Animal Science 434 The Follicular Phase of the

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Animal Science 434 The Follicular Phase of the Estrous Cycle

Animal Science 434 The Follicular Phase of the Estrous Cycle

Preovulatory Gn. RH Surge Tonic Gn. RH Release Hours Gn. RH (pg/ml) Tonic and

Preovulatory Gn. RH Surge Tonic Gn. RH Release Hours Gn. RH (pg/ml) Tonic and Preovulatory Surge of Gn. RH Hours

Hypothalamus Progesterone (-) Gn. RH Estradiol (-) Anterior Pituitary Inhibin (-) LH, FSH LH

Hypothalamus Progesterone (-) Gn. RH Estradiol (-) Anterior Pituitary Inhibin (-) LH, FSH LH CL Estradiol LH, FSH Ovary Follicle

Preovulatory Gn. RH Surge Tonic Gn. RH Release Hours Gn. RH (pg/ml) Tonic and

Preovulatory Gn. RH Surge Tonic Gn. RH Release Hours Gn. RH (pg/ml) Tonic and Preovulatory Surge of Gn. RH Hours

The Follicular Phase

The Follicular Phase

Hypothalamus Progesterone (-) Gn. RH Estradiol (-) Anterior Pituitary Start of Follicular Phase Inhibin

Hypothalamus Progesterone (-) Gn. RH Estradiol (-) Anterior Pituitary Start of Follicular Phase Inhibin (-) LH, FSH LH CL Estradiol LH, FSH Ovary Follicle

Hypothalamus Gn. RH Estradiol (-) Anterior Pituitary CL Regression Inhibin (-) LH, FSH Estradiol

Hypothalamus Gn. RH Estradiol (-) Anterior Pituitary CL Regression Inhibin (-) LH, FSH Estradiol LH, FSH Ovary Follicle

Hypothalamus Gn. RH Ends in LH surge and ovulation Estradiol (+) Anterior Pituitary Inhibin

Hypothalamus Gn. RH Ends in LH surge and ovulation Estradiol (+) Anterior Pituitary Inhibin (-) LH, FSH Estradiol LH, FSH Ovary Follicle

The Follicular Phase

The Follicular Phase

Primary Primordial Follicular Progression Tertiary Secondary

Primary Primordial Follicular Progression Tertiary Secondary

Growth and Atresia of Follicles Atresia

Growth and Atresia of Follicles Atresia

Fate of follicles and oocytes At birth 100, 000 12 months 75, 000 4

Fate of follicles and oocytes At birth 100, 000 12 months 75, 000 4 -6 years 21, 000 Aged cow 2, 500 100 Days of Gestation 2. 9 million • 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 or Ovum Pick-up (OPU) - rescue some follicles from atresia

Initial Follicular Growth Small Antral Follicle 50 - 60 days Gonadotropin Independent FSH Recruitment

Initial Follicular Growth Small Antral Follicle 50 - 60 days Gonadotropin Independent FSH Recruitment

Follicular Waves in Cattle

Follicular Waves in Cattle

Follicular Size Atresia Recruitment Dominance Ovulation Selection FSH Sensitive Pool Ovulation 9 Day 16

Follicular Size Atresia Recruitment Dominance Ovulation Selection FSH Sensitive Pool Ovulation 9 Day 16 21

Follicular Size Atresia Recruitment Dominance Progesterone Ovulation Selection FSH Sensitive Pool Ovulation 9 Day

Follicular Size Atresia Recruitment Dominance Progesterone Ovulation Selection FSH Sensitive Pool Ovulation 9 Day 16 21

Follicular Size Progesterone Atresia Ovulation FSH Dominance Selection FSH Recruitment 9 FSH Day estradiol

Follicular Size Progesterone Atresia Ovulation FSH Dominance Selection FSH Recruitment 9 FSH Day estradiol inhibin FSH estradiol (-) inhibin (-) estradiol (-) 16 21

Follicular Size Progesterone Atresia Dominance Selection Recruitment Ovulation 9 Day 16 21

Follicular Size Progesterone Atresia Dominance Selection Recruitment Ovulation 9 Day 16 21

Follicular Size Progesterone Ovulation 9 Day 16 21

Follicular Size Progesterone Ovulation 9 Day 16 21

Follicular Size Progesterone Ovulation 9 Day 16 21

Follicular Size Progesterone Ovulation 9 Day 16 21

Progesterone Follicular Size Ovulation Dominance Selection Recruitment Ovulation 9 Day 16 21

