bluuebunny/crossref_metadata_2025 huggingface dataset:
Modeling Structural Adaptation of Microcirculation
Authors: PRIES AXEL R. , SECOMB TIMOTHY W.
Published: September 2008

The functional properties of microcirculation crucially depend on its angioarchitecture, (i.e., vessel arrangement and morphology). The microcirculation is subject to continuous dynamic structural adaptation (i.e., remodeling) controlled by hemodynamic and metabolic stimuli. Due to the complexity of the interactions among stimuli, reactions, and functional properties, an adequate understanding of structural adaptation requires mathematical models in addition to experimental investigations. Mathematical models have been developed that allow the prediction of realistic vascular properties, based on generic patterns of vascular responses. These models can be used to investigate and predict distributions of vessel morphology consistent with certain putative adaptation principles of terminal vascular beds in response to local hemodynamic and metabolic conditions. They have suggested new hypotheses, including the importance of conducted responses in network adaptation, and can explain the mechanisms underlying observed structural and functional network properties. In the future, the value of such models can be enhanced by including the effects of longitudinal stretch and pulsatility, the relationship between acute tone and structural adaptation, and the description of molecular and cellular mechanisms underlying structural responses of microvessels.
Retrograde Flow and Myosin II Activity within the Leading Cell Edge Deliver F-Actin to the Lamella to Seed the Formation of Graded Polarity Actomyosin II Filament Bundles in Migrating Fibroblasts
Authors: Anderson Tom W. , Vaughan Andrew N. , Cramer Louise P.
Published: September 2008

In migrating fibroblasts actomyosin II bundles are graded polarity (GP) bundles, a distinct organization to stress fibers. GP bundles are important for powering cell migration, yet have an unknown mechanism of formation. Electron microscopy and the fate of photobleached marks show actin filaments undergoing retrograde flow in filopodia, and the lamellipodium are structurally and dynamically linked with stationary GP bundles within the lamella. An individual filopodium initially protrudes, but then becomes separated from the tip of the lamellipodium and seeds the formation of a new GP bundle within the lamella. In individual live cells expressing both GFP-myosin II and RFP-actin, myosin II puncta localize to the base of an individual filopodium an average 28 s before the filopodium seeds the formation of a new GP bundle. Associated myosin II is stationary with respect to the substratum in new GP bundles. Inhibition of myosin II motor activity in live cells blocks appearance of new GP bundles in the lamella, without inhibition of cell protrusion in the same timescale. We conclude retrograde F-actin flow and myosin II activity within the leading cell edge delivers F-actin to the lamella to seed the formation of new GP bundles.
Fission Yeast Kinesin-8 Klp5 and Klp6 Are Interdependent for Mitotic Nuclear Retention and Required for Proper Microtubule Dynamics
Authors: Unsworth Amy , Masuda Hirohisa , Dhut Susheela , Toda Takashi
Published: September 2008

Fission yeast has two kinesin-8s, Klp5 and Klp6, which associate to form a heterocomplex. Here, we show that Klp5 and Klp6 are mutually dependent on each other for nuclear mitotic localization. During interphase, they are exported to the cytoplasm. In sharp contrast, during mitosis, Klp5 and Klp6 remain in the nucleus, which requires the existence of each counterpart. Canonical nuclear localization signal (NLS) is identified in the nonkinesin C-terminal regions. Intriguingly individual NLS mutants (NLSmut) exhibit loss-of-function phenotypes, suggesting that Klp5 and Klp6 enter the nucleus separately. Indeed, although neither Klp5-NLSmut nor Klp6-NLSmut enters the nucleus, wild-type Klp6 or Klp5, respectively, does so with different kinetics. In the absence of Klp5/6, microtubule catastrophe/rescue frequency and dynamicity are suppressed, whereas growth and shrinkage rates are least affected. Remarkably, chimera strains containing only the N-terminal Klp5 kinesin domains cannot disassemble interphase microtubules during mitosis, leading to the coexistence of cytoplasmic microtubules and nuclear spindles with massive chromosome missegregation. In this strain, a marked reduction of microtubule dynamism, even higher than in klp5/6 deletions, is evident. We propose that Klp5 and Klp6 play a vital role in promoting microtubule dynamics, which is essential for the spatiotemporal control of microtubule morphogenesis.
Rap1 Activation in Collagen Phagocytosis Is Dependent on Nonmuscle Myosin II-A
Authors: Arora Pamela D. , Conti Mary Anne , Ravid Shoshana , Sacks David B. , Kapus Andras , Adelstein Robert S. , Bresnick Anne R. , McCulloch Christopher A.
Published: September 2008

