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  • 1
    Electronic Resource
    Electronic Resource
    Preparation of ultrathin free-standing targets for (e,2e) spectroscopy (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 4396-4403 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We describe in detail the procedures used for the preparation of ultrathin (∼10 nm) free-standing membranes for (e,2e) spectroscopy. Such a thin target is needed to minimize electron multiple scattering before and after an (e,2e) event. The development of a rf plasma source which allows in situ thinning and thickness monitoring is of key importance to the success of the target preparation. Materials (C, Si, Ni, Cu, Al2O3, SiO2, CuO) with different properties and structures are usually prepared in different ways. For insulating targets it is important to have a conducting sublayer to avoid the charging problem. A well prepared target usually has a thin area larger than the (e,2e) beam size (∼0.2 mm in diameter) and yields high quality (e,2e) data from which the electron energy-momentum density in a chosen direction is determined. Efforts demonstrated in this article indicate that the preparation of ultrathin free-standing films is a challenging area where significant technical development is needed.© 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148402
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  • 2
    Electronic Resource
    Electronic Resource
    Cadmium induces senescence symptoms in leaf peroxisomes of pea plants (2001)
    Oxford, UK : Blackwell Science, Ltd
    Plant, cell & environment 24 (2001), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The effect of growing pea (Pisum sativum L.) plants with a toxic CdCl2 concentration (50 µm) on the metabolism and proteolytic activity of leaf peroxisomes was studied. In peroxisomes purified from plants treated with cadmium, an increase in the total protein concentration and in the activity and protein level of the photorespiratory enzyme glycolate oxidase was found. The glyoxylate cycle enzymes, malate synthase and isocitrate lyase, whose activity is normally very low in leaf peroxisomes, were enhanced by Cd treatment. The activity of the endogenous proteases of leaf peroxisomes was determined. Two leucine-aminopeptidase isozymes (AP1-AP2) were detected, and their activity was slightly higher in Cd-treated plants. Five endopeptidases (EP1-EP5) were present in pea leaf peroxisomes, and in plants grown with Cd the activity of isozymes EP1-EP4 was increased. The ultrastructural analysis of pea leaves showed that Cd produced a disorganization of the chloroplast structure, with an increase in the number of plastoglobuli, and the formation of vesicles in the vacuoles. Taken together, these results indicate that Cd induces senescence symptoms in leaf peroxisomes, and probably a metabolic transition of leaf peroxisomes into glyoxysomes, and suggest that the peroxisomal proteases could participate in the metabolic changes produced by Cd.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.2001.00750.x
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  • 3
    Electronic Resource
    Electronic Resource
    Reactive oxygen species-mediated enzymatic systems involved in the oxidative action of 2,4-dichlorophenoxyacetic acid (2004)
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 27 (2004), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 2,4-dichlorophenoxyacetic acid (2,4-D) is an analogue compound to the plant hormone indole-3-acetic acid (IAA), which is used either as a growth-promoting substance or as a herbicide, depending on its concentration. In this work, the effect of 2,4-D on the growth and ROS metabolism of pea (Pisum sativum L.) leaves is reported. The herbicide considerably reduced the plant growth and negatively influenced several physiological parameters in a dose-dependent manner. At structural level, damage of the mesophyll cells and the enlargement and dilation of thylakoids were observed in 2,4-D-treated plants. 2,4-D notably affected xanthine oxidase and superoxide dismutase activities, as well as the activity and transcript levels of the ascorbate–glutathione cycle enzymes, ascorbate peroxidase, monodehydroascorbate reductase, and glutathione reductase. Furthermore, in herbicide-treated plants, an increase in the H2O2 production, levels of lipid peroxidation, endopeptidase activity and oxidatively modified proteins took place. Results obtained showed that an overproduction of superoxide radicals (O2−) and hydrogen peroxide (H2O2) could take place in plants treated with 2,4-D, thus contributing to the generation of oxidative stress, with the concomitant degradation of proteins. A model of the role of ROS-mediated enzymatic systems in the oxidative mode of action of 2,4-D and other auxinic herbicides is proposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.2004.01219.x
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  • 4
    Electronic Resource
    Electronic Resource
