Bovine Intro & Biochem

sihirlifil's version from 2017-09-13 14:27

Basic Cow Cycle & Control of Corpus Luteum

Question Answer
(Know how to draw the cow cycle)(yay art)
Proestrus begins with the completeion ofLuteolysis
What happens during proestrus?Progesterone (P4) rapidly declines
Estrogen increases
Baseline concentration of LH increases
What happens during estrus?Female stands to be mounted
Estrogen rises to a peak then declines after surge
LH surge follows estrogen surge
Ovulation triggered by LH surge.
Estrus akaStanding heat
What is metestrus?Period of the corpus hemorrhagicum (CH), which is the developing corpus luteum (CL)
After ovulation, the corpus luteum develops… what happens with estrogen, LH, and P4as a result?Low blood concentrations of estradiol
Low LH levels
Rising P4 levels
Behavioral estrus (standing heat) is brought to an end when?Dominance of P4 and low estrogen levels
During metestrus, what happens to the corpus luteum?Matures to full progesterone production
The diestrus phase consists of what?Period of the mature CL from significant P4 secretion until luteolysis
When is PGF2a secreted? By what?Secreted by uterus near the end of diestrus (around day 18)
What happens to P4 after PGF2a secretion?Immediate drop in concentration
What prevents the PGF2a surge?Presence of embryo
In the nonpregnant beast, PGF2a released from the ___ reaches the ___ and CL, and causes regression of the luteal tissue and rapid ___ of the CL, and ___ in P4 production.Uterus; ovary; shrinkage; reduction
Maternal recognition of pregnancy =Physiological process whereby the conceptus signals its presence to the maternal system and prolongs the lifespan of the corpus luteum
Why is maternal recognition of pregnancy important?Signal prevents PGF2a from being released and wiping out the CL (hey mom I’m here, don’t kill me plz)
LH surge lasts how long? what does that mean for the cow?8-12 hours = really short estrus
___ triggers resumption of Meiosis I and ovulation (when)LH, at the onset of estrus
Onset of estrus coincides withPeak estrogen and LH
Duration of estrus may be how long?<12 hours
Ovulation typically occurs ___ after onset of estrus24-30 hours (i.e. usually not until standing heat is over)
Clear mucus vaginal discharge noted duringEstrus
Metestrus starts during which day of the cycle?0.5, lasts until ~5 (when diestrus begins)
During metestrus, how does the CL respond to PGF2a?Refractory i.e. doesn’t respond to clinical treatments --> doesn’t undergo luteolysis
Bloody vaginal discharge noted duringMetestrus (2-3 days after ovulation)
Blood comes from the uterus
Bleeding in cows believed to be due to? What about dogs? Humans?Estrogen stimulation/withdrawal
Dogs: estrogen stimulation
Humans: (who cares but) Post-luteal menstrual bleeding from P4 withdrawal, loss of support for endometrial proliferation
Diestrus is from day ___ to ___4-5 (significant P4 production) to 16-18 (luteolysis)
In nonpregnant cow, PGF2a pulses secreted for how long? Which day of the cycle?36 hours at day 16-17
4 events that may delay/prevent luteolysis:Removal of uterine horn ipsilateral to the ovary that contains the CL
Destruction of the endometrium (infection etc.)
Ligation of uterine vein ipsilateral to the ovary that contains the CL
Segmental aplasia
Source of luteolysinEndometrium
How does luteolysin reach the CL?Uterine vein --> ipsilateral ovarian artery
How are the uterine vein & ovarian artery arranged to exchange PGF2a? In which species?Wrapped around each other in ewe, cow, sow (not mare!)
When can you administer PGF2a in a cow to cause luteolysis?Day 5-18 (during diestrus)
Estrus will follow in +/- 3 days
What is the pregnancy recognition signal in a cow? (2)Embryo must be in uterine horn ipsilateral to CL-containing ovary by day 16 to prevent luteolysis
Interferon-tau secreted by elongating conceptus’ trophectoderm (future chorion), which acts on the endometrium to suppress PGF2a release
Sequence of events for parturitionFetal adrenal --> corticosteroids --> increased estrogen --> oxytocin --> PGF2a --> decreasing P4
PGF2a: derived from? Produced where?From arachidonic acid, produced in uterus
LH: from where? used when?From pituitary, used clinically when LH effect desired
Progesterone: produced by?CL, placenta, and all steroid-producing tissues
Estrogen: produced by?Ovary and many other steroid-producing tissues
Oxytocin: what is it? produced where?Peptide fragment produced in neurosecretory cells of the hypothalamus. Stored and released from posterior pituitary
Pituitary hormones with MW >25,000 Da =LH
Placental/chorionic hormones with MW >25,000 Da =eCH (Equine chorionic gonadotrophin)
hCH (human chorionic gonadotrophin)
Functions of LH (4)Ovulation
Stimulates Meiosis I completion
Stimulates Leydig cells in testis (testosterone production)
Functions of FSH (2)Stimulates follicular growth
Stimulates spermatogenesis
What is eCG? What is it used for (ironically)?Form of equine LH, but acts like FSH when used in other species
What is hCG? Used for what?Commonly used assay for human pregnancy. Used for LH effects in animals
Why do we care if a molecule is small or big?Molecules with MW >5,000-10,000 Da are antigenic and pose some risks when used as drugs
LH, FSH, eCG, and hCG (the bigs) require special handling to maintain molecular and pharmacologic integrity (freezing, lyophyilization)
Steroids with MW less than 1,200 DaP4
Estrogen (E2-beta)
Nonsteroids with MW less than 1,200 DaPGF2a

