Molecular model of the contractile ring BIRON, D; ALVAREZ-LACALLE, E; TLUSTY, T ...
Physical review letters,
08/2005, Letnik:
95, Številka:
9
Journal Article
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Odprti dostop
We present a model for the actin contractile ring of adherent animal cells. The model suggests that the actin concentration within the ring and consequently the power that the ring exerts both ...increase during contraction. We demonstrate the crucial role of actin polymerization and depolymerization throughout cytokinesis, and the dominance of viscous dissipation in the dynamics. The physical origin of two phases in cytokinesis dynamics ("biphasic cytokinesis") follows from a limitation on the actin density. The model is consistent with a wide range of measurements of the midzone of dividing animal cells.
One of the most fascinating anti-predator responses displayed by parasites is that of hairworms (Nematomorpha). Following the ingestion of the insect host by fish or frogs, the parasitic worm is able ...to actively exit both its host and the gut of the predator. Using as a model the hairworm, Paragordius tricuspidatus, (parasitizing the cricket Nemobius sylvestris) and the fish predator Micropterus salmoïdes, we explored, with proteomics tools, the physiological basis of this anti-predator response. By examining the proteome of the parasitic worm, we detected a differential expression of 27 protein spots in those worms able to escape the predator. Peptide Mass Fingerprints of candidate protein spots suggest the existence of an intense muscular activity in escaping worms, which functions in parallel with their distinctive biology. In a second step, we attempted to determine whether the energy expended by worms to escape the predator is traded off against its reproductive potential. Remarkably, the number of offspring produced by worms having escaped a predator was not reduced compared with controls.
Hairworms (nematomorpha) alter the behaviour of their insect hosts, making them commit ‘suicide’ by jumping into an aquatic environment required by the adult parasite for the continuation of its life ...cycle. To explore the physiological and neuronal basis of this behavioural manipulation, we first performed a biochemical study to quantify different neurotransmitters or neuromodulators (monoamines and amino acids) in the brain of crickets (
Nemobius sylvestris) uninfected and infected by the hairworm
Paragordius tricuspidatus. We also analysed several polyamines and amino-acids having no known neuromodulatory function. The presence/absence of the parasite explained the largest part of the variation in compound concentrations, with infected individuals displaying on average lower concentrations than uninfected individuals. However, for three amino acids (taurine, valine and tyrosine), a significant part of the variation was also correlated with the manipulative process. In order to compare neurogenesis between infected and uninfected crickets, we also performed a histological study on mushroom bodies in the cricket's brain. The mitotic index exhibited a two-fold increase in infected crickets as compared with uninfected crickets. This is the first study to document changes in the brain of insects infected by nematomorphs.
ABSTRACT
Background: In many surveys, nurses cite work interruptions as a significant contributor to medication administration errors.
Objectives: To review the evidence on (1) nurses' interruption ...rates, (2) characteristics of such work interruptions, and (3) contribution of work interruptions to medication administration errors.
Approach: Search strategy: CINHAL (1982–2008), MEDLINE (1980–2008), EMBASE (1980–2008), and PSYCINFO (1980–2008) were searched using a combination of keywords and reference lists. Selection criteria: Original studies published in English using nurses as participants and for which work interruption frequencies are reported. Data collection and analysis: Studies were identified and selected by two reviewers. Once selected, a single reviewer extracted data and assessed quality based on established criteria. Data on nurses' work interruption rates were synthesized to produce a pooled estimate.
Results: Twenty‐three studies were considered for analysis. A rate of 6.7 work interruptions per hour was obtained, based on 14 studies that reported both an observation time and work interruption frequency. Work interruptions are mostly initiated by nurses themselves through face‐to‐face interactions and are of short duration. A lower proportion of interruptions resulted from work system failures such as missing medication. One nonexperimental study documented the contribution of work interruptions to medication administration errors with evidence of a significant association (p = 0.01) when errors related to time of administration are excluded from the analysis. Conceptual shortcomings were noted in a majority of reviewed studies, which included the absence of theoretical underpinnings and a diversity of definitions of work interruptions.
Conclusions: Future studies should demonstrate improved methodological rigor through a precise definition of work interruptions and reliability reporting to document work interruption characteristics and their potential contribution to medication administration errors, considering the limited evidence found. Meanwhile, efforts should be made to reduce the number of work interruptions experienced by nurses.
Parasitic manipulations of host behaviour are known from a wide range of host-parasite associations. However, the understanding of these phenomena is far from complete and detailed investigation of ...their proximate causes is needed. Many studies report behavioural modifications, such as altered feeding rates in tsetse fly (Glossina) infected with the mature transmissible stage (i.e. metacyclic) of the trypanosomes. Here, bidimensional (2D) gel electrophoresis and mass spectrometry were employed to analyse and compare the head proteome between four Glossina palpalis gambiensis categories (uninfected, refractory, mature infection, immature infection). Twenty-four protein spots specifically present or absent in the head of metacyclic-infected flies were observed. These protein spots were subsequently identified and functionally classified as glycolitic, neurotransmiter synthesis, signalling, molecular chaperone and transcriptional regulation proteins. Our results indicate altered energy metabolism in the head of metacyclic-infected tsetse flies. Some of the proteins identified, such as casein kinase 2 and jun kinase have previously been shown to play critical roles in apoptosis in insect neurones. In addition, we found two pyridoxal-dependent decarboxylases (dopa decarboxylase and alpha methyldopa hypersensitive protein), suggesting a modification of serotonin and/or dopamine in the brain of metacyclic-infected tsetse flies. Our data pave the way for future investigation of the alteration of the glossina central nervous system during infection by trypanosomes.
