Management of warfarin in atrial fibrillation: Views of health professionals, older patients and their carers

Objective: To identify the views of health professionals, patients and their carers on strategies to improve the use and management of warfarin in older patients with atrial fibrillation. Design: Qualitative study based on analysis of group interviews. Setting: A major metropolitan teaching hospital, from 1 March to 30 April 2003. Participants: 14 patients (≥ 65 years) with established atrial fibrillation and taking warfarin, three carers, 12 specialists, eight general practitioners, six community pharmacists, nine hospital pharmacists, and 11 nurses volunteered in response to flyers promoting the study. Results: Suggested strategies to improve warfarin management targeted support services for GPs and patients. Hospital-based clinicians felt that dissemination of trial evidence to GPs to support treatment recommendations is required, and that GPs need to enlist allied health professionals in the management of patients taking warfarin. GPs preferred access to practical advice from expert colleagues on the day-to-day management. Patients requested more information about warfarin therapy, as access to information is inadequate, particularly from primary sources (GPs, community pharmacists). Verbal and written information are equally important, but a single counselling session or supply of a booklet was viewed as inadequate. Participants identified various interventions for all levels of warfarin management; from the collective input, a framework for management strategies was developed. Conclusions: Health professionals and patients require more customised information to support warfarin use and management

Warfarin use in the elderly: The nurses' perspective

Objective: To explore the barriers to warfarin use from the perspective of nurses working in aged care. Design: A qualitative study, involving a semi-structured group interview, during March-April 2001. Setting and Subjects: Eleven nurses, employed within the catchment of the Northern Sydney Area Health Service, who were involved in the care of elderly warfarinised patients. Main outcome measure: Identification, via thematic analysis, of the main themes underpinning the nursing perspective on warfarin use in this setting, with regard to their perceived role/s, experiences with patients, and potential strategies for managing the therapy. Results: Five main themes were identified: perceived patient attitude toward warfarin; barriers to the use of warfarin; expressed lack of confidence in the processes involved; nurses' role in warfarin use; and strategies to improve warfarin use. Nurses were concerned about warfarin use in the elderly, but felt they had a limited capacity to intervene. Conclusion: Nurses are potentially underutilised as a resource and support for both patients and prescribers, in the management of warfarin therapy

Balancing risk versus benefit: The elderly patient's perspective on warfarin therapy

Warfarin theraphy is underused in the target at-risk elderly population. Clinicians perceive that older patients are reluctant to use this theraphy, however the perspective of patients or their carers has yet to be explored. Objective: To explore in-depth the perspectives of elderly patients and/ or their carers regarding the use of warfarin therapy. Method: A qualitative study, using semi-structured group interviews was undertaken. The audio-taped discussions were transcribed verbatim, then thematically analysed to identify emergent themes. Group discussions were conducted at a major Sydney teaching hospital, over a 2-month period. Individuals aged 65 years or older (and/or their carers) who were using long-term (6 months) warfarin therapy were recruited by voluntary response to study flyers. Results: 17 patients and carers (mean age 77.2 SD=7.5 years) participated in one of two focus groups. Five core themes emerged regarding warfarin therapy: inadequate knowledge and understanding about it, patients/carers variable experience of information provision, cycle of reactions to being on it, issues in its practical management, and the spectrum of experiences with it. Overall, participants were very accepting of the therapy, describing a high level of compliance, despite initial fears and anxieties, and a relative lack of knowledge. Patients felt somewhat abandoned in their management of warfarin due to the lack of ongoing support services in the community, and inadequate information provision. Conclusions: Elderly patients and their carers appear to be quite accepting of warfarin therapy, in contrast to the perceptions of health care professionals. More effort is needed, however, in terms of information provision, particularly in the form of community-based services, to assist patients in the long-term management of warfarin

A demonstration of 'broken' visual space

It has long been assumed that there is a distorted mapping between real and ‘perceived’ space, based on demonstrations of systematic errors in judgements of slant, curvature, direction and separation. Here, we have applied a direct test to the notion of a coherent visual space. In an immersive virtual environment, participants judged the relative distance of two squares displayed in separate intervals. On some trials, the virtual scene expanded by a factor of four between intervals although, in line with recent results, participants did not report any noticeable change in the scene. We found that there was no consistent depth ordering of objects that can explain the distance matches participants made in this environment (e.g. A > B > D yet also A < C < D) and hence no single one-to-one mapping between participants’ perceived space and any real 3D environment. Instead, factors that affect pairwise comparisons of distances dictate participants’ performance. These data contradict, more directly than previous experiments, the idea that the visual system builds and uses a coherent 3D internal representation of a scene

Codon Size Reduction as the Origin of the Triplet Genetic Code

The genetic code appears to be optimized in its robustness to missense errors and frameshift errors. In addition, the genetic code is near-optimal in terms of its ability to carry information in addition to the sequences of encoded proteins. As evolution has no foresight, optimality of the modern genetic code suggests that it evolved from less optimal code variants. The length of codons in the genetic code is also optimal, as three is the minimal nucleotide combination that can encode the twenty standard amino acids. The apparent impossibility of transitions between codon sizes in a discontinuous manner during evolution has resulted in an unbending view that the genetic code was always triplet. Yet, recent experimental evidence on quadruplet decoding, as well as the discovery of organisms with ambiguous and dual decoding, suggest that the possibility of the evolution of triplet decoding from living systems with non-triplet decoding merits reconsideration and further exploration. To explore this possibility we designed a mathematical model of the evolution of primitive digital coding systems which can decode nucleotide sequences into protein sequences. These coding systems can evolve their nucleotide sequences via genetic events of Darwinian evolution, such as point-mutations. The replication rates of such coding systems depend on the accuracy of the generated protein sequences. Computer simulations based on our model show that decoding systems with codons of length greater than three spontaneously evolve into predominantly triplet decoding systems. Our findings suggest a plausible scenario for the evolution of the triplet genetic code in a continuous manner. This scenario suggests an explanation of how protein synthesis could be accomplished by means of long RNA-RNA interactions prior to the emergence of the complex decoding machinery, such as the ribosome, that is required for stabilization and discrimination of otherwise weak triplet codon-anticodon interactions