    The influence of life-history strategy on lipid metabolism in overwintering juvenile Atlantic salmon (2002)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 60 (2002), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: From November to May, the lipid mass in the viscera and carcass of juvenile Atlantic salmon Salmo salar that were undergoing smolt transformation prior to seaward migration (‘early migrants’) were significantly greater than those of their siblings that would delay migration for at least a further year. During winter (November-February), the depletion of lipid associated with the viscera was significantly greater in early migrants, whilst lipid depletion in the remaining carcass was greater in delayed migrants. Early migrants continued to deplete both lipid compartments in spring (February-May), whereas delayed migrants depleted visceral lipid but replenished carcass lipid over the same period. Fatty acid accumulation rates (a measure of storage lipid synthesis rates) were two to six times greater in visceral than in carcass lipid throughout the study, suggesting that lipid turnover is much more rapid in the viscera. There were no differences in fatty acid accumulation rates between migrant groups in November, despite the much lower food consumption rate of delayed migrants at that time, suggesting that these fish allocated a larger proportion of their nutritional resources to lipid synthesis. In the carcass lipid of early migrants, and in both the visceral and carcass lipid of delayed migrants, the fatty acid accumulation rate was negatively correlated with lipid mass. Fatty acid accumulation rates increased from November to February in both visceral and carcass lipid in the two migrant groups. The fatty acid accumulation rate in carcass lipid was significantly higher in delayed migrants than in early migrants in February, but not in May. These results support the hypothesis that life history strategies involving rapid growth will result in a relatively low allocation of resources to lipid reserves.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.2002.tb01693.x
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  • 5
    Electronic Resource
    Electronic Resource
    Competitive ability is related to metabolic asymmetry in juvenile rainbow trout (2001)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 59 (2001), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Of 55 size–matched pairs of juvenile rainbow trout Oncorhynchus mykiss, each consisting of one high and one low relative metabolic rate fish (relative size difference 〈5%), the high relative metabolic rate fish was dominant in 36 pairs (65·5%), significantly more often than expected by chance. The probability of a fish winning was related to its relative metabolic rate (measured prior to introduction into the test arena); the higher the relative metabolic rate of a fish compared to its opponent, the greater its probability of being dominant. In the 36 pairs of fish where the low relative metabolic rate fish was the subordinate, its competitive ability was significantly correlated with how closely the two fish were matched in terms of their relative metabolic rates. The smaller the difference between the relative metabolic rates of the dominant high relative metabolic rate fish and subordinate low metabolic rate fish, the greater the competitive ability and feeding success of the low relative metabolic rate subordinate. However, no such relation was found in the 19 pairs of fish where the high relative metabolic rate fish was the subordinate. In these pairs, the competitive ability of the subordinate high relative metabolic rate fish was correlated with its size relative to its dyad partner. The larger the dominant low relative metabolic rate fish, the lower the competitive ability of the subordinate high relative metabolic rate fish.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.2001.tb00167.x
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  • 6
    Electronic Resource
    Electronic Resource
    Temporal repeatability of relative standard metabolic rate in juvenile Atlantic salmon and its relation to life history variation (2000)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 57 (2000), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: There was a strong correlation between the relative standard metabolic rate (rSMR) values of individual Atlantic salmon Salmo salar L. measured 5 and 22 weeks after first feeding in June and October respectively (Pearson's r=0·68, 26 d.f., P〈0·001). However, this is a conservative estimate of repeatability as two separate regressions were used to calculate SMR in October due to the separation of the population into an upper modal group made up of early migrants and a lower modal group comprised of delayed migrants. SMR values in June and October were similar (paired t test, t=-0·85, 27 d.f., P〉0·05) when expressed as the percentage deviation from those predicted for a fish of that size based on the body mass/SMR relations in June or October indicating that relative standard metabolic rates were stable over time when food was not limiting. rSMR status was maintained in 19 of the 28 fish (i.e. 68%) between the two measures. rSMR status was correlated with life history strategy: salmon fry with a high SMR in June were more likely to become smolts during the autumn than those with a low SMR.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.2000.tb00788.x