Objective: To document characteristics of nurses’ work interruptions (WIs) during medication administration.
Design: A descriptive observational study design was used along with a sample of 102 ...medication administration rounds. Data were collected on a single medical unit using a unit dose distribution system during fall 2007.
Method: Data collection on WIs relied on direct structured observation. The following WI characteristics were recorded: source, secondary task, location, management strategies, and duration.
Results: 374 WIs were observed over 59 hours 2 minutes of medication administration time (6.3 WI/hr). During the preparation phase, nurse colleagues (n= 36; 29.3%) followed by system failures such as missing medication or equipment (n= 28; 22.8%) were the most frequent source of WIs. Nurses were interrupted during the preparation phase mostly to solve system failures (n= 33; 26.8%) or for care coordination (n= 30; 24.4%). During the administration phase, the most frequent sources of WIs were self‐initiation (n= 41; 16.9%) and patients (n= 39; 16.0%). The most frequent secondary task undertaken during the administration phase was direct patient care (n= 105; 43.9%). WIs lasted 1 min 32 s on average, and were mostly handled immediately (n= 357; 98.3%).
Conclusions: The process of medication administration is not protected against WIs, which poses significant risks.
Clinical Relevance: Interventions to reduce WIs during the medication administration process should target nurses and system failures to maximize medication administration safety.
A single consistent scheme of calculational methods and nuclear data called ERANOS-ERALIB1 was produced in 1996 to calculate fast reactor neutronic parameters. It represents a significant improvement ...on previous schemes such as CARNAVAL-IV, PROPANE and VASCO, each of which were required in order to calculate one specific application. The nuclear data library ERALIB1 has been obtained by a consistent statistical adjustment based on 355 integral data from 71 different systems. The performance of ERALIB1 is excellent, as demonstrated during its validation for which all the
k
eff SUPER-PHENIX data were reproduced to within 70 pcm.
The only restriction on this satisfactory performance is related to the rather poor prediction of the sodium void reactivity effect. This was due to very bad nuclear data for
23Na, and the unsatisfactory methods used to calculate the sensitivity coefficients for the sodium void reactivity variation Δ
ρ
Na. To improve the performance relative to this point and to enlarge the domain of validation several actions have been undertaken:
•
a revision of the formalism and algorithms used to calculate the derivatives of Δ
ρ
Na to the sodium cross section data,
•
a significant enlargement of the integral data base related to this aspect of the sodium void effect. Compared to the initial data base established in support of ERALIB1, several additional (18) sodium void configurations corresponding to voids of different volumes at different core locations have been studied.
In order to broaden the range of application of the improved library, which will be called ERALIB1.A, significant effort has been devoted to additional configurations which have firstly been evaluated, and then if judged suitable, included in the adjustment process. They are related to two specifically targeted experimental programmes:
•
a study of neutron deep penetration. Several configurations of the JANUS experimental programme (shielding constructed of separate steel, iron and sodium plates) have been analysed. With this complementary information ERALIB 1A becomes applicable for accurate predictions of shielding configurations,
•
a study of steel reflectors for a fast reactor of the SUPER-PHENIX type. The measurements performed in the MASURCA (the CIRANO experimental programme) and FCA facilities include spectral indices (F25(r)/F25(0),...) at different positions in the reflector. As a consequence of these measurements, important information has been obtained for additional “secondary” structural material isotopes, such as
57Fe,
60Ni and
53Cr.
Significant effort has also been devoted to the analysis of 29
β
eff experiments. The result of this is an improvement of the uncertainty on
ν
d(
E) which guarantees a prediction of
β
eff with the required accuracy (3% for critical configurations, and 5% for power reactors).
The consistent statistical adjustment method by Gandini et al. (1973) has been completed. Rigorous criteria have been introduced to identify any data which are suspect and/or inconsistent in the integral data base. These data may introduce additional bias in the adjusted library, and for that reason they must be discarded before adjustment.
We explored the idea that hosts infected with manipulative parasites might mitigate the costs of infection by collaborating with the parasite rather than resisting it. Nematomorphs are usually ...considered to be manipulative parasites of arthropods because they cause hosts to seek an aquatic environment, which is needed by the adult parasite. We placed infected cricket hosts in situations of forced noncompliance and compared some fitness parameters (life expectancy, gonad development, and reproductive behaviors) in noncompliant hosts and hosts allowed to express parasite-induced behavior. Compared to uninfected controls, reduced survival was observed in both males and females from the two categories of infected hosts, collaborative or not. A substantial proportion of collaborative females produced eggs or had developed ovaries while such phenomena were never observed among noncollaborative ones. Collaborative females retained a nymphal phenotype, but adult males nevertheless courted and produced spermatophores to such females. However, collaborative females had difficulties mounting males, taking spermatophores and/or ovipositing. In contrast to females, all males were entirely castrated by the parasite regardless of their behavior, collaborative or not. Thus, bringing the parasite into water does not effectively mitigate the costs of infection for the host.
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