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what does protestrus begin with?
completion of luteolysis
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during proestrus, maximal amount of estrogen triggers what?
a sustained surge of LH lasting 8-12 hours
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Estrogen peak and LH surge are at the onset of what?
estrus
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How long does proestrus last?
3-4 days
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How long does estrus last?
12-18 hours
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When does ovulation occur in cows?
24-30 hours after the onset of estrus, not typically during standing heat
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what is the color of the cows vaginal mucus discharge during estrus?
clear
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How long does metestrus last?
3-4 days
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What is the period following estrus and ovulation during which the CL achieves mature function ( progesterone production)
classical definition of metestrus
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What is the period following ovulation during which the immature CL will not respond to pharmacological dose of PGF2a by undergoing luteolysis ?
clinical definition of metestrus
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When is a bloody vaginal discharge often visable in the cow?
after estrus and ovulation, during met estrus
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In the non-pregnant cow, pulses of PGF2a are secreted by the uterus at day 16/17 for 36 hours causing what?
immediate dropping progesterone concentration
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The presence of an embyro in the cow prevents the surge of what?
PGF2a
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Where does the corpus luteum develop from in the cow?
after ovulation, from the follicle wall
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Granulosa cells differentiate into what?
large luteal cells
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What type of cells are 30% of steroidogenic cells, but secrete 70% of P4?
Large luteal cells
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LLC have the most of what type of receptors?
PGF2a receptors
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What do LLC produce?
oxytocin
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What cells differentiate into Small Luteal Cells?
Theca cells
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What type of cells are 70% of steroidogenic cells but secrete 30% of the progesterone?
Small luteal cells
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In which type of cells, Small or Large luteal cells, is LH required for maximum progesterone secretion?
small luteal cells
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What does progesterone stimulate?
progesterone receptors and accumulation of phospholipids in the uterine epithelium
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Progesterone and progesterone receptors block the expression of what?
estrogen receptors and oxytocin receptors
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Oxytocin from pituitary and CL binds to oxytocin receptors on uterine luminal epithelium and superficial uterine gland duct epithelium to stimulate what?
prostaglandin secretion
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In the nonpregnant cow, PGF2a released from the uterus reaches the ovary and CL via the what?
ipsilateral uterine vein and ovarian artery
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What prevents luteolysis in the cow?
hysterectomy early after ovulation
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The source of luteolysin (the chemical that causes luteolysis) is the what?
endometrium
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How much PGF2a in the mare causes luteolysis?
1mg
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In mares, PGF2a released from the uterus, reaches the ovary by what route?
systemic route, opposed to local route in cow
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How much PGF2a in the cow causes luteolysis?
25mg
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What is the process where the conceptus signals its presence to the maternal system and prolongs the lifespan of the corpus luteum?
maternal recognition of pregnancy
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Where must an embryo be by day 16 post-estrus in the cow to prevent luteolysis?
the uterine horn ipsilateral to the ovary that contains the CL
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In ruminants IFN-t is the pregnancy recognition signal secreted by what?
the elongating conceptus which acts on the endometrium
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What does IFN-t suppress?
PGF2a release
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Conceptus trophectoderm synthesizes and secretes what?
IFN-t
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IFN-t suppresses transcription of what receptors, which are thought to be necessary for expression of oxytocin receptors?
estrogen
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By inhibition of increases in oxytocin receptor expression, IFN-t prevents the endometrium from releasing what?
luteolytic pulses of PGF2a
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What is the product throught to have a central role in affecting how luteolysis is suppressed?
IFN-t
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What is derived from arachadonic acid and produced in the uterus?
prostaglandin (PGF2a)
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What is a large molecule protein from the pituitary?
LH
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What is a steroid produced by the corpus luteum and placenta and by all steroid producing tissues?
progesterone
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What is a steroid, produced in the ovary and many other steroid producing tissues?
estrogen
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What is a peptide fragment, produced in the neurosecretory cells of the hypothalamus, and stored in and released from the posterior lobe of the pituitary (and by the corpus luteum in the cow)?
oxytocin
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