4,005 research outputs found
Selection against genetic defects in conservation schemes while controlling inbreeding
We studied different genetic models and evaluation systems to select against a genetic disease with additive, recessive or polygenic inheritance in genetic conservation schemes. When using optimum contribution selection with a restriction on the rate of inbreeding (ÎF) to select against a disease allele, selection directly on DNA-genotypes is, as expected, the most efficient strategy. Selection for BLUP or segregation analysis breeding value estimates both need 1â2 generations more to halve the frequency of the disease allele, while these methods do not require knowledge of the disease mutation at the DNA level. BLUP and segregation analysis methods were equally efficient when selecting against a disease with single gene or complex polygene inheritance, i.e. knowledge about the mode of inheritance of the disease was not needed for efficient selection against the disease. Smaller schemes or schemes with a more stringent restriction on ÎF needed more generations to halve the frequency of the disease alleles or the fraction of diseased animals. Optimum contribution selection maintained ÎF at its predefined level, even when selection of females was at random. It is argued that in the investigated small conservation schemes with selection against a genetic defect, control of ÎF is very important
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Carbonyl sulfide (OCS): Large-scale distributions over North America during INTEX-NA and relationship to CO2
An extensive set of carbonyl sulfide (OCS) observations were made as part of the NASA Intercontinental Chemical Transport Experiment-North America (INTEX-NA) study, flown from 1 July to 14 August 2004 mostly over the eastern United States and Canada. These data show that summertime OCS mixing ratios at low altitude were dominated by surface drawdown and were highly correlated with CO2. Although local plumes were observed on some low-altitude flight legs, anthropogenic OCS sources were small compared to this sink. These INTEX-NA observations were in marked contrast to the early springtime 2001 Transport and Chemical Evolution over the Pacific experiment, which sampled Asian outflow dominated by anthropogenic OCS emissions. To test the gridded OCS fluxes used in past models, the INTEX-NA observations were combined with the sulfur transport Eulerian model (STEM) regional atmospheric chemistry model for a top-down assessment of bottom-up OCS surface fluxes for North America. Initial STEM results suggest that the modeled fluxes underestimate the OCS plant sink by more than 200%. Copyright 2008 by the American Geophysical Union
Acupuncture for chronic neck pain: a pilot for a randomised controlled trial
Background: Acupuncture is increasingly being used for many conditions including chronic neck pain. However the evidence remains inconclusive, indicating the need for further well-designed research. The aim of this study was to conduct a pilot randomised controlled parallel arm trial, to establish key features required for the design and implementation of a large-scale trial on acupuncture for chronic neck pain. Methods: Patients whose GPs had diagnosed neck pain were recruited from one general practice, and randomised to receive usual GP care only, or acupuncture ( up to 10 treatments over 3 months) as an adjunctive treatment to usual GP care. The primary outcome measure was the Northwick Park Neck Pain Questionnaire (NPQ) at 3 months. The primary analysis was to determine the sample size for the full scale study. Results: Of the 227 patients with neck pain identified from the GP database, 28 (12.3%) consenting patients were eligible to participate in the pilot and 24 (10.5%) were recruited to the trial. Ten patients were randomised to acupuncture, receiving an average of eight treatments from one of four acupuncturists, and 14 were randomised to usual GP care alone. The sample size for the full scale trial was calculated from a clinically meaningful difference of 5% on the NPQ and, from this pilot, an adjusted standard deviation of 15.3%. Assuming 90% power at the 5% significance level, a sample size of 229 would be required in each arm in a large-scale trial when allowing for a loss to follow-up rate of 14%. In order to achieve this sample, one would need to identify patients from databases of GP practices with a total population of 230,000 patients, or approximately 15 GP practices roughly equal in size to the one involved in this study (i.e. 15,694 patients). Conclusion: This pilot study has allowed a number of recommendations to be made to facilitate the design of a large-scale trial, which in turn will help to clarify the existing evidence base on acupuncture for neck pain
The Response of Electron Pitch Angle Distributions to the Upper Limit on Stably Trapped Particles
