Reproductive Endocrinology II

Question 1

At 6 weeks gestation PGCs reach the _____ and proliferate to form ______.

Answer 1

gonadal ridge, oogonia.

Question 2

When do some oogonia leave the mitotic pool and enter meiosis (to become “primary oocytes”)?

Answer 2

10-12 weeks.

Question 3

Primary oocytes are….

Answer 3

Arrested in prophase of meiosis I, and will remain arrested until recruited during an ovarian cycle (after puberty).

Question 4

At 20 weeks gestation there are….

Answer 4

6-7 million germ cells.

Question 5

At birth the number of germ cells has decreased to….

Answer 5

1-2 million.

There is no proliferation of oocytes after birth!

Question 6

By puberty the number of germ cells has decreased to…

Answer 6

300,000 to 400,000.

Question 7

Over the life of a woman only ______ oocytes will reach the mature (Graffian) follicle stage.

Answer 7

400-500.

Question 8

The oocyte develops within the _______.

Answer 8

Ovarian follicle.

Question 9

What are the two major period of development for oocytes?

Answer 9

1) Preantral / early antral (~300 days)
2) Antral (~40 days)

*Selection & Maturation (~20 days; occurs during the ovarian / menstrual cycle)

Question 10

What are the 3 phases of the ovarian cycle and describe them.

Answer 10

1) Follicular Phase: the follicle grows and oocyte develops inside the follicle.
2) Ovulation: the follicle ruptures and the oocyte is released into fallopian tube.
3) Luteal Phase: the ovulated follicle forms the “corpus luteum.”

Question 11

Menstrual is for ______.

Describe this type of ovarian cycle.

Answer 11

“primates.”

-It involves a period of menses; and the females are always sexually receptive.

Question 12

Estrous is for _______.

Describe this type of ovarian cycle.

Answer 12

“most other mammals.”

-There is no period of menses; and females are receptive only during period of estrus.

Question 13

Where is Inhibin B derived from?

Where is Inhibin A derived from?

Answer 13

• B ~> is derived from the developing ovarian follicle

- A ~> is derived from the corpus luteum.

Question 14

What do Inhibin B & A do? (BUT… When do they act?)

Answer 14

They suppress FSH secretion.

• Inhibin B acts during the mid-to-late follicular phase.
• Inhibin A acts during the luteal phase. (when pregnancy is possible)

Question 15

What happens right between (the gap) the follicular phase and the luteal phase?

Answer 15

There is a spike in LH to stimulate ovulation (‘ejection’ of the oocyte).

Question 16

When does progesterone rise during the menstrual cycle? (Why?)

Answer 16

During the late follicular phase.

*To promote thickening of the endometrium and ready zygote for implantation

Question 17

When does estradiol (NOT ESTROGEN) rise during the menstrual cycle? (Why?)

Answer 17

During the luteal phase. (It, along with intermediate levels of progesterone, tries to ready the womb for ‘implantation’)

Question 18

What do FSH and LH stimulate during the follicular cycle?

Answer 18

They stimulate the follicle to grow!

Question 19

What does progesterone production (by the corpus luteum) serve to do?

Answer 19

1) Inhibit LH secretion so that another cycle will not begin.
2) Stimulate the uterus to prepare it for implantation of the zygote.

Question 20

During the 2nd trimester progesterone production by the corpus luteum regresses, what replaces it?

Answer 20

Progesterone production by the placenta. This is also when miscarriages can happen the most!

Question 21

What is luteolysis?

Answer 21

The degeneration of the corpus luteum. (This forms ‘scar tissue’ inside the ovary)

Question 22

What causes luteolysis in 1) domestic animals 2) primates?

Answer 22

1) Prostaglandin F2α (produced by the uterus)

2) Corpus luteum which makes a luteolytic estrogen (estrone).

Question 23

Some birds and reptiles…

Even though many are ‘induced ovulates’

Answer 23

…Exhibit estrus behavior (sexual behavior that appears to be correlated with follicular development). Not a typical ‘estrous cycle.’

Question 24

What is vitellogenesis?

*What stimulates it?

Answer 24

A period of yolk production that is cyclical only insofar as ovulation induces another cycle.

*Estrogen.

Question 25

'Primordial follicles' are ______ to grow and develop into ________.

Answer 25

recruited, primary follicles.

Question 26

Where does the oocyte develop?

Answer 26

Within the ovarian follicle.

Question 27

In bird and mammals 'recruitment' is ___________. | So subsequent development depends on _________.

Answer 27

homone-independent, gonadotropins.

Question 28

How long does it take the ovarian follicle to develop to the point where hormones influence its growth and function?