Rap1 enhances integrin-mediated adhesion but the link between Rap1 activation and integrin function in collagen phagocytosis is not defined. Mass spectrometry of Rap1 immunoprecipitates showed that the association of Rap1 with nonmuscle myosin heavy-chain II-A (NMHC II-A) was enhanced by cell attachment to collagen beads. Rap1 colocalized with NM II-A at collagen bead-binding sites. There was a transient increase in myosin light-chain phosphorylation after collagen-bead binding that was dependent on myosin light-chain kinase but not Rho kinase. Inhibition of myosin light-chain phosphorylation, but not myosin II-A motor activity inhibited collagen-bead binding and Rap activation. In vitro binding assays demonstrated binding of Rap1A to filamentous myosin rods, and in situ staining of permeabilized cells showed that NM II-A filaments colocalized with F-actin at collagen bead sites. Knockdown of NM II-A did not affect talin, actin, or β1-integrin targeting to collagen beads but targeting of Rap1 and vinculin to collagen was inhibited. Conversely, knockdown of Rap1 did not affect localization of NM II-A to beads. We conclude that MLC phosphorylation in response to initial collagen-bead binding promotes NM II-A filament assembly; binding of Rap1 to myosin filaments enables Rap1-dependent integrin activation and enhanced collagen phagocytosis.
The Sur7 Protein Regulates Plasma Membrane Organization and Prevents Intracellular Cell Wall Growth inCandida albicans
Authors: Alvarez Francisco J. , Douglas Lois M. , Rosebrock Adam , Konopka James B.
Published: September 2008

The Candida albicans plasma membrane plays important roles in cell growth and as a target for antifungal drugs. Analysis of Ca-Sur7 showed that this four transmembrane domain protein localized to stable punctate patches, similar to the plasma membrane subdomains known as eisosomes or MCC that were discovered in S. cerevisiae. The localization of Ca-Sur7 depended on sphingolipid synthesis. In contrast to S. cerevisiae, a C. albicans sur7Δ mutant displayed defects in endocytosis and morphogenesis. Septins and actin were mislocalized, and cell wall synthesis was very abnormal, including long projections of cell wall into the cytoplasm. Several phenotypes of the sur7Δ mutant are similar to the effects of inhibiting β-glucan synthase, suggesting that the abnormal cell wall synthesis is related to activation of chitin synthase activity seen under stress conditions. These results expand the roles of eisosomes by demonstrating that Sur7 is needed for proper plasma membrane organization and cell wall synthesis. A conserved Cys motif in the first extracellular loop of fungal Sur7 proteins is similar to a characteristic motif of the claudin proteins that form tight junctions in animal cells, suggesting a common role for these tetraspanning membrane proteins in forming specialized plasma membrane domains.
Dynein Light Intermediate Chain: An Essential Subunit That Contributes to Spindle Checkpoint Inactivation
Authors: Mische Sarah , He Yungui , Ma Lingzhi , Li Mingang , Serr Madeline , Hays Thomas S.
Published: September 2008

The dynein light intermediate chain (LIC) is a subunit unique to the cytoplasmic form of dynein, but how it contributes to dynein function is not fully understood. Previous work has established that the LIC homodimer binds directly to the dynein heavy chain and may mediate the attachment of dynein to centrosomes and other cargoes. Here, we report our characterization of the LIC in Drosophila. Unlike vertebrates, in which two Lic genes encode multiple subunit isoforms, the Drosophila LIC is encoded by a single gene. We determined that the single LIC polypeptide is phosphorylated, and that different phosphoisoforms can assemble into the dynein motor complex. Our mutational analyses demonstrate that, similar to other dynein subunits, the Drosophila LIC is required for zygotic development, germline specification of the oocyte, and mitotic cell division. We show that RNA interference depletion of LIC in Drosophila S2 cells does not block the recruitment of a dynein complex to kinetochores, but it does delay inactivation of Mad2 signaling and mitotic progression. Our observations suggest the LIC contributes to a broad range of dynein functions.
Cardiolipin Mediates Cross-Talk between Mitochondria and the Vacuole
Authors: Chen Shuliang , Tarsio Maureen , Kane Patricia M. , Greenberg Miriam L.
Published: September 2008

Cardiolipin (CL) is an anionic phospholipid with a dimeric structure predominantly localized in the mitochondrial inner membrane, where it is closely associated with mitochondrial function, biogenesis, and genome stability ( Daum, 1985 ; Janitor and Subik, 1993 ; Jiang et al., 2000 ; Schlame et al., 2000 ; Zhong et al., 2004 ). Previous studies have shown that yeast mutant cells lacking CL due to a disruption in CRD1, the structural gene encoding CL synthase, exhibit defective colony formation at elevated temperature even on glucose medium ( Jiang et al., 1999 ; Zhong et al., 2004 ), suggesting a role for CL in cellular processes apart from mitochondrial bioenergetics. In the current study, we present evidence that the crd1Δ mutant exhibits severe vacuolar defects, including swollen vacuole morphology and loss of vacuolar acidification, at 37°C. Moreover, vacuoles from crd1Δ show decreased vacuolar H+-ATPase activity and proton pumping, which may contribute to loss of vacuolar acidification. Deletion mutants in RTG2 and NHX1, which mediate vacuolar pH and ion homeostasis, rescue the defective colony formation phenotype of crd1Δ, strongly suggesting that the temperature sensitivity of crd1Δ is a consequence of the vacuolar defects. Our results demonstrate the existence of a novel mitochondria-vacuole signaling pathway mediated by CL synthesis.
Cyclic AMP Inhibits the Proliferation of Thyroid Carcinoma Cell Lines through Regulation of CDK4 Phosphorylation
Authors: Rocha Ana Sofia , Paternot Sabine , Coulonval Katia , Dumont Jacques E. , Soares Paula , Roger Pierre P.
Published: September 2008

