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Search Results: 1 - 10 of 504269 matches for " David A Bennett "
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Plaque complement activation and cognitive loss in Alzheimer's disease
David A Loeffler, Dianne M Camp, David A Bennett
Journal of Neuroinflammation , 2008, DOI: 10.1186/1742-2094-5-9
Abstract: iC3b, C9, Bielschowsky, and Gallyas staining was performed on aged normal (n = 17), mild cognitively impaired (n = 12), and AD (n = 17–18) inferior temporal gyrus specimens. Plaques were counted in 10× fields with high numbers of Bielschowsky-stained plaques. One-way ANOVA was used to determine between-group differences for plaque counts and measures of cognitive function, and linear regression was used to evaluate global cognition as a function of Bielschowsky-stained plaques. Terms for iC3b- and C9-stained plaques were then added sequentially as additional predictors in a "mediation analysis" model.Complement was detected on plaques in all groups, and on neurofibrillary tangles only in AD specimens. iC3b, C9, and Bielschowsky-stained plaque counts increased 2.5- to 3-fold in AD vs. other groups (all p ≤ 0.01). C9 staining was present on some diffuse plaques, as well as on neuritic plaques. Bielschowsky-stained and complement-stained plaque counts were highly correlated, and were negatively correlated with cognitive measures. When the Bielschowsky plaque count was used as a predictor, its correlations with cognitive measures were statistically significant, but when iC3b and C9 plaque counts were added as additional predictors, these correlations were no longer significant. This loss of significance was attributed to multicollinearity, i.e., high correlations between Bielschowsky-stained and complement-stained plaque counts.Both early-stage (iC3b) and late-stage (C9) complement activation occurs on neocortical plaques in subjects across the cognitive spectrum; contrary to previous reports, C9 is present on some diffuse plaques. Because of high correlations between complement-stained and Bielschowsky-stained plaque counts, quantitative assessment of the extent to which complement activation may mediate the relationship between plaques and cognitive function could not be performed. Additional studies with animal models of AD (if late-stage complement activation can be
Correlates of health and financial literacy in older adults without dementia
Jarred S Bennett, Patricia A Boyle, Bryan D James, David A Bennett
BMC Geriatrics , 2012, DOI: 10.1186/1471-2318-12-30
Abstract: We conducted a cross-sectional study using data from the Rush Memory and Aging Project, a community-based cohort study of aging in northeastern Illinois. The study consisted of 556 older persons without dementia, each determined by a clinical evaluation. Health and financial literacy were measured using a series of questions designed to assess the ability to understand and process health and financial information, concepts, and numeracy; the two scores were averaged to yield a total literacy score. Health promoting behaviors, including engagement in cognitive, physical, and social activities, were assessed using self report measures. Indicators of heath status, including cognition (global cognition and five specific cognitive abilities), functional status (basic and instrumental activities of daily living, mobility disability), and mental health (depressive symptoms, loneliness) were assessed.In a series of regression models adjusted for age, sex, and education, higher total literacy scores were associated with more frequent participation in health promoting behaviors, including cognitive, physical and social activities (all p values <0.05). Higher total literacy scores were associated with higher cognitive function, less disability, and better mental health (all p values?<?0.05). Literacy remained associated with health promoting behaviors and health status in fully adjusted models that also controlled for income and the number of chronic medical conditions. Most of the findings were similar for health and financial literacy except that health literacy was more strongly associated with health promoting behaviors whereas financial literacy was more strongly associated with mental health.Health and financial literacy are associated with more frequent engagement in health promoting behaviors and better health status in older persons without dementia.
Relation of neuropathology with cognitive decline among older persons without dementia
Patricia A. Boyle,Lei Yu,David A. Bennett
Frontiers in Aging Neuroscience , 2013, DOI: 10.3389/fnagi.2013.00050
Abstract: Objective: Although it is now widely accepted that dementia has a long preclinical phase during which neuropathology accumulates and cognition declines, little is known about the relation of neuropathology with the longitudinal rate of change in cognition among older persons without dementia. We quantified the burden of the neuropathologies of the three most common causes of dementia [i.e., Alzheimer’s disease (AD), cerebrovascular disease (CVD), and Lewy body disease (LBD)] and examined their relation with cognitive decline in a large cohort of persons without dementia proximate to death.
Risk Aversion is Associated with Decision Making among Community-Based Older Persons
Patricia A. Boyle,Aron S. Buchman,David A. Bennett
Frontiers in Psychology , 2012, DOI: 10.3389/fpsyg.2012.00205
Abstract: Background: Risk aversion is associated with many important decisions among younger and middle aged persons, but the association of risk aversion with decision making has not been well studied among older persons who face some of the most significant decisions of their lives. Method: Using data from 606 community-dwelling older persons without dementia from the Rush Memory and Aging Project, an ongoing longitudinal epidemiologic study of aging, we examined the association of risk aversion with decision making. Risk aversion was measured using standard behavioral economics questions in which participants were asked to choose between a certain monetary payment ($15) versus a gamble in which they could gain more than $15 or gain nothing; potential gamble gains ranged from $20 to $300 with the gain amounts varied randomly over questions. Decision making was measured using a 12 item version of the Decision Making Competence Assessment Tool. Findings: In a linear regression model adjusted for age, sex, education, and income, greater risk aversion was associated with poorer decision making [estimate = ?1.03, standard error (SE) = 0.35, p = 0.003]. Subsequent analyses showed that the association of risk aversion with decision making persisted after adjustment for global cognitive function as well as executive and non-executive cognitive abilities. Conclusion: Similar to findings from studies of younger persons, risk aversion is associated with poorer decision making among older persons who face a myriad of complex and influential decisions.
