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Development of the respiratory response to hypoxia in the isolated brainstem of the bullfrog Rana catesbeiana
Results indicate that pre-metamorphic tadpoles are capable of maintaining respiratory activity for 3 h or more during severe hypoxia and rely to a great extent upon anaerobic metabolism to maintain respiratory motor output.
Regulation of the respiratory central pattern generator by chloride-dependent inhibition during development in the bullfrog (Rana catesbeiana).
- L. Broch, R. Morales, A. V. Sandoval, M. Hedrick
- Biology, MedicineThe Journal of experimental biology
- 15 April 2002
It is hypothesized that maturation of the bullfrog respiratory CPG reflects developmental changes in glycinergic and/or GABAergic synaptic inhibitory mechanisms and that lung ventilation in the tadpole brainstem may be driven by a pacemaker-like mechanism since Cl(-)-free aCSF failed to abolish lung ventilation.
Temperature and pH/CO2 modulate respiratory activity in the isolated brainstem of the bullfrog (Rana catesbeiana)
Control and interaction of the cardiovascular and respiratory systems in anuran amphibians.
THE EFFECTS OF ALTERED AQUATIC AND AERIAL RESPIRATORY GAS CONCENTRATIONS ON AIR-BREATHING PATTERNS IN A PRIMITIVE FISH (AMIA CALVA)
Results indicate that Amia calva respond to changes in intravascular PO2; however, externally facing chemoreceptors that stimulate air-breathing in aquatic hypoxia cannot be discounted.
Blood viscosity and optimal hematocrit in a deep-diving mammal, the northern elephant seal (Mirounga angustirostris)
While the increased hematocrit of elephant seal blood reflects increased oxygen storage capacity, blood oxygen transport may actually be reduced by the effects of increased blood viscosity on blood flow.
A meta-analysis of in vivo vertebrate cardiac performance: implications for cardiovascular support in the evolution of endothermy
This analysis indicates that the greatly increased heart rate and cardiac stroke work leading to increased blood flow rate and blood pressure was necessary to support the metabolic requirements of endothermy.
Time domains of the hypoxic ventilatory response in ectothermic vertebrates
- C. Porteus, M. Hedrick, J. Hicks, Tobias Wang, W. Milsom
- BiologyJournal of Comparative Physiology B
- 11 February 2011
In amphibians and reptiles with incompletely divided hearts the magnitude of the ventilatory response will be modulated by hypoxia-induced changes in intra-cardiac shunting that also improve the match between O2 supply and demand, and these too change in a time-dependent fashion.
Development of respiratory rhythm generation in ectothermic vertebrates
- M. Hedrick
- Biology, Environmental ScienceRespiratory Physiology & Neurobiology
- 15 November 2005
Net cardiac shunts in anuran amphibians: physiology or physics?
The analysis indicates that the net cardiac shunt in the cane toad is predicted primarily by the physical, rather than physiological, characteristics of the parallel pulmonary and systemic vascular circuits.