Reproduction Exam 4

What is syngamy?

when male and female pronuclei fuse

When does syngamy occur?

after completion of DNA replication

What is syngamy mediated by?

cytoskeleton components

DNA is replicating but ______ is not

cytoplasm

_________ is happening at early embryogenesis but not cytokinesis

mitotic division

What happens at cellular division?

cells get smaller but there's more DNA

Why is cellular division more efficient?

only putting energy in DNA replication

What is a blastomere?

each individual cell in an embryo (8-cell embryo = 8 blastomeres)

What is a totipotent cell?

cell has capability to turn into any type of cell necessary to develop into whatever fetus needs

What is the challenge with cloning?

taking an already differentiated cell and reverting it back to being totipotent

How long does a cell stay totipotent in an early embryo?

about 4-5 days

What is compaction?

when blastomeres stick together

What happens after compaction?

embryo turns into a morula

What is a morula?

embryo where you can't count the number of cells anymore

During compaction, how do cells stick together?

gap junctions and tight junctions

Cells _______ create gap junctions which turn into cells that are part of the ________

inside; fetus inner cell mass

Cells ________ create tight junctions which turn into cells that are part of the _________

outside; placenta/trophoblast

What happens when cells are pluripotent?

cells have made at least 1 decision but not a final decision
cells can still become any cell type in the fetus or placenta
no longer totipotent and there's no going back

What's the first decision cells make in an early embryo?

whether to be a part of the fetus or placenta

What is the consequence of developing junctions?

embryo has to hatch out of the zp

How does the embryo hatch out of the zp?

via tight junctions

Sodium pumps going into the embryo causes what?

fluid accumulation
inner cell mass gets squished to side by the fluid pocket

What is a blastocoele?

fluid pocket

Presence of a blastocoele makes the embryo a __________

blastocyst

Why is an embryo becoming a blastocyst a milestone of development?

can ID which embryos will/won't make it this far to have right amount of surrogate mothers in embryo transfer

Where is the embryo when it's a morula or blastocyst?

in uterus

In embryo transfer, we collect on day ____ in sheep/goats or day ______ in cows

6; 7

Why is it harder to collect embryos on day 3?

embryo is still in the oviduct and we flush the uterus not the oviduct
would have to do surgery to flush oviduct

Why not collect embryos on day 10?

zp is broken which increases chance of damage to embryo which decreases pregnancy rates

When or how many cells dying in an embryo indicates what?

how successful a pregnancy will be

In a 2-cell embryo, 1 blastomere has _______ edges and the other has ________ edges

smooth; rough

What are the embryo grades?

1 = > 85% living cells
2 = 50-84% living cells
3 = 35-49%

If blastomere is lost early, pregnancy rates _______

decrease significantly

What is implantation?

when embryo implants itself into the uterus

Implantation is different in humans/rats because the blastocyst ____________

buries itself in the endometrium

Invasive implantation indicates how invasive the _______ is

placenta

Humans and rats have a __________ placenta

hemochorial

__________ is a transient structure in the placenta where gametes come from

yolk sac

The yolk sac establishes ___________ cells

primordial germ

The amnion surrounds the ______ and is what ruptures when ________

fetus; water breaks

What does the allantois do?

stores extra nutrition to help the fetus grow

Which species does not have an allantois? Which ones do?

humans don't
livestock have both allantois and amnion

What's the role of progesterone in supporting embryonic development?

tested in sheep and sheep treated with progesterone had bigger embryos and elongation occurred earlier (day 12)

When does elongation usually occur?

day 14

Increased progesterone causes what?

increased uterine secretion = increased embryonic development

Downside of increased progesterone is?

decreased estrus cycle from 16.5 days to 14.5 days

Which species go through elongation and which don't?

ruminants and pigs do
humans and horses don't

Why do embryos elongate?

to increase surface area for more nutrients

Ruminants either _____ or _____ the corpus luteum

kill or maintain

What happens if there's no embryo?

oxytocin is released which causes pulses of PGF2alpha to induce luteolysis

How does the embryo stop the release of oxytocin in ruminants?

embryo produces interferon tau to maintain pregnancy

Which stage of embryo produces IFNT?

elongated embryo

What helps spread IFNT signal so uterus can get maximum signaling?

increased surface area from elongated embryo

Failure of what can cause early embryo death?

elongation

IFNT binds to its receptors on the ________ and blocks ______ receptors so it doesn't matter if ________ is present because it can't bind to its receptors

endometrium; oxytocin; oxytocin

__________ cells fuse with cells from the mom with maternal ________

binucleated; epithelium

What do binucleated cells initiate?

formation of placenta

What does the elongated conceptus in pigs produce to prevent luteolysis?

estrogen

What does estrogen do to prevent luteolysis?

