Osteogenesis imperfecta (OI) is a genetic disease of collagen or collagen-related proteins that adversely impacts bone mass and fracture resistance. Little is known regarding the role that microdamage plays in OI and whether or not OI bone is more prone to damage accumulation than bone with unaffected collagen. The Brtl/+ mouse is a heterozygous model for OI which contains a Gly349Cys substitution in one COL1A1 allele, and demonstrates a low ductility phenotype. At 8 weeks of age, Brtl/+ demonstrates an increase in osteoclast number, which mimics the upregulated bone turnover often found in OI patients. We hypothesize that upregulated osteoclast activity in Brtl/+ is due, in part, to increased remodeling associated with microdamage repair. In the present study, we used Brtl/+ to investigate the susceptibility of OI bone to microdamage. The mouse ulnar loading model was used to induce microdamage and to test the hypothesis that Brtl/+ is more susceptible to damage accumulation than age-matched wild type (WT) counterparts. Linear elastic fracture mechanics (LEFM) was used to investigate the fracture toughness properties of both Brtl/+ and WT bones to determine if there is any correlation with toughness and the degree of microdamage. Results show that Brtl/+ ulnae subject to normal cage activity demonstrate an inherently larger amount of microdamage than WT controls. Following axial compressive loading, Brtl/+ ulnae are more prone to damage than WT counterparts despite demonstrating a greater resistance to whole-bone deformation. Fracture toughness results demonstrate that Brtl/+ specimens, despite not exhibiting a significant difference, display a trend toward lower fracture toughness values than their WT counterparts. Correlations show that microdamage levels tend to increase as fracture toughness decreases. Together, these findings may have strong clinical implications for explaining increased fragility and remodeling activity in OI patients.
the fission cross-sections of 235U and 239pa for Na Be, La Be, Na-D and Ga D photoneutrons have been measured absolutely. The neutron source strength was measured using a manganese bath to compare the photoneutron yield from the sources with the standard source NBS-II. Fission counts were accumulated with the source positioned symmetrically between two identical fission foils in an experiment package suspended in a low-albedo laboratory. Fission fragments passing through limited solid angle apertures were recorded on polyester track-etch films. The masses of the foil deposits were determined by microbalance weighings and confirmed by thermal neutron fission and alpha counting. After making a correction for the calculated energy distribution of the source neutrons, values of 1.471 + 0.029, 1.274 + 0.026, 1.162 + 0.025 and 1.195 _+ 0.026 barns were obtained for the 235U fission cross-section at the source median energies of 140, 265, 770 and 964keV, respectively. Corresponding values of 1.469 + 0.045. 1.515 _+ 0.038, 1.670 _+ 0.039 and 1.643 + 0.038 barns were determined for 239pu.
Background Recruitment to dementia prevention clinical trials is challenging, and participants are not representative of US adults at risk. A better understanding of the general public’s interest in dementia prevention research participation is needed to inform future recruitment strategies. Objective To examine US adults’ characteristics associated with self-reported likelihood to participate in dementia prevention clinical trials. Design We conducted a cross-sectional survey using the October 2018 wave of the University of Michigan National Poll on Healthy Aging. Setting The National Poll on Healthy Aging is a nationally representative survey of adults using KnowledgePanel (Ipsos Public Affairs LLC), a probability-based panel of the civilian, noninstitutionalized US population. Participants We analyzed data from 1,028 respondents, ages 50 to 64 years, who completed a web survey module on brain health. Measurements We used logistic regression models to examine associations between sociodemographic and dementia-related factors (e.g., family history) and self-reported likelihood to participate in a dementia prevention clinical trial of a new medicine (“very” or “somewhat likely” vs. “not likely” survey responses). Among respondents not likely to participate, we examined frequency of reasons endorsed for this decision, stratified by age, sex, and race and ethnicity. Results Of the 1,028 respondents, half were female, 68% Non-Hispanic White, 13% Hispanic, and 12% Non-Hispanic Black. Twelve percent of respondents reported being very likely to participate in a dementia prevention trial, 32% somewhat likely, and 56% not likely. Factors associated with higher likelihood to participate were higher perceived risk of dementia [OR, 2.17 (95% CI, 1.61, 2.93)], a positive family history of dementia [OR, 1.75 (95% CI, 1.27, 2.43)], and having discussed dementia prevention with a doctor [OR, 2.20 (95% CI, 1.10, 4.42)]. There were no differences in likelihood to participate by sociodemographic characteristics. Among 570 respondents not likely to participate, 39% said they did not want to be a guinea pig, 23% thought dementia would not affect them, 22% thought there would be too high a chance for harm, 15% indicated study participation would take too much time, and 5% reported fear of learning information about oneself. There were no differences across age, sex, and racial and ethnic groups. Conclusions In this study, perceived risk of dementia, family history, and discussion of prevention with a doctor were associated with likelihood to participate in a dementia prevention clinical trial, whereas sociodemographic factors including race and ethnicity were not. Findings suggest that recruitment interventions focused on increasing knowledge of dementia risk and prevention trials and involving healthcare providers may b...
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