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Peter B. Frappell – One of the best experts on this subject based on the ideXlab platform.

  • Hypoxic Acclimation leads to metabolic compensation after reoxygenation in Atlantic salmon yolk-sac alevins
    Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, 2017
    Co-Authors: Elias T. Polymeropoulos, Nicholas G. Elliott, Peter B. Frappell

    Abstract:

    Hypoxia is common in aquatic environments and has substantial effects on development, metabolism and survival of aquatic organisms. To understand the physiological effects of hypoxia and its dependence on temperature, metabolic rate (MO2) and cardiorespiratory function were studied in response to acute hypoxia (21 → 5 kPa) at different measurement temperatures (Ta; 4, 8 and 12 °C) in Salmo salar alevins that were incubated under normoxic conditions (PO2 = 21 kPa) or following hypoxic Acclimation (PO2 = 10 kPa) as well as two different temperatures (4 °C or 8 °C). Hypoxic Acclimation lead to a developmental delay manifested through slower yolk absorption. The general response to acute hypoxia was metabolic depression (~ 60%). Hypoxia acclimated alevins had higher MO2s when measured in normoxia than alevins acclimated to normoxia. MO2s were elevated to the same degree (~ 30% per 4 °C change) irrespective of Ta. Under severe, acute hypoxia (~ 5 kPa) and irrespective of Ta or Acclimation, MO2s were similar between most groups. This suggests that despite different Acclimation regimes, O2 transport was limited to the same degree. While cardiorespiratory function (heart-, ventilation rate) was unchanged in response to acute hypoxia after normoxic Acclimation, hypoxic Acclimation led to cardiorespiratory changes predominantly in severe hypoxia, indicating earlier onset and plasticity of cardiorespiratory control mechanisms. Although MO2 in normoxia was higher after hypoxic Acclimation, at the respective Acclimation PO2, MO2 was similar in normoxia and hypoxia acclimated alevins. This is indicative of metabolic compensation to an intrinsic MO2 at the Acclimation condition in hypoxia-acclimated alevins after re-exposure to normoxia.

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  • Hypoxic Acclimation leads to metabolic compensation after reoxygenation in Atlantic salmon yolk-sac alevins Part A Molecular & integrative physiology
    Comparative Biochemistry and Physiology, 2017
    Co-Authors: Elias T. Polymeropoulos, Nicholas G. Elliott, Peter B. Frappell

    Abstract:

    Hypoxia is common in aquatic environments and has substantial effects on development, metabolism and survival of aquatic organisms. To understand the physiological effects of hypoxia and its dependence on temperature, metabolic rate (MO2) and cardiorespiratory function were studied in response to acute hypoxia (21→5kPa) at different measurement temperatures (Ta; 4, 8 and 12°C) in Salmo salar alevins that were incubated under normoxic conditions (PO2=21kPa) or following hypoxic Acclimation (PO2=10kPa) as well as two different temperatures (4°C or 8°C). Hypoxic Acclimation lead to a developmental delay manifested through slower yolk absorption. The general response to acute hypoxia was metabolic depression (~60%). Hypoxia acclimated alevins had higher MO2s when measured in normoxia than alevins acclimated to normoxia. MO2s were elevated to the same degree (~30% per 4°C change) irrespective of Ta. Under severe, acute hypoxia (~5kPa) and irrespective of Ta or Acclimation, MO2s were similar between most groups. This suggests that despite different Acclimation regimes, O2 transport was limited to the same degree. While cardiorespiratory function (heart-, ventilation rate) was unchanged in response to acute hypoxia after normoxic Acclimation, hypoxic Acclimation led to cardiorespiratory changes predominantly in severe hypoxia, indicating earlier onset and plasticity of cardiorespiratory control mechanisms. Although MO2 in normoxia was higher after hypoxic Acclimation, at the respective Acclimation PO2, MO2 was similar in normoxia and hypoxia acclimated alevins. This is indicative of metabolic compensation to an intrinsic MO2 at the Acclimation condition in hypoxia-acclimated alevins after re-exposure to normoxia.

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  • hypoxic Acclimation leads to metabolic compensation after reoxygenation in atlantic salmon yolk sac alevins part a molecular integrative physiology
    Comparative Biochemistry and Physiology, 2017
    Co-Authors: Elias T. Polymeropoulos, Nicholas G. Elliott, Peter B. Frappell

    Abstract:

