Food insecurity and HIV clinical outcomes in a longitudinal study of urban homeless and marginally housed HIV-infected individuals.

BACKGROUND: Food insecurity is common among HIV-infected individuals and has been associated with poor health. Little longitudinal research has examined the association of food insecurity with HIV clinical outcomes, or the extent to which adherence mediates these associations. DESIGN: Observational cohort study METHODS: HIV-infected homeless and marginally housed individuals in the San Francisco Research on Access to Care in the Homeless cohort completed quarterly structured interviews and blood draws. We measured food insecurity using the validated Household Food Insecurity Access Scale. Primary outcomes were: antiretroviral therapy (ART) nonadherence (<90% adherence), incomplete HIV viral load suppression more than 100 copies/ml, and CD4⁺ cell counts less than 200 cells/µl. We estimated model parameters using generalized estimating equations, adjusting for sociodemographic and clinical variables. RESULTS: From May 2007 to March 2010, we followed 284 participants for a median of 22 months. At baseline 54.6% of participants were food-insecure. Food insecurity was associated with increased odds of ART nonadherence [adjusted odds ratio (AOR) = 1.48; 95% confidence interval (CI), 1.19-1.85], incomplete viral load suppression (AOR = 1.29, 95% CI 1.04-1.61), and CD4⁺ cell counts less than 200 cells/µl (AOR = 1.26, 95% CI 1.01-1.56). When we included ART adherence in adjusted models for incomplete viral suppression and CD4⁺ cell counts less than 200 cells/µl, the magnitude of the effect decreased slightly. CONCLUSION: Food insecurity was associated with poor HIV outcomes, including nonadherence, in a longitudinal study of US-based HIV-infected unstably housed individuals. Efforts to address food insecurity should be included in HIV-treatment programs, and may help improve health outcomes.

Cascade of reduced speed and accuracy after errors in enzyme-free copying of nucleic acid sequences.

Nonenzymatic, template-directed synthesis of nucleic acids is a paradigm for self-replicating systems. The evolutionary dynamics of such systems depend on several factors, including the mutation rates, relative replication rates, and sequence characteristics of mutant sequences. We measured the kinetics of correct and incorrect monomer insertion downstream of a primer-template mismatch (mutation), using a range of backbone structures (RNA, DNA, and LNA templates and RNA and DNA primers) and two types of 5'-activated nucleotides (oxyazabenzotriazolides and imidazolides, i.e., nucleoside 5'-phosphorimidazolides). Our study indicated that for all systems studied, an initial mismatch was likely to be followed by another error (54-75% of the time), and extension after a single mismatch was generally 10-100 times slower than extension without errors. If the mismatch was followed by a matched base pair, the extension rate recovered to nearly normal levels. On the basis of these data, we simulated nucleic acid replication in silico, which indicated that a primer suffering an initial error would lag behind properly extended counterparts due to a cascade of subsequent errors and kinetic stalling, with the typical mutational event consisting of several consecutive errors. Our study also included different sequence contexts, which suggest the presence of cooperativity among monomers affecting both absolute rate (by up to 2 orders of magnitude) and fidelity. The results suggest that molecular evolution in enzyme-free replication systems would be characterized by large "leaps" through sequence space rather than isolated point mutations, perhaps enabling rapid exploration of diverse sequences. The findings may also be useful for designing self-replicating systems combining high fidelity with evolvability.

Polycarbonate bottle use and urinary bisphenol A concentrations.

BACKGROUND: Bisphenol A (BPA) is a high-production-volume chemical commonly used in the manufacture of polycarbonate plastic. Low-level concentrations of BPA in animals and possibly in humans may cause endocrine disruption. Whether ingestion of food or beverages from polycarbonate containers increases BPA concentrations in humans has not been studied. OBJECTIVES: We examined the association between use of polycarbonate beverage containers and urinary BPA concentrations in humans. METHODS: We conducted a nonrandomized intervention of 77 Harvard College students to compare urinary BPA concentrations collected after a washout phase of 1 week to those taken after an intervention week during which most cold beverages were consumed from polycarbonate drinking bottles. Paired t-tests were used to assess the difference in urinary BPA concentrations before and after polycarbonate bottle use. RESULTS: The geometric mean urinary BPA concentration at the end of the washout phase was 1.2 microg/g creatinine, increasing to 2.0 microg/g creatinine after 1 week of polycarbonate bottle use. Urinary BPA concentrations increased by 69% after use of polycarbonate bottles (p < 0.0001). The association was stronger among participants who reported > or = 90% compliance (77% increase; p < 0.0001) than among those reporting < 90% compliance (55% increase; p = 0.03), but this difference was not statistically significant (p = 0.54). CONCLUSIONS: One week of polycarbonate bottle use increased urinary BPA concentrations by two-thirds. Regular consumption of cold beverages from polycarbonate bottles is associated with a substantial increase in urinary BPA concentrations irrespective of exposure to BPA from other sources.