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排序方式: 共有159条查询结果,搜索用时 0 毫秒
151.
Michael P. Gardner Carmen Martin-Ruiz Rachel Cooper Rebecca Hardy Avan Aihie Sayer Cyrus Cooper Ian J. Deary John Gallacher Sarah E. Harris Paul G. Shiels John M. Starr Diana Kuh Thomas von Zglinicki Yoav Ben-Shlomo the Halcyon study team 《PloS one》2013,8(7)
Background
Telomeres are involved in cellular ageing and shorten with increasing age. If telomere length is a valuable biomarker of ageing, then telomere shortening should be associated with worse physical performance, an ageing trait, but evidence for such an association is lacking. The purpose of this study was to examine whether change in telomere length is associated with physical performance.Methods
Using data from four UK adult cohorts (ages 53–80 years at baseline), we undertook cross-sectional and longitudinal analyses. We analysed each study separately and then used meta-analytic methods to pool the results. Physical performance was measured using walking and chair rise speed, standing balance time and grip strength. Telomere length was measured by quantitative real-time polymerase chain reaction (PCR) in whole blood at baseline and follow-up (time 1, time 2).Results
Total sample sizes in meta-analyses ranged from 1,217 to 3,707. There was little evidence that telomere length was associated with walking speed, balance or grip strength, though weak associations were seen with chair rise speed and grip strength at baseline (p = 0.02 and 0.01 respectively). Faster chair rise speed at follow-up, was associated with a smaller decline in telomere length between time 1 and time 2 (standardised coefficient per SD increase 0.061, 95% CI 0.006, 0.115, p = 0.03) but this was consistent with chance (p = 0.08) after further adjustment.Conclusions
Whereas shortening of leukocyte telomeres might be an important measure of cellular ageing, there is little evidence that it is a strong biomarker for physical performance. 相似文献152.
Birkedal R Shiels HA 《American journal of physiology. Regulatory, integrative and comparative physiology》2007,293(2):R861-R866
Intracellular Na(+)-concentration, [Na(+)](i) modulates excitation-contraction coupling of cardiac myocytes via the Na(+)/Ca(2+) exchanger (NCX). In cardiomyocytes from rainbow trout (Oncorhyncus mykiss), whole cell patch-clamp studies have shown that Ca(2+) influx via reverse-mode NCX contributes significantly to contraction when [Na(+)](i) is 16 mM but not 10 mM. However, physiological [Na(+)](i) has never been measured. We recorded [Na(+)](i) using the fluorescent indicator sodium-binding benzofuran isophthalate in freshly isolated atrial and ventricular myocytes from rainbow trout. We examined [Na(+)](i) at rest and during increases in contraction frequency across three temperatures that span those trout experience in nature (7, 14, and 21 degrees C). Surprisingly, we found that [Na(+)](i) was not different between atrial and ventricular cells. Furthermore, acute temperature changes did not affect [Na(+)](i) in resting cells. Thus, we report a resting in vivo [Na(+)](i) of 13.4 mM for rainbow trout cardiomyocytes. [Na(+)](i) increased from rest with increases in contraction frequency by 3.2, 4.7, and 6.5% at 0.2, 0.5, and 0.8 Hz, respectively. This corresponds to an increase of 0.4, 0.6, and 0.9 mM at 0.2, 0.5, and 0.8 Hz, respectively. Acute temperature change did not significantly affect the contraction-induced increase in [Na(+)](i). Our results provide the first measurement of [Na(+)](i) in rainbow trout cardiomyocytes. This surprisingly high [Na(+)](i) is likely to result in physiologically significant Ca(2+) influx via reverse-mode NCX during excitation-contraction coupling. We calculate that this Ca(2+)-source will decrease with the action potential duration as temperature and contraction frequency increases. 相似文献
153.
