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Reproduction > Pregnancy Recognition > Flashcards

Pregnancy Recognition Flashcards

1
Q

pregnancy recognition

A

the critical series of events by which the conceptus initially signals its presence to the dam and enables pregnancy to continue

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2
Q

importance in pregnancy recognition

A

in (almost) all species= key event is preventing luteolysis, which must occur in order for pregnancy to continue

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3
Q

progesterone

A

progesterone from the CL is required to maintain a state of uterine quiescence

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4
Q

luteolysis

A

occurs in absence of pregnancy in order to initiate another estrous cycle- occurs when not pregnant

prostaglandin F2a is the hormone responsible for destruction of the CL (lysis)

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5
Q

process of luteolysis

A

during first half of luteal phase, prostaglandin F2a secretion by endometrium is minimal (diestrus= progesterone dominant)

prostaglandin F2a secretion occurs in large pulses at end of luteal phase- sufficient pulses result in luteolysis

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6
Q

mechanism of luteolysis

A

estrogen induces the synthesis of oxytocin receptors (causes contraction)- makes irritable, causes contraction

progesterone blocked synthesis of oxytocin receptors- quiescent

oxytocin binding stimulates prostaglandin release- in early diestrus progesterone prevents oxytocin receptors synthesis and prostaglandin release

in late diestrus, progesterone loses ability to block oxytocin receptor synthesis- oxytocin binding stimulates prostaglandin release

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7
Q

Oxytocin receptors

A

common in late luteal phase

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8
Q

prostaglandin cycling

A

early on in cycle OTr repressed (lower PGF2a and high P4)- progesterone high during diestrus

during luteolysis OTr increases in number and can more readily bind oxytocin and the receptor number increases greater as P4 falls and PGF2a increases

high OTr end up lysing CL, why progesterone falls

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9
Q

Progesterone cycling

A

high around day 13 of estrus before drops as oxytocin receptors increases and PGF2a increases which ultimately decreases progesterone secretion

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10
Q

Luteolysis category

A

categorized as luteolysis once progesterone decreases due to oxytocin receptors and PGF2a

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11
Q

Progesterone

A

required for pregnancy maintenance

species with CL as sole source of progesterone= pig, goat, llama, dog and cat

species with both CL and placental progesterone= horse, sheep and cow

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12
Q

intact uterus experiments- luteolysis

A

CL lifespan same as in normal cycle 15-17 days

if uterectomy performed and ovaries remain CL has prolonged lifespan similar to gestation

partial uterectomy contralateral to CL then CL normal lifespan

partial uterectomy ipsilateral to CL will extend lifespan

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13
Q

Experiment conclusion from sheep

A

uterus responsible for luteolysis

uterus must be near the CL

without uterus no PGF for luteolysis and luteolysis is delayed for duration of gestation

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14
Q

counter current exchange

A

ovarian artery and UOV

travel across gradient

endometrium-utero-ovarian vein-ovarian artery (vein to artery)

why horn opposite the CL results in normal luteolysis

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15
Q

PGF 2a

A

to ovary, causes luteolysis

Horse does not use counter current mechanism to deliver PGF to ovary for luteolysis

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16
Q

Luteolysis mechanism in horses

A

horses= different and PGF doesn’t always travel to ovary by counter current exchange

PGF travels systemically- mare more sensitive to PGF and PGF not as rapidly metabolized as in ruminant

17
Q

general mechanism of luteolysis

A

precise intracellular mechanism of luteal destruction is not fully understood

reduced blood flow- vasoconstriction (ischemia) or capillary degeneration= cut off blood supply so shrink and disappear

apoptosis of luteal cells

18
Q

maternal recognition of pregnancy

A

in almost all species, luteolysis must be prevented for pregnancy to continue

embryonic secretion of substances

contact with uterine epithelium- elongation/expansion and migration around the uterus

19
Q

Mare contact with epithelium

A

movement of the conceptus

20
Q

cow and sow contact with epithelium

A

expansion

contact endometrium by getting longer

in Cow Interferon-T needed for maternal recognition

21
Q

maternal recognition in ruminants

A

luteolysis occurs on day 18 in cow, 14 in ewe

trophoblast cell of conceptus produce INF-t between days 10 and 21

22
Q

Interferon t

A

INF-t binds to endometrium and block endometrial synthesis of estrogen receptors and oxytocin receptors (decrease response to estrogen and oxytocin, interferes with luteolysis)

oxytocin cannot bind and therefore does not stimulate endometrial production of PGF2a

23
Q

maternal recognition in sow

A

luteolysis days 13-15

conceptus produces estradiol between 11 and 12 days post ovulation (estradiol changes where prostaglandin goes and directs to uterine lumen)

estrogen causes rerouting of endometrial PGF2a away from circulation and into uterus lumen, lumen PGF2a= little access to circulation so no luteolysis

24
Q

Pregnancy porcine

A

when pregnant, estrogen acts to sequester PGF2a in the lumen of the uterus

able to maintain CL and pregnancy

25
Q

embryonic motility in horse

A

must occur between 11 and 16 days post ovulation

26
Q

mare maternal recognition

A

luteolysis day 15-16 post ovulation

not well defined, conceptus derived signal has not been IDed

whatever signal is it suppresses oxytocin receptors in endometrium and prevents PGF2a release from endometrium

oviductal transport initiated by PGE2 which is secreted by conceptus beginning on day 5 of pregnancy- without pregnancy oocytes retained in oviduct

27
Q

early maternal recognition in mare experiments

A

between 11 and 16 days conceptus migrates throughout uterus several times per day

migration necessary for survival

without movement, would think not pregnant

28
Q

Summary

A

maternal recognition must occur for conceptus to survive

while species variations in mechanism do exist, all signals will ultimately prolong lifespan of CL

29
Q

Maternal recognition in Bitch

A

no signal needed for pregnancy recognition

CL maintained for duration of normal gestation regardless of pregnancy status

with parturition decrease progesterone

30
Q

maternal recognition in Queen- not pregnant

A

ovulation without conception

luteal phase 30-45 days and luteolysis will occur prior to time of normal gestation (lack CL support)

induced ovulation

31
Q

maternal recognition in Queen- pregnant

A

mating, ovulation and conception

luteal phase 62-65 days

fetoplacental relaxin stimulates prolactin

prolactin luteotropic= due to late timing of this luteal support, some would not consider prolactin a signal for maternal recog.
prolactin does result in longer diestrus in pregnant state than in nonpregnant

32
Q

relaxin and queen

A

relaxin produced during pregnancy

produce prolactin which supports CL and continues progesterone production

Reproduction (22 decks)

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