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:
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 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
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
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?
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.
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
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
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.
Non-breeding emperor penguins were captured near the McMurdo sound ice edge or at Terra Nova Bay Maintained at an isolated dive hole upload.wikimedia.org/wikipedia/commons/d/d8/D
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 Wikipedia.org warneronline.com PO2 electrode Time-depth recorder Thermistor
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
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
Values obtained by applying P O2 profiles to a linear regression equation and solving for S O2
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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.