Answer 28

One year.

Question 29

What are the two major periods of development of the ovarian follicle?

Answer 29

1) Preantral / early astral: gonadotropin independent ~ 300 days 2) Antral: gonadotropin dependent ~ 40 days

Question 30

When does 'selection' occur in the ovarian follicle's development?

Answer 30

Mid-late luteal phase. *This makes sense. The eggs are 'selected' during menstruation.

Question 31

When does 'maturation' occur in the ovarian follicle's development?

Answer 31

During the follicular phase.

Question 32

In fishes, amphibians and reptiles ______ of the ovarian follicle to grow is controlled by _______.

Answer 32

recruitment, gonadotropins. *This makes sense. The eggs are 'selected' during menstruation.

Question 33

When does estrogen induce vitellogenesis by the liver? (In what animals?)

Answer 33

During 'recruitment' of the ovarian follicle in fishes, amphibians and reptiles.

Question 34

How many follicles begin final maturation during each ovarian cycle?

Answer 34

6-12

Question 35

What causes only one follicle to ovulate during the ovarian (menstrual) cycle?

Answer 35

(When it reaches a certain size)... The largest follicle makes more FSH receptors, which allows it to grow faster than the other ones (it can respond to lower levels of FSH). -It also secretes an inhibitor that blocks the growth of the remaining follicles (no inhibitor receptors).

Question 36

During the primary / secondary follicle the occyte is arrested in ______.

Answer 36

Meiotic Prophase I

Question 37

What substance needs to be decreased in order for the oocyte to mature (leave meiotic prophase I)?

Answer 37

Oocyte Maturation Inhibitor (OMI)

Question 38

Gonadotropins act on the follicle cells to stimulate what? ~>And where are they released?

Answer 38

Production of sex steroids. They are released into the circulation and also into the antrum (lumen) of the follicle.

Question 39

What do sex steroids do for oocyte maturation?

Answer 39

They act as a Maturation Inducing Substance (MIS). ~>They allow oocytes to progress through metaphase of meiosis II and germinal vesicle breakdown. (GV ~ oocyte nuclear membrane).

Question 40

When does final oocyte maturation (completion of meiosis II) occur?

Answer 40

At fertilization.

Question 41

Describe the physiological characteristics of oocyte maturation.

Answer 41

- oocytes are arrested in prophase of meiosis I; no GV to be seen. - stimulation by progesterone causes them to continue meiosis and arrest at metaphase of meiosis II - the nuclear membrane breaks down (GVBD) and the nucleus migrates to the top of the oocyte; it displaces pigment granules and produces a white spot.

Question 42

Basal LH maintains production of an _______ by the granulosa cells.

Answer 42

Oocyte Maturation Inhibitor (OMI). *Its chemical identity is unknown

Question 43

What does an Oocyte Maturation Inhibitor (OMI) do?

Answer 43

It increases cAMP levels in the oocyte, inhibiting oocyte maturation.

Question 44

What surrounds the oocyte after ovulation, and what is it made out of?

Answer 44

The cumulus oophorus; and it is made of membrana granulosa cells. *Overall goal is to inhibit oocyte maturation.

Question 45

The preovulatory LH surge inhibits production of the ______? *Think, it must make sense.

Answer 45

Oocyte Maturation Inhibitor (OMI).

Question 46

The dec. in the _____ causes a dec. in _____ in the oocyte which removes the inhibition on oocyte maturation. *What else follows along with this?

Answer 46

Oocyte Maturation Inhibitor (OMI), cAMP. *An inc. in intracellular [Ca^2+]

Question 47

The maturation inducing substance (MIS) acts on the oocyte to promote what 3 things?

Answer 47

- meiotic maturation - germinal vesicle breakdown - breakdown of the nuclear membrane

Question 48

What female sex steroid do frogs depend on for oocyte maturation? What do fishes depend on?

Answer 48

FROGS: progesterone FISH: 17α, 20β-dihydroxyprogesterone

Question 49

The Maturation Inducing Substance (MIS) acts on the occyte via _______ and induces an inc. in _______ and the production of ________.

Answer 49

- steroid membrane receptors - intracellular [Ca^2+] - Maturation Promoting Factor (MPF)

Question 50

What is a Maturation Promoting Factor (MPF)?

Answer 50

A substance that induces meiosis in an oocyte, but also mitosis in other cells.

Question 51

What is a Maturation Promoting Factor (MPF) made out of? (In fishes and amphibians, maybe reptiles)

Answer 51

1) Cyclin b (reg. subunit): this is reg. by the MIS (inducing subs.) 2) Cdc2 Kinase (cat. subunit): this is constitutively expressed.

