of
Trichinella
using the variation in three genes (nuclear small-subunit rDNA, and second internal transcribed spacer, mitochondrial large-subunit rDNA, and cytochrome oxidase I DNA) from all 11 recognized taxa. We conclude that (
i
) although Trichinellidae may have diverged from their closest extant relatives during the Paleozoic, all contemporary species of
Trichinella
diversified within the last 20 million years through geographic colonization and pervasive host switching among foraging guilds of obligate carnivores; (
ii
) mammalian carnivores disseminated encapsulated forms from Eurasia to Africa during the late Miocene and Pliocene, and to the Nearctic across the Bering Land Bridge during the Pliocene and Pleistocene, when crown species ultimately diversified; (
iii
) the greatest risk to human health is posed by those species retaining an ancestral capacity to parasitize a wide range of hosts; and (
iv
) early hominids may have first acquired
Trichinella
on the African savannah several million years before swine domestication as their diets shifted from herbivory to facultative carnivory.
Isothermal micro-calorimetry: a tool to predict seed longevity?
Authors: Hay Fiona R. , O'Neill Michael A.A. , Beezer Anthony E. , Gaisford Simon
Published: May 2006

This paper describes the exploratory use of isothermal micro-calorimetry (IMC) to measure directly the heat flow produced as seeds age. Heat flow was recorded in primed and non-primed (control) seeds of Ranunculus sceleratus L., aged in a micro-calorimeter at 35°C at three different seed water contents [c. 0.12, 0.075 and 0.045 g H2O (g dw)−1]. The rate of heat flow and total heat generated (an indicator of extent of reaction) were generally greater in control seeds, which aged at a faster rate, than in primed seeds. Total heat generated over a given period also increased with increasing water content. The power–time curves did not indicate first- or second-order rate kinetics, consistent with the probability that seed ageing is complex and involves a number of reactions. Even after the capacity to germinate had ceased, there was a residual power signal. As a method, IMC gave consistent results using independent samples at different times. Therefore, short-term experiments at relatively high water contents and/or temperatures may have the potential to predict the relative longevity of seed-lots, at least within a species.
Germination of fresh and frost-treated seeds from dry Central Asian steppes
Authors: Wesche K. , Pietsch M. , Ronnenberg K. , Undrakh R. , Hensen I.
Published: May 2006

We tested the germination of fresh and frost-treated seeds of 26 species of southern Mongolian mountain and desert steppes, covering the major growth forms of woody and herbaceous perennials and short-lived species in the region. In the field, germination depends on rains that are largely restricted to the summer months between June and August. Thus, germination tests were performed at alternating conditions of 10°C in darkness and 20°C in light (12 h/12 h), which correspond to temperatures at the study site in early and late summer. Seeds of both woody and herbaceous perennials germinated well under the chosen conditions and apparently did not require stratification or scarification. In contrast, germination of annual species was mostly below 30%, while seed viability was equally high in all three growth forms. Winter conditions, simulated by freezing dried seeds at −18°C, hardly changed seed germination in the perennial species, but several short-lived species responded with increased germination. Short-lived species are not abundant in the real vegetation, which is governed by perennials. Thus, we conclude that the important species in Mongolian mountain steppes germinate readily without a dormancy-breaking treatment. A review of the available literature revealed that a complete lack of dormancy, or presence of only conditional dormancy, is also widely described for other species of Central Asian deserts and steppes, which is in contrast to data from North American prairies.
An alkaline α-galactosidase transcript is present in maize seeds and cultured embryo cells, and accumulates during stress
Authors: Zhao Tian-Yong , Corum III J. Willis , Mullen Jeffrey , Meeley Robert B. , Helentjaris Timothy , Martin David , Downie Bruce
Published: May 2006

