Lecture 10: Pregnancy recognition (Pozor)

Question 0

what is a single-celled embryo called?

Answer 0

zygote

Question 1

mechanisms necessary to establish pregnancy (7)

Answer 1

1. successful fertilization
2. cleavage - forming an embryo
3. “descent” of an embryo to the uterus
4. maternal recognition of pregnancy
5. implantation
6. organogenesis and growth
7. placentation

Question 2

what is the conceptus called during early embryonic stage?

Answer 2

embryo

Question 3

what is the conceptus called during the pre-implantation stage?

Answer 3

embryo proper and extraembryonic membranes

Question 4

what is the conceptus called during the post-implantation phase

Answer 4

fetus and placenta

Question 5

definition of embryo

Answer 5

it has not acquired an anatomical form which is readily recognizable in appearance as a member of the specific species

Question 6

definition of a fetus

Answer 6

a potential offspring that is still within the uterus, but is generally recognizable as a member of a given species

Question 7

when does maternal recognition of pregnancy typically occur?

Answer 7

10 - 16 days post ovulation

Question 8

what is the vital part of maternal recognition of pregnancy

Answer 8

the conceptus must provide a timely biochemical signal or a pregnancy will terminate

Question 9

effect of prostaglandin (PGF2-alpha) duringluetolysis in the ruminant

Answer 9

• its responsible for luteolysis
• and supplied by endometrium
• necessary factors: oxytocin receptors on endometrial cells, synthesis and release of luteal oxytocin from the ovary

Question 10

where oxytocin binding receptors located in the ruminant?

Answer 10

in the uterus

Question 11

what is the effect of estrogen during luteolysis in the ruminant?

Answer 11

estrogen upregulates oxytocin receptor synthesis

Question 12

what is the effect of progesterone in early diestrous on oxytocin receptors in the ruminant?

Answer 12

it prevents oxytocin receptor synthesis

Question 13

what is the effect of progesterone in LATE diestrus on oxytocin receptor synthesis in the ruminant?

Answer 13

progesterone loses the ability to block oxytocin receptor synthesis in late diestrus

Question 14

what is the effect of oxytocin binding to its receptor during late diestrus in the ruminant

Answer 14

it stimulates prostaglandin release which ultimately causes the CL to lyse

Question 15

what secretes prostaglandin?

Answer 15

endometrial cells

Question 16

how does prostaglandin reach the ovary to lyse the CL?

Answer 16

• delivered to the ovary via the ovarian artery
  via:
  countercurrent exchange mechanism: cow, ewe, sow
  systemic circulation: mare

Question 17

Interferon properties (4)

Answer 17

1. antiviral
2. antiproliferative
3. immunomodulatory
4. antiluteolytic

Question 18

effect of INF-tau in the ruminant

Answer 18

decreases estrogen receptors - suppression of estrogen driven up-regulation of oxytocin receptors

Question 19

how is luteolysis blocked in swine?

Answer 19

1. blastocyst - produces estradiol
2. estradiol causes rerouting of PGF2alpha
3. PGF2alpha is secreted into the uterine lumen and is destroyed
4. luteolysis does not occur

sufficient number of conceptuses (2 per horn) are necessary to block luteolysis!!

Question 20

how is luteolysis blocked in the mare?

Answer 20

embryonic mobility is necessary (up to 14 days after ovulation)

• no interferon-like factors involved
• equine embryo synthesizes and releases various facotrs
• oxytocin receptors greatly suppressed - similar as in ruminants

Question 21

maternal recognition in the bitch and queen unique

Answer 21

NO SIGNAL is needed for pregnancy recognition in the bitch or in the queen.
- the CL is maintained for the duration of normal gestation regardless of pregnancy status