31° South: phenotypic flexibility in adaptive thermogenesis among conspecific populations of an arid-endemic bird - from organismal to cellular level

2018 ◽  
Author(s):  
Ângela M. Ribeiro ◽  
Clara Prats ◽  
Nicholas B. Pattinson ◽  
M. Thomas P. Gilbert ◽  
Ben Smit
Keyword(s):  
Aerobic Capacity ◽  
Skeletal Muscles ◽  
Cellular Level ◽  
Arid Zones ◽  
Phenotypic Flexibility ◽  
Metabolic Capacity ◽  
Adaptive Thermogenesis ◽  
Available Energy ◽  
Two Indices ◽  
Small Bird

ABSTRACTIn north-temperate small passerines, overwinter survival is associated with a reversibly increased maximum cold-induced metabolism (Msum). This strategy may incur increased energy consumption. Therefore, species inhabiting ecosystems characterized by cold winters and low productivity (i.e., low available energy) may be precluded from displaying an increase in maximum metabolic rates. To examine whether Msumis a flexible phenotype in such challenging environments, and ultimately uncover its underpinning mechanisms, we studied an arid-endemic small bird (Karoo scrub-robin) whose range spans a primary productivity and minimum temperature gradient. We measured Msum, body condition, mass of thermogenic muscles and two indices of cellular aerobic capacity from populations living in three environmentally different regions. We found that Msumwas seasonally flexible, associated with aerobic capacity of limb muscles, but not increasing with lower temperatures, as predicted. Notwithstanding, the cold limit (temperature at which birds reached their maximum metabolic capacity) decreased in winter. These results indicate that birds from arid-zones may respond to cold conditions by altering thermosensation, rather than spending energy to produce heat in skeletal muscles.

Load-matched acute and chronic exercise induce changes in mitochondrial biogenesis and metabolic markers

2021 ◽  
Author(s):  
Natalia Almeida Rodrigues ◽  
Claudio Alexandre Gobatto ◽  
Lucas Dantas Maia Forte ◽  
Filipe Antônio de Barros Sousa ◽  
Adriana Souza Torsoni ◽  
...  
Keyword(s):  
Aerobic Capacity ◽  
Skeletal Muscles ◽  
Acute Exercise ◽  
Citrate Synthase ◽  
Liver Glycogen ◽  
Chronic Exercise ◽  
Total Load ◽  
Metabolic Markers ◽  
Target Proteins ◽  
Glycogen Stores

We investigated the effects of the acute and chronic exercise, prescribed in different intensity zones, but with total load-matched on mitochondrial markers (COX-IV, Tfam, and citrate synthase (CS) activity in skeletal muscles, heart, and liver), glycogen stores, aerobic capacity and anaerobic index in swimming rats. For this, two experimental designs were performed (acute and chronic efforts). Load-matched exercises were prescribed below and above and on the anaerobic threshold (AnT), determined by the Lactate Minimum test. In chronic programs, two training prescription strategies were assessed (monotonous and linear periodized model). Results show changes in glycogen stores but no modification in the COX-IV and Tfam contents after acute exercises. In the chronic protocols, COX-IV and Tfam proteins and CS adaptations were intensity and tissue dependents. Monotonous training promoted better adaptations than the periodized model. Training at 80% of the AnT improved both performance variables, emphasizing the anaerobic index, concomitant to CS and COX-IV improvement (soleus muscle). The aerobic capacity and CS activity (gastrocnemius) were increased after 120% AnT training. In conclusion, acute exercise protocol did not promote responses in mitochondrial target proteins. An intensity and tissue dependence are reported in the chronic protocols, highlighting training at 80 and 120% of the AnT. Novelty: • Load-matched acute exercise did not enhance COX-IV and Tfam contents in skeletal muscles, heart, and liver. • In chronic exercise, COX-IV, Tfam, and citrate synthase activity adaptations were intensity and tissue dependents. •Monotonous training was more efficient than the periodized linear model in adaptations of target proteins and enzymatic activity.

scholarly journals Aerobic capacities in the skeletal muscles of Weddell seals: key to longer dive durations?