Raffinose family oligosaccharides (RFO) accumulate in many developing seeds and are degraded during seed germination. However, acidic α-galactosidase (AGAL) activity and subcellular location do not correlate with raffinose depletion; alkaline α-galactosidases (AGA) may be responsible for RFO hydrolysis in germinating seeds. Three cDNA clones for AGA/SEED IMBIBITION PROTEIN were obtained from the Pioneer Hi-Bred maize expressed sequence database. Two of the clones were expressed in Escherichia coli, and the recombinant proteins, when incubated with naturally occurring galactosides or p-nitrophenyl α-d-galactose, exhibited AGA activity with maximum catalysis at pH 7.5 (ZmAGA1) or pH 8.5 (ZmAGA3). No raffinose biosynthetic capacity was observed with either enzyme. Maximal α-galactosidase activity in mature dehydrated, germinating and germinated maize (Zea mays) seeds occurred at pH 7.5. ZmAGA1 was the sole family member detected in seeds and maize Hi-II, embryo-derived, callus cells. Its transcript accumulated when seed germination was interrupted by heat, cold or dehydration stress, but not in response to NaCl. Tissue prints localized transcripts to the scutellum or the embryo axis, depending on the stress applied. In maize Hi-II callus cells, transcripts accumulated when callus was subjected to heat stress (42 °C), during which ZmAGA1 transcript accumulation was further induced by sucrose. Galactosides in a variety of forms, including raffinose, partially repressed the sucrose-induced accumulation of transcript in heat-stressed callus.
A functional network involved in the recycling of nucleocytoplasmic pre-60S factors
Authors: Lebreton Alice , Saveanu Cosmin , Decourty Laurence , Rain Jean-Christophe , Jacquier Alain , Fromont-Racine Micheline
Published: May 2006

Eukaryotic pre-ribosomes go through cytoplasmic maturation steps before entering translation. The nucleocytoplasmic proteins participating in these late stages of maturation are reimported to the nucleus. In this study, we describe a functional network focused on Rei1/Ybr267w, a strictly cytoplasmic pre-60S factor indirectly involved in nuclear 27S pre-ribosomal RNA processing. In the absence of Rei1, the nuclear import of at least three other pre-60S factors is impaired. The accumulation in the cytoplasm of a small complex formed by the association of Arx1 with a novel factor, Alb1/Yjl122w, inhibits the release of the putative antiassociation factor Tif6 from the premature large ribosomal subunits and its recycling to the nucleus. We propose a model in which Rei1 is a key factor for the coordinated dissociation and recycling of the last pre-60S factors before newly synthesized large ribosomal subunits enter translation.
Stress fibers are generated by two distinct actin assembly mechanisms in motile cells
Authors: Hotulainen Pirta , Lappalainen Pekka
Published: May 2006

Stress fibers play a central role in adhesion, motility, and morphogenesis of eukaryotic cells, but the mechanism of how these and other contractile actomyosin structures are generated is not known. By analyzing stress fiber assembly pathways using live cell microscopy, we revealed that these structures are generated by two distinct mechanisms. Dorsal stress fibers, which are connected to the substrate via a focal adhesion at one end, are assembled through formin (mDia1/DRF1)–driven actin polymerization at focal adhesions. In contrast, transverse arcs, which are not directly anchored to substrate, are generated by endwise annealing of myosin bundles and Arp2/3-nucleated actin bundles at the lamella. Remarkably, dorsal stress fibers and transverse arcs can be converted to ventral stress fibers anchored to focal adhesions at both ends. Fluorescence recovery after photobleaching analysis revealed that actin filament cross-linking in stress fibers is highly dynamic, suggesting that the rapid association–dissociation kinetics of cross-linkers may be essential for the formation and contractility of stress fibers. Based on these data, we propose a general model for assembly and maintenance of contractile actin structures in cells.
Competitive intra- and extracellular nutrient sensing by the transporter homologue Ssy1p
Authors: Wu Boqian , Ottow Kim , Poulsen Peter , Gaber Richard F. , Albers Eva , Kielland-Brandt Morten C.
Published: May 2006

