Dalhousie University

About: Dalhousie University is a education organization based out in Halifax, Nova Scotia, Canada. It is known for research contribution in the topics: Population & Health care. The organization has 25660 authors who have published 58465 publications receiving 2082403 citations. The organization is also known as: Dalhousie College & The Governors of Dalhousie College and University.

A universal model of diagnostic reasoning.

Abstract: Clinical judgment is a critical aspect of physician performance in medicine. It is essential in the formulation of a diagnosis and key to the effective and safe management of patients. Yet, the overall diagnostic error rate remains unacceptably high. In more than four decades of research, a variety of approaches have been taken, but a consensus approach toward diagnostic decision making has not emerged. In the last 20 years, important gains have been made in psychological research on human judgment. Dual-process theory has emerged as the predominant approach, positing two systems of decision making, System 1 (heuristic, intuitive) and System 2 (systematic, analytical). The author proposes a schematic model that uses the theory to develop a universal approach toward clinical decision making. Properties of the model explain many of the observed characteristics of physicians' performance. Yet the author cautions that not all medical reasoning and decision making falls neatly into one or the other of the model's systems, even though they provide a basic framework incorporating the recognized diverse approaches. He also emphasizes the complexity of decision making in actual clinical situations and the urgent need for more research to help clinicians gain additional insight and understanding regarding their decision making.

Patterns and ecosystem consequences of shark declines in the ocean.

Abstract: Whereas many land predators disappeared before their ecological roles were studied, the decline of marine apex predators is still unfolding. Large sharks in particular have experienced rapid declines over the last decades. In this study, we review the documented changes in exploited elasmobranch communities in coastal, demersal, and pelagic habitats, and synthesize the effects of sharks on their prey and wider communities. We show that the high natural diversity and abundance of sharks is vulnerable to even light fishing pressure. The decline of large predatory sharks reduces natural mortality in a range of prey, contributing to changes in abundance, distribution, and behaviour of small elasmobranchs, marine mammals, and sea turtles that have few other predators. Through direct predation and behavioural modifications, top-down effects of sharks have led to cascading changes in some coastal ecosystems. In demersal and pelagic communities, there is increasing evidence of mesopredator release, but cascading effects are more hypothetical. Here, fishing pressure on mesopredators may mask or even reverse some ecosystem effects. In conclusion, large sharks can exert strong top-down forces with the potential to shape marine communities over large spatial and temporal scales. Yet more empirical evidence is needed to test the generality of these effects throughout the ocean.

Neurobiology of butyrylcholinesterase.

Abstract: Butyrylcholinesterase is a serine hydrolase related to acetylcholinesterase that catalyses the hydrolysis of esters of choline, including acetylcholine. Butyrylcholinesterase has unique enzymatic properties and is widely distributed in the nervous system, pointing to its possible involvement in neural function. Here, we summarize the biochemical properties of butyrylcholinesterase and review the evidence that this enzyme has important roles in cholinergic neurotransmission and could be involved in other nervous system functions and in neurodegenerative diseases.

Reduction in Neural-Tube Defects after Folic Acid Fortification in Canada

Abstract: Results A total of 2446 subjects with neural-tube defects were recorded among 1.9 million births. The prevalence of neural-tube defects decreased from 1.58 per 1000 births before fortification to 0.86 per 1000 births during the full-fortification period, a 46% reduction (95% confidence interval, 40 to 51). The magnitude of the decrease was proportional to the prefortification baseline rate in each province, and geographical differences almost disappeared after fortification began. The observed reduction in rate was greater for spina bifida (a decrease of 53%) than for anencephaly and encephalocele (decreases of 38% and 31%, respectively). Conclusions Food fortification with folic acid was associated with a significant reduction in the rate of neural-tube defects in Canada. The decrease was greatest in areas in which the baseline rate was high.

Laboratory evolution of postponed senescence in drosophila melanogaster.

Abstract: Evolutionary genetics seems to have found the fundamental cause of senescence: the decline in the sensitivity of natural selection to gene effects expressed at later ages in most populations of organisms with separate somatic and germline tissue. (Here "senescence" refers to decline in age-specific fitness-components after the onset of reproductive maturity.) This idea traces back to Haldane (1941) and Medawar (1946, 1952), with considerable elaboration and elucidation since then (Williams, 1957; Hamilton, 1966; Edney and Gill, 1968; Emlen, 1970; Charlesworth and Williamson, 1975; Charlesworth, 1980; Rose, 1983a). While there are still clear limitations to the mathematical formulation of this theory (cf. Hamilton, 1966; Charlesworth, 1980), the basic formal analysis leads to a straightforward conclusion: the first partial derivative of fitness with respect to appropriately scaled changes in age-specific life-history characters usually declines in magnitude with the age of these changes. The force of natural selection thus declines with age. This overall theory and its particular subsidiary variants lead to a number of empirically testable corollaries (Rose, 1983a, 1983b). Some of these corollaries are specific to the subsidiary variants of the theory (Rose and Charlesworth, 1980, 1981a, 1981b; Rose, 1983b), sothattests of them individually do not test the theory as a whole. Fortunately, there are two corollaries which follow from the general theory itself: the reproductive schedule of an outbred population will give rise to natural selection acting to (i) accelerate senescence in populations with a relatively earlier age of reproduction and (ii) postpone senescence in populations with a relatively later age of reproduction (Edney and Gill, 1968; Rose, 1983a). The former prediction has been corroborated by Sokal (1970) using Tribolium castaneum, while the latter has been corroborated by Wattiaux (1968a, 1968b) and by Rose and Charlesworth (1980, 198 lb), using Drosophila species. Once a theory has been well-developed mathematically and then empirically corroborated, attention turns to experiments in which the theory either is not clearly corroborated or is ostensibly refuted. It would be misleading to claim that all relevant experimental results directly corroborate the evolutionary theory of senescence. Sokal (1 970) and Mertz (1975) using Tribolium castaneum and Taylor and Condra (1980) using Drosophila pseudoobscura found heterogeneity between lines in experiments with replication, such that some lines did not exhibit the predicted response to the imposed selective regime. Taylor and Condra (1980) also found a difference in the response of the sexes which was later attributed to the pattern of female mating preference (Taylor et al., 1981). More problematic still are the studies from the Lints laboratory, one of which failed to obtain a direct response to artificial selection for longevity (Lints et al., 1979), while another gave puzzling fluctuations in life-history attributes (Lints and Hoste, 1974, 1977). Lints (1978, 1983) has made a great deal of these problems, contending that they cast doubt on all proposed evolutionary theories of senescence. While it can be argued that these puzzling results are due to technical artifacts such as inbreeding, genetic disequilibrium, and inadequate controls (cf. Rose and Charlesworth, 1981b), the only ef-