We use Van Allen Probes electron data during 70 geomagnetic storms to examine the response of equatorial pitch angle distributions (PADs) at L*Â =Â 4.0â4.5 to a theoretical upper limit on stably trapped particle fluxes. Of the energies examined, 54 and 108Â keV electron PADs isotropize to a previously assumed level within 6Â hr of reaching the limit, near-identically across all 70 storms, consistent with rapid pitch angle scattering due to chorus wave interactions. In around 30% of events, 54Â keV electrons completely exceed the KP limit, before being quickly subdued. 470 and 749Â keV PADs show clear indications of an upper limit, though less aligned with the calculated limit used here. The consistency of an absolute upper limit shown across all events demonstrates the importance of this phenomena in both the limiting effect on electron flux and consistently influencing electron PAD evolution during geomagnetic storms. These results also highlight the need for further investigation, particularly related to the limiting of higher energy electrons
Embryological staging of the Zebra Finch, Taeniopygia guttata
Zebra Finches (Taeniopygia guttata) are the most commonly used laboratory songbird species, yet their embryological development has been poorly characterized. Most studies to date apply Hamburger and Hamilton stages derived from chicken development; however, significant differences in development between precocial and altricial species suggest that they may not be directly comparable. We provide the first detailed description of embryological development in the Zebra Finch under standard artificial incubation. These descriptions confirm that some of the features used to classify chicken embryos into stages are not applicable in an altricial bird such as the Zebra Finch. This staging protocol will help to standardize future studies of embryological development in the Zebra Finch. J. Morphol. 274:1090-1110, 2013. (c) 2013 Wiley Periodicals, Inc
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How Emerging Organizations Take Form: The Role of Imprinting and Values in Organizational Bricolage
We examine how emerging organizations acquire shape by drawing on multiple organizational forms, a process we call organizational bricolage. Studying Indymedia London, a grassroots media collective, we propose a grounded theory of organizational bricolage that identifies how various types of organizational forms are selected and how they are instantiated into the organization. Whereas extant research has emphasized imprinting as a primary mechanism shaping newly founded organizations, we point to the additional role of organizational values. Emerging organizations augment their imprinted forms by using ancillary forms aligned with their organizational values and reinforce their core features by differentiating themselves from antagonistic forms that conflict with their values. We contribute to the literature on organizational formation by developing a process model that details how imprinted forms are subsequently modified. Moreover, we extend theories of bricolage by specifying the limits to the relative arbitrariness of bricolage as an activity, and we contribute to the study of organizational values by suggesting that they act as a focusing device shaping organizational structure
Delineation of individual human chromosomes in metaphase and interphase cells by in situ suppression hybridization using recombinant DNA libraries
A method of in situ hybridization for visualizing individual human chromosomes from pter to qter, both in metaphase spreads and interphase nuclei, is reported. DNA inserts from a single chromosomal library are labeled with biotin and partially preannealed with a titrated amount of total human genomic DNA prior to hybridization with cellular or chromosomal preparations. The cross-hybridization of repetitive sequences to nontargeted chromosomes can be markedly suppressed under appropriate preannealing conditions. The remaining single-stranded DNA is hybridized to specimens of interest and detected with fluorescent or enzymelabeled avidin conjugates following post-hybridization washes. DNA inserts from recombinant libraries for chromosomes 1, 4, 7, 8, 13, 14, 18, 20, 21, 22, and X were assessed for their ability to decorate specifically their cognate chromosome; most libraries proved to be highly specific. Quantitative densitometric analyses indicated that the ratio of specific to nonspecific hybridization signal under optimal preannealing conditions was at least 8:1. Interphase nuclei showed a cohesive territorial organization of chromosomal domains, and laserscanning confocal fluorescence microscopy was used to aid the 3-D visualization of these domains. This method should be useful for both karyotypic studies and for the analysis of chromosome topography in interphase cells
Evolutionary and pulsational properties of white dwarf stars
Abridged. White dwarf stars are the final evolutionary stage of the vast
majority of stars, including our Sun. The study of white dwarfs has potential
applications to different fields of astrophysics. In particular, they can be
used as independent reliable cosmic clocks, and can also provide valuable
information about the fundamental parameters of a wide variety of stellar
populations, like our Galaxy and open and globular clusters. In addition, the
high densities and temperatures characterizing white dwarfs allow to use these
stars as cosmic laboratories for studying physical processes under extreme
conditions that cannot be achieved in terrestrial laboratories. They can be
used to constrain fundamental properties of elementary particles such as axions
and neutrinos, and to study problems related to the variation of fundamental
constants.
