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Jessica U. Meir and Paul J. Ponganis.  Made up of four heme groups (oxygen binding)  Reversibly binds O 2 with a cooperative binding behavior.  Low.

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Presentation on theme: "Jessica U. Meir and Paul J. Ponganis.  Made up of four heme groups (oxygen binding)  Reversibly binds O 2 with a cooperative binding behavior.  Low."— Presentation transcript:

1 Jessica U. Meir and Paul J. Ponganis

2  Made up of four heme groups (oxygen binding)  Reversibly binds O 2 with a cooperative binding behavior.  Low partial pressure of oxygen (P O2 ) = Low binding affinity of oxygen  As P O2 increases, so does the affinity of oxygen  P 50 = concentration of oxygen in which Hb is 50% saturated

3  Vena Cava ◦ Made up of the superior and inferior vena cava ◦ Functions to return the deoxygenated blood from the body back to the heart  Aorta ◦ Largest artery in the body ◦ Distributes oxygenated blood to all parts of the body

4  Tallest and heaviest of all living penguins  Endemic to Antarctica  Flightless ◦ Streamlined body ◦ Wings stiffened and flattened into flippers  Diet consists of fish, crustaceans, and cephalopods  During hunting can dive to depths of 535m and remain submerged for over 23 mins (Wienecke et al,2007).  How are they doing this?

5  Exceptional low tolerance to O 2 ◦ Biochemical and molecular adaptations  A shift in the O 2 - hemoglobin (Hb) dissociation?  O 2 -Hb dissociation curve of whole blood of emperor penguins have yet to be defined.

6  Generally, Hb of birds has a lower O 2 affinity than that of mammals ◦ May reflect a shift toward favoring O 2 unloading at the tissues P 50 Avian respiratory system is inherently more efficient at oxygen consumption (Powell et al., 2000) P 50 of most birds are much higher than those of mammals (Lutz, 1980) Mammals Birds

7  Certain penguins and the bar-headed goose have P 50 values in the mammalian range. ◦ Favoring O 2 uptake from the lungs when P O2 is low. ◦ Determination of the P 50 and dissociation curve in whole blood still remains necessary

8  The researchers characterized the O 2 -Hb dissociation curves of the emperor penguin in whole blood ◦ Investigate the adaptation of Hb in this species ◦ Address blood O 2 depletion during diving, by applying the dissociation curves to previously collected P O2 profiles to estimate in vivo Hb saturation.

9  Non-breeding emperor penguins were captured near the McMurdo sound ice edge or at Terra Nova Bay  Maintained at an isolated dive hole

10  P O2 electrodes and thermistors inserted percutaneously into the aorta or vena cava connected to a P O2 / temperature recorder  Mk9 time-depth recorder (TDR)  Penguins allowed to dive 1-2 day before removal of equipment PO2 electrode Time-depth recorder Thermistor

11  Determined with the mixing technique of tonometered blood ◦ Analysis was completed within 6h of blood collection ◦ Mixed 0% oxygen and 100% oxygen to achieve desired hemoglobin saturation at various points along the curve with subsequent measurements of the P O2 ◦ i-STAT analyzer – pH and P CO2 ◦ Tucker chamber analyses – O 2 content

12  CO 2 Bohr effect – changing CO 2 concentration  Dissociation curves – pH values of 7.5, 7.4, 7.3, and 7.2.  All data from all penguins were combined  Lactic Acid effect- added lactic acid to sample  Validate equipment and methods, S 02 was determined for chicken and pinniped species with previously published data Tonometer

13  Values obtained by applying P O2 profiles to a linear regression equation and solving for S O2

14  Cyanomethemoglobin technique  Hb concentration – oxygen content for initial and final dive time points calculated from the corresponding S O2 ◦ Hb concentration of 18.3g dl -1 ◦ Initial S O2 was estimated at 7.5 and the final S O2 at 7.4 ◦ % O 2 content depletion = (initial O 2 content-final O 2 content)/initial O 2 content x 100 ◦ Rate of O 2 content depletion = (initial O 2 content – final O 2 content)/dive duration

15  ANOVA – differences between arterial and venous results  Spearman rank order correlation tests – correlation between dive duration and final S O2, pre-dive S 02, percentage O 2 content depleted and depletion rate

