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ANIMAL PRODUCTION - Reproduction > 11 – Establishment of Pregnancy > Flashcards

11 – Establishment of Pregnancy Flashcards

1
Q

Pregnancy

A
  • Period between fertilization and birth
  • *driven by development of LIVE BIRTH (viviparity) on to mammalian biology
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2
Q

Pregnancy involves main features of

A
  • Internal fertilization (ex. NOT fish)
  • Retention of fertilized egg, embryo, fetus WITHIN female reproductive tract
  • Direct maternal nourishment
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3
Q

Monotremes

A
  • Do NOT have a LIVE birth
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4
Q

Marsupials

A
  • Fetus is born LIVE
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5
Q

Advantages of pregnancy

A
  • Protection from
    o Thermal extremes
    o Osmotic stress
    o Predation
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6
Q

Disadvantages of pregnancy

A
  • Increased maternal energy use
  • Reduced maternal mobility and FECUNDITY
  • Risk of injury (mother and fetus) from immunological and inflammatory responses in utero
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7
Q

Hatching and blastocyst expansion

A
  • Embryos (especially some domestic species) change shape and size
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8
Q

2 groups of mammals in terms of development within uterus and implantation

A
  1. Pre-attachment period within uterus is long (ex. mostly domestic animals)
  2. Blastocyst implants quickly after entering the uterus (ex. primates)
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9
Q

Pre-attachment period within uterus is long (ex. mostly domestic animals)

A
  • Extensive extra-embryonic membrane develop (amnion, allantois and chorion)
  • Maternal recognition of pregnancy signal is produced and signal must occur BEFORE attachment period to uterus
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10
Q

Blastocyst implants quickly after entering the uterus (ex. primates)

A
  • Develop of extra-embryonic membranes occurs AFTER implantation
  • *MRP signal rapidly increased AFTER implantation
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11
Q

Dog (‘attachment’)

A
  • 7-10 days for zygote to reach uterine tubes
  • Intrauterine migration from day 12-17=evenly spaced throughout each horn
  • Fixation and implantation at day 17
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12
Q

Cat (‘attachment’)

A
  • Blastocysts appear to reach uterus by day 6
  • Ellipsoid after that and hatch from zona by day 11
  • Intrauterine migration and begin implantation by day 12
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13
Q

Ruminants and pig: elongation

A
  • Become tubular and then FILAMENTOUS
  • Ex. pigs: by day 12-25 filamentous structure=1m long
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14
Q

Elongation of any conceptus provides

A
  • Maximum surface area of contact between trophectoderm/trophoblast AND maternal uterine epithelium
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15
Q

Ruminant elongated embryo can extend into

A
  • The non-pregnant uterine horn
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16
Q

Horses: elongation

A
  • Do NOT elongate=remains spherical
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17
Q

Histotrophe

A
  • Products from it come from the endometrial glands
  • Nourish embryo during pre-implantation period
    o Survival, development, production of MRP factors, implantation and placentation
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18
Q

What are the secretory products of the endometrial glands?

A
  • Enzymes
  • GFs
  • Cytokines
  • Hormones transported into lumen
  • Transport proteins (ex. for glucose)
  • Nutrients (ex. AA, glucose)
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19
Q

Endometrial glands undergo substantial _____during gestation

A
  • Hyperplasia AND hypertrophy
    o Increase SA for maximum production of histotrophe
  • Ex. ruminants, horse (less in primates)
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20
Q

Luteolysis must be prevented

A
  • In order to establish a pregnancy
    o *don’t want CL to be lost or broken down
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21
Q

Maternal recognition of pregnancy (MRP)

A
  • Dogs and cats: luteal phase is close to duration of actual gestation=no signal required from conceptus
  • Others: luteal phase ends before embryo normally implants=need a signal to prolong a single or number of CL
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22
Q

2 types of recognition signalling from conceptus to maternal system

A
  • Luteotrophic
  • Anti-luteotrophic (PRIMARY one we usually talk about)
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23
Q