In this work, we review the essentials of the physics of white dwarf stars.
Special emphasis is placed on the physical processes that lead to the formation
of white dwarfs as well as on the different energy sources and processes
responsible for chemical abundance changes that occur along their evolution.
Moreover, in the course of their lives, white dwarfs cross different
pulsational instability strips. The existence of these instability strips
provides astronomers with an unique opportunity to peer into their internal
structure that would otherwise remain hidden from observers. We will show that
this allows to measure with unprecedented precision the stellar masses and to
infer their envelope thicknesses, to probe the core chemical stratification,
and to detect rotation rates and magnetic fields. Consequently, in this work,
we also review the pulsational properties of white dwarfs and the most recent
applications of white dwarf asteroseismology.Comment: 85 pages, 28 figures. To be published in The Astronomy and
Astrophysics Revie
Aqueous tear assessment in dogs: Impact of cephalic conformation, interâtest correlations, and testâretest repeatability
Objective - To characterize diagnostic findings, testâretest repeatability, and correlations among lacrimal tests in dogs of diverse cephalic conformations.
Animal studied - Fifty healthy dogs (25 brachycephalic, 25 nonbrachycephalic).
Procedures - A series of diagnostics were performed in each dog, allowing for a 10âminute interval between tests and repeating each test 24 hours later under similar conditions: corneal tactile sensation (CTS), strip meniscometry test (SMT), phenol red thread test (PRTT), endodontic absorbent paper point tear test (EAPPTT), Schirmer tear testâ1 without (STTâ1) or with nasolacrimal stimulation (NLâSTT1), and Schirmer tear testâ2 (STTâ2).
Results - Mean ± SD test values were lower in brachycephalic vs. nonbrachycephalic dogs (except for SMT; 7.4 ± 2.0 mm/5 seconds vs 7.3 ± 2.4 mm/5 seconds), with statistically significant differences noted for CTS (1.8 ± 0.5 cm vs 3.4 ± 0.8 cm), PRTT (37.2 ± 4.0 mm/15 seconds vs 41.1 ± 5.5 mm/15 seconds), STTâ1 (20.1 ± 3.4 mm/min vs 23.3 ± 5.7 mm/min), STTâ2 (13.0 ± 3.4 mm/min vs 16.9 ± 3.9 mm/min), and NLâSTT1 (23.2 ± 3.6 mm/min vs 27.1 ± 5.4 mm/min), and nonsignificant differences for EAPPTT (16.6 ± 2.7 mm/15 seconds vs 17.5 ± 2.9 mm/15 seconds). Nasolacrimal stimulation increased STTâ1 values by 18% on average. Correlations among tests were generally weak to moderate (r \u3c .70) except for a strong correlation between STTâ1 and NLâSTT1 (r = .83, P \u3c .001). Test reliability was good although testâretest repeatability was generally poor to moderate, as depicted by low intraclass correlation coefficients (ICC †0.75) and wide 95% limits of agreement, except for CTS (ICC = 0.91).
Conclusions - Corneal sensitivity and aqueous tear secretion are lower in brachycephalic dogs. A comprehensive assessment of the ocular surface requires the combination of several diagnostic tests. The nasolacrimal reflex may provide a useful diagnostic and therapeutic tool in dogs
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