- Library Home /
- Search Collections /
- Open Collections /
- Browse Collections /
- UBC Theses and Dissertations /
- Investigations into the diving response of northern...
Open Collections
UBC Theses and Dissertations
UBC Theses and Dissertations
Investigations into the diving response of northern elephant seals (Mirounga angustirostris) using magnetic resonance imaging and spectroscopy Thornton, Sheila J.
Abstract
To examine the physiological and biochemical changes that occur during diving, northern elephant seal pups were subjected to forced dive protocols while undergoing Magnetic Resonance Imaging and Spectroscopic analysis. Splenic volume measurements were obtained in the predive, dive and postdive state. Splenic contraction was initiated immediately upon facial immersion, reducing to 14.0 - 17.8% of its predive volume by minute 3 of the dive. A corresponding increase in hepatic sinus volume occurred, suggesting a direct shift of blood from the spleen to the sinus. In the postdive period, the spleen gradually dilated, achieving its maximum volume at 18-22 minutes after the dive (3.35% of body mass; n = 5). Stroke volume (SV) measurements were obtained during diving using phase contrast MR imaging. Mean resting SV was 104.94 mis ± 4.12 SEM, while SV during the dive increased significantly to a mean value of 126.12 ± 3.93 SEM. These data are in contrast to the findings of previous studies on pinnipeds, which indicate either the maintenance or decline of stroke volume during the dive. Pre-dive, postdive or diving heart rates did not correlate with mass or with stroke volume during any state. However, diving SV correlated with the ratio of diving HR to predive HR (P = 0.01, R = 0.99). These findings indicate that the effect of diving on stroke volume is altered by the degree of bradycardia rather than the absolute HR. MR spectroscopy analysis was used to investigate changes in locomotory muscle phosphocreatine (PCr) levels during diving. End-dive PCr levels ranged from 36.84 - 103.93% of resting (average 80.85% ± 5.89 SEM). Animals who exhibited a significant decrease in PCr during diving showed a correlation between end-dive PCr and intracellular pH values. Plasma lactate levels indicated that all dives were within the aerobic diving limit. This study demonstrates that in northern elephant seals, PCr hydrolysis does occur during aerobic dives, indicating that the depletion of [PCr] is driven by an alteration in muscle [H⁺] rather than by changes in [adenylate]. The decrease in muscle pH is attributed to respiratory acidosis caused by significant CO₂ accumulation during hypoperfusion.
Item Metadata
Title |
Investigations into the diving response of northern elephant seals (Mirounga angustirostris) using magnetic resonance imaging and spectroscopy
|
Creator | |
Publisher |
University of British Columbia
|
Date Issued |
2000
|
Description |
To examine the physiological and biochemical changes that occur during diving, northern
elephant seal pups were subjected to forced dive protocols while undergoing Magnetic
Resonance Imaging and Spectroscopic analysis. Splenic volume measurements were
obtained in the predive, dive and postdive state. Splenic contraction was initiated
immediately upon facial immersion, reducing to 14.0 - 17.8% of its predive volume by
minute 3 of the dive. A corresponding increase in hepatic sinus volume occurred,
suggesting a direct shift of blood from the spleen to the sinus. In the postdive period, the
spleen gradually dilated, achieving its maximum volume at 18-22 minutes after the dive
(3.35% of body mass; n = 5). Stroke volume (SV) measurements were obtained during
diving using phase contrast MR imaging. Mean resting SV was 104.94 mis ± 4.12 SEM,
while SV during the dive increased significantly to a mean value of 126.12 ± 3.93 SEM.
These data are in contrast to the findings of previous studies on pinnipeds, which indicate
either the maintenance or decline of stroke volume during the dive. Pre-dive, postdive or
diving heart rates did not correlate with mass or with stroke volume during any state.
However, diving SV correlated with the ratio of diving HR to predive HR (P = 0.01, R =
0.99). These findings indicate that the effect of diving on stroke volume is altered by the
degree of bradycardia rather than the absolute HR. MR spectroscopy analysis was used to
investigate changes in locomotory muscle phosphocreatine (PCr) levels during diving.
End-dive PCr levels ranged from 36.84 - 103.93% of resting (average 80.85% ± 5.89
SEM). Animals who exhibited a significant decrease in PCr during diving showed a
correlation between end-dive PCr and intracellular pH values. Plasma lactate levels
indicated that all dives were within the aerobic diving limit. This study demonstrates that in
northern elephant seals, PCr hydrolysis does occur during aerobic dives, indicating that the
depletion of [PCr] is driven by an alteration in muscle [H⁺] rather than by changes in
[adenylate]. The decrease in muscle pH is attributed to respiratory acidosis caused by
significant CO₂ accumulation during hypoperfusion.
|
Extent |
14032734 bytes
|
Genre | |
Type | |
File Format |
application/pdf
|
Language |
eng
|
Date Available |
2009-07-23
|
Provider |
Vancouver : University of British Columbia Library
|
Rights |
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
|
DOI |
10.14288/1.0089695
|
URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
|
Graduation Date |
2000-11
|
Campus | |
Scholarly Level |
Graduate
|
Aggregated Source Repository |
DSpace
|
Item Media
Item Citations and Data
Rights
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.