    Hypoxia is common in aquatic environments and has substantial effects on development, metabolism and survival of aquatic organisms. To understand the physiological effects of hypoxia and its dependence on temperature, metabolic rate (MO2) and cardiorespiratory function were studied in response to acute hypoxia (21→5kPa) at different measurement temperatures (Ta; 4, 8 and 12°C) in Salmo salar alevins that were incubated under normoxic conditions (PO2=21kPa) or following hypoxic Acclimation (PO2=10kPa) as well as two different temperatures (4°C or 8°C). Hypoxic Acclimation lead to a developmental delay manifested through slower yolk absorption. The general response to acute hypoxia was metabolic depression (~60%). Hypoxia acclimated alevins had higher MO2s when measured in normoxia than alevins acclimated to normoxia. MO2s were elevated to the same degree (~30% per 4°C change) irrespective of Ta. Under severe, acute hypoxia (~5kPa) and irrespective of Ta or Acclimation, MO2s were similar between most groups. This suggests that despite different Acclimation regimes, O2 transport was limited to the same degree. While cardiorespiratory function (heart-, ventilation rate) was unchanged in response to acute hypoxia after normoxic Acclimation, hypoxic Acclimation led to cardiorespiratory changes predominantly in severe hypoxia, indicating earlier onset and plasticity of cardiorespiratory control mechanisms. Although MO2 in normoxia was higher after hypoxic Acclimation, at the respective Acclimation PO2, MO2 was similar in normoxia and hypoxia acclimated alevins. This is indicative of metabolic compensation to an intrinsic MO2 at the Acclimation condition in hypoxia-acclimated alevins after re-exposure to normoxia.

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Andrew E Mckechnie – One of the best experts on this subject based on the ideXlab platform.

  • phenotypic flexibility of metabolic rate and evaporative water loss does not vary across a climatic gradient in an afrotropical passerine bird
    The Journal of Experimental Biology, 2020
    Co-Authors: Matthew J Noakes, Andrew E Mckechnie

    Abstract:

    Small birds inhabiting northern temperate and boreal latitudes typically increase metabolic rates during cold winters or Acclimation to low air temperatures (Taccl). Recent studies suggest considerable variation in patterns of seasonal metabolic acclimatization in birds from subtropical and tropical regions with milder winters, but there remains a dearth of Acclimation studies investigating metabolic flexibility among lower-latitude birds. We used short-term thermal Acclimation experiments to investigate phenotypic flexibility in basal metabolic rate (BMR), thermoneutral evaporative water loss (EWL) and summit metabolism (Msum) in three populations of white-browed sparrow-weavers (Plocepasser mahali) along a climatic and aridity gradient. We allocated individuals to one of three Taccl treatments (5 °C, 20 °C and 35 °C; n=11 per population per Taccl) for 28 days, and measured post-Acclimation BMR, EWL and Msum using flow-through respirometry. Our data reveal the expected pattern of lower BMR and EWL (∼ 12 % and 25 % lower respectively) in birds at Taccl=35 °C compared to cooler Taccl treatments, as observed in previous Acclimation studies on subtropical birds. We found no variation in the reaction norms of BMR and EWL among populations in response to Acclimation, suggesting previously documented differences in seasonal BMR acclimatization are the result of phenotypic flexibility. In contrast to higher-latitude species, Msum did not significantly vary in response to thermal Acclimation. These findings support the idea that factors other than enhancing cold tolerance may be driving patterns of metabolic variation in subtropical birds.

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  • phenotypic flexibility in the basal metabolic rate of laughing doves responses to short term thermal Acclimation
    The Journal of Experimental Biology, 2007
    Co-Authors: Andrew E Mckechnie, Kinesh Chetty, Barry G Lovegrove

    Abstract:

    SUMMARY Many birds exhibit considerable phenotypic flexibility in maintenance
    energy requirements, and up- or downregulate basal metabolic rate (BMR) over
    time scales of days to weeks during thermal Acclimation. However, the extent
    to which individual birds can reverse the direction of BMR adjustments over
    short time scales remains unknown. In this study, we examined metabolic
    responses to short-term thermal Acclimation in laughing doves Streptopelia
    senegalensis . In 30 wild-caught doves (mean body mass=92.6 g) divided
    into three experimental groups of 10 birds each, initial BMR averaged
    0.760±0.036 W. Thereafter, each group was acclimated to one of three
    Acclimation air temperatures ( T acc =10, 22 or 35°C) for
    21 days, during which time the doves were housed in individual cages.
    Following the first Acclimation period (Acclimation I), BMR (W) was
    significantly lower and was negatively and linearly related to
    T acc [BMR=0.714-0.005 T acc ].
    Acclimation I BMR varied from 0.546±0.039 W in doves acclimated to
    T acc =35°C to 0.665±0.058 W at
    T acc =10°C. A second Acclimation period of a further 21
    days (Acclimation II) revealed that the direction of BMR adjustments could be
    reversed within individuals, with Acclimation II BMR again negatively and
    linearly related to T acc . The slope of the relationship
    between BMR and T acc following Acclimation II was not
    significantly different to that following Acclimation I. BMR exhibited
    consistent inter-individual variation, with a low but significant
    repeatability of 0.113. The within-individual BMR variation of up to 26% that
    we observed in laughing doves reveals that BMR is a highly flexible trait in
    this species, and reiterates the need to take phenotypic plasticity into
    account in comparative analyses of avian energetic parameters.

