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Animal Production > Parturition > Flashcards

Parturition Flashcards

1
Q

Parturition

A

The act of giving birth to young
-foaling, calving, farrowing, lambing, whelping, queening

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2
Q

Key components for parturition

A
  1. Fetus
  2. Fetoplacental unit
  3. UTerine Musculature
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3
Q

Fetus role in parturition

A

-provides a major input on the length of gestation

eg. Fetal hypothalamic-pituitary-adrenal (HPA) axis

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4
Q

Fetoplacental units role in parturition

A

-Fetal HPA and gonads, placenta, endometrium

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5
Q

Uterine musculatures role in parturition

A

**myometrium
Includes biochemical ripening of the cervix and transition from quiescent to powerfully coordinated contractile muscle

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6
Q

Parturition model

A

Multifactorial
-used ewe research for many years to determine that there are many factors involved in parturition

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7
Q

Pituitary and adrenal glands role in parturition

A

-Very small or no pituitary and/or adrenal glands resulted in prolonged pregnancies
**seen in cow herd and sheep

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8
Q

Plant teratogens role in pituitary and adrenal glands

A

-maternal ingestion of plant teratogens (alkyloids) can cause malformations of embryos (pituitary and adrenal glands)

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9
Q

What results in the activation of the fetal HPA axis during pregnancy?

A

Likely due to:
-development of critical synapses in hypothalamus
-hypothalamus responding to placental hormones (eg. estrogens)
-Fetal stressors (eg. BP, glucose)

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10
Q

Fetal sheep HPA axis activation

A

Increased fetal cortisol concentrations within the last 15-20 days of gestation
-Increased cortisol from increased fetal adrenal glands and in response of ACTH
-Increased ACTH occurs in response to arginine vasopressin and corticotropin releasing hormone (CRH) produced by placenta and hypothalamus

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11
Q

Building blocks of prostaglandins

A
  1. phospholipids become arachidonic acid
  2. AA become prostaglandin E2 (PGE2)
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12
Q

Fetal HPA axis prostaglandin synthesis

A

Increased fetal cortisol will effect intrauterine prostaglandin synthesis:

-Estrogen-independent pathway
1.Fetal cortisol stimulates trophoblasts to produce PGE2
2.PGE2 works with P450 hydroxlase to form C19 steroids (eg. Dehydroepiandrosterone)
3.Steroids and P450 aromatase form estrogen

-Estrogen-dependent pathway
1. Estrogen stimulates endometrial PGHS-II to produce PGF2alpha
2.PGF2alpha leads to uterine contractility

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13
Q

Pregnenolone use

A

Shift between using it for producing progesterone to producing estrogen

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14
Q

Ruminants (cow and goat) fetal HPA axis

A

-Progesterone is highly produced by the CL so PGF2alpha may also induce luteolysis

-Estradiol production stimulates production of Contractile associated proteins (CAPs)

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15
Q

Components of CAPs

A

-gap junction proteins
-oxytocin receptors
-prostaglandin receptors
-calcium channels

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16
Q

Estrogens role in parturition

A
  1. Stimulate cervical and vaginal mucus secretion for lubrication to aid in birth.
  2. Promotes cervical ripening
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17
Q

Prostaglandin effects on myometrium and cervix

A

Different receptors present in the tissues

1.PGE2 in myometrium (EP1 and EP2 receptors) leads to myometrial contractility BUT PGE2 in EP2 of cervix= cervical ripening

  1. PGF2alpha binding to FP in myometrium= myometrial contractility, but binding to EP4 in cervix= cervical ripening
18
Q

Ferguson’s Reflex

A
  1. Uterine contractions of parturition force fetus toward cervix and vagina
  2. stimulate pressure sensitive neurons in the cervix that will synapse with hypothalamus neurons
  3. Leads to increased oxytocin secretion and cycle of greater contractions with greater pressure on cervix (positive feedback)
19
Q

Oxytocin effects on uterus

A

Two actions:

  1. Oxytocin binds to receptors and increases intracellular Ca levels allowing for myosin phosphorylation and actin myosin binding= uterine contractions
  2. Oxytocin leads to increased PGF2alpha synthesis and therefore uterine contraction
20
Q

Myometrium contractile activation

A

Myometrium need to be electrically and metabolically coupled for power
>increase in gap junction production and communication just prior to and during labour
**when Cx43 gap junction gene removed, parturition is impaired

21
Q

Fetal growth induced uterine distension

A

Two signals:

