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Cardiovascular responses of snakes to hypergravitySnakes 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.
Document ID
20040089485
Document Type
Reprint (Version printed in journal)
Authors
Lillywhite, H. B. (University of Florida Gainesville 32611-8525, United States)
Ballard, R. E.
Hargens, A. R.
Rosenberg, H. I.
Date Acquired
August 21, 2013
Publication Date
June 1, 1997
Publication Information
Publication: Gravitational and space biology bulletin : publication of the American Society for Gravitational and Space Biology
Volume: 10
Issue: 2
ISSN: 1089-988X
Subject Category
Life Sciences (General)
Funding Number(s)
CONTRACT_GRANT: IBN91-05247
CONTRACT_GRANT: HL 24640
Distribution Limits
Public
Copyright
Other
Keywords
Review, Tutorial
NASA Discipline Cardiopulmonary
NASA Center ARC
Review