ANSC 4045 Exam 2

starts a new follicular wave

Answer the following questions based on the estrus synchronization protocol below. What is the effect of GnRH on Day 0?

Ovulation

Answer the following questions based on the estrus synchronization protocol below. What is the effect of GnRH on Day 26?

CL regression

Answer the following questions based on the estrus synchronization protocol below. What is the effect of PGF2a on Day 24?

Resynch or double resynch

Answer the following questions based on the estrus synchronization protocol below. What is the name given for this synchronization protocol?

Never. This protocol uses times AL and doesn't require checking for estrus.

Answer the following questions based on the estrus synchronization protocol below. When would you check for estrus with this protocol?

-Females release an ovulatory surge of LH in a cyclic manner (once each estrous cycle) -Males lack a surge center and instead release LH in regular pulses (every 3-6 hours) without any cyclicity or surges.

Both males and female produce Luteinizing hormone in the anterior pituitary. What is the major difference between males and females in the releasing pattern of LH?

Females release an ovulatory surge of LH in a cyclic manner (one each estrous cycle.) Males lack a surge center and instead release LH in regular phases (every 3-6 hours) without any cyclityt or surges.

Both males and females produce Lutenizing hormone in the anterior pituitary. What is the major difference between males and females in the releasing pattern of LH?

Pregnenolone (Progesterone is acceptable)

Cholesterol is then converted to what hormone?

Timed AI is when the producer intentionally times the artificial insemination so that the females in the herd ovulate and become pregnant at the same time.

Define "timed AI"

Release of Sertoli cells into the lumen and semiferous tubules

Define spermiation

Long day: regularly repeated estrous cycles only throughout the spring and summer. Animals enter anestrus and stop cycling in fall and winter months (ex: horses)

Describe reproductive cyclicity in the long day seasonal polyestrus instance and give an example of a species discussed in class that exhibits this type of cyclicity.

No true estrous cycles. Instead, estrus only occurs approximately once yearly followed by long periods of anestrus (Ex: wolves and dogs)

Describe reproductive cyclicity in the monoestrus instance and give an example of a species discussed in class that exhibits this type of cyclicity.

Regular, repeated estrous cycle occurring throughout the year (ex: cows, pigs)

Describe reproductive cyclicity in the polyestrus instance and give an example of a species discussed in class that exhibits this type of cyclicity.

Short day: regularly repeated estrous cycles only throughout the fall and winter. Animals enter anestrus and stop cycling in spring and summer months (ex: sheep and goats)

Describe reproductive cyclicity in the short day seasonal polyestrus instance and give an example of a species discussed in class that exhibits this type of cyclicity.

does not have regular repeated estrous cycles throughout the year; has one estrous cycle because luteal phase is as long as gestation Ex: dog

Describe the monoestrous reproductive cyclicity and give an example of a species discussed in class that exhibits this type of cyclicity

Regular, repeated estrous cycles throughout the year Ex: cow

Describe the polyestrous reproductive cyclicity and give an example of a species discussed in class that exhibits this type of cyclicity

-Long day: spring breeding season; estrous cycles in the spring and summer; anestrus in the fall and winter Ex: Mare -Short day: autumn breeding season; estrous cycles in the fall and winter; anestrus in the spring and summer Ex: Ewe

Describe the seasonal polyestrous reproductive cyclicity and give an example of a species discussed in class that exhibits this type of cyclicity (both types)

Protamines

During spermiogenesis nuclear histones are replaced by small arginine rich nuclear proteins essential for DNA condensation. What are these proteins called?

-Menopause is caused by a depletion of follicular reserves resulting in a cessation of cyclicity and progesterone and estrogen levels being maintained at basal levels. -This only occurs in menstrual cycles (most species do not outlive their reproductive lifespan)

Explain the cause of menopause. Does menopause occur in the estrus cycle, menstrual cycle or both?

Menopause (only menstrual) is caused by depletion of follicular reserves resulting in a cessation of cyclitity and progesterone and estrogen levels being maintained at basal levels.

Explain the cause of menopause. Does menopause occur in the estrus cycyle, menstrual cycle or both?

-During the first wave progesterone is high which prevents follicles from acquiring dominance or ovulating so all follicles become atretic. -During the second wave, progesterone levels have fallen so one follicle acquires dominance and ovulates while other follicles undergo atresia.

Explain the difference between the first and second follicular waves in a 2-wave cow. What is the primary cause of this difference?

Low GnRH causes low levels of FSH and LH which result in a lack of follicle growth and prevents ovulation.

Explain the role of Gonadotropin Releasing Hormone levels on causing anestrus.

