Browsing by Subject "united-states"

Now showing 1 - 7 of 7

Open Access
Favorable Climate Change Response Explains Non-Native Species' Success in Thoreau's Woods
(2010) Willis, Charles G; Ruhfel, Brad R; Primack, Richard B; Miller-Rushing, Abraham J; Losos, Jonathan B; Davis, Charles C
Invasive species have tremendous detrimental ecological and economic impacts. Climate change may exacerbate species invasions across communities if non-native species are better able to respond to climate changes than native species. Recent evidence indicates that species that respond to climate change by adjusting their phenology (i.e., the timing of seasonal activities, such as flowering) have historically increased in abundance. The extent to which non-native species success is similarly linked to a favorable climate change response, however, remains untested. We analyzed a dataset initiated by the conservationist Henry David Thoreau that documents the long-term phenological response of native and non-native plant species over the last 150 years from Concord, Massachusetts (USA). Our results demonstrate that non-native species, and invasive species in particular, have been far better able to respond to recent climate change by adjusting their flowering time. This demonstrates that climate change has likely played, and may continue to play, an important role in facilitating non-native species naturalization and invasion at the community level.
Open Access
Global Trends in Typhoid and Paratyphoid Fever
(2010) Crump, John A; Mintz, Eric D
Typhoid and paratyphoid fever continue to be important causes of illness and death, particularly among children and adolescents in south-central and Southeast Asia, where enteric fever is associated with poor sanitation and unsafe food and water. High-quality incidence data from Asia are underpinning efforts to expand access to typhoid vaccines. Efforts are underway to develop vaccines that are immunogenic in infants after a single dose and that can be produced locally in countries of endemicity. The growing importance of Salmonella enterica serotype Paratyphi A in Asia is concerning. Antimicrobial resistance has sequentially emerged to traditional first-line drugs, fluoroquinolones, and third-generation cephalosporins, posing patient treatment challenges. Azithromycin has proven to be an effective alternative for treatment of uncomplicated typhoid fever. The availability of full genome sequences for S. enterica serotype Typhi and S. enterica serotype Paratyphi A confirms their place as monomorphic, human-adapted pathogens vulnerable to control measures if international efforts can be redoubled.
Open Access
How Do Gasoline Prices Affect Fleet Fuel Economy?
(2009) Timmins, CD; Li, S; von Haefen, R
Exploiting a rich dataset of passenger vehicle registrations in 20 US MSAs from 1997 to 2005, we examine the effects of gasoline prices on the automotive fleet's composition. We find that high gasoline prices affect fleet fuel economy through two channels: shifting new auto purchases towards more fuel-efficient vehicles, and speeding the scrappage of older, less fuel-efficient used vehicles. Policy simulations suggest that a 10 percent increase in gasoline prices from 2005 levels will generate a 0.22 percent increase in fleet fuel economy in the short run and a 2.04 percent increase in the long run.
Open Access
Lessons Learned from the Anaerobe Survey: Historical Perspective and Review of the Most Recent Data (2005-2007)
(2010) Snydman, David R; Jacobus, Nilda V; McDermott, Laura A; Golan, Yoav; Hecht, David W; Goldstein, Ellie JC; Harrell, Lizzie; Jenkins, Stephen; Newton, Duane; Pierson, Carl; Rihs, John D; Yu, Victor L; Venezia, Richard; Finegold, Sydney M; Rosenblatt, Jon E; Gorbach, Sherwood L
Background. The rationale and lessons learned through the evolution of the National Survey for the Susceptibility of Bacteroides fragilis Group from its initiation in 1981 through 2007 are reviewed here. The survey was conceived in 1980 to track emerging antimicrobial resistance in Bacteroides species. Methods. Data from the last 11 years of the survey (1997-2007), including 6574 isolates from 13 medical centers, were analyzed for in vitro antimicrobial resistance to both frequently used and newly developed anti-anaerobic agents. The minimum inhibitory concentrations of the antibiotics were determined using agar dilution in accordance with Clinical and Laboratory Standards Institute recommendations. Results. The analyses revealed that the carbapenems (imipenem, meropenem, ertapenem, and doripenem) and piperacillin-tazobactam were the most active agents against these pathogens, with resistance rates of 0.9%-2.3%. In the most recent 3 years of the survey (2005-2007), resistance to some agents was shown to depend on the species, such as ampicillin-sulbactam against Bacteroides distasonis (20.6%) and tigecycline against Bacteroides uniformis and Bacteroides eggerthii (similar to 7%). Very high resistance rates (>50%) were noted for moxifloxacin and trovafloxacin, particularly against Bacteroides vulgatus. During that period of study, non-B. fragilis Bacteroides species had >40% resistance to clindamycin. Metronidazole-resistant Bacteroides strains were also first reported during that period. Conclusions. In summary, resistance to antibiotics was greater among non-B. fragilis Bacteroides species than among B. fragilis and was especially greater among species with a low frequency of isolation, such as Bacteroides caccae and B. uniformis. The emergence of resistance among the non-B. fragilis Bacteroides species underscores the need for speciation of B. fragilis group isolates and for clinicians to be aware of associations between species and drug resistance.
