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21.
Analyzing a randomized trial on breast self-examination with noncompliance and missing outcomes 总被引:1,自引:0,他引:1
Recently, instrumental variables methods have been used to address non-compliance in randomized experiments. Complicating such analyses is often the presence of missing data. The standard model for missing data, missing at random (MAR), has some unattractive features in this context. In this paper we compare MAR-based estimates of the complier average causal effect (CACE) with an estimator based on an alternative, nonignorable model for the missing data process, developed by Frangakis and Rubin (1999, Biometrika, 86, 365-379). We also introduce a new missing data model that, like the Frangakis-Rubin model, is specially suited for models with instrumental variables, but makes different substantive assumptions. We analyze these issues in the context of a randomized trial of breast self-examination (BSE). In the study two methods of teaching BSE, consisting of either mailed information about BSE (the standard treatment) or the attendance of a course involving theoretical and practical sessions (the new treatment), were compared with the aim of assessing whether teaching programs could increase BSE practice and improve examination skills. The study was affected by the two sources of bias mentioned above: only 55% of women assigned to receive the new treatment complied with their assignment and 35% of the women did not respond to the post-test questionnaire. Comparing the causal estimand of the new treatment using the MAR, Frangakis-Rubin, and our new approach, the results suggest that for these data the MAR assumption appears least plausible, and that the new model appears most plausible among the three choices. 相似文献
22.
The emerging role of immune activation and inflammation in the pathogenesis of human immunodeficiency virus (HIV) disease has stimulated the search for new approaches for managing HIV infection. Recent evidence suggests that an imbalance between matrix metalloproteinases (MMPs) and endogenous tissue inhibitors of MMPs (TIMPs) might contribute to HIV-associated pathology by inducing remodelling of the extracellular matrix. Here, we discuss the evidence and the potential mechanisms for altered MMP or TIMP function in HIV infection and disease. Furthermore, we outline the possible medical implications for the use of compounds that target MMP activity, and we propose that antiretroviral drugs, particularly HIV protease inhibitors (PIs), and compounds with anti-inflammatory properties, such as statins, natural omega-3 fatty acids and tetracyclines, which inhibit MMP function, might represent useful therapeutic approaches to mitigate potential MMP-related damage during HIV infection. 相似文献
23.
Angela Marie Abbatecola Fabrizia Lattanzio Liana Spazzafumo Anna Maria Molinari Michele Cioffi Raffaele Canonico Luigi DiCioccio Giuseppe Paolisso 《PloS one》2010,5(4)
Background
The mechanisms related to cognitive impairment in older persons with Type 2 diabetes (DM) remains unclear. We tested if adiposity parameters and body fat distribution could predict cognitive decline in older persons with DM vs. normal glucose tolerance (NGT).Methodology
693 older persons with no dementia were enrolled: 253 with DM in good metabolic control; 440 with NGT (age range:65–85 years). Longitudinal study comparing DM and NGT individuals according to the association of baseline adiposity parameters (body mass index (BMI), waist-hip-ratio (WHR), waist circumference (WC) and total body fat mass) to cognitive change (Mini Mental State Examination (MMSE), a composite score of executive and attention functioning (CCS) over time.Findings
At baseline, in DM participants, MMSE correlated with WHR (β = −0.240; p = 0.043), WC (β = −0.264; p = 0.041) while CCS correlated with WHR (β = −0.238; p = 0.041), WC (β = −0.326; p = 0.013) after adjusting for confounders. In NGT subjects, no significant correlations were found among any adiposity parameters and MMSE, while CCS was associated with WHR (β = −0.194; p = 0.036) and WC (β = −0.210; p = 0.024). Participants with DM in the 3rd tertile of total fat mass showed the greatest decline in cognitive performance compared to those in 1st tertile (tests for trend: MMSE(p = 0.007), CCS(p = 0.003)). Logistic regression models showed that 3rd vs. 1st tertile of total fat mass, WHR, and WC predicted an almost two-fold decline in cognitive function in DM subjects at 2nd yr (OR 1.68, 95%IC 1.08–3.52).Conclusions
Total fat mass and central adiposity predict an increased risk for cognitive decline in older person with DM. 相似文献24.