In the first wave, progesterone is high which prevents follicles from acquiring dominance or ovulating so all follicles become atretic

Explain why the first wave of follicles in the cow all become atretic

Sertoli cells FSH supports spermatogenesis

Follicle Stimulating Hormone acts on which cells in the testes? What role does the interaction between FSH and these cells play?

Sertoli cells FSH supports spermatogenesis

Follicle Stimulating acts on which cells in the testes? What role does it play?

cats, ferrets, camelids, rabbits

Give an example of a species that is an induced ovulator

Increased tone

How does estrogen affect the myometrium of the uterus during the follicular phase?

Countercurrent exchange between the uterine vein and ovarian artery

How does prostaglandin F2a travel from the uterus to the ovary in the ewe or the cow? (Be sure to name the mechanism and the structures involved)

High progesterone prevents follicles from growing to develop dominance

In a two wave cow, what prevents ovulation during the first wave?

Ovulating dominant follicle Start new follicle wave

In an ovulation synchronization protocol or timed AL prototcol what are the two functions of a Gonadotropin Releasing Hormone (GnRH) injection?

CIDR and MGA

List 2 exogenous sources if progesterone discussed in class

lactation, pregnancy, high stress

List 3 factors that could cause anestrus in a normally cycling animal.

shorter calving season, maintain proper calving interval, timed AI

List 3 of the benefits of estrous synchronization.

time consuming, females must be cycling normally, cows need a minimum of 45 days post-calving

List 3 of the costs of estrous synchronization

proliferative, secretory, menses

List and describe the main stages or phases of endometrial development during the menstrual cycle`

•Provides a continual supply of male gametes (up to decades) through stem cell renewal. •Provides genetic diversity. •Provides billions of sperm daily (domestic animals).

List the 2 functions that spermatogenesis plays in animal breeding.

middle piece, principal piece, terminal piece

List the 3 pieces of the tail on a mature spermatozoa.

Mitochondria

Lutenizing hormone binds luteal cells and stimulates the uptake of cholesterol into which organelle?

On the diagram below draw the changes in relative concentrations for Progesterone (P4), Estradiol (E2), Follicle Stimulating Hormone (FSH), Luteinizing Hormone (LH) and Prostaglandin F2a (PGF) for the cow. Notice that the X axis starts at -6 with 0 being the day of estrus and ends at +6 of the next cycle. Be sure to include all 5 hormones and label with the abbreviations given.

On the diagram below draw the changes in relative concentrations for Progesterone (P4), Estradiol (E2), Follicle Stimulating Hormone (FSH), Luteinizing Hormone (LH) and Prostaglandin F2a (PGF) for the cow. Notice that the X axis starts at -6 with 0 being the day of estrus and ends at +6 of the next cycle. Be sure to include all 5 hormones and label with the abbreviations given.

*Please remember that this was both the convention discussed in class and noted in the question above that estrus occurs on day 0 of the estrous cycle*

On the diagram below draw the changes in relative concentrations for Progesterone (P4), Estradiol (E2), Follicle Stimulation Hormone (FSH), Luteinizing Hormone (LH) and Prostaglandin F2a (PGF) for the cow. Notice that the X axis starts at -6 with 0 being the day of estrus and ends at + 6 of the next cycle. Be sure to include all 5 hormones and label with the abbreviations given.

presence of the conceptus

PGF2a causes luteolysis in females. What is the signal that blocks PGF2a secretion during pregnancy?

morphologically abnormal

Potential fertility of a male can be related to the percentage of ___ sperm within an ejaculate.

Short cycle for the female- bringing her back into estrus faster than she would naturally

Prostaglandin F2alphahelix can be administered to induce luteolysis. Why might this be beneficial?

At least 6 days

Prostaglandin F2alphahelix to be effective, how long do you have to wait until after ovulation before administering it?

Oxytocin receptors in the endometrium

Release of the prostaglandin F2a is stimulated by the binding of a specific hormone to receptors in the uterus. What is that hormone? In what part (tissue) of the uterus are these receptors located?

Oxytocin Receptors in the endometrium

Release of the prostaglandin F2alpha is stimulated by the binding of a specific hormone to receptors in the uterus. What is that hormone? In what part of the uterus are those receptors located?

-Proliferation Phase: spermatogonia; mitotic generation of spermatogonia and stem cell renewal -Meiotic Phase: spermatocytes; meiotic division to reduce haploid state, crossing over to increase genetic diversity -Differentiation Phase: spermatids; spermatogenesis differentiation and change of round cell shape to elongated spermatids

Spermatogenesis is divided into three phases. What are they and what happens to the germ cells during each phase? Include the names for the germ cell types in each phase.

-Proliferative phase: spermatogonia, mitotic generation of spermatogonia and stem cell renewal -Meiotic phase: spermatocytes, meiotic division to reduce tp haploid state, crossing over to increase genetic diversity -Differentiation phase: spermatids, spermiogenesis, differentiation and change of cell shape from round cells to elongated spermatids

Spermatogenesis is divided into three phases. What are they and what happens to the germ cells during each phase? Include the names for the germ cell types in each phase?

