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Capacitation
1951Austin - ratChang - rabbit Fertilization does not occur until several
hours after sperm are placed in the uterus or oviduct
Chang Experiment - 1951
0
20
40
60
80
100
-2 -1 0 2 4 6 8Time of Insemination (hr relative to
ovulation)
OvulationOvulation
Per
cen
t F
erti
liza
tio
n
AfterAfter BeforeBefore
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
Zona Pellucida
Cumulus Cells
Follicular Fluid
Effect of CapacitationEpididymal Ejaculated
SeminalPlasmaand/or
EpididymalSecretions
+
Capacitated
FemaleTract
+
Plasma Membrane
Cytoplasm
Nucleus
AcrosomeAcrosome
GAG
Cholesterol
Chol-Acceptor
Ca2+
Ca2+
pH
cAMPActivity ofEnzymes
Activity ofEnzymes
D F
Capacitation
No change in sperm morphologyMotility change
– hyperactivation
cAMP
Power output
cAMP
Power output
The Acrosome ReactionPlasma Membrane
Acrosome
Fused PlasmaMembrane and
Outer AcrosomalMembrane
Fused PlasmaMembrane and
Outer AcrosomalMembrane
Nucleus
AcrosinHyaluronidase
AcrosinHyaluronidase
Zona Pellucida
ZP3
Attachment
Binding
Acrosome ReactionInduction
Acrosome Reaction
Sperm Interaction with the Zona
Maturation Promoting Factor(MPF)
Metaphase Promoting FactorMetaphase Promoting Factor
MPF MPF
MPFMPF
Primary Oocyte
GV-Intact
GVBD Metaphase I
PB-1
Secondary OocyteMetaphase II
Ovulation
LH Surge
Initiation of Calcium Pulse by Soluble Sperm Component
Endoplasmic Reticulum
Ca2+
PLCzetaPIP2
DAG
IP3
Ca2+
Oocyte
Zona Pellucida
PerivitellineSpace
Oocyte
MII
AIIMPF X
Ca2+Ca2+
Pronuclei
Decondensation
Pronuclei
Zygote
TII
PBII
3
Blocks to Polyspermy
1
2
4
Species
1.Mammals
3.InvertebratesAmphibiansFishRabbits
4.AmphibiansAvians
Sperm acrosomalregion binds to spermreceptor on zona
Sperm penetrateszona
Initiates -Zona &VitellineReaction
Initiates completion ofMeiosis II and releaseof 2nd polar body
Zona and VitellineReactions blockpolyspermy
PerivitellineSpace
VitellineMembrane
CorticalGranule
ZP3
Binding
Initiation ofAcrosomeReaction
Continuation ofReaction
Acrosome-ReactedSperm
PenetrationExcluded Sperm
ZonaReaction
CorticalGranuleRelease
Fusion
1st Polar BodyZona
Pellucida
Redrawn fromWasserman, P.M. 1988 Scientific American. p78