Jessica U. Meir and Paul J. Ponganis

Made up of four heme groups (oxygen binding)

Reversibly binds O2 with a cooperative binding behavior.

Low partial pressure of oxygen (PO2) = Low binding affinity of oxygen

As PO2 increases, so does the affinity of oxygen

P50 = 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 O2

◦ Biochemical and molecular adaptations A shift in the O2- hemoglobin (Hb) dissociation?

O2-Hb dissociation curve of whole blood of emperor penguins have yet to be defined.

Generally, Hb of birds has a lower O2 affinity than that of mammals◦ May reflect a shift toward favoring O2 unloading at

the tissues

P50

•Avian respiratory system is inherently more efficient at oxygen consumption (Powell et al., 2000)

•P50 of most birds are much higher than those of mammals (Lutz, 1980)

Mammals

Birds

Certain penguins and the bar-headed goose have P50 values in the mammalian range.◦ Favoring O2 uptake from the lungs when PO2 is

low. ◦ Determination of the P50 and dissociation curve in

whole blood still remains necessary

www.tropicalbirding.com/tripReports/TR_NorthI

The researchers characterized the O2-Hb dissociation curves of the emperor penguin in whole blood◦ Investigate the adaptation of Hb in this species◦ Address blood O2 depletion during diving, by

applying the dissociation curves to previously collected PO2 profiles to estimate in vivo Hb saturation.

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Non-breeding emperor penguins were captured near the McMurdo sound ice edge or at Terra Nova Bay

Maintained at an isolated dive hole

www.phys.unsw.edu.au/nature/antarctica_map2.gif

upload.wikimedia.org/wikipedia/commons/d/d8/D

PO2 electrodes and thermistors inserted percutaneously into the aorta or vena cava connected to a PO2 / temperature recorder

Mk9 time-depth recorder (TDR) Penguins allowed to dive 1-2 day before

removal of equipment

Wikipedia.orgwarneronline.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 PO2

◦ i-STAT analyzer – pH and PCO2

◦ Tucker chamber analyses – O2 content

CO2 Bohr effect – changing CO2

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, S02 was

determined for chicken and pinniped species with previously published data Tonometer

Values obtained by applying PO2 profiles to a linear regression equation and solving for SO2

Cyanomethemoglobin technique Hb concentration – oxygen content for initial

and final dive time points calculated from the corresponding SO2 ◦ Hb concentration of 18.3g dl-1 ◦ Initial SO2 was estimated at 7.5 and the final SO2 at

7.4◦ % O2 content depletion = (initial O2 content-final

O2 content)/initial O2 content x 100

◦ Rate of O2 content depletion = (initial O2 content – final O2 content)/dive duration

ANOVA – differences between arterial and venous results

Spearman rank order correlation tests – correlation between dive duration and final SO2, pre-dive S02, percentage O2 content depleted and depletion rate

Max SO2, initial SO2, final SO2, Δ SO2 were all significantly different between arterialand venous compartments.

Blood O2 store depletions rates between the two compartments were not significant

P50 = 28±1 mmHg at pH 7.5

Fixed Bohr effect was not significantly Different that of CO2

[Hemoglobin] = 18.3±1.1 gdl-1

Sa,O2 remained near 100% for much of the dive

Sv,O2 quite variable among dives with markedfluctuations, transient increases during the dive,and a large range of final values.

Pre-dive and initial Sv,O2 = higher than emperor penguins at rest

Significant amount of overlap betweenarterial and venous values

With only one exception, Sv,O2

decreased below 20% only in dives thatWere longer than measured ADL

Final Sa,O2 and Sv,O2 demonstrated a strong and significant neg correlation to dive time

% O2 content depleted showed a strongpositive correlation with dive durations

Blood O2 store depletion rate had a significant positiverelationship to dive duration

Because of its potential to contribute to tolerance to low O2 in this species, the O2-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 O2 is available at any

PO2

Prevent such events as shallow water blackouts

◦ Increase O2-Hb affinity allows for more complete depletion of respiratory O2 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 Sv,O2 values reached very low levels in dives that were longer than the ADL◦ Wide range of final Sv,O2, and venous PO2 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 Sa,O2 values remained high◦ Minimize the risk of shallow water blackouts

Because of pulmonary gas exchange with the blood, Sa,O2 remained close to 100% during dive◦ Preserving a high O2 content in the arterial

compartment Brain

Pre-dive and initial Sv,O2values = higher than Pv,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 O2 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 rate2. 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.