2002 ◽  
Vol 205 (23) ◽  
pp. 3601-3608 ◽  
Author(s):  
S. B. Kanatous ◽  
R. W. Davis ◽  
R. Watson ◽  
L. Polasek ◽  
T. M. Williams ◽  
...  
Keyword(s):  
Aerobic Capacity ◽  
Skeletal Muscles ◽  
Marine Mammals ◽  
Fiber Type ◽  
Weddell Seal ◽  
Weddell Seals ◽  
Terrestrial Mammals ◽  
Hypoxic Conditions ◽  
Long Duration ◽  
Energy Conserving

SUMMARYIn contrast to terrestrial animals that function under hypoxic conditions but display the typical exercise response of increasing ventilation and cardiac output, marine mammals exercise under a different form of hypoxic stress. They function for the duration of a dive under progressive asphyxia,which is the combination of increasing hypoxia, hypercapnia and acidosis. Our previous studies on short-duration, shallow divers found marked adaptations in their skeletal muscles, which culminated in enhanced aerobic capacities that are similar to those of atheltic terrestrial mammals. The purpose of the present study was to assess the aerobic capacity of skeletal muscles from long-duration divers. Swimming and non-swimming muscles were collected from adult Weddell seals, Leptonychotes weddelli, and processed for morphometric analysis, enzymology, myoglobin concentrations and fiber-type distribution. The results showed that the skeletal muscles of Weddell seals do not have enhanced aerobic capacities compared with those of terrestrial mammals but are adapted to maintain low levels of an aerobic lipid-based metabolism, especially under the hypoxic conditions associated with diving. The lower aerobic capacity of Weddell seal muscle as compared with that of shorter-duration divers appears to reflect their energy-conserving modes of locomotion, which enable longer and deeper dives.

scholarly journals Breathing while altricial: the ontogeny of ventilatory chemosensitivity in red-winged blackbird (Agelaius phoeniceus) nestlings

2016 ◽  
Vol 311 (6) ◽  
pp. R1105-R1112 ◽  
Author(s):  
Edward M. Dzialowski ◽  
Tushar S. Sirsat ◽  
Sarah K. G. Sirsat ◽  
Edwin R. Price
Keyword(s):  
Oxygen Consumption ◽  
Tidal Volume ◽  
Aerobic Capacity ◽  
Minute Ventilation ◽  
Bird Species ◽  
Developmental Changes ◽  
Agelaius Phoeniceus ◽  
Breathing Frequency ◽  
Metabolic Capacity ◽  
Precocial Birds

Altricial bird species, like red-winged blackbirds, hatch at an immature state of functional maturity with limited aerobic capacity and no endothermic capacity. Over the next 10–12 days in the nest, red-winged blackbirds develop increased metabolic capacity before fledging. Although ontogeny of respiration has been described in precocial birds, ontogeny of ventilatory chemosensitivity is unknown in altricial species. Here we examined developmental changes in chemosensitivity of tidal volume (Vt), breathing frequency (ƒ), minute ventilation (V̇e), and whole animal oxygen consumption (V̇o2) from hatching to just before fledging in red-winged blackbirds on days 1, 3, 5, 7, and 9 posthatching (dph) in response to hypercapnia (2 and 4% CO2) and hypoxia (15 and 10% O2). Under control conditions, there was a developmental increase in V̇e with age due to increased Vt. Hypercapnic and hypoxic chemosensitivities were present as early as 1 dph. In response to hypoxia, 1, 3, and 9 dph nestlings increased V̇e at 10% O2, by increasing ƒ with some change in Vt in younger animals. In contrast to early neonatal altricial mammals, the hypoxic response of nestling red-winged blackbirds was not biphasic. In response to hypercapnia, 3 dph nestlings increased V̇e by increasing both ƒ and Vt. From 5 dph on, the hypercapnic increase in V̇e was accounted for by increased Vt and not ƒ. Chemosensitivity to O2 and CO2 matures early in nestling red-winged blackbirds, well before the ability to increase V̇o2 in response to cooling, and thus does not represent a limitation to the development of endothermy.

scholarly journals A Physiology-Guided Classification of Active-Stress and Active-Strain Approaches for Continuum-Mechanical Modeling of Skeletal Muscle Tissue

2021 ◽  
Vol 12 ◽  
Author(s):  
Thomas Klotz ◽  
Christian Bleiler ◽  
Oliver Röhrle
Keyword(s):  
Skeletal Muscle ◽  
Skeletal Muscles ◽  
Cellular Level ◽  
Muscle Physiology ◽  
Extensive Discussion ◽  
Active Stress ◽  
Active Strain ◽  
Biomechanical Behavior ◽  
Biophysical Mechanism ◽  
Stress Transmission

