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Intermediate Pond Sizes Contain the Highest Density, Richness, and Diversity of Pond-Breeding Amphibians
We present data on amphibian density, species richness, and diversity from a 7140-ha area consisting of 200 ponds in the Midwestern U.S. that represents most of the possible lentic aquatic breeding habitats common in this region. Our study includes all possible breeding sites with natural and anthropogenic disturbance processes that can be missing from studies where sampling intensity is low, sample area is small, or partial disturbance gradients are sampled. We tested whether pond area was a significant predictor of density, species richness, and diversity of amphibians and if values peaked at intermediate pond areas. We found that in all cases a quadratic model fit our data significantly better than a linear model. Because small ponds have a high probability of pond drying and large ponds have a high probability of fish colonization and accumulation of invertebrate predators, drying and predation may be two mechanisms driving the peak of density and diversity towards intermediate values of pond size. We also found that not all intermediate sized ponds produced many larvae; in fact, some had low amphibian density, richness, and diversity. Further analyses of the subset of ponds represented in the peak of the area distribution showed that fish, hydroperiod, invertebrate density, and canopy are additional factors that drive density, richness and diversity of ponds up or down, when extremely small or large ponds are eliminated. Our results indicate that fishless ponds at intermediate sizes are more diverse, produce more larvae, and have greater potential to recruit juveniles into adult populations of most species sampled. Further, hylid and chorus frogs are found predictably more often in ephemeral ponds whereas bullfrogs, green frogs, and cricket frogs are found most often in permanent ponds with fish. Our data increase understanding of what factors structure and maintain amphibian diversity across large landscapes.
Journal Article
Intraspecific priority effects in response to egg hatching delay in a pond-breeding salamander
As reproduction phenologies shift with climate change, populations can experience intraspecific priority effects, wherein early hatching cohorts experience an advantage over late-hatching cohorts, resulting in altered demography. Our study objective was to identify how variation in egg hatching phenology alters intraspecific interactions in small-mouthed salamanders,
Ambystoma texanum.
We addressed two research questions: (Q1) How are demographic responses altered by variation in the temporal duration of hatching between cohorts, and (Q2) How does the seasonality of hatching delays affect demographic responses? We manipulated hatching phenologies of
A. texanum
eggs and reared larvae in outdoor mesocosms to metamorphosis. For Q1, hatching delay exhibited non-linear relationships with survival and body size, with the greatest asynchrony in cohort additions resulting in the highest mortality and largest body sizes. For Q2, hatching delay effects were stronger (i.e., survival was lower and body sizes larger) when they occurred later in the season, potentially due to temperature differences that larvae experienced. Overall, our results demonstrate that changes in intraspecific interactions due to phenological shifts can be context-dependent, depending on the strength (i.e., temporal duration) and seasonality of such processes. Identifying context-dependencies of phenological shifts will be critical for predicting changes in organismal demographics with climatic shifts.
Journal Article
Lessons in science safety with Max Axiom, super scientist : an augmented reading science experience
\"Follow along carefully as Max Axiom teaches the most important lesson in science: Safety! From hot tips for using hot plates to cool answers to burning questions, young readers will hone their super safety skills. Download the free Capstone 4D app for an augmented reality experience that goes beyond the printed page. Videos, writing prompts, discussion questions, and hands-on activities make this updated edition come alive and keep your collection current.\"-- Provided by publisher.
Book
Amphotericin forms an extramembranous and fungicidal sterol sponge
NMR structural data and biophysical and biological experiments show that the antifungal compound amphotericin is toxic because it acts as a sterol sponge by interacting with ergosterol on the fungal membrane and extracting it from within the membrane to the surface of the membrane.
For over 50 years, amphotericin has remained the powerful but highly toxic last line of defense in treating life-threatening fungal infections in humans with minimal development of microbial resistance. Understanding how this small molecule kills yeast is thus critical for guiding development of derivatives with an improved therapeutic index and other resistance-refractory antimicrobial agents. In the widely accepted ion channel model for its mechanism of cytocidal action, amphotericin forms aggregates inside lipid bilayers that permeabilize and kill cells. In contrast, we report that amphotericin exists primarily in the form of large, extramembranous aggregates that kill yeast by extracting ergosterol from lipid bilayers. These findings reveal that extraction of a polyfunctional lipid underlies the resistance-refractory antimicrobial action of amphotericin and suggests a roadmap for separating its cytocidal and membrane-permeabilizing activities. This new mechanistic understanding is also guiding development of what are to our knowledge the first derivatives of amphotericin that kill yeast but not human cells.