Recent studies of Saccharomyces cerevisiae revealed sensors that detect extracellular amino acids (Ssy1p) or glucose (Snf3p and Rgt2p) and are evolutionarily related to the transporters of these nutrients. An intriguing question is whether the evolutionary transformation of transporters into nontransporting sensors reflects a homeostatic capability of transporter-like sensors that could not be easily attained by other types of sensors. We previously found SSY1 mutants with an increased basal level of signaling and increased apparent affinity to sensed extracellular amino acids. On this basis, we propose and test a general model for transporter- like sensors in which occupation of a single, central ligand binding site increases the activation energy needed for the conformational shift between an outward-facing, signaling conformation and an inward-facing, nonsignaling conformation. As predicted, intracellular leucine accumulation competitively inhibits sensing of extracellular amino acids. Thus, a single sensor allows the cell to respond to changes in nutrient availability through detection of the relative concentrations of intra- and extracellular ligand.
Mechanisms imposing the Vβ bias of Vα14 natural killer T cells and consequences for microbial glycolipid recognition
Authors: Wei Datsen G. , Curran Shane A. , Savage Paul B. , Teyton Luc , Bendelac Albert
Published: May 2006

Mouse and human natural killer T (NKT) cells recognize a restricted set of glycosphingolipids presented by CD1d molecules, including self iGb3 and microbial α-glycuronosylceramides. The importance of the canonical Vα14-Jα18 TCR α chain for antigen recognition by NKT cells is well recognized, but the mechanisms underlying the Vβ8, Vβ7, and Vβ2 bias in mouse have not been explored. To study the influences of thymic selection and the constraints of pairing with Vα14-Jα18, we have created a population of mature T cells expressing Vα14-Jα18 TCR α chain in CD1d-deficient mice and studied its recognition properties in vitro and in vivo. Transgenic cells expressed a diverse Vβ repertoire but their recognition of endogenous ligands and synthetic iGb3 was restricted to the same biased Vβ repertoire as expressed in natural NKT cells. In contrast, α-GalCer, a synthetic homologue of microbial α-glycuronosylceramides, was recognized by a broader set of Vβ chains, including the biased NKT set but also Vβ6, Vβ9, Vβ10, and Vβ14. These surprising findings demonstrate that, whereas Vβ8, Vβ7, and Vβ2 represent the optimal solution for recognition of endogenous ligand, many Vβ chains that are potentially useful for the recognition of foreign lipids fail to be selected in the NKT cell repertoire.
Automatic Detection of Patients with Nosocomial Infection by a Computer-Based Surveillance System: A Validation Study in a General Hospital
Authors: Pokorny L. , Rovira A. , Martín-Baranera M. , Gimeno C. , Alonso-Tarrés C. , Vilarasau J.
Published: May 2006

Objective.

To validate an automated system for the detection of patients with nosocomial infection (NI) in an intensive care unit (ICU).

Design.

Retrospective analysis of data from the hospital information system. We applied 3 different NI suspicion criteria (positive microbiology reports, antibiotic administration, and diagnosis of clinical infection) and compared the results to those of a prospective NI incidence study done in the ICU during the same period (1999-2002).

Setting.

A 250-bed general hospital in Barcelona, Spain.

Patients.

From April 15, 1999, through June 30, 2002, 1380 patients were admitted to the ICU. Of these, 1043 had an ICU stay of more than 24 hours and were included in the study.

Results.

At least one NI suspicion criterion was present for 242 patients (23.2%); 2 criteria were present for 184 patients (17.6%); and all 3 criteria were present for 112 (11.7%). Comparison of hospital information system data to the results of the prospective study indicated that the combination of 2 criteria demonstrated the most satisfactory sensitivity (94.3%; 95% confidence interval [CI], 79.5%-99.0%) and specificity (83.6%; 95% CI, 76.8%-88.9%). The positive predictive value was 55.9% (95% CI, 42.5%-68.6%); the negative predictive value was 98.5% (95% CI, 94.2%-99.7%). The system could assign a site of infection for 90.4% of the NIs detected.

