Transcript Animal Science 434

Animal Science 434
Lecture 11: The Follicular Phase of
the Estrous Cycle
Tonic and Preovulatory Surge of GnRH
Hypothalamus
Progesterone
(-)
GnRH
Estradiol (-)
Anterior
Pituitary
Inhibin (-)
LH, FSH
Estradiol
LH
CL
LH, FSH
Ovary
Follicle
Tonic and Preovulatory Surge of GnRH
Follicular Phase
Hypothalamus
Progesterone
(-)
GnRH
Estradiol (-)
Anterior
Pituitary
Inhibin (-)
LH, FSH
Estradiol
LH
CL
LH, FSH
Ovary
Follicle
Hypothalamus
GnRH
Estradiol (+)
Anterior
Pituitary
Inhibin (-)
LH, FSH
Estradiol
LH, FSH
Ovary
Follicle
Follicular Phase
Follicular Progression
Primordial
Primary
Secondary
Tertiary
Growth and Atresia of Follicles
Atresia
Fate of follicles and oocytes
Total # of follicles
At birth
100,000
12 months
75,000
4-6 years
21,000
Aged cow
2,500
Follicles undergo atresia at all stages of development.
Maximum number of oocytes ovulated for a cow
17 cycles/year x 8 year = 136 oocytes ovulated / lifespan
Fate of follicles and oocytes
Total # of follicles
At birth
12 months
100,000 100 Days of Gestation
2.9 million
75,000
4-6 years
21,000
Aged cow
2,500
Follicles undergo atresia at all stages of development.
Maximum number of oocytes ovulated for a cow
17 cycles/year x 8 year = 136 oocytes ovulated / lifespan
Superovulation; rescue follicles from undergoing atresia
with FSH treatment.
Initial Follicular Growth
Small Antral
Follicle
50 - 60 days
Gonadotropin
Independent
FSH
Recruitment
Follicular Waves in Cattle
Follicular Size
Atresia
Recruitment
Dominance
Ovulation
Selection
FSH Sensitive Pool
Ovulation
9
16
Day After Ovulation
21
Follicular Waves in Cattle
Progesterone
Follicular Size
Atresia
Recruitment
Dominance
Ovulation
Selection
FSH Sensitive Pool
Ovulation
9
16
Day After Ovulation
21
Follicular Waves in Cattle
Follicular Size
Progesterone
Atresia
Ovulation
FSH
Dominance
Selection FSH
Recruitment
9
FSH
estradiol
inhibin
FSH
estradiol (-)
inhibin (-)
estradiol (-)
inhibin (-)
estradiol (-)
16
Day After Ovulation
21
Follicular Waves in Cattle
Follicular Size
Progesterone
Atresia
Dominance
Selection
Recruitment
Ovulation
9
16
Day After Ovulation
21
Follicular Waves in Cattle
Follicular Size
Progesterone
Ovulation
9
16
Day After Ovulation
21
Follicular Waves in Cattle
Follicular Size
Progesterone
Ovulation
9
16
Day After Ovulation
21
Follicular Waves in Cattle
Progesterone
Follicular Size
Ovulation
Dominance
Selection
Recruitment
Ovulation
9
16
Day After Ovulation
21
Two Follicular Waves
Follicular Size
Progesterone
Dominance
Atresia
Ovulation
Selection
Recruitment
Ovulation
10
Day After Ovulation
21
Follicular Wave Emergence
• Recruitment = Emergence
• FSH always controls emergence
• Increase in FSH precedes emergence
Species Variation in Follicular Waves
•
•
•
•
•
Cattle - 2 or 3 / cycle Cl-progesterone
Sheep - 4 or 5 / cycle
Pigs - 1 / cycle
Cl-progesterone,
Horses - 1 / cycle
Human - 1 / cycle
inhibin
Gonadotropin Action
Within
the Follicle
Antral Follicle
Theca Internal
Granulosa
LH
Theca Interna
Receptor
cAMP
Cholesterol
PKA
Testosterone
FSH
Receptor
cAMP
Testosterone
PKA
Granulosa
Estradiol
LH
Theca Interna
Selection
Receptor
Dominant Follicle
Express LH Receptor
cAMP
Cholesterol
PKA
Testosterone
LH
FSH
Receptor
Receptor
cAMP
Testosterone
cAMP
PKA
Granulosa
Estradiol
Ovulation
Germinal Epithelium
Tunica
Albuginea
Theca Externa
Theca Interna
Basement Membrane
Granulosa
Blocking of these events in the
follicle prevents ovulation.