Leydig cells Luteinizing hormone

Testosterone is produced in the testes, specify the hormone that induces its production and the cell type where it is produced.

P4

The CIDR is an exogeneous source of what hormone?

First ovulation after a period of anestrus is termed a Silent Ovulation. Since hormones are basal during anestrus, the first ovulation is silent before the brain is primed by progesterone in the first diestrus period.

The first ovulation occuring after a period of anestrus is NOT accompanied by behavioral estrus. What is this condition called? Why does it occur?

-First ovulation after a period of anestrus is termed a Silent Ovulation -Progesterone must prime the brain during a period of diestrus before estrogen can influence estrus behavior. --Since hormones are basal during anestrus, the first ovulation is silent before the brain is primed by progesterone in the first diestrus period

The first ovulation occurring after a period of anestrus is NOT accompanied by behavioral estrus. What is this condition called? Why does it occur?

The size of the follicles present at the time of luteolysis induction.

The length of time between Prostaglandin F2alpha and ovulation can be variable depending on what ovarian factor?

GnRH days 0 and 8

To make this protocol a Fixed Time AI protocol, what hormone should be incorporated and on what day(s) should it be administered?

-The hypothalamus: negative -The anterior pituitary: negative -The endometrium of the uterus: positive -The myometrium of the uterus: negative -The alveolus of the mammary gland: positive

Use the words positive, negative or no effect to describe how progesterone from the corpus luteum affects the following structures -The hypothalamus: -The anterior pituitary: -The endometrium of the uterus: -The myometrium of the uterus: -The alveolus of the mammary gland:

Hypothalamus: negative Anterior pituitary: negative Endometrium of the uterus: positive Myometrium of the uterus: negative Alveolus of the mammary gland: positive

Use the words positive, negative, or no effect to describe how progesterone from the corpus liteum affects the following structures: Hypothalamus: Anterior pituitary: Endometrium of the uterus: Myometrium of the uterus: Alveolus of the mammary gland:

estradiol and inhibin

What 2 hormones, secreted by follicles in the late follicular phase inhibits release of Follicle Stimulating Hormone from the anterior pituitary?

-Timed AI; to know exact breeding date and to ensure cows all calve at close to the same date -Reduce necessity for estrus detection -Shorter calving season Use of reproductive technologies/genetic improvement -Maintain proper calving interval

What are 2 reasons a producer may wish to synchronize estrus in a herd of dairy cattle?

-Menstrual cycle has a longer follicular phase -Menstrual cycle has a shorter luteal phase -Endometrial sloughing and mensus is present in the menstrual cycle -Menopause occurs in the menstrual cycle

What are four ways in which the menstrual cycle differs from the estrous cycle?

PGf2a, GnRH, Progesterone

What are the three hormones most commonly used in estrus synchronization protocols in the United States?

PGF2alpha GnRH Progesterone

What are the three hormones most commonly used in estrus synchronization protocols?

Increased follicular pressure Weakening/decreased thickness of the follicle walls

What are the two main follicular changes that cause ovulation to occur?

increased follicular pressure weakening/decreased thickness of the follicle walls

What are the two main follicular changes that cause ovulation to occur?

Follicular: estrogen Luteal: progesterone

What are the two primary phases of the estrous cycle and what is the dominant steroid for each phase?

Follicular phase --> proestrus and estrus Luteal phase --> metestrus and diestrus

What are the two primary phases of the estrous cycle? List the stages which each phase is divided into.

-increased blood flow -increased mucosal secretions -genital swelling -change in tissue electoconductivity -leukocytosis -increased myometrial tone -uterine gland growth

What are two effects of estradiol on the female reproductive tract?

pregnancy, lactation, presence of young, poor nutrition, high stress

What are two reasons why a cow may enter anestrus?

Resumption of Meiosis (meiotic maturation)

What change occurs within the oocyte around the time of ovulation that is required for it to become competent for fertilization?

Resumption of meiosis (meiotic maturation)

What change occurs within the oocyte around the time of ovulation that is required for it to become competent to be fertilized?

resumption of meiosis (meiotic maturation)

What change occurs within the oocyte around the time of ovulation that is required for it to become competent to be fertilized?

Measuring the scrotal circumference helps to estimate potential spermatozoa production in the animal.

What does measuring the scrotal circumference help estimate?

Negative -- prevents secretion

What effect does progesterone have on Gonadotropin releasing hormone?

lengthening days; the stimulus is a change in the number of hours of daylight

What external stimulus induces seasonal anestrus in ewes? (Be specific)

-dominance -early selection and late selection -recruitment -atresia

What four stages does the dynamics of antral follicle growth consist of?

