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Lecture 16: Fertilization

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1 Lecture 16: Fertilization
Animal Science 434 John J. Parrish

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3 Capacitation 1951 Austin - rat Chang - rabbit
Fertilization does not occur until several hours after sperm are placed in the uterus or oviduct

4 Chang Experiment Ovulation After Before Percent Fertilization

5 Capacitation The changes within sperm that confer upon the sperm the ability to acrosome react in response to the appropriate stimulus. Zona Pellucida Cumulus Cells Follicular Fluid

6 Effect of Capacitation
Epididymal Ejaculated Seminal Plasma + Capacitated Female Tract +

7 Model of Capacitation D F Acrosome Nucleus Cytoplasm Plasma Membrane

8 D F Chol-Acceptor D F GAG D F D F D F Ca2+ Cholesterol Acrosome Ca2+ pH cAMP Nucleus Activity of Enzymes Cytoplasm Plasma Membrane

9 Capacitation No change in sperm morphology Motility change
hyperactivation cAMP Power output

10 The Acrosome Reaction Fused Plasma Plasma Membrane Membrane and
Outer Acrosomal Membrane Plasma Membrane Acrosin Hyaluronidase Acrosome Nucleus

11 Modification of the Equitorial Region

12 The Zona Pellucida ZP1 ZP2 ZP3

13 Sperm Interaction with the Zona
Attachment Zona Pellucida Binding ZP3 Acrosome Reaction Induction Acrosome Reaction

14 Secondary Binding Zona Pellucida ZP2 ZP2 Zona Penetration ZP2 ZP2 Motility

15 Zona Pellucida

16 Sperm tract through zona pellucida

17 18-24 hr 6-12 hr

18 Maturation Promoting Factor (MPF)
LH Surge Metaphase Promoting Factor Primary Oocyte GVBD Metaphase I MPF MPF GV-Intact MPF PB-1 MPF Ovulation Metaphase II Secondary Oocyte

19 Zona Pellucida Oocyte Ca2+ Ca2+ Perivitelline Space

20 Calcium Transients During Bovine Fertilization

21 Initiation of Calcium Pulse by Soluble Sperm Component

22 Calcium Pulse Initiated by IP3
ER

23 X Zona Pellucida Oocyte Pronuclei Ca2+ AII TII MPF Perivitelline MII
PBII MPF MII Perivitelline Space

24 X Zygote Zona Pellucida Oocyte Decondensation Pronuclei Pronuclei Ca2+
MII AII MPF X Ca2+ Pronuclei TII PBII Perivitelline Space

25 Zona Block to Polyspermy
Zona Pellucida Oocyte Ca2+ Cortical Granules Zona Block to Polyspermy Perivitelline Space

26 Blocks to Polyspermy Species 1. Mammals
3. Invertebrates Amphibians Fish Rabbits 4. Amphibians Avians 1 2 3 4

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30 Perivitelline Space 1st Polar Body Vitelline Membrane Zona Pellucida
Sperm acrosomal region binds to sperm receptor on zona Perivitelline Space Initiates completion of Meiosis II and release of 2nd polar body 1st Polar Body Vitelline Membrane Zona Pellucida Initiates - Zona & Vitelline Reaction Cortical Granule ZP3 Binding Fusion Cortical Granule Release Zona Reaction Initiation of Acrosome Reaction Excluded Sperm Continuation of Reaction Acrosome-Reacted Sperm Penetration Zona and Vitelline Reactions block polyspermy Sperm penetrates zona Redrawn from Wasserman, P.M Scientific American. p78


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