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Post Embryonic Development

Post Embryonic Development. Metamorphosis- Amphibians and Insects Tissue Regeneration Aging. Metamorphosis: Overview. Direct Developers Indirect Developers. Metamorphosis: Amphibians. Hormones Thyroxine (T4) triiodothyronine (T3) Hormones cause: Growth Death Remodeling

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Post Embryonic Development

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  1. Post Embryonic Development • Metamorphosis- Amphibians and Insects • Tissue Regeneration • Aging

  2. Metamorphosis: Overview • Direct Developers • Indirect Developers

  3. Metamorphosis: Amphibians • Hormones • Thyroxine (T4) • triiodothyronine (T3) • Hormones cause: • Growth • Death • Remodeling • Respecification

  4. Hormones: Growth • Growth and rearrangement • Limbs • Eyes

  5. Hormones: Cell Death • T3 and tail degeneration • Concomitant with adult leg generation.

  6. Hormones: Remodeling • Digestive tract • Skull and gills • Nervous system

  7. Hormones: Biochemical Respecification • Tadpole is ammonotelic • After morphogenesis, Frogs are ureotelic.

  8. Hormone function during Metamorphosis • T4 secreted by Thyroid. • TRa= receptor for T3; ubiquitous • TRb= receptor induced by hormones • Stages of Hormone activity in Metamorphosis • Premetamorphosis • Prometamorphosis • Metamorphic climax

  9. Hormone function during Metamorphosis • T4 secreted by Thyroid. • TRa= receptor for T3; ubiquitous • TRb= receptor induced by hormones • TR/RXR complexes • Stages of Hormone activity in Metamorphosis • Premetamorphosis • Prometamorphosis • Metamorphic climax

  10. Metamorphosis: Insects

  11. Insect Imaginal Discs

  12. Metamorphosis: Fly and Leg formation • Wingless (Wg); Wnt homolog • Decapentaplegic (Dpp); BMP homolog • Distal-less and Dachshund • 20-hydroxyecdysone (20-E)

  13. Metamorphosis: Fly and Leg formation • Wingless (Wg); Wnt homolog • Decapentaplegic (Dpp); BMP homolog • Distal-less and Dachshund • 20-hydroxyecdysone (20-E)

  14. Metamorphosis: Fly and Leg formation • Wingless (Wg); Wnt homolog • Decapentaplegic (Dpp); BMP homolog • Distal-less and Dachshund • 20-hydroxyecdysone (20-E)

  15. Imaginal Discs: Wing Fig. 15.14

  16. Imaginal Discs: Wing

  17. Imaginal Discs: Wing • Figure 15.15

  18. Hormonal Control of Insect Metamorphosis • Fig. 15.16

  19. Regeneration • Stem-cell mediated regeneration • Epimorphosis • Morphallaxis • Compensatory regeneration “I’d give my right arm to know the secret of regeneration” -Oscar E. Schotte (1950)

  20. Regeneration: Epimorphic • Limb regeneration in Salamanders • Regeneration blastema • Wound epidermis • Apical epidermal cap (AEC)

  21. Regeneration: Epimorphic

  22. Epimorphic regeneration requires nerves and AEC • Newt anterior gradient protein (nAG). • Fig 15.22

  23. Morphallactic Regeneration: Hydra • Basal disc/hypostome • Head activation/inhibition gradients • Hypostome= “organizer” • Basal disc activation/inhibition Fig. 15.25 And 15.26

  24. Morphallactic Regeneration: Hydra • Basal disc/hypostome • Head activation/inhibition gradients • Hypostome= “organizer” • Basal disc activation/inhibition Fig. 15.25 And 15.26

  25. Compensatory Regeneration: Liver

  26. Aging

  27. Genetics and Aging • How can evolution select for a way to degenerate? • How can evolution select for phenotypes that can postpone reproduction or sexual maturity?

  28. Aging • DNA repair enzymes • p53 • Insulin Signaling

  29. We’re staying alive… Fig. 15.35

  30. DNA methylation and Early Bird Specials. Fig 15.36 and 15.37

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