Lecture Exam 3

  NAME ______________________________ 

             This examination is conducted on the honor system.  The printing or signing of your name above pledges you to neither give nor receive assistance with this exam.  Disregarding this pledge will result in a grade of zero (0) for this examination.

            Put the most appropriate answer in the allotted space for full credit.  Be specific, concise, yet complete.  READ ALL QUESTIONS CAREFULLY AND GOOD LUCK!

            Question                                  Credit                                       Credit Given

                 I.                                             15                                                 _____

                 II.                                               30                                              _____

                 III.                                           5                                               _____

                 IV.                                           20                                             _____

                 V.                                            10

     VI.                                           20                                                  _____

                                                            TOTAL                                       ______

I.                   True/False.  Answer T for true and F for false. (15)

________1. Ovulation in spontaneous ovulators is dependent upon basal circulating levels of progesterone and the positive feedback of estradiol on the GnRH and subsequently LH surge.

________2. Sertoli cells are the somatic cell component within the seminiferous tubule and orchestrate spermatogenesis through endocrine and paracrine effects and direct interaction with germ cells.

________3. Waiting 10 days and then administering PGF2 can synchronize estrous cycles of cattle presently on days 19 through 6 of the cycle_a.

________4. Glycerol is a non-permeating cryoprotective agent used routinely in freezing bull semen for artificial insemination.

________5. Artificial insemination technique is dictated primarily by the size of the species and anatomical configuration of the mucosal folds.

________6. FSH and LH are glycoprotein hormones with identical a subunits but unique b subunits.

________7. Spermiogenesis includes chromatin condensation, formation of a mitochondrial helix, and acquisition of motility.

________8. Differentiation of the hypothalamus toward a male pattern of gonadotropin release requires the conversion of testosterone to estradiol.

________9. Effects of luteal oxytocin on PGF_2a synthesis during diestrus are mediated by an increase in endometrial oxytocin receptors.

________10. In the bull, stages of spermatogenesis last approximately 13.5 days.

________11. Dominant follicles are characterized by the production of thecal androgens which are converted to estradiol by the granulosa cells.

________12. Ovum transport through the ampulla of the oviduct is accomplished primarily by ciliary action.

________13. A duplex reproductive tract is formed by fusion of the paramesonephric ducts to the level of the cervix in the rabbit and vagina in marsupials.

________14. Synchrony between donor and recipient estrous cycles is critical for successful embryo transfer in cattle and can be achieved through estrus synchronization. techniques.

________15. Signal transduction for gonadotropins (FSH and LH) requires binding to a membrane receptor, generation of cAMP, and activation of protein kinase A.

II.                Fill in the blanks with the most appropriate word or phrase. (15)

1. An early step in gastrulation is formation of the ____________________, which determines the long-axis of the embryo.
2. Distribution of the umbilical (fetal) circulation to the placenta is accomplished by growth and expansion of the ____________________ membrane.
3. In mammalian gastrulation, the hypoblast gives rise to ____________________.
4. Endometrial cups differentiate in response to migration of epithelial cells from the ____________________ into the endometrium.
5. X- and Y-chromosome bearing sperm can be separated by flow cytometric techniques based on differences in ____________________ content.
6. A masculinized heifer born co-twin to a bull is called a ____________________.
7. Recipient oocytes for nuclear transfer (cloning) must be matured and ____________________ prior to injecting the donor nucleus and activation.
8. Embryonic stem cells are obtained by the isolation and culture of the ____________________ from the blastocyst.
9. Implantation in primates is classified as ____________________ based on the degree of maternal tissue erosion.
10. Histological classification of the placenta is based on the number of ____________________ separating maternal and fetal blood.
11. ____________________ are the nuclear proteins in sperm which are important for nuclear condensation and are replaced by histones during fertilization.
12. In  most species, the sperm ____________________ is the microtubule-organizing center for the aster which draws male and female pronuclei together prior to syngamy.
13. Identical twins are most often a result of duplication of the ________________ within a single trophoblast.
14. Gonads, mesonephric, and paramesonephric ducts are derived from ____________________ during gastrulation.
15. Reproductive losses in cattle occur primarily at the ____________________ stage of reproduction.

III.             Complete the following table for 3 types of cystic ovaries found in cattle.   List the types of cysts, indicate whether they are pathological or not, and list 2 identifying features for each type.  (6)

IV. Provide a brief description or definition of the following terms. (20)

1. true hermaphrodite

2. segmental aplasia

3. embryonic chimera

4. placentome

5. zonary placenta

6. superficial implantation

7. hemochorial placenta

8. amnion

9. uterine involution

10. cryptorchid

V.  Initiation of Parturition.  Complete the following narrative describing the initiation of parturition in domestic animals.  (10)

At a critical age and/or size, the fetus becomes stressed in utero and responds by releasing ____________________ from the anterior pituitary, which in turn acts on receptors in the fetal adrenal to stimulate ____________________ secretion.    This cascade of events leads to activation of enzymes required for converting ____________________ to ____________________ as well as secretion of ____________________  by the endometrium.  The resulting increases in these hormones stimulates____________________ contractions, which press the fetus against the ____________________.   Through a neuroendocrine reflex, ____________________ is released from the posterior pituitary.  An increase in estradiol near term stimulates ____________________ secretion by the cervix and anterior vagina.  In addition to effects on smooth muscle, PGF_2a causes ____________________ in species such as the pig. 

VI.  Discussion.  Answer either question A. or B.

A. Maternal recognition of pregnancy (MRP).  Discuss the general significance of maternal recognition of pregnancy in mammals.  Explain current concepts for the mechanism for MRP in cattle, sheep, swine, and horses.   For each species, indicate whether the mechanism is luteotrophic or anti-luteolytic.   Beyond initial recognition of pregnancy, describe 2 other species-specific mechanisms involved in progesterone support for early pregnancy maintenance.

B. Sperm transport and capacitation.  Discuss the potential fates of mature cauda epididymal sperm from the time of intromission and ejaculation through zona pellucida penetration but preceding fertilization.  Include in your discussion the concepts of sperm losses from the female tract, rapid and sustained sperm transport, sperm barriers and reservoirs, capacitation and the acrosome reaction.   Describe biochemical and cytological changes in sperm during capacitation and the acrosome reaction and the role of the zona pellucida in the acrosome reaction.