Open Access
Limited educational attainment and radiographic and symptomatic knee osteoarthritis: a cross-sectional analysis using data from the Johnston County (North Carolina) Osteoarthritis Project
(2010) Callahan, Leigh F; Shreffler, Jack; Siaton, Bernadette C; Helmick, Charles G; Schoster, Britta; Schwartz, Todd A; Chen, Jiu-Chiuan; Renner, Jordan B; Jordan, Joanne M
Introduction: Applying a cross-sectional analysis to a sample of 2,627 African-American and Caucasian adults aged >= 45 years from the Johnston County Osteoarthritis Project, we studied the association between educational attainment and prevalence of radiographic knee osteoarthritis and symptomatic knee osteoarthritis. Methods: Age-and race-adjusted associations between education and osteoarthritis outcomes were assessed by gender-stratified logistic regression models, with additional models adjusting for body mass index, knee injury, smoking, alcohol use, and occupational factors. Results: In an analysis of all participants, low educational attainment (= 12 years), by using fully adjusted models. In the subset of postmenopausal women, these associations tended to be weaker but little affected by adjustment for hormone replacement therapy. Men with low educational attainment had 85% higher odds of having symptomatic knee osteoarthritis by using fully adjusted models, but the association with radiographic knee osteoarthritis was explained by age. Conclusions: After adjustment for known risk factors, educational attainment, as an indicator of socioeconomic status, is associated with symptomatic knee osteoarthritis in both men and women and with radiographic knee osteoarthritis in women.
Open Access
Regulation of male germ cell cycle arrest and differentiation by DND1 is modulated by genetic background
(2011) Cook, Matthew S; Munger, Steven C; Nadeau, Joseph H; Capel, Blanche
Human germ cell tumors show a strong sensitivity to genetic background similar to Dnd1(Ter/Ter) mutant mice, where testicular teratomas arise only on the 129/SvJ genetic background. The introduction of the Bax mutation onto mixed background Dnd1(Ter/Ter) mutants, where teratomas do not typically develop, resulted in a high incidence of teratomas. However, when Dnd1(Ter/Ter); Bax(-/-) double mutants were backcrossed to C57BL/6J, no tumors arose. Dnd1(Ter/Ter) germ cells show a strong downregulation of male differentiation genes including Nanos2. In susceptible strains, where teratomas initiate around E15.5-E17.5, many mutant germ cells fail to enter mitotic arrest in G0 and do not downregulate the pluripotency markers NANOG, SOX2 and OCT4. We show that DND1 directly binds a group of transcripts that encode negative regulators of the cell cycle, including p27(Kip1) and p21(Cip1). P27(Kip1) and P21(Cip1) protein are both significantly decreased in Dnd1(Ter/Ter) germ cells on all strain backgrounds tested, strongly suggesting that DND1 regulates mitotic arrest in male germ cells through translational regulation of cell cycle genes. Nonetheless, in C57BL/6J mutants, germ cells arrest prior to M-phase of the cell cycle and downregulate NANOG, SOX2 and OCT4. Consistent with their ability to rescue cell cycle arrest, C57BL/6J germ cells overexpress negative regulators of the cell cycle relative to 129/SvJ. This work suggests that reprogramming of pluripotency in germ cells and prevention of tumor formation requires cell cycle arrest, and that differences in the balance of cell cycle regulators between 129/SvJ and C57BL/6 might underlie differences in tumor susceptibility.
Open Access
Role of oxidative stress on diesel-enhanced influenza infection in mice
(2010) Gowdy, Kymberly M; Krantz, Quentin T; King, Charly; Boykin, Elizabeth; Jaspers, Ilona; Linak, William P; Gilmour, M Ian
Numerous studies have shown that air pollutants, including diesel exhaust (DE), reduce host defenses, resulting in decreased resistance to respiratory infections. This study sought to determine if DE exposure could affect the severity of an ongoing influenza infection in mice, and examine if this could be modulated with antioxidants. BALB/c mice were treated by oropharyngeal aspiration with 50 plaque forming units of influenza A/HongKong/8/68 and immediately exposed to air or 0.5 mg/m(3) DE (4 hrs/day, 14 days). Mice were necropsied on days 1, 4, 8 and 14 post-infection and lungs were assessed for virus titers, lung inflammation, immune cytokine expression and pulmonary responsiveness (PR) to inhaled methacholine. Exposure to DE during the course of infection caused an increase in viral titers at days 4 and 8 post-infection, which was associated with increased neutrophils and protein in the BAL, and an early increase in PR. Increased virus load was not caused by decreased interferon levels, since IFN-beta levels were enhanced in these mice. Expression and production of IL-4 was significantly increased on day 1 and 4 p.i. while expression of the Th1 cytokines, IFN-gamma and IL-12p40 was decreased. Treatment with the antioxidant N-acetylcysteine did not affect diesel-enhanced virus titers but blocked the DE-induced changes in cytokine profiles and lung inflammation. We conclude that exposure to DE during an influenza infection polarizes the local immune responses to an IL-4 dominated profile in association with increased viral disease, and some aspects of this effect can be reversed with antioxidants.