Progesterone Follicular Size Ovulation Dominance Selection Recruitment Ovulation 9 Day 16 21

Two Follicular Waves

Two Follicular Waves

Follicular Size Progesterone Atresia Dominance Ovulation Selection Recruitment Ovulation 10 Day 21

Follicular Size Progesterone Atresia Dominance Ovulation Selection Recruitment Ovulation 10 Day 21

Follicular Wave Emergence • Recruitment = Emergence • FSH always controls emergence • Increase

Follicular Wave Emergence • Recruitment = Emergence • FSH always controls emergence • Increase in FSH precedes emergence

Species Variation in Follicular Waves • • • Cattle - 2 or 3 /

Species Variation in Follicular Waves • • • Cattle - 2 or 3 / cycle Cl-progesterone Sheep - 4 or 5 / cycle Pigs - 1 / cycle Cl-progesterone, inhibin Horses - 1 / cycle If first wave Human - 1 / cycle stops/fails, then a second wave emerges!!!

Gonadotropin Action Within the Follicle

Gonadotropin Action Within the Follicle

Antral Follicle Theca Internal Granulosa

Antral Follicle Theca Internal Granulosa

Theca Interna LH Receptor c. AMP Cholesterol FSH d Testosterone Receptor Bloo PKA c.

Theca Interna LH Receptor c. AMP Cholesterol FSH d Testosterone Receptor Bloo PKA c. AMP Test. Granulosa Estradiol PKA

Theca Interna Selection Dom. Foll. Express LH Receptor c. AMP Cholesterol FSH PKA Testosterone

Theca Interna Selection Dom. Foll. Express LH Receptor c. AMP Cholesterol FSH PKA Testosterone Receptor c. AMP LH Receptor c. AMP Test. PKA Granulosa Estradiol d Receptor Bloo LH

Ovulation

Ovulation

Germinal Epithelium Tunica Albuginea Theca Externa Theca Interna Basement Membrane Granulosa

Germinal Epithelium Tunica Albuginea Theca Externa Theca Interna Basement Membrane Granulosa

Blocking of these events in the follicle prevents ovulation. • protein synthesis • steroid

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

Preovulatory LH Surge Cumulus Expansion Oocyte Separates From Follicular Wall Ovulation

Cumulus Expansion Hyaluronic Acid and Protein Production Unexpanded Expanded

Cumulus Expansion Hyaluronic Acid and Protein Production Unexpanded Expanded

Cumulus and Oocyte Separation

Cumulus and Oocyte Separation

Preovulatory LH Surge Cumulus Expansion Protein synthesis changes in and around Follicle Progesterone Plasminogen

Preovulatory LH Surge Cumulus Expansion Protein synthesis changes in and around Follicle Progesterone Plasminogen Activator Oocyte Separates From Follicular Wall Ovulation Prostaglandin Synthesis PGE and PGF

Preovulatory LH Surge Cumulus Expansion Protein synthesis changes in and around Follicle Progesterone Plasminogen

Preovulatory LH Surge Cumulus Expansion Protein synthesis changes in and around Follicle Progesterone Plasminogen Activator Oocyte Separates From Follicular Wall Histamine, PGE 2 Increased Blood Flow to Ovary and Follicle Vascular Prostaglandin Permeability Synthesis PGE and PGF Plasminogen Edema Ovulation Foll. pressure

Preovulatory LH Surge Cumulus Expansion Protein synthesis changes in and around Follicle Progesterone Plasminogen

Preovulatory LH Surge Cumulus Expansion Protein synthesis changes in and around Follicle Progesterone Plasminogen Activator Oocyte Collagen. (inact. ) Plasmin Separates From Collagenase (act. ) Follicular Wall Weakens Wall Ovulation Histamine, PGE 2 Increased Blood Flow to Ovary and Follicle Vascular Prostaglandin Permeability Synthesis PGE and PGF Plasminogen Edema Foll. pressure

Preovulatory LH Surge Cumulus Expansion Protein synthesis changes in and around Follicle Progesterone Plasminogen