  1. Growth of the fetus as a whole distends uterus and stimulates expression of CAPs that aid in parturition
    -Cx43 (GJ protein)
    -oxytocin receptors
    -prostaglandin receptors
  2. Primes the myometrial cells to properly adhere (through fibronectin) to one another to promote coordinated contractions
22
Q

Sow parturition differences

A

-Fetal participation initiating farrowing is not clear
-Estrogens are likely not involved in stimulating PG release (because exogenous estrogens do not induce farrowing)

23
Q

Mare parturition differences

A

-Maternal progesterone levels in last 3rd of pregnancy is low. The metabolites of progesterone and pregnenolone called progestagens are responsible for uterine quiescence
**progestagens in maternal plasma will decrease as the fetal cortisol increases

-Use fetal gonads for parturition

24
Q

Fetal gonad use in mares parturition

A

Parturition in mare requires the fetal gonads to supply androgens for estrogen biosynthesis
**more so than adrenal glands

-All means that they do not use progesterone or pregnenolone. Placenta lacks P450 C17 hydroxylase

25
Q

Dog parturition differences

A

-no fetal cortisol secretion data
-Involves a rapid decline in maternal progesterone prior to birth, coinciding with increased PGF2alpha release from placental trophoblasts.
*prostaglandins may not be luteolytic

-maternal oxytocin levels indicate it is not responsible for parturition

26
Q

Cat parturition differences

A

-Prostaglandin levels in plasma are unreported, wild cats have indicated increases towards parturition

-Estradiol levels peal 1 week before parturition and decline by labour

27
Q

Impact of endocrine changes on fetal maturation

A
  1. stimulate closure of ductus arteriosus and foramen ovale

2.maturation of fetal lungs
-production of alveolar surfactant (stimulated by fetal cortisol)
-reabsorption of fetal fluids by lungs stimulated by adrenaline

3.Glucose homeostasis
-accumulate in liver glycogen stores in late gestation stimulated by cortisol

  1. Maturation of thyroid gland
28
Q

Phases of parturition

A

Phase 0- quiescence
Phase 1- activation
Phase 2- Stimulation
Phase 3- Involution

29
Q

Quiescence

A

95% of gestation marked by myometrial quiescene and non-dilated cervix

30
Q

Activation phase

A

softening of cervix, myometrium becoming prepared for contractions with increased CAPs and uterotrophic factors

31
Q

Stimulation phase

A

-increased contractility
-large surges in prostaglandin and oxytocin released, dilatation of cervix, delivery of fetus

32
Q

Involution phase

A

-Afterbirth delivered.
-uterus and cervix begin to be remodeled back to non-pregnant stage

33
Q

When do pregnancy needs to be prevented?

A

-mismating
-twins
-risk to dam’s health

34
Q

Pregnancy termination in pigs

A

Terminated at any stage with PGF2alpha
*repeated injections may be needed

35
Q

Pregnancy termination in goats

A

-Terminated at any stage with PGF2alpha

36
Q

Pregnancy termination in cows

A

-Terminated from 4-100 days post ovulation with PGF2alpha
-since placenta contributes sufficient progesterone after 150 days until 270 days, need to use long acting corticosteroids and PGF2alpha

37
Q

Pregnancy termination in sheep

A

-Between day 4-12, PGF2alpha is effective

-Day 12-21 and days 25-40 are resistant, possibly due to IFN-tau

-Greater than day 45- placenta progesterone production increases, so progesterone antagonists or corticosteroids needed to terminate

38
Q

Cat pregnancy termination

A

-intramuscular injection of estradiol cypionate within 40 h of mating can prevent pregnancy

-PGF2alpha effective for abortion

-Aglepristone effective in mid-pregnancy

39
Q

Dog pregnancy termination

A

-tactical use of estrogens within 5 days of mating inhibits transport of zygotes from oviduct to uterine horns

-PGF2alpha can be used from day 10-14, but progesterone receptor antagonists are most effective and acceptable for terminations

40
Q

Horse pregnancy termination

A

Early on until day 35 (before endometrial cup)- administer PGF2alpha or an analogue to induce luteolysis
**treat for 10-15 days

41
Q

Horse twin pregnancies

A

-surgical removal of fetus (high risk to remaining fetus and mare)
-ultrasound guided injection of fetus with procaine penicillin G into fetal thorax or abdomen to induce fetal death
**success rates 30-60%

Animal Production (17 decks)

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