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