Neuroprotecting globins

in the marine mammal brain

Photo credit: democraticunderground.com

What adaptations do they use in order to hold their breath for such a long, long time?

Mammalian breath hold capabilities( in minutes)

Human* 1

Polar bear 1.5

Sea otter 5

Porpoise 15

Seal 15-28

Greenland Whale 60

Sperm whale 90

Bottlenose whale 120

*Crazy Swiss man, Peter Colat, 19 min. 21 s

Photo credit: news.discovery.com

Photo credit: puertogaleradive.com

Basis for this field of research:

Energy we think they gain from one breath

<<Energy we think they spend while submerged

Basis for this field of research:

Energy we think they gain from one breath

<<Energy we think they spend while submerged

If above is true, you would expect:

Evidence heavy reliance onanaerobic metabolism

Photo credit: puertogaleradive.com

Basis for this field of research:

Energy we think they gain from one breath

<<Energy we think they spend while submerged

If above is true, you would expect:

Evidence heavy reliance onanaerobic metabolism

Photo credit: puertogaleradive.com

Basis for this field of research:

Energy we think they gain from one breath

<<Energy we think they spend while submerged

Photo credit: puertogaleradive.com

Then, above statement must not be true…

Basis for this field of research:

Energy we think they gain from one breath

<<Energy we think they spend while submerged

Photo credit: puertogaleradive.com

Then, above statement must not be true…

Now what?

Basis for this field of research:

Energy we think they gain from one breath

<<Energy we think they spend while submerged

Photo credit: puertogaleradive.com

Then, above statement must not be true…

Now what? Look for adaptations!

What researchers found:

1870 Paul Bert - limits blood volume

1930s & 1940s -• Body size• Total blood volume• RBC mass• Hematocrit • Muscle [myoglobin]

Figure credit: Hochachka and Somero 2002

What researchers found:

1870 Paul Bert - limits blood volume

1930s & 1940s -• Body size• Total blood volume• RBC mass• Hematocrit • Muscle [myoglobin]

Photo credit: doc.govt.nz

Dive response concept:

• Apnea• Bradycardia• Peripheral vasoconstriction• Hypometabolism

Helps us understand balance:• Energy in one breath• Energy used in

prolonged dive

Interrelatedness of dive response components:

Apnea Bradycardia

Interrelatedness of dive response components:

Apnea Bradycardia(even in humans)

Interrelatedness of dive response components:

Apnea Bradycardia Drop in cardiac output

(CO = stroke volume x heart rate (vol/min))

Drop in arterial BP

Interrelatedness of dive response components:

Apnea Bradycardia Drop in cardiac output

Drop in arterial BP

Interrelatedness of dive response components:

Apnea Bradycardia Drop in cardiac output

X

BP remains stable

Interrelatedness of dive response components:

Apnea Bradycardia Drop in cardiac outputwhile

Vasoconstriction

Figure credit: Hochachka and Somero 2002

BP remains stable

Interrelatedness of dive response components:

Apnea Bradycardia Drop in cardiac outputwhile

Vasoconstriction

Hypometabolism

BP remains stable

Interrelatedness of dive response components:

Apnea Bradycardia Drop in cardiac outputwhile

Vasoconstriction

Hypometabolism

(energy saved in bypassing non-vital organs 2-3ºC drop in body temperature)

How would you monitor these responses?

How would you monitor these responses?

• Heart monitors• Backpack cameras• Lactate dehydrogenase levels

Figure credit: Davis et al. 1999

Figure credit: Kooyman et al. 1981

Figure credit: Kooyman et al. 1981

Figure credit: Kooyman et al. 1981

Figure credit: Kooyman et al. 1981

Figure credit: Hochachka and Somero 2002

Photo credit: ctap4.org

Dive response concept:

• Apnea• Bradycardia• Peripheral vasoconstriction• Hypometabolism

How do these relate to:

• Body size• Total blood volume• RBC mass• Hematocrit • Muscle [myoglobin]

Figure credit: Williams et al. 2000

Behavioral adaptations:

• Dive duration• Gliding• Resting

Proposing a new adaptation for the list…

Photo credit: wikipedia.com

Globins

• Proteins with heme group• Involved in oxygen binding and transfer

• Hemoglobin (Hb)• Myoglobin (Mb)• Cytoglobin (Cb)• Neuroglobin (Nb)

Photo credit: brainviews.com

Cerebral cortex

• Thin sheet of neural tissue• Plays role in:

• Memory• Attention• Perceptual awareness• Thought• Language• Consciousness

Researchers still think blood oxygen levels in diving mammals are too low to sustain activity…

Researchers still think blood oxygen levels in diving mammals are too low to sustain activity…

Williams et al. 2008 Hypothesis:

• Enhanced levels of neuroprotecting globins are an additional adaptation for a diving lifestyle

Williams et al. 2008 Methods:

• Group globins:• Circulating (Hb)• Resident (Cb and Nb)

• Measure in cerebral cortex of 16 species• Running, swimming, diving• Prolonged mortality events• Spectrophotometric determination• mRNA expression

Williams et al. 2008 Results:

• Globin levels correlated with activity group

Figure credit: Williams et al. 2008

Williams et al. 2008 Results:

• Hb and RNGs significantly higher in diving marine mammals compared to terrestrial species

Figure credit: Williams et al. 2008

Williams et al. 2008 Results:

• RNG levels inversely correlated with dive duration

Figure credit: Williams et al. 2008

Williams et al. 2008 Discussion:

• Elevated RNG and Hb levels are adaptations for activity type

• Enhance diving response

• Cope with low oxygen levels during prolonged dives

• Circulating and resident globins provide complementary support

Questions for Discussion

• How do you expect the following to interact with and effect adaptive globin responses?

• Body size• Phylogenetic history• Habitat• Activity level

• What does hypoxia really mean?

• Post mortem sampling concerns…

• Standardize globin concentrations to total blood volume?