Journal Article
Statistics for business and economics
Clarity and cutting-edge examples have made 'Statistics for Business and Economics' the definitive textbook for students across the United Kingdom, Europe, Middle East, and Africa. This new edition builds on the text's well-respected foundations to deliver a clear, up-to-date and comprehensive revision. All the key concepts, combined with the latest technologies and applications, are introduced with hallmark precision, making this your complete introduction to business statistics.
Book
Reconciliation of the carbon budget in the ocean’s twilight zone
The discrepancy between the components of the oceanic carbon budget — export of carbon from the surface and its conversion into carbon dioxide by water-column biota at depth — is reconciled using field data and a steady-state model which indicates that synergy between microbes and zooplankton is an important factor.
Balancing the 'twilight zone' carbon budget
Biological processes in the ocean's twilight zone — the barely-lit waters at depths of about 50–1,000 metres) — influence the export of carbon from surface waters to the deep ocean. It is not clear to what extent the surface carbon supply meets the energy needs of the marine biota that convert the sinking carbon into carbon dioxide, as estimates of the amount of available carbon are much lower than corresponding estimates of metabolism. Here Sarah Giering
et al
. present a balanced carbon budget (to within observational uncertainties) for the twilight zone in the eastern North Atlantic Ocean. They suggest that a synergy between zooplankton and microbes has an important role in processing organic carbon, and show that the amount of available organic carbon meets the respiration needs of these organisms.
Photosynthesis in the surface ocean produces approximately 100 gigatonnes of organic carbon per year, of which 5 to 15 per cent is exported to the deep ocean
1
,
2
. The rate at which the sinking carbon is converted into carbon dioxide by heterotrophic organisms at depth is important in controlling oceanic carbon storage
3
. It remains uncertain, however, to what extent surface ocean carbon supply meets the demand of water-column biota; the discrepancy between known carbon sources and sinks is as much as two orders of magnitude
4
,
5
,
6
,
7
,
8
. Here we present field measurements, respiration rate estimates and a steady-state model that allow us to balance carbon sources and sinks to within observational uncertainties at the Porcupine Abyssal Plain site in the eastern North Atlantic Ocean. We find that prokaryotes are responsible for 70 to 92 per cent of the estimated remineralization in the twilight zone (depths of 50 to 1,000 metres) despite the fact that much of the organic carbon is exported in the form of large, fast-sinking particles accessible to larger zooplankton. We suggest that this occurs because zooplankton fragment and ingest half of the fast-sinking particles, of which more than 30 per cent may be released as suspended and slowly sinking matter, stimulating the deep-ocean microbial loop. The synergy between microbes and zooplankton in the twilight zone is important to our understanding of the processes controlling the oceanic carbon sink.
Journal Article
Pharmacokinetics, Safety and Tolerability of Oral Semaglutide in Subjects with Renal Impairment
Background
Semaglutide, a glucagon-like peptide-1 (GLP-1) analogue, has been co-formulated with the absorption enhancer sodium
N
-(8-[2-hydroxybenzoyl] amino) caprylate (SNAC) as a tablet for oral administration. This trial (NCT02014259) investigated the pharmacokinetics, safety and tolerability of oral semaglutide in subjects with and without renal impairment.
Methods
Subjects were categorised as having normal renal function (
n
= 24), mild (
n
= 12), moderate (
n
= 12) or severe (
n
= 12) renal impairment, or end-stage renal disease (ESRD) requiring haemodialysis (
n
= 11) and received once-daily oral semaglutide (5 mg for 5 days followed by 10 mg for 5 days) in the fasting state, followed by 30 min fasting after dosing. Semaglutide plasma concentrations were measured during dosing and for up to 21 days after the last dose.
Results
Semaglutide exposure (area under the plasma concentration–time curve from time zero to 24 h after the tenth dose and maximum concentration after the tenth dose) did not vary in a consistent pattern across the renal function groups. Similarly, there was no apparent effect of renal impairment on the semaglutide half-life (geometric mean range 152–165 h). Except for one subject in the ESRD group, semaglutide was not detected in urine. Haemodialysis did not affect the pharmacokinetics of semaglutide. Adverse events were in line with those observed for other GLP-1 receptor agonists and no safety concerns were identified.
Conclusion
There was no apparent effect of renal impairment or haemodialysis on the pharmacokinetics of oral semaglutide. Based on this trial, renal impairment should not affect dose recommendations for oral semaglutide.
Journal Article