Evaluation of a recombinant human gelatin as a substitute for a hydrolyzed porcine gelatin in a refrigerator-stable Oka/Merck live varicella vaccine
Liska Vladimir,Bigert Stacey A,Bennett Philip S,Olsen David
Journal of Immune Based Therapies and Vaccines , 2007, DOI: 10.1186/1476-8518-5-4
Abstract: Background The labile nature of live, attenuated varicella-zoster virus (Oka/Merck) requires robust stabilization during virus bulk preparation and vaccine manufacturing in order to preserve potency through storage and administration. One stabilizing ingredient used in a varicella-zoster virus (VZV) vaccine is hydrolyzed porcine gelatin which represents the major protein/peptide-based excipient in the vaccine formulation. Methods In this comparative study, a recombinant human gelatin fragment (8.5 kD) was assessed as a potential replacement for hydrolyzed porcine gelatin in an experimental live, attenuated VZV (Oka/Merck) vaccine. VZV (Oka/Merck) was harvested in two formulations prepared with either a hydrolyzed porcine gelatin or a recombinant human gelatin. Moreover, the viral stability in the experimental VZV (Oka/Merck) vaccines was evaluated under accelerated and real-time conditions in a comparative study. Results and discussion The stabilizing effect of recombinant human gelatin on VZV (Oka/Merck) potency change during vaccine lyophilization was similar to the experimental vaccine containing porcine-derived gelatin. Vaccine viral potency changes were comparable in stabilized VZV (Oka/Merck) formulations containing either hydrolyzed porcine gelatin or recombinant human gelatin. No statistically significant difference in potency stability was observed between the vaccine formulations stored at any of the temperatures tested. Conclusion The recombinant human gelatin demonstrated similar ability to stabilize the live attenuated VZV (Oka/Merck) in an experimental, refrigerator-stable varicella vaccine when compared to the vaccine preparation formulated with hydrolyzed porcine gelatin used in currently marketed varicella vaccine.
Capacities of Quantum Erasure Channels
Charles H. Bennett,David P. DiVincenzo,John A. Smolin
Physics , 1997, DOI: 10.1103/PhysRevLett.78.3217
Abstract: The quantum analog of the classical erasure channel provides a simple example of a channel whose asymptotic capacity for faithful transmission of intact quantum states, with and without the assistance of a two-way classical side channel, can be computed exactly. We derive the quantum and classical capacities for the quantum erasure channel and related channels, and compare them to the depolarizing channel, for which only upper and lower bounds on the capacities are known.
Early resuscitation in the emergency room: dramatic effects that we should not ignore
David Bennett
Critical Care , 2002, DOI: 10.1186/cc1444
Abstract: The most surprising finding in the study reported by Rivers et al. [1] was the baseline value of 48% for central venous saturations. This demonstrates that patients with severe sepsis/septic shock when first admitted to the emergency room of a large US hospital must have extremely low cardiac outputs, implying severe hypovolaemia, although there is also likely to be significant myocardial depression. Those of us working in the intensive care unit (ICU) environment rarely encounter values as low as this in septic patients, presumably because most patients will have already received at least some volume resuscitation before admission to the ICU.Rivers et al. chose central venous saturation and lactate as targets for their 'early goal-directed therapy' protocol, with the aim of achieving central venous saturation of greater than 70% and lactate of less than 2 mmol/l while the patients remained in the emergency room. These were presumably chosen as relatively simply measured variables that act as surrogates for cardiac output. The strict protocol they employed involved aggressive volume resuscitation, including early blood transfusion and inotrope administration, during the 7-h period that the patients remained in the emergency room before transfer to the ICU.In the protocol group the targets were achieved within 3 h; those patients received 1.5 l extra fluid during the period spent in the emergency room, with 64% receiving blood transfusions as compared with only 18.5% in the control group. In addition, 13.7% of patients in the protocol group received inotropes versus fewer than 1% in the control group. Just over 50% of patients in both groups were ventilated during this period.Sixty-five hours after admission to the ICU (the staff of which had no knowledge as to which group the patients had been assigned) the situation was reversed, with the control group now receiving significantly more fluid, blood transfusions and vasopressors. In addition, only a further 2.6% of p
The high-risk surgical patient revisited
David Bennett
Critical Care , 1998, DOI: 10.1186/cc116