The well-established sliding filament and cross-bridge theory explain the major biophysical mechanism responsible for a skeletal muscle's active behavior on a cellular level. However, the biomechanical function of skeletal muscles on the tissue scale, which is caused by the complex interplay of muscle fibers and extracellular connective tissue, is much less understood. Mathematical models provide one possibility to investigate physiological hypotheses. Continuum-mechanical models have hereby proven themselves to be very suitable to study the biomechanical behavior of whole muscles or entire limbs. Existing continuum-mechanical skeletal muscle models use either an active-stress or an active-strain approach to phenomenologically describe the mechanical behavior of active contractions. While any macroscopic constitutive model can be judged by it's ability to accurately replicate experimental data, the evaluation of muscle-specific material descriptions is difficult as suitable data is, unfortunately, currently not available. Thus, the discussions become more philosophical rather than following rigid methodological criteria. Within this work, we provide a extensive discussion on the underlying modeling assumptions of both the active-stress and the active-strain approach in the context of existing hypotheses of skeletal muscle physiology. We conclude that the active-stress approach resolves an idealized tissue transmitting active stresses through an independent pathway. In contrast, the active-strain approach reflects an idealized tissue employing an indirect, coupled pathway for active stress transmission. Finally the physiological hypothesis that skeletal muscles exhibit redundant pathways of intramuscular stress transmission represents the basis for considering a mixed-active-stress-active-strain constitutive framework.

scholarly journals Transition from ectothermy to endothermy: the development of metabolic capacity in a bird ( Gallus gallus )

2005 ◽  
Vol 273 (1586) ◽  
pp. 565-570 ◽  
Author(s):  
Frank Seebacher ◽  
Tonia S Schwartz ◽  
Michael B Thompson
Keyword(s):  
Gene Expression ◽  
Lactate Dehydrogenase ◽  
Dehydrogenase Activity ◽  
Aerobic Capacity ◽  
Anaerobic Capacity ◽  
Internal Heat ◽  
Gallus Gallus ◽  
Metabolic Capacity ◽  
Lactate Dehydrogenase Activity ◽  
Evolutionary Innovation

The evolution of endothermy is one of the most significant events in vertebrate evolution. Adult mammals and birds are delineated from their early ontogenetic stages, as well as from other vertebrates, by high resting metabolic rates and consequent internal heat production. We used the embryonic development of a bird ( Gallus gallus ) as a model to investigate the metabolic transition between ectothermy and endothermy. Increases in aerobic capacity occur at two functional levels that are regulated independently from each other: (i) upregulation of gene expression; and (ii) significant increases in the catalytic activity of the main oxidative control enzymes. Anaerobic capacity, measured as lactate dehydrogenase activity, is extremely high during early development, but diminishes at the same time as aerobic capacity increases. Changes in lactate dehydrogenase activity are independent from its gene expression. The regulatory mechanisms that lead to endothermic metabolic capacity are similar to those of ectotherms in their response to environmental change. We suggest that the phylogenetic occurrence of endothermy is restricted by its limited selective advantages rather than by evolutionary innovation.

scholarly journals Aerobic capacity modulates adaptive thermogenesis: Contribution of non-resting energy expenditure

2020 ◽  
Vol 225 ◽  
pp. 113048
Author(s):  
Sromona Dudiki Mukherjee ◽  
Lauren G. Koch ◽  
Steven L. Britton ◽  
Colleen M. Novak
Keyword(s):  
Energy Expenditure ◽  
Aerobic Capacity ◽  
Resting Energy Expenditure ◽  
Adaptive Thermogenesis ◽  
Resting Energy

Phenotypic flexibility of glucocorticoid signaling in skeletal muscles of a songbird preparing to migrate

2019 ◽  
Vol 116 ◽  
pp. 104586 ◽  
Author(s):  
Devaleena S. Pradhan ◽  
Raymond Van Ness ◽  
Cecilia Jalabert ◽  
Jordan E. Hamden ◽  
Suzanne H. Austin ◽  
...  
Keyword(s):  
Skeletal Muscles ◽  
Phenotypic Flexibility ◽  
Glucocorticoid Signaling
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