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

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
DAG
Oocyte
PIP2
PLCzeta
IP3
Ca2+
Ca2+
Endoplasmic Reticulum

22. Sperm Receptor - Calcium Pulse Initiation
PLC
Ca++
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

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