Pseudoreplication in physiology:More means less

This article reviews how to analyze data from experiments designed to compare the cellular physiology of two or more groups of animals or people. This is commonly done by measuring data from several cells from each animal and using simple t tests or ANOVA to compare between groups. I use simulations to illustrate that this method can give erroneous positive results by assuming that the cells from each animal are independent of each other. This problem, which may be responsible for much of the lack of reproducibility in the literature, can be easily avoided by using a hierarchical, nested statistics approach

Screening and prevention in Swiss primary care: a systematic review

BACKGROUND AND OBJECTIVES: Prevention is a challenging area of primary care. In Switzerland, little is known about attitudes to and performance of screening and prevention services in general practice. To implement prevention services in primary care it is important to know about not only potential facilitators but also barriers. Primary care encompasses the activities of general practitioners, including those with particular interest and/or specializations (eg, pediatrics, gynecology). The aim of this study was to review all studies with a focus on prevention services which have been conducted in Switzerland and to reveal barriers and facilitators for physicians to participate in any preventive measures. METHODS: The Cochrane Library, PubMed, EMBASE and BIOSIS were searched from January 1990 through December 2010. Studies focussing on preventive activities in primary care settings were selected and reviewed. The methodological quality of the identified studies was classified according to the guidelines in the Consolidated Standards of Reporting Trials (CONSORT) statement. RESULTS: We identified 49 studies including 45 descriptive studies and four randomised controlled trials (RCTs). Twelve studies addressed the prevention of epidemics, eleven out of them vaccinations. Further studies focused on lifestyle changes, physical activity counselling, smoking cessation, cardiovascular prevention and cancer screening. Perceived lack of knowledge/training and lack of time were the most commonly stated barriers. Motivation, feasibility and efficiency were the most frequently reported supporting factors for preventive activities. The methodological quality was weak, only one out of four RCTs met the applied quality criteria. CONCLUSION: Most studies focussing on screening and prevention activities in primary care addressed vaccination, lifestyle modification or cardiovascular disease prevention. Identified barriers and facilitators indicate a need for primary-care-adapted education and training which are easy to handle, time-saving and reflect the specific needs of general practitioners. If new prevention programs are to be implemented in general practices, RCTs of high methodological quality are needed to assess their impact

Calcium Handling Defects and Cardiac Arrhythmia Syndromes

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Phenol-Explorer 2.0: a major update of the Phenol-Explorer database integrating data on polyphenol metabolism and pharmacokinetics in humans and experimental animals

Phenol-Explorer, launched in 2009, is the only comprehensive web-based database on the content in foods of polyphenols, a major class of food bioactives that receive considerable attention due to their role in the prevention of diseases. Polyphenols are rarely absorbed and excreted in their ingested forms, but extensively metabolized in the body, and until now, no database has allowed the recall of identities and concentrations of polyphenol metabolites in biofluids after the consumption of polyphenol-rich sources. Knowledge of these metabolites is essential in the planning of experiments whose aim is to elucidate the effects of polyphenols on health. Release 2.0 is the first major update of the database, allowing the rapid retrieval of data on the biotransformations and pharmacokinetics of dietary polyphenols. Data on 375 polyphenol metabolites identified in urine and plasma were collected from 236 peer-reviewed publications on polyphenol metabolism in humans and experimental animals and added to the database by means of an extended relational design. Pharmacokinetic parameters have been collected and can be retrieved in both tabular and graphical form. The web interface has been enhanced and now allows the filtering of information according to various criteria. Phenol-Explorer 2.0, which will be periodically updated, should prove to be an even more useful and capable resource for polyphenol scientists because bioactivities and health effects of polyphenols are dependent on the nature and concentrations of metabolites reaching the target tissues. The Phenol-Explorer database is publicly available and can be found online at http://www.phenol-explorer.eu. Database URL: http://www.phenol-explorer.eu

Poliovirus RNA Polymerase Mutation 3D-M394T Results in a Temperature-Sensitive Defect in RNA Synthesis

AbstractMutant ts10 is an RNA-negative temperature-sensitive mutant of Mahoney type 1 poliovirus. Mutant ts10 3Dpolwas purified from infected cells and was shown to be rapidly heat-inactivated at 45° when compared to wild-type polymerase. Sequencing of mutant ts10 genomic RNA revealed a U to C transition at nt 7167 resulting in an amino acid change of methionine 394 of 3Dpolto threonine. The 3D-M394T mutation was engineered into a wild-type infectious clone of poliovirus type 1. The resultant mutant virus, 3D-105, had a temperature-sensitive phenotype in plaque assays. The translation and replication of wild-type, ts10, and 3D-105 virion RNAs were all characterized in HeLa S10 translation-RNA replication reactionsin vitro.The optimum temperatures for the replication of the wild-type and mutant viral RNAs in the HeLa S10 translation-replication reactions were 37 and 34°, respectively. To characterize the temperature-sensitive defect in the replication of the mutant RNA, we used preinitiation RNA replication complexes which were formed in HeLa S10in vitroreactions containing guanidine HCl. Negative-strand RNA synthesis in 3D-M394T mutant preinitiation replication complexes was normal at 34° but was rapidly and irreversibly inhibited at 39.5°. To differentiate between the initiation and elongation steps in RNA replication, we compared the elongation rates in mutant and wild-type replication complexes at 39.5°. The results showed that the elongation rates for nascent negative strands in both the mutant and wild-type replication complexes were identical. Therefore, the results indicate that the heat-sensitive step in negative-strand synthesis exhibited by the 3D-M394T replication complexes is in the initiation of RNA synthesis and not in the elongation of nascent chains