How cyclic AMP (cAMP) could positively or negatively regulate G1 phase progression in different cell types or in cancer cells versus normal differentiated counterparts has remained an intriguing question for decades. At variance with the cAMP-dependent mitogenesis of normal thyroid epithelial cells, we show here that cAMP and cAMP-dependent protein kinase activation inhibit S-phase entry in four thyroid carcinoma cell lines that harbor a permanent activation of the Raf/ERK pathway by different oncogenes. Only in Ret/PTC1-positive TPC-1 cells did cAMP markedly inhibit the Raf/ERK cascade, leading to mTOR pathway inhibition, repression of cyclin D1 and p21 and p27 accumulation. p27 knockdown did not prevent the DNA synthesis inhibition. In the other cells, cAMP little affected these signaling cascades and levels of cyclins D or CDK inhibitors. However, cAMP differentially inhibited the pRb-kinase activity and T172-phosphorylation of CDK4 complexed to cyclin D1 or cyclin D3, whereas CDK-activating kinase activity remained unaffected. At variance with current conceptions, our studies in thyroid carcinoma cell lines and previously in normal thyrocytes identify the activating phosphorylation of CDK4 as a common target of opposite cell cycle regulations by cAMP, irrespective of its impact on classical mitogenic signaling cascades and expression of CDK4 regulatory partners.
The Hsk1(Cdc7) Replication Kinase Regulates Origin Efficiency
Authors: Patel Prasanta K. , Kommajosyula Naveen , Rosebrock Adam , Bensimon Aaron , Leatherwood Janet , Bechhoefer John , Rhind Nicholas
Published: September 2008

Origins of DNA replication are generally inefficient, with most firing in fewer than half of cell cycles. However, neither the mechanism nor the importance of the regulation of origin efficiency is clear. In fission yeast, origin firing is stochastic, leading us to hypothesize that origin inefficiency and stochasticity are the result of a diffusible, rate-limiting activator. We show that the Hsk1-Dfp1 replication kinase (the fission yeast Cdc7-Dbf4 homologue) plays such a role. Increasing or decreasing Hsk1-Dfp1 levels correspondingly increases or decreases origin efficiency. Furthermore, tethering Hsk1-Dfp1 near an origin increases the efficiency of that origin, suggesting that the effective local concentration of Hsk1-Dfp1 regulates origin firing. Using photobleaching, we show that Hsk1-Dfp1 is freely diffusible in the nucleus. These results support a model in which the accessibility of replication origins to Hsk1-Dfp1 regulates origin efficiency and provides a potential mechanistic link between chromatin structure and replication timing. By manipulating Hsk1-Dfp1 levels, we show that increasing or decreasing origin firing rates leads to an increase in genomic instability, demonstrating the biological importance of appropriate origin efficiency.
BEST: Bayesian estimation of species trees under the coalescent model
Authors: Liu Liang
Published: September 2008

Summary: BEST implements a Bayesian hierarchical model to jointly estimate gene trees and the species tree from multilocus sequences. It provides a new option for estimating species phylogenies within the popular Bayesian phylogenetic program MrBayes. The technique of simulated annealing is adopted along with Metropolis coupling as performed in MrBayes to improve the convergence rate of the Markov Chain Monte Carlo algorithm.

Availability:  http://www.stat.osu.edu/~dkp/BEST.

Contact:  lliu@oeb.harvard.edu
FunNet: an integrative tool for exploring transcriptional interactions
Authors: Prifti Edi , Zucker Jean-Daniel , Clement Karine , Henegar Corneliu
Published: September 2008

Summary: We describe here an exploratory tool, called FunNet, which implements an original systems biology approach, aiming to improve the biological relevance of the modular interaction patterns identified in transcriptional co-expression networks. A suitable analytical model, involving two abstraction layers, has been devised to relate expression profiles to the knowledge on transcripts’ biological roles, extracted from genomic databases, into a comprehensive exploratory framework. This approach has been implemented into a user-friendly web tool to promote its open use by the community.

Availability:  http://www.funnet.info

Contact:  edi.prifti@crc.jussieu.fr
Frank Albert Cotton. 9 April 1930 — 20 February 2007
Authors: Chisholm Malcolm H. , Lord Lewis of Newnham
Published: September 2008

F. Albert Cotton was born in west Philadelphia on 9 April 1930. He was named Frank Abbott Cotton by his parents in honour of thedoctor and friend of the family who delivered him. However, when he was not yet two years old his father, who was a mechanical engineer, died and guided by his mother he took his father's name, Albert. Although this was never legally recorded he became Frank Albert Cotton by common usage, or F. Albert Cotton, and to his friends he was Al. His family ancestry can be traced to England and Europe from whence his great grand parents had emigrated. His mother was only 32 years of age when his father died and, being widowed at the time of the great depression without a significant financial resource, she was placed in rather a predicament and forced to seek work. At first she did office work but thiswas not well paid and she discovered she could earn more as a waitress, and this she did for nearly the next 30 years.
The fitness and functionality of culturally evolved communication systems
Authors: Fay Nicolas , Garrod Simon , Roberts Leo
Published: September 2008