Conclusion.

The hospital information system was a useful tool for retrospectively detecting patients with an NI during the ICU stay. Given its high sensitivity, it may be useful as an alert for the NI team.
Use of Multistate Models to Assess Prolongation of Intensive Care Unit Stay Due to Nosocomial Infection
Authors: Beyersmann J. , Gastmeier P. , Grundmann H. , Bärwolff S. , Geffers C. , Behnke M. , Rüden H. , Schumacher M.
Published: May 2006

Background.

Reliable data on the costs attributable to nosocomial infection (NI) are crucial to demonstrating the real cost-effectiveness of infection control measures. Several studies investigating this issue with regard to intensive care unit (ICU) patients have probably overestimated, as a result of inappropriate study methods, the part played by NIs in prolonging the length of stay.

Methods.

Data from a prospective study of the incidence of NI in 5 ICUs over a period of 18 months formed the basis of this analysis. For describing the temporal dynamics of the data, a multistate model was used. Thus, ICU patients were counted as case patients as soon as an NI was ascertained on any particular day. All patients were then regarded as control subjects as long as they remained free of NI (time-to-event data analysis technique).

Results.

Admitted patients (n = 1,876) were observed for the development of NI over a period of 28,498 patient-days. In total, 431 NIs were ascertained during the study period (incidence density, 15.1 NIs per 1,000 patient-days). The influence of NI as a time-dependent covariate in a proportional hazards model was highly significant (P< .0001, Wald test). NI significantly reduced the discharge hazard (hazard ratio, 0.72 [95% confidence interval, 0.63-0.82])—that is, it prolonged the ICU stay. The mean prolongation of ICU length of stay due to NI ( ± standard error) was estimated to be 5.3 ± 1.6 days.

Conclusions.

Further studies are required to enable comparison of data on prolongation of ICU length of stay with the results of various study methods.
Prospective 3-Year Surveillance for Nosocomial and EnvironmentalLegionella pneumophila: Implications for Infection Control
Authors: Boccia S. , Laurenti P. , Borella P. , Moscato U. , Capalbo G. , Cambieri A. , Amore R. , Quaranta G. , Boninti F. , Orsini M. , Branca G. , Fadda G. , Spica V. Romano , Ricciardi G.
Published: May 2006

Objectives.

To perform a 3-year, prospective surveillance program for legionnaires disease (LD) in a large university hospital in Rome, and to assess the usefulness of the hospital water monitoring program in predicting the risk of nosocomial LD.

Methods.

Samples from patients with new cases of nosocomial pneumonia were sent for legionella laboratory investigations. Meanwhile, water samples for bacteriological analysis were collected every 6 months from high- and medium-risk hospital wards (10 in total).Legionella pneumophilaisolates collected were serotyped and analyzed by pulsed-field gel electrophoresis.

Results.

From June 2001 through May 2004, the pneumonia surveillance identified one case of nosocomial LD among 43 cases of nosocomial pneumonia (2.3%). Environmental investigations detectedL. pneumophilain 12 (18.7%) of the 64 water samples, of which 50% belonged to serogroup 1. TheL. pneumophilacount and the percentage of positive locations never exceeded 102colony-forming units/L and 20%, respectively, except when the LD nosocomial case occurred (positive water samples, 40%; I. pneumophila count, <102colony-forming units/L). Genotyping showed 3 prevalent clones ofL. pneumophilain the water distribution network, of which one persisted over the 3 years. One clone contained 3 differentL. pneumophilaserogroups (2, 4, and 6).

Conclusions.

