ANSC 4045
Where does the hormone which causes luteolysis (regression of the CL) come from?
(hormone = prostaglandin) Uterus (cow) Ovary (woman)
Describe the 4 phases of spermatid differentiation.
-Golgi phase: first steps in development of acrosome -Cap phase: acrosome forms distinct cap over nucleus -Acrosomal phase: acrosome spreads over nucleus. Nuclear and cytoplasmic elongation -Maturation phase: final assembly to form spermotozoan
Explain the role of Gonadotropin Releasing Hormone levels on causing anestrus.
Anestrus can cause a decrease in GnRH levels which then causes decrease in FSH and LH hormonal release which in return results in a lack of follicle growth and prevents ovulation.
Follicular phase: Beginning: End: Stages: Major endocrine Influence: Ovary: Uterus: Cervix and Vagina:
Beginning: luteolysis End: ovulation Stages: proestrus/estrus Major endocrine Influence: estrogen Ovary: growing follicles Uterus: increase Cervix and Vagina: increase mucus production
Luteal Phase: Beginning: End: Stages: Major endocrine Influence: Ovary: Uterus: Cervix and Vagina:
Beginning: ovulation End: luteolysis Stages: metestrus/diestrus Major endocrine Influence: progesterone Ovary: developing functional corpus luteum Uterus: decrease Cervix and Vagina: decrease mucus production
What is the effect of total uterectomy on the lifespan of the corpus luteum in the ewe?
CL persists for longer than normal, approximately the length of pregnancy
Chart: Day 0: GnRH Day 7: PGF2alpha Day 10: GnRH Day 17: GnRH Day 24: PGF2alpha Day 26: GnRH Day 27: AI What is the effect of PGF2α on Day 24?
CL regression
What is a CIDR and how is it used in an estrus synchronization protocol? (4 points)
Controlled Internal Drug Release, inserted into the vagina to supply continuous release of progesterone. Prevents any follicles from acquiring dominance
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)
Countercurrent exchange between the uterine vein and ovarian artery
Explain the difference between the first and second follicular waves in a 2-wave cow. What is the primary cause of this difference?
During the first wave progesterone is high so all follicles become atretic During the second wave progesterone levels have fallen so one follicle has dominance while others undergo atresia.
Both males and females 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 LH surge once each estrous month. Males lack a surge center so they release LH every 3-6 hours in pulses.
What are the two primary phases of the estrous cycle? List the stages which each phase is divided into.
Follicular - Proestrus, estrus Luteal- metestrus, diestrus
What are the two primary phases of the estrous cycle and what is the dominant steroid for each phase?
Follicular - estrogen Luteal- Progesterone
Chart: Insert CIDR on day 0 Inject PGF2Falpha on day 6 Remove CIDR on day 7 Estrous detection and AI on days 8-10 To make this protocol a Fixed Time AI protocol, what hormone should be incorporated and on what day(s) should it be administered?
GnRH administered on days 0 and day 8
List 3 of the benefits of estrous synchronization.
Group females for parturition, reduced time for estrous detection, shorter calving season, more uniform weaning weights, maintain proper calving interval
Where in the testes is there a high concentration of testosterone?
High concentration of testosterone in the seminiferous tubules
How does estrogen affect the myometrium of the uterus during the follicular phase?
Increased tone
What role does inhibin play in the estrus cycle? Where is it produced and at what stage of the cycle is it highest?
Inhibin is produced by follicles, it's highest when during proestrus role is it has negative feedback action on FSH
Testosterone is produced in the testes, specify the hormone that induces its production and the cell type where it is produced.
LH. It is produced in the Leydig cells.
Which cells in the testes produce testosterone?
Leydig cells
What is luteolysis? How does this affect Gonodotropin Releasing Hormone (GnRH) levels?
Luteolysis is destruction/ death of the CL GnRH levels to increase
Chart: Insert CIDR on day 0 Inject PGF2Falpha on day 6 Remove CIDR on day 7 Estrous detection and AI on days 8-10 What is the effect of PGF2a on day 6?
Luteolysis of a present CL
List 2 exogenous sources of progesterone discussed in class.
MGA, CIDR
What are four ways in which the menstrual cycle differs from the estrous cycle.
Menstrual cycle is longer, beginning of cycle starts with menses, ovulation happens in the middle of the cycle, endometrial sloughing, a significant amount of E2 and inhibin made by CL
What is the difference between a monotonous and a polytocous species?
Monotocous gives birth to a single offspring Polytocous has a litter of offspring
How is spermatozoal viability measured?
Motility evaluation
Use the words positive, negative or no effect to describe how progesterone from the corpus luteum affects the following structures. The anterior pituitary
Negative
Use the words positive, negative or no effect to describe how progesterone from the corpus luteum affects the following structures. The hypothalamus
Negative
Use the words positive, negative or no effect to describe how progesterone from the corpus luteum affects the following structures. The myometrium of the uterus
Negative
Chart: Day 0: GnRH Day 7: PGF2alpha Day 10: GnRH Day 17: GnRH Day 24: PGF2alpha Day 26: GnRH Day 27: AI When would you check for estrus with this protocol?