This paper assesses whether human communication systems undergo the same progressive adaptation seen in animal communication systems and concrete artefacts. Four experiments compared the fitness of ad hoc sign systems created under different conditions when participants play a graphical communication task. Experiment 1 demonstrated that when participants are organized into interacting communities, a series of signs evolve that enhance individual learning and promote efficient decoding. No such benefits are found for signs that result from the local interactions of isolated pairs of interlocutors. Experiments 2 and 3 showed that the decoding benefits associated with community evolved signs cannot be attributed to superior sign encoding or detection. Experiment 4 revealed that naive overseers were better able to identify the meaning of community evolved signs when compared with isolated pair developed signs. Hence, the decoding benefits for community evolved signs arise from their greater residual iconicity. We argue that community evolved sign systems undergo a process of communicative selection and adaptation that promotes optimized sign systems. This results from the interplay between sign diversity and a global alignment constraint; pairwise interaction introduces a range of competing signs and the need to globally align on a single sign-meaning mapping for each referent applies selection pressure.
Studying cumulative cultural evolution in the laboratory
Authors: Caldwell Christine A , Millen Ailsa E
Published: September 2008

Cumulative cultural evolution is the term given to a particular kind of social learning, which allows for the accumulation of modifications over time, involving a ratchet-like effect where successful modifications are maintained until they can be improved upon. There has been great interest in the topic of cumulative cultural evolution from researchers from a wide variety of disciplines, but until recently there were no experimental studies of this phenomenon. Here, we describe our motivations for developing experimental methods for studying cumulative cultural evolution and review the results we have obtained using these techniques. The results that we describe have provided insights into understanding the outcomes of cultural processes at the population level. Our experiments show that cumulative cultural evolution can result in adaptive complexity in behaviour and can also produce convergence in behaviour. These findings lend support to ideas that some behaviours commonly attributed to natural selection and innate tendencies could in fact be shaped by cultural processes.
Establishing an experimental science of culture: animal social diffusion experiments
Authors: Whiten Andrew , Mesoudi Alex
Published: September 2008

A growing set of observational studies documenting putative cultural variations in wild animal populations has been complemented by experimental studies that can more rigorously distinguish between social and individual learning. However, these experiments typically examine only what one animal learns from another. Since the spread of culture is inherently a group-level phenomenon, greater validity can be achieved through ‘diffusion experiments’, in which founder behaviours are experimentally manipulated and their spread across multiple individuals tested. Here we review the existing corpus of 33 such studies in fishes, birds, rodents and primates and offer the first systematic analysis of the diversity of experimental designs that have arisen. We distinguish three main transmission designs and seven different experimental/control approaches, generating an array with 21 possible cells, 15 of which are currently represented by published studies. Most but not all of the adequately controlled diffusion experiments have provided robust evidence for cultural transmission in at least some taxa, with transmission spreading across populations of up to 24 individuals and along chains of up to 14 transmission events. We survey the achievements of this work, its prospects for the future and its relationship to diffusion studies with humans discussed in this theme issue and elsewhere.
Introduction. Cultural transmission and the evolution of human behaviour
Authors: Smith Kenny , Kalish Michael L , Griffiths Thomas L , Lewandowsky Stephan
Published: September 2008

The articles in this theme issue seek to understand the evolutionary bases of social learning and the consequences of cultural transmission for the evolution of human behaviour. In this introductory article, we provide a summary of these articles (seven articles on the experimental exploration of cultural transmission and three articles on the role of gene–culture coevolution in shaping human behaviour) and a personal view of some promising lines of development suggested by the work summarized here.
Large-scale gene trapping in C57BL/6N mouse embryonic stem cells
Authors: Hansen Gwenn M. , Markesich Diane C. , Burnett Michael B. , Zhu Qichao , Dionne Karen M. , Richter Lizabeth J. , Finnell Richard H. , Sands Arthur T. , Zambrowicz Brian P. , Abuin Alejandro
Published: September 2008

We report the construction and analysis of a mouse gene trap mutant resource created in the C57BL/6N genetic background containing more than 350,000 sequence-tagged embryonic stem (ES) cell clones. We also demonstrate the ability of these ES cell clones to contribute to the germline and produce knockout mice. Each mutant clone is identified by a genomic sequence tag representing the exact insertion location, allowing accurate prediction of mutagenicity and enabling direct genotyping of mutant alleles. Mutations have been identified in more than 10,000 genes and show a bias toward the first intron. The trapped ES cell lines, which can be requested from the Texas A&M Institute for Genomic Medicine, are readily available to the scientific community.
Ab initio identification of functionally interacting pairs of cis-regulatory elements
Authors: Friedman Brad A. , Stadler Michael B. , Shomron Noam , Ding Ye , Burge Christopher B.
Published: September 2008