• protein synthesis
• steroid synthesis
• prostaglandin
synthesis
• plasminogen activator
synthesis
Preovulatory LH Surge
Cumulus
Expansion
Oocyte
Separates
From
Follicular
Wall
Ovulation
Cumulus Expansion
Hyaluronic Acid and Protein
Production
Unexpanded
Expanded
Cumulus and Oocyte
Separation
Preovulatory LH Surge
Cumulus
Expansion
Protein synthesis changes
in and around Follicle
Progesterone
Plasminogen
Activator
Prostaglandin
Synthesis
PGE and PGF
Oocyte
Separates
From
Follicular
Wall
Ovulation
Preovulatory LH Surge
Cumulus
Expansion
Protein synthesis changes
in and around Follicle
Progesterone
Plasminogen
Activator
Histamine
PGE2
Increased Blood
Flow to Ovary and
Follicle
Vascular
Prostaglandin
Permeability
Synthesis
PGE and PGF
Plasminogen
Oocyte
Separates
From
Follicular
Wall
Edema
Ovulation
Follicular
pressure
Preovulatory LH Surge
Cumulus
Expansion
Protein synthesis changes
in and around Follicle
Progesterone
Plasminogen
Activator
Collagenase (inactive)
Plasmin
Histamine
PGE2
Increased Blood
Flow to Ovary and
Follicle
Vascular
Prostaglandin
Permeability
Synthesis
PGE and PGF
Plasminogen
Oocyte Collagenase (active)
Separates
Follicular Wall
From
Weakens
Follicular
Wall
Ovulation
Edema
Follicular
pressure
Preovulatory LH Surge
Cumulus
Expansion
Protein synthesis changes
in and around Follicle
Progesterone
Plasminogen
Activator
Collagenase (inactive)
Plasmin
Histamine
PGE2
Increased Blood
Flow to Ovary and
Follicle
Vascular
Prostaglandin
Permeability
Synthesis
PGE and PGF
Plasminogen
Oocyte Collagenase (active)
Separates
Follicular Wall
From
Weakens
Follicular
Wall
Ovulation
Contraction
of Smooth
Muscle
Edema
Follicular
pressure
Types of Ovulators
Spontaneous
Ovulators
Induced
Ovulators
Induced Ovulators
Nerve
endings
sensing
copulation
Copulation
Sensory Neurons
Penis
Hypothalamus
Blood
LH
Time (hr)
GnRH
Posterior Pit.
Stimulation
LH
Anterior Pit.
Spinal Chord
LH
Nerve
endings
sensing
copulation
Copulation
Sensory Neurons
Penis
Cats
• Induced Ovulators
• Single copulation
– Only works 50% of the time
• Multiple copulations
– Higher LH surge
Spontaneous Ovulators
• Retain some neural control of
ovulation
– heifers can alter the timing of the LH
surge by clitoral stimulation
– human rape cases result in higher than
expected pregnancy rates
Oogenesis
Migration to germinal ridge
Mitotic divisions
Primordial Germ Cells
Oogonia
Initiation of Meiosis
Interphase
DNA synthesis
Meiotic prophase begins
Primary
Oocyte
Growth
Gonadotropin
Independent
Gonadotropin
Dependent
Follicle Cells
Prophase of Meiosis
leptotene
zygotene
pachytene
diplotene
dictyotene
Meiotic Arrest
zona pellucida formation
mRNA production
protein synthesis
cortical granule formation
nuclear maturation
cytoplasmic maturation
Oogonia in Egg Nest
Fetal Pig Ovary
Oogonia and Primary Oocytes
Primary Oocytes in Primordial Follicles
Primary Oocyte in Primary Follicle
Fetal Oocyte Development
Mitosis
Fertilization
Meiosis
Birth
Cow
280 d
Sow
114 d
Mouse
19 d
Ovulation of Tertiary Follicle
Formation of the Zona Pellucida
Corona Radiata
Oocyte
Zona Pellucida
Corona Radiata
Zona Pellucida
Oocyte
Gap Junctions
During Oocyte Growth and Before the LH Surge
• OMI - Oocyte
Maturation Inhibitor
cAMP
OMI
cAMP
GV
PKA
pre-MPF
MPF
• MPF - Maturation
promoting factor
• GV - germinal vesicle
(nucleus)
Gap Junctions Allow Cell to Cell Communication!
The LH Surge
Gap Junctions are Destroyed!
The LH Surge
cAMP
GVBD
PKA
GV
pre-MPF
MPF
Gap Junctions are Destroyed!
Resumption
of Meiosis
LH Surge
4N
Resumption of
Meiosis
First polar body
emitted, arrest at
metaphase II of meiosis
2N
4N
Primary Oocyte
Secondary
Oocyte
Ovulation
(most species)
Zygote (pronucleate egg)
N N
2N
Sperm
Penetration
LH Surge
4N
Primary Oocyte
Ovulation
• Dog
• Fox
Resumption of
Meiosis
First polar body
emitted, arrest at
metaphase II of meiosis
4N
Sperm
Penetration Secondary
Oocyte
• Dog
• Fox
2N
Ovulation
(most species)
Zygote (pronucleate egg)
N N
2N
Sperm
Penetration