@entity26 -limited thermal tolerance in Antarctic fish investigated by MRI and XXXX -MRS.

@entity871 @entity26 @entity9715 @entity14243
The hypothesis of an @entity26 -limited thermal tolerance was tested in the Antarctic teleost Pachycara brachycephalum. With the use of flow-through respirometry, in vivo @entity9715 -NMR spectroscopy, and MRI, we studied energy metabolism, intracellular pH ( @entity14243 ), blood flow, and oxygenation between 0 and 13 degrees C under normoxia (PO(2): 20.3 to 21.3 kPa) and @entity871 (PO(2): 45 kPa). @entity871 reduced the metabolic increment and the rise in arterial blood flow observed under normoxia. The normoxic increase of blood flow leveled off beyond 7 degrees C, indicating a cardiovascular capacity limitation. Ventilatory effort displayed an exponential rise in both groups. In the liver, blood oxygenation increased, whereas in white muscle it remained unaltered (normoxia) or declined ( @entity871 ). In both groups, the slope of @entity14243 changes followed the alpha-stat pattern below 6 degrees C, whereas it decreased above. In conclusion, aerobic scope declines around 6 degrees C under normoxia, marking the pejus temperature. By reducing circulatory costs, @entity871 improves aerobic scope but is unable to shift the breakpoint in pH regulation or lethal limits. @entity871 appears beneficial at sublethal temperatures, but no longer beyond when cellular or molecular functions become disturbed.