Male: Meiosis & Spermatogenesis

Question Answer
(Be able to draw meiosis diagram)(circles & x’s and stuff)
Spermatogenesis is the process where…Primary spermatocyte becomes secondary spermatocye via first division, then become spermatids after second division
___ drives testosterone productionLH
The 3 hormones that drive spermatogenesisTestosterone, LH, FSH
Meiosis consists of ___ cell divisions2
When does meiosis occur in the male?Not until after puberty
Sperm cell in Meiosis I =Primary spermatocyte
The 4 parts of Prophase ILeptotene
Pachytene (synaptonemal complex) (wtf)
What’s happening during Prophase I?Crossing over/chiasmata (most complicated element)
What’s happening during Metaphase, Anaphase, and Telophase I?Division
Maternal and paternal chromosomes do not separate into chromatids, just move into separate cells as intact replicated sister chromatids with crossover elements (from LZPD)
Sperm cell in Meiosis II =Secondary spermatocyte
T/F Prophase II is really important in spermatogenesisF. Replication already happened during Prophase I
What’s happening during Metaphase, Anaphase, and Telophase II?Typical mitosis, but with half the 2n number of chromosomes
Spermatids =The 4 cells that result from Meiosis I and II in the male
T/F Spermatids undergo cell division to become spermatozoaFalse
(Draw the sperm cell with droplets and such)(ugh)
How long does spermiogenesis take?Weeks (slow process)
What happens during spermiogenesis? Where? Are they ready to fertilize yet?Spermatids develop into spermatozoa in the seminiferous tubules
Not capable of fertilization when released into epididymis
During spermiogenesis, chromosomes become what? Golgi? Mitochondria? anything else?Chromosomes condense into compact head/nucleus
Golgi form acrosome
Mitochondria gather on opposite pole of cell from acrosome
Flagella forms on pole opposite the acrosome
When spermatozoa are released from the seminiferous tubules, what is the droplet like?Only 1 drop at proximal neck of cell
When spermatozoa have passed through the epididymis, what is the droplet like?Moved from proximal to distal end of the middlepiece (part with the mitochondria)
Passage through the epididymis causesMaturation of spermatozoa
Release of spermatozoa from the seminiferous tubule =Spermiation
What happens to the distal cytoplasmic droplet during ejaculation & mixture with seminal fluids?Pinched off
What enhances the sperm cell fertilizing ability?Contact with accessory sex gland fluids, then the uterus (capacitation)
(What do Sertoli cells do?)(Keep messages flowing between all cells undergoing the maturation process)

Female: Meiosis, Oogenesis, Fertilization

Question Answer
(Draw oogenesis)(yup)
When does Prophase I take place in most species?Before birth
When does oogenesis usually stop until?Cell(s) selected for ovulation after puberty
How do Primary oocytes form?Form follicles around themselves, develop zona pelucida, are encased in granulosa cells, and fluid builds up inside the follicle as it grows
Follicle cells producesEstrogen
Follicle development is driven by which hormones?FSH, LH
LH stimulates what? Leads to?Ovulation and resumption of Meiosis I, which results in ovulation of secondary oocytes
Secondary oocytes stop developing at which stage?Metaphase II
Which species ovulate primary oocytes and need time between ovulation and fertilization?Dogs
T/F The primary oocyte divides into 2 cells of equal sizeFalse
Produces first polar body and secondary oocyte
What does the first polar body (PB1) contain?One set of chromosomes
What does the secondary oocyte contain?Most of the cytoplasm and organelles from the primary oocyte (only 1 set of chromosomes goes into PB1)
What does the first polar body ultimately do?Disintegrates or divides but remains inert (has little cell machinery to operate as normal 2ry oocyte)
T/F All of the elements of oogenesis take place surrounded by the zona pelucidaTrue
Zona pelucida =Thick shell of glycoproteins that remains intact for a +/- a week after ovulation
When does the secondary oocyte complete Meiosis II? (Which stage has it been stuck in again?)When activated by fertilization (after Metaphase II)
What happens to the secondary oocyte when fertilized?Divides into a large cell and second polar body (PB2)
The secondary oocyte is arrested in Metaphase II until…Spermatozoan contacts the cell membrane of the egg
Steps for spermatozoan entering 2ry oocyteAcrosome reaction releases acrosomal enzymes
Penetration of Zona Pelucida
Inner acrosomal membrane makes contact with oocyte
Oocyte cell membrane and sperm cell membrane fuse
Spermatozoan enters oocyte cytoplasm
Cortical granules in oocyte triggered to prevent polyspermy
While the spermatozoan untangles its chromosomes (after penetrating oocyte), what happens?Activated 2ry oocyte divides into a fertilized egg (technically ‘ootid’) and second polar body
(“Graphically display” the events that result in cleavage w/ chromosomes etc)(ok)
Spermatozoan takes how long to reconstitute chromosomes? What is it doing exactly?12 hours to replicate and undergo mitosis (oocyte is completing Meiosis II at this time)
Less than a day after fertilization, the spermatozoan and fertilized egg both haveNucleus with respective chromosomes (pronuclei), and each chromosome has replicated into sister chromatids
After the pronuclei have formed in both cells, what happens?Metaphase spindle is formed, pronuclei dissolve
Cell undergoes division that resembles mitosis
T/F The zona pelucida prevents expansion with each successive cell divisionTrue
Each division produces smaller and smaller cells, called cleavage divisions

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