Showing papers by "Jeff D. Williamson published in 2008"

Ginkgo biloba for prevention of dementia: a randomized controlled trial.

Abstract: Context Ginkgo biloba is widely used for its potential effects on memory and cognition. To date, adequately powered clinical trials testing the effect of G biloba on dementia incidence are lacking. Objective To determine effectiveness of G biloba vs placebo in reducing the incidence of all-cause dementia and Alzheimer disease (AD) in elderly individuals with normal cognition and those with mild cognitive impairment (MCI). Design, Setting, and Participants Randomized, double-blind, placebo-controlled clinical trial conducted in 5 academic medical centers in the United States between 2000 and 2008 with a median follow-up of 6.1 years. Three thousand sixty-nine community volunteers aged 75 years or older with normal cognition (n = 2587) or MCI (n = 482) at study entry were assessed every 6 months for incident dementia. Intervention Twice-daily dose of 120-mg extract of G biloba (n = 1545) or placebo (n = 1524). Main Outcome Measures Incident dementia and AD determined by expert panel consensus. Results Five hundred twenty-three individuals developed dementia (246 receiving placebo and 277 receiving G biloba) with 92% of the dementia cases classified as possible or probable AD, or AD with evidence of vascular disease of the brain. Rates of dropout and loss to follow-up were low (6.3%), and the adverse effect profiles were similar for both groups. The overall dementia rate was 3.3 per 100 person-years in participants assigned to G biloba and 2.9 per 100 person-years in the placebo group. The hazard ratio (HR) for G biloba compared with placebo for all-cause dementia was 1.12 (95% confidence interval [CI], 0.94-1.33; P = .21) and for AD, 1.16 (95% CI, 0.97-1.39; P = .11). G biloba also had no effect on the rate of progression to dementia in participants with MCI (HR, 1.13; 95% CI, 0.85-1.50; P = .39). Conclusions In this study, G biloba at 120 mg twice a day was not effective in reducing either the overall incidence rate of dementia or AD incidence in elderly individuals with normal cognition or those with MCI. Trial Registration clinicaltrials.gov Identifier: NCT00010803

Do red blood cell-beta-amyloid interactions alter oxygen delivery in Alzheimer's disease?

Abstract: Oxygen delivery requires that Red Blood Cells (RBCs) must be deformable to pass through the microcirculation. Alzheimer’s disease (AD) is a progressive neurodegenerative disorder characterized by abnormal extracellular deposition of β-amyloid peptide (Aβ) and neuronal loss. We have analyzed RBC morphology in blood from subjects with AD and found that >15% of the RBCs are elongated as compared to 5.9% in normal controls (p<0.0001). To determine whether these morphology changes can be associated with the greater exposure of RBCs to Aβ in AD subjects, we investigated the in vitro effect ofAb fibrils on blood.Morphological analysis of RBCs treated with Aβ1-40 or Aβ1-42 fibrils show 8.6% or 11.1% elongated cells, respectively. In contrast, only 2.9% or 1.3% of RBCs are elongated when blood is treated with buffer or mock fibrils generated from Aβ42-1. Elongated RBCs are expected to be less deformable. This prediction is consistent with our earlier studies showing impaired deformability of RBCs treated with Aβ fibrils. An additional factor previously reported by us, expected to impair the flow of RBCs through the microcirculation is their adherence to endothelial cells (ECs) when Aβ1-40 fibrils are bound to either RBCs or ECs. This factor would be more pronounced in AD subjects with elevated levels of Aβ on the vasculature. These results suggest that Aβ interactions with RBCs in AD subjects can result in impaired oxygen transport and delivery, which will have important implications for AD.

Comparison of the design differences between the Ginkgo Evaluation of Memory study and the GuidAge study.

Abstract: The epidemic of late life dementia, prominence of use of alternative medications and supplements, and initiation of efforts to determine how to prevent dementia have led to efforts to conduct studies aimed at prevention of dementia. The GEM (Ginkgo Evaluation of Memory) and GuidAge studies are ongoing randomized double-blind, placebo-controlled trials of Ginkgo biloba, administered in a dose of 120 mg twice per day as EGb761, to test whether Ginkgo biloba is effective in the prevention of dementia (and especially Alzheimer’s disease) in normal elderly or those early cognitive impairment. Both GEM and GuidAge will also add substantial knowledge to the growing need for expertise in designing and implementing clinical trials to test the efficacy of putative disease-modifying agents for the dementias. While there are many similarities between GEM and Guidage, there are also significant differences. We present here the first comparative design and baseline data fromGEM and Guidage, two of the largest dementia primary prevention trials to date.

Florida Subtropical Peaches: General Concepts and Cultivars Recommended for Grower Trials

Abstract: HS1125, a 9-page illustrated fact sheet by J. Ferguson, P. Andersen, J. Chaparro, and J. Williamson, discusses general concepts of subtropical production for commercial growers and homeowners and recommends cultivars for grower trials. Includes a table of chilling hours for several Published by the UF Department of Horticultural Sciences, January 2008.