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  • 7
    Electronic Resource
    Electronic Resource
    The performance of all-female diploid and triploid Atlantic salmon smolts on transfer together to sea water (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 48 (1996), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: On transfer to sea water for 45 days, the return of appetite was later and growth rates tended to be lower for triploid Atlantic salmon, Salmo salar, reared together with diploid Atlantic salmon. All mortalities comprised of triploid salmon (29%) and were attributable to failed smolt syndrome. No correlation was found between the growth of diploid or triploid fish in fresh water and their subsequent growth on transfer to sea water.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.1996.tb01448.x
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  • 8
    Electronic Resource
    Electronic Resource
    A stable isotope analysis of trophic polymorphism among Arctic charr from Loch Ericht, Scotland (2004)
    Oxford, UK; Malden, USA : Blackwell Science Ltd
    Journal of fish biology 65 (2004), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Analysis of nitrogen stable isotope ratios (δ15N) in white muscle and liver shows temporal stability in the trophic levels at which the two sympatric morphs of Arctic charr Salvelinus alpinus from Loch Ericht feed. The results confirm an ontogenetic dietary switch to a more piscivorous diet, occurred in all individuals of one of the morphs, above a size threshold of 16·5 cm fork length, indicating that this occurs at a high frequency in this population and that once made, the return to feeding to a lower trophic level is infrequent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.0022-1112.2004.00526.x
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  • 9
    Electronic Resource
    Electronic Resource
    Stable isotope analysis reveals ecological segregation in a bimodal size polymorphism in Arctic charr from Loch Tay, Scotland (2003)
    Oxford, UK : Blackwell Science Ltd
    Journal of fish biology 62 (2003), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The serendipitous discovery of a body-size dimorphism amongst the sexually mature Arctic charr Salvelinus alpinus of Loch Tay is described. Sexually mature Arctic charr, collected by gill netting on spawning areas, showed a clear and distinct bimodal size distribution with no overlap in fork length distributions. The upper (19–29 cm LF) and lower modes (8–16 cm) were not solely the result of sex or age differences. Analysis of stable isotope ratios of C and N in muscle showed highly significant differences in mean δ13C and δ15N between populations, demonstrating a difference in trophic ecology between the two body-size morphs. Overlap in the range of δ13C and δ15N values for the two morphs, however, suggested that they occasionally shared a common diet. Data from other studies strongly indicated that the proximate and ultimate mechanisms that control body-size dimorphisms in Arctic charr differed between sites. Clear differences in trophic ecology in the Loch Tay Arctic charr suggested that the available feeding opportunity may differ for the two morphs. The most likely proximate mechanism resulting in this dimorphism is growth rate differences resulting from differences in food availability for the two subgroups occupying alternative foraging niches in Loch Tay.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1095-8649.2003.00044.x
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  • 10
    Electronic Resource
    Electronic Resource
    Feeding rank and dominance in Tilapia rendalli under defensible and indefensible patterns of food distribution (1999)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 55 (1999), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In four scatter-fed groups of Tilapia rendalli, the distribution of food between individuals was not significantly different from that expected if the food was shared uniformly between all the fish in the group for nine of the 12 radiographic assessments of feeding behaviour. Individual fish maintained the same feeding rank over time, indicating a stable feeding hierarchy, in only one of the four scatter feeding groups. In contrast, in four point source feeding groups, the distribution of food between individuals differed significantly from uniformity in 10 of the 12 radiographic assessments of feeding behaviour and stable feeding hierarchies were maintained over time in three of the four groups. Thus, scatter feeding promoted a more uniform distribution of food between individuals within the group and prevented the formation of feeding hierarchies. There was no significant correlation between individual feeding rank and dominance index in all four scatter feeding groups. In contrast, significant positive correlations were found between individual feeding rank and dominance index in all four point source feeding groups. The results of this study confirm that feeding rank can be used as a correlate of relative social status under defensible feeding conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.1999.tb00722.x
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