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61.
Foundation species structure environments and create refuge from environmental stress. In New England high salt marsh, the
grass Spartina patens is a foundation species that reduces salinity, anoxia, desiccation, and thermal stresses through canopy shading and root
proliferation. In a factorial S. patens-removal and warming field experiment, foundation species removal strongly impacted every aspect of the community, reiterating
the important role of the foundation species S. patens in the high marsh. Given this central role, we hypothesized that facilitation by the foundation species would be even more
important under warmer conditions by ameliorating more severe thermal stress. However, the ecological role of S. patens was unaffected by experimental warming, and, independent of the presence of the foundation species, warming had only weak
effects on the salt marsh ecological community. Only the foundation species itself responded strongly to warming, by significantly
increasing aboveground production in warmed plots. Apparently, amelioration of thermal stress is not as important for salt
marsh ecosystem function as S. patens’ moderation of salinity and desiccation stresses. From these experimental results, we anticipate that climate change-associated
thermal stress will not greatly affect S. patens-dominated high marsh communities. In contrast, foundation species loss, an emergent conservation issue in Atlantic salt marshes,
represents a critical threat to salt marsh ecosystem function. 相似文献
62.
Eliza Redden Uyunbilig Borjigin Keryn Hutton Geoff Hinch Jonathan Hill Muren Herrid 《Cryobiology》2009,58(2):190-195
Cryopreservation has become an integral component of any cell transplantation technique helping to overcome the issues associated with known spatial and temporal barriers between donor and recipient. The aim of this study was to develop a protocol for large quantity cryopreservation of bovine testicular germ cells. The impact of 3 different packaging methods (5 ml semen straw, 20 ml freezing bag and 1.5 ml cryovial) and varying cell densities (3 × 106, 9 × 106, or 18 × 106 cells/ml) on the survival of testis germ cells was examined. Cells processed in 5 ml semen straws had a significantly higher viability (70.7 ± 1.2%, P < 0.05) compared to those cells in 20 ml freezing bags (46.7 ± 0.1%) or 1.5 ml cryovials (46.3 ± 2.2%). For 5 ml straws, a 20 min cooling prior to cryopreservation resulted in a higher post thaw viability (73.2 ± 0.6%) than a 10 min cooling (56.0 ± 2.2%), while the density of the cell suspension did not impact on post thaw viability. Thus cryopreservation of testicular germ cells in 5 ml straws at a density between 3 × 106 and 18 × 106 cells/ml in liquid nitrogen vapour for 20 min cooling appears to be a simple and practical way to preserve cells. Subsequent testing of frozen/thawed cells exhibited viable cultures and retained the ability to proliferate. The freezing protocol does not preferentially preserve type A spermatogonia. However, the cell surface properties of somatic cells appear to be affected by the freezing procedure and therefore the frozen/thawed cells are less suitable for enriching type A spermatogonia by differential plating. 相似文献
63.
64.
F. M. R. Walshe 《BMJ (Clinical research ed.)》1941,2(4223):858-859
65.
Research to date in young children and adults shows a strong, inverse relationship between sleep duration and risk for overweight and obesity. Fewer studies examining this relationship have been conducted in adolescents. The purpose of the article is to describe the relationship between sleep and weight in a population of adolescents, controlling for demographics, energy intake, energy expenditure, and depression. This is a cross-sectional study of 723 adolescents participating in population-based studies of the etiologic factors related to obesity. We examined the relationship between three weight-related dependent variables obtained through a clinical assessment and three sleep variables obtained through self-report. Average caloric intake from dietary recalls, average activity counts based on accelerometers, and depression were included as covariates and the analysis was stratified by gender and grade level. Our results show that the relationship between sleep duration and BMI is evident in middle-school boys (β = -0.32, s.e. = 0.06: P < 0.001) and girls (β = -0.18, s.e. = 0.08: P = 0.02) but largely absent in high-school students. Differences in sleep patterns have little association with weight in males, but in high-school girls, waking up late on weekends as compared to weekdays is associated with lower body fat (β = -0.80, s.e. = 0.40: P = 0.05) and a healthy weight status (β = -0.28, s.e. = 0.14: P = 0.05). This study adds to the evidence that, particularly for middle-school boys and girls, inadequate sleep is a risk factor for early adolescent obesity. Future research needs to examine the relationship longitudinally and to study potential mediators of the relationship. 相似文献
66.