Cooperatively acting pairs of cis-regulatory elements play important roles in many biological processes. Here, we describe a statistical approach, compositionally orthogonalized co-occurrence analysis (coCOA) that detects pairs of oligonucleotides that preferentially co-occur in pairs of sequence regions, controlling for correlations between the compositions of the analyzed regions. coCOA identified three clusters of oligonucleotide pairs that frequently co-occur at 5′ and 3′ ends of human and mouse introns. The largest cluster involved GC-rich sequences at the 5′ ends of introns that co-occur and are co-conserved with specific AU-rich sequences near intron 3′ ends. These motifs are preferentially conserved when they occur together, as measured by a new co-conservation measure, supporting common in vivo function. These motif pairs are also enriched in introns flanking alternative “cassette” exons, suggesting a role in silencing of intervening exons, and we showed that these motifs can cooperatively silence splicing of an intervening exon in a splicing reporter assay. This approach can be easily generalized to problems beyond RNA splicing.
Nitric Oxide Interacts with Salicylate to Regulate Biphasic Ethylene Production during the Hypersensitive Response
Authors: Mur Luis A.J. , Laarhoven Lucas J.J. , Harren Frans J.M. , Hall Michael A. , Smith Aileen R.
Published: September 2008

C2H4 is associated with plant defense, but its role during the hypersensitive response (HR) remains largely uncharacterized. C2H4 production in tobacco (Nicotiana tabacum) following inoculation with HR-eliciting Pseudomonas syringae pathovars measured by laser photoacoustic detection was biphasic. A first transient rise (C2H4-I) occurred 1 to 4 h following inoculation with HR-eliciting, disease-forming, and nonpathogenic strains and also with flagellin (flg22). A second (avirulence-dependent) rise, at approximately 6 h (C2H4-II), was only seen with HR-eliciting strains. Tobacco leaves treated with the C2H4 biosynthesis inhibitor, aminoethoxyvinylglycine, suggested that C2H4 influenced the kinetics of a HR. Challenging salicylate hydroxylase-expressing tobacco lines and tissues exhibiting systemic acquired resistance suggested that C2H4 production was influenced by salicylic acid (SA). Disrupted expression of a C2H4 biosynthesis gene in salicylate hydroxylase tobacco plants implicated transcriptional control as a mechanism through which SA regulates C2H4 production. Treating leaves to increase oxidative stress or injecting with SA initiated monophasic C2H4 generation, but the nitric oxide (NO) donor sodium nitroprusside initiated biphasic rises. To test whether NO influenced biphasic C2H4 production during the HR, the NO synthase inhibitor NG-nitro-l-arginine methyl ester was coinoculated with the avirulent strain of P. syringae pv phaseolicola into tobacco leaves. The first transient C2H4 rise appeared to be unaffected by NG-nitro-l-arginine methyl ester, but the second rise was reduced. These data suggest that NO and SA are required to generate the biphasic pattern of C2H4 production during the HR and may influence the kinetics of HR formation.
Subclade of Flavin-Monooxygenases Involved in Aliphatic Glucosinolate Biosynthesis
Authors: Li Jing , Hansen Bjarne Gram , Ober James A. , Kliebenstein Daniel J. , Halkier Barbara Ann
Published: September 2008

Glucosinolates (GSLs) are amino acid-derived secondary metabolites with diverse biological activities dependent on chemical modifications of the side chain. We previously identified the flavin-monooxygenase FMOGS-OX1 as an enzyme in the biosynthesis of aliphatic GSLs in Arabidopsis (Arabidopsis thaliana) that catalyzes the S-oxygenation of methylthioalkyl to methylsulfinylalkyl GSLs. Here, we report the fine mapping of a quantitative trait locus for the S-oxygenating activity in Arabidopsis. In this region, there are three FMOs that, together with FMOGS-OX1 and a fifth FMO, form what appears to be a crucifer-specific subclade. We report the identification of these four uncharacterized FMOs, designated FMOGS-OX2 to FMOGS-OX5. Biochemical characterization of the recombinant protein combined with the analysis of GSL content in knockout mutants and overexpression lines show that FMOGS-OX2, FMOGS-OX3, and FMOGS-OX4 have broad substrate specificity and catalyze the conversion from methylthioalkyl GSL to the corresponding methylsulfinylalkyl GSL independent of chain length. In contrast, FMOGS-OX5 shows substrate specificity toward the long-chain 8-methylthiooctyl GSL. Identification of the FMOGS-OX subclade will generate better understanding of the evolution of biosynthetic activities and specificities in secondary metabolism and provides an important tool for breeding plants with improved cancer prevention characteristics as provided by the methylsulfinylalkyl GSL.
The Mitochondrial Cycle of Arabidopsis Shoot Apical Meristem and Leaf Primordium Meristematic Cells Is Defined by a Perinuclear Tentaculate/Cage-Like Mitochondrion
Authors: Seguí-Simarro José M. , Coronado María José , Staehelin L. Andrew
Published: September 2008

