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Repro > Fertilization Mechanisms > Flashcards

Fertilization Mechanisms Flashcards

1
Q

Where does fertilization occur?

A

Ampulla of fallopian tubes

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2
Q

Describe the process for sperm maturation in the epididymis.

How long does it take to transit epididymis?

A

Sperm surface acquires new surface proteins from epididymal secretions. It travels from caput to corpus to caudal and gradually develops motility.

Process takes 80-90 days

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3
Q

What is capacitation? Where does capacitation occur?

A

Ability to fertilize an egg. It occurs within female reproductive tract (cervix, uterus, fallopian tube)

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4
Q

What change is responsible for development of hyper activated motility?

A

cAMP production

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5
Q

List some of the changes that occur in sperm during capacitation: (5)

A 
Loss of cholesterol from plasma membrane
Changes in surface charge of proteins 
Elevation of intracellular pH and bicarbonate
CatSper ion channels allow Ca entry
Hyperactivated motility
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6
Q

How do sperm penetrate cumulus cells (ZP)?

A

Group effort
Assisted by sperm motility
PH20/SPAM1–>Surface hyaluronidase

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7
Q

Which Zona Pellucid glycoprotein is essential? What is its function? What are consequences of KO?

A

ZP3: Binds capacitated sperm and induces acrosome reaction

ZP3 KOs are sterile and do not contain a zona pellucida

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8
Q

What are functions of other ZP glycoproteins? What are consequences of KO?

A

ZP1: “holding”– also induces acrosomal excocytosis
KO: loose/filamentous ZP, embryos hatch early

ZP2: prevents polyspermy

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9
Q

What happens following sperm-ZP binding?

A

Acrosomal reaction

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10
Q

What are the leading candidates for the corresponding ZP receptor on sperm?

A

CHO binding candidates (80%): GaL Tase

Protein core binding candidates (20%)

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11
Q

What is necessary for sperm to fuse with egg plasma membrane? Why?

A

Acrosomal reaction is necessary– it exposes sperm proteins necessary for oocyte binding

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12
Q

How is the acrosome reaction triggered?

A

Complex receptor-mediated signaling results in calcium release within sperm.
Fusion of sperm plasma membrane with outer acrosomal membrane
Exocytosis of digestive enzymes to breakdown ZP

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13
Q

What two things are required to penetrate Zona Pellucid? What enzyme assists in releasing proteins from sperm surface?

A

Penetration requires motile force from flagellar movement and enzymatic hydrolysis

Angiotensin converting enzyme (ACE) releases proteins from sperm surface

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14
Q

What is a hallmark of the initiation of egg activation? How is it triggered?

A

An increase in cytosolic calcium follows egg fertilization. It is triggered by phospholipase C (PLC)

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15
Q

What are the changes that occur in egg activation? (4)

A

Release of meiotic arrest and progression into mitosis
Changes in maternal mRNA, protein synthesis
Exocytosis of cortical granules to block polyspermy
Cytoskeletal rearrangements

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16
Q

How does cortical granule release block polyspermy?

What is the timing? Onset and duration

A

Ovastacin is released from granules and cleaves ZP2–>Sperm cannot bind to zona pelucida

Block occurs 1-2 hours after insemination and persists for hours to days

17
Q

Where is the block to polysperm in humans?

A

At both membrane and zona pellucida

18
Q

What is the word for oocyte activation? How else can activation occur? (6)

A 
Parthenogenesis can result from 
Mechanical trauma
Temperature shock
Chemical stimuli
Electrical signals
SrCL2
ICSI
19
Q

How does intrauterine insemination work? When would you use it?

A

Abnormal semen analysis:

Remove seminal plasma; promote capacitation and use techniques that chose motile sperm.

20
Q

What is globoozoospermia? How do you achieve pregnancy for patients with condition?

A

Sperm that lack acrosomal head. Use intracytoplasmic sperm injection (ICSI)

21
Q

Can sperm from testes or epididymis be used for IVF? How?

A

Extract from testicles. Activate with pentoxyphylline then do ICSI

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