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Record Details

Record 5 of 290
Cardiovascular responses of snakes to hypergravity
Author and Affiliation:
Lillywhite, H. B.(University of Florida, Department of Zoology, Gainesville 32611-8525, United States)
Ballard, R. E.
Hargens, A. R.
Rosenberg, H. I.
Abstract: Snakes have provided useful vertebrate models for understanding circulatory adaptation to gravity, attributable to their elongate body shape and evolutionary diversificaton in terms of ecology and behavior. Recently we have studied cardiovascular responses of snakes to hypergravic acceleration forces produced acutely in the head-to-tail direction (+Gz) on a short-arm centrifuge. Snakes were held in a nearly straight position within a horizontal plastic tube and subjected to a linear force gradient during acceleration. Carotid blood flow provided an integrated measure of cardiovascular performance. Thus, cardiovascular tolerance of snakes to stepwise increments of Gz was measured as the caudal Gz force at which carotid blood flow ceased. Tolerance to increasing Gz varies according to adaptive evolutionary history inferred from the ecology and behavior of species. With respect to data for six species we investigated, multiple regression analysis demonstrates that Gz tolerance correlates with gravitational habitat, independently of body length. Relative to aquatic and non-climbing species, carotid blood flow is better maintained in arboreal or scansorial species, which tolerate hypergravic forces of +2 to +3.5 Gz. Additionally, semi-arboreal rat snakes (Elaphe obsoleta) exhibit plasticity of responses to long-term, intermittent +1.5 Gz stress. Compared to non-acclimated controls, acclimated snakes show greater increases of heart rate during head-up tilt or acceleration, greater sensitivity of arterial pressure to circulating catecholamines, higher blood levels of prostaglandin ratios favorable to maintenance of arterial blood pressure, and medial hypertrophy in major arteries and veins. As in other vertebrates, Gz tolerance of snakes is enhanced by acclimation, high arterial pressure, comparatively large blood volume, and body movements. Vascular studies of snakes suggest the importance to acclimation of local responses involving vascular tissue, in addition to centrally mediated responses to fluid shifts.
Publication Date: Jun 01, 1997
Document ID:
20040089485
(Acquired Sep 07, 2004)
Subject Category: LIFE SCIENCES (GENERAL)
Document Type: Journal Article
Publication Information: Gravitational and space biology bulletin : publication of the American Society for Gravitational and Space Biology (ISSN 1089-988X); Volume 10; 2; 145-52
Publisher Information: United States
Contract/Grant/Task Num: IBN91-05247; HL 24640
Description: In English
Distribution Limits: Unclassified; Publicly available; Unlimited
Rights: Copyright
NASA Terms: ADAPTATION; CARDIOVASCULAR SYSTEM; HEART FUNCTION; HEMODYNAMICS; HIGH GRAVITY ENVIRONMENTS; PHYSIOLOGICAL RESPONSES; POSTURE; SNAKES; BEHAVIOR; CENTRIFUGING; PHYSIOLOGY; PROSTAGLANDINS
Other Descriptors: ADAPTATION, PHYSIOLOGICAL; HEMODYNAMIC PROCESSES/PHYSIOLOGY; HYPERGRAVITY/ADVERSE EFFECTS; POSTURE/PHYSIOLOGY; SNAKES/PHYSIOLOGY; ANIMALS; BEHAVIOR, ANIMAL; CARDIOVASCULAR PHYSIOLOGY; CENTRIFUGATION/ADVERSE EFFECTS; COMPARATIVE STUDY; PHYSIOLOGY, COMPARATIVE; PROSTAGLANDINS/METABOLISM; SUPPORT, NON-U.S. GOV'T; SUPPORT, U.S. GOV'T, NON-P.H.S; SUPPORT, U.S. GOV'T, P.H.S; REVIEW; REVIEW, TUTORIAL; NASA CENTER ARC; NASA DISCIPLINE CARDIOPULMONARY
Availability Source: Other Sources
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