Maternal Recognition of Pregnancy, Placentation, Pregnancy, and partrition

What is the signal of maternal recognition in pigs?

Estradiol

Cattle have what type of placental classification?

Cattle have a Cotyledonary-Epitheliochorial placenta

What is the signal of maternal recognition in pigs?

Estradiol

Cattle have what type of placental classification?

Cattle have a Cotyledonary-Epitheliochorial placenta

Pigs have what type of placental classification?

Pigs have a diffuse-Epitheliochorial type placental classification

What are the precursor cells that will develop into the chorion?

Mesoderm and trophectoderm

What are the precursor cells that will develop into the amnion?

Mesoderm

T/F: The process of placentation is more invasive in women than domestic species

True: placentation is more invasive in women than domestic species

T/F: The process of placentation is more invasive in rodents than domestic species

True: Placentation is more invasive in rodents than domestic species

What type of placenta do dogs have?

Dogs have Endotheliochorial-Zonary placenta type

Within the placenta of a mid-pregnant ewe you would observe cholesterol being converted into pregnenolone by?

Cytochrome P450 side chain cleavage (scc) will convert cholesterol to pregnenolone, and 3 Beta-hydroxysteroid dehydrogenase (3B-HSD) will convert pregnenolone to progesterone

During parturition, what type of signal is sent to the posterior pituitary from the cervix?

The cervix sends oxytocin and pressure receptors

During parturition, describe 3 effects of estradiol on the reproductive tract of mom:

1. Enhances secretion to lubricate birth canal

2. Increase OT-R (oxytocin receptors)

3. Helps assist a signal to cause contractions in the myometrium

What is corticotropin releasing hormone, where is it produced, and what endocrine gland does it target?

Corticotropin releasing hormone: Stimulates synthesis and secretion of cortisol

Produced: Released form hypothalamus, stimulating anterior pituitary to release ACTH

Endocrine gland targeted: Adrenal Cortex

At the onset of parturition, identify one enzyme that you would expect to differ in the placenta during the shift in steroidgensis

Progesterone is the major steroid produced by the placenta. During parturition, progesterone will decrease. The enzyme 3B-HSD converts pregneolone to progesterone, so this enzyme may be impacted by parturition.

What occurs to the myometrium when progesterone decreases?

A decrease in P4 during pregnancy will lift the block on myometrial activity causing contractions

What are the five cellular mechanisms that mediate the transfer of materials from the blood or extracellular space across the trophoblast?

1. Simple Diffusion

2. Restricted diffusion

3. Facilitated diffusion

4. Active transport

5. Receptor-mediated endocytosis

Simple Diffusion

Lipophilic molecules across the trophoblast (oxygen)

Restricted diffusion

Restricted diffusion of hydrophilic molecules through aqueous channels (mannitol: Sugar molecule). Size of molecule can also be impacted by this.

Facilitated diffusion

Requires a transporter protein (D-glucose). Goes from high concentration to low

Active transport

Requires a transporter protein and goes from LOW to HIGH concentration.

Ex: Amino acids- important for muscle growth!

Receptor-mediated endocytosis

Receptor-mediated endocytosis: A cellular process where cells import specific molecules by binding them to cell surface receptors, forming a vesicle to bring molecules inside

Immunoglobulins (antibodies): Proteins produced by the immune system to fight infections

What are some important substances transported between mother and fetus?

Glucose, lactose, amino acids, lipids, ions, calcium, phosphorous, magnesium, trace minerals, proteins, respiratory gases, various drugs

What are some functions of estradiol?

1. Support growth of follicles

2. Induce expression of heat behavior

3. Induce ovulation

4. Relax the cervix

5. Induce mucus production by the cervix

6. Contractions in uterus and oviduct to direct sperm to the oocyte

What are some functions of progesterone?

1. Prevents expression of heat behavior

2. Prevents ovulation

3. Closes the cervix

4. Prevents contractions of the uterus and oviduct

5. Supports pregnancy

The growing fetus will develop within two layers of fetal membranes. What are these fluid-filled membranes?

Amnion (adjacent to the membrane) and Chorioallantois (outside the amnion)

Where does placental attachment occur?

Along the outer surface of the chorioallantois

In pigs, what is the placental attachment the is attached along the entire fetal membrane?

In pigs, the attachment is called “diffuse”

In ruminants, attachment occurs at specific sites called _______, and have __________ placental attachment

In ruminants, attachment occurs at specific sites called cotyledons, and have Cotyledonary placental attachment

In ruminants, how do cotyledons of the chorioallantois attach to the uterus?

The cotyledons of the chorioallantois attach to caruncles along the inner surface of the uterus

When the fetus is large enough, pressure of the fetus on the cervix releases what hormone?

Oxytocin is released due to pressure against the cervix and will induce contractions, further pressing fetus again cervix=positive feedback cycle

The germ layer endoderm will give rise to what major types of tissues?

1. Digestive system

2. Respiratory system

3. Endocrine glands

The germ layer mesoderm will give rise to what major types of tissues?