The low incidence of nosocomial cases of LD appears to be associated with a low percentage (<20%) of positive water samples per semester and with a low contamination level (<102colony-forming units/L). An infection control system for nosocomial LD should, therefore, be based on both environmental and clinical surveillance, together with the appropriate maintenance of the hospital water distribution system.
High Rate of Negative Results of Tuberculin and QuantiFERON Tests Among Individuals With a History of Positive Skin Test Results
Authors: Friedman Lloyd N. , Nash Esther R. , Bryant June , Henry Susan , Shi Julia , D'Amato Joyce , Khaled Ghada H. , Russi Mark B. , O'Connor Patrick G. , Edberg Stephen C. , Pisani Margaret A. , Cain Hilary C. , Tanoue Lynn , Weissman David N.
Published: May 2006

Objectives.

To evaluate individuals at high risk for tuberculosis exposure who had a history of a positive tuberculin skin test (TST) result in order to determine the prevalence of unsuspected negative TST results. To confirm these findings with the QuantiFERON-TB test (QFT), an in vitro whole-blood assay that measures tuberculin-induced secretion of interferon-γ.

Methods.

This survey was conducted from November 2001 through December 2003 at 3 sites where TST screening is regularly done. Detailed histories and reviews of medical records were performed. TSTs were placed and read by 2 experienced healthcare workers, and blood was drawn for QFT. Any subject with a negative result of an initial TST during the study (induration diameter, <10 mm) underwent a second TST and a second QFT. The TST-negative group comprised individuals for whom both TSTs had an induration diameter of <10 mm. The confirmed-negative group comprised individuals for whom both TSTs yielded no detectable induration and results of both QFTs were negative.

Results.

A total of 67 immunocompetent subjects with positive results of a previous TST were enrolled in the study. Of 56 subjects who completed the TST protocol, 25 (44.6%; 95% confidence interval [CI], 31.6%-57.6%) were TST negative (P<.001). Of 31 subjects who completed the TST protocol and the QFT protocol, 8 (25.8%; 95% CI, 10.4%-41.2%) were confirmed negative (P<.005).

Conclusions.

A significant proportion of subjects with positive results of a previous TST were TST negative in this study, and a subset of these were confirmed negative. These individuals' TST status may have reverted or may never have been positive. It will be important in future studies to determine whether such individuals lack immunity to tuberculosis and whether they should be considered for reentry into tuberculosis screening programs.
An Outbreak of Scabies in a Long-Term Care Facility: The Role of Misdiagnosis and the Costs Associated With Control
Authors: Beer Gretha de , Miller Mark A. , Tremblay Lucie , Monette Johanne
Published: May 2006

In August 2003, an outbreak of scabies was detected in a Canadianlong-term care facility. The outbreak was likely associated with 2index cases, 1 involving classic scabies and the other involving Norwegian scabies. The scabies control costs totaled CDN$200,000, and the facility received negative publicity for a short period after the outbreak.
Detection and Quantification of Dental Unit Water Line Contamination by Oral Streptococci
Authors: Petti Stefano , Tarsitani Gianfranco
Published: May 2006

Objective.

(1) To investigate the prevalence of oral streptococci (OS) and biological indicators of water contamination by oral fluids in water from dental unit water lines (DUWs) by detection and quantification and of saprophytes indigenous to the oral cavity. (2) To test whether measurement of the total cultivable mesophilic flora (TCF), the parameter commonly used to monitor water quality in DUWs, is an effective predictor for OS contamination.

Design.

Survey of 21 dental units equipped with antiretraction devices. Water samples were collected from air-water syringes, cup fillers, tap water, and before and during the working day.

Setting.

Units were from 7 public dental offices selected for convenience from among those in proximity of the microbiological laboratory.

Methods.

For detection of OS, samples were plated on an enriched medium, to revitalize the organisms. Colonies were subcultured on a selective medium and biochemically identified (lower detection limit, 1 cfu/mL). For measurement of the TCF, samples were plated on a nutrient-poor medium. Cultures with colony counts greater than 200 cfu/mL were considered to be TCF positive. The sensitivity and specificity of TCF positivity in predicting OS detection was calculated.

