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1.
In species susceptible to mass‐dependent flight costs, mass recession prior to fledging may ensure that fledglings have appropriate wing loading. Our objectives were to determine if mass recession by chimney swift Chaetura pelagica nestlings is intrinsically controlled or facultatively adjusted by nestlings, and if mass recession is driven by changes in parental (i.e. reduced provisioning rates) or nestling (i.e. reduced begging) behavior. Nestling swifts (n = 50 in 17 broods) were divided into three treatment groups: controls, half‐weighted, or weighted. Half‐weighted and weighted nestlings had 0.6–0.7 or 1.2–1.3‐g lead weights, respectively, glued to body feathers on their backs during the period from 16 to 26 d post‐hatching. Weighted nestlings lost more mass than control and half‐weighted nestlings. After accounting for the added weights, control nestlings also had a higher wing loading than weighted nestlings. Video recordings revealed that provisioning rates of adult swifts did not vary throughout the nestling period, but the percent time nestlings spent begging increased slightly with age. Differences in mass recession among nestlings in different treatment groups resulted in convergence toward similar wing loading values likely optimal for flight efficiency. Mechanism(s) involved in this process remain unclear because provisioning rates were similar (from day 12 to 26 post‐hatching) whereas percent begging time by nestlings tended to increase with nestling age. However, weighted nestlings may have lost more mass than control nestlings by soliciting less food from adults than siblings, being more active, losing more water due to tissue maturation, or through some combination of two or more of these factors. 相似文献
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C Sagan 《Journal of theoretical biology》1973,39(1):195-200
An examination of the probable photochemistry of the primitive reducing atmosphere of the Earth reveals a window, approximately bounded at 2400 Å to short wavelengths by H2S, and possibly at 2700–2900 Å to longer wavelengths by aldehydes. The solar untraviolet flux in this 2600 Å window, delivered to unprotected organisms at the surface, corresponds to a contemporary mean lethal dose in ≤ 0·3 seconds. Extreme selection pressure for ultraviolet protection must have come into being. In addition to the early evolution of pyrimidine dimer ligases, catalase and peroxidase reduction mechanisms, and photoreactivation, it is suggested that two evolutionary paths developed. In one, heterotrophs lived below the oceanic thermocline and are suggested as perhaps the ancestors of the prokaryotes. In the other, organisms living near the oceanic surface surrounded themselves with ultraviolet absorbing layers of purines and pyrimidines. The resulting organisms have dimensions of tens to hundreds of microns (μm) and are suggested to be the ancestors of the eukaryotes. Subsequent specialization of this initially inert shielding, e.g., into ribosomal RNA, may have occurred. 相似文献
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Selena M Sagan Yanouchka Rouleau Cynthia Leggiadro Lubica Supekova Peter G Schultz Andrew I Su John Paul Pezacki 《Biochimie et biologie cellulaire》2006,84(1):67-79
The hepatitis C virus (HCV) replicates on a membrane protein complex composed of viral proteins, replicating RNA, and altered cellular membranes. Small-molecule inhibitors of cellular lipid-cholesterol metabolism such as 25-hydroxycholesterol, cerulenin, lovastatin, and GGTI-286 all show a negative effect on HCV replication. Perturbation of host cell lipid and cholesterol metabolism can disrupt replication complexes by altering membranous structures where replication occurs. Changes in cholesterol and (or) lipid composition can have a general effect on membrane structure. Alternatively, metabolic changes can exert a more subtle influence over replication complexes by altering localization of host proteins through alterations in lipid anchoring. Here, we use Huh-7 cells harboring subgenomic HCV replicons to demonstrate that 25-hydroxycholesterol, cerulenin, lovastatin, and GGTI-286 do not disrupt the membranous web where replication occurs, whereas cholesterol-depleting agents such as beta-cyclodextrin do. Cellular imaging suggests that the HCV RNA can remain associated with subcellular compartments connected with replication complexes in the presence of metabolic inhibitors. Therefore, at least 2 different molecular mechanisms are possible for the inhibition of HCV replication through the modulation of cellular lipid and cholesterol metabolism. 相似文献
6.
Isabella Soreca Andrea Fagiolini Ellen Frank Bret H. Goodpaster David J. Kupfer 《Chronobiology international》2013,30(4):780-788
We explored whether obesity in patients with bipolar disorder is associated with their chronotype. A group of 29 patients with bipolar I disorder, not currently experiencing an affective episode, were assessed for total body fat, mood symptoms, and self-reported circadian chronotype and sleep quality. Chronotype explained 19% of the variance in body fat, after age, sex, mood state, and sleep quality were accounted for. This association suggested that evening chronotype patients have a higher percentage of total body fat. Evening chronotype could be a proxy for as yet unknown specific causes of the high rate of obesity and obesity-related diseases in bipolar disorder. 相似文献
7.