Allin MP Kontis D Walshe M Wyatt J Barker GJ Kanaan RA McGuire P Rifkin L Murray RM Nosarti C 《PloS one》2011,6(10):e24525
Background and Purpose
Individuals born very preterm (before 33 weeks of gestation, VPT) are at risk of damage to developing white matter, which may affect later cognition and behaviour.Methods
We used diffusion tensor MRI (DT-MRI) to assess white matter microstructure (fractional anisotropy; FA) in 80 VPT and 41 term-born individuals (mean age 19.1 years, range 17–22, and 18.5 years, range17–22 years, respectively). VPT individuals were part of a 1982–1984 birth cohort which had been followed up since birth; term individuals were recruited by local press advertisement. General intellectual function, executive function and memory were assessed.Results
The VPT group had reduced FA in four clusters, and increased FA in four clusters relative to the Term group, involving several association tracts of both hemispheres. Clusters of increased FA were associated with more severe neonatal brain injury in the VPT group. Clusters of reduced FA were associated with lower birth weight and perinatal hypoxia, and with reduced adult cognitive performance in the VPT group only.Conclusions
Alterations of white matter microstructure persist into adulthood in VPT individuals and are associated with cognitive function. 相似文献67.
Linklater WL Gedir JV Law PR Swaisgood RR Adcock K du Preez P Knight MH Kerley GI 《PloS one》2012,7(1):e30664
Species translocations are remarkable experiments in evolutionary ecology, and increasingly critical to biodiversity conservation. Elaborate socio-ecological hypotheses for translocation success, based on theoretical fitness relationships, are untested and lead to complex uncertainty rather than parsimonious solutions. We used an extraordinary 89 reintroduction and 102 restocking events releasing 682 black rhinoceros (Diceros bicornis) to 81 reserves in southern Africa (1981-2005) to test the influence of interacting socio-ecological and individual characters on post-release survival. We predicted that the socio-ecological context should feature more prominently after restocking than reintroduction because released rhinoceros interact with resident conspecifics. Instead, an interaction between release cohort size and habitat quality explained reintroduction success but only individuals' ages explained restocking outcomes. Achieving translocation success for many species may not be as complicated as theory suggests. Black rhino, and similarly asocial generalist herbivores without substantial predators, are likely to be resilient to ecological challenges and robust candidates for crisis management in a changing world. 相似文献
68.
Kadali KK Simons KL Skuza PP Moore RB Ball AS 《Journal of microbiological methods》2012,88(3):348-355
The isolation and assessment of hydrocarbonoclastic bacteria often represents a key strategy in the bioremediation of hydrocarbon-contaminated sites. However the isolation and assessment of such bacteria is often a lengthy and expensive procedure. The aim of this study was to identify potential isolates for use in the remediation of hydrocarbon contaminated sites using a combination of selective isolation plating, the Biolog system and subsequent multivariate analyses. The use of weathered oil as the main C source restricted the number of isolates growing to 5×10(2)CFUg soil(-1). Isolates (n=96) were then assessed individually using Biolog MT2 plates with seven different hydrocarbons (dodecane, tridecane, hexadecane, octadecane, eicosane, naphthalene and phenanthrene). The results indicated that all isolates were able to grow on at least one hydrocarbon from the seven chosen. This confirmed that the isolation media developed was selective in isolating hydrocarbonoclastic bacteria only. Cluster analysis of Biolog data separated the isolates into two discrete clusters with cluster 2 identifying hydrocarbonoclastic bacteria that are effective in degrading a variety of contaminants. Further study on the isolates from cluster 2 was carried out based on their phylogenetic analysis. Phylogenetic analysis of 28 bacterial isolates from cluster 2 based on the 1500bp sequences from 16S rDNA genes using MRBAYES confirmed all isolates as being hydrocarbonoclastic, providing supportive evidence that isolates from cluster 2 have a potential use in bioremediation. This approach could improve both the speed and efficiency of the commercial bioremediation process. 相似文献
69.