Results.

Prevalence rates for OS contamination and for TCF positivity were, respectively, 34.4% (11 of 32 samples) and 25.0% (8 of 32 samples) for syringes, 27.8% (10 of 36 samples) and 8.3% (3 of 36 samples) for cup fillers, and 0.0% (0 of 7 samples) for tap water. OS contamination levels ranged from 1 to 6 cfu/mL. No statistically significant differences were found between samples obtained before and during the working day. TCF positivity did not predict OS contamination effectively, because of low sensitivity.

Conclusions.

Given the absence of OS in tap water, the reported prevalence of OS contamination suggests that oral fluids are aspirated during dental therapy with relatively high frequency and that DUWs can potentially expose successive patients to bloodborne cross-infections.
Toronto's gay village (1969–1982): plotting the politics of gay identity
Authors: Nash Catherine Jean
Published: May 2006

Between the late 1960s and the early 1980s, a loose association of gay social spaces consolidated into what is now known as the ‘gay village’ in the Church and Wellesley street areas in downtown Toronto. Scholars argue that, while these residential and commercial districts evolved prior to the formation of organized gay political organizations, they suggest that the emergence of these districts as political and commercial districts was a direct result of deliberate local gay activism. I argue here that contrary to this literature and for much of its history, the gay movement was largely opposed to the existence of specifically gay‐identified spaces, particularly those operated by both heterosexual and homosexual businesspersons. Toronto's gay activists, using different ideological frameworks, struggled to constitute a homosexual identity that stood mainly in opposition to the so‐called ‘ghetto gay’ and to construct alternative spaces that were seen as more appropriate to the formation of a properly politicized homosexual identity. Nevertheless, by the early 1980s, as the gay village continued to thrive and as the players in gay movement politics changed, the gay ghetto became the gay village and was celebrated as a location of political strength and social necessity. This article explores that material and symbolic transformation.
Spatial/temporal mismatch: a conflation protocol for Canada Census spatial files
Authors: Schuurman Nadine , Grund Darrin , Hayes Michael , Dragicevic Suzana
Published: May 2006

The Canada census is one of the chief sources of demographic and socio‐economic data for researchers in this country. Census variables are linked to geography files that allow researchers using geographic information systems (GIS) to view and analyze spatial data. Some of the most useful analysis, however, is based on changes in attribute values over time and space. Analysis of spatio‐ temporal events such as shifting migration patterns or changes in the distribution of health status permits a more dimensioned perspective than the viewing of static spatial phenomena. The analysis of spatio‐temporal phenomena is limited by major changes in the spatial framework (e.g., location of road networks and other spatial entities) between national censuses. This paper addresses this limitation by (i) illustrating the extent of spatial mismatch between the 1996 and the 2001 census; (ii) examining attempts to rectify this problem in other jurisdictions and (iii) presenting a ‘made‐in‐Canada’ solution for conflation of census geometries. We believe that this solution will enhance the ability of Canadian researchers to describe and analyze socio‐economic, health and demographic shifts across time and space. The research is supported by an ftp site for downloading the census geography rectification software presented in this paper.
From a radial operating theatre to a self‐contained operating table
Authors: Ofek E. , Pizov R. , Bitterman N.
Published: May 2006

Equipment congestion and a disarray of wires, tubes and lines (the spaghetti syndrome) is a common scenario in operating theatres. The radial arrangement of input and output signals and their interconnecting lines has been identified as the main source of clutter and congestion in this environment. Our aim was to present a comprehensive design concept for reducing electrical and physical clutter in the operating theatre. Data were collected from different operating theatres, including identification and sorting of equipment, cables, tubes and lines according to the direction and the features of the transmitted information and materials. We suggest a concept of a self‐contained, ‘built‐in’ operating table as a design solution for avoiding the clutter and congestion caused by the radial configuration. The operating table will function as a central integrated unit for management of the entire process of patient flow and control of supply systems and environmental conditions.
Decision analysis in anaesthesia: a tool for developing and analysing clinical management plans
Authors: Yentis S. M.
Published: May 2006