Andreas Katsiaras Anne B Newman Andrea Kriska Jennifer Brach Shanthi Krishnaswami Eleanor Feingold Stephen B Kritchevsky Rongling Li Tamara B Harris Ann Schwartz Bret H Goodpaster 《Journal of applied physiology》2005,99(1):210-216
We examined the muscle fatigue characteristics in older men and women and determined whether these were related to the size, strength, or quality of muscle. A total of 1,512 men and women aged 70-79 yr from the Health, Aging, and Body Composition Study participated in this study. Muscle cross-sectional area and attenuation were determined with computed tomography. Skeletal muscle fatigue and strength (peak torque) of the knee extensors and flexors were measured using isokinetic dynamometry. Men were more fatigue resistant than women for both knee extension (fatigue index: 70.4 +/- 15.3 vs. 66.9 +/- 14.3%; P < 0.05) and knee flexion (67.9 +/- 16.4 vs. 64.9 +/- 17.6%; P < 0.05). Peak torque and muscle quality (specific torque) were higher in men than women for knee extension (99.6 +/- 28.2 vs. 63.0 +/- 16.8 N x m and 1.62 +/- 0.43 vs. 1.51 +/- 0.39 N x m/cm2; both P < 0.05) and for knee flexion (74.0 +/- 26.4 vs. 49.6 +/- 15.9 N x m and 2.47 +/- 1.29 vs. 2.22 +/- 0.78 N x m/cm2; both P < 0.05). Total work and power output was greater in men compared with women for both the quadriceps (1,353 +/- 451 vs. 832 +/- 264 J and 87.7 +/- 33.5 vs. 53.3 +/- 19.2 W; both P < 0.05) and the hamstrings (741 +/- 244 vs. 510 +/- 141 J and 35.4 +/- 16.0 vs. 23.7 +/- 10.2 W; both P < 0.05). In both genders, the quadriceps was able to perform more work with greater power compared with the hamstrings. Those who were stronger actually had greater fatigue after adjusting for age, race, physical activity, and total body fat. In conclusion, older men were more fatigue resistant than women, although in both men and women greater fatigue was not related to muscle weakness. 相似文献
8.
Tracy Goodpaster Julie Randolph-Habecker 《The journal of histochemistry and cytochemistry》2014,62(3):197-204
Immunohistochemistry on mouse tissue utilizing mouse monoclonal antibodies presents a challenge. Secondary antibodies directed against the mouse monoclonal primary antibody of interest will also detect endogenous mouse immunoglobulin in the tissue. This can lead to significant spurious staining. Therefore, a “mouse-on-mouse” staining strategy is needed to yield credible data. This paper presents a method that is easy to use and highly flexible to accommodate both an avidin-biotin detection system as well as a biotin-free polymer detection system. The mouse primary antibody is first combined with an Fab fragment of an anti-mouse antibody in a tube and allowed sufficient time to form an antibody complex. Any non-complexed secondary antibody is bound up with mouse serum. The mixture is then applied to the tissue. The flexibility of this method is confirmed with the use of different anti-mouse antibodies followed by a variety of detection reagents. These techniques can be used for immunohistochemistry (IHC), immunofluorescence (IF), as well as staining with multiple primary antibodies. This method has also been adapted to other models, such as using human antibodies on human tissue and using multiple rabbit antibodies in dual immunofluorescence. 相似文献
9.
Antimicrobial and cell-penetrating peptides have inspired developments of abiotic membrane-active polymers that can coat, penetrate, or break lipid bilayers in model systems. Application to cell cultures is more recent, but remarkable bioactivities are already reported. Synthetic polymer chains were tailored to achieve (i) high biocide efficiencies, and selectivity for bacteria (Gram-positive/Gram-negative or bacterial/mammalian membranes), (ii) stable and mild encapsulation of viable isolated cells to escape immune systems, (iii) pH-, temperature-, or light-triggered interaction with cells. This review illustrates these recent achievements highlighting the use of abiotic polymers, and compares the major structural determinants that control efficiency of polymers and peptides. Charge density, sp. of cationic and guanidinium side groups, and hydrophobicity (including polarity of stimuli-responsive moieties) guide the design of new copolymers for the handling of cell membranes. While polycationic chains are generally used as biocidal or hemolytic agents, anionic amphiphilic polymers, including Amphipols, are particularly prone to mild permeabilization and/or intracell delivery. 相似文献
10.
Camille Rolland-Debord David Lair Tiphaine Roussey-Bihouée Dorian Hassoun Justine Evrard Marie-Aude Cheminant Julie Chesné Faouzi Braza Guillaume Mahay Vincent Portero Christine Sagan Bruno Pitard Antoine Magnan 《PloS one》2014,9(1)