COntrolled Internal Drug Release (A device that is inserted into the vagina to supply continuous release of progesterone) Prevents any follicles from acquiring dominance, causes persistence of the CL so that females will come into estrus together within ~2 days of removal

What is CIDR and how is it used in an estrus synchronization protocol?

The remianing structure following regression of the CL

What is a corpus albicans?

-Anestrus is a period of acyclicity when the female does not exhibit estrous cycles. Can be caused by: -Pregnancy - signaled by fetal presence and maternal recognition of pregnancy -Lactation- signaled by frequent suckling and offspring presence

What is anestrus? Give one example of why anestrus might occur and what signal causes anestrus in your example?

Luteolysis is destruction/death of the CL removal of negative feedback by progesterone of GnRH secretion resulting in new follicular phase

What is luteolysis? How does this affect Gonadotropin Releasing Hormone (GnRH) levels?

Luteolysis is destruction of the CL Progesterone levels decrease, removing negative feedback on GnRH and allowing GnRH levels to increase.

What is luteolysis? How does this affect Gonadotropin Releasing Hormone level?

-Menstrual cycle has a longer follicular phase (50%) than the estrous cycle (20%) -Menstrual cycle has a shorter luteal phase than the estrous cycle -Endometrial sloughing and menopause only occur in the menstrual cycle -In the menstrual cycle ovulation occurs mid cycle while it occurs at the start of the estrous cycle -The fertile phase is longer in the menstrual cycle than in the estrous cycle

What is one major difference between estrous and menstrual cycles?

CIDR, MGA, Altrenogest, Regumate, Synchromate

What is one source of exogeneous progesterone that was discussed in class for estrus synchronization in cattle?

Anestrus is a period of acyclicity when the female is not in the estrous cycle

What is the definition of anestrus?

A monotonous species has a single oocyte that can be fertilized while a polytocous species has more than one

What is the difference between a monotonous and a polytocous species?

luteolysis

What is the effect of PGF2a on day 6?

CL persists for longer than normal, approximately the length of pregnancy

What is the effect of total uterectomy on the lifespan of the corpus lutem in the ewe?

CL lifespan persists longer, approximately time of pregnancy

What is the effect of total uterectomy on the lifespan of the corpus luteum in the ewe?

Uterectomy has no effect on the lifespan of the CL in women

What is the effect of total uterectomy on the lifespan of the corpus luteum in women?

Total uterectomy has no effect on the lifespan of the CL in women

What is the effect of total uterectomy on the lifespan of the corpus luteum in women? Why?

CIDR + PGF2a

What is the name or description given to this type of synchronization protocol?

Cytoplasmic bridges link the developing sperm cells through all three phases of spermatogenesis

What is the significance of the cytoplasmic bridges between the developing sperm cells during all three phases of spermatogenesis?

recruitment and early selection: follicle stimulating hormone late selection and dominance: luteinizing hormone

What pituitary hormone provides the primary stimulus for follicular development during the following stages? recruitment and early selection: ___ late selection and dominance: ___

Inhibin is produced by follicles, is highest when large dominant follicles are present (proestrus) and has negative feedback action on FSH.

What role does inhibin play in the estrus cycle? Where is it produced and at what stage of the cycle is it highest?

copulation

What stimulus is required to induce ovulation in induced/reflex ovulators?

acrosome

What structure in the head of the spermatozoa is important for penetration of the zona pellucida during fertilization?

in the cow: uterus in the woman: ovary

Where does the hormone which causes luteolysis (regression of the CL) come from in the cow and in the woman?

semineferous tubules

Where, within the testes, does spermatogenesis occur?

Leydig cells

Which cells in the testes produce testosterone?

Timed AI is generally when the producer artificially inseminates the herd at the same time and synchronization of ovulation is important to insure that as many animals in the herd become pregnant as possible.

Why is synchronization of ovulation or the follicular waves necessary for timed AI?

The cycle of seminiferous epithelium is important for the constant production of spermatozoa so mature spermatozoa is always available which determines fertility and viability of the spermatozoa

Why is the cycle of the seminiferous epithelium important for production of spermatozoa?

-Silent ovulation is the first period of anestrus NOT accompanied by behavioral estrus -Progesterone must prime the brain during a period of diestrus before estrogen can influence estrus behavior --> Since hormones are basal during anestrus, the first ovulation is silent before the brain is primed by progesterone in the first diestrus period

Why is the first ovulation following a period of anestrus referred to as a "silent ovulation"? Why is it silent?

not a mature CL yet; still developing

Why is there no effect on luteolysis when a single injection of prostaglandin F2a is given between days 0 and 5 after ovulation?