Plant cells exhibit a high rate of mitochondrial DNA (mtDNA) recombination. This implies that before cytokinesis, the different mitochondrial compartments must fuse to allow for mtDNA intermixing. When and how the conditions for mtDNA intermixing are established are largely unknown. We have investigated the cell cycle-dependent changes in mitochondrial architecture in different Arabidopsis (Arabidopsis  thaliana) cell types using confocal microscopy, conventional, and three-dimensional electron microscopy techniques. Whereas mitochondria of cells from most plant organs are always small and dispersed, shoot apical and leaf primordial meristematic cells contain small, discrete mitochondria in the cell periphery and one large, mitochondrial mass in the perinuclear region. Serial thin-section reconstructions of high-pressure-frozen shoot apical meristem cells demonstrate that during G1 through S phase, the large, central mitochondrion has a tentaculate morphology and wraps around one nuclear pole. In G2, both types of mitochondria double their volume, and the large mitochondrion extends around the nucleus to establish a second sheet-like domain at the opposite nuclear pole. During mitosis, approximately 60% of the smaller mitochondria fuse with the large mitochondrion, whose volume increases to 80% of the total mitochondrial volume, and reorganizes into a cage-like structure encompassing first the mitotic spindle and then the entire cytokinetic apparatus. During cytokinesis, the cage-like mitochondrion divides into two independent tentacular mitochondria from which new, small mitochondria arise by fission. These cell cycle-dependent changes in mitochondrial architecture explain how these meristematic cells can achieve a high rate of mtDNA recombination and ensure the even partitioning of mitochondria between daughter cells.
Clinical trial: the effects of a fermented milk product containing Bifidobacterium lactis DN‐173 010 on abdominal distension and gastrointestinal transit in irritable bowel syndrome with constipation
Authors: AGRAWAL A. , HOUGHTON L. A. , MORRIS J. , REILLY B. , GUYONNET D. , GOUPIL FEUILLERAT N. , SCHLUMBERGER A. , JAKOB S. , WHORWELL P. J.
Published: September 2008

Background  A sensation of abdominal swelling (bloating) and actual increase in girth (distension) are troublesome features of irritable bowel syndrome (IBS), which is more common in patients with constipation, especially those with delayed transit.

Aim  To establish whether a fermented dairy product containing Bifidobacterium lactis DN‐173 010 reduces distension in association with acceleration of gastrointestinal transit and improvement of symptoms in IBS with constipation.

Methods  A single centre, randomized, double‐blind, controlled, parallel group study in which patients consumed the test product or control product for 4 weeks. Distension, orocaecal and colonic transit and IBS symptoms were assessed on an intention‐to‐treat population of 34 patients.

Results  Compared with control product, the test product resulted in a significant reduction in the percentage change in maximal distension [median difference – 39%, 95% CI (−78, −5); P = 0.02] and a trend towards reduced mean distension during the day [−1.52 cm (−3.33, 0.39); P = 0.096]. An acceleration of orocaecal [−1.2 h (−2.3,0); P = 0.049] as well as colonic [−12.2 h (−22.8, −1.6); P = 0.026] transit was observed and overall symptom severity [−0.5 (−1.0, −0.05); P = 0.032] also improved.

Conclusions  This probiotic resulted in improvements in objectively measured abdominal girth and gastrointestinal transit, as well as reduced symptomatology. These data support the concept that accelerating transit is a useful strategy for treating distension.
What does stable isotope analysis reveal about trophic relationships and the relative importance of allochthonous and autochthonous resources in tropical streams? A synthetic study from Hong Kong
Authors: LAU DANNY C. P. , LEUNG KENNETH M. Y. , DUDGEON DAVID
Published: September 2008

1. Analysis of the stable isotope signatures of carbon (C) and nitrogen (N) of foods and consumers has led to some preliminary understanding of the relative importance of autochthonous and allochthonous resources in tropical streams. However, robust generalizations about the dynamics of food webs in these habitats, and their response to shading gradients or season, are still lacking. In addition, the feasibility of employing a baseline δ15N value for estimating trophic positions (TPs) of consumers in small tropical streams has yet to be explored.

2. We analysed data on stable isotope signatures of food sources and aquatic consumers obtained from 14 studies carried out in small streams in monsoonal Hong Kong (22°30′N, 114°10′E) between 1996 and 2006. Emphasis was placed on determining the relative importance of leaf litter and autochthonous foods in supporting consumer biomass, and the extent to which trophic base and TP vary among streams and seasons.

3. Although allochthonous leaf litter was generally 13C‐ and 15N‐depleted relative to autochthonous foods, there were marked isotopic shifts of food sources and consumers in response to season (dry versus wet) and stream shading. Consumer taxa were generally more 13C‐ and 15N‐enriched in the unshaded streams, but seasonal effects were more variable. Despite these changes, there was consistent evidence that stream food webs were based on periphytic algae and/or cyanobacteria with leaf litter serving as a minor food.

4. Heptageniidae (Ephemeroptera), Tipulidae (Diptera), Elmidae (Coleoptera) and shrimps (Atyidae) were used as a baseline for calculating the TPs of other consumer taxa. The maximum TPs in shaded streams remained fairly constant between seasons (dry = 3.93; wet = 3.97), while those in unshaded streams were higher and showed seasonal fluctuations (dry = 5.13; wet = 4.39).

