129 research outputs found
Dominance-related seasonal song production is unrelated to circulating testosterone in a subtropical songbird
AbstractCirculating testosterone (T) is widely considered to play a key role in the production of sexual displays by male vertebrates. While numerous studies support a role for circulating T in promoting the production of song in male birds, this understanding is based primarily on evidence from seasonally breeding northern temperate species, leaving it unclear whether this mechanism generalizes to other regions of the world. Here we investigate whether variation in circulating levels of T can explain the marked within- and among-individual variation in male song performance observed in a subtropical population of the year-round territorial white-browed sparrow weaver (Plocepasser mahali mahali). Our findings reveal that both circulating T and male song production peaked at a similar time point, halfway through the population-level breeding season. However, while dominant males were more likely to sing and sang for longer than subordinate males, within-group paired comparisons revealed no dominance-related differences in circulating T. Moreover, comparisons both among and within individual dominant males revealed that song duration, syllable rate and proportion of time spent singing were all unrelated to circulating T. Together, our findings suggest that natural variation in male song production, at least in this population of white-browed sparrow weavers, is achieved principally through mechanisms other than variation in circulating T concentration. More widely, our results are in line with the view that male song production is not exclusively regulated by gonadally synthesized steroids
Exposure to Household Air Pollution from Biomass Cookstoves and Blood Pressure Among Women in Rural Honduras: A CrossâSectional Study
Growing evidence links household air pollution exposure from biomass cookstoves with elevated blood pressure. We assessed crossâsectional associations of 24âhour mean concentrations of personal and kitchen fine particulate matter (PM2.5), black carbon (BC), and stove type with blood pressure, adjusting for confounders, among 147 women using traditional or cleanerâburning Justa stoves in Honduras. We investigated effect modification by age and body mass index. Traditional stove users had mean (standard deviation) personal and kitchen 24âhour PM2.5 concentrations of 126 Îźg/m3 (77) and 360 Îźg/m3 (374), while Justa stove usersâ exposures were 66 Îźg/m3 (38) and 137 Îźg/m3(194), respectively. BC concentrations were similarly lower among Justa stove users. Adjusted mean systolic blood pressure was 2.5 mm Hg higher (95% CI, 0.7â4.3) per unit increase in natural logâtransformed kitchen PM2.5 concentration; results were stronger among women of 40 years or older (5.2 mm Hg increase, 95% CI, 2.3â8.1). Adjusted odds of borderline high and high blood pressure (categorized) were also elevated (odds ratio = 1.5, 95% CI, 1.0â2.3). Some results included null values and are suggestive. Results suggest that reduced household air pollution, even when concentrations exceed air quality guidelines, may help lower cardiovascular disease risk, particularly among older subgroups
Study Protocol for a Stepped-Wedge Randomized Cookstove Intervention in Rural Honduras: Household Air Pollution and Cardiometabolic Health
Growing evidence links household air pollution exposure from biomass-burning cookstoves to cardiometabolic disease risk. Few randomized controlled interventions of cookstoves (biomass or otherwise) have quantitatively characterized changes in exposure and indicators of cardiometabolic health, a growing and understudied burden in low- and middle-income countries (LMICs). Ideally, the solution is to transition households to clean cooking, such as with electric or liquefied petroleum gas stoves; however, those unable to afford or to access these options will continue to burn biomass for the foreseeable future. Wood-burning cookstove designs such as the Justa (incorporating an engineered combustion zone and chimney) have the potential to substantially reduce air pollution exposures. Previous cookstove intervention studies have been limited by stove types that did not substantially reduce exposures and/or by low cookstove adoption and sustained use, and few studies have incorporated community-engaged approaches to enhance the intervention
Exposure to Household Air Pollution from Biomass Cookstoves and Levels of Fractional Exhaled Nitric Oxide (FeNO) among Honduran Women
Household air pollution is estimated to be responsible for nearly three million premature deaths annually. Measuring fractional exhaled nitric oxide (FeNO) may improve the limited understanding of the association of household air pollution and airway inflammation. We evaluated the cross-sectional association of FeNO with exposure to household air pollution (24-h average kitchen and personal fine particulate matter and black carbon; stove type) among 139 women in rural Honduras using traditional stoves or cleaner-burning Justastoves. We additionally evaluated interaction by age. Results were generally consistent with a null association; we did not observe a consistent pattern for interaction by age. Evidence from ambient and household air pollution regarding FeNO is inconsistent, and may be attributable to differing study populations, exposures, and FeNO measurement procedures (e.g., the flow rate used to measure FeNO)