Abstract: The range of volumes of colloid given to the protocol group of patients was considerable, and the cardiovascular effects of the infusion were monitored using an intra-oesophageal Doppler device which measures descending aortic blood velocity and converts it into cardiac output using a built-in nomogram. Sinclair et al showed that, following colloid infusion, the protocol group of patients had significantly increased cardiac output and stroke volume when compared to their own baseline values and the control patients. This simple manoeuvre led to a 39% reduction in hospital stay and complication rate.The obvious question is, could they have achieved the same result simply by administering the volume of colloid without monitoring cardiac output, albeit with a relatively noninvasive device that is placed in the oesophagus. This is an important question because it is likely to determine whether such an approach to the management of similar high-risk patients will be generally accepted and become the standard.Others, including Shoemaker et al [2], Boyd et al [3] and more recently Bishop et al [4], have clearly shown that the recognition and very early optimisation of cardiac output in a wide range of high-risk surgical patients produces highly significant reductions in both morbidity and mortality. This approach is time consuming and requires, in some cases, admission to the intensive care unit some hours prior to surgery and the insertion of PA catheters for the measurement and manipulation of cardiac output. This makes the approach unattractive to many clinicians, with their doubts being further amplified by the recent controversies. Shoemaker et al (pers comm) have estimated that as many as 8-10% of all surgical patients should be considered at high risk from developing significant post-operative morbidity and mortality. These patients warrant further extensive study and the Sinclair investigation is a welcome addition to the growing list of papers that demonstrate the
Magellanic Cloud Gravitational Microlensing Results: What Do They Mean?
David Bennett
Physics , 1998, DOI: 10.1016/S0370-1573(98)00077-5
Abstract: I review recent results from gravitational microlensing surveys of the Large Magellanic Cloud. The combined microlensing optical depth of the MACHO and EROS-1 surveys is tau_LMC = 2.1{+1.3/-0.8}* 10^{-7} which is substantially larger than the background of tau < 0.5* 10^{-7} from lensing by known stars but is below the expected microlensing optical depth of tau = 4.7*10^{-7} for a halo composed entirely of Machos. The simplest interpretation of this result is that nearly half of the dark halo is composed of Machos with a typical mass of order 0.5 Msun. These Machos could be old white dwarfs, but it is not obvious that the generation of stars that preceded these white dwarfs could have gone undetected. Perhaps, the Machos could be non-baryonic, but there is no compelling model for the formation of non-baryonic Machos. Therefore, some authors have tried to develop alternative models which attempt to explain the LMC microlensing results with non-halo lenses. Many of these models postulate previously unknown dark stellar populations which contribute significantly to the total mass of the Galaxy and are therefore simply variations of the dark matter solution. However, models which postulate an unknown dwarf galaxy along the line of sight to the LMC or a distortion of the LMC which significantly enhances the LMC self-lensing optical depth can potentially explain the LMC lensing results with only a small amount of mass, so these can be regarded as true non-dark matter solutions to the Macho puzzle. All such models that have been proposed so far have serious problems, so there is as yet no compelling alternative to the dark matter interpretation. However, the problem can be solved observationally with a second generation gravitational microlensing survey that is significantly more sensitive than current microlensing surveys.
Cognitive function is associated with risk aversion in community-based older persons
Patricia A Boyle, Lei Yu, Aron S Buchman, David I Laibson, David A Bennett
BMC Geriatrics , 2011, DOI: 10.1186/1471-2318-11-53
Abstract: Using data from 369 community-dwelling older persons without dementia from the Rush Memory and Aging Project, an ongoing longitudinal epidemiologic study of aging, we examined the correlates of risk aversion and tested the hypothesis that cognition is negatively associated with risk aversion. Global cognition and five specific cognitive abilities were measured via detailed cognitive testing, and risk aversion was measured using standard behavioral economics questions in which participants were asked to choose between a certain monetary payment ($15) versus a gamble in which they could gain more than $15 or gain nothing; potential gamble gains ranged from $21.79 to $151.19 with the gain amounts varied randomly over questions. We first examined the bivariate associations of age, education, sex, income and cognition with risk aversion. Next, we examined the associations between cognition and risk aversion via mixed models adjusted for age, sex, education, and income. Finally, we conducted sensitivity analyses to ensure that our results were not driven by persons with preclinical cognitive impairment.In bivariate analyses, sex, education, income and global cognition were associated with risk aversion. However, in a mixed effect model, only sex (estimate = -1.49, standard error (SE) = 0.39, p < 0.001) and global cognitive function (estimate = -1.05, standard error (SE) = 0.34, p < 0.003) were significantly inversely associated with risk aversion. Thus, a lower level of global cognitive function and female sex were associated with greater risk aversion. Moreover, performance on four out of the five cognitive domains was negatively related to risk aversion (i.e., semantic memory, episodic memory, working memory, and perceptual speed); performance on visuospatial abilities was not.A lower level of cognitive ability and female sex are associated with greater risk aversion in advanced age.Compelling economics, behavioral economics, and neuroeconomics studies have shown that r
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