5. Although variations in consumer isotope signatures in response to season and shading gradients did not confound our interpretation of the stream food base, changes in consumer δ15N did affect the calculation of consumer TPs. Misleading estimates of consumer TPs are likely if samples are collected from a narrow range of streams and/or during one season. Overestimation of the TPs of specialist herbivores (e.g. fish grazers) is also possible when autochthonous resources are substantially more 15N‐enriched than allochthonous foods.
Menorrhagia and reproductive health in rare bleeding disorders: a study from the Indian subcontinent
Authors: VIJAPURKAR M. , MOTA L. , SHETTY S. , GHOSH K.
Published: September 2008

Abstract.  At this centre, 130 women with rare bleeding disorders (RBD) were investigated over the past 15 years. Fifty patients were above the age of menarche (age of menarche in India is 10 years). Of these 44 presented with menorrhagia. Other complications in these patients involved bleeding because of ruptured graffian follicle (1), severe haemorrhage following caesarean section (1), recurrent pregnancy losses (3), hysterectomy to control menorrhagia (2), laser ablation of endometrium (1) and irradiation of ovary (1). Three patients voluntarily chose to remain unmarried because of the problems associated with menorrhagia which they assumed will interfere with married life. All the 45 patients had iron deficiency anaemia. The spectrum of RBD in these patients comprised Glanzmann’s thrombasthenia (17), Bernard‐Soulier syndrome (2), storage pool disorder (2), factor V (FV) deficiency (3), combined FV and factor VIII deficiency (5), factor XI deficiency (3), factor XIII deficiency (1), factor X deficiency (5), factor VII deficiency (2), α2‐antiplasmin deficiency (1) and afibrinogenemia (3). RBD in women is diagnosed late and often they are not optimally managed hence suffer both iatrogenic and non‐iatrogenic complications in this country.
Inferring recent changes in the ecological state of 21 Danish candidate reference lakes (EU Water Framework Directive) using palaeolimnology
Authors: Bjerring Rikke , Bradshaw Emily Gwyneth , Amsinck Susanne Lildal , Johansson Liselotte Sander , Odgaard Bent Vad , Nielsen Anne Birgitte , Jeppesen Erik
Published: September 2008

The European Water Framework Directive (WFD) requires that all natural European waterbodies should be assigned to one of five ecological categories defining the degree to which present‐day conditions deviate from those uninfluenced or only negligibly impacted by anthropogenic activities (the reference condition). By 2015, all relevant waterbodies must have obtained ‘good’ ecological quality.

We describe the changes in ecological state in 21 Danish lakes using ad 1850 as a benchmark for reference conditions. Sediment samples representing 1850, 1900, 1950 and 2000 were analysed for diatom and cladoceran subfossils. Ecological status since 1850 was evaluated using correspondence analysis and dissimilarity measures to assess assemblage changes, and existing transfer functions were applied to infer changes in total phosphorous concentrations from diatoms (DI‐TP) and submerged macrophyte coverage (SUB‐COV) and benthi‐planktivorous fish catch per unit effort (BP‐CPUE) from cladoceran subfossils.

Eighteen lakes underwent significant changes, most markedly during the past 50–100 years, in either or both diatom and cladoceran community structure. Low floristic and faunal alteration was found only in three lakes; these were, however, already nutrient‐rich in 1850.

In 1850, most lakes were already characterized by high DI‐TP (median of 17 lakes = 86 µg TP L−1), high inferred BP‐CPUE and low inferred SUB‐COV, and these eutrophic conditions still prevail. In addition, the accumulation rate of sediment and cladoceran subfossils and the pelagic dominance of diatoms and cladocerans have increased.

When applying the thresholds proposed by a recent WFD classification for Danish lakes to the DI‐TP values, only one lake could be described as having a ‘good’ ecological state with a concurrent low community change since 1850, limited to the cladoceran community, however. This suggests that this lake alone may serve as a potential reference site.

Synthesis and applications. Our study, demonstrating the potential of a palaeolimnological approach to assess deviations from reference conditions, suggests that Danish reference lakes may be difficult to find, most probably due to the country's long history of cultural impact. Lake managers consequently face great challenges in their endeavour to ensure ‘good’ ecological state by 2015. Therefore, further restrictions on land‐use and nutrient loading in lake catchments are needed as is the initiation of restoration activities to improve the ecological state of the lakes.
Stressors in the ICU: a comparison of patients’ and nurses’ perceptions
Authors: Pang Pounds Siu Kau , Suen Lorna Kwai Ping
Published: September 2008

Aims and objectives.  The aim of the study was to compare the stressors as perceived by patients in an intensive care unit (ICU) against those of nurses on the basis of their perceptions of patients’ stressors.

Background.  Getting admitted to an ICU is viewed as a stressful event by patients. However, numerous studies have indicated that nurses do not always accurately perceive the stressors of their clients. Therefore, it is important for nurses to know what seems most stressful from the patients’ perspective so that appropriate nursing measures can be directed towards minimising such stressors.

Design.  Survey.

Methods.  As a convenience sample, 60 patients and 54 critical care nurses were recruited. The Intensive Care Unit Stressor Questionnaire (Chinese) (ICU‐CSQ) was used to collect the perceptions of stressors by the patients. Nurses were also asked to rate the items in the said questionnaire according to how they believe patients would rate them.

Results.  In every comparison, nurses evaluated the items to be significantly more stressful than patients did. Overall perceived stress levels of nurses were also significantly higher than those of their patients (z = −8·78, p < 0·001).

Conclusions.  Nurses tended to rate the items as more stressful than did the patients, perhaps over‐emphasising the stressful nature of the ICU. The findings also highlight the importance of cultural beliefs on the perceived stress levels among the Chinese population.