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Dirk K Hincha – One of the best experts on this subject based on the ideXlab platform.

  • natural variation in freezing tolerance and cold Acclimation response in arabidopsis thaliana and related species
    Advances in Experimental Medicine and Biology, 2018
    Co-Authors: Ellen Zuther, Joachim Kopka, Alexander Erban, Dirk K Hincha

    Abstract:

    During low-temperature exposure, temperate plant species increase their freezing tolerance in a process termed cold Acclimation. The molecular mechanisms involved in cold Acclimation have been mostly investigated in Arabidopsis thaliana. In addition, other Brassicaceae species related to A. thaliana have been employed in recent years to study plant stress responses on a phylogenetically broader basis and in some cases with extremophile species with a much higher stress tolerance. In this paper, we briefly summarize cold Acclimation responses in A. thaliana and current knowledge about cold Acclimation in A. thaliana relatives with special emphasis on Eutrema salsugineum and two closely related Thellungiella species. We then present a transcriptomic and metabolomic analysis of cold Acclimation in five A. thaliana and two E. salsugineum accessions that differ widely in their freezing tolerance. Differences in the cold responses of the two species are discussed.

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  • Global changes in gene expression, assayed by microarray hybridization and quantitative RT-PCR, during Acclimation of three Arabidopsis thaliana accessions to sub-zero temperatures after cold Acclimation
    Plant Molecular Biology, 2015
    Co-Authors: Mai Q. Le, Majken Pagter, Dirk K Hincha

    Abstract:

    During cold Acclimation plants increase in freezing tolerance in response to low non-freezing temperatures. This is accompanied by many physiological, biochemical and molecular changes that have been extensively investigated. In addition, plants of many species, including Arabidopsis thaliana , become more freezing tolerant during exposure to mild, non-damaging sub-zero temperatures after cold Acclimation. There is hardly any information available about the molecular basis of this adaptation. Here, we have used microarrays and a qRT-PCR primer platform covering 1,880 genes encoding transcription factors (TFs) to monitor changes in gene expression in the Arabidopsi s accessions Columbia-0, Rschew and Tenela during the first 3 days of sub-zero Acclimation at −3 °C. The results indicate that gene expression during sub-zero Acclimation follows a tighly controlled time-course. Especially AP2/EREBP and WRKY TFs may be important regulators of sub-zero Acclimation, although the CBF signal transduction pathway seems to be less important during sub-zero than during cold Acclimation. Globally, we estimate that approximately 5 % of all Arabidopsis genes are regulated during sub-zero Acclimation. Particularly photosynthesis-related genes are down-regulated and genes belonging to the functional classes of cell wall biosynthesis, hormone metabolism and RNA regulation of transcription are up-regulated. Collectively, these data provide the first global analysis of gene expression during sub-zero Acclimation and allow the identification of candidate genes for forward and reverse genetic studies into the molecular mechanisms of sub-zero Acclimation.

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  • Natural genetic variation in Acclimation capacity at sub-zero temperatures after cold Acclimation at 4 degrees C in different Arabidopsis thaliana accessions.
    Cryobiology, 2008
    Co-Authors: Wolfgang R. Engelsberger, Dirk K Hincha

    Abstract:

    Abstract Freezing tolerance is an important factor in the geographical distribution of plants and strongly influences crop yield. Many plants increase their freezing tolerance during exposure to low, nonfreezing temperatures (cold Acclimation) and Acclimation may continue at mild freezing temperatures in a process termed sub-zero Acclimation. There is considerable natural variation in the cold Acclimation capacity of Arabidopsis that has been used to study the molecular basis of this trait, but much less is known about the molecular basis of sub-zero Acclimation. Freezing tolerance of detached leaves from the accessions C24, Columbia-0, Rschew, and Tenela was investigated using an electrolyte leakage assay. Sub-zero Acclimation could be achieved by shifting plants from 4 °C to −3 °C, or by using detached leaves, either in the presence or absence of ice nucleation. The magnitude of the increase in freezing tolerance depended on both temperature and duration of sub-zero Acclimation and while Columbia-0 showed no significant increase in freezing tolerance, the other three accessions increased their freezing tolerance significantly. The levels of several sugars that have been shown to be induced during cold Acclimation at nonfreezing temperatures were not strongly changed during sub-zero Acclimation and there was no correlation between the increases in freezing tolerance and sugar levels in the different accessions. Expression of the three cold induced CBF transcription factor genes and five of their representative target COR genes was moderately increased during sub-zero Acclimation, but again there was no correlation to changes in freezing tolerance, indicating that the genetic and molecular basis of sub-zero Acclimation is most likely different from that of cold Acclimation at above freezing temperatures. Further studies will be needed to reveal novel signal transduction pathways and protective mechanisms important in sub-zero Acclimation.

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