Traditional medical decision making is unstructured and incorporates evidence haphazardly. I present a more structured approach based on decision analysis, a model that considers all relevant options and outcomes informed by evidence where appropriate. This method is useful both for planning clinical management and for analysing decisions already taken.
Population pharmacokinetics of tipifarnib in healthy subjects and adult cancer patients
Authors: Perez‐Ruixo Juan Jose , Piotrovskij Vladimir , Zhang Steven , Hayes Siobhan , Porre Peter De , Zannikos Peter
Published: May 2006

Aims

To characterize the population pharmacokinetics of tipifarnib.

Methods

A total of 1083 subjects treated orally with a solution, capsule or tablet formulations of tipifarnib, given as a single dose or as multiple twice‐daily doses (range 25–1300 mg) were combined with data from 1, 2 and 24 h intravenous infusions. A total of 3445 concentrations in the index data set were fitted by an open three‐compartment linear disposition model with sequential zero‐order input into the depot compartment, followed by a first‐order absorption process, and lag time, using NONMEM V. The effect of patient covariates on tipifarnib pharmacokinetics was explored. The model was evaluated using goodness of fit plots and relative error measurements for 3894 concentrations in the test data set. Computer simulations were undertaken to evaluate the effect of covariates on tipifarnib pharmacokinetics.

Results

Tipifarnib oral bioavailability (26.7%) did not differ between the formulations. The absorption rate from the solution was faster than from the solid forms. Whereas the absorption rate and systemic clearance were more rapid in healthy subjects, the extent of absorption and the steady‐state volume of distribution were comparable in cancer patients and healthy subjects. Systemic clearance in cancer patients (21.9 l h−1) exhibited a statistically significant relationship with total bilirubin. The typical volume of the central compartment in cancer patients (54.6 l 70 kg−1) was directly proportional to body weight. The clinical relevance of these covariates in cancer patients is questionable as there was a substantial overlap in simulated concentration‐time profiles across a wide range of covariate values.

Conclusions

A population PK approach has been used to integrate data gathered during clinical development and to characterize the pharmacokinetics of tipifarnib. Individualization of dose based on body weight or total bilirubin concentration in adult cancer patients is not warranted.
Transglutaminase differentially regulates growth signalling in rat perivenous and periportal hepatocytes
Authors: Maruko A. , Ohtake Y. , Konno K. , Abe S. , Ohkubo Y.
Published: May 2006

Abstract.   The influence of transglutaminase 2 (TG2) activity on the proliferative effect of epidermal growth factor (EGF) and on EGF receptor affinity in periportal hepatocytes (PPH) and perivenous hepatocytes (PVH) has been investigated using a primary culture system. PPH and PVH subpopulations have been isolated using the digitonin/collagenase perfusion technique. DNA synthesis was assessed by [3H] thymidine incorporation into hepatocytes. The assay for binding of [125I] EGF to cultured hepatocytes was analysed by Scatchard plot analysis. Pretreatment with the TG2 inhibitor monodansylcadaverine (MDC) greatly increased EGF‐induced DNA synthesis in both PPH and PVH. Furthermore, [125I] EGF binding studies in PVH treated with MDC indicated that high‐affinity EGF receptor expression was markedly up‐regulated, whereas in PPH, there was no significant effect. Treatment with retinoic acid (RA), an inducer of TG2 expression, significantly decreased EGF‐induced DNA synthesis in both PPH and PVH. Binding studies in the presence of RA revealed that the high‐affinity EGF receptor was down‐regulated and completely absent in both PPH and PVH. These results suggest that TG2 was involved in the differential growth capacities of PPH and PVH through down‐regulation of high‐affinity EGF receptors.