Unformatted text preview: ’t Synthesize Vitamin C Why the Appendix? Silverthorn, Ch 21 Shamsa Rashid Photography © 2007 Why Do We Get Sick?
Proximate Reasons (Pathophysiology) examples…
• Hypertension is due to an increase in vascular resistance
• Sickle cell anemia is due to mutation in hemoglobin gene
• Cerebral palsy is due to asphyxia during birth
• Cystic fibrosis is due to mutation in chloride channel gene
Ultimate Reasons (Evolutionary Medicine)
Why has evolution left our bodies vulnerable to disease?
1. Selection is about fitness, not health
2. Constraints and trade-offs are inevitable
3. Human evolution is too slow to cope with challenges
4. Our evolved defenses may be harmful or seem harmful Evolution is Too
Slow to Cope
has been rapid …
… but human evolution
has been slow. Both figures from Gluckman et al (2009) Bacterial evolution
is much faster. Evolved Defenses May Be Harmful
Evolution has given us powerful immune defenses
But, excessive reactions can cause harm:
• Fever (pyrexia) can cause seizures, brain damage
• Allergies, asthma, anaphylaxis
• Autoimmune disease
Hygeine hypothesis suggest co-evolution with microbiota: Bach, J-F (2002) New England J Med 347:911-920 Hygeine Hypothesis: Evidence for Mechanisms
Science 336: 489-493 (2012) www.taconic.com Inflammatory Bowel Disease
Invariant Natural Killer T-Cells Normal
High *Effects reversed by infection in neonates but not adults. Role of Invariant Natural Killer T-Cells
(inhibit immune cells) Natural Killer Cell
(cytotoxic, non-specific) CD8+ Cells
(cytotoxic T-cells) CD4+ Cells
(helper T-cells) Figure from Cerundolo et al. (2009) Nature Rev. Immunol. 9:28-38 Human Milk Colostrum Early Later http://en.wikipedia.org/wiki/Breast_milk These oligosaccharides are used to nourish beneficial bacteria.
Harmful bacteria cannot use/digest oligosaccharides. no other primates have so many oligosaccharides.. symbiotic relationship:
nutrient with bacteria that co-evolve with us (symbiotic ba...
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