Luteotrophic

A
  • A hormone(s) act on CL to maintain luteal function
24
Q

Anti-luteotrophic

A
  • A hormone(s) to prevent uterine release of luteolytic-promoting substances
  • Ex. prostaglandin F2-alpha
25
Signalling from conceptus to maternal system result in maintenance of CL to produce progesterone to:
- Support secretory functions of endometrium, embryonic development, implantation, placentation - Negative feedback on hypothalamus and A. pituitary to INHIBIT follicular development (ovulation) - Prevention of return to estrus in polyestrous species
26
Day of attachment is ALWAYS going to be
- After the mother has got the recognition signal - *if no signal or recognition=attachment will NOT occur
27
What prevents luteolysis in cow, ewe and goat?
- Interferon (IFN) Tau - Acts on endometrial cells of uterus and inhibits oxytocin receptor production o Oxytocin now WONT stimulate pulsatile PGF2alpha synthesis - Increases SECRETION of proteins from endometrial glands
28
Physiological mechanism: paracrine effects on endometrium in ewe and goat
- IFN-tau binds to own receptor and produces an INHIBITORY protein that blocks the estrogen signalling o Blocks the production of oxytocin receptor=NO or limited production of PGF2alpha
29
Physiological mechanism: paracrine effects on endometrium in cow
- IFN-tau blocks the oxytocin receptor DIRECTLY o NO or limited production of PGF2alpha
30
Physiological mechanism: endocrine (IFN Tau)
- Can be transported from utero-ovarian vein to ovarian artery and then to CL - *sustain CL function to produce P4 - *prevent lytic events of any PGF2alpha on CL
31
IFN Tau can have paracrine effects on endometrium to stimulate
- Conceptus elongation o Production of small cytokines o Induce expression of genes in endometrium for uterine attachment o Stimulate endometrial gland development and function
32
Non-pregnant sow
- Oxytocin from endometrium, P. pituitary and CL promote PGF2alpha production in endometrium=can reach the ovary and initiate luteolysis
33
Pregnant sow
- Estrogen=MPR signal from conceptus o Must be secreted between days 11-15 - Estradiol re-routes PGF2alpha to uterine lumen=destroyed=PREVENTS LUTEOLYSIS
34
Estradiol in sow (from conceptus between day 15-25 of gestation)
- Induces expression of genes in uterus responsible for conceptus attachment - Stimulate production of endometrial prolactin receptors - *promote uterine gland development and INCREASE ion and nutrient transport from conceptus - Promote immune response (TOLERANCE) of progesterone-primed endometrium to implantation
35
Osteopontin (OPN)
- Secreted by uterine luminal epithelium - Responsible for endometrial remodelling and conceptus adhesion - ‘glue’
36
Estradiol from conceptus stimulates uterine epithelia to secrete
- Prostaglandin E2 (PGE2)
37
PGE2
- Reaches CL from utero-ovarian vein to ovarian artery (like Tau in ruminants) - *provides luteoprotective role in CL=maintains CL function
38
MRP signal in equine: unknown
- Day 6.5: trophectoderm of blastocyst begins to secrete a GLYCOPROTEIN containing capsule beneath the ZP - Capsule remains until day 22 of pregnancy
39
Importance of equine conceptus
- If remove conceptus at various points=lengthen time required to return to estrus - Embryo does produce something that is important o Estradiol and estrone (not really involved in CL lifespan) - PGF2 alpha is blocked (due to COX2 activity) - NO INF secretion
40
During pre-attachment phase in equine
- Horse conceptus is moved over endometrial surface by UTERINE CONTRACTIONS (12-14 times a day) o Not elongations - Endometrial production of PGF2alpha is significantly REDUCED
41
Migration of horse embryo is critical
- Capsule prevents elongation - NEED the movement due to no increase in SA - *allows for maternal recognition
42
Attachment or implantation
- Movement and transient attachment followed by FIRM adhesion o Trophectoderm to uterine luminal and superficial glandular epithelium
43
Phase 1 of attachment
- Shedding of ZP=hatching
44
Phase 2 of attachment
- Pre-contact period - Blastocysts migrate and undergo orientation w/o contact with epithelia - Initiate pregnancy recognition signalling
45
Phase 3 of attachment
- Trophectoderm associates with endometrial epithelium for UNSTABLE adhesion - Ruminants: microvilli development begins
46
Phase 4 of attachment
- Trophectoderm FIRMLY adheres to luminal epithelium - Some: attachment to superficial glandular epithelium
47
Phase 5 of attachment (carnivores, primates and rodents)
- INVASIVE implantation through uterine luminal epithelium into uterine stroma
48
Uterine receptivity represents the
- Interactions between the developmentally competent conceptus and uterine endometrium
49
Uterine receptivity is the
- Restricted period of the uterine cycle o Pre-contact o Apposition and firm adhesion and invasion - *driven by actions of progesterone, estrogens and IFN-tau (ruminants) - **loss of mucins from luminal epithelial cells of the endometrium - Conceptus has similar receptors and ECM secretion for binding to endometrium
50
Mucins
- Anti-adhesive cell surface glycoproteins
51
Loss of mucins
- ‘unmasks’ surface adhesion molecules on endometrium - Selectins - Integrins
52
Selectins (surface adhesion molecules on endometrium)
- Low affinity contacts - For initial attachment of the conceptus
53
Integrins (surface adhesion molecules on endometrium)
- Higher affinity contacts - *AND MATERNAL ECM (osteopontin, fibronectin)=stable adhesion of conceptus
54
Clinical relevance: pregnancy loss
- High rate of pregnancy loss=decreased reproductive performance
55
What are the 2 critical periods that are responsible for majority of pregnancy losses (dairy cattle)
- From fertilization to blastocyst development (10-50%) - MRP, conceptus elongation, uterine receptivity (20%)
56
Beef cattle clinical relevance
- fertilization (50%) - MRP (16%) - after attachment (<6%) *4/5 pregnancies are lost without even realizing you were pregnant

ANIMAL PRODUCTION - Reproduction (17 decks)

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