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2-Evol Perspectives Figs-Complete BW

Silverthorn ch 21 shamsa rashid photography 2007 why

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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 Anthropogenic change 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 Asthma Invariant Natural Killer T-Cells Normal Microbiota Germ Free* Rare Rare Low Common Common High *Effects reversed by infection in neonates but not adults. Role of Invariant Natural Killer T-Cells B-Lymphocytes (secrete antibodies) Dendritic Cells (present antigens) Myeloid-Derived Suppressor 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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