Effect of Correlated tRNA Abundances on Translation Errors and Evolution of Codon Usage Bias

Despite the fact that tRNA abundances are thought to play a major role in determining translation error rates, their distribution across the genetic code and the resulting implications have received little attention. In general, studies of codon usage bias (CUB) assume that codons with higher tRNA abundance have lower missense error rates. Using a model of protein translation based on tRNA competition and intra-ribosomal kinetics, we show that this assumption can be violated when tRNA abundances are positively correlated across the genetic code. Examining the distribution of tRNA abundances across 73 bacterial genomes from 20 different genera, we find a consistent positive correlation between tRNA abundances across the genetic code. This work challenges one of the fundamental assumptions made in over 30 years of research on CUB that codons with higher tRNA abundances have lower missense error rates and that missense errors are the primary selective force responsible for CUB

Vertical Binocular Disparity is Encoded Implicitly within a Model Neuronal Population Tuned to Horizontal Disparity and Orientation

Primary visual cortex is often viewed as a “cyclopean retina”, performing the initial encoding of binocular disparities between left and right images. Because the eyes are set apart horizontally in the head, binocular disparities are predominantly horizontal. Yet, especially in the visual periphery, a range of non-zero vertical disparities do occur and can influence perception. It has therefore been assumed that primary visual cortex must contain neurons tuned to a range of vertical disparities. Here, I show that this is not necessarily the case. Many disparity-selective neurons are most sensitive to changes in disparity orthogonal to their preferred orientation. That is, the disparity tuning surfaces, mapping their response to different two-dimensional (2D) disparities, are elongated along the cell's preferred orientation. Because of this, even if a neuron's optimal 2D disparity has zero vertical component, the neuron will still respond best to a non-zero vertical disparity when probed with a sub-optimal horizontal disparity. This property can be used to decode 2D disparity, even allowing for realistic levels of neuronal noise. Even if all V1 neurons at a particular retinotopic location are tuned to the expected vertical disparity there (for example, zero at the fovea), the brain could still decode the magnitude and sign of departures from that expected value. This provides an intriguing counter-example to the common wisdom that, in order for a neuronal population to encode a quantity, its members must be tuned to a range of values of that quantity. It demonstrates that populations of disparity-selective neurons encode much richer information than previously appreciated. It suggests a possible strategy for the brain to extract rarely-occurring stimulus values, while concentrating neuronal resources on the most commonly-occurring situations

Generic Algorithm to Predict the Speed of Translational Elongation: Implications for Protein Biogenesis

Synonymous codon usage and variations in the level of isoaccepting tRNAs exert a powerful selective force on translation fidelity. We have developed an algorithm to evaluate the relative rate of translation which allows large-scale comparisons of the non-uniform translation rate on the protein biogenesis. Using the complete genomes of Escherichia coli and Bacillus subtilis we show that stretches of codons pairing to minor tRNAs form putative sites to locally attenuate translation; thereby the tendency is to cluster in near proximity whereas long contiguous stretches of slow-translating triplets are avoided. The presence of slow-translating segments positively correlates with the protein length irrespective of the protein abundance. The slow-translating clusters are predominantly located down-stream of the domain boundaries presumably to fine-tune translational accuracy with the folding fidelity of multidomain proteins. Translation attenuation patterns at highly structurally and functionally conserved domains are preserved across the species suggesting a concerted selective pressure on the codon selection and species-specific tRNA abundance in these regions

Magnitude, precision, and realism of depth perception in stereoscopic vision

Our perception of depth is substantially enhanced by the fact that we have binocular vision. This provides us with more precise and accurate estimates of depth and an improved qualitative appreciation of the three-dimensional (3D) shapes and positions of objects. We assessed the link between these quantitative and qualitative aspects of 3D vision. Specifically, we wished to determine whether the realism of apparent depth from binocular cues is associated with the magnitude or precision of perceived depth and the degree of binocular fusion. We presented participants with stereograms containing randomly positioned circles and measured how the magnitude, realism, and precision of depth perception varied with the size of the disparities presented. We found that as the size of the disparity increased, the magnitude of perceived depth increased, while the precision with which observers could make depth discrimination judgments decreased. Beyond an initial increase, depth realism decreased with increasing disparity magnitude. This decrease occurred well below the disparity limit required to ensure comfortable viewing

Impacts of past abrupt land change on local biodiversity globally

Abrupt land change, such as deforestation or agricultural intensification, is a key driver of biodiversity change. Following abrupt land change, local biodiversity often continues to be influenced through biotic lag effects. However, current understanding of how terrestrial biodiversity is impacted by past abrupt land changes is incomplete. Here we show that abrupt land change in the past continues to influence present species assemblages globally. We combine geographically and taxonomically broad data on local biodiversity with quantitative estimates of abrupt land change detected within time series of satellite imagery from 1982 to 2015. Species richness and abundance were 4.2% and 2% lower, respectively, and assemblage composition was altered at sites with an abrupt land change compared to unchanged sites, although impacts differed among taxonomic groups. Biodiversity recovered to levels comparable to unchanged sites after >10 years. Ignoring delayed impacts of abrupt land changes likely results in incomplete assessments of biodiversity change