Relevance to clinical practice.  Findings in this study have strong implications in clinical practice, especially in a critical care setting. Nurses must attempt to identify and endeavour to cope with the situations that patients listed as most stressful. Moreover, attention must be drawn towards measures aimed at relieving the stress of patients by taking into account their cultural values so that culture‐specific interventions for reducing their stress can be established.
The status of training and education in information and computer technology of Australian nurses: a national survey
Authors: Eley Robert , Fallon Tony , Soar Jeffrey , Buikstra Elizabeth , Hegney Desley
Published: September 2008

Aims and objectives.  A study was undertaken of the current knowledge and future training requirements of nurses in information and computer technology to inform policy to meet national goals for health.

Background.  The role of the modern clinical nurse is intertwined with information and computer technology and adoption of such technology forms an important component of national strategies in health. The majority of nurses are expected to use information and computer technology during their work; however, the full extent of their knowledge and experience is unclear.

Design.  Self‐administered postal survey.

Methods.  A 78‐item questionnaire was distributed to 10,000 Australian Nursing Federation members to identify the nurses’ use of information and computer technology. Eighteen items related to nurses’ training and education in information and computer technology.

Results.  Response rate was 44%. Computers were used by 86·3% of respondents as part of their work‐related activities. Between 4–17% of nurses had received training in each of 11 generic computer skills and software applications during their preregistration/pre‐enrolment and between 12–30% as continuing professional education. Nurses who had received training believed that it was adequate to meet the needs of their job and was given at an appropriate time. Almost half of the respondents indicated that they required more training to better meet the information and computer technology requirements of their jobs and a quarter believed that their level of computer literacy was restricting their career development. Nurses considered that the vast majority of employers did not encourage information and computer technology training and, for those for whom training was available, workload was the major barrier to uptake. Nurses favoured introduction of a national competency standard in information and computer technology.

Conclusions.  For the considerable benefits of information and computer technology to be incorporated fully into the health system, employers must pay more attention to the training and education of nurses who are the largest users of that technology.

Relevance to clinical practice.  Knowledge of the training and education needs of clinical nurses with respect to information and computer technology will provide a platform for the development of appropriate policies by government and by employers.
Views of xerostomia among health care professionals: a qualitative study
Authors: Folke Solgun , Fridlund Bengt , Paulsson Gun
Published: September 2008

Aim.  To explore and describe views of xerostomia among health care professionals.

Background.  Xerostomia (dry mouth) is caused by changes in quality and quantity of saliva due to poor health, certain drugs and radiation therapy. It is a common symptom, particularly among older people and has devastating consequences with regard to oral health and general well‐being.

Methods.  Data were obtained and categorised by interviewing 16 health care professionals. Qualitative content analysis was chosen as the method of analysis.

Design.  Qualitative.

Results.  The latent content was formulated into a theme: xerostomia is a well‐known problem, yet there is inadequate management of patients with xerostomia. The findings identified three categories expressing the manifest content: awareness of xerostomia, indifferent attitude and insufficient support.

Conclusions.  Although xerostomia was recognised as commonly occurring, it was considered to be an underestimated and an ignored problem. Proper attention to conditions of xerostomia and subsequent patient management were viewed as fragmentary and inadequate. Additional qualitative studies among patients with xerostomia would be desirable to gain further understanding of the problems with xerostomia, its professional recognition and management.

Relevance to clinical practice.  A holistic view, positive professional attitudes and enhanced knowledge of xerostomia seem essential to augment collaboration among health care professionals and to improve compassion for and support of patients with xerostomia.
A literature review of principles, policies and practice in extended nursing roles relating to UK intensive care settings
Authors: Srivastava Namita , Tucker Janet S , Draper Elizabeth S , Milner Michelle ,   on behalf of the UK PICU Staffing Study
Published: September 2008

Aims.  To provide an overview of the literature relating to the principles, policy and practice of extended nursing roles in UK intensive care settings to date; to review and critically assess evidence of impact, outcomes and effect on practice and provide suggestions for future research.

Background.  It is known that career development opportunities, new technologies, patient needs, as well as the reduction in junior doctors’ hours, are driving the development of new roles for nurses. Policy initiatives aim to expand nursing roles to support professional substitution. In adult, neonatal and paediatric intensive care, specialist trained nurses and designated advanced nursing practitioners are increasingly taking on extended practice of clinical tasks previously undertaken by medical staff. As yet there are no statutory regulations on the perceived scope and definition of the role of extended and advanced roles.

Design.  Systematic review.

Methods.  Search of electronic databases and selection of policy and peer‐reviewed reports and reviews of extended nursing roles or advanced nursing practitioners in UK intensive care settings.

Results.  Chronological review shows policy development proceeding in a relatively ad hoc way. There is limited information available about how extensively or effectively extended nursing roles are being implemented in intensive care settings in the UK, particularly in adult and paediatric intensive care. To test local initiative findings for reliability and generalisability, a more robust evidence base is required.

Conclusions.  More data are needed on definition and outcomes of extended nursing roles in intensive care and care process measures should be developed to better inform implementation of nurse role development in the UK.

Relevance to clinical practice.  The review of policy and research evidence in this paper may better inform clinicians working in adult, neonatal or paediatric intensive care, as they continue to be challenged by expansion and development of their role. It may also help to form a basis and evaluation for future research into extended and advanced nursing roles in intensive care settings.