1. Skeleton

2. Muscle

3. Heart and blood vessels

4. Reproductive organs

The germ layer ectoderm will give rise to what major types of tissues?

1. Nervous system

2. Skin

3. Hair

In order for pregnancy to advance beyond the blastocyst stage, the conceptus must provide a signal to maintain maternal production of ___________ and form a placenta with the maternal uterus

The conceptus must provide a signal to maintain maternal production of progesterone

What is the major pre-requisite for maternal recognition of pregnancy and implantation of the embryo into the uterus?

Development of the trophectoderm

How does the maternal recognition of pregnancy signals prevent/delay luteolysis?

The signal of maternal recognition of pregnancy stops luteolysis by interfering with prostaglandin-induced regression of the CL OR by boosting the luteotropic signal

What are the cells of the embryo that send signals to uterine epithelial cells to prevent luteolysis?

Trophoblast

What is the peptide produced by trophoblasts that signal the uterus to prevent luteolysis in ewes?

The peptide signal ovine interferon (oIFn-t) produced by the trophoblast will be detected by the uterus to prevent luteolysis

What is the peptide produced by trophoblasts that signal the uterus to prevent luteolysis in cows?

The pregnancy-recognition signal in cows is bovine interferon (bIFN-t)

Explain how the estradiol signal in swine prevents luteolysis?

Estradiol produced by the trophoblast acts on endometrial cells to redirect release of prostaglandins from the mucosa into the lumen of the uterus , thereby reducing uptake of the luteolysin by blood

Describe how the signal interferon-t in ewes and cows prevent luteolysis

Trophoblast of the embryo produces interferon-t and acts on uterine endometrial cells to black expression of oxytocin receptors (OT-R) which are required for oxytocin to induce release of PGF2a, the luteolytic hormone

What is the equine blastocyst capsule that causes the signal of maternal recognition to be unknown?

Elastic glycocalyx

What is the secondary messenger in the uterine endometrial cell that will cause the blocking of estrogen stimulation of oxytocin receptors when in contact with IFN-t?

IFN-t inhibits ERa, thus blocking the estrogen stimulation of oxytocin receptors

What are the 3 ways interferon-tau exert its antiluteolytic effects:

1. Inhibiting effects of estrogen and/or progesterone necessary for synthesis of endometrial receptors for oxytocin

2. Inhibiting endometrial synthesis and/or recycling of OT receptors directly

3. Inducing the endometrium to synthesize an inhibitor of an enzyme(s) necessary for synthesis of PGF2alpha

What hormone and enzyme activates PGF2alpha?

Hormone: Oxytocin is released from the posterior pituitary activated by E2 to target OT-R on the endometrium (endometrial cells)

Enzyme: Cox-2 converts arachidonic acid to PGF2alpha

What uterine layer causes contractions?

Myometrium

Though the signal of maternal recognition is unknown in mares, what are the hypothesized signals?

The hypothesized signal in mares is E2 and coceptus secretory proteins (CSP’s)

Why is luteal regression the default mechanism when theire is no embryonic signal?

Lutealization is a default mechanism since it saves energy and reproductive efficiency

What part of the embryonic membrane is avascular?

The chorion is avascular

How is the allantochorion created?

The allantois expands and eventually fuses with the chorion to form the allantochorion

What are all 6 layers of the epitheliochorial placenta type based on maternal/fetal barrier?

1. Fetal endothelium

2. Fetal connective tissue (includes basement membrane of chorion)

3. Fetal chorionic epithelium

4. Maternal endometrial epithelium

5. Maternal connective tissue (Includes the basement membrane of endometrium)

6. Maternal endothelium

Name all 4 species that have an epitheliochorial maternal-fetal barrier type placenta:

1. Cow

2. Ewe (sheep)

3. Mare (horse)

4. Pig

Name the 2 species that have a endotheliochorial maternal-fetal barrier type placenta

1. dogs

2. cats

What are the 4 layers of the endotheliochorial placental classification of the maternal/fetal barrier?

1. Fetal endothelium

2. Fetal connective tissue

3. Fetal chorionic epithelium

4. Maternal endothelium

What the 3 layers of the hemochorial placenta classification of the maternal-fetal barrier?

1. Fetal endothelium

2. Fetal connective tissue including the basement membrane of the chorion

3. Fetal chorionic epithelium

During partition, the increase of PGF2alpha does what 2 things?

1. Luteal regression (decreases P4 further)

2. Relaxin (hormone) release from CL (relaxation of ligaments in pelvis, enlarging pelvic opening)

What are the impacts of the increase of E2 during parturition?

• Enhances secretion to lubricate the birth canal (cervical and vaginal)

• Increases OT and PGF2a (FP) receptors

In addition to PGF2a, what do prostaglandins do to assist in parturition?

The enzyme cox-2 converts arachidonic acid to prostaglandins to help assist in luteal regression and contractions. PGF2a binds to FP on the myometrium causing smooth muscle contractions