Mass Transport: Circulatory System with Emphasis on Nonendothermic Species

Mass transport can be generally defined as movement of material matter. The circulatory system then is a biological example given its role in the movement in transporting gases, nutrients, wastes, and chemical signals. Comparative physiology has a long history of providing new insights and advancing our understanding of circulatory mass transport across a wide array of circulatory systems. Here we focus on circulatory function of nonmodel species. Invertebrates possess diverse convection systems; that at the most complex generate pressures and perform at a level comparable to vertebrates. Many invertebrates actively modulate cardiovascular function using neuronal, neurohormonal, and skeletal muscle activity. In vertebrates, our understanding of cardiac morphology, cardiomyocyte function, and contractile protein regulation by Ca2+ highlights a high degree of conservation, but differences between species exist and are coupled to variable environments and body temperatures. Key regulators of vertebrate cardiac function and systemic blood pressure include the autonomic nervous system, hormones, and ventricular filling. Further chemical factors regulating cardiovascular function include adenosine, natriuretic peptides, arginine vasotocin, endothelin 1, bradykinin, histamine, nitric oxide, and hydrogen sulfide, to name but a few. Diverse vascular morphologies and the regulation of blood flow in the coronary and cerebral circulations are also apparent in nonmammalian species. Dynamic adjustments of cardiovascular function are associated with exercise on land, flying at high altitude, prolonged dives by marine mammals, and unique morphology, such as the giraffe. Future studies should address limits of gas exchange and convective transport, the evolution of high arterial pressure across diverse taxa, and the importance of the cardiovascular system adaptations to extreme environments. © 2017 American Physiological Society. Compr Physiol 7:17-66, 2017.

Different Patterns of Vasoactive Intestinal Polypeptide (VIP)-Immunoreactive and Acetylcholinesterase (AChE)-Positive Innervation in the Internal Carotid Artery and Cerebral Arterial Tree of the Quail

The innervation pattern of vasoactive intestinal polypeptide-immunoreactive (VIP-IR) nerves in the quail internal carotid artery (ICA) and cerebral arterial tree was investigated and compared with that of acetylcholinesterase-positive (AChE-P) nerves. The supply of VIP-IR nerves to the two arterial systems was distinctly richer than that of AChE-P nerves. It was focused mainly on the walls from the distal ICA to the caudal half of the anterior ramus (AR) through the cerebral carotid artery (CCA). Indeed, double staining clearly showed that numerous VIP+/AChE-axons were distributed over these arterial regions where VIP+/AChE+ or AChE+/VIP- axons were sporadic or often lacking. The finding that nerve bundles accompanying the ICA within the carotid canal contained abundant VIP+/AChE- nerve cells suggests that cerebrovascular VIP-IR nerves in the quail have their major source at these neurons and enter the cranial cavity through the CCA. Another significant finding was that a small number of nerve cells, which were mostly stained for AChE alone and occasionally for VIP alone or both, occurred in the major arteries located more rostral than the middle AR. Thus, the quail cerebral arterial tree, at least the rostral segment of the anterior circulation, is multiply innervated by these three distinct categories of the extracranial and intracranial VIP-IR and AChE-P neurons.