ANSC Repro Exam #3

Preparation for listing questions, long explanations/steps, and important info

Explain the hypothalamic, pituitary, hormonal, and gonadal regulation of Spermatogenesis

1. Tonic production of GnRH

2. GnRH promotes release of LH and FSH from anterior pituitary

3. LH acts on Leydig cells to stimulate testosterone production

4. Testosterone produced goes to the sertoli cells, where they’re enzymatically converted into di-hydro testosterone (DHT) and enter circulation

5. Leydig and sertoli cells both have aromatase and produce small amounts of estradiol

6. Inhibin suppresses FSH production, creating negative feedback on the FSH release

7. Testosterone, DHT, and Estradiol cause negative feedback on the hypothalamus, creating the basal pulses every 4-6 hours

What are the final products of the testes at the end of Spermatogenesis?

testosterone, DHT, and small amounts of estradiol

List and describe the stages of Spermatogenesis

1. Proliferation: stem cell renewal

2. Meiosis: increase the number of sperm cells being produced. crossover events occur to create degree of uniqueness between sperm

3. Differentiation: sperm take on functional characteristics (stream-line appearance and development of a tail)

List the phases of Differentiation and what occurs at each

1. Golgi Phase: produce proacrosomic granules which are placed on the top of the spermatid’s nucleus

2. Cap Phase: acrosomic vesicle starts to spread over the nucleus

3. Acrosomic Phase: DNA is reshaped and condensed in nucleus to achieve the stream-line conformation

4. Maturation Phase: head fully condenses to achieve stream-line appearance

What information can scrotal circumference tell you?

1. sperm producing capacity: bigger testes = more sperm produced

2. age of attainment of puberty in daughter: bigger testes = will reach puberty sooner

3. will kind of divulge quality: smaller testes = lower quality; however, normal and large sizes are the same quality

Explain Sexing Semen

• The goal is to breed a female with a certain gender of semen

• DNA has Y and X: Y has less DNA because it is smaller

• Dye binds to DNA (more binding means more sperm)

• Dyed DNA is excited by a laser

• Detector tells the computer the amount of DNA present in order to determine gender

• Computer assigns charge and adds a droplet before going through chute system

• A magnetic field separates based on X or Y chromosome determination

Describe locomotion of a primate during ovulation

ovulation causes increased locomotion

What hormone regulates the transport of sperm from the epididymis into the ductus deferens?

oxytocin

List and describe the steps needed for males to attain an erection

1. males have a flaccid penis with a nearly nonexistent blood pressure

2. sexual arousal in the form of auditory, tactile, or visual stimuli stimulate the male and activate the NANC neurons

3. vasodilation of the helicine arteries and release of nitric oxide by NANC neurons increases blood flow

4. contractions of the bulbospongiosus and ischiocavernosus muscles clamps the veins of the penis, preventing blood from leaving and block venous outflow to attain an erection

Which hormone is responsible for reversing the effects of the vasodilatory molecules?

phosphodiesterase 5 (PDE5) converts cGMP into GMP, causing the penis to return to flaccid state

Describe the effects of Familiarity on Frequency of Mounting

• males with familiar females in a new environment experience an increase in the frequency because of fear of competition

• males in a familiar place with novel females experience an even greater frequency because not sure when/if he’ll get the chance to breed these females again

• familiarity causes a decrease in the rate of security drive

What are the 2 most popular ways sperm are lost in the female reproductive tract?

retrograde loss and phagocytosis

Spermeation

release of sperm from the seminiferous tubules into the rete tubules

What are the 2 types of mucosal layers present in privileged pathways? Describe their viscosities

1. Sulfomucins: closer to the lumen; highly viscous

2. Sialomucins: located in the dips; watery and less viscous

What are the 2 binding events that occur during fertilization?

1. Acrosomal Reaction

2. Cortical Reaction

Acrosomal Reaction

• ZP proteins bind with zona binding regions on the plasma/acrosomal membrane

• binding softens the ZP for sperm to penetrate, but only right where the sperm bound

Cortical Reaction

• proteins bind to the membrane of the oocyte

• causes the ZP to harden and become impenetrable, preventing polyspermy

For AI, you must get through how many cycles of seminiferous epithelium to complete spermatogenesis?

5

What are the functions of each component of the semen extender?

• Nutrition: egg yolk, buttermilk, or glucose

  • after thawing, semen is yellow if egg yolk was used and white if buttermilk was used

• pH Buffer (stabilize pH): Na Citrate or Na Phosphate

  • keeps sperm alive

• Control metabolic and bacterial activity (kill bacteria): Antibiotics like penicillin and streptomycin

• Cryoprotectant for temperature shock: Glycerol

  • only used if FREEZING

  • changes osmolarity to wrinkle the plasma membrane, preventing cell death by stopping breakage when water expands

Intracytoplasmic Sperm Injection (ICSI)

• originally developed to solve fertility defect in humans where sperm with good DNA had poor motility

• Useful for equine use because:

  • stallion semen doesn’t cryopreserve well

  • IVF doesn’t work

  • stallion has long generation interval so producer is likely to want to preserve genetics for a while

What are the challenges associated with Spermatogoneal Stem Cell Transplantation?

• difficult to identify stem cells

• must safely and permanently produce recipient males

  • remove surrogate’s SSC

What are the 2 categories of Male Contraceptives and what are some examples?

• Chemical: hormonal or gene targeting

  • Nifedipine (prevents sperm from binding to oocyte) and “Dry Orgasm” Pill (ejaculate lacks sperm)

• Physical: ultrasou