Preovulatory LH Surge Cumulus Expansion Protein synthesis changes in and around Follicle Progesterone Plasminogen Activator Oocyte Collagen. (inact. ) Plasmin Separates From Collagenase (act. ) Follicular Wall Weakens Wall Ovulation Histamine, PGE 2 Increased Blood Flow to Ovary and Follicle Vascular Prostaglandin Permeability Synthesis PGE and PGF Plasminogen Contraction Sm. Muscle Edema Foll. pressure

Types of Ovulators

Types of Ovulators

Spontaneous Ovulators

Spontaneous Ovulators

Induced Ovulators

Induced Ovulators

Induced Ovulators Nerve endings sensing copulation Copulation Sensory Neurons Penis

Induced Ovulators Nerve endings sensing copulation Copulation Sensory Neurons Penis

Blood LH Hypothalamus LH Time (hr) Stimulation Gn. RH Posterior Pit. Anterior Pit. Spinal

Blood LH Hypothalamus LH Time (hr) Stimulation Gn. RH Posterior Pit. Anterior Pit. Spinal Chord

Induced Ovulators LH Nerve endings sensing copulation Copulation Sensory Neurons Penis

Induced Ovulators LH Nerve endings sensing copulation Copulation Sensory Neurons Penis

Cats • Induced Ovulators • Single copulation – Only works 50% of the time

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

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 Move to germinal ridge Mitotic divisions Primordial Germ Cells Oogonia Follicle Cells Meiosis

Oogenesis Move to germinal ridge Mitotic divisions Primordial Germ Cells Oogonia Follicle Cells Meiosis Interphase DNA synthesis Meiotic prophase Primary Oocyte Prophase of Meiosis Leptotene, Zygotene Pacytene, Diplotene Dictyotene Meiotic Arrest

Gonadotropin Independent Gonadotropin Dependent Growth zona pellucida formation m. RNA production Protein synthesis Cortical

Gonadotropin Independent Gonadotropin Dependent Growth zona pellucida formation m. RNA production Protein synthesis Cortical granule formation nuclear maturation cytoplasmic maturation Remains primary oocyte until LH surge

Oogonia in Egg Nest Fetal Pig Ovary

Oogonia in Egg Nest Fetal Pig Ovary

Oogonia Primary Oocytes

Oogonia Primary Oocytes

Primary Oocytes in Primordial Follicles

Primary Oocytes in Primordial Follicles

Primary Oocyte in Primary Follicle

Primary Oocyte in Primary Follicle

Fetal Oocyte Development Fertilization Mitosis Meiosis Birth Cow 280 d Sow 114 d Mouse

Fetal Oocyte Development Fertilization Mitosis Meiosis Birth Cow 280 d Sow 114 d Mouse 19 d

Ovulation of Tertiary Follicle

Ovulation of Tertiary Follicle

Corona Radiata Formation of the Zona Pellucida Oocyte

Corona Radiata Formation of the Zona Pellucida Oocyte

Corona Radiata Zona Pellucida Oocyte Gap Junctions

Corona Radiata Zona Pellucida Oocyte Gap Junctions

During Oocyte Growth and Before the LH Surge • OMI - Oocyte Maturation Inhibitor

During Oocyte Growth and Before the LH Surge • OMI - Oocyte Maturation Inhibitor • MPF - Maturation promoting factor c. AMP OMI c. AMP GV PKA pre-MPF • GV - germinal vesicle (nucleus) Gap Junctions Allow Cell to Cell Communication!

The LH Surge Gap Junctions are Destroyed!

The LH Surge Gap Junctions are Destroyed!

The LH Surge c. AMP GVBD PKA Resumption of Meiosis GV pre-MPF Gap Junctions

The LH Surge c. AMP GVBD PKA Resumption of Meiosis GV pre-MPF Gap Junctions are Destroyed!

LH Surge Resumption of Meiosis 4 N 4 N 2 N Ovulation (most species)

LH Surge Resumption of Meiosis 4 N 4 N 2 N Ovulation (most species) Secondary Oocyte Primary Oocyte N N Zygote (pronucleate egg) First polar body emitted, arrest at metaphase II 2 N Sperm Penetration

LH Surge Resumption of Meiosis 4 N 4 N Primary Oocyte Ovulation • Dog,

LH Surge Resumption of Meiosis 4 N 4 N Primary Oocyte Ovulation • Dog, Fox Zygote (pronucleate egg) First polar body emitted, arrest at metaphase II 2 N Ovulation (most species) Sperm Pen. Secondary • Dog, Fox Oocyte N N 2 N Sperm Penetration