16 Max SO2, initial SO2, final SO2, Δ SO2 were all significantly different between arterial and venous compartments. Blood O2 store depletions rates between the two compartments were not significant

17 P 50 = 28±1 mmHg at pH 7.5 Fixed Bohr effect was not significantly Different that of CO 2 [Hemoglobin] = 18.3±1.1 gdl -1

18 S a,O2 remained near 100% for much of the dive S v,O2 quite variable among dives with marked fluctuations, transient increases during the dive, and a large range of final values. Pre-dive and initial S v,O2 = higher than emperor penguins at rest

19 Significant amount of overlap between arterial and venous values With only one exception, S v,O2 decreased below 20% only in dives that Were longer than measured ADL

20 Final S a,O2 and S v,O2 demonstrated a strong and significant neg correlation to dive time % O 2 content depleted showed a strong positive correlation with dive durations Blood O 2 store depletion rate had a significant positive relationship to dive duration

21  Because of its potential to contribute to tolerance to low O 2 in this species, the O 2 -Hb dissociation curve of the emperor penguin is left-shifted relative to most birds. ◦ Similar to other penguin species and bar-headed goose. ◦ Left-Shifted curve = more O 2 is available at any P O2  Prevent such events as shallow water blackouts ◦ Increase O 2 -Hb affinity allows for more complete depletion of respiratory O 2 store

22  Biochemical adaptation behind left-shifted O2-Hb dissociation curves = specific amino acids substitutions. ◦ Specific substitutions not altered in emperor penguins  Does show differences from human Hb  Might be other structural features

23  Final S v,O2 values reached very low levels in dives that were longer than the ADL ◦ Wide range of final S v,O2, and venous P O2 for dives of similar durations.  Reflect differences in the peripheral vascular response  Regulation of blood flow to muscle and other organs  Arterio-venous (A-V) shunts  Final S a,O2 values remained high ◦ Minimize the risk of shallow water blackouts

24  Because of pulmonary gas exchange with the blood, S a,O2 remained close to 100% during dive ◦ Preserving a high O 2 content in the arterial compartment  Brain

25  Pre-dive and initial S v,O2 values = higher than P v,O2 values of emperor penguins at rest. ◦ Arterialized venous values imply some degree of a- v shunting (or lack of tissue uptake)  To convert (venous blood) into bright red arterial blood by absorption of oxygen in the lungs. ◦ Lack of lactate build up, muscle temperature profiles, dramatic bradycardia and lack of association between heart rate and stroke frequency also support Shunting

26  Used values to calculate intrapulmonary shunting = 28% at rest ◦ Might be overestimated  Capillary O 2 content  Using pre-dive values, intrapulmonary shunting = 14.3% ◦ Hyperventilation and tachycardia characteristic improves ventilation-perfusion matching prior to the dive

27  Calculation of the blood O2 store to overall metabolic rate was made ◦ Included dives in which SO2 increased during the dive and then exclude them  Respiratory depletion was 2.3 and 5.3 times that in the venous and arterial blood compartments  Simultaneous air sac and blood PO2 data would allow calculation of the net contribution of these O2 store to diving metabolic rate  Not currently feasible ◦ Consistent with 1.A significant contribution from the exceptionally large muscle O2 store to diving metabolic rate 2.The low field metabolic rate and the true bradycardia exhibited by emperor penguins

28  Enhanced O2 affinity of emperor penguin Hb ◦ Similar to the high-altitude geese and other penguins species  SO2 profiles during diving demonstrated ◦ The maintenance of Sa,O2 levels near 100% throughout most of the dive ◦ A wide range of final Sv,O2 values and optimization of the venous blood O2 store resulting from arterialization and near depletion of venous blood O2 during longer dives ◦ Estimated contribution of the blood O2 store to diving metabolic rate was low and highly variable  Influx of O2 from the lungs into the blood during diving and variable rates of tissue O2 uptake

29  Overall = Very well planed experiment ◦ Tedious work & detailed explanations for everything  Surgery ◦ Invasive?  Introduction – more background information on important topics (Shunting etc.)  Use a lot of calculations in the discussion  Second guessing them selves.

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