Greg J. Wilson Andrew D. Walshe Mark R. Fisher 《European journal of applied physiology and occupational physiology》1997,75(5):455-461
The aims of the present study were: (1) to assess aerobic metabolism in paraplegic (P) athletes (spinal lesion level, T4–L3)
by means of peak oxygen uptake (V˙O2peak) and ventilatory threshold (VT), and (2) to determine the nature of exercise limitation in these athletes by means of cardioventilatory
responses at peak exercise. Eight P athletes underwent conventional spirographic measurements and then performed an incremental
wheelchair exercise on an adapted treadmill. Ventilatory data were collected every minute using an automated metabolic system:
ventilation (l · min−1), oxygen uptake (V˙O2, l · min−1, ml · min−1 · kg−1), carbon dioxide production (V˙CO2, ml · min−1), respiratory exchange ratio, breathing frequency and tidal volume. Heart rate (HR, beats · min−1) was collected with the aid of a standard electrocardiogram. V˙O2peak was determined using conventional criteria. VT was determined by the breakpoint in the V˙CO2−V˙O2 relationship, and is expressed as the absolute VT (V˙O2, ml · min−1 · kg−1) and relative VT (percentage of V˙O2peak). Spirometric values and cardioventilatory responses at rest and at peak exercise allowed the measurement of ventilatory
reserve (VR), heart rate reserve (HRr), heart rate response (HRR), and O2 pulse (O2 P). Results showed a V˙O2peak value of 40.6 (2.5) ml · min−1 · kg−1, an absolute VT detected at 23.1 (1.5) ml · min−1 · kg−1
V˙O2 and a relative VT at 56.4 (2.2)% V˙O2peak. HRr [15.8 (3.2) beats · min−1], HRR [48.6 (4.3) beat · l−1], and O2 P [0.23 (0.02) ml · kg−1 · beat−1] were normal, whereas VR at peak exercise [42.7 (2.4)%] was increased. As wheelchair exercise excluded the use of an able-bodied
(AB) control group, we compared our V˙O2peak and VT results with those for other P subjects and AB controls reported in the literature, and we compared our cardioventilatory
responses with those for respiratory and cardiac patients. The low V˙O2peak values obtained compared with subject values obtained during an arm-crank exercise may be due to a reduced active muscle
mass. Absolute VT was somewhat comparable to that of AB subjects, mainly due to the similar muscle mass involved in wheelchair
and arm-crank exercise by P and AB subjects, respectively. The increased VR, as reported in patients with chronic heart failure,
suggested that P athletes exhibited cardiac limitation at peak exercise, and this contributed to the lower V˙O2peak measured in these subjects.
Accepted: 22 April 1997 相似文献
70.
Leveraging nature's backup plans to incorporate interspecific interactions and resilience into restoration 下载免费PDF全文
Clare E. Aslan Judith L. Bronstein Haldre S. Rogers Keryn B. Gedan Jedediah Brodie Todd M. Palmer Truman P. Young 《Restoration Ecology》2016,24(4):434-440
Interspecific interactions are important structuring forces in ecological communities. Interactions can be disturbed when species are lost from a community. When interactions result in fitness gains for at least one participating organism, that organism may experience reduced fitness as a result of interaction disturbance. However, many species exhibit traits that enable individuals to persist and reproduce in spite of such disruptions, resulting in resilience to interaction disturbance. Such traits can result in interaction generalization, phenotypic and behavioral plasticity, and adaptive capacity. We discuss examples of these traits and use case studies to illustrate how restoration practitioners can use a trait‐based approach to examine species of concern, identify traits that are associated with interspecific interactions and are relevant to resilience, and target such traits in restoration. Restoration activities that bolster interaction resilience could include, for example, reintroducing or supporting specific functional groups or managing abiotic conditions to reduce interaction dependence by at‐risk species (e.g. providing structural complexity offering shelter and cover). Resilience may also be an important consideration in species selection for restoration. Establishment of resilient species, able to persist after interaction disturbance, may be essential to restoring to a functioning ecological community. Once such species are present, they could help support more specialized species that lack resilience traits, such as many species of concern. Understanding the conditions under which processes linked to resilience may enable species to persist and communities to reform following interaction disturbance is a key application of community ecology to ecological restoration. 相似文献