Transcript Ingestion of Prokaryotes Leads to Eukaryotes

On Building a Heart:
Lessons from Man and Nature
Duke Cameron MD
Cardiac Surgeon-in-Charge
Professor of Surgery
Johns Hopkins
Disclosure
I am not an expert on this subject
Solomon Victor
(1938-2006)
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Cardiac surgeon, humanitarian,
evolutionary biologist
Practiced in public sector in Madras and
Chennai
Longstanding interest in evolution of
hearts and established a museum of
comparative cardiac anatomy
Theories: “every heart beat is under
neural control”, “contractile properties of
systemic and pulmonary veins”, and
“anticipatory evolution.”
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Earth is 4.6 Bn years old
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Life started 4 Bn years
ago
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Earliest form of life were
anaerobes, fed by
hydrogen, sulfur and CO2
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Photosynthetic
cyanobacteria appear 2.8
BYA and yield oxygen
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Enzymes for oxygen
metabolism derived from
sulfur based enzymes,
but with more efficiency
Ingestion of Prokaryotes Leads to Eukaryotes
Multiple mitochondria led to increased energy generating capacity
Annals of the New York Academy of Sciences
Volume 1047, Issue 1, pages 13-29, 9 JAN 2006
Single cell Eukaryotes split into more than 60 lines
Had cytoskeleton,
flagellum, actomyosin,
and directed movement
Annals of the New York Academy of Sciences
Volume 1047, Issue 1
Opisthokonts, Ancestors of Multicellular Life
Poriphera
(sponges)
Annals of the New York Academy of Sciences
Volume 1047, Issue 1, pages 13-29, 9 JAN
Development of the Coelem
Coelem served three functions: digestion,
gas exchange, and reproduction
The Coelem
• Eventually differentiated into separate
tubes (vascular, intestinal, and respiratory)
• Vascular became a closed system
• Digestive and respiratory remained open
• Respiratory became one ended
• Intestinal remained
Next step: development of a neural cord…..
…and then vertebrae
Evolution of the Heart
Why did we evolve 4 chamber hearts
and separate the circulations?
• Maintenance of endothermy and more
movement increased the need for more
efficient oxygen delivery
• Larger and more erect species required
higher systemic blood pressure, yet the
pulmonary circulation needed lower
pressure
Even though cardiac evolution has marched toward greater
differentiation and specialization, there still exists
tremendous variability in nature’s solution for nutrient
distribution and gas exchange
Octopus Hearts
Copper-based oxygen binding; mostly free plasma
Frog and Lizard Hearts
Double arches and variable septations
Hibernation
Ground squirrel
• Body temp even
sub-zero (-2° C)
• HR 4 bpm
• Intermittent arousal
• Looses 40% BW
• No food or water
for months
Evolution of the Heart and the
Core Cardiac Transcription Factors
Summary
• Evolution has produced higher
performing, more differentiated
hearts
• Unique solutions for unusual
environments are still in place
• Nature’s pleomorphism should
inspire us to explore novel means to
meet the circulatory challenge