Lichtner M Mengoni F Mastroianni CM Sauzullo I Rossi R De Nicola M Vullo V Ghibelli L 《Apoptosis : an international journal on programmed cell death》2006,11(5):781-787
The reduction of neutrophils apoptosis is one of the main non-virological effects of protease inhibitor (PI) therapy. We explore
here whether this may be due to the cross-inhibition of calpain, an important non-virological target of PI in vitro. We found that the high basal level of neutrophils apoptosis in AIDS patients is strictly related to an increased intracellular
calpain activity. Both alterations disappear after PI treatment, with apoptosis and calpain going back to normal levels after
3 months of PI therapy, independently of a proficient antiviral effect. PI drugs exerted a similar antiapoptotic and anticalpain
effects on neutrophils in ex vivo experiments: strikingly, the effects were mimicked by commercially available calpain inhibitors. This study shows, for the
first time, that apoptosis of neutrophils in AIDS patients is mediated by calpain, and that neutrophil survival in PI treated
AIDS patients is a non virological effect due to calpain inhibition.
Miriam Lichtner and Fabio Mengoni are equally contributed. 相似文献
25.
RC Tappel JM Kucharski JM Mastroianni AJ Stipanovic CT Nomura 《Biomacromolecules》2012,13(9):2964-2972
As applications for biodegradable and biologically produced poly[(R)-3-hydroxyalkanoates] (PHAs) grow into more specialized areas, the need to precisely control the repeating unit composition and consequently the physical properties of these polymers has become essential. A previous study reported our development of Escherichia coli LSBJ in order to produce PHA polymers composed of single repeating units ranging from 4 to 12 carbon atoms. This investigation expands the scope of our effort toward controlling the repeating unit composition of a variety of PHA copolymers. The sizes for the repeating units within the copolymers were modulated by feeding specific ratios of fatty acids with defined carbon lengths to E. coli LSBJ, which resulted in defined mole ratios for the repeating units. Various physical properties of the copolymers (including the Young's modulus, elongation to break, and glass-transition temperature) were shown to be strongly dependent upon the mole ratios of repeating units. This work demonstrates that copolymers of PHAs with repeating units from 4 to 12 carbons can be incorporated accurately to obtain any desired mole ratio within the PHA copolymers. Our methodology may thus be extended to generate tailor-made PHA copolymers with prescribed values for key sets of physical properties. 相似文献
26.
Antinori A Marcotullio S Ammassari A Andreoni M Angarano G Armignacco O Carosi G Cinque P d'Arminio Monforte A Di Perri G Ensoli B Floridia M Galli M Mastroianni C Matteelli A Mazzotta F Moroni M Pal G Puoti M Puro V Rizzardini G Sagnelli E Vella S Vullo V Lazzarin A;Italian HIV Guidelines Working Group 《The new microbiologica》2012,35(2):113-159
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29.
In this contribution the results of a zoogeographical analysis, carried out on the 123 endemic leaf beetle species (Coleoptera: Chrysomelidae) occurring in Italy and its immediately adjacent regions, are reported. To assess the level of faunistic similarity among the different geographic regions studied, a cluster analysis was performed, based on the endemic component. This was done by calculating the Baroni Urbani & Buser’s similarity index (BUB). Finally, a parsimony analysis of endemicity (PAE) was used to identify the most important areas of endemism in Italy. 相似文献
30.
Lichtner M Mastroianni CM Rossi R Russo G Belvisi V Marocco R Mascia C Del Borgo C Mengoni F Sauzullo I d'Ettorre G D'Agostino C Massetti AP Vullo V 《PloS one》2011,6(5):e19872