229 research outputs found
The relationship of telomere length to baseline corticosterone levels in nestlings of an altricial passerine bird in natural populations
Indexación: Web of Science; Scopus.Background: Environmental stressors increase the secretion of glucocorticoids that in turn can shorten telomeres via oxidative damage. Modification of telomere length, as a result of adversity faced early in life, can modify an individual's phenotype. Studies in captivity have suggested a relationship between glucocorticoids and telomere length in developing individuals, however less is known about that relationship in natural populations.
Methods: In order to evaluate the effect of early environmental stressors on telomere length in natural populations, we compared baseline corticosterone (CORT) levels and telomere length in nestlings of the same age. We collected blood samples for hormone assay and telomere determination from two geographically distinct populations of the Thorn-tailed Rayadito (Aphrastura spinicauda) that differed in brood size; nestlings body mass and primary productivity. Within each population we used path analysis to evaluate the relationship between brood size, body mass, baseline CORT and telomere length.
Results: Within each distinct population, path coefficients showed a positive relationship between brood size and baseline CORT and a strong and negative correlation between baseline CORT and telomere length. In general, nestlings that presented higher baseline CORT levels tended to present shorter telomeres. When comparing populations it was the low latitude population that presented higher levels of baseline CORT and shorter telomere length.
Conclusions: Taken together our results reveal the importance of the condition experienced early in life in affecting telomere length, and the relevance of integrative studies carried out in natural conditions.https://frontiersinzoology.biomedcentral.com/articles/10.1186/s12983-016-0133-
Magnetic Field Stimulated Transitions of Excited States in Fast Muonic Helium Ions
It is shown that one can stimulate, by using the present-day laboratory
magnetic fields, transitions between the sub-levels of fast
ions formating in muon catalyzed fusion. Strong fields also cause the
self-ionization from highly excited states of such muonic ions. Both effects
are the consequence of the interaction of the bound muon with the oscillating
field of the Stark term coupling the center-of-mass and muon motions of the
ion due to the non-separability of the collective and internal
variables in this system. The performed calculations show a possibility to
drive the population of the sub-levels by applying a field of a few
, which affects the reactivation rate and is especially important to the
-ray production in muon catalyzed fusion. It is also shown that
the splitting in due to the vacuum polarization slightly
decreases the stimulated transition rates.Comment: 5 figure
Present Effects of Past Wildfires on Leaf Litter Breakdown in Stream Ecosystems
We investigated the present effects from a 10-year-old wildfire on leaf litter breakdown rates in 3 headwater streams in central Idaho. These systems experienced a massive debris flow one year after the fire. Based on soil instability and burn patterns, we identified 3 stream conditions: unburned, burned only, and burned/scoured. We placed leaf bags containing willow leaves (Salix sp.) in each stream type and removed bags at various time intervals until all bags were collected 100 days after their introduction. Leaf material was dried and weighed, and decay rate coefficients were calculated. Macroinvertebrates colonizing the bags were enumerated and identified, and selected taxa were placed into trophic groups. We found that the unburned stream had the fastest leaf litter breakdown rate, the lowest level of incident light reaching the stream, and the largest amount of benthic organic matter. The burned/scoured stream was nearly opposite in all respects. Numbers of 2 detritivore invertebrate taxa, Serratella tibialis and Zapada oregonensis, were highest in the unburned stream but lowest in the burned/scoured stream. A third taxon, Baetis sp., showed the opposite relationship. Presence of predatory invertebrates did not affect detritivore abundance or leaf decay rate in the bags. Our research suggests that recovery response variables of some stream systems may not have returned to prefire levels even a decade after the initial wildfire. In this study, the recovery of our streams appears to be connected to the return of the riparian zone, though fire-induced debris flows may slow or alter final recovery of the stream system
Improved tests of extra-dimensional physics and thermal quantum field theory from new Casimir force measurements
We report new constraints on extra-dimensional models and other physics
beyond the Standard Model based on measurements of the Casimir force between
two dissimilar metals for separations in the range 0.2--1.2 m. The Casimir
force between an Au-coated sphere and a Cu-coated plate of a
microelectromechanical torsional oscillator was measured statically with an
absolute error of 0.3 pN. In addition, the Casimir pressure between two
parallel plates was determined dynamically with an absolute error of mPa. Within the limits of experimental and theoretical errors, the results
are in agreement with a theory that takes into account the finite conductivity
and roughness of the two metals. The level of agreement between experiment and
theory was then used to set limits on the predictions of extra-dimensional
physics and thermal quantum field theory. It is shown that two theoretical
approaches to the thermal Casimir force which predict effects linear in
temperture are ruled out by these experiments. Finally, constraints on Yukawa
corrections to Newton's law of gravity are strengthened by more than an order
of magnitude in the range 56 nm to 330 nm.Comment: Revtex 4, 35 pages, 14 figures in .gif format, accepted for
publication in Phys. Rev.
Lepton Dipole Moments and Rare Decays in the CP-violating MSSM with Nonuniversal Soft-Supersymmetry Breaking
We investigate the muon anomalous magnetic dipole moment (MDM), the muon
electric dipole moment (EDM) and the lepton-flavour-violating decays of the
lepton, and , in the CP-violating
Minimal Supersymmetric Standard Model (MSSM) with nonuniversal
soft-supersymmetry breaking. We evaluate numerically the muon EDM and the
branching ratios and , after taking
into account the experimental constraints from the electron EDM and muon MDM.
Upon imposition of the experimental limits on our theoretical predictions for
the aforementioned branching ratios and the muon MDM, we obtain an upper bound
of about on the muon EDM which lies well within the
explorable reach of the proposed experiment at BNL.Comment: Latex, 26 pages, 8 figures, accepted for publication in Phys. Rev.
Simultaneous analysis of free amino acids and biogenic amines in honey and wine samples using in loop orthophthalaldeyde derivatization procedure
This work presents a RP-HPLC method for the simultaneous quantification of free amino acids and biogenic amines in liquid food matrices and the results of the application to honey and wine samples obtained from different production processes and geographic origins. The developed methodology is based on a pre-column derivatization with o-phthaldialdehyde carried out in the sample injection loop. The compounds were separated in a Nova-Pack RP-C18 column (150 mm × 3.9 mm, 4 μm) at 35 °C. The mobile phase used was a mixture of phase A: 10 mM sodium phosphate buffer (pH 7.3), methanol and tetrahydrofuran (91:8:1); and phase B: methanol and phosphate buffer (80:20), with a flow rate of 1.0 ml/min. Fluorescence detection was used at an excitation wavelength of 335 nm and an emission wavelength of 440 nm. The separation and quantification of 19 amino acids and 6 amines was carried out in a single run as their OPA/MCE derivatives elute within 80 min, ensuring a reproducible quantification. The method showed to be adequate for the purpose, with an average RSD of 2% for the different amino acids; detection limits varying between 0.71 mg/l (Asn) and 8.26 mg/l (Lys) and recovery rates between 63.0% (Cad) and 98.0% (Asp). The amino acids present at the highest concentration in honey and wine samples were phenylalanine and arginine, respectively. Only residual levels of biogenic amines were detected in the analysed samples
Cichlid biogeography: comment and review
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72313/1/j.1467-2979.2004.00148.x.pd
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