[MARMAM] new publications

Marina Piscitelli piscitellim at gmail.com
Thu Sep 12 12:43:21 PDT 2013


Dear MARMAM subscribers,

 We are happy to share two new publications listed below:

 (1)  Lillie MA, Piscitelli MA, Vogl AW, Gosline JM, and Shadwick RE. 2013.
Cardiovascular design in fin whales: high-stiffness arteries protect
against adverse pressure gradients at depth. J Exp Biol 216 : 2548-2563.

Abstract

Fin whales have an incompliant aorta, which, we hypothesize, represents an
adaptation to large, depth-induced variations in arterial transmural
pressures. We hypothesize these variations arise from a limited ability of
tissues to respond to rapid changes in ambient ocean pressures during a
dive. We tested this hypothesis by measuring arterial mechanics
experimentally and modeling arterial transmural pressures mathematically.
The mechanical properties of mammalian arteries reflect the physiological
loads they experience, so we examined a wide range of fin whale arteries.
All arteries had abundant adventitial collagen that was usually recruited
at very low stretches and inflation pressures (2-3kPa), making arterial
diameter largely independent of transmural pressure. Arteries withstood
significant negative transmural pressures (-7 to -50kPa) before collapsing.
Collapse was resisted by recruitment of adventitial collagen at very low
stretches. These findings are compatible with the hypothesis of
depth-induced variation of arterial transmural pressure. Because transmural
pressures depend on thoracic pressures, we modeled the thorax of a diving
fin whale to assess the likelihood of significant variation in transmural
pressures. The model predicted that deformation of the thorax body wall and
diaphragm could not always equalize thoracic and ambient pressures because
of asymmetrical conditions on dive descent and ascent. Redistribution of
blood could partially compensate for asymmetrical conditions, but inertial
and viscoelastic lag necessarily limits tissue response rates. Without
pressure equilibrium, particularly when ambient pressures change rapidly,
internal pressure gradients will develop and expose arteries to transient
pressure fluctuations, but with minimal hemodynamic consequence due to
their low compliance.

Article is available online at the Journal of Experimental Biology website
or by email from Margo Lillie at lillie at zoology.ubc.ca



(2) Piscitelli MA, Raverty SA, Lillie MA, and Shadwick RE. 2013. A review
of cetacean lung morphology and mechanics. J Morph *Early View online. *(DOI:
10.1002/jmor.20192)

Abstract

Cetaceans possess diverse adaptations in respiratory structure and
mechanics that are highly specialized for an array of surfacing and diving
behaviors. Some of these adaptations and air management strategies are
still not completely understood despite over a century of study. We have
compiled the historical and contemporary knowledge of cetacean lung anatomy
and mechanics in regards to normal lung function during ventilation and air
management while diving. New techniques are emerging utilizing pulmonary
mechanics to measure lung function in live cetaceans. Given the diversity
of respiratory adaptations in cetaceans, interpretations of these results
should consider species-specific anatomy, mechanics, and behavior.

Article is available online at the Journal of Morphology early view or by
email from Marina Piscitelli at piscitellim at gmail.com. Please note there is
substantial online supplemental material (appendices) online as well.

Best Wishes,

Marina
______________________________
Marina A. Piscitelli, Ph.D. Candidate
Department of Zoology
The University of British Columbia
6270 University Blvd.
Vancouver, BC CANADA V6T 1Z4
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