Question 52

The maturation inducing substance (MIS) could be _____. (In mammals)

Answer 52

Estradiol | Androgens (testosterone, androstenedione)

Question 53

Testosterone has been shown to also activate the ______ pathway and inc. activity of _________.

Answer 53

MAPK, cyclin-dependent kinase (CDK1/cdc2)

Question 54

Testosterone promotes mouse oocyte maturation and activation of the MAPK and CDK1/cdc2 signaling pathways in a ______.

Answer 54

Transcription-independent manner.

Question 55

What does it mean that "in non-mammalian species growth of the ovarian follicle and vitellogenesis (yolk formation) and oocyte maturation are temporally distinct processes controlled by different sex steroids?"

Answer 55

E2 ~> vitellogenesis | P4 ~> oocyte maturation

Question 56

LH stimulates _______ production by the theca.

Answer 56

androgen

Question 57

FSH stimulates _______ production by the granulosa.

Answer 57

estrogen

Question 58

What is SF-1 and what does it do?

Answer 58

Steroidogenic Factor; it controls expression of enzymes involved in steroidogenesis, and it influences gonad and adrenal development.

Question 59

What is StAR and what does it do?

Answer 59

Steroidogenic Acute Regulatory Protein; it mediates cholesterol uptake by the mitochondria.

Question 60

Name Five Types of Hormonal Contraception

Answer 60

1) Birth Control Pill 2) Depo-Provera; long-lasting it suppresses the ovarian cycle for 3 months 3) Transdermal Patch 4) NuvaRing; contraceptal vaginal ring 5) Emergency Contraception a) RU486 (mifepristone) ~> abortion; P4 antagonist b) The morning after pill (Plan B); high does of progestin it suppresses LH release, and inhibits uterine lining

Question 61

Name the four Inhibitors of Ovarian Function

Answer 61

1) GnRH analogs; can suppress the ovary [receptors are also here] (SUPERACTIVE analog will suppress the pituitary) 2) Antiestrogens: Tamoxifen 3) Antiprogestins: Mifepristone 4) Antiandrogens: cyproterone acetate

Question 62

Name the four Hormones and Fertility Control substances.

Answer 62

1) Artificial insemination 2) Anovulation (cannot ovulate; relieve inhibition of ovary) 3) In vitro fetilization (IVF) 4) Egg donation

Question 63

Hormones and reproductive behavior. How do they relate?

Answer 63

1) Sexual behavior 2) Hormones and imprinting 3) Maternal behavior 4) Organizational versus activational effects of hormones

Question 64

What hormone (which also causes smooth muscle / uterine contractions) is elevated at birth to cause 'imprinting' of mother to child?

Answer 64

Oxytocin

Question 65

Maternal behavior is induced by _______ acting on the brain. *But the actions of [ ] require prior exposure to _________ like _______.

Answer 65

Prolactin *steroid hormones, estrogen / pregesterone

Question 66

What are the organizational actions of sex steroids?

Answer 66

Steroid hormone needs to be present during a critical developmental period; they organize sex-specific wiring in the brain.

Question 67

What are the activational actions of steroids?

Answer 67

The production of said steroid (the one that 'organized') later in life activates sex-specific behavior.

Question 68

Male sexual bahavior is 'organized' by ______ during early development. Later in life the behavior is activated by _______.

Answer 68

androgens (2x)

Question 69

Female lordosis (spine arching) is 'organized' by the lack of ______ such as [ ] during early development. Later in life the behavior is activated by ___&___ .

Answer 69

steroid, [androgens], estrogens and progestins

Question 70

In rats location of 'pup' in uterus influences several behaviors later in life (because it determines the degree of her exposure to androgens in utero) *Which pups have great inter-female aggression?

Answer 70

2M females (between two brothers). Males prefer to spend time with 0M females.

Question 71

What are the interesting characteristics of the spotted hyena?

Answer 71

- Matriarchal society. - Females are extremely aggressive, have male-like muscular development (MASCULINZIED) - Ovaries of the mother secrete androstenedione which can be converted to testosterone by the placenta. (may be responsible for masculinization)

Question 72

Rodents: If female rat pups are treated with T they will exhibit...

Answer 72

Male mounting behavior when injected with T after puberty.

Question 73

In the Hyena the _______ fetus may be exposed to high levels of androgens derived from the maternal ovary.

Answer 73

late-stage

Question 74

In the spotted hyena treatment of adult females with __________ reduces aggressive behavior towards to male.

Answer 74

anti-androgens