Blockade of sodium‑calcium exchanger via ORM-10962 attenuates cardiac alternans

Repolarization alternans, a periodic oscillation of long-short action potential duration, is an important source of arrhythmogenic substrate, although the mechanisms driving it are insufficiently understood. Despite its relevance as an arrhythmia precursor, there are no successful therapies able to target it specifically. We hypothesized that blockade of the sodium‑calcium exchanger (NCX) could inhibit alternans. The effects of the selective NCX blocker ORM-10962 were evaluated on action potentials measured with microelectrodes from canine papillary muscle preparations, and calcium transients measured using Fluo4-AM from isolated ventricular myocytes paced to evoke alternans. Computer simulations were used to obtain insight into the drug's mechanisms of action. ORM-10962 attenuated cardiac alternans, both in action potential duration and calcium transient amplitude. Three morphological types of alternans were observed, with differential response to ORM-10962 with regards to APD alternans attenuation. Analysis of APD restitution indicates that calcium oscillations underlie alternans formation. Furthermore, ORM-10962 did not markedly alter APD restitution, but increased post-repolarization refractoriness, which may be mediated by indirectly reduced L-type calcium current. Computer simulations reproduced alternans attenuation via ORM-10962, suggesting that it is acts by reducing sarcoplasmic reticulum release refractoriness. This results from the ORM-10962-induced sodium‑calcium exchanger block accompanied by an indirect reduction in L-type calcium current. Using a computer model of a heart failure cell, we furthermore demonstrate that the anti-alternans effect holds also for this disease, in which the risk of alternans is elevated. Targeting NCX may therefore be a useful anti-arrhythmic strategy to specifically prevent calcium driven alternans

Nutrient and Phytoplankton Dynamics on the Inner Shelf of the Eastern Bering Sea

In the Bering Sea, the nitrogen cycle near Nunivak Island is complicated due to limited nutrient replenishment across this broad shelf, and substantial nitrogen loss through sedimentary processes. While diffusion at the inner front may periodically support new production, the inner shelf in this region is generally described as a regenerative system. This study combines hydrographic surveys with measurements of nitrogen assimilation and benthic fluxes to examine nitrogen cycling on the inner shelf, and connectivity between the middle and inner shelves of the southern and central Bering Sea. Results establish the inner shelf as primarily a regenerative system even in spring, although new production can occur at the inner front. Results also identify key processes that influence nutrient supply to the inner shelf and reveal coupling between the middle shelf nutrient pool and production on the inner shelf

Variability of Disk Emission in Pre-Main Sequence and Related Stars. II. Variability in the Gas and Dust Emission of the Herbig Fe Star SAO 206462

We present thirteen epochs of near-infrared (0.8-5 micron) spectroscopic observations of the pre-transitional, "gapped" disk system in SAO 206462 (=HD 135344B). In all, six gas emission lines (including Br gamma, Pa beta, and the 0.8446 micron line of O I) along with continuum measurements made near the standard J, H, K, and L photometric bands were measured. A mass accretion rate of approximately 2 x 10^-8 solar masses per year was derived from the Br gamma and Pa beta lines. However, the fluxes of these lines varied by a factor of over two during the course of a few months. The continuum also varied, but by only ~30%, and even decreased at a time when the gas emission was increasing. The H I line at 1.083 microns was also found to vary in a manner inconsistent with that of either the hydrogen lines or the dust. Both the gas and dust variabilities indicate significant changes in the region of the inner gas and the inner dust belt that may be common to many young disk systems. If planets are responsible for defining the inner edge of the gap, they could interact with the material on time scales commensurate with what is observed for the variations in the dust, while other disk instabilities (thermal, magnetorotational) would operate there on longer time scales than we observe for the inner dust belt. For SAO 206462, the orbital period would likely be 1-3 years. If the changes are being induced in the disk material closer to the star than the gap, a variety of mechanisms (disk instabilities, interactions via planets) might be responsible for the changes seen. The He I feature is most likely due to a wind whose orientation changes with respect to the observer on time scales of a day or less. To further constrain the origin of the gas and dust emission will require multiple spectroscopic and interferometric observations on both shorter and longer time scales that have been sampled so far.Comment: 42 pages, 10 figure

Reinventing grounded theory: some questions about theory, ground and discovery

Grounded theory’s popularity persists after three decades of broad-ranging critique. In this article three problematic notions are discussed—‘theory,’ ‘ground’ and ‘discovery’—which linger in the continuing use and development of grounded theory procedures. It is argued that far from providing the epistemic security promised by grounded theory, these notions—embodied in continuing reinventions of grounded theory—constrain and distort qualitative inquiry, and that what is contrived is not in fact theory in any meaningful sense, that ‘ground’ is a misnomer when talking about interpretation and that what ultimately materializes following grounded theory procedures is less like discovery and more akin to invention. The procedures admittedly provide signposts for qualitative inquirers, but educational researchers should be wary, for the significance of interpretation, narrative and reflection can be undermined in the procedures of grounded theory