Reproduction Flashcards
What structure is present in the vagina of a newborn rat? At what point does this structure begin to degenerate and cornify and fully disappear? What occurs similarly in male rats?
Compact plate. Degenerates and cornifies by 20-35 days, opens 40-80 days. Preputial separation.
What conditions does persistence of the vaginal compact plate cause? What are sequalae (2) of these conditions?
Imperforate vagina or vaginal septum. Infertility or metritis.
When does puberty occur in females? Is this earlier or later than males? Is it before or after full reproductive competency is reached?
2-3 months. Before males. Before full reproductive competency is reached.
How long is the estrous cycle? Additional time in the estrous cycle typically occurs during what phases?
4-5 days (1 day per phase). Extra days added to proestrus or diestrus.
Describe the appearance of the uterus during proestrus. In what age of rats is this more common?
Uterus can balloon with fluid, is not hydrometra. Prepubertal rats.
When does ovulation occur within the estrus period and within the day cycle? How long is the ova viable for?
8-11 hours after estrus, typically between midnight and 2am. Viable for 10-12 hours.
When do testes descend in rats? When is sperm first produced, sperm production maximum, and fertility/puberty occur? When are more degenerate germ cells appreciated?
Descend 15 days. Sperm at 45 days, maximum sperm production > 75 days. Fertility puberty 62-65 days. More degenerate germ cells at < 75 days.
At which day does female-oriented sexual behavior decline? What is one hypothesis?
Decline after 150 days, may be due to decrease in serum testosterone.
When does coitus occur?
Latter portion of dark period.
When does implantation of the blastocyst occur? How long does this period take?
Implantation between 5-7 days, takes 12-24 hours.
What are indicators of estrus in the rat? (4)
Ear quivering when back or head is stroked, lordosis with pelvic area stimulated, swollen vulva, dry, cornified vaginal walls.
What is the appearance of a vaginal cytology during estrus? How else can estrus be identified? What are two disadvantages of this method?
25-100% cornified epithelial cells. Estrus can be detected via electrical impedence, but it gives less specific information about the phase of estrus and may cause pseudopregnancy.
What is the conception rate in rats?
85%
What indicators of pregnancy can be appreciated on what days? (4)
Ultrasound 9-10d, palpation 10-12d, heart beat on doppler 12d, mammary gland and nipple development by 14d,
What are two impacts of continuous light on rat reproduction? What are two impacts of chronic low light on rat reproduction?
Continuous light: Persistent estrus, cystic follicles without a CL.
Chronic night light: Earlier vaginal opening, ovarian atrophy
What are two impacts of caloric restriction on rat reproduction?
Cessation of estrous, delayed sexual maturation.
What is the impact of high ambient temperature on male reproduction? Why does this occur? How early can this occur, and at what temperatures?
Male infertility due to irreversible degeneration of seminiferous epithelium. As young as 4d at temperatures as low as 26.6 C.
When does nest building occur?
5 days prepartum through lactation.
What is an indicator of impending parturition? How dong does parturition typically take?
Clear mucoid discharge 1.5-4 h before first pup. Parturition 1-3.5 h, with nursing of pups following the birth of all pups.
Which litter is usually the largest? When do litter sizes and pregnancy rates decline? When is maternal behavior enhanced?
2nd litter. Litter sizes decline at 9 months, pregnancy rates at 12 months. Maternal behavior highest at 19-20 months.
What are two factors that can lead to loss of fetuses? When are fetuses typically lost?
Increasing age and stressors.
Describe newborn rats.
Atricial and nidicolous
What is the relationship between fetal birth rate and litter size? Why might this be a problem on studies? What other factor impacts pup size?
Inverse relationship between fetal birth weight and litter size. Toxicology impact - Tendency of a test substance to cause a decrease in fetal weight may be masked if it causes fetal loss. Older dams have heavier pups.
Describe the days of development of rat pups.
2.5-3.5 d = External acoustic meatus open
Incisors = 6-8 d
Fully haired = 7-10 d
Hear = 9 days
Eyelids open = 14-17 d
Retina matures 30-40 d
How do pups receive maternal antibodies? (3) When is the maximum and when does transfer cease?
In utero, colostrum, and milk. Max at 14 days, ceases at 21 days.
Male embryos cease development in the presence of what antibody?
HV antibody
Pups are generally weaned at what age? How early can they be weaned? Before what age are they missing what key reflect?
Weaned 20-21d, or as early as 17d. Missing micturition reflex before 15d.
What are two protocols for synchronizing estrus?
Lutenizing hormone releasing hormone agonist, then breed in 4d. Methoxyprogesterone followed by pregnant mare’s serum.
What is a disadvantage of electroejaculation? How is this technology typically used?
Rapid coagulation of semen due to coagulating glands and seminal vesicles. Used to assess repro soundness.
How is sperm for AI or sperm cryopreservation typically collected? From which site?
Terminal dissection from the head of the epididymis.
How is pseudopregnancy induced? (2)
Mating with vasectomized male or mechanical/electrical stimulation.
What is a protocol to induce superovulation? When are embyros collected?
PMSG then HCG. Collected at 1-5 days.
Describe cryopreservation in rats.
Less common than in mice. Embryos used to test culture reagents and environments for human IVF.