Kitchen Concentrations of Fine Particulate Matter and Particle Number Concentration in Households Using Biomass Cookstoves in Rural Honduras
Cooking and heating with solid fuels results in high levels of household air pollutants, including particulate matter (PM); however, limited data exist for size fractions smaller than PM2.5 (diameter less than 2.5 Îźm). We collected 24-h time-resolved measurements of PM2.5 (n = 27) and particle number concentrations (PNC, average diameter 10â700 nm) (n = 44; 24 with paired PM2.5 and PNC) in homes with wood-burning traditional and Justa (i.e., with an engineered combustion chamber and chimney) cookstoves in rural Honduras. The median 24-h PM2.5 concentration (n = 27) was 79 Îźg/m3 (interquartile range [IQR]: 44â174 Îźg/m3); traditional (n = 15): 130 Îźg/m3 (IQR: 48â250 Îźg/m3); Justa (n = 12): 66 Îźg/m3 (IQR: 44â97 Îźg/m3). The median 24-h PNC (n = 44) was 8.5 Ă 104 particles (pt)/cm3 (IQR: 3.8 Ă 104â1.8 Ă 105 pt/cm3); traditional (n = 27): 1.3 Ă 105 pt/cm3 (IQR: 3.3 Ă 104â2.0 Ă 105 pt/cm3); Justa (n = 17): 6.3 Ă 104 pt/cm3 (IQR: 4.0 Ă 104â1.2 Ă 105 pt/cm3). The 24-h average PM2.5 and particle number concentrations were correlated for the full sample of cookstoves (n = 24, Spearman Ď: 0.83); correlations between PM2.5 and PNC were higher in traditional stove kitchens (n = 12, Ď: 0.93) than in Justa stove kitchens (n = 12, Ď: 0.67). The 24-h average concentrations of PM2.5 and PNC were also correlated with the maximum average concentrations during shorter-term averaging windows of one-, five-, 15-, and 60-min, respectively (Spearman Ď: PM2.5 [0.65, 0.85, 0.82, 0.71], PNC [0.74, 0.86, 0.88, 0.86]). Given the moderate correlations observed between 24-h PM2.5 and PNC and between 24-h and the shorter-term averaging windows within size fractions, investigators may need to consider cost-effectiveness and information gained by measuring both size fractions for the study objective. Further evaluations of other stove and fuel combinations are needed
Exposure to household air pollution from biomass cookstoves and blood pressure among women in rural Honduras: A crossâ sectional study
Growing evidence links household air pollution exposure from biomass cookstoves with elevated blood pressure. We assessed crossâ sectional associations of 24â hour mean concentrations of personal and kitchen fine particulate matter (PM2.5), black carbon (BC), and stove type with blood pressure, adjusting for confounders, among 147 women using traditional or cleanerâ burning Justa stoves in Honduras. We investigated effect modification by age and body mass index. Traditional stove users had mean (standard deviation) personal and kitchen 24â hour PM2.5 concentrations of 126Ă ĂÂźg/m3 (77) and 360Ă ĂÂźg/m3 (374), while Justa stove usersâ exposures were 66Ă ĂÂźg/m3 (38) and 137Ă ĂÂźg/m3 (194), respectively. BC concentrations were similarly lower among Justa stove users. Adjusted mean systolic blood pressure was 2.5Ă mm Hg higher (95% CI, 0.7â 4.3) per unit increase in natural logâ transformed kitchen PM2.5 concentration; results were stronger among women of 40Ă years or older (5.2Ă mm Hg increase, 95% CI, 2.3â 8.1). Adjusted odds of borderline high and high blood pressure (categorized) were also elevated (odds ratioĂ =Ă 1.5, 95% CI, 1.0â 2.3). Some results included null values and are suggestive. Results suggest that reduced household air pollution, even when concentrations exceed air quality guidelines, may help lower cardiovascular disease risk, particularly among older subgroups.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/146816/1/ina12507.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/146816/2/ina12507_am.pd
Verticalization of bacterial biofilms
Biofilms are communities of bacteria adhered to surfaces. Recently, biofilms
of rod-shaped bacteria were observed at single-cell resolution and shown to
develop from a disordered, two-dimensional layer of founder cells into a
three-dimensional structure with a vertically-aligned core. Here, we elucidate
the physical mechanism underpinning this transition using a combination of
agent-based and continuum modeling. We find that verticalization proceeds
through a series of localized mechanical instabilities on the cellular scale.
For short cells, these instabilities are primarily triggered by cell division,
whereas long cells are more likely to be peeled off the surface by nearby
vertical cells, creating an "inverse domino effect". The interplay between cell
growth and cell verticalization gives rise to an exotic mechanical state in
which the effective surface pressure becomes constant throughout the growing
core of the biofilm surface layer. This dynamical isobaricity determines the
expansion speed of a biofilm cluster and thereby governs how cells access the
third dimension. In particular, theory predicts that a longer average cell
length yields more rapidly expanding, flatter biofilms. We experimentally show
that such changes in biofilm development occur by exploiting chemicals that
modulate cell length.Comment: Main text 10 pages, 4 figures; Supplementary Information 35 pages, 15
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