Rikke Birkedal Jennifer Christopher Angela Thistlethwaite Holly A. Shiels 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2009,179(8):961-969
In cardiomyocytes, ryanodine receptors (RYRs) mediate Ca2+-induced Ca2+-release (CICR) from the sarcoplasmic reticulum (SR) during excitation–contraction (e–c) coupling. In rainbow trout heart,
the relative importance of CICR increases with cold-acclimation. Thus, the aim of this study was to investigate the effect
of temperature acclimation (4, 11 and 18°C) on RYR intracellular localization and expression density. We used immunocytochemistry
to assess intracellular localization in ventricular myocytes and Western blotting to assess RYR expression in both atrial
and ventricular tissue. In ventricular myocytes, RYRs were localized peripherally in transverse bands aligning with sarcomeric
m-lines and centrally around mitochondria and the nucleus. Localization did not change with temperature acclimation. RYR expression
was also unaffected by temperature acclimation. The localization of RYRs at the m-line is similar to neonatal mammalian cardiomyocytes. We suggest this positioning is indicative of myocytes which rely predominantly
on transsarcolemmal Ca2+-influx, rather than CICR, during e–c coupling. 相似文献
154.
Nicholas Carter Stephen Jeffery Alan Shiels Yvonne Edwards Terry Tipler David A. Hopkinson 《Biochemical genetics》1979,17(9-10):837-854
A third form of human carbonic anhydrase (CA III), found at high concentrations in skeletal muscle, has been purified and characterized. This isozyme shows relatively poor hydratase and esterase activities compared to the red cell isozymes, CA I and CA II, but is similar to these isozymes in subunit structure (monomer) and molecular size (28,000). CA III is liable to posttranslational modification by thiol group interaction. Monomeric secondary isozymes, sensitive to beta-mercaptoethanol, are found in both crude and purified material and can be generated in vitro by the addition of thiol reagents. Active dimeric isozymes, generated apparently by the formation of intermolecular disulfide bridges, also occur but account for only a small proportion of the total protein and appear only when the concentration of CA III is particularly high. 相似文献
155.
Landslides are excellent illustrations of the dynamic interplay of disturbance and succession. Restoration is difficult on landslide surfaces because of the high degree of spatial and temporal heterogeneity in soil stability and fertility. Principles derived from more than a century of study of ecological succession can guide efforts to reduce chronic surface soil erosion and restore both biodiversity and ecosystem function. Promotion of the recovery of self-sustaining communities on landslides is feasible by stabilization with native ground cover, applications of nutrient amendments, facilitation of dispersal to overcome establishment bottlenecks, emphasis on functionally redundant species and promotion of connectivity with the adjacent landscape. Arrested succession through resource dominance by a single species can be beneficial if that species also reduces persistent erosion, yet the tradeoff is often reduced biodiversity. Restoration efforts can be streamlined by using techniques that promote successional processes. 相似文献
156.
Cloned cDNAs coding for eye-lens fibre cell-membrane proteins, MIP and MP70, were used to detect restriction fragment length polymorphisms (RFLPs) in genomic DNA from inbred mice with autosomally inherited cataracts. Whereas distinct RFLPs associated with the MIP gene were identified in the Cba Cat and Nct mutants, no such genetic variation was associated with the MP70 gene. RFLPs associated with the mouse MIP gene may provide informative DNA markers in gene linkage studies of murine hereditary cataracts. 相似文献
157.
The gene encoding the major intrinsic protein (Mip) of eye-lens-fibre cell membranes has been assigned to region D1 of mouse Chromosome 10 by in situ hybridisation of a cDNA for rat MIP to G-banded metaphase chromosomes. The mouse Mip gene maps within or near to a segment homoeologous with human chromosome 12q and may be linked to the Cat locus at the distal end of mouse Chromosome 10. 相似文献
158.
Samantha A. Hook Charlotte McMurray Daniel M. Ripley Natasha Allen Timo Moritz Bianka Grunow Holly A. Shiels 《Journal of fish biology》2019,95(6):1465-1470
Eighteen captive small-spotted catsharks Scyliorhinus canicula were successfully identified from hatching to 1 year of age using the free computer recognition software, I3S classic. The effect of increasing the time interval between recognition attempts on the accuracy of the software was investigated, revealing that recognition fiedelity decreases with increasing time intervals for younger (0 to 15 weeks), but not older (15 weeks onwards) sharks. Identification by I3S was validated using genetic analyses of seven microsatellite markers, revealing a 100% success rate. Thus, this non-invasive recognition method can be used as an inexpensive and effective alternative to invasive tagging, improving animal welfare and complementing ex-situ conservation methods. 相似文献
159.