post embryonic development metamorphosis- amphibians and insects tissue regeneration aging
TRANSCRIPT
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Post Embryonic Development• Metamorphosis- Amphibians and Insects• Tissue Regeneration• Aging
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Metamorphosis: Overview
• Direct Developers• Indirect Developers
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Metamorphosis: Amphibians• Hormones
– Thyroxine (T4)– triiodothyronine (T3)
• Hormones cause:– Growth– Death– Remodeling– Respecification
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Hormones: Growth• Growth and rearrangement• Limbs• Eyes
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Hormones: Cell Death• T3 and tail degeneration• Concomitant with adult leg
generation.
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Hormones: Remodeling• Digestive tract• Skull and gills• Nervous system
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Hormones: Biochemical Respecification• Tadpole is ammonotelic• After morphogenesis, Frogs
are ureotelic.
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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
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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
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Metamorphosis: Insects
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Insect Imaginal Discs
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Metamorphosis: Fly and Leg formation• Wingless (Wg); Wnt
homolog• Decapentaplegic (Dpp);
BMP homolog• Distal-less and Dachshund• 20-hydroxyecdysone (20-E)
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Metamorphosis: Fly and Leg formation• Wingless (Wg); Wnt
homolog• Decapentaplegic (Dpp);
BMP homolog• Distal-less and Dachshund• 20-hydroxyecdysone (20-E)
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Metamorphosis: Fly and Leg formation• Wingless (Wg); Wnt
homolog• Decapentaplegic (Dpp);
BMP homolog• Distal-less and Dachshund• 20-hydroxyecdysone (20-E)
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Imaginal Discs: Wing
Fig. 15.14
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Imaginal Discs: Wing
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Imaginal Discs: Wing
• Figure 15.15
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Hormonal Control of Insect Metamorphosis
• Fig. 15.16
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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)
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Regeneration: Epimorphic
• Limb regeneration in Salamanders
• Regeneration blastema• Wound epidermis• Apical epidermal cap (AEC)
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Regeneration: Epimorphic
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Epimorphic regeneration requires nerves and AEC• Newt anterior gradient
protein (nAG). • Fig 15.22
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Morphallactic Regeneration: Hydra• Basal disc/hypostome• Head activation/inhibition
gradients• Hypostome= “organizer”• Basal disc
activation/inhibition Fig. 15.25And 15.26
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Morphallactic Regeneration: Hydra• Basal disc/hypostome• Head activation/inhibition
gradients• Hypostome= “organizer”• Basal disc
activation/inhibition Fig. 15.25And 15.26
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Compensatory Regeneration: Liver
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Aging
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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?
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Aging• DNA repair enzymes• p53• Insulin Signaling
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We’re staying alive…
Fig. 15.35
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DNA methylation and Early Bird Specials.
Fig 15.36 and 15.37