binds to uterine epithelium so PGF2alpha goes out apically so it changes direction of hormone travel causing outward release of PGF2alpha

What is the theory called for the pigs maternal recognition?

endocrine/exocrine theory of maternal recognition in pigs

_______ embryos elongate faster than ruminants

pig

Why do pig embryos elongate faster than ruminants?

litter bearing so there's competition to stake a bigger claim to to be bigger and have more placenta

In pigs what activates STAT1 only in the uterus?

interferon gamma

Horses don't have elongation so how does the embryo signal to the mom?

embryo migrates within the uterus and emits signal

What is the fetal signal in humans for maternal recognition?

human chorionic gonadotropin (hCG)

What are the benefits from embryo transfer?

identifying an elite donor, get a lot of oocytes from her, put them in recipients, allowing for more offspring from this one cow

How does superovulation work?

overrules inhibin by giving FSH to get a lot of dominant follicles

What product is used to give FSH?

folltropin-V

How often are FSH injections given?

4 days, twice daily

What is a limiting factor of ET especially for non-domesticated species?

multiple times going through a chute

Dosage of FSH _________ because of overstimulation which causes poor ________

decreases; oocyte quality

Why do we decrease FSH dosage?

to allow follicles to transition from being FSH dependent to LH dependent because LH allows for maturation

IVF occurs in a _______ and you get the oocyte via ________

petri dish; ovum pick up

How do they do ovum pick up?

aspirated oocytes via ultrasound and aspiration needle

Once cultured embryos reach day ______ or ________ it goes into the recipient

7; blastocyst

What is the old method of IVF?

superovulate donor then right before ovulation, aspirate

Why don't they do the IVF in cattle?

expensive and animal becomes refractory

What is the new method of IVF?

no hormones are given and once follicles reach tertiary stage, aspirate/collect immature oocytes, 24 hours to mature oocytes, then fertilize

What are the benefits of the new method of IVF?

can aspirate every 10 days without hormones allows for more oocytes over long period of time
good in subspecies like goats because you can use 1 straw of semen for 10 different does' oocytes

What are some setbacks of the new method of IVF?

efficiency is lower but amount of aspirating cancels it out
makes a lot of low quality embryos

What are the 2 methods of cryopreservation?

1. controlled time/temp descent displace
2. vitrification

What's wrong/beneficial with controlled time/temp descent-displace?

takes a long time, ice crystal damage
pro-exposure to toxic cryoprotectants is reduced

What's wrong/beneficial with vitrification?

high levels of cryoprotectants are needed which can be toxic
no ice crystal damage

Vitrification came from _______ because you can recognize this specie's embryo due to its dark color and difficulty freezing from ________

pigs; lipids

Embryo splitting causes ______ pregnancy rates and helps with research because it can eliminate the _______ component

decreased; genetic

Which stage is the best for embryo splitting and why?

morula because ICM is in the middle of the embryo

Why is it hard to split at the blastocyst stage?

have to split the embryo between ICM but it's hard to ID at blastocyst stage

At what stage can we remove the blastomere and ID genetics and what does this help with?

stage 8
helps to ID genetic abnormalities

What is the old method for GMOs and what does it do?

transgenesis via viral vector incorporates gene of interest into viral vector, infects new cells with the viral vector using HIV virus

What is the new version for GMOs and what does it do?

CRISPR can go in and edit genes

Placenta actively _________ in the mom, humans have lipid ______ while in livestock species lipid has to be ________

metabolizes; transport; synthesized

What are the functions of the placenta?

O2/CO2/nutrient transport
metabolism
removal of toxins and waste
endocrine organ
immunological (masks fetus from mom's immune system)
suppression of fetal cortisol exposure

What are the by products of metabolism that can build up if placenta doesn't transport efficiently?

urea, ammonia

Placenta is an ________ organ mainly for _______ gland development for hormones _______ and _______

endocrine; mammary; prolactin; lactogens

What can the placenta metabolize?

synthesis of cholesterol, fatty acids, glycogen, amino acids

Placenta can maintain pregnancy in sheep but not ________ by providing enough _________

goats; progesterone

Almost all transport is _______ in placenta. __________ consumed transport is where 10 comes from mom and 5 goes to placenta while 5 goes to fetus. __________ transport is where something goes into placenta, placenta transforms it into something else for fetus

active; partially; metabolized

What can transport across placenta?

water, ions, amino acids, glucose, vitamins, small hormones, many drugs/pharmaceuticals/toxins, viruses

What cannot be transported across the placenta?

immunoglobulins, lipids, large peptide hormones, proteins

How does the fetus get immunoglobulins and protein?

colostrum
placenta can chop up proteins from mom and turn it into amino acids so the baby can make protein from those