Never, this protocol uses timed AI and doesn't require checking for estrus
Monoestrus
No true estrous cycles. Instead estrus only occurs approximately once yearly followed by long periods of anestrus. Eg; wolves and dogs
Chart: Day 0: GnRH Day 7: PGF2alpha Day 10: GnRH Day 17: GnRH Day 24: PGF2alpha Day 26: GnRH Day 27: AI What is the effect of GnRH on Day 26?
Ovulation
Chart: Day 0: GnRH Day 7: PGF2alpha Day 10: GnRH Day 17: GnRH Day 24: PGF2alpha Day 26: GnRH Day 27: AI What is the effect of GnRH on Day 0?
Ovulation of any pre-existing follicles and starts a new follicular wave
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 located in receptors in the endometrium
What are the three hormones most commonly used in estrus synchronization protocols?
PGF 2a GnRH Progesterone
Use the words positive, negative or no effect to describe how progesterone from the corpus luteum affects the following structures. 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 endometrium of the uterus
Positive
PGF2 alpha causes luteolysis in females. What is the signal that blocks PGF2 alpha secretion during pregnancy?
Presence of a conceptus
Chart: Insert CIDR on day 0 Inject PGF2Falpha on day 6 Remove CIDR on day 7 Estrous detection and AI on days 8-10 The CIDR is an exogenous source of what hormone?
Progesterone
Chart: Insert CIDR on day 0 Inject PGF2Falpha on day 6 Remove CIDR on day 7 Estrous detection and AI on days 8-10 What is the name or description given to this type of synchronization protocol?
Progesterone System: CIDR + PGF2a. Progesterone and induced luteolysis
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 to haploid state, crossing over to increase genetic diversity Differentiation phase - spermatids, spermiogenesis, differentiation and change of cell shape from round cells to elongated spermatids
List and describe the main stages or phases of endometrial development during the menstrual cycle.
Proliferative phase: thickening of endometrial lining Secretory phase: maintains thickness lining Menses: sloughing off of lining
List the 2 functions that spermatogenesis plays in animal breeding.
Provides a continual supply of male gametes, provides genetic diversity
What four stages does the dynamics of antral follicle growth consist of?
Recruitment, Selection, Dominance, Atresia
Polyestrus
Regular, repeated estrous cycles occurring throughout the year Eg; cows, pigs
Chart: Day 0: GnRH Day 7: PGF2alpha Day 10: GnRH Day 17: GnRH Day 24: PGF2alpha Day 26: GnRH Day 27: AI What is the name given for this synchronization protocol?
Resync or double ovsynch
Follicle Stimulating acts on which cells in the testes? What role does it play?
Sertoli cells FSH supports spermatogenesis
Seasonally polyestrus animals (DEFINE AND GIVE AN EXAMPLE FOR BOTH TYPES)
Short day; Regularly repeated estrous cycles only throughout the fall and winter. Animals enter anestrus and stop cycling in spring and summer months. Eg; sheep and goats Long day; Regularly repeated estrous cycles only throughout the spring and summer. Animals enter anestrus and stop cycling in fall and winter months. Eg; horses
The first ovulation occurring after a period of anestrus is NOT accompanied by behavioral estrus. What is this condition called? Why does it occur?
Silent ovulation occurs due to basal hormones during anestrus in which the first ovulation is silent before the brain is primed by progesterone in the first diestrus period.
Within the testes, where does spermatogenesis occur?
Takes place entirely within the seminiferous tubules
Why is there no effect on luteolysis when a single injection of prostaglandin F2a is given between days 0 and 5 after ovulation?
The CL is not mature yet
Define spermiation
The release of spermatozoa from the Sertoli cells into the lumen of the seminiferous tubules
What is a corpus albicans?
The remaining structure following regression of the Corpus luteum
The length of time between Prostaglandin F2a and ovulation can be variable depending on what ovarian factor?
The size of the follicles present at the time of luteolysis induction
List 3 of the costs of estrous synchronization.
Time, requires normally cycling females, need good nutrition program, more intensified labor requirement at breeding and calving, requires facilities, actual cost of synchronization products
What is the effect of total uterectomy on the lifespan of the corpus luteum in women
Uterectomy has no effect on the lifespan of the CL in women. luteolysis doesn't come from the uterus in woman
Why is the synchronization of ovulation or the follicular waves necessary for timed AI?
You need to synchronize the animals so they ovulate very close to a predetermined time.
What is anestrus? Give one example of why anestrus might occur and what signal causes anestrus in your example?
anestrus is a period of acyclicity occuring in the post-puberty female when the estrus cycle temporarily pauses and the related hormones are basal. Seasons - due to change in hours of daylight
What is the significance of the acrosome?
important for fertilization
Explain the cause of menopause. Does menopause occur in the estrus cycle, menstrual cycle or both?
it is caused by the depletion of follicular reserves and only occurs in menstrual cycles.
What change occurs within the oocyte around the time of ovulation that is required for it to become competent for fertilization?
meiotic maturation
List 3 factors that could cause anestrus in a normally cycling animal.
pregnancy, stress, seasonal, lactation, lack of nutrition
Explain why the first wave of follicles in the cow all become atretic.
progesterone levels become high, preventing follicles from showing dominance or ovulating.
During spermiogenesis nuclear histones are replaced by small arginine rich nuclear proteins essential for DNA condensation. What are these proteins called?
protamines
Why is the cycle of the seminiferous epithelium important for production of spermatozoa?
provides constant supply of mature spermatozoa
